DE1593587A1 - Process for the production of ureas - Google Patents

Description

DR. F. ZUMSTEIN - DR. E. ASSMANN OR. R. KOENIGSBtERQER - DIPL-PHYS R. HOLZBAUER

TELEPHONE 88 * 4 7 «and» »1011

TCLEeRAMME: »JMPAT eTeCH (CORNER ACCOUNT: MÖNCHEN β) Ι BO

8ΑΝΛΚΟΝΤΟ BANKHAJUe H. BUYER

70 / jsö

10 3020-58 700/65

TOIO K0AT3Ü INDUSTRIES, Incorporated, Tokyo, Japan Process for the production of urea.

The present invention relates to an improved method for producing urea.

In order to produce urea in an ammonia synthesis process, it is already known to wash an ammonia synthesis crude gas containing carbon dioxide with an absorbent of liquid ammonia mixed with a medium capable of dissolving ammonium carbamate at a pressure which is at least so is as high as the urea synthesis pressure, so that practically all of the carbon dioxide in the raw gas can be absorbed in the absorbent, and then to keep the absorbate produced at a urea synthesis temperature. According to such a method, it is unnecessary to remove and regenerate carbon dioxide by conventional methods in the Ammoniakayηthesever fahr s, which results in a great reduction in the cost of urea. However, there is still room for improvement in terms of the efficiency of carbon dioxide absorption and in terms of heat utilization C

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It is an aim of the present invention to create an effective method for the synthesis of urea in an ammonia synthesis process _{or the like}

According to the present invention, an ammonia synthesis raw'je; ·., which is made from a carbonaceous hollow using conventional methods. material or a hydrocarbon was obtained and that Hydrogen, carbon dioxide, carbon dioxide, nitrogen and others Contains gases such as methane, in a washing gas conversion Reactor introduced, so that the carbon monoxide contained in the raw gas reacts with steam and thereby hydrogen and carbon dioxide forms. That withdrawn from the water gas conversion reactor Hot ammonia synthesis raw gas is used in the heating zone Distillation column used to generate heat for the distillation of unreacted carbon dioxide and ammonia from a urea To supply synthesis effluent stream · It is then sent to a Pressure of 150 to 400 kg / cm compressed and in a washing tub

aur

lonne introduced, the / a pressure is kept in this range. In the wash column the gas is washed with an absorbent, the liquid ammonia and such a medium, zn the ammonium carbamate solve is capable of containing, Z ₀ as water, an aqueous solution of urea, an aqueous solution of ammonia or an aqueous solution of Ammonium oarbamate. So that all of the carbon dioxide contained in the raw gas is absorbed by the absorbent, the temperature of the upper part of the scrubbing

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column maintained below 100 ⁰ C, keeping the temperature of the column at 130 .Oodene oils 180 ⁰ C and the Molverhältnia NlWuO ₂ in the resulting absorbate in the bottom of the column at 2 his 3 * 6: maintained. 1 If the temperature and composition of the absorbance at the bottom of the washing column is selected in the above-mentioned ranges, the escape of carbon dioxide from the top of the washing column is switched off and the amount of ammonia in the gas leaving the washing column can be reduced »

The abeorbate from the Hoohdruok washing column, together with liquid ammonia, which is added if necessary, is broken into a urea synthesis reactor and kept at the temperature and pressure customary for urea synthesis, among other things to achieve a urea synthesis effluent, the urea, unconverted ammonia and unconverted carbon dioxide Contains water. The urea synthesis effluent outside the urea synthesis reaction vessel is depressurized, carbon dioxide and ammonia are not distilled off by using the heat of the ammonia synthesis process, which comes from the water conversion reactor, and the resulting aqueous solution is not converted into a conventional urea building stage ? ndioxyd abdeetillierto and ammonia are used for the production Wim ATdnoniuiflBulfat or Amwoniumnitrat "or Bie be / V absorbed into ater or an aqueous solution of urea oh conventional cathode and the Harnstoffsyiithesereaktor or

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fed to the above-mentioned washing column, on the other hand that is Ammonia key nt he se crude gas that comes from the scrubbing column, also the practically all of the carbon dioxide removed from the motorcade was cooled, the ammonia is removed by condensation. that carbon monoxide is removed by a conventional method if necessary, compressed to an ammonia synthesis pressure and then subjected to a conventional ammonia synthesis. The educated Ammonia is separated as liquid ammonia by cooling and returned to the scrubbing column.

