CN206705995U

CN206705995U - For producing the integrated system of urea and urea ammonium nitrate

Info

Publication number: CN206705995U
Application number: CN201621223027.8U
Authority: CN
Inventors: J·多布里; J·H·门嫩
Original assignee: DSM IP Assets BV
Current assignee: DSM IP Assets BV
Priority date: 2016-09-28
Filing date: 2016-09-28
Publication date: 2017-12-05
Anticipated expiration: 2026-09-28

Abstract

Disclose a kind of integrated system for being used to produce urea and urea ammonium nitrate.The system includes (i) urea production unit, the urea production unit includes urea synthesizing part and in the downstream of composite part and the urea purification part of fluid communication therewith, the urea synthesis section is divided including fluid communication each other to form the reactor in urea synthesizing loop, stripper and condenser, and the unit of (ii) for generating ammonium nitrate.

Description

For producing the integrated system of urea and urea ammonium nitrate

Technical field

The present invention is combine production method and ammonium nitrate urine in particular, to urea liquid on field of urea production The production of plain solution (UAN), urea liquid are applied to reduction engine exhaust gas, for example by diesel engine (DEF：Automobile environment-protection Urea) caused by NO in waste gas_X.The invention further relates to the equipment for implementing methods described.

Background technology

Urea is generally by ammonia and carbon dioxide production.It can by by excess ammonia together with carbon dioxide between 12 Hes 40MPa pressure and urea synthesizing part is concomitantly introduced at a temperature of 150 DEG C and 250 DEG C and is prepared.Typical urea Production equipment further comprises recovery section and finishing part.In recovery section, unconverted ammonia and carbon dioxide are recovered And it is recycled to composite part.Recovery section generally follows evaporation section.Wherein urea concentration by the evaporation of water and further Increase, obtains highly concentrated solution, it is commonly known as urea melt.In finishing part, generally, urea melt is made into the phase The granular solids of prestige, generally include technology as such as granulation, granulation or pelletizing.

Still there is considerable CO2 in evaporation section and especially NH3 is eliminated.By being handled in scrubbing tower come clear Except ammonia.It then arrives at treatment unit for waste water, and it is that cost is very high and operation of energy intensive.

Urea product interested is to be used to reduce NOx, such as the solution used in selective reduction, and it can be with right and wrong It is catalyzed thermal process or SCR (SCR) process.Example for SCR solution is automobile environment-protection urea (DEF), Terminology used herein typically refers to the urea liquid for reducing NOx.

DEF is solution of the 32.5wt.% urea in softened water, is formed as up to 0.3wt.% biuret and most The mostly 0.2wt.% basicity as ammonia.DEF is commercially bought, trade name The Hes of Arla 32 AUS-32, and be injected into the tail gas of internal combustion engine to capture NO_x, to prevent it from leaking in air.DEF purpose is to pass through React NO below_xIt is converted into harmless nitrogen and water：Urea+NO_x→N₂+H₂O.The NO come from internal combustion engine_xReduction it is extensive Ground is implemented, because NO_xIt is the main source for the environmental pollution for indicating global warming, such as global warming potential (GWP), Tropospheric ozone formation potential (TOFP) and ozone layer destroying potential (ODP).

The production of automobile environment-protection urea (DEF) is generally completed by the way that solid urea product is dissolved in softened water.Solid Urea product, such as produced by one of foregoing finishing technique, and be combined with softened water, solution is mixed until urea is complete Fully dissolved.This method has the defects of such, wherein needing considerable input in urea finishing technique, and needs to remove Byproduct (such as using or during arranging caused by additive) such as formaldehyde or biuret (it is urea byproduct) to be to obtain To the product for it is expected specification.Common biuret concentration is 0.9-1.1wt.% in product after arrangement.This is so as to causing final DEF Thus Biuret Content in product obtains underproof material more than 0.3wt.%.Permitted at present according to ISO22241 specification Permitted to be up to 0.3%.Higher biuret concentration causes DEF solution in capture NO_xAspect it is poorly efficient because less urea can It is used for capture NO_x.In addition, in the production process for being granulated and being granulated, substantial amounts of water is eliminated, and it is later in dissolving step It is added into.This needs substantial amounts of energy, result in extra cost.

Improved process disclosed in EP1856038A1, using the recovery section directly from urea melt equipment or The aqueous solution of urea obtained after from it, and the aqueous solution of urea is diluted with water to obtain desired solution.Urea is water-soluble Liquid can be admitted to evaporation section in addition to remove water from urea melt to be produced by fluid bed granulation, pelletizing or granulation Solid urea.In this way, the demand to evaporation water is eliminated, but aqueous solution of urea contains relative high levels Ammonia, which is beyond that the specification of final DEF products.EP1856038A1 disclose in solution ammonia level (as free ammonia or with The form of aminoquinoxaline) it can be reduced by being dissociated aqueous solution of urea, such as by heating or reducing pressure, appoint Selection of land is by adding the combination of stripping fluid or foregoing approach.Steaming of the step actually with the conventional finish part of urea equipment It is identical to send out step, and can be by implementing with the evaporation step identical equipment, therefore sometimes referred to as " evaporation walks Suddenly " or " prevapourising step ".Prevapourising step is designed to produce aqueous solution of urea after being diluted with water, and meets that automobile environment-protection is urinated The requirement of element.

