Oxidative filtration for flyash & tar removal from 1.0 MWth fixed-bed biomass air gasification

Mini-Review on Hot Gas Filtration in Biomass Gasification: Focusing on Ceramic Filter Candles

“…Summary of Some Typical CaFCs in the Hot Gas Filtration for Biomass Gasification presence of steam in the gas could inhibit the blinding effect to a certain extent, owing to the steam gasification of carbon that may take place on the filter surface. 20 A similar filter-blinding phenomenon was discovered by our group at the intermediate temperature (300−600 °C) as well, 37 due to the polycondensation of gasified chars and tars (Section 5.2). 34 As shown in Table 4, the pressure drop (ΔP) during the wood gasification was over twice that of the charcoal gasification with a low tar content, which gave rise to an unstable operation of wood gasification-filtration.…”

“…35,36 According to this, a new concept of high-temperature oxidative filtration for biomass air gasification (BAG) had been verified both by laboratory and pilot tests, which leads to a simultaneous decrease of ΔP and tar concentration, by continuously introducing a small amount of additional air (∼2%O 2 ) into the raw BAG gas. 37 The X-ray photoelectron spectroscopy (XPS) and nuclear magnetic resonance spectroscopy (NMR) results proved that more surface oxygencontaining organic functional groups could be generated via the partial oxidation of the char PMs in the BAG+2%O 2 atmosphere at 400 °C, possibly inhibiting the aromatization of aromatic clusters and the formation of heavy tar compounds to some extent. 34 Tuomi et al 38 also pointed out that thermal reactions of tars could be promoted by the catalytic reactions induced by the unreacted biomass char on the filter surface at high temperatures.…”

“…Meanwhile, it also allows an efficient particulate removal (>99.0%), and a steady oxidative filtration with low pressure drop (<2.0 kPa) was operated for over 200 h during the pilot-scale woody biomass gasification in 400−600 °C. 37 3.3. Catalytic Filter Candles (CaFC).…”

“…Very recently, a novel oxidative filtration concept was practiced by our group on both the bench scale 35 and pilot scale, 37 in order to decrease the pulse-cleaning frequency and pressure drop by the partial oxidation of carbonaceous PMs in the biomass-derived product gas. With the introduction of a low concentration of oxygen into the product gas in 300−500 °C, the carbonaceous PMs were oxidized to a maximum while maintaining a minimum degradation of product gas at the optimum reaction conditions, 35 and the frequent jet-pulse cleaning is not necessary for the oxidative filtration with a longterm pulse interval of 5−8 h. 37 4. COMPUTATIONAL FLUID DYNAMICS NUMERICAL STUDIES IN HOT GAS FILTRATION CFD is a powerful tool that uses a numerical analysis and data structures to model and analyze hot gas filtration that involves complex multiphase fluid flows with mass, momentum, and heat transfers.…”

“…The most important challenges of hot gas filtration are related to the behavior of tars in the biomass-derived producer gas. 37,38 For process simplification and intensification, therefore, the utilization of catalytic ceramic filters for hot gas filtration is one of the most popular technologies for HT gas cleanup, which provides a simultaneous abatement of PMs, tars, and some poisonous gases (e.g., NH 3 , volatile organic compounds (VOCs)). 77 As illustrated in Figure 14A,B, recent research in this field was mostly focused on increasing the filtration temperature closer to the outlet temperature of the biomass gasifier (800− 850 °C), which could increase the system efficiency and reduce the production costs by avoiding the extra cooling and heating steps upstream and downstream of the hot gas filtration.…”