Processing cocoa beans consists of processes such as cleaning and sorting, roasting and crushing.
The cocoa beans that arrived at the factory warehouses are first cleaned of impurities in the form of dust, pebbles, burlap fibers, paper, etc., and sorted by size to obtain evenly roasted cocoa beans *.
After cleaning and sorting, the cocoa beans are fried and then fed to the grinder.
Equipment for cleaning cocoa beans. The working body of the equipment for cleaning cocoa beans from impurities is a system of movable or fixed sieves.
Mobile screens can reciprocate, rotate and vibrate. The reciprocating movement of the sieves in a horizontal or inclined plane is carried out by crank, connecting rod, eccentric
The method of separating particles by size using sieves is called sieve. However, the size of many impurities can correspond to the sizes of the main raw material, and then such impurities cannot be separated by a sieve method. Therefore, for the separation of impurities that differ from the raw materials by aerodynamic characteristics,
The main parameter determining the possibility of separation of raw materials from impurities by aerodynamic characteristics is the speed of movement, i.e., the speed of air at which the particle will be in equilibrium. With a large value of the speed of soaring, the particle will move along with the air flow, and with a small value it will fall to the bottom of the air separation device.
The air separation method is often combined with the method of separating particles by size (sieve method). The most widespread are machines with flat vibrating screens, but machines with cylindrical screens are also used.
The listed machines can be divided into sieve (with flat and cylindrical sieves) by design
In fig. 5.26 is an MTLA Buhler air-sieve cleaner (Switzerland), designed for high-speed cleaning of cocoa beans before serving them in long-term storage silos, as well as for cleaning cocoa beans before roasting (drying). The quality of cleaning is achieved through the use of sieves with holes of various configurations and diameters. Sieves can have round, oblong or triangular holes, as well as combinations of such holes.
The machine (see fig. 5.26, a) consists of the following main units: 1 receiving hopper, 3 screen body and 4 vertical air separator. The screen body is supported by 5 flexible spring supports mounted on the 8 frame. 7 motor vibrators are attached to the body on both sides with 6 faceplates. By changing the inclinations of the motor-vibrators, it is possible to choose the optimal oscillation mode of the screen body, which ensures good cleaning of cocoa beans at maximum machine performance. To monitor the status of the sieves, a removable 2 lid is provided. If necessary (replacing screens, etc.), the 7 receiving hopper pivotally attached to the screen body can be folded down.
Fig. 5.26. Air-sieve cleaning machine MTIA: a - general view; 6 - cleaning circuit
The machine works as follows (see fig. 5.26, b). Cocoa beans through the 9 suction pipe through the 8 flexible hose come to the 7 distribution surfaces located in the 6 receiving hopper. The outlet port of the 9 inlet has a spiral shape, which contributes to the expansion of the outlet stream. When falling onto the 7 surface, the unwashed cocoa beans are distributed over the entire width of the 4 sieve and move along it due to the vibration of the 2 sieve body. The 5 damper controls the thickness of the cocoa bean coming in for cleaning. Right on the 4 sieve are large stones, ropes, branches and other impurities that are larger than cocoa beans. Large impurities are collected in the 77 tray and removed from the body. The pass through the 4 sieve falls on the 3 sieve, whose openings (8 ... 9 mm) are smaller than the diameter of the cocoa beans. Therefore, they move together on the 3 screen and drop into the vertical channel of the 12 air separator. Small impurities (sand, etc.) going through the 3 sieve are collected at the bottom of the sieve body and removed from the machine through the 7 channel.
The cocoa beans cleared of large and small impurities, falling down in the vertical channel of the 72 air separator, are blown with air, which picks up dust, leaves, shell particles and other light impurities. Together with the air, the impurities are separated from the cocoa beans and are carried along the 14 channel from the air separator. The quality of cleaning cocoa beans from light impurities is determined by the speed of air, which is regulated by the 13 flap and the position of the 15 moving wall.
Two sieves located in the sieve body are fastened to wooden frames, which divide the sub-sieve space into cells by longitudinal and transverse bars (partitions). Each cell contains 10 rubber or plastic balls that move freely around the mesh tray. Striking with vibrations on the main sieve, they clean them from adhering particles, reducing the size of the holes.
Air-sieve cleaning machines manufactured by Bühler have a capacity of 20 ... 1000 t / h, if they are installed in front of the silos, and 5 ... 24 t / h, if they are installed in the workshop in front of the drying apparatuses.
