GB1497716A - Method and apparatus for producing calcium phosphates - Google Patents

Abstract

1497716 Calcium phosphates NORSK HYDRO AS 11 March 1975 [19 March 1974] 10093/75 Heading C1A Calcium phosphates such as mono-calcium phosphate, di-calcium phosphate or mixtures thereof are produced by direct reaction between phosphoric acid and calcium carbonate, wherein a preheated aqueous suspension of finely grained (as defined below) calcium carbonate is brought to react with preheated phosphoric acid by introducing the reactants into a short, open ended, tubular reactor (as defined below), whereby evolution of gas and intensive mixing of the reactants in the reaction zone take place, the gas formed expelling or ejecting the foaming mixture from the reaction zone, the reaction being substantially completed while the individual particles in the mixture are freely suspended in air or gas, whereafter the particles are collected. The expression "fine grain" is used to define a substantially homogeneous particulate material which when used in the method of the invention gives a product which is non- sticky and free-flowing. The "short tubular reactor" has a tubular reaction chamber of only sufficient length in relation to its capacity to enable a thorough mixing of the reactants and optimum build up of pressure before ejection thereof, and which is not so long, in relation to the normal throughput of the mixture, to enable the reactions to be completed or substantially completed before ejection of the mixture. The reactor (Fig. 2) may have three sections arranged one after the other, these being a mixing chamber 55, a reaction or pressure chamber 56 and discharger tube 53. The reactant feed lines 51, 52 may be connected tangentially with the mixing chamber. A rod 54 may be arranged at the rear of the reactor for use if the reactor becomes clogged. Apparatus (Fig. 1) for carrying out the process comprises a housing 7, defining a gas-filled free-fall chamber, the short tubular reactor 5, open at one end and having discharge means 53 (Fig. 2) for discharging the reacting mixture into the top of the chamber, and means 8 at the base of the chamber for collecting the resultant reaction product after its discharge from the reactor, the reactor having a pair of feed lines 51, 52 for the supply of calcium carbonate suspension and phosphoric acid respectively and the collecting means including a reaction product discharging device 10 for discharging the product from the chamber. The discharging device may discharge the product to a press 11, granulating device 12, dryer 13 and screen 14 The upper end of the chamber may be fitted with a gas outlet which is connected to a cyclone separator 9a and exhaust fan 9.