Ltdr plant for complex wasteless preparation of gas

The invention relates to installations for low-temperature reflux with rectification of NTDR and can be used in the gas industry for field preparation of natural gas.

The known method of low-temperature gas separation [RU 2543867, publ. 03/10/2015, IPC B01D 3/14, B01D 3/28], carried out on a unit including an inlet separator, a two-section reflux condenser, a low-temperature separation unit as part of a reducing device and a low-temperature separator, as well as a condensate weathering unit.

The disadvantages of the known installation are the low quality of the commercial gas and the low yield of gas condensate due to incomplete recovery of cold process streams.

Closest to the proposed invention is a complex gas treatment unit [RU 2624710, publ. 07/05/2017, IPC F25J 3/00, C07C 7/00, C10G 5/06], including an inlet separator, the first and second recuperative heat exchangers, a reflux condenser connected with a reflux gas supply line equipped with a reducing device, with a low-temperature separator equipped with gas outlet line to the heat-exchange section of the reflux condenser, as well as reducing devices and a condensate stabilization unit (fractionation unit).

The disadvantage of this unit is the low yield of hydrocarbons C₂₊ due to mixing of condensates of different composition and temperature before stabilization, as well as due to losses of hydrocarbons C₂₊ with flare gases.

The objective of the invention is to increase the yield of hydrocarbons C₂₊.

The technical result is to increase the yield of hydrocarbons C₂₊ by installing a demethanizer, providing fractionation of condensates, as well as by eliminating the output of flare gases by connecting the fractionation unit with a demethanizer.

The technical result is achieved by the fact that in the proposed installation, which includes an inlet separator, the first and second recuperative heat exchangers, a reflux condenser with a heat exchange section equipped with a reflux gas supply line with a reducing device, a separator equipped with a prepared gas outlet line, as well as a fractionation block, the feature is the fact that a demethanizer is installed as a separator, which is equipped with a demethanized condensate supply line to the fractionation unit and a prepared gas outlet line with a heat-exchange section of a reflux condenser and a first recuperative heat exchanger, in addition, the demethanizer is connected to an inlet separator and a reflux condenser by condensate supply lines with reducing devices, and to the second recuperative heat exchanger - by input / output lines circulating irrigation, the reflux gas supply line is connected to the prepared gas output line, and the fractionation unit is equipped with product output lines and is connected to the demethanizer by the off-gas supply line.

Reducing devices can be made in the form of a throttle valve, gas-dynamic device or expander. The fractionation unit may include, for example, fractionation columns. As products, for example, propane-butane fraction and stable gas condensate can be removed. As the rest of the installation elements, any devices of the corresponding purpose known from the prior art can be placed.

The demethanizer can be equipped with an LNG outlet, and heat can be supplied to the bottom of the demethanizer by any known method (electric heating, heating with a heat carrier, hot jet, etc.). A separator can be installed in front of the reflux condenser, connected to the demethanizer by a condensate supply line with a reducing device.

Increasing the yield of hydrocarbons C₂₊ achieved by equipping the unit with a demethanizer, in which preliminary fractionation of condensates is carried out, preventing the carryover of hydrocarbons C₂₊, as well as by eliminating the formation of flare gases by connecting the fractionation unit with a demethanizer ..

The installation includes an inlet separator 1, a reflux condenser, a demethanizer 3, recuperative heat exchangers 4 and 5, reducing devices 6-9 (expanders are conventionally shown), as well as a fractionation unit 10.

During the operation of the installation (Fig. 1), the raw gas supplied through line 11 is separated in the separator 1 into condensate discharged through the line 12, and the gas, which is cooled in heat exchangers 4 and 5, is reduced in device 6 and sent to the reflux condenser 2, from which condensate is discharged through line 13, and reflux gas through line 14. Condensates, reduced in devices 8 and 9, are fed to the demethanizer 3, and output: from the top along the line 15 - the prepared gas, which is mixed with the reflux gas reduced in the device 7, is heated in the heat exchange section of the reflux condenser 2 and in the heat exchanger 4, from the middle part along the line 16 - the circulating reflux stream, which is heated in the heat exchanger 5 and returned to the demethanizer 3 , from the bottom of the demethanizer 3 through line 17 - demethanized condensate, which is sent to the fractionation unit 10 for separation into products discharged through lines 18. The resulting off-gas through line 19 is returned to the demethanizer 3. The dotted line shows the possible: supply of off-gas from line 19 to line 15, the location of the separator 20 in front of the dephlegmator 2 with the line 21 for supplying condensate to the demethanizer 3 with a reducing device 22, heating the bottom of the demethanizer 3 with a heat flow 23, the selection of LNG through line 24 and compression of the treated gas in the compressor station 25. The lines of supply of the inhibitor of hydrate formation (methanol) and the output of its waste solution are not shown conventionally.

Thus, the proposed installation allows you to increase the yield of hydrocarbons C₂₊ and can be used in the gas industry.