chapter 2 biomass conversion processes · chapter 2 biomass conversion processes problems and...

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Chapter 2

Biomass Conversion Processes

Problems and Discussion Issues

Heat Energy Conversion Efficiency

2.1 One tonne [1.1 tons] of dried manure is converted into heat energy. Determine the efficiency

if this biomass is converted into heat. The total amount of heat produced during the process is

15,000 MJ. The heating value of the manure was reported at 19.7 MJ/kg [8,500 Btu/lb].

Solution:

a. Efficiency equation as presented in Equation 2.1 is given as follows:

100(%) xinput

outputEfficiency

b. Substituting for the variables with correct units to estimate efficiency as follows:

%1.761001000

1

1

1

/7.19

0000,15(%) x

kg

tonmetricx

tonmetricx

kgMJ

MJEfficiency

Energy of Feedstock and Biofuel Product

2.2 One hundred kg [220 lbs] of soybean oil was converted into biodiesel. Assuming 100%

conversion efficiency, compare the energy of the biodiesel with that of the vegetable oil if the

energy content of refined soybean oil was found to be 27.87 MJ/L [100,000 Btu/gallon].

How much energy in units of Joules with appropriate prefixes (or in million Btu or MMBtu)

was in the biodiesel that was produced if the resulting energy content of the ester was 32.94

MJ/L [118,170 Btu/gal]. The density of bodiesel product was 888.7 kg/m3 [7.4 lb/gal] and the

density of refined soybean oil was 912.7 kg/m3 [7.6 lb/gal].

9

Solution.

a. Energy content of refined oil

MJm

L

kg

m

L

MJoilkgMJEnergy 054.3

1000

7.912

87.27100)(

3

3

GJMJ

GJMJGJEnergy 1.3

1000054,3)(

MMBtuBtu

MMBtu

lbs

gal

gal

BtuoillbsMMBtuEnergy 97.2

000,000,1

1

4.7

000,100220)(

b. Energy content of the ester of oil is calculated from

GJMJ

GJ

m

L

kg

m

L

MJoilkgGJEnergy 17.3

000,1

1000

7.888

94.32100)(

3

3

MMBtuBtu

MMBtu

lbs

gal

gal

BtuoillbsMMBtuEnergy 42.3

000,000,1

1

6.7

170,118220)(

Note that there is more energy contained in the ester product than the refined oil.

Methanol was also added as a reactant containing additional amounts of energy. This

calculation does not imply that more energy is produced than the energy in the refined

vegetable oil. The yield of biodiesel may also be less than 100%.

Ethanol Yield Per Unit of Area

2.3 A certain variety of sweet sorghum has a sugar content 15.9% by weight and the biomass

yield is 57.8 tonnes/hectare [25.74 tons/acre] and a stalk sugar yield of around 9.2 tonnes/ha

[4.1 tons/acre] (ICRISAT Data, 2007. ICSA 749, SSV 74 variety). Estimate the ethanol yield

per hectare based on rules of thumb presented in this chapter (i.e. 1.8 kg sugar/L or 15 lbs

10

sugar/gallon). Compare this with the 5,000 L/ha [ 535 gal/acre] yield reported in some

literatures.

Solution:

a. As rule of thumb recommended in this chapter, 1.8 kg/L [15 lbs of sugar per gallon] of

ethanol will be used as conversion factor.

ha

L

kg

ethanolL

tonne

kg

ha

tonnes111,5

8.11

000,12.9

b. This is slighly higher than the reported 5,000 L/ha ethanol yield [535 gal/acre].

Number of Animals Needed for Power Generation

2.4 An irrigation pump is to be powered by biogas using methane-driven internal combustion

engine. 540 watts of power is required to the pump. The biogas engine has an overall

conversion efficiency of 24% (thermal and mechanical) and the irrigation must be completed

in ten hours each day. Estimate the number of swine animals needed for this application.

Assume the energy content of biogas of 19.3 MJ/m3 [550 Btu/ft3]. Further assume that each

mature swine will produce 164 L biogas/day.

