Direct Fired Thermal Oxidizer

A thermal oxidiser destroys volatile organic compounds (VOCs), hazardous air pollutants (HAPs) and odorous gases by oxidising them at high temperature in a dedicated combustion chamber. The waste gas is heated by a burner to a high temperature and held there for a set residence time with enough turbulence to mix the gas and oxygen, which converts the pollutants to CO₂ and water. Temperature, residence time and turbulence are the three design variables that set the destruction efficiency. A direct fired thermal oxidiser (DFTO) is the simplest form, with a burner and chamber and no heat recovery, and CRA designs and manufactures DFTOs in-house in Noida.

A thermal oxidiser and a flare both destroy hydrocarbons by high-temperature oxidation and differ in design and duty. A thermal oxidiser burns the gas in a chamber with a closely controlled temperature, an engineered residence time for a specified destruction efficiency, PLC-based controls and optional heat recovery, and suits continuous or batch VOC streams. An enclosed flare burns gas at conditions that vary with the relief flow, with a wide turndown, and suits emergency relief and variable vents. An open elevated flare burns at height with a visible flame and very wide turndown for large relief. CRA supplies both technologies.

Yes. A thermal oxidiser can be designed to treat the combined stream from several process vents, which gives a lower total capital cost than individual units, a smaller footprint, centralised monitoring and a single emission point for permitting. The engineering covers flow balancing through the manifold, isolation dampers for each source, the combined VOC load, chemical compatibility so that streams do not react before oxidation, and mixed inlet temperatures. A combined unit makes sense when the sources are close together and run on coordinated schedules. Separate units are better for dispersed sources, very different schedules, incompatible streams or segregated permits. CRA analyses the vent data to set the configuration.

A direct fired thermal oxidiser (DFTO) is the right choice for high-VOC or high-heating-value streams, batch operations, emergency vents and applications with fluctuating flow, where fast response, simplicity and reliability matter more than heat recovery. It suits VOC concentrations above 25% LEL where operation becomes autothermal, intermittent duty where heat recovery equipment would sit idle, emergency relief that needs instant availability, wide turndown of 20:1 or more, particulate-laden streams that would foul a heat exchanger, and projects where capital cost is the main driver. It has a burner and a chamber with few moving parts, heats up quickly and needs little maintenance. CRA builds DFTOs for these duties.

Destruction efficiency figures are similar across thermal oxidiser suppliers, so they rarely separate one from another. The useful checks are whether the chamber was sized against the plant's actual vent profile including upset and turndown cases, whether the burner management system is designed to NFPA 86, how the system behaves when it trips on a load swing, and whether any heat recovery was engineered against the plant's real steam or hot oil demand. CRA designs and manufactures RTO, recuperative, direct fired, acid gas, sulphur tail gas and low NOx thermal oxidisers in-house, and supplies the burner, chamber, heat recovery and controls as one engineered package.