THERMAL GAS-DYNAMIC SEPARATOR

The gas and oil industry currently faces a host of problems associated with preparation of natural and petroleum gases for transporting and processing. The causes of these problems are the following: 1) low pressure of the crude natural gas in a majority of large fields occurring in the final stage of development as well as low pressure of the associated petroleum gas; 2) high requirements on quality of preparation of hydrocarbon gases in terms of due points up to -25 degrees C to -30 degrees C and below at working pressures. Conventional methods of gas preparation at the fields, which are based on low-temperature separation applying throttle effect, are practically unsuitable in such conditions. For this purpose, more suitable is preparation of the gases in plants containing expander-compressor units (ECU). But ECU is a complex costly machine in terms of capital and operational costs and imposes severe restrictions to ingress of mechanical impurities and dropping liquid into it, which is not always achievable for supersaturated gases, so its use is extremely limited and in many technologies is not profitable. To solve the problem of low-temperature preparation of the above-referred hydrocarbon gases, a thermal gas-dynamic separator (TGS) is proposed. The TGS does not contain moving parts but performs the function of an ECU, namely, cooling of the gas by isoentropic process, separation of the condensed components from the gas phase, and restoration of the pressure of the purified gas. This article describes a pilot-scale TGS design, discusses the principle (theoretical foundations) of its operation, and reports some industrial test data for natural gases from the Senomanian and Valanginian deposits. In the tests, the TGS operated in the 0.8-1.48 Mach number range, and the difference in temperatures of the original and cooled gas varied in this case varied from 24 to 67 degrees C. The prepared gas had the minimum due point temperatures with respect to its aqueous component ranging from -31 to -32 degrees C. In this case, the pressure of the purified gas at the separator outlet was about 60-70 % of the initial gas pressure at the inlet.