Assessment of Heat Exchangers for the Integration of Concentrated Solar Energy into the Catalytic Hydrothermal Gasification of Biomass

Abstract

Using concentrated solar energy to power a hydrothermal gasification (HTG) of biomass requires thermal energy storage (TES) to compensate for the inherent intermittence of solar irradiation. The energy transfer from the TES to the HTG process is accomplished through a heat‐transfer fluid (HTF) passing through a heat exchanger (HX) incorporated into the salt‐separation step of the HTG process. The HX performance determines the temperature profile inside the salt separator, thereby influencing the removal of the salts from the feedstock. In this work, we compare the performances of three HX types based on exploiting fluidized beds, porous media, and axially finned tubes. The effect of the HX configuration on the temperature profile inside the salt separator is assessed through CFD simulations considering pure water as the model feed to the separator. We find that all considered HX types could provide the desired temperature profile within the separator. However, the estimate for the power required to pump the HTF through the fluidized‐bed HX is roughly two orders of magnitude higher than those for the axially finned tubular and porous‐media HXs.

Hydrothermal Treatment of Biomass Feedstocks for Sustainable Production of Chemicals, Fuels, and Materials: Progress and Perspectives

“…HTG is an attractive technology for the conversion of organic carbon rich biomass into biogases such as hydrogen and methane . Application of renewable solar energy to heat the hydrothermal reactor may improve both the yield and energy efficiency of the HTG process. , Boujjat et al conducted the solar energy-based thermochemical gasification of two types of biomass, namely beech wood and waste (SRF: solid recovered fuel) in two types of heating conditions: (1) solar-only reactor system (i.e., steam gasification), and (2) hybrid reactor system (steam gasification plus oxygen addition) . This study shows that the solar-only system was effective for syngas (CO + H 2 ) production in both types of substrates.…”

“…could be impacted by the concentrating solar technology design parameters (e.g., source of heat, heating rate, and amount of heat), which could ultimately influence the thermal efficiency and performance of the solar-based reactor. 28,29 Accordingly, the advancements on the integration of solar energy with HTC, 632,633 HTL, 634−639 and HTG 646,648 are discussed in this section for enhanced biomass valorization.…”

“…The operational parameters namely biomass concentration, temperature, and holding time under subcritical conditions considerably impact the yields and properties of bioproducts produced by solar-based hydrothermal treatment of biomass. , Solar-based biomass valorization chemistry (e.g., heat and mass transfer rate, reaction kinetics, thermodynamics, etc.) could be impacted by the concentrating solar technology design parameters (e.g., source of heat, heating rate, and amount of heat), which could ultimately influence the thermal efficiency and performance of the solar-based reactor. , Accordingly, the advancements on the integration of solar energy with HTC, , HTL, − and HTG , are discussed in this section for enhanced biomass valorization. The key results obtained from these studies are summarized in Table .…”