CN111960435B - Novel ammonia concentration and separation process - Google Patents
Novel ammonia concentration and separation process Download PDFInfo
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- CN111960435B CN111960435B CN202010645945.4A CN202010645945A CN111960435B CN 111960435 B CN111960435 B CN 111960435B CN 202010645945 A CN202010645945 A CN 202010645945A CN 111960435 B CN111960435 B CN 111960435B
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/02—Preparation, purification or separation of ammonia
- C01C1/024—Purification
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/002—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by condensation
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
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- C01C1/02—Preparation, purification or separation of ammonia
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Abstract
The invention discloses a novel ammonia gas concentration and separation process which is mainly characterized in that an independent ammonia gas concentration system is additionally arranged, the synthesis efficiency is improved, the ammonia separation effect is improved, and the synthesis pressure is reduced by reducing the ammonia content in circulating gas, so that the power consumption of a synthetic ammonia system is reduced. The method comprises the following steps: sending the outlet gas of the ammonia synthesis tower or (and) tail gas after ammonia separation of the ammonia separation system into an ammonia gas concentration system; the penetrating gas of the ammonia concentration system is sent to the inlet of a circulating gas compressor, and enters a synthesis tower after being compressed by the circulating compressor; the absorbed ammonia gas is regenerated by using the outlet gas of a circulating compressor or synthetic raw material gas (single component or mixed component), and the regenerated gas rich in ammonia is sent into an ammonia separation system. The method has the characteristics of improving the efficiency of synthesizing the catalyst and effectively reducing the power consumption of the system.
Description
Technical Field
The invention relates to the technical field of synthetic ammonia processes, in particular to a novel ammonia gas concentration and separation process in a synthetic ammonia process technology.
Background
The synthetic ammonia refers to ammonia directly synthesized from nitrogen and hydrogen at high temperature and high pressure in the presence of a catalyst, and is a basic inorganic chemical process. Ammonia is one of the most important basic chemical products, the yield of the ammonia is the first of various chemical products, and the ammonia is also a large household of energy consumption, and about 10 percent of energy in the world is used for producing synthetic ammonia. Ammonia is mainly used in agriculture, and synthetic ammonia is the basis of nitrogen fertilizer industry. China synthetic ammonia output is the first place in the world, and the main trend of the future synthetic ammonia technology development is large-scale, low energy consumption, structure adjustment, clean production and long-period operation.
As shown in fig. 1, in the current production process of synthetic ammonia, ammonia generated by nitrogen and hydrogen under high temperature and high pressure and in the presence of a catalyst is liquefied and separated from ammonia in the gas at the outlet of an ammonia synthesis tower by adopting a cooling and freezing mode. The gas which is not liquefied enters the reactor to continue the reaction after being pressurized by a circulating compressor. And the process is circulated.
In the current ammonia synthesis process, the disadvantages of the ammonia separation process are as follows: (1) the refrigeration system has high power consumption; (2) The circulating gas after ammonia separation contains about 3 percent of ammonia and is circulated back to the reactor, so that the reaction is inhibited from entering towards the positive reaction direction, the ammonia synthesis efficiency is reduced, the amount of the circulating gas is increased, and the power consumption of a circulating compressor is increased.
In recent years, processes related to ammonia separation are also being improved. For example, chinese patent publication nos. CN202289790U and CN103818929A are both directed to optimization of equipment or optimization of cold and heat.
Data disclosed in paragraph 0014 of patent document CN103818929A are used: and (3) taking out the synthesis gas containing 10 to 15 percent of ammonia at the higher temperature of the ammonia synthesis tower. According to the condition of the domestic ammonia synthesis industry at present, the synthesis pressure is generally about 150 to 220 kilograms. Assuming that the synthetic ammonia pressure is 180 kg (18 Mpa), the ammonia content of the circulating gas is 3%, a simple calculation is carried out:
when the ammonia content before the primary ammonia separation is 10%, the temperature at which liquefaction starts is about 45 ℃, and when the temperature continues to decrease to 7 ℃. The ammonia content in the recycle gas is reduced to about 3 percent.
When the ammonia content before the primary ammonia separation is 15%, the temperature at which liquefaction starts is about 61 ℃, and when the temperature continues to decrease to 7 ℃. The ammonia content in the recycle gas is reduced to about 3%.
