Production of Syn Gas / High BTU Gaseous Fuel - Argonne National ...
PRODUCTION OF SYN GAS / HIGH BTU GASEOUS FUEL FROM THE PYROLYSIS OF BIOMASS DERIVED OIL S. Panigrahi, A. K. Dalai*, and N. N. Bakhshi Catalysis and Reaction Engineering Laboratories Department of Chemical Engineering University of Saskatchewan Saskatoon, SK. S7N 5C9, Canada Phone: (306) 966-4771 Fax: (306) 966-4777 E- mail: [email protected] Introduction The gradual shortage of oil reserves has created considerable interest in using alternative source of energies, which are renewable in nature. As we enter the 21st century, new, clean burning, renewable fuels may revolutionize the energy industry. The renewable energy technologies (RET) of the European commission have the target of doubling their contribution from the present 5.6% to about 12% in the future1. Amongst all the renewable energy sources, biomass represents high potential and will play a vital role in the near future. Two approaches, namely pyrolysis and gasification of biomass, have been attempted to convert biomass into a useful form of energy2,5. The pyrolysis process is generally carried out by subjecting the biomass to a high temperature under an inert or oxygen deficient atmosphere. In the past, biomass was used for the production of hydrogen and medium Btu gas6. Extensive studies have been done on pyrolysis of cellulose, wood and biomass materials7-12. Waste biomass materials such as Kraft and Alcell lignins have been converted to hydrogen and medium Btu gas by steam gasification6,13,14. The fast pyrolysis process of biomass generally gives three products viz. gas, biomass-derived oil and char. The bio-oil thus produced contains unsaturated hydrocarbons and is thus highly unstable. This biomass-derived oil (BDO) has found a variety of applications in various areas. Unlike fossil fuels, BDO is renewable, cleanly burns, and is greenhouse gas neutral. It does not produce any SOx (sulfur dioxide) emission during combustion and produces approximately half the NOx (nitrogen oxide) emission in comparison with fossil fuels. Therefore, it is a potential raw material for renewable fuel and can be used as a fuel oil substitute13 . However, several challenges are identified in bio-oil applications resulting from their properties. Extensive research on analyzing physical properties has been carried out earlier15-20. Rick and Vix have reviewed on product standards of BDO21. Most of the BDO are polar, viscous and corrosive, and contains 40-50 % oxygen. They have a high water content that is detrimental for ignition. Soltes and Lyn reported that most of the pyrolytic oils quickly form a solid mass when exposed to air4. Therefore, they can’t be used as such as conventional fuel5. The conversion is due to the presence of organic acids in the oils. Over time, reactivity of some components in the oils leads to formation of larger molecules that result in high viscosity and in slower combustion4. Diebold and Czernik developed additives to stabilize the viscosity of biocrude during long-term storage, which demonstrated the ability to drastically reduce its aging rate, defined by the increase in viscosity with time22. Some research has been done on catalytic upgradation of BDO14,23,24. The product gas consisted of H2 CO, CO2. CH4, C2-C4, higher hydrocarbons. The BDO has been converted to hydrogen via
catalytic steam reforming followed by a shift conversion step25,26. The hydrogen yield was as high as 85%. Baker & Elliott have reported the catalytic upgrading of BDO produced at high-pressure conditions27. The yield of gasoline range hydrocarbons was 6090%. The bio-oil thus produced contained unsaturated hydrocarbons and was highly unstable. An attempt has been made in this research to produce clean fuels including hydrogen, high Btu gaseous fuel and synthesis gas by pyrolysis of BDO in the absence of a catalyst. In this work, the reactor temperature and inert gas flow rate were varied from 650 to 800 0C, and from 18 to 54 ml/min, respectively. In all experiments, the BDO flow rate was maintained at 4.5-5.5 g/h. Table 1. Properties of Biomass and BDO Biomass Feedstock
Pine/ Spruce 100% 33 wood
Pine/ Spruce 53% Wood 47% bark
Bagasse
BDO (used in the present study)
-
33
33
Moisture, wt.% Ash Content, wt.% Bio-oil PH Water Content, wt.% Lignin Content, wt.% Solids Content, wt.% Ash content, wt.% Density, g/cc @20oC Calorific Value, MJ/kg Kinematic Viscosity cSt @20oC cSt @40oC cSt @80oC
2.4
3.5
2.1
0.42
2.6
2.9
2.3 23.3
2.4 23.4
2.6 20.8
2.5 21.5
24.7
24.9
23.5
25.0
< 0.10
< 0.10
< 0.10
-
< 0.02
< 0.02
< 0.02
0.160.18
1.20
1.19
1.20
16.6
16.4
15.4
1.181.24 17.519.1
73 4.3
78 4.4
57 4.0
110 45.6 -
Experimental Biomass-derived oil was obtained from DynaMotive, which was produced from Asphene wood materials using a patented technology28. On an average, 1 kg (dry) of biomass produces 0.75 kg of oil, 0.1 kg of char and 0.15 kg of gas29. Biomass derived oil is a liquid mixture of oxygenated compounds containing various chemical functional groups such as carbonyl, carboxyl and phenolic30,31. Biomass derived oil is made up of the following constituents: 20-25 % water, 25-30% water insoluble pyrolytic lignin, 5-12 % organic acids, 5-10% non polar hydrocarbons, 510% anhydrosugars and 10-25 % other oxygenated compounds31.
