Coal Age

MAY 2018

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30 May 2018 clean coal conversion continued The quality of the carbon char is directly related to the quality of the coal feed. It has been shown that all types of coal ranking from lignite, sub-bituminous to bitumi- nous can be converted into a high-value carbon char for various industrial appli- cations. One example of the quality of the carbon char produced is shown in Table 1. This carbon char has application as a carbon reductant in the steel and alloy in- dustry, a carbon injection application and further converted into coke briquettes. The analytical analysis, shown in Ta- ble 1, is carbon char made from conver- ting Blue Gem coal, located in nearby Corbin, Kentucky, in the mild gasification reactor at an operating temperature of the coal at 800°C. A number of important observations can be made from the analysis data shown in Table 1: • The moisture is reduced in the car- bon char; • The volatiles are reduced from 36.7% to a level of 2.57%; • The fixed carbon in the carbon char has increased to a level of 92.48%; and • The sulfur has been reduced in the carbon char by about 23% to a level of 0.55%. In addition, the carbon char is ag- glomerated into larger particle sizes than the initial coal as shown in Figure 6. This increase in size is important and is contributed to the Free Swelling Index of the Blue Gem coal and provides an in- crease in porosity and reactivity making this carbon char an excellent carbon pro- duct for applications as a reductant in electric arc furnaces. Currently, the Virginia carbonite plant is in a 24/7 production operation converting Blue Gem coal fines into an agglomerated char for testing in the al- loy industry as a carbon reductant in the smelting of silicon from quartz at the West Virginia Manufacturing Plant in Al- loy, West Virginia. High-fixed-carbon char is being shipped on a regular basis as shown in Figure 7 for testing. As mentioned previously, carbon char has its own commercial markets and can be made from all ranks of coal. However, one of the largest commercial markets is the further processing of the carbon char into formed coke briquettes for the steel and foundry industry as shown in the flow dia- gram in Figure 2. To produce quality coke briquettes to meet both the blast furnace and foundry cupola furnace applications requires a certain quality of coal with both low ash and low sulfur and special coking properties. Figure 8 shows several hundred tons of foundry-size coke briquettes that have been produced, sold and successfully tested in a number of commercial foundries including those at General Motors, Neenah Foundries, US Pipe foundries and others. Although using lower cost coals in a briquetting formed coking process was the primary driving force in the 1990s. Today, the use of the continuous coking process is based more on environmental factors than the use of low cost/rank coals. Neverthe- less, it has been possible to make, through the use of the mild gasification process, an acceptable quality coke from some of the low-cost thermal type coals. As the coal is introduced continuously into the process through closed hoppers, all the volatiles removed from the coal are captured and condensed into usable coal oil liquids. Any non-condensable gas, which consists most- ly of methane gas, are combusted for process heat and co-generation. The environmental emissions normally associated with feed coal and coke removal systems in conven- tional coke-oven batteries are non-existent in this continuous mild gasification process. The Virginia Carbonite commercial demonstration plant has the capability of producing thousands of tons of carbon char and formed coke briquettes. The pro- duction of the formed coke briquettes en- tering and being removed from the existing tunnel kiln are shown in Figures 9 and 10. Figure 5—The Continuous Mild Gasification Reactor and Thermal Oxidizer. Table 1—Analytical analysis of coal and carbon char produced the mild gasification reactor at the Virginia Carbonite Plant in Norton, Virginia. Figure 6—The increase in size of the fine Blue Gem Coal particles of 2 mm by 0 to a carbon char size of +¾-in. x 0 with 90% greater than 1/8-in. Proximate Carbon Analysis Coal (%) Char (%) Moisture 0 9.15 0 2.04 Ash 0 1.34 0 2.91 Volatiles 36.70 0 2.57 Fixed Carbon 52.81 92.48 Sulfur 0 0.71 0 0.55

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