Research of the process of biomass briquetting by auger mechanism

Abstract

The analysis of the process of auger briquetting of plant materials into fuel and feed is carried out. The patterns of this phenomenon are the basis for determining the rational parameters of the working bodies. When designing briquette presses it is necessary to consider deformation of biomass taking into account change of physical and rheological properties at the moment of interaction with the auger mechanism.
A significant advantage of auger briquetting is the combination of technological and transport processes. They occur continuously at a certain rate. The properties of dispersed dry biomass are due to the fact that the raw material particles are separated by a layer of air. Molecular attraction forces act through the layers, which provide dry diffusion during briquetting. An important factor is the duration of the briquette in the chamber of the forming device at a certain temperature.
It is determined that the process of compaction of biomass by the auger mechanism to the state of briquettes occurs in three stages. At the first stage there are stresses that lead to deformation of raw materials of nonlinear nature. In the second stage, the increasing load leads to a critical combination of stresses, when an equilibrium is established between the internal forces of resistance of biomass and the forces of action of the working bodies.
In the third stage, a further increase in load leads to the development of plastic deformations.
The phenomenon of biomass compaction by an auger working body is theoretically investigated. The obtained formulas determine the relationship between the pressure in the channel of the auger mechanism with its length. The pressure increases exponentially as biomass move from the receiving hopper to the forming channel. These equations are reliable to the accepted assumptions about the constancy of the friction coefficients and the validity of the model of displacement of pressurized biomass without reverse flows.
It is established that with the departure of the material from the auger coil and increased friction surfaces, the total value of the restraining moment increases. This leads to a relative rotation of the layers and each subsequent layer rotates slower than the previous one. Therefore, at the turn, the speed of rotation of biomass is the highest, and at the distance of rotation decreases and the material moves only gradually.
The auger briquetting has a significant disadvantage, in particular with increasing density of briquettes, the productivity of the press decreases. This problematic issue is the direction of further research.