METHOD OF BORIC ACID'S PRODUCTION WITH SIMULTANEOUS PRODUCTION OF TECHNICAL-GRADE SODIUM NITRATE BY SODIUM TETRABORATES' DECOMPOSITION BY MEANS OF NITRIC ACID

摘要

Natural hydrates of sodium tetra-borate, such as e.g. kernite, rasorite and tincal or hydrates chemically prepared get dissolved in hot water or in wash waters after boric acid crystallisation or from sludge washing together with a mix of crystalline sodium nitrate and boric acid in the second degree of crystallisation; the solution is obtained after the addition of adsorption or coagulating additives, gets filtered by stoichiometric or a close quantity of nitric acid, i.e. within 0.99 and 1.01 moles of HNO3 to 1 mole of B2O3 contained in the raw material. The reaction is cooled down to a temperature of 15 to 40 degrees Celsius. The developed crystalline boric acid is filtered off, then washed and dried. After the first degree crystallization, the mother solutions are then thickened to a content of 650 to 900 g of NaNO3 per litre and cooled down again to 15 to 40 degrees Celsius, by which a residual of crystalline H3BO3 is separated out and a part of the NaNO3 gets filtered out and returned back into a dissolving process. After the second degree crystallization, the mother solution is used as technical sodium nitrate for further processing, e.g. for the production of KNO3, or it gets further thickened and solidified to a solid and technical sodium nitrate (NaNO3).