| With the continuous development of our economy, science and technology, our demand for packaging paper and paperboard is increasing. Moreover, due to lack of fiber resources and advocacy of recycling the waste, energy saving, emission reduction, cost saving and reduction of chemicals, over 65 percent of the raw material used for paper-making in China is waste paper. The Pulper is the first and important equipment in producing waste paper stock, and the most wildly used kind of pulper is the vertical hydraulic pulper. As a result, to do research on developing pulpers of high efficiency, low energy-consumption and running balance is of great importance.In this paper, based on high efficiency, low energy-consumption and running balance, firstly analyzed were various kinds of vertical hydraulic pulpers at home and abroad that were patented or being used; then, simulated with FLUENT software were the 5% concentration of pulp suspension flow fields inside the O-shaped and D-shaped tank; and, as a result, obtained and analyzed were the distribution of pressure, velocity and turbulence intensity of both flow fields. On the base of qualitative and quantitative theoretical analysis of various worldwide types of the vertical hydraulic pulpers, a new highly-efficient, energy-saving and running-balanced type of the cell structure was put forward as a patent for invention. After that, the 5% concentration of pulp suspension flow fields inside the new-type tank were simulated with FLUENT software, and distributions of pressure, velocity and turbulence intensity were obtained and analyzed by comparing them with the ones inside the O-shaped and D-shaped tanks. At last, a repulping experiment was carried out using laboratory-sized pulpers to verify the conclusion.The results achieved were:(1) The flow field inside the O-shaped was symmetrical and balanced, but the high-turbulence intensity area was limited to the rotor spinning region, and the turbulence intensity of the upper part was 1159% lower than that of the bottom part. The flow field at the edge of the top of the flow field was of none velocity and was short of power.(2) The flow field inside the D-shaped was with obviously increased turbulence intensity, and, at the center of the D-shaped tank, the radius of low-turbulence intensity area was only 13% of the O-shaped tank. However, 22.67% energy consumption inside the D-shaped was caused by radially hitting the wall than that inside the O-shaped, and the D-shaped was with unbalanced running because of its unsymmetrical flow field. From the aspect of mechanics, the D-shaped flow caused stronger vibration and the nonsymmetry force on the rotor, which would reduce the lifespan of equipment.(3) A new highly-efficient, energy-saving and running-balanced type of the cell structure was put forward as a patent for invention(ZL2015100011941). The new-type tank was drum-shaped and with spiral baffles on the wall, and the baffles were in the opposite direction of pulp flow, 45°spiral, interval and with a trapezoid vertical section and grooves on the top.(4) The ellipsoidal upper structure and baffles of the new tank pushed pulp flow to the rotor at the center and bottom of the tank, moreover, the turbulence intensity near the baffles was 100% higher than the areas around it, so pulping efficiency was greatly increased. The velocity of pulp at the wall of the inverted cone was 5m/s, but the velocities of those at bottom walls of the O-shaped and D-shaped tanks were both 0, which indicated that energy consumption of the new-type tank caused by pulp radially hitting the wall could be obviously decreased.(5) According to the repulping experiment using 3 laboratory-sized pulpers, the repulping efficiency of the drum-shaped pulper was more than that of the O-shaped one by 18.22% and was more than that of the D-shaped one by 1.32%. The amplitude RMS of the drum-shaped tank during repulping activity was lower than that of the D-shaped one by 55.22%, which meant the flow field inside the drum-shaped one is symmetrical and balanced. |
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