CN88102271A - The method of concentrating urea solution - Google Patents
The method of concentrating urea solution Download PDFInfo
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- CN88102271A CN88102271A CN198888102271A CN88102271A CN88102271A CN 88102271 A CN88102271 A CN 88102271A CN 198888102271 A CN198888102271 A CN 198888102271A CN 88102271 A CN88102271 A CN 88102271A CN 88102271 A CN88102271 A CN 88102271A
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C273/00—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups
- C07C273/02—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups of urea, its salts, complexes or addition compounds
- C07C273/14—Separation; Purification; Stabilisation; Use of additives
- C07C273/16—Separation; Purification
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Abstract
A kind of with moisture by in the urea soln evaporation and the method for concentrating urea solution, wherein the fs of the air-flow of constant basis through further decomposing feeds evaporation stage, and the required heat of evaporation stage to be most of condensation by this air-flow of at least a portion at least provided, and when needing, the temperature of the urea soln of discharging is to be controlled by the condensation of low-pressure steam.
Description
The present invention relates to moisture is evaporated and the method for concentrating urea solution by urea soln.
When preparing urea, at first generate the urea synthesis solution that contains carbaminate and free ammonia in the building-up reactions section by carbonic acid gas and excess ammonia.Carbamate decomposition ammonification and carbonic acid gas, and a part of ammonia and water in the solution of degradation production, the process several stages is by separating in the solution.The result generates a kind of aqueous solution of urea, wherein contains the urea of 70-75 weight part of having an appointment, and wherein still has ammonia and carbonic acid gas.And the usefulness that this solution is unsuitable for making fertilizer and produces resin.Press general method, must at first treated generation solid urea, in this process, the water of about 25-30 weight part and surplus ammonia and the carbonic acid gas of depositing are removed its major part through evaporation at least, or with urea by crystallization in the solution, and with crystal melting, the urea melt of gained changes into saccharoid more thus.Because urea soln is exposed to the generation that high temperature can cause urea decomposition and biuret, and this biuret does not wish to produce when urea should and be produced resin as fertilizer, therefore generally with the urea soln vapourisation under reduced pressure, to avoid too high vaporization temperature.In addition, from economic aspect, evaporative process often is that two steps of branch or multistep are carried out, wherein in first step or other step, under low slightly decompression, most of moisture is removed, thus in the final step evaporative process of then carrying out, can quite carry out under the low pressure, up to making the urea fusant, it is substantially free of moisture, and moisture be to be less than 0.5 weight part.Yet, also can be with solution (wherein generally containing 90-97% weight part urea) by the first evaporation step gained, for example directly send into into the particle process and need not further to concentrate.
In the actual evaporation operation, by a vertical pipeline group, be by low-pressure steam is obtained in condensation in the shell of pipeline and evaporate required heat with the spissated solution of desire.
The someone proposed, and can utilize the heat that is produced by gas and liquid process materials flow, and this materials flow is resulting by the concentrating urea solution in the urea synthesis, for example can specially apply for No. 8602770 referring to non-early stage disclosed Holland.In this patent application, address a kind of urea synthesis method, wherein in synthetic section, under the 125-350 bar pressure, at first generate urea soln, in this solution, except that containing urea and water, also contain carbaminate and free ammonia.Urea synthesis solution is through multistep catabolic phase treating processes, comprising being that the first step of carrying out under the low pressure is handled at synthesis pressure or than synthesis pressure, handle with second step of under the 4-40 bar pressure, carrying out, whereby with the decomposition carbaminate, and from solution, degradation production is removed with the moisture of free ammonia and some amount.Then, rest solution concentrates by two step urea soln evaporative processes.Required heat is that condensation by gaseous mixture obtains in first evaporation stage, and this gaseous mixture comes second catabolic phase under the comfortable 4-40 bar pressure.Described gaseous mixture be urea synthesis solution by will be through extracting through expanding, subsequently expansible reaction mixture and gaseous mixture by first catabolic phase is carried out heat exchange and generate, and latter's condensation generates carbaminate.If the shortage of heat that is discharged in the condensation process is in satisfying the required heat demand of this evaporation valency section, then needing provides extra heat by the condensation of other low pressure evaporation.
