Parametric study of co-gasification of ternary blends of rice straw,polyethylene and polyvinylchloride

Parametric study of co-gasification of rice straw (RS), high-density polyethylene (PE) and Polyvinylchloride (PVC) was carried out to investigate the effect of temperature, flow rate of steam, typical plastics and their blends on the quality and volume of synthetic gas. The additions of plastic enhance H₂ content in the synthetic gas. The study found that increase in temperature increases the yield of synthetic gas, H₂ and CO content and lower heating value (LHV) of synthetic gas. The steam to biomass ratio seems to have a very small effect on gas composition. Likewise the increase in PE content in the feed blend increases the hydrogen content and gas yield. Similar results were obtained by increasing PVC content. Co-gasification experiments of ternary blends of RS, PE and PVC were also conducted. The ternary blends of 20 % RS, 40 % PE, 40 % PVC produced synthetic gas with higher H₂ content, higher synthetic gas production rate and higher LHV of synthetic gas. This work confirms that synergistic interactive effect takes place during the co-gasification of ternary blends of PE, PVC and RS due to volatile-char interaction and mineral catalytic effects. This work also suggests that carefully designed co-gasification unit can handle waste with varying composition of biomass and plastic to produce improved quantity as well as quality of synthetic gas.     

100 kW steam plasma process for treatment of PCBs (polychlorinated biphenyls) waste

Non-transferred DC steam (H₂O) plasma working with 100 kW was applied to minimize production of the toxic byproducts such as dioxins and furans of which formation is not avoidable in the conventional incineration. In the steam plasma process of polychlorinated biphenyl (PCB) mixture waste, content of combustible gas that can be used as gaseous fuel was about 30% based on wet gas. For the mixture of 27% PCB and 73% CCl₄, total toxic equivalent concentration of PCDD/PCDF was about 0.056 ng TEQ/N m³. It is concluded that the steam plasma torch process was more effective for waste-to-energy and hazardous waste treatment than the air plasma torch process injected steam and the conventional incineration process.     

Enhancement investigations on thermal properties of PMMA/PE composite film reinforced with nano ɤ-Fe2O3 nanoparticles

ABSTRACT

In the present study, PMMA/PE-?-Fe₂O₃ nanocomposites of various compositions were produced through ultrasound-assisted technique. Thermogravimetric analysis and UV-visible results indicated that the thermal stability is enhanced distinctly, without a sacrifice in optical clarity. The improvement of thermal properties was attributed to the homogeneous and good dispersion of ?-Fe₂O₃ nanoparticles in PMMA/PE/?-Fe₂O₃. And the excellent thermal properties performance of the ?-Fe₂O₃ fillers improved the tribological properties of PMMA/PE composites.     

Fabrication and characterization of PE/MMT nanocomposites via copolymerization of ethylene and in situ formed α-olefins

An iron-based ethylene oligomerization catalyst, {[(2-ArN = C(Me))₂C₅H₃N]FeCl₂}(Ar = 2-CH₃-4-OCH₃(C₆H₄)) (Fe-Cat.) was synthesized and PE/MMT nanocomposites were prepared successfully employing the obtained catalyst supported on MMT and rac-Et(Ind)₂ZrCl₂ (Zr-Cat.) with ethylene as the single monomer and MAO the cocatalyst. The iron-based catalyst could oligomerize ethylene to α-olefins and they copolymerized with ethylene the same time to form PE/MMT nanocomposites in the interlayer of MMT under rac-Et(Ind)₂ZrCl₂. The catalytic system was of high polymeric activities towards ethylene copolymerization and produced branched PE matrix. Characterization of the resultant PE/MMT nanocomposites was performed with ¹³C nuclear magnetic resonance (NMR), X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA) etc. Also investigated were the mechanical properties of the resulting PE/MMT nanocomposites.     

