Operational Parameters Research Articles

Factors influencing K-struvite purity via phosphorus coprecipitation in synthetic urine: Verification, Quantification, and Modelling

Due to the plethora of nitrogen (N), phosphorus (P), potassium (K) in urine, it is bound to trigger phosphorus coprecipitation, thereby adversely affecting K-struvite purity in the coprecipitates. To obtain high pure K-struvite, the present study was to innovatively explore the effect of residual NH4+ concentration, pH and initial Mg2+ concentration on phosphorus coprecipitation in synthetic urine. Importantly, a Back-Propagation Artificial Neural Network (BPANN) model was innovatively proposed to simulate and predict crystal purities in the coprecipitates. It was revealed that K-struvite, struvite, hydroxyapatite and cattiite dominated the coprecipitates. Comparatively, the content of calcium in synthetic urine is far lower than that of phosphorus and potassium, resulting in low hydroxyapatite purity in the coprecipitates. Notably, cattiite purity is highly dependent of Mg2+ concentration, because it was low at the Mg2+ concentration of <10mmol/L, but increased up to above 50% at the Mg2+ concentration of 50mmol/L. At 10mmol/L Mg2+and pH 10, K-struvite purity in the coprecipitates decreased from 64.6% to 43.3% following the increase of NH4+concentration from 0 to 300mg/L. The BPANN model well simulated and predicted the purities of the crystals in the coprecipitates from synthetic urine. At 10mmol/L Mg2+and 100mg/L NH4+, an increase in pH from 8.5 to 10 can facilitate K-struvite crystallization in synthetic urine. The adjustment of pH and initial Mg2+concentration can significantly mitigate the inhibitory effect of residual NH4+on K-struvite crystallization. The BPANN model herein can effectively obtain optimized operational parameters for the full-scale implementation of slow-release NPK fertilizers from urine, which can also provide an effective reference for nutrient recovery from various waste streams.

Research progress in the application of infrared blanching in fruit and vegetable drying process.

Fruits and vegetables offer substantial nutritional and health benefits, but their short shelf life necessitates effective preservation methods. Conventional drying techniques, while efficient, often lead to deterioration in food quality. Recent advancements highlight the potential of infrared blanching (IRB) as a preparatory process to improve drying outcomes. This review systematically evaluated the application of IRB for various fruits and vegetables, including tomatoes, potatoes, carrots, mangoes, apples, peaches, strawberries, grapes, and green beans. IRB demonstrated notable improvements in texture, color retention, and nutrient preservation in dried products. Key operational parameters for effective IRB include product thickness (2-5cm), treatment duration (30s to several minutes), and the distance from the infrared (IR) emitter (10-30cm). These factors collectively ensure efficient heat penetration and energy transfer. Regarding IR generators, far-IR heaters are advantageous due to their uniform heating capabilities, whereas near-IR heaters deliver rapid heating. Catalytic IR generators are also emerging as promising options for industrial-scale applications. This review further explores the principles and mechanisms of IRB, particularly its impact on drying kinetics and the retention of vitamins, antioxidants, and bioactive compounds. Evidence indicates that IRB can reduce drying times by up to 50%, increase drying rates, and lower energy consumption by approximately 17%, achieving energy efficiency levels of 80%-90%. However, limitations such as the shallow penetration depth of IR radiation remain challenging. Potential solutions, such as the development of hybrid blanching methods, are discussed to optimize the drying process further and enhance the quality of dried fruits and vegetables.

Investigating the Impact of Water-Glycol Mixture Ratios as Heat Transfer Fluid on the Performance of a Rotary Magnetic Refrigerator

Abstract Magnetic refrigeration offers an eco-friendly and sustainable alternative for cooling applications. The selection of an appropriate working fluid is critical for heat removal and regeneration efficiency in Active Magnetic Regenerators (AMRs). This study evaluates various working fluids, focusing on water mixed with an antifreeze agent, glycol, to extend the temperature range and prevent corrosion. The thermophysical properties of such mixtures differ from pure water, influencing the refrigerator’s performance. A parametric investigation using a numerical model of a rotative magnetic refrigerator was conducted to analyze the effects of varying the water-glycol mixture ratios. The study systematically varied operational parameters, such as rotation frequency and mass flowrate, to determine optimal performance conditions. Results indicate that the performance, measured by the Coefficient of Performance (COP), cooling load, and efficiency, declines with increasing glycol content, particularly at lower temperature spans. Increased viscosity in the mixture necessitates higher pumping power and torque for optimal operation, affecting the optimal rotational frequency. This study underscores the importance of balancing the mixture composition to enhance temperature range while minimizing negative impacts on performance, advocating for mixtures with lower glycol content.

