Bed Material Research Articles

Goat Manure Potential as a Substrate for Biomethane Production—An Experiment for Photofermentation

This article presents the current state of biogas (biomethane) production technology—an example of the use of goat manure in terms of photofermentation efficiency. The theoretical and experimental potential of biomethane using biodegradability for anaerobic fermentation of goat manure was indicated. Goat manure was tested for its elemental composition to determine the suitability of this raw material for biogas production. The quality of biogas produced under atmospheric conditions from goat manure placed in a reactor (photodigester) was assessed. An attempt was made to determine the process conditions for immobilization on a goat manure bed (depending on the research material collected), which allows for demonstrating the activity of the fermentation bacterial flora, thus influencing the amount of biogas (biomethane) produced in the reactor. A mechanism for the photofermentation process involving the production of biomethane was developed. The novelty of this article is the development of the use of goat manure in an innovative way, pointing to the development of the biomethane industry. When comparing goat manure, active group (compact bed), it should be noted that K 3.132%, Na 0.266%, Ca 1.909% and Mg 0.993% are lower values compared to the material with values of K 3.397%, Na 0.284%, Ca 1.813% and Mg 0.990% which are higher. This is undoubtedly due to the presence of nutrients in the deposit that support the biomethane production process. The active group (compact bed) material A shows a dynamic increase in biomethane production with lower nutrient values. However, material B, having a higher percentage of ingredients, shows stabilization of biomethane production after the sixth month of the process. Technological trends and future prospects for the biomethane sector were initiated.

Effects of the inclusion of two extracts derived from the olive industry on growth performance, antiparasitic protection, and antioxidant activity in broiler chicken diets from 0 to 45 d

The objective of the present study was to investigate the optimal inclusion rate of 2 independent extracts with different properties derived from the olive industry [triterpenic acid extract (TAE) and a polyphenol extract (PE)] on productive performances in broiler chickens from 0 to 45 d under challenging conditions. In addition, antiparasitic protection of the TAE was evaluated at d 21 and d 28 through intestinal scoring and oocyst counts, as well as the blood antioxidant activity of the PE at d 45. Wood shavings as bedding material came from a commercial farm with a coccidia load sufficient to create a subclinical coccidiosis situation with minor macroscopic lesions, and a nutritional challenge was imposed using poor raw materials to cause intestinal dysbiosis. There were 9 dietary treatments (8 replicates/treatment and 15 broiler chickens/pen), a positive control (PC) supplemented with commercial coccidiostat (Na monensin), 4 increasing concentrations of TAE (30, 60, 90, and 120 ppm), and 4 increasing concentrations of PE (10, 20, 30, and 40 ppm). For the overall experiment the PC had greater average daily gain (ADG) and average daily feed intake (ADFI) (P < 0.001) than the mean of TAE treatments. Besides, the ADG, body weight, and ADFI increased linearly throughout the whole experiment as the TAE level of the feed increased. With respect to the anticoccidial activity, the 120 ppm TAE treatment showed greater concentration of E. acervuline DNA copies at 21 d than the 30 ppm TAE treatment (P < 0.05), the rest of the treatments being intermediate. Concerning the PE treatments, for the overall experiment, ADG was the greatest in the PC treatment (P < 0.001), and the ADFI was similar in the PC treatment to the mean of PE treatments. There was no effect of the PE on antioxidant activity. In conclusion, under the conditions of this study, the inclusion of TAE does not reach the productive performance indicators achieved by a commercial coccidiostat in our intestinal challenge situations. Also, the inclusion of PE has a positive effect on productive performance on the overall period.

