ME_63-_ENERGY_AUDIT_OF_APH

ENERGY AUDIT OF AIR PRE-HEATER UNIT AT
WANAKBORI THERMAL POWER STATION
A PROJECT REPORT
Submitted by
AKASH BHAVSAR (110370119109)
HAMZA DHILAWALA (110370119101)
DIPESH BADGUJAR (110370119102)
KARTIK YADAV (110370119155)
In part fulfillment for the award of the degree
Of
BACHELOR OF ENGINEERING
In
Mechanical Engineering Department
Parul Institute of Engineering & Technology
P.O. Limda, Ta. Waghodia,
Dist.Vadodara-391760,
Gujarat, India.
Gujarat Technological University, Ahmadabad
APRIL 2015

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CERTIFICATE
Date: / /
This is to certify that the dissertation entitled “ENERGY AUDIT OF AIR
PRE-HEATER UNIT AT WNAKBORI THERMAL POWER STATION”
has been carried out by
AKASH BHAVSAR (110370119109)
HAMZA DHILAWALA (110370119101)
DIPESH BADGUJAR (110370119102)
KARTIK YADAV (110370119155)
Under my guidance in partial fulfillment for the degree of Bachelor of
Engineering in Mechanical (Final Year) of Gujarat Technological University,
Ahmadabad during the academic year 2014-15.
Prof. Deman Sahu
Project Guide (Internal)
Prof. N. H. Gandhi Mr. Dinker M. Jethva
Project Head Exe. Engr. Training Dept.
WTPS, GSECL.
Prof. Sohail M. Siddiqi
Head of the Department,
Department of Mechanical Engineering
External Examiner

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ACKNOWLEDGEMENT
We have taken efforts in this project. However, it would not have been possible
without the kind support and help of many individuals and organizations. We would like to
extend our sincere thanks to all of them.
With immense pleasure we express our deep and sincere gratitude, regards and
thanks to our project guide Asst. Prof. Deman Sahu for his excellent guidance,
invaluable suggestions and continuous encouragement at all the stages of our project
work. His wide knowledge and logical way of thinking have been of great value for us. As
a guide he has a great influence on us, both as a person and as a professional.
We wish to express our warm and sincere thanks to Prof. Sohail M. Siddiqi
(Head of Department of Mechanical Engineering, PIET) and Prof. Nirav H. Gandhi
(Project Head) for his support & the facilities provided by him in college.
We would like to express my special gratitude and thanks to our industrial guide
Mr. D. M. Jethva & Mr. Hitesh Nylani for giving us such attention and time for the
project work.
At last, we cannot forget our family members supporting us spiritually throughout
our life and our friends without whom it was really not possible for us to do this
dissertation. Finally, thank you to Parul Institute and all the other people who have
supported us during the course of this work.

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ABSTRACT
Air pre-heater is a heat transfer surface in which air temperature is
raised by transferring heat from other media such as flue gas .Hot air is
necessary for rapid combustion in the furnace and also for drying coal in
milling plants. So an essential boiler accessory which serves this purpose is
air pre-heater. The air pre-heater are not essential for operation of steam
generator, but they are used where a study of cost indicates that money can
be saved or efficient combustion can be obtained by their use. The decision
for its adoption can be made when the financial advantages is weighed
against the capital cost of heater in the project work we have taken up the
operation and performance analysis of Air pre-heater of 210 MW power
generation unitat WANAKBORITHERMAL POWER STATION, GUJARAT.
In analysis of performance preventive measures for corrosion of heating
elements has been studied, and also air heater leakage, corrected gas outlet
temperature and finally gas efficiency has been calculated.

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TABLE OF CONTENTS
CERTIFICATE......................................................................................................................1
AKNOWLEDGEMENT........................................................................................................2
ABSTRACT ..........................................................................................................................3
TABLE OF CONTENT.........................................................................................................4
1. INTRODUCTION.................................................................................................... 6
1.1 ENERGY SCENARIO ....................................................................................... 6
1.1.1 POWER CAPACITY IN INDIA......................................................... 7
1.1.2 TOTAL INSTALLED CAPACITY .................................................... 7
1.2 CONVENTIONAL ENERGY SOURCES......................................................... 8
1.2.1 RENEWABLE POWER...................................................................... 8
1.2.2 OFF-GRID RENEWABLE POWER PROGRAMME ....................... 9
1.3 ENERGY AUDIT - A TOOL........................................................................... 11
1.3.1 DEFINITION & OBJECTIVES OF ENERGY MANAGEMENT....11
1.3.2 ENERGY AUDIT: TYPES AND METHODOLOGY.......................12
1.3.2.1 NEED FOR ENERGY AUDIT ...........................................13
1.3.2.2 TYPE OF ENERGY AUDIT...............................................13
2. LITERATURE REVIEW................................................................................... 19
3. PROJECT WORK................................................................................................ 22
3.1 INTRODUCTION TO WTPS ......................................................................... 22
3.2 LAY-OUT OF COAL FIRED POWER PLANT ............................................ 22
3.3 AIR PRE-HEATER ......................................................................................... 23
3.3.1 NEED OF AIR PRE-HEATER ......................................................... 23
3.3.2 AIR PRE-HEATER AT WTPS......................................................... 24
3.3.3 MAIN COMPONENTS OF RAPH................................................... 25
3.4 AIR PRE-HEATER AUDIT............................................................................ 26
3.4.1 INTRODUCTION ............................................................................. 26
3.4.2 OBJECTIVE OF AUDIT .................................................................. 27

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3.4.3 PARAMETERS REQUIRED FOR ANALYSIS .............................. 28
3.5 TEST PROCEDURE ....................................................................................... 28
3.5.1 UNIT OPERATION .......................................................................... 28
3.5.2 TEST DURATION............................................................................ 29
3.5.3 MEASUREMENT LOCATIONS ..................................................... 29
3.5.3.1 TRAVERSE LOCATION- GAS SIDE.............................. 30
3.5.3.2 TRAVERSE LOCATIONS- AIR SIDE............................. 30
3.5.3.3 PORTS AND PROBS......................................................... 31
3.5.4 DATA COLLECTION PROCEDURE ............................................. 32
3.5.4.1 CONTROL ROOM DATA ................................................ 32
3.5.4.2 FLUE GAS & AIR TEMPERATURE ............................... 32
3.5.4.3 FLUE GAS COMPOSITION ............................................. 33
3.5.4.4 SPECIAL TEST INSTRUMENTS..................................... 34
3.6 ANALYSIS AND DATA COLLECTION...................................................... 34
3.6.1 MEASUREMENT OF FLUE GAS O2 ............................................. 35
3.6.2 APH PERFORMANCE INDICES COMPUTATION...................... 36
3.7 MEASUREMENT TABLES (BEFORE)........................................................ 38
3.8 CALCULATIONS (BEFORE)........................................................................ 39
3.9 AREAS TO BE CONSIDERED FOR IMPROVEMENT ............................... 41
3.10 STEPS TAKEN FOR IMPROVEMENT OF APH PERFORMANCE ......... 44
3.11 MEASUREMENT TABLES (AFTER) ........................................................ 45
3.12 CALCULATIONS (AFTER) ........................................................................ 46
3.13 COMPARISON OF PARAMETERS............................................................ 48
3.14 CONCLUSION OF AUDIT .......................................................................... 49
REFERENCES .................................................................................................................. 50

