Thermax Limited is an Indian company established in 1966 that provides sustainable energy and environmental solutions. It offers integrated solutions for heating, cooling, power, water, and air pollution control. The document focuses on Thermax's internally circulating fluidized bed circulating boiler (IR-CFBC) technology. The IR-CFBC uses a unique two-stage particle separation system and U-beam impact separators to efficiently separate solids from flue gas. This compact design results in lower maintenance costs compared to conventional circulating fluidized bed boilers. The IR-CFBC also has advantages like high combustion efficiency, low emissions, and improved performance during variable and low loads.

1. THERMAX LIMITED
OUR VISION
To be a globally respected, high-performance
organization offering sustainable solutions in
energy and environment.

2. Organization And Experience
Thermax Limited, established in the year 1966 is a leading company in energy and
environment management and is one of the few companies in the world that offers integrated,
innovative solutions in the areas of heating, cooling, power, water and waste management, air
pollution control and chemicals. The sustainable solutions that Thermax develops for clients
are environment-friendly and enable efficient deployment of energy and other natural
resources. Thermax is headquartered in Pune, India and has many Regional and Overseas
Sales and Service Offices.
Boiler & Heater Group
The Boiler & Heater Group (B&H) is the largest business divisions of Thermax corporate
engaged in the manufacture of high capacity Boilers and Fired Heaters.
Our organization has sound financial base and has capability of handling large complex
projects. We have a strong project management team which has access to the latest computer
aided project management techniques and has executed a number of large projects in
challenging time frames. We have successfully installed Integrated Planning System, which
utilizes the Primavera Software. Every Project Activity up to L3 level is monitored and
controlled. We have also installed BaaN LN system integrating the complete operations of the
company including Sales, Manufacturing, Project Management, Engineering, Procurement and
Field services.
Our engineering office is geared up to undertake process and detailed engineering of very
large size complex projects involving high pressure boilers, package boilers, etc. We also have
access to Babcock & Wilcox know-how through the manualized & well-documented Babcock &
Wilcox engineering practices. The engineering office has access to the latest computer
programs of Babcock & Wilcox. We have manufacturing facility in Pune and envisaging
continuous growth opportunity we have set up an additional manufacturing facility at Savli,
Dist. Vadodara in Gujarat state, India. We have a port assembly facility at Mundra where we
assemble large package boilers.
We are a licensee of Babcock & Wilcox Company, USA for IR-CFBC boilers design,
manufacturing and supply.

3. IR-CFBC BOILER
TECHNOLOGY OF CHOICE

4. FEATURES & ADVANTAGES OF THERMAX IR-CFBC BOILER
Compact, economical design and construction
Compared with hot cyclone-type CFBC designs, the IR-CFBC has significantly lower
furnace exit gas velocity and requires significantly less building volume. By relying on
internal recirculation, the IR-CFBC design eliminates J-valves, loop seals, high-
pressure blowers, and soot blowers, which are required with other CFBC designs.
Two stage separation for better bed inventory control
The unique IR-CFBC boiler design employs a patented two-stage particle separation
system to provide high-solids loading and a uniform furnace temperature profile. The
benefits of this technology include superior combustion efficiency, high operational
thermal efficiency, low emissions, low maintenance, low pressure drop, and high
turndown, resulting in improved overall plant performance. Our two-stage system
includes a primary U-beam impact separator and a secondary multi-cyclone dust
collector (MDC) which work together to provide a combined particle collection
efficiency in excess of 99.8%.
Impact separation with ‘U-beam’ particle separators
U-beams, a staggered array of stainless steel channels at
the furnace exit plane, capture nearly all of the solids
suspended in the flue gas leaving the furnace and
internally recirculate these solids to the lower furnace. U-
beam is Fit & Forget Technology does not require any
attention & maintenance.

