The Adsorption Enhanced Decarburization Of Syngas With The Coupling Of Chemical-looping

In order to remove CO and CO2 from raw gas of synthesis ammonia,the traditional decarburization of this syngas utilizes CO shift, CO2 removal and methanation process in industry. This decarburization process is complex and its energy consumption is high. In this paper, based on the adsorption enhanced decarburization of syngas with the coupling of chemical-loopings principle,the syngas decarburization and the solid regeneration are carried out.A new modified adsorbent(codenamed MV-CaO) is prepared to enhance the adsorption performance of adsorbent through adding one transition metal oxide(codenamed MV),and the adsorption and desorption performance of MV-CaO are studied.On this basis,using iron oxide as oxygen carrier and catalyst, the syngas flow rate,temperatue,the mass ratio of adsorbent to iron catalyst,the molar ratio of steam to syngas in syngas decarburization stage are investigated with MV-CaO as adsorbent in a fixed-reactor.In solid regeneration stage,in order to improve the regeneration performance,the thermal coupling of solid particles,regeneration temperature and the inlet way of carrier gas are studied.Multiple cyclic experiments are carried out to investigate the stability of this system.The detailed results are listed as follows.The adsorption performance of MV-CaO is better than that of CaO.When the MV loading is 1.97wt.%in this adsorbent,the highest decarburization capability is obtained.MV is catalytic to the adsorption and desorption of CO2.In syngas decarburization stage,the optimal conditions are determined, namely the syngas flow rate is 40mL/min, temperature is 550℃,pressure is 0.1MPa,the molar ratio of steam to syngas is 7:1, the mass ratio of adsorbent and iron catalyst is 2:1.Under these conditions, the cumulative treatment capacity of syngas on unit iron catalyst can achieve 0.70 L/g during decarburization stage, the carbonation rate of MV-CaO is 37.20%,while CO and CO2 are completely removed from syngas.In solid regeneration stage,the heat from the oxidation of iron catalyst can promote the thermal decomposition of the carbonate of MV-CaO and shorten the calcination time,so the thermal coupling is realized by the oxidation of iron catalyst and the decomposition of adsorbent;the optimal temperature for solid regeneration is 850℃;the regeneration time of solid particles can be shortened within 90min by two-stage inlet way of carrier gas and under this condition,the oxidation rate of iron catalyst is above 98%,the decomposition rate of the carbonate of MV-CaO is above 94%. Through 13 cyclic times of decarburization-regeneration reaction,the decarburization capability of this process showes apparent decline after circulating three times.This capability reaches a new balance till the seventh cycle is carried out.The final regeneration rate of MV-CaO is stable above 94%,this showes that the performance of adsorbent after regeneration is stable and can be used repeatedly. The reason for the decline of decarburization capability may be explained through the physical changes which are caused by sintering occurring in the solids.