238 results found
Alhuthali S, Delaplace G, Macchietto S, et al., 2022, Whey protein fouling prediction in plate heat exchanger by combining dynamic modelling, dimensional analysis, and symbolic regression, Food and Bioproducts Processing, Vol: 134, Pages: 163-180, ISSN: 0960-3085
Heat treatment of whey protein solution is a common industrial practice to texturise dairy derived products and meet shelf-life requirements. Thermal treatment is frequently interrupted for cleaning which consumes a large amount of water at different pH to remove deposits from the heating surface. Although it has been a research topic for decades, fouling growth models are still poorly predicted beyond the model training dataset. Here, parameters in a dynamic 2D plate heat exchanger (PHE) model were fitted to capture deposit mass when three variables are manipulated. These are whey protein concentration (0.25–2.5% w/w), calcium concentration (100 and 120 ppm) in the feed and PHE configuration, represented by the number of heating channels (5 and 10 channels). The PHE model consists of thermal, reaction, and fouling sub-models to account for the key events behind deposit formation. The PHE fouling model has a single parameter that needs re-estimation if the processed whey protein solution and process conditions are slightly changed. In the past, this case specific re-estimation has hindered the prediction capability of the model. In this regard, dimensional analysis of the PHE and symbolic regression were used to create a mathematical relationship for the fouling model adjustable parameter, enabling estimation of deposit mass for a wider range of whey derivatives and process conditions. The modelling approach was validated for three different scenarios representing different thermal profiles and whey powder. The proposed methodology increases the ability to predict fouling for different operating conditions and whey protein solutions.
Tseng WF, Macchietto S, 2022, Re-design and scheduling of dairy thermal treatment processes for continuous operation, Computer Aided Chemical Engineering, Pages: 523-528
Heat treatment processes of liquid dairy products (pasteurisation, sterilisation) are energy, water and wastes intensive. They are normally conducted in an energy integrated system of 3 plate heat exchangers (PHEs), in batch mode heating-cleaning cycles. During cleaning, the whole process is interrupted, causing loss of production. A new semi-continuous pasteurisation process is proposed here comprising a design modification (an additional plate heat exchanger and holding tube), the calculation of (time-varying) pasteurisation time and its use in a new logic for switching between heating and cleaning, and suitable scheduling of equipment in a rotation strategy. All schemes are studied using a detailed distributed dynamic model of the process. The simulation results for a typical high-temperature-short-time (HTST) case study show that the rotational scheduling of the PHEs and tubes results in a semi-continuous operation where milk production can be maintained indefinitely. Substantially higher productivity (+ 23% throughput), reduced energy, and total cost (-47%) are achieved relative to the traditional batch mode operation.
Lozano-Santamaria F, Macchietto S, 2021, Assessment of a Dynamic Model for the Optimization of Refinery Preheat Trains under Fouling, HEAT TRANSFER ENGINEERING, Vol: 43, Pages: 1349-1364, ISSN: 0145-7632
Santamaria FL, Luceno JA, Martin M, et al., 2021, Optimal operation and cleaning scheduling of air coolers in concentrated solar plants, COMPUTERS & CHEMICAL ENGINEERING, Vol: 150, ISSN: 0098-1354
- Author Web Link
- Citations: 1
Sharma A, Macchietto S, 2021, Fouling and cleaning of plate heat exchangers: Dairy application, FOOD AND BIOPRODUCTS PROCESSING, Vol: 126, Pages: 32-41, ISSN: 0960-3085
- Author Web Link
- Citations: 8
Darko WK, Santamaria FL, Bouvier L, et al., 2021, Thermal treatment in dairy processes: Validation of protein deposition models, Computer Aided Chemical Engineering, Pages: 2003-2008
