CN113776278B - Nitrogen-containing natural gas denitrification liquefying device and process - Google Patents

Nitrogen-containing natural gas denitrification liquefying device and process Download PDF

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Publication number
CN113776278B
CN113776278B CN202111038208.9A CN202111038208A CN113776278B CN 113776278 B CN113776278 B CN 113776278B CN 202111038208 A CN202111038208 A CN 202111038208A CN 113776278 B CN113776278 B CN 113776278B
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channel
inlet
gas
denitrification
nitrogen
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CN113776278A (en
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马忠
池红军
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Sichuan Shudao Equipment Technology Co ltd
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Sichuan Shudao Equipment Technology Co ltd
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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
    • F25J3/0233—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 1 carbon atom or more
    • 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
    • F25J3/0209—Natural gas or substitute natural gas
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
    • C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
    • C10L3/10—Working-up natural gas or synthetic natural gas
    • C10L3/101—Removal of contaminants
    • C10L3/105—Removal of contaminants of nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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    • 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
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    • 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
    • F25J3/0257—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 nitrogen
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    • 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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/02—Processes or apparatus using separation by rectification in a single pressure main column system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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    • 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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/40—Features relating to the provision of boil-up in the bottom of a column
    • 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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/74—Refluxing the column with at least a part of the partially condensed overhead gas
    • 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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/78—Refluxing the column with a liquid stream originating from an upstream or downstream fractionator column
    • 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
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/02—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
    • F25J2205/04—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum in the feed line, i.e. upstream of the fractionation step
    • 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
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/06—Splitting of the feed stream, e.g. for treating or cooling in different ways
    • 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
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/04—Recovery of liquid products
    • 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
    • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/60—Processes or apparatus involving steps for increasing the pressure of gaseous process streams the fluid being hydrocarbons or a mixture of hydrocarbons
    • 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
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/90—Processes or apparatus involving steps for recycling of process streams the recycled stream being boil-off gas from storage
    • 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
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/18—External refrigeration with incorporated cascade loop
    • 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
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/66—Closed external refrigeration cycle with multi component refrigerant [MCR], e.g. mixture of hydrocarbons
    • 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
    • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
    • F25J2290/34—Details about subcooling of liquids

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  • Oil, Petroleum & Natural Gas (AREA)
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  • General Chemical & Material Sciences (AREA)
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Abstract

The invention discloses a nitrogen-containing natural gas denitrification liquefying device and process, and solves the technical problem that BOG is continuously increased due to the fact that non-condensable gases such as nitrogen and the like of a natural gas liquefying device are accumulated in a circulating mode in the prior art. The device comprises a main heat exchanger (2), a heavy hydrocarbon separator (3), a denitrification tower (4), a denitrification tower condenser (5), a denitrification tower reflux tank (6), an LNG storage tank (7), a BOG heater (8), a BOG compressor (9) and an MR separator (10). The invention comprises the steps of liquefying and denitrifying raw material natural gas, and reliquefying and denitrifying BOG; the cold quantity at the top of the denitrification tower is derived from the light refrigerant with higher nitrogen content separated at low temperature, so that the yield of methane of the device is ensured; the heat source at the bottom of the tower comes from high-temperature raw material gas, so that the nitrogen content in the liquefied natural gas is ensured to be lower than 1%. The method has the advantages of simple flow, low production cost, high methane extraction rate, high denitrification efficiency, strong operability, safety, reliability, low energy consumption, good environmental protection benefit, economic benefit and the like.

Description

Nitrogen-containing natural gas denitrification liquefying device and process
Technical Field
The invention relates to a natural gas liquefaction device, in particular to a nitrogen-containing natural gas denitrification liquefaction device and a process.
Background
In recent years, natural gas is listed as the preferred fuel in many countries, and the development and utilization of natural gas are the main stream of energy development in the world today. The natural gas is mainly composed of hydrocarbons and also contains a small amount of non-hydrocarbon non-condensable gases such as nitrogen, argon, helium and the like. When the content of non-condensable gases (such as nitrogen, argon, helium and the like) in the natural gas is high, the heat value of the natural gas is influenced, and the energy consumption in the liquefaction process is high. According to European standard (EN 1160), the nitrogen content (mole fraction) in Liquefied Natural Gas (LNG) products should be less than 5%, and experience shows that the rolling phenomenon in LNG storage and transportation can be effectively avoided as long as the nitrogen content in LNG is controlled to be less than 1% and monitoring of boil-off gas is enhanced.
In the natural gas liquefaction process, BOG generated by an LNG large tank is often compressed by a BOG compressor, one part of the BOG is used as fuel gas of a liquefaction plant, and the other part of the BOG needs to be fed into a cold box again for reliquefaction. In this process, non-condensable gases such as nitrogen are circulated and accumulated in the device, and if the removal of non-condensable gases such as nitrogen is not performed, the production of BOG in the LNG tank is increased, and a vicious circle is formed.
Disclosure of Invention
The invention aims to provide a nitrogen-containing natural gas denitrification liquefying device and process, and aims to solve the technical problem that BOG is continuously increased due to circulation accumulation of non-condensable gases such as nitrogen in a natural gas liquefying device in the prior art.
