Liquefied natural gas (LNG) light hydrocarbon separation process

Abstract

The invention relates to an LNG (Liquefied Natural Gas) light hydrocarbon separation process. The device comprises a raw material split-flow preheating unit, a pre-separation unit, a demethanization unit and a deethanization unit. The raw material distributing and preheating unit comprises a low-temperature pump, a distributor, a heat exchanger and a heater; the pre-separation unit comprises a separator, a mixer, a compressor and a heat exchanger; the demethanizing unit comprises a demethanizing tower, a mixer, a compressor and a heat exchanger; the deethanizer comprises a deethanizer, a throttle valve, a flow divider, a compressor and According to the process, two-stage logistics segmentation and multi-stage network heat exchange technologies are adopted, high-concentration methane and ethane can be separated, the recovery rate of ethane is high, meanwhile, the flow of materials can be flexibly adjusted, the load of equipment is reduced, and in addition, compared with other processes, the process is lower in energy consumption and lower in equipment cost.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical separation, relates to LNG light hydrocarbon separation, and specifically relates to a light hydrocarbon separation process utilizing LNG cold energy. Background Art

[0002] my country's demand for natural gas is increasing, but due to its limited resources, it needs to be imported in large quantities from abroad. Therefore, the construction of LNG receiving stations is being stepped up to make up for the shortage of natural gas pipeline imports. LNG is liquefied from natural gas at room temperature and pressure under low temperature and high pressure. The volume is about 1 / 600 of the original. LNG contains more methane, a small amount of ethane, propane and other hydrocarbons, and some nitrogen.

[0003] LNG can recover methane, ethane and other hydrocarbons through the light hydrocarbon separation process. 2+ Light hydrocarbons are high value-added products with multiple uses. Ethane and propane can replace gasoline to produce ethylene, which can reduce the investment of ethylene plants by 30%, reduce energy consumption by 30%-40%, and reduce the overall cost by 10%. Therefore, it is of great significance to use LNG as a separation process for low-carbon hydrocarbons and recover methane and ethane. It can effectively meet the domestic demand for ethylene, reduce the country's heavy dependence on oil, and improve the economic benefits of LNG use.

[0004] For the separation of LNG light hydrocarbons, there are problems such as insufficient utilization of LNG cold energy, excessive equipment load, and excessively high comprehensive energy consumption of the process. Therefore, a new process for separation of LNG light hydrocarbons is proposed. This process makes full use of the cold energy of LNG, greatly reduces the comprehensive energy consumption, and the equipment operates at low pressure without causing excessive load. Summary of the invention

[0005] Regarding the separation of LNG light hydrocarbons, there are problems such as insufficient utilization of LNG cold energy, excessive equipment load, and excessively high comprehensive energy consumption of the process. Therefore, a new process for separation of LNG light hydrocarbons is proposed. This process adopts two-stage logistics segmentation and multi-stage network heat exchange technology, which can separate high-concentration methane and ethane, and the ethane recovery rate is also high. At the same time, it can flexibly adjust the flow rate of materials and reduce equipment load. In addition, this process has lower energy consumption than other processes.

[0006] In order to achieve the above object, the present invention provides a novel LNG light hydrocarbon separation process, including a feedstock splitting preheating unit, a pre-separation unit, a demethanization unit and a deethanization unit;

[0007] The raw material splitting and preheating unit includes a cryogenic pump P-1, a splitter TE-1, a splitter TE-2, a heat exchanger HX-1, a heat exchanger HX-2, a heat exchanger HX-3, and a heater E-1; the pre-separation unit includes a separator S-1, a mixer M-1, a compressor K-1, a heat exchanger HX-1, and a heat exchanger HX-2; the demethanization unit includes a demethanization tower T-1, a mixer M-1, a compressor K-1, a heat exchanger HX-1, and a heat exchanger HX-2; the deethanization unit includes a deethanization tower T-2, a throttle valve V-1, a splitter TE-3, a compressor K-2, and a heat exchanger HX-3;

