SA03240221B1 - Process to increase the capacity of the urea production unit - Google Patents

Abstract

Abstract: The invention relates to a process to increase the capacity of a urea production unit, which includes a pressing section, a high-pressure synthesis section, and a urea extraction section, in which urea molten is formed, and optionally a granulation section. The urea extraction sector of the urea production unit, all or part of it, is returned to the melamine unit, and the remaining gases from the melamine unit, in whole or in part, are returned to the high-pressure synthesis sector and / or the urea extraction sector of the urea production unit.17,

Description

‎Y —_ _ A process for increasing the capacity of a urea production unit Full Description BACKGROUND The invention relates to a process for increasing the capacity of a urea production unit comprising a press section and a sector 0. The capacity of a urea production unit and its sectors relate here and later to the amount of urea that has been or can be synthesized. Several different processes have been developed to increase the capacity of the urea production unit. Examples of such processes are described, for example, in: “Revamping urea plant”, Nitrogen No. 157, 1985, pp. 37-42

The disadvantage of the processes known so far is that it is necessary to increase the capacity of the 0 urea production unit to supply the capacity of all sectors that make up the urea production unit.

A process has now been developed to increase the capacity of the urea production unit, which enables an increase in the capacity of the urea sector

High pressure synthesis and urea extraction sector only.

This is achieved by additionally installing a melamine unit, and urea molten is fed from a strip

Urea extraction of all or part of the urea production unit to the melamine unit and the residual gases from the melamine unit in whole or in part are returned to the high pressure synthesis sector and/or

Urea extraction sector for the urea production unit.

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creamy

Because residual gases are returned from the melamine unit to the high pressure synthesis section and/or

Urea recovery sector of the urea production unit (OB) Urea production increases without sector capacity expansion

sack. The urea produced is further titrated; In the form of urea melted into a unit

melamine» so that there is no need to increase the capacity of the granulation sector; also. The advantage of this process 0 is that additionally produced urea is obtained while increasing the capacity of only a portion of the

Ga ll so that Clay extended capacity Low investment costs.

If there was no granulation sector in the urea production unit (OY), molten urea was extracted

In a different way or removed as is OB This process is useful laf because in any case

The snap section does not need to be extended. In the framework of the present invention can be a unit of production

0 Urea for example is a “conventional urea unit” or a urea separator or a combination of a conventional urea unit and a urea separator. For both types of urea production units, the compression section is the section in which carbon dioxide and/or ammonia are supplied at high pressure; The pressure in the GAZ sector is high pressure.

10 What is meant by the traditional urea production unit is that the urea production unit Uy Jd occurs as ammonium carbamate that has not been converted into urea and unconverted ammonia output Uy carbon dioxide at a pressure essentially lower than the pressure in the synthesis reactor itself. In the conventional urea production unit, the high-pressure synthesis section is usually formed a0 03 from Jolin synthesis, with which the urea synthesis section is formed, which is then removed to the urea extraction section.

In a conventional urea production unit, the synthesis reactor generally operates at a temperature of about 100-100 °C and a pressure of 11-40 MPa. After (dad) and dissolution and condensation in the urea extraction sector, the raw materials that have not been converted into urea are separated in the traditional urea production unit at a pressure between 1.8 and 10 MPa and are returned in the form of an ammonium carbamate stream to the urea synthesis unit. Likewise, in the traditional urea production unit,

Ammonia Uy carbon dioxide is fed directly to the synthesis reactor. Jy that in a urea recovery reactor at low pressure usually A=, , + MPa almost all unconverted ammonia and carbon dioxide residues are removed from the urea synthesis solution resulting in a urea-in-water solution. This urea-water solution is then converted at low pressure; by evaporating the water into concentrated molten urea. Separation of the sl-urea mixture into molten urea concentrate occurs. Separation of the urea-water mixture, Gla, occurs by crystallization; Generally instead of the aforementioned evaporation, and then the crystals are melted to form molten urea. Then optionally the urea melt can be further processed in the granulation section and urea granules are formed

The one obtained has the desired particle size.

0 And what is meant by the urea separation unit is that the urea unit in which the ammonia and carbon dioxide that have not been converted into urea are removed for the most part occurs at a pressure, which by default is essentially equal to the pressure in the synthesis reactor. In the urea separation unit, the synthesis reactor, the separator, and the carbamate condenser together form the high-pressure synthesis section. The bulk of the JIE occurs as unconverted ammonium carbamate and excreted excess ammonia

1 in a separator” whether or not a separating gas is added. In the separation process, carbon dioxide and/or ammonia can be used as separating gas” before these ligands are fed into the reactor.

