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INFLUENCE OF REGENERATIVE AIR PREHEATER PERFORMANCE ON BOILER EFFICIENCY AT TNB POWER STATION (500MW) IN MALAYSIA

BITS ZG629T: Dissertation

By

MANOJ KUMAR M

ID No. 2011HZ79057

Dissertation work carried out at

Sreevari Engineers Private Limited, Trichy.

BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE

PILANI (RAJASTHAN)

April 2013

INFLUENCE OF REGENERATIVE AIR PREHEATER PERFORMANCE ON BOILER EFFICIENCY AT TNB POWER STATION (500MW) IN MALAYSIA

BITS ZG629T: Dissertation

By

MANOJ KUMAR M

ID No. 2011HZ79057

Dissertation work carried out at

Sreevari Engineers Private Limited, Trichy.

Submitted in partial fulfillment of

M.S. Manufacturing Management Degree Programme

Under the Supervision of

Mr. Elanghovan R S, Generaal Manager,

Sreevari Engineers Private Limited, Trichy.

BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE

PILANI (RAJASTHAN)

April 2013

2

CERTIFICATE

This is to certify that the Dissertation entitled INFLUENCE OF

REGENERATIVE AIR PREHEATER PERFORMANCE ON BOILER EFFICIENCY AT TNB POWER STATION (500MW) IN MALAYSIA by MANOJ KUMAR M having IDNo. 2011HZ79057 for the partial fulfillment of the requirements of BITS ZG629T in M.S. Manufacturing Management Degree of BITS, embodies the bonafide work done by him under my supervision.

 

 

 

_______________________

 

 

 

Signature of the Supervisor

Place: Trichy

Mr. Elanghovan R S,

General Manager.

 

 

 

Date:

Sreevari Engineers Pvt Ltd,

Trichy.

 

 

 

.

3

ABSTRACT

Birla Institute of Technology & Science, Pilani

Work-Integrated Learning Programmes Division

First Semester 2012-2013

ID No.

: 2011HZ79057

NAME OF THE STUDENT

: MANOJ KUMAR M

EMAIL ADDRESS

: manoj4krish@gmail.com

STUDENT’S EMPLOYING

: Sreevari Engineers Pvt Ltd, Trichy

ORGANIZATION & LOCATION

 

SUPERVISOR’S NAME

: ELANGHOVAN R S

SUPERVISOR’S EMPLOYING

: Sreevari Engineers Pvt Ltd, Trichy

ORGANIZATION & LOCATION

 

SUPERVISOR’S EMAIL ADDRESS

: elango@sreevariengineers.com

DISSERTATION TITLE

: Influence of regenerative air preheater

 

performance on boiler efficiency at TNB

 

power station (500MW) in Malaysia

ABSTRACT:

 

With the increased emphasis on the efficiency of fossil-fuel-fired, steam generation facilities, the performance of ancillary equipment is becoming increasingly important. The air heater is a source of lost thermal efficiency in two ways -- air leakage into flue gas side and poor heat recovery. Moreover air leakage is the prime source of deteriorating efficiencies in most of the newly commissioned boilers. This dissertation gives an account of logical steps involved in analyzing all the factors affecting the performance of air heater, carrying out necessary improvements during planned overhaul and determining the improved results obtained thereafter.

The facility under study is one the leading Government owned thermal power station of 500MW in Malaysia. The project starts with data collection of existing operating condition of the system from distributed control system (DCS) of Boiler. Then the most critical factor which affects the performance is determined after analyzing the data collected. Finally the necessary improvements or modifications are physically carried out during planned major overhaul of Boiler. The improved performance levels of air heater will lead to increase in efficiency of boiler.

4

The existing efficiency of the boiler is observed to be 83%. The aim is to increase the efficiency of the boiler and obtain monetary benifits. The dissertation project will describe the above work in detail.

Broad Areas of Dissertation: Maintenance Engineering

Signature of the Student

Signature of the Supervisor

Name:

Name:

Date:

Date:

Place:

Place:

5

ACKNOWLEDGEMENT

This dissertation report is the result of a four-month process and would not have been possible without the support and encouragement by a number of people. I take this opportunity to express my gratitude to all.

