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Acoustic emission technique in conjunction with multiscale processing method has been utilized to investigate the flow behavior of the dense-phase pneumatic conveying system at high pressure. A clearly defined classification of microscale, mesoscale, and macroscale signals has been put forward with the aid of wavelet transform and V statistics analysis. The detailed signals d1–d4, d5–d7, d8–d10 were recomposed into the microscale, mesoscale, and macroscale signals, respectively, which represent microscale particle-wall interactions, mesoscale interaction between gas phase and solid phase (such as bubbles, plugs, dunes), and macroscale flow-induced pipe vibration. Further analysis shows that as the mass flow rate of pulverized coal increases, the energy fraction (energy of detailed signal divided by the energy of original signal) of microscale signals decreases while that of mesoscale signals increases, which indicates that particles are more likely to move as particle aggregates than individual particles when mass flow rate increases. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2635–2648, 2016

A new graphical tool has been developed for the HEN design of WAHEN. An ΔH-F diagram is proposed to deal with the heat exchange matches. Nonisothermal stream mixing and splitting can be achieved by the transformation of stream composite curve in the ΔH-F diagram. A matching composite curve is proposed for the design of HEN with parallel structure. The structure of HEN can be simplified by adjusting the shape of the matching composite curve. Both small scale and large scale examples are illustrated. Results show that the proposed method is as good as the previous methods for small scale problem, while it gets a better result for large scale problem. © 2015 American Institute of Chemical Engineers AIChE J, 2015

Electrostatics and hydrodynamics in the fluidized bed are mutually affected, and excess accumulation of electrostatic charges has a severe impact on hydrodynamics. However, there is a serious lack of experimental investigation of electrostatic effect on hydrodynamics. This work provides a first insight into the electrostatic effects on bubble behaviors experimentally by injecting a trace of liquid antistatic agents (LAA) into a fluidized bed. Different amounts of LAA (0–50 ppm) were injected to make the electrostatic charges vary in a wide range and the bubble behaviors were investigated simultaneously. Results showed that the charges on particles decreased with increasing amount of LAA, which resulted in larger bubble sizes, stronger fluctuations of dynamic bed height, and less wall sheeting, respectively. The maximum reduction ratio of bubble sizes due to electrostatic effect was 21%. When particles were charged, the bubble sizes were significantly smaller than those estimated from the classical correlation. This discrepancy was attributed to the neglect of electrostatic effect in classical correlation. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1160–1171, 2015

During the last decade, the design methods of hydrogen and water networks have been improved greatly. Since the resulting network structure featuring minimum utility consumption is not unique, other properties such as disturbance resistance have drawn more and more attention. In this article, a novel concept, Mixing Potential, is proposed to improve the disturbance resistance ability of the networks in the design stage. This concept originates from measuring the concentration fluctuation of a single sink, and could be calculated by its graphical and algorithmic definition, respectively. In addition, a sufficient condition for minimizing the Mixing Potential of a single sink has been proved. Based on this sufficient condition, a graphical and its corresponding algorithmic method are proposed to design the hydrogen and water networks with minimum utility consumption. Literature examples illustrate that the disturbance resistance ability of the network can be improved by adjusting the satisfying order of sinks. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3762–3772, 2014

The self-diffusion coefficients of C6–C16 long-chain α-olefins and their mixtures in semi-crystalline polyethylene were measured through the pulsed field gradient nuclear magnetic resonance (PFG-NMR). The effects of chain length, polyethylene (PE) type, and co-monomer type in PE on the diffusion coefficients were investigated. Moreover, the influence of halohydrocarbon, cycloalkanes, and arene solvents on the diffusion coefficients of C12 α-olefin in PE was characterized. The results have demonstrated that the diffusion coefficient of the single-component α-olefin in PE decreases exponentially with the increase of the carbon number of α-olefin, and the crystallinity and crystal morphology of PE play a more important role than the co-monomer type in determining the diffusion coefficients of α-olefins. In addition, the apparent diffusion coefficients were used to represent the diffusion behaviors of the α-olefin mixtures in PE. Owing to the presence of other hydrocarbon solvents, namely trichloromethane, cyclohexane, and benzene, the diffusion coefficients of C12 long-chain α-olefin in PE are significantly enhanced, and such promoting effect of the hydrocarbon solvents in polyolefin elastomer (POE) is much stronger than those in high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44143.

