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The knowledge of fluid–particle flow behavior is necessary. Unfortunately, computational fluid dynamics (CFD) studies are mostly focused on developing numerical methods in detail. Instead, the CFD studies should also subtly shift to become a tool for digitalizing fluid science to guide the practical industrial aspects. Therefore, this simulation study intends to reveal the air and rice husk flow behaviors in a vertical suspension furnace, complete with presenting digital simulation data, aiming to alleviate the escape particle amount. According to this study, the escaped particle amount was suppressed under more sphere particle, smaller particle size, and feed inlet pipe that sunk into the burner. The properties change from rice husk to ash, along with temperature escalation (as in combustion phenomena), enlarging the escaped particle amount, so the cyclone should be installed to handle it. In addition, the results of digital turbulent data from CFD simulation have succeeded in intriguing and revealing the fluid–particle flow behavior in the vertical suspension furnace. The data show a close match to the real phenomena occurring inside this furnace which reflects the standard k–ε model can conclusively predict fluid–particle flow behavior without conflicting Newton's second law of particle motion. [ABSTRACT FROM AUTHOR]

Abundant availability and large silica content in rice husk black ash (RHBA) make the use of it very interesting to study. Many works only deal with lab‐scale rice husk ash extraction while the studies on bench‐scale RHBA extraction are still limited. This study, hence, presents the influence of pretreatment, extraction variables, and posttreatment on bench‐scale RHBA processing to bio‐silica. The pretreatment through acid leaching was carried out using HCl. The extraction was implemented under varying process variables such as alkaline‐to‐feed ratio (RA/F), extraction duration, and acid precipitation agent. According to this study, the highest extraction yield up to 98% was gained under RA/F 6 g/g and 1‐h extraction. The amorphous bio‐silica had an asymmetric siloxane bond and white appearance with a purity exceeding 95% and surface area up to 406.98 m2/g. Meanwhile, precipitation under HCl and H2SO4 had little impact on product purity and surface area. This study exhibits that acid leaching is executed to release mineral impurities but is still not sufficient to remove the remaining carbon content in bio‐silica. However, the contribution of refining process is able to do so. Moreover, the produced bio‐silica is suitable for adsorbent purposes which could adsorb up to 83.5% of 3‐monochloropropanediol compound. [ABSTRACT FROM AUTHOR]

• Silica content in rice husk ash is high and attractive to be utilized. • Rice husk ash acid leaching and extraction is performed to produce green silica. • The highest green silica quality has a 96.44% purity and 400.69 m2/g surface area. • Amorphous and mesoporous green silica is suitable for industrial silica gel. • The green silica is sustainable and produced from a low-cost of raw material. The acid leaching process is believed to increase the silica extracted from rice husk ash (RHA). This study intended to investigate the influence of acid leaching sequences in RHA extraction on green silica purity and surface area. The sequences were RHA leaching (T1), aged gel leaching (T2), dried product leaching (T3), and without leaching as a control. The T1 sequence has been proven to improve the green silica purity and surface area reaching 96.44% and 400.69 m2/g, respectively. For T2 and T3 sequences, the green silica has a much lower surface area and purity compared to T1. The values were 87.69% and 55.49 m2/g for T2 as well as 62.46% and 11.40 m2/g for T3. Without acid leaching, the purity and surface area of green silica significantly reduced to 56.94% and 5.72 m2/g. This study concludes that green silica from T1 sequence has successfully obtained high purity, high surface area, and indicates an amorphous and mesoporous particle. It is suitable to be utilized as an industrial silica gel for moisture adsorber which more sustainable and greener process. [Display omitted] [ABSTRACT FROM AUTHOR]