CN102620522A - Process and device for producing liquefied natural gas (LNG) and removing hydrogen and nitrogen through throttling flash evaporation - Google Patents
Process and device for producing liquefied natural gas (LNG) and removing hydrogen and nitrogen through throttling flash evaporation Download PDFInfo
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Abstract
The invention relates to a process and a device for producing liquefied natural gas (LNG) and removing hydrogen and nitrogen through throttling flash evaporation. The process comprises two parts: a low-temperature liquefied work procedure and a throttling flash evaporation separation work procedure, wherein the low-temperature liquefied work procedure comprises the steps that mixed refrigerant provides cold quantity, and the natural gas liquefaction is realized in a cold box; the throttling flash evaporation separation work procedure comprises the step that methane-rich mixed gas containing hydrogen gas, nitrogen gas and carbon monoxide adopts a primary or secondary throttling flash evaporation flow process for removing the hydrogen gas, the nitrogen gas and the carbon monoxide; the methane-rich mixed gas containing the hydrogen gas, the nitrogen gas and the carbon monoxide enters the primary or secondary throttling flash evaporation work procedure for removing the hydrogen gas, the nitrogen gas and the carbon monoxide after methane components are liquefied through the cold box, in the obtained LNG product, the hydrogen gas content is lower than or equal to 2000 ppm, the nitrogen gas content is smaller than or equal to 4 percent, and the carbon monoxide content is smaller than or equal to 6 percent. The invention provides a liquefaction process of the natural gas rich in methane gas and containing the hydrogen gas, the nitrogen gas and the carbon monoxide, while the hydrogen gas, the nitrogen gas and the carbon monoxide are removed, the LNG is obtained, the process route is simple, the operation stability is enhanced, and in addition, compared with the original process, the process has the advantages that the equipment investment and the system energy consumption are respectively reduced, and in addition, the device starting and stop are convenient and fast.
Description
Technical field
The technology that the invention provides a kind of throttling flash distillation dehydrogenation gas, nitrogen, carbon monoxide and produce liquefied natural gas.Gas behind coal based synthetic gas, oven gas and the coke-oven gas methanation etc. also contain nitrogen, hydrogen, carbon monoxide except that containing methane, for obtaining liquefied natural gas, need it is removed to a certain degree, could be as liquefied natural gas (LNG) product output.
Background technology
Under the pressure of environmental protection and energy cost pressure; Natural gas promotes at social every field proportion as primary energy just gradually; Its application expands aspects such as generating, automobile usefulness gas, industrial gas, city dweller's usefulness gas, chemical industry usefulness gas gradually to, and market demand increases sharply.The defeated method of supplying of traditional natural gas pipe still is a main flow; But limited by material condition and user distribution; There is quite a few resource can't carry out pipe long-distance and carries, need to select the mode of liquefaction, change methane into liquid and adopt again flexibly that means of transportation is sent to user terminal with it.And liquefied natural gas (LNG) volume has only with 1/625 of amount gas volume, can reduce after the liquefaction and store and cost of transportation, and can improve the combustion value of unit volume.The continuous development of liquefied natural gas industry is had higher requirement at aspects such as energy consumption, investment and efficient to natural gas liquefaction and device.
Be rich in methane gas for some; The synthetic natural gas that for example obtains behind coal based synthetic gas and the coke-oven gas methanation etc.; It is formed except that methane, also contains nitrogen, hydrogen, carbon monoxide etc., for obtaining highly purified liquefied natural gas; Need wherein nitrogen, hydrogen, carbon monoxide are removed to a certain degree, could be as liquefied natural gas (LNG) product output.
Gas separating method commonly used at present generally has low-temperature liquefaction separation, transformation absorption and film separation etc., and the low-temperature liquefaction isolation technics is applied to this field of natural gas just gradually.Accompanying drawing 1 is depicted as the flow process of an employing low-temperature liquefaction rectifying separation explained hereafter LNG, comprises low-temperature liquefaction and rectifying separation two parts; Low-temperature liquefaction provides cold in ice chest, to realize the liquefaction of natural gas by azeotrope; The rectifying separation operation comprises that the methane gas that is rich in of hydrogen, nitrogen, carbon monoxide adopts distillation process to remove hydrogen, nitrogen, carbon monoxide, obtains qualified LNG.But this technological process is comparatively complicated, and system reaches that to stablize required time longer.
