DK145081B - PROCEDURE FOR MANUFACTURING URINE FROM AMMONIA AND CARBON Dioxide - Google Patents

PROCEDURE FOR MANUFACTURING URINE FROM AMMONIA AND CARBON Dioxide Download PDF

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DK145081B
DK145081B DK662269AA DK662269A DK145081B DK 145081 B DK145081 B DK 145081B DK 662269A A DK662269A A DK 662269AA DK 662269 A DK662269 A DK 662269A DK 145081 B DK145081 B DK 145081B
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reactor
carbamate
ammonia
urea
carbon dioxide
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DK145081C (en
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P Forlani
I Paris
U Zardi
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Snam Progetti
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    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C273/00Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups
    • C07C273/02Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups of urea, its salts, complexes or addition compounds
    • C07C273/04Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups of urea, its salts, complexes or addition compounds from carbon dioxide and ammonia
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00Technologies relating to chemical industry
    • Y02P20/141Feedstock
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00Technologies relating to chemical industry
    • Y02P20/50Improvements relating to the production of bulk chemicals
    • Y02P20/582Recycling of unreacted starting or intermediate materials

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  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Lead Frames For Integrated Circuits (AREA)

Description

i 145081in 145081

Opfindelsen angår en fremgangsmåde til fremstilling af urinstof.The invention relates to a process for producing urea.

Det er kendt, at det ved fremstilling af urinstof ud fra ammoniak og carbondioxid er muligt at opnå total 5 omsætning af reaktanterne ved recirkulation af de reaktanter, som ikke er blevet omsat, i et eller flere trin.It is known that in the production of urea from ammonia and carbon dioxide, it is possible to achieve a total reaction of the reactants by recirculating the reactants which have not been reacted in one or more steps.

I nogle kendte processer, der arbejder efter dette princip, gennemføres den totale recirkulation af de uomdan^ nede reaktanter i to eller flere recirkulationstrin, der 2 10 opererer ved faldende tryk i området fra 40 kg pr. cm ned til atmosfæretryk.In some known processes operating in accordance with this principle, the total recirculation of the unreacted reactants is carried out in two or more recirculation stages operating at decreasing pressure in the range of 40 kg per liter. cm down to atmospheric pressure.

Dette er blevet forbedret ved en fremgangsmåde, i hvilken det uomsatte carbamat recirkuleres fuldstændigt til urinstofsyntesereaktoren i et enkelt trin ved 15 højt tryk.This has been improved by a process in which the unreacted carbamate is completely recycled to the urea synthesis reactor in a single step at high pressure.

I denne fremgangsmåde sker dekomponeringen af car-bamatet ved syntesetrykket, idet den gennemføres i nærværelse af en strøm af enten gasformig ammoniak eller gasformig carbondioxid, som er ført ind i reaktoren.In this process, the decomposition of the carbamate occurs at the synthesis pressure, carried out in the presence of a stream of either gaseous ammonia or gaseous carbon dioxide introduced into the reactor.

20 Selv ved disse forbedrede fremgangsmåder bliver imidlertid små mængder ammoniumcarbamat og betydelige mængder stripningsmiddel i den urinstofholdige opløsning, der kommer ud af stripperen. Yderligere rensning af urinstofopløsningen finder almindeligvis sted derefter i.However, even with these improved methods, small amounts of ammonium carbamate and significant amounts of stripping agent remain in the urea-containing solution coming out of the stripper. Further purification of the urea solution usually takes place thereafter.

25 flere trin med trykområder på fra 15-30 atmosfærer ned til atmosfæretryk.25 more steps with pressure ranges ranging from 15-30 atmospheres down to atmospheric pressure.

Det tilsigtes med den foreliggende opfindelse at tilvejebringe en fremgangsmåde, som ikke kræver en serie kostbare og komplicerede apparater, sådan som det 30 er nødvendigt ved de fremgangsmåder, der for tiden berettes til adskillelse af de uomsatte forbindelser fra urinstofopløsningen.It is an object of the present invention to provide a process which does not require a series of expensive and complicated apparatus as is necessary in the methods currently reported for separating the unreacted compounds from the urea solution.

