CN85105141A - Production method of urea - Google Patents
Production method of urea Download PDFInfo
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- CN85105141A CN85105141A CN85105141.3A CN85105141A CN85105141A CN 85105141 A CN85105141 A CN 85105141A CN 85105141 A CN85105141 A CN 85105141A CN 85105141 A CN85105141 A CN 85105141A
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- steam
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- urea
- interchanger
- ammonia
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Abstract
When urea synthesis solution is infeeded, make it when the top of vertical type separator that the package type heat exchanger is arranged flows downward, ammonia and carbonic acid gas are directed, and by the pipe side of above-mentioned interchanger, upwards flow from the bottom of interchanger.With steam liquid stream and steam flow are heated at the shell-side of interchanger.Unreacted ammonium carbamate is separated from urea synthesis solution with excess of ammonia, becomes the mixed gas of ammonia and carbonic acid gas.The shell-side of above-mentioned interchanger is separated into some heating compartment, and middle pressure steam is infeeded the top compartment of interchanger, and the steam that pressure is lower than the upper strata compartment that is right after infeeds the compartment below each.
Description
The improvement of the stripping process heating means in the relevant urea production operation of the present invention.More specifically say the improvement of the process for producing urea that the present invention is relevant, comprise improvement to the urea synthesis liquor heating method of accepting the stripping processing, in this stripping process, separation degree according to the material that does not change, in between the lattice heating that temperature condition reduces gradually, order is carried out from the top down, thereby prevents the hydrolysis of urea and the reduction of quality, and the consumption that can save steam.
In existing skill field, extractive urea synthesis solution from reactor for synthesis of urea is generally split in the decomposition process at follow-up stripping with steam, the material that does not change greatly, such as ammonium carbamate, decompose and separate with the too much ammonia that the inside is contained.For the separation of the unreacting substance of obtaining excellent in efficiency, stripping one decomposition course generally carries out in high temperature.
In traditional urea production process, 20-25 kilogram/cm is generally adopted in the heating that stripping one decomposes
2The middle pressure steam of g carries out.But because the temperature of steam is quite high, the continuous hydrolysis of the urea of producing, and along with the decomposition of the material that does not change with separate, the biuret that urea quality is descended constantly has follows formation quite in a large number.
In stripping process, the state of urea synthesis liquid film falls to dirty along the internal surface of vertical heating tube, and carbonic acid gas or ammonia, then in heating tube as gas to rising.
In the urea soln that flows downward of stripping process operations, quite a large amount of unreacted ammonium carbamates or superfluous ammonia are arranged, but exist in the solution that flows downward in the stripping tower top even when the temperature in the stripping tower is quite high, the hydrolysis of urea and the formation of biuret have only quite little volume production to give birth to.But when solution continues when dirty, unreacted integral part progressively increases, thereby when the temperature of lower of stripping tower is too high, hydrolysis and biuret be formed with considerable increasing.
Yet, if a stripping tower that whole urea solns are delivered into, a steam heating in its structure with a pressure stage, so in the bottom of stripping tower, quite high superheated is just arranged, so just cause the quite serious reduction of output, the downgrade of urea product.
The present invention has a well heater of using as stripping in contrast, is divided into some heating compartment at its shell-side, sends the steam of different pressures grade to the inside, keeps each compartment that optimal temperature is arranged.
Make traditional stripping and split the well heater that decomposition course is used, generally use a shell and tube heat exchanger.But in the present invention, use a kind of special shell and tube heat exchanger, its shell-side is divided into some compartments, and each uses the steam heating of different pressures grade.
In the top of interchanger, the temperature of urea soln can be up to a certain degree, but when solution when the bottom of interchanger is mobile, temperature preferably decreases.Therefore,, set up to the highest, reduce in the bottom of interchanger in the highest part of interchanger preferably the pressure of the steam of sending to, extremely low thereby the formation amount of hydrolysis and biuret also becomes.
About separating the method for interchanger, a kind of method of using a plurality of shell and tube heat exchanger is arranged.But the most handy space bar is divided into some compartments to the shell-side of interchanger, for this cause, has used a branch of single-piece pipe, and tube expansion, keeps the space sealing between pipe and the dividing plate.
