36 results about "Dihydrate Calcium Sulfate" patented technology

A process and system for producing phosphoric acid. Phosphate rock is dissolved in phosphoric acid in a reaction vessel to form a slurry. The slurry is then reacted in a first stage of crystallization with sulfuric acid to produce calcium sulfate hemihydrate and phosphoric acid. The product acid is separated from the hemihydrates via filtration, and the filter cake is then reacted, in a second crystallization step, with additional sulfuric acid to produce dihydrate calcium sulfate (gypsum) and recovery solution. The gypsum is separated from the recovery solution via filtration and removed as a by-product. The recovery solution is recycled back to the transformation tank and to the hemihydrate filtration step. A feed acid tank combines wash solution, recovery solution and product acid. Once adjusted to a target P2O5 concentration, it is fed to the initial reactor vessel to dissolve the phosphate ore.

The invention relates to a method for preparing the calcium sulfate with the sulfate-contained brine and the calcium-salt-contained brine; the two refined brines in a crystallization control reactor are uniformly and consecutively mixed with the cycling liquid inside a cycling lifting device to form dihydrate calcium sulfate crystal with large grain diameter; the dehydrate calcium sulfate crystalis centrifugally washed and dried to prepare the product of the high-purity dehydrate calcium sulfate. The flow rate of the refined sulfate-contained brine that is continuously added in a reaction crystallization barrel is determined according to the ratio between the flow rate of the refined sulfate-contained brine and the flow rate of the cycling liquid in the cycling lifting device in the reactor of 1:10 to 1:30. The flow rate of the refined calcium-salt-contained brine that is consecutively added is determined according to the mol ratio of 1:1 between the sulfate radical ion and the calcium ion in the refined sulfate-contained brine and the calcium-salt-contained brine.

The invention relates to a coated granular fertilizer, preferably wherein granules are sulfate-based or phosphate-based. When sulfate based granules, as in ammonium sulfate, the coating substance is an inorganic salt of alkaline earth elements, preferably calcium, such that when applied to the surface of fertilizers, forms calcium sulfate, preferably a calcium sulfate-dihydrate, as a protective coating. For a reactive coating of a thiosulfate, free sulfuric acid present on the granule reacts to provide an elemental sulfur coating. For ammonium phosphate-based granules, coatings may comprise compounds of Ca++, Al+++ and / or Fe+++ salts thereby forming a calcium, an aluminum, an iron, or mixed cation phosphate protective coating. Thiosulfate is also effective with phosphate based granules which are manufactured with sulfuric acid. Granules coated according to the disclosure have advantageous properties as the coating can be applied in a specified and sparing manner due to its tendency to adhere to surfaces during the reaction. Coated fertilizer granules of the disclosure are also advantageous in that, with regard to the applied amount of coating, they provide increased resistance to dusting in long term warehouse storage, to moisture uptake and to oxidative heating. Coating components also add nutrients to plants that can provide nutrients over a longer period of time such as a slow-release characteristic.

The invention relates to a method for preparing calcium sulfate crystal whiskers (CaSO4) by using impurity-containing gypsum as a raw material. The method comprises the following steps of: removing main impurities in the raw material which is the low-priced impurity-containing gypsum resource in a mode of roasting, acid-complex leaching and alkaline leaching and simultaneously thinning crystal grains to obtain a superfine dihydrate calcium sulfate precursor which is high in purity and dispersibility; and preparing the anhydrous calcium sulfate crystal whiskers with a length of 20 to 2,000mu m, a diameter of 0.5 to 20 mu m, a length-diameter ratio of 40 to 1,000 and a weight percent content of over 95 percent in a mode of hydrothermal conversion-roasting of a fluxing agent. The method has the advantages of low-priced and easily bought raw materials, simple process, wide application range, and high added value. The calcium sulfate crystal whiskers prepared by the method have a big length-diameter ratio and regular shape, and can be used as reinforcing, heat insulating or flame retardant materials in industries of plastics, rubbers, coatings, papermaking, building materials and the like.

The invention relates to a restoration agent for saline-alkali land soil, which consists of free gypsum dehydration, nature organic substance, microbial fertilizer and inorganic nutrient with weight ratio of 60-70:25-35:1-4:3-6; the content of dihydrate calcium sulfate in the free gypsum dehydration is over 80 percent; the nature organic substance consists of weathered coal and grass carbon with weight ratio of 1.0:0.93; the content of effective bacteria in the microbial fertilizer is 2.0 hundred millions / g; and the inorganic nutrient consists of urea, ordinary superphosphate and potassium chloride with weight ratio of 1.0:2.42:075. The restoration agent can utilize calcium ions in the free gypsum dehydration for replacing sodium ions in the soil so as to lower the alkalinity in the soil and provide calcium and sulfur elements for crops, while the nature organic substance can lower and regulate the slat content and the alkalinity in the soil. In addition, the nature organic substance,the microbial fertilizer and the inorganic nutrient can supply large amount of nutrient elements such as nitrogen, phosphorus, potassium and the like to the crop for normal growth, thereby being capable of improving the yield of the crop.

Calcium sulfate composite particles for bone augmentation are disclosed. The composite particles are composed of aggregated calcium sulfate nanoparticles of a diameter from about 50 to about 800 nm, which include a mixture of calcium sulfate dihydrate and calcium sulfate hemihydrate. The composite particles have a diameter from about 200 to about 1,200 μm, and a mean half-life no less than 18 days. Further disclosed is a bone grafting material for bone augmentation. The bone grafting material includes a mixture of the calcium sulfate composite particles and a second type of calcium sulfate particles having a particle diameter from about 2 to about 60 μm, at a ratio from 1:1 to 4:1. The method of using the composite particles and the bone grafting material for bone augmentation is also disclosed.