Rotary Drum Research Articles

Numerical study of forced axial segregation of binary density granular system in a split rotary drum

• Segregation of binary density particles in a split drum was studied. • The effects of sub-drum speed on segregation were analyzed. • The effects of split position on segregation dynamics were investigated. Driving and controlling the segregation in a rotary drum is both a theoretical and a practical challenge in powder technology. A novel horizontal split drum design composed of two reverse rotating sub-drums was explored to drive axial segregation of granular matter. DEM (Discrete Element Method) simulations were performed to study the particle dynamics and segregation performance of binary density particles in the split drum. Then, the effects of drum speed, the speed ratio of the two sub-drums, and the split position on the axial segregation were analyzed. It was found that true axial segregation occurred in the split drum and heavier particles tend to accumulate in the region near the split. An increase in drum speed can accelerate the segregation but it has no obvious influence on the final axial distribution of particles. The results obtained indicate when two sub-drums rotate at different speeds, the concentrated region of heavier particles moves towards the low-speed sub-drum. These findings could lead to new designs for a broad range of particle processing industries.

Modelling the final discharge angle in flighted rotary drums

Rotary drums equipped with longitudinal flights are mainly used to dry granular solids and handle high throughputs. The design of the flights is a crucial task because they decisively influence the distribution of the particles over the dryer cross section. In a previous work, the authors derived a mathematical model for the particle flow in rotary drums with rectangular flights. In this model, the final discharge angle was underpredicted resulting in errors when calculating the contact area of the particles in the air-borne phase. Therefore, a new model was developed in this study to predict the final discharge angle based on a forces balance approach on a single particle. This approach includes the Coriolis force acting on the last discharging particles sliding down the inclined flight sheet. The model was solved by using the vector analysis method. Experiments were performed at rotary drums with 0.5 m and 1.0 m in diameter, respectively, and 0.15/0.3 m in length using glass beads and quartz sand as bed materials. Each drum was equipped with 12 flights around the shell. The model validation was performed by varying the bed material, drum diameter, flight length ratio, and the rotating speed. The model predictions have shown that as the flight length ratio and the Froude number increased, the final discharge angle attained higher values. The model predictions agree well with the measurements.Graphic abstract

Biological treatment of Climbing Hempweed biomass through optimized composting technologies - Toxicity assessment and morphological study of Abelmoschus esculentus.

Climbing Hempweed (CH) is one of the top ten most obnoxious weeds on the planet, as well as one of the most destructive weeds. Its disastrous spread on the agricultural field has hampered the production of a wide range of crops. Various management techniques have been used to eradicate the weed, but none have been completely successful. As a result, management through the use of weed biomass will aid in the eradication of the weed as well as the production of a value-added product. To utilize invasive weed CH for the production of rotary drum compost (R1) and rotary drum followed by vermicompost (V1), two composting technologies were used. These technologies are being compared on several physicochemical parameters to determine their efficacy. V1 compost had the highest total Kjeldahl Nitrogen (TKN) (3.01%), potassium (3.45%), and total phosphorus (16.42g/kg) levels, while R1 compost had 2.58% TKN, 2.8% potassium, and 14.25g/kg total phosphorus. Subsequently, the increasing trends in mitotic index (%) of R1 and V1 samples imply that the cytotoxic effects of CH were decreased due to composting and vermicomposting processes. Genotoxicity assessment revealed that an aberration percentage of 1.64 was observed in 100% concentration of V1 (after 30 days) and 4.34% in R1(after 20 days). R1 and V1 were used to evaluate the performance of Abelmoschus esculentus where the highest fruit harvest was seen at 25% amended R1 compost and 35% amended V1 compost. The application of 25-35% R1 compost and 35-40% V1 compost was found to be the most beneficial for the development of Abelmoschus esculentus. There was no significant difference in heavy metal (Mn, Fe, Cu, Co, and Zn) content in the fruit of Abelmoschus esculentus post-application of R1 and V1 compost.

