Witold Kawalec

Efficient material handling is critical for mining productivity, safety energy and cost control. This paper analyzes the energy efficiency of five alternative designs for a 3 km inclined underground conveyor system for copper ore transport, considering route geometry, belt specifications, drive configurations, and operational parameters. Two main design approaches were examined: a single long conveyor and two shorter conveyors. Variants differed in belt tensile strength, the use of intermediate drives, and system layout. Calculations results achieved by using dedicated QNK-TT software (version 4.45.21.08.10.18.11) show differences in the specific energy consumption index between variants for both average and peak capacities and highlight that high-capacity performance requires non-standard solutions: either higher belt strength or an intermediate drive system. The study shows that conveyor energy efficiency depends strongly on load level, with near-maximum throughput yielding the best performance. The authors conclude that conveyor system component selection should be based on a multi-criteria evaluation—including the capacity margin, operational safety and maintenance complexity—rather than energy efficiency alone.

Efficient material handling is critical for mining productivity, safety energy and cost control. This paper analyzes the energy efficiency of five alternative designs for a 3 km inclined underground conveyor system for copper ore transport, considering route geometry, belt specifications, drive configurations, and operational parameters. Two main design approaches were examined: a single long conveyor and two shorter conveyors. Variants differed in belt tensile strength, use of intermediate drives, and system layout. Calculations results achieved by using dedicated QNK-TT software show differences in specific energy consumption index between variants for both average and peak capacities and highlight that high-capacity performance requires non-standard solutions: either higher belt strength or an intermediate drive system. The study shows that conveyor energy efficiency depends strongly on load level, with near-maximum throughput yielding the best performance. The authors conclude that conveyor system components selection should be based on a multi-criteria evaluation—including capacity margin, operational safety and maintenance complexity — rather than energy efficiency alone.

The “carbon neutral power generation” policy of the European Union requires the phasing out of fossil fuel power plants. These plants still play a crucial role in the energy mix in many countries; therefore, efforts are put forward to lower their CO₂ emissions. The available solution for an existing coal plant is the implementation of biomass co-firing, which allows it to reduce twice its carbon footprint in order to achieve the level of natural gas plants, which are preferable on the way to zero-emission power generation. However the side effect is a significant increase in the bulk fuel volumes that are acquired, handled, and finally supplied to the power plant units. A necessary extension of the complex logistic system for unloading, quality tagging, storing, and transporting biomass may increase the plant’s noise emissions beyond the allowed thresholds. For a comprehensive assessment of the concept of expanding the power plant’s biofuel supply system (BSS), a discrete simulation model was built to dimension system elements and verify the overall correctness of the proposed solutions. Then, a dedicated noise emission model was built for the purposes of mandatory environmental impact assessment procedures for the planned expansion of the BSS. The noise model showed the possibility of exceeding the permissible noise levels at night in selected locations. The new simulations of the BSS model were used to analyze various scenarios of biomass supply with regard to alternative switching off the selected branches of the whole BSS. The length of the queue of unloaded freight trains delivering an average quality biomass after a period of 2 weeks is used as a key performance parameter of the BSS. A queue shorter than 1 freight train is accepted. Assuming the rising share of RESS in the Polish energy mix, the thermal plant’s 2-week average power output shall not exceed 70% of its maximum capacity. The results of the simulations indicate that under these constraints, the biofuel supplies can be sufficient regardless of the nighttime stops, if 50% of the supplied biomass volumes are delivered by trucks. If the trucks’ share drops to 25%, the plant’s 2-week average power output is limited to 45% of its maximum power. The use of digital spatial simulation models for a complex, cyclical-continuous transport system to control its operation is an effective method of addressing environmental conflicts at the design stage of the extension of industrial installations in urbanized areas.

One of the methods to lower CO2 emissions from an existing coal plant is the implementation of biomass co-firing. Thus the carbon emission level of gas-fired power plants (550 kg/MWh) can be achieved. The result is a significant increase of the fuel volumes that are acquired, handled and finally supplied to the power plant units. A necessary extension of a complex logistic system for transporting biomass may increase noise emissions. Environmental regulations require to analyze the impact of this expansion on possible exceedance of the allowed noise thresholds. For a comprehensive assessment of the concept of expanding the power plant's biofuel supply system (BSS), a digital simulation model was built to dimension system elements and verify its correctness of the proposed solutions. Then, a dedicated noise emission model was built for the purposes of mandatory environmental impact assessment procedures for the planned expansion of the BSS, which showed the possibility of exceeding the permissible noise levels at night in selected locations. The article presents the results of a simulation analysis of the efficiency of the BSS in a power plant located in an urbanized environment, taking into account optional shutdowns of facilities generating too much noise at night. The results of the simulation indicate the possibility of securing fuel supplies also under strict restrictions. The use of digital, spatial simulation models of a complex, cyclical-continuous transport system to control its operation in conditions of constraints is an effective method of solving environmental conflicts at the design stage of the extension of industrial installations in urbanized areas.

