Prospects for the use of a vibratory jaw crusher with an inclined crushing chamber for processing of brittle materials

Obtaining a powder product from brittle materials is associated with significant difficulties: an insufficient number of production capacities as well as with their low efficiency. This indicates relevance and need for research aimed at creating new designs and technological schemes. Glass containers were selected for research from among all types of glass waste. Presented are a structural diagram and description of a horizontal pendulum impact tester, on which studies were carried out on destruction of a bottle by impact load. The impact tester gives an opportunity to determine impact energy, impact speed, acceleration, movement of the impactor. An analysis of the above figures shows that one blow is enough to destroy a bottle. Rational mode is when impact load is distributed along the length of the bottle. This mode can be implemented in a vibratory jaw crusher with an inclined crushing chamber, which includes the following main elements: a passive jaw located on shock absorbers, an active jaw pivotally mounted in the body and connected to it by means of elastic links, a two-shaft inertial vibration exciter. The presented granulometric characteristic of the crushed bottle shows a high efficiency of using a vibratory jaw crusher. The yield of the product sized less than 5.5 mm was 95%, and that sized less than 100 microns - 16%. The crusher has enough parameters to adjust particle size distribution over a wide range.


Introduction
In nature, there are a number of materials (quartzite, basalt, marble, etc.) with high compressive strength and low resistance to impact loads.At the same time, a significant percentage of the equipment used for their disintegration consist of jaw and cone crushers, in which the destruction of the material is carried out by compression [1].In high-tonnage production, these metal-intensive overall machines currently have no adequate replacement.In the technological schemes for obtaining fine-grained and powder materials with a productivity of 1…10 t/h and a size of the raw material corresponding to average crushing, there is a need to improve existing grinding methods [2] and develop new grinders that combine crushing and grinding operations in one design.
Ideally brittle materials, along with diamond and quartz, include glass, which can serve as a standard in determining the efficiency of using crushing and grinding equipment.At the same time, interest in obtaining glass powder is currently growing in the world.This problem is relevant, because it is associated with a wide range of properties that make simple 1254 (2023) 012049 IOP Publishing doi:10.1088/1755-1315/1254/1/012049 2 and special purpose glass powders a versatile material [3][4][5].Depending on their composition, powders can meet a variety of requirements and can be used in the sphere of electrical insulation, sealing or bonding of various materials, for 3D printing of complex glass bodies, as additives in polymers, concrete, etc. [6][7][8].Powder production is a complex and energy-intensive process [9], which includes all stages of glass production.The raw materials for glass production are lowiron quartz sands, soda ash, limestone, dolomite, etc., which require preliminary enrichment, washing, drying, and grinding.The resulting glass mass is again subjected to crushing, grinding, separation, which creates a high cost of production.
At the same time, hundreds of thousands of tons of glass waste are generated annually, but only a small part of them goes into secondary resources [10].It is known that one ton of cullet saves 1.5 tons of mineral glass raw materials, incl.100-130 kg of soda ash, 40-50 kg of sodium sulfate and 300-350 kg of quartz sand.Recycling glass allows to save huge areas of land that otherwise should turn into environmentally hazardous landfills [11].This testifies to the relevance and necessity of carrying out analytical, experimental, design developments aimed at increasing efficiency of obtaining fine-grained and powder materials directly of glass wastes.
Study purpose is to evaluate the effectiveness of using vibratory jaw crushers for processing brittle materials to obtain a fine-grained and powder commercial product.

