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外文翻譯
英文原文
TECHNICAL NOTE
SOME FACTORS WHICH AFFECT THE GENERATION OF FLAKY PARTICLES BY A CONE CRUSHER
A．C．APLING and N．B．BARRETTT
§Department of Mining and Mineral Engineering，University of Leeds，Leeds LS2 9JT，UK
Lindley Plant，Heage，Derbyshire，UK
(Received 6 October 1995,"accepted 15 March 1996)
ABSTRACT
The products from a series of pilot scale tests have been analysed for size and flakiness to evaluate some of the factors affecting the generation of flaky material in a cone crusher．Two different feed sources characterised in terms of resistance to crushing and tensile failure were used to evaluate the influence of crusher set．feed rate and of material type on the resultant product character．
Keywords
Industrial minerals；crushing；particle morphology；comminution
INTRODUCTION
Aggregate producers must meet both size and shape specifications．The BS
Flakiness Index
F.I.= Mass flaky material in range×100 / Total mass material in range (1)
avoids a rigorous definition of particle shape by simply assigning particles according to their ability to pass a special slotted gauge．
The shape of crushed product depends on the material characteristics and the comminution method．Early work concluded that impact machines give the least and cone crushers the most flaky product and low reduction ratios favour the production of non—flaky product【2】．Cone crushers have much lower running costs particularly for harder abrasive materials and are in widespread use in the aggregate industry．
THE PROGRAMME OF WORK
Work has been undertaken with the Objective of evaluating the effects of feed rate and crusher setting on the generation of flaky material by a cone crusher from two different natural materials．Two feed rates and five crusher sets covering the range of the machine were used．The lower feed rate ensured free crushing，with particles crushed independently and loaded directly by the crusher faces．A higher level allowed material build up in the crusher feed cavity giving choked conditions where loading is achieved through a particle bed．
THE MATERIALS
The two feed materials were of similar size．The first contained two major rock types；carboniferous limestone 77％，and millstone grit(gritstone)，23％(Redland Aggregates，Masham，North Yorkshire)，the second also contained two major rocks；a metamorphic type known locally as ‘granite’，88％and ‘shale’，12％(Tarmac，Cliff Hill Quarry，Leicestershire)．
Particle characterisation
Flakiness Index【1】determination was undertaken for all materials larger than 4．0 mm．For smaller sizes，a microscope was used to distinguish flaky particles and the index determined from the weights of the two categories．A conversion factor was established between the methods．Size analysis of all materials was determined by standard sieve analysis．
Crushability
The simpler Rock Impact Hardness Number (RIHN)【3】was used rather than the recommended aggregate strength tests【4】which require extensive laboratory apparatus．Its linear relationship with tensile strength 【5】，suggests a good correlation with generation of particles by cleavage，an important mechanism in the generation of flaky particles 【6】．The Crushability Work Index(CWI)【7】was determined for comparison．Both Cliff Hill species were substantially harder than those from Masham．
THE PILOT SCALE TESTS
Tests were conducted using a Standard Symons 2-foot Cone Crusher fitted with a fine bowl having a feed opening of 57．2 thin．a(chǎn)nd recommended minimum discharge setting of 6．4 mm，【8】．Products and feed for each of twenty tests were analysed for size and shape．
DISCUSSION OF RESULTS
Full analytical results，presented elsewhere【9】，allow the characterisation of the products in terms of
1) the mass fraction in each size fraction
2) the flakiness index of each fraction
3) the flakiness index of the total product
4) the distribution of flaky and non—flaky material by size
and permitted the identification of conditions favourable for the generation of non—flaky material．
Factors affecting size distribution of product
The Masham product was generally finer than that from the harder Cliff Hill material due，in part，to its crushing behaviour．Only the Masham material showed any difference between feed rates，generating more fines during choke feeding．The granular structure of this material would tend to encourage this．A tendency for the crushing faces to be forced apart by the harder Cliff Hill feed under crowded conditions would reduce its production of fines．
Factors affecting Flakiness Index of different sizes
The pattern illustrated in Figure 1 was observed in all cases．Product flakiness of 100% at the largest size，falls as size decreases，passing through a minimum，before then increasing．All larger particles tend to be flaky but at decreasing set particles of similar size have to be increasingly flaky (thin) to enable passage through the crusher cavity．
For the Masham feed the flakiness of coarser sizes is slightly lower for choke feeding，more especially at finer sets．suggesting that under these conditions flaky material is more likely to be broken as a consequence of the restricted opportunities for favourable orientation within the crushing chamber．
Fig．1 Flakiness Index versus size--Masham Products for different feed rates and crusher sets
