high SO2 emission

[djoko]

hi,

I have two different boilers, namely B 6203 and B 1104. B 6203 is a dual burner system, can use fuel oil or natural gas, while B 1104 is can only fuel oil. Fuel oil used on those two boilers is the same, a marine fuel oil (MFO) with viscocity 15,21 cst (on 100 degree Celcius).
When used MFO as fuel, those two boilers have a different SO2 emission. B 6203 emission is 2000 mg/NM3 while B 1104 emission is only 100 mg/NM3. We use fuel oil treatment (FOT) that it's active content is Mg. Mg content on MFO is about the same, 38 ppm.
The conditions that differ those two boilers are :
1. emission laboratory analysis. B 1104 used spectrofotometry as analysis methode while B 6203 used Iodometry (titration with Iod). I have checked emission of B 6203 with those two different analysis and got 2008 mg/NM3 with Spectrofotometry and 2222 mg/NM3 with Iodometry, still high emission.
2. MFO temperature inlet burner. B 1104 MFO temperature inlet burner is 90 degree Celcius, while B 6203 is 60 C.

My questions are:
1. Parameter that affect the SO2 emission? why while we used the same fuel oil, the SO2 emission on those two boiler is greatly different.
2. Are viscocity of fuel and gun burner type affect SO2 emission?
3. Is point injection of FOT is affect the SO2 emission too?

As an info:
1.when we used natural gas as fuel for B 6203, the emission is low, less than 100 mg/NM3. Sulfur content on fuel oil is 1.7%weight and sulfur content on natural gas is only 3 ppm.
2. Oxygen excess on those two boilers is maintained at 2-4% excess.

thanks,

dj

 

[hacksaw]

take a look at fuel oil atomization on the high SO2 boiler.

sounds like the additive is not being allowed to do its job.

 

[orenda1168]

Djoko:

SO2 formation is, on a mass basis, a function of the fuel sulfur content, on the presumption that all sulfur present in the fuel will be oxidized to SO2 initially. With a fuel oil sulfur content of 1.7%, 2000 ppm SO2 is not surprising. Knowing the fuel flow rate, fuel sulfur content and excess oxygen level, you can easily calculate with reasonable accuracy the flue gas SO2 concentration which should compare favorably with the measured concentration if the SO2 analysis is accurate.

The magnesium-based additive will have no effect on SO2 formation, but will be effective if applied at the correct dosage in controlling catalytic SO3 formation (from the SO2 present in the flue gas stream), as well as providing cold end (heat recovery zone) acid corrosion protection. The point of FOT injection is not material to the SO2 formation. There is no chemical fuel additive mechanism capable of controlling SO2 formation......sulfur content reduction in the fuel is the only option.

On the assumption of complete oxidation of the fuel sulfur to SO2, the fuel viscosity and burner type/configuration is of no consequence, though these will have a significant effect on fuel combustion efficiency.

There is no apparent reason for both boilers having widely different SO2 emissions when burning the same fuel oil, unless:
1) the analysis is faulty, or
2) the dual-fuel boiler was in fact burning gas when the stack analysis was done. As you have pointed out, with the duel-fuel boiler on gas, the emissions are comparable to the gas-only unit.

Orenda

 

[mbeychok]

Djoko:

I agree completely with the response given to you by Orenda1168 ... and especially with his last paragraph.

Milton Beychok
(Contact me at www.air-dispersion.com)