滾壓機(jī)設(shè)計影響喂料系統(tǒng)的壓應(yīng)力

1、隹怵蟠寢訾泵菟躓熄鋯鱉 妲誆輕羊鳋女獨觶梳玖冠伍液瘟熵巧訶眄扛顛著陀銳磊鰥乙潰始鳴勉鏌揉甩緘絡(luò)拼厶笤蒯尼猜攖符疑巰銬錳冢不簏拾霏楫癥詰菪覡鋏妯充汞貿(mào)扼嶸攻婧 外文翻譯獒毫堯尸胲巳倉疰喇垛煨脞瀠冢喋碳祈乓員鱸愚紀(jì)鈕航然喀臘熘壙傘烀平解仇韉白槭恩蔣冶窄吠挨鋮頌枯轄拋明戕竅擾松阿閽囡钚劁唱翡歿和癩搖琢稞昂庶浜圄螈跗諦緹倬碥圪鈾頑沁菀蚵逑僬獠醍樓凈專 業(yè) 過程裝備與控制工程 陔偽徊攢公耄狄翻銠諤蘄學(xué) 生 姓 名 鞘籪次披懷講旦直僑蠢洌班 級 班鑰怪蘿熒蚵罰沒洋黨橙學(xué) 號 塑怵溲犬绔諒攏斑薪重眨指 導(dǎo) 教 師 鲞鼐噸竽荑紙?zhí)`撞娜澄量.垤釘島花漂恣響躥鞫筒邦綺馮磙雒鰨莼騁挖庖興奶 訾智拿閡看蒞浜蕉票逕冱隹

2、樸糠伯殂悝啊奴罄偷門滾壓機(jī)設(shè)計影響喂料系統(tǒng)的壓應(yīng)力請凰蝙鱈故的蓉稗咔攢錸P. Guigon它劁皓馭漠橫及手椹勞激摘要鐳竊瘓匣伉投渭痙烘毯謗在文章的第一部分，敘述了滾壓機(jī)的主要特點。 然后,講述了喂料和擠壓質(zhì)量之間的關(guān)系。 對于某個靜態(tài)差距(無負(fù)載) ，滾壓機(jī)的處理量是由螺旋喂料速度決定的,與滾筒的速度快慢和需要壓實的生產(chǎn)材料無關(guān)。當(dāng)處理量是多種多樣的時候，控制差距是一個獲得相同質(zhì)量壓坯的好方法。對強(qiáng)烈環(huán)節(jié)緊湊的應(yīng)力分布的解釋和說明，這些應(yīng)力是分布在由一根周期旋轉(zhuǎn)的螺桿喂料的滾壓機(jī)上的。 珀秘諂郄發(fā)旅岌蛄促籬郛關(guān)鍵詞：輥壓； 喂料裝置； 壓坯異質(zhì)； 差距控制炭跎瘟采咂展螟皂禁妤錁1引言罰啤吞孔酒

3、砍漯諑跏膃坡由于滾壓機(jī)簡單、低營運成本的理念，而且用材廣泛，所以被用在了許多不同的行業(yè)(化工、制藥、 食品加工、采礦、礦產(chǎn)、冶金)上。廣泛的垃圾回收或處理就是一個新興的應(yīng)用領(lǐng)域。滾壓機(jī)的擠壓要比第一眼看上去的復(fù)雜。 對很多參數(shù)和對滾壓機(jī)理的缺乏了解導(dǎo)致了滾壓機(jī)沒有產(chǎn)品的優(yōu)越性。 這篇文章將講述滾壓機(jī)的主要部分。 文中將注意力集中在了解喂料裝置是如何影響壓實質(zhì)量的。距肚回綴絨淬鱘鱈錚磕圉2. 滾壓機(jī)的概說1-5 嗽悚捉咧笫鲇報沒夠讖躍滾壓機(jī)的滾壓是一個連續(xù)的過程。 功能原理很簡單：料粉是通過重力方式或者通過一根連接兩個方向相反正在旋轉(zhuǎn)的輥子的螺桿喂入。 由材料和滾筒表面產(chǎn)生的摩擦在輥子之間的狹小

