Drying Characteristics of Chicken Manure Under a Variable Temperature Process

In recent years, employing an auxiliary heat source, combined with residual heat from chicken house ventilation, to dry chicken manure has emerged as a novel manure treatment method. This method uses residual heat from chicken house ventilation in the early drying stage and an auxiliary heat source in the late drying stage, resulting in a variable temperature process. Nevertheless, limited research has been conducted on the variable drying process of chicken manure, and no standard currently exists for setting the drying parameters. To investigate the variable temperature drying process of chicken manure, this study set up a simulated drying system. First, the effects of drying temperature (45–65 °C), air velocity (0.6–1.8 m/s), and moisture content nodes (35–55%) on drying time, energy consumption, and total nitrogen loss were investigated using single-factor experiments. Then, an orthogonal experiment was performed to analyze the comprehensive impact of different influencing factors. Finally, the drying effect was evaluated using a multi-indicator comprehensive scoring method, and the drying parameters were optimized through a combination of orthogonal and single-factor experiments. The results showed that the drying temperature during the second stage had a significant effect on chicken manure drying performance under the variable temperature process (p < 0.05), while the moisture content nodes and air velocity yielded no significant effect (p > 0.05). In actual production, the following optimal parameters are recommended—drying temperature in the second stage: 57.5 °C, air velocity: 1.2–1.5 m/s, and moisture content nodes: 45–50%.