CN1061591A - Process for producing urea - Google Patents
Process for producing urea Download PDFInfo
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- CN1061591A CN1061591A CN 90106181 CN90106181A CN1061591A CN 1061591 A CN1061591 A CN 1061591A CN 90106181 CN90106181 CN 90106181 CN 90106181 A CN90106181 A CN 90106181A CN 1061591 A CN1061591 A CN 1061591A
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- ammonia
- ammonium
- urea
- bicarbonate
- decomposition
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Abstract
The invention discloses a kind of process for producing urea, comprise operations such as urea synthesis, decomposition, recovery, granulation, it is raw material that this technology is selected bicarbonate of ammonia and ammonia for use, reaction generates the first ammonium in first ammonium reactor, perhaps generate the first ammonium in decomposition, recovery system, again the first ammonium is heated after the pressurization, send into urea synthesis in the urea reaction tower.Produce finished urea through decomposition, recovery and granulation then.When transforming urea plant as to bicarbonate of ammonia factory, this technology saved traditional CO
2Remove operation, this technology and bicarbonate of ammonia production combine, and can build up a multiple chemical fertilizers production producer that produces bicarbonate of ammonia and urea.
Description
The present invention relates to the production technique of urea, melamine urea etc.
Existing urea production process all is with ammonia (NH
3) and carbonic acid gas (Co
2) be raw material, produce urea (seeing " nitrogen fertilizer process design manual " urea, Chemical Industry Press, in September, 1988) through urea synthesis, decomposition, recovery and evaporation (or crystallization) granulation four big operations.Wherein, urea synthesis be divided into two the step carry out, that is:
The first step is that ammonia and carbon dioxide reaction generate ammonium carbamate (NH
2CooNH
4), hereinafter to be referred as the first ammonium, reaction formula:
The dehydration of the second ground beetle ammonium generates urea, reaction formula:
Reaction (1) formula is a reversible strong exothermal reaction, and the speed of response that generates the first ammonium is very fast, reach chemical equilibrium easily, and carbonic acid gas is converted into urea after reaching balance, must just can carry out in liquid phase.
The compressed machine pressurization of atmospheric carbon dioxide 20～25MPa, liquefied ammonia is forced into 20～25MPa through ammonia pump, recovery system first ammonium liquid is forced into 20～25MPa through first ammonium pump and all sends in the urea synthesizer respectively, and keep under the temperature condition about 200 ℃, carbonic acid gas and ammonia generate the first ammonium rapidly, form urea soln with reclaiming the conversion reaction of dewatering of first ammonium.
In urea synthesis process, because the urea Equilibrium limit, the raw material that enters synthetic tower can not all be converted into urea.Therefore unreacted intact carbonic acid gas and ammonia are arranged in the solution that synthetic tower comes out, and the first ammonium (also becomes Co through decomposing
2And NH
3), these Co
2And NH
3All must from urea liquid, separate, so produced decomposition process.Decompose the Co of coming out
2And NH
3Must recycle again as raw material, so produced recovery process.After the pure urea soln that decomposition process obtains is sent to evaporation moisture content, obtain the urea of melting attitude, obtain finished urea through granulation.
Because these unreacted reactants adopt different separation and recovery methods, so obtain different urea production process flow processs.
Fig. 1 represents aqueous solution recycle to extinction schema.
Fig. 2 represents the vaporizing extract process schema.
Fig. 3 represents aqueous solution recycle to extinction improvement C method schema.
Aqueous solution recycle to extinction flow process shown in Figure 1 adopts the method for decompression heating to make the first ammonium in the solution be decomposed into Co
2And NH
3With the isolating method of urine, be typical aqueous solution recycle to extinction flow process.
In the different steps of decomposing, in the time of heating, make a kind of gas by containing unreacted urea soln, change the vapour-liquid equilibrium of urine, impel the first ammonium to be decomposed into Co
2And NH
3Separate with urine, Here it is uses the gas stripping process flow process, as shown in Figure 2.
Aqueous solution recycle to extinction shown in Figure 3 improvement C method is that evaporation prilling operation in aqueous solution recycle to extinction flow process adopts vacuum-evaporation and lowers the temperature concentratedly, and crystallization goes out urea crystal, separates moisture content with whizzer again, and then with powdery crystallization heating melting granulation.