4、空間里帶出料粉，在這些空隙里粉末產(chǎn)生的強(qiáng)大應(yīng)力導(dǎo)致了其結(jié)構(gòu)緊湊。 如果滾筒是平滑的或者是槽型的，物料被壓緊成致密片 而口袋卷筒將形成煤球型的(如圖1所示)。瑁賑衛(wèi)啞察翎焉駟施霹爸域裂彀畫仇刁艙磕肫詔氌圖1：滾壓機(jī)中的壓塊和壓坯癟刃穎艋桌岷鷗撒抒掠榭2.1. 壓實機(jī)制 怎羋讠就昆嗡難敉璀搓墓輥子之間的空間，一般分為三區(qū)，在這三個區(qū)由不同的機(jī)制作用。喂料區(qū)：在這個區(qū)顆粒的整理應(yīng)力很小而且致密性很純粹； 壓實區(qū)：在這個區(qū)擠壓力作用明顯；擠壓區(qū)：顆粒開始塑性變形和/或被壓碎。在喂料區(qū)和壓實區(qū)之間的角度是鈍角或者是銳角。 眥陡躥胲位苡葺霖廩庹惝夜卉蟣縝躕淅訥蓮載摑鏵圖2：由壓電傳感器測量的應(yīng)力分布酚閡喚

5、涅賁覆許扌景鱉莫2.2. 典型應(yīng)力偌佇滔雯況綴宓瓶蕢藿穩(wěn)輥子間隙間的壓應(yīng)力的正常分布如圖2所示。在喂料區(qū)當(dāng)滾筒作用在粉末上的壓力很小時(小于0.1兆帕)， 它不能用壓電傳感器測量。 只有壓實區(qū)的應(yīng)力才可以用它測量。 應(yīng)力擴(kuò)增在小于直角的情況下發(fā)生。 應(yīng)力增加至最大值，這個最大值相當(dāng)于到達(dá)中性角度。 在許多情況下，角度的改變不和輥子間隙成比例，是因為材料覆蓋在滾筒的表面。 直角之后，壓坯被排出。 彈出物對應(yīng)的壓力急劇下降。郄碘毹潮瘠轡闔攉堆麼啊2.3.滾壓機(jī)所具有的優(yōu)缺點：桉擠褶怨鋁菹喲銥灞飯咕滾壓機(jī)滾壓物料有以下幾個優(yōu)點：柙偷眈紆樾賃桅囂琴臀驕 (1)允許連續(xù)運行和有多功能的高生產(chǎn)能力:適合重

6、工業(yè)每小時幾百噸的生產(chǎn) (礦產(chǎn)、肥料等)。蒯瞍瓞衤返齡嬋巴毖賞啷 (2)壓實成本低。 帶動滾筒和螺桿運轉(zhuǎn)的能量是有限的。通常，干燥這一步是不需要的。茸糧垌皚酃煸鉤序鷲蟮髕 (3)需要壓實的熱材料的氣溫高達(dá)1000攝示度是可能的。稹捺閼患循致蔦菡列內(nèi)宗然而，這項技術(shù)目前還有一些弊端：壩留鈥洵船悻篪隸蔣抽轂壓坯的外形和尺寸比沖模擠壓出來的不規(guī)則。料粉的泄漏也要重點解決。未壓碎的料粉也需要再擠壓。使用真空除塵系統(tǒng)可以大大減少(可降百分之幾)細(xì)粉的泄漏2。哩竺庹匭氦意用毒善汛釣班晾壹皈噻葬沁俸痙艟釃圖3：滾壓機(jī)的結(jié)構(gòu)謚哳鱗錄扛纘燴沱鍋肴艄 2.4.技術(shù)苣淌牖褡母斟蘆貌比材豢 無論制造商是誰，滾壓機(jī)的原

7、理都是一樣的,而且滾壓機(jī)都有相似的結(jié)構(gòu)配置。 市場上賣的滾壓機(jī)的輥子有水平放置的，有垂直放置的，有傾斜放置的，(如圖3所示)。兩種不同的結(jié)構(gòu)設(shè)計要根據(jù)滾壓機(jī)放置位置的合理性來選擇最優(yōu)的設(shè)計方案。杷嗾蝻珉棒潑削盡夭委婢在懸臂軸設(shè)計中，棍子是被置于框體外面的（如圖3所示）。 這種設(shè)計通常被用于小型機(jī)器；這樣的設(shè)計便于輥子的維修。 比較大型的機(jī)器用中間軸的設(shè)計結(jié)構(gòu)，這就意味著，軸的兩端是由鉸鏈連接軸承旋轉(zhuǎn)的，而且輥子是位于框體里面的。制造商對A、B、C三種結(jié)構(gòu)的優(yōu)點持有不同的意見。一般來說，一個輥子的軸承在機(jī)體里的作用是固定不變的，然而其他可移動的輥子的軸承是靠水壓力調(diào)節(jié)的遼魘兕杳灣踐建榭藹詘校2.

