YQP36預(yù)加水盤式成球機設(shè)計
YQP36預(yù)加水盤式成球機設(shè)計,yqp36,加水,盤式成球機,設(shè)計
新型水泥生產(chǎn)工藝的可行性研究要求
英國WS Atkins專家R.Hogg, D Frame 和M.E. Asim討論大型水泥設(shè)備工程的理論可行性。
針對西班牙語和法語的版本請參考本雜志的后面特別翻譯部分。
楊聞達譯
引言
開始建造一套完整的新型水泥生產(chǎn)工藝設(shè)備或在已有的水泥生產(chǎn)設(shè)備上進行主要設(shè)備生產(chǎn)能力的擴充改造，這些計劃都應(yīng)該在詳細的技術(shù)經(jīng)濟分析的基礎(chǔ)上實施。這樣的研究涉及到采用最好的技術(shù)方案、總的成本和總的運營支出這些方面，同時也涉及到生產(chǎn)、所需的勞動力及在一定時間段內(nèi)投資回收的運營規(guī)模，它能體現(xiàn)出工程較好的經(jīng)濟可行性。
一項典型的可行性研究主要需解決以下問題：
市場調(diào)查分析。
生料的供給。
廠址選定及設(shè)備的安裝研究。
工程及工藝的概念設(shè)計。
互換性分析。
包括基礎(chǔ)設(shè)施的支出預(yù)算。
工程時間表。
投資分析，風(fēng)險評估，財務(wù)結(jié)構(gòu)的發(fā)展。
項目費用。
財務(wù)狀況的討論。
所有的可行性研究報告必須包含技術(shù)方面的問題，它在解釋市場研究與合理的資金規(guī)劃之間的完整關(guān)系上是很重要的。
預(yù)先可行性研究
為了使所有的費用最低化，為了能很快地達到工程可行性的預(yù)定指標，預(yù)先可行性分析是必需的。
預(yù)先可行性研究是在以很低費用支出的條件下完成的。當(dāng)有充足的準備條件時它又能顯示出完整可行性分析的公正性。預(yù)先可行性研究要調(diào)查市場、尋求原材料、籌集資金和準備運營費用，從而擬訂一份商業(yè)計劃。這樣就知道可能的投資回收、對風(fēng)險的分析和所在的運營環(huán)境。
典型的預(yù)先可行性研究過程從開始將需4到6周才能完成，而研究中的大多數(shù)工作都是在辦公桌上參照內(nèi)部的數(shù)據(jù)庫來完成的?，F(xiàn)場考察過程是根據(jù)水泥生產(chǎn)、本地建筑、民事工程費用支出、土地費用、特殊地方的獨特性以及在當(dāng)?shù)毓S運營所要求的費用支出確定合適的生料。辦公桌上的研究工作注重于現(xiàn)在工廠、機械設(shè)備、財務(wù)、對市場的考察及主要設(shè)備安置和工藝路線的確定。
在預(yù)先可行性研究清楚地展現(xiàn)出這項工程是值得進行的后，完整的可行性研究才能開始。
完整可行性研究
市場調(diào)查
市場研究的主觀目的是滿足在一定區(qū)域背景和工廠計劃的市場范圍內(nèi)對各種水泥的需要。市場研究尋求滿足現(xiàn)在以及預(yù)計在以后長達5到7年這段時間內(nèi)的水泥使用需求。這樣的預(yù)測與市場的指導(dǎo)價結(jié)合，形成在計劃操控下可能的收入趨向。
這方面的專家必須要有對全球水泥工業(yè)的相關(guān)認識，以及能對市場最新的狀況和可能的發(fā)展趨勢有所把握，這樣才能進行可行性研究。各個公司和地區(qū)都是這樣的，同時又體現(xiàn)了各自獨特的背景，這樣的背景卻是必須要充分把握的。通常所運用的方法是首先研究公司和分析它的優(yōu)勢和劣勢，戰(zhàn)略性方向和動向。在證實公司為實現(xiàn)其目標制訂的成功性很大的近期規(guī)劃中，這方法是不可或缺的。
所運用的方法的第二階段是通過調(diào)查涉及工業(yè)大范圍的公開數(shù)據(jù)，進行市場觀察，現(xiàn)場研究，將原先的討論實踐到具體的背景下。
公開數(shù)據(jù)是研究者和專家對已知的客觀趨向進行分析和對未知的新信息進行推敲和比較所得出的。單單依靠幾個月前的舊信息，且忽視在水泥生產(chǎn)方面的國際性觀點、趨勢是不夠的，這樣所得到的水泥需求也總是失去指導(dǎo)性的。
收集那些公布的數(shù)據(jù)是一個持續(xù)的過程，但是是在確定調(diào)查研究的基地后的工作，并且已收集的信息應(yīng)該通過第一手獲得的工業(yè)資料和觀點盡可能被證實。公司、政府組織和其他的工業(yè)協(xié)會總是希望提供他們自己的市場評估，并且需要注意不去妥協(xié)于任何被強加的觀點，準備給出自己的見解。