Used evaporation stage is interpreted as a kind of enriching stage in following explanation, wherein is concentrated by resulting urea soln in the urea synthesis, makes its urea content up to about 97%(weight).
Have been found that when the carbamate decomposition stage operates for the second time it is under certain constant compression force under the 4-40 bar pressure, and when urea synthesis solution with in first condensing zone, be condensed into when carrying out heat exchange between the gaseous mixture of carbaminate through extracting through being expanded to this pressure, be when carrying out under given heating surface, then the urea soln that contains by this stage discharging has constant and forms.This composition is irrelevant in the extraction degree of extracting among distinguishing with the carbaminate that is present in the urea synthesis solution actually.Therefore, join the total amount of extracting the heat that contains urea soln in the district and joining the heat of heat exchanger in first condensing zone and keep constant.Because in both cases vaporization heat is much at one, this also mean the amount of the decomposition gas that in extracting the district, is generated and in first condensing zone because heat supply and the total amount of decomposition gas amount also is a constant.Because the air-flow of gained is to be condensed in first condensing zone in extracting the district, and the gained air-flow is condensation in evaporation stage in the heat exchanging process of first condensing zone, thereby infeeds the airshed that the heat that extracts in the district has just determined to add evaporation stage.Therefore, with the variation that joins the vapor pressure that extracts the district, it is possible controlling the airshed that adds evaporation stage.
Interference-free in order to guarantee urea production, and make good final product, just need to make that temperature and concentration from the urea soln that evaporation stage discharged can keep constant, be 95%(weight as concentration), temperature is 130 ℃.When producing urea, when especially the urea soln that is produced being evaporated, there are many factors can influence its concentration and temperature, for example be back to solids or the urea soln of desiring concentrated solution, or the factors such as fluctuation of used vacuum tightness.And the fluctuation of urea concentration and/or temperature in evaporation stage generally can obtain levelling by the heat that adjustment infeeds this evaporation stage.
As No. 8602770 described those marks of above-mentioned Netherlands patent applications, in the evaporation urea soln, used heat is by containing NH
3, CO
2And H
2The condensation of the mixture of the gas of O, and by low-pressure steam condensation provided, if the quantity of steam body is held its Schwellenwert, then Gong Ying heat must be proofreaied and correct by adjusting the gaseous mixture amount of desiring condensation.In actual production, this just means that joining the vapor pressure that extracts in the district just needs to change.The shortcoming that this method produces is that the disturbance meeting of evaporation stage exerts an influence to the high pressure section of urea synthesis, can make whole process of production complicated like this.
The object of the present invention is to provide a kind of method, can avoid above-mentioned shortcoming by this, and wherein can solve the fluctuation problem of the heat supplied of evaporation stage, thereby can the high pressure section operation of urea synthesis not had a negative impact by easy measure.More particularly, the objective of the invention is to, guaranteed that the evaporation stage process can operate under the uncorrelated situation of urea synthesis process before with it, in one process of back, can generate first air-flow of its catabolic phase that carries out subsequently.Described purpose can realize by the applied in any combination according to different measure of the present invention.At first, guaranteed to infeed the constant gas of evaporation stage, it is irrelevant with institute's heat requirement in this stage.Also guaranteed in addition,, then the suitable partial condensation of air-flow can have been implemented as adjusting pressure by the control valve of exhaust line if evaporation stage institute heat requirement changes.In addition on the one hand, the steam heating district is set in the evaporation stage, as can provides extra heat by the condensation of low-pressure steam to it when needing.By the aforesaid combination measure, can use short-cut method evaporation stage is operated and controlled.