Ved fremgangsmåden ifølge opfindelsen til fremstilling af urinstof ud fra ammoniak og carbondioxid 35 omsætter man ammoniak og carbondioxid til fremstilling af en urinstofopløsning indeholdende uomsat carbamat, dekomponerer det uomsatte carbamat og stripper dekom-poneringsprodukterne med inert gas, såsom nitrogen og 2 1 <45 O 8 1 hydrogen, og det ejendommelige ifølge opfindelsen er, at dannelsen af urinstofopløsningen udføres i to separate reaktorer, idet al ammoniak og carbondioxid, der fødes til processen, i den første reaktor reagerer under 5 dannelse af ammoniumcarbamat, og ammoniumcarbamatet i den anden reaktor overføres i urinstof og vand, hvorhos ammoniumcarbamats dekomponeringsprodukter og den til stripningen anvendte inerte gas recirkuleres til den første reaktor, hvorfra den inerte gas sendes tilbage 10 til stripningsoperationen.In the process of the invention for producing urea from ammonia and carbon dioxide, ammonia and carbon dioxide are reacted to produce a urea solution containing unreacted carbamate, decomposing the unreacted carbamate and stripping the decomposition products with inert gas such as nitrogen and 2 1 hydrogen, and the peculiar feature of the invention is that the formation of the urea solution is carried out in two separate reactors, with all ammonia and carbon dioxide fed to the process reacting in the first reactor to form ammonium carbamate and the ammonium carbamate in the second reactor being transferred into the urea and water from which the decomposition products of ammonium carbamate and the inert gas used for the stripping are recycled to the first reactor, from which the inert gas is returned to the stripping operation.

Fremgangsmåden ifølge den foreliggende opfindelse kan give et urinstofudbytte, som er forbedret i forhold til dem,der er kendt i teknikken, (baseret på omsætningsudbytte pr. passage i urinstofsyntesezonen), under 15 reduktion af i hvert fald vandindholdet i syntesekredsløbet.The process of the present invention can provide a urea yield which is improved over those known in the art (based on conversion yield per passage in the urea synthesis zone), at least reducing the water content of the synthesis circuit.

En hovedfordel ved fremgangsmåden skyldes den kendsgerning, at det er tilstrækkeligt at benytte blot én pumpe eller kompressor i hele urinstofsyntesekreds-20 løbet, som omfatter den totale recirkulation af de uom-dannede reaktanter, som det vil fremgå af den følgende beskrivelse.A major advantage of the process is due to the fact that it is sufficient to use only one pump or compressor throughout the urea synthesis cycle, which comprises the total recycling of the unreacted reactants, as will be apparent from the following description.

En anden fordel er muligheden for at benytte carbondioxid ved et tryk, der er lavere end trykket i 25 urinstofreaktoren, med den deraf følgende reduktion af den nødvendige kompressionsenergi.Another advantage is the possibility of using carbon dioxide at a pressure lower than the pressure in the urea reactor, with the consequent reduction of the necessary compression energy.

Ved gennemførelse af fremgangsmåden ifølge opfindelsen føres effluentet fra urinstofsyntesereaktoren almindeligvis til toppen af et strippertårn, hvori det 30 strømmer nedad i modstrøm med den inerte gas under egnede temperatur- og trykforhold for dekomponering af carbamatet og fraskillelse af det, tilligemed den frie ammoniak, fra urinstofopløsningen. Bundeffluentet fra stripperen er en urinstofopløsning med et vandindhold, 35 der er mindst lig med den støkiometriske mængde. Dette væskeformige effluent koncentreres derpå sædvanligvis, praktisk talt uden tab ved omdannelse til carbondioxid og ammoniak. Det ses således, at alle de tidligere be- 3 U5081 nyttede trin til carbamatdekomponeringen, til genvindingen og til recirkuleringen til urinstofreaktoren af uom-satte forbindelser, ved forskellige tryk, kan elimineres.In carrying out the process according to the invention, the effluent from the urea synthesis reactor is usually fed to the top of a stripper tower, where it flows downstream with the inert gas under suitable temperature and pressure conditions for decomposing the carbamate and separating it, as well as the free ammonia solution, from the . The bottom effluent from the stripper is a urea solution having a water content at least equal to the stoichiometric amount. This liquid effluent is then usually concentrated, virtually without loss upon conversion to carbon dioxide and ammonia. Thus, it is seen that all the steps previously used for the carbamate decomposition, for the recovery, and for the urea reactor of unreacted compounds, at various pressures, can be eliminated.

Det gasformige effluent fra toppen af stripperen 5 består af inerte gasser, carbondioxid, ammoniak og vand (i gasfase) og recirkuleres til den første reaktor og holdes på strippertrykket og ved en egnet temperatur.The gaseous effluent from the top of stripper 5 consists of inert gases, carbon dioxide, ammonia and water (in the gaseous phase) and is recirculated to the first reactor and kept at the stripper pressure and at a suitable temperature.

