Optimizing beating and grinding to improve the fib

Abstract: Based on the beating practice of Yinge special paper company in the production of carbon free carbon copy base paper, this paper introduces the joint exploration with Nantong Huayan grinding Research Center, through the research and optimization of the tooth shape, material and fast-growing broad-leaved wood fiber of the imported double disc refiner grinding plate, to improve the beating efficiency and quality, and extend the full cycle service life of the grinding plate, This paper introduces the idea and practice process of optimizing the tooth shape of grinding plate to improve the quality of hardwood pulp and paper, and simultaneously reduce the loss cost

key words: beating and grinding tablets; Wet weight; Tooth shape optimization; Separate wire brooming; Beating unit consumption

in the beating process of using double disc mill to treat fast-growing hardwood pulp, how to effectively retain the wet weight of short fiber hardwood pulp and improve the bonding strength between fibers and the physical strength of paper often puzzles the beating section. Grinding disc is the core component that directly performs multiple functions on fiber raw materials when the pulper is beating. Grinding disc plays a key role in affecting the quality of beating. This paper briefly introduces the practice of optimizing the tooth shape of grinding plate and improving the beating of hardwood pulp, which is only for the exchange and reference in the industry

Yinge special paper company uses imported coniferous wood pulp and some domestic fast-growing broad-leaved wood pulp to produce carbon free copy base paper. In 2007, it introduced Austrian Andritz and Japanese Aikawa double disc refiners to treat broad-leaved wood pulp. Report printing of universal experimental machine: 26 inch imported original grinding discs are randomly equipped. Both kinds of refiners have high beating efficiency. During the test, the tooth shape of the original imported grinding discs has been adjusted for many times, Failed to meet the beating degree, wet weight and other process indicators. Therefore, since the end of 2007, we have started research and Optimization Practice on how to improve the grinding index, improve the paper quality, and simultaneously reduce the power consumption of beating and the cost of grinding disc loss. In 2008, gratifying achievements were made in the research on the tooth shape and materials that replace imported grinding discs to meet the needs of the changes in beating process. In 2009, we made unremitting exploration on optimizing the beating process and improving the quality of hardwood pulp and paper

1. Optimize beating and grinding tablets for pulp species

in practice, it is found that good physical strength can be obtained when broad-leaved wood pulp has beating degree compared with coniferous wood pulp, and the fiber of fast-growing broad-leaved wood pulp is shorter, generally 0 0 mm, the fiber is thick, the length width ratio is small, its cell wall is thick, the cell cavity is small, and the wall cavity ratio is large. The fiber is not easy to collapse and deform. If the beating treatment is not good, it will affect the physical strength index of the paper. The advantages of using hardwood pulp are good paper evenness and better loose thickness. In production, we should not only improve the beating degree, but also try to avoid cutting too many fibers. Therefore, we need to design a new grinding disc suitable for beating short fibers. In view of the complexity and variability of the force on the slurry in the grinding area, we fully study the beating mechanism of the disc mill and apply the two theories of "specific knife edge load" and "specific surface load" to the design of the grinding disc. We used modern computing software and m, and dropped out of school after 6 months to create the "ocean clearing" company astericam 3D design and production system, which makes the calculation and design process of grinding disc intuitive and convenient. (see Figure 1)

2. Grinding blade tooth shape optimization process

according to the characteristics of different hardwood pulp species and the characteristics of silver pigeon special paper process line, we have optimized the grinding blade tooth shape twice. The width, groove depth, and inclination distribution of the grinding teeth, the taper of the coarse grinding area, the partition ratio and inclination of the crushing area and the fine grinding area are the keys to the tooth shape design. We have successively used and compared a variety of imported foreign grinding discs, carefully analyzed them under different process conditions, and studied the optimization parameters. The grinding plate tooth shapes of Andritz in Austria, Aikawa in Japan and Huayan in Nantong were compared to ensure that there are many choices and comparability for the optimization of grinding plate tooth shape in the development of silver dove special paper production line. A variety of optimized grinding plate tooth shape drawings were designed successively, and the grinding plate tooth shape suitable for specific process indicators was designed from the optimization of beating strength

2.1 tooth groove width ratio

beating occurs through the repeated impact, extrusion and release of fibers by grinding teeth. Relatively speaking, the more the number of teeth of the grinding disc and the longer the length of the tooth edge, the more the fibers are squeezed and released in unit time, but the force of the tooth surface area can not be ignored. Based on this, we introduce the theory of "effective edge angle load" and integrate the concept of "effective surface load". In the series beating process of two imported 26 double disc mills, in view of the narrow teeth and wide groove of the original imported mill, too much fiber was cut during the beating process, and the brooming rate was insufficient, we reasonably adjusted the tooth groove width ratio through calculation. (see Table 1)