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1. INTRODUCTION
1.1 ENERGY SCENARIO
About 70% energy generation capacity is from fossil fuels in India.
Coal consumption is 40% of India's total energy consumption which is
followed by crude oil and natural gas at 24% and 6% respectively. India is
dependent on fossil fuel import to fulfill its energy demands. The energy
imports are expected to exceed 53% of the India's total energy consumption.
In 2009-10, 159.26 million tones of the crude oil was imported which
amounts to 80% of its domestic crude oil consumption. The percentage of oil
imports is 31% of the country's total imports. The demand of electricity has
been hindered by domestic coal shortages. Cause of this, India's coal imports
is increased by 18% for electricity generation in 2010.
India has one of the world's fastest growing energy markets due to
rapid economic expansion. It is expected to be the second largest contributor
to the increase in global energy demand by 2035. Energy demand of India is
increasing but has limited domestic fossil fuel reserves. The country has
ambitious plans to expand its renewable energy resources and plans to install
the nuclear power industries. India has the world's fifth largest wind power
market and plans to add about 20GW of solar power capacity. India increases
the contribution of nuclear power to overall electricity generation capacity
from 4.2% to 9%. The country has five nuclear reactors under construction.
Now, India has became third highest in the world who is generating the
electricity by nuclear and plans to construct 18 additional nuclear reactors by
2025, then India will become second highest in the world.

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1.1.1 Power Capacity in India
The energy generated by different resources in the given table. This
table also shows the growth of installed power capacity in India.
Thermal (%) Hydro (%) Nuclear (%) Renewable
Time period (MW) (>25MW) (MW) Power (%)
(MW
1.4.2002 70.85% 25% 2.59% 1.55%
74429 26269 2720 1628
1.4.2007 64.06% 25.51% 2.87% 7.55%
87015 34654 3900 10258
31.9.2010 63.95% 22.41% 2.7% 10.90%
106518 37328 4560 18,155
Table 1.1: Growth of Installed Power Capacity in India
(Source: Ministry of New and Renewable Energy, Government of India)
1.1.2 Total Installed Capacity (October 2012)
The installed capacity with respect of various resources is as on
30.06.2012 from the Ministry of Renewable Energy. Note: The Hydro
generating stations with installed capacity less than or equal to 25 MW are
indicated under RES.
Source TotalCapacity(MW) Percentage
Coal 120,103.38 57.38
Hydroelectricity 39,291.40 18.77
Renewable energy source 24,998.46 11.94
Gas 18,903.05 9.03
Nuclear 4780 2.28
Oil 1,199.75 0.57
Total 2,09,276.04
Table 1.2: Installed capacity in respect of various resources
(Source: Ministry of Renewable Energy, Government of India)

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Sector TotalCapacity(MW) Percentage
State Sector 86,881.40 41.51
Central Sector 62,373.63 29.66
Private Sector 60,321.28 28.82
Total 2,09,276.04
Table 1.3: Sector wise Generation Total Capacity
(Source: Ministry of Renewable Energy Government of India)
1.2 Conventional Energy Sources
India is not endowed with large primary energy reserves in keeping with
large geographical growing population which increase final energy indeed.
Region Target MU Generation* Deviation (+/-)
MU MU (%)
Northern 51044.00 55839.79 (+)4795.79 (+)9.40
Western 14193.00 15041.53 (+)848.53 (+)5.98
Southern 31882.00 30518.04 (-)1363.96 (-)4.28
Eastern 9988.00 8991.10 (-)996.90 (-)9.98
N-Eastern 4245.00 3905.33 (-)339.67 (-)8.00
All India 111352.00 114295.79 (+)2443.79 (+)2.64
Table 1.4: Region Wise Energy generation in India
Source: Central Electricity Authority (CEA)
Energy audit throughout the India indicates that coal is the main energy
resource of the country. The coal contribution is 70% of the total energy
production. The region wise energy generation is indicated in table. The
generation is compared with initiative target in the given table.
1.2.1 Renewable Power
The Government has been promoting private investment for the setting up
of projects for power generation from renewable energy sources and special
tariffs being provided at the State level.

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Resource Potential Up to Plan Plan Plan Cumulative 12th
(MW) 9th Up to Up to Target Achievement Plan
10th 11th Up to Projection
30.09.10 (2017)
Wind
Power 48,500 1667 5,427 9,000 4,714 12,809 27300
Small
Hydro 15,000 1,438 538 1,400 759 2,823 5000
Power
Bio
Power* 23,700 390 795 1,780 1,079 2,505 5100
Solar 20-30
Power MW/sq 2 1 50 8 18 4000
km
Total l3,497 6,761 12,230 6,560 18,155 41,400
Table 1.5: Share of Different Renewable Sources in India
(Source: Ministry of New and Renewable Energy, Government)
These include capital subsidies, accelerated depreciation and customs
duties. The capital subsidy being provided depends on region and the
renewable resources. The capital subsidies vary from 10% to 90% of
project cost. The higher level of capital subsidies are given for projects in
the North-Eastern Region or Special category States. Generation Based
incentives have been introduced recently for Wind Power to attract private
investment by Independent Power Producers. They are not availing
Accelerated Depreciation benefit and feed in tariffs for solar power.
1.2.2 Off-Grid Renewable Power Programs
Most importantly, it provides energy access to large rural populations in
which includes those in unreachable areas. Those meet the un-obtained
demand in many other areas.

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S.No. Resource/System Achievement up to
30.09.2010
1. Biomass Power 263.1 MW
2. Biomass Gasifier 128.2 MWeq
3. Waste to Energy 60.8 MWeq
4. Solar PV Power Plants 2.9MWp
5. Hybrid Systems 1.1 MWp
6. Family type Biogas Plants 4.27 million
7. SPV Home Lighting system 6,19,428 nos.
8. Solar lantern 8,13,380 nos.
9. SPV Street Lighting System 1,21,227 nos.
10. SPV Pumps 7,495 nos.
11. Solar Water Heating - Collector Area 3.77 million sq m
Table 1.6: Achievement in Off Grid Power System
(Source: Ministry of New and Renewable Energy, Government of India)
Perhaps the outmost areas can get electricity only through renewable
sources. Secondly, very important, unrecognized consequence attributed to
off-grid applications. In this way or other, they replace fossil fuels. These
can make a significant contribution to reduction in their consumption which
is most important from the point of view of energy security. For instance,
solar PV replaces diesel or furnace oil in various areas, rural lighting
replaces kerosene, a biogas plant or solar cooking system replace cooking
gas. Renewable energy can also meet the requirement of process heat in
small enterprises and replace small diesel generator sets which consume
diesel oil. It has a giant strength in its ability to supply power in a
decentralized and distributed mode which has the advantage of
consumption at the production point and reduces land and environmental
concerns.

