Process Control of a Compost-Reactor Turning Operation Based on a Composting Kinetics Model

Abstract

Composting is a biochemical as well as a heterogeneous process, and the turning operation is important to maintain aerobic conditions and improve the efficiency of the composting process. Therefore, the turning frequency is an important factor for the precise control of the composting reactor. It is necessary to determine the changes in the physical and chemical parameters of the composting process and to simulate them. Pretreated vinegar residue and wool washing sludge were mixed at a mass ratio of 6:4 for the composting process. The composting reactor’s temperature, CO2, CH4, and organic matter content were collected during the composting process. According to the principles of composting, a kinetic model of composting based on the change in CO2 gas concentration and heat balance in the composting reactor is developed, which provides a theoretical basis for the subsequent control of the composting reactor. The comparison of the model predictions to the measured results of the composting reactor shows that the SSE, R2, and RMSE for the organic matter content simulation are 8.122, 0.943, and 1.274 g/kg, respectively, and the SSE, R2, and RMSE for the temperature simulation are 29.54, 0.959, and 2.71 °C, respectively. Based on the prediction of the temperature in the reactor based on the composting kinetics model, the process control for the turning operation is proposed to achieve precise control of the composting process. The results show that the duration of high temperature in a composting reactor is prolonged for 2 days, the degradation rate of organic matter occurs at a more rapid speed, and the operation efficiency of the production line can be improved by more than 10%. This indicates that the decision-making method based on the composting kinetics model can improve the composting efficiency.