The isothermal and nonisothermal crystallization behavior of high density polyethylene (HDPE) containing various zero, one, and two dimensional (0-D, 1-D, and 2-D) carbon nanofillers were investigated by means of differential scanning calorimetry. For a given temperature, the isothermal crystallization incubation time of HDPE became longer with the addition of lower dimensional carbon nanofillers, and the isothermal crystallization rate got slower. The values of Avrami and Tobin exponents indicated that the isothermal crystallization of HDPE followed two-dimensional crystal growth in the presence of 2-D and 1-D carbon nanofillers, while exhibited three-dimensional heterogeneous crystal growth in the presence of 0-D carbon nanofillers. Contrary to the isothermal study, the nonisothermal crystallization of HDPE was accelerated in the presence of lower dimensional nanofillers. The nonisothermal crystallization data were finally analyzed using Ozawa and Mo methods. It was observed that only Mo approach could successfully describe the nonisothermal crystallization process of HDPE and HDPE/carbon nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

This article presents an approach to designing a large-scale water system, which integrates water-using operations and wastewater treatment units in different production sections within the same network. This approach uses a mixed-integer nonlinear programming (MINLP) model for water reuse and regeneration reuse in batch and semicontinuous processes. The application of this mathematical formulation to large-scale industrial problems with changing daily production schedule leads to huge and complex mathematical models. Two alternative multilevel strategies are proposed to solve such problems by means of temporal decomposition. The approach is illustrated with a brewery case study that integrates water consumers in two production sections. The results obtained show that, despite the high piping cost, integration of both sections yields better result than the separate water network design in each section. © 2011 American Institute of Chemical Engineers (AIChE).

The thermo-oxidative degradation behavior of high-density polyethylene (HDPE) was investigated during oven aging at 100°C. 1H low-field solid-state nuclear magnetic resonance (NMR) was used to characterize the behaviors of molecular chains and the changes in phase content of HDPE during aging. NMR free induction decays (FIDs) were fitted by three components corresponding to the crystalline phase, interphase, and amorphous phase, respectively. The prolongation of aging led to a progressive increase in the crystalline phase at the expense of the other two phases. A slight decrease in chain mobility of the crystalline phase and interphase was observed simultaneously. The results obtained from other traditional technical approaches are also discussed in the context of the molecular dynamics properties revealed by NMR. The reduction in molecular weight, in chain mobility and the increase in crystallinity during thermo-oxidation were the main factors, which caused the loss of mechanical performance of HDPE. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Reactor blends of ultrahigh-molecular-weight polyethylene (UHMWPE) and low-molecular-weight polyethylene (LMWPE) were synthesized by two-step polymerization using a hybrid catalyst. To prepare the hybrid catalyst, styrene acrylic copolymer (PSA) was first coated onto SiO2/MgCl2-supported TiCl3; then, (n-BuCp)2ZrCl2 was immobilized onto the exterior PSA. UHMWPE was produced in the first polymerization stage with the presence of 1-hexene and modified methylaluminoxane (MMAO), and the LMWPE was prepared with the presence of hydrogen and triethylaluminium in the second polymerization stage. The activity of the hybrid catalyst was considerable (6.5 × 106 g PE (mol Zr)−1 h−1), and was maintained for longer than 8 h during the two-step polymerization. The barrier property of PSA to the co-catalyst was verified using ethylene polymerization experiments. The appearance of a lag phase in the kinetic curve during the first-stage polymerization implied that the exterior catalyst ((n-BuCp)2ZrCl2) could be activated prior to the interior catalyst (M-1). Furthermore, the melting temperature, crystallinity, degree of branching, molecular weight and molecular-weight distribution of polyethylene obtained at various polymerization times showed that the M-1 catalyst began to be activated by MMAO after 40 min of the reaction. The activation of M-1 catalyst led to a decrease in the molecular weight of UHMWPE. Finally, the thermal behaviors of polyethylene blends were investigated using differential scanning calorimetry. Copyright © 2011 Society of Chemical Industry

Blends of linear polyethylene (LPE) and branched polyethylene (BPE) display very good mechanic properties that can be beneficial for various applications such as shear thinning and melt elasticity. LPE, BPE and amorphous polyethylene can be produced using nickel diimine (DMN) catalyst under various polymerization conditions, while LPE can be obtained using metallocene catalyst. Thus, LPE/BPE blends can be achieved by in situ polymerization using a hybrid DMN/metallocene catalyst. A novel hybrid catalyst made of DMN and Cp2TiCl2 was designed and used for ethylene polymerization. A synergistic effect of the two active sites in the hybrid DMN/metallocene catalyst was observed. Blends of linear and low branched polyethylene were synthesized when polymerization was conducted at low temperature (0 °C), while blends of linear and highly branched polyethylene were obtained at high temperature (50 °C). However, the miscibility of the polymers obtained at 50 °C was dramatically reduced as compared to those obtained at 0 °C. Mesoporous particles (MCM-41) consisting of aluminosilicate with cylindrical pores were used to support the hybrid catalyst, in which MCM-41 provides sufficient nanoscale pores to facilitate the polymerization in well-controlled confined spaces. Blends of LPE and BPE were synthesized by in situ polymerization without adding comonomer and characterized. The miscibility of the polymer blends can be improved by supporting the hybrid catalyst on MCM-41. Copyright © 2009 Society of Chemical Industry