The defects of main is that prevapourising step discharges from aqueous solution of urea and has inert ammonia, its can need to be eliminated with Meet emission intensity regulation, it is necessary to special condensation/washing part and subsequently at the waste water together with urea melt integration of equipments Part is managed to reclaim the ammonia of release.

Urea ammonium nitrate (UAN) is a kind of chemical fertilizer, and it is generally used with the aqueous solution of urea and ammonium nitrate.Ammonium nitrate passes through Ammonia and strong salpeter solution are reacted and produced, while the pH of solution is maintained in narrow scope.Then by obtained solution with Aqueous solution of urea is mixed to obtain UAN.Typical UAN products include 28wt.% to 32wt.% total nitrogen and are usually 29wt.% to 38wt.% urea and the ammonium nitrate from 36wt.% to 48wt.%, residue are water.

UAN demand is generally influenceed by strong seasonal fluctuation, and this causes the equipment for it is expected searching operation UAN Mode, which make it that economically attractive application can also be carried out low to UAN demands in the period of.Therefore should be noted It is that the aqueous solution of urea produced in the representative UAN equipment for producing final UAN products is commonly used for producing DEF. In aqueous solution of urea ammonia density (>2000ppm wt.) usually above DEF production in allow concentration (<0.2wt.%).And And because UAN products are liquid, long-distance transportation is inconvenient and expensive.

It is expected in this way to combine urea and UAN production, enabling compensate UAN low demand. Be especially desired to the arrangement for urea and UAN production being combined as providing, wherein obtaining the urea for meeting to be used as DEF requirements The aqueous solution.Additionally, it is desirable to provide more economical mode handles ammonia waste from Urea Evaporation part.

As background technology remote, with reference to US4,174,379.It is disclosed that the stream for producing urea and UAN Journey.Urea is produced by once-through type urea production process.The urea production process of the type is out-of-date, and with modern flow With substantially different features, the flow is substantially single stripping process.For example, when direct current process congenitally produce it is low During the biuret of content, biuret is the steam stripped inevitable byproduct from urea reaction solution.It is believed that this is As caused by relatively high temperature and concentration dominant in Urea Stripping Tower.As mentioned above, for DEF, biuret is only Allow to exist (especially as defined in applicable ISO and DIN standards) with extremely low level.Therefore, produced in stripping process In the activity of urea, the urea liquid that production is applied to be converted into DEF is particularly challenging.

The content of the invention

In order to preferably solve foregoing one or more needs, one aspect of the present invention is provided for producing ammonium nitrate urine The flow of element, it comprises the following steps：

- nitric acid and ammonia is reacted in ammonium nitrate production unit under conditions of it can obtain aqueous ammonium nitrate solution；

- carbon dioxide and ammonia is reacted under urea-formation condition to obtain including water, urea, aminoquinoxaline, and not The CO2 and NH3 of reaction reaction solution；

- stripped the reaction solution to obtain unreacted ammonia and carbon dioxide, and steam stripped reaction solution；

The ammonia of the recovery and carbon dioxide are recycled as being formed to the original material of urea；

- the stripping reaction solution separated into air-flow to obtain urea current and include CO2 and NH3；

- using the NH3 in the air-flow as reactant it is supplied to the ammonium nitrate production unit；

- mix at least partly described urea current to obtain urea ammonium nitrate solution with the aqueous ammonium nitrate solution.

On the other hand, the invention provides the integrated system for urea and urea ammonium nitrate production, the system to include (i) urea production unit, the unit include urea synthesizing part and in the downstream of composite part and the urine of fluid communication therewith Plain purification part, the urea synthesis section are divided including the reactor of fluid communication, stripper and condenser each other that can be formed Urea synthesizing loop, the urea purification part are suitable to CO2 and NH3 from the aqueous solution of urea including the CO2 and NH3 Separate, and (ii) is used for the unit from ammonia and nitric acid generation ammonium nitrate；Wherein the NH3 of urea equipment purification part is gone out Mouth is connected to the NH3 entrances of the unit for producing ammonium nitrate, and the wherein aqueous solution of urea outlet by purification part and nitre The aqueous ammonium nitrate solution outlet of sour ammonium production unit is connected to mix the aqueous solution of urea and the aqueous ammonium nitrate solution Unit.