Det gasformige effluent kan imidlertid, før det sendes til carbamatreaktoren, kondenseres delvis for at genvin-10 de dets varme. De inerte gasser, der kommer ud i praktisk talt ren form fra carbamatreaktoren, kan ved hjælp af en recirkulationsblæser føres frem til carbamatsynte-sereaktoren.However, the gaseous effluent, before being sent to the carbamate reactor, may be partially condensed to recover its heat. The inert gases coming out in practically pure form from the carbamate reactor can be fed to the carbamate synthesis reactor by means of a recirculation fan.

I den ovenfor beskrevne udførelsesform føres det 15 væskeformede effluent fra carbamatreaktoren til urinstof syntesereaktoren ved hjælp af en pumpe. Trykket i den anden reaktor, urinstofreaktoren, er i dette tilfælde højere end i den første reaktor, carbamatreaktoren, hvorhos det sidstnævnte tryk sædvanligvis ligger 20 i området 45-250 atmosfærer.In the embodiment described above, the liquid effluent is fed from the carbamate reactor to the urea synthesis reactor by means of a pump. The pressure in the second reactor, the urea reactor, in this case is higher than in the first reactor, the carbamate reactor, the latter pressure usually being in the range of 45 to 250 atmospheres.

Det er imidlertid også muligt at udføre opfindelsen under opretholdelse af et højere tryk i carbamat-syntesereaktoren end i urinstofsyntesereaktoren.However, it is also possible to carry out the invention while maintaining a higher pressure in the carbamate synthesis reactor than in the urea synthesis reactor.

Særligt egnet til udførelse heraf er en udførel-25 sesform for fremgangsmåden ifølge opfindelsen, der består i, at gasstrømmen, der kommer fra toppen af stripperen, først sendes til en kondensator for kondensation af vand og carbamat, og derpå til en vaskekolonne for absorption af det resterende carbondioxid i ammoniak, 30 hvorhos den således opnåede væske indføres ved foden af carbamatreaktoren, medens gasfasen fra vaskekolonnen blandes med carbondioxidtilførslen til reaktoren.Particularly suitable for carrying them out is an embodiment of the process according to the invention, which consists in that the gas stream coming from the top of the stripper is first sent to a condenser for condensation of water and carbamate, and then to a washing column for absorption of the remaining carbon dioxide in ammonia, the liquid thus obtained being introduced at the foot of the carbamate reactor, while the gas phase from the wash column is mixed with the carbon dioxide supply to the reactor.

Valget af tryk i carbamatsyntesereaktoren afhænger af det effektive tryk af C02/ nemlig partialtrykket af 35 carbondioxid i tilfælde af, at det ikke er en praktisk talt ren gas. I tilfælde af, at trykket i carbamatsyntesereaktoren er højere end i urinstofsyntesereaktoren, kan det gasformige effluent fra stripperen, for at lette 4 145081 recirkuleringen af de inerte gasser til carbamatsyntese-reaktoren, føres til delvis kondensering i den nævnte kondensator, under genvinding af varme, og derpå til vaskekolonnen, hvor strømmen vaskes med ammoniak. Den 5 del af effluentet fra vaskekolonnen, der er flydende, føres ved hjælp af en pumpe til carbamatsyntesereakto-ren, mens det gasformige effluent bestående af inerte gasser og af ammoniak ved hjælp af en blæser føres til carbamatsyntesereaktoren.The choice of pressure in the carbamate synthesis reactor depends on the effective pressure of CO 2 / namely the partial pressure of 35 carbon dioxide in case it is not a practically pure gas. In case the pressure in the carbamate synthesis reactor is higher than in the urea synthesis reactor, the gaseous effluent from the stripper to facilitate the recirculation of the inert gases to the carbamate synthesis reactor can be partially condensed in said condenser, under heat recovery. and then to the wash column where the stream is washed with ammonia. The 5 part of the effluent from the washing column which is liquid is fed by a pump to the carbamate synthesis reactor, while the gaseous effluent consisting of inert gases and of ammonia is fed to the carbamate synthesis reactor.

