CN216498390U - Device for denitrifying hydrocarbon-containing exhaust gas and recovering hydrocarbons - Google Patents

Abstract

The utility model discloses a device for denitrifying hydrocarbon-containing exhaust gas and recovering hydrocarbons, which comprises a first cooler, a first gas-liquid separator, a first membrane separator, a compressor, a second cooler, a second gas-liquid separator, a second membrane separator and a third membrane separator which are sequentially connected with one another through pipelines along the material flow direction, wherein an outlet at the permeation side of the first membrane separator is connected with an inlet of the compressor, and an outlet at the interception side of the first membrane separator is connected with a flare system; the outlet of the permeation side of the second membrane separator is connected with the process device, and the outlet of the interception side of the second membrane separator is connected with the inlet of the third membrane separator; the permeate side outlet of the third membrane separator is connected to the inlet of the compressor and the retentate side outlet is connected to the inlet of the first membrane separator. Through the three-stage membrane separation process, the nitrogen concentration in the hydrocarbon-containing exhaust gas can be removed to be below 1 percent, the hydrocarbon recovery rate is above 95 percent, and the hydrocarbon is returned to the process device to realize the reutilization; compared with cryogenic and pressure swing adsorption processes, the full-membrane process flow is adopted, so that the equipment investment is low, the operation is simple and convenient, and the operation energy consumption is low.

Description

A device for denitrifying and recovering hydrocarbons from exhaust gas containing hydrocarbons

technical field

The utility model relates to the technical field of hydrocarbon recovery, in particular to a device for denitrifying hydrocarbon-containing exhaust gas and recovering hydrocarbons.

Background technique

Hydrocarbons are important raw materials in the petrochemical production process, and the recycling of hydrocarbons in the exhaust gas of petrochemical production plants has extremely high economic value. Industrial hydrocarbon-containing exhaust gas generally contains a lot of nitrogen. Nitrogen is an inert component, which does not participate in the polymerization reaction and is insoluble in hydrocarbon solvents. If it is directly returned to use without removing it, it will cause the nitrogen concentration in the reactor to increase continuously. The proportion of reaction materials such as hydrocarbons is constantly decreasing, which affects the reaction. Therefore, it is necessary to remove nitrogen from hydrocarbon-containing exhaust gas.

Cryogenic, pressure swing adsorption and membrane separation processes can be used for denitrification of hydrocarbon-containing exhaust gas. The cryogenic process is to condense and liquefy hydrocarbons by reducing the exhaust gas to a lower temperature, while nitrogen has a low liquefaction temperature and is not easy to condense, so most of it is in the gas phase, thereby being removed. The yield of hydrocarbons in the cryogenic process is high, but the liquefaction temperature is low, ethylene refrigeration is required, and the investment and energy consumption are large, and there is still a certain amount of nitrogen dissolved in the liquid product which cannot be removed, and cannot fully meet the recycling requirements. Require. In addition, if there is water in the exhaust gas, the cryogenic process requires a dehydration and drying unit before feeding, which increases the investment and complexity of the system. Pressure swing adsorption is a traditional purification process that removes nitrogen from exhaust gas to lower concentrations. However, when the hydrocarbon concentration is high, the required adsorption capacity is large, and there are also problems such as large equipment investment and high operating cost.

Compared with other technologies, the membrane separation process has the advantages of small footprint, low investment, simple operation and maintenance, greater operational flexibility and flexibility, and is increasingly used in the separation and recovery of hydrocarbons and nitrogen. However, the existing membrane process usually only pays attention to the recovery rate of hydrocarbons, and the nitrogen content in the recovered gas phase hydrocarbons is relatively high, which cannot be directly returned to the process unit for reuse.

Utility model content

The utility model provides a device for denitrifying hydrocarbon-containing exhaust gas and recovering hydrocarbons, so as to overcome the technical problems of high investment and operation energy consumption in cryogenic and pressure swing adsorption processes and low nitrogen removal rate in the existing membrane separation process.

