How To Control Printing And Dyeing Unorganized Exhaust Gas?

Moderator: air conditioning Printing and dyeing industry Speaking, though not as urgent as some industries, it is also another important environmental protection work besides waste water treatment. As we all know, the exhaust gas in printing and dyeing production is organized and partly unorganized. The emission of unorganized exhaust gas is easy to be ignored. What are the main links of unorganized exhaust gas? What are the hazards of these unstructured exhaust gases? How can we control these unstructured exhaust gases? This is the two expert who invited Li Weiqing and Wang Lili of Voight Bao Environmental Protection Technology Co., Ltd. in Fujian province to explore the prevention and control of non woven waste gas in printing and dyeing production.

　　 What are the exhaust gases emitted by Q in printing and dyeing production?

Li Weiqing: unorganized exhaust gas is an air pollutant that does not discharge regularly through the exhaust cylinder. Emissions from low exhaust tanks are organized emissions, but can also be caused under certain conditions. Unorganized emission The same consequences. Therefore, when implementing the "unorganized emission monitoring concentration limit" index, the concentration of pollutants at the monitoring points caused by the low exhaust cylinder will not be deducted.

Wang Lili: unorganized emissions according to source height classification belongs to the surface source, and has a greater impact on the surrounding environment. The general exhaust gas height below 15m is also considered to be unorganized emissions.

　　 In the printing and dyeing process of Q, what links will produce unorganized exhaust gas?

　　 Li Wei Qing There are a certain amount of unstructured waste gas spills in the process of boiling bleaching, dyeing, printing, wastewater treatment and so on. For example, in the boiling and bleaching part, because part of the machine's weaving and bleaching is carried out on the boiling and bleaching line or on the open type dyeing machine. In this case, because the whole process is open, there will be a certain amount of waste gas generated for unorganized emissions. Boiling and Bleaching Auxiliaries include penetrant, wetting agent and so on. The ingredients of scouring and Bleaching Auxiliaries include sulfated castor oil, sodium alkyl sulfate, secondary alkyl sulfate, Sodium Alkylbenzene Sulfonate, alkylnaphthalene sulfonate and so on.

The dyeing process is basically wet processing, resulting in less emissions. In the drying process, the organic matter added to the dyeing process will be released. In the dyeing process, no tissue waste gas pollution is mainly in the drying process, and drying is the process of volatilizing the water on the fabric. Because the fabric will adsorb part of the auxiliaries or chemicals during dyeing and finishing. Therefore, during the drying process, the adsorbent auxiliaries and chemicals will also volatilize and produce a certain amount of waste gas. Drying waste gas contains more organic volatiles, including benzene series and naphthalene derivatives.

In the soaping and washing process, soap and water washing are carried out in water bath. The water bath temperature is between room temperature and boiling point. At the same time, because of the less amount of additives and chemicals, the amount of waste gas produced is not large, mainly because of the evaporation of water vapor. Some of the auxiliaries contain a certain amount of organic solvents, which can be volatilized during soaping and washing, such as isopropanol and acetone. Some volatile acids also volatilized, such as acetic acid. Because the water bath is open, so all of these emissions are unorganized emissions, although the amount of production is not large, if a large number of small amounts of, then the harm to the human body is not small.

The main air pollutants in the printing process come from the solvent used to prepare slurry auxiliaries, and the exhaust gas emission process is unorganized emissions. The addition of auxiliaries in the printing process will be released after drying. Size is related to the dyes chosen for printing. Commonly used slurry is synthetic slurry (such as polyvinyl alcohol, polyacrylic acid), carboxymethyl cellulose, sodium alginate and so on. The size of the slurry does not evaporate. The solvents and ingredients used for preparing slurry are volatile.

Wang Lili: after dyeing, the exhaust gas generated by heat setting is an important exhaust gas, and the pollutants in the exhaust gas are also the most important pollutants. Although these exhaust gases are organized emissions, but in the long-term use of equipment, they can not guarantee the absolute seal of equipment and pipelines, and more or less will escape from the exhaust gas. The escaping of these exhaust gases can not be ignored for a long time.

