THE USE OF DEM SIMULATION FOR CONFIRMING THE PROCESS OF PARTICULATE MATERIAL MIXING

At the present time in the research of particulate materials, computer methods that work independently with individual particles are coming to the forefront. One such method is the Discrete Element Method – DEM, which is already widely used. Its usage, however, is complex, mostly due to the input data – what the properties of the researched material are, plus their interaction in processes. And despite the progress, it is still always necessary to validate the experimental equipment and to verify the individual simulations by an experimental measuring or by theoretical knowledge. This study focuses on the verification of the simulation of the mixing of a particulate material with the help of the DEM method, whereby simulations are compared with an experimental measurement and theoretic calculations. The theoretical calculation was carried out by the Novosad model, while the experimental material was granulated polyethylene with strictly defined mechanical-physical properties

MODIFICATION OF POWDER MATERIAL BY COMPACTION PROCESSING

There are different criteria for assessing the appropriateness of an agglomeration technology in the deployment processing of dry, fine and dirty dust burdening in the communal and working environment. Besides the benefit of the environment components, the agglomeration technology offers the possibility of re-processing the material as the primary raw material within a wide range of industries. Preliminary tests have shown that the compressed material remains in the memory from the previous compression. For returning the already processed material into a primary production, it is essential that it is reformed without the need for additional materials, a requirement that can be problematic. This article deals with the modification of a powder material (powder dust from the manufacture of friction components) and the investigation of its properties before and after the compaction processing

DESIGN OF PARTICULATE MATERIAL COMPACTOR ROLLS DIAMETER

At present, in a period of an industrial expansion great emphasis is placed on the environment. That means aiming for a reduced energy consumption, and also lessening dustiness from very fine powder material. This category also includes particulate material agglomeration processes. Because this process is very energy-intensive, it is necessary to correctly design these devices. The aim of this paper is to focus on a theoretical design of a production compactor with the rolls diameter for an experimental particulate material, based on Johanson’s theory and experimentally measured material properties. The material used for experimental measurements was an NPK-based industrial fertilizer consisting of several components. The results of this paper is the dependence of the ratio of the maximum compression pressure to the initial compression pressure from the rolls diameter of the proposed compactor

THE DEVELOPMENT OF A NEW ADSORPTION-DESORPTION DEVICE

The aim of this work was to construct a new adsorption-desorption device based on the principle of separation of volatile organic compounds, e.g., ethanol. As an adsorbent, it is possible to use granulated activated carbon (GAC) in the adsorption and desorption process. In this study, two kinds of GACs were used and marked as GAC1 and GAC2. A particle size distribution and water vapour sorption for the selected GACs were measured. An experiment with distilled water was performed as a preliminary study of the new device’s functionality. After the determination of the time necessary for the adsorption and desorption, the experiments were carried out with a model mixture (5% v/v ethanol-water mixture), which resulted in a product with the ethanol content of 39.6 %. The main advantage of this device would be the potential competition of conventional distillation

ANALYSIS OF STATIC ANGLE OF REPOSE WITH RESPECT TO POWDER MATERIAL PROPERTIES

This paper investigates the Angle of Repose (AoR) of powder materials with respect to their morphological and rheological properties. Glass beads, sand, flour and semolina of different particle sizes were used as the experimental materials. The investigated material was analysed with respect to particle shape and size. The rheological properties of the material were obtained by a shear cell test. The AoR was analysed in terms of cohesion, bulk density, particle size and circularity. More cohesive materials such as the flour samples exhibited the largest AoR > 40°, indicating their poor flowability. Glass bead samples with a high circularity value had significantly lower AoR than the flour. The Angle of Internal Friction values were not dependent on those of the AoR. Using a dimensional analysis, a mathematical model was developed to determine the AoR values based on the material properties. By the application of this model, highly accurate calculation of the value of AoR is made possible

Second asymptomatic carotid surgery trial (ACST-2): a randomised comparison of carotid artery stenting versus carotid endarterectomy

