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One of the major challenges in reusing cooling tower blowdown water (CTBD) utilizing membrane processes is its remaining organic compounds, e.g., humic substances leading to biofouling. Besides, the possible abundance of chloride in CTBD imposes the concern of the formation of chlorinated by-products. To choose a pre-treatment process for the studied CTBD composition, various advanced oxidation processes (AOPs), including electrooxidation (EO), photocatalytic degradation (PCD), heat-activated persulfate oxidation (PS), UVC/vacuum UV (UVC/VUV), and UVC processes, were evaluated and compared based on two main targets: i) highest removal and mineralization of the organics, especially humic substances; and ii) lowest formation of chlorinated by-products including adsorbable organic halides and oxychlorides. All the processes were conducted in the natural condition of the real CTBD, while solution pH was monitored. Based on results of chemical oxygen demand, total organic carbon, dissolved organic carbon, UV254 absorbance, liquid-chromatography–organic carbon detection (LC-OCD), and fluorescence excitation-emission matrices (FEEM), it is concluded that PS leads to complete removal of organic compounds along with the lowest formation of low molecular weight organic acids and organic neutrals. FEEM and LC-OCD data also indicated that EO, PCD, and UVC/VUV processes brought about substantial removal of organic compounds and broke down the humic substances into low molecular weight building blocks and organics. Besides, EO exhibited the highest AOX and oxychlorides formation, while these were limited when using the other AOPs. Summarizing, PS, PCD, and UVC/VUV were efficient processes for the degradation and mineralization of organics without generating significant amounts of chlorinated by-products.

Biochemical means of tea quality evaluation is quite accurate, but it requires very costly instruments and takes a long time to conduct the experiment. Researches show that thearubigin (TR) and theaflavin (TF) are the two most important biochemical compounds present in tea liquor on which liquor characteristics of black CTC tea depends. Consequently, this fact may be the basis of determining tea quality by assessment of TR and TF via electronic tongue (ET) response. This technique is free from subjective factors. In literature, there are only two research works using this technique so more research work is required to address the problem. This chapter proposes a modeling technique of ET response using sparse decomposition technique to estimate TR and TF content in a given tea sample. For each tea sample, sparse model coefficients obtained from the ET response is considered as a characteristic attribute of it. Experimental results using dissimilar regression models show high prediction accuracies which justify the efficacy of the proposed method.

The reuse of cooling tower blowdown (CTBD) in the cooling tower itself requires CTBD deionization and a pre-treatment before deionization to remove organic compounds (OCs) that induce membrane fouling. This study assesses the potential of electrochemical oxidation (EO) with a boron-doped diamond (BDD) and a Ti/RuO2 mixed-metal oxide (MMO) anode for CTBD pre-treatment. Also, the influence of the applied current density (j), initial pH, hydrodynamic conditions, and supporting electrolyte on the process performance was evaluated. Results show that COD and TOC removal were 85 and 51%, respectively, with the BDD-anode; however, they were 50 and 12% with MMO-anode at a j-value of 8.7 mA cm−2 and neutral pH. An increased j-value increased the COD and TOC removal; however, different pHs, hydrodynamic conditions, and the addition of supporting electrolytes had a minor impact on the removal with both anodes. Liquid chromatography-organic carbon detection analysis showed that the OC in CTBD mainly consisted of humic substances (HS). EO with the BDD-anode resulted in 35% HS mineralization, while the rest of the HS were partially oxidized into low molecular weight compounds and building blocks. However, HS mineralization was limited with the MMO-anode. The mineralization and oxidation were accompanied by the formation of organic and inorganic chlorinated species. These species increased the toxicity to Vibrio fischeri 20-fold compared to the initially low-toxic CTBD. Thus, EO with a BDD-anode is a promising pre-treatment technology for the removal of OCs before CTBD deionization, but measures to minimize the chlorinated species formation are required before its application.

