DE2143583C3 - Process for the production of urea - Google Patents

Description

Saving of thermal energy, which is expended in a usual carbon dioxide separation process must become;

Saving of thermal or mechanical energy when separating the ammonia is to be used from the unconverted gases;

ίο Savings in operating costs by eliminating the ammonia separation stage;
Saving of mechanical energy to compress COj up.-J
Saving the operating costs for COi compression.

The integrated processes for urea production are well known. So with one of the US Pat. No. 3303,215 known method compresses the raw gases for ammonia synthesis and converts them into a column was introduced, the upper part of which was used for COj absorption with the help of ammonia solutions and a subsequent carbamate formation is used, while the lower part of this column is used for conversion of the carbamate formed η serves the urea.

The strong heat development during the carbamate formation and the presence of inert gases (H; + N;), which reduce the partial pressure of the NH ₁ and the CO2, make a leg at high pressures (about 250 kg / cm- ') necessary in order to protect the reaction participants to reverberate in the liquid phase. In the case of such a procedure, no device is specified for removing the heat which is developed, and the equilibrium becomes colder as a result of the introduction

ti of absorbent solutions. The Um Conversion of the CarbaniJtN into urea takes place in the same device, namely in the lower part of this Device carried out As already stated above, make the difficult heat dissipation and the Presence of inert gases (H? + N;) it is necessary in order to achieve a sufficiently high carbon dioxide partial pressure manage to work at relatively high pressures

The absorbent solution is made by anhydrous Ammonia is formed, to which an aqueous solution of the

ι =, decomposition product of the flour-converted carbamate is given. Line such decomposition will occur at low pressure

The raw gases for ammonia synthesis are the absorption of CO? and after further treatment

k> gen for the ammonia synihesis. which at high pressure, is carried out in particular at a pressure between 400 and 5 (K) kg'cm-is used.

From the fact that the ammonia produced, that for the preparation of the aqueous absorption solution

") i is used, isi anhydrous at the beginning and because of the high synhesive pressure it can be concluded that the ammonia separation from the synthesis effluents in a suitable manner, in particular by freezing out water and by evaporating ammonia.

h «takes place.

In another, from US-PS JJ 49 12b known, integrated processes are not the entire Syniheserohgasc to absorb the therein contained ('(). · used, but partly in

h'i usual way for the production of pure CO. This is done because the Carbamaibildunj; and its conversion to urea be carried out in / by various devices.

whereupon - to keep the temperature of the zone in which urea forms within acceptable values - Ammonia and carbon dioxide are supplied to the develop the required heat through the reaction to form the carbamate.

The absorption of the CO ₂ from the crude synthesis gases for the production of carbamate is carried out at lower pressures than is the case with urea synthesis, with aqueous solutions containing the decomposition products of the carbamate, which has not been converted into urea, and optionally added Containing ammonia. ·

The carbamate decomposition products are then partly washed out in the column into which the synthesis gases are _{introduced to absorb CO 2} , and partly in a second column into which dilute ammonia solution is introduced as an absorber. The solution emerging from this second column is introduced into the aforementioned first column as an absorbent.

The .Syntheserohgase are after the separation of CO »and the subsequent known treatments introduced into the ammonia synthesis stage.

According to DE-OS 18 16 099, the method for the production of urea in combination with the Ammonia synthesis an NH i / Hj / N; stream derived from ammonia synthesis under synthesis pressure im Washed countercurrent with water, an aqueous solution of urea or of NHj and COj and the so sublime ammonia solution is fed to the urea synthesis, while the ammonia-free gas mixture is recycled back into the ammonia synthesis.

A.UN of DE-OS 19 07 025 is a process for the production of urine in connection with an ammonia synthesis from the - obtained in this synthesis - ammonia and carbon dioxide with the formation of a concentrated ammonium carbamate solution, which under the usual temperature and pressure conditions in a urea solution containing remaining unreacted ammonium carbamate is converted ammonium carbamate solution is dabe ¹ erhallen by absorption of the obtained in the raw gases (synthesis gas) for the synthesis of ammonia carbon dioxide in a concentrated ammonia Lö solution This concentrated ammonia solution originating: from the absorbance of the effluent from the ammonia synthesis in water or in a dilute Λπιπιο -niak solution. The decomposition products of the unconverted ammonia carbamals driven off from the urea solution are fed back into the urea synthesis device.

