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Keywords = rice husk gasification char

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9 pages, 2561 KiB  
Article
Experimental and Adsorption Kinetics Study of Hg0 Removal from Flue Gas by Silver-Loaded Rice Husk Gasification Char
by Ru Yang, Yongfa Diao, Hongbin Liu and Yihang Lu
Coatings 2024, 14(7), 797; https://doi.org/10.3390/coatings14070797 - 26 Jun 2024
Cited by 2 | Viewed by 1390
Abstract
Coal holds a significant position in China’s energy consumption structure. However, the release of Hg0 during coal combustion poses a serious threat to human health. Traditional activated carbon for Hg0 removal is expensive; finding efficient, inexpensive and renewable adsorbents for Hg [...] Read more.
Coal holds a significant position in China’s energy consumption structure. However, the release of Hg0 during coal combustion poses a serious threat to human health. Traditional activated carbon for Hg0 removal is expensive; finding efficient, inexpensive and renewable adsorbents for Hg0 removal has become a top priority. Rice husk gasification char (RHGC) is a solid waste generated by biomass gasification power generation, which, loaded with silver to remove Hg0, could achieve the purpose of waste treatment. This paper examines the Hg0 removal performance of silver-loaded rice husk gasification char (SRHGC) under different operating conditions through experimental analysis. This study employed quasi-first-order, quasi-second-order, and internal diffusion kinetics adsorption equations to model the amount of Hg0 removed by SRHGC at different temperatures, thereby inferring the reaction mechanism. The results indicate that Hg0 removal efficiency of SRHGC increased by about 80%. The Hg0 removal ability was directly related to silver load, and the amount of Hg0 removed by SRHGC did not a exhibit a simple inverse relationship with particle size. Additionally, the Hg0 removal efficiency of SRHGC declined with increasing adsorption temperature. The removal of Hg0 by SRHGC conformed to the quasi-second-order kinetic equation, with the adsorption rate constant decreasing as the temperature rose, consistent with experimental observations. This paper provides both experimental and theoretical references for future modification and optimization of RHGC for coal-fired flue gas treatment, and also offers valuable insights into Hg0 removal by carbon-based adsorbents. Full article
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23 pages, 11800 KiB  
Article
Numerical Simulations of Gasification of Low-Grade Coal and Lignocellulosic Biomasses in Two-Stage Multi-Opposite Burner Gasifier
by Anees u Rehman, Imran Nazir Unar, Masroor Abro, Khadija Qureshi, Sikandar Almani and Abdul Sattar Jatoi
Processes 2023, 11(12), 3451; https://doi.org/10.3390/pr11123451 - 18 Dec 2023
Cited by 2 | Viewed by 1611
Abstract
Thermochemical processes utilizing biomass demonstrate promising prospects for the generation of syngas. In this work, a gasification process employing combination of an indigenous low-grade coal with two distinct biomass sources, namely rice husk (RH) and wood sawdust (WS), was explored. The gasification of [...] Read more.
