Flue Gas Recirculation of the Alstom Sequential Gas Turbine Combustor Tested at High Pressure

Abstract

Concerning the efforts in reducing the impact of fossil fuel combustion on climate change for power production utilizing gas turbine engines Flue Gas Recirculation (FGR) in combination with post combustion carbon capture and storage (CCS) is one promising approach. In this technique part of the flue gas is recirculated and introduced back into the compressor inlet reducing the flue gas flow (to the CCS) and increasing CO2 concentrations. Therefore FGR has a direct impact on the efficiency and size of the CO2 capture plant, with significant impact on the total cost. However, operating a GT under depleted O2 and increased CO2 conditions extends the range of normal combustor experience into a new regime. High pressure combustion tests were performed on a full scale single burner reheat combustor high-pressure test rig. The impact of FGR on NOx and CO emissions is analyzed and discussed in this paper. While NOx emissions are reduced by FGR, CO emissions increase due to decreasing O2 content although the SEV reheat combustor could be operated without problem over a wide range of operating conditions and FGR. A mechanism uncommon for GTs is identified whereby CO emissions increase at very high FGR ratios as stoichiometric conditions are approached. The feasibility to operate Alstom’s reheat engine (GT24/GT26) under FGR conditions up to high FGR ratios is demonstrated. FGR can be seen as continuation of the sequential combustion system which already uses a combustor operating in vitiated air conditions. Particularly promising is the increased flexibility of the sequential combustion system allowing to address the limiting factors for FGR operation (stability and CO emissions) through separated combustion chambers.

Selective exhaust gas recirculation in combined cycle gas turbine power plants with post-combustion CO2 capture

“…The feasibility of operating GT26/24 sequential combustion gas turbine engines with EGR has been investigated conducting process simulations (Guethe, Cruz Garcia and Burdet, 2009) and experimental combustion tests in a full-sized industrial lean premix burner (Burdet et al, 2010), and in a single burner reheat combustion test rig (Guethe et al, 2011). The engine operates at higher pressure ratio and the sequential combustion system, which consists of a generic lean premix dry low-NOx burner followed by reheat burner with a high-pressure expansion stage in between, allows to decouple the two main limiting factors for operation with EGR, i.e.…”

“…flame stability and CO emissions. The premix burner flame is sustained and stable for O 2 concentrations in combustion gases within a range from 2 to 5 vol%, which leads to CO2 concentrations in flue gases within a range from 6 to 9 vol% (Burdet et al, 2010;Sander et al, 2011) and CO emissions are lowered in the reheated burner, which runs stable in auto ignition mode due to the high inlet temperature (Guethe et al, 2011).…”

Chemiluminescence as diagnostic tool in the development of gas turbines

“…The original image is recorded, background-subtracted and rotated to compensate for the distortion caused by the fibre. The view field shows approximately the first third of the combustor and the flow direction SEV-chemiluminescence image recorded at full pressure conditions with UV fibroscope and DUX 11 filter (taken from [33]) at side view perpendicular to the flow is indicated in Fig. 12.…”

“…The spectra were obtained at an Alstom full scale test rig running at full engine pressure at the DLR Cologne facilities on a prototype engine reheat burner. The reheat test rig has also been described in [33]. The view direction is upstream of the combustor through a wide-angle lens covering almost all of the flame extension through the hot gas near the emissions probe.…”

“…As briefly explained already in [33] images were taken at the high pressure test cell at DLR Cologne at full scale GT burners with an UV transparent fibroscope filtered with DUX 11 filter. The light was detected on an intensified camera with variable opening times between 20 µs to be able to detect fast phenomena in the kHz order up to −800 µs for good light averaging.…”