2017-TCMA 18th Technical Workshop and Exhibition

The 18th TCMA Technical Workshop and Exhibition

Venue: The Greenery Resort, Khao Yai

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The 18th TCMA Technical Workshop and Exhibition

Venue: The Greenery Resort, Khao Yai

Conclusion:

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The 18th TCMA Technical Workshop and Exhibition

Venue: The Greenery Resort, Khao Yai

Technical Paper: Ball Mill Optimization
Using Smartest Fill – Level Control

Mr. Dirk Schmidt
KIMA Echtzeitsysteme GmbH

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The 18th TCMA Technical Workshop and Exhibition

Venue: The Greenery Resort, Khao Yai
It seems to be an open secret that expert systems has been proven all over the world to optimize
the operation of ball mills. High-level control systems since more than decades has been guided
cement producers to a much more efficient and more consistent operation. Today we know that
this system does not make the operators unnecessary but offers the control team in the CCR
more time for other work. While these ‘ auto pilots’ control the mills -and kilns of course- there is
more time for manual adjustments and more precise operation in other fields of the plant.
On the other site each controller, independent of a human operator or an ‘auto pilot system’, is
only as good as the information (instrumentation) it guiding him. The unique technology Kima ‘E’ is
using with structure born sound to measure for instance separately the fill-level of chamber #1
and chamber #2 in cement mills, can be today declared as the cutting-edge technology for this
application within the industry. This article describes the success story of the SmartFill™ fill-level
measurement system developed more than 15 years back by KIMA Echtzeitsysteme in Juelich,
between the cities of Aachen and Cologne in Germany.

Pic. 1 SmartFill so-called ‘ OMU – On-mill-Unit’ with level sensors for chamber 1 and chamber 2
directly installed on the mill tube

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The 18th TCMA Technical Workshop and Exhibition

Venue: The Greenery Resort, Khao Yai

‘Expert systems’ established technology as it should be

A sophisticated and well developed expert system today is easy to use and should be open to
be maintained by the plant personal itself. Times when ‘ experts’ -process engineers with
programmer skills- from remote should visit the plant frequently for ‘ adjustments’ and
‘modifications’ are (or should be) history. A modern high-level control system does allow process
people by simple graphical tools and logic blocks via drag-and-drop to create and modify by
their self the individual plant control loops. I do not speak here about set-point corrections but
adding new instrumentation into the control loop, changing logical combinations e.g. when new
parameter have to be considered like new fuel types in the combustion or the change from
manual input parameters to new continuous measurement signals.

Pic.2 Logical functions and Co

The modular and open control software SmartControl™ developed by KIMA Echtzeitsysteme
considers this consequently. A large success is the use for grinding processes when ball mills have
to be controlled as single chamber or two-chamber mill incl. center discharge, for raw meal,
slag, coal but especially of course for cement production. The control logic can include in front
installed roller presses and of course the separator control. The solution for grinding processes is
sold under the name MillMaster.

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The 18th TCMA Technical Workshop and Exhibition

Venue: The Greenery Resort, Khao Yai
Mill Master comes with a multitude of function blocks that are assembled to a control group in a
special programme called ‘Control Designer’. The intuitive user interface offers clear visualization
is absolute flexible and very easy to learn. It was designed to offer process engineers without any
programmer skills the opportunity to generate the control logic and adapt/manipulate it by their
self without the need of external support (from Kima ‘E or others).
Pre-defined functions and structures are simply created via ‘ drag and drop’ from a large
catalogue of functions helps focusing on the essentials. A huge library of existing structures gives
most applications already a complete settled solution which has only more to be adapted by
limit value and set point adjustments.
By the way: The name of Kima ‘Echtzeitsysteme’ means ‘real time systems’ and is given because
of the unique experience in developing and using this digital filter since more than 20 years. To
smoothen highly variating process instrumentation signals for control purposes such filters
compare to traditional ones does not have a delay time. Picture 3 shows in the green line a
highly fluctuating measurement signal as it is usual in the process industry. A classical filter would
smoothen the signal but from the calculation itself it would always have a delay time – a killer e.g.
for in-situ measurements and process leading values in control loops at all.