The method according to the invention is explained in more detail with the aid of the attached flow chart. Methane, containing methane, is introduced into a water gas conversion reactor 2 through line 1 and the carbon monoxide contained in the gas is reacted with steam in the reactor so that it is converted into carbon dioxide and hydrogen , or by first going through a high temperature water gas conversion reactor and then through a Niedio. ₆ temperature wa8eergaBreaktor conducts. The gas from the water gas conversion reactor contains Zo E. 15 to 35 Vol .- # CO ₂ , 6 * to 85 V0I.-5S H ₂ , 0.5 to 25 Vol .- ^ N ₂ , 0.1 to 5 V0I.- 50 CO and C.1 to 2 VoI «. ~ # other fks «:, ζ« 'Λ · CM Ea

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! 593587

is usually at a temperature of 18C to 40O ⁰ C ₉ although the temperature can also be different "which depends on the type of thermal conversion process used" as mentioned above. The gas from the conversion reactor is then passed through a heating line 3, a heating coil 5 into a high-pressure distillation column 4 and then through a heating coil 8 into a high-pressure distillation column 7.In the coils 5 and 8, aaa gas gives off its essential and latent heat, acting as a source of heat for the distillation the most unused echlendioxyde and attttoniake are used in the urinary throat drainage and are cooled at the same time.

She's distillation of unreacted »Kohlendχe-ya and ammonia • JJL AEFE HarmtoffeyatheBtabflufi nioht to the two-stage distillation at high and low pressure" as '5 two described above £ 3 * - is. Oeeohrftnk-fes, however, can only be carried out one Viedrigiruekdeatillatioaesonritt, or ir.

insist on something of the; starred Hernsbhfeigt · Di # sue des ÄOfiMruakkolonne 4 der WiMQrürm®kkulQWi $. ? by fei-iungen ' i- vaz? ■ eMeetil len ness uttflefietstec §aee Eohlendiosyc um. On-donliik can AELE &_£:;;; - sw * .iiffi £; vom * jsm & ulixnevü.tB% & ÜBT Äwsponiiiisiiv.-rat veri if you & άηηβη nach üblicfees Met

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will win us an aqueous solution of Aaaoniuscarbamat ssu, which is reused for the synthesis of urea. The discharged from the liederdruok column 7 through line 10 aqueous solution of urea is passed through a customary production line and converted into crystalline or granular urea;

The Ansoniaksyntheee Bohgas from the Uelcsahlange θ In the Mlederdruokkoloim · 7 is introduced into a cooler 12 through line 11, »dt water is cooled» with an oaskoapressor 13 to a urea synthesis pressure of 150 to 400 kg / o »and sometimes to 200 up to 300 kg / o * " ² embossed and passed in a Wasoh column U"

If the amount of lahlendioxyi ir äea Aswoniakeynthese-Bohgas larger than all the «töohlOBetrisofe · Meng® ;, 4i @ for the synthesis Clay urea? is comparison with the amount of ammonia that comes out If the same Bohsaterlalgas is necessary, a part of the AnraoniakrohiBaterA / igasf ", which contains the excess fobltnclcxva ^ ahgetrax ^ tk .f In a carbon dioxide absorption-

g «l * i'.at au® c®i *

hlar washed with 'iiiz ^ M absorbent, sB «

" ';Aiiii" s9rten®ts ümr to the upper weft Semi -tfird part of the obtained f-uf àéíèê # y @ ise has been removed, f r.-il sjeaen gas from

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-. 7 -

which the carbon dioxide has not been removed to be combined. In this case, the sensible heat of the raw gas, before it enters the cooler 12, can be used as a heat source for removing carbon dioxide from the absorbent which was used to absorb the carbon dioxide.

