Low-cost Online System for Detecting Unburned Fuel in a Large Industrial Biomass-fired Boiler

Abstract

Combustion of biomass is challenging due to the heterogeneous character of the fuel, which makes monitoring of the process important. Unburned carbon residue is one of the indicators of the inefficiency of the process, since it shows that the combustion has been incomplete. Nonetheless, there is a lack of measurements which could be used for monitoring the amount of unburned carbon in the bottom ash of energy boilers. In this paper we present a simple, low-cost online system for detecting unburned fuel, which has been tested on the bottom ash conveyor of a large-scale biomass-fired boiler. The system, which can be used for capturing online images from the process, includes an ordinary systems camera and a control computer placed in a protective case. The images are then analyzed and an index which indicates the amount of unburned carbon in the bottom ash is calculated. The results show that the system yields useful online information on the process, and a trend line can be used for monitoring the long-term changes. The system can be programmed to alarm when there is a growing trend in the carbon index, for example, and it has several potential applications in the future.