DE1618867A1 - Process for the production of urea - Google Patents

Description

DR. ELISABETH JUNQ AND DR. VOLKER VOSSIUS -1 Ci O Q 57

PATENT LAWYERS • MÖNCHEN 23 · * IEOΕββΤΛΑΙβί1 «■ TELEPON i4§6S7 · tCLEQH AMM-AONSSSE: INVENT / MONCHEN

28. Resin ICt

C 596 fVo / kä «. . .

POS-10236 SUMlTOKO

SUMITOM) CHEMICAL COMPANY, Osaka, Japan

"Process for the production of urea"

Priority: March 29, 1966, Japan, Filing No .: 19832/66.

Technically, urea is made from ammonia and carbon dioxide Ammonium carbamate at temperatures between about 160 and 230 C. and pressures of about 140 to 400 atmospheres. The reaction proceeds according to the following equations:

(1) 2üH ₃ * CQ ₂ * NK ₂ COOIiH

₂ * NK ₂

(2) SH ₂ C (KiItIi ₄ NH ₂ COJiH ^ <■

In the first stage of the reaction, ammonium oartaminate is formed as an exothermic reaction »In the second stage , which under usual

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relatively long under temperature and pressure conditions and is endothermic and is a reversible reaction, cleaves Ammonium carbamate removes water and turns into urea. Grind the latter equilibrium reaction involves the rate of carbon dioxide uras to urea usually about 50 to 80 # «, being equivalent to id contains the reaction product of the Harristüxfsynthetstufe still in proportion large numbers of unreacted components, such as ammonium carbamate and excess ammonia. There were therefore numerous procedures have already been developed to remove the unused components from the. Separate the reaction product and put it in the Harastoff-Syivthöaeotufe. to restore "

For example, Japanese patent specification 5 269/63 describes ζ · Β. a ^1; 2.? - drive, with deia the pressure of the reaction product from the urea synthesis stage is reduced to 10 to 35 at and the same -

63 heated in time the Reaktionsprodukfc _P um / a liquid 'IEIL and a gaseous rope on au separate _β' During the heating f vir.i the separated liquid part with an inert gas such Stickstof _(treated to a gröaseren part of the unreacted Ammoniuttcarbaminats decompose to Annoniak and carbon dioxide and "ataustreifen is ^ eaetztem ammonia. this gives an aqueous urea solution" these gases along with not and at hospitable matured Gaee be separated from the inert gas and used as an aqueous ArMaoniuncarbaminatlÖ3ung again, while the inert gas is recirculated .

Furthermore, there is a method in Japanese Patent Publication 19964/63 described? with dea daa reaction product from the urine ßoff «synthesis stage with carbon dioxide under a bridge of

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_{ViLrU 5} treats at least 10 atmospheres in order to decompose the ammonium carbamate and strip the decomposition products from the reaction product »and return the stripped gases back to the urea synthesis stage.

In this method, Jed ⁰⁰ ** is the iiealttioneprodukt in not used, the heat generated in the urea synthesis and the decomposition of the ammonium Wäriiequelle "carbaminats. enths: iten is, but ax is recovered in the ForavonJ & iLcf * If the separation of the unreacted constituents saxa the reaction product in a with tierej-i Drueii. atm is caused by IC to 35, it is necessary to continue the Jieinperatur in the absorption of the separated not uagesetztenBeetaÄdt8ileverhältnisraäes2 ^ th low hai _"what's the consequence is that the utilization of Absprptions * - heat as effective Wärmeqtuelie is difficult," If the .ieaktionsprodukt with carbon dioxide is treated under the urea synthesis reaction "pressure, is also used separately as Hocharuckdaiapf as a heat source *

The purpose of the invention is to provide a process for the production of urea, in which the separated unreacted constituents _t namely aniiaonia and ^^ carbon dioxide are completely circulated, and the unreacted constituents _r in the heating product from the UrnstoXf-Synthesestüfe are contained, with the help of the heat generated by the urea f => Syöthesereak ti on and at the same time treated with an inert gas, whereby the unreacted Beatana parts are separated from the reaction product vrerdeno Kan receives απSer the reaction pressure of the ureas

Synthesis an aqueous urea solution that is practically free of unreacted ingredients. JJi e absorption treatment, and the circulation of the unreacted, separated bed parts is also carried out under the Hainstoff synthesis process.

