industrial waste gas pollutionIt is one of the main sources of pollution in our country at present. If it is not treated in time, it is easy to produce diseases and affect people's health after being absorbed by the human body. Therefore, effective measures must be taken to control waste gas, especially organic waste gas, to improve air quality and reduce the occurrence of diseases. In this paper, the treatment of organic waste gas technology and methods are analyzed and discussed.
 

Main composition and characteristics of 1. organic waste gas

By analyzing the composition of most organic waste gas, it can be concluded that its composition mainly includes: formaldehyde, benzene, toluene, xylene and other benzene series, acetone butanone, ethyl acetate, oil, furfural, styrene, acrylic acid, resin, additives, paint mist and some organic gases containing carbon hydrogen and oxygen. Organic waste gas has the following characteristics: toxic, explosive, flammable, insoluble in water, soluble in organic solution, difficult to deal. If it is not effectively managed, it will pose a threat to people's health. By adopting the corresponding treatment technology, the organic waste gas can be effectively treated, and some of the treated substances can also be reused.

Second, organic waste gas treatment technology and methods
 

After years of research, there are many technologies and methods that can effectively treat organic waste gas, and have achieved good results.
 

1. Photodecomposition method

Using this method to treat organic waste gas can be achieved through the following aspects: one is the use of light decomposition, when the light wavelength reaches the corresponding value, the organic waste gas can be decomposed; the second is to add a catalyst to decompose the organic waste gas in the form of light. For example, when organic chlorides and chlorofluorocarbons are irradiated with ultraviolet rays of 185mm, they can be decomposed in a very short time. In the process of photolysis, some intermediate substances are usually produced, but these substances may be treated by prolonged light irradiation or sodium hydroxide solution. The third is photocatalytic degradation, which is activated by ultraviolet irradiation of TiO2 to generate H2O into OH-radicals, which will dissolve organic waste gas into CO2 and H2O.
 

When we choose a catalyst to eliminate organic waste gas, we can use a common fluorescent lamp as a light source to eliminate the odor in organic waste gas or reduce its pollution concentration. However, as far as the current experience is concerned, the technology and effect of using catalysts for degradation still need to be improved.
 

 

2. Adsorption method
 
(1) Direct adsorption method

Using activated carbon, direct adsorption of organic waste gas. Its adsorption rate is very high, can reach more than 96%, the method of small investment, simple. However, when activated carbon is in a saturated state of adsorption, the degree of adsorption of organic waste gas will be greatly reduced, only about 35% of the adsorption, adsorption of "triphenyl" waste gas can only reach 20% to 25%, that is to say, a ton of activated carbon adsorption of "triphenyl" gas is only 200-250kg. However, the saturated activated carbon cannot be regenerated. If the activated carbon adsorption effect is to be improved, the activated carbon needs to be replaced, so the treatment cost is high and there is a secondary pollution problem.
 
(2) Adsorption-regeneration method

The method uses fiber activated carbon or granular activated carbon adsorbent adsorption of organic waste gas, close to saturation with superheated steam blowback activated carbon for desorption regeneration, water vapor and desorption out of the "three benzene" gas by condensation, separation, recovery of "three benzene" liquid. The use of this method has the advantages of fast desorption and good condensation adsorption effect, but it has obvious shortcomings: for example, it must have corresponding steam and high corrosiveness; and the need for secondary separation of the recovered liquid, and the residual water in the activated carbon must be dried. After that, the secondary adsorption is carried out, which is costly.
 
This method is suitable for waste gas treatment with high concentration, small air volume and certain recycling value, otherwise it is not suitable to choose this process. In addition, the technology needs to be further improved and improved.
 
(3) Adsorption-catalytic oxidation.




 

Adopt a new type of activated carbon to adsorb organic waste gas with low concentration, and then use hot air to heat it after the adsorption reaches the corresponding saturation, and then use the "three benzene" and other waste gas in the adsorption, and then use the catalytic combustion method to achieve the purpose of organic waste gas purification. In addition, the hot gas can be recycled and used for waste heat.
 
