biocoal report 4 balbic 2013 biocoal production technology web 1
DESCRIPTION
Biocoal Report 4 BALBIC 2013 Biocoal Production Technology Web 1TRANSCRIPT
Baltic Bioenergy and Industrial Charcoal
REVIEW OF CURRENT BIOCOAL PRODUCTION
TECHNOLOGY
Tony Kiuru, Jukka Hyytiäinen
The Development of Bioenergy and Industrial Charcoal
(Biocoal) Production (Report of BalBiC project cb46)
Report 4/2013 Production and Logistics
Title: Review of current Biocoal production technology
This report has been written for The Development of Bioenergy and Industrial Charcoal
(Biocoal) Production (BalBiC) project, partially financed by the Central Baltic INTER-
REG IV A Programme 2007–2013.
The content of this publication reflects the authors’ views; the Managing Authority is not
responsible for the information published by the project partners.
Publisher: University of Helsinki, Department of Forest Sciences
Authors:
Tony Kiuru1, Jukka Hyytiäinen
1
1) Department of Forest Sciences, Faculty of Agriculture and Forestry, University of
Helsinki, P.O. Box 27, FIN-00014 Helsingin yliopisto, Finland
Printer:
Unigrafia Viikki, Infokeskus, Helsinki 2013
Table of Contents
1 Introduction .................................................................................................................. 1
2 Basic information about biocoal production ................................................................ 2
2.1 Biomass as a feedstock ...................................................................................... 2
2.2 Properties of biocoal .......................................................................................... 2
3 Applications of biocoal ................................................................................................. 6
4 Information on the general process for making biocoal ............................................... 7
4.1 Pyrolysis ............................................................................................................ 8
4.2 Torrefaction ....................................................................................................... 9
4.3 Process parameters ............................................................................................ 9
4.4 Heat integration ............................................................................................... 11
5 Current technological applications for biocoal production ........................................ 13
5.1 Different possibilities for a biocoal production system ................................... 13
6 Current biocoal production systems and technology developers ............................... 23
6.1 Global initiatives.............................................................................................. 23
6.2 Initiatives in the Baltic area ............................................................................. 26
7 Development aspects in the production technology ................................................... 30
8 References .................................................................................................................. 31
PREFACE
In recent years, interest in biocoal has grown significantly, mainly because of the im-
proved properties of biocoal over those of untreated wood. The most interesting features
of these properties are its improved transportability, high bulk energy density, hydropho-
bicity and grindability. These properties make biocoal much like coal, which is widely
used in energy production. In addition to these properties, interesting as they are from the
viewpoints of transportation and energy production, biocoal also offers applications for
agriculture and environmental management.
The BalBiC project uses the definition of biocoal from Wang et al., who defined it as an
umbrella concept which covers all thermally degraded biomass products with different
features and applications.1 The term biocoal is presently rather imprecise, and several
terms such charcoal, bio-char, char, torrefied wood, torrefied pellets, green coal, black
chips, black pellets, and others are interrelated. Several lexical varieties of the term exist
in Finnish, including puuhiili, grillihiili, TOPpelletti, torefiointi/paahdettu biomassa, bio-
hiilipelletti, and Biocarbon, among others. The term biocoal in the BalBiC project focuses
on the solid product and large-scale industrial applications such as substituting fossil coal
in coal-fired power plants.
The aim of this report is to provide a comprehensive review of the current production
technology used to produce biocoal. The purpose of this report is also to describe current
on-going initiatives in the world which focus on biocoal production. The study reviews a
wide range of the literature on the current state of biocoal production.
The report was produced within Work Package 4 of the BalBiC project. BalBiC is a joint
project of the University of Helsinki, Latvian State Forest Institute Silava and Forestry
Development Centre Tapio. The project was partly funded by the Central Baltic Interreg
IV A programme.
1
1 Introduction
Biocoal is a solid fuel produced from biomass in a pyrolysis process. Depending on the
process conditions, the solid product of pyrolysis is called charcoal or torrefied wood. In
this study, we refer to these two products as biocoal. Biocoal is a CO2-neutral and renew-
able fuel that has several advantages over other biobased fuels, namely high energy con-
tent and coal-like properties. This makes biocoal an attractive fuel for existing coal-fired
power plants.
The suitability and properties of biocoal for energy production have recently been the
most discussed applications of biocoal by far. Although interest in energy production is
presently the major driver for launching new development projects related to biocoal pro-
duction, the authors remind the reader of all the other current and potential applications
for biocoal, including environmental management, metallurgy and producing activated
carbon.
Tens of on-going initiatives are currently underway in the world to develop an economi-
cally and technologically feasible solution for biocoal production. These initiatives are
located mainly in Europe and North America. Of the known initiatives, only a few actual-
ly produce biocoal. No commercial-scale production plants currently exist in the world,
mainly because upscaling the process leads to difficulties in handling the process condi-
tions and in maintaining consistent quality in the end product, which is essential for the
development of biocoal markets. Smaller demonstrations or pilot-sized plants, however,
have avoided these problems , so more testing in large-scale is needed.
This report first discusses some basic information about the properties of the feedstock
used to produce biocoal as well as some of the main properties of biocoal that are interest-
ing for different applications. After reviewing the general information on biocoal, this
report provides an overview of a typical biocoal production setup, describes the main pro-
cess parameters and explores the differences between pyrolysis conditions.
The main part of this report aims to describe the different technological applications used
to produce biocoal. At the end of the report appears a list of some of the on-going initia-
tives in the world and in the Baltic area.
2
2 Basic information about biocoal production
2.1 Biomass as a feedstock
When the production of biomass is organised in a sustainable manner, biomass is kept as
a clean and renewable material. Fulfilling the sustainability criteria also keeps the con-
sumption of end products produced from biomass sustainable and carbon neutral.2 Most
of the challenges of utilising biomass come from the heterogeneity of biomass feedstock.
Different feedstocks have their own unique chemical compositions, which directly affect
the properties and yield of the biocoal produced from it. Biomass is generally composed
of three major constituents: cellulose, hemicellulose and lignin. The weight proportions of
the main constituents differ between feedstocks. The other components of biomass are
grouped as extractives and minerals. These proportions influence the distribution of bio-
coal productsamong the process conditions in current use.3, 4
Among the variations in chemical composition are several factors that also affect the pro-
cess. These factors include the low energy density, high moisture content and high oxy-
gen content of biomass. For example, moisture content affects the reaction time and yield
of biocoal, because the process itself requires more energy for the carbonisation process.
Difficulties in grinding untreated biomass can also be considered a drawback, since oper-
ations such as the co-firing of biomass in the pulverised systems of operating coal plants
require a small particle size. Biomass is also prone to fungal attacks and biodegradation
during storage.5, 6
Variations in biomass must also be taken into account in biocoal production, usually by
adjusting the operating conditions. Although the properties of untreated biomass listed
above strongly impact the properties and yield of biocoal, the operating conditions in use
can still significantly affect end-product quality (i.e., calorific value, hydrophobicity,
grindability, etc.). The operating conditions, such as peak temperature, significantly affect
the quality of biocoal, can be adjusted fairly easily. The significance of operating condi-
tions on end-product quality places great importance, but attributes such as the availabil-
ity, cost and sustainability of the feedstock in industrial biocoal production are also im-
portant aspects to be considered.7
The nature of biomass is relevant when using untreated biomass. For example, if biomass
is directly used for energy production, a much higher load of biomass is required to pro-
duce the same amount of energy as from fossil fuels. The high moisture and oxygen con-
tent of biomass lowers its heating value, because the combustion of moist biomass causes
water to evaporate, which is an endothermic process that draws heat from the actual com-
bustion reactions, which are exothermic. The moisture content of biomass is related to the
higher heating value (HHV) and the lower heating value (LHV). A higher moisture con-
tent in the biomass lowers both the HHV and LHV. Most of the energy obtained from
biomass serves to remove moisture, so a lower moisture content leads to the release of
more energy.6
2.2 Properties of biocoal
Reviewing the literature on the properties of biocoal reveals a variety of experimental
studies on the properties of biocoal. Many of these studies differ from each other accord-
3
ing to the process conditions used. This is why the results for a single property of biocoal
may vary significantly between studies. In this report, the given properties of biocoal are
indicative and intended to provide a broad overview of its various properties.
The typical properties of biocoal described in the literature include its content of volatile
matter, fixed carbon and ash. Antal and Grønli3 described volatile matter content as the
measured weight loss that occurs during heating, when the residual solid is carbonised
charcoal. The ash content is determined by heating the carbonised charcoal residue of the
volatile matter to burn away all the combustible matter; what remains is considered ash.
The fixed carbon content is defined as the percentage left after deducting the volatile mat-
ter and ash from the total content.
The typical volatile matter content ranges from 40% to 5%.8 According to Domac et al.,
9
the content of volatiles in charcoal intended for barbecue is 20-30%m, while the volatile
content of metallurgical charcoal is typically 10-15%m. The fixed carbon content varies
between 78 and 90%m, taking into account the ash content, which varies between 1.5 and
5%m.
In addition, several other qualities also serve to describe the properties of biocoal. Table 1
describes the qualities that are especially interesting from the point of view of energy
production and transportation. Table 1 presents the moisture content, calorific value and
mass density properties of torrefied wood, wood pellets, TOP pellets, charcoal and coal.
The table also shows two important factors that make biocoal more attractive than un-
treated wood; the moisture content is lower and the calorific value is higher than for un-
treated wood. These two factors significantly lower total transportation costs and also
improve the energy efficiency of biomass combustion.
