FIELD OF THE INVENTION
The present invention relates to a low NOX emitting solid fuel fired wall burner
apparatus for boilers in thermal power plants.
BACKGROUND OF THE INVENTION
Burner is an important element in efficiently firing the fossil fuels under given
conditions at desired power ratings. Therefore, design of burner plays a crucial
role in deciding combustion efficiency, flame stability, presence of hazardous
pollutants, amount of unburnt carbon in the exhaust and flame impingement to
furnace walls. There are many variants of burner have been reported in the
literature based on application, requirement of multi-fuel firing, fuel properties
and regulations on flue gas emissions. The important components of any burner
are fuel nozzle, primary air supply, secondary air supply and supply of air in
different stages, artificial turbulence generator, ignition source, flame scanner
and view port.
The burner concepts are fairly well established and their applications are
frequently found in power plants, refineries, steel plants, heat treatment
furnaces, glass industries and metallurgic industries. In all power plants gas or oil
burners are frequently used as a start-up burner (SUB). In the case of solid fuel

fired wall burners, an oil gun would be provided at the center of the burner for
start-up purpose. The oil gun is an important element for combustion of liquid
fuels, which is used for atomization of liquid fuel along with atomizing medium.
Based on properties of oil either air or steam is used as atomizing medium. The
solid fuel fired burners usually have a pulverized fuel supply duct through which
pulverized solid fuel along with air will be supplied, the solid fuel particles would
be suspended in the air and it catches fire as soon as it enter the furnace
through burner. That is why oil is fired first in the burner to make the furnace
temperatures are high enough to devolatilize the coal particles and then burn
hence flame sustains uninterruptedly.
Solid fuel fired wall burners are commonly observed in design of innovative liquid
and gas fired burner applications for example in US Pat. No. US 8,479,668 B2,
for coal firing applications, in which coal is fired centrally with a conical exit and
similarly air is also supplied with conical outlet into the furnace and swirl is added
only to the secondary air. Moreover the wall burner does not consists of oil gun.
US Pat. No. US 2014/0290544 Al, described pulverulent fuel firing system with
plasma ignition torch for igniting the fuel. No swirl block provided for the core
air/oxygen or secondary air/oxygen.
In World Pat. No. WO 2012/163107 Al, described a dense-phase swirl pulverized
coal burner in which the primary air duct consists of several stages of pulverized
coal concentration rings with higher outer density and lower inner density of
pulverized coal. This burner was provided with swirl block only in the outermost
secondary air.

In the German Pat. No. DE102007030269B4, described a pulverized coal burner,
in which swirl block provided to the primary stream. Adjustable swirl vanes are
also provided for secondary air flow with a complicated spin mechanism.
In Japanese Pat. No. JP2014153014A, describes a pulverized coal burner, in
which the pulverized coal enters the burner through a cylindrical nozzle
tangentially. The burner is provided with plasma torch for flame ignition. The
coal nozzle inner surface of the outer tube extending along an axial direction,
provided with a plurality of deflector angle. Furthermore, the outer cylinder is
further provided with a recessed groove. The air for complete combustion was
send in different stages through common windbox.
In Chinese Pat. No. CN100453901C, describes a solid fuel burner, in which oil
gun placed at the center and solid fuel send to burner in the surrounding pipe.
But in the solid fuel transportation line has temporarily reduced its dimension
using a sudden expander near pipe entry and similarly another concentrator has
been placed downstream to the expander. Furthermore additional air nozzle
were provided downstream to the concentrator. Secondary air supplied in
different stages for combustion solid fuels.
In European Pat. No. EP690264A2, 'describes a pulverized coal burner and
method of using it, in which oil is placed at the center and coal was supplied
concentrically in the surrounding pipe. The coal pipe was provided with venture
for controlling a concentration distribution of the pulverized coal and air required
for complete combustion is supplied in multiple stages. They have claimed lower
NOx even at lower loads of the pulverized coal. The secondary and tertiary air
flow was supplied with swirling generators for flame stabilization.

In Japanese Pat. No. JP2002115810A, describes about low NOx solid fuel burner
in which a concentrator has been placed in the coal flow line and air required for
complete combustion supplied in stage with swirling action. This burner was
designed to minimize the furnace size by eliminating the two stage combustion.
In Japanese Pat. No. JP08312917A describes about low NOx combustion method
and device for pulverized coal, in which the coal flow pipe line is divided into
right and left partitions. The pulverized coal along with primary air passes
through these partitions with turning flow and at the end of pulverized coal
nozzle has flame stabilizer. The air for complete combustion has send with
different stages.
Although many novel wall burner concepts were available for power plant
applications and different industrial applications but the present invention
significantly deviate from others in terms of swirl arrangement, air controlling
mechanism. In the present invention, a wall burner is designed for high
combustion efficiency and lower NOx emissions by optimizing the different
proportions of air flow.
OBJECTS OF THE INVENTION
It is an object of the present invention to propose a low NOX emitting solid fuel
fired wall burner apparatus for boilers in thermal power plants.

