All-Year Air Conditioning, Ventilation, Gas Supply

   Air conditioning implies the control of temperature, humidity, purity and motion of the air in an enclosure. In our modem world of science and highly developed technology air conditioning is of great significance for industrial processes as well as for human comfort.

   Air conditioning for human comfort is employed in both large and small installations, such as theatres, office buildings, department stores, residences, airplanes, railways, cars and submarines.

   All-year air-conditioning systems must provide means for performing all the processes required for winter and summer air conditioning. The basic pieces of equipment are the filters, preheat coils, humidifiers, dehumidifiers, reheat coils, additional cooling coils, fans and controls. The control of air purity can be achieved in various degrees. As a minimum control some sort of filtering must be done near the entrance of the air-conditioning system. Possibly the most efficient filtering device is the electrostatic precipitator.

   As far as ventilation is concerned the modern theory to this effect can be summed up in the statement that for places of general assembly the purpose of ventilation is to carry away excess heat and odours and that normally 10 cu. ft per minute of outside air per person is sufficient to accomplish this objective. In buildings such as homes, the leakage of air through cracks in doors and windows is usually sufficient to meet this requirement. Although ventilation was formerly concerned with the supply of fresh air to and the removal of hot and contaminated air from the space it gradually came to be associated with 1 cleaning of air.

Для спеціальностей ЕО, ГІВ, ОПГ, РР:

ВАРІАНТ I

Environmental Benefits of Surface Mining

By Peter N. Grimshaw

   Most forms of economic activity affect the environment in ways which can be claimed to be detrimental. Some of the worst results were produced in the pasty by mining. However, handled correctly, surface mining can have beneficial effects and the author discusses this, talking examples from coal mining activities in Great Britain.

   SURFACE mining by its very nature causes severe disturbance to the surface of earth and, with associated activities , is undoubtedly detrimental to human, animal and plant life in the short-term. Any long-term permanent effects, albeit often conjectural, are rightly the subject of much critical attention and debate.

   If, however, after taking into account a wide range of economic, social and environmental factors, surface mining is deemed a necessity, then not only can the inevitable and traumatic losses to the quality of both the natural and manmade environments during extraction operations be minimized, but actual long-term gains can result. The planning for, and creation of, such environmental benefits rarely receives the attention it deserves; but recognition of these benefits is necessary if a board and balanced perspective on this emotive form of economic activity is to be achieved.

   Environmental benefits from opencast mining can range from something as small-scale as the planting of wild roses on a former site which were then harvested as the basis of a health preparation, to the possible rehabilitation of Cutacre colliery tip, claimed to be the largest of its type in Europe. This is on the proposed 600 ha Lomax site between Little Hulton, Atherton and Tyldesley in Lancashire.

ВАРІАНТ II

Kiruna Iron Ore Mine, Sweden

   With an ore body 4km long, 80m thick reaching a depth of 2km, LKAB’s Kiruna is the world’s largest, most modern underground iron ore mine. Since mining began here over 100 years ago, LKAB has produced over 950Mt of ore, yet only one-third of the original ore body has been extracted. Since mid-1999, Kiruna’s haulage level at a depth of 775m has been replaced by the next level down at 1,045m, which will support production until 2018. The operation employs 1,800 people, of whom 400 work in the mine.

   In 2004, Kurina produced 14.5Mt of iron ore products out of LKAB’s total of 22.3Mt, maintaining the general relationship that it produces around two-thirds of the company’s total Swedish production. 11.5Mt of Kiruna’s output was sold as pellets. In 2004, LKAB achieved sales of iron ore products totaling 22.8Mt, of which 17/2 Mt were exported and 5.6Mt were delivered to customers in Sweden.

GEOLOGY AND RESERVES

   The Kiruna ore body was formed at around 1,600Ma following intense volcanic activity with the precipitation of iron-rich solutions on to a syenite porphyry footwall. The ore bed was then covered by further volcanic deposits (quartz porphyry) and sedimentary rocks before being tilted its current dip of 50 to 60. The ore contains a very pure magnetite-apatite mix, containing more than 60% iron and an average of 0.9% phosphorus. Black ore contains less apatite than grey ore.