Table 1. Indicative properties of torrefied wood, wood pellets, TOP pellets, charcoal and
coal.10-13
Unit
Torrefied wood
biomass 11
Wood pellets
11 TOP pellets
11 Charcoal
12 Coal
10, 13
Moisture
content (%) % wt 3 - 35 7.0 - 10.0 1.0 - 5.0 10 - 16.0 6.0 - 10
Calorific value
(LHV) as
received
MJ/kg 19.9 - 10.5 16.2 - 15.6 21.6 - 19.9 31.8 - 27.2 26.1 - 23.6
Calorific value
(LHV) dry MJ/kg
3 20.4 - 17.7 17.7 22.7 - 20.4 35 - 30 28.3 - 26.0
Mass density
(bulk) kg/m
3 230 - 550 500 - 650 750 - 850 100 - 500
900 -
100013
2.2.1 Particle size distribution, pore-size and particle surface area
Downie et al.14
found that raising the peak temperature from 450°C to 700°C reduced the
particle size of biocoal. They attributed the smaller particle size distribution to the de-
creasing tensile strength of the material, when it reacts more completely. The experiments
used sawdust and woodchips. Similar to Downie et al., Phanphanich and Mani15
reported
4
on how the particle size distribution reacted to higher heating temperatures. Phanphanich
and Mani carried out their experiments in the torrefaction temperature range with logging
residues and woodchips. The average particle size for both of the raw materials decreased
as the torrefaction temperature rose from 225°C to 300°C. The average particle size of
logging residues was slightly larger than for the woodchips. For particles larger than those
mentioned, Lu et al.16
concluded that particle size and shape dramatically affect the py-
rolysis conversion time.
The particle surface area and pore-size distribution are interesting properties of biocoal
when it is used, for example, to affect the physical characteristics of soil. Pore structure
and surface area vary significantly based on the structure of the biomass feedstock as well
as on the process conditions. From several studies of the surface area and peak tempera-
ture, Downie et al.14
concluded that surface area increased as the peak temperature rose.
They also discovered a linear relationship between surface area and pore volume. Higher
surface area values and pore-size distributions increase the liquid and gas absorption ca-
pacity of biocoal.
2.2.2 Hydrophobicity
Biocoal is known to be more hydrophobic and resistant to biological decay after thermal
treatment process than untreated wood.17
The hydrophobicity of biocoal means that its
moisture uptake is lower than for untreated wood, mainly because the hydrophobicity of
biocoal stems from changes in the chemical structure of the biomass. According to Berg-
man,11
when biomass is completely dried, the number of OH groups decreases, which
reduces the capacity of the biomass to form hydrogen bonds with water. In addition to
this weakened hydrogen bonding capacity, non-polar unsaturated structures form on the
biocoal, which also tend to be hydrophobic.
Bergman11
determined this hydrophobicity by immersing produced torrefied pellets in
water for 15 hours. The pellets were evaluated according to two factors: the state of the
pellet after the period and its water uptake during the period. The water uptake was meas-
ured gravimetrically. The results showed that pellets of untreated biomass swelled and
rapidly lost their form, whereas torrefied pellets did not disintegrate and showed only
modest water uptake (7-20% based on mass) depending on the production conditions.
2.2.3 Grindability
Thermally treating biomass improves its grindability mainly because biomass loses its
tenacity and fibrous structure.18
Grindability, like energy content and hydrophobicity, is
generally known to improve as the peak temperature rises. The main benefit of improved
grindability is to lower energy consumption during milling, which reduces total electricity
costs.
Phanphanich and Mani15
found that the energy required to grind torrefied woodchips and
logging residues was significantly lower than for untreated biomass. Grinding torrefied
wood chips required approximately ten times less energy than did untreated chips, and
torrefied logging residues required six times less energy than did untreated logging resi-
dues.
The power sector usually expresses the grindability of coal on the Hardgrove Index
(HGI). Comparisons of coal, wood pellets and torrefied wood have found that thermal
5
treatment significantly improves the grindability of biomass. The expected HGI value for
coal is from 50 to 80, while wood pellets show an HGI in the low 20s. The HGI of torre-
fied wood falls in the low to mid 50s, which is significantly higher than for wood pellets.
The higher HGI value indicates milling consumes less energy. The higher HGI of ther-
mally treated biomass offers advantages when, for instance, co-firing biomass in existing
coal power plants.19
2.2.4 Pelletability
Producing a homogenous and standard quality end product from thermally treated bio-
mass requires an important process in the industrial use of biocoal known as densifica-
tion. Densification reduces problems associated with the heterogeneous properties of bi-
omass and its low bulk density. The densification of treated biomass offers several ad-
vantages such as reduced costs and better handling in transportation and storage.20
A study by Li et al.21
examined densifying torrefied sawdust into pellets and found that
the higher the degree of torrefaction, the more the energy required to densify the torrefied
sawdust. During torrefaction, the reduction of hemicellulose and lignin reduces the num-
ber of hydroxyl groups. Hydroxyl groups are crucial for particle binding in the absence of
adhesives. Increasing the degree of torrefaction reduces the hardness of the pellets made
from torrefied sawdust. Stelte et al.22
also found problems similar to those of Li et al.
when they tried to produce pellets from torrefied spruce at higher torrefaction tempera-
tures (over 250°C). According to Stelte et al., the solution to the bonding problems is to
use an additive with a high bonding capacity, after the torrefaction process, to compensate
for the reduction in hydrogen bonding.
Although studies show that producing pellets from torrefied material is problematic,
Shang et al.23
notes that studies of pellet manufacturing from torrefied wood use single
pellet presses, which differ from industrial pellet mills, which currently manufacture
commercial pellets made from torrefied biomass that show good durability.
6
3 Applications of biocoal
In recent years, biocoal has attracted the attention mainly of the energy sector because of
biocoal’s enchained properties, which form during pyrolysis. Biocoal (charcoal) has tradi-
tionally been used in developing countries for cooking, in agriculture for soil preparation,
and in industry or metallurgy as activated carbon.
In the energy sector, the main properties of particular interest in biocoal are its higher
energy density, hydrophobicity and grindability. Biocoal’s higher bulk energy density
decreases the total transportation costs, so longer transportation distances become more
economically viable. Biocoal’s higher hydrophobicity facilitates storage and avoids mate-
rial losses thanks to its lower fungal degradation. The improved grindability of biocoal
also makes it an interesting option for co-firing in existing coal plants, because the raw
material can be ground to a sufficiently small particle size.24
For metallurgy purposes, biocoal provides strong reducing properties. Heating ores con-
taining metal, oxides, and sulfides in the presence of carbon facilitates metal extraction,
as the carbon readily combines with oxygen and sulfur. Hardwood species such as euca-
lyptus comprise most of the biocoal used in blast furnaces. Biocoal is generally consid-
ered good, if not better, than coke in metallurgy, although obtaining adequate supplies of
biocoal to satisfy the high demands of the large iron and steel industries is a challenge,
since achieving competitive steel prices requires large amounts of biocoal. Achieving
large supplies of biocoal is currently possible only in countries with extensive forested
areas and inexpensive biocoal production. An example of such a country would be Bra-
zil.25
Biocoal has value not only in fuel and metallurgical applications, but also in gas and liq-
uid absorption applications such as activated charcoal. Activated charcoal is charcoal that
has been chemically treated at high temperatures. The treatment process produces a pure
carbon product with very high surface area containing micropores that increase its absorp-
tive capacity. Activated charcoal can be used, for example, in air and water filters.25
Biocoal can also be used in agriculture to improve crop yields and soil properties. The
high surface area of biocoal may affect the water holding capacity of treated soil.26
Liang
et al.27
also found that biocoal can absorb and retain cations in exchangeable form, thanks
to its large surface area and greater negative surface charge. The ability of soils to retain
cations in exchangeable form increases in proportion to the amount of organic matter in
the soil.28
Biocoal also affects the soil’s properties by increasing its capability to absorb
phosphate, although the mechanism by which this occurs remains unknown.28
These at-
tributes of biocoal may impact soil quality and nutrient availability for plants, which may
potentially increase crop yields.
In the future, coal may be used in many ways. Recent studies promise huge applications
for coal in, for example, products such as graphene (a strong, flexible, transparent and
conductive carbon film), lightweight materials for cars and airplanes, and cell phones that
roll up in your pocket. We will use biocoal for all kinds of purposes in the coming years.
7
4 Information on the general process for making biocoal
The biocoal production process generally entails three different phases: the pre-drying
phase of the biomass, the pyrolysis or torrefaction phase, and the cooling phase of the
treated biomass. The thermal treatment process after the pre-drying phase is known as
pyrolysis or torrefaction depending on the peak temperature used. A more precise de-
scription of how these two processes differ appears later in this section. Following the
thermal treatment process, biocoal is first cooled, after which it can then be pelletised or
briquetted for transportation or storage. Alternatively, biocoal can be directed toward
combustion if the biocoal is intended for energy production.
In the production of biocoal, volatile gases and liquids are normally separated from the
system for further processing. Such liquids and gaseous products can be used forcombus-
tion in the biocoal production process or further processed into, for example, transporta-
tion fuels. If the process aimes to produce biocoal, the volatiles are combusted in an af-
terburner and the flue gas is used either directly or indirectly for heating during the actual
process or in the pre-drying phase. A general picture of the process appears in Figure 1.
Figure 1. General description of the biocoal production process.
