The separation and purification of water vapor and particulate matter by chimney exhaust white smoke purification is the result of the synergistic effect of physical separation and chemical conversion. Its core logic is to first capture pollutants by physical means, then chemically treat specific components, and finally achieve clean emission of white smoke. This composite treatment method can not only cope with the complex mixture system in white smoke, but also take into account purification efficiency and operation stability.
Physical methods are the basis of the purification process. The first step is to separate particulate matter through "inertial collision" and "interception effect". When the dusty white smoke flows through the grille or baffle inside the chimney exhaust white smoke purification at high speed, the airflow suddenly changes direction. Larger particles (such as dust and carbon black particles with a diameter greater than 10 microns) cannot turn with the airflow due to inertia, and will hit the baffle surface and settle. This process can remove about 60% of coarse particles. For fine particles with a diameter of 1-10 microns, separation is achieved through "membrane filtration" - the porous filter material (such as glass fiber felt, polytetrafluoroethylene membrane) in the chimney exhaust white smoke purification forms a dense three-dimensional mesh structure. The particles are intercepted or adsorbed by the fibers when passing through with the airflow. With the electrostatic force on the surface of the filter material (given by electret treatment), the capture rate of ultrafine particles below 0.5 microns can reach more than 90%.
The physical separation of water vapor mainly depends on "condensation and precipitation" and "demist capture". The water vapor in white smoke mostly exists in the form of saturated steam or tiny droplets. The chimney exhaust white smoke purification uses a cooling device (such as a finned heat exchanger) to reduce the smoke temperature from 120-180℃ to below the dew point, so that the supersaturated water vapor condenses into larger droplets. These droplets slide along the wall under the action of gravity to complete the initial dehydration. The remaining tiny droplets (5-50 microns in diameter) are intercepted by the demister - the corrugated plates or baffles of the demister cause violent disturbances in the airflow, and the droplets adhere to the plate surface due to centrifugal force, gradually converge into water flow and discharge. After these two steps of treatment, the water vapor content in the white smoke can be reduced by 70%-80%, visually reducing the perception of "white smoke".
The chemical method mainly targets soluble pollutants and odor components in white smoke, and the two mechanisms of "adsorption" and "oxidation" are commonly used. For industrial white smoke containing sulfur oxides and nitrogen oxides, the activated carbon or molecular sieve adsorption layer in the chimney exhaust white smoke purification captures these gas molecules in the pores through the van der Waals force of the porous structure, and uses the chemically active sites on the surface of the adsorbent (such as the hydroxyl groups on the activated carbon) to react with the pollutants and convert them into stable
compounds. For white smoke formed by volatile organic compounds (VOCs), the "photocatalytic oxidation" process can be used. Under ultraviolet irradiation, the titanium dioxide catalyst produces hydroxyl radicals, which oxidize and decompose organic molecules into carbon dioxide and water, eliminating odor and avoiding secondary pollution.
The synergy of physical and chemical methods is reflected in the process design of "pretreatment-deep purification". Physical separation first removes most of the particulate matter and water vapor, reducing the load of subsequent chemical treatment. If a large amount of particulate matter covers the surface of the adsorbent, it will block its pores; and excessive water vapor will reduce the activity of the catalyst and affect the oxidation efficiency. When the physically purified white smoke enters the chemical treatment unit, the concentration of pollutants has been greatly reduced, so that the adsorbent and catalyst can play a more efficient role and extend the replacement cycle. For example, the chimney exhaust white smoke purification of a power plant first removes 90% of the dust and water vapor by physical means, and then after activated carbon adsorption treatment, the sulfur oxide emissions are reduced by 40% compared with single chemical treatment.
For white smoke with different components, the ratio of physical and chemical methods will be dynamically adjusted. For boiler white smoke mainly composed of water vapor and particulate matter, physical separation is dominant, and chemical treatment is only auxiliary (such as a small amount of activated carbon to remove slight odor); while white smoke containing complex chemical pollutants in chemical production needs to strengthen the chemical oxidation or adsorption link, and physical means mainly play a pretreatment role. This flexibility enables chimney exhaust white smoke purification to adapt to a variety of scenarios, ensuring that the purification effect meets the standard and avoiding energy waste.
During the purification process, "gas-liquid separation" is also required to prevent secondary pollution. The wastewater produced by physical condensation may contain dissolved acidic substances or heavy metals. Chimney exhaust white smoke purification will introduce it into the neutralization tank, adjust the pH value by adding alkaline agents (such as sodium hydroxide), and then remove solid impurities by precipitation and filtration. After meeting the standard, it will be reused or discharged. The waste adsorbent produced by chemical treatment is classified and treated according to the nature of the pollutants. For example, activated carbon that adsorbs heavy metals needs to be stabilized and solidified to avoid leakage of harmful substances.
Ultimately, the particle concentration of white smoke after physical and chemical synergistic treatment can be reduced to below 10mg/m³, the water vapor content is significantly reduced, and the emission of harmful substances meets environmental protection standards, achieving dual purification from the visual and component aspects. The advantage of this composite purification method is that it can not only quickly treat a large number of pollutants through physical means, but also deeply remove difficult-to-separate components through chemical methods, providing a systematic solution for chimney white smoke from different sources.
