• Energy Research

The design of heat exchanger networks (HEN) in the process industry has largely focused on minimisation of operating and capital costs using techniques such as pinch analysis or mathematical modelling. Aspects of operability and flexibility, including issues of disturbances affecting downstream processes during the operation of highly integrated HEN, still need development. This work presents a methodology to manage temperature disturbances in a HEN design to achieve maximum heat recovery, considering the impact of supply temperature fluctuations on utility consumption, heat exchanger sizing, bypass placement and economic performance. Key observations have been made and new heuristics are proposed to guide heat exchanger sizing to consider disturbances and bypass placement for cases above and below the HEN pinch point. Application of the methodology on two case studies shows that the impact of supply temperature fluctuations on downstream heat exchangers can be reduced through instant propagation of the disturbances to heaters or coolers. Where possible, the disturbances have been capitalised upon for additional heat recovery using the pinch analysis plus-minus principle as a guide. Results of the case study show that the HEN with maximum HE area yields economic savings of up to 15% per year relative to the HEN with a nominal HE area.

The design of heat exchanger networks (HEN) in the process industry has largely focused on minimisation of operating and capital costs using techniques such as pinch analysis or mathematical modelling. Aspects of operability and flexibility, including issues of disturbances affecting downstream processes during the operation of highly integrated HEN, still need development. This work presents a methodology to manage temperature disturbances in a HEN design to achieve maximum heat recovery, considering the impact of supply temperature fluctuations on utility consumption, heat exchanger sizing, bypass placement and economic performance. Key observations have been made and new heuristics are proposed to guide heat exchanger sizing to consider disturbances and bypass placement for cases above and below the HEN pinch point. Application of the methodology on two case studies shows that the impact of supply temperature fluctuations on downstream heat exchangers can be reduced through instant propagation of the disturbances to heaters or coolers. Where possible, the disturbances have been capitalised upon for additional heat recovery using the pinch analysis plus-minus principle as a guide. Results of the case study show that the HEN with maximum HE area yields economic savings of up to 15% per year relative to the HEN with a nominal HE area.

The paper presents the techno-economic modelling of CO2 capture process in coal-fired power plants. An overall model is being developed to compare carbon capture and sequestration options at locations within the UK, and for studies of the sensitivity of the cost of disposal to changes in the major parameters of the most promising solutions identified. Technological options of CO2 capture have been studied and cost estimation relationships (CERs) for the chosen options calculated. Created models are related to the capital, operation and maintenance cost. A total annualised cost of plant electricity output and amount of CO2 avoided have been developed. The influence of interest rates and plant life has been analysed as well. The CERs are included as an integral part of the overall model.

The paper presents the techno-economic modelling of CO2 capture process in coal-fired power plants. An overall model is being developed to compare carbon capture and sequestration options at locations within the UK, and for studies of the sensitivity of the cost of disposal to changes in the major parameters of the most promising solutions identified. Technological options of CO2 capture have been studied and cost estimation relationships (CERs) for the chosen options calculated. Created models are related to the capital, operation and maintenance cost. A total annualised cost of plant electricity output and amount of CO2 avoided have been developed. The influence of interest rates and plant life has been analysed as well. The CERs are included as an integral part of the overall model.

Abstract A problem when exploiting renewable energy sources, such as wind and solar radiation, is their fluctuating availability. In the presented work, the Heat Integration methodology for batch processes based on Time Slices has been extended to cover the integration of solar thermal energy, thus allowing for dealing with such variations. A procedure for identifying the number and durations of Time Slices for a problem featuring variable renewable energy supply has been formulated, and developed for solar energy utilisation. The main procedural steps involve partitioning of the measured/forecasted heat availability profile using a large number of candidate time boundaries, and then approximating it by a piecewise-constant profile using high-precision. The approximation profile is obtained by subjecting the candidate superset of time-boundaries to MILP optimisation, thus minimising integral inaccuracy compared to the forecasted availability profile. The Time Slice definitions are completed by approximating the heat loads within the Time Slices. The integration of solar thermal energy can be performed for the specified Time Slice, after the optimal number of Time Slices with approximated constant load has been selected. Using heat storage, the heat can be transferred between Time Slices.

Abstract A problem when exploiting renewable energy sources, such as wind and solar radiation, is their fluctuating availability. In the presented work, the Heat Integration methodology for batch processes based on Time Slices has been extended to cover the integration of solar thermal energy, thus allowing for dealing with such variations. A procedure for identifying the number and durations of Time Slices for a problem featuring variable renewable energy supply has been formulated, and developed for solar energy utilisation. The main procedural steps involve partitioning of the measured/forecasted heat availability profile using a large number of candidate time boundaries, and then approximating it by a piecewise-constant profile using high-precision. The approximation profile is obtained by subjecting the candidate superset of time-boundaries to MILP optimisation, thus minimising integral inaccuracy compared to the forecasted availability profile. The Time Slice definitions are completed by approximating the heat loads within the Time Slices. The integration of solar thermal energy can be performed for the specified Time Slice, after the optimal number of Time Slices with approximated constant load has been selected. Using heat storage, the heat can be transferred between Time Slices.

Integrated and combined cycles (ICC, CC) traditionally involve gas and steam turbines only. The paper analyses the further integration of high-temperature fuel cells (FC) having high electrical efficiency reaching up to 60% compared with 30–35% for most gas turbines. The previous research on FC hybrids indicates achieving high efficiencies and economic viability is possible. The ICC of various FC types—their performance and the potential for utilisation of renewables—are analysed considering also power generation capacity and site heat integration context. Further research and development with industrial relevance are outlined focusing on CO2 emissions reduction.