WO1999050235A1 - Apparatus and process for the preparation of urea from carbon dioxide and ammonia - Google Patents

Apparatus and process for the preparation of urea from carbon dioxide and ammonia Download PDF

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Publication number
WO1999050235A1
WO1999050235A1 PCT/IT1999/000078 IT9900078W WO9950235A1 WO 1999050235 A1 WO1999050235 A1 WO 1999050235A1 IT 9900078 W IT9900078 W IT 9900078W WO 9950235 A1 WO9950235 A1 WO 9950235A1
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Prior art keywords
reaction
compartment
liquid
carbon dioxide
ammonia
Prior art date
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PCT/IT1999/000078
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French (fr)
Inventor
Vincenzo Lagana'
Claudio Gatti
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Siirtec-Nigi S.P.A.
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Filing date
Publication date
Application filed by Siirtec-Nigi S.P.A. filed Critical Siirtec-Nigi S.P.A.
Publication of WO1999050235A1 publication Critical patent/WO1999050235A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J10/00—Chemical processes in general for reacting liquid with gaseous media other than in the presence of solid particles, or apparatus specially adapted therefor
    • B01J10/002—Chemical processes in general for reacting liquid with gaseous media other than in the presence of solid particles, or apparatus specially adapted therefor carried out in foam, aerosol or bubbles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/009—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping in combination with chemical reactions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/14—Fractional distillation or use of a fractionation or rectification column
    • B01D3/16—Fractionating columns in which vapour bubbles through liquid
    • B01D3/22—Fractionating columns in which vapour bubbles through liquid with horizontal sieve plates or grids; Construction of sieve plates or grids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/02—Apparatus characterised by being constructed of material selected for its chemically-resistant properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J4/00—Feed or outlet devices; Feed or outlet control devices
    • B01J4/04—Feed or outlet devices; Feed or outlet control devices using osmotic pressure using membranes, porous plates
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C273/00—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups
    • C07C273/02—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups of urea, its salts, complexes or addition compounds
    • C07C273/04—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups of urea, its salts, complexes or addition compounds from carbon dioxide and ammonia
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/02—Apparatus characterised by their chemically-resistant properties
    • B01J2219/025—Apparatus characterised by their chemically-resistant properties characterised by the construction materials of the reactor vessel proper
    • B01J2219/0277—Metal based
    • B01J2219/0286—Steel
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/10—Process efficiency
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/141—Feedstock
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/582—Recycling of unreacted starting or intermediate materials