Study on separation of 6–0 mm low rank high sulfur lignite by FGX dry separation bed

ABSTRACT Coal is an essential primary energy for the national economy and people’s livelihood. In recent years, with the rapid growth of the consumption of high-quality coal resources, Lignite with a low degree of metamorphism has been extensively exploited and utilized. In this paper, desulfurization and ash reduction treatment of 6–0 mm fine-grade low-grade high-sulfur Lignite was carried out using a FGX dry separation bed (FGX FGX compound dry separation bed). The migration and distribution of differentiated density particles in the bed under the action of cascade air flow were mainly studied, and the influence of vibration intensity (amplitude and frequency) on the separation effect of fine-grade low-grade high-sulfur Lignite was explored. At the same time, the material distribution characteristics of each section in the direction of the discharge edge of the bed were systematically analyzed, the material distribution area of the bed was determined, the optimal operating parameters (A = 2.8 mm, f = 26 Hz, V = 2.29 m/s) were obtained, and the sorting test was carried out under the optimal parameter conditions. The test results show that when the vibration frequency f = 26 Hz, the sulfur segregation degree of bedding materials reaches the maximum Ss = 0.36, and the sulfur content of materials in I, II, and III regions is 0.85%, 5.47%, and 18.78%, respectively. The stratification effect of bedding materials is the best. When A = 2.8 mm, the material sulfur segregation reaches the minimum value of Ss = 0.28, and the average sulfur content of materials in I, II, and III regions is 0.78%, 5.46% and 18.27%, the material is stratified according to density. When the airflow rate is 2.55 m/s. The stratification effect of bed material is best according to density. The clean coal yield is 69.87%, and the sulfur content is 0.98%. The gangue yield is 30.13%, and the sulfur content is 18.66%. The Ep value of energy deviation is 0.11 g/cm3, which realizes high precision dry desulfurization and upgrading fine-grade, low-grade, and high sulfur lignite.

Understanding FABA composition in coal-fired power plants: Impact of operating conditions and combustion efficiency on ash characteristics – A case study in PT Bukit Asam, South Sumatra, Indonesia

Coal-fired power plants are integral to global electricity production due to their cost-effectiveness and widespread availability of coal. This research investigates the operational dynamics of these plants, emphasizing the production of fly ash and bottom ash (FABA) as crucial by-products. The study focuses on three power plants in South Sumatra, Indonesia, operated by PT Bukit Asam Tbk. Fly ash and Bottom ash (FABA) and feed coal samples were collected to determine how the operational conditions of a power plant impact the composition of FABA. The mineralogical composition of FABA has been determined accurately with X-Ray diffraction analysis. Significant feed oxides in coal and FABA were identified using inductively coupled plasma atomic emission spectroscopy (ICP-AES). The primary characteristics of FABA mostly consist of unburned carbon, which may exceed levels as high as 76.05 %. The existence of unburned carbon residues is evidence of an inefficient coal grinding operation and low combustion efficiency of carbon in the boiler. The abundance of quartz in the FABA corresponds to its condition of being unmelted when heated to a temperature of 850 °C. A decrease in operating temperature results in a lower percentage of amorphous glass. The presence of quartz and reduced plagioclase concentration in FABA components correspond to the utilization of boiler-incompatible sand as bed material. In addition a consequence of a decrease in combustion temperature, pyrite exhibits partial decomposition, resulting in the formation of a tiny amount of hematite, while the other pyrite is still into its original form. A relatively small amount of spinel was associated to a mineral composed of Fe-oxide. Spinel is formed as a secondary mineral through the decomposition of Fe sulfides and other Fe-bearing minerals that exist in coal. This study evaluates the combustion efficiency and operational characteristics of power plants by applying the shrinking reactive core model by the assistance of Matlab®. The results demonstrate that since the efficiency of coal combustion increases, the concentration of unburned carbon in the FABA decreases. The modeling corresponds with the current findings in the field.

Bedding material properties and slurry C/N ratio affect the availability of nitrogen in cattle slurry applied to soil

Bedding material properties and slurry C/N ratio affect the availability of nitrogen in cattle slurry applied to soil

Enhancing the load ramp-up capability of the subcritical CFB power unit by considering the evolution of internal stored energy

The substantial inertia of the boiler restricts the flexibility of circulating fluidized bed (CFB) power units. To enhance the load ramp-up capability of the CFB power unit, we proposed a novel control strategy considering the spatial-temporal evolution of its internal stored energy. A dynamic model of the subcritical CFB power unit with a capacity of 300 MW was developed, incorporating the mechanism and control modules. By analyzing the spatial-temporal evolution of the stored energy in bed material, flue gases, refractory materials, economizer, evaporation subsystem, superheater subsystem, reheater subsystem, and turbine subsystem, we identified that the over-utilization of chemical and thermal stored energy in the bed materials is the primary factor restricting load ramp-up, while the thermal stored energy of the economizer is suitable for further utilization. Under the optimized control strategy that utilizes deviations of stored energy per mass of bed materials as a feedforward mechanism, the deviations of the key operating parameters during the load ramp-up process are significantly reduced, and the load ramp-up rate of the subcritical CFB power unit can be improved from 2.0 % Pe/min to 3.0 % Pe/min.

