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Study On The Regulation And Intensification Of Easily Runaway Reaction Process

Posted on:2013-04-20Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y Y CheFull Text:PDF
GTID:1261330401969899Subject:Chemical Engineering
Abstract/Summary:PDF Full Text Request
Typical energetic compound synthesis often involves easily runaway reaction. In the process, the temperature rapidly change and coupling effects among the temperature, velocity, and concentration fields are significant. If the process conditions are not properly controlled, a large amount of byproducts are easily produced, which results in reaction runaway and temperature explosion. In the dissertation, tank and tubular reaction processes widely used in the energetic compound synthesis have been studied, a novel impeller applied to easily runaway reaction has been developed, a new pattern of stirred tank reactor and tubular reactor have been designed, simulated, and optimized, thus the security regulation of easily runaway reaction processes has been fully realized in the industrial production of energetic compounds.The main contents are generalized as follows:1. In the easily runaway semi-batch reaction processes, the actual impeller installation height is often low, the impact of fluid on the blade back is very remarkable, and a high stirred speed has been set so as to mixing evenly, which cause high energy consumption. Through the research on heat transfer performances in the stirred tank reactor with nine types of impellers under different dimensions and rotational speeds, the adequate impeller was determined, and thus a novel impeller (CBY-H) applied to easily runaway reaction was devised. The new impeller reduces the impact of fluid on the blade back surface and the vibration of agitators, allows smooth transmission and escape of gases generated in the reaction as well. In addition, the power consumption of the new impeller is much lower than general hydrofoil impeller.2. Due to the complexity and diversity of impeller, forecasting techniques based on computational fluid dynamics (CFD) have been widely used in the design of impellers. Comprehensive understandings of flow field distribution and the magnitude of stirring power and heat transfer coefficients are of great significance in optimization and design of mixing equipments used in the energetic compound synthesis. In the dissertation, the velocity field distribution in the unbaffled stirred tank reactor and stirring power of CBY-H paddle have been detailedly studied by CFD method. The flow field characteristics and energy consumption of CBY-H were evaluated through simulation results compared with the standard CBY impeller. The convective heat transfer coefficients of CBY and CBY-H impeller have been meanwhile determined and correlated, which could be applied to guide the industrialization and optimization design of impellers.3. Due to many energetic compound synthetic processes involving ammonium sulfate+ammonium nitrate+water ternary electrolyte systems, the thermal conductivity and density of ammonium sulfate+water, ammonium nitrate+water, and ammonium sulfate+ammonium nitrate+water have been measured covering a temperature from (278.15to333.15) K over a wide range of concentrations. The correlation equations of the thermal conductivity and density for corresponding systems determined could be used to optimize the easily runway processes.4. In the energetic compound synthesis, the majority of chemical reactions carried out in stirred tank reactors is highly exothermic. When the reaction heat is not effectively removed, it will lead to reaction heat accumulation and temperature further increasing, thereby causing local overheating of the reactor and emerging of hot spots and runaway instability phenomena, which further leads to the reaction out of control and thermal explosion, and thus threatens the safety of properties and lives. In the dissertation, the easily runaway tank condensation process has been studied to determine the structure of the reactor for released heat rapid transmission, a novel type of condensation reactor has been designed, the mathematical model for the easily runaway condensation process has been established, the runaway and out-of-control cases of the condensation reaction in the synthetic process have been simulated, the appropriate prevention and emergency measures have been proposed, the process conditions of the condensation reaction process have been optimized, and thus the safe-operation and high-yield production technology of the energetic compound has been acquired as well. The stable batch experiments have been carried out in the pilot-scale equipments. It is found that simulation results are consistent with results of the actual process optimization, which therefore could be used for guiding and forecasting the industrial production of the energetic intermediate.5. The preparation process of the energetic compound from the energetic intermediate contains several stages, including mixing, nitrolysis and thermolysis. Because of complex reaction mechanism and excessive side reactions, the nitrolysis reaction is the control step of the process. In the dissertation, the easily runaway tubular nitrolysis process has been studied, the mathematical flow-diffusion-reaction model for the tubular reactor used in the easily runaway nitrolysis process has been established, the flow characteristics of the spiral tubular reactor has been simulated using pulse injection, axial diffusion coefficient, Peclect number and Da number of the actual nitrolysis reaction have been calculated by analysis of residence time distribution, the yield of manufacturing the target energetic product through tubular reaction has been simulated as well. The stable batch experiments have also been carried out in the pilot-scale equipments. It is found that the agreement between the simulation and experimental results is pretty good, which therefore could be used for guiding and forecasting the industrial production of the energetic compound. Meanwhile, a new type of tubular reactor with spring internally installed applied to the process of gases generated in the reaction has been developed. The newly designed tubular reactor has more excellent heat transfer performances than ordinary ones, and can effectively prevent the slug flow generated in the binary gas-liquid phases. In addition, it has an outstanding reaction performance.
Keywords/Search Tags:easily runaway reaction, heat transfer, intensification, thermal conductivity, stirredtank reactor, tubular reactor, impeller
PDF Full Text Request
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