CA2586286C - Process for increasing the capacity of an existing urea process - Google Patents
Process for increasing the capacity of an existing urea process Download PDFInfo
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- CA2586286C CA2586286C CA2586286A CA2586286A CA2586286C CA 2586286 C CA2586286 C CA 2586286C CA 2586286 A CA2586286 A CA 2586286A CA 2586286 A CA2586286 A CA 2586286A CA 2586286 C CA2586286 C CA 2586286C
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- condenser
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- 238000000034 method Methods 0.000 title claims abstract description 120
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 title claims abstract description 46
- 239000004202 carbamide Substances 0.000 title claims abstract description 45
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 95
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 82
- 239000007789 gas Substances 0.000 claims abstract description 58
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 42
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 36
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 28
- KXDHJXZQYSOELW-UHFFFAOYSA-M Carbamate Chemical compound NC([O-])=O KXDHJXZQYSOELW-UHFFFAOYSA-M 0.000 claims description 36
- 229910000069 nitrogen hydride Inorganic materials 0.000 claims description 6
- 238000011084 recovery Methods 0.000 description 57
- 239000007788 liquid Substances 0.000 description 5
- 239000006096 absorbing agent Substances 0.000 description 4
- 239000002912 waste gas Substances 0.000 description 4
- BVCZEBOGSOYJJT-UHFFFAOYSA-N ammonium carbamate Chemical compound [NH4+].NC([O-])=O BVCZEBOGSOYJJT-UHFFFAOYSA-N 0.000 description 3
- KXDHJXZQYSOELW-UHFFFAOYSA-N carbonic acid monoamide Natural products NC(O)=O KXDHJXZQYSOELW-UHFFFAOYSA-N 0.000 description 3
- 238000005201 scrubbing Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910001868 water Inorganic materials 0.000 description 2
- 230000005494 condensation Effects 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 238000012790 confirmation Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000011552 falling film Substances 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
-
- 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
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Treating Waste Gases (AREA)
Abstract
The invention relates to a process for increasing the capacity of an existing urea process comprising, in the high-pressure section of the process, a reactor in which carbon dioxide and ammonia react to form urea, a thermal stripper in which the process stream from the reactor is stripped by supplying heat or an ammonia stripper in which the process stream from the reactor is stripped by supplying heat with the aid of ammonia as stripping gas and a condenser in which the stripping gases are condensed, whereupon the condensate formed is returned to the reactor, in which process the N/C ratio in the reactor is between 2.8 and 3.3 mol/mol, the pressure in the high-pressure section of the process is between 13.5 and 16.0 Mpa, at least a portion of the process stream from the reactor is stripped in a CO2 stripper in which the process stream from the reactor is stripped by supplying heat and with the aid of carbon dioxide as stripping gas and the condensing capacity in the high-pressure section of the process is increased.
Description
PROCESS FOR INCREASING THE CAPACITY OF AN EXISTING UREA PROCESS
The invention relates to a process for increasing the capacity of an existing urea process comprising, in the high-pressure section of the process, a reactor in which carbon dioxide and ammonia react to form urea, a thermal stripper in which the process stream from the reactor is stripped by supplying heat or an ammonia stripper in which the process stream from the reactor is stripped by supplying heat with the aid of ammonia as stripping gas and a condenser in which the stripping gases are condensed, whereupon the condensate formed is returned to the reactor.
Such an existing process is described in for example Ullmann's Encyclopedia of Industrial Chemistry, Vol. A27, 1996, p. 344-350 as the Snamprogetti Self-Stripping Process.
In such a process ammonia and carbon dioxide are contacted in a reactor at a pressure of 15.0-16.5 MPa and at an N/C ratio of 3.0-4.0 mol/mol.
The process stream that forms in the reactor is passed to a high-pressure stripper in which this process stream is heated in order to decompose the ammonium carbamate and to discharge the excess ammonia, along with the ammonia and carbon dioxide from the decomposed ammonium carbamate, as a gas stream from the high-pressure stripper.
Ammonia, too, can be used here as a stripping gas. The gas stream from the high-pressure stripper is partly condensed in the high-pressure condenser, to which a carbamate stream from the medium-pressure recovery section is also added.
Subsequently, the gas/liquid stream from the high-pressure condenser is supplied to a high-pressure separator, the liquid fraction being returned to the reactor via an ejector.
The gas from the high-pressure separator is passed to the medium-pressure recovery section.
A process known to one skilled in the art is to increase the capacity of existing processes by replacing those process items that form a bottleneck in the process with larger equipment items. An example of an equipment item which would need to be replaced by a larger unit is for example the urea reactor. Such a process is described in for example EP-0751121-A1. This patent publication discloses that the capacity of a Snamprogetti Self-Stripping Process can be increased by adding a second reactor or by replacing the existing reactor with a larger reactor.
A drawback of expanding the reactor in this manner is that the costly high-pressure ammonia pumps also need to be replaced by larger pumps when the original process conditions are maintained. The condenser and the stripper, too, will CONFIRMATION COPY
The invention relates to a process for increasing the capacity of an existing urea process comprising, in the high-pressure section of the process, a reactor in which carbon dioxide and ammonia react to form urea, a thermal stripper in which the process stream from the reactor is stripped by supplying heat or an ammonia stripper in which the process stream from the reactor is stripped by supplying heat with the aid of ammonia as stripping gas and a condenser in which the stripping gases are condensed, whereupon the condensate formed is returned to the reactor.
Such an existing process is described in for example Ullmann's Encyclopedia of Industrial Chemistry, Vol. A27, 1996, p. 344-350 as the Snamprogetti Self-Stripping Process.
In such a process ammonia and carbon dioxide are contacted in a reactor at a pressure of 15.0-16.5 MPa and at an N/C ratio of 3.0-4.0 mol/mol.
