Title: MULTI-CHANNEL STATIC MIXER FOR FLUE GAS–AMMONIA MIXING
FIELD OF THE INVENTION
This invention describes a designed arrangement of multichannel static mixer
system for De-NOx application to ensure uniform and homogenous mixing of flue
gas with anhydrous ammonia for complete conversion of NOx to N2 and water
vapour.
More particularly the present invention relates generally for mixing of two fluids at
high ash condition with minimal pressure loss particularly in coal-fired power plant
where De-NOx system used for reducing the NOx to desired level.
BACKGROUND OF THE INVENTION
Emission regulations for unburned hydrocarbons, nitrogen oxides such as NO, NO2
and N2O (called as NOx) and particulates are becoming more stringent throughout
the world.
The major sources of NOx from stationary sources are power generation,
stationary engines, industrial boilers, process heaters and gas turbines. Post
combustion NOx control technologies that are currently being applied to coal-fired
utility boilers include selective non catalytic reduction (SNCR), selective catalytic
reduction (SCR), and combined SNCR/SCR systems (hybrid SNCR/SCR)
respectively. SCR can be applied as a stand-alone NOx control or with other
technologies, including selective non-catalytic reduction (SNCR) and combustion
controls such as low NOx burner (LNB) and flue gas recirculation (FGR).
SCR is typically implemented on stationary source combustion unit/s requiring a
higher level of NOx reduction than achievable by selective non-catalytic reduction
(SNCR) or combustion controls. SCR systems can be designed for NOx removal
efficiencies up to 100%, though in practice, commercial coal, oil, and natural gas–
fired SCR systems are often designed to meet over 90% efficiency. However, the
reduction may be less than 90% whenSCR follows other NOx controls such as LNB
or FGR that achieve relatively low emissions on their own.

Either ammonia or urea may be used as the NOx reduction reagent in SCR
systems. Urea is generally converted to ammonia before injection. Majority electric
utilities that operate SCR systems use (80%) use ammonia (anhydrous and
aqueous), and ~20% use urea.
Achieving targeted performance requirements of De-NOx in coal-fired power plants
mainly relies on an optimized design of every components used in SCR system.
The requirement of high performance SCR system have forced a need for a high
degree of uniformity in flue-gas flow and composition at the entrance to the
catalyst bed. The ultimate goal is to achieve the most uniform profile possible at
the SCR catalyst face with regard to NOx concentration, ammonia to NOx molar
ratio, velocity and temperature.
Flow mixing is a common device unit operation in a large number of processes,
and it is used in many different applications where a defined degree of
homogeneity of a fluid is desired (Regner et al., 2006). In particular, a mixing
device, e.g., a static mixer is usually installed to improve the rate of mixing of NH3
with flue gas and to enhance the uniformity of gas. However, the increase in the
system pressure drop because of mixing must be minimized.
There have been many attempts to develop static mixers for mobile SCR
applications, and computational fluid dynamics (CFD) has been widely used in the
design optimization of spray nozzles, flow mixing characteristics, NOx reduction
processes, and urea decomposition &provided an extensive review of static mixers
in the processing industry, presenting guidelines for the selection of static mixers.
Several types of mixers, including cone, 2-stage, and butterfly mixers, flow mixer
with twisted blades and observed that turbulent flow has a dominant effect on the
flow mixing index or uniformity index in the short distance immediately behind the
flow mixer
US8684593B2 reported design of pair vane used for mixing of flue gas with
ammonia. This pair vane is basically designed in such a way that it create swirls in
flow path and mixes the secondary flow with the primary flow. In this design, the
pressure reduces and increases in every pair of blades till the outlet of static

mixer, but one need to have longer static mixer (i.e approximately 2 m in length)
to achieve uniform mixing of secondary and primary flow. In our proposed design,
flow mixing achieved in much lesser length of static mixer (approx. 1000mm)
based on the design of cross blades at up & downward direction & flow dividers in
this static mixer system.
US8359832B2 describes that wire mesh along with baffle deflector for mixing two
fluids and as well as for directing the flow in the flow path. But there was only
limited information about pressure losses in the static mixer system due to the
baffle deflector. In our proposed design, design of blades and multi-channel
opening for the flow, ensures that uniform flow mixing across cross section.
US20120106290A1 reported the design and calculation of motionless mixers for
mixing a fluid in a conduit. Static mixer consist of the number of cross-bars over
the width of channel, the number of parallel cross-bars per element, and the angle
between opposite cross-bars. The design of static mixer is applicable in pharma
industry for mixing of two fluid based on the design of blades and cross bars
elements. This static mixer may be suitable for De-NOx system but it will leads
higher pressure drop due to cross-bar elements & ash flow through it and hence
increasing in the operational cost. In our proposed design, design of blades,
connecters & multi-channel opening ensures that homogeneous flow mixing at
minimal pressure drop of 6 mm H2O (tested and verified in the field test). In
addition to that, there was no ash flow stagnant found during the field testing
using this static mixer.
WO2002009858A2 reported that invention of static mixer element for mixing of
two fluids. Static mixer element includes a directional flow axis which points in an
intended downstream direction opposite to an intended upstream direction. The
static mixer element also includes inter-digitated static mixer blades. The blades
each have a concave side which faces generally in the intended upstream direction
at an acute angle with respect to the intended upstream direction. The static mixer
element is placed in a pipe with the directional flow axis of the static mixer
element pointing downstream.

