Using Hydrogen to Decarbonize Industrial Fired Heaters

Switching from fuel gas to a low-carbon hydrogen fuel is a promising option for decarbonizing industrial facilities.

With the urgent need to improve sustainability, organizations in the chemical process industries (CPI) are exploring ways to decarbonize their processes and reduce greenhouse gas (GHG) emissions. For an industrial facility, GHG emissions are typically classified into three categories:

• Scope 1 emissions are those that occur directly from the facility, such as emissions that occur during the operation of equipment and processes.
• Scope 2 emissions are those that occur due to the purchase of energy, such as electricity generated by fuel firing or purchased steam from an outside supplier.
• Scope 3 emissions are those that occur either upstream or downstream in the value chain, including emissions that occur during the production of a feedstock or hydrogen that is purchased. For a refinery that makes fuels (e.g., jet fuel or diesel), Scope 3 emissions account for those fuels being used in transportation vehicles and the combustion products released to the atmosphere.

The Scope 1 emissions are the emissions that the facility owner has the most control over, although they can often exert influence over Scope 2 and Scope 3 emissions based on business decisions and other commercial agreements. For most industrial facilities, the vast majority of Scope 1 GHG emissions are carbon dioxide (CO₂) emissions from the combustion of hydrocarbon fuel in steam boilers and process heaters.

An industrial facility looking to reduce Scope 1 and Scope 2 CO₂ emissions should consider five primary techniques:

1. increase energy efficiency
2. use electrification to shift fired heater/steam boiler energy needs to low-carbon electrical power
3. use a renewable fuel (e.g., bio-gas) in fired equipment
4. use carbon capture on the fluegas from the fired equipment
5. convert the heater to essentially 100% hydrogen fuel.

Techniques 1 and 2 can provide incremental benefits but rarely offer substantial reductions. Technique 3 is often limited by the availability of renewable fuels to replace a facility’s current fuel source. Techniques 4 and 5 are the most common ways for the majority of facilities to achieve significant reductions in their CO₂ emissions.

Technique 4 (carbon capture) requires the facility to have a suitable disposition for the recovered CO₂ (i.e., capturing the CO₂ and either storing or consuming it in another process). Also, many facilities have several heaters spread out over many units, and plot space may be very limited, making this option challenging and very expensive.

This article expands on Technique 5 (converting heaters to 100% hydrogen fuel). Hydrogen is often categorized into colors based on its production technique. The two primary ways to produce low-carbon hydrogen are to make green hydrogen via electrolysis of water, using low-carbon electricity, or to make blue hydrogen via steam methane reforming (SMR) or autothermal reforming (ATR) and capture the CO₂ produced.

It should be noted that using hydrogen may introduce new risks to a facility — particularly if the facility does not currently have hydrogen present. Hydrogen is a low-molecular-weight molecule and is prone to material diffusion (hydrogen embrittlement) as well as leakage. Hydrogen piping materials may have special material considerations to minimize these effects. Compared to methane, hydrogen has a higher upper flammability range. The two compounds are similar in autoignition temperature and low flammability range. However, the ignition energy required for hydrogen is roughly ten times less than that of methane, meaning it poses a much higher risk of ignition (both inside the system and outside the system as a result of leaks).

This article lays out the basics of this decarbonization approach and discusses potential project scope, including addressing possible issues. Information on calculating project economics is also presented.

Combustion fundamentals

The general hydrocarbon...