In addition, Chinese invention patent application 201019087060.0 discloses a kind of process method for preparing LNG from coke oven tail gas, and this method discloses, and thick product gas gets into molecular sieve to remove remaining moisture content and CO after refrigerated separation is fallen most of condensate liquid
2, after compressor rises to 5.0MPa, cooling and precooling, get into two-stage throttling flash system, to isolate non-product gas.This method is included in normal temperature de-oiling desulfurization under the pressurized conditions, three grades of catalyst hydrogenation conversions, two-stage dry desulfurization, three grades of methanation reactions, molecular sieve adsorption remove residual moisture and CO
2, a plurality of steps such as methanation gas cryogenic liquefying, not concrete openly throttling flash process, it is mainly used in desulfurization, employed unstripped gas is the oven gas of coke-oven plant through purified treatment, contains micro-tar, benzene, naphthalene, ammonia, hydrogen cyanide, Cl
-, H
2S, unsaturated hydrocarbons, thiophene, thioether, mercaptan, COS and CS
2Deng organic sulfur.
Summary of the invention
The object of the present invention is to provide the method that removes hydrogen, nitrogen, carbon monoxide a kind of high methane gas (being rich in the gas of methane) and natural gas (LNG) is produced in methane component liquefaction from hydrogen, nitrogen, carbon monoxide; Make the present invention when hydrogen, nitrogen, carbon monoxide are removed, obtain qualified liquefied natural gas; Its technological process is simple; Workable, and equipment investment expense and system energy consumption all reduce.
According to a first aspect of the invention, the technology that the present invention provides a kind of throttling flash distillation dehydrogenation gas, nitrogen, carbon monoxide and produces liquefied natural gas, this technology comprise low-temperature liquefaction operation and throttling flash separation operation two parts; The low-temperature liquefaction operation comprises by azeotrope provides cold in ice chest, to realize the liquefaction of natural gas; Throttling flash separation operation comprises that the gaseous mixture of the methane rich of hydrogen, nitrogen, carbon monoxide adopts one-level or two-step throttle flash distillation flow process to remove hydrogen, nitrogen, carbon monoxide; The methane-riched gas mixture of wherein hydrogeneous, nitrogen, CO gas gets in one-level or two-step throttle, the flash distillation operation and removes nitrogen, hydrogen and carbon monoxide after ice chest is with methane component liquefaction, obtain hydrogen content≤4000ppm (preferred≤3500ppm, more preferably≤3000ppm; Further preferably≤2500ppm, further preferred≤2000ppm, especially preferred≤1700ppm, preferred≤1500ppm especially; Most preferably≤1000ppm), and nitrogen content≤8% (preferred≤7%, more preferably≤6%, further preferably≤5%; Further preferably≤4%, better≤3%, especially preferred≤2%, preferred≤1.5% especially; More preferably≤1%, most preferably≤0.5%), carbon monoxide content≤9% (preferred≤8%, more preferably≤7%; Further preferably≤6%, further preferably≤5%, better≤4%, better≤3% again; Especially liquefied natural gas (LNG) product preferred≤2%, preferred≤1.5% especially, more preferred≤1%, most preferably≤0.5%).
Generally speaking, in the low-temperature liquefaction operation, the cold of ice chest is provided or is mainly provided by azeotrope by azeotrope; One gas phase refrigerant flow thigh is cooled to uniform temperature through a gas phase channel of ice chest; A reverse a specific order (for example final stage, the penultimate stage etc.) heat exchanger that gets into the plate-fin heat exchanger group is that heat exchanger provides cold after the choke valve throttling again; This vapor phase stream thigh passes through cryogen backward channel, cooling box then; One liquid-phase mixing cryogen at first gets into first liquid channel of ice chest; In the plate-fin heat exchanger group, drawn ice chest after precooling to the uniform temperature; An a specific order that after the choke valve throttling, oppositely gets into the plate-fin heat exchanger group once more (for example returns the previous stage of the heat exchanger progression of heat exchanger package for gas phase refrigerant flow thigh; The first order for example; Or penultimate stage or level third from the bottom (when the level more than three)) heat exchanger is that heat exchanger package provides cold and converges with an azeotrope stream strand above-mentioned vapor phase stream thigh that returns from heat exchanger package then, after converging through cryogen backward channel, cooling box.The low-temperature liquefaction part is accomplished in ice chest, and the cold of ice chest is mainly provided by azeotrope.Preferably; For instance; One gas phase refrigerant flow thigh is cooled to-148 ℃～-173 ℃ through a gas phase channel of ice chest; Reverse entering heat exchanger package final stage heat exchanger is that heat exchanger provides cold behind second choke valve throttling to 0.2～0.8MPaA again; One liquid-phase mixing cryogen at first gets into first liquid channel of ice chest, therein by precooling to-10 ℃～-80 ℃ approximately, be that heat exchanger package provides cold and the azeotrope stream that returns with first-class heat exchanger after the plate-fin heat exchanger group strand is that above-mentioned vapor phase stream thigh converges through the first order heat exchanger that gets into the plate-fin heat exchanger group behind first throttle valve throttling to 0.2～0.8MPaA once more; Process cryogen backward channel after converging, cooling box.
