Abstract: The crude phenol plant with concentrated sulfuric acid method is upgraded to solve problems
that occurred in coal tar refinery plant. Improvement is done，i.e. pH sensor，temperature sensor，flow
meter and control valve are added based on existing decomposer. Fuzzy control algorithm is adopted to
automatically control the additional amount of sulfuric acid in crude phenol production. After upgradation
of the plant，the quality of crude phenol is ensured even under full-load operation. In addition，acid
mist generation and phenolic product losses carried away by aci d mist are dramatically reduced.

Key words: Coal tar refinery, Crude phenol, Decomposition reaction, pH value, Fuzzy contro