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A plate heat exchanger (PHE) is a modern, effective type of heat transfer equipment capable of increasing heat recuperation and energy efficiency. For PHEs, enhanced methods of heat transfer intensification can be further applied using the analysis and knowledge already available in the literature. A review of the main developments in the construction and exploration of PHEs and in the methods of heat transfer intensification is presented in this paper with an analysis of the main construction modifications, such as plate-and-frame, brazed and welded PHEs. The differences between these construction modifications and their influences on the thermal and hydraulic performance of PHEs are discussed. Most modern PHEs have plates with inclined corrugations on their surface that create a strong, rigid construction with multiple contact points between the plates. The methods of PHE exploration are mostly experimental studies and/or CFD modelling. The main corrugation parameters influencing PHE performance are the corrugation inclination angle in relation to the main flow direction and the corrugation aspect ratio. Optimisation of these parameters is one way to enhance PHE performance. Other methods of heat transfer enhancement, including improving the form of the plate corrugations, use of nanofluids and active methods, are considered. Future research directions are proposed, such as improving fundamental understanding, developing new corrugation shapes and optimisation methods and area and cost estimations. [ABSTRACT FROM AUTHOR]

Increasing energy usage efficiency requires enhanced heat energy recuperation between process streams in the industry and civic sector with waste heat utilization. The condensation of different vapours is the process encountered in many industrial applications. Increasing the heat recuperation in this process is possible with efficient heat transfer equipment, among which a Plate Heat Exchanger (PHE) is at the leading position. A number of research works have been conducted in recent years concerning construction development and heat transfer enhancement in conditions of limited pressure drop to increase PHE performance in condensation processes. The results of studies on heat transfer and pressure drop in the two-phase condensing flow inside channels of PHE with different geometries of corrugations are discussed. In many implementations, the total pressure drop allowable for gaseous streams in heat exchangers is relatively small. The structure of two-phase flow in PHE channels of complex geometry is very different than in tubes and flat wall channels. The relative differences in approaches to enhance PHE performance in condensation processes based on its modelling, optimisation and design are analyzed. The directions and prospects for future developments are formulated, and potential savings for the economy and the environmental footprint is presented. [ABSTRACT FROM AUTHOR]

The supercritical CO2 Brayton cycle is widely utilized by various industries because of its compactness and efficiency. However, in the actual process, there are always temperature fluctuations that affect the normal operation of the whole supercritical CO2 Brayton cycle system, in order to weaken the temperature fluctuations without adding additional components, a new structure of PCHE with PCM embedded in PCHE was designed in this study. Fluent was used to simulate the working conditions and compare with the commonly used PCHE under the same working conditions. It was found that the structures with porosity of 0.8 to 0.9, the percentage reduction of temperature fluctuations on the hot side was 26.84 %, 26.78 % and 26.49 %, respectively, and the percentage reduction of temperature fluctuations on the cold side was 40.30 %, 40.81 % and 41.63 %, respectively, and the percentage reduction of heat exchange was 1.8 %, 1.9 % and 2.3 %, respectively. [ABSTRACT FROM AUTHOR]

The cooling of gaseous streams that include condensable components is frequently encountered in different industrial applications requiring the use of Heat Exchanger Networks (HENs) for optimal heat recuperation. Plate Heat Exchanger (PHE) with enhanced heat transfer can effectively work with condensation of vapours from a mixture with non-condensable gases. For their integration in HENs, a reliable method for estimation of PHE heat transfer area is required. The description of this method is presented. It is based on the mathematical model of the condensation process in PHE and proposes the approach of estimating minimal PHE heat transfer area that can be achieved by variation of plates size and corrugations geometry. The variables are corrugation inclination angle (varied at 30°, 45° and 60° levels) and corrugation height (varied from 2.5 to 5.5 mm with the step equal to 0.5 mm). The method is illustrated by a case study. Based on this method, the software for estimation of PHE heat transfer area as an element of HEN in condensation of steam from its mixture with air is developed. It can be included in software packages for HEN optimisation as a DLL module. [ABSTRACT FROM AUTHOR]