Boa in the scrubbing column 14 conducted ammonia synthesis crude gas is bit liquid ammonia and an agent that is essential to dissolve ammonium carbamate, a »B. Waeser, an aqueous solution of ammonia, an aqueous solution of urea, an aqueous solution of aismonium oarbamate or a mixture of these «washed * scdaE üue. All of the carbon dioxide contained in the Rohgaa is eesorblert «Ds © flues Ig an At -'- rssiaL and ase solution medium tatfealtsia © Ab8orbe? i« jr-ai ^ gc-v ^ crj; ': * - ^. ; l · :. ■ * ■ '■ * "' 3 ^f / -er mixed © -wurden * Be is however, preferred, λ .-. Β ^ cterch a line 15 ai the upper part of the column and the liquid ammonia through a line 16 in the middle part of the column, as shown in Fließscheae, € inzuleitsn _s When a cyolisches method is used for the synthesis of urea, can be obtained by absorption of unreacted carbon dioxide and ammonia, a medium sit such as water or an aqueous solution of Barnstoff obtained solution of the column 14 as the dissolving medium.

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The liquid ammonia is preferably introduced into the tank column 14, which, as described below, was separated in the ammonia separation device 25 and the pressure was set (decreased or increased) to the pressure of the water column, since the hydrogen and nitrogen contained in the liquid ammonia is dissolved, which kcrrint from the ammonia synthesis vessel, obtained in this way and the rate of urea synthesis is not reduced. The temperature at the top of the wash column 14 is maintained at 10O ⁰ C and preferably at 60 to 100 ⁰ C. The temperature at the bottom of the column is maintained at 130 to 180 ⁰ C. The amounts of liquid ammonia and solution medium are adjusted so that the molar ratio of in the absorbate in the lower part of the column between 2.0: 1 and 3.6: 1.

The absorbst removed from the scrubbing column 14 is in a Urea synthesis reactor 18 introduced through line 17 and there at a temperature of 160 to 200 ⁰ C under a pressure

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from 150 to 400 kg / cm and preferably from 200 to 300 kg / cm held to synthesize urea. When urea synthesis is carried out using an excess of ammonia, additional liquid ammonia is introduced into the urea synthesis reactor 18 by conduit, if necessary. As additional liquid ammonia *: the liquid ammonia that was isolated in the cooler 2.2 can be used.

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»9 -

de, or a fur or the Geuaurtiaenge dee Aimuoni iks, which was separated in the separator 25. In this Pail the temperature of the Harnetoffeynthesereaktors 18 can be maintained within the temperature range mentioned oban by the liquid ammonia to a suitable temperature below 200 ⁰ C prior to the introduction is heated. The additional liquid ammonia can be heated by heat exchange with the gas containing ammonia, hydrogen and nitrogen coming from the ammonia synthesis tank 23 described below.

The Harnetoffsyntheseabfluß, which is discharged from dea Harnstoi £ synthesis reactor 18 is directed to 10 to 30 kg / cm expanded in the high pressure distillation column 4 through line 20 and thence through the high-temperature Ammoniaksynthet e raw gas: .U3 the water gas conversion reactor 2, as above beacl rubbed, heated sodafi the unreacted carbon dioxide and ι maybe reacted ammonia contained in the effluent, abdertilliert and removed at 130 to 160 ⁰ C. The discharge from the high pressure

distillation column 4 is stretched to Oi to 5 kg / cm, in

/ ■ · ■

the low-pressure distillation column 7 is passed through the Aj & £ O # ia] T3yni? 2 £ se ~ Hc! 2 £ Sg, which enters through lines 5 and 8, so that the ves ^ lelbesuie ciofat ragagsetstt isuHoniakgaa bal 100 to 140 ⁰ C distilled off verdea.