Preferably, said one-level throttling, flash separation flow process adopt a choke valve and two flash tanks.
Under preferred situation; In said one-level throttling, flash separation flow process, the gaseous mixture that is rich in methane through ice chest be cooled to uniform temperature (general to-145 ℃ to-170 ℃ scopes, preferred-147 ℃ of-165 ℃ of scopes extremely; Further preferred-148 ℃ to-162 ℃ of scopes; More preferably-150 ℃ to-160 ℃ of scopes) methane component liquefaction that will be wherein, get into flash distillation under inlet temperature, pressure condition in the ice chest outlet flash tank afterwards, after returning the ice chest re-heat, the part hydrogen rich gas that ice chest outlet flash drum overhead obtains goes out system; The flash tank bottom liquid is through the 3rd choke valve throttling to 0.15～1.0MPaA; Get into afterwards in the first order flash tank and be divided into gas-liquid two-phase, obtain the mist of hydrogen, nitrogen, carbon monoxide and methane, return and go out system after ice chest reclaims cold from first order flash drum overhead; Liquefied natural gas is drawn from first order flash tank bottom, obtains the LNG product.Gained LNG product has hydrogen content, nitrogen content, the carbon monoxide content in the scope defined above.
Preferably, said two-step throttle, flash separation flow process adopt two choke valves and three flash tanks.
Under preferred situation, in said two-step throttle, flash separation flow process, the gaseous mixture that is rich in methane is cooled to uniform temperature (general extremely-145 ℃ to-170 ℃ scopes through ice chest; Preferably-147 ℃ to-165 ℃ of scopes, further preferred-148 ℃ to-162 ℃ of scopes, more preferably-150 ℃ to-160 ℃ of scopes) methane component liquefaction that will be wherein; Get into flash distillation under inlet temperature, pressure condition in the ice chest outlet flash tank afterwards; Go out system after the part hydrogen rich gas that ice chest outlet flash drum overhead obtains returns the ice chest re-heat, ice chest outlet flash tank bottom liquid gets into gas-liquid separation in the first order flash tank through the 3rd choke valve throttling to 0.3～1.5MPaA; First order flash drum overhead obtains most hydrogen and small amount of nitrogen, carbon monoxide, methane; Go out system after returning the ice chest re-heat, bottom liquid continues through the 4th choke valve throttling to 0.15～1.0MPaA, gets into afterwards in the flash tank of the second level to be divided into gas-liquid two-phase; Second level flash drum overhead is mainly contained the mist of nitrogen, carbon monoxide and methane; Go out system after returning the ice chest re-heat, liquefied natural gas is drawn the flash tank bottom from the second level, obtains the LNG product.Gained LNG product has hydrogen content, nitrogen content, the carbon monoxide content in the scope defined above.
In order more to be expressly understood the present invention, the technical scheme of method of the present invention (or being called technology) is summarized as follows:
1, a kind of throttling flash distillation dehydrogenation gas, nitrogen, carbon monoxide and the technology of producing liquefied natural gas, this technology comprises low-temperature liquefaction operation and throttling flash separation operation two parts; The low-temperature liquefaction operation comprises by azeotrope provides cold in ice chest, to realize the liquefaction of natural gas; Throttling flash separation operation comprises that the gaseous mixture of the methane rich of hydrogen, nitrogen, carbon monoxide adopts one-level or two-step throttle flash distillation flow process to remove hydrogen, nitrogen, carbon monoxide; The methane-riched gas mixture of wherein hydrogeneous, nitrogen, CO gas is after ice chest is with methane component liquefaction; Get in one-level or two-step throttle, the flash distillation operation and remove nitrogen, hydrogen and carbon monoxide; Obtain hydrogen content≤4000ppm; Nitrogen content≤8%, the liquefied natural gas product of carbon monoxide≤9%.
2, according to above 1 described technology; It is characterized in that: the gaseous mixture of the methane rich of hydrogen, nitrogen, carbon monoxide liquefies methane component through ice chest; Get into afterwards and remove the foreign gas component in the flash tank; Liquid phase becomes gas-liquid two-phase through choke valve at the bottom of by flash tank, then gets into again and removes the foreign gas component in the flash tank, so carries out one-level or two-step throttle, flash distillation; The nitrogen that each flash drum overhead obtains, hydrogen, carbon monoxide and methane return cooling box system after the ice chest re-heat, and the liquid-phase product that is obtained by final stage flash tank bottom is liquefied natural gas.