10 Den foreliggende opfindelse kan anvendes på en yderst interessant måde, hvis der som inert gas for stripningen benyttes en blanding af ammoniaksyntese-gasserne, nemlig nitrogen og hydrogen. I dette tilfælde sendes carbondioxidet til carbamatsyntesereaktoren sam-15 men med en blanding for ammoniaksyntesen. Den gas, der kommer fra fremstillingszonen for ammoniaksyntesegas-serne, sendes således til carbamatreaktoren umiddelbart efter omdannelsen til carbondioxid og hydrogen af car-bonmonooxid, der eventuelt måtte være indeholdt i denne 20 syntesegas, under egnede tryk- og temperaturforhold.The present invention can be used in an extremely interesting way if a mixture of the ammonia synthesis gases, namely nitrogen and hydrogen, is used as the inert gas for the stripping. In this case, the carbon dioxide is sent to the carbamate synthesis reactor together with a mixture for the ammonia synthesis. Thus, the gas coming from the zone of production of the ammonia synthesis gases is sent to the carbamate reactor immediately after the conversion to carbon dioxide and hydrogen of carbon monoxide, which may be contained in this synthesis gas, under suitable pressure and temperature conditions.

En anden nyttig mulighed er at benytte det gasformige udtag fra ammoniaksyntesen som inerte gasser for stripningen. I dette tilfælde opnås der en delvis forenkling af ammoniaksyntesens kølesystem, og de tab 25 af ammoniak, som altid forekommer med dette gasformige udtag, elimineres.Another useful option is to use the gaseous outlet from the ammonia synthesis as inert gases for the stripping. In this case, a partial simplification of the cooling system of the ammonia synthesis is achieved and the losses 25 of ammonia which are always present with this gaseous outlet are eliminated.

Ammoniumcarbamatsyntesen kan f.eks. udføres ved de temperaturer, der sædvanligvis benyttes. Sædvanligvis gennemføres syntesen ved en temperatur i området 30 100-200°C, fortrinsvis i området 110-160°C.The ammonium carbamate synthesis may e.g. is carried out at the temperatures usually used. Usually, the synthesis is carried out at a temperature in the range of 100-200 ° C, preferably in the range 110-160 ° C.

Omdannelsen af ammoniumcarbamat til urinstof udføres sædvanligvis ved en temperatur i området 150-300°C, fortrinsvis i området 180-250°C.The conversion of ammonium carbamate to urea is usually carried out at a temperature in the range 150-300 ° C, preferably in the range 180-250 ° C.

Opfindelsen forklares nærmere ved hjælp af den 35 medfølgende tegning, som viser eksempler på udførelsesformer for opfindelsen.The invention is further explained by means of the accompanying drawing, which shows examples of embodiments of the invention.

Fig. 1 viser skematisk et anlæg til gennemførelse af fremgangsmåden ifølge opfindelsen og 5 145081 fig. 2 et andet anlæg for gennemførelse af fremgangsmåden ifølge opfindelsen.FIG. 1 schematically shows a plant for carrying out the method according to the invention and FIG. 2 shows another plant for carrying out the method according to the invention.

Idet der først henvises til fig. 1, vises der en ammoniumcarbamatsyntesereaktor 1, til hvilken der føres 5 ammoniak gennem en ledning 2, vand gennem en ledning 3 og carbondioxid gennem en ledning 4. Desuden føres der til reaktor 1 gennem en ledning 5 en gasformig strøm fra toppen af et strippertårn 6, hvilken strøm består af inert gas, ammoniak, carbondioxid og vand.Referring first to FIG. 1, an ammonium carbamate synthesis reactor 1 is shown to which 5 ammonia is passed through a conduit 2, water through a conduit 3, and carbon dioxide through a conduit 4. In addition, a gaseous stream from the top of a stripper tower 6 is fed to reactor 1 , which consists of inert gas, ammonia, carbon dioxide and water.

10 Den gasfase, som forlader toppen af reaktoren 1 via en ledning 7, består i det væsentlige af den inerte gas. Denne gas recirkuleres til den nedre del af stripperkolonnen 6 ved hjælp af en blæser 8 og en ledning 9.The gas phase leaving the top of the reactor 1 via a conduit 7 consists essentially of the inert gas. This gas is recycled to the lower part of the stripper column 6 by means of a fan 8 and a conduit 9.

15 En væskeformig fase bestående af ammoniumcarbamat, ammoniak og vand forlader bunden af reaktoren 1 gennem en ledning 10 og presses ved hjælp af en pumpe 11 gennem en ledning 12 til en opvarmer 13 og derfra til bundregionen af en urinstofsyntesereaktor 14. I 20 urinstofsyntesereaktoren 14 omsættes det meste af am-moniumcarbamatet til urinstof. De gasformige produkter fra denne reaktor 14, nemlig urinstof, uomsat ammoniumcarbamat, ammoniak og vand, forlader toppen af reaktoren 14 gennem en ledning 15 og passerer gennem et 25 ekspansionsorgan eller en reguleringsventil 16 ind i topregionen af stripperkolonnen 6.A liquid phase consisting of ammonium carbamate, ammonia and water leaves the bottom of the reactor 1 through a conduit 10 and is pressed by means of a pump 11 through a conduit 12 to a heater 13 and thence to the bottom region of a urea synthesis reactor 14. The urea synthesis reactor 14 is reacted. most of the ammonium carbamate for urea. The gaseous products of this reactor 14, namely urea, unreacted ammonium carbamate, ammonia and water, leave the top of reactor 14 through a conduit 15 and pass through an expansion member or control valve 16 into the top region of the stripper column 6.