In order to achieve the above purpose, the present invention provides the following technical solutions:
The invention provides a nitrogen-containing natural gas denitrification liquefying device, which comprises a main heat exchanger, a heavy hydrocarbon separator, a denitrification tower condenser, a denitrification tower reflux tank, an LNG storage tank, a BOG heater, a BOG compressor and an MR low-temperature separator, wherein the main heat exchanger is connected with the denitrification tower reflux tank;
The main heat exchanger is internally provided with a raw material natural gas channel I, a raw material natural gas channel II, a BOG channel, a liquefied natural gas channel I, a nitrogen-rich tail gas channel I, a high-pressure liquid-phase refrigerant channel I, a high-pressure gas-phase refrigerant channel II, a high-pressure liquid-phase refrigerant channel II and a reflux refrigerant channel I;
a nitrogen-rich tail gas channel II and a reflux refrigerant channel II are arranged in the denitrification tower condenser;
The inlet end of the raw material natural gas channel I is connected with an external purified raw material gas pipeline, the outlet end of the raw material natural gas channel I is connected with an inlet 3-A of a heavy hydrocarbon separator, an outlet 3-B of the heavy hydrocarbon separator is connected with an external heavy hydrocarbon warming and storing pipeline, a pipeline of an outlet 3-C of the heavy hydrocarbon separator is divided into a pipeline I and a pipeline II, the pipeline I is connected with an inlet 4-F of a denitrification tower, the pipeline II is connected with an inlet end of a raw material natural gas channel II, an outlet end of the raw material natural gas channel II is connected with an inlet 4-A of the denitrification tower, an outlet 4-C of the denitrification tower is connected with an inlet end of a nitrogen-rich tail gas channel II, an outlet end of the nitrogen-rich tail gas channel II is connected with an inlet 6-A of a reflux tank of the denitrification tower, the outlet 6-C of the reflux tank of the denitrification tower is connected with the inlet 4-D of the denitrification tower, the outlet 6-B of the reflux tank of the denitrification tower is connected with the inlet end of a nitrogen-rich tail gas channel I, the outlet end of the nitrogen-rich tail gas channel I is connected with an external nitrogen-rich fuel gas removal pipeline, the inlet end of the liquefied natural gas channel I is connected with the outlet 4-E of the denitrification tower, the outlet end of the liquefied natural gas channel I is connected with the inlet 7-A of an LNG storage tank, the outlet 7-B of the LNG storage tank is connected with the inlet 8-A of a BOG heater, the BOG compressor is connected with the outlet 8-B of the BOG heater and the inlet end of the BOG channel respectively, the outlet end of the BOG channel is connected with the inlet 4-B of the denitrification tower, the inlet end of the high-pressure liquid phase refrigerant channel I is connected with an external high-pressure refrigerant liquid phase pipeline, the high-pressure liquid-phase refrigerant channel I is connected with the inlet 110-A of the return refrigerant channel I, the inlet of the high-pressure gas-phase refrigerant channel I is connected with an external high-pressure refrigerant gas-phase pipeline, the outlet of the high-pressure gas-phase refrigerant channel I is connected with the inlet 10-A of the MR low-temperature separator, the outlet 10-B of the MR low-temperature separator is connected with the inlet of the high-pressure liquid-phase refrigerant channel II, the outlet of the high-pressure liquid-phase refrigerant channel II is connected with the inlet 110-B of the return refrigerant channel I, the outlet 10-C of the MR low-temperature separator is connected with the inlet of the high-pressure gas-phase refrigerant channel II, the outlet of the high-pressure gas-phase refrigerant channel II is divided into a pipeline III and a pipeline IV, the pipeline III is connected with the inlet 110-C of the return refrigerant channel I, the outlet of the return refrigerant channel II of the denitrification tower condenser is connected with the inlet 110-C of the return refrigerant channel I, and the return refrigerant channel I is connected with the return refrigerant channel I.
Alternatively or preferably, the main heat exchanger and the denitrification tower condenser can be any one of a plate-fin heat exchanger, a coiled tube heat exchanger and a shell-and-tube heat exchanger.
Optionally or preferably, the denitrification tower is a packed tower or a plate tower.
Optionally or preferably, a regulating valve B is arranged on a connecting pipeline between the outlet end of the BOG channel and the inlet 4-B of the denitrification tower; the connecting pipeline between the outlet end of the raw material natural gas channel II and the inlet 4-A of the denitrification tower is provided with a regulating valve c; a regulating valve e is arranged on a connecting pipeline between the outlet end of the high-pressure liquid-phase refrigerant channel I and the inlet 110-A of the backflow refrigerant channel I; a regulating valve f is arranged on a connecting pipeline between the outlet end of the high-pressure liquid-phase refrigerant channel II and the inlet 110-B of the reflux refrigerant channel I; and a regulating valve g is arranged on a connecting pipe between the pipeline III and the inlet 110-C of the return refrigerant channel I.
Optionally or preferably, the pipeline I is provided with a regulating valve a, the tower bottom of the denitrification tower is provided with a temperature digital controller b, and the temperature digital controller b logically controls the regulating valve a.
Optionally or preferably, a regulating valve d is arranged on a connecting pipeline between the LNG storage tank outlet 7-B and the BOG heater inlet 8-A, a pressure digital controller e is arranged on the LNG storage tank, and the pressure digital controller e logically controls the regulating valve d.
Optionally or preferably, a regulating valve h is arranged on a connecting pipeline between the outlet end of the liquefied natural gas channel I and the inlet 7-A of the LNG storage tank, a liquid level digital controller a is arranged at the tower bottom of the denitrification tower, and the liquid level digital controller a logically controls the regulating valve h.
Optionally or preferably, a regulating valve i is arranged on a connecting pipe between the outlet 6-B of the reflux tank of the denitrification tower and the inlet end of the nitrogen-rich tail gas channel I, a pressure digital controller d is arranged on the reflux tank of the denitrification tower, and the pressure digital controller d logically controls the regulating valve i.
Optionally or preferably, a regulating valve j is arranged on a connecting pipe between the pipeline IV and the inlet end of the reflux refrigerant channel II of the denitrogenation tower condenser, a temperature digital controller c is arranged on a connecting pipe between the outlet end of the nitrogen-rich tail gas channel II and the inlet 6-A of the reflux tank of the denitrogenation tower, and the temperature digital controller c logically controls the regulating valve j.
