PAUL OKONKWO - Academia.edu (original) (raw)

Papers by PAUL OKONKWO

Nigerian Journal of Technology, Oct 15, 2013

Nigerian Journal of Technology

A pilot-size dealumination unit to handle 2.5kg of metakaolin per batch was designed and fabricat... more A pilot-size dealumination unit to handle 2.5kg of metakaolin per batch was designed and fabricated and test run. The metakaolin was prepared from Kankara kaolin. The metakaolin was completely split into silica and alumina. The silica component which was inert to the sulphuric acid used during the reaction and was obtained as a solid product. While the alumina which reacted with the sulphuric acid was obtained in liquid form as aluminum sulphate, known as alum. The dealumination unit comprises of the dealumination reactor, known as dealuminator, acid holding tank and metakaolin slurry mixing tank. The material of construction selected for the dealumination reactor was stainless steel type 304 lined internally with glass to withstand the corrosive environment of the concentrated sulphuric acid at the reaction temperature > 140°C. The capacity of the componentsare; acid holding tank 5 liters;metakaolin slurry mixing tank 20 liters, with 70 W capacity motor and the dealuminator 50 ...

African Journal of Pure and Applied Chemistry, 2013

Limestone calcination reaction seems to be a very simple and straight-forward reaction. However, ... more Limestone calcination reaction seems to be a very simple and straight-forward reaction. However, there are numerous critical variables that exert profound effect on lime burning operations. The factors and variables that affect the burning of limestones must be considered in the selection, design and optimization of the calcininig equipment. Limestone burning in a vertical kiln often presents complex problems which can be solved from the conception by consideration of the prevailing factors that determine the progress of calcinations reactions. The evaluation of the influence of these factors on the progress of the burning of Jakura limestone in a vertical shaft lime kiln is the thrust of this work. Basic kinetic parameters such as: diffusivity, mass transfer coefficient, conductivity, heat transfer coefficient, convective parameter, and diffusive parameter of the lime layer of the calcining limestone particle were obtained from the calcinations tests. Computer programs were develop...

The kinetics of calcination of a high calcium type of limestone was studied. Ukpilla limestone fo... more The kinetics of calcination of a high calcium type of limestone was studied. Ukpilla limestone found in the central region of Nigeria was studied. The limestone composition shows that the limestone has 51.29% calcium oxide and 41.53% loss on ignition and magnesium oxide content of 2.23%. The following parameters were determined; diffusion coefficient of lime layer, and mass transfer coefficient, conductivity of lime layer and beat transfer coefficient, convective parameter and diffusive parameter for temperatures 900 0 C, 1000 0 C, 1060 0 C and 1080 0 C. The reaction was found to be limited by mass and heat transfers across the tune layer of the calcining article, the optimal temperature of calcination was found to be 1060 0 C. Diffusivity and mass transfer coefficient decreases with increase in calcination temperature. The thermal conductivity increases with increase in temperature. The diffusive and convective parameter decreases with increase in temperature. The reactivity of lim...

Academic Journal of Interdisciplinary Studies, 2014

Neem oil was extracted using food grade ethanol in an agitated pilot scale solvent extractor. The... more Neem oil was extracted using food grade ethanol in an agitated pilot scale solvent extractor. The maximum percentage yield was 36.86% and was obtained when flat blade turbine impeller was operated at 84 rpm for 40 minutes contact time at 50oC extraction temperature and particle size of 0.425 – 0.710mm. The Gas Chromatography and Mass Spectrometer result shows the composition of the extracted neem oil to be 40.41% oleic acid, 27.65% stearic acid, 25.36% palmitic acid, 3.90% octanal, 1.23% elaidic acid, 0.97% lactone and 0.48% methyl stearate,. This percent composition compares favourably with standard values. The composition of the neem oil suggests its application for industrial usage. The properties of the neem oil extracted were found to be: specific gravity, 0.9111; pH, 6.5; refractive index, 1.4668; iodine value, 70.21g/g; acid value, 34.33mgKOH/g and Saponification value, 180.95 mgKOH/g. These values compare favourably with standard values. DOI: 10.5901/ajis.2014.v3n5p39

