Investigation On The Adsorption And Anti-attrition Performance Of CaO-based Pellets For CO₂ Capture At High Temperatrue

In the era of global warming,reducing carbon dioxide emissions has become the consensus of the world.Among the many CO₂ separation methods,calcium looping process technology?CaL?has attracted extensive attention due to its high adsorption capacity and low cost.However,the development of this technology still faces two huge challenges.On the one hand,the CaO-based CO₂ adsorbent will gradually decrease in adsorption efficiency due to sintering during the high temperature adsorption and desorption process.On the other hand,CaO-based adsorbents require to be shaped into pellets of a certain size to be applied in industrial fluidized beds,and at the same time,serious attrition problems may occur,and even the adsorbent may escape from the device,affecting the recycling of the adsorbent and reducing the economics of the calcium looping process technology.The extrusion-spheronization method is a simple method of making the sorbent powder into spherical particle which have a certain mechanical strength.However,this method exists that improve the mechanical strength of the adsorbent pellets at the cost of reducing the adsorption performance of the adsorbent.This paper mainly conducts related researches on the above problems,and hopes to obtain CaO-based adsorbent materials with excellent adsorption performance and anti-attrition property.Firstly,four kinds of pore-forming materials were screened and used to prepare a variety of adsorption pellets by extrusion-spheronization method,besides,the effect of pore-forming materials addition amount and pore-former particle size on the properties of adsorbed pellets were studied,and the mechanism of the pore former on the sorbent pellets were revealed.In addition,the effect of Y₂O₃/MgO addition on the performance of calcium-based adsorbents was investigated.The effects of different mixing methods,deionized water volume in wet ball-milling process and ration of Y and Mg addition on the performance of synthetic adsorbent pellets were discussed.The main results are as follows:?1?It was found that calcium-based sorbent particles with 5%polyethylene pore former had maximum CO₂ adsorption?0.155 g/g?and good mechanical properties?4.0N?,which were about 14%higher and 25%improved,comparing to pure calcium hydrate pellets.These were mainly due to the improvement of the inner pore structure of the sorbent pellet for the using of polyethylene,resulting in an increase in the reaction rate of the chemical control stage of the sorption.At the same time,the low addition amount of the pore-former decomposed at low temperature,which reduced the mechanical strength loss caused by the pellets being calcined at high temperature.?2?The size of the pore former particles had an effect on the properties of the adsorbent particles.The smaller the pore former particles,the larger the adsorption amount of the adsorbent.In terms of mechanical properties,the adsorbent particles reached the maximum compressive strength when the pore size of the pore former was12?m.?3?Results showed that wet planetary ball-milling was the best way for sorbent pellets preparation.It was found that the pellets prepared at the optimum liquid-solid ratio of 1:1 and Y₂O₃/MgO mass ratio of 2:1 had the best cyclic adsorption performance.Besides,after 62 cycles of adsorption and desorption,it had a CO₂ capture capacity of0.140 g/g,which was 31.2%higher than that of pure calcium hydroxide pellets.This was mainly owning to homogeneously distributed small grains and solid supports as well as enhanced pore structure in the wet ball-milled pellets.?4?In the study of mechanical and anti-attrition propertis.It was found that the sorbent pellets with the best liquid-solid ratio and Y₂O₃/MgO mass ratio had better mechanical and anti-attrition properties.Its mechanical strength was 9.0 N,which was about 172.7%higher than that of pure calcium hydroxide pellets.After 10 hours of attrition test,its attrition rate was 0.419%,which was only 1/3 of pure calcium hydroxide pellets.The research work on calcium-based adsorbents in this paper enriched the knowledge of this direction,and provided a basis for industrial use of calcium recycling technology to a certain extent.