Above-mentioned traditional process for producing urea exists following shortcoming to have much room for improvement:
1. all be to adopt Co
2And NH
3Be raw material, its Co
2The source all be special Co that removes in the preparation of the unstripped gas of synthetic ammonia
2Operation obtains, these Co
2Pressurize after (generally all is) with unstripped gas, just send to and remove Co at the pressure more than the 1.8MPa
2Operation, and that obtain is normal pressure Co
2Gas, consumed power is bigger, sends to the urea operation again and also will be forced into more high pressure, needs to consume very high-power (accounting for urea operation power consumption 55%) again.Simultaneously, remove Co
2The solution of operation is that pharmaceutical chemicals is formulated, and materials such as bases, heavy metal, organic amine have harm to operator and ecotope.
2.Co
2The construction that removes operation is expensive bigger, obtains the Co of urea per ton
2Need about 200 yuan of investments (calculating) to produce the urea ability per year.
3. the factory products structure with aforesaid method production urea is single, lacks the market handiness.
Based on the deficiency that exists in above-mentioned traditional process for producing urea, the inventor has proposed a kind of novel method of urea synthesis.
This method is a raw material with bicarbonate of ammonia and ammonia, and in 1.5～2.0MPa, reaction generates the first ammonium under 100 ℃ ± 5 ℃ temperature in first ammonium reactor, and reaction formula is as follows:
Again the dehydration of first ammonium is generated urea, reaction formula is:
Reaction (3) formula is a reversible little thermopositive reaction, and the speed that generates the first ammonium is fast, reaches chemical equilibrium easily, and similar with (1) reaction formula, and to be converted into the production rate of first ammonium very high for bicarbonate of ammonia after reaching chemical equilibrium, and reaction (4) formula is identical with (2) formula.Producing 1 ton of required bicarbonate of ammonia of urea with this method is 1.3～1.5 tons, 0.28～0.30 ton of ammonia.
Fig. 4 is the process flow sheet of invention.
Fig. 5 is the applicating flow chart of the present invention on original urea production process.
Fig. 4 is to be raw material with bicarbonate of ammonia and ammonia, with reclaiming the first ammonium solution, and under the temperature condition of 100 ℃ ± 5 ℃ of the pressure of 1.5～2.0MPa, preparation first ammonium solution, and become an independent process.And then the first ammonium solution through being forced into 20～25MPa, heat to about 200 ℃, send into urea synthesizer and carry out urea synthesis, make urea soln.This law makes urea soln and traditional urea synthetic method, and to make the urea soln composition identical, just water content slightly high (this is that generating in the product has and the identical water molecules of first ammonium molecule number because during preparation first ammonium solution).Each operation is the same with traditional urea synthetic method later on, and decomposition, recovery, evaporation (or crystallization) granulation are arranged.
Fig. 5 is with the raw material ammonium bicarbonate soln, partly sends into decomposing system, obtains gas phase Co
2Enter recovery system with ammonia, as one of raw material sources of first ammonium, another part ammonium bicarbonate soln is sent into the recovery system liquid phase partly, absorb and the high pressure absorption through low pressure, make the high density first ammonium solution of 1.5～2.0MPa and 100 ℃ ± 5 ℃, after again the pressurization of first ammonium solution being heated up, send into synthetic tower and make urea soln, and then through decomposing, reclaim, evaporate (or crystallization) granulation.
Reaction formula is:
The present invention compared with prior art has following technical characterictic:
1. raw material is bicarbonate of ammonia and ammonia.
The first ammonium can than under the mild conditions (about 100 ℃ of temperature, pressure 1.5～2.0MPa) decompose and recovery system in prepare, saved the Co of traditional Wyler's process
2Remove operation, saved the investment of founding the factory, reduced consumption.
3. present method is used for that following characteristics are arranged when bicarbonate of ammonia factory transform urea plant as:
(1) bicarbonate of ammonia factory keeps the continuation use, and established device can continue to bring into play function.
(2) factory products have handiness, and two kinds of bicarbonate of ammonia product and urea products can be arranged, and also can have wherein anyly, have market-oriented selectivity.
