High Solid Loading Research Articles

Comparative study on the mild pretreatment processes for enzymatic hydrolysis of wheat straw with high-solid loading

Comparative study on the mild pretreatment processes for enzymatic hydrolysis of wheat straw with high-solid loading

Additive manufacturing of Al2O3 ceramic core with applicable microstructure and mechanical properties via digital light processing of high solid loading slurry

Ceramic cores are essential intermediate mediums in casting superalloy hollow turbine blades. The developing of additive manufacturing (AM) technology provides a new approach for the preparation of ceramic cores with complex structure. In this study, alumina oxide (Al2O3) ceramic cores with fine complex geometric shapes were fabricated by digital light processing (DLP) in high resolution. The maximum solid content of 70 vol% of ceramic slurry was adopted in the printing process, which is important for the regulation of deformations and mechanical properties. The effects of the printing parameters, including exposure intensity, printing layer thickness and sintering temperature on the microstructures and mechanical properties of printed samples were investigated. The decrease of residual stress and similar shrinkage in X, Y, and Z directions could be obtained by adjusting the printing parameters, which are crucial to prepare complex ceramic cores with high quality. Besides, the flexure strength and open porosity of ceramic cores reached 34.84 MPa and 26.94%, respectively, which were supposed to meet the requirement of ceramic cores for the fabrication of superalloy blades.

3D printing of high solid loading zirconia feedstock via screw-based material extrusion

Zirconia ceramic (3Y-TZP) feedstocks with solid loadings from 50 vol% to 68 vol%, in a 60:40 paraffin wax to LDPE ratio binder system, were prepared and printed using a screw-based material extrusion printer. A two-step debinding process involving solvent debinding (cyclohexane + ethanol) and thermal debinding (140 °C–600 °C at 0.2 °C/min) followed by sintering at 1500 °C for 2 h was employed. Tests performed include TGA, density test, Vickers hardness and fracture toughness, XRD, and SEM. The TGA result showed two significant drops in weight starting at 180 °C and 380 °C, which corresponds to the decomposition of paraffin wax and LDPE, respectively. A minimum of 40 wt% of soluble binder was removed from the green sample after solvent immersion for 3 h at 40 °C for solid loadings ≥55 vol%. High solid loading feedstocks produced samples with comparable density, Vickers hardness and fracture toughness, which are 97.5%, ∼12.3 GPa, and ∼5.5 MPa m1/2, respectively; while XRD and SEM shows no adverse tetragonal to monoclinic phase transformation and grain growth, respectively. This study demonstrates that 3D printing of granular 3Y-TZP ceramic feedstock via screw-based material extrusion technique is feasible even with high solid loadings, which is usually difficult to fabricate into flexible filaments and print due to high viscosity.

Solid feeding and co-culture strategies for an efficient enzymatic hydrolysis and ethanol production from sugarcane bagasse

The feasibility of second-generation (2G) processes still highly depends on improvements in the hydrolysis and fermentation steps, ensuring the whole use of biomass sugars in an integrated approach. The main bottlenecks are the differences between the optimal conditions for both steps, limitations for high solid load (HSL) hydrolysis, and hexoses and pentose co-fermentation. To overcome these problems, the present work explored a feeding strategy to improve HSL enzymatic hydrolysis of hydrothermally pretreated sugarcane bagasse (PSB), at optimal and suboptimal temperatures, further integrated with a non-recombinant yeast co-culture (Saccharomyces cerevisiae and Kluyveromyces marxianus) for sugar co-fermentation. The entire PSB fraction was used without conditioning. Efficient enzymatic hydrolysis was achieved using a feeding strategy in a helical stirred bioreactor (64 and 75% cellulose conversion with 22.5% of solids, 72 h at 35 and 50 °C, respectively), obtaining hydrolysates with high glucose and xylose concentrations (100 g/L). Simultaneous saccharification and co-fermentation (SSCF) provided high glucose (98%) and xylose (52%) conversion in 24 deep-well plates, with ethanol yield of 0.23 getOH/gS, but faced problems of cell viability loss in the bioreactor. Sequential SCF (SqSCF) co-culture stood out as a promising strategy for the use of biomass sugars. The results of this study provide significant contribution to the intensification and feasibility of 2G production, in addition to highlighting the difficulties faced for process integration aiming at the full conversion of sugars coming from high solid load enzymatic hydrolysis.

