Design of single-effect mechanical vapor compression

This paper presents a comprehensive design model of the single effect mechanical vapor compression process. Previous literature models focused on determination of the heat transfer area and compressor power consumption. Several new design features included in this study are the evaporator dimensions, demister dimensions, dimensions of the non-condensable gases venting orifice, and capacity of the vacuum system. The model equations include fundamental mass and energy equations; power consumption of the vapor compressor; and a well tested set of correlations for calculations of the physical properties of the vapor and liquid streams, heat transfer coefficients, and thermodynamic losses. Dependence of system variables on temperature and salinity makes the system equations nonlinear and requires an iterative solution. System performance is discussed as a function of the product flow rate, brine boiling temperature, temperature difference of the saturated boiling brine and compressed vapor, and length of the evaporator tube. Comparison of the design results against available field data shows good agreement for the predictions of specific power consumption and specific heat transfer area.     

Treatment of contaminated wastewater

The environmental impacts of petroleum are often negative because they are toxic to almost all lifestyles, and there is a possibility of causing climate change. Oil pollution in the air and in the water can be toxic and dangerous to the human body. Preliminary researchers have thoroughly studied and discussed the methods of treatment of oily wastewater. Removing oily wastewater from the oil without damaging the environment is an important problem for the oil industry. The three-phase solid, water, and oil blends can be separated from each other when a continuous oil–water separator system is used. Oil contaminated wastewater is generally treated by gravity sedimentation, coagulation, flotation, coagulation composite flotation, demulsification, membrane separation, flocculation treatment, chemical precipitation, and biological treatment and filtration.     

Improved stoves in India: A study of sustainable business models

Burning of biomass for cooking is associated with health problems and climate change impacts. Many previous efforts to disseminate improved stoves – primarily by governments and NGOs – have not been successful. Based on interviews with 12 organizations selling improved biomass stoves, we assess the results to date and future prospects of commercial stove operations in India. Specifically, we consider how the ability of these businesses to achieve scale and become self-sustaining has been influenced by six elements of their respective business models: design, customers targeted, financing, marketing, channel strategy, and organizational characteristics. The two companies with the most stoves in the field shared in common generous enterprise financing, a sophisticated approach to developing a sales channel, and many person-years of management experience in marketing and operations. And yet the financial sustainability of improved stove sales to households remains far from assured. The only company in our sample with demonstrated profitability is a family-owned business selling to commercial rather than household customers. The stove sales leader is itself now turning to the commercial segment to maintain flagging cash flow, casting doubt on the likelihood of large positive impacts on health from sales to households in the near term.     

Catalytic activity of MnTUD-1 for liquid phase oxidation of ethylbenzene with tert-butyl hydroperoxide

Manganese was incorporated into silica matrix of TUD-1 using tetraethylene glycol (TEG) as the template. Three samples with Si/Mn ratio of 115, 44 and 18 were prepared and characterized by various techniques. MnTUD-1 is shown to be mesoporous with tetrahedrally coordinated Mn when Si/Mn?=?115; and nano-particles of manganese oxides are visible at higher loading of manganese (Si/Mn?=?44 and 18). The catalytic activity of MnTUD-1 was explored in the liquid-phase oxidation of ethylbenzene with tert-butylhydroperoxide (TBHP) as oxidant. Influence of various reaction parameters such as time, Si/Mn ratio, oxidant and solvent were studied. Finally the catalytic activity also compared with well-known microporous and mesoporous catalysts like MnAlPO-5, Mn containing MCM-41, MCM-48 and SBA-15.     

Review of OECD study into “Projected costs of generating electricity—2010 Edition”

This joint report by the International Energy Agency (IEA) and the OECD Nuclear Energy Agency (NEA) is the seventh in the long established series of studies into electricity generating costs. It presents the main results of the work carried out in 2009 for calculating the costs of generating baseload electricity. The study is quite comprehensive in covering almost all financial aspects facing investors in the electricity generating system. Therefore this study although useful, its usefulness lies in explaining methodologies, mentioning factors that affect investment and cost, educating planners and improving investment evaluation and planning methodologies, its resulting figures and cost comparisons are however controversial. Generation planning and investments are case and country specific, and should be studied correspondingly and as close as possible to the timing of decision making to take account of trends. Most likely such case specific results will differ from figures calculated in the study. Therefore we need to emphasize a key conclusion of the study which is “that country-specific circumstances determine the LCOE”; it is this that needs to be considered and not the results represented in the study.     