When the ammonia content before the primary ammonia separation is 20%, the temperature at which liquefaction starts is about 73 ℃, and when the temperature continues to decrease to 7 ℃. The ammonia content in the recycle gas is reduced to about 3%.
When the ammonia content before the primary ammonia separation is 30%, the temperature at which liquefaction starts is about 92 ℃, and when the temperature continues to decrease to 7 ℃. The ammonia content in the recycle gas is reduced to about 3%.
From the above calculation data, it can be found that the higher the ammonia content before the first-stage ammonia separation is performed, the higher the critical temperature at which the liquid ammonia starts to be liquefied from gaseous ammonia. At present, a factory can generally provide circulating water primary cooling gas at about 32 ℃, the ammonia content is improved, most ammonia can be liquefied by using cooling water, and only a small part of ammonia is cooled by refrigerating equipment. Therefore, the refrigerating capacity of the refrigerating equipment can be greatly reduced, and the refrigerating equipment needs to consume a large amount of electric power for cooling.
Disclosure of Invention
In order to overcome the defects of high power consumption of a refrigeration system and high circulation quantity of ammonia gas in circulating gas in the prior art, the invention provides a novel ammonia gas concentration and separation process, which can improve the content of ammonia in gas entering the refrigeration system, can obviously reduce the power consumption of a refrigeration process, reduce the content of ammonia in the circulating gas, obviously improve the ammonia synthesis efficiency, reduce the circulation quantity of the circulating gas and further reduce the power consumption of a circulating compressor.
In order to achieve the purpose, the invention adopts the following technical scheme:
a novel ammonia concentration and separation process is characterized by comprising the following steps:
pre-cooling the outlet gas: cooling the outlet gas of the synthesis tower;
concentration and separation: introducing the cooled outlet gas into a concentration and separation system for concentration and separation of liquid ammonia;
and (3) through gas circulation: the penetrating gas discharged after concentration and separation is compressed by a circulating gas compressor and then returns to the synthesis tower;
wherein, the concentration and separation steps have two schemes:
the first scheme is as follows: 1) Cooling the cooled outlet gas, and separating liquid ammonia; 2) Introducing the cooled and separated tail gas into a concentration system to adsorb ammonia gas in the tail gas and discharging the permeated gas; 3) Introducing the regenerated gas into the concentration system and heating to desorb ammonia gas to obtain ammonia-rich regenerated gas; 4) Mixing the ammonia-rich regenerated gas with the outlet gas of the synthesis tower, cooling and separating, and circulating in the same way;
scheme II: 1) Introducing the outlet gas cooled to below 80 ℃ into a concentration system to adsorb ammonia gas in the outlet gas and discharging the permeated gas; 2) Introducing regeneration gas into the concentration system and heating to desorb ammonia gas to obtain ammonia-rich regeneration gas; 3) Mixing the ammonia-rich regenerated gas with the outlet gas of the synthesis tower for cooling and separation; 4) Mixing the cooled and separated tail gas with the outlet gas, introducing the mixture into a concentration system to adsorb ammonia gas in the mixture, and discharging the permeated gas.
In the above-mentioned scheme, through setting up the tail gas that concentrated system will on the one hand after the ammonia separation through concentrated system entering circulating gas compressor, reduce the ammonia content in the circulating gas, can promote the reaction to go on toward the ammonia synthesis direction during making the ammonia synthesis, on the other hand makes the ammonia content in the gas before getting into the ammonia separation promote, and simultaneously, the ammonia content after the concentration becomes controllable condition, can carry out the control of certain limit according to the adsorption efficiency of adsorbent and the ammonia content of letting in regeneration tolerance after concentrating, consequently, reduce the required refrigeration capacity of ammonia separation, reduce the consumption.
The first scheme adopts concentration after separation, and the gas after ammonia separation is concentrated and then returns to the separation system for separation, so that the ammonia separation efficiency is indirectly improved.
The second scheme adopts the steps of firstly concentrating the outlet gas and then carrying out freeze separation, so that the separation process can be applicable to the low-pressure ammonia synthesis process, the ammonia content of the outlet gas of the ammonia synthesis tower is reduced, the separation is carried out after concentration, the efficiency of the freeze separation cannot be rapidly increased due to the reduction of the ammonia content of the outlet gas, meanwhile, the ammonia content of the circulating gas entering a circulating gas compressor after concentration is lower, the ammonia synthesis reaction can be promoted to be carried out towards the ammonia synthesis direction, and the ammonia conversion rate of the low-pressure ammonia synthesis process is changed and compensated.
