RU101787U1 - INSTALLATION OF LOW-TEMPERATURE SEPARATION OF A HYDROCARBON GAS - Google Patents

Abstract

 A low-temperature hydrocarbon gas separation unit comprising a gas pre-cooling unit including a heat exchanger, a propane cooler and a first stage separator, a gas condensation and cooling unit including heat exchangers, strippers, a turbo-expander unit, consisting of a turbo-expander and a turbocompressor, second-stage separators and a separator the third stage with a discharge line for the methane fraction of high pressure, a block for the extraction of ethane and a wide fraction of light carbohydrates prenode, including heat exchangers, a deethanizer, a demethanizer, consisting of a stripping section equipped with a remote pump for supplying bottoms liquid to the deethanizer, and a reinforcing section with a discharge line for the methane fraction of medium pressure and a valve installed on it, a helium concentrate production unit, and connecting pipelines, characterized the fact that the discharge line of the methane fraction of medium pressure at the outlet of the reinforcing section of the demethanizer is connected by a jumper to the discharge line of the methane fraction of high pressure at exit the separator of the third stage and is equipped with shutoff valves.

Description

The utility model relates to installations for the low-temperature separation of hydrocarbon gas in order to obtain target products and can be used at gas processing enterprises.

A known installation for separating gas mixtures containing a gas line of the processed gas, heat exchangers, separators, a helium distillation column with a liquid phase removal line, an expander, a demethanizer column with column supply lines, a bottoms liquid removal line, a pump, a liquid supply line to a deethanizer column.

The gas purified, dried and cooled to minus 30 ° С is divided into flows, which are separately cooled to 69 ° С and partially condensed in heat exchangers due to the cold throttled and expanded in the expander inverse fractions of separation gases, demethanization and power supply of the demethanizer column. Then the flows are mixed and separated, while the liquid is throttled and sent to the separation, from where the evaporated helium and light hydrocarbons are fed into the lower part of the helium distillation column. The liquid phase of the column is divided into two streams, one of which is throttled, partially evaporated in a heat exchanger and separated in a separator. The released liquid is throttled, mixed with the liquid released during cooling and separation of the gas supplied to the processing, and fed as a feed to the demethanizer column. The steam released during cooling and separation of the first part of the liquid phase of the helium column is expanded in the expander, combined with the rest of the liquid phase of the helium column, separated and the liquid is sent as cold irrigation to the demethanizer column. The bottom liquid of the demethanizer column is divided into ethane and broad fractions of light hydrocarbons (BFLH) in the deethanizer column [USSR Author's Certificate No. 1645796, IPC F25J 3/02, publ. 04/30/91].

Also known is a low-temperature hydrocarbon gas separation unit consisting of a gas pre-cooling unit including a heat exchanger, a propane cooler and a first-stage separator, a gas condensation and cooling unit including heat exchangers, stripping columns, a turbo-expander unit consisting of a turbo-expander (item 20) and a turbocharger, second stage separators and a third stage separator (pos. 17) with a high pressure methane fraction (MPHE) discharge line to the expander (p oz. 20), a unit for the separation of ethane and a wide fraction of light hydrocarbons, including heat exchangers, a deethanizer, a demethanizer, consisting of a stripping (pos. 25) section equipped with an external pump (pos. 29) for supplying bottoms liquid to the deethanizer (pos. 26) , and a reinforcing (pos. 24) section with a discharge line for the methane fraction of medium pressure (MFSD) and a valve installed on it (without position) [see the drawing of pos. 24 is connected from above to pos. 8 by the line on which the valve is installed (position without number)], a helium concentrate production unit and connecting pipelines [RF Patent No. 32583, 7 IPC F25J 3/00, publ. 09/20/2003 in bull. No. 26], which is the closest in combination of essential features and the achieved result and is taken as a prototype.

The main disadvantage of the known installations is that when the pump, supplying bottoms liquid from the stripping section of the demethanizer to the deethanizer, needs to be stopped for repairs, the installation must be stopped. Due to downtime, the production of target products and the efficiency of the installation are reduced.

The objective of the claimed utility model is to increase the efficiency of the installation of low-temperature separation of hydrocarbon gas.

The task was to install a low-temperature separation of hydrocarbon gas containing a gas pre-cooling unit including a heat exchanger, a propane cooler and a first stage separator, a gas condensation and cooling unit, including heat exchangers, stripping columns, a turbo-expander unit consisting of a turbo-expander and a turbocompressor, and second separators stages and a third stage separator with a methane fraction extraction line for high pressure, an ethane separation unit and a wide light hydrocarbon fractions, including heat exchangers, a deethanizer, a demethanizer, consisting of a stripping section equipped with a remote pump for supplying bottoms liquid to the deethanizer, and a strengthening section with a methane fraction discharge line of medium pressure and a valve installed on it, a helium concentrate production unit, and connecting pipelines , it is decided that the discharge line of the methane fraction of medium pressure at the exit from the reinforcing section of the demethanizer is connected by a jumper to the discharge line of the methane fraction of high pressure at the outlet of the third stage separator and is equipped with shutoff valves.

