With many power plant owners and operators looking to blend hydrogen with natural gas to lower their carbon footprints, the question often asked is what will that mean for heat recovery steam generators (HRSGs)? The good news is that hydrogen has been present in boilers and HRSGs for decades. The industry has built-up extensive experience in dealing with what can be a tricky gaseous ingredient. While hydrogen does present challenges, they are within the capabilities of the vendor community.
As the density of hydrogen is about eight times lower than methane and has a lower Btu value per unit of volume, a lot more of it is required for combustion compared to natural gas. Hydrogen has about one-fifth of the heating value of natural gas, yet its flame temperature is about 4,000°F versus 3,600° for natural gas. This can cause material and stress problems for the gas turbine and HRSG as well as higher NOx levels.