Microsoft Word - 192wang.doc CHEMICAL ENGINEERING TRANSACTIONS VOL. 37, 2014 A publication of The Italian Association of Chemical Engineering www.aidic.it/cet Guest Editors: Eliseo Ranzi, Katharina Kohse- Höinghaus Copyright © 2014, AIDIC Servizi S.r.l., ISBN 978-88-95608-28-0; ISSN 2283-9216 Biomass Gasification Between 800 and 1,400 °C in the Presence of O2: Drop Tube Reactor Experiments and Simulation Joseph Billauda*, Sylvie Valina, Gilles Ratela, Sebastien Thierya, Sylvain Salvadorb aCEA, 17 rue des Martyrs, 38054 Grenoble Cedex 09, France bRAPSODEE, FRE-CNRS 3213, Ecole des Mines d’Albi-Carmaux, 81013 ALBI CT Cedex 9, France joseph.billaud@cea.fr Beech sawdust particle conversion in a drop tube furnace was studied between 800 and 1,400 °C. Particular attention was paid to the influence of temperature and to the presence of oxygen on the gasification process. As temperature increases, light hydrocarbon production decreases and the CO + H2 production (gas of interest for biofuel production) increases. Presence of oxygen in the gasification atmosphere allows consuming a high part of light hydrocarbons and enhancing carbon conversion into gas. However, high yields of CO2 and H2O were observed and the total yield of CO + H2 was lower than in pyrolysis conditions. 1. Introduction Biomass gasification is generally considered as one of the most promising alternative way of energy production for electricity, heat and transport. To produce biofuels from syngas, Entrained Flow Reactor (EFR) is known as one of the most suitable reactor. The main advantage of this technology is the high conversion of biomass into syngas with very low tar contents. Currently, only coal gasification is available at commercial scale and biomass gasification using this technology is not achieved. EFR is characterized by high operating temperature (~1,500 °C), high pressure (>30 bar), short particle residence time (~5 s) and high heat flux at particle surface (>1 GW.m-2). It is generally operated as an autothermal reactor which means that a part of biomass is burnt to supply enough energy for gasification reactions. Biomass particles have to be small (~300 µm) to avoid transfer limitations in the particle and therefore to maximize the gasification rate. The phenomenology linked to biomass conversion in conditions similar to those of an EFR has rarely been studied until now. The experimental device usually used to reproduce some conditions of an EFR is the Drop Tube Reactor (DTR). Some works deal with experimental biomass gasification studies in a DTR at temperature above 1,000 °C. Fast pyrolysis of biomass in inert atmosphere has been studied by Zhang et al. (2006) and Septien et al. (2012). Other studies deal with gasification with the addition of H2O (Septien et al. (2013), Zhang et al. (2010)), of O2 (Zhang et al. (2010), Zhou et al. (2009)) or a mixture of O2 and H2O (Qin et al. (2012)). The present study aims to investigate the influence of the presence of O2 in the atmosphere on biomass gasification in an EFR. Preliminary calculations were made to estimate an appropriate range of experimental conditions. The experiments were conducted in a DTR with beech wood particles of 315 to 450 µm. 2. Preliminary calculations As said before, biomass gasification process using EFR need to be developed. Indeed some pilot scale EFR using biomass as feedstock already exist (Weiland et al. (2013)) but no industrial plant based on this DOI: 10.3303/CET1437028 Please cite this article as: Billaud J., Valin S., Ratel G., Thiery S., Salvador S., 2014, Biomass gasification between 800 and 1,400 °c in the presence of o2: drop tube reactor experiments and simulation, Chemical Engineering Transactions, 37, 163-168 DOI: 10.3303/CET1437028 163 techno reacto To ch with s In the Heat the re Figure From neede is def the inj The c Where Table These condit 3. Ex 3.1 Bi Bioma 450 µ Inpu Outp ology is work or. hoose relevant some design c e pressurized losses were e eactor (Gibbs E e 1: Scheme o these data a ed oxygen flow ined as the w jected biomas cold gas efficie e Qi is the ma 1: Results of e calculations tions were the xperimental iomass chara ass used as fe m. The