8、5.滾動和擠壓系統(tǒng)喙哈憶聲省姆繃辰蘩司罪輥子選擇的方法一般有兩種:幾何特征(光滑、槽、 和容器設(shè)計)和表面硬度。 對于壓塊，容器造型的優(yōu)先使用，這是為了減少排除物的問題和擠壓造成的破壞：作用于壓坯上的最大允許壓力很大程度上取決于輥子的直徑。 越大的壓力被用于越大的機(jī)器上。 輥子的驅(qū)動組件必須保證兩根軸間有一個恒定的轉(zhuǎn)距和一個相等的速度，這是為了阻止輥子較早的被磨損壞和破壞壓坯的剪應(yīng)力的形成。為了防止壓塊，兩個輥子間的旋轉(zhuǎn)速度必須一樣。一般來說,液壓系統(tǒng)是用來維持滾動軸承座的. 采用這種系統(tǒng)，應(yīng)用力的調(diào)整范圍可以更廣泛。 殿豐閆訶牢晰耀繇桄昵柿2.6.喂料系統(tǒng)及隔離吲眥孱以樞煊封靈恁抄茨喂料系統(tǒng)

9、是一個好的擠壓過程的關(guān)鍵。它必須完成一個統(tǒng)一的連續(xù)的物料流動，這是為了恰當(dāng)而充分的填滿輥子間的量從而使壓坯形成不均勻質(zhì)。 該喂料系統(tǒng)還用于密封和除塵裝置。 兩種不同類型的喂料系統(tǒng)主要是依靠流動特性和粉末的密度來區(qū)分使用的。致密性需要制作壓坯有足夠的質(zhì)量保證：重力的自由向下喂料和強(qiáng)迫喂料(粉末是被一個或幾個螺桿推向輥子的)。 擋肛慣綸科噲咱館洙跡顴2.7.粉末的除塵靜民倪藏蠊鼽臚嗜裕廢幸 粉末中的空氣有兩種逃走的方法:通過料粉的軸中心，來到喂料裝置處；通過輥子之間的空隙和面夾板。 一些空氣可以在棍子內(nèi)被壓縮， 這是一個限制生產(chǎn)量和壓實質(zhì)量的關(guān)鍵因素2。 在壓實區(qū)使用真空除塵可以有效的優(yōu)化輥壓質(zhì)量

10、和減小未擠壓的粉末的泄漏。 猛羆襠寵帚銻煊訕杞賄擺3. 在實驗室滾壓機(jī)中喂料和壓實相互關(guān)系的闡述鈾翡椐澇成潔艙糸忐徇婷3.1.實驗室滾壓機(jī)瓦嚀鏡粟套筆收脞庹駁蠣實驗室進(jìn)行實驗的過程如圖示4所示。 滾壓機(jī)配備了垂直安裝的130毫米直徑50毫米寬的圓盤。滾壓機(jī)的詳細(xì)描述和須知將在3-6給出。辱服塢八儀唔鍰嬈抻艘詰 亮嵇鑠攖裘擲謝孓詞額碾圖4：實驗室的滾壓機(jī)：（1）輥子（2）軸承座（3）輥軸（4）水平支撐系統(tǒng)（5）螺旋喂料（6）攪拌器（7）喂料漏斗（8）金屬夾（a）壓電變換器（b）移動變換器疙牌焦跨耔揎寧疴金田詛3.2. 滾壓機(jī)的吞吐量啄胨岈尻抉英氨牛蛸欒黲對于細(xì)粉而言，滾壓機(jī)的進(jìn)料量是由兩個因素限

11、制的。一方面，進(jìn)料量是由細(xì)粉的除塵能力限制的。而另一方面，壓實速度又是由顆粒的彈性度限制的。一般來說，當(dāng)達(dá)到臨界流量時壓實的質(zhì)量比較差。在這種情況下，要么是由壓實引起的風(fēng)流影響了喂料（除塵能力差），要么是壓實的速度太快。這項研究的所有實驗都將在低于這個臨界流量時進(jìn)行。因此，當(dāng)出現(xiàn)細(xì)粉壓實沒有產(chǎn)生帶鋼或者帶鋼的質(zhì)量差的問題時，不是由除塵能力差或滾壓速度過高（擠壓時間短）引起的。戳沽暝椅償段賡闥巧嶝筮3.3.擠壓率好的擠壓場合極笱昭儋痦扣蘭鈐臆庫擠壓速度和螺桿轉(zhuǎn)速的范圍大可在實驗室滾壓機(jī)中得到解決。因此，我們研究了在擠壓帶鋼成形中滾壓速度和螺桿速度對它的影響。為了清楚地發(fā)覺高低滾壓速度的限制對擠壓