When employing is of the present invention, the most favourable with two to three compartments.Four or more compartment can certainly use, but comes comparison with a spot of improved effect, and then cost is too big.
Pressure rating used herein is approximately as follows:
Using two compartments, its stripping pressure is at 150-200 kilogram/cm
2In the scope of g.
Vapor pressure in the last compartment is 15-25 kilogram/cm
2g
Vapor pressure in the following compartment is 8-25 kilogram/cm
2g
Vapor pressure in tradition one compartment is 15-25 kilogram/cm
2g
(usefulness for referencial use)
As with three compartments the time
Vapor pressure in the last compartment is 15-25 kilogram/cm
2g
Vapor pressure in the middle compartment is 11-15 kilogram/cm
2g
Vapor pressure in the following compartment is 8-11 kilogram/cm
2g
The major objective of method of the present invention is not only and is improved output and improve the quality, but also has produced the effect of extra saving steam consumption.Therefore, because as previously discussed, use the pressure that needs, just can more reasonably use steam in the place of needs.So if can use the pressure of various different gradess in suitable place, it is best that Here it is so.
But in existing skill field now, also do not have this perfect condition, from this situation, the inventor has found in the situation that a urea manufacturing equipment may run into usually, a kind of method of reasonable use steam.
In present popular stripping process, the consumption of middle pressure steam is quite big, and on the other hand, has quite a large amount of low pressure vapor to produce as byproduct.
The middle pressure that (notes) " middle pressure steam and low-pressure steam " used herein refers to is about 10-30 kilogram/cm
2G, low-pressure steam then is about 1-10 kilogram/cm
2G.
In the agglomeration process or similar process of stripping gas, the vapor pressure of obtaining in many cases is 3-6 kilogram/cm
2G.A steam part of Chan Shenging is used in the urea production equipment like this, and other part is discharged to the outside of equipment.But because pressure is low, this steam does not have much purposes.And opposite, from the outside middle pressure steam of supplying with of urea production equipment, it is just suitable but will to reduce feed rate as far as possible.
In this case, if a kind of method is arranged, thereby the use of the corresponding minimizing middle pressure steam of maximum use low-pressure steam as far as possible is bound to very receive an acclaim.
Method of the present invention as previously discussed, the position of heating compartment is low more, and the pressure of steam that infeeds compartment is also low more.Therefore, in this case, can use middle pressure steam, the traditional method by this skill is reduced to favourable level to pressure.But method of the present invention in contrast, and middle pressure steam is used as actuating fluid, removes to compress the servo-actuated fluid with a nozzle.Its result, the some of the low-pressure steam that produces in agglomeration process can be gone utilization again.Because as the heat content in the steam of heating medium, basic not variation under pressure change to a certain degree is so partly low-pressure steam can be utilized the use of corresponding minimizing middle pressure steam.
A kind of situation of representing among Fig. 1 is that the shell-side of well heater is divided into two compartments, and has used a nozzle.
With the amount of certain driving gas, improve the amount of gas of the pressure of gas by nozzle, generally the pressure ratio with pressurize changes specifically, if submit pressure ratio in the stage to, the servo-actuated fluid then descends to the ratio of actuating fluid so.If two stages are arranged,, then have relatively large servo-actuated fluid pressurized with respect to actuating fluid so with top comparison.
More particularly, a part of steam of returning from the nozzle of fs is in the subordinate phase of back, the a part of steam of returning as the nozzle place, in the subordinate phase of back, pressurized as the servo-actuated fluid of nozzle, be fed to then in the corresponding pressurization compartment and go.According to this method, a large amount of low-pressure steam can be utilized.The situation of two nozzles of use as shown in Figure 2.
When the number of compartment, the grade of steam and the amount of steam are determined to close according to the requirement of urea manufacturing, use the steam system of nozzle just to set up.
Now again the present invention is explained with reference to the following numeral of utilizing for example:
Example:
In this example, the pressure of steam and amount are used kilogram/cm respectively
2G and kilogram/ton urea are represented.Middle pressure steam and low-pressure steam are respectively 25 kilograms/cm
2G and 5 kilograms/cm
2G.