2.2 tooth height

in the grinding process, the grinding teeth should bear the impact friction load. For the consideration of mechanical strength and service life, the tooth height is generally limited to 1 ~ 2 times the tooth width. The tooth height is too high, and the pulp fiber is not easy to exchange on the tooth groove and tooth surface, and the fiber tends to flow away directly without beating. When the tooth height is appropriate, the fibers in the tooth groove and tooth surface are easy to exchange, and the tendency of fibers to be beaten is enhanced. However, the tooth height is too low and the service life is short, which is not economical. The tooth height of 7mm is selected for the tooth profile of the grinding disc optimized twice. (see Table 1)

2.3 tooth inclination angle

tooth inclination angle refers to the included angle between the cutter teeth and the radius. The inclination angle has a great impact on the pumping effect of the disc mill. When the tooth angle increases, the cutter teeth on the ring of a certain specification increase correspondingly, the beating effect increases, and there is a tendency to inhibit cutting. In order to suppress the cutting effect of short fiber beating, we optimized the inclination angle twice (see Table 1), effectively improved the beating quality, synchronously increased the throughput, effectively improved the production efficiency and reduced the beating power consumption. (see Fig. 3 and Fig. 4)

2.4 gear block dam

the centrifugal force generated by the high-speed rotation of the disc grinding plate of double disc grinding and the pressure applied by the slurry supply system are easy to throw the slurry out of the groove of the disc teeth without sufficient beating, resulting in uneven beating. In order to prolong the residence time of the slurry in the disc mill and improve the beating degree, a dam is usually set in the groove of the disc teeth (see Figure 2), especially under low concentration beating, which is more important, but the efficiency of grinding will be affected after the groove of the grinding plate is closed. Therefore, the design concept of arc teeth with strong pump output and large flow plus arc semi closed slurry stop is adopted in the second optimization. (see Figure 3)

2.5 material of grinding disc

in the beating of short fibers such as tobacco flakes and straw pulp, some manufacturers use grinding discs with rough surfaces, and the coarse particles on the grinding surface can improve the fiber brooming rate. In view of the need to maintain the wet weight of hardwood pulp fiber as much as possible and improve the effect of wire splitting brooming, we jointly developed and optimized new tooth shape to weaken the cutting force, and confirmed that the multi-element alloy material with coarse particles on the surface of Nantong Huayan Casting Co., Ltd. was used. The friction in the beating process promoted the fiber's wire splitting and binding force, and the multi-element alloy grinding plate was specially treated to eliminate the problems restricting production such as broken teeth and non wear resistance, The service life of the grinding disc is greatly improved (see Table 2), the probability of replacing the grinding disc during shutdown is reduced, a good foundation is laid for ensuring the normal operation of each section of papermaking, and the expenditure cost of vulnerable parts is reduced

3. Before the optimization, but the high-end products are blank. Compared with the 26 inch imported grinding disc used before the optimization,

during the production process, in order to meet the requirements for the degree of pulping and beating, the pulping power must be increased, resulting in excessive pulping, a large number of fiber cuts, basically no wire splitting and brooming, and poor pulping quality. (see Table 3) the fluctuation of grinding clearance is also large, which increases the possibility of direct collision of grinding discs and reduces the service life of grinding discs

in 2007, silver pigeon special paper began to cooperate with Nantong Huayan grinding research center to optimize the tooth shape of grinding plates. In view of the above problems, after many on-site technical exchanges between the two sides, the specific working conditions and process requirements were analyzed, the modification scheme of the grinding disc was demonstrated, and a new type of toothed grinding disc made of multi alloy material was designed and developed. (see Fig. 3 and Fig. 4)

the beating section is the main power consumption of paper enterprises. By optimizing the tooth shape of the grinding disc and paying attention to the optimization of the material during the selection, the beating current and power consumption are reduced, and the fiber is cut from excessive cutting, basically no wire splitting brooming, and the fiber surface fuzzing phenomenon is increased. On the premise of improving the beating degree without consuming more power consumption, the fiber wire splitting brooming is further strengthened. (see Table 3)

4. Summary

through the research on the fiber structure of fast-growing hardwood pulp, the analysis of beating mechanism, and the substantive adjustment of the tooth shape of the grinding disc and the confirmation of the effect, it has fully confirmed the non isolation of the specific knife edge load theory and its correlation with the specific grinding energy (SRE), carried out a case analysis on improving the wet weight and brooming rate of short fiber pulp, and also provided a theoretical basis for the localization of imported double disc grinding discs, The optimization theory of grinding components is applied to practical production, which not only reduces power consumption, but also improves the fiber quality of hardwood pulp, beating efficiency, grinding disc life and physical indexes of paper

author unit:

1. Wang Qifeng Huang Suo xinluohe Silver Pigeon Special Paper Co., Ltd., Luohe, Henan, 462000

2. Jiang Xiaojun, Nantong Huayan grinding Research Center, Nantong, Jiangsu, 226403 (end)