0 synthesis. It is also possible to apply "thermal separation" here which means that the ammonium carbamate is completely decomposed by the heat supply and the present ammonia and carbon dioxide are removed from the urea solution. Sey Execute the class in one or more steps. And there is a process

.” It is known, for example, that first complete thermal separation takes place, after which the CO separation step takes place with more heat supply. Optionally the lad gas stream is returned from the separator; which contains ammonia and carbon dioxide; to the reactor via a high-pressure carbamate condenser. Vt

T _ M Als "

The synthesis reactor in the urea separator generally operates at a temperature of -10

0 A, preferably at a temperature of 1760-770 C. And the pressure is in the synthesis reactor

From 11-71 MPa, preferably from 1.5 = 1.58 MPa.

Urea separation processes are described in “Ullmann's Encyclopedia of Industrial Chemistry: Volume VT E Fifth Edition”; Pages 0-744 Yo and Examples of Separation Processes Urea is a separation process

.snamporgetti and the self-separation process ¢ IDR and the process (ACES) and the process » Stamicarbon® CO,

After the separator, the separated urea synthesis solution is expanded to 1 or 3 reduced pressures

Over the stages of pressure in the urea extraction strip and evaporates» and a molten is obtained

Concentrated urea and the low-pressure ammonium carbamate stream return to the high-pressure synthesis segment. 0 Depending on the process, this ammonium carbamate can be extracted in a single-step process or in a single-step process

In a multi-step process operating at different pressures.

The idles are molten urea into granules in the granulation section. And instead of the G58 granulation sector

La treatment of molten urea into granules in a granulation tower.

And the added unit of melamine can be a unit of Uy for the gas phase process, but also Uy for the yo process of pressure JW. The gas phase process is a low pressure process; Wy operates a melamine reactor

at pressures between 1.1 and 0 “MPa. Melamine production processes are described as Jl

In the "Ullmann" Encyclopedia of Industrial Chemistry; Volume A Fifth Edition; pages

17-4

Sky achieve capacity increase in the high pressure synthesis sector and urea extraction sector in the urea production unit in different ways based on the technology of the original urea production unit. It is preferred

The urea production unit is a urea separation unit.

All or part of the urea molten leaving the urea extraction sector is fed to the melamine unit, where the molten urea is fed; Generally after a few initial 'old las'; to the reactor. In the melamine unit, urea is converted to melamine according to the simultaneous reaction:

(NC NH,); +3 CO, +6 NH; °C 2 CO (NH;) 6 and the residual gases from the melamine process "mainly carbon dioxide and ammonia gas" can be recycled as "but also in the form of a carbamate-containing stream"; to the urea unit. The carbamate-containing stream is a liquid stream which contains carbon dioxide and ammonia and the gases continue to react in whole or in part to form ammonium carbamate (Aa)

0 to here La (the word "carbamate" for short) according to the following reaction:

2NH; +Co, —> H; N-CO- ONH,4 The carbamate-containing stream contains water. Carbon dioxide; als, ammonia, and carbamates are dissolved in water. Water is usually present in the stream containing carbamates to prevent crystallization of the carbamates

1 The residual gases that are returned can also be divided into a stream which is rich in al carbon dioxide and a stream which is rich in ammonia before it is sled to the urea production unit. The advantage of this splitting process is that different gas streams can be returned to different places in the urea production unit. For example, the carbon dioxide alkylated stream can be fed to the separator as a lay separating stream. The ammonia alkylated stream is returned to the carbamate condenser. Sky

ve also returned part of the ammonia-laden stream to the melamine unit, where it can be used in melamine production.

As a result of the residual gas supply from the melamine unit; The residual gases can satisfy part of the CO requirements, in the high pressure synthesis section of the urea production unit. With regard to the total amount of CO, which is fed to the urea unit, the weight ratio of D60 coming from the melamine unit reaches greater than le, preferably ST from 01, and more preferably more than Ye, and 0 is especially preferred more than 740. And the weight ratio will be less than 7080 and it is more preferable that it be less than 7/70 and the most Sais should also be less than Le and if the remaining gases that are fed to the urea unit also contain 3011 and NH; and CO, added and coming from the melamine unit is greater than 75 and more preferably greater than v0 and most preferably greater than +70 in relation to the total amount of NH; 5 CO, to 0 is fed to the urea production unit. The weight ratio will usually be less than Yemen and more preferably less than Ye and more preferably less than Se Bale The remaining gases coming from the melamine unit condense in the gas phase to form a water-filled stream containing carbamate. This aqueous and carbamate-containing stream must be connected to the synthesis pressure and the water level in this aqueous and carbamate-containing stream must also be reduced before the carbamate-containing stream can be returned to the urea unit. Given below are several different models as examples of treatment of residual gases or the stream filled with water containing carbamates from the gas-phase melamine unit. It should be noted that the invention does not comply with the aforementioned models. For example, a water-laden stream with a weak carbamate content of 0 can be made by adsorption, after which the adsorbed gases condense; Gy consists mainly of Gls carbon dioxide and ammonia and is supplied by pump to the high pressure synthesis section of the urea production unit. The aqueous and carbamate-containing stream may also be connected to the synthesis pressure first and subsequently separated in a separate SUL ST separator. This separation operation can be performed ol but