Preferably, the ammonia desorption is followed by a cold blowing step, wherein the cold blowing step comprises the following steps: and introducing cold blowing gas to cool the adsorbent.
Preferably, the cold blow gas is one or more of recycle compressor outlet recycle gas and single or mixed component synthesis feed gas.
Preferably, the regeneration gas is one or more of recycle compressor outlet gas or tail gas of a cold blowing process or single-component or mixed-component synthesis feed gas.
Preferably, the concentration system comprises two or more parallel adsorption towers, and an adsorption air inlet pipe, an adsorption air outlet pipe, a hot blowing air inlet pipe, a hot blowing air outlet pipe, a cold blowing air inlet pipe and a cold blowing air outlet pipe which are connected with the adsorption towers through a main pipeline, wherein an adsorption air inlet valve is arranged between the adsorption air inlet pipe and the main pipeline, an adsorption air outlet valve is arranged between the adsorption air outlet pipe and the main pipeline, a hot blowing air inlet valve is arranged between the hot blowing air inlet pipe and the main pipeline, a hot blowing air outlet valve is arranged between the hot blowing air outlet pipe and the main pipeline, a cold blowing air inlet valve is arranged between the cold blowing air inlet pipe and the main pipeline, and a cold blowing air outlet valve is arranged between the cold blowing air outlet pipe and the main pipeline.
Preferably, the concentration system further comprises a secondary air inlet pipe and a middle air outlet pipe, a secondary air inlet valve is arranged between the secondary air inlet pipe and the main pipeline, a middle air outlet valve is arranged between the middle air outlet pipe and the main pipeline, and the adsorption air outlet pipe is communicated with the secondary air inlet pipe through a pipeline.
Preferably, the cold blowing air outlet pipe is communicated with the hot blowing air inlet pipe through a connecting pipeline, and a heater is arranged on the connecting pipeline.
Preferably, the adsorbent packed in the adsorption column has a specific surface area of more than 200m 2 Per g of porous mass. Such as activated alumina, activated carbon, silica gel, molecular sieves, and the like
Preferably, the heating in the desorption process adopts one or more of regeneration gas heating and heating in an adsorption tower.
The beneficial effects of the invention are: (1) the power consumption of the freezing process is obviously reduced; (2) The ammonia content in the recycle gas is reduced, the ammonia synthesis efficiency is improved, and the recycle quantity of the recycle gas is reduced, so that the power consumption of a recycle compressor is reduced.
Drawings
FIG. 1 is a schematic process flow diagram of the prior art;
FIG. 2 is a schematic process flow diagram of example 1 of the present invention;
FIG. 3 is a schematic process flow diagram of example 2 of the present invention;
FIG. 4 is a schematic view of a concentration system according to example 1 of the present invention.
In the figure, G1 is regeneration gas, G2 is ammonia-rich regeneration gas, G3 is tail gas after ammonia separation, and G4 is through gas.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention are clearly explained and illustrated below with reference to the accompanying drawings, but the following embodiments are only preferred embodiments of the present invention, not all embodiments. Based on the embodiments in the implementation, other embodiments obtained by those skilled in the art without any creative effort belong to the protection scope of the present invention.
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary only for explaining the present scheme and are not construed as limiting the scheme of the present invention.
These and other aspects of embodiments of the invention will be apparent with reference to the following description and attached drawings. In the description and drawings, particular embodiments of the invention have been disclosed in detail as being indicative of some of the ways in which the principles of the embodiments of the invention may be practiced, but it is understood that the embodiments of the invention are not limited correspondingly in scope. On the contrary, the embodiments of the invention include all changes, modifications and equivalents coming within the spirit and terms of the claims appended hereto.
