Problem Table Algorithm Research Articles

A generic algorithm-based application for pinch-exergy prediction in process industries: A case study

In the industrial sector, efficient production and optimal use of thermal energy are primary concerns for managers and engineers. Considerable research has been devoted to improving and promoting thermal energy efficiency, especially energy recovery in the context of sustainability. Pinch analysis is one of the most powerful methods in this regard. To maximise the energy recovery (MER), the pinch method is well-established in designing an optimal heat exchange network (HEN). Exergy analysis is combined with the pinch method to minimise the work potential loss (exergy loss) while ensuring maximum heat recovery. This study presents a generic algorithm built using Python language to predict and quantify energy and exergy targets in industrial processes. It provides a framework to guide experts and planners in efficiently using the combined analysis tools. The generic algorithm is based on advanced numerical and graphical tools. It provides exergy problem table algorithm (Ex–PTA) and grand composite curve (EHR and HRP) tools. For Δ T min = 10°C, the generic algorithm is implemented in a building complex case study. The energy targets for heating and cooling requirements are 316.2625 kW and 0 kW, respectively. The obtained exergy targets are less attractive given an improvement from advanced utility integration; this is due to the treated system (medium-temperature system) and not to the reliability and efficiency of the generic algorithm. To evaluate the generic algorithm calculations, they are executed in a low-temperature process in which pinch exergy analysis (PExA) has already been performed. The simulated and generated results are identical, demonstrating the reliability and effectiveness of the developed generic algorithm.

Simultaneous retrofit of direct and indirect Heat Exchanger Storage Network (HESN) via individual batch process stream mapping

This paper proposed a novel methodology to retrofit Heat Exchanger Storage Networks (HESN) of batch processes using a modified graphical retrofit tool, namely batch Stream Temperature Enthalpy Plot (batch STEP). Unlike other graphical retrofit tools, batch STEP maintains individual characteristic of process streams as well as serves as the one-stop retrofit tool to retrofit direct and indirect HESN simultaneously. The conventional batch heat integration typically aimed to synthesise new Heat Recovery Loops (HRLs) for heat recovery enhancement without exploiting the benefits of reusing existing HRLs in saving the additional volume of heat storage units (HSUs) and space allocated for retrofit. Thus, this paper extends the STEP continuous retrofit methodology to batch processes by introducing a batch STEP diagram for identification of the potential process streams to be integrated into existing HRLs and potential modifications of existing HRLs operating temperature. The methodology also introduces HRL– problem table algorithm (HRL-PTA) and heuristics to target the maximum indirect heat recovery and integrate process streams into the existing HRLs systematically. The methodology proposed achieves plant savings of 23.9%–60.0% for hot utility, 25.9%–42.2% for cold utility and a reduction of 6.3%–8.1% for additional volume of HSUs required in two illustrative case studies.

Heat exchanger network design for the optimization of total annual cost of the Catalytic Reforming Unit

This research involved the energy integration of the Catalytic Reforming Unit of a Refinery using Aspen Pinch 11.1 Software. The operating data of the unit was analyzed on composite and grand composite curves from the Software to obtain an optimum minimum temperature of 15oC, pinch temperature of 149.5oC and hot and cold utilities targets of 37094 kW and 22440 kW respectively. Problem table algorithm (PTA) was used as a sensitivity tool to test the accuracy of these values; the exact same values were obtained with less than 0.4% difference between the energy targets. This integration achieved a minimum heat recovery (QREC) of 55465.00 kW with an increase in the number of heat exchangers from eighteen (18) to twenty one (21) with total area of 1995.80m2. Power law correlation was used for the heat exchanger costing to obtain a minimum Annual Capital Cost of $5,918.25/yr, Annual Energy Cost of $2,892.28/yr and Total Annual Cost (TAC) of $57,442.90/yr. By extension, these will certainly reduce the annual operating cost in terms of cost of utilities as well as minimize pollution emissions. Pinch analysis provides the best target for the minimum energy consumption as well as minimum total annualized cost.

