Dry noodle drying production line operation rules

First, the cold wind fixed zone:

Usually, the method of enhancing the air flow without heating is adopted, and a large amount of dry air is used to promote the dehumidification of the noodles, and the shape of the noodles is initially fixed to remove the surface moisture. The surface is hardened, and the plastic body changes to elasticity. In rainy days (or rainy weather), the fan and the tide should be opened in advance. In winter, the temperature is slightly advanced. Because the surface of the wet surface evaporates slowly, it is not easy to fix the strip, avoiding excessive temperature and making the noodle wet. Excessive evaporation of surface moisture affects the humidity reduction in the internal evaporation stage, and the moisture retention is excessive, causing the noodles to stretch, the thin strips on the broken strips, and the mutual adhesion.

Second, the internal evaporation zone (moisture and sweat):

This area is mainly diffused in water, strengthens ventilation, and makes the air circulation smooth. At this time, the temperature rises across the area, not to be "urgent", to make the temperature form a "gradient", maintain a certain humidity, on the one hand, transfer to the noodle center Thermal energy, reducing the temperature difference between the surface and the inside, on the other hand, accelerating the diffusion of internal moisture, so that the surface water vaporization rate is consistent with the internal water transfer rate, and the water slowly evaporates. If the temperature and humidity difference is too large, Causes the surface layer to dry quickly, the surface "conjunctiva", "closed door", "cracking" and other phenomena, the internal and external water imbalance, zui after the hanging surface outside the wet inside, resulting in noodles sour noodles, crisp noodles and other quality problems, short storage period .

Operation: When the production starts, when the noodles enter the second row of Zone 2 (or the surface thickness >0.8mm*), the temperature will be sent, and the fourth row will consider the tide (observed humidity value>normal water content 25.5%± 0.5). In rainy days (the rainy season), the tide can be appropriately advanced, the temperature is increased by 1-2 ° C, and the humidity is reduced by 2-5%. When the production is over, the noodles enter the second zone, the boiler stops refueling, the fourth row closes the inlet valve, and the air supply and the moisture are stopped according to the dry moisture of the noodle.

Third, the total evaporation zone (heating and cooling):

After the noodles in the stage of “sweating and sweating”, the internal water is transferred to the surface layer to make the water accumulate on the surface, and the noodles have a certain strength. It is necessary to further increase the temperature, appropriately reduce the relative humidity, and make the noodle water in a high temperature and low humidity state. Fully and timely evaporate. If not heated, the surface moisture migrates again to the inner layer to achieve an internal and external moisture concentration balance. If the noodle is thicker (>0.8mm) round, this area acts as an extension of the moisture-preserving sweat zone, and the moisture is kept, so that the internal moisture is transferred to the surface layer, there is no sandwich, and then the moisture is discharged at the tail of the high temperature zone. The internal and external diffusion balances and completes the whole process of the main drying stage.

Fourth, cooling and cooling:

After the main drying stage, most of the noodles have been removed, and the noodles have been basically fixed. At this time, only the flow of air is required, the temperature of the noodles is slowly lowered, and a small amount of water is removed to achieve product quality. The requirements of the standard water content, the role of this stage has two aspects, one is to take the slowing process, adjust the surface and internal moisture content is extremely unbalanced, eliminate the internal stress caused by the drying shrinkage of the noodles, increase the toughness and flexibility of the noodles Second, after the noodles are dried at a high temperature, the temperature of the noodles is still high, and the temperature of the medium entering the cooling stage is low, so the heat transfer inside the noodles cannot be stopped, and the temperature balance with the temperature of the inside and outside of the noodles is stabilized until it is stable. Therefore, the temperature is balanced by the residual temperature, and the noodle water is detected at any time during the operation, and the moisture is discharged at a proper time to lower the air temperature and the surface water of the noodle (13.5% ± 0.5).

Summary: The control of each of the above drying stages is the basic principle and method of mastering. In practice, according to the rationality of the process arrangement, the different factors of climate and season, the flexible use of the process characteristics, the four zones have their own drying effects and Requirements, but each drying stage affects each other. The size of dehydration during the drying process should not be excessively concentrated in the front or back section or in a high temperature zone, etc., and should be properly distributed according to certain rules. Practice has proved that in the pre-drying stage, the excessive drying of the air medium can accelerate the conversion of the wet noodles from the plastomer to the elastomer, but the evaporation of the moisture on the surface of the wet noodles will cause the humidity in the internal evaporation stage to become low and the moisture retention is poor. The velocity of the evaporation phase of the surface layer is greater than the velocity of the outward migration of the internal moisture, which leads to the phenomenon of "conjunctiva". Similarly, the relative humidity from the internal evaporation stage to the pervaporation stage cannot be reduced too much, and the surface evaporation is too fast, and the phenomenon of "cracking" and "conjunctival" occurs. Therefore, special attention should be paid to the selection and control of drying parameters and the speed of noodle dehydration. The general principle is to maintain the balance between internal diffusion and outflow rate.