Polyolefin elastomer plant refrigeration system combining an lng separation plant and an ethylene cracker plant

Abstract

The present application relates to the field of petrochemical industry, and particularly relates to a polyolefin elastomer device refrigeration system combined with an LNG separation device and an ethylene cracking device. The refrigeration system comprises: a heat exchange unit, a hot material inlet of the heat exchange unit being in communication with an outlet of a working medium of a cold energy utilization unit in the polyolefin elastomer device; a hot material outlet of the heat exchange unit being in communication with an inlet of the working medium of the cold energy utilization unit in the polyolefin elastomer device; a cold material inlet of the heat exchange unit being in communication with a C2 + hydrocarbon material outlet of the LNG separation device; and a cold material outlet of the heat exchange unit being in communication with a cracking raw material inlet of the ethylene cracking device. The present application can realize overall energy optimization utilization of the system, and further reduce energy consumption of the polyolefin elastomer device on the basis of ensuring stable operation of the device.

Description

Technical Field

[0001] This invention relates to the field of petrochemicals, and more specifically to a refrigeration system for a polyolefin elastomer unit in a combined LNG separation unit and an ethylene cracking unit. Background Technology

[0002] In recent years, with the rapid development of the polyethylene industry, the production capacity of polyethylene plants has increased year by year, the technology has become increasingly advanced, and polyethylene output has reached a large scale. The issues of energy conservation, consumption reduction, and carbon emission reduction in polyethylene plants have also received increasing attention. To meet the design specifications of the feeding, recycling, and downstream systems of polyolefin elastomer plants, low-temperature water heat exchange equipment is required. Polyolefin elastomer plants require low-temperature refrigerants at different temperature ranges for heat exchange to ensure stable operation. Generally, the low-temperature refrigerant required by traditional polyethylene plants is provided by refrigeration units, and the energy consumption of refrigeration units is one of the important indicators affecting the overall energy consumption of polyethylene plants.

[0003] Following research, Mitsui Chemicals' Osaka plant, combining its ethylene plant with Osaka Gas's LNG cold energy utilization, has developed the world's first large-scale cold energy energy-saving process technology. In this new process, Mitsui Chemicals positions existing chillers as reserve units to address LNG cold energy shortages. When the LNG cold energy supply falls below the ethylene plant's cold energy requirements, the reserve chillers compensate for the shortfall. Since officially adopting this process in 2011, Mitsui Chemicals' Osaka plant has achieved high efficiency and energy savings in its ethylene plant, marking a successful precedent for cross-company and cross-industry collaboration.

[0004] Sinopec Tianjin LNG Company and Sinopec Tianjin Nangang Ethylene Project are located in the same industrial zone. Through a mutually beneficial cooperation model of exchanging cold and heat resources, they have already exchanged the low-temperature LNG cooling capacity previously used by the natural gas branch for seawater and propylene gasification with the surplus heat from the newly built 1.2 million tons / year ethylene plant. This coupled development approach achieves comprehensive regional development, reduces carbon emissions, and lowers the energy consumption per ton of product for the ethylene plant, thereby enhancing competitiveness through green advantages.

[0005] Currently, in domestic ethylene and downstream integrated plants, each unit has different cooling energy requirements at different temperatures. Heat exchange equipment is installed to facilitate heat exchange and reduce user temperatures. However, in reality, ethylene and downstream units operate independently, with limited heat exchange within each unit, lacking inter-unit energy coupling and utilization, and failing to optimize energy allocation between units.

[0006] The polyolefin elastomer unit at Sinopec's Tianjin Nangang Ethylene Project requires significant amounts of cold energy in its feeding, recovery, and post-processing units. The current design does not integrate this with the plant's overall cold energy utilization, relying instead on refrigeration units for cooling. This increases energy consumption, including water and electricity. The polyolefin elastomer unit uses lithium bromide refrigeration units, which have low cooling efficiency (approximately 50%), and uses the unit's own hot water for power, resulting in a substantial loss of hot water resources. Summary of the Invention

[0007] To address the above issues, this invention addresses the cold energy resource requirements of downstream polyolefin elastomer units in ethylene production by integrating them with upstream cold energy resources through an intermediate medium. It provides a refrigeration system for a polyolefin elastomer unit that combines an LNG separation unit and an ethylene cracking unit. Ethylene propane feedstock from LNG is cooled by a vaporizer and transferred to the cryogenic water closed-loop circulation system of the polyolefin elastomer unit. This achieves optimized energy utilization across the upstream and downstream units, further reducing energy consumption while ensuring stable unit operation.