The difference between the claimed utility model is that the medium pressure methane discharge line at the outlet of the reinforcing section of the demethanizer is connected by a jumper to the high pressure methane fraction discharge line at the outlet of the third stage separator and is equipped with shutoff valves.

The presence in the installation of a jumper connecting the discharge lines of the methane fraction of medium pressure at the outlet of the reinforcing section of the demethanizer with the line of removal of the methane fraction of high pressure at the outlet of the third stage separator, as well as shutoff valves, allows the installation to continue to operate in the event of a failure or removal of the remote pump for repair feeding bottoms liquid from the stripping section of the demethanizer to the deethanizer by creating high pressure up to 3.9 MPa in the demethanizer. As a result, the bottoms liquid flows by gravity into the deethanizer, the pressure in which is constantly maintained at about 2.9 MPa.

The technical result is to ensure spontaneous flow of bottoms liquid from the stripping section of the demethanizer to the deethanizer with the remote pump turned off, which eliminates the need for simple installation and improves its efficiency.

The drawing shows a diagram of the inventive installation of low-temperature separation of hydrocarbon gas.

The installation contains the following blocks.

A gas pre-cooling unit, including a feed gas supply pipe 1, a heat exchanger 2, a propane refrigerator 3, a first stage separator 4, installed in series.

The gas condensation and cooling unit, including heat exchangers 5–9, second-stage separators 10–11, a third-stage separator 12 with a high-pressure methane fraction outlet line 13, stripping columns 14–15, a condenser 16, and a turbo-expansion unit consisting of a turbo-expander 17 and turbocharger 18.

The unit for the separation of ethane and a wide fraction of light hydrocarbons, including heat exchangers 19-20, deethanizer 21, demethanizer, consisting of strengthening 22 and stripping 23 sections. The strengthening section 22 has a mid-pressure methane fraction removal line 24 (MFSD) with a valve 25 (pressure regulator) installed on it, which is connected by a jumper 26 to the MFVD exhaust line 13. On the jumper 26, shutoff valves 27 are installed. The stripping section 23 is equipped with a remote pump 28 for supplying bottoms liquid to the deethanizer 21, as well as shutoff valves 29-31.

A block for producing a helium concentrate, including a helium distillation column 32, a boiler 33, heat exchangers 34-35.

Installation low-temperature separation of hydrocarbon gas works as follows.

Natural (raw) gas, previously drained and purified from sulfur compounds in special plants, is supplied to the installation via pipeline 1 to the gas pre-cooling unit at a pressure of 4.8-5.2 MPa at a temperature of no higher than 45 ° C. The gas flow passes sequentially through a heat exchanger 2, a propane cooler 3, where it is pre-cooled and partially condensed due to the cold of the reverse flow of MFSD and boiling propane. Cooling is carried out to a temperature not exceeding minus 28 ° С. Then the stream enters the separator 4 of the first stage, where due to the partial condensation of hydrocarbons, the liquid phase is released. The liberated liquid phase is removed from the separator 4 and fed to the demethanizer strengthening section 22, and the gas phase in one stream enters further cooling and condensation in the heat exchanger 5 of the condensation and gas cooling unit and then into the separator 10 of the second stage, in the other stream enters through the heat exchanger 8 and further to the separator 10 of the second stage. The combined stream enters the separator 10 of the second stage, where the condensed liquid is separated at a temperature not lower than minus 80 ° C. The liquid from the separator 10 is throttled to the separator 11. During the throttling process, the liquid partially evaporates, while helium dissolved in the incoming liquid passes into the vapor phase, and the liquid is additionally enriched with ethane. The gas phase containing helium from the separator 11 enters the first stripping column 14 as a stripping gas. The remaining liquid is directed to the power of the strengthening 22 sections of the demethanizer.

The vapor phase from the separator 10 is directed to complete condensation by one stream through heat exchangers 6 and 7, and by another stream through the heat exchanger 9, at the exit of which the combined stream of supercooled liquid is throttled to the first stripping column 14 as a supply. In the column 14, as a result of heat and mass transfer, helium is released from the liquid, which enriches the gas phase, which enters the annular space of the condenser 16, where the condensation of hydrocarbon gases occurs due to the cold of the reverse flow of the medium pressure methane fraction passing through the pipe space.

The stripped gas enriched with helium to 0.55% vol. Enters the upper part of the second stripping column 15, where about 10% of the initial gas entering the column is stripped. Stripped gas with a helium content of up to 5.5% vol. then it is throttled to the distillation column 32 of the helium concentrate production unit, in which helium concentrate with a helium content of at least 80% vol. is released due to countercurrent condensation of the source gas. The enrichment of gas with helium occurs in the distillation column 32 as a result of cooling and condensation of the gas passing sequentially through the heat exchanger 33 due to the cold boiling liquid of the cube of the column 32 and the heat exchanger 34 due to the cold boiling under pressure of 0.12 MPa nitrogen. The bottoms liquid of the column 32 is throttled to 0.44 MPa and enters the tube space of the heat exchanger 34, and then is discharged as a low-pressure methane fraction (MFND).

