Nitric acid production is among the most significant industrial point sources of nitrous oxide, which is a greenhouse gas with a global warming potential approximately 298 times that of carbon dioxide, yet the large installed base of legacy dual-pressure plants continues to operate with non-selective catalytic tail gas treatment systems that offer limited greenhouse gas abatement and impose rigid thermal constraints on the gas turbine cycle. A steady-state digital twin of an industrial dual-pressure nitric acid plant producing 52 t per hour of 60 wt.% nitric acid is developed, validated against measured plant data, and used to evaluate two selective catalytic retrofit configurations. The first heats raw tail gas to catalyst ignition temperature using the existing process heater, then raises the purified gas to turbine inlet conditions by mixing with flue gas from a newly installed combustion chamber. The second achieves the required temperature rise internally through catalytic fuel gas oxidation within an additional catalyst shelf in a two-bed reactor, eliminating supplementary combustion equipment entirely. The first configuration reduces total greenhouse gas emissions by 37% in carbon dioxide equivalent terms, eliminates ammonia slip, and enables a 5% production capacity increase worth 5.75 million EUR per year, at a capital cost of 4.77 million EUR and a discounted payback period of 16 months. The second achieves a 43% emissions reduction at a capital cost of 1.34 million EUR, reduces annual utility costs by 1.75 million EUR, and recovers its investment within 2.6 months without increasing electricity demand. The results demonstrate that selective catalytic tail gas treatment retrofit is a value-generating investment rather than a compliance cost. Projected across the global fleet of unabated dual-pressure plants, equivalent adoption could reduce sectoral nitrous oxide emissions by more than 21 Mt of carbon dioxide equivalent per year, representing over half the identified global industry mitigation potential.

The rapid increase in e-waste has become a significant global concern, influenced by swift technological advancements, shorter product lifecycles, and rising consumer demand. This situation leads to considerable environmental and health hazards, primarily due to the presence of toxic materials, energy demands, and the inadvertent loss of valuable resources when waste is not adequately managed. This review synthesises contemporary theories related to sustainable e-waste management, featuring concepts such as principles of the circular economy, energy efficiency and innovative recycling technologies. The review explores a range of actions, including regulatory strategies, mechanical pre-treatment methods, focusing on reagent-free recovery techniques, and the utilisation of digital solutions to enhance traceability and operational efficiency. The findings indicate substantial improvements in formal e-waste collection rates in areas with strong legislative frameworks, enhanced metal recovery efficiencies through refined hydrometallurgical and pyrometallurgical techniques and minimised environmental footprints through reagent-free and energy-conserving practices. The review emphasises the importance of viewing e-waste recycling not just as a waste management issue but as a fundamental element of resource security and sustainable industrial practices. By assessing recent developments, this work advocates for closed-loop recycling as an essential driver in the global shift towards a resilient, low-carbon, energy-efficient and circular economy.

Processing sewage sludge presents a significant challenge, necessitating concerted efforts to transform this waste into valuable resources such as syngas and biochar, which can be utilized across energy, chemical, agricultural, and other sectors. This paper examines the continuous gasification of sewage sludge in an inert environment. A systematic analysis of various process parameters was conducted to evaluate their impact on overall system performance, with particular emphasis on optimizing syngas yield, enhancing hydrogen content in the syngas, and maximizing energy output. The analyses were performed using a rigorously developed simulation model implemented within the UniSim Design environment based on specific assumptions and conditions. This model enabled a comprehensive investigation of the interrelationships among process variables and their influence on key performance metrics. Based on the insights gained, targeted recommendations were formulated to improve the efficiency and output of the gasification process. Optimal parameters identified for the reference sewage samples include a pyrolysis temperature range of 700-800 degrees C, a gas shift reactor temperature of 900-1000 degrees C, a feed water content of 8 % (by mass), and a slag recycle ratio of 0.8 (by mass) resulting to maximum yield of syngas of 46 % (by mass). The simulation model was validated with various sludge samples from the literature, illustrating the diversity of optimal parameters. These recommendations are aimed at enhancing syngas yield, increasing the hydrogen fraction in the syngas, and achieving higher overall energy output, thus contributing to the optimization of the process. The findings of this study provide insights into the factors that affect process performance and lay the groundwork for further advancements in the production and utilization of syngas derived from sewage sludge as a feedstock.

