Gas recirculatio systems peculiarities in tunnel kiln applying waste wood fuel

Abstract

The clay brick burning tunnel kiln, 105 m long, has been rebuilt in order to pass from liquid fuel to waste wood. The greatest attention has been paid for reduction of temperature difference along height of kiln channel. For this purpose, two gas recirculation systems have been developed. The first one (ventilating) is operated in the preheating zone of up to 450°C, the other (injecting-streaming) from 450° C to 650°C. It has been established that in the preheating zone of tunnel kiln, the ventilating gas recirculation system reduces the temperature drop along height of kiln channel in the different zones from (250-321)°C to (-27-89)°C, while the injecting-streaming gas recirculation system reduces the temperature drop along height of kiln channel in the different zones from (142-232)°C to (-2-22)°C. The introduced gas recirculation systems balance the temperature along height of kiln channel, therefore, the cold products situated at the bottom of the kiln car cannot get into the burning zone. During burning of waste wood in the tunnel kiln, the temperature difference in the burning zone is not high and the temperature at the bottom of channel can be higher than that on the top. It has been established that in the different burning zones of tunnel kiln the temperature drop along height of channel is varying from (-54-79)°C. When the recirculation systems are used, the power-producing efficiency of the kiln grows up. The efficiency of this tunnel kiln by burnt material reaches 80 t/24 h. heat input for production makes 2,3 GJ/t.