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Only a third of the people living in Sub-Saharan Africa have access to electricity. While the benefits of electricity services for the society continue to increase, solar home system (SHS) provides a long-term rural electrification and development solution. SHS is thought out to be a robust and cost-effective option for supplying basic electrification under Kenya’s metrological conditions. This paper begins with an in-depth justification of the need for SHS in rural areas, and then it presents an overview of SHS financing, benefits and barriers, followed by a crucial component of existing SHSs in Kenya, Pay-As-You-Go (PAYG) technology. It ends with succinct analysis of the payment models highlighting the benefits, challenges and methods adopted in overcoming those challenges. Lessons from this review suggest that solar firms face a myriad of challenges operating in poor rural areas in Kenya; credit risk is a major concern for solar firms as well as financiers which makes payment models notably challenging. Technical performance of SHS is becoming well proven, and end users desire a wide range of component preferences and service levels that are of benefit. The challenges faced by solar firms using different payment models show that there is a dire need for integration of SHS with rural electrification policy in Kenya. The principal conclusion is that PAYG model offers the best option for SHS dissemination, though energy-as-a-service implementation has a great potential of improving the dissemination process in rural communities as it offers a promising mechanisms from a sustainability point of view.

This work employed a novel rotor-stator reactor (RSR) to intensify the degradation process of o-phenylenediamine (o-PDA) by ozone. The effects of different operating parameters including initial pH, temperature, rotation speed, liquid volumetric flow rate and inlet ozone concentration on the removal efficiency of o-PDA were investigated in an attempt to establish the optimum conditions. The removal efficiency was evaluated in terms of degradation ratio and chemical oxygen demand (COD) reduction ratio of the o-PDA wastewater. Results indicate that the removal efficiency decreased with increasing liquid volumetric flow rate but increased with an increase in pH and inlet ozone concentration. Also, the removal efficiency increased up to a certain level with an increase in rotation speed and temperature. Additionally, a comparison experiment was carried out in a stirred tank reactor (STR), and the results show that the degradation and COD reduction ratios reached a maximum of 94.6% and 61.2% in the RSR as compared to 45.3% and 28.6% in the STR, respectively. This work demonstrates that ozone oxidation carried out in RSR may be a promising alternative for pre-treatment of o-PDA wastewater.

Efficient waste management, especially in relation to swaste reuse, has become a pressing societal issue. The waste bittern generated during salt production and discarded oyster shells present formidable environmental challenges and a waste of resources for some coastal regions. Therefore, this work developed a two-stage circular process for the environmentally friendly and efficient utilization of both waste materials. In the first stage, CO2 gas and an organic extraction phase comprising Tri(octyl-decyl)amine (R3N) and isoamyl alcohol were introduced into the waste bittern to obtain MgCO3·3H2O (s). The second stage involved reacting the reacted organic extraction phase with oyster shell powders to produce CaCl2·2H2O (s) and CO2 (g) and regenerate R3N. This work focused on investigating the yield of MgCO3·3H2O and the regeneration ratio of R3N, which are crucial indicators for the two stages involved in the process. The results indicate that, under optimal operating conditions, a maximum yield of 87% for MgCO3·3H2O was achieved, and the regeneration ratio of R3N reached 97%. Furthermore, the reaction mechanism and thermodynamic functions of the R3N regeneration process were elucidated as a crucial element in achieving a circular process. The findings of this work offer a sustainable solution to environmental pollution from waste bittern and oyster shells, and provide a promising avenue for green chemical production.

The drying process is a significant step in the manufacturing process of enteric hard capsules, which affects the physical and chemical properties of the capsules. Thus, the drying characteristics of plant-based enteric hard capsules were investigated at a constant air velocity of 2 m/s in a bench scale hot-air dryer under a temperature range of 25 to 45 °C and relative humidity of 40 to 80%. Results indicate that the drying process of the capsules mainly occur in a falling-rate period, implying that moisture transfer in the capsules is governed by internal moisture diffusion rate. High temperature and low relative humidity reduce drying time but increase the drying rate of the capsules. Investigation results of the mechanical properties and storage stability of the capsules, however, reveal that a fast drying rate leads to plant-based enteric hard capsules of low quality. Scanning electron microscopy further demonstrates that more layered cracks appear in capsules produced under a faster drying rate. The Page model yielded the best fit for describing thin-layer drying of the capsules based on the coefficient of determination and reduced chi-square. Moreover, it was established that the effective moisture diffusivity of the capsules increases with an increase in drying temperature or reduction in relative humidity.

Oxygen is a harmful substance in many processes because it can bring out corrosion and oxidation of food. This study aimed to enhance the removal of dissolved oxygen (DO) from water by employing a novel rotor–stator reactor (RSR). The effectiveness of the nitrogen stripping coupled with vacuum degassing technique for the removal of DO from water in the RSR was investigated. The deoxygenation efficiency (η) and the mass transfer coefficient (KLa) were determined under various operating conditions for the rotational speed, liquid volumetric flow rate, gas volumetric flow rate, and vacuum degree. The nitrogen stripping coupled with vacuum degassing technique achieved values for η and KLa of 97.34% and 0.0882 s−1, respectively, which are much higher than those achieved with the vacuum degassing technique alone (η = 89.95% and KLa = 0.0585 s−1). A correlation to predict the KLa was established and the predicted KLa values were in agreement with the experimental values, with deviations generally within 20%. The results indicate that RSR is a promising deaerator thanks to its intensification of gas–liquid contact.

