Method for applying liquefied natural gas cold energy to cold utilization facility of EOEG device and cold energy utilization system

Abstract

The invention provides a method for applying liquefied natural gas cold energy to a cold facility for an EOEG device and a cold energy utilization system, and relates to the technical field of energy-saving facilities. The method comprises the following steps: by taking an ethylene glycol aqueous solution as a secondary refrigerant, carrying out cold exchange on liquefied natural gas and the ethylene glycol aqueous solution to respectively obtain a cooled ethylene glycol aqueous solution and low-temperature gasified natural gas; and then the cooled ethylene glycol aqueous solution, ethylene oxide generated by the EOEG device and circulating chilled water are subjected to cold exchange in sequence, and then the liquefied natural gas cold energy is applied to the EOEG device. And meanwhile, the low-temperature gasified natural gas and the ethylene carbonate primary product generated by the EOEG device are subjected to cold exchange, so that the purpose of reducing the temperature of the ethylene carbonate primary product is achieved. Therefore, by means of the cold energy application method of the liquefied natural gas, the problems that due to the fact that an existing EOEG device product storage tank cold facility and an existing device production cold facility are independently arranged, operation procedures are complex, the occupied area is large, and energy consumption is high are effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy-saving facilities, and in particular to a method for utilizing liquefied natural gas cold energy in cold facilities for EOEG devices and a cold energy utilization system. Background Art

[0002] Liquefied natural gas (LNG) will be gasified before use. The conventional method is to gasify LNG directly through a seawater vaporizer (ORV). A large amount of cold energy is taken away by seawater without being used, which also aggravates the low-temperature pollution of the ocean. At the same time, large refineries or chemical companies set up fuel gas pipelines as fuel for daily operations. The source of fuel gas is the waste gas generated during the operation of the equipment, and its output is unstable. Therefore, natural gas pipelines are generally set up as a supplement to fuel gas. Natural gas enters the fuel gas pipeline network after long-distance transportation and decompression from the gate station outside the factory, which will also cause energy waste. Setting up independent LNG storage tanks in large refineries or chemical companies and setting matching pressurization facilities according to the pressure of the fuel gas pipeline network can save energy.

[0003] Therefore, it is necessary and urgent to study the utilization of the cold energy generated by LNG in the gasification process and combine it with the refrigeration equipment of refineries or chemical enterprises, and combine it with the specific refrigeration capacity and quality of the refining and chemical enterprises, so as to save a lot of energy.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] As a chemical plant for producing ethylene oxide (EO) and ethylene glycol (EG), the EOEG plant uses a large amount of cold energy in the separation and refining process of EO products and the storage process of EO. Traditional processes use ice machines for refrigeration, which causes a great waste of energy. Different production units require different cold sources and qualities, and use different refrigeration units, resulting in problems such as large floor space and complex operating procedures.

[0006] The ethylene carbonate (EC) primary product in the present invention refers to the ethylene carbonate primary product used when ethylene carbonate is used to synthesize ethylene glycol in an EOEG device, also known as: EC primary product.

[0007] The purpose of the present invention is to provide a method and system for utilizing liquefied natural gas cold energy with simple process, small footprint and easy operation. The present application can use liquefied natural gas cold energy for cold facilities of EOEG devices through the setting of system devices and process flow control. Specifically, liquefied natural gas cold energy can be used for the preparation of chilled water of EOEG devices, the cold preservation of EO products and the cooling of EC primary products.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0009] The present invention provides a method for using liquefied natural gas cold energy for cold facilities of EOEG devices, the method comprising:

[0010] (A) by exchanging cold energy of liquefied natural gas with ethylene glycol aqueous solution, a cooled ethylene glycol aqueous solution and low-temperature gasified natural gas are obtained respectively;

[0011] (B) exchanging the cooling ethylene glycol aqueous solution with the ethylene oxide and circulating chilled water produced by the EOEG device in sequence, thereby applying the cold energy of the liquefied natural gas to the EOEG device;

[0012] And / or, the low temperature gasified natural gas is exchanged with the primary product of ethylene carbonate produced by the EOEG device, and the cold energy of the liquefied natural gas is applied to the EOEG device.

[0013] Further, the concentration of the ethylene glycol aqueous solution is 50-60wt%;

[0014] Furthermore, after the cooling in step (A), the temperature of the cooled ethylene glycol aqueous solution is -15 to -25°C, and the temperature of the low-temperature gasified natural gas is -55 to -75°C.

