COMPARATIVE EVALUATION OF DIFFERENT DESIGNS OF COMPRESSOR-EJECTOR UNIT FOR GAS PUMPING DURING REPAIR WORKS ON MAIN GAS PIPELINES

The article describes the problem of resource saving in the process of mainline transport on the example of rational use of process gas, contained in the section switched off before repairs. At present, according to normative and technical documentation, in such cases the section is discharged from process gas by blowing through gas vents to the atmosphere. In order to save resources and reduce environmental impact it is offered to pump gas from the isolated section to the neighbouring pipeline in the technological corridor. The article presents different designs of the compressor-ejector unit and calculates its operation modes for emptying a section of the main gas pipeline in the technological corridor of two parallel gas pipelines with a length of 125 km each and operating pressure of 7.5 MPa. In the presented scenarios the compressor location relative to the ejector was changed: on the active gas line, on the pumped gas line, on the ejector outlet. Parameters of system «plant – gas pipelines» operation were calculated in hydrodynamic simulator with creating a separate model for each design of the plant. The character of changes in parameters during gas transportation along the technological corridor in case of shutdown of one 25 km long section on one of the parallel gas pipelines and gas extraction by the compressor-ejector unit using technological gas from the section before the shutdown is shown. The dependence curve of pumped gas flow rates and pressures vs. time in the given designs of the compressor-ejector unit is presented. The optimal compressor location is determined in view of maximizing the evacuated gas volume and, accordingly, minimizing the evacuation time.