This study investigated the effect of different inorganic salts on the treatment of simulated secondary effluent (SE) by ozone (O3) in a rotating packed bed (RPB) – (O3-RPB process), with Escherichia coli (E. coli) and UV254 of fulvic acid as the indicators. The inactivation efficiency of E. coli and removal percentage of UV254 were studied under different rotation speeds of the RPB and varying concentrations of inorganic salts such as NaHCO3, Na2SO4 and CaCl2. Results indicate that both the inactivation efficiency of E. coli and removal percentage of UV254 increased with an increasing rotation speed of the RPB but decreased with an increase in concentrations of the inorganic salts. Analyses on the mechanism of the treatment process reveal that the inorganic salts consume O3 and ·OH to generate products with lower oxidation ability, and thus result in a poor treatment effect on the effluent. This work provides fundamentals for the O3-RPB process in the treatment of SE from urban wastewater treatment plants.

Using plant-based polysaccharide gels to produce hard capsules is a novel application of this technology in the medicinal field, which has garnered significant attention. However, the current manufacturing technology, particularly the drying process, limits its industrialization. The work herein employed an advanced measuring technique and a modified mathematical model to get more insight into the drying process of the capsule. Low field magnetic resonance imaging (LF-MRI) technique is adopted to reveal the distribution of moisture content in the capsule during drying. Furthermore, a modified mathematical model is developed by considering the dynamic variation of the effective moisture diffusivity (Deff) according to Fick’s second law, which enables accurate prediction of the moisture content of the capsule with a prediction accuracy of ±15%. The predicted Deff ranges from 3 × 10−10 to 7 × 10−10 m2·s−1, which has an irregular variation with a time extension. Moreover, as temperature increases or relative humidity decreases, there is an increased acceleration of moisture diffusion. The work provides a fundamental understanding of the drying process of the plant-based polysaccharide gel, which is crucial for enhancing the industrial preparation of the HPMC-based hard capsules.

Alternating current (AC) dielectric barrier discharge induced non-thermal plasma (NTP) has been used to experimentally investigate conversion of Nitrogen Oxide (NO) over CeO2/TiO2 catalyst. The role of heterogeneous catalyst (TiO2/CeO2) has also been investigated, NO conversion has been examined in terms of various operating parameters including temperature, voltage, flue gas flow rate, specific energy density, water vapour content and oxygen content. The conversion mechanism of NO was distinctly discussed. To understand the effects of NTP on CeO2/TiO2 catalyst properties and the influence of CeO2/TiO2 catalyst on NTP, SEM, BET, XRD, TPR were carried out. SEM reveals that increase in temperature during NTP catalytic reactions affect the morphology of the catalyst hence decreasing NO oxidation efficiency, the results also show that surface area and pore properties of the catalyst plays a significant role in plasma catalytic reaction. The maximum NO oxidation conversion efficiency attained was 93% at SED of 91JL−1.

This study investigates the effect of varying cost and process parameters on bioethanol production rate and the minimum bioethanol selling price (MBSP) during large-scale production of second-generation bioethanol from Sila sorghum stalks found in Kenya. Aspen Plus was used to model and simulate the process that was considered in this study. The flow rate of biomass was varied between 10,000 and 300,000 kg/h which gave rise to a bioethanol flow rate of between 2134.49 and 62,707.33 kg/h. Bioethanol production rate decreased from 21,759.5 to 19,397.6 kg/h when the feed stage position in the beer column increased from 2 to 8. MBSP increased from $0.81/L to $1.11/L when the cost of biomass was varied from $20/tonne to $100/tonne. MBSP increased from $0.9/L to $1.0/L when the cost of enzymes was varied by − 50% and + 50%. MBSP increased from $0.83/L to $1.54/L when discount rate varied by 5% and 30%. MBSP increased from $0.85/L to $1.06/L when fixed capital investment was varied by -35% and + 35%. MBSP reduced from $1.28/L to $0.95/L when plant life varied from 10 to 30 years. MBSP increased from $0.89/L to $0.99/L when income tax rate varied from 0 to 40%. The study indicates that second-generation bioethanol is able to compete with gasoline in Kenya when no levies and taxes are imposed on the MBSP, at a plant life of 15 years and beyond and at an income tax rate of between 0 to 40%.

A gas-microemulsion reaction precipitation method was employed to prepare nano-Ce 0.5 Zr 0.5 O 2 by absorption of NH 3 into water-in-oil (W/O) microemulsion in a rotor–stator reactor . The effects of different operating conditions including final pH of the microemulsion, reaction temperature, initial Ce 3+ and Zr 4+ concentration, rotation speed, and gas–liquid volumetric ratio were investigated. Nano-Ce 0.5 Zr 0.5 O 2 with an average diameter of about 5.5 nm, a specific surface area of 215.6 m 2 /g and a size distribution of 4–8 nm was obtained under the optimum operating conditions. The as-prepared nano-Ce 0.5 Zr 0.5 O 2 was loaded with Au to prepare nano-Au/Ce 0.5 Zr 0.5 O 2 catalyst which was subsequently used for CO oxidation test. CO conversion rate reached 100 % at room temperature, indicating high catalytic activity of the nano-Au/Ce 0.5 Zr 0.5 O 2 catalyst.