CN114835653B - Closed-loop energy-saving melamine production process and device for co-production with urea - Google Patents
Closed-loop energy-saving melamine production process and device for co-production with urea Download PDFInfo
- Publication number
- CN114835653B CN114835653B CN202210388847.6A CN202210388847A CN114835653B CN 114835653 B CN114835653 B CN 114835653B CN 202210388847 A CN202210388847 A CN 202210388847A CN 114835653 B CN114835653 B CN 114835653B
- Authority
- CN
- China
- Prior art keywords
- melamine
- gas
- urea
- separator
- desublimation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 229920000877 Melamine resin Polymers 0.000 title claims abstract description 83
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 title claims abstract description 82
- 239000004202 carbamide Substances 0.000 title claims abstract description 68
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 title claims abstract description 67
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 51
- 239000007789 gas Substances 0.000 claims abstract description 75
- 238000000746 purification Methods 0.000 claims abstract description 37
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 28
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 26
- 238000000354 decomposition reaction Methods 0.000 claims abstract description 21
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000007787 solid Substances 0.000 claims abstract description 14
- 239000012159 carrier gas Substances 0.000 claims abstract description 13
- 238000000926 separation method Methods 0.000 claims abstract description 9
- 239000008247 solid mixture Substances 0.000 claims abstract description 9
- 239000003054 catalyst Substances 0.000 claims abstract description 8
- 239000010935 stainless steel Substances 0.000 claims abstract description 8
- 229910001220 stainless steel Inorganic materials 0.000 claims abstract description 8
- 229910000975 Carbon steel Inorganic materials 0.000 claims abstract description 7
- 239000010962 carbon steel Substances 0.000 claims abstract description 7
- 238000001816 cooling Methods 0.000 claims abstract description 7
- 239000007788 liquid Substances 0.000 claims abstract description 6
- 238000000034 method Methods 0.000 claims description 28
- 230000008569 process Effects 0.000 claims description 25
- 239000000725 suspension Substances 0.000 claims description 10
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 239000007864 aqueous solution Substances 0.000 claims description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 14
- 239000000047 product Substances 0.000 description 14
- 229910021529 ammonia Inorganic materials 0.000 description 7
- 239000001569 carbon dioxide Substances 0.000 description 7
- 229910002092 carbon dioxide Inorganic materials 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 238000005265 energy consumption Methods 0.000 description 5
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 description 4
- 229910000013 Ammonium bicarbonate Inorganic materials 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 4
- 235000012538 ammonium bicarbonate Nutrition 0.000 description 4
- 239000001099 ammonium carbonate Substances 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 230000008901 benefit Effects 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 230000005611 electricity Effects 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- PAWQVTBBRAZDMG-UHFFFAOYSA-N 2-(3-bromo-2-fluorophenyl)acetic acid Chemical compound OC(=O)CC1=CC=CC(Br)=C1F PAWQVTBBRAZDMG-UHFFFAOYSA-N 0.000 description 2
- OWIKHYCFFJSOEH-UHFFFAOYSA-N Isocyanic acid Chemical compound N=C=O OWIKHYCFFJSOEH-UHFFFAOYSA-N 0.000 description 2
- MKKVKFWHNPAATH-UHFFFAOYSA-N [C].N Chemical compound [C].N MKKVKFWHNPAATH-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000004134 energy conservation Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000004806 packaging method and process Methods 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- 235000017550 sodium carbonate Nutrition 0.000 description 2
- 239000002351 wastewater Substances 0.000 description 2
- 238000001321 HNCO Methods 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- XLJMAIOERFSOGZ-UHFFFAOYSA-N anhydrous cyanic acid Natural products OC#N XLJMAIOERFSOGZ-UHFFFAOYSA-N 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 238000012824 chemical production Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 230000002860 competitive effect Effects 0.000 description 1
- 238000006481 deamination reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000029087 digestion Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000036961 partial effect Effects 0.000 description 1
- 238000005192 partition Methods 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D251/00—Heterocyclic compounds containing 1,3,5-triazine rings
- C07D251/02—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings
- C07D251/12—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members
