(1) Diversity of chemical separation technologies
Due to the wide range of applications of chemical separation technology, the diversity of separation technology is determined. According to the mechanism, it can be roughly divided into five categories: 1 to form a new phase for separation (such as distillation, crystallization); 2 to add a new phase for separation (such as extraction, absorption); 3 for separation with a separator (such as membrane separation); Separation by solid reagents (such as adsorption, ion exchange); 5 separation by external force field and gradient (such as centrifugal extraction separation and electrophoresis, etc.), their characteristics and design methods are different.
In 1987, Keller summarized some common separation techniques and application maturity relationships. Distillation, extraction, absorption, crystallization, etc. are still the separation techniques currently used in many applications. Although the liquid membrane separation is ingeniously designed, it still has limitations in technology, and has been applied only in drug release.
(2) The complexity of chemical separation technology
The importance and diversity of chemical separation technology determines its complexity. Even for the more mature technologies of rectification and extraction, the design of large-scale equipment for multi-component systems is still a difficult task. The problem is the lack of basic characteristic data and reliable design methods for large towers. For high temperature, high pressure, multi-component and strong non-ideal systems, not only the equilibrium data and molecular diffusion coefficients are difficult to calculate accurately, but also physical property data such as interfacial tension viscosity are difficult to obtain.
The basic characteristic data of the coupling separation technique such as catalyst and reaction extraction is even more scarce. The main difficulty in the enlargement of large-scale tower design is that the two-phase flow and mass transfer characteristics in the tower are very complicated, and the digital model is not perfect. The balance-level model that has been in use for more than a hundred years is simple and straightforward, but the disadvantages of the multi-component separation process are obvious. The non-equilibrium model is called "may create a new era of plate separation equipment design and simulation". However, the lack of mass transfer coefficient experimental data and too many model parameters make its engineering application difficult. The software that has been developed is powerful and has been applied in engineering design, but engineering experience and pilot test are still indispensable.
(3) Forward-looking of separation technology
With the development of basic industries such as energy, resources, environment, new materials and high-tech, classification technology faces new opportunities and challenges. Separation processes in the petrochemical sector must further save energy and reduce consumption, making full use of energy and resources. The pace of large-scale production equipment is accelerating, and energy consumption and costs are continuously decreasing. In biopharmaceutical engineering, with the development of genetic engineering and cell engineering, biopharmaceuticals have developed rapidly. Super-extraction with CO2 as a solvent has the advantages of non-polluting products and high selectivity. Methods such as chromatographic separation and electrophoresis separation have been successfully applied in production and laboratory research due to their high efficiency and normal temperature and pressure characteristics. With the strengthening of environmental awareness, the "three wastes" treatment has attracted attention. From the perspective of industrial ecology, the "waste" discharged from many processes is no longer "useless", but is not fully utilized. "Three waste treatment" is a new challenge to separation technology.
(4) Particularity of separation technology
Competition promotes the strengthening of the separation process, and the strengthening of the separation process includes two aspects of the new device and the new process. Any new chemical separation technology that can make equipment compact, energy efficient and sustainable for development is among the strengthening of the separation process. This is one of the important trends in the development of chemical separation technology.
Coupling separation techniques are of interest. New coupling and separation technologies such as catalyst rectification, membrane rectification, adsorption rectification, reactive extraction, complex adsorption, reverse micelle, membrane extraction, fermentation extraction, chemical adsorption and electrophoretic extraction have been greatly developed and industrialized. Coupling separation techniques may solve many of the tasks that traditional separations are difficult to accomplish. Motor-coupled chromatography can efficiently separate vitamins.
Information technology has driven the development of separation technology. Separation of science and technology is multidisciplinary, and the combination of information technology and traditional chemical methods accelerates the advancement of separation technology.
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