Processing optimization of pine rod gasification catalyzed by bentonite/limonite modified dolomite

Abstract: In order to improve the catalytic activity, anti-carbon deposition and regeneration performance of dolomite catalyst which was easy to accumulate carbon and deactivate during biomass catalytic gasification, a fixed-bed suction gasifier test system was adopted in this study. Firstly, rod-shape particles were prepared from pine chips wastes using Fe-Dol-Ben (bentonite/limonite modified dolomite) as catalyst and fixed-bed downdraft gasifier as main body. An experimental system for biomass steam gasification was established. Then the high temperature steam catalytic gasification test was carried out with the above two raw materials. Finally, the effects of several factors on the catalytic gasification performance of pine wood and carbon deposition on the catalyst surface were studied. The factors affecting the catalytic gasification performance and carbon deposition on the catalyst surface were gasification temperature (temperature range is 700-1000 ℃), iron content (mass percentage range is 5%-20%) and the number of catalyst used (catalyst used number is 1-4). The results showed that the mass percentage of iron in FeDol-Ben catalyst was 15%, the gasification temperature was 900 ℃, and the volume fraction of hydrogen in gasification gas reaches the maximum of 58.38% under the condition that the mass ratio of steam to pine wood was 1. The results also showed that with the increasing of gasification temperature, the carbon deposition in FeDol-Ben catalyst decreased gradually, reaching the minimum value at 1 000 ℃, 80% lower than that at 700 ℃. In addition, the volume fraction of hydrogen in gasified gas increased first and then decreased with the increasing of iron content. At the same time, the carbon content decreased first and then increased, and the catalytic effect was better when the iron mass content was 15%. Under the same conditions as bentonite and pre-modified dolomite, the carbon deposition of Fe-Dol-Ben catalyst decreased by 80.6% and 53.6%, respectively. The experiment of catalyst regeneration and reuse showed that the crystal phase of the catalyst was basically the same as that of the pre-catalyst after the Fe-Dol-Ben catalyst regeneration at 700 ℃. The volume fraction of hydrogen in gasification gas decreased with the increasing of the number of times of regeneration, and the carbon deposition of the catalyst increased gradually. The results also showed that the volume fraction of hydrogen was still close to 50% after four times of catalytic gasification, which maintained the catalytic effect. In summary, considering the gasification effect, carbon deposition and economic factors, the optimization conditions were iron content of 15% and gasification temperature of 900 ℃. The study can provide reference for the development of bentonite/limonite modified dolomite catalyst and biomass high temperature steam catalytic gasification technology.