[0008] The raw material splitting preheating unit, the LNG inlet pipeline is connected with the cryogenic pump P-1 and the splitter TE-1; the splitter TE-1 splits into two streams, one stream is connected with the heat exchanger HX-1 and the heat exchanger HX-2 in sequence; one stream is connected with the splitter TE-2; the splitter TE-2 splits into two streams, one stream is connected with the demethanizer T-1; the other stream is connected with the heat exchanger HX-3 and the heater E-1;

[0009] In the pre-separation unit, the outlets of the heat exchanger HX-2 and the heater E-1 are connected to the inlet of the separator S-1; the top of the separator S-1, the mixer M-1, the compressor K-1, the heat exchanger HX-2, and the inlet of the heat exchanger HX-1 are connected in sequence to separate methane;

[0010] In the demethanization unit, the bottom of the separator S-1, the compressor K-2, and the outlet of the splitter TE-2 are connected to the demethanizer T-1; the top of the demethanizer T-1, the mixer M-1, the compressor K-1, the heat exchanger HX-2, and the inlet of the heat exchanger HX-1 are connected in sequence to separate methane;

[0011] In the deethanization unit, the bottom of the deethanizer T-1, the throttle valve V-1, and the inlet of the deethanizer T-2 are connected in sequence; the top of the deethanizer T-2, the splitter TE-3, the compressor K-2, and the deethanizer T-1 are connected in sequence to separate ethane; the bottom of the deethanizer T-2 and the heat exchanger HX-3 are connected in sequence to separate C 3+ ;

[0012] The above-mentioned LNG light hydrocarbon separation process has a low stream operating pressure, does not impose a large load on the equipment, and has a wider application prospect;

[0013] In the above-mentioned LNG light hydrocarbon separation process, the heat exchangers include heat exchanger HX-1, heat exchanger HX-2, and heat exchanger HX-3, which are mainly used to realize heat exchange and transfer in the production of the device and are conventional equipment in the field. In the present invention, the heat exchanger HX-1 is provided with a first heat exchange channel and a second heat exchange channel;

[0014] A stream of material diverted by diverter TE-1 is connected to the head end of the first heat exchange channel, and the end of the first heat exchange channel is connected to the heat exchanger HX-2 through a pipeline; the head end of the second heat exchange channel produces methane through a pipeline, and the end of the second heat exchange channel is connected to the heat exchanger HX-2 through a pipeline.

[0015] In the present invention, the heat exchanger HX-2 is provided with a third heat exchange channel and a fourth heat exchange channel;

[0016] The head end of the third heat exchange channel is connected to the end of the first heat exchange channel of the heat exchanger HX-1 through a pipeline, and the end of the third heat exchange channel is connected to the separator S-1 through a pipeline; the head end of the fourth heat exchange channel is connected to the end of the second heat exchange channel of the heat exchanger HX-1 through a pipeline, and the end of the fourth heat exchange channel is connected to the compressor K-1 through a pipeline.

[0017] In the present invention, the heat exchanger HX-3 is provided with a fifth heat exchange channel and a sixth heat exchange channel;

[0018] The first end of the fifth heat exchange channel produces C through the pipeline 3+ The end of the fifth heat exchange channel is connected to the bottom of the deethanizer T-2 through a pipeline; the head end of the sixth heat exchange channel is connected to the splitter TE-2 through a pipeline, and the end of the sixth heat exchange channel is connected to the heater E-1 through a pipeline.