A Study on the Calibration of Wheat Seed Interaction Properties Based on the Discrete Element Method

The interaction properties of the seeds have to be calibrated to simulate the realistic behavior of the seed bulk. Here, a simple and accurate calibration method of DEM interaction properties of seeds with adequate equipment to simulate each seed’s behavior remains a challenge. In this research, the rotary drum is chosen as simple equipment to calibrate particle–particle and particle–material interaction properties, as there is a lack of research on whether the rotary drum is adequate equipment to calibrate particle–material interaction properties. Therefore, this article calibrates particle–particle and particle–material static and rolling interaction coefficients using a rotary drum. The calibration of particle–material static and rolling friction coefficients are described using the rotating drum with a 45 degrees inclination. The particle–particle static and rolling friction coefficients were calibrated according to the angle of repose when the rotary drum is vertical.

Thermophilic-mesophilic biodegradation: An optimized dual-stage biodegradation technique for expeditious stabilization of sewage sludge

The present study investigated the stabilization of fresh sewage sludge through a dual-stage biodegradation process; rotary drum composting in series with vermicomposting. After thermophilic exposure in a rotary drum composter, the partially degraded feedstock was separated into S1 without vermiculture, S2 and S3 with Eudrilus eugeniae and Eisenia fetida vermi-monocultures, respectively. The S3-derived vermicompost exhibited an 80% and 88% reduction in CO2 and ammonium-nitrogen evolution rates, respectively, demonstrating the expedient stabilization of sludge. The robust, more than 85% seed germination index supported S2 and S3 derived vermicompost viability. A significant decrease in heavy metals was evinced with S2 and S3-derived vermicompost; the S1-derived end product exhibited higher Zn, Cr, and Pb levels in the absence of vermicomposting. Furthermore, soil amended with 20% vermicompost from S3 displayed 50% more plant growth than S1. Thus, the optimized thermophilic-mesophilic dual-biodegradation technique stabilizes sewage sludge quickly, has a lot of potential in sludge management facilities around the world, and produces a marketable end product.

Development and evaluation of a battery operated ginger (Zingiber officinale) washer for small and marginal farmers

Ginger (Zingiber officinale Rosc.) is a commercial crop grown for its aromatic rhizomes which is used both as a spice and medicine. Being a root crop and owing to its physical structure, ginger rhizomes contain heavy soil load which makes washing as an important and prime post-harvest operation. Manual washing of ginger is a laborious and time consuming process. An experiment was conducted at the ICAR-Indian Agricultural Research Institute, New Delhi during 2020 with an objective to develop a continuous rotary drum type battery operated ginger washer and to evaluate its performance.The machine consists of the frame, feeding and discharge chutes, rotary drum with internal flights, pressure pump and nozzle assembly, battery and a drive unit. The developed washer was evaluated at different feed rate and residence time to appraise the washing efficiency, microbial washing efficiency, bruise index and colour of washed ginger. Increase in feed rate significantly reduced the washing and microbial efficiencies but increased mechanical damage. Washing and microbial efficiencies increased with increase in residence time.Significant difference in the colour was found between washed and unwashed ginger.The best set of conditions under which the washer could be operated was 150 kg/h and 25 sec, at which the machine was found to have mechanical washing efficiency of 92.48%, microbial washing efficiency of 93.18% and 4.54% bruise index. Besides eliminating drudgery of washing operation, the developed washer was found to save time, water and operating cost as compared to manual washing.

Modelling of gas-solid-liquid flow and particle mixing in a rotary drum

Solid-liquid rotary drums have been widely practised in various industries, while the complex multiphase hydrodynamics hinders the understanding and optimisation of these apparatuses. In this work, the computational fluid dynamics-discrete element methoddata (CFD-DEM) coupled with volume of fluid (VOF) is developed to describe the gas-solid-liquid flow and mixing behaviours in a rotary drum considering inter-particle collisions, inter-phase interactions, and interface morphology. A smoothing method is used to link the quantities between the particle and computational grids, allowing the fine grids to resolve flow details such as the gas-liquid interface position and curvature. After model validations, the typical mixing behaviours of gas-solid-liquid flow in a rotary drum are studied. The effects of liquid presence and rotating speed on particle-scale behaviours (e.g., repose angle, active-passive zone depth, solid residence time and contact force chain) and the time evolved mixing performance (e.g., mixing index and dispersion) are studied. The results show a positive correlation of the active depth, mixing degree, and particle dispersion with the rotating speed. The liquid presence leads to a deeper active depth, prolonged solid residence time in the active zone, and lower contact force. The work sheds light on the design and process optimization of rotary drums.

