文档介绍：NETL 2003 Conference on SCR
& SNCR for NOx Control
Mixing Performance
Characterization for
Optimization and Development
on SCR Applications
Kevin Rogers
Babcock & Wilcox Co.
.1
Efficient Design Optimization Requires
Reliable Performance Predictions
Influence Need for
of Bend Second Mixer ? Influence of Hood
and Vane and Hood Internal
Design Vane Designs
Influence of
Mixer Design
& Proximity to
Downstream MIXER-2
Arrangement
MIXER-1
Influence
of AIG
Design
.2
Mixing Test Stands:
Physical Test Stands:
Base Mixer Development
parisons
CFD Validation
Numerical Test Stands:
Extended Mixer Development
parisons
Multiple Scenario & Sensitivity
Analyses
.3
Mixing Effectiveness:
ξσ
1
m =
σ 0
where,
ξm = Mixing Effectiveness
σ0 = Standard Deviation Entering the Mixer
σ1 = Standard Deviation at Downstream Assessment Plane
.4
Modified Mixing Effectiveness :
(Provides an improved accounting for the length efficiency
of the mixer design and the effect of its placement in a
given arrangement)
ξσ'
' 1
m = '
σ 0
where,
ξm’= Modified Mixing Effectiveness
σ0’= Std Deviation @ Assessment Plane w/o Mixer
σ1’= Std Deviation @ Assessment Plane with Mixer
.5
Theoretical Effect of Reynolds
Number
3
NSc ≅ 10
γ 2 =
L/D
NSc ≅ 1
NRe Source: Beek & Miller, Chem. Eng. Prog. 1959
.6
Mixing Efficiency :
ζ
∆Pm
Mixer Shock Loss Coefficient =
m ρV 2
2
ξσ
Mixing Effectiveness Parameter 1
m =
σ 0
ξ
Dimensionless Mixing Efficiency m
η m =
ζ m
.7
CFD Testing – Effect of Velocity
25
w/mixers & Vg = m/s
20 w/mixers & Vg = m/s
w/mixers & Vg = m/s
w/o mixers & Vg = m/s
15 w/o mixers & Vg = m/s
w/o mixers & Vg = m/s
NH3 Cv, % 10
5 AIG Injection Point Concentration, Na = 23 points/m2
Constant Shock Loss Coefficient - Yielding Higher Pressure Drop at Higher
Velocity for Equivalent Mixing Effectiv