The optimisation of heat treatment processes in the dairy industry is of high practical interest. Models are key to understanding and optimising equipment design, operating conditions, energy and water utilization, heating and cleaning cycles and economics. Decades of research have led to the development of many models, however, there is still a lack of understanding about the role and mechanism of denaturation and deposition of proteins from whey solutions. Extensive validation of the more recent thermal and fouling models against experimental data is also incomplete. Here, five sets of detailed data from dynamic experiments in typical Plate Heat Exchangers (PHEs) are used to validate a 2D-distributed, dynamic model under fouling. The model accounts for the exchanger geometry, operating conditions and prevailing local conditions. Three reaction mechanisms for β-lactoglobulin (β-LG) protein unfolding, aggregation and deposition are considered, one of which is novel. First, a validation was carried out of the thermal PHE model alone (i.e. under clean conditions, with no fouling) against a water-water dynamic experiment, with excellent results. The exit temperatures predictions match the experimental observations within <1C on average. The fouling model was then validated against four dynamic water-whey protein solutions (WPS) experiments (hot water heating a cold WPS stream) covering different conditions. Some of the model deposition constants were obtained through parameter estimation. Comparison of predicted and measured quantities (exit temperatures and amount of deposit in each channel at the end of the experiments) show that neither the aggregate protein deposition model nor the unfolded deposition model on their own can describe the observations. It is shown that a new modification that combines both mechanisms results in an improved fitting of the data in all experiments. The combined deposition scheme results indicate that both mechanisms are imp
Taurgalinov R, Santamaria FL, Macchietto S, 2021, Compartmental Modelling of Shell Side Fouling in a Shell and Tube Heat Exchanger, Computer Aided Chemical Engineering, Pages: 1137-1142
Accurate and fast models are required to optimise the design, control and operations of shell and tube heat exchangers (STHE) subject to fouling. To date, research effort has mainly focused on tube side fouling. Techniques proposed for the shell side fouling are limited to i) mechanistic thermo-hydraulic models with simple Flow Stream Analysis (FSA) and ii) Computational Fluid Dynamics (CFD) models. The former ignore flow dynamics on the shell side. The latter cannot quantitatively predict fouling, are computationally very heavy and cannot be utilised for optimisation and control. In the paper, we combine the benefits of FSA and CFD methods by creating a hybrid Compartmental Model (CM). For an actual exchanger subject to crude oil fouling we analyse its outcomes and compare them to CFD and FSA methods. A preliminary CFD study yields detailed shell side velocity field information, based on which an appropriate compartments network is created. A simulation is performed using a two dimension (2D) distributed dynamic STHE model which utilises a FSA for the shell side. A dynamic model for the compartments with a shell side threshold fouling model is developed, utilising selected results from the CFD (velocity data) and 2D-FSA (heat duty) studies. Results from the CM model and comparison with the CFD and 2D-FSA models, for the same operation, provide valuable insights regarding the role of shell side velocities in predicting overall exchanger performance. Computationally, for this case study, the CM model is solved 5.5 times faster than the distributed dynamic model and 36 times faster than the CFD model, indicating the approach has good potential for use in design and operations optimisation.
Lozano Santamaria F, Luceño JA, Martin M, et al., 2020, Stochastic modelling of sandstorms affecting the optimal operation and cleaning scheduling of air coolers in concentrated solar power plants, Energy, Vol: 213, ISSN: 0360-5442
The operation performance of air-coolers in concentrated solar power plants decays due to particulate deposition on heat transfer surfaces. The deposition process can be seen as a stochastic phenomenon. A modelling approach is proposed to capture the uncertainty and the effect of extreme events, such as sandstorms, affecting the performance of plants located in dry places through dust or sand deposition on the air coolers. A case study of a concentrated solar power plant located in Dubai is analysed. Sandstorms generate acute and drastic fouling of the air coolers, and this is modelled as a stochastic process using historical aerosol dispersion data. Ten scenarios are generated by sampling the probability distribution of sandstorms occurrence and intensity. The optimal operation (cleaning schedule and airflow profiles) of the air coolers is established using Benders decomposition to solve the resulting large-scale mixed integer non-linear programming problem. The results of the stochastic scenarios demonstrate that substantial savings of $ 0.6 M - $ 2.7 M per year are achieved by the optimal operation. Cost is minimised by a combined reactive and proactive cleaning policy which accounts for the frequency, intensity and seasonal variability of sandstorms, in addition to the variability on local radiation and weather conditions.
