ABB helps Jura optimize energy costs for its cement plant in Switzerland

ABB Ability™ System 800xA, ABB Ability™ Expert Optimizer and ABB Ability™ Knowledge Manager for cement combine to enable plant--wide automation to help Jura achieve enhanced productivity and quality at its plant in Switzerland

In its endeavor to reduce energy use, Jura implemented a complete automation solution from ABB for its plant in Italy. The primary goal of this automation project was to reduce energy demand in all areas, combined with the search for the optimal operating point, consistent with productivity and quality targets, while staying compliant with environmental emission limits.

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Cement producers are large consumers of thermal and electrical energy, which globally is available at steadily increasing costs. Efforts to reduce demands by using higher efficiency equipment and substituting fuels and raw materials to lower production costs are some efforts in recent years to offset this increase in energy costs. Finding the optimal operating point within the boundaries of dynamically variable constraints of quality and productivity targets, depends on the right price mix of fuels and timely purchase of electrical energy, while constantly reducing demand for these resources.

Cement manufacturing is a complex and energy-intensive process. A key operation in this process is the conversion of ground raw materials (CaCO₃, clay and/or shale) into clinker in the kiln. This operation, involving intensive heating up of raw materials in a conventional control of the cement kiln requires an experienced operator who constantly interprets process conditions and makes frequent adjustments to set points established by the controller. This task is made more difficult by complex responses, time delays and interactions between individual process variables. As a result, conventional kiln control operates at temperatures higher than optimum, leading to unnecessarily high energy usage.

ABB implemented a complete solution for Jura, driven by digital technologies that aided in the gathering of information followed by modeling of the process to identify the best possible way of running the plant at all times to achieve all objectives.

One key component of this solution was variable speed drives (VSDs) and the other model predictive control (MPC). Both of these components, coming together by the use of advanced digital technologies, was key to enabling optimized energy usage at the plant in Switzerland.

The large fans that draw air through the kiln, precalciner, mills and filters into the exhaust stack, supported by smaller fans to push air into the grate cooler, require precise airflow adjustment and control. These adjustments need to account for a variety of factors, including atmospheric conditions, process conditions and ventilation. This is where VSDs installed at the plant played a key role in driving energy efficiency; and, depending on the required flow rate, helped achieve power savings of up to 70% when compared with fixed-speed motors.

At the Jura plant, ABB used a multidrive system, which offered all the benefits of VSD plus a range of additional benefits including reduced cabling requirements, energy-savings from motor-to-motor braking, reduced space requirement and elimination of low voltage distribution required for single drives.

In addition to the VSDs, ABB implemented an MPC solution. The MPC is based on on a receding horizon philosophy - wherein a sequence of future optimal control actions is chosen according to prediction of short-to-medium term evolution of the system during a given time. When measurements or new information become available, a new sequence is computed which then replaces the previous one. The objectives of each new sequence run are the the optimization of performance and protection of the system from constraint violations.

This combination played a key role in helping Jura achieve all its objectives from automation at the plant and realize wide-ranging benefits.

As a result of implementing the complete solution from ABB, Jura realized a wide range of benefits at its plant in Switzerland. These include:

• Monitoring and reporting on production, process operations, energy and emission resulting in better utilization of energy, equipment, inventories and capacities
• Advanced kiln control operating kiln in an optimum manner ensuring good quality products, lower burning zone temperature (BZT) and lower energy costs
• Kiln fuel mix optimization through an Alternative Fuels Optimization Module resulting in economically optimal reactions to changing conditions in fuel, waste and raw meal quality; while ensuring enforcement of environmental, contractual and technical constraints