In order to achieve the above object, the technical scheme of the present utility model is:

A device for denitrifying and recovering hydrocarbons from exhaust gas containing hydrocarbons, comprising a first cooler, a first gas-liquid separator, a first membrane separator, a compressor, a second cooler, a second gas-liquid separator, a first The second membrane separator and the third membrane separator are sequentially connected to the first cooler, the first gas-liquid separator, the first membrane separator, the compressor, the second cooler, and the second gas-liquid separator through pipelines along the flow direction. a separator, a second membrane separator and a third membrane separator;

The permeate side outlet of the first membrane separator is connected to the inlet of the compressor, and the retentate side outlet of the first membrane separator is connected to the flare system;

The permeate-side outlet of the second membrane separator is connected to the process device, and the retentate-side outlet of the second membrane separator is connected to the inlet of the third membrane separator;

The permeate-side outlet of the third membrane separator is connected to the inlet of the compressor, and the retentate-side outlet of the third membrane separator is connected to the inlet of the first membrane separator.

Further, each of the first membrane separator, the second membrane separator and the third membrane separator includes at least one membrane separation component.

Further, the structure of the membrane separation module is a combination of one or more of the spiral wound type, the plate-and-frame type and the hollow fiber type.

Further, all the membrane separation components have built-in organic hydrocarbon separation membranes.

Further, the first cooler and the second cooler are both water coolers.

Beneficial effects: The utility model provides a device for denitrifying hydrocarbon-containing exhaust gas and recovering hydrocarbons. Through the three-stage membrane separation process, the nitrogen concentration in the hydrocarbon-containing exhaust gas can be removed to less than 1%, and the hydrocarbons can be recovered. Compared with cryogenic and pressure swing adsorption processes, it has less equipment investment, simple operation and low operating energy consumption.

Description of drawings

In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description The drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative labor.

1 is a schematic structural diagram of a device for denitrifying and recovering hydrocarbons from a hydrocarbon-containing exhaust gas disclosed by the utility model;

In the figure: 1, the first cooler, 2, the first gas-liquid separator, 3, the first membrane separator, 4, the compressor, 5, the second cooler, 6, the second gas-liquid separator, 7, The second membrane separator, 8, the third membrane separator.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present utility model more clear, the technical solutions in the embodiments of the present utility model will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present utility model. The embodiments described above are a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

This embodiment provides a device for denitrifying and recovering hydrocarbons from exhaust gas containing hydrocarbons, as shown in FIG. 1 , including a first cooler 1 , a first gas-liquid separator 2 , a first membrane separator 3 , and a compressor 4. The second cooler 5, the second gas-liquid separator 6, the second membrane separator 7 and the third membrane separator 8, the air inlet of the first cooler 1 is connected to the tower top of the process device through the pipeline 10, The air outlet of the first cooler 1 is connected to the air inlet of the first gas-liquid separator 2 through a pipeline 11 , and the air outlet of the first gas-liquid separator 2 is connected to the first membrane separation through a pipeline 12 The inlet of the first membrane separator 3, the outlet of the permeate side of the first membrane separator 3 is connected to the inlet of the compressor 4 through the pipeline 13, and the outlet of the retentate side of the first membrane separator 3 is connected to the torch system through the pipeline 21, so The outlet of the compressor 4 is connected to the air inlet of the second cooler 5 through the pipeline 14, the air outlet of the second cooler 5 is connected to the air inlet of the second gas-liquid separator 6 through the pipeline 15, The gas outlet of the second gas-liquid separator 6 is connected to the inlet of the second membrane separator 7 through the pipeline 16 , the permeate side outlet of the second membrane separator 7 is connected to the process device through the pipeline 17 , and the second membrane separator 7 The outlet on the retentate side of the membrane separator 7 is connected to the inlet of the third membrane separator 8 through a pipeline 18 , and the outlet on the permeate side of the third membrane separator 8 is connected to the inlet of the compressor 4 through a pipeline 19 . The outlet of the retentate side of the three-membrane separator 8 is connected to the inlet of the first membrane separator 3 through a pipeline 20 . Through the three-stage membrane separation process, the nitrogen concentration in the hydrocarbon-containing exhaust gas can be removed to less than 1%, and the hydrocarbon recovery rate is more than 95%, which can be returned to the process device for reuse; The pressure swing adsorption process has low equipment investment, simple operation and low operating energy consumption.

In a specific embodiment, the first membrane separator 3 , the second membrane separator 7 and the third membrane separator 8 each include at least one membrane separation component, and the number of membrane separation components can be flexibly increased according to needs, with flexibility big advantage.

In a specific embodiment, the structure of the membrane separation module is a combination of one or more of a spiral wound type, a plate-and-frame type and a hollow fiber type.

In a specific embodiment, each of the membrane separation components has a built-in organic hydrocarbon separation membrane, and the organic hydrocarbon separation membrane is an organic polymer membrane with preferential permeability to hydrocarbons, and the material is preferably silicone rubber.

