CN102620522B - 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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- CN102620522B CN102620522B CN201210065878.4A CN201210065878A CN102620522B CN 102620522 B CN102620522 B CN 102620522B CN 201210065878 A CN201210065878 A CN 201210065878A CN 102620522 B CN102620522 B CN 102620522B
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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 technique that the invention provides a kind of throttling flash distillation dehydrogenation, nitrogen, carbon monoxide and produce liquefied natural gas.Gas after coal based synthetic gas, oven gas and coke-oven gas methanation etc. are except containing methane, also contain nitrogen, hydrogen, carbon monoxide, for obtaining liquefied natural gas, need be removed to a certain degree, could serve 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 just gradually as primary energy, its application expands the aspects such as generating, automobile use gas, industrial gas, city dweller's use gas, chemical industry use gas gradually to, and market demand increases sharply.The defeated method of supplying of traditional natural gas tube is still main flow, but limited by material condition and user distribution, there is quite a few resource cannot carry out pipe long-distance conveying, need to select the mode of liquefaction, change methane into liquid and adopt again means of transportation to be flexibly sent to user terminal.And liquefied natural gas (LNG) volume only has with 1/625 of amount gas volume, can reduce storage and cost of transportation after liquefaction, and can improve the combustion value of unit volume.The development of liquefied natural gas industry, has higher requirement at aspects such as energy consumption, investment and efficiency to natural gas liquefaction and device.
Be rich in methane gas for some, the synthetic natural gas such as, obtaining after coal based synthetic gas and coke-oven gas methanation etc., it forms except methane, also contain nitrogen, hydrogen, carbon monoxide etc., for obtaining highly purified liquefied natural gas, nitrogen wherein, hydrogen, carbon monoxide need be removed to a certain degree, could serve as liquefied natural gas (LNG) product output.
Conventional gas separating method generally has low-temperature liquefaction separation, pressure-variable adsorption and film separation etc. at present, and low-temperature liquefaction isolation technics is applied to this field of natural gas just gradually.The attached flow process that Figure 1 shows that an employing low-temperature liquefaction rectifying separating technology production LNG, comprises that low-temperature liquefaction separates two parts with rectifying; Low-temperature liquefaction provides cold in ice chest, to realize the liquefaction of natural gas by azeotrope; Rectifying separation circuit 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, 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 the method discloses, and thick gas product, after refrigerated separation is fallen most of condensate liquid, enters molecular sieve to remove remaining moisture content and CO
2, after compressor rises to 5.0MPa, cooling and precooling, enter two-stage throttling flash system, to isolate non-gas product.The method is included in normal temperature de-oiling desulfurization under 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, multiple steps such as methanation gas cryogenic liquefying, with no specific disclosure of throttling flash process, it is mainly used in desulfurization, the unstripped gas using 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 and methane component liquefaction is produced to natural gas (LNG) a kind of high methane gas from hydrogen, nitrogen, carbon monoxide (being rich in the gas of methane), 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 technique that the invention provides a kind of throttling flash distillation dehydrogenation, nitrogen, carbon monoxide and produce liquefied natural gas, this technique comprises low-temperature liquefaction operation and throttling flash separation operation two parts, 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, wherein hydrogeneous, nitrogen, the methane-riched gas mixture of CO gas is after ice chest liquefies methane component, enter one-level or two-step throttle, in flash distillation operation, remove nitrogen, hydrogen and carbon monoxide, obtain hydrogen content≤4000ppm (preferably≤3500ppm, more preferably≤3000ppm, further preferably≤2500ppm, further preferably≤2000ppm, especially preferably≤1700ppm, particularly preferably≤1500ppm, most preferably≤1000ppm), and nitrogen content≤8% (preferably≤7%, more preferably≤6%, further preferably≤5%, further preferably≤4%, better≤3%, especially preferably≤2%, particularly preferably≤1.5%, more particularly preferably≤1%, most preferably≤0.5%), carbon monoxide content≤9% (preferably≤8%, more preferably≤7%, further preferably≤6%, further preferably≤5%, better≤4%, better≤3% again, especially preferably≤2%, particularly preferably≤1.5%, more particularly preferably≤1%, most preferably≤0.5%) liquefied natural gas (LNG) product.
