Liquefied natural gas heavy hydrocarbon removal system

Abstract

The utility model belongs to the technical field of natural gas cryogenic cooling, and particularly discloses a heavy hydrocarbon removal system for liquefied natural gas. Comprising a first adsorption tower, a regenerated gas heater, a second adsorption tower, a heavy hydrocarbon removal regenerated gas cooler, a heavy hydrocarbon removal cold energy recovery heat exchanger, a primary heavy hydrocarbon separator, a heavy hydrocarbon removal evaporator, a secondary heavy hydrocarbon separator, a natural gas mixed refrigeration compressor unit and a third adsorption tower. A single-component refrigeration compressor unit special for heavy hydrocarbon removal is omitted, and heavy hydrocarbon removal is completed by obtaining cold energy from a natural gas mixed refrigeration compressor unit. And the temperature reduction range of the heavy hydrocarbon removal evaporator is expanded to 0 DEG C < =-60 DEG C from the original 0 DEG C < =-40 DEG C, so that the operation flexibility and the adaptive capacity of heavy hydrocarbon removal equipment are improved. And moreover, the investment of dynamic equipment is reduced, the equipment failure rate is reduced, and the total investment is reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of natural gas cryogenics, and in particular relates to a liquefied natural gas heavy hydrocarbon removal system. Background Art

[0002] The process flow of natural gas liquefaction unit: Gaseous natural gas needs to be stabilized at the station, the compressor increases the pressure, removes acid gas, removes water, and removes heavy hydrocarbons, and finally enters the natural gas liquefaction equipment (cold box) to cool to -162℃ and become liquid natural gas (LNG), and the natural gas mixed refrigeration compressor unit (MR refrigeration compressor unit) provides cooling capacity.

[0003] The device for removing heavy hydrocarbons consists of a natural gas heavy hydrocarbon removal adsorption tower, a heavy hydrocarbon removal regeneration gas cooler, a heavy hydrocarbon removal regeneration gas heater, a heavy hydrocarbon removal cold recovery heat exchanger, a heavy hydrocarbon removal separator, and a heavy hydrocarbon removal special refrigeration compressor unit (propane refrigeration compressor).

[0004] The refrigeration compressor unit (propane refrigeration compressor) dedicated to heavy hydrocarbon removal provides cooling capacity. The heavy hydrocarbons separated from the first and second hydrocarbon separators are reheated and then stored in the heavy hydrocarbon tank. The regenerated gas separated from the second separator passes through the heavy hydrocarbon removal cooling capacity recovery heat exchanger and then returns to the front end of the dehydrogenation adsorption tower and is mixed with the first gas source before entering the dehydrogenation adsorption tower to realize the recycling of the regenerated gas.

[0005] The working process of the refrigeration compressor unit dedicated to heavy hydrocarbon removal (propane refrigeration compressor) is as follows: the gaseous propane refrigerant is compressed, cooled (T≈40℃) and separated by the screw compressor, converted into liquid and then enters the economizer, where it is cooled to T≈30℃ in the heavy hydrocarbon removal evaporator, providing cooling capacity for cooling the regenerated gas from the heavy hydrocarbon removal.

[0006] At present, the cold energy preparation for removing heavy hydrocarbons often adopts independent dedicated refrigeration compressor units, which has the following problems:

[0007] 1. The cooling capacity is low, and the temperature reduction range of the evaporator is 0℃≤-40℃.

[0008] 2. There are many control points and the overall investment of the project is high.

[0009] 3. The number of moving equipment increases, so the failure rate of the equipment is high. Utility Model Content

[0010] The utility model aims to provide a liquefied natural gas heavy hydrocarbon removal system, which can improve the refrigeration capacity, reduce the investment in dynamic equipment, and reduce the equipment failure rate and total investment.