Investigating the influence of weirs and small dams on coarse sediment connectivity in low-energy rivers: A case study of the orne and vire rivers in Normandy, France

The removal of weirs has become emblematic of efforts to restore the good ecological status of rivers in France (Water Framework Directive -WFD- in 2006; the French Eel national management plan in 2007); however, it is increasingly facing opposition for the recreational and cultural considerations it brings (Germaine and Lespez, 2017). Previous studies have highlighted that bedload can pass through or over these weirs, although they acknowledged the difficulty in applying their conclusions to all geographic contexts. In this context, we aimed to determine the influence of these structures on the bedload connectivity in low-energy, highly human modified rivers. In this way, the objective of this study is threefold: generate knowledge about the mobility of a potential bedload in low-energy, highly anthropized contexts, better understand the influence of weirs and dams on these bedlaod dynamics, and identify the associated morphological changes. We monitored the bedload fraction of the Orne and Vire rivers (France) for 4 years using 848 pebbles equipped with passive transponders injected upstream of 2 dams and 4 weirs of different size and 2 reference sites where a weir or dam had been removed. While tracers' mobility was low (∼3–5 m yr−1 for T < 2 yrs), it was highly influenced by the presence of transverse structure (shorter distances and frequency of mobilization), even small ones. After 4 years of monitoring, no tracers crossed any of the weirs. This reduction in mobility was also due to decrease of shear stress within the reservoir as well as the physical barrier created by the weir. This interruption in bedload continuity resulted in a downstream coarsening of bed material downstream of the weirs but not at sites that had been restored for several years. Ultimately, the results of this study contribute to the scientific debate by focusing on two river reaches that have been greatly influenced by human activities for centuries.

Effects of repeated drawdown flushing on riverbed fine sediment dynamics downstream from a dam

Sediment accumulation in reservoirs is frequently a problem, impelling dam managers to implement strategies such as drawdown flushing to limit siltation. Drawdown and other sediment removal methods may induce riverbed clogging downstream of dams, especially in river sections where water is diverted, thereby reducing transport capacity. In this study, we investigate the effects of drawdown flushing downstream of the Plan d’Arem run-of-the-river dam (Upper Garonne, Spain – France border) using an adaptive inter-site comparison strategy to consider a range of spatial and temporal conditions, which allow us to separate the effects of dam storage and flushing from other potential factors. Drawdown flushing has been undertaken three times during the study period over a short span of time (2 months). We couple bed material sampling, which provides direct information on bed composition, with airborne infrared thermal imaging to better interpret whether fine sediment interstitial storage within the bed is associated with clogging. We also measure bed surface grain size and bed mobility in order to investigate their potential role in controlling fine sediment dynamics. We identify surface grain size and water diversion as the main factors controlling fine sediment spatial distribution, with coarse-grained bed-surfaces and by-passing promoting fine sediment enrichment. As a result, sites located upstream and within the by-passed reached of the Plan d’Arem dam show higher fine sediment interstitial storage than sites downstream from the by-passed reach. Results from thermal imagery demonstrate such interstitial storage does not induce clogging effect. The reaches with the most important sediment storage host a high number of cool-water patches, indicating water exchanges with the hyporheic zone. Post-flushing bed composition indicates systematic export of fine sediments from the bed matrix at all sites after the first operation, afterwards fine levels remain low after the second and the third flushing. The low impact of dam flushing in term of clogging is interpreted by the fact that the interstitial material is very sandy.

