Phosphate rock reactions

NSP is produced by the reaction of phosphate rock and sulfuric acid. This reaction quickly yields a soHd mass containing monocalcium phosphate monohydrate and gypsum, CaSO 2H20, according to the simplified equation... 

Chemistry ndProperties. The chemistry of phosphoric acid manufacture and purification is highly complex, largely because of the presence of impurities in the rock. The main chemical reaction in the acidulation of phosphate rock using sulfuric acid to produce phosphoric acid is... 

The complete chemistry of TSP production has been studied and reported in great detail (34). As in the production of NSP there are also reactions with impurity minerals. In fact, the increasing amounts of such impurities in U.S. commercial phosphate rocks, especially those from Florida, are now reflected in somewhat lowered amounts of citrate-soluble P2O5 product. The range of constituents in commercial TSP from wet-process acid and phosphate... 

Liquid Dispersion Spray columns are used with slurries or when the reaction product is a solid. The absorption of SO9 by a hme slurry is an example. In the treatment of phosphate rock with sulfuric acid, offgases contain HF and SiF4. In a spray column with water, solid particles of fluorosilic acid are formed but do not harm the spray operation. The coefficient /cl in spray columns is about the same as in packed columns, but the spray interfacial area is much lower. Considerable backmixing of the gas also takes place, which helps to make the spray volumetri-caUy inefficient. Deentrainment at the outlet usually is needed. 

Phosphoric acid made by the wet process, in which phosphate rock is treated with sulfuric acid, is highly inert toward lead in any concentration for temperatures up to 150°C, However, in the dry process, where hydrogen phosphate (H3PO4) is made directly from phosphorus or phosphorus pentoxide (P2OS), a chemical reaction with lead occurs. 

For a century after its discovery the only source of phosphorus was urine. The present process of heating phosphate rock with sand and coke was proposed by E. Aubertin and L. Boblique in 1867 and improved by J. B. Readman who introduced the use of an electric furnace. The reactions occurring are still not fully understood, but the overall process can be represented by the idealized equation ... 

C04-0146. The largest single use of sulfuric acid is for the production of phosphate fertilizers. The acid reacts with calcium phosphate in a 2 1 mole ratio to give calcium sulfate and calcium dihydrogen phosphate. The mixture is crushed and spread on fields, where the salts dissolve in rain water. (Calcium phosphate, commonly found in phosphate rock, is too insoluble to be a direct source of phosphate for plants.) (a) Write a balanced equation for the reaction of sulfuric acid with calcium phosphate, (b) How many kilograms each of sulliiric acid and calcium phosphate are required to produce 50.0 kg of the calcium sulfate-dihydrogen phosphate mixture (c) How many moles of phosphate ion will this mixture provide ... 

Phosphoric acid is produced in the reaction between sulfuric acid and calcium phosphate rock ... 

The manufacture of fertilizers was discussed in Chapter 14. Phosphate rock is digested with sulfuric acid to convert CaC03 into a more soluble form that contains a higher percentage of phosphorus. Sulfuric acid is used as a catalyst in alkylation reactions, petroleum refining, manufacture of detergents, paints, dyes, and fibers, and other processes. It is also used as the electrolyte in the lead-acid battery that is used in automobiles. Sulfuric acid is an enormously important chemical commodity that it would be hard to do without. 

Furnace Also called the Readman process. A process for making elementary phosphoms in an electric furnace. The raw materials are phosphate rock, coke, and silica. Large amounts of electric power are consumed, so the process is economic only where cheap power is available. The overall reaction is ... 

Haifa Also called IMI. One of the two Wet Processes for producing phosphoric acid by the acidulation of phosphate rock the other is the Dorr process. The Haifa process uses hydrochloric acid for the acidulation and solvent extraction for the purification. It is economic only where by-product hydrochloric acid is available. The overall reaction is ... 

In addition to straightforward precipitation reactions, components may dissolve and react with components already present, including atoms on colloidal surfaces. For example, phosphate may dissolve from phosphate rock and react with iron present in the soil solution or on particle surfaces to form an iron phosphate that is insoluble. 