The paper provides an updated overview of the main achievements and ideas presented at the most recent PRES conferences and in the fields which have been covered by them. The conference history now reached a quarter of the century - from 1998 to 2022. The PRES conferences have become one of the main vehicles for spreading Process Integration (PI) into various research directions and fields of possible implementation. The PRES went successfully during the last period challenged by COVID-19 pandemics. Not all conferences managed to adapt well. However, PRES successfully implemented the hybrid mode and learned how to use it efficiently for enlarging the number of speakers as well as the audience while still keeping very intensive and beneficial cross-fertilisation and networking. Some experiences have been shared in this paper. The hybrid mode helped successfully intensify the research efforts on the research challenge, which remained as a consequence of the COVID-19 pandemics - an increased amount of waste and during the life and economy recovery also increasing environmental footprints. This short overview includes (i) Process Integration with Pinch Analysis (ii) Process Integration with another approach (iii) Development of heat exchanger systems for Process Integration (iv) Other extensions of Process Integration for wider Process Systems Engineering and recently (v) Circular economy (vi) Environmental footprints and nexuses and just (vii) COVID-19 pandemics energy and environmental consequences and recovery. This paper presents an attempt to demonstrate and make suggestions for the future growth of the Process Integration branching out during the next years. [ABSTRACT FROM AUTHOR]

Ash deposition in flue gas heat exchanger affects its heat transfer performance and lifecycle, which becomes a crucial factor restricting the efficient recovery and utilization of flue gas waste heat. In this paper, a numerical method was established to investigate the characteristics of ash deposition in tube bundle heat exchangers. An integrated fouling model including transport, rebound, deposition, and removal of particles was employed to predict the behaviour of particles. Then, the effects of particle diameter and flue gas velocity on collision mass, deposition mass, absolute deposition ratio, and relative deposition ratio were studied. At last, the thermal–hydraulic and ash deposition characteristics of three different tube shapes were compared. The results showed that the low-velocity regions on the circumference were the primary locations of particle deposition, and the medium-diameter particles were the main deposition components. With the increase in flue gas velocity, the deposition mass of large-diameter particles decreased, and that of small-diameter particles increased. The use of an elliptical tube and flattened round tube with an apex angle of 60°had also excellent thermal–hydraulic and anti-fouling performances. Consequently, the ash deposition and wear can be reduced by increasing flue gas velocity, filtering medium and large-diameter particles, and using elliptical and flattened round tubes. [ABSTRACT FROM AUTHOR]

Czech-Chinese Project Transmission Enhancement and Energy Optimised Integration of Heat Exchangers in Petrochemical Industry Waste Heat Utilisation is a joint project of Czech Republic, SPIL, Brno University of Technology – VUT Brno and the People‘s Republic of China, Xi’an Jiaotong University, Xi’an, Shaanxi. The 3 y project contributes to solving the energy situation and reduction of emissions. The use of low-grade heat is an effective means of saving energy and reducing greenhouse gases, which is increasingly sought after both for large companies also in local industrial facilities and even households. It has been increasing the emphasis on the use of low-potential energy results in increased demand for sophisticated heat exchangers. Methods, standards and the creation of modular structures optimised for different outputs based on the practical use of research results are being developed for various sources of waste heat, types of circulating media and technical operating parameters. Layout and construction designs allow designers to professionally design and manufacture suitable heat exchangers for specific conditions of the production process from the very beginning and a wide scope of conditions and requirements. Utility models and software modules were created and supported with research publications. [ABSTRACT FROM AUTHOR]

As an essential part of Heat Integration, the heat exchanger network (HEN) plays a vital role in large-scale industrial fields. The optimisation of HEN can increase energy efficiency and considerably save the operating and investment cost of the project. This study presents a novel approach for simultaneous optimisation of plant operating variables and the HEN structure of an existing natural gas purification process. The objective function is the total energy consumption of the studied process. A two-stage method is developed for optimisation. In the first stage, a particle swarm optimisation (PSO) algorithm is developed to optimise variables including tower top pressure, tower bottom pressure, and reflux ratio on the HEN, thereby changing the initial temperatures of cold and hot streams in the HEN. In the second stage, a shifted retrofit thermodynamic grid diagram (SRTGD)-based model and the corresponding solving algorithm was applied to retrofit the HEN. The case study shows that the optimal operating conditions of towers and temperature spans of heat exchangers can be solved by the proposed method to reduce the total energy consumption. The case study shows that the total energy consumption is reduced by 41.5 %. [ABSTRACT FROM AUTHOR]