Fuel Chemistry Division Preprints 2002, 47(1), 118
Product Gas Analysis. It may be noted that the reactor had a long preheating section. Thus, there was sufficient time for the BDO to achieve desired temperature in the reactor to crack and to produce gas, coke and liquid. The amount of the product gas was measured for each experiment, and was analyzed for its compositions using two GCs (Carle GC-500 series and HP5890). The HP5890 GC was equipped with a thermal conductivity detector and Carbosive S II column and analyzed H2, CO, CO2 and CH4 where as the Carle GC, equipped with a flame ionization detector and combination of packed and capillary columns (Stable wax), analyzed hydrocarbons. Temperature programming of the oven was used in this case for analysis of the product gas. Results and Discussion The properties of BDO used in our study are compared to those reported in literature (see Table 1). The data in Table 1 indicate that the properties of BDO are quite comparable to those obtained from other sources. In this investigation the effects of reactor temperature and the nitrogen flow rate on the BDO conversion and product gas composition was studied. The material balance for each experiment was found to be between 92-98wt.%.
100
BDO Conversion Vol. of Product Gas
90
Vol. of Product Gas (mL)
Effect of Nitrogen Flow Rate. The effects of nitrogen flow rate (18 to 54 mL(STP)/min) on the conversion of BDO, product gas yield and its composition have been studied at constant pyrolysis temperature of 800 0C and contact BDO flow rate of 4.5 mL/h and the results are shown in Figure 2.
BDO Conversion (wt.%) .
The water includes those present in the wood 5-8% (see Table 1) as well as that is produced during the pyrolysis. Elemental analysis showed that the biomass-derived oil contained 43.6 wt % C, 8 wt. % H, 0.5 wt % N, and 47.9 wt% was O (obtained by difference). The viscosity of the fresh biomass-derived oil at 25 0C was 8x10-2 pa.s, which increased slowly upon storage32. Experimental Procedure. The experimental set-up used in our research consisted of an Inconel tubular continuous down flow micro reactor (12.7 mm i.d. and 200 mm long, placed co axially in the furnace). The reactor contained quartz chips (used for better temperature distribution and to avoid high pressure drop in the reactor) through which desired flow of an inert gas such as nitrogen was maintained through a Brooks mass flow controller (Model 0152/0154). The reactor temperature was controlled using a temperature controller using a thermocouple attached to the outer wall of the reactor and connected to the temperature controller. The temperature was measured by placing a thermocouple at the center of the quartz bed. A schematic diagram of the experimental set up used for the pyrolysis of BDO is shown in Figure 1. In this study, o the reactor temperature was varied in the range of 650 to 800 C where as the carrier gas flow rate was varied from 18 to 54 mL/min (STP). Biomass-derived oil was introduced at a predetermined rate using a micro metering syringe pump (Eldex, model A-60-S) at the rate of 4.5-5.5 ml/hr through a specially designed nozzle, which helped to spray liquids into the reactor along with the inert gas. Each experiment was performed at atmospheric pressure only for a period of 30-45 min, depending upon the operating conditions. In most cases, the run was terminated after 30 minute of operation. At the end of the run, the pump and the heating of furnace were shut off and the reactor was cooled down to the ambient temperature. The reactor was then removed from the reaction system and was weighed to determine the amount of coke formed. The product gas was cooled with a water-cooled heat exchanger and then with an ice-salt bath (to liquefy the condensable) before it was collected over saturated brine solution. The condensed liquid product was retained in a trap cooled by an ice-salt mixture and weighed. After each run, the mass of the gas, char and condensed liquid were calculated for bio oil conversion and mass balance.
2500 2000
80
1500
70
1000
60
500 10
30
50
Nitrogen flowrate ( mL / min)
Figure 2 Effects of carrier (nitrogen) gas flow rate on conversion of BDO and volume of gas produced during pyrolysis of BDO at 800 0C and BDO flow rate of 4.5 mL/h
Figure 1: Schematic diagram of experimental setup for pyrolysis of BDO.
By varying nitrogen flow rate from 20 to 30mL/min, the conversion of BDO to gas and char was increased from 75 to 83wt.%. The increased conversion of BDO may be due to the increased heat and mass transfer caused due to the turbulences created by the higher flow rate of nitrogen. Beyond nitrogen flow rate of 30mL/min, the conversion of BDO was ~ 83wt.% and did not change with respect to nitrogen flow. It was also observed that with the increase in flow rate of nitrogen, the amount of gaseous product was increased. For example, the volume of product gas was increased from 900 to 1780 ml by changing the nitrogen flow rate from 18 to 54 ml/min i.e., from 100 grams of BDO, 39 l and 65 l of product gas were obtained at N2 flow rates of 18 and 54 ml/min, respectively. Higher gas yield at higher nitrogen flow could be due to higher syn gas production, which is explained below. The effect of nitrogen flow rate on product gas composition was also evaluated and is shown in Figure 3. It is observed that the production of hydrogen remained approximately constant with the
Fuel Chemistry Division Preprints 2002, 47(1), 119
.
increase in nitrogen flow rate from 18 to 45 mL/min. However, there is a sharp increase in the hydrogen production with further increase in nitrogen flow rate. The formation of methane was high 30 mol% at lower nitrogen flow rate of 20 mL/min. Higher residence time due to low flow rate of nitrogen is responsible for cracking of BDO producing more methane. At higher flow rate (4254 mL/min) of N2, the concentration of methane was low (~20-24 mol%). At 800 0C methane could react due to partial oxidation and combustion producing more hydrogen. CO gas yield was increased when the nitrogen flow was increased from 18 to 54 ml and reached maximum for N2 flow of 42 – 50 mL/min. This may be due to the reaction of CO2 with carbonaceous material producing more CO. The total amount of synthesis gas (hydrogen and CO) also increased from 22 to 65 mol% as nitrogen flow increased from 18 to 54 mL/min. The effect of nitrogen flow rate on the production of other gases such as ethane and higher hydrocarbons was not very significant.
