Existing designs of screw presses produced by modern industry, when squeezing the pulp do not take into account the special technological properties of castor seeds, which are very different from other oilseeds and, thus, unable to meet production requirements, namely to ensure the productivity of castor oil extraction and the required quantity and quality of the final product. Accordingly, the cake remaining after pressing has a high oil content. This requires the introduction of further technological operations to reduce the oil content of the cake, which, in turn, increase the cost of the final product.
This state of affairs creates a national economic task, the essence of which is the poor performance of the technological operation of pressing the pulp of castor seeds and, accordingly, low technical and economic efficiency.
There is a fundamental scientific and technical problem to increase the efficiency of castor oil extraction by determining the technological modes and optimal design and technological parameters of screw presses, which can increase the yield of castor oil compared to existing presses.
The first section of the dissertation establishes castor seeds' main physical and mechanical properties and the rheological properties of castor seed pulp. In addition, the requirements that castor seed pulp must meet before pressing in each previous process were summarized: the quality of the castor bean collapse and separation, the quality of the beet grinding in the pulp and the parameters of wet heat treatment of castor bean pulp. The analysis of methods of obtaining oil materials and the corresponding designs of machines is carried out.
The second section was devoted to the theoretical study of the process of pressing the pulp of castor seeds in screw presses. In the course of research, mathematical models of pressure in the channel, heat balance and oil filtration during pressing of castor seed pulp were built. It is established that a sufficient number of pressing turns of the screw press is eight turns, then the relative oil concentration reaches the maximum value Sf/C0 = 1. In this case, the pulp pressure created on the first pressing turn should be P = 0.063 MPa, at this pressure value, the relative oil concentration will be Cf/C0 = 0.135; on the other - P = 0.32 MPa, Sf/C0 = 0.439; on the third - P = 1.28 MPa, Sf/C0 = 0.65; on the fourth - P = 3.32 MPa, Sf/C0 = 0.803; on the fifth - P = 5.19 MPa, Sf/C0 = 0.861; on the sixth - P = 8.59 MPa, Sf/C0 = 0.914; on the seventh - P = 11.18 MPa, Sf/C0 = 0.942; on the eighth - P = 14 MPa, Sf/C0 = 1.
In the third section of the program, a technique of experimental research and experimental installation for carrying out research are developed, and the application of necessary measuring devices is proved.
In the fourth section, the optimization is carried out with the definition of the second-order model of the most influential structural and technological parameters of the screw press (compression ratio, compression temperature and gap in the gauge plates) of each pressing turn: on the first pressing turn the compression ratio is 1.42; on the other - 1.79; on the third - 2.09; on the fourth - 4.67; on the fifth - 5.35; on the sixth - 6.21; on the seventh - 7.29; on the eighth - 9.29. The temperature of the pulp in the press should be 105 ºC, and the gap between the gap plates from the first to the fourth pressing turn - 1.5 mm, from the fifth to the eighth - 1 mm.
The efficiency of the pressing process on the corresponding pressing turns of the screw press is determined: on the first pressing turn after pressing, the relative weight of oil is 0,0812; with the addition of the second - 0.272; with the addition of the third - 0.368; with the addition of the fourth - 0.409; with the addition of the fifth - 0.454; with the addition of the sixth - 0.47; with the addition of the seventh - 0.489; with the addition of the eighth - 0.496. With the maximum oil content of castor seeds at the level of 55 percent, it was found that due to the optimization of design and technological parameters of screw presses, the oil content of castor oil was reduced by at least 3.1%.
The law of compression for screw presses during pressing of castor seed pulp is established, which allows determining the optimal degree of compression of the corresponding pressing turn.
It is found that a sufficient number of compression turns in screw presses for pressing castor seeds is 8. Accordingly, when used while pressing several such compression turns, the relative weight of the oil will be.
The annual economic effect of using the developed screw press for pressing castor seed pulp for the productivity of 0.22 t / h is 458924.4 UAH with a payback period of 0.4 years.
