Self-optimizing process control

The central processes in the above-mentioned industries are technical firings. However, the firing serves different purposes in each industry.

In the power industry, the focus is on generating steam to produce the requested electrical power.

At the same time, the firing system typically must meet the following requirements:

1. Maximum utilization of the fuel
2. Minimization of emissions (especially CO and NOx)
3. Processing of a wide range of fuels

In a waste incineration plant, the primary objective is to inertize the waste before it is landfilled, while at the same time reducing its volume. This reduces land consumption by landfills and allows recycling of the remaining recyclables.

The additional requirements for a waste incineration plant partly have other priorities than in the other industries:

1. Stable operation even with fluctuating waste properties
2. Maximum burnout (inertizing)

Maximization of throughput

In the cement industry, on the other hand, high temperatures are required for the chemical transformations of the starting materials so that they obtain the properties required for the production of cement.

Additional process control requirements are also imposed in the cement industry. High priority is given to the following objectives, for example:

1. Continuous product quality in line with specifications
2. Reduction of specific energy consumption and NOx emissions
3. Reduction of CO₂-emissions and fuel costs by using alternative fuels

A technical firing system usually functions optimally when the correct amount of combustion air for the current fuel mix is continuously and everywhere available. This task should actually be performed by the plant's control system.

Very often, however, the existing process control system has been implemented once and has been used unchanged ever since. The control parameters used for the configuration of the individual control loops have therefore not been adapted to changes in the plant behavior, so that this central task is not optimally fulfilled.

This is where PiT Navigator steps in. PiT Navigator is a modular software system for optimizing the control of technical processes in general and of firing processes in particular. It extends the existing control system and uses advanced methods for model predictive control of complex processes. These include the use of data-based process models, which are used to predict process behavior. With this methodology, PiT Navigator can already act when the process measurement technology has not yet detected a change in the controlled process variable.

If required, PiT Navigator can be combined with additional camera-based sensor technology for observation and analysis (thermography) of the furnace or the central flame.

Another functionality of PiT Navigator is the adaptivity or the learning ability of the process control realized with it. Over time, the characteristics of a technical process can change. Examples for causes of such changes are:

• Wear of essential components
• Formation of deposits
• Changed material properties of the starting materials
• Environmental conditions

As a result, the behavior of the process changes and the behavior of the control system no longer matches the real plant. PiT Navigator identifies such changes and updates both the process models and the associated control parameters on the basis of the new reality.

The connection to the control system is established by default via an industrial interface, which delivers process measurement values from the control system to PiT Navigator (read) and returns setpoints for the controlled actuators to the control system (write). Thus, the use of PiT Navigator as closed-loop control directly improves the situation described above.

These functionalities of PiT Navigator lead to a smoother technical combustion process. The unavoidable control deviations become smaller. As a result, the limits of the process can now be approached more closely and the existing plant technology can be used optimally. As a secondary effect, the efficiency and utilization of the fuel increases, so that in the end the operation is more economical than without PiT Navigator. In the past, payback periods of less than one year have been realized for such projects.

PiT Navigator has been successfully used in the above-mentioned industries for years. The system can be configured so variably that, in addition to the optimization of the firing system, the operation of the mills or the control of a "highly efficient" SNCR system in a cement plant can also be optimized.

We are convinced of PiT Navigator. Therefore, we prove in every project that the use of PiT Navigator has improved the process quantitatively. Examples of typical successes include:

• Increase in steam generator efficiency
• Reduction of specific energy consumption in cement production (kiln and mills)
• Reduction of standard deviation of free lime
• Reduction of the steam fluctuation in waste incineration