CN110772986A - Melamine tail gas purification method, melamine tail gas purification device and application thereof - Google Patents
Melamine tail gas purification method, melamine tail gas purification device and application thereof Download PDFInfo
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- CN110772986A CN110772986A CN201911212029.5A CN201911212029A CN110772986A CN 110772986 A CN110772986 A CN 110772986A CN 201911212029 A CN201911212029 A CN 201911212029A CN 110772986 A CN110772986 A CN 110772986A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- 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
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8621—Removing nitrogen compounds
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
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- B01D2259/65—Employing advanced heat integration, e.g. Pinch technology
Abstract
The invention provides a melamine tail gas purification method, a melamine tail gas purification device and application thereof, and relates to the technical field of chemical industry, wherein the melamine tail gas purification method comprises the following steps: and purifying and decomposing the mixture of the melamine tail gas and the water to obtain the purified melamine tail gas. The method is simple and convenient to operate and easy to realize, corrosive media in the melamine tail gas are decomposed, the problem of corrosion is solved, and the purified melamine tail gas obtained after decomposition mainly contains ammonia and carbon dioxide, so that the follow-up treatment is facilitated.
Description
Technical Field
The invention relates to the technical field of chemical industry, in particular to a melamine tail gas purification method, a melamine tail gas purification device and application thereof.
Background
The global melamine production per year is about 200 ten thousand tons, and the tail gas production is about 400 ten thousand tons, so from the aspects of recycling economy and environmental protection, the melamine tail gas needs to be recycled, and NH in the melamine tail gas is recycled
3And CO
2. In the prior art, tail gas is directly used for producing other products, however, a small amount of unreacted substances and byproducts, such as byproducts containing isocyanic acid and cyanuric acid, and the like, especially isocyanic acid contained in the tail gas, are extremely strong in acidity, volatility and corrosiveness in an aqueous solution, if the tail gas of melamine is used for fertilizers such as compound fertilizers, plant growth is influenced, and if the tail gas of melamine is used for urea production, corrosion of a urea system is caused, and utilization of the tail gas is limited.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
The invention aims to provide a method for purifying melamine tail gas, which is simple and convenient to operate and easy to realize, corrosive media in the melamine tail gas are decomposed, the problem of corrosivity is solved, and the purified melamine tail gas obtained after decomposition mainly contains ammonia gas and carbon dioxide, so that the follow-up treatment is facilitated.
The invention provides a melamine tail gas purification method, which comprises the following steps:
and purifying and decomposing the mixture of the melamine tail gas and the water to obtain the purified melamine tail gas.
Further, the temperature of the melamine tail gas is 80-220 ℃;
preferably, the pressure of the melamine off-gas is between 0.2 and 10 MPa;
preferably, the temperature of the purification decomposition is 200-400 ℃;
preferably, the purification decomposition is carried out under the catalytic action of a catalyst;
preferably, the catalyst comprises at least one of a cobalt-based catalyst, an iron-based catalyst, and a titanium-based catalyst;
preferably, the temperature for purifying the decomposed melamine tail gas is 200-400 ℃;
preferably, the pressure of the purified and decomposed melamine tail gas is 0.2-1 MPa;
preferably, the clean decomposition is carried out in a fixed bed reactor.
Further, heating the mixture of the melamine tail gas and the water and then performing the purification decomposition;
preferably, the heating temperature is 200-400 ℃;
preferably, the heating means comprises molten salt heating and/or electric heating, preferably molten salt heating;
preferably, said heating is carried out after preheating said mixture of melamine tail gas and water;
preferably, the temperature of the mixture of melamine tail gas and water after preheating is 150-280 ℃.
Further, the mixture of the melamine tail gas and the water is preheated by using the product after the purification and decomposition to obtain the purified melamine tail gas;
preferably, the temperature of the cleaned melamine off-gas is between 80 and 200 ℃.
Further, the water is water vapor, and the mass ratio of the melamine tail gas to the water vapor is 10-1000: 1.
a melamine tail gas cleanup unit comprising:
a clean-up decomposer comprising a melamine off-gas inlet and a melamine off-gas outlet;
wherein, water and melamine tail gas enter the purification decomposer from the melamine tail gas inlet for purification and decomposition to obtain purified melamine tail gas;
preferably, the clean-up decomposer comprises a fixed bed reactor;
preferably, the fixed bed reactor comprises a multilayer fixed bed reactor.
