Water In Column Research Articles

Distribution of Heavy Hydrogen and Oxygen Isotopes in Water Distillation

The possibility of high-precision determination of mass transfer characteristics of stainless steel packings in the separation of hydrogen and oxygen isotopes by vacuum distillation of water in columns with a diameter of 60–250 mm was shown. An algorithm for calculating the parameters of separation and the concentration profile of deuterium and oxygen-18 during their simultaneous separation in a closed type unit with product selection by vacuum distillation of water was presented.

Multi-compartment distribution of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in an urban catchment system

Ecotoxicological risks of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in surface waters are difficult to model because data on PFASs distribution in multiple compartments (sediments, suspended particles and aqueous phase) are difficult to predict. This study quantified the distribution of 21 PFASs including PFCAs: C6-C13 perfluoroalkyl carboxylates, C4, C6, C8 and C10 perfluoroalkane sulfonates, 5 perfluorooctane sulfonamide substances (FOSAMs, including EtFOSA, FOSA, MeFOSAA, EtFOSAA, FOSAA), 2 N-alkyl perfluoroalkane sulfonamidoethanols (MeFOSE and EtFOSE), bis (perfluorooctyl) phosphinic acid (C8/C8 PFPIA), and 5:3 fluorotelomer carboxylic acid (5:3 acid) between bulk water and suspended particles in water column, and pore water and benthic sediments from a tropical urban water body. The distribution of PFASs between sorbed and dissolved phase was largely dependent on the perfluoroalkyl chain length (NCF2). PFCAs with NCF2 > 11 and perfluorodecane sulfonate (PFDS, NCF2 = 10) were found predominantly in the suspended particles and sediments. By contrast, short-chain PFASs (NCF2 ≤ 7) were detected predominantly in the dissolved phase. Sediment acts as a sink for long-chain PFASs while short-chain PFASs are more easily transported via the aqueous phase. Compared with benthic sediments, suspended particles, especially those in the top water layer, carried much higher concentrations of PFASs (by a factor of >100), indicating the stronger sorption capability of suspended particles. The wide variation in PFAS concentrations in suspended particles (∑PFASs concentrations: < 26.8–1,284 ng/g d.w.) suggests that some suspended particles were preloaded with different concentrations of PFASs in the water column which could highly affect the distribution of PFASs in the aquatic environment. Pore water contained 1–2 times higher concentrations of PFASs (∑PFASs: <20.25–159.34 ng/L) than overlying bulk water (∑PFASs: <14.2–79.98 ng/L), indicating the accumulation of PFASs in pore water. Distribution coefficients (KD) were calculated using paired solids concentration and dissolved concentration in both water and sediment column (KD-SP and KD-SED respectively) and were compared with values derived from a laboratory batch experiment. The averaged Log KD-SP/Log KD-SED showed significant positive correlation with NCF2, except for short-chain PFASs (NCF2 <5) which presented higher Log KD values than estimated. The discrepancies found between KD (Log KD-SP > Log KD –desorption > Log KD –sorption > Log KD-SED) suggest that the distribution of PFASs in the field, especially between suspended particles and bulk water could not be well represented by lab results and that using the water concentrations in the bottom layer for estimation of pore water concentrations could lead to bias results.

Root architecture governs plasticity in response to drought

AimsRoot characteristics are important for predicting plant and ecosystem responses to resource scarcity. Simple, categorical traits for roots could be broadly applied to ecosystem function and restoration experiments, but they need to be evaluated for their role and behaviour under various stresses, including water limitation. We hypothesised that more complex root architectures allow more plastic responses to limited water than do tap roots.MethodsWe carried out two greenhouse experiments: one with a range of grassland plant species; the other with only species of Asteraceae to test the responsiveness of root architectural classes to location of limited water in the soil column. Using trait screening techniques and X-ray tomography, we measured the plasticity of the roots in response to water location.ResultsPlasticity of root biomass was lowest in tap rooted species, while fibrous and rhizomatous roots allocated biomass preferentially to where the soil was wettest. X-ray tomography indicated that root morphology was least plastic in rhizomatous species.ConclusionsOur results provide a starting point to effective categorisation of plants in terms of rooting architecture that could aid in understanding drought tolerance of grassland species. They also demonstrate the utility of X-ray tomography in root analyses.

