Q & A > Question Details
What is the standard value of SOX & NOX in furnace stack outlet? Are the Values different in case of fuel oil firing and fuel gas firing?
10/07/2010 A: Prakash Pimparkar, Environmental Consulting Services , prakash.pimparkar@yahoo.in
SOX quantity in the exhaust gas is twice the sulphur feed rate in the fuel. For example if we are using 100 tonnes of fuel per hour and fuel sulphur content is 2 % then feed rate of sulphur would be 2 tonnes per hour and if all of it burns then it will form 4 tonnes of SOX (64/32 ). Normally you may assume about 95% of sulphur would be oxidised that makes it 0.95*4 = 3.8 tonnes per hour. Out of this about 99 % would be as SO2 and rest may be present as SO3.THis is for estimation purpose you may refer USEPA emission factors to arrive at more accurate estimates
NOx quantity similarly depends upon Nitrogen in fuel (particularly for coal). NOX however is also formed by the fixartion of Nitrogen in the combustion air and this depends upon many factors but primarily flame temperature, residence time in the furnace and the turbulence in the furnace (design features) that is why calculation of NOX is not as straightforward as calculation for SOX. Here again you can refer US EPAs air emission factors to get more accurate estimates.
As far as emission limits are concerned they vary from country to country
09/02/2009 A: keith bowers, B and B Consulting, kebowers47@gmail.com
Depends almost totally on composition of fuel used. No 'standard value. From the total sulphur and nitrogen values of the fuel, you can calculate the SO2 values using stoichimetric combustion + 15% excess air. NOx is also so calculated. The ratio between NO2 and NO3 is difficult to predict without knowing the type of fuel, composition, type of burner and details there-of. Even with prue methane, SOME NOx will form, but burner details are important.
09/02/2009 A: Samuel Sinanan, IPSL, Samuel.Sinanan@ipsl.co.tt
The quantities of SOx and NOx in the stack gases depends on the sulphur and nitrogen content of the fuel being combusted. Without knowing the specifics of the composition of the fuel gas and fuel oil that you have, in generaal you expect that the fuel oil will have much greater sulphur and nitrogen content giving higher SOx and NOx generated with combusted.