Fenton's reagent is used to treat the spent caustic of oil industry by oxidizing waste caustic. It is carried out in oxizider reactor at around 55 C. Temperature should be maintained inbetween 50-60 C to ensure proper utilization of chemicals (Fenton's reagent) otherwise side reactions would prevail. To maintain temperature as quoted above, stub in exchanger is provided in oxizider in which cooling water is used as a service fluid to maintain the temperature via temperature control valve. To calculate the duty of heat exchanger, it is necesarry to know the heat of reaction of Fenton's reagent. Or second option is to manually enter the reaction chemistry of Fenton's Reagent so that Aspen Plus will automatically calculate heat of reaction. Hope now you are clear about my objective.