Method for removing hydrogen fluoride

A method for removing hydrogen fluoride from gas to be treated containing the hydrogen fluoride, comprising:

• a first adsorption step of introducing the gas to be treated into a first adsorption treatment section including sodium fluoride, bringing the gas to be treated into contact with the sodium fluoride of the first adsorption treatment section, and allowing the hydrogen fluoride in the gas to be treated to adsorb on the sodium fluoride of the first adsorption treatment section to obtain first adsorption-treated gas, the first adsorption-treated gas being the gas to be treated in which a hydrogen fluoride concentration has been lowered;
• and
• a second adsorption step of introducing the first adsorption-treated gas into a second adsorption treatment section including sodium fluoride, bringing the first adsorption-treated gas into contact with the sodium fluoride of the second adsorption treatment section, and allowing the hydrogen fluoride in the first adsorption-treated gas to adsorb on the sodium fluoride of the second adsorption treatment section to obtain second adsorption-treated gas, the second adsorption-treated gas being the first adsorption-treated gas in which a hydrogen fluoride concentration has been lowered, wherein
• a temperature of the sodium fluoride of the first adsorption treatment section when the gas to be treated is brought into contact with the sodium fluoride in the first adsorption step is higher than a temperature of the sodium fluoride of the second adsorption treatment section when the first adsorption-treated gas is brought into contact with the sodium fluoride in the second adsorption step,
• in the first adsorption step, a ratio of a mass of the hydrogen fluoride per unit time in the gas to be treated introduced into the first adsorption treatment section to a mass of the sodium fluoride of the first adsorption treatment section before the adsorption is 0.05 HF-mg/NaF-g/h or more and 70 HF-mg/NaF-g/h or less, and
• in the second adsorption step, a ratio of a mass of the hydrogen fluoride per unit time in the first adsorption-treated gas introduced into the second adsorption treatment section to a mass of the sodium fluoride of the second adsorption treatment section before the adsorption is 0.001 HF-mg/NaF-g/h or more and 5 HF-mg/NaF-g/h or less.