1、1：錘磨機(jī)：錘片式粉碎機(jī)在飼料加工過程中可能存在的成分需要某種形式的處理方式來完成。這些飼料成分包括粗糙的谷類植物，按要求減小玉米粒度可以提高原料的性能和營(yíng)養(yǎng)價(jià)值。有許多不同的方法可以減小飼料微粒的粒度。在這里我們主要介紹錘磨機(jī)和滾子磨機(jī)，具體介紹如下：錘片式和滾子式粉碎機(jī)都可以加工出滿足要求的圓形飼料，但是要選擇其他機(jī)器來滿足同樣要求的飼料粒度時(shí)就需要再加工前選擇合適的加工方式。過度減小飼料粒度將會(huì)浪費(fèi)電能、 造成機(jī)械設(shè)備不必要的磨損和家畜的消化問題。為了深入了解實(shí)際加工過程中產(chǎn)生材料粒度減小的原因請(qǐng)參考一下內(nèi)容：微粒尺寸減小。錘片式粉碎機(jī)優(yōu)點(diǎn)：可以生產(chǎn)的飼料粒度范圍廣可以用于加工脆性材料和

2、纖維操作簡(jiǎn)單相對(duì)于滾子式粉碎機(jī)來說它的早期投入低需要的維護(hù)很少它粉碎的飼料微粒一般都是圓形的而且表面光滑缺點(diǎn)：相對(duì)于滾子粉碎機(jī)它的效率較低產(chǎn)生熱量（能量損失）微粒大小不均勻（相差大）易產(chǎn)生噪音和灰塵、污染環(huán)境總體設(shè)計(jì)如圖所示，錘片粉碎機(jī)的主要零件包括：傳送部分：用于將物料送到粉碎室的通道。錘片可以自由轉(zhuǎn)動(dòng)轉(zhuǎn)子部分：由一系列錘片組成的轉(zhuǎn)子裝在水平軸上工作粉碎物料，錘片可以自由轉(zhuǎn)動(dòng)并懸浮平行于軸桿穿過轉(zhuǎn)子盤。錘片的作用是擊碎物料減小它們的粒度。篩板： 利用重力和空氣的輔助來分離飼料微粒。粉碎機(jī)篩孔要能確保粉碎粒度最大物料的通過。粉碎室設(shè)計(jì)材料引入到粉碎室的路徑由一個(gè)變量的速度靜脈接駁。這種類型的路

3、徑有它自己的發(fā)動(dòng)機(jī)由可編程的控制器連接錘片式粉碎機(jī)的主傳動(dòng)電機(jī)。各線路接駁的速度控制，以保持最佳電量的主電機(jī)負(fù)載。錘片的設(shè)計(jì)和布局錘片的設(shè)計(jì)和布局由操作參數(shù)，如轉(zhuǎn)子轉(zhuǎn)速、電動(dòng)機(jī)功率和篩板間隙決定。錘片的的最佳設(shè)計(jì)和布局可以提供最大的飼料原料接觸。粉碎機(jī)中轉(zhuǎn)子的轉(zhuǎn)速大約為1800 轉(zhuǎn) /分時(shí)應(yīng)當(dāng)用的錘片為25 厘米（ 10 英寸）長(zhǎng)，6.35 厘米（ 2.5 英寸）寬，6.4 毫米（ 0.25 英寸）厚。對(duì)于轉(zhuǎn)速約為3600 轉(zhuǎn) / 分的的錘片一般應(yīng)為15 到 20 厘米（ 6-8 英寸）長(zhǎng)，5 厘米（ 2英寸）寬，6.4 毫米（ 0.25 英寸）厚。對(duì)于轉(zhuǎn)速為1800 轉(zhuǎn) /分的錘片式粉碎機(jī)來

4、說，錘片數(shù)量應(yīng)該是2.53.5/ 馬力，而對(duì)于轉(zhuǎn)速為 3600 轉(zhuǎn) / 分的粉碎機(jī)來說錘片的數(shù)量為12/ 馬力。錘片應(yīng)該是平衡的，而且它們?cè)谳S桿上的排列在運(yùn)動(dòng)時(shí)不至于相互碰撞。錘片和篩板之間的距離一般應(yīng)為1214 毫米 （ 1/2英寸）為了減小谷粒的大小。錘片末端線速度是微粒粒度的關(guān)鍵，末端線速度是錘片末端或者遠(yuǎn)離轉(zhuǎn)子邊緣的速度，它可以通過軸的轉(zhuǎn)速乘以軸的直徑和圓周率再除以12in/ft 來求得，詳見下面公式：英尺 / 分 = D n/12D 轉(zhuǎn)子直徑n 轉(zhuǎn)速在錘片粉碎機(jī)中常見的速度變化范圍一般為5000-7000 米 /分 （ 16,000-23,000 英尺 /分） 。 當(dāng)末端線速度增大到

5、23000 英尺 /分時(shí)就必須要考慮粉碎機(jī)的材料和所有零件結(jié)構(gòu)是否能滿足要求。在轉(zhuǎn)速為2.3 萬(wàn)英尺 /分時(shí)改變軸的轉(zhuǎn)速是不值得推薦的方法。粉碎機(jī)中主要的力是沖擊力。在錘片和飼料顆粒之間增加的任何距離; 增加距離的重要性；或者有利于改善飼料微粒的大小。距離的增大可以通過提高錘片的速度來實(shí)現(xiàn)。篩片設(shè)計(jì)粉碎機(jī)中篩板的篩孔數(shù)量取決于微粒大小和粉碎效率。篩板設(shè)計(jì)必須保證飼料的最大微粒通過和提供最大的開放面積。在保證篩板強(qiáng)度的情況下篩孔的最佳排列方式直線排列與開放區(qū)域呈60角交錯(cuò)。這種方法可以設(shè)計(jì)出的篩片有40的用的是3.2mm（ 1/8 英寸） 的篩孔并直線排列兩孔中心距為4.8mm（ 3/16 英寸

6、） 。操作者應(yīng)該特別注意粉碎機(jī)篩板有效面積與功率的比值。對(duì)于小麥類植物一般推薦使用的比例為55 平方厘米/ 馬力（ 8-9 平方英寸）（ Bliss1990 ） 。如果沒有足夠的功率面積比將產(chǎn)生熱量。當(dāng)溫度達(dá)到44 -46 （120-125F ）時(shí)粉碎機(jī)的生產(chǎn)能力將下降50 .飼料的排出是粉碎機(jī)設(shè)計(jì)的標(biāo)準(zhǔn)。粉碎機(jī)的度電產(chǎn)量不僅受生產(chǎn)效率的影響還受物料粒度的影響。當(dāng)選用正確的有效篩板面積百分比和合適的錘篩間隙是粉碎的物料就能及時(shí)的從粉碎室中排出。Anderson（1994） 曾聲明物料微粒不能全部通過篩片是因?yàn)橐徊糠治锪狭髟诃h(huán)流層外層（ 靠近篩面） 隨著轉(zhuǎn)子高速旋轉(zhuǎn)。這些微粒通過與篩片表面和彼此

7、之間的摩擦來減小自身的尺寸。但過度減小微粒的尺寸也會(huì)產(chǎn)生反效果：能源都浪費(fèi)在熱量上，產(chǎn)量也會(huì)受到限制物料微粒也會(huì)變得過小。多數(shù)的新型錘片式粉碎機(jī)都有吸風(fēng)系統(tǒng)，可以將空氣吸進(jìn)粉碎室用于粉碎物料。吸風(fēng)的目的是造成粉碎室負(fù)壓, 打破篩片表面的物料流促使室內(nèi)殘留的物料通過篩孔。有些粉碎機(jī)設(shè)計(jì)有兩片篩片，這種篩片可以使用大的篩孔便于更多的減少滯留在篩片表面的物料數(shù)量。錘片式粉碎機(jī)錘片錘片式粉碎機(jī)中錘片用來沖擊物料使其尺寸變小，使得它更用以與其他物料混合。錘片的布局、形狀、 材料都是很重要的。錘片有單孔的和雙孔之分，雙孔的錘片可以使用兩次，一端磨損還可以使用另外一端。錘片安裝在粉碎機(jī)軸桿上轉(zhuǎn)動(dòng)擊打物料。錘

8、片的外形尺寸A 厚度B 寬度C 軸孔半徑D 錘片伸出長(zhǎng)度E 錘片總長(zhǎng)錘片粉碎機(jī)常用篩片粉碎機(jī)中篩片是用來分離物料微粒的。粉碎機(jī)可以將物料粉碎的的足夠小，通過空氣壓縮系統(tǒng)的輔助微?？梢皂樌耐ㄟ^篩孔。粒度：粒度大?。汗阮愔参锸菑淖钔鈱娱_始被擊碎的而后是微粒內(nèi)部。微粒的大小不僅與篩片表面的微粒數(shù)量有關(guān)而且還與粉碎速度有關(guān)。增加表面積是最重要的。對(duì)消化系統(tǒng)來說谷物的內(nèi)部物質(zhì)是重要，像淀粉和蛋白質(zhì)等營(yíng)養(yǎng)成分。這些營(yíng)養(yǎng)成分可以改善消化道的吸收作用，增加動(dòng)物的體能。微粒的成球形、物理性能可以提高物料的混合性便于轉(zhuǎn)載和運(yùn)輸。錘片式粉碎機(jī)粉碎機(jī)是通過高速旋轉(zhuǎn)地錘片不斷地打擊物料來降低其微粒尺寸的。錘片以488

9、0 米 /分（ 16,000 英尺 /分）或者7015 米 /分（ 23,000 英尺 /分）的線速度轉(zhuǎn)動(dòng)。能量的轉(zhuǎn)移可以將物料達(dá)成許多微粒。微粒的大小取決于錘片線速度、錘片設(shè)計(jì)和布局、篩片的設(shè)計(jì)和篩孔大小以及吸風(fēng)系統(tǒng)的共同作用。因?yàn)殄N片粉碎機(jī)中主要用來粉碎物料的力是沖擊力，所以增加錘片與物料間的沖擊可以提高物料的卸出，對(duì)粒度的減小也是有利的。Anderson（1994） 聲稱當(dāng)擊打速度和篩孔的大小保持不變時(shí)，可以通過增加轉(zhuǎn)子直徑來增加錘片的末端線速度，進(jìn)而生產(chǎn)出粒度更小的物料。 錘片粉碎的物料一般是圓形的且表面光滑。微粒大小不一也就是說既有大微粒也有小粒度微粒。粉碎機(jī)軸桿錘片式粉碎機(jī)的錘片是

10、固定在軸桿上的，并可以繞軸桿轉(zhuǎn)動(dòng)。軸桿的大小取決于粉碎機(jī)的設(shè)計(jì)。輥?zhàn)臃鬯闄C(jī)輥?zhàn)臃鬯闄C(jī)是通過力和機(jī)器特性相結(jié)合的方式來實(shí)現(xiàn)物料粉碎的。如果輥?zhàn)右韵嗤乃俣刃D(zhuǎn)則粉碎時(shí)用的力主要是壓力。若輥?zhàn)右圆煌乃俣刃D(zhuǎn)粉碎時(shí)主要的力有切應(yīng)力和壓應(yīng)力。 如果是帶槽的輥?zhàn)訉?huì)撕裂或粉碎物料，槽寬的輥?zhàn)臃鬯闄C(jī)比細(xì)槽的粉碎機(jī)粉碎的物料粒度要小。設(shè)計(jì)合理的輥?zhàn)臃鬯闄C(jī)噪聲低且低污染、維護(hù)方便。輥?zhàn)臃鬯闄C(jī)的運(yùn)轉(zhuǎn)速度較低因而不易產(chǎn)生熱量而且物料水分損失也較少。粉碎的微粒大小幾乎一樣，也就是說物料微粒很均勻。微粒形狀不規(guī)則大多是長(zhǎng)方體或立方體而不是圓形的。相對(duì)于錘片式粉碎機(jī)來說輥?zhàn)邮椒鬯闄C(jī)中小尺寸微粒在輥?zhàn)由系母街室?1

11、5。輥?zhàn)臃鬯闄C(jī)優(yōu)點(diǎn)：效率高微粒粒度均勻低噪聲、低污染缺點(diǎn)：幾乎不用于粉碎纖維類植物粉碎的微粒形狀不規(guī)則前期投入可能要高（取決于系統(tǒng)的設(shè)計(jì)）必要時(shí)維護(hù)保養(yǎng)費(fèi)用要高總體設(shè)計(jì)有很多制造公司生產(chǎn)輥?zhàn)臃鬯闄C(jī)，但他們都有共同的設(shè)計(jì)特點(diǎn)如下所述：傳送部件將物料連續(xù)的送到粉碎室以供粉碎一對(duì)輥?zhàn)铀焦潭ㄔ谥Ъ苌弦粋€(gè)轉(zhuǎn)子固定不動(dòng)另一個(gè)輥?zhàn)娱g歇地靠近或遠(yuǎn)離它輥?zhàn)哟蠖际且韵嗤乃俣确聪蛐D(zhuǎn)或者其中一個(gè)轉(zhuǎn)動(dòng)較快，輥?zhàn)颖砻嬉苍S是光滑的也或許是有許多溝槽。軸桿，幾對(duì)輥?zhàn)涌赡苁枪潭ㄔ诹硪粋€(gè)支架的輥?zhàn)由系姆鬯闄C(jī)中物料通常以連續(xù)不變的速度通過輥?zhàn)右员ＷC粉碎機(jī)輥?zhàn)拥淖罴堰\(yùn)轉(zhuǎn)。最簡(jiǎn)單的粉碎系統(tǒng)是一個(gè)儲(chǔ)料器和一個(gè)手工操作的卸料門。這種

12、類型的粉碎室最適合于粗糙的加工過程。對(duì)于研磨來說輥?zhàn)臃鬯槭侵档锰岢?。這種類型的粉碎機(jī)中輥?zhàn)游挥趦?chǔ)料器的下方，有一個(gè)手工操作或自動(dòng)控制的可調(diào)卸料門。一對(duì)輥?zhàn)拥闹睆绞?12 英寸（ 23 到 30.5 厘米） ，它們的長(zhǎng)徑比可以達(dá)到4： 1。輥?zhàn)又g的排列方式是非常重要的，物料粒度取決于輥?zhàn)又g的間隙。如果間隙不一致其粉碎性能將變壞從而導(dǎo)致維護(hù)成本增加、生產(chǎn)率下降，總之生產(chǎn)成本增加?？烧{(diào)節(jié)的間距, 通過使用自動(dòng)或手動(dòng)氣動(dòng)或液壓缸通過電腦操作或可編程序控制器來實(shí)現(xiàn)。每對(duì)輥?zhàn)佣际欠聪蛐D(zhuǎn)的。輥?zhàn)涌焖傩D(zhuǎn)可以提高物料的粒度，每對(duì)輥?zhàn)拥霓D(zhuǎn)速不同粉碎得到的物料粒度也不同。典型的范圍是1.2:1 到 2.0

13、:1 （由快到慢），對(duì)于一個(gè)9 英寸23 厘米）的輥?zhàn)拥湫偷乃俣仁?300 英尺 /分 （ 395米 /分） ， 而對(duì)于一個(gè)12 英寸（ 30.5厘米）的輥?zhàn)觼碚f速度為3140 英尺 / 分（ 957 米 / 分） 。對(duì)于靠單獨(dú)電機(jī)驅(qū)動(dòng)的兩個(gè)高速旋轉(zhuǎn)地輥?zhàn)涌捎闷Щ蜴溳唩頊p小速度。在底部的第三對(duì)高速滾子可以有單獨(dú)的驅(qū)動(dòng)電機(jī)，另外輥?zhàn)颖砻娴陌疾劭梢愿纳扑俣鹊牟町惒⑻岣叻鬯樾?。輥?zhàn)臃鬯闄C(jī)通過將一對(duì)輥?zhàn)幼驳搅硪粚?duì)輥?zhàn)又?，第二?duì)裝在第三對(duì)之上的方式來提高粉碎效果，這種方式產(chǎn)生的微?？梢越档?00 微米，其粉碎能力是錘片式粉碎機(jī)的兩倍。粉碎粗糙類谷物時(shí)輥?zhàn)臃鬯闄C(jī)比錘片式粉碎機(jī)有優(yōu)勢(shì)其度電產(chǎn)量可能要比

14、錘片式粉碎機(jī)高85，飼料生產(chǎn)行業(yè)中谷類植物的典型粒度為600-900 微米，降低了生產(chǎn)成本。2：Hammer mills: hammer-millsIn 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

15、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 desir

16、ed 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 pou

17、ltry. For more in depth information regarding what actually occurs to the ingredients during size reduction please refer to this link: particle size reduction.Hammer-millsAdvantages:are able to produce a wide range of particle sizesWork with any friable material and fiberease of useLower initial inv

18、estment when compared with a roller millMinimal maintenance neededParticles produced using a hammer-mill will generally be spherical, with a surface that appears polished.Disadvantages:Less energy efficient when compared to a roller millmay generate heat (source of energy loss)produce greater partic

19、le size variability (less uniform)Hammer-mills are noisy and can generate dust pollutionGeneral DesignThe 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 ser

20、ies 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 perfora

21、ted 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 designMaterials are introduced into the paths of the hammers by a variable speed vein feeder. This type of feede

22、r 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 configurationThe design and placement of hammers is determined by operating

23、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,

24、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

25、, 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 cr

26、itical 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 sp

27、eeds 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

28、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 targ

29、et; 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 DesignThe amount of open area in a hammer mill screen determines the particle

30、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 op

31、en 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 horsepo

32、wer 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 als

33、o 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 hole

34、s 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

35、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

36、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 materia

37、l on the face of the screen.Hammer Mills HammersHammers 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

38、 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

39、ThicknessWidthDiameter to fit rod sizeSwing LengthTotal LengthHammer Mill Perforated ScreensHammer 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

40、hammer mill with the aid of the pneumatic system.Particle Size ReductionSize 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 a

41、nd 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 grains interior is exposed to digestive enzymes, allowing increased access to nutritional components such as starch and protein. The enhanced breakdown of these

42、 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 mill

43、s: 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

44、7,015m/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.Bec

45、ause 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. Th

46、e 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 pr

47、oduced 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 RodsHammers are attached to rods ins

48、ide the hammer mill, which are what they are swung on. Dimensions of rods are dependant on brand and style of the hammer mill.Roller millRoller 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

49、 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

50、 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

51、 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 millsAdvantages:energy efficientuniform particle-size distributionlittle noise and dust generationDisadvantages:lit

52、tle or no effect on fiberparticles tend to be irregular in shape and dimensionmay have high initial cost (depends on system design)when required, maintenance can be expensiveGeneral DesignThere are many manufacturers of roller mills, but they all share the following design features shown adjacent pi

53、cture:a delivery device to supply a constant and uniform amount of the material to be grounda pair of rolls mounted horizontally in a rigid frameone roll is fixed in position and the other can be moved closer to or further from the fixed rollthe rolls counter rotate either at the same speed or one m

54、ay rotate faster; roll surface may be smooth or have various grooves or corrugationsbar; 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

55、 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