Integration of paper-based analytical devices with digital microfluidics for colorimetric detection of creatinine.

Digital microfluidics (DMF) is a platform that enables the automated manipulation of individual droplets of sizes ranging from nanoliter to microliter and can be coupled with numerous techniques, including colorimetry. However, although the DMF electrode architecture is highly versatile, its integration with different analytical methods often requires either changes in sample access, top plate design, or the integration of supplementary equipment into the system. As an alternative to overcome these challenges, this study proposes a simple integration between paper-based analytical devices (PADs) and DMF for automated and eco-friendly sample processing aiming at the colorimetric detection of creatinine (CR, an important biomarker for kidney disease) in artificial urine. An optimized and selective Jaffé reaction was performed on the device, and the reaction products were delivered to the PAD, which was subsequently analyzed with a bench scanner. The optimal operational parameters on the DMF platform were a reaction time of 45 s with circular mixing and image capture after 5 min. Under optimized conditions, a linear behavior was obtained for creatinine concentrations ranging from 2 to 32 mg dL-1, with limits of detection and quantitation equal to 1.4 mg dL-1 and 2.0 mg dL-1, respectively. For the concentration range tested, the relative standard deviation varied from 2.5 to 11.0%, considering four measurements per concentration. CR-spiked synthetic urine samples were subjected to analysis via DMF-PAD and the spectrophotometric reference method. The concentrations of CR determined using both analytical techniques were close to the theoretical values, with the resultant standard deviations of 2-9% and 1-4% for DMF-PADs and spectrophotometry, respectively. Furthermore, the recovery values were within the acceptable range, with DMF-PADs yielding 96-108% and spectrophotometry producing 95-102%. Finally, the greenness of the DMF-PAD and spectrophotometry methods was evaluated using the Analytical Greenness (AGREE) metric software, in which 0.71 and 0.51 scores were obtained, respectively. This indicates that the proposed method presents a higher greenness level, mainly due to its miniaturized characteristics using a smaller volume of reagent and sample and the possibility of automation, thus reducing user exposure to potentially toxic substances. Therefore, the DMF-PADs demonstrated great potential for application in the clinical analysis of creatinine, aiding in routine tests by introducing an automated, simple, and environmentally friendly process.

In situ quantification of fungicide residue on wheat leaf surfaces using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry imaging technology.

To overcome the time-consuming off-site limitations in conventional pesticide detection, this contribution presents an in situ quantitative analysis detection strategy for pesticides on leaf surfaces using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry imaging technology. Taking fungicide metrafenone as a representative, we initially screened seven commonly used matrices, and identifying α-cyano-4-hydroxycinnamic acid as the most effective one in positive mode. Subsequently, coating the matrix using sublimation spraying method resulted in the highest mass intensity. The optimal combination of operation parameters were established with imaging step size of 30μm×30μm, laser diameter of 75μm, and laser energy of 4.01μJ/pulse. Under these conditions, a lowest detection limit of 0.6ng/mm2 was reached for metrafenone, demonstrating extremely high sensitivity and strong repeatability. This method exhibits great potential for the analysis of various pesticides, including triadimefon and tebuconazole, thereby offering innovative approaches to the analysis of pesticide residues.

Development and Performance Evaluation of a Coffee Cherry Size Grading Machine

The coffee cherry processing industry traditionally relies on the dry method, involving harvesting, drying, and dehulling. Conventional dehulling machines with fixed drum clearances struggle to handle natural size variations, leading to inefficiencies and increased cherry breakage. To address these challenges, an innovative coffee cherry-size grading machine has been developed, utilizing an inclined oscillating sieve technique powered by a diesel engine through a belt drive. Key components include a feeding hopper, reciprocating grading sieve assembly, support frame, and power transmission system. A comprehensive performance evaluation focused on grading efficiency and capacity, exploring various operational parameters: feed rates (5, 10, 15 kg min-1), sieve angles (7˚, 9˚, 11˚), and speeds (80, 140, 200 rpm). Using a split-split-plot block design for data analysis, the study yielded promising results. Maximum grading efficiency of 88.40% was achieved at 15 kg min-1 feed rate, 8 rpm speed, and 7˚ sieve angle, with a capacity of 137.11 kg h-1 and 4.96% sieve clogging rate. ANOVA revealed significant influences of operational speed and sieve inclination angle on performance parameters. These findings offer valuable insights for optimizing coffee cherry processing, potentially enhancing efficiency and quality in the industry.