Further, still include:
the tail gas heater comprises a mixed gas inlet and a mixed gas outlet, and the mixed gas outlet is communicated with the melamine tail gas inlet;
preferably, the tail gas heater comprises a molten salt heater and/or an electric heater, preferably a molten salt heater.
Further, still include:
the tail gas heat exchanger comprises a cold medium inlet and a cold medium outlet, and the cold medium outlet is communicated with the mixed gas inlet;
preferably, the tail gas heat exchanger comprises a shell and tube heat exchanger;
preferably, the shell and tube heat exchanger comprises a single-tube-pass heat exchanger and/or a single-shell-pass heat exchanger;
preferably, the tail gas heat exchanger is formed by overlapping two devices.
Further, the tail gas heat exchanger also comprises a heat medium inlet and a heat medium outlet, and the heat medium inlet is communicated with the melamine tail gas outlet.
Use of a device as described above for the purification of melamine off-gas.
Compared with the prior art, the invention can at least obtain the following beneficial effects:
according to the invention, the melamine tail gas is innovatively purified and decomposed to remove corrosive media (such as isocyanic acid, cyanuric acid and the like) in the melamine tail gas, raw materials (such as urea and the like) which are not completely reacted during the production of melamine can be decomposed into carbon dioxide and ammonia gas, so that the main components in the purified melamine tail gas obtained after purification and decomposition are changed into carbon dioxide and ammonia gas without substances such as isocyanic acid and the like, and the problem of corrosion of isocyanic acid on the post-processing of the tail gas is solved; in addition, since the main components of the melamine off-gas itself are also ammonia and carbon dioxide, the medium components in the melamine off-gas after decomposition become simple, and the post-treatment, for example, return to a urea plant or ammonia-carbon separation, becomes easier. Moreover, the melamine tail gas purification method has the advantages of simple flow, stable operation and lower cost.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a schematic view showing the construction of an apparatus for purifying melamine off-gas in one embodiment of the present invention;
fig. 2 is a schematic view showing the construction of an apparatus for purifying melamine off-gas in another embodiment of the present invention;
fig. 3 is a schematic view showing the construction of an apparatus for purifying melamine off-gas in another embodiment of the present invention;
fig. 4 is a schematic view showing the construction of an apparatus for purifying melamine off-gas in another embodiment of the present invention.
Icon: 100-a clean decomposer; 110-melamine tail gas inlet; 120-melamine off-gas outlet; 200-a tail gas heater; 210-a mixed gas inlet; 220-mixed gas outlet; 300-a tail gas heat exchanger; 310-cold medium inlet; 320-a cold medium outlet; 330-heat medium inlet; 340-heat medium outlet.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
In one aspect of the present invention, there is provided a method for purifying melamine off-gas, comprising:
and purifying and decomposing the mixture of the melamine tail gas and the water to obtain the purified melamine tail gas.
According to the invention, the melamine tail gas is innovatively purified and decomposed to remove corrosive media (such as isocyanic acid, cyanuric acid and the like) in the melamine tail gas, raw materials (such as urea and the like) which are not completely reacted during the production of melamine can be decomposed into carbon dioxide and ammonia gas, so that the main components in the purified melamine tail gas obtained after purification and decomposition are changed into carbon dioxide and ammonia gas without substances such as isocyanic acid and the like, and the problem of corrosion of isocyanic acid on the post-processing of the tail gas is solved; in addition, since the main components of the melamine off-gas itself are also ammonia and carbon dioxide, the medium components in the melamine off-gas after decomposition become simple, and the post-treatment, for example, return to a urea plant or ammonia-carbon separation, becomes easier. Moreover, the melamine tail gas purification method has the advantages of simple flow, stable operation and lower cost.
It is to be noted that melamine is also called melamine, and that melamine off-gas refers to off-gas resulting from the production of melamine, and that urea (CO (NH) is used in the present invention
2)
2) Production of melamine (C)
3H
6N
6) The specific equation is as follows:
CO(NH
2)
2→C
3H
6N
6+6NH
3+3CO
2
the production of melamine is accompanied by the production of byproducts isocyanic acid and cyanuric acid, so that the melamine tail gas contains ammonia, carbon dioxide, isocyanic acid and cyanuric acid, unreacted urea and the like; NH in melamine tail gas
3And CO
2Can be used for producing urea, ammonium nitrate, compound fertilizer, sodium carbonate and other products.