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.

Second-generation district heating (DH) systems based on coal combustion remain prevalent and inefficient in Central and Eastern Europe, particularly in Poland. This study investigates the technical and economic feasibility of integrating geothermal energy into an existing high-temperature DH system with a peak demand of 60 MW. Three retrofit scenarios are analyzed: (1) a geothermal doublet with a direct heat exchanger; (2) Scenario 1 extended by an absorption heat pump (AHP) powered by a gas boiler; and (3) Scenario 2 enhanced with an additional geothermal doublet. A detailed hour-by-hour simulation of thermal performance was conducted for each configuration. The share of geothermal heat in total production increases from 35% in Scenario 1 to nearly 70% in Scenario 3, enabling all variants to meet the efficiency thresholds defined in the EU Energy Efficiency Directive. An economic assessment using Net Present Value (NPV) and Internal Rate of Return (IRR) indicates that Scenario 1 is the most cost-effective, yielding an IRR above 17% and a 4-year discounted payback period. Although Scenario 3 achieves higher decarbonization, it requires significantly greater capital investment. The findings highlight that geothermal retrofitting, particularly with direct heat exchangers, offers a realistic and economically justified path for transforming legacy DH systems toward carbon neutrality.

This study presents a novel methodology for sizing air-water heat pumps (ASHP) for space heating and hot water supply in buildings. Utilizing long-term local climatic data, the developed tool determines the coefficient of performance (COP) and feasibility of ASHP. The sizing algorithm incorporates peak heat demand, unitary final energy demand, and seasonal heat demand across various detached house sizes. Annual local heating system operation time and key economic indicators are derived for each case across 3 European countries. A new approach is precise investigation of 10-year outdoor temperatures and apply it to heat pump (HP) modeling, which enabled a distinction between so-called warm and cold years. The results underscore substantial variations in net present value (NPV) between warm and cold years, illustrating the critical influence of precise climate data on the performance of HPs. The study revealed that for a 160 m2 house in Poland, annual electricity consumption by HPs ranged from 3736 kWh during warm years to 12,908 kWh during cold years, showing a significant variation in performance based on climate conditions. The comprehensive tool allows for precise adjustments of heating systems to actual local climate conditions, improving both economic and environmental outcomes. This comparative assessment aids in the optimal selection of HPs, ensuring energy efficiency and sustainability in residential heating systems. Building on studies from various climatic regions, this work addresses the knowledge gap in performance and explores the feasibility of HP in a changing climate using precise modeling techniques.

This study examines the performance and economic feasibility of air-water heat pumps across diverse European climate zones under varying energy price scenarios. Focusing on four regions (Poland, Lithuania, Croatia, and Spain), the analysis evaluates the seasonal coefficient of performance and net present value during cold and warm years. Results indicate that seasonal coefficient of performance is highly sensitive to climatic variability, with efficiency decreasing in colder regions up to 67 % noted in Poland and Lithuania. while remaining stable in warmer climates, with a variation of approximately 4 % observed in Spain. Economic analysis reveals that in the high electricity price scenario, only Spain achieved positive net present values in both periods, with smaller heat pumps (8 kW) being the most cost-effective. Conversely, in the high gas price scenario, all regions demonstrated positive net present values, particularly for larger units (13 kW) in cold years. This indicates the differing impacts of energy price variations on the operational efficiency and cost-effectiveness of heat pump systems in diverse climatic contexts. These findings emphasize the importance of adapting heat pump sizing to local climatic conditions and implementing energy policies that balance electricity and gas prices. Future studies should aim to develop more comprehensive approaches to capture the interplay between climatic variability and economic feasibility.

