Since the 1990s, domestic feed expansion technology has been greatly developed, and 160kw commercial models have been widely used. However, domestic feed expansion technology started late, basic research is very weak, and it is still in the stage of imitation and improvement. There are few reports on this. This paper will give an overview of the development and application of feed expansion technology in recent years, in order to provide reference for the improvement of domestic expansion technology. 1. The latest development of puffing technology 1.1 Density Control System Density control is the most challenging aspect of expanded feed production, especially for aquafeed production, where sinking feed should sink in the desired manner. If the sinking feed floats on the surface of the water, it not only reduces the feed conversion rate, but also pollutes the environment as a waste of nutrients. The difficulty is even greater when using a "low-energy formula" sinking feed that produces a relatively low oil content. At present, it is commonly used in China to puff the raw materials and then granulate them. Generally, formula adjustment and operating parameter adjustment can be adopted to control the product density, such as reducing the spindle speed, adding more steam and adding water, increasing the formula oil content, reducing the feed amount and enhancing the expansion chamber cooling. Some more powerful measures can also be taken. Such as: vent or decompression zone on the puffing chamber, which is the method commonly used by extruder manufacturers (Wenger); ― Increase the opening rate of the template or change the thickness of the template to reduce the pressure difference at the template; spiral and puffing cavity structure; ―Adjust the formula, especially to reduce the carbohydrate content. Although these measures have a role in controlling the degree of expansion, they are not sufficient to produce a sinking material in a controlled manner. As a result, Sprout-Matador has developed a new density control system for the production of aquatic materials, which can be called the most significant advancement in puffing technology in recent years. In the extruder, the material is subjected to mechanical shearing and high temperature and high pressure. Due to the high pressure, the temperature does not reach the boiling point of the water, but when the material is extruded from the template, it enters the normal pressure, the boiling point appears, and the water forms a "flash". The material is expanded into a porous structure containing a large number of pores, causing a change in product density. The higher the carbohydrate content, the more pores are formed. High porosity means low density and the material can float in the water. For high oil products, the porous structure facilitates the absorption of sprayed grease (especially when vacuum sprayed) and forms a higher density product. However, it is more difficult to control the production of heavy oil and low fat. The density system developed by Sprout-Matador uses pressurized cutting or post-die pressurization to maintain a certain positive pressure in the cutting chamber, as the boiling point of the water increases with pressure as the material enters from the expansion chamber. After the cutting chamber, the flashing can be reduced to control the expansion of the material. Since the starch molecules are solidified instantaneously in the cutting chamber, the material does not expand again after entering the normal pressure from the cutting chamber. The positive pressure of the cutting chamber is generally maintained at 0.3-2.0 bar. In this range, the pressurization has a significant effect on the product expansion, but the pressurization above 2.0 bar has little effect on the product expansion. For example, for sea bream, squid and squid feeds with medium fat content, the expansion degree is 50% (water boiling point 100 °C) under normal pressure cutting, and pressure cutting is used, and the positive pressure of 1 bar can reduce the expansion degree by 50%. That is to say, the product density is increased from about 440 g/l to 550 g/l. This technology is mainly used to produce difficult feeds, such as low-fat products, and it can be used without positive pressure on the oil products. Compared with other density control methods such as open exhaust and decompression zones, this press cut is unique in producing some challenging products: control of product density (±5g/l) is any other means; ―Compared with the model of opening and exhausting port, the material can be increased by % when producing low-fat or high-starch-type feed because the material is less disturbed during the whole expansion chamber; ― No need to control other expansion factors, such as spiral and puffing chamber structure, feed amount, etc., thus reducing the need for manual operation; ―Because the expansion degree is controlled outside the extruder, the operator only needs to monitor the visual quality of the product, and it is easier to control the external positive pressure than to control the pressure of the expansion chamber. Domestic extruders basically have no density control measures. They only make simple considerations in the configuration of spirals and puffing chambers. Some manufacturers imitate Wenger's exhaust devices, but they are less maneuverable due to some factors in technology and processing. Pressurized cutting is relatively easy to implement, the air pump can be used to maintain the required pressure, the discharge can be used to shut off the fan, and because the required pressure is not high, the sealing of the moving parts is not too big a problem. This technology is easy to realize from the aspects of equipment production, operation and use, and density control of puffed products. It is a new direction for the development of puffing technology. 1.2 quenching and technology The quenching and tempering technology is an indispensable part before puffing. At present, the research on the tempering device is still deep in China, and there are products for both single-axis and double-axis. The quenching and tempering involved in this paper is actually pre-conditioning with waste steam. In principle, it is very simple, that is, the steam released from the puffed "flash" and the hot air at the front end of the cooler are sent back to the conditioner, thereby reducing fuel consumption and reducing CO2 and SO2 emissions, and at the same time, in the exhaust gas. The odorous substance is absorbed. Dust emissions are also reduced due to partial circulation of the cooling air. As a world-renowned extruder manufacturer, Kahl has developed an Eco-processor and has conducted detailed research on the production of expanded feed. Since the environmentally-friendly conditioner uses the extruder/expander outlet steam and the hot air at the front of the cooler for pre-conditioning, the material temperature can be raised from 20 °C to 40 °C without steam addition, which usually takes 2%. Steam (20Kg / t product). In other words, it is equivalent to saving 1.2Kg of fuel per ton of product, and accordingly CO2 and SO2 emissions are also reduced. At the same time, the odorous substances in the exhaust gas are absorbed by the materials, and it is particularly important to reduce the odor emission in the vicinity of the residential area. Compared with ordinary granulation, expansion production can save 5 degrees per ton of product. 　 2. Puffing technology application 2.1 Puffed pig feed Domestic puffed pigs have only emerged in recent years, and basically only produce piglets. The advantages of nutrition, hygiene and other aspects of puffed piglets have been mentioned. This article will explain the superiority of puffing for pig production from another perspective. Studies have shown that the use of puffing technology to produce pig feed can reduce the emission of environmental pollutants during the production process of the feed mill, during the fattening process of the pigs, and during the storage and transportation of the feces. In actual production, it was found that liquid manure discharged from pigs fed with expanded material was reduced. Studies at the University of Kansas (KSU) have shown that feeding a puffed material reduces the need for water in pigs, and the special structure of the puffed material results in less water for the animal when it is fed. Tests on expanded piglets have also been shown to reduce the amount of urine and manure excreted by pigs, thereby reducing the cost of storage and transport of manure. Similar to the traditional method, but replace the stringers and joists with aluminum forming systems, or replace the steel beams with support frames and replace them with metal pillars. This also makes the method more systematic and reusable. Aluminum beams are made as telescopic units so that they can span different distances of support. The telescopic aluminum beam can be used and reused in the structure of various sizes. 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The latest development and application of feed expansion technology