Sorting of raw materials and purification of impurities. The main methods of purification of raw materials. Equipment for mechanical cleaning of raw materials
Purification of grain raw materials. Grain raw materials supplied to feed mills contain in their mass various kinds of weed impurities of organic and mineral origin, seeds of weed, harmful and poisonous plants, metal-magnetic impurities, etc. Raw materials containing pieces of glass and other dangerous hard-to-separate impurities are of particular danger. The use of such raw materials for the production of animal feed is prohibited.
Grain raw materials are cleaned from large and small impurities at feed mills by passing it through air-sieve separators.
Purification of farinaceous raw materials. Mealy raw materials (bran, flour, etc.) supplied to feed mills from flour and cereal factories may contain random large impurities - pieces of rope, pieces of rags, wood chips, etc. Mealy raw materials from these impurities at feed mills are cleaned on flat sieves with straight-return movement of the sieve frame, cylindrical burats with circular movement. At large feed mills, ZRM screenings are used to clean farinaceous raw materials.
In addition to the machines listed, a two-tier screening machine DPM is used, the flow diagram of which is shown in Figure 111.
The product to be cleaned, through the receiving box 1 with the help of metering rolls 2, is directed in two streams to the upper 3 and lower 4 sieves, which perform rectilinear-return oscillations. The passages through the sieves enter the prefabricated bottoms 5 and 6 and are removed from the machine through windows 7 and 8 and channels 9 and 10.
To separate light impurities from grain and husk films after peeling oats and barley, aspiration columns, aspirators with double blowing are used.
Purification of raw materials from metal-magnetic impurities. Compound feed containing metal-magnetic impurities in excess of the permissible norms is unsuitable for feeding to animals, as it can cause them serious illnesses. Particularly dangerous are particles with sharp cutting edges, the presence of which can cause injury to the digestive organs.
In addition, the presence of metal-magnetic impurities in raw materials can cause damage to machines and mechanisms, as well as cause explosions and fires.
At feed mills, as well as at flour and cereal factories, metal-magnetic impurities are separated using special magnetic barriers, consisting of static horseshoe-shaped magnets and electromagnets.
Places for installation of magnetic fences and the number of magnetic horseshoes in the fences, depending on the type of product produced and the productivity of the feed mill, are regulated by the Rules for the organization and conduct of the technological process at feed mills.
Magnetic barriers are installed on the lines:
- grain raw materials - after the separator, before crushers;
- mealy raw materials - after the screening machine;
- cake and corn - in front of crushers;
- feed products of food production - after the separator, before crushers;
- peeling oats - in front of the scouring machine;
- preparation of hay - before each hay crusher;
- dosing and mixing - after each dispenser and after the mixer;
- briquetting - in front of the divider;
- granulation - before each press.
The A9-KLSh/30 unit is designed for peeling root crops (potatoes, carrots, beets, etc.) using the steam-thermal method. The essence of the method lies in the fact that the fruits are briefly kept in a steam environment with a pressure of about 0.8 MPa, then the pressure is sharply reduced. Under the influence of high steam temperature, the liquid of the subcutaneous layer of the root quickly heats up to a temperature above 100 ° C, and with a sharp release of pressure, it instantly turns into steam, sharply increasing the pressure in the subcutaneous layer, as a result of which the skin is separated.
The A9-KLSh/30 unit (Fig. 1) consists of an inclined double screw conveyor 1 for cyclic supply of root crops in turn into two autoclave chambers 2 for steam-thermal treatment, equipped with valves controlled by pneumatic cylinders; a continuous screw conveyor 10 for moving the steamed tubers unloaded from the autoclave chambers to an inclined screw conveyor 4 feeding the tubers for further processing; frame 9, on which two components of the apparatus are placed; communications: steam 3, water 5, compressed air 7; electrical equipment 8 and platform b for maintenance.
The washed tubers are fed by an inclined double screw conveyor to one of the autoclave chambers. Before loading, the chamber is oriented with a loading funnel vertically upwards, while the shutter is located in the lowest position and provides free entry of tubers into the chamber. After loading a given portion of tubers, the shutter moves to the uppermost position (towards the chamber mouth) with a pneumatic cylinder and a lever system and provides preliminary sealing of the chamber. The final sealing of the chamber neck with a shutter is carried out with live steam supplied under a pressure of 0.7 ... 0.8 MPa. In this case, the camera receives a rotational movement and after a certain time, a quick release of pressure and the opening of the shutter with the unloading of tubers occur.
Processed tubers are taken out of the apparatus for further processing by two screw conveyors.
Technical characteristic of the A9-KLSh/30 unit: productivity is 9600 kg/h; autoclave chamber capacity 2750 l; loading per cycle 2200 kg; steam consumption 1550 kg / h, water at a pressure of 0.2 MPa 2 m 3 / h, compressed air at a pressure of 0.6 MPa 9.5 m3 / h, electricity 8.5 kW * h; overall dimensions 7850x4850x4550 mm; weight 7450 kg.