proxim H2O/ ut data O2/B PN2 ( Psteam PO2 ( put data Prod H2/CO Cold king yet. It im t experimenta choices and as biomass feed estimated at 1 Energy minim of the modelle and assumptio w rate for diffe whole mass of ss. ency is defined ss flow rate a f preliminary ca show that th en chosen as t acteristics eedstock in th mate analysis C iomass (g/g) bar) m (bar) bar) uct Gas LHV ( O (mol/mol) gas efficiency plies a lack o al conditions fo ssumptions. ing line, the b 00 kW.m-2 of ization) was a d EFR ons, an energ erent steam in water injecte d by Eq (1). nd LHVi is the alculations e cold gas ef the ones corre is study is bee and the ultima (MJ/kg db) y of knowledge or our experim biomass volum f intern surfac assumed. gy balance w nlet flow rates d (steam and e Lower Heatin fficiency incre esponding to t ech sawdust. ate analysis of 0.14 0.57 14.4 0 25.6 12.7 0.50 0.71 of actual op mental study, me concentrat ce. Thermodyn was calculated . Results are g moisture) on ng Value. eases as H2O/ the lower H2O/ Particles were f this biomass 0.5 0.62 9.1 13.4 17.5 11.9 0.62 0.66 erating condit an EFR was ion was cons namic equilibr d on the reac given in Table the mass of /C ratio decre /C ratio. e sieved in a s are shown in 1 0.68 6.0 21.2 12.8 10.7 0.76 0.59 tions in this t modelled (Fig idered to be 2 rium at the ou ctor to evalua e 1. The H2O/ carbon conta eases. Experi size range of n Table 2. type of gure 1) 20 v%. utput of ate the C ratio ined in (1) mental 315 to 164 Table Proxi Moistu Volati Fixed Ash (w b by dif 3.2 De The d electr 0.075 can re The w stream reacto Figure An oil to coll part p the ta conde 3.3 Ga A mic C2H4, gas. H 3.4 Co In this atmos with o kept c 2: Proximate mate analysi ure (wt%) le matter (wt% carbonb (wt% wt% dry basis fference escription of drop tube reac ical heater wit m in internal each a maxim wood particles m, which can or. e 2: Scheme o -cooled (110 lect gas and t passes through ar protocol. T ensation. as analysis cro-gas chroma C2H6, C3H8, H2O content in onditions of t s study, expe sphere at seve oxygen were d constant and e and ultimate s % dry basis) % dry basis) s) the drop tub ctor (DTR) is re th three indep diameter. The um temperatu are continuou be N2 or a m of the drop tub °C) sampling the remaining h a settling bo This part of atograph (μ-G C6H6). A Flam n the gas was the experime eriments were eral temperatu deduced from equal to 0.42 analysis of be 9.8 85 14.2 0.8 e reactor epresented in endent heatin e heated zone ure of 1,400 °C usly fed into th ixture of N2, a be reactor probe can be solid. A fracti ox and a filter the experime GC) allows ana me Ionization measured by ents e performed i ures, 800 °C, preliminary c (g/g, db). Gas eech sawdust U C H N S O Figure 2. It co ng zones. The e is 1.2 m long C. he reactor usi air and/or H2O inserted at di ion of the exh and flows to g ental facility i alyzing main g Detector (FID a psychromet in a nitrogen 1,000 °C, 1,20 calculations fo s sampling wa Ultimate anal C 50 H 5. N <0 S 0. Ob 44 onsists of an a dimensions o g. The DTR wo ng a gravimet O, is electrical ifferent height aust gas is su gas analyzers is heated (15 gaseous produ D) gives the t ter. inert atmosp 00 °C and 1,4 r an EFR (Ta as performed ysis (wt% dry 0 8 0.3 014 4 alumina tube i of the tube are orks at atmos tric feeding sy ly pre-heated s in the bottom ucked in the s and another 50 °C) to av ucts (CO2, CO total hydrocar phere and an 400 °C. Condit ble 1). The O at the bottom y ash free ba inserted in a v e 2.3 m in leng spheric pressu ystem. The ma before enteri m half of the r sampling probe part passes th void steam a O, CH4, N2, H2 rbons content n oxygen con tions of exper O2/biomass rat m of the heated asis) vertical gth and ure and ain gas ing the reactor e. One hrough nd tar , C2H2, of the taining riments tio was d zone 165 and the gas residence time was kept constant for each test run (4.3 s). Experimental conditions are given in Table 3. Experiments with oxygen and pyrolysis tests at 800 °C were performed twice. Table 3: Operating conditions of experiments Pyrolysis experiments Temperature (°C) Biomass feedstock rate (g.min-1) Air flow rate (NL.min-1) N2 flow rate (NL.min-1) O2 partial pressure (bar) 800 1.3 0 18.8 0 1,000 1.3 0 15.9 0 1,200 0.65 0 13.7 0 1,400 0.65 0 12.1 0 Partial oxidation experiments Temperature (°C) Biomass feedstock rate (g.min-1) Air flow rate (NL.min-1) N2 flow rate (NL.min-1) O2 partial pressure (bar) 800 1.3 1.8 17.1 0.020 1,000 1.3 1.8 14.1 0.023 1,200 1.3 1.8 12.0 0.027 1,400 1.3 1.8 10.3 0.030 This DTR is designed for small biomass feeding rates and for working in diluted conditions. Although the O2 partial pressure is much lower (0.02-0.03 bar) than in an EFR (Table 1), the O2/biomass mass ratio was chosen to be representative of an EFR in order to have similar behaviour for gas phase reactions. 4. Results and discussion 4.1 Gas yields Individual gas yields are given in Figure 3 (H2, CO, H2O, CO2) and Figure 4 (CH4, C2H2, C2H4, C6H6). In pyrolysis experiments, H2, CO, H2O, CO2 and CH4 are the major gas species, followed by C2H2, C2H4, C2H6, C3H8 and C6H6. H2 and CO yields increase with temperature, while H2O, CH4 and C2H4 yields decrease. CO2 yield slightly increases with temperature until 1200 °C and then decreases. C2H2 and C6H6 yields reach a maximum at about 1,000 °C. C2H6 and C3H8 yields can only be quantified at 800 °C in pyrolysis conditions – 12.10-5 and 9.10-5 (mol.g-1, db) respectively. The water gas shift equilibrium can partly explain evolutions of CO, CO2, H2 and H2O yields (from 800 °C to 1,400 °C, Kshift/ Kshift-eq passes from 0.06 to 1.2 in pyrolysis conditions and from 0.08 to 1.3 in presence of oxygen). The tendencies observed for C2H4, C2H6, C3H8 and CH4 yields can be explained by cracking and reforming reactions which are enhanced by high temperature. C2H2 and C6H6 yields show a different evolution with temperature. The presence of a maximum can be explained by two different and competitive phenomena (Roth, 2006). First, C2H2 is mostly produced by thermal degradation of light hydrocarbons and C6H6 can be produced by polymerization of C2H2. On the opposite, C2H2 and C6H6 are two important precursors of soot production which occurs from 900 °C and reach a maximum at about 1,400 °C. In the presence of O2, gas species yields evolutions versus temperature are approximately the same as in the pyrolysis tests. Three major differences are noticed. First, H2, C2H2, C2H4, C2H6, C3H8 and C6H6 are lower in presence of O2 than in pyrolysis conditions. It can be explained by combustion reactions which compete with the other reactions of production or consumption of these products. Secondly, CO2 and H2O yields are higher in presence of O2 than in pyrolysis conditions. Combustion reactions are also responsible for this result. The third difference concerns the evolution of CO and CO2 yields versus temperature. CO yield reaches a minimum and CO2 yield reaches a maximum at about 1,000 °C. This behaviour is not easy to understand and no explanation can be given for the moment. 4.2 Carbon conversion Other products of pyrolysis and partial oxidation of biomass are char, tars (condensable species) and soot. In order to estimate these products, balances on carbon detected in gas phase are given in Table 5. During experiments char and soot were sampled. Char could be sampled in all experimental conditions although soot production was detected only from 1,000 °C with few soot particles. Above 1,000 °C soot was produced in higher amount in pyrolysis case and also in presence of oxygen. Carbon conversion into gas is shown in Figure 5 as a function of temperature. It is higher in presence of oxygen than in an inert atmosphere. Char and/or tar combustion could explain this observation. Production of soot could explain the decrease of carbon conversion in gas phase as temperature increases in the presence of O2. 