Key Takeaways & Executive Findings
- •• • Optimal heat exchange medium flow rate is 2–3.5 kg·h⁻¹ for a 0.01 m diameter, 5 m long channel reactor producing AAOF at 2 kg·h⁻¹, ensuring effective heat removal while maintaining process temperature above 100 °C. • • Flow rates below 0.1 kg·h⁻¹ cause outlet temperature to exceed 120 °C, approaching the onset decomposition temperature of 121.7 °C, posing a high risk of thermal runaway; thus, a safety interlock is recommended below this threshold. • • Flow rates above 4.5 kg·h⁻¹ cool the system below 100 °C, failing to meet the required process temperature, indicating a narrow operational window for safe and efficient production. • • The study establishes a two-level safety threshold: at 1 kg·h⁻¹, heat balance begins to destabilize, triggering alarms; below 0.1 kg·h⁻¹, automatic emergency shutdown is activated, demonstrating a proactive thermal safety management strategy.
Abstract
The channel reactor offers advantages of high-efficiency mass and heat transfer, providing a basis for transitioning mixed-controlled strongly exothermic reactions from batch to continuous industrial production. This study focuses on the synthesis of 3-amino-4-aminoximiofurazan (AAOF). Reaction calorimetry experiments provided fundamental heat release data, which, combined with material and energy balances, yielded exothermic model parameters for a channel reactor. A heat transfer-exothermic model was constructed, and numerical solutions simulated jacket heat transfer, heat transfer rates, and heat exchange medium effectiveness. Thermal safety risks in the continuous flow process were analyzed, leading to a heat exchange control strategy. Results show that for a reactor tube of 0.01 m diameter and 5 m length, producing AAOF at 2 kg·h⁻¹ with heat transfer oil in co-current flow, the mass flow rate significantly affects safety: below 0.1 kg·h⁻¹, outlet temperature exceeds 120 °C, approaching the onset decomposition temperature (121.7 °C), risking thermal accumulation and runaway; optimal heat removal occurs at 2–3.5 kg·h⁻¹; above 4.5 kg·h⁻¹, temperature drops below 100 °C, failing to meet process conditions. The optimal heat exchange medium flow range is 2–3.5 kg·h⁻¹, providing foundational data and process parameters for safe design and stable operation of AAOF synthesis in channel reactors.
1. Introduction
The continuous flow reactor, with its low hold-up volume and high heat and mass transfer efficiency, offers a promising solution for the safe production of strongly exothermic and high-risk reactions. However, for mixed-controlled reactions, where the heat release rate is managed by the addition rate of reactants, the high heat release at the reactor inlet can create localized hot spots, leading to thermal runaway. Traditional batch thermal safety data are not directly applicable to continuous systems due to differences in residence time distribution and heat transfer conditions. The 2024 Shandong Youdao Chemical explosion highlighted the dangers of neglecting heat release rates in continuous processes, underscoring the need for process-specific thermal safety assessments.
This study addresses the bottleneck of adapting batch calorimetry data to continuous channel reactors for the synthesis of 3-amino-4-aminoximiofurazan (AAOF), a key precursor for energetic materials. By constructing a heat transfer-exothermic model based on reaction calorimetry and numerical simulation, we systematically analyze the impact of heat exchange medium flow rate on temperature profiles and thermal safety. Our findings define a safe operational window for flow rate, providing critical parameters for the design and control of continuous AAOF synthesis, thereby enabling the safe transition from batch to continuous processing for this mixed-controlled reaction.
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SANG Sheng-jie, TONG Zhi-ke, MIAO Yu-xin, SHI Jun-li, ZHANG Huan-ling, LI Shuo, LI Xiang-zhi, BI Fu-qiang, CAO Duan-lin, ZHAO Lin-xiu (2026). Simulation Study on Heat Transfer Characteristics of Continuous Synthesis Process of 3-Amino-4-aminoximiofurazan. Chinese Journal of Energetic Materials (含能材料). https://doi.org/10.11943/CJEM2026051
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Frequently Asked Questions
What is the critical heat exchange medium flow rate below which thermal runaway becomes imminent, and what safety measures are recommended?
Below 0.1 kg·h⁻¹, the outlet temperature exceeds 120 °C, approaching the onset decomposition temperature of 121.7 °C, risking thermal runaway. The study recommends an automatic interlock shutdown below this threshold, cutting off reactant feed and increasing coolant flow.
How does the heat exchange medium flow rate affect the temperature profile along the reactor, and what is the optimal range for AAOF synthesis?
Flow rates between 2 and 3.5 kg·h⁻¹ provide optimal heat removal, maintaining temperatures within the desired process window (above 100 °C but below decomposition). Lower flows lead to overheating, while higher flows (above 4.5 kg·h⁻¹) cool the system below 100 °C, which is insufficient for the reaction.
What are the key parameters used to construct the heat transfer-exothermic model, and how were they obtained?
Key parameters include specific reaction heat, adiabatic temperature rise, and heat transfer rate, calculated from reaction enthalpy, density, concentration, and heat capacity. Data were obtained from reaction calorimetry (RC1) and accelerating rate calorimetry (ARC) experiments.
What safety thresholds are established for flow rate monitoring, and what actions are triggered at each level?
A two-level safety threshold is set: at 1 kg·h⁻¹, heat balance begins to destabilize, triggering audible and visual alarms and alerts to the central control system. Below 0.1 kg·h⁻¹, automatic interlock shutdown is initiated, cutting off reactants and increasing coolant flow.
How does this study address the challenge of transferring batch calorimetry data to continuous flow systems?
The study assumes equivalence between batch reaction time and continuous residence time under identical conditions, allowing batch heat data to be migrated to the continuous model. This approach is validated by the model's ability to predict temperature profiles and identify safe operating windows.
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