Dry Sorbent Injection of Sodium 

by Solvay Chemicals

Emission Control and Measur

Workshop

March 24-25, 2010
Presentation Outline

z What are the sodium sorbents?

– We’ll talk about Trona and Sodium Bic

z How effective are sodium sorbents 

SO2 and SO

3? 

– We’ll review some data.

z Which sorbent is better?

– We’ll discuss the factors affecting the 

z What parameters impact the effect

DSI?

– We’ll look at how we optimize system

limit effectiveness.
What Is Trona?

z It is a naturally formed sodium sesquicarbonate r

– (Na2CO3• NaHCO3•2H2O)

– The Green River WY deposit is the largest and pu

z Solvay mills this rock into a fine powder

– Average particle size 30 – 35 microns– Material for FGD is sold under the trade name SO– Select 200 is the product known as trona in the ind

z Select 200 is very dry, typically less than 0.03% 

– It is a good idea to keep it dry, wet trona is tough t– Contact with water will cause problems.

z Select 200 can compact while storedz Select 200 calcines instantly at 280oF

– Trona gives up water when it calcines– At 140oF Trona begins to calcine
Sodium Bicarbonate

z Sodium Bicarbonate is a downstream pro

Trona

– It is the same baking soda you add to food– It is a purified processed product made from s

more expensive

– But is much more reactive with SO

2

z Bicarbonate has to be milled prior to use

– Milling on site to d90 less than 20 microns wit

gives the best results

– Premilled material with a D90 less than 40 m

– Handling issues become severe as d90 appro

z New capacity for sodium bicarbonate

– A new process that skips the soda ash step m

economical Flue Gas grade.

Advantages of Sodium DSI

z Dry Sorbent Injection systems are the low

option to treat acid gases.

– Small utilities and industrial boilers can’t affor

z Sodium DSI is compatible with ESP part

– Even with higher loading, sodium salts reduc

usually lower opacity and particulate emission

z Sodium DSI is also effective on HCl and z Removal rates can adapt to changing co

adjusting the feed rate.

– Fuel changes, load changes, regulation chan
Trona compared to Lime

z Trona is more efficient than lime so less 

needed

z Trona is easier to handle and less prone z Trona enhances ESP performancez Trona can be added further upstream, ev

economizer

z Lime is less expensive per ton on a deliv

– Delivered trona costs are highly freight depen

z Lime is more compatible with beneficial u

– Sodium levels in the ash of less than 1.5% ar

acceptable
What we mean by NSR

z Normalized Stoichiometric Ratio

– MW trona is 226 MW SO2 is 64 MW SO– 2 moles trona for every 3 moles SO2 or 45– 2 moles trona for every 3 moles SO3 or 45– MW bicarbonate is 84– 2 moles bicarbonate for every mole of SO2 – To fully calculate the amount of sorbent for an 

gasses must be accounted for. For trona, figu
Trona Performance Curve
Sodium Bicarbonate Performance Curve
Comparison of SO2 Treatment RateTrona and Sodium Bicarbonate (SB

0

102030405060708090

100

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.

NSR

SO2 Removal Rate (%)

Trona 2006 Trona 2007 SBC

• The 2006 data was obtained during a test us• The 2007 data was generated from a perma• Unmilled trona Select 200: d90 = 140 μm, d50 
Should You Use Trona or SodiBicarbonate

z Sodium bicarbonate becomes more economical to use 

following situations exist

– An ESP is the particulate control device– Higher SO

2 removals are required

– Injection is after the air heater

• Bicarbonate needs less than 800

o

F

• Trona efficiency increases as temperature and 

increase

– On site milling is available– Freight costs are high– Fly ash disposal costs are high

z Use of sodium sorbents results in higher sodium conte

customers should check the fly ash properties for benedisposal.
Effect of Sodium Bicarbonate Particle Size

Effect of SBC Particle Size at Same SO

2 Remov

0

10002000300040005000600070008000

10 20 30 40 50 

SBC Particle Size d90 (micron)

SBC Feedrate (lb/h)

* Outlet SO2 concentration @ 0.3 lb/mm
Fly Ash Considerations

z Higher sodium content in the fly asz Ashes from SO2 treatment typically 

for applications in concrete or struc

z Solubility of sodium compounds in 

(i.e. Na2SO4, Na2CO3)

z Disposal issues should be investig

the process. Customers encourageproperties and work closely with thmarketers.
Other Benefits

z High removal efficiencies for HCl az Mercury removal is enhanced at lo

have high sulfur coal

z Selenium and arsenic are also rem

flue gas.
Contact the SOLVAir Group of Solvay Chemicals

z Business Manager

– Mike.Wood@solvay.com

z Sales

– Michael.Atwell@solvay.com– Stan.Carpenter@solvay.com

z Technical

– Yougen.Kong@solvay.com– Heidi.Davidson@solvay.com