The paper presents an experimental investigation on enhanced heat transfer and pressure loss characteristics by using single, double, triple, and quadruple twisted-tape inserts in a round tube having a uniformheat-fluxedwall. The investigation has been conducted in the heat exchanger tube inserted with various twisted-tape numbers for co-and counter-twist arrangements for the turbulent air flow, Reynolds number (Re) from 5300 to 24000. The typical single twisted-tape inserts at two twist ratios, y/w = 4 and 5, are used as the base case, while the other multiple twisted-tape inserts are at y/w = 4 only. The experimental results of heat transfer and pressure drop in terms of Nusselt number (Nu) and friction factor (f), respectively, reveal that Nu increases with the increment of Re and of twisted-tape number. The values of Nu for the inserted tube are in a range of 1.15-2.12 times that for the plain tube while f is 1.9-4.1 times. The thermal enhancement factor of the inserted tube under similar pumping power is evaluated and found to be above unity except for the single and the double co-twisted tapes. The quadruple counter-twisted tape insert provides the maximum thermal performance.

The fabrication of superhydrophobic surfaces and the studies on water flow characteristics therein are of great significance to many industrial areas as well as to science and technology development. Experiments were carried out to investigate slip characteristics of water flowing in circular superhydrophobic microtubes within laminar flow region. The superhydrophobic microtubes of stainless steel were fabricated with chemical etching-fluorination treatment. An experimental setup was designed to measure the pressure drop as function of water flow rate. For comparison, superhydrophilic tubes were also tested. Poiseuille number Po was found to be smaller for the superhydrophobic microtubes than that for superhydrophilic ones. The pressure drop reduction ranges from 8% to 31%. It decreases with increasing Reynolds numberwhen Re <900, owing to the transition from Cassie state to Wenzel state. However, it is almost unchanged with further increasing Re after Re >900. The slip length in superhydrophobic microtubes also exhibits a Reynolds number dependence similarly to the pressure drop reduction. The relation between slip length and Darcy friction factor is theoretically analyzed with consideration of surface roughness effect, which was testified with the experimental results.

Recovery of carbon monoxide from flue gases by selective absorption of carbon monoxide in an imidazolium chlorocuprate(I) ionic liquid is considered in this work as an alternative to the use of molecular volatile solvents such as aromatic hydrocarbons. The present work evaluates the CO mass transfer rates from the gas phase to the ionic liquid solutions in the absence of chemical reaction. To that end, carbon dioxide was employed as an inert model gas and absorption experiments were performed to assess the influence of different process variables in a batch reactor with flat gas-liquid interface. The experimental mass transfer coefficients showed significant variation with temperature, (3.4-10.9)×10^-7 m·s^-1 between 293 and 313 K; stirring speed, (10.2-33.1)×10^-7 m·s^-1 between 100 and 300 r·min^-1; and concentration of copper(I), (6.6-10.2)×10^-7 m·s^-1 between 0.25 and 2mol·L^-1. In addition, themass transfer coefficients were eventually found to followa potential proportionality of the type k_L∝μ^-0.5 and the dimensionless correlation thatmakes the estimation of themass transfer coefficients possible in the studied range of process variables was obtained: Sh=10^-2.64·Re^1.07·Sc^0.75. These results constitute the first step in the kinetic analysis of the reaction between CO and imidazolium chlorocuprate(I) ionic liquid that determines the design of the separation units.

The kinetics of the decomposition of dimethylhexane-1,6-dicarbamate to 1,6-hexamethylene diisocyanate was studied. A consecutive reaction model was established and the reaction orders for the two steps were confirmed to be 1 and 1.3 by the integral test method and the numerical differential method, respectively. The activation energies of the two steps were (56.94±5.90) kJ·mol^-1 and (72.07±3.47) kJ·mol^-1 with the frequency factors exp(12.53±1.42) min^-1 and (14.254±0.84) mol-0.33·L0.33·min^-1, respectively. Based on the kinetic model obtained, the progress of the reaction can be calculated under given conditions.