The invention provides a nitrogen-containing natural gas denitrification liquefaction process, which comprises the following steps of:
S1, a natural gas treatment process, wherein purified natural gas after purification and pressurization enters a raw material natural gas channel I of a main heat exchanger through a purified raw material gas pipeline and is precooled to minus 60 ℃, then enters a heavy hydrocarbon separator for gas-liquid separation, low-temperature liquid at the bottom is heated from a liquid phase outlet 3-B of the heavy hydrocarbon separator to heavy hydrocarbon for storage, low-temperature gas at the top leaves from a gas phase outlet 3-C of the heavy hydrocarbon separator and is divided into two parts, the main part returns to a raw material natural gas channel II of the main heat exchanger and is continuously cooled to minus 162 ℃, then is regulated to 0.2Mpa through a regulating valve C and is sent to an inlet 4-A of a denitrification tower for rectification, the other small part is regulated to 0.2Mpa through a regulating valve a and is sent to an inlet 4-F of the denitrification tower, and the tower kettle of the denitrification tower is provided with a temperature digital controller B, and the temperature of the tower kettle of the denitrification tower is regulated through a regulating valve a. The low-temperature gas at the top outlet 4-C of the denitrification tower enters a nitrogen-rich tail gas channel II of a denitrification tower condenser to be cooled to-165 ℃, then enters a denitrification tower reflux tank to carry out gas-liquid separation, the low-temperature liquid at the bottom returns to an inlet 4-D of the denitrification tower from a liquid phase outlet 6-C of the denitrification tower reflux tank, the low-temperature gas at the top enters a nitrogen-rich tail gas channel I of a main heat exchanger from a gas phase outlet 6-B of the denitrification tower reflux tank to be subjected to heat exchange and temperature rise to 35 ℃ and then is sent to a cold box, and the product liquid at the bottom outlet 4-E of the denitrification tower is sent to a liquefied natural gas channel I of the main heat exchanger to be continuously cooled to-162 ℃, and then is decompressed to 0.05MpaG through a regulating valve h and then is sent to an LNG storage tank. The LNG storage tank is provided with a pressure digital controller e, the pressure of the LNG storage tank is maintained by a gas BOG at the top of the LNG storage tank through a regulating valve d, the BOG which is discharged out of the LNG storage tank is rewarmed to normal temperature through a BOG heater, then compressed to 0.9MpaG through a BOG compressor, cooled to 40 ℃, cooled to 162 ℃ below zero in a BOG channel which enters a main heat exchanger, then regulated to 0.2MpaG through a regulating valve B, and then sent to an inlet 4-B of a denitrification tower for rectification separation.
S2, in the cooling liquid treatment process, the high-pressure liquid-phase refrigerant is sent to a high-pressure liquid-phase refrigerant channel I of the main heat exchanger through a high-pressure refrigerant liquid-phase pipeline to be cooled to minus 60 ℃, and then is throttled and cooled by a regulating valve e to return to a return refrigerant channel I, so that the upper part of the main heat exchanger is provided with cold energy. The high-pressure gas-phase refrigerant is sent to a high-pressure gas-phase refrigerant channel I of a main heat exchanger through a high-pressure refrigerant gas-phase pipeline and is cooled to minus 110 ℃, then enters an MR low-temperature separator for gas-liquid separation, low-temperature liquid at the bottom is returned to a high-pressure liquid-phase refrigerant channel II of the main heat exchanger from a liquid-phase outlet 10-B of the MR low-temperature separator and is cooled to minus 162 ℃, then is returned to a return refrigerant channel I of the main heat exchanger after being throttled and cooled by a regulating valve f, top low-temperature gas is returned to a high-pressure gas-phase refrigerant channel II of the main heat exchanger from a gas-phase outlet 10-C of the MR low-temperature separator and is cooled to minus 162 ℃, then is divided into two parts, one part is throttled and cooled by a regulating valve g and is returned to the return refrigerant channel I of the main heat exchanger, and the other part is throttled and cooled by a regulating valve j and then enters a return refrigerant channel II of a denitrification tower condenser for cooling nitrogen-enriched gas from a gas-phase outlet 4-C of the denitrification tower and is returned to the return refrigerant channel I of the main heat exchanger after being throttled and cooled by nitrogen enriched to minus 163 ℃. And the mixed refrigerant which flows back is subjected to rewarming to normal temperature in a main heat exchanger return refrigerant channel I and then is discharged out of the cold box.
Based on the technical scheme, the embodiment of the invention at least has the following technical effects:
(1) The invention provides a nitrogen-containing natural gas denitrification liquefying device, which is improved in the connection relation of the device from the aspect of uniformly distributing heat compared with the prior art. According to the invention, the temperature of the tower kettle of the denitrification tower is controlled by adopting the raw gas pumped in the main heat exchanger to enter the tower kettle of the denitrification tower, the nitrogen content in LNG is controlled, the setting of a reboiler of the denitrification tower is reduced, compared with the existing device, the flow is simpler, the heat utilization efficiency is higher, the operability is strong, the cold source at the top of the denitrification tower is from the nitrogen and methane separated from the high-pressure gas-phase refrigerant at low temperature, the refrigeration temperature is low, the methane recovery rate is high, and the whole energy consumption of the device and the BOG quantity generated by flash evaporation of the LNG storage tank are reduced by reasonably configuring the operation flow of the gas. Meanwhile, the device increases the reliquefaction denitrification process of the BOG, effectively solves the problem of circulation accumulation of nitrogen in the liquefaction treatment process of natural gas, reduces the phenomenon of rolling caused by high nitrogen content of LNG, also avoids the situation that safety accidents are possibly caused due to inconsistent densities of the upper part and the lower part of the storage tank, and has the advantages of safety, reliability, wide practicability and the like.
