CN110330018B - Device for preparing dry ice and separating ethylene by using LNG cold energy and working method - Google Patents
Device for preparing dry ice and separating ethylene by using LNG cold energy and working method Download PDFInfo
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- CN110330018B CN110330018B CN201910444287.XA CN201910444287A CN110330018B CN 110330018 B CN110330018 B CN 110330018B CN 201910444287 A CN201910444287 A CN 201910444287A CN 110330018 B CN110330018 B CN 110330018B
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/50—Carbon dioxide
- C01B32/55—Solidifying
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/0204—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the feed stream
- F25J3/0219—Refinery gas, cracking gas, coke oven gas, gaseous mixtures containing aliphatic unsaturated CnHm or gaseous mixtures of undefined nature
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
- F25J3/0238—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of CnHm with 2 carbon atoms or more
Abstract
The invention discloses a device for preparing dry ice and separating ethylene by using LNG cold energy and a working method, wherein the device comprises: an ethylene refining system and a dry ice manufacturing system. LNG cold energy is shunted through a three-way valve, one path of LNG cold energy sequentially enters a second heat exchanger and a first heat exchanger of the ethylene refining system to provide deep cold energy for the ethylene refining system, the other path of LNG cold energy is converged with LNG cold energy coming out of the first heat exchanger and then enters a dry ice manufacturing machine, and the vaporized and heated LNG is introduced into a gas turbine to be supplied to the gas turbine for power generation, so that the stepped utilization of the LNG cold energy is realized. The cracked gas enters an ethylene refining system, a carbon component, a hydrogen-rich gas, a carbon dioxide component and heavier components are separated by using the cold energy of LNG and according to the difference of the weight of the components, and finally ethylene is prepared by using an acetylene hydrogenation device. The invention realizes the functions of low-cost ethylene refining and dry ice manufacturing.
Description
Technical Field
The invention relates to a device for preparing dry ice and separating ethylene by using LNG cold energy and a working method thereof. Belongs to the field of energy utilization.
Background
In recent years, with the rapid development of the natural gas industry, the efficient utilization of natural gas has become a research hotspot. The use of natural gas in various fields has become a trend in the future due to the irreparable damage to the atmosphere caused by the combustion of coal and petroleum. The system is based on the background that a large amount of energy is consumed by a chemical plant, basic chemical raw material ethylene is manufactured for the chemical plant by using cold energy released by LNG, and meanwhile, carbon dioxide which is a byproduct of the chemical plant is used as a raw material to manufacture dry ice, so that benefits are obtained, zero carbon emission is realized, and the environment is protected. The energy conservation and emission reduction are realized to a great extent, and the method has great practical significance for environmental protection.
LNG is cryogenic liquid at-160.0 ℃ under normal pressure, needs to be gasified and heated to above 0 ℃ before being supplied to downstream users, and is usually realized by seawater or fuel, and a large amount of cold energy is released during the vaporization of LNG, thereby causing great waste of energy. According to the current LNG production process, the power consumption is about 850kW · h/t (per ton of LNG), while about 230kW · h of cold energy is released at the receiving terminal where 1.0t of LNG is vaporized. LNG is used as a cold source, and process streams in cracking gas separation are used as cold traps, so that research on providing cold load required by an ethylene cryogenic separation process by partially replacing a three-machine compression refrigeration system with LNG cold energy can be performed, and LNG gasification cost and energy consumption of ethylene cryogenic separation can be reduced.
In the prior art, chinese patent No. CN 103542693A proposes an ethylene cryogenic separation method for large-scale ethylene plants, which includes three coolers and two expansion-recompression machines to recover cold energy to supply cold for the system, and the coolers and the expansion-recompression machines consume a large amount of electric energy, which increases the energy consumption of the system. The invention utilizes LNG vaporization for cooling, does not need to set a cooler and an expansion-recompression machine, only needs to set a heat exchanger, and utilizes the cold energy generated by LNG vaporization for direct cooling, and research results show that the utilization rate of LNG cold energy in the ethylene separation process reaches 76.5 percent, 30 ten thousand tons of ethylene produced can replace the cold energy load of about 22000kW in the original process, the power consumption of a refrigerant compression refrigeration system of about 20000kW is saved, the energy consumption cost of an ethylene cryogenic separation device is greatly reduced, and the LNG vaporization cold energy is huge, and the optimal and effective utilization of resources can not be achieved when the LNG vaporization cold energy is singly used for preparing ethylene, so the invention is connected with a system made of dry ice in parallel, thereby not only fully utilizing the LNG cold energy, but also realizing zero carbon emission of a chemical plant.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and further provides a device for preparing dry ice and separating ethylene by using LNG cold energy and a working method.