The object of the invention is now to improve the above method by avoiding the heat / u drove from the outside for the dehydration of the ammonium carbamate to urea in the urea synthesis device, the avoidance of condensation of the carbainate decomposition products in a separate stage and the ability to control the amount of water that goes into the Urea synthesis device arrives, with regard to set optimal urea yield.

According to the invention, this object is achieved by means of additional measures. In this case, both the ammonia and the carbon dioxide are absorbed in jev.cils cüv-in film exchangers of a known type according to the counter-current principle. Two gas flows are introduced into the NH film exchanger, namely one from ammonia _{synthesis and the other from methanation to remove CO and CO 2} from the synthesis gas for ammonia synthesis; In the COj film exchanger, an ammonia solution and preferably liquid ammonia, which is the condensate of part of the top product of the CO ₂ flaw, is introduced both below and above

Finally, the carbamate decomposition products in a gaseous state are sent directly to the urea synthesis device fed

The reference »Int. Chem. Eng. ”, Vol. 7. 1967, No. 2. Page 258, studies on the mass transfer in film exchangers can be found. However, there is not a simultaneous mass transfer and heat exchange - .eh. because it is emphasized that the Temperaluruiffeicn /.wischen the gaseous and the liquid phase at the inlet and outlet not may be allowed than 0.5 C ^0.

In the method according to the invention, however, there is an essential heat exchange in addition to a mass transfer necessary, because this is the only way to obtain such a highly concentrated ammonia solution as one with packed columns or other heat exchangers (as according to DE-OS 19 07 025) can not achieve. A transfer of applicability of film exchangers from the cited reference to the method according to the above DE-OS in Direction towards the present invention is not possible, because the teaching from the literature reference is not directly applicable to the invention Procedure. It could not be foreseen that for the required ammonia concentration and for the Use of minimal amounts of WaSw or Dilute ammonia solution only removes the film can be used, because according to DE-OS FJI body columns. Washing towers. Plate columns and In general, columns are equally well suited to one another, as they are usually used for distillation Stripping off and applying absorption. Finally, the referenced reference is only intended to infer that one with a film exchanger a Ammonia absorption does not, however, reach the formation of an ammonia solution of this concentration can, so that by COj absorption a large-scale i »usable carhamat formation appears promising

The situation is similar with the inventive application of film exchangers for the CO _; -Absorptive tone. Namely, the DE-OS applied in accordance with the CO absorption _r no Filrt exchanger, si escapes a portion of the carbon dioxide and enters dtn Ammoniakabscrber. which is extraordinarily harmful. According to the above DE-OS, not only the raw gases from the ammonia synthesis containing CO ₂ , but also the gases from the carbamate decomposition in the scraper are introduced _{into the CO 2 absorber.} The carbamate Zersei · z.iing is performed there in the presence of an inert stripping agent, so that this inert Abs'.reifmittel also reaches the IR absorber and CO ..- course don h5 dip Paiiialdrucke of CO and NH _{1 1} and thus the llinsetz . degree of conversion to the carbamate is significantly reduced. According to the above DK-OS one can / was also use NH as Ahsircifmitlel; in this case then arrive

the disintegration in the form of the maturing ammonia in the Ammonia absorption / onc or the decomposition / ungsgiisc are absorbed by an absorption liquid wedge and then not explained in detail Way processed. However, if they were fed back to the urea synthesis, uncontrollable ones would arrive Amounts of water in the synthesis reactor, which lead to a reduction in the urea yield could.

In the above I) E-OS it is mentioned quite generally, that the decomposition gases can be recycled, but there is no further indication that they can be used together the stripping ammonia in gaseous form in the urea synthesis reactor should lead. This DE-OS was unable to do anything with regard to this measure according to the invention Give hints. Usually the carbamate decomposition products are condensed and form carbamate return.

According to DEOS 18 16 099, ammonia must be used before Absorption can be cooled to get a certain amount of liquid ammonia. this happens in a conventional column in which the liquid phase runs downwards and fills the entire tube volume. the Gases rise (vertical tube bundle exchanger). According to the method according to the invention, however, takes place no separate condensation of the ammonia from the decomposition products takes place, but this happens only in the urea reactor itself. As a result, as much thermal energy is applied as for the endothermic one Dehydration of the carbamate to form urea is required. being moreover due to the excess Ammonia in the urea reactor also increases the urea yield.

