US1925645A - Process for the manufacture of fertilizers rich in p2o5 - Google Patents

Description

Patented Sept. 5, 1933 PROCESS FOR THE MANUFACTURE OF FERTILIZERS RICH IN P205 Vlaclislav Pi'istoupil, Aussig on the Elbe,

Czechoslovakia N Drawing. Application March 9, 1931, Serial No. 521,398, and in Czechoslovakia March 15,

Claims.

The present invention relates to a process for the production of fertilizers rich in phosphoric acid from crude phosphates and to the products obtained thereby, it consists in subjecting the 5 crude phosphates at an elevated temperature to the action of phosphorus pentoxide preferably in the form of vapour. Under these conditions the combination of the P205 with the crude phosphate takes place quickly and completely with the formation of fertilizing substances, which can be easily distributed, having for example a P205 content up to 60% and over.

This P205 content can be regulated within fairly wide limits according to the quantities of P205 1 employed. Thus for example fertilizers can be manufactured which correspond, to calcium pyrophosphate, calcium metaphosphates or mixtures of these, that is to say in which the molecular proportion CaO:P2O5 amounts to about 1: to 1:1. Fertilizers still richer in phosphoric acid, for example in which the molecular proportion of CaO to P205=112 can also easily be obtained from the crude phosphates.

The fertilizers obtained in this manner are not hygroscopic have good covering power and the solubility of the phosphoric. acid is satisfactory for fertilizing purposes. The solubility can be still further increased by effecting a sudden cooling or quenching of the hot, preferably molten, products, care being preferably taken that a large superficial area is produced. The cooling or quenching can be effected for example by pouring the molten product on to cold iron plates or by allowing it to flow into cold water.

One method of carrying the process into effect is to produce the P205 necessary for the reaction by the combustion of elemental phosphorus, preferably in the form of vapour, and to use the heat 40 of combustion for maintaining the reaction temperature. This method of carrying out the process is particularly advantageous as it enables the phosphorus-containing gases which are formed in the manufacture of phosphorus by reduction of phosphates to be directly utilized. In this case the phosphorus contained in the phosphorus furnace gases is burnt to P205 in known manner and the heat resulting from this combustion is utilized for maintaining the reaction. The available amount of heat can be still further improved by utilizing the 00 content of the phosphorus furnace gases for the development of heat.

Example Phosphorus-containing gas is burnt with air in the lower part of a stationary, heat-insulated shaft which is charged with filling material. The gases of combustion containing P205 spread upwards in the shaft and bring it to the necessary temperature of about 1200 0. Crude phosphate in fine-grained form or in the form of small pieces is continuously fed from above into the shaft.

It lies at first on the filling materials. After it has been partly converted by the P205, it first becomes tacky and finally liquid and flows over the filling material in the opposite direction to the stream of gas. It thereby takes up further quantities of P205 and finally collects in the lower part of the furnace where it is run off from time to time and preferably allowed to flow directly into cold water for quenching.

The product obtained can easily be ground to have a size of grain suitable for fertilizing purposes. The phosphoric acid content of the final product, which also depends to some extent on the dimensions of the furnace, can be regulated as desired within wide limits by varying the rate of charging and the speed and composition of the phosphorus-containing gases.

Instead of taking place in the above-described apparatus, the conversion of the crude phosphate may take place for example in an apparatus of the following kind. The molten reaction mass is placed in a heat-insulated, fire-proof container. Into this mass there dips'a system of pipes in which the combustion of the gases containing phosphorus vapour is effected. The heat developed is directly transferred to the melt and maintains the necessary temperature. The P2O5-containing combustion gases are driven through the melt'in as fine a distribution as possible, whereby the P205 content is taken up by the mass. The crude phosphate to be converted is continually introduced into the melt and the product of the reaction is run off from time to time in portions and quenched. I

I claim:-

1. Process for the production of 'fertilizersrich in phosphoric acid from crude phosphates which comprises treating the crude phosphates with phosphorus pentoxide at glowing'heat.

2. Process for the production of fertilizers rich in phosphoric acid from crude phosphates which comprises treating thecrude phosphates with 5 phosphorus pentoxide at glowing heat and suddenly cooling the products of the reaction.

3. Process for the production of fertilizers'rich in phosphoric acid from crude phosphates which comprises treating a crude phosphate with phos- 1,925,645 phorus pentoxide vapour at a temperature of- 5. Process for the production of fertilizers rich in phosphoric acid from crude phosphates which comprises burning phosphorus to form phosphorus pentoxide treating the crude phosphate with the pentoxide formed at glowing heat, and using the heat of combustion of the phosphorus to maintain the reaction temperature.

VLADISLAV PRISTOUPIL.