Process optimization method for prolonging the life of refiner plate

Grinding plates are the "heart" consumable part of the refiner used for fiber cutting and separation in the pulp and paper industry. The status of use of grinding discs and the process life time play a decisive role in refining production, energy consumption, safe operation of refiners and various economic indicators. How to use suitable grinding discs for specific production to achieve optimal results has always been the focus of research and development in this field. How to prolong the life of the grinding plate in the refining process is worth exploring.

1 Effect of disc wear on production

Poor quality of pulping and declining production capacity during the pulping process may be caused by abrasive wear. Choosing the best timing for replacement is an important technical issue in production.

The damage of the second disc mill (produced by Kaverner Hymac) used in the 75 t/d chemical pulp production line of a paper mill in Lanzhou, Yunnan, caused the pulping and beating degree to be only 20°SR. Up to 2%, the surface strength of LWC paper produced by copying is slightly lower.

The former Shanghai Paper Machinery Plant 2362 paper machine of Mudanjiang Hengfeng Paper Group Co., Ltd. was put into production in 1992 and can only produce mid-range cigarette paper with an air permeability of around 30coresta. The plant purchases poplar, eucalyptus, birch, forging wood, etc., and has many types of refining. The beating equipment is easy to wear, and the grinding tooth profile and material are not stable. The pulp quality cannot produce high-grade cigarette paper.

The "white spots" on the tracing paper are fine fibers, resin blocks, or a combination of the two, sometimes appearing in full width, especially prominent. Minfeng Special Paper Co., Ltd. found that: when disc grinding discs are used for too long, the infeed volume is increased, the spacing between the blades is reduced, the defiberizing effect is weakened, the cutting effect is strengthened, fine fibers are increased, and the abrasive discs should be replaced regularly. .

The practice of Qiqihar Paper Co., Ltd. introducing the 200t/d all poplar APMP production line of ANDRITZ to produce low-volume offset newsprint shows that instead of poplar, birch and other fiber types are not as good as poplar and it is more important to control the beating process; the life of the grinding plate is about 2500 hours. The longer the grinding time is, the lower the beating degree, the passivation of the tooth surface, the weakening of the slurry cutting ability, the degree of beating of the slurry is decreased, the acceleration of the grinding process is high, the wear of the grinding teeth is serious, and the degree of beating It cannot be mentioned and the slurry cannot smoothly pass through the plate, resulting in plugging of the feeding screw.

The grinding discs of MRZ 58/62 (made by Andritz Spraut Bauer) of Qiqihar Paper Co., Ltd. have two refining zones: one is the broken ring zone, and the broken ring zone of the grinding disc consists of 6 teeth. Composition, material 174PH, large tooth dams, large distance between teeth; one for the grinding ring area, composed of 18 teeth, material for the alloy 440, moderate density of the dam, the middle distance is small; disc grinding and fixed disc grinding Between 0.9 and 1.1mm gaps between the sheets. Among them, the concentration of the grinding slurry entering a stage of grinding is controlled at 28% to 35%, the degree of beating in the second stage disc refining is approximately 17°SR, and the concentration is controlled at 22% to 25%; In order to ensure the quality of the slurry, the beating concentration of the disc mill must be reduced. In the crushing zone, the grinding teeth are damaged or blocked by the tooth groove, and the grinding disc wears badly. If the grinding ability is reduced by 30%, the grinding disc must be replaced.

2 Process methods and measures to improve the service life of the grinding plate

2.1 Improve the precision and control of the refiner

Heilongjiang Stare Paper Co., Ltd. φ450 double disc mill, due to too long, the chassis inside the static disc at the moving plate and the moving plate at the corrosion, wear a difference of 3 ~ 4mm, φ410 straight port at the wear increased to φ420 or so, fixed The wear and corrosion of the screw hole of the grinding plate becomes large and a horn type appears, resulting in that the grinding plate cannot fit well with the body. The erosive surface of the moving seat and the inner plane of the housing is about 3~4mm, and then the straight mouth platform is used; the screw hole is drilled to a depth and changed to M14, and the bolts and pads are used for sealing and fastening, and the use effect is equivalent. Replacement of new parts saved spare parts funds.

The structure of the grinding plate, tooth profile, tooth surface inclination and inclination have a direct impact on the safe operation and pulp quality of the equipment. Fine-tooth pulping has a lower beating strength; fine-tooth pulping increases the uniformity of the fiber treatment, maintains the fiber length, more quickly hydrates the fiber cell walls, and promotes better fiber binding. The high beating strength increases the cutting of the fibers, and tends to produce more fine fibers. At the same tensile index, the fine tooth slurry has high opacity, bulk and breathability; the hardwood pulp is used for fine tooth grinding. The film can not only save energy consumption, but also reflect its high permeability and opacity, but also take into account the strength of the fiber. The fine-toothed grinding discs are suitable for beating pulp and non-wood fiber. The fine-toothed grinding discs are not casted but are welded by special methods. The service life is 3 to 4 times that of ordinary cast irons. The grinding lamella is designed with a certain degree of inclination to avoid a sudden increase in mechanical energy and localized wear of the tooth flanks. If the inclination is too small, the feeding resistance will increase, causing the feeding load to increase. If the slope is large, it will cause uneven wear and affect the life of the grinding plate.