H2 CO2 C 2H 6 O le f in
60 50
CO CH4 C 3H 8 H 2+C O
Nitroge n flow
C2H4, mol%
C3H6, mol%
HigherC3H6 Olefins, mol%
Total olefins, mol%
18
31.5
3.8
3.6
38.9
30
31.1
3.1
9.0
43.2
42
18.4
2.4
7.1
27.9
54
6.9
0.1
4.4
11.4
The effect of nitrogen flow at 800 0C on the heating value of product gas is shown in Figure 4. Due to optimum production of hydrocarbons at a nitrogen flow rate of 30mL/min and 800 0C, the heating value of gas was high (1738 Btu/SCF). At these conditions, the conversions of bio-oil and olefin yield were as high as 83 wt.% and 43mol%, respectively. However, the syn gas yield of 65mol % was optimum at nitrogen flow rate of 54mL/min at 800 0C (See Figure 3).
40 30
2000
20
Hating Value of Gas (Btu/SCF)
Composition of Product Gas (mol %)
70
Table 2. The Effects of N2 Flow Rate on Total Olefin Production and its Distribution at a Reaction Temperature of 800 0C
1600
10
1200
0 10
20
30
40
50
60
N itr o g e n F lo w R a te ( m L /m in )
800 400
Figure 3. Effects of carrier (nitrogen) gas flow rate on product gas composition for pyrolysis of BDO at 800 0C and BDO flow rate of 4.5 ml/h The effects of N2 flow rate on total olefin production and its distribution are shown in Figure 3 and Table 2, respectively. The production of olefins (mostly ethylene and propylene) initially after showing a slight increasing trend followed a decreasing pattern with nitrogen flow rate (see Figure 3). The olefin content of approximately ~ 43mol% was obtained corresponding to a nitrogen flow rate of 30mL/min (see Table 2). Probably at lower N2 flow rate (20-30 mL/min) BDO had higher residence time for cracking and thus producing more olefins. At higher flow rate (42-54 mL/min) of N2, the concentration of olefins was lower (~10-25 mol%) where as syn gas formation was higher.
18
30 42 54 Nitrogen Flow Rate (mL/min)
Figure 4. Effects of carrier (nitrogen) gas flow rate on total heating value of produt gas during pyrolysis of BDO at 800 0C Effects of temperature. The effects of temperature (650-800 0C) on the conversion of bio-oil, gas yield and its composition have been studied keeping nitrogen and bio-oil flow rates constant, respectively, at 30mL/min and 4.5g/h. Effects of temperature on conversion of BDO and volume of gas produced are shown in Figure 5. The results show that as the temperature is increased from 650 to 800 0C, the conversion of bio-oil to gas and char is increased from 57 to 83 wt. %. Also, as expected, the production of gas is increased with temperature. For example, the product gas volumes obtained at 650 and 750 0C were 730 and 1020 mL, respectively. This corresponds to the fact that from 100 grams of BDO, 26 l to 45 l of gas could be produced with increase in temperature from 650 to 750 0C at constant N2 flow rate of 30 mL/min. However, beyond this temperature, its effect on the gas production was negligible.
Fuel Chemistry Division Preprints 2002, 47(1), 120
19.2
650
12.8 17.0 2.5
7.2
0.9
40.3
99.9
700
16.3 9.2
3.4
21.6
7.2
1.1
41.2
99.8
750
9.3
6.5
2.1
23.2
9.0
1.3
48.5
99.9
800
12.8 7.7
2.6
27.4
5.5
0.6
43.2
99.8
The effects of temperature on the product gas composition and olefins formed from BDO are given in Table 3. It is also evident from data in this table that the production of maximum olefins is at 48.5 mol% at 750 0C. The methane concentration increases from 19.2 to 27.4 mol% as the temperature increases from 650 to 7500C. Thus it is possible to produce a gas stream having an olefin content of as high as ~48-mol % from BDO. The results also show that the concentration of CO2, C2, C3 paraffin do not change with temperature.
1200
100
BDO Conversion (wt. %)
800
80 600
70 400
60
Conversion BDO
Total Gas Vol. (mL)
1000
90
200
Total Gas Vol., mL 0
50 600
650
700
750
800
850
o
Temperature ( C) Figure 5. Effects of temperature on conversion of BDO and volume of gas produced during pyrolysis of BDO at a nitrogen flow rate of 30 mL (STP)/min
1800
40000
.
C2H6, mol%
Total Total C3H8, olefin, mol% mol%
35000 Btu of gas/ 100 g of BDO
H2, CO, CO2, Temp., mol mol mol CH4, 0 C % % % mol%
Heating valu of product gas (Btu/ SCF) .