The inventive method enables a considerable reduction in investment costs, since it. if other conditions remain the same, fewer devices and fewer Operating costs needed and the consumption of mechanical energy and thermal energy per Ton of urea produced significantly reduced.

In the process according to the invention for the production of urea, the raw gases from the ammonia synthesis, coming from a steam cleaning stage or in any other conventional manner and Are formed and in which the carbon monoxide has been almost completely converted, in one way Compressed pressure, which is slightly higher than that required for urea synthesis.

After compression, this gas stream, which still contains all the carbon dioxide, is used for production of urea is required. out into the lower part of a vertical tube exchanger, in which it is in Inside the tubes, in countercurrent, meets an ammonia solution flowing down in the form of a film and forms carbamate, the heat of reaction being generated by a coolant, e.g. B. Water that is used to feed the Boiler is used and that flows around the shell side of the film exchanger, is discharged. The selection An apparatus of this type is not intended to be a limitation, as is any other film exchanger can be used.

The carbamate formed comes out of the lower part in the form of a very concentrated solution which is used to convert it into urea! of the exchanger, in which the temperature is kept between 100 and 250 ^° C. and the pressure between 100 and 250 kg / cm ² . the end. Such a conversion is described below. The absorption solution must also be introduced into the lower part of the exchanger. The de-carbonated gasirum, which is saturated with ammonia, is released from the upper part of the exchanger and passed into a cooler, in which part of the saturated ammonia is condensed and reintroduced into the exchanger, preferably in the lower part of the exchanger .

The cooled gas is methanized after it has been preheated in Auslauschern. At the end of the ίο methanation stage, after recovering the heat obtained by cooling, the gas is introduced into another vertical tube exchanger, in which the gas comes into countercurrent contact with a film of a dilute ammonia solution which absorbs the ammonia contained in the gases. This film exchanger is also cooled by a coolant which flows along the jacket in such a way that a temperature of 10 to 60 ° C. and a pressure of 100 to 250 kg / cm ³ prevail in the exchanger. In this case, too, the choice of the device used is not restrictive, since every film exchanger can be used accordingly. The gases resulting from the ammonia synthesis enter this exchanger and encounter water or a dilute ammonia solution in countercurrent, which absorbs practically all of the ammonia contained in the gases.

From the lower part of this second exchanger

Trill out a very concentrated ammonia solution (e.g. 75 to 85 percent by weight). used as an absorbent is introduced into the first film exchanger, in which it forms carbamate CO? absorbed.

In the upper part of the second exchanger there is a gas outlet for a part '! C; Gas flow from the Ammonia synthesis originates, arranged to avoid an accumulation of the inert gases.

The gaseous mixture saturated with water in this way is dewatered.

The gases are dehydrated by the fact that liquid ammonia, which mixes well with such gases and partially evaporates, into a device

introduces, which allows a large exchange surface between the gas and the ammonia.

Both the condensation that occurs as a result of the cooling by ad / abatic evaporation of a part of ammonia, as well as the solution of the ammonia itself, which is produced by a large Exchange surface between the gas and the ammonia is made easy, cause a separation of the last traces of water from the gases, the separation already to a large extent in one Heat exchanger takes place in which part of the cold content of the dehydrated gas is recovered and in which the gas is fed in countercurrent to the gas to be treated.

A short distance downstream of the ammonia contact point, the z. B. can be formed by a Venturi tube is a gas-liquid separator arranged, from which the cooled gases are fed into the heat exchanger mentioned above and a very concentrated ammonia solution emerges, which is preferably added to the urea solution that - as will be described below - downstream of the urea reactor from the carbamate decomposition device exit.

The weak ammonia solution is also preferably used as such a separated solution added, which is formed in the heat exchanger.

in which the cold content of the cm watered C i; iscs recovered.

The gases treated in this way are reduced to the ammonia pressure. the / between 100 and 250 kg / cm ² , compressed and then introduced into the corresponding 'device.

The gases exiting the above device are cooled and then placed in an ammonia absorption device and devices for further treatment introduced.