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1.3 To increase the Efficiency of the Power System: Energy
Audit a Tool
Energy audit is a powerful tool for exposure operational and equipment
improvements that will reduce energy costs, lead to higher performance and
save energy. Sometimes, the energy audit is also called an “energy
assessment” or “energy study”. Energy audits can be done as a stand-alone
effort but may be conducted as part of a larger analysis across an owner’s
entire group. The purpose of an energy audit is to find out how, when, where
and why energy is used. The energy audit is also used to identify
opportunities in improving the efficiency. Energy auditing services are
offered by engineering firms, energy services companies and energy
consultants. The energy auditors do the audit process.
The first thing energy auditor needs to be aware of end user
expectations and then audit starts with an analysis of historical and current
utility data. This sets the stage for an onsite inspection. The most important
outcome of an energy audit is a list of recommended energy efficiency
measures (EEMs). Energy audit serves the purpose of identifying energy
usage within a facility, process or equipment, and then identifies
opportunities for conservation, called energy conservation measures (ECMs).
Audit provides the most accurate picture of energy savings opportunities.
Energy audits can be targeted to specific systems i.e. boiler, turbine, generator
and any motor etc.
1.3.1 Definition & Objectives of Energy Management
The fundamental goal of energy management is to produce goods and
provide services with the least cost and least environmental effect. The term
energy management means many things to many people. One definition of
energy
management is:

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"The judicious and effective use of energy to maximize profits (minimize
costs) and enhance competitive positions"
(Cape Hart, Turner and Kennedy, Guide to Energy Management Fairmont
press inc. 1997)
Another comprehensive definition is:
"The strategy of adjusting and optimizing energy, using systems and
procedures so as to reduce energy requirements per unit of output while
holding constant or reducing total costs of producing the output from these
systems"
The objective of Energy Management is to achieve and maintain optimum
energy procurement and utilisation, throughout the organization and:
• To minimise energy costs / waste without affecting production & quality
• To minimise environmental effects.
1.3.2 Energy Audit: Types And Methodology
Energy Audit is the key to a systematic approach for decision-making in
the area of energy management.It attempts to balance the total energy inputs
with its use, and serves to identify all the energy streams in a facility. It
quantifies energy usage according to its discrete functions. Industrial energy
audit is an effective tool in defining and pursuing comprehensive energy
management programme.
As per the Energy Conservation Act, 2001, Energy Audit is defined as "the
verification, monitoring and analysis of use of energy including submission of
technical report containing recommendations for improving energy efficiency
with cost benefit analysis and an action plan to reduce energy consumption".

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1.3.2.1 Need for Energy Audit
In any industry, the three top operating expenses are often found to be
energy (both electrical and thermal), labour and materials. If one were to
relate to the manageability of the cost or potential cost savings in each of the
above components, energy would invariably emerge as a top ranker, and thus
energy management function constitutes a strategic area for cost reduction.
Energy Audit will help to understand more about the way energy and fuel are
used in any industry, and helpful in identifying the areas where waste can
occur and where scope for improvement exists.
The Energy Audit would give a positive orientation to the energy cost
reduction, preventive maintenance and quality control programmes which are
vital for production and utility activities. Such an audit programme will help
to keep focus on variations which occur in the energy costs, availability and
reliability of supply of energy, decide on appropriate energy mix, identify
energy conservation technologies, retrofit for energy conservation equipment
etc.
In general, Energy Audit is the translation of conservation ideas into
realities, by lending technically feasible solutions with economic and other
organizational considerations within a specified time frame.
The primary objective of Energy Audit is to determine ways to reduce
energy consumption per unit of product output or to lower operating costs.
Energy Audit provides a "Bench-mark" (Reference point) for managing
energy in the organization and also provides the basis for planning a more
effective use of energy throughout the organization.
1.3.2.2 Type of Energy Audit
The type of Energy Audit to be performed depends on:
- Function and type of industry

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- Depth to which final audit is needed, and
- Potential and magnitude of cost reduction desired
Thus Energy Audit can be classified into the following two types.
i) Preliminary Audit
ii) Detailed Audit
1.3.2.3 Preliminary Energy Audit Methodology
Preliminary energy audit is relatively quick exercise to:
• Establish energy consumption in the organization
• Estimate the scope for saving
• Identify the most likely and the easiest areas for attention
• Identify immediate (especially no-/low-cost) improvements/ savings
• Set a 'reference point'
• Identify areas for more detailed study/measurement
• Preliminary energy audit uses existing, or easily obtained data
1.3.2.4 Detailed Energy Audit Methodology
A comprehensive audit provides a detailed energy project implementation
plan for a facility; since it evaluates all the major energy using systems. This
type of audit offers the most accurate estimate of energy savings and cost. It
considers the interactive effects of all projects, accounts for the energy use of
all major equipment, and includes detailed energy cost saving calculations
and project cost.
In a comprehensive audit, one of the key elements is the energy balance.
This is based on an inventory of energy using systems, assumptions of current
operating conditions and calculations of energy use. This estimated use is
then compared to the utility bill charges.

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Detailed energy auditing is carried out in three phases: Phase I, II and III.
Phase I - Pre-Audit Phase
Phase II - Audit Phase
Phase III - Post Audit Phase
A Guide for Conducting Energy Audit at a Glance
Industry-to-industry, the methodology of Energy Audits needs to be
flexible. A comprehensive ten-step methodology for conduct of Energy Audit
at field level is presented below. Energy Manager and Energy Auditor may
follow these steps to start with and add/change as per their needs and industry
types.
Ten Steps Methodology for Detailed Energy Audit
Phase-I: Pre-Audit Phase
Step 1: Walk through audit
Step 2: Conduct brief meeting with all divisional heads
Phase-II: Audit phase
Step 3: Primary data gathering
Step 4: Conduct survey and monitoring
Step 5: Conduct detailed trial/experiments
Step 6: Analysis of energy use
Step 7: Identification and development of Energy Conservation Opportunity
Step 8: Cost benefit analysis
Step 9: Reporting and presentation to top management
Phase-III: Post Audit phase
Step 10: Implementation and follow-up

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Phase I -Pre Audit Phase Activities
A structured methodology to carry out an energy audit is necessary for
efficient working. An initial study of the site should always be carried out, as
the planning of the procedures necessary for an audit is most important.
Initial Site Visit and Preparation Required for Detailed Auditing
An initial site visit may take one day and gives the Energy
Auditor/Engineer an opportunity to meet the personnel concerned, to
familiarize him with the site and to assess the procedures necessary to carry
out the energy audit.
During the initial site visit the Energy Auditor/Engineer should carry out the
following actions: -
• Discuss with the site's senior management for the aims of the energy audit.
• Discuss economic guidelines associated with the recommendations of the
audit.
• Analyse the major energy consumption data with the relevant personnel.
• Obtain site drawings where available - building layout, steam distribution,
compressed air distribution, electricity distribution, etc.
• Tour the site accompanied by engineering/production
The main aims of this visit are:
• To finalise Energy Audit team
• To identify the main energy consuming areas/plant items to be surveyed
during the audit.
• To identify any existing instrumentation/ additional metering required.
• To decide whether any meters will have to be installed prior to the audit eg.
KWh, steam, oil or gas meters.
• To identify the instrumentation required for carrying out the audit.
• To plan with time frame

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• To collect macro data on plant energy resources and major energy
consuming centres
• To create awareness through meetings/ programmes
Phase II- Detailed Energy Audit Activities
Depending on the nature and complexity of the site, a comprehensive audit
can take from several weeks to several months to complete. Detailed studies
to establish, and investigate, energy and material balances for specific plant
departments or items of process equipment are carried out. Whenever
possible, checks of plant operations are carried out over extended periods of
time, at nights and at weekends as well as during normal daytime working
hours, to ensure that nothing is overlooked. The audit report will include a
description of energy inputs and product outputs by major department or by
major processing function, and will evaluate the efficiency of each step of the
manufacturing process. Means of improving these efficiencies will be listed,
and at least a preliminary assessment of the cost of the improvements will be
made to indicate the expected payback on any capital investment needed. The
audit report should conclude with specific recommendations for detailed
engineering studies and feasibility analyses, which must then be performed to
justify the implementation of those conservation measures that require
investments.
The information to be collected during the detailed audit includes:
1. Energy consumption by type of energy, by department, by major items of
process equipment, by end-use
2. Material balance data (raw materials, intermediate and final products,
recycled materials, use of scrap or waste products, production of by-products
for re-use in other industries, etc.)
3. Energy cost and tariff data
4. Process and material flow diagrams