The process stream that forms in the reactor is passed to a high-pressure stripper in which this process stream is heated in order to decompose the ammonium carbamate and to discharge the excess ammonia, along with the ammonia and carbon dioxide from the decomposed ammonium carbamate, as a gas stream from the high-pressure stripper.
Ammonia, too, can be used here as a stripping gas. The gas stream from the high-pressure stripper is partly condensed in the high-pressure condenser, to which a carbamate stream from the medium-pressure recovery section is also added.
Subsequently, the gas/liquid stream from the high-pressure condenser is supplied to a high-pressure separator, the liquid fraction being returned to the reactor via an ejector.
The gas from the high-pressure separator is passed to the medium-pressure recovery section.
A process known to one skilled in the art is to increase the capacity of existing processes by replacing those process items that form a bottleneck in the process with larger equipment items. An example of an equipment item which would need to be replaced by a larger unit is for example the urea reactor. Such a process is described in for example EP-0751121-A1. This patent publication discloses that the capacity of a Snamprogetti Self-Stripping Process can be increased by adding a second reactor or by replacing the existing reactor with a larger reactor.
A drawback of expanding the reactor in this manner is that the costly high-pressure ammonia pumps also need to be replaced by larger pumps when the original process conditions are maintained. The condenser and the stripper, too, will CONFIRMATION COPY
probably need to be replaced by units having a higher capacity.
The drawback of replacing the reactor and high-pressure ammonia pumps is that high costs are involved.
The aim of the invention is to develop a process for increasing the capacity of a urea process whereby replacement of costly equipment is avoided as much as possible.
This is achieved by = the N/C ratio in the reactor being between 2.8 and 3.3 mol/mol, = the pressure in the high-pressure section of the process being between 13.5 and 16.0 MPa, = at least a portion of the process stream from the reactor being stripped in a COZ
stripper in which the process stream from the reactor is stripped by supplying heat and with the aid of carbon dioxide as stripping gas and = the condensing capacity in the high-pressure section of the process being increased.
The N/C ratio is the molar ratio between ammonia (N) and carbon dioxide (C) in the reactor. In the existing urea process, this ratio was between 3.0 and 4.0 mol/mol. One measure taken to increase the capacity of the existing process is to lower the N/C ratio to a value between 2.8 and 3.3 mol/mol.
In the existing urea process the pressure in the high-pressure section of the process was between 15.0 and 16.5 MPa. In increasing the capacity of the existing urea process, this pressure is reduced to a pressure of between 13.5 and 16.0 MPa.
In increasing the capacity, a third requirement is that the process stream from the reactor, comprising urea, ammonia, carbon dioxide, water and ammonium carbamate, be at least partly stripped in a CO2 stripper, in which the process stream from the reactor is stripped by supplying heat and with the aid of carbon dioxide as stripping gas. In the existing process this implies that a CO2 stripper is added. The increased-capacity process then comprises a thermal stripper or an ammonia stripper as well as a CO2 stripper in which a portion of the process stream from the reactor is stripped. One skilled in the art can readily control the optimum distribution of the process stream among the two types of stripper.
It is also possible to convert the existing thermal stripper or ammonia stripper into a CO2 stripper whereby the whole process stream from the reactor is stripped in a CO2 stripper. The existing thermal stripper or ammonia stripper can, of course, also be replaced with a new CO2 stripper. The option to be chosen by one skilled in the art is dictated by the condition of the existing thermal stripper or ammonia stripper, bearing in mind that, in increasing the capacity, replacing high-cost equipment is avoided wherever the equipment is in good physical condition.
However, on account of the technical simplicity of the process it is preferable to strip the whole gas stream from the reactor in a CO2 stripper.
A fourth requirement for increasing the capacity of an existing urea process is to increase the condensing capacity in the high-pressure section of the process. This can be accomplished in various ways. For example, it is possible to add a high-pressure scrubber or a second high-pressure condenser. Alternatively, it is possible to increase the condensing capacity of the existing condenser.
The off-gases from the condenser are at least partially condensed in the high-pressure scrubber.
The high-pressure scrubber can be designed in two ways:
1: Substantially complete scrubbing of ammonia and carbon dioxide from the off-gas to be achieved by cooling with the aid of a heat exchanger followed by scrubbing with a medium-pressure carbamate solution.
2: Partial scrubbing of ammonia and carbon dioxide from the off-gas, with the ammonia and carbon dioxide only being condensed in a heat exchanger. In this design, the carbamate solution originating from a medium-pressure recovery section is supplied to the high-pressure scrubber and/or the high-pressure condenser.
For increasing the condensing capacity it is also possible to add a high-pressure condenser in which the off-gases from the existing high-pressure condenser are condensed in a carbamate stream supplied from the medium-pressure recovery section to the additional high-pressure condenser.
The high-pressure condenser to be added can be designed as a falling-film condenser or as a kettle type condenser.
The added high-pressure condenser may be arranged in parallel with or in series with the existing high-pressure condenser. Steam or hot water may be generated in the additional high-pressure condenser. When the added high-pressure condenser is arranged in parallel the off-gas stream from the stripper and the carbamate stream from the medium-pressure recovery section are split and directed to both high-pressure condensers. The carbamate stream that is formed in the high-pressure condensers is returned to the reactor and the off-gases from the high-pressure condensers are directed to the medium-pressure recovery section.
In the series arrangement the off-gas from the existing high-pressure condenser is condensed in the added high-pressure condenser, with at least a portion of the carbamate stream from the medium-pressure recovery section being supplied to the added high-pressure condenser. The carbamate stream from the added high-pressure condenser can be supplied to the existing high-pressure condenser either separately or together with a portion of the carbamate stream from the medium-pressure recovery section. The carbamate stream from the existing high-pressure condenser is returned to the reactor and the off-gases from the high-pressure condensers are discharged to the medium-pressure recovery section. It is also possible to combine the carbamate streams from both high-pressure condensers and to return them, optionally via a separator, to the reactor.
Preferably, the condensers are installed at a low elevation (near the ground). Such installation requires the use of ammonia-driven ejectors.
