2024年6月10日发(作者：)
外文原文：
Hammer mills: hammer-mills
In the feed processing process there may be a number of ingredients that require
some form of processing. These feed ingredients include coarse cereal grains, corns
which require particle size reduction which will improve the performance of the
ingredient and increase the nutritive value. There are a many ways to achieve this particle
size reduction, here we are looking at using hammer-mills, for information on roller mills,
see the related links at the bottom of this page.
Both hammering and rolling can achieve the desired result of achieving adequately
ground ingredients, but other factors also need to be looked at before choosing the
suitable method to grind. Excessive size reduction can lead to wasted electrical energy,
unnecessary wear on mechanical equipment and possible digestive problems in
livestock and poultry. For more in depth information regarding what actually occurs to
the ingredients during size reduction please refer to this link: particle size reduction.
Hammer-mills
Advantages:
- are able to produce a wide range of particle sizes
- Work with any friable material and fiber
- ease of use
-Lower initial investment when compared with a roller mill
- Minimal maintenance needed
- Particles produced using a hammer-mill will generally be spherical, with a surface
that appears polished.
Disadvantages:
- Less energy efficient when compared to a roller mill
- may generate heat (source of energy loss)
- produce greater particle size variability (less uniform)
- Hammer-mills are noisy and can generate dust pollution
General Design
The major components of these hammer-mills, shown in the picture, include: - a
delivery device is used to introduce the material to be ground into the path of the
hammers. A rotor comprised of a series of machined disks mounted on the horizontal
shaft performs this task. - Free-swinging hammers that are suspended from rods
running parallel to the shaft and through the rotor disks. The hammers carry out the
function of smashing the ingredients in order to reduce their particle size. - a perforated
screen and either gravity- or air-assisted removal of ground product. Acts to screen the
particle size of the hammer mill to ensure particles meet a specified maximum mesh size.
Feeder design
Materials are introduced into the paths of the hammers by a variable speed vein
feeder. This type of feeder can have its motor slaved by a programmable controller to
the main drive motor of the hammer mill. The operational speed of the feeder is
controlled to maintain optimum amperage loading of the main motor.
Hammer design and configuration
The design and placement of hammers is determined by operating parameters such
as rotor speed, motor horsepower, and open area in the screen. Optimal hammer design
and placement will provide maximum contact with the feed ingredient. Hammer mills in
which the rotor speed is approximately 1,800 rpm, should be using hammers which are
around 25cm (~ 10 inches) long, 6.35cm (~2.5 inches) wide, and 6.4mm (0.25 inches)
thick. For a rotor speed of about 3,600 rpm, hammers should be 15 to 20 cm (~ 6-8
inches long, 5 cm (~ 2 inches) wide, and 6.4 mm (0.25 inches) thick.
The number of hammers used for a hammer mill of 1,800 rpm, should be 1 for every
2.5 to 3.5 horsepower, and for 3,600 rpm, one for every 1 to 2 horsepower. Hammers
should be balanced and arranged on the rods so that they do not trail one another. The
distance between hammer and screen should be 12 to 14 mm (~ 1/2 inch) for size
reduction of cereal grains.
The velocity or tip speed of the hammers is critical for proper size reduction. Tip
speed is the speed of the hammer at its tip or edge furthest away from the rotor, and is
calculated by multiplying the rotational speed of the drive source (shaft rpm) by the
circumference of the hammer tip arc. See the following formula:
A common range of tip speeds seen in hammer-mills is commonly in the range
between 5,000 and 7,000 m/min (~ 16,000 and 23,000 feet per minute). When the tip
speeds exceed 23,000 feet per minute, careful consideration must be given to the design
of the hammer mill, the materials used in its construction, and the fabrication of all the
components. Simply changing the rotational speed of the drive source is not a
recommended method of increasing hammer speed in excess of 23,000 feet per minute.
Impact is the primary force used in a hammer-mill. Anything which increases the
chance of a collision between a hammer and a target; increases the magnitude of the
collision; or improves material take-away provides an advantage in particle size
reduction. The magnitude of the collisions can be escalated by increasing the speed of
the hammers.