3, according to above 1 or 2 described technology, it is characterized in that: said one-level throttling, flash distillation flow process adopt a throttling arrangement and two flash tanks; Said two-step throttle, flash distillation flow process adopt two throttling arrangements and three flash tanks.
4, according to above 3 described technologies, it is characterized in that
When carrying out one-level throttling, flash distillation; The gaseous mixture of the methane rich of hydrogen, nitrogen, carbon monoxide liquefies methane component through ice chest; Middle part from previous stage flash tank (being ice chest outlet flash tank) gets into the previous stage flash tank afterwards; The top gas phase of previous stage flash tank is returned in the ice chest cooling box after the re-heat; The liquid phase that previous stage flash tank bottom obtains gets into the one-level flash tank of back through the middle part from back one-level flash tank (being first order flash tank) after the choke valve, and the top gas phase of back one-level flash tank is returned in the ice chest cooling box after the re-heat, and the bottom liquid phases of back one-level flash tank is liquefied natural gas product; Or
When carrying out two-step throttle, flash distillation; The gaseous mixture of the methane rich of hydrogen, nitrogen, carbon monoxide liquefies methane component through ice chest; Middle part from previous stage flash tank (being ice chest outlet flash tank) gets into the previous stage flash tank afterwards; The top gas phase of previous stage flash tank is returned in the ice chest cooling box after the re-heat; The liquid phase that previous stage flash tank bottom obtains gets into the one-level flash tank of back through the middle part from back one-level flash tank (being first order flash tank) after the choke valve; The top gas phase of back one-level flash tank is returned in the ice chest cooling box after the re-heat; The bottom liquid phases of back one-level flash tank is through getting into the one-level flash tank of back from the middle part of back one-level flash tank (being second level flash tank) again after the choke valve again, and the top gas phase of back one-level flash tank is returned in the ice chest cooling box after the re-heat again, and the bottom liquid phases of back one-level flash tank is liquefied natural gas product again.
5, according to any one described technology in the above 1-4 item, it is characterized in that: in its low-temperature liquefaction operation part, the cold of ice chest is provided or is mainly provided by azeotrope by azeotrope; One gas phase refrigerant flow thigh is cooled to uniform temperature through a gas phase channel of ice chest; A reverse a specific order heat exchanger that gets into the plate-fin heat exchanger group is that heat exchanger provides cold after the choke valve throttling again; This vapor phase stream thigh passes through cryogen backward channel, cooling box then; One liquid-phase mixing cryogen at first gets into first liquid channel of ice chest; In the plate-fin heat exchanger group, drawn ice chest after precooling to the uniform temperature; Another a specific order heat exchanger that after the choke valve throttling, oppositely gets into the plate-fin heat exchanger group once more is that heat exchanger package provides cold and strand is that above-mentioned vapor phase stream thigh converges with the azeotrope that returns from heat exchanger package stream then; Process cryogen backward channel after converging, cooling box.
According to a second aspect of the invention, the present invention provides a kind of throttling flash distillation dehydrogenation gas, nitrogen, carbon monoxide and produces the device of liquefied natural gas.Be the employed equipment of said method.
In one embodiment, this device comprises an ice chest, three choke valves and two flash tanks,
Wherein, this ice chest comprises:
Liquid-phase mixing cryogen inlet; It is connected with first liquid channel of ice chest, and the end of an a specific order of the heat exchanger of this first liquid channel from ice chest (for example one-level, secondary, three grades etc.) is drawn a pipeline, via the first throttle valve; Be connected with a cryogen backward channel of ice chest
Gas phase cryogen inlet, it is connected with first gas phase channel of ice chest, and this first gas phase channel is drawn a pipeline from the end of another a specific order of heat exchanger (for example one-level, secondary, three grades etc.), via second choke valve, is connected with above-mentioned cryogen backward channel,
A high methane gas import and a methane rich mixed flow thigh outlet of being connected with second gas phase channel of ice chest, this methane rich mixed flow thigh outlet is connected with the methane rich mixed flow thigh inlet of ice chest outlet flash tank,
The first mist import and first mixed gas outlet that are connected with the 3rd gas phase channel of ice chest, this mist import is connected with the top gas phase channel of ice chest outlet flash tank,
The second mist import and second mixed gas outlet that are connected with the 4th gas phase channel of ice chest, this mist import is connected with the top gas phase channel of first order flash tank,
Ice chest outlet flash tank and first order flash tank include: a methane rich mixed flow thigh inlet, and a top gaseous phase outlet, a bottom liquid phases outlet,
The outlet of ice chest outlet flash tank bottom liquid phases is connected with the 3rd choke valve one end through pipeline, and the 3rd choke valve other end is connected with the methane rich mixed flow thigh inlet of first order flash tank.
