(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2002/0110512 A1
`Rigby et al.
`(43) Pub. Date:
`Aug. 15, 2002
`
`US 2002O110512A1
`
`(54)
`
`(76)
`
`(21)
`(22)
`
`(63)
`
`PROCESS FOR MANUFACTURING
`POTASSIUM NITRATE FERTLIZER AND
`OTHER METAL NITRATES
`
`Inventors: William J. Rigby, Naperville, IL (US);
`Keith D. Cochran, Killen, AL (US);
`Timothy G. Holt, Florence, AL (US)
`Correspondence Address:
`EMRICH & DTHMAR
`ATTORNEYS AND COUNSELORS
`SUTE 3000
`300 SOUTHWACKER DRIVE
`CHICAGO, IL 60606 (US)
`Appl. No.:
`10/000,412
`
`Filed:
`
`Nov. 2, 2001
`Related U.S. Application Data
`Continuation-in-part of application No. 09/100,994,
`filed on Jun. 22, 1998, now patented.
`
`Publication Classification
`
`(51) Int. Cl." ....................................................... C01D 9/00
`
`(52) U.S. Cl. ............................................ 423/398; 423/395
`
`(57)
`
`ABSTRACT
`
`A process for producing potassium nitrate and other metal
`nitrates from the chlorides, Sulfates, oxides of these metals.
`The proceSS uses nitrogen dioxide as a true fluidizing
`medium in shallow beds of the aforementioned Solids at
`moderately elevated temperatures in a continuous counter
`current process to convert the metal chlorides, Sulfates, and
`oxides, into metal nitrates and effluent gas and water vapor.
`The process may be carried out in a Series of true fluidized
`beds arranged in a vertical configuration So that the Solids
`flow downward due to the fluidized process and the nitrogen
`dioxide gas flows counter currently in an upward direction
`producing pure metal nitrates at the bottom and nitrosyl
`chloride gas and/or water vapor at the top.
`
`NOCL
`GAS OUT
`77A
`
`78A
`
`
`
`Mois
`
`J9.
`
`83 AR oRN,
`Noah WATER (27.
`FEED)
`
`Human Power of N Company
`EX1067
`Page 1 of 10
`
`

`

`Patent Application Publication Aug. 15, 2002. Sheet 1 of 3
`
`US 2002/0110512 A1
`
`
`
`
`
`GAS
`
`S-
`FLUIDIZED is:
`BED
`,
`
`GAS
`
`
`
`15
`
`17
`DSENGAGING
`ZONE
`
`1 O
`
`PERFORATED PATE
`&/OR MESH
`
`FLUIDIZED BED
`FIG. 1
`
`Page 2 of 10
`
`

`

`Patent Application Publication Aug. 15, 2002. Sheet 2 of 3
`US 2002/0110512 A1
`|
`NOCL- Out
`
`
`
`31
`Number of Fluidized
`Beds Determined
`By NO2Removal
`Efficency
`SOE
`
`SEAt
`CONVEYOR OR
`CON V
`Out
`
`Page 3 of 10
`
`

`

`Patent Application Publication Aug. 15, 2002. Sheet 3 of 3
`
`US 2002/0110512 A1
`
`
`
`J.O.
`
`83 AR OR N.
`Noah WATER (27.
`FEED)
`
`Page 4 of 10
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`

`US 2002/0110512 A1
`
`Aug. 15, 2002
`
`PROCESS FOR MANUFACTURING POTASSUM
`NITRATE FERTILIZER AND OTHER METAL
`NITRATES
`
`RELATED APPLICATIONS
`0001. This is a continuation-in-part to application Ser.
`No. 09/100,994 filed Jun. 28, 1998.
`
`FIELD OF THE INVENTION
`0002 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 compo
`Sition 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 retain
`ing essentially the same crystal size as the original potas
`sium 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
`0.003
`(N.P.K.) in the life cycle of all plants. Fertilizers therefore
`generally contain all three in one form or another. Potas
`sium, however is generally present as a chloride Since it is
`the most readily available, least expensive potassium com
`pound. 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 depos
`its. 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.
`0004. 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 Solu
`tions.
`
`KCI+NaNOaKNO+NaCl
`
`0005. This process has been displaced by more efficient
`operations as will be shown as follows:
`
`RELATED ART
`0006 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. Potas
`sium 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 com
`mon 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:
`
`0007. The potassium chloride and nitric acid must be
`reacted at 100 C. to produce potassium nitrate, nitrosyl
`chloride and water as follows:
`
`0008. The nitrosyl chloride is then oxidized to chlorine
`and nitrogen dioxide, NO, with nitric acid. See Chemical
`Process Industries, 4" Ed., Shreve and Brink, McGraw-Hill,
`Inc., New York (1977), pp. 272-273.