Table 3. The Composition Data as a Function on Temperature at Nitrogen Flow Rate of 30 mL/min
1600 30000
1400 25000 Btu/100 g of BDO Btu/Scf
20000 600
700
800
1200 900
Figure 6. Effects of temperature on heating value of product gas for pyrolysis of BDO at nitrogen flow rate of 30 mL/min. The effects of reaction temperature on the olefins composition are shown in Table 4. The effects of reaction temperature on the heating value and energy content of the gas produced at nitrogen flow rate of 30 mL/min are shown in Figure 6. The results indicate that the heating value of the product gas was increased from 1300 to 1700 Btu/SCF with increase in temperature from 700 to 800 0C. This could be due to increase in methane concentration from 19 to 27 mol % in the product gas. Table 4. Effects of Temperature on Distribution Olefins Formed During the Pyrolysis of BDO at a Nitrogen Flow Rate of 30 mL/min and BDO Flow Rate of 4.5 –5.5 mL/h Temperature 0 C 650
C2H4, mol% 20.8
700 750 800
23.0 26.4 31.1
C3H6, mol% 9.4
Higher C3H6Olefins, mol% 10.1
Total olefins, mol% 40.3
9.1 10.2 3.1
9.1 12.0 9.0
41.2 48.6 43.2
It is observed that the concentration of olefins (of which 60-70 mol % is ethylene) is varied in a range of 40 to 48mol % in the product gas with increase in temperature from 700 to 800 0C. However, syn gas production is decreased by 20 mol % in spite of higher production of hydrogen with the temperature increase. The increase in hydrogen production with increased temperature occurred probably because at high temperatures pyrolysis of the BDO subunits, which evolved more hydrogen. Conclusions The present study identifies the pyrolysis of biomass-derived oil as a source of gaseous fuel. In this process, the product gases essentially consisted of H2, CO, CO2, CH4, C2H4, C2H6, C3H8, and C4+ components. This process can be utilized for producing hydrocarbons and synthesis gas for various applications. By adjusting the parameters such as inert gas flow rate and reactor temperature, the composition of the product gas from biomassderived oil can be tuned in the desired direction. The conversion of biomass-derived oil at a flow rate of 4.5 – 5.5 g/h could be increased from 57 to 83 wt.% due to increasing the reactor temperature from 650 to 800 OC at a nitrogen flow rate of 30
Fuel Chemistry Division Preprints 2002, 47(1), 121
mL/min. At 800 0C and nitrogen flow rate of 30 mL/min, composition of various product gas components ranged between: Syn gas 16-30 mol %, CH4 19-27 mol % and C2H4 23-31 mol %. A large amount of total product gas was obtained from BDO at 800 0 C and N2 flow rate of 30 mL/min. Heating values ranged between 1300 – 1700 Btu/SCF. Thus, the present study shows that there is a strong potential for making syn gas, methane, ethylene and high heating value gas from the pyrolysis of biomass-derived oil. References 1. Chantal, P.D; Kaliaguine, S; Grandmaison, K.L; Mahay, A. Appl. Catal. 1984, 10, 317. 2. Sharma, R.K; Bakhshi, N.N. DSS contract file # 23440-09467/01-SZ, Bio-energy Dev. Prog., Energy Mines and Resources, Ottawa, 1992 3. Diebold, J; Soltes, E.J; Miline, T.A. ACS Symp. Ser.376, Amer. Chem. Soc., Washington, DC, 1988, 264. 4. Soltes, E.J; Lin, S.L. ACS Symposium Series 1987, 264, 178185. 5. Churin, E.P; Grange, B. Elseiver Appl. Sci., London, UK, 1990. 2, 616 6. Chaudhari, S.T; Ferdous, D; Dalai, A.K; Bej. S.K; Thring, R.W; Bakhashi, N.N. Fifth International conference on Biomass Conversion, Austria, 2000 7. Boutin, O; Ferrer, M; Lede, J. J. Anal. Appl. Pyrol. 1988 47, 13. 8. Radlein, A.G.D; Piskorz, J; Scott, S.D. J.Anal. Appl. Pyrol. 1987,12, 51. 9. Piskorz, J; Radlein, A.G.D; Scott, S.D; Czernik, S. J. Anal. Appl. Pyrol. 1989, 16, 127. 10. Liu, N.A; Fan, W.C. Fire and Materials. 1998, 22,103. 11. Koullas, D.P; Nikolaou, N; Koukios, E.G. Bioresource Energy, 1998, 63: 261. 12. Maschio, G; Lucchesi, A; Stoppato, G. Bioresource Technology, 1994, 48, 119. 13. Iqbal, M; Dalai, A.K; Thring, R.W; Bakhshi N.N. 33rd International Engineering Conference on Energy Conversion, Colorado, 1998. 14. Bakhshi, N.N; Dalai, A.K; Thring R.W. Division of Fuel Chemistry, 217th ACS National Meeting, California, 1999, 4, 278. 15. Elliot, D.C. IEA Co-operative project D1 Biomass liquefaction Test Facility project , Washington, Pacific Northwest Laboratory, 1983, 4, 87. 16. Bridgwater, A.V; Kuester, J.L. Research in thermo chemical biomass conversion, Phoenix, Arizona, New York: Elsevier Applied Science, 1988, 1177. 17. Milne, T.A; Brennan, A.H; Glenn, B.H. Sourcebook of methods of analysis for biomass and biomass conversion process. London, Elsevier Applied Science, 1990, 327. 18. McKinley, J.W; Overend, R.P; Elliott, D.C. In Proc. Biomass pyrolysis oil properties and combustion meetings, Estes Park, CO. Golden, CO: NREL. NREL-CP-430-7215, 1994, 34. 19. Diebold, J.P; Milne, T.A; Czernik, S; Oasmaa, A; Bridgwater, A.V; Cuevas, A; Gust, S; Huffman, D; Piskorz, J. Development in thermo chemical biomass conversion. Banff. Glasgow: Blackie Academic and professional, Eds.; 1997,1, 533. 20. Piskorz, J; Radlein, D; Majerski, P; Scott, D.S. In Proc. Biomass pyrolysis oil properties and combustion meetings, Estes Park. CO. Golden. CO. NTIS, 1994, 22.