‚raw‘ signal
classic filter
optimised filter

Pic. 3 Digital filters developed by Kima ‘E’ as real time information without any delay time

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The 18th TCMA Technical Workshop and Exhibition

Venue: The Greenery Resort, Khao Yai
Beside the high sophisticated digital filters, the MillMaster contains as well predictive models
which give not only a real time information but can predict trends into the future. So called ‘soft-
sensors’ can be generated which use more-dimensional input vectors -so a group of significant
process data- to determine already the outcome of a longer time taking process minutes and
hours in advance. This model prediction is a very useful tool for complex phenomes in non-linear
processes. Please consider that KIMA ‘ E’ is not controlling processes based on MPC –model
predictive control but uses this technology to get future trends in the control loop as soft sensor
information. Both, sensors signal and control loop are so much more stable in view of
unpredictable situations.

Pic. 4: Predictors for (here three process variables) support the behind connected fuzzy controller to take the
right action

Control loop and strategy
Each controller is only as good as its instrument for the targeted value. And each grinding
process is only as good as the mill capacity is used. The classical strategies for controlling a ball
mill are all influence the efficiency of the grinding process indirectly. Fresh material = constant;
Reject material = constant; Total feed = constant. All these strategies give the operator an
impression that his process is very constant. That is not the case because these strategies heavily
tend to oscillate. Measureable is that using a most precise fill-level measurement.

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The 18th TCMA Technical Workshop and Exhibition

Venue: The Greenery Resort, Khao Yai
For this reason, KIMA decided almost 20 years back to develop a fill-level measurement called
SmartFill which is based on structure born sound. The highly reproducible and stabile signals
which give the filling of chamber 1 and chamber 2 in a 2-compartment mill separately offer
high-level control systems fundamental new information. Consequently, the leading cement
producing companies in the world implemented or recommended in their own developed
expert systems the use of SmartFill ‘electronic ears’. KIMA Echtzeitsysteme uses the optimal filling
of the mill as well as main control parameter. The grinding becomes very stable which allows an
easier compensation of occurring disturbances. Mainly the hardness of the grinding material
varies and so the remaining time of the same within the mill. Picture 5 makes clear that all delay
times within the production circle are more or less constant ( T1-T5) only the time the material
spends in the ball mill itself ( T mill) is not known and definitely variating with the grind ability.
Logical that the fresh feed into the mill should be adjusted accordingly and be used to keep the
level inside the mill constant.

Pic.5: All time delays are constant for the control loop expect the time the material stays in the mill

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Venue: The Greenery Resort, Khao Yai
Also sophisticate controllers need reliable sensors

Compare to classical PID controllers the fuzzy components in expert systems like KIMA E’ s
MillMaster can compensate signal drifts as a result of wear in various parts of the process.
Compare to classical fill-level technologies the SmartFill Sensors includes the same feature –as it
was already described in other published literature. Competing systems / technologies are all
installed away from the original source of interest – the mill body. Microphones as well as vibration
sensors measuring the variation of sound or vibrations in bearing foundations are all indirect and
failure sensitive raw information. A microphone ‘listens’ in the same way too sensitive to other mills,
motors or gear boxes nearby as the vibrations of motors, wearing sprockets from drives or similar
disturb vibration analysis. It is not a secret that this type of systems must be re-calibrated very
often on a monthly basis.
With more than 700 (seven-hundred) SmartFill systems installed on ball mills in 47 countries and on
each continent this product is the cutting-edge technology in the market. Nearly 80% of these
sensors are implemented in high-level control systems and strategies which have the optimum fill
level as consequent target value.

Pic 6: A SmartFill On-Mill-Unit (OMU) with cable trays to the structure born sound sensors for chamber 1 and 2
as well as the optional thermocouple measuring the gas /material temperature within the diaphragm

With a constant fill level, inside of the one or two mill chambers not only the optimum production
volume is reached. Keeping this level(s) constant secures a more constant product quality as well
as the particle size distribution becomes thinner. And another logical effect is the reduced wear
of liners and balls which was reported from plenty of users in HeidelbergCement,
Dyckerhoff(Buzzi), LafargeHolcim and other producers. So, it is not surprising, that when it comes
to certain guarantees, OEM’s of grinding plants considers the SmartFill in their projects.
To secure to their customers in greenfield or modernization projects a constant product quality
and constantly high production, the measurement system with sensors box mounted directly on
the mill body is considered right from the specification.