Chloride ion-selective electrodes The most important region of application is the determination of chlorides in waters, including sea water (for a review, see [167]), in serum [110,112,371] (review in [167]) and in soil [151,219,341], The determination of chloride ions in sweat made screening for cystic fibrosis possible in new-born babies (review, [45,55a, 262]). Br , I and S " interfere in the determination of chlorides in phosphate rocks [81]. Sulphite can be determined directly using an electrode with an Hgj CI2 - HgS membrane [398] on the basis of the reaction... 

Phosphorus is manufactured by the reduction of commercial-quality phosphate rock by coke in an electric furnace, with silica used as a flux. Slag, ferrophosphorus (from iron contained in the phosphate rock), and carbon monoxide are reaction byproducts. The standard process, as shown in Figure 2, consists of three basic parts phosphate rock preparation, smelting in an electric furnace, and recovery of the resulting phosphoms. Phosphate rock ores are first blended so that the furnace feed is of uniform composition and then pretreated by heat drying, sizing or agglomerating the particles, and heat treatment. 

Normal Superphosphate. Normal superphosphate is produced by the reaction between ground phosphate rock and sulfuric acid, followed by three to eight weeks of curing time. Obnoxious gases are generated by this process. 

By far the most important derivative of sulfuric acid is phosphoric acid. It has been unknowingly used as fertilizer for hundreds of years. The wet process method of manufacture was important until 1920, when furnace acid began increasing in popularity. The wet process, however, has made a comeback because of plant design improvements 60% of phosphoric acid was made by this method in 1954, 88% in 1974, and over 90% currently. The furnace process is used only to make concentrated acid (75-85%) and pure product. It is very expensive because of the 2000 °C temperature required. In the furnace process phosphate rock is heated with sand and coke to give elemental phosphorus, which is then oxidized and hydrated to phosphoric acid. A simplified chemical reaction is ... 

Yellow phosphorus (known also as white phosphorus) is produced by reducing phosphate rock (calcium phosphate or calcium fluorophosphate) with carbon in the presence of silica as flux heat of reaction is furnished by an electric-arc furnace. 

All phosphorus fertilizers come from wet process phosphoric acid or directly from phosphate rock. Normal superphosphate, triple or concentrated superphosphate, and ammonium phosphate are the three common types used. Normal or ordinary superphosphate (NSP or OSP) is mostly monocalcium phosphate and calcium sulfate. It is made from phosphate rock and sulfuric acid and is equated to a 20% P2O5 content. It led the market until 1964. The production of normal superphosphate is similar to that for the manufacture of wet process phosphoric acid (Chapter 2, Section 3) except that there is only partial neutralization. Normal superphosphate is no longer used to any great extent. The following reaction is one example of an equation that represents this process. 

Hydrogen fluoride may be made from silicon tetrafluoride produced from phosphate rocks. A major step in the process involves reaction of sflicon tetrafluoride with recycled ammonium fluoride solution ... 

Probably the most important commercial reaction of sulfuric acid involves making phosphoric acid from phosphate rock ... 

Sulfuric acid is universally used in the chemical industry in the production of numerous products. Its largest use, accounting for approximately two-thirds of its total use, is in the production of fertilizer. Adding acid to phosphate rock produces phosphate fertilizer. Superphosphate fertilizer is produced by adding sulfuric acid to the phosphate rock fluorapate, [Ca3(P04)2]3CaF2, according to the reaction ... 

Two major methods are utilized for the production of phosphoric acid from phosphate rock. The wet process involves the reaction of phosphate rock with sulfuric acid to produce phosphoric acid and insoluble calcium sulfates. Many of the impurities present in the phosphate rock are. also solubilized and retained in the acid so produced. While they are of no serious disadvantage when the acid is to be used for fertilizer manufacture, their presence makes the product unsuitable for the preparation of phosphatic chemicals. 

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