This paper describes an upgraded concept of the sustainability metric named Sustainability Profit (SP) from various micro- and macroeconomic perspectives and how it can be used for the synthesis of production systems in order to increase their circularity. An upgraded concept of SP is presented from three different perspectives: a microeconomic one, representing the company level, a macroeconomic perspective, combining the company and country (government) levels, and a wider macroeconomic one, with the addition of individuals (employees). Basic indicators of circularity, which measure the share of materials and energy reuse, are incorporated in order to synthesize more sustainable systems involving reuse of materials and energy. The concept is demonstrated on two case studies of supply network synthesis. The first case study is a supply network of fossil and renewable electricity production from various energy sources with fixed electricity demand, and the second case study is a larger-scale, renewable-based supply network for producing food, biofuels and electricity, and is applied to Central Europe. The results indicate that, by maximizing SP using the upgraded concept, overall circularity is favoured, and trade-offs between different sustainability pillars are obtained. The study could further be extended to account for uncertainty and more detailed Eco- and Social profit analysis and circularity measures as a good decision support tool in evaluating sustainable production systems.
COBISS.SI-ID: 21620246
Synthesis of non-isothermal water networks consisting of water-usage, wastewater treatment, and heat exchanger networks has been recognised as an active research field in process systems engineering. However, only brief overviews of this important field have so far been provided within the literature. This work presents a systematic and comprehensive review of papers published over the last two decades and highlights possible future directions within this field. This review can be useful for researchers and engineers interested in water and energy integration within process water networks using systematic methods based on pinch analysis, mathematical programming, and their combination.
COBISS.SI-ID: 19125270
The synthesis of heat exchanger networks in chemical plants is vital for energy saving. Most papers presented on this subject have focused on processes having single periods of operation. However, in reality, chemical processes may be multi-period in nature due to changes in environmental conditions, requirements for start-ups and shut-downs, etc. For processes of this nature, it is imperative to use a mathematical based approach so as to adequately handle the multidimensional nature of the problem. In this paper, a modified version of the stage-wise superstructure of Yee and Grossman (1990) is adapted to the synthesis of heat exchanger networks having multiple periods of operations. A new set of solution approaches, which involves solving multi-period MINLP models in a two-step approach is presented. The newly developed method is applied to three examples, out of which two were taken from the literature. In the two examples taken from the literature, the solutions obtained from this study performed better than those presented in the literature.
COBISS.SI-ID: 20351254
This paper presents a robust computational methodology for the synthesis and design of flexible HEN (Heat Exchanger Networks) having large numbers of uncertain parameters. This methodology combines several heuristic methods which progressively lead to a flexible HEN design at a specific level of confidence. During the first step, a HEN topology is generated under nominal conditions followed by determining those points critical for flexibility. A significantly reduced multi-scenario model for flexible HEN design is formulated at the nominal point with the flexibility constraints at the critical points. The optimal design obtained is tested by stochastic Monte Carlo optimization and the flexibility index through solving one-scenario problems within a loop. This presented methodology is novel regarding the enormous reduction of scenarios in HEN design problems, and computational effort. Despite several simplifications, the capability of designing flexible HENs with large numbers of uncertain parameters, which are typical throughout industry, is not compromised. An illustrative case study is presented for flexible HEN synthesis comprising 42 uncertain parameters.
COBISS.SI-ID: 18589462
This paper examines the influence of alternating magnetic fields on water scale precipitation on diffusers in vertical multistage pumps in real drinking water systems. The exact conditions in pumping stations were simulated in the laboratory using in-house techniques. The testing device consists of two lines, the first a control line and the other for testing, where a permanent magnet was installed. The influence of magnetic fields intensity, post-magnetisation time, temperature and saturation index on calcium carbonate nucleation and crystallisation was studied. The precipitate was analysed using X-ray powder diffraction (XRD) and a scanning electron microscope (SEM). It was found that the precipitate in water from the control line was in the form of calcite, while after the magnet treatment it was in the form of a non-adhesive aragonite powder that could be easily removed with the turbulent flow through the pump diffuser. The results suggest that the magnetic field has a noticeable effect on the transforming process of clusters in the solutions.
COBISS.SI-ID: 20523798
We present a new method for the synthesis of mass exchanger networks (MENs) involving packed columns. Simultaneous synthesis of MENs is typically done through the use of mixed-integer nonlinear program (MINLP) optimization, with simplifications made in the mathematical representations of the exchangers due to computational difficulty in solving large non-convex mixed-integer problems. The methodology proposed in this study makes use of the stage-wise based superstructure MINLP formulation for the network synthesis. This stage-wise superstructure model incorporates fixed mass transfer coefficients, fixed column diameters, no pressure drops, and unequal compositional mixing for models. In this paper, the simplified MINLP model is further improved by including a detailed individual packed column design in a non-linear programming (NLP) sub-optimization step, where orthogonal collocation is utilized for the partial differential equations, and optimal packing size, column diameter, column height, pressure drops, and fluid velocities. Detailed designs are then used to determine correction factors that update the simplified stage-wise superstructure models to more accurately portray the chosen design. Once the MINLP is updated with these correction factors, the model is re-run, with new correction factors obtained. This iterative procedure is repeated until convergence between the objective function of the MINLP and that of the NLP sub-optimization is achieved, or until a maximum number of iterations is reached. The methodology is applied to two examples and is shown to be robust and effective in generating new topologies, and in finding superior networks that are physically realizable.
COBISS.SI-ID: 21152790
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 ?Tmin. 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.
COBISS.SI-ID: 21528598
In this paper, risk assessment is considered simultaneously during the synthesis of Heat Exchanger Networks (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 was tested. The individual heat exchanger 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 in addition to toxicity, 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.
COBISS.SI-ID: 20534806
The model glycoside compound quercetin-3-O-rutinoside (rutin) was subjected to subcritical water within the temperature range of 120-220 °C, and the hydrothermal degradation products were analyzed. Two kinetic models describing the degradation of this compound in two different atmospheres (N2 and CO2), used for pressure establishment in the reactor, have been developed and compared. Reaction was considered a successive one with three irreversible steps. We confirmed that rutin degradation to quercetin follows first-order kinetics. At higher temperatures quercetin is further degraded in two degradation steps. Formations of 3,4-dihydroxybenzoic acid and catechol were described with the zero-order kinetic models. Reaction rate constants for hydrolysis of glycoside to aglycone in a CO2 atmosphere are higher compared to those in a N2 atmosphere, whereas at higher temperatures reaction rate constants for further two successive reactions of aglycone degradation are slightly lower in the presence of CO2. The difference in reaction activation energies is practically negligible for both gases. Furthermore, degradation products of sugar moieties, that is, 5-hydroxymethylfurfural and 5-methylfurfural, were also detected and analyzed.
COBISS.SI-ID: 29993767
In recent years, a great deal of interest has been focused on the development of novel atomic force microscopy (AFM)-based methods. From first being an unstable method, AFM has emerged as the perfect tool for the study of phenomena at the nanoscale, which includes quantitative single molecule studies. Numerous novel AFM methods play a crucial role in the invention of novel drugs, their delivery systems, based on either polymers or inorganic/metallic matrices, and in the examination of disease-related tissue changes. Such contemporary progressive studies are a perfect example of interdisciplinary research, which results in exemplary findings and discoveries. This work focuses especially on the literature published in the last decade; however the most important earlier discoveries are also included.
COBISS.SI-ID: 19422230