Maximum Solid Concentration Research Articles

A Comprehensive Assessment of Water Quality and Mass Balance of the Bhairab River, Khulna

Abstract: Water is a vital component for all organisms on Earth. Water is essential for the survival of all living organisms on Earth. Water is vital for life, much like oxygen, since no kind of life can survive without it. Water often includes several physical, chemical, and biological contaminants. Surface water sources mostly consist of rivers, lakes, ponds, glaciers, and precipitation. The sources are becoming degraded due to contemporary urbanization, escalating population, domestic trash, and industry. The Bhairab River is not far from the sick worry. The water quality of the area is rapidly deteriorating due to the significant influx of contaminants it gets. This research focuses on evaluating the water quality and mass balance of the Bhairab River. In order to achieve the current objective of the research, a stretch of 22.9 kilometers from Jailkhana Ferighat to Shuvorada Kheya Ghat, Fultola, was split into 10 sample sites. The water samples were collected monthly from each monitoring site during the year of 2021 for laboratory analysis. A total of nine water quality indicators, including Fecal Coliform, Temperature, Biochemical Oxygen Demand (BOD), pH, Turbidity, Total Solids (TS), Phosphate, Dissolved Oxygen (DO), Nitrate, and Chloride, were analyzed using standardized methods. The water quality evaluation was conducted by calculating the WQI using the National Sanitary Foundation (NSF) technique. The mass balance has been determined by means of analysis. The current study is being undertaken using both primary and secondary data sources. The investigation reveals that the primary parameters exhibit varying degrees of correlation with each other. In December, the temperature reached a minimum of 16.8 °C, while in May, it peaked at 37.5°C. The pH reached its peak at 8.80 in August, while it had its lowest point at 7.94 in January. The pH variation is minimal and similar throughout the board. The measured turbidity level was 564 NTU, which is the average value. The maximum total solids (TS) concentration recorded was 3346 mg/L, while the minimum concentration was 2460 mg/L. The phosphate content reached its peak at 8.12 mg/L in S5, while it was at its lowest at 4.26 mg/L in S4. The maximum nitrate concentration measured was 26.4 mg/L, while the minimum concentration was 12.80 mg/L. The maximum biochemical oxygen demand (BOD) recorded was 1.80 mg/L at location S6, whereas the minimum BOD was 0.60 mg/L at location S3. The concentration of BOD was consistently low during each month. The highest fecal coliform (FC) concentration observed in November was 1024 N/100ml, while the lowest concentration was 572 N/100ml. The drinking water quality standard for fecal coliform (FC) in Bangladesh is zero per 100 milliliters. The greatest, average, and lowest values surpass the allowable limit set by BDS. The water quality index determined for the year 2021 for Ten Stations has an average value of 43, indicating a similar level of water quality throughout the stations. According to the range of NSF water quality index, the Bhairab River has a poor quality rating. Therefore, this water is not safe for drinking without undergoing treatment. The Bhairab River has a Mass Balance value of 362349.09 gallons per day

