Section 1 Concept and theory of steaming and stir-frying

1. The concept and method of steaming and frying

(1) The concept of steaming and frying

Steaming and stir-frying is a process in which raw embryos are processed by adding water (wetting), heating (steaming embryos), and drying (frying embryos) to make them into cooked embryos.

In the process of oil production, the steaming and frying process is a very important process. In the process of steaming and frying, the structure of the embryo continues to undergo a series of changes based on the initial damage in the crushing process and the embryo rolling process. For example, cells are further damaged, proteins are coagulated and denatured, and phospholipids and gossypol are isolated and combined. These changes are not only conducive to the extraction of oil from the embryo, but also to the improvement of the quality of crude oil.

(2) The method of steaming and frying

The methods of steaming and frying the embryos can be divided into three types: moist steaming and frying, high-moisture steaming and frying, and heating and steaming.

Second, the role of steaming

(1) Destruction of cells

The raw embryo is the embryo obtained by cleaning the oil, crushing the large oil, and then rolling the embryo. After the oil has been processed through the crushing and flaking process, its cell structure has been damaged to a certain extent. As mentioned earlier, mainly its cell wall is partially destroyed.

When the raw embryo enters the steaming and frying process, its cell structure will be further damaged. In order to elucidate the process by which it is destroyed, it is necessary to review the state of the presence of lipids within the protoplasm of oil bodies in oilseed cells.

Oil mainly exists in the protoplasm of the oil body of the cell, and it exists in two states: one is free oil, which is distributed in the channels of the micellar network as tiny particles, and accounts for a large proportion of oil; The other is the bound lipid, which is combined with the hydrophobic group of the protein and is enclosed within the globulin, while the hydrophilic group of the globulin is exposed on the outer surface. The proportion of bound oils is relatively small.

When steaming and frying, because the surface of the protein and other components in the cell has a strong hydrophilic base, when the raw embryo is wetted, the water penetrates into the complete cell, is absorbed by the protein and other components, and swells. Under the combined action of mechanical agitation, the cell wall is ruptured and the oil body protoplast flows out. At the same time, the ultra-microscopic channels in the protoplasm are also compressed, forcing part of the oil dispersed in the channels to be squeezed out and gathered on the surface of the embryo. In the production process, the cooked embryos after steaming and frying can often see the flash of oil. This is the reason.

(2) Coagulation and denaturation of proteins

Protein denaturation is a situation in which physical, chemical and properties change due to the destruction of its structure under the influence of external conditions (temperature, moisture, pressure, etc.). After protein denaturation, it coagulates into a solid state, and its solubility decreases, so it is also called coagulation denaturation. During the process of steaming and frying, under the action of temperature and moisture, the hydrophilic group of the protein absorbs water and expands, and the stable structure is destroyed and denatured. In this way, the oil that was originally enclosed in the globulin was turned to the outside. Therefore, the oil is easier to extract. Experiments and production have proved that the higher the degree of protein modification, the higher the oil yield.

There are three factors that affect the degree of protein denaturation:

One is temperature.

The degree of protein denaturation increases with increasing temperature. When the temperature rises to the range of 70-135℃, the denaturation speed of protein is faster. When the temperature exceeds 135°C, the protein denaturation speed will be slow, and the embryo will be coked, which will affect the quality of oil and cake. Therefore, the steaming temperature generally does not exceed 130 ℃.

The second is moisture.

When the temperature and time of steaming and frying were the same, the degree of denaturation of cottonseed protein increased with the increase of steaming and frying water. It can be seen that the high-moisture steaming method is conducive to the sufficient denaturation of proteins.

The third is the cooking time.

When the steaming temperature and moist moisture are constant, the longer the steaming time, the higher the degree of protein denaturation. Generally, the denaturation is faster in the initial stage. Therefore, the steaming and frying time should not be too long in production practice. When the vertical five-layer steaming frying pan is used for steaming and frying the embryos for pressing, the steaming and frying time is generally controlled at about 60 minutes.

(3) Make phospholipids swell by water absorption

1. Presence of phospholipids in oil

Phospholipids exist in both free and bound forms in oil. The phospholipids in the combined state refer to the complexes formed by combining phospholipids with proteins, carbohydrates and other substances. As for the content of bound phospholipid and free phospholipid, the former is usually more than the latter. Therefore, the phospholipid content in crude oil not only depends on the phospholipid content of the oil itself, but also depends on the phospholipid, especially the change of the combined phospholipid in the process of steaming and frying.

2. Changes of phospholipids during steaming and frying

Generally speaking, phospholipids, like lipids, are mainly present in the interior of proteins when they are combined with the hydrophobic groups of proteins. When steamed and fried, the structure of the protein is destroyed due to the coagulation and denaturation of the protein, so that the phospholipids combined with the hydrophobic group of the protein are "released". This part of phospholipids can be dissolved in the oil when making oil. The reason why the phospholipid content of hot-pressed soybean oil is higher than that of cold-pressed soybean oil is because of this. "Eat enough" water, and let this part of the phospholipids in it first absorb water and swell to form a cohesive state. At this time, the phospholipids that have been swollen and agglomerated by water absorption are no longer soluble in the oil. Therefore, these phospholipids remain in the oil production. In the cake meal and reduce its content in crude oil.

To sum up, in the process of steaming and frying, if the water content of the embryo can be increased as much as possible and the phospholipids can absorb water and swell, it is of great significance to reduce the phospholipid content in the crude oil and further improve the quality of the crude oil. Especially when processing cottonseed, it has a more obvious effect on improving the quality of wool cotton oil.

(4) Binding gossypol to protein

Cotton kernels usually contain 1.4%-2.1% (calculated as dry material) of gossypol, and cotton hulls also contain a small amount of gossypol (generally less than 0.01%). Since gossypol is subjected to the action of water, heat and air during the wet steaming and frying process, complex chemical changes will occur. These changes will directly affect the color of crude oil, the difficulty of removing gossypol during the refining process, and also affect the refining rate. Therefore, it is necessary to discuss the changes of gossypol in wet steaming and high-moisture steaming.

1. Structure of Gossypol

The molecular formula of gossypol is C30H30O8, and the molecular weight is 518.

2. Properties of Gossypol

(1) Physical properties. Gossypol is a yellow crystalline substance and is a toxic phenolic pigment. It usually exists in both free and bound forms. Gossypol in the free state is called free gossypol, or gossypol for short. Gossypol in the bound state is called bound gossypol.

Free gossypol is easily soluble in oil, ether, chloroform, acetone and other solvents, but insoluble in water and is toxic; combined gossypol is insoluble in oil, but the conjugate formed with phospholipid (conjugated gossypol) is soluble in oil and is not toxic. .

(2) Chemical properties.

① Neutralize with alkali to generate salt. Gossypol has two nuclei, two aldehyde groups and six hydroxyl groups in its molecule. Among the six hydroxyl groups, two of the hydroxyl groups adjacent to the aldehyde group are acidic. It can react with alkali to form a salt that is soluble in water but insoluble in oil and organic solvents. This salt can be removed together with the soapstock in the alkali refining process of the oil.

② with aniline to generate diphenylamine gossypol. The two active aldehyde groups of free gossypol can be condensed with two aniline molecules to release two molecules of water to generate diphenylamine gossypol. This reaction is often used as the basis for quantitative analysis of gossypol. Because diphenylamine gossypol is insoluble in organic solvents, it is even more difficult to dissolve in petroleum ether.

③ denaturation of gossypol. Under the action of water, heat, air and sunlight, gossypol will lose its active aldehyde group and change its chemical properties. This phenomenon is called denaturation of gossypol. This kind of gossypol that has changed the original chemical properties is called denatured gossypol.

Denatured gossypol is neutral and can no longer react with alkali, nor can it interact with aniline. Its color is darker than free gossypol, brown-red or brown-black. It can be seen that the denatured gossypol contained in cotton oil will make the oil darker, and it is difficult to remove in the alkali refining process. Therefore, the generation of denatured gossypol should be avoided as much as possible in the process of oil production.

④ Combine with phospholipids to generate bound gossypol. Free gossypol can interact with phospholipids to form bound gossypol. The effect of this combined gossypol on the color of cotton oil is much more severe than that of denatured gossypol alone. Therefore, it is also necessary to avoid the combination of free gossypol and phospholipids in the process of oil production.

