RESEARCH PROJECT TO REMOVE SILOXANES FROM DIGESTER GAS

Cyclic organic silicon monomers (siloxanes) used in the manufacture of personal hygiene, health care and industrial silicone products are found in wastewater and solid wastes deposited in landfills. In wastewater treatment plants, they collect in solids processes and volatilize into digester gas. When this gas is combusted to generate power (such as in gas turbines, boilers or internal combustion engines), siloxanes are converted to silicon dioxide (SiO2) precipitants, which in turn deposit on the exhaust stages of the equipment. Deposition on turbine blades, heat exchangers and emissions control equipment is common, resulting in loss of heat transfer efficiency, premature equipment failure and poisoning of catalytic converters. The Los Angeles County Sanitation Districts (Districts) investigated removal technologies in an 85 standard m3 per hour (scmh) [50 standard ft3 per minute (scfm)] pilot plant. Potential removal systems include adsorption with solid media, condensation at −28°C (−18°F), and liquid sorption in a venturi scrubber with 1% by weight detergent solutions.