- GU may also be supplied with carbon dioxide and/or ammonia as a separator gas. The GL stream consisting mainly of carbon dioxide and ammonia leaving the carbamate separator is returned to the high pressure synthesis section of the urea production unit. One method of recovering the residual gases is as follows: the residual gases are fed into one or 0 number of successive condensation and partial compression steps; and thawed with separation steps to reduce the water content of the residual gases. In addition, by step by step increasing the pressure of the residual gases (optionally by transition partial condensation) J) a pressure somewhat higher than the pressure in the high pressure synthesis section of the urea unit, the resulting gas stream can be fed into the high pressure flight section of the urea unit. The remaining gases may for example be fed to the Urea reactor or to a carbamate separator or condenser or to lines between them. General description of the invention In a preferred embodiment of the process, residual gases coming from the melamine unit are fed in a gas phase or stream containing carbamates to a carbamate condenser or to a line leading to a carbamate condenser. vo it is also possible for the residual gases or the carbamate-containing stream to be fed into the cb pl recovery section and then ole] to the high-pressure synthesis section along with the carbamate-containing stream from the urea recovery section. The advantage of this process is that there is no need to deliver residual gases to OY (Ile) pressure. The urea extraction section has a much lower pressure than the high pressure synthesis section. The all stream is preferably extracted with carbamate-containing water coming from the melamine unit and the containing stream The carbamate coming from the urea recovery section of a urea production unit and the resulting stream containing carbamate is returned to the high pressure synthesis section of the urea production unit.In this way, one recovery section can suffice and there is no blockage

And

for two extraction sectors; One to extract the carbamate-containing stream coming from the urea unit

and one to extract the carbamate-containing stream coming from the melamine unit. And for reasons

investment would be beneficial.

Preferably, the amount of water present in the stream containing carbamates coming from a unit

0 Melamine in the gas phase, which is sent to the urea unit, is less than Tt by weight” and on necrosis

Special preferably less than 0 AY by weight. Preferably, the stream containing carbamate, which

It is sent to the urea unit at least 701 by weight slo, and it is particularly preferred for

less than “Ye by weight” to prevent the formation of solids in the carbamate-containing stream.

Se feed gas stream coming from high pressure melamine process; consisting mainly of ammonia 0 and carbon dioxide” to the urea recovery sector and/or to the pressure synthesis sector.

The urea separation unit could be fed there, for example, to the urea reactor or to the urea reactor

separator” or to a carbamate condenser; or to lines in between. It is preferable to be fed current

Gas coming from the melamine process to the high pressure synthesis section of the urea separator. And the most

Preferably, the gas stream coming from the melamine process is fed to the carbamate condenser or to a ve line leading to the carbamate condenser.

The Lad gas stream may be fed to a Jf separator installed between the reactor and separator or to a vessel

A compound flash between the separator and the carbamate condenser. This first interval works repressively

for heat.

The advantage of using the gas stream coming from the high-pressure melamine unit is that a nearly waterless gas stream consisting mainly of ammonia and carbon dioxide can be obtained vs.

Urea separation which, due to its almost waterless nature, gives an improved efficiency in the unit

Urea compared to a unit of urea that is fed with a stream of water containing carbamates from one unit

Melamine in the gas phase. Furthermore; According to that process, the gas stream coming from the unit

-1.- For melamine it is not necessary to undergo a dehydration step because the gas stream is already almost free of water and has a sufficiently high pressure. Excess heat can also be used under pressure to produce an additional stream.

