Chemistry of inorganic compounds – Nitrogen or compound thereof – Oxygen containing
Reexamination Certificate
2001-11-02
2002-11-05
Silverman, Stanley S. (Department: 1754)
Chemistry of inorganic compounds
Nitrogen or compound thereof
Oxygen containing
C423S398000, C423S399000, C423S101000, C423S143000, C423S162000, C423S194000
Reexamination Certificate
active
06475457
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for the reaction of water moistened particulate metal chlorides, sulfates or oxides with nitrogen dioxide gas in a fluidized state, with the production of a solid having a composition composed of the metal and the nitrate ion. More particularly, the invention relates to the production of potassium nitrate or calcium nitrate and nitrosyl chloride gas (depending on the composition of the particulate) using nitrogen dioxide gas and water moistened particulate potassium chloride or calcium sulfate in an energy efficient process using counter current flow and fluidized bed technology. The unique aspects of this process is that it permits the reaction to take place at a rapid rate at moderately elevated temperatures while retaining essentially the same crystal size as the original potassium chloride or calcium sulfate. The counter current aspects of the invention permit the production of potassium nitrate or calcium nitrate and nitrosyl chloride gas (depending on the solid) essentially free of nitrogen dioxide.
BACKGROUND OF THE INVENTION
Potassium is one of three essential elements (N.P.K.) in the life cycle of all plants. Fertilizers therefore generally contain all three in one form or another. Potassium, however is generally present as a chloride since it is the most readily available, least expensive potassium compound. For many crops (e.g., citrus, tobacco) a fertilizer containing small amounts of chlorides is toxic. Thus, there is created a sizable demand for manufactured potassium nitrate as a non-chloride source of potassium. However, it must be produced at a relatively low cost to compete with existing processes such as that produced from natural deposits. The use of potassium nitrate as a fertilizer was first suggested by Glauber in 1655. A few years later its value was discussed by Digby in what is said to be the earliest known record of the actual use of fertilizers as distinct from decaying organic matter. The world supply of potassium nitrate was formerly derived from incrustations on the soils around habitations in tropical countries, chiefly India, Sri Lanka, Mexico and Egypt. Its presence there is due to the decomposition of organic matter by nitrifying organisms in soils containing soluble potassium compounds.
Much of the potassium nitrate in commerce was formerly made by the “Conversion Process” in which sodium nitrate and potassium chloride undergo a double decomposition. This process depends on the wide variation in the solubility of potassium nitrate in hot and cold solutions.
KCl+NaNO
3
àKNO
3
+NaCl
This process has been displaced by more efficient operations as will be shown as follows:
RELATED ART
Potassium nitrate, otherwise known as saltpeter or nitrate of potash, is important in the production of fertilizers, explosives, glass, and numerous other industrial chemicals. It is one of the oldest known “industrial” chemicals. Potassium nitrate has been used on a large scale since around the year 1300, when the Chinese discovered that saltpeter could be combined with sulfur and charcoal to produce the common explosive known as black powder. The ever-growing demand for potassium nitrate for these and other such uses has resulted in a prolonged search for improved potassium nitrate production processes, and various methods have been invented to produce potassium nitrate. For example, large quantities of potassium nitrate are commercially produced by the reaction of potassium chloride with nitric acid in the presence of oxygen, yielding the following overall reaction:
2KCl+2HNO
3
+1/2O
2
→KNO
3
+Cl
2
+H
2
O
The potassium chloride and nitric acid must be reacted at 100° C. to produce potassium nitrate, nitrosyl chloride and water as follows:
3KCL+4HNO
3
→3KNO
3
+NOCl+Cl
2
+2H
2
O
The nitrosyl chloride is then oxidized to chlorine and nitrogen dioxide, N
0
2
, with nitric acid. See Chemical Process Industries, 4
th
Ed., Shreve and Brink, McGraw-Hill, Inc., New York (1977), pp. 272-273.
Smith et al, in U.S. Pat. No. 2,963,345, disclose a process for producing potassium nitrate, which involves agitating solid particulate potassium chloride with liquid nitrogen peroxide under anhydrous conditions at a temperature of 15° C.; excess nitrosyl chloride vapors produced by the reaction are continuously withdrawn to maintain the reaction. Potassium nitrate and unreacted potassium chloride are then separated by addition to a brine that contains dissolved potassium nitrate and potassium chloride; the brine solution is heated to about 85° C. to dissolve the potassium nitrate, but not the solid particles of potassium chloride. The solid particles of potassium chloride are then separated by filtration. Large volumes of potassium nitrate are also produced by the reaction of sodium nitrate with potassium chloride, the overall reaction being:
KCl+NaNO
3
→KNO
3
+NaCl
This process requires that potassium chloride be dissolved in a hot solution of sodium nitrate; upon heating, sodium chloride crystals are formed. The hot potassium nitrate solution is then run through the sodium chloride crystals forming at the bottom of the reaction vessel. However, a mixture of potassium nitrate and sodium chloride is formed, so additional processing operations are required to separate potassium nitrate.
Lehto, in U.S. Pat. No. 3,983,222, discloses a continuous process for producing potassium nitrate, which includes the steps of extracting nitrate from aqueous solutions with an organic amine salt dissolved in an organic solvent, separating the organic phase containing the extracted nitrate from the aqueous phase, and stripping the organic base with a potassium salt stripping solution having a pH of at least 0.5. The stripping solution also contains nitrate ions and potassium ions with the concentration of potassium nitrate maintained high enough to induce crystallization of potassium nitrate from the stripping solution continuously.
Dotson et al, U.S. Pat. No. 4,465,568, uses an electrolytic process to produce chloride free mixtures of sodium nitrate and potassium nitrate.
Baniel et al. discloses in U.S. Pat. No. 2,902,341 a process for the preparation of water soluble metal sulfates, phosphates, or nitrates by the reaction in aqueous medium of the chlorides of the respective metals with free sulfuric phosphoric or nitric acid, respectively. Hydrochloric acid is extracted from the aqueous liquid with a solvent of limited mutual miscibility with water but being a solvent for hydrochloric acid but not for any of the metal salts. While this process has been exploited commercially, it lacks the simplicity and efficiency of the instant method. Large volumes of liquids must be handled; crystallization, extraction, separation, and distillation processes are required to recover the desired salts and solvents. Volatile organic solvents are utilized in the extraction process requiring stringent environmental and safety standards. The major plant utilizing this process has suffered serious fires, disrupting production for significant periods of time.
Bianchi et al discloses in U.S. Pat. No. 4,776,930 a process for the production of potassium nitrate by reacting a solution of potassium carbonate with nitric acid. This process utilizes expensive raw materials (potassium carbonate produced by electrolytic process) and requires substantial energy to recover the potassium nitrate from the solution.
Abidaud et al discloses in U.S. Pat. No. 5,110,578 a process for potassium nitrate via ion exchange on a continuous basis using relatively weak solutions of nitric acid and potassium chloride. High purity solid potassium nitrate is produced by crystallization. Significant energy is required to produce solid potassium nitrate by this process due to the dilute solutions produced (15% wt KNO
3
and 0.5% wt KNO
3
) which must be neutralized by potassium hydroxide (KOH).
Manour et al discloses in U.S. Pat. No. 4,378,342 a method of producing potassium nitrate by reacting potassium chloride with
Cochran Keith D.
Holt Timothy G.
Rigby William J.
Emrich & -Dithmar
Nave Eileen E.
Rigby William J.
Silverman Stanley S.
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