Composite SiOx/hydrocarbon plasma polymer films prepared by RF magnetron sputtering of SiO2 and polyethylene or polypropylene

Composite SiO_x/hydrocarbon plasma polymer films have been prepared by RF sputtering of silica and hydrocarbon polymer (polyethylene (PE) or polypropylene (PP)) targets placed on two balanced magnetrons. The morphology and composition of the composite films have been analysed by means of AFM, RBS/ERDA, FTIR, and XPS. The obtained films demonstrated wide range of wettability and hardness in dependence on the preparation conditions. When the ratio of RF powers delivered to the individual targets P_SiO2/P_PE(P_PP) changed from 0.1 to 10 the static contact angles of water varied from 75° to 25° and from 80° to 33° for composite films obtained from PE and PP, respectively. The hardness of the composite films varied from 2400 to 3400 N/mm² and from 1600 to 2000 N/mm² for the above-mentioned cases, respectively. Peculiar properties of the composite SiO_x/hydrocarbon plasma polymer films have been discussed with respect to the elemental composition and nature of the chemical bonds established on the surface of the films.     

Decomposition mechanism of organic compounds by DC water plasmas at atmospheric pressure

The purpose of this paper is to investigate the decomposition mechanism of organic compounds by water plasmas. The plasma torch can generate 100%-steam by DC discharge without a commercially available steam generator. Methanol or ethanol used as a model substance of water-soluble organic compounds was mixed with water for plasma supporting gas. The main gases after the decomposition were H₂, CO, and CO₂. The 50 wt.% of carbon was transformed into solid carbon in 5 mol%-ethanol decomposition, while the solid-carbon formation from 5 mol%-methanol was negligible. Larger amount of solid-carbon formation from ethanol decomposition indicates the different mechanism between methanol and ethanol decomposition.     

Prediction of in vivo plasma concentration–time profile from in vitro release data of designed formulations of milnacipran using numerical convolution method

The aim of this study was to predict the in vivo plasma drug level of milnacipran (MIL) from in vitro dissolution data of immediate release (IR 50?mg and IR 100?mg) and matrix based controlled release (CR 100?mg) formulations. Plasma drug concentrations of these formulations were predicted by numerical convolution method. The convolution method uses in vitro dissolution data to derive plasma drug levels using reported pharmacokinetic (PK) parameters of a test product. The bioavailability parameters (C_max and AUC) predicted from convolution method were found to be 106.90?ng/mL, 1138.96?ng/mL?h for IR 50?mg and 209.80?ng/mL, 2280.61?ng/mL?h for IR 100?mg which are similar to those reported in the literature. The calculated PK parameters were validated with percentage predication error (% PE). The % PE values for C_max and AUC were found to be 7.04 and ?7.35 for IR 50?mg and 11.10 and ?8.21 for IR 100?mg formulations. The C_max, T_max, and AUC for CR 100?mg were found to be 120?ng/mL, 10?h and 2112.60?ng/mL?h, respectively. Predicted plasma profile of designed CR formulation compared with IR formulations which indicated that CR formulation can prolong the plasma concentration of MIL for 24?h. Thus, this convolution method is very useful for designing and selection of formulation before animal and human studies.     

A novel ATH/SBA-15 suppressant prepared by in-situ synthesis and its inhibition mechanism on PE dust deflagration flame

