DETERMINATION OF THE MODE OF FUNCTIONING OF THE CENTRIFUGAL-GRAVITATIONAL SEPARATOR OF THE GRINDING DEVICE

The peculiarity of harvesting legumes is the need to process their heap on grater devices with subsequent separation. To improve the technical and economic performance of seed heap processing equipment, it is advisable to combine wiping and separation operations by combining a grater working body and a separating rotating sieve of cylindrical or conical shape. The analysis of influence of geometry of rotary sieve drums allows to define the rational form and parameters of work of the separating device which will provide the necessary quality of seed material. Analysis of the literature on the processes of sieve separation of grain and seed mixtures showed the advantages of centrifugal separators with a rotating sieve surface. Improving the efficiency of separation of mixtures by rotary sieves is achieved by the simultaneous use of centrifugal, Coriolis and gravitational forces. The aim of the study is to increase the efficiency of separation of seed heaps of legumes after treatment with a grater device by determining the trajectory of the seeds along the rotational surfaces. Earlier, the authors developed a grater-separating unit in which a cylindrical perforated drum is used to remove unworn seeds. This design does not use the surface of the sieve effectively enough. To increase the uniformity of the load on the steaming surface of the rotary drum, it is advisable to reduce its area in the direction of seed movement. To do this, use a conical separating surface to reduce the radius of the cone in the direction of movement of the material. When considering the movement of a particle, it is represented as a material point with mass m moving along a conical surface that rotates around a vertical axis. As a result of theoretical researches the dependence which defines time of stay of a particle on a sieve depending on a coordinate (length of a generating cone) is received. A graphical interpretation of this dependence for certain values of design parameters is also presented. As a result of research, it was found that increasing the residence time of the material on the sieve due to the use of a conical surface increases the yield of pure seeds, and also contributes to the uniform loading of the sieve surface, which improves the quality of the source material.

DPM model segregation validation and scaling effect in a rotary drum

Discrete phase method (DPM) model was used to analyse rotary drum systems for segregation behavior. DPM simulations were performed for comparison with a dynamic segregation experimental measurement from the literature. This included dynamic segregation and time-averaged particle velocity field, which were validated with experimental data. In addition, a direct DPM and parcel scaled DPM simulation study was performed to analyse the effect of drum and particle parcel size scaling. The segregation dynamics was evaluated using the Lacey mixing index. This work shows segregation dynamics decreases with increasing drum size while keeping the same particle size. It further shows that for a given drum size the segregation dynamics deviate after a certain particle parcel scaling limit. The parcel scaling limit also increases with increasing drum size.

Assessment of the Mixing of Polydisperse Solid Particles in the Rotary Drum and Slant Cone Mixers Using Discrete Element Method

In spite of wide applications of powders in industry, there is a lack of sufficient knowledge regarding the mixing of poly-disperse particles in rotary drum and slant cone mixers. The main objective of this study was to explore the mixing quality of mono-disperse, bi-disperse, tri-disperse, and poly-disperse particles inside rotary drum and slant cone mixers as a function of the drum speed, particle size, agitator speed, and the initial loading method through the discrete element method (DEM). To achieve this objective, experimental work and simulations were carried out. DEM results were validated using experimental data obtained from both sampling and image analysis techniques. DEM simulation results were in good agreement with the experimentally determined data, both qualitatively and quantitatively. Three major loading methods were defined: side-side, top-bottom, and back-front. Also, the mixing metric was utilized to measure the mixing quality. For bi-disperse particles inside the slant cone mixer, the mixing index increased to a maximum and decreased slightly before reaching a plateau at the drum speed of 15 rpm with different loading methods as a direct result of the segregation of particles of different sizes. The same behavior was observed in the rotary drum for bi-disperse, tri-disperse, and poly-disperse particles. The effect of agitator speed on the mixing performance for bi-disperse particles inside the slant cone mixer was also investigated. The addition of the agitator increased the mixing quality and reduced the segregation of particles with different sizes. The best mixing qualities for the tri-disperse and poly-disperse particles inside the rotary drum were recorded for the top-bottom smaller-to-larger loading method. For the slant cone mixer, highest mixing indices for tri-disperse and poly-disperse particles with the top-bottom smaller-to-larger loading method were obtained at drum speeds of 15 and 55 rpm, respectively. The impact of segregation for both mixers was reduced by introducing additional intermediate size particles.

Assessment of the Mixing of Polydisperse Solid Particles in the Rotary Drum and Slant Cone Mixers Using Discrete Element Method

In spite of wide applications of powders in industry, there is a lack of sufficient knowledge regarding the mixing of poly-disperse particles in rotary drum and slant cone mixers. The main objective of this study was to explore the mixing quality of mono-disperse, bi-disperse, tri-disperse, and poly-disperse particles inside rotary drum and slant cone mixers as a function of the drum speed, particle size, agitator speed, and the initial loading method through the discrete element method (DEM). To achieve this objective, experimental work and simulations were carried out. DEM results were validated using experimental data obtained from both sampling and image analysis techniques. DEM simulation results were in good agreement with the experimentally determined data, both qualitatively and quantitatively. Three major loading methods were defined: side-side, top-bottom, and back-front. Also, the mixing metric was utilized to measure the mixing quality. For bi-disperse particles inside the slant cone mixer, the mixing index increased to a maximum and decreased slightly before reaching a plateau at the drum speed of 15 rpm with different loading methods as a direct result of the segregation of particles of different sizes. The same behavior was observed in the rotary drum for bi-disperse, tri-disperse, and poly-disperse particles. The effect of agitator speed on the mixing performance for bi-disperse particles inside the slant cone mixer was also investigated. The addition of the agitator increased the mixing quality and reduced the segregation of particles with different sizes. The best mixing qualities for the tri-disperse and poly-disperse particles inside the rotary drum were recorded for the top-bottom smaller-to-larger loading method. For the slant cone mixer, highest mixing indices for tri-disperse and poly-disperse particles with the top-bottom smaller-to-larger loading method were obtained at drum speeds of 15 and 55 rpm, respectively. The impact of segregation for both mixers was reduced by introducing additional intermediate size particles.