On the other hand, the present invention is the method for modernizing urea equipment, and the urea equipment includes urea synthesis section Point and include fluid each other in the downstream of composite part and the urea purification part of fluid communication therewith, the urea synthesis section point To form the reactor in urea synthesizing loop, stripper and condenser, the urea purification part is suitable to CO2 and NH3 for UNICOM Separated from the aqueous solution of urea including the CO2 and NH3, methods described, which is included in urea equipment, to be added for by ammonia With the unit of nitric acid production ammonium nitrate, it is connected to wherein the NH3 of urea equipment purification part is exported for producing ammonium nitrate The NH3 entrances of unit, and it is wherein that the ammonium nitrate of the aqueous solution of urea outlet of purification part and ammonium nitrate production unit is water-soluble Liquid outlet is connected to the unit for mixing the aqueous solution of urea and the aqueous ammonium nitrate solution.

On the other hand, the invention provides a kind of method for the equipment modernization that will produce ammonium nitrate, the equipment bag Include for the unit by ammonia and nitric acid nitric acid synthesis ammonium, methods described be included in for produce ammonium nitrate equipment in add urea Production unit, equipment described whereby are integrated in a manner of aforementioned paragraphs describe.

Brief description of the drawings

Fig. 1 to 5 is the device feature related to embodiments of the present invention and the schematic diagram of process stream.

Fig. 1 is to show a kind of embodiment figure that NH3 and CO2 are supplied to urea synthesis zone.Wherein NH3 is fed into Reactor for synthesis of urea, and CO2 is fed into high-pressure stripper.The urea synthesis solution of formation is directed to purification part.Its It is middle to remove unreacted NH3 and CO2 from synthetic solvent.The part of obtained urea current be used to obtain DEF, partly quilt For being mixed with ammonium nitrate (not shown) to obtain UAN.The NH3 of removing, it is not to be re-circulated to urea synthesizing, but is sent To the unit (not shown) for producing ammonium nitrate.

Fig. 2 is the figure for showing the another embodiment that NH3 and CO2 are supplied to urea synthesis zone.Here urea is water-soluble Liquid is sent in pond.Flow is selected from here so that aqueous urea to be used for UAN production, for DEF production, or for both Production.This has the benefit for the aqueous solution of urea for providing buffering capacity, and which increase the flexibility of flow.

Fig. 3 is to show the steam air lift by using direct steam injection, and is sprayed by using LP steam and send tail gas To the figure of the unit of production ammonium nitrate.

Fig. 4 is showing the figure of the DEF productions using hot vapour stripper.According to the DEF of the present invention and UAN integrated metaplasia Production, the tail gas from hot vapour stripper are sent to AN averagers, cleaned without being delivered to gas treatment and waste water treatment section.

Fig. 5 is showing the configuration similar to Fig. 4, so as to use condenser and steam jet ejector as alternative route with Tail gas is delivered into AN parts to be used to neutralize.

Embodiment

The present invention is based on the wise insight for integrating the production of DEF productions and liquid UAN chemical fertilizer.Due to the number of equipment Amount less, zero-emission and the possibility for cancelling waste water treatment section, it provides economically attractive, flexible adaptation market and needed Ask, and the flow of environment and energy close friend.According to the present invention, the ammonia waste gas from urea production is sent to the AN of UAN equipment Part, wherein ammonia waste gas (it can be liquid ammonia or or be (can be attenuable) gaseous ammonia) are neutralized with shape by nitric acid Into AN, UAN is thus mixed into.So waste gas is not passed to external environment, but stays in flow.

Especially, when by DEF productions and the integrated production of UAN liquid fertilizers, or even including being given birth to by stripping process Produce the surprising urea concentration of low-shrinkage two that can also be realized in the flow of urea between 0.01wt.% and 0.3wt.%.It is believed that The low Biuret Content enables in particular to obtain by the recycle sections with relatively low pressure (LP).Normally, urea strips The LP recycling (recovery) of equipment partly includes multiple device features, wherein in some regions application high temperature (such as on 135 DEG C of left sides It is right).Biuret Content easily increases, and this is due to the longer residence time in the LP parts.The possibility for cancelling device has Beneficial to the residence time (such as being defined to single rectifying column) reduced in LP parts.This, which is accordingly provided, can reduce contracting two The benefit that urea is formed.

In addition, in the flow of the present invention, the steam from recovery section is sent to ammonium nitrate part.In traditional flow In, these steam are condensed to form carbamate solution, are subsequently returning to HP composite parts.This is actually resulted in water circulation To composite part.In embodiment interested, urea is being set as being specifically used in devices of the DEF with UAN co-productions Production.Especially, from there through submerged condenser/reactor, (it is urea reactors and drowning pipe carbamate condensation to urea Device is integrated) production, such as pool reactor, it is horizontal submerged condenser/reactor.In the configuration without by water/ Carbamate recycle is into urea synthesizing.This is favourable, because it make it that urea synthesizing is more effective.

Further, due to the present invention allow production dedicated for DEF urea, can use different process settings with Minimize the generation of biuret.For example, by reducing the temperature in stripper.This can have suitable effect, because contracting Two ureas are mainly formed in its exit.Temperature and rise pressure are reduced in LP parts to reduce the formation of ammonia content and biuret It is and possible.

