Cleaner production practices in the coating industry

0 Introduction:
coatings are widely used in automobiles, home appliances, hard metal, building materials, oil pipeline surface coating. As an important part of the national economy, the coatings industry is affected by the demand from both downstream industries and civilian industries, and is currently growing at an average annual rate of 10%. Paint production is expected to reach 12.3 million t in 2015,
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. In 2009, China has overtaken the United States to become a large paint country, huge production and rapid growth so that the paint industry has become a "emission big household", from the "three waste" alone, the paint industry clean production audit is imperative.1 Definition of cleaner production
Cleaner production refers to the continuous adoption of improved design, the use of clean energy and raw materials, the use of advanced technology and equipment, improved management, comprehensive utilization and other measures to reduce pollution from the source, improve the efficiency of resource utilization, reduce or avoid the production services and products in the use of pollutants and emissions, in order to reduce or eliminate harm to human health and the environment.2 Paint industry clean production status
paint industry clean production includes many ways, but also a long-term goal, only the cooperation of large and medium-sized enterprises can not achieve the desired effect, many small factories on clean production is not active, and in terms of capital, technology will also have corresponding problems. In order to cooperate with cleaner production, the state has introduced measures to ensure the smooth progress of clean production. Global economic integration and modern industrial production put forward higher requirements for clean production in China's coatings industry. For this reason, the state has issued laws and regulations on clean production, as well as laws and regulations supporting the technical standards, in order to standardize the paint industry to implement clean production has played an important role.3 Analysis of clean production potential in the coatings
3. 1 Primary auxiliary materials and energy
3. 1. 1 Raw auxiliary material consumption
the main raw material consumed in the production of coatings is polyester resin. In order to produce coatings that meet the standard requirements and obtain good economic and technical indicators, all raw materials must meet certain quality requirements. Polyester resin coating is a coating with polyester resin as the main film-forming substance. It is made up of polyols and polyic acids. The difference with polyurethane coatings is that polyester coatings do not contain ammonia "-NH-" in their molecules. Polyester resin coatings are widely used in medium and high-grade coatings, low-polluting high-solid powder, powder coatings. The most commonly used saturated polyester resin in the coating industry is a polyester resin containing hydroxyl energy group, which is cured into a film by interlinking with isocyanate, ammonia resin and other resins. It is characterized by high gloss, good plumpness, high hardness, good flexibility, good wear and heat resistance, good light preservation and color preservation. It is advisable to do wet and hot motor paint coating (155, 180 grade), impregnated insulation paint, metal primer, automotive midway and high-grade industrial coatings and varnishes, outdoor high decorative coatings and so on.
3. 1. 2 Equipment and energy consumption
production of coatings of power consumption equipment including micro-powder machine, high-speed mixer, twin screw extruder, air compressor, electric hoist, circulating water pump and so on. The main power consumption equipment is micro-powder machine, high-speed mixer and twin screw extruder, accounting for about 80% of the total power consumption in workshop production. Paint production industry is a high energy consumption industry, but also the most energy-saving potential industry. Saving energy and improving energy efficiency is one of the goals of clean production.
3. 2 Technical process aspects
coating production technology process is divided into 8 parts: 1) sampling: according to customer requirements formula production samples, testing qualified after production; 2) ingredients: according to the formula to take raw materials, confirm accuracy after input mixer; 3) Mix and stir: Stir 3 min with 500 r/min and release; 4) Feed extruse: turn on the warm-up to 200 degrees C, start extrusing; 5) Press: tablet machine out of the film, the thickness is suitable; 6) Crushing: after drying by drying the main line into the crusher crushing, into the collection room recycling packaging; 7) Packaging: internal plastic bag packaging, outer carton packaging; 8) Storage (delivery): after packaging sampling, after passing the storage, in accordance with the order arrangements for delivery.
3. 3 Waste
dust from coating companies is mixed dust, which is toxic due to its different chemical composition and can lead to mixed dust lung and occupational poisoning. In the process of coating production process mixing and mixing stage, will produce a large amount of dust, not only caused a large number of raw auxiliary materials waste, but also the dust produced by the inhalation of employees, will cause great harm to the human body. Therefore, employees should wear dust masks on their protection. The waste rate of materials lost in the production process is 0. 3%。 Ingredients, cans, stirring when the splash mainly because dust in the stirring process will have splashes, can be stirred by the mixing bucket cover, which can reduce the volatile dust and strengthen the management of employees, reduce the loss of human error.
