The role of the bypass valve device on the dust collector The main reason for designing the bypass device of the bag-type dust collector converted from the coal-fired power plant is that: when the bag-type dust collector fails and cannot operate normally, the production process system cannot be stopped in time; or when the system has just started ignition, In order to protect the filter bag from being damaged by the high-temperature flue gas, the high-temperature dusty flue gas is temporarily passed directly into the chimney from the bypass. The bypass device can be designed in both internal and external forms. The external bypass is to set a bypass line between the dust collector 's inlet and outlet flue, which directly shorts the bag dust collector 's inlet and outlet flue. By setting two pneumatic butterfly valves in the middle of the pipeline, the on / off of the bypass is controlled. Because the external bypass needs to add a bypass pipe around the bag dust removal equipment of the original power plant, which occupies limited space and increases equipment investment, the bag dust collector converted from the dust collector of the coal-fired power plant power plant is generally Both are designed as built-in bypasses. The built-in bypass device is the same in structure and principle as the offline device, so the design process of the built-in bypass is basically the same as the design process of the offline device: first determine the diameter and stroke of the bypass valve; then calculate the force of the valve plate, Choose the right cylinder and valve stem diameter. The difference is that the air velocity through the bypass valve port can be as high as 18m / s. This is to ensure that the pressure difference between the inlet and outlet of the dust collector does not exceed 15OOPa when the flue gas is bypassed. Because the bypass passage of the bag filter of the power plant is directly connected to the chimney, the seal of the bypass valve is guaranteed when the dust collector works normally. It is reliable! This puts forward higher requirements for the structure and seal of the bypass device. Compared to offline devices, the design of the bypass device pays more attention to the reliability of the seal.
When the boiler system of a coal-fired power plant operates normally, the temperature of the flue gas entering the dust collector is generally between 140 ° C and 170 ° C. This requires that the sealing material of the bypass valve is resistant to high temperatures (> 200 ° C), and resistant to strong acids and alkalis. Therefore, the sealing material of the bypass valve is generally selected from high temperature resistant fluorine rubber, and the sealing rubber is made into a "9" hollow structure. In addition, in order to ensure the reliability of the seal, the bypass valve is designed as a sandwich structure, and the opening and closing of the bypass valve is controlled by the action of the upper and lower valve plates driven by the cylinder. In the middle of the bypass valve body, a pipe is opened to connect with the atmosphere. The pneumatic butterfly valve is also used to control the on-off between the pipe and the atmosphere. The purpose of this design is to ensure that there is always a positive pressure air flow in the sandwich structure of the bypass valve, and the outer sides of the upper and lower valve plates communicate with the clean air and the smoke, respectively, and always bear the role of negative pressure. In this way, it can be ensured that the flue gas cannot enter the clean air passage through the bypass valve.