Process system using LNG vaporizer instead of refrigeration compressor

Abstract

The present invention provides a process system using an LNG vaporizer instead of a refrigeration compressor, comprising an LNG vaporizer assembly, a first-section buffer tank, a second-section buffer tank, a first user assembly, and a second user assembly, wherein the LNG vaporizer assembly is connected to the first user assembly; the first user assembly is connected to the first-section buffer tank; the first-section buffer tank is connected to the second user assembly; the second user assembly is connected to the second-section buffer tank; the second-section buffer tank is connected to the LNG vaporizer assembly; the second-section buffer tank is connected to the first-section buffer tank; the LNG vaporizer assembly comprises an LNG vaporizer. The present invention has the advantages of simple process, low energy consumption, little investment, and stable operation.

Description

A process system for replacing refrigeration compressors with LNG vaporizers Technical Field

[0001] This invention belongs to the field of petrochemical technology, and in particular relates to a process system in which an LNG vaporizer replaces a refrigeration compressor. Background Technology

[0002] In traditional petrochemical plants, olefin separation units often utilize propylene compressors to pre-cool the feedstock or condense the overhead material. Typically, propylene cycle refrigeration compressors can provide refrigerant at four temperature levels: 5°C, -8°C, -25°C, and -40°C, for different systems. Depending on the composition of the separated substances, some units may require even lower-temperature ethylene refrigeration compressors to provide the separation energy. A multi-stage propylene / ethylene refrigeration compressor represents a closed-loop thermodynamic process involving compression, condensation, expansion, and evaporation refrigeration. The compressor system is a critical piece of equipment for the stable operation of the olefin separation unit. It is also a core piece of equipment with significant investment, long manufacturing cycles, and high safety requirements, making it a crucial element in the overall process design.

[0003] The vaporization of cryogenic LNG releases a significant amount of cold energy, approximately 850 kJ / kg. This energy should be fully recovered and utilized to achieve energy conservation and improve economic efficiency. Traditional LNG receiving terminals often use open-frame vaporizers (ORVs) or submerged combustion vaporizers (SCVs) to vaporize LNG. This not only wastes cryogenic cold energy but also causes thermal pollution to nearby waters. Therefore, for oil refining or petrochemical plants, when LNG is readily available nearby, the most profitable conventional approach to utilizing LNG cold energy is cryogenic separation of cracking products in C2+ separation and ethylene production units. However, simulations show that this method is more suitable for recovering the cold energy of "wet" LNG. Furthermore, due to the cryogenic nature of LNG, if the process is designed for direct heat exchange between LNG and refrigerant users in chemical separation units, the stability of unit operation and control must be considered. Additionally, the stringent design conditions for LNG (design pressure 4 MPag, design temperature -150°C) necessitate the use of stainless steel in these devices, increasing the equipment investment. Summary of the Invention

[0004] In view of this, the present invention aims to provide a process system in which an LNG vaporizer replaces a refrigeration compressor, in order to solve at least one of the problems in the above-mentioned background art.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] A process system that uses an LNG vaporizer to replace a refrigeration compressor includes an LNG vaporizer assembly, a refrigerant assembly, a first-stage buffer tank, a second-stage buffer tank, a first-user assembly, and a second-user assembly.

[0007] The LNG vaporizer assembly is connected to the first user assembly, the first user assembly is connected to the first-stage buffer tank, the first-stage buffer tank is connected to the second user assembly, the second user assembly is connected to the second-stage buffer tank, and the second-stage buffer tank is connected to the LNG vaporizer assembly.

[0008] The LNG vaporizer assembly includes the LNG vaporizer.

[0009] In this invention, the specific structural form of the LNG vaporizer can be designed and selected according to the composition and flow rate of the LNG feedstock.

[0010] LNG feedstocks can be classified into heavy LNG feedstocks and light LNG feedstocks based on their composition.

[0011] Since LNG is a mixture containing C1, C2, and C3, in order to prevent fluctuations in the composition of the components from affecting the system stability requirements, when the C1 content in the LNG feedstock is less than 95%, the material composition is complex and the boiling range is wide, and it is defined as heavy LNG. When the C1 content in the LNG feedstock is greater than 95%, the material composition is simple and the boiling range is small, and it is defined as light LNG.

[0012] Furthermore, the LNG vaporizer assembly also includes a refrigerant storage tank and a refrigerant pump. The LNG vaporizer is connected to the refrigerant storage tank, which is connected to the first user assembly. The refrigerant pump is installed on the pipeline between the refrigerant storage tank and the first user assembly. A heat exchanger is installed on the pipeline between the refrigerant pump and the first user assembly. The top outlet of the buffer tank is connected to the heat exchanger.

