Design Issues for the Methane-Steam Reformer of a Chemically Recuperated Gas Turbine Cycle

Significant research effort is currently centered on developing advanced gas turbine systems for electric power generation applications. A number of innovative gas turbine cycles have been proposed lately, including the Humid Air Turbine (HAT), and the Chemically Recuperated Gas Turbine (CRGT). The potential of the CRGT cycle lies in the ability to generate power with a high efficiency while achieving ultra-low NO emissions without the need for selective catalytic reduction of the exhaust gases. However, much of the work that has been published on such cycles is restricted to a discussion of the thermodynamic potential of the cycle, and little work has focussed on discussion of some of the specific design issues associated with such a cycle. More specifically, design of the chemical recuperation heat recovery device involves a complex design trade-off in order to achieve a design with acceptable hot and cold-side pressure drops and acceptable overall dimensions. The design of such a heat recovery device is more complex than that of a traditional heat recovery steam generator (HRSG), since the methane steam reformer must not only allow sufficient heat transfer to occur, but also allow a sufficient cold side residence time, so that the methane steam reforming reactions can come close to equilibrium, ensuring maximal methane conversion. In this work, the authors present a code capable of performing the design of a methane steam reformer heat recovery device based on a heat exchanger geometry similar to that of a traditional HRSG. The purpose of the paper is to discuss the key parameters relevant to the design of a CRGT MSR reactor, and how these parameters interact with the rest of the cycle. Various design options are discussed, and the results of a parametric analysis are presented, leading to the identification of several suitable geometries.