Adapted Time Slice Model of Pinch Analysis for Direct-Indirect Heat Recovery in Buildings

Heat integration techniques such as pinch analysis can play a significant role in saving energy in the design of buildings. The application of pinch analysis in this sector encounters difficulties due to the highly time-dependent behavior of energy streams such as waste heat and solar thermal collectors, as well as the possible need for heat storage units (HSUs). The existing pinch models in the literature either bear little relation to reality because they ignore the time dependency of the streams, or they do not respect the pinch analysis minimum temperature difference of the system, which leads to temperature penalties. This study introduces a novel and straightforward adapted time slice model of pinch analysis, beneficial for energy targeting in buildings. First, an algorithm for the selection of the appropriate time slice duration is proposed. Then, additional steps are embedded in the conventional problem table algorithm to account for both direct heat transfer (co-existing streams) and indirect heat transfer (time mismatched streams requiring thermal energy storage). i.e., the modified table includes both external and internal streams, respectively. The detailed application of the proposed model is demonstrated through the analysis of a direct-indirect heat recovery system for a residential test building equipped with waste heat and solar energy, considering a summer’s day. This case study, or sample calculation, determines the HSU specifications, including their design temperatures and volumes. A heat exchanger evaluation quantifies both their number and their thermal conductances, which are an economic indicator of the system capital cost.

Heat Integration for the Air-Conditioning Application using Waste Heat Recovery in the Cast Iron Industry

The energy demand in the cast iron industry has been increasing for the past decades. Besides this, there is also high-energy demand for air conditioning, especially in the hot climate of the United Arab Emirates (UAE). Process integration tools can identify and measures the potential of energy saving via Heat Integration. The current paper presented a case study for industrial buildings' cooling demand via absorption chiller utilizing waste heat from a cast iron industry located in the Emirates Industrial Area, Sharjah, UAE. The Heat Integration approach has been applied via Pinch Analysis and Problem Table Algorithm to identify the minimum hot and cold utilities. Hot streams consist of four high-temperature furnaces exit gases. The heat exchanger network has been designed to fulfill the energy requirement using ProSim Simulis Pinch software (version 2.0). The minimum hot and cold utilities were predicted at 8,793 W and 1,600 W. The Pinch Point was found at 30 (C with more than 80 % of energy recovery. Moreover, the current study can achieve the lowest fuel consumption with fewer emissions, reduced utility consumption, less cost, and superior performance. The paper also includes several recommendations for the improvement of the cast iron industry's overall efficiency.

THERMAL INTEGRATION OF COMPRESSION REFRIGERATION UNITS IN DAIRY FACILITIES

The heat integration of an ammonia compression refrigeration unit, that is used in different dairy facilities, was carried out by the pinch analysis methods. The schematic diagram of such unit with a cooling capacity of 1000 kW was taken as a basis. The main cycle temperatures, refrigerant consumption and its specific heat capacity were calculated for a given refrigerating capacity. Based on these data, a stream table was formed, that included a hot stream of a refrigerant – ammonia – and also two cold streams: water for chemical water treatment and water for technology. The hot stream of ammonia was divided into three streams: cooling of ammonia vapors, condensation and subcooling. Heat capacities flowrates and heat loads (stream enthalpy change) of the streams were determined. The minimum temperature difference in heat exchangers DTmin = 8°С was determined on the basis of technical and economic calculations for this process. The composite curves were plotted for the minimum temperature difference. The pinch temperatures were determined by the problem table algorithm for the hot and cold streams. The minimum values of hot and cold utilities load (QHmin and QСmin) were determined. The heat recovery capacity was determined, which was 701.8 kW. A grid diagram was built and heat exchangers are arranged in accordance with CP and N rules. The retrofit of process flowsheet is proposed on the basis of the grid diagram that includes the installation of three heat exchangers, one cooler and two heaters to achieve the target temperatures and flow rates. The use of Alfa Laval plate heat exchangers is proposed as heat exchange equipment. The payback period of the design is about two years.

