Browsing by Author "Chakma, S."

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    Basic concepts of ultrasound and its effects on fuel processing
    (Bentham Science Publishers, 2023) Poddar, M.K.; Dikshit, P.K.; Chakma, S.
    Ultrasound-assisted technique is well-known for process intensification via chemical and physical changes under the influence of acoustic cavitation. Acoustic cavitation is the phenomenon of nucleation, growth, and collapse of cavitation bubbles into a liquid medium that augments the reaction kinetics and the final process yield. This chapter provides a fundamental and detailed understanding of the acoustic cavitation phenomenon. It includes the history and origin of the acoustic wave and its formation, the concept of cavitation bubbles, bubble nucleation and growth mechanism, cavitation effects, and its types. Numerous process parameters, such as applied frequency, intensity, temperature, dissolved gas content, etc., also directly or indirectly influence the cavitation threshold are also highlighted. Further, the ultrasound's physical and chemical effects involving various chemical and biochemical processes to enhance the process yield are also reviewed. The mode of generation of ultrasound energy and its measurement technique are also briefly discussed. Finally, an overview of modeling and simulation of radial motion of single bubble growth, its oscillation in both ultrasound-assisted and conventional systems, and bubble growth rate under rectified diffusion are also discussed in detail. © 2023 Bentham Science Publishers. All rights reserved.
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    Biohydrogen production from waste substrates and its techno-economic analysis
    (Elsevier, 2023) Dikshit, P.K.; Poddar, M.K.; Chakma, S.
    The demand for alternative energy is increasing considerably due to the fast depletion of fossil fuel reserves and increasing greenhouse gases emission, causing serious climate change. Among various alternative energy sources, biohydrogen (H2) has achieved major traction due to its distinct properties like high-energy content, recyclability, and production of water on the combustion process. Although several processes are adopted for hydrogen production from a wide range of substrates, utilization of organic feedstock using dark fermentation has proven to be one of the most promising methods among all. However, the raw material cost, which contributes around 70%–80% of the total production expenses, is the major hurdle in the successful commercialization of this process. Organic wastes can be used as an alternative to pure carbons for the reduction of production cost. This chapter summarizes biohydrogen production from various waste substrates, its production process, microorganisms involved, fermentation approaches, and various factors that influence the production along with major advantages and challenges. Additionally, techno-economic analysis of biohydrogen production on an industrial scale from various organic wastes is also discussed in detail. © 2023 Elsevier Ltd. All rights reserved.