CN211159295U - Melamine tail gas purifying device - Google Patents
Melamine tail gas purifying device Download PDFInfo
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- CN211159295U CN211159295U CN201922121457.9U CN201922121457U CN211159295U CN 211159295 U CN211159295 U CN 211159295U CN 201922121457 U CN201922121457 U CN 201922121457U CN 211159295 U CN211159295 U CN 211159295U
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Abstract
The utility model provides a melamine tail gas purification device relates to chemical industry technical field, and melamine tail gas purification device includes: a clean-up decomposer comprising a melamine off-gas inlet and a melamine off-gas outlet; and 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. The device simple structure, the medium that has corrosivity in the melamine tail gas is decomposed in purifying the resolver, has solved the corrosivity problem, and the main component is ammonia and carbon dioxide in the purification melamine tail gas that obtains after the decomposition, the subsequent processing of being convenient for.
Description
Technical Field
The utility model belongs to the technical field of the chemical industry technique and specifically relates to a melamine tail gas cleanup unit is related to.
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 recycled3And CO2. 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 this, the present invention is especially provided.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to provide a melamine tail gas purification device, the device simple structure, the medium that has corrosivity among the melamine tail gas is decomposed in purifying the ware that decomposes, has solved the corrosivity problem, decomposes the melamine tail gas of the purification that the back obtained in principal ingredients be ammonia and carbon dioxide, the subsequent processing of being convenient for.
In a first aspect, an embodiment of the present invention provides a melamine tail gas purification device, include:
a clean-up decomposer comprising a melamine off-gas inlet and a melamine off-gas outlet;
and 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.
In an alternative embodiment, the clean-up decomposer comprises a fixed bed reactor.
In an alternative embodiment, the method further comprises:
and 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.
In an alternative embodiment, the tail gas heater comprises a molten salt heater and/or an electric heater.
In an alternative embodiment, the tail gas heater is a molten salt heater.
In an alternative embodiment, the method further comprises:
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.
In an alternative embodiment, the tail gas heat exchanger comprises a shell and tube heat exchanger.
In an alternative embodiment, the shell and tube heat exchanger comprises a single-pass heat exchanger and/or a single-shell-pass heat exchanger.
In an alternative embodiment, the tail gas heat exchanger is an overlapping arrangement of two devices.
In an alternative embodiment, 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.
Compared with the prior art, the utility model discloses can gain following beneficial effect at least:
the utility model discloses utilize purification decomposer to purify and decompose melamine tail gas innovatively to get rid of the corrosive medium (such as isocyanic acid and cyanuric acid etc.) in the melamine tail gas, can also decompose into carbon dioxide and ammonia with the raw materials (such as urea etc.) that do not react completely when producing melamine, and then make the principal ingredients in the purification melamine tail gas of obtaining after the purification decomposition become carbon dioxide and ammonia and do not contain substances such as isocyanic acid, solved the corrosion problem of isocyanic acid to the post-processing of back tail gas; 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.
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 embodiments or the technical solutions in 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 for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic view showing the structure of an apparatus for purifying melamine off-gas according to an embodiment of the present invention;
FIG. 2 is a schematic view showing the structure of an apparatus for purifying melamine off-gas according to another embodiment of the present invention;
FIG. 3 is a schematic view showing the structure of an apparatus for purifying melamine off-gas according to another embodiment of the present invention;
fig. 4 is a schematic view showing the structure of an apparatus for purifying melamine off-gas according to 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 embodiments of the present invention will be clearly and completely described below with reference to the accompanying 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, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations.
In an aspect of the present invention, the utility model provides a melamine tail gas purification method, include:
and purifying and decomposing the mixture of the melamine tail gas and the water to obtain the purified melamine tail gas.
The utility model discloses purify and decompose melamine tail gas innovatively to get rid of the corrosive medium (such as isocyanic acid and cyanuric acid etc.) in the melamine tail gas, can also decompose into carbon dioxide and ammonia gas with the raw materials (such as urea etc.) that do not react completely when producing melamine, and then make the principal ingredients in the melamine tail gas of purification that obtains after the purification decomposes become carbon dioxide and ammonia gas and do not contain substances such as isocyanic acid, solved the corrosion problem of isocyanic acid to the post processing of back tail gas; 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 simple flow, stable operation and lower cost.
It should be noted that melamine is also called melamine, and melamine tail gas refers to tail gas generated in the production of melamine, and in the present invention, urea (CO (NH) is used2)2) Production of melamine (C)3H6N6) The specific equation is as follows:
CO(NH2)2→C3H6N6+6NH3+3CO2
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 gas3And CO2Can be used for producing urea, ammonium nitrate, compound fertilizer, sodium carbonate and other products.