Generally, in 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 by a gas phase channel of ice chest, an a specific order (such as final stage, the penultimate stage etc.) heat exchanger that oppositely enters again plate-fin heat exchanger group after choke valve throttling provides cold for heat exchanger, then this vapor phase stream thigh passes through cryogen backward channel, cooling box, first one liquid phase azeotrope enters the first liquid channel of ice chest, in plate-fin heat exchanger group, after being chilled to uniform temperature in advance, draw ice chest, an a specific order that again oppositely enters plate-fin heat exchanger group after choke valve throttling (for example returns to the previous stage of the heat exchanger progression of heat exchanger package for gas phase refrigerant flow thigh, the for example first order, or penultimate stage, or level third from the bottom (when have more than three level time)) heat exchanger provides cold and then converges with the above-mentioned vapor phase stream thigh of azeotrope stream thigh returning from heat exchanger package for heat exchanger package, process cryogen backward channel after converging, cooling box.Low-temperature liquefaction part completes 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 DEG C～-173 DEG C by a gas phase channel of ice chest, after second choke valve throttling to 0.2～0.8MPaA, oppositely enter again heat exchanger package final heat exchanger and provide cold for heat exchanger, first one liquid phase azeotrope enters the first liquid channel of ice chest, be chilled in advance therein approximately-10 DEG C～-80 DEG C, the first order heat exchanger that again enters plate-fin heat exchanger group after first throttle valve throttling to 0.2～0.8MPaA provide for heat exchanger package cold and with the azeotrope stream strand that first-class heat exchanger is returned from plate-fin heat exchanger group be that above-mentioned vapor phase stream thigh converges, process cryogen backward channel after converging, cooling box.
Preferably, described one-level throttling, flash separation flow process adopt a choke valve and two flash tanks.
In the preferred case, in described one-level throttling, in flash separation flow process, the gaseous mixture that is rich in methane is cooled to uniform temperature (general extremely-145 DEG C to-170 DEG C scopes through ice chest, preferably-147 DEG C to-165 DEG C scopes, further preferably-148 DEG C to-162 DEG C of scopes, more preferably-150 DEG C to-160 DEG C scopes) by methane component liquefaction wherein, enter afterwards in ice chest outlet flash tank in inlet temperature, flash distillation under pressure condition, after returning to ice chest re-heat, the part hydrogen rich gas that ice chest outlet flash drum overhead obtains goes out system, flash tank bottom liquid is through the 3rd choke valve throttling to 0.15～1.0MPaA, enter afterwards in first order flash tank and be divided into gas-liquid two-phase, obtain hydrogen from first order flash drum overhead, nitrogen, the mist of carbon monoxide and methane, return after ice chest reclaims cold and go out system, liquefied natural gas is drawn from first order flash tank bottom, obtain LNG product.Gained LNG product has hydrogen content, nitrogen content, the carbon monoxide content in scope defined above.
Preferably, described two-step throttle, flash separation flow process adopt two choke valves and three flash tanks.
