CN1321977C - Method for concentrating thin urine using falling film type evaporation heater - Google Patents
Method for concentrating thin urine using falling film type evaporation heater Download PDFInfo
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- CN1321977C CN1321977C CNB2005100214016A CN200510021401A CN1321977C CN 1321977 C CN1321977 C CN 1321977C CN B2005100214016 A CNB2005100214016 A CN B2005100214016A CN 200510021401 A CN200510021401 A CN 200510021401A CN 1321977 C CN1321977 C CN 1321977C
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Abstract
The present invention discloses a method for concentrating thin urine using a falling film type evaporation heater. After a circulation work section and before an evaporation work section in a urea fabrication process using a CO<2> steam stripping method, under the action of a liquid distributing device, urine forms film-shaped flow from top to bottom on the inner wall of each tube array. Temperature adjusting water in a high-pressure scrubber supplies heat out of the tube. Part of moisture is evaporated, and thus, the concentration of urine is enhanced. A vacuum condition of a pre-concentration system is maintained by a pre-concentration surface condenser, and an original section of evaporation jet pump of a urea device. The utility model has the advantages that 1. a bottle neck of a vaporization system is completely removed; 2. the operating condition of the vaporization system is more independent and stabler, and is not influenced by high circulating pressure and halfway free ammonia decomposition any longer; 3. waste heat of the temperature adjusting water in the high-pressure scrubber is comprehensively utilized, and an energy-saving effect is noticeable; 4. the waste heat utilization of the high-pressure temperature adjusting water is the best scheme and is the first application of a film type evaporation technology to a urea device using a CO<2> steam stripping method.
Description
Affiliated technical field
The present invention relates to a kind of concentration method, particularly a kind of method that adopts the falling film type evaporation heater concentrating thin urine.
Technical background
In the process of evaporation concentration urine, when the urine temperature is close to or higher than urea fusing point (132.6 ℃), will supervene some side reactions, wherein mainly be isomerization condensation reaction, hydrolysis reaction and the decomposition reaction of urea.The existence of these side reactions will cause the reduction of urea productive rate or the increase of steam consumption quota; Also will influence the urea product quality.
1) a kind of generation of side reaction biuret
The primary product of the condensation reaction of urea has biuret, tricyanic acid, trimeric cyanamide etc.Under the operational condition in the urea evaporative process, mainly be the formation reaction of biuret.Studies show that according to relevant, biuret both can be (as the urea synthesis reaction process in the aqueous solution, the decomposition course of unreacted reactant) generate, also in the end generate in the anhydrous melts of evaporation stage, its isomerization generative process can be expressed as 3 chemical equation:
2NH
2CONH
2＝H
2NCONHCONH
2+NH
3
NH
2CONH
2＝HNCO+NH
3
NH
2CONH
2+NH
3＝H
2NCONHCONH
2
By reaction formula as seen, biuret both can be generated by the chemical reaction between two urea molecules, also can be generated by the chemical reaction between another intermediate product cyanic acid molecule and the urea molecule.Relevant studies show that: 1. the production rate of biuret is along with the increase of vaporization temperature increases.Therefore in actual production, vaporization temperature should be low as much as possible, keeps getting final product for high 3～5 ℃ than melting temperature.2. the increasing amount of biuret is to increase along with the growth of the residence time.
Based on the generation research of biuret, the increment of mainly taking following measures control biuret to generate.1. adopt and rise the quick vertical column tube evaporimeter of membrane type.Thereby shortened the residence time in heating zone.2. adopt vacuum-evaporation, vacuum-evaporation can reach and reduce evaporation operation temperature and urea soln in the residence time of heating zone two purposes.On the one hand, reduce because the boiling point of urea soln is reduction (increase of vacuum tightness) with working pressure, for example 99.0% (quality %) fusing urea is under the 5.733kpa at pressure, and ctystallizing point is 130 ℃; Pressure is under the 6.67kpa, and its boiling point is 135.5 ℃; Pressure is when 7.47kpa, and its boiling point rises to 140 ℃.Promptly under lower pressure, can the lower service temperature of corresponding employing.On the other hand, when operating under vacuum, because the density of water vapour is very little, the speed that evaporated vapor flows through the heating tubulation is very high, and urine residence time in the tubulation section can be reduced to less than centisecond.2. evaporating thermal source adopts low-pressure saturated steam keeping under the certain temperature Impetus Condition, adopt low-pressure saturated steam, the tubulation inner wall surface temperature is low, also low with contacted urea droplets of inside pipe wall or urea melting liquid film temperature of superheat, thereby can reduce the increment of biuret.