Solution.

a. From the efficiency equation, we have the following energy required from the biogas

input

outputEfficiency% Watts

WattsInput 250,2

)24.0(

540

b. If the biogas will be needed in 10 hours the energy required will be calculated as follows:

c. day

kWh

day

hrsWatts

5.2210250,2

11

d. If this is to be the input energy required, then the number of animals can be calculated as

follows:

e. hdsm

L

kWh

MJ

MJ

m

L

dayhd

day

kWhheadsAnimals 26

1000

1

6.3

3.19164

5.22)(

3

3

Pyrolysis Conversion Efficiency

2.5 Determine the conversion efficiency for the pyrolysis of one tonne [1.1 ton] of switchgrass

using the following resulting data (please neglect the electrical and heat energy to the

pyrolyzer). The energy content of the switchgrass is 19.77 MJ/kg [8,520 Btu/lb]. Determine

also the overall system losses.

a. The amount of biochar produced is 227 kg [500 lbs] with a heating value of 28.97 MJ/kg

[12,480 Btu/lb]

b. The amount of bio-oil produced is 227 liters [60 gallons] with a heating value of 30.66

MJ/L [110,000 Btu/gal]

c. The amount of syngas produced is 110.5 cubic meter [3,900 cubic feet] with an energy

content of 11.17 MJ/m3 [300 Btu/ft3]

Convert the units into its equivalent English units.

Solution.

a. The energy balance may simply be written as energy from the biomass being equal to the

energy in the biochar, bio-oil, syngas, and system losses

lsgbobcb EEEEE

The energy input is calculated first

12

GJtonne

kg

kg

MJtonne77.19

000,177.191

MMBtuton

lb

lb

Btuton74.18

000,2520,81.1

b. The energy output is calculated next

Biochar

GJkg

MJkg58.6

97.28227 MMBtu

lb

Btulbs24.6

480,12500

Biooil

GJL

MJL96.6

66.30227 MMBtu

gal

Btugal6.6

000,11060

Syngas

GJm

MJm23.1

17.115.1103

3

MMBtuft

Btutf17.1

30039003

3

LossesGJGJGJGJ 23.196.658.677.19

Losses = 5 GJ

LossesMMBtuMMBtuMMBtuMMBtu 17.16.624.674.18

Losses = 4.73MMBtu

c. The overall conversion efficiency (metric) is calculated as follows:

%100

b

sgbobc

E

EEEEfficiencyConversionOverall

%7.74%10077.19

23.196.658.6

EfficiencyConversionOverall

Note that there will be slight discrepancies in converting to English due to rounding

errors.

13

Gasification Carbon Efficiency

2.6 Determine the carbon efficiency for a gasification conversion process using the following

data:

- The ultimate analysis of manure biomass showed that carbon content is 45% and manure

char carbon content of 31%

- The biomass was gasified at a rate of 4.5 kg/min.

- The char production rate was measured at 1.14 kg/min

- Assume that (tar production is negligible).

Solution.

a. The carbon in synthesis gas is calculated from the difference between the fuel amd the

char as follows:

charbiomasssyngas CCC min/67.131.0min

14.145.0

min

5.4kg

kgkgCsyngas

b. Carbon conversion efficiency will be calculated based on carbon in syngas divided by the

carbon in the biomass as follows:

c. %100BiomassOriginalinCarbon

GasSynthesisinCarbonEfficiencyConversionCarbon

%5.82%10045.05.4

67.1

EfficiencyConversionCarbon

Area Required for a Power Plant

2.7 How many acres would be required to build a 50 MW (energy output) biomass power plant

(operated 365 days a year and 24 hrs/day) if the heating value of the biomass (dry) is 17.4

MJ/kg [7,500 Btu/lb]. The biomass yield is 9 tonnes/ha [4 tons (dry)/acre/yr]. Assume a

conversion efficiency of 50%.

14

Solution:

a. The energy input must be equal to (50 MW/0.5 = 100 MW)

This is a simple conversion process using dimensional analysis to the correct units of acres

as follows:

hectacrestonnes

hax

kg

tonnex

yr

dx

day

hrsx

hr

sx

MJ

kgx

sMW

MJx

MW138,20

91000

365243600

4.17

100

acrestons

acrex

lbs

tonx

yr

dx

day

hrsx

hr

sx

Btu

lbx

J

Btux

sW

Jx

MW

Wxx

MW820,49

42000

365243600

75001055

101100 6

b. Answer = 20,138 hectares. There will be rounding off errors from converting into English

System of units.