In all cases the size at which flakiness index is a minimum is broadly related crusher set，increasing as the crusher set increases．Overall product flakiness，calculated as the weighted mean of the index for individual size fractions is generally less under choke feeding，and reduces as set decreases．
Factors affecting sizes for peak production
Fig．2 Product distribution by shape and size--Masham choke feeding ac stated stated sets
An alternative measure of product character given by the distribution of flaky (F) and non—flaky(N) material by size，illustrated in Figure 2，also reveals differences in behaviour．
Examination of the data revealed，despite the scatter of the results，that for both materials
（1）peak production(both shapes)is related to set and in all cases tends to increase and occur in larger sizes as set increases．
（2）peak flake production occurs in a size larger than that for non—flake
Peak flake and non-flake production is similar under different feed conditions with the Cliff Hill material but increases and occurs at higher sizes as set increases．whilst for the Masham feed maximum production occurs at increasing size but flake production decreases whilst non-flake increases．Choke feeding conditions，especially at finer sets，tends to result in more non—flake and 1ess flake production although the effect on the Cliff Hill material is noticeable only at the finest set．Large sizes consist almost entirely of flaky material which escapes breakage due to favourable orientation．
General Discussion
If the form of the product size distribution is similar then a smaller crusher set should reduce overall flakiness since any increase in flakiness of the coarser sizes will be counter balanced by an increased proportion of non—flaky finer sizes．For the Masham feed this tends to be the case．The results for Cliff Hill are 1ess clear．Earlier work [2]suggested that flakiness decreases at high feed rates and also at larger crusher sets．These results appear to contradict the latter finding．However overall flakiness masks the effects on individual size fractions，some of which may not be required as product．Larger sized ftaky particles generated by crushing at large sets could presumably be removed by screening leaving the finer non—flake as product．
The increased peak non—flake production for larger crusher sets with the weaker Masham material suggests that these conditions favour the generation of a product，following rejection of coarse sizes by screening，of low flakiness．
Contrary to earlier work [2] the minimum flakiness size is always less than the size at which total production is a maximum and does not correspond to the size of maximum non—flake production．Equivalence of these two sizes would clearly generate the maximum quantity of non．flaky product，normally the objective．The ratio of maximum production sizes to minimum flakiness size allows examination of the effect of crushing conditions on non．flake production，shown in Figure 3，revealing a broad trend for these sizes to approach each other as crusher set decreases．This suggests that the most favourable conditions occur for smaller sets，that iS high reduction ratios．Although peak non—flake production increases as set increases it is accompanied by greater flake product in the same size．
The dilemma then is whether the requirement is maximum production of non—flake and that generation of flaky material in the same size is not a problem．in which case a low reduction ratio seems to be required．or whether the minimum flakiness index iS required．that is the generation of flaky material iS to be minimised in a particular size．If this is the case then a much smaller set seems to produce the required result．The choice then is between maximum production of non—flake or minimum flakiness index．In reality a compromise between the two requirements will often generate the maximum product of the required specification and close control on the set of the crushing machines will be required to ensure optimum conditions are met at all times．
The large variation in the data leads to a degree of uncertainty in relation to its interpretation and reflects the difficulty of obtaining data in relation to large sized material，nevertheless it is believed that some important trends have been identified which are of relevance to the performance of cone crushers．The work here highlights the importance of gathering further information in order properly to quantify these effects．
Fig．3 Size ratio versus crusher set
CONCLUSIONS
The broad conclusions reached from the current work can be summarised as follows；
1.Maximum flakiness occures at the maximum product size and reaches a minimum at a smaller size，related to crusher set，before increasing in the finer size ranges．
2.Flakiness of a specific size fraction increases as crusher set decreases in the coarser size range but decreases for the finer size ranges．
3.Choke feeding results in lower flakiness only for small crusher sets in the coarser sizes．This effect is reduced for the harder material．
4.The size where maximum material is generated increases as set increases．The minimum flakiness size is always less than the size for maximum production of non—flake which in turn is less than the size for maximum flake production．
5.As crusher set decreases there is a tendency for the size at which maximum production of non—flake occurs more closely to approach the size for minimum flakiness．
ACKNOWLEDGEMENTS
Thanks are due to Warren Spring Laboratories (DTI) for the support of this work.