Effect of Crop Load on Yield and Quality Parameters in Apple cv. Gala Redlum

The present study was conducted at the experimental field of the Division of Fruit Science, Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir during the year 2021-2022. The primary objective of this study was to assess the impact of varying crop loads on the growth, yield, quality, and return bloom of Gala Redlum apples, with specific emphasis on trunk cross-sectional area (TCSA). The experimental design involved a Randomized Complete Block Design (RCBD) with three replications, utilizing 4-year-old Gala Redlum plants. The trees were subjected to manual thinning, resulting in crop loads of 4, 6, 8, 10 fruits per cm² of TCSA, with a non-thinned control group. Notably, the maximum fruit yield (18.52 kg/tree) was observed in the control group (no thinning), while the minimum yield (7.57 kg/tree) was recorded in the C2 group (4 fruits per cm² of TCSA), followed by C3 (11.03 kg/tree). Furthermore, the impact of different TCSA ranges on fruit yield was statistically significant. The maximum fruit yield (14.45 kg/tree) was observed in the S2 group (10-12 cm² TCSA), while the minimum yield (12.16 kg/tree) was noted in the S1 group (8-10 cm² TCSA). Yield efficiency, measured as yield per unit of TCSA, reached its highest (1.838 kg/cm²) in the control group and is lowest (0.766 kg/cm²) in the C2 group (4 fruits per cm² of TCSA). The results further revealed that the C2 group (4 fruits per cm² of TCSA) exhibited the maximum Total Soluble Solids (TSS) content (14.73 °Brix), total sugars (11.62%), and TSS: Acid ratio (61.45). Similarly, the C3 group (6 fruits per cm² of TCSA) demonstrated elevated TSS (14.20 °Brix), total sugars (10.99%), and TSS: Acid ratio (54.66). Additionally, the S2 group (10-12 cm² TCSA) recorded the highest TSS (13.75 °Brix), total sugars (10.51%), and TSS: Acid ratio (50.53). The combination of C2S2 and C3S2 treatments exhibited superior results, with the highest TSS (14.82 °Brix), total sugars (11.77%), and TSS: Acid ratio (62.64). Fruit firmness (8.81 kg/cm²) and fruit acidity (0.327%) were maximized in the C1S1 treatment combination.

Eliminating Luck and Chance in the Reactivation Process: A Systematic and Quantitative Study of the Thermal Reactivation of Activated Carbons

Increasing environmental concerns, stricter legal requirements, and a wide range of industrial applications have led to growing demand for activated carbon worldwide. The energy-intensive production of fresh activated carbon causes significant CO2 emissions and contributes to global competition for renewable carbon-based raw materials. Although (thermal) reactivation of spent activated carbon can drastically reduce the demand for fresh material, the reactivation process itself is still mostly based on experience and empirical knowledge locked into activated carbon companies. Despite the vast number of papers published in the field, practically relevant, systematic, and quantitative knowledge on the thermal reactivation process is barely available. This paper presents a simple and robust methodology for the development of a predictive model for the production of reactivated carbon with a defined product quality under energetically optimized conditions. An exhausted activated carbon sample was subjected to 26 reactivation experiments in a specially designed laboratory rotary kiln, whereas the experiments were planned and evaluated with statistical design of experiments. The influence of the reactivation conditions (heating rate, heating time, H2O/N2 volume ratio, and CO2/N2 volume ratio) on the specific surface area, energy consumption, yield, and adsorption capacity for diatrizoic acid were evaluated. The BET surface of the reactivated carbons ranged between 590 m2/g and 769 m2/g, whereas the respective fresh carbon had a BET surface of 843 m2/g. The adsorption capacity for diatrizoic acid measured as the maximum solid phase concentration qm derived from the Langmuir equation varied between 24.4 g/kg and 69.7 g/kg (fresh carbon: 59.6 g/kg). It was possible to describe the dependency of the quality criteria on different reactivation parameters using mathematical expressions, whereas the response surface methodology with nonlinear regression was applied to build the models. A reactivation experiment under statistically optimized conditions resulted in energy savings up to 65%, whereas the properties of the reactivated sample were close to the predicted values.

Compressive Stress Dewaterability Limit in Fluid Fine Tailings

Reclamation of fluid fine tailing (FFT) storage facilities to their pre-disturbance equivalent landforms is hampered because micrometer size fines, whose surface-area-to-volume ratio is remarkably high, are occupied with siloxane and hydroxy groups, which bind water strongly. The purpose of this study is to differentiate the forms of water physically distributions in FFT and determine their propensities for dewaterability under compressive stresses. Two thermal and two mechanical methods were used to analyze water distributions in FFT. Dynamic and isothermal thermogravimetric analyses of FFT gave a transition from predominately bulk water to coevolution with water of higher enthalpy of vaporization at 81% (w/w) solids. Differential scanning calorimeter studies were used to determine the non-freezable water amount, with the premise that water that does not freeze by −30 °C is also unlikely to be removable by compressive stresses encountered in tailing treatment processes. The solid weight percent of FFTs with the non-freezable water was 79.6%. A 1D finite-strain model simulation using the constitutive relations of void ratio and effective stress, void ratio, and hydraulic conductivity show that deep-pits filled with such clayey-silt FFT will consolidate to a maximum solids content of 74% (w/w). For separation by centrifugation, the solids content plateaued to a mean of 74% (w/w) for total centrifugal force of ≥30 mega Newtons. These solid contents represent upper thresholds and demonstrate dewatering limit property of an FFT under compressive stresses.