Drying Pyrolysis
process Cooling
Combus-
tion
Biomass Biocoal
Process
gases
Heat to process
Utility fuel
Pelletising
Combustion
Biocoal production
8
4.1 Pyrolysis
Although the general process description has many different phases, the biocoal itself
forms in pyrolysis, where biomass is heated in the absence of oxygen. Free oxygen in the
system would allow the biomass to ignite and burn to ashes. Without oxygen, however,
biomass is forced to decompose into three end products: solids (charcoal, torrefied wood),
liquids (tar and aqueous solutions or organics) and gases.29
Figure 2. Three stages of thermal degradation of a solid biomass particle under inert at-
mosphere.30
It is important to note that the pyrolysis process entails primary and secondary pyrolysis,
both of which affect the final product distribution. Figure 2 presents the different stages
of thermal degradation of solid biomass. According to Neves et al.,30
the degradation of
biomass consists of three stages: drying, primary pyrolysis and secondary pyrolysis. In
the first phase, known as the drying stage, the particle is introduced to transient heat,
which dries the biomass particle and the evaporation of moisture starts to occur.
In the primary pyrolysis stage, after the drying stage, the pyrolytic volatiles begin to es-
cape from the biomass. The primary volatiles are produced from the thermal scission of
chemical bonds in the individual constituents of the biomass (cellulose, hemicellulose,
lignin and extractives). The volatiles comprise permanent gas species, such as CO2, CH,
and CO4, as well as condensable species, such as organic compounds and water. The con-
stituents of the biomass decompose at different temperatures The primary pyrolysis stage
is complete at a relatively low temperature of approximately 500°C, yielding a solid
product called char or charcoal.30
At higher temperatures, the primary volatiles may participate in secondary reactions,
which can occur separately or simultaneously with the primary reactions. For example,
the primary char can remain active during secondary reactions, which can lead to the
polymerisation of organic vapours to secondary char. If secondary reactions occur during
pyrolysis, the charcoal actually produced contains both “primary” charcoal and “second-
9
ary” charcoal. Depending on the operating conditions, the secondary conversion of prima-
ry volatiles can modestly to significantly influence the final composition and yield of the
volatiles.3, 30
4.2 Torrefaction
Torrefaction is a pre-treatment process of biomass under inert conditions carried out at
operating temperatures between 200°C and 300°C with a slow heating rate of less than
50°C/min. The process is carried out under conditions of atmospheric pressure and in the
absence of oxygen. The torrefaction temperature range is usually distinct from that of
pyrolysis, because in most cases, torrefaction maximises the yield of biocoal. In some
instances, torrefaction is also referred as roasting, mild pyrolysis, slow pyrolysis and
thermal-pretreatment.18, 31
During the torrefaction process, the biomass dries completely and turns into solid prod-
ucts and volatiles. The volatiles include non-condensable gases and condensable liquids.
The gases produced are mostly CO2, CO and methane (CH4), and the liquids include wa-
ter, acetic acid and other oxygenates.18, 32
4.3 Process parameters
The main process parameters, which are adjusted during pyrolysis, are the peak tempera-
ture, the residence time and the heating rate. All of these parameters affect the total yield
and properties of biocoal. The biomass moisture content, tree species used and its varying
chemical composition also significantly affects the yield and properties of biocoal. In the
first published report of the BalBiC project, Rautiainen et al.33
discuss the effect of the
main process parameters on the properties and yield of biocoal from different wood spe-
cies. Table 2 presents values that indicate how the conditions and temperature of the py-
rolysis process affects the yields of liquid, char and gas.
Of the process parameters, the peak temperature generally has the most significant effect
on the properties of biocoal. The literature describes the peak temperature as the highest
temperature reached during the pyrolysis process. Raising the peak temperature decreases
the yield of biocoal and increases the heating value of the remaining biocoal.
The heating rate influences mainly the distribution of different end products. If the de-
sired product is biocoal, the heating rate should be slow, as in conventional pyrolysis,
where the heating rate is 0.1-1°C/s. Although a slow heating rate should maximise the
yield of biocoal, Antal and Grønli3 have discovered that this is not always consistent. The
higher the heating rate, the more gaseous and liquid products form. If the heating rate is
exceptionally high, the process is called Flash-pyrolysis. In Flash-pyrolysis, the yield of
gaseous products is high.12
The last main process parameter, known as the residence time, describes the time that a
particle spends inside a particular system. Generally, a longer residence time reduces the
total yield of solid biocoal. On some occasions, a slightly higher heating value has been
reported. Several studies, such as Prins et al.34
, Pach et al.35
and Bergman et al.36
, have
reported on the effect of residence time on the properties of biocoal.
10
Table 2. Indicative product yields (dry wood basis) under different pyrolysis modes and
conditions.37
Mode Conditions Temperature Liquid Char Gas
Fast Moderate temperature, short hot vapour
residence time ≈ 1 second Around 500°C 75% 12% 13%
Intermediate Moderate temperature, moderate hot
vapour residence time ≈ 10-20 second Around 500°C 50% 20% 30%
Slow (Carbonisation) Low temperature, very long solids resi-
dence time Around 400°C 30% 35% 35%
Gasification High temperature, long solids and va-
pour residence time Around 800°C 5% 10% 85%
In the literature, the definition of different pyrolysis processes and the specific process
parameters used in them vary. In Table 3 presents a broad view of the different pyrolysis
processes and their main operating parameters. The pyrolysis process can be divided into
roughly three subclasses: conventional pyrolysis, fast pyrolysis and flash pyrolysis.38
Generally, pyrolysis conditions significantly affect product distribution. Low process
temperature and long residence time maximizes biocoal production, whereas high tem-
perature and long residence time maximises gas production; moderate temperature and
short residence time maximises liquid production.39
Table 3. Main operating process parameters for pyrolysis processes.38
Parameter Conventional pyrolysis Fast pyrolysis Flash pyrolysis
Operating temperature (°C) 300 - 700 600 - 1,000 800 - 1,000*
Heating rate (°C/s) 0.1 - 1 10 - 200 ≥ 1,000
Solid residence time (s) 600 - 6,000 0.5 - 5 < 0.5
Particle size (mm) 5 - 50 < 1 Dust
*Up to 2,000°C with solar furnaces
11
Product
Natural gas
or biomass
Biomass
input
Combustion
Gas cleaning
Drying Pyrolysis process
Heat exchange
Gas cleaning Emission
Cooling Pelletising
2
1
3
4.4 Heat integration
Many current biocoal manufacturers have a heat integration system in their production
process. The basic design of a heat integration system is to combust the volatiles in an
afterburner and use the flue gas to directly or indirectly heat the biomass pre-drying pro-
cess or the actual biocoal production process.40
Handling the moisture content of the biomass is important when the aim is to optimise the
carbonising process. The higher the moisture content, the more energy is required to dry
the biomass. If the moisture content is high, the carbonising process lasts longer and more
of the biomass remains uncarbonised, thereby reducing the quality of the biocoal. If very
moist biomass is dried rapidly, the charcoal becomes porous, thereby reducing the
strength of the charcoal.12
The pyrolysis gases from biomass contain organic acids and primary tars. These com-
pounds must be cracked in the afterburner, because condensation of the tars on the prod-
uct or internals of the afterburner and system can generate problems. The operation of the
afterburner depends heavily on the process gases obtained. A high moisture content in the
pyrolysis gases reduces the calorific value, which will eventually lower the thermal effi-
ciency of the entire biocoal production plant. Because the gases obtained from the process
contain some organic compounds even after combustion, additional flue gas cleaning is
necessary.40
Figure 3. Heat integration options for the pyrolysis process (adapted from Kleinschmidt 40
).
12
In Figure 3, the first option (shown in red) for heat integration is the recirculation of flue
gases to directly heat the pyrolysis process. Although the flue gases contain a certain per-
centage of oxygen, which reduces the total efficiency of the pyrolysis process, the loss in
the heat exchange is minimal. Large volumes of flue gases will, however, require invest-
ments for ducts, fans and compressors, which may increase electricity consumption.40
In the second option (shown in blue), the torrefaction gas or pyrolysis gas is recirculated
to directly heat the process itself. The heat is transferred efficiently, as in the first option,
but the gas contains a higher concentration of organic acids and cyclic organic compo-
nents, which leads to more tar formation during the process. The volume of gas will be
lower than in the flue gas option.40
In the third option (shown in green), steam (super critical) is used directly or indirectly to
heat the pyrolysis process. The directly heated system produces efficient heat transfer,
and the process also remains inert. The use of steam affects the process gas (torrefaction
gas or pyrolysis gas), which will have a relatively low calorific value because it is saturat-
ed with moisture. The high moisture content leads to inefficient combustion of the vola-
tiles (acids), causing the recycled steam flow to be contaminated with volatiles and tars.
Condensation of the volatiles and tars in cold spots can cause problems in the recycling
system. In the indirectly heated system, hot spots may occur where the biomass comes
into contact with the reactor wall. The presence of hot spots increases the risk that the
carbonisation will be too intense, which would then lower the yield of end products. Heat
is also transferred less efficiently.40
13
5 Current technological applications for biocoal production
5.1 Different possibilities for a biocoal production system
Existing reactor designs, which include ovens, rotary drums, ablative reactors, rotating
cone reactors, multiple-hearth furnaces, screw reactors, fixed beds, moving beds, fluid-
ised beds, oscillating belt reactors and microwave reactors, are currently tested for their
suitability to biocoal production. Most of the technologies described in this section were
originally used for drying biomass or for fast pyrolysis processes. The technologies used
for drying can be modified and used for the production of biocoal also. Some of the tech-
nologies described in this report are especially developed and used for torrefaction tem-
peratures. The technologies originally used in fast pyrolysis processes normally yield the
desired liquid or gaseous end products, although biocoal has in many cases been produced
as a side product. Such biocoal has then been used to heat the fast pyrolysis process.