The fresh carbamate solution, together with the circulated carbamate and ammonia, is introduced into the lower part of the urea synthesis device in the same zone in which the steam resulting from the carbamate decomposition is introduced, the vapors condensing and those used to form the thermal O! Eich ^{| j} e ^u 'i ^ hts'.'er Rc ^a ^ t' ⁿⁿ * vnrrirh.

result in the required amount of heat. The temperature, which can be regulated by the amount of vapors introduced into the reaction device from 150 to 25O "C and the pressure from 100 to 250 Atmospheres extend. The urea, carbamate and urea solutions that come from the top of the Reaction device leak are by gravity or by a suitable device in introduced the carbamate decomposition device which is heated by the condensing steam. It is also possible to use vaporized NHi that flows in the Ge_, enstrom and serves as a stripping means, wherein under these conditions some carbamate and most of the dissolved ammonia stripped off and be returned to the reaction device. The urea solution obtained in this way is relaxed and like the inert gases removed from the device and other usual treatments subjected.

It should be noted, however, that the process according to the invention has the ability to synthesize ammonia Carrying out higher pressures does not exclude, although the specified pressure range is preferred. ·

It is also possible in the process according to the invention at significantly lower pressures than they are for the ammonia synthesis required to work. In In most cases, the ammonia synthesis is carried out with the separation of the ammonia from the synthesis effluents at low pressure by condensing ammonia in heat exchangers by evaporation be cooled by ammonia. The inventive effective drainage system of the return gas allows the ammonia to be separated from the synthesis effluent in a cheaper and more efficient manner, by being able to use in this way a device which simultaneously has a single Surface enables very good heat and material exchange

Another very important feature of the process according to the invention is that it advantageously becomes possible to use the main devices of the process, such as the ammonia synthesis device, the absorber for the ammonia which is produced from this device. exits, the COj absorber. in which the carbamate is formed, the device for converting carbamate into urea and the decomposition device for the carbamate. that has not been converted to urea. operate / u at substantially the same pressure, which t is between 100 and 150 atmospheres. However, it is not excluded to work at different pressures at different stages. In such a chamber, the pressure ranges can be between JO and 300 atmospheres. Furthermore, it allows the operating pressure - with regard to Harnsluffabschnitt of the method - in which the present invention "<method and the insertion of the Carbamatzerset / gases formed .ungsvorrichtung directly into the lower part of the Harnstoffsynihesevorrichtung besides solving thermal problems of such a device the condenser relevant to Eliminate η which is always a critical point in the urea operating equipment because of the considerable corrosion problems.

The heat of carbamate formation is mainly generated by preheating z. B. Recovered water. s that is introduced into the boiler and that flows outside the tubes in a stream with the liquid film in order to bring it to a TcrripcraiüT. the higher one! than the temperature of carbamate crystallization. to keep.

The drying of the moist synthesis gases takes place i 'by putting some of the in the urea section ammonia to be recycled, which generates the energy required for ammonia separation saved and a corresponding injection pump is not required.

The urea cycle was designed so that) Disadvantages such as the absence of the educational warmth c the carbamate in the device and the introduction of a large amount of water into the cycle, be eliminated.

ι The required heat is applied by Using the heat content of the gases emerging from the carbamate decomposition device by introduces these gases directly into the synthesizer.

In this way, both the reaction participants

; mer preheating stage as well as the carbamate condensation stage. thereby the urea synthesis process

is considerably simplified by only adding the

Synthesis device and the carbamate decomposition

device are required. The thermal equilibrium

weight of the converted urea can be desired

if by changing the in the synthesizer

recirculated amount of carbamate decomposition gases

can be varied. Continue to influence the introduction

the amount required to form the ammonia solution

Water and then the fresh carbamate solution

the NHi / CO »ratio and result in the same

Temperature a decrease in the yield.

In an isobaric cycle process, as is the case with the process according to the invention. it becomes possible to achieve large ammonia circulations in a closed circuit between the decomposition device and the synthesis device with a small amount of heat to be supplied, the conditions of the ammonia solution being very close to the critical conditions. Such conditions allow it. _{to develop NHyCO 2} ratios of 4: 1 to 8: 1 in the synthesis device, whereby very high yields are obtained and the supply of large amounts of heat is avoided. From the above it can be seen that the integrated ammonia / urea process according to the invention allows all the advantages that can result from the integration of the two processes to be achieved, with further advantages resulting from a substantial reduction in the urea production costs.

Based on the preferred shown in the drawing Embodiment, the invention is explained in more detail below.

