Pretreatment methods for gasification of biomass and Fischer–Tropsch crude production integrated with a pulp and paper mill

In this paper, the influence on the system performance and greenhouse gas (GHG) emissions of different biomass pretreatment methods before gasification and Fischer–Tropsch (FT) crude production was evaluated. Entrained flow gasification has the benefit of producing a practically tar-free synthesis gas with nearly complete carbon conversion. This gasifier type requires a relatively dry fuel, with small particle size, at high pressure. The size can be acquired by milling, which is energy intensive and feeding is challenging. Torrefaction of biomass facilitates milling; it thus requires less electricity, however, the torrefaction process requires heat. Pyrolysis decomposes the biomass into gaseous, liquid, and solid parts, respectively. This further makes feeding easier, but comes with a greater heat demand than torrefaction. The impact of the different pretreatment methods on the overall energy system has been evaluated using process integration methodology. The results show that the excess heat from an FT process with a biomass input of 300 MW_HHV can replace the bark boiler in a large chemical pulp and paper mill, producing 350,000 tonnes of bleached paperboard annually. With the preconditions given for this study, thermal pretreatment of biomass may be beneficial in terms of wood-to-FT crude efficiency, with efficiencies up to 68 %, assuming 40 % electrical efficiency. Pretreatment using pyrolysis performed the best in regards to GHG emissions, if CO₂ from acid gas removal was vented, while milling, with an annual reduction of around 700,000 tonnes of CO₂,_eq, had the best results if the CO₂ was captured and sequestrated.     

Development and Verification of a Scheme for Fractionation of HAWs with TODGA Extractive Agent in a “Light” Diluent

Radiochemistry - The technology of fractionation of trans-plutonium elements (TPEs) and REEs with the use of 0.15 M TODGA (tetraoctylamide of diglycolic acid) + 5% n-decanol in Isopar-M as...     

Large- and small-nanopore silica prepared with a short-chain cationic fluorinated surfactant

A cationic partially fluorinated surfactant with four carbons in the chain 1-(3,3,4,4,4-pentafluorobutyl)pyridinium chloride is employed as a structure-directing agent to synthesize nanoporous silica. Samples are prepared in dilute ammonia solutions at room temperature with a range of surfactant:Si ratios. The sample with the largest surfactant:Si ratio forms particles with wormhole-like micropores with an average diameter of 1.6?nm, which corresponds to the anticipated small size of the surfactant aggregates. On the other hand, the sample with the smallest surfactant:Si ratio forms a gel that, upon drying, has uniform 11.1 nm pores. The formation and stabilization of the latter large-mesopore structure is unusual for a sample prepared and dried under ambient conditions, and may reflect favourable roles of the surfactant both in inducing gelation and in stabilizing the pore structure during drying.     

Evolution of morphology and structure with growth of thickness of condensed films of Pd–Cu on a surface with open porosity

Cross sections obtained by the method of a focused ion beam and fractures of the PdCu/Al₂O₃ nanocomposite synthesized by magnetron sputtering (MS) of alloy-type target PdCu and condensation in vacuum on the surface of nanoporous Al₂O₃ produced by anodic oxidation of aluminum foil are investigated using the methods of high-resolution scanning electron microscopy implemented on the basis of a Helios 600i setup (FEI, United States). Regularities of the formation of the structure and morphology of crystallites of vacuum condensate of Pd–Cu solid solution with a thickness of 0.1–4 μm on a surface with open porosity are disclosed. Approaches to the formation of the gradient structures near a free surface are discussed, and the conditions of the initiation of MS mechanisms of the formation of discrete, porous, and anisotropic condensates are found. Approaches to nonselective filling of nanopores in a dielectric by metal clusters and forming of the gradient structure of the nanocomposite PdCu/Al₂O₃ are carried out.     

Modeling and calculation of slurry-chemistry effects on chemical–mechanical planarization with a grooved pad

During chemical–mechanical planarization (CMP), a rotating wafer is pressed against a rotating pad, while a slurry is dragged into the pad–wafer interface. Here, taking into account the dependence of local material removal rate (MRR) on the slurry’s chemical activity, the effects of pad groove geometry and various other process parameters on the spatial average and non-uniformity of MRR are examined. Technically, the slurry flow is calculated by following an existing approach that integrates two-dimensional fluid-film lubrication theory and contact-mechanics models. A slurry impurity transport equation is then used to calculate the impurity concentration that determines the slurry’s chemical activity and hence the local MRR. The numerical results obtained here indicate that the presence of pad grooves generally decreases the average slurry impurity concentration, and increases the average contact stress on the pad–wafer interface. However, as a grooved pad has less contact area for effective interaction with the wafer surface, the average MRR may or may not be increased, depending upon the specific setting of process parameters. Meanwhile, it appears that the retaining ring generally used to keep the wafer in place also plays an important part in reducing the MRR non-uniformity.     