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The ammonia syntbeai raw gas from der'Waechkolonne 14 is introduced into a cooler 22 through Lei-tun «21, ^{cooled in the cooler to a temperature below 40 0} C, and the accompanying ammonia gas BU condense, which is removed and through line 19 into the Urea synthesis reactor 18 is recycled if desired. The heater 22 can be replaced by a wax column in which the raw gas is washed with water in order to absorb the accompanying ammonia gas. Thereafter, coblen monoxide present in the ammonia theae is removed by a customary method, B ₉ Bo by washing with nitrogen or a methane-forming reaction, if necessary adjusted so that the molar ratio of hydrogen to nitrogen is about 3: 1, introduced into the ammonia theaereactor 23 and there known ammonia synthesis conditions subject. Eb does not need to become butene. That is, if the ammonia synthesis pressure is higher than the pressure in the Wasohkölonne 14, the pressure of the ammonia synthesis crude gas from the scrubbing column 14 on the Auuonia synthesis pressure. is increased.

Bas Qaagemisch aua ammonia, hydrogen and nitrogen aue the AsMonlekaynthesereaktor 23 wild cooled and introduced into the Ammoniakabschei · 25 through line 24 and the Aaatoniak formed is as a liquid Aamoniak aua the SSAE separated The fliiasige Ajsaoniak from the separator? 5 is in. The. Arch column 14 through line 16 and / or into the urea sy ^ her.ei'eaktor 10

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usually introduced through line 19, the separated in the Abtreiinvorriohtung 25, which is mainly from Gas fuel and nitrogen ordered, is in the ammonia system η the self-actuator 23 through line 26 surttokleitung.

The following example explains the invention. The Prosentangata! »• interpret Volue-jt, if not stated otherwise ·

example

394 * Vh. Crude gas, a de t 56.3 hydrogen, carbon monoxide 13.2 £ _v 7.4 Ji carbon dioxide, 22.6% nitrogen and 0.5% other gases "as Kethan contains, operating at a temperature in a Waseergaeumwandlungareaktor 2, is from 25O ° C and a Druok 25 held kg / o · introduced after having been passed through a HochteBperatur-Vae8ergaBUBwandlungereak \ or held at a Xemperetcr tone 400 ⁰ O and a Druok of 27 kg / cm. Danpf was carried out at a rate of 155 kg / btd. also introduced into converter 2. The Kohlennonoxyd of the raw gas react to nit Danpf in the converter 2 to form a drain, the 17.9% carbon dioxide, 61.3 ^ Vaeserstoff, 20.0 ° 1 nitrogen, 0.4 and 0.4 Konlennonoxyd £ • 1 · iidere Contained gases. The Oonverterabflufl had a temperature of about 250 C and a pressure of about 25 kg / cn and was passed through a hot water column 5 "ur high pressure distillation column, where it

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lightened a urea synthesis flow, as described below, so that both the largest rope of the unconverted ammonia and unconverted carbon dioxide was driven out converted Aaaonlaks and carbon dioxide from the urea synthesis effluent, which comes from the high pressure distillation column 4, delivered. From the heating coil 8 of the converter effluent wurae passed into the cooler 12 where it was cooled to a temperature of about 4O ⁰ C Hit water. It was then fed to the compressor 13, where its pressure was increased to 270 kg / cm.

