MEMORANDUM

From: The Office of Air Qu ality 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 util ized because the low cost per unit of heat input

relative to bituminous coal a nd 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 effici ency 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 co al is also easier to handle, c onvey, and pulverize – reducing the burden on the coal-handling system. In additi on, an EGU boiler (and th e corresponding control equipment) designed for dried coal is smaller an d has lower capital costs than a comparable EGU designed to burn coal that has not been dried. The pre-combus tion drying of low-rank coals can improve the overall efficiency and several adva nced coal drying technologies are available.

Coal upgrading is a term used to describe processes th at reduce the moisture cont ent of the coal and that create a stable product that avoi ds spontaneous combustion and mois ture 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 su mmary 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 sour ces. Inclusion of a t echnology 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 th e Integrated Environmenta l Control Model (IECM) available at the following internet site: http://www.cmu.edu/epp/iecm/

.

y = 5E

‐ 10x 2

‐ 2E

‐ 05x + 1.1839
R2 = 1 y = 7E

‐ 10x 2

‐ 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 15,000RelativeHeatRate

Coal Heating Value (Btu/lb) 

## Impact of Coal Quality on Heat Rate

IECM

Nat. Coal CouncilCoal 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 chemi cal stabilization through a binderless briquetting process. The BCB process produces stable transporta ble briquettes with a lowe r moisture content and corresponding higher heating value th an 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 moistu re and mercury from th e coal through heat and pressurization of low rank coals. The final pr oduct (K-Fuel®) has a higher heating value, lower mercury content, is physically and chemically stab le, and can be handled and transported similar to

untreated coal.

PristineTM

PristineTM is a continuous process wher e coal is heated gradually in an inert atmosphere, using a set of multi-state heating chambers. The patented multi-st age 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. Th e 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 spon taneously. The end product (PRISTINE TM ) 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) pr oprietary coal-to-liquids process convert subbituminous and lignite low-rank coals into synthetic crude oil and increasing the hea ting 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 merc ury and water from the feed coal.

The CCI Process converts each ton of low-rank coal in to 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 sh earing attritioning mill which reduces the particle size to approximately 10 μ m. This reduction in partic le size releases the water th at has been trapped within the porous structure of the raw coal. The plastic attritioned coal is ex truded into pellets or blocks and the moist product is conveyed for drying by evaporat ive loss of water to the atmosphere. Several companies have developed variations on this process:

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

exothermic chemical reaction in combination with wast e 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 plan t's solid fuel. This process can be used to dry brown coals during the pelletizing pro cess, but is also applicab le to other fuel types.

La Trobe Lignite Developments has patented a co mbination of mechanical, thermal and chemical processes that can be app lied to brown coal for drying before pr oducing a pellet or briquette. The outputs are hydrocarbon gases, water a nd metallurgical coke equivalent.

Drycol

DBAGlobal Australia Pty, Ltd. is de veloping a coal drying technology with the trade name Drycol. The process uses the controlled applica tion 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-energi zed heating chamber for drying. The fine grade coal is dried sufficiently so that when it is recombin ed with the larger grade co als, the moisture content of the aggregate coal is within a target moisture c ontent range. Microwave en ergy is effective for drying

coal because water that is contained with and within the coal is preferen tially heated rather than heating the coal. Correspondingly the heating rate of coal is much less and linke d to heat transfer via

conduction from water molecules. Provided that th e residence time of the coal in the microwave applicator chamber is controlled such that the co al 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.

DryFining TM

Great River Energy developed a lo w 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 se nt to a fluidized bed coal dryer. The dried coal leaving the fluidized bed is sent to a pulverizer and then to the boiler. Air leavi ng 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 a nd mercury can be sorted out and returned to the mine rather than utilized in the boiler. Net gain s in overall efficiency of 2 to 4% are reported for the process.

WTA

RWE Power in Germany is developing a steam fluidi zed 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 pr ocess first dries then mills the lignite

. For the WTA process, lignite is first milled to a fine particle size by hamme r mills in direct series with a two-stage fluidizedbed dryer. The dried fuel exiting the stationary bed is separated fr om the gas stream and mixed with coarser lignite solids collected from the bottom of the dryer bed and then fed dire ctly 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 techno logies for low-rank coals includ e: 1) NOAIR and CANONA flash heat drying from Green Global T echnologies Ltd, 2) high velocity air flow/grinding (e.g., DXCoal’s DevourX machine, LF Pumping’s LamiFlo TM Drying System), 3) hydrotherm al dewatering (wet coal isheated under pressure to over 250°C and the coal structure breaks dow n 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) superh eated steam drying (e.g., Pinches Consolidated Industries; GEA Process Engineering), and 6) microbial hydrolysis (e.g., Terra Genesis).