Biodiesel synthesis via heterogeneous catalysis: application of new material based on mixed oxides (Na-FeAlO) obtained from the microstructural transformation of red mud

ABSTRACT This paper investigated the application of a new material based on mixed oxides (Na-FeAlO) as a catalyst, which was synthesized from red mud (RM) and sodium carbonate and named CLV98/900, in the production of fatty acid alkyl esters (FAAE) from waste cooking oil (WCO) via transesterification reaction. The synthesized catalysts were characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD), and Fourier transform infrared spectrometer (FTIR). The characterization of the catalyst indicated that the microstructural transformation of red mud into CLV98/900 efficiently obtained new crystallographic phases. The influence of several operational parameters, such as oil/alcohol molar ratio (1/15 – 1/45), temperature (65–75°C), percentage of catalyst (0–5%) and reaction time (60–180 min), was evaluated on the yield and conversion, resulting in yield values that ranged from 2% to 74%, 25% to 67.5%, 8% to 67.5% and 2% to 74%, respectively. In parallel, the conversion values ranged from 52% to 82%, 58% to 82%, 4% to 63% and 54% to 74%, respectively. The operational parameters fixed at an oil/ethanol molar ratio of 1/30, 70°C, 1% catalyst and 60 min provide the highest yield (82%) and conversion (82%). GC-MS analysis confirmed the formation of biodiesel. Therefore, CLV98/900 shows excellent potential as a catalyst for biodiesel production via WCO transesterification.

Study on defluoridation of water by using activated carbon derived from chestnut shell as adsorbent

The present work intended to produce new cost-effective alkali-activated adsorbents from chestnut shells with the purpose of removing fluoride from water, and to explore the effect of pyrolysis temperature on fluoride decontamination at different operational and environmental parameters. The microstructure and morphological characteristics of the resulting activated carbons were thoroughly investigated using BET, FTIR, XRD and SEM. The effectiveness of the prepared adsorbent materials in treating and remediating fluorinated water was evaluated. The impacts of several factors, including the dose of the adsorbent, the initial contamination level of fluoride, and pH on the fluoride removal efficiency were investigated were investigated. In accordance with the data, the highest adsorption was found to be at a 6 pH during 5 hours of processing duration and 0.5 g/L of dosage of adsorbent. The experimental results were well-fit by the Freundlich isotherm model and the pseudo-second-order kinetic model. The highest fluoride removal efficiency was found to be 78% at adsorption medium pH 6 and initial fluoride concentration of 10mg/L by the adsorbent prepared at 800 °C. Additional research on adsorption along with rejuvenation revealed that the reduction in adsorption potential to 10% following four repetitions of operation involving regeneration, thereby showcasing the adsorbent's versatile applicability for repeated use.

Thermal-structural numerical analysis of the brake and disc system of a Formula SAE 2024 type vehicle

The results of the numerical evaluation process of the brake and disc system of a Formula SAE type vehicle in its 2024 version are presented. Through the process of evaluating fundamental equations for the brake system, the type of disc and its properties are selected. physical. Using finite element analysis based on a thermal-structural evaluation, disc operating parameters are evaluated, which in comparison with those presented by other competitors in the Formula SAE competition, show similar numbers in the performance expected by the brake system and in particular of the disc considered in the design of the vehicle.

Chromium Removal Using a Basalt Rock Adsorbent in a Packed Bed Column for Efficient Environmental Protection.

