EP1781626A2 - Procede haute pression permettant la production de melamine pure dans un reacteur de synthese vertical - Google Patents

Procede haute pression permettant la production de melamine pure dans un reacteur de synthese vertical

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Publication number
EP1781626A2
EP1781626A2 EP05768190A EP05768190A EP1781626A2 EP 1781626 A2 EP1781626 A2 EP 1781626A2 EP 05768190 A EP05768190 A EP 05768190A EP 05768190 A EP05768190 A EP 05768190A EP 1781626 A2 EP1781626 A2 EP 1781626A2
Authority
EP
European Patent Office
Prior art keywords
reactor
melamine
urea
reaction medium
stage
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP05768190A
Other languages
German (de)
English (en)
Inventor
Di Faramarz Bairamijamal
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AMI Agrolinz Melamine International GmbH
Original Assignee
AMI Agrolinz Melamine International GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by AMI Agrolinz Melamine International GmbH filed Critical AMI Agrolinz Melamine International GmbH
Publication of EP1781626A2 publication Critical patent/EP1781626A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D251/00—Heterocyclic compounds containing 1,3,5-triazine rings
    • C07D251/02—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings
    • C07D251/12—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members
    • C07D251/26—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members with only hetero atoms directly attached to ring carbon atoms
    • C07D251/40—Nitrogen atoms
    • C07D251/54—Three nitrogen atoms
    • C07D251/56—Preparation of melamine
    • C07D251/60—Preparation of melamine from urea or from carbon dioxide and ammonia
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J10/00—Chemical processes in general for reacting liquid with gaseous media other than in the presence of solid particles, or apparatus specially adapted therefor
    • B01J10/005—Chemical processes in general for reacting liquid with gaseous media other than in the presence of solid particles, or apparatus specially adapted therefor carried out at high temperatures in the presence of a molten material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/18—Stationary reactors having moving elements inside
    • B01J19/1862—Stationary reactors having moving elements inside placed in series
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/18—Stationary reactors having moving elements inside
    • B01J19/1868—Stationary reactors having moving elements inside resulting in a loop-type movement
    • B01J19/1875—Stationary reactors having moving elements inside resulting in a loop-type movement internally, i.e. the mixture circulating inside the vessel such that the upwards stream is separated physically from the downwards stream(s)
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/18—Stationary reactors having moving elements inside
    • B01J19/1887—Stationary reactors having moving elements inside forming a thin film
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/24—Stationary reactors without moving elements inside
    • B01J19/245—Stationary reactors without moving elements inside placed in series
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/24—Stationary reactors without moving elements inside
    • B01J19/2455—Stationary reactors without moving elements inside provoking a loop type movement of the reactants
    • B01J19/246—Stationary reactors without moving elements inside provoking a loop type movement of the reactants internally, i.e. the mixture circulating inside the vessel such that the upward stream is separated physically from the downward stream(s)
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/24—Stationary reactors without moving elements inside
    • B01J19/247—Suited for forming thin films
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J3/00—Processes of utilising sub-atmospheric or super-atmospheric pressure to effect chemical or physical change of matter; Apparatus therefor
    • B01J3/04—Pressure vessels, e.g. autoclaves
    • B01J3/042—Pressure vessels, e.g. autoclaves in the form of a tube
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00051—Controlling the temperature
    • B01J2219/00074—Controlling the temperature by indirect heating or cooling employing heat exchange fluids
    • B01J2219/00076—Controlling the temperature by indirect heating or cooling employing heat exchange fluids with heat exchange elements inside the reactor
    • B01J2219/00081—Tubes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00162—Controlling or regulating processes controlling the pressure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00164—Controlling or regulating processes controlling the flow
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/582—Recycling of unreacted starting or intermediate materials

