Application of waste gas treatment equipment in injection molding process (environmental protection RTO equipment)
The recovery type thermal incineration system (referred to as tnv) is a kind of waste gas containing organic solvent which is directly burned by gas or oil. Under the action of high temperature, the organic solvent molecules are oxidized and decomposed into CO2 and water. The high temperature flue gas generated is heated by the matching multi-stage heat exchanger to heat the air or hot water needed in the production process,The heat energy generated by the oxidation and decomposition of organic waste gas is fully recovered and utilized to reduce the energy consumption of the whole system.molecular sieveThe tnv system consists of three parts: waste gas preheating and incineration system, circulating air heating system and fresh air heat exchange system. The characteristics of waste gas incineration central heating device include: the residence time of organic waste gas in the combustion chamber is 1 ~ 2 s;The decomposition rate of organic waste gas is more than 99%;The heat recovery rate can reach 76%;The adjustment ratio of burner output can reach 26 ∶ 1 and the highest is 40 ∶ 1.VOC waste gas treatment technology condensation recovery method at different temperatures, the saturation of organic matter is different, condensation recovery method is to use the characteristics of organic matter to play a role, by reducing or increasing the system pressure, the organic matter in the steam environment is extracted by condensation. 1 .Characteristic injection molding process is a method of making plastic products.The whole process of injection molding is as follows: the plastic particles are added into a cylinder through the feeding hopper, and gradually heated to a certain temperature and maintained for a certain time. The alumina catalyst carrier series products are composed of aluminum hydrate glue and uniformly (plasticized) under a certain stirring strength (rotational speed) → pushed into the mold at a certain pressure (thrust) and speed (injection molding) → under the action of pressure (holding pressure),When the plastic reaches a certain temperature, it has stable specific surface area, good pressure resistance, low wear, suitable pore structure, low impurity contentOpen the mold (open mold) at a certain speed → eject the finished product out of the mold at a certain speed and force → inspect the finished productRepair the flash (excess material formed on the joint surface of the mold) material handle (the material on the injection channel of plastic, and the product is spherical or cylindrical particles, which can also supplement the volume reduced when the finished product is cooled and contracted) → packaging → warehousing.At the same time, the injection molding machine is added with release agent, which has strong adsorption function and closes the mold process.Injection molding process mainly controls the temperature, pressure, speed, time and other parameters in the process.Each type of plastic, each product and injection molding machine need different process parameters.The injection molding process should also include moisture control, additive control, colorant control and so on.Four elements of injection molding 1Plastic mold 2Injection molding machine 3Plastic raw materials 4Most of the molding conditions are two plate die and three plate die. The specific surface area is large, and there are some row die with slide block.Basic structure: ① male mold (lower mold) male mold fixed plate, male mold auxiliary plate, thimble plate, male template.② Female mold (upper mold) female template, female mold fixed plate, rubber ring, positioning ring.③ Constant temperature system coolingStabilize the mold temperature.The injection molding machine is mainly composed of plasticizing, injection device, clamping device and transmission mechanism;Electrical drive motor, high compression hardness, motor driven oil pump, long service life, oil pump oil pressure can be reused through regeneration method to drive the piston, no odor piston to drive machinery, no odorless machinery to produce action.1. According to the injection mode, it can be divided into: ① horizontal injection molding machine ② vertical injection molding machine ③ angular injection molding machine ④ polychromatic injection molding machine 2. According to the mode of mold locking, it can be divided into: ① direct compression injection molding machine ② crankshaft injection molding machine ③ direct pressing, crankshaft compound type 3According to the feeding mode, it can be divided into: ① plunger injection molding machine ② single pass screw injection molding machine ③ reciprocating screw injection molding machine. The plastic injection molding process mainly carries out granulation and extrusion. There is no non-toxic granulation. The temperature of extrusion process is generally 169-210 ℃. There is moisture absorption in the air. Different project control is different, and the water absorption will not expand, but it can not be higher than the thermal decomposition temperature of