Cement Mill Control DB MS

8/11/2019 Cement Mill Control DB MS

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BLUE CIRCLE TECHNICAL CENTRE

CEMENT MILL CONTROL

DAVID BAIRD + MARK STOERKERDAVID BAIRD + MARK STOERKER


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CEMENT MILL CONTROL

AIMS OF THIS PRESENTATION

To describe the various Control Loops available for

automatically controlling Cement Mills.

To identify the benefits to be gained.

To establish Where we are at present .

To ask the ?-Where do we go from here ?

To help you to develop an Action Plan to improve millcontrol within HBM.


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OPEN CIRCUIT

CEMENT MILL

CONTROL LOOPS


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Open Circuit Mill ControlsClinker

Gypsum

Other

Feed TPH

Mill sonicChamber 1 exit

temperature

Cement SSA m2/kg

and temperature

Water injection

Mill outlet

temperature


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CLOSED CIRCUIT

CEMENT MILL

CONTROL LOOPS


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CLOSED CIRCUIT CEMENT

MILL CONTROL LOOPS

AUTOMATIC LOOPSConstant Feed Rate-( tph )

Ratio control of Feed Components-( % Clinker.Gypsum,MAC)

Total Feed Control (Rejects and fresh feed).Sonic control (Folaphone)- Chamber 1 noise level.

Separator (H.E.S.) -airflow control.

Milling temperature control-( water injection % -C1+2)

Power -Mill Motor and Bucket Elevator KW.


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CEMENT MILL CONTROLLOOPS 1

CONSTANT FEEDRATE AND RATIOCONTROL OF FEED COMPONENTS

Accurate weight and Ratio control of the clinker /

gypsum / Limestone / MAC / Pozzolan is essential if weare to avoid.

STEP changes/variability in cement quality.

STEP changes in mill performance / stability due to

feed grindability changes.


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Effect of Gypsum, Limestone + PozzolanEffect of Gypsum, Limestone + Pozzolan

on Cement mill performanceon Cement mill performance

1% SO3 = + 30 m2/kg Surface Area

1% Gypsum = + 5% Production

1% Gypsum = + 12 m2/kg Surface Area

1% Limestone = -2.5% B.C.I Grindability

1% Limestone = +2%Production at constant SSA.

1% Pozzolan = -0.4 to -0.67 % B.C.I.Grindability


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CLINKER CHEMISTRY VARIATIONSCLINKER CHEMISTRY VARIATIONS--AFFECT ON MILLAFFECT ON MILL

PERFORMANCEPERFORMANCEconsumption and Chemistry for two closed circuit mills

No 2 Mill SRC

N1 Mill (OPC)

N1 Mill (OPC)

N2 Mill (SRC)

Mill Only Kwh/t

L.S.F.

LSF

C2S

C3

S

32.5 33.0 33.5

C2S

C3S

Mills under

AutomaticTotal Feed

Control

LSF

+5% C2S =+ 1 kWh/tonn


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BLUE CIRCLE TECHNICAL CENTRE

ESTIMATING THE COSTS OFPOOR MILL CONTROL


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C em ent S S A V ariations

300

340

380

420

460

Tim e

S

S

A

-m

2/k

T arg et G ood C on trol P oor C on trol

Control +/- m2/kg Range kWh/tonne Avg. kWh/t

Poor 40 340 420 37.0 50.8 43.9

Good 10 340 360 37.0 40.3 38.6

Savings 5.3 kWh/t


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OvergrindingOvergrinding --Power PenaltyPower Penalty

m2/ kg

Variability

Max

m2/ kg

Chamber 1

kWh/tonne

Penalty

kWh/tonne

0 340 9.0 0

+/- 10 350 9.4 0.4

+/- 40 380 10.6 1.6

When we overgrind, we waste power in Chamber 1:When we overgrind, we waste power in Chamber 1:


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CEMENT MILL CONTROL LOOPS 2SOUND CONTROL-CHAMBER 1

Can act as protection against overfilling Chamber 1by cutting feed if noise level drops due to other factors

ie blockages within the mill or at the mill discharge.

Feed cuts off at fixed sound level.A modification used at Aberthaw is to use Sonic to

input to the Total Feed Control Loop. This forward

feeds the effects of gradual build up in filling level.


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Folaphone (Mill Sonic) Location

Sensor 25 mm

from shell

Rigid stand

0.5 m from end of

mill Chamber 1

Mill

centerline or

below

This bloody

thing willnever work!

Direction of Mill


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CEMENT MILL CONTROL LOOPS 3MILLING TEMPERATURE CONTROL

Essential for Cement quality control and to avoid Millinternal coating problems.