Another object of the present invention is to propose a low NOX emitting solid
fuel fired wall burner apparatus for bbilers in thermal power plants in which a
deflector plate is provided for better mixing between solid fuel particles and
secondary and stage air flows.
A still another object of the present invention is to propose a low NOX emitting
solid fuel fired wall burner apparatus for boilers in thermal power plants in
which includes circumferential split vanes for efficient air flow control between
secondary air and stage air flow ducts.
A further object of the present invention is to propose a low NOX emitting solid
fuel fired wall burner apparatus for'boilers in thermal power plants, which
provides efficient swirl effect for air flows.
NUMMARY OF THE INVENTION
In this present invention, a low NOx wall mounted pulverized solid fuel burner
has been disclosed for thermal power plant applications. This burner is primarily
designed to install in the wall of the furnace for firing the solid fuels. Number of
such burners can be arranged in series or parallel or both to get rated power
output from the power plant.
The present invention of wall burner consists of an oil gun at the center of the
burner and in a first annular pipe i.e., surrounding the oil gun and solid fuel
injection pipe was inserted. Through this pipe, pulverized solid fuel along with

primary air is supplied for combustion. A guide pipe is provided at the center of
burner to insert/withdraw oil gun easily. Towards the downstream of the guide
pipe, near the burner throat, a plurality of deflector plates are fixed to the guide
pipe to concentrate the pulverized solid fuel particles near the burner exit. The
rich mixture of pulverized coal and air mixture helps in maintaining the coal
flame sustainably. The deflector plates prevent the solid fuel particles to clog the
oil gun's spray holes in nozzle. These deflector plates also provides a thorough
mixing of the pulverized solid fuel particles with the secondary air. This will
provide complete combustion of solid fuel particles in shorter time. Apart from
primary air supplied for transporting the solid fuel, the rest of air used for
complete combustion of solid fuel is supplied through a common wind box
disposed 90° to the wall burner axis. The wind box is partitioned into two ducts
bend 90° towards burner axis and becomes parallel to the burner principle axis.
The first part is called "secondary air" duct which is placed immediately after the
primary air ducting and the second part of air supply is called "stage air" duct
which placed over the secondary air duct concentrically. The same air supply
ducts are used while firing oil as per stoichiometric requirement. The secondary
air duct and stage air duct were provided with swirl blocks on the horizontal pipe
portion in the present invention. The axial swirl block provides efficient swirl to
the respective air supplies flowing through it. Therefore, it provides higher
stability to the flame, complete combustion of solid fuel particles in shorter
residence time.
According to another aspect of the invention, the oil gun can be used for firing
either Light Diesel Oil (LDO) or Heavy Fuel Oil (HFO) or any other liquid fuel
during start-up or shut down. The oil gun is designed for 30% of Burner
Maximum Continuous Rating (BMCR) load. The liquid fuel gun consists of two

pipes for sending fuel and atomizing medium, these two pipes are commonly
connected to a diffuser plate and a spray nozzle. To atomize liquid fuel properly,
fuel is pressurized between 3 - 15 bar and
corresponding atomizing medium also pressurized in the range between 3 - 15
bar based on requirement. The pressure of liquid fuel and atomizing media will
be decided based on choice of atomizing nozzle such as Y-jet or T-jet. Here the
atomizing medium can be air or steam depending upon the type of liquid fuel.
According to another aspect of the invention, during solid fuel firing small
amount of air is passed through guide pipe of oil gun as cooling medium and
small quantity of atomizing medium is also passed through the oil gun nozzle tip
to avoid further damage and deposition of nozzle holes.
According to another aspect of the invention, the air supply for solid fuel
combustion is proportioned between primary, secondary and stage in such a way
that stable flames establishes in the furnace and produces lower NOx. In the
present design different proportions of air flow is distributed to primary duct,
secondary duct and stage air duct. The air flow is optimized in such way that the
air flow ensures flame stability even at very low flow rates of the solid fuel. This
flexibility is highly advantageous during start-up and shut-down of the boiler.
According to another aspect of the invention, the preheated air supply from
forced draft (FD) fan to the wall burner is split into two portions, one portion of
air is utilized for transporting the pulverized solid fuel to burner and the other
portion of air send through the burner wind box. The burner has air flow

