Analysis of the elimination process of polymerisation inhibitors from styrene by means of adsorption

This work is focused on the analysis, modelling and scale‐up of a process of styrene purification. The first step in synthetic rubber production is to eliminate 4‐tert‐butylcatechol (TBC) which is added to styrene to prevent homopolymerisation during transport and storage. This process is carried out on an industrial scale by means of adsorption onto activated alumina. Equilibrium experiments at 10 °C correlated to the Langmuir–Freundlich equation: with a weighted standard deviation of 3.38%. Fixed bed column experiments were carried out on a laboratory scale to obtain breakthrough curves. A mathematical model that considers film and pore mass transfer resistances described satisfactorily the experimental results with a value of D_p = 3.96 × 10^?9 m² s^?1 which was obtained from correlation of experimental data to simulated curves. Finally, a pilot plant was built and operated in order to verify the validity of the mathematical model and parameters obtained previously. © 2002 Society of Chemical Industry     

A mathematical model for computer simulation of the direct continuous esterification process between terephthalic acid and ethylene glycol. Part II: Reaction rate constants

It has been confirmed that the reaction model proposed previously, which can express simultaneously the oligomer properties and the distillate properties under low esterification pressure, is applicable to a continuous direct esterification process in a practical plant. The experimental data of the first esterification reactor (RA-1) was obtained under low reaction pressures (atomospheric or 1 kg/cm²G) with the pilot plant throughput based on poly(ethylene terephthalate) (PET) polymer production of about 50 kg/h. The Arrhenius' parameters, frequency factor, and apparent activation energy, were determined fitting the experimental data of the pilot plant by using the Simplex method as an optimization technique. The activation energy of diethylene glycol (DEG) formation, E₇, is about twice as much as those of the esterifications, E₁, E₂, E₃, and E₄. The activation energies are E₁, = 19640 cal/mol, E₂ = 18140, E₃ = 22310, E₄ = 18380, E₅ = 2810, E₆ = 14960, and E₇ = 42520 cal/mol. Good agreement was obtained between experimental data and calculated predictions for several oligomer and distillate properties. The vapor-liquid equilibrium can be expressed by Raoult's law with little problem of practical use.     

Hydrodynamic behaviour and oxygen transfer rate in a pilot plant fermenter: I. Influence of viscosity

The effects of varying impeller speed, aeration rate and viscosity on mixing time, power consumption and oxygen transfer rate were studied in the pilot plant fermenter. The rheological behaviour of erythromycin fermentation broth was simulated by colloidal starch solutions at apparent viscosities of 0.02–0.20 Pa/s. The volumetric oxygen transfer rate coefficient was determined by the sulphite and static method. The experimental results showed that at low viscosities, up to of 0.02 Pa/s, the suitable range of impeller speed is 250–300 min^?1 at aeration rate 0.6–0.8 VVM from the point of view of power input (2.6–2.8 kW/m³) and sufficient coefficient K_La (160–200 h^?1). At viscosities higher than 0.02 Pa/s (with pseudoplastical character) the suitable range of impeller speed is 300–350 min^?1 at the same aeration rate. Then the power input for mixing is 3.0–3.5 kW/m³ and the coefficient K_La ～ 50 h^?1.     

Hydrodynamic behaviour and oxygen transfer rate in a pilot plant fermenter. I. Influence of viscosity

The effects of varying impeller speed, aeration rate and viscosity on mixing time, power consumption and oxygen transfer rate were studied in the pilot plant fermenter. The rheological behaviour of erythromycin fermentation broth was simulated by colloidal starch solutions at apparent viscosities of 0.02–0.20 Pa/s. The volumetric oxygen transfer rate coefficient was determined by the sulphite and static method. The experimental results showed that at low viscosities, up to of 0.02 Pa/s, the suitable range of impeller speed is 250–300 min^?1 at aeration rate 0.6–0.8 VVM from the point of view of power input (2.6–2.8 kW/m³) and sufficient coefficient K_La (160–200 h^?1). At viscosities higher than 0.02 Pa/s (with pseudoplastical character) the suitable range of impeller speed is 300–350 min^?1 at the same aeration rate. Then the power input for mixing is 3.0–3.5 kW/m³ and the coefficient K_La ～ 50 h^?1.     

