Optimization of refinery preheat trains: predictive maintenance and operations improvement

Deciding which heat exchanger to clean, when to clean and how to clean in refinery pre-heat trains is a challenging activity that typically relies on operator’s experience. In this paper, an algorithm that allow identifying the most economic cleaning schedule for a given refinery configuration and operating conditions is presented. The method relies on an advanced framework that incorporates rigorous heat exchanger models capable of predicting the fouling behaviour of the refinery as a function of configuration of the individual units and the network, process conditions and time. An industrial case study is presented to illustrate the benefits of the approach, showing that significant improvements over current practice can be obtained

Impact of crude oil fouling composition on the thermohydraulic performance of refinery heat exchangers

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.Crude oil fouling studies generally focus on the thermal impact of organic deposits. The hydraulic limit given by pressure drop is, however, frequent cause of shutdowns and cleaning. Inorganic matter is often found in deposit analysis, but ignored in most studies. A case study is presented based on published plant data from the Esfahan Refinery (Iran). A detailed thermo-hydraulic model of heat exchangers undergoing fouling, together with the available data and reasonable assumptions, is applied to study the exchanger most affected by fouling. Novel modifications are made to: i) capture the effect of inorganics on the deposit conductivity; and ii) use pressure drop measurements, instead of temperature, to fit key fouling parameters. Good agreement is obtained between model and plant data. This demonstrates the need and benefit of considering fouling layer composition and both temperature and pressure drop data in the fitting of model parameters and interpretation of plant data. The potential of using such a model for early detection of operative problems is highlighted.This research was partially performed under the UNIHEAT project. EDB and SM wish to acknowledge the Skolkovo Foundation and BP for financial support. The support of Hexxcell Ltd, through provision of Hexxcell Studio™, is also acknowledged.am201

Crude Oil Fouling Deposition, Suppression, Removal, and Consolidation—and How to Tell the Difference

This research was partially performed under the UNIHEAT project for which EDB and SM wish to acknowledge the Skolkovo Foundation and BP for financial support. The support of Hexxcell Ltd, through provision of Hexxcell Studio, is also acknowledged

A model-based method for visualization, monitoring, and diagnosis of fouling in heat exchangers

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

Organic and inorganic fouling in heat exchangers – Industrial case study: Analysis of fouling state

Skolkovo Foundation; B

Cross Sectional Examination of a Fouled Tube Removed from a Crude Oil Preheat Exchanger

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

Organic and Inorganic Fouling in Heat Exchangers – Industrial Case Study: Analysis of Fouling Rate

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

Identification of Host Genes Involved in Geminivirus Infection Using a Reverse Genetics Approach

Geminiviruses, like all viruses, rely on the host cell machinery to establish a successful infection, but the identity and function of these required host proteins remain largely unknown. Tomato yellow leaf curl Sardinia virus (TYLCSV), a monopartite geminivirus, is one of the causal agents of the devastating Tomato yellow leaf curl disease (TYLCD). The transgenic 2IRGFP N. benthamiana plants, used in combination with Virus Induced Gene Silencing (VIGS), entail an important potential as a tool in reverse genetics studies to identify host factors involved in TYLCSV infection. Using these transgenic plants, we have made an accurate description of the evolution of TYLCSV replication in the host in both space and time. Moreover, we have determined that TYLCSV and Tobacco rattle virus (TRV) do not dramatically influence each other when co-infected in N. benthamiana, what makes the use of TRV-induced gene silencing in combination with TYLCSV for reverse genetic studies feasible. Finally, we have tested the effect of silencing candidate host genes on TYLCSV infection, identifying eighteen genes potentially involved in this process, fifteen of which had never been implicated in geminiviral infections before. Seven of the analyzed genes have a potential anti-viral effect, whereas the expression of the other eleven is required for a full infection. Interestingly, almost half of the genes altering TYLCSV infection play a role in postranslational modifications. Therefore, our results provide new insights into the molecular mechanisms underlying geminivirus infections, and at the same time reveal the 2IRGFP/VIGS system as a powerful tool for functional reverse genetics studies