Definitions

  • the present application relates to a high-pressure process for the preparation of pure melamine by pyrolysis of urea in a vertical synthesis reactor and a reactor for carrying out this process.
  • plastic melt in general, ureas and, optionally, gaseous ammonia without the presence of a catalyst such as at temperatures of 325-450 0 C and pressures zwi ⁇ rule 50 and 250 bar into liquid melamine and off-gas, mainly consisting of ammonia and Carbon dioxide, implemented.
  • the liquid melamine which also contains by-products in addition to unreacted urea, is subsequently worked up, for example, by quenching with water, by sublimation or by relaxation under certain conditions, and then isolating the pure melamine.
  • the melamine reactors known from the conventional melamine processes are usually vertical tank reactors of the loop reactor type, as described, for example, in AT 409 489 B.
  • Such a reactor has a central tube lying on the inside and a heating bundle with circulating molten salt between the central tube and the reactor wall.
  • the molten salt serves to provide the heat necessary for the endothermic Melamtnsynthese.
  • the urea melt and, if appropriate, the ammonia are fed into the lower region of the melamine reactor and react in the outer space between the molten salt flow through the bundle tubes to melamine melt and offgas.
  • the reaction mixture rises due to its low density upwards, where a separation between melamine melt and offgas takes place.
  • the melamine melt flows downward by gravity in the central tube, where it meets with fresh urea melt and rises again in the reaction space between the bundle tubes.
  • This circulation of melamine melt in the synthesis reactor is considered a natural cycle. records and ensures a certain residence time in the reactor, which should serve as complete as possible urea conversion to melamine. After the residence time, the melamine melt is discharged via an overflow in the upper reactor area and fed to the further work-up.
  • a disadvantage of this melamine reactor is the fact that the ratio of the heat exchange surface of the bundle tubes to the reaction volume is relatively low, so that relatively high Salzschmelzetempe ⁇ temperatures are necessary for the supply of the necessary heat of reaction. These cause increased corrosion at Rohrbün ⁇ del, so that annually a chemical cleaning of the tube bundle is necessary, which is undesirable due to the loss of production.
  • a further disadvantage results from the fact that a wide residence time distribution is achieved in the single-stage loop reactor, ie that the proportion of unreacted urea in the discharged melamine melt is comparatively high. Since the unreacted urea is discharged together with the by-products in the subsequent melamine workup, it equals a melamine loss.
  • WO 99/00374 describes a multi-stage melamine reactor consisting of several apparatuses connected in series in series.
  • the synthesis reactor is a conventional loop reactor.
  • the separated from offgas melamine melt is then fed to a horizontal tubular reactor in which the fuel turnover is to be completed.
  • the reaction mixture is subsequently introduced into an off-gas separator and the melamine obtained is sent for further processing.
  • a CO 2 stripper is switched to the first tubular reactor, then the pressure of the melamine melt is increased before another tubular reactor stage and finally an off-gas separator follows.
  • the reactor described has the disadvantage that numerous devices connected in series are necessary, which causes high investment costs and complex operation of the system.
  • the AT 410 210 B discloses a process for the preparation of melamine by Pyroly ⁇ se of urea, which urea is introduced into a tank reactor and melamine melt formed in the tank reactor is cooled in a subsequent cooling reactor by supplying a small amount of urea.
  • a cooling reactor any reactor can be used, for example, a stirred reactor, a falling film reactor or a combined reactor, the upper part is designed as a tank reactor and the lower part as a falling film reactor.
  • the amount of urea to be added to the cooling reactor is about 1 to 5% by weight of the total amount of urea required for the preparation of the melamine. In this method, the same disadvantages occur with respect to the melamine synthesis as in a single-stage loop reactor.
  • this object is achieved, on the one hand, by the fact that in a high-pressure process for producing pure melamine by pyrolysis of urea in a vertical synthesis reactor, the synthesis reactor has three stages arranged vertically one above the other, wherein
  • the smaller part of the total quantity of substance is introduced as urea melt into the lower region of the vertical central tube of the uppermost tank reactor.
  • the melt usually has a temperature of about 135 to 300 0 C and comes from a urea scrubber, in which they with the hot Pre-heated reaction offgas.
  • gaseous ammonia is introduced into the first tank reactor.
  • the reaction of urea to a first melamin- containing reaction medium and offgas at about 330 to 400 0 C, preferably at about 330 to 380 0 C, more preferably from about 330 to 360 0 C instead.
  • the pressure is about 50 to 600 bar, preferably about 50 to 250 bar, more preferably about 70 to 170 bar.
  • the melamine-containing reaction medium flows downwards due to gravity in the interior of the central tube and, after mixing with freshly fed urea melt, rises again upwards.
  • This circulation of the first melamine-containing reaction medium causes a residence time in the first tank reactor which is less than 15 minutes. After the residence time, the first melamine-containing reaction medium is collected at the top of the first tank reactor and flows via a connecting tube into the central tube of the second tank reactor below.
  • the greater part of the total amount of urea is introduced as urea melt into the lower region of the verti ⁇ cal central tube of the second tank reactor.
  • gaseous ammonia may also be introduced.
  • the temperature, the pressure, the reaction sequence with internal circulation and the residence time in the second tank reactor are the same as in the first tank reactor.