⑤ Combine with protein to generate bound gossypol. Free gossypol can be combined with protein to form bound gossypol. Its coloring ability is also very strong. Because protein is insoluble or extremely difficult to dissolve in oil, this bound gossypol can only be left in solid materials, and can be used as feed because it has lost its toxicity. Therefore, it is desirable for gossypol to form bound gossypol with protein during steaming and frying. However, the portion of the protein that is bound has lost its nutritional value.

3. Artificial control of gossypol during steaming and frying

Through the above analysis of the physicochemical properties of gossypol, we can see that some of the properties of gossypol are beneficial to the production process, such as: with alkali bamboo to generate salt, and combined with protein to generate bound gossypol. Some are also unfavorable for production, such as free gossypol denaturation and binding with phospholipids, both of which will darken the color of the oil. However, gossypol and phospholipids are inherent substances in cottonseed, and some of them are inevitably transferred into the oil during the oil making process. So, can effective measures be taken to reduce the content of gossypol and phospholipids to a minimum in the process of oil production?

The solution to this problem is the high-moisture steaming method. In the wet stage at the beginning of steaming and frying, add enough water to make it reach 18%-22% (and the wet steaming and frying method is 12%-18%). In this way, on the one hand, the phospholipids first absorb water and swell and remain in the embryo, reducing their content in the crude oil, thereby reducing the chance of combining with gossypol; on the other hand, it is easier to combine gossypol with protein to generate Combined with gossypol, it remains in the embryo. It can be seen that the high-moisture steaming method is especially suitable for the production of cottonseed oil.

(5) Other functions

1. Reduce grease viscosity

During steaming and frying, the temperature of the material embryo can be kept at a high temperature due to the heating effect, which reduces the viscosity of the oil in it, thereby increasing the fluidity of the oil. Therefore, the oil is easily extracted when making oil.

2. Adjust the plasticity of the blank

In the process of steaming and frying, through the adjustment of moisture and temperature, the embryo can have suitable plasticity and pressure resistance, so as to adapt to the oil pressing of oil presses with different pressing chamber pressures.

Generally speaking, different types of oil presses have different pressures in their pressing chambers, which requires us to properly adjust the moisture and temperature of the embryo during the steaming and frying process. When the temperature is low, the plasticity is small, and the pressure resistance is large; while the temperature is high and the moisture is high, the plasticity is large, and the pressure resistance is small. In view of this, we usually choose a high temperature and low moisture process, and combine the two factors of temperature and moisture. In the case of controlling a certain temperature, the moisture of the material embryo is adjusted to achieve its suitable plasticity, and then achieve the ideal pressing effect.

3. Destructive effect on enzymes

In the process of steaming and frying, due to the increased temperature, the enzymes (enzymes) existing in the embryo are destroyed and microorganisms can be killed. Generally, enzymes can be completely destroyed when the temperature reaches 80 °C, because enzymes themselves are also two kinds of proteins, and the destruction of enzymes is also caused by the denaturation of proteins. Therefore, it is the truth that the pressed cakes steamed and fried at high temperature are easy to store. For example, the lipase contained in fresh rice bran is destroyed after being steamed and fried, and the quality of the obtained oil will not be greatly affected after being stored for a period of time before making oil.

Section 2 Steaming and Stir-frying Process

1. Moist steaming method

The wet steaming and frying method refers to the process of moistening the raw embryos at the beginning of heat treatment, so that they can be steamed and fried for a long time under certain humidity and temperature conditions, so that the cooked embryos can reach a certain pressing condition. process.

(1) General process requirements

The general technical requirements of the wet steaming and frying method are that the embryos are steamed with high moisture, the steaming and frying are uniform, and the sufficient steaming and frying time is ensured, so that when the moisture content is low and the temperature is high, the subsequent pressing process is followed.

(2) Specific requirements

The wet steaming and frying method can be divided into three steps: moistening, steaming and frying. The specific requirements of each step are as follows:

1. Wet link

(1) Wetting method. There are three kinds of wetting methods, one is to inject direct steam into the raw embryo. The advantage of this method is that the wetting is uniform and the effect is better. However, it does not meet the principle of "moisture first and then heat" and cannot fully meet the technological requirements. Because there is not enough water at first, the changes of protein, gossypol, etc. are unfavorable; the second is that the water is moist. This method conforms to the principle of first dampness and then heat, but the humidity is uneven; the third is the use of water vapor. When applying this method, water can be added to the conveying auger first, and steam is sprayed in the steaming wok successively. Compared with the previous two methods, this method has better effect, and can meet the requirements of first humidity and then heat.