In the preferred case, at described two-step throttle, in flash separation flow process, the gaseous mixture that is rich in methane is cooled to uniform temperature (general extremely-145 DEG C to-170 DEG C scopes through ice chest, preferably-147 DEG C to-165 DEG C scopes, further preferably-148 DEG C to-162 DEG C of scopes, more preferably-150 DEG C to-160 DEG C scopes) by methane component liquefaction wherein, enter afterwards in ice chest outlet flash tank in inlet temperature, flash distillation under pressure condition, after returning to ice chest re-heat, the part hydrogen rich gas that ice chest outlet flash drum overhead obtains goes out system, ice chest outlet flash tank bottom liquid is through the 3rd choke valve throttling to 0.3～1.5MPaA, enter gas-liquid separation in first order flash tank, first order flash drum overhead obtains most hydrogen and a small amount of nitrogen, carbon monoxide, methane, after returning to ice chest re-heat, go out system, bottom liquid continues through the 4th choke valve throttling to 0.15～1.0MPaA, enter afterwards in the flash tank of the second level and be divided into gas-liquid two-phase, second level flash drum overhead is mainly contained nitrogen, the mist of carbon monoxide and methane, after returning to ice chest re-heat, go out system, liquefied natural gas is drawn from second level flash tank bottom, obtain LNG product.Gained LNG product has hydrogen content, nitrogen content, the carbon monoxide content in scope defined above.
In order more clearly to understand the present invention, the technical scheme of method of the present invention (or being called technique) is summarized as follows:
1, throttling flash distillation dehydrogenation, nitrogen, carbon monoxide a technique of producing liquefied natural gas, this technique comprises low-temperature liquefaction operation and throttling flash separation operation two parts; 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; Wherein the methane-riched gas mixture of hydrogeneous, nitrogen, CO gas through ice chest by after methane component liquefaction, enter in one-level or two-step throttle, 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 the technique described in above 1, it is characterized in that: hydrogen, nitrogen, the gaseous mixture of the methane rich of carbon monoxide liquefies methane component through ice chest, enter afterwards and in flash tank, remove foreign gas component, liquid phase becomes gas-liquid two-phase through choke valve at the bottom of by flash tank, then enter again and in flash tank, remove foreign gas component, so carry out one-level or two-step throttle, flash distillation, the nitrogen that each flash drum overhead obtains, hydrogen, carbon monoxide and methane return to cooling box system after ice chest re-heat, the liquid-phase product being obtained by final stage flash tank bottom is liquefied natural gas.
3, according to the technique described in above 1 or 2, it is characterized in that: described one-level throttling, flash distillation flow process adopt a throttling arrangement and two flash tanks; Described two-step throttle, flash distillation flow process adopt two throttling arrangements and three flash tanks.
4, according to the technique described in above 3, it is characterized in that
When carrying out one-level throttling, when flash distillation, hydrogen, nitrogen, the gaseous mixture of the methane rich of carbon monoxide liquefies methane component through ice chest, enter previous stage flash tank from the middle part of previous stage flash tank (being ice chest outlet flash tank) afterwards, the top gas phase of previous stage flash tank is returned in ice chest cooling box after re-heat, the liquid phase that previous stage flash tank bottom obtains through after choke valve from after the middle part of one-level flash tank (being first order flash tank) enter in rear one-level flash tank, the top gas phase of rear one-level flash tank is returned in ice chest cooling box after re-heat, the bottom liquid phases of rear one-level flash tank is liquefied natural gas product, or
When carrying out two-step throttle, when flash distillation, hydrogen, nitrogen, the gaseous mixture of the methane rich of carbon monoxide liquefies methane component through ice chest, enter previous stage flash tank from the middle part of previous stage flash tank (being ice chest outlet flash tank) afterwards, the top gas phase of previous stage flash tank is returned in ice chest cooling box after re-heat, the liquid phase that previous stage flash tank bottom obtains through after choke valve from after the middle part of one-level flash tank (being first order flash tank) enter in rear one-level flash tank, the top gas phase of rear one-level flash tank is returned in ice chest cooling box after re-heat, the bottom liquid phases of rear one-level flash tank is after from again, the middle part of one-level flash tank (being second level flash tank) enters again after choke valve in one-level flash tank, again, the top gas phase of one-level flash tank is returned in ice chest cooling box after re-heat, again, the bottom liquid phases of one-level flash tank is liquefied natural gas product.