12、成形的影響我們使螺桿速度固定選擇它的擠壓速度。在滾壓速度低時將發(fā)過度擠壓，而在滾壓速度高時將不形成帶鋼。紛歙扣膻囟柵蹤輇搶艷怯三個操作條件規(guī)定如下：季乃廨韶攜菊嵫崽騙孚閣當(dāng)喂料不足時，由螺旋喂料提供的大量粉末的操作滾壓率會太小。在這種情況下，不能擠壓微粒物質(zhì)。斕偏鄰媯弁枸饜貴蠱熔艏當(dāng)喂料過多時，由螺旋喂料提供的大量粉末的操作滾壓率會太大。滾子與滾子之間空隙的增大是很重要的。在喂料過多的情況下，擠壓出來的物質(zhì)質(zhì)量會差而且未擠壓的粉末的流失也很嚴(yán)重。晏倡貞滯郝玀亞酥鈄蝦佬好的擠壓率是在處于喂料不足和喂料過多之間的擠壓率。當(dāng)擠壓材料時產(chǎn)生的帶鋼具有足夠的凝聚力和力學(xué)強(qiáng)度時，才會有好的擠壓率。琚腱洞招

13、儺湘蒽鄰杯沫貪淳軍躥置刨考棼炭葜瞥凄圖5：不同輥子對應(yīng)不同旋轉(zhuǎn)速度的壓坯的輸出誚競戴庭釓鄶氈棠鐋叔閱波訊殷兌鬼塹蝙暑鋃湊豐圖6：輥子的不同速度對應(yīng)不同的旋轉(zhuǎn)速度而且物料的輸出依靠旋轉(zhuǎn)速度而不是和輥速成正比逗逮哪鈕驕冗衰課硇氨聃當(dāng)螺桿轉(zhuǎn)速固定時，滾壓吞吐量是由多種能夠形成好的擠壓的滾壓速度衡量的（如圖5所示）。對于固定的旋轉(zhuǎn)速度，滾壓機(jī)的吞吐量也是個常數(shù)。在圖6中，吞吐量是由多種滾壓速度下的旋轉(zhuǎn)速度決定的。這個吞吐量要比螺桿單獨作用時的吞吐量小。由滾動產(chǎn)生的壓力改變了粉末在螺桿內(nèi)的滑動狀態(tài)。鐨捩咭仉鎪鳩蝕踝俟稼醣 3.4. 軋輥輥縫的變化貓輥摑鮞炬穹汰嘈黑骯壢如果上布的軋輥能縱向移動，當(dāng)傳動力是

14、恒定時軋輥的縫就能從初值增加到一個恒定值。恒定值是軋輥作用在壓實材料上的平均壓應(yīng)力的作用。它也是輥速度vr的作用，軋輥的生產(chǎn)量是QC,材料的壓實密度是Qs，軋輥寬是L，壓實材料的摩擦系數(shù)是f3：e=QcLVrs(1-) 輥縫測量有許多工作要點（輥速度和螺旋轉(zhuǎn)動速度），國際質(zhì)量曲已給出(如圖7所示)。怯腳晁貫菪蕤邳逞拙蝗榷闃恃撈汁誄叉壅放袱冕衽圖7：輥子和螺桿的速度之間的標(biāo)準(zhǔn)間隙差距，初次間隙是0.8mm鎊嫉槳橛砜旒淫叮到您笨3.6. 應(yīng)力的波動與鐳的不同成分的關(guān)系如表6船腺闔嘞嘌枝乙纟景給霸緊湊的密度分布的特點是通過衡量一個氯化鈉晶體的傳遞分布。 適當(dāng)?shù)膲毫δ苁孤然c晶體支離破碎。因此，同樣的

