HCl in the stack
HCl in the stack
(OP)
What are the main sources of HCl in flue gases condensate downstream a wet FGD system?
How can I calculate the concentration of HCl in the stack condensate given the Cl content of fuel, of process water (used for lime milk preparation) and of calcium sulfate (cake)and given the water condensation mass rate on the stack (per sq meter)?
fvincent
Figener S/A





RE: HCl in the stack
RE: HCl in the stack
Thanks for your answer
The saturated gases come from a wet FGD and so are clearly below H2SO4 dew point, so that an acid mist is carried by these gases.
The stack is not insulated so that we can expect water condensation depending on the rate of heat transfer to outside air.
My question refers to HCl presence: how can we calculate the HCl (or in general, chlorides) in the condensate, according to Cl content of fuel, lime slurry and sulfate cake (considering that filtrate is sent back to lime slurry preparation?
fvincent
Figener S/A
RE: HCl in the stack
RE: HCl in the stack
You should either select suitable chloride resistant materials if the stack is unlined - anything from Corten through to the special high nickel alloys, or if your stack is insulated you might be wise to line it with one of the proprietry products available specially for this purpose and suitable for temps up to about 200°C (stack wall temp, not process gas temp).
Hope this helps!
RE: HCl in the stack
RE: HCl in the stack
The problem with any acid, not just HCl and H2SO4, is that it isn't the total amount that controls the corrosion. It is the location that happens to have enough present.
= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm
RE: HCl in the stack
For HCl calculation I guess you could assume that all chlorides in fuel burn to form HCl. Not sure to what extend that would be true, without testing, but it would be a worst case. Now, you calculate vol or wt% HCl in the flue gas.
Then for HCl-water liquid phase in equilibrium with HCl-Water-Air vapour phase, get water-concentration vs temperature and vs pure-component-partial-pressure-data. Liquid-concentration vs vapour-pressure equilibrium data is avaialble at Vulcan Chemicals web site, for example, i believe (they sell HCl). etc. Assume liquid-vapour equilibrium and from there assume ideal gas, as an approximation. From the % volume or % wt HCl in vapour (PV=nRT) that you calculated above, calculate %wt HCl in liquid phase (for your specified tempeture). A good chemical thermodynamics book or even Perry's handbook could help in review of Dalton's Law (? in vapour phase, partial pressure of a pure component represents the volume concentration of a pure component if i recall correctly), etc, which is used in the calculations. Then you could estimate HCl content in condensate at a given temperature (keeping EdStainless's comment in mind! when specifying temperature)
Good luck.