去除木屑的筛选方法--旋振筛

旋转筛

     典型的旋转筛装料时，是将木屑和木片直接倒在筛选和进料端的层面上，落料层面的快速旋转运动使成堆的木片铺展开，成一定角度倾斜安装的筛选机使物料沿筛层向下滑动落到木屑筛选层。当碎木屑在筛选过程中遇到合适的筛孔就会通过，而不能通过的大木块和大木片继续沿筛层向前运行。只要筛板没有破，筛选出来的木屑尺寸应该相当均匀，并且和筛孔

的尺寸相吻合。旋转筛之所以可行，是因为本质上这是一个碎物接近筛孔的问题，是碎物遇到尺寸合适的筛孔的概率，仔细观察过该过程的科学家们撰写的论文中提到——是否有可能算出任一碎物遇到并通过一个合适开度的筛孔的概率，上述理论被用来计算木材处理工业中旋转筛选型及应用的“传统智慧”因数，结果发现二者出奇的一致。碎物在筛板上不能找到筛孔的影响因素通常有几个，首先是来自其他尺寸相近及较大物料的竞争。这可能是一个简单的装料率的问题——只要能够为竞争碎物提供足够的机会接近筛板，那么筛选机就会有足够的筛选能力。

     在筛板上形成一种特定流态非常重要，在该流态下流动性好，呈湍流状态，大量的大尺寸物料并不会妨碍木针抵达筛板表面。为了达到这种流态化，筛选机需要一定的转速和频率，传统筛的典型转速为 180 r/min，在该速度下，物料

可能以塞流状运行而不会形成理想的流态。目前的筛选机操作速度为235～300 r/min，这种高频率及运动振幅的调整创造了所需的流态条件。筛体的操作速度和振幅有一定的关系，转速慢的筛体通常转动半径较大，高速筛转动的振幅非常小，

这对平衡块驱动系统驱动的筛选及控制其离心力是很有必要的。筛体旋转速度快、振幅小，筛选效果好；而筛体旋转速度较慢，但是要有足够的振幅，粗筛效果还是可以的。多数锯木厂中，一台筛选机同时拥有精筛和粗筛这两个功能。筛板的倾斜角度几乎都是 7°～8°，有些木材产品筛选所用的筛引用了石料、矿物筛选所用筛。采矿所用的筛呈 20°～25°角，当筛板角度为 20°～25°时，木片在筛板表面的停留时间非常短，从而影响筛选效率。木材产品的筛选中，老式筛通常有一个笨重的铸造底座或者组合底座来抵销筛筐转动过程中产生的。
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Sawdust is usually produced in chipping process of wood powder mixed with wood chips orsawdust in the sawmill some operation process, is the need to remove the components in prior to pulping. The traditional method is to configure different sieve mesh layer vibration sieve(rotary screen) in the treatment of rotary screen, some limitations led to the development of other technologies, including now used for roll screen. These new technologies include a lot of technological innovation, the application range is more extensive, wood chip removal and some other screening method.

Rotary screen

Rotary screen loading typical, sawdust and wood chips will be poured directly on the screen andthe feed end level, falling fast rotating movement of material level make piles of wood spreadinto a certain angle, screening machine installation of the material along the screen layer sliding down to the sawdust layer of screening. When the chips met the right mesh will in the course of screening by, and not through the big wooden and large chips continue to run forward along thescreen layer. As long as the sieve plate is not broken, screening out the wood size should befairly uniform, and the sieve

Size consistent. Rotary screen is feasible, because this is essentially a debris near the meshproblem, is the probability of debris encountered suitable sieve size, carefully observe the writing of the scientists of the process mentioned in the paper -- whether it is possible to work out anydebris encountered and through a suitable opening sieve probability, the theory is used to calculate the wood processing industry rotary screening and application of "conventional wisdom" factor, the results showed that two were surprisingly consistent. Debris not on the sieve plate sieve effect factor and found there were usually several, the first is from other similar sizeand larger materials competition. This may be a simple loading rate problem -- as long as youcan provide enough opportunity to get close to the plate for competitive debris, so screening machine will have adequate screening ability.

On the sieve plate to form a specific pattern is very important in the flow of good fluidity, aturbulent state, a lot of big size material does not obstruct the wooden needle arrived in thesieve surface. In order to achieve this kind of fluidization, screening machine need speed andfrequency of some typical traditional screen, speed is 180 r/min, the speed at which, material

Flow is likely to plug flow like running without the formation of ideal. Screening machineoperating speed at present is 235 ~ 300 r/min, the high frequency and motion amplitudeadjustment to create flow conditions required. There is some relationship between the sievebody of the operation speed and amplitude, slow speed rotating sieve body usually larger radius, high speed screen rotation amplitude is very small,

This drive to balance block system driven by screening and control of the centrifugal force isvery necessary. The sieve body rotation speed, small amplitude, the screening effect is good;and the screen body rotation speed is slow, but there must be sufficient amplitude, screeningeffect can still. The majority of the sawmill, a screening machine also has fine screen and screenthese two functions. The tilt angle of the sieve plate is almost 7 degrees to 8 degrees, and somewood products used in screening sieve cited stone, mineral screening using sieve. The miningsieve is 20 DEG to 25 DEG angle, when the sieve plate at an angle of 20 DEG to 25 DEG, woodis very short residence time in the sieve surface, thus affecting the efficiency of screening.Screening of wood products, old-fashioned screen usually have a heavy casting base orcombined base to generate offset screen basket to rotate in the process of.
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