Search Results (125)

Solid fuels are still widely used in household heating in Europe and North America. Emissions from boilers are released in proximity to people. Therefore, there is a need to minimise the toxicity of emissions affecting human health to the greatest extent possible. This study compares the genotoxic potential of the emissions of four boilers of modern and old design (automatic, gasification, down-draft, over-fire) operating at reduced output to simulate the real-life combustion fed by various fossil and renewable solid fuels (hard coal, brown coal, brown coal briquettes, wood pellets, wet and dry spruce). Organic emissions were tested for genotoxic potential by analysing bulky DNA adducts and 8-oxo-dG adduct induction. There was no consistent genotoxic pattern among the fuels used within the boilers. Genotoxicity was strongly correlated with polycyclic aromatic hydrocarbon (PAH) content, and even stronger correlation was observed with particulate matter (PM). In all measured variables (PM, PAHs, genotoxicity), the technology of the boilers was a more important factor in determining the genotoxic potential than the fuels burned. The highest levels of both bulky and 8-oxo-dG DNA adducts were induced by organics originating from the over-fire boiler, while the automatic boiler exhibited genotoxic potential that was ~1000- and 100-fold lower, respectively. Full article

Shifting towards electrified industrial energy systems is pivotal for meeting global decarbonization objectives, especially since process heat is a significant contributor to greenhouse gas emissions in the industrial sector. This review examines the changing role of heat exchanger networks (HENs) within electrified process industries, where electricity-driven technologies, including electric heaters, steam boilers, heat pumps, mechanical vapour recompression, and organic Rankine cycles, are increasingly supplanting traditional fossil-fuel-based utilities. The analysis identifies key challenges associated with multi-utility integration, multi-pinch configurations, and low-grade heat utilisation that influence HEN design, retrofitting, and optimisation efforts. A comparative evaluation of various methodological frameworks, including mathematical programming, insights-based methods, and hybrid approaches, is presented, highlighting their relevance to the specific constraints and opportunities of electrified systems. Case studies from the chemicals, food processing, and cement sectors demonstrate the practicality and advantages of employing electrified heat exchanger networks (HENs), particularly in terms of energy efficiency, emissions reduction, and enhanced operational flexibility. The review concludes that effective strategies for the design of HENs are crucial in industrial electrification, facilitating increases in efficiency, reductions in emissions, and improvements in economic feasibility, especially when they are integrated with renewable energy sources and advanced control systems. Future initiatives must focus on harmonising technical advances with system-level resilience and economic sustainability considerations. Full article

The combustion of fossil fuels is a major source of greenhouse gas emissions, drives climate change, and has intensified the search for cleaner energy alternatives such as biomass. Biomass derived from renewable organic materials, is considered a sustainable and carbon-neutral energy source. While biomass represents a renewable and clean energy source, its combustion, especially in pellet form, can produce various pollutants such as CO₂, SO₂, NO₂, CO, and PM. This study focuses on analyzing the combustion of six different pellet brands and the emissions they produce. A dedicated experimental procedure was designed and implemented to evaluate the combustion performance. The temperature shows a gradual increase in ambient temperature around 2.5 °C across all tests, with a similar behavior, the temperature of flue gas shows a similar behavior between tests with temperatures peaking around 300 °C and 340 °C. In the tests conducted, all pellets complied with the legal emission limits defined by legislation. The efficiency calculated using the direct method was lower by around 55%, primarily due to the use of an older boiler (manufactured in 2004) and short duration of the test. The indirect method shows better efficiency, around 70%, influenced by lower moisture content of the pellets. The results indicate that B pellets had a superior performance compared to the others evaluated. Full article

This article examines the energy efficiency and climate impact of various heating methods commonly employed across industrial sectors. Fossil fuel combustion heat sources, which are predominantly employed for industrial heating, contribute significantly to atmospheric pollution and associated asset losses. The electrification of industrial heating has the potential to substantially reduce the total energy consumed in industrial heating processes and significantly mitigate the rate of global warming. Advances in electrical heating technologies are driven by enhanced energy conversion, compactness, and precision control capabilities, ensuring attractive financial payback periods for clean, energy-efficient equipment. These advancements stem from the use of improved performance materials, process optimization, and waste heat utilization practices, particularly at high temperatures. The technical challenges associated with large-scale, heavy-duty electric process heating are addressed through the novel innovations discussed in this article. Electrification and the corresponding energy efficiency improvements reduce the water consumed for industrial steam requirements. The article reviews new technologies that replace conventional process gas heaters and pressure boilers with efficient electric process gas heaters and instant steam generators, operating in the high kilowatt and megawatt power ranges with very high-temperature capabilities. Financial payback calculations for energy-optimized processes are illustrated with examples encompassing a range of comparative energy costs across various temperatures. The economics and implications of waste heat utilization are also examined in this article. Additionally, the role of futuristic, radical technical innovations is evaluated as a sustainable pathway that can significantly lower energy consumption without compromising performance objectives. The potential for a new paradigm of self-organization in processes and final usage objectives is briefly explored for sustainable innovations in thermal engineering and materials development. The policy implications and early adoption of large-scale, energy-efficient thermal electrification are discussed in the context of temperature segmentation for industrial-scale processes and climate-driven asset losses. Policy shifts towards incentivizing energy efficiency at the manufacturing level of heater use are recommended as a pathway for deep decarbonization. Full article

