Process for granulating ammonium phosphate containing fertilizers

• US 4,154,593 A
• Filed: 02/16/1977
• Issued: 05/15/1979
• Est. Priority Date: 08/27/1976
• Status: Expired due to Term

• Current Assignee: Mississippi Chemical Corporation (CF Industries Holdings Incorporated)
• Original Assignee: Mississippi Chemical Corporation (CF Industries Holdings Incorporated)
• Inventors: Brown, Marion L., Tucker, Gerald L., Johnson, Charles A. III
• Primary Examiner(s): Hart, Charles N.
• Assistant Examiner(s): Therkorn, Ernest G.
• Application Number:
  US05/769,323
• Time in Patent Office: 818 Days
• Field of Search: 71/33, 71/34, 71/43, 71/64 D, 71/64 DA, 71/44, 71/53, 71/63, 423/309, 423/310, 423/312, 423/313, 23/259.1, 422/189
• US Class Current: 71/33
• CPC Class Codes: C05B 19/00 Granulation or pelletisation of phosphatic fertilisers, other than slag granulating apparatus B01J2/00; granulating slag C04B
• CPC Class Codes: C05B 7/00 Fertilisers based essentially on alkali or ammonium orthophosphates C05B11/00 takes precedence

Abstract

A process for granulating ammonium phosphate containing composition for use as a fertilizer which comprises feeding a slurry or melt of ammonium phosphate, wherein said slurry or melt is capable of further reaction with ammonia, into a kneading mill, feeding recycled particles from the subsequent classification and crushing procedure into said kneading mill, wherein the said slurry or melt added to the mill is from 5 to 95% wt. of the total slurry or melt, feeding ammonia into said mill to react with at least a portion of the reactable components of said slurry or melt, generating a heat of reaction, subjecting said mixture to a kneading action within said mill until the heat of reaction and the kneading action cause a repeated disposition of fertilizer material onto the solids and cause a repeated drying of said deposit, passing the product from said kneading mill into a rotary drum granulator, feeding additional ammonium phosphate containing slurry or melt to a said granulator in an amount of from 95% to 5% wt. based on the total slurry or melt, feeding additional amounts of ammonia to said granulator wherein at least a portion of the reactable components of said slurry or melt is reacted, giving off a heat of reaction, subjecting said mixture to a rotary action until said heat of reaction and tumbling action of the rotary granulator effects a further deposition of fertilizer material onto the solids, passing the product from said granulator into a dryer so as to remove excess water, subjecting said dried product to a classification apparatus so as to separate out particles which are outside the product size range, recycling at least a portion of said particle mixture to said kneading mill, and recovering said dried particles of product size. Commensurate apparatus is provided to perform said process.

Claims

1. A process for granulating an ammonium phosphate containing composition for use as a fertilizer which comprises:

feeding a slurry or melt of ammonium phosphate containing less than 20 wt.% water, wherein said slurry or melt is capable of further reaction with ammonia, into a kneading mill,

feeding recycled particles from the subsequent classification and crushing procedure into said kneading mill at a recycle ratio of 2;

1 to 4.5;

1,

wherein the said slurry or melt added to the mill is from 25 to 75% wt based on the total slurry or melt which is to be granulated,

feeding ammonia into said mill to react with at least a portion of the reactable components of said slurry or melt, generating a heat of reaction,

subjecting said mixture to a kneading action within said mill until the heat of reaction and the kneading action cause a repeated deposition of fertilizer material onto the solids and cause a repeated drying of said deposit,

passing the product from said kneading mill into a rotary drum granulator,

feeding additional ammonium phosphate containing slurry or melt having a water content of less than 20 wt.% to said granulator in an amount of from 75 to 25% based on the total slurry or melt which is to be granulated,

feeding additional amounts of ammonia to said granulator wherein at least a portion of the reactable components of said slurry or melt is reacted giving off a heat of reaction,

subjecting said mixture to a rotary action until said heat of reaction and tumbling action of the rotary granulator effects a further deposition of fertilizer material onto the solids,

passing the product from said granulator into a drier so as to remove excess water,

subjecting said dried product to a classification apparatus so as to separate out particles which are outside the product size range,

recycling at least a portion of said particle mixture to said kneading mill, and

recovering said dried particles of product size.

