Search Results (190)

To address the limitations of traditional hardened concrete road surfaces in coal mine tunnels, which are prone to damage and entail high maintenance costs, this study proposes using modular concrete blocks composed of fly ash and coal gangue as an alternative to conventional materials. These blocks offer advantages including ease of construction and rapid, straightforward maintenance, while also facilitating the reuse of substantial quantities of solid waste, thereby mitigating resource wastage and environmental pollution. Initially, the mineral composition of the raw materials was analyzed, confirming that although the physical and chemical properties of Liangshui Well coal gangue are slightly inferior to those of natural crushed stone, they still meet the criteria for use as concrete aggregate. For concrete blocks incorporating 20% fly ash, the steam curing process was optimized with a recommended static curing period of 16–24 h, a temperature ramp-up rate of 20 °C/h, and a constant temperature of 50 °C maintained for 24 h to ensure optimal performance. Orthogonal experimental analysis revealed that fly ash content exerted the greatest influence on the compressive strength of concrete, followed by the additional water content, whereas the aggregate particle size had a comparatively minor effect. The optimal mix proportion was identified as 20% fly ash content, a maximum aggregate size of 20 mm, and an additional water content of 70%. Performance testing indicated that the fabricated blocks exhibited a compressive strength of 32.1 MPa and a tensile strength of 2.93 MPa, with strong resistance to hydrolysis and sulfate attack, rendering them suitable for deployment in weakly alkaline underground environments. Considering the site-specific conditions of the Liangshuijing coal mine, ANSYS 2020 was employed to simulate and analyze the mechanical behavior of the blocks under varying loads, thicknesses, and dynamic conditions. The findings suggest that hexagonal coal gangue blocks with a side length of 20 cm and a thickness of 16 cm meet the structural requirements of most underground mine tunnels, offering a reference model for cost-effective paving and efficient roadway maintenance in coal mines. Full article

District heating systems in northern China predominantly rely on coal-fired heat sources, necessitating sustainable alternatives to reduce carbon emissions. This study investigates a biomass combined heat and power (CHP) system integrated with cascaded absorption heat pump (AHP) technology to recover waste heat from semi-dry flue gas desulfurization exhaust and turbine condenser cooling water. A multi-source operational framework is developed, coordinating biomass CHP units with coal-fired boilers for peak-load regulation. The proposed system employs a two-stage heat recovery methodology: preliminary sensible heat extraction from non-saturated flue gas (elevating primary heating loop (PHL) return water from 50 °C to 55 °C), followed by serial AHPs utilizing turbine extraction steam to upgrade waste heat from circulating cooling water (further heating PHL water to 85 °C). Parametric analyses demonstrate that the cascaded AHP system reduces turbine steam extraction by 4.4 to 8.8 t/h compared to conventional steam-driven heating, enabling 3235 MWh of annual additional power generation. Environmental benefits include an annual CO₂ reduction of 1821 tonnes, calculated using regional grid emission factors. The integration of waste heat recovery and multi-source coordination achieves synergistic improvements in energy efficiency and operational flexibility, advancing low-carbon transitions in district heating systems. Full article