Santamaria FL, Macchietto S, 2020, Stability of optimal closed-loop cleaning scheduling and control with application to heat exchanger networks under fouling, Processes, Vol: 8, Pages: 1-33, ISSN: 2227-9717
Heat exchanger networks subject to fouling are an important example of dynamic systems where performance deteriorates over time. To mitigate fouling and recover performance, cleanings of the exchangers are scheduled and control actions applied. Because of inaccuracy in the models, as well as uncertainty and variability in the operations, both schedule and controls often have to be revised to improve operations or just to ensure feasibility. A closed-loop nonlinear model predictive control (NMPC) approach had been previously developed to simultaneously optimize the cleaning schedule and the flow distribution for refinery preheat trains under fouling, considering their variability. However, the closed-loop scheduling stability of the scheme has not been analyzed. For practical closed-loop (online) scheduling applications, a balance is usually desired between reactivity (ensuring a rapid response to changes in conditions) and stability (avoiding too many large or frequent schedule changes). In this paper, metrics to quantify closed-loop scheduling stability (e.g., changes in task allocation or starting time) are developed and then included in the online optimization procedure. Three alternative formulations to directly include stability considerations in the closed-loop optimization are proposed and applied to two case studies, an illustrative one and an industrial one based on a refinery preheat train. Results demonstrate the applicability of the stability metrics developed and the ability of the closed-loop optimization to exploit trade-offs between stability and performance. For the heat exchanger networks under fouling considered, it is shown that the approach proposed can improve closed-loop schedule stability without significantly compromising the operating cost. The approach presented offers the blueprint for a more general application to closed-loop, model-based optimization of scheduling and control in other processes.
Gangar N, Macchietto S, Markides C, 2020, Recovery and utilization of low-grade waste heat in the oil-refining industry using heat engines and heat pumps: an international technoeconomic comparison, Energies, Vol: 13, Pages: 2560-2560, ISSN: 1996-1073
We assess the technoeconomic feasibility of onsite electricity and steam generation from recovered low-grade thermal energy in oil refineries using organic Rankine cycle (ORC) engines and mechanical vapour compression (MVC) heat pumps in various countries. The efficiencies of 34 ORC and 20 MVC current commercial systems are regressed against modified theoretical models. The resulting theoretical relations predict the thermal efficiency of commercial ORC engines within 4–5% and the coefficient of performance (COP) of commercial MVC heat pumps within 10–15%, on average. Using these models, the economic viability of ORC engines and MVC heat pumps is then assessed for 19 refinery streams as a function of heat source and sink temperatures, and the available stream thermal energy, for gas and electricity prices in selected countries. Results show that: (i) conversion to electrical power with ORC engines is, in general, economically feasible for heat-source temperatures >70 ◦C, however with high sensitivity to energy prices; and (ii) steam generation in MVC heat pumps, even more sensitive to energy prices, is in some cases not economical under any conditions—it is only viable with high gas/low electricity prices, for large heat sources (>2 MW) and higher temperatures (>140 ◦C). In countries and conditions with positive economics, payback periods down to two years are found for both technologies.