In the description of the present invention, it is to be understood that the terms "thickness", "upper", "lower", "horizontal", "top", "bottom", "inner", "outer", "circumferential", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used merely for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., and "a plurality" means one or more unless specifically limited otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "fixed," and the like are to be construed broadly and can include, for example, fixed connections, removable connections, or integral connections, either mechanical or electrical, or communicating with each other; they may be directly connected or indirectly connected through intervening media, or they may be interconnected within two elements or in a relationship where two elements interact with each other unless otherwise specifically limited. The specific meanings of the above terms in the present invention can be understood according to specific situations by those skilled in the art
Example 1:
as shown in fig. 2, a novel ammonia concentration and separation process comprises the following steps:
pre-cooling the gas outlet: cooling the outlet gas of the synthesis tower;
concentration and separation: introducing the cooled outlet gas into a concentration and separation system for concentration and separation of liquid ammonia;
and (3) through air circulation: introducing the concentrated and separated penetrating gas into a circulating gas compressor, compressing and returning the penetrating gas to the synthesis tower;
wherein, the concentration and separation steps are as follows:
1) Introducing the cooled outlet gas into a separation system in the concentration and separation system for cooling and separation to separate liquid ammonia; 2) Introducing the cooled and separated tail gas into a concentration system in a concentration and separation system to adsorb ammonia gas in the tail gas and discharging the permeated gas; 3) Introducing regeneration gas into the concentration system and heating to desorb ammonia gas to obtain ammonia-rich regeneration gas; 4) And mixing the ammonia-rich regenerated gas with the outlet gas of the synthesis tower, cooling and separating, and circulating.
It should be noted that, a waste heat recovery system may be disposed behind the ammonia synthesis tower, and the concentration and separation system includes a concentration system and a separation system, where the separation system employs a freeze separation process, in this embodiment, the separation system includes a pre-cooler, a water condenser, a primary ammonia separator, a heat exchanger, an ammonia condenser and a secondary ammonia separator, and the mixed gas of the outlet gas or the outlet gas and the ammonia-rich regeneration gas first enters the pre-cooler for cooling, then enters the primary ammonia separator through the water condenser to perform ammonia separation on the mixed gas of the outlet gas or the outlet gas and the ammonia-rich regeneration gas, the gas after the primary ammonia separation enters the heat exchanger, and then enters the secondary ammonia separator through the ammonia condenser to perform freeze separation on the gas after the primary ammonia separation, and the gas after the freeze separation is then introduced into the heat exchanger to transfer the residual cold to the gas after the primary ammonia separation, and then the tail gas after the ammonia separation is obtained at the outlet of the heat exchanger.
Then, introducing the tail gas after ammonia separation into a concentration system, wherein the concentration system is a temperature swing adsorption system, and the tail gas after ammonia separation is adsorbed by an adsorbent in an adsorption tower, so that most of ammonia is removed; the unadsorbed penetrating gas comes out from the top of the tower and enters a circulating gas compressor; and regenerating the adsorbed ammonia gas by adopting synthesis gas (single component or mixed component) to form ammonia-rich regenerated gas, mixing the ammonia-rich regenerated gas with the gas at the outlet of the synthesis tower for cooling and separation, simultaneously introducing cold blowing gas into the adsorption tower to cool the adsorbent after desorption and regeneration of the ammonia gas, and circulating the steps. The cold blowing in this example uses a mixed component synthesis feed gas, i.e., a mixed gas of hydrogen and nitrogen, as the cold blowing gas.
Each cycle of the temperature swing adsorption ammonia concentration process comprises the processes of adsorption, hot blowing and cold blowing, and concretely comprises the following steps,
(1) The adsorption process is as follows: and (3) tail gas enters from the bottom of the adsorption tower after ammonia separation, ammonia gas is adsorbed by the adsorbent, and gas which is not adsorbed penetrates out of the adsorption bed from the top of the adsorption tower. The penetrating gas enters a circulating gas compressor.
(2) The hot blowing process comprises the following steps: and (3) heating the regenerated gas, allowing the regenerated gas to enter the adsorption tower from the top of the adsorption tower for adsorption, discharging the regenerated gas from the bottom of the adsorption tower, and heating the adsorbent bed to regenerate the adsorbed ammonia gas. And (4) feeding the ammonia-rich regeneration tail gas into a separation system.
(3) The cold blowing process comprises the following steps: and after the hot blowing process is finished, cold blowing gas enters the adsorption tower from the top of the adsorption tower, is discharged from the bottom of the adsorption tower, and restores the temperature of the adsorbent bed to the normal temperature.
The tail gas of the cold blowing process can be heated to be used as the regenerated gas of the hot blowing process, or directly enter a cooling and freezing ammonia separation system, or directly enter the inlet of a circulating compressor after being cooled, and the technical personnel in the field can determine the regeneration gas according to the actual situation. In this example, the tail gas of the cold blowing process was used as the regeneration gas in the hot blowing process.
