Impregnation Stage Research Articles

Improved impregnation efficiency and pulp yield of softwood kraft pulp by high effective alkali charge in the impregnation stage

Abstract A pulp yield increase up to 2% can be achieved by impregnation with a liquor containing 2 M effective alkali (EA) concentration instead of 1 M. The yield increase is due to higher cellulose and glucomannan contents in the pulp, which can be rationalized by less yield loss by peeling, as impregnation is more effective at an elevated EA level. A rapid loading of chips with alkali can be realized due to a high diffusion rate. When the temperature becomes higher in the cooking stage, enough alkali is available for delignification reactions without the risk of alkali depletion in the chip core, so that the delignification is more homogeneous.

The role and mechanism of K2CO3 and Fe3O4 in the preparation of magnetic peanut shell based activated carbon

The impact of K2CO3 and Fe3O4 on the porosity development and the magnet evolution within magnetic peanut shell based activated carbon (MPSAC) was systematically studied. At the impregnation stage, K2CO3 was found to undergo one anionic hydrolysis. The formed KOH disrupted the key ester linkages between lignin and carbohydrates and removed a part of guaiacyl lignin. At the pre-carbonization stage, the introduction of K2CO3 greatly modified the carbonization behavior of peanut shell, shifting the weight loss peak from 350°C to 255°C. Meanwhile, a primary pore structure was developed, and some nanoscopic K2CO3 was detected. At the activation stage, a series of K-related species such as K2CO3·1.5H2O, K2CO3, K2O and K was formed, which was connected with the development of abundant micropores within MPSAC. Magnetic additive Fe3O4 functioned as an activation promoting agent while providing the Fe source. Above 500°C, the porosity structure increased the contact area between Fe3O4 and the reduction gases including CO and H2. Fe3O4 was reduced and successively converted into FeO and Fe with the increase of activation temperature. After that the Fe source was further converted into Fe3C.

Improving the impact resistance of p-aramid fabrics by sequential impregnation with shear thickening fluid

A simple and effective method for impregnation of p-aramid (Kevlar®) fabric with shear thickening fluid (STF) has been developed in this research. Kevlar fabric was impregnated with STF in two stages in a sequential manner. Three levels of pressure (0.5, 1 and 2 bar) were used in each stage of impregnation. It was observed that impact energy absorption by Kevlar fabrics, impregnated with STF in this newly developed method, increased significantly as compared to untreated Kevlar fabrics and Kevlar fabrics treated with STF in conventional way (single step impregnation). Better results were obtained when the first impregnation pressure was higher than that of the second, even with same combination of pressures. Such fabrics also showed a much higher STF add-on (~18 %) as compared to that of fabrics impregnated in single step (3-5 %). Low velocity ballistic tests also confirmed the advantages of the new method as sequentially impregnated fabric showed 124.8 % and 24.4 % increase in impact energy absorption compared to untreated and STF impregnated Kevlar fabrics in single step, respectively.

NiMo/alumina hydrodesulphurization catalyst modified by saccharose: Effect of addition stage of organic modifier

NiMo/Al2O3 catalysts, obtained by one‐pot simultaneous impregnation, were modified by saccharose (SA, at Ni/SA = 1 mol ratio) addition. To address the influence of stage of saccharide impregnation on the hydrodesulphurization activity of sulphided catalysts, three different preparation methodologies were followed: (a) modification of already calcined (400 °C) NiMo/Al2O3 by SA impregnation; (b) SA deposition directly onto the alumina support, prior to Ni + Mo impregnation; (c) simultaneous Ni + Mo + SA deposition. Materials were characterized by N2 physisorption, X‐ray diffraction, infrared (IR) spectroscopy, UV‐vis spectroscopy, and temperature‐programmed reduction (TPR), and tested on liquid‐phase dibenzothiophene (DBT) conversion (batch reactor, T = 320 °C, P = 7.2 MPa, n‐hexadecane as solvent). The last methodology resulted in the catalyst with the highest DBT hydrodesulphurization (HDS) activity, on a pseudo‐first order kinetic constant basis. A decreased proportion of tetrahedral Mo6+ species due to diminished interaction with the carrier, increased reducibility of octahedral Mo6+, and Ni complexation as well seemed to play determining roles in the trends of the activity observed. Simultaneous saccharose addition during NiMo phase impregnation required no additional preparation steps to efficiently integrate the organic modifier.