21. Rick F, and Vix U. In Bridgwater, A.V; Grassi, G. Biomass Pyrolysis liquids upgrading and utilization. London & New York: Elsevier Applied Science, Eds.; 1991. 177-218. 22. Diebold, J.P; Czernik, S. Energy & Fuels,1997, 11(5), 1081. 23. Mathews JF, Tepylo MJ, Eager RL and Pepper JM. Can. J. Chem. Eng., 1985, 63, 686. 24. Srinivas, S.T; Dalai, A.K; Bakhshi, N.N. Can. J. Chem. Eng., 1985, 78, 343. 25. Wang, D; Czernik, S; Montane, D; Mann, M; Chornet, E. Industrial and Engineering Chemistry Research, 1994, 36(5), 1507. 26. Czernik, S; Wang, D; Chornet, E. Proceedings of the 1998 U.S. DOE Hydrogen Program Review, 28-30 April, Alexandria, Virginia. NREL/CP-570-25315. National Renewable Energy Laboratory,1998, 2, 557. 27. Baker, E.G; Elliot, D.C. Thermo chemical Biomass Conversion, Eds.; Elsevier Appl. Sci., London UK, 1988, 883-895. 28. Cottam, M.L; Bridgwater, A.V. Thermo chemical Biomass Conversion, Blackie Academic and Professional, London, Eds.; 1994, 2, 1343. 29. Bridgwater, A.V. Advances in Thermo chemical Biomass Conversion Blackie Academic and Professional, London,Eds.; 1994, 2, 1314. 30. Bridgwater AV, In Fast Pyrolysis of Biomass: A handbook, Eds.; PL Press. 1999. 31. Morris, K.W. 4th Biomass conference of Americas, 1999. 32. Piskorz, J. United States Patent No. 5,728,271. 33. Morris, K.W; Johnson, W; Thamburaj, R. 1st World Conference and Exhibition on Biomass for Energy and Industry in Seville, Spain, 2000.
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catalytic steam reforming followed by a shift conversion step25,26. The hydrogen yield was as high as 85%. Baker & Elliott have reported the catalytic upgrading of BDO produced at high-pressure conditions27. The yield of gasoline range hydrocarbons was 6090%. The bio-oil thus produced contained unsaturated hydrocarbons and was highly unstable. An attempt has been made in this research to produce clean fuels including hydrogen, high Btu gaseous fuel and synthesis gas by pyrolysis of BDO in the absence of a catalyst. In this work, the reactor temperature and inert gas flow rate were varied from 650 to 800 0C, and from 18 to 54 ml/min, respectively. In all experiments, the BDO flow rate was maintained at 4.5-5.5 g/h. Table 1. Properties of Biomass and BDO Biomass Feedstock
Pine/ Spruce 100% 33 wood
Pine/ Spruce 53% Wood 47% bark
Bagasse
BDO (used in the present study)
-
33
33
Moisture, wt.% Ash Content, wt.% Bio-oil PH Water Content, wt.% Lignin Content, wt.% Solids Content, wt.% Ash content, wt.% Density, g/cc @20oC Calorific Value, MJ/kg Kinematic Viscosity cSt @20oC cSt @40oC cSt @80oC
2.4
3.5
2.1
0.42
2.6
2.9
2.3 23.3
2.4 23.4
2.6 20.8
2.5 21.5
24.7
24.9
23.5
25.0
< 0.10
< 0.10
< 0.10
-
< 0.02
< 0.02
< 0.02
0.160.18
1.20
1.19
1.20
16.6
16.4
15.4
1.181.24 17.519.1
73 4.3
78 4.4
57 4.0
110 45.6 -
Experimental Biomass-derived oil was obtained from DynaMotive, which was produced from Asphene wood materials using a patented technology28. On an average, 1 kg (dry) of biomass produces 0.75 kg of oil, 0.1 kg of char and 0.15 kg of gas29. Biomass derived oil is a liquid mixture of oxygenated compounds containing various chemical functional groups such as carbonyl, carboxyl and phenolic30,31. Biomass derived oil is made up of the following constituents: 20-25 % water, 25-30% water insoluble pyrolytic lignin, 5-12 % organic acids, 5-10% non polar hydrocarbons, 510% anhydrosugars and 10-25 % other oxygenated compounds31.
Fuel Chemistry Division Preprints 2002, 47(1), 118
Product Gas Analysis. It may be noted that the reactor had a long preheating section. Thus, there was sufficient time for the BDO to achieve desired temperature in the reactor to crack and to produce gas, coke and liquid. The amount of the product gas was measured for each experiment, and was analyzed for its compositions using two GCs (Carle GC-500 series and HP5890). The HP5890 GC was equipped with a thermal conductivity detector and Carbosive S II column and analyzed H2, CO, CO2 and CH4 where as the Carle GC, equipped with a flame ionization detector and combination of packed and capillary columns (Stable wax), analyzed hydrocarbons. Temperature programming of the oven was used in this case for analysis of the product gas. Results and Discussion The properties of BDO used in our study are compared to those reported in literature (see Table 1). The data in Table 1 indicate that the properties of BDO are quite comparable to those obtained from other sources. In this investigation the effects of reactor temperature and the nitrogen flow rate on the BDO conversion and product gas composition was studied. The material balance for each experiment was found to be between 92-98wt.%.
100
BDO Conversion Vol. of Product Gas
90
Vol. of Product Gas (mL)
Effect of Nitrogen Flow Rate. The effects of nitrogen flow rate (18 to 54 mL(STP)/min) on the conversion of BDO, product gas yield and its composition have been studied at constant pyrolysis temperature of 800 0C and contact BDO flow rate of 4.5 mL/h and the results are shown in Figure 2.
BDO Conversion (wt.%) .
