In this research, the chemistry of peroxide bleaching effect on rice straw pulp has been thoroughly studied both with lignin model compounds and with degradation of carbohydrates. Rice straw was cooked in by soda-(ethanol, diethylene glycol, dimethyl formamide) and kraft type. After three stage peroxide bleaching of organosolv pulps, some similarity in behavior of brightness and peroxide consumption for each alkali percentage has been observed. Final brightness of 63–70% ISO was attained for all tested pulps. The carbohydrates reaction in peroxide delignification results in a loss of viscosity due to attack by hydroxyl radicals to the carbohydrates chains. The yield loss in chemical pulping due to degradation and dissolution of polysaccharides (particularly hemicellulose) is substantial and constitutes a serious drawback of the process. The high obtained bleached yield for organosolv pulps (in the range of 90–91% o.d.p.) point to limited organosolv carbohydrate degradation during peroxide bleaching.
The viscoelastic behavior of aqueous solutions of Alcoflood polymers (AFPs) was investigated in terms of the complex modulus, storage modulus, and loss modulus using a RheoStress RS100 rheometer. AFP solutions with a wide range of concentrations were examined (100–10,000 ppm). Three different AFPs AF1235, AF1275, and AF1285 were tested. The linear viscoelastic range for these three AFPs over the concentration range of 100–10,000 ppm was around 2 Pa. The polymer concentration controlled the behavior of complex modulus versus frequency. The critical polymer concentration was found 1000 ppm. The apparent complex modulus, for polymer concentrations less than 1000 ppm, changed slightly with the power index around 2. For concentrations higher than 1000 ppm, the apparent complex modulus and power index significantly increased with the polymer concentration up to 10,000 ppm. The behavior of storage modulus of the AFPs was similar to that of complex modulus, whereas the loss modulus was different. At 1000 ppm, the AFPs showed a viscous behavior for frequencies less than 0.15 s–1, and a predominantly elastic behavior for frequency greater than 0.15 s–1. At high concentrations, AF1275 and AF1285 always showed an elastic response, whereas AF1235 showed an elastic response only if the frequency exceeded 0.3 s–1.
Fluidized bed combustors are commonly operating with complex bed materials of feeding solid wastes, sorbent, bottom ash, sinter and particle split. In the present study, the effects of gas velocities to the fluidized (draft tube) and the moving (annulus section) beds and the weight percent of additive (alumina) on the solid circulation rate (Gs), gas bypassing flow rates (QDA, QAD, Qor) and pressure drop across the orifices (ΔPor) of binary bed materials have been determined in a square internally circulating fluidized bed (0.28 m width × 2.6 m height) with an orifice-type square draft tube (0.1 m width × 0.9 m height). The gas bypassing flow rate through an orifice (Qor), Gs and ΔPor increase with increasing weight percent of the additive. The solid circulation rate has been correlated with ΔPor and the opening area ratio based on the orifice theory. Also, ΔPor, QDA, QAD and Qor have been correlated with gas velocities to the fluidized and the moving beds and Archimedes number.
This paper describes a method for fabricating dielectric BaTiO3 (BT) micropatterns. The method used in the present work is a combination of a laser-induced pyrolysis method and a nano-crystalline seeding technique. BT nano-crystalline particles used for the seeding are prepared by hydrolysis of a BT complex alkoxide. A precursor solution of a BT complex alkoxide containing the BT nano-crystalline particles and polyvinylpyrollidone (PVP) is spin-coated on a Pt substrate. Micropatterns with a line width of ca. 1–2 μm are fabricated by irradiating an Ar+ laser beam with a beam waist diameter of 0.74 μm at a laser energy density of 27 MW/cm2 and a scanning speed of 25 μm/s on the spin-coated BT films, and then stripping laser-unirradiated regions on the films with an HCl aqueous solution. The use of BT particles prepared in the presence of PVP with a small molecular weight provides clear micropatterns and high dielectric constant. The dielectric constant and dissipation factor of the micropattern fabricated at 20 vol% BT particles with an average size of 12.9 nm prepared in the presence of PVP with a molecular weight of 10000 attain 78.7 and 0.089, respectively, for a measurement frequency of 100 kHz.
