High Solid Loading Research Articles

Impact of anthracite blending and SDS addition on slurryability and stability of Indian high ash coal water slurry

ABSTRACT The conventional modes of transporting coal frequently result in substantial fiscal challenges and environmental deterioration. Slurry-based hydraulic transportation of coal through pipelines has proven to be a feasible and efficient method, offering economic benefits, reliability and minimal ecological damage. Due to the limited and rapidly depleting reserves of high-rank coal, the scientific community is compelled to utilize high ash coal (HAC) to meet the growing demands of the population. The HAC slurry is characterized by poor slurryability, stability and low calorific value. This research presents a straightforward solution to enhance the slurryability and stability of Indian HAC while improving its calorific value. Anthracite and anionic additive sodium dodecyl sulfate (SDS) were added in Indian HAC to prepare a high solid loading blended slurry with improved stability. The rheological characteristics, stability and zeta potential of prepared slurry samples were assessed and analyzed to determine the optimum anthracite proportion and SDS concentration. The optimum anthracite proportion and SDS concentration for low apparent viscosity and maximum stability were 30% and 0.6%, respectively. The inclusion of anthracite and SDS at optimal proportion yielded a slurry with 66% solid concentration, indicating a surge of 14% in the maximum possible solid loading.

Effect of sintering temperature on the microstructures and mechanical properties of ZrO2 ceramics fabricated by additive manufacturing

The optimization of the sintering process for ceramic stereolithography-based additive manufacturing is attracting high interest important due to its correlation with the final properties of the fabricated parts. In this work, a photosensitive zirconia suspension with low viscosity and high solid loading (48 vol%) was prepared using surface-modified zirconia ceramic powders, resulting in an improvement in long-term stability. The correlations between the sintering temperature (1400–1520 °C) and mechanical properties were investigated. The results showed that and the as-sintered zirconia parts exhibited a relatively high density of 99.5 ± 0.1 % and three-point flexural strength of 821 ± 65 MPa as well as excellent fracture toughness (4.37 ± 0.22 MPa m1/2) sintering at 1480 °C, which was attributed to the highly homogeneous microstructure without obvious pores or crack. The obtained insights regarding the correlation between sintering temperature, relative density, and flexural strength can provide practical guidance for the future applications of zirconia ceramics.

A novel eco–friendly solid–state degumming method for extraction of hemp fibers

Hemp represents a valuable resource of natural fibers on account of its environment favorable characteristics and excellent fiber quality. To fabricate hemp fibers, the traditional alkaline boiling degumming is used in the industry, which consumes a lot of water and generates a substantial amount of wastewater. In the present study, a novel eco–friendly solid–state degumming method was developed by using ethanolamine (ETA). The ETA degumming exhibited a high lignin removal rate (87.5%) at a high solid loading (30%), decreasing water consumption by 33.3%. Moreover, the ETA solution was readily reused up to five times without purification. The degummed hemp fibers possessed commendable fitness (4.2 dtex) and breaking strength (3.75 cN/dtex) without change of the crystalline cellulose structure. Besides, the lignin in wastewater was confirmed to be aminated, which is beneficial to the potential valorization of the by–product. Thus, the solid–state ETA degumming method holds significant potential for the fabrication of hemp fibers.

Optimisation study of Ulmus pumila woody biomass fractionation by steam explosion for bioproducts production

Ulmus pumila represents a promising lignocellulosic biomass source for biofuels and bioproducts production since it can grow in low rainfall and extreme temperature zones. A first step in the conversion process is biomass fractionation to enhance the performance of the hydrolysis and subsequent biological conversion steps. The aim of this work is to optimise the main variables (temperature, residence time and the addition or not of sulphuric acid) of steam explosion to pretreat Ulmus pumila biomass. The optimal conditions to maximise both glucose and xylose recovery were 204.8 °C and 30 mg H2SO4/g biomass, obtained through a multilevel factorial design of experiments. Additionally, enzymatic hydrolysis using high solid loads (15% and 20% (w/w)) and different enzyme doses was studied. As a result, steam explosion at optimal conditions followed by enzymatic hydrolysis with 20% solid loading and 60 mg protein/g cellulose of enzyme allow the recovery of 70% of the potential sugars.