Diaz-Bejarano E, Coletti F, Macchietto S, 2020, A model-based method for visualization, monitoring, and diagnosis of fouling in heat exchangers, Industrial & Engineering Chemistry Research, Vol: 59, Pages: 4602-4619, ISSN: 0888-5885
A critical review of current methods for monitoring the performance of heat exchangers in the presence of fouling highlights a number of pitfalls. An improved analysis method and visualization of operation data (the TH-λ plot) are proposed, which enable to accurately and rapidly estimate the location and extent of fouling, the properties of the deposit, and their impact on exchanger performance. The method uses advanced dynamic thermo-hydraulic models to analyze the data. The visualization presents this information in a way easily interpreted by field engineers. The superior features are demonstrated on various applications, where traditional methods give poor visibility or outright wrong information about underlying events. These include organic fouling deposition and aging, incomplete cleaning, multicomponent deposits, and changes in fouling behavior. First, the basic concepts are illustrated with idealized examples (constant inlet conditions, using simulated data). The approach is then applied to three real refining case studies, with pressure drop either measured or generated via soft sensors. The results show that the advanced dynamic models used enable to properly integrate and interpret highly variable data measurements, explain complex underlying thermal and hydraulic effects, adequately monitor performance, and rapidly detect changes in fouling behavior. The approach provides a new practical tool for monitoring of heat exchanger performance and early fouling diagnosis.
Lozano Santamaria F, Macchietto S, 2020, Online integration of optimal cleaning scheduling and control of heat exchanger networks under fouling, Industrial and Engineering Chemistry Research, Vol: 59, Pages: 2471-2490, ISSN: 0888-5885
Fouling mitigation is paramount to maintaining the reliable and efficient operation of a heat exchanger network (HEN). From the operational perspective, fouling can be mitigated by changing the flow distribution in the network (control actions), or performing periodic cleanings of the units (scheduling actions). Flow control and scheduling have usually been considered independently, ignoring their interaction. This paper presents an online methodology and implementation that integrates control and scheduling decisions for fouling mitigation in HEN, using first principle models of the heat exchangers subject to fouling. A multiloop NMPC/MHE scheme is proposed to estimate the current state of the HEN, and then define the optimal flow distribution and cleaning schedule over a moving horizon. It is shown that this online scheme reacts rapidly to disturbances and copes with model-plant mismatch by updating the model parameters at an appropriate frequency. The methodology is demonstrated on a real industrial case study involving crude oil fouling in the preheat train of a refinery. Application of the methodology shows that (i) significant economic benefits result relative to the actual historical operation, (ii) the online integration achieves a lower operating cost than that of the optimization of control or scheduling individually, (iii) the effect of disturbances is important and the scheme rejects them efficiently, (iv) updating the prediction models deals effectively with plant-model mismatch and process variability, and gives a sufficiently accurate representation of the underlying process, and (v) the computational effort required to solve all optimization problems is low and allows for the practical online implementation of the scheme.
Oyewunmi O, Lozano Santamaria F, Markides C, et al., 2020, Modelling two-phase flows in renewable power generation systems, 5th Thermal and Fluids Engineering Conference (TFEC)
Santamaria FL, Honein E, Macchietto S, 2020, Optimization of Retrofit and Cleaning Schedules for Heat Exchanger Networks Subject to Fouling, Editors: Pierucci, Manenti, Bozzano, Manca, Publisher: ELSEVIER SCIENCE BV, Pages: 1417-1422
Santamaria FL, Macchietto S, 2020, Online Optimal leaning Scheduling and Control eat Exchanger Networks under Fouling with Disturbances, Editors: Pierucci, Manenti, Bozzano, Manca, Publisher: ELSEVIER SCIENCE BV, Pages: 1201-1206
Zhu M, Santamaria FL, Macchietto S, 2020, A General Dynamic Model of a Complete Milk Pasteuriser Unit Subject to Fouling, Editors: Pierucci, Manenti, Bozzano, Manca, Publisher: ELSEVIER SCIENCE BV, Pages: 247-252
- Author Web Link
- Citations: 1
Bailey T, Liu P, Macchietto S, 2019, Optimisation of energy and water supply systems for the Dubai Waterfront, 9th International Conference on Foundations of Computer-Aided Process Design, Publisher: Elsevier, Pages: 107-112, ISSN: 1570-7946
Santamaria FL, Macchietto S, 2019, Integration of optimal cleaning scheduling and control of heat exchanger networks under fouling: MPCC solution, Computers and Chemical Engineering, Vol: 126, Pages: 128-146, ISSN: 0098-1354
Fouling is a major source of energy inefficiencies that decreases the performance of process units. Fouling mitigation alternatives are required to ensure a sustainable, profitable, and safe operation. In heat exchanger networks, two mitigation alternatives are: flow distribution control, and periodical cleanings. This paper addresses the optimal control and optimal cleaning scheduling, individually and simultaneously, for heat exchangers in refining operations. The problem is formulated as a MINLP, which uses an accurate model of the process, logic disjunctions, and a continuous time representation. To solve it efficiently, it is reformulated as a mathematical program with complementarity constraints (MPCC). The modelling and solution strategies are demonstrated in several case studies, from small to moderately large networks for realistic applications. The formulation is versatile, and large network problems are solved in a reasonable computational time. The integration of optimal scheduling and control decreases the operational cost substantially relative to independent mitigation alternatives.
