Simple Guide to the Different Boiler Fuel Types

Simple Guide to the Different Boiler Fuel Types

Whether it's a fire-tube boiler, tubeless boiler, hot water boiler, water-tube boiler, or any other classification, all systems will utilize one or more than one of the different boiler fuel types. In fact, many boiler models are actually distinguished and characterized by the different boiler fuel types it uses. 

The type of fuel a boiler uses is critical for a range of reasons, but it plays a direct role in determining the operating costs as well as your facility’s environmental impact. As a result, it’s vital to understand and be familiar with all of the different boiler fuel types. Let’s take a closer look at each of the different boiler fuel types.

Six Different Boiler Fuel Oil Types

There are a total of six different types of fuel oil: residual oils and distillate types of diesel. Both of these categories of fuel oil can be divided into numbered subcategories, Number 1 through Number 1:

  1. No. 3 fuel oil and No. 4 fuel oils are combinations of distillate diesel and residual oils

  2. No. 1 and fuel oil No. 2 are distillate types of diesel

  3. Fuel oil No. 5 & 6 are residual oils

In either case, the two most commonly used categories of boiler fuel oil types are No. 2 distillate diesel as well as No. 6 residual oil, which is also called “bunker fuel.” While No. 2 distillate types of fuel oil has a lower energy density, it emits less combustion greenhouse gas.

Yet, the most significant value offered by fuel oil types is its energy density. For instance, whenever fuel oil energy is measured in BTUs it is extremely high. In comparison to other boiler fuel types, no other type — gas, liquid, or solid — has a higher energy density than residual oil and distillate diesel. The exceptionally high energy density allows boilers that operate off of fuel oils to be very efficient. Savvy facility owners enhance their efficiency by using a pre-combustion fuel catalyst

Boiler Fuel Types: Propane

Another common type of boiler fuel is propane, and it offers a range of desirable attributes. Since the mid 1990s, there has been a readily available surplus of propane across the United States. Second to fuel oils, propane has the second highest energy density, which makes this fuel an exceptionally efficient solution that is very easy to come by.

However, there are a myriad of concerns and questions over the eco-friendliness of propane, which is a byproduct of natural gas. And even though propane is readily available, it’s relatively expensive when you compare it to other boiler fuel types.

Propane boilers can be found in three out of the five different types of boiler configurations: cast iron, fire tube, and water tube. Although propane has a high energy density when compared to other boiler fuels, it is approximately 20% less than diesel, which produces about 15% less BTU per gallon than fuel oil.

This means propane is more expensive than diesel and fuel oil and produces less energy than  No. 2 diesel. In addition, the fuel density of propane is about 65% of fuel oil’s density.

Natural Gas Types of Boiler Fuels

As the most common type of residential boiler fuel in the United States, natural gas is relatively inexpensive and readily available. Similar to propane, the energy density of natural gas (62%) is low compared to No. 2 diesel. The energy density of natural gas is less than 50% of the energy density of fuel oil. Yet, considering natural gas burns cleanly and is easy to transport, it is a wildly popular residual type of boiler fuel.

The key concern surrounding natural gas is it can be up to 90% methane gas, which is a dangerous greenhouse gas that can be 34% more potent than CO2. Although methane gas may be inert whenever it is burned, it causes significant damage to the ozone once it makes its way into the atmosphere. Even though natural gas is cheap, it comes with a hefty environmental impact.

Electric Types of Boiler Fuel

Without the use of a flue, electric boilers are exceptionally efficient because no heat is lost. In addition, electric boilers are usually inexpensive to purchase and small. Yet, the cost of electricity means that electric boilers are typically only used for residential uses. 

Even when electric boilers are used in small facilities and home, the price of power makes it much more expensive when compared to fuel-fired boilers according to data by the Environmental Protection Agency.

With respect to emissions, 85% of the electricity created in United States comes from nuclear-power plants or from coal. In addition, the majority of coal-fired boilers operate on crushed coal. As a result, most electric boilers are either powered by nuclear or solid fuel furnaces — indirectly.

Coal Boiler Fuel Types

Solid fuel boilers that operate on coal are cheap to operate as well as inexpensive to purchase and install. Coal produces large amounts of waste in the form of bottom ash, fly ash, and very  high emissions. The energy density of most types of coal is very low, but can depend on the actual type of coal:

  1. Lignite, Bituminous, and Sub-bituminous coals are among the lowest fuel densities of all fuel types, but

  2. Anthracite coal actually has a higher energy density than propane, natural gas, and even gasoline. Only diesel fuel, fuel oil, and kerosene have higher megajoule per meter cubed outputs than Anthracite types of coal. 

In addition, Anthracite coal boasts a significantly lower CO2 emission than other types of coal.

Wood Types of Fuel

While only used for residential purposes, wood boilers are the least expensive in every attribute. Wood types of fuel deliver a low BTU production, large volumes of waste material, and large sums of emissions. Although wood is available virtually everywhere and inexpensive, wood boilers are dirty and inefficient.

Biofuel Types of Boilers

Biofuel boilers are basically boilers that burn wood, but the wood comes in the form of logs, pellets, wood chips, wood construction debris, corn husks, combustible plant material, as well as recycled wood. The biggest advantage to using biomass boilers is that biofuel is a renewable resource. 

However, biofuels can be expensive — whether it’s a repurposed product or recycled, which makes biomass boilers typically more expensive than boilers that use other types of fuels. Most importantly, biomass has the least energy density of all fuels. It’s approximately 38% less dense than coal, which means for the emissions produced and the costs, it doesn’t deliver a substantial return in BTUs.

Contact ATI of New York Today

From food production to factories to schools to hospitals, boilers are a critical piece of equipment across a range of different industries. Boilers can vary greatly in intensity and size as well as utilize different methods of heat exchange and boiler fuels. 

The product and sales engineers at ATI of New York will listen to your needs and help you choose the best boiler to achieve your facility's goals. As the preferred manufacturer’s representative, we are home to a world-class lineup of boiler equipment from the top producers in the world. Read to learn more?

Contact ATI of New York today to learn more about our cutting-edge lineup of boilers.

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