Gas clean-up unit and gas purification method

A gas clean-up unit, comprising:

• a first conversion unit configured to perform a first conversion process of converting hydrogen cyanide contained in gas to be treated to ammonia, in presence of a first catalyst and at a first predetermined temperature;
• a second conversion unit configured to perform a second conversion process of converting carbonyl sulfide in the gas to be treated that has been subjected to the first conversion process to hydrogen sulfide, in presence of a second catalyst and at a second predetermined temperature that is lower than the first predetermined temperature;
• a cleaning unit configured to perform a cleaning process of bringing the gas to be treated into gas-liquid contact with cleaning liquid to remove the ammonia by cleaning;
• and
• a desulfurization unit configured to absorb and removes hydrogen sulfide in the gas to be treated by bringing the gas to be treated that has been subjected to the cleaning process into gas-liquid contact with absorbent,
• wherein the cleaning unit includes a first cleaning unit configured to perform a first cleaning process of bringing the gas to be treated that has been subjected to the first conversion process into gas-liquid contact with cleaning liquid, and a second cleaning unit configured to perform a second cleaning process of bringing the gas to be treated that has been subjected to the second conversion process into gas-liquid contact with cleaning liquid.