The critical consequence of climate change resulting from global warming is the increase in temperature. In combined cycle power plants (CCPPs), the Electric Power Output (PE) is affected by changes in both Ambient Temperature (AT) and Sea Surface Temperature (SST), particularly in plants utilizing seawater cooling systems. As AT increases, air density decreases, leading to a reduction in the mass of air absorbed by the gas turbine. This change alters the fuel–air mixture in the combustion chamber, resulting in decreased turbine power. Similarly, as SST increases, cooling efficiency declines, causing a loss of vacuum in the condenser. A lower vacuum reduces the steam expansion ratio, thereby decreasing the Steam Turbine Power Output. In this study, the effects of increases in these two parameters (AT and SST) due to global warming on the PE of CCPPs are investigated using various regression analysis techniques, Artificial Neural Networks (ANNs) and a hybrid model. The target variables are condenser vacuum (V), Steam Turbine Power Output (ST Power Output), and PE. The relationship of V with three input variables—SST, AT, and ST Power Output—was examined. ST Power Output was analyzed with four input variables: V, SST, AT, and relative humidity (RH). PE was analyzed with five input variables: V, SST, AT, RH, and atmospheric pressure (AP) using regression methods on an hourly basis. These models were compared based on the Coefficient of Determination (R²), Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE), Mean Square Error (MSE), and Root Mean Square Error (RMSE). The best results for V, ST Power Output, and PE were obtained using the hybrid (LightGBM + DNN) model, with MAE values of 0.00051, 1.0490, and 2.1942, respectively. As a result, a 1 °C increase in AT leads to a decrease of 4.04681 MWh in the total electricity production of the plant. Furthermore, it was determined that a 1 °C increase in SST leads to a vacuum loss of up to 0.001836 bar_a. Due to this vacuum loss, the steam turbine experiences a power loss of 0.6426 MWh. Considering other associated losses (such as generator efficiency loss due to cooling), the decreases in ST Power Output and PE are calculated as 0.7269 MWh and 0.7642 MWh, respectively. Consequently, the combined effect of a 1 °C increase in both AT and SST results in a 4.8110 MWh production loss in the CCPP. As a result of a 1 °C increase in both AT and SST due to global warming, if the lost energy is to be compensated by an average-efficiency natural gas power plant, an imported coal power plant, or a lignite power plant, then an additional 610 tCO₂e, 11,184 tCO₂e, and 19,913 tCO₂e of greenhouse gases, respectively, would be released into the atmosphere. Full article

Global trends in environmental protection place emphasis on the reduction of CO₂ emissions, a key factor in the greenhouse effect. Commercial power generation, mainly based on coal, is the largest emitter of CO₂, which justifies work on its reduction. Technologies involving CO₂ capture from flue gases based on adsorption methods are not yet widely used, and therefore, there is a lack of complete data on their impact on power units. With the use of computer simulations, relevant information can be obtained, eliminating the need for costly tests on actual systems. A model of a reference power unit and CO₂ separation system based on adsorption methods was developed in the IPSEpro environment. Simulations were carried out, analysing the impact of parameters such as temperature and pressure of the flue gas and of bled steam on the efficiency of the separation system. Optimal adsorption and desorption conditions were determined, and the separation model was then integrated into a power unit. The analysis of CO₂ capture in power units indicates that while complete separation of CO₂ from the flue gas of an 830 MWe unit is technically feasible, it results in substantial efficiency losses and high energy consumption. Capturing and liquefying CO₂ leads to a power output reduction of approximately 358 MWe and a 15.4% decrease in efficiency. Simulation analyses allowed the impact of the CO₂ capture system on the operation of the unit to be assessed and the amount of non-emitted gas to be estimated, thus reducing the environmental harm of the power plant. Full article

Carbon capture, utilization, and storage (CCUS) is a key technology for decarbonizing existing or newly designed fossil fuel power plants, which in the short to medium term remains essential to offset the variability of nonprogrammable renewable sources in power generation. In this paper, the authors focus on the CO₂ compression phase of CCUS systems, integrated with power plants, and propose, according to the technical literature, a plant layout aimed at minimizing energy consumption; then, they carry out the preliminary design of all compressors, identifying compact and efficient configurations. The case study concerns an advanced ultra-supercritical steam plant (RDK8 Rheinhafen-Dampfkraftwerk in Karlsruhe, Germany) with a nominal net thermal efficiency of 47.5% and an electrical output of 919 MW. The main results obtained can be summarized as follows. The overall compression in the IGC configuration requires only six stages and each compressor is single-stage, while in the inline configuration, ten stages are needed; the diameters in the IGC solution, also due to a higher rotational speed, are smaller, despite the in-line solution being multistage. An interesting further investigation could be related to modifications of the plant scheme, especially to test whether CO₂ liquefaction at an intermediate stage of compression could result in reductions in energy consumption, as well as even more compact design solutions. Full article

