Current Production Rate Research Articles

Fast Monte Carlo Simulation-based Process Design and Planning for Carbon Nanotube Synthesis

Although nanostructures have been considered for industrial applications, the current production and yield rate remains rather low, hovering in 10-20%. An effective process planning and design for nanomanufacturing is considered necessary to improve quality of nanostructures and consequentially the yield rate. Key to quality assurance in nanomanufacturing is to derive desired geometric features, which are determinant to physical and chemical properties (e.g., Young's modulus), of nanomaterials, such as carbon nanotubes (CNTs). While atomistic simulation models are widely used to study those nano-scale phenomena and consequentially the process design, they suffer from an overwhelming computational overhead. In this paper, we present a meso-scale fast Monte Carlo (MC) simulation approach to investigate large-scale CNT synthesis in chemical vapor deposition, and identify key parameters (here, catalyst diameter, temperature, and CNT length) to maximize the Young's modulus.

Hydrodynamic evaluation of long term impacts of climate change and coastal effluents in the Arabian Gulf

A comprehensive basin wide hydrodynamic evaluation has been carried out to assess the long term impacts of climate change and coastal effluents on the salinity and seawater temperature of the Arabian Gulf (AG) using Delft3D-Flow model. The long term impacts of climate change scenarios A2 and B1 of the IPCC-AR4 on the AG hydrodynamics were evaluated. Using the current capacity and production rates of coastal desalination, power, and refinery plants, two projection scenarios until the year 2080 with 30year intervals were developed namely the realistic and the optimistic discharge scenarios. Simulations of the individual climate change scenarios ascertained overall increase of the AG salinity and temperature and decrease of precipitation. The changes varied spatially with different scenarios as per the depth, proximity to exchange with ocean water, flushing, vertical mixing, and flow restriction. The individual tested scenarios of coastal projected discharges showed significant effects but within 10–20km from the outfalls.

Oil Production, Refining and Transportation in Canada

The article deals with fuel and energy complex of Canada as one of the largest manufacturers of primary energy in the world, which provides up to 6 percent of the world energy supply. Only the Russian Federation, PRC, the United States of America and the Kingdom of Saudi Arabia have larger production volumes. However, oil plays the most significant role in Canada's energy exports. It is estimated that its proven reserves are sufficient to meet the demand for 140 years at current production rate. The relevance of the study, including the analysis of fuel and energy complex of Canada, is due to the fact that such comparison and synthesis of data on the amount of recoverable oil reserves, the volume of its production, imports, exports and transit of oil and oil products, the distribution of oil for transportation (via pipelines, rail, sea, road), strategic oil field, refining and transportation of oil and oil products development projects, as well as implementation of Canada's best practices in the Russian Federation, is being developed for the first time. In addition, the data given in previously published articles on the subject, due to the dynamic development of the industry, are obsolete and do not reflect the real situation.

Long-term continuous production of H2 in a microbial electrolysis cell (MEC) treating saline wastewater

A biofilm-based 4 L two chamber microbial electrolysis cell (MEC) was continuously fed with acetate under saline conditions (35 g/L NaCl) for more than 100 days. The MEC produced a biogas highly enriched in H2 (≥90%). Both current (10.6 ± 0.2 A/m2Anode or 199.1 ± 4.0 A/m3MEC) and H2 production (201.1 ± 7.5 LH2/m2Cathode·d or 0.9 ± 0.0 m3H2/m3MEC·d) rates were highly significant when considering the saline operating conditions. A microbial analysis revealed an important enrichment in the anodic biofilm with five main bacterial groups: 44% Proteobacteria, 32% Bacteroidetes, 18% Firmicutes and 5% Spirochaetes and 1% Actinobacteria. Of special interest is the emergence within the Proteobacteria phylum of the recently described halophilic anode-respiring bacteria Geoalkalibacter (unk. species), with a relative abundance up to 14%. These results provide for the first time a noteworthy alternative for the treatment of saline effluents and continuous production of H2.

