New low temperature technologies of natural gas processing

摘要

Over the past 10 years a number of companies have been working at improvement of supersonic technologies of natural and associated gas processing. During this period, technologies have evolved from a theoretical research and laboratory experiments to a large industrial plants. Main principle, which lies at the basis of these technologies is target components separation due to the deep gas cooling, achieved in a supersonic swirling gas flows. In such cooling process, heavy fractions, contained in natural gas, are condensed, and condensate droplets are separated from the gas due to the flow swirling. In the world there are only 4 supersonic gas separation units, which are in currently operating. The majority of currently operated industrial units of supersonic separation are designed for the gas treatment and for LPG extraction. Heavy fractions, heavier than propane and water, are separated from the gas in these devices. As compared to the existing low temperature processes of gas processing, in which the gas cooling is usually effected by gas expansion in a Joule-Thomson valve or in turbo-expander, either by the use of chillers, supersonic separation technology has the following advantages: high reliability, caused by the absence of revolving mechanical parts, high efficiency, associated with the capability of providing very low gas temperatures inside the supersonic device, low operating expenses, the ability of devices to operate without constant manned supervision. High flow speeds in supersonic separation devices enables devices to be small in size. Thus, at a gas flowrate of 100 MMSFD and a gas pressure of 100 bar, the supersonic separation device has a length of about 2 meters. This makes the supersonic separation technology especially interesting for using on offshore platforms. A high reliability of these devices, caused by the absence of rotating mechanical elements, will likely lead to a wide-scale application of these technologies in a subsea production complex. A significant progress was recently being made in the development of supersonic technology for the separation of acid components (such as CO_2 and H_2S) from natural gases. In this case, acid components separation is carried out under the conditions, corresponding to the formation of CO_2 crystals. However, due to the fact that the period, when droplets are in a supersonic nozzle, lasts for 0.0001 - 0.001 seconds, crystallization processes have no time to develop, and as it was shown by the tests it is possible to ensure acid gas removal. Herewith, the concentration of acid components in gas can be reduced to 2 -3% mol. at any concentration in the inlet gas.