For increasing the capacity of the existing urea process still further it is preferred to increase the reaction capacity of the existing process also.
This can be accomplished by, for example, by increasing the reaction volume of the existing reactor.
It is known to those skilled in the art that in a urea process the condensing capacity and the reaction capacity can be increased at the same time by adding equipment to the high-pressure section of the process in which condensation and reaction can be carried out simultaneously.
Examples of such equipment are a pool condenser, a pool reactor and a combi-reactor.
The pool condenser is disclosed in for example EP-0155735-A1. The pool condenser can be installed horizontally or vertically. In the pool condenser, the off-gas from the stripper(s) is condensed and, additionally, a portion of the quantity of urea to be produced is formed in the pool condenser. The liquid stream that is passed from the pool condenser to the existing reactor thus comprises both carbamate and urea.
The pool reactor is disclosed in for example US-A-5767313. The pool reactor comprises a condenser section and a reactor section in an apparatus placed in horizontal position.
The combi-reactor is disclosed in for example US-B1-6392096, in US-B2-6680407 and in US-A-5936122. The combi-reactor comprises a condenser section and one or two reactor sections in an apparatus placed in vertical position. The condenser section may be placed above or below the reactor section. If two reactor sections are present, the condenser section is located between the two reactor sections.
In the pool reactor or the combi-reactor the off-gas from the stripper(s) is condensed in the condenser section, whereupon urea is formed in the reactor section or the reactor sections. At least a portion of the carbamate stream from the medium-pressure recovery section is supplied to the condenser section of the pool reactor or combi-reactor. The process stream from the reactor section is passed to the CO2 stripper and optionally the thermal or ammonia stripper.
A pool reactor and a combi-reactor may also be used for replacing the existing reactor and condenser.
The invention also relates to a urea plant comprising, in the high-pressure section of the process, a reactor, a thermal stripper or an NH3 stripper and a condenser, in which, besides the thermal stripper or NH3 stripper, a CO2 stripper is also present in the high-pressure section of the process.
The urea plant may also comprise a high-pressure scrubber or a second condenser if the condensing capacity in the high-pressure section of the process has been increased If both the condensing capacity and the reaction capacity in the high-pressure section of the process have been increased, the urea plant may comprise a pool condenser, a pool reactor or a combi-reactor.
The invention also comprises a urea plant comprising, in the high-pressure section of the process, a pool reactor or a combi-reactor, a thermal stripper or an NH3 stripper and a C02 stripper.
The invention is elucidated with reference to the following examples without being limited thereto.
Figure 1 represents the Snamprogetti Self-Stripping Process according to the state of the art. In a reactor (R) ammonia and carbon dioxide are contacted at a pressure of 15 MPa at an N/C ratio of 3.5 mol/mol. The process stream from the reactor is directed to a stripper (S) in which the process stream from the reactor is stripped with the aid of heat. Subsequently, the urea-containing process stream from the stripper is passed to the medium-pressure recovery section (MP) in which this process stream is recovered further and in which process a carbamate stream is formed. In addition, a gaseous stream is separated in the medium-pressure recovery section, which stream is directed to a section (N) in which ammonia gas is recovered. This ammonia gas is returned to the reactor (R) via the ejector (E). The urea-containing stream passes from the medium-pressure recovery section to a low-pressure recovery section (LP). On leaving the low-pressure recovery section, the urea stream (U) is concentrated and recovered further. The carbamate stream from the low-pressure recovery section is returned to the medium-pressure recovery section.
The stripping gases from the stripper are mixed in mixer (M), together with the carbamate stream from the medium-pressure recovery section and are directed to the condenser (C). Here, the stripping gases are partly condensed.
The gas/liquid stream from the condenser is supplied to a separator (A). The liquid fraction is returned from the separator to the reactor by means of the ejector (E) which is driven by the ammonia feed. The gas stream from the separator passes to the medium-pressure recovery section.
The capacity of a process according to figure 1 is 1550 tonnes/day.
Figure 2 represents a Snamprogetti Self-Stripping Process with increased capacity according to the invention. In a reactor (R), whose reaction volume has been increased, ammonia and carbon dioxide are contacted at a pressure of 14.0 MPa at an N/C ratio of 3.0 mol/mol. The process stream from the reactor is directed to the strippers (Sn and Sb). In the stripper (Sb) the process stream from the reactor is stripped with the aid of heat and in the stripper (Sn) with the aid of heat and with carbon dioxide as stripping gas. Subsequently, the urea-containing process stream from the stripper (Sb) passes to the medium-pressure recovery section (MP) in which this process stream is recovered further, whereby a carbamate stream is formed.
The urea-containing process stream from the stripper (Sn) passes to a newly installed low-pressure recovery section (LPn), in which this process stream is recovered further, whereby a low-pressure carbamate stream is formed.
Additionally, in the medium-pressure recovery section a gaseous stream is separated, which is directed to a section (N) in which ammonia gas is recovered. This ammonia gas is returned to the reactor (R) via the ejector (E). The urea-containing stream is also directed from the medium-pressure recovery section to the low-pressure recovery section (LPb). On leaving the low-pressure recovery sections (LPb and LPn), the urea streams (U) are concentrated and recovered further. The carbamate streams from the low-pressure recovery sections are returned to the medium-pressure recovery section.
The drawback of replacing the reactor and high-pressure ammonia pumps is that high costs are involved.
The aim of the invention is to develop a process for increasing the capacity of a urea process whereby replacement of costly equipment is avoided as much as possible.
This is achieved by = the N/C ratio in the reactor being between 2.8 and 3.3 mol/mol, = the pressure in the high-pressure section of the process being between 13.5 and 16.0 MPa, = at least a portion of the process stream from the reactor being stripped in a COZ
stripper in which the process stream from the reactor is stripped by supplying heat and with the aid of carbon dioxide as stripping gas and = the condensing capacity in the high-pressure section of the process being increased.