Scale‐up of Mini‐Plant Extractors on Energy Dissipation‐Based Population Balances

The new scale‐up concept for extraction columns relies on three identities being kept idem, as is the total specific flow rate, energy dissipation, and mean droplet residence time in a compartment. The droplet population balance‐based model allows maintaining hydrodynamic similarity in different geometries, as is in a mini‐ or a pilot plant. This leads to similar breakage and coalescence probabilities giving comparable droplet size distributions, thus mass transfer area and extraction efficiency. A new breakage frequency term has been developed relying on the energy dissipation rate and is thus independent from geometric constraints. The traditional scale‐up rules are based either on a constant tip velocity (≈ N) or on a constant energy input (≈ N³), whereas here it follows a constant energy dissipation (≈ N²). A step‐by‐step approach to the new procedure proved by case samples is given. Data from literature pilot experiments could be verified by computer simulations, without using adaptable parameters. All parameters in the correlations where derived in a lab‐scale apparatus and the coalescence parameters were obtained in the mini‐plant experiments. Derivation between simulated and experimental pilot data for stage numbers was less than 14 %, operating parameters (rotational speed N, throughput) were underestimated by 4 % leading to a slightly smaller HETS (Height Equivalent of Transfer Stages) value as measured, affecting the column height with less than 1 %.     

Determination of interfacial area in a tapered bubble column

BACKGROUND: Investigations of hold up (ε_g) and interfacial area (a) in cylindrical bubble columns have been reported extensively but reported similar investigations in tapered bubble columns are sparse in the existing literature. Thus the current article reports the experimental determination of ε_g and a using a tapered bubble column. RESULTS: The present system generated ε_g (0.556 to 0.641) in a CO₂? NaOH system 20% higher than in an air–water system (0.466 to 0.534) and values were higher than in existing systems. Also, the values of ε_g in the air–water system were higher than reported for a column with shorter tapered angle. Values of ε_g fitted very well with the well‐known Akita and Yoshida correlation. The observed values of a (235 and 700 m² m^?3) were higher than values obtained (2 to 600 m² m^?3) in existing systems. The energy dissipation was 203 to 335 W m^?3, which was lower than that (100 to 1200 W/m³) in existing systems. A correlation developed to predict the pressure drop in terms of Euler number was statistically highly significant. CONCLUSION: The present research a chieved higher values of hold up and interfacial area, and lower values of energy dissipation per unit volume of dispersion compared with existing systems. Findings of the present study coupled with previous studies indicate that the tapered bubble column developed could find potential application not only in air pollution control but also in gas‐liquid mass transfer operations. Copyright © 2011 Society of Chemical Industry     

Foam breaking — key process in detoxification of kraft mill effluents by foam separation

A study was undertaken to demonstrate on pilot plant scale the performance of a turbine foam breaking system and to develop the design parameters for large scale application. Among various configurations a 3-blade vaned-disc turbine was found to be optimal for foam breaking. Major process variables controlling foam breaking were system design, tip velocity, rotation speed, and foam load. A foam breaking system with only restricted liquid draw-off performed 3 - 16 times better than a conventional flow through system. A 38 cm diameter turbine operating at 1800 τ/min (3600 cm/s tip velocity) collapsed up to 1.2 m³/min (42 ft³/min) of foam. Design equations developed for sizing of foam breakers suggest that a 61 cm (2-ft) diameter 21 kW turbine will collapse 4.7 m³/min of foam. For a 95 × 10³m³/d foam separation plant, approximately 12 foam breakers are required. Capital costs are estimated at $108,000.     

