Efficiency Improvement of Boiler

8/13/2019 Efficiency Improvement of Boiler

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Energy Saving Through Improved

Boiler and Pipeline Schemes


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Why Efficiency is important

Natural GastheBaseline Primary EnergyFirst Fueldepleting fast.

Coal Resource, the Second Fuel Initially base onpower plant grade imported Coal and gradually

develop the mine.

Energy Efficiency & Conservation/Demand-sidemanagement (DSM) the THIRD FUELbecauseEnergy saved = Energy generated


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Typical Thermal Systems

Boiler Pipeline

Turbine

Heat Exchanger

Process Steam

Steam Generation

Steam Transmission

Steam Utilisation


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Typical Energy Balance of a Boiler


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Typical Heat losses from Boiler

Heat losses with Flue Gases (1822 %)

If enough heat from the flue gases are extracted by the boiling water, the

temperature of the stack gases would be limited. If the stack gases leaving theboiler are too hot, less efficient is the boiler. The gases may be too hot if :

The burner is producing more heat than required for a specified load on theboilerair and fuel flow mechanisms may need calibrations.

The heat transfer surfaces within the boiler are not functioning correctly andthe heat is not being transferred to water the heat transfer surfaces may becontaminated, and require cleaning.

Heat Losses from Boiler Structure (1 -4 %)

It is desired that the heat would be transmitted to the boiling water and not to the

surrounding. In most modern boilers the heat-exchange section (eg. shell) is well

insulated, generally with glass wool, insulation paints etc. to prevent such losses.

Heat Losses from Blowdown ( 3 5 %)

Blow-down of the boiler water needs to be done to keep the Total Dissolved

Solids (TDS) within limits to limit corrosion. Heat losses from blow-down can be

reduced by using blow-down recovery arrangements


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Energy Saving through Improved Boiler Schemes

Typical Heat Path Through a Fire-Tube Shell Boiler


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Modern Packaged Boiler


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The objectives of a Boiler Plant

To release the energy in the fuel as efficiently as possible.

To transfer the released energy to water, and to generate

steam as efficiently as possible.

Meet the steam requirement at desired -temperature, pressure, quantity and quality.

Separate the water from steam and make it available,

where the energy can be transmitted to the applicationas efficiently as possible.


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The combustion process of the fuel is happening efficiently

The important factors to achieve this include :

Type and Quality of fuel used

Type of burner used

Air-Fuel ratio of combustion

Technology used for controlling the combustion process

Heat losses from boiler

Emission of harmful gases to the atmosphere


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The transfer of heat from the flue gases to water is happening

efficiently

The important factors to achieve this include :

Material used in construction of the heat transferring components

Layout of the heat transfer surfacesparallel/counter flow,

single/multi-pass

Amount of scales and films on heat exchanging surfaces

Heat recovery devices used in the systemeg. economiser,

air pre-heater, blow-down heat recovery etc.


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Boiler Efficiencies

Boiler efficiency (%) =

Heat Exported to steam

Heat Provided by the fuel 100

Heat exported to steam : depends on - temperature, pressure, quality and flow rate

Heat provided from fuel : depends on the calorific value of fuel and quality of

combustion

Typical net boiler efficiencies

Type of Boiler Net Efficiency (%)

Packaged, Three pass 87

Water Tube Boiler with Economiser 85

Economic, Two pass 78

Lancashire Boiler 65

Lancashire Boiler with Economiser 75


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Surveyof boiler

A base line survey was done to evaluate the exact conditionof the boilers installed in different types of industrialfacilities in Titas Franchise Area;

The Survey focused on those Boilers whose capacity is 1000kg/hr or more;

This survey includes energy efficiency improvementmeasures in a steam distribution system and steamconsuming processes (i.e. demand-side);

Waste heat recovery potential were brought in to account;


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Baseline Methodology Boiler Specifications were collected with capacity and age;

Burner details were collected with control system; Stack temperature and chimney condition were monitored;

Blow down control system was inspected and blow down rateand time was recorded ;

Boiler accessories installations brought out in to account forefficiency enhancement;

Water treatment, Softening plant and chemical dousingsystem were monitored;

Steam distribution system and steam consuming processes

line was inspected for accountable heat losses; Condensate recovery potential was searched for;

Boiler operation technique and maintenance procedure wereexamined.


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Major findings of the survey Only 11% Boiler has stack Economizer installed with them.

No boiler has any air pre-heating unit. 90% boiler users dont have any feed water treatment plant; they only

utilize softener to reduce hardness of feed water. Most of the Boiler usersuse manual chemical dousing system for pH Control.

No assembly (Flue gas analyzer) was found with any of the boilers tomonitor air fuel ratio & amount of excess air. A significant amount ofBoiler users don't have any burner & blower tuning expert, some of the

users adjust air fuel ratio with the help of boiler suppliers and it is doneone or two times in a year whereas its required a continuous monitoring.

Some of the burners have manual control system; the operator kept fullburner opening either it is required or not.

Almost every boiler's maintenance for scaling and corrosion is performedonly two times in a year during Eid vacation.

10-15% Steam lines & all most all the fittings in steam lines were notinsulated among the visited boilers.

Only 5% users have a condensate recovery system whereas 50-60%condensate recovery is possible.

A significant amount of Steam line leakage & fittings leakage wasobserved.


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Cause of Inefficiency

During survey the following major cause of inefficiency

were found out:

Improper Air Fuel Ratio;

Manual control system of burner and blower;

Use of untreated boiler feed water; Manual Blow Down;

Inadequate Insulation;

Lack of proper maintenance for scaling and corrosion;

Distribution System Loss;

Lack of knowledge and awareness;


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Scope of improving boiler efficiency

Below are some ways to improve boiler efficiencies:

Reducing excess air and maintain a proper air fuel ratio;

Installing Economizer;

Reducing scale and deposits;

Reducing blow down;

Recovering Waste Heat from Blow down; Stopping Dynamic Operation;

Reducing Boiler Pressure;

Operating at Peak Efficiency;

Preheating Combustion Air; Condensate Recovery; Flash steam Recovery;


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OtherSources of Heat Recovery

There are a huge potential of waste heat

recovery in most of the industries.

Those industries that have captive power plants canproduce steam from waste heat introducing EGBs

(Exhaust Heat Boiler). 1 MW gas engine generator could produce 600kg/hr steam

when it is running at 100% load;

Rather than this there are some other industries like silicateand chemical industries which have a huge scope ofutilizing waste heat to produce steam from furnace wasteheat.


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Recommendations

(implement able in long term basis )

Stack economizers and Air pre heating

units should be installed in all boilers;

All the condensate recovery potentialshould be utilized

Possible waste heat recovery techniques

must be applied.


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References :

1. Boiler Efficiency and Combustion, http://www.spiraxsarco.com2. Steam Engineering Principles and Heat Transfer, http://www.spiraxsarco.com3. Steam Distribution Systems, http://www.Steampipelines/Steam_scottis.html4. Introduction to Heat Transfer, Frank P. Incropera, David P. Dewitt, Published by

John Wiley and Sons, ISBN 0-471-30458-1.

5. Energy_Notes_Items, http://www.process-heating.com/CDA6. Pal P. , Energy Conservation in Steam Distribution Network,Proceedings of the

Indian Chemical Engineering Congress, Chandigar, India, 1999.

7. Energy Concepts-Chimney and Natural Draft, http://energyconcepts.tripod.com


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Thank You All

Efficiency Improvement of Boiler

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