這個階段中，在已經(jīng)把握好那些廣泛收集的公開數(shù)據(jù)和工業(yè)主張后，專家的工作就是正確地定義特定產(chǎn)品所針對的市場，另外還有市場中可能的變化。這些變化總要靠具有歷史意義的關(guān)系來預(yù)料的。例如，這些關(guān)系包括國民生產(chǎn)總值和所有建設(shè)活動的關(guān)系，經(jīng)濟增長和房屋建造的關(guān)系，或者是水泥消耗和人口數(shù)量的關(guān)系。圖1說明了這一點。如不考慮那些客觀意見和不認清水泥使用者對不同型號的水泥需求的變化，這樣的預(yù)測是錯誤的。對這些方面的分析在一些非發(fā)達國家是尤其重要的。在這些非發(fā)達國家，不樂觀的生長率在顯著的短時間內(nèi)會改變建設(shè)活動的平衡性。
另外可能會給市場帶來負擔(dān)的商業(yè)信息是收費表、進口關(guān)稅和部分的津貼。即使是在自由經(jīng)濟時期，經(jīng)濟的很多方面都與戰(zhàn)略的重要性，以及政府為維持國內(nèi)匯率總會通過確定一定的價格表，或提高進口關(guān)稅的措施有關(guān)。如果取消進口關(guān)稅或者價格只依據(jù)供求關(guān)系來變化，這在市場條件下將是很重大的變化；譬如，國內(nèi)公司會突然發(fā)現(xiàn)他們自己毫無競爭能力。隨著進口商品的價格越來越低，水泥粉磨和熟料的需求平衡可能會有顯著變化，這取決于政府所采納的政策的變化，而專家的主要工作之一就是預(yù)計它們。
最后要強調(diào)的一點是競爭者的反應(yīng)。它也許是在決定市場研究的各方面問題中的唯一并且是最重要的難題。要想得知其他的投資計劃、政府許可、可能的競爭數(shù)據(jù)、在競爭者中主要的競爭者和合作伙伴，這樣的過程是很困難也是很費時的，同時它也總是遠遠不夠的。競爭者不單單是國內(nèi)的或者是長期以來以同樣的可預(yù)測的銷售途徑來銷售他們的產(chǎn)品的，現(xiàn)在越來越多的公司希望靠縱向的統(tǒng)一他們的運營來減少對供求方的依賴性。這將能幫助建造他們自己的工廠或發(fā)展他們自己的用于直接進口水泥的深水港。其他的公司也許會決定轉(zhuǎn)變成賣方，例如，賣罐裝混凝土。某些大客戶也許會和這樣的一個公司簽訂長期合作協(xié)約或?qū)で蟾蟾鼜V遠的市場去買進水泥。研究的組合方式有很多，這取決于公司在昂貴的廠房和機械設(shè)備投資的金額。這樣的研究是為了了解投資所要針對的顧客，也是為投資者們確定這樣的投資確實擁有一個最廣闊的市場的。
原材料的考證
對于生料礦藏的儲量和質(zhì)量，我們必須對它們有很準確的認知。對原材料廣范圍的搜尋可以以研究臺上的研究及借助《國家地質(zhì)勘探》這本書的數(shù)據(jù)和使用的地質(zhì)圖譜為指導(dǎo)來開始。這樣的搜尋將包括調(diào)查無線的照圖記錄和衛(wèi)星圖片，例如查看Landsat或SPOT衛(wèi)星圖片。
緊接著研究臺上的工作是現(xiàn)場考察那些規(guī)劃地點，這工作是由地質(zhì)專家通過現(xiàn)場考察以往鑒定的地理水平線和巖石層，從而能深入地研究。第一步取樣品工作。在可能有很好跡象的巖石層、山中開辟的道路、現(xiàn)在已有的開采進行引導(dǎo)性挖掘，或者在計劃開采的測試點進行引導(dǎo)性鉆孔。礦區(qū)的樣品測試需要提供儲存的氧化鈣、硅、鋁和鐵含量原始指標。這樣的測試是簡單的、快捷的、經(jīng)濟的。地質(zhì)專家能調(diào)整礦區(qū)調(diào)查工作和最大化地收集發(fā)現(xiàn)的有用信息。
最有指望的樣品收集工作是在測試實驗室進行化學(xué)分析后，掌握了充足的化學(xué)質(zhì)量的數(shù)據(jù)和已確定可能的數(shù)量時，決定開始完全開鑿工作。
主要的生料成分或者石灰石是鉆孔所要的核心。對地質(zhì)進展需要進行詳細記錄，如把核心開采出來、記錄，并把它們分類放入核心箱內(nèi)（圖2）；從鉆核中獲得個別的和混合性的樣品，并送到習(xí)慣于對水泥生料進行測試的實驗室。為了減少鉆孔成本，對第一次鉆的孔的原始結(jié)果進行快速分析并知道結(jié)果是必要的，同時也是為了更深遠地確定隨后鉆孔的地點、角度和方向。
化學(xué)分析的數(shù)據(jù)和源于核心的地質(zhì)記錄，這些信息可以用于確定地質(zhì)結(jié)構(gòu)和儲量。最佳的采石發(fā)展計劃和對移動型設(shè)備的要求才可以有所發(fā)展。
次要的生料成分，如粘土或頁巖，需要通過擴大型鉆孔或用移動型液壓開采機進行測試定點開采，也或者一定情況下實行人工開采來證實。這些原料需要進行類似于石灰石的記錄和化學(xué)分析。