Accelerating the Consolidation of Thickened Tailings Using Sand Co-Disposal

Only grams or kilograms of valuable resources are extracted for each tonne of ore processed, generating immense amounts of tailings. Returning tailings-containment dams to their equivalent pre-disturbance landscape state is many stakeholders’ acceptable management strategy. The depositing of thickened fluid fine tailings (FFT), which the industry has relied upon to develop geotechnically stable dry landscapes, has not materialised due to the low hydraulic conductivity of such placements. The addition of sand to thickened FFT is proposed to accelerate the consolidation of thickened FFT in a co-disposal scheme, and this study evaluates its impact. In the continuum of solid wastes from mining operations, sand is the next-larger-sized grade of solids after “fine” that is produced in high proportions. Blends of highly-plastic FFT and fine-grade sand tailings at varying sand-to-fine ratio (SFR) values were tested. Sand lowered the liquid limit but did not significantly affect the plastic limit of FFT. The changes in liquid and plastic limits for SFR ≥ 1 blends were under 5% of water content. The maximum unit weight for the co-disposal mixes was obtained at SFR 3. Despite increases in unit weights, hydraulic conductivity increased with increasing SFR, while the trend for compression rates was in the reverse order. Void ratio—effective pressure—hydraulic conductivity power law relationships at varying SFR were obtained from the consolidation measurements. The constitutive constants of these relationships were used to model settlement of 30 m deep pits over a 25-year period. For all the deposits studied, the dewatering converged to a maximum solids content characteristic of each SFR in the order 74, 85, 88, and 94% (w/w) for thickened FFT and SFRs 1, 2, and 3, respectively. The numerically calculated average solid contents of the deep-pit placements grew closer with increasing SFR becoming 59, 77, 82, and 86% (w/w), respectively. Balancing the consolidation-rate gains and the land footprint required for storage with SFR increase, the optimal composition for co-disposal for this material and similar tailings is SFR 1.

Agitation and its control on excess pore water pressure and debris‐flow behaviour

AbstractExcess water pressure strongly affects the rheology and flow behaviour of debris flows, and the mechanisms for development and persistence of the pressure can be diverse. Using nine experimental slurries prepared with the sediments collected from the deposit of a large‐magnitude debris flow by modifying maximum grain size and solid concentration, the influence of agitation on excess water pressure is investigated with a cylinder apparatus, consisting of a coaxially mounted bucket and impeller driven by a variable‐speed motor. Agitation proceeding in three dynamic stages raises relative excess water pressure (R) by 17%–34% of the peak R in the static stage, showing that agitation can significantly increase excess water pressure. The magnitude of the steady R increases with the level of agitation, which is measured by impeller speed and slurry temperature, and the steady R in a slurry is agitation‐level‐dependent below its potential maximum value. The transfer of particle weight to water in debris flows can occur under zero or very low to extremely low effective stresses. Agitation raises excess water pressure essentially by promoting dispersion of the finest‐grained grains in water and that of progressively larger grains in gradually coarser‐grained slurries. The flow resistance of the tested slurries, characterized by net torque exerted on the impeller by the motor, decreases with increasing liquefaction ratio, demonstrating that agitation enhances debris‐flow mobility by raising excess water pressure. It is of importance to dampen agitation by building proper mitigation measures in remedial practices.