2) a kind of hydrolysis of side reaction urea
Urea and water effect generate NH
3And CO
2, as be retained within the system, reclaimed, can not cause damage.But urea generation hydrolysis reaction will reduce the urea productive rate, increase the consumption of steam and water coolant.The hydrolysis reaction formula of urea in the aqueous solution as shown in the formula.
NH
2CONH
2+H
2O＝2NH
3+CO
2
Hydrolysis of urea speed is subjected to temperature, the residence time and strength of solution and free NH
3Influence very big.1. hydrolysis of urea is thermo-negative reaction, improves temperature and promotes hydrolysis.When temperature was lower than 110 ℃, the hydrolysis rate of urea was very slow; Greater than 110 ℃ of then hydrolysis rate quickenings; Hydrolysis rate increases severely more than 145 ℃; In the ebullient aqueous solution of urea, hydrolysis will be more violent.2. become to increase progressively relation about starting point concentration, the residence time that studies show that water in hydrolysis of urea rate and the solution, i.e. the starting point concentration height of water (being that urea concentration is low more), the residence time is long, and then the hydrolysis of urea rate is just big.3. there is free NH in the urea soln
3, can play a part to suppress hydrolysis of urea, free NH
3Amount increases, and then the hydrolysis of urea rate reduces.
In the evaporative process, the measure that reduces the hydrolysis of urea rate is to adopt vacuum operating to reduce temperature and to shorten the residence time of urea soln in equipment, pipeline.
3) a kind of side reaction urea decomposition reaction
Urea is under the molten state (dual circulation and granulation) and decomposition reaction easily takes place generates cyanic acid and ammonia and escape into gas phase.Reverse again generation urea when temperature reduces.
NH
2CONH
2＝HNCO+NH
3
Following formula moves right with the rising of temperature.Under traditional dual circulation condition, the urea decomposition rate can reach 0.40%～0.42% (quality %).Contain a small amount of urea in the dual circulation phlegma, except the entrainment of secondary steam, almost half is the result by gas phase HNCO backward reaction.So the urea of evaporation condensate can not be belonged to the result of the too high generation of secondary steam flow velocity fully.
In sum, urea soln is a kind of typical thermosensitive solution, and three kinds of main side reaction generating capacities in the evaporative process all increase with the raising of temperature and the growth of the residence time.Therefore, in adopting all urea plants of sprinkling pelleting, the final evaporation of urine has all selected heat transfer coefficient big, and the residence time is short, the relatively low vacuum of vaporization temperature, rises the film heater pattern.This type evaporates why operational condition is so harsh, mainly be since the urea crystals temperature up to 132.6 ℃, urea soln will reach high density or fusing urea state, must select to be higher than the operational temperature conditions of its Tc, thereby take place fast when having caused multiple side reaction.In addition, because this type evaporation needs high vacuum condition, the squirt pump power steam consumption of therefore keeping its vacuum condition is big especially.
The evaporation preconcentration technique thermal source that domestic well-known expert releases be with in press minute to vent one's spleen and be thermal source, because of inside and outside all are processing medium facility investment height.Relevant capacity expansion revamping of the same trade, design has steam-heated ' rising membrane type ' urine preconcentration technique, and its high pressure scrubber heat of condensation is not recycled, and is all taken away by water coolant, this is a big defective in the comprehensive utilization of device energy.The urea plant that domestic other company's daily outputs are 2700 tons, wherein also adopted with temperature adjustment water be thermal source rise membrane type urine preconcentration technique, employing rises film-type evaporation must must have high vacuum condition to obtain low-density high velocity air, thereby guarantee the liquid film flow state in the pipe, therefore, the setting of squirt pump is indispensable, is unfavorable for energy-conservation.
