GB2073751A - Improvements in urea synthesis - Google Patents
Improvements in urea synthesis Download PDFInfo
- Publication number
- GB2073751A GB2073751A GB8110277A GB8110277A GB2073751A GB 2073751 A GB2073751 A GB 2073751A GB 8110277 A GB8110277 A GB 8110277A GB 8110277 A GB8110277 A GB 8110277A GB 2073751 A GB2073751 A GB 2073751A
- Authority
- GB
- United Kingdom
- Prior art keywords
- silicon carbide
- plant
- urea
- valve
- pressure reducing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 title claims abstract description 29
- 239000004202 carbamide Substances 0.000 title claims abstract description 29
- 230000015572 biosynthetic process Effects 0.000 title claims abstract description 11
- 238000003786 synthesis reaction Methods 0.000 title claims abstract description 11
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims abstract description 28
- 229910010271 silicon carbide Inorganic materials 0.000 claims abstract description 28
- 238000000034 method Methods 0.000 claims abstract description 22
- 230000003628 erosive effect Effects 0.000 claims abstract description 16
- 230000007797 corrosion Effects 0.000 claims abstract description 15
- 238000005260 corrosion Methods 0.000 claims abstract description 15
- 239000012530 fluid Substances 0.000 claims abstract description 15
- 239000000463 material Substances 0.000 claims description 27
- 230000002194 synthesizing effect Effects 0.000 claims description 15
- 239000011248 coating agent Substances 0.000 claims description 4
- 238000000576 coating method Methods 0.000 claims description 4
- 239000000758 substrate Substances 0.000 claims description 2
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 7
- 229910052726 zirconium Inorganic materials 0.000 description 6
- 229910001093 Zr alloy Inorganic materials 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910000963 austenitic stainless steel Inorganic materials 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000005240 physical vapour deposition Methods 0.000 description 1
- 238000007750 plasma spraying Methods 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000002459 sustained effect Effects 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K25/00—Details relating to contact between valve members and seat
-
- 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
-
- 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
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K27/00—Construction of housing; Use of materials therefor
-
- 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
- B01J2219/0204—Apparatus characterised by their chemically-resistant properties comprising coatings on the surfaces in direct contact with the reactive components
- B01J2219/0218—Apparatus characterised by their chemically-resistant properties comprising coatings on the surfaces in direct contact with the reactive components of ceramic
Abstract
Plant components, especially pressure reducing valves, are prone to corrosion and cavitation-induced erosion by high temperature, high pressure and high speed process fluids in the synthesis of urea. To protect such components against attack it is proposed to make them wholly of, or coat them with, corrosion and erosion resistant silicon carbide. In a pressure reducing valve of plug and seat form, the plug tip (4) and seat (5) are protected with silicon carbide. <IMAGE>
Description
SPECIFICATION
Improvements in urea synthesis
The present invention relates to improvements in urea synthesis.
Corrosion of structural materials constitutes a serious problem in plant employed in urea synthesis since the synthesis process involves the handling of high temperature and highly corrosive processing fluid at high pressure. In particular, pressure reducing valves require the use of special material where the valves are located between synthesizing towers, in which processing fluid pressurized to 1 50-250 atmospheres (1 5.2-25.3 x 106 P3) iS introduced for synthesizing urea, and decomposition vessels in which unreacted ammonium and carbon dioxide are separated and recovered. Special material is required because highly corrosive processing fluid of high temperature and high pressure is fed in, its pressure is reduced by the pressure reducing valve, and thereafter it flows out with high velocity.Therefore, excessive chemical and physical damage arises in portions of unprotected valves from corrosion and erosion due to cavitation, rendering the life of a pressure reducing valve made of ordinary material very short.
Conventionally, stainless steel or zirconium and zirconium alloys have been the materials used for urea synthesizing process equipment.
Austenitic stainless steel, when used as a material for urea process equipment, poses a problem because its insufficient corrosionresistance results in dissolution due to corrosion during usage, and leads to premature failure of pressure reducing valves.
Zirconium and zirconium alloys have tentatively been used for actual application since they have high corrosion-resistance in the urea synthesis environment. However, the hardness of zirconium and zirconium alloy is low; for instance, the hardness of zirconium of 99.5% purity is as low as 1 50 Brinell Hardness, almost the same as that of mild steel. Therefore, zirconium and zirconium alloy are vulnerable to physical attack. For instance, in a urea synthesizing plant in which a pressure reducing valve made of or having its vulnerable parts protected by zirconium is installed, the valve is rapidly damaged by erosion due to cavitation during the water or ammoniacal water circulation operation prior to producing urea, resulting in valve failure.In order to alleviate the problem lately, a pressure reducing valve of such physically strong material as stainless steel has been used during the water or ammoniacal water circulation operation, and thereafter the valve is replaced with one of a highly corrosionresistant material such as zirconium before starting the actual urea producing process. Thus, the present practice is that a valve of one material is replaced with a valve of another material, depending on the type of fluid fiowing through the valve, but this practice naturally makes the operation of a urea synthesizing plant inconvenient and inefficient. Moreover this practice creates the possibility of unexpected damage arising through variations of operating conditions as weli as putting the safety of plant operated under high temperature and high pressure conditions at risk.