The invention thus provides a process for the production of urea by reaction of ammonia with carbon dioxide at elevated temperature and under pressure ₉ which is characterized iet ₉ that the ammonia and carbon dioxide in a first synthesis Heaktionszonee the 140 to 400 kg / cm, and between 160 and 250 ⁰ C, and then introduced into a second synthesis reaction zone, which is kept at the same or slightly lower pressure, here causes the urea synthesis, the reaction product from the second synthesis reaction zone »it with the help of in The heat generated in the first synthesis reaction zone is thermally treated and at the same time treated with an inert gas to separate unreacted components and but to obtain an aqueous urea solution under the pressure of the second synthesis reaction zone, the separated gaseous components under essentially the same pressure as in the second Syntheß® ~ R «atetion8z © n @ in a watery The resulting aqueous ammonia carbaminate solution or -aufechläsiaiung, which optionally

Contains urea, mainly in the second Syntaeee-Re- ^! Action zone returns »and the separated inert gas is returned to the treatment of the reaction product.

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Is according to the * erf indungsgemäaeen method, the urea Synti »e« t in two stages carried out, and in this Pali the developed at the first stage heat is veiiwendiet as heat Uelie to decompose the JtofficmiuingarljaiBinats, daör included in Keaktioaspröiiukt uei second synthesis Keaktionszone . This has the Foi i «v Iceine that separate Wäjpiite ^ ual eyfordejRÜcli ^ n istJ'Weiterhin treatment is in combination with the tiiermiBcti ^ performed Abetr * Lfbehandlung with an inert gas, utilizing the Keaktionswärme * eodaes the separation of non-reacted _<p components, the are included in the Reactionsprodukt "slightly ι can be completely effected id, so that it is under the pressure de3 urea ^ synthesis möglioh, a wäasrißQ urea solution to be obtained en ;, of Liicht ÜjageS9tzten ingredients is" are üecientepreohenü m virtually free in erjJndungegenäsaen Verfani unlike the steps of the conventional method for the Z "rsetzunß and removal of ammonium carbamate, üiö duroh heating the Heaktionsprqduktes the urea synthesis step unt <c gradual reduction in pressure can be effected, but can no longer necessary · üb a step for separating uer niclr unreacted components from the reaction product be connected under a pressure n, which is lower than the pressure of urea synthesis "and usually between 1 and 30 atmospheres 1 3 - in this case, or if some of the unreacted constituents are to be used for other purposes - can aai under the pressure of Urea synthesis also remove an aqueous Han solution that contains part of the unused bed parts.

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Furthermore, the entire separation of the non uageavtzten Be constituents from the Heaktionsprodukt obtained-Syntheaestufe Harnatoff in, and the AbBorptionsbehandlung d% x separated, not ttogesetetexi components under substantially the same Druokbedingungen »carried out as in the Harnetoff synthesis" and therefore lets the walls work very well and has an effect on us and regained. For example, the heat of absorption of the high pressure absorption stage is generated at a relatively high temperature, such as 100 to 130 ° C., so it can be used effectively. At the same time, the absorptive "" treatment of the separated "unreacted constituents" is carried out more effectively and completely, and the absorption liquid required for the absorption device is low, so that the waaeerae ^ e introduced into the liamstoff synthesis stage is particularly small.

One of the disadvantages of using the known peat harvesting an inert gas to separate the unreacted bedding ile was that the inert gas to be circulated was in large Quantity required 1st. Make the method according to the invention but the amount of inert gas is reduced to "in Kindestmaaa" by stan treating the non-implemented stock parts at relatively high temperatures due to the effects Utilization of the reaction heat of the Haniatoff-Syntheee durohfUhr As a result, the circular list of inert gas can be used because: no separated »unreacted constituents contains» little effect · Kan can also carry out the process like this · », the» «on from an aqueous urea solution which, under the pressure of the The synthesis of urea is formed "" in an energy source.

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Pig. 1 aelfet schematically an embodiment of the invention Milling process on an industrial scale

Through line 1 is gas or liquid? Asuaoiiia *. introduced and compressed with the aid of a pump 2, the formation of liquid ammonia is vaporized in line 3: and the preheater switched on. the line 4 is fed in with carbon dioxide and compressed with the aid of the compressor. In this case the molar ratio of air to throat diocide represents the theoretical McL ratio or it is close to the theoretical ratio of carbon dioxide lies "between 1 * 9 Ms 2 _e ls 1. In the event that we" a part of the carbon dioxide is introduced directly through the line 42, the control valve 43 and the line 44 into the second synthesis reaction zone IO. Biese! Lassnanme ulm & t eur Control of the temperatures of the heat exchanger® of the heat exchanger 8 of the first syatli * se «" H «aktioziezosie T • A lot of carbon dioxide, which through the Leitusig 44 in you swsite S ^ ntfeee« - Eeaktionssone 10 is initiated _a amounts from 0 to SO f £ _g beeogti on the Qssantaeng · aa carbon dioxide, which is sucked through line 4. ΏΙ & the first synthesis reaction line and the broad synthesis reaction W can be arranged in a safe way. "

