China manufacturing industries are full of strong and consistent exporters. We are here to bring together China factories that supply manufacturing systems and machinery that are used by processing industries including but not limited to: stone crusher, crushing machine, rock crusher. Here we are going to show you some of the process equipments for sale that featured by our reliable suppliers and manufacturers, such as Stone Jaw Crusher. We will do everything we can just to keep every buyer updated with this highly competitive industry & factory and its latest trends. Whether you are for group or individual sourcing, we will provide you with the latest technology and the comprehensive data of Chinese suppliers like Stone Jaw Crusher factory list to enhance your sourcing performance in the business line of manufacturing & processing machinery.
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Jiangxi Victor International Mining Equipment Co., Ltd. is a large mineral processing manufacturer which is specialized in designing, producing, installing and debugging as well as providing processing line design and course training of mineral processing. Presently our company is a large manufacturer in China, with covering an area of 48, 000 square meters and 20, 000 square meters for workshop, with various large modernized machinery facilities, professional R&D team and installation team. With ...
China manufacturing industries are full of strong and consistent exporters. We are here to bring together China factories that supply manufacturing systems and machinery that are used by processing industries including but not limited to: stone cutting machine, marble cutting machine, mining machine. Here we are going to show you some of the process equipments for sale that featured by our reliable suppliers and manufacturers, such as Marble Mining Machinery. We will do everything we can just to keep every buyer updated with this highly competitive industry & factory and its latest trends. Whether you are for group or individual sourcing, we will provide you with the latest technology and the comprehensive data of Chinese suppliers like Marble Mining Machinery factory list to enhance your sourcing performance in the business line of manufacturing & processing machinery.
Small rock crusher, also called as mini stone crushing machine, is such a machine which is designed for the large rocks decrease becoming small rock, gravel, or rock dust. It will produce the gravel stones and the mining ores, or the filling material used to beautify and erosion control. They can be used with the cement making machine. Small rock crusher can move (though usually is very heavy), and it also can be fixed.
As China's economic construction is growing, the domestic real estate and high-speed way construction develops rapidly, which make small rock crusher industry has a rapid development. Small rock crusher production specifications will be from single crusher development to a variety of specifications and various types of a variety of small crusher. Compound crusher, one of the new types of small rock crusher, also develops gradually. It has a significantly improvement of compound rock crusher recent years.
Small rock crusher design is novel which adopts the design principle of the new concept crushing technology. This machine can satisfy the crushing requirements of different material. Small rock crusher will meet the new technology of "more crushing less grinding" requirements. It has large crushing ratio, uniform and fine end products. The unit power consumption is low and it has fewer requirements for the crushed materials' humidity requirements. It is also suitable for any hard brittle materials or other various kinds of minerals. Through large engineering, the small rock crusher shows that it has good application prospect in the field of mineral processing equipment.
There are many factors impacting the small rock crusher production capacity: The hardness of the material. More hard material, it is more difficult to break, and this will cause serious wear. When the machine crushes hard materials, it has slow crushing speed and the crushing capacity will be small. The humidity of materials. When the material has large moisture content, it is easy adhesion when the small rock crusher works. It is also easy to jam in the process of the material transporting, which will reduce the crushing capacity. The fineness of crushed materials. If you need the high fineness, which means the end products are very fine, the crushing capacity will be small. The composition of the material. Before crushing, it will influence the crushing capacity if the materials have much more fine powder. Because the fine powder will affect the delivery, you should separate the fine powder before crushing stage.
According to different customers' various needs, SBM can offer you the advanced machines and high technology, especially the small rock crusher for sale. The small crushing equipment is suitable for the crushing of materials in the industries of metallurgy, building, road paving, chemical and silicate. It can crush kinds of ores and rocks with the hardness of medium and above medium. All around and considerate service is also provided to all the clients.