Cameron IT, Engell S, Georgakis C, et al., 2019, Education in Process Systems Engineering: Why it matters more than ever and how it can be structured, Computers and Chemical Engineering, Vol: 126, Pages: 102-112, ISSN: 0098-1354
© 2019 Elsevier Ltd This position paper is an outcome of discussions that took place at the third FIPSE Symposium in Rhodes, Greece, between June 20–22, 2016 (http://fi-in-pse.org). The FIPSE objective is to discuss open research challenges in topics of Process Systems Engineering (PSE). Here, we discuss the societal and industrial context in which systems thinking and Process Systems Engineering provide indispensable skills and tools for generating innovative solutions to complex problems. We further highlight the present and future challenges that require systems approaches and tools to address not only ‘grand’ challenges but any complex socio-technical challenge. The current state of Process Systems Engineering (PSE) education in the area of chemical and biochemical engineering is considered. We discuss approaches and content at both the unit learning level and at the curriculum level that will enhance the graduates’ capabilities to meet the future challenges they will be facing. PSE principles are important in their own right, but importantly they provide significant opportunities to aid the integration of learning in the basic and engineering sciences across the whole curriculum. This fact is crucial in curriculum design and implementation, such that our graduates benefit to the maximum extent from their learning.
Diaz-Bejarano E, Coletti F, Macchietto S, 2019, Modeling and prediction of shell-side fouling in shell-and-tube heat exchangers, Heat Transfer Engineering, Vol: 40, Pages: 845-861, ISSN: 0145-7632
Fouling is a challenging, longstanding, and costly problem affecting a variety of heat transfer applications in industry. Mathematical models that aim at capturing and predicting fouling trends in shell-and-tube heat exchangers typically focus on fouling inside the tubes, while fouling on the shell side has generally been neglected. However, fouling deposition on the shell side may be significant in practice, impairing heat transfer, increasing pressure drops, and modifying flow paths. In this paper, a new model formulation is presented that enables capturing fouling on the shell side of shell-and-tube heat exchangers including the effect of occlusion of the shell-side clearances. It is demonstrated by means of an industrial case study in a crude oil refinery application. The model, implemented in an advanced simulation environment, is fitted to plant data. It is shown to capture the complex thermal and hydraulic interactions between fouling growth inside and outside of the tubes, the effect of fouling on the occlusion of the shell-side construction clearances, and to unveil the impact on shell-side flow patterns, heat transfer coefficient, pressure drops, and overall exchanger performance. The model is shown to predict the fouling behavior in a seamless dynamic simulation of both deposition and cleaning operations, with excellent results.
