Particulate matter, also known as dust, is a variety of solid or liquid particles uniformly dispersed in an aerosol system. Particulate matter can be divided into primary particulate matter and secondary particulate matter. Primary particulate matter is particulate matter that is released into the atmosphere by a direct source of pollution, such as soil particles, sea salt particles, burning soot, and so on. Secondary particulate matter is caused by the photochemical oxidation between certain polluting gas components in the atmosphere (such as sulfur dioxide, nitrogen oxides, hydrocarbons, etc.) or between these components and normal components in the atmosphere (such as oxygen) , Catalytic oxidation reaction or other chemical reaction to produce particulate matter, such as sulfur dioxide conversion to sulfate.
The particulate matter that has attracted attention has been divided into two categories:
The composition of particulate matter is very complicated. The components closely related to human activities mainly include ionic components (represented by sulfuric acid and sulfate particulate matter and nitric acid and nitrate particulate matter), trace elements (including heavy metals and rare metals, etc.) and organic components. According to the composition, atmospheric particulate matter can be divided into two categories, and particulate matter containing only inorganic components is called inorganic particulate matter. Organic particles are called organic particles. [4]
Under standard conditions (ie pressure
Particles below 1 micron settle slowly in the atmosphere
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Serial number
Technical name
Technical content
Scope of application
I. Key technologies for power plant boiler flue gas emission control
1
Limestone / lime-gypsum wet flue gas desulfurization technology for coal-fired power plant boilers
Limestone or lime is used as a desulfurization absorbent. In the absorption tower, the absorbent slurry and the flue gas are fully contacted and mixed. The sulfur dioxide in the flue gas reacts with the calcium carbonate (or calcium hydroxide) in the slurry and the oxidized air in the chemical reaction It is removed, and the final desulfurization by-product is calcium sulfate dihydrate, that is, gypsum. The desulfurization efficiency of this technology is generally greater than 95% and can reach more than 98%; SO2 emission concentration is generally less than 100mg / m3 and can reach less than 50mg / m3. The unit investment is approximately 150 ~ 250 yuan / kW; the operating cost is generally lower than 1.5 cents / kWh.
Coal-fired power station boiler
Key Technologies for Controlling Flue Gas Emissions from Industrial Boilers and Kilns
twenty one
Limestone-gypsum wet desulfurization technology
Limestone is used as a desulfurization absorbent. In the absorption tower, the absorbent slurry and the flue gas are fully contacted and mixed. The sulfur dioxide in the flue gas reacts with the calcium carbonate (or calcium hydroxide) in the slurry and the oxidized air to react. After removal, the final desulfurization by-product is calcium sulfate dihydrate, that is, gypsum. The desulfurization efficiency of this technology is generally greater than 95% and can reach more than 98%; SO2 emission concentration is generally less than 100mg / m3 and can reach less than 50mg / m3; the unit investment is approximately 150 ~ 250 yuan / kW or 15 ~ 250,000 yuan / m2 Sintered area; operating cost is generally less than 1.5 cents / kWh.
Industrial boiler / steel sintering flue gas
3. Key technologies for purifying typical toxic and harmful industrial waste gas
41
Volatile organic gas
(VOCs) Recycling, Desorption, Diversion, Recovery, Adsorption and Purification Technology
The activated carbon is used as an adsorbent, and the inert gas circulation heating desorption splitting condensation recovery process is used to purify and recover the organic gas. The recovery liquid can realize the recycling of organic matter through the subsequent refining process. The purification and recovery efficiency of organic gas components by this technology is generally greater than 90%, and can also reach more than 95%. The unit investment is approximately 90 ~ 240,000 yuan / thousand (m3h-1), and the cost of recovering organic matter is approximately 700 ~ 3000 yuan / ton.
Petrochemical, pharmaceutical, printing, surface coating, coating, etc.
4. Key Technologies for Motor Vehicle Emission Control
59
Catalytic exhaust purification technology for gasoline vehicles
The core components of automobile exhaust gas purifiers are prepared by adopting an optimized formula of a full Pd type three-effect catalyst and a positioning coating technology of a vacuum adsorption honeycomb catalyst. Vacuum coating technology can precisely control the amount of catalyst coating and effectively improve product consistency. The full Pd catalyst formula has a Pd content in the range of about 1 to 3 g / L depending on the engine model, which can reduce the cost by more than 50% compared with the ordinary Pd-Pt-Rh three-way catalyst used on the same engine. Purifiers produced by using this catalyst and coating technology can simultaneously purify CO, HC and NOx in automobile exhaust gas, and the purification effect can be greater than 95%, and the catalyst life span is more than 100,000 kilometers, which meets the exhaust gas emission standard requirements equivalent to China VI and above.
Automotive exhaust pollutant treatment
V. Key Technologies for Purifying Typical Air Pollutants in Houses and Public Places
64
Central air-conditioning air purification unit and indoor air purification technology
According to different places, adopting central air-conditioning systems with different wind disks and / or spaces, filters and purification components are installed, and various purification technologies such as filtration, adsorption, (photo) catalysis, and antibacterial / sterilization are integrated to achieve indoor temperature and air quality. Full adjustment.
Indoor and public air purification
65
Purification technology of harmful microorganisms in indoor air
The layered material was developed as a carrier-supported antibacterial agent for silver ions, which solved the problem of discoloration of silver ions when used at high temperatures while maintaining good antibacterial properties. Developed organic-inorganic compound antibacterial spray, which has a good antibacterial effect on indoor harmful microorganisms, such as E. coli, Staphylococcus aureus, Candida albicans, and Legionella, and also has a good inhibitory effect on Bacillus subtilis.
Indoor and public air purification
six,
The elimination of particulate matter in the atmosphere is closely related to the particle size and chemical properties of the particulate matter [10] . Generally, there are two methods of elimination:
1. Dry settlement: refers to the settlement of particles under the action of gravity, or after collision with other objects. There are two mechanisms for this settlement. One is the effect of gravity on particles, which causes it to land on the surface of soil, water or plants, buildings and other objects. The larger the particle size, the greater the sedimentation rate. Another settling mechanism is particles with a particle size of less than 0.1 m, namely Aitken particles. They diffuse by Brown's motion, collide with each other to condense into larger particles, and diffuse to the ground through collision or removal by atmospheric turbulence. [11]
2. Wet deposition: refers to the process of removing particulate matter from the atmosphere through rainfall, snow, etc. It is an effective method to remove atmospheric particulate matter and trace gaseous pollutants. Divided into two mechanisms, including rain removal and scouring. Rain removal means that some particulate matter can be used as cloud condensation nuclei and become the center of cloud droplets. Through condensation process and collision process, it can be enlarged into raindrops, which will grow to form rain and fall to the ground. Was removed. Rain removal has higher removal efficiency for particles with a radius of less than 1 m, especially for particles with hygroscopicity and solubility. Scouring is the process of inertial collision or diffusion and adsorption of particulate matter under the cloud with falling raindrops during rainfall, thereby removing particulate matter. Erosion is mainly targeted at particles with a radius of 4 m or more. [11]
The control of primary particulate matter emission is mainly using a dust collector. For secondary particles, only their precursors can be controlled. The formation and change of secondary particulate matter is one of the major research topics in environmental science. [2]