  • the formed offgas is discharged at the top of the second tank reactor.
  • a second melamine-containing reaction medium is formed, which is collected at the top of the apparatus and introduced via a connecting tube into the upper part of the underlying flow tube reactor.
  • the second melamine-containing reaction medium contains ammonia, carbon dioxide and by-products when discharged from the apparatus. Furthermore, unreacted urea is contained in an amount of about 1 to 3% by weight.
  • the second melamine-containing reaction medium flows from the upper into the lower apparatus area due to gravity.
  • the residence time can be controlled via the vertical height of the flow tube reactor.
  • the unreacted urea reacts to melamine, so that at the lower end of the flow tube reactor a raw melt melt is discharged, which is then fed to any further workup. Resulting off-gases are withdrawn at the top of the flow tube reactor.
  • the temperature and the pressure in the flow tube reactor are the same as in the first two tank reactor stages.
  • the smaller part is from 30 to 40% by weight and the major part is from 70 to 60% by weight of the total amount of urea. In this way, optimal reaction behavior in the reactor cascade is achieved.
  • Advantageous tank reactors are the type of loop reactors with natural circulation or loop reactors with natural circulation and additional forced convection.
  • loop reactors internal circulation is achieved solely by the different density of the reaction media. Additional stirring devices can increase the circulation.
  • the flow tube reactor is a falling film reactor.
  • the falling-film reactor it is achieved that the chemical equilibrium between the reactants can be set at any point above the reactor height, and thus the urea can virtually completely react.
  • a falling film reactor ensures a uniform residence time of the melt without axial dispersion around the tubes.
  • material-damaging tip overheating on the reactor tubes is avoided by a uniform fall film thickness.
  • the tank reactor is preferably a loop reactor with natural circulation, the urea being introduced in finely divided form into the lower region of each loop reactor via a tube, at the lower end of which there is an injector. Further preferably, the tank reactor is a loop reactor with natural circulation and forced convection with two stirrers, the urea via a pipe is introduced near the stirrer in the lower region of each loop reactor.
  • the supply of urea in a region of high flow ensures that good mixing takes place between the urea melt and the circulating melamine-containing reaction medium.
  • the urea supply pipes can be designed as coaxially guided pipes, wherein the urea flows in the inner pipe and between the inner and outer pipe is a high-temperature insulation of Kera ⁇ mik.
  • gaseous NH 3 is introduced into the third stage from below.
  • a simultaneous removal of the CO 2 contained in the melamine-containing reaction medium can take place in the flow tube part in a countercurrent procedure.
  • the removed CO 2 is discharged together with the offgas at the top of the Appa ⁇ rates.
  • the temperature of the introduced NH 3 may be equal to, higher or lower than the temperature of the melamine-containing reaction medium in the flow tube part.
  • a further advantage of the NH 3 introduction is that it removes by-products present in the melamine.
  • the heating of the three reactor stages takes place with a salt melt as the heating medium, the molten salt and the melamine-containing reaction medium in the first and second tank reactor being passed in countercurrent and in the flow tube reactor in cocurrent.
  • maximum heat input is achieved at the lowest possible temperature difference between molten salt and melamine-containing reaction medium in the tank reactor stages. In the flow tube stage, this promotes continuous equilibration during the reaction.
  • Particularly preferred is an embodiment of the method in which the temperature in the first, second and third stage is the same and as close as possible to the crystallization point of the melamine at the prevailing pressure.
  • a particularly high melamine purity can be achieved because the content of by-products the closer the temperature of the melamine is kept to the crystallization point, the lower it is.
  • Another possibility is to operate the first two stages at the same temperature and the third stage at a lower temperature.
  • the off-gas is withdrawn from each stage and subsequently the off-gas streams are combined with one another and fed to an off-gas scrubber. This allows an efficient removal of the off-gas at the respective place of origin, so that the equilibration in each reaction stage is made possible.
  • the pressure in the first, second and third stages is the same. Via a pressure equalization line, all three reactor stages are connected mitein ⁇ other. In this way, the pressure of all three devices can be adjusted via a common pressure control valve.
  • the invention further provides a vertical synthesis reactor for carrying out the process according to the invention with three stages arranged vertically one above the other, wherein the first, top and second, middle stage tank reactors, in particular loop reactors containing central tube, feed lines for urea and optionally NH 3 , supply and discharge lines for heating medium, discharges for Off ⁇ gas and melamin digitiziges reaction medium, heaters for supplying Reak ⁇ tion heat in the region between the central tube and reactor wall, optionally measuring and control devices and optionally convection devices are, and wherein the third, lowest level a flow tube reactor containing supply lines for melamine-containing reaction medium, and optionally NH 3, inlets and outlets for the heating medium discharge lines for off-gas and crude melamine melt, Schueinrichtun ⁇ gene for supplying heat of reaction and optionally measuring and crizeinrichtun gen is.
  • the first, top and second, middle stage tank reactors in particular loop reactors containing central tube, feed lines for urea and optionally NH 3 , supply and discharge lines
