Research Repository :: Browsing by Author "Said, Mahir M."

Browsing by Author "Said, Mahir M."

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Analysis of Pyrolysis Kinetics and Energy Content of Agricultural and Forest Waste
(2014-03) Said, Mahir M.; John, Geoffrey R.; Mhilu, Cuthbert F.; Manyele, Samwel
Selected agricultural and forest wastes included rice husk, coconut husk, cashewnut shell, eucalyptus, pine and mangrove were used for thermal characterization. The studied materials have heating value between 13 and 23 kJ/kg, such that the biomass material can be used as a fuel by directly burning, but their energy content is lower as compared to coal and other fossil fuels. The energy content of the biomass material can be improved through pyrolysis process for the mentioned materials, the cashew nut shell had higher energy content than other biomass material due to its high hydrogen to carbon ratio and low oxygen to carbon ratio. Thermochemical characteristic depicted high degradation at a heating rate of 10 K/min. All studied materials except mangrove and pine, maximum degradation occurred at 5 K/min. The reactivity of coconut husk was highest whilst cashew nut shell had the least reactivity. The activation energy for cashew nut shell obtained was 336.41 kJ/mole and the activation energy of the other biomass ranged between 220 and 130 kJ/mol. The coconut husk, pine, eucalyptus and rice husk are more reactive than mangrove and cashewnut shell.
The Combustion Characteristics of Biomass Syngas from High Temperature Air, Entrained Flow and Circulating Fluidized Bed Gasifiers
(SSRN Electronic Journal, 2014-02-21) Said, Mahir M.; Chaula, Zephania; John, Geoffrey R.; Mhilu, Cuthbert F.
The study has been performed to determine fundamental combustion characteristics of syngas. Three technologies were selected to produce the syngas; High Temperature Agent Gasifier (HTAG), Entrained Flow Gasifier (EFG) and Circulating Fluidized Bed Gasifier (CFBG). Although the material used for production of syngas was the same, wood biomass, the compositions of syngas obtained were different. The adiabatic flame temperatures were determined at different air to fuel ratio. The maximum adiabatic temperature for HTAG, EFG and CFBG syngas at stoichiometric condition were 1846 K, 2250 K and 2234 K respectively. It has been observed that combustion of CFBG syngas produces more nitrogen oxide (NOx) than when using syngas of EFG. The high NOx in CFBG is caused by the high methane content, which increases the adiabatic flame temperature to 2200 K at stoicheometric condition. The lowest NOx emission was observed in HTAG syngas. The adiabatic temperature increased linearly with the preheating temperature, whilst oxygen enrichment increased the adiabatic temperature. It has been concluded that syngas produced from EFG and CFBG are better candidate as gaseous fuel in combustion chamber than HTAG syngas.
Effect of mild hydrothermal pretreatment on biomass pyrolysis characteristics and vapors: A Mass and Energy Balance Perspective
(2015) Cuvila, Carlos Alberto; Said, Mahir M.; Kantarelis, Efthymios; Saffaripour, M.; Yang, Weihong
Mozambique has vast forestry resources and also considerable biomass waste material such as bagasse, rice husks, sawdust, coconut husks and shells, cashew nut shell and lump charcoal waste. The potential of the total residues from the agricultural sector and the forest industry is estimated to be approximately 13 PJ. This amount of energy covers totally the production of charcoal which amounted to approximately 12.7 PJ in 2006. Although biomass is an attractive renewable source of energy, it is generally difficult to handle, transport
Energy Recovery routes from Municipal Solid Waste, A case study of Arusha-Tanzania
(Journal of Energy Technologies and Policy, 2014-01) Omari, Arthur; Said, Mahir M.; Njau, Karoli N.; John, Geoffrey R.; Mtui, Peter
A study of energy recovery from municipal solid waste was undertaken. The energy content of the solid waste is 12MJ/kg. The elemental composition shows that the municipal solid waste contains 50% and 5% of carbon and hydrogen respectively. The energy flow (exothermic and endothermic) and thermal degradation analysis were carried out using differential scanning calorimetry and thermo-gravimetric analyser respectively. Experiments were performed at heating rate of 10 K/min, 20 K/min, 30 K/min and 40 K/min in the nitrogen atmosphere at temperature between room temperature and 1273 K. The thermal degradation kinetic parameters values of activation energy (E a) ranged from 205.9 to 260.6kJ/mol. It has been observed that municipal solid waste is less reactive to combustion as compared to coal and biomass, but its reactivity can be improved through pre-treating process so as to reduce noncombustible materials such as oxygen and ash content. Also pyrolysis and gasification can be used to convert MSW to liquid or gaseous fuel.