I stripperen 6 dekomponeres det uomsatte ammoniumcarbamat i det væsentlige fuldstændigt til ammoniak og carbondioxid. Disse dekomponeringsprodukter, tillige-30 med inert gas, noget vand og den ammoniak, som kom ind i stripperkolonnen 6 via ledningen 15, forlader toppen af kolonnen 6 gennem ledningen 5 og recirkuleres til carbamatsyntesereaktoren 1. Dekomponeringen af det uomsatte ammoniumcarbamat i kolonnen 6 lettes ved den 35 opadgående strøm af inert gas, som kommer ind gennem ledningen 9. Det strippede urinstof forlader bunden af kolonnen 6 via en ledning 17 i form af en vandig opløsning.In stripper 6, the unreacted ammonium carbamate is substantially completely decomposed into ammonia and carbon dioxide. These decomposition products, along with inert gas, some water, and the ammonia entering the stripper column 6 via conduit 15 leave the top of column 6 through conduit 5 and recycle to the carbamate synthesis reactor 1. The decomposition of the unreacted ammonium carbamate in column 6 is facilitated by the upward flow of inert gas entering through line 9. The stripped urea leaves the bottom of column 6 via a line 17 in the form of an aqueous solution.

145081 6145081 6

Idet der nu henvises til tegningens fig. 2, vises der et anlæg, som på mange måder ligner det i fig. 1 viste. For tydelighedens skyld angiver referencetal, der er ligesom de i fig. 1 viste, tilsvarende komponen-5 ter. I modsætning til anlægget ifølge fig. 1 er trykket i carbamatsyntesereaktoren 1 i anlægget i fig. 2 højere end i urinstofsyntesereaktoren 14. Følgelig er det muligt i anlægget ifølge fig. 2 at udelade kompressorerne 8 og 11 og ekspansionsorganet 16, som er vist i 10 fig. 1.Referring now to FIG. 2, a system is shown which in many ways is similar to that of FIG. 1. For the sake of clarity, reference numerals which are similar to those in FIG. 1, corresponding components 5. Unlike the system of FIG. 1 is the pressure in the carbamate synthesis reactor 1 of the plant of FIG. 2 higher than in the urea synthesis reactor 14. Accordingly, it is possible in the system of FIG. 2 to omit the compressors 8 and 11 and the expansion member 16 shown in FIG. First

En anden hovedforskel mellem de to anlæg er, at i det i fig. 2 viste anlæg føres gasfasen, der kommer ud fra toppen af stripperkolonnen 6, i en ledning 18 til en kondensator 19, hvor der kondenseres vand, og der 15 kommer også carbamat i kondensatet, hvorpå det hele via en ledning 20 føres til en kolonne 21, hvor eventuelt ukondenseret carbondioxid absorberes i ammoniak, som føres ind i kolonnen 21 via en ledning 22, som udgrener sig fra ledning 2.Another major difference between the two plants is that in the embodiment shown in FIG. 2, the gas phase coming from the top of the stripper column 6 is passed in a conduit 18 to a condenser 19 where water is condensed and 15 also carbamate enters the condensate, whereupon the whole is fed to a column 21 via a conduit 20 wherein any uncondensed carbon dioxide is absorbed in ammonia which is introduced into column 21 via a conduit 22 which branches off from conduit 2.

20 Væskefasen fra kolonne 21 føres gennem en led ning 23 og en pumpe 24 til den lavere region af reaktor 1. Gasfasen fra kolonne 21, som omfatter de inerte gasser, ammoniak og noget carbondioxid, føres gennem en ledning 25 til en recirkulationsblæser 26 og derfra 25 til ledningen 4, hvor den følger det tilførte carbondioxid.The liquid phase from column 21 is passed through a conduit 23 and a pump 24 to the lower region of reactor 1. The gas phase from column 21, which comprises the inert gases, ammonia and some carbon dioxide, is passed through a conduit 25 to a recirculation fan 26 and from there. 25 to line 4, where it follows the carbon dioxide supplied.

