A review on heat and mass integration techniques for energy and material minimization during CO2 capture <s> State of the art in the application of heat integration techniques <s> Cement plants and power plants are two of the most significant sources of greenhouse gases emissions. Many CO 2 reduction options have been proposed in literature for both sectors. They are mainly focused on CO 2 capture in power plants, but, in the short‐term, industrial processes are going to play an important role in achieving this objective. In particular, one of the disadvantages in cement plants is that CO 2 has two sources: fuel combustion and lime calcination. For this reason, proposed solutions could partially reduce a limited quantity of emissions. The sector is forced to use CO 2 capture systems for further reductions. Preliminary results about the implementation of post‐combustion and oxyfuel combustion systems for CO 2 capture show low energetic penalties and important emissions reduction. Nevertheless, a detailed analysis, not only of CO 2 emissions, but of raw materials and its disposal, primary energy and waste energy, could give optimum results from an environmental, energetic, and economic perspective. The combination/integration by industrial symbiosis of a power plant, a cement plant and a CO 2 capture system is proposed in this work. Calcium‐looping is chosen as the most suitable CO 2 capture option for this application. The re‐use of waste CaO coming from CO 2 capture in the cement plant, and the utilization of waste energy from a clinker cooling and capture system to produce additional power are the main advantages of this proposal. Process flow diagrams and heat and mass balances are calculated and presented in this work. Results show a low value of the CO 2 avoided cost, 12.4 €/t, that is smaller than in any other combination of power plant with capture system or cement plant plus capture system, making this proposal economically very attractive. Moreover, an important amount of CO 2 emissions is avoided ‐ 94% ‐ due to the energetic efficiency augmentation, the reduction of raw and decarbonizated materials, and the CO 2 capture system. © 2011 Society of Chemical Industry and John Wiley & Sons, Ltd <s> BIB001 </s> A review on heat and mass integration techniques for energy and material minimization during CO2 capture <s> State of the art in the application of heat integration techniques <s> Heat and mass such as water and solvents are two key utilities in process industry. Simultaneous reduction of both utilities can reduce plant capital as well as operating costs. Though there are mathematical modeling techniques that can produce global optimal solutions, graphical methods are often preferred to provide insights through visualization. This paper presents a new graphical approach named superimposed mass and energy curves (SMEC) for simultaneous mass and heat reduction applicable to both mass transfer-based and non-mass transfer-based systems. Source and demand allocation curves and heat surplus diagram are superimposed on a plot of flowrate versus mass load/temperature to guide design towards the minimum utility targets. This method provides a useful visualization tool on the simultaneous effects of mass and energy reduction. Application of the graphical procedure on case studies involving water and ammonia solvents achieved the minimum mass consumption and near optimal energy usage. <s> BIB002 </s> A review on heat and mass integration techniques for energy and material minimization during CO2 capture <s> State of the art in the application of heat integration techniques <s> A large amount of low grade energy is often wasted without heat recovery in the process industry. Over-the-fence heat integration for district heating (DH) can be suggested to utilize this waste heat and therefore alleviate the carbon footprint of the integrated energy system. The economic performance of over-the-fence process integration depends on the cost of fuel, electricity and distance for the transfer of waste heat to DH network. A new design methodology has been developed to systematically evaluate the economic benefit of integration of low grade heat with local DH networks. A site-wide analysis tool using site composite profiles is incorporated in the developed design method in order to identify the quality and quantity of low grade heat available from the site. The optimization framework developed identifies economically acceptable distance for the over-the-fence heat recovery from the industrial site to local community, subject to economic parameters and engineering constraints. A case study has been carried out to demonstrate the design methodology, and the results from the case study illustrate techno-economic and engineering barriers in practice for the implementation of low grade heat recovery beyond the site. <s> BIB003 </s> A review on heat and mass integration techniques for energy and material minimization during CO2 capture <s> State of the art in the application of heat integration techniques <s> The optimal design of heat exchanger networks (HENs) has a great influence on the profitability of a plant. The optimisation is based on trade-offs between investment and operational cost. The full lifetime of the HEN and future utility prices have to be considered