The most important thing to consider when comparing the types of fuel used in boilers is that modern boilers, particularly commercial ones, are designed to be more fuel-efficient than their old, outdated counterparts.
Newer boilers are also built to be durable and harness the maximum heat possible that is generated by the fuel. If you wish to get the best performance from your commercial boiler, you must first use the right fuel type and then optimize the boiler for maximum efficiency.
The type of fuel you use in your commercial boiler directly affects its efficiency, operating costs, safety, and environmental impact. Therefore, to find the right one for your needs, it’s helpful to familiarize yourself with the most common fuel types available to use in your boiler. This post highlights the various types of fuel used in boilers to help you choose the right one for your commercial boiler.
Common Types of Fuels Used in Commercial Boilers
The term fuel generally refers to the material or substance, either natural or artificial, that the boiler converts into heat. Most boiler fuels combust to produce heat energy, but some, such as electricity, do not and are considered alternative fuels.
- Solid fuels include coal and wood (including biomass and biofuel)
- Liquid fuels can be subcategorized into residual oils and distillates. This category and its subcategories cover petrol, various types of diesel and its distillates, and LSHS (Low Sulfur Heavy Stock).
- Gaseous fuels include natural gas, coal gas, producer gas, and liquefied petroleum gas (LPG). In this category, the most notable are natural gas and LPG.
- Alternative and agro-waste fuels include electric boilers, and those fueled by biogas, and other combustible fuels recovered from waste materials.
Many boilers are designed to use any fuel of the same form. For instance, a gas boiler should burn most types of gaseous boiler fuel while oil boilers can use most types of liquid fuel with minimal reconfiguration.
The Pros and Cons of The Best Types of Fuel Used in Boilers
Finding out what boiler fuel is ideal for your business can be challenging because each fuel type has its benefits and drawbacks. Factors such as cost of installation, running costs, usage location, and environmental impact will likely shape your decision. This brief guide covers the most important pros and cons of the most common boiler fuel types to help you make the best and most efficient fuel for your boiler.
1. Natural Gas Boiler Fuel
According to Global Market Insights, the US commercial boiler market in 2020 was worth a whopping $1.5 billion. As the gas network infrastructure expands all over the country, gas-fired boilers continue to be the best selling styles on the market. Besides, gas fuel types have proven to be efficient and more convenient than most other types of boiler fuel.
Pros of Natural Gas (NG) Boiler Fuels
- NG is cheap and readily available.
- NG is greener than oil and other fossil fuels. Gas fuel emits about half the amount of CO2 that oil does.
- NG is an efficient fuel with good returns on every unit of energy used.
- NG-powered boilers do not need large storage tanks or special equipment.
- Water vapor in the exhaust is a byproduct of burning natural gas. The latent energy in this is available for recapture in condensing boilers, with efficiencies of 95+%.
Cons of Natural Gas (NG) Boiler Fuels
- NG fuel can become prohibitively expensive for businesses not on the gas main network.
- NG services can be “interruptable”. In cases of high demand, certain users can be curtailed, temporarily.
- The initial installation costs of gas lines can be quite high.
- NG is not green energy; it is still a fossil fuel and emits CO2.
2. Oil Boiler Fuel
There are two types of boiler oil fuel: kerosene, popular in domestic boilers, and gas oil (this is then divided into different grades of oil – light to heavy), often used in commercial boilers. Boilers that burn oil are most common in places with little to no access to gas boiler fuel. The oil is often supplied by a truck and pumped into a storage tank close to the boiler.
Pros of Oil Boiler Fuel
- Oil is the cheapest fuel for commercial users with no access to main gas lines.
- Oil is easy to control and manage. The boiler can burn it at any time to produce heat when needed.
- Oil produces less water vapor during combustion, leading to less stack losses and a high non-condensing efficiency. For businesses with few options, gas oil is an excellent source of fuel for their boilers.
- Businesses can purchase and stock up on fuel at any time.
Cons of Oil Boiler Fuel
- Oil storage tanks can take up valuable space on a business premises.
- Compared to gas and electric fuels, oil is not as convenient. A business must continuously refill the oil tank to keep using the boiler.
- If oil is used as the backup fuel, routine testing of the oil system is a must
- Oil stored for long periods of time must be kept in good condition with the use of fuel polishers and other treatment equipment.
- Oil prices can fluctuate wildly, especially during conflict or instability around the world.
- Oil is a dirtier fossil fuel with higher emissions.