Optimal Sizing of a Trigeneration Plant Integrated with Total Site System Considering Multi-period and Energy Losses

Rising awareness for the environment as well as concerns over the sustainability of fossil fuels has encouraged developed and developing countries to find alternative ways to enhance the thermal efficiency of current power systems. The thermal efficiency of power plants can be increased from 30 – 40 % up to 80 – 90 % through the implementation of a trigeneration system by recovering dissipated waste heat for other purposes. The trigeneration system can be defined as a technology that can produce simultaneous power, heating, and cooling energy from the same fuel source. Trigeneration System Cascade Analysis (TriGenSCA) methodology is an optimisation approach based on Pinch Analysis that has been used to establish the guidelines or the proper size of the trigeneration system. This paper proposes a modification of TriGenSCA by considering a multi-period of energy consumption to optimise the size of the utility in the centralised trigeneration system by considering the transmission and storage of energy losses in the Total Site system. There are six steps involved including data extraction, identification of time slices, Problem Table Algorithm (PTA), Multiple Utility Problem Table Algorithm (MU PTA), Total Site Problem Table Algorithm (TS PTA), and modified TriGenSCA. The methodology has been tested on the centralised nuclear trigeneration system in a Total Site System as a case study and results shown that thermal energy needed by the Pressurized Water Reactor (PWR) trigeneration system with transmission losses is 2,427 MW whereas thermal energy needed by the PWR trigeneration system without transmission losses is 2,424 MW. The TriGenSCA with consideration of transmission and storage energy losses is useful for engineers and designers to determine the exact value of energy for trigeneration plant.

Heat integration applied on low thermal energy system: Building complex case study

The tertiary-building sector is one of the most important energy consumers in the Morocco, especially thermal energy. Its intensive use of energy is highly related to the building’s inefficient processes. The Moroccan strategy for energy efficiency aims mainly to save 12% of energy consumption by 2020 and 15% by 2030, which reinforce the appearance of many energy saving alternatives ranging from sensitization and construction laws to engineering applications. The present paper addresses the problem of the building complex energy efficiency in order to improve its performance thermally. The proposed approach in this work is based on the pinch technology which is a technique widely used to integrate and optimize the energy of thermal systems and which has demonstrated its successfulness for industrial process. The simulation results reveals that the potential thermal energy saving reaches 21.16%, with heat exchange network design initially proposed to clearly show the potential recovered. Based on the composite curves (CCs), the problem table algorithm (PTA) and the grand composite curve (GCC), the pinch point temperature is turned out to be 15°C with 316,99 kW of hot utility. The obtained results reveal that the proposed pinch technology perform its effectiveness not only in the industrial sector but also in the building-tertiary.

Natural gas liquid (NGL) distillation process using driving force and thermal pinch analysis methods: Energy and economic assessment

Distillation column is one of the effective unit operations that is commonly used to separate chemical mixtures. The only drawback of this separation process is its huge energy consumption especially for a multicomponent separation process which involves a series of distillation columns. Therefore, an optimal sequence must be determined to address the issue. This research proposes the methodology to determine the optimal sequence of distillation columns by using driving force method. Then, thermal pinch analysis is applied to obtain further energy saving in the process. The case study selected is a distillation process to recover 5-component of natural gas liquid (NGL) mixture. Based on the input data, the driving force sequence is determined first and simulated together with a conventional sequence (direct sequence). Then, the extracted data from the simulation will be used for thermal pinch analysis via problem table algorithm (PTA). From the results of PTA, energy consumption between both sequences were compared including the energy consumption before and after the thermal pinch analysis. In addition, economic analysis has been performed as well to indicate which sequence has lower capital and operating costs based on the proposed heat exchanger network (HEN). According to the results, the combination of the driving force and thermal pinch analysis methods has successfully recorded 48% of energy savings and operating cost, and 58.2% capital cost saving compared to the conventional sequence (direct sequence). Therefore, it can be said that the proposed framework has a great potential to be employed towards the process and economic feasible distillation process.

