Seminar “Reed for Bio-energy and Construction”

Reed as bio-energy: opportunities to use it in boiler-houses and as biogas

sourceÜlo Kask

Tallinn University of Technology

11.03.2011, College of Landbased Studies, Piikiö, Finland

Content

• Reed resources and location

• Reed as bio-fuel characteristics

• Reed based bio-fuels

• Suitable burning equipment

• Conclusions

Reed resources and location in Estonia

Estonian reed resources by countiesEnergy content, MWh/y

CountyReed bedsarea, ha

(2000)

Corrected reed bedsarea, ha (2007) **

Harvestablearea, ha/y

Yield,t/ha Theoretical Realistic

1 2 3 4 5 6 7

Harju 265 809 400 9,3 29 643 14 657

Hiiu 674 2 000 1 000 8,0 63 040 31 520

Saare 4 937 7 387 3 700 4,5 130 972 65 601

Pärnu 1 343 2 441 1 200 6,0 57 705 28 368

Viljandi 577 904 450 6,3 22 439 11 170

Valga 491 287 140 6,5 *** 7 350 3 585

Võru 497 674 340 6,5 *** 17 261 8 707

Lääne-Viru 379 362 180 8,5 12 123 6 028

Tartu 4 201 2 108 1 050 4,9 40 697 20 271

Põlva 170 847 420 9,7 32 371 16 052

Lääne 10 457 8 367 4 200 6,0 197 796 99 288

Ida-Viru * - 1 023 500 6,5 *** 26 199 12 805

Järva * - 84 40 6,5 *** 2 151 1 024

Jõgeva * - 479 240 6,5 *** 12 267 6 146

Rapla * - 124 60 6,5 *** 3 176 1 537

Total 23 993 27 899 12 970 655 196 326 766

Remarks to previous table* In the Ida-Viru, Järva, Jõgeva, and Rapla counties the reed bed areas have

been omitted before 2007.** Values in column 3 were corrected in 2007, based on orthographic photos

and partially on satellite images in the Saare, Lääne, Pärnu and Hiiu County.

*** The average yield in Estonia according to the winter measurements of 2006 and 2007. In other counties the real average data of yield measurements (TUT TED) have been used.Column 4 shows the estimated possibly and sustainably harvestable area of reed beds (approximately half of corrected area).According to the winter measurements in 2006, at the moisture content of 20% the average energy content of reed is 3.94 MWh/t (TUT TED).As to produce pellets from all harvested reed, total amount of primary energy can rise to 373 GWh/y (energy content 4.5 MWh/t). Approximately 15 000 single family houses could be heated during the year.

Reed as bio-fuel characteristics

The most significant combustion parameters are: moisture content, calorific value, content of volatiles, ash content and composition. Thesehave been determined in the TUT TED.

Combustion characteristic of reedElemental composition of dry reed fuel, %

Ranges AverageElement

Winter Summer Winter Summer

Carbon, C 46,96–48,34 46,13–47,11 47,5 46,5Hydrogen, H 5,50–5,60 5,93–6,42 5,6 6,2Oxygen, O 42,75–43,84 39,7–42,2 43,3 40,7

Nitrogen, N 0,23–0,34 0,57–1,17 0,3 1,0Sulphur, S 0,03–0,09 0,12–0,45 0,04 0,2

Chlorine, Cl 0,05–0,18 0,28–0,48 0,1 0,4

Combustion characteristicThe reed combustion characteristics vary to some extent depending both on the site of growth (on the shore of sea or lake, river deltas, wetland treatment systems) and seasonally (harvested either in summer or winter).

Combustible matter, %Fuel source

Cp Hp Sp Np Op

Lake reed 46-48 6-8 0,02-0,2 0,24-1,32 37-47

Seashore reed 46-48 6-8 0,01-0,3 0,23-1,81 37-47

Peat 55-60 6-7 0,4-0,6 2-3 30-35

Wood 50-55 6-7 0,05 0,5 40-45

Moisture content dynamics of reed from October till May in 2002–2006

Combustion characteristicHeating value of dry matter of reed fuel

Ranges AverageParameters:Calorific value, MJ/kg

Energy content, MWh/tWinter Summer Winter Summer

Qp/qb, 18,62–19,16 18,33–18,77 18,92 18,51

Qük/qgr, d 18,62–19,16 18,31–18,75 18,91 18,49

Qak/qnet, d 17,48–18,01 17,02–17,44 17,77 17,21

Qa20/qnet, 20 * 13,68–14,86 13,16–13,49 14,17 13,31

E20/ E20, MWh/t* 3,80–4,13 3,65–3,75 3,94 3,70

*at moisture content 20 %

Combustion characteristic

Seashore reed Lake reedMain characteristics

Winter Summer Winter SummerMoisture, % 23,7 60,4 21,1 60,5Yield of dry matter, t/ha 6,9 8,7 8,1 7,4Volatile matter, % 82,0 75,7 82,3 77,1Ash content of dry matter (at 550 ºC), % 3,5 6,3 3,1 5,7Net calorific value of dry matter, MJ/kg(Qa

k/qnet, d)17,5

The yield and characteristics slightly depend on harvesting period and site of growth of reed.