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5. Generation and distribution of site services (eg. Compressed air, steam).
6. Sources of energy supply (e.g. electricity from the grid or self-generation)
7. Potential for fuel substitution, process modifications and the use of co-
generation systems (combined heat and power generation).
8. Energy Management procedures and energy awareness training programs
within the establishment.
Phase III :Report Preparation
Prepare Audit Report: Go over the results of findings and recommendations
in a final report. The report should include a description of the facilities and
their operation. It should also include a debate of all major energy-consuming
systems and an explanation of all recommended ECMs with their specific
energy impact implementation costs and benefits.
Present and Review Report with Facility Management: Clarify the process
and all activities performed to confirm the report’s conclusion. Provide
economic results as a formal presentation of the final recommendations.
Explain the data on the benefits and costs which make a decision or set
priorities on implementation of ECMs.
After the audit: Read the report and understand the contents and give the
prioritize improvements according to choice i.e. Energy reduction, Cost, Need
(equipment failure) etc.

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2. LITERATURE REVIEW
Title of Invention: Quad sectorregenerative air preheater for circulating
fluidized bed combustion boiler
Date of Filing/Application: 07/07/2008
Name of Applicant/Assignee: Bharat Heavy Electricals Limited (Ind)
Summary of Invention: Quad sector Air preheater consists of one gas sector,
first secondary sector, one primary sector and second secondary sector
compartmented by sector plates and the rotor is driven by the rotor drive and
is surrounded by the rotor housing and constructed between the cold end
connecting plate at one end and hot end connecting plate at other end. The
rotor is supported by the support bearing at the bottom and guide bearing at
the top. The cylindrical rotor revolves at a very low speed and the plates are
alternatively, exposed to the gas and air flows. In the Quad sector Air
preheater design, the primary air sector is sandwiched on either side by
secondary air sectors (i.e. one gas sector, first secondary sector, one primary
sector and second secondary sector in that order) which helps minimizing the
air leakage to the gas side.
Title of Invention: Regenerative Air Preheater Design To Reduce Cold
End Fouling
Application No.: 1638/DEL/2011
Name of Inventor: 1)BIRMINGHAM JAMES WILLIAM (US)
2)SEEBALD JAMES DAVID (US)
Summary of Invention: The invention in a preferred form is an air preheater
that is more resistant to 'fouling' under varying boiler loads. It is an object of
the invention to provide an air preheater that is more resistant to corrosion. It
is an object of the invention to provide an air preheater that adjusts to varying

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boiler loads. It is an object of the invention to provide an air preheater that
adjusts flue gas velocity under varying boiler loads.
Title of Invention: An improved sealing system for rotary regenerative
air preheater to reduce leakage of high pressure air stream to low
pressure gas stream.
Application No.:1316/KOL/2007
Name of Inventor: 1 Shri Krishnamurthy Narayanan (Ind)
2 Shri Ganapathy Ramamurthy Venkataraman (Ind)
Summary of Invention: Accordingly there is provided an improved air
preheater sealing system which reduces the leakage of high pressure air
stream to low pressure gas stream. In the present invention, the diaphragm
plate is split into a top diaphragm plate and a bottom diaphragm plate and a
first component of the improved sealing system is mounted in between the
top and bottom diaphragm plates radial to the rotor post in addition to the
existing radial seal fixed above the diaphragm plate. Similarly, a second
component of the improved sealing system is mounted between the top
diaphragm and bottom diaphragm plates axial to the rotor post in addition to
the existing axial seal fixed on the diaphragm plate. During operation of the
Air preheater, the rotor gets turn down causing an increase in the gap between
the top diaphragm and the bottom diaphragm plates. Because of the provision
of the web seals, according to the invention, no passage is available for
leakage of the high pressure air stream to the low pressure gas stream and
thus the leakage is reduced. The inventive concept resides in configurating
the diaphragm plates as 'the splitting diaphragm plates' for example, the top
and bottom diaphragm plates and mounting the web seals between the top and
bottom diaphragm plates. Accordingly, the web seals function as a sealing
means for the gap between the top and bottom diaphragm plates during
operation of the Air preheater and thereby leakage of high pressure air stream
to low pressure gas stream is reduced considerably.

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Title of Invention: Air preheater adjustable basket sealing system
Publication Number: US5836378 (A)
Name of Inventor: MARK E BROPHY (US)
HARLAN E FINNEMORE (US)
Summary of Invention: The present invention provides an arrangement of
means in an air preheater for sealing gaps around the baskets at the periphery
of the rotor, thereby eliminating flow paths that would allow portions of the
air and gas stream to bypass the heat transfer surface. More particularly, the
present invention provides a circumferential sealing system for sealing gaps
between the heat exchange baskets and the rotor shell portions. The present
invention also provides means in an air preheater to minimize the size of the
peripheral seal structure, effectively reducing the weight of the rotor. The
present invention further eliminates the cold-end covers and attachment
studding, thereby reducing the cost of manufacture.
Title of Invention: Adjustable axial sealing plate for rotary regenerative
air preheater
Name of Applicant: ABB AIR PREHEATER, INC (US)
Summary of Invention: The present invention provides an arrangement of
means in an air preheater for mounting and adjusting axial seal plates using a
reduced number of adjustable mountings and replacing the remaining
adjustable mountings with adjustable compression stops which engage but are
not attached to the axial seal plates. This reduces cost and facilitates
installation.

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3. PROJECT WORK
3.1 INTRODUCTION TO WTPS
 Wanakbori Thermal Power Station (WTPS)of Gujarat State Electricity
Corporation Ltd. (GSECL) is located at about 7 km away from Sevalia
Railway station on board gauge Anand-Godhra railway line and 13 km
away from Balasinor and on the bank of river Mahi in Kheda district of
Gujarat.
 Total installed capacity of Wanakbori TPS is 7x210MW= 1470 MW.
The capacity and commissioning date of all the units are given below:
3.2 GENERAL LAYOUT OF COAL FIRED POWER PLANT

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3.3 AIR PRE-HEATER
An air preheater (APH) is a general term used to describe any device
designed to heat air before another process (for example, combustion in a
boiler) with the primary objective of increasing the thermal efficiency of the
process. They may be used alone or to replace a recuperative heat system or
to replace a steam coil.
The purpose of the air preheater is to recover the heat from the boiler flue gas
which increases the thermal efficiency of the boiler by reducing the useful
heat lost in the flue gas. As a consequence, the flue gases are also conveyed to
the flue gas stack (or chimney) at a lower temperature, allowing simplified
design of the conveyance system and the flue gas stack. It also allows control
over the temperature of gases leaving the stack.
3.3.1 NEED OF AIR PRE-HEATER
 Stability of combustion is improved by use of hot air.
 Intensified and improved combustion.
 Burning poor quality fuel efficiently.
 High heat transfer rate in the furnace and hence lesser heat transfer area
requirement.
 Less unburnt fuel particle in flue gas thus complete combustion is
achieved.
 Intensified combustion permits faster load variation. In the case of
pulverized coal combustion, hot air can be used for drying the coal as
well as for transporting the pulverized coal to burners.