(2) The invention provides a nitrogen-containing natural gas denitrification liquefaction process, which sequentially carries out heavy hydrocarbon removal treatment and nitrogen removal treatment on natural gas to be treated and carries out heating compression reprocessing on generated BOG, and has the advantages of simple flow, low production cost, high methane extraction rate, strong operability, safety, reliability and the like.
Drawings
Fig. 1 is a schematic structural view of an embodiment of the present invention.
In the figure: 1. purifying a raw material gas pipeline; 2. a main heat exchanger; 3. a heavy hydrocarbon separator; 4. a denitrification tower; 5. a denitriding tower condenser; 6. a denitrification tower reflux tank; 7. an LNG storage tank; 8. a BOG heater; 9. a BOG compressor; 10. an MR cryoseparator; 11. a regulating valve b; 12. a regulating valve c; 13. a regulating valve d; 14. a regulating valve e; 15. a regulating valve f; 16. a regulating valve g; 17. a regulating valve h; 18. a regulating valve i; 19. a regulating valve j; 20. a fuel gas line; 21. a return refrigerant line; 22. a high pressure refrigerant gas phase line; 23. a high pressure refrigerant liquid line; 24. a liquid level digital controller a; 25. a temperature digital controller b; 26. a temperature digital controller c; 27. a pressure digital controller d; 28. a pressure digital controller e; 29. a regulating valve a; 101-raw material natural gas channel I, 102-raw material natural gas channel II, 103-BOG channel, 104-liquefied natural gas channel I, 105-nitrogen-rich tail gas channel I, 106-high pressure liquid phase refrigerant channel I, A7-high pressure gas phase refrigerant channel I, 108-high pressure gas phase refrigerant channel II, 109-high pressure liquid phase refrigerant channel II, 110-back flow refrigerant channel I, 501-nitrogen-rich tail gas channel II and 502-back flow refrigerant channel II; 30. a pipeline I; 31. a pipeline II; 32. a pipeline III; 33. pipeline IV.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, based on the examples herein, which are within the scope of the invention as defined by the claims, will be within the scope of the invention as defined by the claims.
Examples
As shown in fig. 1:
The invention provides a nitrogen-containing natural gas denitrification liquefying device, which comprises a main heat exchanger 2, a heavy hydrocarbon separator 3, a denitrification tower 4, a denitrification tower condenser 5, a denitrification tower reflux tank 6, an LNG storage tank 7, a BOG heater 8, a BOG compressor 9 and an MR low-temperature separator 10;
The main heat exchanger 2 is internally provided with a raw material natural gas channel I101, a raw material natural gas channel II 102, a BOG channel 103, a liquefied natural gas channel I104, a nitrogen-rich tail gas channel I105, a high-pressure liquid-phase refrigerant channel I106, a high-pressure gas-phase refrigerant channel IA 7, a high-pressure gas-phase refrigerant channel II 108, a high-pressure liquid-phase refrigerant channel II 109 and a reflux refrigerant channel I110;
a nitrogen-rich tail gas channel II 501 and a reflux refrigerant channel II 502 are arranged in the denitrification tower condenser 5;
The inlet end of the raw material natural gas channel I101 is connected with an external purified raw material gas pipeline 1, the outlet end of the raw material natural gas channel I101 is connected with an inlet 3-A of a heavy hydrocarbon separator 3, an outlet 3-B of the heavy hydrocarbon separator 3 is connected with an external heavy hydrocarbon heating and storage pipeline, the pipeline of an outlet 3-C of the heavy hydrocarbon separator 3 is divided into a pipeline I30 and a pipeline II 31, the pipeline I30 is connected with an inlet 4-F of a denitrification tower 4, the pipeline II 31 is connected with an inlet end of a raw material natural gas channel II 102, an outlet end of the raw material natural gas channel II 102 is connected with an inlet 4-A of the denitrification tower 4, an outlet 4-C of the denitrification tower 4 is connected with an inlet end of a nitrogen-rich tail gas channel II 501, an outlet end of the nitrogen-rich tail gas channel II 501 is connected with an inlet 6-A of a denitrification tower reflux tank 6, the outlet 6-C of the reflux tank 6 of the denitrification tower is connected with the inlet 4-D of the denitrification tower 4, the outlet 6-B of the reflux tank 6 of the denitrification tower is connected with the inlet end of the nitrogen-rich tail gas channel I105, the outlet end of the nitrogen-rich tail gas channel I105 is connected with the external nitrogen-rich fuel gas removal pipeline 20, the inlet end of the liquefied natural gas channel I104 is connected with the outlet 4-E of the denitrification tower 4, the outlet end of the liquefied natural gas channel I104 is connected with the inlet 7-A of the LNG storage tank 7, the outlet 7-B of the LNG storage tank 7 is connected with the inlet 8-A of the BOG heater 8, the BOG compressor 9 is connected with the outlet 8-B of the BOG heater 8 and the inlet end of the BOG channel 103 respectively, the outlet end of the BOG channel 103 is connected with the inlet 4-B of the denitrification tower 4, the inlet end of the high-pressure liquid-phase refrigerant channel I106 is connected with an external high-pressure refrigerant liquid-phase pipeline 23, the outlet end of the high-pressure liquid-phase refrigerant channel I106 is connected with the inlet 110-A of the reflux refrigerant channel I110, the inlet end of the high-pressure gas-phase refrigerant channel IA 7 is connected with the external high-pressure refrigerant gas-phase pipeline 22, the outlet end of the high-pressure gas-phase refrigerant channel IA 7 is connected with the inlet 10-A of the MR low-temperature separator 10, the outlet 10-B of the MR low-temperature separator 10 is connected with the inlet end of the high-pressure liquid-phase refrigerant channel II 109, the outlet end of the high-pressure liquid-phase refrigerant channel II 109 is connected with the inlet 110-B of the reflux refrigerant channel I110, the outlet 10-C of the MR low-temperature separator 10 is connected with the inlet end of the high-pressure gas-phase refrigerant channel II 108, the pipeline is divided into a pipeline III 32 and a pipeline IV 33, the pipeline III 32 is connected with the inlet 110-C of the reflux refrigerant channel I110, the pipeline 33 is connected with the inlet 502 of the reflux refrigerant channel I of the reflux tower 5, and the reflux tower 502 is connected with the inlet 502 of the reflux refrigerant channel I of the reflux tower 110.