通過使用生料的化學(xué)分析結(jié)果，可以進行設(shè)計生料混合比了。所使用的室內(nèi)程序有很多附加技術(shù)要求。第一，所有的標準方程必須要適合如石灰的濕度、含硅比例、含鋁比例、液壓部件的條件。這些方程需要編到程序中。第二，混合比設(shè)計必須通過調(diào)整混合物的成分和觀察在標準比例范圍下的反應(yīng)結(jié)果來改進。最后，費用支出方面可以加到生料上以獲得好生料混合物。這樣可以減少生料的費用，同時也能滿足以上標準。
過程工藝設(shè)計
對于特定的工廠，最佳的工藝路線是依靠包括生料礦藏的物理和化學(xué)性質(zhì)的許多方面來設(shè)計的。廠房和機械設(shè)備是基于以下幾個方面來選擇的：
生料礦藏的儲備。
生料的濕度和其他的物理性質(zhì)。
不希望存在的化學(xué)成分。
礦物學(xué)（特別是硅的成分和含量）。
生料的粗糙度、耐磨性和燃燒特性。
主要生料成分內(nèi)所缺乏的附加特性要求。
燃料品種及相應(yīng)的費用支出。
環(huán)境保護要求。
可用電力、高效要求和費用支出要求。
建造的地形和要求。
市場規(guī)定。
勞動力和保養(yǎng)規(guī)定。
受潮問題、沖擊問題和自然儲藏的生料成分的性質(zhì)，這些決定著如何地開采主要和次要的生料成分、如何地處理和改善運輸條件。儲藏的地質(zhì)環(huán)境和生料成分的硬度也將決定怎樣計劃開采場和怎樣決定開采的方法。
生料的濕度和伴隨著濕度變化而導(dǎo)致其他性質(zhì)的變化，兩者對主要的破碎機和備料系統(tǒng)的選擇有著重要的作用。當(dāng)考慮到生料磨系統(tǒng)預(yù)熱裝置所排出廢氣的最佳溫度時，濕度起到很大的作用。在回轉(zhuǎn)窯系統(tǒng)裝置、所用的旋風(fēng)級別的數(shù)量和為了將生料烘干而采用的生料磨加熱裝置間，熱量必須保持平衡。
在生料中不希望存在的化學(xué)元素的成分有鉀、鈉、氧化鎂、氯和硫酸銅。在選擇回轉(zhuǎn)窯系統(tǒng)的類型時要仔細考慮這些。不同的非純生料會含有硫酸銅及窯內(nèi)燃料中也存在硫酸銅。這將導(dǎo)致我們必須對分流系統(tǒng)的承受力和外形尺寸加以考慮。
在不同的國家，對生料的礦物研究也有很大的不同。在回轉(zhuǎn)窯的煅燒工程中，生料成分開采的方法和化學(xué)成分對化合反應(yīng)后生成的化合物的特性有著很明顯的影響作用。明顯地，礦物研究將使窯內(nèi)燃料的損耗和回轉(zhuǎn)窯的煅燒環(huán)境有很多變化，當(dāng)為了獲得較經(jīng)濟的水泥從而對一定比例的化學(xué)成分進行化合時，必須要預(yù)料生料將怎樣的反應(yīng)。這樣的預(yù)計過程是基于實驗室內(nèi)以部分的可行性研究為指導(dǎo)的燃燒和粉磨測試。
從所有潛在和能看到的水泥設(shè)備的控制器的工作記錄上可看出，能量和燃料的使用是兩個關(guān)鍵控制參數(shù)。水泥工業(yè)都意識到最大化利用熱能的重要性。從窯內(nèi)廢氣到生料或者是從熱的廢渣到燃燒氣體中安裝終端熱交換器的方法已經(jīng)很好地被采用了。
如今，越來越多的人們在不斷地尋找高效利用能源方法和高燃燒率的燃料。一定范圍采用節(jié)能的工藝和設(shè)備都作為考慮對象。以經(jīng)濟為標準，這方面也是很重要的，同時市場證實了在這方面有很大的支配能力和能相應(yīng)的減少產(chǎn)品的成本。所以人們廣泛地接受了這些。
在生料磨和水泥熟料磨中所采用的含有球磨機、高效選粉機、低壓旋風(fēng)預(yù)熱裝置及垂直的高壓輥式磨和最近介紹的水平輥式磨（因此稱為Horomill）的生料磨系統(tǒng)能使得能量的損耗有很大降低。對于好的生產(chǎn)工藝的選擇必須確保它能使電力消耗得以降低。
采用擁有隔熱壁的高效循環(huán)裝置和增多預(yù)熱器的數(shù)量以最大化利用回轉(zhuǎn)窯內(nèi)所排出的廢氣的熱量，這將很大地減少燃料的消耗。設(shè)計采用輔助設(shè)備，例如回轉(zhuǎn)窯的廢氣排放管道、回轉(zhuǎn)窯的煅燒設(shè)備、流量控制閥和其他設(shè)備都會對燃料消耗有側(cè)面的影響。
如今，另一個有所發(fā)展的是采用對從冷卻機到生料磨中所有的熱廢氣進行傳遞的裝置，從而節(jié)省熱能來滿足對生料的烘干要求。淘汰一些接收裝置或其他帶有輔助設(shè)備的冷卻收塵系統(tǒng)，這樣的準備工作在減少工廠運營資本上有著很大的優(yōu)越性。
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外文翻譯
專 業(yè) 機械設(shè)計制造及其自動化
學(xué) 生 姓 名 楊 聞 達