In some embodiments of the invention, the temperature of the purification decomposition is 200-. With respect to the above temperature range, when the temperature of the purification decomposition is too low, the decomposition efficiency is lowered, and when the temperature of the purification decomposition is too high, energy is wasted and new by-products are generated by the reaction.
In some embodiments of the invention, the purification decomposition is carried out under catalysis by a catalyst comprising at least one of a cobalt-based catalyst, an iron-based catalyst, and a titanium-based catalyst. This makes the effect of purification and decomposition better.
In some embodiments of the invention, the clean decomposition is carried out in a fixed bed reactor. Therefore, the gas from the fixed bed reactor can not carry the catalyst out, a separation system is not needed, and the process is simple.
In some embodiments of the invention, the temperature of the melamine tail gas is from 80 to 220 ℃ (e.g., 80 ℃, 100 ℃, 120 ℃, 140 ℃, 160 ℃, 180 ℃, 200 ℃, or 220 ℃, etc.) and the pressure of the melamine tail gas is from 0.2 to 10MPa (e.g., 0.2MPa, 1MPa, 3MPa, 5MPa, 7MPa, 9MPa, or 10MPa, etc.). Therefore, the temperature and the pressure of the melamine tail gas are proper, and the subsequent purification and decomposition are facilitated.
In some embodiments of the present invention, the temperature of the purified and decomposed melamine tail gas is 200-400 ℃ (for example, 200 ℃, 220 ℃, 240 ℃, 260 ℃, 280 ℃, 300 ℃, 350 ℃ or 400 ℃ and the like), and the pressure of the purified and decomposed melamine tail gas is 0.2-1MPa (for example, 0.2MPa, 0.4MPa, 0.6MPa, 0.8MPa or 1MPa and the like).
In some embodiments of the invention, the purification decomposition is performed after heating the mixture of melamine tail gas and water at a temperature of 200-400 ℃ (e.g., 200 ℃, 220 ℃, 240 ℃, 260 ℃, 280 ℃, 300 ℃, 350 ℃, 400 ℃, etc.). Therefore, the subsequent purification decomposition is more favorably carried out.
In some embodiments of the invention, the heating comprises molten salt heating and/or electrical heating, preferably molten salt heating. Therefore, the heating effect is better.
In some embodiments of the invention, the heating is performed by preheating the mixture of melamine tail gas and water, which after preheating has a temperature of 150 ℃ and 280 ℃ (e.g., can be 150 ℃, 170 ℃, 210 ℃, 230 ℃, 250 ℃, 270 ℃, or 280 ℃, etc.). Thereby facilitating subsequent heating.
It is to be noted that the temperature of the melamine off-gas after preheating is lower than the temperature of the melamine off-gas after heating and will not be described in any greater detail here.
In some embodiments of the invention said pre-heating of said mixture of melamine tail gas and water with products of said purified decomposition results in said purified melamine tail gas. Therefore, the waste heat of the purified and decomposed melamine tail gas is fully utilized, the energy consumption is saved, the temperature of the preheated melamine tail gas is reduced, and the follow-up treatment is facilitated.
It is understood that the purification of the products of decomposition refers to the purification of the products of decomposition of melamine off-gas, the main constituents comprising carbon dioxide and ammonia.
In some embodiments of the invention the temperature of the cleaned melamine tail gas is between 80 and 200 ℃ (for example it may be 80 ℃, 100 ℃, 120 ℃, 150 ℃, 160 ℃, 180 ℃, or 200 ℃ etc.). Thereby, the temperature requirements of the subsequent treatment are met.
In some embodiments of the invention, the water is water vapor and the mass ratio of melamine tail gas to water vapor is from 10 to 1000: 1 (e.g., 10: 1, 20: 1, 50: 1, 100: 1, 200: 1, 300: 1, 400: 1, 500: 1, 600: 1, 700: 1, 800: 1, 900: 1, 1000: 1, etc.). Therefore, the corrosive medium in the melamine tail gas can be sufficiently decomposed, so that the problem of the corrosion of the melamine tail gas can be solved.
In another aspect of the present invention, the present invention provides a melamine off-gas purifying apparatus, which, referring to fig. 1, comprises:
a clean-up decomposer 100, said clean-up decomposer 100 comprising a melamine off-gas inlet 110 and a melamine off-gas outlet 120;
wherein, water and melamine tail gas enter the purification decomposer 100 from the melamine tail gas inlet 110 for purification and decomposition to obtain purified melamine tail gas.