[0013] In this invention, the heat exchanger is used to achieve heat exchange between the gas phase at the outlet of a buffer tank and the liquid phase at the outlet of the refrigerant pump. Preferably, the outlet of the refrigerant pump is connected to the shell side of the heat exchanger, and the gas phase outlet at the top of the buffer tank is connected to the tube side of the heat exchanger.

[0014] A start-up component is also provided between the refrigerant pump and the first user component;

[0015] Preferably, the start-up assembly includes a start-up valve, a start-up vaporizer, and a start-up heat source supply system. In this invention, the start-up assembly is connected in parallel with the heat exchanger.

[0016] During the start-up phase, the heat source of low-pressure steam carried by the intermediate medium methanol is transferred to propylene, and the propylene is vaporized to provide stable operating conditions for the entire system. After the system establishes pressure and material balance, the start-up line is cut off.

[0017] Furthermore, the first user component includes the original water-cooled user terminal component and / or the first user terminal component;

[0018] The first user terminal component and the original water-cooled user terminal component are connected in parallel through the first parallel pipeline, and the first parallel pipeline is equipped with a first valve.

[0019] The first user terminal component includes several first users, and the original water-cooled user terminal component includes several original water-cooled users. The several original water-cooled users are connected in parallel through a second pipeline, and each of the second pipelines is equipped with a second valve.

[0020] The operating temperature of the first user component is 5-10℃.

[0021] The original water-cooled user-end components remain the same; the cooling water users in the original system are redesigned to exchange heat with refrigerant at 8°C. Although the thermal efficiency of the 8°C refrigerant user is not as high as that of the -40°C refrigerant user, this design effectively avoids the freezing of water-containing process materials on the surface of the heat exchange tubes. At the same time, due to the increased temperature difference, the size and weight of each water-cooled user's equipment are significantly reduced, and the use and consumption of circulating water are also greatly saved.

[0022] LNG feedstock from the boundary area undergoes indirect heat exchange with cryogenic gaseous propylene in LNG vaporizer 3. After being condensed into liquid propylene, the cryogenic gaseous propylene is pressurized by a cryogenic pump and divided into two sections. The first section of cryogenic propylene, set to an energy level of 8°C through the first valve 9 and the second valve 10 of the regulating valve group, condenses or cools down the original water-cooled user end 7 and the first user end 8 in the system. The refrigerant propylene then enters the buffer tank 1 and heat exchanger 6 for heat exchange. The refrigerant propylene, set to -40°C through the third valve 12 and the fourth valve 13 of the regulating valve group, serves as the refrigerant with the highest cold energy level and exchanges cold energy with the material in the system at the second user end 11, which operates at a temperature below 0°C. This achieves both the self-exchange of heat and cold of propylene within the system and the graded utilization of energy levels, reducing the investment cost of cryogenic equipment and improving the heat exchange efficiency of the equipment.

[0023] Furthermore, the first user component is connected to a first-stage buffer tank, the first-stage buffer tank is connected to the second user component, and the second user component is connected to the second-stage buffer tank; the first and second-stage buffer tanks are connected to their respective affiliated user terminals via pipelines.

[0024] The bottom outlet of a buffer tank is connected to the inlet of the first user component;

[0025] The bottom outlet of the second-stage buffer tank is connected to the inlet of the first user component;

[0026] This setting is conducive to making full use of the cooling capacity of liquid propylene.

[0027] Preferably, the second user component includes a second user terminal, and several second user terminals are connected in parallel through a third parallel pipeline, and each second user terminal is provided with a third valve at its inlet end;

[0028] The inlet end of the third parallel pipeline of the second user component is connected to the heat exchanger, and a fourth valve is provided on the pipeline between the second user component and the heat exchanger.

[0029] The operating temperature of the second user component is -35~-45℃.

[0030] Furthermore, the bottom of the second-stage buffer tank is connected to the bottom of the first-stage buffer tank via a connecting pipeline, and a liquid phase reflux pump is installed on the connecting pipeline, which is connected to the inlet end of the first user component.

[0031] A fifth valve is installed at the bottom of a buffer tank;

[0032] The bottom of the second-stage buffer tank is equipped with a sixth valve.

