MEMORANDUM 

From: The Office of Air Quality Planning and Standards 

 U.S. Environmental Protection Agency 

To: EGU NSPS Docket (EPA-HQ-OAR-2011-0044) 

Date: December, 2011 

Subject: Coal Cleaning and Upgrading 

Introduction 

Low-rank coals (lignite and subbituminous) are often utilized because the low cost per unit of heat input 

relative to bituminous coal and the low sulfur content. However, a major disadvantage of low-rank 

coals is their high moisture content, typically 25 to 40%. When this coal is burned, considerable energy 

is required to vaporize and heat the moisture, thus reducing the efficiency of the EGU. As fuel moisture 

decreases, the heating value of the fuel increases so that less coal needs to be fired to produce the same 

amount of electric power. Drier coal is also easier to handle, convey, and pulverize – reducing the 

burden on the coal-handling system. In addition, an EGU boiler (and the corresponding control 

equipment) designed for dried coal is smaller and has lower capital costs than a comparable EGU 

designed to burn coal that has not been dried. The pre-combustion drying of low-rank coals can 

improve the overall efficiency and several advanced coal drying technologies are available. 

Coal upgrading is a term used to describe processes that reduce the moisture content of the coal and that 

create a stable product that avoids spontaneous combustion and moisture reabsorption. The final 

product from these coal upgrading processes have a higher heating value and generally emit less 

pollutants. The following is a brief summary of some of the coal upgrading technologies, including 

propriety technologies. This summary is not intended to be a comprehensive list of available 

technologies. The performance values given here are those that have been provided by the technology 

provider in publically available sources. Inclusion of a technology in this summary is not intended to be 

an endorsement of that technology by the US EPA the US Government. 

The following figure illustrates the impact of the coal heating value on the relative heat rate of an EGU. 

The impact of coal quality was obtained using the Integrated Environmental Control Model (IECM) 

available at the following internet site: http://www.cmu.edu/epp/iecm/. 

y = 5E‐10x2 ‐ 2E‐05x + 1.1839

R2 = 1

y = 7E‐10x2 ‐ 3E‐05x + 1.2318

R2 = 0.9988

1.00

1.02

1.04

1.06

1.08

1.10

1.12

5,000 7,500 10,000 12,500 15,000

RelativeHeat Rate

Coal Heating Value (Btu/lb)

Impact of Coal Quality on Heat Rate

IECM

Nat. CoalCouncil
Coal Upgrading Technologies 

BCB technology

White Energy’s binderless coal briquetting (BCB) technology upgrades low rank coals through a 

thermal drying process followed by physical and chemical stabilization through a binderless briquetting 

process. The BCB process produces stable transportable briquettes with a lower moisture content and 

corresponding higher heating value than the original feed coal. 

K-Fuel® 

The K-Fuel® process was originally developed at Stanford Research Institute in 1975 by Edward 

Koppelman. The patented process removes moisture and mercury from the coal through heat and 

pressurization of low rank coals. The final product (K-Fuel®) has a higher heating value, lower 

mercury content, is physically and chemically stable, and can be handled and transported similar to 

untreated coal. 

PristineTM

PristineTM is a continuous process where coal is heated gradually in an inert atmosphere, using a set of 

multi-state heating chambers. The patented multi-stage treatment process removes moisture, volatile 

materials, and contaminants, including organic sulfur, mercury, and facilitates the removal of ash. The 

volatile chemicals emanating from coal are recovered for useful purposes. The methane is returned to 

the process and used for heating the incoming coal. The light hydrocarbons can be used as a fuel source 

or sold to refiners to be blended with crude oil and refined to produce transportation fuels and chemicals. 

The heavy gases are condensed onto the coal surface and seal the openings to limit the ability of the coal 

to re-absorb moisture or combust spontaneously. The end product (PRISTINETM) maintains the 

structural integrity of the original coals and is sufficiently rigid to withstand the rigors of coal handling 

and transport, yet requires reduced energy for pulverization at the power plant just before combustion. 

Rinker‐England-Skov (RES) coal conversion process

ConvertCoal, Inc. (CCI) proprietary coal-to-liquids process convert subbituminous and lignite low-rank 

coals into synthetic crude oil and increasing the heating value of the feed coal by approximately 40%. 

In the process, the feed coal is milled to 1⁄4 x 1⁄2-inch, then dried and pyrolyzed at about 1,000°F to 

recover approximately half of the volatile matter as coal-tar oil. The CCI process typically removes 

two-thirds or more of the sulfur and the majority of the volatile mercury and water from the feed coal. 

The CCI Process converts each ton of low-rank coal into approximately 0.8 barrels of synthetic crude oil 

refinery feedstock, 0.5 tons of upgraded coal, and 0.3 tons of water. 