The discharge of chromium(VI) into the environment is becoming a significant global concern. Despite the existence of numerous techniques for chromium(VI) removal, substantial challenges persist in effectively mitigating this issue. Therefore, this study investigates the feasibility of using low-cost basalt rock as an adsorbent for chromium(VI) removal. The adsorbent was prepared through size reduction and activation and subsequently characterized by using X-ray diffraction and Fourier transform infrared procedures. The characterization revealed that the adsorbent predominantly consists of SiO2 and Al2O3 and contains functional groups that facilitate the adsorption mechanism. The adsorption potential of the basalt rock was initially evaluated in a batch adsorption procedure, which yielded an adsorption capacity of 14 mg/g. The batch adsorption results were best fitted by the Langmuir adsorption isotherm, with an R 2 > 0.9, indicating monolayer adsorption. Subsequently, continuous adsorption was conducted using a fixed-bed column to assess the influence of operational parameters and evaluate the desorption behavior of the adsorbent by using fixed-bed models. Breakthrough curves were utilized to assess the fixed bed performance, revealing that increased column depth and decreased flow rate extend the saturation time of the bed. The experimental data from the fixed-bed column fit the bed depth service time and Yoon-Nelson models well. The adsorbent demonstrated successful reuse across four consecutive cycles, with the regenerated basalt rock adsorbent exhibiting a chromium(VI) adsorption capacity of 2 mg/g in the fourth cycle, retaining approximately 23% of its initial adsorption capacity. The findings of this research indicate that the basalt rock-based adsorbent possesses significant potential for removing chromium(VI) from aqueous solutions in a continuous adsorption bed column.

A comparative study of double-pass recycle type hybrid photovoltaic thermal designs

ABSTRACT Photovoltaic (PV) panels play a crucial role in solar systems but are susceptible to efficiency losses caused by rising surface temperatures. This research explores four distinct recycle-type double-pass hybrid PV/T designs, employing steady-state models to cool the PV panels. The first and second designs mount the PV panel on the absorber plate, while the third and fourth designs position it directly over the absorber plate without a glass cover, allowing the sun’s radiation to fall directly on the PV module. The study investigates the significant impacts of varying values of ṁ (0.03–0.15 kg/sec), G (0.3–1.8), D (1.0–6.0), I (300–1000 W/m2), and P (0.4–0.95) on thermal and electrical efficiency, as well as net electrical power generation, taking into account pressure loss during the flow. Through the analytical study, Design-IV demonstrates the highest net electrical power, estimated at 54.82W, which is 6.27% higher than Design-III, achieved at a recycling ratio, mass flow rate, depth ratio, and packing factor of 0.9, 0.15 kg/s, 3, and 0.5, respectively. Additionally, the input parameters are optimized using the Response Surface Methodology (RSM) technique. The analysis of variance (ANOVA) reveals a significant coefficient (R2) value approaching unity, indicating a strong fit of the response model to the analyzed data. By considering both single and multi-objective optimization scenarios, the study identifies optimal parameters for each PV/T design through the interaction of operational parameters. This research contributes to enhancing the efficiency and performance of double-pass recycle-type hybrid PV/T systems, enabling sustainable and effective utilization of solar energy resources.

Discharge and Gas Parameters Optimization for Toluene Degradation in a Perpendicular Magnetic Field‐Assisted Dielectric Barrier Discharge Reactor

ABSTRACTIn this study, we employed a nanosecond‐pulsed gear‐cylinder dielectric barrier discharge (DBD) assisted by a perpendicular magnetic field (MF) for toluene degradation. The effects of key discharge and gas parameters, as well as their optimal combinations with the perpendicular MF, on toluene degradation were systematically investigated. The results indicated that the maximum toluene degradation efficiency was achieved under conditions of short pulse rising times and widths, low gas flow velocities, and minimal oxygen concentrations. This optimal performance was attributed to three main factors: high mean electron energy, the generation of appropriate active oxygen species, and an extended residence time for plasma‐toluene molecule interactions. Furthermore, by meticulously adjusting the operational parameters, augmenting the number of magnetized energetic electrons in the perpendicular MF, and intensifying the ionization process, we observed a notable enhancement in both discharge intensity and toluene degradation efficiency.

Numerical study of a three-stage metal hydride hydrogen compressor considering alloy bed deformation

ABSTRACT Metal-hydride hydrogen compressors offer a promising alternative for compressing hydrogen to high pressures. Before conducting experimental investigations, an in-depth numerical analysis is essential for designing suitable reactors, optimizing operating parameters, and evaluating performance. This work presents a comprehensive numerical model for a three-stage MHC, focusing on higher delivery pressures exceeding 300 bar with an absorption pressure of 15 bar. The model uniquely incorporates alloy bed deformation, a factor previously overlooked. It is found that the selected alloys can compress 82 L of hydrogen up to 340 bar at 363 K in 5.4 hr, achieving a productivity of 15.2 L/h. A crucial observation revealed a maximum radial variation in bed permeability of 96.9%, highlighting the importance of considering bed deformation during the sorption process. Additionally, the bed exhibited a significant 206.7% variation in the reacted fraction from the center to the periphery. To optimize MHC performance while slightly compromising the weight ratio, the study recommends limiting reactor diameters to 20–30 mm. Furthermore, the analysis of source and sink temperatures showed that sink temperature has a more substantial impact on compression performance, providing valuable insights for optimizing operating conditions to enhance MHC efficiency.

