Drop Tube Furnace

For studying experimentally the combustion processes in the Oxyfuel Process the Institute of Energy Systems possesses a Drop Tube Furnace. This consists of a 2 m long electrically heated ceramic tube of 15 cm diameter, in which temperatures of up to 1600 °C can be obtained.

By means of a burner pulverised coal, mixed with primary combustion gas, is fed into the furnace. The mixture then burns inside the reactor. As oxygen carrier it is possible to use air or a varying mixture of O2, CO2, N2, whilst a steam generator supplies additionally steam. Furthermore, small amounts of impurities, such as NOx or SO2 can be added, to replicate the gas composition of the recirculating flue gas.

The main combustion gas (O2, CO2) and impurity components (NO, NO2, SO2, CO) are measured. After coal combustion in the furnace, which requires approximately 2 seconds, the combustion gases are quenched with air. This results in an instantaneous "freezing" of the combustion process, so that the exhaust gas, after particle removal in a cyclone, can be released directly to the atmosphere. The coals being tested, as well as the resulting ashes from the furnace, are analysed through proximity and elementary analyses.

Below is the construction of the Drop Tube Furnace schematically shown, together with the key operation characteristics of the facility.

  • Combustion Chamber: 150 mm in Diameter, 2 m Long
  • Wall Temperature: 900 – 1600 °C, 5 independently regulated Modules
  • Test Atmospheres: Air and various Mixtures of O2, CO2, H2O, N2
  • Primary, secondary and tertiary combustion gas with the further possibility of gas staging
  • Residence times up to 2 s
  • Measurements of CO2, O2, NOx, SO2, CO and of the Temperature



Dr Eur-Ing S Rafailidis