The raw synthesis gas, which contains the carbon dioxide required for the formation of nitrogen, is increased to a pressure which is slightly higher than that required for the synthesis of urea. compressed and then via line I in the lower part of the exchanger ? introduced. This device is a film exchanger. in which the synthesis gas flowing inside the tubes comes into contact with a layer of an ammonia solution which is brought in via line 26, whereby the carbamate is formed. The heat of reaction is z. B. by circulating Hcizkcssclbctriebswasser outside the pipes. The water used for this is introduced via line 32 and exits from line 33. A very concentrated carbamate solution is formed, which is fed via line 23 into the urea synthesis device.

The gas freed from carbon dioxide. which contains traces of CO. and is saturated with ammonia (as a result, Since it comes into contact with ammonia, that is a nuisance Cias to being saturated with ammonia) becomes over the line 3 is passed into the cooling device 4, in which part of the ammonia condenses, and via the line 27 is returned to exchanger 2. The cooled gas is then methanated. to the CO and the CO ;. to eliminate the poisons for the ammonia synthesis catalyst. Through the line 5 is this gas passed into the preheater 6, in which it is heated with the methanized gas. It will then after a further preheating in the heat exchanger 7 and then in the device 8. in which the Methanation takes place, transferred. The methanis'cr After the heat recovery, the gas is in the preheater 6 (the one for which the device 8 leaving stream represents a pre-cooler) in the cooler 9 further cooled and together with the off The gas exiting the synthesis device 20, cooled in the cooler 22, enters the film mauve 12 out, in which the ammonia contained in the gas through a introduced via the line 28 layer Water or a dilute ammonia solution flowing down the tubes. The heat of reaction is generated by cooling water, which enters via line 30 and exits from line 31 and flows through the pipes, discharged. The freed of ammonia gas is via line 13 in the Cooling condenser 14 transferred, in which the condensation a dilute ammonia solution is carried out, which via the lines 49 and 50 in the line 47 is performed, and that in addition in the Venturi tube 15 with the help of introduced liquid ammonia the line 24 is cooled and dried. All the water present is made up of ammonia separated and in the form of a concentrated ammonia solution from the separator 16 via the line 25 drained. This concentrated ammonia solution is introduced into line 47 via line 50. That dried gas is after recovery of the cooling energy in the device 14 via the line 17 to the Compressors 18 and from there via line 19 into the synthesis device 20. The exhaust will be Discharged from the film absorber 12 via the line 29. The concentrated carbamate solution from the exchanger 2 is mixed with a carbonate solution fed in via line 48 and in the lower part of the urea synthesis device 35 is introduced.

The ammonia recycled from other mutes is also fed into the lower part of the animal via line 43 .Synthesis device introduced. This Air.moniakstrom is divided into two streams, one stream via the line 24 into the venturi 15 to the

. Dewatering is introduced by quenching, while the other stream in the exchanger 41, in which he is introduced via line 42, evaporated and then partially via line 39 into the carbamate decomposer 38, in which NHj is used as a stripping agent,

ι and partially via line 40 in the lower part of the Synthesis device 35 is introduced.

From the upper part of the synthesis device, the inert gases are discharged via line 36, while from line 37 a solution of urea, water and carbamate with a large excess Ammonia escapes and is introduced into the decomposer 38, in which it is evaporated in countercurrent Ammonia flows, which is introduced into the /.ersetzer 38 via line 39. In the coat of /.ersetzers 38 a heating means is introduced, which over line 45 enters and exits via line 46. In this way, both due to the stripping takes place! effect of the vaporized ammonia as well as due to the heat added to the solution introduced from the synthesizer causes decomposition of the Main amount of the carbamate present and its removal in the form of a gas phase as NHj and CO; along with large amounts of ammonia vapor stan. Via the line 44, the ammonia flow carried carbonate decomposition products are introduced into the lower part of the synthesis device 35. the aqueous urea solution which dissolves the ammonia in equilibrium and is practically carbamate-free is. is withdrawn via line 47 and the added further treatments; possibly it is flour required, evaporated ammonia as a scraper to introduce into the decomposer; line 39 is then superfluous.