Its fully-enclosed layout features high integration. It integrates the functions of high-efficiency sand making, particle shape optimization, filler content control, gradation control, water content control, and environmental protection into a single syst
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Why lithium? Great question. In my opinion, its simultaneously the simplest and most complex metal. Lithiums simplicity comes from the fact that its been used in industry for quite some time, and most of the general public know the metal in its battery form. Its complexity relates to the science behind how and why its presently used, but more importantly, the role lithium will play in the future. Lithium isnt rare, but the lithium market is definitely under developed in comparison to most other industrial commodities, leaving the space to a select few conglomerate giants and a group of junior companies. The fact is, lithium has a ton of applications, from lubricating grease and glass fabrication, to glazes for ceramics, and finally, batteries. In particular, lithium is and will continue to play an increasingly important role in the battery-powered clean air future. Lets take a closer look at the lithium narrative
Pegmatites are commonly found throughout the world, but lithium-rich granite pegmatites are much less common, making up less than 1%. Granite pegmatite-ore bodies are the hard-rock source of lithium. The lithium minerals that occur in granite pegmatites are spodumene, apatite, lepidolite, tourmaline and amblygonite. Spodumene is the most commonly occurring lithium hard-rock mineral, which, once upon a time, made it the number one source of lithium metal in the world. It has since been surpassed by brines, which, for a number of reasons, have become the largest contributor to lithium production.
Lithium hard-rock recovery can be broken down into a few key steps: crushing of the ore, concentration by froth floatation, followed by hydrometallurgy and precipitation from an aqueous solution. From here, depending on the application, the producer will typically create either lithium hydroxide or lithium carbonate, which can be sent to factories to be manufactured into its final form. When evaluating a hard-rock lithium deposit, there are a few key things to look for: Lithium Grade Arguably the most important figure in any type of deposit. Typically, the higher the grade of lithium, the more economic the deposit. By-Products Not to be confused with harmful impurities, by-products can help reduce the cost per ton because they have value. For lithium hard-rock deposits, tantalum, beryllium and caesium are examples of profitable by-products of the refinement process. Impurity Levels High concentrations of impurities (non-profitable by-products) can lead to higher refinement costs and could limit their use in end use applications, such as glass and ceramics. Location Poor proximity to infrastructure can make a high grade lithium mine a lot less profitable or not even economically feasible.
Lithium brine deposits are accumulations of saline groundwater that are enriched in dissolved lithium. Lithium concentrations are typically measured in parts per million (ppm), milligrams per litre (mg/L) and weight percentage. Brine is pumped up from the ground and placed into man-made ponds, where the lithium is concentrated via evaporation. Depending on the climate and weather in the region of the brine deposit, lithium concentration can take a few months to a year. Typically, lithium concentrations range between 1 and 2%. Unlike their hard-rock cousins, these concentrations can be sent to processing plants for end use production. All lithium brine deposits have a few common characteristics (Bradley, Munk, Jochens, Hynek, Labay. USGS A Preliminary Deposit Model for Lithium Brines, 4). Arid climates Closed basin containing a playa or salar Tectonically driven subsidence Associated igneous or geothermal activity Suitable lithium source-rocks One or more aquifers Sufficient time to concentrate a brine
Evaporation Rate evaporation is dependent upon the climate in which the deposit is located. Hours of sunlight, humidity, wind levels and temperature all have an effect on the evaporation rate. A low evaporation rate could make the difference between an economic deposit and an uneconomic one.
Impurity Levels The magnesium to lithium ratio and the sulphate to lithium ratio are very important figures to look at when examining a brine deposit, because separating these impurities from the lithium is one of the largest expenses in the brine refinement process. For both of these ratios, youre looking for low figures.
Brines are todays answer to lithium demand as they are more wide spread, typically larger in resource scale, and generally have lower production costs. Countries such as Chile, Argentina and China extract the majority of their lithium production from brine deposits.
Lithium reserves exist on 5 continents: North America, South America, Africa, Asia and Australia. As the table shows, however, there are reserves on 5 continents but the concentration is in South America, where theres approximately 66% of the worlds reserves.
The Lithium Triangle refers to Chile, Argentina and Bolivia. Beginning with Chile, the number 2 producer of lithium in the world and 1st in reserves, their reserves are held in brine deposits. Its main brine deposit is The Salar de Atacama, which is located in the Antofagasta region. The Salar de Atacama is approximately 3000 square kilometres and has an estimated 6.8 Mt of lithium reserves.
