Processing cocoa beans consists of processes such as cleaning and sorting, roasting and crushing.
The cocoa beans that have 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
Cocoa Bean Cleaning Equipment. The working body of the equipment for cleaning cocoa beans from impurities is a system of mobile or fixed sieves.
Movable sieves can perform reciprocating, rotational and vibratory motion. The reciprocating movement of the sieves in a horizontal or inclined plane is carried out by a crank, eccentric or
The method of separating particles by size using sieves is called sieve. However, the size of many impurities can correspond to the size of the main raw material, and then such impurities cannot be separated by the sieve method. Therefore, for the separation of impurities that differ from the raw materials on the aerodynamic characteristics, use air separation.
The main parameter determining the possibility of separating raw materials from impurities according to aerodynamic characteristics is the speed of soaring, that is, 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 pneumo-separating channel
The method of air separation is often combined with the method of separating particles by size (sieve method). The most widely used machines with flat vibrating screens, but also used machines with cylindrical screens.
The listed machines can be subdivided into sieve (with flat and cylindrical sieves) and air-sieve
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 components: 1 receiving hopper, 3 sieve body and vertical air
4 airless separator. The sieve body rests on flexible 5 spring supports mounted on the 8 frame. The 7 motor vibrators are attached to the body on both sides with 6 faceplates. By changing the slopes of the motor-vibrators, it is possible to choose the optimal mode of oscillation of the sieve body, which ensures good cleaning of cocoa beans with maximum machine productivity. A removable 2 cover is provided to monitor the condition of the screens. If necessary (replacement of sieves, etc.), the receiving bin 7 can be pivoted down to the sieve body.
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.
Figure 5.27. Vertical single-channel installation STT firm "Buhler" (Switzerland)
Equipment for roasting cocoa beans. The equipment for roasting cocoa beans includes a vertical single-channel installation STT by Buhler (Switzerland), which is designed for both pre-drying and roasting whole cocoa beans and cocoa nibs, hazelnut kernels, almonds, peanuts, etc. P.
The installation (fig. 5.27) is a vertical 77 frame structure, on which the necessary components are mounted, and has three zones, where the product is dried or roasted in areas // and // and the product is cooled in areas ///. Accordingly, the zones are equipped with 7, 2, 10 filters, 3 and 9 steam or oil heaters, 4, 12, 15 augers for dust removal and 5, 77 and 14 branch pipes. Zones // and /// are separated by the 13 flap.
The product enters the 8 hopper fitted with a pneumatically operated 7 damper. After passing through the slit slot, the product falls into a narrow vertical channel 6, the sides of which are formed by gratings covered with wire mesh. The grates are freely extended along the guide rails, which makes them easy to clean. The width of the channel and thus the thickness of the layer can be changed. The product descends along the channel gradually and evenly, remaining loose due to the free movement of the product particles. Since there are no collisions and vibration, it is possible to avoid increased compression and the formation of chips.
In zones / and //, air is sucked through 10 and 2 filters, cleared of dust, heated in 9 and 3 heaters, gives off heat to the processed product and is discharged from the dryer through 5 and 11 connections. The air that has passed through the product carries away dust, which, after passing through the channel, is deposited and is expelled by the 4 and 12 augers. In the same way, air moves in zone III, only there is no air heating in it. If you stop the flow of air into it, then in this area you can perform
The fried and cooled product is discharged from the dryer through the discharge device 16 (rotary air lock). Roasting time can be adjusted by changing the capacity of the unloading device.
Located at the entrance to the plant and between the roasting and cooling zones, the sector flaps 7 and 13 make it easy to start and operate the unit at idle (at this time, the flaps are in the closed state)
Air supply to the installation, its additional cleaning after the dryer are carried out by three separate cyclone-precipitators and three fans. The air cleaning system works under vacuum. Thus, the absence of a fan dryer design significantly reduces the risk of fire.
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.
At the end of each sieve, the grains of the cocoa-peeled fractions are collected in 10 unloading devices and are led out of the machine into the sloping 14 vibro-chatter (shown with a dotted line) located on the left side of the sieve block.
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 15 sieve unit receives oscillatory motion from two electric motors - 16 vibrators.
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.
Grinding aggregates are used for fine grinding of cocoa nibs. The particle size of cocoa nibs, granulated sugar, etc. in chocolate should not exceed 30 ... 60 microns. Therefore, peeled cocoa nibs and granulated sugar are ground, for which special equipment is used, in particular grinding units. The grinding units include hammer, pin, disc, 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
11 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 disc filter, which prevents the balls from exiting, flows into the 27 collection tank and is pumped for further processing by the 28 pump.
To pump the suspension through a ball mill, it is necessary to create pressure up to 0,25 MPa. The pressure is monitored by an 21 pressure gauge. At the end of the work, the suspension from the ball mill and the intermediate collector is produced through a three-way valve 22.
The considered grinding unit is a combination of three grinding installations. Depending on 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 seeds and kernels of nuts.