Thermal Oxidizer Residence Time and Chamber Volume

Computed at the flow the chamber actually sees. The gas expansion is the arithmetic trap and it is close to a factor of four at ordinary operating temperatures, not the threefold that gets quoted: gas at 1,600 degF occupies nearly four times the volume it did at 70, so it moves through the chamber that much faster. A chamber sized on the inlet flow in STANDARD cubic feet therefore gives a residence time several times what the unit achieves, and a unit that appears to have a full second on standard flow can have a quarter of that in reality. Sizing must use the actual flow at chamber temperature, and the difference between the two is reported here rather than described. Destruction needs three things and residence is only one of them. Temperature, time and turbulence all have to be present, and they trade against each other but not freely: destruction is a kinetic process, so a lower temperature can in principle be compensated by longer residence, but the relationship is exponential in temperature and roughly linear in time, so a modest temperature shortfall takes a large time increase to make up. Turbulence is not in the arithmetic at all -- a chamber with the right volume and the wrong mixing has dead zones and short-circuits, and its measured destruction efficiency will not match its calculated residence. Halogenated compounds and high destruction efficiency requirements both push the temperature and the time upward, and destruction efficiency itself is MEASURED by stack test rather than calculated, which is why permit language states it as a performance requirement. This computes an ideal-gas expansion and a residence time from ENTERED conditions; it does not compute destruction efficiency, model the kinetics of any compound, size the burner or the heat recovery, address the flame arrestor and the lower explosive limit constraints on the inlet stream, or evaluate the products of combustion, which for halogenated streams include acid gases needing their own control. The oxidizer manufacturer, the stack test, and the permit govern.

expansion factor = chamber absolute temperature / the reference absolute temperature; actual flow = inlet standard flow x that factor; chamber volume = actual flow x required residence / 60; and the residence an entered chamber delivers is that relation inverted.

Residence time = chamber volume / the ACTUAL gas flow at chamber conditions, with the ideal-gas expansion taken on absolute temperature (degrees Rankine, offset 459.67). The three T's of thermal destruction -- temperature, time and turbulence -- are all required and only time is computed here. It does not compute destruction efficiency, which is MEASURED by stack test, model the kinetics of any compound, size the burner or heat recovery, address flame arrestor and lower-explosive-limit constraints on the inlet, or evaluate combustion products.

One ideal-gas ratio and one volume.

Estimate. AHJ and licensed professional govern.

Field names used by the API: inlet_scfm, chamber_temp_f, standard_temp_f, required_residence_s, chamber_volume_ft3, expansion_factor, actual_acfm, volume_required_ft3, actual_residence_s, standard_basis_residence_s

• Ideal gas real gas behaviour at chamber conditions is not modelledthe oxidizer manufacturer
• Turbulence is not computed mixing decides whether the volume is usablethe burner and chamber design
• Destruction efficiency is measured it is a stack test result, not a calculationthe permit