Innovative sustainable products can contribute to slowing climate change while simultaneously driving economic growth. In this study, we describe a ‘green’ technology to produce a porous, lightweight cellulose-mycelium foam (CMF) in which fungal mycelium is grown for applications such as filtration, packaging, and bioremediation. Fluorescent microscopy revealed incomplete fiber degradation after 25 days of fungal growth, and that mycelium grew along fibers and within the pores of the CMF. The physio-mechanical properties of the CMF were investigated via compressibility, thermogravimetric analysis, and dry and wet tensile strength for samples grown for 0, 15, and 25 days. Thermal stability increased with mycelium growth, showing extrapolated onset temperatures of 227.5 °C, 312.7 °C, and 325.5 °C for 0, 15, and 25 days, respectively. Tensile strength and compressibility were notably improved with mycelial growth. CMF permeability, filtration efficiency, and pressure drop were tested, and we observed a decrease in permeability with mycelium growth in foam fiber, and hydraulic filtration efficiency measured 99.9% for particles sized 20 µm or larger. Living CMF neutralized potassium hydroxide leaks from alkaline batteries, decreasing pH from 12 to 6 over a 60-day period. These results demonstrate a wide range of material improvements, showing promise for practical filtration, thermal insulation, and bioremediation applications while being both sustainable and biodegradable.

We develop a multi-objective economic model predictive control (m-econ MPC) framework to control and optimize a nonlinear mechanical pulping (MP) process. M-econ MPC interprets economic MPC as a multi-objective optimization problem that trades off economic and set-point tracking performance. This interpretation allows us to construct a stabilizing constraint that guarantees closed-loop stability. The framework infers unmeasured states of the MP process (associated with product consistency) by using a moving horizon estimator (MHE). The MP process dynamics are described by using a nonlinear Wiener model. Examples from a two-stage high-consistency MP process are employed to demonstrate that significant improvements in economic performance are achievable.

Hydrocyclones are widely employed in both heavy and light industries. However, exact mechanisms underlying enhanced-separation technologies developed by optimizing operating parameters and conditions in hydro cyclones remain unclear. Accordingly, many research groups have conducted numerous investigations to expand the application range of hydrocyclones by optimizing operating parameters and conditions. This paper presents a comprehensive state-of-the-art review of the aforementioned hydrocyclone enhanced-separation technologies, which are classified into two groups: (i) operating parameters, including feed flow rate, feed pressure, feed density difference, feed particle parameters (concentration, size, shape, and arrangement), and feed fluid parameters (viscosity and rheology); and (ii) operating conditions, including electrical hydrocyclones, magnetic hydrocyclones (electromagnetic field and permanent magnetic field), magnetic fluids hydrocyclones, electro-chemical hydrocyclones, flocculant-assisted hydrocyclones, hydrocyclones enhanced by flotation, hydrocyclones enhanced by control particles; hydrocyclones enhanced by adjusting back pressure, and hydrocyclones enhanced by monitoring and automatic control. These enhanced-separation technologies were analyzed and summarized based on the critical separation-performance parameters, such as separation efficiency, cut size, split ratio, energy consumption, capacity, and separation sharpness. It is hoped that both reviewed contents and proposed challenges may be helpful to the researchers and eventually yield some perspective knowledge, which results in the improvement of economic feasibility of separation by hydrocyclones.

The effect of fibre length on the yield stress of recycled old corrugated containers (OCC) pulp fibre suspensions was investigated. Two types of OCC pulps were divided into four fractions based on the fibre length with a Bauer-McNett classifier. The yield stress of each fraction was measured using the shear stress ramp method at pulp consistency ranging from 0.5% to 2.5% (w/v). The results showed that both pulp consistency and fibre length had significant effects on the yield stress of OCC pulp suspensions, and the yield stress was greater with increasing fibre length and pulp consistency. Moreover, the effect of consistency in OCC pulp suspension with long fibres on the yield stress was stronger than in the slurry with short fibres.

Bleached NBSK (Northern Bleached Softwood Kraft) pulp was fractionated using a pilot pressure screen. Then the fractionated fibres were characterized using a Fibre Quality Analyzer (FQA) and Scanning Electron Microscope (SEM). It was found that the mean fibre length and width significantly decreased after fractionation. Aspect ratio (length divided by width) of the fractionated fibres was lower than NBSK fibres. The SEM analysis indicated that the diameter of the NBSK fibres was in the range of 100 to 200 mm, while the fractionated fibre diameters were found to be 10 to 40 nm. The fibre length of the fractions varied from a few hundred nanometres to a few micrometres. The fractionated fibres were incorporated into sodium alginate-based biodegradable films during solution casting. It was found that the fractionated fibres significantly improved the mechanical properties of the sodium alginate films.

