An analytical equation of state is developed for molten aluminum in the temperature range 1600–2400 K. The equation is derived from that by Ihm, Song and Mason (Ihm et al., 1991) in conjunction with the corresponding states correlations of Ghatee and Boushehri (1996). The densities predicted at corresponding temperatures and pressures are fairly consistent with the experiment, at most within ±1%.

View full abstract

Most binary vapor–liquid data are reported as P–x–y data sets. Barker’s method, the conventional procedure for extracting the adjustable parameters of an activity coefficient model, utilizes just the P–x data component. An alternative but analogous procedure relies on experimental y–x information and is based on the dimensionless group Ψ = αP₂^*/P₁^*. In this approach data points at the composition limits are more heavily weighed than those in the mid-range. It is found that Ψ = Ψ(x₁) is nearly temperature invariant for non-ideal systems that contain an associating component. This suggests the utility of temperature-independent model parameters and facilitates their estimation.

View full abstract

This work aims to experimentally investigate the slip velocities of well-mixed particles of two sizes with the liquid flow in a vertical column.
Tap water is used for the liquid phase. Sieved glass beads having average diameters of 152, 256, 359, 510, and 915 μm are used for the solid phases by pairing particles of different diameters, where the diameter ratio is less than 3.36. It is observed that the slip velocities of smaller and larger particles increase and decrease, respectively, as compared to those in a single-sized particle system of an identical total solid holdup; further, the changes in the slip velocity of a dominant component are smaller than those of an accessory component, and not only are the sizes of the two particles approximately the same, the slip velocities increasingly vary for every component. It is also observed that the differences in the slip velocities of both components from those in the single-sized particle system increase with an increase in the total solid holdup, and that the slip velocities of both particles assume approximately identical values when the total solid holdup exceeds approximately 0.5.
The slip velocities of the smaller and larger particles in the two-sized particle system are correlated with the total solid holdup, the ratio of the solid holdup of each component, and ratio of the particle diameter by a novel model.
Moreover, we estimate the magnitude of the effects of the drag force, net buoyant forces, and the collision to clarify whether these effects are significant under the current experimental conditions. The results show that the effect of the collision is sufficiently small to be neglected, and that the calculated drag coefficients from our model neglecting the collision effect are in good agreement with that of the experiment.

View full abstract

Carbon molecular sieve (CMS) membranes were prepared from polyimides with sulfonic acid triethylammonium salt (SO₃NH(C₂H₅)₃) and/or hexafluoroisopropylidene (–C(CF₃)₂–) groups by pyrolyzing precursor composite membranes at the temperatures ranging from 773 to 973 K in an N₂ flow for 1 h. The precursor membranes were prepared by coating the polyimides on ceramic porous support tubes. The sulfonic acid salt and the –C(CF₃)₂– group decomposed in the ranges of 573 to 673 K and 723 to 973 K, respectively. The composite CMS membranes prepared here had a defect-free top layer of 1.5 to 5 μm thick. The CMS membrane derived from the polyimide with both the thermally decomposable groups displayed the highest gas permeances. The decomposition of sulfonic acid groups followed by the decomposition of the –C(CF₃)₂– group just before the substantial decomposition of the polyimide backbone seemed to significantly enhance the micropore structure of the resultant pyrolytic layer. Compared to the CMS composite or hollow-fiber membranes reported in the literature, the membranes prepared in this study displayed higher O₂ and CO₂ gas permeances with reasonably high ideal separation factors for O₂/N₂ and CO₂/N₂ separations.

