Boiler Efficiency: Definition
According to Wikipedia“Boiler Efficiency is a relationship between energy supplied to the boiler and energy output received from the boiler.
Boiler Efficiency usually expressed in (%) percentage
Boiler Efficiency: Calculation Formula
“Boiler efficiency (%) = heat exported by the fluid (water, steam) / heat provided by the fuel x 100.”
Boiler Efficiency Importance:
Boiler heat loss is loss of money, if your business losing money then it is a serious concern. Efficient boiler is the solution. Thermodyne Engineering Systems provide you various ways to improve your boiler efficiency, but to understand these ways we must know where the heat losses are actually occurring in your boiler system.
All the heat losses cannot be fully recovered but they can be reduced to large amount thereby improving your boiler efficiency which will save you a lot of money.
Boiler Efficiency: Heat Loss Types
There is various type of heat losses in the boiler.
Some of them are:-
Heat Loss Due to Unburnt Carbon
During the combustion process most of the fuel gets burnt but some of the fuel particles remain unburnt and are deposited along with the ash. If the size of fuel particles fed to the furnace is large, the surface area of contact of air and fuel particles decreases and quantity of unburnt increases. This accounts for potential fuel losses which would otherwise have been burnt to generate heat.
Dry Flue Gas Losses
This account for major heat losses amongst all. If the flue gases leaving the boiler is at high temperature than the temperature for which it is designed, then most of the heat is getting wasted leading to reduced boiler efficiency.
Heat Loss Due to Moisture in Fuel
If the fuel which is fed to furnace for combustion has a very high moisture content, most of the ignition heat required to burn the fuel will be wasted to evaporate the moisture content and then it will burn the fuel.
Heat Loss Due to Radiation and Convection
These losses cannot be measured but they increase with an increase in boiler surface temperature.
Loss due to sensible heat in bottom ash
Ash which is formed after the fuel is burnt, is generally at high temperature. No utilization of this heat will lead to significant heat losses.
Blowdown of impurities deposited at the bottom of the shell is considered a necessary activity because these impurities absorb heat. So in order to remove these impurities some amount of water is released from the shell which also leads to heat losses.
Boiler Efficiency Improvement Steps:
After Analysing heat losses in industrial boilers , boiler engineers or technicians can help you to increase your boiler efficiency by 6% – 10%.
Here are the few boiler efficiency boosting steps listed below:
- Complete combustion of fuel so that no unburnt is left behind is a good practice and will add to the boiler efficiency.
- Unburnt carbon coming out of the furnace can be re-injected again into the furnace so that complete combustion of fuel can take place.
- Bottom ash from the boiler is generally at high temperature and has a lot of sensible heat. This heat can be utilized to preheat the air or water used in a boiler.
- The optimum ratio of fuel to air and keeping the excess air as low as possible keeping in mind the complete combustion of fuel can increase the furnace temperature thereby increasing the radiation heat. Reducing excess air by 5% can increase boiler efficiency by 1%.
- Moisture free fuel should be fed to the boiler so that no amount of heat is lost in removing the moisture from fuel and all the heat can be efficiently used to convert water to steam.
- Most heat losses are due to the high temperature of dry flue gases leaving the boiler. Boiler maintenance should be done regularly and removing the scale deposited on the heat transfer tubes should be given prime importance as this scale prevents the transfer of heat between flue gas and water.
- Continuous blowdown of water is necessary to keep water impurities to optimum level but this also lead to heat losses, so in order to reduce the heat losses, it is important to check the number of blowdowns to be done in a day as well as this heat from water can be recovered by installing blowdown heat recovery system for preheating water or air entering a boiler.
- Radiation and convection losses though cannot be measured but can be reduced by regular maintenance of boiler and using insulation to prevent heat losses to the surrounding.
- Steam which is used in a process after transferring its heat gets converted to condensate water. This condensate is generally at high temperature and can be recovered using Condensate Recovery Module which can be reused to preheat water or air.
Other ways of improving your boiler efficiency are by installing Waste Heat recovery boilers / devices. Heat from the flue gases leaving the boiler can be recovered using equipment such as Economisers, Air pre-heaters, superheaters or using this waste heat in your process.
Boiler Efficiency Improvement Services in India:
Thermodyne Engineering System has 20 years of experience in design and fabrication of this equipment and can provide you numerous solutions of recovering your waste heat from the boiler.
Contact our boiler engineering to boost your boiler’s efficiency and save money.
Ankit Taneja, an IIT Roorkee alumni, is Boiler Design Engineer at Thermodyne Engineering Systems, one of the top steam boiler manufacturer in India. Ankit like to spend time in research and design new boilers for clients at thermodyne.