Coal Drying Technologies 

Densification

The general densification process takes run-of mine brown coal and mills it to approximately 50 mm 

lumps. These lumps are fed into a low intensity shearing attritioning mill which reduces the particle size 

to approximately 10 μm. This reduction in particle size releases the water that has been trapped within 

the porous structure of the raw coal. The plastic attritioned coal is extruded into pellets or blocks and 

the moist product is conveyed for drying by evaporative loss of water to the atmosphere. Several 

companies have developed variations on this process: 

Environmental Clean Technologies Ltd. has commercialized the COLDRY process, which uses an 

exothermic chemical reaction in combination with waste heat from a co-located power station to dry and 

pelletize brown coal. This process can be applied to lignite and sub-bituminous coal. 
Jott Engineering has developed the Jott Solid Fuel Dryer System (JDS), which uses low-grade waste 

energy from the cooling water system at the power plant to dry the plant's solid fuel. This process can 

be used to dry brown coals during the pelletizing process, but is also applicable to other fuel types. 

La Trobe Lignite Developments has patented a combination of mechanical, thermal and chemical 

processes that can be applied to brown coal for drying before producing a pellet or briquette. The 

outputs are hydrocarbon gases, water and metallurgical coke equivalent. 

Drycol 

DBAGlobal Australia Pty, Ltd. is developing a coal drying technology with the trade name Drycol. The 

process uses the controlled application of microwave radiation to dry coal. Coal feed stock is first 

separated into fine grade coal and one or more larger grades. The fine coal is loaded onto a conveyor 

and conveyed continuously through a microwave-energized heating chamber for drying. The fine grade 

coal is dried sufficiently so that when it is recombined with the larger grade coals, the moisture content 

of the aggregate coal is within a target moisture content range. Microwave energy is effective for drying 

coal because water that is contained with and within the coal is preferentially heated rather than heating 

the coal. Correspondingly the heating rate of coal is much less and linked to heat transfer via 

conduction from water molecules. Provided that the residence time of the coal in the microwave 

applicator chamber is controlled such that the coal temperature remains less than 90°C, there is no 

opportunity for short chain hydrocarbons to volatilize from the coal matrix, and therefore coal quality 

does not degrade. 

DryFiningTM 

Great River Energy developed a low temperature fluidized bed coal drying technology for low-rank 

coals in partnership with the U.S. DOE as part of the DOE’s Clean Coal Power Initiative. The 

DryFiningTM process passes warm cooling water from the steam turbine exhaust condenser through an 

air heater where ambient air is heated before being sent to a fluidized bed coal dryer. The dried coal 

leaving the fluidized bed is sent to a pulverizer and then to the boiler. Air leaving the fluidized bed is 

filtered before being vented to the atmosphere. In addition to using power plant waste heat to reduce 

moisture, DryFiningTM also segregates particles by density. This means a significant amount of higher 

density compounds containing sulfur and mercury can be sorted out and returned to the mine rather than 

utilized in the boiler. Net gains in overall efficiency of 2 to 4% are reported for the process. 

WTA 

RWE Power in Germany is developing a steam fluidized bed drying technology for lignite called WTA. 

A fundamental difference compared to the DryFiningTM process is that the WTA process first mills then 

dries the lignite while the DryFiningTM process first dries then mills the lignite. For the WTA process, 

lignite is first milled to a fine particle size by hammer mills in direct series with a two-stage fluidizedbed dryer. The dried fuel exiting the stationary bed is separated from the gas stream and mixed with 

coarser lignite solids collected from the bottom of the dryer bed and then fed directly to the boiler. The 

heat needed for the drying of the fuel is supplied by external steam, which is normally taken from the 

turbine with the heat transfer taking place in tube bundles located inside the bed. Based on the 

development work completed to date of the WTA technology, the net gain in cycle efficiency is reported 

to be on the order of 4 percentage points, depending on the moisture content of the raw coal and the final 

moisture of the dried lignite. 

Other Technologies

Other coal drying/upgrading technologies for low-rank coals include: 1) NOAIR and CANONA flash 

heat drying from Green Global Technologies Ltd, 2) high velocity air flow/grinding (e.g., DXCoal’s 

DevourX machine, LF Pumping’s LamiFloTM Drying System), 3) hydrothermal dewatering (wet coal is 
heated under pressure to over 250°C and the coal structure breaks down and shrinks, releasing the water 

as a liquid; e.g., Exergen, Ignite Energy Resources), 4) heating coarse crushed coal under pressure to 

approximately 200°C (e.g., Aquex), and 5) superheated steam drying (e.g., Pinches Consolidated 

Industries; GEA Process Engineering), and 6) microbial hydrolysis (e.g., Terra Genesis).