Mazlan Abdul Wahid

Biogas flameless combustion: a review

Biogas which is produced by the anaerobic digestion of biomass and organic wastes by micro-organisms is biodegradable. Biogas is a type of renewable energy sources that can be used for lighting, heating, and transportation and small-scale power generations. Although it seems that biogas is not economical due to its low calorific values, various investigations have been conducted by various researchers. Flameless combustion of fossil fuel was introduced during last decade and it has been proven that it could be the best technique for biogas combustion due to its low production of NOx pollution. In this paper, the review of biogas, its resources, and the utilization of biogas on flameless combustion is illustrated.

Pollutant in palm oil production process

Palm oil mill effluent (POME) is a by-product of the palm industry and it releases large amounts of greenhouse gases (GHGs). Water systems are also contaminated by POME if it is released into nonstandard ponds or rivers where it endangers the lives of fish and water fowl. In this paper, the environmental bottlenecks faced by palm oil production were investigated by analyzing the data collected from wet extraction palm oil mills (POMs) located in Malaysia. Strategies for reducing pollution and technologies for GHG reduction from the wet extraction POMs were also proposed. Average GHG emissions produced from processing 1 ton of crude palm oil (CPO) was 1100 kg CO2eq. This amount can be reduced to 200 kg CO2eq by capturing biogases. The amount of GHG emissions from open ponds could be decreased from 225 to 25 kg CO2eq/MT CPO by covering the ponds. Installation of biogas capturing system can decrease the average of chemical oxygen demand (COD) to about 17,100 mg/L and stabilizing ponds in the final step could decrease COD to 5220 mg/L. Using a biogas capturing system allows for the reduction of COD by 80% and simultaneously using a biogas capturing system and by stabilizing ponds can mitigate COD by 96%. Other ways to reduce the pollution caused by POME, including the installation of wet scrubber vessels and increasing the performance of biogas recovery and biogas upgrading systems, are studied in this paper. Implications: Around 0.87 m3 POME is produced per 1 ton palm fruit milled. POME consists of around 2% oil, 2–4% suspended solid, 94–96% water. In palm oil mills, more than 90% of GHGs were emitted from POME. From 1 ton crude palm oil, 1100 kg CO2eq GHGs are generated, which can be reduced to 200 kg CO2eq by installation of biogas capturing equipment.

Effect of diluted and preheated oxidizer on the emission of methane flameless combustion

In combustion process, reduction of emissions often accompanies with output efficiency reduction. It means, by using current combustion technique it is difficult to obtainlow pollution and high level of efficiency in the same time. In new combustion system, low NOxengines and burners are studied particularly. Recently flameless or Moderate and Intensive Low oxygen Dilution (MILD) combustion has received special attention in terms of low harmful emissions and low energy consumption. Behavior of combustion with highly preheated air was analyzed to study the change of combustion regime and the reason for the compatibility of high performance and low NOx production. Sustainability of combustion under low oxygen concentration was examined when; the combustion air temperature was above the self-ignition temperature of the fuel. This paper purposes to analyze the NOx emission quantity in conventional combustion and flameless combustion by Chemical Equilibrium with Applications (CEA) software.

Combined Convection Heat Transfer of Nanofluids Flow over Forward Facing Step in a Channel Having a Blockage

Numerical simulations of two dimensional laminar combined convection flows using nanofluids over forward facing step with a blockage are analyzed. The continuity, momentum and energy equations are solved using finite volume method (FVM) and the SIMPLE algorithm scheme is applied to examine the effect of the blockage on the heat transfer characteristics. In this project, several parameters such as different types of nanofluids (Al2O3, SiO2, CuO and ZnO), different volume fraction in the range of 1% - 4%, different nanoparticles diameter in the range of 25nm-80nm were used. Effects of different shapes of blockage (Circular, Square and Triangular) were studied. The numerical results indicated that SiO2nanofluid has the highest Nusselt number. The Nusselt number increased as the volume fraction and Reynolds number increase, while it decreases as the nanoparticles diameter increases. Circular blockage produced higher results compared to triangular and square one.

Evaluation of palm oil combustion characteristics by using the Chemical Equilibrium with Application (CEA) software

Variety of edible and nonedible oils can be used as the feedstock for biodiesel production. Among the edible oil source includes both virgin vegetable oils and waste vegetable oils. Rapeseed, soybean, and palm oils are most commonly used to produce biodiesel. In addition to its sources, the combustion process, the amount of produced energy, and the rate of emissions from biofuel inflammation also are crucial in to the ability of biodiesel to meet global energy demands. The level of energy produced and the rate of emissions can be evaluated with Chemical Equilibrium with Applications (CEA) software. This paper attempts to scrutinize and determine the palm oil combustion properties under various thermodynamic conditions using the CEA software.