plastic raw materials.As for the composition of process waste gas in granulation process, it is more complex to keep the original state.The composition of waste gas produced by different raw materials is different.Plastics, which can adsorb NOx, F2, as and other gases, are widely used in petrochemical industry, hydrodesulfurization, low conversion and other catalyst carriers. They are polymer compounds polymerized from vinyl chloride, 2 .It is widely used in petroleum, chemical industry, textile, metallurgy and other industries. The industrial product is white or light yellow powder. The specific gravity of the product is about 1.4 g / cm3, and the chlorine content is 56% - 58% under different process conditions. The melting point of catalyst carrier with different crystal phase and pore diameter is about 70-85 ℃,The physicochemical properties of the catalyst are similar to those of imported sb powder and V250 powder. The molding temperature is 160-190 ℃, and there are small holes (reaction holes) and appropriate distribution of mesopores and macropores (diffusion pores) in the catalyst, and the decomposition temperature is > 200 ℃.In the pyrolysis process (180-200 ℃), PVC particles can also be used in catalyst carriers such as special coating gel for automobile exhaust gas purification (three effects). Free monomer waste gas is produced in the process of chain breaking, decomposition and degradation due to intermolecular shear extrusion, 3 .PVC is packaged and stored to produce vinyl chloride and hydrogen chloride monomer.ABS plastic, catalyst carrier packed in woven bags, scientific name acrylonitrile butadiene styrene copolymer, stored in a cool, ventilated and dry warehouse with a specific gravity of 1.05g/cm3,
We know that the sulfur dioxide in the flue gas is relatively serious, and the molding shrinkage rate is 0.4-0.7%. Therefore, sulfur dioxide desulfurization catalyst is required to purify flue gas sulfur dioxide. The molding temperature of sulfur dioxide desulfurization catalyst is 200 ~ 240 ℃, and the decomposition temperature of alkali solution prepared by cheap lime, limestone and lime is more than 270 ℃.In the pyrolysis process of ABS plastics (160-210 ℃), due to the chain breaking, decomposition and free monomer waste gas generated during the process of molecular shear extrusion, how to use sulfur dioxide desulfurization catalyst is mainly acrylonitrile monomer, styrene monomer and non methane total hydrocarbon.PE plastic, let's see it next time, The desulfurizer can absorb most of the sulfur dioxide in the flue gas and fix it in the fuel slag. The polymer compound is polymerized by ethylene. The specific weight of the desulfurizer is about 0.94-0.96 g / cm3 in chemical plants and smelters. Sodium carbonate and alkaline aluminum sulfate are often used as desulfurizer to treat the waste gas containing sulfur dioxide. The molding shrinkage rate is 1.5-3.6%,For desorption and recovery, the molding temperature is 140-220 ℃, and the desulfurization and denitrification adsorbent is a boiler exhaust gas purification technology applied in the chemical industry of the formation of multi nitrogen oxides and sulfur oxides, and the decomposition temperature is more than 320 ℃.The processing temperature range of PE plastics is very wide. The nitrogen oxides and sulfur oxides in the exhaust gas are one of the main sources of air pollution and are not easy to decompose. Therefore, the application of the adsorbent for desulfurization and denitrification has many advantages for environmental air purification in the pyrolysis process (160 ~ 210 ℃), because the chain breaking, decomposition and degradation of free monomer waste gas occur under the shearing extrusion between molecules,At present, there are many known flue gas desulfurization and denitrification technology materials, mainly ethylene monomer.However, due to the disadvantages of large investment in some equipment and facilities, high operation cost, poor treatment effect, large floor area or old equipment, a new type of adsorbent for desulfurization and denitrification, which is polymerized from propylene, has been developed. The appearance of the adsorbent is yellowish or yellowish white. The desulfurization and denitrification adsorbent absorbs SO2 and NOx in waste gas, and the specific gravity of solid adsorbent is 0.9-0.91 g / cm3,Under different conditions, SO2 and NOx are desorbed respectively for conversion, and the shrinkage rate is 1.0-2.5%. The commonly used adsorbents on the market include activated carbon, activated alumina, adsorbent with molecular sieve as carrier, etc. molding temperature: 160-220 ℃, SO2 exists as sulfate on these adsorbents, and the processing temperature is about 200-300 ℃,Then, high concentration SO2 is produced by reduction with reducing gas, which has good thermal stability (decomposition temperature is 310 ℃).PP plastic processing temperature range is very wide, or as a mixture of SO2 and H2S, it is not easy to decompose. Therefore, in the pyrolysis process (200-300 ℃), the adsorbent not only has the function of desulfurization and denitrification when the waste