RU2382301C1 - Unit for low-temperature separation of hydrocarbon gas - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to hydrocarbon gas processing by low-temperature condensation and can be used in oil-and-gas processing industry. Proposed unit comprises hydrocarbon gas feed pipeline, hydrocarbon gas cooler communicated with first fractionating column furnished with branch pipes to discharge residue gas and to feed shower at tope part and branch pipe to feed condensate into second fractionating column. The latter incorporates branch pipes to discharge deethanisation gas phase and to feed shower at top part, as well as branch pipe to discharge liquid phase enriched with heavy hydrocarbons C_3+higher at bottom part. Residue gas discharge branch pipe is communicated with residue gas heat exchanger and, further, with hydrocarbon gas cooler. Deethanisation gas phase discharge branch pipe is communicated with heat exchanger and, further on, with a tank furnished with deethanisation gas phase discharge branch pipe and liquid phase discharge branch pipe communicated with branch pipe feeding shower into second fractionating column. Proposed unit comprises additionally heat exchanger device with heat exchange chamber communicates, in first heat carrier circuit, with bottom part of the first fractionating column and, in second heat carrier circuit, with the tank deethanisation gas phase discharge branch pipe and residue gas heat exchanger.

EFFECT: increased extraction of fraction C_3+higher from hydrocarbon gas.

6 cl, 3 dwg

Description

The invention relates to techniques for processing hydrocarbon gases by low-temperature condensation and can be used in the oil and gas processing industries.

A known installation described in the method of liquefying natural gas (see RF patent No. 2093765, IPC ⁶ F25J 1/00, publ. 10/20/1997), including a hydrocarbon gas supply pipe, a hydrocarbon gas cooling unit connected to the first column equipped with a methane-enriched residual gas outlet pipe and an irrigation supply pipe in the upper part and a liquid phase outlet pipe in the lower part that is connected to a liquid phase inlet pipe in a second column having a gas phase outlet pipe and an irrigation supply pipe in the upper hour the outlet pipe of the liquid phase enriched in hydrocarbons heavier than methane in the lower part, while the outlet pipe of the residual gas enriched in methane is connected to the heat exchanger and then to the cooling unit for the hydrocarbon gas, the outlet port of the gaseous phase is connected to a propane refrigerator and then with a tank having gas and liquid phase outlet pipes, the gas phase outlet pipe being connected in series with a heat exchanger, separator and an irrigation supply pipe to the first column, and a liquid output pipe Phase connected to the pipe supplying irrigation to the second column, and further - a heat exchanger.

Common features of the known and proposed installations are:

- hydrocarbon gas supply pipeline;

- a hydrocarbon gas cooling unit connected to the first column;

- the first column, equipped with a nozzle for the exit of the residual gas enriched in methane, and a nozzle for supplying irrigation in the upper part and a nozzle for exiting the liquid phase in the lower part, connected to the nozzle for supplying a liquid phase to the second column;

- a second column equipped with a gaseous phase outlet pipe and an irrigation supply pipe in the upper part and a liquid phase outlet pipe enriched in hydrocarbons heavier than methane in the lower part;

- outlet pipe for residual gas enriched in methane, connected to a heat exchanger and further to a hydrocarbon gas cooling unit;

- a outlet pipe for the gaseous phase from the top of the second column, connected to a heat exchanger and then to a tank equipped with outlet pipes for the gas and liquid phases;

- a pipe for exiting the liquid phase from the tank, connected to a pipe for supplying irrigation to the second column;

- pipelines and shut-off and control valves.

The disadvantages of the known installation are:

- increased pressure in the first column, which requires a higher pressure at the inlet of the installation to obtain the required level of cold due to the expansion of the gaseous phase from the low-temperature separator;

- reduced pressure in the second column, leading to an increase in the loss of target heavy hydrocarbons with an upper gaseous product, which in turn leads to an increase in the content of heavy hydrocarbons in the irrigation of the first column and an increase in losses of the target heavy hydrocarbons with an upper gaseous product from it.

