THE CATALYTIC TAR CONVERSION TO PRODUCE CLEAN SYNGAS FROM BIOMASS GASIFICATION PROCESS

• Main Author: WALUYO (NIM : 33013008), JOKO
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/28298
• Institution: Institut Teknologi Bandung

<br /> <br /> Tar content in gas produced from biomass gasification has been long identified to cause substantial problems in the implementation of the gasification. Tar may cause blockage and corrosion in equipment and also catalyst deactivation. Tar removal by a catalyst can reduce waste and increase the calorific value of syngas. In the present study, modified natural zeolite were used as tar cracking catalyst, in which tar was produced from pyrolysis and biomass gasification processes. The tar limits allowed for the synthesis of chemical compounds is less than 1 g/Nm3. <br /> <br /> <br /> In the early study, biomass pyrolysis experiments and thermodynamic simulation were performed. The biomass used in this research was coconut shell and palm kernel shell. The pyrolysis of coconut shells was run in updraft pyrolyzer, whereas pyrolysis of palm kernel shells was done on turbular reactor. The updraft pyrolyzer operates autothermally, that heat is generated from partial combustion of biomass, while the heat supply for the turbular reactor is obtained from electrical furnace. Tar pyrolysis results in this main composition of toluene, phenol, naphthalene acetic acid and furfural. Thermodynamic simulation was used to estimate the concentration of tar gasification and the approximate ratio of steam/tar output of the gasifier. the simulation result is estimated that the tar concentration of updraft gasifier is 50 g/Nm3 and the mole ratio of steam/tar is 30. <br /> <br /> <br /> The modification of the natural zeolite was carried out by ion exchange with NH4NO3 and acid leaching by varying the concentrations of 1 M, 3 M, and 6 M HNO3 solutions at 90°C and 6 hours of acid leaching time. The modified zeolite is characterized by crystallinity and tektural morphology using XRD and SEM, elemental components and Si/Al ratio using XRF and EDX, and surface area, pore volume and pore size using nitrogen physisorbtion using BET method. The natural zeolite of Wonosari is dominated by mordenite and clinptilolite phase crystals. Ion exchange and acid leaching in natural zeolites can remove impurities by 69% and 100% for Na and K respectively. <br /> <br /> <br /> The zeolite catalyst activity test was carried out through steam reforming process with toluene as tar model at temperature 750°C, 1 bar, steam/toluene ratio 10 and GHSV 5040/h. The process of acid leaching using HNO3 acid has an effect on catalyst activity. The greater the acid concentration, it will lead to reduced impurities and reduced aluminum which also affects the increasing surface area and pore volume so that the conversion of tar cracking can be increased. <br /> <br /> <br /> Acid leaching on zeolites using 6M HNO3 resulted in a tar conversion of 57.5%. TGA test results showed no significant carbon deposits on the use of modified mordenite zeolites. Addition of Nickel to modified zeolite, can increase the activity of steam reforming catalyst, with tar conversion of 76.7% and 95.6% for 5% Ni and 10% Ni respectively. The kinetic parameters for the Zeolite catalyst with 5% nickel impregnation resulted in activation energy of 113.92 kJ/mol and pre-exponential factor of 3.99 x 106 m3/kg.hr. The reaction is controlled by the reaction of the catalyst surface, as indicated by the results of Thiele modulus, Weisz-Prater and Mears criterion. <br /> <br /> <br /> The catalyst test was also conducted insitu for pyrolysis and gasification of palm kernel shells. Gasification was operated using steam as a gasifying agent. The purpose of this study was to investigate the distribution of pyrolysis and gasification products, as well as modified zeolite activity in tar degradation. The pyrolysis is carried out at a fixed bed reactor with a diameter of 1.5 cm, a flow rate of N2 200 mL/min, a heating rate of 75°C/min to desired pyrolysis temperature. Variations of pyrolysis temperature used are 400, 500, 600 and 750°C. The gasification variations used are the ratio of steam / biomass 0; 0.75; 1.5 and 2.25 and temperature 750, 800, 850°C. Use of the modified zeolite catalyst (ZA66) on pyrolysis tar cracking could result in conversions up to 27%. Whereas in biomass gasification, the use of ZA66 catalyst can reduce the tar content from 4.6 g/Nm3 to 1.9 g/Nm3 at S/B = 1,5 and 750°C. <br /> <br /> <br /> The increasing steam/biomass ratio, resulting in increased tar conversion as well as the increase of H2 concentration. In the ratio of S/B 2.25 produced tar content of 0.72 g/Nm3 and yield H2 of 42.6 mol/kg of biomass. The reaction temperature effect on the concentration of the tar out of gasifier and the acquisition of concentration and yield of the gas product such as H2, CO and CO2. The higher reaction temperature resulted in lower tar and CO2 concentrations and increased yield of H2 and CO. In thermodynamic chemical reaction equilibrium, increasing temperature cause CO production is higher than CO2. The catalytic gasification shows that syngas production has high H2 content, and has H2/CO ratio 2, so the syngas is suitable for synthesis methanol and DME <br />