Deactivation of SCR catalysts during long term exposure in a biomass cofired power plant

1
Deactivation of SCR catalysts during long term
exposure in a biomass co-fired power plant

• Weigang Lin
• Department of Chemical and Biochemical
  Engineering
• Technical University of Denmark

October 1, 2009
2
Background

• Impact of long term exposure on SCR catalyst
  during co-firing biomass is not clear
• Such test was performed in Studstrup power plant
  with two units SSV3 and SSV4
• Present work evaluates deactivation of the
  catalyst elements exposed in Studstrup

3
Exposure procedure

• Reactivity of all catalysts for exposure were
  tested
• SSV3 and SSV4 start to operate on Feb. 15, 2005
• 1st exchange of 4 catalysts on March 7, 2006
• 2nd exchange of 4 catalysts on March 27, 2007
• End of exposure on Oct. 3, 2008
• Total number of catalysts 18 4 4 26

4
Experimental apparatus
Gas inlet
d
i
r
c
e
a
v

o
c
i
m
l
a
e
x
r

o

3
d
H
i
l
N
o
S
Gas outlet
5
Testing conditions

• Temperature of catalyst reactor 350C
• Gas flow 150 Nm3/h.
• NOx inlet 330 ppm
• NH3/NOx 1.2 mol./mol.
• SO2 500 ppm for some tests

Rate constant
Relative reactivity k/k0
Catalyst clogging is corrected
6
Results - reactivity of fresh catalysts
BASF catalysts
HTAS catalysts
46.3 1.2 Nm/h
7
Results
Relative reactivity as a function of total
exposed time
8
Conclusions

• All fresh elements have more or less the same
  reactivity (46.3 1.2 Nm/h)
• The relative reactivity (k/k0) of the catalysts
  decreases with exposure time
• The deactivation of the catalysts appears
  significant and slowly develops with exposure
  time
• With exposure time of nearly 20000 hours,
  deactivation degree varies in the range of 17
  35
• More details will be revealed by SEM-EDX in the
  near future

9
Acknowledgement

• Bo Sander, DONG Energy A/S
• Joakim Reimer Jensen, Haldor Topsøe A/S
• Jens Bjerkvig
• Francesco Castellino