| The emission of CO2is going to increase every year due to the more and more energy consumption with the rapid development of human society. It is widely accept that fossil fuel utilization represents a major source of anthropogenic CO2. CO2capture and sequestration is an effective measure to reduce CO2emission during the Utilization of fossil fuels. Ca-based sorbent has the advantages of high adsorption capacity, renewable, high-temperature separation and enrichment CO2in many CO2capture technologies. The technology of coal chemical looping gasification or Ca-looping for CO2separation and capture based on the cycylic calcination/carbonation reaction of Ca-based CO2sorbent is an effective measure to reduce CO2emission and receiving more and more attention. However, it now has the problems of the rapid decay in activity, abrasion and sintering, etc. To solve the above-mentioned problems, the experiments under pressurized steam-containing conditions and high-aluminate modification conditions were carried out from the characteristics of carbonation reaction in this artistic.The effect of carbonation pressure (0.1～0.7MPa), steam concentration (0～60vol%) and carbonation temperature (650～800℃) on the cyclic calcination/carbonation performance of CaO-based sorbent for CO2capture was investigated using a high pressure TGA and compared with the effect of carbonation pressure in pressurized without steam-containing conditions and steam concentration in atmospheric steam-containing conditions and carbonation temperature in atmospheric steam-containing conditions on the multi-cycle performance of CaO-based sorbent. Microstructure analysis from Scanning Electron Microscope images was provided to understand the influence mechanism of steam on cyclic carbonation of CaO-based sorbent at pressurized conditions. The results show that the effect of reaction pressure on the cyclic performance of sorbent under pressurized steam-containing conditions is similar to that of pressurized without steam-containing conditions. The conversion increases first and then decays with the improvement of pressure. The highest conversion is achieved under the pressure of0.5Mpa in the pressurized steam-containing conditions and0.3Mpa in pressurized without steam-containing conditions. Conversion increases with the increasement of steam concentrations in the range of0～20vol%under pressurized steam-containing conditions. When steam concentration is higher than20vol%, conversion decays. However, conversion increase with the increasement of steam concentration. But the degree of increasement is smaller and smaller under atmospheric steam-containing conditions. The conversion of0.6is achieved after10cycles. The sorbent is more sensitive to the changes of temperature under atmospheric steam-containing conditions than that in pressurized steam-containing conditions.The modification method using high-aluminate cement was put forward to overcome the problems of sintering, abrasion and fragile caused during the Ca-based sorbent Utilization. The effects of high-aluminate cement content, reaction temperature, particle diameter and CO2partial pressure on the carbonation performance of modified absorbent were investigated. The results show that the highest conversion is abtained when the high-aluminate cement content is5wt%. the conversion is0.45after20cycles. The higher carbonation conversions of modified sorbent by high-aluminate cement and natural sorbent were acquired at the temperature of700℃and650℃, respectively. The change law of conversion is opposite with the increase of CO2partial pressure in the carbonation and calcination atmosphere. The ability of CO2capture is gradually lower as the particle size increases due to the increase of the diffusion resisitence. The reasons for the improvement of CO2capture by high-aluminate cement modified sorbent were revealed using SEM, XRD and Nitrogen Adsorption Instrument. |
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