Enhanced ethanol production from paper sludge waste under high-solids conditions with industrial and cellulase-producing strains of Saccharomyces cerevisiae

Reported ethanol titres from hydrolysis-fermentation of the degraded fibres in paper sludge (PS) waste, generally obtained under fed-batch submerged conditions, can be improved through fermentation processes at high solids loadings, as demonstrated in the present study with two industrial PS wastes at enzyme dosages appropriate for solids loadings up to 40% (w/w). The industrial yeast,Saccharomyces cerevisiaestrain Ethanol Red®, was compared to two genetically engineeredS. cerevisiaestrains, namely Cellusec® 1.0 and Cellusec® 2.0, capable of xylose utilisation, and xylose utilisation and cellulase production, respectively. High-solids batch fermentations were conducted in 3 L horizontal rotating reactors and ethanol titres of 100.8 and 73.3 g/L were obtained for virgin pulp and corrugated recycle PS, respectively, at 40% (w/w) solids loading using Ethanol Red®. Xylose utilisation by Cellusec® 1.0 improved ethanol titres by up to 10.3%, while exogenous cellulolytic enzyme requirements were reduced by up to 50% using cellulase-producing Cellusec® 2.0.

Microstructure and properties of silicon nitride ceramics fabricated by vat photopolymerization in combination with pressureless sintering

Silicon nitride (Si3N4) ceramics have been successfully manufactured using vat photopolymerization (VPP) technology. The formulated photocurable paste achieved a high solid loading (48 vol%) while maintaining low viscosity (3.2 Pa s at a shear rate of 30 s−1). Si3N4 ceramics doped with Al2O3–Y2O3 sintering aids were prepared using pressureless sintering at different temperatures (1650 °C, 1700 °C and 1750 °C) for 2 h. The resultant material exhibited a flexural strength of 613.3 ± 53.1 MPa, Vickers hardness of 12.6 ± 0.4 GPa, and a fracture toughness of 7.5 ± 0.3 MPa m1/2. X-ray diffraction (XRD) analysis has demonstrated a complete transformation from α-Si3N4 to β-Si3N4 at a sintering temperature of 1750 °C, where the resultant ceramic exhibited distinctive grain growth anisotropy. By investigating the shrinkage at different sintering temperatures, the sample at 1750 °C has a larger shrinkage in the Z-direction, which is also related to its anisotropic grain growth. Scanning electron microscopy (SEM) images have revealed the presence of elongated grains at a sintering temperature of 1750 °C. The combined effect of elongated grains and growth anisotropy serves to significantly enhance the overall mechanical properties of the material. This study advances current research on the preparation of high-performance Si3N4 ceramics by combining VPP technology with pressureless sintering.

Fabrication and characterization of ZrO2(3Y)/Al2O3 micro-ceramic gears with high performance by vat photopolymerization 3D printing

To date, overcoming the trade-off between high solid loading and print accuracy and strength, achieving high-performance and fine ZrO2 micro-ceramic components through vat photopolymerization 3D printing remains challenging. In this study, the effects of dispersant, particle size and solid content on the dispersion, rheological behavior and stability of ZrO2 ceramic slurry were systematically studied, and complex, fine and high-performance ZrO2 micro-ceramic gears were successfully prepared. Then, the microstructure, mechanical properties, tribological properties and surface quality were evaluated. The results show that the rheological behavior of the slurry is the best when the optimal dispersant content is 3.5 wt%. With the increase of solid content, the sintering shrinkage of ZrO2(3Y)/Al2O3 ceramics decreased, while the relative density, compressive strength, flexural strength, fracture toughness and hardness increased. The prepared micro-ceramic gears not only have fine structure, but also have dense microstructure and good mechanical properties. The relative density, compressive strength, flexural strength, fracture toughness and hardness strength of ZrO2(3Y)/Al2O3 ceramics can reach 98.53 %, 1900 MPa, 648 MPa, 6.4 MPa × m1/2 and 13.40 GPa, respectively. In particular, this study couples the printing accuracy and strength with the solid load. By adjusting the relationship between the fixed load and the shrinkage rate, the printing of samples with different sizes is realized, which breaks through the accuracy limit of the printing equipment and provides a new idea for the preparation of micro-ceramic gears.