[0015] Furthermore, after the step (B) of cooling the ethylene glycol aqueous solution and exchanging cooling with ethylene oxide, the temperature of ethylene oxide decreases from -1°C to -5°C to -7°C to -10°C, and the temperature of the ethylene glycol aqueous solution is -10 to -20°C.

[0016] Furthermore, after the step (B) cools the ethylene glycol aqueous solution and exchanges it with the circulating chilled water, the temperature of the circulating chilled water decreases from 10°C to 16°C to 5°C to 10°C, and the temperature of the ethylene glycol aqueous solution is 0 to 10°C.

[0017] Furthermore, the temperature of the ethylene carbonate primary product in step (B) is 110-125° C.;

[0018] After the low-temperature gasified natural gas and the primary product of ethylene carbonate are exchanged for cold, the temperature of the primary product of ethylene carbonate is 85-100°C, and the temperature of the low-temperature gasified natural gas is increased to 10-20°C.

[0019] The present invention provides a liquefied natural gas cold energy utilization system for an EOEG device, the cold energy utilization system comprising: a liquefied natural gas ethylene glycol cold exchange device, an ethylene glycol cold exchange device and a low-temperature natural gas cold exchange device;

[0020] The liquefied natural gas glycol cooling device comprises: a liquefied natural gas storage tank, an ethylene glycol start-up buffer tank, and a liquefied natural gas glycol cooling device. The liquefied natural gas storage tank and the ethylene glycol start-up buffer tank are respectively connected to the liquefied natural gas glycol cooling device through pipelines, and after cooling, a cooling ethylene glycol aqueous solution and a low-temperature gasified natural gas are generated;

[0021] The ethylene glycol cooling device comprises: an ethylene glycol-EO heat exchanger and an ethylene glycol-chilled water heat exchanger; the cooled ethylene glycol aqueous solution is sequentially passed through the ethylene glycol-EO heat exchanger and the ethylene glycol-chilled water heat exchanger to exchange cooling with ethylene oxide and chilled water respectively;

[0022] The low-temperature natural gas cooling device comprises: an NG-EC primary product cooler, an EC reactor buffer tank, and an EC primary product cooler; the low-temperature gasified natural gas and the ethylene carbonate primary product in the EC reactor buffer tank are cooled in the NG-EC primary product cooler, and after the cooling, the ethylene carbonate primary product enters the EC primary product cooler for cooling and then flows back to the EC reactor buffer tank.

[0023] Furthermore, a liquefied natural gas pressure pump is provided between the liquefied natural gas storage tank and the liquefied natural gas glycol cooler;

[0024] And / or, a normally open valve and an ethylene glycol booster pump are sequentially arranged between the ethylene glycol start-up buffer tank and the liquefied natural gas ethylene glycol cooler;

[0025] Furthermore, the low-temperature natural gas refrigeration device further comprises: a first flow control transmitter, a second flow control transmitter, a first temperature regulating valve and a second temperature regulating valve;

[0026] The first temperature regulating valve is arranged at the outlet of the EC primary product cooler, and the second temperature regulating valve is combined with the first temperature regulating valve at the outlet of the EC primary product cooler;

[0027] The first flow control transmitter and the second flow control transmitter are respectively connected to the first temperature regulating valve and the second temperature regulating valve in a decoupling control manner, and are used to control the temperature of the ethylene carbonate primary product at the outlet of the EC primary product cooler.

[0028] Furthermore, the ethylene glycol cooling device further comprises: an EO product tank and an EO circulation pump;

[0029] The EO product tank is used to store ethylene oxide. The EO product tank is cyclically connected to the ethylene glycol-EO heat exchanger through a pipeline. An EO circulation pump is provided between the EO product tank and the ethylene glycol-EO heat exchanger.