From the compressor 13, the converter effluent was introduced close to the bottom of the water column 14 at a rate of 443 nr / hour *. At one point in the cement of the column, liquid ammonia was introduced at a rate of 183 kg / day. IAHE the top of the column was AmwoniumcarbamatlÖBung that 39.9 wt «ft ammonia, 35.1 wt -fi carbon dioxide and 25 |.. O contained £ by weight water, eit a rate of 288 kg / hr. · introduced the head of the column was maintained at 14 • Jjier temperature of 9O ⁰ C and the ground at a temperature vonH5 ° C. The carbon dioxide contained in the Oonvertergasbeschiokung for column 14 was absorbed in the water and ammonia with formation of an absorbate which is 3 mol

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1593S87

- Contained 13 AnmonlBk per haul of carbon dioxide "

The absorbate was aged at a rate of 627 kg / hour * Susannen at 100 kg / hour. liquid ammonia was introduced into a urea synthesis reactor 18, where it was kept at 185 C and 230 kg / cn to form urea. The effluent from reactor contained 28.9 wt. 5ε urea, 14.2 wt , 3 percent by _e - # ammonia and 18.6 wt .- $ * water. The urea synthesis effluent was increased at a rate of 727 kg / hour. sent through the distillation column / 4 and 7, Inder the unreacted carbon dioxide and ammonia gas were driven off .. The resulting 73 ßew, - ^ lge aqueous solution of urea was drawn off through line 10 and then converted into crystallized or granular urea.

The gaseous effluent from Vaschkolonne 14 contained 23.3 # nitrogen, 71.8 i * is hydrogen, 4.0 $ ammonia and 0.4 # KohJenmonoxyd. The gaseous wax column effluent was passed at a rate of 364 g / hour into a vasoh column 22 where ammonia was absorbed in water and separated from the gas mixture. Thereafter, the Gaeabstrom a MethanbilduneBreaktion was subjected to carbon monoxide to be removed and the resulting gas mixture together with the hereinafter described Gasgenlsoh from the Amsioniakabscheider 25 the Ammoniakßynthesereaktor 23 Ettgeführtj at a temperature of 320 ⁰ C and a pressure

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of 280 kg / cm was kept by a circulation compressor (circulating οοπι- preeeor) . The stick contained in the gas mixture material and hydrogen reacted in the Amiaoniaksynthesereaktor 23 to form ammonia "The effluent from reactor 23 contained 15.1 1> ammonia, 57.6 $ hydrogen, nitrogen and 17.1 S 10.2 5» other Gases and was at a rate of 186 ar / h. the ammonia separator 25, where ammonia was separated in liquid form and fed to the washing column 14 through line 16 * The nitrogen, hydrogen and others

mixture
Gases containing gas / from ammonia separator 25 wui'de for. Reac tor ~ 23 zurilokgeleitet :.

After the above-mentioned procedure v ^ dc Urnst of i 'obtained at a rate of 210 kg / hour.

According to the method according to the invention for the synthesis of urea in an ammonia synthesis process, if carbon dioxide, that in an ammonia synthesis raw gas aue dem Waßaergasuiawanct · - treatment reactor is contained, absorbed under certain conditions the escape of carbon dioxide from the top of the washing column are practically reduced to 0 and the amounts of ammonia that the Ammo & iE.ceyntheae-Rohgae., because ε from the head of the Column comes, escort ^ can be reduced to a minimum. In addition, the raw gas in the ammonia synthesis can be used

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The heat contained in the water-gas conversion reactor is used to distill carbon dioxide and ammonia that have not been converted from the urea synthesis process. In the inventive method, the heat used is equivalent to I ₉ 85 tons of steam per ton of urea, if the rate of synthesis of urea is £ 40, compared to 1.35 tons of steam per ton of urea, if the rate of synthesis of urea is 50 # and. 1 ton of steam per ton of urea if the urea synthesis rate is $ 60> »

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Claims (1)