All of the existing technologies have pros and cons for biocoal production purposes and
many of the technologies, if used to maximise the production of biocoal, still require ad-
ditional modifications to be efficient enough for industrial purposes. In addition to known
technologies, some ongoing initiatives round the world have developed their own techno-
logical applications, especially for biocoal production. Section 5.2 describes some of the-
se current initiatives.
Several important, critical issues remain to be solved, however, to improve the efficiency
of the biocoal production process and consistency in the high quality of the end product.
The reactors must be modified or built so that the reaction chamber is gas-tight, can han-
dle exothermic reactions during the process, and is capable of handling the formation of
tar-rich volatiles, which condense in and clog the system. The system should also be
made more energy efficient by using the emitted process gases.19
The technologies can be categorised by the way biomass is fed into the system and how
the system is heated. The ways in which biomass is fed into the system can be categorised
into three different categories: continuous, semi-continuous and batch-type systems. In
the continuous system, the biomass is fed at a constant rate, while the batch-type system
is refilled with new biomass only after the pyrolysis process is complete. In the semi-
continuous system, the process works at a constant rate, while the biomass is separated
into batch-type vessels. Each of these vessels remains in the system until carbonisation is
complete and is then replaced by a new vessel full of fresh biomass.9
The way in which the process is heated divides different technologies into two categories:
directly heated and indirectly heated, depending on how heat is brought into the process.
In direct heating, the biomass comes in direct contact with the heat carrier. In indirect
heating, in contrast, a heat exchange surface provides the heat, and the biomass does not
come in direct contact with the heat carrier.41
The pyrolysis reactors may operate at atmospheric pressure, under pressure or in a vacu-
um. Most pyrolysis reactors operate at atmospheric pressure, because the operating condi-
tions are simple to attain and incur no additional costs from auxiliary equipment. Using a
vacuum during the pyrolysis process increases the amount of liquids produced, but also
requires a more complex, airtight pyrolysis system. Pressurised pyrolysis processes
should produce a higher yield of char and gases.42
14
The applications used to separate biocoal from the other pyrolysis products depend on the
size distribution of the biocoal particles and the reactor design used in the process. Bio-
coal can be separated, for example, by screening or with filters and cyclones.
5.1.1 Ablative reactors
Ablative reactors are systems that introduce fast pyrolysis and a short residence time to
biomass particles introduced into the system. Ablative reactors differ mainly in the shape
of the reactor. The plate-type ablative reactor appears in Figure 4. The ablative reactor
permits the use of larger particles than do fluidised bed systems. Heat is transferred to the
biomass through a hot molten layer on the hot reactor surface, and no inert gases are re-
quired, as in fluidised bed processes.6
The drawbacks of the reactors are that the system is mechanically complex with several
moving parts. Heat losses may also be high, because the surface temperature must remain
higher than the reaction temperature. The reactions are also limited by the heat transferred
to the reactor rather than by the absorption rate of the biomass particle.6 Cone-type abla-
tive reactors also have difficulties adjusting the residence times for biomass particles.43
Figure 4. Simplified diagram of a plate-type ablative reactor.44
5.1.2 Rotating cone reactor
The rotating cone reactor introduced a rapid heating and short residence time for solids
fed into the reactor. The biomass fed into the system is mixed with sand to provide more
efficient heat transfer. The biomass and sand are fed into the system from the bottom of
the rotating cone, and the biomass is pyrolysed in the upward spiral motion. The system
heats the particles on a heated surface, and no heat carrier gas is necessary. In a flash py-
rolysis process, wood dust was decomposed into condensable gases (70%) with a part of
non-condensable (15%) gases and char (15%). Adjusting the pyrolysis conditions could
achieve higher charcoal yields. A simplified picture of the rotating cone pyrolysis process
appears in Figure 5.6
15
Figure 5. Simplified diagram of the rotating cone pyrolysis process.44
5.1.3 Rotary drum reactor
The rotary drum reactor is a rotating drum in which biomass is directly or indirectly heat-
ed with hot steam or gases. In the direct contact system, hot gases are contacted with bi-
omass inside the rotating drum. In the indirectly heated system, the drying is accom-
plished with hot air or steam that passes through the outer wall of the dryer or the inner
central shaft. If contamination caused by direct contact with the flue gases is a problem,
the indirectly heated system is preferable. A picture of a rotary drum reactor appears in
Figure 6.41
The rotary drums can be divided according to their structure into single-pass and triple-
pass dryers. In the single-pass rotary dryer, all the material remains inside s single cylin-
der. The triple-pass dryer is a design modified to allow three passes of air and material.
Because of the plugging risk, the triple-pass dryer is most suitable for material smaller
than one inch. Single-pass dryers can be used to heat larger material. In the triple-pass
dryer, the material first enters the inner cylinder with hot air, where smaller or drier mate-
rial is blown into the larger concentric cylinder. After the second pass, the air and materi-
al moves to the third outermost cylinder, where the material then leaves the system. There
is also a hybrid direct/indirect rotary dryer, where hot flue gases pass through the central
shaft (where it heats the material by conduction); these same gases from the shaft then
come into direct contact with the heated material.41
The most commonly used dryer is the directly heated single-pass rotary dryer. The rotat-
ing drum promotes heat and mass transfer by lifting the solids in the dryer and causing the
particles to tumble through hot gases. In the dryer, biomass and hot air can flow co-
currently or in opposite directions inside the reactor. With the co-current flow, the hottest
gases contact the wettest material first. The driest solids can be exposed directly to the
hottest gases with the opposite direction flow, if the high temperature is not a concern.
The direct exposure to high flue gas temperatures dries the most thoroughly, but the risk
of fire increases.41
16
Figure 6. Drawing of a rotary drum reactor.45
5.1.4 Fixed-bed reactors
Fixed-bed reactors are divided into counter-current (updraft) and co-current (downdraft)
systems, depending on the directions in which the fuel bed moves relative to the gas. Both
of the systems appear in Figure 7. Both systems typically consist of four different zones
(drying, distillation, reduction and hearth) through which the biomass passes. First, the
biomass is dried in the drying zone before entering the distillation zone, where the bio-
mass decomposes and is converted to volatile gases and char. In the reduction zone, the
gases and char will be converted to CO and H2, but some of the remaining char passes
through the reduction zone, where it can be combusted to generate heat in the hearth
zone.4, 6
In the counter-current system, the fuel bed moves downwards, and the gas upwards. The
hot gas provides energy for heating, drying and pyrolysis of the biomass. The entering air
or oxygen is at temperatures as high as 1200°C when it reacts with the char in the com-
bustion zone. In the pyrolysis zone, these same gases are at temperatures ranging from
400°C to 800°C when they come into contact with the dry biomass. Counter-current sys-
tems can accept very moist biomass (up to 60% moisture content), but using moist bio-
mass increases the tar content of the gases that leave the reactor near the pyrolysis zone.
Above the pyrolysis zone, the entering biomass is dried. The updraft system requires con-
trol of the feedstock particle size to secure a fixed bed of uniform space between the
packed feedstock.4, 6
The co-current system can serve to dry wet fuels and can be used with various particle
sizes. In the co-current system, the fuel bed and gas flow in the same direction. The gases
leave the reactor near the hottest zone. The advantage of this system is that it requires far
fewer organic components than does the counter-current system, because the volatiles
enter the high-temperature combustion zone. The feedstock must be uniform in size with
few fines. The problem with both systems is the slagging of ash in different parts of the
system.46, 47
17
Figure 7. Diagram of a counter-current and co-current fixed bed reactor.39
5.1.5 Fluidised bed systems
In the fluidised bed system, heat is transferred to the biomass through a bed of non-
combustible material, such as sand, that remains in a fluidised action with air flowing
from the bottom of the combustion chamber.48
The system is divided into the fluid bed zone and the freeboard zone. In the bottom zone,
the velocity (volume/unit cross-sectional area) of the gas is controlled to keep the bed in a
fluidised state. In the upper zone, the particles return to the bed when the cross-sectional
area of the system is increased to produce a gas velocity below the fluidisation velocity.
The biomass is then fed into the system with a feed chute above the bed or with an auger
extending into the bed.46
The fed biomass then mixes with the sand and begins heating up. The sand serves as a
heat reservoir that maintains a constant mean temperature in the beds during the process.
The overall complex, circulating flow provides good mixing behaviour for the bed. As the
particles pyrolyse, they simultaneously eject product gases and form char. The product
gases first mix with the fluidisation gases before they are removed from the system and
cooled, so they can be collected (e.g., for condensable tars). The particles in the remain-
ing char erode to smaller particle sizes and are removed with the flow gas from the sys-
tem. The automatically self-cleaning system makes the fluidised bed reactors suitable for
continuous processing.49
Depending on the air velocity they use, fluidised-bed reactors can be divided into circulat-
ing fluidised-bed (CFB) or bubbling fluidised-bed (BFB) systems. Both systems appear in
Figures 8 and 9. The CFB system is always built to recirculate particles, and the turbulent
mixing in CFB systems is more intensive than in BFB systems, due to the high velocity.