(2) Keep airtight. The wetting link requires airtightness, and the plug plate of the air outlet is closed to prevent a large amount of steam from escaping, so as to improve the wetting effect.

(3) The filling should be sufficient. The moistening process is usually carried out in the first layer of the vertical five-layer steaming wok. Generally, the amount of wet raw embryos is required to be 80%-90% of the capacity of the layer of the pot, so that the raw embryos have sufficient time to interact with each other. Contact with water vapor to achieve the purpose of uniform wetting.

2. Steam embryo link

The wet embryos are then steamed. The steaming of the embryo is also carried out in a closed condition, so that the water can fully penetrate into the interior of the embryo, and it is guaranteed that the protein, phospholipid, gossypol and other substances will change after a certain period of time, and its cell structure will be destroyed.

(1) Well sealed and fast heating. The embryo steaming process requires that the temperature be raised quickly in a closed condition, so that the material layer space can maintain a high humidity, reduce the chance of the embryo contacting with the air, avoid oxidation, and reduce the denaturation of gossypol. Generally, the embryo steaming process is carried out in the second and third layers of the vertical five-layer steaming wok. The two layers must close the plug plate of the air outlet, so that the material embryo can be fully steamed.

(2) The filling should be sufficient. It is generally required that the charging amount of the second and third layers of the vertical five-layer steaming frying pan is about 80% of the capacity of the pot body of the layer.

(3) Temperature control. The operating temperature of the embryo steaming process is generally controlled at 95-100°C.

(4) Elapsed time. The raw embryos are fed from the vertical five-layer steaming wok, and successively go through the moistening link and the embryo steaming link, and the elapsed time is controlled for about 40 minutes.

3. Fried embryo link

Stir-fried embryos are a process of drying and dehydration immediately after steaming embryos to further change substances such as proteins. The fried embryo is first processed in the lower two layers of the steaming wok, and then transferred to the adjustment wok on the upper part of the oil press through the conveying equipment for processing.

(1) Exhaust air in time. During the frying process, exhaust air in time. During the operation, pay attention to open the exhaust branch pipe insert of the vertical five-layer steaming wok and fry the germ layer, so that the exhaust is smooth.

(2) The loading should be less. The frying germ layer should be filled with less material, so that the material layer is thinner and the space is left larger. Generally, the charging amount is 40%-50% of the volume of the pot to facilitate exhaust.

(3) Elapsed time. Generally, the process of frying embryos is first carried out on the fourth and fifth layers of the vertical five-layer steaming wok, and then transferred to the regulating wok to continue frying the embryos. The frying process takes time, the first stage is controlled at about 20 minutes, and the latter stage is controlled at about 30 minutes. In this way, the raw embryo passes through the moistening link, the steaming and frying link and the frying link for a total of about 90 minutes of cooking time. Of course, according to the different requirements of different oils and oil pretreatment, the time experienced by each link can also be adjusted accordingly, including the position of the equipment in the steaming and frying links.

(4) Pay attention to the insulation of the conveying equipment. In the process of frying the embryos, the embryos should be transferred from the vertical five-layer steaming wok to the regulating wok, and the conveying equipment used in the conveying process should pay attention to heat preservation. For example, vertical auger and sky auger with an O-shaped cross-sectional area are used for transportation, and the outer wall can be added as a thermal insulation layer.

2. High-moisture steaming method

The difference between this method and the wet steaming method

Comparing the two methods, the main difference lies in the moisturizing part of the high-moisture steaming method, and the amount of water added is much more than the former. The maximum moisture content of the embryo after wetting can be as high as 20%-22% for cotton kernels. Generally, it can be controlled at 16%-22%. In addition, compared with the previous method, this method is more conducive to the denaturation of proteins in the embryo, and can promote the combination of proteins with phospholipids, gossypol and sugars, so that the denatured gossypol is reduced as much as possible to become combined gossypol, which can further improve the oil yield. rate and oil and meal quality.

Section 3 Steaming and frying equipment 

There are two types of steaming and frying equipment: wet steaming and frying equipment and soil steaming and frying equipment. The former is mainly a vertical layer type steaming wok, with three layers, four layers and five layers. The latter has cylindrical wok and so on. In addition, there are drying equipment for direct leaching oil pretreatment. They are introduced separately below.