Energy Required to Raise Water Temperature

2.8 How much energy is needed to raise the temperature of a liter of water from an initial

temperature of 25oC to a final temperature of 100oC (boiling point of water) at standard

temperature and pressure (STP). Compare this energy to the energy content of a kg of rice

hull waste with an energy content of 17 MJ/kg. Assume the density of water at STP is 1.0.

Solution:

a. The heat capacity equation is used to arrive at the following values (note a liter of water

is equal to a kg of water at STP).

MJkJCCkg

kJkgMJQ o

o3143.03.314)25100(

19.41)(

b. Thus, a kg of rice hull has several times more energy than that required to boil a liter of

water. In short, this is only equivalent to 1.85% of the energy of the rice hull.

15

Biogas Conversion Efficiency

2.9 Determine the conversion efficiency of a biogas for power generation facility with the

following data: electrical power output is 300kW, gas consumption is around 0.96 million

cubic meters of methane each year. Landfill gas has approximately 60% methane. Assume

about 8000 hrs of operation each year with a biogas heating value of 5 kWh/Nm3. Note that

N stands for normal in this HV unit.

Solution:

a. This problem is again a simple efficiency and input and output energy or power equation.

The output power will be 300 kW.

b. The input power will be the total amount of biogas used assuming 60% is methane and is

calculated from the following:

3636

3 106.16.0

1096.0)( m

mmBiogas

c. The energy efficiency equation is used to estimate efficiency as follows:

%30%100000,85106.1

300%100(%)

3

36 hrs

kWh

m

mx

kW

input

outputEfficiency

d. Thus, the conversion efficiency is approximately 30% .

Steam Cycle Conversion Efficiency

2.10 A biomass (wood) power plant uses steam to generate electrical power. Around 160,000

kg of water per hour enters the boiler at a pressure of 12.5 MPa and a temperature of 200oC.

Steam leaves the boiler at 9 Mpa and at 500oC. The power output of the turbine is 40,000

kW. The rate of biomass input is 30,000 kg/hr with a heating value of 22 MJ/kg. Determine

the efficiency of steam generator and the overall thermal efficiency of the plant. Hint: In

16

calculating the energy absorbed by the steam, you may use the enthalpy equation, E =

m*(h2-h1). The enthalpy values are found from steam tables at 9 Mpa and 500oC and at 12.5

Mpa and 200oC.

Solution:

a. The heat transferred to the water to generate steam can be calculated by the enthalpy

changes at the different pressure and temperature combinations. From steam tables, the

enthalpy at 12.5 MPa and 200oC was 857.1 kJ/kg while the enthalpy at the other

condition is 3386.1 kJ/kg.

)(*)( 200,5.12500,92 CMPaCMPaOH hhmEwatertodtransferreEnergy

hrMJkgMJhrkgE OH /640,404/)8571.03861.3(*/000,1602

hrMJkgMJhrkgE fuel /000,660/22*/000,30

b. Equation 2.8 may then be used to calculate the efficiency of the steam generator as

follows:

%3.61%100/000,660

/640,404(%)

hrMJ

hrMJgeneratorsteam

c. Equation 2.9 will be used to estimate the overall thermal efficiency of the system as

follows (or simply output divided by the biomass input fuel)

%8.21%1006.3

000,3022000,40(%)

kWh

MJ

kg

hr

MJ

kgkWth

Biomass Energy Conversions Homework #2 Biomass Energy Conversions Overview

1. Determine the efficiency of converting granulated sugar into ethanol. The energy content of granulated sugar was found to be 6,850 Btu/lb [15.9 MJ/kg]. A gallon of ethanol with an energy content of 84,000 Btu was produced from 15 lbs of sugar.

2. How much glycerin was produced (in lbs) from converting a million lbs of biodiesel from canola oil in a year? Note that since the governing equation is in units of mass, to convert to units on a volume basis, one needs the density of the material. Report the glycerin yield in gallons if the density of glycerin is 10.5 lbs/gal.

3. How many lbs of pure sugar (i.e. glucose) is needed to produce 1 million gallons of ethanol? Assume the density of ethanol to be 6.66 lbs/gal.

4. Determine the amount of manure needed each day (in lbs) to generate 1MW of electrical power for 24 hrs using an engine. Assume that the amount of biogas produced per lb of manure was 3 ft3 and the overall engine conversion efficiency was 20% (both thermal and mechanical). The heating value of biogas was assumed to be 550 Btu/ft3.