Recent global challenges necessitate shifting towards a more circular and efficient economic model. The European Union actively pursues this direction, emphasising energy security and diversification. Notably, industrial facilities and district heating systems are among the largest consumers of fossil fuels and contributors to pollution despite significant strides in renewable energy adoption. This paper explores the potential for energy collaboration between industrial sites and district heating networks, aiming to reduce heat loss and primary energy consumption. Using a systematic graphical approach based on pinch point analysis, energy efficiency and identifying the thermodynamically available heat from industrial processes for integration into district heating systems were investigated. This study examines the simultaneous optimisation of heat transfer in district heating systems alongside the cooling processes in industrial operations. Specifically, the fertiliser, polymer and cement industries were analysed to assess their compatibility with district heating networks. The findings reveal substantial potential for energy and emission reductions, with maximum recoverable heat from a light hydrocarbon distillation estimated at 28.85 GWh/y for low-temperature district heating, a notable 76.60 GWh/y from a nitric acid plant for high-temperature systems, and 186.48 GWh/y for high-temperature district heating. Corresponding emissions reductions are projected at 6.03 ktCO2/y, 16.00 ktCO2/y and 38.95 ktCO2/y for the respective case studies. The insights from this research offer valuable contributions to both scientific knowledge and practical applications in enhancing energy efficiency and promoting partnerships between industry and district heating systems.

The article describes the results of experimental studies of the kinetic regularities of beet pulp drying by the filtration method. The influence of the main process parameters on the rate of moisture removal, including the height of the wet layer of material H (0,04 m, 0,08 m, 0,12 m, 0,16 m), temperature T (60 °C, 70 °C, 80 °C, 90 °C) and the velocity of the thermal agent v0 (1.24 m/sec, 1.76 m/sec, 2.29 m/sec, 2.82 m/sec), was investigated. The kinetic dependencies for the periods of complete and partial saturation of the thermal flow with moisture were derived. This allows us to describe the change in the material moisture content and duration of the filtration drying process. Verifying of the accuracy of the obtained dependencies presents a maximum relative error of 36.54 % and an average deviation of 8.46 %, which is acceptable for practical calculations of drying equipment.

This article presents the results of experimental studies investigating the energy consumption per 1 kg H2O required for the filtration drying of beet pulp. The optimal process parameters for the removal of 1 kg of moisture from the dried beet pulp were determined, which included the height of the layer of dried material H=120 mm, the thermal agent temperature T = 90 °C and the thermal agent velocity v0 = 1.76 m/s. Regarding these parameters, the total energy consumption for drying by the filtration method from the initial moisture content of 88.12 % wt. to the final moisture level of 14 % wt. is 3,515 kW· h/kg H2O. Based on the experimental data, a calculation was made for an industrial filtration drying unit, for which the cost of removing 1 kg of moisture from beet pulp was determined: 3,28 kW· h/kg H2O. To evaluate the efficiency of the filtration drying process, we conducted a comparative analysis of the drying of beet pulp at a comparable capacity in a drum dryer. According to the calculations, the energy costs for removing 1 kg of moisture from beet pulp in a drum dryer are 3.11 kW· h/kg H2O. Considering the estimation of calculations and a significant reduction in the drying time with the filtration method (~10 times), it is possible to conclude that filtration drying is a beneficial and efficacious technique for beet pulp drying.

Industry and district heating systems are the biggest pollutants and consumers of fossil fuels, despite a huge effort in renewable energy implementation. The European Union keeps circularity and efficiency principles, with a main focus on energy security and diversity. This paper considers the energy partnering possibilities between industrial facilities and district heating systems reducing the waste of heat and primary energy consumption. The systematic graphical approach based on pinch point analysis is used for energy targeting and finding the thermodynamically available maximum heat for utilisation in district heating networks. The case study analysed the specific processes of the fertiliser and polymer industries. The integration of the gas fractioning plant and nitric acid plant with low and high-temperature district heating resulted in energy savings of 25.23 GWh/y, 72.01 GWh/y, and emission savings of 5,071 tCO2/y and 14,473 tCO2/y respectively.