The dry ice manufacturing system and the ethylene refining system are coupled, so that the low-cost refining of the basic raw material ethylene of the chemical plant is realized, and meanwhile, the byproduct carbon dioxide of the chemical plant is captured and prepared into dry ice by utilizing LNG cold energy, so that LNG cold energy is not wasted, benefits are provided for the chemical plant, the environment is protected, and the economic efficiency and the environmental protection performance of the whole operation of the system are improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
the device for preparing dry ice and separating ethylene by using LNG cold energy comprises a dry ice manufacturing system and an ethylene refining system, wherein the dry ice manufacturing system comprises: the LNG pump is connected with a right port of the three-way valve through a pipeline, a left port of the three-way valve is connected with a right lower port of the dry ice making machine through a pipeline, an outlet of the high-pressure carbon dioxide gas storage tank is connected with an inlet of the dry ice making machine through a pipeline, an outlet of the dry ice making machine is connected with the dry ice thermal insulation box through a pipeline, a right upper port of the dry ice making machine is connected with the gas turbine through a pipeline, and the gas turbine is connected with the generator through a shaft; the ethylene refining system comprises: first heat exchanger of pyrolysis gas jar, first precutting tower, second heat exchanger, vapour and liquid separator, acetylene hydrogenation unit, demethanizer, ethylene jar, deethanizer, carbon three and heavier components discharge port, the pyrolysis gas jar passes through the pipe connection the interface under the first heat exchanger left side, the interface passes through the pipe connection under the first heat exchanger right side the interface under the first heat exchanger left side, the interface passes through the pipe connection on the first heat exchanger the interface under the first precutting tower, the interface passes through the pipe connection under the second heat exchanger left side interface, the interface passes through the pipe connection on the vapour and liquid separator the interface on the acetylene hydrogenation unit, the interface passes through the pipe connection on the acetylene hydrogenation unit right side the ethylene jar, the interface passes through the pipe connection under the vapour and liquid separator the interface on the demethanizer left side interface, the interface passes through the pipe connection under the demethanizer the tower left side interface, the three-way valve lower interface passes through the pipe connection on the second heat exchanger the interface on the second heat exchanger right side the interface on the first heat exchanger, the interface passes through the pipe connection under the first deethanizer and the dry ice ethane discharge port under the first heat exchanger the deethanizer connects the pipeline connection under the third ethane splitter.
Further, the demethanization process of the demethanizer adopts a high-pressure method or a low-pressure method.
Further, a regulating valve is arranged between the high-pressure carbon dioxide gas storage tank and the dry ice manufacturing machine.
Further, a catalyst is arranged in the acetylene hydrogenation device, and the catalyst is palladium or palladium-silver.
Further, a second pre-cutting tower is arranged between the first pre-cutting tower and the deethanizer, and the second pre-cutting tower is connected with the carbon three and heavier component discharge port through a pipeline.
Further, the first heat exchanger and the second heat exchanger are both tube heat exchangers or plate-fin heat exchangers.