Computational Analysis of the Interaction between Impregnation, Forming and Curing in Pultrusion

Numerical and analytical models dealing with different physics involved in pultrusion are combined in the optic of an integrated analysis of the process. The impregnation stage is simulated by means of a CFD multiphase model, evaluating the pressure and velocity field in the liquid resin. Composite temperature and degree of cure are inferred using 3D thermo-chemical models. Finally, contact conditions, stresses and strains are derived applying computational simulation and analytical models, in order to predict the final pulling force. Different product sizes are considered, simulating suitable processing condition.

Effect of compaction treatment on laminated CFRP composites fabricated by vacuum‐assisted resin‐transfer molding

Carbon fiber‐reinforced polymer (CFRP) composites were fabricated using ordinary and compaction setups (OS and CS, respectively) in the vacuum‐assisted resin‐transfer molding (VARTM) process. The mechanical properties and acoustic emission (AE) spectra of the CFRP composites were compared among fabricated samples. The CFRP plates with sequences of [+30/−30]6 were sectioned to make specimens for Mode I interlaminar fracture tests and three‐point bending tests. The difference between the material properties and AE characteristics of the OS and CS specimens were statistically compared using one‐way analysis of variance. The OS specimens had a thicker resin layer, a higher resin fraction, larger average fracture toughness, and AE energy corresponding to the Mode I fracture, whereas the CS specimens had more macro‐scale voids and higher bending strength. AE analysis showed that frequency bands in the interlaminar fracture tests corresponding to matrix‐related fracture were dominant for the OS specimens, whereas those corresponding to the mixed fracture mode of the fiber and matrix fracture were dominant for the CS specimens. In the bending tests, mixed fiber‐matrix fractures were dominant for the OS specimens, and fiber‐related fractures were dominant for the CS specimens. In conclusion, the compaction treatment diminished interlaminar fracture toughness, due to the enhanced formation of macro‐scale voids around the fiber bundles during the resin impregnation stage. However, the bending strength improved with an increased fiber volume fraction. POLYM. COMPOS., 38:217–226, 2017. © 2015 Society of Plastics Engineers

Comparative study of anatomical specimens using plastination by araldite HY103, polypropylene resin, 6170H19 Orthocryl and silicone – A qualitative study

BackgroundMost of the organs and tissues are preserved in formalin with its own set of disadvantages. Plastination is a unique method of permanently preserving tissue in a life like state. Plastination developed by western authorities is a labour and equipment intensive affair. Most common polymer used is S10, however this study uses easily available alternative polymers for plastination. MethodVarious polymers like Epoxy resins, Polypropylene resins, Orthocryl and silicone were used in plastinating the anatomical specimens. Specific methods were used for solid, hollow organs and brain specimens. The specimens were made to undergo stages of fixation, dehydration, impregnation and curing. The results were studied and interpreted under various parameters. ResultsThe results were interpreted under various parameters like shrinkage, retention of colour, odour, pliability and retention of gross anatomy. The study concluded that Orthocryl and Epoxy resins retained maximum colour with minimal shrinkage while maximum discolouration was with polypropylene plastinates. Brain sections were best preserved in Orthocryl. ConclusionThe study concluded that indigenous methods and materials can produce quality plastinates which can be an important adjunct to traditional methods of teaching however more studies need to be done for refinement.

Physiognomy and timing of metasomatism in the southern Vourinos ultramafic suite, NW Greece: a chronicle of consecutive episodes of melt extraction and stagnation in the Neotethyan lithospheric mantle