24
 This being a non-pressure part will not warrant shut-down of units due
to corrosion of heat transfer surface which is inherent with lowering of
flue gas temperature
 Lower grades of coals can be burnt efficiently with hot air
 Faster load variations are possible.
3.3.2 AIR PRE-HEATER AT WTPS
At WANAK BORI THERMAL POWER STATION APHs of Tri-sector
Rotary Vertical Inverted Regenerative are used.
In Regenerative type the heating medium flows through a closely packed
matrix to raise its temperature and then air is passed through the matrix to
pick-up the heat. Either the matrix or the hoods are rotated to achieve this and
hence there is slight leakage through sealing arrangements at the moving
surfaces. Designed for coal-fired applications the Tri-sector air preheater
permits a single heat exchanger to perform two functions: coal drying and
combustion air heating. Because only one gas duct is required, the need for
ductwork expansion Joints, and insulation is greatly reduced when compared
with a separate air heating system. Equipment layout is simplified, less
Structural steel is needed to install the System and less cleaning equipment is
required.
The duct arrangement of a Tri-Sector shows the air and gas flows through
the unit. The size and location of the primary air duct can vary, depending on
the flow and temperature requirements. The design has three sectors - one
for the flue gas, one for the primary air that dries the coal in the pulverized,
and one for secondary air that goes to the boiler for combustion.

25
3.3.3 MAIN COMPONENTS OF RAPH
• Rotorassembly
• Rotorhousing assembly
• Hot end Connecting plate assembly.
• Cold end connecting plate assembly.
• Heating elements

26
• Sealing system (Radial, Axial & Bypass )
• Guide bearing assembly.
• Supportbearing assembly.
• Lubrication. oil circulation system
• Main Drive assembly. and air-line components
• Cleaning device assembly.
• Washing & Deluge pipe assembly.
• Fire sensing device assembly.
• Rotorstoppagealarm.
3.4 AIR PRE HEATER ENERGY AUDIT BY
PERFORMANCE TEST
3.4.1 Introduction
This procedure provides a systematic approach for conducting routine APH
performance tests on tubular and rotary regenerative APH.
APH leakage % can be determined using this procedure, which is defined
as the weight of air passing from the airside to the gas side of the air heater.
This index is an indicator of the condition of the APH’s seals. As air heater
seals wear, air heater leakage increases. The increase in air heater leakage
increases the station service power requirements of the forced draft and
induced draft fans, increasing unit net heat rate and at times limiting unit
capacity.
APH gas side efficiency can also be determined using this procedure and is
defined as the ratio of the temperature drop, corrected for leakage, to the
temperature head, expressed as a percentage.

27
Gas side efficiency is an indicator of the internal condition of the APH. As
conditions inside the air heater worsen (baskets wear, ash plug gage, etc.), the
APH gas side efficiency decreases. This is generally accompanied by an
increase in exit gas temperature and a decrease in APH air outlet temperature,
resulting in an increase in unit heat rate.
X-Ratio depends on the moisture in coal, air infiltration, air & gas mass
flow rates, leakage from the setting and specific heats of air & flue gas. X-
ratio does not provide a measure of thermal performance of the APH, but is a
measure of the operating conditions. A low X-ratio indicates excessive gas
weight through the APH or that airflow is bypassing the air heater. A lower
than design X-ratio leads to higher than design gas outlet temperature & can
be used as an indication of excessive tempering air to the mills or excessive
boiler infiltration.
3.4.2 OBJECTIVE OF THE AUDIT
1. To identify abnormal changes in air heater leakage or efficiency and
provide information for identifying the cause of performance
degradation.
2. To provide information to allow accounting for the contribution of
APH performance degradation to unit heat rate and capacity.
3. To crosscheck the readings of important station instruments.

28
3.4.3 PARAMETER REQUIRED FOR APH PERFORMANCE
MONITORING:
3.5 Test Procedure
3.5.1 Unit Operation- Operating Conditions of Test Runs
Test runs are conducted at an easily repeatable level at defined baseline
conditions at full load with same number of mills in service and same total air

29
levels as previous tests. The operating conditions for each test run are as
follows.
1) No furnace or air heater soot blowing is done during the test.
2) ii. Unit operation is kept steady for at least 60 minutes prior to the test.
3) Steam coil Air heaters’ (SCAPH) steam supply is kept isolated and gas
recirculation dampers if any, are tightly shut.
4) No mill change Over is done during the test.
5) All air and gas side damper positions should be checked and recorded.
6) The test is abandoned in case of any oil support during the test period.
7) Eco hopper de-ashing or Bottom hopper de-ashing is not done during
the test.
8) Regenerative system should be in service with normal operation.
3.5.2 Test Duration
The test run duration will be the time required to complete two traverses for
temperature and gas analysis. Two separate test crews should sample the gas
inlet and outlet ducts simultaneously.
3.5.3 Measurement Locations
The number and type of instruments required for conducting this test depend
on the unit being tested. The following table lists the measurement locations.
Measurement Temperature Gas Analysers Pressure
AH Gas Inlet Yes Yes Yes
AH Gas Outlet Yes Yes Yes
AH Air Inlet Yes Yes
AH Air Outlet Yes Yes

30
3.5.3.1 Traverse Locations – Gas side
1) The gas inlet traverse plane should be located as close as possible to
the air heater inlet. This is done to ensure that any air ingress from the
intervening duct / an expansion joint is not included in air heater
performance assessment.
2) The gas outlet traverse plane should be located as far downstream from
the air preheater as possible, to allow mixing of the flow to reduce
temperature and 02 stratification. However, it should not be located
downstream of other equipment or access ways that might contribute to
air ingress (e.g. Mechanical collectors, ESP’s, man ways, ID fans).
3) Iii.ASME PTC 19.10 provides guidelines for the number, location and
orientation of ductwork ports.
3.5.3.2 Traverse Locations – Air side
1) The air inlet traverse plane should be located after any air heating coils
and as close as possible to the air heater inlet. Since the entering air
temperature is usually uniform, a single probe with 2/ 3 temperature
measurement points is adequate.
2) The air outlet traverse plane should be located as far downstream from
the air heater as possible to allow mixing of the flow to reduce the gas
stratification.

31
3.5.3.3 Ports and Probes
Typical Test Port and probe sketches are provided below.
1) Tubes numbered 1,2 & 3 are carbon steel 3/8” OD tubes and tube no. 4
is carbon steel 12-15 mm OD

32
2) Tubes numbered 1, 2 & 3 are for gas sampling while tube no. 4 is for
carrying thermocouple wires for temperature measurement.
3) Tube no. 4 has 2 no. 6 mm dia hole for thermocouple wire tip
protrusion (made elliptical for ease in wire insertion)
4) If d is flue gas duct width at the test cross-section then lengths of tube
1, 2 & 3/4 from flange is d/6 +i , d/2+i, 5d/6 +i respectively (i is the
thickness of the insulation + flange).
5) Tube protrusions beyond the flange are 80 mm for tube 1 and 120 mm
for tube 2 & 150 mm for tubes 3 & 4 (approx.).
6) The probe flanges match the port flanges.
3.5.4 Data Collection Procedure
3.5.4.1 Control Room Data
A separate test log for control room data is created in unit DAS for data
collection at an interval of five minutes or less and averaged over the test
period.
3.5.4.2 Flue Gas & Air Temperatures
The online measurements of flue gas and air temperatures at air heater inlet
and outlet are used for efficiency computations. It’s important to ensure that
the online measurements of air and flue gas temperatures are representative of
average temperatures in the duct. The on line feedback of flue gas exit
temperature after air heaters can be affected by gas stratification and may
require more number of thermocouples than presently installed. In some
layouts, the online thermocouples for flue gas temperature measurement are
mounted too close to air heaters in a cluster and need to be relocated for
representative measurement. Similarly the location and number of
temperature sensors on airside at air heater inlet and outlet should be

