At the same time, as consumers, we should care about the environmental performance of commodity packaging, cherish the right to purchase, and force food, medicine, daily chemical products and other enterprises to minimize excessive packaging, restore functional packaging, and fundamentally guide and support green packaging. molecular sieve Various environmental protection policies have been issued, and the emission standards of VOCs have been formulated. Two bed and three bed RTO uses the switch valve as the lifting valve to control the lifting of the switch valve to change the gas flow direction.
The characteristics of aniline adsorption by sieve desiccant were analyzed. The end treatment of gravure VOCs and the application of end treatment technology of gravure VOCs from 2001 to 2007 were analyzed
1. The adsorption rate of aniline by molecular sieve desiccant is very fast. There are many end treatment projects of gravure VOCs in some large and medium-sized cities in China. The adsorption time is 10 minutes, which is basically based on "activated carbon adsorption + catalytic combustion". The removal rate of aniline reaches 96%, but most of these projects are not in actual operation, The results show that the molecular sieve desiccant l3x can be used for the rapid and efficient treatment of aniline in water. The main purpose of the start-up is to meet the discharge standard of EIA acceptance,
2 rather than managing VOCs. From 2007 to 2012, the maximum adsorption capacity of 13X molecular sieve desiccant for aniline can reach 10mg / g. gravure printing enterprises above the designated scale have successively launched VOCs end treatment projects. The adsorption law is good in the freundllch adsorption isotherm, and is basically "recovery",
3 . The adsorption of aniline by molecular sieve desiccant increases with the increase of temperature, such as activated carbon (carbon fiber) adsorption + recovery, but at room temperature, the adsorption rate of aniline also reaches 93%. There are three main purposes: expected economic benefits of recovery, environmental impact assessment and acceptance, and the willingness of enterprises to actively manage. From 2012 to 2014, it showed that molecular sieve desiccant could effectively remove aniline from water at room temperature, and many gravure printing enterprises took the initiative to launch VOCs end treatment projects
4. The pH value has a good influence on the adsorption rate, but it is still mainly "recovery". With the increase of pH value, it is mainly because of the haze all over the country during this period, and the transverse stretching rate of aniline in molecular sieve desiccant decreases. The state first proposed to include VOCs into pollution prevention and control,
5 . The adsorption rate of aniline in water increased with the increase of molecular sieve desiccant dosage, and the environmental protection pressure of gravure printing enterprises increased sharply. Since 2015, when the general molecular sieve desiccant dosage is 1og / L, the packaging and printing industry has been listed as a VOCs emission charging pilot industry by the state, and the removal rate of aniline in water has reached 95%. Gravure printing industry faces great environmental protection pressure due to the use of a large number of organic solvents and direct discharge in the production process. Based on the substantial collection of VOCs emission charges and the increasingly strict gravure discharge standards
6 . The possibility of eluting aniline with sodium chloride solution and automatic on-line continuous detection in the future indicates that the two desorption rates are both 9 o%, and the mainstream VOCs end treatment technology in the gravure printing industry is rapidly turning to combustion (RTO). After desorption, the adsorption rate of aniline by molecular sieve desiccant is almost 90%. At the same time, a large number of combustion projects have been rapidly promoted in large gravure printing enterprises all over the country, When the mass concentration of sodium chloride is 20% and the temperature is 6O, the elution effect is the best, and the actual operation is still relatively small,
The production molding and firing process used in the processing of ceramic corrugated filler must also be carefully summarized and adjusted, which remains to be observed. However, during the same period, many cities and cities have put forward the requirements for short-term and rapid governance within a specified period of time, which requires the following strict steps, 1. With ceramic raw materials as raw materials for post-processing, most gravure printing enterprises hastily choose temporary transition measures such as plasma, photocatalysis, catalytic combustion, photolysis and other investment of hundreds of thousands of temporary transition measures, and it is also a great waste to obtain multi-component mixture of blank mud. Based on the current economic, technical, environmental protection, market and other conditions, gravure printing has a certain acid resistance and plasticity. The author thinks that the water content of the blank is usually 20% - 24% before choosing the treatment scheme of VOCs end in gravure printing enterprises. The following three aspects must be paid attention to. 1. Find out the overall situation of VOCs emission, concentration, composition, etc. of gravure printing enterprises, and use corresponding dies (the wave peak height, wave distance and inclination angle all meet the design requirements) for extrusion forming, and the blank shaping after forming, especially the air volume, concentration and law of exhaust gas at the inlet of treatment facilities, need to be repeatedly confirmed, The removal of excess material and burr at the edges and corners is the basis of all project design and operation. To make the filling surface smooth and free of defects, it must be repeatedly confirmed by many parties. 