why bauxite is used to manufacture cement clinker

the cement manufacturing process

the cement manufacturing process

Different minerals need to be mined in order to make cement. Limestone (containing the mineral calcite), clay, and gypsum make up most of it. The US Geological Survey notes that cement raw materials, especially limestone, are geologically widespread and (luckily) abundant. Domestic cement production has been increasing steadily, from 66.4 million tons in 2010 to about 80.5 million tons of Portland cement in 2014 according to the U.S. Geological Survey 2015 Cement Mineral Commodity Summary. The overall value of sales of cement was about $8.9 billion, most of which was used to make an estimated $48 billion worth of concrete. Most construction projects involve some form of concrete.

Cement manufacturing is a complex process that begins with mining and then grinding raw materials that include limestone and clay, to a fine powder, called raw meal, which is then heated to a sintering temperature as high as 1450C in a cement kiln. In this process, the chemical bonds of the raw materials are broken down and then they are recombined into new compounds.The result is called clinker, which are rounded nodules between 1mm and 25mm across. The clinker is ground to a fine powder in a cement mill and mixed with gypsum to create cement.The powdered cement is then mixed with water and aggregates to form concrete that is used in construction.

Clinker quality depends on raw material composition, which has to be closely monitored to ensure the quality of the cement. Excess free lime, for example, results in undesirable effects such as volume expansion, increased setting time or reduced strength. Several laboratory and online systems can be employed to ensure process control in each step of the cement manufacturing process, including clinker formation.

Laboratory X-Ray Fluorescence (XRF) systems are used by cement QC laboratories to determine major and minor oxides in clinker, cement and raw materials such as limestone, sand and bauxite. Read Analysis of Clinker and Cement with Thermo Scientific ARL OPTIMX WDXRF Sequential Spectrometer to learn why XRF is the technique of choice for elemental analysis in cement industry. Combination X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD) systems accomplish both chemical phase analysis for a more complete characterization of the sample. Clinker phase analysis ensures consistent clinker quality. Such instrumentation can be fitted with several XRF monochromators for major oxides analysis and a compact diffraction (XRD) system which has the capability of measuring quartz in raw meal, free lime (CaO) and clinker phases as well as calcite (CaCO3) in cement.

Cross Belt Analyzers based on Prompt Gamma Neutron Activation Analysis (PGNAA) technology are installed directly on the conveyor belt to measure the entire material stream continuously and in real time to troubleshoot issues in pre-blending stockpile control and quarry management, raw mix proportioning control, and material sorting. Read PGNAA Improves Process and Quality Control in Cement Production to learn what makes PGNAA particularly suited for cement analysis.

Accurate cement production also depends on belt scale systems to monitor output and inventory or regulate product loadout, as well as tramp metal detectors to protect equipment and keep the operation running smoothly. The Cement Manufacturing Process flow chart sums up where in the process each type of technology is making a difference.

Need a Belt scale system for your bulk material handling? To help you decide which belt scale system is best for your mining operation, weve outlined the options in an easy-to-read belt scale system selection guide so you can decide which belt scale system is right for you. Click on the image, take a look at the chart, and see if it helps you decide.

re: natural gas vs. coal (above) The cost of natural gas is still around 3$ per million btu, while coal is 2$. So for a process like this that just needs heating value coal would be much preferred, and worth the cost for back end pollution control. Gas is becoming preferred for electric generation because a combined cycle plant has around 65% cycle efficiency, vs. 38% for coal-fired.

what are cement clinkers? (with pictures)

what are cement clinkers? (with pictures)

Cement clinkers are formed by the heat processing of cement elements in a kiln. Limestone, clay, bauxite, and iron ore sand in specific proportions are heated in a rotating kiln at 2,770 Fahrenheit (1,400 Celsius) until they begin to form cinder lumps, which are also known as cement clinkers. These are usually ground with gypsum to produce the fine powder later mixed with liquid to produce cement, although some manufacturers ship clinkers in their lump form to cut down on dust.

Cement is heavily relied upon to produce mortar, grouts, and concrete, and cement clinkers are the first stage, post firing, in making cement. Cement has strong bonding qualities when mixed with gypsum and water to form a hydration reaction, and it forms approximately one tenth of concrete, mixed with rocks, sand, and other materials and used in building construction all over the world. Concrete's high versatility makes it an ideal tool for building projects of all shapes and sizes, from skyscrapers to pool sides. Concrete can also be recycled when it has outlived its usefulness and converted back into cement clinkers through careful processing.

The most commonly used cement in the world is Portland cement, which is formed at high temperatures that chemically combine the ingredients into new components, including calcium silicates and calcium aluminates. When the cement clinkers are ground with approximately 5% gypsum, they form Portland cement. These compounds allow cement to set when combined with water and to form strong bonds that can withstand pressure, water immersion, and other elements.

Natural raw materials can be utilized in a kiln to form cement clinkers, although other materials with the proper chemical composition are also used, such as fly ash from coal burning, furnace slag, and other industrial byproducts. Depending upon the purpose for which the cement is intended, slightly different chemical formulations are used to increase strength, add sulfate resistance, make cement that is tolerant to low temperatures, form expansion cement that will not shrink after setting, or create masonry cement, which is not intended for concrete mixtures. If consumers are unsure about which cement formulation is appropriate for a project, they should consult a knowledgeable source to confirm that they are using the most suitable material for their needs.

Manufacture of cement clinkers has environmental ramifications, beginning with the dust, noise, and vibration caused by mining for natural raw materials. Cement kilns also eat through a substantial amount of fuel, and polluting equipment is used at most stages of cement manufacture. However, some of these effects are offset by the reuse of slag, fly ash, and silicate byproducts. Furthermore, many cement manufacturers use other agricultural and industrial byproducts to fuel the kilns, helping to dispose of these materials.

Cement, when mixed with water, forms a very strong alkaline solution. Gloves and eye protection should be worn at all times when working with cement, and cement should be washed from the skin immediately to prevent skin injury. Once cement hardens, it can be handled without precautions.

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a InfoBloom researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a InfoBloom researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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