Experimental and theoretical investigation of CO2 and air bubble rising velocity through kerosene and distilled water in bubble column

This paper concerns with developing of parameters which influence terminal velocities of air and CO2 bubbles in distilled water and kerosene pools. The objective of this study is to validate and correct the formulas that were developed by previous investigators for prediction of terminal velocities. The investigation revealed that the terminal velocity of a single rigid spherical bubble in Newtonian fluids can be developed by balancing of mechanical forces acting on the bubble. However, for large bubbles, because of deforming of the bubble which is a result of interfacial tension, the effect of surface tension should be considered in the terminal velocity prediction formula. By using PSO algorithm and plotting experimental data of terminal velocity against the size of gas bubbles, the suitable equation for each of systems was chosen. Results showed that Jamialahmadi model is more practical for terminal velocity prediction. Jamialahmadi model requires a modification to be utilized for air-kerosene, CO2-kerosene, air- distilled water and CO2-distilled water systems. The developed PSO algorithm model is accurate for prediction of experimental data with an average R2 value of 0.9722.

Do Precision Chemical Amendment Applications Impact Sodium Movement in Dryland Semiarid Saline Sodic Soils?

Core Ideas Worldwide, salinity and sodicity problems in the dryland systems are increasing.Standard restoration methods created for irrigated systems may not be appropriate in dryland systems.Bypass water flow that occurs in northern Great Plains saline/sodic soils may impact restoration success.New approach EC/SAR ratio to assess saline and sodic soil behavior. Expanding sodicity and salinity problems have placed many northern Great Plains (NGP) soils at the sustainability tipping point. This study assessed the impact of chemical restoration on water and salt transport in undisturbed soil columns collected from three hillslope model landscape positions. The backslope (Redfield), footslope (White Lake), and toeslope (Pierpont) soils had moderate (3.27 ± 0.59), high (7.3 ± 3.34), and very high (13.29 ± 3.2) sodium adsorption ratio (SARe) values, respectively. The soils were treated with KBr and one of four soil amendments (none, H2SO4, CaSO4, and CaCl2). The rapid movement of Br− through the columns suggested that bypass water flow occurred. In addition, a comparison with widely used salinity models (final EC = 0.8 × initial EC/pore volume [PV]) underestimated the leaching requirements by 69, 79, and 41% in the backslope, footslope, and toeslope soils. In the footslope soils with high SAR values, H2SO4 was more effective at promoting Na+ leaching than gypsum or CaCl2. However, in back slope and toeslope soils with moderate and very high SAR values, the chemical amendments were not, and were equally effective at facilitating Na+ leaching, respectively. These findings suggest that chemical amendments should target treatments to problem areas, and that bypass flow can influence their effectiveness. The LOESS regression model suggested that the electrical conductivity (ECe)/SARe ratio was useful for assessing Na+ risks, and that to maintain a water flow rate of 1 mm h−1 in a soil with a SARe value of 1, an ECe value of ≥2 was required.

