ACID DEW POINT

Sir,

   I need more information about Acid dew Point. While starting the Kiln, after firing  we divert the hot  gas to outside by a bypass duct and not allow the flue gas to Kiln Bag house till the preheater outgoing temp crosses  140C+ for fear of Acid Dew point and its effect on the bags.When the temp crosses 140+ we will take it into the Bag house. What about stopping the plant. When firing is off and cooling is going on whether the outgoing gas henceforth going through the kiln bag house damages the bags if temp comes down to below 140C. whether we have to divert the gas again through bypass duct if the temp reaches below 140C

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re ACID DEW POINT

Hi,

No there is no need when you are shooting it down because the dust on the bags are dry. But when you are starting up the moistrue on the bags will react with the SO3 and NOx in the flow gas and form acids that can damage the BH casing and bags.

Regards;

F.Jalali

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re ACID DEW POINT

Thank you Fjalali for the answer.I need one more clarification about the acid dew point which i hope you will help me. Now the plant is running normal with Waste heat recovery plant as well. When they take all the hot gas from preheater for their plant whats left off enters the bag filter and there if the temp reduces comes down below 140-120 C  then whether this will damage the bags in the Bag filter?. As per you if the bag is dry then acids should not damage the Bags. Do you agree ? Pl reply me.

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re ACID DEW POINT

Hi there,

No during the operation there are no moisture on the bags so the gases SO2 and NOx will so and won’t convert to acids. As long as your temperature are above 130 there are no acid formation, but depending on your SO2 and NOx concentrations and moisture levels you can have the possibility to form them.

See the sulfuric acid dew point chart.

Regards;

FJALALI

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