Effects of the inlet particle spatial distribution on the performance of a gas-solid cyclone separator

The present study was aimed at the inlet particle spatial distribution of a gas-solid separator with high solid loading and investigated its effects on cyclone performance and the inner flow pattern. The flow fields of a cyclone with different rectangular particle flow areas on the inlet surface were numerically simulated using a four-way coupling method. The simulated results indicate that reducing the inlet particle flow area and lowing the inlet particle position can effectively reduce the scattered particles inside the cyclone separator and enhance the separation performance. Vertically gathering the particles to the centerline can also weaken the particle back-mixing. The particles near the roof account for the swirling particle ceiling phenomenon. The inlet particle spatial distribution affects the pressure drop mainly by affecting the gas tangential velocity in the cylinder body. Moreover, compared to the horizontal particle distribution on the inlet surface, the vertical particle distribution has greater effects on cyclone performance.

酸化スズナノ粒子サスペンションを用いたマイクロスケールのパターニング

This review focuses on our results on the fabrication of large-area patterning of tin oxide suspensions by the “micromolding in capillary” (MIMIC) method, one of the soft lithography techniques. Usually, suspensions with high solid loadings have been experimented, but since the filling mechanism of the MIMIC method is capillary action, the viscosity increases during the process, resulting in a smaller patterning area. We have confirmed that a low solids ethanol suspension of tin oxide nanoparticle can be used to achieve large-area patterning, forming a stripe pattern with a thickness of almost 1/3 the depth of the mold channel, resulting in a dense structure. Confirming the patterning mechanism, we found that controlling solvent evaporation during the process was very effective. It is expected that this MIMIC process for low solids loading suspensions of nanoparticles will be widely deployed for other types of ceramic suspensions.

3D Printing of Robust 8YSZ Electrolytes with a Hyperfine Structure for Solid Oxide Fuel Cells

Fully stabilized zirconia (8YSZ) has been considered a promising candidate for fabricating electrolytes of solid oxide fuel cells (SOFCs) due to the excellent oxygen ionic conductivity. Recently, structural optimization of a fully stabilized zirconia (8YSZ) electrolyte via vat photopolymerization (VP) technology has shown great potential in improving performance. Generally, preferable mechanical strength is required along with conductivity for the electrolyte structure. However, investigation on the mechanical properties of printed 8YSZ parts has been absent. Herein, an optimized 8YSZ photosensitive slurry was developed and the overall performance of the printed parts was tested systematically. The slurry with a high solid loading (50 vol %) exhibited a low viscosity (1.2 Pa·s, shear rate of 30 1/s). The printed parts showed superior mechanical (fracture toughness of 3.31 ± 0.38 MPa·m0.5, flexural strength of 372 ± 11 MPa) and electrochemical (ion conductivity of 4.03 × 10–2 S/cm at 800 °C) properties. Besides, the characteristic size of the prepared complex three-dimensional (3D) electrolyte structure was as small as 100 μm. Results indicated that the electrolytes achieved both comparable mechanical and electrochemical properties to those of conventional processes. Therefore, VP technologies open up an avenue for the fabrication of robust and geometrically hyperfine 8YSZ electrolytes with good electrochemical performance.

CFD simulation and experimental validation of multiphase flow in industrial cyclone preheaters

A hybrid multiphase model (Dense Discrete Phase Model, DDPM) coupled with a k-ω sst turbulence model, which includes gas–solid heat exchange was developed for the simulation of industrial-scale cyclone preheaters operating under high solid loadings. The model results are validated by experimental measurements from an industrial cyclone preheater with a diameter of 1.6 m, with respect to the pressure drop, gas and particle exit temperature, local gas velocity profiles, measured using the LDA, and gas temperature profiles, measured using thermocouple and FTIR. Reasonable agreement between the data from experiments and simulations was obtained. In addition, the major trends, such as changes in the pressure drop, overall heat transfer rate, and flow pattern, caused by the changes in the operating parameters can be captured accurately by the model.