The southern Vourinos massif, located in the Hellenides orogenic belt, forms part of the mantle section of the homonymous Neotethyan ophiolite complex in the NW Greek mainland. The southern domain of the massif is comprised voluminous and strained peridotite outcrops with variable pyroxene and olivine modal abundances, ranging from harzburgite (sensu stricto) to olivine-rich harzburgite and fine- to coarse-grained dunite. These peridotites are intruded by a complex network of undeformed websterite to olivine-rich websterite dykes. The peridotite lithologies are characterized by high Cr# [=Cr/(Cr + Al)] values in Cr-spinel (0.54–0.80), elevated Mg# [=Mg/(Mg + Fe2+)] ratios in olivine (0.91–0.94), poor Al2O3 content in clinopyroxene (up to 1.85 wt%) and very low bulk-rock abundances of Al2O3 (up to 0.66 wt%), CaO (up to 0.84 wt%), V (up to 45 ppm), Sc (up to 11 ppm) and REE, which are suggestive of their strongly depleted nature. They also display a wide range of fO2 values that vary between the fayalite–magnetite–quartz (FMQ-2) and FMQ+1 buffers, signifying their genesis under anoxic to oxidizing conditions. Simple batch and fractional melting models cannot satisfactorily explain their ultradepleted composition, whereas whole-rock Ni/Yb versus Yb systematics can be simulated by up to 27 % closed-system, non-modal, dynamic melting of a primitive mantle source, implying their multifarious origin in a progressively changing, in space and time, geotectonic setting. Chromian spinel chemistry (Cr# vs. TiO2) provides evidence for two consecutive melt–peridotite interaction events pertaining to patent metasomatism. The first incident is related to the release of IAT melts from the deep parts of the southern Vourinos mantle segment, which reacted with harzburgites transforming them into olivine-rich harzburgites and replacive dunites, whereas mixing of different pulses of IAT melts with distinct SiO2 activities generated heterogeneously deformed, cumulitic dunites. The second event is linked to the genesis of MORB/IAT magmas that originally invaded harzburgites. The MORB/IAT melts, although intensely reactive at the stage of harzburgite impregnation, lost their ability to react and stagnated in the peridotite groundmass as they approached the conceivable boundary with olivine-rich harzburgite. Microtextural observations and compositional data support that the interstitial, unstrained clinopyroxene ± olivine aggregates recognized in the harzburgite varieties represent intergranular melt blebs that ‘chilled’ in the mantle during an episode of rapid lithosphere exhumation. This is further corroborated by the absence of lavas with MORB/IAT geochemical affinities from the Vourinos extrusive sequence. Microstructural features of websterite veins suggest that their genesis cannot be ascribed to the melts that penetrated the peridotites that cross cut. In contrast, they retain marks of olivine assimilation from the wall rocks that was facilitated by interaction with olivine-undersaturated, arc-derived tholeiitic melts released at a late phase from the ultradepleted southern Vourinos mantle suite.

Recent progress in the thermocatalytic processing of biomass into advanced fuels

Recent progress in the thermocatalytic processing of biomass into advanced fuels

Synthesis of porous zirconium and titanium dioxides by hydrolysis of tetrabutoxyzirconium (tetrabutoxytitanium) with atmospheric moisture in the absence of acid-base catalysts with the use of cellulose and activated charcoal as matrices

Synthesis of porous zirconium and titanium dioxides was accomplished by a procedure that includes impregnation of cellulose and activated charcoal matrices with tetrabutoxyzirconium (tetrabutoxytitanium) solutions, hydrolysis of the precursors with atmospheric moisture at 25°C, burning the matrix, and incineration of xerogels at 850°C. Relationship between precursor solution concentration at impregnation stage, matrix type, and physicochemical properties of prepared materials was established.

Nanoparticles deposit location control on porous particles during dry impregnation in a fluidized bed

This work deals with the synthesis of composite materials, catalytic or not, by an innovating technique named dry impregnation in a fluidized bed. This process permits the obtainment, in only one apparatus, of composite materials which, by the traditional way, must successively undergo the stages of impregnation, filtration, drying and calcination/activation. Its principle consists in the spraying of a solution containing a metallic precursor into a hot fluidized bed of porous particles as a chosen support. After the impregnation step, the decomposition of metallic precursor and metal activation can be operated in the same reactor. It is found that the competition between two phenomena (drying and capillary) controls the deposit location.This paper presents experimental results obtained during the dry impregnation of coarse and fine porous particles using different types of precursors: inorganic precursors (metallic salts), metal organic complexes and a colloidal suspension containing preformed metallic nanoparticles (rhodium). The effect of drying parameters (solvent content in gas phase and temperature) on deposit distribution within the support grains at the local scale is examined.It appeared that a fast drying leads to a deposit located only at the external particle surface (similar to a surface coating), whereas a uniform deposit on the whole particle volume is obtained with slow drying conditions. It indicates that dry impregnation in fluidized beds is very flexible and, by a simple modification of the operating conditions, we can fix the deposit location.