Combustion characteristicAsh

• The ash as a solid residue formed by combustion plays an important role in the selection and running of combustion equipment and its auxiliary devices.

• The ash content of reed harvested in winter is 2.1–4.4 %, in average 3.2 %, but for summer harvested reed it is significantly higher being 5.1–6.4 %, in average 5.8 %.

Combustion characteristicChemical composition of reed ash at (550 oC), %

Ranges Average.Component Winter Summer Winter Summer

SiO2 65,34–85,50 25,90–48,33 77,77 37,10Fe2O3 0,13–0,84 0,17–1,69 0,29 0,70Al2O3 0,1–1,69 0,11–1,12 0,57 0,61CaO 3,07–7,27 4,02–11,53 4,42 6,84MgO 0,4–1,45 1,87–4,88 1,22 3,33Na2O 1,96–9,05 0,87–10,98 3,19 3,61

K2O 0,99–5,69 14,89–31,33 4,26 24,77

Other 1,57 – 19,4 17,28 – 33,5 8,28 23,04

Reed ash

• The chemical composition of reed ash for summer and winter harvest differs essentially for the content of SiO2 and K2O.

• The reed harvested in winter would be a much better fuel to burn in the combustion equipment from the point of view of ash composition.

• The ash of reed harvested and dried in summer contains in significant amounts alkali metals that influence both ash fusibility, fouling - formation of ash deposits on the heating surfaces - and corrosion.

Content of some elements in winter reed ash, mg/kg. (ENAS Oy)

Pilliroo tuhaanalüüs, ENAS OY

0

10 000

20 000

30 000

40 000

50 000

60 000

70 000

80 000

90 000

Ca Mg Na K Mn Cd Cr Cu Pb Ni Zn S Fe Al P

Sisa

ldus

mg/

kg, k

uiva

ines

Rocca al MarePeipsi järvSaaremaa

Fusibility characteristics of summer reedSamples from different places I 06 01 I 06 02 I 06 03 I 06 04 I 06 05 I 06 06 I 06 07

Point of deformation (IT) OC, 700 650 670 640 730 690 580

Softening temperature (ST) OC 990 1000 1040 960 1030 910 760

Formation of hemisphere (HT) OC 1130 1110 1120 1060 1150 1080 910

Flow temperature (FT) OC 1170 1130 1160 1090 1170 1120 990Fusibility characteristics of winter reedPoint of deformation (IT) OC, 800 1040 1220 790 1050

Softening temperature (ST) OC 1240 1040 1200

Formation of hemisphere (HT) OC 1290 1230 1270

Flow temperature (FT) OCup to 1340 don't melt

1270 1290

up to 1350 don't meltup to 1330

don't melt up to 1330 dont' melt up to 1375

don't melt

Fusibility characteristics of reed (summer and winter reed 2006)

Reed ash

• It is important to note that the summer reed ash cone fused down at the temperature lower than 1 200°C, initial deformation took place at temperatures below 800°C (see at the Table, slide 16).

• On the other hand ash of the winter reed has not fused down even at 1 350°C; only one sample shows evidence the deformation temperature only ~ 800°C.

• We are able to state that average ash-fusibility temperatures for summer and winter reed ashes differ 200 K.

• This proves that the reed as a boiler fuel must be most definitely harvested in winter, when the nutrients and minerals have accumulated in the roots (rhizome) and leaves have fallen.

Samples of ash of reed fuels (left: pellets; right: stalks

Burning tests of reed briquettes in home oven

Ash fusibility of reed and wood mixture

y = -2E-05x3 + 0,0875x2 - 11,239x + 1459,5R2 = 0,9845

1050

1100

1150

1200

1250

1300

1350

1400

1450

1500

0 20 40 60 80 100

Share of wood ash in mixture, %

Flow

tem

pera

ture

(FT)

, °C

The flow temperature of the mixture of reed and wood ash has minimum point at certain rate what is approximately 100 K less from corresponding wood ash flow temperature.

Minimum occurs at the share of wood ash 50÷70 % in mixture and it is different for separate fusibility characteristics. For point of deformation the minimum is at the share of wood ash 45 %, for flowing temperature –65%.

Recommended maximum proportions of Reed Canary Grass together with wood or peat when a fuel-mix is used in a fluidized bed boiler. (Source: Vapo Ltd, Novox Ltd.).

