Zeolite runner adsorption concentration ten RTO treatment of furniture factory painting waste gas

In view of the actual situation of VOCs in the furniture painting process with complex composition, large air volume and low concentration, this article focuses on the adsorption and concentration of zeolite (molecular sieve) runners and ten thermal combustion VOCs treatment technologies. This technology is particularly suitable for treating large air volume and low concentration organic waste gas. It can effectively improve processing efficiency and reduce operating costs, and the VOCs removal efficiency can reach more than 93%.
 
  1 Introduction
 
  Spray painting is one of the most important processes in the furniture manufacturing industry, which determines the appearance, color, quality, grade and value of furniture products to a large extent. As far as the current furniture industry is concerned, VOCs mainly come from the volatilization of organic solvents and diluents in the paint process, and different types of paints emit different types and contents of VOCs during use. When painting the same area, use Solvent-based coatings produce the most VOCs, followed by water-based coatings, and powder coatings the least. Although the country currently requires the furniture industry to vigorously promote the use of water-based and UV-curable coatings, the replacement ratio will reach more than 60% by the end of 2020, but in view of the immaturity of water-based and UV-curable coating technology in the furniture industry, the industry still uses solvents. Type paint is the main type, and the spray painting process produces a lot of paint dust and VOCs, so it puts forward high requirements on the VOCS management of the furniture industry.
 
  Take a large-scale home furnishing company in Wuxi as an example. The company set up two painting lines to spray wooden doors and bathroom cabinets. The spraying waste gas specifically includes: paint mixing waste gas, paint spray waste gas, and drying waste gas. The main pollutants are ethyl acetate, styrene, Xylene, butyl acetate, ethanol, methyl isobutyl ketone, isocyanate monomer, 2-hydroxy-2-methyl-1-phenyl-1-propanone, toluene, 2-methyl-2-acrylic acid-2- Hydroxyethyl ester phosphate, acrylic acid, 3-chloro-1,2-epoxypropane, ethylbenzene, methyl ethyl ketone, cyclohexanone, petroleum, 1,2,4-trimethylbenzene, ethylene glycol , Particulate matter, the air volume of the process is about 215000m3/h, and the concentration of spraying and VOCs is 120~330mg/m3. The exhaust gas has the main characteristics of large air volume, low concentration, complex exhaust gas components, and no recovery value.
 
  For the organic waste gas with large air volume and low concentration after being absorbed by zeolite molecular sieve, it can be converted into small air volume, medium and high concentration organic waste gas. Therefore, the company’s painting waste gas adopts zeolite runner adsorption and concentration ten RTO treatment, which has the advantages of high purification efficiency and low investment. , Which can ensure that the exhaust gas from painting is up to standard and the process technology is reasonable and feasible.
 
  2. Zeolite runner concentration ten RTO technical principle
 
  This technology is a combined process of zeolite runner adsorption and regenerative incineration technology. The purification system is mainly composed of a three-stage dry filter device, a zeolite runner concentration adsorption device, RTO, fan, heat exchanger, and PLC automatic control system. The combined technology concentrates large air volume and low concentration organic waste gas into small air volume, high concentration concentrated gas through the adsorption and concentration of the zeolite runner, and the high concentration concentrated gas is decomposed into CO2 and H2O and other inorganic components by RTO high temperature combustion. The zeolite runner concentration device uses three continuous temperature-variable adsorption and desorption procedures of adsorption-desorption-concentration. Through the rotation of the runner, the runner (divided into adsorption zone, desorption zone, and cooling zone) is simultaneously completed VOCs adsorption, desorption and regeneration.

  Combination technology process: when the organic waste gas after the three-stage dry filter device removes dust and particulate matter flows through the concentration runner, the organic matter in it will be adsorbed in the adsorption zone of the runner, and the waste gas after adsorption purification (approx. 85%~95% of the air volume is discharged into the atmosphere, and a small part of the exhaust gas (about 5%~15% of the processed air volume) cools the cooling zone of the runner and is heated to 180~220℃ by the heat exchanger. After the temperature, it flows into the desorption zone. The organic matter in the desorption zone is separated from the adsorbent-zeolite into the heated air flow, the runner is regenerated, and the high-concentration VOCs after desorption are sent to the RTO high-temperature incineration, and the high-temperature flue gas after the reaction Entering the regular honeycomb ceramic regenerator, 95% of the heat is absorbed by the regenerator and "stored", and the temperature drops to close to the RTO inlet temperature, usually not exceeding 50°C. After the temperature of the heat storage body rises, the air flow direction is switched through a switching valve or a rotating device, and heat storage and heat release are performed respectively, so as to realize effective heat recovery and utilization.
 
  3. Brief introduction of zeolite runner concentration ten RTO
 
  The zeolite runner concentration and RTO waste gas treatment equipment used in the case mainly includes a mixing manifold unit, a three-stage dry filter, a temperature rise and humidity control unit, a zeolite runner concentration unit, and a regenerative oxidation furnace unit.
 
  3.1 Three-stage dry filter
 
  The three-stage dry paint mist filter can completely remove dust and paint mist, and the purification efficiency of dust above 0.5μm in the gas is ≥98%. Its principle is to separate the paint mist particles from the exhaust gas by changing the direction of inertial force of the paint mist particles through the material fibers. The multiple fibers of the material gradually increase the impact rate and improve the filtration efficiency. When filtering, it can effectively pass through different filter material combinations, use the material space to accommodate paint mist, and achieve higher filtration efficiency is the unique performance of dry materials.
 
  When the filter system pressure reaches the set alarm value, the alarm system sends out an alarm signal, which is connected to the central control room to remind the operator to replace the filter material.
 
  The zeolite concentration runner is divided into three functional areas: adsorption zone, desorption zone and cooling zone. The zeolite molecular sieve runner runs continuously in each functional zone.
 
  In the adsorption zone: After the exhaust gas passes through the pre-filter, it is sent to the adsorption zone of the zeolite molecular sieve runner. In the adsorption zone (the area of the adsorption zone is S1), the VOCs in the organic waste gas are adsorbed by the zeolite molecular sieve, and the unadsorbed waste gas is directly discharged into the chimney and discharged to the standard under the driving of the adsorption fan.
 
  In the desorption zone: VOCs adsorbed on the zeolite runner are reversely desorbed and concentrated at high temperature in the desorption zone (the area of the desorption zone is S2). The desorption temperature is about 200°C, and the concentration factor is generally 5-25 times. Concentration factor:
 
  n=(S1×V1)(/S2×V2), where S1/S2=10:1,
 
  V1/V2=(0.5~2.5). The desorption gas enters the RTO incineration system driven by the desorption fan.
 
  In the cooling zone: in order to ensure high adsorption efficiency, the runner after high temperature desorption needs to be cooled. After cooling the adsorbent material of the runner, the cooling air is preheated as the source gas of the desorption gas, and then exchanges heat with the high-temperature purified gas from the RTO combustion chamber. The temperature increases to 180~200℃ and then enters the desorption zone of the runner in reverse. Perform high temperature desorption.

  The zeolite molecular sieve runner equipment is airtight as a whole, and the pollution source is mainly the waste zeolite material produced by the replacement of zeolite molecular sieve. However, according to the actual case operation of the project, the general life of the adsorbent material is more than 5 years.