To reduce greenhouse gas (GHG) emissions, decarbonize coal, and also create a circular economy model, solid recovered fuel (SRF) has been developed as an alternative fuel/energy source in the international community, especially in developed countries with a high dependence on imported energy. This mini review offers updates on the regulatory promotion of the production of SRF, focusing on the reuse of biomass or lignocellulosic waste as a starting material in Japan, South Korea, and Taiwan. In this regard, the status of renewable energy and the policies for bioenergy in Japan, South, and Taiwan are first addressed in this work. It is found that the terms for defining refuse/waste/biomass-derived fuel are different across East Asia. However, SRF is increasingly used for the substitution of fossil fuels in industrial utilities (including boilers, incinerators, and kilns), as well as for steam (heat) utilization and/or power generation. With the international policies of pursuing staged carbon reduction by 2030 and carbon neutrality by 2050, the regulatory promotion of the use of bio-SRF has been actively adopted by these countries or regions. Regarding the quality requirements of SRF and concerns about air pollutant emissions, this work also offers updates on regulatory standards, especially in Taiwan. Finally, prospects for the production of bio-SRF and concerns regarding its use are addressed to support the development of a sustainable and circular society. Full article

The prolonged operation of thermal power plants inevitably leads to component aging and a gradual decline in performance. This deterioration increases the gross heat rate and reduces electrical output, resulting in higher fuel consumption and lower electricity production. Consequently, these issues can cause significant financial losses and threaten the plant’s competitiveness. This paper presents a comprehensive methodology for improving the performance of existing plants. The methodology consists of two crucial elements: steam turbine testing and numerical simulation of the process. The tests should be comprehensive to ensure accurate measurements and reliable conclusions. The developed method for process simulation enables the calculation of overall performance, like specific heat rate and thermal efficiency, as well as the performance of individual components under various operational conditions. Comparing numerical results with experimental data can effectively identify operational problems. Based on these findings, targeted overhauls and other corrective measures can substantially improve the plant’s thermal efficiency and financial performance. The system was demonstrated through a case study of a 120 MW coal-fired steam turbine. The test revealed that it consumes more than 10% additional heat compared to its original design specifications. The analysis identified operational issues and recommended improvement measures, focusing exclusively on the steam turbine set while excluding the boiler. Full article

In coal chemical industries, the optimal allocation of gas and steam is crucial for enhancing production efficiency and maximizing economic returns. This paper proposes an optimal scheduling method using operating zone models and entropy weights for an energy system in a gas-to-methanol process. The first step is to develop mechanistic models for the main facilities in methanol production, namely desulfurization, air separation, syngas compressors, and steam boilers. A genetic algorithm is employed to estimate the unknown parameters of the models. These models are grounded in physical mechanisms such as energy conservation, mass conservation, and thermodynamic laws. A multi-objective optimization problem is formulated, with the objectives of minimizing gas loss, steam loss, and operating costs. The required operating constraints include equipment capacities, energy balance, and energy coupling relationships. The entropy weights are then employed to convert this problem into a single-objective optimization problem. The second step is to solve the optimization problem based on an operating zone model, which describes a high-dimensional geometric space consisting of all steady-state data points that satisfy the operation constraints. By projecting the operating zone model on the decision variable plane, an optimal scheduling solution is obtained in a visual manner with contour lines and auxiliary lines. Case studies based on Aspen Hysys are used to support and validate the effectiveness of the proposed method. Full article

In order to deeply absorb the power generation of new energy, coal-fired circulating fluidized bed units are widely required to participate in power grid dispatching. However, the combustion system of the units faces problems such as decreased control performance, strong coupling of controlled signals, and multiple interferences in measurement signals during flexible operation. To this end, this paper proposes a model predictive control (MPC) scheme based on the extended state Kalman filter (ESKF). This scheme optimizes the MPC control framework. The ESKF is used to filter the collected output signals and jointly estimate the state and disturbance quantities in real time, thus promptly establishing a prediction model that reflects the true state of the system. Subsequently, taking the minimum output signal deviation of the main steam pressure and bed temperature and the control signal increment as objectives, a coordinated receding horizon optimization is carried out to obtain the optimal control signal of the control system within each control cycle. Tracking, anti-interference, and robustness experiments were designed to compare the control effects of ESKF-MPC, ID-PI, ID-LADRC, and MPC. The research results show that, when the system parameters had a ±30% perturbation, the adjustment time range of the main steam pressure and bed temperature loops of this method were 770~1600 s and 460~1100 s, respectively, and the ITAE indicator ranges were 0.615 × 10⁵~1.74 × 10⁵ and 3.9 × 10⁶~6.75 × 10⁶, respectively. The overall indicator values were smaller and more concentrated, and the robustness was stronger. In addition, the test results of the actual continuous variable condition process of the unit show that, compared with the PI strategy, after adopting the ESKF-MPC strategy, the overshoot of the main steam pressure loop of the combustion system was small, and the output signal was stable; the fluctuation range of the bed temperature loop was small, and the signal tracking was smooth; the overall control performance of the system was significantly improved. Full article

