Abstract: The present invention provides a method capable of sufficiently reducing impurities with excellent separation efficiency even from a crystal-containing slurry that contains a low-purity mother liquor and has poor solid-liquid separation properties. The present invention relates to a method for producing a compound, the method including: 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; and a step of returning a portion of a circulation liquid containing a melt obtained in the melting step to the hydraulic wash column, wherein the circulation liquid returned in the returning step in an amount of more than 30% by mass relative to 100% by mass of the melt serves as a washing liquid for crystals.

Abstract: Provided is a method for purifying a compound capable of providing a high purity compound in high yield and at low cost. The present invention relates to the method for purifying a compound using a purification apparatus, the purification apparatus including: a crystallizing unit including a crystal forming section; and a wash column including a mechanism that forcibly transfers crystals. The crystallizing unit includes N tanks connected in series, wherein N is 2 or greater, a 1st tank is a most downstream tank, a (N)th tank is a most upstream tank, at least the 1st tank is a crystallization tank including a cooling mechanism, and a 2nd and subsequent tanks are each a crystallization tank or a ripening tank. The purification apparatus includes a line that feeds a compound-containing liquid to be purified to at least one of the N tanks.

Abstract: The present invention aims to provide a compound purification apparatus capable of providing a high purity compound in high yield and at low cost.

Abstract: Provided is a method for obtaining high-quality products safely and stably. The present invention relates to a method for producing a compound, the method including feeding a slurry containing crystals of the compound to a hydraulic wash column; melting crystals in a crystal-containing circulation slurry discharged from the hydraulic wash column; discharging a mother liquor using a filter from the crystal-containing slurry in the hydraulic wash column; and 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 and a pipe that feeds the crystal-containing slurry to the hydraulic wash column.

Abstract: The present invention provides a method for obtaining high-quality products. The present invention relates to a purification apparatus that purifies crystals, the purification apparatus including: 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 filters the crystal-containing slurry in the hydraulic wash column; a pipe that is connected to the filter and discharges a mother liquor; and a unit that melts crystals in a circulation slurry discharged through the discharging port, wherein a distance between a lower end of the filter and an average bottom surface level of the hydraulic wash column is 1000 mm or more.

Abstract: A method for producing (meth)acrylic acid comprising: a step of obtaining a (meth)acrylic acid-containing gas by subjecting a (meth)acrylic acid production raw material to a catalytic gas phase oxidation reaction; a step of obtaining a (meth)acrylic acid-containing liquid by bringing the (meth)acrylic acid-containing gas into contact with a collection solvent and/or condensing the (meth)acrylic acid-containing gas by cooling; a step of obtaining crude (meth)acrylic acid by introducing the (meth)acrylic acid-containing liquid into a low-boiling separation column; a step of obtaining purified (meth)acrylic acid and a refining residue containing a glyoxal compound by purifying the crude (meth)acrylic acid; and a step of returning at least a part of the refining residue to the low-boiling separation column; wherein a returning position of the refining residue to the low-boiling separation column is located closer to a bottom side of the low-boiling separation column than a supply port of the (meth)acrylic acid-co

Abstract: A method for producing (meth)acrylic acid comprising: a step of obtaining a (meth)acrylic acid-containing gas by subjecting a (meth)acrylic acid production raw material to a catalytic gas phase oxidation reaction; a step of obtaining a (meth)acrylic acid-containing liquid by bringing the (meth)acrylic acid-containing gas into contact with a collection solvent and/or condensing the (meth)acrylic acid-containing gas by cooling; a step of obtaining crude (meth)acrylic acid by introducing the (meth)acrylic acid-containing liquid into a low-boiling separation column; a step of obtaining purified (meth)acrylic acid and a refining residue containing a glyoxal compound by purifying the crude (meth)acrylic acid; and a step of returning at least a part of the refining residue to the low-boiling separation column; wherein a returning position of the refining residue to the low-boiling separation column is located closer to a bottom side of the low-boiling separation column than a supply port of the (meth)acrylic acid-co

Abstract: The objective of the present invention is to provide a method for efficiently producing acrylic acid while troubles not only in a waste oil handling after distillation of acrylic acid but also in a purification system of acrylic acid during distillation are reduced. The method for producing acrylic acid according to the present invention is characterized in comprising the step of supplying at least crude acrylic acid and an alcohol solvent to an acrylic acid distillation apparatus to distill acrylic acid, wherein a boiling point of the alcohol solvent is higher than a boiling point of acrylic acid by not lower than 50° C.

Abstract: The objective of the present invention is to provide a method for efficiently producing acrylic acid while troubles not only in a waste oil handling after distillation of acrylic acid but also in a purification system of acrylic acid during distillation are reduced. The method for producing acrylic acid according to the present invention is characterized in comprising the step of supplying at least crude acrylic acid and an alcohol solvent to an acrylic acid distillation apparatus to distill acrylic acid, wherein a boiling point of the alcohol solvent is higher than a boiling point of acrylic acid by not lower than 50° C.