Precision control behavior of hot air temperature based on a granular continuous feeding biomass combustion furnace

The promotion and application of biomass combustion furnaces transform agricultural and forestry waste into valuable resources, significantly reducing environmental pollution from open burning of biomass while decreasing reliance on fossil fuels like coal, oil, and natural gas. This effectively establishes a "carbon-neutral" clean energy recycling model. However, existing biomass combustion furnaces often suffer from issues such as slagging in the furnace, low heat exchange efficiency in the heat exchanger, and large fluctuations of hot air temperature, leading to frequent shutdowns of the combustion furnace, low utilization of biomass energy, and degradation quality of dried crops during the drying process. The key components of the biomass furnace were optimized in this study, including an anti-ignition granular continuous feeding furnace and a progressively enhanced heat exchanger. Numerical simulations of the velocity, pressure, and temperature fields within the biomass combustion furnace were performed using COMSOL. The simulation results indicated that the velocity streamlines in the furnace tend to stabilize with negligible distribution discrepancies, the temperature gradient decreased appropriately, and the pressure drop in the heat exchanger remained minimal. Furthermore, to address the low temperature control accuracy issue of the hot air in the biomass furnace, an experimental study was conducted on four influencing factors: rotational speed of the particle feeding auger (90–146 r/min), the air valve opening degree (0–100%), frequency of the exhaust fan (40–60 Hz), and rotational speed of the hot air fan (450–1450 rpm). The study aimed to investigate the influence of these parameters on the control accuracy. Performance validation of the hot air furnace was carried out at the Agricultural Comprehensive Service Center in Wencheng Township, Suiping County, Zhumadian City. Two sets of hot air temperature control tests were conducted with target temperatures set at 45°C and 48°C, respectively. The experimental results demonstrated an average steady-state response time of 220 s and an average heat exchange efficiency of the biomass furnace of 91.98%. The average deviations between the measured hot air temperature and the set points were -0.7°C and 0°C for the two targets, with temperature fluctuations of ±0.8°C and ±1.05°C, respectively. These results indicate that the designed granular continuous-feeding biomass furnace can achieve rapid response and high-precision control of the hot air temperature. A granular continuous-feeding biomass combustion furnace with anti-ignition continuous feeding and a stepwise enhanced heat exchanger was developed. Through COMSOL simulation and single-factor experiments, a PID control model was established, achieving a heat exchange efficiency of 91.98% and hot air temperature fluctuation of ±1.05°C.