Due to concave nature of the blades used in this static mixer element it’s very
much possible that high concentration of ash will be clogged in the flow path for
De-NOx application.
However, in our proposed invention, there was no clogging of ash found based on
the design of blade connecters and multi-channel opening and up and downward
blades, where ash flow will get splitted and mixed in every channels.
Similar reports are found in US20060187752A1, EP 0815929 A1, US 20030048694
A1 & EP1324819A1.
Most of these inventions are blending of two streams (including polymer) for
industrial applications where pressure difference across static mixer is very high.
Therefore the intention of the present invention is to provide a static mixing
system solution for two fluid stream mixing without stagnation of ash in the flow
path, no flow deviation and with insignificant pressure loss.
OBJECTS OF THE INVENTION
An object of the invention is to design a cross blades based multi-channel mixing
system to achieve uniform flow over catalyst bed.
Further objectives of this invention is to avoid any ash clogging along the flow path
by incorporating blade element angle & mixing length in flue gas flow path.
SUMMARY OF THE INVENTION
This invention describes a design of multi-channel static mixer system for De-NOx
application to ensure uniform & homogenous mixing of flue gas with anhydrous
ammonia for complete conversion of NOX to N2 & water vapour. This static mixer
consists of angled cross blades, channel-blade connector, angled cross blades
connector, ammonia injection nozzle and in-line duct. Secondary flow (ammonia) is
injected through the nozzle to in-line duct where primary flow (flue gas from power
plant) is flowing from one end to another. Design of cross blades and channel

connector are carried out using CFD approach to divide and mix the two stream
along the flow path. In this approach, ammonia mixes with flue gas before enters to
the channel and flow is divided in the channel in order to achieve cross mixing
through cross-blades connector. Channel blades are connected to create more
mixing channels to achieve uniform mixing across cross sectional area.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
It is to be noted, however, that the appended drawings illustrate only
typicalembodiments of the present subject matter and are therefore not to
beconsidered for limiting of its scope, for the invention may admit to other
equallyeffective embodiments. The detailed description is described with reference
tothe accompanying figures. In the figures, the left-most digit (s) of a
referencenumber identifies the figure in which the reference number first appears.
Thesame numbers are used throughout the figures to reference like features and
components.
Figure 1 shows the mechanical arrangement of overall invented method of multi-
channel static mixer system. The proposed multi-channel static mixer system
consists of 5 multi-channel sets to achieve homogeneous mixing of two fluids along
the flow length. Each multi-channel set consist of Channel “a” & Channel “b”.
Overall multi-channel static mixer system consists of primary flow inlet (flue gas) (1),
injector (2), static mixer duct (3), mixed flow outlet (4), SS rods (5), flow divider (6)
& Cross blades (7)
Figure 2 shows that the construction of Channel “a” & its parts shown in Figure 3.
In Figure 4 shows that the construction method for connecting SS rods with cross
blades. All flow dividers are welded with SS Rods as shown in the Figure 5. Each
flow divider (6) is welded with 3 cross blades (8) horizontally downward as shown in
the Figure 5.

Figure 6 shows that the construction of Channel “b”. Figure 7 shows that the
construction method for connecting cross blades and SS rods. Figure 8 shows that
the construction method for connecting cross blades & flow dividers.
Invention will now be described in detail in an exemplary embodiment asdepicted in
the accompanying drawings. There can however be otherembodiments of the same
invention, all of which are deemed covered by this description.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 1 shows the mechanical arrangement of overall invented method of multi-
channel static mixer system. The proposed design consists of 5 sets of multi-channel
mixers along the injector (2) to achieve homogeneous mixing of flue gas and
ammonia. Each Multi-channel consists of Channel “a”. Channel “b” and its placed one
after another with 100mm distance in multi-channel static mixer system. 5 sets of
multi-channels mixers are constructed & arranged in sequence one by one inside the
square duct along the longitudinal direction of fluids flow.
Overall multi-channel static mixer system consists of primary flow inlet (flue gas) (1),
injector (2), static mixer duct (3), mixed flow outlet (4), SS rods (5), flow divider (6)
& Cross blades (7). The primary flow considered to be from left to right in the
satanic mixer system and in enters at duct’s side 1, secondary flow (NH3) is injected
through Injector (2) in-order to mix it with mainstream primary flow and mixed flow
(4) exit in the outlet of static mixer system. Since this static mixer system designed
specifically for controlling De-NOx in flue gas from high ash coal-fired power plants,
the design of blades arrangement to ensure uniform mixing of flow at minimal
pressure loss.
Figure 1a. shows that the construction& arrangement of MC 1 which consist of
channel “a” and channel” b” as like all other Multi-channels (MC)

