The application of powder dosing weighing system in the production of water-based coatings

0 Foreword
at present, the domestic paint production to use a large number of powders, accounting for about 30% to 40% of its raw materials, and varieties. So much powder in the production process of artificial feeding labor intensity, will produce a large amount of dust, flying dust on the health of workers is extremely harmful, and pollution of other products being produced and packaged, directly affect product quality, but also cause environmental pollution. Now, on the one hand, with the development of economy, the improvement of the comprehensive quality of the whole people, workers' health consciousness gradually improves, workers are more inclined to choose low labor intensity and health and environmental protection in the choice of work, for some high labor intensity production and manufacturing enterprises, gradually facing the problem of labor difficulties; On the other hand, with the implementation of the national "12th Five-Year Plan", for paint manufacturers to put forward higher energy conservation and environmental protection requirements, at the same time, the fully closed integrated coating manufacturing process as the "12th Five-Year Plan
environmental protection planning objectives
. The gradual use of automated production instead of manual operation has become a new trend in the development of the coating industry.1 The introduction of weighing ingredients conveying system
in order to ensure product quality, reduce labor intensity, improve the field working environment, improve the company's image, all paint manufacturers are trying to improve the conditions of the production workshop, try their best to solve the serious dust pollution from the production environment, workers labor intensity and other problems. With the development of pipeline pneumo transmission technology, it has completely solved the problems of powder storage, dusting and product pollution, and is widely used in rubber tires, ink, chemical industry, electric power, food, medicine and other industries, but rarely used in the coating industry. When Jiabao Chemical Group Co., Ltd. prepared to invest in the construction of the new plant in Shanghai, taking into account the factors of product quality, production efficiency, labor costs and production environment, it decided to adopt a new closed integrated production process, the production of latex paint in the new plant in Shanghai as a pilot project. Combined with the current domestic and foreign paint production situation, after many inspections, decided to use a pneumopower conveyor system combined with weighing process to achieve automatic ingredients of powder.
1.1 system principle introduction
the air force conveyor is divided into suction type and pressure delivery type two kinds. The suction type uses a Roz fan or vacuum pump as a gas source equipment, the gas source equipment is installed at the end of the system, when the fan is running, the whole system forms a negative pressure, there is pressure difference air inside and outside the pipe is sucked into the conveyor pipe, while the material and part of the air are inhaled at the same time, and is transported to the separator. In the separator, the material is separated from the air. The pressure feed type is the use of Roz fan or air compressor as the gas source equipment, and the gas source equipment is arranged in the front end of the system, more suitable for dispersion from one place to several places, as well as long-distance, high-capacity transport. Figure 1.the
pressure delivery device indicates
1.2 system characteristics
the conveying principle and application practice from the pneumoconic transport show that it has a series of advantages:
(1) transmission efficiency is high, the conveyor pipeline can be flexibly arranged, so that the plant equipment process configuration is reasonable;
(2) to achieve bulk transport, high efficiency, reduce packaging and handling transport costs;
(3) system closed, dust flying out less, good sanitation conditions,
(4) less moving parts, easy maintenance, easy to achieve automation;
(5) ensures the quality of the conveyed material by avoiding moisture, defacation or mixing with other debris,
(6) can be transported from a concentration of points to one place or by a dispersed location over a distance, and
(7) can be transported by inert pneumatic force for materials with unstable chemical properties.
can be combined with the production process when used for internal conveying on the factory floor, which helps to simplify the process and equipment. In addition, automatic ingredients system can reduce the labor intensity of workers, reduce workers misoperation, high ingredient accuracy, high product stability, product quality is easier to control.
1.3 System Configuration
According to the annual production capacity of the Shanghai plant of 80,000t and the equipment configuration conditions of 5 dispersed cylinders from 3 to 10 m3, after the production capacity and production cycle, the time series of the demand for powder supply of multiple dispersed cylinders and the calculation of the energy consumption of the whole system, it was decided to use the positive pressure and dense phase of the air compressor as the power source to achieve a set of weighing devices to supply 5 dispersed cylinders of powder. The overall configuration of the design system is shown in Figure 2.The overall configuration of the
meter system
1.3.1 process introduction
through manual unpacking of small packaging, tons of bag packaging raw materials in the unpacking station 1 for unpacking, double pressure delivery tank 2 alternate pressure to feed raw materials into 100 m3 storage in the large storage warehouse 4. Can also be through the raw material tank car 3 directly to the transmission line 5, the raw material pressure to the large storage warehouse. Materials in large storage tanks, in accordance with the requirements of the process formula set in the system for automatic weighing, 3 large storage tanks corresponding to 1 pressure delivery scale 6, 2 pressure delivery scale alternate weighing and delivery. Weighed material is transported to buffer tank 7 and the total weight of a single batch of material is checked in the buffer tank. The material in the buffer tank is fed into the dispersion cylinder 8 at a uniform speed set by the system. The system's secondary conveyor line is separately equipped with a uncontracted station 9, pressure delivery tank 10, can achieve the large storage of raw materials other than the type of raw materials, there is a certain degree of flexibility. The system has an efficient dust filtration device 11 at the disinfase feed position and the end of the pneumon transport to prevent dust leakage from polluting the environment.