Result is can to obtain more urea in DEF solution to be used to capture NOx, is caused higher in the de- NOx applications of heat The DEF final products of effect.The efficiency of as a result selective non-catalytic reaction (SNCR) technology can be raised to 20%.Pass through the way Footpath, less urea are converted into biuret, it means that being based on the present invention relative to existing scheme can also produce more DEF final products, while the raw material that DEF final products per ton need have lacked about 1%.Further, since no longer need pre- steaming Hair, condensation and wastewater treatment, eliminate substantial amounts of fund input.This can be by using the pressurization directly from recovery section Urea liquid and realize.

The urea production process implemented in the present invention has obtained current.Make the current different from need wastewater treatment Evaporation, The inventive process provides the flexible Application to it.By the way that it is combined with ammonium nitrate, at least part stream is used for UAN production.Meanwhile the ammonia obtained from the separating step for obtaining the urea current is used for the production of ammonium nitrate.

Preferably, the amount for the urea current of UAN productions at least produces with the amount of the ammonia by being separated in urea production The amount of ammonium nitrate is suitable.

This can understand that is, urea ammonium nitrate solution includes 29wt.% to 38wt.% by reference to the fact Urea and 36wt.% to 46wt.% ammonium nitrate.It is therefore preferred that the aqueous solution of urea part mixed with ammonium nitrate solution Amount be at least enough to provide as supplying to the amount of desired ammonium nitrate obtained by the NH3 of ammonium production unit amount.

According to the present invention, the selection for further using urea current is given.This can either be used to obtain DEF, and its is another An outer part (or even all) can also be used for UAN production.It will be appreciated from, if more urea are used for UAN production, further amounts of ammonium nitrate is also provided accordingly.This can be the ammonium nitrate from extraneous source, can be by Ammonia and the ammonium nitrate of nitric acid produced on-site, or both are.

In the method for the invention, by by aqueous urea and the aqueous ammonium nitrate mixture manufacturing UAN, to obtain nitric acid Ammonium urea liquid.By making ammonia and nitric acid reaction produce ammonium nitrate.

The industrial production of ammonium nitrate is related to the acid-base reaction of ammonia and nitric acid：

HNO3+NH3→NH4NO3

Ammonia is generally used with its anhydrous form gas and nitric acid is

(the usual concentration range of concentration：40 arrive 80wt.%, such as about 60wt.%).Pass through exothermic reaction, ammonium nitrate Concentration of the solution generally about 70% to 95%, such as 83% to 88% are readily formed.Manufacture solid ammonium nitrate product, Such as when particle or spherolite, excessive water is evaporated to reach the ammonium nitrate of 95% to 99.9% concentration (AN) content, works as preparation The step can be removed during urea ammonium nitrate solution.The UAN solution can be by the way that aqueous solution of urea and ammonium nitrate solution be mixed To prepare.

Nitric acid for ammonium nitrate production can be fed intake to obtain by outside.Preferably nitric acid is prepared in situ, because For the visual angle of economy, this is than the usual more attractive of transport dependent on nitric acid.

Preferably, method of the invention is implemented in the integrated system for producing urea and urea ammonium nitrate.This is System includes (i) urea production unit and (ii) for the unit from ammonia and nitric acid production ammonium nitrate.Urea production unit includes vapour Carry type urea synthesizing part and, downstream and the urea purification part of fluid communication, the urea purification part are fitted therewith Separated in by CO2 and NH3 from the aqueous solution of urea including the CO2 and NH3.According to the present invention, by urea production list The NH3 outlets of first purification part are connected to the NH3 entrances of production ammonium nitrate unit, the NH3 that will be separated from urea production Supply feeding intake for ammonium nitrate production.In addition, make the urea current that will be obtained from urea production unit with from ammonium nitrate production The preparation for the liquid ammonium nitrate mixing that unit obtains.Therefore, by the outlet of the aqueous solution of urea of urea production unit purification part and The aqueous ammonium nitrate solution outlet of ammonium nitrate production unit, is connected to and mixes the aqueous solution of urea and the aqueous ammonium nitrate solution Unit.

The invention further relates to such integrated system for being used to produce urea and urea ammonium nitrate.The system of the present invention is also It can include or may not include the unit of production nitric acid.The key industry method for producing nitric acid is to come from ammonia.

Therefore, in the presence of platinum or rhodium mesh catalyst under about 500K high temperature and 9 bars of pressure, anhydrous ammonia is by oxygen Turn to nitric oxide.

4NH3(g)+5O2(g)→4NO(g)+6H2O(g)

Nitric oxide is then reacted with the oxygen in air to form nitrogen dioxide.

2NO (g)+O2 (g) → 2NO2 (g) (Δ H=-114kJ/mol)

It is then absorbed into water to form nitric acid and nitric oxide.