Figure 2 shows that the construction of Channel “a” & its parts shown in Figure 3.
Channel “a” consists of SS Rods (5), Flow dividers (6) and cross blades (7). In
Channel “a”, all SS rods (5) are divided vertically by flow dividers (6) exactly at
25mm in both sides of SS rods and each SS rod is welded with one cross blade at
the middle of SS rod’s length as shown in Figure 4. All flow dividers are welded with
SS Rods as shown in the Figure 5. Each flow divider (6) is welded with 3 cross
blades (8) horizontally downward as shown in the Figure 6. All these three cross
blades are welded 30 degree inclined towards downwards of flow direction in each
flow divider. One cross blade is welded 30 degree upward at middle of each SS rod
along the flow direction in Channel “a”.
Figure 6 shows that the construction of Channel “b”. Channel “b” consists of SS Rods
(5), Flow dividers (6) and cross blades (7) as described in the Channel “a”. In
Channel “b”, all SS rods (5) are divided vertically by flow dividers (6) exactly at
middle of SS rod’s length and each SS rod is welded with two cross blade at the
sides of SS rod’s length as shown in Figure 7. Two cross blades are welded 30
degree inclined towards downwards of flow direction in each SS rods. In Channel
“b”, all flow dividers are welded with SS Rods as described in Channel “a”. Flow
divider (6) is welded with 3 cross blades (8) horizontally 30 degree upward as shown
in the Figure 8.
As mentioned earlier each multi-channel set consists of Channel “a”. Channel “b” and
its placed one after another with 100mm distance in multi-channel static mixer
system. All these 5 multi-channel sets are fabricated separately and installed in a
rectangular duct along with provision for injector for injecting the secondary fluid
(NH3) in multi-channel static mixer’s system. Injector is “L” type bend pipe having a
diameter of 8mm with the tip diameter of 3mm.
Two types of channel variation (at first 3 channels in Channel “a” and 2 channels in
Channel “ b”) are considered along the flow path to achieve cross mixing between
the flows from first row blades to next till the end of static mixer system. At first

the flow is separated in both longitudinal and cross sectional wise due to cross
blades & flow dividers respectively. Up-down cross blades are designed in such a
way that flow from first row is further separated at the middle of the second row
blades to ensure further mixing.
To avoid increase in pressure loss, the no of channels are reduced in the second row
by considering the mixing at the middle of the second row blade based on the above
approach. This arrangement is repeated till the end of static mixer system in order to
maintain the same pressure difference across each row till the static mixer ducts
outlet. Angle of cross blades is designed as 30o angle along the flow path to avoid
pressure loss and free ash flow in flue gas flow path. Enough space has been
provided between static mixer’s duct bottom surface to bottom blades tip for easy
cleaning of ash (if any) settled in bottom of the ducts.
While performing the invention, the following things are ensured.
i) Mixing length is provided between the channels to ensure mixing of the streams
immediately after the flow separation at the blades
ii) Cross blades in every rows are designed such a way that flow from first cross
blades enters exactly middle of the second row cross blades for further mixing of
primary and secondary flows
iii) Cross blades, flow dividers and Stainless Steel rods are designed to ensure
turbulent flow through multiple cross blades and channels to provide multi-
channel mixing. Duct length provided between channels and cross blades to
ensure the sequence of creating turbulence, two-stream mixing and uniform
flow.
iv) Every multi-channel set placed one after another in a rectangular duct of 150mm
x 150mm x 1000mm at every 100mm length of duct. These multi-channels sets
are designed in such a way to achieve homogeneous mixing of two fluids (i.e
Primary and secondary).
v) Each multi-channel consists of Channel “a” & Channel “b” and its arranged
sequentially with 40 mm distance in between to provide enough space for mixing
of fluids across channels.

