Energy and economic optimization for automobile painting process

Simultaneous design of heat exchanger network for heat integration using hot direct discharges/feeds between process plants

A novel Random Walk algorithm with Compulsive Evolution for heat exchanger network synthesis

PurposeThe purpose of this paper is to present a novel and applied method for optimum designing of plate-finned heat exchanger network. Considering the total annual cost as the objective function, a network of plate-finned heat exchanger is designed and optimized.Design/methodology/approachAccurate evaluation of plate-finned heat exchanger networks depends on different fin types with 10 different geometrical parameters of heat exchangers. In this study, fin numbers are considered as the main decision variables and geometrical parameters of fins are considered as the secondary decision variables. The algorithm applies heat transfer and pressure drop coefficients correction method and differential evolution (DE) algorithm to obtain the optimum results. In this paper, optimization and minimization of the total annual cost of heat exchanger network is considered as the objective function.FindingsIn this study, a novel and applied method for optimum designing of plate-finned heat exchanger network is presented. The comprehensive algorithm is applied into a case study and the results are obtained for both counter-flow and cross-flow plate-finned heat exchangers. The total annual cost and total area of the network with counter-flow heat exchangers were 12.5% and 23.27%, respectively, smaller than the corresponding values of the network with cross-flow heat exchanger.Originality/valueIn this paper, a reliable method is used to design, optimize parameters and the economic optimization of heat exchanger network. Taking into account the importance of plate-finned heat exchangers in industrial applications and the complexity in their geometry, the DE methodology is adopted to obtain an optimal geometric configuration. The total annual cost is chosen as the objective function. Applying this technique to a case study illustrates its capability to accurate design plate-finned heat exchangers to improve the objective function of the heat exchanger network from the economic viewpoint with the design of details.

A systematic method to customize an efficient organic Rankine cycle (ORC) to recover waste heat in refineries

Optimal design of controllable heat-exchanger networks under multi-directional resiliency-target constraints

Simultaneous Synthesis and Optimization of Refrigeration Cycles and Heat Exchangers Networks

A mixed-integer nonlinear programming (MINLP) algorithm to account for the effects of the allowable pressure drops for process streams on the structure and cost of heat exchanger networks is presented. Because MINLP models for large problems typically show significant convergence problems, the synthesis model is decomposed into two levels. For a given energy recovery level, an MINLP model is formulated in an inner loop using assumed values for the film heat-transfer coefficients for each stream. In the outer loop, with the use of the areas provided by the MINLP model and thermal-hydraulic models that relate the exchanger area, pressure drops, and film coefficients, updated values of the film coefficients are calculated for each stream according to the specified values for allowable pressure drops. The algorithm provides a network that makes use of the allowable pressure drops specified for the process streams at the total minimum yearly cost. The algorithm shows excellent convergence properties, can incor...

Pinch analysis is vital in optimizing heat exchanger networks (HENs). Targeting methods are used when determining cost effectiveness with pinch analysis. However, the existing targeting methods for the capital cost of HEN are not suitable for wide application scenarios. Therefore, we developed a high-accuracy general capital-cost-targeting method. It is built on a final structure that was evolved from the spaghetti structure of HEN through four loop elimination stages. This structure helps to reduce the prediction deviation of the method. To achieve high adaptability while establishing this method, we considered the different heat exchanger cost categories, different cost laws for one stream pair, and area limitations of heat exchangers that may be encountered in practice. In addition, allowing streams to use individual temperature difference contributions enhances the method’s predictive capacity. The potential defects of the method found in numerical experiments and case studies were corrected with improvement measures. As a result, the accuracy and stability of the targeting method were further enhanced, with absolute target deviations generally within 10% and often within 5%. This study provides a benchmark for the optimal capital cost of HEN, allowing for a better economic effect when applying pinch analysis.

