Editor’s note: The printing and dyeing industry has problems in resource conservation and environmental protection in the entire process from the source of raw materials to the fabric packaging and delivery. Modern clean production must not only consider the end-of-pipe management of the printing and dyeing industry, but also require comprehensive utilization of resources, substitution of scarce resources and polluting raw materials, secondary energy utilization, and energy conservation, consumption reduction, and water conservation to achieve rational use of natural resources and reduce Resource depletion, reducing waste and pollutant emissions, promoting the environmental compatibility of the production and consumption processes of industrial products, and reducing the risks to humans and the environment in the printing and dyeing industry.
Common environmental problems in the printing and dyeing industry
A. Incoming materials The nature is unstable, that is, the nature and concentration of impurities and other residues attached to the cloth are highly random. The production process used at the front end of the product chain cannot be controlled during the evaluation cycle.
B. The use of various toxic and harmful additives.
C. The pollution of the dye itself.
D. Process wastewater in each link is the main source of pollution.
E. The process is traditional and the equipment is old.
Clean production control in the printing and dyeing industry: raw materials
For incoming materials The attached residue cannot be controlled, and the following restrictions can be implemented according to the Eco-Label standard:
A. Pollutant emissions from companies producing fabrics must meet standards;
B. Production must adopt clean processes advocated by the country;
C. The harmful residues of raw materials are limited to not exceeding the standard when leaving the factory;
D. Try to choose a source of stable supply.
Cleaner production control in the printing and dyeing industry: alternative auxiliaries
In printing and dyeing During the process, a variety of functional additives are needed, such as caustic soda, penetrating agents, bleaching auxiliaries, color-fixing agents, etc. Environmental protection mainly considers their biodegradability, toxicity, teratogenicity, carcinogenicity, environmental hormones, etc., when using There are varying degrees of pollution during the process. Priority should be given to environmentally friendly alternative additives to reduce environmental pollution.
A. Desizing agent
The use of biological enzyme desizing process can also quickly break the PVA molecular chain. Enzymatic desizing also has the characteristics of high efficiency, low wastewater production, low pH value, and high biodegradability of wastewater.
B. Bleaching auxiliaries
Most of the traditional processes use organic Integrating agents, sodium hypochlorite, etc. have good stabilizing effects but poor biodegradability. Hydrogen peroxide can be used, which has good bleaching effect and is easy to decompose. It can also save energy, reduce equipment investment, and simplify equipment.
C. Fixing agent
Effect screening for each variety , only use aldehyde-free varieties.
D. Softener
Choose non-toxic, harmless, Easily biodegradable natural functional additives. The ester bond of the non-ionic fatty acid polyoxyethylene ester surfactant is easily hydrolyzed, has low foaming, non-toxicity and good biodegradability, and can be used as an environmentally friendly soft component.
E. Reducing agent
Caustic soda is generally used after fabric dyeing For reduction cleaning, the water washing load is heavy. There are some environmentally friendly reducing agents that can work under acidic conditions and greatly reduce the water washing load.
F, finishing agent
Use low-formaldehyde, formaldehyde-free resin Finishing agent. After etherification modification of 2D resin, the formaldehyde content is greatly reduced, but there is still 20~100 mg/kg of free formaldehyde. Developed formaldehyde-free resins such as BTCA are more expensive and not as effective as 2D.
Clean production control in the printing and dyeing industry: printing materials
should be solid For fuels with high color rate and good color fastness that can meet the application performance, the fuel supplier can be asked to provide the dye index number and compare it with the banned dye index number to avoid avoidance. Color pollution caused by printing and dyeing wastewater can absorb light and enter rivers, lakes, seas and surface water, reducing the transparency of the water body, affecting the growth of aquatic organisms and microorganisms, not conducive to the self-purification of the water body, and also causing visual pollution. Seriously polluted water bodies will also be affected. human health.
A. Reactive dyes
The main environmental issues of reactive dyes are The fixation rate is low, generally only 50%~65%: Inhalation allergies are mainly caused by powdered dyes, so liquid reactive dyes should be used as much as possible: In order to suppress the negative charge on the fiber surface, the high dosage of inorganic salts makes wastewater treatment difficult: Metal complexes Among the complex dyes, most of them contain chromium, cobalt and nickel, which have dark color chromatography. It is difficult to reach the limit in Oeko-Tex standard 100, so they must be replaced by non-metallic complex dyes: the copper-containing dyes have a special color and cannot be replaced, but The copper content limit is wider (25~50mg/kg). When dyeing with reactive dyes, use a cationic modification process to increase the dye uptake rate of reactive dyes and reduce the residual amount of dyes in wastewater.
B. Disperse dyes
Prohibited in Oeko-Tex Standard 100 21 of them are all disperse dyes. Among the 26 internationally recognized allergenic dyes, 25 are disperse dyes. Disperse dyes should be used less or less in the dyeing process. Most of the newly developed disperse dyes do not contain halogens, so there is no AOX problem.