The other key player in The Lithium Triangle is Argentina, the number 3 producer of lithium in the world and 3rd in reserves. Argentinas source of lithium, like Chile, is found in brines. Although Bolivia currently makes up the smallest portion of The Lithium Triangle, its thought to have the largest undeveloped lithium brine in the world, Salar de Uyuni. USGS Mineral Commodity Summaries estimates that this prized salt flat contains 9 million tonnes of identified lithium resource.
China is the number 4 producer of lithium in the world and 2nd in reserves. Chinas lithium deposits are found both in hard-rock and brine sources. Its lithium-rich pegmatite deposits are found in Jiajika, Barkam, Altai, Koktokay and the Nanping district, while its lithium-rich brines, which possess the vast majority of its reserves, are found mainly on the Quighai-Tibet plateau.
Currently, Australia is the number 1 producer of lithium in the world. Australias lithium is held in hard-rock deposits, mainly the Greenbushes deposit, which is currently in production. Finally, the Mount Cattlin and Mount Marion projects, which arent yet in production, are expected to alleviate some of the supply crunch for world demand in the future.
A major impact to the lithium supply story could come from a technological breakthrough in the refinement of lithium brines. Current research and development dollars spent by South Korean giant, POSCO, and privately owned, Energi Corporation, are exploring methods of refining lithium brine without the use of evaporation. The current major cost in the brine refinement process is the removal of impurities such as magnesium, calcium, iron and potassium via evaporation and additives. If they are successful, it will revolutionize the lithium mining industry, as more deposits will become economical and existing mining operations could change production methods to capitalize on cheaper processing costs. When or if this occurs, is a big question.
That said, the fact that R&D dollars are being spent in lithium refinement is a major plus, in my books. With this much interest, I think you can almost guarantee a strong future for lithium, worldwide.
Lubricant Grease An estimated 2.38 billion pound market, in which lithium-based greases make up 75%. Lithium-based greases generally have good stability, high temperature characteristics and water-resistance properties.
Glass Lithium typically sourced from the mineral spodumene reduces the viscosity and thermal expansion of glass and, therefore, leads to increased melting efficiencies and/or larger effective furnace capacities. The end result is a substantial energy savings for the glass manufacturers.
Ceramics Lithium is used in the ceramics industry to produce glazes. The glazes improve a ceramic pieces shock absorption and stain resistance, protecting the piece against damage. Lithium carbonate is typically used for this application.
Batteries have essentially three main components: cathode, anode and electrolyte. When the cathode and anode are connected via a wire, for example, electrons flow from the anode through the wire to the cathode, creating an electrical current.
Currently, there are an estimated 80 different lithium-ion battery chemistries in production, with these varying chemistries all exhibiting different characteristics, such as capacity and voltage. Lithium is typically found in the cathode of the battery, commonly in the form of lithium cobalt oxide, while the electrolyte is commonly in the form of a lithium salt, such as LiPF6, LiBF4 or LiCLO4. The anode material is commonly carbon-based, with graphite being the most popular.
Projected demand for 2025 is much different, not only in overall demand tonnage, but the percentages each application encompasses. The future is expected to be bright for batteries in the non-traditional markets; electric cars, e-bikes, and energy storage.
The interesting thing about this projected demand curve is that it is linear. The reason I think thats interesting is that most things in life dont follow a linear path, especially those things that are rapidly changing, such as the lithium market. Now, the opposite could be true, the demand could be flat or declining in the future, but I tend to think that the future for lithium will be exponential.
For those who dont know what an exponential function looks like, think of a hockey stick turned upwards with the blade in the air. Basically, it looks linear for a while, constant growth, and then boom to the moon it goes.