The N/C ratio is the molar ratio between ammonia (N) and carbon dioxide (C) in the reactor. In the existing urea process, this ratio was between 3.0 and 4.0 mol/mol. One measure taken to increase the capacity of the existing process is to lower the N/C ratio to a value between 2.8 and 3.3 mol/mol.
In the existing urea process the pressure in the high-pressure section of the process was between 15.0 and 16.5 MPa. In increasing the capacity of the existing urea process, this pressure is reduced to a pressure of between 13.5 and 16.0 MPa.
In increasing the capacity, a third requirement is that the process stream from the reactor, comprising urea, ammonia, carbon dioxide, water and ammonium carbamate, be at least partly stripped in a CO2 stripper, in which the process stream from the reactor is stripped by supplying heat and with the aid of carbon dioxide as stripping gas. In the existing process this implies that a CO2 stripper is added. The increased-capacity process then comprises a thermal stripper or an ammonia stripper as well as a CO2 stripper in which a portion of the process stream from the reactor is stripped. One skilled in the art can readily control the optimum distribution of the process stream among the two types of stripper.
It is also possible to convert the existing thermal stripper or ammonia stripper into a CO2 stripper whereby the whole process stream from the reactor is stripped in a CO2 stripper. The existing thermal stripper or ammonia stripper can, of course, also be replaced with a new CO2 stripper. The option to be chosen by one skilled in the art is dictated by the condition of the existing thermal stripper or ammonia stripper, bearing in mind that, in increasing the capacity, replacing high-cost equipment is avoided wherever the equipment is in good physical condition.
However, on account of the technical simplicity of the process it is preferable to strip the whole gas stream from the reactor in a CO2 stripper.
A fourth requirement for increasing the capacity of an existing urea process is to increase the condensing capacity in the high-pressure section of the process. This can be accomplished in various ways. For example, it is possible to add a high-pressure scrubber or a second high-pressure condenser. Alternatively, it is possible to increase the condensing capacity of the existing condenser.
The off-gases from the condenser are at least partially condensed in the high-pressure scrubber.
The high-pressure scrubber can be designed in two ways:
1: Substantially complete scrubbing of ammonia and carbon dioxide from the off-gas to be achieved by cooling with the aid of a heat exchanger followed by scrubbing with a medium-pressure carbamate solution.
2: Partial scrubbing of ammonia and carbon dioxide from the off-gas, with the ammonia and carbon dioxide only being condensed in a heat exchanger. In this design, the carbamate solution originating from a medium-pressure recovery section is supplied to the high-pressure scrubber and/or the high-pressure condenser.
For increasing the condensing capacity it is also possible to add a high-pressure condenser in which the off-gases from the existing high-pressure condenser are condensed in a carbamate stream supplied from the medium-pressure recovery section to the additional high-pressure condenser.
The high-pressure condenser to be added can be designed as a falling-film condenser or as a kettle type condenser.
The added high-pressure condenser may be arranged in parallel with or in series with the existing high-pressure condenser. Steam or hot water may be generated in the additional high-pressure condenser. When the added high-pressure condenser is arranged in parallel the off-gas stream from the stripper and the carbamate stream from the medium-pressure recovery section are split and directed to both high-pressure condensers. The carbamate stream that is formed in the high-pressure condensers is returned to the reactor and the off-gases from the high-pressure condensers are directed to the medium-pressure recovery section.
In the series arrangement the off-gas from the existing high-pressure condenser is condensed in the added high-pressure condenser, with at least a portion of the carbamate stream from the medium-pressure recovery section being supplied to the added high-pressure condenser. The carbamate stream from the added high-pressure condenser can be supplied to the existing high-pressure condenser either separately or together with a portion of the carbamate stream from the medium-pressure recovery section. The carbamate stream from the existing high-pressure condenser is returned to the reactor and the off-gases from the high-pressure condensers are discharged to the medium-pressure recovery section. It is also possible to combine the carbamate streams from both high-pressure condensers and to return them, optionally via a separator, to the reactor.
Preferably, the condensers are installed at a low elevation (near the ground). Such installation requires the use of ammonia-driven ejectors.
For increasing the capacity of the existing urea process still further it is preferred to increase the reaction capacity of the existing process also.
This can be accomplished by, for example, by increasing the reaction volume of the existing reactor.
It is known to those skilled in the art that in a urea process the condensing capacity and the reaction capacity can be increased at the same time by adding equipment to the high-pressure section of the process in which condensation and reaction can be carried out simultaneously.
Examples of such equipment are a pool condenser, a pool reactor and a combi-reactor.
The pool condenser is disclosed in for example EP-0155735-A1. The pool condenser can be installed horizontally or vertically. In the pool condenser, the off-gas from the stripper(s) is condensed and, additionally, a portion of the quantity of urea to be produced is formed in the pool condenser. The liquid stream that is passed from the pool condenser to the existing reactor thus comprises both carbamate and urea.
The pool reactor is disclosed in for example US-A-5767313. The pool reactor comprises a condenser section and a reactor section in an apparatus placed in horizontal position.
The combi-reactor is disclosed in for example US-B1-6392096, in US-B2-6680407 and in US-A-5936122. The combi-reactor comprises a condenser section and one or two reactor sections in an apparatus placed in vertical position. The condenser section may be placed above or below the reactor section. If two reactor sections are present, the condenser section is located between the two reactor sections.
In the pool reactor or the combi-reactor the off-gas from the stripper(s) is condensed in the condenser section, whereupon urea is formed in the reactor section or the reactor sections. At least a portion of the carbamate stream from the medium-pressure recovery section is supplied to the condenser section of the pool reactor or combi-reactor. The process stream from the reactor section is passed to the CO2 stripper and optionally the thermal or ammonia stripper.
A pool reactor and a combi-reactor may also be used for replacing the existing reactor and condenser.