This study presents an advanced NO_x reduction strategy for a 330 MW lignite-fired boiler using an immunological AI system: the SILO (Stochastic Immune Layer Optimizer) combustion optimizer inspired by artificial immune systems. The immunological AI optimizer adaptively models multi-variable interactions and fireball shape in real time, optimizing fuel–air mixing to reduce NO_x formation at the source. Unlike reactive secondary methods, the combustion optimizer reshapes the combustion process to reduce emissions while improving efficiency. Real-time temperature data from the AGAM acoustic system inform the combustion optimizer’s fireball modeling, ensuring combustion uniformity. A urea-based SNCR system serves as a secondary layer, controlled based on local furnace conditions to target thermal zones. Field results confirmed that SILO reduced NO_x emissions below 200 mg/Nm³, decreased urea consumption by up to 34%, and improved boiler efficiency by 0.29%. The architecture offers a scalable, DCS-integrated solution for aligning fossil-fueled operations with tightening emission standards. Full article

Heavy fuel oil (HFO) is a widely used fuel in compression ignition engines, primarily in Brazilian thermoelectric plants, mainly due to its availability, low cost, and low operational expenses. However, heavy fuel oil is not compatible with most diesel engines and combustion systems in use and must be treated to maintain combustion process efficiency. The high viscosity of heavy fuel oil must be reduced before being introduced into the engine. To achieve this, appropriate heating devices are added to the fuel lines, with steam being the primary working fluid in these devices. Steam-generating boilers that burn fossil fuels, including HFO itself, are the most viable option from an economic standpoint and in terms of utilizing locally available fuels for this function. However, the need to mitigate the effects of environmental pollution has encouraged the adoption of other types of boilers, such as electric ones. In this work, a case study of a combustion steam generator installed in a Brazilian thermoelectric plant is developed. This study involves the thermodynamic and combustion modeling of the steam generator through the balancing of the respective thermodynamic and combustion equations. The models and the proposed chemical formula of HFO were validated, and through simulations using real data collected during the boiler’s operation throughout 2024, it was also possible to estimate the carbon dioxide emissions produced. Additionally, a hypothetical scenario was simulated in which the combustion boiler currently installed in the plant is replaced by two electric boilers. A simple economic analysis demonstrated that such a replacement would result in a total steam production cost of only 25% of the amount spent on the current combustion boiler, in addition to reducing $C{O}_2$ emissions to the atmosphere by 62.55 tons. Full article

Heat pumps are widely regarded as a key technology for sustainable heating, offering a pathway to significantly reduce fossil fuel dependency and combat the climate crisis. However, replacing individual gas boilers with heat pumps in multi-unit residential buildings remains a substantial challenge despite its immense potential to lower urban greenhouse gas emissions. To address this, the following paper describes the development of a compact, modular heat pump system designed to replace conventional gas boilers, focusing on the building and testing of a prototype for such a modular heat pump system. The prototype supports multiple functionalities, including space heating, cooling, and domestic hot water production. The performance advantages of two different compressor technologies were exploited to optimize the efficiency of the complete system and the pressure lifts associated with applications for heating and domestic hot water production. Thus, measurements were conducted across a range of operating points, comparing different heat pump module types. In the case of the piston compressor module, the Carnot efficiency was in the range of 47.2% to 50.4%. The total isentropic efficiency for floor heating and domestic hot water production was above 0.45 for both piston and rotary compressors. Full article

