Introduction of dry and wet feed pellet machines

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Dry extruder

Extruder without steam conditioner, the raw material is not pre-conditioned before entering the extrusion system.

The dry type fish feed machine is as floowing.

Wet extruder

With steam conditioner, the raw material is pre-conditioned and tempered before entering the extrusion system.

Look the wet type fish feed pellet machine.

It can be seen from the definition that the most important difference between the dry and wet method is whether the material is pre-conditioned with steam before entering the extrusion. I have always understood the dry and wet method as the two working modes or modes of the extruder, rather than the essential difference in structure. From the working mode: according to whether the material is quenched and tempered by steam before entering the extruder barrel (extrusion cavity), it is divided into dry extruder and wet extruder. If it is quenched and tempered by steam, it is a wet method; otherwise, it is a dry method. 


The purpose of steam conditioning: to increase the temperature of the material, soften and partially pre-ripen the material, and add a certain amount of water. For most materials, wet puffing is more efficient than dry puffing. Considering only the temperature factor for a simple analysis, if the expected curing temperature of the material is 130 °C, the extrusion part of the dry puffing screw increases from room temperature (20 °C). To reach this value, the temperature needs to be increased by 110°C.


If wet production is used, the temperature after conditioning is 80°C, and the material temperature that needs to be raised in the screw extrusion part is 50°C. Therefore, the required mechanical energy is less than the dry method. More energy Can be used to increase production. In addition, due to the softening of the material, the wear on the screw and barrel will also be reduced.


Many users, including some equipment manufacturers, literally understand that adding water is a wet process. From the above analysis, we can know that simply adding water can not be called wet method, it just supplements part of the water, and cannot improve the temperature of the material, soften and partially pre-ripen the material.


Due to the different properties of the material entering the barrel during the production of dry/wet methods, the wet method entering the barrel is a moist and hot soft material, and the dry method entering the barrel is a raw and cold hard material. Therefore, the main system and the extrusion screw are The configuration requirements are also different.


In general, a dry process machine equipped with a steam conditioning system can be used for wet process production, and the efficiency will be improved, but it is not as efficient as the dedicated wet process model; the impact of the hard material on the shafting should be considered in the dry process of the wet process model. Dry production can be performed for some materials, but the efficiency will be reduced, and it is not suitable for some materials. In other words, a dry machine can be produced wet, while a wet machine may not necessarily be used dry.

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