In a specific embodiment, the first cooler 1 and the second cooler 5 are both circulating water coolers.

The workflow of this embodiment is:

The raw material gas (from the top exhaust gas of the polyolefin unit, the ethylene content is about 70%, the nitrogen content is about 12%, the pressure is 1.3MPa-1.5MPaG, and the temperature is 70°C-120°C), firstly enters the first cooler from the inlet line 10 1. Lower the temperature to 40°C, and then enter the first gas-liquid separator 2 through the pipeline 11 to remove the condensate, and the non-condensable gas enters the first membrane separator 3 through the pipeline 12. In the first membrane separator 3, hydrocarbons preferentially permeate the membrane to be enriched on the permeate side, and the nitrogen-rich tail gas obtained from the interception side is sent to the torch system for discharge through pipeline 21; the nitrogen concentration in the permeate gas is about 5%, and it enters through pipeline 13 The compressor 4 increases the pressure to about 1.5MPaG, and then enters the second cooler 5 through the pipeline 14. After water cooling, it enters the second gas-liquid separator 6 through the pipeline 15 to remove a small amount of condensed liquid after compression and condensation. The second membrane separator 7 is entered via line 16 . In the second membrane separator 7, the hydrocarbons preferentially permeate the membrane and are enriched on the permeate side to obtain a product gas with a nitrogen concentration of less than 1%, which is sent to the process unit via pipeline 17 for reuse; Membrane separator 8. In the third membrane separator 8, the nitrogen concentration on the permeate side is lower than that of the permeate gas of the first membrane separator 3, and returns to the inlet of the compressor 4 through the pipeline 19, and merges with the permeate gas of the first membrane separator 3 to further reduce the second membrane separator. The nitrogen concentration of the intake air of the membrane separator 7; the nitrogen concentration of the interception side of the third membrane separator 8 is lower than that of the raw material gas, and returns to the inlet of the first membrane separator 3 through the pipeline 20, and merges with the treated raw material gas to further reduce the first The nitrogen concentration in the inlet of the membrane separator 3 is further recovered at the same time, so as to improve the recovery rate of hydrocarbons to more than 95%.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present utility model, but not to limit them; although the present utility model has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that : it can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the various embodiments of the present utility model Scope of technical solutions.

Claims (5)

1. A device for denitrifying hydrocarbon-containing exhaust gas and recovering hydrocarbons, characterized in that it comprises a first cooler (1), a first gas-liquid separator (2), a first membrane separator (3), a compressor The machine (4), the second cooler (5), the second gas-liquid separator (6), the second membrane separator (7) and the third membrane separator (8) are connected in sequence through pipelines along the flow direction. First cooler (1), first gas-liquid separator (2), first membrane separator (3), compressor (4), second cooler (5), second gas-liquid separator (6) , the second membrane separator (7) and the third membrane separator (8); The outlet on the permeate side of the first membrane separator (3) is connected with the inlet of the compressor (4), and the outlet on the retentate side of the first membrane separator (3) is connected with the torch system; The outlet of the permeate side of the second membrane separator (7) is connected to the process device, and the outlet of the retentate side of the second membrane separator (7) is connected to the inlet of the third membrane separator (8); The outlet on the permeate side of the third membrane separator (8) is connected to the inlet of the compressor (4), and the outlet on the retentate side of the third membrane separator (8) is connected with the first membrane separator (3). ) entry connection. 2 . The device for denitrifying hydrocarbon-containing exhaust gas and recovering hydrocarbons according to claim 1 , wherein the first membrane separator ( 3 ), the second membrane separator ( 7 ) and the third membrane separator ( 7 ) and the third The membrane separators (8) each comprise at least one membrane separation module. 3. A device for denitrifying and recovering hydrocarbons from a hydrocarbon-containing exhaust gas according to claim 2, wherein the structure of the membrane separation module is one of a spiral wound type, a plate-and-frame type and a hollow fiber type. one or more combinations. 4 . The device for denitrifying and recovering hydrocarbons from a hydrocarbon-containing exhaust gas according to claim 2 or 3 , wherein the membrane separation components have built-in organic hydrocarbon separation membranes. 5 . 5. A device for denitrifying hydrocarbon-containing exhaust gas and recovering hydrocarbons according to claim 1, wherein the first cooler (1) and the second cooler (5) are both water coolers .

Images