[0033] Furthermore, the first LNG vaporizer includes a first LNG shell and a first LNG tube bundle. The first LNG shell contains several U-shaped first LNG heat exchange tubes arranged laterally within the shell. The gaseous refrigerant exchanges heat with the first LNG feedstock within the shell on the surface of the U-shaped tube bundle within the tube bundle of the first LNG vaporizer, achieving saturated LNG delivery. Furthermore, the upper end of the tube bundle of the first LNG vaporizer has a first gaseous refrigerant inlet, and the lower part of the tube bundle has a first liquid refrigerant outlet. The first gaseous refrigerant inlet and the first liquid refrigerant outlet are connected via the U-shaped first LNG heat exchange tube bundle.

[0034] The first LNG vaporizer's first LNG shell includes a first-stage shell, a transition section shell, and a second-stage shell, with the first-stage shell and the second-stage shell connected by the transition section shell; the diameter of the first-stage shell is smaller than the diameter of the second-stage shell; the lowest point of the first-stage shell is flush with the lowest point of the second-stage shell.

[0035] The inlet end of the U-shaped first LNG heat exchange tube bundle is located on one side of a first shell section; the U-shaped end of the U-shaped first LNG heat exchange tube bundle is located inside the second shell section.

[0036] Several staggered single-bow baffles and a first support plate are provided between the U-shaped first LNG heat exchange tube bundle and the first LNG shell; an overflow weir is provided inside the first LNG shell, and the overflow weir is located on the outside of the U-shaped end inside the two shell sections. Furthermore, the single-bow baffles are located at the top inside the first shell section.

[0037] The single-baffle plate and the first support plate are provided with several through holes to support the heat exchange tubes and to ensure that the heat exchange tubes can pass through the holes;

[0038] The first LNG vaporizer has a first LNG inlet at the bottom of its first section shell; a first LNG vapor phase outlet at the top of its second section shell; a first LNG recombinant liquid phase outlet at the bottom of its second section shell; the first LNG recombinant liquid phase outlet is connected to a recombinant liquid phase external delivery pipe and is located on the side of the overflow weir away from the U-shaped first LNG heat exchange tube bundle.

[0039] The first LNG vapor phase outlet is located on one side of the overflow weir, and the first LNG recombinant liquid phase outlet is located on the other side of the overflow weir.

[0040] The first gaseous refrigerant inlet of the first LNG vaporizer is connected to the second-stage buffer tank, and the first liquid refrigerant outlet of the first LNG vaporizer is connected to the refrigerant storage tank.

[0041] Furthermore, the second LNG vaporizer includes a second LNG shell and a second LNG tubing bundle;

[0042] The second LNG tube bundle is a U-shaped second LNG heat exchange tube bundle, which includes several second LNG heat exchange tubes, and the several second LNG heat exchange tubes are arranged laterally inside the second LNG shell;

[0043] The gaseous refrigerant exchanges heat with the second LNG feedstock located in the second LNG tube bundle within the second LNG shell, enabling the superheated delivery of the second LNG.

[0044] Furthermore, the bottom of the tube box of the second LNG vaporizer is provided with a second LNG inlet, the top of the tube box of the second LNG vaporizer is provided with a second LNG outlet, the second LNG inlet is connected to the inlet of the U-shaped second LNG heat exchange tube bundle, and the second LNG outlet is connected to the outlet of the U-shaped second LNG heat exchange tube bundle.

[0045] The shell-side inlet of the second LNG vaporizer is provided with an external guide ring and 2 to 3 air inlet slots are evenly arranged. The second gaseous refrigerant is connected to the cavity between the shell side of the second LNG vaporizer through the air inlet slots.

[0046] The bottom of the casing of the second LNG vaporizer is provided with a second liquid refrigerant outlet;

[0047] The second LNG shell is equipped with several second baffles, and the second baffles are equipped with several through holes to support the U-shaped second LNG heat exchange tube bundle;

[0048] The second gaseous refrigerant inlet of the second LNG vaporizer is connected to the second-stage buffer tank, and the second liquid refrigerant outlet of the second LNG vaporizer is connected to the refrigerant storage tank.

[0049] Furthermore, the first gaseous refrigerant and the second gaseous refrigerant include propylene.

