Based on the investigation of the present situation and wastewater discharge of printing and dyeing enterprises in Changzhou area, this paper discusses the emission reduction from three aspects: engineering emission reduction, structural emission reduction and management emission reduction. The feasible reduction scheme and emission reduction measures of printing and dyeing wastewater are discussed. Vigorously promote the application of cleaner production technology in enterprises.
Printing and dyeing wastewater has long plagued enterprises and governments and restricted the development of the industry. The Textile Industry Adjustment and Revitalization Plan lists remarkable achievements in energy conservation and emission reduction as one of the important goals to be achieved by the industry in the past three years, and emphasizes that by 20 1 1, the energy consumption per unit added value of the whole industry will be reduced by 5% annually, the water consumption will be reduced by 7% annually, and the wastewater discharge will be reduced by 7% annually. To achieve this goal, the task is arduous.
Based on the investigation data of wastewater discharge from printing and dyeing enterprises in Changzhou, the production technology, equipment, management and wastewater discharge of more than 20 different types of printing and dyeing factories were investigated and analyzed, and the effective ways to realize the emission reduction of printing and dyeing wastewater were studied, so as to promote the popularization and application of cleaner production and energy saving and emission reduction technologies in printing and dyeing enterprises.
1 project emission reduction is the key, focusing on application, promotion, reform and innovation.
Changzhou textile printing and dyeing industry is developed, and the advantages of industrial clusters are outstanding. There are 7 textile printing and dyeing parks, and the park mode creates good conditions for centralized treatment of decentralized printing and dyeing wastewater. However, statistics show that about 30% of small and medium-sized enterprises have not entered the park, and most of them have outdated equipment, traditional technology, slow pace of technological transformation and innovation, and there is still huge room for improvement in process optimization, process control, production management and resource recycling.
1. 1 Increase the renovation of existing equipment.
1. 1. 1 Choose efficient water-saving equipment, with small bath ratio and short process.
At present, the advanced dyeing and finishing equipment at home and abroad has been greatly improved in automatic control, on-line detection, energy-saving and consumption-reducing devices and so on. It can accurately control various technical parameters and ensure the optimization of material consumption. It has become an inevitable choice for enterprises to eliminate equipment with high energy consumption and high water consumption and choose new equipment with energy saving and emission reduction. The equipment worthy of attention is as follows.
(1) Small bath ratio equipment. Intermittent production enterprises such as knitting and chemical fiber can save more than 50% water by replacing the old overflow machine with a small bath ratio overflow machine; Replacing the overflow machine with blower can save water by 50%, steam by 50% and additives by 30%. For example, Germany has a new generation of normal temperature SYN series air flow dyeing machines.
(2) High efficiency and short process equipment. Efficient short process is the earliest, most effective and basic method adopted in the sustainable development of dyeing and finishing industry, which has great potential, but the attention and investment are not enough at present. Popularization and application of AG liquid device and high-efficiency water washing device is a wise move to alleviate the pollution of pretreatment wastewater, which accounts for more than 60% of the total printing and dyeing wastewater. For example, Flex of Küsters (Koster) in Germany? German MenZel company's NiP and Optimax high liquid delivery devices, Swiss Berninge company's BEN series high-efficiency washing machines, etc.
(3) Low rolling allowance, high efficiency and energy saving rolling mill. Installing an efficient and energy-saving rolling mill in the proper position of continuous processing equipment can reduce the residual rolling rate by about 20% compared with ordinary rolling mills. When entering the next washing process, less than 20% of residual liquid can be taken, which can greatly reduce the washing burden. This scheme can be used for mercerizing, dyeing, printing and other pre-washing processes.
1. 1.2 Strengthen the transformation of existing equipment and production links.
Due to the financial crisis, printing and dyeing enterprises are facing difficulties, and it is unrealistic to realize a large number of equipment updates. Therefore, strengthening the technical transformation of existing equipment is an effective way for most printing and dyeing enterprises to save energy and reduce emissions. The successful case of a printing and dyeing company is as follows.
(1) The flat washer is changed from straight row to counter current one by one. Generally, the amount of water discharged directly into the sewer per hour by each horizontal washing tank is about1.5t. Based on the average of 5 grids for each continuous horizontal washing tank, the water discharge per hour is about 7.5t.. The reformed scouring, bleaching and dyeing flat washing machine can save water by 4.5 t per hour and more than 20,000 t per year.