15、氯化鈉晶體不是到處都能傳遞光的。 因為氯化鈉的透光性能是與局部緊湊地方的壓力有關(guān)的。 承受較少壓力的地方因此出現(xiàn)暗色(如圖11所示)。機(jī)械性能良好可以作為獲得緊湊性的特點，例如粉碎被使用過的氯化鈉(硼粉74時)。 施加在物料上的壓力既不符合輥寬度也不符合時間常數(shù)。 期刊的分布不均。 周期現(xiàn)象就是螺旋反饋線的周期。 事實上，施加在滾軸間隙上的壓力分布與喂料系統(tǒng)壓力的分布有關(guān)。喂料系統(tǒng)的壓力有來自螺旋饋線的。喂料壓力的不均勻是由于最后螺旋的螺桿的傳動力不均勻。擅完鋃藍(lán)疚麂疾蜩棖說隗 揄特膣瓤剎毯筱美詠蜍紳圖11：氯化鈉的透光性（氯化鈉d50，Am74），上圖叨沒灬擒尜薰恭廷俞磕坤 氯化鈉照片的標(biāo)準(zhǔn)

16、灰色度，下圖身難褫桅沒卅匠琵褊璽幬4. 結(jié)論肭濠括湟酮霾痔冕疝嬖呦喂料和壓縮特性之間相互作用得到了證明。 因為使用螺旋給料器，大的壓應(yīng)力產(chǎn)生了，并被當(dāng)作滾動和轉(zhuǎn)動的作用力。壓力的大小僅由螺桿給料器決定，和生產(chǎn)材料以及棍子的轉(zhuǎn)速都沒有關(guān)系。結(jié)果表明差距曲線可以近似于國際質(zhì)量曲線。因此，當(dāng)壓力的量不同時，控制差距是一個好方法，可以用這種方法來獲得相同的壓應(yīng)力。對墻的觀測表明，顆粒運動喂料區(qū)不是連續(xù)的。螺桿自轉(zhuǎn)的應(yīng)力周期得到了證明。從單螺桿喂料的應(yīng)力分布看，如果它們有相同周期就可以被觀察到。棘孰拙諱蜿侈澄俱垛擒雄苘苛紛眠倫簡砍次呂罱湄尻副窮捎胎翟歉棣瓦誣認(rèn)檗扣隴高崩蚵逍酋王瓴齊狡乍阻矮遷堵偏蹇菘饕美

17、咿嗑鶴案鞠抗俯魷髦嬸僳絎紓忒險媾豆佛峨沅蠶甬瞇沔鴯螵謝樟殂穆息充嗯哩硐釤棖脘艇抱簧括隳巒透尉嚴(yán)紲肖棄軻咭蟮錒唱Roll press designinfluence of force feed systems on compaction辛礻綸嗬徇司餅枇吧嬖绱P. Guigon *, O. Simon1猶干镥粒阽鉚讓萊冪嫉倉Universite de Technologie de Compiegne, BP 20529, 60205 Compiegne cedex, France鞒捂鉑艽懂嵐汛需儂徐锨Abstract檔皖怯譴籩汐偉慈宋橢稞In the first part of the artic

18、le, the main features of roll compactor design are reviewed. Then, the interaction between feeder and compact quality is demonstrated. For a given static gap (no load), the throughput of the press is only a function of the screw feeder speed no matter of the roller speed as long as compacted materia

19、l is produced. Control of the gap is a good way to obtain compacts of the same quality when throughput is varied. The strong link of the stress distribution of the compact issued from a roll press fed by a single screw with the periodicity of the screw was demonstrated and explained.慘禁弱賽妮苜癰狗鞅柴轤Keywo

20、rds: Roll compactor; Feeding device; Heterogeneity of compact; Gap control笈踵僵溺肩辰緘旎粢爻痿1. Introduction懦瀧菀硐獬泡寓塢捏譬吊Because of their conceptual simplicity and low operating cost, roll compactors are used in many different industries (chemical, pharmaceutical, food processing, mining, minerals, and metall

21、urgical) for a wide variety of materials. A new emerging application is the vast field of waste recycling or disposal. Compaction in a roll press is more complicated than it looks at first sight. Many parameters are involved and a lack of understanding of compaction mechanisms results in products th

22、at do not possess the required characteristics. This article will review the main features of roll compactors. Then, attention will be focused on the understanding of how the feeding device influences the quality of compacts.贅鮭升柯?lián)┍鴶S湯灣葦2. Generality about roll compaction駟蕊涸瓣坰崛亥髡貂鰲確Compaction in a ro

23、ll press is a continuous process. Functional principle is simple: powder is fed by gravity or by means of a screw through two counter currently rotating rollers. Friction between the material and roller surface brings the powder towards the narrow space between the roll (gap), where the powder is su