Patent claims 1c process for the division of urea »characterized in that the carbon monoxide, which is present in a high gas containing hydrogen, carbon monoxide, carbon dioxide and nitrogen, is converted into hydrogen and carbon dioxide with water vapor in a water gas conversion zone to form a water gas conversiona effluent, the hydrogen, carbon dioxide, nitrogen and contains unreacted carbon monoxide and water vapor, converts ammonia and carbon dioxide in a urea synthesis reactor to form a urea synthesis effluent, which contains water, urea, unconverted carbon dioxide and unconverted ammonia, converts heat from the water gas synthesis effluent _{9 to the urea synthesis effluent} In order to distill off unreacted ammonia and carbon dioxide in the urea synthesis effluent, the water gas conversion effluent is compressed to a pressure of 150 kg / cm to 400 kg / cm, the water gas effluent with liquid ammonia and a medium that Dissolving ammonium carbamate allows ₉ in a washing zone to absorb in the liquid ammonia and the medium the carbon dioxide contained in the water gas conversion effluent to form an absorbate containing the ammonia and carbon dioxide and a gaseous effluent from the washing zone, the hydrogen and Contains nitrogen, where- 209817/1509 BATH ORIGINAL 1893587 at the composition of the absorbate at 2.0 to 3s6 mol Ammonia is kept per pint of carbon dioxide, which is absorbed in The urea synthesis reactor is recycled to remove the ammonia and carbon dioxide contained therein with the formation of urea implement ο 2 "Process according to claim 1, characterized in that the water-gas conversion effluent is ^{kept at a temperature of 180 to 400 0} C" 3 · The method according to claim 1, characterized in that the water gas conversion effluent heat with the urea » synthesis effluent in a high pressure distillation zone and then can be exchanged in a low-pressure distillation zone. Method according to claim 1, characterized in that the medium which allows ammonium carbamate to be yoked is introduced into the upper part of the washing zone and the liquid ammonia is introduced into the middle part of the washing zone _{or the like} 5 »The method according to claim 1, characterized in that the liquid ammonia in the washing zone in the mixture Ddt the medium, allowed to dissolve the ammonium arbamate, initiated willo 209817/1509 BATH 6, method according to claim 1, characterized in that as Medium that allows araaonium carbamate to dissolve. Water, an aqueous solution of ammonia, an aqueous solution of urea or an aqueous solution of ammonium carbamate are used will ο 7ο The method according to claim 1, characterized in that as much liquid ammonia is introduced into the washing zone to the composition of the absorbate is 2.0 to 3–6% ammonia to keep per mole of carbon dioxide » 8o method according to claim 1, characterized in that the temperature at the top of the washing zone below 100 ⁰ C and at the bottom of the wash zone is maintained at 130 to 180 ⁰ C. 9 »The method of claim 1, characterized in that the gaseous effluent from the scrubbing zone ammonia synthesis is subjected to conditions in a Amiucniaksynthesezone to form ammonia, said effluent from the ammonia synthesis zone also hydrogen and nitrogen ^ lind then the ammonia contained in Ammoniaksyntheseabstrom condensed and the wax zone is returned to absorb the carbon dioxide contained in the water gas conversion waste * 1oo method of claim 9t characterized in that the material introduced into the liquid-Harnstoffsyntheaezone Abeorbat mi t 20 98 17/1509 BATH ORIGINAL ammonia is added. 11 · The method according to claim 10, characterized in that the liquid ammonia is preheated to a temperature below 20O ⁰ O before the addition of eum Absortet · 12 _o The method of claim 11, characterized in that the liquid ammonia Dess by heat exchange with the Aramoniaksyntheseabstrois is preheated " 13. The method according to claim 1, characterized in that in the urea synthesis ^{zone the temperature is kept in the range of 160 die 200 0} C and the pressure is kept at 150 to 400 atti * 14. The method according to claim 3 »characterized in that the _t tfassergasumwandlungaabstrom in the Hoehdruckdestillations" zone at a temperature of 130 to 160 ° 0, and a pressure from 10 to 30 atu and the NiederdruckdestiXXationeiione "at a temperature of 100 to 140 ⁰ C and a pressure before 0 Ms 5 atu is held » 209817/1509 BATH ORIGINAL Blank page