[0030] Furthermore, the ethylene glycol cooling device also includes: a chilled water circulation pump, a chilled water buffer tank, and a cold heat exchanger for EOEG;

[0031] The chilled water buffer tank is used to store chilled water. The chilled water buffer tank, ethylene glycol-chilled water heat exchanger and EOEG are circulated and connected by a cold heat exchanger. A chilled water circulation pump is arranged between the chilled water buffer tank and the ethylene glycol-chilled water heat exchanger.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention provides a method for using liquefied natural gas cold energy for cold facilities of EOEG devices. The method uses ethylene glycol aqueous solution as a refrigerant, exchanges cold energy of liquefied natural gas with ethylene glycol aqueous solution, and obtains cooled ethylene glycol aqueous solution and low-temperature gasified natural gas, respectively; then, the cooled ethylene glycol aqueous solution is exchanged with ethylene oxide and circulating chilled water produced by the EOEG device in sequence, and then the liquefied natural gas cold energy is applied to the EOEG device to meet the cold demand. At the same time, the low-temperature gasified natural gas is exchanged with the primary product of ethylene carbonate produced by the EOEG device to achieve the purpose of lowering the temperature of the primary product of ethylene carbonate and saving cooling water. Therefore, the liquefied natural gas cold energy application method of the present application effectively alleviates the problems of the existing EOEG device product storage tank cold facilities and the device production cold facilities being independently set up, resulting in complex operating procedures, large floor space, high energy consumption, and other problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 This is a schematic diagram of the overall structure of the liquefied natural gas cold energy utilization system for the EOEG device provided in Example 1 of the present invention.

[0036] Icons: 1-LNG storage tank; 2-LNG booster pump; 3-LNG ethylene glycol cooler; 4-NG-EC primary product cooler; 5-EC reactor buffer tank; 6-EC primary product cooler; 7-first flow control transmitter; 8-second flow control transmitter; 9-first temperature control valve; 10-second temperature control valve; 11-normally open valve; 12-ethylene glycol-EO heat exchanger; 13-ethylene glycol-chilled water heat exchanger; 14-ethylene glycol start-up buffer tank; 15-ethylene glycol booster pump; 16-EO circulation pump; 17-EO product tank; 18-chilled water circulation pump; 19-chilled water buffer tank; 20-EOEG cold heat exchanger. DETAILED DESCRIPTION

[0037] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] According to one aspect of the present invention, a method for using liquefied natural gas cold energy for cold facilities of EOEG devices comprises:

[0039] (A) by exchanging cold energy of liquefied natural gas with ethylene glycol aqueous solution, a cooled ethylene glycol aqueous solution and low-temperature gasified natural gas are obtained respectively;

[0040] (B) exchanging the cooling ethylene glycol aqueous solution with the ethylene oxide and circulating chilled water produced by the EOEG device in sequence, thereby applying the cold energy of the liquefied natural gas to the EOEG device;

[0041] And / or, the low temperature gasified natural gas is exchanged with the primary product of ethylene carbonate produced by the EOEG device, and the cold energy of the liquefied natural gas is applied to the EOEG device.

[0042] The present invention provides a method for using liquefied natural gas cold energy for cold facilities of EOEG devices. The method uses ethylene glycol aqueous solution as a refrigerant, exchanges cold energy of liquefied natural gas with ethylene glycol aqueous solution, and obtains cooled ethylene glycol aqueous solution and low-temperature gasified natural gas, respectively; then, the cooled ethylene glycol aqueous solution is exchanged with ethylene oxide and circulating chilled water produced by the EOEG device in sequence, and then the liquefied natural gas cold energy is applied to the EOEG device to meet the cold demand. At the same time, the low-temperature gasified natural gas is exchanged with the primary product of ethylene carbonate produced by the EOEG device to achieve the purpose of lowering the temperature of the primary product of ethylene carbonate and saving cooling water. Therefore, the liquefied natural gas cold energy application method of the present application effectively alleviates the problems of the existing EOEG device product storage tank cold facilities and the device production cold facilities being independently set up, resulting in complex operating procedures, large floor space, high energy consumption, and other problems.

[0043] In a preferred embodiment of the present invention, the concentration of the ethylene glycol aqueous solution is 50-60 wt%;

[0044] In a preferred embodiment of the present invention, after the cooling in step (A), the temperature of the cooled ethylene glycol aqueous solution is -15 to -25°C, and the temperature of the low-temperature gasified natural gas is -55 to -75°C.

[0045] As a preferred embodiment, the present invention gasifies liquefied natural gas to produce low-temperature gasified natural gas at -55 to -75°C, and simultaneously cools room-temperature ethylene glycol to an ethylene glycol aqueous solution at a temperature of -15 to -25°C by cold exchange.

[0046] In a preferred embodiment of the present invention, after the step (B) of cooling the ethylene glycol aqueous solution and exchanging cooling with ethylene oxide, the temperature of ethylene oxide decreases from -1°C to -5°C to -7°C to -10°C, and the temperature of the ethylene glycol aqueous solution is -10 to -20°C.