A substantial part of the freshwater used in the industry is consumed in cooling towers. Cooling towers discharge saline cooling tower blowdown (CTBD), and the reuse of CTBD in the cooling tower can lower the industrial freshwater footprint. This reuse requires CTBD desalination and a pre-treatment that removes organic chemicals before physico-chemical desalination technologies to be applied efficiently. In the present study, the pre-treatment of CTBD by a combination of electrochemical oxidation (EO) with a boron-doped diamond (BDD) or mixed-metal oxide (MMO) anode and a vertical flow constructed wetland (VFCW) was assessed in both possible configurations. The integrated VFCW-EO systems removed more organic chemicals, such as COD, TOC, and the corrosion inhibitor benzotriazole than the EO-VFCW systems. However, the EO resulted in highly toxic effluent to Vibrio fischeri and the plants in the VFCW. This toxicity was the result of the production of unwanted chlorinated organic compounds and ClO3− and ClO4− by both the BDD- and MMO-anode during EO. These toxic EO by-products were removed substantially in the VFCW during EO-VFCW treatment but did impact the removal efficiency and viability of the VFCW. Moreover, significant water loss was observed in the VFCW due to evapotranspiration. In conclusion, the negative impact of EO effluent on the VFCW and evapotranspiration of the VFCW should be considered during application.

Liquor characteristics of black cut, tear, and curl tea mostly depend on two biochemical components like theaflavin (TF) and thearubigin (TR). Evaluation of tea quality can be done efficiently by estimating the concentration of TF and TR without using biochemical tests as it takes much time, which requires laborious effort for sample preparation, storage, and measurement. Moreover, the required instruments for this test are very costly. In this paper, we have proposed an efficient method of TF and TR prediction in a given tea sample using electronic tongue (ET) signal. Combinations of transformed features, like discrete cosine transform, Stockwell transform (ST), and singular value decomposition, of ET signals are fused to develop regression models to predict the contents of TF, TR, and TR/TF. Three different regression models such as artificial neural network, vector-valued regularized kernel function approximation, and support vector regression are used to evaluate the performance of the proposed method. High prediction accuracy using fusion of features ensures the effectiveness of the proposed method for prediction of TF and TR using ET signals.

We evaluated electrochemical degradation (ECD) and photocatalytic degradation (PCD) technologies for saline water purification, with a focus on rate comparison and formation and degradation of chlorinated aromatic intermediates using the same non-chlorinated parent compound, 4-ethylphenol (4EP). At 15 mA·cm-2, and in the absence of chloride (0.6 mol·L-1 NaNO3 was used as supporting electrolyte), ECD resulted in an apparent zero-order rate of 30 μmol L-1·h-1, whereas rates of ?300 μmol L-1·h-1 and ?3750 μmol L-1·h-1 were computed for low (0.03 mol·L-1) and high (0.6 mol·L-1) NaCl concentration, respectively. For PCD, initial rates of ?330 μmol L-1·h-1 and 205 μmol L-1·h-1 were found for low and high NaCl concentrations, at a photocatalyst (TiO2) concentration of 0.5 g·L-1, and illumination at λmax ≈ 375 nm, with an intensity ?0.32 mW·cm-2. In the chlorine mediated ECD approach, significant quantities of free chlorine (hypochlorite, Cl2) and chlorinated hydrocarbons were formed in solution, while photocatalytic degradation did not show the formation of free chlorine, nor chlorine-containing intermediates, and resulted in better removal of non-purgeable hydrocarbons than ECD. The origin of the minimal formation of free chlorine and chlorinated compounds in photocatalytic degradation is discussed based on photoelectrochemical results and existing literature, and explained by a chloride-mediated surface-charge recombination mechanism.

This article describes the direct hot extrusion process and the typical sequence of operations for producing extruded aluminum shapes from soft and medium-grade aluminum alloys, hard alloys, and aluminum-matrix composites. It discusses key process variables, including extrusion speed and exit temperature, and their effect on product quality. The article also provides information on extrusion presses, press dies, and tooling, and addresses quality issues such as surface defects, blistering, and internal cracking. It concludes with a discussion on the drawing of solid section and aluminum tube.