Preferably, the first-class heat exchanger end of this first liquid channel from ice chest drawn a pipeline, via the first throttle valve, is connected with a cryogen backward channel in the entering ice chest; This first gas phase channel is drawn a pipeline from the end of final stage heat exchanger, via second choke valve, is connected with above-mentioned cryogen backward channel in the entering ice chest.
In another embodiment, this device comprises an ice chest, four choke valves and three flash tanks,
Wherein, this ice chest comprises:
Liquid-phase mixing cryogen inlet; It is connected with first liquid channel of ice chest, and the end of an a specific order of the heat exchanger of this first liquid channel from ice chest (for example one-level, secondary, three grades etc.) is drawn a pipeline, via the first throttle valve; Be connected with a cryogen backward channel of ice chest
Gas phase cryogen inlet, it is connected with first gas phase channel of ice chest, and this first gas phase channel is drawn a pipeline from the end of another a specific order of heat exchanger (for example one-level, secondary, three grades etc.), via second choke valve, is connected with above-mentioned cryogen backward channel,
A high methane gas import and a methane rich mixed flow thigh outlet of being connected with second gas phase channel of ice chest, this methane rich mixed flow thigh outlet is connected with the methane rich mixed flow thigh inlet of ice chest outlet flash tank,
The first mist import and first mixed gas outlet that are connected with the 3rd gas phase channel of ice chest, this first mist import is connected with the top gas phase channel of ice chest outlet flash tank,
The second mist import and second mixed gas outlet that are connected with the 4th gas phase channel of ice chest, this second mist import is connected with the top gas phase channel of first order flash tank,
The 3rd mist import and the 3rd mixed gas outlet that are connected with the 5th gas phase channel of ice chest, the 3rd mist import is connected with the top gas phase channel of second level flash tank,
Ice chest outlet flash tank, first order flash tank, second level flash tank include: a methane rich mixed flow thigh inlet, and a top gaseous phase outlet, a bottom liquid phases outlet,
The outlet of ice chest outlet flash tank bottom liquid phases is connected with the 3rd choke valve one end through pipeline; The 3rd choke valve other end is connected with the methane rich mixed flow thigh inlet of first order flash tank; The outlet of first order flash tank bottom liquid phases is connected with the 4th choke valve one end, and the 4th choke valve other end connects the methane rich mixed flow thigh inlet of second level flash tank.
Preferably, the first-class heat exchanger end of this first liquid channel from ice chest drawn a pipeline, via the first throttle valve, is connected with a cryogen backward channel in the entering ice chest; This first gas phase channel is drawn a pipeline from the end of final stage heat exchanger, via second choke valve, is connected with above-mentioned cryogen backward channel in the entering ice chest.
In addition, adopt three grades of throttlings, the flash separation technological process of three choke valves and four flash tanks also to belong to protection scope of the present invention.
Advantage of the present invention:
1, the present invention adopts the process route of brand-new separating hydrogen gas, nitrogen, carbon monoxide, will liquefy to carry out economic and reliable with separating synchronously;
2, flow process that the present invention adopts is comparatively simple, has saved rectifying column, and operational stability is better, has reduced the equipment investment maintenance cost, and the simple operation of start-stop car, and is simple to operate.
Description of drawings
Fig. 1 is the process chart of prior art; Wherein E1 ' is an ice chest, and V1 ', V2 ', V3 ' are choke valve, and T1 ' is a rectifying column.
Fig. 2 is an one-level throttling flash distillation dehydrogenation nitrogen process chart of the present invention; Wherein E1 is an ice chest, and V1, V2, V3 are choke valve, and T1, T2 are flash tank.
Fig. 3 is a two-step throttle flash distillation dehydrogenation nitrogen process chart of the present invention; Wherein E1 is an ice chest, and V1, V2, V3, V4 are choke valve, and T1, T2, T3 are flash tank.
The specific embodiment
Technology of the present invention comprises low-temperature liquefaction operation and throttling flash distillation operation two parts; The low-temperature liquefaction operation comprises by azeotrope provides cold in ice chest, to realize the liquefaction of natural gas; Throttling flash distillation operation comprises that the gaseous mixture of the methane rich of hydrogen, nitrogen, carbon monoxide adopts one-level or two-step throttle flash distillation flow process to remove hydrogen, nitrogen, carbon monoxide; The methane-riched gas mixture of wherein hydrogeneous, nitrogen, CO gas is after ice chest is with methane component liquefaction; Get in one-level or two-step throttle, the flash distillation operation and remove nitrogen, hydrogen and carbon monoxide; Obtain hydrogen content≤4000ppm; Nitrogen content≤8%, the liquefied natural gas product of carbon monoxide≤9%.