A carbon dioxide “between 0 and 15 MPa” and preferably between “aly from ammonia” and in particular the pressure of the gas stream coming from the melamine unit is high. From zero = ?MPa is higher than the pressure in the urea reactor. The pressure of the gas stream coming from the urea unit can first be reduced and preferred between Vo and 001 lm. The temperature of this gas stream is between 1 K and

Yr. In another embodiment, the gas stream coming from the high-pressure melamine unit is first converted into a carbamate-containing stream by condensation and/or absorption in another carbamate-containing stream before this stream is returned to the urea unit. Preferably, the carbamate-containing stream coming from the high-pressure melamine unit and returned to the urea unit should have a water content of less than 01/wt. A pressure that is essentially equal to the pressure Ky in the melamine reactor. Preferably, the condenser should be designed in the form of a heat exchanger. A refrigerant is fed to the shell side and a gas stream consisting of AU and in these, carbon dioxide and ammonia is fed through the tube bundle. And since the temperature of 770 m; Steam boiler feed water 001 condensing can be used in the condenser mentioned between ». as a coolant” which has the additional advantage that the heat of condensation can be usefully used to produce a low pressure stream (3,” to 1 MPa). And if there is no useful use also, the cooling water is also used, ually, in the vicinity of the unit for the mentioned low-pressure stream,” it is possible, as a coolant.

11 - - And because condensation occurs at pressure (lo), Ale temperatures can be reached here, so that the water content can be less than what is in the stream containing carbamates coming from the melamine process in the gas phase without any risk of forming undesirable solids Preferably, the molar ratio COYNE in the carbamate stream should be equal to or greater than 0, preferably less than 6, and in particular less than 4. In one embodiment, virtually all urea from the urea unit is fed into the melamine unit This is understood as cal apart from the usual zonal loss 3) excess water; to the air or at technical role such as filters/adsorbents)” There is no separate urea product stream leaving the urea unit except for the melamine unit. In a special model, virtually all residual gases 0 from the melamine unit can be sent to the urea unit. And this is understood from him that; Apart from the loss of residual gas lanl there is no separate residual gas stream leaving the melamine unit” except for the urea unit. If the remaining gases are sent to the urea unit as a liquid carbamate stream, in one embodiment the temperature of the carbamate stream can be increased by more than Ye m ; A ST of 1m is preferred to enhance the transformation in the urea reactor. This heater can be placed in the urea unit or in the melamine ve unit. The carbamate stream may be heated as is or after being mixed with another carbamate stream from the urea unit. And the temperature after heating the liquid carbamate stream is less than Cp You and preferably less than 0177°C. The invention also relates to a urea unit comprising a pressing section, a pressure synthesis section (dle), a section for urea extraction, and optionally a cmd section, of which the pressure section section and the urea recovery section have a greater capacity than the pressing section and/or the acetic granulation section. It is preferable that The residual gases from the melamine unit are fed to the high pressure synthesis section or urea recovery section of the urea unit.It is preferable that the capacity of the high pressure synthesis section and urea recovery section of the urea unit is from *- 700 by weight greater than the capacity of the pressing section and/or the optional granulation section. a

Y — \ -_ ’ A brief explanation of the drawings Figure 1: It shows the production unit of Uriya Gs for the previous art, Figure ? It shows the urea production unit of the present invention, and the quantity of 10141 and UM2 together was ST of the amount of UM produced in the urea unit according to the previous art described in Facility o No. 1 Figure 9: Shows the urea production unit According to previous art » The LPC contained IY by weight water. Figure 4: Shows the urea production unit according to the present invention. The quantity of UML and 2 together was greater than the amount of UM produced in the urea unit of the previous art described in JS 01 No. JY. Detailed description Z. The invention will be clarified later on the basis of figures from No. 1 to No. ct without being bound by those forms. Figure 1 shows a urea production unit ¢ Las, art clad) consisting of a press section (COM) 0 in which 30 carbon dioxide (0©) and ammonia (NH) are delivered to the synthesis press. From COM, CO, and NH, the transition was made to the high-pressure (HP) synthesis sector, where urea was formed, followed by the extraction of urea formed in the urea extraction sector (00). After that, the formed urea molten (UM) was fed to the granulation section (GRAN). Figure No. Y shows the urea unit: according to the invention; It consists of a compression section (COM) with which 306 carbon dioxide (CO) and ammonia (NH3) are delivered to the synthesis pressure. And from (COM, CO, » and 1111, the transition to the high pressure (HP) synthesis sector, where urea was formed, followed by the extraction of the urea formed in the urea extraction sector (008). After that, 17.6 was fed.