According to the invention, through reasonably designing the gas and liquid flow in the nitrogen removal flow of the nitrogen-containing natural gas, the heat and cold of each product component are fully utilized, the energy consumption for treating the nitrogen-containing natural gas with the same volume is effectively saved, and the treatment cost of the nitrogen-containing natural gas is reduced; meanwhile, a nitrogen removal reprocessing line of the BOG is additionally arranged in the pipeline of the device, so that the nitrogen content of the natural gas stored in the LNG storage tank after the treatment is further reduced, the problem of rolling caused by high nitrogen content of the LNG due to the circulating accumulation of the nitrogen in the liquefaction treatment process of the natural gas is effectively solved, the situation that safety accidents are possibly caused due to inconsistent densities of the LNG storage tank is avoided, and the device has the advantages of safety, reliability, wide practicability and the like.
Alternatively or preferably, the main heat exchanger 2 and the denitrification tower condenser 5 can be any one of a plate-fin heat exchanger, a coiled tube heat exchanger or a shell-and-tube heat exchanger.
Optionally or preferably, the denitrification tower 4 is a packed tower or a plate tower.
Optionally or preferably, a regulating valve B11 is arranged on a connecting pipeline between the outlet end of the BOG channel 103 and the inlet 4-B of the denitrification tower 4; the connecting pipeline between the outlet end of the raw material natural gas channel II 102 and the inlet 4-A of the denitrification tower 4 is provided with a regulating valve c12; a regulating valve e14 is arranged on a connecting pipeline between the outlet end of the high-pressure liquid-phase refrigerant channel I106 and the inlet 110-A of the return refrigerant channel I110; a regulating valve f15 is arranged on a connecting pipeline between the outlet end of the high-pressure liquid-phase refrigerant channel II 109 and the inlet 110-B of the reflux refrigerant channel I110; the connecting pipe line between the pipeline III 32 and the inlet 110-C of the return refrigerant channel I110 is provided with a regulating valve g16.
According to the invention, the adjusting valves with different functions are reasonably arranged in the denitrification device, so that the production flow of the denitrification device can be adjusted and managed according to the actual requirements in the production process in order, and the operability of the device is higher.
Optionally or preferably, the pipeline I30 is provided with a regulating valve a29, the tower bottom of the denitrification tower 4 is provided with a temperature digital controller b25, and the temperature digital controller b25 logically controls the regulating valve a29.
Optionally or preferably, a regulating valve d13 is arranged on a connecting line between the outlet 7-B of the LNG storage tank 7 and the inlet 8-a of the BOG heater 8, a pressure digital controller e28 is arranged on the LNG storage tank 7, and the pressure digital controller e28 logically controls the regulating valve d13.
Optionally or preferably, a regulating valve h17 is arranged on a connecting pipeline between the outlet end of the liquefied natural gas channel I104 and the inlet 7-A of the LNG storage tank 7, a liquid level digital controller a24 is arranged at the tower bottom of the denitrification tower 4, and the liquid level digital controller a24 logically controls the regulating valve h17.
Optionally or preferably, a regulating valve i18 is arranged on a connecting pipeline between the outlet 6-B of the denitrification tower reflux tank 6 and the inlet end of the nitrogen-rich tail gas channel I105, a pressure digital controller d27 is arranged on the denitrification tower reflux tank 6, and the pressure digital controller d27 logically controls the regulating valve i18.
Optionally or preferably, a regulating valve j19 is arranged on a connecting pipe between the pipeline IV 33 and the inlet end of the reflux refrigerant channel II 502 of the denitrification tower condenser 5, a temperature digital controller c26 is arranged on a connecting pipe between the outlet end of the nitrogen-rich tail gas channel II 501 and the inlet 6-A of the denitrification tower reflux tank 6, and the temperature digital controller c26 logically controls the regulating valve j19.
According to the invention, the controllers with different functions and the adjusting valves capable of being logically controlled are respectively added in the denitrification device, so that the device can further control the corresponding valves according to the requirements of each device in the denitrification treatment process on the data such as temperature, pressure or liquid level, and the like, the denitrification process of natural gas is more accurately adjusted, and the scientificity, convenience and operability of the whole device are improved.