Primary refined coarse softwood thermomechanical pulp was treated with alkaline peroxide prior to low-consistency (LC) refining. The effects of the pre-treatments on pulp quality, refinability, and electrical energy consumption were assessed. Four pre-treatments were conducted with alkali charges of 2.5 and 6% and peroxide charges of 3 and 4%. The pulps were refined to specific energies up to 600 kWh/t by multiple passes through an LC refiner at intensities of 90 and 150 kWh/t. It was found that alkaline peroxide treatments increased tear strength and protected the fibre from cutting, especially during high intensity refining below a specific energy of 300 kWh/t. Treatment with 6% NaOH and 4% or 3% H2O2 led to lower brightness gains and scattering coefficients but increased the tensile strength index by 31%, potentially lowering the total electrical energy required to achieve strong pulp. The enhancement of tensile strength caused by the highly alkaline peroxide mostly resulted from increased bonding, which was attributable to acid group generation rather than the promotion of further fibrillation during LC refining.

A novel methodology was used to create a highly porous foam-formed paper that is bonded with highly refined cellulose fiber. In this process, cellulose pulp suspension at various consistencies (0.5, 1.0, 1.5, and 2%) was dispersed in water, followed by foam formation under high shear forces in the presence of a surfactant. Various drying methods were used to achieve foam formation. These included freeze-drying (FD), vacuum-dewatered air-drying (VAD), and dewatered freeze-drying (VFD). Increasing the pulp's consistency and changing the drying techniques from freeze-drying to air-drying resulted in a more compact morphological structure and increased density of foam-formed paper samples. Densification of foam-formed samples was measured using a Dynamic Mechanical Analysis (DMA) machine and a sample with densification at lowest strain value was obtained by a 10 wt% addition of microfibrillated cellulose fiber (MFC). At 10 wt% MFC addition, denser foam-formed paper samples with enhanced microstructure were obtained. Air filtration efficiency and acoustic properties of foam-formed paper were also characterized and optimized by the addition of MFC.

Latency removal in the mechanical pulping process occurs in a continuous stirred-tank reactor and non-ideal mixing lowers the performance. In order to optimize the latency removal process and reduce the energy consumption in the operation, a kinetic study was carried out. In the study, the phenomenon of latency and knowledge related to latency removal were critically reviewed and discussed. Latency removal was characterized by the change of Canadian Standard Freeness (or freeness), and its dependences on treatment conditions, i.e., disintegration temperature, power input, pulp consistency and time, were determined. Kinetic models of latency removal for secondary refiner thermomechanical (TMP) and bleached chemithermomechanical (BCTMP) pulps have been developed, which were based on the rate of latency elimination characterized by the decrease of freeness.

To study the influence of mechanical treatments on the yield stress of chemical pulp suspensions, a traditional rheometer, coupled with local velocity measurements (ultrasonic Doppler velocimetry), was used to measure the yield stress of two types of commercial chemical pulp suspensions with different freeness values at mass concentrations (consistencies) ranging from 0.5 to 1.5%. Over the range of consistencies tested, the yield stress was found to depend on the consistency through a power law relationship for all tested samples. Moreover, the results showed that as the freeness decreased, the yield stress of hardwood suspensions increased to a maximum value then decreased. This variation in yield stress was also observed in softwood suspensions with mass concentrations above 1%. However, when the consistency was lower than 0.75%, the yield stress of softwood suspensions increased with decreasing freeness.This behaviour can be understood based on the underlying fibre properties of fibrillation, curl, and stiffness, suggesting that fibre morphology plays a significant role on the yield stress of pulp suspensions over the concentration range studied.