Direct radiative impacts of desert dust on atmospheric water content

The direct and indirect radiative impact of naturally produced dust particles influences climate from regional to global scale, introducing one of the largest uncertainties in future climate projections. By absorbing and scattering solar radiation, aerosols reduce the amount of energy reaching the earth's surface, while at the same time they enhance the greenhouse effect by absorbing and emitting longwave radiation (direct dust effect). In this study an attempt is made to quantify the feedback of this energy redistribution in the atmospheric water content in the Arabian Peninsula (one of the main sources of atmospheric mineral dust globally). To this end the SKIRON/dust modeling system was used for 2 years (2014–2015) and two sets of simulations were performed: in the first one the dust particles exert no feedback on the radiative transfer due to dust particles (control run), while in the second set dust interacts with radiation (direct radiative effect). Both simulations have been evaluated in their ability to describe the impacts on surface humidity, with the simulations including the dust feedback showing improved results. These direct feedbacks lead to an increase in the mass of water in the atmospheric column that can reach a maximum daily average of 0.5 g per kg of dry air. Water vapor is the most important greenhouse gas and through this process dust enhances its own greenhouse effect, further increasing the surface temperature and humidity, making life difficult for people living in an already harsh desert climate.© 2018 American Association for Aerosol Research

A Simplified Model for the Retrieval of Precipitable Water Vapor From GPS Signal

In this paper, a simplified latitude and day-of-year (DoY)-based model is proposed for the retrieval of precipitable water vapor (PWV) from global positioning system (GPS) signal. Conventionally, PWV, the total amount of water in a vertical column of a unit cross-sectional area, is estimated from the GPS signal delay and a dimensionless conversion factor PI. This PI value is found to rely on a water vapor weighted mean temperature (T m ) value which varies widely across the day, month, and year for different regions. It is, therefore, both time specific and site specific. Analysis of the PI value and its effect on the retrieved PWV from the data obtained for tropical, subtropical, and temperate regions show that although the PI value is time and site specific, the change in the median value of PI for different years is minimal and is dependent only on factors like the latitude coordinates of the particular site and the DoY. Therefore, using the data obtained from 174 different sites, a latitude-coordinate and DoY-based PI value model for the retrieval of PWV is proposed in this paper. The proposed model has been successfully validated using data from different databases: the International GNSS Service Global Positioning System National Aeronautics and Space Administration (IGS GPS NASA) database, the International GNSS Service Global Positioning System Global Geodetic Observing System (IGS GPS GGOS) database, and the very-long-baseline interferometry (VLBI) database. Results show strong agreement between PWV values calculated using the proposed model and those calculated using the temperature dependent models with 99%, 98%, and 93% of error within ±1 mm for IGS GPS NASA, IGS GPS GGOS, and VLBI databases, respectively. Moreover, the proposed model allows for the ease of PWV retrieval, which is useful in meteorological studies and also applicable in satellite communications.

Fixed-bed adsorption of Tricaine Methanesulfonate onto pyrolysed paper mill sludge

The removal of Tricaine Methanesulfonate from water in a fixed-bed column packed with pyrolysed paper mill sludge was evaluated for application in Recirculating Aquaculture Systems. Breakthrough adsorption curves were determined for this pharmaceutical, under different operating conditions. In a laboratory-scale approach, with synthetic effluent, a bed adsorption capacity of 125mgg−1 was obtained under a flux of 56Lmin−1m−2, with 400mgL−1 of MS-222 with 4.5cm bed depth. The performance of the continuous adsorption in a column packed with biological paper mill sludge-based carbon, using real aquaculture wastewater as matrix, was not significantly affected. Then, scale-up was carried out and the bed depth service time model was applied and provided good predictions. Finally, the thermal regeneration of the exhausted adsorbent was assessed, which revealed satisfactory results for one cycle reusability after saturation; however, considering the nature of its precursor, the use of new adsorbent could be more profitable than its regeneration, functioning also as an additional option for the management of such wastes.

Tracer experiments in periodical heterogeneous model porous medium

It is established that solute transport in homogenous porous media follows a classical ’S’ shape breakthrough curve that can easily be modelled by a convection dispersion equation. In this study, we designed a Model Heterogeneous Porous Medium (MHPM) with a high degree of heterogeneity, in which the breakthrough curve does not follow the classical ’S’ shape. The contrast in porosity is obtained by placing a cylindrical cavity (100% porosity) inside a 40% porosity medium composed with 1mm glass beads. Step tracing experiments are done by injecting salty water in the study column initially containing deionised water, until the outlet concentration stabilises to the input one. Several replicates of the experiment were conducted for n = 1 to 6 MHPM placed in series. The total of 116 experiments gives a high-quality database allowing the assessment of experimental uncertainty. The experimental results show that the breakthrough curve is very different from the ’S’ shape for small values of n, but the more n increases, the more the classical shape is recovered.

