Abstract: A method and apparatus for outgassing raw materials includes the steps of and means for heating the material to a temperature of about 800.degree. C. and maintaining that temperature for a first bake out period during which the material is maintained at a pressure of about 200 millitorr and for a second bake out period during which the material is maintained at a pressure of about 5 millitorr or less. During the first bake out period, an inert gas is backstreamed through the raw material.

Abstract: A precipitation system is provided for the production of strong, coarse alumina hydrate (Al.sub.2 O.sub.3.3H.sub.2 O) from Bayer process aluminate liquors. In the system three distinct, but interconnected processing stages are utilized which comprise an agglomeration stage, a growth stage and a seed generation stage. In the agglomeration stage hydrate particles agglomerate to form coarse particles; in the growth stage these particles grow and acquire strength; while in the seed generation stage alumina hydrate seed is generated to be used in the agglomeration and growth stages.The precipitation system combines the advantages of both the American and European Bayer processes in that it results in the production of a strong, coarse product hydrate and an increased yield.

Abstract: A detector for thermoluminescence dosimetry (TELDE.TM.) based on an ionic compound is shaped as a pellet. The pellet is composed of a plurality of single-crystal particles bonded together by molecular forces. A method for manufacturing such a detector is carried out by melting a powdered ionic compound in vacuum and then slowly cooling it whereby a pellet is formed.

Abstract: In a process of the preparation of alumina from an alumina value containing material wherein a caustic sodium aluminate process liquor is subjected to a treatment to reduce the level of zinc impurity by the addition of ZnS seed in the presence of sulfide ion, the improvement comprising:(I) forming the zinc sulfide seed a by process comprising the steps of:(A) dissolving ZnO in NaOH to produce a caustic Na.sub.2 ZnO.sub.2 solution; and(B) reacting the solution of (A) with Na.sub.2 S to form ZnS, the Na.sub.2 S being present at a level sufficient to provide a concentration of Na.sub.2 S of at least about 0.150 g/l of Na.sub.2 S when the product of this step is added to the process liquor;(II) adding the product of step (B) to the process liquor to precipitate as ZnS, zinc contained as sodium zincate in the process liquor; and(III) filtering the process liquor to yield an NaAlO.sub.2 liquor containing less than 15 mg/l and preferably below about 10 mg/l zinc as ZnO.

Abstract: A method of crystallizing a solution of aluminium sulphate to form crystal agglomerates having an essentially uniform grain size and being in the form of granules having a characteristic appearance and good storage properties. A solution having a temperature of 105.degree.-115.degree. C. and a concentration of 14.5-16.8% by weight of Al.sub.2 O.sub.3 is brought to crystallize onto a bed of crystalline aluminium sulphate in a drum, the length of which is considerably larger than the diameter, a temperature of 70.degree.-95.degree. C. being maintained in the bed. Part of the crystalline product discharged from the drum is ground and recycled to the drum in an amount of 40-200 percent by weight of added solution and air is passed through the drum to remove moisture evolved by the crystallization so as to form a final product with more than 75% by weight present in the crystalline state and containing 15.0-18.0% by weight of Al.sub.2 O.sub.3.

Abstract: A process for the preparation of pure aluminum chloride hexa hydrate is disclosed, in which the crystallisate mixture from the mother solution (centrifugate) and starting solution (wash solution) is treated first to the coldest of a number of crystallization steps, pumped to the hottest step by retrograde feeding, and in which only from the hottest step is a portion of the mother solution now rich in impurities removed.

Abstract: A process for the production of sodium aluminate comprising drying an aluminate solution containing from 45 to 350 g/l of caustic Na.sub.2 O with a molecular ratio of caustic Na.sub.2 O to Al.sub.2 O.sub.3 from 1.1 to 1.8 in a fluidized bed of solid particles at 250.degree.-400.degree. C. of sodium aluminate using a gas heated to 750.degree.-950.degree. C. containing no carbon dioxide as a fluidizing medium and a heat carrier in an amount from 2000 to 25000 nm.sup.3 per 1 m.sup.3 of aluminate solution; feeding said aluminate, solution for drying by atomizing it at a velocity from 25 to 35 m/s thereby obtaining sodium aluminate in the form of pellets of a size from 0.5 to 8 mm with a bulk weight from 1.2 to 1.4 t/m.sup.3 completely soluble in water and alkaline solutions, with a maximum content of hygroscopic moisture of 0.3% by weight and a maximum content of water of crystallization of 5% by weight.