Additive manufacturing of composite glass/ceramic structures with self-similar geometries

The Hilbert curve fractal pattern was used to create a self-filling structure with designed porosity that would be ideal for applications such as biomedical components, circuit boards, and building materials. 3-Dimensional Hilbert curve structures were designed and analysed by Finite Element Analysis for various functions in fluid transport, heat transfer, and structural applications. A bespoke glass/zirconia composite paste was optimised for the fabrication of these structures by ceramic stereolithography, achieving a thixotropic photosensitive paste with a high solid loading of 69 %. Optimisation of process parameters and sintering schedule was carried out to allow accurate fabrication of the composite glass/zirconia structures. 3-Dimensional Hilbert curve structures were successfully fabricated by stereolithography and the designed structures have potential uses as highly efficient components in various industries.

Development and optimization of PZT suspensions with high solid loading and low viscosity for stereolithography-based additive manufacturing

Achieving synergy between high solid loading and low viscosity for ceramic suspensions a critical issue in the field of stereolithography. In this work, we successfully obtained a well-dispersed PZT suspension with high solid loading (55 vol%) and low viscosity (3047.5 mPa s at 60 rpm) by adding appropriate amounts of dispersant (1 wt% KOS110) and thickening agent (2 wt% PEG300), providing a foundation for crack-free photosensitive lead zirconate titanate (PZT) samples. This work presented a simple approach for achieving synergy between the high solid loading and low viscosity of ceramic suspensions for stereolithography-based additive manufacturing.

Optimisation and application of high solid loading stereolithography 3D printing ceramic cores slurry

The properties of ceramic slurry play a crucial role in the production of high-quality ceramic cores. In stereolithography 3D printing process, ceramic slurry should have high solid loading as far as possible. In this work, slurry with high solid loading and low viscosity was successfully prepared by changing the resin composition. When HDDA:TMPTA was 6:2, slurry exhibited low viscosity, high stability and excellent curing properties. Ceramic cores were successfully prepared by the optimized slurry with a solid loading of 60 vol%. The effects of sintering temperature on ceramic cores were studied. As the increase of sintering temperature, the bulk density gradually increased and the open porosity decreased. The ceramic cores exhibited excellent properties at 1250 °C. This work provided a theoretical basis for the optimisation and application of slurry on stereolithography 3D printing ceramic cores.

Maximizing Bioethanol Production from Eucalyptus globulus Using Steam Explosion Pretreatment: A Multifactorial Design and Fermenter Development for High Solid Loads

Steam explosion pretreatment is suitable for bioethanol production from Eucalyptus globulus wood. Multifactorial experiment designs were used to find the optimal temperature and residence time required to obtain the best glucose yield from the enzymatic hydrolysis of pretreated materials. The chemical composition, crystallinity index, morphology and polymerization degree of the pretreated materials were correlated with enzymatic accessibility. Simultaneous saccharification and fermentation (SSF) using a fed-batch strategy was applied to three different laboratory-scale fermenters. The optimization of the pretreatment was obtained at 208 °C and 11 min. However, the enzymatic hydrolysis performance did not show significant differences from the material obtained at 196 °C and 9.5 min, which was determined to be the real optimum, owing to its lower energy requirement. The vertical fermenter with type “G” blades and the horizontal fermenter with helical blades were both highly efficient for reaching ethanol yields close to 90% based on dry wood, and ethanol concentrations close to 9.0% v/v.