Microbial electrosynthesis is a useful form of technology for the renewable production of organic commodities from biologically catalyzed reduction of CO2. However, for the technology to become applicable, process selectivity, stability and efficiency need strong improvement. Here we report on the effect of different electrochemical control modes (potentiostatic/galvanostatic) on both the start-up characteristics and steady-state performance of biocathodes using a non-enriched mixed-culture inoculum. Based on our results, it seems that kinetic differences exist between the two dominant functional microbial groups (i.e., homoacetogens and methanogens) and that by applying different current densities, these differences may be exploited to steer product selectivity and reactor performance.

This study focused on the generation of electricity from whey in a bio-fuel cell (BFC). Whey or Milk Serum is the liquid remaining after milk has been curdled and strained. It is a by-product of the manufacture of cheese or casein in Foods and Sweets Company. It was selected as electrolyte in biofuel cell due to containing higher amount of branched-chain amino acids (BCAA's).The pH value of fresh whey was 3.1-3.8. Three categories of whey were used in the experiments included fresh whey, preserved by thermal treatment and preserved with 2% phenol by volume. It was observed that microorganism growth was zero in the sample with 2% phenol and growth rate was medium in the sample preserved by thermal treatment and that was higher in the fresh sample. In this biofuel cell, voltage was increased with the increase of surface area of electrodes. For a single compartment containing 8 unit cells, resultant voltage and current were 2.86V and 450?A and four compartment 32 unit cells in series, the values were 10.90V and 8.05mA respectively. When anode area was increased to reduce polarization, power generation was initially high but the decreasing rate of power was also elevated. Finally, for commercial electrodes, maximum power and minimum internal resistance were recorded. The maximum Current, Voltage and Power for commercial electrodes in a single compartment containing 10 unit cells were 78mA, 3.88V and 0.30264W respectively. DOI: http://dx.doi.org/10.3329/jce.v28i1.18105 Journal of Chemical Engineering, Vol. 28, No. 1, December 2013: 22-26

In this study, a cost effective, simple, environment friendly way of fermentable reducing sugar production from rice straw has been carried out by using naturally grown raw wood rotting enzyme. The rotten bark of three trees was collected as the source of enzyme, called enzyme strain. The yield of reducing sugar from rice straw by enzyme strain at various operating condition was studied. A kinetic model expression has been developed for the enzymatic hydrolysis process based on the Michaelis – Mentens approach. Comparison between the experimental data and theoretical data predicted from the rate model render sound accord with a mean deviation of about 0.679. Strain collected from the Rain tree (Samanea Saman) showed the maximum production of reducing sugar. The absence of light gives 36.36% higher production than that of the presence of light. The optimum pH is found as 5. Strain concentration at 0.0233g/ml shows the maximum sugar production as 0.09854 mg/ml in 10 days. Substrate concentration at .0143mg/ml gives maximum production of 0 .15991 mg/ml in 16 days. From this study the optimum condition was found as 0.157 mg/ml fermentable reducing sugar in 11 days. This study provides an alternative and attractive cost effective source of fermentable sugar which can be further converted to valuable product such as bio-ethanol to meet the worlds increasing energy demand. DOI: http://dx.doi.org/10.3329/jce.v28i1.18108 Journal of Chemical Engineering, Vol. 28, No. 1, December 2013: 32-35

