Abstract: Control of sulfate and perchlorate impurity levels is provided in a procedure for manufacturing crystalline sodium chlorate by electrolyzing an aqueous solution of sodium chloride and crystallizing sodium chlorate from the resulting aqueous solution of sodium chlorate and sodium chloride. The mother liquor from the crystallization, or a portion thereof, is treated simultaneously with calcium chloride to remove sulfate ions by precipitating calcium sulfate and with potassium chloride to remove perchlorate ions by precipitating potassium perchlorate.

Abstract: An improved process for converting particles containing calcium sulfide into calcium oxide by subjecting the particles to repeated cycles of oxidation and reduction. The impenetrable layer of calcium sulfate which forms during the oxidation phase of each cycle is destroyed by the subsequent reducing phase. By repeating the cycle many times, the particles are converted completely into calcium oxide at a reasonable temperature of about 1000.degree. C. The process can be carried out in either fixed bed, moving bed, or fluidized bed reactors by varying the composition of the gas supplied to the reactors in a periodic manner. Alternatively, the process can be conducted in fluidized bed reactors which have separate oxidizing and reducing zones located one above the other. In one design air is supplied through a gas distributor at the bottom of the fluidized bed to create an oxidizing zone in the lower part of the bed.

Abstract: A wet scrubbing method for removal of sulfur dioxide from a gaseous stream uses a magnesium-enhanced lime scrubbing aqueous slurry, where a solids content in the aqueous slurry in a wet scrubbing unit is maintained at an amount of between 13 to 20 percent by weight. A bleed stream is removed from the aqueous scrubbing slurry at a pH of between 4.5-5.6 and fed to an oxidizing unit wherein calcium sulfite is oxidized to gypsum. The gypsum and residual solids in the discharge from the oxidizing unit are separated to produce a clarified solution, which is returned to the wet scrubbing unit.

Abstract: A process and plant for drying and then separating moist salts, such as magnesium sulfite, in which the moist magnesium sulfite is heated to a temperature greater than or equal to about 200.degree. C. in a dryer and the passed through a solid materials lock into a separating plant. The dryer is heated by a circulating stream of exhaust vapors which is heated in a heat exchanger by exhaust gas generated in the separating plant so that the water of crystallization of the magnesium sulfite as well as residual humidity is eliminated during the drying process. Vapor-free acid anhydride, usually sulphur dioxide, is prepared in the separating plant from the dehydrated salt and a metal oxide, e.g., MgO, is recovered or otherwise used. The acid anhydride may be liquified and has a large degree of purity.

Abstract: The invention discloses a wet process flue gas desulfurization apparatus and method for use with a tank oxidation system. The apparatus comprises: an absorption tower having a slurry containing a calcium compound which is supplied to the bottom tank, a circulation pump for feeding the slurry in the tank into a flue gas inlet in an upper part of the absorption tank to be in contact with flue gas, and air feed means for feeding air for oxidizing into the tank, thereby absorbing and oxidizing sulfur dioxide in the flue gas by the slurry to obtain gypsum as a byproduct, wherein a vacuum type belt filter is disposed along an outer surface of a side wall of the absorption tower, and part of the slurry that is discharged from the circulation pump is led into the belt filter to be dehydrated, thereby separating and recovering gypsum.

Abstract: A flue-gas scrubbing-liquor regeneration process that is based on contacting N-S compounds contained in a flue-gas scrubbing liquor with a lime/limestone solution in a double draw-off crystallizer under suitable pH conditions for precipitating calcium salts of N-S compounds. The precipitated crop is filtered and then hydrolyzed in a sulfuric acid environment to produce gypsum and ammonium sulfate in solution. The hydrolyzed slurry is filtered and the filtrate is neutralized with lime to liberate ammonia gas that is then sparged through a sulfuric acid solution to cause the precipitation of commercial-grade ammonium sulfate.

