gypsum crystal habit modifiers- wet FGD system
gypsum crystal habit modifiers- wet FGD system
(OP)
for wet FGD systems on coal fired plants that produce marketable gypsum:
Kindly advise if anyone has a concise and documented explanation of why hydrated calcium sulphate ( gypsum) crystals form large particles when firing high sulphur coal at full load which are easily de-watered, but the crystal habit changes to small, planar crystals which cannot be dewatered under the following conditions:
-fires a coal which has much lower sulphur content than the design coal
- has upset increases in Al and Fe due to ESP mishaps allowing excess flyash to be captured by the FGD slurry - possible FeF or AlF blinding or crystal habit modification?
- high hardness in the FGD makeup water , which includes high sediments of FeO and quartz fines
Some proposed fixes that were suggested were to lower the slurry's solids density by 33%, and/or increase the slurry's calcium to sulphate ratio. However, fiddling around with major process variables without any knowledge or explanation as to what the h*&^ is occurring is not good practice.
Kindly advise a reference that documents an solution and its explantaion, if available.
Kindly advise if anyone has a concise and documented explanation of why hydrated calcium sulphate ( gypsum) crystals form large particles when firing high sulphur coal at full load which are easily de-watered, but the crystal habit changes to small, planar crystals which cannot be dewatered under the following conditions:
-fires a coal which has much lower sulphur content than the design coal
- has upset increases in Al and Fe due to ESP mishaps allowing excess flyash to be captured by the FGD slurry - possible FeF or AlF blinding or crystal habit modification?
- high hardness in the FGD makeup water , which includes high sediments of FeO and quartz fines
Some proposed fixes that were suggested were to lower the slurry's solids density by 33%, and/or increase the slurry's calcium to sulphate ratio. However, fiddling around with major process variables without any knowledge or explanation as to what the h*&^ is occurring is not good practice.
Kindly advise a reference that documents an solution and its explantaion, if available.





RE: gypsum crystal habit modifiers- wet FGD system
There is a lot of information written about his particular process. I'll see what I can do next week, hopefully some contacts.
RE: gypsum crystal habit modifiers- wet FGD system
RE: gypsum crystal habit modifiers- wet FGD system
I took no notes, but as I recall the subject was discussed parallel to discussions of some PH changes from HOAD.
I'm trying to contact some people that should know about this or possibly lead me to someone who does.
RE: gypsum crystal habit modifiers- wet FGD system
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RE: gypsum crystal habit modifiers- wet FGD system
I'll forward this info the the FGD mfr and ask for their review of its effectiveness.
In the meantime, we are switching to hi sulphur coal,which will probably solve the issue in the interim.
RE: gypsum crystal habit modifiers- wet FGD system