3. 4 Environmental management and staff quality
It is an important guarantee for the sustainable development of enterprises to continuously strengthen environmental management, improve the quality and professional skills of employees, strengthen the awareness of environmental protection and energy conservation, and establish and improve the energy management system of enterprises. The environmental awareness and level of environmental protection of enterprises have become the symbol of the management ability and management level of enterprises.4 Examples of clean production audit of a coating enterprise
4. 1 Enterprise profile and problems
A paint enterprise mainly produces epoxy/polyester, pure epoxy, pure polyester three types of powder coatings with light, semi-light, lightless, stripes and other color varieties, design annual production capacity of 2,000 t. Powder coating is a variety of different resins, pigments, fillers, etc. in accordance with the formula after mixing after stirring, extrusion, pressure sheet, crushed powder-like paint, when used by heating curing on the product surface, product gloss, hardness, weather resistance, etc. are higher than solvent-based coatings. The production process is shown in Figure 1.
1) The raw materials used in the production of powder coatings are mainly resins, fillers, pigments and additives. When the raw auxiliary materials are stacked, there is a certain amount of loss and waste; There is also a certain loss of hanging bags. And in the process of use, the lack of necessary management and control procedures, waste scattered phenomenon is serious.
2) The main energy consumption of enterprises is electricity. The main high-power energy consumption equipment has micro-powder machine, twin screw extruder, high-speed mixer and so on. Enterprises use more high-power equipment, some motors did not carry out frequency-changing process upgrade; Some of the equipment exists "big horse cart" phenomenon, resulting in unnecessary waste of power resources. The maintenance and maintenance of the equipment is not perfect, the motor noise is large.
3) The mixed mixing and crushing process in the production process of an enterprise produces a large amount of dust, resulting in a large amount of dust floating in the production workshop, resulting in poor working environment and hygiene. All kinds of machinery and equipment in the production workshop produce great noise, which causes harm to the health of the workers, and it is recommended to adopt protective measures or equipment.
4) Enterprise process control manual control accounts for a large proportion, lack of automatic control, measurement detection and analysis instruments are incomplete, monitoring data is less, can not achieve optimal control.
5) Employees' awareness of energy conservation is weak, invisibly resulting in energy waste, and employees' awareness of cleaner production needs to be improved and strengthened, and the importance and necessity of cleaner production have not yet been fully understood. There is insufficient understanding of the link between cleaner production and daily work, and there is a lack of initiative to strictly implement the clean production strategy in daily work.
4. 2 Identification of cleaner production programmes
On the basis of on-site research and preliminary understanding of the enterprise situation, using a simple comparison method and discussing with experts to determine the audit focus on unit product power consumption, consumption of raw materials per unit of products and dust content in exhaust gases, by comparing the evaluation benchmarks in the Clean Production Evaluation Index System (Trial) promulgated by the National Development and Reform Commission, identifying problems and gaps, and setting clean production targets accordingly, as shown in Table 1.
4. 2. 1 No/ low-cost scheme
through enterprise research and production site inspection, closely around raw materials, equipment, process control, waste generation and reuse, operation and management, etc., with targeted, operability, less money, high results and so on, in the pre-assessment phase put forward 19 clean production no low-cost program. These programs are basically put forward by the production front-line personnel, fully reflect the actual situation in production, are urgent problems to be solved. The implementation of these programs has obviously improved the production level and management level of enterprises, while bringing obvious economic, environmental and social benefits to enterprises.
