technical NOTES

7.6 Comparative Features of Vertical Roller Mill and Roller Press for Clinker Grinding

S. N. SALIENT FEATURES ROLLER PRESS VRM

1 Welding of grinding

rollers for clinker grind-

ing

Stud type rollers are

provided hence welding

is not required. Hence

consistent production is

achieved throughout life

of the rollers i.e. guaranteed

1 5000 hrs. but practically

can be achieved more than

30000 hours.

Welding of rollers is essential

after every 1000/2000

hrs to maintain consistent

production which need 3-day

stoppage. But recently

Sinter cast rollers which has

less wear and 1 year life are

being incorporated

2 Requirement of grind-

ing aid in the process in

clinker grinding

No grinding aid is required

for normal operation of the

roller press. Using grinding

aid shall result to increase

of production.

Grinding aid is essential

to maintain the bed stability

on higher Blaine. Cost of

the grinding aid is approx.

Rs. 4-5/ton of cement.

3 Requirement of hot air

for clinker grinding

Roller press with ball mill

cement grinding process

does not require hot air and

during the kiln shut down it

can be operated with cold

clinker,

Vertical roller mill needs

hot air to dry out the

added moisture in the

product which is require

d for maintain stable bed

to reduce the vibration

level. The mill is difficult to

operate during kiln

shutdown since it needs

hot gas generator.

Resulting increase of

operating cost.

4 Quality of finish

cement product

Quality of cement product

is better since it gives better

strength after 180 days.

Quality of cement

product is slightly lower.

5 One day strength of

cement

one day strength of

cement is approx. 14-16 MPa

One-day strength of

cement produced VRM

is comparatively less i.e.

approx. 10-11 MPa

6 Production of higher

Blaine of cement

System is very suitable for

higher Blaine (above 4000

Blaine) cement

System is suitable up to

4000 Blaine cement.

7 Flexibility of system in

clinker grinding

Two roller presses

system is more flexible

to run the plant as per

market requirement.

Maintenance can be done

without suffering the

market requirement.

On account of shut down,

market is going to suffer

or we have to invest in

cement Silo to keep the

buffer stock of cement.