iron ore production in the Pilbara

Activities involved in finding, mining and processing iron ore at our Pilbara operations have been simplified in the following diagram. Rio Tinto operates 11 iron ore mines in the Pilbara and the specific sequence of activities varies from mine to mine. Excellence in planning, scheduling and quality control are fundamental to the process.

Resource development

1. Exploration and evaluation

The team identifies and quantifies ore bodies, by using a range of geological, geophysical and metallurgical techniques. In its simplest form exploration involves drilling in remote areas to sample areas.

2. Metallurgical assessment

The data from exploration activities is logged, mapped, Grinding mill analysed and interpreted through models.

3. Mine planning and scheduling

The team develops a detailed plan of which ore bodies to mine in what sequence, to deliver the required product quality at an  appropriate cost. The process of mine planning commences many years before a mine is developed, and continues on a day-to-day basis once the mine is operational.

Iron ore Mine operations

Drill and Blast

Areas for open-pit mining are selected using the mine plan. Identified areas are tagged, and then holes are drilled in an appropriate pattern by rigs. The drill holes are filled with an explosive, most often ANFO (Ammonium Nitrate/Fuel Oil) and then charged. The resulting blast breaks the material to a size required for digging.

Load and Haul

The broken material is loaded for transport by face shovels, excavators or front-end loaders into haul trucks. Haul trucks at our operations are typically in the 190 tonne and 240 tonne class. Overland conveyors are used to transport partially crushed feed at sites

where there are long distances between the pits and process plants.

Process

Processing of the ore ranges from simple crushing and screening to a standard size, through to processes that beneficiate or upgrade the quality of the iron ore products. This is done by physical processes, which remove impurities by differences in particle density or size gravity or size separation. Processing may be wet or dry.

Stockpile and rail-load out

The processed ore is stockpiled and blended to meet product quality requirements, before being reclaimed and conveyed to rail load-out. The ore is loaded into ore cars for transport to the port facilities.

Rail and port operations

Rail

Ore is railed up to 460 kilometres to the coast along a dedicated privately owned rail system. A typical train consist comprises 2 GE Dash 9 locomotives, 230 ore cars and is over 2.4 kilometres long. A single driver, supported by centralised track control, operates the train.

Ore car dumping

Once the train arrives at the port the ore cars go through the car-dumper. The ore cars are rotated and the ore flows out into bins and then is discharged onto conveyors.

Stockpile

The ore is stockpiled according to product type and the quality control plan. The travelling stackers create 250m long stockpiles. Rotary bucket-wheel reclaimers later reclaim the ore, which will be conveyed to the ship loader.

Ship-loading

Vessels are loaded at the berths alongside the ore wharf. Lump ore is rescreened to remove undersize material. Reclaimed ore is conveyed along the wharf and the ore is loaded into the vessel’s holds by travelling, slewing and luffing shiploaders.

Biomass pellet hammer mills and crushers

Before pellet or briquette compression can take place, the raw material must be reduced to a suitable particle size. Depending on the raw material size, a one or two stage size reduction process will be needed.

Depending on your chosen raw material, the equipment you require for size reduction may change. For example, if you wish to process logs or large pieces of wood into pellets or briquettes, a chipper/crusher is the first piece of equipment required for size reduction.

A chipper/crusher simply works on the principle of a rotating blade. As the wood comes into contact with the blade, small pieces (chips) are removed. The chips produced are generally still too large to be used in the briquette machine or pellet mill, therefore secondary particle size reduction of the chips is required in a hammer mill.

To reduce the size of wood chips and other suitably sized biomass raw materials to the correct particle size, a hammer mills is used. A hammer mill works on the principle of attrition. A rotating centre with a collection of flailing hammers impact at high speeds, shattering the material into particles. A screen with the desired particle size ensures the correct particle size is produced.

Once particle size reduction has taken place, a fan is used to extract the particles from the based of the hammer mill. However the particles are now mixed in the air stream, and need to be separated. To separate the particles from the air stream, a cyclone separator is used.

The cyclone has a vertical position, and the air stream and particles are injected into the top of the cyclone. The gas stream, due to the shape of the cyclone is sent into a spiral. During the spiral action, the particles are separated from the air stream and leave the based of the cyclone. The separated air then leaves the cyclone through a central pipe through the top. The particles are now a suitable size for briquette or pellet compression, depending they have a suitable moisture content of around 12% for briquette compression, and 15% for the pellet mill.