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The first synthesis reaction is carried out under a pressure of 140 to 400 kg / cm and at a temperature between 160 and 230 C. A suitable Syntheeo reaction zone 7 has 5 to 20 plates 13 »on which serpentine« »heat exchanger 8 arranged in a sense · You can also use a double tube heat exchanger instead of the one on the plates 1? arranged snake heat from Use exchanger 8. In this case, the compressed ammonia and carbon dioxide coating creams are preferred led into the head space of the heat exchanger. As plate 1? are generally pearl plates, sieve plates or the like Plates used as they are for distillation, absorption or r used for stripping · The heat exchanger 8 will a arranged on the upper surface of the plates. The reaction pro duct from the first synthesis reaction zone (the heat exchange r 8) is introduced into the second synthesis reaction zone 10 through the line 45, the pressure control device 41 and the line 9 and there are worlds unplaced · At the same time, those are recovered unreacted constituents in an Absprptionsflüesig ice it were absorbed »through line 40 to the second Synthesis reaction zone in the form of an aqueous ammonial calleohen Ammonium carbaminate solution or r-digestion initiated »the optionally contains urea. The second synthesis reaction is carried out under the same or slightly lower pressure as the first synthesis reaction * Furthermore, the temperature of the second synthesis reaction is preferably the same as that of the first synthesis reaction. With the help of the pressure control device device 41 can be the pressure in the second synthesis reaction Set zone 10 slightly to a lower value than in the V / ä exchanger 8. This measure enables smooth-time

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increase the Reaktionsdruoic in Wärmeaue exchanger θ welter su wan to further increase the "aaktionsteraperatur result has. This makes it possible to reduce the heat transfer required in the device 7. When the second synthesis reaction is carried out at a lower pressure than the first synthesis reaction, the pressure of the second synthesis reaction is usually set to such a value as 1 to 50 kg / cm lower than that Pressure i: i of the first synthesis reaction. The heat of reaction in d & x second :: synthesis reaction zone vdrd is removed with the aid of a heat exchanger which is connected to the second synthesis reaction zone 10 through lines 17 and 19. The heat exchanger 18 can either be a jacket tube exchanger or a container s "iin, which is provided with a simple coil inside" through which a cooling medium flows, if the Wänneauetaue © her 18 is a stove _f is introduced through the line 20 water and pressure steam withdrawn through line 21 *. In the second synthesis reaction, the molar ratio of ammonia and carbon in dioxide is in the range from 2 to 5 s 1 · The reaction product from the second synthesis reaction zone 10 is through line 11 into the head of the device 7 initiated and guided onto the plates 13 with the aid of a distributor plate 12. In this case, we: the reaction product from the second synth @ se ~ action zone 10 UIe Keaktionewäru © of the first urea synthesis reaction with the help of the Wäraeaust & iieelie ^ 8 "^ ob © i da® AsuiioniiiisQarb.j '" ffi £ nat added is _e da®-contained in the H @ aktiöxi® product »is» Id.:-

b © id © ^ tiiesaisohea B@liaadS.Mag das Eesktione-lies g © wötolieh swis @ lÄ © n 110 tsmd 180 Oo Bm, & on the plates 13 -WQShrniü & nM RtaktioEispEOayJst tfisd in Sagsastros wit

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brought together and treated with an inert gas introduced through line 28. In this case, the constituents that have not been converted are stripped off and drawn off in the form of an aqueous urea solution under the pressure of the device 7 through the line 14. This aqueous urea solution is depressurized with the aid of the reducing valve 15 and then drawn off through line 16. On the other hand, the Inertgasstroia in counter-current to the plates of the device 7 with the thermally-treated Re is reaction product _s brought together around the non unoccupied ingredients strip * This Inertgasetrom is then passed through line 22 contained as an unreacted components the gas stream in the lower part a high-pressure Absorptionskolonr »= 23 led. The effective amount of the inert gas used is usually in the range from 0.2 to 2.0 mol per column of unreacted constituents. The most varied of gases which are inert to the reaction product of the urea synthesis stage can be used as inert gases. In the art, however, air and nitrogen are generally used for this. An absorption liquid is introduced into the top of the high pressure absorption column 23 through the duct 29, the pump 30 and the line 31. The contact of gas and liquid is effected mainly in the packed beds 24 and 25, and the unreacted components contained in the inert gas are absorbed in the absorption liquid. i & the HoeMruck-Absorption8i..olonneant «rprakf; if the same pressure is operated as in the second synthesis-Üeaktioaiszone 10, the resulting amount of an acceptable liquid can be comparatively small. Alii absorption liquid become Wassar, a wäse '.' Ige Amraoniumcarbamina ^ ioaufi ^ ^ fIer eiii @ watery Harnetdfflöaun £

