Material and type of boiler evaporator
Thread Content
Our waste heat boiler is equipped with 3 evaporators, 1 superheater, and 2 economizers. One of the evaporators has a plain-tube structure and is made of 20G material; the other two have a finned structure and are also made of 20G material, with the fins being made of 409L material. The superheater features a vertical coiled-tube structure and is made of 12CrlMoVG material. The economizers consist of horizontal coiled tubes with fins, the fins being made of ST12 material while the coiled tubes are made of 20G material. 1. What is the function of the fins? Increase the contact area? 2. Why are these made of different materials? What are the advantages?
1. The function of fins is to increase the heat transfer area and enhance heat transfer. Perhaps the flue gas temperature in the finned tube area is low, and the heat transfer coefficient on the flue gas side is small; therefore, the fins are installed on the flue gas side, that is, outside the tubes. 2. The material of the pipe is primarily evaluated based on whether its strength at the metal wall temperature meets the required standards. The medium inside the tubes of the evaporator and economizer is water; it has a low temperature and a high heat transfer coefficient ； The medium inside the superheater tubes is steam; due to the high temperature and low heat transfer coefficient, the temperature of the metal walls is higher than that in the evaporator and economizer. Therefore, 12Cr1MoVG, which has a higher allowable stress at high temperatures, is used. The fin material may be chosen based on the different flue gas temperatures in the locations of the evaporator and economizer, hence materials with varying temperature resistance are used.
Use smooth tubes in areas where dust tends to accumulate; especially in industries where the flue gases are sticky, dust buildup on finned tubes is difficult to remove, which can affect heat transfer efficiency. Based on the analysis of flue gas composition in various industries, materials that are resistant to high temperatures and corrosion must be selected for certain parts! If you need to replace or repair components of the waste heat boiler, feel free to contact me! 13222382858