Carbon Dioxide Reforming of Methane in Directly Irradiated Solar Reactor With Porcupine Absorber

Abstract

A new solar volumetric reactor for CO2 reforming of CH4 was tested at the Solar Tower of the Weizmann Institute of Science. The reactor design was based on extensive previous experimental work with a volumetric receiver for heating air and simulation of volumetric reformer The main parts of the reactor were a conical quartz window and a Porcupine absorber as the surface where chemical and thermal energy conversion took place. A specially developed ruthenium catalyst was used. The CO2 to CH4 ratio was about 1:1.2, and the total inlet flow rate was between 100 slpm and 235 slpm (slpm denotes standard liter per minute). The maximum absorber temperature was kept below 1450 K. The conversion of CH4 reached 85%. The total power absorbed was between 10.3 kW and 18.2 kW. of which the thermal power part was 2.3^.5 kW and the stored chemical enrichment was 7.5-13.7 kW. The results indicate that this type of volumetric reactor can be used effectively for CO2 reforming of CH4. and further work aimed at improving the total efficiency of the system is in progress.

A review of solar methane reforming systems

“…The maximum methane conversion achieved was 85% [69]. Increasing the flow rate or pressure reduced the conversion, but the effect of changing the pressure was outweighed by the change in temperature or flow rate [69].…”

“…The porcupine absorber was also tested for with dry reforming to examine the effects of the gas pressure and flow rate [69]. The maximum methane conversion achieved was 85% [69].…”

Efficiency potential of indirectly heated solar reforming with open volumetric solar receiver

“…The requirements concern the temperature, pressure and composition of the syngas. The composition is taken account for through the term M, that refers to the molar ratio (z) of hydrogen, carbon dioxide and carbon monoxide, as shown in Equation (6). It should obtain values close to 2.05 in order to ensure high conversion of methane and high methanol yield [31].…”

“…2. Directly irradiated receiver reactors, where the absorbing surface is also the reaction surface (demonstrated in the CAESAR project in 1991 by Buck et al [5] and in 2011 by Rubin and Karni [6]). …”

Hydrogen from solar energy, a clean energy carrier from a sustainable source of energy

“…The product of Equation is called syngas where, by using the catalytic water‐gas shift reaction (CO + H 2 O = H 2 + CO 2 ), the produced CO can be shifted to hydrogen, and the separation of the produced H 2 and CO 2 can be performed by the pressure swing adsorption technique . Several solar steam‐gasification and solar‐steam reforming reactors have been tested to develop solar hydrogen production. Some of these systems have already been employed in the industry burning fossil fuels to maintain the required process heat, which results in the efficiency reduction due to the irreversibility of external combustion.…”