Design comparison of biomass boiler dust removal system

2019-10-29

The rationality of the design of the biomass boiler bag filter is directly related to the level of dust removal efficiency, whether the production conditions are normal, whether the equipment operation is reliable, safe and the service life of the filter bag.

1. The design of a first-level cyclone dust removal. The cyclone dust collector can collect dust with a particle diameter of 5μm or more, allowing the highest import dust concentration to be 1000g/m3, the highest temperature is 450°C, the inlet airflow speed is 12~20m/s, the resistance loss is 588pa~1960pa, and the dust removal efficiency is 50%~ 90%. The flow field model test shows that the inlet performance of the screw-shell structure is better. After the angle of the tangent to the cylinder is 180° with the airflow, it is tangent to the outer edge of the cylinder. When the lower pneumatic ash conveying system is not working properly, in order to prevent the ash from causing damage to the internal flow field of the dust collector, a bypass ash port is added to the lower part of the ash hopper to ensure that the bypass is used after the ash pumping device fails. Under the ash, the manual ram and the ash discharge valve are arranged on the bypass pipe. The main wear parts of the cyclone dust collector are distributed at the entrance of the volute and the lower half of the cone. There are four methods such as boronizing method, coating method, lining method and dust-removing device with wear-resistant materials. The design is made of turtle shell net lining. The method improves wear resistance.

2. KDM type spray pulse bag bag filter design. All heated parts of the housing take full account of thermal expansion and make the necessary compensation. The air inlet of the dust collector ash hopper is equipped with a regulating valve, and its closing can ensure that the dust collector is completely offline, so that the dust collector can be inspected and maintained. Increase the dip angle of the ash bucket, improve the fluidity of the dust in the ash bucket, and set a powerful air cannon on the ash bucket to ensure smooth ash discharge. The ash bucket is provided with baffles, which are staggered in the air inlet of the ash bucket to balance the flue gas flow, and at the same time, the large particle dust in the flue gas is slowly settled at the bottom of the ash bucket through the collision deflector to reduce the load of the filter bag filtration. The structural design of the middle box is mainly considering the degree of negative pressure resistance of the wall and the degree of negative pressure resistance of the inclined partition. The upper box is a key part of the design of the entire dust collector. Its design is directly related to whether the dust collector can operate normally. When designing the upper box, the design has a certain slope (about 2°) to facilitate the smooth discharge of rainwater. The pulse injection system consists of a pulse valve, a gas distribution box, a blow pipe and a pipe connection. The blowing system is the core component of the bag filter. Its design can determine whether the dust collector can be used normally. The design of the blowing pipe mainly considers the diameter of the blowing pipe, the diameter of the nozzle and the number of nozzles, the structure of the blowing short pipe and the height of the end face of the blowing pipe from the mouth of the filter bag. When designing the pneumatic system, the emphasis is placed on the determination of the gas storage tank, the flow of the gas supply to the pipeline, and the determination of the pipeline specifications.

3. Protection system design. In the event of an abnormality in the biomass boiler, the dust collector must be bypassed for protection. There are usually two types of bypass, one with an external bypass and the other with a built-in bypass. A pneumatic poppet or electric actuator is provided at the bypass inlet, and is incorporated into the automatic control system and manual opening and closing. The valve plate of the bypass damper requires sealing and requires zero leakage when closed. The dust removal system is provided with a bypass pipe, and the flue gas is discharged through the bypass pipe without passing through the filter bag under the condition of boiler oil injection and abnormal smoke temperature, thereby effectively protecting the dust remover. At the same time, the precipitator is equipped with a pre-spraying device (pipe powder spraying device) for the protection of the precipitator filter bag during pre-spraying.

4. Design of pneumatic ash conveying system. The design of the pneumatic ash conveying system has been improved and optimized, which fundamentally solves the problem that the traditional ash conveying gas consumption is large and the ash conveying system has a high failure rate. Adjusting the position of the blow-off valve and the ash bell mouth, solving the problem of large blow-up gas volume and blockage of the pump, completely overcomes the phenomenon that the pump has less ash and is easy to block the pipe. When designing the ash conveying pipeline, the number of elbows should be reduced as much as possible, the reducing pipe should be properly arranged, and the elbow with large radius of curvature should be used. The pneumatic conveying system has good wear resistance, low conveying resistance, uniform and stable transportation, high efficiency and low energy consumption. Etc.

5. Design of electrical control. For the use characteristics of the biomass boiler dust collector, the whole set of dust collectors is equipped with a differential pressure gauge and a temperature detecting instrument for equipment control, on-line detection and protection. An electric heating device is arranged in the ash hopper and the ash hopper of the bag filter, and a temperature measuring point is set in the ash hopper. When the ash wall temperature is higher than the design value (adjustable), the electric heating device is automatically turned off, and when the ash wall temperature is lower than the set temperature, the electric heating device is automatically turned on. The system adopts PLC for automatic control, sets differential pressure and timing cleaning control mode and has detection and alarm functions such as pressure, temperature and material level. The dust collector sets the flue gas temperature on-line detecting device. When the flue gas temperature is too high or too low and exceeds the preset alarm value, the bypass system valve is automatically opened to discharge the flue gas to protect the filter bag. The warehouse pump starts with the weighing and conveying method, which greatly improves the utilization of compressed air and reduces equipment wear.

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