controllers for supplying air in stages. The air staging has been carried out with
circumferential split vanes placed all around the perimeter. The ducts have been
provided with circumferential split vanes for opening/closing and controlling of
the air flow through it. Number of vanes for operating the secondary and tertiary
are same and these vanes are connected to each other. All these vanes are
connected to a common shaft for easier operation by moving the shaft from the
burner front, the air flow can be controller effectively to each of the air staging.
According to another aspect of the invention, secondary air swirl block has fixed
vanes, which has been welded on to the primary air pipe and the stage air duct
has been provided with movable swirl block, which can be adjusted from during
combustion to get optimum combustion parameters.
According to another aspect of the invention, for ignition of the liquid fuel a high
voltage spark ignition system was used. This has been inserted very near to the
liquid fuel nozzle tip. Similarly, two flame scanner are systems are provided to
sense the liquid fuel flames and solid fuel flames. For liquid flame ultraviolet (UV)
flame scanner will be used and for solid fuel flames infrared (IR) scanner will be
used. In addition, a view port is also provided to physically observe the flame
condition during operation.

According to another aspect of the invention, pulverized fuel will be ignited after
establishing the liquid fuel flames. Once the furnace walls temperature reaches
auto ignition temperature of solid fuel then the pulverized fuel will be injected.
Similarly during shut down, the liquid fuels will be fired to completely burn the
solid fuel left in the transportation line.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 illustrates the cross sectional view of low NOx wall burner configuration
with fuel and air flow arrangements, flame ignition rod and viewport along its
principle axis, according to the invention.
Figure 2 illustrates the P-view (burner cover plate view) of Figure 1 with oil gun,
flame scanners and adjustable secondary and stage air controlling levers.
Figure 3 illustrates the Q-view (burner throat view) of Figure 1 with oil gun,
flame scanners in the low NOx wall burner.
Figure 4 illustrates the swirl block arrangement of the secondary and stage air
supplies in the low NOx wall burner.
Figure 5 illustrates a secondary and stage air supply circumferential vanes for
controlling air flow into the low NOx wall burner.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE
INVENTION
The present invention details the design of low NOx wall burner for firing solid
fuels in power plants. However, the same design can be applied other industrial
applications such as steel plants, refineries, process captive power plants and
heat treatment furnaces applications.
Figures 1 to 5 show the detailed arrangements of a low NOx wall burner, where
Figure 1 illustrates the longitudinal cross sectional view of the wall burner.
Burner consists of an inner most liquid fuel gun (1) for atomizing the liquid fuel.
The liquid fuel gun (1) is inserted into a guide pipe (2) and it was placed at the
center of the wall burner. The liquid fuel and atomizing medium exits through
the nozzle tip (3) into the combustion chamber. The air for complete combustion
of liquid fuel is supplied through the primary flow pipe (4), secondary air duct (7)
and stage air duct (8). While firing the solid fuels, pulverized fuel is send along
with primary air through a 90° bend pipe (5) and which is connected to a
horizontal pipe (4) and the mixture of pulverized fuel and air injected into the
furnace through diffuser plates (6). Oyer the primary air pipe (4) secondary air
pipe (7) is placed concentrically and over which stage air duct is placed (8)
concentrically. Oil gun (1) is placed at the center, first annular duct is primary air
flow pipe (4), secondary annular space is secondary air duct (7) and tertiary
annular space is stage duct (8). After segregating primary air flow for solid fuel
transportation, remaining air is send through a common wind box (11), which is
90° to the wall burner axis. This wind box is further split into secondary air flow
and stage air flow ducts, these ducts bend 90° again aligns with wall burner axis.

These secondary and stage air ducts have been provided with swirl blocks (9)
and (10) respectively for better mixing of the air and fuel flow through swirling
flows by inducing turbulence.
The secondary air flow and stage air from main duct (11) is controlled by
circumferential split vanes (12) and (13) respectively. These split vanes are
interconnected flexible rods and these will be controlled using a lever.
For ignition of liquid fuel a high voltage spark igniter (14) is provided and a
viewport (15) is provided to monitor the flame physically in the furnace. The wall
burner front section is insulated with wool (16) to contact with hot surfaces while
handling prevent heat coming out. Therefore burner operation is smooth.
Figure 2 illustrates the wall burner cover plate side view of the Figure 1. Where
liquid fuel gun (1), primary air flow duct (4), flame igniter (14) and view port
(15) can be seen. Flame scanner for liquid fuel (17) and flame scanner for solid
fuel (18) are also placed either side to monitor the flame presence in the
furnace.
Figure 3 illustrates the arrangement of burner throat view, i.e., burner
downstream towards furnace. Where oil gun (1) at the center, swirl blocks for
secondary air flow (9), swirl blocks for stage air flow (10), flame igniter (14) and
other monitoring systems can be seen.
Figure 4 illustrates the arrangement of swirl block (9) and (10) for secondary air
and stage air respectively where, the secondary air swirl block is placed in the
secondary air annular space over the primary air flow duct (4) and a movable
stage air swirl block is placed in the stage air annular space. The number of swirl

