The different types of coal

Lignite (brown eoal) Relatively low carbon content c. 70 percent Germany, Russia, USA, China 

Sub-bituminous Harder than lignite, 10-20 pereent moisture, 71-77 percent earbon Widespread 

Bituminous Coking and thermal coals, harder than sub-bituminous coals Widespread 

Anthracite High carbon content c. 90 percent, low moisture contenL hardest coal type with semi-metallic lustre South Afnca, China 

Oil and natural gas are the preferred fuels of the twenty-first century. They gained importance in the 1950s and have since overtaken coal on the groimds that they are cleaner and more efficient fuels and because oil has many uses other than as a fuel. These include lubricants and the production of organic chemicals such as solvents, and fibres such as nylon and plastics. 

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Over millions of years, as the layers of forming coal were pushed deeper and the pressure and temperature increased, the final conversion to coal took place (Figure 6.6). Different types of coal were formed as a result of different pressures being applied during its formation. For example, anthracite is a hard coal with a high carbon content, typical of coal produced at greater depths. Table 6.1 shows some of the different types of coal along with their carbon contents. 

There are many compositional differences between the coals mined from the different coal deposits worldwide. The different types of coals are most usually classified by rank which depends upon the degree of transformation from the original source (i.e., decayed plants) and is therefore a measure of a coal s age. As the process of progressive transformation took place, the heating value and the fixed carbon content of the coal increased and the amount of volatile matter in the coal decreased. 

The use of coal as a popular fuel in Britain, from the time of the industrial revolution, has led to the development of a system of classification in which code numbers are used to denote the different types of coal. The system relies heavily on the coke-forming characteristics of the various coals as well as on the types of coke produced by a standard of coking test (the Gray-King carbonization assay). The system also employs the amounts of volatile matter produced in percentage by the various coals (Table 2.11). 

Throughout the last century or so, many scientists have subscribed to the theory that the coal source material has not formed by the degradation of plant material in situ in a peat swamp environment but rather accumulated from the deposition of transported material in aqueous environments such as lakes, seas, and estuaries (Moore, 1940 Stutzer, 1940 Francis, 1961). Indeed, the concept of transportation of the source material also led to the belief that not one but several processes were responsible for the different types of coal. Thus, there was much thought and discussion which actually led to serious questions about the autochthonous theory of coal formation and also brought discredit on the idea that coals form a prescribed and definite progression from peat to anthracite. 

Table 4.2. The different types of coal (based on World Coal Institute, 2002)...

Some general comments may be made of some of the different types of fuels. The use of coal has been on the decline, and there has been an increase in petroleum and natural gas... 

Frankland discovered the fundamental principle of valency—the combining power of atoms to form compounds. He gave the chemical bond its name and popularized the notation we use today for writing chemical formulas. He codiscovered helium, helped found synthetic organic and structural chemistry, and was the father of organometallic chemistry. He was also the first person to thoroughly analyze the gases from different types of coal and—dieters take note—the first to measure the calories in food. 

There are several different types of coal, each displaying different properties resulting from their age and the depth to which they have been buried under other rocks. In some parts of the world (e.g., New Zealand), coal development is accelerated by volcanic heat or crustal stresses. 

The electrostatic precipitator in Example 2.2 is typical of industrial processes the operation of most process equipment is so complicated that application of fundamental physical laws may not produce a suitable model. For example, thermodynamic or chemical kinetics data may be required in such a model but may not be available. On the other hand, although the development of black box models may require less effort and the resulting models may be simpler in form, empirical models are usually only relevant for restricted ranges of operation and scale-up. Thus, a model such as ESP model 1 might need to be completely reformulated for a different size range of particulate matter or for a different type of coal. You might have to use a series of black box models to achieve suitable accuracy for different operating conditions. 

The results of elementary analyses of lignin isolated from fresh (2, 3) and rotted straw and data for different types of coals and humic acids isolated from these and from chernozem are shown in Table III to illustrate further steps of coalification. The following points should be noted ... 

