Direct Fired Thermal Desorption System Configurations
There are two categories of direct fired thermal desorption systems: Counter flow and parallel flow. Both varieties consist of an inclined rotary desorber with a burner mounted at one end injecting an open flame. The difference between configurations is the direction of material flow in relation to the burner.
Counter Flow Thermal Desorbers
In a counter flow system, contaminated materials are introduced into the desorber and travel toward the burner mounted at the opposite end. Volatilized organics, entrained particulate and combustion gasses travel against the flow of material, exiting the desorber where the cold material enters. Mixing with the contaminated cold fed material reduces the temperature of the exiting gas to less than 500°F. This relatively low temperature allows the particulate laden gas stream to be routed directly to a fabric filter baghouse where greater than 99% of the entrained solids are separated from the gas. The particulate free gas is then typically routed to a thermal oxidizer where the organics are converted to carbon dioxide and water vapor. When treating chlorinated compounds, the oxidizer exhaust gases may be routed to a quench duct to reduce the gas temperature followed by a packed-bed scrubber where HCL formed in the oxidizer is neutralized with a caustic sodium hydroxide (NaOH) solution.