Scrubber plume 3

[jdbanks]

I am interested in the formation of SO3 aerosol plumes from combustion operations involving sulfur in the material being burned. Particularly I'd like to find some way to influence the SO2 / SO3 conversion ratio in order to minimize the plume.

 

[LeslieP]

Have you considered installing a post-combustion fume scrubber, using either caustic or lime? That is a sure-fire way to reduce emissions.<br>
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[jdbanks]

Yes, I've considered the "ultimate" solution.<br>
In many cases, however, the plume is just slightly more prominent than allowed by law. If a process change can nudge it back over the line, lots of money can be saved by the plant operator. I'd like to hear from anyone, but preferably someone who has tried and succeeded.

 

[ail]

Drying of Air with the help of 98% H2SO4.The air is ambient.The outgoing air should be less than ppm of moisture.What will be the column dia,height of packing,type of packing,circulation rate?

 

[Rocco8]

In sulfuric acid plants they use Brink's demisters to remove sulfuric acid aerosol mists. You must check their temperature limitation however.

With regards to influencing the SO2/SO3 ratio it is impossible. With 1.5% excess O2 there will always be 1.5 mole% SO3 and 98.5 mole% SO2 at 1800 F. I ran a sinulation and had to go oxygen deficient inorder to eliminate the SO3. At this point I had incomplete combustion.

 

[Flareman]

Can you combine your Sulfur laden flue gas with another hot stream at the discharge point for dilution and additional thermal input? This should change the pattern of atmospheric cooling and downstream dilution and sometimes (!) can prevent a visible downstream plume.

 

[jdbanks]

Thank you for the idea. Typically the incinerator stack is isolated from the rest of the plant, so dilution with another hot stream is usually not available for cost reasons. We could reheat the stack gas using a separate burner at the stack, but I think calculating the minimum fuel needed to prevent SO3 plume formation is not possible!

 

[jayboz]

I am wondering what could cause a blueish plume if the so2 and so3 are low, the so2 around 450-500ppm and so3 below 7 ppm.

 

[Easel]

SO3 hydrates to H2SO4 and leaves a system as a <1 micron fume. Being so small, the opacity contribution is much greater than its mass contribution. It cannot be scrubbed with caustic. It must be captured by impaction (Brinks type filter mentioned earlier) or by electrostatic precipitation. Many units use wet ESPs for SO3 removal. The recent moves to incease SO2 removal at utilities will increase SO3 emissions and their opacity.

 

[aleximor]

jayboz:
Is there any ammonia in the surrounding air? That will give you a lovely blue plume!

 

[jayboz]

Alex,
yes they are injecting ammonia for contro; of Nox i believe. Why does ammomnia cause a blue plume? ANd this unit has the SCR's on it also, but there hasnt been any high levels at SO3 at this plant, as thought. There has been no testing to see what ammonia is coming out of the stack and i believe there will be testing for this soon, but the SCR will be out of service until next March probably. Thats what i do, go around testing the plants for SO3 after the SCR's are in service. Thnx for the replies.

Easel,
We have saw a rise in SO3 with some plants with SCR's, but at this one there has been no increase, the other plant that did increase is scrubbed and has put in three systems to decrease the SO3. MAg, Water and Lime.

 

[aleximor]

Jayboz
Ammonia will react with any SO2/SO3 in the exhaust gas to form solid ammonium sulphite/sulphate. The blue colour is due to the extremely small (sub-micron) particle size, which also makes such fumes fairly difficult to arrest. It sounds as if the SCR unit needs tuning up a bit; in most &quot;environmentally advanced&quot; countries the permitted ammonia emission levels from SCR are very low.

 

[jayboz]

Thnx for the reply. The blue plume seems to be common for the 3 scr's i have been around, with all three having different so2 and 3 levels. The scr's are new to the area and they are still tuning them up i guess.

 

[mstainbrook]

I work with NH3 and SO3 Flue Gas Conditioning Systems (for ESP tungin) and I agree the excess NH3 and SO3 will cause the blue plume. Additonaly Many Coal fired boilers that have added SCRs have to now closely monitor their NH3 slip. Additionly, the SCR catalysts may be converting SO2 in the flue gas (venadium in the catalyst) and increasing the SO3 content.

I would review the NH3 slip on the SCR before adding additional equipment. mstainbrook
stainbrook@angelfire.com
IT/Controls/Environmental Equip Eng