Reduced power consumption in stirred vessel with high solid loading by equipping punched baffles

Solid–liquid suspension in stirred tank is a common operation in the chemical industry. The power consumption, flow pattern and flow field instability of three systems named as unbaffled stirred tank, traditional baffled stirred tank and punched baffled stirred tank (Pun-BST) were studied by using the computational fluid dynamic analysis. Results showed that perforating holes in the baffles could reduce power consumption of mixing. Meanwhile, the punched baffle system could maintain the solids in suspension as traditional baffle system. The results also showed that the baffles could increase the “effective flow” of stirred tank even though the whole velocity of the vessel is lower than un-baffled vessel. In addition, both the solid–liquid suspension and “effective flow” were related to instability of the flow field. Perfect solid–liquid suspension results always along with obvious instability of the flow field. But, the strengthening effect of punched baffle on flow field instability mainly happened in the near-wall area. It’s because the collision and aggregation among sub-streams induced by holes intensified the unstable fluid flow. On the whole, the Pun-BST system provided much better mixing characteristics and recommended to apply in the industrial process.

Microstructural evolution and tribological behavior of suspension plasma sprayed CuO as high-temperature lubricious coatings

Suspension plasma spraying (SPS) was used to produce three different CuO coatings by varying spray distance and solid loading within the suspension. The low spray distance (30 mm) and high solid loading (20 wt%) in the suspension resulted in the deposition of dense coatings as compared to other spray conditions (i.e., a distance of 40 mm and solid loading of 10 wt%). The tribological performance of the dense coating was investigated at 25 °C and 300 °C under dry sliding conditions. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman analysis were used to characterize the coating, and corresponding wear tracks to determine the wear mechanisms. The results showed that the friction coefficient of the CuO coating decreased from 0.7 at 25 °C to 0.46 at 300 °C. Similarly, the wear rate at 300 °C decreased by 50% compared to the wear rate at 25 °C. Ex-situ analysis showed an increased oxygen content on the worn surfaces at 300 °C and the formation of a smooth uniform tribofilm. At 25 °C, a thicker transfer film was observed on the counterface, which leads to a different velocity accommodation mode and, thus, relatively high friction.

Additive manufacturing of calcium carbonate parts through vat-photopolymerization and sintering in carbon dioxide atmosphere

Although calcium carbonate is more commonly used in powder form, it could have exciting applications in bulk form, such as bone scaffolds, synthetic corals, and artificial rocks. Additive manufacturing (vat-photopolymerization) is a promising strategy for producing parts with complex geometries. However, two main challenges arise: 1) Producing a CaCO3 suspension with high solid loading and low viscosity suitable to ordinary bottom-up 3D printers; 2) Debinding and sintering the CaCO3 parts without causing their thermal decomposition. The first challenge was addressed by following a systematic methodology to select the monomer and dispersant, resulting in a printable 35 vol% CaCO3 suspension with low viscosity (0.28 Pa s at 30s−1). The second challenge was overcome by debinding in air atmosphere to remove all organics, followed by sintering in CO2 above 500 °C to avoid the calcination of CaCO3. The presented results are an important advance for the fabrication of calcium carbonate parts with complex geometries.