Enhancing the Electrochemical Surface Area of Tin Based Porous Electrodes for Carbon Dioxide Reduction to Formate

Conversion of CO2 to value added chemicals can provide an attractive alternate pathway for making petrochemicals without petroleum based raw materials, storing renewable energy in chemical form, as well as providing greater acceptance to CO2 as a valuable resource of chemical manufacture. This work deals with the electrochemical reduction of CO2 to formate / formic acid, with specific focus on economic feasibility of this process. The current density or rate of production of product directly affects the overall capital expenditure of a large scale process by affecting the reactor requirements. In this paper, the various approaches studied to enhance the electrochemical surface area of the electrodes will be presented. Electroplating of tin of carbon fiber substrates provided a 5-10 times area enhancement. Nano particles of tin (~ 5 nm size) were formed on high surface area activated carbon black (Vulcan XC-72). The porous electrode structure is optimized based on the binder content and loading on the base substrate. Studies were also performed to ascertain the effects of tin oxide on the reduction of CO2 to the desired product. The time evolution of the performance of such electrodes with respect to both, the overall current density as well as the selectivity towards formate product will be presented. Characterization of the electrode and particle morphology based on ‘before’ and ‘after’ experiment SEM and TEM analysis will also be presented.

Microbial electrolysis cell with spiral wound electrode for wastewater treatment and methane production

The aim of this study was to develop a microbial electrolysis cell (MEC) constructed with spiral wound electrode and to evaluate its effectiveness for wastewater treatment and methane (CH4) production. The spiral wound design can provide more than 60m2/m3 of specific surface area of the electrode and low internal resistance. With acetate as the substrate and increasing applied voltages from 0.7 to 1.3V, the average current density and CH4 production rate increased from 46 to 132A/m3 and from 0.08 to 0.17m3/m3d, respectively. With the increasing applied voltages, the energy efficiencies decreased from 157% to 69%, while the COD removal rates increased from 0.31 to 0.69kg COD/m3d. The optimal applied voltage of the spiral-wound-electrode MEC was about 0.95V. Fed with dairy wastewater, the MEC also showed good performance with the average current density of 24A/m3, CH4 production rate of 0.03m3/m3d, energy efficiency of 66%, and COD removal rate of 0.20kg COD/m3d.

Electrolysis of carbon dioxide for carbon monoxide production in a tubular solid oxide electrolysis cell

An active carbon recycling energy system (ACRES) based on carbon recycling has been proposed as a new energy transformation system. This energy transformation system reduces the carbon dioxide (CO2) emissions in the atmosphere during the iron-making process. An experimental study for electrochemical CO production by CO2 electrolysis based on the ACRES concept was carried out using a tubular solid oxide electrolysis cell. Experimental results show that the CO and oxygen (O2) production rates at 800, 850, and 900°C were almost proportional to the current passing through the cell. Both ionic conductivity and the chemical kinetics of CO2 decomposition increased with increasing temperature. The highest current density and CO production rate at 900°C were 2.97mA/cm2 and 0.78μmol/(mincm2), respectively. On the basis of the electrolytic characteristics of the cell, the scale of the combined ACRES CO2 electrolysis/iron-making system was estimated.

Estimating the residency expansion required to avoid projected primary care physician shortages by 2035.

The purpose of this study was to calculate the projected primary care physician shortage, determine the amount and composition of residency growth needed, and estimate the impact of retirement age and panel size changes. We used the 2010 National Ambulatory Medical Care Survey to calculate utilization of ambulatory primary care services and the US Census Bureau to project demographic changes. To determine the baseline number of primary care physicians and the number retiring at 66 years, we used the 2014 American Medical Association Masterfile. Using specialty board and American Osteopathic Association figures, we estimated the annual production of primary care residents. To calculate shortages, we subtracted the accumulated primary care physician production from the accumulated number of primary care physicians needed for each year from 2015 to 2035. More than 44,000 primary care physicians will be needed by 2035. Current primary care production rates will be unable to meet demand, resulting in a shortage in excess of 33,000 primary care physicians. Given current production, an additional 1,700 primary care residency slots will be necessary by 2035. A 10% reduction in the ratio of population per primary care physician would require more than 3,000 additional slots by 2035, whereas changing the expected retirement age from 66 years to 64 years would require more than 2,400 additional slots. To eliminate projected shortages in 2035, primary care residency production must increase by 21% compared with current production. Delivery models that shift toward smaller ratios of population to primary care physicians may substantially increase the shortage.