3NO2 (g)+H2O (l) → 2HNO3 (aq)+NO (gas) (Δ H=-117kJ/mol)

It is reoxidized that nitric oxide loops back progress.Alternately, final step can be implemented in atmosphere：

4NO2(g)+O2(g)+2H2O(l)→4HNO3(aq)

Obtained aqueous nitric acid can be concentrated by distillation, generally reach for about 68% (in mass).

Benefit on the method and system of the present invention is that nitric acid can be in the scene system with the infrastructure for ammonia It is standby, because this is also used as the feed of urea production.

If the system of the present invention includes being used for the unit for producing nitric acid, the unit generally will feed intake from extraneous source, and By the outlet of the nitric acid of the nitric acid entrance fluid communication with the unit with producing ammonium nitrate.

Urea production unit can be traditional urea stripping facility, also comprehensively be set in the downstream of synthesis and recovery section It is equipped with evaporation section, waste water treatment section and finishing part.But as the important benefits of the present invention, can be in no evaporation part Divide and the urea of waste water treatment section strips the urea produced in production unit for DEF and UAN.Moreover, conventional arrangement portion Dividing and (being used to form solid urea form such as particle, bead and granule) to be removed.Because in the flow of the present invention, DEF can be diluted to obtain by will separate the part urea current obtained from urea reaction solution with softened water.This is obtained The solution being applicable in the NOx reduction units.

The method of the present invention can also be implemented such that to produce DEF in solid form.Therefore, can be to molten from urea reaction The part urea water stream that acquisition is separated in liquid carries out flash crystallization.This is used to form solid urea powder, and it is suitable to by using soft Change water dilution and be converted into the solution suitable for NOx reduction units.This has very big benefit, because transport solid urea powder End will need than needing to have more attraction economically for transporting using DEF as solution using DEF as solution to transport Substantial amounts of water is transported in EDF production scene.

For producing solid urea product by flash crystallization, with reference to WO2013/055219.Wherein disclosed production It is by applying mechanical force in urea crystals.This can save the step with life for production for the powder that can be diluted Produce DEF.Especially, the urea powder of free-flowing can be obtained by obtaining urea current as described above, by the material Stream carries out flash crystallization under subatmospheric pressure, includes the product of solid crystal urea and including water and ammonia to obtain Steam, wherein the solid crystal urea product contains the water less than 0.2wt.%；And preferably wrap in such a situa-tion Fill solid crystal urea product so that the water content in the product of packaging is maintained at below 0.2wt.%.Thus, flash crystallization quilt Preferably implement under the pressure less than 15kPa, more preferably from 1 to 10kPa.In addition, flash distillation is preferably implemented as dry type sudden strain of a muscle Steam.

Flash distillation can be carried out in flashing apparatus, such as dry type flash column.Dry type flash column is characterized in that liquid flow passes through Crystallization and evaporation are essentially converted to solid and steam.Process conditions in dry type flash column are selected so that the liquid of residual The scale of construction is substantially zeroed.This allows gas and solid thoroughly to separate, basic without adhesion and incrustation.Another benefit of dry type flash distillation It is the presence because without slurry, did not both need separation of solid and liquid for example to centrifuge, it is not required that remelted.This permission is very simple Porcess system.Such dry type flash column is preferably between 1 and 15kPa, more preferably under the pressure between 2 and 10kPa The container of operation.Urea liquid is allocated by liquid distributor in the dry type flash column.By expansion, urea and contracting Two ureas spontaneously crystallize in solids, and the evaporation of the residual component including water, ammonia and a small amount of carbon dioxide.

The particle size of the solid urea product obtained by adiabatic flash is at 0.1 micron to 1000 microns, preferably 1 micron To in the range of 800 microns.

In this embodiment, flow of the invention allows the powder that production flows freely, its can with bag (20kg) or Sack (i.e. 500kg or 1000kg bag) is packed, and it can produce DEF solution by easy emptying at the scene.

The urea powder produced by the flow has a low-down two ureas content, and typically less than 0.5%, it is preferably few In 0.4%, it is scaled is less than 0.20% or less than 0.15% weight in final DEF solution.This means thus identical Solids content under the amount of active urea in solution will be higher.Biuret specification is up to 0.3% for final DEF solution Weight meter.When granule be used to prepare solution, the Biuret Content in solution is generally between 0.27 and 0.36wt%.

In the embodiment of the inventive method, the solid crystal urea product of acquisition is wrapped in such a situa-tion Dress so that the water content in the product of packaging is maintained at less than 0.2wt.%.The low water content is used for ensuring that solid urea is born It is moisture absorption, the powder of solution can be discharged and re-form from its packaging by remaining.According to the present invention, the product of packaging Water content is maintained below aforementioned levels until product be used to prepare solution.

In practice this means that by the powder packaging of the tool low water content in need of acquisition in non-seepage of water packaging (example Such as container or packed).Suitable packaging material includes high density polyethylene (HDPE).Other plastics for being suitable for packing hygroscopic material are these Known to field.Packaging material can be non-porous and seal.Moreover, packaging can be formed by multilayer material.