The process flow has the advantages that the ammonia content in the recycle gas entering the synthesis tower can be reduced, the ammonia content of tail gas after freezing separation in the prior art is about 3%, the adsorption efficiency of the adsorbent adopted in the embodiment is about 75%, the ammonia content of the penetrating gas discharged by the adsorption system is controlled to be about 0.5%, and the ammonia content of the outlet gas of the synthesis tower is basically unchanged, so that the level of the prior art can reach about 18%, and the ammonia content in the raw material gas is reduced to improve the ammonia conversion rate in the synthesis tower in the ammonia synthesis process. On the other hand, the adoption of the process can reduce the total amount of the circulating gas due to the reduction of the ammonia content in the circulating gas, and reduce the power consumption of a circulating gas compressor.
The second advantage of adopting the above process flow is that the tail gas after the freeze separation is concentrated by a temperature swing adsorption method, the ammonia content after the concentration becomes a controllable condition, the ammonia content after the concentration can be controlled in a certain range according to the adsorption capacity of the adsorbent and the amount of the introduced regeneration gas, the ammonia content of the ammonia-enriched regeneration gas after the ammonia concentration is controlled to be about 40%, the ammonia content is controlled to be 19.3% in the embodiment when the ammonia-enriched regeneration gas is mixed with the outlet gas (the ammonia content is 18%) of the synthesis tower, the ammonia liquefaction rate reaches 39.6% under the action of the condensed water at 35 ℃, while the ammonia liquefaction rate is only 31.8% under the action of the condensed water at 35 ℃ of the synthesis gas with the ammonia content of 18% in the existing process, the process of the invention improves the ammonia liquefaction rate during the primary ammonia separation, thereby reducing the refrigeration amount requiring the secondary ammonia separation, and effectively reducing the power consumption during the cooling separation.
Specifically, as shown in fig. 4, the concentration system includes two or more parallel adsorption towers, in this embodiment, four adsorption towers, i.e., an adsorption tower a, an adsorption tower B, an adsorption tower C and an adsorption tower D, are used, each adsorption tower is connected to an adsorption air inlet pipe 2, an adsorption air outlet pipe 3, a hot blowing air inlet pipe 4, a hot blowing air outlet pipe 5, a cold blowing air inlet pipe 6 and a cold blowing air outlet pipe 7 through respective main pipes (1a \\/1b \/21c \/21d), an adsorption air inlet valve (2a \/2b \/21c \/21d) is provided between the adsorption air inlet pipe and the main pipes, an adsorption air outlet valve (31a \/B \/31c \/31d) is provided between the adsorption air outlet pipe and the main pipes, a hot blowing air inlet valve (41a \/7161b \/51 \/41b \/41d) is provided between the hot blowing air inlet pipe and the main pipes, and a cold blowing air outlet pipe (616161516151b \/6151 \/51 \/514D) are provided between the hot blowing air inlet pipe and the cold blowing air inlet pipe (41a).
Further, the concentration system also comprises a secondary air inlet pipe 9 and a middle air outlet pipe 8, wherein a secondary air inlet valve (91A \, 91B \, 91C \, 91D) is arranged between the secondary air inlet pipe and the main pipeline, a middle air outlet valve (81A \, 81B \, 81C \, 81D) is arranged between the middle air outlet pipe and the main pipeline, and the adsorption air outlet pipe is communicated with the secondary air inlet pipe through a connecting pipeline 11. Because the ammonia synthesis reaction is the conversion process of going on in succession, consequently set up secondary intake pipe and middle outlet duct and set up corresponding valve, will adsorb and pass through the pipeline intercommunication between outlet duct and the secondary intake pipe moreover, can realize the series-parallel connection between four adsorption towers so through the switching of valve. The four adsorption towers are grouped in pairs, wherein two adsorption towers are in the adsorption process, and the other two adsorption towers are in the regeneration process, so that the two groups of adsorption towers can be circularly and alternately used. Specifically, in the adsorption process: the tail gas passes through the absorption intake pipe after the ammonia separation and lets in, adsorption tower A's absorption admission valve is opened, tail gas gets into adsorption tower A and adsorbs after the ammonia separation, adsorption tower A's middle air outlet valve is opened, then gaseous outlet duct in the middle of getting into through adsorption tower A's main line, then open adsorption tower B's secondary admission valve, gaseous secondary intake pipe that lets in through the connecting line to it carries out the secondary absorption to get into adsorption tower B, then adsorption tower B's absorption outlet valve is opened, the penetrating gas after the absorption is discharged through adsorbing the outlet duct.