Experimental example
The invention provides a nitrogen-containing natural gas denitrification liquefaction process, which specifically comprises the following processing steps:
S1, a natural gas treatment process, wherein purified natural gas after purification and pressurization enters a raw material natural gas channel I101 of a main heat exchanger 2 through a purified raw material gas pipeline 1 and is precooled to minus 60 ℃, then enters a heavy hydrocarbon separator 3 for gas-liquid separation, bottom low-temperature liquid is heated from a liquid phase outlet 3-B of the heavy hydrocarbon separator 3 to heavy hydrocarbon for storage, top low-temperature gas leaves from a gas phase outlet 3-C of the heavy hydrocarbon separator 3 and is divided into two parts, the main part returns to a raw material natural gas channel II 102 of the main heat exchanger 2 and is continuously cooled to minus 162 ℃, then is regulated to 0.2Mpa G through a regulating valve C12 and is sent to an inlet 4-A of a denitrification tower 4 for rectification, the other small part is regulated to 0.2Mpa G through a regulating valve a29 and is sent to an inlet 4-F of the denitrification tower 4, and the tower kettle of the denitrification tower 4 is provided with a temperature digital controller B25, and the temperature of the tower kettle of the denitrification tower 4 is regulated through the regulating valve a 29. The low-temperature gas at the outlet 4-C at the top of the denitrification tower 4 enters a nitrogen-rich tail gas channel II 501 of a denitrification tower condenser 5 and is cooled to-165 ℃, then enters a denitrification tower reflux tank 6 for gas-liquid separation, the low-temperature liquid at the bottom returns to an inlet 4-D of the denitrification tower 4 from a liquid phase outlet 6-C of the denitrification tower reflux tank 6, the low-temperature gas at the top enters a nitrogen-rich tail gas channel I105 of a main heat exchanger 2 from a gas phase outlet 6-B of the denitrification tower reflux tank 6 for heat exchange and heating to 35 ℃ and then is sent to a cold box, and the product liquid at the outlet 4-E at the bottom of the denitrification tower 4 is sent to a liquefied natural gas channel I104 of the main heat exchanger 2 for continuous supercooling to-162 ℃, is decompressed to 0.05MpaG by a regulating valve h17 and then is sent to an LNG storage tank. The LNG storage tank 7 is provided with a pressure digital controller e28, the pressure of the LNG storage tank 7 is maintained by gas BOG at the top of the LNG storage tank through a regulating valve d13, BOG which is discharged out of the LNG storage tank 7 is rewarmed to normal temperature through a BOG heater 8, compressed to 0.9MpaG through a BOG compressor 9, cooled to 40 ℃, cooled to-162 ℃ in a BOG channel 103 which enters the main heat exchanger 2, then regulated to 0.2MpaG through a regulating valve B11, and sent to an inlet 4-B of the denitrification tower 4 for rectification separation.
S2, in the cooling liquid treatment process, the high-pressure liquid-phase refrigerant is sent to a high-pressure liquid-phase refrigerant channel I106 of the main heat exchanger 2 through a high-pressure refrigerant liquid-phase pipeline 23 to be cooled to minus 60 ℃, and then is throttled and cooled by a regulating valve e14 to return to a return refrigerant channel I110, so that the upper part of the main heat exchanger 2 is provided with cold energy. The high-pressure gas-phase refrigerant is sent to a high-pressure gas-phase refrigerant channel IA 7 of the main heat exchanger 2 through a high-pressure refrigerant gas-phase pipeline 22 to be cooled to minus 110 ℃, enters the MR low-temperature separator 10 to be subjected to gas-liquid separation, the bottom low-temperature liquid is returned to a high-pressure liquid-phase refrigerant channel II 109 of the main heat exchanger 2 from a liquid-phase outlet 10-B of the MR low-temperature separator 10 to be cooled to minus 162 ℃, then is throttled and cooled by a regulating valve f15 and then returns to a refrigerant channel I110 of the main heat exchanger 2, the top low-temperature gas is returned to a high-pressure gas-phase refrigerant channel II 108 of the main heat exchanger 2 from a gas-phase outlet 10-C of the MR low-temperature separator 10 to be cooled to minus 162 ℃, and is divided into two parts, one part is throttled and cooled by a regulating valve g16 and returns to the refrigerant channel I110 of the main heat exchanger 2, and the other part is throttled and cooled by a regulating valve j19 and then enters a return refrigerant channel II 502 of the denitrification tower condenser 5 to cool nitrogen gas from a gas-phase outlet 4-C to be returned to the main heat exchanger 2 after nitrogen is enriched to be cooled to minus 163 ℃ and returns to the refrigerant channel I110. The mixed refrigerant which flows back is cooled to normal temperature in the main heat exchanger 2 and then discharged out of the cold box after the return refrigerant channel I110 is rewarmed.
Experimental data
The data of each component in the following table can be obtained through the examples and experimental examples of the invention:
according to the material balance calculation, the nitrogen content of the LNG discharged from the main heat exchanger is 0.7228%, the LNG is accordant with common acceptance in industry to be less than 1%, and the recovery rate of methane is 99.74%.
