Energy performance assessment of boilers

1. ENERGY PERFORMANCE ASSESSMENT OF BOILERS
1.1 Introduction
Performance of the boiler, like efficiency and evaporation ratio reduces with time, due to poor combustion, heat transfer fouling and poor operation and maintenance. Deterioration of fuel quality and water quality also leads to poor performance of boiler. Efficiency testing helps us to find out how far the boiler efficiency driftsaway from the best efficiency. Any observed abnormal deviations could therefore be investigated to pinpoint the problem area for necessary corrective action. Hence it is necessary to find out the current level of efficiency for performance evaluation, which is a pre requisite for energy conservation action in industry.

1.2 Purpose of the Performance Test
• • To find out the efficiency of theboiler To find out the Evaporation ratio

The purpose of the performance test is to determine actual performance and efficiency of the boiler and compare it with design values or norms. It is an indicator for tracking dayto-day and season-to-season variations in boiler efficiency and energy efficiency improvements

1.3 Performance Terms and Definitions
Heat output x100 Heat input

1. BoilerEfficiency, η =

=

Heat in steam output (kCals) x100 Heat in fuel input (kCals )

2. Evaporation Ratio

=

Quantity of steam generation Quantity of fuel consumption

1.4 Scope
The procedure describes routine test for both oil fired and solid fuel fired boilers using coal, agro residues etc. Only those observations and measurements need to be made which can be readily applied and isnecessary to attain the purpose of the test.

Bureau of Energy Efficiency

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1. Energy Performance Assessment of Boilers

1.5 Reference Standards
British standards, BS845: 1987

The British Standard BS845: 1987 describes the methods and conditions under which a boiler should be tested to determine its efficiency. For the testing to be done, the boiler should be operated under steady loadconditions (generally full load) for a period of one hour after which readings would be taken during the next hour of steady operation to enable the efficiency to be calculated. The efficiency of a boiler is quoted as the % of useful heat available, expressed as a percentage of the total energy potentially available by burning the fuel. This is expressed on the basis of gross calorific value (GCV). This deals with the complete heat balance and it has two parts: Part One deals with standard boilers, where the indirect method is specified Part Two deals with complex plant where there are many channels of heat flow. In this case, both the direct and indirect methods are applicable, in whole or in part.
ASME Standard: PTC-4-1 Power Test Code for Steam Generating Units

This consists ofPart One: Direct method (also called as Input -output method) Part Two: Indirect method (also called as Heat loss method)
IS 8753: Indian Standard for Boiler Efficiency Testing

Most standards for computation of boiler efficiency, including IS 8753 and BS845 are designed for spot measurement of boiler efficiency. Invariably, all these standards do not include blow down as a loss in the efficiencydetermination process. Basically Boiler efficiency can be tested by the following methods: 1) The Direct Method: Where the energy gain of the working fluid (water and steam) is compared with the energy content of the boiler fuel. 2) The Indirect Method: Where the efficiency is the difference between the losses and the energy input.

1.6 The Direct Method Testing
1.6.1 Description This is alsoknown as ‘input-output method’ due to the fact that it needs only the useful output (steam) and the heat input (i.e. fuel) for evaluating the efficiency. This efficiency can be evaluated using the formula: Heat Output Boiler Efficiency = x100 Heat Input

Bureau of Energy Efficiency

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1. Energy Performance Assessment of Boilers

Steam Output

Flue Gas

Fuel Input 100% + Air...