The story of the rise of “energy” usually centers on the Industrial Revolution and the coal-powered steam engine in nineteenth-century Western Europe. Although it often escapes notice, the Caribbean was actually the site of the first known use of a steam engine to power industrial manufacturing (on a sugar plantation) and the world’s first oil well (drilled by a US company in southern Trinidad). These “firsts” point toward energy’s roots in colonial and imperial projects of extraction in the Caribbean, revealing the centrality of race and the plantation in understanding energy capitalism and the current climate crisis. This article traces a Caribbean-attuned genealogy of “energy”. Today, energy is taken for granted as an abstract universal, but the concept was bound to specific forms of racial governance during the transition from sugar to fossil fuels as apex capitalist commodities. In tracing this genealogy, I rewrite the first two “laws of energy” as ethico-political statements on racial governance rather than descriptions of a pre-existing natural order. Adding to scholarship that has laid bare the relationship between biological sciences and race, I argue that energy sciences have also been central to sustaining (while occluding) racialized hierarchy. I then look at conceptions of energy in perhaps the world’s oldest petro-state (Trinidad, with brief comparisons to neighboring Venezuela) to elaborate Caribbean-attuned, speculative alternatives to the “laws of energy”. Full article

In this study, the mechanisms of SO₂ adsorption on lignite char and char-supported Fe-Zn-Cu sorbent (FZC sorbent) were investigated. The FZC sorbent was prepared by the impregnation of metal components on raw coal followed by steam gasification. Flue gas desulfurization experiments were carried out on a fixed-bed reactor at 100–300 °C by using simulated flue gas containing SO₂/O₂/H₂O balanced by N₂. The flue gas composition was monitored by using an online flue gas analyzer. The solid samples before and after desulfurization were analyzed by using X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Thermogravimetric Analysis–Mass Spectroscopy (TG-MS), and Brunauer–Emmett–Teller (BET) surface area analysis. The experimental results showed that both lignite char and the FZC sorbent can effectively adsorb SO₂ under the present experimental conditions. The presence of O₂ and H₂O in the flue gas promoted the adsorption of SO₂ on the FZC sorbent. The SO₂ adsorption capacity of the FZC sorbent increased with the increase in the temperature up to 250 °C. When the temperature was further increased to 300 °C, the SO₂ adsorption capacity of the sorbents decreased rapidly. Under optimum experimental conditions with a space velocity of 1500 h⁻¹, a desulfurization temperature of 250 °C, and 5% (vol) O₂ and 10% (vol) H₂O in the flue gas, the sorbents exhibited the longest breakthrough time of 280 min and breakthrough SO₂ adsorption capacity of about 2200 mg (SO₂) per gram sorbent. Full article

Biomass tar, an inevitable byproduct of biomass pyrolysis and gasification, poses a significant challenge due to its tendency to condense in pipelines, causing clogging and operational issues. Catalytic steam reforming can convert tar into syngas, addressing the tar issue while simultaneously producing hydrogen. However, the reforming catalyst is highly susceptible to deactivation by coking, especially when dealing with highly concentrated polymeric hydrocarbons such as tar. This study focused on enhancing the durability of tar-reforming catalysts. Nickel-based catalysts were prepared using carbon supports known for their high coking resistance, such as carbon black (CB), activated carbon (AC), and low-rank coal (LRC). Their performance was then tested for the steam reforming of high-concentration toluene, a representative tar. All three carbon supports (CB, AC, LRC) showed high catalytic performance with NiMg catalysts at 500 °C. Among them, the mesoporous CB support exhibited the highest stability when exposed to steam, with NiMg on CB (NiMg/CB) remaining stable for long-term continuous operation without any deactivation due to coking or thermal degradation. Full article

