Practical experience with longitudinal and transversal recirculation systems in a tunnel kiln

»1 Recirculation ventilators installed in recesses in the ceiling – Patent Four Industriel Belge (from the original Patent document GB898090/BE576409)

»2 Laterally and roof ducted recirculation system with external ventilators – Patent Hanley
(from the original Patent document)

»3 Recirculation system with internal ducted ventilators – Patent Brown Boverie & Cie AG
(from the original Patent document)

»4 Initial firing curve

»5 Longitudinal recirculation gas flow

»6 System overview

»7 Gas/solid ratio

»8 Firing curve after modifications

»9 Installed power of burners

»10 End of firing zone in direction of travel of the brick with the high speed barrier group

»11 View against direction of travel of the bricks. In the background the HT micropulsating burners, in the foreground the injection burners connected to the recirculation system

»12 View in direction of travel of the bricks. In the foreground the HT mircro-Pulsating burners, in the background the injection burners connected to the recirculation system

»13 Total firepower

»14 Firing curve pre-heating zone cross-section recirculation turned off

»15 Firing curve pre-heating zone cross-section recirculation turned on

The objective of this project was to substantially reduce the specific energy consumption of a 168-m-long Lingl tunnel kiln, built in the 1970s, at a plant owned by Vela SpA – Borgonato, Corte Franca BS. The tunnel kiln is used for firing hollow and cored bricks. To achieve the desired results, it was not only necessary to make a number of modifications to the kiln and dryer, but also to adapt the feedstock used. This report focuses on the modifications to the kiln.

1 Introduction

The reduction of the specific energy requirement in the brick production process is, under the current economic constraints, of paramount importance. Various scenarios [1] indicate that energy prices could triple within a relatively short period of time and well within the average service life of many still existing brick plants. The solution discussed here should be regarded as part of an overall strategy that also incorporates the use of alternative fuels.

The tunnel kiln suffers from insufficient homogenization of temperatures in the kiln chamber. The operation of a tunnel kiln...