In some embodiments of the present 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 purification 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 present invention, the temperature of the melamine tail gas is 80 to 220 ℃ (for example, 80 ℃, 100 ℃, 120 ℃, 140 ℃, 160 ℃, 180 ℃, 200 ℃ or 220 ℃ and the like) and the pressure of the melamine tail gas is 0.2 to 10MPa (for example, 0.2MPa, 1MPa, 3MPa, 5MPa, 7MPa, 9MPa or 10MPa and the like). 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 present invention, the purification and decomposition are performed after heating the mixture of melamine tail gas and water at a temperature of 200-400 ℃ (for example, 200 ℃, 220 ℃, 240 ℃, 260 ℃, 280 ℃, 300 ℃, 350 ℃, or 400 ℃, etc.). Therefore, the subsequent purification decomposition is more favorably carried out.
In some embodiments of the present invention, the heating means comprises molten salt heating and/or electric heating, preferably molten salt heating. Therefore, the heating effect is better.
In some embodiments of the present invention, the heating is performed after preheating the mixture of melamine tail gas and water, and the temperature of the preheated melamine tail gas and water is 150-280 ℃ (for example, 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 present invention, the mixture of melamine tail gas and water is preheated by the product after the purification decomposition to obtain the 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 present invention, the temperature of the purified melamine tail gas is 80-200 ℃ (e.g., 80 ℃, 100 ℃, 120 ℃, 150 ℃, 160 ℃, 180 ℃, or 200 ℃, etc.). Thereby, the temperature requirements of the subsequent treatment are met.
In some embodiments of the present invention, the water is water vapor, and the mass ratio of the melamine tail gas to the water vapor is 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 device for purifying melamine tail gas by using the method for purifying melamine tail gas described above, referring to fig. 1, the device 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 present invention, the purification 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 present invention, the fixed bed reactor comprises a multilayer fixed bed reactor. Therefore, the purifying and decomposing effect is better.
In some embodiments of the present invention, referring to fig. 2, the above apparatus further includes:
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 exhaust gas heater comprises a molten salt heater and/or an electric heater. Therefore, the heating effect is better. In some preferred embodiments of the present 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 present invention, the investment of the heating system can be saved by more than 50% by heating the molten salt heater.
In some embodiments of the present invention, referring to fig. 3, the above apparatus further includes:
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 present invention, the tail gas heat exchanger comprises a tubular heat exchanger, preferably, the tubular 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 present invention, the tail gas heat exchanger is arranged by overlapping 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 includes 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 heat medium refers to a medium for heating, in the present invention, the heat medium refers to purifying decomposed melamine tail gas, the cold medium refers to a medium for heating, and in the present invention, the cold medium refers to a 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.
The utility model discloses an among some concrete implementation manners, utilize to purify and decompose back melamine tail gas and carry out the heat transfer as heat medium, compare with the mode that does not adopt above-mentioned mode to carry out the heat transfer and practice thrift the energy consumption more than 50%.
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 present invention, the specific flow of purifying and decomposing the melamine tail gas by using the above device 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 another aspect of the present invention, the present invention provides a use of the device described above in the purification of melamine tail 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 with reference to the following 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.
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; although the present invention has been described in detail with reference to the foregoing embodiments, it should 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; such modifications and substitutions do not depart from the spirit and scope of the present invention.
Claims (10)
1. A melamine tail gas purification apparatus, comprising:
a clean-up decomposer comprising a melamine off-gas inlet and a melamine off-gas outlet;
and 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.
2. Melamine tail gas cleaning plant according to claim 1, characterized in that the clean-up decomposer comprises a fixed bed reactor.
3. A melamine off-gas cleaning device according to claim 1 or 2, further comprising:
and 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.
4. Melamine tail gas cleaning plant according to claim 3, characterized in that the tail gas heater comprises a molten salt heater and/or an electric heater.
5. Melamine tail gas cleaning apparatus according to claim 4, characterized in that the tail gas heater is a molten salt heater.
6. A melamine tail gas cleaning device according to claim 3, 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.
7. Melamine tail gas cleaning device according to claim 6, characterized in that the tail gas heat exchanger comprises a tube heat exchanger.
8. Melamine tail gas cleaning plant according to claim 7, characterized in that the shell and tube heat exchanger comprises a single-pass heat exchanger and/or a single-shell heat exchanger.
9. Melamine tail gas cleaning plant according to claim 7, characterized in that the tail gas heat exchanger is an arrangement of two devices in superposition.
10. An arrangement according to any one of claims 6-9, characterized in that the off-gas heat exchanger further comprises a heat medium inlet and a heat medium outlet, the heat medium inlet being in communication with the melamine off-gas outlet.
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| CN201922121457.9U CN211159295U (en) | 2019-11-29 | 2019-11-29 | Melamine tail gas purifying device |
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| CN201922121457.9U CN211159295U (en) | 2019-11-29 | 2019-11-29 | Melamine tail gas purifying device |
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| CN211159295U true CN211159295U (en) | 2020-08-04 |
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