A bacterial isolate Pseudomonas sp. was isolated from the solid waste slump collected from a local duping site of Sylhet district and was efficiently utilized for the removal of dye (Orange 3R) from simulated synthetic waste water in a lab scale Stirred Tank Sequencing Batch Bioreactor (STSBBR) in batch mode. A reactor with 2 L capacity (working volume 0.5 L) equipped with suitable control means and stirring mechanism was operated at room temperature and pH 6.6 ± 1 in fill-react-settling-draw mode with different initial dye concentrations (50, 100, 150, 200 & 300 ppm) where the hydraulic retention time was maintained for 12-72 hours depending on the adaptation of waste water by the bacterial strain. The efficiency of the reactor was analyzed with respect to three strands and found to be negative correlation with the concentration of the dye. Overall color, COD, and BOD in the Stirred tank bioreactor system (STSBBR) were removed by 49.67, 37.45 and 33.89%, respectively with 50 ppm dye concentration and HRT of 24 h. The efficiency of the reactor was found to be in negative correlation with the concentration of the dye. This STSBBR system was found very effective for efficient biological treatment of such dyeing industry waste water by the bacterial strain Pseudomonas sp. DOI: http://dx.doi.org/10.3329/jce.v27i2.17808 Journal of Chemical Engineering, IEB Vol. ChE. 27, No. 2, December 2012: 77-82

As the gradual up-growing trend of industrialization and urbanization leading steady increment of demand of energy; eco-friendly, bio degradable, cost competitive and promising source of energy with high sustainability is toughly needed for the new era of modern world. Hydrolysis of cellulose by cellulase enzymes is a vital candidate for this option. It is a solid-liquid heterogeneous reaction; strongly affected by the non-reaction resistances caused most notably by the crystalline structure; reaction environment parameters as temperature, pH, characteristics of enzyme, cell & substrate loading and hence must have to be defined for specific enzyme-substrate amalgamation. In this present investigation, glucose was produced from rice straw using cellulytic enzyme pseudomonas sp., isolated from municipal solid waste. Glucose yield was found to increase as the rice straw particle size decreased from 0.5 mm to 45 ?m, while the optimal temperature and pH were found within the range of 30°C and 7.0 respectively. The concentration and rate of glucose production was observed to depend on pretreatment of rice straw, substrate concentration and enzyme loading. A kinetic model rate expression has been developed for such a process based on the Michaelis – Mentens and Line weaver–Burk approach. Comparison between the experimental data and those predicted from the rate model indicate good agreement with a mean absolute deviation of about 0.304916. DOI: http://dx.doi.org/10.3329/jce.v27i2.17778 Journal of Chemical Engineering, IEB Vol. ChE. 27, No. 2, December 2012: 20-24

The major focus of this paper is to present experimental data, collected for three gases – nitrogen, helium, and carbon dioxide, at the deteriorated turbulent heat transfer (DTHT) regime in gas up-flow with near uniform heat flux. The data were collected for a range of (1) inlet Reynolds number from 1800 to 42,700, (2) inlet buoyancy number Bo∗ up to 1 × 10−5and (3) inlet acceleration parameter Kv up to 5 × 10−6. Based on the new experimental data, the traditional thresholds for the DTHT regimes are updated, and a new heat transfer regime map is proposed and compared to the existing experimental data.

To compare the stability features of a supercritical water-cooled reactor (SCWR) design with that of a typical boiling water reactor (BWR), a stability analysis model for a typical BWR has been developed in addition to an already-developed model for the SCWR as presented in a companion paper. The homogenous equilibrium two-phase flow model, which is adequate at high pressures, is applied to the BWR stability analysis. The reactor core is simulated by three channels according to the radial power distribution and the inlet orifice coefficients. Similar to the SCWR model, the neutronic kinetic equation is expanded based on A modes (reactivity modes). The model is evaluated based on the Peach Bottom Atomic Power Station stability test data, and the results agree well with the experiment. The SCWR is found to be less sensitive to the coolant density neutronic reactivity coefficient than the typical BWR, since most of the neutronic moderation function is provided by the water rods, where the density variation is either zero (if the water rods are insulated) or small (if the water rods are not insulated). The BWR is found to be less sensitive to changes in power level than the SCWR but has the same sensitivity level to the flow rate as the SCWR. A stability envelope that combines the single-channel and in-phase stability modes is developed. The decay ratios for the SCWR together with those for the typical BWR and the new Economic Simplified Boiling Water Reactor at nominal operational conditions are shown in the map. The stability sensitivity to operating conditions is also shown in the map, by increasing the power to 120% of nominal value and decreasing the flow rate to 80% of nominal value. It is found that the SCWR is more sensitive to the single-channel stability compared to the core-wide in-phase stability for all cases.