- C07D251/26—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members with only hetero atoms directly attached to ring carbon atoms
- C07D251/40—Nitrogen atoms
- C07D251/54—Three nitrogen atoms
- C07D251/56—Preparation of melamine
- C07D251/60—Preparation of melamine from urea or from carbon dioxide and ammonia
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D7/00—Sublimation
- B01D7/02—Crystallisation directly from the vapour phase
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/005—Separating solid material from the gas/liquid stream
- B01J8/0055—Separating solid material from the gas/liquid stream using cyclones
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/005—Separating solid material from the gas/liquid stream
- B01J8/006—Separating solid material from the gas/liquid stream by filtration
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D251/00—Heterocyclic compounds containing 1,3,5-triazine rings
- C07D251/02—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings
- C07D251/12—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members
- C07D251/26—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members with only hetero atoms directly attached to ring carbon atoms
- C07D251/40—Nitrogen atoms
- C07D251/54—Three nitrogen atoms
- C07D251/62—Purification of melamine
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/141—Feedstock
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Crystallography & Structural Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention provides a closed-loop energy-saving melamine production process for co-production with urea, which comprises the following steps: s1, reacting; s11, taking pure ammonia gas of a urea medium-pressure system as carrier gas, and enabling liquid urea to enter a urea decomposition area of a reactor to carry out urea decomposition in a porous catalyst environment; s12, enabling the decomposed mixed product to enter a melamine synthesis zone of the reactor for melamine synthesis; s13, sequentially feeding the synthesized mixed product into a first-stage purification zone and a second-stage purification zone of the reactor for purification to obtain a first mixed gas with the temperature of 345-360 ℃; the reactor is a stainless steel device which is internally arranged in a carbon steel shell; s2, desublimation and separation; s21, cooling the first mixed gas by a grade I heat exchanger, then introducing the cooled first mixed gas into a desublimation separator, and simultaneously introducing low-temperature gas into the desublimation separator to obtain a gas-solid mixture; s22, separating the gas-solid mixture by adopting a first cyclone separator arranged in the desublimation separator to obtain melamine solid and treated gas respectively.
Description
Technical Field
The invention relates to the technical field of chemical production, in particular to a closed-loop energy-saving melamine production process and device for co-production with urea.
Background
At present, a fluidized bed reactor is adopted in the production method of melamine by a gas phase method, and firstly urea is subjected to the condition of catalyst at the temperature of 390+/-5 ℃ to generate gaseous melamine+ammonia+carbon dioxide and a small amount of other high-boiling-point products. Then the high temperature process gas is cooled to about 350 ℃ to sublimate the high boiling point product into solid, and the solid impurities are removed by filtration. Then cooling the hot process gas at 350 ℃ to 200 ℃ by using the process cold gas at about 140 ℃ in a mixed direct heat exchange mode to enable melamine to be sublimated into solid. And finally, separating gas and solid, packaging the melamine finished product to obtain the melamine finished product, and introducing the gas except the internal circulating gas into a tail gas matching device. The tail gas matching devices are respectively provided with an ammonia-carbon separation device; a co-production ammonium bicarbonate device; a soda ash co-production device; a combined production ammonium nitrate device; co-production urea plants, and the like.
The existing gas phase method has three defects, and technological improvement is broken through to realize better energy conservation and consumption reduction.
The defect 1 is that the electricity consumption is high, and the electricity consumption of the current ton melamine products is between 650 and 900 ℃ according to different advanced degrees of the process. The electricity consumption mainly comes from two main units of a carrier gas compressor and a cold air blower.
The disadvantage 2 is that the reactor obtains 390 ℃ high-temperature process gas, the temperature of the high-temperature process gas is finally reduced to below 140 ℃, and the heat energy between the high-temperature process gas and the high-temperature process gas is not effectively utilized, so that the heat energy is wasted, and the energy conservation is not facilitated.