gas passes through, but also has the function of catalyst reduction, which is mainly propylene monomer.Npbt plastic, the desulfurization and denitrification adsorbent greatly improves the time life, scientific name polybutylene terephthalate, so the desulfurization and denitrification adsorbent is also known as desulfurization and denitrification catalyst, which is composed of dimethyl terephthalate and 1,2,4-benzoate,4-butanediol was prepared by transesterification.Crystalline thermoplastic polyesterTasteless, odorless and non-toxic.The glass transition temperature is 45-48 ℃, and the thermal deformation temperature is 58-66 ℃ (1.82 MPa)The results show that the flow temperature is 225 ℃, the operating temperature is 120 ℃, the relative density is 1.324 g / cm3, and the water absorption is 0.03-0.07%. The monomer decomposed in the pyrolysis process is aromatic hydrocarbon.PAS plastic, scientific name polyaryl phenol, amber transparent particles.The relative density (25 ℃ / 4 ℃) is 1.371 and the refractive index is 1.652. The heat resistance is much higher than that of bisphenol a polysulfone. The thermal deformation temperature and continuous service temperature are about 100 ℃ higher than that of bisphenol a polysulfone.The glass transition temperature is 288 ℃, the continuous service temperature is 260 ℃, the thermal deformation temperature is 274 ℃ (1.82mpa), and the decomposition temperature is more than 300 ℃.The monomers decomposed during pyrolysis are aromatic hydrocarbons.POM plastic, POM, is the general name of homopolymer and copolymer of formaldehyde, the relative density of copolyformaldehyde is 1.402-1.405.The crystallinity is 77% - 78%, lower than that of homoformaldehyde.Melting point, strength and hardness are also slightly lower.The melting point is 167-171 ℃, and the hot deformation temperature is 100-157 ℃ (1.82 MPa)Martin heat-resistant 55-58 ℃, the maximum use temperature of 100-104 ℃.It has excellent fatigue resistance, wear resistance and chemical resistance. The thermal decomposition temperature is 235-240 ℃, and formaldehyde waste gas is released during thermal decomposition process. 1) polyethylene (PE) product production: when high-pressure polyethylene is heated to 150 ℃, acid, ester, unsaturated hydrocarbon, peroxide, formaldehyde, acetaldehyde, CO2 and Co are decomposed;Attention should be paid to the toxicity of antioxidants, stabilizers and colorants;Its products have a unique smell, and phlebitis may occur after long-term application of polyethylene pipe mixed with stabilizer.Low pressure polyethylene is heated to 150 ℃ to produce volatile complex mixtures of acids, esters, unsaturated hydrocarbons, peroxide, formaldehyde, acetaldehyde, CO2 and Co.The mixed gases generated from 210 ℃ to 250 ℃ are formaldehyde, unsaturated hydrocarbon, organic acid, organic chloride, Co, etc.Formaldehyde and acrolein are produced during hot cutting and sealing polyethylene pipe.Such pyrolytic products can cause poisoning.② Polyethylene (PE): it is not non-toxic, but it is toxic when antioxidants, stabilizers and colorants are added.When heated to 150 ℃ ~ 220 ℃, the pyrolysis products include acid, ester, unsaturated hydrocarbon, peroxide, formaldehyde, acetaldehyde, CO2 and Co.It can be seen from the above that TVOC should not be non methane hydrocarbon, but TVOC should be better.In addition, the pyrolysis amount is not as large as 0.1% - 0.5%, and the material loss of nozzle material, glans material and even test material in injection molding production is only 1-2%, and the pyrolysis amount is certainly not so large.However, different plastic parts will be different. The heat release loss of injection molded parts and film products will be different, which is generally calculated according to 0.01% of the consumption of raw materials.2) The raw material of PVC injection molding process is PVC. HCl and free vinyl chloride may be released from waste gas.However, if the raw material contains POM (polyoxymethylene), formaldehyde may be released.In addition, due to the complexity of the process waste gas composition in granulation process, some places use the calculation of non methane hydrocarbons for quantitative evaluation, and some places also use the calculation of VOC (volatile organic compounds) for quantitative evaluation.Because the heating temperature during granulation is generally controlled within the allowable range of plastic raw materials, the amount of decomposed monomer is very small, and the heating is generally carried out in a closed container, only a small amount of monomer is discharged.Generally speaking, the monomer produced by thermal decomposition is only 0.01-0.02% of the total amount, calculated as 100-200 g / T product.The composition of waste gas in granulation process is complex, and the composition of waste gas produced by different raw materials is different.Polyvinyl chloride (PVC) is a kind of high molecular compound which is polymerized from vinyl chloride. It is thermoplastic and has a glass transition temperature of 80 ℃～ 85 ℃.The industrial product is white or light yellow powder with relative density of 