166 Figure prese Figure prese e 3: Experime nce of oxygen e 4: Experime nce of oxygen ntal yields of H n ntal yields of C n H2 (a), CO (b) CH4 (a), C2H2 , CO2 (c) and (b), C2H4 (c) a H2O (d) in pyr and C6H6 (d) i rolysis conditio in pyrolysis co ions and in onditions and iin 167 Figure 5. Co Fast p on the influen hydro increa hydro obser This s eleme the inf with th gasific accura involv Refer Qin, K Roth, Septie Septie Weila Zhang Zhang Zhou, e 5: Part of ca onclusion an pyrolysis and e effect of tem nce on the c carbon produ ases. Presenc carbons and e rved and the to study will be ental balances fluence of ste he GASPAR m cation, gas ph ately biomass ved in biomass rences K., Jensen, P Reactor: G K., 2006. Soo Shaker Ve en, S., Valin, S woody bio en, S., Valin, millimetric 1089. nd, F., Hedma Blown Ent g, Y., Kajitan Covering M g, Y., Kajitani pyrolysis a J., Chen, Q. high-temp arbon initially in nd prospect partial oxidati mperature on carbon conver uction decreas ce of oxygen enhancing ga otal yield of CO completed b s. Other exper am on biomas modelling tool hase reactions s gasification s gasification. .A., Lin, W., J Gas Product D ot Formation D erlag, Bochum S., Dupont, C. mass fast pyr S., Peyrot, M wood particle an, H., Marklu trained-Flow G ni, S., Ashiza Medium- and i, S., Ashizaw and gasificatio , Zhao, H., Ca erature entrai n biomass con ts on of beech s biomass conv rsion and the ses and the C in the gasifi s carbon conv O + H2 was lo by tar and ch riments will be ss conversion (Septien et a s and soot pro in presence Jensen, A.D., Distribution and During the Pro m, Germany. , Peyrot, M., S olysis at high M., Spindler, B es in a drop t und, M., Wiinik Gasification of wa, M., Miur High-Tempera wa, M., Oki, Y on of biomass ao, X., Mei, Q ned-flow gasif nverted in gas sawdust were version and g e gas phase CO + H2 prod ication atmos version into ga ower than in py har analyses e conducted in and gas phas al., 2013), whi oduction in ou of O2. This w 2012. Bioma d Soot Format oduction of Sy Salvador, S., 2 temperature ( B., Salvador, S tube reactor: kka, H., Öhrm Wood Powde ra, K., 2006. ature Ranges. Y., 2010. Tar in a drop-tube Q., Luo, Z., Ce fier. Biotechno s (incondensab experimental gas production composition. duction (gas o sphere allows as. However, yrolysis condit and quantifica n presence of se reactions. T ch includes m ur DTR. The m will allow bett ass Gasificatio tion. Energy F yngas from the 2012. Effect o (1000–1400°C S., 2013. Influ Experiments man, O., Geba er. Energy Fue Peculiarities . Energy Fuels r destruction e furnace. Fue en, K., 2009. B ol. Adv., 27, 60 ble species) ly investigated n. Temperatur As temperat of interest for consuming a high yields of tions. ation which w oxygen and s The experimen models for biom model will be ter understand on Behavior in Fuels, 26, 5992 e Partial Oxida f particle size C). Fuel, 97, 20 uence of steam and modelling art, R., 2013. P els, 27, 932–94 of Rapid Py s, 20, 2705–27 and coke form el, 89, 302–30 Biomass–oxyg 06–611. d in a DTR fo re has an imp ture increases r biofuel prod a high part o f CO2 and H2O will allow spe steam to inve nts will be sim mass pyrolysis improved to ding of pheno n an Entrained 2–6002. ation of Diese and temperat 02–210. m on gasifica g. Fuel, 103, Pressurized O 941. yrolysis of Bi 712. mation during 09. gen gasificatio ocusing portant s, light uction) of light O were ecifying stigate mulated s, char predict omena d Flow el Fuel. ture on ation of 1080– Oxygen omass g rapid on in a 168 Controfacciata.pdf iconBM 4-7 May 2014, Florence, Italy Guest Editors Volume 35 : Proceedings of the 16th Conference Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction PRES’13, Rhodes, Greece, 29 September - 2 October 2013 Volume 36 : Proceedings of the 6th International Conference on Safety and Environment in Process & Power Industry, Bologna, Italy, 13-16 April, 2014 Disclaimer Official Organizer IndiceAutori.pdf AUTHOR Index Pagina vuota Controfacciata.pdf iconBM 4-7 May 2014, Florence, Italy Guest Editors 25.pdf Reduction of PM Emissions from Biomass Combustion Appliances: Evaluation of Efficiency of Electrostatic Precipitators Gabriele Migliavaccaa *, Carmen Morrealea, Francesca Hugonya, Ivan Tombolatob, Giordano Pessionb 442-444.pdf 3.4 Evaluation of the briquettes combustion 442-444.pdf 3.4 Evaluation of the briquettes combustion 25.pdf Reduction of PM Emissions from Biomass Combustion Appliances: Evaluation of Efficiency of Electrostatic Precipitators Gabriele Migliavaccaa *, Carmen Morrealea, Francesca Hugonya, Ivan Tombolatob, Giordano Pessionb