1. Vertical five-layer steaming wok

(1) Structure

The vertical five-layer steaming and frying pan is composed of the pot body, the wetting device, the stirring device, the automatic feeding door; the heating system pipeline, the exhaust pipe, the transmission device and the base. Its structure is shown in Figure 4-4, and the following parts are carried out introduce.

Figure 4-4 The structure of the vertical five-layer steaming wok

1- Pot body 2- Direct steam nozzle 3- Automatic feeding door 4- Discharging door 5- Rigid coupling

6-Reducer 7-Elastic coupling 8-Motor 9-Exhaust pipe 10-Access door

1. Pot body

The pot body is composed of pot wall, heating side jacket and bottom jacket, inspection door and other components. In the bottom jacket, a steam guide baffle is also installed to prevent the short circuit of the steam.

The specifications of the pot body are φ1000, φ1200, φ1500, φ1800, φ2100 mm in diameter. There are three, four, and five layers of the pot body. Commonly used are five layers. The structure of each layer is basically the same, except that the bottom wall has a discharge port and is equipped with a discharge valve. All other layers have feeding openings.　　

2. Wetting device

Wetting methods include air jet, water spray and water vapor combined spray.

The air jet is to inject steam at the upper end of the central axis of the first layer of the pot body, down the stirring shaft, and spray out through the exhaust holes on the wall of the welding pipe behind the stirring blade of this layer, and mix it into the material embryo to achieve the purpose of wetting.

The diameter of the vent hole on the welded pipe is 2.0-2.4 mm. Another method of air injection is to install a circle of air injection pipes at the inner wall of the pot in this layer close to the bottom plate, and air injection to wet. However, this method is easy to form a dead corner of the stacking material, and the accumulated material is easy to coking, so it is not desirable.

The lotus tent head can be installed by spraying water, and evenly sprinkled into the surface layer of the first layer of the pot body. Water can also be pre-sprayed in the conveying equipment, and then enter the first layer of the pot after wetting.

When both water and air are sprayed, the water pipe and air pipe can be connected and sprayed to make it both uniform and hot water, and its moisturizing effect is better.

3. Stirring device

The stirring device consists of the central shaft, stirring blades and other parts. The stirring blade speed is 25-35 rpm. The orientation of a pair of stirring blades in the upper and lower layers of the pot is staggered to make the load even.

4. Automatic feeding door

Below the discharge port of the pot body, the connecting device has an automatic feeding door for the material embryo to flow into the lower pot body.

The material door is made of steel plate in an arc shape, and is sleeved on the rotating shaft through the support plate and the through hole of the pot wall. The rotating shaft is also sleeved with an arc-shaped counterweight carriage. It forms a certain angle with the arc-shaped material door. When the material level of the lower pot body is insufficient or there is no material, the carriage will automatically sag. After the material door is opened, it is in a state of receiving incoming materials. After the material layer of the lower pot body gradually rises, with the periodic creep of the material layer when the stirring blade is stirred and rotated, the carriage in contact with the surface layer of the material embryo also floats accordingly, and gradually rises as the material layer rises. Close the feed door small until it is fully closed. The automatic feeding gate thus plays the role of automatically controlling the feeding amount.

The size of the opening and closing of the material door inside the pot and the height of the material layer in the pot are all reflected by the swing of the pointer on the outer wall of the pot which is connected with the shaft of the material door.

The common rotating shaft of the material door and the carriage is composed of two half shafts, the purpose is to make the material flow smoothly and reduce the obstruction. The inner half shaft is suspended by a support plate welded to the bottom of the pot.

5. Transmission

The transmission device of the vertical frying pan is composed of a motor, a reducer and a transmission shaft. The rotating shaft of the motor is connected with the input shaft of the reducer through an elastic coupling. The output shaft of the reducer is connected with the stirring shaft of the stirring blade of the device through the rigid coupling, so as to drive the stirring blade to rotate. Usually, the rotating speed of the stirring blade is about 30 rpm.