[0047] As a preferred embodiment, after the above-mentioned cooled ethylene glycol aqueous solution is exchanged with ethylene oxide, the temperature of ethylene oxide can be reduced from -5°C to -7°C, thereby realizing the cooling and maintenance of ethylene oxide in the process flow of the EOEG device and meeting the cooling demand of the EO product tank 17.

[0048] In a preferred embodiment of the present invention, after the step (B) cools the ethylene glycol aqueous solution and exchanges it with the circulating chilled water, the temperature of the circulating chilled water decreases from 10°C to 16°C to 5°C to 10°C, and the temperature of the ethylene glycol aqueous solution is 0 to 10°C.

[0049] As a preferred embodiment, after the above-mentioned cooling of the ethylene glycol aqueous solution is exchanged with ethylene oxide, the temperature of the circulating chilled water can be reduced from 16°C to 10°C, thereby meeting the cooling demand for chilled water in the production process of the EOEG device.

[0050] In a preferred embodiment of the present invention, the temperature of the ethylene carbonate primary product in step (B) is 110-125° C.;

[0051] After the low-temperature gasified natural gas and the primary product of ethylene carbonate are exchanged for cold, the temperature of the primary product of ethylene carbonate is 85-100°C, and the temperature of the low-temperature gasified natural gas is increased to 10-20°C.

[0052] As a preferred embodiment, the present invention utilizes the heat-reheated NG (natural gas) generated by the EC (ethylene carbonate) reaction of the EOEG device to achieve the purpose of lowering the temperature of the EC primary product and saving cooling water.

[0053] According to one aspect of the present invention, a liquefied natural gas cold energy utilization system for an EOEG device, the cold energy utilization system comprising: a liquefied natural gas ethylene glycol cold exchange device, an ethylene glycol cold exchange device and a low-temperature natural gas cold exchange device;

[0054] The liquefied natural gas glycol cooling device comprises: a liquefied natural gas storage tank 1, an ethylene glycol start-up buffer tank 14, and a liquefied natural gas glycol cooling device 3. The liquefied natural gas storage tank 1 and the ethylene glycol start-up buffer tank 14 are respectively connected to the liquefied natural gas glycol cooling device 3 through pipelines, and after cooling, a cooling ethylene glycol aqueous solution and a low-temperature gasified natural gas are generated;

[0055] The ethylene glycol cooling device comprises: an ethylene glycol-EO heat exchanger 12 and an ethylene glycol-chilled water heat exchanger 13; the cooled ethylene glycol aqueous solution sequentially passes through the ethylene glycol-EO heat exchanger 12 and the ethylene glycol-chilled water heat exchanger 13 to exchange cooling with ethylene oxide and chilled water respectively;

[0056] The low-temperature natural gas cooling device includes: an NG-EC primary product cooler 4, an EC reactor buffer tank 5, and an EC primary product cooler 6; the low-temperature gasified natural gas and the ethylene carbonate primary product in the EC reactor buffer tank 5 are cooled in the NG-EC primary product cooler 4, and after the cooling, the ethylene carbonate primary product enters the EC primary product cooler 6 for cooling and then flows back to the EC reactor buffer tank 5.

[0057] The present invention provides a liquefied natural gas cold energy utilization system for an EOEG device, and the cold energy utilization system includes: a liquefied natural gas ethylene glycol cold exchange device, an ethylene glycol cold exchange device, and a low-temperature natural gas cold exchange device. Among them: the liquefied natural gas ethylene glycol cold exchange device includes a liquefied natural gas storage tank 1, an ethylene glycol start-up buffer tank 14, and a liquefied natural gas ethylene glycol cold exchanger 3; the ethylene glycol cold exchange device includes an ethylene glycol-EO heat exchanger 12, and an ethylene glycol-chilled water heat exchanger 13; the low-temperature natural gas cold exchange device includes an NG-EC primary product cooler 4, an EC reactor buffer tank 5, and an EC primary product cooler 6. Through the setting of the above-mentioned cold energy utilization system, the present invention transports LNG cold energy through the refrigerant ethylene glycol, which is used for the cold demand of the EO product tank 17 and the cold demand of the EOEG device production, and utilizes the hot reheating NG generated by the EC reaction of the EOEG device to achieve the purpose of lowering the temperature of the EC primary product and saving cooling water.