Abstract: Process for producing alpha-hemihydrate calcium sulfate from FGD sludge comprising treating an aqueous slurry of the sludge with a stabilizing effective amount of a stabilizing polyhydric alcohol to stabilize the .alpha.HH to obtain .alpha.HH crystal growth, at atmospheric pressure and a temperature greater than 80.degree. C. and a pH selected from 3 to 6. The polyhydric alcohol may be selected from ethylene glycol, glycerol and a carbohydrate. The process offers a commercially viable method of making .alpha.HH from FGD sludge wastes.

Abstract: A method and apparatus for forming a slurry of metal oxide in a mineral or the like (e.g. of magnesium or calcium oxide) and introducing the slurry to an acid neutralization process in a time period before substantial hydration of the oxide has occurred.

Abstract: A method of wet flue gas desulfurization of combustion gases that incorporates both calcium scrubbing with forced oxidation and ammonia scrubbing of the gas in a scrubber tower. The end product or result from such a process is gypsum and ammonia sulfate which may be used in agriculture.

Abstract: The process for purifying gypsum suspensions, particularly those formed in a flue gas desulfurizing plant, includes feeding the gypsum suspension (9) to a first hydrocyclone (1), which is operated to produce an underflow (11) with a comparatively high underflow concentration and an overflow fed to a collecting tank (2). The underflow (11) of the first hydrocyclone stage is further diluted to a form another underflow with a lower solids content in a suspension tank (3) and then is fed to a second hydrocyclone stage (4), the overflow of which is also fed to the collecting tank (2). Depending on purity of the gypsum required or attained, the gypsum contained in an underflow (14) of the second hydrocyclone stage (4) is either immediately dewatered and removed or is first fed to one or more hydrocyclone stages, which operate analogously. The combined overflows (15) of the first and second or further hydrocyclone stages are fed from the collecting tank (2) to a third hydrocyclone stage (6).

Abstract: This invention provides new inorganic composite materials for hard tissue replacement. The new composite material comprises solid material of calcium sulfate which is fully or partially converted to calcium phosphate from aqueous solution. This composite material has good biocompatibility and controllable resorption, and will be very useful for bone substitute material in orthopaedic and dental applications. The fully converted material which comprises mainly apatite calcium phosphate is also useful for chromatography application. A process to prepare these new composite materials is also described.

Abstract: A process for producing hydrogen and/or hemihydrate calcium sulphate from calcium sulphite. Waste solid containing calcium sulphite and other calcium salts is treated by the addition of aqueous sulphur dioxide solution or sulphuric acid solution to produce a liquid phase product. The liquid phase product may be separated from any remaining solid phase material and then subjected to the addition of sulphuric acid in a second step, wherein calcium sulphate hemihydrate is produced. The addition of sulphuric acid to the liquid phase results in the evolution of sulphur dioxide which may be used as such or in sulphur dioxide electrolysis cells in order to produce hydrogen and sulphuric acid. An especially unique feature of the process is that the sulphuric acid produced in generating hydrogen can be recycled to the step where the calcium sulphate crystals are produced.

Abstract: Both the drying and also the removal of the water crystalization take place carefully in a respective fluidized bed apparatus (A, B) without any danger of overheating. This is achieved by a complete homogenous fluidization through indirectly heated hot gas. A substantial quantity of energy is transferred via heat exchanger systems (4 or 12) in the fluidized layer. These are heated by heat carrying media. The constructional design of the fluidized bed apparatuses (A, B) which have a rectangular base outline ensures a narrow dwelltime spectrum and a pronounced temperature/moisture profile without the aid of differentially fluidized chambers. Because of the comparatively cold infeed zone and the careful heating which thereby arise the characteristics of the crystals are favourably influenced. The product is characterized by high quality homogenity. In the case of the calcining of moist gypsum no undesired gypsum modifications arise.

Abstract: A cyclic process of subjecting calcium sulfide particles to alternating oxidizing and reducing conditions. The impenetrable shell of calcium sulfate which forms during the oxidation phase of the cycle is destroyed by the subsequent reducing phase. By repeating the cycle many times the particles are converted completely into calcium oxide at a reasonable temperature of about 1000.degree. C. The process can be carried out in a fluidized bed reactor either by maintaining both oxidizing and reducing zones within the same fluidized bed or by varying the gas phase throughout the fluidized bed in a periodic manner.