In industrial propylene polymerization technology of Innovene and Chisso, agglomeration of polymer particles in horizontal stirred bed reactors (HSBR) has significant negative impacts on the reactor efficiency. If the hydrodynamic change could be detected early enough, then large chunks may not be formed nor cause an unscheduled shutdown of the plant. A novel non-invasive acoustic emission (AE) technique combined with an attractor comparison method is presented. It is based on the comparison of the time series of AE signals acquired from a normal state with the time series measured during operation of the bed. The nature of the method is to determine whether or not two time series are generated by the same mechanism. A statistical characteristic S is used to test the null hypothesis that the two multidimensional probability distributions are identical. Experiments were carried out at room temperature in a 475 mm i.d. laboratory HSBR. The results demonstrated that the method is sensitive to small changes in the particle size distribution. It is, therefore, indicated that the proposed method not only can offer “early and accurate warning,” but also has the potential to locate the agglomeration in HSBR with multiple AE sensors. © 2009 American Institute of Chemical Engineers AIChE J, 2009

This investigation was performed to study the underlying structure characteristics of acoustic emission (AE) signals, which could be helpful not only to understand a relatively complete picture of hydrodynamics in multiphase flow systems, but also to extract the most useful information from the original signals with respect to a particular measurement requirement. However, due to AE signals are made up of emission from many acoustic sources at different scales, the resolution of AE signals is often very complicated and appears to be relatively poorly researched. In this study, the structure characteristics of AE signals measured both in gas–solid fluidized bed and liquid–solid stirred tank were researched in detail by resorting to wavelet transform and rescaled range analysis. A general criterion was proposed to resolve AE signals into three physical-related characteristic scales, i.e., microscale, mesoscale, and macroscale. Multiscale resolution of AE signals implied that AE signals in microscale represented totally the dynamics of solid phase and could be applied to measure particle-related properties. Furthermore, based on the structure characteristics of AE signals, useful features related to particles motion were extracted to establish two new prediction models, one for on-line measurements of particle size distribution (PSD) and average particle size in gas–solid fluidized bed and the other for on-line measurement of the suspension height in liquid–solid stirred tank. The prediction results indicated that (1) measurements of PSD and average particle size using AE method showed a fairly good agreement with that using sieve method both for laboratory scale and plant scale fluidized beds, and (2) measurements of the suspension height using AE method showed a fairly good agreement with that using visual method. The results thus validated that the extracted features based on analyses of structure characteristics of AE signals were very useful for establishing effective on-line measurement models with respect to some particular applications. © 2009 American Institute of Chemical Engineers AIChE J, 2009

A series of iron and cobalt complexes ligated with different bis(imino)pyridyl ligands were synthesized and used in ethylene polymerization. The reaction temperature and Al/Fe ratio had a great influence on the activities and properties of the polymer in the iron system when methylaluminoxane was used as the cocatalyst. Bimodal polyethylene, unimodal polyethylene, and oligomers were achieved with ethylene polymerization according to the structures of the ligands and polymerization conditions. The cobalt systems showed low activities when bis(imino)pyridyl was used as the ligand in comparison with the iron system catalysts. Ethylene oligomerization was conducted, and the main products were 1-butylene and 1-hexene. A fast deactivation process was observed from the curve of the polymerization kinetics. The polymerization mechanism was examined. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The wideline proton NMR spectra of polyethylene powder samples were analyzed in terms of contributions from three components:(1) a rigid part with immobile chains, (2) a soft region with liquid-like character which produces a Lorentzian contribution to the spectrum, and (3) an intermediateregion in which the rotation of methylene groups about C–C bonds is partially hindered. The relative mass fractions as well as chain mobilities varied greatly among samples produced by different polymerization techniques. The NMR crystallinity agreed well with that estimated by WAXD and was much higher than DSC crystallinity, indicating an inclusion of the contribution from a crystalline-amorphous interphase. The crystalline defects in the rigid part could be significantly affected by processing parameters when employing the same type of polymerization technique. The intermediate region in the NMR spectra was analyzed according to the comparison between bimodal high density polyethylene and corresponding linear unimodal one. It was found that the mass fraction of the NMR interphase could be an indication of the percentage of tie molecules between crystalline lamellae and thus may significantly affect the mechanical properties of polymeric material.

