Experimental Study On Decarbonization By Aqueous Ammonia Under Oxy-enrich Combustion

Oxy-fuel combustion is a clean coal power generation technology, which cancapture CO2directly and control pollutant emissions integratedly. While air separationenergy consumption leads to a dramatic decline in economics. In order to seek a newCO2emission reduction technology for lower investment energy consumption and bettereconomics, this paper presents an oxy-enrich combustion technology. As a new CO2emission reduction technology, instead of pure oxygen in oxy-fuel combustion,oxy-enrich combustion uses air+pure oxygen for coal combustion. The purpose is toimprove the economics of CO2emission reduction.In this paper, experimental studies on carbon removal by aqueous ammonia underoxy-enrich combustion (30%~40%v/v CO2in flue gas) in a packed column were carriedout，compared with MEA. Effects of different operating and design parameters on CO2removal efficiency, including CO2concentration, aqueous ammonia concentration, pHvalue, aqueous ammonia flow, packing height, flue gas temperature and total flue gasflow, were investigated. The research results show that: when aqueous ammoniaconcentration is higher than4%, the CO2removal efficiencies under aircombustion(15%CO2) and oxy-enrich combustion(35%CO2) are94.65%and94.36%respectively, nearly the same; increasing aqueous ammonia concentration, pH value,aqueous ammonia flow and packing height all can improve the removal efficiency, butwhen pH value is10.5, a certain fluctuation occurs in the removal efficiency curve; withflue gas temperature increasing, the removal efficiency increases firstly, and thendecreases, the optimal temperature is50℃; when total flue gas flow increases, theremoval efficiency declines. Under comparable conditions, by comparing, the resultsshow that carbon removal by aqueous ammonia is better than MEA.Compared with oxy-fuel combustion, oxy-enrich combustion technology need lesscirculating flue gas and oxygen volume, so the investment and energy consumption ofASU (air separation unit) and circulating blower reduce. Compared with conventionalcombustion, flue gas volume into CO2capture device under oxy-enrich combustionreduces greatly, contributing to reducing the volume of absorber and regenerationcolumn and decarburization energy consumption. According to the experimental results, economic evaluation of decarbonization by aqueous ammonia under oxy-enrichcombustion is calculated by using IECM, combined with the economic model. It isfound that CO2avoided cost under oxy-enrich condition is lower than AA underair-combustion and oxy-fuel combustion, and the corresponding CO2avoided cost is201.91RMB/tCO2,248.18RMB/tCO2,206.21RMB/tCO2, decreased by about46.27RMB/tCO2and4.3RMB/tCO2, respectively.