Process Development Of Acid Gas Removal Process From Wild Coal Gas-derived Gas In A Certain Plant

Rectisol process refers to a process that uses methanol as an absorbent to selectively absorb CO₂,H₂S,COS and other acid gas components in the gas below-40°C condition.This process has the advantages of strong selectivity,good absorption effect and low energy consumption,etc.,and is widely used in the process of coal-to-natural gas,coal-to-methanol,coal-to-ethylene glycol,and acid gas removal from wild coal gas-derived gas processes.At the same time,because the low temperature methanol wash can operate under a wide range of pressures,ranging from 2.0 MPa to 8.0 MPa,for different feed gas conditions,Rectisol process has a wide range of applications under different feed conditions.The wild coal gas-derived gas involved in a certain plant produced by the conversion and shift reaction of two kinds of wild coal gas with different compositions produced by the retort reaction of coal.There are few domestic reports dealing with this type of special feed gas up-to-date.The feed condition is less than 2.5MPa,which is a low-pressure feed condition for Rectisol process.As the absorption capacity of methanol for acid gas components such as CO₂is reduced at low pressure,the equipment investment will increase and the design difficulty will increase accordingly.The carbon content in the unshifted gas feed gas of Derivative Gas I is only 8.57%,and the sulfur contents in the shifted feed gas and unshifted gas feed gas are only0.02%.Compared with the feed gas of the traditional Rectisol process,the carbon content and sulfur content are lower,so the purification process is required to have a stronger absorption capacity,and higher requirements are placed on the selectivity and removal rate of sulfur absorption by solvent methanol.In Derivative Gas II,in addition to the CO₂ and H₂S impurities contained in Derivative Gas I,it also contains C₂-C₄ low-carbon components and benzene components.Among them,low-carbon components need to avoid being enriched in the Rectisol system.The components need to be removed in advance to avoid affecting the subsequent absorption process.At the same time,because the feed conditions of Derivative Gas II are no different from Derivative Gas I except for the impurity content,and the feed conditions of Derivative Gas II are more stringent,the heat exchange network design for Derivative Gas II has a better guiding effect on production practice.On the basis of Linde's one-step Rectisol process,three sets of low-temperature methanol washing processes are designed according to the feed characteristics and process characteristics of the feed.Rectisol process I uses an 8-tower process,and Rectisol process II uses a 12-tower process.In the calculation,the PSRK method is used to calculate the whole process of the Rectisol process.For the key parameters,sensitivity analysis and design regulations are used to optimize the process flow,so that the final design process meets the process requirements and reduces the cost required for production.Using pinch point analysis to design Rectisol process III,compared with Rectisol process II,cold utilities consumption is reduced by 61.70%,hot utilities consumption is by 61.14%,and fixed equipment investment is reduced by 37.89%,indicating that Rectisol process III has a lower cost Energy consumption and cost.In this paper,Rectisol processes?and?are designed for two raw gas derived gas with different feed composition.Through calculation and design,the best essence plan is determined.This research will guide the road to the practical application of Rectisol process engineering with similar feed conditions in the future.In addition,the pinch point analysis method is used to design Rectisol process III,which optimizes equipment investment and energy consumption,provides the ideas for energy-saving design of similar low-temperature methanol wash processes with good application prospects.