WPCA/PCUG NOx Round Table 200

Cleveland, Ohio

Hans Hartenstein 

Comparison of Deactivation 

Different Catalyst Typ
Three different types of catalyst deactivation 

• Thermal deactivation due to rutilization a

overheating the catalyst – same for all caand makes that use TiO

2 as ceramic subs

• Physical deactivation by means of:

• Cell and/or pore pluggage, i.e. fly ash, • Surface blinding layers i.e. CaSO

4, eut

Same for all catalyst types and makes as flue gas and/or fly ash characteristics.

• Chemical deactivation as a result of the r

flue gas constituents with the catalyst’s cactive centers mostly consisting of V

2

O

5.

Catalyst Deactivation Ba
Chemical catalyst deactivation is primarily ca

reaction of cation species in the flue gas with active V

2

O

5. The main catalyst poisons in coal 

• Non-metals, mainly phosphorus (P) as gas

• Alkali metals, mainly sodium (Na) and pot• Alkaline earth metals, mainly calcium (Ca

(Mg) and to a lesser extent barium (Ba) 

• Metalloids, mainly arsenic (As) as gaseou

Chemical Catalyst Deactiv
Chemical deactivation follows the same princi

of type and make of SCR catalyst containing cactive V

2

O

5 as the main ingredient. All known 

commercially used in coal-fired units fall in thi

Chemical deathe catalyticV

2

O

5 sites by 

Chemical Catalyst Deactiv
In conclusion, theory suggests that all comme

SCR catalyst regardless of type and make deachemically the same way and also at the same exposed to the same conditions including:

• The same flue gas composition and temp• The same basic SCR reactor design (sam• The same location (layer) within the SCR 

However, various claims to the contrary were 

years, especially related to arsenic poisoning • “Arsenic resistant” catalyst, e.g. through add

• “Arsenic tolerant” catalyst, e.g. through mig

arsenic to center of thin wall.

• “Arsenic proof” catalyst, e.g. by means of tri-

structure. 

Chemical Catalyst Deactiv
• Southern Company has 14 high-dust SCRs in 

Florida and Georgia operational since the ear

• Evonik has 17 high-dust SCRs in Germany ope

since 1987.

• Evonik has managed more than 30 high-dust 

Florida, Illinois, Indiana, Kentucky, Maryland, Jersey and New York some operational since 

These units have / had all types (corrugated, hplate) and makes (Argillon, BASF, CERAM, CorHaldor Topsœ, Hitachi, IHI, KWH) of regeneratnew catalyst installed within the same reactor at the same time.

Database for Actual Deacti
Differentiation according to catalyst poisons c

the following categories:• low arsenic, mid calcium – e.g. Northern App• mid arsenic, mid calcium – e.g. Eastern Kenn• high arsenic, low calcium – e.g. Southern Illin

and Northern Ala

• high calcium, high alkali – e.g. PRB• high alkali, high phosphorus – e.g. biomass, li

Database for Actual Deacti
Database for Actual Deacti

Eastern Bituminous - Low Arsenic, Mid Calciu

161820222426283032343638404244

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 90,

SCR operating hours

activty K [m/h] 

layer 1, new plate X layer 2, new plate Xlayer 3, new plate X layer 4, new plate Xlayer 5, new plate X layer 6, new plate Ylayer 1, new plate Y
Database for Actual Deacti

Eastern Bituminous - Mid Arsenic, Mid Cal

0.81.01.21.41.61.82.02.22.42.62.8

0 10,000 20,000 30,000 40,000 50,000 60,000 70,0

SCR operating hours

DeNOx potential P = K/Av 

layer1, new plate layer 2, new plate layer 3, nlayer 4, regenerated honeycomb layer 1, regenerated plate layer 2, relayer 3, regenerated plate
Database for Actual Deacti

Eastern Bituminous - High Arsenic, Low Calciu

2022242628303234363840424446485052

55,000 65,000 75,000 85,000 95,000 

SCR operating hours

activty K [m/h] 

layer 1, new plate Ylayer 2, regenerated plate Xlayer 3, new plate Ylayer 5, new corrugated Xlayer 6, new corrugated Xlayer 2, new plate X
Database for Actual Deacti

Eastern Bituminous - Various Coals

0.450.550.650.750.850.951.05

0 5,000 10,000 15,000 20,000 25,000 

SCR operating hours

relative activity

low arsenic, mid calcium, nmid arsenic, mid calcium, rehigh arsenic, low calcium, n
• Central and Southern Appalachian coals with 

and mid calcium contents.

