A gas-fired tunnel kiln had been in continuous use for over fifty years. Super duty fireclay brick lined the kiln’s preheat zone while high duty silica brick lined the burning zone. Refractory products such as high purity high alumina brick and phosphate bonded bauxite brick were fired in the tunnel kiln. Firing temperatures in the kiln ranged from 2500°F to 2770°F. Often, the brick at the middle of the hacks on kiln cars were under-burned.
Emisshield ST-2 was applied to the tunnel kiln refractory using a HVLP sprayer. Prior to the application, the refractory brick was vacuumed to remove any loose materials that adhered to the brick. A good substrate was ensured by removing bricks of broken refractory. The coating was applied only in preheat and burning zones of the tunnel kiln.
After the kiln was put into service after EMISSHIELD application, it was immediately observed that the firing temperatures were 30°F to 60°F higher, if earlier burner settings were maintained. The burners were therefore turned down to bring the firing temperature to a value appropriate to the ware fired. As a result, the average gas usage decreased from 476 MCF to 371 MCF per day during the first month of service after coating. This translated to about 22.1% savings in gas usage. In subsequent months, slower push rates were used and the fuel savings were not as high as for higher push rates.
In the first year of operation of the kiln, the average fuel saving was 16% while monthly fuel savings ranged from nearly 8% to 26%. After EMISSHIELD was applied, under-burning of ware was practically eliminated and the kiln atmosphere was cleaner. Moreover, the EMISSHIELD high emissivity coating ensured even radiative heating, resulting in more complete combustion of fuel.
This information has been sourced, reviewed and adapted from materials provided by ANH Refractories Europe.
For more information on this source please visit ANH Refractories Europe.