Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
  • C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
  • C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
  • C01D5/06—Preparation of sulfates by double decomposition

Definitions

• the present invention relates to processes for producing potassium and sodium sulfate, and, more particularly, to processes for producing potassium sulfate and sodium sulfate from potash and hydrated sodium sulfate.
• Glauber's salt Na 2 SO 4 *10H 2 O.
• Natural Glauber's salt deposits (“mirabilite") exist in cold climates. Glauber's salt can also be obtained by cooling a natural brine, a solution obtained by solution-mining, or a process stream. The cooling is effected
• Anhydrous sodium sulfate is typically produced from Glauber's salt by evaporative crystallization in a multiple-effect or mechanical vapor recompression (MVR) evaporator, by dehydration in a rotary dryer, or by
• Glauber's salt often contains insoluble matter which is unacceptable in high-grade anhydrous
• Glauber's salt can be melted to produce low quality "salt cake” grade sodium sulfate. The saturated mother liquor is then filtered and evaporated to produce high- grade sodium sulfate.
• Stage 1 of composition 'a' (at 25°C) (see Figure lb), is cooled to about 0°C ( Figure la), precipitating Glauber's salt for reuse and possibly some sodium chloride, depending on the water balance in the system.
• the sodium chloride is
• the hot brine is reacted with Glauber's salt recovered from the cooling crystallization stage to produce a glaserite suspension, which is returned to Stage 1.
• the quantity of water added to the reaction stages is set such that glaserite
• Stage 1 Figure lb
• the glaserite is then reacted with potash and water to produce the potassium sulfate product and a liquor of composition V.
• the liquor is returned to Stage 1.
• the effluent liquor from Stage 1 is evaporated at high
• Type I processes are particularly complex, requiring a large
• Glauber's salt is a relatively inexpensive source of sodium
• the additional water from the Glauber's salt decreases the conversion in the reaction stages and increases the sulfate composition of the Stage 1 effluent.
• Some cyclic processes cannot be operated using Glauber's salt while others require additional unit operations (e.g., evaporation).
• Another inexpensive source of sodium sulfate is aqueous sodium sulfate.
• the water-to-sodium sulfate ratio in aqueous sodium sulfate is higher than that of Glauber's salt, such that the problem of excess
• a process for producing potassium sulfate or potassium sulfate and sodium sulfate from potash and a sodium sulfate/water source comprising the steps of: (a) subjecting a sodium sulfate source to conversion with potash in an aqueous medium to yield glaserite precipitate and a first mother liquor; (b) converting the glaserite precipitate with potash and water to produce a potassium sulfate precipitate and a second mother liquor; (c) returning the second mother liquor to step (a); (d) evaporating the first mother liquor such that a sodium chloride and anhydrous sodium sulfate solids mixture is precipitated in a third mother liquor; (e) subjecting the solids from step (d) to a sodium sulfate/water source to produce anhydrous sodium sulfate; and (f) returning the third mother liquor for conversion to potassium salts.
• the source of sodium sulfate is Glauber's salt, semi-anhydrous sodium sulfate, i.e., a mixture of sodium sulfate and Glauber's salt or partially hydrated sodium sulfate, or any sodium sulfate solution which can yield sodium sulfate in the presence of sodium chloride, such as vanthoffite solution.
• Glauber's salt semi-anhydrous sodium sulfate
• semi-anhydrous sodium sulfate i.e., a mixture of sodium sulfate and Glauber's salt or partially hydrated sodium sulfate
• any sodium sulfate solution which can yield sodium sulfate in the presence of sodium chloride, such as vanthoffite solution.
• the invention takes advantage of the fact that the solubility behavior of potassium chloride differs greatly with the
• the present invention also makes use of the fact that the solubility of sodium sulfate decreases with increasing concentration of sodium chloride.
• sodium chloride/sodium sulfate solid mixture produced at high temperature can be added to the sodium sulfate feed source, such that the