(3) bicarbonate of ammonia is to produce under the pressure of the 0.7MPa left and right sides, obtains bicarbonate of ammonia and removes Co than synthesis ammonia system solution method
2Obtained Co
2Energy consumption much lower.
(4) make the urea raw material with bicarbonate of ammonia, when reconstruction urea, the solution method that can not build synthesis ammonia system removes Co
2Device has been saved investment, has shortened the construction period.Chemical bases, heavy metal, organic amine etc. have been reduced in the solution simultaneously to the harm of operator and environment.
(5) this law does not need to build Co at urea system
2Compression section.
4. be the device of raw material processing other products at urea, if unreacted urea or by product Co are completely arranged
2, NH
3To be reclaimed and with urea plant, just can change the urea raw material is that bicarbonate of ammonia is made raw material.Such as producing trimeric cyanamide, just can transform bicarbonate of ammonia as and make raw material with Dutch DSM method.
Implementing best way of the present invention is exemplified below:
Embodiment one: press accompanying drawing 4, get 0.29 ton of 1.35 tons in bicarbonate of ammonia and ammonia, mix with the first ammonium solution that recovery system is retrieved, in first ammonium reactor,, make the first ammonium solution under 100 ℃ of conditions, be forced into about 20MPa through high pressure carbamate pump again at 1.7MPa, remove methylamine preheater then, after being heated to 188 ℃～200 ℃, entering urea synthesizer and change into urea, its urea soln is sent to through decompression and is decomposed workshop section.
The solution that comes out from urea synthesizer goes first decomposition tower to flow from top to bottom through being decompressed to 1.7MPa, tower top utilizes self sensible heat and lower heating boiling, also produce steam and play the stripping effect, the first ammonium rate of decomposition of failing to transform is reached about 87%, total ammonia evaporates and reaches 90%, from cat head exhaust gas temperature maintenance about 155 ℃, contain a large amount of diaminos, carbonic acid gas and water vapor remove high-pressure absorber, urea soln temperature at the bottom of the tower is about 145 ℃, contain urea about 50% and also have undecomposed first ammonium and ammonia, send to the second decomposition tower top through being decompressed to 0.15～0.17MPa, flow from top to bottom and utilize sensible heat, and lower heating boiling, produce steam and produce the stripping effect, make ammonia and Co
2Further decompose and send from the top, temperature is 137～140 ℃, removes low-pressure absorber, and the bottom urine concentration is that 70% temperature is 130 ℃, sends to the flash distillation pine, under the 250mmHg column pressure, further steams ammonia and Co
2, and evaporation part moisture content.Flash distillation eases out the solution that comes and enters first vaporizer, in the 225mmHg(absolute pressure) under the pressure, urine concentration is brought up to 85% send to second vaporizer through separator again, in the 25mmHg(absolute pressure) under the pressure urine simmer down to 98.7% melting shape, send to the prilling tower top and spray granulation, tower bottom obtains finished urea and sends to packing.
155 ℃ the gas that recovery system, the first decomposition tower top are come out is sent to first vaporizer as the thermal source concentrating urea, and temperature is reduced to 110 ℃, enters high-pressure absorber, through absorbing ammonia and Co
2Afterwards, 45 ℃～50 ℃ of top air outlet temperatures, deammoniation condenser successively, the indifferent gas washing tower removes tail gas absorber then.
The gas that second decomposition tower comes out is sent to low-pressure absorber, first condenser and second condenser, and then remove tail gas absorber, almost all remaining ammonia and Co
2Sponge.
Tail gas absorber absorbs ammonia and Co
2The lower concentration ammonium bicarbonate solution, after circulation absorbs index concentration, go to the low pressure absorption tower to make absorption liquid, to improve the Co in the solution with pumping
2With the content of ammonia, and then this solution is forced into more than the 1.7MPa with first ammonium pump, sends to high-pressure absorber and make absorption liquid, further absorb ammonia and Co
2To improve the first ammonium concentration, this moment, temperature reached about 90 ℃～100 ℃, entered first ammonium reactor again, finished the effect of recovery system, and made high density first ammonium liquid with adding bicarbonate of ammonia and ammonia.This first ammonium liquid is forced into 20MPa through high pressure carbamate pump, and methylamine preheater is heated to 188～200 ℃, and enters urea synthesizer.