班 級 B材機022
學(xué) 號 0210120211
指 導(dǎo) 教 師 楊 曉 紅
機械工程學(xué)院畢業(yè)設(shè)計（論文）選題申報表
機械設(shè)計制造及其自動化 專業(yè)
指導(dǎo)教師楊 曉 紅 學(xué)生姓名 楊 聞 達 2006年 1月 4日
設(shè)計（論文）
題 目
YQP36預(yù)加水盤式成球機
設(shè)計
題目類別
畢業(yè)設(shè)計
題 目 來 源
結(jié)合生產(chǎn)實際
題目性質(zhì)
工程設(shè)計
設(shè)計原始數(shù)據(jù)
生產(chǎn)能力Q=25t/h
設(shè)計內(nèi)容
結(jié)合生產(chǎn)實際，完成預(yù)加水盤式成球機設(shè)計。
物
化
成
果
形
式
□工程設(shè)計類要求
說明書字數(shù)
圖紙數(shù)
其他附件
□工程研究類要求
論文字數(shù)
附件要求
□軟件開發(fā)類要求
說明書字數(shù)
附件要求
1、 設(shè)計說明書1份，達1萬字以上，且要符合規(guī)范要求（電子文檔）。
2、 中文摘要不少于400字。并有對應(yīng)英文摘要（電子文檔）。
3、 設(shè)計圖樣總的繪圖量折合A0不少于3平方米（CAD）；具體設(shè)計的圖樣有：
（1）預(yù)加水盤式成球機總裝圖一張；
（2）機架部件圖一張；
（3）傳動部件圖一張；
（4）機架及傳動部件相關(guān)零部件圖若干張。
4、翻譯3000以上漢字的課題相關(guān)外文資料。
5、實習(xí)小結(jié)（電子文檔）。
專業(yè)系審查意見：
專業(yè)系主任（簽名）：
學(xué)院審批意見：
院長（簽名）：
注：
一、題目類別：1、畢業(yè)設(shè)計；2、畢業(yè)論文
二、題目性質(zhì)：1、工程設(shè)計；2、技術(shù)研究；3、軟件開發(fā)；4、理論研究
三、題目來源：1、結(jié)合科研；2、結(jié)合生產(chǎn)實際或工程建設(shè)；3、結(jié)合課程和實驗室建設(shè)；4、自擬題目
Feasibility study requirements for a new cement plant
R.Hogg, D Frame and M.E. Asim, WS Atkins Consultants, UK, discuss the theory and practice of undertaking large cement plant projects.
FOR SPANISH AND FRENCH VERSIONS PLEASE REFER TO THE SPECIAL TRANSLATED SECTION AT THE BACK OF THE ISSUE
Introduction
The decision to start the construction of an entirely new cement plant facility, or a major capacity extension at an existing cement works, should always be based on a detailed techno-economic feasibility study. Such a study will indicate to the promoter the viability of the business in terms of the best technical solution, the overall capital and operating casts, the magnitude of the operation in terms of production and workforce needed, and the return on his investment over a period of time.
A typical feasibility study deals with the following issues:
Marketing study.
Raw materials proving.
Site studies.
Conceptual engineering and process design.
Analysis of alternatives.
Project cost including infrastructure.
Project schedule.
Investment analysis, risk assessment, development of financial structures.
