The environment of the shaft sealing device of the reactor

The environment of the reactor shaft seal device The following discusses the characteristics of different types of reactors and the issues to be considered in the design of mechanical seals. 1. Side-entry reactor with stirring shaft. From the lubrication point of view, this type of mechanical seal for reaction axe generally does not have the problem of poor lubrication of the mechanical seal for the kettle, but the liquid level of the medium in the kettle must be maintained at a certain level. From a mechanical and technological point of view, the design of this kettle has many shortcomings. In the reactor with the shaft extending from one side, the shaft is in a cantilever state, so it is prone to vibration, and the mechanical seal is more sensitive to vibration. If the shaft extends from both sides, the shaft must be centered with the support device of the mechanical seal on the kettle body, and it is difficult to meet this requirement, so the balance between the shaft and the kettle is very complicated. In the case of large changes in the operating temperature, the shaft has a large expansion and contraction. If the excessive expansion and contraction are all borne by the mechanical seal, the mechanical seal is likely to fail. However, the speed of this type of kettle is not high, as long as the corresponding measures are taken, this problem can be solved. 2. Insert the reactor at the bottom of the stirring shaft. The polymerization reactor has gradually developed in the direction of large volume, and its stirring shaft has also changed from the top-insertion type to the bottom-insertion type. The characteristic of the bottom plug-in reactor is that the stirring shaft is short and the bending stress on the shaft is small, so the calculation shaft diameter is small, which saves labor and materials. The rigidity of the short shaft and the long shaft is good, and the deformation is small. But the seal is at the bottom of the kettle. Although it can ensure the lubrication of the seal, the solid impurities are easy to deposit around the seal, causing abrasive wear on the end face of the friction pair, and it is easy to cause the moving parts to block and scale. In this case, the mechanical seal is always under the pressure of the liquid. When the seal needs to be repaired or replaced, the material in the kettle must be emptied. When the material is a high-viscosity polymer, it is more difficult to completely empty it. For this reason, it is necessary to carry out a special design of the mechanical seal and adopt special measures at the same time, in order to expect the rice noodles to have good working performance and easy maintenance. 3. Insert the reactor at the top of the stirring shaft. The top plug-in agitated shaft reactor is widely used, and the problems encountered in its sealing are different from the previous ones. Because the seal is placed in the upper part of the kettle, it is in the gas phase space (the liquid is only when the material is full of the kettle), in order to avoid dry friction of the seal, a certain lubricating cooling method is required. The top-inserted and vertically installed mixing shaft has a large aspect ratio and may have low processing and installation accuracy, so it will inevitably produce greater deflection. During movement, the following factors will aggravate the vibration of the stirring shaft. 1) Uneven mixing blades 2) The liquid level is too low or there is vortex. 3) The feed is uneven, or the reaction is not well controlled. 4) Pressure and temperature fluctuations. 5) The pressure and temperature changes cause the deformation of the stirring shaft and the kettle body. 6) The speed of the stirrer changes suddenly, or the temperature drops to increase the viscosity of the polymer. The top-inserted reactor has a large length-to-diameter ratio of the stirring shaft, and an intermediate bearing is usually provided to provide a relatively vibration-free working environment for the seal and make the seal run smoothly. The general requirement for the structure of the mechanical seal is easy and simple to load and unload. The reaction kettle is a large-scale equipment. It is necessary to install the mechanical seal parts on the kettle one by one. It is difficult to ensure its accuracy. Many of the failures of the mechanical seal of the kettle are caused by poor installation. The so-called simplified structure for loading and unloading, specifically, is to design the mechanical seal into a flange as a combination assembly, and after commissioning in the workshop, it is installed on the kettle together during installation without adjustment; thus, installation errors can be avoided; Remove it when disassembling, repair and replacement of the old assembly can be carried out in the repair shop. In this way, the installation and maintenance process of the seal is greatly accelerated, thereby greatly reducing the downtime loss in production.