Why do I think this? Mainly because of the politicized nature of green energy. Whether its the 450 Scenario or some other push to reduce carbon emissions, governments across the world are allocating more and more policy and CASH to the cause. The final inflection point could be massive and it could happen before 2025, in my opinion
The 450 Scenario calls for long-term concentrations of local greenhouse gases to be at 450 ppm CO2 equivalent by 2040. To put that into perspective, we globally emitted 32,381 Mt of CO2 in 2014 (International Energy Agency, 2016 Key World Energy Statistics, 45). Under the 450 Scenario, that number reduces dramatically to 18,777 Mt of CO2.
Using the United States as an example, Statista states that there were around 260 million registered vehicles in the United States in 2014. The U.S. Energy Information Administration (EIA) estimates that U.S. fossil fuel consumption for transportation in 2015 resulted in a combined 1,545 million tonnes of CO2, which is 29% of the total CO2 emissions by the country.
Therefore, my estimated carbon emissions per U.S. vehicle is around 6 tonnes per year. If the United States figures to comply with the goals of the 450 Scenario, to drop transportation emissions to 26%, in-line with the rest of the world, they will need a reduction of 3% (29% to 26%) (International Energy Agency, 2016 Key World Energy Statistics, 46). The following calculation shows that a reduction of this magnitude would affect approximately 7.7 million vehicles.
Insideevs.com reports that there were 116,099 full electric vehicles sold in the United States in 2015, and 441,179 worldwide. If you linearly distribute the number of vehicles affected by the 450 Scenario on a 23-year time horizon (2017 to 2040), 7,725,000 / 23 = 335,870 vehicles per year would need to be sold, or almost 3 times the number of current sales per year.
How does this equate to lithium demand? Well, it isnt an easy calculation as there are a lot of assumptions, but I did find an estimate of 47 lbs (0.021 t) of lithium per Tesla Model S (sedan). If 335,870 Tesla Model S were sold in the United States in a given year, this would translate into 335,870 x 0.021 t of 7,053 t of lithium, or 37,544 t of lithium carbonate (conversion from Li to LiCO3 1 : 5.323)
I believe this 3% improvement scenario for vehicles per year is conservative. In reality, I think demand in the next 5 years could easily be twice as much. Deutsche Bank believes demand will hit 2.4 million in global electric vehicles sold in 2025. They estimate total demand in terms of lithium carbonate equivalent to be 534 kt, of which batteries would make up 45% (Deutsche Bank, Lithium 101 Report, 24).
I believe its undeniable that lithium will play a major role in powering our clean air future. The trend is your friend and in this case it is only the beginning of what appears to be a major turning point in the way we live our day to day lives.
The quarrying operation cuts a block of stone free from the bedrock mass by first separating the block on all four vertical sides, and then undercutting or breaking the block away from the bedrock. If the block is large, it is called a quarry block and will be cut into smaller blocks at the quarry. If the block is small enough to be moved from the quarry it is called a mill block and may be sold as it is or taken to a mill for further processing.
Rock commonly has two, and sometimes three, natural directions of cleavage, which influence both quarrying and rock dressing methods. The direction of easiest cleavage is called the rift, the second easiest is the grain, and the third and most difficult, if present, is the head grain or run. If there is no head grain, the third rectangular direction is called the hardway. Modern technology and quarrying methods are less dependent on cleavage than were earlier methods.
Two of the oldest methods for quarrying are channel cutting and drilling and broaching. A channeling machine cuts a channel in the rock using multiple chisel-edged cutting bars that cut with a chopping action. In drilling and broaching, a drilling tool first drills numerous holes in an aligned pattern. The broaching tool then chisels and chops the web between the drill holes, freeing the block. Both channel cutting and drilling and broaching are slow, and the cutting tool requires frequent sharpening. Both methods have generally been replaced with other more efficient methods.
Line drilling or slot drilling is a more modern technique for quarrying, which consists of drilling a series of overlapping holes. The drill is mounted on a quarry bar or frame that aligns the holes and holds the drill in position.
Flame cutting or jet channeling is a common method for cutting granite. Flame from a torch is passed over the rock and the intense heat creates a thermal shock, which causes the rock to spall. This technique does not work in quartz-free rocks, or carbonate rocks that fuse or calcine. Jet channeling creates a wide irregular kerf, which wastes rock; it is also very loud, which is a potential health hazard to workers. Channels can also be cut into rocks using a water jet. A high-pressure pulsating jet of water is directed at the rock, which causes it to disintegrate.