Definitions

  • the invention refers to an improved process for the urea synthesis starting from ammonia and carbon dioxide as well as an apparatus to perform said improved process.
  • the reaction between ammonia and carbon dioxide is carried out at a temperature in the range of 150 to 250°C and under a pressure of 1.5xl0 4 to 4xl0 4 kPa.
  • Ammonia which is liquid under such conditions, reacts with carbon dioxide to yield ammonium carbamate as intermediate product that, by dehydration, is converted into urea according to the following reaction scheme 2NH 3 + CO 2 — > (NH 3 ) 2 CO 2 (NH 3 ) 2 CO 2 — > (NH 2 ) 2 CO 2 + H 2 O
  • the above reactions take place in a reaction vessel wherein the liquid phase may flow countercurrently or concurrently with respect to the gas phase.
  • ammonium carbamate synthesis reaction is exothermic, while carbamate dehydration to urea is an endothermic reaction. It results therefore that the urea synthesis process starting from ammonia and carbon dioxide depends on mass and heat transfer phenomena as well as thermodynamic and kinetic reaction factors.
  • reaction vessels are vertically arranged with a tubular structure, i.e. they have one of the dimensions much larger than the other one.
  • the ratio between reaction vessel diameter and its height is in the range of 1 :10 to 1 :30.
  • Such a configuration if from one side ensures a sufficient reaction mixture residence time under the reaction conditions, on the other side it promotes the generation of reaction product and reactant mixing phenomena (back-mixing), as well as it makes easy the gas phase flowing through preferential paths (channeling).
  • the gas phase essentially CO 2
  • having a much lower density tends to flow rapidly upwards in form of large 2 bubbles along preferential paths near to the reaction vessel internal wall. Said bubbles do not easily react with ammonia.
  • liquid phase whose density increases, because of urea and ammonium carbamate formation, tends to flow downwards preventing the reaction equilibrium from shifting towards the reaction products formation.
  • efficiency of the reaction or conversion rate of CO 2 to urea is defined as the molar ratio of CO 2 moles converted into urea in the reaction vessel and CO 2 moles entered the reaction zone, both as CO gas and in form of liquid recycle carbamate.
  • the reaction efficiency depends on NH 3 /CO and H 2 O/CO molar ratios as well as the final reaction temperature. In fact the reaction efficiency increases as the NH /CO 2 molar ratio and final temperature increase while the reaction efficiency decreases as the H 2 O/CO molar ratio increases.
  • commercial reaction vessels designed in accordance to the more advanced technology, usually operate within the following ranges: Pressure 1.40x 10 4 to 1.90x 10 4 kPa
  • the number of compartments depends on the reaction vessel height and it may be comprised between five to twenty.
  • the object of the present invention is to install, inside the reaction vessel for the urea synthesis from ammonia and carbon dioxide, a device enabling the gas phase to redistribute itself within the liquid phase increasing to the maximum extent the exchange surface between gas bubbles and liquid solution in order to reach the maximum heat and mass transfer and reduce to the minimum extent the channeling and backmixing phenomena while keeping at a reasonable level the cost of the equipment.
  • the urea synthesis reaction from ammonia and carbon dioxide is carried out in a reaction vessel equipped with conventional perforated plates suitably arranged along the axis of the reaction vessel, whose perforation sizes are in the range of 5 to 20 millimeters or even more, the reaction vessel being characterized in that a device is installed above each perforated plate which is able to further divide the bubbles coming from the underlying perforated plate.
  • perforated plates operate only as a gas-liquid separator and a gas distributing means.
  • the device able to divide the gas bubbles coming from the underlying perforated plate consists of a number of superimposed layers of a 50 to 70 mesh net.
  • the number of net layers (net pack) will be such that it will ensure the statistical formation of gas ducts of 0.4 - 3 mm size.
  • the net may consist of a single layer, in such a case the size shall not be more than 10 mesh.
  • the net pack can be secured to the internal section of the reaction vessel by any known means.
  • a relatively large mesh metal grating panel supports the net pack.
  • the grating panel may act as a conventional perforated plate.
  • the net pack can be easily removed and replaced without complicate disassembling operations that are required in the small size perforation plate 4 maintenance.
  • Net embodying the gas phase redistributing device according to the invention may be made of urea grade stainless steel or titanium.
  • the liquid phase free from gas phase because of the separating action in the reaction vessels compartment, enters the subsequent compartments through perforations provided on the cylindrical wall of the distributing plate beneath the liquid level, in order to create a liquid seal preventing the gas from flowing through said perforations.
  • Liquid phase flowing upward to the overlying compartment, crosses the gas phase which has been passed through the redistribution device and mixes again with said gas phase.
  • Gas phase being in form of very small bubbles, exhibits a maximum exchange surface with liquid phase and therefore it promotes the completeness of the reaction between CO2 gas and free ammonia within the liquid phase. Therefore as the reaction mixture flows along the reaction vessel its composition approaches the equilibrium value.
  • the present invention can be applied either to the revamping of existing urea synthesis reaction vessels or to newly designed vessels.
  • Fig. 1 show a cross section of a stage or compartment of urea synthesis reaction vessel equipped with the device for further dividing the gas bubbles coming out of the reaction mixture.
  • Biphasic fluid 1 of a reaction vessel compartment 6 flows upward concurrently with the gas phase.
  • biphasic fluid 1 reaches distributing plate 2, because of the pressure drop caused by the perforations, separates in a low gas content liquid biphasic phase and a gas phase which locates itself upon the residual liquid phase level.
  • Gas phase passing through perforations 5 of distributing plate 2 meets a net pack 3, dividing the gas flow in a homogeneously distributed way along the entire pack section; then the gas phase passes into the overlying reaction compartment to mix again with the previously separated liquid phase.
  • the abovesaid process starts in the lower part of the reaction vessel wherein fresh reactants and recycled carbamate are fed and terminates in the upper part of the reaction vessel wherein a urea and carbamate solution is recovered together with a gas phase in equilibrium with the liquid one and comprising ammonia, CO 2, water and inert gases.
  • the sizes of the apparatus employed in the example are:

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Dispersion Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

Apparatus for the urea synthesis from ammonia and carbon dioxide of the kind comprising a number of separate reaction compartments; the compartment separating means consist of one or more net layers wherethrough the gas phase coming out of the reaction mixture is passed in form of very small bubbles and then is redistributed into the liquid phase in the subsequent compartment.

Description

1
Description
APPARATUS AND PROCESS FOR THE PREPARATION OF UREA FROM CARBON D IOXIDE AND AMMONIA
Field of the invention The invention refers to an improved process for the urea synthesis starting from ammonia and carbon dioxide as well as an apparatus to perform said improved process. The reaction between ammonia and carbon dioxide is carried out at a temperature in the range of 150 to 250°C and under a pressure of 1.5xl04 to 4xl04kPa. Ammonia, which is liquid under such conditions, reacts with carbon dioxide to yield ammonium carbamate as intermediate product that, by dehydration, is converted into urea according to the following reaction scheme 2NH3 + CO2 — > (NH3)2CO2 (NH3)2CO2 — > (NH2)2CO2 + H2O The above reactions take place in a reaction vessel wherein the liquid phase may flow countercurrently or concurrently with respect to the gas phase.
While the liquid ammonia and gaseous carbon dioxide reaction rate is very fast and the reaction reaches immediately the equilibrium, carbamate dehydration is very slow and it requires a long reaction residence time. It is therefore necessary to provide a reaction volume large enough to ensure that the reaction proceeds to a value very close to equilibrium.
Moreover it has to be taken into account that ammonium carbamate synthesis reaction is exothermic, while carbamate dehydration to urea is an endothermic reaction. It results therefore that the urea synthesis process starting from ammonia and carbon dioxide depends on mass and heat transfer phenomena as well as thermodynamic and kinetic reaction factors.
In order to provide the reaction mixture with a sufficient residence time and the transfer thereof, commercial reaction vessels are vertically arranged with a tubular structure, i.e. they have one of the dimensions much larger than the other one. Generally the ratio between reaction vessel diameter and its height is in the range of 1 :10 to 1 :30. Such a configuration, if from one side ensures a sufficient reaction mixture residence time under the reaction conditions, on the other side it promotes the generation of reaction product and reactant mixing phenomena (back-mixing), as well as it makes easy the gas phase flowing through preferential paths (channeling). In fact the gas phase (essentially CO2), having a much lower density, tends to flow rapidly upwards in form of large 2 bubbles along preferential paths near to the reaction vessel internal wall. Said bubbles do not easily react with ammonia. On the other hand liquid phase, whose density increases, because of urea and ammonium carbamate formation, tends to flow downwards preventing the reaction equilibrium from shifting towards the reaction products formation.
It is worthwhile to recall that efficiency of the reaction or conversion rate of CO2 to urea, is defined as the molar ratio of CO2 moles converted into urea in the reaction vessel and CO2 moles entered the reaction zone, both as CO gas and in form of liquid recycle carbamate. The reaction efficiency depends on NH3/CO and H2O/CO molar ratios as well as the final reaction temperature. In fact the reaction efficiency increases as the NH /CO2 molar ratio and final temperature increase while the reaction efficiency decreases as the H2O/CO molar ratio increases. State of the art Nowadays commercial reaction vessels, designed in accordance to the more advanced technology, usually operate within the following ranges: Pressure 1.40x 104 to 1.90x 104kPa
Temperature 185 to 195°C
Molar ratios NH3/CO2 3.0 to 4.0
H2O/CO2 0.3 to 0.6
Conversion yield E = 55% to 75%. An improvement has been proposed and practiced consisting in installing inside the urea synthesis reaction vessel a set of perforated plates in order to divide the reaction zone into a number of uniformly superimposed compartments so that the abovementioned undesired phenomena are reduced to the minimum extent. More particularly said arrangement allows to reduce the size of gas bubbles, increasing therefore the exchange surface between phases of the gas bubbles coming out from the reaction mixture that can be more easily been adsorbed in the liquid phase.