Simulation study of direct hydration of cyclohexene to cyclohexanol using isophorone as cosolvent

Cyclohexanol is an important intermediate in the production of adipic acid and ε-caprolactame, and these in turn are used as intermediates for the production of nylons, plasticizers, and pesticides. Traditionally, cyclohexanol is obtained from the oxidation of cyclohexane, however, the process suffer lots of drawbacks including the low selectivity of cyclohexanol, high energy requirement, the explosion risk, and numerous by-products formations. In this paper, a process simulation of reactive distillation using isophorone as cosolvent for the direct hydration of cyclohexene to cyclohexanol was performed. Results showed that the novel process not only got rid of drawbacks owned by the traditional oxidation method, but also improved the conversion and reaction rate of the reactants greatly. Process simulation results also demonstrated that with the increasing Damköhler number (Da), a reactive azeotrope emerged when Da numbers exceeded a critical value of 0.07. Therefore, the reactive distillation could only be practical when Da numbers is below 0.07. During the simulation, the cyclohexene conversion increased with excess water and cosolvent isophorone in the reactive distillation column. Finally, a high-purity cyclohexanol product (99.9mol.%) can be obtained using a decanter and two distillation columns for reactive distillation, with a high cyclohexene conversion of 99.14%, and the isophorone purity well fitted for recycling, and the energy consumption was studied.

Observations of pockmark flow structure in Belfast Bay, Maine, Part 1: current-induced mixing

Field observations of current profiles and temperature, salinity, and density structure were used to examine vertical mixing within two pockmarks in Belfast Bay, Maine. The first is located in 21 m water depth (sea level to rim), nearly circular in shape with a 45 m rim diameter and 12 m rim-to-bottom relief. The second is located in 25 m water depth, more elongated in shape with an approximately 80 m (36 m) major (minor) axis length at the rim, and 17 m relief. Hourly averaged current profiles were acquired from bottom-mounted acoustic Doppler current profilers deployed on the rim and center of each pockmark over successive 42 h periods in July 2011. Conductivity–temperature–depth casts at the rim and center of each pockmark show warmer, fresher water in the upper water column, evidence of both active and fossil thermocline structure 5–8 m above the rim, and well-mixed water below the rim to the bottom. Vertical velocities show up- and down-welling events that extend into the depths of each pockmark. An observed temperature change at both the rim and center occurs coincident with an overturning event below the rim, and suggests active mixing of the water column into the depths of each pockmark. Vertical profiles of horizontal velocities show depth variation at both the center and rim consistent with turbulent logarithmic current boundary layers, and suggest that form drag may possibly be influencing the local flow regime. While resource limitations prevented observation of the current structure and water properties at a control site, the acquired data suggest that active mixing and overturning within the sampled pockmarks occur under typical benign conditions, and that current flows are influenced by upstream bathymetric irregularities induced by distant pockmarks.

Numerical simulation of below ground nitrate dynamics in soil columns subjected to reclaimed water

