Shaikh A. Razzak

Apparent kinetics of high temperature oxidative decomposition of microalgal biomass.

The oxidative thermal characteristics of two microalgae species biomass Nannochloropsis oculta and Chlorella vulgaris have been investigated. The apparent kinetic parameters for the microalgal biomass oxidation process are estimated by fitting the experimental data to the nth order rate model. Also, the iso-conversional methods Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) were used to evaluate the apparent activation energy. The results indicate that biomass of different microalgae strains exhibit different thermal behavior and characteristics. In addition, growth parameters and medium composition can affect the biomass productivity and composition. This would have significant impact on the thermal decomposition trend of the biomass. The kinetic modeling of the oxidation reaction with direct model fitting method shows good prediction to the experimental data. The apparent activation energies estimated by KAS and FWO methods for N. oculta were 149.2 and 151.8kJ/mol, respectively, while for C. vulgaris were 214.4 and 213.4kJ/mol, respectively.

Hydrodynamics and mass transfer of CO2 in water in a tubular photobioreactor.

Microalgae cultivation has received growing importance because of its potential applications in CO2 bio‐fixation, wastewater treatment and biofuel production. In this regard, proper design of photobioreactors is crucial for large‐scale commercial applications. The hydrodynamics of a photobioreactor has great influence on the transfer of CO2 from gas phase to liquid phase. Considering the facts, the present research focused on studying the gas holdups and mass transfer from the gas to liquid phase in a tubular photobioreactor at various superficial liquid velocities ranging from 8.4 to 22.4 cm/s and superficial gas velocities ranging from 3.66 to 8.1 cm/s. It was found that the gas holdups were radially distributed. The highest gas holdups were observed at the center zone while the lowest holdups are found near the reactor wall. CO2 mass transfer coefficient in the photobioreactor was also estimated under different superficial liquid velocities (0.206, 0.355 and 0.485 cm/s) and gas velocities (0.67, 1.16 and 1.37 cm/s). The overall mass transfer coefficient was estimated by fitting the experimental data and comparing results with an unsteady state differential mole balance equation solved by Runge‐Kutta‐Gill method. Model predictions were comparable to experimental results.

Dynamics of energy sector and GHG emissions in Saudi Arabia

The energy sector is the main contributor to GHG emissions in Saudi Arabia. The tremendous growth of GHG emissions poses serious challenges for the Kingdom in terms of their reduction targets, and also the mitigation of the associated climate changes. The rising trend of population and urbanization affects the energy demand, which results in a faster rate of increase in GHG emissions. The major energy sector sources that contribute to GHG emissions include the electricity generation, road transport, desalination plants, petroleum refining, petrochemical, cement, iron and steel, and fertilizer industries. In recent years, the energy sector has become the major source, accounting for more than 90% of national CO2 emissions. Although a substantial amount of research has been conducted on renewable energy resources, a sustainable shift from petroleum resources is yet to be achieved. Public awareness, access to energy-efficient technology, and the development and implementation of a legislative framework, energy pricing policies, and renewable and alternative energy policies are not mature enough to ensure a significant reduction in GHG emissions from the energy sector. An innovative and integrated solution that best serves the Kingdoms long-term needs and exploits potential indigenous, renewable, and alternative energy resources while maintaining its sustainable development stride is essential. Policy relevance The main contributor to GHG emissions in Saudi Arabia is the energy sector that accounts for more than 90% of the national CO2 emissions. Tremendous growth of GHG emissions poses serious challenges for the Kingdom in their reduction and mitigating the associated climate changes. This study examines the changing patterns of different activities associated with energy sector, the pertinent challenges, and the opportunities that promise reduction of GHG emissions while providing national energy and economic security. The importance of achieving timely, sustained, and increasing reductions in GHG emissions means that a combination of policies may be needed. This study points to the long-term importance of making near- and medium-term policy choices on a well-informed, strategic basis. This analytical paper is expected to provide useful information to the national policy makers and other decision makers. It may also contribute to the GHG emission inventories and the climate change negotiations.

