New tunnel kiln concept for energy-efficient firing of bricks
In industrial practice, tunnel kilns for firing bricks generally operate on the countercurrent principle. The brick load passes through the kiln in the opposite direction to the hot combustion gases, which are introduced into the firing zone via high-speed burners. As a result, the charge heats up to the sintering temperature. The fired bricks are then cooled in the so-called cooling zone with blown in ambient air before they leave the kiln.
The disadvantage of the current method is that the ambient air used for cooling is drawn out of the kiln behind the cooling zone and the amount of heat contained in it can only be partially used. Furthermore, the flow through the brick load in the kiln is not optimal, as the flow resistance is considerably higher here than in the gaps between the kiln wall and the load. Therefore, the firing zone is stretched as long as possible in order to ensure mixing of the flow with the high-speed burners used, thus enabling a more uniform temperature distribution in the charge. However, a longer firing zone is also associated with higher energy consumption.
The aim of the research project is the development of a new tunnel kiln concept with a focus on reducing energy consumption. Several fans are to be placed in the furnace chamber to circulate the furnace gas within the firing channel. On the one hand, the fans should produce a more homogeneous temperature distribution in the charge, but at the same time also increase the convective heat transfer. This allows the length of the cooling or firing zone to be reduced. In addition, the ambient air used for cooling remains in the furnace and is used to heat the charge. The joint research project comprises the experimental and numerical design of the fans and their arrangement, as well as the determination of the resulting heat transfers.
The IGF project 13 EWBG / 3 of the Forschungsgemeinschaft Ziegelindustrie is funded by the Federal Ministry of Economics and Energy through the AiF within the framework of the programme for the promotion of joint industrial research (IGF) on the basis of a resolution of the German Bundestag. For further information please contact the Forschungsvereinigung Ziegelindustrie e.V., Kochstraße 6–7, 10969 Berlin or forschungsgemeinschaft@ziegel.de