Computer simulation is a good guide and reference for development and research on petroleum refining processes. Traditionally, pseudo-components are used in the simulation, in which their physical properties are estimated by empirical relations and cannot be associated with actual chemical reactions, as nomolecular structure is available for pseudo-components. This limitation can be overcome if real components are used. In this paper, a real component based method is proposed for the simulation of a diesel hydrotreating process by using the software of Unisim Design. This process includes reaction units and distillation units. The chemical reaction network is established by analyzing the feedstock. The feedstock is characterized by real components, which are obtained based on true boiling point curve. Simulation results are consistent with actual data.

In this paper, by combining a stochastic optimization method with a refrigeration shaft work targeting method, an approach for the synthesis of a heat integrated complex distillation system in a low-temperature process is presented. The synthesis problem is formulated as a mixed-integer nonlinear programming (MINLP) problem, which is solved by simulated annealing algorithm under a random procedure to explore the optimal operating parameters and the distillation sequence structure. The shaft work targeting method is used to evaluate the minimum energy cost of the corresponding separation system during the optimization without any need for a detailed design for the heat exchanger network (HEN) and the refrigeration system (RS). The method presented in the paper can dramatically reduce the scale and complexity of the problem. A case study of ethylene cold-end separation is used to illustrate the application of the approach. Compared with the original industrial scheme, the result is encouraging.

To overcome the large time-delay in measuring the hardness of mixed rubber, rheological parameters were used to predict the hardness. A novel Q-based model updating strategy was proposed as a universal platform to track time-varying properties. Using a few selected support samples to update the model, the strategy could dramatically save the storage cost and overcome the adverse influence of lowsignal-to-noise ratio samples.Moreover, it could be applied to any statistical processmonitoring systemwithout drastic changes to them,which is practical for industrial practices. As examples, the Q-based strategy was integrated with three popular algorithms (partial least squares (PLS), recursive PLS (RPLS), and kernel PLS (KPLS)) to form novel regression ones, QPLS, QRPLS and QKPLS, respectively. The applications for predicting mixed rubber hardness on a large-scale tire plant in east China prove the theoretical considerations.

Physical properties including refractive index, density, viscosity and conductivity for binary mixtures of 1-butyl-3-methyl imidazolium chloride ([BMIM]Cl) and different organic solvents at 298.15 K have been investigated. Excess molar volumes have been calculated and obtained data has been fitted by the Redlich-Kister equation. The density and refractive index were found to increase with increasing concentration of [BMIM]Cl, however, exceptions do exist as in the case of dimethyl sulfoxide (DMSO)/[BMIM]Cl. For DMSO/[BMIM]Cl, the density decreases with increasing concentration. The addition of different organic solvents was able to disrupt the interactions within mixtures, leading to freemobility of ions. The freemobility of ions has been found to enhance conductivity and decrease viscosity to varying extents in allmixtures studied. It has been observed that solubility parameters, dielectric constants and composition of the solvents used play a vital role in determining the resultant properties. The data obtainedwill play an important role in understanding the effect of the addition of organic solvents in ILs to enhance their applicability.

The aimof present study was tomeasure and correlate the solubility of poorly water-soluble flavonoid diosmin in water, ethanol, isopropyl alcohol (IPA), polyethylene glycol-400 (PEG-400) and β-cyclodextrin (β-CD) aqueous solution (0.02 mol·L^-1). The solubility of diosmin was measured using the shake flask method from (298.15 to 333.15) K at atmospheric pressure. The experimental solubilities of diosmin were regressed by the modified Apelblat model with a relative deviation in the range of 0.048% to 5.940%. The correlation coefficients were observed in the range of 0.9957 to 0.9995. The solubility of diosmin was found to be increased with temperature in all sample matrices investigated. The mole fraction solubility of diosmin was found to be higher in β-CD aqueous solution and PEG-400 as compared to water, ethanol and IPA. Based on solubility data of present study, diosmin was considered as practically insoluble in water, insoluble in ethanol & IPA and soluble in PEG-400 and β-CD aqueous solution.