An efficient method for computational flow-based simulation of heat transfer in a rotary kiln with pilot scale validation

• Counter-current rotary kiln 5.27 m long, operated with two different feeds of gravel. • Temperature measurements taken along the kiln under various operating conditions. • Novel fast efficient computational model developed to predict bed temperature. • Predicted temperature profile in reasonable agreement with the measurements. • Model allows rapid, but reliable assessment of kiln design and operating conditions. Rotary kilns are used to carry out heating and chemical transformation in several mineral processing operations. A series of experimental runs was carried out using the realistic but controlled arrangement of a pilot rotary kiln to obtain temperature data for the validation of a novel model that couples a computational fluid dynamics model of the flame to a granular bed model through heat transfer terms. The rotary kiln was 5.27 m long, with an internal diameter of 410 mm, and two different feeds of inert standard commercial gravel were used in the runs, with the kiln operating in counter-current operation. Each of the feeds was run through the kiln under various operating conditions (feed rate, kiln rotation speed, fuel rate and weir height), and kiln temperature profiles were measured during each run. The effect of various operating parameters on heat transfer within the kiln was then determined. A fast and efficient computational model of the pilot kiln was developed to predict the burner flame and heat transfer in the kiln; the granular bed was modelled using a one-dimensional model which was coupled in a pragmatic way to the computational fluid dynamics gas phase model. Dependence of the predicted temperature profile on operating parameters is in reasonable agreement with the measurements, and the model can be run rapidly for efficient assessment of a large number of design and operating condition options. While there have been an increasing number of papers published in recent years reporting very detailed models of the motion in granular beds in rotary drums that are extremely valuable for a fundamental understanding of issues such as segregation, such models are very computationally intensive, and are still not feasible for industrial-scale kilns in which the particles are small. This paper indicates that good predictions of process parameters such as bed temperature are possible without such very time-consuming computations. Moreover, the experimental temperature measurements will be useful for future rotary kiln studies.

Polymethyl methacrylate-g-carboxy-methylcellulose as an amphiphilic coating material for slow-release fertilizer

In the perspective of preparing coating material of water-soluble fertilizer with controlled and slow-release property, polymethyl methacrylate (PMMA) was grafted from carboxymethyl cellulose (CMC) through in-situ polymerization using potassium persulfate (KPS) as initiator. The prepared copolymers (PMMA-g-CMC) were fully characterized using Transform Infrared Spectroscopy (FTIR), Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC), Dynamic light scattering (DLS), X-Ray diffraction (XRD), Brunauer Emmett Teller (BET), Scanning electron microscopy (SEM) and mechanical tensile testing. The molecular weight (Mn) was also evaluated using the size exclusion chromatography (SEC). Next, conventional water-soluble diammonium phosphate (DAP) fertilizer was coated by the prepared copolymers using laboratory rotary drum. The coating effectiveness was evaluated in terms of its uniformity and thickness. The successfully coated nanomaterials significantly delay the release rate of nitrogen (N) and phosphorus (P) in water and soil, compared to their release using uncoated fertilizers. Finally, aerobic biodegradation of the coating agent was also demonstrated.

Disposal of Garden Waste by Analysing Selected Physico-Chemical and Biological Parameters Using In-Vessel Composting at a Community Level

For composting of garden waste, the selection of reactor is an important factor for efficient degradation. The present study evaluates working performance of rotary drum reactor (RDR) and aerated in-vessel (AIV) for composting of garden waste. 500 kg garden waste was mixed with 50 kg cow-dung slurry and 10 kg compost and fed into both the reactors for 45 days composting period. The reactors vary in their system configuration, shape and orientation, blade design, rate of aeration, odour control, leachate production and energy requirements. Rotary drum was rotated daily six times in clockwise and anti-clockwise direction and AIV was rotated daily for 3-5 minutes using motor. Rise in temperature started within 24 hours of composting and reached 65°C (RDR) and 59°C (AIV) on second day itself and thermophilic phase continued for 5 (RDR) and 7 (AIV) days. Moisture content reduction after composting period was 15.25 and 18.45 %, C/N ratio was 16.14 and 13.33, total volatile solids reduction was 23.74 and 29.78 % and CO2 evolution rate was 6.18 and 4.14 mg/g VS/day in RDR and AIV respectively. Reduction of hemicellulose, cellulose, and lignin was more in AIV as compared to RDR. The percentage reduction of acid insoluble lignin was 36.10 and 29.01 % and the percentage reduction of acid soluble lignin was 48.85 and 43.3% in in AIV and RDR respectively. AIV gave better performance for composting of garden waste due to its blade design and structural configuration. The novelty of the present study lies in its approach to empower communities to select best alternative as per their waste generation, budget available, land and labour requirements and behaviour of citizens towards waste.

