Method for producing compound

A method for purifying a compound, the method comprising:

• a step of feeding a slurry containing crystals of the compound to a hydraulic wash column;
• a step of melting crystals in a crystal-containing circulation slurry discharged from the hydraulic wash column;
• a step of discharging a mother liquor using a filter from the crystal-containing slurry in the hydraulic wash column;
• and
• a step of introducing a liquid having a temperature equal to or higher than the temperature of the mother liquor immediately after being discharged in the mother liquor discharging step into a nozzle attached to the hydraulic wash column from outside the hydraulic wash column, the nozzle being other than a nozzle at a return port for a circulation liquid containing a melt obtained in the melting step and a pipe that feeds the crystal-containing slurry to the hydraulic wash column;
• wherein the nozzle attached to the hydraulic wash column is at least one selected from the group consisting of an instrumentation nozzle, a sampling nozzle, a pressure control valve nozzle, a pipe insert nozzle, and an emergency injection nozzle.

A purification apparatus that purifies crystals, the purification apparatus comprising:

• a hydraulic wash column that includes a discharging port for a crystal-containing circulation slurry and a return port for a circulation liquid containing a melt of discharged crystals;
• a pipe that feeds a crystal-containing slurry to the hydraulic wash column;
• a filter that discharges a mother liquor from the crystal-containing slurry in the hydraulic wash column;
• a pipe that is connected to the filter and transports the mother liquor;
• a nozzle at an introduction port that introduces a liquid to the hydraulic wash column, the nozzle being other than a nozzle at the return port and a pipe that feeds the crystal-containing slurry to the hydraulic wash column, and is at least one is at least one selected from the group consisting of an instrumentation nozzle, a sampling nozzle, a pressure control valve nozzle, a pipe insert nozzle, and an emergency injection nozzle;
• and
• a unit that melts crystals in a circulation slurry discharged through the discharging port.