Fog removal technology overall solution

The purpose of dehumidifying fog or liquid particles during the process is to: purify the gas itself; 

Remove harmful liquids to ensure the normal operation of subsequent industries; 

Prevent damage to the device sequence equipment; 

Avoid emissions of environmentally unacceptable gases; 

Recovery of valuable liquids from industrial processes.

 Basic types of mist liquids:

The first type of liquid particles formed by mechanical action, its particle size is usually 10 ~ 100μm, such liquid particles can be removed by relatively cheap and easy to install defromer, such as metal mesh defromer, baffle defromer, etc.

The second category of fog particles with a particle size below 3μm requires a filtration device with high adsorption capacity and a balance between filtration efficiency and acceptable pressure loss. Droplet size can often be accurately estimated. In the preliminary evaluation, experience has shown that droplets generated by mechanical action are mostly between 5 and 10μm in size, while the mist indicated by boiling or bubbling liquid will form droplets with a diameter of only a few microns, so the performance requirements of equipment such as evaporators must be carefully considered. The mist that passes over the surface of the packing or heat exchanger is mainly composed of large and easily removed droplets. However, when the saturated steam condenses to form a liquid, it often produces a very small fog. This is the case in compressors: lubricating oils are locally heated and vaporized in the compressor, and then quickly condensed to form very small "smoky-like" fogs.

Filter fog removal principle:

After the gas containing mist passes through the fiber bed from one side of the filter, the clean gas is discharged from the other side, and the harmful substances are caught and collected by the demister. The collected liquid particles gather on the fiber surface of the demister to form large droplets, and when the droplets are large enough, they fall off the demister due to the action of gravity.

Fog removal mechanism: 

For liquid particles larger than 3μm, the removal process is mainly based on impinging. When the particle size is smaller, the diffusion caused by Brownian motion is dominant, that is, when the gas passes through the filter bed, the surrounding gas molecules hit the fine fog particles, causing the particles to do irregular diffusion movement relative to the fiber surface. The efficiency of a single fiber is very low, but the filter bed is composed of thousands of fibers, and its overall fog removal efficiency is very high. In order not to hinder the diffusion motion caused by Brownian motion, a low gas filtration speed is required. The technical staff studied the selection of different surface properties, different diameters and different densities of fibers for testing, and finally determined the fiber material that can obtain the highest efficiency and the appropriate filling density. In this way, the filter bed can have a higher fog removal efficiency within the allowed pressure drop range; And the technical personnel also found that if the hydrophobic fiber dimension material is selected, the liquid trapped by the acid fog does not accumulate when it passes through the bed, and the liquid particles trapped by the fiber are in a droplet shape on the fiber surface rather than a membrane shape, so the fiber bed resistance is reduced and stable, and will not cause "secondary entrain".

Chlor-alkali, PVC industry

Fiber mist eliminator provides high quality and efficient products for chlorine gas drying, hydrogen gas treatment, hydrogen chloride gas deacidification and acetylene, vinyl chloride, hydrogen chloride and other process gas treatment in PVC production. Fiber fog eliminator is used in many aspects of chlor-alkali industrial production process. The purified brine is used by direct current in the ionic membrane electrolyzer, the cathode produces hydrogen and caustic soda, and the anode produces chlorine and anodic liquid (210 ~ 230g/L NaCl). The temperature of the wet chlorine gas coming out of the electrolytic cell is usually above 85℃, and the moisture contained in the wet chlorine gas is as high as 0.4%. After cooling and cleaning in the water washing tower, it enters the titanium tube cooler (temperature 12 ~ 18℃). Due to the cooling effect, a large amount of water mist contained in the wet chlorine gas mostly exists in the form of micron droplets. The effective removal of entailed droplets determines the consumption of sulfuric acid in the chlorine gas drying process. The application of the fiber defogger has proved that it can effectively remove the fog droplets contained in the moisture chlorine gas (defogging efficiency) : ≥ 1μm 100%, ≤ 1μm 99.5% acid consumption: ≤ 15Kg/t.NaOH. After the chlorine gas enters the drying tower and is further dried by 98% H2SO4, a large number of sulfuric acid droplets are carried in the chlorine gas, which is easy to cause pipeline blockage and corrosion of the intercooler and turbine. John Manwer fiber defogger can effectively remove sulfuric acid droplets contained in dry chlorine gas (defogging efficiency) : ≥ 1μm 100%, ≤ 1μm 99.5%. The electrolytic cell releases chlorine and hydrogen gas, and the wet chlorine gas is passed through the water washing tower to remove the entrain brine and impurities. The fiber demister for this section is made of highly efficient special chemical grade glass fiber and vinyl FRP or titanium skeleton. After passing through the drying process, the wet chlorine gas is transformed into dry chlorine gas with sulfuric acid droplets. Here the fiber defogger is installed in the turbine compressor downstream of the drying tower to collect sulfuric acid to improve product purity and protect the safe and smooth operation of the turbine. The fiber demister for this section is made of highly efficient hydrophobic glass fiber and passivated 316L stainless steel skeleton. The hydrogen precipitated from the electrolytic cell contains sodium hydroxide and other impurities, and the fiber fog eliminator is used to remove sodium hydroxide and impurities to purify hydrogen gas and prevent corrosion of the compressor. In the case of high PH and high corrosion, use polypropylene or stainless steel skeleton. In the production process of calcium carbide PVC, the removal of acetylene gas, chlorine gas and mixed gas fog particles with John Manwer fiber defogger can effectively purify each process gas, thereby improving the quality of PVC finished products and protecting the safety of equipment operation.