Nigerian Journal of Technology, 2017

Thermal stability of transitional alumina phases produced from ammonium alum using Kankara kaolin... more Thermal stability of transitional alumina phases produced from ammonium alum using Kankara kaolin as starting material was studied. Wet beneficiation method was employed to purify the starting material, after which it was calcined and dealuminated with sulphuric acid. The elemental composition, mineralogical, and physiological analyses were carried out using X-ray fluorescence (XRF), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) techniques respectively. The ammonium alum was thermally treated by varying the calcination temperature from 700 to 1200°C and varying the time of calcination from 1 to 4 h. The formation of gamma alumina began at calcination temperature of 825°C for calcination time of 3 h, which was found to be lower than reported works of 900°C. It was found to be stable at higher temperature of 1125°C, above which phase transformation to alpha alumina was observed. The observed wide range of thermal stability of the gamma alumina phase gives it good advant...

Nigerian Journal of Technology, 2015

Nigerian Journal of Technology, 2015

Chemical and Process Engineering Research, 2015

A pseudo homogeneous two-dimensional (2D) model of an industrial Fluid Catalytic Cracking (FCC) r... more A pseudo homogeneous two-dimensional (2D) model of an industrial Fluid Catalytic Cracking (FCC) riser is here presented. The FCC riser models of previous researchers were mostly based on the assumption of negligible mass transfer resistance and 1D plug flow. These assumptions undermine the accuracy of the models by overpredicting the optimum residence time of the riser. In this work the coke content of FCC catalyst was modeled as a function of the reactor temperature with the aim of predicting the operating conditions that will reduce coke on catalyst without undermining the yield of the key product (gasoline). Mass transfer resistance was incorporated in the reactor model to enhance the accuracy of the results. Catalyst deactivation was modeled based on the exponential decay function. The mass transfer coefficient and the catalyst effectiveness factor were estimated from empirical correlations obtained from literature. Data used for the simulation were sourced from an existing plant (KRPC) as well as from open literature. Finite difference numerical scheme was used to discretise the model governing equation. At the end of the investigation, three different operating temperature regimes were identified from the simulated results for the coking of FCC catalyst (low temperature, optimal temperature and high temperature regimes). An optimum operating temperature range of 786K-788K and an optimum catalyst-tooil ratio (COR) range of 4.60-4.71 were predicted for the riser.

Nigerian Journal of Technology, 2015

Gamma alumina is a Gamma alumina is a Gamma alumina is a Gamma alumina is a good material for cat... more Gamma alumina is a Gamma alumina is a Gamma alumina is a Gamma alumina is a good material for catalyst support and its surface properties is of great importance. In this good material for catalyst support and its surface properties is of great importance. In this

Asian Journal of Environment & Ecology, 2017

Applied Clay Science, 2015

Synthesis of gamma alumina from Kankara kaolin using simple novel dealumination, precipitation an... more Synthesis of gamma alumina from Kankara kaolin using simple novel dealumination, precipitation and calcination steps and the product characterization have been presented. The raw clay was wet beneficiated, metakaolinized and dealuminated. Amorphous aluminum hydroxide was precipitated from the aluminum sulfate produced, using sodium hydroxide solution as the precipitating agent. Chemical, mineralogical, physiochemical, morphological and thermal analyses of the products were carried out using XRF, XRD, BET, FTIR, SEM, TEM and TGA/DTA. The aluminum hydroxide produced was subjected to thermal treatment at variable calcination temperatures in the range of 300 to 900°C, gradual phase transformation was observed, a fully formed gamma alumina phase was observed at 900°C. XRF analysis of the various materials at each stage of processing showed a progressive trend of increase in Al 2 O 3 content, at calcination of 900°C the Al 2 O 3 content was 91.02 wt.%. The XRD pattern of the alumina obtained at 900°C was similar to that of commercial gamma alumina. The BET surface area, pore volume and pore diameter of the as-synthesized gamma alumina were 102.6 m 2 /g, 0.0305 cm 3 /g and 11.89 Å respectively and the crystal size was 10 nm. This novel process is an industrially feasible alternative to the conventional Bayer process, and it offers a solution to the environmental hazards posed by the wastes generated by the Bayer process.

