Seminar “Reed for Bio-Energy and Construction”
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Seminar “Reed for Bio-energy and Construction” Reed as bio-energy: opportunities to use it in boiler-houses and as biogas source Ülo 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 counties Reed beds Energy content, MWh/y Corrected reed beds Harvestable Yield, County area, ha area, ha (2007) ** area, ha/y t/ha (2000) Theoretical Realistic 12 3 4567 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. These have been determined in the TUT TED. Combustion characteristic of reed Elemental composition of dry reed fuel, % Ranges Average Element Winter Summer Winter Summer Carbon, C 46,96–48,34 46,13–47,11 47,5 46,5 Hydrogen, H 5,50–5,60 5,93–6,42 5,6 6,2 Oxygen, 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 1,0 Sulphur, 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 characteristic The 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 characteristic Heating value of dry matter of reed fuel Parameters: Ranges Average Calorific value, MJ/kg Energy content, MWh/t Winter Summer Winter Summer Qp/qb, 18,62–19,16 18,33–18,77 18,92 18,51 k Qü /qgr, d 18,62–19,16 18,31–18,75 18,91 18,49 k Qa /qnet, d 17,48–18,01 17,02–17,44 17,77 17,21 20 Qa /qnet, 20 * 13,68–14,86 13,16–13,49 14,17 13,31 20 E / E20, MWh/t* 3,80–4,13 3,65–3,75 3,94 3,70 *at moisture content 20 % Combustion characteristic The yield and characteristics slightly depend on harvesting period and site of growth of reed. Seashore reed Lake reed Main characteristics Winter Summer Winter Summer Moisture, % 23,7 60,4 21,1 60,5 Yield of dry matter, t/ha 6,9 8,7 8,1 7,4 Volatile matter, % 82,0 75,7 82,3 77,1 Ash content of dry matter (at 550 ºC), % 3,5 6,3 3,1 5,7 Net calorific value of dry matter, MJ/kg k 17,5 (Qa /qnet, d) Combustion characteristic Ash • 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 characteristic Chemical 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 37,10 Fe2O3 0,13–0,84 0,17–1,69 0,29 0,70 Al2O3 0,1–1,69 0,11–1,12 0,57 0,61 CaO 3,07–7,27 4,02–11,53 4,42 6,84 MgO 0,4–1,45 1,87–4,88 1,22 3,33 Na2O 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 90 000 80 000 Rocca al Mare 70 000 Peipsi järv 60 000 Saaremaa 50 000 40 000 30 000 Sisaldus mg/kg, kuivaines 20 000 10 000 0 Ca Mg Na K Mn Cd Cr Cu Pb Ni Zn S Fe Al P Fusibility characteristics of reed (summer and winter reed 2006) Fusibility characteristics of summer reed Samples 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 990 Fusibility characteristics of winter reed Point of deformation (IT) OC, 800 1040 1220 790 1050 O 1240 1040 1200 Softening temperature (ST) C up to 1350 O 1290 up to 1330 up to 1330 1230 1270 Formation of hemisphere (HT) C don't melt up to 1375 up to 1340 don't melt dont' melt O 1270 don't melt 1290 Flow temperature (FT) C don't melt 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 1500 y = -2E-05x3 + 0,0875x2 - 11,239x + 1459,5 1450 R2 = 0,9845 1400 1350 1300 1250 1200 1150 Flow temperature (FT), °C 1100 1050 0 20406080100 Share of wood ash in mixture, % 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.