Comparison of Sodium Bicarbonate and T

SO

2 Mitigation at A Coal-Fired Power P

Yougen Kong

Jim Vysoky

Solvay Chemicals Inc.

ELECTRIC POWER 2009

Rosemont, Illinois

May 12-14, 2009
Presentation Outline

• Plant Description• Dry Sorbent Injection of Sodium Bica• Results• Summary 
Plant

• Two units: 45 and 109 MW• One stack• Down-fired boiler• PRB coal

– Moisture: 24.59%– Ash: 4.86%– Heating value: 9,092 Btu/lb– Sulfur: 0.27%– SO2: 0.59 lb/mmBtu

• Tubular air preheater• Fabric filters for PM control• Have used trona for SO2 control for both units since 1980s
Silo

Economizer

Air Heater

Boiler

Air

Mill

Trona

Bag H

Trona Injection System
Trona Storage Silo

Three silos for two units. Silo size: 6100 ft

3 – 150 ton
Trona Injection

• 103’ from fabric filter 

inlet

• Duct: 17’3” wide 9’9”

tall

• Two separate 

sorbent supply systems. 

• One system for each 

duct side.

• Each supply system 

feeds 6 injection lances . 

• Two sides – 12 

injection lances total.

• Normally run only 

one system.
Arrangement of Injection Lan

West Air Heater Exit Duct (view from the Boiler) 

A Side Injector 
Why Sodium Bicarbonate (NaHC

• Sodium Bicarbonate is more effec

than trona in SO

2 removal. In othe

words, less sorbent is needed for same SO

2 removal.

– Lower sodium concentration in fly a– Less waste disposal– More expensive
What is Sodium Bicarbona

• NaHCO

3

- Baking soda

• SOLVAir® Select SBC (sodium bicarbonate

manufactured at Solvay Chemicals’ ParachColorado plant.

• Starting January 2010, a new plant in Green 

Wyoming, will start to produce low cost sodbicarbonate based sorbent - SOLVAir® Sele

• Either Select SBC or Select 300 is a coarse 

and requires milling prior to use. An air-clais often used to reduce the particle size befinjection although other types of particle sireduction devices may be appropriate.
Solvay Parachute Plant in Colora

• SOLVAir® Select SBC (sodium bicarbona
Solvay Plant in Green River, Wyomi

• SOLVAir® Select 200 (trona)• SOLVAir® Select 300 (sodium bicarbonate)
Dry Sorbent Injection of Sodium Bicarb

• Some studies in 1970s and 1980s showed go

performance of sodium bicarbonate for SO

2

mitigation.

• Have not achieved wide applications due to:

• Product availability• High cost

• Solvay Chemicals is building a plant in Gree

Wyoming, to produce low-cost sodium bicarbased sorbent with a patented process:

• Phase I: 125,000 tons/year starting 01/201• Phase II: Another 125,000 tons/year is for
Heating Up Sodium Bicarbonate Makes Diff

Sodium Bicarbonate 

T > 275 °F

2NaHCO

3

Na

2CO

3 CO

2

H

2

O

+ +

Activated Sodium Carb
Acid Mitigation Chemical React• Na

2CO

3 + SO

2

+ 1/2O

2

→ Na

2SO

4 + CO

• Na

2CO

3 + SO

3

→ Na

2SO

4 + CO

2

• Na

2CO

3 + 2HCl

→

2NaCl + H

2O + CO

• Na

2CO

3 + 2HF

→

2NaF + H

2O + CO

2

Na

2SO

4, NaCl and NaF are collected in fly as
• Sorbent injection rate /Normalized Stoichiome

Sorbent injection rate /Normalized Stoichiome

Ratio (NSR) Ratio (NSR)

• Sorbent particle size Sorbent particle size

• Sorbent residence time in flue gas stream Sorbent residence time in flue gas stream• Sorbent penetration and mixing with flue gas Sorbent penetration and mixing with flue gas • Particulate control device used (ESP or Bagh

Particulate control device used (ESP or Bagh

• Flue gas temperature Flue gas temperature

– Minimum 275 Minimum 275 oF

– The higher, the better up to 1500 The higher, the better up to 1500 oF

Parameters Affecting Performan
Effect of Sorbent Particle Size on SO2 Remov

(Lab Results on Fabric Filter)

Effect of Sorbent Particle Size on SO

2 Removal @ NSR

0

20406080

100

0 10 20 30 40 50 60 70 80 

Particle Size d90 (micron)

SO2 Removal Rate (%)
Trona

 SOLVAir® Select 200 

(Na2CO3.NaHCO3.2H2O)

 D50: ~ 32 μm

 D90: ~ 162 μm

 After milling with a pin mill

 D50: ~ 24 μm

 D90: ~ 74 μm
Sodium Bicarbonate

 SOLVAir® Select SBC (sodium 

bicarbonate NaHCO

3

)

–

D50: 110 μm

–

D90: 234 μm

 After Milling with a pin mill

–

D50: 28 μm

–

D90: 71 μm
SO2 Removal Rates with Trona and Sodium Bicarbonate 

• Flue gas temperature at the injection ports: ~ 290 oF

• Tested on 100 MW unit

0

10203040506070

0.0 0.2 0.4 0.6 0.8 1.0 

NSR

SO

2 Removal Rate (%) SBC Trona Unmilled SBC
NO2 Formation

05

1015202530

0 20 40 60 80 1

SO2 Removal Rate (%)

NO

2 Concentration (ppm)

Sodium Bicarbonate Trona

High NO2 can cause brown plume
NO

2 Brown Plume

• Two other trials showed NO

2 brown pl

• Over 30 trona or sodium bicarbonate s

have not shown this problem.

• The exact mechanism of NO

2 formatio

unknown. 

• The following measures can help avoid 

brown plume: 

– Injection at high temperatures (i.e. upstrea

preheater)

– Use SCR or SNCR to lower NOx concentra

before injection.

– Good mixing between injected sodium so

flue gas.
Summary

• Sodium Bicarbonate was able to remove more 

Trona at the same NSR. At the same SO2 remo

40% less reagent is required with sodium bica

• Less fly ash generated with Sodium Bicarbona

less sorbent needed.

• There is some economical advantage to switc

trona to sodium bicarbonate. 
For more information, please visit www.sol

Questions?