rather than optimising HEN on a yearly basis using current utility prices. Single-period optimisation and synthesis models for HENs reflect current utility prices only. These prices can fluctuate rather quickly and the optimal solution may be very different from a year to year. Deterministic and stochastic multi-period mixed-integer nonlinear programming (MINLP) models for HEN synthesis have been developed to account for future price projections, where the utility cost coefficients are forecasted for the lifetime of the process. An optimal design is then determined for each projection and these designs are compared against a design with fixed current prices by applying the Incremental Net Present Value and other economic measures. In case studies the difference between utility consumption, using previous optimisation methods and new, were significant; e.g. in Case Study 2 the utility savings were 18.4% for hot and 32.6% for cold utility yielding an increase of the Net Present Value (NPV) by 7.8%. <s> BIB004 </s> A review on heat and mass integration techniques for energy and material minimization during CO2 capture <s> State of the art in the application of heat integration techniques <s> Heat (energy), water (mass), and work (pressure) are the most fundamental utilities for operation units in chemical plants. To reduce energy consumption and diminish environment hazards, various integration methods have been developed. The application of heat exchange networks (HENs), mass exchange networks (MENs), water allocation heat exchange networks (WAHENs) and work exchange networks (WENs) have resulted in the significant saving of energy and water. This review presents the main works related to each network. The similarities and differences of these networks are also discussed. Through comparing and discussing these different networks, this review inspires researchers to propose more efficient and convenient methods for the design of existing exchange networks and even new types of networks including multi-objective networks for the system integration in order to enhance the optimization and controllability of processes. <s> BIB005 </s> A review on heat and mass integration techniques for energy and material minimization during CO2 capture <s> State of the art in the application of heat integration techniques <s> Abstract Power Pinch Analysis (PoPA) is a technique for the optimal power allocation in hybrid systems comprising of renewable energy sources. The graphical PoPA tools have recently been proposed to determine targets for the minimum amount of outsourced electricity and the maximum amount of excess electricity to be stored and reused in the hybrid power systems. The numerical techniques for PoPA have so far not been developed. This work introduces two new PoPA numerical tools known as the Power Cascade Analysis (PoCA) and the Storage Cascade Table (SCT). The tools can be used to determine (1) the minimum target for outsourced electricity, (2) the amount of excess electricity for storage during start up and normal operations, (3) the amount of transferrable power, (4) the maximum storage (e.g. battery) capacity for the off-grid systems, (5) the amount of electricity transferrable to the grid, (6) the amount of outsourced electricity needed at each time interval and (7) the time interval where the maximum power demand occurs. While the graphical techniques provide useful visualisation insights, the numerical tools enable more rapid and precise allocation of power as well as the determination of electricity targets. <s> BIB006 </s> A review on heat and mass integration techniques for energy and material minimization during CO2 capture <s> State of the art in the application of heat integration techniques <s> A considerable number of studies have been performed for improving the efficiency of production processes, of energy supply and utilisation, while reducing emissions of greenhouse gases, volatile organic compounds and other pollutants. This has been a very important task which this journal has been targeting. As a response to these industrial and societal requirements considerable research effort has been targeted to process integration and process intensification. This article has made an attempt for a short assessment of those advanced engineering approaches. <s> BIB007 </s> A review on heat and mass integration techniques for energy and material minimization during CO2 capture <s> State of the art in the application of heat integration techniques <s> The synthesis of mass exchange networks (MENs) is an important systematic tool for screening mass-separating agents (MSAs) and satisfying the mass transfer demands while considering process, environmental, and economic requirements. Most of the MEN research has focused on single-component problems. Much less attention has been given to the multicomponent problem. Therefore, the aim of this paper is to develop a systematic method to deal with the multicomponent MEN synthesis problem. The concept of interception is introduced to account for compatible mass transfer of the multiple components in a way that can be practically realized in mass exchange units. A mixed-integer nonlinear programming (MINLP) model is established to embed potential configurations of interest. Linearization, disjunctive programming, and