Estimation of the installed cost of heat exchanger networks

Pinch technology is one of the most powerful methodologies of process integration that allows industries to increase their profitability through reductions in energy, water and raw materials consumption. In this study, reduction in the total annual cost of heat exchanger network (HEN) of Fluid Catalytic Cracking (FCC) unit in Kaduna Refining and Petrochemical Company (KRPC), Kaduna was determined. With the help of pinch technology, the reduction was achieved by first determining optimum minimum temperature difference by trading off energy cost and capital cost targets as a function of minimum temperature difference. Thereafter, the total annual cost obtained at the optimum minimum temperature difference was compared with total annual cost of existing design. The results of the analysis showed that the optimum minimum temperature difference was 12℃, the total annual costs of the existing design and the optimum-minimum-temperature-difference based cost were $8.7 and $7.1 Million respectively. This amounted to percentage reduction in the total annual cost of 18.4% which means that about $1.6 Million would been saved annually using the optimum minimum temperature difference to design the HEN of the FCC unit.
 Keywords: Pinch technology, FCC unit, Cost targeting, Area targeting, Trade-off

Optimal design of heat exchanger network considering the fouling throughout the operating cycle

Margin design, online optimization, and control approach of a heat exchanger network with bypasses

The objective in this study was to conduct a technical-economic study of the esterification process of used vegetable oils (UVOs) for the production of biodiesel from the point of view of energy savings achieved by implementing heat exchange networks (HENs). Used vegetable oils (UVOs) can be employed as an input in the production of biodiesel by catalytic transesterification. But, previously it is necessary to reduce its level of free fat acids (FFA) by the acid-catalyzed esterification process in order to prevent undesirable saponification reaction. To carrying out an optimal design of the technology required in the process, simulation tools have an important role for process engineering and optimization of resources. Computer programs such as Aspen PlusTM and Aspen Energy AnalyzerTM provide an environment to perform process modeling and network design optimal heat exchange. In this paper, from the Aspen PlusTM simulation of the process of catalytic esterification in acid medium of UVOs, the technical-economic evaluation process was conducted with and without network of heat exchange in order to analyze the different investment options. The comparison of the two projects (with and without the implementation of HENs) was performed by determining the net present value (NPV). On the scale set for the project, the total cost of the equipment of heat exchange for the esterification process designed with HENs was US$ 4,782.50 higher than the corresponding to the process without HENs application. However, it should be noted that the cost of services decreased by 30% annually, and on the other hand, comparing the process, it was observed that the NPV of the HENs process was 29.5% higher, which leads to the conclusion that the project which includes heat exchange networks is technically and economically feasible.

A methodology is presented for optimizing hybrid renewable energy‐fossil fuel systems with short‐term heat storage. The considered system is an absorption‐refrigeration (AR) cycle integrated with a heat exchanger network (HEN) requiring cooling below ambient temperature. The AR cycle can be driven by multiple energy sources including excess energy from hot process streams, renewable energy sources (solar and biofuels), and fossil fuels. A two‐step approach based on mixed integer nonlinear programming methods is used for the optimization. First, the problem of optimal energy integration in the hybrid energy system without heat storage is solved on a monthly basis by minimizing simultaneously the total annual cost and the overall greenhouse gas emissions. In the second step, the multi‐tank thermal energy storage (TES) design problem is solved. The design involves the identification of the optimal number of storage tanks, their sizes, configuration and operation policies. The TES optimization is carried out on an hourly basis while incorporating the design targets determined by the first step. © 2013 American Institute of Chemical Engineers AIChE J, 60: 909–930, 2014

The design of cost optimal heat exchanger networks is a difficult optimization problem owing both to the nonlinear models required and the combinatorial size of the search space. When stream splitting is considered, the combinatorial aspects make the problem even harder. This article describes the implementation of a two-level evolutionary algorithm based on a string rewriting grammar for the evolution of the heat exchanger network structure. A biological analogue of genotypes and phenotypes is used to describe structures and specific solutions, respectively. The top-level algorithm evolves structures while the lower level optimizes specific structures. The result is a hybrid optimization procedure that can identify the best structures including stream splitting. Case studies from the literature are presented to demonstrate the capabilities of the novel procedure.