NEW MAGNESIUM – ENHANCED LIME FGD 

PROCESS 

Bob Roden, Lew Benson, and Kevin Smith 

Carmeuse North America - Technology Center 

Pittsburgh, PA 15225 

ABSTRACT 

Dravo Lime Inc. has developed a new magnesium-enhanced lime (MEL) based wet FGD 

process. This new process is an improvement upon the older magnesium-enhanced lime 

based FGD process, which has been in use for the past 25 years and serves 15,700 MW 

of generating capacity. In the year 2000, 4300 MW of the older magnesium-enhanced 

lime FGD capacity was converted to improved versions of that produce gypsum rather 

than calcium sulfite. 

This paper describes the new process, the installations using this process and discusses 

performance data. This new process can obtain the high SO2 removal efficiency of 99% 

which is the major hallmark of the older process while scrubbing flue gas with high inlet 

SO2. In addition, this process can produce gypsum of purity close to 98% and obtain a 

reagent utilization of 99.9%. The new process can also produce byproduct Mg(OH)2

(magnesium hydroxide) if desired. 

INTRODUCTION 

The Thiosorbic® or the old conventional natural oxidation MEL FGD process has been in 

commercial use in the US since the early 1970’s and has served the needs of the coal 

fired utility industry extremely well and continues to do so now. It served a base of 

15,700 MW of generation capacity till recently. The significance of the MEL FGD has 

always been its capability for very high SO2 removals due primarily to the highly alkaline 

scrubbing liquor resulting from the presence of soluble magnesium sulfite and smaller 

scrubber sizes. Since the scrubber liquor typically contains less than 100 ppm of 

dissolved calcium ions and thus precludes potential for gypsum scaling when the soluble 

magnesium concentration is maintained at the desired level, the system also has a high 

availability. The byproduct of this well known process is principally calcium sulfite 

solids with some natural oxidation (10-20% mole percent) present. Table 1 shows the list 

of utilities currently using the MEL FGD. Those units utilizing the new process to 

produce gypsum are noted with an asterisk. 
Table 1. List of Utilities with MEL FGD 

COMPANY UNIT MW 

Alabama Electric Cooperative Lowman 2 * 258

 Lowman 3 * 258

Allegheny Energy Supply Harrison 1 680

 Harrison 2 680

 Harrison 3 680

 Mitchell 3 300

 Pleasants 1 * 684

 Pleasants 2 * 684

American Electric Power Conesville 5 444

 Conesville 6 444

 Gavin 1 1,397

 Gavin 3 1,397

Applied Energy Services Beaver Valley * 140

Arizona Public Service Four Corners 1 170

 Four Corners 2 170

 Four Corners 3 220

WKE Green 1 231

 Green 2 223

 Henderson 1 175

 Henderson 2 175

CINergy East Bend 2 640

 Zimmer 1 * 1,397

Orion Power Elrama 1 80

 Elrama 2 80

 Elrama 3 100

 Elrama 4 165

First Energy Mansfield 1 917

 Mansfield 2 917

 Mansfield 3 * 917

* These units have the new MEL oxidized process 

In the year 2000 four of the major utility plants converted to improved versions of the 

MEL oxidized FGD process. Some of these larger plants and other smaller conversions 

were covered in detail in earlier presentations .1, 2, 3 Three of the four larger plants 

produces gypsum to supply feed material to new modern high-speed wallboard plants. 

Prior to this conversion the plants were land-filling the FGD solids via a fixated land 

based disposal method following primary (and in one case a secondary) dewatering 

followed by mixing with fly ash and stabilizing with lime. It is well known in this 

industry that dewatering primarily sulfite solids from the unoxidized MEL FGD system 

produces at best a filter cake of 40-50% solids which needs a large amount of fly ash 

(usually all that is available in the plant) to fixate the wet material. This continues to be 
one of the drawbacks of the unoxidized MEL FGD process. The new process enables the 

utility customer to consider alternate uses for the fly ash since it is not needed for 

stabilization. 