Vacuum tomato peeling machine developed in Bulgaria. Tomatoes are cleaned by heating them for 20 ... 40 s in a water bath at 96 ° C, followed by processing in a vacuum chamber at a pressure of 0.08 ... 0.09 Pa.
Rice. 1. Unit A9-KLSh/30
The cleaning process takes place in the following phases: destruction of the cohesive force between the skin and subcutaneous layer; tearing the skin and removing it from the surface of the fruit; removal of the remains of the skin. In the first phase, under the action of heat, the parenchymal layer quickly heats up, while hydrolysis of protopectin occurs. The second phase is based on the difference between the partial pressure of water vapor in the subcutaneous layer and the pressure in the vacuum chamber. By reducing the pressure in the chamber, the subcutaneous layer overheats. The pressure of the resulting water vapor overcomes the resistance of the skin and causes it to break and separate.
The automatic rotary machine for peeling tomatoes (Fig. 2) consists of a tub 3, a rotor 4, perforated inner 5 and outer 6 cylinders, a heating coil 2, a drum 10, a filling chute 9, an unloading chute 11, an upper 13 and a lower 14 covers, hydraulic cylinder 16, console 17 and drive 20. The machine has an outlet pipe 1, an axis of rotation 7, a ring 8, a vent hole 12, a depressurization valve 15, a vacuum valve 18 and a vacuum pipeline 19.
Rice. 2. Tomato peeling machine
The machine operates with periodic rotation of the rotor. The working cycle consists of loading raw materials, creating a vacuum and unloading peeled tomatoes.
With the start of the machine, the bath is filled with water, with the help of an overflow device, its constant level is ensured. The water is heated to 96°C and maintained at this temperature during the processing of the tomatoes.
Filled through the chute, the drum takes place between two perforated cylinders that close the holes and prevent the fruit from escaping. Passing through heated water, the tomatoes are blanched. The next rotation pushes the drum under the vacuum chamber, which advances towards the axis of rotation and occupies the drum. Moreover, it simultaneously hermetically closes on both sides. A vacuum is created through the valve in the drum, and the tomatoes are peeled. The vacuum valve then closes and the depressurization valve opens. The vacuum chamber returns to its original position, the next working cycle begins.
In the rotary machine, a high degree of cleaning of tomatoes (up to 98%) and a stable mode of operation are achieved.
fire cleaning
The essence of the fire cleaning of potatoes and vegetables is to remove the skin by roasting the tubers at a temperature of 1100–1200 ° C for 6–12 seconds, followed by washing in washers with brushes (pilers).
During steam cleaning, potatoes and vegetables are treated with steam at a pressure of 0.6–0.7 MPa for 0.5–1 min. Under the action of steam, the skin bursts and can be easily removed in the washing machine.
Steam cleaning production lines are not yet used in public catering establishments, since the latter are not yet equipped with installations that produce high-pressure steam. Such lines are available at food industry enterprises that produce semi-finished products from potatoes and vegetables for public catering establishments.
In the food industry, foreign production lines are used, on which potatoes are cleaned by the alkaline steam method: tubers are processed with hot (77 ° C) 7–10% alkali for 6–10 minutes and high-pressure live steam (0.6–0.7 MPa). ) within 0.5–1 min. Under the action of alkali and steam, the skin, together with the eyes, is easily removed during the subsequent washing of the potatoes. They wash it very carefully, first in a bath of water, and then with high-pressure water jets (0.7 MPa), since not only the skin, but also the alkali solution must be removed from the tubers.
Abroad, potato peeling is also used only with alkali. After alkaline cleaning, the potatoes are washed with water jets under pressure, then treated with dilute solutions of organic acids (citric, phosphoric) to neutralize alkali residues.
The use of alkali from a hygienic point of view is undesirable, since it can penetrate into the pulp of the tubers and, despite their thorough washing and neutralization of the alkali, partially remain in the potatoes. Therefore, this cleaning method cannot be considered promising for public catering in our country. Currently, in the food industry, alkaline steam cleaning on production lines is being replaced by steam cleaning.
At catering establishments, lines with a mechanical cleaning method are mainly used, since they do not require expensive equipment and are easy to maintain.
Purification of cereals and legumes from impurities is carried out on grain separators.
The grain is cleaned from impurities that differ in size on a system of sieves, from light impurities - by double blowing with air when the grain enters the separator and when it leaves it, from ferrous impurities - by passing through permanent magnets.
On the separator, depending on the type of processed cereals, stamped sieves with round or oblong holes are installed (Table 5).
The receiving, sorting and descending sieves during the operation of the separator with the help of a crank mechanism make reciprocating oscillations. Large coarse impurities (straw, stones, wood chips, etc.) are separated on the receiving sieve, grain and other impurities larger than grain are separated on the sorting sieve. Passage through a skhodny sieve separates impurities smaller than grain.
Upon entering the receiving channel, the grain "is exposed to the action of an air flow that captures all impurities that have a large windage. Secondarily, the air flow acts on the grain when it enters the output channel of the machine.
The technological effect of the separator is expressed by the following formula:
Where x is the effect of grain cleaning,%;
A - contamination of grain before entering the separator,%;
B - contamination of grain after passing through the separator, %.
