Chemical Engineering

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Fuel blending Options in cement pyro processing of Messebo Cement factory by Co firing of Sawdust and Coal
(Mekelle University, 2024-01-25) Guesh Tewele G/her
This research assesses the technical, economic, and environmental viability of co-firing biomass fuels (eucalyptus sawdust, olea sawdust, and pine sawdust) alongside coal in cement manufacturing at Messebo Cement Factory. The evaluation emphasizes fuel blend composition, calorific values, combustion properties, and the potential for emissions reduction. Employing a mass-based fuel blend composition model, the study determines the molar composition of the blended fuels while examining their performance across 10%, 15%, and 20% co-firing ratios. Key results indicate that co-firing biomass significantly lowers CO₂ emissions compared to coal. At a co-firing rate of 10%, eucalyptus sawdust emits 0. 46426 kg of CO₂ per kg of cement, in contrast to 0. 760 kg for coal by itself. This results in a CO₂ emissions reduction of 0. 304875%, which escalates to 1. 009417% at a co-firing rate of 20% for olea and pine sawdust. The flame temperature of 1770 K (1497°C) for 10% eucalyptus co-firing satisfies kiln operational specifications, confirming its technical feasibility. From an economic standpoint, substituting 10% of coal with eucalyptus yields approximately 75,297,000 birr in annual savings, with savings rising to 150,600,000 birr at a 20% co-firing rate. The cost of eucalyptus (0. 38205 birr/kg of cement) is considerably lower than that of coal (1. 637 birr/kg of cement), leading to a 7. 67% decrease in fuel expenses at a 10% co-firing rate. Moreover, 10% eucalyptus co-firing decreases coal consumption by 5. 6%, which further boosts economic and environmental advantages. Environmental benefits encompass significant reductions in SO₂ and NOₓ emissions. For instance, 20% eucalyptus co-firing decreases SO₂ emissions by 19. 15264 units and NOₓ emissions by 12. 49865 units. Pine sawdust exhibits the greatest reduction in SO₂ (19. 77646 units at 20% co-firing), while olea sawdust achieves the most substantial reduction in NOₓ (13. 02422 units at 20% cofiring). A lower ash content (18. 67% at 20% co-firing) and minimal sulfur content in biomass further enhance combustion efficiency and lessen environmental impacts. The study also underscores the practical use of pine sawdust as an alternative fuel, which lowers the air-to-fuel ratio, excess air ratio, oxygen demands, flame temperature, as well as SO₂ and NOₓ emissions. Locally sourced pine sawdust offers benefits such as decreased transportation expenses, reduced moisture content, and less biological degradation. It can be processed and burned in a manner similar to coal or pet coke, needing only slight modifications. The thesis concludes that co-firing biomass fuels, especially pine sawdust, represents a feasible and sustainable approach to cement production, delivering considerable environmental and economic advantages. It suggests additional actions like waste heat recovery, alternative raw material usage, carbon capture, and the integration of renewable energy to further enhance system efficiency. Co-firing coal with biomass provides significant benefits for cement kiln pyro processing but necessitates precise optimization and execution suited to specific operational circumstances
Optimization of Fermentation Process Conditions in Ethanol Production from Sugarcane Molasses: The Case of Desta Alcohol and Liquor Factory
(Mekelle University, 2025-08-11) Teklemariam Negash
Alcohol distillery processes are one of the agro based industries that produces different types of alcohol liquors to serve communities as a drink and raw material for other industries. Desta Alcohol and Liquor Factory (DALF) is one of Ethiopia's leading distillery alcohol producers, well-known for its iconic beverage brands. However, the company's alcohol fermentation process has significant inefficiencies and inconsistency in ethanol yield as realized by the existing process. Hence, this study aimed to optimize fermentation process conditions in line with systemic pretreatment of sugarcane molasses to reduce its ash content and calcium content. The experimental ethanol fermentation was carried out in four main stages, mainly sugarcane molasses pretreatment and characterization, yeast propagation, fermentation, and characterization of the fermented mash. The sugarcane molasses was pretreated using hot-acid pretreatment and characterized its physico-chemical properties followed the standard methods. After pretreatment, propagation of yeast in the treated molasses supplemented with DAP was carriedout in an incubator at 30 ℃ for 24 hours. The fermentation of sugarcane molasses was carriedout as per the RSM-CCD specified factors. In order to examine and optimize the effect of molasses concentration, inoculum size, pH, and temperature on fermentation process, 24 full factorial central composite design (CCD) was used using Design Expert® v.13 software. Pretreatment effectively reduced the ash and calcium content to 6.8% and 0.013%, respectively. The ANOVA analysis revealed that the ethanol yield was significantly impacted by the fermentation process factors and their interactions (p value < 0.05). As a result of the RSM optimization, the optimum ethanol yield of 10.958% (v/v) was found at 22.725 °Brix molasses concentration, 10.132% (v/v) inoculum size, 4.943 pH, and 32.82 ℃ temperature. For comparison, without pretreatment an ethanol yield of 9.37% (v/v) was found at the optimized fermentation conditions. The characteristics of the fermented molasses mash revealed that Brix of 9.67 °Brix, temperature of 32.5 ℃, specific gravity of 0.98, and pH of 4.93. The pretreated molasses and optimized process resulted in higher ethanol yield and distinct molasses mash characteristics. The rough design and techno-economic analysis shows that hot-acid pretreatment is both technically feasible and financially viable, supporting its implementation at DALF.
