ESMI Technical Information

Thermal Desorption

The ESMI Low Temperature Thermal Desorption Unit (LTTDU) is a direct-fired desorption system. The LTTDU consists of seven principal components: a feed system; a rotary thermal desorption unit (primary treatment unit), soil cooling (pugmill), discharge conveyors, cyclone, thermal oxidizer (secondary treatment unit), evaporative cooling chamber, and a baghouse.

Contaminated media is heated at relatively low temperatures in the primary treatment unit (PTU). The PTU, a long rotating steel cylinder, is directly heated by a burner located at the feed or discharge end of the unit. Contaminated Soils are heated to temperatures sufficient to cause contaminants to volatilize and desorb (physically separate) from the soil. After leaving the PTU, soils are cooled, re-moistened to control dust, and stabilized (if necessary) to prepare them for reuse. Treated soil may be reused onsite for establishing grades.

Products of combustion combined with the desorbed contaminants are introduced to the process air stream. The induced draft (ID) fan, located at the end of the baghouse, is the motive force for the treatment of the air stream. The ID Fan continuously moves the air stream through the unit by negative pressure. This negative pressure controls fugitive emissions and particulate separation within the LTTDU.

Larger particles that become entrained in the air stream are removed in the dual cyclone. Volatilized contaminants continue through the dual cyclone to the oxidizer (STU) and are reduced to CO2 and H2O. The air stream is then cooled in the evaporative cooling chamber (ECC) and final particulate removal occurs in the baghouse. The ID fan then exhausts the controlled air stream to the atmosphere.