Figure 1 depicts the highly porous crystalline structure of the typical MEL FGD 

byproduct calcium sulfite. 

Figure 1. SEM Image and Analysis for Typical Calcium Sulfite Feed Material 

ANALYSIS TYPICAL VALUES 

Filter Cake 

Solids, wt % 40-50 

CaO, wt % 30-35 

MgO, wt % 3.0-4.0 

Particle Size D50 6-10 micron 

Dravo Lime Inc., working together with a utility customer (in one instance) and on its own spent 

a lot of its resources over the past several years developing the MEL oxidation process options. 

The incentives for the utilities to consider switching to the new oxidized MEL process relate to, 

among others, a perceived window of demand for synthetic gypsum for the new efficient 

wallboard plants and avoidance of investment to prepare more landfill area needed for extended 

periods into the future. The environmentally aesthetic desire to produce a usable product from 

an otherwise waste is also a significant factor. The new wallboard plants are capable of using 

100% synthetic gypsum thus minimizing the need for dependence on mined natural rock. 

The recently converted major oxidized MEL operations are: 

• Unit #3 of First Energy’s Mansfield station in Shippingport, PA. (917 MW). The 

gypsum is supplied to a new National Gypsum wallboard plant. 

• Pleasants Units 1 and 2 of Allegheny Energy on Willow Island, WVA. (2 x 684 MW). 

The gypsum is supplied to a new US Gypsum wallboard plant. 

• Zimmer station of CINergy, Moscow, OH. (1,397 MW). The gypsum is supplied to a 

new Lafarge Gypsum wallboard plant. 

• Lowman Station Units 2 and 3 of Alabama Electric, Leroy, AL. (2 x 258 MW). The 

gypsum is sold to a cement producer and agricultural interests. 
Two of the converted stations listed in Table 1 also make a byproduct magnesium hydroxide 

[Mg(OH)2]. The byproduct Mg(OH)2 is a desirable acid neutralization reagent and can be used 

in the utility plant for a number of beneficial purposes. 

BLEED STREAM OXIDATION (BSO) 

Process Chemistry 

Dravo’s conventional Thiosorbic® FGD process takes advantage of the relative high solubility of 

magnesium to increase the alkalinity of the scrubbing liquor. Magnesium enhanced quicklime 

contains 3-7% MgO and 90-95% CaO that when slaked, produces a reagent slurry comprised of 

magnesium hydroxide, Mg(OH)2, and calcium hydroxide, Ca(OH)2, that is added to the recycle 

tank for pH control of the scrubbing liquor. 

When SO2 from the flue gas is absorbed in an aqueous solution it forms sulfurous acid, H2SO3. 

SO2 + H2O ➜ H2SO3

The capacity for SO2 absorption is limited unless an alkaline species is available to react with the 

sulfurous acid present. The magnesium hydroxide [Mg(OH)2] from the lime slurry reacts with 

dissolved sulfur dioxide (as H2SO3) in either the recycle tank or absorber to form the soluble 

alkaline salt, magnesium sulfite (MgSO3). 

Mg(OH)2 + H2SO3 ➜ MgSO3 + 2H2O 

This species rapidly neutralizes additional absorbed SO2 forming magnesium bisulfite 

[Mg(HSO3)2], providing additional SO2 scrubbing capacity as compared to systems where 

magnesium sulfite is not present. 

MgSO3 + H2SO3 ➜ Mg(HSO3)2

Sulfites reacting with Ca(OH)2 produces calcium sulfite hemihydrate [(CaSO3•1/2H2O)] that 

immediately precipitates in the recycle tank. One mole of calcium hydroxide [Ca(OH)2] from 

the blend of magnesium hydroxide and lime slurries reacts with one mole of Mg(HSO3)2 to form 

one mole of calcium sulfite solids [CaSO3 (s)] and regenerate one mole of MgSO3 to sustain the 

cycle of absorption of SO2 in the absorber. 