(2) The steam of the dryer directly enters the nearby flat washing tank. Through the pipeline transformation, the condensed water and steam in the dryer are directly discharged into the flat washing tank at the end of the flat washing machine, which realizes the full utilization of the steam and high-temperature condensed water of the dryer, omits the steam trap of the dryer, avoids steam leakage, reduces the temperature of biochemical treatment sewage, and is simple and safe to operate.
(3) Modify the random switch of spraying equipment in the heat exchanger beside the continuous pad dyeing machine. In this way, the conventional energy-saving effect of the heat exchanger can be achieved, and at the same time, the waste caused by the car stopper forgetting to turn off the spraying equipment one by one when parking can be reduced.
1.2 Vigorously promote mature cleaner production technologies.
Through investigation, it is found that about 80% of printing and dyeing enterprises in Changzhou still use traditional technology, which has long production process and high water and energy consumption. Therefore, the popularization and application of cleaner production technology after reasonable screening, scientific optimization and innovation is the key to realize the emission reduction goal of printing and dyeing wastewater.
1.2. 1 Pretreatment Cleaner Production Technology
(1) multifunctional scouring agent? One-step process of hydrogen peroxide immersion bath. This process is suitable for the pretreatment of cotton cheese and knitted fabric. It integrates alkaline agent, stabilizer, chelating agent, penetrant, emulsifier and detergent, which simplifies the feeding procedure, finishes boiling and bleaching in one step, and can be dyed directly after being washed by deoxyenzyme without draining. At least 10 t of water is saved per ton of cloth, the pH value of waste liquid is reduced by 0.5, and CODcr is also reduced. The reference process of scouring and bleaching of cotton baled yarn in a yarn-dyed factory: loading yarn → feeding working solution (multifunctional scouring agent 2 ~ 3 g/L, 30% hydrogen peroxide 4 ~ 6 g/L, bath ratio 1: 7 ~ 1: 8) → scouring and bleaching (100℃ 40 min). 10 min)→ pickling (HAC 1 g/L, 50℃, 15 min) → deoxyenzyme washing (0.5 ~ 1 g/L, 35℃, 15 min) → No.
(2) Compound enzyme? Low alkali cooking technology. At present, biological enzyme pretreatment of cotton shuttle fabric has not been realized, but it can be realized by "cold pad-batch with enzyme" and low alkali steaming? Oxygen bleaching process has replaced the traditional three-step method. This process is suitable for most cotton fabrics, including yarn carding. The whiteness, wool efficiency and strength of the treated fabric completely meet the quality requirements, and the CODcr value of wastewater can be reduced by about 20%, which greatly improves the biodegradability. The reference process of cotton carding machine in an enterprise: singeing → rolling enzyme solution (compound enzyme 5 g/L, JFC2G/L, 50 ~ 60℃, pH 8 ~ 9) → moisturizing stacking 10 h → hot water washing twice → rolling dilute alkali solution (caustic soda10 ~10)
1.2.2 Cleaner production technology of printing and dyeing
(1) New pad dyeing process for coatings. Pigment dyeing technology is an innovative technology, which can fundamentally establish a good ecological environment from the source, fully consider clean production, save energy and reduce consumption, and also produce special style dyeing. The dyeing process can be considered as "zero pollution discharge" or little discharge. In this technology, firstly, the fiber is modified by cation, and then the anionic coating is selected for dyeing, so as to realize the local adsorption of the coating on the fiber, and the product has high dyeing fastness and K/S value. Changzhou Gaodong Printing and Dyeing is the forerunner of this dyeing technology. The recommended process is: semi-finished products → cationic modification (deepening agent 3 ~ 5 g/L, soaking and rolling at room temperature) → drying → coating pad dyeing (adding wet fastness improver 20 ~ 40 g/L, soaking and rolling at room temperature) → drying → tentering.