Recently, polyethylene (PE) dust explosions have become a serious threat to the petrochemical industry. In order to prevent the occurrence of PE dust explosion, a novel aluminum hydroxide (ATH)/Santa Barbara Amorphous type 15 (SBA-15) powder explosion suppressant with the uniform dispersion of ATH was prepared by in-situ synthesis method. For ATH/SBA-15 inhibitor, SBA-15 molecular sieve and ATH was used as the carrier and active component of explosion inhibition, respectively. The inhibition effect on PE dust deflagration was studied by flame propagation experiment. The results showed that when the addition amount of ATH/SBA-15 exceeded 40 wt%, PE dust deflagration flame was almost completely inhibited. Furthermore, the Coats-Redfern method was used to study the thermal decomposition kinetics model. It was found that the thermal decomposition kinetics model of PE before and after the addition of explosion suppressants followed the random nucleation and growth reaction mechanism (A3 model). Further fitting analysis showed the apparent activation energy of PE increased significantly after adding ATH/SBA-15 inhibitor, confirming that ATH/SBA-15 had a significant inhibitory effect on PE deflagration in thermodynamics. Finally, combining with a series of characterization results, it was founded that the ATH/SBA-15 suppressant played the efficient synergy of physics and chemistry, which was efficient in inhibiting PE deflagration. The physical inhibition mainly includes: the free radicals adsorption by SBA-15 molecular sieve, the coating effect of ATH, the endothermic effect and the reduction in O₂ concentration by H₂O decomposed from ATH. Meanwhile, the chemical inhibition mainly lies in the elimination of the free radicals O· and H· in the explosion process by ATH.     

Long-term oxidation kinetics of aluminide coatings on alloy steels by low temperature pack cementation process

The long-term oxidation kinetics of the P92 steel and iron aluminide diffusion coating formed on its surface by the pack cementation process have been investigated at 650 °C over a period of more than 7000 h both in 100% steam and in air under normal one atmospheric pressure by intermittent weight measurement at room temperature. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques were used to analyse the oxidised surfaces. For the P92 steel substrate, the scale formed by oxidation is largely magnetite (Fe₃O₄) in steam and haematite (Fe₂O₃) in air. Despite this difference in the type of oxide scales formed, it was found that the long-term oxidation kinetics of the P92 steel substrate in both steam and air can be described by a logarithmic time relationship: Δm _t = k _lln(t/t° + 1); the constants k _l and t° were subsequently determined using a closest fit process for oxidations in steam and air. For the coating, the oxide scale formed in both steam and air was Al₂O₃, which provided the long-term oxidation resistance. It was observed that the long-term oxidation kinetics of the coating in both steam and air can be best described by Δm _t = Δm ₀ + k _c t ^1/3; the rate constant k _c of oxidation in steam and air was then determined by the least squares method. For both the P92 steel substrate and coating, the rate of oxidation is faster in steam than in air at 650 °C particularly in the case of the P92 steel substrate.     

Inorganic salts and extractability of fresh and frozen fish proteins

Changes in protein extractability (PE) were followed in minced cod meat and in meat washed with distilled water containing added NaCl, KCl, MgCl₂, CaCl₂, and phosphates. In minces stored for 24 h at 4°C and pH 5.5–7.2 the PE decreases with increasing acidity. The same is also true in samples containing 0.2 M of added NaCl 100 g⁻¹ or KCl 100 g⁻¹, while in the presence of MgCl₂ and CaCl₂ in the same concentration PE is very significantly lower than in the control and does not depend so much upon the acidity of the mince.In water extracted and frozen minces after two weeks at−20°C at pH 7.2 and 6.4 the PE is 25% and 50% lower, respectively, than before freezing. NaCl, KCl, MgCl₂, and CaCl₂ added to the washed meat in concentrations corresponding to μ = 0.15 decrease the PE after two weeks of frozen storage by about 7%, 20%, 16%, and 43%, respectively.At μ>0.25, KCl, phosphates, and KCl+CaCl₂ have, during two weeks, a protective effect on PE. In water extracted mince PE decreases after 1 d at −20°C by 15%, which corresponds to a drop in PE in unextracted samples at pH 6.9 only after five weeks. A mixture of salts added to the water extracted mince, corresponding in composition and μ to those in cod flesh, brings about, after prolonged frozen storage, a drop in PE much higher than that in extracted samples.     