Mechanistic insight into the adsorption and interaction of lignite, organic ingredients, and dispersant in coal wastewater slurry

The conversion of coal gasification wastewater into coal wastewater slurry (CWWS) for combustion and gasification fuels is a promising approach that combines resource recovery with effective wastewater management. In this work, the influence of organic ingredients derived from coal gasification wastewater on the slurrying capabilities of lignite, particle dispersion/aggregation behavior, and adsorption characteristics between lignite and sodium methylene dinaphthalene sulfonate (NNO) in CWWS was thoroughly investigated. The interaction mechanism of lignite, NNO, and the organic ingredients in the slurry systems revealed subsequently by molecular dynamics (MD) simulations. Results indicated that the maximum solid concentration for coal gasification wastewater simulated by organic ingredients increased by 1.64% with a decrease in pseudo-plasticity and stability. The presence of dodecane, phenolic and heterocyclic nitrogen compounds caused the dissociation and coalescence of particles in the CWWS and further formation of creaming or clarifying layer. The adsorption processes of NNO and the organic ingredients on lignite particles exhibited competitive adsorption, following the pseudo-second-order kinetic and the Freundlich thermodynamic models. The adsorbed organic ingredients enhanced the hydrophobicity and electrostatic repulsion of the particle surface in CWWS, increasing the hydrophobic C-C/C-H content from 64.73% to 71.27%. Moreover, the MD simulation results revealed that the adsorption conformations at the lignite-water interface in CWWS changed from “single-point and single-layer” adsorption of NNO to “multi-point and multi-layer” adsorption of NNO and organic ingredients driven by hydrophobic effect, van der Waals force, π-π stacking effect, and hydrogen bonding.

The resource utilization of coal gasification wastewater by co-slurry with lignite: Slurryability, dispersion/aggregation behavior, and co-slurrying mechanisms

Coal gasification wastewater (CGW) as a substitute for clean water to prepare coal water slurry, which serves as gasification/combustion feedstock, can simultaneously achieve wastewater management and resource utilization. The purpose of this work was to investigate the effects of internal components (i.e., oils, phenols, nitrogen heterocyclic compounds, and inorganic cations) in CGW on the slurryability and dispersion/aggregation behavior of lignite and their co-slurrying mechanisms through experimental and the extended DLVO (eDLVO) theoretical calculations. Results showed that compared to lignite water slurry (LWS), the maximum solids concentration (ωmax) of coal gasification wastewater slurry (CWWS) increased by 0.80%, with a lower pseudo-plasticity. The organic compounds adsorbed competitively on the hydrophobic regions of lignite improved the slurrying capability of CWWS by decreasing the wettability, Zeta potential, roughness and pore structure of the particles. By contrast, the static stability of CWWS decreased, and its kinetic stability index (TSI) increased from 0.23 to 0.33. From the backscattering spectra, dodecane caused the creaming process of the slurry, while the clarification process was attributed to phenol and nitrogen heterocyclic compounds. Inorganic cations, especially NH4+ and Ca2+, significantly reduced the hydrophilic and negative charges on the particle surface, which were the main unfavorable factors leading to particle aggregation and sedimentation. The eDLVO theoretical calculation results exhibited that inter-particle interaction in CWWS was determined by the hydrophobic energy (Eh) and electrostatic energy (Ee) and their dropped from 1.79 × 10−16 J and 5.16 × 10−17 J to −4.67 × 10−16 J and 2.59 × 10−17 J respectively.

Improving the slurryability of high ash coal by blending anthracite of different particle size range

ABSTRACT Hydraulic transportation of lignite and high ash coal (HAC) is economically unviable due to their poor slurryability and stability. The study suggests and shows how the proper selection of appropriate size range and proportion of anthracite for blending can aid in the economical preparation of highly concentrated HAC slurry. Fine (+0–53 µm), coarse (+53–106 µm), and coarser (+106–150 µm) anthracite particles were added to the HAC sample. The proportion of anthracite particles was varied in the range of 10–40% (by weight), to obtain 12 blended tetra-modal samples. To determine the optimum size range and proportion of anthracite, the stability and rheological characteristics of both tri-modal HAC and blended tetra-modal coal samples were assessed. The addition of a fine anthracite sample (+0–53 µm) has an adverse impact on the rheological characteristics. The optimum size range and proportion of anthracite particles for enhanced slurryability and low apparent viscosity are found to be +106–150 µm and 30%, respectively. Optimal blending yields a 68% maximum solid concentration slurry. By taking advantage of both the tetra-modal particle size distribution and anthracite’s high slurryability characteristics, the maximum achievable solid concentration of HAC slurry increases by 17%.