The structure of a room temperature asymmetrical dicationic ionic liquid (ADIL), 1-(pyridinium-1-yl) propane-(1-methylpiperidinium) bi[bis(trifluoromethanesulfonyl)imide] ([PyC₃Pi][NTf₂]₂), was studied by the X-ray diffraction method.Meanwhile, thermal analysis of [PyC₃Pi][NTf₂]₂ was also studied using non-isothermal thermogravimetric analysis (TGA). The title crystal belongs to the triclinic with space group P1 and unit-cell parameters a=0.95217 (8) nm, b=1.05129 (11) nm, c=1.70523 (14) nm, α=89.759 (8)°, β=80.657 (7)°, γ=68.007 (9)°, and F(000) = 792. Thermal stability and thermal decomposition kinetics of the title compound were also investigated using TGA under the atmosphere of highly pure nitrogen. Heating curves at different rates were correlated with kinetic equations Friedman and ASTM (also called iso-conversion method). The values of average activation E (kJ·mol^-1) and pre-exponential constant lgA are 149.58 kJ·mol^-1 and 8.83, respectively, which were obtained by the two methods. The kinetic model function, activation energy and pre-exponential constant of this reaction using the multivariate non-linear-regression method were f(α)=(1-α)(1+4.1870α), 151.04 kJ·mol^-1 and 8.81, respectively, which were basically consistent with iso-conversion methods.

Magnetically modified palygorskite composites were synthesized with γ-Fe₂O₃ dispersing on the external surface of clay mineral. The magnetic clay was characterized with Fourier transform infrared, X-ray diffraction, transmission electron microscopy, and vibrating sample magnetometer. Candida sp. 99-125 lipase was immobilized on magnetic palygorskite composites by physical adsorption with enzyme loading of 41.5mg·g^-1 support and enzyme activity of 2631.6 U·(g support)^-1. The immobilized lipase exhibit better thermal and broader pH stability and excellent reusability compared with free lipase.

Alcaligenes faecalis C16 was found to have the ability to heterotrophically nitrify and aerobically denitrify. In order to further understand its nitrogen removal ability and mechanism, the growth and ammoniumremoval response were investigated at different C/N ratios and ammoniumconcentrations in the medium with citrate and acetate as carbon source separately. Furthermore, experiments of nitrogen sources, production of nitrogen gas and enzyme assay were conducted. Results show that the bacterium converts NH₄⁺-N and produces NH₂OH during the growing phase and nitrite accumulation is its distinct metabolic feature. A. faecalis C16 is able to tolerate not only high ammonium concentration but also high C/N ratio, and the ammonium tolerance is associated with carbon source and C/N ratio. The nitrogen balance under different conditions shows that approximately 28%-45% of the initial ammonium is assimilated into the cells, 44%-60% is denitrified and several percent is converted to nitrification products. A. faecalis C16 cannot utilize hydroxylamine, nitrite or nitrate as the sole nitrogen source for growth. However, nitrate can be used when ammonium is simultaneously present in the medium. A possible pathway for nitrogen removal by C16 is suggested. The preliminary enzyme assay provides more evidence for this nitrogen removal pathway.

A strain capable of phenol degradation, heterotrophic nitrification and aerobic denitrification was isolated from activated sludge of coking-plant waste water ponds under aerobic condition. Based on its morphology, physiology, biochemical analysis and phylogenetic characteristics, the isolate was identified as Diaphorobacter sp. PD-7. Biodegradation tests of phenol showed that the maximum phenol degradation occurred at the late phase of exponential growth stages, with 1400 mg·L^-1 phenol completely degraded within 85 h. Diaphorobacter sp. PD-7 accumulated a vast quantity of phenol hydroxylase in this physiological phase, ensuring that the cells quickly utilize phenol as a sole carbon and energy source. The kinetic behavior of Diaphorobacter sp. PD-7 in batch cultures was investigated over a wide range of initial phenol concentrations (0-1400 mg·L^-1) by using the Haldanemodel, which adequately describes the dynamic behavior of phenol biodegradation by strain Diaphorobacter sp. PD-7. At initial phenol concentration of 1400 mg·L^-1, batch experiments (0.25 L flask) of nitrogen removal under aerobic condition gave almost entirely removal of 120.69 mg·L^-1 ammonium nitrogen within 75 h, while nitrate nitrogen removal reached 91% within 65 h. Moreover, hydroxylamine oxidase, periplasmic nitrate reductase and nitrite reductase were successfully expressed in the isolate.