[0011] In order to achieve the above-mentioned purpose, the technical scheme of the utility model is as follows: a liquefied natural gas heavy hydrocarbon removal system, comprising a first adsorption tower, a regeneration gas heater, a second adsorption tower, a heavy hydrocarbon removal regeneration gas cooler, a heavy hydrocarbon removal cold recovery heat exchanger, a first heavy hydrocarbon separator, a heavy hydrocarbon removal evaporator, a second heavy hydrocarbon separator, a natural gas mixed refrigeration compressor unit and a third adsorption tower;

[0012] The dehydrated natural gas is divided into two gas sources, wherein the first gas source enters the third adsorption tower for adsorption of heavy components, and the dehydrogenated natural gas enters the natural gas deep cold liquefaction unit for liquefaction; the second gas source enters the first adsorption tower for cold blowing and cooling the first adsorption tower; the regeneration gas heater is used to heat the natural gas coming out of the first adsorption tower; the heated natural gas enters the second adsorption tower to resolve the hydrocarbons adsorbed in the second adsorption tower;

[0013] The regenerated gas flowing out of the second adsorption tower enters the heavy hydrocarbon removal regeneration gas cooler, the heavy hydrocarbon removal cold recovery heat exchanger, the first heavy hydrocarbon separator, the heavy hydrocarbon removal evaporator and the second heavy hydrocarbon separator in sequence; the heavy hydrocarbons separated by the first heavy hydrocarbon separator and the second heavy hydrocarbon separator enter the heavy hydrocarbon tank after reheating; the regenerated gas separated by the second heavy hydrocarbon separator returns to the front end of the third adsorption tower after passing through the heavy hydrocarbon removal cold recovery heat exchanger, and enters the third adsorption tower for adsorption after mixing with the first gas source;

[0014] The cooling capacity of the heavy hydrocarbon removal evaporator is provided by the natural gas mixed refrigeration compressor unit; the gaseous refrigerant of the natural gas mixed refrigeration compressor unit is compressed, cooled and separated by a centrifugal compressor, converted into liquid refrigerant, and then enters the natural gas liquefaction cold box for cooling, and the cooled liquid refrigerant enters the heavy hydrocarbon removal evaporator; the refrigerant coming out of the heavy hydrocarbon removal evaporator returns to the inlet of the natural gas mixed refrigeration compressor unit for compression.

[0015] Furthermore, a first temperature transmitter is provided inside the heavy hydrocarbon removal evaporator, a heavy hydrocarbon removal regeneration gas pipeline is connected between the outlet of the heavy hydrocarbon removal evaporator and the secondary heavy hydrocarbon separator, a second temperature transmitter is provided on the heavy hydrocarbon removal regeneration gas pipeline, and a flow regulating valve is provided on the connecting pipeline between the outlet of the natural gas mixed refrigeration compressor unit and the inlet of the heavy hydrocarbon removal evaporator; the control signal of the flow regulating valve is issued by the second temperature transmitter.

[0016] Furthermore, the dehydrogenated natural gas passes through a dust filter and a mercury remover and enters a downstream natural gas cryogenic liquefaction unit.

[0017] Furthermore, the second gas source enters the first adsorption tower in the cold purge state to perform cold blowing and cooling on the first adsorption tower.

[0018] Furthermore, the heated natural gas enters the second adsorption tower in a heated state, and the hydrocarbons adsorbed in the second adsorption tower are analyzed out.

[0019] The beneficial effects of this technical solution are: the single-component refrigeration compressor unit dedicated to heavy hydrocarbon removal is eliminated, and the cold capacity is obtained from the natural gas mixed refrigeration compressor unit to complete the removal of heavy hydrocarbons. The refrigeration capacity is increased, and the temperature reduction range of the heavy hydrocarbon removal evaporator is expanded from the original 0℃≤-40℃ to 0℃≤-60℃, thereby improving the operational flexibility and adaptability of the heavy hydrocarbon removal equipment. It also reduces the investment in dynamic equipment, reduces the equipment failure rate and reduces the total investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the middle dehydrogenation part of the liquefied natural gas heavy hydrocarbon removal system of the utility model;

[0021] Figure 2 A partial schematic diagram is provided for the intermediate cooling capacity of the liquefied natural gas heavy hydrocarbon removal system of the utility model. DETAILED DESCRIPTION

[0022] The following is further described in detail through specific implementation methods:

[0023] The figure marks in the drawings of the specification include: natural gas mixed refrigeration compressor unit 1, heavy hydrocarbon removal regeneration gas cooler 2, heavy hydrocarbon removal cold recovery heat exchanger 3, primary heavy hydrocarbon separator 4, secondary heavy hydrocarbon separator 5, regeneration gas heater 6, heavy hydrocarbon removal evaporator 7, flow regulating valve 8, first temperature transmitter 9, second temperature transmitter 10, heavy hydrocarbon removal regeneration gas pipeline 11.