A mathematical model was developed to simulate nitrate mass transport and transformations in soil during continuous application of reclaimed water in a laboratory scale soil column. The coupled material balance equations for both ammonia nitrogen (NH3-N) and nitrate nitrogen (NO3- -N) within the total soil volume were solved to simulate the NO3—N concentrations with time along the soil depth. The model is one-dimensional and based on the Galerkin technique of the Finite Element Method. It incorporates convection-dispersion processes of NH3-N and NO3--N, nitrification, denitrification and adsorption of ammonium on to soil grains. The adsorption of ammonium was assumed to be represented by the linear form of the Freundlich isotherm. The accuracy and validity of the developed model was examined by comparing simulated data with the experimental data. Optimization of the first order rate constants for nitrification (k1) and denitrification (k2) was conducted by varying both k1 and k2 within a wide range until the simulated NO3--N concentrations fitted properly with the corresponding measured values. Optimum k1 and k2 were found to be 0.188 d-1 and 0.0248 d-1, respectively. A sensitivity analysis of the kinetics of nitrate dynamics showed that the concentration of belowground nitrate is largely affected by the flow velocity (v), D, k1 and k2.

Comparative Effect of Different Coagulants on Physical Properties of Drill Cuttings

The paper presents the study on the physical properties of the cuttings. Culvert capacity of the drill cuttings with different coagulants is considered. The water permeability of the studied samples varies depending on the quality of the composition and the dosage of a coagulant used. The coagulants have been proposed as aluminium sulphate, iron sulphate, calcium chloride, gypsum, phosphogypsum, serpentine, blast furnace slag, calcium carbonate and carnallite. Iron and aluminium sulphates, calcium chloride, gypsum and phosphogypsum appear to be the most effective when acting on the water permeability in the drill cuttings. With regard to the variants incorporating the complete response curve, the optimal dose of ameliorant can be determined after maximum filtration of water in the column. This method allows the dose of coagulant to be determined by the filtration threshold. The optimal dose for iron sulphate is 0.8 g; with this parameter the volume of filtered water reaches 16.80 ml / day.The use of effective coagulants allows displacement of sodium and potassium cations from the absorption complex and fundamentally improves its physical and chemical properties; this is clearly seen by the change of the filtration capacity of the considered sample. Phosphogypsum – a waste material of chemical industry of Ural chemical plants - is of the greatest interest. It can significantly improve the properties of the considered sample when transforming two waste materials (drill cuttings and phosphogypsum) to a neutral environmentally-friendly state.

Kinetics and reactive stripping modelling of hydrogen isotopic exchange of deuterated waters

This work presents results of experimental kinetics and modelling of the isotopic exchange between hydrogen and water in a reactive stripping column for water dedeuteriation. The missing physical properties of deuterium and tritium isotopologues in hydrogen gas and water forms were predicted and validated using existing literature data. The kinetic model relevant to a styrene-divinyl-benzene co-polymer–supported platinum catalyst was used for modelling, by Aspen plus modular package, impact of design parameters including temperature, total pressure, gas to liquid flowrate ratio, pressure drop and flow mixing, on the separation of deuterium and further the separation of tritium. The modelling by the rate-based non-equilibrium, including design correlations of model of mass and heat transfers, chemical kinetic constants, mass transfer coefficients and overall exchange rate constants, allowed access to separation trends in a good agreement with published data. The synergy between the rates of chemical isotopic exchange and gas/liquid mass transfer, and by inference the performance of reactive stripping, was particularly sensitive to high temperatures, low hydrogen flow rates, pressure drops and internals properties. Extension to tritium confirmed a slightly slower mass transport compared with deuterium leading to potentially under-estimated design features for detritiation processing when deuterium is used instead.

Novel plant-wide process design for producing dichlorohydrin by glycerol hydrochlorination

Abstract Dichlorohydrin is an important intermediate for synthesizing epichlorohydrin, a high volume of commodity chemical largely utilized in the production of epoxy resins. In this study, a green process using an atom-efficient and environment-friendly route is used to synthesize dichlorohydrin by reacting glycerol, an available by-product in the biodiesel production, and hydrochloric acid under the homogeneous catalyst of acetic acid. A more accurate kinetic model is firstly established. Two plant-wide processes with continuous stirred-tank reactors and reactive distillation columns are then proposed and analyzed. In these processes, dichlorohydrin is obtained by decanting the overhead product of the reactive distillation column and withdrawing from organic liquid. Furthermore, some amounts of byproduct water in the reactive distillation column is withdrawn from a side stream to increase the reaction conversion. Finally, a novel intensification scheme known as thermally coupled reactive distillation or reactive divided-wall distillation is used to design the dichlorohydrin synthesis process. Simulation results demonstrate that this novel intensified plant-wide process gives much economical benefit for the dichlorohydrin production by glycerol hydrochlorination.