Shortcomings 3. The existing tail gas matching schemes have obvious shortcomings. For example, the co-production ammonium bicarbonate device has low process energy consumption, and each carbon molecule in the tail gas can be additionally added with one water molecule, so that the product yield is increased and the discharged water is reduced. However, the matching capacity of the ammonium bicarbonate is three times that of the melamine, so that the ammonium bicarbonate matched with the melamine is difficult to sell, and the capacity of the melamine is severely limited by the market demand capacity of the matched product. The co-production ammonium nitrate device has the condition that the capacity of the matched product market is limited by the melamine productivity no matter the co-production sodium carbonate device. The matched ammonia-carbon separation is carried out, the mixed ammonia and the carbon dioxide are separated into pure ammonia and pure carbon dioxide, the productivity of melamine is not restricted, but the energy consumption is high, the production cost is high, and the competitive capacity is not realized. The existing tail gas co-production urea device has the defects that the water content of the absorption liquid is high due to low pressure of the tail gas, the water digestion capacity of the urea device is insufficient, and the triamine productivity is restricted. Whether the tail gas matching scheme reasonably restricts the further development of the melamine technology.
Disclosure of Invention
The invention provides a closed-loop energy-saving melamine production process and device for co-production with urea, which can effectively solve the problems.
The embodiment of the invention is realized by the following technical scheme:
the invention provides a closed-loop energy-saving melamine production process for co-production with urea, which comprises the following steps:
s1, reaction
S11, taking pure ammonia gas of a urea medium-pressure system as carrier gas, and enabling liquid urea to enter a urea decomposition area of a reactor to carry out urea decomposition in a porous catalyst environment;
s12, enabling the decomposed mixed product to enter a melamine synthesis zone of a reactor for melamine synthesis, wherein the system pressure during melamine synthesis is 0.7-25bar;
s13, sequentially feeding the synthesized mixed product into a first-stage purification zone and a second-stage purification zone of the reactor for purification to obtain a first mixed gas with the temperature of 345-360 ℃;
the reactor is a stainless steel device which is internally arranged in a carbon steel shell;
s2, desublimation separation
S21, cooling the first mixed gas by a grade I heat exchanger, then introducing the cooled first mixed gas into a desublimation separator, and simultaneously introducing low-temperature gas into the desublimation separator to obtain a gas-solid mixture;
s22, separating the gas-solid mixture by adopting a first cyclone separator arranged in the desublimation separator to obtain melamine solid and treated gas respectively.
The invention further provides a closed-loop energy-saving melamine production device for co-production with urea, which is used for realizing the closed-loop energy-saving melamine production process for co-production with urea, and comprises a reactor, a level I heat exchanger and a desublimation separator which are sequentially communicated; a feed inlet is formed in the bottom of the side wall of the reactor, and an air outlet is formed in the top of the reactor; the inside of the reactor is sequentially divided into a urea decomposition area, a melamine synthesis area, a level I purification area and a level II purification area from bottom to top, wherein a first heat exchange tube is arranged in the urea decomposition area, a second heat exchange tube is arranged in the melamine synthesis area, and a third heat exchange tube is arranged in the level I purification area.