This paper reviews the Process Integration (PI) development related to the recent Conferences on Process Integration for Energy Saving and Pollution Reduction (PRES conferences) and makes suggestions for the future growth of PI branching out in the future. The conference history is now close to a quarter of the century– from 1998 to 2021, and has been flourishing despite the difficult COVID-19 period. The paper overviews the progresses in Process Integration with Pinch Analysis, heat exchangers and Process Integration, extensions of Process Integration for wider process system engineering, integration of renewable energy sources, Circular Economy, extended environmental footprints, extended water-energy nexus contribution to environmental assessment, COVID-19 pandemics environmental consequences, and ecosystem remediation and waste stream clean-up. Considerable progress in Process Integration has also been achieved thanks to PRES conferences. This overview is an attempt to demonstrate the contribution delivered and make suggestions for the future growth of the PI branching out during the next years. It has become apparent that further improvements of the PI technologies are necessary and possible for achieving sufficient reductions of resource demands and pollution so that available renewables and end-of-pipe cleaning can serve them, minimising the environmental impacts. The key methodology developments enabling this are multi-constraint Pinch Analysis and the joint use of several PI methods for delivering comprehensive macro-analyses. [ABSTRACT FROM AUTHOR]

With the long-term operation of Heat Exchanger Networks (HENs), fouling is a frequent problem. This is related to decreasing long-term heat transfer performance. Fouling decrease the heat transfer coefficient and reduce the efficiency of heat exchange. Different fluid types have different characteristics in corrosiveness and contribute to different results for fouling. The current graphical tools cannot fully tackle the HEN cleaning and retrofit design in the long-term operation. This paper proposes a new graphical tool called Time vs Temperature Diagram (TTD) for HEN long-term management, taking fouling into consideration. It visualises the long-term temperatures change of each heat exchanger on hot and cold streams. The effect of heat exchanger cleaning can be shown visually in this diagram. This diagram can help to determine the cleaning and retrofit plan over a long period. An example is illustrated to show how to apply this diagram. [ABSTRACT FROM AUTHOR]

Heat exchanger network (HEN) retrofit is an effective way to reduce energy consumption and improve energy efficiency. A key criterion in industrial practice to evaluate the performance of a retrofit plan is the minimising total annualised cost. However, when pursuing the goal of minimising total annualised cost by graphical tools, sub-optimal solutions are inevitable because of the difficulty in finding the balance of utility cost and investment. In this study, a method based on constrained particle swarm optimisation (PSO) algorithm is developed for the annual cost minimisation when retrofitting HENs. The proposed method is applied based on an initial retrofit plan obtained by graphical tools. It can achieve the aim of total annualised cost reduction by adjusting the inlet and outlet temperatures of each heat exchanger through PSO with the consideration of different utility prices and investment. The results show that this method can find optimal temperature spans for heat exchangers to reduce the total annualised cost. [ABSTRACT FROM AUTHOR]

The condensation of vapour in the presence of noncondensing gas inside the channels of Plate Heat Exchanger (PHE) is studied on the example of steam condensation from its mixture with air. The mathematical one dimensional model of the process is developed. It is represented by the system of ordinary differential equations accounting for the change of process local parameters along the channel length. The identification of correlations for heat and mass transfer coefficients, as also pressure losses in condensing two-phase flow, is performed based on a comparison of modelling results with experimental data. The experimental model of PHE channel corrugated field consists of four corrugated plates forming three channels. The plate length is 1 m, its width is 0.225 m and a height of corrugations 0.005 m. The corrugations inclination angle to the main flow direction is 60 °. The correlations for two-phase flow are based on single-phase correlations obtained for a considered channel. For mass transfer coefficient, the most accurate results are obtained using approach accounting for transverse mass flux influence based on a stagnant film model with correction for density variation across the turbulent boundary layer. For the prediction of pressure drop in two-phase condensing flow the separate phases, model is used at low Reynolds numbers of the liquid film and dispersed annular flow model further on channel length, with growing mass flow rate of condensed liquid. The resulting mathematical model with correlations identified on experimental data can be used for the design of PHE for condensation of steam from its mixture with air. [ABSTRACT FROM AUTHOR]

