Problems of Removing Loos Biological Material from a Vacuum Accumulator

. Precise fragmentizer RPW17-TN he allows to the crumbling oily materials of biological (flax seeds, white mustard). The ambition of the product of crumbling from the reservoir is the indispensable element of the process. The introduction of pneumatic transportation changes the working arrangement and the fall of the efficiency of the process of crumbling causes, even to the zero – what joins with blocking fragmentizer. The discussion was undertaken in the article over the possible law suits and constructional solutions of the industrial use of emptying the hypotensive reservoir.


Introduction
In the process of comminuting organic and inorganic materials, apart from obtaining a model form of the comminuted material, the problem is the removal of material from the comminution area. There are used gravity, mechanical and pneumatic solutions. The grinding process itself, carried out with a variable pressure parameter of the grinding chamber, gives various effects. In the case of organic materials and the RPW-17TN multiknife shredder, grinding under negative pressure brings excellent results. This allows the process to run smoothly and reduces the amount of biological substance left on the knives. The problem in this case is the discharge of the particulate material from the shredder chamber. When analyzing the existing technical solutions, there is not much choice left in this case. The available solutions are screw and bucket conveyors, in the latter case their special structure is called a "disc" conveyor [10,11]. Choosing the right method is very important, because the process of receiving the comminuted material has an impact on the parameters of the comminution model. the following are controlled: rotational speed, efficiency of filling material, negative pressure value in pneumatic transport of crushed seeds from the crusher to the final hopper and final efficiency. Assuming a constant aspirator output (D), changes in the pneumatic transport (according to the diagram in Fig. 1) as a result of too much filling with material (A) result in a reduction with an inappropriate particle size composition. Based on various simulations, a material flow model was developed [4]. Thanks to the recognition of changes taking place in the pneumatic conduit, it was possible to optimally fill the crusher with material, obtaining the maximum efficiency of the process and the desired form of seed grinding. The shredded material was collected in the tank (B), which after a certain batch required stopping the process and emptying the tank. The batch processing limited the achievement of industrial efficiency of grinding flax seeds for the preparation of dietary supplements. In the preparation of dietary supplements based on oilseeds, the crushed particles should be in the range of 0.6 -0.8 mm, which guarantees very good mixing with any liquids as well as high digestibility and absorption. The special design of the RPW-17TN precision shredder allows for precise cutting of the input material and no fat extrusion. In the industrial application of the shredder according to the scheme in Fig. 2, a satisfactory efficiency of 300 -320 kg / h was obtained and the fragmentation was λ100% <0.8 mm. This effect was obtained thanks to the creation of a technological line with elements as shown in Fig. 3, especially after using a selection conveyor with a V-1 valve.

Influence of pressure change in the grinding chamber on the process parameters
The efficiency of the grinding process can be improved by considering a process in which a fluid stream flows through the grinding chamber. The air with the disintegrated material suspended in it can be compared to such a fluid with basic properties such as density, viscosity, adhesion to the walls of the conduit, etc. The crusher is a chamber with negative pressure or overpressure in relation to atmospheric pressure. Which option is selected is of course related to the loading and unloading of the shredder chamber. But first of all, with the form and properties of the material before and after the grinding process. An important parameter of such a process is the pressure difference in relation to the environment, the most important is the pressure difference in front of and behind the shredder chamber. This difference determines the speed of the flow of the fluid crushed through the chamber (Fig.3). It should be remembered that such a fluid has a strong tendency to sediment and that solid particles are willing to settle and block the flow. Therefore, apart from the flow velocity, mention should be made of the constant flow rate of the fluid. The introduction of the variability causes a momentary variable acceleration of the particles, which in practice reduces the deposition in the grinder.
Plate conveyors are a frequently used solution in the transport of biological materials, such as seeds, nuts, candies, etc. (Fig.2). Wherever there would be problems with keeping the conveyor clean. The disc-shaped elements moving inside the fitted tube are transported while cleaning the conveyor [2,8]. An additional advantage of such conveyors is the easy change of direction and plane of transport. The elements of these conveyors are made of plastics, which reduces their weight and facilitates adaptation to various transport conditions. In the existing technologies, there is a process of disintegration in an open air flow, in order to create a vacuum (Fig.3). Product separation is achieved by rotating the stream in the cyclone. In this way, not only can the particles of crushed material be separated from the air, it is also possible to segment the material into bulk sections. In such technology, unfortunately, complete air purification requires expensive filters. It is also not possible to introduce a pressure variation in the flow.

