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Limestone Mining

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Each year aggregate companies in Iowa produce approximately 35 million tons of raw material from more than 500 locations to supply a myriad of construction projects across the state. The bulk of this supply is extracted from pits and quarries where gravel deposits and limestone bedrock are close to the land surface. However, at eight locations across the state (Jasper, Louisa, Marion, Poweshiek, Scott, Story, Van Buren, and Webster counties), where geologic and market conditions permit, limestone for aggregate is extracted from underground mines.

Though more costly than quarrying, underground mining of limestone can be both economical and necessary in some areas of the state. Shallow rock units, which were once acceptable, may no longer meet newer engineering standards for construction aggregate. In other instances, it is not economical to strip both the overlying glacial deposits and the poorer quality, shallow bedrock in order to quarry. An operator must decide whether to cease production and move to an alternate location, if one exists, or to shift operations underground. Numerous factors are weighed to determine the feasibility of such a production change:

  • Is the needed quality rock present in sufficient thickness and at suitable depth?
  • Are the market conditions satisfactory to warrant the added expense of underground start-up and production?

In the last decade several Iowa stone producers have opted to shift production underground.

Contents

[edit] What is Limestone?

Limestone is calcareous sedimentary rocks formed at the bottom of lakes and seas with the accumulation of shells, bones and other calcium rich goods. It is composed of calcite (CaCO3). The organic matter upon which it settles in lakes or seas, are preserved as fossils. Over thousands and millions of years, layer after layer is built up adding weight. The heat and pressure causes chemical reaction at the bottom and the sediments turn into solid stone, the limestone.
The rock which contain more than 95% of calcium carbonate is known as high-calcium limestone. Recrystallised limestone takes good polish and is usually used as decorative and building stone.


[edit] What is Limestone Used For?

Cement is a mixture of limestone, clay and other materials processed by high temperature calcination. Glass is made from limestone, quartz sand, soda ash and other mixtures, and obtained by high temperature melting, iron with limestone used as flux to remove gangue. In steelmaking limestone is used to form slag materials to remove sulfur, phosphorus and other harmful impurities. Calcium carbide (main ingredient is CaC2) is from the limestone and coke reacted in the furnace. Soda ash is produced by limestone, salt, ammonia and other raw materials through multi-step reaction (Solvay method). Soda limestone and soda ash reaction (Caustic method) make caustic soda. Using pure limestone and chlorine reaction to bleach. The chemical processing of limestone make the calcium chloride, calcium nitrate, calcium sulfite etc. Limestone is used to soften water and can remove temporary hardness of the water. Burning limestone processed into a more pure calcium carbonate powder, is used as filler of rubber, plastic, paper, toothpaste, cosmetics, etc. The soda lime made by caustic soda with lime for carbon dioxide absorbent. Quicklime is used as a dryer and disinfectant. In agriculture, lime sulfur mixture is mixed with lime, as well as Bordeaux mixture and other pesticides. The application of hydrated lime to the soil can neutralize the soil acidity and improve soil structure, supply plant-available calcium. Brush the tree trund with lime liquid can protect trees.

[edit] Limestone Crushers

In stone quarry, there are several types of stone crushers that can be used in limestone crushing plant.

Limestone jaw crusher is the widely used primary crusher, it is mainly used in primary crushing process. Fixed jaw plate, and movable jaw plate are wearable parts. Different jaw crushers have different output, the capacity is 1-5 t/p, 30-50tph, 50-80tph, 80-120tph, 120-200tph, 200-300tph, 300-400tph, 400-500tph.

Impact crusher is also common crushing machine used in limestone quarry. It has the functions of crushing and shaping, can make very good cubic shape. The stone materials are mainly used for road, highway, water conservancy, airport, civil construction etc. The market prices of stones made by impact crusher is higher than that by fineness jaw crusher or compound cone crusher; the quick wear parts cost of impact crusher is also high for high hardness stones.

Limestone mobile crusher is the complete crushing unit, includes feeding, crushing, screening process. for example, limestone mobile jaw crusher includes vibrating feeder, vibrating screen, primary jaw crusher, vibrating screen, and belt conveyor. There are other models, such as limestone mobile impact crusher, limestone mobile cone crusher, crawler type mobile crusher.

[edit] Limestone Crushing and Grinding Process:

Limestone is important building materials, and raw materials for cement production. Natural limestone is big, we must crush them into suitable size through limestone crushing process or grind them into sand or powder in limestone grinding process.

Limestone crushing process need limestone crusher equipment. In this process, we usually use jaw crusher, cone crusher, mobile crusher such as limestone mobile jaw crusher, mobile impact crusher, mobile cone crusher, crawler type mobile crusher. These machines are used to crush limestone into smaller size. According to the different products, we choose the different crushing process. Usually limestone crushing plant includes primary crushing process and secondary crushing process. If the product is sand, the limestone particles must do stone shaping through sand making machine. If you need the stone powder, using limestone grinding machines to grind these crushed limestone particles into powder. In this grinding process, hammer mill, ball mill, vertical mill are usually used.

[edit] Limestone Crushing Plant

In cement plant, limestone is the important raw material to make cement. It goes through crushing, grinding process, then make into powder.

In casting sand production line, limestone is crushed into the particles with 58 - 57 mesh. This limestone sand is better than the performance of quartz sand in manufacturing of machinery.

SBM is a mining machine manufacturer in China, and provides all kinds of stone crushers and grinding mills, such as aggregate crusher (limestone crusher, marble crusher, granite crusher, gravel crusher), ore crusher, coal crusher, cement mill, concrete crusher, and gold mining equipments. We can also design the special complete crushing plant according to the requirements of customers. Now, our products have exported to more than 130 countries, such as USA, UAE, Germany, Indonesia, India, Vietnam, Philippines, Rusia, Canana, South Africa, Zimbabwe, Russia, Ukraine, Japan, Poland, France, Brazil, Mexico

In the limestone crushing plant, there are hammer crusher and impact crusher for big reduction ratio. Usually these limestone crushers' reduction ratio is 10~35. Take the example that if the first input size of limestone rocks is 200mm, the final particles' size should be less than 10um. Under this, hammer crusher or impact crusher is the suitable limestone crushing equipment.

The limestone Jaw Crusher is widely used in mining, building materials, chemical industry, metallurgy and so on. The Jaw Crusher is suitable for primary and secondary crushing all kinds of minerals and rocks with compressive strength less than 320 MPa.