Der er gjort foranstaltning, i form af en ledning 27, for at noget af de inerte gasser, der passerer gennem ledningen 7, kan slippes ud af systemet.A provision has been made, in the form of a conduit 27, for some of the inert gases passing through the conduit 7 to be released from the system.

30 Opfindelsen forklares nærmere i de efterfølgende eksempler, hvor strømmængdeforholdene er baseret på 1 mol produceret urinstof.The invention is further explained in the following examples, where the flow rate ratios are based on 1 mole of urea produced.

Eksempel 1Example 1

Fremstillingen af urinstof blev i dette eksempel 35 udført i et anlæg af den i fig. 1 viste type.The preparation of urea in this example 35 was carried out in a plant of the type shown in FIG. 1.

Et mol CO2 blev gennem ledningen 4 ved et tryk på 80 absolutte atmosfærer ført ind i carbamatreaktoren 145081 7 1, hvor det blev absorberet af en modgående strøm af 2 mol NH3, som kom ind gennem ledningen 2, og 0,2 mol H2O, som blev indført gennem ledningen 3. Desuden blev der i reaktoren 1 indført stripperstrømmen, der kom 5 fra stripperen 6 og bestod af 3,3 mol inerte gasser, 3,71 mol NH3, 0,831 mol CO2 og 0,635 mol vand. Ud af reaktoren 1 strømmede en væskefase og en gasfase. Væskefasen kom ud ved en temperatur på 130°C og bestod af 1,831 mol ammoniumcarbamat, 2,048 mol NH3 og 1,835 mol 10 vand. Den blev komprimeret til et tryk på 153 absolutte atmosfærer, opvarmet til en temperatur på 210°C og derpå ført ind i urinstofreaktoren 14. Den gasformige fase fra reaktoren 1 bestod i det væsentlige af 3,3 mol inerte gasser, som kom fra stripperen, og som blev 15 recirkuleret til denne ved hjælp af kompressoren 8. I urinstofsyntesereaktoren omdannedes det carbamat, som kom fra carbamatreaktoren 1 via ledning 10, pumpe 11 og opvarmer 13, delvis til urinstof; effluentet fra urinstofreaktoren 14 bestod af 1 mol urinstof, 0,831 20 mol ammoniumcarbamat, 1,835 mol vand og 2,048 mol NH3 og blev via ledning 15 ført til stripperkolonnen 6, hvori de 0,831 mol carbamat, som ikke var blevet omdannet til urinstof, blev dekomponeret til gasformig NH3 og CC>2. De 2,048 mol fri ammoniak gik også i gasfasen.One mole of CO2 was passed through line 4 at a pressure of 80 absolute atmospheres into the carbamate reactor 14, absorbed by a countercurrent flow of 2 moles of NH3 entering through line 2, and 0.2 moles of H2O, which In addition, in the reactor 1, the stripper stream, which came 5 from stripper 6, consisted of 3.3 moles of inert gases, 3.71 moles of NH3, 0.831 moles of CO2, and 0.635 moles of water. Out of the reactor 1 flowed a liquid phase and a gas phase. The liquid phase came out at a temperature of 130 ° C and consisted of 1.831 moles of ammonium carbamate, 2.048 moles of NH3 and 1.835 moles of water. It was compressed to a pressure of 153 absolute atmospheres, heated to a temperature of 210 ° C and then fed into the urea reactor 14. The gaseous phase of the reactor 1 consisted essentially of 3.3 moles of inert gases coming from the stripper. and which was recycled thereto by the compressor 8. In the urea synthesis reactor, the carbamate which came from the carbamate reactor 1 via conduit 10, pump 11 and heater 13 was partially converted to urea; The effluent from the urea reactor 14 consisted of 1 mole of urea, 0.831 moles of ammonium carbamate, 1,835 moles of water and 2,048 moles of NH NH3 and CC> 2. The 2,048 moles of free ammonia also entered the gas phase.