Abstract: A simple process for preparing acicular calcium sulphate dihydrate is provided in which a slurry of calcium carbonate containing 100 to 800 grams per liter calcium carbonate is mixed with a solution of sulphuric acid containing 80 to 500 grams per liter sulphuric acid in proportions which produce a calcium sulphate slurry having a pH from 0.5 to 1.5. The process can be used to neutralise by-product sulphuric acid from the preparation of titanium dioxide with crushed limestone. Preferably the calcium sulphate slurry is stirred after formation to reduce the level of unreacted carbonate. The calcium sulphate produced has an aspect ratio of at least 4:1 and has excellent properties for use in paper. The process enables the production of acicular calcium sulphate without employing special crystallisation procedures.

Abstract: This invention relates to an improved process for producing gypsum calcium sulfate dihydrate flakes from powdered gypsum calcium sulfate dihydrate obtained from the desulfurization of flue gas by the wet limestone process. The flakes have sufficient size and strength such that the gypsum calcium sulfate dihydrate can be handled and processed in conventional equipment commonly used by wallboard manufacturers and others in the construction industry, The intermediate calcium sulfate dihydrate from the desulfurization process is dewatered to about 5 to 12% by weight and then compressed into a thin sheet under a compaction or compression load of 4 tons force to 15 tons force per linear inch of sheet width. A linear speed of from 0.5 to 2.5 feet per second is maintained during compaction providing a compaction residence time of from about 0.2 to 1.2 seconds.

Abstract: The invention relates to a method for separating sulphate from an aqueous electrolyte in an alkali metal chlorate process, thereby reducing the operating cost and increasing the possibility of further closing the electrolytical production of alkali metal chlorate. Calcium ions are added to a portion of the electrolyte, for precipitating calcium sulphate. By adjusting the pH within the range of from 4.6 up to about 7, and combining the temperature, content of ions and the molar ratio between sulphate and calcium ions added in a suitable manner, the calcium sulphate will precipitate predominantly as gypsum and essentially without inclusions and/or co-precipitation of chromium-containing compounds or chlorate. The precipitate is subsequently removed from the portion of electrolyte, whereafter the thus purified portion of electrolyte is recycled to the chlorate process.

Abstract: Disclosed herein is a method for producing plasters that contain chloride contents of less than 0.5% by weight from calcium-containing impure products or residues having a high chloride content (e.g., about 10% or higher based on the total product or residue weight). The method does not require the addition of fly ash, SiO.sub.2 or Al.sub.2 O.sub.3. The method comprises temperature and water-mediated conversion of calcium chloride to calcium oxide in the calcium-containing product or residue using water, steam and/or substances that generate water to obtain calcium oxide and hydrochloric acid; and sulfating calcium components in the product or residue using oxygen and sulfur-containing, largely calcium-free substances. The product so obtained is an anhydride plaster which can optionally be hydrated.

Abstract: An improved composite material is produced by mixing gypsum and host particles of a stronger substance, such as wood fibers, in a dilute slurry; heating the slurry, under pressure, to convert the gypsum to calcium sulfate alpha hemihydrate; and substantially dewatering the hot slurry before rehydrating the hemihydrate back to gypsum. The resulting material is a homogoneous mass comprising gypsum crystals physically interlocked with the discrete host particles.According to a further aspect of the invention, an improved wallboard, having fire resistance, dimensional stability and excellent strength properties, is produced by compressing the composite mass before hydrating it to a final set.

Abstract: A method is provided for removing sulfur dioxide from a hot gaseous stream while directly producing .alpha.-hemihydrate gypsum from a scrubber effluent. A portion of an aqueous scrubbing medium containing calcium and magnesium sulfite is removed from a scrubbing unit and passed to a pressurized oxidation vessel where the sulfites are contacted with an oxidizing gas at an elevated temperature to convert calcium sulfite directly to .alpha.-hemihydrate gypsum and magnesium sulfite to magnesium sulfate. The .alpha.-hemihydrate is separated from the aqueous medium removed from the pressurized oxidation vessel.