Plan is with by the way that by aforementioned powder, it is dissolved in softened water to use to obtain DEF.It should be understood that it is also It can be used for preparing UAN, such as in the case where there is high demand to UAN so should be preferable.In the case of later, Powder can also be dissolved in ordinary tap water.

In the flow of the present invention, urea can strip flow by any suitable urea and be synthesized.Such stream Cheng Tongchang is implemented in stripping apparatus.Urea synthesis section in stripping apparatus point includes at least one reactor, stripper and cold Condenser.These are generally operated under high pressure (HP), and HP reactors, HP strippers and HP amino first are typically referred in this area Hydrochlorate condenser.Reactor, stripper and condenser be each other fluid communication to form urea synthesizing loop.This is for ability Other explanation is not needed for field technique personnel.Generally, reactor can produce the urea synthesizing aqueous solution.The solution will enter Row is stripped to produce stripper solution and atmospheric carbon dioxide and ammonia.Gas component will be condensed within the condenser, obtain amino Ammonium formate, it is re-circulated to reactor.Depending on the type of condenser, there can also be a considerable amount of amino within the condenser Ammonium formate is converted into urea.Moreover, condenser and reactor can be integrated into single equipment.

In the flow of the present invention, further separation is carried out to stripper solution with obtain urea current and including CO2 and NH3 air-flow.The separation generally occurs under the pressure less than composite part.Such low pressure can be middle pressure (MP), low pressure (LP), or both can be included.MP and LP recycle sections (also referred to as recovery section) be well known to a person skilled in the art.It is right Main pressure is usually the 1-10 MPa orders of magnitude for MP parts, more typically 1-5MPa, is arrived for LP parts for 0.1 1MPa, more typically 0.2 arrives 0.6MPa.The equipment of the present invention and the scrap build method of the present invention are by providing appropriate MP And/or LP recycle sections are configured as being suitable for carrying out described flow.

The urea stripping flow being commonly used is carbon dioxide stripping flow, such as in Ullmann ' s Encyclopedia Of Industrial Chemistry, the A27 volumes, 1996, described in the 333-350 pages.In the flow, composite part Followed by one or more recovery sections.Composite part includes reactor, stripper, condenser and scrubbing tower, wherein operating Pressure is between 12 and 18MPa and is preferably ranges between 13 and 16MPa.In composite part, the urea liquid of urea reactors is left Stripper is supplied to, wherein a large amount of unconverted ammonia and carbon dioxide are separated from aqueous solution of urea.Such stripping Tower can be shell and tube exchanger, wherein urea liquid is fed into the top of pipe side and is added to the carbon dioxide for synthesis The bottom of stripper.In shell-side, steam is added with heated solution.Urea liquid leaves heat exchanger in bottom, while steam phase exists Leave stripper in top.Leaving the steam of the stripper includes ammonia, carbon dioxide and a small amount of water.The steam can be Condensed in horizontal or rectilinear falling-film heat exchanger or latent trumpet cooler.Horizontal drowning pipe heat exchanger is in Ullmann ' s Encyclopedia of Industrial Chemistry, the A27 volumes, 1996, the 333-350 pages was described.Described cold The heat discharged in condenser by carbamate condensation exothermic reaction is normally used for producing steam, and the steam is used under The Urea treatment part of trip is used to urea liquid is heated and concentrated.Because generated in latent trumpet cooler certain Liquid residence time, part urea reaction is had occurred that in the condenser.By the ammonia for including condensation of formation, titanium dioxide The solution of carbon, water and urea is sent to reactor together with uncooled ammonia, carbon dioxide and inert vapor.In the reactor above The reaction from carbaminate to urea mentioned reaches balance.Leave the ammonia and carbon dioxide in the urea liquid of reactor Mol ratio generally between 2.5 and 4mol/mol.It is also possible to condenser and reactor being combined as a whole formula equipment.Integral type is set Standby example such as Ullmann ' s Encyclopedia of Industrial Chemistry, the A27 volumes, 1996, Described in 333-350 pages.The urea liquid for leaving the formation of urea reactors is provided to stripper, and including uncooled ammonia It is sent to the inert vapor of carbon dioxide straight with the washing part of the pressure operation similar with reactor, or the steam Ammonium nitrate part is picked to be used to neutralize (i.e. with nitric acid reaction to form ammonium nitrate).In washing part, ammonia and carbon dioxide quilt It is washed from inert vapor.The carbamate solution of the formation of recovery system from downstream is used as washing in part Absorbent.Leaving the urea liquid of the stripper in the composite part needs at least 45wt% urea concentration, and is preferably At least 50wt%, to be handled in the one of stripper downstream individually recovery system.Recovery section includes heater, liquid Body/gas separator and condenser.Pressure in the recovery section arrives 600kPa between 200.In the heater of recovery section In, most ammonia and carbon dioxide are separated from urea and aqueous phase by heating urea solution.Usual steam is used as adding Thermit powder.Urea and aqueous phase, containing left on a small quantity from recovery section and be sent to the dissolving of the Urea treatment part in downstream ammonia and Carbon dioxide, Urea treatment part urea liquid by from the solution evaporation water concentrate.