Insight into the pollution characteristics of road and roof runoff in Changsha, China

Non-point source pollution from rainwater runoff presents a serious challenge for urban water management in many cities undergoing urbanization and experiencing climate change. To alleviate water resource conflicts in Changsha, China, this study comprehensively evaluated the pollution characteristics and first flush effect (FFE) of runoff from asphalt roads and colored steel plate roofs under seven rainfall events in April-May 2022. The runoff was collected and purified using bioretention ponds. The results showed that the peak runoff pollutant concentrations occurred within the first 20min of runoff generation and then decreased to relatively stable levels, with maximum total suspended solids (TSS) concentration and chemical oxygen demand (CODCr) reaching 873.5 and 207.32mg/L, respectively, for road runoff and 162 and 73.31mg/L for roof runoff, respectively. The main pollutants were TSS and CODCr, followed by ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3--N), total phosphorus (TP), and nitrite nitrogen (NO2--N). Concentrations of pollutants and FFE for roof runoff were lower than those for road runoff. Road runoff had a more obvious FFE for TP and NH4+-N, whereas the roof runoff showed the presence of TP and NO3--N. An important implication is that treating the first 30% of surface runoff from rainfall events with long antecedent dry days or high rainfall amounts is necessary to improve water quality before discharge or utilization. The study also found that road and roof runoff, after treatment with bioretention ponds, exhibit good water quality, thus, allowing their use as reclaimed water or for miscellaneous purposes in urban areas. Overall, this study provides useful information for designing management measures to mitigate runoff pollution and reuse in Changsha.

Preparation of the modified sludge-semi-coke water slurry and analysis of its slurring performance and mechanism

The sludge-semi-coke water slurry (S-SCWS) and modified sludge-semi-coke water slurry (MS-SCWS) can be used as liquid fuels for combustion and gasification. These slurries have apparent economic advantages in sludge recovery and utilization. High concentration MS-SCWS can be prepared by low-temperature thermal alkali-modified sludge. In this paper, the modified sludge was characterized by Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), and nitrogen adsorption-desorption methods. The adsorption experiments of composite anionic dispersant (NNO/PCE) on semi-coke, sludge and modified sludge demonstrate that low temperature thermal alkali method changes the properties of sludge particles including hydrophilicity, pore structure, surface properties, mineral composition and zeta potential. The apparent viscosity of MS-SCWS prepared from modified sludge was investigated under different modification conditions, such as temperature (25 °C–90 °C), time (60 min–150 min), and the does of sodium hydroxide (15 wt%-30 wt%). Under the optimized low-temperature thermal alkali experimental conditions, the maximum solid concentration of MS-SCWS reached from 66.67% to 68.1%, when the amount of NNO/PCE dispersant dosage was 0.8 wt%, the apparent viscosity decreased from 711.2 mPa·s to 434.2 mPa·s, and the water separation rate (WSR) declined from 6.09% to 0%, while the stability improved significantly. The adsorption kinetics of NNO/PCE dispersant on the surface of semi-coke, sludge, and modified sludge particles showed that the quasi-second-order adsorption kinetic equation can better describe the adsorption process of dispersant on the particle surface. The result of isothermal adsorption experiment showed that the saturated adsorption capacity of NNO/PCE on the surface of semi-coke particles was significantly higher than that of sludge and modified sludge. The adsorption of NNO/PCE on all particle surfaces was monolayer adsorption. The low-temperature thermal alkali pre-treatment of municipal sludge could change its physical and chemical properties. This method is an effective way to develop and utilize sludge on a large scale. • MS-SCWS was prepared by semi-coke powders, modified sludge and dispersant. • The maximum solid concentration of MS-SCWS reached from 66.67% to 68.1% • The electrostatic interaction of particles improved the stability of the MS-SCWS. • The adsorption of dispersants on semi-coke powders was monolayer adsorption. • The interaction mechanism between the dispersants and particles was proposed.

