The Study On The Path And Performance Of Syngas Methanation Process

With the increasing demand for energy in the world,the traditional fossil energy is becoming more and more unable to meet the needs of people.The emergence of energy crisis,the depletion of fossil resources,and the shortage of energy will become the most urgent problem to be solved in the face of economic development.It is a new research direction to utilize old energy sources,improve energy utilization ratio and make full use of traditional energy.In recent years,with the transformation of industrial gases and the conversion of gaseous compounds into gas,the process of natural gas digestion has attracted more and more interest.This process includes the digestion of gaseous substrates mainly composed of H₂,CO and CO₂ by anaerobic microorganisms,which can be used as carbon and energy sources.In this study,the simulated synthetic gas was used as the raw material,and the experiment was carried out under the high temperature continuous condition with the microorganism,the experiment of different feed ratio under the semi continuous condition and the additive experiment under the semi continuous condition.The main contents and conclusions are as follows:?1?experiments of biogenic methanation efficiency and transformation path of syngas under continuous conditions:According to the survey results of gasification technology,it is found that the daily gas production and gas producing components of the fixed bed gasification technology are suitable to combine with microbial anaerobic digestion to combine biological methane.At the same time,the content of simulated synthetic gas is H₂:CO:CH₄:CO₂=35:30:15:20?vol%?,according to the product gas component of the technology.The anaerobic digestion process of synthetic gas is simulated by over regulating speed and intake volume.The reaction temperature is 55?and the reaction volume of the anaerobic fermentation tank is 4 litres,and the amount of methane biological methanation process under different conditions is determined.The experimental results show that as the speed increases from 300 rpm to 800 rpm,the processing capacity of the high temperature digestive system is increased from 10 mL/min to 35 mL/min,and the gas and liquid mass transfer process can be enhanced by increasing the speed.The mass transfer rate of gas and liquid in the reaction process can be increased and the processing capacity of the reaction system can be improved by increasing the speed of the reaction.The rotational speed is 300 rpm.Under the condition,the intake rate of the system is less than 10mL/min,the intake rate is 10 mL/min under 500 rpm,the system capacity is 3.6 L/?L·d?,the intake rate is 35 mL/min at 800 rpm speed,and the system gas processing amount is 12.6 L/?L·d?.The total methane content of the whole process is 46±3%.Therefore,the increase of the speed does not increase the percentage of methane in the gas production,because the process mainly improves the mass transfer rate of the whole digestion process,and does not increase or strengthen the conversion rate of the microorganism to the intake during the reaction process;the main reaction path of the digestive system is from the process.The route of acetic acid production at low rotational speed is converted to hydrogen production at high rotational speed.?2?effects of different H₂/CO ratios on conversion efficiency and transformation path under semi-continuous conditions:The results of synthesis gas digestion under continuous conditions showed that the methane content was generally not high in the result of gas production,and the methane content would not change with the increase of speed or the intake of air.The proportion of H₂/CO in part?1?was 1.25:1.The reaction results of different stages showed that there was still some CO remaining after hydrogen reaction in the raw gas,so the proportion of H₂/CO in the anaerobic digestion process was improved,and the proportion of H₂/CO was tested by 3:1,4:1 and 5:1,respectively.The experimental results show that the ratio of H₂/CO to 3:1,4:1 and 5:1,methane content in gas production increased significantly,66.37±4.04%,70.61±6.06%?73.35±2.39%,respectively.Under the condition of low H₂/CO ratio,the reaction path of carbon monoxide mainly passes through acetic acid production route,and the high H₂/CO ratio is mainly the route of hydrogen production.The methane yield can be improved by increasing the H₂/CO ratio of the inlet gas to improve the methanation and digestion reaction of syngas.?3?effect of active additives on conversion efficiency and transformation path under semi-continuous conditions:In addition to abiotic factors,microbes themselves have an important influence on the digestion process.Microbial growth not only requires a large number of elements such as carbon?C?,nitrogen?N?,phosphorus?P?,and sulfur?S?,but also requires a variety of trace elements.Trace element is an important component of maintaining anaerobic microbial growth and metabolism and activity of anaerobic digestion enzyme system.In this experiment,the microelement active agent was added to the reactor.The concentration of trace elements iron,cobalt and nickel was 0.57 g/L,0.25 g/L and 0.025g/L respectively.The addition frequency was once a week and each time was 6mL.By improving microbial activity,we explored the efficiency changes and reaction pathways in the digestive process.The experimental results show that after adding trace elements,the methane production phase in the digestion process will be promoted,the content of VOAs in the measured liquid phase decreases obviously,indicating that the utilization rate of VOAs in the methanation process is obviously improved,and the methane content in the gas production is about 79.76±7.35%.