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Coconut Fiber Pyrolysis: Bio-Oil Characterization for Potential Application as an Alternative Energy Source and Production of Bio-Degradable Plastics

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World Journal of Engineering and Technology 2024年第2期12卷 310-319页

作者： Patrick Ssemujju Lubowa hiram ndiritu Peter Oketch James Mutua Department of Mechanical and Mechatronics Engineering Pan African University Institute for Basic Sciences Technology and Innovations Nairobi Kenya Department of Mechanical Engineering Jomo Kenyatta University of Agriculture and Technology Nairobi Kenya

The current energy crisis could be alleviated by enhancing energy generation using the abundant biomass waste resources. Agricultural and forest wastes are the leading organic waste streams that can be transformed into useful alternative energy resources. Pyrolysis is one of the technologies for converting biomass into more valuable products, such as bio-oil, bio-char, and syngas. This work investigated the production of bio-oil through batch pyrolysis technology. A fixed bed pyrolyzer was designed and fabricated for bio-oil production. The major components of the system include a fixed bed reactor, a condenser, and a bio-oil collector. The reactor was heated using a cylindrical biomass external heater. The pyrolysis process was carried out in a reactor at a pressure of 1atm and a varying operating temperature of 150˚C, 250˚C, 350˚C to 450˚C for 120 minutes. The mass of 1kg of coconut fiber was used with particle sizes between 2.36 mm - 4.75 mm. The results show that the higher the temperature, the more volume of bio-oil produced, with the highest yield being 39.2%, at 450˚C with a heating rate of 10˚C/min. The Fourier transformation Infrared (FTIR) Spectroscopy analysis was used to analyze the bio-oil components. The obtained bio-oil has a pH of 2.4, a density of 1019.385 kg/m3, and a calorific value of 17.5 MJ/kg. The analysis also showed the presence of high-oxygenated compounds;carboxylic acids, phenols, alcohols, and branched oxygenated hydrocarbons as the main compounds present in the bio-oil. The results inferred that the liquid product could be bestowed as an alternative resource for polycarbonate material production.

关键词： Batch Pyrolysis Technology Coconut Fiber Bio-Oil Fourier Transformation Infrared Analysis

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Performance Simulation of a Modified Geothermal Grain Dryer Based at Menengai Well 3 in Kenya

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World Journal of Engineering and Technology 2022年第1期10卷 59-87页

作者： Levi Kulundu hiram ndiritu Gareth Kituu James Kimotho Mechanical Engineering Department Pan African University Institute for Basic Sciences Technology and Innovation Nairobi Kenya College of Engineering and Technology Jomo Kenyatta University of Agriculture and Technology Nairobi Kenya

Geothermal energy can be effectively utilized for grain drying to reduce carbon emissions and also cut operational costs associated with conventional methods. The main challenges encountered in the use of the geothermal grain dryer, such as in Menengai, Kenya, include uneven grain drying and long throughput times. Grains near the hot air inlet dry at a faster rate compared to those near the exhaust end. Therefore, the grains must be recirculated within the dryer to achieve uniform moisture distribution. Grain recirculation is energy-intensive as it utilizes electricity running the elevator motors in addition to the suction pump. A Computational Fluid Dynamics (CFD) model was developed to study the airflow pattern and its impact on drying of maize. The model was simulated in ANSYS 21 and validated using experimental data. Finite volume discretization method was employed for meshing. Pressure-based segregated solver was used in the Computational Fluid Dynamics (CFD) simulation. Also, K-Omega turbulent model was used for enhancing wall treatment. The findings indicate that non-uniform hot air distribution across the grain buffer section causes uneven drying. Introducing filleted flow-guides results in a relatively uniform velocity, temperature, and turbulence kinetic energy distribution across the dryer. The average velocity and temperature magnitudes in lower compartments increased by 153.3% and 0.25% respectively for the improved dryer. In the upper compartments, the velocity and temperature increase were 176.5% and 0.22% respectively.