Investigation of Pesticidal and Insecticidal Activity of Essential Oil Extracted from Selected Local Plants (Juniper Procera and Aloe Vera Leaves)
(Mekelle University, 2025-08-18) Letebrhan Gebremicheal Tesfay
This study aimed to investigate the pesticidal and insecticidal activities of essential oils extracted from locally available Juniper procera and Aloe Vera leaves against cochineal and cockroach insects. The essential oils were extracted using Soxhlet extraction. To determine the optimal conditions for maximum essential oil yield, the study evaluated a range of temperatures (70°C 90°C), particle sizes (<0.5mm – 4mm), and extraction times (4hr–6hr). The maximum yield obtained for Juniper procera leaves essential oil was 4.5% under optimal conditions of 80.01°C, 5.82 hours of extraction time, and a particle size of 0.5mm. For Aloe Vera leaves essential oil, the maximum yield was 23.33%, obtained with a particle size of less than 0.5mm, a temperature of 80°C, and an extraction time of 4.5 hours. The pesticidal and insecticidal activities of Juniper procera and Aloe Vera leaves essential oils, as well as their mixture, were investigated against cochineal insects (cactus pests) and cockroaches. The study evaluated the effect of essential oil concentration and exposure time on the mortality of both insect types. For each essential oil and the mixture, the same concentrations were applied to the selected insects, and mortality was observed at 1, 2, and 3 days post application. The results indicated that Juniper procera essential oil exhibited slightly better pesticidal activity against cochineal insects, with lethal concentrations (LC50 and LC90) of 4.52 b mg/ml and 18.06 mg/ml, respectively. The mixture of both essential oils showed intermediate activity (LC50 = 6.52 mg/ml, LC90 = 20.76 mg/ml), while Aloe Vera essential oil demonstrated the least activity against cochineal insects (LC50 = 7.98 mg/ml, LC90 = 22.72 mg/ml). Similarly, Juniper procera essential oil displayed slightly superior insecticidal activity against cockroaches (LC50 = 3.20 mg/ml, LC90 = 9.12 mg/ml), followed by the essential oil mixture (LC50 = 4.31 mg/ml, LC90 = 10.40 mg/ml), and then Aloe vera essential oil (LC50 = 5.08 mg/ml, LC90 = 11.85 mg/ml).
Energy audit and Design of Heat recovery system in preheater of Messebo Cement Factory
(Mekelle University, 2025-08-25) Temesgen Adhena
The cement industry is one of the most energy-intensive sectors, accounting for a significant share of global fuel and electricity consumption. Energy costs typically represent 30–40% of the total production cost of cement, making energy efficiency a critical factor for competitiveness and sustainability. This study presents a comprehensive **energy audit and waste heat recovery (WHR) system design** for a cement manufacturing plant, with the objective of identifying energy-saving opportunities, optimizing thermal and electrical consumption, and reducing overall operating costs. The **energy audit** was conducted to evaluate energy flows within major plant sections, including the raw mill, preheater, kiln, clinker cooler, and cement mill. The audit identified considerable waste heat losses, particularly from the **preheater exhaust gases** and **clinker cooler hot air**, which together account for more than 25–30% of total thermal energy input. The technical assessment shows that the designed WHR system has the potential to generate up to **4MW of electricity**. This reduces dependency on the national grid and lowers production costs. In conclusion, the integration of a WHR system in the cement plant not only improves **energy efficiency and cost competitiveness**, but also aligns with global sustainability goals and national energy policies. The study strongly recommends implementation, supported by the demonstrated technical feasibility, economic viability, and environmental benefits.