Method for producing electronic-grade sulfuric acid by static fusion crystallization

The invention discloses a method for producing electronic-grade sulfuric acid by static fusion crystallization. The method comprises the following steps of: cooling high-purity electronic-grade sulfuric acid for crystallization to obtain seed crystals; adding raw material sulfuric acid into a tube-in-tube crystallizer, cooling, adding sulfuric acid seed crystals in an amount which is 0.2 to 5 mass percent of the raw material, gradually cooling for crystallization, and growing the crystals after the crystallization is finished; discharging residual liquid, gradually raising the temperature for sweating, discharging sweating liquid after the sweating is finished, raising the temperature again, fusing to analyze the crystals, and thus obtaining a primary crystallization product; and performing secondary static fusion crystallization on the obtained primary crystallization liquid by repeating the operation steps, and thus obtaining a secondary crystallization product of which the quality can reach a level of a metal oxide semiconductor (MOS) to a BV-III level. The electronic-grade sulfuric acid produced by the method can reach the level of the MOS to the BV-III level. By the method, a static fusion crystallization method is used for preparing and producing the electronic-grade sulfuric acid for the first time; and the method has the advantages of low energy consumption, high product purity, wide level range and high economic benefit and is simple.