Nanosilica supported CaO: A regenerable and mechanically hard CO2 sorbent at Ca-looping conditions

This work presents a CO2 sorbent that may be synthesized from low-cost and widely available materials following a simple method basically consisting of impregnation of a nanostructured silica support with a saturated solution of calcium nitrate. In a first impregnation stage, the use of a stoichiometric CaO/SiO2 ratio serves to produce a calcium silicate matrix after calcination. This calcium silicate matrix acts as a thermally stable and mechanically hard support for CaO deposited on it by further impregnation. The CaO-impregnated sorbent exhibits a stable CaO conversion at Ca-looping conditions whose value depends on the CaO wt% deposited on the calcium silicate matrix, which can be increased by successive reimpregnations. A 10wt% CaO impregnated sorbent reaches a stable conversion above 0.6 whereas the stable conversion of a 30wt% CaO impregnated sorbent is around 0.3, which is much larger than the residual conversion of CaO derived from natural limestone (between 0.07 and 0.08). Moreover, particle size distribution measurements of samples predispersed in a liquid and subjected to high energy ultrasonic waves indicate that the CaO-impregnated sorbent has a relatively high mechanical strength as compared to limestone derived CaO.

Alternative processing strategies to reduce the weight loss of cooked chicken breast fillets subjected to vacuum cooling

In this paper, two processing strategies were evaluated aiming to reduce/compensate the weight loss of chicken breast fillets subjected to cooking and vacuum cooling: immersion cooking followed by pulsed immersed vacuum cooling (ICk-PIVC); and a new approach that incorporates a vacuum impregnation stage to the immersion cooking followed by vacuum cooling (ICk-VC-VI). Both strategies were compared to processes of cooking followed by vacuum cooling (ICk-VC), and cooking followed by cold-chamber cooling (ICk-CC). The ICk-PIVC led to smaller global weight loss and cooling time (22.9%, 61min) as compared with the ICk-CC (25.3%, 82min) and to a cooling weight loss 76% lower than that observed to ICk-VC at the cost of a cooling time 54% larger. In contrast, the ICk-VC-VI permitted to obtain products with global weight loss (25.4%) and mechanical properties that are similar to those of fillets subjected to ICk-CC, while avoiding the larger cooling times of the ICk-PIVC.

Alkaline Peroxide in Synergy with Mechanical Refining as Factor in the Development of EFB Paper Properties

Pulp from the oil palm empty fruit bunches (EFB) was extracted via Alkaline Peroxide Pulping (APP). The pulping process was conducted through three main steps; dewaxing of EFB, impregnation of alkaline peroxide (AP) into EFB and refining of biomass to finally produce the pulp. The varying peroxide levels and number of impregnation stages were found to affect the refining energy consumption and the properties of the resultant pulp and paper. Diagnosis by electron microscopic imaging revealed a strong correlation between paper properties development and paper surface morphologies. By multiplying the stages of the low alkaline peroxide level (2:2.5% AP) impregnation, refining energy could be reduced by 30% while improving brightness and paper mechanical properties. Higher alkaline peroxide level (4:5% AP) could reduce the refining energy by 50% while still improving brightness. Beyond these AP levels (8:10% AP), refining energy could be reduced by 67% by increasing the number of impregnation stages, with positive effects on brightness and paper mechanical properties. The findings suggest that increasing the AP impregnation stages had exposed more active sites to react with AP. The enhanced AP accessibility to EFB structures facilitated mechanical fibrillation of EFB vascular bundles through the refining process. The proper synergy between AP and the adopted mechanical refining was the factor that triggered the liberation of nanocells from EFB biomass and this had ultimately improved paper properties.