Consolidation experiments were carried out on pre-consolidated cakes of tofu (soybean curd) and okara (soybean curd refuse), which were soft colloids, by using a compression-permeability (C-P) cell. The variations in the average consolidation ratio of the cake over time, which is a measure of the degree of consolidation, were evaluated on the basis of the data of cake thickness versus time. Both the traditional Terzaghi model and the Terzaghi–Voigt model failed to describe consolidation behaviors of tofu gel and okara cake. A new multi-stage creep model consisted of a number of Voigt elements connected in series has been developed in order to elucidate the complicated consolidation behaviors of tofu and okara. It was shown that the consolidation behaviors of tofu and okara were accurately described using the present model. The consolidation of tofu gel, which has a high water-holding ability, was slower than that of okara, and the fraction of creep consolidation, especially ternary consolidation was more pronounced in tofu than in okara. The model calculations accurately described the dependence of consolidation behavior on consolidation pressure and the type and concentration of coagulants. It was found that the adjustable fitting parameters of consolidation appearing in the model formula remained nearly unaffected by the consolidation pressure in the range investigated. The consolidation rate approached a minimum value in the case of the tofu gel with high firmness prepared with a MgCl2 concentration of 0.05 mol/l.
In this study, a Monte Carlo simulation using an aggregate mean free path model is carried out for the aggregate formation of carbon black in the furnace process at different temperatures. A comparison of the results of two dimensional shape analysis of calculated aggregates and transmission electron microscope images of carbon black obtained from the furnace process shows that the aggregate shapes became complicated with an increase in temperature. In the furnace process, three factors (mean thermal velocity, particle number density, and primary particle diameter) vary simultaneously with temperature. Therefore, investigating the effect of each factor on the aggregate shape requires additional simulations while changing the individual factors. The results of two dimensional aggregate shape analysis shows that an increase in mean thermal velocity and particle number density contributes to complicating the aggregate shape and a decrease in primary particle diameter contributes to its simplification. On the other hand, the mean thermal velocity and particle number density are influenced by both the temperature and primary particle diameter; a decrease in primary particle diameter obviously contributes greatly to an increase in these factors and indirectly contributes to complication of the aggregate shape. Therefore, primary particle diameter is the most important factor in controlling the aggregate shape of carbon black in the furnace process.
The behavior of microdischarges and their effects on chemical reaction in a micro-plasma reactor are investigated. A model of the micro-plasma reactor has been constructed to understand the relations of the behavior of microdischarges and chemical reactions. The ozone generation reaction was chosen as a model reaction. The microdischarge properties required for the modeling are acquired by the analyses of microdischarge pictures taken with an ICCD camera, and the electrical characteristics are measured by analyzing Lissajous figures. In the model, we divide the reactor into discharge regions including the effective discharge regions and interval regions, and the non-discharge regions, while considering the appearance and disappearance of microdischarges. To take into account the randomly distributed microdischarges over the reactor, the number of microdischarge columns to meet is also calculated. The properties of microdischarges obtained by experiment are applied to the numerical simulation, and the numerical results agree with experimental ones.
The effects of a catalytically reactive wall on ozone reduction are studied using a micro-DBD plasma reactor, where atmospheric non-thermal plasma is generated by a dielectric barrier discharge (DBD). We introduce a manganese dioxide catalyst on the internal wall of the micro-DBD plasma reactor. To evaluate the effect of the catalyst, three types of the reactors are prepared. The narrower gap length enhanced the catalytic ozone reduction for all of the reactor configurations. We constructed a model covering both plasma and catalytic reaction, and the numerical results conclude that the effects of catalytic reactive wall in the micro-DBD plasma reactor are explained by considering the acceleration of mass transfer from the bulk to the wall.
