Experimental Study On Carbon Capture By Ammonia At Low Temperature

The excessive combustion of fossil fuels results in the remarkably increased carbon dioxide emissions,which exacerbate the global greenhouse effect.For avoiding the continuous rise of global temperature,it is of great concern to reduce carbon dioxide concentration.Carbon capture and storage as a key technology to reduce carbon dioxide emissions has gained wide attentions.Due to strong absorption capacity and low energy consumption,aqueous ammonia is regarded as an ideal alternative for carbon dioxide mitigation.However,the strong volatility of ammonia gives rise to the unexpected ammonia escape and additional environmental pollution,which seriously inhibits its commercial applications.Therefore,it is of benefit to the carbon dioxide absorption by aqueous ammonia to propose the ammonia escape inhibition measures.In this work,the aqueous ammonia with the Cr3+and Ni2+ mixed at low temperatures is proposed and experimentally investigated to inhibit ammonia escape and enhance carbon dioxide absorption.By taking total ammonia escape,carbon dioxide absorption rate and ammonia escape per unit carbon dioxide absorption as evaluation criteria,the effects of Ni2+ and Cr3+on ammonia escape are compared.The results show that the increased reaction temperature and ammonia concentration result in the aggregated ammonia escape.The ammonia slip gets weakened but the carbon dioxide absorption is hardly affected with Ni2+ and Cr3+used.The additive Ni2+is basically superior to Cr3+in restraining ammonia escape,that the maximum inhibition efficiency of Ni2+is 50.5%while Cr3+is only 39.9%.By adding additives,the reaction temperature can be raised to reduce the energy consumption of carbon dioxide absorption.It is recommended to take comprehensive measures of ammonia freezing and additives for the carbon dioxide absorption by ammonia solution.In addition,the effects of ammonia concentration,ammonia temperature,carbon dioxide volume fraction and the ratio of diameter to height of spray tower on ammonia decarbonization at low temperatures were studied.The results show that ammonia concentration has a positive correlation with ammonia escape rate and carbon dioxide absorption rate;the higher the ammonia temperature is,the greater the ammonia escape degree is,and the greater the carbon dioxide absorption rate is;the increase of carbon dioxide volume fraction and aspect ratio will inhibit ammonia escape,but also reduce the carbon dioxide absorption rate.This experiment supplemented the data of the process of ammonia water absorbing carbon dioxide at low temperature,and laid a foundation for the application of the process of ammonia escaping inhibition by the combination of chilled ammonia and additives.