An object of the present invention is to provide a urea synthesizing plant and process capable of long, sustained and stable operation irrespective of process conditions, and seeks to resolve the aforementioned problems of erosion due to cavitation and corrosion.
According to the present invention, there is provided a urea synthesizing process plant characterized in that portions of plant equipment which are exposed to corrosive and/or cavitationinduced erosion are protected against corrosion and/or erosion by silicon carbide material.
The invention comprehends a urea synthesis process performed in process plant as defined in the last preceding paragraph.
The invention also provides a pressure reducing or recycle line valve for a urea synthesizing process plant, wherein parts thereof with which urea process fluids come into contact are protected against corrosion and/or cavitationinduced erosion by silicon carbide or a coating of silicon carbide.
The invention will now be described in more detail by way of example only with reference to the accompanying drawing, in which the sole figure is a schematic sectional view through a pressure-reducing fluid flow valve in accordance with the invention.
As heretofore mentioned, plant for a urea synthesizing process tends to incur excessive attack by corrosion, and by erosion due to cavitation, in such equipment as a pressure reducing valve. In order to prevent such damage, it is necessary to use materials having high corrosion-resistance and high erosion or wearresistance in the equipment or components susceptible to such attack. Silicon carbide-is a material meeting these corrosion and erosion resistance requirements. Suitable silicon carbide materials include either silicon carbide per se or a coated composite material in which a base of metal, ceramic or graphite is coated with silicon carbide. Coating techniques which may be employed include plasma spraying, chemical vapor deposition or physical vapor deposition.A silicon carbide material having a high density is preferable to other silicon carbide materials; most preferably its specific gravity is not less than 2.9.
Plant according to the present invention is protected by a silicon carbide material used e.g. in the pressure reducing valve illustrated in the drawing. The valve schematically shown comprises a valve body 1 having fluid inlet port 2, a valve plug 3 and valve seat ring 5. A processing fluid'under high temperature and high pressure in use enters the valve body 1 through the inlet port 2 and, with the valve open to flow, passes through the clearance between the tip 4 of the plug 3 and the upper edge of inner surface 6 of the valve seat ring 5, the pressure of the processing fluid then being reduced. The rate of pressure reduction is controlled by up-and-down movement of the valve plug 3. In actual operation, the tip 4 of the valve plug and the inner surface 6 are exposed to the processing fluid flowing at a high speed and are subject to corrosion and the erosion due to cavitation.Thus materials having high corrosionresistance and high wear-resistance are required in these portions of the pressure reducing valve. A silicon carbide material is used in embodiments of the present invention.
Only a pressure reducing valve has been discussed in the above example, but silicon carbide materials can be used in any portion of the plant equipment which is exposed to highly corrosive processing fluid in urea synthesis. Use of the silicon carbide materials is especially effective in areas where high velocity fluid flow is encountered. For instance, use of silicon carbide materials is very effective in valves in recycling lines.
In regard to the present invention, processes in which silicon carbide materials are used are the conventional urea synthesizing processes. As stated earlier, the parts protected by the use of silicon carbide can be made solely of silicon carbide or can be composites consisting of substrates coated with silicon carbide.
According to the present invention, the use of highly corrosion-resistant and wear-resistant silicon carbide in urea synthesizing plants has eliminated the needs of prior practice for replacing valves which are damaged by corrosion or cavitation-induced erosion during operation, and alternatively for changing valves to those of different materials depending on the type of processing fluid used, these needs arising from the lack of appropriate materials. The use of silicon carbide also has prevented damage caused by varying operational conditions from occurring, improved the safety and stability in the operation of a urea synthesizing plant under high temperature and high pressure conditions and promoted enhanced operational plant efficiency.
Claims (9)
1. A urea synthesizing process plant characterized in that portions of plant equipment which are exposed to corrosive and/or cavitationinduced erosion are protected against corrosion and/or erosion by silicon carbide material.
2. Plant according to claim 1, wherein the said portions are made wholly of silicon carbide.
3. Plant according to claim 1, wherein the said portions comprise a structural substrate and the silicon carbide is a coating thereon.
4. Plant according to any of claims 1 to 3, wherein the silicon carbide material is used in pressure reducing valves of the plant.