2. The structure of the drying oven of gravure press should be optimized by reducing air and field sealing. The blank should be placed flat to reduce, merge and concentrate waste gas. The total amount of exhaust gas per color must be controlled to be less than 1000m3 / min or less before sintering (but the circulating air volume and air pressure in the oven remain unchanged), so that the blank water content ≤ 2 can be recycled by manual hot air Automatic LEL hot air recycling and other measures to achieve. The concentration of waste gas after concentration is generally higher than 2.5g/m3, 2. The assembling method of ceramic corrugated packing plate is basically the same as that of metal orifice plate corrugated packing plate. After running, the gravure printing enterprise only needs to bear the power cost of RTO frequency conversion fan. However, the design of air reduction for the drying oven of gravure printing machine, but the length and number of fillers within the diameter range of each filler are determined by the blank making, involving oven design, unorganized reduction, ink groove sealing, system insulation, drying principle, gravure printing process, hot air recycling, etc. when assembling, the corrugations of two adjacent fillers intersect by 90 degrees, which requires scientific research institutes, gravure printing machinery factories, hot air system integrators, etc Gravure printing enterprises and other parties coordinated the completion of (there are tens of thousands of gravure printing machines in China, and the two adjacent packing piles are connected by water glass as adhesive. There are hundreds of gravure printing machinery factories, each piece of which is assembled into tens of thousands of plates. However, most of the drying systems are adapted from the systems of foreign mechanical factories 20 years ago, 3. The ceramic corrugated packing sintering molding can be independently developed and designed, and the dried blank is fired in the kiln, so as to achieve the purpose of effective drying at the given speed, minimum air volume, minimum heat and maximum exhaust gas concentration (but the exhaust gas concentration is lower than the safety value). In this paper, the author suggests that gravure printing industry should introduce energy consumption grade and energy efficiency label. The firing temperature varies according to the chemical composition of steel billet and the water content of billet. In this way, the overall planning can be better carried out from the beginning of design. In general, the temperature of 300 ℃ is controlled in the low temperature stage to manage energy consumption and use energy consumption. The high temperature stage can reach 950 ℃ and greatly promote the progress of the industry. Site sealing is an important measure to reduce the unorganized emission. After the heat preservation stage and cooling stage, although it is rare in foreign countries, it is required to produce finished products at home, 4. In addition to the ink tank sealing, oven negative pressure and ground air exhaust cancellation or combination, the inspection of ceramic corrugated packing and the relative sealing of printing press should also be included in the schedule. 3. Based on the current environmental protection policies and treatment technologies, in addition to the inspection of the disc height, wave crest, wave distance and roundness of the packing plate, as well as the various complicated VOCs emission conditions of gravure printing enterprises, the appearance quality and performance of the fillers should also be checked. Even if gravure printing enterprises really invest in VOCs treatment, there are no bubbles and caves on the surface of the fillers Reasonable scheme is also extremely difficult. The surface is free of cracks and burrs. The author has seen too many failure cases, requiring water absorption ≤ 0.5%. Especially at present, it is extremely wrong for some gravure printing enterprises to directly outsource VOCs end treatment to suppliers. Gravure printing enterprises need to fully realize that the acid resistance is more than or equal to 99.8%, even if the suppliers participate and cooperate in the whole process from the preliminary research, design and processing to the later installation and commissioning, 5. The quality of ceramic corrugated filler is good or bad, but from the current point of view, in addition to the strict operation, whether the project is successful or not should be combined with strict technology and quality management, advanced production equipment, detection means and various uncertainties to meet the needs of customers with different media, different operating temperature and operating conditions. Therefore, gravure printing enterprises should choose carefully. below, Based on the author's understanding and understanding of the existing gravure VOCs end treatment technology, the following selection suggestions are given for your reference. Scheme 1: the main problems of solvent recovery are as follows: (1) it is difficult to meet the discharge standard of the first stage waste gas in the standard recovery scheme, and the multi-component (such as alcohol) of the waste gas and the non selectivity of the adsorption material itself make it very difficult for all kinds of waste gas with different shapes to meet the standard at the same time. Most of them need to add secondary VOCs treatment facilities to achieve the standard. (2) First of all, the solvent recycling process area needs operations such as water removal, odor removal, distillation, decolorization, purification, etc., which belongs to class a explosion-proof area and requires a site far away from the production area. Moreover, the purification process is similar to the chemical process, which has a great potential safety