Grinding with VRM Systems

VRM

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HGRS Tikaria_Mill Workshop SEPT-07

Vertical Roller Mill (VRM) - 3 Sections

1. Separation

2. Grinding

3. Drive

Separation

FeedMaterial

Grinding

Drive

Raw mealExhaust gases

Transport

Drying

gases

Energy

Hot

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HGRS Tikaria_Mill Workshop SEPT-07

Vertical Roller Mill (VRM) - Detailsfeed gate(air lock)

mill casing

waterinjection

dam ring

louvre ringnozzle of

material scraper

mill outlet duct

speed reducer withtable bearingand motor

clutch

grinding table

hot gas inlet

hydraulic cylinder

table liner

roller with tyreor segments

roller axlerocker arm

discharge flapseparator

tailings cone

separatorguide vanes

cage rotorseparator

product dischargemill exhaust

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HGRS Tikaria_Mill Workshop SEPT-07

VRM - Working principleVertical roller mill

Feed size:f (Roller Ø )

Material bed

Feed material

Max Particle size in feed: 5-8 % of roller diameter

Grinding force =

Roller weight + (pressure) Force

Table moves with drive

Roller rolls freely with table

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HGRS Tikaria_Mill Workshop SEPT-07

VRM - Material Flow insideGas & Product Material

Feed Material

Separator Rejects

Internal Circulation

Large Material falls through to scraper

Internal gas flow

Material & Gas

Material

Gas

Separator:

removes fine material

rejects coarse material

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HGRS Tikaria_Mill Workshop SEPT-07

VRM - Some Common Mill Configurations

G.Pfeiffer Loesche FLS Atox Polysius

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HGRS Tikaria_Mill Workshop SEPT-07

static separator conventional rotor type cage rotor typewith guide vanes

F T

P

F F FT T

P

F F

T

P

T F

P

F =

P =

T = Tailings

Product

Feed

F T

VRM - Built-in Separator

Cage Rotor typeConventional

Rotor type

Static type

Separation control:

1. Vane adjustment

2. Speed control

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HGRS Tikaria_Mill Workshop SEPT-07

VRM - Separator Fotos

Angle affects product sizing

Rotor speed affects product fineness

Rotor seal affects separator efficiency

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HGRS Tikaria_Mill Workshop SEPT-07

VRM - External Circulation

Used for reducing gas flow pressure lost over the mill

(less pneumatic internal circulation)

collecting conveyor

fresh feed

louvre ring

scraper

bucket elevator

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HGRS Tikaria_Mill Workshop SEPT-07

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)

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HGRS Tikaria_Mill Workshop SEPT-07

VRM - Example flowsheet

Control points

1 gas flow

2 pressure

difference

3 return gas flow

pressure

4 outlet

temperature

5 external

recirculation

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HGRS Tikaria_Mill Workshop SEPT-07

VRM - Accessories

Rotary valve Pendulum valve

Weigh belt Metal extraction

Reduces false air entering with feed material. Good for dry, small size material.

Reduces false air entering. Better for lumpy or humid feed material.

Weighs the passing material ensuring a continuous grinding bed in the mill

Metal objects damage the roller & table. The magnet removes them