Exhaust gas and odor treatment system
AGENTS and Sources of Air Pollution
Main causes of air pollution:
Pollutants in the environment can be said to exist in many different forms, but can be classified into two main categories:
– Gases: SOx, NOx, COx, H2S… and toxic vapors.
– Solid: ash, dust, smoke and aerosols
Sources of man-made pollution:
Most of human activities create waste and pollutants into the environment, especially in daily life, industry and traffic.
Sources of waste from daily life: Every day people have used a large amount of fuels such as coal, firewood, oil, gas for cooking and for other purposes. In the process of burning, they will consume oxygen of the atmosphere, and at the same time create a lot of smoke, CO, CO2, ... These wastes are often concentrated in a small space (kitchen), the exhaust gas is slow. should create a large concentration in human living space.
Sources of waste due to transportation: With the advancement of science and technology, people have created many mechanical equipment, shown by the flow of vehicles on the street, they run on gasoline, so they produce a lot of smoke and CO. , CO2, NO and HC, etc. This influence depends mainly on the quality of traffic on the road. Leaded gasoline is also an agent that greatly affects human health.
Waste sources from industrial production: A trend that goes against the quality of the environment is the process of urbanization and industrialization, which is the process of reducing green areas and rivers, replacing them with high-rise buildings, industrial factories. With the flue gas chimneys, various pollutants are suspected, making the air quality in urban areas greatly affected.
The wastes of industrial zones are very diverse, their effects on the environment are also different, so for research, it is necessary to consider specifically for each type of factory.
Solutions to prevent and treat air pollution
Planning solution
The fact has shown that many industrial plants are located right between residential areas and urban areas, causing a lot of dust, smoke, noise and pollutants; many chimneys are located at the windward direction towards residential areas; in humid human settlements; ventilation, lighting is not guaranteed, etc. All of these disadvantages are due to the lack of reasonable planning measures during construction. Faced with that situation, the state now requires establishments to have an environmental impact assessment for old facilities to take remedial measures; For works that have just begun to be implemented, it is necessary to report possible impacts on the environment, to ensure that there are no major impacts during the construction process and also during the operation and use. use later
Hygienic isolation solution
Usually, the closer to the source of pollution, the greater its influence, so it is necessary to define a protection belt around the industrial park, which is the distance from the source of the waste to the residential area. That distance depends on the nature and characteristics of each type of factory, type of production caused, this distance ensures that the concentration of pollutants in residential areas caused by this source does not exceed the standards for permission. In addition, for industrial parks, it is necessary to have walls or use green strips to prevent the spread of dust and noise in the space, in order to minimize environmental pollution to people's living places.
Table 2.1. Regulation of sanitary isolation strips according to hazardous levels of industrial production:
| Toxic level | I | II | III | IV | DRAW |
| Insulation strip (m) | 1000 | 500 | 300 | 100 | 50 |
Ventilation solutions
In a closed room, we can change the polluted inside air (due to heat, dust, toxic gas…) with clean air brought in from outside for a certain period of time (periodic ventilation). ) or for an unlimited period (regular ventilation…). called room ventilation.
a. General ventilation:
The purpose of general ventilation is to bring in air from outside with the necessary flow to dilute the intensity of pollution (by heat, dust, vapor or toxic gas) in the entire factory space, then discharge it out. It is carried out in rooms where the source of the hazard is evenly distributed (schools, theaters, hospitals) or in rooms where it is not possible to predict where the toxic sources will appear (food shops, refreshment bars, etc.) club….)
The disadvantage of the general ventilation system is that the place where there is no hazard is also affected by the source of the toxic spillage elsewhere.
b. Local ventilation:
It is carried out to discharge hazardous substances directly from the source to the outside (local suction) or to blow clean air into necessary and known locations (local blow). The organization and reasonable handling of pollutants must satisfy the following requirements:
- Do not obstruct the manipulation of technology.
Do not allow air containing pollutants to pass through the breathing zone.
- The gas collection velocity is large enough.
Waste gas treatment at source
Before being discharged into the environment through the chimney, they are allowed to pass through treatment equipment to reduce the concentration of pollutants to avoid waste with concentrations exceeding the allowable standards.
a. Exhaust gas treatment by absorption method:
Includes 3 steps:
Step 1: Diffusion of gaseous pollutant molecules in the flue gas mass to the surface of the absorbent solution
Step 2: The penetration and dissolution of a gas into the surface of the absorbent solution.
Step 3: Diffusion of the dissolved gas on the surface of the separator into the depths of the absorbing liquid
During absorption. Pollutants in the exhaust gas are trapped on the surface of the solid and cleaned material. The trapped harmful gases are called adsorbents.
The activities of dehumidifying the air, eliminating harmful gases and odors in the exhaust gas. The recovery of valuable vapors and gases is called the absorption process.
Substances commonly used in exhaust gas absorption methods
- H country2O)
- Basic solutions: KOH, NaOH, Na2CO3, KY2CO3, Ca(OH)2, CaCO3…
Monoethanolamine (OHCH2ONLY2SMALL2), diethanolamine (cheap2 - NH), tritanolamine (R3– NH)
Advantages and disadvantages of the exhaust gas absorption process
| Advantages | Defect |
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Objects used to treat exhaust gas by absorption method
- Mineral processing plant
- Seafood processing factory
- Quarry plant
- Cement factory
- Brick processing factory
b. Exhaust gas treatment by adsorption method:
