Acrylic acid (AA) is used as feedstock for numerous applications. The Lurgi/Nippon Kayaku combined technology produces estergrade acrylic acid (EAA). Main uses are adhesives, paints and coatings (acrylic esters).
The general flow diagram comprises six main sections: reaction, quench, solvent extraction, crude acrylic acid recovery, raffinate stripping and acrylic acid purification.
Reaction (1): Acrylic acid is produced by catalyzed oxidation of propylene in a two-stage tubular, fixed-bed reactor system. The reactors are cooled by circulating molten heat transfer salt. The heat of reaction is used to produce steam.
Quench (2): The AA is recovered from the reactor product gas in a quench tower. The AA solution is routed to an extractor (3). Uncondensed gases are sent to an offgas treater to recover the remaining AA. A side draw of the offgas is sent to incineration. Overhead gas is recycled to the first reactor.
Solvent extraction (3): Liquid-liquid extraction is used to separate water and AA. The top of the extractor is forwarded to a solvent separator. The extractor bottom is sent to the raffinate stripper (5) to recover solvents. Crude acrylic acid (CAA) is separated from the solvents by distillation. The overhead vapor is condensed in an internal thermoplate condenser. The two-phase condensate is separated. The organic phase is recycled. The aqueous phase is sent to the raffinate stripper (5). The column bottom, mostly AA and acetic acid, is routed to the CAA separator (4).
Crude AA recovery (4): In this section, two columns work together to separate solvent and acetic acid from the CAA. The CAA separator produces a concentrated AA bottoms stream. The overhead vapors are condensed in an internal thermoplate condenser and sent to the recovery column. The bottom stream is routed to the ester-grade acrylic acid (EAA) column (6). The recovery column separates solvent and acetic acid from AA. The overhead vapors from the recovery column are condensed by an internal thermoplate condenser and recycled. The bottom stream is returned to the CAA separator.
Raffinate stripping (5): The raffinate stripper recovers solvents from the wastewater streams. The overhead is recycled. Some of the bottom is recycled to the offgas treater; the remaining is removed as wastewater.
Acrylic acid purification (6): CAA is purified in the EAA column. The column base stream is sent to a dedimerizer, which maximizes AA recovery by converting AA dimer back to AA. The overhead EAA product is condensed in an internal thermoplate condenser.
Licensor: Lurgi GmbH / Nippon Kayaku Co., Ltd.