Innovative bedding materials for compost bedded pack barns: enhancing dairy cow welfare and sustainable dairy farming

AbstractCompost bedded pack (CBP) barns are an innovative housing system that improves the comfort and welfare of dairy cows, compared to cubicle style housing or free stalls with artificial surfaces, such as rubber or concrete. This type of bedding system also has the potential to improve lameness scores, overall health, welfare, and productivity of dairy cows. In CBP barns, carbon materials or organic materials are composted in the barn while being used as bedding for livestock. The animals pass manure on these surfaces providing the nitrogen, microorganisms, and moisture necessary for the composting process. Historically, dry sawdust originating from mills, furniture and pallets have been used as a substrate for compost. However, due to these materials becoming increasingly expensive and hard to source, other materials have been trailed as potential substitutes. Furthermore, there is an increasing interest in making dairy production more environmentally friendly by reducing carbon footprint. This review summarises and highlights appropriate alternative materials that, subject to their management, can be successfully used in the CBP barn system. This will act as an aid for farmers and decision makers when choosing materials to be incorporated in CBP barns. Using alternative materials to sawdust, wood chips and wood shavings, which are the current industry standard, will contribute to a more circular economy and sustainable dairy production, while simultaneously contributing to sustainable development goals, and improved animal health and welfare.

Effect of a lime-based bedding conditioner on physical-chemical characteristics and microbiological counts of recycled manure solids.

Bedding materials are aimed at providing a safe and comfortable resting environment for cows. Control of pathogen proliferation in these substrates is crucial to prevent intramammary infections in dairy cows, as these can significantly impact milk quality, cow health, and farm productivity. This is particularly relevant in the case of organic bedding substrates, including manure-derived materials. This study aimed to evaluate the in vitro effect of a lime-based conditioner (LBC), composed of CaCO3MgCO3 and Mg(OH)2, at increasing concentrations on the physical-chemical characteristics and bacterial counts of untreated anaerobically digested manure solids (ADMS) and separated raw manure solids (SRMS). Unused ADMS and SRMS were evaluated at four LBC weight-based concentrations: 0 (as untreated control), 10, 15, and 20% of LBC inclusion. The bedding materials were assessed immediately after LBC addition (0 h) and after 24, 72, and 168 h of storage at 28°C. The dry matter content (DM), and pH were measured for all the time points. Standard microbiological methods were used to assess total bacterial counts (TBC), other Gram-negative bacteria, coliforms, Escherichia coli, and streptococci and streptococci-like organism (SSLO). It was observed a linear increase in both DM and pH with increasing concentrations of LBC. Specifically, for each percentage unit increase of LBC, the DM of ADMS and SRMS increased by 0.73 and 0.71%, respectively. Similarly, for each percentage unit of LBC, the pH of ADMS and SRMS increased by 0.15 and 0.19, respectively. Conversely, a linear decrease in TBC, Gram-negative bacteria, coliforms, E. coli, and SSLO was observed with increasing concentrations of the LBC. Manure-derived materials without the inclusion of the LBC had bacterial counts that tended to remain high or increase over time. Otherwise, bedding materials with LBC application had reduced bacterial counts. Based on the results of the present study, it was observed that the higher the concentration of LBC, the more significant the reduction of bacterial counts. Specifically, bacterial recovery was lower when higher concentrations of LBC were applied. Our findings underscore the potential of LBC in effectively controlling environmental bacteria and improving the physical-chemical characteristics of manure-derived bedding materials to improve cow health and welfare.

The Veterinarian’s Role in Biocontainment Research Animal Facilities and Prevention of Spread of Pathogens: A Case of Nigeria and South Africa

Infections acquired in research laboratories and unintentional pathogen escapes from breaches in biocontainment pose risks to humans and the environment, necessitating the need for effective biosafety and biosecurity management frameworks in biocontainment research animal facilities (BRAFs). We examine key biosafety issues associated with BRAFs, including inadequate decontamination procedures for wastewater and experimental samples, handling high biosafety level pathogens in lower-level laboratories, risks of animal bites and sharps injuries, contamination of bedding and enrichment materials, and improper management and transportation of biohazard samples. Additionally, we discuss the role of veterinarians in research animal facilities and the challenges they encounter in maintaining biocontainment standards. We emphasise the importance of routine monitoring of effluent water to detect possible disease outbreaks. We recommend a thorough investigation of disease outbreaks to identify potential sources of pathogen release from BRAFs, which could serve as hotspots for future disease outbreaks. Findings from such investigations will inform the development of policies aimed at safeguarding human populations from future pandemics and preventing BRAFs from becoming sources of infectious disease outbreaks.

