Manufacture of urea-ammonium sulate from sulfuric acid, ammonia, and urea

• US 3,928,015 A
• Filed: 06/09/1975
• Issued: 12/23/1975
• Est. Priority Date: 10/29/1974
• Status: Expired due to Term

• Current Assignee: Milton R. Siegel, Oscar E. Moore
• Original Assignee: Milton R. Siegel, Oscar E. Moore
• Inventors: Siegel, Milton R., Moore, Oscar E.
• Primary Examiner(s): Spear, Jr., Frank A.
• Assistant Examiner(s): Lander, Ferris
• Application Number:
  US05/580,837
• Time in Patent Office: 197 Days
• Field of Search: 71/28-30,37-41 423/549
• US Class Current: 71/28
• CPC Class Codes: C05C 3/00 Fertilisers containing other salts of ammonia or ammonia itself, e.g. gas liquor
• CPC Class Codes: C05C 9/00 Fertilisers containing urea or urea compounds

Abstract

Urea-ammonium sulfate is produced in a two-stage process wherein sulfuric acid is ammoniated to the bisulfate level in a firststage reactor, then further ammoniated to the ammonium sulfate level in a second-stage reactor with the simultaneous addition thereto of molten urea. The fluid medium of molten urea maintains the ammonium sulfate crystals in a slurry that can be easily transferred and granulated. The novelty of the process lies in the production of solid ammonium sulfate in the fluid medium of molten urea, thereby eliminating the necessity of separate ammonium sulfate production facilities.

Claims

1. A process for the production of solid urea-ammonium sulfate fertilizers from sulfuric acid, ammonia, and urea, which comprises the steps of:

a. simultaneously introducing into a first-stage reacting means a stream of sulfuric acid and a stream of ammonia, said sulfuric acid containing from about 25 to about 95 percent H2SO4 and the relative proportions of said ammonia and said sulfuric acid fed thereto sufficient to yield therein an NH3;

SO4 mole ratio in the range from about 0.7 to about 1.3;

b. retaining the resulting ammonium bisulfate intermediate product in said first-stage reacting means at a temperature in the range from about 200*F to about 350*F for a period of time ranging from about 1 minute to about 15 minutes;

said residence time and said temperatures being sufficient to effect predetermined water vapor disengagement mentioned in step (e) infra from said intermediate bisulfate product in said firststage reacting means;

c. withdrawing from said first-stage reacting means at least a portion of said ammonium bisulfate intermediate product produced therein and simultaneously introducing same, together with a stream of ammonia and a stream of urea, into a secondstage reacting means, the proportion of ammonia fed thereto in relation to said ammonium bisulfate being sufficient to effect therein an NH3;

SO4 mole ratio ranging from about 1.7 to about 2.0, said urea stream fed to said second-stage reacting means containing from about 95 percent to about 100 percent urea by weight and introducted thereinto at a temperature substantially about equal to the temperature of the materIal maintained therein ranging from about 270*F to about 320*F;

d. retaining the resulting homogeneous mixture of urea-ammonium sulfate co-melt and particulate ammonium sulfate in said second-stage reacting means for a period of time ranging from about one to about 300 seconds;

e. offgasing from said second-stage reacting means mainly ammonia and water vapor, the quantity of said water vapor so offgased together with that removed by disengagement from said first-stage reacting means in step (b) supra being sufficient in toto to ultimately yield said solid urea-ammonium sulfate product with a moisture content ranging from about 0.1 to about 5 percent by weight and being substantially effected by the autogenous heat of reaction; and

f. removing at least a portion of the resulting homogeneous mixture of urea-ammonium sulfate co-melt and particulate ammonium sulfate, said urea melt containing upwards of about 50 percent of the input ammonium sulfate as co-melt therewith, to granulation means wherefrom is removed as product said solid urea ammonium sulfate.

2. The process of claim 1 wherein the concentration of the urea introduced into said second-stage reacting means ranges from about 65 percent to about 95 percent by weight and wherein external heat energy is supplied to second-stage reacting means in amounts sufficient to effect water vapor offgasing therefrom in combination with the water vapor disengagement from step (b) thereof to yield an ultimate solid urea ammonium sulfate product having the low moisture content specified in step (e).

3. The process of claim 1 wherein the material offgased in step (e) thereof is treated in scrubbing means and the ammonia recovered therein is recycled back to said first-stage reacting means.

4. The process of claim 2 wherein the material offgased in step (e) thereof is treated in scrubbing means and the ammonia recovered therein is recycled back to said first-stage reacting means.