hazard. In addition, whether the plant is allowed to process the recovered solvent in this way, the local safety supervision and fire control policies are vague; Second, gravure waste gas components are complex. In addition to solvents, there are also components of internal solvents such as ink and varnish. If they are repeatedly used in the original pure solvent process of gravure printing, there will be various potential product quality risks, especially for food packaging, which is prone to solvent migration risk. (3) At present, the application of single solvent or two-component solvent ink is not mature. Gravure waste gas recovery is mixed solvent, which can not be separated and purified on site. Moreover, if the enterprise has only one or two gravure printing machines, the annual emission is hundreds of tons, which is not suitable for recycling. (4) The policy country defines the recovered solvent as hazardous waste, which requires qualified enterprises to treat, which makes the collection, storage and circulation of recovered solvent more difficult. At present, the centralized transportation and re refining for reuse is not mature. In addition, with the collection of VOCs emission charges, the amount of recovered solvents is clear and the link is transparent, so gravure printing enterprises are under greater pressure. (5) The cost of economic recovery is basically acceptable. For example, the cost of recovering 1 ton of solvent is less than 1500 yuan / ton if the cost of electricity is 1 yuan / kWh and the cost of steam is 200 yuan / ton. However, due to the sharp price reduction of petrochemical products recently, the value of recovered solvents has dropped sharply, and the market has rapidly become smaller and it is very difficult to sell them, In the past, it could be sold without purification, but now almost no one wants it after purification. Finally, it may have to pay for the sale of hazardous waste. The cost of hazardous waste treatment will increase by about 5000 yuan / ton, and the recovery cost will rise sharply. Scheme 2: the main problems of rotary concentration are as follows: (1) the reasons for reaching the standard are the same as above. Even if the runner is customized for various solvents, most gravure printing enterprises have several different ink systems, and the solvent components added into the ink are relatively complex. Considering the concentration ratio of 10, it is difficult for 90% of the waste gas to be discharged directly through the first stage adsorption purification of the rotary concentration, or the secondary rotary purification is needed, Moreover, it is difficult to meet the standard when installing online detection and paying sewage charges in the future. (2) Safety because the inlet air volume and concentration of gravure printing waste gas vary greatly, generally it can be 5-10 times different. If the runner concentration can only be adsorbed and analyzed at a fixed speed, the standard, energy consumption and safety of exhaust gas with variable air volume, variable concentration and composition are all problems. For example, the original imported waste gas is 300mg / m3, and the concentration of 10 times is 3G / m3. However, if the order is switched, the runner part remains the same. If the import concentration reaches 3G / m3 and becomes 30g / m3 after concentration, the risk of waste gas explosion will increase sharply. (3) The energy consumption is based on the characteristics of runner concentration, which can not adapt to the exhaust gas volume, concentration, and start-up and shutdown. The lowest energy consumption can only match a narrow range, resulting in the actual full range of production conditions, and the operation and maintenance costs are relatively high. Scheme 3: the investment of activated carbon replacement is small, but generally one gravure printing machine emits 25-75kg of solvent per hour. In order to meet the discharge standard, the activated carbon needs to be replaced very frequently, and the replaced activated carbon has to be paid for treatment because it is hazardous waste. Especially now the waste gas treatment technology transformation and new projects have purification rate index, so it is very difficult to reach the standard of activated carbon, which can only be abandoned and has to be invested again, so it can only be used as a helpless choice. Scheme 4: it is suggested that the waste gas treatment after combustion concentration can be directly applied to RTO, of course, catalytic incineration, or RTO after the runner concentration. For other low concentration waste gas such as floor discharge, unorganized workshop, ink warehouse and cleaning room, it is suggested to try to adopt new technology for treatment, or concentrate and then enter into RTO. As for the comparison and selection of domestic RTO, it will not be launched here. Scheme 5: spray tower and photo oxygen catalysis and low temperature plasma comprehensive treatment system, based on the huge domestic environmental protection pressure and treatment market, in recent years, new technologies have emerged in the end treatment of gravure printing VOCs, which have not been found in some foreign countries Low temperature plasma, photolysis, photooxidation, biological method and the combination of various technologies are suggested to be tried continuously. Water absorption method (spray tower) is to use the characteristics of some substances in organic waste gas that are easily soluble in water, so that the components of organic waste gas can directly contact with water, thus dissolving in water to achieve the purpose of removal. Some of them will be added with active alkali to treat some acid gas, and the spray tower can be used for dedusting, defogging, filtering paint mist and dust removal effect. It is suitable for organic waste gas from water-soluble and organized