Results
A distinctive feature of glass is its high compressive strength and low impact resistance [12, 13], therefore, glass is destroyed by mechanical action without noticeable plastic deformation, which predetermines the development of crushers with the impact principle of loading the material.
From among all types of glass waste, glass containers were selected for the research; they have a fairly well-developed collection scheme at collection points [14].It was also taken into account that the volumetric shape leads to a sharp change in filling of the crushing chamber with material during the process of loading.
Interaction of bottles with the impactor was studied on the developed laboratory installation for destruction of rocks, which is a horizontal pendulum impact tester; its structural diagram is shown in figure 1.
The laboratory installation includes a pendulum (1) with its suspension axis (2) fixed in the bearing units of the housing (3).At the free end of the pendulum there is an impact assembly, consisting of a replaceable load (4) and an impactor (5).The centers of mass of the load and the impactor are located on a common vertical axis at a distance of 1 m from the axis of the pendulum suspension.Fastening of the impactor allows you to set various profiles of the working surface that interacts with glass.The lifting (dropping) height of the impactor is determined by a measuring system containing a curvilinear bar (6) rigidly connected to the pendulum suspension axis and a following mechanism (7).The mechanism is presented in the form of a cylinder with a piston and a clamping spring inside.The rod fixed on the piston has one end in contact with the curvilinear bar, and the other end is connected to the displacement sensor (8).The system works as follows.When the pendulum is raised, the curvilinear bar rotates along with the suspension axis, and so it moves the following mechanism rod according to the given dependence.Accordingly, the displacement sensor rod also moves; the signal from this sensor passes through the VI 6-6tn (9) vibration measuring equipment, the USB oscilloscope (10) and it registers the height of the load drop on the laptop screen (11).This system also allows you to track the nature of interaction of the impactor with the material under study (12).For the same purpose, an acceleration sensor (13) is fixed on the impact assembly; it records changes in acceleration in the vertical plane.At the initial moment of testing, the working surface of the impactor is installed on the surface of the sample located on a massive base (14).Next, the pendulum suspension axis is moved to a position at which the longitudinal surface of the pendulum rod is set in a horizontal position.Movement of the suspension axis is carried out  by means of gaskets 15 (or a screw connection).The horizontal setting of the pendulum rod is controlled by a level (16).
Results of a single impact of a flat impactor on bottles for sparkling wines are given as an example.Impactor mass is 5 kg, drop height is 0.7 m.
The initial application of the load was simulated with different method of feeding the bottle into the inclined crushing chamber of the vibratory jaw crusher.When feeding the bottle into the crushing chamber with the bottom in the direction of the unloading window (figure 2, a), the first impact occurs when the working surface of the upper jaw comes into contact with the ring of strength of the bottle (force P1).The implementation of such a scheme on a pendulum impact tester showed that the bottle is destroyed (figure 3) by a single impact, however more than 50% of the glass breakage has convex shapes, which reduce the filling factor of the transporting container.
When feeding the bottle into the crushing chamber with the neck in the direction of the unloading window (figure 2, b), the first impact occurs when the working surface of the upper jaw comes into contact with the bottle shoulders (force P3).When the impact of the pendulum impact tester interacted with the bottle shoulders, a product with a size of more than 50 mm with a destroyed neck and a whole bottom was mainly formed (figure 4).
The bottle can be loaded into the crushing chamber in a position where the longitudinal axes of symmetry of the bottle and the chamber are perpendicular (figure 2, c, d).When the cylindrical surface is affected by a point load P2 (figure 2, c), with sufficient destruction of the    cylinder, the neck and bottom are not subjected to destruction (figure 5).The preferred result is obtained when the surface of the bottle interacts with a distributed load q (figure 6).
The result obtained shows sufficiency of one impact for the effective destruction of a brittle material with internal cavities, which predetermines the need to create small-sized crushing plants.Conversion of bottle convex shapes into a flat state allows you to significantly increase the filling factor of the shipping container and have a high-quality initial product for processing into commercial products.
The experience of using vibratory jaw crushers to obtain fine-grained materials shows the possibility of implementing the results obtained in similar designs [15,16].
Crushers of this type have a pronounced impact nature of the load applied to crushed materials, as well as the advantages of jaw and rotary crushers.In general terms, the design scheme of vibratory crushers is an oscillatory system with vibrations of 16-32 Hz communicated to the crusher jaws [17,18].
The material crushing process is effectively controlled in a vibratory jaw crusher with an inclined crushing chamber [19].The crusher (figure 7) includes a passive (lower) jaw (1) mounted on elastic elements (5) and simultaneously performing the function of the housing.The active jaw (3) is installed in the racks of the passive jaw by means of the suspension axis (2), relative to which it can perform rotational vibrations.Vibrations of the jaws are generated by a twoshaft inertial vibration exciter (4).Destruction of the material crushed occurs in the crushing chamber formed by the working surfaces of the passive jaw (1) and the active jaw (2).Grinding was carried out on a laboratory sample of a vibratory jaw crusher with a large set of adjustable parameters: the frequency and amplitude of oscillations of the jaws, the magnitude and direction of the disturbing force, the weight of the jaws, the size of the unloading gapt, the rigidity of the elastic elements, the profile of the working surface of the jaws, the grip angle, the angle of inclination of the conveying surface.Crushing was carried out on bottles with a cylinder diameter of 90 mm, identical to those studied on a pendulum impact tester.Based on the fact that the width of the crushing chamber of the laboratory sample is less than the height of the bottle, its loading was carried out according to the scheme of figure 2, a.
At the first contact of the bottle with the working surface of the jaw, the process of bottle destruction corresponded to the destruction on the impact tester.Obtained was a high-quality mass of a flat shape suitable to fill the transport container.However, a feature of the crusher is the possibility of producing marketable products.Subsequently, the resulting flat material moved in the crushing chamber to the discharge window, receiving a high-frequency impact.The resulting presentation of fine-grained material from a crushed bottle is shown in figure 8.A wide range of adjustable parameters allows you to control the process, create rational crushing modes and obtain the required granulometric composition of the finished product.Figure 9 shows the characteristics of crushed glass at a frequency of jaw oscillations of 17 Hz (curve 1) and 21 Hz (curve 2).The mass of the movable jaw is 97 kg, the width of the crushing chamber is 120 mm, and the length is 550 mm.
As can be seen from the graph, increasing the oscillation frequency to 21 Hz (curve 2) eliminates the +5.5 mm class, narrows the size range of the crushed product and increases the yield of powder material.

Conclusion
According to the purpose of the work, the studies carried out on the example of glass container destruction substantiated efficiency of crushing brittle materials in a vibratory jaw crusher with an inclined crushing chamber.
Feeding a cylindrical feedstock with a diameter of 90 mm into the crusher and obtaining a fine-grained product shows the prospects for creating a small-sized vibrating jaw crusher with the implementation of medium, fine crushing and grinding in it, which will significantly reduce the number of units in the production process chain, reduce their cost and expand the range of products obtained fine-grained and powder materials.
A laboratory plant with a horizontal type pendulum impact tester allows you to pre-select the profile of the working surface of the jaws, get a physical picture of the destruction of the material and determine the main dynamic characteristics of the crusher.

Figure 7 .
Figure 7. Structural scheme of the vibratory crusher.