5. A process for the production of solid urea-ammonium sulfate fertilizers from sulfuric acid, ammonia, and urea, which comprises the steps of:

a. simultaneously introducing into a first-stage reacting means a stream of sulfuric acid and a stream of ammonia, said sulfuric acid containing from about 40 to about 70 percent H2SO4 and the relative proportions of said ammonia and said sulfuric acid fed thereto sufficient to yield therein an NH3;

SO4 mole ratio in the range from about 0.9 to about 1.2;

b. retaining the resulting ammonium bisulfate intermediate product in said first-stage reacting means at a temperature in the range from about 230*F to about 270*F for a period of time ranging from about 1 minute to about 7 minutes;

said residence time and said temperatures being sufficient to effect predetermined water vapor disengagement mentioned in step (e) infra from said intermediate bisulfate product in said first-stage reacting means;

c. withdrawing from said first-stage reacting means at least a portion of said ammonium bisulfate intermediate product produced therein and simultaneously introducing same, together with a stream of ammonia and a stream of urea, into a second-stage reacting means, the proportion of ammonia fed thereto in relation to said ammonium bisulfate being sufficient toeffect therein an NH3;

SO4 mole ratio ranging from about 1.8 to about 2.0, said urea stream fed to said second-stage reacting means containing from about 98 percent to about 100 percent urea by weight and introduced thereinto at a temperature substantially about equal to the temperature of the material maintained therein ranging from about 270*F to about 300*F;

d. retaining the resulting homogeneous mixture of urea-ammonium sulfate co-melt and particulate ammonium sulfate in said second-stage reacting means for a period of time raNging from about 1 to about 90 seconds;

e. offgasing from said second-stage reacting means mainly ammonia and water vapor, the quantity of said water vapor so offgased together with that removed by disengagement from said first-stage reacting means in step (b) supra being sufficient in toto to ultimately yield said solid urea-ammonium sulfate product with a moisture content ranging from about 0.1 to about 2 percent by weight and being substantially effected by the autogenous heat of reaction; and

f. removing at least a portion of the resulting homogeneous mixture of urea-ammonium sulfate co-melt and particulate ammonium sulfate, said urea melt containing upwards of about 50 percent of the input ammonium sulfate as co-melt therewith, to granulation means wherefrom is removed as product said solid urea ammonium sulfate.

6. The process of claim 5 wherein the concentration of the urea introduced into said second-stage reacting means ranges from about 65 percent to about 75 percent by weight and wherein external heat energy is supplied to second-stage reacting means in amounts sufficient to effect water vapor offgasing therefrom in combination with the water vapor disengagement from step (b) thereof to yield an ultimate solid urea ammonium sulfate product having the low moisture content specified in step (e).

7. The process of claim 5 wherein the material off-gased in step (e) thereof is treated in scrubbing means and the ammonia recovered therein is recycled back to said first-stage reacting means.

8. The process of claim 6 wherein the material offgased in step (e) thereof is treated in scrubbing means and the ammonia recovered therein is recyled back to said first-stage reacting means.

9. A process for the production of solid urea-ammonium sulfate fertilizers from sulfuric acid, ammonia, and urea, which comprises the steps of:

a. simultaneously introducing into a first-stage reacting means a stream of sulfuric acid and a stream of ammonia, said sulfuric acid containing from about 50 to about 60 percent H2SO4 and the relative proportions of said ammonia and said sulfuric acid fed thereto sufficient to yield therein an NH3;

SO4 mole ratio in the range from about 1.0 to about 1.1;

b. retaining the resulting ammonium bisulfate intermediate product in said first-stage reacting means at a temperature in the range from about 250*F to about 260*F for a period of time ranging from about 1 minute to about 4 minutes;

said residence time and said temperatures being sufficient to effect predetermined water vapor disengagement mentioned in step (e) infra from said intermediate bisulfate product in said first-stage reacting means;

c. withdrawing from said first-stage reacting means at least a portion of said ammonium bisulfate intermediate product produced therein and simultaneously introducing same, together with a stream of ammonia and a stream of urea, into a second-stage reacting means, the proportion of ammonia fed thereto in relation to said ammonium bisulfate being sufficient to effect therein an NH3;

SO4 mole ratio ranging from about 1.9 to about 2.0, said urea stream fed to said second-stage reacting means containing at least about 99 percent urea by weight and introduced thereinto at a temperature substantially about equal to the temperature of the material maintained therein ranging from about 270*F to about 280*F;

d. retaining the resulting homogeneous mixture of urea-ammonium sulfate co-melt and particulate ammonium sulfate in said second-stage reacting means for a period of time ranging from about 1 to about 15 seconds;

e. offgasing from said second-stage reacting means mainly ammonia and water vapor, the quantity of said water vapor so offgased together with that removed by disengagement from said first-stage reacting mEans in step (b) supra being sufficient in toto to ultimately yield said solid urea-ammonium sulfate product with a moisture content ranging from about 0.1 to about 0.5 percent by weight and being substantially effected by the autogenous heat of reaction; and

f. removing at least a portion of the resulting homogeneous mixture of urea-ammonium sulfate co-melt and particulate ammonium sulfate, said urea melt containing upwards of about 50 percent of the input ammonium sulfate as co-melt therewith, to granulation means wherefrom is removed as product said solid urea ammonium sulfate.

10. The process of claim 9 wherein the concentration of the urea introduced into said second-stage reacting means is about 75 percent by weight and wherein external heat energy is supplied to second-stage reacting means in amounts sufficient to effect water vapor offgasing therefrom in combination with the water vapor disengagement from step (b) thereof to yield an ultimate solid urea ammonium sulfate product having the low moisture content specified in step (e).

11. The process of claim 9 wherein the material off gased in step (e) thereof is treated in scrubbing means and the ammonia recovered therein is recycled back to said first-stage reacting means.

12. The process of claim 10 wherein the material offgased in step (ed) thereof is treated in scrubbing means and the ammonia recovered therein is recycled back to said first-stage reacting means.

13. The process of claim 9 wherein said second-stage reacting means is a common pipe reactor.