5, according to the technique described in any one in above 1-4 item, it is characterized in that: in its low-temperature liquefaction operation part, the cold of ice chest is provided or mainly provided by azeotrope by azeotrope; One gas phase refrigerant flow thigh is cooled to uniform temperature by a gas phase channel of ice chest, an a specific order heat exchanger that oppositely enters again plate-fin heat exchanger group after choke valve throttling provides cold for heat exchanger, then this vapor phase stream thigh passes through cryogen backward channel, cooling box; First one liquid phase azeotrope enters the first liquid channel of ice chest, in plate-fin heat exchanger group, after being chilled to uniform temperature in advance, draw ice chest, another a specific order heat exchanger that again oppositely enters plate-fin heat exchanger group after choke valve throttling is that above-mentioned vapor phase stream thigh converges for heat exchanger package provides cold and then flows thigh with the azeotrope returning from heat exchanger package, process cryogen backward channel after converging, cooling box.
According to a second aspect of the invention, the invention provides a kind of throttling flash distillation dehydrogenation, nitrogen, carbon monoxide and produce the device of liquefied natural gas.Be the equipment that said method uses.
In one embodiment, this device comprises an ice chest, three choke valves and two flash tanks,
Wherein, this ice chest comprises:
Liquid phase azeotrope entrance, it is connected with the first liquid channel of ice chest, the end of an a specific order of the heat exchanger of this first liquid channel from ice chest (such as one-level, secondary, three grades etc.) is drawn a pipeline, via first throttle valve, be connected with a cryogen backward channel of ice chest
Gas phase cryogen entrance, it is connected with the first gas phase channel of ice chest, and this first gas phase channel such as, is drawn a pipeline from the end of another a specific order of heat exchanger (one-level, secondary, three grades etc.), via the second choke valve, be connected with above-mentioned cryogen backward channel
The high methane gas import and the methane rich mixed flow thigh outlet that are connected with the second gas phase channel of ice chest, this methane rich mixed flow thigh outlet is connected with the methane rich mixed flow thigh entrance of ice chest outlet flash tank,
With the first mist import and the first mixed gas outlet that the 3rd gas phase channel of ice chest is connected, this mist import is connected with the top gas phase channel of ice chest outlet flash tank,
With the second mist import and the second mixed gas outlet that the 4th gas phase channel of ice chest is connected, 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 entrance, 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 by pipeline, and the 3rd choke valve other end is connected with the methane rich mixed flow thigh entrance of first order flash tank.
Preferably, the first-class heat exchanger end of this first liquid channel from ice chest drawn a pipeline, via first throttle valve, enters in ice chest and is connected with a cryogen backward channel; This first gas phase channel is drawn a pipeline from the end of final heat exchanger, via the second choke valve, enters in ice chest and is connected with above-mentioned cryogen backward channel.
In another embodiment, this device comprises an ice chest, four choke valves and three flash tanks,
Wherein, this ice chest comprises:
Liquid phase azeotrope entrance, it is connected with the first liquid channel of ice chest, the end of an a specific order of the heat exchanger of this first liquid channel from ice chest (such as one-level, secondary, three grades etc.) is drawn a pipeline, via first throttle valve, be connected with a cryogen backward channel of ice chest
Gas phase cryogen entrance, it is connected with the first gas phase channel of ice chest, and this first gas phase channel such as, is drawn a pipeline from the end of another a specific order of heat exchanger (one-level, secondary, three grades etc.), via the second choke valve, be connected with above-mentioned cryogen backward channel
The high methane gas import and the methane rich mixed flow thigh outlet that are connected with the second gas phase channel of ice chest, this methane rich mixed flow thigh outlet is connected with the methane rich mixed flow thigh entrance of ice chest outlet flash tank,
With the first mist import and the first mixed gas outlet that the 3rd gas phase channel of ice chest is connected, this first mist import is connected with the top gas phase channel of ice chest outlet flash tank,
With the second mist import and the second mixed gas outlet that the 4th gas phase channel of ice chest is connected, 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 entrance, 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 by pipeline, the 3rd choke valve other end is connected with the methane rich mixed flow thigh entrance 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 entrance of second level flash tank.