By using this method, various adsorption methods can be used comprehensively to effectively solve the problem of large air volume and low concentration of organic waste gas. This method is a relatively mature method in China. Because organic waste gas contains a variety of impurities such as phosphorus, lead, tin, mercury, etc., it is easy to cause catalyst poisoning.
 
Therefore, when the catalyst is applied, a certain carrier should be added to reduce the use of the catalyst, while increasing its use area, reducing sintering, and improving the stability of the catalyst. The commonly used catalyst carrier has asbestos, clay, activated carbon and other substances, the specific application can be selected according to the actual conditions.
 
3. Process characteristics and technical progress of catalytic combustion technology
 
According to the organic waste gas preheating method and enrichment method, catalytic combustion is divided into the following three types:
 
(1) Preheating: This is the most common way of catalytic combustion. The temperature of organic waste gas is below 100 ℃, the concentration is also low, and the heat cannot be self-sufficient, so it needs to be heated in the preheating chamber before entering the reactor. The combustion-cleaned gas exchanges heat with the untreated exhaust gas in a heat exchanger to recover some of the heat. This technique generally uses gas or electric heating to heat up to the ignition temperature required for the catalytic reaction.
 
(2) self heat balance type: when the discharge temperature of organic waste gas is higher than the light-off temperature (at about 300 ℃) and the organic content is high, the heat exchanger recovers some of the heat generated by the purified gas, and can maintain the heat balance under normal operation without making up the heat. Generally, only an electric heater needs to be set up in the catalytic combustion reactor for light-off.
 
(3) Adsorption-catalytic combustion: When the flow of organic waste gas is large, the concentration is low, the temperature is low, and the catalytic combustion requires a lot of fuel, the organic waste gas can be adsorbed on the adsorbent by adsorption method for concentration, and then through hot air Purge, the organic waste gas is desorbed and concentrated into high concentration organic waste gas (can be concentrated more than 10 times), and then catalytic combustion is carried out. At this time, do not need to make up the heat source, can maintain normal operation.
 
(4) Research progress of catalytic combustion technology
 
With the rapid development of industrial production, the variety of organic waste gas is also increasing. Therefore, people are constantly developing some new processes and technologies of catalytic combustion to further enhance the treatment efficiency of organic waste gas. Catalytic combustion technology involves chemical engineering, environmental engineering, catalytic reaction and automatic detection and control, and is still in the development stage in China. Its future development direction is: 1) to further strengthen the catalyst function, research and development with anti-toxicity, large space velocity, large surface area and low ignition point of non-precious metal catalysts, in order to reduce the cost and operating costs. 2) The catalytic combustion device should be developed in the direction of large-scale, integral and energy-saving.
 
5. Biological law
 
Biological purification is commonly referred to as an oxidation process: biological purification attached to the active microorganisms and moist media on the organic matter as the energy of life in a timely manner, generally converted into inorganic matter (CO2, H2O) and common cell matter. At this stage, the biological purification process mainly includes three kinds: biological filtration, biological trickling filter bed and biological washing bed.
 
III. Summary
 
1, in many organicwaste gas treatment technologyBiological treatment technology is a technology with good application prospects. It has low operating cost, low energy consumption, no obvious secondary pollution, and can treat medium and low concentration organic waste gas of various scales. With the continuous improvement of its technology, it has attracted more and more attention and is widely used in industrial organic waste gas treatment. The research focus of biological treatment technology should be to strengthen the improvement of filler performance, equipment structure and process conditions, as well as the research on the treatment capacity of different strains.
 
2. Adsorption technology is one of the more mature and formed technologies in the treatment of organic waste gas, but it has problems such as insufficient capacity of treatment equipment and regeneration of adsorbent, which limits the application and development of the technology.
 
3. Catalytic combustion technology has the advantages of low investment, simple equipment, convenient operation, thorough purification, and can treat low and high concentration organic waste gas. It is currently the most widely used, economical and effective treatment technology. In the future, the research direction of this technology should focus on how to prevent the deactivation of the catalyst caused by non-VOC substances and the poisoning caused by heavy metals.