TWO-STAGE PROCESS FOR THE PRODUCTION OF CONCENTRATED SODIUM SILICATE SOLUTIONS FROM SODIUM SILICATE LUMP GLASS AND THIN LIQUORS

摘要

Aqueous sodium silicate solutions containing at least 26% of SiO2 and having a ratio of weight of SiO2 to Na2O of from 2.0 to 3.0 can be obtained using thin or waste liquor containing at most 20% of NaOH providing: A) solid sodium silicate glass having a ratio by weight of SiO2 to Na2O of from 3.0 to 3.5 is first dissolved in alkali-free water at 135.degree. to 155.degree.C under the autogenous vapor pressure of the water until an aqueous sodium silicate solution containing more than 20% by weight and less than 30% by weight of SiO2 is formed, after which thin liquor containing at most 20% of NaCH is added in such a quantity as to produce ratios by weight of SiO2 to Na2O of from 1.8 to 2.6 in the mixture of the two components; B) more solid sodium silicate glass is dissolved in this mixture until a concentration of at least 23% of SiO2 in solution is reached. A high volume-time yield for minimal energy consumption and maximal utilization of dilute waste liquor is obtained.