1 Overview
Hydrocracking is one of the main crude oil refining processes.Since the hydrocracking unit operates under high temperature and high pressure, the medium is flammable and explosive hydrogen and hydrocarbons, and the working conditions are special, so the seal must be reliable.So rightvalveThe design and structure put forward higher requirements.At present, the domestic hydrocracking units are based on Chevron's hydrogenation process, and most of them use the direct-flow stop valves of Canada Vilan and Edwards of the United States.According to the requirements of the domestic operating system, and on the basis of referring to foreign advanced product technology, the direct-flow stop valve for the hydrocracking unit is designed.
2. Main technical parameters
The high temperature and high pressure valve is the guarantee for the normal operation of the hydrocracking unit.The main technical parameters of the valve are as follows.
Operating pressure 8.0~20.0MPa
Operating temperature is generally 400~500 degrees
Medium oil (sulfur corrosion when it is greater than 260 degrees)
Hydrogen, hydrogen + hydrogen sulfide
Oil + hydrogen + hydrogen sulfide
3. Structural features
DC typeShut-off valveIt is mainly composed of valve body, valve disc, valve stem, guide frame, clamp, guide block, packing, bonnet, sealing ring and containment ring (Figure 1).Since the medium is high-temperature hydrogen, in order to avoid the material from being corroded by the medium, the valve adopts a direct-flow channel structure. When the valve is fully opened, the valve body channel is streamlined, the medium flow capacity is strong, and the erosion of the sealing surface and the shell is reduced. , And reduce the pressure drop.The guide frame is provided with a pressure balance hole, which can prevent the medium accumulated in the middle cavity from expanding when the temperature rises, causing the pressure boundary of the shell to fail and causing an explosion accident.
5.Conclusion
Due to the high temperature and pressure of the hydrocracking unit, and the medium containing hydrogen, a high-temperature H240+H2S corrosive environment is formed above 2 degrees. Therefore, only the structure of the valve is designed correctly and the reasonable calculation of each component can be Ensure that the valve structure adapts to the hydrocracking chemical conditions, effectively avoid the fugitive discharge of the medium, and ensure that the pressure-bearing boundary of the shell does not fail, thereby ensuring the normal operation of the hydrocracking unit.