According to the ASME Energy Balance Method of calculating industrial boiler efficiency, you should account for convection losses, radiation losses, and stack losses. However, you should dig a little deeper to understand the factors that directly affect these important readings, which ultimately affect industrial boiler efficiency.
In general, the design of your boiler is imperative. Even so, there are several other environmental factors that impact the efficiency of your industrial boiler. Understanding what they are will help you recognize shortcomings in your boiler, which will empower you to resolve these issues and put your system on the fast path toward optimization. Continue reading to learn more the five secret factors that may be killing your industrial boiler efficiency.
1. Excess Air Effect on Industrial Boiler Efficiency
All combustion burners require some degree of excess air. Excess air is defined as the amount of air in a combustion process greater than the amount theoretically required for complete oxidation. To ensure complete combustion of the fuel used, combustion chambers are supplied with excess air. Excess air increase the amount of oxygen to the combustion and the combustion of fuel. When fuel and oxygen from the air are in perfect balance - the combustion is said to be stoichiometric. The combustion efficiency increases with increased excess air until the heat loss in the excess air is larger than the heat provided by more efficient combustion.
With ultra low-emission burners, excess air is used to minimize the production of NOx and carbon monoxide by managing the flame temperature.
The excess air ultimately absorbs a portion of the heat from combustion. As a result, it reduces the efficiency of the transference of heat to the water in the boiler. This issue may be addressed by calibrating the boiler at multiple firing levels and regularly.
2. Flue Gas Temperature
"Stack temperature" or flue gas temperature measures the temperature of the combustion gases when they leave the boiler. If the flue gas temperature is high, it suggests the heat created by the boiler isn't being effectively used to generate steam. In other words, a high flue gas temperature suggests heat is being lost.
When looking to address heat loss through high flue gas temperatures, it commonly involves installing combustion air heaters or installing economizers. These methods are designed to recover heat for the boiler system.
If the boiler depends on biomass, coal, or other solid fuels, it's also imperative to include a regular boiler checklist or maintenance program. Boiler maintenance will ensure the system is operating efficiently and make sure the surfaces of heat transfer in the boiler are clean.
3. Convection and Radiation Losses
Convection and radiation losses are the losses of heat emanating from the boiler during standard operation. Simply put, you can't do anything about convection and radiation losses because they're inevitable. Even though they're inevitable, you can take the right steps to minimize them.
Two effective strategies for reducing losses from convection and radiation are:
- Installing superior insulation
- Controlling the airflow over the boiler surface
When you utilize proper insulation methods, you will bolster industrial boiler efficiency by lowering heat losses and reducing surface temperature. Shielding the boiler from indoor drafts and outdoor winds prevents the loss of heat caused by air flowing over the boiler surface.
4. Fuel Specification
As virtually anyone would expect, fuel specification can have a dramatic effect on your industrial boiler efficiency. Addressing this issue is as simple as establishing the proper specifications for fuel and making sure the actual fuel meets the documentation criteria.
Due to the high content of hydrogen for industrial boilers relying on natural gas, fuel specification should be of the utmost importance. It's important to understand that a significant portion of the hydrogen is transformed into water during combustion. This process can monopolize energy, which could be more aptly used in the process of combustion.
The primary combustible in natural gas is (CH4) or methane. However, there are several lesser traces of:
- Pentane (C5H12)
- Ethane (C2H6)
- Butane (C4H10)
- Propane (C3H8)
The higher the content of hydrogen in the combustion gases, the more water produced through combustion. Simply put, natural gas with higher methane concentrations and lower proportions of other gases will burn much more efficiently.
5. Ambient Temperature
The temperature of the combustion air entering the boiler is called ambient temperature. Another definition for ambient temperature is the temperature of the air impelled by the forced draft fan. Regardless how you define it, ambient temperature can have a relatively noticeable effect on industrial boiler efficiency.
It can also have an impact on industrial boiler efficiency calculations due to it affecting the net stack temperature. Net stack temperature is the difference between the flue gas temp and the ambient temperature.
Although it's tempting to minimize ambient temperature with hopes of lowering flue gas temp, a 40 degree alteration in ambient temperature can affect industrial boiler efficiency by one percent or more.
Achieving the optimum balance is a delicate situation that involves strategic consideration. The majority of industrial boiler efficiency calculations suggest you achieve an ambient temp of 70° or 80° Fahrenheit.
Contact Applied Technologies of New York
After you have come to the conclusion your boiler is operating inefficiently, it's important to understand the underlying causes. Even though the actual equipment should never be overlooked, you must also consider the number of environmental factors that may be affecting the operation of your boiler. In most instances, addressing these environmental factors requires less capital and a much more manageable approach.
Contact Applied Technologies of New York for assistance evaluating your industrial boiler efficiency or to implement a new boiler system to bolster efficiency.