The low-temperature liquefaction part is accomplished in ice chest, and the cold of ice chest E1 is mainly provided by azeotrope.With reference to accompanying drawing 2, one gas phase refrigerant flow thigh is cooled to-148 ℃～-173 ℃ through first gas phase channel of ice chest, and reverse entering heat exchanger package is that heat exchanger package provides cold behind second choke valve V2 throttling to 0.3～0.6MPaA again.One liquid-phase mixing cryogen at first gets into first liquid channel of ice chest E1; Therein by precooling to-10 ℃～-80 ℃ approximately, strand be that cooled above-mentioned vapor phase stream thigh converges and oppositely get into the previous stage heat exchanger through the azeotrope stream that returns with first-class heat exchanger after the plate-fin heat exchanger group behind first throttle valve V1 throttling to 0.2～0.8MPaA be that heat exchanger package provides cold.
Low-temperature liquefaction in two-step throttle, flash distillation flow process part and one-level throttling, flash distillation flow process are identical.The low-temperature liquefaction part of two-step throttle, flash distillation flow process is also accomplished in ice chest E1.With reference to accompanying drawing 3, one gas phase refrigerant flow thigh is cooled to-148 ℃～-173 ℃ through first gas phase channel of ice chest, and reverse entering heat exchanger package is that heat exchanger package provides cold behind second choke valve V2 throttling to 0.2～0.8MPaA again.One liquid-phase mixing cryogen at first gets into first liquid channel of ice chest; Therein by precooling to-10 ℃～-80 ℃ approximately, strand be that above-mentioned cooled vapor phase stream thigh converges and oppositely get into the previous stage heat exchanger through the azeotrope stream that returns with first-class heat exchanger after the plate-fin heat exchanger group behind first throttle valve V1 throttling to 0.2～0.8MPaA be that heat exchanger package provides cold.
Referring to accompanying drawing 2, explain that one-level throttling, flash separation flow process are following:
The gaseous mixture (unstripped gas) that is rich in methane is cooled to uniform temperature (general extremely-145 ℃ to-170 ℃ scopes through ice chest E1 second gas phase channel; Preferably-147 ℃ to-165 ℃ of scopes; Further preferred-148 ℃ to-162 ℃ of scopes; More preferably-150 ℃ to-160 ℃ of scopes) methane component liquefaction that will be wherein, get into flash distillation under inlet temperature, pressure among the ice chest outlet flash tank T1 afterwards, after returning ice chest E1 the 3rd gas phase channel re-heat, the part hydrogen rich gas (first gaseous mixture) that ice chest outlet flash tank T1 top obtains goes out system; Ice chest outlet flash tank T1 bottom liquid is through the 3rd choke valve V3 throttling to 0.15～1.0MPaA; Get into afterwards among the first order flash tank T2 and be divided into gas-liquid two-phase, obtain the mist (second gaseous mixture) of hydrogen, nitrogen, carbon monoxide and methane from first order flash tank T2 top, return and go out system after ice chest E1 the 4th gas phase channel reclaims cold; Liquefied natural gas is drawn from first order flash tank T2 bottom, obtains the LNG product.Gained LNG product has hydrogen content, nitrogen content, the carbon monoxide content in the scope defined above.
Referring to accompanying drawing 3, explain that two-step throttle, flash separation flow process are following:
The gaseous mixture (unstripped gas) that is rich in methane is cooled to uniform temperature (general extremely-145 ℃ to-170 ℃ scopes through ice chest E1 second gas phase channel; Preferably-147 ℃ to-165 ℃ of scopes; Further preferred-148 ℃ to-162 ℃ of scopes; More preferably-150 ℃ to-160 ℃ of scopes) methane component liquefaction that will be wherein, get into flash distillation under inlet temperature, pressure condition among the ice chest outlet flash tank T1 afterwards, after returning ice chest E1 the 3rd gas phase channel re-heat, the part hydrogen rich gas (first gaseous mixture) that ice chest outlet flash tank T1 top obtains goes out system; Ice chest outlet flash tank T1 bottom liquid is through the 3rd choke valve V3 throttling to 0.3～1.5MPaA; Get into gas-liquid separation among the first order flash tank T2, first order flash tank T2 top obtains most hydrogen and small amount of nitrogen, carbon monoxide, methane (second gaseous mixture), goes out system after returning ice chest E1 the 4th gas phase channel re-heat; Bottom liquid continues through the 4th choke valve V4 throttling to 0.15～1.0MPaA; Get into afterwards among the flash tank T3 of the second level and be divided into gas-liquid two-phase, the mist (the 3rd gaseous mixture) of nitrogen, carbon monoxide and methane is mainly contained at flash tank T3 top, the second level, goes out system after returning ice chest E1 the 5th gas phase channel re-heat; Flash tank T3 draws the bottom liquefied natural gas from the second level, obtains the LNG product.Gained LNG product has hydrogen content, nitrogen content, the carbon monoxide content in the scope defined above.
