Steam boilers, as we know, play an indispensable role in any field of industry. To run and handle any industry or processing plant is not everyone’s cup of tea. Various factors are determined and decided upon to ensure that the concerned industries are running smoothly and effectively.
Steam boiler manufacturers provide their efficient and reliable boilers to their clients but are they truly as efficient as they claim? Why is efficiency an imperative factor in choosing a boiler? And most importantly, how can we measure and determine the efficiency of the boiler? Read on to know the details to direct your decision in finding an efficient boiler.
Steam boilers are an important tool in various industries and an unarguable fact is that the initial investment in a boiler is a mere fraction of the total annual investment on its fuels. Hence it is prudent to ensure that the boiler delivers the efficiency as warranted by the steam boiler manufacturer.
Efficiency in Steam Boiler:
In a nutshell, boiler efficiency is the difference between energy input and energy output that can be calculated and indicated with percentage. The boiler efficiency depends on several factors particularly, Combustion efficiency and Thermal efficiency. It is also termed ‘fuel-to-steam efficiency’ that can assist in assessing the future fuel costs and the estimated lifespan of the boiler.
Methods to Ascertain Boiler Efficiency:
There are several ways to determine steam boiler efficiency. Different methods calculate different factors that eventually lead to boiler efficiency. In calculating boiler efficiency, a ratio varying from the expected ratio indicates the need to modify the operation process or get in touch with the steam boiler manufacturer for their superior knowledge and assistance.
Combustion Efficiency:
Combustion efficiency helps to determine the burner’s capability to burn fuels effectively and assess the unburnt fuel and excess air present in depleting. A boiler is considered efficient if both the unburnt fuel and excess air are at lower levels.
When the boiler efficiency deviates from the desired ratio, it is advisable to assess flue gas oxygen and stack temperature because they are important factors affecting Combustion efficiency. The ideal range of Combustion efficiency of steam boilers is between 75% and 89%
Thermal Efficiency:
Thermal efficiency assesses the efficacy of the heat exchanger that enables the transferring of the heat energy to the water or steam. With setting up of soot or water scaling, poor condition of the heat exchanging surface within the boiler results in affecting the thermal efficiency negatively, which, in turn, lowers the overall efficiency of the steam boiler.
Fuel-to-Steam Efficiency or Fuel-to-Water Efficiency:
Fuel-to-Steam efficiency or Fuel-to-Water efficiency (also referred to as ‘Boiler efficiency’ or even Thermal Efficiency) determines the overall efficiency of the boiler. It differs slightly from thermal efficiency by calculating not only the effectiveness of the heat exchanger but also the radiation and convection losses.
The optimum score for fuel-to-steam efficiency ranges from 80% to 85% and acts as the indicator for the overall boiler efficiency.
Factors Affecting the Boiler Efficiency:
Many factors contribute to the efficient performance of a boiler. It is imperative to understand them while assessing the boiler efficiency and take appropriate actions or contacting the steam boiler manufacturer in due course to ensure better efficiency and longer lifespan of the boilers.
Some of the factors that affect the efficiency of steam boilers are:
Flue Gas Temperature:
Flue gas temperature refers to the temperature of the combustion gases when they exit the boiler. In simple words, high flue gas temperature indicates that the heat is being lost during the process. It means that the efficiency of the boiler is below the desired range.
Stack Losses:
Stack temperature is an ideal indicator of boiler efficiency. The stack temperature refers to the temperature of the combustion gas (both dry flue gas and water vapor) exiting the boiler. It demonstrates the heat which did not transfer from the fuel to the water or steam, thus indicating the effectiveness of the heat exchanger. It displays the fuel-to-steam efficiency of the boiler
Radiation and Convection Losses:
Radiation and Convection losses in a steam boiler are inevitable as they are the heat losses that radiate from the boiler vessel. The amount of radiation and convection losses varies due to the factors such as boiler size, boiler type, operating pressure, and air velocity across the boiler. Such factors have an undeniable influence on radiation and convection loss. But ultimately, every boiler faces some type of heat loss that radiates in the boiler vessel.
Ambient Air Temperature:
Ambient air temperature considerably affects the efficiency of boilers. The temperature of the combustion air emerging in the boiler is known as ambient air. To understand this better, a 40 degrees Fahrenheit can vary the boiler efficiency by 1% or more that may have a far-reaching influence on the operations of the steam boilers.
Turndown:
Turndown indicates the capability of the boiler to attain a wide range of output (low to high). Therefore, a higher turndown implies a wide range of output ability of the boiler. Boilers achieving a high turndown ratio can supply steam at lower rates without restarting or shutting down. It shows that when demand load fluctuates, higher turndown can facilitate efficiency improvements.
Fuel Specification:
Fuel specification plays a key role in determining the efficiency of the boiler. Let us consider the example of gaseous fuels as they contain high hydrogen content resulting in high water vapor during combustion. It leads to high vapor loss and low efficiency. That is the reason for oil-fired boilers offering higher efficiency as compared to boilers burning on gaseous fuels.
Tips to Increase Boiler Efficiency:
One has to calculate and determine the factors that are hindering the higher efficiency of boilers. There are several ways to improve the efficiency of the boiler by taking some appropriate and well-timed action:
- Installing a Flue Gas Economizer to assist in recovering the surplus heat
- Improving Boiler Insulation to reduce the radiation and convection losses
- Recovering heat from boiler blowdown
- Cleaning and regular servicing of boiler internals
- Retrofit or Upgrade Boiler Burners or Components
- Adopt and Practice Preventive Maintenance
- Contact Steam Boiler Manufacturer for regular service check
Rakhoh Boilers are a leading and trustworthy steam boiler manufacturer committed to designing, manufacturing, and installing highly efficient and reliable boilers for clients. Our expert and dedicated staff manufacture and install boilers along with providing excellent and cost-effective retrofit and upgrading services to ensure long-lasting, highly efficient, and durable steam boilers.
