Determination And Calculation Of Direct Coal Liquefaction Reaction Heat

Temperature control is a very important link in operation of direct coal liquefaction (DCL) reactor. Consequently, DCL reaction heat is a key parameter in process of reactor design. There are many methods to calculate and determine reaction heat at present, but most of them aim to relatively easy or mild reactions. However, DCL reaction is comparatively complex because of too many kinds of reactants and resultants involved, in addition the reaction conditions are harsher. According to this condition, some literatures put forward a few of means of calculating DCL reaction heat through heat balance. Basing on conservation law of heat, those methods mostly establish mathematical models for parameter estimation and numerical calculation, which can guide the practical application in a sense. However, too many equations and variables involved made the reaction heat complex to calculate, as a result those methods can't be applied widely.The main purpose of this paper is to seek an easy method for calculating DCL reaction heat, which meets the requirement of practical engineering. Firstly, the paper analyze qualitatively the reason why the DCL reaction is an exothermic. The paper use the method of calculating enthalpy at the beginning and end state of the reaction, ignoring the reaction process. Two calculation methods, theoretical one and actual one were put forward, according to the different analysis in the heating process of feed substance. Some standard parameters are used in calculation, for instance, standard heat of combustion and molar heat capacity at constant pressure. The paper mainly applied the method of experiment, the method of calculation and the method combining experiment and calculation for obtaining these parameters, according to the different physical and chemical properties of material. Moreover, the method of simulation for preheater with autoclave is used to obtain intermediate and provide the material basis for determining the parameter. In the process of the calculating the DCL reaction heat, the effect of temperature, pressure and chemical reaction on the enthalpy is comprehensively considered. The result indicates that the value of theoretical reaction heat was -53.854 kJ/molH2; the value of actual reaction heat was-56.156 kJ/molH2. Moreover, based the reaction Mechanism, the paper explained the reason why the theoretical reaction heat is lower than actual reaction heat.