GB361890A - Manufacture of a fertilising agent by the wet oxidation of coal and the like - Google Patents

Abstract

<PICT:0361890/IV/1> Fertilizers are obtained by oxidizing fuel materials such as coal, peat, anthracite, and lignite with nitric acid in excess, and boiling the reaction product until the greater part thereof is soluble in alkali, the nitrogen oxides evolved being reconverted into nitric acid by oxidation and contact with an aqueous medium, and preferably returned to the reaction in a cyclic process. The powdered coal or other starting material may be treated with nitric acid from a tank A in a reaction vessel B having a heating or cooling jacket and stirrers. The nitric oxide evolved excapes through a tower C filled with broken coke or the like and supplied with air through an inlet E. An inlet F for the admission of water to the charge in the reaction vessel is also provided. The oxidation of the nitric oxide to nitrogen peroxide initiated in the tower E is completed in a chamber G, and the fumes then pass through a bubbler H, which normally contains nitric acid from a previous operation. Nitrous acid formed together with nitric acid in the bubbler H is decomposed with the formation of nitric oxide which is again oxidized in the chamber I. The fumes then pass to the bubblers J, J1 containing nitric acid, the three bubblers H, J, J1 being in communication with each other by means of pipes l, l1, and by means of a pipe l2 with a tank A1 from which the tank A is supplied. The strongest nitric acid is recovered in the bubbler H and the weakest in the bubbler J1. The tank A1 is supplied with acid from the bubbler H when this has attained the required concentration; and each of the bubblers is replenished by acid from that containing the next weaker acid. If desired, the acid supplied from the bubbler H to the tank A1 may be diluted to the required strength with acid from one or more of the other bubblers. From the bubbler J1 the fumes pass to bubblers M, P containing a solution of an alkali such as soda ash to absorb the final trace of nitrous fumes. The bubblers M, P are connected through a tower N filled with broken coke and supplied with alkali solution through an inlet O. The solution is drawn through a pipe K to crystallizing pans, the recovered salts being used as fertilizers or worked up for alkali nitrate or nitrite. U is a vacuum pump serving to draw the fumes through the apparatus, and R1, R2, R3 are observation windows. When the reaction with the nitric acid has subsided the charge may be boiled by external heating or by the admission of live steam into the vessel B until the product is about 95 per cent soluble in alkali. The oxidized material is then washed and further treated as desired, for example, dissolved in dilute alkali solution with the aid of steam and thus separated from alkali-insoluble matter. Examples are given. According to the Provisional Specification, fertilizers may be obtained by combining the products with ammonia to form ammonium humate, or by mixing the products with nitrogen-containing salts, for example, the sodium nitrate recovered in the process, the fertilizers thus obtained being also mixed, if desired, with suitable diluents.