[0050] Compared with existing technologies, the LNG vaporizer replacing the refrigeration compressor process system described in this invention has the following advantages:

[0051] The process is simple, energy consumption is low, investment is small, and operation is stable. Based on the optimized design of a light hydrocarbon recovery unit, eliminating the propylene compressor reduced electricity consumption and circulating water usage. Preliminary calculations show that the equipment investment for the LNG cold energy refrigeration system described in this invention can be reduced by 20% or more compared to the equipment investment for propylene compressor refrigeration. Attached Figure Description

[0052] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0053] Figure 1 is an overall schematic diagram of a process system for replacing a refrigeration compressor with an LNG vaporizer according to an embodiment of the present invention;

[0054] Figure 2 is a schematic diagram of the first LNG vaporizer according to an embodiment of the present invention;

[0055] Figure 3 is a schematic diagram of the first LNG tube bundle according to an embodiment of the present invention;

[0056] Figure 4 is a schematic diagram of the second LNG vaporizer according to an embodiment of the present invention;

[0057] Figure 5 is a schematic diagram of the second LNG tube bundle according to an embodiment of the present invention.

[0058] Explanation of reference numerals in the attached figures:

[0059] 1. First-stage buffer tank; 2. Second-stage buffer tank; 3. LNG vaporizer; 4. Refrigerant storage tank; 5. Refrigerant pump; 6. Heat exchanger; 7. Original water-cooled user end; 8. First user end; 9. First valve; 10. Second valve; 11. Second user end; 12. Third valve; 13. Fourth valve; 14. Liquid phase reflux pump; 15. Start-up heat source supply system; 16. Start-up valve; 17. Fifth valve; 18. Sixth valve; 19. First LNG tube bundle; 20. First LNG shell; 21. First gas phase refrigeration. 21. Refrigerant inlet; 22. First liquid refrigerant outlet; 23. Transition section; 24. Single-bow baffle; 25. First support plate; 26. First LNG inlet; 27. First LNG vapor outlet; 28. Overflow weir; 29. ​​First LNG heavy component liquid outlet; 30. Second LNG tube bundle; 31. Second LNG shell; 32. Second LNG inlet; 33. Second LNG outlet; 34. External guide ring; 35. Inlet tank; 36. Second vapor refrigerant inlet; 37. Second liquid refrigerant outlet; 38. Second baffle. Detailed Implementation

[0060] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0061] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Example 1

[0062] As shown in Figure 1, a process system in which an LNG vaporizer 3 replaces a refrigeration compressor includes an LNG vaporizer 3 assembly, a first-stage buffer tank 1, a second-stage buffer tank 2, a first user assembly, and a second user assembly.

[0063] The LNG vaporizer 3 assembly is connected to the first user assembly, the first user assembly is connected to the first-stage buffer tank 1, the first-stage buffer tank 1 is connected to the second user assembly, the second user assembly is connected to the second-stage buffer tank, and the second-stage buffer tank is connected to the LNG vaporizer assembly.

[0064] In this embodiment, the upstream of the second-stage buffer tank 2 is connected to the second user component, and the downstream of the second-stage buffer tank 2 is connected to the LNG vaporizer 3 assembly. The top outlet of the first-stage buffer tank 1 is connected to the heat exchanger 6, and the heat exchanger 6 is connected to the second user component. The LNG vaporizer 3 assembly includes an LNG vaporizer 3, which is selected from the first LNG vaporizer and / or the second LNG vaporizer. LNG feedstock with a C1 content greater than or equal to 95% is considered light LNG feedstock; LNG feedstock with a C1 content less than 95% is considered heavy LNG feedstock. Vaporizers using light LNG feedstock as a cold source are called light LNG vaporizers, and vaporizers using heavy LNG feedstock as a cold source are called heavy LNG vaporizers.

[0065] In practical applications, light LNG vaporizers or heavy LNG vaporizers can be used independently, or the light LNG vaporizer and heavy LNG vaporizer can be connected in parallel via a three-way valve, allowing for selection based on specific circumstances. When the C1 content in the LNG feedstock is less than 95%, the material composition is complex and the boiling range is wide; this is defined as heavy LNG, and the material enters the heavy LNG vaporizer through the three-way valve. When the C1 content in the LNG feedstock is greater than or equal to 95%, the material composition is simple and the boiling range is small; this is defined as light LNG, and the material is switched to the light LNG vaporizer via the three-way valve.