The following example is intended to explain the present invention further with reference to the drawing.

example

An operating facility with a daily capacity of 1000 t NH3 was used, with 990; Ammonia were converted into ammonium carbamate per day, that too! 700 tons of urea processed per day and owbci 10 tons of ammonia per day were used for other purposes.

loaded exchanger 2 were introduced:
Via line 1 raw synthesis gas under the following conditions:

Throughput 151 900NmVh pressure 200 kg / cm ² abs temperature 125 ° C Composition: H ₃ 61.22% by volume CO Ö38% ':! .-% CO, 17.71 vol. ^ C N ₂ 19.95% by volume CH ₄ 0.50% by volume Ar 0.24% by volume

Via line 26, an ammonia solution with the following properties:

Throughput
Composition:

78 350 kg / h

NII ₁
ILO
temperature

78.8Gcw .-% 21.2 wt .- '·':, 45 "C

Liquid ammonia via line 27 is used for the following:

Salt through
temperature

8500 kg / h 40 "C

The following was withdrawn from exchanger 2: Via line 23, a carbamate and ammonia solution with the following properties:

150 C

I 17 050 kg / h

80.00 Gt. ". ¹ - ■". '· 5.90 Weight .-'! ■

Salt through
/.iisii mine use I / ling:
N (LCOf) NlI. "

No;

About the line 5 before. Carbon dioxide released Gas with thundering Riuenschafier .:

Durc'isat /

temperature

pressure

/.u s am men · \ e

154 40ii NmVh 75 ^r C

g / cm- ans

h0 0 / Viii 0.38 \. »Ι.- ¹ '-

! 9.58 Mil.- ' ¹ -0.49 Vol.-' .. 0.23 Vol.- ¹ V. ■

14.30 Vo! - ",

The i: ·. jklion> uiirme before 14 500 000 kcal η was by \. "vrhii / xTi ties boiler feed water to 140" C reclaimed '..

In (.te ;: \ ustaiischer 12 the following materials individual:

l'he "i'c line U gases from the Svnthesevnrnchtung uiror the following conditions

You..:.

Teüincraiur
■ Composition

466 00 Niii'i 198 kB / cm-abs

56.12 Voi.- ¹¹ , ·,

18.7! Vol%

8.77 vol .-%

2.40 Voi.- ^s / (.

14.00VoI- ⁰ Zn

Via line 10 riveted gas the following properties:

Throughput
pressure

temperature
Composition;

NH,

About the
'«• things:

141 960NmVh 198 at
4O = C

64.26 Vo! .-% 21.37 VoI- ¹ Vn

0.94 vol.%

0.25% by volume! 3.18% by volume

Water iin; fr fo ¹ .- '' o <

Throughput /
T (.,] Iperature

16? 90kg / h
-.0 C

the exchanger 12 became the following stiomc discharged:

Via line 13 synthesis gas with the following Characteristics:

Throughput / 513 600 Nm * h pressure 197. "at temperature 45 ° C Composition: H: b7.01 VoI- ¹ Wed Ni 22.34% by volume CH ₄ 7.97 vol. "/ O Ar 2.18 vol% NH ₁ 0.50 vol .- '· ■■■ " water 200 Kl '/ ή

I Via line 29 exhaust gas with the following characteristics: th:

Throughput / ! 3 100 only; / / H: 64.93 VoL- ¹ V ₁ I N: 2L64 Vol .- 'Vo CFL J0.I5 VoI - ", .- Ar 2.78 vol .- "-. NH ₁ 0.50 vol- " ¹ M.

An ammonia solution with oe-ν via line 26 CharacterisiiKa given above

The moist synthesis gas is cooled to -8 C in 14 (325 kg'h of an ammonia are delivered via line 49!
Discharged solution which contains 40% by weight of ammonia ¹ and more - 1 7 ^; C cooled by introducing οη ό Ui kg'h of liquid ammonia, which evaporates almost completely (the last traces of water are discharged via line 25 at 68 kg / h of an ammonia solution, the S7% by weight ¹ '' ammonia contains). At the outlet of the separator 16, m - '. N receives a gas with the iomendei. fiienschatten:

Throughput; · 521,000 Nm '/ r pressure 195 kg / cm-'abs temperature - 17 = C Composition: H: fch.r.üGev- - "/> ■ N; 22.00 weight- ° / p CH, 7.85% by weight Ar 2.15 wt% NHj 2.00 wt. ° / c. HrO £ 3 ppm

This gas is recovered after the Cooling energy in the condenser 14 with the aid of the compressor 18 to a pressure of 207 kg / cnV abs. compressed and introduced into the synthesis unit 20.