Efficient high solid loading enzymatic hydrolysis of hydrogen peroxide/acetic acid-pretreated bamboo for monosaccharides production

High solid loading enzymatic hydrolysis (HSLEH) produces high sugar concentrations with low water and energy inputs. Adequate information has been provided to confirm the excellent enzymatic digestibility of pretreated bamboo biomass with the solid content below 10%. However, the utilization of bamboo biomass for producing high-concentration sugars solution via HSLEH is rarely reported. In this work, hydrogen peroxide/acetic acid (HPAC) pretreatment removed 79% of lignin from bamboo and HPAC-pretreated bamboo was rich in glucan (55.3%) and xylan (20.4%). In the HSLEH of HPAC-pretreated bamboo, xylanase could increase glucose production by 9.4%. Alkaline incubation could increase the glucose production of HPAC-pretreated bamboo by 6.3% and saved 75% cellulase. The addition of Tween 80 (0.03 g/L) could further increase the glucose production of HPAC-pretreated bamboo by 14.1%. As a result, 204.9 g/L glucose and 60.2 g/L xylose, corresponding to glucose and xylose yields of 75.8% and 65.4% respectively, were obtained from the resulting bamboo solid via 400 g/L HSLEH with 10 FPU cellulase/g dry matter and 0.03 g/L Tween 80, which was the highest concentration compared with the previous literatures. This work developed an integrated process to produce very high-concentration sugars solution from bamboo residue via HSLEH.

Solid state fermentation of mung beans by Bacillus subtilis subsp. natto on static, shaking flask and soft elastic tubular reactors.

Given that mung beans constitute a significant nutrient source in many cultures, it is worthwhile to investigate ways to improve their nutritional and functional properties. The effect of fermentation of mung beans by Bacillus subtilis subsp. natto was investigated in various reactor designs, including static, shaking flasks, and soft elastic tubular reactors (SETR). The results showed that all three processes might affect the substrate, resulting in changes in the protein and carbohydrate fractions. We noticed an increase in soluble protein and serine levels, which we attribute to the proteases produced during fermentation. Through XRD, FTIR, and DSC analyses, it was also discovered that whereas static and shaking flask fermentation might raise relative crystallinity and peak temperature, fermentation performed on the SETR decreased these values. It was also possible to notice that SETR might induce a change in the particle size distribution of the substrate through a complex impact of mechanical forces, mixing, and microbial activity, which could be helpful to some aspects of the process. To summarize, fermentation of mung beans by Bacillus. subtilis subsp. natto could be an attractive approach for producing a food ingredient with various functional and nutritional properties. Furthermore, the SETR has been shown to be a viable technique for dealing with high solid load substrates, whether as the reactor for the entire process or as a first stage/pre-treatment step, and its applicability in bioprocesses should be explored further.

Enzymatic Hydrolysis Strategies for Cellulosic Sugars Production to Obtain Bioethanol from Eucalyptus globulus Bark

Cellulosic sugars production for the valorization of lignocellulosic biomass residues in an industrial site has economic benefits and is promising if integrated into a biorefinery. Enzymatic hydrolysis (EH) of pretreated Eucalyptus globulus bark, an industrial residue of low-economic value widely available in Portuguese pulp and paper mills, could be an excellent approach to attain resource circularity and pulp mill profitability. This work evaluated the potential for improving cellulosic sugars concentrations by operating with high solids loading and introducing the additives Triton X-100, PEG 4000 and Tween 80 using a commercial enzymatic consortium with a dosage of 25 FPU gcarbohydrates−1. Additives did not improve enzymatic hydrolysis performance, but the effect of increasing solids loading to 14% (w/v) in batch operation was accomplished. The fed-batch operation strategy was investigated and, when starting with 11% (w/v) solids loading, allowed the feeding of 3% (w/v) fresh feedstock sequentially at 2, 4 and 6 h, attaining 20% (w/v) total solids loading. After 24 h of operation, the concentration of cellulosic sugars reached 161 g L−1, corresponding to an EH conversion efficiency of 76%. Finally, the fermentability of the fed-batch hydrolysate using the Ethanol Red® strain was evaluated in a 5 L bioreactor scale. The present results demonstrate that Eucalyptus globulus bark, previously pretreated by kraft pulping, is a promising feedstock for cellulosic sugars production, allowing it to become the raw material for feeding a wide range of bioprocesses.