Through invaluable discussions and constructive suggestions, my supervisor Mr. Elanghovan R S, General Manager at Sreevari Engineers Private Limited has guided me well.

I would also like to share my gratitude to my additional examiner Mr. Shanthakumar P, Senior Manager- Field Engineering at Sreevari Engineers Private Limited for his always positive; nothing is impossible attitude and help with this project.

A good working environment is essential, and something that has been provided by my colleagues and I thank them all.

6

TABLE OF CONTENTS

Sl. No

Title/Description

Page No.

i

Title Page

2

ii

Certificate

3

iii

Abstract

4

iv

Acknowledgements

6

v

Table of contents

7

vi

Table of figures

8

vii

List of tables

9

1

Chapter 1 – Introduction to Sreevari

10

 

Engineers Private Limited

 

2

Chapter 2 – Plan of work

12

3

Chapter 3 – Brief about the project

13

4

Chapter 4 – Problems with regenerative air

15

 

preheater

 

5

Chapter 5 – Current operating

16

 

performance levels

 

6

Chapter 6 – Cause effect analysis

18

7

LIST OF FIGURES

Figure#

Description

Page No.

1

Corporate revenue data

11

2

Steam boiler schematic

14

3

Regenerative air preheter

14

8

LIST OF TABLES

Table#

Description

Page No.

1

Plan of work

12

2

Data sheet from plant

16

3

Data comparison

17

9

Chapter 1

INTRODUCTION TO SREEVARI ENGINEERS PVT LTD

History:

Sreevari Engineers Private Limited was established in the year 2006 as a group company of Namakkal Transport Corporation (NTC), Chennai dedicated in manufacturing and servicing of steam generation boiler auxiliaries. At the time, the core product of the company was regenerative air preheater and electrostatic precipitator.

In the year 2008, Sreevari Engineers Pvt Ltd, established itself as an independent engineering company at Trichy. As an ISO 9001:2008 certified company for Design, Manufacturing, Supply, Erection, Commissioning and Service supervision of Air Preheater and Electrostatic Precipitator, its product range penetrated into industries like power generation, refineries, fertilizer, chemical, paper, sugar and other process industries.

With 145 employees and sales of about 100 million rupees in 2012, Sreevari Engineers Pvt Ltd is a leading manufacturer and service provider for most of the heat transfer equipments like regenerative air preheater, tubular heat exchangers, feed water heaters and steam coil air preheater.

Service Range:

∑Design and Manufacturing of High Pressure boiler auxiliaries like Rotary Regenerative Air Preheater, Electrostatic precipitators

∑Consulting services and Technical Assistance for Air Preheaters

∑Assessment and Technical Supervision

∑Trouble shooting and assessment for improving the efficiency

Innovating for the future:

At Sreevari Engineers Private Limited, we place an emphasis on innovation and research. Our Engineers have already developed various heat transfer profiles used in regenerative heat exchangers in order to suit Indian power industries for maximizing reliability and performance of the equipments. All developments are made to meet customer requirements

10

Key Figure:

Fig.1

11

 

 

 

Chapter 2

 

PLAN OF WORK

 

 

 

 

 

Mile Stone

Task Description

 

Expected Date of

 

 

 

Completion

1

Problem identification & data

 

25 Jan 2013

 

collection

 

 

2

Data analysis

 

30 Jan 2013

3

Preparation of action plan

 

5 Feb 2013

4

Implementation of action plan

 

25 Feb 2013

 

during overhaul

 

 

5

Reviewing Results

 

1 Mar 2013

6

Observation & validation

 

10 Mar 2013

7

Completion of Project

 

20 Mar 2013

12

Chapter 3

BRIEF ABOUT THE PROJECT

Objective:

The objective of the project is to optimize the performance of regenerative air preheater by analyzing all the relevant operational parameters during plant operation and implement all the necessary action plans during planned major overhaul of TNB (Tenaga Nasional Berhad) power station in Malaysia to achieve monetary benefits from improved boiler efficiency.