After installation of the machine during test starts, determine the rational position of the valves located inside the suction channels. It is also necessary to select air speeds that would ensure maximum entrainment of impurities and minimum - the main raw material.
Fig. 5.27. Scheme of vertical single-channel frying.
Equipment for roasting cocoa beans. The equipment for roasting cocoa beans is the BTT vertical single-channel plant of the Buhler company (Switzerland), which is intended for both preliminary drying and roasting of whole cocoa beans and cocoa nibs, hazelnut kernels, almonds, peanuts, etc. P.
The installation (Fig. 5.27) is a vertical 77 frame construction on which the necessary components are mounted, and has three zones, moreover, in the / and // zones, the product is dried or roasted, and in the /// zone the product is cooled. Accordingly, the zones are equipped with 7, 2, 10 filters, 3 and 9 steam or oil heaters, 4, 12, 15 screws for dust extraction and 5, 77 and 14 branch pipes. Zones // and /// are separated by an 13 shutter.
The product enters the bunker 8, equipped with a gate 7 with a pneumatic drive. Having passed through the slit of the damper, the product enters a narrow vertical installation 8ТТ nal 6, the sides of which are formed by gratings covered with wire mesh. The grates slide freely along the guide rails for easy cleaning. The channel width and thus the layer thickness can be changed. The product descends through the channel gradually and evenly, remaining loose due to the free movement of product particles. Since there is no shock or vibration, excessive crushing and crumbling are avoided.
In the 1 and 2 zones, air is sucked in through 7 filters (9 and 2, it is cleaned of dust, heated in 9 and 3 air heaters, it transfers heat to the processed product and is discharged from the dryer through the 5 and 77 nozzles. The air passing through the product which carries the dust through it the channel settles and is discharged by the 4 and 12 screws. In the same way the air moves in zone III, only there is no air heating in it. If you stop supplying air to it, then in this zone you can perform
The fried and chilled product is discharged from the dryer through an 16 unloading device (rotary lock). The frying time can be adjusted by changing the production
The 7 and 13 sector dampers located at the inlet of the installation and between the frying and cooling zones facilitate the start-up and operation of the installation at idle (at this time, the dampers are
The air supply to the installation, its additional cleaning after the dryer is carried out by three separately standing cyclone precipitators and three fans. The air purification system operates under vacuum. Thus, the absence of fans in the design of the dryer significantly reduces the danger.
The productivity of installations manufactured by Bühler (for cocoa beans) is 200 ... 2000 kg / h.
In some types of plants, cocoa beans move by gravity in a vertical shaft with fixed inclined shelves. Cocoa beans, poured from shelf to shelf, pass through three hot zones, and then enter the cooling zone. The air heated by steam heaters with the help of fans enters the gaps between the shelves of the mine, thus carrying out the transverse blowing of cocoa beans.
Roasted cocoa beans are fed to crushing, resulting in the formation of cocoa nibs and cocoa (cocoa shell),
Equipment for crushing cocoa beans. The equipment for crushing cocoa beans includes a crushing and screening machine (Fig. 5.28), consisting of a bucket elevator, a housing, a grinding mechanism of percussion, a sieve block cascade.
Fig. 5.28. Crushing and Screening Machine
type of air separation system with a precipitation chambers, a fan and a cyclone, electric motors, vibrators.
From the 7 funnel, equipped with a shaking mechanism to prevent product sticking, the roasted cocoa beans enter the 2 bucket elevator. When moving along a small 3 vibrating screen, a small fraction is separated from the cocoa beans, which, bypassing the crushing mechanism, is fed to the 6 upper sieve of the 15 sieve block.
The crushing machine consists of two 4 hexagonal rolls and two 5 corrugated decking, one of which is horizontal and the other is vertical. Getting on the verge of fast-rotating rolls, cocoa beans accelerate and strike against the fixed deck, splitting into pieces. A mixture of grains, shells and unbroken cocoa beans is fed to one of the five screens - an 6 screen, through which the grains and shells pass, and unbroken cocoa beans are returned via 77 to the shoe of the 2 elevator for re-grinding.
Of the five sieves, the 6 sieves are the topmost in the 75 sieve unit, which is supported by the 13 body with the 19 and 18 springs. All five screens are cascaded in a block; the size of the holes in the screens as pouring (sifting) the mixture decreases.