Nitrification by immobilized cells in a micro‐ecological life support system using packed‐bed bioreactors: an engineering study

The nitrifying component of a micro‐ecological life support system alternative (MELISSA) based on microorganisms and higher plants was studied. The MELISSA system consists of an interconnected loop of bioreactors to allow the recycling of the organic wastes generated in a closed environment. Conversion of ammonia into nitrates in such a system was improved by selection of microorganisms, immobilization techniques, reactor type and operation conditions. An axenic mixed culture of Nitrosomonas europaea and Nitrobacter winogradskyi, immobilized by surface attachment on polystyrene beads, was used for nitrification in packed‐bed reactors at both bench and pilot scale. Hydrodynamics, mass transfer and nitrification capacity of the reactors were analysed. Mixing and mass transfer rate were enhanced by recirculation of the liquid phase and aeration flow‐rate, achieving a liquid flow distribution close to a well‐mixed tank and without oxygen limitation for standard operational conditions of the nitrifying unit. Ammonium conversion ranged from 95 to 100% when the oxygen concentration was maintained above 80% of saturation. The maximum surface removal rates were measured as 1.91 gN‐NH₄⁺ m^?2 day^?1 at pilot scale and 1.77 gN‐NH₄⁺ m^?2 day^?1 at bench scale. Successful scale‐up of a packed‐bed bioreactor has been carried out. Good stability and reproducibility were observed for more than 400 days. Copyright © 2004 Society of Chemical Industry     

Effect of scale‐up on wall shear rates in circulating bubble columns

Effective wall shear rates were investigated experimentally in an external loop circulating bubble column made from transparent acrylic resin. The riser (D_R) and downcomer (D_D) diameters were 0.19 m and 0.14 m, respectively. The column working volume (V_R) was 170 dm³, with a scale‐up factor (A_D/A_R) of 0.54, and a dispersion height (H_D) of 2.25 m. Polymer solutions of xanthan gum and carboxymethyl cellulose were used to simulate non‐Newtonian behavior of biological systems. Effective wall shear rates for the non‐Newtonian solutions were found by analogy with Newtonian glycerol solutions, employing downcomer liquid velocity as the measurable and comparable parameter. The experimental shear rate results were found to fit between those of the literature data. A new single correlation taking into account all the relevant data in the literature and the results of this work is proposed. The new correlation is an improvement over the other correlations because it includes two important design constants: scale‐up factor and dispersion height. Copyright © 2005 Society of Chemical Industry     

Supercritical water oxidation of flammable industrial wastewaters: economic perspectives of an industrial plant

BACKGROUND: Supercritical water oxidation (SCWO) is a promising technology that respects the environment, destroys wastes and allows energy recovery. This process has been applied to many model compounds and real wastewaters at laboratory scale. However, SCWO treatments at pilot plant scale of real wastewaters are scarce. The application of this technology to industrial wastewaters has drawbacks such as corrosion, salt deposition and high cost, so industrial scale‐up has been delayed. RESULTS: In a first stage, for safety reasons the feasibility of SCWO applied to flammable industrial wastewaters was evaluated at laboratory scale in an isothermal plug flow reactor with low concentrations (3–10 g COD L^?1), at a constant pressure of 250 bar and at different temperatures in the range 350–500 °C. In a second stage, experiments were conducted with much higher concentrations (20–90 g COD L^?1) in a SCWO reactor at pilot plant scale. Experiments at pilot plant scale demonstrated the possibility of working under autothermal conditions and the results were used to estimate the treatment costs for a SCWO plant with a capacity of 1 m³ h^?1. CONCLUSION: Results demonstrated the technical feasibility of using a SCWO process to treat flammable industrial wastewater at pilot plant scale due to the absence of operational drawbacks related to the flammability of this wastewater, such as plugging, pressurization or preheating problems and uncontrolled reactions (explosion, etc.). The economic feasibility was demonstrated, especially bearing in mind the energy recovery optimization. Copyright © 2011 Society of Chemical Industry     

Bentonite-stabilized CDA/CTA membranes: I. Improved long-term transport properties