Alkaline pretreatment is an effective technology to disintegrate sewage sludge, where alkali dosage and sludge concentration are two important factors. pH value or alkali concentration is usually adjusted in order to determine a proper dosage of alkali. Our work has found that this is not a good strategy. A new parameter, the ratio of alkali to sludge (R_a/s), is more sensitive in controlling the alkali dosage. The sludge concentration C_s and retention time t are two other important factors to consider. The validity of these arguments is confirmed with modeling and experiments. The individual effect of R_a/s, C_s and t was studied separately. Then the combined effect of these three factors was evaluated. The sludge disintegration degree of 44.7% was achieved with the optimized factors. Furthermore, an alkaline-microwave combined pretreatment process was carried out under these optimized conditions. A high disintegration degree of 62.3% was achieved while the energy consumption of microwave was much lower than previously reported.

Anaerobic digestion of Chinese cabbage waste was investigated through a pilot-scale two-stage digester at a mesophilic temperature of 37 ℃. In the acidification digester, the main product was acetic acid, with the maximum concentration of 4289 mg·L^-1 on the fourth day, accounting for 50.32% of total volatile fatty acids. The oxidation reduction potential (ORP) and NH₄⁺-N level decreased gradually with hydraulic retention time (HRT) of acidification. In the second digestion phase, the maximum methanogenic bacterial concentration reached 9.6×10¹⁰ ml^-1 at the organic loading rate (OLR) of 3.5-4 kg VS·m^-3, with corresponding HRT of 12-16 days. Accordingly, the optimal biogas production was 0.62 m³·(kg VS)^-1, with methane content of 65%-68%. ORP and NH₄⁺-N levels in the methanizer remained between -500 and -560 mV and 2000-4500 mg·L^-1, respectively. Methanococcus and Methanosarcina served as the main methanogens in the anaerobic digester.

The rubber composites with good thermal conductivity contribute to heat dissipation of tires. Graphite filled natural rubber composites were developed in this study to provide good thermal conductivity. Graphite was coated with polyacrylate polymerized bymonomers including methyl methacrylate, n-butyl acrylate and acrylic acid. The ratios between a filler and acrylate polymerization emulsion and those between monomers were varied. Eight types of surface modification formulas were experimentally investigated. Modification formula can affect coating results and composite properties greatly. The best coating type was achieved by a ratio of 1:1 between methyl methacrylate and n-butyl acrylate. The coating of graphitewas thermally stable in a running tire. Filled with modified graphite, the tire thermal conductivity reached up to 0.517-0.569 W·m^-1·K^-1. In addition, the mechanical performance was improved with increased crosslink density, extended scorch time and short vulcanization time.

The objective of this work is using the online measurementmethod to study the process of precipitation of nickel hydroxide in a single-feed semi-batch stirred reactor with an internal diameter of D = 240 mm. The effects of impeller speed, impeller type, impeller diameter and feed location on the mean particle size d₄₃ and particle size distribution (PSD) were investigated. d₄₃ and PSD were measured online using a Malvern Insitec Liquid Process Sizer every 20 s. It was found that d₄₃ varied between 13 μm and 26 μm under different operating conditions, and it decreased with increasing impeller diameter.When feeding at the off-bottomdistance of D/2 under lower impeller speeds, d₄₃ was significantly smaller than that at D/3. PSDs were slightly influenced by operating conditions.

The rotating packed bed (RPB) with split packing is a novel gas-liquid contactor, which intensifies the mass transfer processes controlled by gas-side resistance. To assess its efficacy, the mass transfer characteristics with adjacent rings in counter-rotation and co-rotation modes in a split packing RPB were studied experimentally. The physical absorption system NH₃-H₂O was used for characterizing the gas volumetric mass transfer coefficient (k_ya_e) and the effective interfacial area (a_e) was determined by chemical absorption in the CO₂-NaOH system. The variation in k_ya_e and a_e with the operating conditions is also investigated. The experimental results indicated that k_ya_e and a_e for counter-rotation of the adjacent packing rings in the split packing RPB were higher than those for co-rotation, and both counter-rotation and co-rotation of the split packing RPB were superior over conventional RPBs under the similar operating conditions.