[0066] The LNG vaporizer 3 assembly also includes a refrigerant storage tank 4 and a refrigerant pump 5. The LNG vaporizer 3 is connected to the refrigerant storage tank 4, which is connected to the first user assembly. The refrigerant pump 5 is installed on the pipeline between the refrigerant storage tank 4 and the first user assembly. A heat exchanger 6 is also installed on the pipeline between the refrigerant storage tank 4 and the first user assembly. A buffer tank 1 is connected to the tube side of the heat exchanger 6, and the shell side of the heat exchanger 6 is connected to the second user assembly. A start-up assembly is installed between the refrigerant pump 5 and the first user assembly. The start-up assembly includes a start-up pipeline and a start-up valve 16. The start-up valve 16 is installed on the start-up pipeline, which is equipped with a start-up heat source supply system 15 and a start-up vaporizer. The start-up heat source supply system uses steam to heat the methanol in the start-up vaporizer, and then the methanol transfers the heat to the material in the start-up pipeline.

[0067] The first user component includes the original water-cooled user terminal 7 and several first user terminals 8. The original water-cooled user terminal 7 and several first user terminals 8 are connected in parallel through a first parallel pipeline, and a first valve 9 is provided on the first parallel pipeline. The original water-cooled user terminal 7 includes several original water-cooled users. The original water-cooled user terminal 7 is connected in parallel through a second parallel pipeline, and a second valve 10 is provided on the second pipeline. The operating temperature of the user terminals of the original water-cooled user terminal 7 and the first user terminals 8 is 5-10℃.

[0068] The original water-cooled user 7 is the original water-cooled user; the cooling water user in the original system can also be designed to exchange heat with refrigerant at 8℃. Although the thermal efficiency of the 8℃ refrigerant user is not as high as that of the -40℃ refrigerant user, this design can effectively avoid the freezing of water-containing process materials on the surface of the heat exchange tubes.

[0069] The first user component is connected to a first-stage buffer tank 1, the first-stage buffer tank 1 is connected to the second user component, and the second user component is connected to the second-stage buffer tank;

[0070] The bottom outlet of a buffer tank is connected to the inlet of the first user component;

[0071] The bottom outlet of the second-stage buffer tank is connected to the inlet of the first user component;

[0072] The second user component includes several second user terminals 11, which are connected in parallel through a third parallel pipeline, and the second user component is equipped with a third valve 12; the second user component is connected to the heat exchanger 6, and a fourth valve 13 is provided on the pipeline between the second user component and the heat exchanger 6; the operating temperature of the user terminal of the third user terminal 11 is -35~-45℃.

[0073] The bottom of the second-stage buffer tank 2 is connected to the bottom of the first-stage buffer tank via a connecting pipeline, and a liquid phase reflux pump 14 is installed on the connecting pipeline; the bottom of the first-stage buffer tank 1 is equipped with a fifth valve 17; and the bottom of the second-stage buffer tank 2 is equipped with a sixth valve 18. Example 2

[0074] As shown in Figures 2 and 3: The first LNG vaporizer 3 includes a first LNG tube bundle 19 and a first LNG shell 20. The first LNG shell 20 is provided with several U-shaped first LNG heat exchange tubes, which are arranged horizontally inside the first LNG shell 20. The gaseous refrigerant exchanges heat with the first LNG raw material in the shell on the surface of the U-shaped tube bundle within the tube bundle of the first LNG vaporizer.

[0075] The first LNG vaporizer has a first gaseous refrigerant inlet 21 at the top of the tube box and a first liquid refrigerant outlet 22 at the bottom of the tube box. The first gaseous refrigerant inlet 21 is connected to the inlet of the first LNG tube bundle, and the first liquid refrigerant outlet 22 is connected to the outlet of the first LNG tube bundle. The first LNG shell 20 has a transition section 23 in the middle. The shell between the tube box and the transition section is a first-stage shell, and the shell on the other side of the transition section is a second-stage shell. The diameter of the first-stage shell is smaller than that of the second-stage shell. The bottoms of the first-stage shell, the transition section shell, and the second-stage shell are flush. Several staggered single-bow baffles 24 and first support plates 25 are provided between the first LNG shell 20 and the first LNG tube bundle 19. An overflow weir 28 is provided inside the first LNG shell 20, and the overflow weir 28 is located inside the second-stage shell. A single-bow baffle is located inside a first-stage shell; the single-bow baffle 24 and the first support plate 25 are provided with several through holes for supporting the tube bundle; the bottom of the first LNG shell 20 is provided with a first LNG inlet 26, which is located at the bottom of the first-stage shell; the top of the first LNG shell 20 is provided with a first LNG vapor phase outlet 27, which is located inside the second-stage shell; the first LNG heavy component liquid phase outlet 29 is located at the bottom of the second-stage shell and on the side of the overflow weir away from the tube box; the first vapor phase refrigerant inlet 21 of the first LNG vaporizer is connected to the second-stage buffer tank; and the first liquid phase refrigerant outlet 22 of the first LNG vaporizer 3 is connected to the refrigerant storage tank 4. Example 3

