Industrial sludge pelleting and drying process comprises adding dry material as pelleting aid, shaping to rounded pellets and drying to a specified residual moisture content

摘要

A sludge pelleting and drying process, comprising adding dry material as pelleting aid, shaping to rounded pellets and drying to a specified residual moisture content, is new. A sludge pelleting and drying process comprises adding a pelletization promoting dry material, shaping the mixture to pellets with partially round surfaces and drying to a residual moisture content of }10%. An Independent claim is also included for a plant for carrying out the above process, comprising (a) sludge holding containers (6) or troughs and additive holding containers (5) which are equipped with individually controlled delivery mechanisms (e.g. dosing screws) and which are supplied with sludge and additive materials (2) by transport equipment (1); (b) comminution equipment, preferably grinding mills (7), for grinding dry pellets to fine granules and a powder container (8) with a regulated dosing screw; (c) a regulated mixer screw (9) for mixing the sludge with the additive materials and for transporting the mixture to a pelleting machine (10); (d) a vertical and horizontal distributor system (11) for top charging of the wet pellets into one or more trickle drying shafts (12); (e) a transport belt below the or each drying shaft for transporting dried pellets to containers or to an additive material container (5) for re-mixing with sludge; (f) an oil-fired heat generator (20) or a device for recovering waste heat e.g. from flue gases; (g) an air intake bypass (21), equipped with thermostatically controlled motor-driven flaps, slats or the like, for cooling the flue gases to the desired drying temperature; (h) a switching device for switching off heat supply via the bypass so that drying is carried out using only external air; (i) a fan for drawing drying air through the pellets; and (j) a waste air cleaning system (17) in which dust is removed by scrubbing and any residual organic contaminants are destroyed by a bio-filter.