Effective Fermentation of Sugarcane Bagasse Whole Slurries Using Robust Xylose-Capable Saccharomyces cerevisiae

The pre-treatment of lignocellulose material towards cellulosic bioethanol production releases microbial inhibitors that severely limit the fermentation ability of Saccharomyces cerevisiae. This study evaluated to what degree robust xylose-capable strains may improve the fermentability of non-detoxified sugarcane bagasse (SCB) slurries derived from steam explosion (StEX) and further compared this to slurries derived from ammonia fibre expansion (AFEX) pre-treatment. Initial screening in separate hydrolyses and co-fermentation processes using StEx-SCB hydrolysates identified S. cerevisiae TP-1 and CelluXTM4 with higher xylose consumption (≥ 88%) and ethanol concentrations (≥ 50 g/L), and ethanol metabolic yields (≥89% relative to theoretical maximum), even in the presence of approximately 8 g/L of acetic acid. Under industrially relevant pre-hydrolysis simultaneous saccharification and co-fermentation (PSSCF) conditions of high solids loading (15%, w/w) and low enzyme dosage (8 mg protein per gram untreated biomass), the fermentation of StEx-treated SCB whole slurry achieved ethanol yields of 208 and 224 L per Mg raw dry SCB using S. cerevisiae TP-1 and CelluXTM4, respectively. Under the same solids loading and enzyme dosages, the PSSCF of ammonia fibre expansion (AFEXTM) pre-treated SCB achieved ethanol yields of 234 and 251 L per Mg raw dry SCB using TP-1 and CelluXTM4, respectively. The study achieved non-detoxified whole-slurry co-fermentation using StEx pre-treated SCB, with higher ethanol yields than previously reported, by utilising robust xylose-capable strains. The results of this work provide insights into the potential use of inhibitor-tolerant S. cerevisiae strains TP-1 and CelluXTM4 as ethanologens for the fermentation of steam-exploded and undetoxified SCB whole slurries.

Integration of surface modified aqueous ink for multi-functional material extrusion

The possibility to construct functional materials with designed shapes via 3d printing involves higher flexibility in the next-generation of our device. In order to formulate stable colloidal suspension with high solid loading, water-based ink allows particles dispersion by tuning surface chemistry. But it has been limited by material solubility in water. Moreover, tailoring ink formulation of different materials will increase the feasibility of wider materials combinations. Here, a facile method of polyvinylpyrrolidone coating of starting functional materials is been utilized, illustrating with zinc oxide as an example. Inks made with surface modified powder shows a typical shear thinning behavior. In addition, the printed samples are employed as adsorbents for removal of gaseous HCHO, and the sample with higher capping agent molecular weight offers better adsorption performance compared to other samples. Furthermore, compared with commercial Co Foam, the Tafel slope of the 3D Co is only 116.1 mV dec−1, exhibiting good hydrogen evolution reaction electrocatalytic kinetics, and demonstrating its wide potential in electrocatalytic field.

Manufacturing and Characterization of Dental Crowns Made of 5-mol% Yttria Stabilized Zirconia by Digital Light Processing.

We herein report manufacturing of dental crowns made of 5-mol% yttria partially stabilized zirconia (5Y-PSZ) with desired mechanical properties, optical translucency and dimensional accuracy using digital light processing (DLP). To this end, all processing parameters were carefully controlled and optimized. First, 5Y-PSZ particles with a bimodal distribution were prepared via calcination of as-received granules and subsequent ball-milling and then used to formulate 5Y-PSZ suspensions with a high solid loading of 50 vol% required for high densification after sintering. Dispersant content was also optimized. To provide high dimensional accuracy, initial dimensions of dental crowns for 3D printing were precisely determined by considering increase and decrease in dimensions during photopolymerization and sintering, respectively. Photopolymerization time was also optimized for a given layer thickness of 50 μm to ensure good bonding between layers. A multi-step debinding schedule with a slow heating rate was employed to avoid formation of any defects. After sintering at 1500 °C for 2 h, 5Y-PSZ could be almost fully densified without noticeable defects within layers and at interfaces between layers. They had high relative densities (99.03 ± 0.39%) with a high cubic phase content (59.1%). These characteristics allowed for achievement of reasonably high mechanical properties (flexural strength = 625.4 ± 75.5 MPa and Weibull modulus = 7.9) and % transmittance (31.4 ± 0.7%). In addition, 5Y-PSZ dental crowns showed excellent dimensional accuracy (root mean square (RMS) for marginal discrepancy = 44.4 ± 10.8 μm and RMS for internal gap = 22.8 ± 1.6 μm) evaluated by the 3D scanning technique.