Abstract: There is described a process for preparing large crystals of basic aluminum nitrate (BAN) from a nitric acid feed solution containing Al.sub.2 O.sub.3 values comprising the steps of:(1) evaporating water and nitric acid from the solution in a single step evaporation performed at a temperature of between about 270.degree. and about 450.degree. F. and at a pressure of between about atmospheric and about 60 psig to produce an evaporated liquor comprising at least about 16% alumina by weight;(2) holding the evaporated liquor in a quiescent state for a period of between about 20 minutes and about two hours within the temperature range of about 270.degree. F. to about 340.degree. F.;(3) injecting water into the product of step 2, the water being added in an amount sufficient to adjust the composition of the conditioned liquor to a composition expressible as the sum of two components(1) ANN (Al.sub.2 O.sub.3.6HNO.sub.3.15H.sub.2 O or Al(NO.sub.3).sub.3.9H.sub.

Abstract: Process for the manufacture of coarse aluminum hydroxide, containing a maximum of 15 weight percent of the particles in a particle size under 45 micrometers, with a productivity that may be higher than 60 grams of precipitated Al.sub.2 O.sub.3.The process consists of a decomposition in two stages (an agglomeration phase and a growth phase); each stage proceeding within defined temperature ranges with seed material of different constitution. The first (fine) seed amount is added at the start of the decomposition in such an amount, that the ratio of the supersaturation of the aluminate liquor to the surface area of the seed hydroxide per liter of the aluminate liquor presented for decomposition exhibits a value of 7 to 25 grams per square meter. The process exhibits the advantage of the high productivity of the so-called European process and the advantage of the so-called American process by obtaining a coarse product hydroxide.

Abstract: In the production of alumina from aluminous ores by the Bayer process, the present invention provides an improvement for effectively and economically recovering caustic components consisting essentially of sodium aluminate from aluminum hydroxide cakes as seed classified from the product aluminum hydroxide by washing the seed with a washing liquor having a substantially saturated concentration of sodium oxalate and little content of caustic and then removing organic substances such as sodium oxalate from the washed seed by secondly washing said seed with hot water, thereby recovering caustic components without the dissolution of sodium oxalate from the seed into the recovered caustic solution and attaining the removal of sodium oxalate contaminant with high efficiency.

Abstract: A method for preparing corundum particles by a hydrothermal process which comprises adding fine particles of corundum to a starting alumina hydrate, and subjecting the resulting mixture to a hydrothermal reaction or treatment, the alumina in the alumina hydrate being deposited on the surfaces of the fine corundum particles while suppressing formation of new corundum crystal nuclei.

Abstract: Process for recovering aluminum in the form of a specific acid sulfate from an initial solution containing aluminum in the form of dissolved aluminum sulfate hydrate in which the specific acid sulfate is of the formula Al.sub.2 (SO.sub.4).sub.3.0.5H.sub.2 SO.sub.4.11 to 12 H.sub.2 O and in which the initial solution is sequentially treated in a series of crystallizers, wherein successive crystallizers are maintained at a predetermined decreased generally fixed temperature such that in each crystallizer a state of supersaturation of aluminum acid sulfate exists and the parameters attendant operation of each crystallizer insure that a state of static equilibrium of precipitation of product is generally reached before the process solution/slurry is passed to a successive crystallizer, or filtered for recovery of product.

Abstract: A method for sampling and controlling the addition of suspended gases, liquids and solids in a control stream to a process stream is disclosed wherein the surface area of the suspended material acts as the determining feature for control of the process. The measured surface area is compared with a preselected surface area to control the addition of the suspended material. This method is particularly useful for the control of particulate seed material to the process stream in the Bayer process for the production of alumina. The method is also broadly applicable to physical and/or chemical control means in an analytical scheme for controlling and monitoring any process.

Abstract: A method for the production of improved, transparent single crystals having a corundum structure under conditions of minimum thermal strain, comprising the optimum orientation of growth planes of a seed crystal in a melt substantially parallel to the vertical side wall means of a crucible, and heating and subsequent cooling the melt, thereby nucleating on the seed crystal.

Abstract: Crystalline AlH.sub.3 (PO.sub.4).sub.2 .multidot.3H.sub.2 O is obtained from an aqueous solution of aluminum phosphate containing a molar ratio of Al.sub.2 O.sub.3 :P.sub.2 O.sub.5 of from 1:2 to 1:6 and an organic solvent that is miscible with water. Crystallization is enhanced by the addition of AlH.sub.3 (PO.sub.4).sub.2 .multidot.3H.sub.2 O seed crystals to the aqueous solution. The product is useful in reducing the setting time of hydraulic binders.