The number of compartments depends on the reaction vessel height and it may be comprised between five to twenty.
In order to further improve the redistribution of the gas phase the use of perforated plates with a large number of very small perforations has been disclosed. The 3 perforation diameter of such plates, which is responsible of the gas phase redistribution within the liquid reaction mixture, is in the order of some millimeters in order to generate gas bubbles having a diameter of some millimeters.
With the above solution the redistribution degree of the gas phase within the liquid reaction mixture is significantly increased, however plate manufacturing with a large number of small size perforations is quite expensive and the resulting perforated plates exhibit a reduced mechanical strength. Summary of the invention The object of the present invention is to install, inside the reaction vessel for the urea synthesis from ammonia and carbon dioxide, a device enabling the gas phase to redistribute itself within the liquid phase increasing to the maximum extent the exchange surface between gas bubbles and liquid solution in order to reach the maximum heat and mass transfer and reduce to the minimum extent the channeling and backmixing phenomena while keeping at a reasonable level the cost of the equipment. According to the present invention the urea synthesis reaction from ammonia and carbon dioxide is carried out in a reaction vessel equipped with conventional perforated plates suitably arranged along the axis of the reaction vessel, whose perforation sizes are in the range of 5 to 20 millimeters or even more, the reaction vessel being characterized in that a device is installed above each perforated plate which is able to further divide the bubbles coming from the underlying perforated plate.
Therefore in the process and apparatus according to the present invention, perforated plates operate only as a gas-liquid separator and a gas distributing means. The device able to divide the gas bubbles coming from the underlying perforated plate consists of a number of superimposed layers of a 50 to 70 mesh net. The number of net layers (net pack) will be such that it will ensure the statistical formation of gas ducts of 0.4 - 3 mm size.
The net may consist of a single layer, in such a case the size shall not be more than 10 mesh. The net pack can be secured to the internal section of the reaction vessel by any known means.
According to an embodiment of the present invention a relatively large mesh metal grating panel supports the net pack. In such a case the grating panel may act as a conventional perforated plate. The net pack can be easily removed and replaced without complicate disassembling operations that are required in the small size perforation plate 4 maintenance.
Net embodying the gas phase redistributing device according to the invention, may be made of urea grade stainless steel or titanium.
The liquid phase, free from gas phase because of the separating action in the reaction vessels compartment, enters the subsequent compartments through perforations provided on the cylindrical wall of the distributing plate beneath the liquid level, in order to create a liquid seal preventing the gas from flowing through said perforations.
Liquid phase, flowing upward to the overlying compartment, crosses the gas phase which has been passed through the redistribution device and mixes again with said gas phase. Gas phase, being in form of very small bubbles, exhibits a maximum exchange surface with liquid phase and therefore it promotes the completeness of the reaction between CO2 gas and free ammonia within the liquid phase. Therefore as the reaction mixture flows along the reaction vessel its composition approaches the equilibrium value. The present invention can be applied either to the revamping of existing urea synthesis reaction vessels or to newly designed vessels.
Detailed description of the invention
The invention will now be illustrated in more detail with reference to the attached drawing and the following examples, which are provided to better explain the process and apparatus of the invention without limiting the scope thereof.
