Experimental Research Of Waste Ion-exchange Resin-based Activated Carbon For CO₂ Capture In Flue Gas

With the rapid development of global industry,the amount of energy used continues to increase and a large number of CO₂ emissions.The greenhouse effect is due to these massive emission of CO₂.In order to reduce CO₂ emission and promote the sustainable development of human beings,carbon capture,utilization and storage technology(CCUS)has been put forward to reduce the emissions of greenhouse gases especially CO₂.Among the CCUS technology,adsorption has been thought to be a promising technology to achieve CO₂ emission reduction due to low energy consumption,high purity product,simple process,convenient automatic operation and good environmental benefits.The low cost and excellent performance of adsorbent is instrumental in CO₂ adsorption.In this paper,the waste ion-exchange resin is used as a kind of precursor to produce activated carbon for CO₂ adsorption,which has great economic and ecological benefits.It not only can reduce the cost of activated carbon and CO₂ emission reduction,but also solves the disposal problem of waste ion-exchange resin,and further develops the potential performance of the waste ion-exchange resin.In this paper,the effect of preparation parameters on the properties of waste ion-exchangeresin-based activated carbons(WIRACs)and CO₂ adsorption properties of WIRACs,the effect of adsorption conditions on the CO₂ adsorption properties,CO₂ adsorption equilibrium and thermodynamics,CO₂ adsorption and desorption kinetics,CO₂ adsorption/desorption on adsorption bed and the effect of the other gases in flue gas on CO₂ adsorption/desorption have been researched.And the main research contents and results are as follows:(1)The proximate analysis,elemental analysis and thermal stability analysis about waste ion-exchange resin has been done.And the effect of preparation parameters on the pore structure properties and surface functional groups of WIRACs has been studied.The results are as follows:compared with agricultural wastes,the lower volatile matter and higher fixed carbon of waste ion-exchange resin is advantage to the preparation of activated carbon.There are three thermal degradation stages of waste ion-exchange resin:the loss of free waste and bound water,the depolymerization of polystyrene-divinylbenzene structures and the broken of C-H bond in phenol.The surface of WIRACs is rough and the surface functional groups are mainly acidic or neutral functional groups.The pores of WIRACs are mainly atypical slit-like micropores and a small amount of mesopores and macropores.The pore sizes are distributed in the range of 0.9?4 nm,which is propitious to small molecule adsorption.(2)Based on the thermogravimetric analyser(TGA),the effect of preparation parameters,adsorption temperature and CO₂ partial pressure on CO₂ adsorption of WIRACs has been studied.The results are as follows:at the condition of activation temperature 1173 K,activation time 2 h,impregnation rate 1.5 by chemical activation,the CO₂ adsorption capacity of WIRACs is 1.85 mmol/g.At the condition of activation temperature 1073 K,activation time 60 min,activation gas flow 200 mL by physical activation,the CO₂ adsorption capacity of WIRACs is 0.6285 mmol/g.With the increase of adsorption temperature and the reduction of CO₂ partial pressure,CO₂ adsorption capacity gradually decreases.(3)Based on the automatic gas adsorption apparatus,the CO₂ and N₂ pure component adsorption isotherm at different temperature has been researched.Langmuir,Freundlich and Sips adsorption isotherm models have been used to analyze the adsorption equilibrium data.The isosteric heat of adsorption of CO₂ and N₂ and the adsorption selectivity of CO₂/N₂ have been calculated.And CO₂ and N₂ adsorption thermodynamics has been analyzed.The results are as follows:Sips adsorption isotherm model is the best one to describe CO₂ and N₂ adsorption process among the three kinds of adsorption isotherm models.The isosteric heat of adsorption of CO₂ and N₂ decreases with the increase of CO₂ adsorption capacity,and the end is close to a constant value.The separation factor of CO₂/N₂ decreases and closes to a constant value with the increase of pressure.And it decreases with the increase of CO₂ partial pressure,too.The separation factors of chemical activation activated carbon(CA)and physical activation activated carbon(PA)are about 35 and 45,respectively,when CO₂ partial pressure is 15%.The values of thermodynamics parameters ?G??H and ?S are all negative according to the CO₂ adsorption process.(4)Based on the TGA,CO₂ adsorption and desorption kinetics of WIRACs have been studied.The pseudo-first-order,pseudo-second-order,Avrami order and Fractional order kinetic models are used to analyze the CO₂ adsorption process,and the model-free approach and combination approach are used to analyze the CO₂ desorption process.The results are as follows:among the four kinds of adsorption kinetic models,Avrami order and Fractional order models are the best two models to describe the CO₂ adsorption process.CO₂ adsorption is a process of one-dimensional growth of the nuclei with a decreasing adsorption rate.The activation energy of CO₂ adsorption is negative,and with the increase of CO₂ concentration,the absolute value of activation energy decreases and pre-exponential factors increases.According to the model-free method,the extent of conversion is between 0.2-0.7,the desorption activation energy of CA decreases with the increase of CO₂ desorption extent of conversion and the desorption activation energy of PA is almost invariable with the increase of CO₂ desorption extent of conversion.The desorption kinetic models of CA and PA are been built.The results obtained by the combination approach is almost the same as the model-free approach.(5)Based on a small laboratory scale adsorption bed,the chosen chemical activation WIRACs was used to research CO₂ adsorption experiment.The adsorption temperature,gas flow rate,CO₂ concentration and adsorbent filling content are studied,and the results are as follows:with the increase of adsorption temperature,breakthrough time,CO₂ adsorption capacity and adsorption rate decrease.With the increase of gas flow rate,the breakthrough time and CO₂ adsorption capacity decrease and adsorption rate increases.With the increase of CO₂ concentration,breakthrough time decreases and CO₂ adsorption capacity and adsorption rate increase.With the increase of adsorbent filling content,breakthrough time increases and CO₂ adsorption capacity and adsorption rate decrease.(6)Based on the adsorption bed,the effect of desorption temperature,CO₂ concentration and purge gas flow on CO₂ desorption of WIRACs are researched,and the results are as follows:in the process of CO₂ desorption,with the increase of desorption temperature and CO₂ concentration,the purity of CO₂ in product gas and desorption time increase.With the increase of purge gas flow,the purity of CO₂ in product gas increases and desorption time decreases.In the selected range of desorption temperature,CO₂ concentration and purge gas flow,the WIRACs has been folly regenerated,and the CO₂ adsorption capacity after regeneration is almost the same with the first CO₂ adsorption capacity.(7)Based on the adsorption bed,the effect of different NO,SO2 and steam concentrations and temperatures on CO₂ adsorption and desorption performance of WIRACs have been studied.The results are as follows:the presence of NO in flue gas has no effect on CO₂ adsorption in the experimental range.SO2 concentration below 100 ppm has no effect on CO₂ adsorption.CO₂ adsorption capacity decreases when SO2 concentration is more than 100 ppm,and the higher SO2 concentration is,the smaller CO₂ adsorption capacity will be.The presence of steam in flue gas reduces CO₂ adsorption capacity,and the higher steam concentration is,the smaller CO₂ adsorption capacity will be.The CO₂ adsorption and desorption cycle performance of WIRACs is well,indicating that WIRACs can be used a long time.NO and SO2 in flue gas emissions standards has no effect on CO₂ adsorption and desorption cycle.