29-04-2014, 04:49 PM
PROCESS DIAGNOSTIC STUDIES FOR CEMENT MILL OPTIMISATION - CASE STUDY
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ABSTRACT
Grinding technology has been continuously improving with numerous innovations with a view to improve
productivity and reduce power consumption. In order to reduce the manufacturing costs for cement, it is very
important to optimise the existing mill installations as far as the grinding process is concerned and also to use high
quality spare parts and consumables like grinding media .
Ball mills are predominantly used machines for grinding in the cement industry. Although ball mills
have been used for more than one hundred years, the design is still being improved in order to reduce the grinding
costs.
HOLTEC has undertaken Performance Optimisation of the cement grinding circuits by doing process
diagnostic studies in many cement plants. The paper describes the approach for the process diagnostic study for
the optimisation of a ball mill circuit and is supported with typical case study done by HOLTEC in a 1.5 mio t/a
cement plant.
The paper also describes the principle of the mill load control system developed by the Holderbank
Engineering Canada Limited (HEC), Canada for the optimisation of the performance of the ball mills for obtaining
maximum production and minimum specific energy consumption.
INTRODUCTION
The need for process optimisation through diagnostic studies has been increasingly felt as production costs
are shooting upwards in conjunction with increased competition in the market. In order to reduce the manufacturing
costs for cement, it is very important to optimise the existing grinding installations.
Experience has shown that the potential for optimisation is greatest in the cement grinding process in a
cement plant The benefits that can be achieved due to the optimisation of cement grinding system through process
diagnostic study are:
Reduction in specific power consumption
Increase in production
Stable and sustained operation
Increase in availability of the equipment - Less down time
Improved and consistent product quality
Concept
M/s Holderbank Engineering, Canada has developed a control strategy for ball mills which can maintain a
mill production near optimum, with little operator intervention. The main principle of the concept is that maximum
production is obtained from a ball mill when the mill motor power is at a maximum and consequently the specific
energy consumption is at minimum. The maximum power point is dependent upon the feed material characteristics,
mill liner conditions, grinding media charge and product size requirements.
Installations Commissioned
The strategy has been successfully implemented in 33 cement grinding mills and 6 raw grinding mills in a
number of cement plants in America and Canada. The feedback received from the plants has shown increases in
production and reduction in specific energy consumption. These improvements are usually of the order of 5 to 10%
increase in the mill output and 3 to 5% decrease in the specific power consumption.
In addition to the improvements in production and power consumption, consistency in quality and less wear
and tear of the grinding balls and liners are experienced by the plants due to stable running of the mills.