2. The process of claim 1, wherein said slurry or melt is formed by reacting a sufficient amount of phosphoric acid having a P₂ O₅ content of 15 to 70% wt with ammonia to form monoammonium phosphate with a mole ratio of NH₃ :

H₃ PO₄ of from 1.0 to 0.1.

3. The process of claim 2, wherein the total quantity of ammonia added is 2% to 40%, based on the weight of the product.

4. The process of claim 3, wherein 30 to 96% of said ammonia is added to effect the neutralization of the phosphoric acid, and wherein 35 to 2% of said ammonia is added to said kneading mill and 35 to 2% of said ammonia is added to said granulator.

5. The process of claim 1, wherein said slurry or melt is formed by reacting a sufficient amount of phosphoric acid having a P₂ O₅ content of 15 to 70% wt with ammonia to form monoammonium phosphate and diammonium phosphate in an amount of between 100% MAP and 0% DAP, to 0% MAP and 100% DAP.

6. The process of claim 1, wherein potash is fed to said kneading mill in an amount such that up to 50% K₂ O in the form of a potassium compound selected from the group consisting of KCl, K₂ SO₄ and potassium phosphates.

7. The process of claim 1, wherein a solid filler is introduced into said kneading mill.

8. The process of claim 7, wherein said solid filler is potash, dolomite, CaCO₃, gypsum, clay, dust, sea shells, sand, compounds of Zn, Mg, Mn, B, Mb or S or mixtures thereof.

9. The process of claim 1, wherein steam, hot water or hot scrubber water is added to said kneading mill.

10. The process of claim 1, wherein said kneading mill is a pug mill.

11. The process of claim 1, wherein the temperature within said kneading mill and said granulator is from 110°

F. to 234°

F.

12. The process of claim 11, wherein 100 to 25% wt of the recycled particles are fed to said kneading mill and 0 to 75% of said particles are fed to said granulator.

13. The process of claim 1, wherein oversized particles from said classification apparatus are crushed, combined with undersized particles from said classification apparatus and said mixture is recycled to said kneading mill.

14. The process of claim 13, wherein a portion of said recycle mixture is recycled to said granulator.

15. A process for granulating an ammoinium phosphate containing composition for use as a fertilizer which comprises:

feeding a slurry or melt of ammonium phosphate containing less than 20 wt.% water and produced by reacting phosphoric acid having a P₂ O₅ of 15-70% with ammonia, wherein said slurry or melt is capable of further reaction with ammonia, into a pug mill,

feeding potash to said pug mill in an amount of up to 50% K₂ O,

feeding recycled particles from the subsequent classification and crushing procedure into said pug mill at a recycle ratio of 2;

1 to 4.5;

1,

wherein said slurry or melt added to the mill is from 25 to 75% wt based on the total slurry or melt used in the granulators,

feeding ammonia into said mill to react with at least a portion of the reactable components of said slurry or melt, generating a heat of reaction,

subjecting said mixture to a kneading action within said mill until the heat of reaction and the kneading action cause a repeated deposition of fertilizer material into the solids and cause a repeated drying of said deposit,

passing the product from said pug mill into a rotary drum granulator,

feeding additonal ammonium phosphate containing slurry or melt having a water content of less than 20 wt.% to said granulator in an amount of from 75 to 25% based on the total slurry or melt,

feeding additional amounts of ammonia to said granulator wherein at least a portion of the reactable components of said slurry or melt is reacted giving off a heat or reaction,

subjecting said mixture to the action of said rotary drum granulator until said heat of reaction and tumbling action of the rotary granulator effects a further deposition of fertilizer material onto the solids,

passing the product from said granulator into a dryer so as to remove excess water,

subjecting said dried product to a classification apparatus so as to separate out particles which are outside the product size range,

recycling at least a portion of said particle mixture to said pug mill and

recovering said dried particles of product size of 14 to 5 mesh.