Study On The Screening And Application Of Molecular Sieves For Natural Gas Decarbonization By Adsorption

As a simple and efficient gas separation method,the adsorption method has great application potential for the decarbonization of liquefied natural gas（LNG）processing.As the basis of the adsorption process,the performance of the adsorbent directly determines the treatment effect of the process.As an adsorbent with good CO₂ adsorption capacity and adsorption selectivity,zeolite molecular sieve has the potential to become an adsorbent for natural gas adsorption and decarbonization.Analyzing and comparing the relative performance of various molecular sieves,and exploring the influence of different conditions on its adsorption and decarbonization effect,is of great significance for the selection of adsorbents,optimization of operating parameters and industrial design of the natural gas adsorption decarburization process.This paper uses experimental methods to screen different kinds of molecular sieves and study the adsorption characteristics.Through the self-built adsorption and decarbonization experimental device,horizontal comparison experiments of gas adsorption and desorption regeneration were carried out on the 9 initially selected molecular sieves 4A,5A,13X,13X-APG,JLOX-500,NSP-3,JLPM-1,JLPM-3 and HT-51.The results show that when the JLOX-500 molecular sieve adsorbs and separates CH₄/CO₂ mixed gas under the experimental conditions of 25℃and 4MPa,it has better adsorption and decarbonization effect than other molecular sieves.The CO₂ adsorption capacity reaches 4.02 mmol/g,and the separation coefficient is 59.95.Comprehensive analysis of adsorption and regeneration,JLOX-500molecular sieve is the best molecular sieve in the experimental screening range.Subsequently,the optimized molecular sieve was investigated under different conditions to obtain the influence of different working conditions on its adsorption and decarburization performance,as well as the influence of water and regeneration cycles on its performance.The results show that increasing the pressure will increase the dynamic CO₂ adsorption capacity of the JLOX-500 molecular sieve but reduce the separation coefficient.Increasing temperature,increasing gas flow,and reducing the packing height will reduce the CO₂ adsorption capacity and separation coefficient at the same time,and Changes in temperature and filler height have the greatest influence.In addition,molecular sieve is very sensitive to water,and it is easy to inactivate after absorbing water.However,the high-temperature regeneration at 280°C can restore the original treatment effect and also verify the recyclability of molecular sieve by the loop experiment.Finally,based on the preferred molecular sieve,a design calculation of the LNG decarbonization process was carried out on the raw gas containing 6.83%CO₂ and the processing capacity of 1138.25Nm³/d.In the obtained two-tower adsorption process,the height of the adsorption tower is 2.5m,the diameter of the tower is 0.6m,and the molecular sieve filling amount is not less than 330kg per tower,so that the purified gas can meet the processing requirements of CO₂ content of less than 50ppm.The research content of this article provides a certain reference for the selection of adsorbents and parameters for the application of adsorption method to natural gas decarbonization.