The SJ range of crushers and hammer mills can meet all your raw material particle reduction needs. The SJ range can process logs and other large wood pieces up to a 200mm diameter. Other units can process small branches straws, grasses etc up to 50mm in diameter. The particle size is reduced to 3-5mm, which is suitable for briquette and pellet production.

UPVC塑料管和PE塑料管的性能比較

　　1.發展概況

自從上海市建委於1998年發布不允許鍍鋅鋼管再作給水管的決定以來，國內眾多省市紛紛作出了類似決定。 1999年國務院轉發建設部等8部委“提高住宅質量若干意見”的聯合通知，對此項決定也予以肯定。此後我國給水新型管材迅猛發展，開發引

　　進了各種新型管材。在歐美日等先進工業國pvc、pe給水管得到充分發展，某些文獻甚至斷言，50mm及以下的給水管，pvc、pe管的使用量要佔總量的80%～90%以上。在我國禁止用鍍鋅鋼管後，pvc、pe兩種管材也在國內市場佔據了很大的份額。

在我國給水管網中應用的em-technik塑料管主要是pvc管。 pe管應用比較晚，也比較少。近十年來，隨著pe管道在歐洲供水行業的發展應用，pe管道才開始受到人們的關注。特別是近來pvc日益受到環保方面的壓力，有關pvc管中重金屬鉛、鎘的含量是否超標，這些都讓pe管越來越受到人們的關注。而這次，北京在pe管的應用方面走在了全國的前列。北京市從2003年下半年起，供水、供氣管網陸續採用環保型聚乙烯(pe管)。廣西從2003年起，在新建住宅管道安裝中，推廣應用已被確認為無毒無污染的給水用聚乙烯(pe管)。

　　2.pvc、pe管材的現狀和發展

從上個世紀80年代初，國家大力推廣應用upvc管，並製定了​​一系列的政策、制度、標準，也積累了不少經驗。發展到今天，已經具備了完善的產品標準、檢測方法標準及檢測手段、施工工程技術規範等，從而統一了產品的規格尺寸和質量指標，實現了產品的互換性。這說明了pvc給水管道的發展已經進入了成熟期，產品質量和施工質量均有了保障，從而保證了pvc給水管道的使用效果。

而給水用pe管材的國際標準(ISO4427)直到1996年才正式發布。我國於1999年參照ISO4427編寫了國家標準GB/T13663，並在2000年發布實施，但至今pe管件的標準、工程技術規範等仍在繼續完善之中。這說明國內pe管材質量還未穩定，管材管件配套未完善，因而無法確保生產、施工中的質量。

　　3.兩種管材力學性能對比

　　3.1材料常溫下的強度對比

pvc材料短期、長期強度均大大高於pe材料。

3.2最小要求強度(MRS)和安全係數(C)的對比

理論和實際經驗都說明，pvc的MRS和安全係數均大大高於pe，即長期使用的強度和安全性均高於pe。從而同為75mm的管材，採用pvc原料比採用pe原料生產的管材壁厚薄得多，這是由於由於pe材料常溫下強度和長期強度都不如pvc高，只能通過加大壁厚來增加強度。若取相同壁厚，則pe管達不到使用要求的強度。若取相同的管徑，則pvc管材可輸水通徑較pe管大。反之若要達到同樣的輸水量，需要直徑更大的pe管，其工程費用明顯增加。說明pvc材料的較高強度和剛性作為給水管道使用是經濟實惠的。

　　3.3壽命比較

聚氯乙稀(pvc)是極性大分子，較單體氯乙烯(pe)和一些小分子較為穩定，因此比較不容易受環境的影響。但是，現在交聯氯乙烯等高分子的出現，將會在這方面有所提高。

　　4.衛生性能對比

　　4.1pvc和pe均是環保的材料

兩者均可回收再反複利用，是節約資源利於環保的材料。

　　4.2pvc同pe一樣可達到衛生無毒

塑料製品最容易引起人們誤會的是所謂“有毒和無毒”的問題。聚氯乙烯可能是這些誤會中最深的一種。科學的講，對塑料製品不存在有毒和無毒分類的問題，而是普通塑料和食品衛生級塑料的問題。事實上，絕大多數塑料都是無毒的，它們可以製造食品包裝、醫藥用品，甚至用於製作人體中的某些骨骼和器官。