View full abstract

The improvement of Cryptosporidium oocysts removals is an urgent need in drinking water treatment and one of the possible solutions is to use high-performance coagulant such as poly-silicate iron coagulant (PSI) instead of conventional coagulants like poly aluminum chloride (PAC). The efficiency of synthetic Cryptosporidium oocysts (S-Crypto) removal using PSI was evaluated by both jar tests and pilot plant experiments. The residual concentration of S-Crypto could be reduced even though the coagulation was operated under the optimum conditions for turbidity removal. The removal efficiencies of S-Crypto using PSI were up to 42% higher than those using PAC in the pilot plant. The higher performance of PSI is brought about by the presence of ferric species in the coagulant which promotes better sedimentation and not by the higher flocculation performance of the coagulant. In addition, the performance of PSI was independent of temperature, and S-Crypto removal by ferric chloride (FC) was not stable in cold raw water. It was suspected that the bound polymerized silica of PSI increases the stability of coagulation in cold water.

View full abstract

Microfiltration membranes that can be composted after service were developed from biodegradable polyesters, poly(L-lactic acid) (PLLA) and poly(ε-caprolactone) (PCL). The membranes were formed via the thermally induced phase separation method. A 10 wt% PLLA solution in a mixed diluent of 1,4-dioxane and water (87:13 by weight) was prepared in a flat mold and quenched from 52°C (4°C above cloud point temperature) to 0°C. After diluent extraction, the membrane separated yeast cells (6 μm) from their suspensions. A PCL membrane formed by the same method did not reject yeast cells. PCL membranes formed by quenching a 16 wt% PCL solution to 0°C and quenching a 10 wt% PCL solution to –196°C did separate yeast cells from their suspensions. The permeation flux was much higher in the filtration of 1 kg·m^–3 yeast cell suspension with the PLLA and PCL membranes formed by quenching a 10 wt% PLLA or PCL solution to –196°C than in the filtration with the PLLA membrane formed by quenching a 10 wt% PLLA solution to 0°C. The higher flux would be due to the lower resistance of the membranes formed by liquid nitrogen quenching (–196°C) and the mode of depth filtration. Porous biodegradable microfiltration membranes prepared from these polymers have the potential to serve as disposable filters in food and biochemical industries.

View full abstract

Zeolite and activated carbon have been generally used for the adsorption separation process. Zeolite is known as polar adsorbent and activated carbon as non-polar adsorbent. A zeolite/carbon composite adsorbent from the combination of zeolite and activated carbon that consists of hydrophilic and lipophilic fractions was developed and investigated. A surfactant was used as a carbon source, and a functional group of activated carbon is deposited on the surface of zeolite. The effects of the surfactant concentration, carbonization temperature, and carbonization time on adsorption capacity were examined. The optimum condition was found to be a carbonization time of 90 min, a carbonization temperature of 750°C, and a surfactant concentration of 0.07 mol/l. The breakthrough time for H₂S of the developed adsorbent was 20.5 min, 4.5 times higher than that of raw zeolite (4.4 min).

View full abstract

A novel metallic monolith anodic γ-alumina catalyst, prepared through anodization of aluminum, hot water treatment and active metal impregnation, was employed to investigate the selective catalytic reduction of NO under oxygen-rich conditions with propene and diesel fuel as reducing agents.
Using propene as a reducing agent, Pt/Al₂O₃/Al offered the best low-temperature SCR activity (about 573 K), and was resistant to SO₂ poisoning. However, a high undesired selectivity to N₂O and a narrow operating-temperature window were two major disadvantages. At a moderate temperature (about 673 K), Cu-Ce/Al₂O₃/Al showed a favorable de-NO_x activity comparable to Pt/Al₂O₃/Al, a higher N₂ selectivity and a wider operating-temperature window than Pt/Al₂O₃/Al. In particular, adding SO₂ into feedstream dramatically promoted the de-NO_x activity of Cu-Ce/Al₂O₃/Al, and this increase was unchanged with time-on-stream. Among the catalysts tested in this paper, the highest de-NO_x activity was obtained on the alumite support, but at a high temperature (about 773 K). Although the presence of SO₂ strongly inhibited the NO_x reduction of the alumite support, NO_x conversion of 80% could still be maintained in the coexisting SO₂ and H₂O.
When introducing diesel fuel instead of propene as a reducing agent, the over-oxidation of diesel fuel by oxygen remarkably decreased the NO_x reduction of Pt/Al₂O₃/Al and Cu-Ce/Al₂O₃/Al. The alumite support became a promising choice, due to the stable 67% of de-NO_x activity achieved under the same redox conditions. However, the presence of a high concentration of SO₂ substantially depressed the de-NO_x activity of the alumite support. On the contrary, a significant promotional effect of SO₂ on the de-NO_x activity was also observed over Cu-Ce/Al₂O₃/Al, when using diesel fuel as a reducing agent, as observed in the SCR-NO-C₃H₆.