`0009 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 tempera
`ture 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:
`
`0010 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. How
`ever, a mixture of potassium nitrate and Sodium chloride is
`formed, So additional processing operations are required to
`Separate potassium nitrate.
`0011 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 Solu
`tions with an organic amine Salt dissolved in an organic
`
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`US 2002/0110512 A1
`
`Aug. 15, 2002
`
`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 crys
`tallization of potassium nitrate from the Stripping Solution
`continuously.
`0012 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.
`0013 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 hydro
`chloric acid but not for any of the metal salts. While this
`proceSS has been exploited commercially, it lacks the Sim
`plicity and efficiency of the instant method. Large Volumes
`of liquids must be handled; crystallization, extraction, Sepa
`ration, and distillation processes are required to recover the
`desired Salts and Solvents. Volatile organic Solvents are
`utilized in the extraction process requiring Stringent envi
`ronmental and Safety Standards. The major plant utilizing
`this process has suffered serious fires, disrupting production
`for Significant periods of time.
`0014 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 carbon
`ate produced by electrolytic process) and requires Substan
`tial energy to recover the potassium nitrate from the Solu
`tion.
`
`0015. 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 and
`0.5% wt KNO) which must be neutralized by potassium
`hydroxide (KOH).
`0016 Manour et al discloses in U.S. Pat. No. 4,378,342
`a method of producing potassium nitrate by reacting potas
`sium chloride with nitric acid in an organic Solvent. The
`resulting potassium chloride is Separated from the Solution
`which contains hydrochloric acid, nitric acid and the Sol
`vents which are washed and recovered. The remaining
`aqueous Solution of hydrochloric acid contains Some nitric
`acid which is recovered by Solvent extraction producing a
`substantially nitrate free hydrochloric acid. Both the nitric
`acid and Solvent are Separated and returned to the process.
`This process is a refinement of Baniel et all and is thought to
`be practiced by Haife Chemical in Israel. The plant is quite
`
`large producing in excess of 300,000 tons of potassium
`nitrate per year. Nonetheless the proceSS is very capital
`intensive employing many unit processes including distilla
`tion, centrifrigation, refrigeration, and Several different
`trains of extraction. It is also Somewhat hazardous having
`had Serious fires in its Solvent recovery units. It is also a
`labor and energy intensive operation due to the complexity
`of the proceSS and the energy required for refrigeration,
`distillation, and drying operations.
`0017. A commercial process developed in the late 1960s
`for the Potash Division of American Metal Climax at
`Vicksburg, Miss. and still in existence under different own
`ership, reacts potassium chloride with 65% nitric acid and
`recycled Strong 81% nitric acid to produce a nitric acid
`Solution containing potassium nitrate which is recovered by
`Vacuum crystallization, drying, melting and prilling opera
`tions. Complex acid and nitrogen dioxide recovery Systems
`are required and low temperature fractionization to recover
`chlorine from reaction gases. This is an extremely capital
`intensive process. It is also labor and energy intensive
`because of the complexity of the operation and the Signifi
`cant number of unit operations required. All of the prior art
`processes for producing potassium nitrate are expensive or
`difficult to perform.
`0018 Processes that utilize nitric acid at elevated tem
`peratures require Specially constructed equipment to handle
`the highly corrosive reactants, and further, elevated reaction
`temperatures require high-energy inputs. Other prior art
`processes Suffer from low yields of potassium nitrate or an
`impure product. Thus, there is a need for an inexpensive and
`continuous process for producing large quantities of potas
`sium nitrate at ambient temperatures. All of the processes
`outlined in the prior discussion lack the relative simplicity,
`energy, and operating efficiency of the instant invention
`from which the finished product retains essentially the same
`size distribution and purity of the original Solid feeds. The
`reaction proceeds rapidly and to completion. No external
`heat Source is required and the proceSS is continuous with
`halides or Sulfates being fed in the top bed and nitrates
`extracted from the bottom; fluidization and gravity provid
`ing the means by which the product flows from bed to bed
`while counter current flow of gas and or air (the fluidizing
`medium) permits the strongest nitrogen dioxide gas stream
`to contact the most nearly converted feed while the most
`dilute gas contacts the raw feed thus minimizing contami
`nation of the effluent nitrosyl chloride/chlorine gas with
`nitrogen dioxide or nitric oxide gas.
