1. Mechanical separation method
The oil fume is separated by the principle of inertial collision or cyclone separation.
Disadvantages: the baffle filter screen is easy to break, and the waste is directly discharged; Need regular maintenance; The vertical angle of installation shall be less than 15 °; The purification efficiency is not high, and it is only applicable to the occasions with low requirements for pretreatment or purification efficiency.
2. Fabric filtration method
The lampblack exhaust gas first passes through a certain number of metal grids, and large particulate pollutants are intercepted; Then, after passing through filter materials such as fiber mats, particles are removed due to diffusion and interception. The commonly selected filter material is polymer composite material with high oil absorption performance. The equipment has the advantages of less investment, low operation cost, no secondary pollution and convenient maintenance and management; However, it has the disadvantages of large resistance, large land occupation and frequent replacement of filter materials. The purification efficiency is generally 80~92%.
Disadvantages: due to the large resistance of filter material, such as the pressure drop of glass fiber filter material purifier can reach 1500Pa, and the filter material needs to be replaced frequently, the application of filtering purification equipment is limited.
3. Catalyst combustion method
The principle of combustion purification method is to use the heat generated by high temperature combustion to carry out oxidation reaction, and convert the pollutants in the lampblack waste gas into CO2, H2O and other substances, so as to achieve the purification purpose. In the combustion process, let the lampblack exhaust gas pass through the self purification catalyst, and the catalytic reaction of the catalyst is conducive to the transformation of pollutants. Generally, ceramic or metal honeycomb is used as the carrier for oxidation catalysis. This kind of lampblack purification equipment is only applicable to occasions with low lampblack concentration, such as raw food or semi-finished products.
Disadvantages: The development of catalytic combustion purification equipment is not very mature.
4. Wet process
Water or other detergents are used to form a water film by spraying the nozzle, and water mist is used to absorb oil smoke. The soot particles contact with the water mist and water film ejected from the nozzle, and flow down with the water droplets through mutual inertial collision, retention, diffusion and mutual condensation of fine particles, thus separating the soot ions from the air flow. The equipment has simple structure, less investment, small land occupation, low operation cost and convenient maintenance and management.
Disadvantages: it has large resistance, low purification rate of submicron particles, and secondary pollution of oily sewage.
L The purification efficiency of mechanical separation and purification equipment is not high, and it is only suitable for pre-treatment or occasions with low purification efficiency requirements;
L The purification rate of submicron particles by wet scrubbing and purification equipment is very low, and the washing solution generated needs to be treated;
L The filtering and purification equipment needs to purify and replace the filter material, which consumes a lot of energy; The cost of activated carbon adsorption purification equipment is too high;
L The development of catalytic combustion purification equipment is not very mature;
L Electrostatic purification efficiency equipment has shown its advantages with its high purification efficiency, low voltage drop, stable operation, convenient maintenance and management, and its market share is close to 90%.
5. Activated carbon adsorption method
Granular activated carbon or activated carbon fiber felt is used to adsorb pollutant particles in lampblack. The characteristics of this equipment are similar to those of filtration and purification equipment, but the effect of removing oil smoke odor molecules is better.
Disadvantages: The cost of activated carbon is high.
6. Electrostatic treatment
Under the action of the applied high voltage, electrons released from the metal wire surface of the negative electrode or nearby quickly move towards the positive electrode, collide with the gas molecules and ionize. When the lampblack waste gas passes through this high voltage electric field, the lampblack particles will be charged due to the collision and capture of gas ions in a very short time, and will move towards the positive dust collecting plate under the action of the electric field force, so as to achieve the separation effect. The equipment has the advantages of less investment, small land occupation, no secondary pollution and low operation cost. Because it is easy to capture dust with small particle size, the purification efficiency is high, up to 85~95%. Its purification mechanism is different from the gas method in that the separation force is electrostatic force, which directly acts on particles rather than on air flow, so it has the characteristics of low energy consumption and small resistance.