Production cement

Based on the technology developed for using PVA fiber as a replacement for asbestos in cement products, Kuraray has been developing thick fibers for reinforcing concrete (42). Super-thick fibers with a thickness of 39 tex (350 den) (200 p.m in diameter) to 444 tex (4000 den) (660 p.m in diameter) are now available the 39 tex material is used for reinforcing various mortar-based cement products and the 444 tex material for reinforcing concrete in civil engineering works such as tuimels, roads, harbors, and bays. 

PVA fibers have found wide spread industrial use in cement as replacement for asbestos in cement products, reinforcement of mbber material such as conveyor belts and hydraulic mbber hoses used in cars, ropes, fishing nets, etc. Only a small amount of fibers is used in the production of textiles. 

The reinforcing properties of asbestos fibers have been widely exploited in asbestos—cement products mosdy for the constmction industry and sanitation (sheets, pipes). Into the 1990s, asbestos—cement products represent by fat (f 70%) the largest industrial consumption of asbestos fibers. 

Considerable effort has been devoted to finding alternative fibers or minerals to replace asbestos fibers ia their appHcations. Such efforts have been motivated by various reasons, typically, avadabihty and cost, and more recendy, health concerns. During Wodd War I, some countries lost access to asbestos fiber suppHes and had to develop substitute materials. Also, ia the production of fiber reiaforced cement products, many developiug countries focused on alternatives to asbestos fibers, ia particular on cellulose fibers readily available locally at minimal cost. Siace the 1980s however, systematic research has been pursued ia several iudustrialized countries to replace asbestos fibers ia all of their current appHcations because of perceived health risks. 

Type V (High Sulfate Resistance). Type V Pordand cement is used in concrete exposed to severe sulfate attack of 1,500 to 10,000 ppm. Low concentrations of tricalcium aluminate [12042-78-3] give Type V its sulfate resistance. The sulfate resistance is improved with air entrainment and low water to cement ratios in the wet concrete. U.S. production of Type V Pordand cement in 1989 was 0.9% of the total Pordand cement production. 

Table 8. United States Portland Cement Production ...

Coal was the primary kiln fuel in 1989 as seen in Table 10. Energy from coal rose from 39 to 84% of the total energy required for cement production between 1972 and 1989. In the same time period, natural gas dropped to 9%, petroleum products to 1% of the total energy consumed. Waste fuels represented 5% of the energy consumed in 1989 cement production. 

The first rotary Idlns used in the United States were veiy small, 2 by 20 m. Sizes gradually increased and seemed to stop for a period at a maximum size of 4 by 150 m. A few much larger units have been installed for cement production. 

Carbon dioxide is released into the environment by human activities such as fuel burning, cement production, and land use. 

When the kiln material is cooled it forms into crystallized clinkers. These are rather large irregular pieces of the solidified cement material. These clinkers are ground and a small amount of gypsum is added (usually about 1.5 to 3%). The gypsum prevents flash setting of the cement and also controls free CaO. This final cement product is sampled, analyzed and stored. The actual commercial cement is usually a hlend of several different cements. This blending ensures a consistent product. 

The proper amount of water must be mixed with the dry cement product to ensure only sufficient water for hydration of the cement. Excess water above that needed for hydration will reduce the final strength of the set cement and leave voids in the cement column that are filled with unset liquid. Insufficient water for proper hydration will leave voids filled with dry unset cement, or result in a slurry too viscous to pump. 

Industrial finishing systems are applied to a wide variety of substrates, the majority of which are metallic, but they are also applied to paper, wood, wood composites, cement products and plastics. Often a high quality of decoration is required, as well as protection from a number of hazards, such as knocks, abrasions, bending or forming and contact with non-corrosive liquids. Resistance to the weather may be required. Outdoor finishing systems, and many others, are also required to protect metal against corrosion. 

Wood is one of the oldest constructional materials. Historically it was important in world exploration and trade, and the defence of that trade, in the provision of merchant ships and navies. It was also important in the early days of railway engineering and in building construction. Although in many applications wood has been replaced by other materials, this renewable resource now supports the growing industries of manufactured wood products. Prominent amongst these are the panel materials chipboard, flake-board, strandboard, plywood and blockboard, hardboard and softboard, wood-cement products and the products of the very large pulp and paper industries. 

Cement production demands major amounts of fuel. Energy costs can be upwards of 25% of their turnover. Therefore, many cement kilns in the UK, Belgium, the Netherlands, Switzerland and other countries have started to use pretreated waste streams as a fuel. This not only saves fuel input, but indeed often allows a charge for the treatment of waste. In principle, cement kilns can deal with the following types of waste ... 

Anonymous. Cementing products and additives. World Oil, 216(3 [suppl]) C-3- C-18, March 1995. 

Mercury in various cement products was determined with a special mercury oven for solid samples. Calibration was performed with four BCR CRMs and one NIST SRM with different Hg content as well as with a reference solution and excellent agreement found (Bachmann and Rechenberg 1991). 

Non-destructive analysis is especially valuable in an on line situation. X-ray fluorescence has above all become of major importance for the analysis of inorganic process streams. Cement production is an example of the successful application of this technique. The X-ray analyser can be used for the simultaneous assay of the various feedstocks (iron ore, clay and limestone) for Fe203, A1203, Si02 and CaO. In turn the signals from the analyser are used to control the feedstock supplies to the blending mill and to maintain an optimum product composition. 

Asbestos-cement products, 3 311, 313 alternatives to, 3 315 Asbestos-containing insulation, 74 211 Asbestos diaphragms, in caustic soda manufacture, 22 839 Asbestosis, 3 316... 

World oil-shale production fell from its peak of 46 Mt in 1980 to about 16 Mt in 2000 (Brendow, 2003). At present, about 69% of world oil-shale production is used for the generation of electricity and heat, about 6% for cement production and other industrial uses, and 25% is processed into shale oil. Oil shale has been burned directly as a very low-grade, high-ash-content fuel in a few countries, such as Estonia, which is also the only country in Europe where oil shale is of any importance. With a yearly production of about 14 Mt, oil shale still generated more than 90% of the electricity in Estonia at the time of writing, and also most of Estonia s 7000 b/d oil production comes from oil shale. Other countries where surface retorting of oil shale has been used for many years to yield shale oil are Brazil and China, which produced 3100 b/d and 1500 b/d in 2002,... 

Humans started using fossil fuels in a big way in the 1850s. Between 1800 and 1994, 244 PgC was released as a result of fossil fuel emissions and cement production. ... 

Cement production is a source of COj because it involves the precipitation of calcium carbonate from calcium and bicarbonate, i.e.. 

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