Study On Capture Of Carbon Dioxide From Biomass Pyrolysis Gases

Carbon Dioxide（CO₂） is one of the main greenhouse gases which plays an importantrole in the process of global warming. Nowadays, the world is devoted to reducing carbonemissions. China also faces great pressure on CO₂emission reduction. Using biomass gasinstead of fossil fuel is one of the ways of new energy development in China. But the highcontent of CO₂in biomass gas seriously affects its industrial value.So it is necessary to findan effective method to capture CO₂from biomass gas, which not only improves theindustrial value of biomass gas but also helps reducing CO₂emission. This thesis studiedthe CO₂absorption performances by several calcium-based sorbents in fixed-bed reactorand alkali solution in self-made spray-packed tower. The main results were listed asfollows:Solid absorbent research results1、 It was found in the study on CO₂absorption performances of differentcalcium-based materials that calcium hydroxide as the precursor of the absorbents had thebest single absorption performance. Its single-time absorption capacity was that one gramabsorbent could absorb0.31g CO₂（showed0.31g CO₂/（g absorbent））, which about threetimes of that of calcium carbonate.2、 The Study on the regeneration cycle of the absorbents demonstrated thatcalcium-based materials, the precursor of which was dolomite, had the best cycling stabilityfor the maximum absorption capacity could reach0.3g CO₂/（g absorbent） and couldmaintain81%of it after seven cycles.3、Study on the CO₂single and cycle absorption performances of calcium-basedabsorbents modified by metal showed that the absorbents adding La and Al had the bestperformance on single absorption as well as the best cycling stability. Its absorptioncapacity could reach0.1gCO₂/g absorbent. Absorbents adding Mg and Al had the bestcycling stability which could reach0.128g CO₂/g absorbent after six cycles.4、Through comprehensive investigation on all calcium-based absorbents, It showed that absorbents with calcium and magnesium oxidizers had the best cycling stability whichwere suitable to remove low concentration CO₂from biomass gases in industry.Alkali solution absorbents research results1、Study on the fillers showed that different fillers had various effect on CO₂absorption by different absorbents. Among the fillers, No.1, No.2and No.3were semi-coke,albite-fragment and polypropylene plastic ball, respectively, which the sodium hydroxideand MEA had good CO₂absorption behavior in No.1and No.2while No.1was the best.However, the three fillers made no differences in aqueous ammonia.2、Through comparison,25cm is the best height for the self-made spray-packedtower. Under this condition, sodium hydroxide had the best absorption efficiency whileMEA ranked the second and aqueous ammonia was the worst.3、Effects of different operating and design parameters, including concentration ofabsorbent, absorbent volume flow rate, total gas flow rate and concentration of CO₂on CO₂removal efficiency were investigated and found that the best practical operating parameters:the concentration of sodium hydroxide was0.4mol/L, absorbent volume flow rate was1.1L/min, concentration of CO₂was30%and total gas flow rate was4.84L/min, which theCO₂removal efficiency was97%.4、Study on the regeneration cycle of the absorbents showed that when the amount ofcalcium hydroxide regenerant was two times as the sodium carbonate with eightregeneration hours and regenerated twice could reach the best.