Energy saving potential of 6-component aromatic mixture via Energy Integrated Distillation Columns Sequence (EIDCS) method

Distillation column is a well-known unit operation in chemical and petrochemical industries for an intended separation task. However, the energy usage still becomes a problem particularly for a multicomponent system of distillation columns sequence. Therefore, this research aims to investigate the applicability of Thermal Pinch Analysis to be employed in a distillation columns sequence to solve the problem. The method is complemented by the sequencing method of Driving Force which leads to a novel method namely Energy Integrated Distillation Columns Sequence (EIDCS). This systematic method has been designed for optimal distillation columns sequence and further energy saving by Thermal Pinch Analysis. The Driving Force Sequence was firstly determined by the use of Driving Force Plot. Then the shortcut and rigorous simulations have been carried out and the resulting data were extracted for Thermal Pinch Analysis at a fixed value of ΔTmin at 10 °C. Next, the Problem Table Algorithm (PTA) was constructed to indicate the possible energy saving for the distillation columns sequence. Finally, the proposed Heat Exchanger Network (HEN) via Grid Diagram that satisfies the energy requirement was constructed. A case study of 6-component Aromatic Mixture has been selected to evaluate the proposed EIDCS method in this study.

A simulation-based targeting method for heat pump placements in heat exchanger networks

Heat integration of heat pumps and heat exchanger networks is of great interest because it can utilize low-temperature heat source to supply high-temperature heat sink, saving both hot and cold utilities. In this work, a simulation-based targeting method is proposed for placement of heat pumps in heat exchanger networks to reduce energy consumption. This method combines pinch analysis and rigorous process simulation. Based on the powerful fluid property database, the heat pump system is modelled in Aspen HYSYS. The Problem Table Algorithm is employed to target the demands of hot and cold utilities. Aspen HYSYS and Matlab are then coupled to realize the data transfer between the simulation model and mathematical model, formulating a simulation-based optimization model. The Genetic Algorithm is adopted to solve the formulated model to obtain the best placement of the heat pump. Two cases are analyzed with several working fluids to illustrate the applicability of this method.

A Numerical Pinch Analysis Methodology for Optimal Sizing of a Centralized Trigeneration System with Variable Energy Demands

The energy and power sectors are critical sectors, especially as energy demands rise every year. Increasing energy demand will lead to an increase in fuel consumption and CO2 emissions. Improving the thermal efficiency of conventional power systems is one way to reduce fuel consumption and carbon emissions. The previous study has developed a new methodology called Trigeneration System Cascade Analysis (TriGenSCA) to optimise the sizing of power, heating, and cooling in a trigeneration system for a Total Site system. However, the method only considered a single period on heating and cooling demands. In industrial applications, there are also batches, apart from continuous plants. The multi-period is added in the analysis to meet the time constraints in batch plants. This paper proposes the development of an optimal trigeneration system based on the Pinch Analysis (PA) methodology by minimizing cooling, heating, and power requirements, taking into account energy variations in the total site energy system. The procedure involves seven steps, which include data extraction, identification of time slices, Problem Table Algorithm, Multiple Utility Problem Table Algorithm, Total Site Problem Table Algorithm, TriGenSCA, and Trigeneration Storage Cascade Table (TriGenSCT). An illustrative case study is constructed by considering the trigeneration Pressurized Water Reactor Nuclear Power Plant (PWR NPP) and four industrial plants in a Total Site system. Based on the case study, the base fuel of the trigeneration PWR NPP requires 14 t of Uranium-235 to an average demand load of 93 GWh/d. The results of trigeneration PWR NPP with and without the integration of the Total Site system is compared and proven that trigeneration PWR NPP with integration is a suitable technology that can save up to 0.2% of the equivalent annual cost and 1.4% of energy compared to trigeneration PWR NPP without integration.