[0019] The above-mentioned LNG light hydrocarbon separation process comprises a cryogenic pump P-1, a splitter TE-1, a splitter TE-2, a first heat exchange channel of a heat exchanger HX-1, a third heat exchange channel of a heat exchanger HX-2, a sixth heat exchange channel of a heat exchanger HX-3, a heater E-1, a top of a separator S-1, a top of a demethanizer T-1, a mixer M-1, a compressor K-1, a second heat exchange channel of a heat exchanger HX-1, a fourth heat exchange channel of a heat exchanger HX-2 and connecting pipes between adjacent components, which together constitute a methane separation circuit; a bottom of a demethanizer T-1, a throttle valve V-1, a top of a deethanizer T-2, a splitter TE-3, a compressor K-2 and connecting pipes between adjacent components, which together constitute an ethane separation circuit; a bottom of a deethanizer T-2, a fifth heat exchange channel of a heat exchanger HX-3 and connecting pipes between adjacent components, which together constitute a C 3+ Separation circuit.

[0020] The above LNG light hydrocarbon separation process and heat exchange network system include LNG cold energy utilization, LNG and separated methane, C 3+ Heat exchange can produce liquid methane, C 3+ At the same time, LNG is preheated to achieve the effect of light hydrocarbon separation. In addition, the top gas of the deethanizer tower exchanges heat with the cold energy of LNG, so that the energy in the system can be fully utilized.

[0021] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0022] (1) The present invention provides a process for separating light hydrocarbons from LNG. Gas phase methane is obtained through a cryogenic pump, a heat exchanger, a heater, a separator and a demethanizer, and liquid methane products are obtained by pressurization. Based on other invention technology patents, the present invention has been optimized and improved to obtain a new LNG light hydrocarbon separation process. The new process reduces equipment cost and fully utilizes cold energy, reducing waste of resources.

[0023] (2) The present invention provides a light hydrocarbon separation process suitable for LNG, which adopts an optimized network heat exchange technology to obtain high-concentration methane and ethane, high ethane recovery rate, low comprehensive energy consumption of the device, and low device load. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a process flow chart of LNG light hydrocarbon separation according to the present invention;

[0025] Explanation of the reference numerals: P-1-cryogenic pump; TE-1-diverter; TE-2-diverter; E-1-heater; HX-1-heat exchanger; HX-2-heat exchanger; HX-3-heat exchanger; S-1-gas-liquid separator; T-1-demethanizer; M-1-mixer; K-1-compressor; V-1-throttle valve; T-2-deethanizer; TE-3-diverter; K-2-compressor. DETAILED DESCRIPTION

[0026] The following will be combined with the attached Figure 1 The LNG light hydrocarbon separation process technology provided by the present invention is described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present invention.

[0027] This embodiment provides a LNG light hydrocarbon separation process, such as Figure 1 As shown, it includes a raw material separation preheating unit, a pre-separation unit, a demethanization unit and a deethanization unit connected by pipelines.

[0028] The raw material splitting and preheating unit includes a cryogenic pump P-1, a splitter TE-1, a splitter TE-2, a heat exchanger HX-1, a heat exchanger HX-2, a heat exchanger HX-3, and a heater E-1. The heat exchanger HX-1 is provided with a first heat exchange channel and a second heat exchange channel. The heat exchanger HX-2 is provided with a third heat exchange channel and a fourth heat exchange channel. The heat exchanger HX-3 is provided with a fifth heat exchange channel and a sixth heat exchange channel.

[0029] The pre-separation unit includes a separator S-1, a mixer M-1, a compressor K-1, a heat exchanger HX-1, and a heat exchanger HX-2.

[0030] The demethanization unit includes a demethanizer T-1, a mixer M-1, a compressor K-1, a heat exchanger HX-1, and a heat exchanger HX-2.

[0031] The deethanizer unit includes a deethanizer T-2, a throttle valve V-1, a splitter TE-3, a compressor K-2, and a heat exchanger HX-3.

[0032] The LNG inlet pipeline is connected to the cryogenic pump P-1 and the diverter TE-1; the diverter TE-1 diverts into two streams, one of which is connected to the head end of the first heat exchange channel, and the end of the first heat exchange channel is connected to the heat exchanger HX-2; the head end of the third heat exchange channel is connected to the heat exchanger HX-1, and the end of the third heat exchange channel is connected to the separator S-1; one stream is connected to the diverter TE-2; the diverter TE-2 diverts into two streams, one of which is connected to the demethanizer T-1; one stream is connected to the head end of the sixth heat exchange channel, and the end of the sixth heat exchange channel is connected to the heater E-1.