5. Plant according to claim 4, wherein the said valves have valve plugs and valve seatings made of or coated with silicon carbide.
6. A urea synthesis process plant substantially as herein described with reference to the accompanying drawing.
7. A urea synthesis process conducted in plant as claimed in any one of claims 1 to 6.
8. A pressure reducing or recycle line valve for a urea synthesizing process plant, wherein parts thereof with which urea process fluids come into contact are protected against corrosion and/or cavitation-induced erosion by silicon carbide or a coating of silicon carbide.
9. A pressure reducing or recycle line valve for a urea synthesizing process plant, substantially as herein described with reference to the accompanying drawing.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4864180A JPS56147756A (en) | 1980-04-15 | 1980-04-15 | Synthetic method of urea using silicon carbide material in apparatus |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2073751A true GB2073751A (en) | 1981-10-21 |
| GB2073751B GB2073751B (en) | 1984-02-01 |
Family
ID=12808989
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8110277A Expired GB2073751B (en) | 1980-04-15 | 1981-04-01 | Urea synthesis |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS56147756A (en) |
| BR (1) | BR8102284A (en) |
| CA (1) | CA1250314A (en) |
| DE (1) | DE3114218A1 (en) |
| FR (1) | FR2480280A1 (en) |
| GB (1) | GB2073751B (en) |
| IN (1) | IN155840B (en) |
| IT (1) | IT1137354B (en) |
| NL (1) | NL8101499A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20110033018A1 (en) * | 2009-08-10 | 2011-02-10 | Caldera Engineering, Lc | Method for bonding ceramic materials |
| US9238211B1 (en) | 2014-08-15 | 2016-01-19 | Rec Silicon Inc | Segmented silicon carbide liner |
| US9446367B2 (en) | 2014-08-15 | 2016-09-20 | Rec Silicon Inc | Joint design for segmented silicon carbide liner in a fluidized bed reactor |
| US9662628B2 (en) | 2014-08-15 | 2017-05-30 | Rec Silicon Inc | Non-contaminating bonding material for segmented silicon carbide liner in a fluidized bed reactor |
| WO2023191620A1 (en) * | 2022-03-28 | 2023-10-05 | Stamicarbon B.V. | Urea plant with valve; urea production process; use and method |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2608234B2 (en) * | 1992-02-26 | 1997-05-07 | 東洋エンジニアリング株式会社 | Pressure reducing valve for urea synthesis plant |
-
1980
- 1980-04-15 JP JP4864180A patent/JPS56147756A/en active Pending
-
1981
- 1981-03-25 IN IN323/CAL/81A patent/IN155840B/en unknown
- 1981-03-26 NL NL8101499A patent/NL8101499A/en not_active Application Discontinuation
- 1981-04-01 GB GB8110277A patent/GB2073751B/en not_active Expired
- 1981-04-08 DE DE19813114218 patent/DE3114218A1/en not_active Withdrawn
- 1981-04-14 BR BR8102284A patent/BR8102284A/en unknown
- 1981-04-14 CA CA000375434A patent/CA1250314A/en not_active Expired
- 1981-04-14 IT IT21139/81A patent/IT1137354B/en active
- 1981-04-15 FR FR8107634A patent/FR2480280A1/en active Granted
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20110033018A1 (en) * | 2009-08-10 | 2011-02-10 | Caldera Engineering, Lc | Method for bonding ceramic materials |
| US9238211B1 (en) | 2014-08-15 | 2016-01-19 | Rec Silicon Inc | Segmented silicon carbide liner |
| US9446367B2 (en) | 2014-08-15 | 2016-09-20 | Rec Silicon Inc | Joint design for segmented silicon carbide liner in a fluidized bed reactor |
| US9662628B2 (en) | 2014-08-15 | 2017-05-30 | Rec Silicon Inc | Non-contaminating bonding material for segmented silicon carbide liner in a fluidized bed reactor |
| WO2023191620A1 (en) * | 2022-03-28 | 2023-10-05 | Stamicarbon B.V. | Urea plant with valve; urea production process; use and method |
Also Published As
| Publication number | Publication date |
|---|---|
| NL8101499A (en) | 1981-11-02 |
| IN155840B (en) | 1985-03-16 |
| GB2073751B (en) | 1984-02-01 |
| IT1137354B (en) | 1986-09-10 |
| IT8121139A0 (en) | 1981-04-14 |
| JPS56147756A (en) | 1981-11-16 |
| DE3114218A1 (en) | 1982-03-04 |
| BR8102284A (en) | 1981-12-01 |
| CA1250314A (en) | 1989-02-21 |
| FR2480280A1 (en) | 1981-10-16 |
| FR2480280B1 (en) | 1983-07-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |