Most readers will be aware of the importance of measuring the quantity of material returned to the input of a grinding circuit to obtain a measure of the efficiency of the grinding process.
In a cement manufacturing plant the final cement mill is a typical case where the measurement of coarse returns allows for better control of process efficiency as variations in the performance of the grinding circuit occur over time.
In particular if coarse returns flow rate increases then the quantity of raw material injected into the process must be reduced so as not to aggravate the problem.
The measurement of coarse returns in a cement plant is often automated by inserting an impact weigher into the recirculation circuit.
Australian company Flow Force Technologies Pty Ltd has a history of supplying this type of mass flow rate measuring equipment to the cement manufacturing industry over some 15 years in Australia, South East Asia, USA and most recently in Latin America through their associates Master Control in Monterrey, Mexico. See photo.
Calibration of a coarse returns cement impact weigher is best carried out during plant commissioning when the mill is not required for cement production. Ideally if a known amount of cement can be passed through the weigher then the instrument can be calibrated. A reference test weight is then used to obtain a reference flow rate that can be used later on (during maintenance outages) to check and correct for any drift in the weight measurement.
In other processes where it is preferable to calculate process efficiency from measurements of input and output flows the use of two weighing devices together with a single yield measurement display unit can be an attractive method. Flow Force have also supplied this type of solution in Australia.
FlowForce™ MD Brian Lewis, stresses the importance of an integrated approach to plant chute design, including the impact weigher (which effectively forms part of the chute), to ensure optimum performance of the chutes and the impact weigher.
Flow Force can also supply calibration chutes and diverter valves to assist with the initial calibration of the impact weigher. Subsequent calibration checks can be accomplished by using the above mentioned purpose designed test weight.
Other applications handled by FlowForce™ in the cement industry have included feed rate control of fly ash additive; coal dust; and clinker dust.
All Flow Force impact weighers are now available with a 2 megabyte data buffer and production control software to simplify the task of process monitoring using a PC. The PC no longer needs to continuously monitor the process. So even an office PC can be used. When ready to interrogate the measurement system the PC is simply connected to the data buffer serial communications line and the stored data is downloaded from the impact weigher’s data buffer and processed as needed.
For further information call Flow Force on:
Tel: 61 (0)8 8118 6466; Fax: 61 (0)8 8346 3541