5. Determine the estimated chemical formula for the following biomass material with the ultimate analysis as follows by weight: C= 75.5%; H=5.0%; O=4.9%; N=1.2%; S=3.1%. Determine also the air to fuel ratio for a stoichiometric combustion of this material in air.

Biomass Energy Conversions Homework #2 Biomass Energy Conversions Overview

1. Determine the efficiency of converting granulated sugar into ethanol. The energy content

of granulated sugar was found to be 6,850 Btu/lb [15.9 MJ/kg]. A gallon of ethanol with an energy content of 84,000 Btu was produced from 15 lbs of sugar. Solution: a. The input energy is first calculated

Btulbslb

BtuBtuEnergyInput 5.757,10215

5.850,6)(

b. Then the conversion efficiency is calculated next.

2. How much glycerin was produced (in lbs) from converting a million lbs of biodiesel from canola oil in a year? Note that since the governing equation is in units of mass, to convert to units on a volume basis, one needs the density of the material. Report the glycerin yield in gallons if the density of glycerin is 10.5 lbs/gal. Solution: a. From the governing ideal equation, about 100,000 lbs of glycerin may be produced b. To convert the units in gallons the given density is used as follows:

gallonslbs

gallonslbsgallonsGlycerin 524,9

5.10000,100)(

3. How many lbs of pure sugar (i.e. glucose) is needed to produce 1 million gallons of

ethanol? Assume the density of ethanol to be 6.66 lbs/gal. Solution: a. Using the ideal governing equation, the amount of sugar is easily calculated as

follows:

b. Thus, it would take about at least 13 million lbs of pure sugar to achieve this goal.

4. Determine the amount of manure needed each day (in lbs) to generate 1MW of electrical power for 24 hrs using an engine. Assume that the amount of biogas produced per lb of manure was 3 ft3 and the overall engine conversion efficiency was 20% (both thermal and mechanical). The heating value of biogas was assumed to be 550 Btu/ft3. Solution: a. The amount of biogas needed is first calculated

sugarlbsmillionethanolgallonsgal

lbs

ethanollbs

sugarlbslbsSugar 13101

66.6

92

180)( 6

%75.81%1005.757,102

000,84(%)

Btu

BtuEfficiencyConversionEnergy

b. Then the amount of manure is estimated.

5. Determine the estimated chemical formula for the following biomass material with the following ultimate analysis by weight: C= 75.5%; H=5.0%; O=4.9%; N=1.2%; S=3.1%. Determine also the air to fuel ratio for a stoichiometric combustion of this material in air. Solution: a. The molar ratios are first calculated using the MS of each element: C = 75.5/12 g/mol

= 6.3; H = 5.0/1 = 5.0; O = 4.90/16 = 0.31; N = 1.2/14 = .086; S = 3.1/32= 0.1

b. Then, the estimated chemical formula will be the subscript of each element as follows:

c. The stoichiometric combustion equation may be set-up to determine the air-to-fuel ratio as follows:

33

3 ,018,315501

3412

20.0

000,1)( ft

Btu

ft

kWh

BtukWhftBiogas

lbsft

lbftlbsManure 339,10

3018,31)(

33

1.0086.031.053.6 SNOHC

2222210.0086.031.053.6 76.35.75.23.6)76.3(5.7 NOHCONOSNOHC

1.0086.031.053.6

22 )76.3(5.7

SNOHC

NO

Fuel

Air

fuellbsairlbsFuel

Air/4.11

964.89

6.1029

)10.0*32()086.0*14()31.0*16()5*1()3.6*12[(

)]28*76.332(*5.7[

Courtesy of CRC Press/Taylor & Francis Group

Torrefaction (Chapter 8)

Pyrolysis (Chapter 9)

Gasification (Chapter 10)

Combustion (Chapter 13)

Ethanol production (Chapter 6)

Biogas production (Chapter 7)

Biodiesel production (Chapter 5)

Biomass resources

�ermal conversion processes

Biological conversion processes

Chemical conversion processes

FIGURE 2.1Various biomass energy conversion pathways.

002x001.eps


Vegetable oil and fats (100 kg)

Methanol + NaOH (10 kg)

Biodiesel (100 kg)

Glycerin(10 kg)+ +

FIGURE 2.2Simple schematic diagram to convert vegetable oil into biodiesel with glycerin.