Effect of vehicle operating parameters on fuel consumption and the overall energy efficiency of the drive system

This article presents a research methodology that supplements known studies to solve the problem of a correct complementary analysis of vehicles with different drive units. This method can be used at the stage of selecting a car for specific tasks, as well as for in-service technical condition checks. A new method is proposed for analysing the impact of operating conditions on the mileage fuel consumption, unit fuel consumption and overall energy efficiency of vehicles. In the study, it was possible to determine the effect of changing the vehicle speed, road gradient angle and vehicle weight. Tests identifying fuel consumption and efficiency characteristics as a function of vehicle load were carried out using passenger cars with different drive designs. Carrying out tests under laboratory conditions on a chassis dynamometer bench enabled the precise determination of the change in operating conditions. The criteria adopted for the evaluation included fuel consumption and overall vehicle energy efficiency. The variable parameters included speed, vehicle weight, and the road gradient angle. The data for criteria calculation were acquired using a diagnostic tester with a functional parameter recording function. The application of the presented method enabled a comparison of the overall energy efficiency of two vehicles equipped with spark-ignition combustion engines, according to the criteria listed. The experiment showed that in a three-cylinder engine, unit fuel consumption is more sensitive to parameter changes under identical conditions (speed, vehicle weight, road gradient angle) than in a four-cylinder engine. To evaluate the drive units of the test vehicles, characteristics of changes in the overall energy efficiency were used as well. It was observed that in all testing variants, the value increased with increasing road gradient values, with the intensity of η increase not being constant. A car with a four-cylinder engine has a higher energy efficiency at low loads. The proposed methodology is relevant for evaluating vehicles with different drive systems (including hybrid) and adapting drive characteristics to the operating conditions. Partially the presented methodology can also be transferred to EV vehicles - in terms of energy efficiency.

Insight into the Microscopic Interactions Among Steam, Non-Condensable Gases, and Heavy Oil in Steam and Gas Push Processes: A Molecular Dynamics Simulation Study

The SAGP (steam and gas push) process is an effective enhanced oil recovery (EOR) method for heavy oil reservoirs. Understanding the microscopic interactions among steam, non-condensable gasses (NCGs), and heavy oil under reservoir conditions in SAGP processes is important for their EOR applications. In this study, molecular simulations were performed to investigate the microscopic interactions among steam, NCG, and heavy oil under reservoir conditions in SAGP processes. In addition, the microscopic EOR mechanisms during SAGP processes and the effects of operational parameters (NCG type, NCG–steam mole ratio, temperature, and pressure) were discussed. The results show that the diffusion and dissolution of CH4 molecules and the extraction of steam molecules cause the molecules of saturates with light molecular weights in the oil globules to stretch and gradually detach from one another, resulting in the swelling of heavy oil. Compared with N2, CH4 has a stronger ability to diffuse and dissolve in heavy oil, swell the heavy oil, and reduce the density and viscosity of heavy oil. For this reason, compared with cases where N2 is used, SAGP processes perform better when CH4 is used, indicating that CH4 can be used as the injected NCG in the SAGP process to improve heavy oil recovery. As the NCG–steam mole ratio and injection pressure increase, the diffusion and solubility abilities of CH4 in heavy oil increase, enabling CH4 to perform better in swelling the heavy oil and reducing the density and viscosity of heavy oil. Hence, increasing the NCG–steam mole ratio and injection pressure is helpful in improving the performance of SAGP processes in heavy oil reservoirs. However, the NCG–steam mole ratio and injection pressure should be reasonably determined based on actual field conditions because excessively high NCG–steam mole ratios and injection pressures lead to higher operation costs. Increasing the temperature is favorable for increasing the diffusion coefficient of CH4 in heavy oil, swelling heavy oil, and reducing the oil density and viscosity. However, high temperatures can result in intensified thermal motion of CH4 molecules, reduce the interaction energy between CH4 molecules and heavy oil molecules, and increase the difference in the Hildebrand solubility parameter between heavy oil and CH4–steam mixtures, which is unfavorable for the dissolution of CH4 in heavy oil. This study can help readers deeply understand the microscopic interactions among steam, NCG, and heavy oil under reservoir conditions in SAGP processes and its results can provide valuable information for the actual application of SAGP processes in enhancing heavy oil recovery.