The closest in technical essence and the achieved result is the installation of low-temperature separation of hydrocarbon gas (see patent US 4690702, F25J 3/02, С07С 7/09, publ. 09/09/1987), including a hydrocarbon gas supply pipe, a hydrocarbon gas cooling unit connected to the first fractionation column equipped with a methane-enriched residual gas outlet pipe and irrigation supply pipes in the upper part and a liquid phase outlet pipe in the lower part connected to a liquid phase inlet port in the second fr a casing column equipped with a gas phase outlet pipe and an irrigation supply pipe in the upper part and a liquid phase outlet pipe enriched in higher hydrocarbons in the lower part, while the methane-rich residual gas outlet pipe is connected to the residual gas heat exchanger and then to the hydrocarbon cooling unit gas, the outlet pipe of the gas phase is connected to a propane cooler and then to a vessel having nozzles for the exit of the gas and liquid phases, and the nozzle for the exit of the gas phase from the vessel is connected through h a heat exchanger with a nozzle for supplying irrigation to the first fractionating column, and a nozzle for exiting the liquid phase is connected to a nozzle for supplying irrigation to the second fractionating column and additionally through a heat exchanger with a nozzle for supplying irrigation to the first fractionating column.

Common features of the known and proposed installations are:

- hydrocarbon gas supply pipeline;

- a hydrocarbon gas cooling unit connected to the first fractionating column;

- the first fractionation column equipped with outlet pipes for stripping gas and an irrigation supply pipe in the upper part and a condensate outlet pipe in the lower part connected to the condensate inlet pipe in the second fractionation column;

- a second fractionation column equipped with nozzles for the exit of the gas phase of deethanization and irrigation in the upper part and an outlet for the liquid phase enriched with heavy C3 ₊ hydrocarbons _above , in the lower part;

- a stripped gas heat exchanger connected to the outlet pipe of the stripped gas and to the hydrocarbon gas cooling unit;

- an outlet pipe for the gas phase of the deethanization connected to the heat exchange unit and further to a vessel having nozzles for the exit of the gas of deethanization and the liquid phase;

- a nozzle for exiting the liquid phase from the tank, connected to the nozzle for supplying irrigation to the second fractionating column;

- pipelines and shut-off and control valves.

A disadvantage of the known installation is the insufficient degree of cooling and condensation of the deethanization gas supplied to the irrigation of the first fractionating column, due to its cooling only due to the cold of the residual gas of the first fractionating column, which leads to a decrease in the extraction of the target hydrocarbons from the hydrocarbon gas - fraction C _{3 + higher} from the hydrocarbon gas.

The technical problem is to increase the degree of extraction from hydrocarbon gas fraction C _{3 + above} - a wide fraction of light hydrocarbons (NGL).

The problem is achieved in that in the installation of low-temperature separation of hydrocarbon gas, including a hydrocarbon gas supply pipe, a hydrocarbon gas cooling unit connected to a first fractionation column provided with outlet pipes for stripped gas and an irrigation feed in the upper part and a condensate outlet pipe in the lower part connected with a condensate inlet pipe into a second fractionating column equipped with pipes for the exit of the gas phase of deethanization and irrigation in the upper part and the outlet pipe of the liquid phase enriched with heavy C _{3 +} hydrocarbons _above , in the lower part, the stripped gas heat exchanger connected to the outlet pipe of the stripped gas and to the hydrocarbon gas cooling unit, the outlet pipe of the gas phase of deethanization connected to the heat exchange unit and further with a tank having a nozzle for the exit of gas of deethanization and a nozzle for the exit of the liquid phase connected to the nozzle for supplying irrigation to the second fractionating column, pipelines and shut-off and control valves, on the heat exchange device, the heat-exchanger space of the first heat carrier which is connected to the lower part of the first fractionator, and the second heat-carrier - with the deethanizer nozzle exit gas from the vessel and the heat exchanger stripping gas.

In addition, the condensate outlet pipe from the first fractionation column is connected to the condensate inlet pipe to the second fractionation column through a heat exchanger unit made in the form of a heat exchanger of the gas phase of deethanization.

In addition, a propane cooler is additionally installed in the pipeline for the exit of the gas phase of deethanization from the second fractionation column after the heat exchanger of the gas phase of deethanization.

In addition, the condensate outlet pipe from the first fractionation column is connected to the condensate inlet pipe to the second fractionation column through a heat exchanger assembly made in the form of a hydrocarbon gas heat exchanger, which is connected to a hydrocarbon gas supply pipe of the cooling unit.

In addition, the outlet pipe of the liquid phase from the tank is connected to the heat exchange space of the second heat transfer medium of the heat exchange device.

In addition, the outlet pipe of the liquid phase from the tank is connected to the heat exchanger of the stripped gas.