Background: Among asymptomatic patients with severe carotid artery stenosis but no recent stroke or transient cerebral ischaemia, either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce long-term stroke risks. However, from recent national registry data, each option causes about 1% procedural risk of disabling stroke or death. Comparison of their long-term protective effects requires large-scale randomised evidence. Methods: ACST-2 is an international multicentre randomised trial of CAS versus CEA among asymptomatic patients with severe stenosis thought to require intervention, interpreted with all other relevant trials. Patients were eligible if they had severe unilateral or bilateral carotid artery stenosis and both doctor and patient agreed that a carotid procedure should be undertaken, but they were substantially uncertain which one to choose. Patients were randomly allocated to CAS or CEA and followed up at 1 month and then annually, for a mean 5 years. Procedural events were those within 30 days of the intervention. Intention-to-treat analyses are provided. Analyses including procedural hazards use tabular methods. Analyses and meta-analyses of non-procedural strokes use Kaplan-Meier and log-rank methods. The trial is registered with the ISRCTN registry, ISRCTN21144362. Findings: Between Jan 15, 2008, and Dec 31, 2020, 3625 patients in 130 centres were randomly allocated, 1811 to CAS and 1814 to CEA, with good compliance, good medical therapy and a mean 5 years of follow-up. Overall, 1% had disabling stroke or death procedurally (15 allocated to CAS and 18 to CEA) and 2% had non-disabling procedural stroke (48 allocated to CAS and 29 to CEA). Kaplan-Meier estimates of 5-year non-procedural stroke were 2·5% in each group for fatal or disabling stroke, and 5·3% with CAS versus 4·5% with CEA for any stroke (rate ratio [RR] 1·16, 95% CI 0·86–1·57; p=0·33). Combining RRs for any non-procedural stroke in all CAS versus CEA trials, the RR was similar in symptomatic and asymptomatic patients (overall RR 1·11, 95% CI 0·91–1·32; p=0·21). Interpretation: Serious complications are similarly uncommon after competent CAS and CEA, and the long-term effects of these two carotid artery procedures on fatal or disabling stroke are comparable. Funding: UK Medical Research Council and Health Technology Assessment Programme

Systematic Study of the Effects of High Shear Granulation Parameters on Process Yield, Granule Size, and Shape by Dynamic Image Analysis

The aim of the work was to analyze the influence of process parameters of high shear granulation on the process yield and on the morphology of granules on the basis of dynamic image analysis. The amount of added granulation liquid had a significant effect on all monitored granulometric parameters and caused significant changes in the yield of the process. In regard of the shape, the most spherical granules with the smoothest surface were formed at a liquid to solid ratio of ≈1. The smallest granules were formed at an impeller speed of 700 rpm, but the granules formed at 500 rpm showed both the most desirable shape and the highest process yield. Variation in the shape factors relied not only on the process parameters, but also on the area equivalent diameter of the individual granules in the batch. A linear relationship was found between the amount of granulation liquid and the compressibility of the granules. Using response surface methodology, models for predicting the size of granules and process yield related to the amount of added liquid and the impeller speed were generated, on the basis of which the size of granules and yield can be determined with great accuracy

Monitoring of the Apple Ferment Parameters

The aim of this study was to describe an experimental process, of which the main part is the preparation of apple batches and monitoring of the fermentation process. The batch was created from pulped apples to which special yeast cultures were added. Different process parameters of the fermentation were monitored during the experiments, depending on the yeast type and the fermentation temperature conditions. The fermented batch was later used in the distillation process of apple yeast

Chitosan and Sodium Alginate Implementation as Pharmaceutical Excipients in Multiple-Unit Particulate Systems

This study aimed to prepare and evaluate pellets containing acyclovir as a model drug. Pellets were prepared by the extrusion–spheronization process. Aqueous solutions of natural marine polymers (sodium alginate, chitosan) were compared to semi-synthetic hydroxypropyl methylcellulose (HPMC) in the role of binders. The study focused on the characterization of the pellet properties that are crucial for the formulation of the final dosage form, such as in multi-unit pellet system (MUPS) tablets or hard gelatin capsules filled with the pellets. Finally, the mentioned dosage forms were tested for drug dissolution. The morphology of pellets observed by scanning electron microscopy correlated with the shape evaluation performed by dynamic image analysis. Sodium alginate pellets exhibited the lowest value of sphericity (0.93), and many elongated rods and dumbbells were observed in this batch. Chitosan pellets had the highest value of sphericity (0.97) and were also less rough on the surface. The pellets maintained a constant surface geometry during the dissolution studies; they only reduced in size. The most significant reduction in size and weight was assessed after 2 h of dissolution testing. This fact was in line with the drug release from pellets in capsules or MUPS tablets, which was massive during the first hour, in both cases. The dissolution profiles of all of the batches were comparable

Dynamic Image Analysis to Determine Granule Size and Shape, for Selected High Shear Granulation Process Parameters

The aim of this study was to investigate the usage of Dynamic Image Analysis for determination of size, shape and distribution of granules of microcrystalline cellulose, created by high shear granulation. A series of experiments was carried out to analyse the effect of process parameters on a created granule morphology. The amount of the granulation liquid and speed of the impeller have a significant effect on the median size granule value, the sphericity, the granule distribution width, but also on the granulation process yield