1.3.2 System Parameters
The production cycle of the five dispersed cylinders is calculated in accordance with 2 h/lot, and the amount of powder used is calculated at 65%, the system design capacity is: 20 t/h for first-stage pneumotrate and 12 t/h for secondary weighing and conveying capacity. According to the production process requirements of the coating, the static weighing accuracy of the system is less than 0.5%, and the dispersion cylinder feeding error is less than 1%.
1.3.3 Technical difficulties
Through the investigation of the current production situation of the coating industry and the material analysis of raw materials, it is found that one of the bottlenecks restricting the promotion of automatic ingredient systems in the coating industry is the treatment of viscous powders. Because of the small particle size of titanium dioxide, strong adhesion, in the process of transport is likely to cause the blockage of pipes, titanium white powder delivery has been an urgent need to solve a major problem at home and abroad. In view of the difficult problem of viscous powder treatment in the coating industry, combined with many years of experience in powder batching and patented technology, the key equipment of the system for special treatment, pneumo transmission pipeline install pressure sensors in stages, through real-time monitoring of pipeline pressure to open auxiliary pipe valve refringing, not only to avoid line blockage and minimize energy consumption, and can do the system with the start, reduce equipment maintenance. After the actual use of equipment in production, it is verified that the application of these technologies can solve the problem of adhesion and arching of the conveyor pipe in the automatic dosing system of viscous materials such as titanium dioxide, as well as the adhesion and arching of containers.2 Effect of use of weighing ingredient conveyor system
2.1 Comparison of on-site management and operation before and after use of the system (see Table 1)
Comparison of on-site management and operation of the system before and after use
2.2 Analysis of production capacity
Through on-site measured data analysis (see Figure 3), the first-stage pneumodilability can reach 28 t/h, the secondary weighing capacity, pneumodilability can reach 14t/h, exceeding the design capacity, fully able to meet the current production needs.
Field measured data
2.3 part of the investment efficiency analysis
2.3.1 energy saving
according to the annual output of 80,000 t production capacity calculation, after the use of the system each production time can be saved 30% to 50% (including ingredients, feeding time), electricity consumption should be relatively saving 20% to 30%, improve production efficiency.
2.3.2 Environmental protection
system before use, powder feed is basically open feeding, powder flying around, for the workshop environment, workers' health has a great impact; Workers need to clean up the site after the project is completed, which can affect both labor costs and productivity. After the use of the system, with an annual output of 80,000 t production capacity calculation, can save the waste of raw materials at least 3 t/a, the entire production process from unpackased materials to raw materials into the dispersion cylinder is a closed environment, to avoid dust, to improve the working environment of workers, reduce the occurrence of occupational diseases played an important role.
2.3.3 Warehouse utilization rate
production of about 30,000 t paint production enterprises, powder raw materials accounted for about 1,095.5 m2 /month, the use of large storage warehouse storage materials, can save the warehouse floor space, improve the overall turnover of raw materials, improve the utilization rate of the warehouse.
2.3.4 Labor cost
system before use, to an annual output of 80,000 t paint production enterprises, for example, generally need more than 4 people to complete the pollination work, long feeding time, labor intensity. After the use of the system, only 1 person is responsible for the unwring of raw materials and the operation of the central control room. Some powder can be transported directly to the large storage warehouse using the tank car, saving the transportation and management cost of manual loading and unloading, warehouse to workshop. Compared to the system before use, at least 2 to 3 people can be saved to complete the production work.
2.3.5 Other aspects of the
system after use, the degree of production automation significantly improved, production data traceability, ingredients more accurate, product quality and stability significantly improved, equipment operation, maintenance convenience, low failure rate.3 Conclusion
Powder ingredient delivery weighing system has been successfully running for nearly 1 a time, after continuous follow-up research shows that the system can reduce the labor intensity of workers, improve the working environment, improve production efficiency, improve product quality, energy saving and environmental protection, improve the level of automation of paint production, help promote the progress of paint production and automation process.