Stress Corrosion Failure Analysis of Heat Exchange Tubes in Large Slime Steam Rotary Drying Device

1. Advantages of slime steam rotary dryer

Coal slime steam rotary dryer uses saturated steam as heat source to indirectly dry coal slime. It is an energy-saving, environment-friendly, green and efficient technology. It has the characteristics of large processing capacity, high drying efficiency and low energy consumption. It is a major innovation in the field of coal slime drying in China.

2. Working principle of slime steam rotary dryer

The coal slime is sent into the steam rotary dryer through the screw, and is fully contacted with the heating pipe in the dryer for heat exchange. When the material moisture reaches the required value, it is discharged from the dryer through the discharge cover at the other end of the industrial rotary dryer. Since the heat source of the whole drying system is mainly the saturated steam in the heating pipe, the service life of the heating pipe is very important. However, the heat exchange tube of slime steam rotary drying device is generally made of stainless steel, which may be corroded and lead to leakage under the action of slime wear, corrosive medium and thermal stress.

3. Continuous improvement of slime steam rotary dryer

Ge Ya carried out leakage fault analysis and structural improvement research on the structural design of HDPE dryer by using static strength and dynamic characteristic test. Xi Minghua, Zhang Haidong and others investigated the problem of stress corrosion of stainless steel in chloride environment, and considered that the corrosion of stainless steel was mainly caused by the high content of Cl - in water quality, Zhang Yan Xu Kun, Yang Hongbin and others have detected and analyzed the leakage of heat exchange tube of steam tube rotary dryer for dry coal and PTA. It is considered that the smashing and wear of impurities in materials are the main reason for the leakage of heat exchange tube of steam tube rotary dryer.

4. Anti corrosion failure analysis of coal slime steam rotary dryer

(1) The chemical composition of heat exchange tube material meets the standard requirements of stainless steel 0Cr18Ni9, and the raw materials are not used wrong during manufacturing;

(2) The main reason for the leakage of the heat exchange tube of the slime steam rotary dryer of the project is not that the impurities in the slime that are not easy to separate hit the outer wall of the heat exchange tube under gravity, but the stress corrosion failure caused by the influence of the external environment of the tube;

(3) On the premise that the material of heat exchange pipe meets the process requirements, ferritic austenitic steel, nickel base alloy steel, high alloy austenitic steel and other stainless steels with good stress corrosion resistance can be selected.