Laboratory tests of reed-to-biogas productivity from summer reed

Biogas(-methane) potential measurements, 12 samples from all coastal area reed beds of Estonia

Mahu

Kiideva

Rocca al Mare

Peipsi

Chemical analysis

Sample Dry

matter,

%

N, % P, % K, % Ca, % Mg, % Cellulose,

%

Lignine,

%

Hemicellulose,

%

1.Silma 44,31 0,690 0,087 0,568 0,155 0,036 40,16 6,93 30,63

2.Rocca al Mare 28,40 2,183 0,201 2,029 0,253 0,067 35,50 7,21 27,31

3.Puhtu 41,58 1,103 0,097 0,956 0,176 0,085 39,12 8,38 28,37

4.Jõesuu 38,86 0,889 0,078 0,802 0,230 0,063 34,11 7,15 28,48

5.Puhtu (old) 81,78 0,326 0,028 0,084 0,077 0,023 45,65 12,37 28,48

6.Vaibla 27,03 2,089 0,199 1,733 0,298 0,094 33,44 5,03 28,42

7.Kiideva 41,34 0,872 0,113 0,917 0,104 0,065 39,91 7,94 31,33

8.Haapsalu-Aiavilja 39,46 1,166 0,155 0,953 0,213 0,121 32,93 5,96 31,19

9.Lüübnitsa 32,62 1,842 0,179 1,033 0,256 0,058 35,74 8,01 31,62

10.Turbuneeme 33,89 1,377 0,138 1,170 0,229 0,125 35,10 8,02 31,20

11.Haapsalu-Papiniidu 42,64 1,092 0,146 0,774 0,267 0,106 36,70 9,74 30,31

12.Popovitsa 34,43 1,348 0,146 0,917 0,223 0,084 36,30 7,89 31,11

Results

Methane production, mmol

Sample Marked as Colour

TV Inok TV InokLüübnitsa PR 1Popovitsa PR 2Puhtu PR 3Kiideva PR 4.2Aiavilja PR 5Papiniidu PR 6Turbuneeme PR 7Rocca al Mare PR 8.2Silma PR 9.2Vaibla PR 10Jõesuu PR 11.2Rocca al Mare (2) PR 12

Composition of biogas

Biomethane potential measurementsfrom reed samples: conclusions (1)

Biogas of good quality, without impurities (H2S, NH3) but moderate CH4 concentration (49‐55%);

Quick  start‐up of fermentation process (5‐7 days);

Stable fermentation, no accumulation of metabolites (VFAs etc);

Methane potential is in the range of 0.22‐0.26 m3/kg perorganic material.

29

Biomethane potential measurementsfrom reed samples: conclusions (2)

Comparison with previous studies from 2007-2008• The biogas potential is higher from reed grown on soil with  

abundant concentration of nutrients (ie more polluted);

• The biogas potential is higher from reed harvested late in summer as compared to reed harvested in early summer or in autumn;

• Biogas potential is higher from the 2‐step digestion as compared to the single step one. Inoculum should be added at least in a week, after the acid formation stage;

• Biomethane potential was in the range of 0.26‐0.36 m3/kg organic material.

Biogas yield of green reed

ParameterOnly

leaves, Peipsi

Allplant,Mahu

Allplant,

Peipsi

All plant,Rocca al

Mare

Biogas per dry matter, l/g or m3/kg 0,428 0,487 0,450 0,533

Biogas per volatiles, l/g or m3/kg 0,391 0,437 0,417 0,500

Biogas per matter as received, l/gor m3/kg 0,238 0,149 0,166 0,162

Solid reed fuel

Combustion equipment

• The variety of equipment burning herbaceous biomass is rather wide and finding the suitable one depends much on which kind of fuel the user wants to burn, either:

• pressed (pellets, briquettes),• packed (baled),• crushed (shreded).

Combustion equipment

The stocker burner EcoTec The Stocker burner IWABO Villa S 20

Three hours after the ignition of reed pellets the burning process slowed down due to the burner clogging (the same had happened earlier when the combustion of straw pellets was tested).

Pellet burner of KWB EasyFlex (Austria)

The firing system is designed as an underfeed firing system with afterburning ring.

Due to the special arrangement of secondary air jets in the afterburning ring, perfect turbulence, high combustion temperatures and thus cleaner burnout of the combustion gases are guaranteed.

Optionally has the KWBEasyFlex burner extension, in which the burner plate is equipped with an efficient cleaning mechanism. This makes the burner even more reliable when using slagging and ash-rich standard pellets.

Pellet boiler, KWB

Combustion equipmentSimple boiler for burning paled straw, where the air controls performed by

temperature of flue gases

Combustion equipmentScheme of the facility for burning crushed

(scarified) straw

Combustionequipment

Cigar-type burner for straw bales

Combustion equipmentFluidized bed combustion

Circulated FBC, Bubble bed combustion

Conclusions

• Based on the laboratory tests and pilot tests in boiler-houses the use of fuel reed (shred reed and pellets) has proved to be suitable partially.

• In order to gain further experience, tests should be carried out to find suitable fuel handling technologies and combustion equipment and develop combustion regimes for different types of reed.

• It must be considered that these fuels can be added to other biomass-based fuels, however the peculiarities of their co-combustion should be studied.

• One suitable way to handle reed as fuel is to make silage and digest it anaerobically for biogas. Biogas as a engine fuel for CHP and transport vehicles.

Thank you for your attention!

Here we are coming!