The working method of the device for preparing the dry ice and separating the ethylene by utilizing the LNG cold energy comprises the following steps:
(a) LNG is divided into two paths through the LNG pump and the three-way valve, one path of LNG sequentially enters the second heat exchanger and the first heat exchanger to be vaporized and release cold energy, the other path of LNG is converged with LNG coming out of the first heat exchanger and then enters the dry ice maker, the regulating valve controls the air inflow of carbon dioxide entering the dry ice maker according to the cold energy of the LNG, gas-phase carbon dioxide absorbs the cold energy of the LNG in the dry ice maker to prepare dry ice, finished dry ice enters the dry ice thermal insulation box through a dry ice outlet of the dry ice maker to be stored, and the vaporized and heated LNG is introduced into the gas turbine to be used for the generator to generate electricity;
(b) The cracking gas is precooled by the first heat exchanger and then enters the first precutting tower for separation, the carbon one, lighter components and a small amount of carbon two components flow out from the top of the first precutting tower in a gaseous form and enter the second heat exchanger for deep cold separation, the carbon one and carbon two components with the boiling points lower than-162 ℃ are liquefied, the hydrogen with the boiling points of-252 ℃ and a small amount of inert gas are still in a gaseous state, then the gas-liquid mixture enters the gas-liquid separator for gas-liquid separation, hydrogen-rich gas is introduced into the acetylene hydrogenation device to provide necessary hydrogen for the acetylene hydrogenation device to prepare ethylene, the liquefied carbon one and carbon two components enter the demethanizer from the lower outlet of the gas-liquid separator, and the carbon one component flows out from the top of the demethanizer, the carbon dioxide and heavier components enter the deethanizer from the tower bottom, a large amount of carbon dioxide and heavier components separated by the first pre-cutting tower enter the second pre-cutting tower from the tower bottom of the first pre-cutting tower, the carbon dioxide and lighter components and a small amount of carbon three components separated by the second pre-cutting tower enter the deethanizer from the tower top of the second pre-cutting tower, the carbon dioxide components separated by the deethanizer enter the acetylene hydrogenation device from the tower top, the carbon dioxide components and hydrogen-rich gas generate ethylene under the action of a catalyst and are stored in the ethylene tank, and the carbon three and heavier components flow out from the tower bottoms of the deethanizer and the second pre-cutting tower and are finally discharged from the carbon three and heavier component discharge ports.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. the system considers the utilization of LNG resources of the chemical plant, an expansion-recompressor is not required to be arranged, the power consumption of a refrigerant compression refrigeration system of 20000kW is saved for every 30 ten thousand tons of ethylene produced, and the cost of the chemical plant is reduced.
2. The invention recovers a large amount of cold energy generated by LNG vaporization, which is about 830-860kJ/kg, and is used for separating chemical basic raw material ethylene, so that no additional ethylene needs to be purchased in a chemical plant, cold energy is prevented from being directly taken away by seawater, and energy waste is reduced.
3. In the prior invention all of the carbon-dioxide fraction was fed to the deethanizer, resulting in a column load of 140% of the design value and an average ethylene production of only 681t/d. Therefore, the second pre-cutting tower is arranged between the first pre-cutting tower and the deethanizer, so that the condition that the load of the deethanizer is increased due to the heavier components of the cracked gas is avoided, the production efficiency of ethylene is improved, and the production efficiency can reach about 720t/d.
4. The basic composition equipment for preparing the ethylene in the prior invention is 19, while the invention can achieve the corresponding purpose by only 13 equipment, improve the yield and reduce the complexity of the system.
5. The utilization rate of LNG cold energy in ethylene cryogenic separation is about 75%, so this patent connects in parallel a dry ice manufacturing system, and the utilization rate not only can reach more than 80%, has still realized the zero carbon emission of chemical plant.
Drawings
FIG. 1 is a schematic structural diagram of an apparatus for preparing dry ice and separating ethylene by using LNG cold energy according to the present invention;
in the figure: the device comprises a cracking gas tank 1, a first heat exchanger 2, a first pre-cutting tower 3, a second heat exchanger 4, a gas-liquid separator 5, an acetylene hydrogenation device 6, a demethanizer 7, an ethylene tank 8, a deethanizer 9, a second pre-cutting tower 10, a carbon three and heavier component discharge port 11, an LNG pump 12, a three-way valve 13, a dry ice maker 14, a gas turbine 15, a generator 16, a high-pressure carbon dioxide gas storage tank 17, an adjusting valve 18 and a dry ice incubator 19.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, specific embodiments accompanied with figures are described in detail below.