At this time, the adsorption column C and the adsorption column D are in a regeneration state, and the regeneration process is as follows:
and (3) hot blowing process: and introducing the regenerated gas into a hot blowing air inlet pipe, opening hot blowing air inlet valves of the adsorption tower C and the adsorption tower D, allowing the regenerated gas to enter the adsorption tower C and the adsorption tower D, regenerating the adsorption tower C and the adsorption tower D, desorbing the adsorbed ammonia, opening a hot blowing air valve, and discharging the desorbed ammonia out of the adsorption tower along with the regenerated gas through the hot blowing air valve.
And (3) cold blowing process: after hot blowing is finished, cold blowing gas is introduced into the cold blowing gas inlet pipe, the cold blowing gas inlet valves of the adsorption tower C and the adsorption tower D are opened, the cold blowing gas enters the adsorption tower C and the adsorption tower D to cool the adsorbent bed layers of the adsorption tower C and the adsorption tower D, the cold blowing gas outlet valve is opened, and the cold blowing gas is discharged out of the adsorption tower through the cold blowing gas outlet valve.
In this embodiment, the raw material gas of the combined components is used as the cold blowing gas, and the tail gas after the cold blowing is used as the regeneration gas of the hot blowing, so that the cold blowing process and the hot blowing process are integrated as follows: introducing cold-blowing tail gas of the previous cycle into a hot-blowing gas inlet pipe, opening hot-blowing gas inlet valves of an adsorption tower C and an adsorption tower D, introducing regenerated gas into the adsorption tower C and the adsorption tower D, regenerating the adsorption tower C and the adsorption tower D, desorbing the adsorbed ammonia gas, opening a hot-blowing gas outlet valve, and discharging the desorbed ammonia gas out of the adsorption tower along with the regenerated gas through the hot-blowing gas outlet valve; the synthesis raw material gas of the combined components is introduced into a cold blowing air inlet pipe as cold blowing air, cold blowing air inlet valves of an adsorption tower C and an adsorption tower D are opened, the cold blowing air enters the adsorption tower C and the adsorption tower D, adsorbent beds of the adsorption tower C and the adsorption tower D are cooled, a cold blowing air outlet valve is opened, cold blowing tail gas enters a cold blowing air outlet pipe, and the cold blowing tail gas enters a hot blowing air inlet pipe after passing through a heater 10.
In the process, the adsorption tower A and the adsorption tower B are connected in series, the adsorption tower C and the adsorption tower D are connected in series, the adsorption tower A and the adsorption tower B which are connected in series and the adsorption tower C and the adsorption tower D which are connected in series are connected in parallel, due to the existence of the connecting pipeline, the secondary air inlet pipe and the middle air outlet pipe, the adsorption towers can be grouped in pairs, the adsorption towers are connected in parallel in a group, then the two groups of adsorption towers are connected in parallel, the number and the sequence of the valves are changed, and the repeated description is omitted in the embodiment.
The embodiment has the advantages that (1) the power consumption of the freezing process is obviously reduced; (2) The ammonia content in the circulating gas is reduced, the ammonia synthesis efficiency is improved, and the circulating amount of the circulating gas is reduced, so that the power consumption of a circulating compressor is reduced.
Example 2, the remainder of this example refers to example 1 with the following differences:
as shown in fig. 3, the concentration and separation steps are:
1) Introducing the outlet gas cooled to below 80 ℃ into a concentration system to adsorb ammonia gas in the outlet gas and discharging the permeated gas; 2) Introducing the regenerated gas into the concentration system and heating to desorb ammonia gas to obtain ammonia-rich regenerated gas; 3) Mixing the ammonia-rich regenerated gas with the outlet gas of the synthesis tower for cooling and separation; 4) Mixing the cooled and separated tail gas with the outlet gas, introducing the mixture into a concentration system to adsorb ammonia gas in the mixture, and discharging the permeated gas.
The separation process is applicable to a low-pressure ammonia synthesis process, the ammonia content of the outlet gas of an ammonia synthesis tower is reduced due to the fact that low-pressure ammonia synthesis tends to reduce, the efficiency of the freeze separation cannot be increased rapidly due to the reduction of the ammonia content of the outlet gas after concentration and separation, meanwhile, the ammonia content of the circulating gas entering a circulating gas compressor after concentration is lower, so that the ammonia synthesis reaction can be promoted to be carried out towards the ammonia synthesis direction, and the ammonia conversion rate of the low-pressure ammonia synthesis process is changed and compensated.