Embodiment two: press accompanying drawing 5, getting concentration is about 60%, and temperature is that 50～60 ℃ ammonium bicarbonate soln uses the steam of 2.2MPa directly ammonia in the solution and Co at the stripping decomposition tower
2Decomposition is come out, the steam that top of tower went out, Co
2, the first ammonium sent in the urea soln that the direct stripping decomposing urea of the high-pressure decomposition tower synthetic tower of recovery system comes of ammonia is Co
2And ammonia, the high pressure absorption portion that enters recovery system again prepares the first ammonium.Reaction formula is:
The rest part technical process is identical with embodiment one described method.
In the urea system of having produced, mend 5% left and right sides ammonium bicarbonate soln of system's throughput, with pump part solution is sent to the low pressure decomposition tower, another part is sent to the low pressure absorption tower, can make urea system throughput improve about 5%.
Claims (4)
1, a kind of process for producing urea, comprise urea synthesis, decomposition, recovery, granulating working procedure, urea synthesis is raw material to be reacted generate the first ammonium, then with first ammonium dehydration urea synthesis, it is characterized in that selecting for use bicarbonate of ammonia and ammonia is raw material, under 1.5～2.0MPa, 100 ℃ ± 5 ℃ conditions, reaction generates the first ammonium in first ammonium reactor, and reaction formula is:
Perhaps in decomposing recovery system, add the ammonium bicarbonate soln reaction and generate the first ammonium.
2,, it is characterized in that using the steam of 2.2MPa directly ammonia in the solution and Co at the stripping decomposition tower ammonium bicarbonate soln according to claim 1 described novel process
2Decomposition is come out, the vapor C o that top of tower went out
2, the first ammonium sent in the urea soln that the direct stripping of the high-pressure decomposition tower of recovery system decomposes synthetic tower of ammonia is Co
2And ammonia, the high pressure absorption portion that enters recovery system again prepares the first ammonium, and reaction formula is:
3, according to the described novel process of claim 1, it is characterized in that ammonium bicarbonate soln is partly sent into decomposing system, obtain vapour phase Co
2Enter recovery system with ammonia, as one of raw material sources of first ammonium, another part ammonium bicarbonate solution is sent into the recovery system liquid phase part, absorbs and the high pressure absorption makes the highly concentrated solution of 1.5～2.0MPa and 100 ℃ ± 5 ℃ through low pressure, and reaction formula is:
4, according to the described novel process of claim 1, it is characterized in that the proportioning of bicarbonate of ammonia and ammonia is: urea per ton needs 1.3～1.5 tons of bicarbonate of ammonia and 0.28～0.30 ton of ammonia.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 90106181 CN1061591A (en) | 1990-11-22 | 1990-11-22 | Process for producing urea |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 90106181 CN1061591A (en) | 1990-11-22 | 1990-11-22 | Process for producing urea |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN1061591A true CN1061591A (en) | 1992-06-03 |
Family
ID=4879878
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 90106181 Pending CN1061591A (en) | 1990-11-22 | 1990-11-22 | Process for producing urea |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN1061591A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104925809A (en) * | 2015-05-15 | 2015-09-23 | 北京丰汉工程技术有限公司 | Method and system for recovering carbon dioxide from industrial waste gas |
| CN109665976A (en) * | 2018-11-15 | 2019-04-23 | 锦西天然气化工有限责任公司 | A kind of ammonia process recycling flue gas CO2With the technique of urea Joint Production |
-
1990
- 1990-11-22 CN CN 90106181 patent/CN1061591A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104925809A (en) * | 2015-05-15 | 2015-09-23 | 北京丰汉工程技术有限公司 | Method and system for recovering carbon dioxide from industrial waste gas |
| CN104925809B (en) * | 2015-05-15 | 2017-07-11 | 北京丰汉工程技术有限公司 | A kind of method and system that carbon dioxide is reclaimed from industrial waste gas |
| CN109665976A (en) * | 2018-11-15 | 2019-04-23 | 锦西天然气化工有限责任公司 | A kind of ammonia process recycling flue gas CO2With the technique of urea Joint Production |
| CN109665976B (en) * | 2018-11-15 | 2021-10-19 | 锦西天然气化工有限责任公司 | Ammonia process for recovering CO in flue gas2Process for combined production with urea |
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