In view of the structural characteristics and medium characteristics of the polypropylene assembly loop reactor, the structural design of the safety valve of the loop reactor is very different from other common safety valves, as detailed in the following four aspects.
Structural design of inlet valve seat
The polypropylene safety valve seat is completely different from the nozzle-shaped flow channel design of the common safety valve. In order to ensure the continuous flow of the medium material in the reaction process of the loop pipe, the shape of the butting surface is completely connected with the pipeline, and the inlet of the valve seat is designed to be connected with the pipeline. The arc size of the main pipeline of the equipment is the same as the arc size, so as to avoid the inflection point of the pipeline flow due to the change of the local structure of the safety valve, resulting in the dead zone of the flow channel which is easy to cause the medium to condense. When the medium flows through the inlet of the safety valve, it is easy to produce Coagulation, accumulation, or blockage of the safety valve inlet, affecting the normal operation of the safety valve and equipment.
Seal structure design
The sealing structure of the safety valve used in the polypropylene loop reactor adopts a soft-sealed split structure. The main reason is that the polypropylene particle medium is easily retained on the metal sealing surface, so that the sealing performance cannot be well guaranteed. Selecting a soft seal can effectively ensure the online sealing of the stainless steel valve and minimize the influence of the medium on the sealing of the stainless steel valve.
Soft seal split structure, the sealing structure is designed as a split threaded fastening structure, which is divided into three parts: valve disc, sealing ring and pressure block. The sealing ring is fixed in the groove formed by the detachable metal pressure block and the valve disc. In the groove, the overall wrapping design can effectively prevent the sealing ring from being blown out, and the replacement of the sealing ring can be completed relatively easily by removing the pressure block during inspection and maintenance.
Lift structure design
The structure of the flow channel at the throat diameter of the safety valve of the polypropylene assembly loop reactor is different from that of the safety valve. The inlet and the sealing pair are very close. The loop part is designed as an annular flow channel, and a special throttling design. When it is turned on, the pressure can be quickly boosted, so that the safety valve can obtain better lift without affecting the emission performance. According to the empirical data and test results, the proportional relationship of the components of the flow passage is harmonious, and a reasonable recoil area and recoil angle of the recoil plate are designed to obtain sufficient lift and ensure the correct opening and stable discharge of the stainless steel valve.
Bellows back pressure protects assembly design
Polypropylene loop reactor safety valve, in order to prevent the influence of back pressure, the bellows design is carried out according to the back pressure. When the back pressure is high, the multi-layer bellows design is adopted. However, because the medium of the loop reactor contains a large amount of solid particles, when discharging When the solid particles are ejected from the flow channel at a high speed, they may impact the bellows, causing damage to the bellows or entering the inter-wave gap of the bellows, aggregation and crystallization, thus affecting the working performance of the bellows, so it is necessary to design a special back pressure Cherish the assembly. The safety valve bellows protective sleeve is wrapped around the periphery of the bellows, and the gap between the end and the lower joint of the bellows is extremely small. Without affecting the normal working conditions of the bellows and the stainless steel valve, the influence of the medium during discharge is minimized and the medium is avoided. If the solid particles damage the bellows or affect its normal operation, the bellows can be protected to the greatest extent.