Preferably, the first-class heat exchanger end of this first liquid channel from ice chest drawn a pipeline, via first throttle valve, enters in ice chest and is connected with a cryogen backward channel; This first gas phase channel is drawn a pipeline from the end of final heat exchanger, via the second choke valve, enters in ice chest and is connected with above-mentioned cryogen backward channel.
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, and liquefaction is carried out with separating synchronously, economical reliable;
2, flow process that the present invention adopts is comparatively simple, has saved rectifying column, and operational stability is better, has reduced equipment investment maintenance cost, and the simple operation of start-stop car, simple to operate.
Brief description of the drawings
Fig. 1 is the process chart of prior art; Wherein E1 ' is ice chest, and V1 ', V2 ', V3 ' are choke valve, and T1 ' is rectifying column.
Fig. 2 is one-level throttling flash distillation dehydrogenation nitrogen process chart of the present invention; Wherein E1 is ice chest, and V1, V2, V3 are choke valve, and T1, T2 are flash tank.
Fig. 3 is two-step throttle flash distillation dehydrogenation nitrogen process chart of the present invention; Wherein E1 is ice chest, and V1, V2, V3, V4 are choke valve, and T1, T2, T3 are flash tank.
Detailed description of the invention
Technique of the present invention comprises low-temperature liquefaction operation and throttling flash distillation operation two parts; 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; Wherein the methane-riched gas mixture of hydrogeneous, nitrogen, CO gas through ice chest by after methane component liquefaction, enter in one-level or two-step throttle, 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%.
Low-temperature liquefaction part completes 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 DEG C～-173 DEG C by the first gas phase channel of ice chest, then after second choke valve V2 throttling to 0.3～0.6MPaA, oppositely enters heat exchanger package and provide cold for heat exchanger package.First one liquid phase azeotrope enters the first liquid channel of ice chest E1, be chilled in advance therein approximately-10 DEG C～-80 DEG C, be that cooled above-mentioned vapor phase stream thigh converges and oppositely enters previous stage heat exchanger and provides cold for heat exchanger package with first-class heat exchanger is returned from plate-fin heat exchanger group azeotrope stream strand after first throttle valve V1 throttling to 0.2～0.8MPaA.
Low-temperature liquefaction part in two-step throttle, flash distillation flow process and one-level throttling, flash distillation flow process are identical.The low-temperature liquefaction part of two-step throttle, flash distillation flow process also completes in ice chest E1.With reference to accompanying drawing 3, one gas phase refrigerant flow thigh is cooled to-148 DEG C～-173 DEG C by the first gas phase channel of ice chest, then after second choke valve V2 throttling to 0.2～0.8MPaA, oppositely enters heat exchanger package and provide cold for heat exchanger package.First one liquid phase azeotrope enters the first liquid channel of ice chest, be chilled in advance therein approximately-10 DEG C～-80 DEG C, be that above-mentioned cooled vapor phase stream thigh converges and oppositely enters previous stage heat exchanger and provides cold for heat exchanger package with first-class heat exchanger is returned from plate-fin heat exchanger group azeotrope stream strand after first throttle valve V1 throttling to 0.2～0.8MPaA.
Referring to accompanying drawing 2, illustrate that one-level throttling, flash separation flow process are as follows:
The gaseous mixture (unstripped gas) that is rich in methane is cooled to uniform temperature (general extremely-145 DEG C to-170 DEG C scopes through ice chest E1 the second gas phase channel, preferably-147 DEG C to-165 DEG C scopes, further preferably-148 DEG C to-162 DEG C of scopes, more preferably-150 DEG C to-160 DEG C scopes) by methane component liquefaction wherein, enter afterwards in ice chest outlet flash tank T1 in inlet temperature, flash distillation under pressure, after returning to ice chest E1 the 3rd gas phase channel re-heat, the part hydrogen rich gas (the 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, enter afterwards in first order flash tank T2 and be divided into gas-liquid two-phase, obtain hydrogen from first order flash tank T2 top, nitrogen, the mist (the second gaseous mixture) of carbon monoxide and methane, return after ice chest E1 the 4th gas phase channel reclaims cold and go out system, liquefied natural gas is drawn from first order flash tank T2 bottom, obtain LNG product.Gained LNG product has hydrogen content, nitrogen content, the carbon monoxide content in scope defined above.