4. 2. 2 The material balance of the medium/high-cost scheme
the production workshop of the powder coating is shown in Figure 2. As can be seen from Figure 2: the loss is greater each time the feed is produced, accounting for about 0. 6%。 The dust starting rate of dust is about 2% each time it is threw, which not only causes environmental pollution and economic losses, but also wastes energy and resources. Therefore, by installing bag dust removers, shop floor workers can be guaranteed to produce in a reasonable environment, thereby improving productivity, energy conservation and resource utilization.
of an enterprise paint production mainly for cold processing, no thermal reaction process, all the use of electrical equipment. Through the analysis of the power consumption of the enterprise's production of electrical equipment (see Table 2), combined with on-site inspection, it can be seen that the equipment with large power consumption has twin screw extruders, high-speed mixers and micro-powder machines, etc. (Table 3). Of these, 4 twin screw extruders consume 29% of the electricity, 3 micro-powder machines consume 27% of the electricity, and 3 high-speed mixers consume 25%. The main power-consuming equipment in the workshop exists in the "big horse cart" phenomenon, which needs to be converted frequency, therefore, the power cleaning production potential here is greater, the economic benefits of energy-saving transformation will be greater.
The recommendations for the use of the two medium/high-cost schemes are as follows:
1) GF1 installation drive: installing a variable frequency regulator can adjust the speed of the motor according to the needs of the system, eliminate energy saving losses, save energy, improve the operating efficiency and reliability of the equipment. At present, variable frequency speed control device has been widely used in motors, wind turbines and other electrical equipment on energy conservation. Through the statistics on the technical parameters of each equipment operation record on each production line of an enterprise, and the observation of the production process on the spot, it is found that the load of the micro-powder machine fluctuates greatly, and the adjustment of the twin screw extruder is not reasonable enough, so that the actual operating efficiency of the equipment is lower than the design efficiency. It is suggested that enterprises should install variable frequency speed control devices for electric equipments with large power consumption (micro-powder machines, high-speed mixers, twin screw extruders, etc.) to achieve automatic control, so as to help rationally adjust the use of power of each electric equipment, improve production conditions and improve the actual efficiency of electrical equipment. After actual testing, the power saving rate of the micro-powder machine is 35%. A 30 kW.h micro-powder machine with a load of 50% and a daily operation of 24 h, 350 d is expected to invest about 2. 40,000 yuan (inverter unit price of 0.24 million yuan, quantity 10), after the transformation of the annual power saving of about 2. 20,000 kW.h, annual savings of about 2. 090,000 yuan.
2) GF2 bag dust remover: In the process of mixing and producing crushing, an enterprise will produce a large amount of dust, not only caused a large amount of waste of raw materials, but also the dust produced by employees inhalation, will cause great harm to the human body. Bag dust remover dust removal efficiency is high, the range of wind treatment, simple structure, the same high dust removal efficiency, low cost, high temperature resistance, the characteristics of dust insensitive, not affected by dust and resistance and other advantages, it is recommended that an enterprise for mixed mixing and crushing process to install bag dust remover, reduce the dust content of the workshop, and will collect dust back. The total investment of the equipment is expected to be $40,000. Dust collected through the bag dust remover can be reapplyed to production after simple treatment, saving about 10,000 yuan per year on raw auxiliary materials.
4. 3 Benefit analysis
this round of clean production audit, a total of 21 clean production programs, all implemented. The company invested a total of 16. 70,000 yuan, bringing economic benefits 41. 40,000 yuan. Of these, 19 were no/low-cost schemes, with investment of 10. 30,000 yuan, economic benefits 38. 20,000 yuan; Medium / High Cost Scheme 2, Invested 6. 40,000 yuan, bringing economic benefits 3. 20,000 yuan. After all 21 programs have been implemented, enterprises can reduce energy 2. 40,000 kW.h / a, or 2. 95 t/a, CO2 emission reduction 7. 86 t/a. Save 4 t/a of raw materials while reducing shop floor dust content and improving the working environment for workers.
through the current round of clean production audit, before and after the enterprise audit indicators compared to Table 4. Comprehensive Table 4: This round of clean production audit has completed the clean production targets set at the beginning of the audit.
5 Conclusion
A coating enterprise has carried out clean production audit work around raw materials and energy, technology, equipment, process control, products, waste, management and staff quality, and promoted the realization of the goal of "energy saving, consumption reduction, pollution reduction and efficiency", so that the environmental and economic benefits of enterprises have reached a new level. With "clean production always only starting point, no end point" as the guiding ideology, the enterprise is now aiming at the advanced level at home and abroad to find gaps, hoping to continue to implement cleaner production to get faster and better development.