CFB also exchanges heat more efficiently than does BFB.47, 48
18
Figure 8. Simplified diagram of the bubbling fluidised bed process.44
The advantages of fluidised-bed reactors include the flexibility of the fuel size, shape and
properties they can use. The reactor can also be used with very moist fuel (up to 60%
moisture content) and has a high ash content (up to 50%).48
The mixing action in fluidised
beds provides efficient temperature control, as well as heat and mass transfer between the
gas and the particles. These factors make the fluidised-bed interesting for biomass com-
bustion. Despite their compact construction, fluidised-bed systems can achieve higher
heat transfer and reaction rates than can fixed-bed systems.48
Fluidised-bed reactors are
also more suitable for large-scale applications (over 30 MWth) than are fixed-bed reac-
tors.47, 50
Adjusting the particle size, reaction temperature and gas flow rate through the fluidised
bed can change the product distribution. The high flow rates and short residence times of
the fluidised bed might be expected to produce different kinds of biocoal than would slow
pyrolysis.51
Figure 9. Simplified diagram of the circulating fluidised bed process.44
19
5.1.6 Screw conveyor
The auger or screw reactor is a mechanical biomass-mixing reactor. The vessel itself does
not rotate, but mixing devices rotate inside a stationary horizontal reaction vessel.52
Inside
the reactor, the rotating screw moves the biomass forward. Screw-type reactors can be
heated externally or directly with a heat carrier such as sand.51
The heat carrier is normal-
ly heated independently and then mixed with the biomass before entering the reactor. The
operating temperature can be adjusted with the heat carrier. Pressure differences draw the
resultant gaseous products out of the reactor from the open ends. The solid material, in-
cluding the resultant biocoal and the heat carrier, exits from the end of the reactor. Based
on the particle size and density difference, a solid separator device serves to remove the
biocoal from the heat carrier material.52
The auger system can consist of a single or sever-
al auger units. The benefit of the screw conveyor is that the system can operate in a rela-
tively small space.51
Mechanical wear can become a problem in the system.52
A simpli-
fied picture of the screw conveyor appears in Figure 10.
Figure 10. Simplified diagram of the screw conveyor process.44
5.1.7 Microwave
Conventional heating processes transfer energy to materials through conduction, convec-
tion, and radiation. Heat is transferred from the outside to the inside of the material. One
option besides conventional heating that is used in biocoal production is microwave-
based heating. Microwaves deliver energy directly to the materials through molecular
interaction within the electromagnetic field and instead of via thermal transfer; this elec-
tromagnetic energy then turns into thermal energy.53
The interaction reactions between microwaves and materials can be divided into three
types; reflective (conductors), transparent (insulators) and absorptive (dielectrics).53
The
advantages of microwaves over conventional heating are a uniform, selective and high
heating rate, and effective control of the heating process without direct contact.54
The
adjustable parameters that affect the process are the microwave power level, processing
time, water content and particle size.53
Luque et al.55
listed the advantages and disadvantages of microwave-assisted pyrolysis.
The main advantages of the process were its flexibility in using various feedstocks, ener-
gy savings from using the process, and the range and quality of the end products. The
disadvantages include the difficulty in precisely measuring the temperature during the
20
process and scaling up the system. A picture of the Rotawave microwave system appears
in Figure 11.
Figure 11. Picture of a Rotawave microwave reactor.56
5.1.8 Multiple-hearth Furnace
The multiple-hearth Furnace design is normally a vertical cylinder-modelled steel shell
furnace. The biomass enters the hearth from the top and flows downward on 6 to 12 hori-
zontal hearths. A rotating shaft with rabble arms in the centre of the furnace sweeps the
biomass in a spiral motion. The biomass changes direction as it moves from the centre of
the furnace to the outer border and switches between the hearths. The rabble motion
breaks up the solid material for better surface contact with heat and oxygen. The resi-
dence time varies from 0.5 to 3 h depending on the number of hearths and shaft speed.57
The combustion air flows from the bottom to the top counter-current to the incoming sol-
ids. The multiple-hearth furnace can be operated continuously or intermittently, but the
continuous process is preferable, because of its high start-up and standby costs.58
According to Dangtran et al.,57
the multiple hearth is divided into three different zones.
The upper hearths comprise the drying zone (temperature between approximately 420°C
and 540°C), where the heated material loses its water and some organic compounds
through evaporation. The middle hearths constitute the combustion zone (temperature
between approximately 815°C and 930°C), where the material is exposed to high temper-
atures; the residence time in the combustion zone is usually short. The lower hearths form
the cooling zone (temperature between approximately 175°C and 205°C), where the re-
maining material, such as ash, cools as its heat transfers to the incoming combustion air.
A simplified picture of a multiple-hearth furnace appears in Figure 12.
21
Figure 12. A simplified diagram of a continuous multiple-hearth furnace.59
5.1.9 Belt reactors
The belt conveyors serve to move biomass through a heated reaction zone. A picture of
the system appears in Figure 13. Previously, the belt reactors have been used mainly for
drying purposes. When the belt reactor has been used for biocoal production, the process
temperature has been in the torrefaction temperature range. Single or multiple belts can
adjust the heating in different belts. The belts use oscillation to mix the biomass. In belt
conveyor-type reactors, the biomass is a thin layer on a horizontal belt that is then heated
with air or combustion products. The residence time and peak temperature can be adjust-
ed easily. Normally the drying of the biomass is uniform, since the biomass band is usual-
ly in the range of 2 to 15 cm. A small particle size is normally required, especially for
continuous operation.60
Figure 13. Diagramof an oscillating belt reactor.45
22
5.1.10 Compact moving bed
The Compact moving bed consists of a reactor in which biomass is fed from the top of the
system, where it is then allowed to gradually fall, while the heat-carrying gaseous medi-
um enters from the bottom of the reactor. A picture of the system appears in Figure 14.
The solid products are removed from the bottom, as are gaseous products from the top of
the reactor. A typical reaction time in the Compact Moving bed is 30-40 min at a temper-
ature of approximately 300°C. ECN in Holland have used the compact moving bed to
produce biocoal. The operating temperatures have varied in the temperature zone typical-
ly used for torrefaction.61
As a benefit, the reactor has no moving parts inside it, so wear
will not pose a problem. The problems result mainly from the biomass mixing poorly
during the process, which leads to a non-uniform end product. Uneven feedstock particle
size may also lead to un-even heat treatment across the diameter of the reactor.62
Figure 14. Diagram of a compact moving bed reactor.62
23
6 Current biocoal production systems and technology developers
Biocoal production technology is still evolving and new projects related to it are in con-
stant development. The conversation about biocoal production is presently very active.
Several different technologies have been tested in demonstration or pilot-sized production
facilities. One of the main problems in technical development is to find a reactor technol-
ogy that would enable one to optimise and adjust the process conditions in order to max-
imise the yield and product quality with various feedstocks. Optimising for different feed-
stocks should be easy, fast and economically viable. Efficient process performance and a
desirable end product distribution rely on the control of the main process parameters and
the varying quality of the feedstock.
Although much talk and plans have focused on commercial scale biocoal production
plants, no markets currently exist for trading biocoal, and no widely proven technological
applications are able to produce it. This paper presents only some of the potential tech-
nology suppliers and currently ongoing development projects in the world. These descrip-
tions aim to provide a general impression of the related companies, technology applica-
tions and size of the ongoing initiatives. Table 4 at the end of this section presents a list of
development projects that are currently ongoing or are planned. Most development pro-
jects have made or plan to build a pilot-size production plant. Some of the initiatives have
also claimed the end product with their own trademark name. The reader should not get
confused by the various names companies may give to biocoal, because in the end, the
actual product falls under the same umbrella concept presented in the beginning of this
report. The differences between companies and their trademark products stem from the
technology used and the slightly varying process conditions. For more information about
the companies listed, the reader may visit the website of the company in question.
6.1 Global initiatives
6.1.1 Andritz – ACB technology and Moving bed technology - Rotary drum and
Moving bed reactor
Andritz uses two technological platforms in their biocoal production systems: the moving
bed reactor and the rotary drum reactor.
The rotary drum reactor is called ACB (Accelerated Carbonised Biomass) technology.
The ACB system is offered as an integrated solution with their turnkey production unit,
which has process steps for densifying, waste gas utilisation and thermal energy produc-
tion. The company claims a single-line production unit has a commercial production ca-
pacity of 50,000 tons annually. The technology is based on their indirectly heated rotary-
drum technology. The design and manufacturing expertise is based on the Andritz DDS
(drum drying system), which dries municipal, industrial and agricultural sludge. The reac-
tor can process different-sized particles.63
The pressurised moving bed reactor is a co-operation project with the Energy Research
Center of the Netherlands (ECN). The reactor will be located in Standerup, Denmark. In
the project, Andritz has licensed key technology from ECN, and the system uses moving
bed reactor technology from ECN. The system is pressurised for more effective heat
24
transfer due to higher gas flows, lower velocities and pressure drops for increased capaci-
ty.64
6.1.2 Wyssmount (US) - Turbo-dryer (Multiple-hearth furnace)
The Wyssmount Turbo-Dryer is a multiple-hearth furnace-type reactor. The Turbo-Dryer
consists of a reactor, which houses several slowly moving rotating circular trays. The
biomass is fed from the top of the reactor and is then wiped through the trays, which are
heated with air or gas circulated by fans. The temperature can be adjusted in each zone or
the entire reactor can have a uniform internal temperature. The drying conditions can be
adjusted automatically, and the residual time adjusted precisely.65
6.1.3 Stramproy Green Investments (NL) – Oscillating belt reactor
The Stramproy green investment biocoal production plant is located in Steenwijk, Nether-
lands. The company has a CHP station with two biocoal production lines in a single facto-
ry. According to Stramproy, the two production lines – when combined – can produce
approximately 90,000 tons of biocoal annually. The residual heat of the CHP is used in
the drying phase of the biocoal production process. Stamproy uses oscillating belt reactor
technology for their biocoal production.66
6.1.4 Topell energy (NL) - Torbed reactor
Topell energy is a privately funded clean technology company in Duiven, Netherlands,
which has developed a process for biocoal production. The reactor Topell uses is called
the Torbed reactor system. The reactor was developed by a company called Torftech Ltd.
