Process Engineering

Permanent URI for this collection

http://etd.aau.edu.et/handle/12345678/132

Browse

Browsing Process Engineering by Author "Abubeker Yimam (PhD)"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Characterization-and Energy Enhancement of Dawuro Coal Using Froth Flotation and Alkali/Acid Leaching
    (Addis Ababa University, 2023-10) Leager Minwuyelet; Abubeker Yimam (PhD)
    Ethiopia has huge deposits of low-rank coal, which is characterized by calorific-value (an_ average_4,500_kcal/kg), high_ash_content (up to 50%), high moisture content (up to 35%) and high volatile matter. Thus, the country_is_still dependent-on partial import of better quality-coal,_and so, significant amount of money in foreign-exchange is spent to meet the demand. Therefore, this study was carried out on domestic coal beneficiation by applying the froth-flotation and alkali-acid leaching, sequentially, for_enhancing_the_quality_of Dawuro Coal, in Southwestern-Region_of_Ethiopia. The Design-Expert-(version-13) software was_used for the experimental_design_and the RSM_with_BBD were applied for modeling_the_influence of some factors on the_performance_of flotation and_alkali-acid leaching experiments. Flotation experiments were conducted by considering particle_size, collector-and_frother-dosages as independent variables, and_then, alkali- and acid-leaching experiments were carried out, sequentially, both by using leaching concentration, temperature and time as independent variables. For each, ash-reduction was defined as process-response (dependent variable). The test_results revealed that the resulted ash-reduction models were found to_be statistically_significant and also the_predicted_values were in_good_agreement with_the_experimental results – with R2 value of 0.9801, 0.9858, and 0.9711 for ash-reduction in flotation, alkali and acid-leaching, respectively. Results revealed that particle-size for flotation and leaching concentration followed by temperature for both alkali and acid leaching play important role in ash-reduction. The maximum ash reduction of 73.84%, 71.88% and 49.40% were obtained at the working conditions: (125-63 μm particle-size, 55 g/ton diesel-oil/collector, and 370 g/ton n-octanol/frother), (1 mol/dm3 NaOH, 220 oC and 60 minutes), and (1 mol/dm3 HCl, 80 oC and 3 hours) for flotation, alkali and acid leaching, respectively. The result from proximate-analysis shows that the raw-samples of coal contain 10.67% moisture, 33.73% ash, 30.34% volatile matter, 25.26% fixed-carbon, and 0.67% sulfur with 3,643.08 kcal/kg calorific value. The results for the treated coal sample show that the ash content was 8.92%, 2.51% and 1.27%; and sulfur percentage was 0.45%, 0.38% and 0.37% with 4,996.20 kcal/kg, 6,195.29 kcal/kg and 7,124.58 kcal/kg of calorific values for flotation-concentrate, alkali-leached and acid-leached coal samples, respectively. The results of this study confirm that the treated-samples of coal resulted in higher-heating-values and fixed-carbon, and lower-ash and sulfur-contents as_compared to the_raw_sample. Hence, with the determined optimum conditions, applying froth-flotation followed by sequential alkali/acid leaching is effective to increase the heating-values and upgrade the energy/quality of the sample coal, being as suitable energy source for industries like cement_and_steel.
  • No Thumbnail Available
    Item
    Parametric Optimization for Adsorptive Removal of Lead Ions by Magnetic Activated Carbon Prepared from Corn Cob
    (Addis Ababa University, 2022-09) Yoktan Seifu; Abubeker Yimam (PhD)
    Water pollution has been a major challenge to environmental engineers today due to the release of toxic heavy metals from various industries. Among various heavy metals, Lead ion (Pb2+) is considered as highly toxic, and causes various health disorders. Different sources of Lead ion (Pb2+) pollution include effluents from mining, electroplating, painting, and electroplating industries. Among various technologies, adsorptive removal of Lead ion (Pb2+) by using different adsorbents is more promising and economical. Among various adsorbents used, Magnetic activated carbon (MAC) is well known for its high adsorption capacity due to its large surface area, and pore volume. Corn Cob is lingo-cellulosic material that was selected as the precursor for the preparation of Magnetic Activated Carbon. Activated carbon was prepared through prior chemical activation using phosphoric acid following embedding of the prepared Activated Carbon by Iron oxide. The effect of various process parameters such as carbonization temperature, and Carbonization time were investigated on Lead ion (Pb2+) removal efficiency. The results indicated that BET surface area of 504 m2/ g. at approximately 610°C carbonization temperature, and 3hr. of carbonization time was measured. Effect of adsorbent dosage, pH, and initial Pb2+ concentration were studied. Optimum removal of Lead ion was recorded at 0.6 g. adsorbent dosage, pH of 5, and initial Lead ion concentration of 75 mg /l w ith Lead ion removal efficiency of 92.86% and desirability of 0.844 Kinetics and isotherm studies indicated that the adsorption mechanism of Corn Cob based Magnetic Activated Carbon follows pseudo second order (R2=0.9902) while Freundlich isotherm model well fitted the adsorption data with R2=0.9841. In terms of regeneration, adsorption efficiency of CCMAC for six cycles decreased from 89.34 to 34.68%. Corn Cob can be a good precursor for Magnetic Activated Carbon preparation and can be used to remove Pb2+ from wastewater.