Influence of Elevation on Slake Durability Index of Quartz Mica Schist: A Case Study of East Slope of Manjiazhai Open Pit

In order to study the influence of elevation on the slake durability index of the quartz mica schist, the quartz mica schist with different elevations on the east slope of the Manjiazhai open-pit mine is taken as the research object, and based on laboratory tests and statistical analysis, the variation of negative correlation between the slake durability index and elevation is obtained. The disintegration mechanism of quartz mica schist at different elevations is also discussed. The test results show that the disintegration characteristics of quartz mica schist at different elevations are related to its mineral composition, fissure channel size, and rock damage effect. As the slope height increases, the ratio of mica to quartz in the rock increases, and the greater the porosity of the rock, the more fissures in the rock, the greater the permeability coefficient, and the more obvious the change of effective stress of rock under osmotic pressure. At the same time, the higher the slope elevation of open-pit mine, the longer the weathering time of rock, the higher the cumulative damage of rock, and the lower the rock slake durability index. This study provides a new idea for guiding the research on the disintegration characteristics of similar soft rock slopes in the elevation direction.

Mechanical Properties of briquette by mixing rice and micrometer-sized carbon particles from potato and yam skins

The purpose of this study was to utilize waste potato skins (PS) and yam skins (YS) in the production of briquettes with rice waste as a binder. The basic materials used to utilize waste, especially potato skins (PS), yam skins (YS), and rice waste. Experiments were carried out by mixing and molding carbon particles made from an equal mass ratio of PS and YS with rice as binders (i.e., 10, 20, 30, 40, and 50%). PS and YS were dried, carbonized at 250°C for 3 hours, and sieved to get sizes of 250 μm. To make compact briquettes, the molded materials were pressed with 5.66 Pa. Several characterizations were analyzed, including compressed density, relaxed density, relaxation ratio, percentage of moisture content, burning rate, percentage of water resistance index, percentage of durability index, specific fuel consumption, the puncture test, and the hardness test. The characterization results showed that the prepared briquettes have good quality, and the best was for 10% of adhesive. The best durability index was for briquettes with 30% of adhesive. The compressed density and water resistance index were optimum when using 40% of adhesive. In general, briquettes with a low amount of adhesive have a high-density value, low moisture content, and a long flammability. This research is expected to convey information regarding how to reuse rice waste as an adhesive for briquettes.

Mechanical Durability and Grindability of Pellets after Torrefaction Process

Renewable energy sources and their part in the global energy mix are beneficial to energy diversification and environment protection. However, raw biomass is characterized by low heating value, hydrophilic properties, various mechanical durability, and the logistic challenges related to transportation and storage. One frequently used process of combined biomass valorization is torrefaction and pelletization, which increase the heating value, homogeneity, and hydrophobicity of the fuel. However, industrial clients need fuel characterized by favorable grindability, whereas, the individual clients (householders) need fuel with high mechanical durability. Due to the different expectations of final customers regarding biomass fuel properties, it is necessary to investigate the influence of the torrefaction on the mechanical durability of the pellets. In this paper, five various types of pellets and their torreficates (obtained at a temperature of 200 and 300 °C) were examined. Then the mechanical durability index DU and the grindability of the untreated and torrefied pellets were determined. The results indicated that the mechanical durability of untorrefied pellets is significantly greater than torrefied pellets. Interestingly, no significant differences in mechanical durability between torrefied pellets at 200 and 300 °C were observed, For sunflower husk pellets, the DU index amounted to 95.28 ± 0.72 (untorrefied), 47.22% ± 0.28% (torrefied at 200 °C), and 46.34% ± 0.72% (torrefied at 300 °C). Considering the grindability, as the treatment temperature increased the energy demand for grindability decreased. For example, the grindability of pine tree pellets was 15.96 ± 3.07 Wh·kg−1 (untreated), 1.86 ± 0.31 Wh·kg−1 (torrefied at 200 °C), and 0.99 ± 0.17 Wh·kg−1 (torrefied at 300 °C). The highest difference between raw and torrefied pellets was determined for beetroot pomace pellet: 36.31 ± 2.06 Wh·kg−1 (untreated), 3.85 ± 0.47 Wh·kg−1 (torrefied at 200 °C), and 1.03 ± 0.12 Wh·kg−1 (torrefied at 300 °C).