[0058] In a preferred embodiment of the present invention, a liquefied natural gas booster pump 2 is provided between the liquefied natural gas storage tank 1 and the liquefied natural gas glycol cooler 3;

[0059] And / or, a normally open valve 11 and an ethylene glycol booster pump 15 are sequentially arranged between the ethylene glycol start-up buffer tank 14 and the liquefied natural gas ethylene glycol cooler 3;

[0060] In a preferred embodiment of the present invention, the low-temperature natural gas refrigeration device further comprises: a first flow control transmitter 7, a second flow control transmitter 8, a first temperature regulating valve 9 and a second temperature regulating valve 10;

[0061] The first temperature regulating valve 9 is arranged at the outlet of the cooler 6 of the EC primary product, and the second temperature regulating valve 10 is combined with the first temperature regulating valve 9 at the outlet of the cooler 6 of the EC primary product;

[0062] The first flow control transmitter 7 and the second flow control transmitter 8 are respectively connected to the first temperature regulating valve 9 and the second temperature regulating valve 10 in a decoupling control manner, and are used to control the temperature of the ethylene carbonate primary product at the outlet of the EC primary product cooler 6.

[0063] In a preferred embodiment of the present invention, the ethylene glycol cold exchange device further comprises: an EO product tank 17 and an EO circulation pump 16;

[0064] The EO product tank 17 is used to store ethylene oxide. The EO product tank 17 is cyclically connected to the ethylene glycol-EO heat exchanger 12 via a pipeline. An EO circulation pump 16 is provided between the EO product tank 17 and the ethylene glycol-EO heat exchanger 12 .

[0065] As a preferred embodiment, the ethylene oxide (EO) is pressurized from the EO product tank 17 through the EO circulation pump 16 and enters the ethylene glycol-EO heat exchanger 12 with a temperature controlled at -5°C. The temperature of EO leaving the ethylene glycol-EO heat exchanger 12 is controlled at -7°C and enters the EO product tank 17 again.

[0066] In a preferred embodiment of the present invention, the ethylene glycol cooling device further comprises: a chilled water circulation pump 18, a chilled water buffer tank 19, and a cold heat exchanger 20 for EOEG;

[0067] The chilled water buffer tank 19 is used to store chilled water. The chilled water buffer tank 19, the ethylene glycol-chilled water heat exchanger 13 and the EOEG cold heat exchanger 20 are cyclically connected. A chilled water circulation pump 18 is provided between the chilled water buffer tank 19 and the ethylene glycol-chilled water heat exchanger 13.

[0068] As a preferred embodiment, the above-mentioned chilled water is pressurized from the chilled water buffer tank 19 through the chilled water circulation pump 18 and enters the ethylene glycol-chilled water heat exchanger 13. The temperature of the chilled water leaving the ethylene glycol-chilled water heat exchanger 13 is controlled at 10°C. The chilled water enters the chilled water main pipe of the EOEG device and goes to each EOEG to be cooled by the cold heat exchanger 20 and then returns to the chilled water buffer tank 19.

[0069] In a preferred embodiment of the present invention, the outlet pipeline of the ethylene glycol start-up buffer tank 14 is merged with the inlet pipeline of the ethylene glycol booster pump 15 and enters the ethylene glycol booster pump 15, and the valve of the outlet pipeline of the ethylene glycol start-up buffer tank 14 is set to be normally open, and the installation position of the ethylene glycol start-up buffer tank 14 is more than 6 meters higher than the height of the ethylene glycol booster pump 15.

[0070] The technical solution of the present invention will be further described below in conjunction with Example 1.

[0071] Example 1

[0072] Figure 1 It is a schematic diagram of the overall structure of the liquefied natural gas cold energy utilization system for EOEG device of the present invention.

[0073] A liquefied natural gas cold energy utilization system for an EOEG device, the cold energy utilization system comprising: a liquefied natural gas ethylene glycol cold exchange device, an ethylene glycol cold exchange device and a low-temperature natural gas cold exchange device;

[0074] See also Figure 1 The liquefied natural gas glycol cooling device includes: a liquefied natural gas storage tank 1, an ethylene glycol start-up buffer tank 14, and a liquefied natural gas glycol cooling device 3.

[0075] As a preferred implementation of this embodiment, the 50wt% ethylene glycol aqueous solution stored in the ethylene glycol start-up buffer tank 14 is used as a coolant and is pressurized by the ethylene glycol pressure pump 15 and then enters the liquefied natural gas ethylene glycol cooler 3 for cooling. After cooling, the cooled ethylene glycol aqueous solution and the low-temperature gasified natural gas are generated.