Summary of the invention
Purpose of the present invention promptly is to overcome the shortcoming of prior art, a kind of method that adopts the falling film type evaporation heater concentrating thin urine is provided, urine concentration improves 4.5-6%, with limited discarded thermal source is heating medium, the moisture steam rate of urine is lower, the falling film type evaporation film forming required than the rough vacuum conditional decision need not to be provided with again and increase the squirt pump that power steam consumes, use this technology save energy widely, and facility investment is saved more.
Purpose of the present invention is achieved through the following technical solutions: adopt the method for falling film type evaporation heater concentrating thin urine, seal in CO
2After the vaporizing extract process urea manufacture craft circulation workshop section, before the evaporation section, urine forms top-down membranaceous flowing by each root tubulation inwall that acts on of liquid distributor, pipe is outer by high pressure scrubber temperature adjustment water supply heat, part moisture is evaporated, urine concentration improves, and the vacuum condition of preconcentration technique is kept by pre-concentration surface condenser and the original one section evaporation injection pump of urea plant.
Service temperature 90-102 ℃, the working pressure absolute pressure is 35-50kpa.
The urine charging adopts symmetric double to feed liquor.
The urine sparger adopts the distribution mode of four tangential small-holes, and hole diameter is ф 2.5～3.5mm, and separator adopts the wire mesh demister separated urine to drip.
Separator and well heater are connected to an integral device, and separator is last, and well heater is following, and the urine feed entrance point is at the separator hypomere.
By last and narration as can be seen, the present invention has the following advantages: the bottleneck of having removed vapo(u)rization system the first, fully.The second, the operating mode of vapo(u)rization system is independent more, steady, no longer is subjected to circulating pressure height, free ammonia to decompose halfway the influence.Three, the used heat of high pressure scrubber temperature adjustment water has obtained comprehensive utilization, and energy-saving effect is remarkable.Per hour can save about 3.8Mpa steam 5t/h, a year wound economic benefit reaches 3,600,000 yuan; Four, this technology has great dissemination, and it is the preferred plan that high pressure temperature adjustment water used heat utilizes, and also is that the falling film type evaporation technology is at CO
2First Application in the vaporizing extract process urea plant.
Description of drawings
Fig. 1 is a schematic flow sheet of the present invention.
Fig. 2 is that the present invention is at whole C O
2Vaporizing extract process is produced residing position in the urea technique.
Embodiment
The present invention will be further described below in conjunction with accompanying drawing: as shown in Figure 1, present embodiment is for being applied to produce daily 1620 tons of CO
2The technical process of vaporizing extract process urea plant, come from the recycle system, concentration is about 72%, temperature is that 95 ℃ urine is entered urine storage tank Room the 1st, and through the annular intake chamber of urine pump delivery to the separator bottom, the urine flow control is realized by the hand-operated regulator that is provided with on the outlet line.Drop to the upper tubesheet of well heater all around along separator wall through the first urine of dividing of bi-directional symmetrical feed liquor mode, in this position, the top of each root tubulation all is equipped with an interpolation type sparger, four tangential holes on each sparger are assigned to urine each root tubulation of evaporation heater, and at tubulation inwall formation liquid film, in absolute pressure is that the moisture content in the urine partly evaporates under the vacuum condition of 35-50kpa, and heat is by shell-side high pressure temperature adjustment water supply.The liquid of finishing that urine evaporation and concentrating gradually in the falling film type tubulation, temperature 90-102 ℃, concentration improve 4.5-6% returns to go back to urine storage tank Room the 2nd by atmosphere; The secondary steam that evaporates is along rising on the tubulation center, enter separator through the sparger riser, at the separator headspace wire mesh demister is installed, with the urine drop of carrying secretly in the separated secondary steam, be imported into the surface condenser shell-side through the secondary steam after separating, condensation under the water cooling of pipe internal recycle; Do not coagulate gas and be sent to one section evaporative surface condenser to keep the negative pressure of preconcentration technique.
