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- ItemPressurized torrefaction of waste biomass to improve bio coal quality: Synergistic effect between animal waste and wood chips(Elsevier, 2025-04-19) Tshuma, N.M.; Moyo, L.B.; Danha, G.; Mamvura, T.A.; Simate, G.S.; Artur, C.D.; Charis, G.This study aims to investigate the effect blending waste material to improve its fuel properties using pressurized torrefaction. This research explored the benefits of blending animal waste with wood chips to produce a bio-coal with improved fuel properties. The process conditions investigated were temperature and pressure intervals of 200◦C to 280◦C and atmospheric pressure (AP) to 4MPa, respectively. The results showed that an increase in temperature and pressure improved the fixed carbon content of the blend almost threefold from 19.87 % to 66.93 % and the higher heating value (HHV) to 27.32MJ/kg from 13.90MJ/kg at mild torrefaction temperature of 280◦C and gas pressure of 4MPa compared to atmospheric pressure conditions and the lowest temperature investigated. The HHV increased primarily due to a release of bound and unbound moisture and volatile matter. Wood chips had an HHV of 27.00MJ/kg at a torrefaction temperature of 280◦C due to the decomposition of hemicellulose and cellulose which enhanced the thermal stability, fixed carbon content and calorific value. However, animal waste had the least incremental increase in HHV (16.45MJ/kg) due to a high initial content of volatile matter and moisture. The improved properties of the blend of materials indicated that pressurized torrefaction was effective in increasing fixed carbon content through secondary polymerization reactions. Moreover, it facilitated the decomposition of cellulose at a lower temperature than the typical range of 315-400◦C if conducted at atmospheric pressure. This study elucidates the notable role of the synergistic effects of blending feed materials prior to torrefaction towards improving the properties and pyrolysis performance of biomass components.
- ItemApplication of amine-modified tannins gels as coagulants in wastewater treatment(Research Square, 2024-08-28) Thelmmer, M.; Ncube, S.; Moyo, L.B.; Mamvura, T.A.; Danha, G.; Simate, G.S.; Tshuma, N.Tannin (T) is an organic substance that may potentially be used as an inexpensive, environmentally friendly, and effective bio-coagulant to remove impurities from residential and commercial wastewater. In this study, bio-coagulants were prepared using tannins obtained from the wattle tree (Acacia mearnsii). The bio-coagulants were modified using formalin and optionally, ethanolamine (ETA) and ammonium chloride (NH 4 Cl) as amine sources through the Mannich Reaction scheme. Three coagulants were prepared, T-ETA modified tannin, T-NH 4 Cl modified tannin and a mixture of T-ETA: T-NH 4 Cl in molar ratio 1: 1. Aluminium sulphate [Al 2 (SO 4) 3], a metal-coagulant was also used as the standard for comparison. The three coagulants were tested at varied concentrations (500–1250 mg/L) using jar tests on laundry wastewater to see their effect on remediation of wastewater. A mixture of bio-coagulant T-NH 4 Cl and T-ETA was most effective with highest removal efficiencies for turbidity (94%), COD (85%), Total solids (87%) and nitrates (99%). For colour removal T-NH 4 Cl modified tannin showed the highest removal efficiency of 92%. The results support the use of cheaper and environmentally friendly amine modified tannin-based flocculants in laundry wastewater treatment as they showed less toxicity on the treated water.
- ItemProduction of oxalic acid from sawdust using coal fly ash as a catalyst(Springer Nature, 2021-10-19) Kuipa, O., Kasungasunge, G. and Kuipa, P.K; Kuipa, O., Kasungasunge, G. and Kuipa, P.K; Kuipa, O., Kasungasunge, G. and Kuipa, P.KThe production of oxalic acid from sawdust using a mixture of strong nitric acid and concentrated sulphuric acid with coal fly ash as a catalyst has been explored. Operating parameters affecting the reaction were determined to be temperature, mesh size and amount of fly ash catalyst, time and the HNO3 ∶ H2SO4 ratio. A maximum oxalic acid yield of 84% was obtained using a mixture of 60% HNO3 and 40% H2SO4 at 70 °C and a reaction time of 150 minutes. Coal fly ash with particle size of 50–100 μm proved to be a suitable and efficient catalyst, and the optimum quantity of catalyst employed was 5g of fly ash for every 100g of sawdust.
- ItemOptimisation of biodiesel production from dairy efuent scum using calcined egg shell as a transesterifcation catalyst(Springer Nature, 2021-02-01) Kuipa, O.; Marwizi, T.S.; Kuipa, P.K.The production of biodiesel from dairy effluent scum using calcined egg shell as the transesterification catalyst has been explored. Eggshell powder was calcined at 900 °C for 3 h and used as catalyst. The influence of methanol-oil molar ratio, catalyst concentration and reaction temperature were studied using Response Surface Methodology employing a Central Composite Rotatable Design. An empirical model that relates the yield of biodiesel to the studied factors was obtained. The model has high statistical significance at 95% confidence interval with R2 and adjusted R2 values of 96.31% and 95.75% respectively. Results showed that among the three studied factors, the methanol-oil molar ratio had the greatest contribution to the yield of dairy effluent scum derived biodiesel followed by reaction temperature and finally, the catalyst concentration. Significant interaction effects were also present between methanol-oil ratio and catalyst, catalyst and reaction temperature and methanol-oil ratio and reaction temperature. Accordingly, the optimal variable settings were 14.355:1 methanol-oil molar ratio, 3.09% catalyst loading by weight of pre-treated dairy scum oil and 55.20°C reaction temperature; with a corresponding yield of 92.72%.
- ItemUtilization of cellulose in tobacco (Nicotiana tobacum) stalks for nitrocellulose production(Heliyon, 2021-07-13) Muvhiiwa, R.; Mawere, E.; Moyo, L.B.; Tshuma, L.This research explains the conversion of waste tobacco stalks into nitrocellulose to try to recover as much chemical potential contained in the biomass material as possible. Simple pioneering experiments were conducted using pulping tobacco stalks with a moisture content of 10.17 wt% and the soda pulping method being applied to produce cellulose pulp. The cellulose pulp was bleached using calcium hypochlorite to produce a dry white lignin-free pulp, which was subjected to nitration. The mixture used was 67% nitric acid and 98% sulphuric acid, and the acid ratio was varied between 3:7 and 7:3 v/v. Nitration time was varied between 5 and 25 min. This process produced nitrocellulose with all the various conditions. The nitrocellulose obtained with nitrogen content between 11 – 11.5% v/v was characterized using its solubility in acetone. An optimum nitrating mixture of 1:1 v/v with a nitration time of 5 min was used to produce nitrocellulose from tobacco stalks using soda pulping. The results show a great potential for tobacco farming countries to reduce their nitrocellulose import bill using this process.