聚氯乙烯製品有普通級和食品級之分。食品衛生級的pvc製品，對添加劑中重金屬和pvc中氯乙烯單體(vcm)含量方面進行了嚴格要求。但這並不表示普通級pvc製品有毒，而是不適合用在食品衛生領域。更不是有人認為不能用和不能接觸。一般來說，加工pe材料添加劑少，被認為是衛生無毒。而對聚氯乙稀的爭議正源於這兩方面，下面就做一簡單分析。

(1)關於氯乙烯(vcm)單體問題，在生產初期確實存在。然而經過這麼多年的努力和提高，其合成工藝日趨完善，國內氯鹼企業通過引進國外先進技術設備，改造工藝等方法都能生產出vcm含量低於5mg/kg的衛生級樹脂。加之國內大中型加工企業使用先進設備，所以最終產品的vcm含量肯定不會超過1mg/kg，完全符合食品級要求。

(2)穩定劑的爭議主要是重金屬含量問題。對給水管道中使用不同穩定劑各國衛生組織有不同規定。至今在仍有許多國家允許使用低鉛系列穩定劑。他們認為現代加工設備先進，需添加的穩定劑量小，最終能從管道表面被溶解而滲出的鉛非常少，使用時經過最初的沖洗能滲出的鉛基本上不存在，完全達到安全的使用範圍。世界衛生組織(WHO)對飲用水總的鉛含量的規定是低於0.01mg/L。隨著人們生活水平的日益提高，追求高質量的生活水準，衛生無毒也是pvc管道發展的方向。今年來出現了衛生性能更好的有機錫，稀土，鈣-鋅複合劑等穩定劑體系，使pvc管道系統完全不含鉛。 1998年國家新頒布了《生活飲用水輸配水設備及防護材料的安全性評價標準》，其規定鉛含量低於0.005mg/L(比WHO的規定還嚴格)。採用新型衛生級穩定劑生產pvc管道完全能達到該標準要求。

所以只要是通過國家嚴格要求，認證的企業生產的pvc管道，是沒有後顧之憂的。

　　5.施工技術難度和造價

多年的使用數據表明，upvc的整個施工費用為主要的材料的8%～10%，與pe管材相比，施工費用大體相當。由於pe管的安裝較複雜，安裝現場要求必須有施工電源，才能熔化接頭，技術要求高，且熔化接頭的質量要求較高，容易出現操作不當而引起漏水或接頭爆管。而pvc管的接頭安裝方便，安裝現場不需要電​​源，安裝方法簡單，不需要專門培訓就可安裝，很少出現漏水或接頭爆裂。

　　6.​​趨勢

綜上所述，目前在國內應用的塑料管道仍然是以upvc管為主，是有其歷史原因和科學道理的。但是縱觀國際上塑料管的應用經驗及發展情況，pe管的發展速度明顯快於upvc。而人們對於環保和衛生的要求的日趨提高，以及國家的宏觀政策和市場環境將刺激pe管材、管件的發展，前景十分廣闊，預計在未來幾年內的用量將逐步超過upvc管。

　　pe管的優越性

(1)pe管材材質無毒，不腐蝕，不結垢，可有效的提高管網水質;pe管道具有良好的耐水錘壓力的能力，與管材一體的熔接接頭及pe管對地下運動和端荷載的有效抵抗能力，大大提高供水的安全可靠性。

(2)pe給水管專用材料近幾年來得到很大發展，pe材料早期得不到發展的一個重要原因就是由於其的不經濟性。然而高性能的聚乙烯管材專用料開發出來之後，增強了pe管的使用優勢，擴大了pe管的應用領域。

(3)pe管具有很好的柔韌性和可熔接性使其鋪設時更加方便經濟和更加安全可靠。 pe管的鋪設速度快，損壞費用和維護費用低，只要接頭良好就可承受軸向負荷而不發生洩漏和脫開。因此在鋪設時在接合處和彎曲處不需要進行費用不小的錨點，支墩，費用可降低。 pe管道具備獨特的柔韌性，其斷裂伸長率均超過500%，彎曲半徑可以達到管道直徑的20～25倍，還有優良的耐刮傷痕的能力。因此鋪設時很容易移動，彎曲和穿插，適用於非開挖頂管等多種施工方式。而且pe管對於管道基礎的適應能力強，一方面對於管基的要求降低，另一方面鋪設後管基發生變化，也不容易損壞。