Medindo densidade de empacotamento e demanda de água do cimento Portland e MCSs pelo método da energia de mistura

Abstract Wet packing methods evaluate the packing density of fine materials through the determination of the apparent density and voids content of pastes with different water to solids (w/s) ratios. Its goal is to estimate the minimum water demand to achieve the maximum solids concentration in the mixture, a parameter applied to the mix design of cementitious composites based on particle packing theories. Since most methods based on apparent density are time-consuming and require a high volume of materials, this paper aims to evaluate the mixing energy method as an alternative for the wet packing method and to adapt it to be used for SCMs (supplementary cementitious materials). With a reduced time and material to perform the test, results demonstrate a better precision of the mixing energy due to its discrete measurement. The ideal water flow and initial volume of materials to perform the test on cement and SCMs are discussed.

Enhancement of biosludge dewatering using proteins through dual conditioning

AbstractIn pulp and paper mills, effective biosludge dewatering is essential in wastewater treatment to reduce the large volume of biosludge that needs to be treated and disposed. The dewatering process normally requires the use of polymers from petroleum‐based sources. This study explores the potential of using cationic proteins such as protamine for biosludge dewatering through dual conditioning with a small amount of a synthetic anionic polymer such as anionic polyacrylamide (APAM). The results show that dual conditioning provides substantial synergistic enhancements in dewatering. The maximum cake solids content of biosludge achieved by adding protamine (7.5%) alone was 12%. By dual conditioning with a small amount of APAM (0.1%), not only the cake solids content was increased to 16%, but also the amount of protamine addition was substantially lowered to 2%. These results, coupled with the change in zeta potential of the particles in the biosludge samples, suggest that the cationic protamine reduced the negative charge of the particles, allowing smaller particles to agglomerate and providing a positively charged framework for the subsequent addition of the negatively charged APAM. After adding APAM, substantial floc‐bridging occurred, allowing smaller flocs to aggregate into larger flocs. These synergistic effects can lower the wastewater treatment cost by reducing the amount of synthetic polymer and by applying low‐value proteins from natural sources.

Evaluation of low-gravity-solids sedimentation in non-Newtonian synthetic-based drilling fluids monitored by gamma-ray attenuation technique

ABSTRACT Drilling fluids are used in the process of drilling wellbores. They are formulated by a combination of solubles and suspended solids. During drilling, cuttings of rock formation may get in the mix. Some of them are too small and light to be removed from the fluids. They are called low-gravity solids (LGS). In no drilling situations, both solids may settle due to gravity. This project aimed to characterize the physical and rheological properties of synthetic-based drilling fluids and monitor the distribution of solids concentration in batch gravity settling experiments. The interplay of solid content and mud rheology was evaluated by pycnometry, retort, and rheological analysis. The Gamma-ray Attenuation Technique was applied to monitor the solid concentration along the test tube as a function of time. We analyzed two similar muds that slightly differed by the presence LGS The fluids presented non-Newtonian behavior, clear separation of solids in two phases and apparent viscosity changes. After 90 days, the clarified liquid region was formed between 16 and 22 cm from the bottom of the tube. This region took shape between 7 to 80 days, and the maximum solid concentration was approximately 9%. Finally, the LGS increased the fluid resistance of settling.

Conversion of golden oyster mushroom, Pleurotus citrinopileatus to sugar syrup using enzymatic hydrolysis as a substrate for novel bacterial cellulose (Nata) fermentation.

Enzymatic hydrolysis of the golden oyster mushroom (Pleurotus citrinopileatus) generated a new bacterial cellulose (BC). The sugar syrup obtained from the hydrolysis of mushroom powder by commercial enzymes gave maximum total soluble solids (TSS) content at 8.83 ± 0.29°Brix, while 8.82 ± 0.06mg GAE/g substrate of total phenolic content(TPC) was obtained when using initial substrate and enzyme concentrations at 125g/L and 5.0%, respectively. Glutamic acid, aspartic acid, alanine and valine were determined as the main amino acids found in P. citrinopileatus hydrolysis at 524.74 ± 0.03, 247.09 ± 0.04, 176.82 ± 0.07 and 174.57 ± 0.01mg/100g sample, respectively. Thin-layer chromatography revealed that the obtained sugar syrup was glucose. The hydrolyzed mushroom fermented with Komagataeibacter xylinus AGR 60 at 30 ± 2°C for 9days produced optimal conditions at 4.0°Brix of the initial mushroom syrup and 12.0% (v/v) of the starter culture. Maximum BC thickness was 0.88 ± 0.03cm with 7.90 ± 0.07g dry weight, equivalent to 39.50 ± 0.35g/L and 4.39 ± 0.04g/L/day for BC production (P) and BC production rate (R p), respectively. The obtained BC was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, small-angle X-ray scattering and wide-angle X-ray diffraction. These showed the structure and functional properties as a natural source of fiber from the fermentation of a novel substrate.

