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Shallow theory of waste incineration flue gas treatment tech

Below are for dust, acid gases, heavy metal pollutants and dioxin-like substances such as different kinds of pollutants for processing technology and equipment.
1, dust pollution treatment technology
Control dust pollution substance universal equipment mainly include: water film dust catcher, electrostatic precipitator, bag filter, etc. Because of the water film dust catcher dedusting efficiency is not stable, and the dust removal in the process of sewage is created that needs to be processed, so it has to be eliminated. Research has shown that using electrostatic precipitator removal ability of dioxin-like substances is poorer, and easy to cause the dioxin material synthesis, so GB18485-2001 standard, dust removal device must use bag filter.
Bag filter performance is the key to the selection of the filter cloth material. And industrial waste incineration flue gas incinerator flue gas produced, compared with high temperature and high moisture and show the characteristics of weak acid, and dust because contain CaO, CaCl2, CaSO3 easily occur in the composition such as "deliquescence" and stick to the surface of the filter bag is not easy to remove, so must consider these factors in the choice to filter cloth. In recent years, the filter cloth material development and processing technology is developing very rapidly, suitable for the waste incineration flue gas filter material models include: Ryton (PPS), P84 (polyimide) and teflon (ptfe), etc. Teflon has the best comprehensive performance, but the price is higher; Ryton heat-resistant limit is 200 ℃, poor oxidation resistance; P84 and heat-resistant limit as high as 260 ℃, alkali resistance is a bit poor. At present, the ratio of good Ryton and P84 which has been widely applied two kinds of filter cloth. In addition, the coating is used for the filter cloth can be coated processing, strengthen the hydrophobic, filter cloth bag dust.
Because the bag filter dust collected after cooling is easy to stick in the ash hopper wall affect ash, so need to laying thermal insulation layer outside the bag filter surface, if necessary also is needed in the ash hopper set heating device. Ash mouth to avoid congestion and air leakage, often adopted rigid impeller type or rotating disc ash device.
2, acidic gas treatment technology
Acid gas removal techniques can be divided into: wet, dry and semi-dry method three categories. Acidic gas of nitrogen oxides are difficult to remove by conventional methods, but can be by adjusting the incinerator combustion temperature, to control its emissions in GB18485-2001 standard limit (400 mg/Nm3).
(1) the wet acid gas removal techniques
Liquid or slurry sorbent in the wet state reaction with acid gases and remove reaction products, has quick response speed, simple equipment, high removal efficiency, but universal existence serious equipment corrosion, reaction of sewage is easy to cause the secondary pollution and traffic problems higher maintenance costs. The typical technology are: lime slurry washing method, magnesium oxide method, double alkaline, seawater desulfurization method, etc.
(2) dry acid gas removal techniques
Reaction with acid gases and removal of reaction products are conducted in the dry state, a short process, little sewage discharge, and the advantages of small equipment corrosion, but some problems such as large removal efficiency is low, the equipment. The typical technology are: copper oxide fluidized bed type reaction method, SNRB flue gas purification method, electron beam radiation method (EBA), etc.
(3) half dry acid gas removal techniques
Combined with some advantages of wet method and dry method respectively, absorbent in the wet state reaction with acid gases, in the dry state treatment reaction products, high removal efficiency and does not produce waste water. The typical technology are: spray drying method, Cool - Side and GSA method, etc. The spray drying method is relatively mature, reliable, can be applied in waste incineration flue gas treatment. The method is to use efficient atomizer spray the lime into the reaction tower, lime slurry droplet diameter can be atomized below 100 microns, the flue gas with lime a good contact in the form of cocurrent flow or reverse flow and generate a neutralization reaction. Using synthetic flow, the retention period of flue gas in the reaction tower should be in about 20 seconds, and using the reverse flow, the appropriate time for 10 seconds.
Spray drying system is the key equipment atomizer, now more than using rotary atomizer nozzle and dual fluid. Rotary atomizing nozzle atomization effect is good, but because of the high speed rotating parts, so the structure is complex, easy to jam and wear and tear, equipment price and maintenance cost is higher. Although two-fluid nozzle atomizing effect is rotating spray nozzle is a bit poor, but the structure is simple, not easy jam, service life is longer, has been widely used at present. In engineering design, should according to the actual situation to choose suitable atomizer.
Atomization nozzle spray shape should be paid attention to in the design and supply the structure size of the match, and in control when operating the addition of lime quantity, to reduce the reaction tower wall by solid reaction product adhesion and accumulation, can consider to the coating on the inner wall of the tower installation in order to prevent the tower body corrosion and wear. Settlement of reaction product at the bottom of the tower prone to harden and affecting ash effect, so should be given attention to in design ash device, and set the manhole in the appropriate space.
Behind the half dry reaction tower decorated with bag filter, the flue gas from the reaction tower out of a fine fly ash contains unreacted desulfurizer, 0.2 microns CaO fine particles can be captured on the filter bag to continue with the reaction of residual acid gas in flue gas, can improve the efficiency of desulfurization by more than 10%.
3, the processing of dioxin-like substances
Reasonable sorting before garbage into the furnace, as far as possible to remove high chlorine substances such as chlorine phenol, chlorobenzene, PVC, etc., can reduce the generation of dioxin-like substances in the furnace. In order to effectively inhibiting the production of dioxin-like substances, should strictly control the burning temperature in stoker, ensure the flue gas in 850 ℃ high temperature state for more than 2 seconds, improving the burning process of dioxin-like substances decomposition rate; In 200 ~ 400 ℃ temperature range and reducing the flue gas residence time, avoid secondary synthesis of dioxins.
In front of the bag filter Settings on the flue of activated carbon injection device has been proved to be an effective dioxin removal techniques. Powdered activated carbon is loaded in the bin, the inverter output, screw conveyor under the action of compressed air injection flue in front of the bag filter, by activated carbon in the bag filter in the flue of dioxin-like substances on the surface of the filter bag and the adsorption of heavy metal pollutants, can further reduce the emissions of pollutants.
Due to the adsorption properties of activated carbon with high, so the consumption is low, the estimated day processing 100 tons of incinerator of the activated carbon consumption of about 1.5 kg/h. After adopting these measures, can satisfy GB18485-2001 standard of dioxin-like substances emissions targets (1.0 or less ngTEQ/Nm3) requirements.
4, the processing of heavy metal pollutants
According to the form of the heavy metal pollutants, the removal methods of heavy metal pollutants are:
(1) the heavy metal pollutants condenses into solid after fly ash collected by dust removal;
(2) the gaseous pollutants of heavy metals adsorbed on the surface of the fly ash and activated carbon powder for injection and collection dust removal;
(3), water soluble heavy metal pollutants dissolved in spray tower spray water removed by absorption.
Relevant research and engineering practice show that the bag filter and dry reaction tower in conjunction or half dry reaction tower, in addition to mercury, removal efficiency of heavy metals are very good. And activated carbon for mercury has strong adsorption, can effectively reduce the emissions of mercury concentration, activated carbon injection device can also be so effective removal of heavy metal pollutants.
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