Organophilic-modified bentonites of montmorrillonit origin were incorporated into casting solutions of CDA/CTA blend membranes in concentrations up to 2000 ppm. Membrane preparation followed the well-known phase inversion process of Loeb—Sourirajan and Cannon—Saltonstall. Properties of membranes were characterized by short-term and long-term reverse osmosis test runs at conditions of 0.6 mol/l NaCl-solution, 25°C, 80 bar. The comparison of permeate fluxes and salt rejections after 1 hour and 200 hours of operation for the different membrane types yielded the following: Initial performance data were not influenced by filler addition, but flux declines with time were considerably lowered with increasing bentonite incorporation. Maximum permeate fluxes after a test duration of one year (0.308 m³/m²d) and integral product water amounts (107 m³/m²) were obtained by bentonite concentrations of 1000 ppm. As these membranes achieved the highest long-term salt rejections (97.5%), they were installed in an RO pilot plant on board NS Otto Hahn and comparatively investigated with undoped reference membranes. The permeate fluxes and salt rejections of the doped membranes were 0.305 m³/m²d and 94.5% respectively, compared to 0.195 m³/m²d and 92.5% for the undoped membranes.These improved long-term properties were interpreted by means of a double-layer membrane morphology and a flux-time correlation derived from it; the flux stabilization of bentonite-containing CA blend membranes resulted in an enhanced mechanical stability of the porous substructure.     

Minimum spouting velocity of dense particles in shallow spouted beds

Quantitative method is used to experimentally measure the minimum spouting velocity in shallow conical spouted bed. And a new minimum spouting correlation for shallow conical spouted beds is developed. It is based on spherical ZrO₂ particles whose density is as high as 5890 kg/m³ while the other U_ms correlations published so far are mainly based on relatively deep conical beds composed of lower density particles with density around or lower than 3000 kg/m³. The new U_ms correlation can predict U_ms of heavy particles well within the range of the experimental matrix. © 2011 Canadian Society for Chemical Engineering     

Electrolytic removal of ammonia from brine wastewater: scale‐up,operation and pilot‐scale evaluation

Brine wastewater with a high ammonia content from an iodine processing plant (commonly called kansui in Japan) was treated by electrolysis. The system, which can be considered as an indirect electrolytic treatment process, generates chlorine at the anodes and initiates the formation of mixed oxidants like hypochlorous acid. The oxidants then act as agents for ammonia destruction. Laboratory‐scale experiments showed that high ammonia concentrations (as much as 200 mg dm^?3) could be completely removed within a few minutes, and could be considered a good alternative for efficient ammonia removal from saline wastewaters. From laboratory‐scale experiments in the batch and continuous modes, the charge dose was analyzed and used as the operating and scale‐up factor. The value of the charge dose was not severely affected by changes in operating conditions such as electrode spacing and temperature. The charge dose from batch and continuous runs was found to be in the range of 23 C (mg NH₄‐N removed)^?1 to 29 C (mg NH₄‐N removed)^?1. Using the charge dose obtained from laboratory‐scale continuous electrolysis experiments as the scale‐up factor, a pilot‐scale reactor was designed, and the operating conditions were calculated. In the pilot‐scale reactor tests at different flow rates, the effluent ammonia concentrations were reasonably close to the calculated values predicted from the charge dose equation. Copyright © 2004 Society of Chemical Industry     

Biological treatment of a contaminated gaseous emission from a paint and varnish plant—from laboratory studies to pilot‐scale operation

A Vapour‐Phase Bioreactor (VPB), namely a biotrickling filter, was scaled‐up and operated in‐situ for the treatment of gaseous emissions from a paint and varnish industrial plant. A microbial culture able to degrade the target compounds was enriched and a laboratory‐scale VPB was established in order to evaluate the treatment's performance. The VPB presented removal efficiencies higher than 90% when exposed to Organic Loads (OL) of ca 50 g h^?1 m^?3 of reactor. The VPB was exposed to dynamic conditions often found in‐situ (eg night and weekend shutdown periods) and showed a fast capacity to recover, with and without mineral medium recirculation. After a prolonged interruption period (10 months), the VPB was not able to cope with OL of ca 25 g h^?1 m^?3 of reactor and re‐inoculation was required in order to recover the treatment performance. The VPB also showed limited treatment when exposed to higher OL (ca 500 g h^?1 m^?3 of reactor). The VPB was then scaled‐up and a 3 m³ VPB was operated in‐situ, showing removal efficiencies higher than 50% when exposed to an OL of c 5 g h^?1 m^?3 of reactor, thus complying with current legal demands. The addition of a maintenance feed was shown to be a useful tool for VPB pilot‐scale operation when shutdown periods occurred. A factorial design of experiments was carried out, which allowed reduction to one‐tenth of the initial supply of the main mineral medium constituents, namely phosphate buffer, ammonium and magnesium salts, and also elimination of the metal supplement. Overall, the VPBs were shown to be robust equipment, being able to respond actively to dynamic treatment scenarios, particularly night and weekend shutdown periods. Copyright © 2003 Society of Chemical Industry     