Accurate Density and Viscosity Modeling of Nonpolar Fluids Based on the “f-Theory” and a Noncubic Equation of State

Recently, the f-theory, a theory for viscosity modeling based on friction concepts of classical mechanics, has been introduced. This new theory allows accurate viscosity–pressure–temperature (–p–T) modeling based on a van der Waals type of equation of state, one with a repulsive pressure term and an attractive pressure term. Thus, popular cubic equations of state (CEOS), such as the SRK and the PR, have been successfully applied to obtain accurate –p–T models (even close to the critical region) of fluids such as n-alkanes, N₂, CO₂, etc., and some of their mixtures. However, even though it has been shown that a CEOS f-theory-based model can accurately reproduce the viscosity behavior of, at least, nonpolar fluids, the accuracy of the density predictions is still limited by the algebraic structure of the CEOS. In this work, a noncubic van der Waals type of equation of state is introduced for the accurate modeling of both the density and the viscosity behavior of selected nonpolar fluids. The achieved accuracy, for both the density and the viscosity fluid properties, is close to, or within, experimental uncertainty and applies to wide temperature and pressure ranges.     

Effects of tangential and radial velocity on fluid flow and heat transfer for flow through a pipe with twisted tape insert—laminar flow

The present study reports the numerical analysis of fluid flow and heat transfer in a pipe with full length twisted tape insert. The investigation is carried out for five different twist ratios of 4, 5, 6, 8 and 10 at 100 ≤ Re ≤ 1000. The velocity field in terms of streamwise, tangential and radial velocity and temperature field are studied as a function of Reynolds number and twist ratio. The variation of friction factor and Nusselt number with Reynolds number for different twist ratios is also presented. The heat transfer enhancement due to insertion of twisted tape mainly comes from the tangential and radial components of velocities, which are regarded as secondary fluid motion. It is evident from the results that with increase in Reynolds number the axial convection increases. However, with the decrease in the twist ratio, the tangential and radial convection increases, leading to increased heat transfer. The secondary flow affects the thermal boundary layer inside the tube and increases the cross-flow mixing, which increases the heat transfer. The correlations for prediction of friction factor and Nusselt number based on the numerical data are also proposed.     

SEM study of the fractured surfaces of films and blocks prepared from montmorillonite and its complex with α-naphtylamine

Four samples were heated under nitrogen to determine the relations between heat-treatment conditions and the topographies of the fractured surfaces of the resulting samples. The samples used were thin films (several 10m thick) of lithium-montmorillonite (Mont) and its complex (MNC) with-naphtylamine, and the blocks of raw montmorillonite and its complex with-naphtylamine (MNC). Two characteristic topographies were obtained from MNC film. They were of a very dense structure with the memory of a layered structure after heating to about 1173 K at 1 or 5 K min^–1, and a homogeneous fine porous structure after heating to 1173 to 1273 K at 40 K min^–1. An unique porous structure was also obtained from MNC block, several millimetres thick by heating to 873 K for 1H. However, Mont, in both film and block, was not suitable for preparation of the homogeneous structure, regardless of porous or dense structures.     

Preparation and Characterization of Solid Dispersions of Dipyridamole with a Carrier “Copolyvidonum Plasdone®S-630”

Solid dispersions (SDs) of dipyridamole (DIP) with a novel carrier copolyvidonum Plasdone®S-630 (CoPVP) were developed by solvent evaporation method. The solid state of SDs of DIP with CoPVP (SDs CoPVP) was characterized by fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and polarizing microscopy, compared with that of SDs of DIP with polyvinylpyrrolidone Plasdone®K-29/32 (SDs PVP). FT-IR analysis demonstrated the presence of intermolecular hydrogen bonding between DIP and CoPVP or PVP in SDs. DSC and XRD studies indicated that DIP presented in amorphous state in both SDs CoPVP and SDs PVP at higher weight ratios. The dissolution property of SDs CoPVP was significantly improved in comparison of pure DIP and physical mixtures with CoPVP (PM CoPVP). Both SDs CoPVP and SDs PVP powder showed the favorable flowability. However, SDs CoPVP showed better compressibility than SDs PVP. The lower hydroscopicity of SDs CoPVP could be advantageous to the stability to SDs. This study proves the potential of CoPVP as a carrier in the formulations of SDs for poorly soluble drugs.     

Religious commitment and its interaction with scientific professions: a low-church real-science,critique of “science” and “spirituality”

After a brief autobiographical background, as an activist scientist and engineer, the author offers a broad critique of the attempt to relate science and religion at the theoretical level. The important level at which to seek a relation, both scientifically and religiously, is one of practice, not theory. Indeed, because science as theory is itself in the process of reaching its own internal limits, because of the manifest failures of reductionist science and technology, it is time for scientists and engineers to return to Einstein's commitment to pursue science for the common good. The rising popularity of alternative medicine is also cited as a contemporary historical phenomenon that points toward an emerging, fundamental realignment of the science–technology–society relationship.     