[0024] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0025] The embodiment is basically as shown in the attached Figure 1-2 As shown: a liquefied natural gas heavy hydrocarbon removal system includes a first adsorption tower, a regeneration gas heater 6, a second adsorption tower, a heavy hydrocarbon removal regeneration gas cooler 2, a heavy hydrocarbon removal cold recovery heat exchanger 3, a primary heavy hydrocarbon separator 4, a heavy hydrocarbon removal evaporator 7, a secondary heavy hydrocarbon separator 5, a natural gas mixed refrigeration compressor unit 1 and a third adsorption tower.

[0026] The natural gas (T≈40℃, P≈5.0MPa) after molecular sieve dehydration is divided into two gas sources, of which the first gas source enters the third adsorption tower for adsorption of heavy components, and the natural gas after dehydrogenation passes through the dust filter and mercury remover and enters the downstream natural gas deep cold liquefaction unit for liquefaction. The second gas source enters the first adsorption tower in the cold purge state to cool the first adsorption tower; the regeneration gas heater 6 is used to heat the natural gas coming out of the first adsorption tower; the heated natural gas (about 260℃) enters the second adsorption tower in the heated state to analyze the hydrocarbons adsorbed in the second adsorption tower to restore its adsorption capacity.

[0027] The regenerated gas flowing out of the second adsorption tower enters the heavy hydrocarbon removal regeneration gas cooler 2, the heavy hydrocarbon removal cold recovery heat exchanger 3, the first heavy hydrocarbon separator 4 (T≈10°C, P≈4.9MPa), the heavy hydrocarbon removal evaporator 7 and the second heavy hydrocarbon separator 5 (T≈-40°C, P≈4.9MPa) in sequence; the heavy hydrocarbons separated by the first heavy hydrocarbon separator 4 and the second heavy hydrocarbon separator 5 enter the heavy hydrocarbon tank after reheating; the regenerated gas separated by the second heavy hydrocarbon separator 5 returns to the front end of the third adsorption tower after passing through the heavy hydrocarbon removal cold recovery heat exchanger 3, and after mixing with the first gas source, enters the third adsorption tower for adsorption, thereby realizing the recycling of the regenerated gas.

[0028] The cooling capacity of the de-heavy hydrocarbon evaporator 7 is provided by the natural gas mixed refrigeration compressor unit 1; the gaseous refrigerant of the natural gas mixed refrigeration compressor unit 1 is compressed, cooled and separated by a centrifugal compressor, and converted into a liquid refrigerant (T≈40°C), and then enters the natural gas liquefaction cold box for cooling. The cooled liquid refrigerant (T≈-70°C) enters the de-heavy hydrocarbon evaporator 7 to provide cooling capacity for the de-heavy hydrocarbon regeneration gas cooling. The refrigerant coming out of the de-heavy hydrocarbon evaporator 7 returns to the inlet of the natural gas mixed refrigeration compressor unit 1 for compression, forming a recycling of the refrigerant. A first temperature transmitter 9 is provided inside the de-heavy hydrocarbon evaporator 7, a de-heavy hydrocarbon regeneration gas pipeline 11 is connected between the outlet of the de-heavy hydrocarbon evaporator 7 and the secondary heavy hydrocarbon separator 5, a second temperature transmitter 10 is provided on the de-heavy hydrocarbon regeneration gas pipeline 11, and a flow regulating valve 8 is provided on the connecting pipeline between the outlet of the natural gas mixed refrigeration compressor unit 1 and the inlet of the de-heavy hydrocarbon evaporator 7; the control signal of the flow regulating valve 8 is sent by the second temperature transmitter 10. The first temperature transmitter 9 is used to detect the temperature (T≈-60°C) in the de-heavy hydrocarbon evaporator 7, and the flow regulating valve 8 is used to adjust the flow of the low-temperature liquid refrigerant entering the de-heavy hydrocarbon evaporator 7, thereby controlling the temperature in the de-heavy hydrocarbon evaporator 7. The temperature in the de-heavy hydrocarbon regeneration gas pipeline 11 is detected by the second temperature transmitter 10, and the opening of the flow regulating valve 8 is adjusted according to the temperature. Specifically, a controller can be provided, and the controller receives the signal of the second temperature transmitter 10 and then adjusts the opening of the flow regulating valve 8.