in 1998. Topell energy claim the system can produce 60,000 tons annually. The system
applies fluidised-bed technology, but the biomass itself rather than a separate material
forms the actual bed. The reactor consists of an empty cylindrical reactor chamber where
the biomass comes into contact with a high-speed flow of process gas. The high velocity
gas suspends the biomass in a fluid-like state. Contact with the hot process gases and the
biomass yields a high heat and mass transfer. The high velocity allows the use of0 a broad
range of particle sizes in the process. The reactor has no internal moving parts, so the per-
formance and maintenance costs should be low.67
6.1.5 Energy Research Centre of the Netherlands (NL) – PATRIG – (Moving bed
reactor)
As part of the TorTech project, the Energy Research Centre of the Netherlands (ECN)
designed, constructed and commissioned, a pilot-scale biocoal production plant called
PATRIG. The reactor design is based on moving bed technology that uses recycled prod-
uct gas (torgas) to directly heat the biomass. The recycled product gas is then collected
during the process and later circulated and heated with an electrically heated thermal oil
system. The input scale has been set to 50-100 kg/hour depending on the biomass used.
The gas-solid contact allows effective temperature control inside the reactor.61
25
6.1.6 AREVA – Thermya TORSPYD (Moving bed reactor)
The AREVA company announced the acquisition of Thermya technology, thereby ena-
bling them to produce biocoal.68
Areva are now using Thermya TORSPYD technology
for biocoal production. The TORSPYD process is a soft thermal treatment of biomass
based on the moving bed reactor application. The biomass is in the continuous circulation
of two air flows moving in opposite directions.69
Among the benefits of the process, Thermya listed its ability to convert all kinds of lingo-
cellulosic biomass into their solid product called BioCoal. The solid organic particle in-
troduced into the system moves down inside the TORSPYD reactor, where the tempera-
ture rises progressively. During the process, the biomass gradually loses its moisture con-
tent and organic content. Thermya promises that their BioCoal contains less than 1%
moisture, retains 95% of its initial biomass energy and more than 90% of its initial dry
mass.70
The products are homogenous, and the quality is consistent.71
6.1.7 Biolake (NL) – Screw conveyer reactor
Biolake is a young enterprise established by ATO together with five entrepreneurs located
in North Holland. The company uses screw dryers for biocoal production. The biomass is
heated from outside the reactor, which contains several different screws with different
operating temperatures. The biocoal manufacturing process operates between 260°C and
350°C. The system collects the by-product gases and burns them in a boiler. The heat is
then used in the reactor to dry the biomass. Testing of the system is currently underway.53
6.1.8 Rotawave (UK) – Targeted Intelligent Energy System (Microwave)
Rotawave Ltd. have developed a microwave process called Targeted Intelligent Energy
System that transforms biomass into biocoal. The system allows the conversion of bio-
mass to biocoal, ranging from torrefied biomass to charcoal.56
Rotawave list among the
benefits of their system its high thermal energy conductivity, which generates high calo-
rific values and solids yields. Because of the microwaves’ direct interaction with the mo-
lecular structure, the particle size has no influence on the reaction time or on the degree of
pyrolysis.72
26
Table 4. Overview of initiatives seeking to produce biocoal.40, 63, 73-75
Developer Reactor type Location
Topell Energy Torbed Duiven, Netherlands
Integro Earth Fuels Turbo-Dryer Roxboro, USA
Stramproy Green Belt conveyor Steenwijk, Netherlands
4Energy Invest Rotary drum Amel, Belgium
Zilkha Biomass Energy Unknown Crockett, USA
Torrsys Moving bed Vanderhoof, Canada
Agri-tech Screw conveyor Columbia, USA
Biolake Screw conveyor North Holland
Torr-Coal Rotary drum Dilsen Stokkem, Belgium
Fox Coal Screw conveyor Winschoten, Netherlands
BioEnergy Inc Rotary drum O-vik, Sweden
AREVA (Thermya) Moving bed San Sebastian, Spain
Andritz ACB technology Graz, Austria
Andritz Moving bed Standerup, Denmark
River Basin Energy Fluidised bed Laramie, WY, USA
Wyssmont Multiple-hearth furnace USA
6.2 Initiatives in the Baltic area
Currently, no commercial biocoal production plants exist in Finland, although there are
some demonstration-size biocoal production facilities. The most promising biocoal initia-
tive in Finland is probably that of the Biosaimaa cluster, which Miktech co-ordinates. The
Biosaimaa cluster is planning to launch a biocoal pilot plant at the end of 2012, which
would be located in Pursiala, Mikkeli.76
Plans also aim to build a large-scale biocoal pro-
duction plant by 2015. In Latvia, several producers of biocoal exist, but the production
capacities are rather small. The technological applications used in Latvia are tried and
tested technologies. The authors found no plans or ongoing initiatives in Latvia to build a
modern biocoal production facility. The best-known ongoing and most promising future
initiatives in the Baltic Sea region are described below.
6.2.1 Miktech Ltd. / Biosaimaa cluster (Finland)
The project in the Biosaimaa cluster coordinated by Miktech Ltd. probably represents the
most promising initiative to build a biocoal production facility in Finland. The project
27
aims to eventually build a commercial-scale production plant by 2015, but construction of
a pilot plant should still be underway in 2012. The actual production plant is estimated to
produce 200,000 tons of biocoal annually.76
Construction of a pilot plant is planned for Pursiala, Mikkeli, in Eastern Finland. The aim
of the pilot plant is to gain more information about the use of raw materials, end products
and the technique itself. Although construction of the pilot plant is already planned
(Jartek Ltd. will provide the actual process technology, and Promicco Ltd. will provide
the pelletising unit), the equipment and the supplier of the technology have not been final-
ized for upscaling to a commercial-size plant. Negotiations have been ongoing with two
separate companies that would supply the biocoal production technology and a pelletising
unit. The capacity of the pilot plant will be about 2900 tons annually. The pilot plant is
planned to operate for two years, which includes the building and its actual operating
costs. The end product will be tested in the Pursiala power plant of Etelä-Savon Energia
Ltd.76
6.2.2 Kymeenlaakso University of Applied Science / Biotuli demonstration plant
(Finland)
The Biotuli project is a Finnish innovation and development project co-ordinated by Lap-
peenranta University of Technology (LUT). The project does research on new antibacte-
rial products and the opportunities they offer for small- and medium-scale companies.
The project aims to ease the entry of new firms into the biorefining sector. LUT is han-
dling the project in co-operation with the Finnish innovation and development organisa-
tions of the area, local universities and professional companies in the field.77
During the project, Kymenlaakso University of Applied Sciences developed and manu-
factured a small-scale biocoal demonstration plant. The purpose of the demonstration
plant is to carry out cost analyses of biomass use in biocoal production. The research also
focuses on raw material properties and process adjustment. The demonstration equipment
technology is based on three continuously operating linked screw conveyors. The resi-
dence time, flue gas temperature and flow rate, as well as the wood chips heating rate can
be adjusted separately in the single-screw conveyors. The estimated biocoal production
capacity is 25 kilos per hour. The actual process is divided into three phases: in the first
phase, the woodchips are dried at temperatures ranging from 20°C to 100°C. In the se-
cond and third phases, the temperature is raised to the operating temperature (200°–
300°C), where the woodchips remain.78
6.2.3 The city of Nurmes, Eastern Finland (Finland)
The City of Nurmes and Feedstock Optimum Ltd. are planning to build a biocoal produc-
tion facility. The aim is first to build a demonstration plant in 2014 and then to proceed to
build a commercial-scale biocoal production plant in 2015 in Nurmes, Eastern Finland.
The demonstration plant would produce approximately 5,000 tons of biocoal and 4,700
tons of wood oil annually. The actual commercial-size production facility is planned for
2015 and will produce approximately 100,000 tons each of biocoal and wood oil. The
production facility would use about 800,000 cubic metres of woodchips. The demonstra-
tion plant will employ ten persons, and the actual production facility, 30 persons. The
production is based on slow pyrolysis technology.79
28
6.2.4 Fortum Ltd. and Metso Ltd. / Joensuu pyrolysis oil factory (Finland)
Fortum Ltd. and Metso Ltd. have planned to launch in 2013 a fast pyrolysis unit in
Joensuu that is capable of producing 50,000 tonnes of oil. Oil production requires approx-
imately 250,000 solid cubic metres of wood. The production is based on a fluidised bed
boiler. The factory will enrol ten supply chains and employ about 70 persons annually.80
Figure 15 presents a simplified diagram of the pyrolysis reactor. The reactor temperature
is approximately 500°C, and cyclones are used to separate charcoal from the pyrolysis
gases. In this reactor, the char is redirected back to the fluidised bed boiler.80
Figure 15. Simplified diagram of the fast pyrolysis reactor by Fortum Ltd. and Metso
Ltd.80
6.2.5 The Kouvola Region Vocational College / Biosampo initiative (Finland)
The Kouvola Region Vocational College has an initiative called Biosampo which invol-
ces the construction of a small-scale slow pyrolysis plant. The main objective of the pro-
ject is to promote and develop the environmental and bioenergy sectors of South-East
Finland, and to improve the competitiveness of the local countryside. The project aims to
research the effects of thermal treatment on wood.81
The reactor is designed so that the condensable products and biocoal can be collected
from the different process phases. Wood can be heated in different phases to a maximum
temperature of 400°C. The reactor is a batch-type system where the raw material is load-
ed on top of the reactor and sealed into a gas-tight reactor. The inner wall of the reactor is
ceramic, and the outer wall is made of stainless steel. The temperature can be adjusted to
the desired operating temperature and kept constant.81
29
6.2.6 Arheo Ltd. (Latvia)
Arheo Ltd. produces biocoal in their system known asthe “EURO” Coal-burning kiln.
