EQUIPMENT - 4-INCH-DIAMETER BATCH ROTARY KILN
Hazen’s four-inch-diameter batch rotary kiln system is used for bench-scale thermal testing of soils, sludges, waste products, and mineral ores. The batch kiln system provides a quick and cost-effective means for evaluating thermal treatment options while using a small quantity of test material. Thermal desorption tests are performed on soils and sludges to evaluate organic removal as a function of time and temperature. Waste products are often tested to evaluate volume reduction and recovery of a process byproduct. Mineral ores are tested to determine the conditions at which the ore becomes amenable to conventional mineral/metal recovery techniques.
The kiln is made of quartz and is 32 inches in total length. At its center is a section 14 inches long and 4 inches in diameter where the sample material is placed at the beginning of the test. The four-inch-diameter section is indirectly heated by an insulated clamshell furnace, and operating temperatures up to 1000ºC (1800ºF) are attainable. Raised dimples, acting as lifters within the four-inch-diameter section, enhance the mixing and tumbling of the sample as the kiln rotates. A variable-speed electric motor and controller drive the kiln at rotational speeds of up to 10 rpm.
Typical sample charges to the kiln range from 300 to 1000 grams, depending on the material to be tested and the operating conditions. Control parameters include temperature, pressure, gas flow rates, and gas composition. Temperatures are measured within the sample, on the furnace shell, and in downstream gas-treatment equipment. Pressures are measured at the kiln inlet and outlet, and rotameters measure gas flow rates throughout the system. The kiln atmosphere can be oxidizing, inert, or reducing, as required by the specific test objectives.
Process exhaust gases can be treated using condensers, carbon columns, or a thermal oxidizer. Alternatively, the exhaust gases can pass through an emission sampling train to quantify selected constituents such as volatile and semivolatile organic species, dioxin and furan, metals, and particulates. Continuous-emissions monitors measure the concentrations of O2, CO2, CO, SO2, NOx, and THC in the process gases. Selected data are continuously recorded by a data acquisition system.