Cultivation of spirulina maxima in an annular photochemical reactor

An 8-L annular photochemical reactor has been designed and built for the cultivation of micro- or semi-microalgae at the laboratory scale. It may be operated in batch or continuous mode and is controlled for pH, temperature, gas mixture ratio (CO₂ and air), flow rate, light intensity and also illumination type (daylight or plant growth light) and mode (continuous or intermittent). It behaves as a perfect mixed reactor for all concentrations of algal cells. The reactor was used for the cultivation of the blue-green alga Spirulina maxima in a synthetic medium in both batch and continuous operations. At the dilution rate of 0.24 day^?1, the optimal productivity was 0.91 g/L-day for biomass or 0.55 g/L-day for protein. This is equivalent to 14.5 g/m²-day for biomass or 8.7 g/m²-day for protein. The optimal productivity as well as the chemical composition of the algal biomass were comparable to results obtained from pilot plant studies and reported in the current literature.     

Two-Angle Ratio Scattering (STAR) Method for Real-Time Measurement of Agglomerate Soot Concentration and Size: Experimental Measurements

The Scattering by Two-Angle Ratio (STAR) light scattering method described in this (and companion) article has been developed and tested on a range of gas turbine and diesel engines. Research literature on optical parameters has been used (without resorting to arbitrary calibrations) to predict values of the gas phase soot mass concentration, which are in good agreement with gravimetric measurements. More than 90 measurements for gas turbine and diesel engines are shown for both in situ and sampling configurations of STAR. Results are obtained for transient concentrations ranging from less than 1 μg/m³ to 100 mg/m³ at data rates up to 10 Hz. Absolute concentration comparisons with gravimetric measurements agree with an R ² correlation of 97% and have a precision of better than ±5%. These experimental results are consistent with the assumption that primary particle soot properties are nearly invariant for a wide range of engine operating conditions.     

Excess molar volumes and molar enthalpies in the binary mixtures of {x1CH3CHClCH2Cl+x2CH3(CH2)n?1OH} (n=1 to 4) at T=298.15K

The excess molar volumes V _m ^E and excess molar enthalpies H _m ^E at T=298.15 K and atmospheric pressure for the binary systems {x₁CH₃CHClCH₂Cl+x₂CH₃(CH₂) _n−1OH} (n=1 to 4) have been determined from density measurements by using a digital vibrating-tube densimeter and an isothermal calorimeter with flow-mixing cell, respectively. The 1-alkanols are methanol, ethanol, 1-propanol and 1-butanol. The V _m ^E values of the binary mixtures increase with chain length of the 1-alkanols, resulting in entire negative V _m ^E values for methanol, ‘S-shaped’ for ethanol, being nega- tive at low and positive at high mole fraction of 1,2-dichloropropane, and entire positive V _m ^E values for both 1-propanol and 1- butanol. The H _m ^E values for all systems show an endothermic effect (positive values), which exhibits a regular increase in magnitude when the number of -CH₂- group in 1-alkanols is progressively increased and maximum values of H _m ^E varying from 741 J·mol⁻¹ (methanol) to 1,249 J·mol⁻¹ (1-butanol) around x₁=0.63−0.72. The experimental results of both H _m ^E and V _m ^E were fitted to Redlich-Kister equation to correlate the composition dependence. The experimental H _m ^E data were also used to test the suitability of the Wilson, NRTL, and UNIQUAC models. The correlation of excess enthalpy data in these binary systems using UNIQUAC model provides the most appropriate results except for the system containing methanol.     