Introduction to regenerative air preheater:

An air preheater (APH) is a general term 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.

In particular, this project deals with combustion air preheaters used in large boilers found in thermal power stations producing electric power from e.g. fossil fuels, biomasses or waste.

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 (to meet emissions regulations)

Regenerative Air Preheater is more widely used than any other type of heat exchanger for comparable service in the steam generating industry. The reasons for this worldwide acceptance are its high thermal effectiveness, proven performance and reliability, effective leakage control, compactness of its design, and its adaptability to most any fuel burning process. It is both designed and built to operate over extended periods with durable, uninterrupted service. Simplicity of the design also makes it easy and economical to maintain in operation and at scheduled outages

Working principle:

Air pre-heater transfer heat from flue gas to air by means of a rotary matrix in which heat is absorbed by the heating elements passing through the hot gas stream and transferred to the combustion air stream. As leakages increase, more & more air enters the flue gas path. As a result, equipment downstream of air preheater have to handle increased mass of the flue gas& hence fans consume more power.

13

Increased power consumption affects net heat rate. Seal are provided to avoid radial leakages, periphery leakages & also the axial leakages. In addition to this, some air trapped between two diaphragms also finds way to gas side when rotor enters the flue gas side. Fig.3 shows a principle sketch of the pre-heater.

Problems with regenerative air preheater:

∑Seal leakage

∑Erosion of heating elements

∑Choking of heating elements

All of these result in poor thermal performance

Fig. 2

Fig. 3

14

Chapter 4

PROBLEMS WITH REGENERATIVE AIR PREHEATER

Seal Leakages:

Leakage is an unavoidable feature of regenerative air preheater. Air preheaters are designed with a certain percentage of leakage. Leakages are increased over a period of time due to deterioration of sealing system. The most common leakage is the leakage of air into flue gas which results in decreased flow of air for combustion which leads to under performance of boiler.

Erosion of heating elements:

The boiler flue gas contains many dust particles (due to high ash content) not contributing towards combustion, such as silica, which cause abrasive wear to the heating elements, and may also contain corrosive gases depending on the composition of the fuel. This leads to decreased heat transfer area which affects the thermal performance of the system.

Choking of heating elements:

Air heater heating elements are periodically cleaned using soot blowers system in the boiler. Soot blowing is operated based on the pressure difference across the heating elements. Improper soot blowing results in choking of heating elements which ultimately leads to decreased air flow to the boiler combustion system, reduced heat transfer rate, and increased fans loading. The above consequences result in decreased thermal efficiency of the boiler.

15

Chapter 5

CURRENT OPERATING PERFORMANCE LEVELS

Measure:

Data for evaluating the current performance levels were obtained from Distributed Control System (DCS) on 20th Jan, 2013

Name of the Station : TNB – Manjung, Malaysia

 

 

Unit No. : 4

 

 

 

 

 

 

 

 

 

Plant Capacity : 500MW

 

 

 

Data Collected By : Manoj Kumar M

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BEFORE

SI.

Data

Design

Unit

 

 

OVERHAUL

 

 

 

 

No.

 

Parameter

 

Date : 20.01.2013

 

 

 

 

 

 

APH - A

 

APH – B

 

 

 

 

 

 

 

 

1.

Unit Load

 

MW

 

 

488

 

 

 

 

 

 

 

2.

Fuel Consumption

 

T/hr

 

 

187

 

 

 

 

 

 

3.

O2atFlueGasInlet

 

%

2.55

 

1.84

 

 

 

 

 

 

 

4.

O2at Flue Gas Outlet

 

%

5.8

 

5.93

 

 

 

 

 

 

 

5.

Flue Gas Inlet Temp.

 

â—¦C

305.95

 

290.41

 

 

 

 

 

 

 

6.

Flue Gas Outlet Temp.

 

â—¦C

130.5

 

133.6

 

 

 

 

 

 

 

7.