Evaluation of the nitrogen oxide emission level for a steam supply with natural gas into the combustion chamber of a gas turbine unit

Numerical simulation results on the effect of the operation parameters for a combustion chamber of a combined-cycle plant (CCP) with steam injection [1] for the combined production of heat and electric energy upon a reduction in nitrogen oxide emission are represented. Calculations are carried out for lean mixtures with α = 1.2–1.4 and great steam consumptions of 30–42%. The reaction analysis has shown that the main contribution in NO _x formation was given by reactions with the advanced Zel’dovich thermal mechanism, and the reaction contribution with the participation of N₂O into the NO formation was an order of magnitude higher than that by the mechanism of the prompt NO formation. NO₂ does not form at high temperatures and only takes part in the conversion into NO in reactions with the participation of nitric acid. It is shown that the optimum choice of operation conditions for the combustion chamber of the CCP makes it possible to obtain the NO _x content in the combustion products in some mill^?1 (ppm). According to calculations, steam injection does not increase CO emission. A comparison with the experiment is given.     

Effects of Steam Environment on Creep Behavior of Nextel™610/Monazite/Alumina Composite at 1,100°C

The tensile creep behavior of a N610™/LaPO₄/Al₂O₃ composite was investigated at 1,100°C in laboratory air and in steam. The composite consists of a porous alumina matrix reinforced with Nextel 610 fibers woven in an eight-harness satin weave fabric and coated with monazite. The tensile stress-strain behavior was investigated and the tensile properties measured at 1,100°C. The addition of monazite coating resulted in ~33% improvement in ultimate tensile strength (UTS) at 1,100°C. Tensile creep behavior was examined for creep stresses in the 32–72 MPa range. Primary and secondary creep regimes were observed in all tests. Minimum creep rate was reached in all tests. In air, creep strains remained below 0.8% and creep strain rates approached 2 × 10⁻⁸ s⁻¹. Creep run-out defined as 100 h at creep stress was achieved in all tests conducted in air. The presence of steam accelerated creep rates and significantly reduced creep lifetimes. In steam, creep strain reached 2.25%, and creep strain rate approached 2.6 × 10⁻⁶ s⁻¹. In steam, creep run-out was not achieved. The retained strength and modulus of all specimens that achieved run-out were characterized. Comparison with results obtained for N610™/Al₂O₃ (control) specimens revealed that the use of the monazite coating resulted in considerable improvement in creep resistance at 1,100°C both in air and in steam. Composite microstructure, as well as damage and failure mechanisms were investigated.     

Comparison of Diamond‐Like‐Carbon and Alumina‐Oxide articulating with Polyethylene in Total Hip Arthroplasty

To reduce wear in joint bearings of total hip arthroplasty (THA) is the most important issue for improving long term results and implant survival. Due to low wear rates and excellent tribological features in simulator tests Diamond‐Like‐Carbon coating (DLC) of femoral balls is still discussed as an alternative articulation in THA. This clinical prospective study compares survivorship of DLC‐coated femoral heads and of Aluminia‐Oxide‐ (Al₂O₃) heads articulating with Polyethylene (PE). Over a period of two years 101 THA with DLC‐coated heads and PE cups (DLC‐group) and another 101 THA consisting of Al₂O₃ heads (Al₂O₃‐group) and PE cups as well were implanted. Both articulations were based on the same type of cementless hip joint prosthesis. All hips were implanted by one surgeon in consecutive series consisting of 51 Al₂O₃ and 101 DLC‐articulations and further 50 Al₂O₃. All perioperative and follow‐up data was processed with SPSS®. Survival of THA in both groups was evaluated according to Kaplan‐Meier survivorship analysis with an intervall of 90 months (range:78‐101). Qualitative surface analysis was performed in nineteen retrieved DLC‐heads which were revised for aseptic loosening using field scanning electron microscopy (FE‐SEM, XL 30 SFEG Philips, Eindoven NL). 178 patients (88.2 %) were evaluated for follow‐up. Fourteen patients died meantimes (nine DLC, five Al₂O₃) with the implant components not revised. Ten patients (five DLC, five Al₂O₃) were lost to follow‐up. Both groups were comparable regarding patient age, weight and indications for THA with a normal distribution. Survivorship analysis for aseptic loosening 8.5 years following implantation resulted in a significant difference between both groups with a 54 % survival for DLC/PE compared to 88 % for Al₂O₃/PE bearings (p <0.001). No correlation to variables as age, gender or bodyweight could be detected. Surfaces of nineteen retrieved DLC‐heads showed numerous smallest pits of the diamond‐carbon layers in different quantity. SEM showed delamination of the carbon layer which caused excessive debris of polyethylene and in some cases even of the metallic substrate of the heads. Despite modern manufacturing technology and excellent experimental results for its tribochemical characteristics and wear, even “new” DLC‐coating of femoral heads is to be considered critically due to very high rates of clinical failure.     