The invention also relates to a urea plant comprising, in the high-pressure section of the process, a reactor, a thermal stripper or an NH3 stripper and a condenser, in which, besides the thermal stripper or NH3 stripper, a CO2 stripper is also present in the high-pressure section of the process.
The urea plant may also comprise a high-pressure scrubber or a second condenser if the condensing capacity in the high-pressure section of the process has been increased If both the condensing capacity and the reaction capacity in the high-pressure section of the process have been increased, the urea plant may comprise a pool condenser, a pool reactor or a combi-reactor.
The invention also comprises a urea plant comprising, in the high-pressure section of the process, a pool reactor or a combi-reactor, a thermal stripper or an NH3 stripper and a C02 stripper.
The invention is elucidated with reference to the following examples without being limited thereto.
Figure 1 represents the Snamprogetti Self-Stripping Process according to the state of the art. In a reactor (R) ammonia and carbon dioxide are contacted at a pressure of 15 MPa at an N/C ratio of 3.5 mol/mol. The process stream from the reactor is directed to a stripper (S) in which the process stream from the reactor is stripped with the aid of heat. Subsequently, the urea-containing process stream from the stripper is passed to the medium-pressure recovery section (MP) in which this process stream is recovered further and in which process a carbamate stream is formed. In addition, a gaseous stream is separated in the medium-pressure recovery section, which stream is directed to a section (N) in which ammonia gas is recovered. This ammonia gas is returned to the reactor (R) via the ejector (E). The urea-containing stream passes from the medium-pressure recovery section to a low-pressure recovery section (LP). On leaving the low-pressure recovery section, the urea stream (U) is concentrated and recovered further. The carbamate stream from the low-pressure recovery section is returned to the medium-pressure recovery section.
The stripping gases from the stripper are mixed in mixer (M), together with the carbamate stream from the medium-pressure recovery section and are directed to the condenser (C). Here, the stripping gases are partly condensed.
The gas/liquid stream from the condenser is supplied to a separator (A). The liquid fraction is returned from the separator to the reactor by means of the ejector (E) which is driven by the ammonia feed. The gas stream from the separator passes to the medium-pressure recovery section.
The capacity of a process according to figure 1 is 1550 tonnes/day.
Figure 2 represents a Snamprogetti Self-Stripping Process with increased capacity according to the invention. In a reactor (R), whose reaction volume has been increased, ammonia and carbon dioxide are contacted at a pressure of 14.0 MPa at an N/C ratio of 3.0 mol/mol. The process stream from the reactor is directed to the strippers (Sn and Sb). In the stripper (Sb) the process stream from the reactor is stripped with the aid of heat and in the stripper (Sn) with the aid of heat and with carbon dioxide as stripping gas. Subsequently, the urea-containing process stream from the stripper (Sb) passes to the medium-pressure recovery section (MP) in which this process stream is recovered further, whereby a carbamate stream is formed.
The urea-containing process stream from the stripper (Sn) passes to a newly installed low-pressure recovery section (LPn), in which this process stream is recovered further, whereby a low-pressure carbamate stream is formed.
Additionally, in the medium-pressure recovery section a gaseous stream is separated, which is directed to a section (N) in which ammonia gas is recovered. This ammonia gas is returned to the reactor (R) via the ejector (E). The urea-containing stream is also directed from the medium-pressure recovery section to the low-pressure recovery section (LPb). On leaving the low-pressure recovery sections (LPb and LPn), the urea streams (U) are concentrated and recovered further. The carbamate streams from the low-pressure recovery sections are returned to the medium-pressure recovery section.
The stripping gas from the stripper (Sb) passes to the condenser (C).
A portion of the carbamate stream from the medium-pressure recovery section may optionally be added to the condenser. The stripping gases are partially condensed in the condenser. The non-condensed gases are directed from the condenser to the scrubber (SC). The stripping gas from stripper (Sn) and the off-gas from the reactor are also directed to scrubber (SC). In the scrubber practically all gases are condensed in the carbamate stream from the medium-pressure recovery section, which stream is also supplied to the scrubber. The condensate returns to the reactor via ejector (E).
Waste gases (a), containing traces of ammonia and carbon dioxide, are discharged from the scrubber to an absorber.
The capacity of a process according to figure 2 is 2400 tonnes/day.
Figure 3 represents a Snamprogetti Self-Stripping Process with increased capacity according to the invention. In a reactor (R), whose reaction volume has been increased, ammonia and carbon dioxide are contacted at a pressure of 14.0 MPa at an N/C ratio of 3.0 mol/mol. The process stream from the reactor is directed to the strippers (Sn and Sb). In the stripper (Sb) the process stream from the reactor is stripped with the aid of heat and in the stripper (Sn) with the aid of heat and with carbon dioxide as stripping gas. Subsequently, the urea-containing process stream from the stripper (Sb) passes to the medium-pressure recovery section (MP) in which this process stream is recovered further, whereby a carbamate stream is formed.
The urea-containing process stream from the stripper (Sn) passes to a newly installed low-pressure recovery section (LPn), in which this process stream is recovered further, whereby a low-pressure carbamate stream is formed.
Additionally, in the medium-pressure recovery section a gaseous stream is separated, which is directed to a section (N) in which ammonia gas is recovered. This ammonia gas is returned to the reactor (R) via the ejector (E). The urea-containing stream is also directed from the medium-pressure recovery section to the low-pressure recovery section (LPb). On leaving the low-pressure recovery sections (LPb and LPn), the urea streams (U) are concentrated and recovered further. The carbamate streams from the low-pressure recovery sections are returned to the medium-pressure recovery section.
The stripping gas from the strippers (Sn and Sb) passes to the condensers (Cn and Cb). A portion of the carbamate stream from the medium-pressure recovery section may optionally be added to the condenser (Cb). The stripping gases are partially condensed in the condensers. The non-condensed gases are directed from the condensers (Cn and Cb) to the scrubber (SC). The off-gas from the reactor is also directed to scrubber (SC). In the scrubber practically all gases are condensed in the carbamate stream from the medium-pressure recovery section, which stream is also supplied to the scrubber. The condensate returns to the reactor via ejector (E). Waste gases (a), containing traces of ammonia and carbon dioxide, are discharged from the scrubber to an absorber.