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Venue: The Greenery Resort, Khao Yai
Implementation and adaptation to the plant automation

Independently which DCS system is used, the MillMaster reads and writes its data via OPC
connection to the plant controller. The very few set point corrections and limit value adjustments
can be easily implemented in the SCADA and Visualisation displays of the plant. This makes the
way from manual or standard PID control operation to the ‘auto pilot’ very easy.

In manual operation mill input (fresh feed) should be adjusted by a “fresh manual”-value which is
entered in the SCADA system. When MillMaster is running, its calculated “fresh feed set value” is
controlling the fresh feed.

Figure 4: Switching off MillMaster’s (MiMa) outputs to control your mill

Visualisation in the existing plant
SCADA system

This switching logic has to be
implemented for all available set
values (example):

1. fresh feed sv

2. separator rotating cage speed sv

3. separator fan sv

4. grinding aid sv

5. water injection sv..

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The 18th TCMA Technical Workshop and Exhibition

Venue: The Greenery Resort, Khao Yai
This and more set values can be full automated adjusted while the KIMA E’s MillMaster (MiMa) is in
operation. The system reaches usually runtimes of 95-100% of operation. So the operators learn
very fast in a common habitat that driving the mill in the auto-mode gives them time to
concentrate on other issues and works. The process engineers are very thankful that they can
change not only parameters but also adapt easiest new instrumentation into the control
strategy by their own.

Proven results

Already 10 years back, the plant of Lafarge Davenport –today Continental Cement in the USA-
has reported the various benefits of the MillMaster + SmartFill package. Johnathon Sprague,
Instrumentation Supervisor reports:

“The Davenport Lafarge Plant is very satisfied with our new Smartfill and MillMaster systems. Kima
‘ E is very knowledgeable and has been excellent to work with throughout our project. I will
certainly recommend the SmartFill system as a replacement for older microphone technology
commonly used on ball mills, and the MillMaster control system to maximize the benefits of
accurate mill level control.

Since operating and controlling our grinding mills with the MillMaster and SmartFill systems from
KIMA Echtzeitsysteme GmbH we were able to optimize our grinding process in terms of:

• Better information to make process decisions

o There was a plan to add additional block-off plates in the diaphragm, because it was believed
that Chamber 1 was under-loaded and Chamber 2 was full. The day we commissioned the
SmartFill device, we found that Chamber 1 was full and that Chamber 2 was only 60% loaded.
We later took out all of the existing blanks in the diaphragm to allow better flow into C2 and
have the level up around 85-95%.

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o It is now easier to see the effects of process changes because the mill loading is kept constant.
o We were able to reduce grinding aid usage while increasing production
• More stable operation resulting in more consistent lab results
• Less wear on liners and balls. We have mostly eliminated the loose liner bolts that we were
dealing with routinely. This is probably attributed to less direct impact on the liners, because of
stable mill loading.
• Reduced Kw per ton of cement
• Increased production
• The SmartFill system has had no required maintenance except initial setup and calibration.
• The commissioning and the optimization of the MillMaster system was taken care of by KIMA
engineers over VPN connection, freeing up manpower previously devoted to LUCIE
optimization.”
Latest the Opterra cement plant of Karsdorf, Germany, a former Lafarge plant ordered 6
MillMaster + SmartFill packages to optimize their ball mills – all in one building/hall. We certainly will
document the results and publish them later.

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Technical Paper: Energy Saving Grinding Systems with
Roller Press

Mr. Hans -Peter Jeschinowski
KHD Humboldt Wedag gmbh

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Technical Paper: MAAGTM CEM Drive –
Vertical Roller Mill Drive System

Mr. Sujith Varghese George
FLSmidth MAAGTM Gear AG

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