Eggshell membrane is a kind of cheap, abundant resources with great potential utilization value. A variety of active ingredients in it can be used as raw materials for medicine, light industry and other industries. At present, soluble protein, collagen, keratin, sialic acid, hyaluronic acid and antimicrobial protein have been successfully extracted from eggshell membrane and exploited in various fields. This study aimed to separate the eggshell membrane for fully exploiting the potential utilization value of the eggshell, and reduce the amount of waste discharged, which is conducive to protecting the ecological environment on which we depend. In order to reduce energy consumption of eggshell membrane separation, separate eggshell membranes from eggshells by flash evaporation was investigated. The flash separation conditions were optimized considering three independent variables at three different levels by response surface methodology. The results showed that the processing parameters of separating eggshell membranes and eggshells with flash evaporation were 1.0 Mpa pressure, 45% moisture content, and 5 mm eggshells' particle size. Under these conditions, the separation rate was 69.16%. Therefore, flash separation can be a promising approach for separating eggshells and eggshell membranes.
In order to provide theoretical guidance for separating egg membrane from eggshell by using mechanical agitation, CFD was used to explore the flow characteristics in stirred tank, using the Sliding Grid method to deal with the impeller rotational velocity zone in flow field, and using the Euler model to deal with liquid-solid two-phase flow. This study explored the influence of dish-shape bottom or flat-shape bottom, the clearance size between baffle and the side wall, and the axial height of impeller to bottom on suspension state of particles, solids holdup distribution, solid phase velocity and power number by CFD. Simulation results showed that better particles suspension effect in dish-shape tank can reduce particles accumulation at the bottom and power consumption. If there was a small clearance size (S) between the baffle and the side wall of the stirred tank, it would reduce particles accumulation at the bottom, and reduce the power consumption. However, too large S would decrease the suspension height of particles, not only cannot strengthen the main flow, but also lead to most fluid through clearance forming tangential flow, simulation results showed that S=6 mm was perfect. While decreased axial height of impeller (C) to bottom, particles accumulation at the bottom was decreased, but power consumption would increase, simulation results showed that C=H/5 (H is height of liquid surface) was perfect. According to the simulation results, the structure of the stirring tank was optimized. At the same time, the influences of stirring rotational velocity, stirring time, solid-liquid ratio and separating medium temperature on egg membrane recovery were also studied by experiment, and optimal parameter combination of factors was obtained. The experiment results showed while the stirring time was 17.1 min, stirring rotational velocity was 350 r/min, solid-liquid ratio was 1:17 g/mL, the separating medium temperature was 32°C, the membrane recovery rate can reach above 89%. The device improves the recovery and utilization of discarded eggshell, and provides a reference for the solid-liquid two-phase flow and related study.
Eggshells and eggshell membranes have high‐value recycling applications and have been widely used in pharmaceutical, chemical, and food research. The separation of eggshells and eggshell membranes is a prerequisite to efficiently using both. Therefore, the pressure‐vacuum experiment equipment was designed. In this study, research on the separation of eggshells and eggshell membranes from waste eggshells using the pressure‐vacuum experiment equipment was carried out. The flash evaporation experiment process controlled the experimental factors to obtain a sufficient moisture content between the eggshell and eggshell membrane with vigorous flash evaporation. The effects of experimental factors such as superheat (5–10°C), temperature (50–70°C), initial pressure (0.6–0.8 MPa), pressurization time (0–40 min), and particle size (6–8 mm) on the separation rate were investigated in the pressure‐vacuum experiment process. Through single‐factor and orthogonal experiments, it was found that the separation rate was most affected by changes in temperature, initial pressure, and particle size, followed by the interaction of temperature and particle size. The experimental results suggested that the optimum separation of eggshell membranes from eggshells was achieved at higher superheat, higher temperature, higher initial pressure, medium pressurization time, and smaller particle size. Through optimization by response surface methodology, the optimal conditions for the separation of eggshells and eggshell membranes using the flash evaporation method were determined as 15°C of superheat, 70°C of temperature, 0.8 MPa of initial pressure, and 6 mm of particle size. Flash evaporation method is an effective and environmentally friendly method, which provides a new solution for the recycling of waste eggshells. Practical Application In this study, pressure‐vacuum experiment equipment was utilized to reuse of waste eggshells, and an innovative and environmentally friendly method of eggshell membrane and eggshell separation was established. The pressure‐vacuum experiment equipment has a simple structure and low energy consumption. The results of flash evaporation experiments are instructive for further in‐depth studies on the separation of eggshells and eggshell membranes. Furthermore, the separation of eggshells and egg membranes by flash evaporation is of great research value. Most importantly, the separated eggshells and eggshell membrane are available for high‐value applications in food, chemical, and biological fields.
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