relaxation are used to enhance the solvability of the optimization program, which is aimed at minimizing the total annualized cost (TAC) of the MEN. Two case studies from the literature, the recovery of copper from an etching plant and the simultaneous removal of H₂S and CO₂ from coke-oven gas (COG), are solved to illustrate the application of the proposed method. <s> BIB008 </s> A review on heat and mass integration techniques for energy and material minimization during CO2 capture <s> State of the art in the application of heat integration techniques <s> High temperature solid cycles are promising technologies for implementing large-scale CO2 capture facilities in the mid-term. Energy integration plays a major role in the development of these cycles. Waste energy from the capture process may be used to retrofit an existing power plant or to power a new steam cycle, thus diminishing the energy penalty that the process entails. A procedure based on pinch analysis for the integration of these systems, is proposed and tested using limestone as CO2 sorbent. Although Li4SiO4 has been already dismissed for this purpose, it is used to validate the systematic procedure under a very different problem in terms of available heat and initial temperatures of hot streams. In both scenarios the integration was designed to take advantage of all available heat of the process and to power a supercritical steam cycle, quantifying their minimum energy penalty. A sensitivity analysis for each process was also developed, and the heat exchanger network achieved by the proposed algorithm obtained the best results in costs terms. <s> BIB009 </s> A review on heat and mass integration techniques for energy and material minimization during CO2 capture <s> State of the art in the application of heat integration techniques <s> Abstract Over the last decade, energy prices in China have risen dramatically. At the same time, extensive use of coal fired energy provision systems in industry has led to serious environmental and economic problems translating to an economic damage of an estimated 10% of the Gross Domestic Product. This has led to increasing awareness in the process industries of the need to save energy whilst replacing conventional energy sources with renewable ones. An energy audit was conducted for a soy sauce production facility in Beijing, which aimed to reduce its thermal energy demand through process intensification and to integrate renewable energy. Their current supply of thermal energy came directly from a district steam network, which was both directly consumed and downgraded via heat exchangers. It was determined that the best two solar integration locations would be in the pre-heating/mixing of raw ingredients to 60 °C and the subsequent direct steaming of the mixture to 120 °C. Three different systems for supplementing steam were investigated: (1) a traditional solar thermal heating system; (2) a system consisting of mono crystalline photovoltaic panels coupled with either a resistance heater or electric steam generator; and (3) a cascading system consisting of two types of solar thermal collectors, photovoltaic panels, and an electric steam generator. Comparisons of systems 1 and 2 were made for the heating of mixing water, and systems 1, 2, and 3 for saturated steam generation. Results showed that for the heating of process water, flat plate solar collectors performed best with an estimated 20 year Levelised Cost of Energy of 0.063 €/kW h. Steam generation was most cost effective with a cascade system of photovoltaic and flat plate collectors, with an estimated 20 year Levelised Cost of Energy of 0.145 €/kW h. The model predicts that integration of this technology would lead to a reduction of 14% in heating utility demand. <s> BIB010 </s> A review on heat and mass integration techniques for energy and material minimization during CO2 capture <s> State of the art in the application of heat integration techniques <s> Abstract Heat recovery plays an important role in energy saving in the supply chain of steel products. Almost all high temperature outputs in the steel industry have their thermal energy exchanged to preheat inputs to the process. Despite the widespread development of heat recovery technologies within process stages (process heat recovery), larger savings may be obtained by using a wider integrated network of heat exchange across various processes along the supply chain (integrated heat recovery). Previous pinch analyses have been applied to optimise integrated heat recovery systems in steel plants, although a comparison between standard process heat recovery and integrated heat recovery has not yet been explored. In this paper, the potential for additional energy savings achieved by using integrated heat recovery is estimated for a typical integrated steel plant, using pinch analysis. Overall, process heat recovery saves approximately 1.8 GJ per tonne of hot rolled steel (GJ/t hrs), integrated heat recovery with conventional heat exchange could save 2.5 GJ/t hrs, and an alternative heat exchange that also recovers energy from hot steel could save 3.0 GJ/t hrs. In developing these networks, general heat recovery strategies are identified that may be applied more widely to all primary steel production to enhance heat recovery. Limited additional