Simulation And Energy-saving For Solvent Recovering Of Butanone-toluene Dewaxing Process

Lubricant,one of the main products of oil refining processes,consists of base oil and multiple additives.As the main ingredient,base oil has great influence on the basic properties of lubricant.The performance of base oil depends on its chemical composition.In fact,the production process of base oil is to remove the non-ideal components.Paraffin is one of the non-ideal components of base oil,which will crystallize when temperature decreases and thus affect the low-temperature fluidity of lubricant.Therefore,the dewaxing process is essential in the production of base oil in order to improve the low-temperature fluidity of lubricant.The butanone-toluene mixed solvent dewaxing process is the most widely used dewaxing technique in China.In the each subsystem of butanone-toluene dewaxing process,the solvent recovering subsystem accounts for the largest energy consumption.The energy saving and consumption reducing for the solvent recovering system of butanone-toluene dewaxing process is simulated by using Aspen Plus simulation software.The main contents of this paper are as follows:1.A brief overview of the energy integration technology and simulation technology of chemical process system are given.Then,the research background and main contents of this thesis are introduced.2.The solvent dewaxing process and solvent recovering system are analyzed first.Based on the above analysis results and the measurement data of a refinery,the solvent recovering system is simulated with the NRTL property method by using Aspen Plus software.It is shown that the simulation flowrates of the main material streams agree with the measurement data,which illustrates that the model established in this work can reflect the actual operation condition of the system.In addition,the distribution of vapor-liquid load in every tray is analyzed,and the consumption of stripping steam is optimized.3.A retrofit scheme is proposed based on the simulation results of solvent recovery system of butanone-toluene dewaxing process.The parameters of cold and hot streams are first extracted and then the heat exchanger network(HEN)of the system is analyzed with pinch approach to find the unreasonable usage of energy.From the results of pinch analysis and the features of the original HEN,a final retrofit scheme is presented.4.The solvents recovered in the butanone-toluene dewaxing process need to be cooled by air-cooled heat exchangers(ACHE)and water-cooled ones.Based on the related mathematical model of ACHE,the relationship between the total annual cost and air face velocity is analyzed when some factors change.The factors considered include electricity price,design temperature,depreciation time and number of tube rows.