Fig. 1 show a cross section of a stage or compartment of urea synthesis reaction vessel equipped with the device for further dividing the gas bubbles coming out of the reaction mixture.
Biphasic fluid 1 of a reaction vessel compartment 6, flows upward concurrently with the gas phase.
As soon as biphasic fluid 1 reaches distributing plate 2, because of the pressure drop caused by the perforations, separates in a low gas content liquid biphasic phase and a gas phase which locates itself upon the residual liquid phase level.
Gas phase passing through perforations 5 of distributing plate 2, meets a net pack 3, dividing the gas flow in a homogeneously distributed way along the entire pack section; then the gas phase passes into the overlying reaction compartment to mix again with the previously separated liquid phase.
Liquid phase, separated from the gas phase, passes, through a series of perforations 4 present on the cylindrical wall, into the overlying reaction compartment to mix itself 5 again with the previously separated gas phase.
The abovesaid process starts in the lower part of the reaction vessel wherein fresh reactants and recycled carbamate are fed and terminates in the upper part of the reaction vessel wherein a urea and carbamate solution is recovered together with a gas phase in equilibrium with the liquid one and comprising ammonia, CO2, water and inert gases.
Being D the internal diameter of the reaction vessel 6, the sizes of the apparatus employed in the example are:
Gas distributor diameter Dl = 0.95 *D
Net pack diameter D2 = 0.67*D Height of cylindrical part of distributor H = 0.1 * D
Height of cylindrical part of grating panel HI = 100 mm
Gas distributor perforation diameter dv = 10 mm
Liquid outlet perforation diameter dl = 10 mm
EXAMPLE 1 To better show the advantages deriving from the practice of the invention, the following example is reported wherein the results using a reaction vessel without any internal device are compared with the ones involving the use of the device according to the invention.
The tests were made in a 1000 t/d (41667 kg/h) urea manufacturing plant using a reaction vessel operating under the following conditions:
Reaction pressure 1.5 Ox 104kPa
Molar ratios
NH3/CO2 3.1
H2O/CO2 0.5
RESULTS WITHOUT ANY PLATE WITH TWELVE PLATES AND
GAS RIDISTRIBUTOR Outlet reaction 184°C 189°C temperature Conversion yield 58.42% 63.40%
Flow rate and composition Flow rate and composition
NH3 39029 kg/h 31.06 % NH3 39029 kg/h 31.06 %
CO2 21744 kg/h 17.31 % CO2 21744 kg/h 17.31 %
H2O 23198 kg/h 18.46 % H2O 23198 kg/h 18.46 %
Urea 41667 kg/h 33.17 % Urea 41667 kg/h 33.17 %
Tot. 125638 kg/h Tot. 125638 kg/h 6
As it appears from the above results, operative reaction conditions being equal, two different outlet temperatures are obtained and, consequently, two different conversion yields are achieved.
Temperature increases because of the increase of the small gas bubble specific exchange surface, which enable unreacted gaseous CO to change into carbamate associated with production of heat due to the exothermic reaction involved. Therefore urea formation by carbamate dehydration is promoted in that, being an endothermic reaction, its yield is improved by an increase of temperature.
The last important remark is that the amount of solution leaving the reaction vessel is lower when plates are installed due to the fact that, reaction yield being higher, less carbamate recycle to the reaction zone is required which results in a lower amount of materials to be handled.
Owing to the fact that in both cases the reaction volume is constant, the solution residence time is increased so that a further benefit in the urea production is obtained. EXAMPLE 2
In the same plant of the previous example, equipped with a 12 perforated plate reaction vessel in absence of the gas redistribution device according to the invention ( i.e. without the net pack located above the plates) a 62.4% conversion yield was achieved at a temperature 186.5°C.
Flow rate and composition
NH3 39029 kg/h 31.06 %
CO2 21744 kg/h 17.31 %
H2O 23198 kg/h 18.46 %
Urea 41667 kg/h 33.17 %
Tot. 125638 kg/h It is evident from this example that CO2 flow rate coming out of the reaction zone is by
820 kg/h higher than the flow rate determined in the example in which the plates according to the invention are employed.
Said higher amount of CO2 results in higher energy consumption for carbamate recycling to the reaction zone.

