Characteristics Of Runaway And Relief Of H₂O₂ Decomposition Reaction In Diabatic And Hot Environment

Accidents of reaction equipment resulting from overpressures due to chemical reaction runaway takes a big proportion of the totally accidents happened in petrochemical industry. Further studying the runaway risk and obtaining the intensity parameters during runaway process, are the promise for establishing the preventive and protective methods of chemical runaway. Existing studies mainly focus on the calorimetric data testing in adiabatic conditions. However, the chemical equipment is greatly affected by the external thermal conditions such as fire hazard and long-time sunshine, etc. Moreover, the reactor is usually diabatic rather than adiabatic condition. Compared to adiabatic situation, studies on the chemical runaway risk, the establishment criterion of chemical runaway, and weather the DIERS method derived from the adiabatic condition can be used under diabatic and external thermal conditions have not been researched.In this paper, the characteristics of runaway and relief of H2O2 decomposition reaction in diabatic and hot environment was studied by using a 5 L apparatus designed independently. The main content and conclusions are listed below:(1) A 5 L diabatic chemicial runaway reaction relief experimental apparatus was set up. A reactor, relief pipelines and a collector were designed. Continuous heat input was adopted to simulate the external thermal condition. The H2O2 decomposition reaction was chosen as the research object. Parameter testing was accomplished by sensors. The data acquisition was programed.(2) The thermal insulation performances of the apparatus in the paper and VSP2 was quantified. The runaway characteristics in different conditions were compared. Results indicate that compared to adiabatic condition, the runaway characteristics of maximum pressure, maximum temperature, and maximum pressure rising rate are nealy same. However, because of the external heat input, the occurrence time for chemical runaway is greatly shorten, and hence the risk is significantly enhanced.(3) The chemical runaway process of H2O2 decompression reaction was experimentally studied. Results show that the runaway of H2O2 decompression reaction is inevitable in strong alkalis condition of pH = 13. The runaway process is mixed relief system with non-moderating type. Overpressure in reactor results from both the oxygen generated and the vapor. The proportion of vapor is about 10%.(4) The influences of pH value, hydrogen peroxide concentration, original filling rate on the runaway temperature and pressure were conducted. Results illustrate that hydrogen peroxide decomposes rapidly at room temperature in the strong alkaline environment. The stronger the alkaline is, the faster and more violent the runaway process is. Higher hydrogen peroxide concentration results to greater overpressure, higher maximum rising rate of pressure, representing more hazards. The maximum pressure and the maximum pressure rising rate increase with the fill rate increases. The first and second derivative of characteristic parameters P and T were used respectively to establish the runaway criterion.(5) The runaway relief characteristics of hydrogen peroxide decomposition reaction in different conditions were experimental studied. Results represent that there are two pressure peaks during relief process. Relief pressures have litter effect on the secondary peak pressure values at a fixed vent size in various vent diameters and relief pressures. However, for a fixed relief pressure, the greater the discharge diameter is, the slower the secondary peak pressure forms, and the smaller the secondary peak pressure is. Secondary pressure peak disappears if the relief diameter increase to a certain value.(6) The vent areas of the 10% and 15% hydrogen peroxide in diabatic and external thermal condition was calculated by using DIERS method based on the data of 5 L device in this paper, and compared to experimental results. Result demonstrates that values calculated according to DIERS are conservative. But it is feasible in diabatic and external thermal conditions in engineering application due to the conservative but safe result.