Two preparation processes of aerogel
2019-03-04 14:55:36 From: Tradematt-Aerogel
Two preparation processes of aerogel
The two preparation processes of aerogels are introduced. According to the different drying processes, they are mainly divided into supercritical drying process and atmospheric pressure drying process. Other mass production technologies have not been realized, such as vacuum freeze drying and subcritical drying.
Supercritical drying technology is the earliest to achieve batch preparation of aerogel technology, which is relatively mature, and it is also the technology adopted by aerogel enterprises at home and abroad. Supercritical drying is designed to achieve a critical point in the drying process by pressure and temperature control to form a supercritical fluid. The solvent in the supercritical state has no obvious surface tension, so that the gel can be dried. Maintain a good skeleton structure during the process. At present, the batch production technology has generally adopted carbon dioxide as a drying medium, referred to as carbon dioxide supercritical drying technology.
Atmospheric Drying Technology A new type of aerogel preparation process is the most active and most promising aerogel production technology. The principle is to modify the gel skeleton by using hydrophobic groups, to avoid the silicon-hydroxyl groups on the surface of the gel pores and to enhance the elasticity, and to replace the original high specific surface area of water or ethanol with a low surface tension liquid. Directly drying under pressure to obtain aerogel materials with excellent performance. At present, the aerogel preparation technology independently developed by Tradematt (Henan) Industry Co., Ltd. is the world's leading atmospheric drying technology. The following is a brief analysis of the two technical routes:
Equipment input: Supercritical drying technology uses the core equipment as autoclave. The working pressure is up to 7~20MPa. It belongs to the pressure vessel in special equipment. The equipment system is more complicated, and the operation and maintenance cost is also high. Manufacturers of supercritical equipment are prepared, but the number is small, and the owner's bargaining power is weak. The atmospheric pressure drying technology adopts conventional atmospheric pressure equipment. Relative to supercritical drying, because high pressure conditions are not required, equipment investment is low, and the equipment system is relatively simple, because most chemical equipment units can be processed and manufactured, and the owners have strong bargaining power.
Production cost: The production cost of aerogel is mainly concentrated in three sources of silicon source, equipment depreciation and energy consumption. Silicon sources mainly include water glass and silicone. The price of silicone is relatively expensive, but the purity is high and the process adaptability is good. It can be applied to both supercritical drying process and atmospheric pressure drying process. At present, enterprises adopting supercritical drying process at home and abroad basically use silicone. source. Water glass is cheap, but there are many impurities, and the process of removing impurities is cumbersome. Currently, it is mainly used in atmospheric pressure drying technology. In terms of equipment depreciation, due to the high investment in supercritical drying technology equipment, depreciation is higher than atmospheric pressure technology. In terms of energy consumption, the supercritical drying system consumes more power than the atmospheric drying system, and there is little difference in steam consumption. Therefore, in general, the production cost of the atmospheric pressure drying technique is lower than that of the supercritical drying.
Product performance: As far as silica aerogel is concerned, there is no significant or substantial difference between the current supercritical drying technology and the atmospheric pressure drying technology. Basically, the supercritical technology can reach the technical index, and the atmospheric pressure drying process can achieve. In the preparation of non-silica silicon aerogel, the supercritical drying process is much mature, but there is no report on mass production.
Technical threshold: Relatively speaking, the production efficiency, safety, and even process changes of supercritical drying technology are highly dependent on the equipment system. If the equipment manufacturer provides the equipment system is relatively mature and reliable, the owner enters the technical threshold is relatively low, this It is also one of the reasons why many new entrants in the aerogel industry choose supercritical processes, but they are also subject to more constraints. The investment threshold of atmospheric pressure drying technology equipment is low, but the technical threshold is high, and there are high requirements for formula design and process combination optimization. If the technology is not good, not only the production cost may be higher than the supercritical value, but also the performance index. Can not meet the requirements.
Expanding space: Supercritical drying as a high-pressure special equipment, if you want to expand the scale of production, the investment in fixed assets is huge. If the aerogel industry wants to meet the huge market of building insulation in the future, for example, it will reach an annual output of 500,000 cubic meters (this is only the current The scale of small and medium-sized building materials enterprises), the equipment and equipment using supercritical drying technology will be worth billions, which is not conducive to the expansion and strengthening of aerogel enterprises. The atmospheric pressure drying technology, with the expansion of scale, will further increase the input-output ratio, and can obtain a larger production scale with less investment, so it can better adapt to the needs of future large-scale production. In addition, limited by the silicon source, the supercritical raw material cost reduction space is limited, and the production efficiency can only be improved by optimizing the system, while the atmospheric pressure drying has strong acceptance ability for the inexpensive silicon source, and the process optimization also has more degrees of freedom. Have more room for cost reduction.