Heat exchanger network (HEN) retrofit has been widely studied to achieve energy savings. Different types of heat exchangers such as shell and tube, double-pipe, spiral plate, and spiral tube have their working temperature ranges and prices. However, considering the type of heat exchangers in the HEN retrofit process is rarely seen in previous publications. Selecting suitable types of heat exchangers according to their temperature ranges and prices is a crucial aspect in industrial implementation. The above-mentioned issue can be solved by the proposed Shifted Retrofit Thermodynamic Grid Diagram with the temperature range of heat exchangers (SRTGD-TR). The aim is to minimise the total cost, including utility cost and capital cost. The methodology is illustrated using a case study. [ABSTRACT FROM AUTHOR]

Refineries are big consumers of energy and hydrogen. However, most current studies focus on the optimisation of H2 Network or Heat Integration in refineries H2 and heat are not considered together. The presented paper proposes a hierarchical targeting method for H2 and heat using the Onion Model to solve this problem. H2 networks belong to the inner layer of the onion, and heat recovery to the outer layer. The targets for H2 recovery are obtained, followed by Heat Exchanger Network targeting. A case study of an oil refinery shows that both H2 and energy can be significantly reduced. This study shows an approach to achieve a synergy of targeting H2 and heat recovery. It has great significance to the energy-saving and emission reduction of an oil refinery. [ABSTRACT FROM AUTHOR]

Heat exchanger network (HEN) which is designed to achieve the maximum energy recovery (MER) involves the integration and interactions of multiple process streams. Small disturbances on one stream can affect other connecting streams. In order to manage these disturbances, the process to process and utility heat exchangers with bypass streams installation are typically overdesigned. However, overdesign also means higher capital investment. This study presents the cost optimisation of flexible MER HEN design which considers the fluctuation probability using break-even analysis. Data were extracted for the Pinch study and assessment for flexibility and MER was performed. The MER heat exchanger maximum size (MER-HEM) is able to handle the most critical supply temperature fluctuations while minimising the utility consumption. The overdesign factor can affect the total annualised cost at a certain probability of fluctuation occurrence. Thus, the break-even analysis of the MER-HEM is performed to determine the probability that resulted in high savings of total annualised cost. Two Scenarios (A and B) with different fluctuation probabilities were used to demonstrate the methodology. Application of the proposed methodology on an Illustrative Case Study shows that, for the fluctuation at hot stream H1, the MER-HEM gives the optimum annualised total cost for Scenario A with additional savings of 10%. For Scenario B, the MER heat exchanger original size (MER-HEO) is the optimum, giving an additional savings of 4%. For cold stream C1, the MER-HEO is the optimum for Scenario A, giving an extra savings of 4% whereas the MER-HEM is the optimum for Scenario B, yielding an extra savings of 9%. [ABSTRACT FROM AUTHOR]

The modification of heat exchanger networks of industrial enterprises targeting energy saving solutions requires proper heat transfer equipment. The estimation of the optimal design parameters for heat exchangers requires reliable mathematical models for the description of the thermo-hydraulic processes inside the channels, and adequate optimisation methods. This work proposes the novel mathematical model and optimisation algorithm for the selection of welded plate heat exchanger (WPHE) operating in ammonia synthesis column. It enables finding the optimal design with the specified shape of the corrugated plates, distribution of flows and number of plates and passes. The developed algorithm is implemented in Mathcad software. The application of the proposed approach is illustrated by example in which the resulted WPHE with the cross flow in one pass and overall symmetric counterflow of streams has shown a reduction of heat transfer area 25% compared to previously tested in industry WPHE with unsymmetric passes arrangement. [ABSTRACT FROM AUTHOR]

Optimization of Heat Exchanger Networks (HEN) has received considerable attention in last decades, but a few studies on inherent safety. In this paper, risk assessment is considered simultaneously during the synthesis of HENs. As risks depend on the equipment selected, a superstructure enabling selection of direct and indirect heat transfer between hot and cold streams and different types of heat exchangers (HEs) was tested. The individual heat transfer and the overall HEN risk were analyzed. Different individual risk limits have been introduced for certain types of heat transfer, e.g. between two process streams or between utility and process streams. The sensitivity analyses were performed first, considering only toxicity as a risk, but later flammability and explosiveness were also simultaneously tested, in order to consider the most important aspects of safety. The results obtained indicate that rather significant changes in HEN designs can increase safety, while still exhibiting similar economic efficiency. [ABSTRACT FROM AUTHOR]

