Boiler Performance
Boiler Performance
Boiler Performance
Introduction
Performance of the boiler, like efficiency and evaporation ratio reduces with time, due to 1. Poor combustion, 2. Heat transfer fouling 3. Poor operation and maintenance. 4. Deterioration of fuel quality and water quality also leads to poor performance of boiler.
Introduction
Efficiency testing helps us to find out how far the boiler efficiency drifts away 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.To find out the efficiency of the boiler 2.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.
Reference Standards
British standards, BS845: 1987
ASME Standard: PTC-4-1 Power Test Code for Steam Generating Units
ASME Standard: PTC-4-1 Power Test Code for Steam Generating Units
This consists of . Part One: Direct method (also called as Input -output method) . Part Two: Indirect method (also called as Heat loss method)
. Plant people can evaluate quickly the efficiency of boilers . Requires few parameters for computation
. Needs few instruments for monitoring
L1. Loss due to dry flue gas (sensible heat) L2. Loss due to hydrogen in fuel (H2)
L3. Loss due to moisture in fuel (H2O)
1. Fuel
2. Steam
3. Feed water
4. Condensate water
2. Fuel
3. Combustion air, both primary and secondary 4. Draft
TYPICAL INSTRUMENTS
. Blow down loss. The amount of energy wasted by blow down varies over a wide range.
. Soot blower steam. The amount of steam used by soot blowers is variable that depends on the type of fuel. . Auxiliary equipment energy consumption. The combustion efficiency test does not account for the energy usage by auxiliary equipments, such as burners, fans, and pumps.
In this way it is easy to compare the performance of various boilers with different ratings.
INPUT PARAMETERS - 2
12 13 14 15 16 17 18 19 20 21
Proximate Analysis of Coal Moisture AD Moisture AF Ash AD Ash AF Volatile Matter AD Volatile Matter AF Fixed Carbon AD Fixed Carbon AF Gross Cal. Value AD Gross Cal. Value AF % % % % % % % % Kcal/kg Kcal/kg 4.85 12.80 35.97 32.96 26.39 24.19 32.79 30.05 4464.00 4445.00
Sample Inputs
22 23 24 25 26 27 28 29 30 31 32 33 34 35 Ave FG O2 APH in Ave FG CO2 APH in Ave FG CO APH in Ave FG O2 APH Out Ave FG CO2 APH Out Ave FG CO APH Out Ave. FG Temp APH in Ave. FG Temp APH Out Air to APH in Air APH out Total Primary Flow Total Air Flow L Total Air Flow R Design Ambient / Ref air Temp % % PPM % % PPM 0C 0C 0C 0C T/hr 0C 0C 0C 3.50 15.80 39.00 5.00 14.30 50.00 300.00 140.00 31.00 290.00 330.00 360.00 360.00 30.00
Computations - 1
Ultimate Analysis of Coal on As Fired Basis
Carbon%= (Fixed Carbon AD+0.9(Vol.Matter AD-14))*GCVAF/GCVAD Sulphur%= 0.4* GCVAF/GCVAD Hyd.%= Vol.Matter AD *(7.35/(Vol.Matter AD +10)-0.013)* GCVAF/GCVAD Moisture% = Moisture AF
However it is suggested to get a ultimate analysis of the fuel fired periodically from a reputed laboratory.
Theoretical (stoichiometric) air fuel ratio and excess air supplied are to be determined first for computing the boiler losses. The formula is given on the next slide for the same.
Total mass of flue gas (m)/kg of fuel = mass of actual air supplied/kg of fuel + 1 kg of fuel Note-2: Water vapour is produced from Hydrogen in fuel, moisture present in fuel and air during the combustion. The losses due to these components have not been included in the dry flue gas loss since they are separately calculated as a wet flue gas loss.
The mass of vapour that air contains can be obtained from psychrometric charts and typical values are included in the next slide alongwith the formula for calculation of loss.
L Ffw Wb Db BP Fin Cba Cfa Lrad Pfa Pba Mad Maf Aad Aaf Vad Vaf FCad Fcaf CVad Cvaf
115 370.70
C C
730.00 6.00 1.38 2.00 80.00 20.00 4.85 12.80 35.97 32.96 26.39 24.19 32.79 30.05 4464.00 4445.00
% % % %
C S H M
Thanks