Systems analysis of digestate primary processing techniques

In this paper, we performed technology assessment and systems analysis of primary digestate processing techniques to provide a comprehensive analysis of their environmental and cost performance. We compiled more than 100 observations from large-scale biogas plants and considered digestate based on manure, crops and agro-wastes, and food waste under the geographical contexts of Sweden and Belgium. Centrifuge, screw press, and rotary drum were identified as suitable primary processing techniques. We analyzed the climate impact, energy use, and operational cost of digestate management under these scenarios: no processing, partial processing (solid–liquid separation) and full processing (solid–liquid separation followed by ammonia stripping). As expected, the suitable digestate processing varied with the context, transport was often the most critical cost factor, and emissions from storage reduced the climate savings from the use of biofertilizers. However, treating liquid fraction became a main contributor to cost and climate impact under the Belgian conditions. Consequently, the possibility for local application of liquid fraction as biofertilizer could prevent costs and impacts associated with its further treatment. The main novelty of this work is in its integrative and comprehensive approach toward the choices and impacts of primary processing of digestate. We tried to bridge many individual case studies, drew from experiences of biogas plants in different geographical contexts, assessed suitable processing techniques for different digestate types, and analyzed the environmental impacts and cost of digestate management from a life cycle perspective. We believe that such integrated approaches would help decision-making for increased sustainability of the biogas sector.

Fungal bioremediation of agricultural wastewater in a long-term treatment: biomass stabilization by immobilization strategy

Fungal bioremediation emerges as an effective technology for pesticide treatment, but its successful implementation depends on overcoming the problem of microbial contamination. In this regard, fungal immobilization on wood seems to be a promising strategy, but there are two main drawbacks: the predominant removal of pesticides by sorption and fungal detachment. In this study, agricultural wastewater with pesticides was treated by Trametes versicolor immobilized on wood chips in a rotary drum bioreactor (RDB) for 225 days, achieving fungal consolidation and high pesticide biodegradation through two main improvements: the use of a more favorable substrate and the modification of operating conditions. Fungal community dynamic was assessed by denaturing gradient gel electrophoresis (DGGE) analysis and subsequent prominent band sequencing, showing a quite stable community in the RDB, mainly attributed to the presence of T. versicolor. Pesticide removals were up to 54 % diuron and 48 % bentazon throughout the treatment. Afterwards, pesticide-contaminated wood chips were treated by T. versicolor in a solid biopile-like system. Hence, these results demonstrate that the microbial contamination constraint has definitely been overcome, and fungal bioremediation technology is ready to be implemented on a larger scale.

High temperature corrosion of SiC-CaAl12O19 composite refractory by coal slag

Corrosion processes of SiC-CaAl12O19(CA6) composite refractory were carried out by both static crucible test and rotary drum test at 1500 °C and 1600 °C under a reducing atmosphere, respectively. The corrosion mechanism of the SiC-CA6 refractory was analyzed by means of X-ray diffraction(XRD) and scanning electron microscope(SEM). The results show that the corrosion temperature and condition had significant influence on the slag resistance of the SiC-CA6 refractory. But no matter which corrosion methods and which temperatures under the condition of this experiment, the SiC-CA6 refractory exhibited good penetration resistance even though a little corrosion appeared at a higher temperature. During the corrosion process, most of Fe containing oxide in slag could be reduced by CO in atmosphere and SiC in samples to form Fe-Si metal alloys, which precipitated at the interface between the slag and composites. The penetrated slag could react with the SiO2 produced by SiC oxidation and the CA6 matrix to form CaAl2Si2O8 and corundum, filling the pore inside the samples and causing the densification of the reaction layer. Because of the reaction between infiltrated slag and SiC-CA6 refractory, the composition and properties of local slag changed and inhibited the further penetration.