Method of receiving the fragmented product from the shredder
In practice, there are a number of methods of removing materials from the shredder. They can be divided into pneumatic and mechanical. Pneumatic methods, as previously indicated, make it difficult to remove the material from the shredder, in a situation where the shredding chamber has a pressure different from the surrounding pressure. The main problem with this type of transport is air filtration and deposition of the particulate material in the air channels. This is especially dangerous in the case of biological materials, as it causes bacteriological problems and so on. Mechanical transport in the environment of v M Fig. 2. Segment conveyor, -v M speed of material streem (Cabelvey company product).
negative pressure in the shredder is also not an easy solution [1,5]. Can by used a scraper conveyor, bucket conveyor, belt conveyor, chain or segment conveyors, etc. A complete solution to the problem of fragmented biological material is provided by segment-scraper conveyors, also called plate conveyors depending on the shape of the transporting segments (Fig.2). This type of solution allows to maintain the tightness of the system and introduces additional pressure variability, which prevents the deposition of particulate material (Fig.4). The speed of the material stream -v s depends on the pressure difference in front of and outside the grinding chamberP, which is the set value in the vacuum pump. On the other hand, the instantaneous speed variation is caused by the instantaneous pressure value and depends on the speed and efficiency of the conveyor collecting the material -v M . In the design of the shredding system, in which the shredder chamber is to have a pressure different from that of the surroundings, the supply and discharge of the shredded material becomes a problem [9]. By applying positive pressure, the material hopper must be closed or the material is supplied via a closed conveyor. In the case of negative pressure, it is similar, although when discharging with a closed conveyor directly from the chamber, we do not have to use a closed container [12]. Additionally, the variability introduced by the segmented conveyor can improve the comminution process. Such conveyors can be designed to achieve the desired variability [13]. The size of the chamber of a single segment and the speed of displacement are subject to selection, thanks to which the variability can be obtained as shown in the drawing [14]. This variability is a component of the vacuum diagram in the crushing chamber and thus by adjusting the variability and the value of the vacuum, we can influence the grinding process in the crushing chamber [15,16]. The quality of process can by improve, when as a drive can by used gear with variable ratio [5,6,7]. v s v A v M For the previously described vacuum grinding process, the main problem was to maintain and monitor the pressure level during the grinding process. Otherwise, analyzing the problem of such comminution, it can be concluded that this problem also involves the handling and discharge of the comminuted material from the grinder under constant negative pressure. During the research, it turned out that an important aspect of the grinding process is the introduction of pressure variability, which improves the quality of the process and prevents clogging of the grinder with biological material. The disintegration function f(D) is main dependent on the pressure differenceP, but also on the instantaneous pressure difference caused by the pressure change in the conveyor.
Initial results and simulation studies showed very positive results in terms of process efficiency and quality. This opens up new research possibilities, which will allow to develop the presented model of the dependence of the biological material disintegration process on the pressures in the disintegration chamber.

Conclusions
Research on grinding processes has been carried out for many years and in many research center, but new challenges are constantly appearing, for example related to the food industry. The problem of grinding yeast flakes has become such a challenge and the starting point for research on the discharge of the fragmented material from the crusher and the use of variable vacuum in the process. It is a problem that will allow the use of many other materials in human nutrition, the fragmentation of which has not been possible on an industrial scale so far. The problem has been resolved by the authors and is currently at the stage of industrial research.