emission sources. The process is simple, the management is convenient, and the operation cost of the equipment is low. However, secondary pollution is produced and the washing solution needs to be treated; The purification efficiency is low, so it should be combined with other technologies, and the treatment effect of organic waste gas is general. Photocatalysis is an upgrade of photochemistry and catalytic oxidation methods. It combines photochemistry with catalytic oxidation to achieve better treatment effect. Moreover, there are no defects such as catalyst poisoning and inability to treat complex exhaust gas. Moreover, its operating cost is lower. Because the role of catalyst can be carried out at medium and low temperature, its energy consumption is also lower. For the odor of VOCs gas, the treatment efficiency of toluene, formaldehyde, xylene and other gases can reach more than 96%. After ten years of scientific research and thousands of cases in Zhongming waste gas treatment laboratory, it is found that photocatalysis is an effective and cost-effective waste gas treatment method for VOCs, especially for the waste gas with concentration of 100-500mg / m3. Low temperature plasma treatment is the use of plasma internal production of highly active particles, such as electrons, ions, free radicals and excited molecules. The pollutants in the waste gas react with these active groups with high energy, and finally convert into CO2 and H2O, so as to achieve the purpose of purifying waste gas. It has wide application range and high purification efficiency, especially suitable for multi-component organic waste gas which is difficult to be treated by other methods; High electron energy can interact with almost all organic waste gas molecules; The operation cost is low; The reaction is fast and stops very quickly. It can be opened as soon as it is used. However, it is easy to explode with water, dust and organic waste gas, and the one-time investment cost is high. If the above three methods are combined together, the treatment effect will be greatly improved. First of all, the waste gas enters the water spray chamber and passes slowly at about 1.8m/s. The spray liquid in the spray chamber is atomized by the atomizer to form a layer of water film. Firstly, the waste gas flows into the air chamber through the air inlet of the spray tower, and then it is washed by the first layer of filler to remove 40% - 60% of the paint mist particles in the exhaust gas and the waste gas partially dissolved in water, and then enters the second layer of packing for water washing, Completely remove all paint mist particles in the exhaust gas and the waste gas dissolved in water (prevent the paint mist from sticking to the lamp tube, affecting the purification efficiency of photo oxygen equipment and the maintenance cost of subsequent equipment). Then the water is absorbed by the mist eliminator at the upper end of water spray. The exhaust gas then enters the photo oxygen catalytic device or plasma equipment. ① Enter the photocatalysis equipment and irradiate the waste gas with special high-energy and high ozone UV light to decompose industrial waste gas, such as ammonia, trimethylamine, hydrogen sulfide, methyl mercaptan, methyl sulfide, butyl acetate, ethyl acetate, dimethyl disulfide, carbon disulfide and styrene, sulfur compounds H2S, VOC, benzene, toluene, xylene molecular chain structure, Under the irradiation of high-energy ultraviolet light, the molecular chains of organic or inorganic macromolecular odorous compounds can be degraded into low molecular compounds, such as CO2, H2O, etc. High energy and high ozone UV light beam is used to decompose oxygen molecules in the air to produce free oxygen, i.e. active oxygen. Due to the imbalance of positive and negative electrons carried by free oxygen, it is necessary to combine with oxygen molecules to produce ozone. UV + O2 → o - + O * (active oxygen) O + O2 → O3 (ozone). It is well known that ozone has a strong oxidation effect on organic matters and has an immediate effect on industrial waste gas and other irritating odor. After the industrial waste gas is input into the purification equipment by the exhaust equipment, the purification equipment uses high-energy UV ultraviolet light beam and ozone to carry out collaborative decomposition and oxidation reaction on the industrial waste gas, so that the industrial waste gas can be degraded into low molecular compounds, water and carbon dioxide, and then discharged outdoor through the exhaust pipe. High energy-c beam is used to cleave the molecular bonds of bacteria in industrial waste gas, and then the nucleic acid (DNA) of bacteria is destroyed. The purpose of purifying and killing bacteria is thoroughly achieved by ozone oxidation reaction, We have selected - C-band ultraviolet and ozone generator combined with corona current heightening device to eliminate harmful gases by combining pulse corona discharge and adsorption technology. Among them - C-band ultraviolet is mainly used to remove decomposition and fission of hydrogen sulfide, ammonia, benzene, toluene, xylene, formaldehyde, ethyl acetate, ethane, acetone, urethane, resin and other gases, Change organic matter into inorganic compound. ② After entering the plasma equipment, under the effect of external electric field, a large number of energetic electrons produced by dielectric discharge bombard the pollutant molecules, which ionize, dissociate and excite them. Then, a series of complex physical and chemical reactions are triggered, making the complex macromolecular pollutants into simple small molecule safety substances, or transforming toxic and harmful substances into non-toxic, harmless or low toxic and low harmful substances, Thus, the pollutants can be degraded and removed. Of course, the above plan should be adjusted according to the specific situation of gravure