Thermochemical processes utilizing biomass demonstrate promising prospects for the generation of syngas. In this work, a gasification process employing combination of an indigenous low-grade coal with two distinct biomass sources, namely rice husk (RH) and wood sawdust (WS), was explored. The gasification of the selected feedstock was performed using a double-staged multi-opposite burner (MOB) gasifier. A 3D computational fluid dynamics (CFD) model was employed to analyze the effect of kinetic and diffusion rates on the overall gasification performance of an entrained flow biomass gasifier. DPM was employed to track the particles’ trajectory, while the gas phase was treated as the continuous phase, and its behavior was predicted using a standard k-epsilon turbulent model. To calculate both the homogeneous and heterogeneous reaction rates, the finite rate/eddy dissipation model was implemented. The findings indicate that the char conversion efficiency exceeded 95% across all instances. Among the different reaction schemes, scheme E (which involved complete volatile and char combustion reactions) produced better results in comparison with published results, with less than 1% error. Hence, scheme E was validated and utilized for the rest of the simulated cases. The feeding rate has an inverse effect on the overall performance of the gasifier. An increase in feed rate decreases the CO and H2 composition in syngas. The maximum CO value was observed to be 57.59% at a 1.0 O/C ratio with a 0.005 kg/s feed rate, and the maximum H2 value was observed to be 16.58% in the same conditions for Lakhra coal samples. In summary, Lakhra coal exhibited better performance than other biomass samples due to its better fixed carbon and volatiles in its composition. Full article
(This article belongs to the Section Energy Systems)
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30 pages, 6660 KiB  
Review
Recent Advances in Biomass Pyrolysis Processes for Bioenergy Production: Optimization of Operating Conditions
by Dina Aboelela, Habibatallah Saleh, Attia M. Attia, Yasser Elhenawy, Thokozani Majozi and Mohamed Bassyouni
Sustainability 2023, 15(14), 11238; https://doi.org/10.3390/su151411238 - 19 Jul 2023
Cited by 87 | Viewed by 20432
Abstract
Bioenergy has emerged to be among the primary choices for the short- and medium-term replacement of fossil fuels and the reduction in greenhouse gas (GHG) emissions. The most practical method for transforming biomass into biofuel is thermochemical conversion, which may be broken down [...] Read more.
Bioenergy has emerged to be among the primary choices for the short- and medium-term replacement of fossil fuels and the reduction in greenhouse gas (GHG) emissions. The most practical method for transforming biomass into biofuel is thermochemical conversion, which may be broken down into combustion, torrefaction, pyrolysis, hydrothermal liquefaction, and gasification. In this study, producing biofuels using a biomass pyrolysis process was investigated. This study explored the pyrolysis process and operating conditions to optimize the process parameters to maximize the desired product yields and quality. The pyrolysis process produces three main products, which are bio-oil, bio-char, and gas. There are three classifications for the pyrolysis method, with each of them producing a majority of a certain product. First, slow pyrolysis is conducted in the temperature range of 300–950 °C and residence time of 330–550 s. It produces around a 30% oil yield and 35% char yield, and thus, the majority yield of slow pyrolysis is char. Second, fast pyrolysis produces around 50% oil, 20% char, and 30% gas yields with a temperature range of 850–1250 °C and a residence time of 0.5–10 s. The average yield of flash pyrolysis was found to be 75% bio-oil, 12% bio-char, and 15% gas, which is conducted within less than 1 s. It was reported that the pyrolysis of biomass was simulated using ASPEN Plus, where the effects of several parameters, such as the temperature, heating rate, and residence time, on the product yield and composition were investigated. Pyrolysis was performed under different conditions ranging from 400 to 600 °C. The effects of different catalysts on the pyrolysis process were studied. It was found that the addition of a catalyst could increase the yield of bio-oil and improve the quality of the product. The optimal operating condition for the pyrolysis process was determined to be a temperature of 500 °C, which resulted in a higher bio-oil yield. It was found that the biofuel yield was enhanced by selecting appropriate raw materials, such as rice husk, along with the pyrolysis temperature (e.g., 450 °C) and particle size (350–800 µm), and using a low residence time and pressure. Full article
(This article belongs to the Special Issue Advances in Sustainable Valorization of Natural Waste and Biomass)
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21 pages, 3227 KiB  
Article
Towards Circular Economy Solutions for The Management of Rice Processing Residues to Bioenergy via Gasification
by I. Vaskalis, V. Skoulou, G. Stavropoulos and A. Zabaniotou
Sustainability 2019, 11(22), 6433; https://doi.org/10.3390/su11226433 - 15 Nov 2019
Cited by 44 | Viewed by 7379
Abstract
A techno-economic assessment of two circular economy scenarios related to fluidized bed gasification-based systems for combined heat and power (CHP) generation, fueled with rice processing wastes, was conducted. In the first scenario, a gasification unit with 42,700 t/y rice husks capacity provided a [...] Read more.