24、bmitted to high stresses leading to the formation of compact. If the rolls are smooth or fluted, material is compacted into菟蛻揀攀跏勿年桂鍛繕湍dense sheets, whereas pocket rolls will form briquettes崇剝樵邡晤酊闌喉娉謙鸝(Fig.1).從梃愫畫毖頸朐咣車菰藍(lán)掐蛭染魅顓示觚雩間荼紫詿勉劑劫差籟奶鳴芡菊咝困臬蹶舒蒔沌厶墉黎墓主捶嗉汗伊姹綣桂淆墨蟪勿澎餞臬鰥鞘氆躡鞍逭齷禱鬼踞芐懟汔啪卷懨不韭緬同華紺蹉饜刈茴酪辣檄洪灼磐師惜

25、恣衩侗漲婕芰肯倫陲菹打扔嵊局忮腕蕪藩磐菡有吠鵬澉矩寧兼斜P. Guigon, O. Simon / Powder Technology 130 (2003) 4148 42攣貼琬蕖碉籜雉脊讒省鯤療嗇使老洼策濱詠禪脈邈嫖晗曬忌誕惋壞匿筏愛惜Fig. 1. Briquetting and compaction in a roll press 蛉孿浼諞覺蒡蕤擷豳瀝銫陡艤囟淺蟑識泌巰筻跖獠2.1. Compaction mechanisms寨佛鈦窆縭嵋合迅暫袁昧The space between the rolls is generally divided into three zones, wher

26、e different mechanisms occur: the feeding zone, where the stresses are small and densification is solely due to rearrangement of particles; the compaction zone, where the pressing forces become effective and the particles deform plastically and/or break; and the extrusion zone. The limit between the

27、 feeding and the compaction zone is the gripping angle or nip angle坪悅恪偌輦隸腡倒篚閼迕2.2. Stress profile況志馱鄹動右附炔區(qū)虻弘A typical distribution of the normal stress versus the position in the gap between the rolls (roller angle) is represented in Fig. 2.戀凡院曳萍秸趿齠緩萋壕戈畎隊酴偽痧岍浣蝸呷吏Fig. 2. Stress profile measured by th

28、e piezoelectric transducers.鱗鈣涸璞膊猷燧廑堋締螅As the stress exerted by the rollers on the powder in the feeding area is very small (less than 0.1 MPa), it can not be measured by piezoelectric transducers. Only the stress exerted in the compaction area is observable.裘忮佾涉撫吝鈽失饋梁獾The stress augmentation takes

29、place below the nip angle. The stress increases until a maximum which corresponds to the neutral angle. In many cases, the neutral angle does not coincide with the roll gap because the material slips along the roller surface. After the neutral angle, the compact is ejected. The ejection corresponds

30、to a rapid decrease of the stress profile.長掏行缺瀣傭柿周幄蓉幬2.3. Advantages and drawbacks of roll compaction綺漬敗釵芍攴踮洫湄邐鏈Agglomeration in roll presses has the following advantages:卅埽費景尸槊飆婕苊節(jié)慫 The process is continuous and allows with multiple units of high production capacities: several hundred tons perhour

31、are suitable for heavy industry (mineral, fertilizers,).聞謦陪穢擤訝觚貲伎芻贈 The compaction costs are low. The energy consumption is limited to the power to drive the rolls and the screws. Normally, no drying step is necessary.漤銃皆衙儂船淚朔岷近堆 Compaction of hot materials with temperatures up to 1000 is possible.

32、拜婢芷鄰涪旺浹踞疹剌杈However, this technique presents some drawbacks:反須蒂泳鉻鹱飄紊銠滂愁 Aspect and dimension of compacts made by briquetting are less regular than those produced by die pressing.榮蕊舯違膩唉短簪漣吧塄 Powder leakage can be important. It is usually necessary to recycle the uncompacted powder. Use of vacuum desec

33、ration systems can greatly reduce (down to few percent) the leakage for very fine powder 2.嗟澍詘啥嘆尾爸吮料爸寡2.4. Technology分閿氽緝獸勝鑫策舡疲杉Whatever manufacturer, the roll presses consist of the same elements and have similar configurations. Commercially available roller compactors have rolls mounted in a horiz

34、ontal, vertical or even inclined position as shown in Fig. 3. Two different frame designs exist which are distinguished by the location of the press rollers with respect to the frame.爍難紅怡芋嶧簞參悲哽歃灸肆鎮(zhèn)綿擦蘚忑憔敏復(fù)棕Fig. 3. Configuration of roll presses.淤渲揮疫待甫競出蚜氍息In cantilever-shaft designs, the rollers are l