Oxidation behavior of a new Fe–Ni–Cr-based alloy in pure steam at 750 °C

The isothermal oxidation of a new Fe–Ni–Cr-based alloy has been investigated in pure steam at 750 °C for exposure time up to 500 h using secondary electron microscope (SEM)/ X-ray energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Results showed that the alloy was oxidized approximately following a parabolic law with a parabolic rate constant k_p of 2.36 × 10^?13 g²/m⁴/s. As revealed by SEM/EDS and XRD results, a duplex-layered external oxide scale was formed, consisting of a thin outer layer of Ni(Fe, Al)₂O₄ and a thicker inner layer of (Cr, Mn)₂O₃. Underneath the external oxide scale, the internal oxidation of Ti to be TiO₂ occurred particularly along the grain boundaries of the matrix alloy. Internal oxide of Al₂O₃ was also observed but at a deeper depth. Based on the detailed compositional and microstructural characterization of the oxidized zone, the mechanism of the external and internal oxidation in steam is presented.     

Multiwalled carbon nanotubes-supported Nickel catalysts for the steam reforming of propane

Multiwalled carbon nanotubes (MWCNTs)-supported nickel catalysts with different metal-loading contents were synthesized trough deposition–precipitation (DP) method for its subsequent performance study on steam reforming reaction of propane. The metal-loading content was set at 5, 10, 20, and 25% of nickel. Results showed that 20 wt% nickel oxide over MWCNTs (20% NiO/MWCNTs) had the best performance, on the propane steam reforming reaction, in terms of H₂ conversion comparing with the rest of the NiO/MWCNTs catalysts (5, 10, 25 wt% Ni) and a nickel over alumina (Ni/Al₂O₃) commercial catalyst. The features of the NiO/MWCNTs catalysts were studied trough FT-IR, Raman spectroscopy, N₂ adsorption–desorption isotherms, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy measurements. The results evidenced that optimum relation between Ni content, Ni dispersion, and particle size played a main role in the catalyst performance, rendering the 20% NiO/MWCNT as the most promising, among the catalysts studied, for the steam reforming of propane.     

Thermodynamic modeling of thermal processes involving actinides (U,Am, Pu) in the course of heating radioactive graphite in steam

The behavior of actinides (U, Am, Pu) in the course of combustion of radioactive graphite in steam was studied by thermodynamic modeling. Thermodynamic modeling was performed using TERRA program in the temperature interval from 373 to 3273 K to determine the possible composition of volatile actinide species formed in the course of graphite utilization by heating in steam. The modeling shows that the actinides at high temperatures are present in the following forms: U, as UO₃ and UO₂ vapors and as UO₃ ^– and UO₂ ⁺ ions; Am, as Am vapor; and Pu, as PuO₂ and PuO vapors and as ionized PuO⁺. The main reactions within separate phases and at the interface were revealed, and their equilibrium constants were determined.     