About 50% of Italian households’ overall energy consumption is satisfied by natural gas, mainly for space heating, leading to substantial CO₂ emissions. In Italy’s mild climate, fourth-generation district heating (4GDH) networks coupled with renewable energy sources (RESs) could represent a viable option for reaching the ambitious space heating decarbonization objectives set by the EU. In this paper, such a decarbonization pathway, consisting in a centralized heat pump (HP)-powered 4GDH network, with and without the addition of a distributed PV plant, is assessed and compared with the individual natural gas boilers-based Italian reference scenario. A cluster of buildings, comprising 200 dwellings, representative of common households in Rome, has been chosen as the case study. Starting from the cluster’s hourly space heating demand, a semi-dynamic MATLAB/Simulink model has been developed to size the technological components and evaluate their performance with respect to outdoor environmental conditions. The scenario comparison is carried out by means of techno-economic and environmental indicators: the levelized cost of heat (LCOHE), CO₂ emissions, and carbon avoidance cost (CAC). Moreover, a sensitivity analysis has been carried out to address the uncertainty regarding the main economic parameters, namely the electricity and natural gas price and the HP and DH investment cost. The results show that 4GDH-based layouts significantly reduce CO₂ emissions, at the expense of the LCOHE. The sensitivity analysis highlights how a significant reduction in both the electricity price and the DH network capital cost are required for achieving price parity with the fossil-fuel based scenario. Full article

Industrial process heat production is critical to achieving sustainability in our society. Avoiding fossil fuels and reducing electricity consumption for heat production are critical aspects of creating sustainable industries. Exploiting waste heat streams by upgrading them into useful high-temperature heat is an interesting idea for reducing the CO₂ footprint industrial processes. In line with this, the present study’s main objective is to investigate a novel thermochemical heat upgrade system based on the SrBr₂/H₂O working pair for the petrochemical industry, which is practically driven only by low-temperature waste heat streams. This innovative system, which exploits a waste heat stream of 200 °C and upgrades it to 250 °C to make it suitable for industry utilization, achieves a nominal coefficient of performance of 0.605. The examined system is compared with three other alternatives, including a natural gas boiler with 86% efficiency, a hybrid solar thermal unit with an auxiliary natural gas boiler, and a high-temperature heat pump with a coefficient of performance of two. The nominal industrial heat production is 2.2 MW for the thermochemical heat upgrade system. The dynamic investigation is conducted under the climate conditions of Denmark and Greece. The high-temperature heat pump’s annual electricity consumption is 6.94 GWh. In contrast, the annual heat consumed by the natural gas boiler is 16.12 GWh, without integrating the solar thermal unit. For the hybrid system, the maximum daily contribution of the solar thermal system is 87% for the climate conditions of Denmark, and the annual useful heat generated by the concentrating solar system is 1.30 GWh for the Danish climate conditions and 2.82 GWh for the Greek climate conditions. Full article

The transition from fossil fuels to renewable energy sources often requires shifting toward biomass fuels such as agriculture residues and waste, which tend to emit higher emission rates during combustion, and one of them is sulfur compounds. The main objective of this study is to clarify the regularities of the formation of sulfur compounds depending on the technological factors when burning sulfur-containing biomass. The experiments were conducted on two experimental stands—models of 20 kW and 25 kW capacities of industrial boilers equipped with reciprocating grates—by burning sunflower husk pellets and meat bone meal. The influence of incomplete combustion (indicator CO concentration), flue gas recirculation, and combined effects of both factors on concentrations of SO₂, SO₃, and H₂S were investigated during experiments. In addition, 20–90% of the sulfur in the fuel is converted to SO₂, contingent upon the combustion conditions. These findings have practical implications for the design and operation of biomass combustion systems. The highest SO₂ emissions were observed when primary air was mixed with flue gas recirculation and at the highest content of CO. The correlation of SO₂ and SO₃ and SO₂ and H₂S concentrations in flue gases of boilers was investigated. The conversion ratio of SO₂ to SO₃ was determined under different combustion modes and showed that this ratio can reach up to 5%. The sulfur content in ash deposits in different areas of the actual industrial boiler was analyzed. The highest percent of sulfur (S = 20%) in ash was found on the first boiler pass. 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

As part of the transition to low-carbon energy and for the sustainable utilisation of resources, it is necessary to seek a replacement for solid fossil fuels, but unfortunately, it is impossible to completely abandon them for various reasons at the moment, so only partial replacement with new, high-calorific, biomass-based fuels is possible. The purpose of this work is to determine the typical parameters of the co-combustion of carbonisate, coal and their mixtures, taking into account the synergetic effects influencing the combustion intensity of the mixture. Carbonisate was obtained in the process of the gasification of pinewood through the counter-blowing method at a temperature of 800–900 °C, while air was used as an oxidant. Basically, this method of gasification is used for coal in order to obtain high-calorific coke for the metallurgical industry. Also, in this study, for the first time, carbonisate was obtained from 50% pinewood and 50% lignite. The O/C and H/C ratios were determined for carbonisate. A technical and elemental analysis of the investigated fuels was carried out. A thermal analysis in oxidising medium was applied to determining the typical combustion parameters in the process of slow heating of the fuels under study. According to the results of this thermal analysis, typical heating parameters such as the ignition temperature, burnout temperature, maximum mass loss rate, combustion index, etc., were determined. It was noted that the calorific value of carbonised wood is two times higher than that of coal. The combustion index of carbonisates is 2.5–36% lower compared to that of coal. According to the results of the analysis of the interaction of the components among themselves (in the process of their joint combustion), the presence of synergetic interactions between the components was determined, which affected the change in the combustion intensity and heat release intensity. The results of this study may be useful for retrofitting coal-fired boilers to run on a mixture containing carbonisate and lignite. If carbonisate is produced from biomass, the resulting gas could be used as an energy fuel by burning it in a coal-fired boiler. Full article