Fast Pyrolysis and Kinetics of Sugarcane Bagasse in Energy Recovery
(Springer Berlin Heidelberg, 2013-06-05) Said, Mahir M.; John, Geoffrey R.; Mhilu, Cuthbert F.; Manyele, Samwel
The trend for material and energy recovery from biomass-waste along with the need to reduce green house gases has led to an increased interest in the thermal processes applied to biomass. The thermal process applied to biomass produces either liquid fuel (bio-oil) or gaseous fuel. Liquid fuel is more preferred because it is easier to transport from one point to another and also it can be used for production of chemicals. One of the biomass obtained in Tanzania is sugarcane bagasse. The sugarcane bagasse is the fibrous materials that remain after sugarcane is crushed to extract juice. Currently, it is burnt directly in the boilers for production of steam, but it can be used for production of bio-oil. The bio-oil can be optimally obtained by fast pyrolysis, which is a fast thermal decomposition of biomass material at temperature range 523–800 K in the absence of an oxidizing agent. In order to undertake a parametric study on the fast pyrolysis of sugarcane bagasse, it is imperative to establish its thermal characteristics. The paper reports the proximate and ultimate analysis, and thermal degradation of sugarcane bagasse in nitrogen as heating agent. The thermal degradation was conducted in a thermo-gravimetric analyzer from room temperature to 1,000 K at different heating rates of 5, 10, 20 and 40 K min−1. The thermo-gravimetric analyzer was used to study the effect of heating rate on the thermal degradation characteristics and to determine mass loss kinetics. The sugarcane bagasse was observed to be suitable for use in pyrolysis since it contains high volatile level of 80.5 % and fixed carbon of 8.2 %. The peak temperature was observed at 573 K at 10 K min−1 and corresponding activation energy was 387.457 kJ/mol.
Hydrodynamics of a multistage wet scrubber incineration conditions
(Educational Research and Reviews, 2012-03) Said, Mahir M.; Manyele, S. V.; Raphael, L. M.
The objective of the study was to determine the hydrodynamics of the two stage counter-current cascade wet scrubbers used during incineration of medical waste. The dependence of the hydrodynamics on two main variables was studied: Inlet air flow rate and inlet liquid flow rate. This study introduces a new wet scrubber operating features, which are liquid accumulation, together with a detailed analysis of liquid-to-gas ratio and pressure drops. Liquid accumulation at the base of each scrubber helps to prevent the gas from short circuiting to the scrubber solution feed tanks. It was observed that liquid accumulation increases linearly with inlet scrubbing liquid flow rate beyond 0.2 L/s in the absence of flue gas flow. When flue gas is flowing into multistage wet scrubber the accumulation level increases abruptly starting from inlet scrubbing liquid of 0.45 L/s and stabilizes at accumulation level of 0.1 m beyond 0.75 L/s. Increasing the flue gas flow rate increases the minimum inlet scrubbing liquid flow rate at which initial accumulation was observed. The outlet scrubbing solution flow rate and liquid accumulation in the bottom of the scrubber increase as the inlet liquid flow rate increases. Beyond inlet liquid flow rate of 0.75 L/s, the outlet liquid flow rate does not increase any more, the wet scrubber enters flooding range, whereby, the volume of accumulated liquid increases faster with inlet scrubbing liquid flow rate. The maximum liquid-to-gas ratio was observed to be 1.9 L/m[superscript 3] and the minimum liquid-to-gas ratio was 0.1 L/m[superscript 3]. Based on liquid accumulation and minimum flooding conditions, the operating liquid-to-gas ratio was recommended to be 0.6 to 1.9 L/m[superscript 3], while the allowable inlet liquid flow rate ranged between 0.45 and 0.75 L/s, giving a constant accumulation of scrubbing liquid in the wet scrubber. The pressure drop across the wet scrubber remained constant at lower flow rate and increased linearly beyond U[subscript g] = 5 m/s. The maximum pressure drop of the multistage wet scrubber was 75 kPa. (Contains 10 figures and 1 table.)
Modelling the Suitability of Pine Sawdust for Energy Production via Biomass Steam Explosion
(Scientific Research, 2014) Chaula, Zephania; Said, Mahir M.; John, Geoffrey R.; Mhilu, Cuthbert F.
Biomass material as a source of fuel is difficult to handle, transport, store, and utilize in its original form. To overcome these challenges and make it suitable for energy prodution, the material must be pre-treated. Biomass steam explosion is one of the promising pretreatment methods where moisture and hemicellulose are removed in order to improve biomass storage and fuel properties. This paper is aimed to model the suitability of pine saw dust for energy production through steam explosion process. The peak property method was used to determine the kinetic parameters. The model has shown that suitable operating conditions for steam explosion process to remove moisture and hemicellulose from pine sawdust. The temperature and pressure ranges attained in the current study are 260 -317 ℃ (533 -590 K), 4.7 -10.8 MPa, respectively.
The Study of Kinetic Properties and Analytical Pyrolysis of Coconut Shells
(Hindawi Publishing Corporation, 2015) Said, Mahir M.; John, Geoffrey R.; Mhilu, Cuthbert F.; Manyele, Samwel V.
The kinetic properties of coconut shells during pyrolysis were studied to determine its reactivity in ground form. The kinetic parameterswere determined by using thermogravimetric analyser.The activation energywas 122.780 kJ/mol.The pyrolysis products were analyzed using pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). The effects of pyrolysis temperature on the distribution of the pyrolytic products were assessed in a temperature range between 673K and 1073K.The set time for pyrolysis was 2 s. Several compoundswere observed; theywere grouped into alkanes, acids, ethers and alcohols, esters, aldehydes and ketones, furans and pyrans, aromatic compounds, and nitrogen containing compounds.The product compositions varied with temperature in that range. The highest gas proportion was observed at high temperature while the acid proportion was observed to be highest in coconut shells, thus lowering the quality of bio-oil. It has been concluded that higher pyrolysis temperature increases the amount of pyrolysis products to a maximumvalue. It has been recommended to use coconut shell for production of gas, instead of production of bio-oil due to its high proportion of acetic acid.
Thermal Characteristics and Kinetics of Rice Husk for Pyrolysis Process
(International Journal of Renewable Energy Research, 2014-03) Said, Mahir M.; John, Geoffrey R.; Mhilu, Cuthbert F.
The trend for material and energy recovery from biomass-waste along with the need to reduce green house gases has led to an increased interest in the thermal processes applied to biomass. The thermal process applied to biomass produces either liquid fuel (bio-oil) or gaseous fuel. One of the biomass wastes that are produced in large quantities in Tanzania is rice husk. The behaviour of this waste is important to any designing of thermal handling equipment when subjected thermal environment such as burning or thermal degradation. Due to this it is imperative to establish thermal characteristics of the rice husk pursued in a laboratory to understand its thermal degradation behaviour. The thermal degradation was conducted in a thermo-gravimetric analyzer from room temperature to 1273 K at different heating rates. The activation energy was 180.075 kJ/mol and suitable heating rate for high degradation of rice husk is 10 K/min, and gives 77.20 wt% of volatile release which is the suitable heating rate for pyrolysis and energy released was -4437 J/kg, although it has been recommended that the rice to be used for gasification since it contains high amount of char.
Thermal Characterization of Pine Sawdust as Energy Source Feedstock
(International knowledge Sharing Platform, 2014) Chaula, Zephania; Said, Mahir M.; John, Geoffrey R.
Pine sawdust was analyzed for thermal chemical conversion such as combustion, torrefaction, pyrolysis and gasification. The methods used to analyze involved performing proximate analysis, ultimate analysis, heating value and thermal decomposition for determining the biomass characteristics. Based on elemental composition, the pine sawdust exhibited lower energy content of 15.01 MJ/kg than bituminous coal that has about 31.8 MJ /kg. The kinetic parameters of pine sawdust described the individual component decomposition; the easiest component to decompose is hemicelluloses followed by cellulose and lignin. The heat released during thermal degradation of pine sawdust was -4380 J/g under inert condition, this shows pine sawdust potential for production of energy during combustion.
Thermal Degradation and Kinetics of Rice Husk
(International Journal of Renewable Energy Research (IJRER), 2014-06-20) Said, Mahir M.; John, Geoffrey R.; Mhilu, Cuthbert F.
The trend for material and energy recovery from biomass-waste along with the need to reduce green house gases has led to an increased interest in the thermal processes applied to biomass. The thermal process applied to biomass produces either liquid fuel (bio-oil) or gaseous fuel. One of the biomass wastes that are produced in Tanzania is rice husk. It can be used either in pyrolysis and gasification process. In order to undertake a parametric study on the fast pyrolysis of rice husk, it is imperative to establish its thermal characteristics. The paper reports thermal degradation and kinetics of rice husk. The thermal degradation was conducted in a thermo-gravimetric analyzer from room temperature to 1273 K at different heating rates. The rice husk was observed to be suitable for gasification since it contains high ash content of 22.21% and fixed carbon of 12.60%. The suitable heating rate for high degradation of rice husk is 10 K/min, which has peak temperature at 633 K. The resulting activation energy of 180.075 kJ/mol and pre-exponential factor of 2.401E+27 s-1 was determined.

Browsing by Author "Said, Mahir M."

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