The closed-loop energy-saving melamine production process and device for co-production with urea provided by the invention have the following advantages and beneficial effects:
1. the carrier gas adopts the pure ammonia gas of the medium-pressure system matched with urea as the carrier gas, a carrier gas compressor with high energy consumption is omitted, the power consumption of melamine per ton is saved by more than 300 ℃, and the energy-saving effect is obvious;
2. the reactor adopts the integrated design of the stainless steel equipment partition functional areas which are built in the carbon steel shell, improves the conversion rate, prolongs the stable operation period, and the shell carbon steel equipment bears pressure, so that the internal stainless steel equipment belongs to normal pressure, the functions are satisfactorily realized, the stainless steel consumption is greatly reduced, and the investment is remarkably saved;
3. the system pressure is 0.7-22bar (absolute pressure), the matched tail gas adopts an aqueous solution full-circulation method process, an optimal co-production process is provided for melamine tail gas, and the economic benefit is remarkable;
4. greatly reduces the discharge of three wastes. In particular, all the tail gas in the melamine tail gas is used for producing urea, and the urea is also used for producing melamine, so that the carbon emission is greatly reduced, and the environmental pollution is avoided. The invention realizes energy saving and green cycle low carbon development;
5. no water is involved in the reaction and desublimation separation processes, so that the synthetic conversion rate of melamine is effectively ensured.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a closed-loop energy-saving melamine production device for co-production with urea, provided in embodiment 1 of the present invention;
reference numerals: 1-reactor, 11-urea decomposition zone, 111-first heat exchange tube, 12-melamine synthesis zone, 121-second heat exchange tube, 13-I level purification zone, 131-second cyclone separator, 132-third heat exchange tube, 14-II level purification zone, 2-I level heat exchanger, 3-II level heat exchanger, 4-desublimation separator, 5-suspension heat exchanger, 6-air pump, 7-first communication pipe, 71-first ball valve, 8-second communication pipe, 81-second ball valve.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
In one aspect, the present embodiment provides a process for producing closed-loop energy-saving melamine in co-production with urea, including the following steps:
s1, reaction
S11, taking pure ammonia gas of a urea medium-pressure system (absolute pressure is 7-25 bar) as carrier gas, enabling liquid urea to enter a urea decomposition zone of a reactor, and performing urea decomposition under the condition of a porous catalyst, wherein the pressure is 0.7-2.5 MPa;
s12, introducing the decomposed mixed product (HNCO) into a melamine synthesis zone of a reactor to synthesize melamine, wherein the system pressure during melamine synthesis is 0.7-25bar;
wherein the temperature of the melamine synthesis zone is lower than the temperature of the urea decomposition zone, specifically, the temperature of the melamine synthesis zone is 375-380 ℃ and the temperature of the urea decomposition zone is 380-410 ℃;
s13, sequentially introducing the synthesized mixed product into a first-stage purification zone and a second-stage purification zone of the reactor to purify to obtain a first mixed gas (C) with the temperature of 345-360 DEG C 3 N 6 H 6 ，NH 3 ，CO 2 ) Wherein, after the synthesized mixed product enters the I-stage purification zone of the reactor, solid-gas separation is carried out by a second cyclone separator arranged in the I-stage purification zone, and the solid is separatedThe bulk (catalyst) is returned to the melamine synthesis zone, the gas (C 3 N 6 H 6 ，NH 3 ，CO 2 ) Introducing the waste water into a suspension type heat exchanger, cooling the waste water, and then entering a II-level purification area;
the reactor is a stainless steel device which is internally arranged in a carbon steel shell;
s2, desublimation separation
S21, cooling the first mixed gas by a grade I heat exchanger, then introducing the cooled first mixed gas into a desublimation separator, and simultaneously introducing low-temperature gas (NH 3, the temperature of which is 100-150 ℃) into the desublimation separator to obtain a gas-solid mixture;
s22, separating the gas-solid mixture by adopting a first cyclone separator arranged in a desublimation separator to respectively obtain melamine solid and treated gas;
wherein, one part of the treated gas is cooled by a II-stage heat exchanger and then is recycled to the desublimation separator as low-temperature gas, and the other part of the treated gas is led out to a complete aqueous solution full-cycle urea device for producing urea.