Diffusion Dynamics in Pinus sylvestris Kraft Impregnation: Effect of Deacetylation and Galactoglucomannan Degradation

During the impregnation stage of a Kraft cooking, dynamic changes occur in wood properties due to the alkali action. Particularly, its ion transport capacity, the effective capillary cross sectional area (ECCSA), is changed due to chemical reactions and swelling. In this work, the ECCSA in the transverse wood direction has been determined for Pinus sylvestris on the basis of the analogy between capillarity and electrical conductivity. Results show that the behavior of ECCSA can be associated with (a) the degree of removal of native acetyl groups and (b) the galactoglucomannan (GGM) losses due to peeling/stopping reactions and alkaline hydrolysis. Kinetic expressions for both reactions were discussed and a correlation between the ECCSA and both acetyl and GGM contents was established.

Modeling of the simultaneous process of wet spinning-grafting of bast fibers using artificial neural networks

In this study we present the way in which the monochlorotriazinyl-β-cyclodextrin can be grafted on to bast fibers simultaneously with their wet spinning. The modeling of the process was realized by mechanical and chemical processing at different wet spinning-grafting parameters (concentration of β-cyclodextrin and speed of the material in the impregnation stage). The neural modeling of the studied process constitutes the main objective of this paper. In order to obtain physico-mechanical characteristics adequate for a bleached hemp yarn and an optimum grafting degree for the ulterior inclusion operation, it is necessary to establish a soaking time between 20 and 30 s and a solution concentration of 60 g/l monochlorotriazinyl-β-cyclodextrin.

Description of the initial stage of impregnation and extraction processes using a bidisperse model

A model for analyzing the process of impregnation and the inverse process of extraction for a porous solid with two types of pores is considered. The model is suitable for describing the process at small values of time. A solution to the problem with under most typical additional conditions has been obtained, and the kinetic function of impregnation (extraction) and the flux density of matter from the solid have been found.

Modeling of Alkali Impregnation of Eucalyptus Wood

In wood pulping processes, the quality of the impregnation stage has a significant influence on the final pulp properties. In this work, a refined version of a previously published model is used to analyze this operation stage. For liquor containing NaOH and Na 2 S, the study considers the reaction of wood acetyls and acidic groups. The Donnan effect is applied for analysis of ion concentrations in the wood-liquid interphase. The predicted concentration profiles are in acceptable agreement with the experimental results. The model is used afterward to simulate a batch or a cocurrent continuous kraft impregnation process. In the impregnating liquor, the alkali concentration is gradually reduced due to chemical reactions and alkali accumulation in the wood chips. The level of impregnation is finally analyzed considering different chip thickness values corresponding to an industrial chip stock sample.

Permeability Prediction in the Impregnation Stage of Resin Transfer Moulding

The impregnation stage of the Resin Transfer Moulding process can be simulated by solving the Darcy equations on a mould model, with a ‘macro-scale’ finite element method. For every element, a local ‘meso-scale’ permeability must be determined, taking into account the local deformation of the textile reinforcement. This paper demonstrates that the meso-scale permeability can be computed efficiently and accurately by using meso-scale simulation tools. We discuss the speed and accuracy requirements dictated by the macro-scale simulations. We show that these requirements can be achieved for two meso-scale simulators, coupled with a geometrical textile reinforcement modeller. The first solver is based on a finite difference discretisation of the Stokes equations, the second uses an approximate model, based on a 2D simulation of the flow.

Effects of impregnation time on hardwood kraft pulp characteristics and papermaking potential – a mill study

We conducted a series of trials in a commercial-scale pulp mill producing fully bleached birch hardwood kraft pulp to study the effects of impregnation time. Retention time in an impregnation vessel was altered between 5 min and 60 min. Cooking kappa number target and brightness targets were held constant and the rest of the fiber line was operated according to normal practices. After analyzing collected pulp samples to monitor changes in characteristics and papermaking properties, we found that impregnation time has a significant effect on the consumption of effective alkali in the impregnation stage, but the total alkali consumption was not affected when a cooking kappa number was held constant. Reduced impregnation time required higher cooking temperatures to reach the kappa number target. Shorter impregnation times clearly increased the amount of rejects. Viscosity, carbohydrate composition, and fiber saturation point were not significantly influenced by the impregnation time, but some fiber damage occurred with longer impregnation times. The tensile strength and tensile were higher with the shorter impregnation time, whereas tear strength at a given tensile index did not correlate with impregnation time. An obvious reason for the affected papermaking properties was not found.