Research On A Kind Of Perlite Pretreatment Process Optimization And Its Application

Perlite is widely used in casting, heat preservation material, construction and other fields due to its light mass, low thermal conductivity, strong adsorption, no corrosion, no burning, good acid and alkali resistance. It can be used as slag agent or covering agent in the casting production, insulation sound-absorbing board in the construction industry, which are mainly based on its good high-temperature expansion performance. The reason for the expansion of perlite is its internal contain water, but only perlite with appropriate moisture content can obtain high expansion ratio. Therefore, heat pretreatment of crude pearlite should be carried out to obtain appropriate moisture content. Taking a perlite ore in Hebei province as the research object, the heating pretreatment technology of perlite ore was studied, and a new type of expanded perlite slag agent and coating agent were developed in this article. The results of this dissertation has vital significance for the industrial application of perlite.High-temperature expansion performance of perlite being used as indicators, the common heating and microwave heating pretreatment technology were investigated, and the influence of preheating temperature and time, expansion temperature and time, granularity of pearlite and method of heating on the high-temperature expansion performance of perlite were researched. The results show that perlite which is preheated 10 minutes at 350? and roasted 20 seconds at 1100? can reach the highest expansion ratio, and the coarse-grained perlite expansion ratio is higher. Compared with ordinary heating pretreatment, microwave heating pretreatment technology can shorten the pretreatment time of perlite, but it reduces the high-temperature expansion ratio of perlite. Therefore, different pretreatment process being carried out for different application requirements should be chosen. Based on those research results, pretreatment line of perlite is designed.The effects of size distribution of aggregate grain, molding pressure and way of heat curing on the performance of perlite insulation board with expanded perlite as main ingredient and sodium silicate as binder were studied. The waterproof performance of the perlite insulation board was also studied. The results show that size distribution of aggregate grain has important influence on the performance of perlite insulation board, and the optimum size distribution is the small granularity(the sieving mesh is 50 ~ 70) and the middle granularity(the sieving mesh is 30-50) of pearlite mixing in accordance with the proportion of one to one. When the forming pressure being increased from 10 MPa to 20 MPa, flexural strength of the insulation board firstly increases then decreases, and the 24 hours moisture absorption rate firstly decreases then increases. The insulation board which is formed under 15 MPa has a better comprehensive performance. Compared with the perlite insulation board cured by ordinary heating process, the perlite insulation board cured by microwave heating process has better performance. The waterproof performance of the insulation board is improved by some waterproof modifiers like polyvinyl alcohol, methyl silicone oil and fluorine sodium silicate, and waterproof modification of polyvinyl alcohol is best.Based on the formula of commercially available slag agent, covering agent with high quality and composition analysis results of perlite ore, a new kind of the foundry slag agent, covering agent was developed using perlite as main materials, and the actual casting experiment of the product were verified. The results show that the effect of collect slag of the developed perlite slag agent is good, and it is spread quickly on the surface of molten iron. The spreading property and the effect of the molten iron thermal insulation of the developed perlite covering agent are fine, and it confirms that the developed perlite product has practicability.