Ca(OH)2 + Mg(HSO3)2 ➜ CaSO3•1⁄2H2OÈ + MgSO3 + 3/2H2O 

Typical soluble magnesium levels in this process range from 4,000-8,000 ppm. 

What is different in the BSO process is that soluble magnesium levels are elevated to 

concentrations of 10,000 to 20,000 ppm by one or both of the following means: 

1. Recycled liquor from the gypsum production portion of the process contains soluble 

magnesium, sulfates, and chlorides ranging as high as 20,000, 60,000, and 3,500 ppm 

respectively. The low alkalinity return liquor contributes toward enhancing scrubber 
chemistry through an exchange of solid phase sulfite and liquid phase sulfate. Only a 

small amount of ions need exchange to have a beneficial effect on scrubber chemistry. 

MgSO4 + CaSO3 ➜ MgSO3 + CaSO4

2. Magnesium hydroxide can be generated from the back end of the gypsum process and 

blended with lime slurry in any desired ratio of volumes lime slurry to magnesium 

hydroxide slurry. The blended reagent slurry is used in the scrubber circuit to control pH 

in the range around 6.0. 

By either mechanism, more magnesium sulfite is present than is typical in the traditional 

Thiosorbic® FGD process, raising alkalinity of the scrubbing liquor to higher levels. If high SO2

removal efficiency is desired to meet or exceed Phase II emission requirements, scrubber 

alkalinity can be boosted through increasing the relative amount of recovered magnesium 

hydroxide to lime slurry. Soluble magnesium and sulfites increase accordingly to produce 

greater liquor alkalinity. As alkalinity increases, scrubber pH can be allowed to drop lower, 

making more of the soluble sulfites form bisulfite, a mild acid. 

Oxidation and gypsum crystallization is performed external to the scrubber circuit thus 

maintaining high SO2 removal conditions in the scrubber without the addition of additives other 

than lime and recovered magnesium hydroxide. The oxidation reactions are shown below. 

CaSO3•1⁄2H2O + 1⁄2O2 + 3

/2H2O ➜ CaSO4•2H2O 

MgSO3 + 1⁄2O2 ➜ MgSO4

This ex-situ oxidation allows SO2 scrubbing with lower power costs associated with lower L/G, 

less recycle pumps, and physically smaller size of scrubbers. This feature also makes retrofit of 

existing first and second generation FGD systems possible without much complication. The 

presence of bisulfite in slurry bled from the scrubber circuit is taken advantage of in the 

oxidation step, immediately downstream. Through oxidation of magnesium bisulfite, acid is 

produced and oxidizer pH drops to below 6, which is conducive to oxidation. 

Mg(HSO3)2 + O2 ➜ MgSO4 + H2SO4 

The gypsum produced from the BSO process has very consistent physical and chemical 

properties that make it quite suitable for modern high-speed wallboard production processes. 

Note in Figure 2 the highly crystalline structure of the MEL FGD gypsum product compared to 

the calcium sulfite feed material of Figure 1. 

Figure 2. SEM Image and Analysis for Typical Gypsum Product 
ANALYSIS TYPICAL VALUES 

Moisture, wt % 10-12 

pH 5-8 

Purity, wt % 95-98 

CaO, wt % 30-35 

MgO 80-170 ppm 

Chloride 20-40 ppm 

Particle Size D50 80-140 micron 

Options for Magnesium Hydroxide Recovery and Benefits 

As mentioned earlier, MEL FGD using the BSO process can be implemented with or without 

magnesium hydroxide recovery 

A utility might choose to include magnesium hydroxide recovery for the following reasons: 

• In-plant uses of magnesium hydroxide might include neutralization of coal pile run-off 

water and enrichment of the SO2 reagent lime slurry to achieve SO2 removals 

approaching +99% in the scrubber circuit. 

• Raw synthetic magnesium hydroxide slurry was recently tested during two campaigns as 

a boiler injection additive to control SO3 emissions 4

 at First Energy's Bruce Mansfield 

Plant, Unit 3. 

• Mg(OH)2 injection into the boiler may reduce problems associated with ash slagging. 