002x002.eps


Sugar crops

Starchy crops

Lignocellulosic biomass

Ethanol

Ethanol

Ethanol

Yeast

Molds + Yeast

Enzymes + Yeast

+

+

+

FIGURE 2.3Various pathways to convert biomass high in sugar, starch, or lignocellulose into ethanol.

002x003.eps


Complex organics Higher organicacids

Acetic acid

Stage 1:hydrolysis and fermentation

Stage 2:acetogenesis and dehydrogenation

Stage 3:methane fermentation

H2

CH4

FIGURE 2.4Conversion pathway to break down complex biomass organics into methane and carbon dioxide.

002x004.eps


Torrefaction No oxidant 200–320°C 400–600°F

300–1200°C 570–2190°F

300–1200°C 570–2190°F

2000–3000°C 3600–5400°F

No oxidant

Incomplete amountsof oxidant

Excess amounts of oxidant

Pyrolysis

Gasification

Combustion

�ermal process Amounts of air used Process temperatures (°C or °F)

FIGURE 2.5Schematic of various thermal conversion processes.

002x005.eps


FIGURE 2.6(See color insert.) Simple set-up for biomass torrefaction process.

002x006.tif


Enclosedbiomass bin

Biochar bin

Electrically heated tube furnace

Auger

Condenser

Nitrogen purge gas Bio-oil

Syngas

FIGURE 2.7Schematic of simple biomass pyrolysis conversion process.

002x007.eps


Simple updraft gasifier

Filled with biomass at start of process

Firing door

Airblower

Synthesis gasoutlet

Access door to load biomass

Screen supportPlenum

FIGURE 2.8Simple biomass gasifier schematic showing basic component parts.

002x008.eps


Fluidized bed gasifier

Ultimate analysis %C = %H = %O = %N = %S =

Proximate analysis%MC

%VCM %FC and %Ash

Ultimate analysis %C = %H =%O = %N = %S =

Proximate analysis %MC

%VCM %FC and %Ash

Biomass

Gasifying air

Synthesis gas

Biochar

Compositional analysis %CO; %CO2; %H2, %N2,

%O2, %CH4, %C2H6Temperature, Pressure

Incoming airFlow rateDensity

TemperatureRHN2O2

FIGURE 2.9Schematic of energy and mass balances in gasifier.

002x009.eps


Pretreat Ferment Dewater Hydrogenate Oligomerize�ermal

conversion

Biomass

Lime

Carboxylate salts KetonesAlcohols

Hydrogen Hydrocarbonfuels

FIGURE 2.10The MixAlco process to convert biomass into higher alcohols and hydrocarbon fuels.

002x010.eps


Biomassfeed tank

Cycloneseparators

Gascompression

systemFluidizedbedor

downdraftgasifier Syngas scrubber system

Syngas storage tanks

Biostat D-75 fermentor

FIGURE 2.11Schematic of OSU pilot syngas fermentation system. (Adapted from Kundiyana, D. K., R. L. Hunke and M. R. Wilkins, Journal of Bioscience and Bioengineering 109, 492, 2010.)

002x011.eps

Lecture 2Biomass Energy Conversion

Processes

Sergio C. CaparedaBEAN, TAMU

Learning Objectives• Describe the overview of the various biomass conversion processes

• Differentiate between chemical, biological and thermal conversion processes

• Recognize the various units and terminologies used for estimating efficiencies of different biomass energy conversion processes

• Compare new and advanced biomass conversion processes including combinations and hybrids

• Enumerate all applications of various conversion processes and list important products and co‐products produced

Biomass Energy Conversion Efficiency• Energy Conversion Efficiency

• Energy Input (example animal manure)– One metric tonne of animal manure at 15 MJ/kg– Energy contained in manure = 15,000 MJ

• Energy Output (example biogas)– 150 m3 of biogas with energy content of 20.5 MJ/m3

– Energy contained in this biogas = 3,075 MJ

• Energy Efficiency

100(%) xInputEnergy

OutputEnergyEfficiencyConversionEnergy

%5.20100000,15075,3(%) x

MJMJEfficiencyConversionEnergy

Physico-Chemical Thermo-ChemicalBio-Chemical

Manure/Cellulosics

Biodiesel Production

Hydrolysis/Fermentation

Pyrolysis

Gasification

Combustion

Liquefaction

B I O M A S S

Energy and Fuel Products

Biodiesel (esters of oil) Biogas (CH4+CO2)