Air Inlet temperature

 

â—¦C

33.75

 

33.11

 

 

 

 

 

 

 

8.

Air Outlet temperature

 

â—¦C

261.5

 

251.74

 

 

 

 

 

 

 

9.

Air Pressure before GAH

 

mbarg/

8.79

 

-8.09

 

 

 

mmwc

 

 

 

 

 

 

 

 

 

 

 

10.

Air Pressure after GAH

 

mbarg/

4.92

 

4.77

 

 

 

mmwc

 

 

 

 

 

 

 

 

 

 

 

11.

Air Pressure drop across

 

mbarg/

4.02

 

3.24

 

APH

 

mmwc

 

 

 

 

 

 

 

 

 

 

 

12.

Draft GAH Inlet

 

mbarg/

-10.01

 

-9.17

 

 

 

mmwc

 

 

 

 

 

 

 

 

 

 

 

13.

Draft GAH Outlet

 

mbarg/

-5.99

 

-5.93

 

 

 

mmwc

 

 

 

 

 

 

 

 

 

 

 

14.

Air flow at Inlet

 

T/hr

310.73

 

318.62

 

 

 

 

 

 

 

 

15.

Air flow at Outlet

 

T/hr

 

NA

 

NA

 

 

 

 

 

 

 

16.

FD Fan current

 

Amps

87.75

 

86.49

 

 

 

 

 

 

 

17.

ID fan current

 

Amps

90.84

 

90.61

 

 

 

 

 

 

 

18.

ID fan scoop position

 

%

85

 

83

 

 

 

 

 

 

 

19.

FD fan scoop position

 

%

60

 

64

 

 

 

 

 

 

 

 

16

∑Efficiency of the boiler as on 20.01.2013 was 84.46%

Calculations:

∑Seal Leakage = 100 x [(O2(Out)- O2(In))/(20.9- O2(Out))]

Seal leakage = 100 x [(5.87-2.2)/(20.9-5.89)] = 24.45%

∑Average Flue gas out let temperature at Air Heater = 132.05 oC

∑Pressure drop across Air Heater = 4.92 mbar

Comparison with design parameter:

S.No

Parameter under study

 

Design

Actual

1

Air leakage

9%

 

24.45%

2

Flue gas outlet temperature

145.05 oC

132.05 oC

3

Pressure drop

2.1

mbar

4.92 mbar

Predictive evaluation from above observation:

∑High seal leakage shows that the sealing system is not functioning properly

∑High pressure drop indicates that there is either high choking or the heating elements are highly damaged

∑Low flue gas out let temperature also indicates high air side leakage into flue gas

Critical areas for improvement during overhaul:

∑Sealing system

∑Thermal performance

∑Overall mechanical fitness

17

Chapter 6

CAUSE EFFECT ANALYSIS

Fish Bone diagram

Sealing system:

High pressure drop across air heater:

18

BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE, PILANI

WORK-INTEGRATED LEARNING PROGRAMMES DIVISION

Second Semester 2012-2013

BITS ZG629T: Dissertation Mid-Semester Progress Evaluation Sheet

ID No.

: 2011HZ79057

NAME OF THE STUDENT

: MANOJ KUMAR M

EMAIL ADDRESS

: manoj4krish@gmail.com

SUPERVISOR’S NAME

: ELANGHOVAN R S

DISSERTATION TITLE

: Influence of regenerative air preheater

 

performance on boiler efficiency at TNB

 

power station (500MW) in Malaysia

Mile

Task Description

Expected Date

Current

Stone

 

of Completion

Status

1

Problem identification &

25 Jan 2013

Completed

 

data collection

 

 

2

Data analysis

30 Jan 2013

Completed

3

Preparation of action plan

5 Feb 2013

In progress

4

Implementation of action

25 Feb 2013

Yet to start

 

plan during overhaul

 

 

5

Reviewing Results

1 Mar 2013

Yet to start

6

Observation & validation

10 Mar 2013

Yet to start

7

Completion of Project

20 Mar 2013

Yet to start

19