5. Better performance in Varying & Low Load Condition
Effective Bed inventory & Temperature control through controlled solid recycle rate
from MDC to furnace allows better performance & operation of boiler during Varying
& Low Load Condition without affecting steam parameters
Higher Turn Down
Better Turn Down without Auxiliary fuel support (Turn Down of 1:4)
Less Start up & Shut down Time
Due to less Refractory heat retention in IR-CFBC is very low as compared to
CYCLONE Design, which allows Quick Start & Shut Down of the boiler.
Best in class compliance with environmental norms
Better Control on SOx & NOx emission levels through Limestone dosing and lower
operating temperatures (less than 900 Deg C) respectively.
Low auxiliary consumption
IR-CFBC design does not require increasing velocity of gasses leaving furnace as it
required in CYCLONE design to achieve solid separation using centrifugal action,
hence there is minimal pressure drop involved in IR-CFBC as compared to
CYCLONE design hence lower auxiliary consumption.
Higher availability & Lower maintenance
One goal of CFBC boiler manufacturers has been to eliminate thick, uncooled
refractory and hot expansion joints from their designs to reduce the expense and lost
time associated with refractory maintenance. This goal was achieved with the
development of the IR-CFBC boiler. The furnace, U-beam separator, and
superheater enclosures are constructed entirely of top-supported, gas-tight, all-
welded membraned tube walls which do not require hot expansion joints. The small
amount of refractory that is used in the IR-CFBC is applied to selected areas of the

6. water-cooled enclosure surface in a thin layer which is only 16 mm thick in the lower
furnace slightly thicker over the tube face elsewhere in the furnace. As a result, IR-
CFBC requires only 10 to 25% of the total refractory found in a hot cyclone CFBC
design and less than 50% of the refractory used in a water-cooled or steam cooled
cyclone CFBC unit. This construction has significantly reduced the need for refractory
maintenance in operating CFBC units.
No soot blowers
In IR-CFBC Solids recirculated to the furnace are at 300 Deg C also self abrasive
property of circulating bed material NO SOOT formation & uniform furnace
Temperature profile in IR-CFBC design. While in case of Hot Cyclone design solids
are recirculated to the furnace at 800 Deg C hence there are great chances of SOOT
formation & variations in bed temperatures in of Hot Cyclone design.
Multifuel firing capability
Fuels:
Coal, Lignite, Petroleum coke (petcoke), Sludge, Biomass, Agro-wastes, High–
sulphur coal, Washery rejects, Mill rejects, Char, Fly ash etc.
Operating Range
Capacity: Design pressure: Steam temperature:
Upto 1000 Tons/hr Upto 200 kg/cm2
(g) Upto 5600
C
i.e. 196 bar (g)

7. No Interface Erosion
The patented reduced diameter zone (RDZ)
tube section is another feature designed to
reduce maintenance. The RDZ consists of a
reduced diameter tube section mating to a
specially-shaped ceramic tile. The reduced
diameter tube section on each tube slopes
away from the solids falling down the wall.
This eliminates the solids material from
building up and eroding the furnace tubes
where the lower furnace refractory ends.
Low Flue Gas Velocities to Reduce Erosion
Erosion is a major cause of maintenance problems in CFBC boilers due to the high
solids loading in the flue gas. The severity of this erosion is exponentially related to
the velocity of the flue gas through the system. On hot cyclone CFBCs the particle
separator depends upon an extremely high flue gas velocity to provide the energy
needed to efficiently disengage the particles from the flue gas. By comparison, the U-
beam particle separator is designed to operate efficiently with much lower flue gas
velocity (5 TO 6 m/s) at full-load operating conditions. The particle capture efficiency
actually increases as the flue gas velocity through the U-beam separator decreases.
By operating at such a low gas velocity, the potential for erosion in the IR-CFBC is
significantly reduced. To date, because of proper material selection and low flue gas
velocities, the U-beam separators have not required any maintenance due to erosion
throughout years of operation at design load conditions.