The above embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention, and all simple modifications, alterations and equivalents of the above embodiments according to the technical spirit of the present invention are still within the protection scope of the technical solution of the present invention.
Claims (9)
1. The ammonia gas concentration and separation process is characterized by comprising the following steps of:
pre-cooling the outlet gas: cooling the outlet gas of the synthesis tower;
concentration and separation: introducing the cooled outlet gas into a concentration and separation system for concentration and separation of liquid ammonia;
and (3) through air circulation: the penetrating gas discharged after concentration and separation is compressed by a circulating gas compressor and then returns to the synthesis tower;
wherein, the concentration and separation steps have two schemes:
the first scheme is as follows: 1) Cooling the cooled outlet gas, and separating liquid ammonia; 2) Introducing the cooled and separated tail gas into a concentration system to adsorb ammonia gas in the tail gas and discharging the permeated gas; 3) Introducing regeneration gas into the concentration system and heating to desorb ammonia gas to obtain ammonia-rich regeneration gas; 4) Mixing the ammonia-rich regenerated gas with the outlet gas of the synthesis tower, cooling and separating, and circulating in this way;
scheme two is as follows: 1) Introducing the cooled outlet gas into a concentration system to adsorb ammonia gas in the outlet gas and discharging the permeated gas; 2) Introducing regeneration gas into the concentration system and heating to desorb ammonia gas to obtain ammonia-rich regeneration gas; 3) Mixing the ammonia-rich regenerated gas with the outlet gas of the synthesis tower for cooling and separation; 4) Mixing the cooled and separated tail gas with the outlet gas, introducing the mixture into a concentration system to adsorb ammonia gas in the mixture, and discharging the permeated gas.
2. The ammonia gas concentration and separation process as claimed in claim 1, wherein a cold blowing step is further provided after ammonia gas desorption, and the cold blowing step comprises the following steps: and introducing cold blowing gas to cool the adsorbent.
3. The process of claim 2, wherein the cold blow gas is one or more of recycle gas from a recycle compressor and a single-component or mixed-component synthesis feed gas.
4. The ammonia concentration and separation process of claim 1, wherein the regeneration gas is one or more of recycle compressor outlet gas, tail gas of a cold blowing process, or single-component or mixed-component synthesis feed gas.
5. The ammonia gas concentration and separation process according to claim 1, wherein the concentration system comprises two or more parallel adsorption towers, and an adsorption air inlet pipe, an adsorption air outlet pipe, a hot blowing air inlet pipe, a hot blowing air outlet pipe, a cold blowing air inlet pipe and a cold blowing air outlet pipe which are connected with the adsorption towers through a main pipeline, wherein an adsorption air inlet valve is arranged between the adsorption air inlet pipe and the main pipeline, an adsorption air outlet valve is arranged between the adsorption air outlet pipe and the main pipeline, a hot blowing air inlet valve is arranged between the hot blowing air inlet pipe and the main pipeline, a hot blowing air outlet valve is arranged between the hot blowing air outlet pipe and the main pipeline, a cold blowing air inlet valve is arranged between the cold blowing air inlet pipe and the main pipeline, and a cold blowing air outlet valve is arranged between the cold blowing air outlet pipe and the main pipeline.
6. The ammonia gas concentration and separation process according to claim 5, wherein the concentration system further comprises a secondary air inlet pipe and a middle air outlet pipe, a secondary air inlet valve is arranged between the secondary air inlet pipe and the main pipeline, a middle air outlet valve is arranged between the middle air outlet pipe and the main pipeline, and the adsorption air outlet pipe is communicated with the secondary air inlet pipe through a connecting pipeline.
7. The ammonia gas concentrating and separating process as claimed in claim 5, wherein the cold blowing gas outlet pipe is communicated with the hot blowing gas inlet pipe through a connecting pipeline, and a heater is arranged on the connecting pipeline.
8. The process for concentrating and separating ammonia gas as claimed in claim 5, wherein the adsorbent filled in the adsorption tower has a specific surface area of more than 200m 2 Per g of porous mass.
9. The ammonia gas concentrating and separating process as claimed in claim 1, wherein the heating in the desorption process is one or more of regeneration gas heating and heating in an adsorption tower.
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