`
`SUMMARY OF THE INVENTION
`0019. The primary object of this invention is to eliminate
`the problems and inefficiencies of the prior art by providing
`a new process by which metal halides and or Sulfates may be
`reacted with nitrogen dioxide to produce Solid compounds
`containing nitrate anion while liberating a gaseous com
`pound containing the metal alkalication.
`0020. A further object of this invention is to provide a
`new highly energy efficient process for Said reactions.
`
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`US 2002/0110512 A1
`
`Aug. 15, 2002
`
`0021. A further object of this invention is to provide a
`new simple and cost effective process for the manufacture of
`Said compounds.
`0022. A further object of this invention is to provide the
`conditions whereby the new method may be effectively
`performed to produce the Said reactions.
`0023. A further object of this invention is to provide a
`granular product which may be readily blended with existing
`products or may be further granulated to permit coating with
`a slow release coating.
`0024. A further object of the invention is to provide a cost
`effective method to produce a high quality potassium nitrate
`and/or calcium nitrate.
`0.025 A further object of the invention is to provide a
`method to convert gypsum waste from phosphate operations
`to a useful fertilizer, while producing Sulfur dioxide or
`Sulfuric acid for recycle to the operation.
`0026. The invention consists of certain novel features and
`a combination of parts hereinafter fully described, illustrated
`in the accompanying drawings, and particularly pointed out
`in the appended claims, it being understood that various
`changes in the details may be made without departing from
`the Spirit, or Sacrificing any of the advantages of the present
`invention.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`0.027
`FIG. 1 is a elevational representation of a fluidized
`bed;
`0028 FIG. 2 is a side elevational view of fluidized beds
`arranged in Vertical configuration; and
`0029 FIG. 3 is a schematic representation of a number of
`fluidized beds arranged in Series connection.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`0030) Referring now to FIG. 1, there is disclosed a
`fluidized bed 10 comprised of a plurality of particulates or
`an aqueous Slurry of particulates 11 Suspended above a
`perforated plate 12 in a container 15. The container 15 is
`shown as a representation of a cylindrical pipe but may be
`of any desired shape. The container 15 is provided with an
`inlet gas 16 below the perforated plate 12 and a gas outlet 18
`above a disengaging Zone 17. The disengaging Zone 17 is the
`area above the perforated plate 12 necessary for any par
`ticulates or liquid entrained in the gas flowing through the
`perforated plate 12 to fall back into the fluidized bed 10.
`0031) A fluidized bed, as defined in “Fluidization”
`Kearns ed., McGraw Hill 1976, is defined as “dry solid
`particles kept in a randomly moving, Suspended and mod
`erately agitated condition by a stream of pressurized gas
`distributed through the bed so that the particles flow in a
`manner Similar to a gently boiling liquid. This is usually
`accomplished by placing the particles on a perforated plate
`and a pressurized gas is forced through the perforations in
`
`the plate and the gas causes the particles to fluidize.' True
`fluidized bed technology is well known in the art. This
`method may also be applied to a slurry in a manner Similar
`to that employed in the ammonia distillation column in the
`Solvay Process where a slurry of calcium hydroxide is
`reacted with proceSS liquors containing ammonium chloride
`to produce calcium chloride and recovering ammonia by
`Steam distillation all in the same vessel.
`0032 Referring now to FIG. 2, there is another embodi
`ment of the present invention in which a plurality of beds is
`arranged in Vertical configuration. More particularly, a reac
`tor 25 includes a cylindrical vessel 26 having a gas inlet 27
`and a gas outlet 28. A particulate or slurry inlet conduit 30
`houses an inlet Screw mechanism or conduit 31 and a
`particulate or Slurry outlet 35 houses a product Screw or
`other exiting means mechanism 36. The particulate or slurry
`inlet conduit 30 is positioned near the top of the reactor 25
`and the particulate or slurry outlet conduit 35 is positioned
`near the bottom of the reactor 25. The reactor 25 includes a
`gas plenum 40 in communication with the gas inlet 27 and
`an exhaust gas plenum 45 in communication with the gas
`outlet 28. There is a plurality of perforated plates 50A, 50B,
`50C and 50D, each of which support a corresponding
`fluidized bed 55A, 55B, 55C, 55D thereupon comprising a
`plurality of particulates or Slurries in a State of fluidization
`due to the gas entering through the gas inlet 27 and distrib
`uted through the hot gas plenum 40 and thereafter through
`the individual perforated plates, as shown in FIG. 2. Each of
`the fluidized beds 55A through D is provided with a par
`ticulate or slurry overflow conduit 60A-D that communi
`cates Slurry or particulates from each of the fluidized beds to
`the next adjacent downwardly positioned bed. For instance,
`conduit 60A communicates particulates or slurry from bed
`55A to bed 55B and conduit 60B provides communication of
`particulates or slurries from bed 55B to 55C and so on. The
`particulate or slurry overflow conduit 60D provides com
`munication between the bed 55D and the particulate or
`slurry outlet conduit 35. While the reactor 25 includes
`internal overflow conduits 60A-D, external conduits can
`also be employed.