Example 1
As shown in fig. 1, the embodiment provides a closed-loop energy-saving melamine production device for co-production with urea, which is used for realizing the production process, and comprises a reactor 1, a level i heat exchanger 2, a level ii heat exchanger 3 and a desublimation separator 4 which are sequentially communicated, wherein the reactor 1 adopts a double-layer design, the outer layer adopts Q345R carbon steel, the inner layer adopts stainless steel, a feed inlet is arranged at the bottom of the side wall of the reactor 1, an air outlet is arranged at the top of the reactor 1, the interior of the reactor 1 is sequentially divided into a urea decomposition zone 11, a melamine synthesis zone 12, a level i purification zone 13 and a level ii purification zone 14 from bottom to top, a first heat exchange tube 111 is arranged in the urea decomposition zone 11, a second heat exchange tube 121 is arranged in the melamine synthesis zone 12, a second cyclone 131 and a third heat exchange tube 132 are respectively arranged in the level i purification zone 13, a suspension heat exchanger 5 is arranged at the side wall of the reactor 1, the air inlet end of the suspension heat exchanger 5 is communicated with the level i purification zone 13, the air outlet end of the suspension heat exchanger 5 is communicated with the level ii purification zone 14, the interior of the reactor 1 is sequentially divided into a urea decomposition zone 11, the melamine synthesis zone 12, the level i purification zone 13 and the level ii purification zone 14 are sequentially from bottom to top, a first cyclone 4 is arranged in the first cyclone 4 and a second cyclone 4 is further communicated with the air inlet 3, a second cyclone 4 is further communicated with the air inlet 7, a second cyclone 4 is further communicated with the air inlet 3, a second inlet 4 is further communicated with the second inlet 3, a second inlet 4 is further communicated with a second inlet 3, a second inlet 3 and a second separator 4, a second outlet 4 is further communicated with a second inlet 3 is connected with a second inlet 3, a second separator 3 and a second separator 3, and a second separator 3 is further communicated with the outlet 3, and a third separator is further through the outlet 3 is connected through the separator 3, a second communicating pipe 8 is also arranged between the II-level heat exchanger 3 and the I-level heat exchanger 2, and a second ball valve 81 is arranged on the second communicating pipe 8.
Example 2
The embodiment provides a production process of closed-loop energy-saving melamine for co-production with urea, which is realized by the production device of closed-loop energy-saving melamine for co-production with urea provided in embodiment 1, and specifically comprises the following steps:
the liquid urea enters a urea decomposition zone (the temperature is 380 ℃ and the pressure is 18 bar) of the integrated reactor through a urea inlet, and under the environment of a porous catalyst, rapid mass and heat transfer occurs, the urea is rapidly decomposed to generate isocyanic acid and ammonia gas, and partial polymerization reaction occurs to generate melamine and carbon dioxide gas.
All the generated gas and pure ammonia carrier gas enter a melamine synthesis zone (temperature 375 ℃), and the temperature in the zone is reduced to have three effects, 1. The proper temperature reduction is beneficial to the melamine synthesis reaction; 2. the temperature is reduced, deamination reaction can be avoided, and the generation of high-boiling side products is greatly reduced. 3. The heat released by the melamine synthesis reaction can be fully utilized to heat the carrier gas.
After the melamine is synthesized, melamine+ammonia+carbon dioxide gas generated by urea enters a reactor I-level purification area along with carrier gas and a part of catalyst, solids and gas are separated through a built-in cyclone separator, the solids return to the reactor melamine synthesis area, the gas enters a suspension type heat exchanger, returns to a reactor II-level purification area after being cooled, and is filtered and purified to obtain first process gas (melamine+ammonia+carbon dioxide gas, the temperature is 345 ℃), the first process gas is led out of the II-level heat exchanger from a first process gas outlet, and the second process gas is subjected to countercurrent indirect heat exchange with the carrier gas, so that on one hand, required heat can be provided for the carrier gas, and on the other hand, the process gas is properly cooled, and the energy consumption of a cold air fan can be greatly reduced. After the heat exchanger runs for a period of time, the heat exchange tube has melamine wall and fails, so the heat exchanger is provided with two sets, one set is opened and the other set is prepared. When the heat exchange tube is built up, the heat exchanger is regenerated by high-temperature molten salt in the system, the melamine built up is sublimated and gasified, specifically, a first ball valve on the first communicating pipe and a second ball valve on the second communicating pipe are opened, so that high-temperature gas in the desublimation separator enters the I-stage heat exchanger and the II-stage heat exchanger, and the melamine built up is sublimated and gasified.