Application of Support Vector Machine Modeling on Phase Distribution in the Riser of an LSCFB Reactor

Abstract Support vector machine (SVM) modeling approach is applied to predict the solids holdups distribution of a liquid–solid circulating fluidized bed (LSCFB) riser. The SVM model is developed/trained using experimental data collected from a pilot-scale LSCFB reactor. Two different size glass bead particles (500 μm (GB-500) and 1,290 μm (GB-1290)) are used as solid phase, and water is used as liquid phase. The trained model successfully predicted the experimental solids holdups of the LSCFB riser under different operating parameters. It is observed that the model predicted cross-sectional average of solids holdups in the axial directions and radial flow structure are well agreement with the experimental values. The goodness of the model prediction is verified by using different statistical performance indicators. For the both sizes of particles, the mean absolute error is found to be less than 5%. The correlation coefficients (0.998 for GB-500 and 0.994 for GB-1290) also show favorable indications of the suitability of SVM approach in predicting the solids holdup of the LSCFB system.

Applications of Feed-Forward Neural Network to Study Irregular-Shape Particle Effects on Hydrodynamics Behavior in a Liquid–Solid Circulating Fluidized Bed Riser

Abstract Feed-forward neural network (FFNN) modeling techniques are applied to study the flow behavior of different-size irregular-shape particles in a pilot scale liquid–solid circulating fluidized bed (LSCFB) riser. The adequacy of the developed model is examined by comparing the model predictions with experimental data obtained from the LSCFB using lava rocks (dmean 500 and 920 µm) and water as solids and liquid phases, respectively. Axial and radial solid holdup profiles are measured in the riser at four axial locations (H 1, 2, 3 and 3.8 m above the distributor) above the liquid distributor for different operating liquids. In the model training, the effects of various auxiliary and primary liquid velocities, superficial liquid velocities and superficial solid velocities on radial phase distribution at different axial positions are considered. For model validation along with other experimental parameters, dimensionless normalized superficial liquid velocities and net superficial liquid velocities are also introduced. The correlation coefficient values of the predicted output and the experimental data are found to be 0.95 and 0.94 for LR-500 and LR-920 particles, respectively which reflects the competency of the developed FFNN model.

Characterization of aerobic oil and grease-degrading bacteria in wastewater

ABSTRACT A bacterial consortium that degrades cooking oil (CO) has been isolated in wastewater (WW) samples, by enrichment in olive CO. This consortium could degrade 90% of CO within 7–9 days (from an initial 1% [w/v]), and it is more active at alkaline conditions. The 16S ribonucleic acid (RNA) gene analysis showed that it contains five bacterium species: Stenotrophomonas rhizophila, Sphingobacterium sp., Pseudomonas libanensis, Pseudomonas poae and Pseudomonas aeruginosa. This consortium can degrade the free fatty acids (FFA): palmitic, stearic, oleic, linoleic and linolenic acids; glycerol, glucose and amylose; and albumin, but could not efficiently degrade carboxymethyl-cellulose. Each strain could also degrade CO and FFAs. The level of bacterial crude-activity of extracellular lipases was found to be between 0.2 and 4U/ml. Using synthetic WW, the consortium could reduce 80% of the chemical oxygen demand [from 10550 ± 2828 mg/l], 80% of nitrogen (from 410 ± 78 mgl/l) and 57% of phosphorus (from 93 ± 25 mg/l). Thus, this consortium can be utilized in the removal of CO from WW.

Liquids Phase Holdup and Separation Characteristics as a Function of Well Inclination and Flowrate

The maturing Middle Eastern oil fields with natural aquifer support or water injection can pose a challenging produced water handling and disposal issues. The increased water-oil ratio also presents productivity problems: many wells will die prematurely due to increased water holdup. The produced water management cost @US

Hydrodynamics Modeling of an LSCFB Reactor Using Multigene Genetic Programming Approach: Effect of Particles Size and Shape

0.50—1.00 per barrel involving millions of barrels of water (even at a modest WOR of 50% from current 30-35%) will be in billions due to the high daily oil production rate envisaged. In this paper, we focus on various aspects of downhole oil-water separation, which we believe will lessen the cost significantly. The downhole water separation technology developed and applied in the western hemisphere cannot be directly applied here because of the orders of magnitude higher production rates per

Integrated CO2 capture, wastewater treatment and biofuel production by microalgae culturing—A review

Abstract The multigene genetic programming (MGGP) technique based hydrodynamics models were developed to predict the solids holdups of a liquid-solid circulating fluidized bed (LSCFB) riser. Four different particles were considered to investigate the effects of particle size, shape and density on hydrodynamics behavior of the LSCFB riser. In this regard, two spherical shape glass bead particles (500 and 1200 μm), two irregular shape lava rock particles (500 and 920 μm) were employed as solid phase and water as liquid phase. The MGGP models were developed, relating the solids holdup (εs

Catalytic oxidation of volatile organic compounds (VOCs) – A review

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