Design & Optimization Of Membrane Hybrid Process For H₂/light Hydrocarbon Production From Multiple Refinery Gases Based On A Graphic Synthesis Method

Hydrogen is an important feed gas for oil refineries to produce petroleum hydrocarbons and improve the quality of petroleum products,but the production cost of hydrogen is high and mainly comes from non-renewable fossil resources.In the process of petroleum refining,a large amount of refinery gas rich in high-value components such as hydrogen is produced,which is often directly burned as fuel gas,resulting in the low-value application of resource components.Therefore,using effective separation methods and processes to recover hydrogen from refinery tail gas is an important method to improve hydrogen utilization efficiency in recent years.However,refinery tail gas has the characteristics of complex sources,multiple components,and multiple separation methods.It is very difficult to determine the appropriate separation method and optimized separation sequence,and there is a problem of"combination explosion".Therefore,based on the graphic design method of triangular coordinate-vector analysis,this thesis obtained the optimized separation sequence flow and design scheme for the comprehensive recovery of 10 refinery gases.Based on process simulation,combined with sensitivity analysis and response surface method,the process parameters were analyzed.Optimization,as well as the technical and economic evaluation of the entire process system,have realized the efficient recovery of resource components such as hydrogen and light hydrocarbons.First,in the triangular coordinate system,the raw materials are simplified into a ternary system composed of fuel gas,hydrogen and light hydrocarbons,taking the product ownership of the components and the similarity of their separation properties as the merger rule.According to the characteristics of the refinery gas composition,the feed gas located in the optimal sphere of influence of the same separation unit in the triangular coordinate system is combined to obtain two mixed streams,which fall in F1 of pressure swing adsorption（PSA）separation zone and F2 of shallow cooling（SC）separation zone,respectively.Based on the two mixed feedstock streams,by drawing the corresponding separation unit vector pairs,the corresponding separation methods are determined in turn,and the final cascade couple recovery process including shallow condensation,hydrogen membrane separation（GPM）,light hydrocarbon membrane separation（RPM）and pressure swing adsorption are obtained.Afterwards,the condensed light hydrocarbons are separated by a multi-column rectification process to obtain products such as liquefied petroleum gas（LPG）,light naphtha（C₅+）and ethane.Then,the whole process was simulated by Uni Sim Design,and the appropriate values of process parameters such as membrane area（GPM and RPM）,stage cuts,permeate pressure,distillation column reflux ratio and number of plates were preliminarily determined through sensitivity analysis.The"two-way enrichment"effect of the process,the results showed that the stage cuts of GPM and RPM were 0.51 and 0.8 when the areas of GPM and RPM were3772.6 m² and 600 m²,respectively.Finally,the process parameters are optimized using the Response Surface Method（RSM）.According to the established process model,the factors that have a significant impact on the total annual return（TAP）of the response value are first screened out through the Central Composite Design（CCD）experimental design:GPM membrane area,RPM membrane area and compressor K-2 outlet pressure,and then determined the center point of the response surface analysis by the steepest ascending method.Finally,according to the Central composite design center combination experimental design principle,the correlation equation between TAP and the three key factors was fitted and the response surface analysis was carried out.The optimal operating parameters of the condensation-membrane-PSA-rectification coupling system were obtained to maximize the TAP,and the annual operating expenses and total investment were determined by economic evaluation of the process plan.The results showed that the annual production total profit of the optimized process was USD 39.01×10⁶,the payback period is less than 4 months,the recovery rates of hydrogen and light hydrocarbons are 96%and 99%,respectively,and the unit consumption of hydrogen production is only 0.227k Wh Nm^-3.Compared with the foreign patented technology,the energy consumption is reduced by 27%.