Abstract: A wet scrubbing process for removing sulfur dioxide from combustion gases uses an aqueous slurry containing calcium components resulting from the slaking of lime, with the slaked lime formed by mixing lime with water containing a calcium sulfur-oxide salt. The presence of the calcium sulfur oxide salt in the slaking water results in a more easily dewatered sludge that is subsequently removed from the wet scrubbing system.

Abstract: Disclosed is a process for treating waste sulfuric acid generated from a process for producing titanium dioxide pigment by treating titanium slag with sulfuric acid. The waste acid is treated in a first step with a calcium-containing material to produce a gypsum suspension which is filtered and from which a filtrate is recovered. The filtrate is treated in a second step with a calcium-containing substance and clarification solids from the treatment of the titanium slag with sulfuric acid. A precipitate is produced in this second step which is subsequently filtered. The precipitate is suitable for disposal in a landfill.

Abstract: In a process for the conversion of calcium sulfate dihydrate originating in flue gas desulfurization units into an alpha-hemihydrate, a salt solution is used as a medium. The salt solution consists substantially of concentrated scrubbing liquid from the flue gas desulfurization process containing alkali-earth chloride in a chloride concentration of 10% to 60% by weight.

Abstract: A process for producing large, regularly-shaped crystalline gypsum solids in a wet calcium-based flue gas desulfurization system is provided. A chemical crystal modifier, preferably an organophosphonate, is added to the gypsum-containing solids slurry produced by the FGD process under forced oxidation conditions at an addition level which promotes the formation of large, regular gypsum crystals that are easily dewatered. The dewatered gypsum is useful in producing gypsum-based building products and the like.

Abstract: Novel basic aluminum chlorosulfate solutions, having a basicity ranging from 45% to 70% and wherein more than 80% of the SO.sub.4.sup.2- values are complexed, prepared, e.g., by reacting calcium carbonate with a chlorosulfuric solution of aluminum, are useful coagulating and flocculating agents for the removal of impurities from aqueous media, notably to prepare potable water therefrom; the water thus treated contains but trace amounts of residual aluminum values.

Abstract: A process for producing large, regularly-shaped crystalline calcium sulfite solids in a wet calcium-based flue gas desulfurization system is provided. A chemical crystal modifier, preferably an organophosphonate, is added to the calcium sulfite-containing solids slurry produced by the FGD process under inhibited oxidation conditions at an addition level which promotes the formation of large, regular calcium sulfite crystals that are easily dewatered.

Abstract: Nitrogen compounds are a source of soil acidity. In addition nitrates are a major factor in the leaching of other nutrient salts from soils. These salts are then replaced by the available hydrogen ions, rendering the soil even more acidic. Besides supplying nutrients, a desirable fertilizer should offset changes in soil acidity brought about by nitrification. Calcium carbonate accomplishes this. Unfortunately it has not been possible commercially to include calcium carbonate in a fertilizer. If CaCO.sub.3 particles are ground too large they do not dissolve along with the agricultural fertilizer nutrients. If CaO.sub.3 is pulverized to a state necessary for dissolution, because of its hygroscopic properties, it hardens or cakes. It is not sufficiently stable in admixture with the other fertilizer materials for commercial distribution. Herein a fertilizer is provided which improves the condition of the soil, and stimulates microbial activity in the soil.

Abstract: Disclosed is a method of removing fluoride and sulfate ions from an aqueous stream by adding calcium chloride and a source of phosphate ion to the stream to form a first precipitate of calcium sulfate and a compound of calcium, fluoride, and phosphate. The precipitate is separated from the aqueous stream and a source of carbonate ion is added to the stream to form a second precipitate which contains fluoride and calcium. The second precipitate is then separated from the aqueous stream.