  • the tank reactors preferably have collectors in their upper region, which are connected via an internal or external overflow pipe for the melamine-containing reaction medium to the central pipe of the next lower stage. This is a continual it is ensured that the melamine-containing reaction medium overflows from the first into the second tank reactor and from there into the flow tube part.
  • the flow tube reactor preferably has a distributor for the melamine-containing reaction medium in its upper region. In this way, a uniform distribution of the melamine over the entire pipe cross section is achieved.
  • the third stage is a falling-film reactor, the cross-section of which is taken up by a tube bundle of vertical profiled inner tubes and performed outer tubes.
  • a uniform melamine film is achieved on the inner tubes and a good heat transfer is achieved by the salt-flow-through outer tubes.
  • Impeller stirrers, inclined blade stirrers or turbine stirrers can be used, for example, as stirring elements.
  • the tank reactors in the central tube from top to bottom leading urea supply lines with an injector at the bottom.
  • good mixing between urea and reaction medium can be achieved.
  • a reactor which, as heating devices in the tank reactors, has bimetallic compound pipes with smooth inner tubes and outer tubes that are performed.
  • the inner tubes are flowed through by the heating medium by the melamine-containing reaction medium and the outer tubes.
  • the performance of the outer tubes ensures optimum heat exchange performance.
  • the offgas discharges of the three reaction stages have heatable demisters or mist eliminators.
  • melamine components contained in the offgas are already deposited before the offgas scrubber.
  • the melamine melt discharged from the flow tube part of the synthesis reactor is discharged and subsequently worked up in any desired manner. examples For example, it can be solidified by expansion and / or cooling or it is transferred to the gas phase and then desublimed. Another possibility of workup is quenching with an aqueous solution and subsequent crystallization of the melamine.
  • FIG. 2 shows a further embodiment of the reactor according to the invention with two loop reactors with natural circulation as well as additional forced convection and a falling film reactor.
  • Figures 1 and 2 show: (1) and (2) a first and second natural circulation loop reactor, (3) a falling film reactor, (4) and (5) the central tubes of the first and second loop reactors, (6) a collector and the overflow pipe from the first to the second loop reactor, (7) a collector and the overflow pipe from the second loop reactor into the falling film reactor, (8) a distributor, (9) an ammonia distributor, (10) a feed line for the total urea, (11 ) and (12) feed lines for the urea stream into the first and second loop reactor, (13) the discharge line for the melamine melt for further processing, (14), (15) and (16) feed lines for the molten salt, ( 14a), (15a), (16a) discharge lines for the molten salt, (17) a supply line for NH 3 gas, (18), (19), (20) bundle tubes through which the molten salt flows as heat exchangers, offgas lines (21) from the Fall ⁇ film reactor, (22) from the middle reactor and (23) from the upper most reactor (24) and (25) stirring devices with
  • the process according to the invention is carried out as follows: 4620 kg / h urea melt, which is about 35% of the total synthesis resin, having a temperature of 230 ° C. and a pressure of 160 bar are introduced via the supply line 11, at the end thereof Injector (not shown) is sprayed into the lower region of the central tube 4 of a first loop reactor 1 with natural circulation.
  • the reactor 1 is tempered via the bundle tubes 18 by means of molten salt heating to 347.degree.
  • the at this temperature and a pressure of 150 bar formed reaction mixture is separated in the upper region of the loop reactor 1 in offgas, consisting of NH 3 and CO 2 and a first melamin conception conceptions ⁇ medium.
  • the melamine-containing reaction medium passes via the collector and the overflow pipe 6 into the central tube 5 of the underlying second loop reactor 2 with natural circulation.
  • the second loop reactor 2 is e on the bundle of tubes 19 b faced tempered by means of the salt melt to 347 0 C, the pressure is the same as the second Schiaufenreaktor kg in the first loop reactor 1.
  • Simultaneously with the first melamine-Rehabilits ⁇ medium via the supply line 12 8580 / U fed urea melt at a temperature of 230 0 C and a pressure of 160 bar. This corresponds to about 65% by weight of the total synthesis urea.
  • a second melamine-containing reaction medium and offgas is formed at 347 0 C and 150 bar.
  • the offgas is withdrawn via the offgas line 22 at the head of the loop reactor and discharged to the offgas scrubber (not shown).
  • the second melamine-containing reaction medium is passed via a collector and the external overflow pipe 7 from the second loop reactor 2 to the head of a falling film reactor 3 held by means of molten salt at 347 ° C. via the bundle tubes 20.
  • the molten salt flows via the supply line 16 through the jacket tubes of the reactor tube cross-section engaging tube bundle 20 in the discharge line 16 a.
  • the melamine is divided into partial streams and flows over the réelle ⁇ tubes of the tube bundle 20 from top to bottom.
  • gaseous ammonia is introduced from below via the supply line 17 at 345 0 C in an amount of 1350 kg / h via the manifold 9 to remove CO 2 ent contained in the melamine.
  • the pressure in the falling film reactor is the same as in the two loop reactors.
  • the gas formed is discharged together with the CO 2 removed via the offgas line 21 and fed to the offgas scrubber (not shown).
  • a melamine melt with a by-product content of ⁇ 1% by weight is discharged via the discharge line 13.
  • the melamine melt is then introduced at 347 0 C and 150 bar in a quencher (not shown), there with an aqueous solution quenched and then crystallized from the resulting melamine solution, the pure MeI- amine.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