33
reviewed to obtain a representative average. The new locations can be
decided only by doing multiple point temperature measurements in a plane
perpendicular to the flow in the respective ducts. The number of measurement
points is determined as per ASME PTC 19.10, ‘Flue and Exhaust Gas
Analysis’ and would vary with duct configuration and size.
3.5.4.3 Flue Gas Composition
A representative value of flue gas composition (O2 / CO2 /CO) is obtained by
grid sampling of the flue gas at multiple points in a plane perpendicular to the
flow at air heater inlet and outlet using a portable gas analyser. Two complete
sets of data are collected for each traverse plane during each test run to ensure
data repeatability. A typical cross section of the flue gas duct with an 18-point
grid is shown here along with a typical probe. Each dot indicates a sampling
point for measurement of gas composition and temperature.(Fig)
Flue gas samples are drawn by a vacuum pump from the test grid probes and
sent to a portable gas analyser through a gas conditioning A B C D E F
system. Typically gas-conditioning system consists of a wash bottle, partially
filled with water for cleaning the sample, a condenser to condense the water
vapour out of the gas sample and a desiccant column to remove any water
vapour that got through the condenser.

34
3.5.4.4 Special Test Instruments
The portable analysers should be calibrated prior to the tests with calibration
gases. Purity grade Nitrogen should be used for ‘Zero’ calibration, while span
calibration should be done with standard calibration gases.
The instrument accuracy requirements are summarized in the following table.
MEASUREMENT RESOLUTION ACCURACY
Static Pressure 2mmWC 2mmWC
Temperature 0.1oC 1.0oC
GAS ANALYSIS
O2 0.1% +/- 1%
CO2 0.1% +/- 1%
CO 1ppm +/- 2%
A thermocouple (such as chromel–alumel) and digital thermometer
3.6 Analysis & Data collection
The test values can be compared with the design / PG test and historical
values. The comparison can also help in detection of measurement errors, if
any. The air heater gas side efficiency, APH leakage, corrected exit gas
temperature and measured exit gas temperature, gas side to air side
differential pressure and gas side pressure drop can be plotted on a time line
graph showing historical, design, and possibly acceptance test data.
If a significant reduction in air heater gas side efficiency occurs and
operator controllable parameters (air heater soot blowing, damper
adjustments, etc.) are determined not to be responsible, an internal inspection
of the air heater should be performed at the next available shutdown. Possible
causes of performance degradation include: bypass, isolation or recirculation
dampers mispositioned, APH baskets corroded/eroded/fouled air heater
baskets. A fouled air heater will experience a significant increase in gas side
pressure drop. Generally, a decrease in gas side efficiency will increase the
measured exit gas temperature.

35
The leakage rates for trisector air heaters should be between 10 - 13%. The
leakage levels depend on the differential pressure between the air and gas side
of the air heater, the degree of air heater pluggage and the condition of the
seals. A significant increase in air heater leakage warrants a physical
inspection of the air heater. Possible causes of increased leakage are axial and
radial seal mechanical damage or wear; sector plate mechanical damage or
warping; rotor eccentricity or excessive air to gas side differential pressure.
Typically recuperative air heaters should have zero leakage, but tube failures
due to corrosion or mechanical damage can result in leakage. If the unit is
equipped with bypass dampers or recirculation dampers, they should also be
inspected. Generally, an increase in air heater leakage will cause a decrease in
the measured exit gas temperature.
All test instrument readings should be compared to station instrument
readings to determine if any station instruments need calibration / up
gradation. The economic impact of increased air heater leakage is typically
reflected in increased station service power consumption of FD and ID fans.
In extreme cases unit de-rating may be caused due to insufficient fan
capacities.
The results should include a narrative describing any unusual findings, plots
of performance indices on a time line graph showing historical, design and/or
acceptance test data with analysis of variations, if any, and the test data listed
in a tabular form.
3.6.1 Measurement of Flue gas Oxygen and Temperature at
ESP Inlet and ID fan Outlet
Air ingress from eroded ducts, openings, and expansion joints increases the
flue gas volume and leads to loss of draught margins. Increase in oxygen
percentage in the flue gas and drop in temperature of the flue gas provides an
indication of the increase in air ingress. Along with the air heater tests, the

36
oxygen in flue gas at ESP inlet and ID fans’ outlet is measured separately in
each duct and compared to the average oxygen in flue gas at air heater outlet.
Air ingress
Quantification is done with the same formulae as those used for calculation of
AH leakage.
𝐴𝐼𝑅𝑖𝑛𝑔𝑟𝑒𝑠𝑠 =
(O2in−O2out)
(21−O2in)
× 0.9 × 100
3.6.2 APH Performance Indices Computation
1. Air heater leakage is determined by an empirical approximation as
following.
AL =
( 𝐶𝑂2𝑔𝑒− 𝐶𝑂2𝑔𝑙)
𝐶𝑂2𝑔𝑙
× 0.9 × 100
AL = air heater leakage (%)
CO2ge = percent CO2 in gas entering air heater
CO2gl = percent CO2 in gas leaving air heater
CO2 measurement is preferred due to high absolute values; In case of any
measurement errors, the resultant influence on leakage calculation is small.
Alternatively, the air heater leakage may also be determined from the
following equation:
𝐴𝐿 =
(𝑂2𝑔𝑙 − 𝑂2𝑔𝑒)
(21 − 𝑂2𝑔𝑙)
× 0.9 × 100
AL = air heater leakage (%)
O2ge = percent O2 in gas entering air heater (%)
O2gl = percent O2 in gas leaving air heater (%)
The numerical average of the air heater’s gas inlet, gas outlet and air inlet
temperatures is calculated. Then the corrected air heater gas outlet
temperature is calculated using the following formula.

37
𝑇𝑔𝑛𝑙 =
𝐴𝐿 × 𝐶𝑝𝑎 × ( 𝑇𝑔𝑙 − 𝑇𝑔𝑒)
100 × 𝐶𝑝𝑔
+ 𝑇𝑔𝑙
Tgnl = gas outlet temperature corrected for no leakage
Cpa = the mean specific heat between Tae and Tgl
Tae = temperature of air entering air heater(c)
Tgl = temp of gas leaving air heater (c)
Cpg = mean specific heat between Tgl and Tgnl
2. The gas side efficiency is defined as the ratio of the temperature drop,
corrected for leakage, to the temperature head, expressed as a percentage.
Temperature drop is obtained by subtracting the corrected gas outlet
temperature from the gas inlet temperature. Temperature head is obtained by
subtracting air inlet temperature from the gas inlet temperature. The corrected
gas outlet temperature is defined as the outlet gas temperature calculated for
‘no air heater leakage’.
𝐺𝑆𝐸 =
𝑇𝑒𝑚𝑝. 𝑑𝑟𝑜𝑝
𝑇𝑒𝑚𝑝. ℎ𝑒𝑎𝑑
× 100
𝐺𝑆𝐸 =
𝑇𝑔𝑒 − 𝑇𝑔𝑛𝑙
𝑇𝑔𝑒 − 𝑇𝑎𝑒
× 100
Tae = Temperature of air entering air heater (C)
Tgnl = gas out temp corrected for no leakage (C)
3. X ratio is the ratio of heat capacity of air passing through the APH to the
heat capacity of flue gas passing through the APH and is calculated using the
following formulae:
𝑋 − 𝑟𝑎𝑡𝑖𝑜 =
𝑊𝑎𝑖𝑟 𝑜𝑢𝑡 × 𝐶𝑝𝑎
𝑊𝑔𝑎𝑠 𝑖𝑛 × 𝐶𝑝𝑔
For no air-leakage,