Therefore, the present invention relates to moisture is evaporated and the method for concentrating urea solution by urea soln.In this method at first
-in synthetic district, under 125-350 bar pressure and relevant temperature, react the urea synthesis solution that contains carbaminate and free ammonia with generation by carbonic acid gas and excess ammonia,
-at first catabolic phase, under synthesis pressure or lower pressure and heating state, a part of carbamate decomposition, the gaseous mixture of gained partly is condensed at first condensing zone at least, and condensation product sent back to synthetic district,
-another part carbaminate of still staying decomposes at the further catabolic phase of a step or multistep, and the gaseous mixture that generates is separated, and the pressure in the fs of further decomposing remains on the 4-40 crust, and needs heating.Among first condensing zone, the gaseous mixture of condensation and at least a portion urea synthesis solution through extracting exchanges, and its pressure also was lowered in the fs of further decomposing,
-remaining the urea soln that contains concentrates through evaporation, the needed heat of at least a portion is that the condensation by gaseous mixture obtains, and in the fs of further decomposing, being generated of this gaseous mixture,
Described method is characterised in that, the air-flow of constant basis is fed evaporation stage by fs of further decomposition, and the needed heat of evaporation stage at least major part be that condensation by this air-flow of at least a portion is provided, and when needing, the temperature of the urea soln of discharging is that the condensation of low-pressure steam is controlled.
For the continuous flow of the constant basis that obtains to feed evaporation stage, a suitable approach is in leading to the supply air line of evaporation stage pressure controlled valve to be set, and it is set up in a suitable numerical value.
If when the required heat of first evaporation stage produces fluctuation, can adjust, for example adjust by the increase or the minimizing by the gaseous mixture amount of fs of further decomposition that will be condensed with appropriate means.And the increase and decrease of the gaseous mixture quantity that is condensed, can be easily the change of pressure by the gaseous mixture that is condensed adjust, its force value is preferably controlled by pressure controlled valve, and this pressure controlled valve can be arranged at the exhaust line of evaporation stage.By the required temperature and the concentration value of urea soln of evaporation stage discharging, be at least by controlling by the heat that condensation discharged of the gaseous mixture of fs of further decomposition.In general, the amount that can be used as the condensed gas mixture be foot in the heat that is provided for concentrating urea, for example can make this urea soln be condensed into 95%(weight) concentration, and its exhaust temperature is 130 ℃.Yet, can guarantee that preferably most gaseous mixture is condensed as 90%, and it all be condensed.
In order to obtain having the urea soln that is discharged of required temperature and concentration, a certain amount of low-pressure steam is then carried out condensation.For this reason, preferably the condenser jacket tube bottom is designed to the steam heating district.
If whole gaseous mixture is not used for evaporation operation, its remainder can be passed into the condensing zone of the subsequent stage that belongs to further decomposition.
Within the scope of the invention, by the temperature and the concentration of the urea soln of evaporation stage discharging, can control by condensation from the low-pressure steam of the condensation of the constant basis part of the air-flow of fs of further decomposition and non-quantitative.Certainly to control the temperature and the concentration of urea soln also be possible in the condensation of the air-flow of the condensation of the low-pressure steam by constant basis and non-quantitative.But in general, preferably as far as possible with the airshed of the overwhelming majority for example 90-98% be applied to above-mentioned condensation process, and the low-pressure steam amount that will also be condensed correspondingly keeps lowly as far as possible.In the preferred practice, the part of choosing should be, can be in certain scope in the time of if desired, and the gaseous mixture quantity that is condensed can be adjusted all the time.
Can be applied to the step evaporation process according to method of the present invention and produce spissated urea soln, it also can be used as an integral part of multistep evaporative process, becomes first evaporation stage and is used to produce the melt urea that is substantially free of moisture.The inventive method also can be used as an integral part producing crystal urea in addition, wherein before crystallization, at first with urea soln partial concentration precedent such as 75-85%(weight).
Present invention is described and explanation for description and each embodiment, but that they do not produce the present invention is restricted.
In the accompanying drawings, A represents to extract the district, the condensing zone of B for operating under synthesis pressure.Comprise a pipeline group F in this condensing zone, the carbaminate that another part is still retained in pipeline is decomposed, and is illustrated in second catabolic phase of operating under the 4-40 bar pressure at this.C belongs to second to decompose the gas-liquid separator of section, D is the evaporator section of operation under the vacuum decompression, this evaporator section can be designed to be with the upright tubular heater exchhanger of telescopic, heating zone D1 by upper cartridge adds by the heat that condensation produced of the gaseous mixture of the second catabolic phase gained, and is added by bottom steam heating zone D2 by the heat that the low-pressure steam condensation is produced.E is the container that keeps flat, and wherein feeds the carbaminate and the uncooled gaseous mixture of part that are generated in the D1 of heating zone.