Enhancing Broiler Welfare and Foot Pad Quality through the Use of Medicinal Plant-Based Pellets as Bedding Material

The aim of this study was to investigate the impact of different bedding materials on both production performance and foot quality, assessed through the incidence, severity, and microbiological quality of foot pad dermatitis (FPD). A total of 2400 Ross 308 chickens were raised over 42 days, distributed across eight bedding material types (eight groups × four treatments × 75 chickens each). These pellets either lacked medicinal plant components or included 30% of plant parts, such as oregano (Origanum vulgare), summer savory (Satureja hortensis), lemon balm (Melissa officinalis), salvia (Salvia officinalis), and thyme (Thymus vulgaris). Production performance controls included body weight (BW) at 42 days of age, feed conversion ratio (FCR), and mortality. The severity of FPD was evaluated at 28, 35, and 42 days using a scale ranging from S0 to S3. A microbiological analysis of the feet was based on the FPD score. Broilers raised on straw chaff (bedding: 24% oregano and 6% summer savory, 18% oregano and 12% summer savory, and 24% oregano and 6% thyme) exhibited the highest BW. Straw chaff-reared broilers demonstrated the lowest FCR. The highest mortality occurred on 18% oregano and 12% summer savory bedding, which may have been caused by the high share of summer savory, which could be toxic. At 35 and 42 days, broilers in the 24% oregano and 6% summer savory group exhibited the best foot quality, while those on straw chaff and 18% oregano and 12% summer savory had the worst one. The influence of medicinal plants in the pellets was particularly notable in reducing Listeria sp. This reduction was likely due to the presence of carvacrol from summer savory, quercetin from lemon balm, and thymol from thyme. Based on our research, the best bedding materials for foot quality are 24% oregano with 6% summer savory and 18% summer savory with 12% salvia, while 18% summer savory with 12% lemon balm and 18% summer savory with 12% thymus were the most effective in limiting Listeria sp.

A semi-conservative depth-averaged material point method for fast flow-like landslides and mudflows

We present a two-dimensional semi-conservative variant of the depth-averaged material point method (DAMPM) for modeling flow-like landslides. The mathematical model is given by the shallow water equations, derived from the depth-integration of the Navier–Stokes equations with the inclusion of an appropriate bed friction model and material rheology, namely Voellmy and the depth-integrated Bingham viscoplastic stress model, respectively. After assessing the accuracy and performance of the proposed numerical method by means of several idealized benchmarks, we test its behavior in a realistic scenario.

Implementation of Anti-Abrasion Grid in Sumsel-5 580 t/h CFB Boiler (Reliability and Performance Evaluation)

CFB Boiler operated with turbulence model and fast fluidization. This model regime gives CFB boiler great heat distribution and increase boiler efficiency. Disadvantage of regime is due boiler furnace feed with coal, sand and limestone as bed material. Bed material with the high velocity and turbulence regime can be harmful for water and steam tube inside of furnace. Operational challenges such as abrasion and abrasion of boiler components will significantly affect their efficiency and increase possible force shutdown because of boiler tube leakage. This research investigated the implementation of anti-abrasion grids perpendicular to water wall tubes of Sumsel-5 CFB Boiler, installed horizontally and vertically to mitigate abrasion and enhance overall performance. The result showed that anti-abrasion grid installation could increase the lifespan of the CFB boiler, reduce the abrasion rate by more than 50%, and lead to enhanced boiler performance by 0,4%. Anti-abrasion grid installation could also reduce the maintenance cost due to water wall tube repair.