This may allow better fuel flexibility for the utility. 

• For plants where FGD wastewater treatment is required, recovery of magnesium 

hydroxide would substantially reduce load on the treatment plant. 

Although the magnesium hydroxide slurry produced is typically 20-wt.% solids density, it 

may be cost competitive with commercial magnesium hydroxide slurry and especially caustic 

for commercial sale within a reasonable radius from the plant. Caustic availability has 

become an issue lately since caustic production has been curtailed, especially in the 

northwest US, due to escalating power costs. 5

Magnesium hydroxide recovery in the process begins by taking the (magnesium) chloride 

purge stream that also contains high levels of soluble magnesium sulfate and feeding it to a 

regeneration tank. In the regeneration tank, calcium hydroxide from the lime slurry reacts 

with the oxidized liquor to form and precipitate gypsum and magnesium hydroxide solids. 

MgSO4 + Ca(OH)2 + 2H2O ➜ CaSO4•2H2O + Mg(OH)2

MgCl2 + Ca(OH)2 ➜ Mg(OH)2 + CaCl2
Gypsum crystals that form in the regeneration tank are an order of magnitude larger than the 

co-precipitating magnesium hydroxide crystals. Hydroclones are used to exploit this size 

difference in separating gypsum from magnesium hydroxide. 

The overflow streams from the operating primary hydroclones in a single bank flow to a 

common catch basin from which the combined stream flows into the feed well of the 

magnesium hydroxide thickener. Only one thickener may need to be in service at a time 

depending on whether the Mg(OH)2 slurry is exported or not. If slurry is used exclusively on 

site, lower product slurry density of 10 to 15-wt.% may be tolerated and a single thickener 

will suffice. However, if maximum product slurry density is important, a second thickener is 

needed to insure product slurry density exceeds 20-wt.% and provides additional storage of 

magnesium hydroxide. Several flocculating agents available commercially have proven 

effective in promoting solids settling. 

The underflow stream consists of most of the gypsum produced by the regeneration process 

and some residual magnesium hydroxide. This underflow stream is collected in an agitated 

tank and pumped to the oxidizer. Any residual alkali contained in this stream is consumed in 

the oxidizer. 

Figure 3 is a flow diagram of the BSO process and Figure 4 shows the flow diagram of the 

BSO process with a magnesium hydroxide recovery circuit. 
Figure 3. BSO Process without Magnesium Hydroxide Recovery 

AIR

Flue gas in

Flue gas

out

FRESH

WATER

LIME

SLURRY

 SULFURIC ACID FROM

 TRUCK

CAKE WASH

WATER

GYPSUM TO

CONVEYOR

MAKE UP

WATER

 TO WASTE

POND

OXIDIZER

 FILTER

 SULFURIC

 ACID TANK

 FINES CLARIFIER

ABSORBERS

~ ~

A

B

C

D D

C

B

A

8 7 6 5 4 3 2 1

876 54321

Figure 4. BSO Process with Magnesium Hydroxide Recovery 

~

A

B

C

D D

C

B

A

8 7 6 5 4 3 2 1

876 54321

STORAGE

TANK

AIR

Flue

gas in

Flue gas

out

Mg(OH)2

THICKENER

CAKE WASH

WATER

GYPSUM TO

CONVEYOR

MAKE UP

WATER

TO WASTE

POND

LIME SLURRY Mg(OH)2

PRODUCT

BLEED

LIME SLURRY

FRESH

WATER

FILTER

OXIDIZER

ABSORBERS

REGENERATION

TANK

 FINES

 CLARIFIER ~ ~
Retrofit and New Applications 

Retrofit Applications 

The recent applications of improved MEL FGD processes on commercial scale projects at 

the four different sites are primarily retrofits to pre-existing Thiosorbic® MEL FGD 

operations. The actual processes employed at each of these plants vary in process details and 

are adapted to the available equipment and other constraints specific to the plants. Although 

the four applications differ to some degree, all three facilities are supplying gypsum to 

wallboard plants. 

