关键词: 氨吸附, 金属氯化物, 动力学模型, Sigmond函数, 多反应阶段

Abstract:

Metal chloride/ammonia is a common working pair based on chemisorption for refrigeration and heat storage, and the establishment of its kinetic model is the basis of system simulation analysis and performance prediction. However, the existing kinetic models manifest disadvantages of complexity or kinetic parameters varying irregularly, and cannot describe the sorption process of multi-reaction stages independently. Taking MnCl₂/NH₃ and CaCl₂/NH₃ as representative working pairs, the sorption and desorption performances of composite sorbent of chloride and expanded natural graphite treated with sulfuric acid with mass ratio of 4:1 were tested and investigated at the reaction pressures of 0.29 MPa, 0.42 MPa and 0.61 MPa. The experimental results showed that the reaction rate decreased with the deepening of the reaction. Thus, a novel sorption kinetic model based on sorption capacities concerning pressure potential(μ), reaction rate constant(k), and reaction hysteresis constant(n) was built via coupling the Sigmond function and the analogy model. The robustness test results evidenced that the fitting curves of the non-equilibrium kinetic model worked satisfactorily on rebuilding the experimental data points for different chlorides, reaction stages(Ca_2-4-2 and Ca_4-8-4), and reaction directions(sorption and desorption) with the goodness of fit(R²) higher than 0.97. Moreover, the model parameters changed regularly with the various working conditions. At the same reaction pressure, k is negatively correlated with sorption temperature, but positively correlated with desorption temperature, and |n| is negatively correlated with desorption temperature.

Key words: ammonia sorption, metal chloride, kinetic model, Sigmond function, multiple reaction stages