The cooled process gas enters the desublimation separator from a hot gas inlet at the top of the desublimation separator, the cold gas enters the desublimation separator from a cold gas inlet at the top of the desublimation separator, and after the hot gas and the cold gas are mixed, melamine is completely desublimated into solid, and ammonia and carbon dioxide are still gases. The gas-solid mixture with complete desublimation is separated by an internal cyclone separator, and the melamine solid is led out from a melamine outlet at the bottom of the desublimation separator for packaging. The gas is led out of the I-stage heat exchanger from the upper part of the desublimation separator, after heat exchange and temperature reduction, part of the gas is circulated back to the desublimation separator, and the other part of the gas is led out of the system to a complete water solution full circulation urea device.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. The production process of the closed-loop energy-saving melamine for co-production with urea is characterized by comprising the following steps of:
s1, reaction
S11, taking pure ammonia gas of a urea medium-pressure system as carrier gas, driving liquid urea into a urea decomposition zone of a reactor, and performing urea decomposition in a porous catalyst environment;
s12, enabling the decomposed mixed product to enter a melamine synthesis zone of a reactor for melamine synthesis, wherein the system pressure during melamine synthesis is 0.7-25bar;
s13, sequentially feeding the synthesized mixed product into a first-stage purification zone and a second-stage purification zone of the reactor for purification to obtain a first mixed gas with the temperature of 345-360 ℃;
the reactor is a stainless steel device which is internally arranged in a carbon steel shell;
s2, desublimation separation
S21, cooling the first mixed gas by a grade I heat exchanger, then introducing the cooled first mixed gas into a desublimation separator, and simultaneously introducing low-temperature gas into the desublimation separator to obtain a gas-solid mixture;
s22, separating the gas-solid mixture by adopting a first cyclone separator arranged in a desublimation separator to respectively obtain melamine solid and treated gas;
the production device adopted by the production process comprises a reactor, a level I heat exchanger and a desublimation separator which are sequentially communicated;
a feed inlet is formed in the bottom of the side wall of the reactor, and an air outlet is formed in the top of the reactor;
the inside of the reactor is sequentially divided into a urea decomposition area, a melamine synthesis area, a level I purification area and a level II purification area from bottom to top, wherein a first heat exchange tube is arranged in the urea decomposition area, a second heat exchange tube is arranged in the melamine synthesis area, and a third heat exchange tube is arranged in the level I purification area;
the first cyclone separator is arranged in the desublimation separator, and the second cyclone separator is arranged in the I-stage purification zone.
2. Process for the production of closed-loop energy-saving melamine in co-production with urea according to claim 1, characterized in that in step S1 the melamine synthesis zone is at a temperature lower than the urea decomposition zone.
3. The process for the production of closed-loop energy-saving melamine co-produced with urea according to claim 2, characterized in that the melamine synthesis zone has a temperature ranging from 375 ℃ to 380 ℃.
4. The process for the production of closed-loop energy-saving melamine co-produced with urea according to claim 2, characterized in that the urea decomposition zone has a temperature between 380 ℃ and 410 ℃.
5. The process for producing closed-loop energy-saving melamine co-produced with urea according to claim 1, wherein in step S13, after the synthesized mixed product enters the stage i purification zone of the reactor, solid-gas separation is performed by a second cyclone separator built in the stage i purification zone, the solid is returned to the melamine synthesis zone, and the gas is introduced into a suspension heat exchanger and enters the stage ii purification zone after cooling treatment.
6. The process for the production of closed-loop energy-saving melamine co-produced with urea according to claim 1, characterized in that in step S22, a part of the treated gas is cooled by a stage ii heat exchanger and recycled as low-temperature gas to the desublimation separator, and another part of the treated gas is led out to a complete aqueous solution full-cycle urea plant for urea production.
7. The process for producing closed loop energy-saving melamine co-produced with urea according to claim 1, characterized in that a suspension heat exchanger is arranged at the side wall of the reactor, the air inlet end of the suspension heat exchanger is communicated with the level i purification zone, and the air outlet end of the suspension heat exchanger is communicated with the level ii purification zone.