8. PARAMETER IR-CFB (U- Beam)
Solid Separation System
Two Stage Solid Separation System-
• Low Velocity primary impact separators- U beams
• Multycyclone dust collector- Secondary separation system.
• Recycling finer particles increases Furnace heat transfer rate,
improves combustion efficiency and Limestone utilization
Furnace Temperature
Control
Desired Temperature can be maintained within +/- 15o
F interval
for wide range of fuels and operating conditions by adjusting
secondary recycle rate
Refractory:
Thickness, In (mm) Less Refractory 0.6-2.0 (15-20)
Covered Areas Lower furnace, U-beam zone enclosure walls
Hot-Temperature
Expansion Joints
Not required
J- Valve / L- Valve
Not required, hence associated chocking problems of Solid recycle
system are eliminated
Furnace Exit Velocity,
(m/s)
Low Velocity (6.4 – 9.8) means Less Upper Furnace Erosion & High
Reliability
High-Pressure Air Not required hence Roots blowers eliminated
Air cooled Bed Ash
coolers
No Auxiliary Equipment & Water required for Bed Ash coolers.
Soot Blowers Not Required
Start up time
Quick cold start up (~ 4 Hrs) on account of Less refractory, Hence
Better Ramp up Rate
Maintenance Cost
Practically No Maintenance required as less refractory, Stationary
Low Velocity Impact separators - Stainless steel U beams.
Controlled Solid Recycling
System
Controlled & Low temperature ash recycling system means better
bed temperature control & No secondary firing of solid in recycle
path hence eliminate possibility of clinkering & Chocking

9. General Description of THERMAX IR-CFBC Boiler
In the circulating fluidized bed boiler, a stream of
fine particles is repeatedly circulated through the
furnace. The circulating flow is called the
circulating bed.
The fuel is fed into front wall of the primary zone
which operates sub-stoichimetrically. The fuel is
fed by the drag chain feeders to the fuel feed
pipe from where it is pneumatically pushed into
the furnace, at the boiler front.
The circulating bed flow rate is such that a
relatively high solids loading is maintained above
the primary zone. At this loading, a phenomenon
called plasma flow occurs in which clusters of
solids form, flow downward against the flow of
the gas, and then disperse with the solids being
re-entrained to form clusters again. This plasma
flow and the high solid loading means that there
is a high rate of heat transfer between the
circulating bed and the furnace walls.
The flue gas, with the circulating bed entrained,
flows from the furnace to the U-beam separator
where the circulating bed material is removed
from the flue gas.
The hot particles in the gas first strike the first / second row of `U' beams placed at top of the
furnace just before furnace exit. Most of the particles after striking on `U' beams loose their
velocity and drop down straight into the furnace thus achieving internal re-circulation system.
Most of the particle re-circulation takes place by in first phase of internal re-circulation.
The particles escaped through first two rows of U- beams further go and strike the other
three rows of U beams placed in first convection pass of furnace at the top. The rear wall
membrane panel upcoming from bottom of the furnace is connected to rear wall top header.
A screen panel enclosing the 3 rows of U beams forms a cavity just below the 3 rows beam
section. The particles collected in that cavity flows back to furnace by gravity through the
openings provided in rear wall panel. Thus, achieving the second phase of internal re-
circulation.

10. Primary Zone
The B&W design IR-CFB Boiler incorporates a bottom section, or primary zone. This section,
which includes a common fluidized bed zone at the bottom of the furnace, is located below
the elevation of the secondary air ports. Primary air is introduced through bubble caps in the
water-cooled floor of the bottom section of the furnace.
This bottom section serves several purposes:
- The low fluidization velocity and the location of fuel introduction into the common
area of the bed result in increased particle residence time, providing good mixing at all
loads.
- Furnace bed temperature can be maintained essentially constant over the entire load
range. This results in optimum temperatures for combustion and emissions reduction
even at low loads.
- The shape of the primary zone, together with the introduction of fuel and re-injected
material in this zone, promotes the necessary lateral as well as vertical mixing in the
bed at all times.
Steam Generator
The CFB boiler is arranged with a single furnace shaft. The enclosure surface of the
furnace, particle separator and super-heater enclosure pass is made up of water-cooled
membrane tubes. Super-heater and economizer surfaces are located in the convection
pass.
Air Flow
A tubular air heater heats air from the PA & SA fan separately.
The primary air (PA fan) is directed to a wind-box at the bottom of the furnace. Two air
connections are provided in the wind box to distribute the air with common control damper.
The secondary air from the tubular air heater flows to the distributing nozzles located at two
levels across the width of the furnace above the primary zone on both the front wall and rear
wall. Dampers are supplied to vary the proportions of the secondary air to the front and rear
distributing nozzles.
The primary air is introduced into the bottom of the furnace through bubble caps. The
secondary air is introduced into the furnace through nozzles penetrating the membrane
walls.