Using a three-region supercritical water flow model, the core-wide in-phase stability of the U.S. reference supercritical water-cooled reactor (SCWR) design is investigated. The reactor core is simulated as three channels according to the radial power distribution. A method based on λ modes (reactivity modes) expansion of neutronic kinetic equations is applied. A constant pressure drop boundary condition between the feedwater pump and the turbine control valve is assumed. Cases with and without water rods heating are studied. It is found that the stability of the U.S. reference SCWR design is sensitive to the flow restrictions in the hot fluid or the steam line. As long as the restriction in the steam line is small, the design will be stable. A pressure loss coefficient of 0.25 is assumed for the exit valve on the steam line in this analysis. With this value, the SCWR is stable with a large margin. It is concluded that the presence of water rods heating will reduce the stability margin and increase the flow rate sensitivity while maintaining the power sensitivity level. The decay ratios for the three density wave oscillation modes, i.e., single hot channel, coupled neutronic out-of-phase and in-phase, are compared at steady-state conditions. It is found that the single hot channel oscillation mode is the most limiting one in the absence of the water rods heating, while the in-phase oscillation mode is most limiting in the presence of water rods heating.

Increased reliance on passive emergency cooling using natural circulation of gas at elevated pressure is one of the major goals for the gas-cooled fast reactor (GFR). Since GFR cores have high power density and low thermal inertia, the decay heat removal (DHR) in depressurization accidents is a key challenge. Furthermore, due to its high surface heat flux and low velocities under natural circulation in any post-LOCA scenario, three effects impair the capability of turbulent gas flow to remove heat from the GFR core, namely: (1) acceleration effect, (2) buoyancy effect and (3) property variation. This paper reviews previous work on heat transfer mechanisms and flow characteristics of the deteriorated turbulent heat transfer (DTHT) regime and decomposes governing non-dimensional groups to provide an insight for the GFR DHR system design. It is shown that by applying the developed methodology, the GFR's DHR system has a potential for operating in the DTHT regime and the gas DTHT regime is different from the liquid or super-critical fluid's DTHT regime. A description of an experimental facility designed and built to investigate the DTHT regime is provided together with the initial test results. The initial runs were performed in the forced convection regime to verify facility operation against well-established forced convection correlations. The results of the three runs at Reynolds numbers of 6700, 8000 and 12,800 show good agreement with the Gnielinski correlation for heat transfer, which is considered the best available correlation for forced convection over a wide range of Reynolds and Prandtl numbers. However, even in the forced convection regime, the effect of variation of the fluid properties was found to be significant.

A one-dimensional single-channel thermal-hydraulics model has been developed to investigate possible occurrence of density-wave instability in two U. S. Gen-IV reactors cooled by supercritical fluids, i. e., the Supercritical Water-cooled Reactor (SCWR) and Gas-cooled Fast Reactor (GFR). Water density in the SCWR core changes from 780 kg/m3 , to 90 kg/m3 , whereas the density of supercritical carbon-dioxide in the reference GFR changes from 155 kg/m3 to around 110 kg/m3 . The standard frequency domain approach with a decay ratio of induced velocity amplitude of 0.5 has been used to determine the onset of flow instability. With suitable inlet orificing, the hot channel of SCWR has been found to be stable. Sensitivity studies show that the hot channel decay ratio reaches the critical value of 0.5 when either the reactor power is raised to 118% of full power or the core flow rate is reduced to 86% of nominal flow rate. System pressure has only a moderate effect. Detailed 3-D studies, preferably with neutronic feedback, should be carried out for the SCWR design because of its sensitivity to various important parameters. The GFR reference design has been found to be very stable since the density change in the GFR core is rather small compared to that in the SCWR design.Copyright © 2004 by ASME