A variety of saws can be used to excavate dimension stone, including wire saws, belt saws, and chain saws. The introduction of synthetic diamond tools during the 1960s revolutionized stone working. Chain saws or belt saws with diamond-set teeth are used to cut softer stones such as marble, sandstone, and slate. Wire saws with diamond-impregnated beads mounted on a wire cable can cut harder stones like granite.
The quarrying industry is a long established but unpredictable industry, involving hazardous conditions for both plant and personnel. Frequently machinery operates under impact loading conditions with charges that vary in weight from only a few kilograms to several tonnes. Much of the machinery is of traditional design, which has evolved over the years. Such designs are not easily codified, nor their rationale documented, and successful performance relies upon step-by-step progress, and operating conditions within historic experience. Quarrying equipment is very heavy duty and is often thought of as low-tech, especially compared with industries like nuclear and aerospace, but the safety and operational reliability of the industry is still dependent on the same features as in these high-tech industries. In addition, practices which have developed over the years may not be the best available, and because of changes in materials and duty may even become inadequate. This chapter presents the study of a failed rock crusher, and shows where design, material selection, and construction aspects can be improved to facilitate more reliable performance.
The crusher in question was used to crush large boulders of limestone, on site, which had been explosively excavated from the quarry face and had not been otherwise reduced in size. It was of a design that has served the industry satisfactorily for several decades. The one which failed was new, however, and had been operating for only 45 months, well short of the usual lifetime for such equipment.
It is normal for rock crushers of this type to have developed a small amount of cracking on the visible faces of the outer disks of the rotors. This cracking may be repaired from time to time, by welding, and under these circumstances the crushers seem to operate indefinitely. The failure described here involved an unusual mode of cracking which was much more extensive, and which had become so within a short operating period.
The manufacturer's initial thoughts were that the crusher had failed by brittle fracture due to a single excessive load, possibly from a non-friable article, which would tend to overload it. However, there was no independent evidence of this. The study also looked at the possible mechanisms for overloading the crusher, and concluded that this was not possible. Other evidence showed that the material could crack by fatigue by an unusual and highly damaging mechanism, and that this was the most likely reason for the failure.
Many lessons may be drawn from the investigation and could be applied to subsequent plants during manufacture and operation without significantly increasing the manufacturing or running costs, and these were incorporated into a replacement crusher. These succeeded in preventing a recurrence of the mode of cracking that led to failure, but not in eliminating the more common form of cracking. It was thought possible that this mode of cracking was self-arresting, and hence benign. If this could be shown to be the case by analysis, the weld repairs would then become unnecessary and the associated loss of availability and other expense could be avoided. However, the operators declined to support the necessary analytical work, so this avenue could not be investigated. No reason for this rejection was given, but a reluctance to change practices, even when established ones can be shown to be of no benefit, is a common feature in industries which do not have a tradition of applying specialist expertise.
Plans for quarrying must include all operational aspects of mining, including overburden and mineral handling, storage, haul road placement, volumes involved, equipment selection, reclamation and economics. Consideration must be given to annual production; physical, environmental and permitting restrictions (limits of mining, ultimate depth, etc.); desired benching configuration; location of the groundwater table and other impacting factors.
The importance of all these factors being designed appropriately goes beyond the boundary of the quarry and the cost of production. For example, inaccurate calculation of the size of machinery required can easily lead to benches being worked in the order that the material is most easily won rather than the optimum for consistent quality of raw material.
Once material is removed from the quarry face it begins its journey to the raw plant and then to the factory and the customer. If an adequate block model is in place and the composition of each block of material is known before it is despatched from the face, then all the tasks further down the line will be easier than if the material is of unknown composition until the raw meal for the cement kiln has been made.
