Abstract： Because the temperature of acylation liquid reached 130 ℃ in the process of crystallization reaction, the temperature of crystallization tank was low, if the acylated liquid at high temperature in case of crystallization tank wall or bottom with large temperature difference, acylated feed liquid would appear agglomeration on the wall or bottom of crystallization tank due to chilling, the overall crystal form of the product does not meet the requirements, and the crystallization tank wall or its bottom it was also prone to porcelain explosion due to severe thermal shock. After research，before acylation feed liquid was added to crystallization tank， add 200～300 L of dilute acetic acid to the crystallization tank（It comes from dilute acetic acid in the production of acetaminophen by product acid collected during acid extraction of acylation reaction）as bedding acid. The concentration of dilute acetic acid was 45%～50%. After adding the bottom acid, preheat the crystallization tank with high-temperature steam， until the crystallization tank was preheated to the specified temperature； Generally, the crystallization tank can be preheated to 60～80 ℃.
