Factors to improve the efficiency of a vertical screw mixer of bulk materials

Abstract

The paper shows that it is possible to increase the efficiency of a vertical screw mixer of bulk materials and reduce costs by determining the required size of the feeding hole in the lower part of the casing, as well as by installing a screw flange with a reverse winding in relation to the screw spiral inside the screw casing and by installing a replaceable tip with a variable lead angle at the lower end of the screw. The analysis of the process of screw loading in the hopper allowed us to obtain an analytical dependence to determine the required size of the feeding hole, in which mixed materials freely enter the screw spiral. It is proved that the placement of the screw flange on the inner surface of the casing increases the driving force of material by 1.05 – 1.80 times depending on the screw speed, which significantly reduces specific energy consumption for preparation of mixture of the desired quality. The paper provides the formula for calculating the angle of installation of the flange with respect to the screw spiral, in which the maximum effect of the flange on the mixed materials is obtained. In order to ensure the effective capture of mixed materials in the loading zone of the screw, it is proposed to perform the first spiral turn from the lower end of the screw with a variable lead angle and place it on a replaceable tip. A technical solution to the placement of spirals on the double-threaded screw is also proposed.

Theoretical Studies of the Interaction between Screw Surface and Material in the Mixer

“…In order to increase the efficiency of livestock production, it is necessary to use food balanced in nutritional value. The main step in the preparation of balanced feeds is to mix the components [ 1 , 2 , 3 , 4 ]. One of the most commonly used in mixing processes are screw mixers (single, double and multi-screw) [ 5 ], to which the considerations in this paper will be limited.…”

“…Final product mixes must be highly homogeneous. Due to the variety of materials that are mixed with each other (they can be both bulk materials and liquid additives), it is necessary to carry out detailed theoretical considerations and, consequently, to verify developed models by means of experiment, in order to describe the processes of materials mixing to achieve the highest possible process efficiency and product quality [ 4 , 6 , 7 , 8 ]. The flow of materials, and the resulting mixing efficiency, depends on the parameters of the mixed materials (particle size, moisture, porosity, particle shape, friction coefficients) [ 9 , 10 , 11 ], and the design features (geometric, material) of the mixer [ 4 , 12 , 13 ] as well as the parameters of the mixing process itself, e.g., time, rotational speed of the mixing elements, the size of the stream of dosed materials, power and torques [ 14 , 15 , 16 ].…”