Evaluation of sediment generation and transport: a case study of Thwake Dam in Kenya

ABSTRACT The study aimed to evaluate sediment generation, transport, and deposition into the Thwake reservoir. This research sought to assess sediment transport patterns and their potential impact on the reservoir using regional and numerical techniques. The Thwake River basin constitutes 30% of the dam's catchment area and experiences high soil-loss due to its semi-arid climate, steep slopes, and lack of vegetation. The river system in the sub-basin is ephemeral, with the riverbed remaining dry throughout most of the year and experiencing tidal flow only during storm events. Bed-material samples were collected from selected reaches, and sediment properties were evaluated. The study involved analyzing datasets on the reservoir, catchment, and sand-bed channel. Numerical models assessed hydrological and sediment transport information by considering interacting variables and predicting deposition patterns and sediment-yield estimates. The findings indicated that sufficient bed material from sub-basin 3E would be deposited into the reservoir, resulting in delta formation approximately 5 km downstream of the tail waters at minimum dam operating level. The mass cumulative sediment inflow from 3E into the reservoir was estimated as between 14 and 26.3 metric tons per annum, representing reservoir loss and useful life under 50 years.

Online Monitoring of the Temperature and Relative Humidity of Recycled Bedding for Dairy Cows on Dairy Farms

In large-scale dairy farming, the use of high-temperature-fermented dairy manure bedding instead of rice husk-based bedding and other commercial types of bedding is widely favored. Strip-stacking aerobic fermentation is the main production method of dairy manure bedding, but it has problems including unstable fermentation and the secondary breeding of pathogens. In this work, a multi-probe, integrated, online monitoring system for temperature and relative humidity was used for fermentation process optimization. The effects of the temporal and spatial distribution of fermentation temperature and relative humidity on the nutrient content curve and the moisture and ash content of manure bedding materials were systematically studied. The effect of the fermentation process on the retention rate of effective bedding materials (cellulose, hemicellulose, and lignin) was analyzed. The experiments proved that high-quality bedding material can be obtained through reasonable stacking fermentation. The fabricated bedding material has a total dry base content consisting of cellulose, hemicellulose, and lignin of 78%, an ash content of 6%, and a nutrient content of 17%. The obtained bedding material was produced to increase the bed rest rate and continuously inhibit the bedding bacteria content, keeping it at a low level for 5 days. This study proves that temperature and humidity monitoring can guide the optimization of the strip-stacking fermentation process of dairy manure and that it can be applied to large-scale farms to improve fermentation parameters.

Evaluation of heat transfer conditions during polydisperse gas–solid flow in an industrial fluidised bed reactor

Knowledge of heat transfer conditions in large-scale circulating fluidised bed reactors plays an essential role in their proper design and optimization of theirs. This work presents an evaluation of the heat transfer conditions taking into account the coordinate height of the furnace chamber and the fluidised bed flow regime in the reactor. Experimental tests used method and measurement technique that provides reliable temperature data. The vertical and horizontal temperature profiles were obtained at different 966MWth fluidised bed reactor operating conditions. Four characteristic areas can be distinguished in the furnace chamber: the bottom region with a high-temperature gradient from 10.6 °C/m to 22.7 °C/m; the dense region with a medium temperature gradient from 4.7 °C/m to 7.3 °C/m; the dilute area with the lowest temperature gradient from 0.7 °C/m to 3.1 °C/m and the exit region with a temperature gradient (4.3 °C ≤ grad T ≤ 9.6 °C) similar to dense region. The horizontal temperature profiles confirmed a core-annular flow structure inside the furnace chamber. At the pressure drop below 5 kPa, the low variation of average temperature (from ±0.7 °C to ±4.2 °C) inside the furnace chamber of the CFB reactor was observed. As a result of fly ash recirculation of 3.86 kg/s, the lowest temperature gradient 0.2 °C/m was achieved in the bottom region of the furnace chamber. In the range of bed material circulation rates of 32 to 68 were registered temperature fluctuations 115 °C. The experimental results also showed the variation of the bed temperature was small and kept at a very low level of ±13 °C whereas the fluidised bed reactor was operated with a fluidisation velocity range of 1.8 to 2.4. Obtained findings provide unique data on heat transfer conditions in industrial facilities and thus fill the gap in literature data for CFB reactors. Based on main tests carried out in a large-scale CFB reactor, it can be concluded that detailed experimental data on thermal conditions provide important information to validate guidelines and for verifying empirical relationships, which are used in the design, optimization, and scaling of heat transfer surfaces in commercial fluidised bed reactors.