REFERENCES
1.BS 812．Testing Aggregates．Pnn 1．Methods for determining particle size and shape．British
Standards Institute，London(1975)．
2.Shergold，H．E．，A study ol the granulators used in the production of roadmaking aggregates．
Dept．Scientific and Industrial Research，Road Research Laboratory，Technical Paper 44，HMSO
(1959)．
3.Brook。N．，F(xiàn)ines measurement of the impact testing of rocks，／nf．J．Rock Mech．Min．Scf．＆
Geomech．Abstr．，23(4)，333(1986)．
4. BS 812．Testing Aggregates．Part 2 Methodsfor determining physical properties．British Standards Institute，London(1 975)．
5. Townhill．Rewston，P．＆Hamis，A．，The relationship between Rock Impact Hardness Number
fRIHN)and tensile strength．Leeds University Mining Association Journal，l 19(1988)．
6. Kelly，E．G．＆Spottiswood，DIJ．，The breakage function；what is it reaUy?Minerals Eng．，3(5)，405(1990)．
7. Bond，F(xiàn)．C．，Crushing and grinding calculations--part 1．Brit．Chem．Eng．，6(6)，378(1990)．
8. Nordberg Symons Cone Crusher Process Manual，Bulletin No 1 10，Nordberg Manufacturing
Company，Milwaukee．
9. Barrett，N．B．，The computer simulation of cone crusher circuits for the aggregate industry．PhD Thesis，University of Leeds，Sept．1992．
中文譯文
影響圓錐破碎機的片狀粒子的一些因素
摘 要
人們從一系列小規(guī)模等級測試的產(chǎn)品尺寸和薄片狀上來分析和評估影響圓錐破碎機世代薄片材料的一些因素。兩種不同進料來源的特征根據(jù)破碎的阻力和拉伸的損壞來評價破碎裝置、進料率和材料類型對破碎產(chǎn)物的影響。
關(guān)鍵字：
工業(yè)的，礦石，決定性，粒子生態(tài)學，破碎
介 紹
所有的生產(chǎn)者都必須遵守尺寸和形狀規(guī)范。英國標準中片狀指數(shù)為：
F.I.=（片狀材料質(zhì)量/總體材料質(zhì)量）×100％
根據(jù)微粒的能力來通過一種特殊的狹槽測量，這種簡單的分配粒子要避免對微粒的外形作嚴格的定義。
壓碎的產(chǎn)品形狀依賴于材料的性質(zhì)和壓碎的方法。早期的研究工作得出的結(jié)論是沖擊機械的給料最少但圓錐破碎機可產(chǎn)生最薄的的產(chǎn)品, 而且對無薄片產(chǎn)品有較低的縮減比。圓錐破碎機的運行成本很低，尤其對堅硬的研磨材料而言。所以這種破碎機在整個工業(yè)中被廣泛的應用。
工作的程序
在對進料速率和破碎機設(shè)置客觀評估的基礎(chǔ)上，工作已經(jīng)開始實施，其中，圓錐破碎機能把兩種不同的自然原料破碎成一種片狀的物料。兩種進料速率和五種破碎裝置覆蓋了一系列使用的破碎機械，很低的進料速度確保了自由破碎的進行，粒子被獨立的壓碎而且直接被破碎面裝載，更高水平的破碎是原材料在裝填完成時被堵塞的情況下允許破碎機進料腔增大。
