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Biomass has received wide attention as a substitute for fossil fuel in the generation of energy because of its renewability and carbon neutrality. However, raw biomass combustion is hindered by physical properties such as low energy density and high moisture content. Biomass torrefaction is a mild pyrolysis thermal treatment process carried out at temperature of 200 to 300°C under inert conditions to improve the fuel properties of parent biomass. This yields a higher energy per unit mass product but releases non-condensable and condensable gases which results in energy and mass losses. The condensable gases (volatiles), can result in tar formation on condensing hence, system blockage. Fortunately, the hydrocarbon composition of volatiles also represents a possible auxiliary energy source for torrefaction. The present study investigated energy recovery from volatiles through clean co-combustion with NG for feedstock drying and/or the thermal treatment process of pine wood chips. The research also studied the effect of torrefaction pretreatment temperatures on the amount of energy recovered for various combustion air flow rates. For all test conditions, blue visual flames and low CO and NOx emissions at the combustor exit consistently signified clean and complete premixed combustion. Torrefaction temperature at 283–292 °C had relatively low energy recovered from volatiles, mainly attributed to higher moisture content evolution and low molecular weight of volatiles evolved. At lowest torrefaction pretreatment temperature, smaller amount of volatiles was generated with most energy recovered from the volatiles. Energy conservation evaluation on the torrefaction reactor indicated that about 40% of total energy carried by the exiting volatiles and gases has been recovered by the co-fire of NG and volatiles at the lowest temperature while 20% and 22% of the total energy were recovered at the intermediate and highest torrefaction temperature respectively.

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Biomass gasification is one of the most promising routes to produce green hydrogen, power, fuels, and chemicals, which has drawn much attention as the world moves away from fossil fuels. Syngas produced from gasification needs to go through an essential gas cleanup step for the removal of tars and particulates for further processing, which is one of the cost-inducing steps. Existing hot gas cleanup strategies involve the particulate removal step followed by catalytic tar reforming, which could be integrated into a single unit operation using porous ceramics owing to their advantages including high-temperature resistance, high corrosion resistance, flexibility, and robust mechanical integrity. Ceramic filters have proven to be effective at filtering particulates from hot gas streams in various applications including combustion, incineration, gasification, and pyrolysis. These materials have also been evaluated and used to an extent as catalyst support to remove contaminants such as nitrogen oxides (NOx), volatile organic compounds (VOC), and in particular, tars, however, the use of these ceramic materials to remove both tars and particulates in one unit has not received much attention, although it has a promising potential to be a cost-effective hot gas cleanup strategy. Thus, this review presents the ability of catalytic ceramic filters to boost energy efficiency by converting unwanted byproducts while simultaneously eliminating PM in a single unit and is shown to be valuable in industrial processes across the board. This article presents a comprehensive and systematic overview and current state of knowledge of the use of porous ceramics for catalytic hot gas filtration applications with an emphasis on biomass syngas cleanup. In addition, a similar strategy for other applications such as combustion exhaust streams is presented. Prospects and challenges of taking this approach, and the necessary research and development to advance the novel use of reactive ceramic filters within biomass-fed thermal systems are presented. Major challenges include the low surface area of the ceramic filter media and high-pressure drop across the filter media, which can be overcome by wash coating or dip coating mechanisms and porosity tailored to meet the requirements. Owing to limited R&D efforts in this area, a systematic approach toward developing these integrated hot gas filtration systems is much needed, which will ultimately contribute to cost-effective green hydrogen production.