It should be noted that the parameters and conditions in the purification decomposer are consistent with those of the purification decomposer described above, and are not described in detail herein.
In some embodiments of the invention, the clean decomposer comprises a fixed bed reactor. Therefore, the gas from the fixed bed reactor can not carry the catalyst out, a separation system is not needed, and the process is simple.
In some embodiments of the invention, the fixed bed reactor comprises a multi-layer fixed bed reactor. Therefore, the purifying and decomposing effect is better.
In some embodiments of the invention, referring to fig. 2, the apparatus further comprises:
a tail gas heater 200, wherein the tail gas heater 200 comprises a mixed gas inlet 210 and a mixed gas outlet 220, and the mixed gas outlet 220 is communicated with the melamine tail gas inlet 110. Thus, the preheating of the melamine tail gas and the water facilitates the subsequent purification decomposition.
It should be noted that the mixture of melamine tail gas and water is heated in the tail gas heater, the mixture of melamine tail gas and water enters the tail gas heater from the mixed gas inlet, the heated mixture of melamine tail gas and water is discharged from the mixed gas outlet, and the parameters and conditions in the tail gas heater are consistent with the heating described above, and are not described in detail herein.
In some embodiments of the invention, the tail gas heater comprises a molten salt heater and/or an electric heater. Therefore, the heating effect is better. In some preferred embodiments of the invention, the tail gas heater is a molten salt heater. Therefore, the tail gas heater which takes the special molten salt of the melamine device as the heating medium is convenient to heat and saves energy consumption.
In some embodiments of the invention, the molten salt heater heating can save more than 50% of the heating system investment.
In some embodiments of the invention, referring to fig. 3, the apparatus further comprises:
the tail gas heat exchanger 300 comprises a cold medium inlet 310 and a cold medium outlet 320, and the cold medium outlet 320 is communicated with the mixed gas inlet 210. Thus, the heat exchange of the melamine off-gas in advance facilitates the subsequent heating of the melamine off-gas.
The mixture of the melamine tail gas and the water is preheated in a tail gas heat exchanger, the mixture of the melamine tail gas and the water enters the tail gas heat exchanger from a heat medium inlet, and the preheated mixture of the melamine tail gas and the water flows out from a heat medium outlet; the parameters and conditions in the tail gas heat exchanger are identical to those of the preheating described above and will not be described in any greater detail here.
In some embodiments of the invention, the tail gas heat exchanger comprises a shell and tube heat exchanger, preferably the shell and tube heat exchanger comprises a single-tube-pass heat exchanger and/or a single-shell-pass heat exchanger. Therefore, the heat exchange effect is better.
In some embodiments of the invention, the tail gas heat exchanger is an overlapping arrangement of two devices. Therefore, the occupied area is saved, the length of the connecting pipeline is reduced, and the investment is saved.
In some embodiments of the present invention, referring to fig. 4, the tail gas heat exchanger 300 further comprises a heat medium inlet 330 and a heat medium outlet 340, and the heat medium inlet 330 is communicated with the melamine tail gas outlet 120. Therefore, the waste heat of the purified and decomposed melamine tail gas is fully utilized, the temperature of the tail gas is reduced, and the energy consumption is saved.
It should be noted that the above-mentioned heat medium refers to the medium used for heating, in the present invention, the heat medium refers to the melamine tail gas after purification and decomposition, the above-mentioned cold medium refers to the medium used for heating, in the present invention, the cold medium refers to the mixture of melamine tail gas and water; and the mixture of the melamine tail gas and the water enters the tail gas heat exchanger from the cold medium inlet, the preheated mixture of the melamine tail gas and the water flows out from the cold medium outlet, the gas flowing out of the purification decomposer enters the tail gas heat exchanger from the heat medium inlet, and the gas flows out from the heat medium outlet after heat exchange to obtain the purified melamine tail gas.
In some embodiments of the invention, the purified and decomposed melamine tail gas is used as a heat medium for heat exchange, so that the energy consumption is saved by more than 50% compared with a mode of not adopting the mode for heat exchange.
It should be noted that the above-mentioned components can be communicated with each other by a pipe, for example, the heat medium inlet 330 can be communicated with the melamine off-gas outlet 120 by a pipe arranged between the heat medium inlet 330 and the melamine off-gas outlet 120 to communicate the heat medium inlet 330 with the melamine off-gas outlet 120.