The invention is not restricted to any specific urea production process.Other flows and equipment include setting based on such as complete alternation Standby, the HEC flows developed by Urea Casale, by Toyo Engineering Corporation exploitations ACES flows and By those of the technology of the flow of Snamprogetti exploitations.All these and other flows can be used for the method for the present invention.

In one embodiment, urea purification part includes the rectifying column with case tube heat exchanger and gas/liquid separation, Wherein aqueous solution of urea flows through pipe and steam is used for shell-side.Stripping gas can also be used in another embodiment.

The purpose of purification part is that CO2 and ammonia are removed in the aqueous solution of urea produced from composite part.Aqueous solution of urea Generally include urea, aminoquinoxaline and unreacted CO2 and NH3.As it is known to the person skilled in the art, CO2 and NH3 is urinating With aminoquinoxaline in balance in the plain aqueous solution.It is exothermic reaction to form aminoquinoxaline by CO2 and ammonia.From the aqueous solution Middle removing CO2 and NH3 can the influence that reduces of heated and/or pressure, selectively using stripping reagent.CO2 and ammonia conversion To gas phase (evaporation) will change aminoquinoxaline balance, thus promote aminoquinoxaline dissociation, its correspondingly facilitate CO2 and The evaporation of ammonia.

In urea equipment, the equipment for purification step is generally planned to the major function of completion to name with it.Art Language carbaminate recovery system, dissociator, stripper, (pre-) evaporator are conventional.Purification step can with standard urinary Implement in the equipment of the same type used in the recovery section of plain equipment.Such as rectifying column can be used.Alternately, can be with Shell-and-tube heat exchanger is used in container top optionally together with gas/liquid separation or by single gas/liquid separation.Purifying Step can be implemented in one or more steps.Other configurations and equipment are known to those skilled in the art. As optional stripping reagent, CO2, ammonia or steam can be used.In standard recovery part, raw material ammonia and CO2 are circulated Urea synthesizing part is returned to, therefore does not expect to use steam as steam stripping agent, because this will cause water to be recycled to urea synthesis section The increase divided.The present invention can avoid the limitation.If as preferable, no ammonia is recycled to composite part, purification part it The presence of water is not a problem afterwards.

The part urea current obtained from the purification part of urea equipment be used to prepare DEF.DEF production units use, For example, shell-and-tube or board-like is passed through using (heat) stripping (Fig. 3) of steam under pressure or in a heat exchanger based on directly injection The mode of heat exchanger uses the evaporation (Fig. 4) of steam under pressure, to carry out product matter to the ammonia content at urea synthesizing section port Amount control.Such stripping is used to remove excess of ammonia, to meet the DEF final products specifications of 0.2wt.% ammonia.

If it is necessary, at least level in pressurizeed the tail gas condensing come from hot vapour stripper and with steam jet ejector, and Merge the averager for delivering to ammonium nitrate part with the synthesis tail gas of routine.Alternately, these tail gas are transmitted directly to ammonium nitrate Averager (or after averager) part (Fig. 3 and 5) of production unit.Thus, the ammonia of release be used to neutralize nitric acid with life Produce ammonium nitrate.In this way, by using the ammonia from hot vapour stripper, it is possible to reduce for the conventional of neutralization reaction Ammonia, reduce the original ammonia consumption of ammonium nitrate equipment.The arrangement can be arranged with any urea synthesizing and is used together.This method promotees Efficient small special DEF productions are entered, or it can be produced with the extensive DEF of the production capacity similar to urea synthesizing It is combined.

Foregoing steam stripped alternative is will to be optimized in the urea melt concentration in the stage of urea synthesizing.In ammonia or In the case of carbon dioxide is steam stripped, following variable is used to obtain the urea melt solution for being suitable for DEF and producing：

- steam stripping efficiency (0.70-0.95) higher in HP strippers

- pressure (4-8bar) higher in low-pressure section

- pressure higher in receiving portions (15-40bar) is pushed back in

- higher the temperature (90-145 DEG C) used by low-pressure distillation heater

- condensation or the increase of reactor efficiency.

The present invention can be used in the method modernized to existing urea equipment.Such equipment includes urine Plain composite part and downstream and the urea purification part of fluid communication, the urea purification part are suitable for CO2 therewith Separated with NH3 from the aqueous solution of urea including the CO2 and NH3.Methods described includes adding for by ammonia to urea equipment With the unit of nitric acid production ammonium nitrate.Thus the NH3 outlets of urea equipment purification part are connected to the unit of production ammonium nitrate NH3 entrances.Moreover, the aqueous ammonium nitrate solution for the aqueous solution of urea of purification part being exported and being produced the unit of ammonium nitrate exports It is connected to the unit for mixing the aqueous solution of urea and the ammonium nitrate solution.