Providing the installation with a heat exchanger connected via the first heat carrier to the bottom of the first fractionating column, and through the second heat carrier, to the outlet pipe for the deethanization gas from the tank and to the topped gas heat exchanger, allows to further cool the deethanization gas due to the cold liquid from the bottom of the first fractionating column, which means and it’s better to condense it, i.e. get more fluid to irrigate the first fractionation column. In addition, the cooling of the deethanization gas, first in the heat exchanger with the liquid at the bottom of the first fractionating column, and then in the stripped gas heat exchanger with a stream of stripped gas, makes it possible to control the temperature of the first fractionation column and, by lowering the temperature of its upper part, reduce the content of NGL in the upper product of this column. This, in turn, makes it possible to increase the degree of NGL recovery in the second fractionation column, since the less C _{3 +} hydrocarbons are lost with the upper product of the first fractionation column, the more their content in the lower product of this column, which is the raw material for the second fractionation column, increases .

The connection of the condensate outlet pipe from the bottom of the first fractionation column to the condensate inlet pipe of the second fractionation column through a heat exchanger made in the form of a heat exchanger of the gas phase of deethanization or a heat exchanger of hydrocarbon gas allows only internal flows (or a stream of gas phase of deethanization coming from the top) to be used for heat exchange the second fractionation column, or stream of the original hydrocarbon gas), without resorting to the additional use of propane cold, thereby nizhaya operating costs.

The additional installation of a propane cooler in the pipeline for the exit of the deethanization gas phase from the second fractionating column after the deethanization gas phase heat exchanger allows additionally cooling the stream of the deethanization gas phase obtained in the second fractionation column with propane cold during processing of the hydrocarbon raw material and avoiding the temperature increase in the first fractionating column from - due to the heat of condensation of hydrocarbons and, consequently, reduce recovery I NGL, and also to eliminate the dependence of the degree of NGL extraction on the temperature of the feed hydrocarbon feed to the plant in summer and winter, and thus maintain a high degree of NGL extraction.

The connection of the outlet pipe of the liquid phase from the tank with the heat exchange space of the second heat transfer medium of the heat exchanger device or with the topped gas heat exchanger allows to increase (if necessary) the amount of irrigation supplied to the first fractionation column. The amount of liquid phase taken from the tank can be up to 90% and is determined by the maximum recovery of C 3+ hydrocarbons _above (or the minimum C _{3 +} hydrocarbon content _above in the gas phase of the first fractionation column). With an increase in the selection of the liquid phase from the vessel supplied for mixing with the deethanization gas, the recovery of BFLH increases due to an increase in the amount of irrigation of the first fractionation column, and then, when the optimum point is reached, the extraction begins to decrease due to an increase in the propane content in the deethanization gas, which occurs due to for reducing the irrigation of the second fractionating column (the selection of liquid for injection into the gas of deethanization reduces the residual amount of liquid that can be supplied for irrigation of the second fractionating col nna).

Figure 1 presents a schematic flow chart of a low-temperature separation of hydrocarbon gas, figure 2, 3 - variants of the circuit according to claim 3, 4 of the claims, respectively.

The installation comprises a hydrocarbon gas supply pipeline I, which sequentially connects the equipment of a hydrocarbon gas cooling unit, including heat exchangers 1, 2, 3, a low-temperature separator 4, a turboexpander 5 and a throttle 6. The output from the turbo-expander 5 and the throttle 6 is connected to the first fractionation column 7 provided the outlet gas outlet pipe 8 and the irrigation supply pipe 9 in the upper part and the condensate outlet pipe 10 in the lower part. The condensate outlet pipe 10 from the first fractionation column 7 is connected to the condensate supply pipe 11 to the second fractionation column 12, equipped with a deethanization gas phase outlet pipe 13 and an irrigation supply pipe 14 at the top and a liquid phase enrichment pipe 15 enriched with heavy C _{3 +} hydrocarbons _above , in the lower part.

The outlet pipe 8 of the stripped gas is connected in series with the heat exchanger 16 of the stripped gas, the heat exchangers 3, 1 and the compressor part of the turboexpander 5. The output from the heat exchanger 16 of the stripped gas is also connected to the inductor 17.

