Fouling in industrial heat exchangers is one of the most challenging, longstanding and costly problems the oil industry worldwide is facing today. In particular, crude oil fouling in refinery pre-heat trains leads to increased operating costs, maintenance issues, environmental impact of operations and health&safety hazards.
Hexxcell technology assists heat exchanger engineers, R&D specialists and plant personnel to assess, predict and mitigate fouling in refinery heat exchangers.
Hexxcell’s proprietary technology, originally developed at Imperial College London, and further devloped in close collaboration and proejcts with oil majors icludes the state-of-the-art software Hexxcell Studio™ for the prediction of fouling in refinery heat exchangers.
Hexxcell Studio™ – Accurate prediction of fouling in refinery heat exchangers
Hexxcell Studio™ is a comprehensive software framework that integrates solutions for monitoring, design and retrofit analysis of heat exchangers and their networks in a unified platform.
Hexxcell Studio™ incorporates the most advanced mathematical model available in industry for the simulation, design and optimisation of a multi–pass shell–and–tube heat exchanger undergoing crude oil fouling. It is also implemented in a user-friendly flowsheeting environment that provides a consistent, robust and flexible system for the solution of engineering heat transfer fouling problems at all stages, from R&D to operations support.
Hexxcell Studio™ has proven useful in assessing the economic impact of fouling, predicting its behaviour in the future, guiding operations to mitigate it and identifying retrofit design opportunities.
Under the bonnet – Advanced mathematical model
At the core of the Hexxcell Studio™ system, an advanced mathematical model based on technology originally developed at Imperial College London, allows to accurately calculate time-varying fouling rates as a function of local conditions in the heat exchanger. The model accounts for the complex interactions between thermal and hydraulic phenomena and equipment geometry.
Deployment in Industry – Easy to use environment
Implemented in a user-friendly flowsheeting environment with state-of-the-art numerical solution methods, Hexxcell Studio™ provides a consistent, robust and flexible system for the solution of engineering heat transfer fouling problems at all stages of the engineering workflow, from R&D to operations support.
A key benefit is the ability to consider and analyse, using consistent models and assumptions, the trade-offs between design activities and operational aspects. It provides a unified framework that helps preventing “silos” between company functions allowing easy sharing of assumptions, validations and developments between R&D, engineering design, operations and operations support functions.
Thermal and hydraulic model: Distributed heat balances are written in cylindrical coordinate which makes it possible to overcome the thin slab approximation – often used in other models – accounting for curvature effects of the heat exchanger tubes on the heat flux.
Tube-side fouling: A moving boundary approach is used to capture the growth of the fouling layer over time at any given point across the tube length, the corresponding reduction in cross–sectional flow area. A fouling rate model used in a distributed way, allows calculating the local value of fouling resistance at each point along the exchanger length as opposed to an average value for the whole exchanger.
Shell-side fouling: Effects of fouling in the shell-side is taken into account, including growth on the tube outer surfaces and occlusion of geometrical clearances.
Geometry: The heat exchanger configuration is accounted for (e.g. number of tube–side passes, tube diameter and length, baffle spacing, pitch arrangement, etc.).
Physical properties: The variation of physical properties with temperature and space for both shell–side and tube–side fluids is taken into account. Different thermophysical property models/packages (including proprietary ones) can be used.
Ageing of deposits: an ageing model (Coletti et al., 2010) is implemented to describe the structural changes of the fouling deposit over time, hence its thermal conductivity.