Lump formation incement silos

Lumps formed incement silo

Reasons for Lump formation in cement silo

Entry of humidAir through aerationBlowers and lack ofventing

Entry of moistureAlong with cement

Storage time ofin the cement

Temperature ofcement

surface conditionsOf cone and the Side walls

SO3 and AlkalisIn the cement

Temperature of cement

Cement temperature must be less than 80 Deg C whenconveyed into silo. If it is more than 80 deg C the crystalline waterfrom Gypsum gets dehydrated and moisture moves to the colderpart ie center cone and the walls .This moisture Hydrates the finecement and causes cake formation. Presence of alkalis acclerates prehydration.In our 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)

60 80 100 120 140

100

80

60

40

20

0

Cement temperature Deg C , stored

Per

cent

age

of h

eavi

est c

oatin

g

SO3=2.7 %260 M2/kg

Intensity of coating formation as a functionOf cement temperature stored in cement silo

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 hydratedAnd dislodged causing blockage.

To have a glassy surface, the walls and floor are coated with epoxy Or materials which can form fine surface whichfacilitates smooth out flow flow of material

Storage timeHigh storage time and high cement temperature, both canaid cake formation.

Our cement in silo 4 and 5 is more than 12 days In silo 3 it is 2 to 3 days.

Our cement

Effect of gypsum content on cake formationHigher gypsum addition or higher SO3 in cement accelerates the hydrationof cement In silo. Anhydrate gypsum reduces coating formation ie., Caso4

Ratio of anhydrate/gypsum(CaSO4.2H2O) ratio

Addition of anhydrate(Gypsum without water)Can reduce lumpFormation in silo.

Ultimate solution

1.Reduce the cement temperature from 90 deg C to 70step by step

2. Reduce the storage time present 10 days to 6 days

3. Silo venting must be on when cement is extracted and aeration is done. When RH is high It can accelerate the hydration

Thanks for your kind attention

K.P.PRADEEP KUMARSr G M OperationChettinad cements LtdKarikkali works