[0033] The end of the third heat exchange channel and the outlet of the heater E-1 are connected to the inlet of the separator S-1; the top of the separator S-1, the mixer M-1, and the compressor K-1 are connected to the end of the fourth heat exchange channel, and the head end of the fourth heat exchange channel is connected to the heat exchanger HX-1; the end of the second heat exchange channel is connected to the heat exchanger HX-2, and methane is separated at the head end of the second heat exchange channel.

[0034] The bottom of the separator S-1, the compressor K-2, and the outlet of the splitter TE-2 are connected to the demethanizer T-1; the top of the demethanizer T-1, the mixer M-1, and the compressor K-1 are connected to the end of the fourth heat exchange channel, and the head end of the fourth heat exchange channel is connected to the heat exchanger HX-1; the end of the second heat exchange channel is connected to the heat exchanger HX-2, and methane is separated at the head end of the second heat exchange channel.

[0035] The bottom of the demethanizer T-1, the throttle valve V-1, and the inlet of the deethanizer T-2 are connected in sequence; the top of the deethanizer T-2, the splitter TE-3, the compressor K-2, and the demethanizer T-1 are connected in sequence to separate ethane; the bottom of the deethanizer T-2 is connected to the end of the fifth heat exchange channel, and the first end of the fifth heat exchange channel separates C 3+ .

[0036] The above-mentioned LNG light hydrocarbon separation process comprises a cryogenic pump P-1, a splitter TE-1, a splitter TE-2, a first heat exchange channel of a heat exchanger HX-1, a third heat exchange channel of a heat exchanger HX-2, a sixth heat exchange channel of a heat exchanger HX-3, a heater E-1, a top of a separator S-1, a top of a demethanizer T-1, a mixer M-1, a compressor K-1, a second heat exchange channel of a heat exchanger HX-1, a fourth heat exchange channel of a heat exchanger HX-2 and connecting pipes between adjacent components, which together constitute a methane separation circuit; a bottom of a demethanizer T-1, a throttle valve V-1, a top of a deethanizer T-2, a splitter TE-3, a compressor K-2 and connecting pipes between adjacent components, which together constitute an ethane separation circuit; a bottom of a deethanizer T-2, a fifth heat exchange channel of a heat exchanger HX-3 and connecting pipes between adjacent components, which together constitute a C 3+ Separation circuit.

[0037] The above LNG light hydrocarbon separation process and heat exchange network system include LNG cold energy utilization, LNG and separated methane, C 3+ Heat exchange can produce liquid methane, C 3+ At the same time, LNG is preheated to achieve the effect of light hydrocarbon separation. In addition, the top gas of the deethanizer tower exchanges heat with the cold energy of LNG, so that the energy in the system can be fully utilized.

[0038] The LNG light hydrocarbon separation process provided by the present invention has a low stream operating pressure, imposes little load on equipment, and has a broader application prospect.

[0039] The above is to help readers understand the principles of the present invention, and the protection scope of the present invention is not limited to such specific statements and embodiments. For ordinary technicians in this technical field, several combinations and improvements can be made without departing from the principles of the present invention, and these combinations and improvements are also within the protection scope of the present invention.