The capacity of a process according to figure 3 is 2400 tonnes/day.
Figure 4 represents a Snamprogetti Self-Stripping Process with increased capacity according to the invention. In a reactor (R), whose reaction volume has been increased, ammonia and carbon dioxide are contacted at a pressure of 14.0 MPa at an N/C ratio of 3.0 mol/mol. The process stream from the reactor is passed to the stripper (Sn). In the newly added stripper (Sn), which replaces the existing stripper, the process stream from the reactor is stripped with the aid of heat and with carbon dioxide as stripping gas. The urea-containing process stream from the stripper is then directed to the medium-pressure recovery section (MP) in which this process stream is recovered further, whereby a carbamate stream is formed.
In the medium-pressure recovery section a gaseous stream is also separated, which stream passes to a section (N) in which ammonia gas is recovered.
This ammonia gas returns to the reactor (R) via ejector (E). The urea-containing stream is directed from the medium-pressure recovery section to the low-pressure recovery section (LP). On leaving the low-pressure recovery section, the urea stream (U) is concentrated and recovered further. The carbamate stream from the low-pressure recovery section is returned to the medium-pressure recovery section.
The stripping gas from the stripper (Sn) is supplied to the newly installed pool condenser (PC), which replaces the existing condenser. A
portion of the carbamate stream from the medium-pressure recovery section may optionally be added to the pool condenser. The stripping gases are partially condensed in the pool condenser. The non-condensed gases are directed from the pool condenser to the scrubber (SC). The reactor off-gas is also directed to scrubber (SC). In the scrubber, practically all gases are condensed in the carbamate stream from the medium-pressure recovery section, which stream is also supplied to the scrubber.
Waste gases (a), containing traces of ammonia and carbon dioxide, are discharged from the scrubber to an absorber. The condensate returns to the pool condenser. The condensate that forms in the pool condenser is returned to the reactor via the ejector (E).
The capacity of a process according to figure 4 is 2610 tonnes/day.
A portion of the carbamate stream from the medium-pressure recovery section may optionally be added to the condenser. The stripping gases are partially condensed in the condenser. The non-condensed gases are directed from the condenser to the scrubber (SC). The stripping gas from stripper (Sn) and the off-gas from the reactor are also directed to scrubber (SC). In the scrubber practically all gases are condensed in the carbamate stream from the medium-pressure recovery section, which stream is also supplied to the scrubber. The condensate returns to the reactor via ejector (E).
Waste gases (a), containing traces of ammonia and carbon dioxide, are discharged from the scrubber to an absorber.
The capacity of a process according to figure 2 is 2400 tonnes/day.
Figure 3 represents a Snamprogetti Self-Stripping Process with increased capacity according to the invention. In a reactor (R), whose reaction volume has been increased, ammonia and carbon dioxide are contacted at a pressure of 14.0 MPa at an N/C ratio of 3.0 mol/mol. The process stream from the reactor is directed to the strippers (Sn and Sb). In the stripper (Sb) the process stream from the reactor is stripped with the aid of heat and in the stripper (Sn) with the aid of heat and with carbon dioxide as stripping gas. Subsequently, the urea-containing process stream from the stripper (Sb) passes to the medium-pressure recovery section (MP) in which this process stream is recovered further, whereby a carbamate stream is formed.
The urea-containing process stream from the stripper (Sn) passes to a newly installed low-pressure recovery section (LPn), in which this process stream is recovered further, whereby a low-pressure carbamate stream is formed.
Additionally, in the medium-pressure recovery section a gaseous stream is separated, which is directed to a section (N) in which ammonia gas is recovered. This ammonia gas is returned to the reactor (R) via the ejector (E). The urea-containing stream is also directed from the medium-pressure recovery section to the low-pressure recovery section (LPb). On leaving the low-pressure recovery sections (LPb and LPn), the urea streams (U) are concentrated and recovered further. The carbamate streams from the low-pressure recovery sections are returned to the medium-pressure recovery section.
The stripping gas from the strippers (Sn and Sb) passes to the condensers (Cn and Cb). A portion of the carbamate stream from the medium-pressure recovery section may optionally be added to the condenser (Cb). The stripping gases are partially condensed in the condensers. The non-condensed gases are directed from the condensers (Cn and Cb) to the scrubber (SC). The off-gas from the reactor is also directed to scrubber (SC). In the scrubber practically all gases are condensed in the carbamate stream from the medium-pressure recovery section, which stream is also supplied to the scrubber. The condensate returns to the reactor via ejector (E). Waste gases (a), containing traces of ammonia and carbon dioxide, are discharged from the scrubber to an absorber.
The capacity of a process according to figure 3 is 2400 tonnes/day.
Figure 4 represents a Snamprogetti Self-Stripping Process with increased capacity according to the invention. In a reactor (R), whose reaction volume has been increased, ammonia and carbon dioxide are contacted at a pressure of 14.0 MPa at an N/C ratio of 3.0 mol/mol. The process stream from the reactor is passed to the stripper (Sn). In the newly added stripper (Sn), which replaces the existing stripper, the process stream from the reactor is stripped with the aid of heat and with carbon dioxide as stripping gas. The urea-containing process stream from the stripper is then directed to the medium-pressure recovery section (MP) in which this process stream is recovered further, whereby a carbamate stream is formed.
In the medium-pressure recovery section a gaseous stream is also separated, which stream passes to a section (N) in which ammonia gas is recovered.
This ammonia gas returns to the reactor (R) via ejector (E). The urea-containing stream is directed from the medium-pressure recovery section to the low-pressure recovery section (LP). On leaving the low-pressure recovery section, the urea stream (U) is concentrated and recovered further. The carbamate stream from the low-pressure recovery section is returned to the medium-pressure recovery section.