Pressure drop is an important consideration in Total Site Heat Integration (TSHI). This is due to the typically large distances between the different plants and the flow across plant elevations and equipment, including heat exchangers. Failure to consider pressure drop during utility targeting and heat exchanger network (HEN) synthesis may, at best, lead to optimistic energy targets, and at worst, an inoperable system if the pumps or compressors cannot overcome the actual pressure drop. Most studies have addressed the pressure drop factor in terms of pumping cost, forbidden matches or allowable pressure drop constraints in the optimisation of HEN. This study looks at the implication of pressure drop in the context of a Total Site. The graphical Pinch-based TSHI methodology is extended to consider the pressure drop factor during the minimum energy requirement (MER) targeting stage. The improved methodology provides a more realistic estimation of the MER targets and valuable insights for the implementation of the TSHI design. In the case study, when pressure drop in the steam distribution networks is considered, the heating and cooling duties increase by 14.5% and 4.5%. [ABSTRACT FROM AUTHOR]

Abstract: Large amounts of thermal energy are transferred between fluids for heating or cooling in industry as well as in the residential and service sectors. Typical examples are crude oil preheating, ethylene plants, pulp and paper plants, breweries, plants with exothermic and endothermic reactions, space heating, and cooling or refrigeration of food and beverages. Heat exchangers frequently operate under varying conditions. Their appropriate use in flexible heat exchanger networks as well as maintenance/reliability related calculations requires adequate models for estimating their dynamic behaviour. Cell-based dynamic models are very often used to represent heat exchangers with varying arrangements. The current paper describes a direct method and a visualisation technique for determining the number of the modelling cells and their size. [Copyright &y& Elsevier]

To incorporate exchanger dimensions as a design objective in plate and fin heat exchangers, a variable that must be taken into consideration is the geometry of the finned surfaces to be used. In this work, a methodology to find the surface geometry that will produce the required heat transfer coefficient and pressure drop to achieve the design targets was developed. The geometry of secondary surfaces can be specified by the fin density, which represents the number of fins per unit length. All other geometrical features, as well as the thermo-hydraulic performance, can be derived from this parameter. This work showed the way finned surfaces are engineered employing generalised thermo-hydraulic correlations as a part of a design methodology. It also showed that there was a volume space referred to as volume design region (VDR) where heat duty, pressure drop, and dimensions could simultaneously be met. Such a volume design region was problem- and surface-specific; therefore, its limits were determined by the heat duty, the pressure drop, and the type of finned surface chosen in the design. The application of this methodology to a case study showed that a shell and tube heat exchanger of 227.4 m2, with the appropriate fin density using offset strip-fins, could be replaced by a plate and fin exchanger with any combination of height, width, and length in the ranges of 0–0.58 m, 0–0.58 m, and 0–3.59 m. The approach presented in this work indicated that heat exchanger dimensions could be fixed as a design objective, and they could effectively be achieved through surface design. [ABSTRACT FROM AUTHOR]

Energy is a fundamental element supporting societal development, particularly with the increasing dependency on the Internet of Things. It is also the main contributor to environmental impacts and subsequently, a potential sector for mitigation. Sustainable energy system design considers energy savings and energy efficiency, waste and consumption reduction, process efficiency enhancement, waste heat recovery, and integration of renewable energy. Emerging tools range from advanced Process Integration, modelling, simulation, and optimisation, to system analysis and assessment. This review covers selected emerging studies promoting sustainable system design, including the recent developments reported in the Special Issue (SI) of the 22nd Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction (PRES'19). The primary emphasis was to enhance the economic and environmental performance. However, social factors were also highlighted as essential for future sustainable development. The discussion and analysis in this review focus on the most recent developments of (a) heat integration and heat transfer; (b) integrated and newly developed heat exchangers, (c) integration of renewables, and (d) roles in economic and environmental sustainability. The key results are highlighted, and future research ideas are suggested according to their links to a broader context. [ABSTRACT FROM AUTHOR]