vi) In channel (a), three Stainless Steel Rods have 8mm diameter placed across
cross section of rectangular duct’s horizontally & each Stainless Steel Rods are
placed 35 mm distance vertically from top duct’s surface. The cross blades are
very thin and having a dimension of 50 mm long, 40mm depth & 1mm thickness.
Each Stainless Steel rods welded with one cross blade (30 degree upward in the
direction flow) at middle of static mixer duct to divert the flow in upward
direction at the middle of static mixer system.
vii) Each flow divider having dimension of 25mm length, 3 mm thickness & 150mm
height along the flow direction is welded with 3 cross blades which are 30
degree downward to divert the flows in downward direction at both ends of
Stainless Steel rods. Flow separation takes place at flow dividers along the flow
of direction & flow is guided by the cross blades to downwards with minimal
pressure loss.
viii) Three Stainless Steel Rods have 8mm diameter placed across cross section of
rectangular duct’s horizontally & each Stainless Steel Rods are placed 35 mm
distance vertically from top duct’s surface. The cross blades are very thin and
having a dimension of 50 mm long, 40mm depth & 1mm thickness. Each
Stainless Steel rods welded with two cross blade (30 degree downward in the
direction flow) at sides of Stainless Steel rods to divert the flow in downward
direction in channel “b “.
ix) Mixing length of 40mm has been provided between the channels to ensure the
separated flow in up & downward along the flow direction in channel “a” to be
stabilized before it enters on to channel “b”.
x) Arrangements of cross blades and flow dividers are designed to ensure the
mixed flow from Channel “a” has to be separated in the middle of Channel “b”.
In this manner the flow is separated and mixed in all the channels with mini9mal
pressure drop of 2 mmhg.
xi) The turbulence are created through multiple cross blades in each SS rods and
channels to provide multi-channel mixing at every rows to ensure uniform mixing
of primary and secondary flow.
Space between the up-down cross blades & blade tip to duct bottom ensures
that the no ash flow clogging along the flue gas flow path.

WE CLAIM
1. A multi-channel static mixer for mixing flue gas and ammonia comprising :
a duct (3) having a flow inlet (1) for entry of flue gas;
an injector (2) for entry of ammonia;
a mixed flow outlet (4) for exit of mixed gases after thorough mixing;
the intermediate passage between the primary flow inlet (1) and the mixed
flow outlet (4) consisting of 5 sets of multi-channel mixers (MC 1; MC 2; MC 3;
MC 4 & MC 5) placed one after another within the rectangular duct, the said
multi-channel mixer (MC) comprising cross blades (7,8) arranged in multi-
direction on flow dividers (6) and a plurality of stainless steel rods (5) for
thorough mixing of gases in both longitudinal and cross section wise in upward
and down direction before it is taken out through the outlet (4).
2. The multi-channel static mixer as claimed in claim 1, wherein each multi-channel
consists of channel (a) on the left side and channel (b) on the right side of
channel (a), with all the multi-channel sets having same repeated sequence of
channels (a & b).
3. The multi-channel static mixer as claimed in claim 2, wherein channel (a) consists
of three numbers of stainless steel rods (5) placed horizontally at equal intervals
and mounted over a pair of dividers (6), the said dividers having circular holes for
accommodating the stainless steel rods (5) and welded for rigidity.
4. The multi-channel static mixer as claimed in claim 3, wherein the flow dividers (6)
are having slots at 30° angle downward direction for accommodating cross blades
(8) and welded therein.
5. The multi-channel static mixer as claimed in claim 3, wherein the stainless steel
rods (5) are provided with slots in a manner that when the cross blades (7) are
inserted in it and welded therein, it tilts toward upward direction opposite to the
cross blades (8) fixed on the flow divider (6).

6. The multi-channel static mixer as claimed in claim 2, wherein the channel (b)
consist of a single flow divider (6) placed in the middle portion of similarly placed
three numbers of horizontally placed stainless steel rods (5) as in channel (a) such
that the gas flow passing through the central portion of channel (a) is divided by
the flow divider (6) in channel (b) and the gas flow which comes after being
divided by flow divider (6) of channel (a) get mixed on either side of flow divider
(6) in channel (b).
7. The multi-channel static mixer as claimed in claim 6, wherein three numbers of
cross blades (8) are mounted on three slots of single flow dividers (6) and 3 sets
each of cross blades (7) are mounted on the slots of stainless steel rods (5) at
locations on either side of flow divider (6) of channel (b) so that the gases divided
out of dividers (6) of channel (a) are mixed in the channel path of channel (b)
where there is no divider thus ensuring a thorough mixing of gases.
8. The multi-channel static mixer as claimed in claims 1 to 7, wherein the mixing of
gases is continued repeatedly in the 5 multi-channel sets consisting of channel
(a & b).