Project finance.
Discussion with financing institutions.
Whilst any feasibility study must include technical aspects, it is important to realize the full implications of marketing research and accurate financial projections.
Pro-feasibility study
In order to minimize front end expenditure and to quickly obtain a firm indication of the likely project viability, a pre-feasibility study is performed.
The pre-feasibility study is carried out at low cost, but in sufficient detail to show whether a full feasibility study is justified. The pre-feasibility study will examine the market place, the raw materials, capital and operating costs, and develop a business plan to show the likely returns on the investment, and identify the risks and scale of operation involved.
Typically this exercise will take four to six weeks to complete, commencing with a site visit. However, the study is largely performed by desk research and reference to the in-house date base. The site visit is used to determine the suitability of raw materials for cement manufacture, local building and civil engineering costs, cost of land and peculiarities of the particular site location, and local cost of consumables required in the operation of the plant. The desk research concentrates upon current plant and machinery costs, financial and marketing considerations and preliminary plant sizing and determination of the process route.
In the event of the pre-feasibility study showing a clear indication that it is worthwhile to proceed with the project, then a full feasibility study can be initiated.
Full feasibility study
Market research
The objective of the market study is to establish the demand for the various types of cement in the context of the region or market area of the proposed plant. The study seeks to establish the current and forecast cement usage over a 5-7 year period. The forecast is then used together with the indicated selling prices to generate the likely revenue stream for the proposed operation.