In some embodiments of the invention, the specific process for purifying the melamine decomposition off-gas by means of the above-described apparatus may be as follows:
after being mixed, the melamine tail gas and the water vapor enter the tail gas heat exchanger 300 from the cold medium inlet 310, the melamine tail gas and the water vapor are preheated in the tail gas heat exchanger 300, and the preheated melamine tail gas and the water vapor flow out from the cold medium outlet 320;
the preheated melamine tail gas and the water vapor enter the tail gas heater 200 from the mixed gas inlet 210, the preheated melamine tail gas and the water vapor are heated in the tail gas heater 200, and the heated melamine tail gas and the water vapor flow out from the mixed gas outlet 220;
the heated melamine tail gas and water vapor enter the purification decomposer 100 from a melamine tail gas inlet 110, the unreacted urea, isocyanic acid and other acidic media are purified and decomposed in the purification decomposer 100 to obtain a mixed gas with the main components of ammonia and carbon dioxide, and the mixed gas flows out from a melamine tail gas outlet 120;
the mixed gas flowing out of the purification decomposer 100 enters the tail gas heat exchanger 300 from the heat medium inlet 330 to preheat the melamine tail gas and the water vapor, the temperature of the mixed gas after the preheating is performed is reduced, and the mixed gas is discharged from the heat medium outlet 340 to obtain the purified melamine tail gas.
In a further aspect of the invention, the invention provides the use of a device as described above for the purification of melamine off-gas.
It should be noted that the above applications include, for example, the production of ammonium nitrate by reaction with nitric acid, the return of the tail gas to the urea plant directly, or the return of the tail gas to the urea plant after ammonia-carbon separation, or the production of soda ash or baking soda by reaction with sodium chloride.
Some embodiments of the present invention will be described in detail below with reference to specific examples. The embodiments described below and the features of the embodiments can be combined with each other without conflict.
Examples
Example 1
The melamine tail gas purification method comprises the following steps:
melamine tail gas of a melamine device producing 5 million tons of melamine every year is taken as a raw material, the temperature of the melamine tail gas is 140 ℃, the pressure is 0.4Mpa, water vapor is added to form mixed gas (the mass ratio of the melamine tail gas to the water vapor is 10: 1), the mixed gas is heated by a tail gas heat exchanger and a tail gas heater in sequence,
wherein, in the tail gas preheater, heat exchange is carried out with clean tail gas (the temperature is 300 ℃) from the decomposer, and the temperature of the melamine tail gas and the water vapor is increased to 250 ℃; in the tail gas heater, the temperature of the melamine tail gas and the water vapor is increased to 300 ℃, and the pressure of the heated melamine tail gas and the water vapor is 0.4 Mpa; the heating medium of the heater is molten salt (a mixture of potassium nitrate, sodium nitrate and sodium nitrite);
the gas from the tail gas heater enters a tail gas purification decomposer which is a fixed bed reactor and is internally provided with a catalyst (iron-based catalyst), the melamine tail gas and the water vapor are decomposed into ammonia and carbon dioxide under the action of the catalyst,
the temperature of the gas decomposed from the tail gas purification decomposer is 300 ℃, and the gas returns to the tail gas heat exchanger to preheat the melamine tail gas and the steam, and the clean melamine tail gas with the temperature of 170 ℃ is obtained after preheating.
Example 2
The melamine off-gas purification process was the same as in example 1 except that: the temperature of the melamine tail gas is 140 ℃, the pressure is 0.4MPa, the melamine tail gas contains 1 wt% of isocyanic acid, and the mass of the water vapor accounts for 2% of the mass of the melamine tail gas. The melamine tail gas is heated from 140 ℃ to 300 ℃ by the tail gas heater.
Example 3
The melamine off-gas purification process was the same as in example 1 except that: the decomposition temperature is lowered. The temperature of the melamine off-gas was 140 ℃ and the pressure 0.4MPa, the melamine off-gas containing 1% by weight of isocyanic acid. The mass of water vapor accounts for 2% of the mass of the melamine tail gas. The melamine off-gas is heated from 140 to 200 ℃ in the off-gas heater.