Working with one of our utility customers, tests were conducted at pilot scale for extended 

periods of time and a process was developed to oxidize the sulfite solids from a thickener 

underflow at the Mansfield station. 1

 This plant needed to use feed from a scrubber operation 

where all of the fly ash is removed in the wet scrubber and the feed to the oxidizer therefore 

contained a large proportion of this fly ash. One of the process challenges was to minimize 

the coarse fly ash content upstream and fine fly ash content downstream of the oxidizer. 

Following the oxidizer circuit the fine ash was separated by using a Hydroseparator®. This 

plant has been routinely producing acceptable quality gypsum for the modern wallboard 

plant. 

Another application was to take the oxidizer feed from the scrubber bleeds, which would 

otherwise be routed to a gravity thickener for settling. In this plant the scrubbers are supplied 

a mixed reagent of lime slurry and recovered Mg(OH)2 from the back end of the process. 

The scrubber has a rich magnesium based chemistry to maintain high SO2 removals. The 

oxidizer receives a stream of recycled gypsum seed crystals and these grow as the oxidation 

process progresses. This plant produces a high purity gypsum. 

The third application of the oxidized MEL process is at the Zimmer station of CINergy. This 

1,397 MW plus system uses the low pH bleed from the scrubber modules using a specially 

designed scoop placed strategically inside each of the scrubber modules. This plant also used 

a converted existing thickener underflow tank 3

 as the external oxidizer. This method of 

oxidizing the low pH bleed from the scrubber gives the most cost effective and simple 

oxidation system for process control purposes. Zimmer currently uses sulfuric acid to 

maintain oxidizer pH during scrubber operation upsets. These are the major unique design 

features of this plant. 

In the case of retrofits from existing unoxidized MEL to oxidized MEL processes it is 

important to address the specifics of the existing plant equipment and operating needs to 

determine the optimum retrofit process modification. The most likely process for those 

applications where there is a need for minimizing the process control circuits and the retrofit 

costs is the bleed stream oxidation (BSO) with or without Mg(OH)2 recovery. 

If the plant can use the recovered Mg(OH)2 at the station for 1) SO3 control 4

 or for 2) other 

possible benefits (to be established) and 3) a greater fuel flexibility towards optimizing ash 

fusion properties in the boiler, a utility will have to seriously consider producing Mg(OH)2. 

The high cost of commercial Mg(OH)2 has prevented to date a number of high sulfur burning 
utilities from considering this option. It is known that the minimization of SO3 will let the air 

preheater exit temperature be lowered and not be limited by the high acid dewpoint; low SO3

levels will also reduce the frequency with which the preheater needs to be cleaned. 

New Applications 

All of the retrofit oxidation MEL projects to date use an external oxidizer. The external 

oxidizer allows the advantage of running the scrubbers at conditions optimal for SO2 removal 

while permitting optimization of the oxidizer operation independently from the scrubber 

circuit. Optimization of the oxidizer gives better quality control of the gypsum product. 

Application of the oxidized MEL process today will most likely be the bleed stream 

oxidation process with or without Mg(OH)2 recovery. As mentioned earlier the BSO process 

has the minimum equipment needs and is easy to control. An external oxidizer would be the 

preferred design for flexibility. 

A byproduct Mg(OH)2 recovery system would become feasible if there is a need for 

Mg(OH)2 in the plant for: 

• Boiler injection for SO3 reduction (new SCR may dictate this need also) 

• Treatment of water prior to disposal to reduce TDS and maintain desired pH control 

• Boiler injection for better slag fusion properties (may allow greater fuel flexibility) 

Production of Mg(OH)2 can be accomplished with minimal additional equipment. If 

quantities of Mg(OH)2 in excess of that available by using the conventional 3-7% MgO lime 

reagent is needed, this can be accomplished by increasing the reagent MgO content by 

blending the lime with dolomitic fines. 