11. Gas Flow and Solids Flow
The flue gas generated plus entrained solids pass from the furnace to the U-beam
separators. Nearly all the entrained solids are collected in the U-beam separator and fall
back into the furnace. The flue gases continue through the convention pass, air heater, ESP
and ID fan. Solids collected in the hopper below MDC are re-injected into the furnace to
further enhance combustion efficiency.
The Hot Particle capture in MDC and External Re-circulation System:
The particles escaped from the series of
U beams travels with flue gas pass
through MDC, through the plain tube
inline economizer and multi-tubular air
heater tubes, takes a turn to reach inlet
of ESP. A hopper provided at the bottom
of APH collects some amount of
particles.
Mechanical dust collector (MDC) is
located down stream of economizer. Fly
ash particles collected in the MDC will be
conveyed to the furnace through air
slides for better control of furnace
temperature profile.
A Fuel and sorbent solids entering the furnace
B Upward solids flow
C Solids reflected by roof
D In-furnace U-Beam recycles
E External U-Beam recycles
F Multicyclone recycles
G Solids not captured by multicyclone
H Bed drain

12. Water and Steam Flow
Feed water enters the unit at the economizer inlet, flows through the economizer banks in
the convection pass to the outlet headers and then to the feed water inlet connection in the
drum.
Water is then withdrawn from the drum through supplies to feed the enclosure walls and
division wall. Steam water mixtures from the various circuits flow through heaters and riser
tubes to the drum. Good circulation is maintained at all loads.
BOILER PRESSURE PARTS:
1. DRUM:
The drum will be manufactured in
accordance with the Indian Boiler
Regulations. The drum will be radio
graphed, stress relieved and
hydrostatically tested. Each drum will
be equipped with manholes and
gaskets. A continuous blow down
connection with an internal pipe is
provided on the steam drum for
continuously removing solids during
the operation. Nozzles for safety valves, air vent, water level gauges, pressure
gauges, are provided.
For removing moisture, steam drum is equipped with drum internals like girth baffle,
cyclone type primary separators and secondary scrubbers. For uniform distribution,
perforated feed water pipe, and continuous blow down pipe are provided. The boiler
offered is top supported.
2. FURNACE:
The boiler furnace is in machine welded membrane wall construction. The furnace
tubes will be manipulated from carbon steel tubes. The furnace side wall tubes are
suitably bent for providing the spreaders, peepholes, access doors, and will be
welded at top and bottom to respective side wall top and bottom headers. The roof
tubes will be suitably staggered to allow super heater coils to pass through. The
headers shall be manufactured from seamless pipes. The headers shall be provided
with drain connections, air vent connection and hand holes for inspection as required.
3. FURNACE DIVISION WALLS:
Inside the furnace water cooled division wall is provided.

13. 4. ECONOMISER:
The economizer shall be bare tube continuous inline type with inlet and outlet
headers, enclosed second pass.
Necessary drains, vents, temperature, pressure gauges, etc. shall be furnished as
per Indian Boiler Regulation requirement.
5. SUPERHEATER:
The super heaters are provided in two sections i.e. primary & secondary. The super
heater assembly is designed to raise the steam temperature as specified. The main
outlet is from secondary super heater.
6. ATTEMPERATOR:
Spray type interstage attemperator is provided. The final steam temperature shall be
maintained within ±5°C over specified load range on both the conditions.
7. RISERS & DOWNCOMERS:
Generously sized riser and
feeder pipes are provided to ensure
positive circulation at all loads.
8. DRAFT SYSTEM:
The boiler is designed for balanced draft operation and adequately rated ID and PA
fans are provided. The boiler is equipped with ID fan and PA fan along with
necessary interconnecting air and gas ducting, dampers etc.

