In the process of pulping and papermaking, there are many technological points that need vacuum dehydration. For example, the vacuum suction tank of the mesh part, the volt roll, the vacuum suction roll, the vacuum pressing part and the vacuum suction tank of the upper and lower wool cloth, etc. The vacuum capacity of Liquid ring vacuum pump is a commonly used method for vacuum dewatering of papermaking pulping. There are three indexes to judge whether the selection of Liquid ring vacuum pump in a pulp and paper vacuum system is reasonable: the pumping capacity, the working point shaft power and the matching power of the motor. When selecting the type, on the premise that the pumping capacity meets the technological requirements of the production line, the working point shaft power of the water-ring vacuum pump should be reduced as much as possible, because the smaller the shaft power consumed by the water-ring vacuum pump, the lower the cost of pulping and papermaking. The matching power of the motor is also small, the total installed capacity is also small, and the electrical configuration cost can also be reduced. Generally speaking, the output of a paper production line with annual output is certain. For paper mills, in order to reduce energy consumption, save energy, and reduce paper production costs, the correctness of Liquid ring vacuum pump selection is very critical and very important. To illustrate this problem, we first understand the working characteristics of the Liquid ring vacuum pump. Liquid ring vacuum pump is a kind of volumetric pump. When the type of Liquid ring vacuum pump is determined, its volume is also determined. For Liquid ring vacuum pump, there are two main factors affecting its pumping capacity: the volume of pump and the speed of pump operation.
(1) Under the same working conditions (rotational speed and vacuum), the pumping capacity of the larger water-ring vacuum pump is larger than that of the smaller water-ring vacuum pump. That is to say, the larger volume of Liquid ring vacuum pump can obtain the smaller volume of Liquid ring vacuum pump at high speed with lower speed.
(2) For the water-ring vacuum pump, there is the following calculation relationship between its pumping capacity, working point shaft power and rotational speed: Ill: QI/Q2 = nl/n: 1 type: Q – pumping capacity of water-ring pump; n – rotational speed of water-ring pump. Pl/P2= (nl/n2) “(2) formula: P_ one Liquid ring pump working point shaft power; n — Liquid ring pump speed. Formulas (1), (2) show that the pumping capacity of the Liquid ring vacuum pump is proportional to its rotational speed, and the power of the working point axis is proportional to its 1.7 power of rotational speed. That is to say, when the Liquid ring vacuum pump is selected, it can be obtained by increasing its operating speed to obtain a larger pumping capacity, but the disadvantage is to consume more shaft power. Analyzing the above two points, we can draw a conclusion that there are two types of selection schemes to obtain the same pumping volume, namely, the first one is to select a larger volume Liquid ring vacuum pump to operate at a lower speed, and the second one is to select a smaller volume Liquid ring vacuum pump to operate at a higher speed. Here are the differences between the results of the two selection schemes of a Liquid ring vacuum pump.
When selecting the type of Liquid ring vacuum pump, the principle should be followed: on the premise of satisfying the technological requirements of the production line, the shaft power consumed by the working point of the Liquid ring vacuum pump and the matching power of the motor should be reduced as much as possible. The following examples illustrate the advantages and disadvantages of the above two methods.
(1) the volume of gas extraction should be large: 2063 – 2006=57 (M ‘/min).
(2) The axle power consumed by the working point is less: 1966-1747= (219 kW) is calculated on the basis of 330 working days per year and 24 hours per day: the annual power saving is 219 kW-330 days, and the x 24 hours = l’734480 degrees. According to the industrial power consumption of 0.8 yuan per degree, the first scheme saves electricity cost by 0.8 x 1’734480_10 000 = 1.39 million yuan. (3) the installed capacity should be small: 2582 – 2292=290 kilowatts.
From the analysis of the problems, the following conclusions can be drawn: in the vacuum system of pulp and paper making, the scheme of selecting larger volume Liquid ring vacuum pump to operate at lower speed is better than that of selecting smaller volume Liquid ring vacuum pump to operate at higher speed, which has great advantages in saving energy and reducing paper making cost. It is worth noting that when choosing the type, choosing the Liquid ring vacuum pump with smaller volume will make less investment than choosing the Liquid ring vacuum pump with larger volume for users. Because the volume is smaller, the manufacturing cost of the Liquid ring vacuum pump is relatively low. In order to improve their competitive advantage in product price, some manufacturers of Liquid ring vacuum pumps often adopt the marketing strategy of selecting smaller volume Liquid ring pumps to run at a higher speed in order to achieve their goal of winning the bid. Users should pay attention to this point. In terms of the interests of users, we advocate that when selecting the type of Liquid ring vacuum pump, we should choose the scheme with larger volume of Liquid ring vacuum pump to operate at lower speed. After all, when purchasing large volume Liquid ring vacuum pumps, the cost of more investment can be recovered from the operation cost of Liquid ring pumps in less than half a year. The energy consumption of Liquid ring vacuum pump in papermaking vacuum system is analyzed with an example of vacuum degree selection.
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