25 Ammoniumcarbamatdekomponeringen fremmes ved reduktion af partialtrykkene af CO2 og NH3·25 The ammonium carbamate decomposition is promoted by reducing the partial pressures of CO2 and NH3 ·

Denne reduktion blev opnået ved såvel ekspandering af blandingen, således at dens tryk faldt til 80 absolutte atmosfærer, som ved i bunden af stripperen at 30 tilføre de inerte gasser bestående af den gasfase, der kommer ud fra carbamatreaktoren 1, til hvilken der var blevet sat mere inert gas for at erstatte eventuelle tab. Udfra stripperen 6 kom der gennem ledningen 17 en væskefase, som bestod af 1 mol urinstof og 1,2 mol 35 vand, og gennem ledningen 5 en gasfase bestående af 6,5 mol af de inerte strippergasser Indeholdende 0,831 mol C02 og 3,71 mol NH3· Denne strøm blev sendt til carbamatreaktoren 1, hvor C02 NH3 atter blev bragt 145081 8 til reaktion som allerede beskrevet i det foregående.This reduction was achieved by both expanding the mixture so that its pressure dropped to 80 absolute atmospheres and by adding to the bottom of the stripper the inert gases consisting of the gas phase coming out of the carbamate reactor 1 to which had been added. more inert gas to replace any losses. From the stripper 6, a liquid phase consisting of 1 mole of urea and 1.2 moles of water was passed through the conduit 17 and through the conduit 5 a gas phase consisting of 6.5 moles of the inert stripper gases containing 0.831 moles of CO 2 and 3.71 moles NH3 · This stream was sent to the carbamate reactor 1, where CO2 NH3 was again reacted as already described above.

Eksempel 2Example 2

Den i dette eksempel beskrevne fremgangsmåde blev udført i et anlæg ligesom det i fig. 2 beskrevne. I det-5 te tilfælde var trykket i carbamatreaktoren højere end i urinstofreaktoren. Den gasformige strøm i ledning 4 bestod af 1 mol carbondioxid og af inerte gasser, i dette tilfælde af hydrogen og nitrogen; den blev blandet med den recirkulerede gas, og den resulterende blanding 10 bestående af inerte gasser, carbondioxid og ammoniak blev ført til bunden af carbamatsyntesereaktoren 1, hvor der blev opretholdt et tryk på 151 absolutte atmosfærer. Til carbamatreaktoren blev der også ført ammoniak i en mængde på 2 mol gennem ledningen 2 og 15 vand i en mængde på 0,2 mol gennem ledningen 3. Udfra bunden af reaktor 1 kom der en carbamatopløsning, som via ledningen 10 kom ind i opvarmeren 13 og efter opvarmning til 210°C blev ført til urinstofsyntesere-aktoren uden anvendelse af nogen pumpe.The procedure described in this example was carried out in a plant similar to that of FIG. 2. In this case, the pressure in the carbamate reactor was higher than in the urea reactor. The gaseous stream in conduit 4 consisted of 1 mole of carbon dioxide and of inert gases, in this case hydrogen and nitrogen; it was mixed with the recycled gas and the resulting mixture 10 consisting of inert gases, carbon dioxide and ammonia was fed to the bottom of the carbamate synthesis reactor 1, maintaining a pressure of 151 absolute atmospheres. To the carbamate reactor ammonia was also passed in an amount of 2 moles through the conduit 2 and 15 water in an amount of 0.2 mole through the conduit 3. From the bottom of reactor 1 came a carbamate solution which entered via the conduit 10 into the heater 13 and, after heating to 210 ° C, was passed to the urea synthesizer without the use of any pump.

20 Urinstofsyntesereaktoren 14 blev holdt på et tryk på 150 absolutte atmosfærer. Ud af denne reaktor kom gennem ledning 15 en opløsning indeholdende 1 mol urinstof, 0,831 mol carbamat, 2,048 mol fri ammoniak og 1,835 mol vand; denne opløsning blev ført til strip-25 peren 6, hvor det carbamat (0,831 mol), som ikke var blevet omsat til urinstof, blev spaltet i NH^ og CO2 og overført til den gasformige fase, der kom ud via ledningen 18, fulgt af de 2,048 mol fri ammoniak.The urea synthesis reactor 14 was maintained at a pressure of 150 absolute atmospheres. From this reactor came through line 15 a solution containing 1 mole of urea, 0.831 moles of carbamate, 2,048 moles of free ammonia, and 1,835 moles of water; this solution was passed to the strip 6, where the carbamate (0.831 mol) which had not been converted to urea was cleaved in NH 2 and CO 2 and transferred to the gaseous phase coming out via line 18 followed by the 2,048 moles of free ammonia.