Differences in the kinds of plant materials from which the coal was derived uccount for different types of coal. 

Devise an experiment which you could carry out in the school laboratory to determine the amount of sulfur in two different types of coal. 

Coals from ten different mines were burned under monitored conditions in three different types of coal fired utility boilers in order to determine the influence of coal composition and boiler combustion conditions on the leaching and sorbent characteristics of the fly ash produced. The leaching and removal exhibited by the fly ashes with regard to pH, Cd, Sn, Ni, Pb, Mo, Cu, Fe, Cr, Zn, Mn, As and organics were examined. 

Three different types of coal fired boilers were utilized in this study. One type (A) was a dry bottom boiler with direct fired burners located on opposite walls. The second type (B), wet bottom boilers 11 and 12, was operated in parallel with the same coal stream split to feed both boilers simultaneously. The third boiler types (C D) were dry bottom, tangentially fired boilers. 

In view of the abundance of natural gas resources found since the 1980s, and natural gas being a considerably cleaner fuel than petroleum or coal for the fuel processors, the main goals of the major worldwide fuel cell programs are to develop fuel cell power plants and portable power sources using natural gas or natural gas-derived fuel cells. A chart of all types of fuel cells, using natural gas as a fuel, is presented in Scheme 9.2 the applications being considered for the different types of fuel... 

There are different types of coal, defined by their moisture content, appearance, and ability to bum at particular temperatures. Lignite or brown coal is the lowest member of the coal family. It contains up to 45% moisture. Bituminous is more dense coal, dark brown to black, with a moisture content... 

Four different types of coal were used for the alkylation tests (Figure 2) a high volatile coal with 34.4X (volatile matter), a medium volatile coal with 24.2%, a low volatile coal with 19.4% and a semi-anthracite with 14.4%. 

Shell built a 6t/day lab/pilot-scale gasifier to test different types of coal in 1976. It also conducted tests to collect the fundamental data on cleanup of the syngas produced by this gasifier and to assess the technologies to meet environmental regulations. 

The ability to gasify different types of coal including low-rank coal and petroleum coke. The carbon conversion is over 98%. The amount of sulfur, oxygen, and ash in the coal does not significantly impact the Shell gasification process. 

Schingnitz, M. and Mehlhose, F. The GSP-process entrained-flow gasification of different types of coal. Clean Coal Technology Conference, Sardinia, Italy, 2005. 

Liquid-Liquid Partitioning of Fine Solids This process involves separation of small-particle solids suspended in a feed hquid, by contact with a second liquid phase. Robbins describes such a process for removing ash from pulverized coal [U.S. Patent 4,575,418 (1986)]. The process involves slurrying pulverized coal fines into a hydrocarbon liquid and contacting the resulting slurry with water. The coal slurry is cleaned by preferential transfer of ash particles into the aqueous phase. The process takes advantage of differences in surfacewetting properties to separate the different types of solid particles present in the feed. 

Because of its universal application to industrial processes there is a considerable background to attempts to characterise different types of coal in respect of their propensity to fouling and slagging. In general these are empirical assessments often involving the composition in terms of the major constituents of the coal. 

What are the four "stages" of coal formation How do the four types of coal differ ... 

Table 1.2 contains a survey of major gasification processes that have proved reliable and safe and are today used for syngas production on an industrial scale. In addition to the operating parameters, the survey also provides data about the suitability of these processes for different types of coals. However, these data have to be taken with a grain of salt No absolute rating of the coals is possible in view of their wide variety of properties. Future methanol producers will have to make their choice between these processes on the basis of two main criteria -the properties of the available coals and the resulting economics of gasification. 

Table 1.9 contrasts the gasification results from three different types of coal - a high-volatile bituminous coal from Illinois, a low-bituminous coal from 2 mbia, and a lignite from Greece [1.1,9]. l th the Illinois coal from Table 1.9, a cold gas efficiency of approximately 67 % can be reached from the dried coal, and approximately 66 % from the moist coal. 

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