Experimental evaluation of a double-pipe heat exchanger for syngas cooling from soaked palm shell gasification

Abstract

The growing demand for renewable and low-carbon energy has intensified the exploration of biomass residues as alternatives to fossil fuels. Palm shell, an abundant by-product of the palm oil industry, has favorable fixed carbon content and calorific properties for thermochemical conversion through gasification. However, syngas produced from biomass gasification is typically discharged at elevated temperatures, requiring cooling for safe handling and downstream applications. This study experimentally assessed the thermal performance of a water-cooled double-pipe heat exchanger integrated with an open downdraft gasifier using soaked palm shell as feedstock. The evaluation focused on reactor temperature distribution, syngas temperature reduction, heat transfer rate, and cooling effectiveness during continuous operation. The gasification zone, located at a reactor depth of 26–77 cm, maintained a temperature range of 600–900°C during operation. The heat exchanger reduced the syngas temperature from 188.1°C to 35.2°C, corresponding to a heat transfer rate of 1,281.3 W and cooling effectiveness of 97.74% under the tested conditions. These results indicate that the double-pipe heat exchanger provided effective cooling of biomass-derived syngas and can support thermal management in small-scale biomass gasification systems. The results also demonstrate the potential of integrating syngas cooling with downdraft gasification for safer handling and improved downstream compatibility.