CATALYTIC CRACKING OF QAIYARAH ASPHALTENES USING 5áMOLECULAR SIEVES

ABSTRACT

Qaiyarah crude oil is one of the heaviest crude oils in the middle east and contains a large proportion of asphattenes (15-17% wt.). Catalytic cracking of hexane-asphaltenes was performed employing 5A molecular sieves. Fractionation of the cracking products was conducted using solvent extraction and column chromatography. 6A molecular sieves in the zeolite form showed a superior cracking behavior, and do not reveal any poisoning by sulphur. Pmr results may indicate production of liquid hydrocarbons from asphaltenes.     

FEED-FORWARD BACK-PROPAGATION NEURAL NETWORK FOR THE ELECTRO-OXIDATION OF DISTILLERY EFFLUENT

The aim of the present work is to demonstrate the technical feasibility of treating high-strength distillery wastewater in an electrochemical flow reactor and to predict the result using an artificial neural network (ANN) model. The experiments were conducted using oxide coated on expanded titanium (Ti/Ru_0.3Ti_0.7O₂) as anode and stainless steel as cathode in a batch reactor with electrolytic recirculation. Pollutant degradation was measured as chemical oxygen demand (COD) for various operating parameters such as effluent flow rate, current density, and supporting electrolyte concentration. Experiments were conducted for various flow rates, supporting electrolyte concentrations, and current density. An ANN was used for modeling the experimental results. The model was developed using a feed-forward back-propagation network with different layers and neurons. It can be concluded that the network configuration of 3-3-3-1 simulation gives the best result in predicting the experimental results with a high correlation coefficient (R ² = 0.9987). Using this network model, the effluent COD removal can be predicted quickly and easily.     

A neural network procedure for kanban allocation in JIT production control systems

In this paper, we develop a Generalized Systematic Procedure (GSP) for determining the optimum kanban allocation in just-in-time (JIT) controlled production lines. This procedure is based on a meta-model that incorporates (1) a factorial design approach to select the appropriate kanban combinations, (2) a simulation model to simulate the JIT production line, and (3) a trained neural network model to evaluate the line performance over the entire domain of possible kanban combinations. The GSP is then applied to a case problem and the results are presented.     

Probabilistic neural computing with advanced nanoscale MOSFETs

The use of intrinsic nanoscale MOSFET noise for probabilistic computation is explored, using the continuous restricted Boltzmann machine (CRBM), a probabilistic neural model, as the exemplar architecture. The CRBM is modified by localising noise in its synaptic multipliers, exploiting random telegraph signal (RTS) noise in nanoscale MOSFETs. A look-up table (LUT) technique is adopted to link temporal noise data to the synaptic multipliers of a CRBM, trained to model simple, non-trivial data distributions. It is shown that, for such distributions at least, the CRBM with intrinsic nanoscale MOSFET noise can be trained to provide a useful model.     

Impact of furfural on biological hydrogen production kinetics from synthetic lignocellulosic hydrolysate using mesophilic and thermophilic mixed cultures

The impact of furfural on hydrogen production and microbial growth kinetics was assessed using mixed anaerobic cultures at mesophilic and thermophilic conditions. Mesophilic experiments showed a hydrogen yield of 1.6 mol H₂/mol initial sugars at 1 g/L furfural which is a 45% enhancement from the control (0 g/L furfural) at a substrate-to-biomass ratio (S°/X°) of 4 gCOD/gVSS. On the other hand, thermophilic experiments showed no enhancement at 1 g/L furfural but rather a 53% decrease in hydrogen yield from its control. Furfural inhibition threshold limit was observed to be greater than 1 g/L for mesophilic experiments and less than 1 g/L for thermophilic experiments. In both cases, 4 g/L was the most recalcitrant furfural concentration, with propionate and lactate the most predominant soluble metabolites in the mesophilic and thermophilic experiments respectively. It was also noted that in the presence of furfural, hydrogen-producers in both mesophilic and thermophilic mixed cultures were inactivated as no hydrogen was produced until furfural was completely degraded irrespective of sugars degradation. This study also presents the kinetics of microbial growth and substrate degradation obtained using the Monod model on MATLAB^®, ignoring an inhibition term. IC₅₀ of the mesophilic and thermophilic experiments were 1.03 g/L and 0.5 g/L respectively indicating that the thermophilic hydrogen producers were more strongly affected by furfural than the mesophilic cultures.