Referring to accompanying drawing 3, illustrate that two-step throttle, flash separation flow process are as follows:
The gaseous mixture (unstripped gas) that is rich in methane is cooled to uniform temperature (general extremely-145 DEG C to-170 DEG C scopes through ice chest E1 the second gas phase channel, preferably-147 DEG C to-165 DEG C scopes, further preferably-148 DEG C to-162 DEG C of scopes, more preferably-150 DEG C to-160 DEG C scopes) by methane component liquefaction wherein, enter afterwards in ice chest outlet flash tank T1 in inlet temperature, flash distillation under pressure condition, after returning to ice chest E1 the 3rd gas phase channel re-heat, the part hydrogen rich gas (the 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, enter gas-liquid separation in first order flash tank T2, first order flash tank T2 top obtains most hydrogen and a small amount of nitrogen, carbon monoxide, methane (the second gaseous mixture), after returning to ice chest E1 the 4th gas phase channel re-heat, go out system, bottom liquid continues through the 4th choke valve V4 throttling to 0.15～1.0MPaA, enter afterwards in the flash tank T3 of the second level and be divided into gas-liquid two-phase, nitrogen is mainly contained at flash tank T3 top, the second level, the mist (the 3rd gaseous mixture) of carbon monoxide and methane, after returning to ice chest E1 the 5th gas phase channel re-heat, go out system, liquefied natural gas is drawn from second level flash tank T3 bottom, obtain LNG product.Gained LNG product has hydrogen content, nitrogen content, the carbon monoxide content in scope defined above.
Claims (3)
1. throttling flash distillation dehydrogenation, nitrogen, carbon monoxide a technique of producing liquefied natural gas, this technique comprises low-temperature liquefaction operation and throttling flash separation operation two parts, 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, wherein the methane-riched gas mixture of hydrogeneous, nitrogen, CO gas through ice chest by after methane component liquefaction, enter in one-level or two-step throttle, 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%, hydrogen, nitrogen, the gaseous mixture of the methane rich of carbon monoxide liquefies methane component through ice chest, enter afterwards and in flash tank, remove foreign gas component, liquid phase becomes gas-liquid two-phase through choke valve at the bottom of by flash tank, then enter again and in flash tank, remove foreign gas component, so carry out one-level or two-step throttle, flash distillation, the nitrogen that each flash drum overhead obtains, hydrogen, carbon monoxide and methane return to cooling box system after ice chest re-heat, the liquid-phase product being obtained by final stage flash tank bottom is liquefied natural gas, wherein one-level throttling, flash separation flow process adopts choke valve and two flash tanks and two-step throttle, flash separation flow process adopts two choke valves and three flash tanks,
In described one-level throttling, in flash separation flow process, the gaseous mixture that is rich in methane is cooled to-145 DEG C of temperature to-170 DEG C of scopes by methane component liquefaction wherein through ice chest, enter afterwards in ice chest outlet flash tank in inlet temperature, flash distillation under pressure condition, after returning to ice chest re-heat, the part hydrogen rich gas that ice chest outlet flash drum overhead obtains goes out system, flash tank bottom liquid is through the 3rd choke valve throttling to 0.15～1.0MPaA, enter afterwards in first order flash tank and be divided into gas-liquid two-phase, obtain hydrogen from first order flash drum overhead, nitrogen, the mist of carbon monoxide and methane, return after ice chest reclaims cold and go out system, liquefied natural gas is drawn from first order flash tank bottom, obtain LNG product, gained LNG product has the hydrogen content in scope defined above, nitrogen content, carbon monoxide content,
