You need to construct a material balance around your Claus/TGU to produce the composition, flow, temp and pressure of the process gas feeding the thermal oxidizer. You need to know the fuel gas composition and also the specify the combustion temperature and oxygen concentration you want in the flue gas. Normal combustion chamber temps for a thermal oxidizer are 500-750C but some applications require higher temps. The optimal flue gas oxygen concentration is approximately 3 percent.
All of this can be done very easily with VMGsim which has the best sulfur plant simulation capabilities due to its power and flexibility. It is also very easy to use and the support is also excellent. Once you specify the tail gas flow, fuel gas comp, O2 concentration and chamber temp, VMGsim can solve for the fuel flow and combustion air flow. You also need to consider the following for thermal incinerators: necessary TRS destruction efficiency (i.e. residual COS, CS2 and H2S), residual CO and H2 (H2 burns much more easily than CO), NOx and SOx (will be low if O2 is kept near optimum value of 3 percent), VOCs(including BTEX).
Other important details include burner selection, temp measurement, flame scanners, sight ports, placement and method of tail gas introduction, mass based CEM, refractory, forced or natural draft, superheater, breach, stack (carbon steel castable lined, SS tip, velocity), sample ports for analyzers and Pitot tube traverses for RATA tests, power at platforms, fall arrest system, manways, stack top temp (there will be losses of 25 to 100C from chamber), control scheme, BMS and ESD. Well it started out as an easy question…… 🙂
John O’Connell
Sulfur Specialist at Saudi Aramco