Heat exchanger network (HEN) retrofit is a vital task in the process design to improve energy savings. Various types of heat exchangers such as shell and tube, double-pipe, compact plate, and spiral tube have their working temperature ranges and costs. Selecting suitable types of heat exchangers according to their temperature ranges and costs is a crucial aspect of industrial implementation. However, considering the type of heat exchangers in the HEN retrofit process is rarely seen in previous publications. This issue can be solved by the proposed Shifted Retrofit Thermodynamic Grid Diagram with the Shifted Temperature Range of Heat Exchangers (SRTGD-STR). The temperature ranges of six widely used heat exchanger types are coupled in the grid diagram. This diagram enables the visualisation of identifying the potential retrofit plan of HEN with heat-exchanger type selection. The retrofit design aims to minimise utility cost and capital cost. An illustrative example and a case study are presented to show the effectiveness of the method. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Highlights • Large-scale HEN synthesis is a first step towards Total Site synthesis. • Two-step MILP/MINLP approach was developed for larges-scale HEN synthesis. • Number of potential matches is significantly reduced, solutions are directed to global optima using MILP TransHEN model. • MINLP model HENSyn use reduced superstructure for HEN synthesis. • Problem with 173 process streams and multiple hot utilities solved. Abstract Although different methodologies for the synthesis of heat exchanger network (HEN) problems have been introduced in the last forty years, there are still significant challenges to be addressed, such as solving large-scale problems. This study focuses on synthesizing large-scale HENs using mathematical programming to achieve near globally optimal solutions based on a two-step MILP/MINLP approach. In the first step a mixed-integer linear programming (MILP) model, TransHEN, is used that obtains a globally optimal solution at selected Δ T min. By utilisation of this model, the most promising matches are selected based on feasibility and viability. The second step entails using the matches selected in the TransHEN of Step 1 in a mixed-integer nonlinear programming (MINLP) model, HENsyn, using a reduced superstructure, to generate a feasible HEN. This study presents also a simultaneous Total Site synthesis with direct heat transfer between processes, and is the first step in the wider project of synthesising an entire Total Site with direct and indirect heat transfer; and is the first step in the wider scope of synthesising an entire Total Site with direct and indirect heat transfer; however, in order to attain this goal, a tool capable of an appropriately handling large number of streams is required. The newly developed procedure has been tested on several case studies, two of which are presented in this paper. For Case study 1 the results obtained lie within the range of best solutions obtained by other authors. Case study 2, consisting of 173 process stream and involving multiple hot utilities, shows the applicability of the developed method to handle large-scale HEN problems. [ABSTRACT FROM AUTHOR]

Heat exchanger leakage leads to the shutdown of the whole set of equipment, which affects the economy of the production and directly threatens the safe operation of equipment. This contribution aims to add a quantitative leakage risks characterisation of including or excluding specific process streams into the dataset for Heat Integration (HI). This has been achieved by formulating a mathematical model of the HEN, where the objective function contains leakage risk assessment embedded into the total cost, based on risk severity and mean occurrence frequency. Equations for investment calculation are linearised, and a novel iteration algorithm is developed to solve the model. A sensitivity analysis of the resulting cost against the levels of potential risk is performed. The results show that there is a turning point with the increase of risk level that changes HEN topologies. It allows engineers to use a quantitative criterion for HI. [ABSTRACT FROM AUTHOR]

Heat Pinch Analysis retrofit projects are typically performed by evaluating and maximising the heat recovery potentials within the individual process units. Once the potential improvements from the individual units have been assessed, the Total Site (TS) Heat Integration analysis is performed. Such approach may steer designers away from the promising retrofit opportunities and to lead towards suboptimal heat exchanger networks (HEN). This paper presents an effective retrofit framework for a TS system to determine the most cost-effective retrofit options and maximise the potential savings. Instead of performing the typical unit-wise process retrofit, the strategy is to determine the baseline total site consumption and benchmark targets, and to identify retrofit options from the TS context. This TS retrofit framework has been tested on a case study involving a petrochemical plant comprising of multiple process sections. The results of the analysis show that significant energy savings can be realised when both direct and indirect heat recovery retrofit options are evaluated. Further energy savings can be achieved via the Plus–Minus Principle that helps pinpoint the correct locations of heat surpluses and deficits and lead to the appropriate TS retrofit solution. As a conclusion, energy retrofit projects should be approached from the TS context, followed by the unit-wise retrofit (i.e., retrofit of the individual process sections). [ABSTRACT FROM AUTHOR]