High titer (>100 g/L) ethanol production from pretreated corn stover hydrolysate by modified yeast strains

Developing a reliable lignocellulose pretreatment method to extract mixed sugars and engineering efficient strains capable of utilizing xylose are crucial for advancing cellulosic ethanol production. In this study, chemical and characterization analyses revealed that alkali cooking can significantly remove lignin from lignocellulose crops. The highest amount of mixed sugar was obtained from corn stover hydrolysates with a 15 % solid loading. Our genetically engineered yeast strain ΔsnR4, derived from a well-staged WXY70, demonstrated excellent performance in low 10 % solids loading corn stover hydrolysate, producing a high ethanol yield of 0.485 g/g total sugars. When a combined NaOH-ball milling pretreatment strategy was applied at high solids loading, ΔsnR4 exhibited the maximum ethanol titer of 110.9 g/L within 36 h, achieving an ethanol yield of 92.9 % theoretical maximum. Therefore, ΔsnR4 is highly compatible with high solid loading NaOH-ball milling pretreatment, making it a potential candidate for industrial cellulosic ethanol.

Studying the combined effect of layer thickness and solid loading percentage for improving the compressive strength of 3D printed β-TCP scaffold by LCD technique

Customized 3D printed bio-ceramic scaffolds with complex shapes can be fabricated by Liquid Crystal Display (LCD) technology. In this study we investigated the combined effect of the solid loading percentage of the β-Tricalcium phosphate (β-TCP) bio-ceramic powder and the 3D printing layer thickness on the compressive strength of the 3D printed bio-ceramic scaffolds using LCD technique. Three different high solid loadings (40, 60 and 80 vol%) of β-TCP were mixed with resin in the presence of Oleic acid prior to the 3D printing. The β-TCP:resin slurry was used to fabricate scaffolds by using three different layer thicknesses (50 μm, 100 μm and 150 μm). The 3D printed green scaffolds were thermally debinded at 530 °C for 8 h and sintered at 1000 °C for 6 h based on the TGA and DSC thermal analysis of the β-TCP-resin slurry. The x-ray diffraction (XRD) and the Fourier transform infrared (FTIR) spectroscopy analysis confirmed that the β-TCP structure is preserved after scaffold fabrication. The Scanning Electron Microscopy (SEM) analysis showed the surface morphology of the scaffolds with internal pores, micro porosity, and localized delamination. The main finding of the results suggests that decreasing the layer thickness and the solid loading will enhance the compressive strength of the scaffold. Maximum compressive strength attained was (0.19 ± 0.01 MPa) for scaffolds with 40 % solid loadings, layer thickness of 50 μm and porosity 83.49 %. These results demonstrate the potential of using the low-cost LCD 3D printing in fabricating a customized porous β-TCP scaffolds for bone tissue engineering.

Cellulase immobilization on zeolitic imidazolate frameworks for boosting cellulose hydrolysis at high solids loading

This study investigates the cellulase immobilization onto zeolitic imidazolate frameworks (ZIFs) to enable efficient cellulose hydrolysis at high solids loading. Different ZIF carriers (ZIF-8, ZIF-8-NH2, Fe3O4@ZIF-8, and Fe3O4@ZIF-8-NH2) were prepared and characterized. The resulting ZIF-immobilized cellulases were subsequently analyzed for their loading capacity and enzyme activity, as well as their biochemical properties such as temperature stability, pH stability, storage stability, enzyme leaching, and enzyme kinetics. Results revealed that the cellulase immobilized on Fe3O4@ZIF-8-NH2 exhibited an exceptional loading capacity of 359.89 mg/g and a relative enzyme activity of 69.39%. Remarkably, at a solid loading of 15% (w/w) and an enzyme dosage of 5 FPU/g cellulose, the Fe3O4@ZIF-8-NH2 immobilized cellulase demonstrated a 20.44% higher hydrolysis yield compared to the free cellulase. Furthermore, this immobilized enzyme system displayed robust reusability, retaining 71.03% of its initial activity even after 10 cycles of reuse. A proposed mechanism of enhanced enzymatic hydrolysis by ZIF-immobilized cellulases was also presented. These findings have significant implications for the future application of ZIF-immobilized cellulases in efficient and cost-effective lignocellulosic bioconversion.