Performance assessment of in-vessel composter through heavy metal immobilization and humification of Parthenium hysterophorus

The bioconversion of Parthenium hysterophorus was performed through rotary drum composter and examined the mechanism of humification and heavy metals immobilization in the process. The 20th day compost contains a significant increase in humic substances of 28.7% compared to the initial day mix. The bioavailable fractions of heavy metals have reduced by 30 to 55% in the 20th day compost compared to the initial day mix. The leaching potential of cadmium has been reduced by 69% in the 20th day compost. The immobile fractions (F5) of Cd, Ni and Pb have been increased to 100, 99 and 78% in the 20th day compost. The mitotic index was increased by 1.7 and 51.6% in 25% dosed compost extract compared to the control and P. hysterophorus extract respectively. The transition of heavy metals to immobile fraction indicated the biodegradation capability of P. hysterophorus through rotary drum composting.

Biodegradation of an intrusive weed Parthenium hysterophorus through in-vessel composting technique: toxicity assessment and spectroscopic study.

Parthenium hysterophorus is a toxic terrestrial weed with its erratic behavior brought on by the presence of toxic compounds. A numerous works have been conducted on the complete eradication of this weed, but due to the residuals exists in soil, the weed re-grows. Current study therefore aims at examining the transformation of this weed by an in-vessel composting approach (rotary drum composter) and the evaluation of toxicity characteristics using Vigna radiata and Allium cepa as bioindicators. The nutritional content such as total Kjeldahl nitrogen (TKN), total phosphorus (TP), and total potassium were increased by 38.8, 39.1, and 49.5%, respectively, and the reactor was effective in reducing the biochemical content such as lignin, hemicellulose, and cellulose by 43.5, 50.7, and 57.3%, respectively, in the final compost. The thermophilic degradation phase in the reactor existed up to the 8th day of the composting process, which exhibits the highest degradation phase. Meanwhile, the degradation of phenolic, aliphatic, and lignocellulose was investigated and validated using Fourier transform infrared spectroscopy (FTIR) and powdered X-ray diffraction (PXRD) analysis. Although P. hysterophorus exhibited phytotoxic and cyto-genotoxic effects in plant models at the beginning of the composting process, the toxicity potential appeared to be reduced after 20days of composting. Therefore, the study's findings proved that the in-vessel composting of P. hysterophorus can produce a nontoxic, nutrient-rich compost product that could be used as a soil conditioner in agricultural farmlands. The insights of the study are not limited to the nutritional, stability, and quality characteristics but also the toxicity characteristics during the composting process.

A Simple Techno-Economic Assessment for Scaling-Up the Enzymatic Hydrolysis of MSW Pulp

A techno-economic assessment (TEA) of enzymatic hydrolyses of a municipal solid waste (MSW)-derived pulp was performed to compare various bioprocessing configurations for the production of platform sugars at both pilot and demonstration scales (two-stage continuous, batch, and two-stage fed-batch). The configurations modeled used either rotary drum and/or continuous stirred tank reactors. By using reaction kinetics and public vendor’s quotes, economic analyses were calculated for each of the proposed systems: capital expenditure (CapEx); operation expenditure (OpEx); revenue and profit; return on investment (ROI); and payback period (PP). The TEA showed that a two-stage continuous configuration with a total residence time of 54 h (6 and 48 h for primary and secondary stages) was the best option for obtaining sugars, showing sevenfold higher enzyme productivity and better profit than the reference systems. Although pilot-scale enzymatic hydrolysis demonstrated an unprofitable process, this was mainly due to the high associated enzyme cost. Increasing the scale diminished this problem, leading to higher profit per processed unit (£/kg lignocellulosic sugars). From an investment perspective, the two-stage 6/48 configuration gave a more attractive ROI and PP than the other designs.

