Shaoyang Textile Machinery Liu Chun: Control Waste Gas Emissions And Achieve Cleaner Production.

Liu Chun graduated from China Textile University in July 1990. He is a senior engineer. Now he works in Shaoyang Textile Machinery Co., Ltd., mainly engaged in research and management of dyeing and finishing machinery.

The drawing and setting machine is an important finishing equipment in the finishing process. The printing and dyeing fume exhaust will have a great impact on the environment.

In the situation of energy saving and emission reduction in the printing and dyeing industry, the energy saving and emission reduction performance of the drawing machine has become one of the main performance requirements of the users.

Only by carefully analyzing the exhaust gas composition of the drawing machine, and putting forward corresponding measures for treating waste gas, can we achieve the goal of reducing emissions and environmental protection.

Printing and dyeing waste gas seriously endangering human health

The working principle of the stenter is that the hot air is used for drying and finishing the fabric, and the equipment is stable and stable. The working temperature is about 200 degrees Celsius.

In the process of fabric shaping, the baking machine will produce a large amount of organic waste and dye auxiliaries (including waxes, solvents, emulsifiers and polymer monomers) because of high temperature baking.

During the heat setting process, the cloth will produce a lot of high temperature exhaust fumes and dust in the drying room of the shaping machine. The composition is complex. It contains not only VOCs (organic volatiles), such as formaldehyde, polybenzene and aromatic hydrocarbons, but also some lubricant additives added in the weaving process, as well as dyes and auxiliaries in the special finishing process of waterproof, flame retardant and other functional fabrics, which contain more complex and diverse components, many of which are harmful to human health.

At present, the annual output of textile auxiliaries in China is 260 thousand ~28 tons, of which the pretreatment agent is about 7.4~7.7 tons. There are about 300 kinds of pretreatment agents, such as detergent, penetration agent, oil agent, refining agent and stabilizer. About 600 tons of dyeing auxiliaries, defoamers, baking powder, promoter, dispersant, binder, fixing agent, fluorescent whitening agent and insurance powder, etc., and about 5 tons of finishing agent, 5 kinds of antistatic agent, softener, resin finishing agent, waterproofing agent and coating agent. The particulate matter 150~250mg/m3 and lampblack 40~80mg/m3 in the exhaust gas of the setter are mainly composed of oil, which originates from the nature of fabric and the above process, such as rich oil additives in the waste gas of chemical fiber fabric.

The volatile oil mist and formaldehyde, polybenzene, aromatic hydrocarbons and other VOCs (organic volatile) exhaust gas inhalation can directly damage the respiratory tract mucosa, stimulate the respiratory tract and lungs of the human body, reduce the immune function of the human body, make people cough, chest tightness, shortness of breath, airway contraction, respiratory resistance increase, and endanger human health.

Printing and dyeing oil mist volatilization in the atmosphere is not easily soluble in water. It is not easy to fall to the ground with rain, but it will float in the air and form a long-term source of pollution.

At the same time, oil mist volatilization in the atmosphere has strong adsorption capacity. It is the carrier and catalyst of various pollutants. Sometimes it will become a aggregation of various pollutants. It is also the source of photochemical reaction (pollution) in the air with other volatile organic compounds.

Emission control is becoming increasingly stringent.

In the fast developing stage of printing and dyeing industry, because of extensive production, the users of the drawing and shaping machine simply discharge their exhaust gas through the exhaust pipe directly to the atmosphere, which not only wastes energy, but also causes serious environmental pollution, which not only causes damage to the health of the operators, but also seriously affects the quality of life of the surrounding residents.

Because there are a lot of smoke and dust in flue gas, such as polyphenylene organic compounds, dyeing auxiliaries, oil and other components, if it is directly discharged without purification, it will cause serious pollution to the air, and it will do great harm to human health and environment.

The pollution problem caused by the exhaust emission of the stenter is also becoming more and more acute. At the same time, because the oil and capillary fibers in the waste gas are likely to cause fires due to electrostatic sparks and cause significant economic losses to the enterprises, the exhaust emission of the machine must be controlled and handled. Therefore, the manufacturers and the printing and dyeing factories pay more and more attention to energy conservation and emission reduction, and adopt various ways to treat the waste gas scientifically, reduce the emissions of harmful substances and reduce the pollution to the environment.

The outline of the thirteenth five year plan for national economic and social development in People's Republic of China put forward that during the "13th Five-Year" period, the number of heavy pollution days in cities above the prefecture level should be reduced by 25%, and the pollution control of fine particulate matter in key areas should be strengthened. Efforts should be made to promote the discharge of pollutants and the total emission reduction, to implement the comprehensive emission control plan for industrial pollution sources, to improve the pollutant discharge standard system, to strengthen the supervision of industrial pollution sources, to control the total amount of volatile organic compounds in key regions and key industries, and to reduce the total emissions of the whole country by more than 10%.

Therefore, environmental protection production has been widely concerned by the society. To further strengthen environmental protection and emission reduction and deal with the urgent need for friendly environmental production is the social responsibility of printing and dyeing enterprises and equipment manufacturers.