The cold source at the top of the denitrification tower of the device is from nitrogen and methane separated from high-pressure gas-phase refrigerant at low temperature, secondary separation is carried out, the refrigeration temperature is low, and the energy consumption is 1-2% lower than that of conventional rectification.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (8)

1. The utility model provides a nitrogen-containing natural gas denitrification liquefaction device which characterized in that: the device comprises a main heat exchanger (2), a heavy hydrocarbon separator (3), a denitrification tower (4), a denitrification tower condenser (5), a denitrification tower reflux tank (6), an LNG storage tank (7), a BOG heater (8), a BOG compressor (9) and an MR low-temperature separator (10);
A raw material natural gas channel I (101), a raw material natural gas channel II (102), a BOG channel (103), a liquefied natural gas channel I (104), a nitrogen-rich tail gas channel I (105), a high-pressure liquid-phase refrigerant channel I (106), a high-pressure gas-phase refrigerant channel I (A7), a high-pressure gas-phase refrigerant channel II (108), a high-pressure liquid-phase refrigerant channel II (109) and a reflux refrigerant channel I (110) are arranged in the main heat exchanger (2);
A nitrogen-rich tail gas channel II (501) and a reflux refrigerant channel II (502) are arranged in the denitrification tower condenser (5);
The inlet end of the raw material natural gas channel I (101) is connected with an external purified raw material gas pipeline (1), the outlet end of the raw material natural gas channel I (101) is connected with an inlet 3-A of a heavy hydrocarbon separator (3), an outlet 3-B of the heavy hydrocarbon separator (3) is connected with an external heavy hydrocarbon warming and storing pipeline, a pipeline of an outlet 3-C of the heavy hydrocarbon separator (3) is divided into a pipeline I (30) and a pipeline II (31), the pipeline I (30) is connected with an inlet 4-F of a denitrification tower (4), the pipeline II (31) is connected with an inlet end of a raw material natural gas channel II (102), an outlet end of the raw material natural gas channel II (102) is connected with an inlet 4-A of a denitrification tower (4), an outlet 4-C of the denitrification tower (4) is connected with an inlet end of a nitrogen-rich tail gas channel II (501), an outlet end of the denitrification tower (501) is connected with an inlet 6-A of a denitrification reflux tank (6), an outlet 6-C of the denitrification tower (6) is connected with an inlet 4-A of the denitrification tower (6), an outlet end of the denitrification tower (4-C) is connected with an outlet end of the denitrification tower (105) of the denitrification tower (4) is connected with an inlet of the denitrification tower (105), the inlet end of the liquefied natural gas channel I (104) is connected with the outlet 4-E of the denitrification tower (4), the outlet end of the liquefied natural gas channel I (104) is connected with the inlet 7-A of the LNG storage tank (7), the outlet 7-B of the LNG storage tank (7) is connected with the inlet 8-A of the BOG heater (8), the BOG compressor (9) is respectively connected with the outlet 8-B of the BOG heater (8) and the inlet end of the BOG channel (103), the outlet end of the BOG channel (103) is connected with the inlet 4-B of the denitrification tower (4), the inlet end of the high-pressure liquid-phase refrigerant channel I (106) is connected with the inlet 110-A of the reflux refrigerant channel I (110), the inlet end of the high-pressure gas-phase refrigerant channel I (A7) is connected with the external high-pressure refrigerant gas phase line (22), the high-phase refrigerant channel I (I) is connected with the inlet 10-B of the reflux refrigerant channel (10-B), the high-phase refrigerant channel I (106) is connected with the inlet 10-B of the reflux refrigerant channel (110), the high-phase separator I (10-B) is connected with the inlet 10-B of the reflux refrigerant channel (110), the outlet 10-C of the MR low-temperature separator (10) is connected with the inlet end of a high-pressure gas-phase refrigerant channel II (108), the pipeline at the outlet end of the high-pressure gas-phase refrigerant channel II (108) is divided into a pipeline III (32) and a pipeline IV (33), the pipeline III (32) is connected with the inlet 110-C of a return refrigerant channel I (110), the pipeline IV (33) is connected with the inlet end of a return refrigerant channel II (502) of a denitrification tower condenser (5), the outlet end of a return refrigerant channel II (502) of the denitrification tower condenser (5) is connected with the inlet 110-C of the return refrigerant channel I (110), and the return refrigerant channel I (110) is connected with a return refrigerant pipeline (21); the main heat exchanger (2) and the denitrification tower condenser (5) can be any one of a plate-fin heat exchanger, a coiled tube heat exchanger or a shell-and-tube heat exchanger; the denitrification tower (4) is a packed tower or a plate tower.
2. The nitrogen-containing natural gas denitrification liquefaction plant according to claim 1, wherein: the connecting pipeline between the outlet end of the BOG channel (103) and the inlet 4-B of the denitrification tower (4) is provided with an adjusting valve B (11); the connecting pipeline between the outlet end of the raw material natural gas channel II (102) and the inlet 4-A of the denitrification tower (4) is provided with a regulating valve c (12); a regulating valve e (14) is arranged on a connecting pipeline between the outlet end of the high-pressure liquid-phase refrigerant channel I (106) and the inlet 110-A of the backflow refrigerant channel I (110); a regulating valve f (15) is arranged on a connecting pipeline between the outlet end of the high-pressure liquid-phase refrigerant channel II (109) and the inlet 110-B of the backflow refrigerant channel I (110); a regulating valve g (16) is arranged on a connecting pipe between the pipeline III (32) and the inlet 110-C of the return refrigerant channel I (110).
3. The nitrogen-containing natural gas denitrification liquefaction plant according to claim 2, wherein: the pipeline I (30) is provided with a regulating valve a (29), the tower kettle of the denitrification tower (4) is provided with a temperature digital controller b (25), and the temperature digital controller b (25) logically controls the regulating valve a (29).
4. The nitrogen-containing natural gas denitrification liquefaction plant according to claim 2, wherein: a regulating valve d (13) is arranged on a connecting pipeline between an outlet 7-B of the LNG storage tank (7) and an inlet 8-A of the BOG heater (8), a pressure digital controller e (28) is arranged on the LNG storage tank (7), and the pressure digital controller e (28) logically controls the regulating valve d (13).
5. The nitrogen-containing natural gas denitrification liquefaction plant according to claim 2, wherein: the liquid level digital control device is characterized in that a regulating valve h (17) is arranged on a connecting pipeline between the outlet end of the liquefied natural gas channel I (104) and the inlet 7-A of the LNG storage tank (7), a liquid level digital controller a (24) is arranged at the tower bottom of the denitrification tower (4), and the liquid level digital controller a (24) logically controls the regulating valve h (17).
6. The nitrogen-containing natural gas denitrification liquefaction plant according to claim 2, wherein: a regulating valve i (18) is arranged on a connecting pipeline between an outlet 6-B of the denitrification tower reflux tank (6) and an inlet end of the nitrogen-rich tail gas channel I (105), a pressure digital controller d (27) is arranged on the denitrification tower reflux tank (6), and the pressure digital controller d (27) logically controls the regulating valve i (18).