Nigerian Journal of Technology, Oct 15, 2013

Nigerian Journal of Technology

A pilot-size dealumination unit to handle 2.5kg of metakaolin per batch was designed and fabricat... more A pilot-size dealumination unit to handle 2.5kg of metakaolin per batch was designed and fabricated and test run. The metakaolin was prepared from Kankara kaolin. The metakaolin was completely split into silica and alumina. The silica component which was inert to the sulphuric acid used during the reaction and was obtained as a solid product. While the alumina which reacted with the sulphuric acid was obtained in liquid form as aluminum sulphate, known as alum. The dealumination unit comprises of the dealumination reactor, known as dealuminator, acid holding tank and metakaolin slurry mixing tank. The material of construction selected for the dealumination reactor was stainless steel type 304 lined internally with glass to withstand the corrosive environment of the concentrated sulphuric acid at the reaction temperature > 140°C. The capacity of the componentsare; acid holding tank 5 liters;metakaolin slurry mixing tank 20 liters, with 70 W capacity motor and the dealuminator 50 ...

African Journal of Pure and Applied Chemistry, 2013

Limestone calcination reaction seems to be a very simple and straight-forward reaction. However, ... more Limestone calcination reaction seems to be a very simple and straight-forward reaction. However, there are numerous critical variables that exert profound effect on lime burning operations. The factors and variables that affect the burning of limestones must be considered in the selection, design and optimization of the calcininig equipment. Limestone burning in a vertical kiln often presents complex problems which can be solved from the conception by consideration of the prevailing factors that determine the progress of calcinations reactions. The evaluation of the influence of these factors on the progress of the burning of Jakura limestone in a vertical shaft lime kiln is the thrust of this work. Basic kinetic parameters such as: diffusivity, mass transfer coefficient, conductivity, heat transfer coefficient, convective parameter, and diffusive parameter of the lime layer of the calcining limestone particle were obtained from the calcinations tests. Computer programs were develop...

The kinetics of calcination of a high calcium type of limestone was studied. Ukpilla limestone fo... more The kinetics of calcination of a high calcium type of limestone was studied. Ukpilla limestone found in the central region of Nigeria was studied. The limestone composition shows that the limestone has 51.29% calcium oxide and 41.53% loss on ignition and magnesium oxide content of 2.23%. The following parameters were determined; diffusion coefficient of lime layer, and mass transfer coefficient, conductivity of lime layer and beat transfer coefficient, convective parameter and diffusive parameter for temperatures 900 0 C, 1000 0 C, 1060 0 C and 1080 0 C. The reaction was found to be limited by mass and heat transfers across the tune layer of the calcining article, the optimal temperature of calcination was found to be 1060 0 C. Diffusivity and mass transfer coefficient decreases with increase in calcination temperature. The thermal conductivity increases with increase in temperature. The diffusive and convective parameter decreases with increase in temperature. The reactivity of lim...

Academic Journal of Interdisciplinary Studies, 2014

Neem oil was extracted using food grade ethanol in an agitated pilot scale solvent extractor. The... more Neem oil was extracted using food grade ethanol in an agitated pilot scale solvent extractor. The maximum percentage yield was 36.86% and was obtained when flat blade turbine impeller was operated at 84 rpm for 40 minutes contact time at 50oC extraction temperature and particle size of 0.425 – 0.710mm. The Gas Chromatography and Mass Spectrometer result shows the composition of the extracted neem oil to be 40.41% oleic acid, 27.65% stearic acid, 25.36% palmitic acid, 3.90% octanal, 1.23% elaidic acid, 0.97% lactone and 0.48% methyl stearate,. This percent composition compares favourably with standard values. The composition of the neem oil suggests its application for industrial usage. The properties of the neem oil extracted were found to be: specific gravity, 0.9111; pH, 6.5; refractive index, 1.4668; iodine value, 70.21g/g; acid value, 34.33mgKOH/g and Saponification value, 180.95 mgKOH/g. These values compare favourably with standard values. DOI: 10.5901/ajis.2014.v3n5p39