In recent years, China has gradually strengthened the management of printing and dyeing waste gas purification and discharge. More and more provinces and municipalities have launched printing and dyeing exhaust emission standards, and the state will also introduce printing and dyeing exhaust emission standards as soon as possible.

And, with the technological progress and the increasing demands of the state for environmental protection,

Emission standards will be higher and higher.

For example, the "dyeing and finishing action" in Shaoxing, Zhejiang in 2006 provided a reference case for the exhaust treatment of the domestic dyeing and finishing machine. The standard of exhaust gas treatment equipment for dyeing and finishing machines in Shaoxing City: after the installation of exhaust gas treatment equipment, the exhaust gas collection rate should reach more than 90%, the removal rate of total particulate matter should reach 80%, the soot removal rate should reach 75%, and the prevention and treatment measures for two times of pollution of waste water and waste oil after purification, the waste oil should be recycled, and energy saving and no two pollution can be achieved.

In 2013, Shaoxing, Zhejiang province took the lead in improving the exhaust gas treatment of the drawing machine, and issued the local standard for the emission limits of the stereotype machine in the printing and dyeing industry, which was formally implemented in May 1, 2013. The standard stipulates that the maximum permitted emissions of particulate matter in the printing and dyeing industry are no more than 30mg/m3, and the lampblack concentration is not more than 40mg/m3.

In 2015, Zhejiang province first released the local standard "air pollutants emission standard for textile dyeing and finishing industry", standard number: DB33/962-2015, and was implemented in April 1, 2015. The standard requires: the highest permitted emissions of exhaust emissions from the textile and dyeing industry production facilities, the concentration of particles is not more than 20mg/m3, and the concentration of soot is not more than 30mg/m3.

Water spray technology has remarkable economic benefits.

There are many kinds of waste gas treatment for stenter shaping machine. There are two kinds of waste gas treatment: electrostatic treatment and water spray treatment.

The principle of electrostatic treatment is: using the corona effect under high voltage direct current, the gas-liquid corona causes the dust particles to be charged. When positive and negative particles are passed through the dust removal electrode, they are adsorbed by negative / positive plates respectively. The oil fume will be condensed into liquid beads and accumulated on the round arm. Under the action of gravity, it will be dripped freely into the collecting tank of the equipment and then collected to achieve the purpose of dedusting and dedusting.

The flow chart of electrostatic fume removal is shown below.

The electrostatic purifier used in waste gas treatment of stenter setting machine mainly has three deficiencies: first, dust must be cleaned first, and then multi stage mechanical filter is usually chosen.

Due to the large amount of fiber and oil in the waste gas of the shaping machine, it is bound to increase the workload of cleaning and maintenance.

The exhaust gas temperature of the setter is sometimes as high as 180~200 degrees. Even if the exhaust gas temperature is low, it is unavoidable to catch fire. At this point, if the system does not have safe and reliable protection measures, the electrostatic purifier will usually be scrapped due to a fire.

Three, electrostatic process requires relatively high technological and structural requirements for purification equipment.

The working principle of the water spray type exhaust gas purifier is,

The generated high temperature waste gas enters the exhaust gas purifier, and enters the spray area after slow flow, uniform flow and diffusion in the waste gas treatment process area of the guide setting machine. The flue gas contacts with the high-pressure water mist in the spray area, and the harmful gas, fiber, dust and oil mist in the exhaust gas are collected by water mist and then poured into the oil water separation tank through the bottom outlet of the purifier.

After spray cleaning and cooling, the gas enters the dewatering area from the spray area. The dehydrated clean gas is discharged into the atmosphere through the exhaust pipe at the top of the purifier.

The water spray treatment process is applied to the waste gas treatment of the drawing machine. The advantages are mainly embodied in the following aspects: no need to install the induced draft fan, make full use of the surplus air pressure of the original exhaust fan, increase the power loss, effectively protect the air duct of the shaping machine, eliminate fire hazards (fire extinguishing function after the operation of the purification system), fully cool the flue gas, effectively recover the waste oil and produce economic benefits; and the purified exhaust gas meets the standard discharge.

The operation and maintenance is convenient, the cost and the maintenance cost are low. It can not only control the waste gas, but also recover the waste oil and produce economic benefit.

The drawing and setting machine has been widely applied and widely promoted in the waste gas purification treatment project.

The water spray process flow chart is shown below.

On the whole, printing and dyeing waste gas treatment can effectively control exhaust gas purification and discharge. The printing and dyeing oil fume will be greatly reduced in the air. It can not only achieve cleaner production, protect human health, protect against the pollution of printing and dyeing fumes, but also achieve the goal of emission reduction and environmental protection. At the same time, it can create certain economic benefits through the recovery of waste oil.

China's textile production has changed from extensive to energy-saving and sustainable development. Energy saving and emission reduction technology has attracted more and more attention and textile printing and dyeing industry.

Waste gas treatment is also a multi income project with remarkable economic and social benefits and wide application prospects.