38
𝑇𝑔𝑎𝑠 𝑖𝑛 − 𝑇𝑔𝑎𝑠 𝑜𝑢𝑡
𝑇𝑎𝑖𝑟 𝑜𝑢𝑡 − 𝑇𝑎𝑖𝑟 𝑖𝑛
3.7 Data Collected [Measurement Tables] Before (27/09/14)
APH (A) Inlet
Deep Mid Shallow Deep Mid Shallow AVG
% O2 1.68 1.7 1.8 1.7 2.12 2.2 1.87
ppm CO 25 25 36 30 30 26 28.67
% CO2 16.93 16.86 16.86 16.96 16.54 16.9 16.84
ppm NO 243 246 250 240 226 247 242
ppm NOx 255 211 - - - - 242.33
mm of
WC
Draft -37 -37 -37 -37 -37 -37 -37
o
C Temp 334 334 336 335 335 336 335
APH (B) Inlet
% O2 1.34 1.45 1.44 2.91 2.76 2.84 2.12
ppm CO 29 24 20 2 4 5 14
% CO2 17.22 17.13 17.14 15.85 15.96 15.91 16.54
ppm NO 230 232 233 235 231 233 232.33
ppm NOx 241 244 234 247 243 245 242.33
mm of
WC
Draft -38 -38 -38 -55 -55 -55 -46.5
o
C Temp 329 331 332 335 324 324 329.17
APH (A) Outlet
% O2 1.96 2.27 1.79 4.91 5.05 4.9 3.48
ppm CO 0 0 0 1 1 2 0.67
% CO2 16.67 16.41 16.89 14.1 13.91 14.1 15.35
ppm NO 251 212 251 201 198 198 218.50
ppm NOx 214 223 264 211 205 208 220.83
mm of
WC
Draft -105 -105 -105 -105 -105 -105 -105
o
C Temp 161 160 161 151 153 152 156.33

39
APH (B) Outlet
% O2 3.82 3.92 3.8 3.73 3.15 1.99 3.4
ppm CO 96 92 39 426 733 81 244.5
% CO2 15.6 15.7 15.6 15.11 15.4 16.6 15.67
ppm NO 231 215 220 199 195 222 213.67
ppm NOx 241 212 235 209 205 233 222.5
mm of WC Draft -110 -110 -110 -110 -110 -110 -110
o
C Temp 151 151 151 151 151 151 151
(A) air inlet temp 41
(A) air outlet temp 287
(B) air inlet temp 41
(B) air outlet temp 287
3.8 Calculation (Before)
AIR LEAKAGE,
AL=
( 𝐶𝑂2𝑔𝑒 − 𝐶𝑂2𝑔𝑙)
𝐶𝑂2𝑔𝑙
× 0.9 × 100
Or
𝐴𝐿 =
(21 − 𝑂2𝑔𝑙)
× 0.9 × 100
GAS OUTLET TEMPERATURE CORRECTEDFOR NO LEAKAGE,
𝑇𝑔𝑛𝑙 =
100 × 𝐶𝑝𝑔
+ 𝑇𝑔𝑙

40
GAS SIDE EFFICIENCY,
𝐺𝑆𝐸 =
𝑇𝑒𝑚𝑝.ℎ𝑒𝑎𝑑
× 100
𝐺𝑆𝐸 =
× 100
X-ratio,
For no air-leakage,
FOR AIR PRE-HEATER A,
AL=
( 3.48− 1.87)
(21− 3.48)
× 0.9 × 100 = 8.29
𝑇𝑔𝑛𝑙 =
8.29 × 0.246 ( 156.33 − 41)
100 𝑥 0.252
+ 156.33 = 165.66
𝐺𝑆𝐸 =
335 − 165.66
335− 41
× 100 = 57.60 %
FOR AIR PRE-HEATER B,
AL=
( 3.40− 2.12)
(21− 3.40)
× 0.9 × 100 = 6.54
𝑇𝑔𝑛𝑙 =
6.54 × 0.246 ( 151 − 21)
100 𝑥 0.256
+ 151 = 158.02

41
𝐺𝑆𝐸 =
329.17 − 158.02
329.17− 41
× 100 = 59.39 %
Result Values
APH (A) APH (B)
% Air Leakage 8.29 6.54
Tgnl 165.66 158.02
Gas Side Efficiency 57.6 59.39
X-Ratio 0.69 0.70
3.9 Areas to be considered for improvement
1. Sealing of APH:
Seals are provided at both the end of the APH to minimize leakage from air
side and gas side of the APH.
Radial seal: The hot and cold radial seals are attach to each diaphragm of the
rotor and are set at a specific clearance from sector plates which separates air
and gas streams.
Circumferential seal: Circumferential seals are located on the entire
circumference of the air heater rotor, on both the hot end and cold end of the
air heater.
Bypass seals: It provides sealing between periphery of the rotor and sealing
surface of the connecting plate and/or the preheater housing. Gaps are
observed around the Baskets and with Diaphragm/Stay plates. It will by-pass
the flue gas: thereby losing the efficiency of the boiler. This is revealed by the
high flue gas outlet temperature.
Axial Seals: Axial seals are provided in the rotor shell in line with radial seals.
Reducing and maintaining low air preheater leakage is vital to minimize
the fan horsepower required to move the air and gas flows through the air
preheater.

42
It also serves to reduce the dilution effect and corrosion potential of the
leaving gas stream due to mixing with colder air at the air inlet temperature.
Seals can wear due to soot blowing, corrosion, erosion, and contact with
the static sealing surfaces.
2. Erosion of APH material:
Erosion caused by fly ash has resulted in the rapid loss of a heat exchange
element as well as damage to perimeter seals, radial seals, and rotor
diaphragms. Two other factors with regard to erosion are actually more
important than ash content:
abrasiveness and ash velocity.
The abrasiveness of fly ash increases as the amount of silica and alumina
increases.
Ash velocity is as much as three times more important than ash content or
abrasiveness when it comes to determining the rate of erosion. One way to
defeat high ash velocity is to increase the fineness of the coal particles leaving
the pulverizer and balancing the coal and air flows to each of the burners.

43
[ Corrosion affected buckets] [ Heating surface chocked due to ash]
3. Blockage of APH baskets:
In every power plant exhaust gases carries some amount of flue gases along
with it which may deposited between the gaps of corrugated heating material
of the APH baskets. This ash and other impurities reduce the rate of heat
conduction between the heating material and may result in high exhaust gas
temperature.
4. Alignment problem of APH unit:
APH unit must be installed in correct position for its smooth operation and
aligned to default values. Faulty alignment of APH unit may lead to excess
space between the seals provided increasing leakage of air. It also causes
noise between teeth of driving wheels of APH.
5. Corrosion:
Due to the some of the chemical component present in flue gases corrosion
of APH material, seals, baskets etc. occurs which also be taken into
consideration.