Addressing the complex physicochemical properties of coal gangue from typical mining areas in Inner Mongolia, this study focuses on this area’s abundant reserves coupled with the low utilization rate and significant strength variability of ecological slope protection materials. Notably, research on the alkalization–carbonization of coal gangue remains scarce. To bridge this gap, we propose a method leveraging the moisture migration behavior of coal gangue porous media. By utilizing continuous displacement high-temperature steam carbon sequestration enhancement technology, internal moisture is gradually and precisely controlled to induce the formation of high-temperature carbonic acid gas. This process facilitates internal carbon sequestration and effectively locks in the sequestration effect. This approach enables effective loading of sulfurized CO₂ composite gases in a reversible manner, achieving passive carbon sequestration driven by moisture migration. Consequently, it enhances the negative carbon content within the aggregates while bolstering their mechanical properties. After alkalization pretreatment with various concentrations and three hours of carbon sequestration, the microhardness of the aggregate surface and transition zone were observed to have increased by 24.3% and 36.4%, respectively. Additionally, the compressive and splitting tensile strengths of coal gangue concrete rose by 4.8 MPa and 0.4 MPa, respectively, while porosity decreased by up to 3.6%, and the proportion of harmful pores dropped from 11.22% to 6.54%. A strong correlation between the proportion of harmless/low-harm pores and strength development was observed. Overall, the high-temperature carbonic acid steam displacement method with sulfurized CO₂ composite gases effectively improves the physicochemical properties of coal gangue aggregates and enhances surface activity and hydration in the interface transition zone, meeting the engineering standards for in situ ecological remediation in Inner Mongolia’s mining areas. Full article

The Paris Agreement emphasizes the need to reduce greenhouse gas emissions, particularly from coal power. One suggested approach is repowering coal-fired power plants (CPPs) with small modular reactors (SMRs). South Korea plans to retire CPPs in the coming decades and requires alternative options for coal-fired energy. This study presents a scoping analysis comparing variable renewable energy (VRE) sources with SMRs for repowering CPPs in the Korean context. The analysis indicates that SMRs may be a more favorable option than VRE sources, particularly due to their load-following capabilities. In this study, two types of SMRs were investigated: high-temperature gas reactors (HTGRs) and pressurized water reactors (PWRs). HTGRs are suitable to fit the high-temperature operating conditions of steam turbines but require multiple units due to their low volumetric flow rates. PWRs, while matching the volumetric flow rate of existing CPP turbines, require additional thermal energy sources to meet the high-temperature operating conditions of steam turbines. Lastly, an analysis of necessary regulatory and legislative changes in South Korea’s nuclear framework is presented, identifying several key regulatory issues for repowering coal with nuclear energy. Full article

In the vicinity of the Adamów power plant, which operates in the catchment area of the Kiełbaska river, there is a significant shortage of water resources caused by the intensive use of water by the energy industry and agriculture. The development of the plant by replacing the outdated coal-fired (lignite-fired) units with modern gas and steam units may contribute significantly to reducing the negative impact on the environment and reduce the demand for water resources relative to coal technology. Gas and steam units are a much more energy-efficient technology. This implies a lower demand for water, a reduction in pollutant emissions, and greater operational flexibility, which enables the units to adapt to changing hydrological and environmental conditions. The high efficiency of these units limits the need for frequent water-refilling, while allowing for a more sustainable and stable production of energy. Based on an analysis of hydrological data for the years 2019–2023, it was estimated that water stress is observed in this catchment area on 198 days per year, which accounts for c.a. 54% of the hydrological year. Therefore, it is assumed that inter-catchment pumping stations with a flow of 0.347 m³∙s⁻¹ will be required. This sets the demand for water at 5.95 million m³ per year. The planned water transfer will be carried out from Jeziorsko reservoir on the Warta river through the catchment area of Teleszyna river. Moreover, there are plans for the reconstruction of the layout of Kiełbaska Duża and Teleszyna rivers, which would involve the restoration of natural run-offs, following the discontinuation of open-pit lignite mining. This will additionally be supported by the reduced demand for water in the water use system when using the modernised power plant. The analysed data made it possible to develop hydrological scenarios that take the future reduction in water stress into account by implementing plans to restore the former hydrographic system in the region. These investments would also foresee the creation of new retention reservoirs (in former mining pits) with a capacity of nearly 900 million m³, which will significantly increase the region’s water resources and retention potential, supporting hydrological and energy security for the years to come. Full article