savings may be obtained from the integration of the steel supply chain with other industries. <s> BIB011 </s> A review on heat and mass integration techniques for energy and material minimization during CO2 capture <s> State of the art in the application of heat integration techniques <s> Abstract The refining sector comprises a lot of different processes, since a wide range of final products are obtained in refineries. In any case, CO 2 emissions levels are high and three units can be considered as the main sources accounting the majority of carbon dioxide emissions to the atmosphere: the utility boilers system, the process heaters and the fluid catalytic cracking unit (FCC). In this study, the substitution of the utility boilers system for an oxy-combustion power plant is presented. The power plant is designed to cover the steam thermal and electricity demands of oil refinery. In addition, a heat integration methodology based on pinch analysis is applied to the whole concept for increasing efficiency. Final results show that more than 380,000 tonnes of CO 2 could be avoided. Afterwards, a complete economic approach is carried out. Although profitability is still low with current economic costs, it is expected that in the medium term, oxy-combustion could be economically feasible in refining sector. To this extent, sensitivity analysis shows affordable values for main economic parameters that can be reached in the next years. A 24 €/MWh natural gas price reduces operational cost for oxy-combustion power plant below the conventional refinery value. An electricity price higher than 67 €/MWh and a CO 2 cost around 20 €/tCO 2 also seem to reduce operational cost below reference case ones. The study concludes with the analysis of some realistic future scenarios that prove the oxy-combustion technology both technically and economically feasible and payback periods between 9 and 11 years with IRR values around 7% can be affordable within the following years. <s> BIB012
Heat integration is mostly applied in energy systems when examining the potential of improving heat exchange between heat sources and heat sinks to reduce the amount of external heating and cooling utilities which is a way of ensuring energy minimization BIB011 BIB003 BIB006 . Heat integration during CO 2 capture could be a reliable method for reducing the high energy penalty associated with most CO 2 capture technologies. Researchers have developed new calculation methods for energy and material minimization as well as design of heat exchanger and coupling of utilities in many energy-intensive processes with minimum temperature difference through heat integration using pinch concepts BIB007 BIB010 BIB009 . However, the application of pinch analysis alone cannot adequately achieve a simultaneous energy and material minimization in a process such as CO 2 capture. This is because, heat transfer occurs in most of these systems with some inefficiency due to unavoidable stack losses. This makes the heat value of the burnt fuel always greater than that absorbed by the process. As a result, energy and material consumption cost may not be easily evaluated directly from the energy targets indicated in the pinch diagrams. It has also been pointed out in previous research BIB010 BIB009 that the loss of some important information can occur when process and utility streams are combined into the same grand composite curve (GCC). This loss of information has led to missed opportunities in designing an optimal network for energy and material minimization. To provide solution to the aforementioned problem posed by the pinch technique, researchers have come up with different methodologies for a simultaneous energy and material minimization during CO 2 capture. For instance, in the studies reported by Romeo et al. BIB001 and Berstad et al.  , calcium looping was recommended as the most suitable CO 2 capture technique for effective energy and material minimization. This is because the researchers envisaged that the waste CaO from CO 2 capture in a cement plant can be combined with waste energy from the clinker cooling and CO 2 capture system which can then be used to generate additional power without the utilization of coal. Furthermore, part of the power generated can be used for CO 2 compression. The purge from the CO 2 capture system can also be used as input to the cement plant, thus reducing the raw material consumption and fuel usage for the calcination of the saved limestone. By applying this method, the authors confirmed a lower CO 2 avoidance cost with the integrated process than with any other combination method (either with power plants and CO 2 capture system, or cement plants with CO 2 capture systems). As such, the authors proposed that if these three processes are integrated, about 94% of CO 2 that would have been emitted into the atmosphere can be avoided because of the energetic efficiency augmentation associated with the integrated processes. However, a major drawback of this integrated process is that both systems have to operate simultaneously and this requires a lot of energy consumption although material usage could be minimized. Furthermore, there could be some effects of sulphur and CaSO 4 formed during the CO 2 capture process on the cement characteristics and the deactivated CaO in the