INCINERATION
Dorr Oliver Incinerator & Animation
The cake residue from the filter presses is then incinerated along with the grit. Presently part of the sludge is hauled off-site to be composted, directly land applied or landfilled. The Lynn incineration system is comprised of two Dorr Oliver fluidized bed incinerators which burn the sludge at approximately 1400 degrees Fahrenheit. The remaining ash is hauled to the off-site landfill for disposal.
On site incineration of the sludge cake occurs in two Dorr Oliver fluidized bed incinerators. A fluidized bed incinerator has sand heated to about 1500 F by oil or gas. The sand is blown around "fluidized" in the incinerator by a hot air blower "fluidizing blower" blowing from the bottom upwards. The sludge is metered onto a serpentex conveyor belt system then weighed on a weigh belt just prior to being feed into the incinerator via the screw feeder of the incinerator. As the sludge enters the incinerator the heated fluidized sand hits the sludge both breaking it apart like a sand blaster and burning it. The gas and ash from the burning process are carried out the top of the incinerator and through a heat exchanger, which preheats the ambient air up to 800 F before it enters the windbox. The exhaust gas then passes through an economizer heat exchanger that recovers more heat, and supplies the solids building with hot water for the boiler and heats the entire solids building in the winter months. About 99.9 percent of the fly ash is then removed in the venturi gas scrubber. The gas stream then flows through a wet electrostatic precipitator (ESP). This device first pH adjusts the gas stream to remove sulfur dioxide. Then the gas passes by high voltage electrical coils which charge any particles of ash still in the gas stream and then removes those particles with an oppositely charged plate much like a magnet. The gas exiting the stack into the air has some water vapor with almost no particulate.
The incinerators are permitted by the states Department of Environmental Protection (DEP). There is a continuous emissions monitoring system (CEM) on each incinerator measuring Sulfur Dioxide (SO2), Oxides of nitrogen (NOx), and Carbon Monoxide (CO). The information from these delicate and sensitive instruments are then collected by a data logger and sent to a computer located in the incinerator control room. These results are then compiled for quarterly and semi-annual reports for both DEP and EPA. The incinerator operators use this information to operate the incinerators within the guidelines of the DEP permit as well as achieve the optimum efficiency and performance without excess emissions.
More information on fluidized bed incinerators can be found at http://www.residua.com/wrftbfbc.html#top .