Numerical study of hydrogen production by the sorption-enhanced steam methane reforming process with online CO<Subscript>2</Subscript> capture as operated in fluidized bed reactors

A three-dimensional (3D) Eulerian two-fluid model with an in-house code was developed to simulate the gas-particle two-phase flow in the fluidized bed reactors. The CO₂ capture with Ca-based sorbents in the steam methane reforming (SMR) process was studied with such model combined with the reaction kinetics. The sorption-enhanced steam methane reforming (SE-SMR) process, i.e., the integration of the process of SMR and the adsorption of CO₂, was carried out in a bubbling fluidized bed reactor. The very high production of hydrogen in SE-SMR was obtained compared with the standard SMR process. The hydrogen molar fraction in gas phase was near the equilibrium. The breakthrough of the sorbent and the variation of the composition in the breakthrough period were studied. The effects of inlet gas superficial velocity and steam-to-carbon ratio (mass ratio of steam to methane in the inlet gas phase) on the reactions were studied. The simulated results are in agreement with the experimental results presented by Johnsen et al. (2006a, Chem Eng Sci 61:1195–1202).     

Coke deposition on and removal from metals and heat-resistant alloys under steam-cracking conditions

The kinetics of coke formation and its removal from nickel, copper and alloys have been studied and the results correlated with the morphology of the deposits. Coke deposition from hydrogen-propylene-steam was fast on nickel and slower on copper and the alloys. The deposition on nickel was filamentary in appearance, resulting from a heterogeneously catalysed process, whereas the deposit on the alloys and on non-catalytic copper was essentially uniform. On the alloys, protection appeared to result from the production of scales, containing predominantly Cr₃C₂ and Cr₂O₃, on the surface. At the same time, carburization of the alloy was reduced, apparently as a result of the formation of a silicon-enriched layer at the base of the scale. Steam was found to have little effect on coke formation. However, in the absence of gas-phase hydrocarbons, coke gasification by steam was rapid for nickel but several orders of magnitude slower for the alloys. The main effect of steam is to aid in the formation of scales that are protective against coking and carburization, by promoting oxide formation.     

Material Effect and Steam Explosion at High Temperature (<Emphasis Type="Italic">T</Emphasis> > <Emphasis Type="Bold">2300</Emphasis> K)

In the frame of nuclear power plant safety, the interaction of molten corium (mixture of materials coming from a power plant) with water can generate dynamic loading of the surrounding structures. This phenomenon is called the steam explosion. Many experiments have been performed in the KROTOS facility with simulation materials (Al₂O₃) and prototypical materials (U,Zr)O₂, and different behaviors attributed to a ‘material effect’ have been observed. Alumina melts produced spontaneous energetic steam explosions, whereas explosions with corium melts (80% UO₂–20% ZrO₂) must be triggered and are less energetic. These differences may be partly attributed to the formation of meta-stable gamma alumina and the ability of liquid alumina to dissolve part of the water, acting like an internal trigger. These results mean that alumina is probably not an adequate simulation of the corium for steam explosion. Paper presented at the Seventh International Workshop on Subsecond Thermophysics, October 6–8, 2004, Orléans, France.     

Thermal degradation kinetics and estimation of lifetime of polyethylene particles: Effects of particle size

The thermal stability and degradation behavior of polyethylene (PE) particles having a diameter varies from few nanometers to micrometers were studied by thermogravimetric analysis (TGA). The PE particles of average diameter ～20, ～10, ～1 μm and <500 nm were studied over a range of temperatures from 25 to 600 °C in N₂ atmosphere and heating rates of 5, 10 and 15 °C min^?1. The three single heating-rate techniques such as Friedman, Freeman–Carroll, and second Kissinger; and three multiple heating-rate techniques such as the first Kissinger, Kim–Park and Flynn–Wall were used to work out the kinetic parameters of the degradation reactions, e.g., activation energy (E_a), order of reaction (n) and frequency factor [ln(Z)]. The lifetime of macro, micro and nanosized PE particles were also estimated by a method proposed by Toop. It was found that the activation energy and lifetime of nanosized PE nanoparticles were moderately high compared to the micron sized PE particles. Moreover, the decomposition temperature, order of reaction (n), frequency factor [ln(Z)] do not only depend on heating rates and calculation techniques, but also on particle size of the PE. The results obtained from the kinetic and lifetime studies for nano and micro sized particles were compared with macro sized PE.