Figure 5 summarizes some of the characteristics of typical byproduct Mg(OH)2 recovered 

from the process. Note in the SEM photograph the fine size of the magnesium hydroxide 

compared to the gypsum crystal present. 

Figure 5. SEM Image and Analysis for Typical Magnesium Hydroxide Product 

Typical Magnesium Hydroxide Chemical 

Analysis 

MgO as Mg(OH)2, wt. % 55-80 

Gypsum as CaSO4• 2H20, 

wt. % 16-26 

Inerts, wt. % 4-19 

Total Suspended Solids, % 12-20 

BET Specific Surface Area, 

m

2

/g 50-55 

Particle Size D50 2-4 micron 
The oxidized MEL scrubber can achieve SO2 removals of 99% with high sulfur coals at L/G 

substantially lower than the LSFO. The oxidized MEL scrubber will have a lower parasitic 

load of at least 0.5% less than the LSFO process. 

Design Considerations 

In addition to meeting ever more strict environmental regulations, recovery of salable 

byproducts that must meet customer minimum specifications necessarily complicates the 

FGD process and forces attention to operating and maintenance details in areas where neither 

was previously required. The magnesium-enhanced lime forced oxidation process has 

several circuits in its operation that require additional attention. 

Scrubber Operation – Slurry density in absorber modules should be maintained at 15 wt.%. 

Mist eliminator wash water is a blend of fresh water and recycled FGD process water to 

maintain less than 50% gypsum saturation in the wash water. 

Lime Slaking – Production of gypsum to meet customer specifications requires attention to 

lime quality and lime slaking. The main issue is minimizing grit production both to insure 

maximum lime utilization and minimal impact on gypsum quality, mainly pH. In a ball-mill 

or vertical mill slaker, grinding of grit to less than 200 mesh allows lime utilization to reach 

99.9% and allows only a minimal amount of unreacted lime into the gypsum product. 

Gypsum pH – The range of gypsum pH specified by wallboard producers is between 5 and 9. 

While gypsum from the MEL process achieves residual alkalinity (as CaCO3) of 0.2 to 0.5 

mg/g, corresponding to lime utilization of 99.9%, a portion of the alkalinity is present as 

CaO. This CaO can elevate gypsum pH. As a result, treatment of the filter cake with a 

minor amount of acid is sometimes required to neutralize the portion of the residual alkalinity 

that is CaO to bring gypsum into specification with respect to pH. 

Water Management – Forced oxidation FGD plants requires special attention to balancing 

water use and loss within the plant because little water leaves in the gypsum product. Lime 

slaking, scrubber mist eliminators, and gypsum vacuum filters require fresh water that must 

be absorbed without placing an undue burden on waste water treatment plants while also 

limiting soluble chloride concentration within the process. Creative ways of balancing these 

competing demands begins in the engineering phase and continues through day-to-day 

operation. Examples of creative water use include reuse of process liquors by treatment and 

handling that reduces potential for both gypsum and calcium carbonate scaling, and 

minimizing water use by filters by having fresh water perform multiple tasks such as belt and 

cloth washing prior to filter cake washing. 

Economics of MEL Process 

Capital and Operating Costs 

Estimating generic capital and operating costs is difficult since any particular station has 

unique requirements and situations to consider. EPA recently evaluated capital and operating 
cost of major FGD processes8

 including the new MEL process. The capital and operating 

costs of the MEL process were competitive with LSFO. 
Effect on Fuel Cost 

Economic advantage can be taken of the MEL process by burning cheaper, higher sulfur fuel. 

The MEL process has a proven ability to handle flue gases from burning of high sulfur (>4%) 

coal. Historically, higher sulfur bituminous coal is usually lower in cost than lower sulfur 

bituminous coal. 6 Recent coal pricing trends indicate an even more dramatic difference 

between moderate and high sulfur bituminous coal.7

 Savings by burning of lower cost, high 

sulfur fuel could more than offsets added FGD costs. 