Fine Sediment in Mixed Sand‐Silt Environments Impacts Bedform Geometry by Altering Sediment Mobility

AbstractGeometric characteristics of subaqueous bedforms, such as height, length and leeside angle, are crucial for determining hydraulic form roughness and interpreting sedimentary records. Traditionally, bedform existence and geometry predictors are primarily based on uniform, cohesionless sediments. However, mixtures of sand, silt and clay are common in deltaic, estuarine, and lowland river environments, where bedforms are ubiquitous. Therefore, we investigate the impact of fine sand and silt in sand‐silt mixtures on bedform geometry, based on laboratory experiments conducted in a recirculating flume. We systematically varied the fraction of sand and silt for different discharges, and utilized an acoustic Doppler velocimeter to measure flow velocity profiles. The final bed geometry was captured using a line laser scanner. Our findings reveal that the response of bedforms to an altered fine sediment percentage is ambiguous, and likely depends on, among others, bimodality‐driven bed mobility and sediment cohesiveness. When fine, non‐cohesive material (fine sand or coarse silt) is mixed with the base material (medium sand), an increased dune height and length is observed, possibly caused by the hiding‐exposure effect, resulting in enhanced mobility of the coarser material. However, weakly cohesive fine silt suppresses dune height and length, possibly caused by reduced sediment mobility. Finally, in the transition from dunes to upper stage plane bed, there are indications that the bed becomes unstable and dune heights vary over time. The composition of the bed material does not significantly impact the hydraulic roughness, but mainly affects roughness via the bed morphology, especially the leeside angle.

MFIX–DEM simulation of gas-solid flow dynamics in a dual fluidized bed system

Abstract To overcome the operational difficulties associated with bubbling and circulating fluidized bed gasifiers, a new gasification technology termed dual fluidized bed gasification (DFBG) has evolved. To strengthen the understanding of the gasification and combustion processes in the DFBG system, a thorough analysis of bed hydrodynamics is of paramount importance. Furthermore, the complexity of the hydrodynamics escalates while incorporating diverse fuels like biomass and coal, along with bed materials fluidized in a single reactor due to its nonlinearity and transience. As a result, the study of hydrodynamics in such a system is indispensable. The present study focuses on the discrete element model (DEM) simulation of the bed hydrodynamic behaviour within the gasifier of a DFBG system. The simulation was conducted using Multiphase Flow with Interphase eXchanges (MFiX) software. The influence of superficial velocity on the number of particles in a gasifier was analyzed using the 2-D discrete element model (DEM). In this numerical investigation, transient variation of pressure drop, axial and radial solid volume fraction, and particle velocity was evaluated, and the data were analyzed using the ParaView software. The simulation results of the gasifier indicated an increase in the bed pressure drop with the rise in inlet air velocity. The effective height of solid volume fraction also increased with the surge in superficial velocity. The solid velocity profile and streamlines were also investigated to understand its variation pertaining to the location within the fluidized bed.

Design of a Compact Multicyclic High-Performance Atmospheric Water Harvester for Arid Environments.

Water scarcity remains a grand challenge across the globe. Sorption-based atmospheric water harvesting (SAWH) is an emerging and promising solution for water scarcity, especially in arid and noncoastal regions. Traditional approaches to AWH such as fog harvesting and dewing are often not applicable in an arid environment (<30% relative humidity (RH)), whereas SAWH has demonstrated great potential to provide fresh water under a wide range of climate conditions. Despite advances in materials development, most demonstrated SAWH devices still lack sufficient water production. In this work, we focus on the adsorption bed design to achieve high water production, multicyclic operation, and a compact form factor (high material loading per heat source contact area). The modeling efforts and experimental validation illustrate an optimized design space with a fin-array adsorption bed enabled by high-density waste heat, which promises 5.826 Lwater kgsorbent -1 day-1 at 30% RH within a compact 1 L adsorbent bed and commercial adsorbent materials.