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:
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
(Question Details) Specific Performance:The pipe of superheater bursts in circulating fluidized bed boiler operation.The bed pressure indicator fluctuates little. Answer: causes of failure:(1) Design Factors.(2) Manufacturing process, installation and maintenance quality.(3) The temperature control device is unreasonable or does not work properly.(4) Effect of operating conditions on overheating and explosion of superheater. Troubleshooting:(1) Report the fact to operator on duty and require operating the boiler in low load.(2) When the overheat damage is serious,please report it to operator on duty and require stoping the boiler immediately to prevent blowout of the near pipes.(3) Adjust the steam temperature as much as possible within the normal range.(4) If the superheater tube is not damaged badly, it has little effect on the temperature level of the steam, and it can be allowed to run in a low load range for a short period of time.