Abstract: For the purposes of solving a problem due to a fly ash and HF in an exhaust gas, maintaining the activity of calcium carbonate as an absorbent, and recovering a high-purity gypsum, there is here provided a method for desulfurizing an exhaust smoke which comprises the steps of leading the exhaust gas containing the fly ash to a gas absorbing step, removing SO.sub.2 and the fly ash from the exhaust gas by the use of an absorbing solution slurry containing calcium carbonate as an absorbent in the gas absorbing step, and blowing air into the absorbing solution slurry circulating through the gas absorbing step to oxidize it and to thereby produce the gypsum, the aforesaid method being characterized by drawing a portion of the absorbing solution slurry therefrom, leading it to a magnetic field to separate and recover the fly ash from the absorbing solution slurry, and then returning, to the gas absorbing step, a portion or all of the absorbing solution slurry from which the fly ash has been separated.

Abstract: A process for preparing hydroxylammonium nitrate which comprises reacting a hydroxylammonium salt, e.g., the sulfate, with an aqueous solution of a nitrate salt, e.g., sodium nitrate, in the presence of an organic solvent, e.g., butanol, in which the hydroxylammonium nitrate is soluble and the by-product salts are insoluble.

Abstract: A process, and the product produced thereby, for the preparation of a waste solidification material from hardened fluorogypsum as a by-product of the manufacture of hydrofluoric acid by reacting fluorospar with sulfuric acid, removing hydrogen fluoride from the reaction product, slurrying the by-product with water, placing the slurried by-product fluorogypsum in settlement ponds until the fluorogypsum hardens, the hardened fluorogypsum having a pH of greater than about 5 to about 13, including heating the hardened fluorogypsum to evaporate substantially all water physically mixed with the fluorogypsum and further heating the fluorogypsum to reduce the water chemically bound to calcium sulfate in the fluorogypsum to form about 0.5% to about 9% by weight.

Abstract: A process for the preparation in an aqueous medium of purified calcium sulfate, with high whiteness, characterized in that it comprises:a) the formation of an aqueous solution by dissolution of impure hemihydrated calcium sulfate, at a concentration at most of 13.0 grams per liter (expressed in dissolved CaSO.sub.4) and at a pH of at least 5.

Abstract: The process for preparing calcium sulfate anhydrite II by heating a flowable powder of flue gas gypsum moistened with less than 20% by weight, and preferably with from 7 to 17% by weight, of diluted sulfuric acid, wherein the sulfuric acid content is from 0.5 to 7% by weight, and preferably 1 to 3% by weight of sulfuric acid, based on the total mixture, is carried out by that the total mixture is direct-fired or is rapidly heated with indirect heat exchangers having relatively high wall temperatures whereby it is heated at temperatures of from 80.degree. C. to 190.degree. C. and releases the water adherent from the diluted sulfuric acid as well as two moles of water of crystallization, and then the virtually anhydrous product is annealed at temperatures of from 80.degree. C. to 190.degree. C. for 0.3 to 24 hours.

Abstract: A method for treating produced gypsum and, in particular, a method for treating flue-gas desulfurization gypsum forms highly active, modifiable gypsum binders of high strength with simultaneously drying, deagglomerating and dehydrating. Pursuant to the invention, produced gypsum (flue-gas desulfurization gypsum), with a particle size ranging up to 200 .mu.m, to which 10% by weight of milled natural gypsum is optionally added, is dehydrated at a material temperature of 335.degree. to 363.degree. K. and at a pressure ranging from 2.5 to 8 kpa, the dehydration being concluded when anhydrite III constitutes 50% to 100% by weight.

Abstract: A method and apparatus for operating a limestone wet scrubbing flue gas desulfurization apparatus comprises first and second pH measuring devices connected respectively to a recirculation line in the scrubber and above the liquid holdup tray in the scrubber. The difference in the pH values measured at these two locations in the system is used to adjust the amount of air supplied to the sump or reaction tank of the scrubber to maximize oxidation in the scrubber and to avoid wasted airflow.

Abstract: A method for enhancing the efficiency of a thermal process such as calcination. The incoming solid particulate material is preheated in the conveyor by partially cooled exhaust vapors from the thermal processor. In passage through the conveyor, the cooled, intermediate temperature vapors contact, fluidize and heat the particulate solids to increase the available throughput of the system.

