Research On A Semi-Industrial Preparation Of Modified CaO-Based Pellets

For the need of industrial application,based on the practical calcium looping process,industrial production and the requirements of cyclic sorption performance,a semi-industrial preparation procedure of CaO-based sorbent pellets with high CO₂ uptake performance was developed.The major researches in this work include the modification of CaO-based sorbents pellets via pore formers and the modification mechanism,the overall performance evaluation of CaO-based sorbent pellets,and the assessment of industrial application investigation.This work provides a possibility for the production of highly efficient CaO-based sorbent pellets.In order to alleviate the negative effect of granulation process,three novel types of pore formers（urea,polyethylene glycol and polyvinyl alcohol）were selected as pore formers to be added into the CaO-based sorbent pellets to study the effect of kinds of pore formers on CO₂capture.It is found that the carbonaceous residue of pyrolysis of polyethylene glycol and polyvinyl alcohol may result in an adverse effect for cyclic stability.The addition of urea is found to be effective in enhancing the cyclic CO₂ uptake capacity,which 5 wt.%urea possessed the optimal CO₂ uptake.A semi-industrial preparation procedure of modification CaO-based sorbent pellets was developed for the calcium looping process,combining the advantages of spray drying technology and extrusion-spheronization methods.The inert support homogeneously dispersed in the precursors of calcium via the wet mixing method could improve the cycling performance of the CaO-based sorbent.Spray-draying technology was chosen to produce a large number of well-mixed precursor powders quickly and efficiently,to meet the demand of scaled industrial production.The CaO-based pellets with excellent mechanical properties and sphericity were manufactured via an extrusion-spheronization method.The CaO-based sorbent pellets with 25%Al-stabilized and 5%urea as pore-making agent still had good CO₂adsorption capacity after 25 cycles under the oxy-fuel calcination condition,.and compared with the natural limestone pellets,the adsorption capacity increased by 867%.Then,the cost analysis of industrial production and the prediction of long series adsorption capacity were carried out,and it was estimated that the manufacturing cost of CAl75-UR5 pellets was 20.77yuan/kg,and the cost for per 1t CO₂ is 460.74 yuan after 200 cycles.Therefore,the semi-industrial preparation procedure of modification CaO-based sorbent pellets in this work can simultaneously satisfy the requirements of cyclic sorption performance,industrial production and practical industrial application.