If a gas stream contains both particulate and gaseous pollutants which should be removed first and why?

Answer 1

In coal based thermal power stations, the flue gas containing particulates & polluting gases are treated in following manner :

1) Boilers with pulverised fuel firing :
coarse particulates removal by cyclone separators
fine ash removal by ESP / bag filters.
Gasious pollutant removal by gas scrubbing ( Dry or wet method )

2) Fluidised bed boilers :
SO2 is captured in the furnace bed by dolomite injection
particulates in flue gas are captured in cyclone separators followed by either ESP or bag filters . Normally gas srubbers are avoided .

Precaution is taken to keep gas temperature above acid dew point upto stack entrance to prevent corrosion .

Answer 2

That is very hard to answer. It actually depends upon what the particulate and the gasseous pollutants are.

If the gasses are corrosive (e.g. acid vapor), you would want to neutralize the acid promptly and this may make more particulate so particulate removal would be second. Also removing the acid reduces acid induced corrosion on the equipment.

If the gasses are of high toxicity you probably want to address this first because you will elminate a risk early in the process. If the particulates are equally toxic it may make little difference.

If treatment of the gas generates a gelatin solid that gums things up, you may wish to do particulate first.

More info is needed and each case would be different.

Answer 3

The particulates are always removed first by filtration.
This is generally followed by separation of free water from the gas, then the glycol or other process of dehydration of the gas.
The treatment processes to remove pollutants, use equipment like absorption towers, pumps, compressors, instrumentation and other systems to do the job and solid particles will cause many problems, like build-up and blockage, erosion of pipelines, valve seats and other parts of the process unit.

Answer 4

It depends upon what are your allowable limits. I would get rid of acidic or corrosive or reactive gaseous elements by scrubbing them thru NaOH, CaO or other agents and after that rid the particulates by mechanical filteration or electrostatic precipitators etc. You really need to identify what the gaseous compounds are that need to be gotten rid of their concentrations, the relative humidity and temperature of the stream and it this is a continuous flow rate or variable.

After all this I would drink 7 shots of scotch before swettling down on nuzzling some brandy and then watch some really intellectuyally stimulating TV like World Wrestling or naked women wrestling and then like a typical engineer go to bed with my left and right hands (we all know engineers dont have dates because rubber dolls dont count).

Good Luck!

Answer 5

Remove the dry particulates first. Otherwise they will just interfere with (gum-up or plug ) subsequent neutralizations, either wet or dry.