Patent ID: 6398840
Filing Date: 2002-06-04
Classification: C05F,Y02A,Y02P,Y10S

Abstract:
A process for treating sludge having a water content of approximately 80% and a solid content of approximately 20% for obtaining a dry particulate product free of biologically polluting agents useful as a fertilizer, which comprises the steps of:a) mixing the sludge with acid until a sludge having a stiff consistency is obtained; b) feeding the mix obtained in step a) to a granulator machine; c) adding sulfuric acid and anhydrous ammonia to the mix in order to produce an exothermic reaction between the sulfuric acid and the anhydrous ammonia which produces sufficient heat to evaporate the water contained in the sludge and to eliminate all the pathogenic and non-pathogenic microorganisms; d) adjusting the quantity of sulfuric acid and anhydrous ammonia added to the granulator to obtain a final dry sludge particulate product having a pH of between about 1.0 and 5.0 and having a maximum humidity of 3.5% by measuring the acidity and humidity of a sample of dry product taken from inside the granulator; e) sieving the dry product in order to separate the dry particulate product into three parts: a first part comprising particles having a normal size of between 4 to 18 mesh screen, a second part comprising particles having a size below the normal size and a third part comprising particles having a size above the normal size; f) recovering the dry particulate product having normal size; g) recycling the particles having a size below and a size above the normal size to step a) in order to be resized, wherein the particles below and above the normal size are powdered before being recycled to the step a).