Hydrogen Combustion Within a Gas Turbine Reheat Combustor

Abstract

This paper describes a novel lean premixed reheat burner technology suitable for Hydrogen-rich fuels. The inlet temperature for such a combustor is very high and reaction of the fuel/oxidant mixture is initiated through auto-ignition, the delay time for which reduces significantly for Hydrogen-rich fuels in comparison to natural gases. Therefore the residence time available for premixing within the burner is reduced. The new reheat burner concept has been optimized to allow rapid fuel/oxidant mixing, to have a high flashback margin and to limit the pressure drop penalty. The performance of the burner is described, initially in terms of its fluid dynamic properties and then its combustion characteristics. The latter are based upon full-scale high-pressure tests, where results are shown for two variants of the concept, one with a pressure drop comparable to today’s natural gas burners, and the other with a two-fold increase in pressure drop. Both burners indicated that Low NOx emissions, comparable to today’s natural gas burners, were feasible at reheat engine conditions (ca. 20 Bars and ca. 1000C inlet temperature). The higher pressure drop variant allowed a wider operating window. However the achievement of the lower pressure drop burner shows that the targeted Hydrogen-rich fuel (70/30 H2/N2 by volume) can be used within a reheat combustor without any penalty on gas turbine performance.

Using Hydrogen as Gas Turbine Fuel: Premixed Versus Diffusive Flame Combustors

“…Not only does the additional compressor imply an economic penalty due to its cost but also a decrease of the net plant efficiency due to its electric consumption. [4] that the autoignition delay time for a hydrogen-rich mixture (H2/N2 = 70/30 by volume) is ten times shorter than natural gas. Moreover, discharge pressure must be 5-10 bar higher because combustors require a fuel injection pressure that may be significantly higher than the air pressure.…”

“…Provided that, in a combustion, the diluting nitrogen takes the place of an equivalent excess air flow rate, the electric, mechanical, and polytropic efficiencies of the nitrogen compressor are significantly lower than the gas turbine (GT) air compressor. It has been noted that adding some nitrogen to the fuel can facilitate fuel/air mixing [4,6], and for this reason, current research projects consider H2-N2 mixtures and not pure H2. Thus, even if pure nitrogen is an energy "free" byproduct of the ASU, nitrogen dilution implies an efficiency penalty.…”

Superior fuel and operational flexibility of sequential combustion in Ansaldo Energia gas turbines

“…The use of inline injection combined with small scale mixing devices in the sequential burner (Pennell et al, 2017) allows the burner to operate on a wide range of fuel types without substantial change in the mixing quality. It has been shown that the mixing of an inline injector is largely independent from the momentum flux of the injected fuel (Poyyapakkam et al, 2012) and for this reason the performance of the burner, in terms of emissions, remains constant across a large range of fuel types and temperatures. By placing the mixing elements carefully in relation to the injectors it is possible to achieve rapid high quality mixing between the fuel and air.…”

“…The careful design of the interaction between the induced vorticity field from these mixing elements and the fuel jet ensures mixing is maintained as the fuel type changes. The development of such a burner concept is considered in more detail in a previous paper (Poyyapakkam et al, 2012).…”

The Influence of Carrier Air Preheating on Autoignition of Inline-Injected Hydrogen–Nitrogen Mixtures in Vitiated Air of High Temperature

“…The fuel blend with a set point value of 70/ 30 vol. % H 2 / N 2 (Φ = 0.40) has been selected in accordance with the European Union framework 6 project ENCAP [19,20] guidelines for achieving carbon-capture targets of up to 90 % carbon capture in an IGCC-CCS plant. The mass flow rate of carrier air was calculated with a fixed set point carrier-to-fuel mass flow ratio (CFR) of 1.0 for all measurement points.…”