[0029] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0030] The above is only an embodiment of the utility model. The common sense such as the known specific structure and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field know all the common technical knowledge in the technical field of the utility model before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for the technicians in this field, without departing from the structure of the utility model, several deformations and improvements can be made, which should also be regarded as the protection scope of the utility model, which will not affect the effect of the implementation of the utility model and the practicality of the patent. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to explain the content of the claims.

Claims

1. Liquefied natural gas heavy hydrocarbon removal system, characterized by: It comprises a first adsorption tower, a regeneration gas heater (6), a second adsorption tower, a heavy hydrocarbon removal regeneration gas cooler (2), a heavy hydrocarbon removal cold recovery heat exchanger (3), a first heavy hydrocarbon separator (4), a heavy hydrocarbon removal evaporator (7), a second heavy hydrocarbon separator (5), a natural gas mixed refrigeration compressor unit (1) and a third adsorption tower; The dehydrated natural gas is divided into two gas sources, wherein the first gas source enters the third adsorption tower to adsorb the heavy components, and the dehydrogenated natural gas enters the natural gas deep cold liquefaction unit to be liquefied; the second gas source enters the first adsorption tower to cool the first adsorption tower by cold blowing; the regeneration gas heater (6) is used to heat the natural gas coming out of the first adsorption tower; the heated natural gas enters the second adsorption tower to resolve the hydrocarbons adsorbed in the second adsorption tower; The regenerated gas flowing out of the second adsorption tower enters the heavy hydrocarbon removal regeneration gas cooler (2), the heavy hydrocarbon removal cold recovery heat exchanger (3), the first heavy hydrocarbon separator (4), the heavy hydrocarbon removal evaporator (7) and the second heavy hydrocarbon separator (5) in sequence; the heavy hydrocarbons separated by the first heavy hydrocarbon separator (4) and the second heavy hydrocarbon separator (5) enter the heavy hydrocarbon tank after being reheated; the regenerated gas separated by the second heavy hydrocarbon separator (5) passes through the heavy hydrocarbon removal cold recovery heat exchanger (3) and returns to the front end of the third adsorption tower, and after being mixed with the first gas source, enters the third adsorption tower for adsorption; The cooling capacity of the heavy hydrocarbon removal evaporator (7) is provided by the natural gas mixed refrigeration compressor unit (1); the gaseous refrigerant of the natural gas mixed refrigeration compressor unit (1) is compressed, cooled and separated by a centrifugal compressor, converted into a liquid refrigerant, and then enters a natural gas liquefaction cold box for cooling, and the cooled liquid refrigerant enters the heavy hydrocarbon removal evaporator (7); the refrigerant coming out of the heavy hydrocarbon removal evaporator (7) returns to the inlet of the natural gas mixed refrigeration compressor unit (1) for compression.

2. The system for removing heavy hydrocarbons from liquefied natural gas according to claim 1, characterized in that: A first temperature transmitter (9) is provided inside the de-heavy hydrocarbon evaporator (7); a de-heavy hydrocarbon regeneration gas pipeline (11) is connected between the outlet of the de-heavy hydrocarbon evaporator (7) and the secondary heavy hydrocarbon separator (5); a second temperature transmitter (10) is provided on the de-heavy hydrocarbon regeneration gas pipeline (11); a flow regulating valve (8) is provided on the connecting pipeline between the outlet of the natural gas mixed refrigeration compressor unit (1) and the inlet of the de-heavy hydrocarbon evaporator (7); and a control signal of the flow regulating valve (8) is issued by the second temperature transmitter (10).

3. The system for removing heavy hydrocarbons from liquefied natural gas according to claim 1, characterized in that: The dehydrogenated natural gas passes through a dust filter and a mercury remover before entering the downstream natural gas cryogenic liquefaction unit.

4. The system for removing heavy hydrocarbons from liquefied natural gas according to claim 1, characterized in that: The second gas source enters the first adsorption tower in the cold purge state to cool the first adsorption tower by cold blowing.

5. The system for removing heavy hydrocarbons from liquefied natural gas according to claim 1, characterized in that: The heated natural gas enters the second adsorption tower in a heated state, and the hydrocarbons adsorbed in the second adsorption tower are analyzed out.

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