Sulfur in coal

Eschka s mixture (sulfur in coal) mix 2 parts of porous calcined MgO with 1 part of anhydrous Na2C03 not a solution but a dry mixture. 

The pyritic sulfur in coal can undergo reaction with sulfate solutions to release elemental sulfur (see Sulfurremoval and recovery). Processes to reduce the sulfur content of coal have been sought (75). The reaction of coal and sulfuric acid has been used to produce cation exchangers, but it was not very efficient and is no longer employed. Efforts have turned to the use of hot concentrated alkaH in a process called Gravimelt. 

Trace elements such as sulfur and nitrogen are also involved in the gasification reactions. Sulfur in coal is converted primarily to H2S under the reducing conditions of gasification. Approximately 5 to 15% of the sulfur is converted to COS, whereas the coal nitrogen is converted primarily to N, trace amounts of NH and HCN ate also formed. 

FIG. 17-69 Design curves for electrostatic precipitators for fly ash. Collection efficiency for various levels of percent sulfur in coal versus a) specific collecting surface, and (h) bus sections per 100,000 ftVmin (4.7 mVs). °C = (°F — 32) X (Ramsdell, Design Criteria for Precipitators for Modern Central Station Power Plants, Amen c m Power Conference, Chicago, III., 1968. )... 

In a new method for determination of sulfur in coal, the samples are oxidised with an aqueous mixture of permanganate and the peroxoacid. During the digestion, a reflux condenser is essential to prevent loss of water, which could lead to explosively violent oxidation. 

Sulph-X A process for trapping sulfur in coal combustion. A proprietary mixture of inorganic salts, including sodium chloride, is mixed with the coal and combines with the sulfur dioxide so that it remains fixed in the ash instead of evolving with the combustion gases. Invented in China and developed in Australia in the 1990s by Coal Corporation Pty. Not to be confused with Sulfex or SULF-X. 

Price FT, Shieh YN (1979) The distribution and isotopic composition of sulfur in coals from the Illinois Basin. Econ Geol 74 1445-1461... 

Williams, E. G. Keith, M. L. 1963. Relationship between sulfur in coals and the occurrence of marine roof beds. Economic Geology, 58, 720-729. 

The standard deviation measures the width of the Gaussian curve. The larger the value of cr, the broader the curve. In any Gaussian curve, 68.3% of the area is in the range from p — la to p + la. That is, more than two-thirds of the measurements are expected to lie within one standard deviation of the mean. Also, 95.5% of the area lies within p 2a. and 99.7% of the area lies within p 3a. Suppose that you use two different techniques to measure sulfur in coal Method A has a standard deviation of 0.4%, and method B has a standard deviation of 1.1%. You can expect that approximately two-thirds of measurements from method A will lie within 0.4% of the mean. For method B, two-thirds will lie within 1.1% of the mean. 

Sulfur in Coal. Sulfur occurs in coal in two forms (I) organic sulfur, which is chemically bonded to the coal, and (2) pyritic sulfur, which occurs... 

Variations in the amount of ash arise from the retention of sulfur that originates from the pyrite. Sulfur in ash is usually determined as sulfate (ASTM D-1757 ASTM D-5016), and the method may give abnormally high amounts of sulfur. This is due to the sulfur retention from pyrite (and marcasite). If the forms of sulfur in coal are known (ASTM D-2492), the amount of pyrite retention can be estimated (see also ASTM D-3174, Note 2). Nevertheless, sulfur retention will give rise to anomalous results. 

ASTM D-2492. Standard Test Method for Forms of Sulfur in Coal. 

Some general problems associated with the determination of sulfur in coal are nonuniform distribution of pyrite particles, failure to convert all the sulfur to sulfate, and loss of sulfur as sulfur dioxide during the analysis. The nonuniform distribution of pyrite necessitates the collection of many sample increments to ensure that the gross sample is representative of the lot of coal in question. Pyrite particles are both hard and heavy and have a tendency to segregate during the preparation and handling of samples. Because the particles are harder, they are more difficult to crush and pulverize and tend to concentrate in the last portion of material that remains from these processes. 

In the method for determining the forms of sulfur in coal (ASTM D-2492 ISO 157), the sulfate and pyrite sulfur are determined directly, and the organic sulfur is taken as the difference between the total sulfur and the sum of the sulfate and pyrite sulfur. 

X-ray fluorescence has been used extensively for determining total sulfur in coal. The economy and speed of such x-ray fluorescence methods when used for multiple determinations (e.g., Al, Si, Ca, Mg, Fie, K, Ti, P, and S) in the same prepared coal sample are probably unsurpassed by any other method. 

High-resolution x-ray spectroscopy was employed successfully to determine the chemical state of sulfur in coal. Fluorescent x-rays from pressed coal powders, excited with x-rays from a chromium target tube, were analyzed using a germanium crystal. The sulfur Ka radiation increased with increasing oxidation number, allowing quantitative determinations of the sulfur types. 

Infrared absorption is one of three standard test methods for sulfur in the analysis sample of coal and coke using high-temperature tube furnace combustion methods (ASTM D-4239). Determination of sulfur is, by definition, part of the ultimate analysis of coal (Chapter 4), but sulfur analysis by the infrared method is also used to serve a number of interests evaluation of coal preparation, evaluation of potential sulfur emissions from coal combustion or conversion processes, and evaluation of the coal quality in relation to contract specifications, as well as other scientific purposes. Infrared analysis provides a reliable, rapid method for determining the concentration of sulfur in coal and is especially applicable when results must be obtained rapidly for the successful completion of industrial, beneficiation, trade, or other evaluations. 

The analysis of the coal used in these runs is given in table II. The coal contained 5.5 percent sulfur and 16.5 percent ash. The pyritic sulfur in coal was 3.08 percent and the organic sulfur 1.95 percent. 

This paper summarizes our understanding of the geochemistry of sulfur in coal in the following areas 1) abundance of sulfur in coals of major coal basins in the U.S., 2) distribution of sulfur in coal lithotypes and macerals, 3) characteristics and geochemical significance of sulfur-containing organic compounds,... 

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