Lignite Coal

Lignite Coal Lignite coal is a natural resource which is readily available. It is often referred to as brown coal. It has some special characteristics which make it different from other coals. Lignite coal is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It is considered to be the lowest rank of coal due to its relatively low heat content. It has lowest carbon (C) content amongst all types of coals. It is mined all around the world and is mainly used as a fuel for steam and electric power generation. Since it is not economical to transport lignite coal, it is not traded extensively on the world market when compared with higher grades of coal. Large reserves of lignite coal are available in limited areas of the world. Australia, USA and China have the major reserves of lignite coal. Germany has the largest number of power plants based on the lignite coal. In USA, most of the reserves are located in the North Dakota province while in India, the lignite coal reserves are in Neyveli in Tamil Nadu and in Rajasthan. Around 17 % of the world’s coal reserves are lignite coal. As the world’s oil and gas reserves decline, other sources have become attractive. That is why there is a sustained interest in the use of lignite coal. Coals are classified by rank according to their progressive alteration in the natural metamorphosis from lignite to sub bituminous coal to bituminous coal and to anthracite. Coal rank depends on the volatile matter, fixed carbon, inherent moisture, and oxygen, although no one parameter defines rank. Typically coal rank increases as the amount of fixed carbon increases and the amount of volatile matter decreases. Coal is a complex combination of organic matter and inorganic ash formed over eons from successive layers of fallen vegetation....

Geology, Prospecting and Exploration for Iron Ore Deposits Apr09

Geology, Prospecting and Exploration for Iron Ore Deposits...

Geology, Prospecting and Exploration for Iron Ore Deposits Iron has been known since antiquity. Iron is ubiquitous in the lithosphere as either a major constituent or in trace amounts. In abundance it ranks fourth behind oxygen, silicon and aluminum. Iron ores have a wide range of formation in geologic time as well as a wide geographic distribution. These ores are found in the oldest known rocks in the crust of the earth, with an age in excess of 2.5 billion years, as well as in rocks formed in various subsequent ages. In fact, iron ores are even forming today in the areas where iron oxides are being precipitated. Several thousands of iron occurrences are known throughout the world. They range in size from a few tons to several hundreds of millions of tons. Iron ore deposits are distributed in different regions of the world under varied geological conditions and in different geological formations. The largest ore concentration is found in banded sedimentary iron formations of Precambrian age. These formations constitute the bulk of iron ore resources of the world. Iron ores occur in a wide variety of geological environments in igneous, metamorphic or sedimentary rocks, or as weathering products of various primary iron bearing materials. Iron ores can be grouped into types of similar geological occurrence, composition and structure. The following is a simplified classification which is based on genesis of the deposits and geological environment. It shows the main modes of occurrence of iron ores as well as it illustrates the varied geology of iron ore deposits. Igneous ores -These iron ore deposits are formed by crystallization from liquid rock materials, either as layered type deposits that possibly are the result of crystals of heavy iron bearing minerals settling as they crystallize to...