The water includes those present in the wood 5-8% (see Table 1) as well as that is produced during the pyrolysis. Elemental analysis showed that the biomass-derived oil contained 43.6 wt % C, 8 wt. % H, 0.5 wt % N, and 47.9 wt% was O (obtained by difference). The viscosity of the fresh biomass-derived oil at 25 0C was 8x10-2 pa.s, which increased slowly upon storage32. Experimental Procedure. The experimental set-up used in our research consisted of an Inconel tubular continuous down flow micro reactor (12.7 mm i.d. and 200 mm long, placed co axially in the furnace). The reactor contained quartz chips (used for better temperature distribution and to avoid high pressure drop in the reactor) through which desired flow of an inert gas such as nitrogen was maintained through a Brooks mass flow controller (Model 0152/0154). The reactor temperature was controlled using a temperature controller using a thermocouple attached to the outer wall of the reactor and connected to the temperature controller. The temperature was measured by placing a thermocouple at the center of the quartz bed. A schematic diagram of the experimental set up used for the pyrolysis of BDO is shown in Figure 1. In this study, o the reactor temperature was varied in the range of 650 to 800 C where as the carrier gas flow rate was varied from 18 to 54 mL/min (STP). Biomass-derived oil was introduced at a predetermined rate using a micro metering syringe pump (Eldex, model A-60-S) at the rate of 4.5-5.5 ml/hr through a specially designed nozzle, which helped to spray liquids into the reactor along with the inert gas. Each experiment was performed at atmospheric pressure only for a period of 30-45 min, depending upon the operating conditions. In most cases, the run was terminated after 30 minute of operation. At the end of the run, the pump and the heating of furnace were shut off and the reactor was cooled down to the ambient temperature. The reactor was then removed from the reaction system and was weighed to determine the amount of coke formed. The product gas was cooled with a water-cooled heat exchanger and then with an ice-salt bath (to liquefy the condensable) before it was collected over saturated brine solution. The condensed liquid product was retained in a trap cooled by an ice-salt mixture and weighed. After each run, the mass of the gas, char and condensed liquid were calculated for bio oil conversion and mass balance.
2500 2000
80
1500
70
1000
60
500 10
30
50
Nitrogen flowrate ( mL / min)
Figure 2 Effects of carrier (nitrogen) gas flow rate on conversion of BDO and volume of gas produced during pyrolysis of BDO at 800 0C and BDO flow rate of 4.5 mL/h
Figure 1: Schematic diagram of experimental setup for pyrolysis of BDO.
By varying nitrogen flow rate from 20 to 30mL/min, the conversion of BDO to gas and char was increased from 75 to 83wt.%. The increased conversion of BDO may be due to the increased heat and mass transfer caused due to the turbulences created by the higher flow rate of nitrogen. Beyond nitrogen flow rate of 30mL/min, the conversion of BDO was ~ 83wt.% and did not change with respect to nitrogen flow. It was also observed that with the increase in flow rate of nitrogen, the amount of gaseous product was increased. For example, the volume of product gas was increased from 900 to 1780 ml by changing the nitrogen flow rate from 18 to 54 ml/min i.e., from 100 grams of BDO, 39 l and 65 l of product gas were obtained at N2 flow rates of 18 and 54 ml/min, respectively. Higher gas yield at higher nitrogen flow could be due to higher syn gas production, which is explained below. The effect of nitrogen flow rate on product gas composition was also evaluated and is shown in Figure 3. It is observed that the production of hydrogen remained approximately constant with the
Fuel Chemistry Division Preprints 2002, 47(1), 119
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increase in nitrogen flow rate from 18 to 45 mL/min. However, there is a sharp increase in the hydrogen production with further increase in nitrogen flow rate. The formation of methane was high 30 mol% at lower nitrogen flow rate of 20 mL/min. Higher residence time due to low flow rate of nitrogen is responsible for cracking of BDO producing more methane. At higher flow rate (4254 mL/min) of N2, the concentration of methane was low (~20-24 mol%). At 800 0C methane could react due to partial oxidation and combustion producing more hydrogen. CO gas yield was increased when the nitrogen flow was increased from 18 to 54 ml and reached maximum for N2 flow of 42 – 50 mL/min. This may be due to the reaction of CO2 with carbonaceous material producing more CO. The total amount of synthesis gas (hydrogen and CO) also increased from 22 to 65 mol% as nitrogen flow increased from 18 to 54 mL/min. The effect of nitrogen flow rate on the production of other gases such as ethane and higher hydrocarbons was not very significant.
H2 CO2 C 2H 6 O le f in
60 50
CO CH4 C 3H 8 H 2+C O
Nitroge n flow
C2H4, mol%
C3H6, mol%
HigherC3H6 Olefins, mol%
Total olefins, mol%
18
31.5
3.8
3.6
38.9
30
31.1
3.1
9.0
43.2
42
18.4
2.4
7.1
27.9
54
6.9
0.1
4.4
11.4
The effect of nitrogen flow at 800 0C on the heating value of product gas is shown in Figure 4. Due to optimum production of hydrocarbons at a nitrogen flow rate of 30mL/min and 800 0C, the heating value of gas was high (1738 Btu/SCF). At these conditions, the conversions of bio-oil and olefin yield were as high as 83 wt.% and 43mol%, respectively. However, the syn gas yield of 65mol % was optimum at nitrogen flow rate of 54mL/min at 800 0C (See Figure 3).