The benefit of sophisticated equipment is that it provides the other possibility using the ammonia reclaimed from urea equipment so that energy Enough save wastewater treatment.

It should be understood that the present invention is also adapted to establish the new urea equipment integrated with ammonium nitrate production unit.Such as with Upper discussion, very big benefit is that new equipment can be built into no evaporation section and waste water treatment section.It should be noted It is, if to more multi-functional different urea products (including solid urea form, such as granule or small in addition to DEF and UAN Ball) require, the new equipment with these parts can also be established.Moreover, just production can be the DEF of dilution as discussed above For powder, the new urea production unit with (flash distillation) crystalline portion is built up in the integrated system of the present invention, still, If desired, without moulding section, because such as granule or small in the form of producing solid urea may be traditionally used Ball.

The present invention is further described with reference to the drawings.It should be understood that accompanying drawing is not limitation of the present invention, example Such as, the invention is not restricted to shown certain types of equipment and specific device systems.All figures are shown with the present invention's The schematic diagram of the related device feature of embodiment and process stream.Part and stream are entered in the accompanying drawings by brief keyword Explanation is gone.

NH3 and CO2 are supplied to urea synthesis zone in Fig. 1.Embodiment is shown, wherein NH3 is fed into urea Synthesis reactor, and CO2 is fed into high-pressure stripper.The urea synthesis solution of formation is directed to purification part.Wherein will Unreacted NH3 and CO2 remove from synthetic solvent.The part of obtained urea current be used to obtain DEF, partly be used for Mixed with ammonium nitrate (not shown) to obtain UAN.The NH3 of removing, it is not to be re-circulated to urea synthesizing, but is sent to For producing the unit (not shown) of ammonium nitrate.

It will be noted that the use of part NH3 to produce ammonium nitrate and another part is recycled into urea synthesizing is possible. However, it is preferred that in order to fully realize the benefit of the present invention, any ammonia is not circulated.

Fig. 2 is similar with Fig. 1.Here aqueous solution of urea is sent in pond.Flow is selected to be used for aqueous urea from here UAN production, for DEF production, or the production for both.This has the benefit for the aqueous solution of urea for providing buffering capacity, Which increase the flexibility of flow.

Fig. 3 shows the steam air lift by using direct steam injection, and is sprayed by using LP steam and send tail gas To the unit of production ammonium nitrate.

Fig. 4 shows the DEF productions using hot vapour stripper.According to the DEF of the present invention and UAN integrated production, come from The tail gas of hot vapour stripper is sent to AN averagers, is cleaned without being delivered to gas treatment and waste water treatment section.

Fig. 5 shows the configuration similar to Fig. 4, so as to using condenser and steam jet ejector as alternative route with general Tail gas delivers to AN parts and is used to neutralize.Although the present invention be described in detail in accompanying drawing and first specification and Description, such explanation and description are considered as illustrative or exemplary and not restrictive；The invention is not restricted to open Embodiment.

For example, the present invention can be operated with embodiment, wherein different places point within recovery section or afterwards From more than one stream of water, to obtain aqueous solution of urea.

In the invention of practice calls protection, from the research to accompanying drawing, disclosure and appended claim, this area Technical staff is it will be appreciated that and realize other modifications of disclosed embodiment.In the claims, word " comprising " is not excluded for Miscellaneous part or step, and indefinite article " a " and " an " are not excluded for multiple situations.Invention some features only mutually from Quoted in the claim of category the fact that be not intended that the combination of these features can not be used to be used.

In a word, the present invention includes the method for being used for the integrated production of two kinds of different urea products.One kind applies to subtract Few NOx aqueous solution of urea (being typically expressed as automobile environment-protection urea-DEF).Another kind is used as the solution of fertilizer, i.e. ammonium nitrate Urea (UAN).DEF and UAN production is integrated as follows：It is used as ammonium nitrate production from the ammonia of urea production recovery Charging.At least part urea current from urea production are mixed to obtain UAN with ammonium nitrate.

Claims

1. a kind of integrated system for being used to produce urea and urea ammonium nitrate, the system include (i) urea production unit, institute Stating urea production unit includes urea synthesizing part and in the downstream of composite part and the urea purification part of fluid communication therewith, The urea synthesis section is divided including fluid communication each other to form the reactor in urea synthesizing loop, stripper and condenser, and (ii) it is used for the unit for generating ammonium nitrate；Wherein the NH3 outlets of urea equipment purification part are connected to for producing ammonium nitrate Unit NH3 entrances, and wherein by the outlet of the aqueous solution of urea of purification part and the nitre of unit for ammonium nitrate production The outlet of sour aqueous ammonium is connected to the unit for mixing the aqueous solution of urea with the aqueous ammonium nitrate solution.

2. system according to claim 1, it also includes being used for the unit for producing nitric acid, and the unit includes the nitre of production The outlet of acid, the outlet and the nitric acid entrance fluid communication of the unit of production ammonium nitrate.