关键词： Filleted Flow-Guides Flow Distribution Geothermal Grain Dryer Computational Fluid Dynamics

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Performance Assessment of Heat Exchangers for Process Heat Integration

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Energy Engineering 2021年第2期118卷 211-224页

作者： Fenwicks Shombe Musonye hiram ndiritu Robert Kinyua Institute of Energy and Environmental Technology Jomo Kenyatta University of Agriculture and TechnologyNairobiKenya College of Engineering and Technology Jomo Kenyatta University of Agriculture and TechnologyNairobiKenya Office of the Deputy Vice Chancellor(Academic Affairs) Jomo Kenyatta University of Agriculture and TechnologyNairobiKenya

Pinch Analysis is an attractive solution for reduction of thermal energy costs in thermo-chemical industries.In this approach,maximum internally recoverable heat is determined and a heat exchange network is designed to meet the recovery targets.The thermal performance of a heat exchanger over its lifetime is however a concern to industries.Thermal performance of a heat exchanger is affected by many factors which include the physical prop-erties of the shell and tube materials,and the chemical properties of the heat transferfluid.In this study,thermal performance of shell and tube heat exchangers designed to meet heat recovery targets in a Pinch Analysis study is simulated.The aim of this paper is to present predictions of thermal performances of shell and tube heat exchan-gers with different heat transferfluids and geometries as they undergo fouling degradation.Engineering approaches based on thermodynamic analysis,heat balance and Kern Design equations,as well as what-if simu-lation modeling are used in this work.Shell and tube heat exchangers were designed to meet internal heat recov-ery targets for three process plants,A,B and C.These targets were published in a separate paper.The effects of degradation of the tubes-due to incremental growth of fouling resistance-on thermal performance of the exchan-ger were simulated using Visual Basic Analysis(VBA).Overall,it was found that growth in fouling reduces ther-mal efficiency of shell and tube heat exchangers with an exponential relationship.An increase of 100%of fouling resistance leads to an average reduction of 0.37%heat transfer.Higher values of logarithmic mean temperature difference(LMTD)and higher ratios of external diameter to internal diameter of the exchanger tubes amplify the effect of fouling growth on thermal performance of the exchangers.The results of this work can be applied in pinch analysis,during design of heat exchangers to meet the internal heat recovery targets,especially in predicting how fouling growth can affect these targets.This can also

关键词： Pinch analysis internal heat recovery thermal performance fouling resistance fouling growth what if simulation shell and tube heat exchangers

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Mesophilic Process and Kinetics Studies of Selected Biomolecules as Potential Enhancers of Biomethanization of Cow Dung in an Anaerobic Tubular Batch Reactor

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Energy and Power Engineering 2022年第3期14卷 147-155页

作者： Paul Njogu Francis Xavier Ochieng Benard Ogembo Stephen Ondimu Christopher Kanali Erick Ronoh Daniel Omondi hiram ndiritu Institute of Energy and Environmental Technology JKUAT Nairobi Kenya School of Biosystems and Environmental Engineering JKUAT Nairobi Kenya School of Mechanical and Manufacturing Engineering JKUAT Nairobi Kenya

Mesophilic biogas production and substrate decomposition is one of the significant limiting steps in biogas generation. The rate of generation and quality often affect the viability of biogas systems. This study assessed the potential for biogas process catalysis using powdered Sorghum bicolor L., Zea mays, and Pennisetum glaucum. The kinetics and biogas generation processes were studied. Experiments were conducted in 1 m3 tubular batch reactors, where batches were dosed with various organic biomolecules. Results show that the use of P. glaucum L. and S. bicolor L. reduced the biogas retention times significantly. Biogas generation commenced after the first day for digesters fed with S. bicolor L. and P. glaucum L. while one with Z. mays and control occurred on day two. The rate of biomethanation and methane content were enhanced. S. bicolor L. led to the highest methane content. Findings reveal that locally available organic biomolecules improved biogas quality and quantity.