Addressing two major limitations in high-solids enzymatic hydrolysis by an ordered polyethylene glycol pre-incubated strategy: Rheological properties and lignin adsorption for enzyme

High-solids enzymatic hydrolysis for biomass has currently received considerable interest. However, the solid effect during the process limits its economic feasibility. This work presented an ordered polyethylene glycol (PEG) pre-incubated strategy for enhancing the auxiliary effect of PEG in a high-solids enzymatic hydrolysis system. The substrate and enzyme were separately pre-incubated with PEG in this strategy. The ordered PEG pre-incubated strategies yielded a maximum glucose concentration of 166.6 g/L from 32 % (w/v) pretreated corncob with an enzymatic yield of 94.1 % by 72 h hydrolysis. Using this method, PEG not only lessened the lignin adsorption to cellulase but also altered particle rheological characteristics in the high-solids enzymatic hydrolysis system as a viscosity modifier. This study offered a new insight into the mechanism behind the PEG synergistic effect and would make it possible to achieve efficient high-solids loading hydrolysis in the commercial manufacture of cellulosic ethanol.

Improving the dissolved oxygen level in high solids loading cellulosic sugar acids fermentation by restructuring the biorefinery chain

Industrial production of biochemicals and biofuels from lignocellulose feedstock frequently requires aerobic fermentation with high dissolved oxygen demand. Efficient oxygen transfer from the air phase to the liquid phase has been considered as a great challenge due to the high viscosity and solid particles derived from the high solids loading lignocellulosic slurry. Here we presented a solution for aerobic sugar acids (gluconic acid and xylonic acid) fermentation by Gluconobacter oxydans in 30% (w/w) solids loading corn stover hydrolysate without solid/liquid separation. The biorefinery chain was restructured by conducting enzymatic hydrolysis before the submerged biodetoxification instead of solid-state biodetoxification. The viscosity of corn stover slurry decreased to ∼0.03 Pa·s after submerged biodetoxification and the gas-liquid oxygen transfer coefficient (kLa) reached 50.0 at the aeration rate of 0.1 vvm and agitation rate of 500 rpm, which is more efficient for sugar acids conversion than that using solid-state biodetoxified corn stover hydrolysate (only 8.8 kLa at 2.4 vvm, 500 rpm). The cellulosic sugar acids titer reached 156.0 ± 6.9 g/L at 0.1 vvm with 92.9% of the theoretical yield in the restructured biorefinery chain. The techno-economic analysis showed that the minimum selling prices of sugar acids produced by this restructured biorefinery chain was $351.7/ton which was 12.9% lower than that produced by the general biorefinery chain. This efficient process setting including one-pot hydrolysis, submerged biodetoxification, and fermentation provides a practical technical route for lignocellulose-based aerobic fermentation under high solids loading.

High solid loading, low viscosity stereolithography 3D printing ceramic cores slurry

The temperature enduring capacity of turbine blades determines the thrust-weight ratio of aero-engines. The heat dissipation efficiency of blades is improved mainly through designing complex internal cooling channel. As a transitional component of blade preparation, the shape of ceramic cores has become gradually complex. The traditional process is difficult to meet the preparation requirements of ceramic core with complex structure due to the limitation of mold. Stereolithography 3D printing provides a feasible technology for the preparation of ceramic cores with complex structures. The key to high-performance ceramic core via the stereolithography 3D printing lies in the prepare ceramic slurry with high solid loading, low viscosity and uniform stability. Choosing suitable dispersant is an effective way to prepare above standard slurry. In this study, the effects of single and dual dispersants on the rheological properties of ceramic slurry were systematically investigated. The action mechanism of the dispersant was analyzed. The functional relationship between solid loading and viscosity was elucidated. The silicon-based ceramic core slurry with 70 vol% solid loading and viscosity of 10520 mPa s (12.6 s−1) was obtained. Through optimizing printing parameters, the complex structure silicon-based ceramic core was fabricated. The influence of solid loading on the microstructure and physical properties of the ceramic core was investigated. The results show that with the increase of solid loading, the shrinkage of ceramic core lowers and the flexural strength of ceramic core strengthens. The successfully preparation of complex structure ceramic core based on high solid loading slurry promotes the extensively implemented of stereolithography 3D printing technology in the field of ceramic core.

