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

Abstract

The increasing use of renewables for energy production is also accompanied by an increasing need for flexible power production, while aiming at carbon free emissions. The potential solutions of energy storage of excess generation from renewables through hydrogen production and pre-combustion carbon capture are gaining momentum. Both scenarios require gas turbines capable of operation with hydrogen-based fuels. At the same time, the composition of natural gas considered for use within gas turbines is becoming significantly more variable due to increased use of liquefied natural gas and a wider range of gas sources and extraction methods. Fuel flexibility, both in terms of the amount of hydrogen and higher hydrocarbons is therefore of utmost importance in modern gas turbine development. This paper provides an overview of key steps taken in the design and development of an operation concept, leveraging the advantage of the GT36 Constant Pressure Sequential Combustion system (CPSC) – a premixed low emission reheat combustion technology, characterised by an extremely broad fuel range capability, composed of two combustion stages in series. The results presented in this paper clearly show that the complementarity behaviour of first and second combustion stages – extensively proven for fuels containing high concentrations of higher hydrocarbons – can be extended to hydrogen. Ultimately, this allows the achievement of ultra-low emissions at full combustor exit temperature maintaining the power and efficiency performance of F and H class engines. Recent validation performed at the high pressure combustion facility at DLR-Cologne, proved fuel flexibility with minimal or no de-rating with hydrogen contents from 0 to 50% in volume, without any modification of the standard GT36 hardware. Based on the current studies, the flexibility of the GT36 CPSC system is envisaged to enable a further increase in hydrogen content allowing this H class engine to be operated with 100% hydrogen.