The electrification of process industries is one of the main challenges when building a low-carbon society since they consume huge amounts of fossil fuels, generating different emissions. Heat pumps are some of the key players in the industrial sector of the carbon-neutral market. This study proposes an approach to improve the economic feasibility of heat pumps within process plants. Initial energy targeting with grand composite curves was used and supplemented with the detailed design of an evaporator and a compressor for different condensation and evaporation pressures. The trade-off between the capital cost of the heat pump and the electricity cost was investigated, and optimal configurations were selected. This case study investigates the gas fractioning unit of a polymer plant, where three heat pumps are integrated into distillation columns. The results demonstrate that the heat recovery is 174 MW and requires an additional 37.9 MW of electricity to reduce the hot utility by 212 MW. The selection of the evaporation and condensation pressures of heat pumps allows 21.5 M EUR/y to be saved for 7 years of plant operation. The emission-saving potential is estimated at 1.89 ktCO2/y.

Maximizing heat recovery in the process industry is important to cut primary energy targets. It is always the trade-off between saved energy and spent capital investment. This issue became more important in the transition to a low-carbon economy. Inter-plant integration can be a source of clean energy, which does not need to be produced but proper targeting gives its economic feasibility and attraction to investments. This paper provides a new extension of the Total Site method accounting optimal amount of energy that can be saved on the inter-plant level. The approach utilises the construction of the Total Site Profiles with real temperature considers heat transfer with intermediate utility and finds cogeneration potential within enthalpy blocks of Total Site heat recovery. Merging of intermediate utilities and optimisation of its temperature were considered together with CHP optimisation. Targeting of the total annual cost was performed based on Total Site Pinch concept finding the optimum temperature approach between site temperature profiles. The case study for monomer production of polymer plant was investigated and 6 different options of Total Site heat recovery were assessed. The minimum total annualised cost of 45.3 mils. EUR was accounted for option with maximum cogeneration potential and the minimum number of heat exchangers. The heat recovered is 160.7 MW, CHP potential is 32.9 MW, and the number of heat exchangers is 144 for a total site minimum temperature approach of 20 degrees C. The results were compared with the traditional Total Site approach and the advantages were highlighted. The sensitivity analysis of the results was performed by applying energy price changes of & PLUSMN; 50% of the base level. The results can be used for the detailed design of the site energy system and further development of Total Site methods.

Chemical engineering is a complicated combination of skills that depends on the curricula, teachers, and teaching environment and it requires huge resources to prepare skilled personnel for chemical and related industries. Chemical plant specialists face new challenges as digital and energy transition, new products and processes, circularity paradigm, etc. All these need awareness of new trends and the capability to solve related industrial problems. This paper presents a computer-aided process engineering-based (CAPE-based) curricula development that supports continuous improvements of chemical plants and speeds up the application of up-to-date knowledge directly to industrial practice. The approach is based on the interplay of engineers, plant managers and university professors in solving the real industrial problem. The procedure is supported by a cloud-based CAPE environment for teaching, training, and producing the project results. The industrial problems are identified by the plant personnel and appropriate engineers are assigned by managers. The specific structure of the curricula presumes face-to-face, online and hybrid training and consulting in a triangle engineer, plant supervisor, and professor to solve a problem in the chemical and petrochemical industry. The pool of university professors is adjusted to cover all necessary tasks, provide up-to-date knowledge, and give a new paradigm to engineering thinking. The fellows improve in machine learning, data science, communication skills, presentation skills, economic assessment, etc., to increase the importance of the company. As the real results of one of the case studies, the steam consumption of the petrochemical plant was reduced by 64 % and the yield of the production unit was increased. Eleven case studies were solved covering energy and resource efficiency, wastewater treatment, by-product recycling, new product development and other issues. As the final project results the mechanical specification of the equipment, new plant layout and economic efficiency were assessed.