The coabsorptions of ethylene and iso-pentane, and ethylene and n-hexane were measured by the use of a pressure decay method. The solubility data of ethylene-iso-pentane and ethylene-n-hexane in semicrystalline polyethylene (PE) of crystallinity of 48.6% were obtained at temperatures 70, 80, and 90 °C, and the total pressure 2 MPa, iso-pentane partial pressure 80–190 KPa, n-hexane partial pressure 20–90 KPa. The presence of iso-pentane or n-hexane in the corresponding ternary system leads to increase the solubility of ethylene, while the solubility of iso-pentane or n-hexane remains unchanged with an increase of the ethylene partial pressure, even slightly decreases. Assumed that the presence of iso-pentane or n-hexane decreases the crystallinity of the polymer sample, a coabsorption model was built to model the solubility of each gas in the ternary systems. The relative root mean square errors of the coabsorption model for ethylene-iso-pentane-PE system and ethylene-n-hexane-PE system are 5.13% and 4.64%, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3654–3662, 2007

A portable, low-field nuclear magnetic resonance scanner, the nuclear magnetic resonance mobile universal surface explorer, is introduced as a tool for investigating the extraction process of mineral oil in the gel-spinning technology of ultrahigh-molecular-weight polyethylene (UHMWPE) fibers. Factors affecting the extraction process were studied systematically; these included the UHMWPE type, extraction agent type, and concentration and ultrasound. We found that the extraction process could be described by a replacement–dilution dual-effect model. The extraction agent not only replaced and extracted the mineral oil but also considerably decreased the viscosity of mineral oil and thus enhanced the molecular motion and diffusion of mineral oil. Although chloroform had a smaller molecular size and lower boiling point, benzene and cyclohexane were found to exhibit more efficient extraction and dilution effects on mineral oil. The extraction efficiency could be characterized by the diffusion of mineral oil in the mineral oil/UHMWPE gel/deuterated extraction agent multicomponent systems during the extraction. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42018.

An absorption model of gases in semicrystalline polymer was built that was based on the activity coefficient theory in polymer solution and associated with crystallinity dependent on temperature. The solubility of ethylene, isopentane, and n-hexane in three types of polyethylene (PE) were obtained by the use of a pressure-decay method at temperatures of 333–363 K and pressures of up to 2 MPa, 80–300 KPa, and 19–100 KPa, respectively. Experimental data from three gases in each PE sample were used for the single-parameter fitting, and fitting error was within about 12%. It was found that a single parameter was merely dependent on the properties of PE used. It was shown that, unlike with the Flory–Huggins model and the UNIFAC–M-H method, correlation between the crystallinity of the semicrystalline polymer and temperature had to be taken into account in order for the solubility data of alkane, olefin, and aromatic hydrocarbons in polyethylene to fit well, especially in the temperature range near the melting point of the polymer. The four free-energy contributions to the total gas activity were experimentally determined to be about 47%–60% combined, the free-volume contribution about 12%–25%, and the elastic effect about 22%–35%, but the interactional contribution was zero. The contributions changed with the size of the gas molecules. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1737–1744, 2007

Fractal theory and methodology were used to investigate the morphology of titanium–magnesium-supported polyethylene catalysts and their relevant polymer particles. Through an analysis of the submicrostructures using scanning electron microscopy images, the surface fractal dimensions of the related particles were estimated with the box-counting method. With consideration given to the fact that the growth process of a polymer is an evolving fractal process, which is controlled on the one hand by the initial conditions, including the initial fractal dimensions of the catalysts and the initial reaction conditions, and on the other hand by the previous morphology characteristics of the system, a novel polymerization fractal growth model was constructed. The simulation results showed good agreement with the experiment data. Moreover, the morphology evolution with the prepolymerization technique was predicted, and it was suggested that the duration of polymerization was 10–30 min. It was proven that the use of the surface fractal dimension as an important parameter describing the surface morphologies of the particles, either of catalysts or polymers, was real and effective. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1463–1470, 2003

A predictive model based on the theory of phase space reconstruction was proposed to study the determinism and predictability of dynamics underlying pressure fluctuations by measuring and analyzing the time series of pressure signals at different locations in a bubble bed with 0.3 m in dia. and 3 m in height. Chaotic invariants (correlation dimension, K2 entropy, and Lyapunov exponent spectrum) of measured and model-generated time series of pressure signals were nearly the same. The model captured some important nonlinear characteristics of the real system, which can be used to study the dynamics of fluidizing system. Deterministic dynamics underlying pressure signals were confirmed to exist. A new characteristic index defined as the determining level of dynamics was used to analyze deterministic degrees at different gas velocities and locations of the wall in the bed. Since prediction errors of pressure fluctuations grow exponentially with time at short time scales and the exponent separation rate between predicted and measured values is proportional to the maximal Lyapunov exponent, the long-term predictability of pressure fluctuations is impossible. This verified chaotic properties of fluctuation dynamics in the fluidized bed with deterministic mechanism and sensitive dependence on initial conditions.