Ethanol (C2H5OH)

SynGas (CO, H2)

Synthetic Fuels

Hydrogen, Methane, Ethane, Propane, Butane, Acetone, Alcohols, Esters, etc

Oil Crops/Algae

Anaerobic digestion

Sugar/Starch/Cellulose

Mixed Alcohols

Biodiesel Production• Schematic of the biodiesel conversion process

• One of the simplest biomass conversion processes (physico‐chemical conversion)

• Complications arise from generating RBD oil (i.e. refined, bleached and deododized oil) from oil seeds prior to conversion process

• Transesterification – the process of converting oils into esters of oil (i.e. soybean oil to soybean oil methyl ester, SME)

How Big is a 1MGY Biodiesel Plant?

• A 1 million gallon per year biodiesel facility needs to produce about 3,000 gallons of biodiesel each day for 333 days to satisfy this requirement as shown in calculations below

• A 3,000 gallon tank may have a diameter of 10 feet and a height of only 5.1 feet (or 401 cubic feet since a cubic feet is 7.48 gallons).

• Thus, a million gallon facility is rather small.

daygallons

daysyear

yeargallons

daygaloductionPrDaily 003,3

3331101 6

US Biodiesel Production

High Price of Crude Vegetable

Oil

Bioethanol Production• Various pathways for the conversion of biomass into ethanol

• The use of microorganisms to convert sugars into ethanol, a biological conversion process

• Understand the nature of microorganisms

Most Popular Microbes for Ethanol Production

• Fermentation of sugar to ethanol– Saccharomyces cerevisiae – common yeast– Ethanol Red – most popular commercial brand in US

• Saccharification of starch to sugars– Aspergillus niger – common mold – Aspergillus awamori – another strain of molds

• Hydrolysis of cellulose into simple sugars followed by fermentation of sugars produced– Trichoderma reesei – a Genencor enzyme producer

US Bioethanol Production • Over 1,620 million gallons in the year 2000• Over 13,230 million gallons in 2010• US is still the world’s top ethanol producer representing more than half (57.5%) of the world’s production in 2010

• Brazil is second with about 6,920 million gallons in 2010.

Biogas Production• Conversion pathway to break down complex organics into methane and carbon dioxide

• Biogas = methane or CH4 (65%) + CO2 (35%) + other gases such as H2S

Utilization of Biogas• Heating value = 500‐600 Btu/ft3 [18.6‐22.3 MJ/m3]

• Direct source of heat• Use in internal combustion engines to generate mechanical energy and electrical power

• The H2S must be scrubbed to prolong the life of engines.

• CO2 must also be separated to improve the conversion efficiency since it has no heating value

• Newer engines that runs of low Btu gas are now available commercially

Thermochemical Conversion of BiomassRelationships among thermal conversion processes on the amounts of air

used as well as relative temperatures of reaction.

Torrefaction

• Torrefaction ‐ a mild thermal treatment of biomass to improve its properties prior to conversion

• Properties enhanced– Improve energy density– Reduced moisture– Improve bulk density for ease of transport– Improve biomass composition

Torrefaction Facilities

3.17.09.0

MassEnergyionDensificatEnergy

Energy Densification in Torrefaction Process

‐ 90% of the energy is retained (or 0.90)‐ 70% of the mass is conserved (or 0.70)

Pyrolysis• Irreversible thermal conversion process in complete absence of oxidant (also called “destructive distillation”)

• Products are condensible liquids (biooil), combustible synthesis gas and recyclable biochar

• Temperature is between 200‐600oC• Products are as follows:

Products Estimated Percentages

Biochar 30‐35%

Organic Liquids 18‐20%

Synthesis Gas 20%

Slow Pyrolysis Set‐up

The pyrolysis setup used for biomass. (A) Purge gas (N2), (B) Gas flow meter 1, (C) Digitally‐controlled furnace, (D) tar/moisture trap, (E) Condenser, (F) Thermocouple reader, (G) Liquid collector, (H) moisture trap, (I) Gas flow meter 2, (J) Sampling/exhaust port, and (K) Gas analyzer.

Pyrolyzer/ReactorB

CA DE

G

H

IJ

K

F

Hood

A

B

C

D

E

F

G

The pyrolysis set‐up used in the experiment showing the following parts: (A) steel container, (B) horizontal tube reactor, (C) horizontal tube furnace, (D) condenser, (E) thermocouple reader, (F) liquid collector/ cold

trap, and (G) displacement tanks.

