Method for treating waste paint sludge

A method for the treatment of a waste stream from a painting operation wherein said waste stream contains water, uncured polymeric paint resin, liquid hydrocarbons and inorganic substances, said method comprising the steps of:

• removing a portion of the water and liquid hydrocarbons from said waste stream thereby producing a high solids paint sludge;
• recycling at least a portion of said removed water and liquid hydrocarbon to said painting operation;
• transporting said high solids paint sludge to an enclosed and substantially sealed rotary screw heat exchanger;
• maintaining a substantially inert environment within said enclosed rotary screw heat exchanger, wherein said inert environment is steam and wherein supplemental water is charged to said rotary screw heat exchanger to maintain a steam pressure within said heat exchanger close to or slightly above atmospheric pressure;
• mixing an inorganic scouring aggregate with said high solids paint sludge and thereafter heating said mixture in said rotary screw heat exchanger to volatilize any remaining water and liquid hydrocarbon and to cure substantially all of said uncured resin, thereby generating a gas stream and a substantially dried particulate solids stream including said scouring aggregate;
• transporting said gas stream through a separator to remove entrained solids and adding said removed entrained solids to said solids stream;
• incinerating said gas stream to thereby generate a hydrocarbon-free effluent;
• removing said scouring aggregate from said particulate solids stream and recycling said removed scouring aggregate to said mixing step;
• and collecting said residual dried particulate solids.

A method for the treatment of paint waste sludge containing water, uncured polymeric paint resin, liquid hydrocarbons, and inorganic substances, said method comprising the steps of:

• removing a portion of the water and liquid hydrocarbons from said sludge thereby producing a high solids paint sludge;
• heating said high solids paint sludge to volatilize any remaining water and liquid hydrocarbon and to cure substantially all of said uncured resin, thereby generating gases and a substantially dried particulate product comprising cured resin and inorganic substances, said heating step being carried out in an enclosed heating chamber wherein said chamber is purged with a gas to maintain an inert environment in which the concentration of flammable gaseous components in said heating chamber is maintained below an explosion limit;
• transferring said gases from said inert environment to a processing zone wherein substantially all hydrocarbons are removed from said gases thereby generating a hydrocarbon-free effluent;
• and collecting said substantially dried particulate product discharged from said heating chamber.