How-to, Tips and Articles: Development of New Premium Carbon Products From Coal

Coal Beneficiation

No molecule left behind—US DOE
Toward zero waste mining—Canada Mining Innovation Council
New products from coal may require new coal specifications that can be achieved through coal beneficiation (AKA coal cleaning or preparation)

Consortium for Premium Carbon Products from Coal

These projects resulted in many potential applications for coal-derived feedstocks. These include:

Use of anthracite as a sorbent to capture CO2 emissions;
Use of anthracite-based carbon as a catalyst;
Use of processed anthracite in carbon electrodes and carbon black;
Use of raw coal refuse for producing activated carbon;
Reusable PACs to recycle captured mercury;
Use of combustion and gasification chars to capture mercury from coal-fired power plants;
Development of a synthetic coal tar enamel;
Use of alternative binder pitches in aluminum anodes;
Use of Solvent Extracted Carbon Ore (SECO) to fuel a carbon fuel cell;
Production of a low cost coal-derived turbostratic carbon powder for structural applications;
Production of high-value carbon fibers and foams via the co-processing of a low-cost coal extract pitch with well-dispersed carbon nanotubes;
Use of carbon from fly ash as metallurgical carbon;
Production of bulk carbon fiber for concrete reinforcement; and
Characterizing coal solvent extraction processes.

Current Customer Specifications

Power Plants

Transportation/efficiency specifications: ash (typically
10-12 % for US Eastern bituminous coal), Btu
Handling specifications: particle size (topsize and limit on fines), moisture (typically ~7-8% for US Eastern bituminous coal)
Mineral composition for slagging/fouling: ash fusion temperatures, ash constituents
Efficient combustion in general: moisture, ash, Btu, grindability
Environmental: sulfur, ash, trace elements
Every power plant has its own specification

Metallurgical

Transportation specifications: ash (typically 8-10 % dry in US)
Handling specifications: particle size (topsize), moisture
“Coke button”—thermoplastic properties
Macerals
Vitrinite reflectance
Related to achieving coke quality (carbon), coke strength, minimize slag (ash content), low sulfur (1-1.5 % dry), phosphorus, other alkalis
Generally very sophisticated blending

New Products - New Coal Specifications

Can be achieved through coal beneficiation or coal cleaning technologies—some tried and true, some improved technologies, some new technologies
Look at the coal data—size analysis and washability data, etc.

Example - Jet Fuel

Produced 2% ash clean coal from a WV coal sample and 6% ash clean coal from a PA coal sample using froth flotation
Goal to produce jet fuel plus a premium coke for the aluminum industry

Example - Silicon Smelting

Silicon smelting, for example, typically uses charcoal @ <0.3% ash

Blue Gem coal (naturally low ash/minimal cleaning needed) has been used
Sinosi Group (China) for silicon metal smelting includes a coal specification of 4% max. ash, 12- 15% VM, 3% max. H2O, 6-30 mm particle size

There is No Such Thing as Coal, There Are Coals (Luckie)

Coal Beneficiation Overview (Luttrell and Honaker)

Where is the Low Ash Coal?

Conventional Coal Beneficiation

Coarse and intermediate size coal would require multiple processing steps to produce coal for:

Minimal refuse disposal at the coal mine/ processing plant site. Ash disposed of at power plants or for beneficial use (concrete additives, for example).
Fine size coal could also require multiple processing steps to produce coal for:

Specialty markets
PC boiler fuel (though sending this fraction to a PFBC would eliminate issues with moisture and fines content)
PFBC fuel (handles low BTU, dewatered fines @~25% moisture)

Minimal refuse disposal at the coal mine/processing plant site. Ash disposal at power plants. (Think rare earth/critical elements or beneficial use of ash for soil supplements.)

New Fine Coal Processes for Fine Waste

OMNIS/CONSOL Energy—creating low ash pellets from thickener underflow; using remaining minerals as a soil amendment (pilot)
Arq/Peabody Energy—low ash, clean coal fines combined with crude oil for use by refineries (construction of commercial plant)
HHS—Minerals Refining Company—coal fines cleaned and dewatered in one step then pelletized (design of commercial plant) to produce low ash product

Beneficiation Processes for Low Rank Coals

Low rank coals have high inherent moisture/low heating value content
Reduction of moisture prior to combustion provides higher combustion efficiency
Several technologies have been developed to reduce this moisture (and some capture the water for beneficial use)

What About HELE Coal-Fired Power Plants?

More efficient (increase from ~33 to 40 %), therefore, inherent CO2 reduction for supercritical and ultra- supercritical units (2-3 % reduction for every 1 % increase in efficiency); leave room for carbon capture technologies to be installed when commercial. Current power plants can be repowered now to reduce CO2!
That’s two gigatonnes of CO2 worldwide. In addition, there are reductions in NOx, SO2, and particulate matter. (worldcoal.org)

Summary

Coal beneficiation, both conventional and new technologies, can be used to produce multiple products—low ash coal for specialty markets, traditional or higher ash for coal- fired power plant markets, ash markets (including beneficial use and source of rare earth/critical elements)
Coal can be part of an economical reduced CO2 power generation strategy!

Opportunities

Test different coal qualities for new markets (need small scale test facility, maybe up to 50-100 tph, to produce sufficient materials for testing—a new Coal Cleaning Test Facility) in order to develop Coal Quality Impact Models to optimize coal specifications for these new markets
Revisit the EPRI/DOE Coal Quality Impact Model (CQIMTM) or Coal Quality Expert (CQETM) and expand for new products from coal
Continue identifying coals and coal products with high levels of rare earth elements and developing processes to recover the REEs/critical elements
Develop new rugged sensors to work in wet, sometimes dusty or sometimes muddy environments
Develop smart manufacturing technologies, such as AI and VR, to work in concert with online analyzers to better control coal quality, especially for multiple product plants
Develop image analysis techniques beyond froth flotation
Develop better procedures for relating coal beneficiation performance to drill core data
Better understand the change in moisture content of coal, especially lower rank coal

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Tuesday, March 3, 2020