View full abstract

Catalytic total combustion of dichloromethane over anodized aluminum film was studied. Conversion of dichloromethane varies with the acidity of the catalysts, which depends on the hydration reaction on the anodized aluminum films. The effect of the hydration reaction time on the conversion of dichloromethane was discussed. The catalyst with a hydration reaction time of 90 min exhibits the highest activity for the oxidation of dichloromethane, because of the strongest acidity. The distribution of products was also discussed. When the reaction temperature was below 623 K, no molecular chlorine was detected. HCl, CO, CO₂ and CH₃Cl were detected in the reactor outlet. With an increased reaction temperature, molecular chlorine was generated. Catalyst deactivation was also investigated in this work. Compared with γ-Al₂O₃, the anodized aluminum film has excellent hydrophilic properties, thus no deactivation was observed during the deactivation experiment that lasted for 120 h at 673 K with 1000 ppm dichloromethane.

View full abstract

In this paper, a novel sliding mode control scheme is developed for continuous stirred tank reactors (CSTRs) in the simultaneous presence of the non-minimum phase behavior and process uncertainties. To circumvent the negative effect of the inverse response in the control scheme a statically equivalent output map (SEOM) is incorporated. Based on a zero-placement method, an effective algorithm for synthesizing the SEOM is presented. Through the help of the SEOM, a gain-adaptive sliding mode controller is constructed to provide stable and robust closed-loop performance. In addition, the potential use of a sliding observer along with the proposed scheme is investigated in this work. Extensive simulation results reveal that the proposed design methodology is applicable and promising for the regulation of CSTRs in the presence of the non-minimum phase and process uncertainties.

View full abstract

Model parameter identification is essential in the area of modeling of chemical processes. These problems become very difficult to solve due to the fact that the contours are basically multi-optima and even rugged in the solution area. In this work, a novel information guided genetic algorithm is developed to solve these model identification problems. The information theory derived by Shannon is implemented to reduce the mutation steps and hence increase the efficiency of this algorithm. The total number of function evaluations to reach the optimum is drastically reduced, and hence solution of complex problems, such as distillation column model identification is made possible.
Several benchmark problems are solved and compared to well-known global optimization approaches. The parameter identification problems of a linear system and a computation intensive distillation system are solved to show the superiority of this approach. Note that this distillation problem is for the first time solved using parallel processing algorithm in this work. This approach should be interesting for many researchers and industries that implement complex chemical engineering systems.

View full abstract

In order to apply the organic liquid hydrides as hydrogen storage and mobile media, continuous hydrogen production from decalin under mild temperature conditions (210–280°C) was attempted by the use of carbon-supported platinum fine particles as a catalyst. Efficient hydrogen evolution from decalin was achieved under the concept of “superheated liquid-film type catalysis” even at 210°C. Effects of the decalin feed flow rate, amount of catalyst and external heating temperatures on the decalin conversion and the evolution rate of hydrogen were also investigated. The conversion of decalin increased with a decreasing decalin feed flow rate, whereas the evolution rate of hydrogen gave a maximum value at a certain feed flow rate of decalin. It was also found that the ratio of the retention volume of decalin to the catalyst amount is an important factor to maintain the catalyst layer at the superheated liquid-film state.