[0076] As shown in Figures 4 and 5:

[0077] The second LNG vaporizer 3 includes a second LNG shell 30 and a second LNG tube bundle 31; the second LNG tube bundle is a U-shaped second LNG heat exchange tube bundle, which includes several second LNG heat exchange tubes; the several second LNG heat exchange tubes are arranged laterally inside the second LNG shell 30; the gaseous refrigerant exchanges heat with the second LNG feedstock located in the second LNG tube bundle inside the second LNG shell. The second LNG vaporizer has a second LNG inlet 32 ​​at the bottom of its tube box and a second LNG outlet 33 at the top. The second LNG inlet 32 ​​is connected to the inlet of the heat exchange tube bundle, and the second LNG outlet 33 is connected to the outlet of the heat exchange tube bundle. The second LNG shell 30 is provided with an outer guide ring 34. Two to three inlet grooves 35 are evenly arranged on the outer guide ring 34 to facilitate the uniform entry of gaseous propylene into the second gaseous refrigerant inlet 36 of the second LNG vaporizer shell 30. After entering the second LNG shell 30, the refrigerant flows through the second baffle plate 38 with several through holes and is then discharged to the second liquid refrigerant outlet 37. The second gaseous refrigerant inlet 36 of the second LNG vaporizer 3 is connected to the second-stage buffer tank, and the second liquid refrigerant outlet 37 of the second LNG vaporizer 3 is connected to the refrigerant storage tank 4. Example 4

[0078] This embodiment uses the process system described in Embodiment 1;

[0079] LNG feedstock from the boundary area undergoes indirect heat exchange with cryogenic gaseous propylene in LNG vaporizer 3. After being condensed into liquid propylene, it is pressurized by a cryogenic pump (refrigerant pump) and divided into two sections. The first section of cryogenic propylene, set to an energy level of 8°C through regulating valve group first valve 9 and second valve 10, condenses or cools down the original water-cooled user-end component 7 and the first user-end component 8 in the system. The refrigerant propylene enters a buffer tank 1, and then exchanges heat with the liquid propylene at the outlet of the refrigerant pump through heat exchanger 6. The propylene, set to -40°C through regulating valve group third valve 12 and fourth valve 13, serves as the refrigerant with the highest cold energy level and exchanges cold energy with the material in the system at the second user-end component 11, which operates below 0°C. In addition, this not only realizes the self-exchange of heat and cold of propylene within the system, but also achieves the graded utilization of energy levels, reduces the investment cost of cryogenic equipment, and improves the heat exchange efficiency of the equipment.

[0080] Application Example 1

[0081] Engineering Example Description

[0082] When the refrigerant is propylene and is heavy LNG as shown in Table 1, simulations show that the subcooling load is large, accounting for 50.71% of the total heat load. Therefore, under this condition, the design of the subcooling section and the maximum recovery of cooling capacity need to be fully considered. In this application, to save investment and space, the specific simplified diagram of the LNG vaporizer equipment design is shown in Figures 4 and 5. Since the material is heavy LNG feedstock, it is referred to as a heavy LNG vaporizer. The tube bundle length of the heavy LNG vaporizer is 6 meters, the shell diameter of the heavy LNG vaporizer is 1.5 meters, and the shell side is uniformly arranged with second baffles 38 with an opening rate of about 25%. In addition, due to the large gas volume at the shell side inlet, in order to avoid the large opening of the shell side cylinder of the heavy LNG vaporizer leading to a reduction in the number of pipes and to prevent pipe vibration caused by excessive gas velocity, this design sets a special flow guiding device at the shell side inlet of the heavy LNG vaporizer. The outer flow guiding ring 34 is 1 meter wide and 0.3 meters high, with 2 to 3 slots symmetrically opened on the flow guiding device to ensure stable fluid flow and a reasonable structure of the heavy LNG vaporizer.

[0083] Application Example 2

[0084] Engineering Example Description

[0085] When the refrigerant is propylene and it is light LNG as shown in Table 1, the material composition is simple and easy to vaporize. However, in order to meet the certain cooling requirements of the chemical separation unit and to recover as much LNG cooling energy as possible, a superheating section needs to be added in this operating condition to utilize the sensible heat cooling energy in the vaporized LNG. The specific simplified diagram of the LNG vaporizer equipment design is shown in Figures 2 and 3.