Advanced steam explosion as thermal hydrolysis process for high solids anaerobic digestion and enhanced methane yield: Proof of concept

Sewage sludge management is one of the major issues faced by wastewater treatment plant (WWTP) operators. Though anaerobic digestion (AD) is one of the most preferred sludge management techniques, the complex microbial floc structure of the sludge creates physical and chemical barriers that limit the rate of microbial degradation resulting in a longer hydraulic retention time (HRT) of 25–30 days. The thermal hydrolysis process (THP) can be used as a pretreatment technique to enhance the rate of biodegradation which results in reduced retention time and increased methane yields. This work investigated the effects of the THP on the semi-continuous anaerobic digestion of high solids sludge (15% total solids, TS) obtained from a municipal wastewater treatment plant (WWTP) operating at higher solids retention time (SRT) of 40 days. The thermal hydrolysis process achieved the effective release of organics into the liquid phase resulting in 37% chemical oxygen demand (COD) solubilization. Two semi-continuous digesters, one fed with untreated sludge (control digester, 5% TS) to mimic the conventional anaerobic digester and the other fed with THP sludge (160 °C, 30 min, 6 bar, 10% TS) were operated under a mesophilic regime and a hydraulic retention time (HRT) of 15 days. The methane yield from the THP digester (0.366 ± 0.010 m3/kg VSadded, 70 ± 1.13% CH4) was 47% higher than the control digester (0.248 ± 0.013 m3/kg VSadded). The volatile solids removal (VSR) was 51 ± 0.6% in the THP digester, i.e., 43% higher over control digester (35.7 ± 1.3%). The fecal coliforms concentration in the digestate of control and THP digesters were 9200 and 200 MPN/g, respectively. Thus, the THP sludge meets the Class A biosolids criteria (<1000MPN/g). THP integrated anaerobic digestion achieved higher solids reduction with enhanced energy recovery, high solids loading with shorter retention time, and generated Class A biosolids.

Preparation and properties of K0.48Na0.52NbO3 ceramics for bone scaffolds via digital light processing

Lead-free piezoelectric ceramics are expected to be used for artificial bone scaffolds since they can generate electrical signals and promote recovery, but it is still difficult to fabricate piezoelectric scaffolds with complex structures. In this work, digital light processing (DLP) technology was used to fabricate potassium sodium niobate (K0.48Na0.52NbO3, KNN) bone scaffolds with gyroid triply periodic minimal surface. Suspension was first optimized to ensure both high solid loading (42 vol%) and high cure depth (>50 μm). KNN porous scaffolds (porosity: 60%) and other samples for tests were printed successfully. Then, influences of sintering temperature on microstructure, relative density and mechanical properties were discussed. Results showed that when sintered at 1090 °C, printed KNN ceramics had the highest relative density (90.11%) and lowest open porosity (5.75%), and exhibited the most satisfying mechanical properties (compressive strength: 33.85 MPa, elastic modulus: 1.87 GPa, flexural strength: 35.40 MPa, hardness: 2.39 GPa), which can meet the requirements of cancellous bone. Finally, the electric properties of samples at room temperature were verified. With d33 being 113.67 ± 2.49 pC/N and Pr being 19.94 μC/cm2, printed KNN ceramics showed comparable piezoelectric and ferroelectric performances with traditionally dry-pressed samples. These results indicated that DLP technology is competitive in preparing KNN piezoelectric bone scaffolds for implantation.

A simple preparation method and the rheological properties of high solid loading slurries for ceramic vat polymerization

Originally used for additive manufacturing of polymer parts, the vat polymerization process was modified to fabricate ceramic parts by filling the resin with ceramic powder. In this study, we present the development of a ceramic slurry for additive manufacturing of ceramics via the vat polymerization process. With the shorter preparation time, the developed ceramic slurry containing 45 vol% solid loading exhibits considerable stability (minimal sedimentation observed over seven days) and low viscosity (<3 Pa s) that can be spread easily with a blade. We demonstrate the printability of the developed slurry by printing various geometries alumina and zirconia. The capability of the slurry was further extended to the printing of alumina platelets to mimic a nature-inspired nacre-like structure. In conclusion, we demonstrated a way to quickly prepare UV-curable ceramic slurry and future work encompasses research on strengthening of the printed ceramics.