The cement industry is working hard to reduce its environmental impact in the most economical way possible. A well-known strategy is to improve the uniformity of input materials, which reduces energy consumption and CO2 emissions, and increases productivity. To achieve these goals, Switzerland-based Online Control has developed the O_Blend Cement control system that optimises the operation of stockpiles, raw and cement mills. O_Blend Cement uses various quality measurements from XRF spectrometers, online analysers (OLA), and possibly XRD spectrometers, and acts as an autopilot capable of handling large variations in input material composition.
The strategy consists of recasting the traditional quality targets into alternative targets, the tracking of which implies optimal operation (ie self-optimising control1 ). For example, for raw mills, silo targets for limestone saturation (LS), silica ratio (SR) and alumina ratio (AR) are reformulated into ‘optimising’ targets that involve:
1. specific targets and limits for LS and alumina
2. min/max ranges for SR and AR. This way, O_Blend Cement will be able to minimise the costs of input materials and meet the quality requirements by tracking these optimising targets using a measurement-based optimisation strategy.
This strategy allows reduction in the operational cost by:
1. increasing consumption of alternative raw materials (ARM) or supplementary cementitious materials (SCM)
2. reducing consumption of correctives or clinker
3. flexibility in choice of the suppliers for ARMs, SCMs and correctives
4. reducing CO2 emissions. For example, it was possible to increase ARM consumption from five to 15 per cent of the total raw mix in a Swiss cement plant.
Part of the O_Blend Cement software, the O_Blend Compensator automatically compensates for OLA biases using XRF measurements of the raw meal. It ensures that the bias-corrected OLA chemistries align with the reference XRF chemistries either at silo ends or over a specified tonnage window. Automated sampling, sample preparation and XRF analysis are important to ensure reliable and representative reference XRF measurements with good accuracy. O_Blend Cement has been installed in more than 70 plants worldwide.
Please login or register for free to download this article.