clinker during production, thus reducing the quality of cement produced from the integrated cement production plant. Nemet et al. BIB004 reported a new methodology for heat integration with emphasis on optimization of heat exchanger networks' cost over a long period. The authors developed a deterministic and stochastic multi-period mixed-integer nonlinear programming (MINLP) model for synthesis of heat exchanger networks in which the utility cost coefficients were forecasted for the lifetime of the process. The stochastic approach was applied to the simultaneous consideration of future price projections of HENs, while the multi-period approach with future price projections was applied for sustainable design of HENs with higher heat recovery and, consequently, with lower utility consumption. The study revealed that utility savings were 18.4% for hot and 32.6% for cold utility, yielding an increase in the net present value (NPV) by 7.8%. As much as this proposed methodology was useful for minimizing heat energy usage, it could not be conveniently applied in the case of CO 2 capture due to the fact that CO 2 capture is a simultaneous heat and mass exchange process, which involves the application of both heat and mass exchange networks. In view of this, the proposed methodology is not sufficient for energy and material minimization studies because it is limited to only heat exchanger networks. Mohd-Nawi et al.  suggested a new algebraic technique for total site carbon integration. This proposed technique is capable of minimizing energy requirement during carbon capture, utilization and storage. The method was applied to a hypothetical case study to determine potential CO 2 exchange using CO 2 headers at different percentage purity as well as a central pure CO 2 generator. The authors reported a 43% reduction in CO 2 emission with reduced energy consumption using this novel technique. The proposed targeting technique could be used by carbon planners to conduct further analysis and feasibility studies involving carbon capture storage and utilization. However, the technique did not include analysis of more carbon capture methods as well as a techno-economic study to ascertain its applicability on a large scale. It is envisaged in this review that a combined application of the aforementioned techniques in integrated symbiotic systems might further minimize energy usage and also reduce energy penalty associated with most CO 2 capture technologies. Escudero et al. BIB012 applied a pinch analysis approach in combination with Aspen plus simulation to evaluate the heat recovery options and to design an optimized heat exchanger network for a specified power plant. The authors used an Aspen Plus simulation model to simulate the power plant (including all the subsystems and the new networks). At the end, the authors reported a net increase of about 32.5% in the net efficiency of the power plant. Energy penalty was also reduced from 10.54 to 7.28 efficiency points using this concept. However, CO 2 capture is a simultaneous mass and heat exchange process, and the authors did not consider the synthesis of mass exchanger networks to take care of external mass separating agents or utilities in their study. Nevertheless, synthesis of a hybrid network that considers simultaneous heat and mass exchange for effective design of a CO 2 capture network as proposed in this paper is capable of minimizing the external mass separating agents and utilities involved in the design. Most methodologies for energy and material minimization investigated in the past come with limitations such as computational difficulties, high cost of technology and material wastage. To fill this gap, this paper proposes the development of integrated methods for CO 2 capture (including mass and heat integration networks) because integration of heat and mass exchange networks have resulted in significant saving of heat energy and mass (materials) in other processes in the past BIB005 BIB002 . Industrial heat and mass exchanger networks are important because of their role in recovering material and process heat in a process effectively. Mass exchanger network synthesis via mathematical programming is also an important strategy for screening mass separating agents as well as satisfying mass transfer demands in a CO 2 capture process while ensuring that environmental and economic requirements are met BIB008 . Synthesis of a combined heat and mass exchanger network using a hybrid technique comprising both pinch analysis and mathematical programming is recommended for problems involving heat and mass exchanger networks such as CO 2 capture. The suggested hybrid approach in this review is new and, as far as could be ascertained, has not been applied in any CO 2 capture study for energy and material minimization. Figure 8a is a composite curve showing reduction of the internal carbon footprint of a CO 2 -emitting power plant while Fig. 8b denotes the benchmark value for CO 2 emission together with internal and external carbon footprints. Figure 8a , b illustrates how a graphical pinch analysis technique enhances the decision-making by prioritizing strategies for carbon footprint reduction in a single power plant. Table 2 gives a summary of the process synthesis techniques, methods and focus area reported till date.