Hot Gas Cleaning and Upgrading with a Calcined Dolomite Located Downstream a Biomass Fluidized Bed Gasifier Operating with Steam−Oxygen Mixtures

Abstract

Cleaning and upgrading of the hot raw gas from a biomass gasifier, bubbling fluidized bed type, is studied at small pilot plant scale (10 kg biomass fed/h) using a calcined dolomite located downstream from the gasifier. Gasification is made with steam−oxygen mixtures at 800−850 °C and atmospheric pressure. Main variables studied are the gas residence time in the bed of dolomite and the gas atmosphere composition, which depends on the gasifying agent (H2O + O2)-to-biomass and H2O/O2 ratios. H2 and CO content in the flue gas increases by 16−23 vol % and decreases by 15−22 vol % (dry basis), respectively. Although CH4 conversion (elimination) higher than 30 vol % has never been reached, tar conversion (elimination) of 90−95 vol % are obtained with space times of 0.06−0.15 kg calcined dolomite h-1 m-3. A detailed study is here presented on how the calcined dolomite significantly cleans and upgrades the flue gas, increasing also the gas yield by 0.15−0.40 m3(STP)/kg daf biomass fed.

Sulfur Tolerant Magnesium Nickel Silicate Catalyst for Reforming of Biomass Gasification Products to Syngas

“…Figure 5a shows To increase the monolith activity, fine-scale MNS powder were washcoated onto the extruded monolith. It was observed that, under the same reaction conditions, approximately 90-100% CH 4 conversion was achieved at 900 °C, while CO selectivity was 60-65% ( Figure 6). H 2 concentration in the product was 55% and H 2 /CO ratio was approximately 1.8.…”

“…The addition of 10-20 ppm H 2 S to the feed had no apparent impact on the performance (both methane conversion and CO selectivity) (Figure 4). In comparison, CH 4 and C 2+ hydrocarbon conversions were decreased by H 2 S on the MNS washcoated monoliths. It is likely that the total amount of active sites on the granules is more than enough for complete hydrocarbon reforming under the testing conditions.…”

“…For example, the C-H bond energy in the hydrocarbons decreases in a sequence of CH 4 (103 kcal/mol) > C 2 H 6 (98 kcal/mol) > C 3 H 8 (95 kcal/mol), which is in reverse order of their reforming activity. In a separate test under the same conditions but without H 2 S, almost complete CH 4 and C 2+ hydrocarbon conversions were achieved (not shown), suggesting the presence of H 2 S decreased monolith catalyst reforming activity.…”

Tar Removal From Biomass Gasification Streams: Processes and Catalysts

“…Um resultado interessante da pesquisa foi a observação da presença do limite difusional intrapartícula, já que a conversão de alcatrão foi influenciada pelo diâmetro de partícula do catalisador (na faixa de 0,63-1,6 mm). 77 Posteriormente, os autores compararam as atividades da dolomita e da olivina em testes de gaseificação, conduzidos em leito fluidizado e borbulhante com ar, confirmando a maior atividade da dolomita. No entanto, coletou-se uma maior quantidade de particulados para a dolomita (4 a 6 vezes mais), devido a sua menor dureza, facilitando a sua quebra e posterior arraste.…”

Biorefinerias para la producción de biocumbustibles de segunda generación.

“…Combina el proceso de intercambio agua-gas con un adsorbente que remueve el CO 2 , que a su vez incrementa la producción de H 2 aumentando la eficiencia de conversión de CO. Este proceso es aplicado como un sistema para remover el carbón de los combustibles fósiles antes de que sean empleados en la producción de energía. El carbono es removido quedando una corriente de hidrógeno que posteriormente es utilizada en turbinas de gas donde no se produce dióxido de carbono [100].…”