Abstract: Process for removing an industrial residue containing sodium sulphate, in which the sodium sulphate in the residue 7 is treated with a calcium salt 12 to precipitate calcium sulphate 13, which is sent to a rock salt deposit 15, from which an aqueous solution of sodium chloride 16 is withdrawn.The process applies to the residues from the desulphurization of fumes by means of sodium bicarbonate.

Abstract: In a wet lime desulfurization of exhaust gases containing SO.sub.2 and fly ash, a method and apparatus for treating absorbent solution slurry-containing fly ash includes diverting at least a part of the absorbent solution slurry containing fly ash particles, separating the diverted absorbent solution slurry by centrifugal separation into the solid gypsum component and a liquid component of a suspension containing fine fly ash particles, adjusting the pH value of the suspension containing fine fly ash particles remaining in a filtrate to 6 to 9 by adding an alkali, supplying the pH adjusted suspension to a thickener, removing concentrated sludge from the thickener, passing overflow H.sub.2 O from the thickener to a limestone slurry tank, and passing slurry from the limestone slurry tank to the absorbent solution slurry as make-up feed. Ill effects caused by fly ash and HF in exhaust gases are avoided, the activity of CaCo.sub.3 in the absorbent slurry is maintained, and highly pure gypsum is recovered.

Abstract: Alkali metal phosphate solutions having a fluorine content of less than 20 ppm, based on P.sub.2 O.sub.5, are prepared by first digesting crude phosphate using sulfuric acid, and separating the calcium sulfate from the crude phosphoric acid. An alkali metal compound is then added to the crude phosphoric acid, and the precipitated solid is filtered off. The prepurified crude phosphoric acid is neutralized to a pH of at least 7, and the solid produced during this operation is separated off. The resultant alkali metal phosphate solutions having a P.sub.2 O.sub.5 content of from 10 to 30% by weight are adjusted to a pH of between 4.8 and 6.0 using phosphoric acid. The solutions are heated to from 60.degree. to 120.degree. C., and from 1 to 6% by weight, based on the weight of the solution, of an alkaline earth metal oxygen compound are added to the alkali metal phosphate solutions with stirring.

Abstract: A process for economically producing tabular acicular gypsum crystals in a continuously stirred reactor is disclosed. The process involves establishing a steady state atmospheric pressure reaction zone of about 20% to about 25% by weight solids of gypsum crystals in water at a temperature of about 50.degree. C. to about 60.degree. C. with continuous mild agitation. Calcium sulfate hemihydrate is fed to the reaction zone at a rate to maintain a low level of supersaturation, and a suspension of gypsum crystals in water containing crystals of a mean particle length at least greater than 45 microns is withdrawn.

Abstract: In a process for preparing calcium sulphate alpha hemihydrate essentially the form of primary crystals, the hemihydrate is milled to specific surface area of 1200 to 4000 cm.sup.2 /g, the fines are removed by screening, and a retarder and liquefier in the form of at least one fruit acid and/or its or their salt(s) are admixed. The product obtained is characterized by delayed onset of rigidity, rapid development of resistance and high resistance, and is used in particular as an injection mortar.

Abstract: Sulfur dioxide (SO.sub.2) can be oxidized to rapidly sulfur trioxide (SO.sub.3) in a high temperature environment. It has been found that the SO.sub.2 oxidation rate can be impeded by a high rate of temperature reduction in a dynamic condition such as in a boiler and the ductwork of a power plant and an industrial plant. The mechanism of the reaction kinetics has been developed. With the understanding of the mechanism, the methods for oxidation of SO.sub.2 to form SO.sub.3 have been developed. The SO.sub.3 rich flue gas is treated with lime (CaO) in a fluidized lime reactor wherein SO.sub.3 reacts with CaO to form CaSO.sub.4 coating on the surface of CaO. The high heat generated from the SO.sub.3 /CaO reaction causes the remaining SO.sub.2 to convert in the reactor to SO.sub.3 which in turn reacts with CaO to form more CaSO.sub.4. Nitrogen oxides can also be removed from flue gas by converting nitric oxide (NO) to nitrogen dioxide (NO.sub.

