Pilot-Scale Fluidized-Bed Co-gasification of Palm Kernel Shell with Sub-bituminous Coal

Abstract

Currently, there are many studies that analyze the co-gasification or co-combustion of biomass with coal in fluidized-bed reactors. Mixing these two materials takes advantage of particle segregation as a result of the differences in density, shape, and size; this phenomenon requires due attention because it can lead to reactor operation issues. Some common problems seen with biomass are gap flow, plug flow, and large bubbles that reduce mass and energy transport, thus lowering the quality of the syngas product. In this study, we found that mixing biomass palm kernel shell (PKS) with coal greatly reduces these problems. Furthermore, we propose that this technique can be applied to other biomasses than the biomass used in our study without observing fluid dynamic issues. Continuous feeding co-gasification tests were performed with PKS and sub-bituminous coal type A (sub-bA coal) in a pilot-scale fluidized-bed reactor using air as the gasifying agent.

Gasification of coal, Chenopodium Album biomass, and co-gasification of a coal-biomass mixture by thermogravimetric-gas analysis

“…The highest gas production (Yg, 76.6 %) is obtained from the mixture (P3), which is consistent with the investigations reported by Emami-Taba et al [11]; the differences with respect to coal (P1, 36.8) and biomass (P2, 42.8) are 39.8 % and 33.8 %. This behavior is comparable with gasification tests of biomass carbon mixtures, performed with ER of 0.3 and 0.4 in other investigations[20,53], in which it was…”

“…The increase in CO2 is commonly observed in tests with ER equal to 0.4 [46], and the presence of oxygen in the biomass [11]. Using air as a gasifying agent does not enhance the concentration of hydrogen since it does not promote the reactions R6 and R8; therefore, the reaction of methanation (R7) becomes irrelevant, but the formation of CO2 is favored [20,41].…”

“…At high temperature, the dehydration reactions have little relevance, so the moisture content in the outgoing gas stream is negligible and reactions R6 and R8 are not observed that when the biomass content in the mixture and the ER ratio are higher, production improves [20]. The conversion of carbon (Ecc) improves with the high content of volatile matter that increases the reactivity of the biomass and promotes the formation of free radicals, favoring the reactions of decomposition, oxidation and gasification; in addition, the increase in hydrogen and oxygen contents from biomass make the conversion of carbon during co-gasification is greater than in coal gasification [11].…”

“…The gas samples were cleaned in a system consisting of a gas bubbling device in isopropanol at 0 °C to capture tar, and a filter with silica gel to remove moisture, before performing the gas chromatographic analysis. The results of the characterization of gases and the process were used to evaluate the performance of the same through parameters such as gas production (Yg), carbon conversion efficiency (Ecc) and thermal efficiency (ETh), which are determined according to equations 1 -4 [20]:…”

“…Carbon conversion efficiency was calculated from Eq.3, where wCO, wCO2, wCH4, wC2H4 are the mass fractions of CO, CO2, CH4, C2H4 in gas, wC and wash are carbon and ash in the fuel, respectively, while the thermal efficiency was calculated according to the HHVg of gas and LHVf of solid fuel. For the previous calculations, it was considered that the moisture content in fuel is extracted during the drying phase [20], nitrogen and air are injected dry to the process; therefore, the incidence of dehydration reactions [18], as well as of evaporation of minerals [21], is considered negligible. Likewise, it is considered that NOx is not produced, because the nitrogen from the biomass leaves as ammonia groups during pyrolysis between 300 and 600 °C; wheareas, the N2 that is in the coal at high temperatures remains strongly linked to structures such as pyrols and quaternary functional groups [22][23][24], making part of rings of aromatic rings in clusters formed during the graffiti of the carbonaceous structure.…”