Macchietto S, 2019, Engineering success: What does it take to get PSE technologies used?, 29th European Symposium on Computer Aided Process Engineering, Publisher: Elsevier, Pages: 85-90, ISSN: 1570-7946
Sharma A, Macchietto S, 2019, A computational study on fouling and cleaning operations in milk pasteurisation using a moving boundary model, 29th European Symposium on Computer Aided Process Engineering, Publisher: elsevier
Veys A, Acha V, Macchietto S, 2019, A financial accounting based model of carbon footprinting: Built environment example, 29th European Symposium on Computer Aided Process Engineering, Publisher: Elsevier, Pages: 1663-1668, ISSN: 1570-7946
Behranvand E, Mozdianfard MR, Diaz-Bejarano E, et al., 2019, Cross sectional examination of a fouled tube removed from a crude oil preheat exchanger, Industrial && Engineering Chemistry Research, Vol: 58, Pages: 9651-9664, ISSN: 0888-5885
A first attempt to characterize intact foulant of a refinery preheater is presented. A tube was removed from an exchanger located postdesalter and preflash-drum at a 4-year shutdown, and dissected into undisturbed cut-out rings. Following visual inspection, elemental analysis (X-ray maps and line scans) was carried out and radial concentration profiles of the existing elements were established. A stratified colored foulant layer inside the tube appeared in sine waves fluctuating at both axial and angular directions, likely evidencing for the first time a shadow effect and erosion process. Results agreed with our studies on a comparable exchanger of the same refinery. They confirm the proposed deposition mechanism and simulation results, indicating formation of a stratified foulant consisting inorganics ranging 50 wt %, the presence of an acute inorganic deposition period along the chronic organic–inorganic fouling, and the identification of the foulant phases arrangement, among possible conductivity mixing models, as cocontinuous and effective medium theory structures.
Diaz-Bejarano E, Behranvand E, Coletti F, et al., 2019, Organic and inorganic fouling in heat exchangers: Industrial case study analysis of fouling rate, Industrial & Engineering Chemistry Research, Vol: 58, Pages: 228-246, ISSN: 0888-5885
Fouling rates in refinery heat exchangers with mixed organic/inorganic deposits (frequent in practice) are estimated using a comprehensive model-based thermohydraulic methodology combining data-driven measurements analysis with advanced models. An industrial case study for a heat exchanger over 4 years demonstrates the method. Following an analysis of the fouling state, the dynamic analysis here estimates organic and inorganic fouling rates using constant or time-varying proportionality ratios. Base-line organics deposition rate is described by a typical correlation, inorganics deposition as a perturbation with constant or time-varying proportionality ratios. Deposition rate parameters are estimated from measured pressure drops and validated against temperatures. Results show that the deposition rate ratio varied substantially over time, revealing acute inorganic deposition periods; accounting for inorganics explains well both thermal and hydraulic performances; the time-varying ratio provided a good fit of the data. This is a highly promising new method for predictive monitoring, detection, and diagnosis of fouling.
Sharma A, Macchietto S, 2019, Fouling and Cleaning of Plate Heat Exchangers for Milk Pasteurisation: A Moving Boundary Model, Editors: Kiss, Zondervan, Lakerveld, Ozkan, Publisher: ELSEVIER SCIENCE BV, Pages: 1483-1488, ISBN: 978-0-12-819940-4
- Author Web Link
- Citations: 4
Santamaria FL, Macchietto S, 2018, Integration of optimal cleaning scheduling and control of heat exchanger networks undergoing fouling: Model and formulation, Industrial & Engineering Chemistry Research, Vol: 57, Pages: 12842-12860, ISSN: 0888-5885
The performance and operability of heat exchanger networks (HENs) is strongly affected by fouling, which involves the deposition of unwanted material, which reduces the heat-transfer rate and increases the pressure drop, the operational costs, and the environmental impact of the process. Periodical cleaning and control of the flow rate distribution in the HEN are used to mitigate the effects of fouling and restore the performance of the units. The optimal cleaning scheduling has been formulated as a mixed-integer linear programming (MILP) or mixed-integer nonlinear programming (MINLP) problem and is solved using various approaches. The optimal control has been formulated as a nonlinear programming (NLP) problem and is used to define the flow rate distribution of the network. Both problems share the same objective: minimization of the total cost of the operation. In principle, the simultaneous solution of the optimal control problem and the optimal cleaning scheduling problem should provide greater savings than the independent or sequential solution of the two problems, since the interactions of the two mitigation alternatives