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Variability Calculator
Excessive variability in the cement manufacturing process is one of the primary causes of the poor performance of cement operations. Chemical and physical variability can result in effects such as increased fuel consumption, reduced refractory life, increased production of off-specification material and over-grinding of cement, all of which lead to increased operating costs. This variability can arise at all stages of the cement manufacturing process - quarry, raw milling, pyro-processing and cement milling, and this variability can be in both the chemical and physical parameters. However, each of these parameters, and the size of variation, has a different impact upon the total overall variability.
Therefore CPI has developed a Variability Calculator which estimates total quality performance for each stage of the process. The calculation is based on the experience gained by CPI over many years and at many plants. By inputting the standard deviation of each of the chemical and physical parameters into the calculator, users can review their performance at each stage of the process, and therefore review at what stage, if any, costly variability is being introduced.
Once the stage of the process where the variability is being introduced has been identified, CPI can then assist in reviewing the exact parameter(s) which is causing the variability and propose solutions to eliminate the variability and thus improve performance.
Which parameter to test?
The results from the Variability Calculator are indicative only; they are based on CPI experience and are not absolute indicators of performance. The results are as a guide only and CPI can provide specific assistance to clients through their Process and Quality Improvement Services. Furthermore the quality of the results is dependent upon the reliability of the data input to the calculator.
Fuel Consumption Calculator
As the main energy-consuming and greenhouse-gas–emitting stage of cement manufacture, reducing fuel consumption is a central concern of cement manufacturing technology. Fuel consumptions can range from the most modern 6 stage Precalciner kilns with fuel consumptions of 680-700 kcal/kg cl to the oldest wet kilns up to 1600 kcal/kg cl. As such it is important to benchmark fuel consumption against similar equipment types.
Therefore CPI has developed a fuel consumption benchmark calculator which estimates benchmark fuel consumption figures for different kiln and cooler combinations.
Causes of high fuel consumption
The four most common causes of higher than benchmark fuel consumption are:- Low output on the kiln Shell heat losses (per tonne clinker) will increase if the system is being run at a lower than optimum output.
- Poor cooler efficiency caused by poor air distribution, poor maintenance, bad design or a combination of all three. It is quite common for coolers to be operating at between 5 and 10% below their maximum efficiency.
- Poor heat transfer in the tower , leading to increased tower exit temperatures. Higher exit temperatures are caused by:
- Poor material distribution across one or more stages of the preheater
- Material dropping down to a lower stage rather than being picked up by the gas stream
- Incomplete combustion in the calciner
- Too low oxygen level in calciner
- High number of unplanned stops This is due to the additional fuel used during heat up when no clinker is produced.
The results from the Fuel Consumption Calculator are indicative only; they are based on CPI experience and are not absolute indicators of performance. The results are as a guide only and CPI can provide specific assistance to clients through their Process Optimisation Services. Furthermore the quality of the results is dependent upon the reliability of the data input to the calculator.