In the textile printing and dyeing industry, waste water treatment is an important part. In the process of wastewater treatment, a certain amount of exhaust gas will also be released. The waste gas discharged from the wastewater treatment process is mainly hydrogen sulfide and ammonia produced in the anaerobic stage. The wastewater discharged from the workshop has a certain temperature and will also emit peculiar smell. The waste gas generated during the wastewater treatment stage is basically unorganized.

　　 How can Q effectively manage these unorganized exhaust gases?

Li Weiqing: to treat these unorganized exhaust gases is generally through the exhaust gas purification system. The diffusion mechanism of air pollutants in the workshop is the diffusion of pollutants attached to the movement of air. As for the pollutants emitted into the workshop air during the production process, as long as the movement of the two airflow in the room is controlled, the diffusion and fluttering of pollutants can be controlled, so as to improve the indoor and outdoor air environment quality inside and outside the workshop. This is the basis of local exhaust ventilation to control the diffusion of air pollutants. The local ventilation method to control the diffusion of air pollutants inside and outside the workshop is simply to set up the gas collecting hood in the local pollution source and collect the polluted air and purify it to the outside. This is the most effective and commonly used method to control the pollution in the workshop. The partial exhaust purification system is composed of gas collecting hood, air duct, purifying equipment, ventilator, chimney and so on.

The capture device of pollutants is divided into an air suction trap and a blow trap device according to the air flow. According to the shape of the trap, it can be divided into a gas collecting hood and an air collector. For closed production equipment, if contaminants occur within the equipment, they will be transported to the workshop through holes and gaps in the equipment. When the negative pressure is not allowed inside the closed equipment or when the contaminant occurs on the surface of the pollution source, the gas collecting hood can be used to capture it. There are generally 3 types of gas collecting hood: closed gas collecting hood, semi closed gas collecting hood and external gas collecting hood.

Wang Lili: after collecting the exhaust gas through the gas collecting hood and the collector pipe, it is treated through the purification equipment. The purification equipment shall be selected according to the quantity, composition, nature of the waste gas and the specifications and performance of the purification equipment. If the product or blueprint without purification equipment is available, it is necessary to design. Through the selection of equipment, the type, specification and quantity of the purification equipment can be determined; or the equipment structure, size, material and processing technology can be determined through design.

Under the most economical and reasonable conditions, the pollutant discharge should be guaranteed to meet the requirements of the relevant standards or ensure that the atmospheric quality within the scope of its impact meets the requirements. Therefore, the design and calculation of the purification equipment and exhaust equipment (chimney or exhaust cylinder) should be linked together. If the air quality is used as the design assessment standard, the diffusion calculation after the discharge of pollutants is needed.

　　 Q what are the suggestions for the treatment of unorganized waste gas in printing and dyeing industry?

Li Weiqing: there are many sources of unorganized emissions in textile printing and dyeing industry, and the gas composition is complex. In addition to the main sources of pollution that I have just mentioned, there are many other points that can not be ignored, such as weighing room, mercerizing machine, singeing machine, calender and so on. In order to unify the principles of waste gas treatment technology and equipment, it is necessary to find a route suitable for waste gas treatment in printing and dyeing industry.

Wang Lili: electrostatic precipitator technology is the most economical exhaust gas treatment plan at present. This scheme can remove particulates with particle size above 0.5um. The exhaust gas of textile printing and dyeing industry does not contain a large number of metal particles, which provides a good condition for the application of electrostatic precipitator technology. Because of the large amount of fiber wool, large particle dust and difficult to remove wax in the exhaust gas, it has the effect of dedusting in the process of electrostatic precipitation. The technology of "spray + electrostatic" or "wet separation + electrostatic" is recommended. The latter has better effect, but occupies a larger area, so it is difficult to popularize.