Heat recovery steam generators |


Compared with natural gas, H2 firing may result in increased


exhaust gas volumetric flow and higher temperature. (Source: NEM Energy)


Above: Hydrogen firing results in higher water content in the GT exhaust. (Source: NEM Energy)


the HRSG and acoustic provisions need to be analysed when designing the unit for H2


Increased water content in the exhaust gas flow


content below about 50%, it becomes significant moving towards 100% hydrogen firing.


A combined cycle power plant running on natural gas produces a gas turbine exhaust gas with a water dew point of around 47-50°C. Mixing hydrogen with the natural gas results in increased water content in the exhaust gas (and consequently increased water dew point). While the increase in water dew point is minimal with an H2


When adapting an HRSG installation for H2 cofiring, the condensate recirculation system needs to take into account the higher minimum water temperature, which is a function of the water dew point. Adaptation of heating surfaces at the cold end might also be considered, although this is only possible to a limited extent (or not at all) for existing installations.


Effects on HRSG performance and gas side pressure drop Converting an existing combined cycle power plant fired with natural gas to hydrogen firing, with additional constraints such as maintaining the same GT back pressure, design temperature and HRSG pressures, can be expected to result in a slight decrease in bottoming cycle performance. This can be attributed to the decrease in mass flow and change in specific heat of the flue gas. For a given heating surface, this implies a decrease in heat transfer and consequently less steam production. However, the reduction of steam production is small, of the order of 1-2%. The increased exhaust water dew point could also have a negative impact on performance, as additional thermal energy


firing.


needs to be used to recirculate the condensate to a higher temperature.


For new installations, in case of a larger volume


flow of flue gas, the gas side pressure drop in H2 fired plants will be slightly higher than for natural gas units, resulting in a slightly lower gas turbine output.


HRSG burner design for H2 firing


The conversion of an existing NG-fired supplementary HRSG burner system into an H2


These include, but are not limited to: change in properties and supply pressure of H2


flame radiation of H2 of H2


; and increase in NOx -


ready system capable of accommodating various blends of NG and H2


; increased


; higher combustion velocity emissions.


Overall, the design adaptations required to transition from an NG-fired supplementary burner system to an H2


-ready system must be carefully


studied on a case-by-case basis to ensure optimal operation and performance of the system. For new build power plants, it is, in principle, feasible to design a supplementary firing system capable of firing H2


and NG blends in presents several challenges.


any ratio ranging from 0%-100%. However the aforementioned challenges with respect to the combustion properties of H2


considered.


Hydrogen readiness certification ‘H2


readiness’ for a combined cycle power plant has already been clearly defined and a TÜV SÜD certification guideline is available. The impact of H2


and NG need to be


firing on a combined cycle plant


is split into focus areas such as fuel gas supply, gas turbine, HRSG, explosion protection, etc. The certification process is carried out for three phases of a power plant project: H2 Readiness Concept Certificate; H2 Project Certificate; and H2


- -Readiness -Readiness Transition Certificate. NEM Energy Group is already in receipt of


-Readiness Concept Certificate from TÜV SÜD, the first HRSG OEM globally to obtain such certification.


the H2


Components complementary to the HRSG, such as the exhaust gas bypass system, transition piece to inlet duct, burner system for supplementary firing, SCR and CO catalysts, are also included in the certification. The H2


readiness


certification for a specific plant in the realisation phase will confirm that the plant (initially running on natural gas) has been built according to the H2


readiness concept of the bidding phase.


Typical duct burner locations for supplementary firing. Burner design for hydrogen needs to consider, among other things, the difference in LHV and supply pressure between H2


and NG. (Source: NEM Energy) 14 | October 2023| www.modernpowersystems.com


Navigating the hydrogen roadmap All in all, the HRSG is impacted by firing hydrogen in the gas turbine and there are various challenges to be considered. However, as of today, HRSGs can be made hydrogen-ready in the design phase to minimise impacts when shifting to hydrogen at a later stage. NEM Energy offers heat recovery products behind GTs to support the hydrogen roadmap for both existing and new build applications.


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55