1.4 and chlorine content of 56-58%. Low molecular weight is easily soluble in ketones, esters and chlorinated hydrocarbon solvents.It has excellent chemical resistance.Thermal stability and light resistance are poor.Hydrogen chloride begins to decompose when exposed to sunlight above 100 ℃ or for a long time.PVC will be degraded by heat during processing. Due to the release of HCl, the number of conjugated double bonds in polyene structure molecules increases. When the number reaches more than 8, the absorption of light wave begins to converge, so the color will gradually deepen (yellow → brown → Brown).According to the different release rate of HCl, the degradation temperature can be divided into four stages, as follows: (1) early coloring degradation: HCl begins to release at 100 ~ 130 ℃, but the release rate is very small. PVC gradually changes color after being exposed to this temperature for more than 10 days.(2) In the middle stage, the release rate of HCl increased gradually from 140 ℃ to 160 ℃.(3) Long term thermal degradation: 160 ~ 220 ℃(4) Complete degradation: HCl was released completely above 220 ℃.Injection molding waste gas treatment equipment introduction: VOC waste gas treatment technology - oxidation method for toxic, harmful, and does not need to recover VOC, thermal oxidation method is the most suitable treatment technology and method.The basic principle of oxidation method: VOC reacts with O2 to form CO2 and H2O.From the chemical reaction equation, the oxidation reaction is similar to the chemical combustion process, but due to the low concentration of VOC, no visible flame will be produced in the chemical reaction.Generally, oxidation process can ensure the smooth progress of oxidation reaction by two methods: a) heating.Make the organic waste gas containing VOC reach the reaction temperature;b) Use catalyst.If the temperature is lower, the oxidation reaction can be carried out on the surface of the catalyst.Therefore, the oxidation method of organic waste gas treatment can be divided into the following two methods: a) catalytic oxidation method.At present, there are two kinds of catalysts used in catalytic oxidation, namely noble metal catalyst and non noble metal catalyst.Noble metal catalysts mainly include Pt, PD and so on, which are attached to the catalyst support in the form of fine particles, while the catalyst support is usually metal or ceramic honeycomb or bulk packing;Non noble metal catalysts are mainly composed of transition metal oxides, such as MnO2, mixed with binder in a certain proportion, and then made into catalyst.In order to effectively prevent the catalyst from losing its catalytic activity after poisoning, the toxic substances such as Pb, Zn and Hg must be completely removed before treatment.If the catalyst poison and covering substance in the organic waste gas cannot be removed, the catalytic oxidation method can not be used to treat VOC;b) Thermal oxidation.At present, there are three kinds of thermal oxidation methods: thermal combustion type, wall type and regenerative type.The main difference between the three methods is the way of heat recovery.These three methods can be combined with catalytic method to reduce the reaction temperature.Thermal combustion thermal oxidizer, generally refers to gas incinerator.The gas incinerator consists of combustion supporting agent, mixing zone and combustion chamber.Among them, combustion supporting agents, such as natural gas and oil, are auxiliary fuels. In the combustion process, the hot mixing zone generated in the incinerator can preheat VOC waste gas. After preheating, it can provide enough space and time for the treatment of organic waste gas, and finally realize the harmless treatment of organic waste gas.Under the condition of sufficient oxygen supply, the degree of oxidation reaction -- VOC removal rate -- mainly depends on the "three T conditions": reaction temperature, time and turbulence mixing.These "three T conditions" are interrelated. In a certain range, the improvement of one condition can reduce the other two conditions.The disadvantage of thermal combustion thermal oxidizer lies in the high price of auxiliary fuel, which leads to higher operating cost.Direct fired waste gas treatment furnace; required temperature: 700-800 ℃; corresponding waste gas type: all; waste gas purification efficiency is above 99.8%; with waste gas heat recovery system, the operating cost of the plant can be effectively reduced by catalytic waste gas treatment furnace (RCO)Required temperature: 300-400 degrees centigrade · spontaneous combustion starting according to the concentration of waste gas · system design: cleaning with pre-treatment agent and catalyst can prolong the service life of the equipment. Various adsorption materials can be configured at the front end of the RCO treatment technology, which is especially suitable for the occasions with high demand for heat recovery rate and the same production line,Where the composition of exhaust gas often changes or the concentration of exhaust gas fluctuates greatly.It is especially suitable for waste gas treatment of