View full abstract

With the aim of developing a non-equilibrium reactor for proton exchange membrane fuel cell (PEMFC) systems and other applications, hydrogen was produced from ethanol using a non-equilibrium plasma reactor combined with a catalyst, which consisted of an alumite catalyst electrode, at atmospheric pressure in a temperature range of 160–300°C under an AC or a pulsed discharge condition.
It was found that non-equilibrium plasma and a catalyst had a synergistic effect on the ethanol conversion rate under an AC discharge. For example, the ethanol conversion rate obtained with the plasma reactor with the alumite catalyst (Cu-Ni/γ-Al₂O₃) electrode under an AC discharge condition of 3 kV of effective voltage at 2 kHz was 2.4 times as large as the arithmetic sum of the ethanol conversion rate obtained with the plasma reactor with a non-catalytic alumite electrode under the same discharge conditions and the ethanol conversion rate obtained with the alumite catalyst (Cu-Ni/γ-Al₂O₃) electrode without any discharge, at 210°C. It was also observed that non-equilibrium plasma and a catalyst had a synergistic effect on the ethanol conversion rate under a pulsed discharge. For example, the ethanol conversion rate obtained with the plasma reactor with the alumite catalyst (Cu-Ni/γ-Al₂O₃) electrode under a pulsed discharge of 7.2 kV of peak-to-peak voltage at a pulse number of 5000 s^–1 was 1.9 times as large as the arithmetic sum of the ethanol conversion rate obtained with the plasma reactor with the non-catalytic alumite electrode under the same discharge conditions and the ethanol conversion rate obtained with the alumite catalyst (Cu-Ni/γ-Al₂O₃) electrode without any discharge, at 180°C.
The energy efficiency, which was defined as mols of hydrogen produced per unit electric power consumption, obtained with the alumite catalyst (Cu-Ni/γ-Al₂O₃) electrode at 270°C under conditions of an AC discharge of 3 kV of effective voltage at 2 kHz was 2.9 times higher than that obtained with the non-catalytic alumite electrode at 270°C under the same discharge conditions. The energy efficiency obtained with the alumite catalyst (Cu-Ni/γ-Al₂O₃) electrode at 270°C under conditions of a pulsed discharge, pulse number of 5000 s^–1 and peak-to-peak voltage of 7.2 kV was 2.6 times higher than that obtained with the non-catalytic alumite electrode at 270°C under the same discharge conditions. And the energy efficiency obtained with the alumite catalyst (Cu-Ni/γ-Al₂O₃) electrode at 270°C under conditions of a pulsed discharge, pulse number of 5000 s^–1 and peak-to-peak voltage of 7.2 kV was 2.7 times higher than that obtained under conditions of an AC discharge, frequency of 2 kHz and effective voltage of 3 kV.
The energy efficiency and the conversion rate increased greatly because of the collaborative activity of the catalyst and non-equilibrium plasma. These results indicate the potential for developing a non-equilibrium reactor using an alumite catalyst electrode.

View full abstract

The phenomenon of a kelp-dominated community changing to a crust-dominated community, which is called “barren-ground”, is progressing in the world, and causing serious social problems in coastal areas. Among several suggested causes of “barren-ground”, we focused on the lack of Fe in seawater. Kelp needs more than 200 nM of Fe to keep its community. However there are the areas where the concentration of Fe is less than 1 nM, and the lack of Fe leads to the “barren-ground.” Coal ash is one of the appropriate materials to compensate the lack of Fe for the kelp growth, because the coal ash is a waste from the coal combustion process and contains more than 5 wt% of Fe. The rate of Fe elution from coal fly ash to water can be increased by 20 times after melting in Ar atmosphere, because 39 wt% of the Fe(III) of coal fly ash was reduced to Fe(II). Additionally molten ash from the IGCC (integrated coal gasification combined cycle) furnace in a reducing atmosphere and one from a melting furnace pilot plant in an oxidizing atmosphere were examined. Each molten ash was classified into two groups; cooled rapidly with water and cooled slowly without water. The flux of Fe elution from rapidly cooled IGCC molten ash was the highest; 9.4 × 10^–6 g m^–2 d^–1. It was noted that the coal ash melted in a reducing atmosphere could elute Fe effectively, and the dissolution of the molten ash itself controlled the rate of Fe elution in the case of rapidly cooled molten ash.

