In the removal of HF from hydrocarbon streams by chemical reaction with solid potassium hydroxide, runaway temperatures and subsequent explosions can occur when excess HF is present in the hydrocarbon charged to the KOH treater. According to the invention, a control system and method are provided which regulate the flow of hydrocarbon charged to the KOH treater responsive to temperature changes within the system indicative of excessive amount of HF in the hydrocarbon stream, thereby preventing the treater temperature from exceeding a preselected maximum allowable value. Several embodiments are provided whereby temperature changes in the KOH treater or a differential temperature across an HF stripper are used as temperature sensing points to control flow of hydrocarbon to the KOH treater.