L'invention concerne un procédé haute pression permettant la production de mélamine pure par pyrolyse d'urée dans un réacteur de synthèse vertical. Ce procédé se caractérise en ce que le réacteur de synthèse comporte trois étages superposés verticalement. a) Dans le premier étage le plus haut, la petite portion de la quantité totale d'urée est introduite dans le tube central d'un premier réacteur à coeur fermé et un premier milieu de réaction contenant de la mélamine est formé ; b) dans le deuxième étage intermédiaire, le premier milieu de réaction contenant de la mélamine et la grande portion de la quantité totale d'urée sont introduits dans le tube central d'un deuxième réacteur à coeur fermé et un deuxième milieu de réaction contenant de la mélamine est formé puis c), dans le troisième étage le plus bas, le deuxième milieu de réaction contenant de la mélamine est introduit dans un réacteur à écoulement piston vertical et une masse fondue de mélamine brute est formée, laquelle masse est ensuite retraitée d'une quelconque manière pour permettre l'obtention de mélamine pure. Ce procédé permet ainsi d'obtenir une conversion uniforme de l'urée, une alimentation en chaleur de réaction plus délicate et réduisant la corrosion, une mise en oeuvre optimale de la réaction ainsi qu'une réaction intégrale de l'urée dans le réacteur de synthèse de mélamine. La synthèse de la mélamine est ainsi plus compacte, plus économique et plus efficace que dans d'autres procédés de production de mélamine.
EP05768190A 2004-07-29 2005-07-27 Procede haute pression permettant la production de melamine pure dans un reacteur de synthese vertical Withdrawn EP1781626A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT0129804A AT414239B (de) 2004-07-29 2004-07-29 Hochdruckverfahren zur herstellung von reinem melamin
PCT/EP2005/008323 WO2006013079A2 (fr) 2004-07-29 2005-07-27 Procede haute pression permettant la production de melamine pure dans un reacteur de synthese vertical