[0076] See also Figure 1 The ethylene glycol cooling device comprises: an ethylene glycol-EO heat exchanger 12 and an ethylene glycol-chilled water heat exchanger 13; the cooled ethylene glycol aqueous solution is sequentially passed through the ethylene glycol-EO heat exchanger 12 and the ethylene glycol-chilled water heat exchanger 13 to exchange cooling with ethylene oxide and chilled water respectively;

[0077] Continue to see Figure 1 The low-temperature natural gas cooling device includes: an NG-EC primary product cooler 4, an EC reactor buffer tank 5, and an EC primary product cooler 6; the low-temperature gasified natural gas and the ethylene carbonate primary product in the EC reactor buffer tank 5 are cooled in the NG-EC primary product cooler 4, and after the cooling, the ethylene carbonate primary product enters the EC primary product cooler 6 for cooling and then flows back to the EC reactor buffer tank 5.

[0078] As a preferred implementation of this embodiment, a liquefied natural gas booster pump 2 is provided between the liquefied natural gas storage tank 1 and the liquefied natural gas glycol cooler 3;

[0079] As a preferred implementation of this embodiment, a normally open valve 11 and an ethylene glycol booster pump 15 are sequentially arranged between the ethylene glycol start-up buffer tank 14 and the liquefied natural gas ethylene glycol cooler 3;

[0080] As a preferred implementation of this embodiment, the low-temperature natural gas refrigeration device further includes: a first flow control transmitter 7, a second flow control transmitter 8, a first temperature regulating valve 9 and a second temperature regulating valve 10; the first temperature regulating valve 9 is arranged at the outlet of the cooler 6 of the EC primary product, and the second temperature regulating valve 10 is combined with the first temperature regulating valve 9 at the outlet of the cooler 6 of the EC primary product;

[0081] As a preferred implementation of this embodiment, the first flow control transmitter 7 and the second flow control transmitter 8 are respectively decoupled and controlled to the first temperature regulating valve 9 and the second temperature regulating valve 10, so as to control the temperature of the ethylene carbonate primary product at the outlet of the cooler 6 of the EC primary product.

[0082] Preferably, the cold source of the cooler 6 for the EC primary product is circulating water, which is in the form of a plate heat exchanger.

[0083] As a preferred implementation of this embodiment, the ethylene glycol cooling device also includes: an EO product tank 17 and an EO circulation pump 16; the EO product tank 17 is used to store ethylene oxide, the EO product tank 17 is connected to the ethylene glycol-EO heat exchanger 12 through a pipeline circulation, and an EO circulation pump 16 is arranged between the EO product tank 17 and the ethylene glycol-EO heat exchanger 12.

[0084] As a preferred implementation of this embodiment, the ethylene glycol cooling device further includes: a chilled water circulation pump 18, a chilled water buffer tank 19, and a cold heat exchanger 20 for EOEG;

[0085] The chilled water buffer tank 19 is used to store chilled water. The chilled water buffer tank 19, the ethylene glycol-chilled water heat exchanger 13 and the EOEG cold heat exchanger 20 are cyclically connected. A chilled water circulation pump 18 is provided between the chilled water buffer tank 19 and the ethylene glycol-chilled water heat exchanger 13.

[0086] As a preferred implementation manner of this embodiment, the outlet pipeline of the ethylene glycol start-up buffer tank 14 is merged with the inlet pipeline of the ethylene glycol booster pump 15 and enters the ethylene glycol booster pump 15, and the valve of the outlet pipeline of the ethylene glycol start-up buffer tank 14 is set to be normally open, and the installation position of the ethylene glycol start-up buffer tank 14 is more than 6 meters higher than the height of the ethylene glycol booster pump 15.

[0087] Specifically, the working process of the liquefied natural gas cold energy utilization system for the EOEG device in this embodiment is as follows:

[0088] (A) The 50 wt% ethylene glycol aqueous solution stored in the ethylene glycol start-up buffer tank 14 is pressurized at a flow rate of 15.25 t / h by the ethylene glycol pressure pump 15 as a coolant and then enters the liquefied natural gas ethylene glycol cooler 3.

