【正文】 。 篩分就是將顆粒大小不同的混合物料，通過(guò)單層或多層篩于分成若干個(gè)不同粒度級(jí)別的過(guò)程。礦物在經(jīng)過(guò)破碎后，常常以各種粒度不同的物料混合存在，有的物料甚至還含有水分、粘土或其他雜質(zhì)，所以需通過(guò)篩分以滿足生產(chǎn)工藝及操作過(guò)程的要求。 篩分機(jī)械分類 篩分機(jī)械的分類方法較多，可按運(yùn)動(dòng)軌跡、傳動(dòng)方式分類，也可按其用途分類。通常分為固定篩和運(yùn)動(dòng)篩兩大類. 。 Types of screens Stationary Screens The grizzly. in its simplest form, consists of a series of heavy parallel bars set in a frame. Sieve bends. has a curved screen posed of horizontal wedge（楔形） bars. Revolving screen is a slightly inclined, rotating cylindrical screen, which can be used wet or dry. Moving Screens Shaking screens . They are widely used dry in coal preparation, but find little use on abrasive metalliferous ores. Reciprocating screen. Reciprocating screens employ a horizontal gyratory motion to the feed end of a rectangular screen by means of an unbalanced rotating shaft. Gyratory screens. This type of screen, which imparts gyratory motion throughout the whole screen cloth, is being widely used for fine screening applications. Vibrating screens. Their main application is in crushing circuits where they are required to handle material ranging, in general, from 25 cm to 5 mm in size.Lesson2 Principles of ClassificationFree Settling 粒度、形狀和比重不同的礦粒群，在水中按沉降速度的不同分成若干窄級(jí)別的作業(yè)，稱為濕式分級(jí)。 在閉路磨礦流程中，分級(jí)設(shè)備的作用在于及時(shí)分出磨礦合格產(chǎn)物，避免過(guò)磨。同時(shí)又可以分出不合格的粗砂，返回再磨。這對(duì)于保證較好的分選效果及提高磨礦效率意義很大。 自由沉降:沉降過(guò)程中，單個(gè)物體在無(wú)限的介質(zhì)中的沉降，稱為自由沉降。 介質(zhì)阻力:介質(zhì)阻力由摩擦阻力(粘滯阻力)和壓差阻力（紊流阻力）所組成，這兩種阻力同時(shí)作用在礦粒上。 摩擦阻力：由于介質(zhì)的粘性，使介質(zhì)分子與礦粒表面存在粘性摩擦力，這種因粘性摩擦力所致的阻力，稱為摩擦阻力。 壓差阻力：由于介質(zhì)的慣性，使運(yùn)動(dòng)礦粒前后介質(zhì)的流動(dòng)狀態(tài)和動(dòng)壓力不同，這種因壓力差所引起的阻力，稱為壓差阻力。 等降比：沉降過(guò)程中，往往存在某些粒度大、密度小的礦粒同粒度小、密度大的礦粒以相同沉降速度沉降的觀象。叫做等降現(xiàn)象。密度和粒度不同但具有相同沉降速度的礦粒，稱為等降顆粒。等降顆粒中，小密度礦粒的粒度與大密度礦粒的粒度之比，稱為等降比。Review of the last lesson Principles of classification Classification is a method of separating mixtures of minerals into two or more products on the basis of the velocity with which the grains fall through a fluid medium. Free settling refers to the sinking of particles in a volume of fluid which is large with respect to the total volume of particle, hence particle crowding is negligible. Resistance to settling particles: In a viscous medium, resistance to the settling particles movement increases with velocity. Factors affecting the terminal velocity: the terminal velocity of a particle in a particular fluid is a function only of the particle size and density. Freesettling ratio is the ratio of particle size required for the two minerals to fall at equal rates.Lesson4 Types of Classifier 1. 分級(jí)機(jī)種類。傳統(tǒng)分為兩類：按照流體流動(dòng)方向分為垂直流分級(jí)機(jī)和水平流分級(jí)機(jī)。垂直流動(dòng)分級(jí)機(jī)主要為水力分級(jí)機(jī)；水平流分級(jí)機(jī)主要包括：沉降錐和機(jī)械分級(jí)機(jī)。 2. 常用設(shè)備：上述分類方法并不科學(xué)，因?yàn)橛行┰O(shè)備并不符合上述分類方法。在磨礦回路中常用的分級(jí)機(jī)主要包括機(jī)械分級(jí)機(jī)和水力旋流器兩種；在重選中常用的分級(jí)機(jī)包括沉降錐和水力分級(jí)機(jī)兩種。 (1) 水力分級(jí)機(jī) 主要用于重選給礦的分級(jí)，目的是將混合粒級(jí)分為不同的窄粒度級(jí)別，便于重選處理。 四室水力分級(jí)機(jī)：力度大小不同的顆粒分別在不同分級(jí)箱中沉積。 （2）沉降錐（脫泥斗） 粗粒沉降速度快，從底部排出，細(xì)泥難沉降從頂部溢流堰排出，達(dá)到脫泥和濃縮的目的。 （3）機(jī)械分級(jí)機(jī)螺旋分級(jí)機(jī) 礦漿從分級(jí)機(jī)的給礦口給入傾斜安裝的U形槽體。隨著螺旋的低速回轉(zhuǎn)和連續(xù)不斷地?cái)嚢璧V漿，使得大部分輕而細(xì)的顆粒懸浮于上面，從溢流堰溢出，成為溢流產(chǎn)品；粗而重的顆粒將沉降于槽底，成為沉砂，由螺旋輸送到分級(jí)機(jī)的返砂排礦口排出。v （4）水力旋流器 是一種利用離心力作用的分級(jí)設(shè)備。構(gòu)造簡(jiǎn)單，沒(méi)有運(yùn)動(dòng)部件，體積很小，占地面積少，單位面積處理能力大，操作維護(hù)方便，成本較低。目前，我國(guó)一些選礦廠已經(jīng)成功地用水力旋流器代替了螺旋分級(jí)機(jī)。 此外，還可用于濃縮、脫泥、選煤等領(lǐng)域。 它存在砂泵動(dòng)力消耗大，設(shè)備磨損嚴(yán)重，以及給礦壓力、給礦量波動(dòng)對(duì)生產(chǎn)指標(biāo)有影響等缺點(diǎn)。Review of the last lesson Types of classifiers Hydraulic classifiers (vertical current classifiers) normally consist of series of sorting columns through each of which a vertical current of water is rising and particles are settling out. Horizontal Current Classifiers include Settling cones and Mechanical classifiers. Settling cones are often used in the aggregate industry to deslime coarse sands products. And, Mechanical classifiers have widespread use in closedcircuit grinding operations and in the classification of products from orewashing plants. The Hydrocyclone is a continuously operating classifying device that utilizes centrifugal force to accelerate the settling rate of particles. It is widely used in closedcircuit grinding operations but has found many other uses, such as desliming, degritting, and thickening. Uint4 Lesson1 Principles of Gravity Concentration 重力選礦是按照礦石中不同礦物之間的密度差異而實(shí)現(xiàn)礦物分離的一種選礦方法. 重力選礦是在一定的流體介質(zhì)中進(jìn)行的，所用介質(zhì)通常為水，亦有時(shí)用空氣或重介質(zhì)(重液或重懸浮液)。 重選可選性準(zhǔn)則（系數(shù)）Review of the last lesson Principles of Gravity Concentration Gravity processes are relatively simple and produce paratively little environmental pollution. It is essential for effective separation that a marked density difference exists between the mineral and the gangue. Some idea of the type of separation possible can be gained from the concentration criterion. The motion of a particle in fluid is dependent not only on its specific gravity, but also on its size. Gravity separators are extremely sensitive to the presence of slimes (ultrafine particles), which increase the viscosity of the slurry and hence the sharpness of separation, and obscure visual cutpoints The feed to jigs, cones, and spirals should, if possible, be screened before separation takes place, each fraction being treated separately Almost all gravity concentrators have an optimum feed pulpdensity, and relatively little deviation from this density cause a rapid decline in efficiency.Lesson2 Jigs 跳汰選礦:礦粒混合物在垂直升降的變速介質(zhì)流中，按密度差異進(jìn)行分層和分離的過(guò)程，謂之跳汰選礦。跳汰選礦的過(guò)程中所使用的介質(zhì)可以是水，也可以是空氣。 跳汰過(guò)程：顆粒群的松散、不同密度礦物顆粒的分層、不同密度礦物顆粒分離。 跳汰機(jī)的構(gòu)造及工作原理 脈動(dòng)機(jī)構(gòu) 跳汰室 篩下室 篩下水 跳汰機(jī)的類型及應(yīng)用 跳汰機(jī)根據(jù)所用分選介質(zhì)的不同，分水力跳汰機(jī)和風(fēng)力跳汰機(jī)兩大類。在實(shí)際使用個(gè)，無(wú)論是選礦還是選煤，國(guó)內(nèi)外應(yīng)用最普遍的是水力跳汰機(jī)；風(fēng)力跳汰機(jī)只在干旱缺水地區(qū)或不能被水浸濕的物料，使用范圍很小。 水力跳汰機(jī)類型很多，根據(jù)設(shè)備結(jié)構(gòu)和水流運(yùn)動(dòng)方式不同，可分為（1）活塞跳汰機(jī)； (2)隔膜跳汰機(jī)， (3)空氣脈動(dòng)跳汰機(jī)； (4)水力脈動(dòng)跳汰機(jī)： (5)動(dòng)篩跳汰機(jī)等。Review of the last lesson Jigs In the jig, the separation of minerals of different specific gravity is acplished in a bed which is rendered fluid by a pulsating current of water so as to produce stratification. The initial acceleration of the mineral grains is thus independent of size and dependent only on the densities of the solid and the fluid. If the mineral particles are examined after a long time they will have attained their terminal velocities and will be mov