As the aquaculture industry develops in the direction of scale, intensification and specialization, the requirements for aquafeeds are also increasing. The rapid increase in aquaculture pond rents, labor costs, and raw material costs has also directly contributed to the rapid growth of aquatic products. According to incomplete statistics, in 2010, the national aquatic product expansion production line has reached more than 200, and the total output is about 5 million tons per month. At present, many enterprises are planning a new expansion line.
Because the puffing process has the advantages of being able to passivate the anti-nutritional factors in the feed, and improve the digestibility of feed nutrients, people are relished; however, while people are swarming, they ignore the expansion process to inactivate anti-nutritional substances. At the same time, a large number of heat-sensitive micronutrients are also inactivated. Under strict test conditions, if the protective effect of the bulking material on water quality is excluded, the bulking material does not exhibit excellent feeding performance relative to ordinary hard pelleted feed. Therefore, even in Guangdong, where the bulking material is most popular, savvy farmers tend to adopt a combination feeding mode of expanded material + hard pellets. It is an indisputable fact that the whole process of puffing feeds easily leads to poor anti-stress ability of fish.
In Europe and the United States, which mainly breeds carp, the granulation of aquatic feed has been carried out by using a puffing process, and the expanded feed has accounted for about 80% of the aquatic feed. At present, the proportion of puffed feed in China's domestic aquatic feed is less than 30%. It is now gradually transitioning from the situation of traditional hard particles to the two types of processing. However, the impact of the expansion process may have an impact on the supply of nutrients, and whether it needs to be adjusted. So far, there are few research institutions in China to pay attention to and systematically think about it. Most of the practices still use traditional hard pellets. Nutritional parameters. However, in view of the different properties of various substances, as the process changes, the amount of retention will also change. Taking aquatic vitamins as an example, under the conditions of puffing, vitamins are easily inactivated by the effects of moisture, heat, shearing force, etc., and there are significant differences in the vitamin inactivation rates. For example, at a puffing temperature of 120 ° C, the retention rate of choline is 96%, VB2 can also reach 93%, while the retention rate of the coated VC with acetyl cellulose as the coating material is only 29%, and VB1 is only 66%. Due to the inconsistent retention rate of various vitamins during processing, the vitamin ratio which originally meets the requirements of the fish body becomes very unbalanced, and the natural vitamins in the raw materials are also seriously damaged, so the fish body is prone to vitamin deficiency. Not surprisingly.
In response to these problems, at present, each aquatic product manufacturer often uses excessive addition to solve the loss of vitamins during the expansion process, but this is extremely uneconomical and inefficient. According to the current method of excessively adding 10-20% vitamin premix, most of the vitamins with low retention rate are not fully compensated, and the vitamins with high retention rate are wasted. Although reducing the loss of vitamins during the expansion process is the most effective way to solve the vitamin imbalance, the selective over-addition has become the most effective way to solve the problem that the high-loss loss of vitamins in the expanded material has not been effectively achieved by external spraying. A more cost-effective means.
It is worth mentioning that the same vitamin has different dosage forms, and they may have the same stability under the hard particle process conditions, but the stability under the expansion process conditions is quite different. Taking vitamin C as an example, at a puffing temperature of 120 ° C, crystal VC, acetyl fiber coated VC, fat coated VC, VC phosphate ester retention rate were 25%, 29%, 63%, 89%, respectively. In fact, most vitamins exist in a variety of dosage forms, and the stability of the dosage form is different. For example, vitamin K has four dosage forms, MSB, MPB, MSBC, MNB, which have a retention rate of 28%, 46%, 40%, and 53% at a puffing temperature of 120 ° C, respectively; and two dosage forms of VB1 under the same conditions. The retention rates of thiamine and methionine were 81% and 66%, respectively. It can be seen that the bulking material should be targeted to select those vitamin monomers with high expansion stability.
In addition, the high temperature and high humidity expansion conditions are conducive to the reaction between anti-nutritional factors and nutrients, especially the phytic acid in plant raw materials is the most prominent. Studies have shown that some of the raw materials contained in plant sterols, unsaturated fatty acids, natural vitamins and foods are easily inactivated or volatilized in the expansion process, and additional supplementation needs to be considered; most minerals are processed by extrusion. There is a slight decrease, so the amount of trace elements added and the dosage form need to be adjusted appropriately.
The puffing process can significantly increase the utilization of energy, especially fat, while the protein utilization rate is slightly reduced. As a result, the energy-protein ratio of the formula is changed, and the result is that the fish body is relatively fattened, which is why the fish body of the Guangdong fish body having a higher penetration rate of the bulking material is higher than other regions. Therefore, the market of the new puffing line needs special attention. If the formula design of the puffing material is simply carried out according to the nutritional parameters of ordinary hard granules, the fish body fatness is likely to be high. For the East China and North China regions where the grease design itself is very high, it is more important to pay attention to this problem. In addition, during the expansion process, the oil will undergo cross-linking reaction. These cross-linked fats can be used by fish, but they cannot be extracted by ether. Therefore, this problem must be considered when designing the label of the expanded material to avoid being judged as unqualified when the product is tested.
In short, aquaculture materials as a new thing, in addition to us need to understand the expansion process, but also need us to understand the various changes derived from the process, such as nutritional parameters, feeding mode, breeding mode. Who is the earliest and most profoundly aware of the changes brought about by the expansion process, who will grasp the new growth point and market discourse right, this is a challenge and an opportunity!
Copper smelting methods can be divided into two categories: pyrometallurgy and hydrometallurgy. More than 85% of the world's refined copper output is recovered from pyrophyllite concentrates and recycled copper by pyrometallurgical process, and the refined copper produced by hydrometallurgy only accounts for about 15%.
In China, copper metal is extracted from copper concentrates mainly by the pyrometallurgical method. The more advanced one is flash smelting, whose output accounts for over 30% of the total copper produced in the country. Due to low energy consumption, large-scale, can effectively control the advantages of environmental pollution. This smelting technology is being developed in the copper industry. Flash smelting furnace according to different working principle can be divided into two types: Outokumpu flash melting, InCo flash melting. The following describes Outokumpu smelting process.
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