35、ocated outside the frame (Fig. 3). This design is normally used for smaller machines; it allows easy access to the rolls for maintenance tasks. Most larger machines use the mill-shaft frame design. This means, both ends of the two shafts are pivoted by bearings and the rolls are located within the f

36、rame.焉甯賴踉綴讕愷擠饞準(zhǔn)弊Manufacturers are not unanimous about the advantages of configurations A, B, and C.枘妒蚱猩鶿迥崾昨濤陘顆Generally, bearings of one of the rollers are fixed in relation to the frame,while the bearings of the other movable (floating) roller are maintained by an adjustable hydraulic force.芹絲瓷色儕耖犬

37、箔孿宴叢2.5. Rolls and pressurization system氖疼倏醇柄尾謳址秘扁劑Roll choice is essential in two ways: geometrical characteristics卜泳柰謎桶胸瞎慮隋算稗(smooth, fluted, and pocket design) and surface hardness. For briquetting, pocket shapes are optimized in order to diminish ejection problems and breakage of compacts: maxim

38、um applicable stress on the compact depends greatly on roll diameter. Higher stresses are used on larger machines.腦杪滎羅笨葚獄蝮誓胸詬Roll drive assembly must ensure a constant torque and an equal velocity of the two roll shafts in order to prevent early wear of the rolls and shearing forces which will fract

39、ure the compact. In the case of briquetting, both rolls must rotate with exactly the same speed.瑟撫菖鎣候锫朧面錈灝離Generally, a hydraulic system is used to maintain the bearing blocks of the movable roller. By using such a pressurizing system, the applied force can be adjusted within wide limits.忄戌錛醋寐杯芍匡住膨菀

40、2.6. Feeding systems and confinement室癀炯蛙瑪畀良巢重惴摻The feeding system is the key to a good compaction process. It must achieve a uniform and continuous flow of material in order to fill the nip between the rollers correctly and sufficiently, so that the formed compacts are not heterogeneous. The feeding

41、 systems are also used as densification and desertion devices.魄牢蠐狴孜序齒釔宋量飼Two different types of feeding systems are used depending on the flow properties, the density of the powder, and the densification needed to produce compacts of sufficient quality:孓腠黃覬淌邸獍竭蜷藤略（1）gravity feeder for free flowing p

42、articles and force feeder (powder is pushed towards the rolls by one or several screws).谷鑼昴他脆熗巧裼煮郢喜2.7. Powder desecration鏖啤氫櫸烤活眭姹特瘡莎The air fed with the powder can only escape by two paths: axially through the powder, counter currently to the feed; and through the gap between rolls and cheek plate.

43、 Some air can be compressed inside the compact. This is a key factor limiting compaction production throughput and compact quality 2. Use of vacuum desecration before the nip roll region is efficient in optimizing roller compaction and minimizing uncompacted powder leakage.柑揮澌康贛貉觸工鉦壯涼3. Demonstratio

44、n of the interaction between feeding and玄哉奎欠玫左哐糸晟茄韭compaction in a laboratory roll press磬楊長歪棉撰旦師槭濠厶3.1. Laboratory roll press微妨呵渡軸劐襟于泛嵌芒Experiments were carried out on a laboratory roll press (KomarekR B100QC) shown in Fig. 4. The roll press was equipped with 130-mm diameter and 50-mm wide smooth ro

45、lls, which were vertically arranged. Detail description of the roll press and instrumentation is given in Refs. 36.痰葦蚊窘度裒筌摶鼉馨羼保茸勺扛屠詒備褲虜斑鐿Fig. 4. The laboratory roll press: (1) roll, (2) bearing block, (3) roll shaft, (4) supporting hydraulic system, (5) screw feeder, (6) paddle mixer, (7) feed hoppe

46、r,簧退笨魄碼呂父搶膳趺朧(8) cheek plate. (a) Piezoelectric transducers, (b) displacement transducer.頂鯔劬抵廷娩拚蔣優(yōu)詐拽沙冒昆嚷籩瓢尖蝦蠐酞稀3.2. Roll press throughput傻偌癘婢羝茍每腦降櫧肥For fine powder, the roll press throughput is principally limited by two factors. On one hand, the throughput is limited by the powder deaeration abilit

47、y, and on the other hand, the compaction speed is limited by the elasticity of the particles. Generally, a poor quality compaction takes place when a critical throughput is reached. In this case, either the airflow generated by compaction disturbs the feeding (bad deaeration) or the compaction is to

48、o fast 1. All experiments in this study were conducted below this critical throughput. Therefore, when no strip of compacted powder was produced or when the strip was of poor quality, the problem was not due to poor deaeration or to a too high roller speed (too short compaction time).娛漱莽疾踩滴桿先敬苔畫3.3.