Hydrocracking is a very important refining process used to upgrade low cost vacuum gas oil (VGO) into precious products like gasoline and diesel. In this present work, the hydrocracking of VGO using a dual functional amorphous catalyst is studied. Hydrocracking is carried out at pilot plant scale under the following reaction conditions: pressure of 156 bar, hydrogen-to-oil ratio of 1780 Nm3/Sm3, LHSV from 0.5 to 2 h–1 and temperatures from 380 to 440°C. The effluent of the reactor based on the most value added products is characterized to dry gas, light naphtha, heavy naphtha, kerosene, diesel and unconverted VGO. Then, a 6-lump discrete lumping approach with a hydrocracking reaction scheme with 15 reactions is developed for the prediction of the yield of hydrocracking products. The pilot tests demonstrated that performing experiments beyond the recommended temperature and LHSV by catalyst vendor not only shows unstable conditions but also changes the hydrocracking behavior of the catalyst. Then, to simulate the behavior of the reactor, two kinds of models, kinetic base model and neuro-fuzzy logic model, were developed to estimate the yields of hydrocracking products and simulate the behavior of the hydrocracking reactor. It is concluded that the fuzzy-logic approach is better than the kinetic base approach in the estimation accuracy, but the kinetic base approach can give information on the reaction path and functionality of the catalyst.
The design of an extraction process is complicated. The key decision here is the selection of extractive solvent, however, is not stand alone. The distillation sequence, which normally follows the extraction unit for solvent recovery and product purification, is entirely influenced by the agent chosen. In many cases, mass throughput of solvents in the extraction unit can be large in order to increase separation performance. This character could raise various concerns in monetary and non-monetary issues such as safety, environment and social aspects. In this work, we propose a structural framework, which facilitates chemical engineers to design extraction processes under sustainable criteria. An activity modeling method, the type-zero method of Integrated DEFinition (IDEF0), is applied for presenting the inter-connected design activities transparently, and for incorporating various sustainability criteria systematically into design. Within the framework, extractive agents and succeeding recovery/purification processes are considered concurrently, which enables rational choices in the entire process. The framework is demonstrated through a case study, where extraction solvents and following separation systems are evaluated under selected sustainability criteria.
In this paper, a simple and efficient design method of multi-loop PI controllers is proposed by extending the Maclaurin series approach to a multi-loop control system. The controller parameter of a multi-loop system is related to that of a SISO non-interacting system with an interaction factor in the simple multiplication form. Based on this relation, analytical tuning rules for a multi-loop PI controller are derived for several representative process models. In order to improve both performance and robustness of the multi-loop control system, the multi-loop Ms criterion is utilized as a performance cost function. The simulation studies confirm the effectiveness of the proposed method.
We provide experimental evidence that spontaneous cracking in silica-poly(vinyl alcohol) aqueous suspensions is significantly suppressed at high Peclet numbers (Pe). The cracking event in drying suspension coating was quantified by measuring numbers of nucleation points per unit area from acquired time-lapse video images. Direct imaging revealed that increases in Pe, i.e. the film shrinkage rate relative to the particle diffusion rate, postponed the secondary crack nucleation and the inter-crack connection to thicker films. The primary nucleation was first suppressed and then enhanced as increasing Pe, resulting in a remarkable morphology transition from ladder-like to distinct star-like cracks.
Various low-value oils, namely, crude palm oil (CPO), crude jatropha oil (CJO), and used frying oil (UFO), were investigated by comparing them as feed oils used in biodiesel (BD) production, with the objective of clarifying the effects of various factors that influence the feed oil characteristics on the required feed pretreatment (FP), operating conditions in transesterification, and the obtained biodiesel yield and purity. First, the low-value oils were characterized in terms of fatty acid compositions and the contents of undesirable impurities. All the feed oils contained mainly C16 and C18 fatty acid chains, and the content of C16 in CPO was higher than the contents of C16 in the other feed oils. The highest contents of impurities, namely, a phospholipid, free fatty acid (FFA), and water were found in CJO. Then, the feed oils were pretreated under various conditions and subsequently transesterified to convert triglycerides to BD in the methyl ester form. The BD productivity and quality could be improved by proper feed pretreatment; deacidification and dehydration were particularly effective. Alkali deacidification is not appropriate for treating CJO since significant oil loss was observed during neutralization of FFA in deacidification. Lastly, the pretreated oils whose impurity contents were sufficiently low were transesterified under varying operating conditions. CPO gave a relatively lower yield but higher purity than the other oils because of the higher C16 content in the feed oil, which had a negative effect on yield but increased the purity in the BD product. For all feed oils, the purity of the obtained BD met the standard for BD purity, and the transesterification yields were improved by carrying out the appropriate FP, as well as adjusting the amounts of alcohol and catalyst in transesterification according to the type of feed oil. The obtained results can be applied to select the appropriate feed oils and maximize BD productivity in the BD production from various low-value oils.