Zhenjiang Dadong Paper Co., Ltd. of Jiangsu Province and Jilin Chengxin Industrial Co., Ltd. developed fine-tooth grinding plates for low-strength beating of fluff pulp. After more than one year of application, it was shown that low-strength beating must be performed with improved knife-rods. Width 2.47mm, knife groove width 2.47mm, knife groove depth 6mm. The grinding material is still made of nickel alloy. In a low-strength fluff pulp line made of cultural paper, the operating conditions are not adjusted, the fiber is rarely cut off, and the splitting is better; the average power consumption of the ton pulp is 173~ The 168 kWh was reduced to 158-146 kWh; the splitting length of the paper was increased from 5632 m to 6546 m, and the folding endurance increased from 26 to 48.

The slope of the high-strength plate crushing zone of the disc refiner of Andritz Sprort Bauer used in the Italian poplar APMP production line is approximately 1:11, the loading load is relatively stable, and the grinding power is stable when the rough grinding zone slope is 1:250. Feeding screw running smoothly, high degree of pulping and beating, wet weight at a good level, long life of the grinding plate, uniform wear of the rack in the longitudinal direction, energy consumption distribution balance; the slope of the refining zone is generally suitable for 1:800 .
Shandong Huatai Paper Group introduced Andritz's stock preparation system and Metso's annual production capacity of 100,000 tons of hardwood BCTMP production lines. The pulp was used for copying high brightness newsprint paper, light rubber paper, and SC paper. A conical grinding machine RGP-82D (φ2000) with a concentration of 45% has a disc gap control system in the inner and outer conical refining zones. The TDC (real disc gap) unit automatically retracts the disc. In order to prevent the disc from direct collision and cause wear. A section of the CD-82 disc mill motor in the production line considers the positive and negative reserves on the configuration and control, so as to adapt to the positive and negative use of the disc grinding machine to extend the service life of the disc and improve the quality of the pulp.

The 200t/d thermomechanical pulp (TMP) production line introduced by Shun Nan Company from Fujian Southern Paper Co., Ltd., which was put into operation in 1998, was first refined with two RGP262 single disc mills (R304, R307). In the second stage, an RGP262A single disc mill (R311) was used to configure three 6T and 7500kW synchronous motors (M304, M307, M311) for atmospheric refining at the Xiangtan Motor Plant, which was controlled by the ABB-MASTER distribution system. In the feed protection device, when the disc grinding gap value is less than the set value, the movable disc can be forced to retreat immediately by 1 mm to avoid abrasion of the disc. However, the disk grinding gap controller may cause damage to the plate due to oil leakage or jamming of the hydraulic servo valve or slipping or damage of the stepper motor coupling.

Yueyang Paper Group's CTMP/APMP pulping production line [16] has a pressure mill 50-1CP and a two-stage atmospheric pressure mill 50-1C manufactured by Andritz Bauer. The 50-1CP terminal display shows the refining power, acceleration, vibration, and feed load. The initial use of the grinding power is relatively high (2.8 ~ 3.3MW), but the acceleration is not high (35% ~ 50%), sharper grinding, adjust the refining concentration and feeding amount, in order to reduce fiber damage; , The power is stable (2.5 ~ 2.8MW), acceleration is increased (50% ~ 60%), slurry quality is stable, moderate energy consumption, damage to the fiber is small, at this time requires to prevent the stocker suddenly broken material, strengthen the advance and retreat of the grinding Knife motor maintenance, in order to ensure the timely retreat of the grinding plate; if the acceleration is increased, but the power is difficult to rise, the quality of pulp into a decline, depending on the degree of wear for re-grinding or scrapped.

2.2 Strengthen hard impurities in raw materials before grinding

The impurity removal of raw materials will affect the service life of the grinding plate. For example, the slurry preparation of the high-grade coated white paperboard/liquid packaging paper line (BM2) of Hongta Renheng Paper Co., Ltd. 150,000 t/a adopts Aaron Cone refiner. Due to the internal circulation of white water, CO32-precipitation that may cause great damage to the grinding plate may be formed in the system, resulting in a rapid decline in beating quality and the chemical cleaning of the system.

Xi'an Paper Machinery Factory (Light Industry Xi'an Machinery Design Research Institute) developed APMP's domestic pulping pilot line to achieve localization of a full set of equipment. The localization rate of key technologies and key equipment has reached 100%. For sediment containing raw materials and some micro-metal fragments, a dehydration machine adopting a new process for bump washing and washing is adopted to achieve a high degree of washing effect, maintain the purity of the slurry, and at the same time protect the subsequent process equipment, enabling high-consistency grinding mills. The sheet wears off from the wear to wear.

In November 2001, the 400,000 t/a low-quantity coated paper production line at the Italian Verzouolo mill was started. The mechanical pulp was produced by six Valmet T1815P pressure mills and 500 t/d air-drying PGW-70 mills. The CL&V slag clarifier feeds at a relatively high concentration (above 1.3%) and removes sand and other impurities before the slag is ground. The average life of the screen slag refiner plate is up to 3500h.

Linqing Yinhe Paper Co., Ltd. 200,000 t/aA high-strength corrugated base paper project [20] introduced Spanish SAICA company's second-hand pulping production line, using 50% semi-chemical wheat straw pulp and 50% US waste AOCC pulp in 4400/5050 type paper. Machine-made high strength in line with the national A-class standard corrugated paper. Set sand-draining wells and magnetic iron remover in the process to separate the stone and iron in the wheat straw, timely deal with the hard debris entering the grinding plate, and ensure that the feed spiral feeding amount is uninterrupted to prevent grinding idling and extend the precision Mill plate life.