A number of MEL customers mention their desire to be as flexible with the type of fuel 

burned as environmental regulations and boiler operation allow. From the environmental 

aspect, it is necessary to maintain emission limits imposed by state and federal governmental 

agencies. Depending on the boiler type, higher sulfur containing fuels have ash slagging 

characteristics that may at least require a derate to remove deposits or be incompatible with 

the boiler altogether. The proven ability of BSO to scrub high sulfur fuels and the option of 

producing highly reactive magnesium hydroxide byproduct, with the potential for effective 

use as a boiler injection additive for slag control, gives the utility fuel flexibility that may not 

have been possible before. 
CONCLUSION 

Several years of R&D efforts by Dravo has culminated in the development of new MEL 

FGD options for the industry. The newly converted commercial operations had their share of 

process difficulties and a number of issues related to the process controls and product quality 

that were solved systematically. Most of these issues are detailed in a number of earlier 

presentations 1, 2, 3 and continued in this paper. These plants are now routinely producing 

gypsum and are supplying the new wallboard plants. Dravo Lime Inc. is continuing its 

efforts to assist the plants in optimizing the operations and addressing any remaining 

operating and product quality related issues. 

The new MEL FGD process retains all of the benefits of the well known Thiosorbic® lime 

based FGD including high SO2 removals with low L/G ratio due to the high liquor alkalinity, 

low parasitic load, and high system availability. In addition, it provides a high purity and 

consistent quality gypsum for use by the modern wallboard plants. 

With fuel price increases in recent months and with utilities thus seeking lower cost coals, the 

BSO process with Mg(OH)2 recovery may afford the utility a greater fuel flexibility. If the 

utility customer desires to make a byproduct Mg(OH)2 for in-plant use as an acid water 

treatment reagent prior to disposal and/or for the recently demonstrated boiler injection 

process in a coal fired boiler for plume opacity control by capturing the SO3

4

, the Mg(OH)2

slurry production process is available and can be implemented with minimal additional 

equipment. 
ACKNOWLDEGMENTS 

The authors wish to acknowledge the assistance of Daniel Berisko, Mario Panella, Sandra 

DeWitt, Sean Tremba and Dr. Shiaw Tseng of the Dravo Lime Technology Center in the 

preparation of this paper. 

REFERENCES 

1. M. Golightley et.al., "Lime-Based Forced Oxidation to Gypsum at First Energy's 

Bruce Mansfield Station", Proceedings: EPRI-DOE-EPA, Combined Utility Air 

Pollutant Control Symposium, Atlanta, GA, August 1999. 

2. K. Smith et.al., "Review of 18 Months of Thioclear® FGD Operation at AES Beaver 

Valley Cogeneration", Proceedings EPRI-DOE-EPA, Combined Utility Air Pollutant 

Control Symposium, Atlanta, GA, August 1999. 

3. W. Brockman et.al., "Concept Development, Pilot Testing, and Design Leading to 

Conversion of the Wm. H. Zimmer FGD System to Bleed Stream Oxidation", 

Combined Utility Air Pollutant Control Symposium, Atlanta, GA, August 1999. 

4. G. Blythe et.al., "Furnace Injection of Alkaline Sorbents for Sulfuric Acid Control", 

The Mega Symposium in conjunction with A&WMA's Mercury Fate, Effects and 

Control Specialty Conference, Chicago, IL, August 2001. 

5. Pioneer Companies, Inc., Press Release, March 7, 2001; "Pioneer Announces Tacoma 

Plant Curtailment".

6. Federal Energy Regulatory Commission, Form 423: Monthly Report of Cost and 

Quality of Fuels for Electric Plants: http://www.fere.gov/electric/f423/f423.htm

7. Coal Outlook, Volumes 24 and 25 (2000, 2001). 

8. Controlling SO2 Emissions: A Review of Technologies, EPA/600/R-00/0093, 

November 2000. 

KEYWORDS 

Magnesium-Enhanced Lime (MEL) 

Flue Gas Desulfurization (FGD) 

Magnesium Hydroxide 

Scrubbers 

Acid Rain 

Forced Oxidation 

Gypsum