Decarbonisation of the industrial sector is a crucial objective in new technological developments responding to global challenges. Energy-intensive industry is one of the biggest pollutants and it is mostly supplied by fossil fuels. This paper presents the methodology for the assessment of electrified options for the process industry based on systematic process integration techniques. The graphical representation was used to analyse the physical processes of the industrial unit. The improved heat recovery and electrified utility targeting were performed by using the Grand Composite Curve and analysing the main process streams and distillation column system. The electrified thermal utility system uses electric steam boilers, water coolers, heat pumps, etc. The case study analyses the natural gas liquid processing and assesses electrified thermal utility. The initial process was simulated in a UniSim environment and obtained thermophysical properties of process streams were used for the analysis. The integrated electrified scenario presumes using a low-pressure steam boiler, water coolers, propylene coolers and 3 heat pumps. Heat recovery was increased by 4 times compared to the initial process and 100% electrified thermal utilities were used. The energy cost was reduced by 41% and the carbon dioxide emissions are reduced by 512,778 tons per capita compared to existing process when using renewable energy for electrified utility. The approach can be used for further development of industry decarbonisation options and electricity targeting in process industries.

The process industries consume a huge amount of heat energy contributing to environmental impact. Energy recovery is a key instrument of energy-saving that can be implemented via a heat exchanger network. Pinch -based approaches presume analysis of energy targets of industrial processes to find the optimal Delta Tmin for heat exchanger network design. Classical Pinch Analysis do not account for the stream splitting in the super targeting procedure while parallel branches are usually needed. The splitters and mixers contribute a lot to the capital cost of the heat exchanger network. Current work proposes the update of super targeting procedure accounting stream splitting and mixing in a Pinch problem. The original algorithm of Composite Curves construction is proposed to analyse the distribution of process streams and stream splitting in subsystems above/below the Pinch before the design of the heat exchanger network. It was then used in a super targeting procedure to precise the capital cost and, as a result, the optimal Delta Tmin. The process stream distribution and stream splitting are analysed in a whole range of Delta Tmin. Identifying all possible starting points for heat exchanger network design. Two new criteria were proposed to estimate the topological complexity of network pre-design and the specific ratio of stream splitting. The case study analyses the ethylene oxide process and calculation of trade-off between capital and energy costs were performed and optimal Delta Tmin = 16 degrees C. The result was compared with two known ap-proaches, which account for the number of heat exchangers without stream splitting. Total annual costs and optimal Delta Tmin was also calculated for different energy prices to show a possible deviation of starting point for heat exchanger network design. The range of optimal Delta Tmin from 9 to 54 degrees C resulted in the range of hot utility prices from 42 to 291 $/kWy, and the emission targets will be from 14,380 to 77,919 tCO2/y. The methodology can be used for the pre-design of the heat exchanger network to better precise the optimal Delta Tmin, capital cost targets, and check the optimum changing for different energy prices.

This study investigates the utility system of the pyrolysis unit of a polymer plant and assesses the decarbonization options of the utility system. The method is based on an integrated approach that includes a steady-state digital twin (SSDT) of investigated process and an update of the existing steam cascade to apply renewable energy and power-to-x. Pyrolysis gas composition was obtained from online analyzers and simulated in a UniSim environment. The simulation model of the whole process, from pyrolysis of liquid feedstock to final monomer separation, was developed and verified on plant data. The energy-saving potential was assessed based on SSDT, and energy-saving measures were proposed. The updated steam cascade of the investigated process was developed, and decarbonization options accounting for steam generation and waste heat utilization were proposed. The final solution gives the energy targets for e-boilers and low-grad heat for Organic Rankine Cycle (ORC).