Screen Design
The amount of open area in a hammer mill screen determines the particle size and
grinding efficiency. The screen must be designed to maintain its integrity and provide
the greatest amount of open area. Screen openings (holes) that are aligned in a
60-degree staggered pattern optimize open area while maintaining screen strength. This
method will result in a 40 percent open area using 3.2 mm (1/8 inch) holes aligned on 4.8
mm (3/16 inch) centers.
Feed producers need to pay particular attention to the ratio of open screen area to
horsepower. Recommended ratio for grains would be 55 cm2 (~ 8-9 inches square) per
horsepower (Bliss, 1990). Not enough open area per horsepower results in the
generation of heat. When the heat generated exceeds 44C to 46C (120-125F), capacity
may be decreased as much as 50 percent.
The removal of sized material from a hammer-mill is a critical design feature. Proper
output of material affects not only the efficiency of operation, but also particle size.
When the correct ratio of screen area to horsepower is used and proper distance
between hammers and screen face is maintained, most of the correctly sized particles
will exit the screen in a timely manner. Anderson (1994) stated the particles that do not
pass through the screen holes become part of a fluidized bed of material swept along
the face of the screen by the high-speed rotation of the hammers. As these particles rub
against the screen and each other their size is continually reduced by attrition. This
excessive size reduction is counterproductive. Energy is wasted in the production of heat,
throughput is restricted, and particles become too small.
Most new hammer mills are equipped with an air-assist system that draws air into
the hammer mill with the product to be ground. Systems are designed to provide
reduced pressure on the exit side of the screen to disrupt the fluidized bed of material on
the face of the screen, thus allowing particles to exit through screen holes. Some full
circle hammer mills are designed so the screen is in two pieces. It is possible to use a
larger whole size on the upward arc of the hammers to further reduce the amount of
material on the face of the screen.
Hammer Mills Hammers
Hammers are used inside the hammer-mill to impact smash ingredients up into
smaller particles, making it more suitable for uniform mixing and usage in feed.
Hammers are available in a huge range of configurations, shapes, facings and materials.
Hammers are available as single holed or with two holes, with two holes allowing the
hammers to be used twice as the wear is done to one end of the hammer; the hammer
can be rotated and used a second time. The hole fits onto a rod inside the hammer mill
and swings to hit the material.
Dimensions of a hammer
A: Thickness
B: Width
C: Diameter to fit rod size
D: Swing Length
E: Total Length
Hammer Mill Perforated Screens
Hammer mills screens are used inside a hammer mill to separate particle sizes.
Particle of small enough diameter that has been successfully grinded by the hammer mill
passes through the screen and leaves the hammer mill with the aid of the pneumatic
system.
Particle Size Reduction
Size Reduction: The initial reduction of cereal grains begins by disrupting the outer
protective layer of the seed (hull), exposing the interior, see the picture. Continued size
reduction increases both the number of particles and the amount of surface area per
unit of volume. It is this increased surface area that is of primary importance. A greater
portion of the grain's interior is exposed to digestive enzymes, allowing increased access
to nutritional components such as starch and protein. The enhanced breakdown of these
nutritional components improves absorption in the digestive tract. The overall effect is
increased animal performance. Size reduction is also used to modify the physical
characteristics of ingredients resulting in improved mixing, pelleting, and, in some
instances, handling or transport.
Hammer mills: Reduce the particle size of materials by impacting a slow moving
target, such as a cereal grain, with a rapidly moving hammer. The target has little or no
momentum (low kinetic energy), whereas the hammer tip is traveling at a minimum of
4,880 m/min (~16,000 feet per min) and perhaps in excess of 7,015 m/min (~ 23,000 feet
per min) (high kinetic energy). The transfer of energy that results from this collision
fractures the grain into many pieces. Sizing is a function of hammer-tip speed; hammer
design and placement; screen design and hole size; and whether or not air assistance is
utilized.
Because impact is the primary force used in a Hammer mill to reduce the size of the
particles, anything that; increases the chance of a collision between a hammer and a
target, increases the magnitude of the collision, or improves material take-away, would
be advantageous to particle size reduction. The magnitude of the collisions can be
escalated by increasing the speed of the hammers. Anderson (1994) stated that when
drive speed and screen size were kept constant, the increased hammer-tip speed
obtained from increased rotor diameter produced particles of smaller mean geometric
size.