In a NiMH-based Fuel Cell/Battery (FCB) system, the performance of the positive electrode composed of a mixture of α-Ni(OH)2 and MnO2 was compared with that of another electrode composed of a mixture of β-Ni(OH)2 and MnO2. When Al-doped α-Ni(OH)2 was used to replace β-Ni(OH)2 for the active material of the positive electrode, more stable operation of Fuel Cell/Battery (FCB) system was achieved. Cyclic voltammetry (CV) results for the Al-doped α-Ni(OH)2 positive electrode showed that the electron transfer number of α-Ni(OH)2 was 1.5 times larger than that of β-Ni(OH)2, which led to an improved discharge capacity. Furthermore, the plateau voltage in the second working voltage for α-Ni(OH)2/MnO2 was more stable compared to that for β-Ni(OH)2/MnO2 in the fuel cell reaction when the cell was overcharged to an SOC of 300%. In addition, the plateau voltage in the first working voltage was higher than that of β-Ni(OH)2 by 0.2 V, which could be attributed to better contact between the polymer gel electrolyte and the electrode in the case of Al-doped α-Ni(OH)2 due to the negligible volume change of Al-doped α-Ni(OH)2 during the overcharge/discharge.
For the purpose of the development of a new recycling technique of thermosetting silane-crosslinked polyethylene (silane-XLPE) turned into thermoplastic polyethylene, the optimum conditions are determined to decompose crosslinking points consisting of siloxane bonds, while keeping the main chain consisting of carbon-carbon bonds in silane-XLPE using supercritical alcohols. As a result, more than 90% of the siloxane bonds are broken selectively and rapidly without the destruction of the main chain and silane-XLPE is converted to thermoplastic polyethylene using supercritical primary alcohols such as methanol at 320–360°C, 10 MPa in 20 min. On the other hand, in the case of supercritical secondary alcohol such as iso-propanol, around two thirds of the siloxane bonds did not decompose even at the high temperature region above 350°C. This is because it was difficult for bulky secondary alcohol to approach the crosslinking points inside the polymer. The reaction rates are measured for the decomposition of the crosslinking points with supercritical methanol and n-propanol. They are expressed by the first-order as well as the second-order reaction models well, because the alcohol concentration is much higher than that of the crosslinking points and can be considered to be constant during the reaction. Arrhenius plots of the second-order rate constants lay well on straight lines for both alcohols and the activation energies are 21.7 kJ/mol for supercritical methanol and 66.5 kJ/mol for supercritical n-propanol.
In this research, compared with common chemical extractants, the efficacies of extracting extracellular polymeric substances (EPS) from activated sludge using cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) were studied. The results indicated that both CTAB and SDS had good extraction ability, and at the dosage of 0.2 g/g DS (dry solid), the amounts of the extracted EPS were 154.7 mg/g VSS and 77.6 mg/g VSS, respectively. SDS extracted EPS by its solubilization property, while CTAB extracted EPS by the synergistic effect of solubilization property, replacement of metal cation from activated sludge and release of intracellular materials. The dewatering performances of activated sludge conditioned with CTAB and SDS were also investigated. Capillary suction time (CST), water content in sludge cake and bound water were used to evaluate the sludge dewatering behaviours. The results showed that, compared with commercial cationic polyelectrolyte, CPAM, CTAB and SDS could significantly reduce the water content in sludge cake and bound water. However, SDS did not help in improving the filtration performance in the whole dosage range. For CTAB, only when the dosage was above 0.1 g/g DS, the filtration rate increased due to the reaggregation of dispersed sludge flocs. The dewatering performances of activated sludge conditioned with CTAB and SDS were dependent on detaching and dissolving of EPS from activated sludge, which resulted in the changes in sludge floc structure.