Theoretical studies results for a mathematical model of a road roller turn

Introduction. At the heart of the creation and improvement of robotic road construction machines and complexes are mathematical modelling methods, the use of which is justified both in the development of the machines themselves and mathematical models that describe the turning processes and determine the movement of the machine along a given trajectory.The method of research. The article presents a generalized design scheme for the rotation of a three-axle road roller, which reflects its main geometric and kinematic characteristics. On the basis of the design scheme, a mathematical model of the rotation of the skating rink was compiled. As a result of the developed mathematical model, a program code was built in the MATLAB software product, which formed the basis of theoretical studies that made it possible to fully study the influence of the design and operational parameters of the machine on the motion trajectory and positioning accuracy.Results. The calculated dependencies have been obtained to determine the influence of such parameters as the speed of the road roller, the angular speed of the drum rotation on the distance of rebuilding on a parallel course and on the displacement of the rotary drum, that is, on the trajectory and positioning accuracy of the road-building machine.Conclusion. On the basis of the design scheme, a mathematical model of the rotation of the roller was compiled, as a result of which studies were carried out aimed at studying the influence of the design and operational parameters of the machine on the trajectory of the road roller and the accuracy of its positioning on the construction site when performing technological operations.

Axial segragation in 3D rotating drums with spherical particles: Experiments

Despite the wide research of powder and solid mixing in science and industry, a majority of researches focus on numerical simulation. Theory on the actual mixing of solid particles in 3D rotary drums is needed. In this work, the axial segregation of binary spherical granular particle is studied experimentally in a 3D tumbler to find the effect of key outer parameters on the mixing results. Experiment results indicate the outer parameter-rotational speed will have significant effect on axial segregation and there is some kind of competition between axial segregation and radial segregation. In addition, The initial loading method has noting to do with axial segregation. These results will provide guidance for particle mixing in cylinder mixer.

Effect of drum structure on particle mixing behavior based on DEM method

The optimization of the drum structure is beneficial to improve the particle motion and mixing in rotary drums. In this work, two kinds of drum structures, Lacy cylinder drum (LC) and Lacy-lifters cylinder drum (LLC), are developed on the basic of cylinder drum to enhance the heat transfer area. The particle motion and mixing process are simulated by DEM method. Based on the grid independence and model validation, the contact number between particles and wall, particle velocity profile, thickness of active layer, particle exchange coefficient, particle concentration profile and mixing index are demonstrated. The influences of the drum structure and the operation parameters are further evaluated. The results show that the contact number between particles and wall is improved in LC and LLC compared to cylinder drum. The particle velocity in LC is higher than that in cylinder drum at high rotating speed, and the particle velocity of the particle falling region is significantly improved in LLC. Compared to cylinder drum and LC, the thickness of active layer in LLC is smaller, while the local particle mixing quality is proved to be the best in the active region. In addition, the particle exchange coefficients between static region and active region in the three drums are compared and LLC is found tending to weaken the particle flow. Besides, the fluctuations of particle concentration in the active region, static region, and boundary region are weakened in LLC, and the equilibrium state is reached earlier. In addition, the overall particle mixing performance in cylinder drum, LC and LLC is analyzed. The particle mixing performance in cylinder drum is the worst, while the difference in mixing quality of LC and LLC depends on the operation conditions.

Residence Time Distribution of Non-Spherical Particles in a Continuous Rotary Drum

The motion of non-spherical particles with sharp edges, as they are commonly involved in practice, was characterized by residence time distribution (RTD) measurement in a continuous drum. Particles with two sizes, 6 and 10 mm, and two densities, 750 and 2085 kg/m3, were used in the experiments. The effects of rotation speed (3–11 rpm), incline angle (2–4°), feed rate, and mixture composition were investigated and compared to the results of other researchers on particles without sharp edges. We also fitted the RTD with an axial dispersion model to obtain a better insight into the flow behavior. MRT of non-spherical particles with sharp edges depends on ω−α similar to other shapes, while the value of alpha is higher for particles with sharp edges (0.9 < α < 1.24), especially at high incline angles. The MRT depends on incline angle, β−b, where b varies between 0.81 (at low ω) and 1.34 (at high ω), while it is close to 1 for other shapes. Feed rate has a slight effect on the MRT of particles with sharp edges and the effect of particle size diminishes when rotation speed increases. The MRT linearly increases with volume fraction of light particles in a mixture of light and heavy particles (from pure heavy to pure light particles).