The water glass is colorless, odorless, and non-toxic. It is not harmful if it is washed on the skin and clothing, but it must be avoided from splashing into the eyes. Water glass has no irritating or harmful gas released during sand mixing, molding, hardening and pouring, and there is no black and acid pollution. However, if the process is improper and the water glass is added too much, the collapsibility of the water glass sand is not good. Dust flying during sand cleaning will also cause pollution. At the same time, the regeneration of old sand is difficult, and the discharge of waste sand causes alkaline pollution to the environment. If these two problems can be overcome, water glass sand can become an environmentally friendly sand with little waste sand emissions. The fundamental measures to solve these two problems are: reduce the addition of water glass to below 2%, which can basically shake off the sand. When the amount of water glass added is reduced, the residual Na2O in the old sand is also reduced. Using a relatively simple dry regeneration method, it is possible to maintain the residual Na2O content in the circulating sand below 0.25%. This reclaimed sand can meet the application requirements of single sand for small and machining bushing medium-sized steel castings. At this time, even if the water glass old sand is not regenerated by the expensive and complicated step wet method, and the simple and cheap dry method is used, it can be fully recycled, and there is basically no waste sand discharge. Can be reduced to less than 1:1. How to effectively regenerate water glass sand? If the residual Na2O in the old water glass sand is too high, after adding water glass to mix the sand, the molding sand does not have enough time to use, and excessive Na2O accumulation will deteriorate the refractoriness of the quartz sand. Therefore, the residual Na2O should be removed as much as possible when the old water glass sand is regenerated.
