- Having accurate sensors, robust actuators, and a reliable distributed control system (DCS) in place is critical. These are the foundation on which the APC is delivered and if the measurement system or DCS is not up to scratch, the APC will not be able to deliver the expected benefits.
- Ability to combine operational data with process knowledge is paramount. Ensuring that the APC is not a black box but can incorporate the operators experience into its models along with the data-based models is key to achieving the targets with minimal efforts.
- Transparency and ease of use is critical to get the operators’ buy-in. It is very important that the operators can relate with the decisions that the APC makes, visualize the predictions, and use the system intuitively for fast and efficient start-ups.
Once APC is implemented, it is equally important to continuously monitor performance and share key performance indicators so it can be sustained. ABB believes that performance can be sustained, and even improved, over many years through close collaboration with a service-based model for long-term successes.
Following the evolution of these critical factors has resulted in APC being applied to many different processes. Take for example the lime kiln operation, which is one of the major consumers of energy in the kraft process and exhibits a lot of variability in energy use, quality and productivity. Although the lime kiln process is straightforward in principle, kiln operators still face difficult issues such as low thermal efficiency, high fuel consumption, process delays, build-up of rings and dust, overheating of refractory, poor quality of lime and increased emissions. OPT800 Lime manages these challenges to achieve optimum control and efficient lime production.
The solution works to optimize lime production rates, reduce energy consumption and emissions, increase re-burned lime availability, decrease residual carbonate variations, and improve overall operation with increased visibility of the process. It combines laboratory results by operators with MPC, thus getting the best of both approaches in a fully product-specific solution, with minimum need for on-site development. This enables tighter control of the lime production process, leading to more stable pulp mill operations.
Looking to the fiberline side of pulp mill operations, mills can achieve optimum pulp quality leveraging APC in the cooking process. When ABB’s OPT800 Cook/C APC module is applied in a continuous pulp digester, it controls an estimated Kappa number in the cooking zone, residual alkali at the extraction stage, chip level in the digester and blow consistency. Typical results include reduced variability in the final Kappa number and reduced steam and alkali consumption, resulting in lower energy and bleaching costs.
Another example of APC implementation is on the wet end of a paper machine. Producing paper on a paper machine involves a series of highly complex processes and variation in any of these processes could lead to the formation of a defect in the sheet or a weakness in the paper web, eventually leading to a sheet break or rejection due to poor quality. Wet End Control helps to monitor and analyze the wet-end processes and can significantly reduce downtime, the usage of chemical additives and production costs, while maximizing production.