C. Sulfur dyes
There is no finished product structure of sulfur dyes Carcinogenicity, but some dye intermediates can cause cancer. If the reaction is incomplete and the filtration is not thorough, it can easily be brought into the finished dye.
D. Vat dyes
Vat dyes have fewer environmental problems. However, chlorinated benzene is sometimes used as a solvent during the manufacturing process, and if the dye post-processing is not sufficient, will remain on textiles, exceeding the limit of less than 1mg/kg in Oeko-Tex standard 100.
Cleaner production control in the printing and dyeing industry: process
Improving the process is to reduce ways of energy consumption.
A. Use low-alkali and alkali-free pre-treatment processes, such as enzyme process and low-temperature plasma technology for desizing and surface modification.
B. Combine the shortening process and adopt the cold pad-batch bleaching process, which combines desizing, scouring and bleaching processes into one, saving energy and consumption by 30%~40% in the pre-treatment stage. , reduce pollution and simplify equipment.
C. Use less water and no water processes, such as supercritical CO?2 dyeing, paint printing and dyeing, foam dyeing and finishing, etc.
Cleaner production control in the printing and dyeing industry: equipment
A. Towards the environment Development in protection, energy saving, consumption reduction, time saving, high efficiency, and short process.
① Use electric singeing machines to replace oil and coal singeing machines to eliminate waste gas emissions.
② Use high-efficiency water washing units, such as powerful water spray circulation systems, ultrasonic waves, etc.
③ Use a rolling mill with a low rolling ratio before drying, and reuse dryer condensate water, such as using a pumpless back-pressure trap, etc.
④ Use automatic control and monitoring facilities, and pay attention to the use of energy-saving instruments.
⑤ Use low liquor ratio equipment and other energy-saving equipment.
B. Develop towards automation technology.
①The transmission system adopts AC frequency conversion multi-unit speed regulation system.
②The control system widely uses programmable controller PLC, or computer-controlled IPC, as well as online monitoring of process parameters to greatly improve the stability and reproducibility of the process.
Cleaner production control in the printing and dyeing industry: recycling
At present, the printing and dyeing industry The industrial wastewater reuse rate is 7%, and the textile industry is about 10%, which is the lowest among all industries in the country. Generally speaking, it is difficult to achieve satisfactory reuse effects by using one method to treat dyeing wastewater. Composite technology must be used, such as the combination of photocatalytic oxidation technology and membrane technology (sodium filtration) to treat dyeing wastewater. Not only will there be no secondary pollution, The salt in it can also be recycled.
A. Desizing wastewater
Wastewater contains alkali, enzymes, etc. Desizing agent and various slurries, this kind of wastewater must be treated. If there is a lot of chemical slurry, the slurry of the desizing wastewater towel can be concentrated by membrane separation method (ultrafiltration recovery), and recycled to reduce the pollution load.
B. Scouring wastewater
Do it under the scouring steamer With four alkali storage tanks, the alkali agent in the wastewater can be appropriately utilized and then discharged after treatment.
C. Bleaching wastewater
Wastewater contains hydrogen peroxide and hypochlorine Bleaching agents such as sodium acid have low COD and BOD values, consume large amounts of water, and cause light pollution. They can be discharged directly or can be reused after slight treatment.
D. Mercerizing wastewater
The mercerizing process towel is washed from the fabric The amount of caustic soda coming down is very large, and most of the caustic soda is recycled. The BOD value and total solid content of the wastewater discharged after recycling are not high, and can be reused after simple treatment.
E. Dyeing wastewater
Dyeing wastewater contains various dyes and For dyeing auxiliaries, the residual liquid can be used to concentrate and specially treat certain dyeing materials, such as using ultrafiltration to recover hydrophobic dyes such as vat dyes to reduce chroma and COD values.
F. Wastewater treatment
Wastewater contains various resins and Various functional finishing agents have a small amount of waste water, but some finishing agents are toxic and should be controlled when discharged.
Cleaner production control in the printing and dyeing industry: management
A. Reasonable arrangements Pre-processing schedule to reduce human errors and waste:
B. Accurately calculate the fuel consumption of each color to reduce waste and emissions:
C. Strictly prevent running, popping, dripping and leaking:
E. Establish an information management and automatic control platform to reduce human errors and waste:
F. Improve the level of thermal energy management in the production process:
G. Conduct technical personnel on the environmental protection of environmentally friendly textiles, energy-saving equipment and commonly used dyes and chemicals Systematic training of knowledge to improve the consciousness of cleaner production:
H. Collect relevant information, timely track the development and latest achievements of raw materials, processes, equipment, energy conservation and environmental protection, and The latest developments in environmentally friendly textile standard assessment items and indicators and other content in order to proactively respond. </p
