Equipment and process for preparing electronic grade nitric acid having a concentration of 68% from industrial grade nitric acid having a concentration of 98%

Abstract

Equipment for preparing electronic grade nitric acid having a concentration of 68% from industrial grade nitric acid having a concentration of 98% is disclosed. The equipment comprises a rectifying tower provided with heating coils made of metal tantalum. The rectifying tower is filled with a glass raschig ring filling material. The diameter of the rectifying tower is 180-250 mm and the height of the rectifying tower is 5-10 m. A process for preparing the electronic grade nitric acid having a concentration of 68% from the industrial grade nitric acid having a concentration of 98% is also disclosed. The diameter of the rectifying tower is set to be 180-250 mm, the height of the rectifying tower is set to be 5-10 m, the reflux ratio is controlled to be 1:2-1:5, the heating coils in the rectifying tower are made of the metal tantalum, and the rectifying tower is filled with the glass raschig ring filling material. According to the equipment and the process, a finished high-purity product of the electronic grade nitric acid can be prepared by one time of distillation, thus saving resources and reducing pollution.

Description

technical field [0001] The invention relates to equipment and a process for preparing electronic-grade 68% nitric acid from 98% industrial-grade 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 w...

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 NO 2 Gas, this part of gas cannot be dissolved in nitric acid again, and must be removed from nitric acid by gas replacement, and 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 produce pollution multiple times; in addition, non-condensable gases will be produced after distillation and condensation. This part of the gas is mainly a mixed gas of nitric acid and nitrogen oxides. Each distillation and condensation of nitric acid will produce this part of gas, 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 glass or tetrafluoroethylene or fluorine-lined or other plastic materials, which have poor thermal conductivity and consume a lot of energy. , while ordinary metals cannot tolerate 98% concentration of nitric acid, resulting in a limited rectification column height for heating materials, and a higher plate number cannot be used 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

Images