The condensate outlet pipe 10 from the first fractionation column 7 can be connected to the condensate inlet pipe 11 to the second fractionation column 12 through a heat exchange unit, which can be made in the form of a heat exchanger 18 of the gas phase of deethanization (see Figs. 1, 2) or in the form of a heat exchanger 19 hydrocarbon gas (see figure 3), which is connected to the pipeline I of the hydrocarbon gas supply of the cooling unit.

The pipe 13 for the exit of the gas phase of deethanization from the second fractionating column 12 can be connected to a heat exchanger 18 of the gas phase of deethanization (see Figs. 1, 2). After the heat exchanger 18 of the gas phase of the deethanization, a propane refrigerator 20 can be additionally installed (see FIG. 2). The outlet 13 of the gas phase of the deethanization can be directly connected to the propane cooler 20 (see figure 3).

The outlet from the heat exchanger 18 of the gas phase of deethanization (see Fig. 1) or from the propane cooler 20 (see Fig. 2, 3) is connected to a pipe 21 for supplying the gas phase of deethanization to a tank 22 provided with a pipe 23 for the exit of gas of deethanization and a pipe 24 liquid phase. The pipe 24 for the exit of the liquid phase from the tank 22 is connected to the pipe 14 for supplying irrigation to the second fractionating column 12.

The installation is additionally equipped with a heat exchanger 25, made, for example, in the form of a thermosiphon, the heat exchange space of which is connected through the first heat carrier to the bottom of the first fractionation column 7, and through the second heat carrier, with a pipe 23 for the deethanization gas outlet from the tank 22 and with a topped gas heat exchanger 16 .

The pipe 24 of the exit of the liquid phase from the tank 22 can be connected to a heat exchanger 25 or to a heat exchanger 16 of stripped gas.

Heavy hydrocarbon-rich outlet pipe 15

With _{3 + above} , from the second fractionating column 12, it is connected in series with the riboiler 26 and the air cooling apparatus 27.

The hydrocarbon gas cooling unit can be additionally equipped with a propane cooler 28 (see Fig. 2, 3) installed in front of the heat exchanger 3.

The unit is equipped with pumps, pipelines and the necessary shut-off and control valves.

Installation works as follows:

Light hydrocarbon gas with a temperature of 40 ° C and a pressure of 4 MPa enters the hydrocarbon gas cooling unit. After the hydrocarbon gas is cooled in heat exchangers 1, 2, 3 to a temperature of minus 46.5 ° С, it partially condenses and enters a low-temperature separator 4, in which gas and liquid phases are separated.

When processing hydrocarbon raw materials of medium or heavy composition, the hydrocarbon gas after heat exchanger 2 is fed for additional cooling to propane refrigerator 28 (see Figs. 2, 3), after which it enters heat exchanger 3.

The gas phase from the low-temperature separator 4 is directed to expand into the expander of the turbine expander 5, after which it is supplied with a temperature of minus 80.8 ° С to the middle part of the first fractionating column 7. The liquid phase from the low-temperature separator 4 is throttled in the choke 6 and with a temperature of minus 63, 4 ° C is fed to the bottom of the first fractionation column 7.

In the first fractionating column 7, at the top of the column minus 85.5 ° C, the bottom temperature of the column minus 54.6 ° C and a pressure of 1.45 MPa, the upper product is stripped gas and the lower product is condensate.

The stripped gas is heated in the stripped gas heat exchanger 16, then heat exchangers 3, 1 pass sequentially and enters the compressor part of the turboexpander 5, where its pressure rises, and then is removed from the installation.

The condensate is supplied to the heat exchanger 18 of the gas phase of deethanization for heating due to the heat of the upper product of the second fractionation column 12.

In the processing of hydrocarbons of medium or heavy composition, the condensate can be heated by the flow of the original hydrocarbon gas in the hydrocarbon gas heat exchanger 19 (see figure 3).

The heated condensate enters the second fractionation column 12, in which at the top of the column 1.4 ° C, the bottom temperature of the column 84.6 ° C and a pressure of 2.42 MPa, the gas phase of deethanization is obtained as the upper product and as the lower product NGL, which is removed from the installation.

The obtained gas phase of deethanization is cooled in the heat exchanger 18 of the gas phase of deethanization by a condensate stream from the bottom of the first fractionation column 7 to a temperature of minus 22.6 ° C, partially condensed and fed to a container 22, in which it is separated into a gas of deethanization and a liquid phase.