As shown in fig. 1, an apparatus for preparing dry ice and separating ethylene by using LNG cold energy according to an embodiment of the present invention includes a dry ice manufacturing system and an ethylene refining system, wherein the dry ice manufacturing system includes: the LNG pump 12 is connected with a right port of the three-way valve 13 through a pipeline, a left port of the three-way valve 13 is connected with a right lower port of the dry ice making machine 14 through a pipeline, an outlet of the high-pressure carbon dioxide gas storage tank 17 is connected with a left port of the adjusting valve 18 through a pipeline, a right port of the adjusting valve 18 is connected with an inlet of the dry ice making machine 14 through a pipeline, an outlet of the dry ice making machine 14 is connected with the dry ice insulation box 19 through a pipeline, a right upper port of the dry ice making machine 14 is connected with the gas turbine 15 through a pipeline, and the gas turbine 15 is connected with the generator 16 through a shaft; the ethylene refining system comprises: a cracking gas tank 1, a first heat exchanger 2, a first pre-cutting tower 3, a second heat exchanger 4, a gas-liquid separator 5, an acetylene hydrogenation device 6, a demethanizer 7, an ethylene tank 8, a deethanizer 9, a second pre-cutting tower 10, a carbon three and heavier component discharge port 11, the cracking gas tank 1 is connected with a left lower port of the first heat exchanger 2 through a pipeline, a right lower port of the first heat exchanger 2 is connected with a left port of the first pre-cutting tower 3 through a pipeline, the upper connector of the first precutting tower 3 is connected with the lower left connector of the second heat exchanger 4 through a pipeline, the right lower port of the second heat exchanger 4 is connected with the left port of the gas-liquid separator 5 through a pipeline, the upper port of the gas-liquid separator 5 is connected with the upper port of the acetylene hydrogenation device 6 through a pipeline, the right interface of the acetylene hydrogenation device 6 is connected with the ethylene tank 8 through a pipeline, the lower interface of the gas-liquid separator 5 is connected with the left interface of the demethanizer 7 through a pipeline, the lower port of the demethanizer 7 is connected with the left port of the deethanizer 9 through a pipeline, the lower port of the three-way valve 13 is connected with the upper right port of the second heat exchanger 4 through a pipeline, the upper left interface of the second heat exchanger 4 is connected with the upper right interface of the first heat exchanger 2 through a pipeline, the upper left interface of the first heat exchanger 2 is connected with the lower right interface of the dry ice maker 14 through a pipeline, the lower port of the first pre-cutting tower 3 is connected with the left port of the second pre-cutting tower 10 through a pipeline, the top opening of the second precutting tower is connected with the left connector of the deethanizer 9 through a pipeline, the tower bottoms of the deethanizer 9 and the second precutting tower 10 are connected with the carbon three and heavier component discharge port 11 through pipelines, and the upper connector of the ethane tower 9 is connected with the lower connector of the acetylene hydrogenation device 6 through a pipeline.
Wherein, the demethanizing process of the demethanizer 7 adopts a low-pressure method, the ethylene recovery rate of the low-pressure method is higher, and the application range is wider; a catalyst is arranged in the acetylene hydrogenation device 6, and the catalyst is palladium-silver; the first heat exchanger 2 and the second heat exchanger 4 are both plate-fin heat exchangers, and the plate-fin heat exchangers are good in heat exchange effect and small in occupied area.