原材料
兩種進給原材料有著相似的尺寸，第一種包括兩種主要的巖石類型，77％的含煤石灰石和和23％的磨石沙礫（即砂巖，紅土聚集體，馬薩姆，英國約克郡 北部），第二種也包括兩種主要的巖石類型， 88％變質(zhì)的眾所周知的花崗巖，和12％的泥板巖（懸崖希爾采石場，英國中部的州） 。
粒子特征
片狀指標對所有大于4 mm 的材料有用。對更小尺寸的來說，顯微鏡用來辨別薄片的微粒，片狀指標用來確定兩種類型的重量。然后在方法中建立一種轉(zhuǎn)換因數(shù)。經(jīng)過標準的過濾，所有材料的的尺寸分析就確立了。
破碎能力
簡單的巖石沖擊硬度值（RIHN）可以被直接應用，而不需要大量試驗裝置儀器的集中強度測試，它與抗拉強度的線性關(guān)系，
小規(guī)模等級測試
這種測試是用兩腳的進料口尺寸為57..2mm的標準圓錐破碎機來進行的。它的最小理論出料粒度為6.4mm,每進行20次測試試驗，就對破碎產(chǎn)物和進給原料的尺寸和形狀上的變化進行一次分析。
結(jié)果討論
由上述試驗，我們經(jīng)過全面的分析，認為影響產(chǎn)物粒度的主要因素有一下幾個方面：
(1)質(zhì)量分率在粒度級份額中所占的幾率；
(2)每個質(zhì)量分率所占幾率的片狀指標；
(3)整個產(chǎn)物中片狀指標；
(4)片狀材料和非片狀材料在尺寸上的分布；
以上是可以證明有利于非片狀物料產(chǎn)生的條件。
影響產(chǎn)品尺寸分布的因素
馬薩姆（地名）生產(chǎn)的原料一般要好于從懸崖或石山上采集的堅硬的原料，部分原因就在于它們的特性不同。在過飽進料中，只有馬薩姆原料向我們展示了進給速率之間的任何不同之處，就是產(chǎn)物變得更細小了。這也許是馬薩姆原料具有規(guī)則的結(jié)構(gòu)引起的．希爾懸崖采石場堅硬的原材料在過飽進料中有被強制破碎的趨勢，從而影響了產(chǎn)品的粒度。
影響不同形狀粒度的因素
圖1向我們展示的可以適用于任何情況。產(chǎn)品的粒度在破碎之前是100％，為最大，經(jīng)過破碎后就會減小,出料后是最小。所有的大尺寸粒子更傾向于成薄片狀，但是有相近尺寸粒子的必須逐漸的成薄片（變薄），以致于能夠通過破碎腔。
對馬薩姆原材料來說，它過飽進料時的產(chǎn)品比較粗糙的尺寸要小一些，尤其當破碎機的設(shè)置達到良好的狀態(tài)時更明顯。這樣我們也可以得到一個推論：在過飽進料的情況下，只要嚴格控制破碎腔中對薄片材料破碎的有利方位,它更容易被破碎的完全。
圖一 馬薩姆原料在不同進給速率和破碎設(shè)置時的產(chǎn)品粒度尺寸
在所有的情況下，片狀指數(shù)都是最小的尺寸，這在很大程度上都與破碎機的設(shè)置有關(guān)。它隨著破碎機設(shè)置的增大而增大，對所有的片狀產(chǎn)物，在過飽進料時，對它們統(tǒng)計的個體粒度份額都有明顯地減小，而且隨著破碎機的設(shè)置的減小而減小。
影響產(chǎn)品最大粒度的因素
薄片材料和非薄片材料的的產(chǎn)物尺寸特性的分布，如圖二所示，也向我們揭露了一些行為上的不同。
圖二 破碎機的設(shè)置一定時，馬薩姆原料在過飽進料的情況下產(chǎn)品形狀和尺寸的分布
盡管結(jié)果有些分散，但仔細分析圖中表明的數(shù)據(jù)，我們就會發(fā)現(xiàn)兩組原材料：
(1) 產(chǎn)物的最大粒度（包括兩種形狀）和破碎機的設(shè)置有關(guān)，而且在所有的情況下粒度都會隨著破碎設(shè)置的增加而增加。
(2) 最大產(chǎn)物粒度在大于非薄片的尺寸中發(fā)生。
不同的進料條件，對懸崖希爾采石場采集的原料來說，薄片材料和非薄片材料的最大產(chǎn)物粒度基本上是相近的，同時較大的尺寸隨著破碎設(shè)置的增大而產(chǎn)生。但對進給的馬薩姆原料來說，最大的產(chǎn)物粒度發(fā)生于增大的破碎設(shè)置時，薄片材料的產(chǎn)物粒度減小時而非薄片材料的產(chǎn)物粒度卻增加。當過飽進料時，尤其在破碎設(shè)置達到最優(yōu)狀態(tài)時，更易于產(chǎn)生較多的非薄片材料和較少的薄片材料，盡管懸崖希爾原料只有在破碎機設(shè)置最優(yōu)時的破碎效果是引人注目的，同樣如此。大的尺寸幾乎都是由薄片材料組成的，因為它們有利的方位，常常逃脫被破碎。