[0086] At this time, the tube bundle length of the light LNG heat exchange tube is 5 meters, the tube bundle diameter of the light LNG heat exchange tube is 1.3 meters (the tube bundle diameter includes the sum of the tube diameter and the tube center distance); the maximum outer diameter of the light LNG shell 20 is 2 meters;

[0087] Three single-bow baffles 24 with an opening ratio of 30% to 40% are evenly arranged inside the light LNG shell. First support plates 25 are evenly arranged in the vaporization section to prevent the tube bundle from vibrating due to exceeding the maximum unsupported span. At the same time, an overflow weir 28 with a height of 200mm above the tube bundle is set at the end of the light LNG tube bundle. In order to prevent heavy components from accumulating in the vaporizer, an opening is set at the lower end of the overflow weir 28 to connect the two sides of the overflow weir, so as to avoid the accumulation of dirt on the side of the overflow weir near the tube box and ensure the safe and stable operation of the vaporizer.

[0088] Table 1 Light / Heavy LNG Feedstock Composition Table

[0089]

[0090] Note: C3+ is 0.9% iC4+, 0.9% nC4+, 0.1% iC5+, and 0.1% nC5+.

[0091] Based on the optimized design results of the light hydrocarbon recovery unit, the equipment investment is significantly reduced when using the process system described in this invention. By eliminating the propylene compressor, both electricity consumption and circulating water usage are reduced. The equipment investment for the LNG cold energy refrigeration system described in this invention is reduced by 20% or more compared to the equipment investment for propylene compressor refrigeration.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process system in which an LNG vaporizer replaces a refrigeration compressor, characterized in that: Includes LNG vaporizer assembly, primary buffer tank, secondary buffer tank, primary user assembly, and secondary user assembly; The LNG vaporizer assembly is connected to the first user assembly, the first user assembly is connected to a first-stage buffer tank, the first-stage buffer tank is connected to the second user assembly, the second user assembly is connected to a second-stage buffer tank, and the second-stage buffer tank is connected to the LNG vaporizer assembly; the LNG vaporizer assembly includes an LNG vaporizer.

2. The process system for replacing a refrigeration compressor with an LNG vaporizer according to claim 1, characterized in that: The LNG vaporizer assembly also includes a refrigerant storage tank and a refrigerant pump. The LNG vaporizer is connected to the refrigerant storage tank, which is connected to the first user assembly. The refrigerant pump is installed on the pipeline between the refrigerant storage tank and the first user assembly. A heat exchanger is installed on the pipeline between the refrigerant pump and the first user assembly. The top outlet of the buffer tank is connected to the heat exchanger. A start-up component is also provided between the refrigerant pump and the first user component; Preferably, the start-up components include a start-up valve, a start-up vaporizer, and a start-up heat source supply system.

3. The process system for replacing a refrigeration compressor with an LNG vaporizer according to claim 1, characterized in that: The first user component includes the original water-cooled user terminal component and / or the first user terminal component; The first user terminal component and the original water-cooled user terminal component are connected in parallel through the first parallel pipeline, and the first parallel pipeline is equipped with a first valve. The first user terminal component includes several first users, and the original water-cooled user terminal component includes several original water-cooled users. The several original water-cooled users are connected in parallel through a second pipeline, and each of the second pipelines is equipped with a second valve. The operating temperature requirement for the first user component is 5-10℃.

4. The process system for replacing a refrigeration compressor with an LNG vaporizer according to claim 3, characterized in that: The first user component is connected to a first-stage buffer tank, the first-stage buffer tank is connected to the second user component, and the second user component is connected to the second-stage buffer tank. The bottom outlet of a buffer tank is connected to the inlet of the first user component; The bottom outlet of the second-stage buffer tank is connected to the inlet of the first user component; Preferably, the second user component includes a second user terminal, and several second user terminals are connected in parallel through a third parallel pipeline, and each second user terminal is provided with a third valve at its inlet end; The inlet end of the third parallel pipeline of the second user component is connected to the heat exchanger, and a fourth valve is provided on the pipeline between the second user component and the heat exchanger. The operating temperature of the second user component is -30~-40℃.

5. The process system for replacing a refrigeration compressor with an LNG vaporizer according to claim 1, characterized in that: The bottom of the second-stage buffer tank is connected to the bottom of the first-stage buffer tank via a connecting pipeline. A liquid phase reflux pump is installed on the connecting pipeline, and the liquid phase reflux pump is connected to the inlet end of the first user component. A fifth valve is installed at the bottom of a buffer tank; The bottom of the second-stage buffer tank is equipped with a sixth valve.