• An integrated software suite for heat recovery system design is presented. • It can be used for equipment design, system analysis and network optimisation. • Designs for heat exchanger, HEN, and WGCTO are integrated. • Case studies are given to demonstrate the developed software. Heat Integration (HI) with heat exchangers requires intimate knowledge and intensive calculations to set energy-saving targets to achieve the goal of efficient energy utilisation. The Shell and Tube Heat Exchanger (STHX) Design Software Module, or SPIL-HX package developed by the SPIL team, offers features that support engineers to design and rate original STHXs, STHXs coupled with the shell-side enhancement technologies, i.e., with segmented baffles and with helical baffles. This software tool also provides design solutions for the Waste Gas Compact Thermal Oxidiser (WGCTO), identifying the unit design capable of simultaneous combustion and heat exchange for waste gases. SPIL-HX package is also capable of automatic Heat Exchanger Network (HEN) synthesis and retrofit. With the built-in algorithm, the software can provide the optimal solution for HI, which significantly reduces operating, capital, and design costs. A user-friendly interface facilitates the use of the developed software. [ABSTRACT FROM AUTHOR]

Abstract: Total Site Heat Integration (TSHI) is a technique of exchanging heat among multiple processes via a centralised utility system. An analysis of the integrated multiple processes, also known as the Total Site (TS) system sensitivity, is needed to characterise the effects of a plant maintenance shutdown, to determine the operational changes needed for the utility production and to plan mitigation actions. This paper presents an improved Total Site Sensitivity Table (TSST) to be used as a systematic tool for this purpose. The TSST can be used to consider various ‘what if’ scenarios. This tool can be used to determine the optimum size of a utility generation system, to design the backup generators and piping needed in the system and to assess the external utilities that might need to be bought and stored. The methodology is demonstrated by using an Illustrated Case Study consisting of three processes. During the TS normal operation, the Total Site Problem Table Algorithm (TS-PTA) shows that the system requires 1065kW of High Pressure Steam and 645.5kW of Medium Pressure Steam as the heating utility, while for the cooling utility, 553.5kW of Low Pressure Steam and 3085kW of cooling water are required. The results of the modified TSST proposed that a boiler and a cooling tower with the system design requiring a maximum capacity of 2.172MW of steam and 4.1865MW of cooling water are needed to ensure an operational flexibility between the three integrated processes. [Copyright &y& Elsevier]

• Model for heat exchanger network (HEN) retrofit with enhancement technologies is formulated. • HEN retrofit model with long-term investment and maintenance planning model is developed. • Service life, depreciation and reliabilities of heat exchangers are considered in the planning model. • Results obtained yield 14% or higher net present value compared to previous retrofit solutions. • A graphical tool is created to track the reliability and maintenance status of heat exchangers. Process Optimisation has been the core topic in chemical process industries for decades. However, the performance of the asset strongly influences the production efficiency as well. In the case of Heat Exchanger Network (HEN), the retrofit decisions are often aimed to maximise energy savings and minimise the associated cost. However, the age and performance of heat exchangers have a great influence on the HEN efficiency as well. This study brings innovative retrofit algorithms, integrating exchangers' lifetime and reliability functions to visualise the benefits of the hybrid process and asset optimisation. The HEN retrofit structures are optimised, considering various heat intensification methods. The model is formulated based on the novel concept of Shifted Retrofit Thermodynamic Grid Diagram (SRTGD). A Mixed Integer Linear Programming (MILP) model is formulated for the investment and maintenance planning. The operating life of the network is discretised into multiple periods, and a decision is made within each period: whether to upgrade the heat exchangers, purchase new heat exchangers – for replacement or adding to the network, maintain the heat exchangers or perform nothing. Two realistic case studies are used to elucidate the application of the method. Under a 20 y planning horizon, the Net Present Value (NPV) obtained are higher than the previous works, i.e. 17% higher for case study 1 with 51% utility savings, and 14% higher for case study 2 with 74% utility savings. The proposed HEN retrofit decisions are proven to be cost-effective. A graphical tool has been developed to track the reliability and maintenance status of the exchangers to provide a significant guide to the economically optimum decisions. [ABSTRACT FROM AUTHOR]