At described two-step throttle, in flash separation flow process, the gaseous mixture that is rich in methane is cooled to-145 DEG C of temperature to-170 DEG C of scopes by methane component liquefaction wherein through ice chest, enter afterwards in ice chest outlet flash tank in inlet temperature, flash distillation under pressure condition, after returning to ice chest re-heat, the part hydrogen rich gas that ice chest outlet flash drum overhead obtains goes out system, ice chest outlet flash tank bottom liquid is through the 3rd choke valve throttling to 0.3～1.5MPaA, enter gas-liquid separation in first order flash tank, first order flash drum overhead obtains most hydrogen and a small amount of nitrogen, carbon monoxide, methane, after returning to ice chest re-heat, go out system, bottom liquid continues through the 4th choke valve throttling to 0.15～1.0MPaA, enter afterwards in the flash tank of the second level and be divided into gas-liquid two-phase, second level flash drum overhead is mainly contained nitrogen, the mist of carbon monoxide and methane, after returning to ice chest re-heat, go out system, liquefied natural gas is drawn from second level flash tank bottom, obtain LNG product.
2. technique according to claim 1, is characterized in that: in its low-temperature liquefaction operation part, the cold of ice chest is provided or mainly provided by azeotrope by azeotrope; One gas phase refrigerant flow thigh is cooled to uniform temperature by a gas phase channel of ice chest, an a specific order heat exchanger that oppositely enters again plate-fin heat exchanger group after choke valve throttling provides cold for heat exchanger, then this vapor phase stream thigh passes through cryogen backward channel, cooling box; First one liquid phase azeotrope enters the first liquid channel of ice chest, in plate-fin heat exchanger group, after being chilled to uniform temperature in advance, draw ice chest, another a specific order heat exchanger that again oppositely enters plate-fin heat exchanger group after choke valve throttling is that above-mentioned vapor phase stream thigh converges for heat exchanger package provides cold and then flows thigh with the azeotrope returning from heat exchanger package, process cryogen backward channel after converging, cooling box.
3. according to the technique of claim 1 or 2, wherein obtain hydrogen content≤2000ppm, nitrogen content≤4%, the liquefied natural gas product of carbon monoxide≤6%.
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| CN103292574B (en) * | 2013-05-02 | 2016-03-02 | 上海交通大学 | Utilize the device and method of decompressor direct liquefaction pipe natural gas |
| CN104263443B (en) * | 2014-09-19 | 2018-01-09 | 北京安珂罗工程技术有限公司 | A kind of method and system of the separation of nitrogen from liquefied natural gas |
| CN108444214A (en) * | 2018-03-09 | 2018-08-24 | 中科瑞奥能源科技股份有限公司 | Dehydrogenation of isobutane technique and system |
| CN112284038B (en) * | 2020-10-10 | 2021-11-05 | 杭州中泰深冷技术股份有限公司 | Mixed refrigerant refrigeration type cold box separation device for alkane dehydrogenation and method thereof |
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| US3964891A (en) * | 1972-09-01 | 1976-06-22 | Heinrich Krieger | Process and arrangement for cooling fluids |
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| CN202599015U (en) * | 2012-03-13 | 2012-12-12 | 新地能源工程技术有限公司 | A device capable of removing hydrogen and nitrogen through throttling and flash and producing liquefied natural gas |
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| US3964891A (en) * | 1972-09-01 | 1976-06-22 | Heinrich Krieger | Process and arrangement for cooling fluids |
| CN1935956A (en) * | 2006-10-19 | 2007-03-28 | 杜文广 | Method for producing liquefied natural gas from coke oven gas by cryogenic separation |
| CN101805648A (en) * | 2010-04-15 | 2010-08-18 | 成都和士通低温科技有限责任公司 | Process method for preparing LNG from coke oven tail gas |
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