A techno-economic assessment of two circular economy scenarios related to fluidized bed gasification-based systems for combined heat and power (CHP) generation, fueled with rice processing wastes, was conducted. In the first scenario, a gasification unit with 42,700 t/y rice husks capacity provided a waste management industrial symbiosis solution for five small rice-processing companies (SMEs), located at the same area. In the second scenario, a unit of 18,300 t/y rice husks capacity provided a waste management solution to only one rice processing company at the place of waste generation, as a custom-made solution. The first scenario of a cooperative industrial symbiosis approach is the most economically viable, with an annual revenue of 168 €/(t×y) of treated rice husks, a very good payout time (POT = 1.05), and return in investment (ROI = 0.72). The techno-economic assessment was based on experiments performed at a laboratory-scale gasification rig, and on technological configurations of the SMARt-CHP system, a decentralized bioenergy generation system developed at Aristotle University, Greece. The experimental proof of concept of rice husks gasification was studied at a temperature range of 700 to 900 °C, under an under-stoichiometric ratio of O2/N2 (10/90 v/v) as the gasification agent. Producer gas’s Lower Heating Value (LHV) maximized at 800 °C (10.9 MJ/Nm3), while the char’s Brunauer Emmet Teller (BET) surface reached a max of 146 m2/g at 900 °C. Recommendations were provided for a pretreatment of rice husks in order to minimize de-fluidization problems of the gasification system due to Si-rich ash. With the application of this model, simultaneous utilization and processing of waste flows from various rice value chain can be achieved towards improving environmental performance of the companies and producing energy and fertilizer by using waste as a fuel and resource with value. Full article
(This article belongs to the Special Issue Biofuels–Bioenergy Waste to Value Added Feedstock)
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15 pages, 294 KiB  
Article
The Impact of Biochar Application on Soil Properties and Plant Growth of Pot Grown Lettuce (Lactuca sativa) and Cabbage (Brassica chinensis)
by Sarah Carter, Simon Shackley, Saran Sohi, Tan Boun Suy and Stephan Haefele
Agronomy 2013, 3(2), 404-418; https://doi.org/10.3390/agronomy3020404 - 7 May 2013
Cited by 225 | Viewed by 26403
Abstract
The effect of rice-husk char (potentially biochar) application on the growth of transplanted lettuce (Lactuca sativa) and Chinese cabbage (Brassica chinensis) was assessed in a pot experiment over a three crop (lettuce-cabbage-lettuce) cycle in Cambodia. The biochar was the [...] Read more.
The effect of rice-husk char (potentially biochar) application on the growth of transplanted lettuce (Lactuca sativa) and Chinese cabbage (Brassica chinensis) was assessed in a pot experiment over a three crop (lettuce-cabbage-lettuce) cycle in Cambodia. The biochar was the by-product of a rice-husk gasification unit and consisted of 28.7% carbon (C) by mass. Biochar application rates to potting medium of 25, 50 and 150 g kg−1 were used with and without locally available fertilizers (a mixture of compost, liquid compost and lake sediment). The rice-husk biochar used was slightly alkaline (pH 7.79), increased the pH of the soil, and contained elevated levels of some trace metals and exchangeable cations (K, Ca and Mg) in comparison to the soil. The biochar treatments were found to increase the final biomass, root biomass, plant height and number of leaves in all the cropping cycles in comparison to no biochar treatments. The greatest biomass increase due to biochar additions (903%) was found in the soils without fertilization, rather than fertilized soils (483% with the same biochar application as in the “without fertilization” case). Over the cropping cycles the impact was reduced; a 363% increase in biomass was observed in the third lettuce cycle. Full article
(This article belongs to the Special Issue Biochar as Option for Sustainable Resource Management)
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