Characteristics of ice grains in the Enceladus plume from Cassini observations

AbstractIce grains in the Enceladus plume have been observed by several Cassini instruments during many Enceladus encounters. In this paper we study the ice grains ranging from less than one nanometer to micrometers in size based on multiple instrument observations. We have analyzed the nanograin data from the E17 and E18 Cassini Plasma Spectrometer (CAPS) energy spectra using the approach of Hill et al. (2012) and studied the charging of the grains using the E3–E6 Radio and Plasma Wave Spectrometer (RPWS)‐Langmuir Probe (LP) data presented by Morooka et al. (2011). To bridge the gap between CAPS nanograin observations and Cosmic Dust Analyzer and RPWS micrograin observations, we propose a composite size distribution and fit it to the E3, E5, E17, and E18 CAPS and RPWS data. The resulting size distribution peaks at ~2 nm and provides a total grain mass density ~20% that of the water vapor measured by Ion and Neutral Mass Spectrometer at the densest part of the plume and a total grain charge density much smaller than that inferred from the RPWS‐LP plasma data. Charge balance with the RPWS‐LP plasma data would require many more grains than provided by the best fit composite distribution to the CAPS and RPWS data and would provide a grain mass density comparable to that of the water vapor. On the basis of these results, we study the subsequent motion of the ice grains and estimate the resulting grain current (~104 to ~105A) and grain mass production rate (~15–65 kg/s).

MODERN EFFICIENCY ESTIMATIONS METHODS FOR DIFFERENT TYPES OF IMPACTS ON WELL BOTTOM-HOLE ZONE

Evaluation of technological efficiency bottom hole treatment today is held after the elections at the current production rate during the year (additional oil through EOR) and declines in produced water. This evaluation method takes a long time SCR. The accuracy of the estimates additional oil is determined by the adequacy of the model approximating production over the forecast period. The method does not reveal the mechanism of enhanced oil recovery, without which there can be found the most effective HMOs. Currently, the various oil and gas companies, according to industry guidance documents, mandatory assessment methods technological and economic efficiency impact on the CCD. However, these methods are only stating a fact increase or decrease the well productivity and profitability, but do not reveal the mechanism through which was achieved the success or failure of an HMO. The article deals with the problem of increasing the efficiency of field development through the development of scientifically based methodology for assessing the state of the well bottom zone, aimed at determining the effectiveness and impact study of its mechanism based on thermo-hydrodynamic studies. Interpretation methods taking into account the influx of HPC allow you to define the parameters of the near-wellbore and remote formation zone An important factor affecting the accuracy of the well test is to determine the operating ranges, which requires combining the traditional well test with a thermometer and the development of appropriate technology to address this problem.

Enhanced biohydrogen production from waste activated sludge in combined strategy of chemical pretreatment and microbial electrolysis

Cascade conversion methods are required to treat waste sludge (WAS) targeting at abundant biomass embedded in its cells and extracellular polymer. Two limiting factors have to overcome to obtain efficient conversion: (i) low release of soluble organics in raw WAS; (ii) limited conversion rate from organics to energy. Combined strategy of effective chemical pretreatment and microbial electrolysis was tested. Four kinds of chemicals (SDS, NaOH, peracetic-acid and P-cyclodextrin) were chosen to enhance volatile fatty acids (VFAs) production and following effects on hydrogen production and energy recovery by microbial electrolysis was further studied. The highest VFAs concentration was accumulated to 4712.69 mgCOD/L by beta-CD within 3 days, which was increased to 4 times of unpretreated WAS. Other three chemicals respectively achieved similar to 2.5-fold increase by SDS and PAA, and similar to 2-fold increase by NaOH. However, the highest hydrogen yield was 8.5 mgH(2)/gVSS with energy efficiency of 138% +/- 8% by SDS pretreatment. The pretreatment substantially affects VFAs components, reflected on cascade changing of current and hydrogen production rate. The cascade conversion indicated that accumulation of acetate and propionate in SDS pretreatment benefited the most hydrogen production in combined strategy. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

A Study on the Preliminary Cost Estimation for Hydraulic Backfill Process in Barapukuria Coal Mine, Dinajpur, Bangladesh