Control of Chamber 1 water injection should be

based upon material temperature at IntermediateDiaphragm

Mill outlet temperature control should be based upon

the material temperature not gas temperature due tothe effects of inleaking air.


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CEMENT MILL CONTROL LOOPS 3

MILLING TEMPERATURE CONTROL (2)

With a High Efficiency Separator-install a gas recyclesystem with 2 damper controls (fresh air and recycle)

to control milling temperatures.

Control of mill airflow is normally manual. Check millexit gas dew point temperature and increase mill airflow

if high water injection is used.

Mill outlet material temperature control should betypically 110 - 115 C to avoid Flash/False set .


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Mill Temperature Control

Thermocouple in

diaphragm Pickup

transmitter

Water injectionchambers 1and 2

Thermocouple 140o

C

Inleak 15o

C

Thermocouple 90o

C


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CEMENT MILL CONTROL LOOPS 4

TOTAL FEED CONTROLEssential for maintaining a constant mill filling level to

achieve optimum grinding efficiency (optimum voidsfilling/powder loading-see C.T.C notes).

The separator characteristics remain more constant

with constant feedrate thus avoid large variations in Cutsize and Recirculating load.

Typical relationship:-

.PLUS 1.4PLUS 1.4 tphtph Rejects = minus 0.6Rejects = minus 0.6 tphtph FreshFresh

Feed FlowFeed Flow


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CLOSED CIRCUIT

CEMENT MILL CONTROLSOME PROBLEM AREAS


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POTENTIAL CONTROL PROBLEMS Inaccurate weigh feeders. Rejects flow spiking.

Undersized Separators with non linear characteristics.

Undersized Separator fan.

Excessive inleaking air over mill (>30%) and

Separator (>10%) dust filter plants.

Undersized Bucket Elevator limiting circulating load.

Poor airslide design causing uneven feed+rejects

flow.

Hold up inside mill due to nibs/poor internals causing

surging.


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Cement

Separator/Fan

Weigh

feeders

Mill Internals

Mill Fan Mill Dust filter

To storage

Elevator/Airslides

POTENTIAL PROBLEM AREASPOTENTIAL PROBLEM AREAS

Main filter


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A VIEW INSIDE- WHAT CAN COMPLICATE

AUTOMATIC CONTROL

Material Surges

Chamber1

Chamber2

Material Surges

Build up of Nibsat diaphragm


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WORN/BROKEN SLOTS ALLOW NIBS TO ENTER CHAMBER 2WORN/BROKEN SLOTS ALLOW NIBS TO ENTER CHAMBER 2

WORNWORN

LINERSLINERS

GAPSGAPS

ININ

SECTIONSSECTIONS

PROBLEM AREASPROBLEM AREAS--MILL INTERNALSMILL INTERNALS


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THE FUTURE-

WHERE DO WE GO FROMHERE?


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POSSIBLE OPTIONS FOR MILL CONTROLPOSSIBLE OPTIONS FOR MILL CONTROL

ABB LINKMAN -- NORTHFLEETNORTHFLEET

MAGOTTEAUX GO CONTROL-- COOKSTOWNCOOKSTOWN

POLYSIUS / FLS MILL EXPERT SYSTEMS

ARTIFICIAL NEURAL NETWORK SYSTEMS,PANTEKETC. -- BOWMANVILLE ?BOWMANVILLE ?

IMPROVE ON LINE ANALYSIS-SSA/PSD -- MALVERNMALVERN ,

SO3, -- ITECA, FLS LAB X 3000.ITECA, FLS LAB X 3000. 45 um ,ETC


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WHAT NEW / OLD PROBLEM AREAS WILL WE FACEWHAT NEW / OLD PROBLEM AREAS WILL WE FACE

WITH THESE NEW SYSTEMS?WITH THESE NEW SYSTEMS?

Level of reliability e.g. on line P.S.D. Analysers and

Sampling systems.

Needs a Works Champion.

Needs commitment and capital to have the best

chance of success.

Expert system must be able to control process-e.g.

avoid artificial limitations imposed by

airslide/elevator/separator speed/mill internal

limitations etc.


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YOUR TASKYOUR TASK

DEVELOP AN ACTION PLAN TODEVELOP AN ACTION PLAN TOIMPROVE AUTOMATIC CEMENTIMPROVE AUTOMATIC CEMENT

MILL CONTROL WITHIN H.B.M.MILL CONTROL WITHIN H.B.M.

BASE YOUR PLAN ON A CLOSEDBASE YOUR PLAN ON A CLOSED

CIRCUIT MILLING SYSTEM.CIRCUIT MILLING SYSTEM.


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HOW MUCH DOES THE LEVEL OF CONTROL

AFFECT MILL PERFORMANCE?

Documents

Cement Mill Control DB MS