blades in the fixed swirl block (9) varies between twenty four and forty eight.
The number of swirl blades in the variable swirl block (10) varies between thirty
and fifty.
Figure 5 illustrates the arrangement of circumferential split vanes (21) and (22)
are used for controlling the secondary air supply and stage air supply
respectively. These circumferential split vanes (21) and (22) are split vanes are
connected with rods (23) and (24) respectively and each of these rods are
interconnected to another set of rods (12) and (13) respectively. With the help
of these rods, air flow control between secondary air and stage air can be
effectively controlled.
Experimentation Results
The wall burner of capacity 3.5 Mkcal/hr has been fabricated and tested at our
facilities with pulverized high ash Indian coal. Important experimental data that
has been observed during the tests are given in Table 1. Here solid fuel was
taken as singareni coal and liquid fuel was taken as LDO. During pulverized coal
combustion stable flame were observed and stable flames were observed even
at burner turndown ratio of 1:4.
The hazardous emissions such as carbon monoxide (CO) and NOx were low
compared with other burners. All experiments were conducted at 15% to 20%
excess air than the stoichiometric requirement.

WE CLAIM :
1. A low NOX emitting solid fuel fired wall burner apparatus for boilers in
thermal power plants, comprising :
(a) an innermost liquid fuel gun (1) with a guide pipe (2), liquid fuel along
with atomizing medium egressing through the nozzle (3) into the boiler
furnace with corresponding air supply is through a plurality of annular
pipe for complete combustion of fuel;
(b) a plurality of deflector plates (6) receiving the pulverized solid fuel along
with primary air pass through the first annular pipe (4), and injecting
into the furnace, wherein corresponding air being supplied through the
second annular duct (7) and the stage annular duct (8);
(c) a fixed swirl block (9) and a movable swirl block (10) for creating
turbulence in the secondary air supply duct (7) and stage air duct (8)
respectively for solid fuel combustion;
(d) a handle (19, 20) for controlling the air flow in the secondary and stage
air duct (7, 8) using circumferential split vanes (21, 22) respectively;
(e) a high energy arc ignition (14) for initiating the liquid fuel flame; and
(f) a flame scanner (17, 18) for monitoring the presence of flame for liquid
and solid fuels respectively.

2. The apparatus as claimed in claim 1, wherein the liquid fuel is fired through
the oil gun (1) under process conditions such as during start-up, shut down,
and during emergency situation.
3. The apparatus as claimed in claim 1, wherein the pulverized solid fuel is
injected through primary pipe (4) into the furnace after the furnace wall
temperature reaches at least 500°C.
4. The apparatus as claimed claim 1, wherein the air required for complete
combustion of solid fuel is delivered through the secondary air duct (7) and
stage air duct (8).
5. The apparatus as claimed in claim 1, wherein the secondary air duct (7)
and stage air duct (8) are provided with the swirl blocks (9,10).
6. The apparatus as claimed in claim. 1, wherein during solid fuel firing a small
quantity of air is supplied through the guide pipe (2) to avoid any damage.
7. The low NOx wall burner apparatus according to claim 1, where the solid
fuel has turn down ratio of 1:4.
8. The apparatus as claimed in claim 1, wherein during the liquid fuel firing an
air stream is supplied through the pipes (4, 7, 8) for complete combustion.

9. The apparatus as claimed in claim 1, wherein the length, angle and number
of swirl blades for said swirl block (9) vary from 120 to 170 mm, 35-55° with
principle axis and 24 to 48 respectively.
10. The low NOx wall burner apparatus according to claim 1, length, angle and
number of swirl blades for swirl block (10) can be are vary from 120 to 170
mm, 30-50° with principle axis and 30 to 50 respectively.

11. The apparatus as claimed in claim 1, wherein the movement of a second
swirl block (10) for stage air can be adjusted along the principle axis of the
burner to attain optimum solid fuel combustion.
12. The apparatus as claimed in claim 1, comprising a flame igniter (14) and
plurality of flame scanners for liquid fuel (17) and solid fuels (18) which are
placed for flame ignition during start-up and flame monitoring respectively.
13. The apparatus as claimed in claim 1, wherein circumferential split vane
mechanism for controlling air flow is was used for secondary air flow duct
(6) and stage air duct (8).
14. The apparatus as claimed in claim.. 1, wherein the number of circumferential
split vanes (21, 22) for the secondary air flow duct (7) and stage the air duct
(8) respectively varies from 8 to 16.

15. The apparatus as claimed in claim 1, wherein the number of circumferential
split vanes (21, 22) are connected to a common lever towards burner front
and controlled by handles (19, 20) for secondary air flow and stage air flow.