Evaporation phase occurs in water wall tubes. Evaporation is the process to convert water into steam. Therefore water wall tubes should be designed and constructed to provide high heat absorption, minimum excess air level and highest boiler efficiency. Construction of water wall tubes should be also constructed to prevent air leakage into steam boiler, eliminate amount of heat losses and permit high heat release and combustion rate in the furnace.
Construction of water wall tubes must provide high quality of the supporting component such as tubes, casing, refractory, lagging, tile, fin, and so on. Best construction will reduce heat loss and maintenance. Construction of water wall tubes can be classified into four types such as:
In a boiler, energy from the fuel is transferred to liquid water in order to create steam. Once the water is heated to boiling point, it is vaporized and turned into saturated steam. When saturated steam is heated above boiling point, dry steam is created and all traces of moisture are erased. This is called superheated steam.
The primary objective of an industrial boiler is the generation of steam. Steam is generated by heat transfer at a constant pressure. The fluid, which is initially in a liquid state, is heated, produces a variation in its phase and becomes saturated vapour.
This saturated steam can then be used for different applications such as sterilization, fluid heating or electricity generation.
Steam carries about 540 Kcal/kg of useful energy whereas hot water and thermal fluid carry much less energy. Steam does not require a pump to transfer the energy. Generally, if the heating temperatures required are <100°C, then hot water can be used and if temperatures >180°C are needed then thermal fluid might be a better choice. For process temperatures between 100°C and 180°C steam is considered a viable option.
For the selection of heat fluid boilers, first step is to determine several parameters: thermal power in the process, the oil temperature, and the use of waste heat.There are several methods for determining the boiler's thermal power:1. Calculation. According to the specific heat capacity of the material to be heated, the heating temperature difference, the processing amount per unit time, etc., the thermal power is equal to the product of the above three points, and the calculation result considers a certain margin amount as the boiler capacity.2. The sum of thermal power in the process equipment can also be used as the basis for the heat power.3. Refer to the experience of the same industry to increase or decrease on the basis of peers.4. If steam heating is used, it can be converted into heat transfer oil of the same tonnage and the capacity is appropriately reduced.The determination of the temperature of the heat transfer oil can be determined according to the characteristics of th
1. They are all a heat conversion device. The heat transfer medium they use is different. The water used in the steam boiler is heated to become steam. The heat transfer medium of thermal oil heater is heat medium oil. The heat is transferred to the heated substance by the heat medium oil.2. When a higher heating temperature is required, such as 280 degrees, the steam pressure of the steam boiler should reach 7MPa or more, and the process piping and heat exchange equipment must also withstand the same pressure. The equipment cost is high and dangerous. Thermal oil heater provides a temperature above 280 degrees, but the pressure is lower than 1MPa.3. The temperature of thermal oil heater can be accurately controlled within 3 degrees and the temperature of the steam changes greatly.4. Thermal oil heater is used alone, the exhaust gas temperature is higher, and the thermal efficiency is lower than that of the steam boiler. However, if used in conjunction with a steam boiler, the
