Research On Adsorbent Modification Based On Enrichment And Separation Of Low-concentration Coalbed Methane

Coal bed methane(CBM)resources is rich in Guizhou province,ranking the second in the country,but for the low concentration of CH₄ in CBM,generally less than 30%(volume ratio),the CBM cannot be used directly,mostly explosion,which lead to energy waste and atmospheric pollution.In order to improve the utilization of low concentrations of coalbed methane,CH₄ separation from the coal-bed methane must enrichment,and increasing CH₄ concentrations.Currently,vacuum pressure swing adsorption technology(VPSA)is more suitable for low concentrations of Guizhou coal bed methane to make CH₄separation and enrichment,the adsorbent is the key technology to achieve industrialization.Since activated carbon has a high specific surface area and rich micropore volume,good mechanical/thermal stability,so that activated carbon is widely used in the field of gas separation,but it is applied to low concentrations of coalbed methane CH₄ separation and enrichment presence aperture distribution of messy,micropore volume is low,weak surface adsorption sites and other shortcomings,leading to poor separation of CH₄from CBM effect.In order to improve the separation of CH₄ from in coal-bed methane use the activated carbon,this paper use metal ions,chitosan/cellulose modified activated carbon,chitosan airgel,Mg O template preparation of porous activated carbon.And using N₂adsorption/desorption isotherms line analysis of activated carbon pore structure and specific surface area,that FTIR analysis of activated carbon surface and Boehm titration group content and composition,SEM analysis of surface morphology of activated carbon,and CH₄ dynamic,static CH₄/N₂ adsorption experiments be used to evaluate the adsorbent CH₄ enrichment separation performance,that the study to develop activated carbon pore structure and surface chemical properties aim to impact the coal-bed methane CH₄adsorption properties.Research contents and results are as follows:The effect from the Metal ion which include Ni³⁺,Mg²⁺,Cu²⁺,Fe³⁺and Al³⁺that modified the activated carbon on the separation and enrichment performance of CH₄ from the coalbed methane.Response surface optimization experiments to determine the nickel nitrate modified active carbon optimal conditions were:nickel nitrate concentration of 0.21mol/L,activation temperature 730?,activation time of 67 min,which under nitrogen atmosphere firing activation.In the process conditions for preparing the modified activated carbon and methane adsorption dynamic testing dynamic methane reserves reached 58.05m L/g.Response surface model 515.445 s optimal value and the actual value of 550 s are similar,indicating there are has some practical value about the model about modified activated carbon process optimization to adsorption of low concentration methane in coal-bed methane.The study on Chitosan(CS)and cellulose(CMC)modified activated carbon to separation and enrichment performance of CH₄from CMB.Investigate the different loading of the CS and CMC that influence of adsorption of CH₄,the CS-CMC composite modified activated carbon adsorption of CH₄ is superior,the CS-CMC(5%)of that has the static adsorption quantity of 1.75 mmol·/g,which 1.87 times of the original AC,its dynamic adsorption of CH₄ is 33.98 m L/g,increased by 85.27%compared with the original AC,and the separation of CH₄/N₂coefficient is biggest,that is 4.97,which 1.81 times of the original AC,selective adsorption effect is obvious.Research on chitosan(CS)as the main raw materials used in the impact of activated carbon airgel sol-gel method for the separation and enrichment performance of CH₄from CMB.The results showed that:when the conditions are:the activation temperature of700?,activation time is 60 min,KOH:Carbonized aerogel=2:1,the preparation of activated carbon airgel which named QAC-2 has a large adsorption of CH₄that reserves of57.63 m L/g,the adsorption of methane dynamic breakthrough time of 546 s,the effect of methane adsorption storage location,and the activated carbon airgel with a reasonable pore structure:that activated carbon ismicro-mesoporous activated carbon material.Study on Mg O template synthesis of modified activated carbon impact on the adsorption of methane.The results showed that:in the activation temperature of 700?,the activated carbon sample has a significant amount of CH₄ adsorption that from the low concentration CBM;Different ratio of magnesium oxide precursor and carbon precursor lead the activated carbon samples different specific surface area and pore structure,its low concentration CBM adsorption of CH₄ are quite different,Mg O(2/8/4)activated carbon sample has the largest specific surface area of 1926.27 m²/g,it has the superior dynamic and static adsorption properties of methane,that CH₄/N₂ in separation factor as high as7.25,it is beneficial for the selective adsorption and storage of methane.