Claims

7CLAIMS
1. Apparatus for the urea synthesis from ammonia and carbon dioxide of the kind comprising a number of separate reaction compartments characterized in that the compartment separating means consist of one or more net layers (3) wherethrough the gas phase coming out of the reaction mixture is passed in form of very small bubbles and then is redistributed into the liquid phase in the subsequent compartment.
2. Apparatus according to claim 1 , characterized in that the separating means are located on top of perforated plates (2) promoting the separation of gas phase from liquid phase.
3. Apparatus according to claim 1, characterized in that the separating means are supported by metal grating panels promoting the separation of gas phase from liquid phase.
4. Apparatus according to any of the previous claims, characterized in that the size of the net constituting the separating means is in the range of 70 to 7 mesh.
5. Apparatus according to any of the previous claims, characterized in that the material constituting the net layers or layer is chosen in the group consisting of urea grade stainless steel and titanium.
6. Apparatus according to any of the previous claims, characterized in that the liquid reaction mixture passes successively in the reaction vessel compartments through perforations (4) made beneath the liquid level in each compartment in order to create a liquid seal preventing gas from passing through these perforations.
7. Improved process for urea synthesis from carbon dioxide and liquid ammonia at a temperature in the range of 150 to 250┬░C and under a pressure in the range of 1.5x104 to 4xl04 kPa with a molar ratio between ammonia and carbon dioxide in the range of 2.5 to 5 and a molar ratio between water and carbon dioxide in the range of 0 to 2 in a suitably superimposed compartment reaction vessel characterized in that the gas phase, separated in each compartment from reaction mixture in form of large bubbles is divided in very small bubbles by passing through one or more net layers (3) to reach the subsequent compartment, said very small bubbles being redistributed within the liquid phase in the subsequent compartment.
PCT/IT1999/000078 1998-04-01 1999-03-31 Apparatus and process for the preparation of urea from carbon dioxide and ammonia WO1999050235A1 (en)

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ITMI98A000700 1998-04-01
IT98MI000700A IT1299000B1 (en) 1998-04-01 1998-04-01 DEVICE AND PROCEDURE FOR IMPROVING CONVERSION IN UREA IN THE REACTION BETWEEN CARBON DIOXIDE AND AMMONIA

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Cited By (4)

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WO2007045574A1 (en) * 2005-10-20 2007-04-26 Basf Se Distribution device for a gas-liquid phase mixture for apparatus
WO2008087086A1 (en) * 2007-01-16 2008-07-24 Basf Se Reactor and method for production of hydrogen sulphide
WO2008087110A1 (en) * 2007-01-16 2008-07-24 Basf Se Reactor, and method for the production of hydrogen sulfide
EP3993899B1 (en) * 2019-07-02 2023-04-26 Casale Sa A reactor for the synthesis of urea

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EP0495418A1 (en) * 1991-01-15 1992-07-22 Urea Casale S.A. System and device for increasing the yield and the production potential of urea reactors
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EP0495418A1 (en) * 1991-01-15 1992-07-22 Urea Casale S.A. System and device for increasing the yield and the production potential of urea reactors
WO1996007474A1 (en) * 1994-09-09 1996-03-14 Urea Casale S.A. Method for in-situ modernization of a urea synthesis reactor

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007045574A1 (en) * 2005-10-20 2007-04-26 Basf Se Distribution device for a gas-liquid phase mixture for apparatus
US8597586B2 (en) 2005-10-20 2013-12-03 Basf Se Shell-and-tube reactor having a distribution device for a gas-liquid phase mixture
WO2008087086A1 (en) * 2007-01-16 2008-07-24 Basf Se Reactor and method for production of hydrogen sulphide
WO2008087110A1 (en) * 2007-01-16 2008-07-24 Basf Se Reactor, and method for the production of hydrogen sulfide
JP2010515657A (en) * 2007-01-16 2010-05-13 ビーエーエスエフ ソシエタス・ヨーロピア Reactor and process for producing hydrogen sulfide
JP2010515659A (en) * 2007-01-16 2010-05-13 ビーエーエスエフ ソシエタス・ヨーロピア Reactor and process for producing hydrogen sulfide
US7871594B2 (en) 2007-01-16 2011-01-18 Basf Se Reactor and method for production of hydrogen sulphide
US8021624B2 (en) 2007-01-16 2011-09-20 Basf Se Reactor, and method for the production of hydrogen sulfide
US8580208B2 (en) 2007-01-16 2013-11-12 Basf Se Reactor and method for production of hydrogen sulphide
EP3993899B1 (en) * 2019-07-02 2023-04-26 Casale Sa A reactor for the synthesis of urea

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