Research Article
Geochemical and Quality Assessment of Lignite Deposits in the Getema Area, Arjo, Western Ethiopia: Implications for Energy Potential
Kokobe Alemayehu*
,
Mitiku Tamene
Issue:
Volume 14, Issue 4, August 2026
Pages:
70-77
Received:
25 March 2026
Accepted:
9 May 2026
Published:
11 July 2026
Abstract: The exploration of domestic fossil fuel resources in Ethiopia is a strategic priority for balancing energy security and reducing reliance on climate-dependent hydropower. This study provides a comprehensive geochemical and quality assessment of 18 representative lignite samples from the Getema area, Western Ethiopia. Field observations across local stream exposures reveal thin, discontinuous seams (0.05 to 0.40 m) within a Mesozoic middle clay unit, often exhibiting visible sulfur staining. To satisfy international reporting standards, sampling locations were georeferenced using precise GPS coordinates. Laboratory analysis, conducted following ASTM D3172-13 and D5373 standards, indicates exceptionally low moisture levels (1.0% to 4.4%), which are attributed to localized thermal maturation from overlying Cenozoic Tertiary Trap Series basalts. Ultimate analysis reveals a robust organic matrix with carbon content reaching 45.6% and measured Gross Calorific Values (GCV) up to 4,850 kcal/kg. Based on these measured heating values and the consolidated physical state of the samples, the deposits are definitively classified as Lignite A. While high ash yields (30.3% to 89.5%) and sulfur levels (up to 4.2%) present industrial challenges, the inherent organic rank suggests a high energy potential that can be effectively unlocked through froth flotation beneficiation for use in the regional cement industry.
Abstract: The exploration of domestic fossil fuel resources in Ethiopia is a strategic priority for balancing energy security and reducing reliance on climate-dependent hydropower. This study provides a comprehensive geochemical and quality assessment of 18 representative lignite samples from the Getema area, Western Ethiopia. Field observations across local...
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Research Article
Simulation of an Acid Gas Cleaning Plant Using a Modified Absorbent (Sulfolane+Diisopropanolamine)
Issue:
Volume 14, Issue 4, August 2026
Pages:
78-87
Received:
30 May 2026
Accepted:
17 June 2026
Published:
17 August 2026
Abstract: The removal of acid gases, particularly carbon dioxide (CO2) and hydrogen sulfide (H2S), from natural gas streams is essential for meeting product specifications, preventing equipment corrosion, and complying with increasingly stringent environmental regulations. Conventional acid gas treatment processes commonly employ either chemical or physical solvents; however, these systems often suffer from limitations such as high energy consumption, reduced absorption efficiency, and increased operating costs. This study investigates the performance of a modified absorbent system comprising Sulfolane and Diisopropanolamine (DIPA) for acid gas removal using Aspen HYSYS simulation software. A rigorous process model consisting of an absorber and solvent regeneration unit was developed based on mass and energy conservation principles. The Peng-Robinson equation of state was employed to accurately represent the thermodynamic behaviour of the gas-liquid system. The simulation results were validated against published literature data using key performance indicators including overall acid gas removal efficiency, CO2 removal efficiency, H2S removal efficiency, lean solvent purity, rich solvent loading, and reboiler duty. The developed model demonstrated excellent agreement with literature values, with deviations below 5%, confirming its reliability for performance evaluation and process optimization. Comparative analysis was carried out for DIPA, Sulfolane, and a combined Sulfolane-DIPA solvent system. The results revealed that the hybrid solvent exhibited superior performance, achieving an overall acid gas removal efficiency of 94%, compared to 88% and 90% obtained for DIPA and Sulfolane, respectively. Similarly, the blended solvent achieved the highest CO2 removal efficiency (85%), H2S removal efficiency (90%), lean solvent purity (98.5%), and rich solvent loading (0.22 mol/mol), while simultaneously requiring the lowest reboiler duty of 385 kW. These findings indicate a synergistic interaction between the chemical absorption capability of DIPA and the physical absorption characteristics of Sulfolane. An economic assessment was also conducted to evaluate solvent-related operating costs. Although the combined solvent system incurred a higher annual solvent cost than the individual solvents, the enhanced acid gas removal performance and lower regeneration energy requirement suggest that the additional expenditure may be justified in applications requiring stringent gas quality specifications. The study demonstrates that the Sulfolane-DIPA blend offers a technically effective and energy-efficient alternative for industrial acid gas treatment and provides a valuable framework for future optimization and scale-up studies.
Abstract: The removal of acid gases, particularly carbon dioxide (CO2) and hydrogen sulfide (H2S), from natural gas streams is essential for meeting product specifications, preventing equipment corrosion, and complying with increasingly stringent environmental regulations. Conventional acid gas treatment processes commonly employ either chemical or physical ...
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Research Article
A Simulation Approach on the Techno-economic Feasibility of Wells in Depleted Oil Reservoirs for Geothermal Well Systems in the Niger Delta
Issue:
Volume 14, Issue 4, August 2026
Pages:
88-107
Received:
1 July 2026
Accepted:
27 July 2026
Published:
20 August 2026
Abstract: Majority of matured and abandoned wells in depleted oil reservoirs in the Niger Delta are becoming economically unviable. Recently, application of geothermal well system has gained acceptance in the re-use of wells in depleted oil reservoirs. Unfortunately, there are limited studies in the conversion of matured and abandoned wells into geothermal well system in the Niger Delta. Therefore, this study evaluates the techno-economic feasibility of applying geothermal well systems (GWS) in wells in depleted oil reservoirs in the Niger Delta. In this study, characterization and screening of the gathered data from wells in depleted oil reservoirs were performed for GWS application, considering a reservoir temperature above 80°C (176°F) and a water cut of more than 85%. The screened well data were modelled using petroleum production software, PROSPER™, to evaluate their performances and estimate geothermal gradients. A model was developed from a simple regression technique in Microsoft Excel software to predict fluid flowing temperature gradient, using the simulated geothermal data. From the result, the temperature gradient varies by 0.011°F/ft. Estimation of overall heat recovery was then calculated with a simplified heat model, considering an open loop vertical coaxial single geothermal well system. The estimated overall heat recovery ranged from 0.1 MW to 8 MW, for the wells under study. Sensitivity analyses were also conducted to assess the impact of various operating parameters on the overall heat recovery. Finally, economic analyses were performed to evaluate the economic viability of converting matured and abandoned oil wells into geothermal well systems; the simplified economic analyses, considering net present value (NPV), showed geothermal well system with heat capacity above 5 MW to be economically viable. The study demonstrates that wells in depleted oil reservoirs in the Niger Delta can be effectively repurposed for geothermal electricity generation.
Abstract: Majority of matured and abandoned wells in depleted oil reservoirs in the Niger Delta are becoming economically unviable. Recently, application of geothermal well system has gained acceptance in the re-use of wells in depleted oil reservoirs. Unfortunately, there are limited studies in the conversion of matured and abandoned wells into geothermal w...
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