[0089] After the ethylene glycol aqueous solution is cooled with LNG, the outlet temperature of the ethylene glycol aqueous solution is controlled at -15°C. After the ethylene glycol aqueous solution enters the ethylene glycol-EO heat exchanger 12 and is cooled with EO, the outlet temperature of the ethylene glycol aqueous solution is controlled at -10°C. After the ethylene glycol aqueous solution enters the ethylene glycol-chilled water heat exchanger 13 and is cooled with chilled water, the temperature is controlled at 10°C, and the ethylene glycol aqueous solution enters the ethylene glycol start-up buffer tank 14 for recycling.

[0090] (B) The liquefied natural gas stored in the liquefied natural gas storage tank 1 is pressurized to 0.45MpaG at a flow rate of 1.75t / h by the liquefied natural gas booster 2, and then enters the liquefied natural gas ethylene glycol cooler 3 to exchange cooling with a 50wt% ethylene glycol aqueous solution, and then vaporizes into NG (natural gas), and the NG outlet temperature is controlled at -55°C. The NG enters the NG-EC primary product cooler 4 to exchange cooling with the EC primary product, and the NG outlet temperature is controlled at 20°C and the pressure is controlled at 0.4MpaG to enter the fuel gas pipeline network of the whole plant as a supplement to the fuel gas.

[0091] At the same time, the EC primary product 1481t / h from the EC reactor buffer tank 5 has a temperature of 117°C, and a first flow control transmitter 7 is provided on the pipeline entering the NG-EC primary product cooler 4. The EC primary product and NG are divided into two streams after cooling in the NG-EC primary product cooler 4.

[0092] The first stream enters the cooler 6 of the EC primary product and exchanges cooling with the circulating water before leaving the cooler 6 of the EC primary product. A first temperature regulating valve 9 is provided at the outlet of the cooler 6 of the EC primary product.

[0093] The second stream is provided with a second temperature regulating valve 10, and is merged with the first stream at the outlet of the cooler 6 of the EC primary product, and a second flow control transmitter 8 is provided on the merged pipeline, and the merged pipeline returns to the EC reactor buffer tank 5 to participate in the subsequent reaction. The first flow control transmitter 7 and the second flow control transmitter 8 use decoupling control to control the first temperature regulating valve 9 and the second temperature regulating valve 10 respectively, with the control weights being 40% and 60% respectively, so that the temperature of the EC primary product entering the merged pipeline of the EC reactor is 98°C.

[0094] The EO after cooling in step (A) is pressurized from the EO product tank 17 through the EO circulation pump 16 and enters the ethylene glycol-EO heat exchanger 12 at a temperature controlled at -5°C. The temperature of the EO leaving the ethylene glycol-EO heat exchanger 12 is controlled at -7°C and enters the EO product tank 17 again.

[0095] In step (A), the chilled water after cooling is pressurized from the chilled water buffer tank 19 through the chilled water circulation pump 18 and enters the ethylene glycol-chilled water heat exchanger 13 at a temperature controlled at 16°C. The temperature of the chilled water leaving the ethylene glycol-chilled water heat exchanger 13 is controlled at 10°C. The chilled water enters the chilled water main pipe of the EOEG device and goes to each EOEG with the cold heat exchanger 20 for cooling and then returns to the chilled water buffer tank 19.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for using liquefied natural gas cold energy for cold facilities of EOEG devices, characterized in that: The method comprises: (A) by exchanging cold energy of liquefied natural gas with ethylene glycol aqueous solution, a cooled ethylene glycol aqueous solution and low-temperature gasified natural gas are obtained respectively; (B) exchanging the cooling ethylene glycol aqueous solution with the ethylene oxide and circulating chilled water produced by the EOEG device in sequence, thereby applying the cold energy of the liquefied natural gas to the EOEG device; And / or, the low temperature gasified natural gas is exchanged with the primary product of ethylene carbonate produced by the EOEG device, and the cold energy of the liquefied natural gas is applied to the EOEG device.

2. The method according to claim 1, characterized in that The concentration of the ethylene glycol aqueous solution is 50-60wt%; After the cooling in step (A), the temperature of the cooled ethylene glycol aqueous solution is -15 to -25°C, and the temperature of the low-temperature gasified natural gas is -55 to -75°C.

3. The method according to claim 1, characterized in that: After the step (B) of cooling the ethylene glycol aqueous solution and exchanging cooling with ethylene oxide, the temperature of ethylene oxide decreases from -1°C to -5°C to -7°C to -10°C, and the temperature of the ethylene glycol aqueous solution is -10 to -20°C.