Example 4
The melamine off-gas purification process was the same as in example 1 except that: the tail gas heater adopts electric heating. The temperature of the melamine off-gas was 140 ℃ and the pressure 0.4MPa, the melamine off-gas containing 1% by weight of isocyanic acid. The mass of water vapor accounts for 2% of the mass of the melamine tail gas. The melamine off-gas is heated from 140 to 250 ℃ in an off-gas heat exchanger. The melamine off-gas is heated from 250 to 300 ℃ in the off-gas heater. And cooling the purified and decomposed tail gas from 300 ℃ to 194 ℃ in a tail gas heat exchanger.
Example 5
The melamine off-gas purification process was the same as in example 1 except that: the decomposition temperature increases. The melamine off-gas is heated from 140 to 340 c in the off-gas heat exchanger. The melamine off-gas is heated from 340 c to 400 c in the off-gas heater. And then cooling the purified and decomposed melamine tail gas from 400 ℃ to 208 ℃ in a tail gas heat exchanger.
The energy consumed and the natural gas consumed for each 1 ton of melamine tail gas heater cleaned in examples 1-5 are given in table 1 below:
TABLE 1
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A method for purifying melamine off-gas, comprising:
and purifying and decomposing the mixture of the melamine tail gas and the water to obtain the purified melamine tail gas.
2. Melamine off-gas cleaning process according to claim 1, characterized in that the temperature of the melamine off-gas is 80-220 ℃;
preferably, the pressure of the melamine off-gas is between 0.2 and 10 MPa;
preferably, the temperature of the purification decomposition is 200-400 ℃;
preferably, the purification decomposition is carried out under the catalytic action of a catalyst;
preferably, the catalyst comprises at least one of a cobalt-based catalyst, an iron-based catalyst, and a titanium-based catalyst;
preferably, the temperature for purifying the decomposed melamine tail gas is 200-400 ℃;
preferably, the pressure of the purified and decomposed melamine tail gas is 0.2-1 MPa;
preferably, the clean decomposition is carried out in a fixed bed reactor.
3. A melamine off-gas cleaning process according to claim 1 or 2, characterized in that said cleaning decomposition is carried out after heating said mixture of melamine off-gas and water;
preferably, the heating temperature is 200-400 ℃;
preferably, the heating means comprises molten salt heating and/or electric heating, preferably molten salt heating;
preferably, said heating is carried out after preheating said mixture of melamine tail gas and water;
preferably, the temperature of the mixture of melamine tail gas and water after preheating is 150-280 ℃.
4. A melamine off-gas cleaning process according to claim 3, characterized in that said pre-heating of said mixture of melamine off-gas and water with the products of said cleaning decomposition results in said cleaned melamine off-gas;
preferably, the temperature of the cleaned melamine off-gas is between 80 and 200 ℃.
5. Melamine off-gas cleaning process according to claim 1, 2 or 4, characterized in that the water is water vapour and the mass ratio of melamine off-gas to water vapour is 10-1000: 1.
6. a melamine tail gas purification apparatus, comprising:
a clean-up decomposer comprising a melamine off-gas inlet and a melamine off-gas outlet;
wherein, water and melamine tail gas enter the purification decomposer from the melamine tail gas inlet for purification and decomposition to obtain purified melamine tail gas;
preferably, the clean-up decomposer comprises a fixed bed reactor;
preferably, the fixed bed reactor comprises a multilayer fixed bed reactor.
7. The apparatus of claim 6, further comprising:
the tail gas heater comprises a mixed gas inlet and a mixed gas outlet, and the mixed gas outlet is communicated with the melamine tail gas inlet;
preferably, the tail gas heater comprises a molten salt heater and/or an electric heater, preferably a molten salt heater.
8. The apparatus of claim 7, further comprising:
the tail gas heat exchanger comprises a cold medium inlet and a cold medium outlet, and the cold medium outlet is communicated with the mixed gas inlet;
preferably, the tail gas heat exchanger comprises a shell and tube heat exchanger;
preferably, the shell and tube heat exchanger comprises a single-tube-pass heat exchanger and/or a single-shell-pass heat exchanger;
preferably, the tail gas heat exchanger is formed by overlapping two devices.
9. The apparatus according to claim 8, characterized in that the tail gas heat exchanger further comprises a heat medium inlet and a heat medium outlet, the heat medium inlet being in communication with the melamine tail gas outlet.
10. Use of a device according to any of claims 6-9 for the purification of melamine off-gas.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114768500A (en) * | 2022-04-11 | 2022-07-22 | 四川金象赛瑞化工股份有限公司 | Method for purifying and decomposing dicyandiamide tail gas |
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