1. The composition and hazards of waste gas
       There are many types of indoor air pollutants in chemical laboratories, with complex composition and intermittent emissions. The main air pollutants include organic gases and inorganic gases. Organic gases include carbon tetrachloride, methane, ether, ethyl mercaptan, benzene, aldehydes, etc. Inorganic gases include nitric oxide, nitrogen dioxide, hydrogen halide, hydrogen sulfide, sulfur dioxide, etc.
       These gases are directly emitted into the atmosphere, which will aggravate the formation of acid rain and constitute a serious social hazard. If people inhale too much, it will cause direct harm.
       2. Laboratory waste gas treatment method
       The current treatment methods for gaseous pollutants can generally be divided into two categories: wet methods and dry methods. Specifically, high-efficiency and low-cost methods need to be selected based on the characteristics of chemical laboratory waste gas.
       A. Wet waste gas treatment
       Wet waste gas treatment uses an acid mist purification tower for waste gas treatment, which is suitable for purifying hydrogen chloride gas (HCl), hydrogen fluoride gas (HF), ammonia gas (NH3), sulfuric acid mist (H2SO4), chromic acid mist (CrO3), hydrogen cyanide acid gas (HCN), and hydrogen sulfide gas (H2S). ), low-concentration NOx exhaust gas and other water-soluble gases, it has the characteristics of good purification effect, compact structure, small footprint, good corrosion resistance, anti-aging performance, convenient installation, transportation, maintenance and management, simple equipment structure, low one-time investment, etc., so it is widely used in the treatment of gaseous pollutants.
       Acid mist purification tower is suitable for installation on the roofs of high-rise buildings. The working principle is that the acid mist exhaust gas is pressed into the purification tower by a fan. After passing through the spray and packing layers, the exhaust gas and the sodium hydroxide absorption neutralizing liquid perform a gas-liquid two-phase full contact absorption and neutralization reaction. After the acid mist exhaust gas is purified, it is deliquidated through the deliquifying layer and then discharged into the atmosphere. The purified acid mist exhaust gas can be lower than the national emission standards.
       B. Dry waste gas treatment
       Dry exhaust gas treatment refers to a process in which when a gas mixture comes into contact with a porous solid, the unbalanced molecular attraction or chemical bonding force existing on the solid surface is used to adsorb a certain component or some components in the mixture on the solid surface. The solid with adsorption effect is called adsorbent. The advantages of this method are simple equipment, convenient operation, and easy to realize automatic control. However, because the adsorbents have different physical and chemical properties and are highly targeted, adsorbents with different physical and chemical properties must be configured to treat waste gases containing different harmful substances to achieve good gas purification. If the time for the waste gas to pass through the adsorbent is short and the content of harmful substances in the waste gas is too high, the waste gas purification effect will be unsatisfactory. When the waste gas passes through the adsorption medium, because the air flow is blocked by the solid medium, the power of the fan must be increased to ensure the normal wind speed of the ventilation system. The adsorbent needs to be replaced or regenerated regularly to ensure the normal operation of the absorption device. Therefore, this method requires a certain amount of cost and manpower in practical applications. This method is generally used for waste gas treatment where the types of harmful substances in the waste gas are relatively stable and the content is low, which facilitates the use of a targeted adsorbent.
       Dry waste gas treatment generally uses organic gas activated carbon adsorption devices. The principle is that activated carbon has many micropores and a large specific surface area. Relying on molecular gravity and capillary action, solvent vapor and volatile substances can be adsorbed on its surface. According to the boiling points of different substances, the adsorbed substances are precipitated with steam. When steam is used as the desorption medium, the precipitated organic solvent vapor condenses with water vapor through the condenser, enters the separation barrel, and recovers the organic solvent after separation.