7. The nitrogen-containing natural gas denitrification liquefaction plant according to claim 2, wherein: the nitrogen-enriched tail gas condenser is characterized in that a regulating valve j (19) is arranged on a connecting pipe between the pipeline IV (33) and the inlet end of a reflux refrigerant channel II (502) of the nitrogen-enriched tail gas condenser (5), a temperature digital controller c (26) is arranged on a connecting pipe between the outlet end of the nitrogen-enriched tail gas channel II (501) and the inlet 6-A of a reflux tank (6) of the nitrogen-enriched tower, and the temperature digital controller c (26) logically controls the regulating valve j (19).
8. A process for the denitrification of nitrogen-containing natural gas, based on a denitrification liquefaction plant for nitrogen-containing natural gas according to any one of claims 1 to 7, comprising the steps of:
S1, a natural gas treatment process, wherein purified natural gas after purification and pressurization enters a raw material natural gas channel I (101) of a main heat exchanger (2) through a purified raw material gas pipeline (1) and is precooled to minus 60 ℃, then enters a heavy hydrocarbon separator (3) for gas-liquid separation, low-temperature liquid at the bottom is heated and stored from a liquid phase outlet 3-B of the heavy hydrocarbon separator (3) to heavy hydrocarbons, top low-temperature gas leaves from a gas phase outlet 3-C of the heavy hydrocarbon separator (3) and is divided into two parts, the main part of the gas is returned to a raw material natural gas channel II (102) of the main heat exchanger (2) and is continuously cooled to minus 162 ℃, then is sent to an inlet 4-A of a denitrification tower (4) for rectification after being regulated to 0.2Mpa through a regulating valve C (12), the other small part of the gas is sent to an inlet 4-F of the denitrification tower (4) after being regulated to 0.2Mpa through a regulating valve a (29), and the temperature of the denitrification tower (4) is provided with a temperature digital controller B (25), and the temperature of the denitrification tower (4) is regulated through the regulating valve a (29); the low-temperature gas at the top outlet 4-C of the denitrification tower (4) enters a nitrogen-rich tail gas channel II (501) of a denitrification tower condenser (5) and is cooled to-165 ℃, then enters a denitrification tower reflux tank (6) for gas-liquid separation, the low-temperature liquid at the bottom returns to an inlet 4-D of the denitrification tower (4) from a liquid phase outlet 6-C of the denitrification tower reflux tank (6), the low-temperature gas at the top enters a nitrogen-rich tail gas channel I (105) of a main heat exchanger (2) from a gas phase outlet 6-B of the denitrification tower reflux tank (6), heat exchange is carried out, the temperature is raised to 35 ℃, then the cold box is carried out, the product liquid at the bottom outlet 4-E of the denitrification tower (4) is fed into a liquefied natural gas channel I (104) of the main heat exchanger (2) for continuous supercooling to-162 ℃, and is decompressed to 0.05Mpa G through a regulating valve h (17) and then fed into an LNG storage tank; the LNG storage tank (7) is provided with a pressure digital controller e (28), the pressure of the LNG storage tank (7) is maintained by a gas BOG at the top of the LNG storage tank through a regulating valve d (13), the BOG which is discharged out of the LNG storage tank (7) is rewarmed to normal temperature through a BOG heater (8), then compressed to 0.9Mpa G through a BOG compressor (9), cooled to 40 ℃, then cooled to-162 ℃ in a BOG channel (103) which enters the main heat exchanger (2), then regulated to 0.2Mpa G through a regulating valve B (11), and then sent to an inlet 4-B of the denitrification tower (4) for rectification separation;
S2, a cooling liquid treatment flow, wherein high-pressure liquid-phase refrigerant is sent to a high-pressure liquid-phase refrigerant channel I (106) of a main heat exchanger (2) through a high-pressure refrigerant liquid-phase pipeline (23) to be cooled to minus 60 ℃, and then is throttled and cooled by a regulating valve e (14) and returned to a reflux refrigerant channel I (110) to provide cold energy for the upper part of the main heat exchanger (2); the high-pressure gas-phase refrigerant is sent to a high-pressure gas-phase refrigerant channel I (A7) of a main heat exchanger (2) through a high-pressure refrigerant gas-phase pipeline (22) and is cooled to minus 110 ℃, then enters an MR low-temperature separator (10) for gas-liquid separation, low-temperature liquid at the bottom is returned to the high-pressure liquid-phase refrigerant channel II (109) of the main heat exchanger (2) from a liquid-phase outlet 10-B of the MR low-temperature separator (10) and is cooled to minus 162 ℃, then is returned to a refrigerant channel I (110) of the main heat exchanger (2) after being throttled and cooled by a regulating valve f (15), top low-temperature gas is returned to the high-pressure gas-phase refrigerant channel II (108) of the main heat exchanger (2) from a gas-phase outlet 10-C of the MR low-temperature separator (10) and is separated into two parts, one part is throttled and cooled by a regulating valve g (16) and then returns to the refrigerant channel I (110) of the main heat exchanger (2), the other part is throttled and cooled by a regulating valve j (19) and then enters a nitrogen-phase refrigerant channel II (163) of a nitrogen-rich nitrogen gas-phase condenser (4) and returns to the nitrogen-rich heat exchanger (2) from the gas-phase refrigerant channel (502) of the main heat exchanger (4); the mixed refrigerant in the back flow is cooled to normal temperature in the back flow refrigerant channel I (110) of the main heat exchanger (2) and then is discharged out of the cold box.
CN202111038208.9A 2021-09-06 2021-09-06 Nitrogen-containing natural gas denitrification liquefying device and process Active CN113776278B (en)

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