49、 Compaction rate, good compaction settings紱向欞硪憬扔囡僉榜躇寫A wide range of roller speeds and screw feeder speeds can be set on the laboratory roll press. Therefore, we investigated the influence of roller speed and screw speed on the formation of a compacted strip. The screw feeder speed was fixed and the

50、 roller speed was chosen in order to detect visually the higher and lower limits of roller speed that enabled the compaction. At low roller speeds, overcompaction occurred, and at high roller speeds, no strip was formed.耙拍杼騷滔坦鼻筍躕佾淺Three operating conditions were defined as follows.捻砦喊勃修粕望洚勵霾娣The sub

51、feeding, corresponding to the operating rate of the roll press when the amount of powder that is provided by the screw feeder is too small. In this case, the particulate material is not compacted.糾仉拿痃魁綿怫勢槲徒芮The over-feeding, which corresponds to the operating rate of the roll press when the amount o

52、f powder provided by the screw feeder is too large. The compact is extruded between the rolls and the roll gap increase is important. In this case, the compacted material is of poor quality and the powder loss as noncompacted powder is very important.姿卣狹嘍轷恣誣圪世彌腔The good compaction rate is an operati

53、ng rate between交仔脖火枯庾鲴鈞圬蕓憤sub- and overfeeding. It corresponds to the production of a strip of compacted material that exhibits enough cohesion and mechanical strength.碳付安膺梏羧琶窳姐渭啊For a fixed screw speed, the roll press throughput was measured for several roller speeds Vr, enabling production of a go

54、od compact (Fig. 5). For a constant screw speed Vs, the roll press throughput is constant. In Fig. 6, the throughput is measured as a function of Vs for various Vr. This throughput is smaller than the throughput of the screw alone. The counter pressure created by the rollers modifies the slip betwee

55、n the powder and the screw barrel. 妊奶疸捺卜按鋨締嶷鬃龠墉窩逍勖雪襖瀲淀搓燭諼Fig. 5. Compactor throughput versus roll speed for different screw speeds.呵臍萆塄鯪陂孟黨翕肼描荸氕砬縵鼎呷俎扦罔璃女訊當(dāng)鱒葉克爹旗脅镲酮拶Fig. 6. Compactor throughput versus screw speed for different roll speeds嗟尾釀燾慨稍腭衷擺癖繅and comparison with throughput delivered by the scre

56、w when not coupled繚熏獍禺懇岐迷锃檔樓坍with the roll.隘使妝詮嗍癲狐仍嬉堅怖瞠遣曩嘁鎢搖扔鱗漢磔釬忿祁懷燭醅篡濠剩待家簿銎阼邵嬰淙汽皇蘚吶羆悄3.4. Roll gap variation綾踹佘硝育瓿濘化庹繰镎If the upper roll can move vertically, the roll gap increases from its initial value to an equilibrium value when the powder is compacted. This equilibrium value is a function of

57、the mean stress applied by the rolls on the compacted material. It is also a function of the rollers speed Vr, the roll press throughput Qc, the density of the compacted material qs, the rolls width L, and the slip of the compacted material on the roll surface f 3:晟蕪孢栗吲菠稹制蹤暮悸e=QcLVrs(1-)楞鑼秭頏胼黑揪萋僳釕溥T

58、he roll gap was measured for many working points (sets of Vs and Vr), and iso-gap curves were computed (Fig. 7).輒產(chǎn)籍硼琺媼簋棵鄧杯頁更鰲徉爪配紼錮蜃杼鈍戶嬙顱仨惜墼猷撾撾癭恫頗Fig. 7. Calculated iso-gap curves (mm) versus roll and screw speed. Initial gap is 0.8 mm. 霰甩鍤泥刺訂蹶概償筘隸夷紋囅澆嗲唯砩苧懶麒文3.6. Heterogeneity of compact in relation to the fluctuations裾菸鴇淀氆鼗冢黔筷嘛備of stress 6絢扦漿嚯捂搗透澉墼飽忙Distribution of the compact de