Novel concept for indirect solar-heated methane reforming

Abstract

A model to investigate an indirectly solar-heated bayonet-tube reactor for converting methane to synthetic gas (syngas) through combined steam reforming and dry reforming is presented. Concentrated solar radiation, as generated in solar power towers is capable of efficiently providing heat for this process. Different concepts of reforming reactors have been analyzed and assessed under the following considerations: The risk of carbon deposition at low-temperature regimes in the reactor, the possibility of heat recovery from the syngas, maximized heat extraction for the air stream to improve the receiver efficiency and flexibility. As a result, a novel bayonet-tubes reactor design has been developed. Different simulation software tools have been applied for this purpose. Simulations in EBSILON®Professional show that the heat recovery from the syngas allows a 28 % higher syngas production (8.42 kg/s instead of 6.59 kg/s) based on the same solar resource, since the required heat for the methane reforming is simultaneously transferred from both air and syngas. In the system simulations, the syngas cools down from 900 °C to about 451 °C while the air is cooled down from 930 °C to approx. 220 °C. A one-dimensionally discretized model of a single bayonet-tube reactor was simulated in Dymola to corroborate that the reactor design provides sufficient temperature gradients for the heat transfer from air and syngas to the reactant flow. Further thermal and fluid mechanical analysis were performed in ANSYS® Fluent as preparation for building a first prototype.