are considered. However, these two problems have been typically considered separately, because of modeling and solution challenges. Also, it is not quite clear what additional benefit a simultaneous solution may bring. The challenges for solving the integrated problem are the large scale of the associated optimization problem and the different time scales involved in each operational layer. Here, a general and efficient formulation is proposed, using a continuous time discretization scheme for the integrated problem of scheduling and control of HENs subject to fouling. A dynamic model of the heat exchangers is proposed that is sufficiently detailed to represent the physics of interest with novel modifications to address simultaneously their control and scheduling in a network. The problem is formulated as a MINLP and solved using deterministic
Diaz-Bejarano E, Behranvand E, Coletti F, et al., 2018, Identification of thermal conductivity mixing models for heterogeneous fouling deposits, 16th International Heat Transfer Conference, IHTC-16, Pages: 4057-4064, ISSN: 2377-424X
© 2018 International Heat Transfer Conference. All rights reserved. Fouling deposition on heat transfer surfaces is a costly problem in pre-heat trains of crude distillation units. Organic and inorganic species found in the deposits are characterized by markedly different thermal conductivity. Fouling heat transfer resistance depends on the extent of inorganic and organic phases, their structural arrangement, and stratification or layering. Understanding and, if possible, detecting the deposit composition would provide additional capabilities in monitoring, troubleshooting, prediction and optimisation of mitigating remedies. This paper aims at elucidating possible arrangements of the inorganic and organic phases by testing various thermal-conductivity mixing models for heterogeneous materials. A novel model describing the deposit layer as a multi-component structure is used with available plant measurements (pressure drop, temperatures, flowrates) to infer the deposit properties (e.g. thickness, conductivity and composition) over time. Various “mixing” models that describe the arrangement of the organic and inorganic phases in fouling deposits are tested. Radial composition profile of the deposit calculated with various mixing models is compared to the experimental composition analysis of deposits collected upon dismantling of the exchanger after four years of operation. The differences between this approach and a traditional analysis based on fouling resistance (that neglects deposit stratification) are discussed. Results show that the four mixing models tested provide an appreciably different level of agreement between compositions calculated from the plant measurements and the experimental characterization. The best agreement with the experimental data was obtained with a Co-Continuous model (all phases continuous), followed closely by an Effective Media Theory model (all phases discrete).
Diaz-Bejarano E, Coletti F, Macchietto S, 2018, Complex crude oil fouling layers: use of model predictions to detect inorganics breakthrough, Applied Thermal Engineering, Vol: 141, Pages: 666-674, ISSN: 1359-4311
Crude oil fouling models have greatly improved in the past two decades. However, most models focus on the deposition of organic species at high temperatures (i.e. greater than 200 °C). In this paper, a deposit model, capable of capturing simultaneously the deposition of both organic and inorganic species, is used to track deposition history in a shell-and-tube heat exchanger at the hot end of a refinery pre-heat train. The model was previously fitted to plant data and the results compared to the experimental characterization of deposits. It is shown that such a model, together with plant data, can be used (i) to describe the development of complex deposit layers; (ii) to detect and diagnose changes in composition of the deposit. From a practical perspective, it is then possible to alert plant operators of unexpected events such as breakthrough of inorganics at an early stage and help in planning corrective actions.
Diaz Bejarano E, Coletti F, Macchietto S, 2018, Identifying the causes of acute fouling in refinery preheat train, 2018 AIChE Spring Meeting and 14th Global Congress on Process Safety, Publisher: American Institute of Chemical Engineers
Crude oil fouling is typically treated in the literature as a phenomenon involving the deposition of organic material on the thermal surfaces of heat exchangers. Little attention is paid to the effects that inorganic species have on the thermal and hydraulic performance of the heat exchangers affected. When deposition of inorganic species occurs, it is often the cause of an upset in operations (e.g. issues with the desalter) that results in episodes of rapid (acute) fouling. In this paper, a method used to detect acute fouling episodes and identifying their causes is presented.
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