Claims (10)
1. a throttling flash distillation dehydrogenation gas, nitrogen, carbon monoxide and the technology of producing liquefied natural gas, this technology comprises low-temperature liquefaction operation and throttling flash separation operation two parts; The low-temperature liquefaction operation comprises by azeotrope provides cold in ice chest, to realize the liquefaction of natural gas; Throttling flash separation operation comprises that the gaseous mixture of the methane rich of hydrogen, nitrogen, carbon monoxide adopts one-level or two-step throttle flash distillation flow process to remove hydrogen, nitrogen, carbon monoxide; The methane-riched gas mixture of wherein hydrogeneous, nitrogen, CO gas is after ice chest is with methane component liquefaction; Get in one-level or two-step throttle, the flash distillation operation and remove nitrogen, hydrogen and carbon monoxide; Obtain hydrogen content≤4000ppm; Nitrogen content≤8%, the liquefied natural gas product of carbon monoxide≤9%.
2. technology according to claim 1; It is characterized in that: the gaseous mixture of the methane rich of hydrogen, nitrogen, carbon monoxide liquefies methane component through ice chest; Get into afterwards and remove the foreign gas component in the flash tank; Liquid phase becomes gas-liquid two-phase through choke valve at the bottom of by flash tank, then gets into again and removes the foreign gas component in the flash tank, so carries out one-level or two-step throttle, flash distillation; The nitrogen that each flash drum overhead obtains, hydrogen, carbon monoxide and methane return cooling box system after the ice chest re-heat, and the liquid-phase product that is obtained by final stage flash tank bottom is liquefied natural gas.
3. technology according to claim 1 and 2 is characterized in that: said one-level throttling, flash distillation flow process adopt a throttling arrangement and two flash tanks; Said two-step throttle, flash distillation flow process adopt two throttling arrangements and three flash tanks.
4. technology according to claim 3 is characterized in that
When carrying out one-level throttling, flash distillation; The gaseous mixture of the methane rich of hydrogen, nitrogen, carbon monoxide liquefies methane component through ice chest; Middle part from the previous stage flash tank gets into the previous stage flash tank afterwards; The top gas phase of previous stage flash tank is returned in the ice chest cooling box after the re-heat; The liquid phase that previous stage flash tank bottom obtains gets into the one-level flash tank of back through the middle part from back one-level flash tank after the choke valve, and the top gas phase of back one-level flash tank is returned in the ice chest cooling box after the re-heat, and the bottom liquid phases of back one-level flash tank is liquefied natural gas product; Or
When carrying out two-step throttle, flash distillation; The gaseous mixture of the methane rich of hydrogen, nitrogen, carbon monoxide liquefies methane component through ice chest; Middle part from the previous stage flash tank gets into the previous stage flash tank afterwards; The top gas phase of previous stage flash tank is returned in the ice chest cooling box after the re-heat; The liquid phase that previous stage flash tank bottom obtains gets into the one-level flash tank of back through the middle part from back one-level flash tank after the choke valve, and the top gas phase of back one-level flash tank is returned in the ice chest cooling box after the re-heat, the bottom liquid phases of back one-level flash tank through after the choke valve after the middle part entering again of back one-level flash tank again the one-level flash tank; The top gas phase of back one-level flash tank is returned in the ice chest cooling box after the re-heat again, and the bottom liquid phases of back one-level flash tank is liquefied natural gas product again.
5. according to any one described technology among the claim 1-4, it is characterized in that: in its low-temperature liquefaction operation part, the cold of ice chest is provided or is mainly provided by azeotrope by azeotrope; One gas phase refrigerant flow thigh is cooled to uniform temperature through a gas phase channel of ice chest; A reverse a specific order heat exchanger that gets into the plate-fin heat exchanger group is that heat exchanger provides cold after the choke valve throttling again; This vapor phase stream thigh passes through cryogen backward channel, cooling box then; One liquid-phase mixing cryogen at first gets into first liquid channel of ice chest; In the plate-fin heat exchanger group, drawn ice chest after precooling to the uniform temperature; Another a specific order heat exchanger that after the choke valve throttling, oppositely gets into the plate-fin heat exchanger group once more is that heat exchanger package provides cold and strand is that above-mentioned vapor phase stream thigh converges with the azeotrope that returns from heat exchanger package stream then; Process cryogen backward channel after converging, cooling box.