Compressor shaft work targeting using new numerical exergy problem table algorithm (ex-pta) in sub-ambient processes

One of the major challenges faced by energy intensive industries is an excessive greenhouse gas emission to the atmosphere due to high consumption of fossil fuels throughout the production processes. Due to high electricity usage in intensive industries, it is strongly advisable to all the engineers and other stakeholders to reduce the amount of energy needed for production, thus reducing carbon footprints. This is because the power generation industry emits approximately 37 % of total carbon dioxide emission to the atmosphere. Process improvement via Process Integration enhances the process energy efficiency, which contributes to the minimisation of fossil fuels and electricity consumption. Sub-ambient processes with refrigeration system are one of the highly energy intensive processes, which consumes a vast amount of electrical energy to run the compressors for fulfilling the process cooling demand. It is crucial to optimise the process-utility heat transfer in the system including the placement of compressors and expanders to minimise the exergy losses and shaft work consumption. This paper presents a combined energy analysis technique of Pinch Analysis and Exergy Analysis to determine exergy losses and compressor shaft work targeting in sub-ambient processes via a novel numerical approach known as the Exergy Problem Table Algorithm (Ex-PTA). The validity of the novel approach is demonstrated by using an illustrated case study. Based on the new numerical method, the total exergy loss in the process is 4.42 kW which is equivalent to 7.4 kW potential savings of compressor shaft work. In the economic analysis, the wasted potential shaft work costs a loss of approximately 19,926 MYR/y which should be avoided to minimise process operating cost.

A Process Integration Method for Total Site Cooling, Heating and Power Optimisation with Trigeneration Systems

Research and development on integrated energy systems such as cogeneration and trigeneration to improve the efficiency of thermal energy as well as fuel utilisation have been a key focus of attention by researchers. Total Site Utility Integration is an established methodology for the synergy and integration of utility recovery among multiple processes. However, Total Site Cooling, Heating and Power (TSCHP) integration methods involving trigeneration systems for industrial plants have been much less emphasised. This paper proposes a novel methodology for developing an insight-based numerical Pinch Analysis technique to simultaneously target the minimum cooling, heating and power requirements for a total site energy system. It enables the design of an integrated centralised trigeneration system involving several industrial sites generating the same utilities. The new method is called the Trigeneration System Cascade Analysis (TriGenSCA). The procedure for TriGenSCA involves data extraction, constructions of a Problem Table Algorithm (PTA), Multiple Utility Problem Table Algorithm (MU PTA), Total Site Problem Table Algorithm (TS PTA) and estimation of energy sources by a trigeneration system followed by construction of TriGenSCA, Trigeneration Storage Cascade Table (TriGenSCT) and construction of a Total Site Utility Distribution (TSUD) Table. The TriGenSCA tool is vital for users to determine the optimal size of utilities for generating power, heating and cooling in a trigeneration power plant. Based on the case study, the base fuel source for power, heating and cooling is nuclear energy with a demand load of 72 GWh/d supplied by 10.8 t of Uranium-235. Comparison between conventional PWR producing power, heating and cooling seperately, and trigeneration PWR system with and without integration have been made. The results prove that PWR as a trigeneration system is the most cost-effective, enabling 28% and 17% energy savings as compared to conventional PWR producing power, heating and cooling separately.

