Lump formation in cement silo
Reasons for Lump formation in Cement Silo
- Temperature of cement.
- Entry of humid air through aeration blowers and lack of venting.
- Surface conditions of cone and the side walls.
- Entry of moisture along with cement.
- SO3 and Alkalis in the cement.
- Storage time of the cement.
Temperature of Cement
Cement temperature must be less than 80 deg C when conveyed into silo. If it is more than 80 deg C, the crystalline water from Gypsum gets dehydrated and moisture moves to the colder part, i.e. center cone and the walls .This moisture hydrates the fine cement and causes cake formation. Presence of Alkalis accelerates prehydration. In Clinker K2O + Na2O is 0.8. In cement 0.63 (PPC) and SO3 is 1.8%.The coating formed is called Syngenite( K2SO4.CaSO4.H2O).
Effect of Surface on Lump Formation
If surface of the inner cone and side walls are rough cement make dead layer and over a period of time they get hydrated and dislodged causing blockage. To have a glassy surface, the walls and floor are coated with epoxy or materials which can form fine surface which facilitates smooth out flow flow of material.
- Reduce the cement temperature from 90 deg C to 70 step by step.
- Reduce the storage time present 10 days to 6 days.
- Silo venting must be on when cement is extracted and aeration is done. When RH is high, it can accelerate the hydration.
(Reference from Mr. Pradeep Kumar)