The disposal of waste paint sludge from the paint finishing system in automotive assembly plants is a massive environmental problem in its own right. Automobile and truck assembly plants in the U.S. alone generate about 30,000,000 gallons (113,550 cubic meters) of wet sludge per year. Costs are now passing $500,000 per year per plant for sludge disposal in many regions of the United States, accompanied by permanent liability for the land-filled sludge under U.S. regulations. Charges for land disposal of paint waste sludges are expected to increase dramatically world wide as stricter environmental regulations are enforced and landfill capacity is exhausted. Public awareness of the potentially hazardous nature of paint waste is growing, which will only lead to stricter laws governing the disposal. Ironically, at the same time this is happening, the paint used to minimize emissions of hydrocarbons to the air (high solids and water borne coatings) create much larger volumes of sludge than do the older more polluting coatings, thus the waste disposal will only worsen.
Concurrently, the control of volatile organic compound (VOC) emissions from industrial painting systems, such as automobile assembly plants, is of increasing importance. Plants have to meet strict regulatory requirements on the level of volatile organic compounds that they emit into the atmosphere. Abatement of such emissions to meet these requirements by stack treatment is difficult and expensive to achieve because of the large air volumes (around 1,000,000 cfm or 472 cubic meters/second per site) and low concentrations (typically about 150 ppm C3) of the VOC emissions that have to be abated.
The waste paint sludge disposal from the painting process may itself contain up to 11% of the volatile organic compounds released by the painting process.
This unique combination provides the rare window of opportunity to make a meaningful reduction in paint system hydrocarbon emissions while reducing system operating costs through the application of innovative technology to waste paint sludge.
In the search for the technology to deal with these problems, many ways to dry paint sludges were investigated. These included; incineration; forced air heating, filter presses, centrifuges and infrared heating, all of which were discarded for being impractical for one reason or another. The search lead to the equipment which was finally developed into the current system, DryPure™. This system removed the objections which had negated other systems from consideration while achieving the goals of drying the sludge and reducing VOC emissions.
The drying system will process a wet sludge as produced in an existing paint sludge system. The heat used to drive off all liquids cures the resin system and the sludge becomes a dry powder.