Particles produced using a hammer mill will generally be spherical in shape with a
surface that appears polished. The distribution of particle sizes will vary widely around
the geometric mean such that there will be some large-sized and many small-sized
particles.
Hammer Mill Rods
Hammers are attached to rods inside the hammer mill, which are what they are
swung on. Dimensions of rods are dependant on brand and style of the hammer mill.
Roller mill
Roller mills accomplish size reduction through a combination of forces and design
features. If the rolls rotate at the same speed, compression is the primary force used. If
the rolls rotate at different speeds, shearing and compression are the primary forces
used. If the rolls are grooved, a tearing or grinding component is introduced. There is
little noise or dust pollution associated with properly designed and maintained roller
mills. Their slower operating speeds do not generate heat, and there is very little
moisture loss. Particles produced tend to be uniform in size; that is, very little fine
material is generated. The shape of the particles tends to be irregular, more cubic or
rectangular than spherical. The irregular shape of the particles means they do not pack
as well. For similar-sized particles, bulk density of material ground on a roller mill will be
about 5 to 15 percent less than material ground by a hammer mill.
Roller mills
Advantages:
- energy efficient
- uniform particle-size distribution
- little noise and dust generation
Disadvantages:
- little or no effect on fiber
- particles tend to be irregular in shape and dimension
- may have high initial cost (depends on system design)
- when required, maintenance can be expensive
General Design
There are many manufacturers of roller mills, but they all share the following design
features shown adjacent picture:
- a delivery device to supply a constant and uniform amount of the material to be
ground
- a pair of rolls mounted horizontally in a rigid frame
- one roll is fixed in position and the other can be moved closer to or further from
the fixed roll
- the rolls counter rotate either at the same speed or one may rotate faster; roll
surface may be smooth or have various grooves or corrugations
- bar; pairs of rolls may be placed on top of one another in a frame.
To ensure optimum operation, material must be introduced between the rolls in a
uniform and constant manner. The simplest feeder is a bin hopper with an agitator
located inside it and a manually set discharge gate. This type of feeder is best suited for
coarse processing. For grinding operations, a roll feeder is suggested. In this type of
feeder, the roll is located below the bin hopper and has a manually set or automatic
adjustable discharge gate. If the gate is adjusted automatically, it will be slaved to the
amperage load of the main motor of the roller mill.
The rolls that make up a pair will be 9 to 12 inches (23 to 30.5 cm) in diameter, and
their ratio of length to diameter can be as great as 4:1. It is very important to maintain
the alignment between the roll pairs. Sizing of the material is dependent upon the gap
between the rolls along their length. If this gap is not uniform, mill performance will
suffer, leading to increased maintenance costs, reduced throughput, and overall
increased operation costs. The gap may be adjusted manually or automatically through
the use of pneumatic or hydraulic cylinders operated through a computer or
programmable controller.
Each pair of rolls is counter rotating. For improved size reduction one of the rolls
rotates faster. This results in a differential in speed between the roll pair. Typical
differentials range from 1.2:1 to 2.0:1 (fast to slow). Typical roll speeds would be 1,300
feet per minute (~ 395 m/min) for a 9-inch (~23 cm) roll to 3,140 feet per minute (~957
m/min) for a 12-inch (~30.5 cm) roll. Usually a single motor is used to power a two high
roll pair, with either belt or chain reduction supplying the differential. In a three high roll
pair, the bottom pair will have a separate drive motor. In addition, the roll faces can be
grooved to further take advantage of the speed differential and improve size reduction.
By placing (stacking) pairs of rolls on top of one another, two or three high, it is
possible to reduce particle sizes down to 500 microns, duplicating the size-reducing
capability of a hammer mill for grain. For coarse reduction of grain, a roller mill may have
a significant advantage (perhaps as high as 85 percent) over a hammer mill in terms of
throughput/kwh of energy. For cereal grains processed to typical sizes (600 to 900
microns) for the feed industry, the advantage is about 30 to 50 percent. This translates
into reduced operating expense.