This study addresses the increasing demand for sustainable water production by investigating the integration of solar energy into a multi-effect desalination (MED) plant located in Zuara, Libya. It is acknowledged that regions with high water demand frequently experience elevated levels of solar radiation; thus, this approach seeks to reduce dependence on fossil fuels and mitigate harmful emissions. Three operational modes were analyzed and compared: (1) daytime-only solar operation, (2) hybrid solar–boiler operation, and (3) solar operation with thermal energy storage. A validated mathematical model, informed by real empirical data, was used to assess energy and exergy efficiencies as well as production costs per cubic meter of desalinated water. The results indicate a trade-off between cost-effectiveness and environmental impact. The fossil fuel-based mode demonstrated the highest energy efficiency but also produced the greatest pollution. Conversely, the solar-only daytime mode, while free of emissions, was the costliest (USD 1.4/m³) due to its limited operational hours. The hybrid mode offered a compromise, presenting lower costs (USD 0.79/m³) and moderate land use, yet it still relied on fossil fuels. The thermal storage mode facilitated continuous, clean desalination at a higher cost (USD 0.97/m³) and required the largest solar field area. This study demonstrates the potential of solar-powered MED plants for sustainable water production, particularly in regions characterized by abundant sunlight and water scarcity. Furthermore, this research provides a comprehensive framework for selecting the optimal operational mode based on specific priorities, such as minimizing environmental impact, reducing costs, or maximizing operational flexibility. Full article

In many countries located in Central–Eastern Europe, there is a need for heating in the autumn and winter seasons. In Poland, this has been met over the years, mainly through the development of centralized heating systems. The heat sources in such systems are based on fossil fuels like coal or gas. New regulations and climate concerns are forcing a transformation of existing systems towards green energy. The research presents two scenarios of such a change. The first focuses on maintaining centralized heat sources but increases the share of renewables in the heat supply. This can be realized by weather-independent, high-power sources such as biomass boilers and/or high-temperature heat pumps (HP) such as sewage heat pumps or ground source HP. The second scenario changes the location of the heat sources to more dispersed locations so that the unit power can be lower. In this case, renewable heat sources can be used at favorable locations in the system. Among the sources included in this scenario are solar panels, photovoltaic panels, micro wind turbines, and ground source heat pumps with local heat storage. These are characterized by low energy density. Their dispersion in the urban space can contribute to the desired energy generation, which would be impossible to achieve in the centralized scenario. Furthermore, the transmission losses are lower in this case, so lower heating medium temperatures are required. The existing district heating network can be used as a buffer or heat storage, contributing to stable system operation. The article presents a comparative analysis of these solutions. Full article

It is well known that fossil fuels, especially coal, are still intensively used when considering the distribution of the main energy demand for electricity generation. Efforts to increase and optimise the efficiency of energy production are accelerating as global demand for energy continues to rise. In meeting the world’s energy needs, thermal power plants have an essential role to play. However, it remains an ongoing concern to improve their performance and sustainability. In this study, based on real operating data at varying ambient temperatures, an exergy analysis and an exergy-based sustainability assessment of a 210 MW coal-fired thermal power plant in Turkey are presented. The results of the energy analysis show that 59.01% of the total energy destruction belongs to the boiler and 12.29% to the intermediate-pressure turbine. This means that these are the main components for energy analysis. According to the obtained results of the exergy analysis, the boiler is the main constituent with the maximum exergy destruction, with a rate of 71.00% among the other constituents at the reference temperature of 25 °C. In addition, the relative irreversibility values were calculated as 79.43% in the boiler, 5.42% in the intermediate-pressure turbine (IPT), and 4.22% in the low-pressure turbine (LPT). These are the components that cause the most intensive irreversibility among the other plant components. Moreover, the component that had the greatest exergy efficiency was the ejector, at 98.62%, followed by the high-pressure heater (HPH-3) at 96.00%, the low-pressure heater (LPH-2) at 88.16%, and the high-pressure turbine (HPT) at 86.12%. The sustainability efficiency indicator (SEI) and the exergetic ecological index (ECEI) for the thermal power plant were 2.50 and 0.245, respectively, according to the exergy-based sustainability indices. The boiler, the turbine group, and the condenser are especially significant for increasing plant efficiency due to their high potential for improvement. Full article