In this study, a preliminary cost investigation is conducted to evaluate the economic feasibility of hydraulic backfill process for the Barapukuria coal mine located in the north western part of Bangladesh. Recently by Longwall Top Coal Caving (LTCC) without stowing or backfill method, the mine is extracting Permian age bitu minous fair quality coal which belongs to Gondowana Fo rmation rests on Precambrian Basement. In fact, where different geological structure s and hydrogeological conditions are the prime obstacles for low recovery along with v isible environ mental impacts like subsidence around the mine area. The Cost analysis demonstrates the economic feasibility of backfill system, a prospective option for mine status devel- opment. In this research, the cost of backfilling incur in unit volu me through the evaluation of required backfill materials price where the total capital cost of the plant is assumed and maintenance cost exclude fro m the calculation. Prior to the calculation, a detail discussion on the available backfill materials is done which gives an overview of the cost scenario of the materials. As the current market value, the result y ields the cost of sand is $0.45 per m3; cement is $187 per cubic met er and ash is $.17 per m3. For the ash, the transportation cost is only considered. The cost for d ifferent mixture of backfill per cubic meter is also deter mined that reveals the availability of the backfill materials and ease of transportation reduces the backfilling cost in the mine. However, the cost is mostly influenced by the cement price. Total material cost for 84%sand, 6% cement and 10% ash mixture is evaluate d as $708.48 M fo r full ext raction and $70.85 million for 10% recovery. In addition, accord ing to current production rate require fill materials cost is $6.20 million per year. In economic evaluation with general project cash flo w chart, this study shows that the returns in three categories such as directly ore ext raction increment, indirectly s ubsidence and reduction of environment pollu- tion. Finally based on the recent revenue criterion and overall cost consideration favors the backfill process in Barapukuria coal mine. For mo re detail, fu rther study on detail cost investigation including defin ite capital cost and operational cost is recom- mended to complete evaluation of economic feasibility in the mine.

Challenges to High-Volume Production of Fuel Cell Materials: Quality Control

As fuel cells become more prominent, new manufacturing and production methods are needed to enable increased volumes with high quality. One necessary component of this industrial growth will be the accurate measurement of the variability of a wide range of material properties during the manufacturing process. Three different quality measurement techniques for fuel cell membranes and membrane-containing assemblies are described. The techniques have been demonstrated to detect as-manufactured and simulated defects at substrate motion rates comparable to current industrial production rates for these materials.

Dispatches

Dispatches

Caribbean-wide decline in carbonate production threatens coral reef growth

Global-scale deteriorations in coral reef health have caused major shifts in species composition. One projected consequence is a lowering of reef carbonate production rates, potentially impairing reef growth, compromising ecosystem functionality and ultimately leading to net reef erosion. Here, using measures of gross and net carbonate production and erosion from 19 Caribbean reefs, we show that contemporary carbonate production rates are now substantially below historical (mid- to late-Holocene) values. On average, current production rates are reduced by at least 50%, and 37% of surveyed sites were net erosional. Calculated accretion rates (mm year−1) for shallow fore-reef habitats are also close to an order of magnitude lower than Holocene averages. A live coral cover threshold of ~10% appears critical to maintaining positive production states. Below this ecological threshold carbonate budgets typically become net negative and threaten reef accretion. Collectively, these data suggest that recent ecological declines are now suppressing Caribbean reef growth potential.

Synthetic Biology: A Promising Technology for Biofuel Production

With the increasing awareness among the masses and the depleting natural resources and oil reservoirs, a replacement for the fossil fuels is urgently required. There are rising global concerns about climate change and energy security. The current biofuel production trends are no doubt promising and increasing steadily. The biofuel markets are getting bigger and better in the European Union, USA, Brazil, India, China and Argentina and contributing to their bio-economies, respectively. In the US, biodiesel production exceeded 1 billion gallons in 2012 and reports claim that the global biofuels market will touch the figure of $185 billion in 2021. However the big question is: will the current biofuel production rate be able to meet the escalating transportation fuel demands?