Analysis of Retention Time and Steam Pressure Variations in the Conditioning Process on the Moisture Content of Feed in the Packaging Process

Pellets are compressed feed, compacted through a mechanical process. Pellets can be molded in the form of lumps and small cylinders with different diameters, lengths, and levels of strength. The right moisture content value will maximize the quality of the pellets and increase the value of the Pellet Durability Index(PDI). Many factors affect the moisture content in the feed such as changing the steam pressure configuration, adding moisture to the mixing process, changing the retention time configuration, and other methods. The method tested was to provide variations on the configuration of retention time and steam pressure on the Pressure Reducing Valve (PRV) which aims to determine the increase in moisture content in the feed. Variations of retention time configuration tested were 50 seconds, 55 seconds, 60 seconds, 65 seconds, 70 seconds with variations in the Steam pressure configuration in the test were 1.4 bar and 1.6 bar. The test results prove that the retention time of 65 seconds with a steam pressure of 1.4 bar is the best configuration with an increase in moisture content of 2.67% with a difference in moisture content of bagging to the mixing of -0.46.

Comparative Durability of Common Stains Used for Exfoliative Vaginal ‎Cytology

In a study to compare the durability of commonly used stains (Giemsa, Leishman, Wright, Eosin, Nigrosin and Gentian violet) for exfoliative vaginal cytology, vaginal smear was obtained from eleven apparently healthy West African Dwarf (WAD) female Goats and processed according to standard technique. Scores (0-3) were given on four parameters namely background of smears, overall staining pattern, cytoplasmic staining and nuclear staining. Quality index one (QI-I) was calculated from the ratio of score achieved to the maximum score possible (12), immediately post staining while quality index–II (QI-II) was obtained 35 days after. Calculation for durability index (DI) was self-derived and equalled to ratio of QI-II to QI-I. The data were presented as mean ± SEM. Multinomial logistic regression model was generated for the QI-I and QI-II using durability index as reference category. Giemsa, Leishman and Wright stains were more durable than others with their mean DI values significantly (P < 0.05) higher than Gentian violet, Nigrosin and Eosin.The model showed 89.2% overall model accuracy for the multinomial logistic regression model and 81.5% for the multinomial Bayes Naïve regression model. In conclusion, Giemsa, Leishman and Wright stains were more reliable and durable for exfoliative vaginal cytology compared to the other stains.

Disintegration Mechanism and Hydrogeochemical Processes of Red-Bed Soft Rock Under Drying-Wetting Cycle

Red-bed soft rock in the drawdown area on bank slopes of landslide easily disintegrates upon exposure to water, and its properties experience comprehensive deterioration, which will cause bank slope instability. To better study disintegration mechanism of the red-bed soft rock, a series of laboratory tests were conducted in this paper to investigate the disintegration characteristics, durability and hydrogeochemical process of red-bed argillaceous siltstone under drying-wetting cyclic conditions. Experimental results showed that, with increasing number of drying-wetting cycles, red-bed argillaceous siltstone gradually disintegrated, from initial appearing the cracks on the surface of the samples to large particles gradually breaking up into small fragments. Significant changes in grain size distribution, and the durability index of the samples progressively decreased. Microstructural analysis showed that the size and distribution of pores and cracks in the sample surface significantly increased, such that the sample surface became disordered and complicated. Notable changed in concentrations of ions in the soaking solutions indicated continuous mineral dissolution and loss during the cyclic drying-wetting. Based on the results obtained from the experiment, it is concluded that the disintegration of samples undergoing drying-wetting cycles was the result of the synergistic action of water and temperature. To be specific, the dissolution of calcite, albite, gypsum, montmorillonite and kaolinite during the wetting procedure, which promotes the decrease in mineral content and increases in pores and cracks. The increases in temperature and the dehydration shrinkage of sample during the drying procedure accelerated the disintegration of the samples.