One-pot generation of lignin microspheres and digestible substrate with a polyol-DES pretreatment in high solid loading

Previous lignin microspheres (LMS) preparation needs multiple steps with very low yield and high cost. Herein, we developed a high-solid deep eutectic solvent (DES) pretreatment for an effective lignin fractionation and enzymatic saccharification of moso bamboo under mild temperature (110 °C) with high-solid loading. Lignin was significantly removed from the plant cell wall, and cellulose properties (e.g., crystallinity and degree of polymerization) were also altered during the pretreatment. As a result, the enzymatic digestibility of the pretreated bamboo was dramatically increased. Uniform micro-spherical lignin was directly produced from the pretreatment system, and its particle size could be regulated by controlling the solid loadings and pretreatment temperatures. The lignin microspheres formation mechanism was investigated by analyzing the lignin's size distribution, molecular weight distribution, chemical structure, and hydrophobicity. The DES showed excellent recyclability, and the recycled DES could still remove 42.78% lignin even after 7th circulation associated with 100% glucan saccharification. The mass balance based on 1000 g biomass showed that 196.28 g LMS was directly recovered, which exhibited a high RhB adsorption. Besides, 404.91 g glucose and 36.67 g xylose were obtained after the enzymatic saccharification process. Specifically, GAPI analysis exhibited a near total green and yellow portions of the pictogram, indicating our DES process was green enough to make this biorefinery sustainable. Overall, the proposed DES generated synergistic productions of digestible solid and LMS which could contribute to establish a green and sustainable biorefinery sequence with diverse outputs in one pot.

Radial flow tubular membrane bioreactor for enhanced enzymatic hydrolysis of lignocellulosic waste biomass

A tubular membrane bioreactor was used for enhanced enzymatic hydrolysis of waste biomass, palm date seeds. The bioreactor successfully handled high solid loadings with effective simultaneous product removal. The effects of substrate concentrations, 14.3, 21.4, and 39.6 g/L, and water flowrates, 0.4, 0.8, and 1.2 mL/min, on the production of total reducing sugars were examined. At substrate concentration of 21.4 g/L, the total reducing sugars yield increased from 28.9 % to 42.7 % after 8 h as the water flowrate increased from 0.4 to 1.2 mL/min. Substrate inhibition was observed at the highest tested substrate concentration of 39.6 g/L. A dynamic model was developed to describe the designed bioreactor, accounting for the simultaneous product separation and the dynamic changes in substrate structure. The nonhydrolyzable substrate fraction parameter was found to significantly affect the model prediction. The novel membrane bioreactor and the developed model enable the industrial valorization of lignocellulosic biomass for bioethanol production.

Techno-economic assessment and life cycle assessment of three potential pathways for biomass liquefaction

Biomass liquefaction can enhance corn-stover slurry transportation by reducing yield stress and overall viscosity, easing biomass handling, especially for slurries at high solids loading (≥30 % (w/v). Implementing a liquefaction process at the front-end of the biorefinery could reduce downtime caused by equipment fouling. Furthermore, liquefaction reduces process complexity by transforming high fiber mass into a pumpable slurry. Three scenarios for liquefaction of corn stover pellets: enzyme process, enzyme mimetic process, and a combined process of enzyme and enzyme mimetic were assessed.The ideal process will have the best performance-to-cost ratio, with minimal impact on the environment. Techno-economic and life-cycle analyses were used to understand the economic and environmental effects of the three liquefaction scenarios and to determine if one or more can achieve cost parity. Results show that the enzyme process had the best performance in terms of cost and emissions (gCO2-equivalent/kg slurry) compared to the other scenarios.