Acrylic Acid Recovery Process with Two-Stage Cooling Separation

The patent divides the dehydration reaction process into multiple stages with different temperature zones. The reaction is conducted in a fixed bed reactor where the temperature is segmented along the reaction path, allowing efficient acrylic acid production in the first stage while preventing oligomerization in subsequent stages through temperature control and rapid cooling.

The patent applies preliminary cooling action by introducing a cooling section immediately after the high-temperature dehydration reaction zone. This rapid cooling prevents the newly formed acrylic acid and unreacted lactic acid from undergoing oligomerization reactions, thereby maintaining high lactic acid recoverability while ensuring efficient acrylic acid production.

The patent employs two separate cooling towers instead of a single cooling tower. The first cooling tower performs preliminary cooling and condensation, while the second cooling tower conducts final cooling and purification. This segmentation of the cooling process enhances separation efficiency and product purity without requiring overly complex equipment design.

The patent introduces an intermediary extraction step between the two cooling towers using a solvent extraction column. This intermediary process facilitates the separation of acrylic acid from the reaction mixture, improving product purity while maintaining reasonable equipment complexity through the use of standard extraction technology.

The patent applies preliminary cooling and condensation actions before distillation by using two cooling towers to reduce the temperature and convert vapors to liquids. This preliminary action prevents lactic acid oligomerization that would occur during high-temperature distillation, thereby reducing lactic acid loss while maintaining energy efficiency through controlled cooling rather than high-energy distillation.

The patent utilizes phase transitions by condensing the reaction products from vapor to liquid phase in the cooling towers before any further separation. This phase transition approach allows for energy-efficient separation based on condensation temperature differences rather than requiring high-energy distillation, thereby reducing both energy cost and lactic acid loss.