Reducing energy costs at the tar deasphalting unit

Abstract

Propane de-asphalting units are used to "clean" tar from asphalt-resin and polycyclic aromatic components. The energy resources used in this case are quite large. To reduce energy consumption, the possibility of heat recovery of the technological flows of the installation and reduction of steam and water consumption during the regeneration of propane from a deasphaltisate solution is being considered. The research was carried out using the Honeywell UniSim Design software system, in which a model of a propane de-asphalting tar installation was developed. The Peng-Robinson method was used to calculate the thermodynamic properties of the fraction components. The analysis of the energy flows of the technological scheme showed that to increase the temperature of the deasphaltisate solution from 79.9 OC to 120 Oc for a tubular evaporator, it is required to bring an energy flow of 2.709e5 kJ/h. At the same time, the value of the heat flux of the target product (deasphaltisate) is 5,746e6 kJ / h, therefore, there is a possibility of heat recovery between the considered flows. An energy-saving technology for the regeneration of propane from a solution of deasphaltisate is proposed, in which the heat of the flow of the extracted deasphaltisate is used in a tubular evaporator instead of hot steam. The conducted computational experiment showed that the calculated reduction in the consumption of hot steam in the K-2 steam column reduces the energy consumption of the installation while maintaining the clarity of the separation of propane and the target product. The absence of a hydrocarbon fraction in the flow of regenerated propane makes it possible to recycle it to feed the extraction column. It is shown that it is possible to reduce water consumption in the K-5 mixing condenser. By reducing the steam consumption used in the K-2 steam column and lowering the water consumption in the K-5 condenser, the amount of water discharged into the sewer is reduced. The proposed technological scheme for the regeneration of propane from a deasphaltisate solution and the installation model can be used in the processes of one- and two-stage deasphaltization of tar for their calculation and design.