The stripping gas from the stripper (Sn) is supplied to the newly installed pool condenser (PC), which replaces the existing condenser. A
portion of the carbamate stream from the medium-pressure recovery section may optionally be added to the pool condenser. The stripping gases are partially condensed in the pool condenser. The non-condensed gases are directed from the pool condenser to the scrubber (SC). The reactor off-gas is also directed to scrubber (SC). In the scrubber, practically all gases are condensed in the carbamate stream from the medium-pressure recovery section, which stream is also supplied to the scrubber.
Waste gases (a), containing traces of ammonia and carbon dioxide, are discharged from the scrubber to an absorber. The condensate returns to the pool condenser. The condensate that forms in the pool condenser is returned to the reactor via the ejector (E).
The capacity of a process according to figure 4 is 2610 tonnes/day.
Figure 5 represents a Snamprogetti Self-Stripping Process with increased capacity according to the invention. In a reactor (R), whose reaction volume has been increased, ammonia and carbon dioxide are contacted at a pressure of 14.0 MPa at an N/C ratio of 3.0 mol/mol. The process stream from the reactor is passed to the stripper (Sn). In the newly installed stripper (Sn), which replaces the existing stripper, the process stream from the reactor is stripped with the aid of heat and with carbon dioxide as stripping gas. The urea-containing process stream from the stripper is then directed to the medium-pressure recovery section (MP) in which this process stream is recovered further, whereby a carbamate stream is formed.
In the medium-pressure recovery section a gaseous stream is also separated, which stream passes to a section (N) in which ammonia gas is recovered.
This ammonia gas returns to the reactor (R) via ejectors (El and E2). The ammonia gas can be heated before it enters ejector (El) and/or (E2). The urea containing stream is directed from the medium-pressure recovery section to the low-pressure recovery section (LP). On leaving the low-pressure recovery section, the urea stream (U) is concentrated and recovered further. The carbamate stream from the low-pressure recovery section is returned to the medium-pressure recovery section.
A portion of the stripping gas from the stripper (Sn) is directed to the newly installed pool condenser (PC), which replaces the existing condenser. A
portion of the carbamate stream from the medium-pressure recovery section may optionally be added to the pool condenser. The stripping gases are partially condensed in the pool condenser. The non-condensed gases are passed from the pool condenser to the scrubber (SC). The reactor off-gas is also directed to scrubber (SC). In the scrubber, practically all gases are condensed in the carbamate stream from the medium-pressure recovery section, which stream is also added to the scrubber. Waste gases (a), containing traces of ammonia and carbon dioxide, are discharged from the scrubber to an absorber. The condensate is returned to the pool condenser. The condensate that forms in the pool condenser is returned to the reactor via the ejector (El).
Another portion of the stripping gas from the stripper (Sn) is returned directly from the stripper to the reactor via an ejector (E2).
This design allows the carbon dioxide to be added as much via the stripper as possible, as a result of which a lower steam consumption is achieved.
The capacity of a process according to figure 5 is 2610 tonnes/day.
In the medium-pressure recovery section a gaseous stream is also separated, which stream passes to a section (N) in which ammonia gas is recovered.
This ammonia gas returns to the reactor (R) via ejectors (El and E2). The ammonia gas can be heated before it enters ejector (El) and/or (E2). The urea containing stream is directed from the medium-pressure recovery section to the low-pressure recovery section (LP). On leaving the low-pressure recovery section, the urea stream (U) is concentrated and recovered further. The carbamate stream from the low-pressure recovery section is returned to the medium-pressure recovery section.
A portion of the stripping gas from the stripper (Sn) is directed to the newly installed pool condenser (PC), which replaces the existing condenser. A
portion of the carbamate stream from the medium-pressure recovery section may optionally be added to the pool condenser. The stripping gases are partially condensed in the pool condenser. The non-condensed gases are passed from the pool condenser to the scrubber (SC). The reactor off-gas is also directed to scrubber (SC). In the scrubber, practically all gases are condensed in the carbamate stream from the medium-pressure recovery section, which stream is also added to the scrubber. Waste gases (a), containing traces of ammonia and carbon dioxide, are discharged from the scrubber to an absorber. The condensate is returned to the pool condenser. The condensate that forms in the pool condenser is returned to the reactor via the ejector (El).
Another portion of the stripping gas from the stripper (Sn) is returned directly from the stripper to the reactor via an ejector (E2).
This design allows the carbon dioxide to be added as much via the stripper as possible, as a result of which a lower steam consumption is achieved.
The capacity of a process according to figure 5 is 2610 tonnes/day.
Claims (12)
1. Process for increasing the capacity of an existing urea process comprising, in the high-pressure section of the process, a reactor in which carbon dioxide and ammonia react to form urea, a thermal stripper in which the process stream from the reactor is stripped by supplying heat or an ammonia stripper in which the process stream from the reactor is stripped by supplying heat with the aid of ammonia as stripping gas and a condenser in which the stripping gases are condensed, whereupon the condensate formed is returned to the reactor, wherein .cndot. the N/C ratio in the reactor is between 2.8 and 3.3 mol/mol, .cndot. the pressure in the high-pressure section of the process is between 13.5 and 16.0 MPa, .cndot. at least a portion of the process stream from the reactor is stripped in a CO2 stripper in which the process stream from the reactor is stripped by supplying heat and with the aid of carbon dioxide as stripping gas and .cndot. the condensing capacity in the high-pressure section of the process is increased.
2. Process according to claim 1, wherein the whole process stream from the reactor is stripped in a CO2 stripper.
3. Process according to claim 1 or 2, wherein the condensing capacity is increased by adding a high-pressure scrubber to which the off-gases from the condenser are supplied.
4. Process according to claim 3, wherein a medium-pressure carbamate stream is also supplied to the high-pressure scrubber.
5. Process according to any one of claims 1-3, wherein the condensing capacity is increased by adding a second high-pressure condenser.
