GB513744A - Alkali-alkaline earth fertiliser and a process of producing same - Google Patents

Abstract

513,744. Rotary furnaces. METALLGES. AKT.-GES. April 19, 1938, No. 11752. Convention date, June 30, 1937. Addition to 473,520, [Group III]. [Class 51 (ii)] [Also in Group III] An alkali-alkaline earth fertilizer is produced by passing a mixture of tribasic calcium phosphate, alkali metal sulphate and an active carbonaceous reducing agent through a rotary tube furnace. preferably equipped with lifting or turning. devices and baffle rings, while air and combustible gas are introduced into the furnace through burner along its length, in such manner that the mixture is heated in the upper part of the furnace with flames adjusted to complete combustion, and is treated in the middle zone of the furnace in a reducing atmosphere at about 700‹-900‹C., and cooled in the bottom part of the furnace by inert gases such as carbon dioxide or nitrogen or mixtures thereof, or by reducing gases, e.g. the combustible gas. to temperatures at which 'it no longer oxidizes, i.e., to below 300‹C. and preferably to below 170‹C. The heat of the process may be exclusively provided by combustion gases, or the quantity of reducing carbon (lignite dust) in the charge may be increased, and burnt in the upper and, if desired, reducing zone of the furnace. As shown, the charge is introduced through pipe 1 into the furnace 2 consisting of an iron shell with a chamotte lining and provided with baffle rings 5. Lifting or turning devices are disposed between the baffle rings. The heating gas and air flow through distributor head 8, and pipes 9, 11 and 10, 12 respectively to burners 13. Regulating valves 14 for the air and gas are provided. Combustible gas passes into the lower zone of the furnace through valved pipe 20, and cools the charge which is discharged at 7. The furnace gases are led away through head 15. Track rings 16 carry the furnace and run on rollers 17, the furnace being rotated by pinions 18, 19.