A New Model for Environmental Assessment of the Comminution Process in the Chain of Biomass Energy Processing †

Abstract

Acquiring energy contained in biomass requires its prior appropriate preparation. These treatments require some energy inputs, which significantly affect the reduction of the energy and the environmental balance in the entire life cycle of the biomass energy processing chain. In connection with the above, the aim of this work is to develop a methodology for the environmental assessment of biomass grinding in the processing chain for energy purposes. The research problem is formulated as follows: Is it possible to provide an assessment model that takes into account the environmental inputs and benefits of the grinding process of biomass intended for further energy use (for example, combustion)? How do the control variables of the grinding machine affect the environmental process evaluation? In response to these research problems, an original, carbon dioxide emission assessment index of the biomass grinding process was developed. The model was verified by assessing the process of rice and maize grinding on a real object—a five-disc mill—with various speed settings of the grinding disc. It was found that the carbon dioxide emission assessment model developed provides the possibility of comparing grinding processes and identifying the grinding process with a better CO2 emission balance, where its values depend on the control parameters of the mill.

The Integrated Energy Consumption Index for Energy Biomass Grinding Technology Assessment

“…The moisture level was determined for each of them on a moisture balance MAC 210/NP (RADWAG, Radom, Poland) in accordance with ISO norm 1446 [82], and, additionally, average grain size before grinding on a CAMSIZER (Retsch Technology GmbH, Haan, Germany) device was also determined in accordance with ISO norm 13322-2:2006 [81]. Next, the prepared material was subjected to grinding on a five-disc grinder for 20 different grinding disc angular speed settings in accordance with the accepted test program [28,79] in Energies 2020, 13, 1417 9 of 26 order to investigate the dependence of the integrated energy consumption index on the total increase in the grinder disc angular speed S∆ω ( Table 3). The minimal speed of the grinder discs accepted to be the point of reference was 20 rad·s −1 .…”

“…The test stand was composed of: a five-disc mill, a control panel with a performance monitoring system, and an integrated system for analysis of the grinding product's particle size ( Figure 2). Test stand for the intelligent monitoring of granular mass characteristics: 1-five-disc grinder, 2-worm feeder, 3-hopper, 4-control unit, 5-reception basket of the product of grinding, 6-weight of the product of grinding, and 7-integrated system for the analysis of the grinding product's particle size [28].…”

“…The grinding unit consists of five multi-hole discs fixed on the grinder shaft ( Table 2). Each disc is powered individually by means of a dedicated motor which enables precise control of the Test stand for the intelligent monitoring of granular mass characteristics: 1-five-disc grinder, 2-worm feeder, 3-hopper, 4-control unit, 5-reception basket of the product of grinding, 6-weight of the product of grinding, and 7-integrated system for the analysis of the grinding product's particle size [28].…”

“…It has also been shown that the energy demand increases as the particle size of the comminution product decreases; i.e., the smaller the particles we want to achieve, the greater the energy input [5,27]. The conducted analyzes have shown that the smaller the particles after comminution, the easier they are conducted; e.g., anaerobic digestion processes and the efficiency of biomass conversion into biofuels increases, due to the increase in the specific surface area of the particles in grinding processes [4,28,29].Current legislation imposes requirements which are supposed to reduce the energy consumption of technological lines, including energy material grinding. Unfortunately, currently used grinding machines and devices consume much energy and are inefficient [2,[30][31][32], which motivates researchers to take up research in order to reduce the energy consumption of grinders and mills.…”

“…It has also been shown that the energy demand increases as the particle size of the comminution product decreases; i.e., the smaller the particles we want to achieve, the greater the energy input [5,27]. The conducted analyzes have shown that the smaller the particles after comminution, the easier they are conducted; e.g., anaerobic digestion processes and the efficiency of biomass conversion into biofuels increases, due to the increase in the specific surface area of the particles in grinding processes [4,28,29].…”