Possibilities and sustainability of “biomass for power” solutions in the case of a coal-based power utility

This paper investigates the possibilities and the sustainability of “biomass for power” solutions on a real power system. The case example is JP Elektroprivreda BiH d.d.—Sarajevo (EPBiH), a typical conventional coal-based power utility operating in the region of South East Europe. Biomass use is one of the solutions considered in EPBiH as a means of increasing shares of renewable energy sources (RES) in final energy production and reducing CO₂ emissions. This ultimately is a requirement for all conventional coal-based power utilities on track to meet their greenhouse gas (GHG) cut targets by 2050. The paper offers a discussion of possible options as a function of sustainability principles, considering environmental, economic and social aspects of biomass use. In the case of EPBiH, the most beneficial would be waste woody biomass and energy crop co-firing on existing coal-based power plants, as suggested by biomass market analyses and associated technological studies. To assess the sustainability of the different biomass co-firing options, a multicriteria sustainability assessment (MSA) and single criteria analysis (SCA) were used. Four different options were considered, based on different ratios of biomass for co-firing: 0 wt%-reference case, and 5, 7 and 10 wt% of biomass. Both the MSA and the SCA confirmed that the option with the highest share of biomass is the most preferable one for the considered case. In addition to that, the CO₂ parameter proved to be a key sustainability indicator, effecting the most decision making with regard to preference of options from the point of sustainability. Following up on the results of the analyses, the long-term projection of biomass use in EPBiH has shown an increase in biomass utilization of up to 450,000 t/y in 2030 and beyond, with associated CO₂ cuts of up to 395,000 t/y. This resulted in a 4 % CO₂ cut achieved with biomass co-firing, compared to the 1990 CO₂ emission level. It should be noted that the proposed assessment model for biomass use may be applied to any conventional coal-based power utility as an option in contributing to meeting specific CO₂ cut targets, provided that the set of input data is available and reliable.     

Fabrication of a Thermally Isolated and Pre-Amplified Transistor Module with Polyimide Micro-Wires for Cryogenic Detectors

We report a pre-amplifying junction field effect transistor (JFET) module on a chip for cryogenic applications such as bolometer and X-ray microcalorimeter. In order to maintain the optimum performance of the JFETs at 130 K, the module has built-in aluminum micro-heaters while the JFETs are thermally isolated from a heat sink. The thermal isolation is achieved by suspending a micromachined silicon support platform (6 μm thick) with polyimide wires. A layer of aluminum electrodes is patterned on top of the polyimide wires for electrical contacts and on top of the silicon platform for the heaters. This process involves reactive-ion-etching (RIE) of silicon and polyimide, patterning of aluminum electrodes over the polyimide, back side deep-reactive-ion-etching (DRIE) of silicon, and releasing of the modules. In this paper, we describe a micromachining process of the JFET modules on silicon-on-insulator (SOI) wafers.      

Numerical simulation of hydrodynamics and heat transfer under conditions of turbulent transverse flow past a “trench” on a plane surface

Results are given of numerical simulation of hydrodynamics and heat transfer under conditions of transverse flow past a two-dimensional trench (a groove whose cross section has the form of a segment of circle) located on a plane isothermal surface. The calculations are performed for an incompressible liquid within two-dimensional Reynolds equations closed with the aid of the Menter and Spalart-Allmares turbulence models using multiblock overlapping grids. Detailed analysis is performed of the effect of the trench depth on the flow structure (configuration of separated-flow regions) and on the distribution of friction, pressure, and heat fluxes along the surface subjected to flow.Translated from Teplofizika Vysokikh Temperatur, Vol. 43, No. 1, 2005, pp. 086–099. Original Russian Text Copyright © 2005 by S. A. Isaev, A. I. Leontiev, and N. A. Kudryavtsev.     

Influence of the Evaporation Coefficient and Temperature Jumps on the Thermophoresis of a Moderately Large Volatile High‐Viscosity Sphere in a Binary Gas Mixture with Allowance for Volume Thermodiffusion and Stefan Effects

The theory of a uniform thermophoretic motion of a volatile highviscosity sphere with the phase transition of one component of a moderately rarefied binary gas mixture on its surface has been constructed on the basis of the hydrodynamic method in the regime with slip. The relative influence of the evaporation coefficient and the boundary temperature jumps on the distributions of the velocities, temperatures, and concentrations of the volatile component and the thermophoresis rate has been analyzed. Allowance has been made for the thermodiffusion terms, Stefan effects, and the heat due to the convective transfer of the substance of the condensed phase. The formula obtained has wider limits of application than the existing results. The conclusions of the traditional theories are successfully generalized to the cases of weak and moderately strong processes of diffusion evaporation of a single highviscosity droplet that moves in a nonuniformly heated binary mixture of gases.