US3607938A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for the synthetic manufacture of urea from ammonia and carbon dioxide
Assignee: Chemical Construction Corp
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Filing: 1968-05-17
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Granted: 1971-09-21
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Expires: 1988-05-17
Abstract
Abstract A process is provided for the synthetic manufacture of urea from ammonia and carbon dioxide, in which the ammonium carbamate contained in the urea synthesis effluent stream is stripped and separated in mixed off-gas and returned to the synthesis reactor. The stripping of the carbamate takes place using previously separated mixed off-gas which is carried in a cycle to the heated stripping zone. A feed gas component which may be ammonia or carbon dioxide is also introduced into the zone, so that the total stripping proceeds either in one stage with ammonia or carbon dioxide addition, or in two stages, with the synthesis effluent stream being divided into two portions which flow in parallel to the separate stages. In the first stage, ammonia is added for stripping, and in the second stage carbon dioxide is added. An amount of at least 40 percent of the synthesis effluent stream is admitted to the first decomposition and stripping stage which operates at synthesis pressure, and a mixture consisting of the remainder of the synthesis effluent stream and the solution flowing from the first stage is added to the second stage, which may be operated at reduced pressure.
Inventors
- 👤 Wilhelm F Braun
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 02:18
CPC Classifications
C; C07; C07C; C07C273/00; C07C273/02; C07C273/04; Y; Y02; Y02P; Y02P20/00; Y02P20/50; Y02P20/582
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
33 words
The process of claim 1, in which said urea synthesis effluent stream contains excess unreacted ammonia, and said excess ammonia is at least partially removed from the liquid phase in said mixed off-gas.
Claim 2
Dependent Claim
14 words
The process of claim 1, in which said heated stripping zone is substantially vertical.
Claim 3
Dependent Claim
55 words
The process of cLaim 1, in which the residual portion of said mixed off-gas remaining after said portion is recycled according to step c (c), is cooled to condense an ammonium carbamate solution, and said ammonium carbamate solution is recycled to said reaction of ammonia and carbon dioxide to produce said urea synthesis effluent stream.
Claim 4
Dependent Claim
48 words
The process of claim 4, in which water is added to said residual portion of said mixed off-gas prior to cooling, and the resulting aqueous ammonium carbamate solution formed after cooling is recycled to said reaction of ammonia and carbon dioxide to produce said urea synthesis effluent stream.
Claim 5
Dependent Claim
48 words
The process of claim 1, in which the portion of the mixed off-gas recycled according to step (c) is added to the middle section of said zone, and said feed gas is carbon dioxide, said carbon dioxide feed gas being added to the bottom section of said zone.
Claim 6
Dependent Claim
46 words
The process of claim 1, in which the portion of the mixed off-gas recycled according to step (c) is added to the bottom section of said zone, and said feed gas is ammonia, said ammonia feed gas being added to the bottom section of said zone.
Claim 7
Dependent Claim
427 words
A process for the synthesis of urea from ammonia and carbon dioxide which comprises a. reacting ammonia, carbon dioxide and recycled aqueous ammonium carbamate solution at elevated pressure, whereby a urea synthesis effluent stream principally containing urea, ammonium carbamate, ammonia and water is formed, b. dividing said urea synthesis effluent stream into a first portion and a second portion, c. passing said first portion downwards through a first heated stripping zone, wherein ammonium carbamate is decomposed and a first mixed off-gas is formed, d. removing said first mixed off-gas from the upper section of said first zone, e. recycling a portion of the first mixed off-gas removed according to step (d) to said first zone below the upper section, whereby the liquid phase in said first zone is stripped, f. passing an ammonia feed gas into the lower section of said first zone, whereby said ammonia feed gas strips the liquid phase in said first zone and combines within said first zone with said mixed off-gas portion recycled according to step (e), g. passing the stripped residual liquid phase removed from the bottom section of said first zone to the upper section of a second heated stripping zone, whereby said residual liquid phase flows downwards through said second zone, h. passing said second portion formed by step (b) downwards through said second zone, whereby said second portion combines with said residual liquid phase from said first zone, and ammonium carbamate is decomposed in said second zone and a second mixed off-gas is formed, i. removing said second mixed off-gas from the upper section of said second zone, j. recycling a portion of the second mixed off-gas removed according to step (i) to said second zone below the upper section, whereby the liquid phase in said second zone is stripped, k. passing a carbon dioxide feed gas into the lower section of said second zone, whereby said carbon dioxide feed gas strips the liquid phase in said second zone and combines within said second zone with said mixed off-gas portion recycled according to step (j), l. removing a residual liquid phase comprising aqueous urea solution from the bottom section of said second zone, m. cooling the residual portions of said first and second mixed off-gas streams remaining after said portions are recycled according to steps (e) and (j), whereby first and second aqueous solutions containing ammonium carbamate are formed by condensation of mixed off-gas, and n. recycling the aqueous solutions formed according to step (m) to urea synthesis as said recycled aqueous ammonium carbamate solution of step (a).
Claim 8
Dependent Claim
18 words
The process of claim 8, in which said first and said second heated stripping zones are substantially vertical.
Claim 9
Dependent Claim
42 words
The process of claim 8, in which water is added to said residual portionS of said off-gas streams prior to cooling according to step (m), and the resulting aqueous solutions containing ammonium carbamate formed after cooling are recycled according to step (a).
Claim 10
Dependent Claim
37 words
The process of claim 8, in which the portion of the first mixed off-gas recycled according to step (e) and said ammonia feed gas of step (f) are added to the bottom section of said first zone.
Claim 11
Dependent Claim
48 words
The process of claim 8, in which the portion of the second mixed off-gas recycled according to step (j) is added to the middle section of said second zone, and said carbon dioxide feed gas of step (k) is added to the bottom section of said second zone.
Claim 12
Dependent Claim
20 words
The process of claim 8, in which said first and said second mixed off-gas streams contain an inert gas phase.
Claim 13
Dependent Claim
49 words
The process of claim 8, in which said portions of first and second mixed off-gas are recycled according to steps (e) and (j) by inducting said portions through injector type nozzles, and passing the feed gas streams of steps (f) and (k) through the respective nozzles at increased pressure.
Claim 14
Dependent Claim
44 words
The process of claim 8, in which the stripped residual liquid phase removed from the bottom section of said first zone according to step (g) is heated, prior to passing said residual liquid phase to the upper section of said second heated stripping zone.
Claim 15
Dependent Claim
65 words
The process of claim 8, in which said first portion of said urea synthesis effluent stream is stripped in said first heated stripping zone at a pressure which substantially equal to the elevated pressure of urea synthesis, and said second portion of said urea synthesis effluent stream is stripped in said second heated stripping zone at a pressure which is reduced below urea synthesis pressure.
Claim 16
Dependent Claim
27 words
The process of claim 8, in which said first portion formed according to step (b) is at least 40 percent of the total urea synthesis effluent stream.
Claim 17
Dependent Claim
22 words
The process of claim 8, in which the molar ratio of total carbon dioxide reacted according to step (a) is about 4:1.
Claim 18
Dependent Claim
31 words
The process of claim 8, in which the molar ratio of recycled mixed off-gas portion to feed gas is greater than 1 in said first and said second heated stripping zones.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-09-20 | 1975-03-22 | 1975-09-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-09-20 | 1979-03-22 | 1979-09-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-09-20 | 1983-03-22 | 1983-09-21 | $7700.00 | Window Closed / Lapsed |