綜合討論
如果產(chǎn)品尺寸形態(tài)的分布是相似的，那么一個小的破碎設(shè)置就會減小所有的產(chǎn)物粒度，因為較粗糙的薄片尺寸的任何增加將會被一個增加的比例比率來平衡。馬薩姆原料的進給就是這樣的例子。但懸崖希爾采石場原料的結(jié)果卻是不清楚的。早期的工作曾給出過這樣的結(jié)論，保持較大的破碎機設(shè)置，而補給速率很高，片狀粒度也可以減小。這個結(jié)論看起來與后面的的發(fā)現(xiàn)有矛盾之處。因為片狀指數(shù)掩飾了對個別的粒度份額的影響，有些并不能如產(chǎn)品的要求的那樣。大的破碎機設(shè)置可以產(chǎn)生的較大尺寸的片狀粒子，這些大的片狀粒子尺寸可以假設(shè)將那些優(yōu)良的非片狀的粒子作為產(chǎn)品。
較脆的馬薩姆原料在大的破碎設(shè)置下，得到的非薄片產(chǎn)物的粒度會隨之增加。這說明了這種狀況有利于產(chǎn)品的產(chǎn)生，降低了產(chǎn)物粒度的尺寸。
與早期的工作相比較，最小的薄片粒子尺寸小于所有破碎產(chǎn)物中的最大值，但和非薄片原料的最大破碎產(chǎn)物的尺寸不相符。客觀上講，這兩種同等的尺寸可以產(chǎn)生最大尺寸的非薄片產(chǎn)物。最大產(chǎn)物的尺寸與最小薄片尺寸的比值驗證了破碎條件對非薄片產(chǎn)物的影響。圖三所示的正好說明了當破碎機設(shè)置減小時，這些破碎產(chǎn)物的尺寸有互相接近的趨勢。同時這也給我們提示了最有利的條件發(fā)生在破碎機設(shè)置值較小的的時候，即減速比較大的時候。盡管非薄片產(chǎn)物的最大粒度隨著破碎機設(shè)置值的增大而增大，但伴隨著相同尺寸的片狀產(chǎn)物。
讓我們感到兩難的是這是不是符合非薄片產(chǎn)物的最大產(chǎn)量，而且片狀原料是否都有相同的尺寸，在這種情況下，低減速比看起來是需要的，或者說最小的薄片粒度是不是必需的，就是將薄片材料減小到合適的尺寸范圍之內(nèi)。如果在這種情況下，較小的破碎機設(shè)置看起來就可以產(chǎn)生所需要的結(jié)果。這樣就可以選擇最大的非薄片產(chǎn)物或最小的片狀產(chǎn)物。實際上，兩種需求的折衷通常會產(chǎn)生符合要求規(guī)格的最大產(chǎn)品，并且很接近破碎機的設(shè)置值，而這些破碎機需要保證隨時都能滿足最優(yōu)條件。
數(shù)據(jù)中的最大變量導致了與其解釋相關(guān)的不確定度，而且反映了獲得與薄片大尺寸原料有關(guān)的數(shù)據(jù)的難度。然而一些重要的的趨向并不能使人相信可以確定圓錐破碎機的運轉(zhuǎn)相關(guān)性。我們在此所做的工作就是為了收集更多更重要的信息以便于更合理的說明這些影響因素。
圖三 破碎機設(shè)置值與破碎產(chǎn)物的尺寸比
結(jié) 論
1.最大的片狀粒度產(chǎn)生在的產(chǎn)物尺寸最大時，反之，最小的片狀粒度產(chǎn)生于產(chǎn)物尺寸較小時。
2.在粗糙的尺寸大小范圍內(nèi)，小部分特殊的薄片產(chǎn)物粒度在破碎機設(shè)置較小時反而會增大。
3.過飽進料只有在破碎機的設(shè)置較小時才可以產(chǎn)生小的產(chǎn)物粒度。但對較硬的材料來說這種影響會減小。
4.大尺寸原料破碎產(chǎn)物的尺寸隨著破碎機設(shè)置的增大而增大，薄片原料的最小尺寸要小于非薄片原料最高產(chǎn)量時的尺寸，反過來非薄片原料的最小尺寸要小于薄片原料最高產(chǎn)量時的尺寸。
5.當破碎機設(shè)置減小時，非薄片原料的最大產(chǎn)物尺寸有互相接近的趨勢，非常接近最小剝落薄片的尺寸。
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