Types, main performance and design parameters of wire mesh demister

Types, main performance and design parameters of wire mesh demister

Types of wire mesh demisters : stainless steel wire mesh demister , metal wire mesh demister , plastic wire mesh demister , pp wire mesh demister , drawer type wire mesh demister , inlaid wire mesh demister , top-mounted wire mesh demister , bottom-mounted wire mesh demister , etc.

Types, main performance and design parameters of wire mesh demister

(1) Demisting efficiency：Demisting efficiency refers to the ratio of the mass of droplets captured by the demister (demister) per unit time to the mass of droplets entering the demister (demister). Demisting efficiency is a key indicator for evaluating the performance of demisters (demisters). There are many factors that affect demisting efficiency, mainly including: flue gas flow rate, uniformity of air flow distribution through the cross section of the demister (demister), blade structure, distance between blades, and layout of the demister (demister).

(2) System pressure drop：Refers to the pressure loss caused by flue gas passing through the demister (demister) channel. The greater the system pressure drop, the higher the energy consumption. The magnitude of the demister system pressure drop is mainly related to factors such as flue gas flow rate, blade structure, blade spacing, and flue gas water load.

When scaling is serious, the system pressure drop will increase significantly, so monitoring the changes in pressure drop will help grasp the system status, discover problems in time, and deal with them.

(3) Flue gas flow rate：Too high or too low flue gas velocity through the cross section of the demister (demister) is not conducive to the normal operation of the demister (demister). Too high flue gas velocity is easy to cause secondary water in the flue gas, thereby reducing the demisting efficiency. At the same time, the high flow rate leads to large system resistance and high energy consumption. Too low flow rate through the cross section of the demister (demister) is not conducive to gas-liquid separation, and is also not conducive to improving the demisting efficiency. In addition, if the designed flow rate is low, the cross-sectional size of the absorption tower will increase, and the investment will also increase accordingly. The designed flue gas velocity should be close to the critical velocity. According to the different demister (demister) blade structures and layout forms, the design flow rate is generally selected between 3.5 and 5.5 m/s.

(4) Demister (fog eliminator) blade spacing：The selection of the blade spacing of the demister (demister) is crucial to ensure the demisting efficiency and maintain the stable operation of the demisting system. If the blade spacing is large, the demisting efficiency is low, the flue gas carries a lot of water, and it is easy to cause fan failure, resulting in abnormal shutdown of the entire system. If the blade spacing is too small, in addition to increasing energy consumption, the flushing effect is also reduced, and the blades are prone to scaling and clogging, which will eventually cause the system to shut down. The blade spacing is selected based on comprehensive factors such as the system flue gas characteristics (flow rate, SO2 content, water load, dust concentration, etc.), absorbent utilization, and blade structure. The blade spacing is generally designed to be 20-95mm. At present, the most commonly used demister (demister) blade spacing in the desulfurization system is mostly 30-50mm.

(5) Defoamer (demister) flushing water pressure：The water pressure of the demister is generally determined based on the characteristics of the flushing nozzle and the distance between the nozzle and the demister (the distance between the nozzle and the demister is generally ≤1m). When the flushing water pressure is low, the flushing effect is poor. If the flushing water pressure is too high, it is easy to increase the water content of the flue gas and reduce the service life of the blades. In general, between the second-stage demisters, the flushing pressure on the front (facing the airflow direction) and the back of each stage of the demister are different. The flushing water pressure of the first-stage demister is higher than that of the second-stage demister. The water pressure on the front of the demister should be controlled within 2.5 × 105Pa, and the flushing water pressure on the back of the demister should be > 1.0 × 105Pa. The specific value needs to be determined according to the actual situation of the project.

(6) Defoamer (demister) flushing water volume：In addition to meeting the requirements of the demister (demister) itself, the water balance requirements of the system must also be considered when selecting the flushing water volume of the demister (demister). Under some conditions, a large amount of water is required for short-term flushing, and sometimes a small amount of water is required for long-term flushing. The specific flushing water volume needs to be determined by the working conditions. Under normal circumstances, the instantaneous flushing water consumption on the demister (demister) section is about 1 to 4 m3/m2·h.

(7) Flushing coverage：Flushing coverage refers to the coverage of the demister (defogger) section by flushing water. Flushing coverage % = nπh2 tg2αA×100 %

Where n is the number of nozzles; α is the spray diffusion angle; A is the effective flow area of the demister (demister), m2; h is the vertical distance between the flushing nozzle and the surface of the demister (demister), m. Depending on different working conditions, the flushing coverage rate can generally be selected between 100% and 300%.

The wire mesh demister is mainly composed of a wire mesh, a wire mesh grid, a wire mesh block, and a supporting device for fixing the wire mesh block. The wire mesh is a gas-liquid filter mesh made of various materials , and the gas-liquid filter mesh is composed of metal wire or non-metal wire. The non-metallic wire of the gas-liquid filter mesh is twisted from multiple strands of non-metallic fibers, and can also be a single strand of non-metallic wire. The wire mesh demister can not only filter out larger liquid foam suspended in the airflow, but also filter out smaller and tiny liquid foam, and is used in gas-liquid separation devices in industries such as chemical, petroleum, tower manufacturing, and pressure vessels .