A computer code (LOCA-COLA) has been developed at MIT for steady state analysis of convective heat transfer loops. In this work, it is used to investigate an external convection loop for decay heat removal of a post-LOCA GFR. The major finding is that natural circulation cooling of the GFR is feasible under certain circumstances. Both helium and CO2 cooled system components are found to operate in the mixed convection regime, the effects of which are noticeable as heat transfer enhancement or degradation. It is found that CO2 outperforms helium under identical natural circulation conditions. Decay heat removal is found to have a quadratic dependence on pressure in the laminar flow regime and linear dependence in the turbulent flow regime. Other parametric studies have been performed as well. In conclusion, convection cooling loops are a credible means for GFR decay heat removal and LOCA-COLA is an effective tool for steady state analysis of cooling loops.Copyright © 2004 by ASME

Bio-Ethanol is a renewable; eco-friendly energy source can be produced from bio-mass (hemicelluloses). Pteris (fern) is grown very fast and has not major economic importance but it is a reliable source of hemicelluloses can be converted to bio-Ethanol. In the hydrolysis of hemicelluloses the concentration of glucose and the reaction rate was observed with respect to the different parameters, like pH, temperature, substrate diameter, substrate loading. In this study we found optimal parameters, NH4OH treatment as the best treatment among H2SO4, NH4OH, and NaOH treatment. In addition, pH 7, temperature 35 o C, substrate diameter 45 μm-63 μm, and substrate loading 0.25gm in 100 ml working volume was found as optimum operation condition for hydrolysis reaction, which was carried out by pseudomonas sp.,isolated from cow dung. In this experiment sugar concentration was measured with UV spectrophotometer using DNS reagent finding the equilibrium time is 72 hours for hydrolysis process and the maximum sugar concentration of 1.7625 mg/l was achieved. Subsequently we study the fermentation process using yeast to produce Bio-Ethanol from reducing sugar solution obtained from the hydrolysis process on optimum reaction condition and yield the Ethanol concentration 0.333 mg/L, measured with UV spectrophotometer. Furthermore, it was also observed that the activity of yeast was sustain, in the reaction condition (pH=7, temperature= 25 o C), only for 50 hours. In sum, it could be conclude that 0.1332 mg of ethanol can be produce from 1gm of pteris where the conversion of reducing sugar to ethanol is 20% approximately in the optimum reaction condition.

The drastic change of fluid density in the reactor core of a supercritical water-cooled reactor (SCWR) gives rise to a concern about density-wave stability. Using a single-channel thermal-hydraulic...

As the last topic of a series of U.S. reference supercritical water-cooled reactor (SCWR) design stability studies, coupled neutronic-thermal-hydraulic out-of-phase stability is analyzed and compared with that of a typical boiling water reactor (BWR). A modal expansion method based on A modes (reactivity modes) of the neutron kinetic equation is applied, and the first subcritical mode of the neutron dynamics model is coupled with the coolant thermal-hydraulic model. The out-of-phase oscillation of the SCWR is found to be dominated by the reactor thermal hydraulics, whereas the BWR is more sensitive to the coolant density reactivity coefficient because of much stronger neutronic coupling. It is also found that the SCWR stability is sensitive to the details of the core simulation model and the hottest channel dominates the stability. The BWR is less sensitive to the core simulation model since it has much stronger neutronic coupling that is controlled by the whole-core average properties. Power and flow rate sensitivity analysis of the out-of-phase stability was also conducted for both the SCWR and the BWR. The SCWR stability is found to be more sensitive to the operating parameters than the typical BWR. Although the water rod heating can improve the SCWR out-of-phase stability, it cannot significantly improve the sensitivity feature.