Views: 4 Author: China xicheng Publish Time: 2021-04-16 Origin: China xicheng
The printing industry should pay attention to emission reduction at the source.
Green printing companies should start from the source, and all raw and auxiliary materials are green and environmentally friendly. Use environmentally friendly paper to meet international environmental protection requirements and sustainable forest planting areas, such as FSC deoxygenated, deacidified, and dignified paper. Use inks containing less than 3.6% VOCs, soy environmentally friendly inks: Soy inks are made by lightly purifying soybean oil and mixing them with additives such as pigments and resins. The content of VOCs is low. Use pre-coated film or water-based film glue and water-based varnish: easy to recycle, no pollution, low VOCs emission. Use fountain solution with VOCs content of less than 17.0% and alcohol-free fountain solution: improve safety factor and reduce VOCs emission. Use environmentally friendly detergents and car wash water: reduce VOCs emissions. Use plant-based dusting, etc. In addition, in the process of use, minimize the use of car wash water, wipe cloth, etc., to minimize VOCs emissions.
VOCs waste gas treatment solution for the printing industry
There are many types of organic waste gas treatment methods in the process of VOCs treatment, with different characteristics. The catalytic combustion method, an adsorption method, photo-oxygen catalysis method, direct incineration method, and catalyst incineration method are commonly used. Therefore, it is necessary to comprehensively consider the types of organic waste gas, the removal efficiency, the equipment investment situation, and the manufacturer's economic crisis. The characteristics of offset printing waste gas are large air volume and low concentration, and it is more challenging to choose a VOCs treatment method.
Green printing companies can adopt a program: purification filtration-activated carbon adsorption-desorption-catalytic combustion process, as follows.
(1) Purification and filtration
The fan uses the exhaust gas containing organic matter to pass through the pretreatment fine filter box to remove the exhaust gas's particulate matter. The filter box is a high-efficiency filter cartridge dust collector, which can automatically clean the dust without replacing the filter material, and the average service life is more than two years. The filter cartridge uses imported polyester fiber as the filter material, and a layer of sub-micron ultra-thin fibers has adhered to the general filter material. The arrangement of the fibers on the adhesion layer is very close. Part of the sub-micron dust particles are blocked on the filter material's surface, and the effective filter area is 100%. The dust removal adopts the pulse jet online dust removal method. The pulse controller automatically controls the dust removal process. There are multiple filter cartridges in the dust collector to increase its effective filtration area. When a certain (air) filter cartridge meets the dust removal setting When required, the spray device is started to clean the dust, and the other filter cartridges typically work so that the dust removal effect is achieved without affecting the operation of the equipment so that the dust collector can operate continuously.
(2) Activated carbon adsorption
Use a high-power centrifugal fan to introduce the printing waste gas into the activated carbon adsorption device. The waste gas passes through the activated carbon adsorption layer. The organic matter is trapped inside the activated carbon by the activated carbon's striking force, and the clean gas is discharged. The VOCs in it are adsorbed and purified by activated carbon and then removed from the outlet.
The low-volume, high-temperature gas enters the desorption box to desorb and regenerate the activated carbon adsorbing VOCs; the high-concentration VOCs gas is discharged from the outlet of the regeneration zone and enters the catalytic combustion device for processing. The regenerated activated carbon continues to be adsorbed after cooling for some time, and the second adsorption tank is automatically switched to desorption. The entire system can continuously cycle the exhaust gas purification and concentration regeneration process.
After some time, when the activated carbon reaches a saturated state, the adsorption stops. At this time, the organic matter has been concentrated in the activated carbon. The catalytic purification device is equipped with a heating chamber, starts the heating device, and enters the internal circulation. When the hot gas source reaches the boiling point of the organic matter, the organic matter escapes from the activated carbon. It enters the catalytic chamber to catalyze and decompose into CO2 and H2O while releasing energy. When the released energy is re-entered into the adsorption bed for desorption, the heating device completely stops working at this time; the organic waste gas maintains spontaneous combustion in the catalytic combustion chamber. The exhaust gas is regenerated, and the cycle continues until the organic matter is completely separated from the activated carbon and decomposed in the catalytic section. The activated carbon has been restored, and the organic matter has been catalytically decomposed.
(4) Catalytic combustion
The desorbed organic gas is sent to the catalytic combustion purification device through the action of the induced draft fan, firstly through the dust removal flame arrester system, then into the heat exchanger, and then into the heating chamber, through the heating device, the gas reaches the combustion reaction temperature, and then passes through the catalytic bed The role of the organic gas is to decompose the organic gas into CO2 and H2O, and then enter the heat exchanger to exchange heat with the low-temperature gas so that the temperature of the incoming gas rises to the reaction temperature. If the reaction temperature is not reached, the heating system can realize compensation heating through the automatic control system to completely burn. This saves energy, and the effective removal rate of exhaust gas can reach more than 98%, which meets the national VOCs emission standard.
Points to note in the treatment of waste gas in the printing industry
①Considering factors such as production technology, operation methods, waste gas properties, treatment methods, etc., classify and collect VOCs unorganized emission waste gas.
②The exhaust hood of the exhaust gas collection system should be set up in accordance with GB/T16758-2008 "Classification and Technical Conditions of Exhaust Hood." At the unorganized discharge position of VOCs farthest from the opening surface of the exhaust hood, the outer cover measures the suction wind speed according to the method specified in GB/T16758.
③The exhaust gas collection system should maintain a negative pressure (absolute pressure is 5kPa lower than the ambient atmospheric pressure).
④VOCs terminal treatment facilities select appropriate treatment technologies according to their respective conditions. The treatment technology with high treatment efficiency (incineration, oxidation) is preferred. In this way, it can cope with all changes; no matter how the policy changes, it can meet the general environment's requirements.