Size coalings

The fluidized-bed system (Fig. 3) uses finely sized coal particles and the bed exhibits Hquid-like characteristics when a gas flows upward through the bed. Gas flowing through the coal produces turbulent lifting and separation of particles and the result is an expanded bed having greater coal surface area to promote the chemical reaction. These systems, however, have only a limited abiUty to handle caking coals (see Fluidization). 

An entrainment system (Fig. 3) uses finely sized coal particles blown into the gas steam prior to entry into the reactor and combustion occurs with the coal particles suspended in the gas phase the entrained system is suitable for both caking and noncaking coals. 

Conventional coal cleaning processes can remove about 50% of pyritic sulfur and 30% of total sulfur. For northern Appalachian region coals it has been shown that a greater sulfur reduction can be achieved by applying physical coal cleaning to finer size coals (Table 3) (8). 

Flotation. The appfication of flotation (qv) to coal cleaning is a relatively new development iu the United States. In 1960, only 0.6% of the clean coal produced came from flotation. However, by 1983 flotation accounted for about 5% of the clean coal production (Table 2). Utilization of the flotation process is expected to grow rapidly because more fine size coal is produced as a result of beneficiation schemes that require significant size reduction of the taw coal prior to cleaning to enhance the fiberation of pyrite and ash minerals. 

The three main types of reactors shown in Fig. 27-6 are in aclual commercial use the moving bed, the fluidized bed, and the entrained bed. The moving bed is often referred to as a. fixed bed because the coal bed is kept at a constant height. These differ in size, coal feed, reactant and product flows, residence time, and reaction temperature. 

Klein-kohle, /. small-sized coal, buckwheat coal, pea coal small coal, slack, -koks, m. small-sized coke, nut coke, klein-komig, a. small-grained, fine-grained, -kristallinisch, a. finely crystalline, in small crystals. 

Table 3 Ash levels in coal and filtered coal extracts for different sized coal...

The results in Table 5 show a large increase in proportion of Mn and Ti, and increases for Mg and Ca from coal to extract. Fe stays about the same and all the others decrease. Previous work Q) has also shown that the elements which increase in proportion also deposit readily and steadily on the hydrocracking catalyst. Thus, any method which reduces the ash level in the filtered extract solution needs to be, if at all posible, selective towards Mn, Ti, Ca, Mg, and Fe. In the case of digestion pressure, as shown by the results above, most trace elements do not significantly change their proportion as the ash level decreases, except for Mn where the situation becomes worse and Mg where there is some improvement. Liquefaction of different-sized coal fractions has little effect on the distribution of elements in the ash as the overall ash level decreases. However, with the use of HAO with different saturates levels, there is a distinct increase in the levels of Ti with decreasing ash level, but a significant decrease in Mn. 

Unit Size Coal HV (AR) Heat Rate Coal Use, Max. LPA Treatment... 

The authors wish to thank L. A. King of the Electrical Research Assoc, for advice on the design of the plasma jet and I. F. Galbraith for its construction. We are also grateful to E. Pritchard for carrying out the gas chromatographic analysis, to R. Bent for the infrared analyses, to M. P. Mendoza for the microchemical analysis, and to R. Wheatley for preparing the sized coals. 

The method employs a cylindrical porcelain jar mill fitted with three lifters that assist in tumbling the coal. A sample (usually 1000 g) of sized coal is tumbled in the mill for a specified time at a specified number of revolutions per minute. The coal is then removed and screened and the friability is reported as the percentage reduction in the average particle size during the test. For example, if the average particle size of the tumbled coal was 75% that of the original sample, the friability would be 25%. As with several other tests, the test parameters can be adjusted to suit the purpose of the investigation, but the precise parameters must be reported with the data. 

Bottom size coal that passes through a standard sieve with the largest openings through which passes a total of less than 15% of the sample should not be confused with particle size (ASTM D-4749). 

Pressure Temperature Coal particle size Coal residence time... 

The Mean particle size (MPS) of coal is an important factor for the COREX Process because a decrease in the MPS reduces the permeability of the char bed resulting in gas channelling, which drops the hot metal temperature and quality. To maintain consistency, the MPS of the coal should be maintained within 20-30 mm, which is a very important factor for efficient plant operation. The COREX technology coal should be sized at +16 mm with a top size as high as 70-80 mm. Fines coal (—16.0 mm) included with the sized coal is separated at the COREX steel mill and used for either... 

Using a source-composition library containing data from 21 studies of coal-fired power plants, we have investigated the effects of particle size, coal type, and pollution control device on the composition of particles emitted from coal-fired power plants. 

One of the first commercial-size, coal gasification plants in the United States was the Great Plains Synfiiels plant that is operated by Dakota Gasification in Beulah, ND. This plant consumes over 5.5 million tonnes of coal per year and produces over 54 billion standard cubic feet (1.4 billion Nm3)of natural gas, 365,000 tonnes per year of ammonia, 24 million gallons of... 

Economics. At the present time, process economics are difficult to evaluate. Costs of hydrogen, low BTU fuel gas, or electric power are dependent on plant size, coal cost, plant location, product purity, and other environmental requirements that must be met. Using mid-1979 dollars, we have estimated 99% purity, 1000 psig hydrogen from a 50MM to 100MM SCF/D plant to cost between 1.25 to 1.60 per 1000 SCF ( 4- 5 per MM BTU) before taxes and profit. 

Fluidized bed Sized coal required Dry coal required for feeding... 

Grinding cost increases with the reduction in size Coal rank... 

---