INCREASING THE YIELD OF MARKETABLE PRODUCTS DURING NATURAL GAS PROCESSING AT A GAS PROCESSING PLANT BY USING DEFLEGMATION TECHNOLOGY

Deethanization unit is a part of the process chain of a gas processing plant included in the ethane gas processing complex, and is designed to separate dehydrated and purified natural gas (NG) into dry stripped gas (DSG), ethane fraction and natural gas liquids (NGL). Low-temperature separation of dried and purified NG is carried out in two stages in column-type apparatuses. One of the most important blocks responsible for ethane fraction recovery depth at the deethanization unit is the gas treatment block before it is fed to the demethanization column. In this unit gas is cooled, separated and reduced, ethane-containing condensates are separated. In the present article the main technologies of natural gas processing are considered. The peculiarity of known technologies is low yield of ethane fraction due to insufficient gas cooling. The aim of the work is to increase the yield of marketable products during natural gas processing at the gas processing plant by using the deflegmation process. In order to achieve this aim, five variants of the gas treatment system before its supply to the demethanization column are analyzed in the article. Calculation studies and optimization of the natural gas treatment unit were carried out in the Aspen HYSYS software package. In order to select the optimal scheme of the gas treatment unit, in the article there were considered the following parameters: ethane fraction recovery depth, ethane concentration in DSG, temperature of the demethanizer top. It is determined that high recovery depth and low ethane losses in the demethanization column are ensured by using deflegmation process in the gas treatment system. The main technological solution is to use deflegmation of separation gas by using technological cold and isoenthalpic (throttling) expansion of gas. The result of the research is a calculation scheme in Aspen HYSYS, in which the ethane recovery depth is 96.7 %.