6. The process system for replacing a refrigeration compressor with an LNG vaporizer according to claim 1, characterized in that: The LNG vaporizer is selected from the first LNG vaporizer and / or the second LNG vaporizer.

7. The process system for replacing a refrigeration compressor with an LNG vaporizer according to claim 6, characterized in that: The first LNG vaporizer includes a first LNG shell and a first LNG tube bundle. The first LNG shell is provided with a plurality of U-shaped first LNG heat exchange tubes, which are arranged laterally inside the first LNG shell. The gaseous refrigerant exchanges heat with the LNG feedstock in the shell inside the tube bundle of the first LNG vaporizer on the surface of the U-shaped tube bundle. Preferably, the upper end of the tube box of the first LNG vaporizer is provided with a first gaseous refrigerant inlet, the lower part of the tube box of the first LNG vaporizer is provided with a first liquid refrigerant outlet, and the first gaseous refrigerant inlet is connected to the first liquid refrigerant outlet through a U-shaped first LNG heat exchange tube bundle; The first LNG vaporizer's first LNG shell includes a first-stage shell, a transition shell, and a second-stage shell, with the first-stage shell and the second-stage shell connected by the transition shell; the diameter of the first-stage shell is smaller than the diameter of the second-stage shell; the lowest point of the first-stage shell is flush with the lowest point of the second-stage shell. The inlet end of the U-shaped first LNG heat exchange tube bundle is located on one side of a first shell section; the U-shaped end of the U-shaped first LNG heat exchange tube bundle is located inside the second shell section. Several staggered single-bow baffles and a first support plate are provided between the U-shaped first LNG heat exchange tube bundle and the first LNG shell; An overflow weir is provided inside the first LNG shell, and the overflow weir is located on the outside of the U-shaped end inside the second shell section.

8. A process system for replacing a refrigeration compressor with an LNG vaporizer according to claim 7, characterized in that: The single-bow deflector is located at the top of a section of the casing; The single-baffle plate and the first support plate are provided with several through holes to allow the heat exchange tubes to pass through; The first LNG inlet is located at the bottom of one section of the casing of the first LNG vaporizer; The top of the two-stage shell is provided with a first LNG vapor phase outlet, and the bottom of the two-stage shell is provided with a first LNG recombinant liquid phase outlet; the first LNG recombinant liquid phase outlet is located on the side of the overflow weir away from the U-shaped first LNG heat exchange tube bundle; the first vapor phase refrigerant inlet of the first LNG vaporizer is connected to the two-stage buffer tank, and the first liquid phase refrigerant outlet of the first LNG vaporizer is connected to the refrigerant storage tank.

9. A process system for replacing a refrigeration compressor with an LNG vaporizer according to claim 1, characterized in that: The second LNG vaporizer includes a second LNG shell and a second LNG tube bundle; The second LNG tube bundle is a U-shaped second LNG heat exchange tube bundle, which includes several second LNG heat exchange tubes; The second LNG heat exchange tube is arranged laterally inside the second LNG shell; The gaseous refrigerant exchanges heat with the LNG feedstock located in the second LNG tube bundle within the second LNG shell. Preferably, the bottom of the tube box of the second LNG vaporizer is provided with a second LNG inlet, the top of the tube box of the second LNG vaporizer is provided with a second LNG outlet, and the second LNG inlet and the second LNG outlet are connected by a U-shaped second LNG heat exchange tube bundle; The shell-side inlet of the second LNG vaporizer is provided with an outer guide ring, and 2 to 3 air inlet slots are evenly opened on the outer guide ring. The second gaseous refrigerant is connected to the cavity between the shell side and the shell side of the second LNG vaporizer through the air inlet slots. The bottom of the casing of the second LNG vaporizer is provided with a second liquid refrigerant outlet; The shell of the second LNG vaporizer is provided with several second baffles, and the second baffles are provided with several through holes to support the U-shaped second LNG heat exchange tube bundle; The second gaseous refrigerant inlet of the second LNG vaporizer is connected to the second-stage buffer tank, and the second liquid refrigerant outlet of the second LNG vaporizer is connected to the refrigerant storage tank.

10. A process system for replacing a refrigeration compressor with an LNG vaporizer according to any one of claims 6-9, characterized in that: The first and second gaseous refrigerants include propylene.

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