The consultant must have considerable experience in the global cement industry and be able to approach a feasibility study with an excellent knowledge of prevailing market conditions and likely trends. Each individual company and market does, however, present a unique set of circumstances which must be fully understood. The normal approach adopted is first to study the company and identify its strengths and weaknesses, strategic direction and motivation. This is essential in providing an immediate picture of the company’s likely success in achieving its aims.
The second stage of the marketing survey, desk research, puts the initial discussions into context by examining a wide range of published data relevant to the industry.
Sources of published data are collated and compared by a team of researchers and consultants in an operation to substantiate known trends and uncover new information. It is not sufficient to rely on information several months old, and without an international perspective, trends in cement production and demand are frequently misleading.
Collecting published data is an on-going process, but having established a background to the study, information should, where possible, be verified using independent sources with firsthand accounts of the industry and its outlook. Companies, government organisations and other industry associations are often willing to provide their own assessment lf markets, but care needs to be taken not to compromise any party prepared to give its view.
Armed with a comprehensive selection of published data and industry opinion, the job of the consultant at this stage is to accurately define not only the market size for a particular product, but the likely change in that market. Such changes are often predicted by historic relationships between, for instance GDP and overall construction activity; economic growth and housing starts of cement consumption and population size. Figure 1 illustrates this point. Without taking into account subjective opinion and recognizing changing user requirements for different cement types, such forecasts can be flawed. Analysis of such factors is particularly important in lesser developed countries where impressive growth rates can change the balance of construction activity over remarkably short periods of time.
Other economic information likely to have a bearing on the market are government tariffs, import duties and sector subsidies. Even in free market areas, many aspects of economies are regarded as being of strategic importance and governments frequently strive to preserve national interests wherever possible by fixing prices of imposing import tariffs. Should import tariffs be relaxed of prices allowed to move in line with supply and demand, there will be an appreciable change in the market conditions. National companies, for instance, might suddenly find themselves uncompetitive. With cheaper imports, the balance between cement grinding and clinker production requirements could change quite dramatically. It would be up t the government to accommodate these changes, but one of the principle tasks of the consultant is to anticipate them.
This last point highlights what is perhaps the single most important yet difficult to determine aspect of a market study: competitor reaction. Knowing of others investment plans, government licensing, likely dates of completion, principle contractors involved and distribution partners is difficult and time consuming, but it is not enough. Competitors are not just nationals of those who have historically sold their product through the same predictable channels of distribution. There are an increasing number of companies who would like to reduce dependence on suppliers by vertically integrating their operations. This could entail building their own plant or developing their own deep water terminal to import cement directly. Others might decide to diversify into selling, for example, ready missed concrete. Some large users might be on verge of entering into long term agreements with one company or looking to buy form further afield. The combinations are numerous but it is up to the company investing in expensive plant and machinery to understand its customers and convince both itself and the investors that it really does have the best view of the market.
Raw materials proving
The volume and quality of the raw material deposits have to be established with accuracy. A wide ranging search for raw materials may start with desk research and consultation with National Geological Survey data and available geological mapping. The search will include examination of aerial photography records and satellite imagery e.g. Landsat or SPOT.
The desk research is followed buy site visits to the proposed location by geologists who take the study a step forward by making on-site examinations of previously identified geological horizons and outcrops. The first samples are taken by channeling from promising outcrops, road cuttings, recent excavations or from purpose excavated test pits. Field testing of the samples is required to provide an initial indication of the calcium carbonate, silica, alumina and iron content of the deposit. The testing is simple, rapid and economical and the geologist can adjust the field investigations and maximize the recovery of useful information.
The most promising samples are chemically analysed in testing laboratories and when sufficient data has been obtained in terms of chemical quality, and the probable volume established, a decision to mount a full drilling campaign can be made.
The primary raw material or limestone, is core drilled and careful records of the geological progression is made as the cores are recovered, recorded and laid sequentially in the core boxes,(Figure 2). Individual and composite samples are taken from the cores and sent to laboratories experienced in the testing of cement raw materials. In order to minimize drilling costs is essential that the initial results of the first borehole are analysed rapidly and the results known in order to make further decisions on location, angle and direction of subsequent boreholes.
The information obtained from the chemical analyses and the geological record derived from the cores in then used to establish the geological structure and the volume of the deposit. The optimum quarry developments are then developed.