   The original reserve at Kiruna was some 1,800Mt. As of the end of 2004, LKAB estimated that the current proven reserve at the mine is 657Mt grading 48.3% iron, with probable reserves of 140Mt at 46.5% iron. Measured, indicated and inferred resources add a further 500Mt-plus to the inventory, with exploration continuing to identify further resources at depth.

ВАРІАНТ III

Garbage Burning

  Although the United States incinerates only about three percent of its municipal waste in modern resources recovery facilities, garbage burning is expected to increase substantially over the next several years because landfill space is disappearing. At the same time, concerns about emissions and residue from garbage burning, particularly dioxin, a highly toxic substance, have led many communities to oppose the building of garbage-burning plants “in their backyard.”

   Questions about the potential benefits and about the environmental and social problems that garbage-burning plants may cause have led many people in the U.S. concerned with resource recovery to look to Europe for information about solid waste management practices and perspectives. This is so because of Europe’s long experience in burning large volumes of garbage to produce energy in densely populated regions. Most importantly, it has often been argued explicitly or by implication that garbage burning in Europe is “safe.” Otherwise, how could it be going on there for so long and how else could these plants be so readily accepted by European communities?

     ВАРІАНТ IV

Nonmetal Mineral Resources

   Nonmetal minerals is a broad class that covers resources from silicate minerals (gemstones, mica, talc, and asbestos) to send, gravel, salts, limestone, and soils. Sand and gravel production comprise by far the greatest volume and dollar value of all nonmetal mineral resources. Sand and gravel are used mainly in brick and concrete constructions, paving, as loose road filler, and for sandblasting. High-purity silica sand is our source of glass. These materials usually are retrieved from surface pit mines and quarries, where they have been deposited by glaciers, winds, or ancient oceans.

   Limestone, like sand and gravel, is mined and quarried for concrete and crushed for road rock. It also is cut for building stone, pulverized for use as an agricultural soil additive that neutralizes acidic soil, and roasted in lime kilns and cement plants to make plaster (hydrated lime) and cement.

   Evaporites are mined for halite, gypsum, and potash. These are often found at or above 97 percent purity. Halite, or rock salt, is used for water softening and melting ice on winter roads in some northern states. Refined, it is a source of table salt. Gypsum (calcium sulfate) now makes our plaster wallboard, but it has been used for plaster ever since the Egyptians plastered the walls of their frescoed tombs along the Nile River some five thousand years ago. Potash is an evaporate composed of a variety of potassium chlorides and potassium sulfates. These highly soluble potassium salts have long been used as a soil fertilizer.

   Sulfur, in the form of pyrite (FeS2), is mined mainly for sulfuric acid production. In the United States, sulfuric acid use amounts to more than 200 lbs per person per year, mostly because of its use in industry, car batteries, and some medicinal products.

ВАРІАНТ V

Core Drilling

   In 1663, the Swiss engineer M. Leskot designed a tube with a diamond set face, for drilling in the Mount Cenis tunnel, where the rock was too hard for conventional tools. The intention was to explore rock quality ahead of the tunnel face, and warn miners of possible rock falls.

   This was the accidental birth of core drilling, a technique now very widely used within the mining industry. Core drilling is carried out is special drillings , using e hollow drill string with an impregnated diamond cutting bit to resist wear while drilling hard rock. The crown-shaped diamond bit cuts a cylindrical core of the rock, which is caught and retained in a double tube core-barrel.

A core-catcher is embedded in, or just above, the diamond bit, to make sure that the core does not fall out of the tube. In order to retrieve the core, the core-barrel is taken to surface, either by pulling up the complete drill string or, if the appropriate equipment is being used, by pulling up only the inner tube of the core-barrel with the special fishing device run inside the drill string at the and of a thin steel wire.

The core is an intact of the underground geology, which can be examined thoroughly by the geologist to determine the exact nature of the rock and any mineralization. Samples of special interest are sent to a laboratory for analysis to reveal any metal contents. Cores from exploration drilling are stored in special boxes, and kept in archives for a long period of time. Boxes are marked to identify from which hole, and at what depth, the sample was taken. The information gathered by core drilling is important, and represent substantial capital investment.

Traditionally, core drilling was a very arduous job, and more operator-friendly equipment, was very slow, and the cost per drilled metre was often prohibitive. Atlas Copco Craelius pioneered several techniques to reduce manual work, increase efficiency and cut the cost per drilled metre. Over the years, the company developed thin walled core barrels, diamond impregnated bits, aluminium drill rods, fast rotating hydraulic rigs, mechanical rod handling, and, more recently, partly or totally computer-controlled rigs. Core drilling has always been the most powerful tool in mineral exploration. Now that it has become much cheaper, faster and easier, it is being used more widely.