Numerical Simulation of Coupled Water and Salt Transfer in Soil and a Case Study of the Expansion of Subgrade composed by Saline Soil

Salt expansion is one of the major problems of subgrade involving saline soils. Salt expansion is induced by the crystallization of salt when the soil water content or temperature decreases. A case of salt expansion in subgrade composed by saline soil is introduced. It is located in G314 Road, which is one of the national highways in China, from Urumqi to Khunjerab. There is 3.40 ∼5.91% salt within 1.0 depth in the ground surface of the G314 (K587 + 035), which belongs to strong sulphate salty soil. The maximum salt expansion is up to 20cm in G314 Road, which has a serious impact on the road. Salt expansion is majorly controlled by the salt crystallization and the transmission of water and salt. Based on the solute transport theory in porous media, the water flow theory and thermal conduction theory, the govern differential equations of coupled salt crystallization, salt transmission and water flow are established in this paper. The coupled water and salt transfer problem of saline soil is solved by a software named as COMSOL with the use of a secondary development module. To verify the method for simulating the coupled water and salt transmission process, the water and salt transfer process in a 1D soil column is simulated and the results are compared with the theoretical solution. The results show that coupled model of water and salt established in this paper can accurately predict salt migration and crystallization of saline soil.

Thermally Coupled Reactive Distillation System for the Separations of Cyclohexene/Cyclohexane Mixtures

Because of the very close boiling points of cyclohexene and cyclohexane, their separation is extremely difficult with conventional distillation systems and reactive separation with water as reactive entrainer offers great economic incentives. In the current work, the synthesis and design of a flow-sheet with two reactive distillation columns (i.e., the hydration and dehydration reactive distillation columns) in series (FSTRDC) is first conducted subject to the minimization of total annual cost (TAC), and this leads to a process design with an excessive use of water. Although the process design facilitates the hydration of cyclohexene into cyclohexanol, it gives rise to a serious remixing effect in the hydration reactive distillation column and poses an unfavorable effect to the decomposition of cyclohexanol into cyclohexene and water in the dehydration reactive distillation column. For the suppression of these deficiencies, the hydration reactive distillation column was then modified to be heated directly...

Ichthyotoxic Karlodinium veneficum (Ballantine) J Larsen in the Upper Swan River Estuary (Western Australia): Ecological conditions leading to a fish kill

Ichthyotoxic Karlodinium veneficum has become a persistent problem in the eutrophic Swan River Estuary (SRE) near Perth, Western Australia. Karlotoxin (KmTx) concentrations and K. veneficum were sampled from March to July 2005, spanning a bloom confirmed by microscopy and genetics (ITS sequence), and a fish kill coincident with end of the bloom. The objective of this study was to investigate K. veneficum cell and toxin dynamics, and water quality conditions, leading up to the bloom and fish kill in this estuarine system. Abundance of K. veneficum increased as diatom abundance decreased over a 3-month period (Jan–Mar) preceding the bloom. Low freshwater flow to the SRE characterized the bloom initiation period, while elevated seasonal flows altered water quality and preceded the end of the bloom and fish kill. The bloom of K. veneficum was localized over a bottom layer of hypoxic water in a stratified water column. Low nitrate levels, DIN:DIP (mol) near unity, and particulate C:N:P of K. veneficum-rich water samples were consistent with nitrogen limitation of phytoplankton. A KmTx 2 congener was present in the concentration range 0–1052ngKmTxmL−1, levels that were sufficient to kill larval fish in the laboratory within 4h. A KmTx cell quota of 2.8pgKmTxcell−1 was estimated for the bloom, which is moderately high for the species. Gill histopathology of fish from this fish kill showed signs of damage similar to those caused by KmTx in the lab. Results from this study suggest that conditions in the SRE, including elevated K. veneficum abundance and KmTx cell quotas, as well as hypoxia in the upper SRE, likely contribute to seasonal fish kills observed in this system.