As shown in Figure 2, adopt the method for falling film type evaporation heater concentrating thin urine, seal in CO
2After the vaporizing extract process urea manufacture craft circulation workshop section, before the evaporation section, dotted portion is that the present invention is at whole C O
2Vaporizing extract process is produced residing position in the urea technique.
Claims (3)
1. adopt the method for falling film type evaporation heater concentrating thin urine, it is characterized in that: seal in CO
2After the vaporizing extract process urea manufacture craft circulation workshop section, before the evaporation section, urine forms top-down membranaceous flowing by each root tubulation inwall that acts on of liquid distributor, pipe is outer by high pressure scrubber temperature adjustment water supply heat, part moisture is evaporated, urine concentration improves, and the vacuum condition of preconcentration technique is kept by pre-concentration surface condenser and the original one section evaporation injection pump of urea plant; Service temperature 90-102 ℃, the working pressure absolute pressure is 35-50kpa; The urine sparger adopts the distribution mode of four tangential small-holes, and hole diameter is φ 2.5～3.5mm, and separator adopts the wire mesh demister separated urine to drip.
2. the method for employing falling film type evaporation heater concentrating thin urine according to claim 1 is characterized in that: the urine charging adopts symmetric double to feed liquor.
3. the method for employing falling film type evaporation heater concentrating thin urine according to claim 1 is characterized in that: separator and well heater are connected to an integral device, and separator is last, and well heater is following, and the urine feed entrance point is at the separator hypomere.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100214016A CN1321977C (en) | 2005-08-03 | 2005-08-03 | Method for concentrating thin urine using falling film type evaporation heater |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100214016A CN1321977C (en) | 2005-08-03 | 2005-08-03 | Method for concentrating thin urine using falling film type evaporation heater |
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|---|---|
| CN1749242A CN1749242A (en) | 2006-03-22 |
| CN1321977C true CN1321977C (en) | 2007-06-20 |
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| CNB2005100214016A Active CN1321977C (en) | 2005-08-03 | 2005-08-03 | Method for concentrating thin urine using falling film type evaporation heater |
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Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102101834B (en) * | 2009-12-17 | 2013-05-15 | 北京中寰工程项目管理有限公司 | Energy-saving modification method of CO2-stripping urea device |
| CN103055526B (en) * | 2011-10-24 | 2015-07-01 | 中国石油化工股份有限公司 | Method for evaporating cyclohexanone-oxime |
| CN102553275A (en) * | 2012-03-16 | 2012-07-11 | 瑞安市四方药化机械有限公司 | Normal temperature evaporation concentrator |
| CN103537105B (en) * | 2012-07-11 | 2015-05-20 | 蓝星(北京)化工机械有限公司 | Multi-phase flow evaporation system with distributor and application of multi-phase flow evaporation system |
| CN103418211B (en) * | 2013-08-23 | 2015-06-10 | 湖北宜化化工股份有限公司 | Process and device for heat utilization of high-pressure temperature-regulation water in shell side of high pressure scrubber in production in urea steam stripping method |
| CN107286058B (en) * | 2017-08-22 | 2023-04-18 | 四川金象赛瑞化工股份有限公司 | Urea first-stage evaporation control system and method |
| CN111137906A (en) * | 2020-03-13 | 2020-05-12 | 安徽六国化工股份有限公司 | Device and method for treating urea dilute urine solution |
-
2005
- 2005-08-03 CN CNB2005100214016A patent/CN1321977C/en active Active
Non-Patent Citations (1)
| Title |
|---|
| 多效降膜蒸发设奋在木糖生产中的应用 刘殿宇，粮油加工与食品机械，第9卷 2001 * |
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| CN1749242A (en) | 2006-03-22 |
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