Abstract: A wet scrubbing process for removing sulfur dioxide from combustion gases uses an aqueous slurry containing calcium components resulting from the slaking of lime, with the slaked lime formed by mixing lime with water containing a calcium sulfur-oxide salt. The presence of the calcium sulfur oxide salt in the slaking water results in a more easily dewatered sludge that is subsequently removed from the wet scrubbing system.

Abstract: A method for production of sulfur dioxide from calcium sulfate by high temperature thermal reduction. Calcium sulfate, preferably in the form of calcined phosphogypsum, is desulfurized using a fossil fuel as a heat source, the combustion products resulting therefrom being used as a reductant. The fuel and reductant may be coal, coke, liquid hydrocarbons or natural gas; high sulfur, medium or low rank coal is preferred. The fuel is combusted with air or oxygen-enriched air. The solid feeds are introduced as finely-divided particles entrained in reactant gases, and the temperature is sufficiently hot to cause residual processed materials to melt and drain from the reaction vessel in the form of a liquid slag, yet not hot enough to produce significant amounts of fine silicon oxide dust. Iron pyrite, sand and/or clay can be added to reduce the slag melting point and to control its viscosity.

Abstract: The specification discloses a spent seed recovery and regeneration process for an MHM power plant employing an alkali metal salt seed material such as potassium salt wherein the spent potassium seed in the form of potassium sulfate is collected from the flue gas and reacted with calcium hydroxide and carbon monoxide in an aqueous solution to cause the formation of calcium sulfate and potassium formate. The pH of the solution is adjusted to supress formation of formic acid and to promote precipitation of any dissolved calcium salts. The solution containing potassium formate is then employed to provide the potassium salt in the form of potassium formate or, optionally, by heating the potassium formate under oxidizing conditions to convert the potassium formate to potassium carbonate.

Abstract: A process which reduces the amount of sulfur compounds present in a feed gas is disclosed. A gas containing sulfur compounds is admixed with an ozone-containing gas. This admixture is then contacted with a scrubbing composition to obtain a gas and a product solution. The gas exhibiting a significant reduction in sulfur compounds as compared to the feed gas. The product solution yields a sulfate-containing compound.

Abstract: Rare earth values are recovered from gypsum starting material by (i) dissolving such gypsum in water and separating therefrom the water-insoluble fractions which contain the rare earth elements (ii) treating such insoluble fractions with a solution of carbonate ions, (iii) next digesting the insoluble fractions thus treated with a mineral acid and converting at least the rear earth values into water-soluble salts thereof, and (iv) recovering such rear earth values from the medium of digestion.

Abstract: In a method and apparatus for calcining calcium sulphate dihydrate or like heat sensitive material, in which a bed of the material is heated in a vessel (41) by the direct introduction of a hot gas through a tube (21) extending downwardly into the bed, the proportion of insoluble anhydrite (II) in the product is reduced by lowering the temperature of the hot gas before it contacts the material of the bed. This is done by indirect heat exchange through the wall of the tube 21 with a relatively cool substance, for example, powdered gypsum or recycled exhaust gases, in an outer tube (26). The cooling material in the outer tube contacts the material in the bed before the latter is contacted by the hot gas.

Abstract: A wet process production of phosphoric acid in which phosphate rock is digested, whereby phosphoric acid is released and calcium sulfate crystals are formed, employs a polymeric crystal modifier in the digestion stage of the process to improve the separation of the raw phosphoric acid product from the calcium sulfate crystals and to increase the concentration of phosphoric acid in the raw phosphoric acid product.

Abstract: A process for producing NH.sub.3 and SO.sub.2 from ammonium sulfate, which comprises(i) reacting ammonium sulfate with a metal oxide or hydroxide at a temperature of not more than 200.degree. C. to form NH.sub.3, water and a metal sulfate and recovering NH.sub.3,(ii) decomposing the metal sulfate in the presence of a reducing agent to form a metal oxide and SO.sub.2 and recovering SO.sub.2, and(iii) recycling the metal oxide to step (i) as such or after it is converted to a metal hydroxide.