Comprehensive analysis of tar reduction method in biomass gasification for clean energy production: A Review

Biomass gasification is a promising renewable energy technology for the production of synthetic gas (syngas), consisting of hydrogen (H₂), carbon monoxide (CO), and methane (CH₄). This technology's primary challenge is tar formation – a heavy hydrocarbon compound that can block equipment, poison catalysts, and deteriorate syngas quality. Therefore, this study aimed to examine different tar reduction methods to support clean energy production through biomass gasification. To achieve this aim, two main approaches were adopted and the first was in-situ, focusing on modifying gasifier design and adjusting operational parameters. The second was ex-situ, which included catalytic reforming, thermal cracking, and plasma technology. The analysis also assessed different catalysts, such as biochar, and dolomite, as well as nickel- and iron-based materials, comparing their efficiency, sustainability, and economic viability. Several key factors influenced tar formation and reduction, namely feedstock type, operating temperature, air ratio, and reactor configuration. The result showed that combining in-situ and ex-situ technologies had substantial potential to significantly reduce tar, improve syngas quality, and optimize system performance. However, some challenges observed were reduced catalyst efficiency, high energy costs, and the need for more sustainable technologies. To improve the performance of gasification systems, this study provided information on catalyst development, operational parameter optimization, and plasma technology integration. Finally, the analysis provided a scientific basis and strategic recommendations to overcome tar problems and encourage the commercial use of biomass gasification towards a clean energy transition.

Carbohydrate Extraction from Brown Algae using Green Technology Approach - Ultrasonic Assisted Extraction (UAE)

Over the past decade, conventional methods have been widely employed for extracting carbohydrate from brown algae, involving significant quantities of acid and alkaline chemicals, lengthy processing times, and high energy requirements. However, in line with the current global emphasis on environmental friendliness, the focus has shifted towards green technologies in the extraction process. Green technologies usually refer to non-conventional methods, with Ultrasonic-Assisted Extraction (UAE) being one of the most commonly utilized techniques. This research paper focuses on the extraction of carbohydrates from brown algae using a green technology approach, specifically UAE. Central composite design (CCD) was used in this study with different combinations of parameters such as temperature (30-60 °C), time (15-45 min) and material to solvent ratio (1:15-1:35). The best operating parameters that obtained the highest carbohydrate yield are the material-to-solvent ratio of 1:35 g/mL, extraction time of 30 min, and extraction temperature of 45 °C. The highest yield of carbohydrate obtained was 7.73 mg/g. These findings will contribute to the development of sustainable and efficient methods for carbohydrate extraction from brown algae using green technology approaches.

Research into mass stress and failure zone parameters during blasting of fractured high benches using blasthole charges

Purpose.The paper focuses on the study of the stress distribution patterns in fractured rock masses during rock breaking on high benches using blasthole explosive charges. The research aims to optimize the parameters of drilling-blasting operations through detailed analysis of stress distribution and formation of failure zones on high benches. This will significantly improve the handling equipment operating efficiency, as well as develop economically feasible blasting patterns tailored to quarry geometry. Methods. The research is based on theoretical modeling of stress propagation caused by detonating the blasthole explosive charges in fractured rock masses. The stress distribution around the charge is calculated using equations derived from elastic deformation and surface wave theory, taking into account the particular characteristics of fractured high benches. The model includes stress propagation, wave transformation, and rock fracture behavior to identify rock crushing zones. Findings. The results have revealed that the main factor of rock failure is tensile stress waves resulting from the reflection of compression waves. The degree of rock crushing and the volume of failure zones depend on the length and diameter of the blasthole explosive charge, the properties of the explosive agent, as well as the network of pre-existing fractures. Originality. A new approach to studying the stress distribution in fractured rock masses during blasting operations is presented. This paper takes into account the influence of existing fractures and the interaction of stress waves with natural disturbances in the rock, thus allowing more accurate prediction of rock crushing. For the mining conditions of the Pustynnoye Deposit, the ratios between the radii of failure zones and the value of breaking stresses have been found, and a function for determining the failure radius has been proposed. Practical implications. The results of this research can be used to optimize the parameters of blasting operations in quarries with fractured high benches. By determining the optimal sizes and placement of charges, it is possible to achieve more efficient rock crushing, reduce equipment wear and improve overall production efficiency.

