Removal of VOCs from exhaust gas using the CADC adsorption-desorption method

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Technical principle: The interactive adsorption method is used to separate and concentrate VOCs in industrial exhaust gases with low concentrations and high flow rates, while the concentrated gases with high concentrations and low flow rates are decomposed and purified using the combustion method. Commonly known as the interactive adsorption concentration + combustion purification method. The flowchart of this method is shown in Figure 1. Several reactors with high adsorption capacity are connected in parallel; under normal conditions, one reactor is always in the desorption state while the remaining reactors are in the adsorption state. The adsorption and desorption processes occur alternately in each reactor, with the reactors operating in sequence according to a certain order. Furthermore, to prevent cross-ventilation between the various reactors as well as air leakage during desorption, the inlets of each reactor, along with the vacuum desorption valves, are equipped with fluororubber sealing materials that are resistant to high temperatures and solvents. The polluted exhaust gas containing VOCs is fed into the reactor by a blower; as this polluted air passes through the adsorption channels, the VOC components in it are absorbed by the adsorbent, thereby purifying the exhaust gas, which is then sent through pipelines to be emitted through the chimney. Over time, the reactor that has approached adsorption saturation stops operating and enters the desorption phase. The system is isolated from the adsorption circuit through valve switching; heating is activated simultaneously, and a vacuum pump is used for desorption. The highly concentrated VOC gases are released and go directly into the combustion chamber (or recovery unit). Since this process involves high-concentration VOC gases that are desorbed, the gas volume is generally only related to the volume of the reactor and the desorption time; the concentration of VOC gases is concentrated to more than 50 times that of the treated air. Therefore, this process is also known as the VOC concentration and removal process. The high-concentration, low-volume VOC gases discharged from the concentration and removal process are sent to a combustion device. After combustion at high temperatures of over 1,000 degrees Celsius, VOCs are completely purified into CO2 and water, and the exhaust gases are released through a chimney. Performance features: (1) Wide application range: It exhibits a high removal efficiency for various VOC gases, with good non-selectivity. It is suitable for treating organic polluted waste gas with low concentrations and high flow rates; through the adsorption, concentration, and separation process, it enables the subsequent combustion, decomposition, and purification steps to handle waste gas with low flow rates and high concentrations. This enables the miniaturization of the combustion decomposition purification device, reducing equipment investment and operating costs. (2) High removal efficiency: The reactor in this system uses a patented adsorption material, which is a highly active ACF combined with micron-sized molecular sieve powder; it possesses a large specific surface area (over 2000 m2/g). Thanks to the effects of van der Waals forces and chemical bonds, organic molecules are adsorbed and trapped within the micropores, resulting in a total VOC interception efficiency of over 98% ； (3) Low operating costs: The core components of this system have a service life of over 3 years, and there is no need to replace any consumables over time. The unique vacuum desorption method is used for purification, which helps to minimize the amount of waste gas while increasing its concentration. As a result, only a small amount of electricity is required for the combustion process; no additional fuel is needed to keep the system running properly ； (4) Fully automatic control: The system is controlled entirely by a microcomputer, and it features patented sealing and valve switching devices. Its streamlined design, along with scientifically optimized timing intervals, ensures the efficient operation of the system. No manual intervention is required. (5) Good economic efficiency: The standardized and modular design facilitates maintenance and repair, and the system has strong scalability, making it easy to increase processing capacity in the future. The post-treatment process can be matched with either a recovery process or an incineration process; organic solvents can be recovered and reused or sold externally, thereby generating profits for users ； It features low gas consumption and low energy usage, **saving on operating costs and delivering significant economic benefits to users. (6) High safety level: The system uses components with explosion-proof ratings, and key parts such as the reactor are equipped with temperature detectors, pressure sensors, and other devices for real-time monitoring of operational conditions, ensuring that the equipment operates within the designated safe range. The burner uses an internal electric heater with adjustable temperature, and no external fuel is required. Multiple flame arrestors are installed between the combustion chamber and the desorption chamber to prevent flames from flowing back into the desorption chamber. (7) No secondary pollution: During normal operation, there is no need to frequently replace consumables as with other methods, and there are no complications related to the disposal of solid waste. Solvent recovery and reuse represent true green and energy-saving practices; high-temperature incineration completely converts waste gases into small-molecule CO2 and water, minimizing environmental pollution. It’s a truly energy-saving and environmentally friendly process!