SimpleSlow

PyrolysisSet‐up

Products of Slow Pyrolysis

Solids/CharLiquid Products: Bio‐oil

Gaseous Product

Gasification• Gasification – use of deficient amount of oxygen to produce combustible synthesis gas (CO+H2)

• A simple updraft gasifier for synthesis gas production from biomass

• HV syngas = 100‐250 Btu/ft3

• Air used is less thanstoichiometric amounts

• Synthesis gas is also calledsyngas or producer gas

Energy and Mass Balances in A Gasification System

About 20‐25%

biochar by weight

Heat content of syngas about 150

Btu/ft3 [5.5 MJ/m3]

Carbon Conversion Efficiency in Gasification

• Carbon Conversion Efficiency (CCE) Equation

• Thus, if carbon in synthesis gas is 50% (by adding all carbon content of all gases) and carbon in original biomass is 70% (from ultimate analysis), the CCE is calculated as follows:

%100biomassoriginalinCarbon

gassynthesisinCarbonEfficiencyConversionCarbon

%4.71%10070.050.0

EfficiencyConversionCarbon

Effect of Steam on the Gasification of Biomass

% Steam 10% 20% 30% 40%Blast Temp (o C) 47 60 70 76Reaction Temp (o C) 795 699 646 601

Gas Composition (%)CO 34.1 26.7 19.1 12.3H2 7.5 13.6 18.3 21.5CO2 1.7 7.0 11.8 15.6H2O 0.4 2.2 5.7 10.7CH4 ‐ 0.1 0.2 0.5N2 56.3 50.4 44.9 39.4GCV (Btu/ft3) 142 139 130 123Gas Yield ft3/lb C 84 89 96 101Heat Available (Btu/lb C) 11,899 12,268 12,537 12,521

Biomass Combustion

• Combustion – conversion of biomass into heat, carbon dioxide (CO2) and water (H2O)

• Total heat produced is the heating value of the biomass being combusted

• Wood fuel combustion is still the most predominant use of biomass in developing countries

• Other countries like India, animal (cow) manure is still popular biomass used for cooking and heating purposes

Most Popular Biomass Combustion System: The Spreader Stoker System

1‐ Refuse charging hopper2‐ Refuse charging throat3‐ Charging ram4‐ Grates5‐ Roller bearings6‐ Hydraulic power cylinders and control valves7‐ Vertical drop off8‐ Overfire air jets9‐ Combustion air10‐ Automatic sifting removal system

Other Unique Biomass Conversion Processes

• The MixAlco TM Process Developed at Texas A&M University by Dr. Mark Holtzapple– Organic acids are produced and further converted into organic salts, thermally converted into ketones and catalytically converted into gasoline

• The Syngas Fermentation System to Produce Ethanol– Syngas is used by microorganisms that produce ethanol

The MixAlcoTM Process• A process that converts biomass into organic acids (methane production is inhibited) and salts. These salts are thermally converted into ketones and hydrogenated into alcohols and further oligomerized into hydrocarbon fuels such as gasoline using suitable catalysts.

The Syngas Fermentation Process• Biomass is gasified to generate synthesis gas. The synthesis gas is used by microorganisms to convert this into ethanol.

Applications of Biomass Conversion Products

• Heat Energy– Use of fuel wood for cooking is still predominant in developing

countries• Electrical Energy and Power

– Use of biomass in steam cycles for power generation • Combined Heat and Power (CHP)• Mechanical Energy

– Use of biogas or synthesis gas in commercial engines • Liquid Biofuels or Biofuels Production

– Biodiesel and bioethanol production• Synthesis Gas Production and Use

– Use of synthesis gas for liquid fuel production• Biochar Production

– Use of biomass conversion co‐products for biochar soil amendment

Concluding Remarks

• Maintain a good balance between biomass usage and sustainability of agricultural land for food production

• Improvement of efficiencies of conversions• Understanding the logistics of biomass conversion processes

• Diversification of biomass resources from non‐food sources as well as lignocellulosic types

• Development of infrastructures for biorefineries(pretreatment, processing, storage and transport)

chapter 2 biomass conversion processes · chapter 2 biomass conversion processes problems and...

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