Application of single-point and hyperspectral imaging near-infrared sensors and machine learning algorithms for real-time biomass characterization

Biomass is typically a material with highly variable properties making its use in industrial combustion processes challenging due to requirements on the steady operation. Property such as moisture content has an impact on fuel ignition characteristics and heat release from the biomass. Ash content negatively influences fluidization of the boiler bed and after-burning of small fuel particles, by forming an impermeable layer on the surface resulting in incomplete combustion and formation of harmful emissions. The large variability of the properties thus creates undesired process instabilities which need to be addressed in a timely manner by appropriate operational/regulatory measures adjusting e.g. fluidization velocity, distribution of combustion air, under-pressure in the furnace etc. Consequently, there is a need for the implementation of sensors able to measure the properties of interest in real-time. In our previous studies, we demonstrated the ability of a single-point near-infrared sensor to measure fuel properties in real-time in a laboratory environment. However, we found that there is limited representativeness of the single-point measurements as also a cross-sectional variation of the fuel properties on the conveyor belt was apparent. Therefore, the implementation of a sensor able to measure also a spatial distribution of the material in the biomass stream is suggested. Literature review shows that it can be achieved by the implementation of a near-infrared hyperspectral imaging camera. The aim of the work is to present research activities at the Future Energy Center, Mälardalen University leading towards the installation of a) single-point and b) hyperspectral imaging near-infrared sensors for real-time moisture and ash content measurements. The study further presents the concept of NIR sensors integration for process optimization and the introduction of new advanced control concepts for steam boilers.