Part of the formed urea molten (UM) was flowed to the granulation section (GRAN) and another part (UM2) to the high-pressure melamine unit (MELAF). The remaining gases (RG) were fed from

HP 3 to carbamate condensate MELAF The quantity of 10141 and UM2 together was ST from the amount of UM produced in the urea Gy unit of the previous art o described in Figure 1. Figure 3 shows a unit Urea according to previous art” consisting of a compression section (COM) Ut 30 Carbon dioxide (CO2) and ammonia (NH) are connected to the synthesis pressure. And from “COM,” “CO,” and “NH,” the move was made to the high-pressure (HP) synthesis sector, where urea was formed, followed by the extraction of the urea formed in the urea extraction sector (0007). The molten urea formed (UM) was fed to the granulation section (GRAM) and the low pressure carbamate stream (LPC) was returned from the UOP to the carbamate condenser in HP and contained Je LPC ?/wt Water. Figure No. 1 shows a urea unit according to the invention, consisting of a press section (COM) in which carbon dioxide (002) and ammonia (001 and 01) are connected to the synthesis pressure. From COM 0 and 60 » And 3011 moved to the high-pressure (HP) synthesis sector where urea was formed, followed by the extraction of the urea formed in the urea extraction sector (0000), after which part of the formed urea molten (UMD) was fed to the granulation sector. (GRAN) and another fraction (MU2) to the gas phase melamine unit (MELAF) and residual gases (RG) from MELAF were fed to the carbamate recovery section (CAR) where they condensed with the carbamate stream low pressure (LPC) 0” of 100. The LPC contained 790 wt. water. The carbamate stream (©) was concentrated and returned with a water content of 0 wt. The quantity of 10141 and lee UM2 is greater than the quantity of UM produced in the urea unit of the prior art described in Figure No.

Claims (1)

1 -_ _- Elements of protection 1 1 - A process to increase the capacity of the pd production unit, which includes the (pS) sector, the high-pressure synthesis ¥ sector, the urea extraction sector, in which urea molten YF is formed, and optionally the granulation sector. The additional molten urea from the urea recovery section 0 of the urea production unit is fed in whole or in part to the melamine unit and the remaining 0 gases from the melamine unit in whole or in part are returned to the high pressure synthesis section and/or the urea recovery section of the urea production unit. 1 7 - A process according to claim No. “1” characterized by the fact that the urea unit is a unit for urea separation. For the gas phase melamine unit. 1 - A process according to any of the elements of protection from No. 1 to No. 7” characterized by the fact that the residual gases from the melamine unit are returned to the urea unit as a stream quenching YF on carbamate. 0 1 - Process according to any Claims No. 1 to No. 4 hy including pressure relief section JW containing a carbamate condenser; characterized by the fact that residual vy gases or carbamate-containing stream are fed to a carbamate condenser or to ; line which leads to the carbamate condenser. — M 1 _ 1 + - a process according to any of the elements of protection either from No. 4 or No. 00 characterized by “that the carbamate-containing stream coming from the melamine unit and the carbamate-containing stream coming from the urea unit are extracted by clan before the stream containing carbamates is returned to the urea unit. 1 a - Wy process for any of the protection elements either of No. 4 or Veh) is characterized by "that the carbamate-containing stream returned to the urea unit contains 0-5 by weight water. 1 + - Process according to any of Claims No. 4 or No. 7; it is characterized by "the carbamate-containing stream returned to the urea unit contains 7-11" by weight water. 1 * - Process according to any element of Protection elements either from No. 1 or No. 7 are distinguished by the fact that the melamine unit is a high-pressure melamine unit. 01 1 - process according to any of the protection elements of either No. 1 or No. oY and No. 1" 1; in which the high-pressure synthesis section includes a carbamate condenser; the residual gases are aly characterized 11 1 - The Gs process of claim 8 is characterized by the fact that the al gases from the melamine unit are returned to the urea unit as a carbamate-containing stream, and the content of YF is Water for this carbamate stream is less than 75 by weight. Vat _ 9 3 _ 11 1 - Process according to any element of protection either from No. 1 or No. AN Y. Characterized by OL by weight of CO gas, in the residual gases coming from the melamine unit 0 be greater than Yo for the total amount of 00 fed to a unit; urea; 19 1 - A process according to any of the elements of protection either from No. 1 or No. NY "characterized by the fact that the weight ratio of CO and NH gases in the residual gases coming from the YF melamine unit is greater than 70 for the total amount of 0© and NH;8 fed into the urea unit 141 - Process according to any claim either No. 1 or No. A and No. (VY Y It is characterized by the fact that the temperature of the stream containing carbamates increases by more than 10 °C before this stream is fed to the high-pressure synthesis sector of the urea unit. into a stream which is rich in ly carbon dioxide and a stream which is rich in ammonia (YF) before all or part of them are returned to the urea unit. The urea extraction sector is characterized by the fact that the high-pressure synthesis sector and the urea extraction sector Y have a greater capacity than the pressing sector. From *- 5 0 by weight L is higher than the capacity of the pressing section and/or granulating section. VV.