40 30
2000
20
Hating Value of Gas (Btu/SCF)
Composition of Product Gas (mol %)
70
Table 2. The Effects of N2 Flow Rate on Total Olefin Production and its Distribution at a Reaction Temperature of 800 0C
1600
10
1200
0 10
20
30
40
50
60
N itr o g e n F lo w R a te ( m L /m in )
800 400
Figure 3. Effects of carrier (nitrogen) gas flow rate on product gas composition for pyrolysis of BDO at 800 0C and BDO flow rate of 4.5 ml/h The effects of N2 flow rate on total olefin production and its distribution are shown in Figure 3 and Table 2, respectively. The production of olefins (mostly ethylene and propylene) initially after showing a slight increasing trend followed a decreasing pattern with nitrogen flow rate (see Figure 3). The olefin content of approximately ~ 43mol% was obtained corresponding to a nitrogen flow rate of 30mL/min (see Table 2). Probably at lower N2 flow rate (20-30 mL/min) BDO had higher residence time for cracking and thus producing more olefins. At higher flow rate (42-54 mL/min) of N2, the concentration of olefins was lower (~10-25 mol%) where as syn gas formation was higher.
18
30 42 54 Nitrogen Flow Rate (mL/min)
Figure 4. Effects of carrier (nitrogen) gas flow rate on total heating value of produt gas during pyrolysis of BDO at 800 0C Effects of temperature. The effects of temperature (650-800 0C) on the conversion of bio-oil, gas yield and its composition have been studied keeping nitrogen and bio-oil flow rates constant, respectively, at 30mL/min and 4.5g/h. Effects of temperature on conversion of BDO and volume of gas produced are shown in Figure 5. The results show that as the temperature is increased from 650 to 800 0C, the conversion of bio-oil to gas and char is increased from 57 to 83 wt. %. Also, as expected, the production of gas is increased with temperature. For example, the product gas volumes obtained at 650 and 750 0C were 730 and 1020 mL, respectively. This corresponds to the fact that from 100 grams of BDO, 26 l to 45 l of gas could be produced with increase in temperature from 650 to 750 0C at constant N2 flow rate of 30 mL/min. However, beyond this temperature, its effect on the gas production was negligible.
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19.2
650
12.8 17.0 2.5
7.2
0.9
40.3
99.9
700
16.3 9.2
3.4
21.6
7.2
1.1
41.2
99.8
750
9.3
6.5
2.1
23.2
9.0
1.3
48.5
99.9
800
12.8 7.7
2.6
27.4
5.5
0.6
43.2
99.8
The effects of temperature on the product gas composition and olefins formed from BDO are given in Table 3. It is also evident from data in this table that the production of maximum olefins is at 48.5 mol% at 750 0C. The methane concentration increases from 19.2 to 27.4 mol% as the temperature increases from 650 to 7500C. Thus it is possible to produce a gas stream having an olefin content of as high as ~48-mol % from BDO. The results also show that the concentration of CO2, C2, C3 paraffin do not change with temperature.
1200
100
BDO Conversion (wt. %)
800
80 600
70 400
60
Conversion BDO
Total Gas Vol. (mL)
1000
90
200
Total Gas Vol., mL 0
50 600
650
700
750
800
850
o
Temperature ( C) Figure 5. Effects of temperature on conversion of BDO and volume of gas produced during pyrolysis of BDO at a nitrogen flow rate of 30 mL (STP)/min
1800
40000
.
C2H6, mol%
Total Total C3H8, olefin, mol% mol%
35000 Btu of gas/ 100 g of BDO
H2, CO, CO2, Temp., mol mol mol CH4, 0 C % % % mol%
Heating valu of product gas (Btu/ SCF) .
Table 3. The Composition Data as a Function on Temperature at Nitrogen Flow Rate of 30 mL/min
1600 30000
1400 25000 Btu/100 g of BDO Btu/Scf
20000 600
700
800
1200 900
Figure 6. Effects of temperature on heating value of product gas for pyrolysis of BDO at nitrogen flow rate of 30 mL/min. The effects of reaction temperature on the olefins composition are shown in Table 4. The effects of reaction temperature on the heating value and energy content of the gas produced at nitrogen flow rate of 30 mL/min are shown in Figure 6. The results indicate that the heating value of the product gas was increased from 1300 to 1700 Btu/SCF with increase in temperature from 700 to 800 0C. This could be due to increase in methane concentration from 19 to 27 mol % in the product gas. Table 4. Effects of Temperature on Distribution Olefins Formed During the Pyrolysis of BDO at a Nitrogen Flow Rate of 30 mL/min and BDO Flow Rate of 4.5 –5.5 mL/h Temperature 0 C 650
C2H4, mol% 20.8
700 750 800
23.0 26.4 31.1
C3H6, mol% 9.4
Higher C3H6Olefins, mol% 10.1
Total olefins, mol% 40.3
9.1 10.2 3.1
9.1 12.0 9.0
41.2 48.6 43.2