Historically, quarrying was very much a local task. This fed the development of the vernacular, local distinctiveness, certainly before transportation became widespread and economical. Local sourcing of stone markedly influences its sustainability credentials, with transportation within the United Kingdom accounting for around 1020% of the EC (comparing Cradle-to-gate (C-G) and Cradle-to-site (C-S)). Importation increases the carbon footprint many times over (Crishna et al., 2010). Local sourcing supports employment, often rural. Energy sources associated with extraction and processing include fuel for plant, modest use of explosives, and electricity and water for processing.
The extraction and processing of dimension stone is fairly consistent in terms of process across the United Kingdom. Extraction processes vary according to the type and characteristics of the stone; however, in the main, the aim is to secure the largest bulk block size within practical constraints. These blocks are then inspected to appraise the most efficient way of cutting into slab form with minimum wastage (Stark, 2005). Typically the stone is seasoned in the yard to harden up, although it may be processed green. Cutting is by plant machinery, the primary cut being to reduce the rough bulk to slab forms, and the secondary cut(s) to dimension stone sizes. Tooling, dressing and other finishing is then undertaken according to the final product required.
Approximately one-third of the rock deposit is estimated to become the primary product of dimension stone, the rest of which comprises overburden or primary waste, which then becomes available for by-product usage (Siegesmund and Trk, 2011). This general approximation is of course dependent on the type of stone being quarried, and the product required.
Once commissioned, even the best-planned industrial development requires monitoring and management to ensure that its operation continues to be environmentally acceptable. This applies equally to established industries. When unexpected environmental problems develop, a rapid response is required to assess the cause and magnitude of the problem and to devise remedial measures.
Dusts produced by quarrying and fluorides emanating from oil refineries are typical pollutants, which need regular monitoring. A range of portable equipment for the identification and quantification of toxic and other gases can be used on an ad hoc basis.
When unpleasant odors resulting from manufacturing processes or waste-disposal operations give rise to public complaints they should be identified and quantified prior to deriving methods of abatement. Such work is often innovative, requiring the design and fabrication of new equipment for the sampling and analysis of pollutants.
Consultants are equipped to monitor the quality of freshwater, estuarine and marine environments and can make field measurements of a variety of waterquality parameters in response to pollution incidents. For example, reasons for the mortality of marine shellfish and farmed freshwater fish have been determined using portable water-analysis equipment. Various items of field equipment are, of course, also employed in baseline studies and monitoring, respectively, before and after the introduction of new effluent-disposal schemes.
Where extreme accuracy is required in the identification of pollutants or in the quantification of compounds that are highly toxic, laboratory analysis of samples is conducted. Highly sophisticated techniques have, for example, been employed in the isolation of taints in drinking-water supplies.
As development proceeds, land is coming under increasing pressure as a resource, not only for the production of food and the construction of new buildings but also for disposal of the growing volume of industrial and domestic waste. The design and management of sanitary landfill and other waste-disposal operations requires an input from most of the environmental sciences, including geologists and geo-technicians, chemists and physicists, biologists and ecologists. Such a team can deal with the control and treatment of leachate, the quantification and control of gas generation, and the placement of toxic and hazardous wastes. This may be needed in designs for the treatment of industrially contaminated land prior to its redevelopment.
The acceptability of some industrial and ephemeral development projects such as landfill or mineral extraction may depend upon an ability to restore the landscape after exploitation has been completed. As more rural development projects come to fruition, ecologists will become increasingly involved in resource management to ensure that yields are sustained and to avert the undesirable consequences of development. Some industrial developments and rearranged plant layout schemes will not be complicated, but when ecology studies are needed, the employment of specialist consultants is recommended.
The sample was sourced from Gosford Quarrying, which is located at 300 Johnston St, Annandale, Sydney. Due to the size and weight limitations, the most suitable sample was chosen and transported to Rock Mechanics Laboratory. A specification sheet was obtained from the Gosford Quarrying store, which gives a general idea of the characteristics of the sample. The sandstone is in a brown and banded color, and primarily names as Mount White Brown. Its geological name is Argillaceous Quartz Sandstone, which is formed in the Triassic age. Based on the specification sheet, the sample is described as medium-grained quartz sandstone with a predominantly argillaceous matrix. The concentration and distribution of iron oxides influence the nature of the color banding and density of color. The bulk density of this sandstone is approximately 2.27t/m3 with 4.4% of absorption. The modulus of rupture is 8.9MPa in dry condition and 2.5MPa when is wet. The compressive strength is around 37MPa (dry) and 22MPa (wet).