`0033 AS will be hereinafter described, nitrogen dioxide
`gas Supplemented with nitrogen or dry air and oxygen if
`necessary is introduced through the inlet 27 and flows
`upwardly at a sufficient pressure to fluidize the beds 55D
`through 55A. As may be understood, the nitrogen dioxide
`concentration in the inlet gas is at its highest value Since
`chemical reactions in each bed with halide or Sulfate par
`ticulates or Slurry reduces the concentration of nitrogen
`dioxide in the gas while increasing the concentration of
`nitrate in the particulates or slurry until in the upper most
`bed 55A, the concentration of the nitrogen dioxide in the gas
`flowing therethrough is at the lowest Such that the gases in
`the exhaust gas plenum 45 is Substantially free of nitrogen
`dioxide. Nitrate concentration in the bed 55D is at the
`greatest as most if not all of the halide or Sulfate has been
`converted to the corresponding nitrate.
`0034. Although the figure shows the use of potassium
`chloride particulates flowing into the bed 55A through the
`
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`US 2002/0110512 A1
`
`Aug. 15, 2002
`
`particulate inlet 30 and potassium nitrate flowing out of the
`bed 55D through the particulate outlet conduit 35, this is for
`purposes of illustration only. It should be understood that the
`particulates may be a slurry and that the chloride may be a
`Sulfate or oxide and the metal may be any one of potassium,
`Sodium, calcium, or mixtures thereof.
`0035) Referring now to FIG. 3, there is shown in dia
`grammatic representation, a System 70 comprised of a
`plurality of reactors 75A, 75B, 75C and 75D, each con
`nected by gas and particulate conduits as will be described.
`More particularly, there is provided in each reactor 75A-D a
`corresponding gas inlet plenum 76A-D, a gas outlet plenum
`77A-D and Solids inlet 78A-D. The flow of materials is the
`same for system 70 as previously described with respect to
`the reactor 25 but in the system 70, there are a number of
`discrete reactors rather than a Single vessel as previously
`described. More particularly, the system 70 includes a gas
`inlet 80 in communication with the gas inlet plenum 76D of
`reactor 75D. The gas inlet 80 is in communication with a
`Source of nitrogen dioxide gas and in those reactions where
`it is necessary with a Source of nitrogen or dry air or oxygen
`83. Recycle of a Small percentage of the effluent gas may be
`required to Supplement fluidization. The recycle gas if
`required is compressed by a blower and combined with the
`nitrogen dioxide gas through the gas inlet conduit 80 to the
`plenum 76D for flow through the various perforated plates
`79A-D in each of the reactors to form the corresponding
`fluidized bed in each of the reactors 75A-D. The product
`outlet 90 removes the formed metal nitrate from the reactor
`75D whereas the gas outlet 77A conducts the gases produced
`or water vapor out of the endmost reactor.
`0036. It is also possible to employ a horizontal vessel
`with a Series of discrete fluidized bed compartments to
`accomplish the reaction Since the fluidization of the beds
`will permit counter current flow of gas and Solids.
`0037. While the preferred embodiment of the instant
`invention is to use a moistened particulate (up to approxi
`mately 2.5% moisture) and nitrogen dioxide gas it is pos
`Sible to use an aqueous slurry of the particulate (up to 66%
`water) and either nitric acid vapor or nitric oxide gas to
`accomplish conversion of the metal particulates to the
`corresponding nitrate. These variations confirmed by experi
`mental work produce a combination of off gases which
`require a more complex recovery System. Fluidization of the
`Slurry is possible by maintaining the desired gas Velocity
`through the perforated distribution plates.