- It is more costly to maintain and service boilers and equipment that use oil fuels.
3. LPG (Liquefied Petroleum Gas)
There are four types of natural gases: methane, ethane, butane, and propane. These fuels are often lumped together with liquefied petroleum gas (LPG) because they have almost similar attributes. Since the mid-90s, these fuels have become popular for commercial users largely because of their high density, making them very efficient.
Pros of LPG
- These gaseous fuels are dense and burn cleanly to produce high returns for every unit of energy used.
- LPG and natural gas fuels for boilers emit a lot less CO2 compared to oil fuels for the same amount of heat produced.
Cons of LPG
- LPG can be quite costly for commercial boilers, especially compared to oil fuels.
- LPG fuel needs a storage tank that can take up valuable space on a business premises. Fuel must be delivered regularly, when it is being utilized by the boiler.
Coal, the most used solid boiler fuel, has a low fuel density compared to liquid and gaseous fuels. Once one of the most commonly used fuels for boilers, its use in recent years has fallen out of favor in commercial and industrial boiler applications, relegated to larger power generation systems.
Pros of Coal
- As one of the oldest and most common fuel sources, coal is cheap and readily available.
Cons of Coal
- Coal has a low energy density.
- Coal produces a lot of ash and smoke waste.
- Current emission requirements require additional emissions treatment systems to meet current standards
- Coal is a dirty fossil fuel with high CO2 emissions and environmental toxins.
5. Biogas (Landfill gas, digester gas, etc.)
Various types of burnable gasses are generated through natural and industrial processes. Examples include landfills (Landfill Gas, LFG), as a byproduct of some food processing plants, and as a byproduct of decay of other natural wastes and chemical processes. This gas, composed primarily of methane and CO2 has a BTU content of roughly half that of Natural Gas (can vary depending on the gas makeup). Since this gas is already being produced as a byproduct of an existing process, it can be readily available and cheap (to produce), but it does bring with it other considerations.
Pros of Biogas
- Free, as it is already produced as a byproduct of an existing process.
- If used in a process at the existing facility, it is already on site and available to use
- Though they produce CO2, the emissions produced are less potent greenhouse gases than the original Methane
Cons of Biogas
- Though free and available, waste gases do require a system to collect and treat the gas as well as special considerations prior to use in boiler, this adds back costs
- Moisture content and gas quality are critically important, there are minimum/maximum requirements, re. Gas composition, to make them suitable for use in boilers.
- The gas is generally more corrosive than other gaseous fuels (NG or LPG), requiring more expensive corrosion-resistant components in gas trains, burners, and boilers.
- The volume of gas produced may not be enough to continuously supply the boiler with enough fuel, requiring a backup/supplemental fuel source. This can increase control complexity or operational supervision, to allow switching fuels over as needed or on the fly.
Wood boilers are not commonly used commercially for many reasons: wood, as a fuel, has a very low energy density, produces a lot of waste, is cumbersome and inconvenient to use, and wood boilers are dirty and inefficient. However, because wood is available everywhere and inexpensive, it can make sense in the right application, such as boilers associated with the lumber industry.
Pros of Wood
- Wood is carbon neutral and renewable energy.
- Dual oil-and-biomass fuel boilers improve the convenience of both fuels while helping lower the user’s carbon footprint.
- The price of wood is low enough to compete with other fuel types despite its low energy density.
Cons of Wood
- Wood takes up a lot of storage space. Wood boilers are also large systems that use up a lot of space on business premises.
- Wood fuel must be kept dry to burn efficiently. This can be demanding, especially in wet places or during rainy seasons. Moisture content greatly affects the boilers output and combustion settings.
- Wood boilers must be regularly cleaned to remove soot and wood debris.
Most boiler types can use one or more different fuel types – perhaps with a few exceptions, such as electric boilers. In general, boiler design dictates the types of fuels that can be burned, as furnace geometry, materials, fuel handling equipment, etc. must all be taken into account. Most commercial boilers are readily able to be trimmed out for natural gas/oil or a combination of gas with backup oil. Industrial Water Tube and Scotch Marine boilers (and some other designs) can be designed to fire solid and biogas fuels. The first step is to assess the fuel input (btu/hr) that will be needed; from there relative fuel costs can be compared, and boiler design/type can be considered.A realistic load profile should be developed as this is useful in comparing realistic fuel cost savings (and Life Cycle Costs) or emissions reductions between different fuels/boilers. All of that combined, leads to an informed decision.
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