Can see from above, in the situation of Fig. 1,5 kilograms/cm of use
2G steam is 30 kilograms (accounting for total quantity of steam 5%), and in the situation of Fig. 2, uses 5 kilograms/cm
260 kilograms of g steam (account for total quantity of steam 10%).Specifically, in situation shown in Figure 2, in whole urea manufacturing equipment, every urea is saved 60 of middle pressure steams, to the corresponding minimizing of low-pressure steam of device external output.
Adopt the result of above-mentioned measure, the formation of biuret and the hydrolysis of urea all reduce, and be as shown in the table:
The accompanying drawing prospectus:
Stripping-decomposition tower (two heating compartment) that Fig. 1 explanation proposes by the present invention.
Stripping-decomposition tower (three heating compartment) that Fig. 2 explanation proposes by the present invention.
Mark number among the figure is represented following apparatus and air-flow:
101 strippings-decomposition tower
102,103 nozzles
11 heating compartment middle pressure steam steam inlets
The 2-1 nozzle drives steam
2-2 servo-actuated steam
2-3 jet exit steam
2-4 heating compartment inlet steam
3-1 drives steam
3-2 servo-actuated steam
3-3 heating compartment inlet steam
Errata
Claims (2)
1, in the reactor for synthesis of urea of respond an ammonia and a carbonic acid gas, produce the method for producing urea in the device, be characterized as the urea synthesis solution liquid stream that makes such generation, flow downward from the top of vertical knockout tower that a package type heat exchanger is arranged, ammonia and carbon dioxide gas stream, bottom from interchanger, by flowing on the pipe side direction of above-mentioned interchanger, with the shell-side of steam at interchanger, to liquid stream and air-flow heating, thereby the unreacted a large amount of ammonium carbamates that decompose from urea synthesis solution are separated with excess of ammonia, become the mixed gas of ammonia and carbonic acid gas, this is a kind of improved method, and the shell-side of above-mentioned interchanger is separated into some heating compartment, and middle pressure steam is infeeded its uppermost compartment, and infeed each pressure of the steam in the compartment below, lower than the steam in the compartment that infeeds above it.
2, improvement as the production method of urea in 1 of the claim the, another feature is for directly infeeding middle pressure steam the compartment of the superiors, the steam of returning from the nozzle that uses middle pressure steam, as actuating fluid, and low-pressure steam as the servo-actuated fluid, infeed undermost compartment, and the steam of returning from second nozzle that uses middle pressure steam as actuating fluid, the steam that a part is return from first nozzle is made servo-actuated steam, for the compartment of layer second from the bottom, the rest may be inferred, the steam of returning from each nozzle of corresponding compartment, except that top compartment, infeed corresponding compartment.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 85105141 CN1011139B (en) | 1984-06-22 | 1985-07-06 | Production method of urea |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59129686A JPS6110545A (en) | 1984-06-22 | 1984-06-22 | Production of urea |
| CN 85105141 CN1011139B (en) | 1984-06-22 | 1985-07-06 | Production method of urea |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN85105141A true CN85105141A (en) | 1987-03-04 |
| CN1011139B CN1011139B (en) | 1991-01-09 |
Family
ID=25741844
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 85105141 Expired CN1011139B (en) | 1984-06-22 | 1985-07-06 | Production method of urea |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN1011139B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112424164A (en) * | 2018-07-26 | 2021-02-26 | 东洋工程株式会社 | Process and plant for the production of urea |
-
1985
- 1985-07-06 CN CN 85105141 patent/CN1011139B/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112424164A (en) * | 2018-07-26 | 2021-02-26 | 东洋工程株式会社 | Process and plant for the production of urea |
| CN112424164B (en) * | 2018-07-26 | 2022-11-29 | 东洋工程株式会社 | Process and plant for urea production |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1011139B (en) | 1991-01-09 |
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| C06 | Publication | ||
| PB01 | Publication | ||
| C13 | Decision | ||
| C14 | Grant of patent or utility model | ||
| C19 | Lapse of patent right due to non-payment of the annual fee |