6. Exhaust pipe

Each layer of the pot body of the steaming frying pan is equipped with an oblique exhaust branch pipe, and the branch pipe and the pot body are connected by flanges. A plug-in plate is installed on the duct to adjust the amount of steam discharged from the pot. The branch pipes then converge into an upright exhaust manifold. The upper part of this pipe is connected with a pipe of the same diameter and is drained straight through the roof.

(2) Working process

When the vertical five-layer steaming wok is working, the raw embryos enter the first layer of the pot and are wetted by the direct steam sprayed by the wetting device. Moisten evenly as you stir. The wet embryos fall into the steaming layer through the automatic feeding door, and are heated by indirect steam during stirring. In order to facilitate the steaming, the insert plate is tightly closed. After steaming, the material falls into the frying embryo layer through the automatic feeding door, and continues to be heated by indirect steam. During this time, the plug plate is pulled out to discharge the steam, so that the moisture is gradually reduced, and finally the embryo is discharged from the bottom discharge port.

(3) Product series

Table 4-3 shows some product series of vertical steam wok.

(4) Operation of vertical steam wok

1. Check each layer of the pot body before driving, remove the sundries, and then adjust the material door to the required position. The method of adjusting the material door is: according to the height of each layer of loading (generally one to three layers are about 80% of the volume, and the other layers are about 40% of the volume), lift the material door pallet to this position (slightly lower). a little), and make the feeding door just seal all the feeding openings, and then tighten the top wire on the swing rod of the feeding door. After the material door is adjusted, the unloading door of each layer is fixed and closed.

2. Turn on the motor and run the empty car. The feeding can be carried out after the operation is normal.

3. Before feeding, first open each condensate water valve, and then slowly open each steam inlet valve, discharge the condensed water until the bottom of the pot heats up, and then start feeding. When the material layer of the first layer of the pot reaches the predetermined height, the unloading door of this layer is opened, and the material embryo is slowly sent to the second layer, and the material is discharged layer by layer according to the above method to the bottom layer of the pot body. Check the temperature and moisture of the material embryo in the bottom pot, if the process requirements are met, the material can be discharged.

4. During the operation, attention should be paid to adjusting the pressure of direct steam and indirect steam and the size of the exhaust valve to control the temperature and moisture of the material embryo in the pot to meet the technological requirements.

5. When parking, first stop feeding, empty each layer of material embryos, close the steam inlet valve at the same time, and finally turn off the motor to stop.

6. When an emergency stop occurs due to a fault, the motor should be turned off immediately, the feeding should be stopped, the steam inlet valve should be closed, and then all the material embryos in the pot should be removed from the inspection door. After the overhaul is completed, restart the feeding according to the driving sequence.

(3) Maintenance points

1. The vertical steam wok must be produced within the highest steam pressure (general gauge pressure is 0.5MPa). A safety valve (pressure limiting valve) should be installed in the steam pipeline of the steam cylinder.

2. The stirring device, automatic feed gate and reducer should be checked frequently to ensure reliable operation.

3. The lubricating oil of the bearing and reducer needs to be added in time, and should be replaced after a period of use. Because the main shaft bearing works at high temperature, lubricating oil should be filled once per shift.

(4) Common faults and solutions (see Table 4-4)

Table 4-4 Common faults and solutions of vertical steam wok

2. Other steaming and frying equipment

(1) Flatbed dryer

According to the different oil production process, some embryos made from pretreated oil are used for pressing or pre-pressing, and some are used for direct leaching.

The embryo used for direct leaching needs to be processed through a drying process in the later stage of pretreatment. In addition to the vertical steam wok that can be used as a drying device, there is also a dedicated drying device. The following introduces a common chain steam dryer in grease factories, also known as flat pull dryer.

1. Structure

The flat dryer is composed of a frame, a heating plate, a baffle, a tensioning device, a feeding hopper, a moisture exhaust hood, an air intake pipe, a condensed water discharge pipe, a transmission mechanism, an observation door and other components. Its structure is shown in Figure 4-8.

The transmission process of the transmission mechanism can be seen from Figure 4-8. The motor drives the reducer, and the output shaft of the reducer drives the bottom chain shaft. The shaft drives the middle shaft through the sprocket chain, and the middle shaft drives the upper shaft. The feeding roller in the feeding hopper is driven by the output shaft of the reducer.