Claims

1. A LNG light hydrocarbon separation process, characterized in that: It includes a feedstock splitting and preheating unit, a pre-separation unit, a demethanization unit and a deethanization unit; The raw material splitting and preheating unit includes a cryogenic pump P-1, a splitter TE-1, a splitter TE-2, a heat exchanger HX-1, a heat exchanger HX-2, a heat exchanger HX-3, and a heater E-1; the pre-separation unit includes a separator S-1, a mixer M-1, a compressor K-1, a heat exchanger HX-1, and a heat exchanger HX-2; the demethanization unit includes a demethanization tower T-1, a mixer M-1, a compressor K-1, a heat exchanger HX-1, and a heat exchanger HX-2; the deethanization unit includes a deethanization tower T-2, a throttle valve V-1, a splitter TE-3, a compressor K-2, and a heat exchanger HX-3; The raw material splitting preheating unit, the LNG inlet pipeline is connected with the cryogenic pump P-1 and the splitter TE-1; the splitter TE-1 splits into two streams, one stream is connected with the heat exchanger HX-1 and the heat exchanger HX-2 in sequence; one stream is connected with the splitter TE-2; the splitter TE-2 splits into two streams, one stream is connected with the demethanizer T-1; the other stream is connected with the heat exchanger HX-3 and the heater E-1; In the pre-separation unit, the outlets of the heat exchanger HX-2 and the heater E-1 are connected to the inlet of the separator S-1; the top of the separator S-1, the mixer M-1, the compressor K-1, the heat exchanger HX-2, and the inlet of the heat exchanger HX-1 are connected in sequence to separate methane; In the demethanization unit, the bottom of the separator S-1, the compressor K-2, and the outlet of the splitter TE-2 are connected to the demethanizer T-1; the top of the demethanizer T-1, the mixer M-1, the compressor K-1, the heat exchanger HX-2, and the inlet of the heat exchanger HX-1 are connected in sequence to separate methane; In the deethanization unit, the bottom of the deethanizer T-1, the throttle valve V-1, and the inlet of the deethanizer T-2 are connected in sequence; the top of the deethanizer T-2, the splitter TE-3, the compressor K-2, and the deethanizer T-1 are connected in sequence to separate ethane; the bottom of the deethanizer T-2 and the heat exchanger HX-3 are connected in sequence to separate C 3+ .

2. The LNG light hydrocarbon separation process according to claim 1, characterized in that: The heat exchanger HX-1 is provided with a first heat exchange channel and a second heat exchange channel; A stream of material diverted by diverter TE-1 is connected to the head end of the first heat exchange channel, and the end of the first heat exchange channel is connected to the heat exchanger HX-2 through a pipeline; the head end of the second heat exchange channel produces methane through a pipeline, and the end of the second heat exchange channel is connected to the heat exchanger HX-2 through a pipeline.

3. The LNG light hydrocarbon separation process according to claim 2, characterized in that: The heat exchanger HX-2 is provided with a third heat exchange channel and a fourth heat exchange channel; The head end of the third heat exchange channel is connected to the end of the first heat exchange channel of the heat exchanger HX-1 through a pipeline, and the end of the third heat exchange channel is connected to the separator S-1 through a pipeline; the head end of the fourth heat exchange channel is connected to the end of the second heat exchange channel of the heat exchanger HX-1 through a pipeline, and the end of the fourth heat exchange channel is connected to the compressor K-1 through a pipeline.

4. The LNG light hydrocarbon separation process according to claim 1, characterized in that: The heat exchanger HX-3 is provided with a fifth heat exchange channel and a sixth heat exchange channel; The first end of the fifth heat exchange channel produces C through the pipeline 3+ The end of the fifth heat exchange channel is connected to the bottom of the deethanizer T-2 through a pipeline; the head end of the sixth heat exchange channel is connected to the splitter TE-2 through a pipeline, and the end of the sixth heat exchange channel is connected to the heater E-1 through a pipeline.

5. A LNG light hydrocarbon separation process according to any one of claims 1 to 4, characterized in that: The heat exchange network system includes the utilization of LNG cold energy, LNG and separated methane, C 3+ Heat exchange can produce liquid methane, C 3+ At the same time, LNG is preheated to achieve the effect of light hydrocarbon separation. In addition, the top gas of the deethanizer tower exchanges heat with the cold energy of LNG, so that the energy in the system can be fully utilized.

Images