The invention relates to a working method of a device for preparing dry ice and separating ethylene by using LNG cold energy, which specifically comprises the following steps:
(a) The LNG is divided into two paths through the LNG pump 12 and the three-way valve 13, one path of the LNG sequentially enters the second heat exchanger 4 and the first heat exchanger 2 to be vaporized and release cold energy, the other path of the LNG from the first heat exchanger 2 is converged and then enters the dry ice maker 14, the adjusting valve 18 controls the carbon dioxide air inflow entering the dry ice maker 14 according to the cold energy of the LNG, the gas-phase carbon dioxide absorbs the cold energy of the LNG in the dry ice maker 14 to make dry ice, the finished product dry ice enters the dry ice incubator 19 through a dry ice outlet of the dry ice maker 14 to be stored, and the vaporized and heated LNG is introduced into the gas turbine 15 to be supplied to the generator 16 to generate electricity;
(b) The cracking gas is pre-cooled by the first heat exchanger 2 and then enters the first pre-cutting tower 3 for separation, carbon one, lighter components and a small amount of carbon two components flow out from the top of the first pre-cutting tower 3 in a gaseous form and enter the second heat exchanger 4 for deep cold separation, the carbon one and carbon two components with the boiling point lower than-162 ℃ are liquefied, the hydrogen with the boiling point of-252 ℃ and a small amount of inert gas are still in a gaseous state, then the gas-liquid mixture enters the gas-liquid separator 5 for gas-liquid separation, hydrogen-rich gas is introduced into the acetylene hydrogenation device 6 to provide necessary hydrogen for the acetylene hydrogenation device 6 to prepare ethylene, the liquefied carbon one and carbon two components enter the demethanizer 7 from the lower outlet of the gas-liquid separator 5, and the carbon one component flows out from the top of the demethanizer 7, the carbon dioxide and heavier components enter the deethanizer 9 from the bottom of the tower, a large amount of the carbon dioxide and heavier components separated by the first pre-cutting tower 3 enter the second pre-cutting tower 10 from the bottom of the first pre-cutting tower 3, the carbon dioxide and lighter components and a small amount of the carbon three components separated by the second pre-cutting tower 10 enter the deethanizer 9 from the top of the second pre-cutting tower 10, the carbon dioxide components separated by the deethanizer 9 enter the acetylene hydrogenation device 6 from the top of the tower, the carbon two components and the hydrogen-rich gas generate ethylene under the action of a catalyst, the ethylene is stored in the ethylene tank 8, and the carbon three and heavier components flow out from the bottoms of the deethanizer 9 and the second pre-cutting tower 10 and are finally discharged from the carbon three and heavier component discharge port 11.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the invention, but rather as the invention extends to all modifications, equivalents and alternatives falling within the spirit and scope of the present invention.
Claims (7)
1. The device for preparing dry ice and separating ethylene by using LNG cold energy is characterized by comprising a dry ice manufacturing system and an ethylene refining system, wherein the dry ice manufacturing system comprises: the LNG pump (12), the three-way valve (13), the dry ice maker (14), the gas turbine (15), the generator (16), the high-pressure carbon dioxide gas storage tank (17) and the dry ice incubator (19), wherein the LNG pump (12) is connected with the right interface of the three-way valve (13) through a pipeline, the left interface of the three-way valve (13) is connected with the right lower interface of the dry ice maker (14) through a pipeline, the outlet of the high-pressure carbon dioxide gas storage tank (17) is connected with the inlet of the dry ice maker (14) through a pipeline, the outlet of the dry ice maker (14) is connected with the dry ice incubator (19) through a pipeline, the right upper interface of the dry ice maker (14) is connected with the gas turbine (15) through a pipeline, and the gas turbine (15) is connected with the generator (16) through a shaft; the ethylene refining system comprises: cracking gas tank (1), first heat exchanger (2), first precutting tower (3), second heat exchanger (4), vapour and liquid separator (5), acetylene hydrogenation device (6), demethanizer (7), ethylene jar (8), deethanizer (9), carbon three and heavier components discharge port (11), cracking gas tank (1) passes through the pipe connection first heat exchanger (2) left side lower clutch, first heat exchanger (2) right side lower clutch passes through the pipe connection first precutting tower (3) left side interface, first precutting tower (3) upper clutch passes through the pipe connection second heat exchanger (4) left side lower clutch, second heat exchanger (4) right side lower clutch passes through the pipe connection gas-liquid separator (5) left side interface, gas-liquid separator (5) upper clutch passes through the pipe connection acetylene hydrogenation device (6) upper clutch, acetylene hydrogenation device (6) right clutch passes through the pipe connection ethylene jar (8), vapour and liquid separator (5) right clutch passes through the pipe connection demethanizer (7) left side interface, demethanizer (7) right clutch connects second heat exchanger (4) upper clutch and right clutch 13) upper clutch, the upper left interface of the first heat exchanger (2) is connected with the lower right interface of the dry ice maker (14) through a pipeline, the lower interface of the first pre-cutting tower (3) is connected with the left interface of the deethanizer (9), the lower interface of the deethanizer (9) is connected with the discharge port (11) through a pipeline, and the upper interface of the deethanizer (9) is connected with the lower interface of the acetylene hydrogenation device (6) through a pipeline.
