The industry always demands higher quality monolithic refractory linings.
The requirements for high quality lining is the adequate drying of the material. Drying or the first heating of the system with a refractory material lining is therefore of great importance. In refractory materials, high, not chemically bound water content is included, which must be expelled by the drying. The heating gradient applied depends on the kind and amount of refractory installed. A too rapid heating has to be avoided, so that the water vapor does not destroy the refractory material. In certain refractory materials (plastic mixes, mortars and mastics) solidification only occurs at higher temperatures.
The system has to be heated up according to a heat drying curve, which has to be to be calculated previously. If necessary intermediate holding times at certain temperatures have to be provided. The durability of the refractory-lining and the subsequent reliability of the system depends to a large amount on the proper implementation of the drying. Until the start of dry – out operation, the refractory lining has to be protected from frost.
The refractory lining is uniformly heated by high velocity burners, so that condensation is avoided in any system area. Appropriate ventilation (eg weak suction draft, etc.) to dissipate the vapor, has to be provided. Any part of the flame envelope that protrudes from the burner nozzle must not impinge directly upon the refractory lining. The hot air is introduced to the system by suitable mixing tubes or manifolds. It is of prime importance that the system is effectively sealed. All openings not required for the discharging of hot gas (including flue gas), must be closed in order to achieve a slight overpressure. Only use fuels that burn substantially residue-free, such as heating oil and natural gas.
The fuel has always to be provided in sufficient quantity so that there is no interruption of the drying process. The temperature data during the drying has to be measured with appropriate thermocouples and recorded over the entire drying out process, using calibrated temperature recorders. Also, the hot air outlet temperatures on all burners have to be recorded.
The temperature logs are passed along with a final report upon completion of drying to the customer.