A Novel Approach to Coal Processing - Electrochemical Solutions to Pollution Reduction and Material Synthesis

Several scientific research have shown that the coal industry is responsible for a large array of pollution including small particle pollution near populated areas, toxic heavy metals and acid rains1. In 2011, EPA estimated that power plants are responsible for half of the mercury air pollutant in the U.S.2 These environmental concerns garnered the interest of both the general public and governments to find new ways to effectively reduce the pollution related to coal power plants. Furthermore, the current worldwide electricity generation is heavily reliant on coal comprising 41.3% accentuating the need for clean coal energy3. For decades coal has been seen as a mere inexpensive fuel for generating energy in power plants. However, a closer look at coal reveals that coal is a heterogeneous and complex mixture of hydrocarbons, rich with minerals4. It has been reported that electrolyzing a slurry of fine coal particles in acidic media can produce hydrogen, consuming less energy than water-electrolysis5. The hydrogen produced by this method is pure enough to be used directly in a commercially available hydrogen fuel-cell. Our research group have successfully electrolyzed coal to synthesize graphene by chemical vapor deposition method (CVD)6. Extensive optimization and control of process parameters was required to produce the graphene structure. The findings from the graphene synthesis process motivated the development of a comprehensive process to generate clean energy and produce high value materials from inexpensive coal. The main advantages of the new process proposed in this study to process coal via electrochemical methods are (i) easy adaptation to the existing infrastructure of the coal industry to facilitate quicker and low-cost integration of the new process, (ii) decreasing the sulfur content of coal after each step to reduce pollution, and (iii) retrieving the metallic content leached from coal to the slurry to avoid toxic and heavy metals such as mercury poisoning of the air and also generate revenue to reduce operating cost. Figure 1 represents a brief comparison between the current coal process and the new coal process proposed in this study. Various optimizations in every step of this coal process such as increasing hydrogen generation during electrolysis, decreasing energy consumption during pyrolysis and CVD, and electrochemical-recovery of minerals will be done with the focus on the process economy. References 1. https://www3.epa.gov/radtown/docs/coal-fired-power-plants.pdf. 2. O. of A. and R. US EPA, https://www3.epa.gov/mats/. 3. http://www.iea.org/publications/freepublications/publication/KeyWorld_Statistics_2015.pdf. 4. Y. De Abreu, P. Patil, A. I. Marquez, and G. G. Botte, Fuel, 86, 573–584 (2007). 5. X. Jin and G. G. Botte, J. Power Sources, 171, 826–834 (2007). 6. S. H. Vijapur, D. Wang, and G. G. Botte, ECS Solid State Lett., 2, M45–M47 (2013). Figure 1