A longstanding concern in plant essential oil extraction is how to optimize extraction efficiency with limited materials. Supercritical CO₂ extraction has been proven effective in enhancing the yield and efficiency of extracting plant essential oils. However, the impact of temperature, pressure, and co-solvent content on extracting Hetian rose essential oil remains unclear. There is a lack of research on the influence of pretreatment methods. This study focuses on investigating supercritical CO₂ extraction of rose essential oils from Xinjiang Hetian. The research analyzes the effects of pressure and temperature on the extraction rate and validates the efficiency by calculating the solubility of essential oils in supercritical fluid. Under conditions of 35 MPa, 40 °C, 10 L/h, and a particle size of 0.8 mm, this study evaluates the extraction efficiency using Xinjiang Hetian rose materials pretreated with salt solutions at concentrations of 5%, 10%, and 20%, as well as enzyme solutions at concentrations of 2%, 5%, and 10%. Results indicate that appropriate solution concentration can enhance the extraction effect and mass transfer process, but excessively low or high concentrations do not contribute to improved extraction reactions. The highest extraction rate (8.99%) is achieved using a salt solution concentration of 10%, while the lowest (4.21%) is obtained with a salt solution concentration of 20%.

This study aims to evaluate the drying performance of a multi-stage solar-assisted heat pump drying system for tomatoes. The method involves theoretical calculations based on the optimal drying process and experimental investigations to assess the impact of different drying temperatures and relative humidity on drying characteristics. The results from the theoretical calculations reveal that the multi-stage solar-assisted heat pump drying system outperforms a single-stage system, particularly under lower ambient temperatures or higher fresh air volumes. In spring/autumn, with 25% fresh air, solar energy accounts for 85.12% of the total energy consumption, achieving a performance coefficient of 39.16, a moisture extraction rate of 40.7 kg/kWh, and energy consumption of 0.02 kWh/kg. Carbon dioxide emissions amount to 10.45 kg/year, with a net reduction of 7.88 kg/year. The experimental results indicate that higher relative humidity increases drying time and reduces the diffusion coefficient, which results in higher material temperatures and greater nutrient loss. The optimal drying process is achieved at 70 °C and 20% relative humidity. In conclusion, the multi-stage solar-assisted heat pump drying system demonstrates superior performance in energy efficiency and sustainability compared to single-stage systems. The optimal drying conditions for tomatoes are identified, and the findings contribute to improving drying processes in food preservation while minimizing environmental impact.

The heating source temperature of the vacuum belt system (VBD) is an important factor affecting the drying rate and the material quality. However, it has problems with large fluctuation, instability, and hysteresis due to interference from various factors, which increases the drying time and energy consumption. To address these issues, this study proposes fuzzy control and integral control synergistic (FCICS) control to realize temperature regulation of the VBD system, enhancing the performance and stability of the heating source. Simulations were conducted in Simulink, and an experimental verification was carried out based on the constructed experimental system. The results show that the FCICS control outperforms the conventional PID control in terms of material warming rate, temperature stability, and energy consumption, and the transient and stable state performance is improved. Specifically, the material warming rate increased by 15%, temperature stability improved by 20%, and energy consumption decreased by more than 1.74% with the FCICS control strategy.

1. Spray drying is a widely adopted method for rapidly converting liquids or slurries into dry powders and is extensively employed in the food, pharmaceutical, and chemical industries due to its hi...