Electronic grade high-purity nitric acid purification method

Abstract

The invention discloses an electronic grade high-purity nitric acid purification method. A rectifying tower is included. A heating coil is arranged inside the rectifying tower. The material of the heating coil is metallic nickel. The rectifying tower is filled with a polypropylene Raschig ring filler. The tower diameter of the rectifying tower is 150-280 mm, and the tower height is 3-15 m. The invention also discloses a process of preparing electronic grade 68% nitric acid from industrial grade 98% nitric acid. The tower diameter of the rectifying tower is set as 150-280 mm, the tower height is set as 3-15 m, and the reflux ratio is controlled to be 1:2-1:5. The material of the heating coil in the rectifying tower is set as metallic nickel. The rectifying tower is filled with the polypropylene Raschig ring filler. By one-time distillation, the electronic grade high-purity nitric acid product can be obtained finally. The resources are saved, and the pollution is reduced.

Description

technical field [0001] The invention relates to a method for purifying electronic-grade high-purity nitric acid. Background technique [0002] Nitric acid is one of the common inorganic strong acids, which plays a great role in the etching of semiconductor, flat panel display, and photovoltaic industries. Generally, the process of preparing electronic grade high-purity 68% nitric acid generally uses reagent grade 70% nitric acid as raw material, and then adopts distillation process to remove metal ions, residues, particles, etc. to meet the specifications applicable to semiconductors. But general industrialized production product is directly 98% nitric acid, and reagent grade 70% nitric acid is the product obtained by diluting, distilling and blowing white cooling by 98% nitric acid, and rectifying again with this as raw material will repeatedly consume steam, cycle Water, compressed air, etc. need secondary distillation, which wastes resources and increases production cost...

AI Technical Summary

Problems solved by technology

[0003] At present, 98% industrial grade nitric acid needs to be distilled twice to produce electronic grade 68% nitric acid, and each distillation of nitric acid will decompose part of NO2 gas, which cannot be dissolved in nitric acid again, and must be removed from the nitric acid by gas replacement. No matter whether this part of gas is directly discharged into the atmosphere or dissolved in water through water absorption, it will cause N pollution and affect the environment. Multiple distillations will cause pollution multiple times; Condensate gas, this part of gas is mainly the mixed gas of nitric acid and nitrogen oxides, every time nitric acid is distilled and condensed, this part of gas will be produced, polluting the environment

[0004] The reason why 98% nitric acid is not directly diluted and rectified into 68% high-purity nitric acid is because the heating method is indirect heating, and the heating coil is made of polypropylene or tetrafluoroethylene or fluorine-lined or other plastic materials, which have poor thermal conductivity and consume a lot of energy. energy, and ordinary metals cannot tolerate 98% nitric acid, resulting in a limited height of the rectification column for heating materials, and it is impossible to use a higher number of plates for rectification

[0005] In summary, at present, the process of electronic grade high-purity 68% nitric acid has the disadvantages of high cost, waste of resources, and easy air pollution