Designing and testing of a new spiral combustion reactor for solid fuels

Increasing energy demand and public awareness on the environment, causes energy supplying companies to search for alternative and more cleaner fuels. One of the ways to achieve this is by co-firing of biomass in coal tired power plants. The main advantage of biomass co-tiring is that it can be used in the existing plants with little or no alteration.

Currently, in coal-fired power plants, the biomass to coal co-firing ratio is still low. The main reason for this low co-firing ratio is the inferior physical and chemical properties of the biomass compared to coal. A thermal pre-treatment of biomass via torrefaction improves the biomass properties to more similar properties like coal. In order to study the combustion properties, different experimental techniques are used. Three widely used techniques are: thermogravimetric analyzer, drop tube reactor and a captive ignition apparatus. However none of these experimental techniques monitors the whole combustion process of a particle moving with the flow, with a single camera.

The goal of this assignment was to build a new spiral combustion reactor (SCR) so that combustion characteristics of solid fuel particles like ignition and combustion time can be studied. This new combustion reactor should have comparable conditions as exist in a power plant with the possibility to monitor the combustion process by flue gas analyses but also by visualizing the whole combustion process through recordings with a high speed camera. The effects of four variables (reactor temperature, torrefaction temperature, oxidizer mixture and particle size) on ignition and combustion time are investigated. It was found that for torrefied beech wood particles, the ignition time decreases and the combustion time increases with increasing torrefaction temperature.