The increasing use of renewable energy sources, such as wind and solar energy, presents challenges to the stability and efficiency of other energy sources due to their intermittent and unpredictable surpluses. The unintended consequence of stabilizing the power supply system is an increase in emissions and external costs from the suboptimal use of coal power plants. The rising number of RES curtailments needs to be addressed by either the adjusting energy supply from fossil fuel or the flexible energy consumption. In Poland’s energy mix, coal-fired power plants are a critical component in ensuring energy security for the foreseeable future. Using domestic lignite to generate a total power of 8.5 GW can stabilize the national power supply, as it is currently done in Germany, where 15 GW of lignite-fueled power units provide the power supply base for the country. The leading Belchatów power plant comprises 10 retrofitted units and one new unit, with a total rating of 5.5 GW. Access to the new coal deposit, Zloczew, is necessary to ensure its longer operation. The other domestic lignite power plants are located in Central Poland at Patnów (0.47 GW from the new unit and 0.6 GW from its three retrofitted counterparts) and located in the Lusatian lignite basin at Turów (operating a brand new unit rated at 0.5 GW and retrofitted units with a total rating of 1.5 GW). The use of this fuel is currently being penalized as a result of increasing carbon costs. However, the continuous surface mining technology that is used in lignite mines is fully electrified, and large amounts of electric energy are required to remove and dump overburden and mining coal and its conveying to power units (the transport of coal from the new lignite mine Zloczew to the Belchatów power plant would be a long-distance operation). A possible solution to this problem is to focus on the lignite fuel supply operations of these power plants, with extensive simulations of the entire supply chain. A modern lignite mine is operated by one control room, and it can balance the dynamic consumption of surplus renewable energy sources (RESs) and reduce the need for reduction. When a lignite supply chain is operated this way, a high-capacity power bank can be created with energy storage in the form of an open brown coal seam. This would enable an almost emission-free supply of cheap and domestic fossil fuel, making it insensitive to changes in the world prices of energy resources for power units operating at the base of the system. Furthermore, extending the life of relatively new and efficient lignite-fired units in Poland would facilitate the decommissioning of older and exhausted hard coal-fired units.

Scientific and technical issues related to the extraction and processing of raw materials are inextricably linked with environmental concerns. The extraction, transportation and processing of raw materials and the creation of new products place a heavy burden on the environment. Therefore, the development of new technologies for the extraction and processing of raw materials which meet the demand for specific products while respecting environmental resources and saving energy can be considered one of the key challenges of modern science. The development of methods to optimize the course of certain processes related to the raw materials industry, limiting its impact on the environment, and the use of modern measurement techniques or modeling are key areas of research and development for the economy. The aim of this Special Issue was to identify certain important issues, including those related to the raw materials industry and the optimization of its processes, obtaining energy from alternative fuels and research on environmental aspects of industrial activities. The results of the research and analyses presented in the articles show that meeting the objectives in the context of sustainable raw materials industry requires: the optimization of the use of mine deposits and the recovery of materials, reductions in energy consumption, minimizations in emissions of pollutants, the perfection of quieter and safer processes and the facilitation of the recovery of materials-, water- and energy-related modern techniques and technologies.

Exploitation of lignite in continuous surface mines requires removing masses of overburden, which are hauled to a dumpsite. There are some technological arrangements where the overburden is transported several dozen meters down to a spreader operating on a lower located dumping level. Depending on an angle of a declined transportation route, there is a possibility to convert the potential gravitational energy of conveyed down overburden masses into electric energy. To recover the maximum percentage of stored energy, an energy-effective and fully loaded belt conveyor should work in a generator mode. Due to the implementation of such a solution, a lignite continuous surface mine, which is a great electric energy consumer, can obtain the status of an electricity prosumer and reduce its environmental impact, in particular demonstrating significant savings in primary energy consumption. Though lignite surface mining is phasing out in Europe, the recuperative, overburden conveyors for downhill transport match up the targets of sustainable mining, understood as getting the maximum benefits from the exploited natural resources. According to the analyzed case study, an investment into the installation of regenerative inverters for the electric power supply of the declined overburden conveyor would pay off within 3–4 years.

The mining industry is facing sustainable development challenges, among which the energy efficiency issues seem to be of major importance. As transport of the mined ore is considered as one of the most energy intensive operations, the improvement of its energy efficiency is a key indicator in terms of sustainable actions taken by mining companies. In open-pit mines, the material handling operations are mostly performed with trucks. Their electrified version—truck trolley systems—surpass diesel trucks’ efficiency while comparing the increased production capacity and the reduction of maintenance cost and fuel consumption. The paper analyzes the opportunities and benefits of the replacement of an ore transport system based on hauling trucks with a regenerative belt conveying in an open-pit mine. Presented case study has been analyzed from energy consumption and environmental impact reduction perspectives. Generally, conception of a regenerative conveyor is based on recuperation of energy or continuous braking needed while a conveyor is running downhill. Energy generated during the braking process (converted from the potential gravitational energy of the conveyed material) is fed back to the electrical grid. Then the regenerative conveyor can be considered as a machine that mines energy as an additional by-product of an exploited deposit. It was shown that difference in transportation cost between haul trucks and energy efficient regenerative conveyors is around 95%. The paper points the conditioning elements to allow the implementation of a regenerative belt conveyor system.

Belt conveyor (BC) transportation systems are considered to be the most effective for handling large volumes of bulk material. With regards to the rules of sustainable development, the improvement of belt conveyor technology is, in many cases, focused on environmental issues, which include the idea of energy usage optimization. The key issue in an energy-efficient transportation system is reducing the value of specific energy consumption (SEC) by increasing conveyor capacity whilst decreasing belt conveyor motion resistance. The main idea of this paper is to conduct an analysis of the modernization of existing belt conveyor transportation systems operated in open-pit lignite mines, in order to achieve relatively small electric energy consumption for a considered transportation task. The first part of the paper investigates the relationship between a conveyor’s SEC and material flow rate for various conveyor design parameters. Then, based on multi-parameter simulations, an analysis of electric energy consumption for a belt conveyor transportation system is carried out. Finally, an energy-saving, environmentally friendly solution is presented.