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Для спеціальностей ГБ, ГІП,ГГ,ІГ, ЗКК:

ВАРІАНТ I

Shaft sinking

Preliminary Consideration

   When coal has been proved to exist in sufficient quantities to be an economic proposition, it is then necessary to fix the site, shape and size of the shaft required to work the area. This requires careful consideration, and many factors have to be taken into account.

   Site of shaft. a) Underground considerations. The inclination is very important. In a flat seam it may be desirable to have the shafts in the centre of the area in order to keep the roads of equal length to the boundary.

   In an inclined seam it may be better to sink somewhat to the dip side, there by utilizing the force of gravity to run the major part of the coal and water to the pit bottom and having short lip haulage and less pumping.

   Faults should be avoided on account of the weak strata and these areas.

   If possible, sinking should keep clear of running sands, heavy watered strata, etc.

b) Surface considerations. The shafts must be reasonably near to efficient transport facilities (rail, road, canal or sea). The nature of the ground should also be carefully considered, as soft ground means costly foundations for buildings and machinery, whilst hilly ground means expensive cuttings for buildings and sidings. A good supply of water conveniently near is desirable for coal cleaning, steam raising and baths.

Shape of shaft. Shafts may be circular rectangular or elliptical in shape. In England the circular shaft is popular. It is the easing and cheapest to sink and is suitable for greater depth and water pressures. It also gives more space for ventilation during winding.

Rectangular shafts are suitable for shallow depths and timber lining and for this reason they were popular in Scotland until recent years, but in the new sinking to deeper coal they have been replaced by circular shafts. They are still extensively in the U.S.A.

Elliptical shafts have never found favour in England although there are some on the Continent.

   ВАРІАНТ II

Thickeners

The separation of solids from a liquid by gravity sedimentation has traces to the early days of civilization. The normal practice at those times was to use jars or pits mainly for the clarification of extracted liquids such as wine or olive oil from contaminating insoluble matter. These batch processes required four separate steps:

· Filling the vessel with slurry.

· Leaving the slurry for a predetermined time until the solid matter has settled to the bottom of the vessel.

· Decanting the clarified supernatant from the upper part of the vessel.

· Removing the settled underflow that has accumulated at the bottom of the vessel.

This cycle, depending on solid and liquid properties that effect settling rate, may require long detention times so often several vessels are incorporated in the layout to operate in sequential steps.

The method of operating on a batch process is still practiced in small flow industries but its shortcomings are obvious so once the plants grew larger the need for continuous operation become inevitable. The trend in this direction started at the late 19^th century when heavy duty application such as iron ore taconites, hematite, coal, aluminum hydrate, copper pyrite, phosphates and other beneficiation processes have grown rapidly. The high time for thickeners was in the 60's when the metallurgical industries were booming and sizes of up to 150 m diameter were constructed. Such jumbo thickeners, when centrally driven, require for most demanding application extra heavy duty drive heads some of which reach a continuous operating torque of 3.300.000 Nm. 

ВАРІАНТ III

Screening Machines

Current screening machines have one thing in common. They all work using electrical motor with a rotating unbalance that generates the shaking. These electrical unbalance motors are bulky and require high maintenance. Furthermore, they waste much of their energy due to useless elastic deformation of the heavy supporting structure, audible and vary loud noise, and excess heat. The latter causes many of the moving components, such motors had a replacement rate of 60 per year instead of the manufacturer recommendation of 20 per year. In this case, the replacement criterion was bases on functionality of motors. It is anticipated that if the replacement criterion is bases on the motors-generated noise, the annual replacement rate would have been significantly increased.

A conventional material screening machine is comprised of four primary and four secondary parts. The primary parts include the key moving components, such as engine, live deck, sieves, and sieve tensioning mechanism. The secondary parts include the non-moving components, such as feed system, supporting structure, hopper, and oversize bins. An electrical engine provides the required shaking by using an unbalanced rotating mass. An engine rests on the live deck on which a sieve tensioning mechanism is installed. The sieves, that do the material separation, are supported by the tensioning mechanism.

ВАРІАНТ IV