6. Process according to any one of claims 1-4, wherein, in addition, the reaction capacity is increased by increasing the reaction volume of the reactor.
7. Process according to either of claims 1-2, wherein the condensing capacity and the reaction capacity are increased by adding, to the high-pressure section of the process, a pool condenser, a pool reactor or a combi-reactor to which the off-gases from the stripper(s) and a medium-pressure carbamate stream are supplied.
8. Process according to claim 1 or 2, wherein the condensing capacity and the reaction capacity are increased by replacing the existing reactor and condenser with a pool reactor or a combi-reactor.
9. Urea plant comprising, in the high-pressure section of the process, a reactor, a thermal stripper or an NH3 stripper and a condenser, wherein, besides the thermal stripper or NH3 stripper, a CO2 stripper is present in the high-pressure section of the process, and wherein the plant also comprises a high-pressure scrubber.
10. Urea plant according to claim 9, wherein the plant comprises, in the high-pressure section of the process, a second condenser.
11. Urea plant according to claim 9, wherein the plant also comprises, in the high-pressure section of the process, a pool condenser, a pool reactor or a combi-reactor.
12. Urea plant comprising, in the high-pressure section of the process, a pool reactor or a combi-reactor, a thermal stripper or an NH3 stripper and a stripper.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL1027697A NL1027697C2 (en) | 2004-12-09 | 2004-12-09 | Method for increasing the capacity of an existing urea process. |
| NL1027697 | 2004-12-09 | ||
| PCT/EP2005/012201 WO2006061083A1 (en) | 2004-12-09 | 2005-11-11 | Process for increasing the capacity of an existing urea process |
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| Publication Number | Publication Date |
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| CA2586286A1 CA2586286A1 (en) | 2006-06-15 |
| CA2586286C true CA2586286C (en) | 2014-02-04 |
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| CA2586286A Active CA2586286C (en) | 2004-12-09 | 2005-11-11 | Process for increasing the capacity of an existing urea process |
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| Country | Link |
|---|---|
| CN (1) | CN101076512B (en) |
| AR (2) | AR051992A1 (en) |
| AU (1) | AU2005313622B2 (en) |
| CA (1) | CA2586286C (en) |
| EA (1) | EA011378B1 (en) |
| EG (1) | EG26100A (en) |
| NL (1) | NL1027697C2 (en) |
| WO (1) | WO2006061083A1 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1923383A1 (en) | 2006-11-20 | 2008-05-21 | Urea Casale S.A. | Method for the modernization of a urea production plant |
| EA019803B1 (en) * | 2006-12-08 | 2014-06-30 | Стамикарбон Б.В. | Process for the preparation of urea |
| EP2107051A1 (en) | 2008-04-02 | 2009-10-07 | DSM IP Assets B.V. | Process for inreasing the capacity of an existing urea plant |
| EP2128129A1 (en) | 2008-05-20 | 2009-12-02 | Urea Casale S.A. | Method for the modernization of a urea production plant |
| CN102020590A (en) * | 2009-09-11 | 2011-04-20 | 江苏恒盛化肥有限公司 | Improved device of low-pressure system of carbon dioxide air stripping urea device |
| ITMI20110804A1 (en) * | 2011-05-10 | 2012-11-11 | Saipem Spa | "HIGH YIELD PROCESS FOR THE UREA SYNTHESIS" |
| EP2784062A1 (en) | 2013-03-27 | 2014-10-01 | Urea Casale SA | Method for revamping a self-stripping urea plant |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3364579D1 (en) * | 1982-06-03 | 1986-08-28 | Montedison Spa | Method for avoiding the corrosion of strippers in urea manufacturing plants |
| US4613697A (en) * | 1982-06-08 | 1986-09-23 | Montedison S.P.A. | Process for the displacement to the gaseous phase of the excess of NH3 |
| US6274767B1 (en) * | 1992-11-19 | 2001-08-14 | Urea Casale, S.A. | Process for the revamping of urea synthesis plants consisting of a stripper with ammonia |
| IT1275451B (en) * | 1995-06-30 | 1997-08-07 | Snam Progetti | PROCEDURE FOR THE SYNTHESIS OF THE UREA INCLUDING TWO SEPARATE AREAS OF REACTION |
| NL1004977C2 (en) * | 1997-01-13 | 1998-07-15 | Dsm Nv | Method to increase the capacity of an existing urea process. |
| NL1017990C2 (en) * | 2001-05-03 | 2002-11-05 | Dsm Nv | Process for the preparation of urea. |
-
2004
- 2004-12-09 NL NL1027697A patent/NL1027697C2/en active Search and Examination
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2005
- 2005-11-11 CA CA2586286A patent/CA2586286C/en active Active
- 2005-11-11 WO PCT/EP2005/012201 patent/WO2006061083A1/en active Application Filing
- 2005-11-11 EA EA200701242A patent/EA011378B1/en not_active IP Right Cessation
- 2005-11-11 AU AU2005313622A patent/AU2005313622B2/en active Active
- 2005-11-11 CN CN2005800424332A patent/CN101076512B/en active Active
- 2005-12-09 AR ARP050105175A patent/AR051992A1/en active IP Right Grant
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Also Published As
| Publication number | Publication date |
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| AU2005313622B2 (en) | 2011-08-25 |
| AU2005313622A1 (en) | 2006-06-15 |
| AR104203A2 (en) | 2017-07-05 |
| EG26100A (en) | 2013-02-17 |
| NL1027697C2 (en) | 2006-06-12 |
| WO2006061083A1 (en) | 2006-06-15 |
| EA011378B1 (en) | 2009-02-27 |
| CA2586286A1 (en) | 2006-06-15 |
| EA200701242A1 (en) | 2007-10-26 |
| CN101076512A (en) | 2007-11-21 |
| CN101076512B (en) | 2010-12-01 |
| AR051992A1 (en) | 2007-02-21 |
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