Combined Pinch and exergy numerical analysis for low temperature heat exchanger network

To reduce the dependence on fossil fuel, Process Integration and energy efficiency are crucial in chemical process industry to minimise the consumption of fossil fuels and electricity demand through Heat Exchanger Network (HEN). Pinch Analysis is well established to optimal HEN design to maximize the energy recovery in a process. The stream matches for energy recovery in HEN is important to ensure the temperature potential is not wasted, which the temperature potential could be converted into mechanical work. Therefore, Exergy Analysis has been introduced to work with Pinch Analysis, which ensure the heat recovery stream matches with appropriate temperature differences to minimise the work potential (exergy) loss. This paper demonstrates how Pinch Analysis and Exergy Analysis is simultaneously applied to determine exergy targets (rejection, requirement and avoidable losses) in low temperature HEN. A novel numerical tool known as Exergy Problem Table Algorithm (Ex-PTA), is proposed in this paper as a numerical method to the conventional graphical representation in Extended Pinch Analysis and Design (ExPAnD) method. The proposed tool produces more realistic and achievable results. The net shaft work requirement of the refrigeration system is also determined together with the system COP. This paper explored the effect of setting heat exchangers' minimum approach temperature (ΔTmin) on the exergy targets for low temperature HEN design. The external utility requirement and unavoidable exergy losses increased with ΔTmin, while avoidable exergy losses and energy recovery reduced with respect to ΔTmin. The net power requirement of the system increased with the ΔTmin increment, however, the system COP reduced due to higher increment rate of compression compared to expansion work generation. The optimal ΔTmin was determined at 2 °C for heat recovery system in the case study based on super-targeting approach, which considers the total annualized cost, operating cost and capital cost.

Energy Integrated Distillation Column Sequence by Driving Force Method and Pinch Analysis

Distillation is a common separation process since its emergence in the early 20th century due to its capability for mass production without compromising the product(s) quality. However, the energy efficiency is still become the challenge for the industry players. Since then, they put so much effort in ensuring the energy efficiency of the process. It is not only for economic purpose but also to address the environmental issue whereby the legislation become stringent over the years. Therefore, this paper aims to investigate the energy efficiency of distillation column sequence by using the pinch analysis method. Rigorous simulation of the distillation for component n-butane, n-hexane, n-heptane and n-nonane has been carried-out for 5 different sequences namely direct, indirect, driving force sequence (indirect-direct), direct-indirect and split for energy analysis. Aspen HYSYS V9 has been used for the simulation while the data was extracted for pinch analysis including the construction of problem table algorithm to obtain the minimum cooling and heating load for each sequence. The results that were analyzed and compared including total heat load, heating load and cooling load. Then the grid diagrams for the best sequence was constructed. From the results of energy analysis, all distillation sequences except for direct-indirect sequence recorded further energy saving compared to the base case whereby the highest saving is driving force sequence at 6.31% total energy saving. It also recorded the highest percentage of heating and cooling load at 4.85% and 9.05% respectively. This paper also strengthens the advantage of driving force method in determining the best sequence since it was proved to produce lower energy consumption compared to others. Then, the energy can be further reduced by using the pinch analysis. Therefore, for this case study, it can be concluded that the heat integration via pinch analysis is a promising method for further saving for any distillation column sequence.

Process modification of Total Site Heat Integration profile for capital cost reduction

The Total Site Profile (TSP) can be a powerful tool to evaluate the potential for further Heat Integration improvement for a Total Site (TS). A systematic Total Site Heat Integration (TSHI) methodology to target decreasing the capital cost of heat transfer units at Total Sites has been developed. The methodology includes a set heuristics that have been developed to identify and prioritise the strategic process changes to apply, as a result of changes in the TSP shape. The TSP and expanded Total Site Problem Table Algorithm (TS-PTA) can provide useful insights for the plant designers to identify “where”, in terms of which temperature interval, and which streams within the entire TS to focus the process modification efforts. The keep hot stream hot (KHSH) and keep cold stream cold (KCSC) principles can be applied to favourably change the TSP shape to provide a larger temperature driving force to further reduce the HTA and capital costs. In one of the case study, the application of KHSH and KCSC on TSP increases the temperature driving force between the medium pressure steam utility and process resulting in a reduction of 3,827 m2 heat transfer area (HTA) and a saving of 10% in heat exchangers cost. The proposed changes to the selected streams should be assessed from feasibility, practicality and economic perspectives. The selected and potentially acceptable process modification options can be conveniently merged with potential retrofit project (e.g. to increase plant capacity) considered for the Total Site.

