Coal Analyzers

Coal can be analyzed by thermogravimetry (TG), oxygen combustion bomb, total sulfur analysis, x-ray fluorescence (XRF), atomic absorption (AA) spec- 

Post-Oil Energy Technology After the Age of Fossil Fuels 

A typical proximate analysis of coal by microcomputer-controlled thermogravimetry. 

Our goal is to gradually replace all coal and fossil fuel power plants with renewable energy ones, but while they exist (and probably will for most of this century), it is very important to reduce the damage they cause by optimizing their operation. In the United States, there are about 1000 coal preparation plants and coal-fired power plants. One key consideration in operating coalburning facilities is the control of C02 and sulfur dioxide (S02) emissions to the atmosphere. The characteristics of coal are monitored for environmental protection, quality assurance, and process control purposes. 

Other procedures include high-temperature tube furnace combustion methods for rapid determination of sulfur in coal and coke, using automated equipment. The instrumental analysis provides a reliable and rapid method for determining sulfur contents of coal or coke. By this method, total sulfur as sulfur dioxide is determined on a continuous basis. 

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Figure 2. Concentration range of elements in 13 raw coals analyzed hy spark-source mass spectrometry. All quantities in ppm wt. ND = not determined.

The accuracy of the x-ray fluorescence method was evaluated by calculating, from the 50 whole coals analyzed, the mean variation of each element from its mean concentration, determined by the other independent methods previously mentioned and listed in Table III. Detection... 

Mercury was the first trace element in coal to arouse environmental concern, prompted by data such as those of Joensuu (8). He reported that as much as 33 ppm mercury occurred in coal and inferred that coal combustion might be a major source of mercury in the environment. Lower values were reported by Ruch et al. (9) in the same year. Sixty-six coals analyzed by them contained 0.02-1.2 ppm mercury, and the mean mercury concentration of 55 Illinois coals in the set was 0.18 ppm. 

Radiochemical yields are quantitative. The relative standard deviation of a measurement is usually better than 10%. Analysis of SRM 1630 gave 2.0 =b 0.13 ppm selenium, and results for the NBS-EPA round-robin coal and fly ash samples agreed within experimental error with the probable certified values of selenium in those samples. The selenium concentrations of 101 coals analyzed by the above method range from 0.45 to 7.7 ppm and have a median value of 1.9 ppm (16). 

Chemical yields are 49-77%. The average relative standard deviation is 10%. Bromine concentrations in 23 coals analyzed ranged from 4 to 29 ppm (4, 16). 

ASTM D-6543. Standard Guide to the Evaluation of Measurements Made by On-Line Coal Analyzers. 

Some coal analyzers use several gamma-ray detectors and operate by the use of neutron pulses. Such analyzers can measure the density and sulfur content of coal along with its heating value, moisture, and volatile matter content. This pulsed fast/thermal neutron analyzer can be self-calibrating and can determine such elements as carbon, oxygen, and sodium. 

An alternative and less complex (and less powerful) approach to the use of probing with neutrons uses a sealed neutron generator based on the DT reaction. This approach is commercially used in fields such as coal analyzers among others, and there have... 

The five coals analyzed are described in Table HI. A map showing the location of known U.S. coal fields is shown in Figure 3. The location on this map of the five coals described here can be made by reference to Table III. 

A development in the 1960s was that of on-line elemental analysis of slurries using x-ray fluorescence. These have become the industry standard. Both in-stream probes and centralized analyzers are available. The latter is used in large-scale operations. The success of the analyzer depends on how representative the sample is and how accurate the caUbration standards are. Neutron activation analyzers are also available (45,51). These are especially suitable for light element analysis. On-stream analyzers are used extensively in base metal flotation plants as well as in coal plants for ash analysis. Although elemental analysis provides important data, it does not provide information on mineral composition which is most cmcial for all separation processes. Devices that can give mineral composition are under development. 

Graphite is frequently, although incorrectly, analyzed by the proximate method used for coal in which the volatile material is deterrnined by strongly beating the sample in a covered or luted cmcible. Some oxidation of the graphite always occurs so that the value obtained for volatile matter is high and thus the "fixed carbon" is too low. The method lacks both accuracy and precision. 

Laboratory procedures for proximate and ultimate analyses are given in the Annual Book of ASTM Standards (Sec. 5, American Society for Testing and Materials, Conshohocken, Pa., 1994) and in Methods of Analyzing and Testing Coal and Coke (U.S. Bureau of Mines Bulletin 638, 1967). 

Multidimensional chromatography has also been applied for the analysis of industrial chemicals and related samples. Industrial samples which have been analyzed by multidimensional chromatography include coal tar, antiknock additives in gasoline (3), light hydrocarbons (4, 5), trihaloalkanes and trihaloalkenes in industrial solvents (6-8), soot and particulate extracts, and various industrial chemicals that might be present in gasoline and oil samples. 

Figure 12.23 SFC-SFC analysis, involving a rotaiy valve interface, of a standard coal tar sample (SRM 1597). Two fractions were collected from the first SFC separation (a) and then analyzed simultaneously in the second SFC system (h) cuts a and h are taken between 20.2 and 21.2 min, and 38.7 and 40.2 min, respectively. Peak identification is as follows 1, tii-phenylene 2, chrysene 3, henzo[g/ i]perylene 4, antliracene. Reprinted from Analytical Chemistry, 62, Z. Juvancz et al, Multidimensional packed capillary coupled to open tubular column supercritical fluid chromatography using a valve-switcliing interface , pp. 1384-1388, copyright 1990, with permission from the American Chemical Society.

Although the petrochemical and metals industries were the primai y focus of the toxic air pollutants legislation, approximately forty of these substances have been detected in fossil power plant flue gas. Mercury, which is found in trace amounts in fossil fuels such as coal and oil, is liberated during the combustion process and these emissions may be regulated in the future. EPA issued an Information Collection Request (ICR) that required all coal-fired plants to analyze their feed coal for mercury and chlorine. Since these data will be used in making a regulatory decision on mercury near the end ot the year 2000, it is critical that the power industry provide the most accurate data possible. 

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. 

Fully-deuterated xetralin was used to study the mechanisms of coal liquefaction. Experiments were conducted with xetralin-di2, deuterium g s and bituminous coal at 400°C and at 15.2-20.7 MPa. The recovered solvent and solvent-fractionated coal products were analyzed for total deuterium content and for deuterium content in each structural position. 

The main part of this research deals with the reaction of deuterium gas and Tetralin-d12 with a bituminous coal. In a separate experiment, naphthalene-d8 was used for investigating the chemistry of hydrogen transfer between coal and a nondonor solvent. In each experiment, the coal products and spent solvent were analyzed for toal deuterium content and for deuterium incorporation in each structural position. 

Product Analyses. The spent solvent mixture was distilled from the coal products, separated by GC and analyzed by NMR. 

H NMR and 2H NMR spectra of fractionated coal products from El0 and El9 were recorded and analyzed to determine and 2H composition for each structural position. In our study, y y and 2Hx,v are defined as the fraction of the JH and 2H determined from the integrals of the NMR spectra of a given soluble fraction where y equals HS, BS or BMS and x = y-alkyl, 0-alkyl, a-alkyl or aromatic structural positions. The spectral range of the NMR integrations are given in Table V. 

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