关键词： Mesophilic Kinetics Biomolecules Biomethanation Reaction Rates Anaerobic

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Effect of Exhaust Gas Recirculation on Performance and Emission Characteristics of a Diesel-Piloted Biogas Engine

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Smart Grid and Renewable Energy 2015年第4期6卷 49-58页

作者： Meshack Hawi Robert Kiplimo hiram ndiritu Department of Mechanical Engineering JKUAT Nairobi Kenya Department of Marine Engineering JKUAT Nairobi Kenya

In this research, a Direct Injection Compression Ignition (DICI) engine was modified into a dual-fuel engine that used biogas as the primary fuel and diesel as pilot fuel, with the focus on reduction of harmful exhaust emissions while maintaining high thermal efficiency. The effect of exhaust gas recirculation (EGR) on engine performance and emission characteristics was studied. The EGR system was developed and tested with different EGR percentages, i.e. 0%, 10%, 20% and 30%. The effect of EGR on exhaust gas temperature and performance parameters like brake specific fuel consumption, brake power and brake thermal efficiency was studied. The performance and emission characteristics of the modified engine were compared with those of the conventional diesel engine. The results showed that EGR led to a decrease in specific fuel consumption and an increase in brake thermal efficiency. With increase in percent (%) of EGR, the percentage increase in brake thermal efficiency was up to 10.3% at quarter load and up to 14.5% at full load for single fuel operation while for dual-fuel operation an increase up to 9.5% at quarter load and up to 11.2% at full load was observed. The results also showed that EGR caused a decrease in exhaust gas temperature;hence it’s potential to reduce NOX emission. However, emissions of HC and CO increased slightly with EGR.

关键词： DICI Engine Dual-Fuel Engine EGR NOX

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Performance of Water in Glass Evacuated Tube Solar Water Heater under Kenya Climatic Condition

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Computational Water, Energy, and Environmental Engineering 2021年第2期10卷 37-48页

作者： Ernest Kyekyere hiram ndiritu Meshack Hawi Polline Mwambe Department of Mechanical Engineering Pan African University Institute for Basic Sciences Technology and Innovation Nairobi Kenya Department of Mechanical Engineering Jomo Kenyatta University of Agriculture and Technology Nairobi Kenya

Solar water heaters which provide a cost-effective and environmental friendly approach to hot water generation are in widespread application. Evacuated tube solar water heaters perform better than flat plate solar water heaters as a result of their greater surface area exposed for sunlight absorption. Water-in-glass evacuated tube solar water heaters are widely used as compared to heat-pipe solar water heaters due to their short payback periods. In this study, the performance of water-in-glass evacuated tube solar water heater is investigated through experiments under the climatic conditions in Kenya. The results revealed a daily efficiency range of 0.58 - 0.65 and a daily final outlet temperature greater than 55°C given an initial temperature of 25°C.

关键词： Solar Water Heater Water-in-Glass Evacuated Tube Solar Collector Solar Irradiation

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Experimental investigation and optimization of the gasification parameters of macadamia nutshells in a batch-fed bubbling fluidized bed gasifier with air preheating

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Energy Storage and Saving 2023年第4期2卷 559-570页

作者： Fredrick Irungu Njuguna hiram M.ndiritu Benson B.Gathitu Meshack Hawi Jotham Muthoka Munyalo School of Mechanical Manufacturing and Materials EngineeringJomo Kenyatta University of Agriculture and TechnologyNairobi62000-00200Kenya School of Biosystems and Environmental Engineering Jomo Kenyatta University of Agriculture and TechnologyNairobi62000-00200Kenya

