Cement production process

1.

CEMENT PRODUCTION
PROCESS

2.

ROLLER MILL

3. Vertical Roller Mill (VRM) - 3 Sections

Transport
Exhaust gases
Raw meal
1. Separation
Drying
Separation
Feed
Material
Grinding
2. Grinding
Hot
gases
Drive
3. Drive
Energy

4. Vertical Roller Mill (VRM) - Details

feed gate
(air lock)
mill exhaust
product discharge
mill outlet duct
separator
cage rotor
separator
guide vanes
tailings cone
separator
discharge flap
mill casing
roller with tyre
or segments
water
injection
rocker arm
roller axle
table liner
dam ring
hot gas inlet
nozzle of
louvre ring
grinding table
hydraulic cylinder
material scraper
clutch
and motor
speed reducer with
table bearing

5.

VRM - Working principle
Vertical roller mill
Grinding force =
Roller weight + (pressure) Force
Material bed
Roller rolls freely
with table
Feed material
Table moves with drive
Max Particle size in feed: 5-8 % of roller diameter
Feed size:
f (Roller Ø )

6.

VRM - Material Flow inside
Separator:
removes fine
material
Gas & Product Material
Feed Material
rejects coarse
material
Internal gas
flow
Separator Rejects
Internal Circulation
Large Material falls through to
scraper
Material
Material & Gas
Gas

7.

VRM - Some Common Mill Configurations
G.Pfeiffer
Loesche
FLS Atox
Polysius

8.

VRM - Built-in Separator
static separator
Static
type
conventional rotor type
Conventional
cage rotor type
Cage
Rotor type
with guide vanes
P
P
Rotor type
F
T
F
F T
P
T F
F
F
P
T
Separation control:
1. Vane adjustment
2. Speed control
TF
FT
F=
Feed
P=
Product
T=
Tailings

9.

Separators of
rd
3
Generation
(Vertical roller mill)
Reject cone
Cage rotor
Guide vane system

10.

VRM - Separator Fotos
Angle affects
product sizing
Rotor speed affects
product fineness
Rotor seal affects
separator efficiency

11.

Potential Problems/clogging
Cage rotor separator casing
partly clogged
guide vane
system
Material deposits
due to insufficient
airflow or airflow
distribution

12.

VRM - External Circulation
fresh feed
bucket elevator
louvre ring
scraper
Used for reducing
gas flow pressure
lost over the mill
(less pneumatic
internal circulation)
collecting conveyor

13.

VRM - Example flow-sheet
Control points
1 gas flow
2 pressure
difference
3 return gas
flow pressure
4 outlet
temperature
5 external
recirculation

14.

VRM - Control & Maintenance
Control
Gearbox
- Vibration monitor
- Temperature monitor
Gas flow
- Temperatures & pressures
Hydraulics
- Pressures
Maintenance
Wear
- Rollers & Table
- Separator (sealing!) & Housing
Lubrication & Hydraulics (filters and seals)

15.

VRM - Control
[kW]
grinding aid DEG [l/h]
[°C]
[t]
[mbar]
[min-1]
[%]
-1]
[min
[l/min]
[mbar]
[%]
[t/h]
[mbar]
[min-1]
Clinker
[t] [%]
Gypsum
[t] [%]
[t/h]
[t/h]
[bar]
[l/h]
[kW]
sampler
[cm2/g]
[%R]
to cement
silo
[mbar]
[°C]
Hot gas
[°C]
[%]
fresh air

16.

Vertical roller mill internals suffering from wear
Outlet duct
Inlet chute
Separator
Separator cone
Mill housing
Armour &
nozzle rings
Rollers and
table liners
Scrapers

17.

Roller and grinding track liners
Grinding track liners:
Monobloc
Segments
Roller liners:
Monobloc
Segments

18.

Wear resistance material alternatives
• Nihard 4
%C
% Cr
% Ni
Weldable
< 3.5
< 10
< 6.5
yes
• High Chromium alloys
%C
% Cr
% Other
Weldable
Example
< 3.6
< 17
Mo + Ni
yes
Chromodur, FMU18, VegalineV16s
< 2.6
< 20
Mn
No
FMU 52
< 3.5
< 28
< 1.2
No
FMU 46

19.

Wear resistance material alternatives
• Metallic inserts roller liner
Soft material base
Hard metallic insert

20.

Wear resistance material alternatives
• Ceramic inserts roller and grinding track liners
Metallic base (High Cr)
Ceramic insert

21.

Wear rate monitoring
2’500 [h] = 50 [mm]
40 [mm] = ~ 2’000 [h]
Minimum allowed thickness

22.

Wear resistance material alternatives
• Surface reconditioning on grinding track and
roller liners
%C
% Cr
% Others
Weldable
Example
<5
< 29
Ni, Mo
yes
Vautid 100, HC-O
< 5.5
~ 22
6 – 7 Ni
yes
CN-O, CNV-O

23.

VRM - Accessories
Pendulum valve
Rotary valve
Reduces false
air entering
with feed
material. Good
for dry, small
size material.
Weigh belt
Weighs the passing material
ensuring a continuous
grinding bed in the mill
Reduces false
air entering.
Better for
lumpy or
humid feed
material.
Metal extraction
Metal objects
damage the
roller & table.
The magnet
removes them