中文译文：
锤磨机：锤片式粉碎机
在饲料加工过程中可能存在的成分需要某种形式的处理方式来完成。这些饲料成分包括粗糙
的谷类植物，按要求减小玉米粒度可以提高原料的性能和营养价值。有许多不同的方法可以减小
饲料微粒的粒度。在这里我们主要介绍锤磨机和滚子磨机，具体介绍如下：
锤片式和滚子式粉碎机都可以加工出满足要求的圆形饲料，但是要选择其他机器来满足同样
要求的饲料粒度时就需要再加工前选择合适的加工方式。过度减小饲料粒度将会浪费电能、造成
机械设备不必要的磨损和家畜的消化问题。为了深入了解实际加工过程中产生材料粒度减小的原
因请参考一下内容：微粒尺寸减小。
锤片式粉碎机
优点：
—可以生产的饲料粒度范围广
—可以用于加工脆性材料和纤维
—操作简单
—相对于滚子式粉碎机来说它的早期投入低
—需要的维护很少
—它粉碎的饲料微粒一般都是圆形的而且表面光滑
缺点：
—相对于滚子粉碎机它的效率较低
—产生热量（能量损失）
—微粒大小不均匀（相差大）
—易产生噪音和灰尘、污染环境
总体设计
如图所示，锤片粉碎机的主要零件包括：
—传送部分：用于将物料送到粉碎室的通道。
—转子部分：由一系列锤片组成的转子装在水平轴上工作粉碎物料，锤片可以自由转动并悬
浮平行于轴杆穿过转子盘。锤片的作用是击碎物料减小它们的粒度。
—筛板：利用重力和空气的辅助来分离饲料微粒。粉碎机筛孔要能确保粉碎粒度最大物料的
通过。
粉碎室设计
材料引入到粉碎室的路径由一个变量的速度静脉接驳。这种类型的路径有它自己的发动机由
可编程的控制器连接锤片式粉碎机的主传动电机。各线路接驳的速度控制，以保持最佳电量的主
电机负载。
锤片的设计和布局
锤片的设计和布局由操作参数，如转子转速、电动机功率和筛板间隙决定。锤片的的最佳设
计和布局可以提供最大的饲料原料接触。粉碎机中转子的转速大约为1800转/分时应当用的锤片
为25厘米（~10英寸）长，6.35厘米（~2.5英寸）宽，6.4毫米（~0.25英寸）厚。对于转速
约为3600转/分的的锤片一般应为15到20厘米（~6-8英寸）长，5厘米（~2英寸）宽，6.4
毫米（~0.25英寸）厚。
对于转速为1800转/分的锤片式粉碎机来说，锤片数量应该是2.5~3.5/马力，而对于转速
为3600转/分的粉碎机来说锤片的数量为1~2/马力。锤片应该是平衡的，而且它们在轴杆上的
排列在运动时不至于相互碰撞。锤片和筛板之间的距离一般应为12~14毫米（~1/2英寸）为了
减小谷粒的大小。
锤片末端线速度是微粒粒度的关键，末端线速度是锤片末端或者远离转子边缘的速度，它可
以通过轴的转速乘以轴的直径和圆周率再除以12in/ft来求得，详见下面公式：
英尺/分=
D×n/12
D —转子直径
n —转速
在锤片粉碎机中常见的速度变化范围一般为5000-7000米/分（~16,000-23,000英尺/分）。
当末端线速度增大到23000英尺/分时就必须要考虑粉碎机的材料和所有零件结构是否能满足要
求。在转速为2.3万英尺/分时改变轴的转速是不值得推荐的方法。
粉碎机中主要的力是冲击力。在锤片和饲料颗粒之间增加的任何距离;增加距离的重要性；或
者有利于改善饲料微粒的大小。距离的增大可以通过提高锤片的速度来实现。
筛片设计
粉碎机中筛板的筛孔数量取决于微粒大小和粉碎效率。筛板设计必须保证饲料的最大微粒通
过和提供最大的开放面积。在保证筛板强度的情况下筛孔的最佳排列方式直线排列与开放区域呈
60°角交错。这种方法可以设计出的筛片有40﹪的用的是3.2mm（1/8英寸）的筛孔并直线排列
两孔中心距为4.8mm（3/16英寸）。
操作者应该特别注意粉碎机筛板有效面积与功率的比值。对于小麦类植物一般推荐使用的比
例为55平方厘米/马力（~8-9平方英寸）（Bliss1990）。如果没有足够的功率面积比将产生热量。
当温度达到44℃-46℃（120-125F）时粉碎机的生产能力将下降50﹪.