In synthetic section (not shown), the urea synthesis solution that under high pressure (pressure be 125-350 crust) and relevant temperature, generates, by the road 1, feed extraction section A and extract, wherein to its heating, and carry out convection current with 2 carbonic acid gas that add by the road and contact.Through pipeline 3, the gaseous mixture through extracting gained is fed among the condensing zone B, this condensing zone can be designed to a for example immerseable condenser, and wherein gaseous mixture to small part is condensed.The reaction mixture that is generated at condensing zone B is through 5 dischargings, and sends synthetic district back to.In the pipeline 4 reducing valve is set, wherein pressure is reduced to the 4-40 crust.By the road 4, the urea synthesis solution through extracting feeds pipeline group F, and opens among the B in condensation and to carry out heat exchange with the condensed gas mixture, and the carbaminate of another part quantity in the urea synthesis solution that still resides in through extracting is decomposed.Reaction mixture feeds gas-liquid separator C through pipeline 6.Gained contains NH thus
3, CO
2And H
2The gaseous mixture of O feeds heating zone D1 through pipeline 7.In addition, the water of some amount or carbamate aqueous solution also feed heating zone D1 through pipeline 10, improve the dew point of the gaseous mixture that is condensed by this.Contain 70-75%(weight by what gas-liquid separator C discharged) urea soln, 9 pipelines that feed evaporator section D therein, (0.3 cling to according to appointment) under a suitable vacuum tightness and are condensed to 90-97%(weight by the road), as 95%(weight) urea soln.Spissated urea soln is 11 dischargings by the road.Carbamate solution and the uncooled part of gaseous mixture in heating zone D1 generation, feed among the level(ling)vessel E through pipeline 12, by wherein with carbamate aqueous solution by pipeline 15, and gaseous mixture fed urea production workshop section (not shown go out) by pipeline 13.Steam line 7 is provided with control valve 8, is used to guarantee under constant pressure, makes gaseous mixture feed heating zone D1 continuously.Gaseous emission pipeline 13 comprises a pressure controlled valve 14, and it can control the degree of condensation of gaseous mixture among the D1 of heating zone by the variation of pressure in this section.The temperature of the urea soln of being discharged by pipeline 11 can join the low-pressure steam that adds district D2 by control and regulate and control.And the control of the add-on of steam can be coupled with pressure controlled valve 14 by a rly..
Disturbance for example can by by the road 11 and the reduction of the temperature of the urea soln that from evaporation stage, discharges characterize.The quantity of steam that set temperature regulator (use TT, TC and TV represent) can cause adding steam heating district D2 in pipeline 11 increases.By being provided for providing the cascade control (PT of the steam of certain requirement for D2, CAS), can make the quantity of steam that adds D2 that the set(ting)value (representing with SP) of control valve 14 is raise, thereby also make the pressure rising of heating zone (use control device PT, PC, PV).This will cause the condensation of more gases in the D1 of heating zone, and make the gaseous mixture amount that discharges by valve 14 reduce urea soln, thereby heating zone D2 was unloaded before disturbance produces.
Disturbance may impel required heat to heighten, so that forces the steam that adds the steam heating district all to open foot, and this can cause cascade control that the setting point of pressure controlled valve 14 is raise greatly, and is closed fully to cause valve.In this case, the gaseous mixture amount that is produced at second catabolic phase is inadequate, must reduce a little at the vapor pressure that extracts section A, and make the carbaminate surplus in materials flow 4 urea solns increase, thereby the gaseous mixture amount in second catabolic phase that makes increases this gaseous mixture process pipeline 7 and control valve 8 feeding heating zone D1.
Advantage according to the inventive method is, in the gaseous emission pipeline 7 of the gas-liquid separator C of second catabolic phase, be provided with control valve 8, can make gaseous mixture amount that this catabolic phase produces can keep constant extracting under the section A constant vapor pressure like this.In addition, because quantitative gaseous mixture condensation is arranged among condensing zone B, thereby the pressure of synthesis stage can keep constant.Pressure controlled valve 14 and relevant cascade control system thereof can guarantee that the disturbance among the evaporation stage D can obtain regulation and control.
