Publish Time: 2022-05-23 Origin: Site
The laboratory will generate corresponding waste gas during the daily operation. If it is directly discharged into the atmosphere without treatment, it will inevitably pollute the surrounding environment and cause organic damage to the human body. At present, the laboratory status and the sources and types of waste gas produced are quite complicated.
Inorganic waste gas and organic waste gas contained in laboratory waste gas.
Inorganic waste gas such as nitrogen oxides, sulfuric acid mist, hydrogen chloride, hydrogen fluoride, hydrogen sulfide and sulfur dioxide.
Benzene, toluene, xylene, styrene, etc.;
Aldehydes and ketones: formaldehyde, acetaldehyde, glutaraldehyde, butyraldehyde, acetone, cyclohexanone, methyl ethyl ketone, acetophenone, etc.;
Esters: isobutyl acetate, ethyl acetate, butyl acetate, methyl acetate, banana water, etc.;
Alcohols: methanol, ethanol, butanol, isopropanol, ethylene glycol, etc.
In view of the characteristics of the types of waste gas generated in the laboratory including inorganic waste gas and organic waste gas, the following principles are sought in the treatment plan:
1. Implement my country's relevant environmental protection policies and relevant regulations, norms and standards.
2. The operation of the waste gas treatment engineering system is stable and reliable.
3. Adopting the processing technology with mature technology, advanced technology and easy operation and management, the system operation, management and maintenance are simple, the project investment is low, and the operation cost is low.
4. The equipment selected in the treatment process should be matched with the existing equipment of the laboratory, without affecting the normal operation of the existing equipment in the laboratory, taking into account the original facilities, and reducing investment costs according to local conditions.
Process selection
1. Using activated carbon adsorption method for organic waste gas, its absorption efficiency can be as high as 90% or more.
(1) Principle of activated carbon adsorption
Activated carbon is a kind of microcrystalline carbon material mainly made of carbonaceous material, with black appearance, developed internal void structure, large specific surface area and strong adsorption capacity. There are a large number of micropores invisible to the naked eye in the activated carbon material. The micropores in 1 gram of activated carbon material can have a surface area of up to 800-1500 square meters after being unfolded, especially higher. That is, in a grain-sized activated carbon particle, the inner surface area of the micropores may be equivalent to the size of a living room area. It is these highly developed, human-like void structures that enable activated carbon to have excellent adsorption properties. The mutual adsorption force between molecules is called "van der Waals force". Although the speed of molecular motion is affected by factors such as temperature and material, it is always in constant motion in the microenvironment. Due to the attractive force between molecules, when a molecule is captured by the inner pores of the activated carbon and enters the pores of the activated carbon, due to the mutual attraction between the molecules, more molecules will be attracted continuously until the activated carbon is filled. up to the internal void.
(2) Activated carbon desorption method
When the internal voids of activated carbon are filled with organic waste gas, that is, adsorbed substances and become saturated, pollutants begin to be released, a phenomenon called penetration. The activated carbon adsorption bed that has reached saturation needs to be regenerated. Generally, heated gas is used to desorb the adsorption bed. On the one hand, the regeneration of the adsorption bed becomes active again, and on the other hand, the pollutants are liberated for recovery or decomposition treatment. This desorption method is called elevated temperature desorption. The adsorption capacity of the substance decreases with the increase of temperature. Increasing the temperature of the adsorbent can desorb the adsorbed components. This method is also called temperature swing desorption. is cyclically changing.
2. Using liquid absorption method for inorganic waste gas, its absorption efficiency can reach more than 90%. Liquid absorption method is a common treatment process for inorganic gas purification, and the process technology is quite mature, stable and reliable. The liquid is used as the absorbent, and the harmful components in the exhaust gas are absorbed by the liquid through the washing and collecting device, so as to achieve the purpose of purification. The absorption system belongs to the gas-film controlled absorption process, and adopts a liquid-phase dispersion type device, namely, a spray packed tower. When it is working, the absorption liquid is evenly sprayed on the top of the packing layer through the spraying device at the top of the packed tower, and flows along the packing layer from top to bottom in a film-like manner, while the exhaust gas enters from the lower part of the tower and passes through the packing layer from the tower. Top discharge. During this process, the exhaust gas is forced to change its direction, speed, and absorbing liquid continuously to collide and contact, so that the exhaust gas and the absorbing liquid have sufficient contact reaction time in the packing layer, so that the harmful components in the exhaust gas can be fully absorbed and purified by the absorbing liquid. The purified gas can be discharged up to the standard after being defogged in the tower.
3. According to the type of waste gas generated in this laboratory, the treatment plan adopts the method of activated carbon adsorption and combination for treatment. First, the activated carbon is used to adsorb organic pollutants, and then the packed spray tower is used to absorb inorganic pollutants.
the reason is:
The inorganic waste gas in the laboratory is mainly acidic waste gas, and alkaline waste gas generally exists in industrial production. The effect of pH on the adsorption efficiency of activated carbon generally decreases with the increase of the pH value of the solution. When the pH value is higher than 9.0, it is difficult to Adsorption, the lower the pH value, the better the effect. Therefore, the activated carbon adsorption is used first, and then the filler spraying combination method is used.