Dynamic modeling and parameters optimization of degrading ethylene by positive corona coupled with Ag-TiO2

Abstract: The quality of horticultural products in cold-storage environment rapidly declines due to its perishability. Ethylene is one of important factors to facilitate the perishing process, because it enhances the respiration intensity and enzymatic activities of horticultural products. We introduce the non-thermal plasma which were produced by positive corona into the horticultural cold-storage, it can remove the volatile organic gases effectively, safely, and stably. However, the corona generates much ozone that may poison fruits and vegetables. A more effectual method to use the non-thermal plasma is coupling it with heterogeneous catalysis technology. To explore the mechanism and kinetics of ethylene degradation and ozone regulation in the photoelectric catalyzed coupling reaction system of direct current positive corona-elemental silver deposit nanometer TiO2. In this paper, the cylinder wall was used as corona discharge reactor, with needle-array-versus- inner-cylinder-wall corona electrode, and with nano-TiO2 as catalysis deposited with nanometer silver. The impacts of silver doping amount, discharge power and gas flow rate and other factors on ethylene degradation and ozone control effect were carried out in the simulation of the horticultural products cold storage environment, verified the intrinsic kinetics of the reaction process by surveying the changes of concentration of ethylene as well as ozone. The results showed that ethylene degradation dynamics model of positive corona discharge coupling activated carbon fiber (ACF) supported Ag doped nano-TiO2 (Ag-TiO2/ACF) was established. Corona discharge coupling Ag-TiO2*/ACF catalytic membrane on degradation of ethylene and control of the ozone concentration has a superior performance by comparing the reaction constant of Runge Kutta method for solving differential equations and least square method for dynamics model. By means of quadratic rotary combination experiment and regression fitting, quadratic multinomial model of reaction constant of corona discharge coupling Ag-TiO2*/ACF catalytic membrane on the degradation of ethylene and the limits of predicted values of ozone concentration was established. The validity of the model was verified, and parameters of reaction system were optimized at the same time. The optimal conditions for storage of apple was that silver doping amount of 0.5%, discharge power of 0.47 W and gas flow rate of 400 L/h. The research can provide a reference for the technology of direct current positive corona discharge coupling nano-TiO2 in the application of storage and transportation equipment of horticultural products.