饲料的排出是粉碎机设计的标准。粉碎机的度电产量不仅受生产效率的影响还受物料粒度的
影响。当选用正确的有效筛板面积百分比和合适的锤筛间隙是粉碎的物料就能及时的从粉碎室中
排出。Anderson(1994)曾声明物料微粒不能全部通过筛片是因为一部分物料流在环流层外层( 靠
近筛面)随着转子高速旋转。这些微粒通过与筛片表面和彼此之间的摩擦来减小自身的尺寸。但过
度减小微粒的尺寸也会产生反效果：能源都浪费在热量上，产量也会受到限制物料微粒也会变得
过小。
多数的新型锤片式粉碎机都有吸风系统，可以将空气吸进粉碎室用于粉碎物料。吸风的目的
是造成粉碎室负压, 打破筛片表面的物料流促使室内残留的物料通过筛孔。有些粉碎机设计有两
片筛片，这种筛片可以使用大的筛孔便于更多的减少滞留在筛片表面的物料数量。
锤片式粉碎机—锤片
锤片式粉碎机中锤片用来冲击物料使其尺寸变小，使得它更用以与其他物料混合。锤片的布
局、形状、材料都是很重要的。锤片有单孔的和双孔之分，双孔的锤片可以使用两次，一端磨损
还可以使用另外一端。锤片安装在粉碎机轴杆上转动击打物料。
锤片的外形尺寸
A— 厚度
B— 宽度
C— 轴孔半径
D— 锤片伸出长度
E— 锤片总长
锤片粉碎机常用筛片
粉碎机中筛片是用来分离物料微粒的。粉碎机可以将物料粉碎的的足够小，通过空气压缩系
统的辅助微粒可以顺利的通过筛孔。
粒度：
粒度大小：谷类植物是从最外层开始被击碎的而后是微粒内部。微粒的大小不仅与筛片表面
的微粒数量有关而且还与粉碎速度有关。增加表面积是最重要的。对消化系统来说谷物的内部物
质是重要，像淀粉和蛋白质等营养成分。这些营养成分可以改善消化道的吸收作用，增加动物的
体能。微粒的成球形、物理性能可以提高物料的混合性便于转载和运输。
锤片式粉碎机
粉碎机是通过高速旋转地锤片不断地打击物料来降低其微粒尺寸的。锤片以4880米/分
（~16,000英尺/分）或者7015米/分（~23,000英尺/分）的线速度转动。能量的转移可以将物
料达成许多微粒。微粒的大小取决于锤片线速度、锤片设计和布局、筛片的设计和筛孔大小以及
吸风系统的共同作用。
因为锤片粉碎机中主要用来粉碎物料的力是冲击力，所以增加锤片与物料间的冲击可以提高
物料的卸出，对粒度的减小也是有利的。Anderson(1994)声称当击打速度和筛孔的大小保持不
变时，可以通过增加转子直径来增加锤片的末端线速度，进而生产出粒度更小的物料。锤片粉碎
的物料一般是圆形的且表面光滑。微粒大小不一也就是说既有大微粒也有小粒度微粒。
粉碎机轴杆
锤片式粉碎机的锤片是固定在轴杆上的，并可以绕轴杆转动。轴杆的大小取决于粉碎机的设
计。
辊子粉碎机
辊子粉碎机是通过力和机器特性相结合的方式来实现物料粉碎的。如果辊子以相同的速度旋
转则粉碎时用的力主要是压力。若辊子以不同的速度旋转粉碎时主要的力有切应力和压应力。如
果是带槽的辊子将会撕裂或粉碎物料，槽宽的辊子粉碎机比细槽的粉碎机粉碎的物料粒度要小。
设计合理的辊子粉碎机噪声低且低污染、维护方便。辊子粉碎机的运转速度较低因而不易产生热
量而且物料水分损失也较少。
粉碎的微粒大小几乎一样，也就是说物料微粒很均匀。微粒形状不规则大多是长方体或立方
体而不是圆形的。相对于锤片式粉碎机来说辊子式粉碎机中小尺寸微粒在辊子上的附着率要低5
﹪—15﹪。
辊子粉碎机
优点：
—效率高
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