2. The device for preparing dry ice and separating ethylene by using LNG cold energy as claimed in claim 1, wherein: the demethanizing process of the demethanizer (7) adopts a high-pressure method or a low-pressure method.
3. The device for preparing dry ice and separating ethylene by using LNG cold energy as claimed in claim 1, wherein: an adjusting valve (18) is arranged between the high-pressure carbon dioxide gas storage tank (17) and the dry ice making machine (14).
4. The device for preparing dry ice and separating ethylene by using LNG cold energy as claimed in claim 1, wherein: the acetylene hydrogenation device (6) is internally provided with a catalyst which is palladium or palladium-silver.
5. The device for preparing dry ice and separating ethylene by using LNG cold energy as claimed in claim 1, wherein the device comprises: a second pre-cutting tower (10) communicated with the first pre-cutting tower (3) and the deethanizer (9) is further arranged between the first pre-cutting tower and the deethanizer, and the second pre-cutting tower (10) is connected with the carbon three and heavier component discharge port (11) through a pipeline.
6. The device for preparing dry ice and separating ethylene by using LNG cold energy as claimed in claim 1, wherein: the first heat exchanger (2) and the second heat exchanger (4) are both tube type heat exchangers or plate-fin type heat exchangers.
7. An operating method of the device for preparing dry ice and separating ethylene by using LNG cold energy based on any one of claims 1-6, characterized in that: the method specifically comprises the following steps:
(a) LNG is divided into two paths through the LNG pump (12) and the three-way valve (13), one path of LNG sequentially enters the second heat exchanger (4) and the first heat exchanger (2) to be vaporized and release cold energy, the other path of LNG is converged with LNG coming out of the first heat exchanger (2) and then enters the dry ice maker (14), the adjusting valve (18) controls the air inflow of carbon dioxide entering the dry ice maker (14) according to the cold energy of the LNG, gas-phase carbon dioxide absorbs the cold energy of the LNG in the dry ice maker (14) to make dry ice, finished dry ice enters the dry ice (19) through a dry ice insulation box of the dry ice maker (14) to be stored, and the vaporized and heated LNG is introduced into the gas turbine (15) to be supplied to the generator (16) to generate electricity;
(b) Cracking gas is pre-cooled by the first heat exchanger (2), then enters the first pre-cutting tower (3) for separation, carbon one and lighter components and a small amount of carbon dioxide components flow out from the top of the first pre-cutting tower (3) in a gaseous form, enters the second heat exchanger (4) for deep cold separation, the carbon one and the carbon dioxide components with the boiling point lower than-162 ℃ are liquefied, hydrogen with the boiling point of-252 ℃ and a small amount of inert gas are still in a gaseous state, then a gas-liquid mixture enters the gas-liquid separator (5) for gas-liquid separation, hydrogen-rich gas is introduced into the acetylene hydrogenation device (6) to provide necessary hydrogen for the acetylene hydrogenation device (6) to prepare ethylene, the liquefied carbon one and the carbon dioxide components enter the demethanizer (7) from a lower outlet of the gas-liquid separator (5), the carbon one component flows out from the top of the demethanizer (7), the carbon two and the heavier components enter the deethanizer (9) from a bottom of the demethanizer (7), a large amount of the carbon one and the heavier components separated by the first pre-cutting tower (3) enter the second pre-cutting tower from a tower top of the second pre-cutting tower (10), the light and the acetylene hydrogenation components enter the deethanizer (9) from a second tower bottom of the demethanizer (10) to generate ethylene-hydrogen-rich gas separation device (10), and the acetylene hydrogenation device (10), and storing the carbon three and heavier components in the ethylene tank (8), and discharging the carbon three and heavier components from the bottoms of the deethanizer (9) and the second pre-cutting tower (10) and finally from the carbon three and heavier component discharge port (11).
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