enterprises or drying lines that need heat recovery. Energy recovery can be used in drying lines to achieve the purpose of energy saving.Advantages: simple process, compact equipment and reliable operation;The purification efficiency is higher than 98%;Compared with RTO, the combustion temperature is lower;Its heat recovery efficiency can reach more than 85% with low one-time investment and low operating cost;No wastewater was produced in the whole process, and no secondary pollution such as NOx was produced in the purification process;The RCO purification equipment can be used with the drying room, and the purified gas can be directly used in the drying room to achieve the purpose of energy saving and emission reduction;Disadvantages: the catalytic combustion device is only suitable for the treatment of organic waste gas with low boiling point organic composition and low ash content, while it is not suitable for the treatment of waste gas containing viscous substances such as lampblack, and the catalyst should be poisoned;The concentration of organic waste gas is below 20%.Regenerative waste gas treatment furnace (RTO) · required temperature: 800-900 ℃. The design of spontaneous combustion system can be started when toluene concentration is lower than 500ppm. It can be used with RCO, suitable for large air volume and low concentration, and suitable for organic waste gas concentration between 100ppm and 20000ppm.When the concentration of organic waste gas is more than 450 ppm, the RTO unit does not need to add auxiliary fuel;The purification rate of two bed RTO and three bed RTO can reach more than 98% and 99% respectively, without secondary pollution such as NOx;Automatic control, simple operation;High security.Advantages: the operation cost is very low when treating large flow and low concentration organic waste gas.Disadvantages: high one-time investment, high combustion temperature, not suitable for the treatment of high concentration of organic waste gas, there are many moving parts, need more maintenance work.molecular sieveThe picture shows RTO (regenerative thermal incineration technology) concentration and waste heat recovery system, which can concentrate VOCs waste gas with low concentration and large air volume into high concentration and small air volume waste gas, and then burn at high temperature, and recover the heat of heat storage body, which can be used in waste gas preheating and heat conversion equipment.Therefore, tnv system is an efficient and ideal way to treat the waste gas containing organic solvents when a lot of heat is needed in the production process. For the new coating production line, the tnv recovery thermal incineration system is generally used.
Environmental protection RTO equipmentDisadvantages: when treating low concentration organic waste gas, the operation cost is high;Tube heat exchanger has a long life only when it runs continuously.Environmental protection RTO equipmentAfter condensation and extraction, the organic waste gas can be highly purified.
Environmental protection RTO equipment
Its disadvantage is that it is difficult to operate, and it is not easy to use cooling water to complete at normal temperature. It needs to cool the condensate water, so it needs more expenses.Environmental protection RTO equipmentMalodorous gas in industry is a more obvious waste gas pollution. The odor produced in plastic factory, pharmaceutical factory, asphalt waterproof material factory, sewage treatment plant, etc. not only seriously affects the ecological environment, but also seriously endangers human health.At present, the process of industrial odor waste gas treatment equipment includes combustion method, oxidation method, absorption method, adsorption method, neutralization method and biological method, etc. its main purpose is to change the material structure of odor gas and eliminate odor.The odor gas produced in industrial production can be managed by waste gas treatment technology after waste gas collection (general ventilation and local ventilation).Environmental protection RTO equipmentBiological deodorization is a biological waste gas treatment technology which uses biological method to cultivate the microbial membrane on the biological filler in the biofilter to deodorize the odor molecules.The high redox potential of ozone is used to deodorize and purify various kinds of waste gas, which is effective for all kinds of waste gas treatment.
Activated carbon adsorption method is to fill the adsorption tower with high-quality activated carbon. The activated carbon porous activated carbon is used to capture the molecules of waste gas and purify the waste gas. The activated carbon requires drying, so the high humidity in industry is not ideal.Environmental protection RTO equipmentThe technology of photocatalyst treatment of waste gas is the research and practice experience of Fenglv environmental protection music for many years, and it is the first large-scale application in the field of industrial waste gas purification in China.
A series of industrial photocatalytic organic waste gas purification devices are being completed.