Experimental depth dose curves of a 67.5 MeV proton beam for benchmarking and validation of Monte Carlo simulation.

To measure depth dose curves for a 67.5 ± 0.1 MeV proton beam for benchmarking and validation of Monte Carlo simulation. Depth dose curves were measured in 2 beam lines. Protons in the raw beam line traversed a Ta scattering foil, 0.1016 or 0.381 mm thick, a secondary emission monitor comprised of thin Al foils, and a thin Kapton exit window. The beam energy and peak width and the composition and density of material traversed by the beam were known with sufficient accuracy to permit benchmark quality measurements. Diodes for charged particle dosimetry from two different manufacturers were used to scan the depth dose curves with 0.003 mm depth reproducibility in a water tank placed 300 mm from the exit window. Depth in water was determined with an uncertainty of 0.15 mm, including the uncertainty in the water equivalent depth of the sensitive volume of the detector. Parallel-plate chambers were used to verify the accuracy of the shape of the Bragg peak and the peak-to-plateau ratio measured with the diodes. The uncertainty in the measured peak-to-plateau ratio was 4%. Depth dose curves were also measured with a diode for a Bragg curve and treatment beam spread out Bragg peak (SOBP) on the beam line used for eye treatment. The measurements were compared to Monte Carlo simulation done with geant4 using topas. The 80% dose at the distal side of the Bragg peak for the thinner foil was at 37.47 ± 0.11 mm (average of measurement with diodes from two different manufacturers), compared to the simulated value of 37.20 mm. The 80% dose for the thicker foil was at 35.08 ± 0.15 mm, compared to the simulated value of 34.90 mm. The measured peak-to-plateau ratio was within one standard deviation experimental uncertainty of the simulated result for the thinnest foil and two standard deviations for the thickest foil. It was necessary to include the collimation in the simulation, which had a more pronounced effect on the peak-to-plateau ratio for the thicker foil. The treatment beam, being unfocussed, had a broader Bragg peak than the raw beam. A 1.3 ± 0.1 MeV FWHM peak width in the energy distribution was used in the simulation to match the Bragg peak width. An additional 1.3-2.24 mm of water in the water column was required over the nominal values to match the measured depth penetration. The proton Bragg curve measured for the 0.1016 mm thick Ta foil provided the most accurate benchmark, having a low contribution of proton scatter from upstream of the water tank. The accuracy was 0.15% in measured beam energy and 0.3% in measured depth penetration at the Bragg peak. The depth of the distal edge of the Bragg peak in the simulation fell short of measurement, suggesting that the mean ionization potential of water is 2-5 eV higher than the 78 eV used in the stopping power calculation for the simulation. The eye treatment beam line depth dose curves provide validation of Monte Carlo simulation of a Bragg curve and SOBP with 4%/2 mm accuracy.

Design and control of a process to produce furfuryl alcohol

The design and control of a process to produce furfuryl alcohol is reported. Furfural is hydrogenated to furfuryl alcohol in a gas phase packed bed reactor with high selectivity and conversion. The product alcohol is separated from unreacted furfural and byproducts water and 2-methyl furan in a single low-pressure distillation column. Catalyst dilution is employed to increase the area available for heat transfer in the reactor. Control studies indicate that single-point temperature control of the distillation column is adequate to maintain product purity and avoid excessive loss of valuable material from the top of the column. A reactor effluent composition controller cascaded onto a reactor temperature controller can compensate for catalyst deactivation by raising the reactor temperature.