The secondary raw materials, clays or shales, may be proven by means of auger drilling of by test pit excavation using mobile hydraulic excavators or in some cases by hand excavation. These materials are similarly recorded and chemically analysed as for the limestones.
Using the chemical analysis of the raw material, computerized raw mix designs can be carried out. The in-house program used has several facilities which can be called upon. Firstly, all the necessary standard equations which must be satisfied for lime saturation, silica ratio, alumina ratio, hydraulic modulus, etc., are built into the program. Secondly, the mix design can be refined by adjusting the compound composition and observing the effect upon the standard ratios. Finally, cost factors can be added to the raw materials to obtain the optimum raw mix which minimizes the most expensive raw materials, but satisfies the above criteria.
Process design
The optimum process route for a specific plant is dependent upon a number of factors including the physical and chemical nature of the raw material deposits. The selection of plant and machinery is made based on the following factors”
Disposition of the raw material deposits.
Moisture content and other physical properties of the raw materials.
Level of undesirable chemical elements.
Mineralogy (particularly the content and size of silica).
Abrasiveness, grindability and the burnability of the raw materials.
Fuel types and relative costs.
Environmental protection requirements.
Electrical power availability, cost and energy efficiency requirements.
Site topography and congstraints.
Market constraints.
Labour and maintenance constraints.
The disposition of the raw materials in terms of dip and strike and physical location dictate how the primary and secondary raw material quarries are opened up, how they are to be worked and how the access roads are to be developed. The geological method of deposition and hardness of the raw materials will also determine how the quarry is to be planned and the methods of extraction determined.
The moisture content of the raw materials and the change in their characteristics as the moisture content alters has an important effect upon the choice of the primary crusher and storage systems. The moisture content has even greater implications when considering the raw milling system to be proposed in conjunction with the optimum temperature of preheater exit gas. A balance has to be struck between the requirements of the kiln system, the number of cyclone stages that can be used, and the heat requirements of the raw mill for raw materials drying.
The level of undesirable chemical elements in the raw materials, such as potassium, sodium, magnesia, chlorides and sulfur requires careful consideration in the selection of the type of kiln system. The varying levels of impurity elements in conjunction with the sulfur in the raw material and possible additional sulfur intake from the kiln fuel, lead to the necessary decisions to be made relating to the acceptance and sizing of a bypass system.
The mineralogy can vary greatly among raw materials in different countries. The method of deposition and the occurrence of the chemical elements in each of the raw materials can have a marked effect on the characteristics of combination in the kiln burning process. Notably this leads to variations in kiln fuel conditions. Predictions upon how the raw-materials will behave when combined in the necessary proportions to obtain a commercial cement, are based upon laboratory burning and grinding tests conducted as part of the feasibility study.
Energy and fuel usage are two key matters high on the agenda of all potential and existing cement plant operators. The cement industry has always been very conscious of making the maximum use of heat energy, and to this end heat transfer from the kiln gases to the raw materials, of from the hot clinker to the combustion air, has always been utilized.
Today more than ever the efficient use of energy and fuel is sought affair and a range of plant and equipments available for consideration. Technical economy of scale is also an important factor and where the market justify large capacity plant, correspond with reductions in the cost of products are achieved.
Energy consumption is be reduced through the use of roll-milling systems for raw meal in plant of tube mills, high efficiency separators in both the raw milling and cement milling departments, low pressure drop cyclones in the preheater of the burning process, and by the preheater of high pressure grinding rolls, and recent introduction of the horizontal roller mill, the so-called Horomill. The selection of the optimum planning processes ensures that the KWh/h electrical power consumption minimised.
Fuel consumption is reduced the introduction of efficient cyclones construction with heat resistant tubes and an increase in the number of stages of preheater to mount maximum use of the hot gases leaving from the kiln. Fuel consumption is also siderable affected by the designation ancillary plant such as the kiln separators, gas ducting, kiln burner, flow control valves and instrumentation.
Another recent development is the transfer of all the hot exhausted gases form the clinker cooler back onto the raw mill, thus saving on the heat required for drying the raw material. This arrangement also has the acute advantage of reducing the capital of the plant by the elimination of a cipitator or other clinker cooler collection system and its associating equipment.
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