• Deactivation is about what was initially expe• Arsenic deactivation seems to have reached 

as deactivation appears to have leveled out.

• Peculiarity: Inverse deactivation was noted in

which means that the deactivation is greater (downstream) layers than on higher (upstream

This is unusual for bituminous coal units but through data showing higher deactivation at layers initially. The trend reversed to what wconsidered normal now.

Mid Arsenic Case Study – Wa
Mid Arsenic Case Study – Wa
Mid Arsenic Case Study – Wa
Mid Arsenic Case Study – Wa
Mid Arsenic Case Study – Wa
Database for Actual Deacti

Southern Illinois Basin - High Arsenic, Low Calc

202530354045

0 5,000 10,000 15,000 20

SCR Operating Hours

activty [m/h] layer 1, n

layer 1, nlayer 3, nlayer 1, nlayer 1, nlayer 1, rlayer 3, n
Database for Actual Deacti

Southern Illinois Basin Coal - High Arsenic, Low 

0.450.550.650.750.850.951.051.15

0 2,000 4,000 6,000 8,000 10,000 

SCR operating hours

activity [m/h]

plate X, plaplate X, plahoneycomb corrugated plate Y, planplate Y, plancorrugated honeycomb honeycomb 
• Important trends in Northern Alabama coal b

• Increasing variability of the As/Ca ratio.

• Increase in absolute arsenic concentratio• Deacrease in heating value and increase 

• Observations: 

• Plate catalyst shows a greater and/or qui

arsenic update than honeycomb (same as 

• Arsenic uptake appears to reach saturatio

now about the same on all layers regardletype and make (same as in Europe).

• SEM shows arsenic gradient across wall o

higher [As] on walls and lower in the middof catalyst type and make (same as in Eu

High Arsenic Case Study – Go
High Arsenic Case Study – Go
High Arsenic Case Study – Go
High Arsenic Case Study – Go
High Arsenic Case Study – Go
High Arsenic Case Study – Go
High Arsenic Case Study – Go
High Arsenic Case Study – Go
High Arsenic Case Study – Go
Database for Actual Deacti

PRB - High Alkali, High Calcium

1520253035404550

0 5,000 10,000 15,000 20,000 25,000 30,000 35,0

operating hours

K-value [m/h] 
• PRB fuel – high calcium, high alkali, high phos

• Deactivation significantly better than initially 

(although, Miller was designed conservatively

• Deactivation due to gypsum layer deposition 

catalyst.

• Inverse deactivation noted – deactivation gre

layers than on higher (top) layer. This is not u

PRB units and has been observed elsewhere 

• Also significant is gross versus effective/avai

potential due to fly ash plugging. Southern Ctrending towards larger pitch whereas the indappears to be going to smaller pitch.

PRB Case Study – Miller 1, 2
PRB Case Study – Miller 1, 2
PRB Case Study – Miller 1, 2

– 8.2 mm 
PRB Case Study – Miller 1, 2

– 9.3 mm 
Conclusions

• Theory suggests that chemical deactivation m

and deactivates rates should be essentially tall catalyst types and makes as they are primdependent on the composition of the coal bur

• Actual field data confirms theory as all make

of catalyst deactivate chemically at essentiarate when exposed to the same flue gas in th

reactor. This is also true for regenerated cata

• Catalyst make and type can be selected only 

• Suitable geometry (pitch, mechanical stre• Lowest price per DeNOx potential unit.

• There is no such thing as arsenic resistant S
Questions