At a temperature of about minus 90 ° С and a pressure of not more than 4.1 MPa, a high-pressure methane fraction (MPHE) is discharged from the bottom of the stripping column 14, most of which (up to 90%) is sent for heating to the heat exchanger 6, then it enters as a vapor-liquid mixture for separation in the separator 12 of the third stage, from where the liquid enters the reinforcing section 22 of the demethanizer as the main reflux.

The vapor phase leaving the separator 12 under a pressure of up to 3.9 MPa enters through the line 13 of the high-pressure methane fraction to the heat exchanger 8 for heating and then to the expansion into the turboexpander 17. At the same time, the shut-off valve 27 on the jumper 26 is in the “closed” position ”, And the valve 25 on line 24 is in the“ open ”position and works as a pressure regulator up to 1.8 MPa. Next, the expanded turboexpander stream is combined with the medium pressure methane fraction stream from the strengthening section 22 of the demethanizer and after recovering the cold, it is successively compressed in the heat exchangers 9, 5 and 2 in the turbocompressor 18 and removed from the unit.

The bottoms liquid stream from the second stripping column 15 is throttled to a pressure of about 1.7 MPa, enters as a refrigerant into the pipe space of the condenser 16 and then combines with a smaller (up to 10%) bottoms liquid stream from the first stripping column 14. Further, this flow is directed to the recovery of cold in heat exchangers 7, 6, 5, 2 and is combined with the methane fraction stream after expansion, is compressed in the turbocompressor 18 of the turboexpander unit, and is withdrawn from the installation.

In the demethanizer 22-23, in the process of rectification of a mixture of hydrocarbons, a methane fraction is obtained as a distillate and a hydrocarbon fraction of C ₂ and higher as a bottom residue. In the strengthening section 22 of the demethanizer, liquid hydrocarbons and gaseous methane are separated. The methane fraction is removed from the upper part of the reinforcing 22 section along line 24, throttled to a pressure of 1.8 MPa and mixed with the expanded turbulent expander flow MFSD. Liquid hydrocarbons from the lower part of the strengthening section 22 enter the stripping section 23 of the demethanizer, flow into the cube in contact with the vapor rising upwards, and are enriched in ethane and NGL, and the methane released from the liquid enters the strengthening section 22. The liquid containing ethane and BFLH is pumped from the cube of the stripping section 23 to a deethanizer 21 with a pressure of up to 2.9 MPa, and the shutoff valves 31 are in the “closed” position and the valves 29-30 are in the “open” position. In the deethanizer 21, in the process of rectification, the ethane fraction is obtained as a distillate, and BFLH as the bottom residue.

In case of failure of the pump 28 or its conclusion for scheduled repairs, the shutoff valves 29 and 30 are closed, the valves 31 are opened, the valve 25 on line 24 is closed, thereby providing a pressure rise in the demethanizer 22-23 to a value of not more than 3.9 MPa then the shutoff valves 27 are opened.

In this case, the MFVD from the reinforcing section 22 at a pressure of about 3.6 MPa and at a temperature not lower than minus 108 ° C is sent via a jumper 26 to combine with the high-pressure methane fraction from the separator 12 of the third stage. The combined MFVD flow is fed to a heat exchanger 8 for heating, then expanded to a turboexpander 17, and then, after recovering cold in heat exchangers 9, 5, 2 and compression in a turbocompressor 18, it is removed from the unit.

The bottom liquid from the stripping section 23 of the demethanizer at a pressure of not more than 3.9 MPa flows by gravity to the deethanizer 21. In the deethanizer 21, in the process of rectification, the ethane fraction is obtained as distillate, and BFLH is used as the bottom residue.

The main advantage of the claimed utility model is the elimination of plant downtime when the pump is being repaired, and the supply of combined MFVD flows from the reinforcing section of the demethanizer and from the third stage separator will allow the turboexpander to be reloaded by about 30%, and thereby generate more cold.

The inventive installation of low-temperature separation of hydrocarbon gas in 2008 passed pilot tests at the third stage of the Orenburg helium plant.

Claims (1)

A low-temperature hydrocarbon gas separation unit comprising a gas pre-cooling unit including a heat exchanger, a propane cooler and a first stage separator, a gas condensation and cooling unit including heat exchangers, strippers, a turbo-expander unit, consisting of a turbo-expander and a turbocompressor, second-stage separators and a separator third stage with a discharge line for the methane fraction of high pressure, a block for the extraction of ethane and a wide fraction of light carbohydrates prenode, including heat exchangers, a deethanizer, a demethanizer, consisting of a stripping section equipped with a remote pump for supplying bottoms liquid to the deethanizer, and a reinforcing section with a discharge line for the methane fraction of medium pressure and a valve installed on it, a helium concentrate production unit, and connecting pipelines, characterized the fact that the discharge line of the methane fraction of medium pressure at the outlet of the reinforcing section of the demethanizer is connected by a jumper to the discharge line of the methane fraction of high pressure at exit the separator of the third stage and is equipped with shutoff valves.