With the Expander increasingly used in actual production, must raise the level of design Expander at the same time, raise the level of use. This article only twin-screw extruder, and other characteristics of the structure of the principle to make a brief description. Expanded want to be helpful to the user's machine.

1. Twin-screw Extruder working principle and advantages
1.1 pairs of Screw Extruder structure
With materials by conveyor to the quenching and tempering equipment, materials in the conditioner in high temperature steam quenched by diarrhea trough Expanded access to institutions, in a pair of parallel engagement of the screw pump sent from the shape of a certain mode of the hole Cut into tablets out in an instant.

1.2 Pairs of Screw Extruder principle Expanded
Figure 2 shows a typical twin-screw extrusion machine extruded body by a pair of parallel engagement of the screw push forward material, the screw is divided into three sections: expected to lose, Compression melting, Uniform section. Lost in the material, material from the hopper into the suspected plane, with the turning of the screw, along the forward direction of the spiral groove transportation, and gradually compacted. Compressed into the melting, due to structural changes in the spiral, increasing the pressure, due to come from outside the barrel, as well as heating materials in two between the screw and screw and barrel to the strong mixing, blending, shearing , The temperature of material to begin melting, until all the melting. As the spiral groove further room for smaller, the materials to further boost heating, cooking has been so full of raw materials starch paste, fat, protein degeneration and a series of complex biochemical reactions, both organizations, arrived in uniform, by diverting the board Puffing out of the cavity material evenly assigned to a template, the pressure at this time is usually 3 ~ 6Mpa (in accordance with the requirements of the Expanded), the temperature can reach 150 ~ 200 ℃, because of the closed sleeve in this high pressure over the squeeze Under the pressure of saturated steam temperature, so water will not evaporate quickly when the material from the shape of a certain mode of the hole in an instant out of time, the rapid release of pressure, rapid evaporation of free water, materials resulting expansion of the water from the rapid loss of material, So that the product quickly cooled to around 80 ℃, which was cured stereotypes, and to maintain its shape after expansion.

1.3 Pairs of Screw Extruder features
Twin Screw Extruder relatively late development in China, because of its Expanded the scope of the larger changes in the characteristics of raw materials, the need to screw speed in a larger range of adjustment than the principle of single screw confidential Expanded much more complex, in particular There are larger structural differences, in particular the barrel, screw, thrust bearings gear box layout of the complex, resulting in an increase in the cost of equipment, such as single screw used a belt drive, and the use of twin-screw extruder gear box drive , Both in manufacturing efficiency and drive quite different. (Twin-screw and single screw-expanding
Machinery distinction see table 1).

2. Twin-screw extruder in aquatic feed
Extrusion is the process of raw materials at high temperatures, high pressure, the moment of the aging process, and set transport, crushing, squeezing, mixing, shearing, forming and milk in one, and the process can be thick, high-fat, high water Copies of the raw materials, production processes are generally beyond compare, it was increasingly used for aquaculture feed, pet food, culture, and other high-end specialty food and feed production.

2.1 Processing process
Micro-crushing raw materials → ingredients, mixed-puffing → → → pelletizing spray drying → → → cooling measures package.
Expanded material advantages of aquatic products 2.2

2.2.1 good water resistance
Expanded in the process of forming a network structure of expanded aquaculture feed particles in the water very good stability, whether floating or sinking feed, feed soaked in water for 12 hours can not keep collapsing, can maintain the water quality of culture, not only significantly reduce feed The waste, but also good for the health of aquatic animal growth provides a good environment.

2.2.2 higher peptic
Expanded materials in the process of high temperature and high pressure, strong shearing of starch, protein, and other material generated by the change to improve the digestibility of such substances, puffing aquatic feed starch gelatinization degree in general more than 85%, while the ordinary Hard particles aquatic feed only about 40%, only the starch digestibility on the hard particles is much higher than ordinary materials and Fisheries strong role could squeeze some of the compact of cellulose, keratin, such as degradation of the parcel so that it can not digest The nutrients can be released so that the substantial increase in digestibility.

2.2.3 excellent palatability
Expanded appropriate course of the temperature and pressure so that the role of the feed particles and finished with a porous texture characteristics of the uniform, and some have a fragrance material, an increase of feed attractant, to stimulate the appetite of the fish, increased feed intake.

2.2.4 broadens the scope of the use of raw materials
The food industry, brewing industry, agriculture and other industries due to the waste contains excessive moisture, grease or cellulose instead of easily processed into other forms of aquatic feed, and the twin-screw mechanism of expanded them to do to make the best use, enriched Feed resources.

2.2.5 facilitate the management culture
Feed not only able to adapt to the fish used to feed, while farmers make an accurate understanding of aquatic animal feed, in a timely manner to adjust the amount. Expanded use of feed to reduce the breeding of the harm the water quality of nutrition, can reduce the frequency of changing the water, for water, and reduce the amount of oxygen-increasing.

2.2.6 improved the safety of animal feed
Extrusion process to be effective in addition to the pathogenic bacteria in raw materials and raw materials in the passive part of the anti-nutritional factors, diet can reduce the amount of drugs. Expanded aquatic products than it expected other forms of aquatic feed more secure, this security is the result obtained through physical methods, without adverse side effects. Greatly reducing the drug residues in aquatic products for human food safety is of great significance.

2.3 aquaculture feed twin-screw Extruder choice
In new and retrofitted aquatic feed production line, the first thing to consider twin-screw Extruder selection, based on production capacity and investment choices to match the size of the Expander in the transformation of production lines should also be considered when the original mill, cooler, dryer The effect of production and production capacity can meet the requirements of the selected Expander, it is necessary to fully consider the possibility of using existing equipment in order to reduce investment.

2.3.1 Expander the effects of expanded
Extruder selected aquatic feed production to meet the effects of expanded several of the following:
A. particles forming rate of ≥ 99%
B. particles floating rate = 100%, the rate of sinking ≥ 99%
C. uniform particle size, color, with very good water resistance
D. floating in the water and is expected to maintain 10h, sinking in water is expected to maintain 3h not bad, leave.

2.3.2 Extrusion machine of life
Different manufacturers of twin-screw Extruder due to transmission, structural characteristics, the use of materials, processing technology, and so different, very different life. Extruder in the selection, first of all should pay attention to the overall design of the structure is reasonable, the parts manufacturing process, the selection is excellent, the wearing parts, such as how to wear followed by the power transmission sector should be noted that the design is reasonable, is effective in reducing transmission process The energy consumption.