The system consists of two kilns which are connected to each other. The system is a semi-
continuous system, where the raw material is fed into two separate vessel trains. Both of
the kilns can be loaded and discharged separately, one train at a time, each consisting of
three vessels. The unit operates in two different phases simultaneously. In the other kiln,
the raw material is first dried. When the raw material is completely dry, it is removed
from the first kiln and moved to the second kiln for the pyrolysis process. The peak tem-
perature in the process varies from 420°C to 480°C. The system uses the hot flue gases to
heat the process itself and also collects condensable liquids from the bottom of the kiln.
According to Arheo Ltd., the system is capable of producing 25-45 tons of biocoal per
month.82
6.2.7 Livanu Karbons Ltd. and Balt Carbon Ltd. (Latvia)
The Livanu Karbons operates in co-operation with a Latvian company called Balt Carbon
Ltd. Balt Carbon is a company that only produces and installs SIFIC/CISR LAMBIOTTE
reactors, which are from Belgium.83, 84
According to Domac et al.,9 the Lambiotte process
is a continuous carbonisation process of wood. The wood is carbonised with a hot inert
gas, which encounters the downward-moving raw material flow. The hot gas stream
(around 900°C) is produced by burning combustible gas in a stove connected to the mid-
dle of the reactor.8 The CISR Lambiotte is a modification of the SIFIC Lambiotte system.
The main differences between these two systems is that the CISR system is smaller, and
therefore a cheaper investment, though it is not equipped with a by-product recovery op-
tion like the SIFIC is.8, 9
Livanu Karbons is a company that produces and exports biocoal from Latvia. Livanu
Karbons has two LAMBIOTTE CISR retorts, both of which are located at their produc-
tion facility in Livani. Their annual production capacity is estimated to be 2,500 tons of
biocoal per retort.83
In addition to the co-operation with Livanu Karbons Ltd., Balt Car-
bon Ltd. is also developing two biocoal production plants, which combine biocoal and
electricity production, in Kaplava (Eastern Latvia) and Ugale (Western Latvia). The ca-
pacities of these plants are 2,000 tons and 8,000 tons of biocoal annually.84
30
7 Development aspects in the production technology
Only a handful of initiatives in the world have produced larger amounts of biocoal. The
main problems in upscaling is optimising the process on a large scale. Although biocoal
has been successfully produced on a smaller scale, upscaling the process makes control-
ling the biocoal quality and process conditions more difficult, because the feedstock and
process conditions inside the reactor may vary more than on a small scale.
In addition to the upscaling problem is that the used technology should be highly energy
efficient, and adjusting a proper heat integration system is crucial for making the process
economically viable. The process should be able to easily separate the gaseous, liquid and
solid products formed during the process.
The end product obtained from the biocoal production process will differ in homogeneity
with respect to the grade of charring, both between different particles as well as within
even a single particle.19
The production technology should also be able to handle variation
in different kinds of feedstock and also take into account variation in the chemical com-
position of the feedstock. For technology developers, the challenge is to produce large
amounts of biocoal of a consistent quality. When material produced varies widely, the
quality and specifications of the end product are difficult to determine. Consistent quality
is needed to produce standard-quality end products, such as biocoal pellets for commer-
cial purposes. Without product validation and a standard for needed quality, developing
the technology and choosing between solutions will be difficult, and commercialisation
will fail. When the product quality can be kept consistent enough, large-scale tests must
be made in, for example, co-firing, storage, and other areas.
31
8 References
1. Wang, L., Lurina, M., Hyytiäinen, J., Mikkonen, E., Bio-coal market study:
Macro and micro environmental factors in the bio-coal sector in Finland, 2012,
University of Helsinki, Department of the Forest Sciences, BalBic-project:
Helsinki, Finland.
2. Demirbaş, A., Biomass resource facilities and biomass conversion processing for
fuels and chemicals. Energy Conversion and Management, 2001. 42(11): p. 1357-
1378.
3. Antal, M.J., Gronli, M., The art, science, and technology of charcoal production.
Industrial & Engineering Chemistry Research, 2003. 42(8): p. 1619-1640.
4. Mohan, D., C.U. Pittman, and P.H. Steele, Pyrolysis of Wood/Biomass for Bio-
oil: A Critical Review. Energy & Fuels, 2006. 20(3): p. 848-889.
5. Bridgeman, T.G., et al., Torrefaction of reed canary grass, wheat straw and
willow to enhance solid fuel qualities and combustion properties. Fuel, 2008.
87(6): p. 844-856.
6. Bhaskar, T., Bhavya, B., Singh, R., Naik, D.V., Kumar, A., Goyal, B. H.,,
Thermochemical Conversion of Biomass to Biofuels, in Biofuels : alternative
feedstocks and conversion processes, A. Pandey, Editor 2011.
7. Lehmann, J., Joseph, S., Biochar for Environmental Management:An
Introduction, in Biohar for Environmental Management Science and
Technology2009. p. 13.
8. Anonymous, Industrial charcoal making, in FAO Forestry Paper.1985: Rome.
9. Domac, J., M. Trossero, and R. Siemons, Industrial charcoal production, 2008,
FAO.
10. Alakangas, E., Properties of fuels used in Finland (Suomessa käytettävien
polttoaineiden ominaisuuksia) [In Finnish].2000, Espoo: Valtion teknillinen
tutkimuskeskus.
11. Bergman, P.C.A., Combined torrefaction and pelletisation:the TOP process.2005,
Petten; [Petten]: Energy research Centre of the Netherlands ; ECN, Energy
research Centre of the Netherlands.
12. Ranta, J., Production of charcoal (Puuhiilen valmistus) [in Finnish], ed. k.
Helsingin yliopisto. Maaseudun tutkimus- ja and t. Valtion teknillinen1994,
Mikkeli: Helsingin yliopisto, maaseudun tutkimus- ja koulutuskeskus.
13. Happonen, K. Biohiilen käyttömahdollisuudet [In Finnish]. BalBiC Kick-off
seminar presentation 9.2.2012. [cited 14.1. 2013]; Available from:
http://www.balbic.eu/fi/ajankohtaista/2012/fi_FI/aloitusseminaarin_esitykset/.
14. Downie, A., Crosky, A., Munroe, P., Physical Properties of Biomass, in Biochar
for Environmental Management, L. Johannes and J. Stephen, Editors. 2009,
Earthscan.
15. Phanphanich, M. and S. Mani, Impact of torrefaction on the grindability and fuel
characteristics of forest biomass. Bioresource technology, 2011. 102(2): p. 1246-
1253.
16. Lu, H., et al., Effects of particle shape and size on devolatilization of biomass
particle. Fuel, 2010. 89(5): p. 1156-1168.
17. Lehmann, J., et al., Stability of Biochar in the Soil, in Biochar for Environmental
Management - Science and Technology, J. Lehmann and S. Joseph, Editors. 2009,
Earthscan.
32
18. Bergman, P.C.A., Torrefaction for Biomass Upgrading. 14th European
Conference and Technology Exhibition on Biomass for Energy Industry and
Climate Protection, 2005.
19. Deutmeyer, M., Bradley, D. Hektor, B. Hess, J.R, Nikolaisen, L. Tumuluru, J.
Wild, M., IEA bioenergy task 40: Possible effect of torrefaction on biomass trade,
2012.
20. Kaliyan, N. and R. Vance Morey, Factors affecting strength and durability of
densified biomass products. Biomass and Bioenergy, 2009. 33(3): p. 337-359.
21. Li, H., et al., Pelletization of torrefied sawdust and properties of torrefied pellets.
Applied Energy, 2012. 93(0): p. 680-685.
22. Stelte, W., et al., Pelletizing properties of torrefied spruce. Biomass and
Bioenergy, 2011. 35(11): p. 4690-4698.
23. Shang, L., et al., Quality effects caused by torrefaction of pellets made from Scots
pine. Fuel Processing Technology, 2012. 101(0): p. 23-28.
24. Schouten, S., Biochar for sustainable agricultural development: A critical review
of biochar for carbon management and the improvement of agricultural
production systems, 2010.
25. Emrich, W., Handbook of charcoal making. Solar Energy R&D in the European
Community Series E: Energy from Biomass. Vol. 7. 1985. 278.
26. McElligott, K.D., Debbie; Coleman, Mark, Bioenergy production systems and
biochar application in forests: potential for renewable energy, soil enhancement,
and carbon sequestration, 2011.
27. Liang, B., et al., Black Carbon Increases Cation Exchange Capacity in Soils. Soil
Sci. Soc. Am. J., 2006. 70(5): p. 1719-1730.
28. Lehmann, J., Bio-energy in the black. Frontiers in Ecology and the Environment,
2007. 5(7): p. 381-387.
29. Lehmann, J. and S. Joseph, Biochar for environmental management : science and
technology2009, London ;: Earthscan. xxxii, 416 p.