Energy utilization of direct coal liquefaction residue via co-slurry with lignite: Slurryability, combustion characteristics, and their typical pollutant emissions

Direct coal liquefaction residue (DCLR) as an auxiliary feed material with lignite to prepare coal water slurry (CWS), which is then used as combustion fuels, enables recycle resources of DCLR and diminishes its impact on the surrounding environment. This paper aims to study the slurryability, combustion characteristics, and typical pollutant emissions of the lignite water slurry (LWS), DCLR water slurry (DCLRWS), and lignite-DCLR water slurry (L-DWS). Results showed that the DCLR and lignite were complementary in physicochemical properties for preparing the L-DWSs. The maximum solid concentration (ωmax) of the DCLR was 73.19 wt% with poor static stability, whereas that of the LWS was 41.70 wt% with high pseudoplasticity. By contrast, the ωmax of the L-DWS-5 prepared from the lignite and DCLR at mass ratio of 5:5 was 53.91 wt% with lower pseudoplasticity and static stability. Meanwhile, combustion experiments confirmed that the introduced DCLR was effective in improving the ignition, burnout, and comprehensive combustion performance of the L-DWS. The Qnet, p of the slurrying samples increased from 6.70 MJ/Kg for the LWS to 14.41 MJ/Kg for the L-DWS-5. And the addition of the DCLR exhibited slight influences on the emissions of NOx and SO2, but significantly increased HCN and other organic compounds such as CnHm, CO, and NH3 emissions. Furthermore, except for Pb and Zn, more than 85% Cr, Cu, and Ni were intercepted in solid residues.

Improve the slurry ability of lignite through co-slurrying and microwave co-pyrolysis with direct coal liquefaction residue

This study is devoted to demonstrating experimentally the advantages of direct coal liquefaction residue (DCLR) on improving the slurry ability of lignite through co-slurry and microwave co-pyrolysis. The results show that: as the lignite/DCLR mass ratio decreased from 10:0–5:5 the maximum solid concentration (MSC) of the mixed slurry increased from 42.14 wt% to 54.25 wt%, simultaneously, the pseudoplasticity and static stability gradually decreased. This is because the organic matter and abundant minerals in DCLR remarkably changed the slurry ability of mixed slurry. And during microwave pyrolysis with the assist of 12 wt% DCLR the slow drying stage of lignite pyrolysis was shortened, and the constant temperature stage was extended, thus, the coal quality was improved, the oxygen-containing functional groups was removed significantly and the BET specific surface area increased. These changes caused the MSC of upgraded lignite water slurry (ULWS) increased to 64.54 wt%; but the “shear-thinning” characteristic became inconspicuous, and the static stability became slightly worse. In general, DCLR could effectively improve the slurry ability of lignite through co-slurry with lignite at a mass ratio of 5:5 and co-pyrolysis with lignite at a microwave power of 1000 W.