`0.038 AS can be seen therefore, there are a variety of
`apparatus and Systems which can accommodate the present
`reaction but in all cases, it is necessary to employ true
`conventional fluidization and to have the particulates flow
`countercurrent to the fluidizing gas and for the concentration
`of nitrogen dioxide to diminish as the gas flows through
`Successive beds while the concentration of Solid nitrates
`increases as the particulates flow in countercurrent relation
`ship to the gas flow. The present invention is directed to a
`method of producing metal nitrates of high quality for
`commercial use. The invention is based on the reaction of
`
`nitrogen dioxide gases in contact with chlorides, Sulfates,
`and oxides of certain members of the alkali metals, alkaline
`metal earths and transition metals in Shallow beds main
`tained in a conventional or true fluidized State, So as to
`rapidly convert without Significant particle size degradation,
`the Solid particulates to Solid compounds consisting of the
`anion of the metal and the nitrate cation while liberating
`water vapor and nitrosyl chloride and chlorine in certain
`instances. By shallow beds is meant a bed having a depth of
`about one to four feet. This new method allows a heretofore
`unknown energy cost efficient and continuous method for
`producing Said compounds.
`0039 The instant method consists of contacting moist
`ened metal chlorides, Sulfates or oxides with nitrogen diox
`ide gas at a moderately elevated temperature in a Series of
`shallow fluidized beds. High conversion (91%) can be
`achieved in a very short period of time, i.e. from Several
`minutes to one to two hours depending on the temperature
`of the gas and fluidized Solids and concentration of nitrogen
`dioxide in the gas, with the liberation of nitrosyl chloride
`and (postulated) Sulfur dioxide, or water depending on the
`initial Solid feed.
`0040 Having described the basic concepts of the instant
`invention reference is made to the following examples,
`which are provided to illustrate but not limit the preferred
`method of the invention and other similar methods of
`producing metal chlorides.
`
`EXAMPLE 1.
`0041. The preferred embodiment of the instant invention
`is to introduce nitrogen dioxide gas and a Small quantity of
`water vapor, preferably at a temperature in the range of 80
`to 600 F. into a series of shallow beds, one to four feet deep,
`of potassium chloride. The nitrogen dioxide gas is preferably
`produced as a product of a commercial operation or by
`oxidation of ammonia. It is apparent that with proper reactor
`design as is known to one skilled in the art, variable bed
`depths as previously described, counter current gas and Solid
`flow and true fluidization, continuous production rates often
`or more tons per hour can be maintained even though
`residence time of Solids in the reactor may be as much as two
`hours.
`0042. The apparatus may consist of a vertical column
`containing a number of perforated plates, connected to each
`other either by internal or external sealed overflows. The
`nitrogen dioxide gases and possibly nitrogen, dry air, or
`oxygen if required are fed into the bottom of the column
`below the bottom-perforated plate. Solid potassium chloride
`moistened to about 2.5% moisture is introduced on a con
`tinuous basis into the top plate. The depth of the bed is
`controlled by the height of the overflow above the perforated
`plate. The solids because of true fluidization behave like a
`liquid and flow down the overflows into the next lower plate,
`which is Sealed to prevent gas up flow by the Solids in the
`overflow connection and in the lower bed. The process
`continues plate by plate until the particulates reach the last
`plate from which they flow into a Seal conveyor. At each
`
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`Aug. 15, 2002
`
`plate, gas and particulates are intimately contacted due to the
`boiling action caused by the fluidization of the particulates.
`Heat eXchange between particulates and gas is exceptionally
`efficient due to this contact in which the reaction proceSS
`proceeds and reaction heat is liberated. Inter-plate cooling
`either external or internal may be required to prevent tem
`perature excursions. A head differential exists between the
`inlet and exit location at each plate resulting in the flow of
`the Solids from inlet to exit. The maximum concentration
`differential between the nitrate in the particulates and the
`nitrogen dioxide gas is maintained in each plate as the
`particulates flow down the reactor, and the gas proceeds
`upward. This is due to the depletion of the nitrogen dioxide
`in the gas Stream as it reacts with the particulates which are
`converted to nitrates. At the bottom plate the maximum
`nitrogen dioxide gas concentration contacts Solid particu
`lates totally or almost totally converted to the nitrates. The
`high concentration nitrogen dioxide gas results in conver
`
`0044) Higher gas temperatures may be employed to
`increase the reaction rate, however, the reaction is exother
`mic, So that rather than adding heat, inter plate cooling
`means either internal or external may be necessary to
`mitigate temperature excursions. Operation at a lower tem
`perature is not a Significant impediment Since with more
`than one bed, proper reactor design, as is known to one
`skilled in the art, variable bed depths as previously described
`and conventional fluidization, continuous production rates
`often or more tons per hour can be maintained even though
`residence time of Solids in the reactor is as much as two
`hours.