30. Neves, D., et al., Characterization and prediction of biomass pyrolysis products.
Progress in Energy and Combustion Science, 2011. 37(5): p. 611-630.
31. Chew, J.J., Recent advances in biomass pretreatment - Torrefaction fundamentals
and technology. Renewable & Sustainable Energy Reviews, 2011. 15(8): p. 4212-
4222.
32. Tumuluru, J.S., et al., A Review on Biomass Torrefaction Process and Product
Properties2011. Medium: ED.
33. Rautiainen, M., Havimo, M., Graduls, K., Biocoal production, properties and
uses, 2012, University of Helsinki, Department of Forest Sciences: Helsinki.
34. Prins, M.J., K.J. Ptasinski, and F. Janssen, Torrefaction of wood - Part 2. Analysis
of products. Journal of Analytical and Applied Pyrolysis, 2006. 77(1): p. 35-40.
35. Pach, M., R. Zanzi, and E. Björnbom, Torrefied Biomass a Substitute for Wood
and Charcoal, in 6th Asia-Pacific International Symposium on Combustion and
Energy Utilization2002: Kuala Lumpur.
36. Bergman, P.C.A., Boersma, A.R., Zwart, R.W.R, Kiel, J.H.A, Torrefaction for
biomass co-firing in existing coal-fired power stations "BIOCOAL", 2005.
37. Anonymous, IEA Bioenergy Annual Report 2006, 2007.
38. Maschio, G., Pyrolysis, a promising route for biomass utilization. Bioresource
technology, 1992. 42(3): p. 219-231.
39. Bridgwater, A.V., Renewable fuels and chemicals by thermal processing of
biomass. Chemical Engineering Journal, 2003. 91(2–3): p. 87-102.
33
40. Kleinschmidt, C., Overview of international developments in torrefaction, in
Central European Biomass Conference 2011.2011: Graz, Austria.
41. Amos, W.A., Report on Biomass Drying Technology. Report on Biomass Drying
Technology, 1998.
42. Garcia-Perez, M., Lewis, T., Kruger, C.E., Part 1: Literature Review of Pyrolysis
Reactors. First Project Report, in Methods for Producing Biochar and Advanced
Biofuels in Washington State. 2010., Department of Biological Systems
Engineering and the Center for Sustaining Agriculture and Natural Resources,
Washington State University, Pullman, WA.
43. Scott, D.S., et al., A second look at fast pyrolysis of biomass—the RTI process.
Journal of Analytical and Applied Pyrolysis, 1999. 51(1–2): p. 23-37.
44. Venderbosch, R.H. and W. Prins, Fast pyrolysis technology development.
Biofuels, Bioproducts & Biorefining; 2010, 2010. 4(2): p. 178-208.
45. Meijer, R. Overview of European torrefaction landscape [Presentation]. in EPRI
Biomass Torrefaction Workshop April 13-14, 2011, Pensacola, FL, US.
46. Bain, R.L. and K. Broer, Gasification, in Thermochemical Processing of
Biomass2011, John Wiley & Sons, Ltd. p. 47-77.
47. Gómez-Barea, A. and B. Leckner, Modeling of biomass gasification in fluidized
bed. Progress in Energy and Combustion Science, 2010. 36(4): p. 444-509.
48. Quaak, P., Energy from biomass : a review of combustion and gasification
technologies / Peter Quaak, Harrie Knoef, Hubert Stassen. World Bank technical
paper. Energy series., ed. H.E. Stassen and H. Knoef1999, Washington, D.C. ::
World Bank.
49. Lathouwers, D. and J. Bellan, Yield Optimization and Scaling of Fluidized Beds
for Tar Production from Biomass. Energy & Fuels, 2001. 15(5): p. 1247-1262.
50. Anonymous, Task 32: Biomass Combustion and Co-firing: An Overview. 2002.
51. Brown, R., Biochar Production Technology, in Biochar for Environmental
Management, L. Johannes and J. Stephen, Editors. 2009, Earthscan.
52. Brown, J.N., Development of a lab-scale auger reactor for biomass fast pyrolysis
and process optimization using response surface methodology. ProQuest
Dissertations and Theses, 2009.
53. Wang, M.J., et al., Microwave-induced torrefaction of rice husk and sugarcane
residues. Energy, 2012. 37(1): p. 177-184.
54. Jones, D.A., et al., Microwave heating applications in environmental
engineering—a review. Resources, Conservation and Recycling, 2002. 34(2): p.
75-90.
55. Luque, R., et al., Microwave-assisted pyrolysis of biomass feedstocks: the way
forward? Energy & Environmental Science, 2012. 5(2): p. 5481-5488.
56. Anonymous. Rotawave Targeted Intelligent Energy System [cited 27.11. 2012];
Available from: http://www.rotawave.com/.
57. Dangtran, K., J.F. Mullen, and D.T. Mayrose, A Comparison of Fluid Bed and
Multiple Hearth Biosolids Incineration. Proceedings of the Water Environment
Federation, 2000. 2000(1): p. 368-384.
58. Biosolids Technology Fact Sheet: Use of Incineration for Biosolids Management.
2002.
59. EPA, Emission Factor Documentation for AP-42, Section 10.7 Charcoal., 1995,
U. S.Environmental Protection Agency, Office of Air Quality Planning and
Standards, Emission Factor and Inventory Group, Washington.
60. Fagernäs, L., et al., Drying of biomass for second generation synfuel production.
Biomass and Bioenergy, 2010. 34(9): p. 1267-1277.
34
61. Verhoeff, F.A., A.; Boersma, A.R.; Pels, J.R.; Lensselink, J.; Kiel, J.H.A.;
Schukken, H, Torrefaction Technology for the production of solid bioenergy
carriers from biomass and waste, 2011. p. 82.
62. Koppejan, J., Sokhansanj, S., Melin, S., Madrali, S., Status overview of
torrefaction technologies, in IEA Bioenergy Task 32 report2012.
63. Anonymous. ANDRITZ ACB torrefaction. [cited 30.11. 2012]; Available from:
http://www.andritz.com/no-index/pf-detail?productid=5867.
64. Greenwood, B.F. Torrefaction Process Plant Design – IBBC Conference 2012. in
International Bioenergy and Bioproducts Conference. 2012. Savannah, Georgia
USA
65. Anonymous. Standard TURBO-DRYER®. 2012 [cited 26.11. 2012]; Available
from: http://www.wyssmont.com/.
66. Pirraglia, A., et al., Technical and economic assessment for the production of
torrefied ligno-cellulosic biomass pellets in the US. Energy Conversion and
Management, 2013. 66(0): p. 153-164.
67. Anonymous. Torbed® reactor system [cited 4.12. 2012]; Available from:
http://www.topellenergy.com/.
68. Anonymous. Biomass: AREVA invests in bio-coal. [cited 4.12. 2012]; Available
from: www.areva.com.
69. Anonymous, French Torrefaction Technology, in Bioenergy Australia newsletter
2010, Bioenergy Australia: Australia.
70. Ratte, J., et al., Mathematical modelling of a continuous biomass torrefaction
reactor: TORSPYD™ column. Biomass and Bioenergy, 2011. 35(8): p. 3481-
3495.
71. Thermya, TORSPYD® Fast Continuous Biomass Depolymerisation System for
non-food cellulosic biomass.
72. Anonymous, The case for energy densification of biomass & the advantage of the
rotawave ties system, 2010, Rotawave: Aberdeen.
73. Anonymous. River Basin Energy Torrefaction. [cited 11.12. 2012]; Available
from: http://www.riverbasinenergy.com/.
74. Melin, S. Torrefied wood - A New Emerging Energy Carrier: Presentation to
Canadian Clean Coal Power Coalition. March 9, 2011 [cited.
75. Boyd, T.d.V., D., Kempthorne, H., Wearing, J., Wolff, I.,. Mass and Energy
Balance for Torrefied Pellet Production. In: Biomass Pelletization Workshop,
May 17-18. . 2011 [cited.
76. Nurminen, F., Environmental Impacts of Torrefied Wood Pellet Production:
Cases Rislog and Pursiala pilot plant, 2012: Mikkeli. p. 73.
77. Anonymous. Biotuli-project. [cited 3.12. 2012]; Available from:
http://www.biotuli-hanke.fi/en/home.
78. Korhonen, R. BIOTULI initiative (BIOTULI-Hanke) [In Finnish]. in Biohiilen
tuotanto ja käyttö, edellytykset ja mahdollisuudet Suomessa ? 2012. Hanasaari,
Finland
79. Haapalainen, H. Uudenlaisesta biohiilestä työpaikkoja sadoille? [In Finnish].
[cited 21.1. 2013]; Available from:
http://yle.fi/uutiset/uudenlaisesta_biohiilesta_tyopaikkoja_sadoille/6457777.
80. Sikanen, L. Joensuu pyrolysis oil factory. Decentralised biorefineries Infocard 12
[cited; Available from:
http://www.forestenergy.org/service_center/hajautetut_biojalostamot/ladattavat_m
ateriaalit/.
35
81. Anonymous. KRK Vidzeme. [cited 6.3. 2013.]; Available from:
http://www.charcoal-krk.lv/en/.
82. Anonymous, Coal-Burning Kiln "Euro" Certificate, 2009: Riga.
83. Anonymous. Livanu Karbons Ltd. 2013 [cited 27.2. 2013.]; Available from:
http://www.livanucarbon.lv/.
84. Anonymous. Balt Carbon Ltd. 2013 [cited 27.2. 2013]; Available from:
http://www.baltcarbon.lv/.