【作者】 杨洋；

【导师】 王勤辉；

【作者基本信息】 浙江大学 ， 动力工程， 2019， 硕士

【摘要】 基于钙基吸附剂的化学链气化和钙基循环等二氧化碳捕集工艺由于可实现煤炭和生物质等含碳燃料的高效低碳利用,近年来得到较大的关注。但目前仍存在多次循环吸收后吸收效率明显下降的问题。针对该问题,目前主要的解决方法有在天然石灰石中加入惰性添加剂以及通过不同的制备方法制备吸附剂。对此,本文首先探究了天然石灰石的循环特性,在此基础上探究并优选了钙基吸附颗粒的制备工艺、添加物质以及掺杂比例,最终得到通过水合法向天然石灰石中加入5%质量分数的高铝水泥得到的钙基吸附颗粒具有较优的吸附效果,进一步探究了碳化/煅烧气氛对新型钙基吸附颗粒吸收效率的影响,并在流化床中验证了新型钙基吸附颗粒具有更好的吸收效率和抗磨损特性,为工业应用提供相应的技术支持。利用热天平研究了天然石灰石的碳化/煅烧速率,在管式炉上研究了碳化温度（600⁸00℃）、煅烧温度（850¹000℃）以及吸附剂粒径对天然石灰石碳化/煅烧循环特性的影响,并通过SEM分析了不同碳化温度下吸附剂的微观孔隙结构。实验结果表明:天然石灰石在碳化和煅烧反应的前三分钟转化率可以达到90%左右;最佳碳化温度为700℃,最佳煅烧温度为850℃,且其反应颗粒粒径越小,相同反应次数之后吸收效率越高。通过SEM图也可以看到,多次循环后吸附颗粒孔隙存在严重的结焦现象。针对天然石灰石多次循环后烧结严重的问题,提出在天然石灰石中加入高铝水泥,改善吸附剂的结构特性。优选了制备方法、添加剂以及添加比例,研究了碳化/煅烧气氛对新型钙基吸附剂碳化/煅烧循环特性的影响,并分析了吸附剂的抗磨损性能。研究结果表明,通过水合法向天然石灰石中加入5%质量分数的高铝水泥制备的新型钙基具有较好的吸附剂吸收效率以及抗磨损性能,20次循环后,吸收效率达0.51,比天然石灰石高0.147,且磨损率只有天然石灰石的29%左右。通过SEM、氮吸附测试、XRD以及微粒模型计算方法分析了新型钙基吸附剂性能优良的机理。同时新型钙基吸附剂碳化时具有最大CO₂碳化浓度,在此浓度之前吸收效率随着气氛中CO₂浓度的上升而增加,超过该浓度后,吸收效率不在变化。而煅烧气氛中CO₂含量越低,吸附剂吸收率越高。在完成新型钙基吸附颗粒的制备及其循环特性研究之后,又在小型流化床上进行了天然石灰石和新型钙基吸附颗粒的碳化/煅烧循环特性实验,实验结果表明,新型钙基吸附颗粒在小型流化床中循环20次后仍有0.44左右的吸收效率,比天然石灰石高0.15左右,同时其循环20次后的磨损量只有天然石灰石的60%左右,这证明新型钙基吸附颗粒具备较好的吸收性能,且具有较好的抗磨损性能,可以满足工业应用。更多还原

【Abstract】 Carbon dioxide trapping processes such as chemical chain gasification and calcium-based recycling based on calcium-based adsorbents have received considerable attention in recent years due to the efficient and low-carbon utilization of carbonaceous fuels such as coal and biomass.However,there are still problems in that the absorption efficiency is significantly reduced after repeated cycles of absorption.In response to this problem,the main solutions at present are the addition of inert additives to natural limestone or preparing absorbents by different preparation methods.In this regard,this paper first explores the cycle characteristics of natural limestone.Then,the preparation process,additive substances and doping ratio of calcium-based adsorption particles are explored.Finally,the calcium-based adsorption particles obtained by adding 5%by mass of high-aluminum cement to natural limestone by hydration have better adsorption effect.Then,exploring the effect of carbonization/calcination atmosphere on the absorption efficiency of new calcium-based adsorption particles.In the fluidized bed,it is verified that the new calcium-based adsorption particles have better absorption efficiency and anti-abrasion characteristics,and provide corresponding technical support for industrial applications.The carbonization/calcination rate of natural limestone was studied by thermobalance.The carbonization temperature（600⁸00℃）,calcination temperature（850¹000℃）and the particle size of the absorbent were studied on the natural limestone carbonization/calcination in the tube furnace.The effect of cycle characteristics and the microscopic pore structure of the absorbent at different carbonization temperatures were analyzed by SEM.The experimental results show that the conversion rate of natural limestone in the first three minutes of carbonization and calcination reaction can reach about 90%;the optimum carbonization temperature is 700℃,the optimum calcination temperature is 850℃,and the smaller the reaction particle size,the higher the absorption efficiency after the same number of reactions.It can also be seen from the SEM image that the particles is serevely coked after repeated cycles.In view of the serious coking problem of natural limestone after repeated cycles,this paper proposes to add high-alumina cement to natural limestone to improve the structural characteristics of the absorbent.Then selecting preparation methods,additives and addition ratios.The effect of carbonization/calcination atmosphere on the cycle characteristics of the new calcium-based absorbent was studied,and the anti-abrasion properties of the absorbent were analyzed.The result shows that the new calcium-based absorbent,adding 5%high-alumina cement to the nature lime by hydration,has good absorption efficiency and anti-abrasion performance.After 20cycles,the absorption efficiency is 0.51,which is 14.7%higher then nature lime,and the wear rate is only about 29%of natural limestone.The mechanism of excellent performance of the new calcium-based absorbent was analyzed by SEM,nitrogen adsorption test,XRD and particle model calculation.At the same time,the new calcium-based absorbent has the maximum CO₂ carbonization concentration when carbonized,and the absorption efficiency increases with the increase of the CO₂concentration in the atmosphere before the concentration,and the absorption efficiency does not change after the concentration is exceeded.The lower the CO₂content in the calcination atmosphere,the higher the absorption rate of the absorbent.After the preparation of the new calcium-based adsorption particles and their cycle characteristics,the cycle characteristics of natural limestone and new calcium-based adsorption particles were tested on a small fluidized bed.The experimental results show that new calcium-based adsorption particles still have an high absorption efficiency,about 0.44,which is about 0.15 higher than that of natural limestone.At the same time,after 20 cycles,the wear amount is only about 60%of natural limestone,which proves that the new calcium-based adsorbent particles have good absorption performance and good wear resistance,which can meet industrial applications.更多还原