[0008] To achieve the above objectives, the present invention provides a refrigeration system for a polyolefin elastomer unit combining an LNG separation unit and an ethylene cracking unit. This refrigeration system includes: a heat exchange unit;

[0009] The heat material inlet of the heat exchange unit is connected to the working medium outlet of the cold energy utilization unit in the polyolefin elastomer device.

[0010] The heat exchange unit's heat material outlet is connected to the working medium inlet of the cold energy utilization unit in the polyolefin elastomer device.

[0011] The cold material inlet of the heat exchange unit is connected to the C2 of the LNG separation unit. + Hydrocarbon material outlet connection;

[0012] The cold material outlet of the heat exchange unit is connected to the pyrolysis feedstock inlet of the ethylene cracking unit.

[0013] Through the above technical solution, the present invention has the following beneficial effects:

[0014] This invention delivers the cold energy generated from the gasification of C2+ hydrocarbon materials separated from LNG to a polyolefin elastomer unit. Through intermediate heat exchange, the upstream cold energy resources can replace the refrigeration unit of the polyolefin elastomer unit. At the same time, the C2+ hydrocarbon materials after heat exchange are transported to an ethylene cracking unit, realizing the overall energy optimization of the system. While ensuring the stable operation of the unit, the energy consumption of the polyolefin elastomer unit is further reduced. Attached Figure Description

[0015] Figure 1This is a schematic diagram and flowchart of the refrigeration system of the polyolefin elastomer unit of a combined LNG separation unit and ethylene cracking unit according to a preferred embodiment of the present invention. Detailed Implementation

[0016] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] This invention provides a refrigeration system for a polyolefin elastomer unit combining an LNG separation unit and an ethylene cracking unit. The refrigeration system includes: a heat exchange unit;

[0018] The heat material inlet of the heat exchange unit is connected to the working medium outlet of the cold energy utilization unit in the polyolefin elastomer device.

[0019] The heat exchange unit's heat material outlet is connected to the working medium inlet of the cold energy utilization unit in the polyolefin elastomer device.

[0020] The cold material inlet of the heat exchange unit is connected to the C2 of the LNG separation unit. + Hydrocarbon material outlet connection;

[0021] The cold material outlet of the heat exchange unit is connected to the pyrolysis feedstock inlet of the ethylene cracking unit.

[0022] This invention delivers the cold energy generated from the gasification of C2+ hydrocarbon materials separated from LNG to a polyolefin elastomer unit. Through intermediate heat exchange, the upstream cold energy resources can replace the refrigeration unit of the polyolefin elastomer unit. At the same time, the C2+ hydrocarbon materials after heat exchange are transported to an ethylene cracking unit, realizing the overall energy optimization of the system. While ensuring the stable operation of the unit, the energy consumption of the polyolefin elastomer unit is further reduced.

[0023] According to a preferred embodiment of the present invention, the refrigeration system further includes at least one refrigeration unit arranged in parallel with the heat exchange unit, the refrigeration unit being used to cool and circulate the working medium from the working medium outlet of the cooling capacity utilization unit in a portion of the polyolefin elastomer device.

[0024] According to a preferred embodiment of the present invention, the refrigeration system includes 1-3 refrigeration units arranged in parallel with the heat exchange unit.

[0025] According to a preferred embodiment of the present invention, the refrigeration unit is a lithium bromide ice machine.

[0026] According to a preferred embodiment of the present invention, the LNG separation device is used to separate LNG into NG and C2. + Hydrocarbon materials, of which C2 + The temperature of the hydrocarbon material is -40 to -10℃.

[0027] According to a preferred embodiment of the present invention, the heat transfer coefficient of the heat exchange unit is 300-900 W / m. 2 K.

[0028] According to a preferred embodiment of the present invention, the cold energy utilization unit includes a heat exchange device for at least one of the following units in a polyolefin elastomer device: a raw material unit, a catalyst and chemical preparation unit, a solvent and monomer recovery unit, and a polymer product post-processing unit.

[0029] According to a preferred embodiment of the present invention, 1 to 3 cooling capacity utilization units are provided, and when there is more than 1 unit, they are arranged in parallel.

[0030] According to a preferred embodiment of the present invention, the working medium of the cold energy utilization unit is selected from at least one of water and aqueous ethylene glycol.