During the processing of hydrocarbons of medium or heavy composition, the obtained gas phase of deethanization after the heat exchanger 18 of the gas phase of deethanization can be further cooled in a propane refrigerator 20 before being fed to the tank 22 (see FIG. 2). In addition, the obtained gas phase of deethanization can be directly fed to the propane refrigerator 20 if the condensate from the first fractionation column 7 is heated by a stream of hydrocarbon gas (see FIG. 3).

From the tank 22, the liquid phase is supplied to the irrigation of the second fractionating column 12, and the deethanization gas enters the heat exchange device 25 installed in the lower part of the first fractionating column 7.

Liquid is supplied to the heat exchange device 25 from the bottom of the first fractionating column 7, which, having passed by gravity, returns to the cube of the first fractionating column 7, which allows to increase the heat exchange efficiency of deethanization gas with this stream and thereby more deeply cool the deethanization gas stream.

From a heat exchanger 25, a deethanization gas with a temperature of minus 60 ° C enters a topped gas heat exchanger 16, where it is cooled by a stream of topped gas. The cooled deethanization gas stream passes through the throttle 17 because the pressure in the second fractionation column 12 is greater than the pressure in the first fractionation column 7, and with a temperature of minus 81.6 ° C, the condensed deethanization gas enters the first fractionation column 7 as an irrigation.

To increase the amount of irrigation feed to the first fractionating column 7, a portion of the liquid phase fed to the irrigation of the second fractionating column 12 from the tank 22, in the amount of 4500 kg / h, is mixed with a stream of chilled deethanization gas exiting the heat exchanger 25 before being fed to topped gas heat exchanger 16.

In the processing of medium or heavy hydrocarbon feedstocks to increase the amount of irrigation feed to the first fractionating column 7, a part of the liquid phase supplied to the second fractionation column 12 to be irrigated from the tank 22 can be mixed with a deethanization gas stream before being fed to the heat exchange device 25 ( Fig. not shown).

The table shows more detailed calculation data of the proposed scheme of low-temperature separation of hydrocarbon gas and prototype for different compositions of hydrocarbon gas.

Claims (6)

1. Installation of low-temperature separation of hydrocarbon gas, including a hydrocarbon gas supply pipe, a hydrocarbon gas cooling unit, connected to the first fractionation column equipped with outlet pipes for stripped gas and an irrigation feed in the upper part and a condensate outlet pipe in the lower part connected to the condensate inlet a second fractionation column equipped with nozzles for the exit of the gas phase of the deethanization and supply of irrigation in the upper part and a nozzle for the exit of the liquid phase, is enriched heavy C3 + hydrocarbons above, in the lower part, a stripped gas heat exchanger connected to a stripped gas outlet pipe and a hydrocarbon gas cooling unit, a gas outlet for a deethanization gas phase, connected to a heat exchange unit and further with a tank having a deethanization gas outlet pipe and a pipe liquid phase outlet connected to the nozzle for irrigation supply to the second fractionating column, pipelines and shut-off and control valves, characterized in that the installation is additionally equipped with heat exchange a device, the heat exchange space of which is connected via the first heat carrier to the lower part of the first fractionation column, and by the second heat carrier, to the outlet pipe for the deethanization gas from the tank and to the topped gas heat exchanger. 2. Installation of low-temperature separation of hydrocarbon gas according to p.
1, characterized in that the condensate outlet pipe from the first fractionation column is connected to the condensate inlet pipe to the second fractionation column through a heat exchange unit made in the form of a heat exchanger of the gas phase of deethanization. 3. Installation of low-temperature separation of hydrocarbon gas according to p.
2, characterized in that the propane cooler is additionally installed on the pipeline for exiting the gas phase of the deethanization from the second fractionating column after the heat exchanger of the gas phase of deethanization. 4. Installation of low-temperature separation of hydrocarbon gas according to p.
1, characterized in that the condensate outlet pipe from the first fractionation column is connected to the condensate inlet pipe to the second fractionation column through a heat exchanger assembly made in the form of a hydrocarbon gas heat exchanger, which is connected to the hydrocarbon gas supply pipe of the cooling unit. 5. Installation of low-temperature separation of hydrocarbon gas according to p.
1, characterized in that the pipe outlet of the liquid phase from the tank is connected to the heat exchange space of the second heat transfer medium of the heat exchange device. 6. Installation of low-temperature separation of hydrocarbon gas according to p.
1, characterized in that the pipe outlet of the liquid phase from the tank is connected to a heat exchanger of stripped gas.

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