Sulfonyl‐Containing Polyimide Dielectrics with Advanced Heat Resistance and Dielectric Properties for High‐Temperature Capacitor Applications

Polymer dielectrics, with advanced dielectric properties and heat resistance, are critical for high‐temperature capacitors in various applications. However, the high performance of heat resistance and dielectric properties are quite difficult to achieve all together due to their mutual implication. Here, by intensively investigating the correlation between molecular structure and properties, polyimide dielectrics with i) enhanced dielectric constant by introducing sulfonyl group, ii) low dissipation factor by introducing flexible linkage, and iii) high T_g (glass transition temperature) by retaining an aromatic structure, are obtained. The sulfonyl‐containing polyimides with different flexible linkages exhibit simultaneously a high dielectric constant (4.50–5.98), low dissipation factor (0.00298–0.00426), and outstanding breakdown strength (most above 500 MV m^?1), as well as superior heat resistance (T_g : 244–304 °C). Specifically, the polyimide (SPI‐1) with sulfonyl group in diamine moiety and para‐para linkage shows stable dielectric properties up to 150 °C, and the discharged energy density and charge–discharge efficiency can be as high as 7.04 J cm^?3 and 91.3% at 500 MV m^?1, respectively.     

Hybrid reverse osmosis — ultrafiltration membranes

A new group of asymmetric non-cellulosic membranes having a performance intermediate between that of a conventional RO membrane and an ultrafilter has been developed. Its main characteristics are high fluxes (4–10 m³/m² day) at low pressures (6–10 at) and moderate rejections for various salts. From 200 mg/l solutions of NaNO₃, Na₂SO₄ and KH₂PO₄ rejections up to 40%, 70% and 90%, respectively, were obtained. The new membranes can withstand large variations in pH (1 to 13) and have excellent chemical and biological stability. The membranes have been tested in a mobile SUF pilot plant operating on oxidation pond effluent. High rejections for BOD, COD, bacteria and suspended solids as well as a 20% reduction in salinity have been obtained.     

A trickling fibrous-bed bioreactor for biofiltration of benzene in air

A novel trickling fibrous-bed bioreactor was developed for biofiltration to remove pollutants present in contaminated air. Air containing benzene as the sole carbon source was effectively treated with a coculture of Pseudomonas putida and Pseudomonas fluorescens immobilized in the trickling biofilter, which was wetted with a liquid medium containing only inorganic mineral salts. When the inlet benzene concentration (C_gi) was 0·37 g m⁻³, the benzene removal efficiency in the biofilter was greater than 90% at an empty bed retention time (EBRT) of 8 min or a superficial air flow rate of 1·8 m³ m⁻² h⁻¹. In general, the removal efficiency decreased but the elimination capacity of the biofilter increased with increasing the inlet benzene concentration and the air (feed) flow rate. It was also found that the removal efficiency decreased but the elimination capacity increased with an increase in the loading capacity, which is equal to the inlet concentration divided by EBRT. The maximum elimination capacity achieved in this study was ∽11·5 g m⁻³ h⁻¹ when the inlet benzene concentration was 1·7 g m⁻³ and the superficial air flow rate was 3·62 m³ m⁻² h⁻¹. A simple mathematical model based on the first-order reaction kinetics was developed to simulate the biofiltration performance. The apparent first order parameter K_l in this model was found to be linearly related to the inlet benzene concentration (K_l=4·64−1·38 C_gi). The model can be used to predict the benzene removal efficiency and elimination capacity of the biofilter for benzene loading capacity up to ∽30 g m⁻³ h⁻¹. Using this model, the maximum elimination capacity for the biofilter was estimated to be 12·3 g m⁻³ h⁻¹, and the critical loading capacity was found to be 14 g m⁻³ h⁻¹. The biofilter had a fast response to process condition changes and was stable for long-term operation; no degeneration or clogging of the biofilter was encountered during the 3-month period studied. The biofilter also had a relatively low pressure drop of 750 Pa m⁻¹ at a high superficial air flow rate of 7·21 m³ m⁻² h⁻¹, indicating a good potential for further scale up for industrial applications. © 1998 Society of Chemical Industry