View full abstract

Laboratory scale submerged membrane activated sludge process (SMASP) units were operated at various sludge retention times (SRTs) (9.6–498 d) and BOD loadings (0.25–1.3 kg/(m³·d)). Under these conditions, the quantity of excess sludge production and the process stability was studied, using synthetic wastewater. The stabilized MLSS was increased with an increase of SRT and BOD loading. The excess sludge production was decreased with an increase of SRT and decrease of BOD loading. The excess sludge production in SMASP at long SRT and low BOD loading was significantly smaller than the conventional activated sludge process. Various test conditions proved that the long SRT and low BOD loading were suitable operational conditions for long stable operation of SMASP.

View full abstract

The present study is concerned with sulfidation treatment of incineration fly ashes containing heavy metals such as lead, zinc and copper with sodium sulfide in order to convert the heavy metals in the fly ashes to heavy metals sulfides. Two types of fly ashes from municipal waste and industrial waste incineration units were employed. The molar ratio of sulfidation agent (Na₂S) to the content of heavy metals in the fly ashes, was varied from 0.15 to 1.5. The sulfidation treatment was conducted by mixing fly ash with Na₂S solution in a plastic container, which was then shaken vertically at amplitude of 5 cm and at a speed of 350 spm for 1–48 h. At the end of the experiment, the slurry was filtered using a 1 μm pore size filter. The concentrations of heavy metals measured in filtrates were used to determine an optimal molar ratio of Na₂S to heavy metals. In addition, the conversion of heavy metals to heavy metal sulfides was calculated based on the consumption of sulfide ions in filtrates using a sulfide ions selective electrode.
As a result, it was found that the concentrations of heavy metals, Pb, Zn, Cu, in the filtrate were lower than 0.1 mg·L^–1, when the fly ash was shaken with Na₂S solution for 3 h at a molar ratio of Na₂S to heavy metals of 0.9. After 48 h, total conversions of all heavy metals in fly ash to metal sulfides determined at a molar ratio of Na₂S to heavy metals of 1.2 were 86.7% and 81.2% for the fly ashes from municipal waste incineration unit and industrial waste incineration unit, respectively.

View full abstract

We applied seaweed to controlling the ammonia-nitrogen content in intensive shrimp aquaculture ponds in developing countries. Sterile Ulva sp. in Kanazawa Bay, Yokohama, Japan, was selected as model algae. The water content in the alga cells was almost the same as the previous result for Ulva lactuca. The rates of ammonia-nitrogen uptake by algae were measured under various conditions including tropical conditions, i.e., higher light flux density and temperature, to know the effects of these conditions. Sterile Ulva sp. could remove ammonia-nitrogen in culture medium effectively. The algae took up ammonia-nitrogen even under no light. Light enhanced assimilation of ammonia-nitrogen in the alga cell. The tropical condition enhanced ammonia-nitrogen uptake by the alga. The ammonia-nitrogen uptake rate decreased with an increasing ammonia-nitrogen content in the alga cell. Based on these experimental results, we studied the mechanism of ammonia-nitrogen uptake by algae in terms of a Michaelis–Menten model with an inhibitory effect. The ammonia-nitrogen uptake obeyed the Michaelis–Menten model with uncompetitive inhibition by the inhibitor working on the complex of ammonia-nitrogen and its carrier, and the ammonia-nitrogen content in an alga cell was positively related to the inhibitory effect on ammonia-nitrogen uptake. Consequently, the uptake by alga was proposed for controlling the ammonia-nitrogen content in shrimp aquaculture ponds in developing countries, and useful information for shrimp pond design was provided.

View full abstract