Gasification of biomass waste has a significant potential to reduce environmental impact and promote sustainability by producing syngas,which is considered as renewable energy.This work investigated the gasification of macadamia nutshells in air-preheated,batch-fed fluidized bed gasifier.The study conducted a parametric analysis to assess the effect of equivalence ratio(ER)and air temperature on the gasifier temperature profile and its performance based on gas composition,higher heating value(HHV),and gas yield.The research was conducted within the range of 0.15-0.35 for the ER and 25-825℃ for the air temperature.Multi-objective numerical optimization was conducted using response surface methodology(RSM).From the parametric study,a distinct temperature profile was observed along the gasifier height,with the peak temperature near the top of the fluidized bed section and the lowest temperature at the top of the gasifier.Air preheating mostly favored gasification temperature at the lower part of the gasifier and showed rare significance at the top.No improvement in gasifier performance was observed beyond an air temperature of 620℃,which was identified as the ideal air-preheating temperature.Analysis of variance(ANOVA)revealed that the ER was the most influential parameter in the production of combustible gasses,syngas HHV and gas yield.Air preheating did not have a significant effect on methane production and gas yield.The most optimal values for ER and air temperature were obtained as 0.195℃ and 620℃,respectively,producing optimal values of 9.54,14.65%,2.03,4.02 MJ⋅Nm^(-3),and 1.82 Nm^(3)⋅kg^(-1) for hydrogen,carbon monoxide,methane,HHV,and gas yield,respectively.

关键词： Biomass gasification Air preheating Optimization Response surface methodology

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Effect of Emulsified Diesel Fuel on Performance and Emissions Characteristics

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Energy and Power Engineering 2019年第9期11卷 333-341页

作者： Cyizere Confidence Eng hiram ndiritu Benson Gathitu Department of Mechanical Engineering Pan African University Institute for Basic Sciences Technology and Innovation Nairobi Kenya

Diesel fuel has been known as the most effective fuel but it is known as a fuel which produces harmful emissions. Later, emulsified diesel fuel was introduced as a better solution but there is no sufficient research data concerning combustion of emulsified fuel. The present work carried out a simulation of non-surfactant emulsified diesel fuel where composition of water in emulsion varied from 0% to 20% to determine the ratio of water to diesel which is more effective in reducing the exhaust emissions especially NOx. For this simulation,5% of water in diesel without surfactant was able to reduce NOx?up to 35%. It was shown that as the percentage of water increases, the power from that fuel combustion reduces.

关键词： Emulsified Diesel Fuel Surfactant Water Content Diesel Fuel Mi-cro-Explosion Emissions Power

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Performance Assessment of a Shell Tube Evaporator for a Model Organic Rankine Cycle for Use in Geothermal Power Plant

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Journal of Power and Energy Engineering 2014年第10期2卷 9-18页

作者： Haile Araya Nigusse hiram M. ndiritu Robert Kiplimo Department of Mechanical Engineering Jomo Kenyatta University of Agriculture and Technology Nairobi Kenya

The global energy demand increases with development and population rise. Most electrical power is currently generated by conventional methods from fossil fuels. Despite the high energy demand, the conventional energy resources such as fossil fuels have been declining and harmful combustion byproducts are causing global warming. The Organic Rankine Cycle power plant is a very effective option for utilization of low grade heat sources for power generation. In the Organic Rankine Cycle heat exchangers such as evaporators and condensers are key components that determine its performance. Researches indicated that shell tube heat exchangers are effectively utilized in this cycle. The design of the heat exchanger involves establishing the right flow pattern of the interacting fluids. The performance of these exchangers can be optimized by inserting baffles in the shell to direct the flow of fluid across the tubes on shell side. In this work heat exchangers have been developed to improve heat recovery from geothermal brine for additional power generation. The design involved sizing of heat exchanger (evaporator) using the LMTD method based on an expected heat transfer rate. The heat exchanger of the model power plant was tested in which hot water simulated brine. The results indicated that the heat exchanger is thermally suitable for the evaporator of the model power plant.

关键词： Shell Tube Evaporator Heat Transfer Co-Efficient LMTD ORC

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