ABSTRACTA series of cellulose acetate (CA) ternary system solutions consisting of the CA, N,N‐dimethylacetamide, and various nonsolvents, such as 1‐propanol, 1‐hexanol, 1‐octanol, 1‐decanol, 1,3‐propane diol, and glycerol, were prepared, and the effects of the component composition on the solutions characteristics and electrospinning were examined. In particular, the effects of the nonsolvent concentration, structure, and degree of miscibility with other components were studied. In some cases, increasing the nonsolvent content increased the solution viscosity and facilitated the electrospinning process. However, we found that electrospinning was also governed by the structure of the nonsolvents and by the solution viscosity. An increase in the number of hydroxyl groups or an increase in the hydrocarbon chain length of the monohydroxyl alcohol nonsolvent improved the fiber formation. The calculated Hansen sphere [D(S‐p)] values of the CA ternary system solution were then used to explain their electrospinnability. The increases in the hydrophilicity and hydrophobicity of system caused by changes in the nonsolvent structure increased the D(S‐p) values and improved fiber formation in electrospinning process. The calculated D(S‐p) values were also shown to be in good agreement with the obtained microscopy images of the electrospun fiber. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42819.

•We examine the effect of plug during transitional flow for a fibre suspension.•Using UDV, we estimated the yield stress and Reynolds stress of the suspension.•With increasing Reynolds number the plug of fibres diminished in a complex manner.•The plug size scales with the ratio of the Reynolds stress to yield stress.•The yield stress varied non-monotonically with flow rate for each suspension tested.

Turbulent drag reduction has been observed to occur over a wide range of additive systems, such as solution of synthetic or natural polymers, and fibre suspensions. In this study, the influence of softwood kraft pulp fibres and synthetic polymer additives on turbulent drag reduction (DR) in a hydrocyclone is investigated. It was demonstrated that cellulose fibre suspensions and aqueous polymeric solutions reduce the fluid energy losses in comparison to water during hydrocyclone operation within the range of reject ratios studied. A maximum drag reduction of 58 % and 55 % was found to occur at a volume split fraction of 50 % for a 0.9 % fibre suspension and a 300 ppm anionic polyacrylamide solution, respectively. Polymer degradation or polymer chain decay displayed adverse effects for 100 ppm and 150 ppm solutions after 22 min of run time at 11.2 kW pumping power and a reject ratio of 25 %. Synergistic effects were observed with pulp suspensions containing both cationic and anionic polyacrylamide (CPAM and APAM, respectively); a maximum DR of 41 % was observed for a 0.7 % fibre suspension containing 100–300 ppm of polymer at a reject ratio of 50 %. Similarly to aqueous polymer solutions, the degradation of 300 ppm APAM or CPAM in a 0.7 % fibre suspension decreased the observed DR up to 38 % after 30 min of run time at 11.2 kW pumping power and a reject ratio of 25 %. The near 43 % reduction in CPAM concentration, due to surface adsorption, when present in a 0.7 % fibre suspension assisted in quantifying the DR variations observed between suspensions containing APAM or CPAM.

Microfibrillated cellulose (MFC)-reinforced sodium alginate-based biodegradable films were prepared by solution casting. The MFC content of the alginate films varied from 3% to 20% by weight. The tensile strength, tensile modulus, stretch, and tear resistance of the neat alginate films were found to be 52 MPa, 2.15 GPa, 6.8%, and 243 mN respectively. It was found that for 10% loading of MFC in alginate films, the strength of the films increased by 57.7%, but the alginate films kept their inherent transparency. Surface morphologies of the prepared films were investigated using scanning electron microscopy (SEM) and suggested homogeneous mixing of MFC with sodium alginate in aqueous media. Results revealed that MFC acted as a strong reinforcing agent for sodium alginate-based biodegradable films for packaging applications.

Low consistency refining is primary means of improving the paper quality by imparting energy to fibres through repeated fibre–bar interactions. Useful part of the energy modifies the morphology of fibres and the remaining, no-load power, overcomes the hydraulic, pumping and mechanical losses in the refiner. In this study, effect of consistency, operational and plate design parameters on no-load power was experimentally determined on two pilot scale refiners with different diameters. Obtained data were used to provide a statistical model for prediction of no-load power. To study the effect of diameter and groove depth, no-load power of some mills were collected.

Turbulent flow over a rough wall with suction or blowing is an industrially important fluid mechanics problem. In the screening of wood pulp fibre suspensions, for example, turbulent flow is induced by a rotor adjacent to a slotted screen cylinder. To better understand the complex hydrodynamics in the critical region between the pulp screen rotor and the slotted screen wall, the stream-wise velocity and aperture velocities were measured using particle image velocimetry. The vortex generated above the aperture is shown to be strongly dependent on aperture velocity and wall roughness. The vortex diminishes in size at higher aperture velocities and increased exit layer height. The experiments also show that the reversal flow in the slot decreases with lower rotor speeds and increased mean slot velocities. This observation challenges the existing models of apertures being cleared by flow reversal driven by a Bernoulli-type suction pulse. In its place, this paper identifies elements of a more sophisticated flow model that considers the depletion of the zone below the rotor as well as the flow in the wake of the foil.