A diamond wire has become a standard stone quarrying tool which enables high production rates and increased output of blocks that are used for monumental purposes in areas where flawed or fragile stone is quarried. Owing to its adaptability to suit most sawing tasks, it has also made rapid progress in stoneyards, where both single-wire and multi-wire stationary machines are increasingly used for block division (Fig.19.16), as well as for profiling of stone slabs. A typical wire saw contains 1011mm diameter diamond impregnated beads mounted at regular intervals on a flexible 5mm diameter steel rope composed of many twisted together high strength stainless steel strands. The multi-wire machines utilise 68mm beads on a 4mm steel rope to minimise kerf widths and thus to maximise the yield of stone slabs per block.
The cutting action consists of pulling a properly pre-tensioned wire saw across the workpiece. The linear wire speeds and cutting rates achieved on stationary machines are similar to those applied in the quarry and depend on the stone type as shown in Table19.5.
The versatility and economic advantages of the wire saw technology have also been recognised in the construction industry, where portable wire saw machines are used for various construction, renovation and controlled demolition purposes. The ability of the diamond impregnated wire to cut cleanly, quickly and accurately, with little noise and vibration, makes this tool an ideal alternative to blasting or jack hammering with flame cutting of the rebar, which were previously used for removal of thick sections of reinforced concrete or brickwork. The cutting rates achievable on construction materials may widely vary from 16m2h1 on reinforced concrete, through 511m2h1 on plain concrete, up to 1018m2h1 on masonry, depending on the type of concrete aggregates, percentage of steel reinforcing, brick composition, and so on.
It is essential for the tool performance that the diamond beads wear in a uniform manner over the whole working surface. In industrial practice, pre-twisting the wire, by applying one anti-clockwise twist per metre before a continuous loop is assembled, gives rise to its rotation in the kerf and consequently prevents bead ovalisation.
Concrete construction is marked by activities related to the quarrying and processing of raw materials, which consist largely of NA. NA are nonrenewable as their geological processes of formation take a long time (millions of years) and their continuous and increased consumption decreases their reserves. Currently, high-grade reserves of the earths NA have been exploited in construction activities to a point where the availability of NA is now scarce, if not practically unrealizable in some regions or countries, particularly in urban areas. As a result, materials are transported for long distances, and this in turn elevates the energy consumed and construction project costs, both leading to a number of environmental problems such as greenhouse gas (GHG) emissions and resource depletion. Environmental concerns over the excessive mining of NA compared to other aggregate types, such as recycled aggregates, can be addressed by changing raw material consumption patterns in concrete construction through dematerialization.
The application of dematerialization in concrete construction can be partially achieved through the use of recycled concrete aggregates and through the structural optimization of a structural component to reduce the volume of materials used, which in turn leads to a reduction in pollution generation.
Mining is the process of extracting buried material below the earth surface. Quarrying refers to extracting materials directly from the surface. In mining and quarrying, water is used and gets polluted in a range of activities, including mineral processing, dust suppression, and slurry transport. In addition, water is subtracted from the environment in the process of dewatering, the process of pumping away the water that naturally flows into the pit or tunnels of the mine. When disposed, this water may also carry pollutants. The mining and quarrying sector includes mining of fossil fuels (coal and lignite mining, oil and gas extraction), mining of metal ores, quarrying of stone, sand, and clay, and mining of phosphate and other minerals. A rich data source of water use in the mining of conventional and unconventional oil and gas, coal, and uranium is provided in the work of Williams and Simmons (2013).
Mudd (2008) provides a useful review of gross blue water use in different types of mining (Table 7.3). In general, he found that the higher the ore throughput, the more likely that, through economies of scale, the unit water use per kilogram of ore is lower. Furthermore, he found that as metallic ore grades decline, there is a strong probability of an increase in water use per unit of metal. Gold has the highest water use per kilogram of metal, with platinum closely behind; this is presumably attributable to the very low grade of gold and platinum ores (i.e., parts per million compared with percent for base metals). It is noted here that net blue water use, the blue WF, will be substantially lower than the figures presented in Table 7.3, because most of the water will remain within the catchment.
