Design and experiment of the animal lipid extraction system combined with heat and pressure

Animal lipid can be extracted from the fat of diseased carcass with the ecological and economic benefits. In this work, an extraction device combined heating and squeezing was designed to improve the yield of lipid. The analysis on statics and heat transfer was conducted to design the key components such as the pressuring, heating and separating units. Subsequently, the equipment selection was carried out, according to the material characteristics of animal skin and flesh tissue. Moreover, the key parameters for the heating, pressuring, and PLC(programmable logic controller) control system were optimized. Furthermore, the performance of the device was tested, taking suet from pig belly as experimental raw material. In addition, the viscosity of the extracted lipid was determined. The adjustable range of temperature was 25 to 300 ℃ in the device, and the pressure range was 0 to 5.0 MPa. Meanwhile, the data of heat and pressure were collected, where the control response time was less than one second. Additionally, the relative error of temperature was between 0.41% and 1.20%, and the absolute error of the pressure was about 0.2 MPa, with the requirements for lipid extraction tests. The results showed that the increasing yield of lipid extraction was found with the rise of temperature under the heating only or the combined heating and squeezing in the temperature range of 70 to 150 ℃. Specifically, the lipid extraction yields were 10.74% to 59.15% and 41.95% to 81.35%, respectively. At the same temperature, the extraction yield of lipid with combined heating and squeezing was higher than that of heating only. In particular, the lipid extraction yield of material S1(size is 10 mm×10 mm×10 mm) increased by 31.21 percentage points at 110 °C. Because the structure of the raw material was hardened under the action of heat, the release of lipid was accompanied in this process. Further, the action of pressure provides the power of lipid movement, for this reason the lipid extraction yield was significantly improved. There was no significant increase in the lipid extraction yield by heating only or the combined heating and squeezing, when the temperature was higher than 130°C. Furthermore, the lipid extraction yield was observed to increase with the decreasing size of material under the action of heating only. However, there was no outstanding size effect on the lipid extraction yield under the heating and squeezing together. Moreover, the animal meat materials were achieved in the complete separation under the combined heating and squeezing. Especially, the optimal conditions were 130℃ operating temperature, 5 min heating time, and 2.0 MPa pressure to achieve a mean lipid yield of 81.35%, while the material size was S2(size is 20 mm×20 mm×20 mm). The lipid viscosity was ranged from 0.004 to 0.091 Pa·s at the temperature range of 50 to 150 ℃. Meanwhile the viscosity curve showed a steady trend, while the viscosity value remained basically unchanged with shear rates higher than 20 s-1. Newtonian fluid characteristics were observed under different shear rates at the same temperature, fully meeting the viscosity standard of industrial lubricating oil.