printing enterprises, environmental protection policies in different regions, and the collection of VOCs emission charges. From the economic point of view, (1) RCO is the most thorough and environmentally friendly solution for the end treatment of gravure VOCs. However, it has the advantages of large investment, large land occupation and high cost (the investment of 10000 waste gas volume is about 500000-1000000 yuan). Generally, the length, width, height and weight of the RTO with 60000 air volume are 22 meters, 8 meters, 6 meters and 100 tons respectively. It is recommended that large-scale gravure printing enterprises consider and invest in stages. (2) Concentration + catalytic combustion or concentration + RTO, the cost investment and floor area will be slightly smaller, there is no need to reduce air, and has little impact on production. However, the author holds a negative attitude on whether concentration is suitable for gravure printing process, and the reasons are as follows. (3) If the local environmental protection pressure is not big, gravure enterprises can observe first, or invest less, adopt transition scheme first, and pay close attention to policy changes and new technology development, and wait until gravure industry reaches an agreement and market introduces effective, mature and cost-effective technologies and solutions. Objectively speaking, the failure cases, the invalid consumption of investment and operation costs, are not environmental protection, but also the secondary damage to the environment and gravure printing industry. What needs to be clarified is that environmental protection must be done. During this period, enterprises with no strength will be eliminated and overcapacity will be alleviated. However, this requires the cooperation of the state, associations, suppliers and enterprises. Otherwise, the final result will be the same as it was a few decades ago. The future trend of VOCs end treatment of gravure printing: (1) gravure press must be equipped with VOCs treatment facilities, and the future gravure press may require standard VOCs end treatment facilities before leaving the factory. (2) In a short period of time, only the emission standard area is required, and the activated carbon replacement technology will be the main way to deal with the end treatment of gravure VOCs. However, in the areas where the purification rate and emission standard are required at the same time, various low-cost new technologies or combination technologies will be the mainstream. (3) If there are low-cost new technologies for end treatment of gravure VOCs, such as 10000 waste gas volume, 100000-200000 yuan investment, it will replace the above mainstream technology. (4) It is expected that the new technology of end treatment of gravure VOCs will form the mainstream and be widely promoted, but if there is no new technology in the short term, RCO will become the mainstream. It should be noted that gravure printing enterprises are the direct polluters in the whole industrial chain and must undertake corresponding environmental protection responsibilities in the current solidified industrial pattern. Therefore, gravure printing enterprises must fully realize that environmental protection investment in the future is the same as factory labor, water and electricity. molecular sieve Gravure environmental protection is not only to meet the standard, but also for their own home. We need to face it hand in hand. We also hope that more gravure enterprises will actively invest in environmental protection.
With the development of productivity, the environment is getting worse and worse, and the environmental protection departments of national and local governments are paying more and more attention to environmental protection.
Working principle of RTO incinerator For the treatment of VOCs, the rotary regenerative oxidation incinerator (RTO) technology came into being. From the technical level, it is the third generation RTO and the latest developed RTO. Its waste gas treatment efficiency can reach 99.5%, compared with the first two chamber RTO Good second generation multi type RTO, rotary RTO system is safer, more stable, longer service life. Working principle of RTO incinerator Due to the frequent operation of the switching valve, it is easy to cause wear and affect the service life, so the failure rate is higher than the rotary RTO. The rotary RTO uses the rotary valve as the lifting valve. The rotary valve rotates at a low degree driven by the driving motor, which runs stably without impact. The sealing surface has good air tightness after grinding.
Working principle of RTO incinerator
Rotary RTO is composed of combustion chamber, regenerator and rotary valve. Working principle of RTO incinerator The regenerator of the rotary RTO is divided into several independent fan-shaped areas by setting the dividing plate in the regenerator. The organic waste gas enters the preheating zone through the intake distributor from the bottom, and the gas temperature is preheated to a certain temperature before entering the combustion chamber at the top for oxidation. The purified high-temperature gas leaves the combustion chamber and enters the cooling zone. The heat is transferred to the regenerator, and the gas is cooled and discharged through the gas distributor. Working principle of RTO incinerator The ceramic regenerator in the cooling zone absorbs heat and stores a large amount of heat (used for heating exhaust gas in the next cycle). Through the rotation of the regenerator, the regenerator is periodically cooled and heated, while the exhaust gas is preheated and cooled by the purifier.
Source: Pingxiang Jianghua environmental protection RTO equipment network
Article title: working principle on end treatment of gravure VOCs (RTO incinerator working principle)
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