2. Working process

When the flat dryer is working, 0.5MPa steam (or heat-conducting oil) is passed into the heating sheet, and the green sheet is put into the feed hopper and falls on the end of the first layer of the heating sheet, and is heated during the dragging process with the scraper. When the blank runs to the end of the first layer, it falls on the heating plate of the second layer, and returns to the drag line to continue to be heated. When running to the end of the second layer, the blanks then fall into the third layer of heating plates, and thus, successively undergo the heating treatment of the fourth, fifth and sixth layers of heating plates. Finally, the dried blanks fall into the screw conveyor at the outlet and are sent out of the machine.

As can be seen from Figure 4-8, the chain scraper carrying the blanks is carried back and forth without empty load. The moisture from each layer is discharged into the upper exhaust hood. After the embryo is dried, the moisture can generally be reduced by about 4 percentage points.

3. Product series

Some product series of chain steam dryer are shown in Table 4-5.

Table 4-5 Some product series of chain steam dryer

4. The operation of the flat dryer

(1) Before starting the machine, remove the sundries and accumulated materials in the machine, check whether the parts are in good condition, check whether the joints of the inlet and exhaust pipes are in good condition; check the lubrication system to ensure that the lubricating oil is sufficient; adjust the tightness of the chain scraper to ensure that the It is advisable to lift the height by hand to 50-8Omm in the middle of the chain length.

(2) Jog the test drive, check the surrounding baffles, receiving plates, etc., and do not hinder the operation of the chain scraper; run without load, check whether the operation is stable, whether the chain meshing is normal, whether there is any abnormal sound, and if there is an abnormal situation, stop the car Check.

(3) After the no-load operation is normal, slowly open the heating medium inlet valve for preheating, and the initial flow rate can be less, and at the same time observe whether there is leakage in the heating medium pipeline. If there is no abnormal situation, the material can be fed to start the load operation.

(4) When the dryer is working normally, there should be a certain amount of material in the hopper, and the material should be kept uniform, so that the thickness of the material on the drying plate is about 40-80mm, and the large material should be balanced to avoid There is no shortage of overflow material to meet the needs of the process.

(5) During normal operation, it is necessary to strengthen the inspection to prevent the scraper chain from deviating on the smooth wheel, and prevent the rod-shaped object from falling into the machine and damaging the scraper chain.

(6) The dryer should stop feeding before stopping. When the scraper chain scrapes the blank from the drying plate, it can be stopped, and the heating medium inlet valve is closed at the same time. In this way, it can prevent the waste heat from scorching and deteriorating the material embryo after parking.

5. Maintenance points

(1) The flat plate dryer belongs to a class of low-pressure heat exchangers, and should be used, managed and maintained in accordance with the relevant regulations in the "Pressure Vessel Safety Supervision Regulations" of the Ministry of Labor. When the thickness of the dryer plate is corroded to a certain extent , the drying board should be reported to the labor department for review.

(2) The dryer must be inspected regularly, with an external inspection at least once a year, and a comprehensive inspection at least once every two years.

(3) Pressure gauges and safety valves should be inspected regularly, at least once a year. Pressure gauges and safety valves that have passed the inspection should have lead seals and inspection certificates; pressure gauges and safety valves that have failed or no seals have been inspected. Not allowed.

(4) When the dryer is not used for a long time, the water stored in the drying plate (when steam is used as the heating medium) should be drained. When reused, it should be inspected according to the regulations of "Pressure Vessel Safety Supervision Regulations".

(5) The mechanical part of the dryer should be maintained at least once every six months. If the transmission part makes an abnormal sound during operation, it should be stopped immediately for inspection and processing.

(6) The cycloidal pinwheel reducer should pay attention to the cleanliness and hygiene of the lubricating oil in the early stage of work, check the oil quality in three months, and replace the lubricating oil every six months.

(4) See Table 4-6 for common faults and treatment methods.

Table 4-6 Common faults and treatment methods of flatbed dryers

(2) Cylinder frying pan

The cylindrical frying pan is a horizontal frying pan, which is a seed frying equipment matched with a small oil press. The main body of this equipment is a spindle-shaped rotating drum, and the inner drum wall is welded with oblique fins, which can turn the frying materials when rotating. Because the fins are directional. Reverse rotation can discharge all the fried ingredients. The drum is usually installed in the furnace and heated by direct fire. And the device is equipped with a reverse motor switch.