At the end of each screen, there is a vertical 7 suction channel on top, under which particles of cocoa nib and shells that have not passed through the corresponding screen (descent) move. The air flow picks up the casing and carries it along the channel to the 8 precipitation chamber. The chamber has a large volume, the air velocity here decreases sharply, the shell falls down and the 9 auger is taken out of the machine into the collecting chute located on the right side of the sieve block. The dusty air from the settling chambers through the channels with the 11 adjusting dampers is sucked off by the 12 fan and sent to the cyclone to separate from the smallest grains and cocoa particles.
Croup fractions, cleaned of cocoa shells, are collected at the end of each sieve in 10 unloaders and through them are removed from the machine into an inclined 14 vibratory gutter (shown by a dashed line) located on the left side of the strainer
The gathering of grains on the bottom sieve contains sprouts (germ) of cocoa beans. The sprout has a length of 4 mm and a width of 1 mm. In roasted cocoa beans, the germ content on average does not exceed 0,8 ... 0,9%. It has a much greater hardness than grains, and much worse than it is crushed in roller mills. The fat content in the sprout does not exceed 3,5%, and in comparison with grains it is of low value and clogging part. To remove the germ, the grains fraction separated on a sieve with 4 cells ... 5 mm is passed through a trier (cleaning mechanism).
The degree of purification of grains from the shell depends on the speed and amount of air passing through the 7 suction channels with 11 adjustment flaps. The air is regulated using handles mounted on the 18 body.
Particles of large grains are better cleaned and therefore go for the manufacture of high-grade chocolate. The finest grains contain cocoa-shell impurities and are used for prescription mixtures of lower grades of chocolate or toppings.
The 75 screen unit receives oscillatory motion from two electric vibrator motors.
There are similar machines with a roll or disc crushing device, where the sieves oscillate in a vertical plane. The sieve block can receive oscillatory movement from the eccentric mechanism, and be attached to the machine body on spring struts or suspensions.
For fine grinding of cocoa nibs, grinding units are used. The particle size of cocoa nibs, granulated sugar, etc. in chocolate should not exceed 30 ... 60 microns. Therefore, cocoa nibs and granulated sugar purified from the shell are crushed, for which purpose special equipment is used, in particular grinding units. The grinding units include hammer, pin, disk, ball and other mills.
The combined grinding unit (fig. 5.29) consists of a hammer mill 5, a disk mill 14, a control
Fig. 5.29. Combined grinding unit
77 sieve filter, 23 ball mill, transfer pumps, dispensers and water communications systems.
The 3 hammer mill is equipped with an 6 vibrating drum, by means of which the cocoa grains are fed into the mill by varying the oscillation amplitude. When cocoa grains are moving along the 7 surface with an adjustable inclination of the 8 magnet, ferrous impurities are extracted. The 5 auger feeds the product inside the mill. The body rotates the 4 rotor with four 10 hammers hinged on it, which accelerate the cocoa nib and hit it on the grooved 9 surface. As a result, the cocoa nibs are crushed, the cells are broken and the outflow of cocoa butter from them. Cocoa nuggets, which are smaller in size than the holes in the 2 mesh, pass through it along with the free cocoa butter. The resulting crushing liquid suspension pump 7 pumped into the receiving funnel disk mill 14. The 77 screw feeds the slurry into the gap between 13 and 75 discs rotating in the same direction, but at different speeds. The degree of grinding grits in the mill is regulated by changing the gap between the discs. The discs are made of corundum and are fixed on metal bases 12 and 16.
The milled slurry flows from the 14 mill and is fed to the 77 sieve filter. Filtration is accelerated due to the fact that the sieve vibrates. The filtered suspension flows down the inclined 18 surface and is collected in an intermediate 19 collector, from which the 20 pump is pumped into the 23 ball mill.
The 23 ball mill is a vertical cylinder with a water jacket, inside which the 25 shaft with horizontal 24 discs rotates. The internal volume of the cylinder is filled with metal balls with a diameter of 4 ... 6 mm. The particles of cocoa nibs moving through a layer of agitated balls are finally ground. The resulting cocoa mass passes through
the 26 disk filter, which prevents the exit of the balls, flows into the 27 collection tank and is pumped to the far-
To pump the suspension through a ball mill, it is necessary to create a pressure of up to 0,25 MPa. The pressure is controlled by an 21 pressure gauge. At the end of the work, the suspension from the ball mill and the intermediate collector is discharged through a three-way valve.
The considered grinding unit is a combination of three grinding plants. Depending on the production tasks, a hammer mill can be used in combination with a disk or ball mill or a disk mill with a ball mill. The unit can be used for grinding not only cocoa beans, but also other fat-containing