The urea synthesis device: r.ij: -! G iS. aie with one push <-or! 195 kg / cm ^{2 is} operated and enables a 70% conversion (conversion); is charged with the following:

Via the line 23C! Eor? ': «;; .-. 2nnieC3rb3r! ^ R : \", d Amir; or ^; ridö-une via the Leiiurg 48 the Carbonniur · "! ^ '.'! fiosuf. .ius ι'εί ^K «iedercinick-F.inhe ^; t of the plant nut olgei'idF-i Properties:

13th 39 950 kg / h 21 43 583 14th Throughput 309 545 kg / h 100 ° C temperature , I8O ° C Throughput Composition: temperature 303% by weight CO ₂ 7.2% by weight Composition: 39.0% by weight 5 NH ₃ 513% by weight CO ₂ 30.1% by weight H ₂ O 18.5% by weight NH ₃ urea 23.0% by weight H ₂ O

Via line 40 ammonia under the following conditions:

Throughput temperature

34 780 kg / h 140 ^° C

Via the line 44 gases which emerge from the carbamate decomposer 38 and the following properties exhibit:

Throughput 117 370 kg / h temperature 190 ° C Composition: CO ₂ 7.9% by weight NK ₃ 853% by weight H ₂ O 6.8% by weight

A urea solution with the following properties emerges from this device 35 via line 37 the end:

The urea solution emerges from the carbamate decomposer 38 via the line 47 and is transferred to the final treatment stage and the following Has properties from:

Throughput 192 175 kg / h temperature 220 ° C Composition: CO ₂ 6.8% by weight NH ₃ 30.5% by weight H ₂ O 25.7% by weight urea 37.0% by weight

The heat required in the carbamate decomposer 38 is supplied by supplying 55,000 kg / h of steam at a pressure of 40 kg / cm ² via line 2 ¹ »45.

In the present example, no vaporized NH _{3 was} introduced into the decomposer 38 via line 39.

For this purpose 2 sheets of drawings

Claims (1)

Claim; Process for the production of urea in connection with an ammonia synthesis by heating a concentrated ammonium carbamate solution, which is obtained by absorption of the carbon dioxide contained in the raw gases for the ammonia synthesis in a concentrated ammonia obtained by absorption of the ammonia synthesis effluent in water or in a dilute ammonia solution Solution has been obtained. and recycling of the gas dried with liquid ammonia from the NHj absorption in the NHj synthesis as well as the ammonia-stripped decomposition products of the remaining carbamate of the urea solution in the urea synthesis, in which an NHj / CO ratio of 4: 1 to 3: 1 is adhered to, thereby marked ι. that both ammonia and carbon dioxide are absorbed in a film exchanger of a known type according to the countercurrent principle, with two gas streams being introduced into the NHi film exchanger, one from the ammonia synthesis and the other from the methanization stage of the top product of the CO film exchanger to remove residual CO: and CO for the ammonia synthesis originates, and in the COrFiImausiauscher both below and above an ammonia solution and preferably liquid ammonia below, get dun . < condensation from the top product of the CO. film exchanger. is fed, and finally the carbamate decomposition / ungsprodukte from the decomposer in a gaseous state is fed directly to the urea synthesis device. Usually the production of urea is done in industrial scale with the help of / wei Bciricbseir. directions that are independent of each other? « For this purpose, an operating facility for on Production of liquid ammonia, the .ils NcDenproduk! Carbon dioxide yields, used and a further facility / urea production via the synthesis of these two mentioned Produkie vcrwcndei. In the case where the end product is mainly urea. ammonia can be described as an intermediate product, whereby the Possibility of integrating the two cabinets Hung results An ideal integration scheme is a scheme at which the possibility of the direct reaction between ammonia and carbon dioxide with the formation of the Carbamates, which can then be converted to urea, is used to make two expensive Separation requirements. those for ammonia production are typical to be avoided, namely the carbon dioxide abatement from the converted gas with the help of solvents and the further compression of the formed by the regeneration of the solvent Carbon dioxide on the atmospheric pressure and the Phase of the separation of ammonia by liquefaction from the unreacted gases from the Synthesis device exit. The advantages obtained according to such a scheme are as follows: