Boiler combustion controls for waste-to-energy power plants

One of the main challenges with waste incineration is the wide variation in waste composition, including differences in some properties that have a significant effect on the incineration process. Because of these vast differences, incineration processes have been developed to cope with large variations in process conditions. Valmet’s improved process controls provides all necessary tools for more stable and efficient waste incineration.

Control solutions for all waste-to-energy power plant processes

Integrated combustion controls

Improved performance and cost savings with control solution for electrostatic precipitator

More detailed process information is required

To be able to control the incineration process, detailed process information is required. The design of the overall control system depends on the specific grate and furnace design of each supplier. Therefore, this section only provides an overview of potential process information, control philosophy and process interventions.

Process information and controlled variables may include

Grate temperatures for various positions
Waste layer thickness on the grate
Pressure drop over the grate
Furnace and flue gas temperatures at various positions
Determination of temperature distribution over the grate surface by optic or infrared measurement systems
CO, O2, CO2 and/or H2O measurements at various positions
Steam production

Basic combustion controls normally include the following control actions

A dosing system for the waste
Frequencies and speed of grate movements in various parts of the grate
Amount and distribution of primary air in the various grate compartments
Temperature of the primary air, if preheating facilities are available
Amount and distribution of secondary air in the furnace and, if available, of re-circulated flue gas

The improved process control has many potential advantages

Better bottom ash quality – due to sufficient primary air distribution and better control of the incineration on the grate
Less fly ash production – due to less variation in the amount of primary incineration air
Better fly ash quality – less unburned material, due to more stable process conditions in the furnace
Less CO and CxHx formation – due to more stable process conditions in the furnace; for example, the omission of cold spots
Less NOx formation – due to more stable process conditions in the furnace, for example, the absence of hot spots
Better utilization of the capacity – because the loss of thermal capacity from variations is reduced
Better energy efficiency – because the average amount of incineration air is reduced
Better boiler operation – as the temperature is more stable, there are fewer temperature peaks and thus less risk of corrosion and clogging fly ash formations
Better operation of the flue gas treatment system – because the amount and the composition of the flue gases are more stable
These advantages also result in less maintenance and better plant availability

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