Enthalpy Table Algorithm for design of Heat Exchanger Network as optimal solution in Pinch technology

The Heat Process Integration with Pinch technology is divided into two separate parts – targeting with super-targeting and design of a solution. Super-targeting determines the minimal values for heat demand and minimal allowed temperature difference in heat exchangers. The second part is design of Heat Exchanger Network as applicable solution. A number of studies explore methods and techniques for design of Heat Exchanger Networks based on data from Pinch analysis. Some of them use different optimization methods and give complex solutions. This paper presents a modified technique for Heat Exchanger Network design. This technique uses a combination of Problem Table Algorithm (PTA) and Pinch Design Method (PDM). The main idea for this technique is the design of sub-networks of heat exchangers for every enthalpy interval determined by the breaking points on the hot and cold composite curves. All these sub-networks were connected into one Heat Exchanger Network in the same order as enthalpy intervals exist in composite curves' graphs. The created Heat Exchanger Network was simplified with the basic rules for network relaxing in Pinch technology. The results of this technique were Heat Exchanger Networks that have high-energy recovery, and it got the optimal solution, or it was close to it. This technique is easy to apply, but in some cases, the primary Heat Exchanger Network's designs could have a very complex composition.

Process modifications to maximise energy savings in total site heat integration

This paper extends the scope of the Pinch Analysis for process modifications of individual processes to total site heat integration (TSHI). The Plus–Minus principle has been adapted to enable the beneficial process modification options to be selected in order to maximise energy savings in TSHI. The Total Site Profile (TSP) is divided into three regions: (a) the region above the horizontal overlap between the Site Sink and Source Profiles, (b) the horizontal overlap region and (c) below the horizontal overlap region. The proposed methodology identifies the options to reduce utility targets in these regions using the TSP, Site Utility Composite Curves (SCC), Utility Grand Composite Curve (UGCC), modified Problem Table Algorithm (PTA), Total Site Problem Table Algorithm (TS-PTA) and some new heuristics. The identified changes on the TSP are then linked to the specific changes at the individual processes. The illustrative case study shows that the Plus–Minus principle application in the TSHI context can further improve heat recovery. The proposed spreadsheet-based methodology combines the advantages of graphical visualisation, as well as the numerical precision.

Algorithmic targeting for Total Site Heat Integration with variable energy supply/demand

Fluctuating renewable energy supply presents a challenge for applying energy-saving methodologies such as Process Integration. Graphical targeting procedures based on the Time Slices (TSLs) have been proposed in previous works to handle the energy supply/demand variability in TSHI. The targeting procedures for TSHI with TSLs include the construction of Composite Curves, Grand Composite Curve and Total Site Profile for each time interval. Heat Integration analysis utilising a numerical algorithm typically offers higher precision and more rapid calculations as compared to the graphical approach. This paper introduces an algorithm to efficiently perform utility targeting for a large-scale TSHI system involving renewable energy and variable energy supply/demand to include TSL. The presented tool is an extension of the Total Site Problem Table Algorithm (TS-PTA), which has been previously used for processes with steady energy supply/demand. Due to its algorithmic nature, the technique presented enables the accurate and rapid determination of the stream origins, and can be embedded into larger algorithms. Optimised heat storage facilities are used to manage the variable energy supply and demand. The Total Site Heat Storage Cascade (TS-HSC) is the core of the algorithm. The new developed tool is incorporated with the heat losses for the thermo-chemical energy storage systems. The process start-up and continuous operations are considered in the novel methodology. The tool is featured to analyse the heat excess in specific TSLs that can be cascaded to the next TSL via energy storage system during start-up and operation. The proposed tool can be also used to estimate the required heat storage capacity.