Embodiment 1
When producing urea, be in the device of a capacity for 1500 tons of daily outputs, in the synthetic high pressure section, keep and carry out under the pressure of 140 crust.Under 17.7 bar pressures, the urea synthesis solution through extracting is fed among the first condensing zone B, and with carry out heat exchange by the condensed gas mixture that extracts gained.Following each quantity with per hour the kilogram numerical table show.
7 can get 32.484 kilograms gaseous mixture (temperature is 158.6 ℃) by the road, remove and contain 17090 kilograms of CO
2, 11180 kilograms of NH
3With 4.183 kilograms of H
2O also contains 31 kilograms of inert gas.Can get 103358 kilograms of solution by pipeline 9, except that containing 62530 kilograms of urea and 208 kilograms of biurets, also contain 3439 kilograms of CO
2, 6843 kilograms of NH
3With 29337 kg of water.This solution generates 95%(weight through concentrating under 0.33 bar pressure in evaporation stage D) urea soln, temperature is 130 ℃.Pressure controlled valve 8 and 14 is used to control constant supply gas and discharging gas, and makes the pressure of heating zone D1 be maintained at 17.6 crust.The air-flow 7 of major part is passed through pipeline 10 and other carbamate solution (23797 kilograms contain 5768 kilograms of CO of adding in the D1 of heating zone
2With 8211 kilograms of NH
3) institute's condensation.In order to make final concn reach required 95%(weight) and temperature be 130 ℃, also need 136 kilograms of low-pressure steam (pressure is 4 crust, and temperature is 145 ℃) are joined steam heating district D2.Quantity reaches 1819 kilograms gaseous mixture and (contains 1138 kilograms of CO
2, 587 kilograms of NH
3, 63 kilograms of H
2O and 31 kilograms of inert gas), 13 periods of low pressure that are disposed to flow process by the road.Pressure with heating zone D1 is reduced to 16.7 crust subsequently, reduces to 15.9 crust again.It is for the required low-pressure steam quantity of steam heater D2 and as shown in table 1 to the influence of the flow of pipeline 13.
Table 1
4 crust materials flows 13 among the experiment D1 D2
The steam flow flow of number pressure
(crust) (kilogram/hour) (kilogram/hour)
1 17.6 135 1818
2 16.7 918 2779
3 15.9 1700 3680
As seen from Table 1, the reduction a little of heating zone D1 pressure means that promptly required quantity of steam increases greatly in steam heating district D2, and has more substantial gaseous mixture be condensed in the periods of low pressure of technical process.
Embodiment 2
In following three groups of experiments, also be the production of 1500 tons of urea of relevant daily output, be 95%(weight by the urine table solution of evaporation stage discharging) solution, temperature is 130 ℃.Among the second catabolic phase C pressure remain on i.e. 17.2 crust of a constant numerical value, and reduce 500 kilograms from the amount of the air-flow 7 of this second catabolic phase is each.The minimizing of air-flow 7 flows can only join the vapor pressure that extracts section A by increase and realize.This effect and to the temperature of concentrated solution, the influence of the flow of the pressure of heating zone D1 and materials flow 13 is as shown in table 2.
Table 2
Experiment air-flow 7 goes into to extract section A materials flow 9 heating zone materials flows 13
The pressure flow of the temperature D1 of the pressure of number flow steam
(kilogram/hour) (crust) (℃) (crust) (hour/hour)
4 33055 15.1 155 16.7 3524
5 32555 15.2 155.5 16.6 3058
6 32050 15.3 156 16.5 2620
As can be seen from Table 2, constant compression force and being bordering under the steady temperature in second catabolic phase has the constant of being bordering in the materials flow 9 of being shifted out by this stage subsequently and forms, and the variation of leading to the vapor pressure that extracts section can cause the variation of air-flow 7 flows.Reduce as air-flow 7 flows, then the flow of the pressure of heating zone D1 and materials flow 13 can reduce.