Advances in aluminum powder usage as an energetic material and applications for rocket propellant

Energetic materials have been widely used for military purposes. Continuous research programs are performing in the world for the development of the new materials with higher and improved performance comparing with the available ones in order to fulfill the needs of the military in future. Different sizes of aluminum powders are employed to produce composite rocket propellants with the bases of Ammonium Perchlorate (AP) and Hydroxyl-Terminated-Polybutadiene (HTPB) as oxidizer and binder respectively. This paper concentrates on recent advances in using aluminum as an energetic material and the properties and characteristics pertaining to its combustion. Nano-sized aluminum as one of the most attractable particles in propellants is discussed particularly.

Review of Development Survey of Phase Change Material Models in Building Applications

The application of phase change materials (PCMs) in green buildings has been increasing rapidly. PCM applications in green buildings include several development models. This paper briefly surveys the recent research and development activities of PCM technology in building applications. Firstly, a basic description of phase change and their principles is provided; the classification and applications of PCMs are also included. Secondly, PCM models in buildings are reviewed and discussed according to the wall, roof, floor, and cooling systems. Finally, conclusions are presented based on the collected data.

Effect of Vertical Baffle Installation on Forced Convective Heat Transfer in Channel Having a Backward Facing Step

In this study, forced convective heat transfer is considered in channel over a backward facing step having a baffle on the top wall. Four different geometries with different expansion ratios and different type of baffles are numerically investigated. The study clearly shows that the geometry with expansion ratio 2 and solid baffle has the highest Nusselt number compared to other geometries. Considering both Nusselt number and skin friction coefficient for all four geometries clearly illustrated an increase in average Nusselt number by increasing the expansion ratio. This study clearly shows that mounting a slotted baffle at the top wall instead of a solid baffle caused a decline in average Nusselt number. It is also found that for geometry with expansion ratio of 3 and a slotted baffle on the top of the channel, skin friction coefficient in both bottom wall and step wall has its minimal compared to other geometries.

Effects of Burner Configuration on the Characteristics of Biogas Flameless Combustion

The purpose of this experimental and numerical investigation is to analyze the effects of burner configuration on the characteristics of biogas flameless combustion. In the four non-premixed studied burners, the inlet jet of the fuel is located at the center of the burner, surrounded by four oxidizer parallel jets in the coaxial burners and four perpendicular jets in the tangential configuration. In the three-dimensional (3D) computational fluid dynamic (CFD) study, a two-step reaction scheme, eddy dissipation concept (EDC), eddy dissipation method (EDM), and the realizable k- ϵ formulation were set for all simulations. The results illustrate that the volume of the flame is wider in a tangential burner and, hence, the temperature uniformity in the tangential flameless burner is more than coaxial configurations. The inside temperature of the furnace and the combustor’s wall temperature are higher in the tangential burner; consequently, higher heat loss from walls was recorded in tangential mode. Despite the higher energy loss from walls in the tangential burner, the efficiency of biogas flameless combustion in the tangential is more than the coaxial burners (66% and 64%, respectively). The concentration of CH4 in the exhaust gases was recorded at 48 ppm and 60 ppm in the tangential and coaxial burners, respectively, which confirms that the combustion of biogas is more complete in the tangential flameless burner. The lower concentration of oxygen in the tangential burner conducts the combustion system to generate higher carbon monoxide (CO) based on the two-step combustion concept.

Numerical Study of Fluid Flow and Heat Transfer Enhancement of Nanofluids over Tube Bank

In the present work, laminar cross flow forced convective heat transfer of nanofluid over tube banks with various geometry under constant wall temperature condition is investigated numerically. We used nanofluid instead of pure fluid ,as external cross flow, because of its potential to increase heat transfer of system. The effect of the nanofluid on the compact heat exchanger performance was studied and compared to that of a conventional fluid.The two-dimensional steady state Navier-Stokes equations and the energy equation governing laminar incompressible flow are solved using a Finite volume method for the case of flow across an in-line bundle of tube banks as commercial compact heat exchanger. The nanofluid used was alumina-water 4% and the performance was compared with water. In this paper, the effect of parameters such as various tube shapes ( flat, circle, elliptic), and heat transfer comparison between nanofluid and pure fluid is studied. Temperature profile, heat transfer coefficient and pressure profile were obtained from the simulations and the performance was discussed in terms of heat transfer rate and performance index. Results indicated enhanced performance in the use of a nanofluid, and slight penalty in pressure drop. The increase in Reynolds number caused an increase in the heat transfer rate and a decrease in the overall bulk temperature of the cold fluid. The results show that, for a given heat duty, a mas flow rate required of the nanofluid is lower than that of water causing lower pressure drop. Consequently, smaller equipment and less pumping power are required.