(2) Salt-free dyeing technology with reactive dyes. This technology and conventional rolling? Baking? Get out? Compared with the steaming process, it fundamentally eliminates the problem that the salt in printing and dyeing wastewater is difficult to remove, and the floating color is not easy to dye back, which improves the dyeing fastness, improves the washing performance of dyed fabrics, reduces the chromaticity of wastewater, reduces the wastewater discharge by more than 30%, and realizes the wastewater reuse rate of 50%. The recommended process of an enterprise: semi-finished product → pad dyeing solution (special dye-fixing alkali agent 10 ~ 20g/L, pad rolling twice, pad rolling rate 60% ~ 65%, room temperature) → steaming (100 ~ 102℃).
1.3 Pay attention to the recycling of dyeing materials.
In the sampling survey, it is found that less than 10% of printing and dyeing enterprises implement the technology of wastewater reuse, most small and medium-sized enterprises do not have light alkali recovery devices, and even fewer enterprises recycle dyes. Therefore, from the perspective of reducing the burden of printing and dyeing wastewater treatment, more attention should be paid to the recovery and utilization of dye auxiliaries.
1.3. 1 Recovery and reuse of dyes
The dyeing residues of vat dyes and sulfur dyes can be treated by ultrafiltration and acid precipitation respectively, and the recovered dyes can be used according to the conventional process. Hydrolyzed dyes in reactive dye dyeing residue can coagulate and precipitate, and the recovered dyes can be used for wool dyeing according to acid dye process.
1.3.2 recycling of mercerizing alkali liquor
Add 1 automatic alkali distribution instrument at the edge of mercerizing alkali rolling tank, filter the concentrated alkali at the front stage of alkali spraying and absorption, return it to the alkali distribution tank, use the alkali at the back stage of alkali spraying and absorption for refining, and install a liquid storage tank to reuse the concentrated alkali left in the working tank during shutdown, which not only improves the process stability, but also saves alkali consumption and reduces the pH value of wastewater.
2. structural emission reduction is the breakthrough, and the focus is on optimization and adjustment.
In view of the present situation of Changzhou printing and dyeing industry and the arduous task of energy saving and emission reduction, it is imperative to take a new road of industrialization, adjust industrial structure and optimize product structure with the theme of energy saving and emission reduction, consumption reduction and clean production.
2. 1 adjust the industrial structure and highlight the advantages of technology research and development.
According to the spirit of the national regulations on promoting industrial restructuring, it is necessary to speed up the resource reorganization of existing printing and dyeing enterprises in Changzhou, intensify the efforts to shut down small-scale enterprises with serious pollution, moderately control the production scale of conventional printing and dyeing products processing enterprises, and take Changzhou Hongda Electric, Hong Jun Printing and Dyeing and Gaodong Dyeing and Finishing as leading enterprises to cultivate a number of new textile printing and dyeing enterprises with high scientific and technological content and strong competitiveness, and change scale advantages into technological advantages and processing advantages into research and development advantages.
2.2 Optimize product structure and develop high value-added varieties.
The products of Changzhou printing and dyeing enterprises are mainly cotton woven fabrics, including denim, yarn-dyed fabrics and corduroy. In recent years, the scale of knitting printing and dyeing is expanding. However, the overall product structure is simple, the variety of colors is single, and there are not many varieties with high-tech content and high added value. It is suggested to improve from the perspectives of eco-textile, energy saving and emission reduction.
(1) Develop green fiber products. Taking Changzhou Xu Rong Knitting Printing and Dyeing Co., Ltd. as an example, the colored cotton and Tencel are discussed. , chitin, polylactic acid and other new fiber blended or interwoven fabrics that meet the ecological requirements and comprehensively utilize resources, develop new varieties and open up new markets.
(2) Develop new printing products. Such as inkjet printing, paperless transfer printing, batik imitation, imitation cowboy products, etc. And moderately control highly polluting printing and dyeing products, such as denim and corduroy.
(3) Developing various functional fabrics. Such as super-softness, wrinkle resistance, waterproof and moisture permeability, flame retardancy, antifouling, antistatic, UV-proof, antibacterial, radiation-proof and electromagnetic wave shielding. , including coating and composite finishing, to improve the functionalization and differentiation of products.
(4) Developing household textiles and industrial textiles. Changzhou has not yet formed a production chain, and there is still huge room for development from the goal of dividing the world into three parts: clothing, household and industrial textiles.
3 emission reduction management is the guarantee, and it is very important to improve execution.
3. 1 adopt advanced scientific methods for real-time monitoring and effective management.