Dekomponeringen af carbamatet fremmes ved reduk-30 tion af partialtrykkene af CO2 og NH^. Denne reduktion blev opnået ved til bunden af stripperen 6 at føre den inerte gasstrøm bestående af H2 og Nj i en mængde på 6,5 mol. Ud af toppen af stripperen 6 kom en gas-formig strøm bestående af 6,5 mol af de inerte gasser 35 H2 og N2 , 3,71 mol ammoniak, 0,831 mol C02 og 0,635 mol E^O. Fra bunden af stripperen 6 kom gennem ledningen 17 en opløsning bestående af 1 mol urinstof og 1,2 molThe decomposition of the carbamate is promoted by reducing the partial pressures of CO 2 and NH 2. This reduction was achieved by passing to the bottom of stripper 6 the inert gas stream consisting of H2 and Nj in an amount of 6.5 moles. Out of the top of stripper 6 came a gaseous stream consisting of 6.5 moles of the inert gases 35 H 2 and N 2, 3.71 moles of ammonia, 0.831 moles of CO 2 and 0.635 moles of E 2 O. From the bottom of the stripper 6 came through the conduit 17 a solution consisting of 1 mole of urea and 1.2 moles

Claims (2)

145081 h2o. Den gasformige strøm i ledningen 18 kom ind i kondensatoren 19, hvor en stor del af carbamatet og af vandet blev kondenseret. Carbondioxidet, som ikke var 5 kondenseret, blev absorberet i ammoniak i kolonnen 21. Det væskeformige effluent fra kolonnen 21 blev ved hjælp af pumpen 24 sendt til carbamatreaktoren 1. De gasser, der kom ud fra kolonne 21, bestod af nitrogen, hydrogen og ammoniak og blev ført til re-10 cirkulationskompressoren 26, hvor de blev komprimeret og sendt videre for at følge den strøm af gasser, der kom ind i reaktor 1 gennem ledningen 4, som beskrevet i det foregående. Den gasformige strøm, som forlod toppen af reaktoren 1 via ledningen 7, bestod af 15 nitrogen og hydrogen og blev sendt til stripperen 6; en del af denne gasformige strøm blev sluppet ud gennem ledningen 27 for at opveje den inerte gas, som kom ind gennem ledningen 4.145081 h2o. The gaseous stream in line 18 entered condenser 19 where a large portion of the carbamate and of the water were condensed. The carbon dioxide, which was not condensed, was absorbed in ammonia in column 21. The liquid effluent from column 21 was sent to the carbamate reactor by means of the pump 24. The gases coming from column 21 consisted of nitrogen, hydrogen and ammonia. and was fed to the recirculation compressor 26 where they were compressed and passed on to follow the flow of gases entering reactor 1 through conduit 4, as described above. The gaseous stream leaving the top of reactor 1 via conduit 7 consisted of nitrogen and hydrogen and sent to stripper 6; a portion of this gaseous stream was discharged through conduit 27 to offset the inert gas entering through conduit 4. 1. Fremgangsmåde til fremstilling af urinstof ud fra ammoniak og carbondioxid, ved hvilken man omsætter ammoniak og carbondioxid til fremstilling af en urinstofopløsning indeholdende uomsat carbamat, dekompone-rer det uomsatte carbamat og stripper dekomponerings-25 produkterne med inert gas, såsom nitrogen og hydrogen, kendetegnet ved, at dannelsen af urinstof-opløsningen udføres i to separate reaktorer, idet al ammoniak og carbondioxid, der fødes til processen, i den første reaktor reagerer under dannelse af ammonium-30 carbamat, og ammoniumcarbamatet i den anden reaktor overføres i urinstof og vand, hvorhos ammoniumcarbamats dekomponeringsprodukter og den til stripningen anvendte inerte gas recirkuleres til den første reaktor, hvorfra den inerte gas sendes tilbage til stripningsoperationen.A process for producing urea from ammonia and carbon dioxide, by reacting ammonia and carbon dioxide to prepare a urea solution containing unreacted carbamate, decomposes the unreacted carbamate and stripping the decomposition products with inert gas such as nitrogen and hydrogen. characterized in that the formation of the urea solution is carried out in two separate reactors, in which all ammonia and carbon dioxide fed to the process react in the first reactor to form ammonium carbamate and the ammonium carbamate in the second reactor is transferred into urea and water , wherein the ammonium carbamate decomposition products and the inert gas used for the stripping are recycled to the first reactor from which the inert gas is returned to the stripping operation. 2. Fremgangsmåde ifølge krav 1, kendeteg net ved, at gasstrømmen, der kommer fra toppen af stripperen, først sendes til en kondensator for konden-Method according to claim 1, characterized in that the gas stream coming from the top of the stripper is first sent to a condenser for the condenser.
DK662269A 1968-12-16 1969-12-15 PROCEDURE FOR MANUFACTURING URINE FROM AMMONIA AND CARBON Dioxide DK145081C (en)

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BE787832A (en) * 1971-09-02 1973-02-22 Stamicarbon PROCESS FOR THE PREPARATION OF UREA
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