Technology optimization for processing of raw materials from heterogeneous carbonate deposits

Purpose. The research is aimed at determining the qualitative and quantitative characteristics of complex limestone processing from the Oleshiv limestone deposit while calculating the energy absorption rates in the processes of processing non-metallic mineral raw materials. Methodology. The authors of the paper sampled limestone in three outcropped locations of the Oleshiv mineral deposit. The degree of limestone purity in marketable products by type of fraction is examined using an X-ray DRON-3 diffractometer. The ultimate compressive strength of limestone is determined in laboratory conditions using a specialized test press KL 200/CE-Tecnotest. Energy absorption rates are calculated based on parameters characterizing the main stages of limestone processing, including crushing, transportation and screening. Findings. The main trends in the field of limestone mining and processing have been analyzed, highlighting previously unresolved problems. On the example of processing limestone from the Oleshiv deposit, a technological scheme for its beneficiation has been developed; qualitative and quantitative parameters of the beneficiation process have been determined; the mineral composition of the fractional marketable product has been studied; the parameters of limestone compressive strength, as well as energy absorption rates in the processing processes to obtain finished products have been found. Originality. The patterns of change in the flux limestone content during its beneficiation with preliminary dry extraction of marketable fractions of 80–130, 40–80 and 20–40 mm have been revealed. The patterns of the finished product yield distribution have been identified, taking into account the movement of clay-sand raw materials in the 0–20 mm fraction and its combination with the preliminary extraction of the 0–40 mm fraction before crushing. Based on mineralogical analysis of limestone composition by fraction types, it has been found that the degree of its purity increases from 85.54 to 94.0 %. The energy absorption rates during limestone processing have been determined, taking into account the physical-mechanical properties of the mineral and the parameters of equipment operation. Practical value. A technological scheme for the beneficiation of limestone from the Oleshiv deposit has been developed, which allows for the production of seven fractions of limestone and one fraction of clay-sand raw materials. This scheme is optimized to maximize the extraction of the useful component, while ensuring high quality of the final product. The dynamics of energy absorption during limestone crushing, transportation, and screening has been determined, which makes it important to develop further recommendations for optimizing energy consumption in crushing processes.

PARAMETERS OF HOT WATER SUPPLY HEAT EXCHANGERS FOR HEAT STATIONS OF INSULATED BUILDINGS AT ONE-STAGE CONNECTION SCHEME

The peculiarities of functioning of centralized heat supply systems of residential microdistricts at carrying out works on ‘insulation’ of buildings in operation, namely, parameters of operation of hot water supply heating units are considered. The influence of the heating load reduction due to the works on increasing the heat transfer resistance of the building structures on the flow rate of network water and heat exchange area of hot water supply heaters has been analyzed. Estimates are made for conditions of use of one-stage parallel scheme connection for heat exchangers to heat distribution networks. The known relations for such most widespread in heat supply systems heat exchangers as plate apparatuses are used at calculations of a heat transfer surface. The range of change of the heat transfer surface of hot water heaters and the flow rate of network water depending on the ratio of the maximum heat loads of hot water supply and heating and the degree of insulation efficiency of the building is determined. Formulas for determining the parameters of hot water supply heat exchangers are proposed. The formulas are valid in the range of reduction of heat consumption for heating of the building from 0 to 35 %. Assessment of the heating load reduction is performed on condition that the thermal modernization of a building constructed in accordance with the building requirements in force several decades ago provides modern requirements for the thermal resistance of building structures. The temperature of water in the heating system of the insulated building is determined depending on the building insulation efficiency, provided that the water flow rate through the heating system of the building before and after its insulation is unchanged. The range of variation of the ratio of hot water supply and heating heat loads accepted for consideration is 0,6–1,2. The obtained results can be used at comparison of connection schemes of heat exchangers for hot water heating for installation on individual heat points of insulated buildings.