Changzhou scientific research institutions and universities have jointly developed the BP neural network water quality and quantity prediction and GIS support system, which provides reference for local governments and industry authorities to timely understand the production and pollution discharge situation of printing and dyeing industry and accurately grasp relevant information, so as to make scientific decisions and effectively guide. Details are as follows.
(1) Artificial neural network is introduced into the water quality simulation and prediction of textile printing and dyeing industry to improve the prediction accuracy. Practice shows that it is feasible to predict the pollution development trend of printing and dyeing industry by using neural network model. It is predicted that the wastewater discharge of Changzhou textile printing and dyeing industry will exceed 99.25 million t/a after 20 10 years.
(2) The GIS support subsystem for pollution control decision-making in Changzhou printing and dyeing industry is developed. The system can integrate water environment information, geographical information and printing and dyeing pollution source information in various regions. With its intuitive, visual and interactive characteristics, it can help environmental management and technical departments to understand the environmental geographic information of this area conveniently and quickly, and realize the accurate location, real-time query and pollution statistics of pollution sources.
3.2 Strengthen refined management to implement energy-saving and emission-reduction measures.
Fine management is the booster of cleaner production technology in printing and dyeing enterprises. It is the need for enterprises to surpass their competitors and themselves, the inevitable choice for enterprises to adapt to the fierce competitive environment, and the inevitable choice for enterprises to seek a lasting foundation. The management modes of some enterprises are worth learning.
(1) Optimize the existing process and refine the operation links. Strengthen the optimization of existing process routes, process prescriptions and conditions to avoid increasing the burden of wastewater treatment due to insufficient absorption. Formulate the operation rules of each process and follow the rules to achieve the goals of shortest process route, lowest material energy consumption and best product quality.
(2) Improve the management system and implement the environmental responsibility system. Formulate clean production, energy conservation and emission reduction management systems, support reward and punishment measures, refine the post responsibility system for water and steam stoppage, implement the environmental responsibility system of individuals, teams and departments, check the implementation from time to time, and realize efficient management through process monitoring.
(3) Strengthen production management and improve the first-time qualification rate of products. The production department should maintain the dyeing and finishing equipment in time to ensure good operation and reduce the product repair rate. In addition to self-checking the production process of the car stopper, professionals regularly check the running status of the equipment, and timely clean, maintain and rectify it to prevent running, running, dripping and leaking.
(4) Strengthen education and training, and improve the awareness and skill level of emission reduction of all employees. Post technical training and education on cleaner production, energy saving and emission reduction were given to employees, so as to improve the skill level of operators, reduce sample copying and operation errors, and achieve a success. Enhance employees' environmental awareness and social responsibility through training.
4 outlook
From 2007 to 2009, China Printing and Dyeing Industry Association issued 9 1 recommendations on advanced technologies for energy saving and emission reduction, mainly involving new technologies and equipment for dyeing and finishing, new fiber processing technology, wastewater recycling technology, printing and dyeing waste recycling technology, online product detection and control technology, and new efficient dye auxiliaries technology, which provided demonstration projects for enterprises to realize energy saving and emission reduction. It can be seen that the current printing and dyeing enterprises not only lack technology, but also lack technical preparation and safeguard measures for the popularization and application of new technologies. Pay equal attention to connotation and extension, and boldly tap the transformation potential from the source of raw materials, technology and equipment. At the same time, through product structure adjustment, production process control, refined management and comprehensive management, energy conservation and emission reduction measures are effectively implemented. Make low bath ratio dyeing, waterless printing and dyeing, zero pollution and other technologies settle in enterprises as soon as possible, change the traditional printing and dyeing production mode with high energy consumption, high pollution and wet processing, and break through the "bottleneck" that restricts the development of enterprises in the industry.
refer to
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[3] Innovative breakthrough in continuous printing and dyeing of modified pigments [EB/OL]. https://www.ellipsis/tech/ 16756 _ 1 . html，2009？ 09 ? 2 1.
[4] Fan Aimin. Fine management [M]. Beijing: China Textile Press, 2005.
[5] China Printing and Dyeing Industry Association issued the first batch of recommended catalogue of advanced technologies for energy saving and emission reduction [EB/OL]. https://www.ellipsis/BBS/default.asp. .