The technological effect of the separator operation is never equal to 100% and tends to this value only in the limit, which is easily explained: on the sieve system, impurities that do not differ in size from the grain (for example, spoiled kernels, non-husked grains, etc.) cannot separate; they will not separate under the action of the air flow, since their windage is close to that of normal grains.
The efficiency of the separator is affected by the load on the sieves, the amount of exhausted air, the clogging of the material entering the separator and the size of the openings of the installed sieves. When striving for the maximum efficiency of the separator, one should keep in mind the possibility of loss of good-quality grain (entrainment by air at high speeds or losses on sieves due to grain size fluctuations).
The operation of the separator should be organized so that these losses are minimal.
During the production of boiled-dried cereals, their nutritional substances, as shown above, undergo the same changes during hydrothermal treatment as in the preparation of an ordinary dish, such as porridge. In cereals, there is an increased ...
The former Kostroma province is one of the few where the production of oatmeal has been developed since very ancient times. At first, this production had a handicraft character. Oatmeal was prepared using a Russian stove for languishing, and ...
LD Bachurskaya, VN Gulyaev Over the past five years, the nature of production at food concentrate enterprises has changed dramatically. New technological regimes, schemes have appeared, a lot of new technological equipment has been introduced, including ...
The invention relates to the food industry. The essence of the invention lies in the fact that for cleaning vegetable raw materials from the skin, a stream of liquid carbon dioxide is fed to the raw material through a supersonic nozzle with the formation of a gas phase used as a carrier and a solid phase used as abrasive bodies at the outlet.
The invention relates to the technology of the food industry and can be used in the mass processing of fruits and vegetables for their peeling. A known method of cleaning plant materials, including its treatment with abrasive bodies in the form of a solid phase of water supplied in an air stream (French patent 2503544, class A 23 N 7/02, 1982). The disadvantages of this method are the complexity due to the need to use various substances, one of which is subjected to pre-treatment to transfer to a solid phase state, and a change in the chemical composition of the surface layers of the purified raw material due to their oxidation with air oxygen and extraction with the liquid phase of water. The objective of the invention is to simplify the technology and exclude changes in the chemical composition of the surface layers of the purified raw material. To change this task in the method of purification of plant raw materials, including its treatment with abrasive bodies of the solid phase of a substance whose melting point is below normal, supplied in a carrier gas flow, according to the invention, carbon dioxide is used as the substance of abrasive bodies and carrier gas, while the creation of a carrier gas flow with abrasive bodies is carried out by supplying a liquid phase of carbon dioxide through a supersonic nozzle. This makes it possible to simplify the technology by creating abrasive bodies directly in the carrier gas flow without pre-treatment and introduction into the gas flow, as well as to exclude the oxidation of the surface layers of the purified raw material by eliminating their contact with atmospheric oxygen and their leaching due to the transition of the material of the abrasive bodies into under normal conditions from the solid state directly to the gas phase, bypassing the liquid phase state. The method is implemented as follows. Liquid carbon dioxide is fed through a supersonic nozzle in the direction of the raw material to be cleaned. As a result of adiabatic expansion in the nozzle channel, part of the liquid carbon dioxide passes into the gas phase, forming a supersonic carrier gas flow. This process occurs with the absorption of heat. As a result, the remaining part of the carbon dioxide passes into the solid phase of finely dispersed crystals, the interaction of which with the surface of the processed raw material leads to peeling off the skin. This process takes place in the absence of air oxygen, because due to the greater molecular weight, and, consequently, the greater density, carbon dioxide displaces the latter from the processing zone, which eliminates the oxidation of the surface layers of the purified raw material. Under normal conditions, the solid phase of carbon dioxide, unlike water, passes immediately into the gas phase, bypassing the liquid. This eliminates the extraction of soluble components of the surface layer of the purified raw material. As a result, the surface layer of the purified raw material is not subject to either quantitative or qualitative changes in the chemical composition. Example 1 Apples are peeled with water crystals in a stream of atmospheric air and carbon dioxide crystals in a stream of its gas phase. A study of the cross section of peeled apples showed that in the control batch, the surface layer of peeled fruits changed color by 3.5 mm in depth. At the same depth, a decrease in the relative content of monosaccharides and vitamin C is observed. In the experimental batch, the section is homogeneous in chemical composition. Example 2. Zucchini is processed analogously to example 1. In the control batch, a change in the chemical composition of the surface layer 1.8 mm thick, similar to example 1, was noted. In the experimental batch, no changes in the chemical composition were found on the cross section. Thus, the proposed method allows, with a simplified technology, to improve the quality of purified raw materials by eliminating changes in the chemical composition of its surface layer.
Claim
1 Method for cleaning plant raw materials, including its treatment with abrasive bodies of the solid phase of a substance whose melting point is below normal, supplied in a carrier gas stream, characterized in that carbon dioxide is used as the substance of abrasive bodies and carrier gas, while creating a gas stream -carrier with abrasive bodies is carried out by supplying a liquid phase of carbon dioxide through a supersonic nozzle.