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An aqueous, ammoniacal ammonium solution or dilution, or optionally urea, is obtained in the absorption column; contains. This solution is _r through line 32 - J urape 35 vmä the LeitungEriH and 40 returned to the second-© Synthesis "lleaktionssoii © IO and reused in diu urea" synthesis "Bin hawking the aqueous solution or slurry is zvae removal of para orpti oaswärme led into the cooler 36. This aqueous solution or slurry is then in the middle part of the high pressure = absorption colonr ·; 23 returned through line 37 and reused together with c.ir absorption liquid from line 29 for the absorption of unreacted components m cases also to the leil in the. Heat exchanger initiated 8 wertisn "This measure is aimed, in accordance with the operating conditions that achieve the Wänaebiianz the main action, the lines 38 and 39 are BeechickungBleitungen or Auslaseleitungen of the cooling medium for the cooler 36" Her cooler 36 is usually provided with a sin steam cooker. " From the top of the high pressure absorption column 23, the inert gas is withdrawn from which the unreacted constituents were separated by absorption with the absorption liquid and circulated through line 26, compressor 27 and line 28. With the aid of the compressor 27, the pressure of the inert gas is usually increased to a value of less than 1 kg / cm, which is necessary for circulation.

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The invention is further illustrated by the example.

example

In the heat exchanger 8, which is operated under a pressure of 250 kg / cni and 2OO ⁰ C, 34 kg / hour of ammonia and 44 kg / hour of carbon dioxide, both preheated to 200 ° C, introduced through line 3 and 6 . The reaction product was through line 45? the pressure control device 41 and the line 9 were introduced into the second synthesis reaction zone 10, which was kept at a pressure of 200 kg / cm and at 180.degree. In this case, 40,116 kg / hour of an aqueous solution were simultaneously fed through the line _p to about 15.5 GeWo-5-β urea, contained about 30 "0 wt .- ^ ammonia and about 51.7 GeWV = $ ammonium carbamate. The reaction product was then introduced into the head of the device 7 through the line 11 and distributed onto the plates 13 through the distributor plate 12. In this case, the reaction product remaining on the plates 13 is thermally treated with the heat made available by the heat exchanger 8 and at the same time, in the opposite direction, treated with 123 kg / hour of nitrogen, which was introduced through the line 28. Line 14 becomes 99 »2 feg /. Hour of an aqueous urea solution in a concentration of 78ρ5 wt. The unreacted _p abgetrenrten ingredients are fed together with the nitrogen through line 22 into the bottom of the high pressure filing Absorptionekolonr.e 23, which is maintained at a pressure of 200 kg / cm and at 130 ⁰ C. In the absorption column 23, the unreacted constituents are in countercurrent at 21.2 kg / hour

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an aqueous urea solution with a concentration of 85% by weight. This urea solution is fed through line 29, pump 30 and line 31 into the head of the absorption column. The aqueous .urea-containing ammoniacal ammonium carbaminate solution is returned from the lower part of the absorption column to the second synthesis reaction zone IC through line 32, pump 33 and lines 34 and 4-0. However, for this aqueous solution, line 35 is withdrawn and passed through the cooler 36 and the duct 37 back into the middle part of the high pressure absorption column 23. The nitrogen withdrawn from the top of the absorption column 23 is circulated through the line 26, the compressor 27 and the line 23. In this case, 3 kg / hour of pressure steam of 4 atmospheres from the heat exchange: * 18 and 28 kg / hour of low pressure steam of 1 atmospheres obtained from the cooler 36,

Claim

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Claims (1)

Pa t en tans ρ r u c ii A process for the production of urea by reacting ammonia old carbon dioxide at elevated temperature and under pressure ,, characterized ge characterizing t _p that άε, Β ammonia and carbon dioxide in a first reaction zone synthesis _£ 2 ο which is kept at 140 to 400 kg / cm and between 160 and 230 C. becomes j, and then into a second synthesis reaction zone « conducts, which is kept at the same or slightly lower pressure ρ here causes the urea synthesis, the reaction product thermally treated from the second synthesis reaction zone with the aid of the heat generated in the first synthesis reaction zone and at the same time for the separation of not unreacted constituents and for obtaining an aqueous urea solution under the pressure of the second synthesis reaction zone with a Treated inert gas, the separated gaseous components under essentially the same pressure as in the second The synthesis reaction zone in an aqueous absorption liquid absorbs the obtained aqueous-ammoniacal ammonium carbamate solution or slurry, which optionally contains urea, mainly into the second synthesis reaction zone returns, and the separated inert gas back for treatment of the reaction product. 209B U / 17
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