North Dakota (ND) has the world’s largest lignite deposit, which has been and continues to be a significant part of the state economy and accounts for about 80% of electric power generation (Lignite Energy Council, 2019). A recently completed research study at the EERC provides new research into one emerging area that could have significant impact on the state’s coal resources, evaluating the potential to make high-value graphene-based solid carbon products from North Dakota lignite.
Graphene has excellent thermal, mechanical, electrical, and optical properties that enable potential applications in multiple industries such as aerospace, sports, automobile, and building and construction. Successful development of technologies to make graphene from ND lignite could open new markets in nonenergy sectors such as electronics, optical devices, lightweight farming tools, military equipment, etc.
An evaluation of high-value solid carbon products from North Dakota lignite was conducted in this study using coal samples from three different mines in the state: Center, Falkirk, and Freedom. The results show that graphene quantum dots (GQDs) can be made from ND lignite. The optical properties of these GQDs show ultraviolet fluorescence ranging from 498 nm to 515 nm.
Development of approaches aimed at enhancing the quality of lignite as a graphene precursor was successful. These methods included advanced coal cleaning and heteroatom removal in autoclave and bench-scale reactions. A new system for low-pressure entrained-coal chemical vapor deposition was designed, assembled, and tested for making graphene films. Although preliminary results obtained from this system were promising, the system will be further investigated for additional improvements and optimization of process conditions.
Further exploratory research is needed to develop new options to improve ND lignite coal as a better graphene precursor and to convert this precursor to graphene. These two key steps are essential to create a technology for making high-value solid carbon products from ND lignite. Graphene is currently made from graphite, which sells for about $1,000/ton (International Energy Agency, 2018). Because of the high selling price of graphene at about $18,000/ton for additive grade, or about $1.4 m/ton for device grade (The Graphene Council, 2018), making graphene from ND lignite, which sells for about $20/ton, opens the door for North Dakota’s economy to benefit from another coal product.
Lignite Energy Council. Value-Added Opportunities for North Dakota Lignite, 2019. https://cdn.lignite.com/wp-content/uploads/2019/01/LEC-value-added-executive-summary-2018-1_14_19-small.pdf (accessed May 28, 2019).
Reid, I. Non-Energy Uses of Coal, CCC/291, 2018. http://www.iea-coal.org/non-energy-uses-of-coal-report-ccc291/ (accessed February 2019).
The Graphene Council, 2019 Graphene Market and Pricing Report. Available online at https://www.thegraphenecouncil.org/store/viewproduct.aspx?id=13785417.