Simulating the effects of harvest and biofuel production on the forest system carbon balance of the Midwest, USA

AbstractForests of the Midwestern United States are an important source of fiber for the wood and paper products industries. Scientists, land managers, and policy makers are interested in using woody biomass and/or harvest residue for biofuel feedstocks. However, the effects of increased biomass removal for biofuel production on forest production and forest system carbon balance remain uncertain. We modeled the carbon (C) cycle of the forest system by dividing it into two distinct components: (1) biological (net ecosystem production, net primary production, autotrophic and heterotrophic respiration, vegetation, and soil C content) and (2) industrial (harvest operations and transportation, production, use, and disposal of major wood products including biofuel and associated C emissions). We modeled available woody biomass feedstock and whole‐system carbon balance of 220 000 km2 of temperate forests in the Upper Midwest, USA by coupling an ecosystem process model to a collection of greenhouse gas life‐cycle inventory models and simulating seven forest harvest scenarios in the biological ecosystem and three biofuel production scenarios in the industrial system for 50 years. The forest system was a carbon sink (118 g C m−2 yr−1) under current management practices and forest product production rates. However, the system became a C source when harvest area was doubled and biofuel production replaced traditional forest products. Total carbon stores in the vegetation and soil increased by 5–10% under low‐intensity management scenarios and current management, but decreased up to 3% under high‐intensity harvest regimes. Increasing harvest residue removal during harvest had more modest effects on forest system C balance and total biomass removal than increasing the rate of clear‐cut harvests or area harvested. Net forest system C balance was significantly, and negatively correlated (R2 = 0.67) with biomass harvested, illustrating the trade‐offs between increased C uptake by forests and utilization of woody biomass for biofuel feedstock.

Entropy hysteresis and nonequilibrium thermodynamic efficiency of ion conduction in a voltage-gated potassium ion channel

Here we have studied the nonequilibrium thermodynamic response of a voltage-gated Shaker potassium ion channel using a stochastic master equation. For a constant external voltage, the system reaches equilibrium indicated by the vanishing total entropy production rate, whereas for oscillating voltage the current and entropy production rates show dynamic hysteretic behavior. Here we have shown quantitatively that although the hysteresis loop area vanishes in low and high frequency domains of the external voltage, they are thermodynamically distinguishable. In the very low frequency domain, the system remains close to equilibrium, whereas at high frequencies it goes to a nonequilibrium steady state (NESS) associated with a finite value of dissipation function. At NESS, the efficiency of the ion conduction can also be related with the nonlinear dependence of the dissipation function on the power of the external field. Another intriguing aspect is that, at the high frequency limit, the total entropy production rate oscillates at NESS with half of the time period of the external voltage.

Red mud as a carbon sink: Variability, affecting factors and environmental significance

The capacity of red mud to sequester CO2 varied markedly due to differences in bauxite type, processing and disposal methods. Calcium carbonates were the dominant mineral phases responsible for the carbon sequestration in the investigated red mud types. The carbon sequestration capacity of red mud was not fully exploited due to shortages of soluble divalent cations for formation of stable carbonate minerals. Titanate and silicate ions were the two major oxyanions that appeared to strongly compete with carbonate ions for the available soluble Ca. Supply of additional soluble Ca and Mg could be a viable pathway for maximizing carbon sequestration in red mud and simultaneously reducing the causticity of red mud. It is roughly estimated that over 100 million tonnes of CO2 have been unintentionally sequestered in red mud around the world to date through the natural weathering of historically produced red mud. Based on the current production rate of red mud, it is likely that some 6 million tonnes of CO2 will be sequestered annually through atmospheric carbonation. If appropriate technologies are in place for incorporating binding cations into red mud, approximately 6 million tonnes of additional CO2 can be captured and stored in the red mud while the hazardousness of red mud is simultaneously reduced.

Chain elongation of acetate and ethanol in an upflow anaerobic filter for high rate MCFA production

Recently, interest has regained for medium chain fatty acids (MCFAs) as a low cost feedstock for bio-based chemical and fuel production processes. To become cost-effective, the volumetric MCFA production rate by chain elongation should increase to comparable rates of other fermentation processes. We investigate the MCFA production process at a hydraulic retention time of 17h in an upflow anaerobic filter to improve the volumetric MCFA production rate. This approach resulted in a MCFA production with a volumetric production rate of 16.6gl−1d−1, which is more than seven times higher than the current production rate. Moreover the rate is now in the range of other fermentation processes like methane, butanol and ethanol production. Increasing the ethanol load lead to higher volumetric production rates and a high MCFA selectivity of 91%. During operation, methane percentages lower than 0.1% were detected in the headspace of reactor.