[0031] According to a preferred embodiment of the present invention, the working medium of the cooling capacity utilization unit is water.

[0032] According to a preferred embodiment of the present invention, pumping equipment and / or valve switches are provided on the connecting pipes of each unit in the refrigeration system.

[0033] The present invention will be described in detail below through embodiments.

[0034] Example 1

[0035] In such Figure 1 The process implemented as shown, which couples the ethylene cracking, LNG separation, and polyolefin elastomer (POE) unit, is as follows:

[0036] In the LNG separation unit, LNG-rich liquid is heated to obtain NG and C2 at a homogeneous temperature of -18°C. + Logistics, C2 + The circulating heat exchange medium in the logistics and POE unit is circulating water heat exchange (the heat exchanger coefficient is 650 W / m). 2 K) provides cooling for the circulating water, which is then used for heat exchange in the catalyst and chemical preparation unit, solvent and monomer recovery unit, and polymer product post-processing unit of the polyolefin elastomer plant. After use, the circulating water splits into three streams, one of which is combined with C2 from the LNG separation unit. +The logistics heat exchange cooling, the other two streams generate cooling capacity through lithium bromide ice machines, and the three cooled circulating water streams are reused by the cooling capacity utilization unit in the polyolefin elastomer device to form a closed loop.

[0037] C2 after heat exchange + The material temperature rises and is pumped to the ethylene cracking unit as cracking feed.

[0038] The refrigeration process for the non-coupled polyolefin elastomer device is as follows:

[0039] C2 obtained by heating LNG-rich liquid in the LNG separator + The circulating heat exchange medium in the logistics and POE unit is not circulating water heat exchange, but directly provides cooling to the circulating water by generating cooling capacity through a lithium bromide ice machine. The remaining processes are the same as the aforementioned coupling process.

[0040] Based on the calculation of the C8 operating condition, the polyolefin elastomer unit will save an overall annual energy consumption of (5132-3956) / 3956*100%=30%.

[0041] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A refrigeration system for a polyolefin elastomer unit combining an LNG separation unit and an ethylene cracking unit, characterized in that, The refrigeration system includes: a heat exchange unit, The heat material inlet of the heat exchange unit is connected to the working medium outlet of the cold energy utilization unit in the polyolefin elastomer device. The heat exchange unit's heat material outlet is connected to the working medium inlet of the cold energy utilization unit in the polyolefin elastomer device. The cold material inlet of the heat exchange unit is connected to the C2 of the LNG separation unit. + Hydrocarbon material outlet connection; The cold material outlet of the heat exchange unit is connected to the pyrolysis feedstock inlet of the ethylene cracking unit.

2. The refrigeration system according to claim 1, wherein, The refrigeration system further includes at least one refrigeration unit connected in parallel with the heat exchange unit, wherein the refrigeration unit is used to cool and recycle the working medium from the working medium outlet of the cold energy utilization unit in part of the polyolefin elastomer device.

3. The refrigeration system according to claim 2, wherein, The refrigeration system includes 1-3 refrigeration units connected in parallel with the heat exchange unit.

4. The refrigeration system according to claim 2 or 3, wherein, The refrigeration unit is a lithium bromide ice machine.

5. The refrigeration system according to any one of claims 1-4, wherein, The LNG separation unit is used to separate LNG into NG and C2. + Hydrocarbon materials, of which C2 + The temperature of the hydrocarbon material is -40 to -10℃.

6. The refrigeration system according to any one of claims 1-5, wherein, The heat transfer coefficient of the heat exchange unit is 300-900 W / m. 2 K.

7. The refrigeration system according to any one of claims 1-6, wherein, The cold energy utilization unit includes heat exchange equipment for at least one of the following units in the polyolefin elastomer plant: a catalyst and chemical preparation unit, a solvent and monomer recovery unit, and a polymer product post-processing unit.

8. The refrigeration system according to any one of claims 1-7, wherein, The cooling capacity utilization unit is set to 1-3 units, and when there is more than 1 unit, they are connected in parallel.

9. The refrigeration system according to any one of claims 1-8, wherein, The working medium of the cold energy utilization unit is selected from at least one of water and ethylene glycol aqueous solution, preferably water.

10. The refrigeration system according to any one of claims 1-9, wherein, The refrigeration system is equipped with pumping devices and / or valve switches on the connecting pipes of each unit.

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