Abstract: An apparatus for the production of pure alumina from alumina and silicate containing raw materials comprising means to feed said raw material into the top of an acid resistant leaching tower; means to continuously feed a leaching liquor containing hydrochloric acid into the bottom of said leaching tower, means to continuously flow said leaching liquor upward through said raw material to leach out the alumina as a solution of aluminum chloride, means to withdraw said solution enriched in aluminum chloride toward the top of said tower zone; means to withdraw said raw material solid residue from the bottom of said tower zone to convey said solid residue from said leaching tower into a separation zone at a level higher than the level of said leaching tower; and means to separate said solid residue from said carrier liquid in said separation zone.

Abstract: Alumina dust, particularly partially calcined alumina dust, is coarsened by forming an aqueous admixture or slurry comprising the alumina dust and finely divided calcium carbonate and introducing the resulting aqueous admixture or slurry into Bayer pregnant liquor and precipitating alumina trihydrate from the resulting Bayer pregnant liquor.

Abstract: Aluminate mother liquor is passed countercurrent to the direction of feed of aluminum hydroxide crystals through at least two stages, each of which has a lower turbulent zone with a high suspension density and which is agitated under conditions which assure particle growth via crystal growth and an upper non-turbulent, stagnant liquid layer from which most crystals settle back into the respective lower turbulent zone. The suspension density in the stages is maintained at a constant level by sending crystal suspension from the lower turbulent zone in all the precipitation stages but the first to the preceding stage. Mother liquor is removed from the upper stagnant zone of all stages but the last stage and sent to the respective following stages. Coarse crystal suspension is removed from the turbulent zone of the first stage for separation of the crystals for further processing, while the mother liquor is returned to the system.

Abstract: The present invention concerns a novel AlH.sub.3 crystallizing liquid comprising crystalline aluminum hydride, an aliphatic ether and an inert organic liquid. The invention also concerns a novel process for providing the crystallizing liquid.

Abstract: Hexagonal plate crystals of aluminum sulfate are produced in chemically pure form by a process which comprises cooling a heated saturated solution of chemically impure aluminum sulfate acidified with sulfuric acid to precipitate crystals of aluminum sulfate, heating the slurry of the cooled solution containing the precipitated aluminum sulfate crystals to a predetermined temperature wherein the temperature is maintained for a time sufficient to dissolve a portion of the crystals in the solution, cooling the heated slurry to precipitate aluminum sulfate crystals, and separating the precipitated crystals from the slurry.

Abstract: Crystalline AlH.sub.3 (PO.sub.4).sub.2.3H.sub.2 O is obtained from an aqueous solution of aluminum phosphate containing a molar ratio of Al.sub.2 O.sub.3 :P.sub.2 O.sub.5 of from 1:2 to 1:6 and an organic solvent that is miscible with water. The product is useful in diminishing the setting time of hydraulic binders.

Abstract: An improved process is provided for the recovery of sodium aluminate crystallized from a digest of caustic and lime with high-silica aluminous materials. The digest solution is concentrated by evaporation and then seeded with Na.sub.2 Al.sub.2 O.sub.4.2.5H.sub.2 O crystals to crystallize alumina from the solution as Na.sub.2 Al.sub.2 O.sub.4.2.5H.sub.2 O. The crystals are then separated from the mother liquor solution by filtration or centrifugation. The crystals are then washed with a solution having a lower caustic content than the mother liquor and an alumina concentration of about 50 grams per liter to remove any mother liquor remaining on the crystals. The sodium aluminate crystals are used as a feed for a subsequent Bayer processing step.

Abstract: A method for producing concentrated alumina slurries containing from about 14 to about 20 weight percent Al.sub.2 O.sub.3 by forming a solvent-aqueous alumina mixture and evaporating solent-aqueous vapor from said mixture to produce said concentrated alumina slurries.

Abstract: An aluminum-containing ore such as a kaolin or montmorillonite clay is treated with a fluorine acid such as HF or H.sub.2 SiF.sub.6 to produce aluminum fluoride (AlF.sub.3) which is recovered from the liquid phase of the reaction mixture by crystallization as AlF.sub.3 . 3H.sub.2 O crystals which are then dried and dehydrated to yield AlF.sub.3. The crystallization mother liquor is recycled to the process to recover its AlF.sub.3 values. The AlF.sub.3 . 3H.sub.2 O crystals and separated solid phase of the reaction mixture are washed to recover AlF.sub.3 values and the wash streams are recycled to the process. To produce alumina, the AlF.sub.3 is pyrohydrolyzed to Al.sub.2 O.sub.3 and HF. The HF is absorbed in the crystallization mother liquor and recycled with the mother liquor to the ore treatment step. All or a part of fluorine acid requirements can also be supplied from any suitable source such as, for example, a wet process phosphoric acid facility which is a plentiful source of inexpensive fluorine.

Abstract: A method for growing single crystals which utilizes calcium nitride as a solvent system in the molten solution growth of bulk aluminum nitride crystals.