Claims (10)
1, with moisture by in the urea soln evaporation and the method for concentrating urea solution, wherein at first
-in synthetic district, under 125-350 bar pressure and relevant temperature, generate the urea synthesis solution that contains carbaminate and trip ammonia by carbonic acid gas and excess ammonia reaction,
-at first catabolic phase, under synthesis pressure or lower pressure and heating state, a part of carbamate decomposition, the gaseous mixture of gained partly is condensed at first condensing zone at least, and condensation product sends synthetic district back to,
-another part carbaminate of still staying decomposes at the further catabolic phase of a step or multistep, and the gaseous mixture that generates is separated, and further the pressure in the fs of decomposing remains on the 4-40 crust, and needs heating.Among first condensing zone, the gaseous mixture of condensation and at least a portion urea synthesis solution through extracting carries out heat exchange, and its pressure has been lowered in the fs of further decomposing,
-remaining urea-containing solution concentrates through evaporation, and the required heat of at least a portion is that the condensation by gaseous mixture obtains, and this gaseous mixture is to generate in the fs of further decomposing,
The method is characterized in that: the air-flow of constant basis is fed evaporation stage by fs of further decomposition, and the needed heat of evaporation stage at least major part be that condensation by this air-flow of at least a portion is provided, and when needing, the temperature of the urea soln of discharging is to be controlled by the condensation of low-pressure steam.
2, by the method for claim 1, it is characterized in that the constant basis air-flow obtained to the pressure controlled valve on the gas supply pipe of evaporation stage via the fs that is arranged at from further decomposition.
3, by claim 1 or 2 method, it is characterized in that, in evaporation stage, carry out the degree of condensation of the air-flow of heat exchange with the urea soln that is concentrated, is to control by the pressure controlled valve that is arranged in the gas discharge pipe.
By the method for claim 3, it is characterized in that 4, the air-flow that part is not condensed can carry out condensation at the subsequent stage that further decomposes.
By each of claim 1-4, it is characterized in that 5, required at least 90% heat in evaporation stage is to obtain by the condensation from the gaseous mixture of fs of further decomposition.
6, by each of claim 1-5, it is characterized in that, the temperature and the concentration of the urea soln of being discharged by evaporation stage is by the condensation from the quantitative part of the air-flow of fs of further decomposition, and the low-pressure steam of non-quantitative is controlled.
7, by each of claim 1-5, it is characterized in that, the temperature and the concentration of the urea soln of being discharged by evaporation stage is by the condensation from the non-quantitative part of the fs air-flow of further decomposition, and the low-pressure steam of non-quantitative is controlled.
By the method for claim 7, it is characterized in that 8, the non-quantitative part of air-flow is based on that pressure in the heating zone of evaporation stage decides.
9, by claim 7 or 8 method, it is characterized in that, from the 90-98%(weight of the air-flow of fs of further decomposition) be condensed.
10, the described concentrating urea solution method that is used for of by specification drawings and Examples.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL8700888 | 1987-04-15 | ||
| NL8700888A NL8700888A (en) | 1987-04-15 | 1987-04-15 | Concn. of soln. of urea obtd. from carbon di:oxide and ammonia - by stepwise decomposition of carbamate, and evapn. using heat from condensn. of gas from decomposition step |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN88102271A true CN88102271A (en) | 1988-11-02 |
Family
ID=19849859
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN198888102271A Pending CN88102271A (en) | 1987-04-15 | 1988-04-14 | The method of concentrating urea solution |
Country Status (2)
| Country | Link |
|---|---|
| CN (1) | CN88102271A (en) |
| NL (1) | NL8700888A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105949087A (en) * | 2016-05-10 | 2016-09-21 | 安徽华瑞医药技术开发有限公司 | Medicinal urea and preparation method thereof |
| WO2016187928A1 (en) * | 2015-05-27 | 2016-12-01 | 广东芬尼克兹节能设备有限公司 | Heat pump-based vaporization-condensation integrated machine and condensation method |
-
1987
- 1987-04-15 NL NL8700888A patent/NL8700888A/en not_active Application Discontinuation
-
1988
- 1988-04-14 CN CN198888102271A patent/CN88102271A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2016187928A1 (en) * | 2015-05-27 | 2016-12-01 | 广东芬尼克兹节能设备有限公司 | Heat pump-based vaporization-condensation integrated machine and condensation method |
| CN105949087A (en) * | 2016-05-10 | 2016-09-21 | 安徽华瑞医药技术开发有限公司 | Medicinal urea and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| NL8700888A (en) | 1988-11-01 |
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