4. The method according to claim 1, characterized in that: After the step (B) cools the ethylene glycol aqueous solution and exchanges it with the circulating chilled water, the temperature of the circulating chilled water decreases from 10°C to 16°C to 5°C to 10°C, and the temperature of the ethylene glycol aqueous solution is 0 to 10°C.

5. The method according to claim 1, characterized in that: The temperature of the primary product of ethylene carbonate in step (B) is 110-125° C.; After the low-temperature gasified natural gas and the primary product of ethylene carbonate are exchanged for cold, the temperature of the primary product of ethylene carbonate is 85-100°C, and the temperature of the low-temperature gasified natural gas is increased to 10-20°C.

6. A liquefied natural gas cold energy utilization system for an EOEG device, characterized in that: The cold energy utilization system comprises: a liquefied natural gas ethylene glycol refrigeration device, an ethylene glycol refrigeration device and a low-temperature natural gas refrigeration device; The liquefied natural gas ethylene glycol cooling device comprises: a liquefied natural gas storage tank (1), an ethylene glycol start-up buffer tank (14), and a liquefied natural gas ethylene glycol cooling device (3). The liquefied natural gas storage tank (1) and the ethylene glycol start-up buffer tank (14) are respectively connected to the liquefied natural gas ethylene glycol cooling device (3) through pipelines, and after cooling, a cooled ethylene glycol aqueous solution and low-temperature gasified natural gas are generated; The ethylene glycol cooling device comprises: an ethylene glycol-EO heat exchanger (12) and an ethylene glycol-chilled water heat exchanger (13); the cooled ethylene glycol aqueous solution passes through the ethylene glycol-EO heat exchanger (12) and the ethylene glycol-chilled water heat exchanger (13) in sequence to exchange cooling with ethylene oxide and chilled water respectively; The low-temperature natural gas cooling device comprises: an NG-EC primary product cooler (4), an EC reactor buffer tank (5), and an EC primary product cooler (6); the low-temperature gasified natural gas and the ethylene carbonate primary product in the EC reactor buffer tank (5) are cooled in the NG-EC primary product cooler (4), and after the cooling, the ethylene carbonate primary product enters the EC primary product cooler (6), is cooled, and then flows back to the EC reactor buffer tank (5).

7. The liquefied natural gas cold energy utilization system according to claim 6, characterized in that: A liquefied natural gas booster pump (2) is provided between the liquefied natural gas storage tank (1) and the liquefied natural gas glycol cooler (3); And / or, a normally open valve (11) and an ethylene glycol booster pump (15) are sequentially arranged between the ethylene glycol start-up buffer tank (14) and the liquefied natural gas ethylene glycol cooler (3).

8. The liquefied natural gas cold energy utilization system according to claim 6, characterized in that: The low-temperature natural gas refrigeration device further comprises: a first flow control transmitter (7), a second flow control transmitter (8), a first temperature regulating valve (9) and a second temperature regulating valve (10); The first temperature regulating valve (9) is arranged at the outlet of the cooler (6) for the EC primary product, and the second temperature regulating valve (10) is combined with the first temperature regulating valve (9) at the outlet of the cooler (6) for the EC primary product; The first flow control transmitter (7) and the second flow control transmitter (8) are respectively connected to the first temperature regulating valve (9) and the second temperature regulating valve (10) in a decoupling control manner, and are used to control the temperature of the ethylene carbonate primary product at the outlet of the EC primary product cooler (6).

9. The liquefied natural gas cold energy utilization system according to claim 6, characterized in that: The ethylene glycol cooling device further comprises: an EO product tank (17) and an EO circulation pump (16); The EO product tank (17) is used to store ethylene oxide. The EO product tank (17) is cyclically connected to the ethylene glycol-EO heat exchanger (12) via a pipeline. An EO circulation pump (16) is provided between the EO product tank (17) and the ethylene glycol-EO heat exchanger (12).

10. The liquefied natural gas cold energy utilization system according to claim 6, characterized in that: The ethylene glycol cooling device also includes: a chilled water circulation pump (18), a chilled water buffer tank (19), and a cold heat exchanger for EOEG (20); The chilled water buffer tank (19) is used to store chilled water. The chilled water buffer tank (19), the ethylene glycol-chilled water heat exchanger (13) and the EOEG cold heat exchanger (20) are cyclically connected. A chilled water circulation pump (18) is provided between the chilled water buffer tank (19) and the ethylene glycol-chilled water heat exchanger (13).

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