It is observed that the concentration of olefins (of which 60-70 mol % is ethylene) is varied in a range of 40 to 48mol % in the product gas with increase in temperature from 700 to 800 0C. However, syn gas production is decreased by 20 mol % in spite of higher production of hydrogen with the temperature increase. The increase in hydrogen production with increased temperature occurred probably because at high temperatures pyrolysis of the BDO subunits, which evolved more hydrogen. Conclusions The present study identifies the pyrolysis of biomass-derived oil as a source of gaseous fuel. In this process, the product gases essentially consisted of H2, CO, CO2, CH4, C2H4, C2H6, C3H8, and C4+ components. This process can be utilized for producing hydrocarbons and synthesis gas for various applications. By adjusting the parameters such as inert gas flow rate and reactor temperature, the composition of the product gas from biomassderived oil can be tuned in the desired direction. The conversion of biomass-derived oil at a flow rate of 4.5 – 5.5 g/h could be increased from 57 to 83 wt.% due to increasing the reactor temperature from 650 to 800 OC at a nitrogen flow rate of 30
Fuel Chemistry Division Preprints 2002, 47(1), 121
mL/min. At 800 0C and nitrogen flow rate of 30 mL/min, composition of various product gas components ranged between: Syn gas 16-30 mol %, CH4 19-27 mol % and C2H4 23-31 mol %. A large amount of total product gas was obtained from BDO at 800 0 C and N2 flow rate of 30 mL/min. Heating values ranged between 1300 – 1700 Btu/SCF. Thus, the present study shows that there is a strong potential for making syn gas, methane, ethylene and high heating value gas from the pyrolysis of biomass-derived oil. References 1. Chantal, P.D; Kaliaguine, S; Grandmaison, K.L; Mahay, A. Appl. Catal. 1984, 10, 317. 2. Sharma, R.K; Bakhshi, N.N. DSS contract file # 23440-09467/01-SZ, Bio-energy Dev. Prog., Energy Mines and Resources, Ottawa, 1992 3. Diebold, J; Soltes, E.J; Miline, T.A. ACS Symp. Ser.376, Amer. Chem. Soc., Washington, DC, 1988, 264. 4. Soltes, E.J; Lin, S.L. ACS Symposium Series 1987, 264, 178185. 5. Churin, E.P; Grange, B. Elseiver Appl. Sci., London, UK, 1990. 2, 616 6. Chaudhari, S.T; Ferdous, D; Dalai, A.K; Bej. S.K; Thring, R.W; Bakhashi, N.N. Fifth International conference on Biomass Conversion, Austria, 2000 7. Boutin, O; Ferrer, M; Lede, J. J. Anal. Appl. Pyrol. 1988 47, 13. 8. Radlein, A.G.D; Piskorz, J; Scott, S.D. J.Anal. Appl. Pyrol. 1987,12, 51. 9. Piskorz, J; Radlein, A.G.D; Scott, S.D; Czernik, S. J. Anal. Appl. Pyrol. 1989, 16, 127. 10. Liu, N.A; Fan, W.C. Fire and Materials. 1998, 22,103. 11. Koullas, D.P; Nikolaou, N; Koukios, E.G. Bioresource Energy, 1998, 63: 261. 12. Maschio, G; Lucchesi, A; Stoppato, G. Bioresource Technology, 1994, 48, 119. 13. Iqbal, M; Dalai, A.K; Thring, R.W; Bakhshi N.N. 33rd International Engineering Conference on Energy Conversion, Colorado, 1998. 14. Bakhshi, N.N; Dalai, A.K; Thring R.W. Division of Fuel Chemistry, 217th ACS National Meeting, California, 1999, 4, 278. 15. Elliot, D.C. IEA Co-operative project D1 Biomass liquefaction Test Facility project , Washington, Pacific Northwest Laboratory, 1983, 4, 87. 16. Bridgwater, A.V; Kuester, J.L. Research in thermo chemical biomass conversion, Phoenix, Arizona, New York: Elsevier Applied Science, 1988, 1177. 17. Milne, T.A; Brennan, A.H; Glenn, B.H. Sourcebook of methods of analysis for biomass and biomass conversion process. London, Elsevier Applied Science, 1990, 327. 18. McKinley, J.W; Overend, R.P; Elliott, D.C. In Proc. Biomass pyrolysis oil properties and combustion meetings, Estes Park, CO. Golden, CO: NREL. NREL-CP-430-7215, 1994, 34. 19. Diebold, J.P; Milne, T.A; Czernik, S; Oasmaa, A; Bridgwater, A.V; Cuevas, A; Gust, S; Huffman, D; Piskorz, J. Development in thermo chemical biomass conversion. Banff. Glasgow: Blackie Academic and professional, Eds.; 1997,1, 533. 20. Piskorz, J; Radlein, D; Majerski, P; Scott, D.S. In Proc. Biomass pyrolysis oil properties and combustion meetings, Estes Park. CO. Golden. CO. NTIS, 1994, 22.
21. Rick F, and Vix U. In Bridgwater, A.V; Grassi, G. Biomass Pyrolysis liquids upgrading and utilization. London & New York: Elsevier Applied Science, Eds.; 1991. 177-218. 22. Diebold, J.P; Czernik, S. Energy & Fuels,1997, 11(5), 1081. 23. Mathews JF, Tepylo MJ, Eager RL and Pepper JM. Can. J. Chem. Eng., 1985, 63, 686. 24. Srinivas, S.T; Dalai, A.K; Bakhshi, N.N. Can. J. Chem. Eng., 1985, 78, 343. 25. Wang, D; Czernik, S; Montane, D; Mann, M; Chornet, E. Industrial and Engineering Chemistry Research, 1994, 36(5), 1507. 26. Czernik, S; Wang, D; Chornet, E. Proceedings of the 1998 U.S. DOE Hydrogen Program Review, 28-30 April, Alexandria, Virginia. NREL/CP-570-25315. National Renewable Energy Laboratory,1998, 2, 557. 27. Baker, E.G; Elliot, D.C. Thermo chemical Biomass Conversion, Eds.; Elsevier Appl. Sci., London UK, 1988, 883-895. 28. Cottam, M.L; Bridgwater, A.V. Thermo chemical Biomass Conversion, Blackie Academic and Professional, London, Eds.; 1994, 2, 1343. 29. Bridgwater, A.V. Advances in Thermo chemical Biomass Conversion Blackie Academic and Professional, London,Eds.; 1994, 2, 1314. 30. Bridgwater AV, In Fast Pyrolysis of Biomass: A handbook, Eds.; PL Press. 1999. 31. Morris, K.W. 4th Biomass conference of Americas, 1999. 32. Piskorz, J. United States Patent No. 5,728,271. 33. Morris, K.W; Johnson, W; Thamburaj, R. 1st World Conference and Exhibition on Biomass for Energy and Industry in Seville, Spain, 2000.
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