Publications (1)

Publication Number Publication Date
EP1781626A2 true EP1781626A2 (fr) 2007-05-09

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP05768190A Withdrawn EP1781626A2 (fr) 2004-07-29 2005-07-27 Procede haute pression permettant la production de melamine pure dans un reacteur de synthese vertical

Country Status (10)

Country Link
US (1) US7375223B2 (fr)
EP (1) EP1781626A2 (fr)
JP (1) JP2008508226A (fr)
CN (1) CN101023065A (fr)
AR (1) AR050275A1 (fr)
AT (1) AT414239B (fr)
MY (1) MY140845A (fr)
RU (1) RU2006145379A (fr)
TW (1) TW200621358A (fr)
WO (1) WO2006013079A2 (fr)

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2098516A1 (fr) 2008-03-04 2009-09-09 Urea Casale S.A. Processus de production de mélamine de grande pureté à partir d'urée
EP2119710A1 (fr) * 2008-05-14 2009-11-18 Urea Casale S.A. Processus de production de mélamine haute qualité à partir de l'urée
IT1391372B1 (it) * 2008-10-07 2011-12-13 Eurotecnica Melamine Luxemburg Zweigniederlassung In Ittigen Procedimento e apparecchiatura per la produzione di melammina da urea
EP2399669A1 (fr) 2010-06-24 2011-12-28 Borealis Agrolinz Melamine GmbH Réacteur de mélamine horizontal haute pression
CN102295615B (zh) * 2011-07-14 2013-10-16 山东大学 一种低温合成三聚氰胺的方法
EP2907567A1 (fr) 2014-02-18 2015-08-19 Casale Sa Réacteur combiné pour la synthèse haute pression de mélamine
CN104258795B (zh) * 2014-09-24 2015-12-30 中国纺织科学研究院 交换反应系统、包含其的改性聚酯生产系统及改性聚酯生产方法
CN107469736A (zh) * 2017-10-12 2017-12-15 重庆农药化工（集团）有限公司 可调节反应压力的反应釜及可调压反应釜系统
IT201800007993A1 (it) * 2018-08-09 2020-02-09 Greenbone Ortho Srl Impianto finalizzato alla trasformazione chimica di materiali nello stato 3d
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WO2006013079A3 (fr) 2006-03-16
CN101023065A (zh) 2007-08-22
JP2008508226A (ja) 2008-03-21
RU2006145379A (ru) 2008-09-10
ATA12982004A (de) 2006-01-15
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US20070232801A1 (en) 2007-10-04

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