水玻璃旧砂再生研究现状与展望

State-of-art and Trends of Sodium Silicate-bonded Sand Reclamation

在分析水玻璃旧砂特性及其再生性能差异的基础上,概述了现有的干法、湿法和化学再生法及其进展,分析了不同再生方法的机理和适用性。干法再生脱膜率低,再生砂回用性差;化学法再生会导致Na2O含量的积累,使得型砂的溃散性和耐火度恶化;湿法再生脱膜率高,耗水量大,污水处理困难,湿砂烘干能耗高。指出了就再生效果而言,湿法再生是水玻璃旧砂再生的方向,而降低湿法再生用水量是关键,其难点在于高模数水玻璃的溶解,用水量的降低还将为废水处理和综合利用奠定基础,最新研究结果表明,湿法再生用水量有望降低到20%,远远低于传统湿法再生方法的用水量(200%以上)。此外,旧砂再生处理系统投资大,使得中小铸造企业废砂处理成为难题,而建立区域性铸造废砂处理中心的思路值得探索和实践。

A brief overview of the characteristics of sodium silicate-bonded sands is presented with the aim of introducing the reclamation technologies of old sands including dry reclamation,wet reclamation,cryogenic reclamation,thermal reclamation and ehemieal reclamation. The principles and applicability of these reelamation methods are also described. Dry reclamation methods are economical but may lead to lower ratios of scrubbing and bench life,and chemical reclamation can cause the accumulation of alkali such as NazO,and lead to collapsibility deterioration. Wet reclamation methods will be the most promising methods in the future for their higher ratio of scrubbing if the volume of water consumed can be reduced further,and the sewage can be treated efficiently. The key is to dissolve the sodium silicate membrane bonded to the surface of the sands which has higher modules. The proposals for future researches in these areas are also provided, which more attention will be paid on the innovative wet reclaiming system which consumes less water and sewage treating or beneficial use system. In fact,it is available to reduce the volume of water consumed for wet reclamation from the ratio of 200% to 20% by some patents disclosed. On the other hand,the establishment of old foundry sand recycling centers will be the good idea proposed. It will help the small enterprises to find a way to dealt with the used sands they produced with less costs.