14. The ID fan shall be of heavy duty construction radial tip / back ward curved
construction, self aligning spherical roller bearings, inspection door, drain, inlet box
and guard. The impeller is provided with tip liners and dynamically balanced. The ID
fans shall be with multi louver damper control. The rpm of ID fan shall be less than
1000.
The PA fan is centrifugal type with suitably sized impeller. The fan impeller shall be
dynamically balanced and is complete with inspection door, foundation bolts and
guard. The PA fan shall be provided with silencer to meet the noise level. The RPM of
PA fan shall be 1500 rpm. The control damper shall be pneumatically operated.
Secondary air fan shall also be provided for over fire air arrangement. PA, ID & SA
fan shall be directly coupled to Motors.
9. AIR PRE- HEATER:
A tubular air pre heater is provided as the last stage of heat recovery unit. The shell
and tube side fluid shall be combustion air and flue gas respectively. The air pre
heater tubes shall be fitted into the tube sheets on both sides. Entire air Pre-heater
shall be supported in a structural steel frame and enclosed within welded steel
casing.
10. STRUCTURAL STEEL:
Steelwork will be provided to support of the boiler & auxiliaries. The supporting steel
structural will be fabricated from rolled steel section / plate section along with suitable
galleries, staircases, ladders and platforms.
11. DUCTING:
All air and flue gas ducting within terminal points shall be provided complete with
stiffeners, dampers, expansion joints and supports as required. The air ducting and
flue gas ducting shall be fabricated from MS plates.
12. BOILER SETTING:
Boiler setting materials shall be furnished as follows:
o Standard refractory bricks/tiles, castable refractory as required to suit the boiler
temperature.
o Mineral wool insulation for boiler, hot ducts, hot lines, economizer, all piping in TL
scope of supply etc.
o 0.5 mm aluminium sheeting for the main boiler block, economizer, and APH etc.

15. 13. HOPPERS:
Bottom drum, economizer, air pre heater hoppers shall be furnished. The hoppers
with valley angle of 55 - 60° shall be constructed of MS plate suitably stiffened as
required. The vertical free elevation of flange bottom all hoppers shall be as listed in
scope of supply description.
14. FUEL FEEDING & FIRING SYSTEM
Boiler is equipped with the fluid bed combustor with feed technique consisting of:
OVER BED FEEDING:
Fuel bunker along with surge hopper above drag chain feeders shall be provided.
VFD driven Drag chain feeders are provided below the surge hopper. These feeders
will finally discharge the fuel through chutes to the furnace.
BOILER TURNDOWN:
Boiler turn down shall be achieved by varying the fuel feed rate and adjusting the
furnace inventory levels.
FLUIDISING NOZZLE:
The design of air and fuel nozzles shall prevent
in-bed spouts/eruptions, which may impinge on
in-bed tubes and erode the same. Besides, the
nozzle design shall permit effective fluidization at
lower loads with shutting down of some
compartments. Fluidizing nozzles shall have
suitably sized stem portion extending from the
bed plate to the furnace side and shall be fitted
with bubble caps of stainless steel material to
facilitate uniform distribution of air and fuel.
15. SECONDARY AIR SYSTEM
High-pressure secondary over fire air tapped from SA fan discharge is injected into
the furnace through heat resistant nozzles mounted on the front and rear walls. The
system is complete with ducting and manually operated air control dampers.

16. 16. FLUID BED COMBUSTOR
Water -cooled distributor plate fluid bed combustor with SS bubble cap fluidizing
nozzles.
Drain pipes shall periodically remove the ash / stones collected. Drain pipes shall be
provided, with ash cooler system. The outlet of flue gas from the ash cooler is
connected to APH hopper.
IR – CFBC Boiler