Effect of stabilization and fatty acids chain length on the crystallization behavior of interesterified blends during storage

In this work, we studied the influence of fatty acid chain length and crystallization temperature on the crystallization behavior during the storage of binary blends modified by chemical interesterification. The blends were produced with soybean oil and fully hydrogenated oils from palm kernel, palm, soybean, microalgae, and crambe, evaluated separately, at a ratio of 50:50 (% w/w). The blends were crystallized by two crystalline stabilization methods. In method I, the samples were maintained at 25 °C for 24 h before the analyses. In method II, the samples were maintained at 5 °C for 24 h, followed by crystalline stabilization at 25 °C for 24 h before the analyses. The interesterification reaction caused considerable changes in the TAGs profile with increasing asymmetric TAGs. These TAGs changes promoted an increase in the crystallization induction time, a decrease in the maximum solids content, and changes in crystals morphology. The increase in the FAs chain length promoted the increased nucleation rate that influenced morphology crystals. Method II promoted a reduction in the medium diameter of crystals and the appearance of the β phase with storage time. For crystallization carried out at higher temperatures (method I), we observed that β’ was favored. Unusual polymorphic transitions were observed with storage time in samples with higher tristearin content. We identified clear correlations between the predominance of β’ phase in the interesterified blends and TAGs of S2U and SU2-type. In addition, the blends with a more diverse range of fatty acids concerning chain size also showed the β’ polymorph. β polymorph, on the other hand, was associated with symmetric TAGs, S3 and U3, and CN-54 type TAG. In this study, we used the Rietveld method to quantify the polymorphs and amorphous content in the blends before and after the randomization reaction. This approach allowed a deeper understanding of the crystalline behavior in the blends, which would be difficult to achieve by performing only a visual analysis of the X-ray diffractograms.

Physicochemical properties and slurry ability changes of lignite after microwave upgrade with the assist of lignite semi-coke

Microwave pyrolysis is a promising technique for the clean and effective utilization of low-rank coal, which has aroused widespread concern during the past decades. This paper applied microwave energy with the assist of 10 wt% lignite semi-coke (LSC) to upgrade lignite and prepared the solid residue into lignite water slurry (LWS). The physicochemical property and slurry ability changes of upgraded lignite were analyzed. The micro-mechanisms on interactions between dispersant molecules and upgraded lignite particles were investigated through Molecular Dynamics (MD) simulations. It turns out that LSC could effectively prompt the rapid heating of lignite in the microwave field. And after microwave upgrade the coal quality of lignite was improved, the oxygen-containing functional groups was removed remarkably. The adsorption conformation of dispersant on the lignite-water interface exhibited a double adsorption, while that on upgraded lignite-water interface gradually showed single-layer and multi-point adsorptions. Besides, the physicochemical property changes varied most when lignite was upgraded under 800 W, which leads to the maximum solid concentration of LWS improved most, from 51.84 wt% to 61.45 wt%. It further increased to 62.43 wt% as the LWS was directly prepared from the solid residues after microwave irradiation. Morever, the pseudoplasticity of LWS became weaker, but the static stability became better. Therefore, LSC, a self-product of lignite, exerted an enormous function on improving the slurry ability of lignite.

Geotechnical Properties Determination of Thickened Fluid Fine Tailings

AbstractFluid fine tailings (FFT) comprising clayey-silt solids pose environmental and financial challenges. Currently, mining operators are depositing thickened FFT in deep-pits counting on self-weight consolidation to form stable ground. The motivation of this study is to model the long-term prospects of such deposits utilizing consolidation and direct shear strength measurements. The tests were conducted using scroll decanter centrifuge separated FFT sediment referred to as cake. Drained direct shear tests of the cake gave a linear Mohr–Coulomb failure envelope of 1.2 kPa cohesion intercept and 9° internal friction angle for normal stresses up to 1 MPa. Hydraulic conductivity of the cake was non-linear with normal stress decreasing to 1.7 × 10–11 m/s at 300 kPa. Consolidation results confirmed that the cake exhibits properties similar to those of active clay minerals. The cake compression index is governed by the same relationship as for active clays. The coefficient of consolidation for the cake was nearly constant and had a mean value of 2.25 × 10–3 m2/y, also similar to that of active clays. The void ratio—effective stress—hydraulic conductivity power law empirical relations were used to simulate settlement with a finite-strain model. Numerical results show that the top portion of an FFT deep-pit deposit remains in the liquid state while the lower portion whose maximum solids content converges to 74% is in plastic state. These mean that options that improve hydraulic conductivity and increase the shear strength of the thickened FFT should be integrated prior to final placement in order to create stable ground.