Pea and Huijbregts (2014) made a detailed estimate of the operational and supply chain blue WF for the extraction, production, and transport to the nearest seaport of high-grade copper refined from two types of copper orecopper sulfide ore and copper oxide orein the Atacama Desert of northern Chile, one of the driest places on earth. The total blue WF (direct and upstream consumption) for the sulfide ore refining process was 96L/kg of copper cathode. The first step in the process, the extraction from the open pit mine, accounts for 5% of the total blue WF; the second step, comminution (crushing, grinding), accounts for 3%; the third step, the concentrator plant, accounts for 59%; the fourth step, the smelting plant, contributes 10%; and the last two steps, electrorefinery and the sulfuric acid plant, contribute 3% and 1%. The supply chain contributes 19%: approximately 9% related to materials and 10% related to electricity. In the case of the copper oxide ore-refining process, the blue WF was 40L/kg of copper cathode. The first step, extraction, accounts for 2%; the second step, comminution and agglomeration, contributes 18%; the third step, the heap leaching process, accounts for 44%; the fourth step, solvent extraction, contributes nothing; and the last step, electrowinning, accounts for 10%. The supply chain contributes 26%: approximately 6% related to materials and 20% related to electricity.
Generally, mining has a significant gray WF, but it is difficult to obtain quantitative data for this. The first source of pollution can come from the overburden, the waste soil and rock that has to be removed before the ore deposit can be reached and that has to be stored somewhere after removal. The strip ratio, the ratio of the quantity of overburden to the quantity of mineral ore extracted, can be much higher than one. The overburden material, sometimes containing significant levels of toxic substances, is usually deposited on-site in piles on the surface or as backfill in open pits, or within underground mines (ELAW, 2010). Through erosion, runoff, and seepage, these toxic substances may reach groundwater or surface water bodies. The second source of pollution comes from the pit itself, where similar processes may spread toxic chemicals into the wider environment. In addition, mine dewatering can bring polluted water from the mine to the streams into which the water is released. The third source of pollution comes from the waste material that remains after concentration of the valuable mineral from the extracted ore and that often contains various toxic substances (like cadmium, lead, and arsenic). This waste, the so-called tailings, is generally stored in tailings ponds, which may leak. Also, there are numerous incidents of tailings reservoir dam breaks, after which the content of the reservoir released itself into the environment. A fourth source of pollution can come from the process of heap leaching. With leaching, finely ground ore is deposited in a large pile (called a leach pile) on top of an impermeable pad, and a solution containing cyanide is sprayed on top of the pile. The cyanide solution dissolves the desired metals and the pregnant solution containing the metal is collected from the bottom of the pile using a system of pipes, a procedure that brings significant environmental risk (ELAW, 2010). Finally, a form of mining that typically results in significant water pollution is the so-called placer mining, in which bulldozers, dredges, or hydraulic jets of water are used to extract the ore from a stream bed or flood plain (ELAW, 2010). Placer mining is a common method to obtain gold from river sediments.
Once the overburden has been removed by processes similar to those used in hard rock quarrying, deposits of sand and gravel are usually extracted by a range of earth-moving plant (Figure 16.6). Some sand and gravel pits extract beneath the local water table and are wet pits, whereas others exploit wholly above the water and are dry pits. Various types of dredger are commonly used for extraction in wet pits, or occasionally large excavators. In dry pits, a great variety of diggers or scrapers may be used, or very occasionally strong water jets known as monitors. In the case of some deposits, wet pit working has the advantage that very fine or clay material can be washed out during the winning and the subsequent transportation of the material to the processing plant.
Fig. 16.6. General view of a sand and gravel pit in Essex, UK. The boulder clay overburden has been removed, the sand and gravel deposit is being worked using earth-moving plant and the base of the sand and gravel rests on London Clay.