Effects of conditioning temperature and pellet mill die speed on pellet quality and relative stabilities of phytase and xylanase

The objective of this experiment was to determine the effect of conditioning temperature and die speed on pellet quality and enzyme stability of phytase and xylanase. Treatments were initially arranged as a 2 × 3 factorial of conditioning temperature (74 and 85°C) and die speed (127, 190, and 254 rpm); however, when conditioning at 85°C it was not possible to pellet at 127 rpm. Thus, data were analyzed in 2 different segments using the GLIMMIX procedure of SAS. First, linear and quadratic contrasts were utilized to test the response to increasing die speed at 74°C. Second, the data was analyzed as a 2 × 2 factorial of conditioning temperature (74 and 85°C) and die speed (190 and 254 rpm). Treatments were arranged in a completely randomized design and replicated 3 times. Diets were conditioned for approximately 30 s and pelleted with a 4.8 mm diameter × 44.5 mm effective length die at a rate of 4.5 MT/h. Pellet durability index (PDI) was determined using the tumble box and Holmen NHP 100 methods. Samples of the unconditioned mash (M), conditioned mash (CM) and pellets (P) were collected and analyzed for phytase and xylanase concentration. Relative enzyme stabilities were expressed as CM:M, P:CM and P:M. Stabilities expressed as P:M were used an indication of enzyme stability through the entire pelleting process. Diets conditioned at 74°C showed no evidence of difference in phytase or xylanase P:M stability when decreasing die speed from 254 to 127 rpm. However, when conditioning diets at 74°C, decreasing die speed increased (linear, P &lt; 0.001) PDI. There was no conditioning temperature × die speed interaction for overall xylanase P:M stability or PDI. However, there was a conditioning temperature × die speed interaction (P &lt; 0.01) for phytase P:M stability. When conditioning diets at 85°C, increasing die speed decreased phytase P:M stability. However, when conditioning at 74°C, increasing die speed did not influence phytase P:M stability. For main effects of conditioning temperature, increasing temperature improved (P &lt; 0.001) PDI with no evidence of difference for xylanase P:M stability. For the main effects of die speed (254 vs 190 rpm), decreasing die speed decreased (P &lt; 0.001) the P:M xylanase stability, but there was no evidence of difference for PDI. The results of this trial indicate that die speed should be taken into consideration when evaluating enzyme stability of both phytase and xylanase as pellet mill models may be operating at different speeds. Additionally, increasing conditioning temperature will improve PDI, but may result in decreased phytase stability.

Finite-difference based response surface methodology to optimize tailgate support systems in longwall coal mining

Designing a suitable support system is of great importance in longwall mining to ensure the safe and stable working conditions over the entire life of the mine. In high-speed mechanized longwall mining, the most vulnerable zones to failure are roof strata in the vicinity of the tailgate roadway and T-junctions. Severe roof displacements are occurred in the tailgate roadway due to the high-stress concentrations around the exposed roof span. In this respect, Response Surface Methodology (RSM) was utilized to optimize tailgate support systems in the Tabas longwall coal mine, northeast of Iran. The nine geomechanical parameters were obtained through the field and laboratory studies including density, uniaxial compressive strength, angle of internal friction, cohesion, shear strength, tensile strength, Young’s modulus, slake durability index, and rock mass rating. A design of experiment was developed through considering a Central Composite Design (CCD) on the independent variables. The 149 experiments are resulted based on the output of CCD, and were introduced to a software package of finite difference numerical method to calculate the maximum roof displacements (dmax) in each experiment as the response of design. Therefore, the geomechanical variables are merged and consolidated into a modified quadratic equation for prediction of the dmax. The proposed model was executed in four approaches of linear, two-factor interaction, quadratic, and cubic. The best squared correlation coefficient was obtained as 0.96. The prediction capability of the model was examined by testing on some unseen real data that were monitored at the mine. The proposed model appears to give a high goodness of fit with the accuracy of 0.90. These results indicate the accuracy and reliability of the developed model, which may be considered as a reliable tool for optimizing or redesigning the support systems in longwall tailgates. Analysis of variance (ANOVA) was performed to identify the key variables affecting the dmax, and to recognize their pairwise interaction effects. The key parameters influencing the dmax are respectively found to be slake durability index, Young’s modulus, uniaxial compressive strength, and rock mass rating.