8. The process for the production of closed loop energy saving melamine co-produced with urea according to claim 1, characterized in that it further comprises a stage ii heat exchanger;
the desublimation separator comprises a first air inlet, a second air inlet, an air outlet and a discharge outlet, wherein the air outlet of the grade I heat exchanger is communicated with the first air inlet of the desublimation separator, the air outlet of the grade II heat exchanger is communicated with the second air inlet of the desublimation separator, and the air inlet of the grade II heat exchanger is communicated with the air outlet of the desublimation separator.
9. The process for the production of closed-loop energy-saving melamine co-produced with urea according to claim 8, characterized in that an air pump is provided between the outlet of the level ii heat exchanger and the second inlet of the desublimation separator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210388847.6A CN114835653B (en) | 2022-04-14 | 2022-04-14 | Closed-loop energy-saving melamine production process and device for co-production with urea |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210388847.6A CN114835653B (en) | 2022-04-14 | 2022-04-14 | Closed-loop energy-saving melamine production process and device for co-production with urea |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114835653A CN114835653A (en) | 2022-08-02 |
| CN114835653B true CN114835653B (en) | 2024-01-19 |
Family
ID=82563794
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202210388847.6A Active CN114835653B (en) | 2022-04-14 | 2022-04-14 | Closed-loop energy-saving melamine production process and device for co-production with urea |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114835653B (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3332947A (en) * | 1965-09-14 | 1967-07-25 | American Cyanamid Co | Production of melamine |
| CN102452992A (en) * | 2010-10-20 | 2012-05-16 | 郗运柱 | Energy-saving process for producing melamine |
-
2022
- 2022-04-14 CN CN202210388847.6A patent/CN114835653B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3332947A (en) * | 1965-09-14 | 1967-07-25 | American Cyanamid Co | Production of melamine |
| CN102452992A (en) * | 2010-10-20 | 2012-05-16 | 郗运柱 | Energy-saving process for producing melamine |
Also Published As
| Publication number | Publication date |
|---|---|
| CN114835653A (en) | 2022-08-02 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN101863848B (en) | System and method for preparing melamine | |
| CN104829494A (en) | Energy-saving urea production system and production process thereof | |
| WO2012146056A1 (en) | Energy-saving low-cost system and process for producing melamine by means of gas quenching | |
| CN102410518B (en) | Low-grade heat energy recycling method for liquid urea washing tower | |
| CN101891695B (en) | Normal pressure one-step circulation method of melamine | |
| CN109053615B (en) | Melamine production system and method | |
| CN105026365B (en) | Urea synthesis method and equipment | |
| CN101492398B (en) | Urea production process of high-efficiency condensation, low-mounting height CO2 air stripping method and high-voltage lamp type full condensation reactor | |
| CN111943897A (en) | Melamine production system and process by high-pressure synthesis low-pressure gas-phase quenching method | |
| CN204661587U (en) | A kind of energy-saving carbamide production system | |
| CN114835653B (en) | Closed-loop energy-saving melamine production process and device for co-production with urea | |
| CN102584730B (en) | Equipment and process for producing melamine under low pressure | |
| CN103601630A (en) | Method utilizing calcium carbide slag and carbon monoxide to synthesize calcium formate | |
| CN111995592B (en) | Method and device for co-production of urea and melamine | |
| CN107207423A (en) | The method for transforming high-pressure melamine equipment | |
| CN114409573B (en) | Improved low energy consumption CO 2 Stripping urea process | |
| CN208562198U (en) | A kind of melamine complete alternation process units | |
| CN1872842B (en) | Associated melamine from carbon ammonium through technique of two-step method under normal pressure | |
| CN1651419A (en) | Melamine and ammonium carbonate joint production technology | |
| CN113860622A (en) | Reverse osmosis strong brine recycling system and method | |
| CN201971766U (en) | Energy-saving less-investment gaseous quenching melamine production system | |
| CN102603661B (en) | Process of using medium-pressure gas-phase quenching method to produce melamine | |
| CN103193251B (en) | Technology for jointly producing ammonium sulfate and chloromethane | |
| CN108558783A (en) | A kind of melamine complete alternation production technology and device | |
| CN1180699A (en) | Technology for producing ammonium carbonate with combined production of melamine |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |