Calculation of the adiabatic temperature rise in “Daily Discussion” – [1. Reaction Engineering and Reactors] (2017.08.07)

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This post was last edited by *amingteda on 2017-8-22 08:27. To improve everyone’s ability to use AspenOne for analyzing and solving problems in chemical processes, the “One Discussion per Day” series has been introduced for learning and discussion. Later, questions will be raised centered on various themes for academic discussion. I hope everyone will engage in active discussions to improve together! The initial topics are set as: 1. Reaction engineering and reactors ； 2. Distillation, extraction, absorption processes and towers ； 3. Heat transfer process and heat exchanger ； 4. Process optimization, design, and control ； 5. Heat exchange network integration and optimization ； 6. Economic evaluation of engineering technology. As is well known, chemical reaction processes are at the core of the chemical industry; under certain temperatures and pressures, the adiabatic temperature rise of a reaction to a certain extent reflects the intensity of the heat effect associated with that reaction process. In other words, dynamic factors are not considered at this stage while taking into account thermodynamic feasibility; the intensity of the heat effect of the reaction is determined by the adiabatic temperature rise. So, which reactor module in Aspen Plus should be used to calculate the adiabatic temperature rise of the reaction? Based on experience, what level of temperature rise/fall constitutes a strong exothermic/endothermic reaction, and what level constitutes a weak exothermic/endothermic reaction? Dear sea friends, please actively participate in the discussions – there will be financial rewards for that. The reference discussion will be released in about a week; the answers are for reference only. ——Jack Xia －－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－ Answer key: 1. The Rstoic module is usually chosen ； 2. Enter the reaction pressure and heat in Blocks/Spec.; set heat = 0 (which means adiabatic operation) ； 3. Blocks/Reactions: Enter the reaction equation, conversion rate (usually set at 99.5 %), or reaction progress ； 4. Run. After running based on the above settings, the final outlet temperature after the reaction is obtained at a certain feed flow rate and reaction concentration; the difference between the outlet temperature and the feed temperature represents the adiabatic temperature rise. This value corresponds to the temperature increase resulting from the heat released when the reference reactant is almost completely reacted; this heat is not transferred to the outside environment but instead heats the products and unreacted substances. This value is of great significance for evaluating the thermic effect of a reaction. Based on the simulation results and experience from pilot experiments, the adiabatic temperature rise obtained through simulations is usually less than 100 °C. In pilot experiments using heat-exchanging reactors, where the conversion rate generally does not reach 100%, no significant reaction hot spots are observed. This indicates that the reaction does have a thermal effect, but this effect is not sufficient to cause a significant accumulation of heat in the reaction bed, leading to the formation of local hot spots. The above characteristics have been confirmed in a certain isomerization reaction and a certain succinic acid cleavage reaction.