6. according to any one technology among the claim 1-4, wherein obtain hydrogen content≤2000ppm, nitrogen content≤4%, the liquefied natural gas product of carbon monoxide≤6%.
7. a throttling flash distillation dehydrogenation gas, nitrogen, carbon monoxide and produce the device of liquefied natural gas, this device comprises an ice chest, three choke valves and two flash tanks,
Wherein, this ice chest comprises:
Liquid-phase mixing cryogen inlet; It is connected with first liquid channel of ice chest, and the end of an a specific order of the heat exchanger of this first liquid channel from ice chest is drawn a pipeline, via the first throttle valve; Get into once more in the ice chest and be connected with a cryogen backward channel of ice chest
Gas phase cryogen inlet, it is connected with first gas phase channel of ice chest, and this first gas phase channel is drawn a pipeline from the end of another a specific order of heat exchanger, and via second choke valve, get into once more in the ice chest and be connected with above-mentioned cryogen backward channel,
A high methane gas import and a methane rich mixed flow thigh outlet of being connected with second gas phase channel of ice chest, this methane rich mixed flow thigh outlet is connected with the methane rich mixed flow thigh inlet of ice chest outlet flash tank,
The first mist import and first mixed gas outlet that are connected with the 3rd gas phase channel of ice chest, this mist import is connected with the top gas phase channel of ice chest outlet flash tank,
The second mist import and second mixed gas outlet that are connected with the 4th gas phase channel of ice chest, this mist import is connected with the top gas phase channel of first order flash tank,
Ice chest outlet flash tank and first order flash tank include: a methane rich mixed flow thigh inlet, and a top gaseous phase outlet, a bottom liquid phases outlet,
The outlet of ice chest outlet flash tank bottom liquid phases is connected with the 3rd choke valve one end through pipeline, and the 3rd choke valve other end is connected with the methane rich mixed flow thigh inlet of first order flash tank.
8. device according to claim 7, wherein, the first-class heat exchanger end of this first liquid channel from ice chest drawn a pipeline, via the first throttle valve, is connected with a cryogen backward channel in the entering ice chest; This first gas phase channel is drawn a pipeline from the end of final stage heat exchanger, via second choke valve, is connected with above-mentioned cryogen backward channel in the entering ice chest.
9. a throttling flash distillation dehydrogenation gas, nitrogen, carbon monoxide and produce the device of liquefied natural gas, this device comprises an ice chest, four choke valves and three flash tanks,
Wherein, this ice chest comprises:
Liquid-phase mixing cryogen inlet, it is connected with first liquid channel of ice chest, and the end of an a specific order of the heat exchanger of this first liquid channel from ice chest is drawn a pipeline, via the first throttle valve, is connected with a cryogen backward channel of ice chest,
Gas phase cryogen inlet, it is connected with first gas phase channel of ice chest, and this first gas phase channel is drawn a pipeline from the end of another a specific order of heat exchanger, via second choke valve, is connected with above-mentioned cryogen backward channel,
A high methane gas import and a methane rich mixed flow thigh outlet of being connected with second gas phase channel of ice chest, this methane rich mixed flow thigh outlet is connected with the methane rich mixed flow thigh inlet of ice chest outlet flash tank,
The first mist import and first mixed gas outlet that are connected with the 3rd gas phase channel of ice chest, this first mist import is connected with the top gas phase channel of ice chest outlet flash tank,
The second mist import and second mixed gas outlet that are connected with the 4th gas phase channel of ice chest, this second mist import is connected with the top gas phase channel of first order flash tank,
The 3rd mist import and the 3rd mixed gas outlet that are connected with the 5th gas phase channel of ice chest, the 3rd mist import is connected with the top gas phase channel of second level flash tank,
Ice chest outlet flash tank, first order flash tank, second level flash tank include: a methane rich mixed flow thigh inlet, and a top gaseous phase outlet, a bottom liquid phases outlet,
The outlet of ice chest outlet flash tank bottom liquid phases is connected with the 3rd choke valve one end through pipeline; The 3rd choke valve other end is connected with the methane rich mixed flow thigh inlet of first order flash tank; The outlet of first order flash tank bottom liquid phases is connected with the 4th choke valve one end, and the 4th choke valve other end connects the methane rich mixed flow thigh inlet of second level flash tank.
10. device according to claim 9, wherein, the first-class heat exchanger end of this first liquid channel from ice chest drawn a pipeline, via the first throttle valve, is connected with a cryogen backward channel in the entering ice chest; This first gas phase channel is drawn a pipeline from the end of final stage heat exchanger, via second choke valve, is connected with above-mentioned cryogen backward channel in the entering ice chest.
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