44
3.10 Steps taken for improvement of APH performance
During the period of shutdown for the Power Plant, some steps were taken
to improve the performance of Air Preheater. The steps taken were:
 Cleaning of the APH baskets to remove ashes which reduce the heat
exchange between flue gas and fresh air.
 Replacement of corrosion affected baskets with new baskets.
 Alignment of the APH rotor is done to prevent Air side leakage of the
air from that part.
 Various sealing inside the Air Preheater are checked and repaired if
damaged to prevent air leakage to the flue gas side.
 Improvement of soot blower system is done which helps to increase the
cleaning of basket in running condition.
 Covering the leakages in outer casing of APH by welding them with
suitable materials.
 It is recommended to check flue-gas path duct for possible leakages by
opening the insulation at joints, windows, expansion joints, stop-gates,
doors.
[Radial seal before and after maintenance] [Circumferential seal after maintenance]

45
3.11 Data Collected [Measurement Tables] After (19/01/15)
APH (A) Inlet
% O2 2.29 2.17 2.98 2.78 2.82 2.68 2.62
ppm CO 22 36 26 13 56 36 31.5
% CO2 16.4 16.5 16.3 15.98 15.93 16.5 16.27
ppm NOx - - - - - -
mm of WC Draft -56 -56 -56 -57 -57 -57 -56.5
o
C Temp 342 342 342 342 342 342 342
APH (B) Inlet
% O2 2.21 2.74 2.72 2.45 2.76 2.66 2.59
ppm CO 18 12 12 6 6 6 10
% CO2 16.47 16 16.02 16.26 16.98 16.1 16.31
ppm NOx - - - - - - -
mm of WC Draft -56 -56 -56 -56 -56 -56 -56
o
C Temp 340 340 340 340 340 340 340
APH (A) Outlet
% O2 2.76 2.66 2.82 3.72 3.62 3.69 3.21
ppm CO 6 3 0 0 0 0 1.5
% CO2 15.9 15.9 15.9 13.39 13.45 13.42 14.66
ppm NOx - - - - - - -
mm of WC Draft -158 -158 -158 -158 -158 -158 -158
o
C Temp 152 152 152 152 152 152 152
APH (B) Outlet
% O2 3.72 3.5 3.55 2.4 2.3 2.33 2.97
ppm CO 0 12 3 0 0 0 2.5
% CO2 15.41 15.31 15.29 16.3 16.4 16.36 15.8
ppm NOX - - - - - - -
mm of WC Draft -160 -160 -160 -160 -160 -160 -160
*C Temp 148 148 148 150 150 150 149

46
(A) air inlet temp 35
(A) air outlet temp 284
(B) air inlet temp 35
(B) air outlet temp 284
3.12 Calculation (After)
AIR LEAKAGE,
AL=
( 𝐶𝑂2𝑔𝑒 − 𝐶𝑂2𝑔𝑙)
𝐶𝑂2𝑔𝑙
× 0.9 × 100
Or
𝐴𝐿 =
(21 − 𝑂2𝑔𝑙)
× 0.9 × 100
GAS OUTLET TEMPERATURE CORRECTEDFOR NO LEAKAGE,
𝑇𝑔𝑛𝑙 =
100 × 𝐶𝑝𝑔
+ 𝑇𝑔𝑙
GAS SIDE EFFICIENCY,
𝐺𝑆𝐸 =
𝑇𝑒𝑚𝑝.ℎ𝑒𝑎𝑑
× 100
𝐺𝑆𝐸 =
× 100
X-ratio,
For no air-leakage,

47
FOR AIR PRE-HEATER A,
AL=
( 3.21− 2.82)
(21− 3.21)
× 0.9 × 100 = 2.99
𝑇𝑔𝑛𝑙 =
2.99 × 0.246 ( 152.50 − 35)
100 𝑥 0.252
+ 152.50 = 155.93
𝐺𝑆𝐸 =
342 − 155.93
342− 35
× 100 = 60.61 %
FOR AIR PRE-HEATER B,
AL=
( 2.97− 2.59)
(21− 2.97)
× 0.9 × 100 = 1.88
𝑇𝑔𝑛𝑙 =
1.88 × 0.246 ( 149 − 35)
100 𝑥 0.256
+ 149 = 151.09
𝐺𝑆𝐸 =
340 − 151.09
340− 35
× 100 = 61.94 %
Result Values
APH (A) APH (B)
% Air Leakage 2.99 1.88
Tgnl 155.93 151.09
Gas Side Efficiency 60.61 61.94
X-Ratio 0.75 0.76

48
3.13 Comparison of parameters
1) Air leakage%
2) Gas side Efficiency
3) Temperature at outlet of APH
APH A APH B
Before 8.29 6.54
After 2.99 1.88
0
1
2
3
4
5
6
7
8
9
APH A APH B
Before 57.6 59.39
After 60.61 61.94
55
56
57
58
59
60
61
62
63
Shallow 1 Mid 1 Deep 1 Shallow 2 Mid 2 Deep 2 AVG
APH A Before 158 156.5 157.5 154 156.5 155.5 156.33
APH B Before 153 151 155 148 150 149 151
APH A After 151 152 153 150.5 152 153.5 152
APH B After 148 149 150 147 151 149 149
140
142
144
146
148
150
152
154
156
158
160

49
3.14 Conclusion of Audit
At the end of this Audit project of Air Preheater, We have concluded that
the performance parameters of the Air preheater such as Air-leakage, Gas
side efficiency, X-ratio, etc improves satisfactorily.
Improvement values of various performance parameters are shown in table
below:
APH A APH B
Air leakage -5.3% -4.66%
Tgnl +9.73oC +6.93oC
Gas side efficiency +2.99% +2.55%
X-ratio +0.6 +0.6
Outlet Temperature -10oC -10oC
It is found that if the outlet temperature increases by 1oC, then the heat rate
produced will also increased by 1 unit. Here we have concluded that after
applying proper steps for the improvement of efficiency the outlet
temperature is increased by 10oC which means it will increase heat rate by 10
units. And that will affect the usage of fuel (coal) consumption for same
amount of power generation in power plant. Calculation has shown that here
we are saving about 3.68% coal consumption by applying this audit process
for the air preheater and improving its performance parameters.

50
REFERENCES
 BEE- BUREAU OF ENERGY EFFICIENCY, INDIA.
(www.beeindia.in)
 P.N.Sapkal, P.R.Baviskar, M.J.Sable, S.B.Barve ¯ “To optimise air
preheater design for better performance”. NEW ASPECTS of FLUID
MECHANICS, HEAT TRANSFER and ENVIRONMENT. ISSN:
1792-4596, ISBN: 978-960-474-215-8, PP.61-69.
 Pipat Juangjandee ¯ “Performance Analysis of Primary Air Heater
Under Particulate Condition in Lignite-Fired Power Plant”
Engineering,Computing and Architecture, ” ISSN 1934-7197,vol
1,issue 2,2007
 Bostjan Drobnic, Janez Oman. ¯ “A numerical model for the analyses
of heat transfer and leakages in a rotary air preheater” , International
Journal of Heat and Mass Transfer 49, PP.5001–5009, 2006.
 Stephen K.Storm,john Guffre, Andrea Zucchelli ”Advancements with
Regenerative Airheater Design, Performance and Reliability”
POWERGEN Europe 7-9 June 2011.
 P.N.Sapkal, P.R.Baviskar, M.J.Sable, S.B.Barve, “Optimization of Air
Preheater Design for the Enhancement of Heat Transfer Coefficient”,
International Journal of Applied Research in Mechanical Engineering
(IJARME), ISSN: 2231 –5950, Volume-1, Issue-2, 2011.
 Guidelines for energy auditing of pulverised coal/lignite fired thermal
power plants, by BEE.


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