Regenerative thermal oxidizer with heat exchanger columns

A regenerative thermal oxidizer comprising:

• a combustion chamber including a burner;
• at least three heat exchangers, each having a heat exchanger passage leading into said combustion chamber and having a heat transfer column located therein;
• an inlet line connected to a source of gas to be cleaned having entrained pollutants and communicating with an inlet branch leading to each of said heat exchangers with an inlet valve located in each inlet branch;
• an outlet line leading from each heat exchanger, each outlet line including an outlet valve, and an outlet branch communicating with each said outlet line;
• gas to be cleaned being delivered through said inlet line into one of said heat exchangers by opening of said inlet valves and closing said outlet valve on said one heat exchanger, gas moving through said heat exchanger and into said combustion chamber where said gas is combusted, the combusted clean gas then being led into a second heat exchanger having a closed inlet valve and an open outlet valve, the gas then being delivered to said outlet line;
• said heat transfer column including a solid body formed of heat resistant, heat retaining material having a plurality of spaced axial gas flow passages, said passages having a dimension of between 0.1 and 0.25 inch, said heat transfer column having a substantially constant cross-sectional area, said flow passages each having a substantially constant cross-sectional area and comprising generally 70-80% of said cross-sectional area of said heat transfer columns, the pressure drop across the heat transfer column being less than 5 inches of water when the superficial flow rate is greater than 100 feet per minute;
• and
• at least one of said heat exchangers including a purge line and a purge valve, said purge line leading to a source of clean air, said purge valve being opened after said heat exchanger is done receiving a gas to be cleaned and before said heat exchanger receives said clean gas, the purge acting to purge any residual gas to be cleaned from said heat exchanger passage.