• the sodium sulfate can be used to produce potassium sulfate, and any excess material is a valuable co-product.
• FIGs. la, lb and lc are solution phase diagrams for Na 2 S0 4 /2NaCl/K 2 S0 4 /2KCl/H 2 0 system at 0°, 25° and 100°C, respectively;
• FIG.2 is a block diagram schematically depicting processes according to the present invention.
• the present invention is of processes for the co-production of
• FIG. 2 illustrates several embodiments of the present invention.
• reaction 10 and sodium sulfate 46 and/or 76 to potassium sulfate 42 is carried out in two reaction stages.
• the reaction can be effected at 15-100°C. But, while reaction kinetics and crystal growth rate improve with increasing temperature, equilibrium data
• Potash 10 sodium sulfate 46 and/or 76, stream 28 from the recovery stage (described below), and brine 40 from the glaserite decomposition stage (described below) are introduced.
• the sodium sulfate source is primarily
• Glauber's salt and/or aqueous sodium sulfate can be added (not shown).
• the term 'potash' is meant to indicate any potassium chloride containing material including, for example, sylvinite.
• the sodium sulfate and potash dissolve, generating a supersaturation with respect to glaserite, such that glaserite is precipitated.
• the system can also be supersaturated with respect to sodium chloride, such that some sodium chloride is co-precipitated.
• the slurry is
• the mother liquor 26 has the following composition in weight %: potassium: 2.5-
• the mother liquor composition corresponds to the points on and above the
• the glaserite decomposition stage 16 is performed at 15-60° C, with the preferred temperature range being 20-40°C, due to the same considerations delineated in the first stage. Potash 10 and water 18 are
• the potassium sulfate slurry 52 is dewatered and washed 22.
• the wet product 42 is then dried.
• the mother liquor 40 removed from the reactor of the glaserite decomposition stage 16 is returned to the glaserite production stage 14; the
• stages 14, 16 and 22 may be effected in a single countercurrent differential contactor.
• the brine can be filtered (not shown) prior to evaporation
• the potassium-enriched brine 28 is cooled 70 and returned to the glaserite decomposition stage 14.
• the sodium salts 30 produced during the evaporative crystallization are subjected, in a suitable vessel 72, to a low-quality and/or water-containing source of sodium
• sulfate 12 such as aqueous sodium sulfate, Glauber's salt, vanthoffite, or similar, with the addition of water as necessary.
• sulfate/water source aqueous sodium sulfate/water source.
• Glauber's salt crystallized from clear brines is generally free of such impurities and can be added directly 33 to vessel 72.
• a Glauber's salt containing impurities 35 can first be melted in a suitable
• melter 34 with the aqueous phase 74 being filtered before being introduced to the stream 30, and the concentrated solids 76 being used to produce glaserite in the first reaction stage 14.
• Another alternative is to feed all or a portion of solid phase 76 directly into filtering and washing vessel 82.
• the solid sodium chloride from stream 30 is not in equilibrium in the sulfate-rich medium 72, and dissolves.
• the dissolved sodium chloride reduces the solubility of sodium sulfate, such that sodium sulfate is precipitated.
• the sodium sulfate slurry 44 is filtered and washed 82
• vessel 72 containing under 20 mole% sulfate, is discharged, utilized in

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Inorganic Chemistry (AREA)
• Preparation Of Compounds By Using Micro-Organisms (AREA)
• Enzymes And Modification Thereof (AREA)

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• 1994
  • 1994-11-28 US US08/348,115 patent/US5529764A/en not_active Expired - Lifetime
• 1995
  • 1995-11-13 RU RU97112472/12A patent/RU2176218C2/ru active
  • 1995-11-13 DE DE69514830T patent/DE69514830T2/de not_active Expired - Lifetime
  • 1995-11-13 EP EP95940022A patent/EP0796222B1/en not_active Expired - Lifetime
  • 1995-11-13 WO PCT/US1995/014960 patent/WO1996016899A1/en not_active Ceased
  • 1995-11-13 ES ES95940022T patent/ES2140723T3/es not_active Expired - Lifetime
  • 1995-11-13 MX MX9702649A patent/MX9702649A/es unknown

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