A novel methodology for estimating the area and perimeter of intersection between two or more intersecting surfaces, without having to determine or order the points of intersection, is presented. No restriction is placed on complexity of the intersecting geometry except that it must represent a closed region. This method is well-suited for cases in which the area and perimeter of intersection are complicated, are not strongly peaked in a very small region, and when relatively low accuracy is tolerable. In this study, we examine the time-dependent evolution of the area and number of bar crossings for 320 different low consistency refiner plate configurations with similar geometrical patterns for stator plate and rotor plate using this methodology. Empirical correlations are presented to relate the plate parameters to bar intersection area. Finally, we interpret our findings in terms of the industrially accepted parameters used to characterize the action of refiner plates.

The objective of this study was to reduce energy demand in the mechanical pulp refining process by substituting second stage high consistency (HC) refining with two stages of optimised low consistency (LC) refining. Primary refining of Spruce-Pine-Fir wood chip mix was carried out using the Advanced Thermo-Mechanical Pulp (ATMP) refining process employing mechanical chip pre-treatment in the RT Pressafiner and Fiberizer prior to highintensity refining with the addition of 3.1% bisulphite. A portion of the primary pulp was subjected to a second stage HC refining, and the other part subjected to two stages of LC refining. The results indicate that the two stages of optimised secondary LC refining reduced the gross refining energy by approximately 300 kWh/odt compared to second stage HC refining. The target tensile index of 40 Nm/g required approximately 1450 kWh/odt of gross HC refining energy, and only 1150 kWh/odt using primary HC followed by secondary LC refining. Compared to HC-refined pulps, at a tensile index of 40 Nm/g, the LC-refined pulps had a similar freeness, light scattering coefficient and density, but lower TEA, stretch, tear index and average fibre length. The different pulp properties are believed to originate from the different fibre length distributions resulting from these two refining methods.

As part of a program to reduce electrical energy consumption in the refining process, the effects of the ozone and alkaline peroxide treatments on fibre and handsheet properties, prior and subsequent to low consistency (LC) refining, were assessed and compared by applying different levels of ozone and a range of peroxide and alkali charges to a primary stage hemlock thermomechanical pulp (TMP). Both highly alkaline peroxide treatments and ozone treatments decreased the specific energy required for strong mechanical pulp. The improvement in pulp strength through alkaline peroxide treatment mainly resulted from pulp surface changes caused by generation of acid groups. The highly alkaline peroxide treatments significantly increased pulp brightness but did not promote the further fibrillation during the subsequent LC refining. On the other hand, ozone treatments provided tensile strength increases, along with small brightness enhancements for the dark hemlock TMP, and increased the tensile gains obtained through LC refining. The effects of ozone treatments on tensile strength before and after LC refining were the result of pulp surface modifications, fibre swelling, and loss of fibre wall integrity due to non-selective chemical attack. High levels of ozone treatment caused tear strength to decrease during subsequent LC refining.

We consider the linear stability of both Newtonian and Bingham fluids in spiral Poiseuille flow in the annular gap between two co-rotating cylinders using the method of normal modes. Only axisymmetric disturbances are considered. We find that for the Newtonian case, linear instability does occur but the margin of stability increases with increasing Re-0. For the Bingham fluid case, we find the eigenvalue problem to be linearly stable over the range [Re-z, Re-0, eta] is an element of [0, 10000] x [0, 5000] x [0.75, 0.9], where Rez is axial Reynolds number, Re-0 is the tangential Reynolds number and eta is the ratio of inner to outer radius of the annular gap and we believe that the flow is linearly stable for all B > 0 where B is Bingham number. In the limit of B -> 0, we demonstrate that we cannot recover the results for the Newtonian fluid. The stability behaviour is singular in this limit and we show that this arises from imposition of boundary conditions for the Bingham fluid eigenvalue-problem at the unperturbed yield surface position, rather than any other effect of the yield stress. (C) 2012 Elsevier B.V. All rights reserved.