`0045. In a series of experiments designed to determine
`the effect of temperature and moisture addition it was found
`that best results were obtained at moderate temperatures and
`about 2% to 3% water. Oxygen was added in the event nitric
`oxide was present, however it appeared to have little or no
`effect. Some of these results are presented below.
`
`% HO
`Run added
`Time
`tO
`Date (min) crystals
`4f15
`120
`O%
`4/23
`120
`O%
`4/29
`120
`O%
`5/6
`40
`3%
`5/8
`2O
`3%
`5/21
`Aborted
`test
`2%
`1%
`3%
`3%
`
`5/21
`5/23
`5/27
`6/4
`
`2O
`60
`70
`50
`
`Fluidization Test Variables
`
`Avg.
`Avg.
`Inlet
`NO,
`Air
`Rate
`Temp
`(F) (Ib/min)
`450-575
`O.34
`280-340
`O.34
`286-355
`O.28
`106-108
`O.24
`98
`0.44
`
`Batch
`size (#
`yrs)
`5
`5
`5
`5
`5
`
`Avg.
`HO
`Rate
`(Ib/min)
`O.O68
`O.47
`1-2 psig
`O.OO
`1 psig
`
`Avg.
`O
`Rate
`(Ib/min)
`O.52
`0.27
`O.13
`O.OO
`0.44
`
`%
`KNO.
`6.88%
`11.0%
`12.15%
`21.64%
`18.37%
`
`5
`2.5
`2
`2
`
`74-78
`85-93
`94-105
`235-272
`
`O.48
`O.39
`O.39
`O.29
`
`O.OO
`O.OO26
`O.OO12
`O.O54
`
`14.54%
`O.65
`5.72%
`O.62
`8.90%
`O.63
`N = 0.34 7.82%
`
`Test #
`3-2
`3-3
`3-4
`3-5
`3-6
`3-7
`
`3-8
`3-9
`3-10
`3-11
`
`Sion of the remaining particulates to their respective nitrate.
`At the top Several plates gas almost depleted of nitrogen
`dioxide contacts the particulate feed and leaves the reactor
`depleted of nitrogen dioxide. Nitrosyl chloride gas if pro
`duced in the Sequential fluidized reaction Zones leaves the
`reaction column and is recovered for processing. The reac
`tion is based on the findings of Whittaker, et all as published
`in Industrial and Engineering Chemistry Vol. 23, No. 12,
`December 1931, in which he demonstrated that nitrogen
`dioxide gas when passed through a Small laboratory fixed
`bed of potassium chloride in the presence of a Small amount
`of water was completely converted to potassium nitrate
`within a period of three hours. The reaction is indicated as
`follows:
`
`0.043 where the reaction products are potassium nitrate
`and nitrosyl chloride, which can be oxidized to chlorine gas
`which can be recovered and nitrogen dioxide which can be
`recycled to the reacting vessel.
`
`EXAMPLE 2
`0046) Another example which demonstrates a less pref
`erable embodiment of the current invention requires use of
`an aqueous slurry of Solids (particularly if they are relatively
`insoluble) into which is introduced nitrogen dioxide gas. The
`Slurry bed is maintained in a fluidized State on a perforated
`Support plate through which the gas passes. Plate design and
`gas flow velocity prevents bypass through the perforations
`while bed depth is maintained by the height of the overflow
`above the plate Surface. Air or nitrogen may be used to
`sustain fluidization while slurry density may vary up to 50%
`Solid or higher although higher particulate concentrations
`are preferred. Operation and process is similar to that
`previously outlined for the moistened solid described in
`Example 1, that is, the requirement of counter current flow
`of gas and slurry and fluidized (agitated), beds is essential.
`The Slurry is filtered or centrifuged on exiting the apparatus,
`and neutralized with a Sodium hydroxide or Soda ash wash.
`The filtrate is recycled to provide a slurry for new feed
`material while a Small purge is maintained to minimize
`unwanted byproducts. This embodiment is effective for
`metal oxides and Sulfates.
`
`Page 9 of 10
`
`

`

`US 2002/0110512 A1
`
`Aug. 15, 2002
`
`CaSO4
`
`Test
`
`Run 96 HO for % CaSO for Batch
`Date Time
`slurry
`slurry
`size (g)
`
`Avg. NO2
`Inlet Temp.
`(°F)
`
`3-42*
`3-43* *
`3-44* * *
`
`9/5
`9/5