Nigerian Journal of Technology, 2017

Thermal stability of transitional alumina phases produced from ammonium alum using Kankara kaolin... more Thermal stability of transitional alumina phases produced from ammonium alum using Kankara kaolin as starting material was studied. Wet beneficiation method was employed to purify the starting material, after which it was calcined and dealuminated with sulphuric acid. The elemental composition, mineralogical, and physiological analyses were carried out using X-ray fluorescence (XRF), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) techniques respectively. The ammonium alum was thermally treated by varying the calcination temperature from 700 to 1200°C and varying the time of calcination from 1 to 4 h. The formation of gamma alumina began at calcination temperature of 825°C for calcination time of 3 h, which was found to be lower than reported works of 900°C. It was found to be stable at higher temperature of 1125°C, above which phase transformation to alpha alumina was observed. The observed wide range of thermal stability of the gamma alumina phase gives it good advant...

Nigerian Journal of Technology, 2015

Nigerian Journal of Technology, 2015

Chemical and Process Engineering Research, 2015

A pseudo homogeneous two-dimensional (2D) model of an industrial Fluid Catalytic Cracking (FCC) r... more A pseudo homogeneous two-dimensional (2D) model of an industrial Fluid Catalytic Cracking (FCC) riser is here presented. The FCC riser models of previous researchers were mostly based on the assumption of negligible mass transfer resistance and 1D plug flow. These assumptions undermine the accuracy of the models by overpredicting the optimum residence time of the riser. In this work the coke content of FCC catalyst was modeled as a function of the reactor temperature with the aim of predicting the operating conditions that will reduce coke on catalyst without undermining the yield of the key product (gasoline). Mass transfer resistance was incorporated in the reactor model to enhance the accuracy of the results. Catalyst deactivation was modeled based on the exponential decay function. The mass transfer coefficient and the catalyst effectiveness factor were estimated from empirical correlations obtained from literature. Data used for the simulation were sourced from an existing plant (KRPC) as well as from open literature. Finite difference numerical scheme was used to discretise the model governing equation. At the end of the investigation, three different operating temperature regimes were identified from the simulated results for the coking of FCC catalyst (low temperature, optimal temperature and high temperature regimes). An optimum operating temperature range of 786K-788K and an optimum catalyst-tooil ratio (COR) range of 4.60-4.71 were predicted for the riser.

Nigerian Journal of Technology, 2015

Gamma alumina is a Gamma alumina is a Gamma alumina is a Gamma alumina is a good material for cat... more Gamma alumina is a Gamma alumina is a Gamma alumina is a Gamma alumina is a good material for catalyst support and its surface properties is of great importance. In this good material for catalyst support and its surface properties is of great importance. In this

Asian Journal of Environment & Ecology, 2017

Applied Clay Science, 2015

Synthesis of gamma alumina from Kankara kaolin using simple novel dealumination, precipitation an... more Synthesis of gamma alumina from Kankara kaolin using simple novel dealumination, precipitation and calcination steps and the product characterization have been presented. The raw clay was wet beneficiated, metakaolinized and dealuminated. Amorphous aluminum hydroxide was precipitated from the aluminum sulfate produced, using sodium hydroxide solution as the precipitating agent. Chemical, mineralogical, physiochemical, morphological and thermal analyses of the products were carried out using XRF, XRD, BET, FTIR, SEM, TEM and TGA/DTA. The aluminum hydroxide produced was subjected to thermal treatment at variable calcination temperatures in the range of 300 to 900°C, gradual phase transformation was observed, a fully formed gamma alumina phase was observed at 900°C. XRF analysis of the various materials at each stage of processing showed a progressive trend of increase in Al 2 O 3 content, at calcination of 900°C the Al 2 O 3 content was 91.02 wt.%. The XRD pattern of the alumina obtained at 900°C was similar to that of commercial gamma alumina. The BET surface area, pore volume and pore diameter of the as-synthesized gamma alumina were 102.6 m 2 /g, 0.0305 cm 3 /g and 11.89 Å respectively and the crystal size was 10 nm. This novel process is an industrially feasible alternative to the conventional Bayer process, and it offers a solution to the environmental hazards posed by the wastes generated by the Bayer process.