Processing wastewater treatment plant sludge, producing novel alkaline absorbent treating other liquid and gaseous effluents, employs high temperature quicklime slaking process
The quicklime particle size is below 5 mm. Its temperature, reached by preheating in an indirect heat exchanger, is 250-650 deg C. A thermal fluid system is integrated. This is heated by the exothermic reaction between quicklime and water contained in the sludge. The process is initiated by suitable preheating of the thermal fluid, in conventional manner. An Independent claim is included for the mixture of slaked lime and carbon having a large surface area, which results from the process and which is eminently suitable for treatment of water, air, gases, smoke and fumes. A further claim is included for plant carrying out the process. This includes the jacketed (2) heat exchanger (1) and rotary spiral agitator (3), thermal fluid line (4), buffer storage (5) with heating (7), rotary lock feeder with flow control (8, 9), outlet lock system (13, 14) and condenser (15). Preferred features: Quantities of sludge injected, provide 1.5-10 times the stoichiometric water requirement of the slaking reaction. Water vapor is released, whilst holding an internal pressure of 1000-10000 Pa. Water in excess of stoichiometric is evaporated directly by the reaction and is condensed conventionally for recycling or discharge. The hot mixture is agitated continuously, maximizing surface area of the powdery slaked lime produced. The sludge contains at least 5% organic matter, which is pyrolyzed by the heat of reaction, destroying all pathogenic organisms, and thermally-cracking the organics, with additional exothermic reaction, for heating the thermal fluid. The reaction forms a porus amorphous carbon of high surface area. The mixture of slaked lime and carbon produced, can be used in processes treating water, air, gases, smoke or fumes. Additionally or alternatively, a further high temperature process can be employed for recovery of quicklime, driving off any CO2 and water.
