Abstract: A process and apparatus for drying material, particularly sludges, with indirectly heated driers includes a system for the thermal decontamination of exhaust air from the drier. Excess exhaust air from the drier loop is fed as secondary air to the heating boiler or furnace separately from the primary air for combustion of the fuel and to thermally clean the exhaust air from the drier. The exhaust drier gas from the drier remains in the furnace for a period to decontaminate the drier gas, after which it is mixed with the flue gases. The mixture is then removed from the furnace. The system is suitable for operation under normal operating temperatures and at low, below normal operating temperatures.

Abstract: A process and apparatus for drying material, particularly sludges, with indirectly heated driers includes a system for the thermal decontamination of exhaust air from the drier. Excess exhaust air from the drier loop is fed as secondary air to the heating boiler or furnace separately from the primary air for combustion of the fuel and to thermally clean the exhaust air from the drier. The exhaust drier gas from the drier remains in the furnace for a period to decontaminate the drier gas, after which it is mixed with the flue gases. The mixture is then removed from the furnace. The system is suitable for operation under normal operating temperatures and at low, below normal operating temperatures.

Abstract: A sludge drying system using exhaust air from a furnace in a direct heat, rotary drum dryer to simultaneously dry and pelletize the sludge. The dried sludge particles exiting the dryer is entrained in the exhaust air. The sludge particles are separated from the exhaust air and then classified according to size. The under sized particles are recycled back to a mixer for mixing with incoming wet sludge. The oversized particles are conveyed to a crusher or mill for reducing the oversized particles down to the desired product size. The medium-sized particles can be selectively directed to be recycled with the undersized particles or collected as product. The exhaust air is treated in a treatment section, and then divided into two exhaust air streams or portions. A first portion of the exhaust air is discharged into the environment, while the second, larger portion of the exhaust air is recycled back to the furnace to be used to dry the sludge in the drier.

Abstract: A sludge drying system using exhaust air from a furnace in a direct heat, rotary drum dryer to simultaneously dry and pelletize the sludge. The dried sludge particles exiting the dryer is entrained in the exhaust air. The sludge particles are separated from the exhaust air and then classified according to size. The exhaust air is treated in a treatment section, and then divided into two exhaust air streams or portions. A first portion of the exhaust air is discharged into the environment, while the second, larger portion of the exhaust air is recycled back to the furnace to be used to dry the sludge in the drier. In one embodiment, the exhaust air treatment section is provided with a spray condenser and a bio-filter. In another embodiment, the exhaust air treatment section is provided with a heat exchanger for exhaust air.