(537e) Simultaneous Optimization of Flow Distribution and Cleaning Schedule for Heat Exchanger Networks Subject to Maintenance Constraints
AIChE Annual Meeting
Wednesday, November 10, 2021 - 4:46pm to 5:05pm
There are two broad fouling mitigation approaches for HENs: (1) at the design or retrofit stage, the geometry of the heat exchanger can be optimized; and (2) at the operation stage, where operational variables, such as flow distribution in HEN and cleaning schedules can be optimized (Rodriguez and Smith, 2007). This work is targeted at existing HENs and hence falls under the latter type. Several studies have been carried out in this category, formulating it as an optimization problem and considering the operating variables and cleaning activities as continuous and binary variables, respectively. The independent and simultaneous consideration of these variables in an optimization framework results in nonlinear programming (NLP) and mixed-integer nonlinear/linear programming problems (MINLP / MILP), respectively. For instance, the optimization of cleaning schedules has been formulated as MINLP and MILP problem (Georgiadis et al.,2000, Smaili et al.,2002, Ishiyama et al., 2011 and Diaby et al., 2016). Similarly, the optimization of flow rates alone has been formulated as an NLP problem (Assis et al., 2015 and da Silva et al.,2015). The simultaneous consideration of cleaning schedules and flow distribution also have been carried out by several authors (Rodriguez and Smith, 2007, Ishiyama et al., 2010 and Santamaria and Macchietto, 2020).
Although all these studies have shown the potential to save significant costs due to fouling, it is important to note that the realization of the cost saving is only possible if the optimal operating conditions and cleaning schedules are properly implemented. The proper implementation of an optimal cleaning schedule often becomes difficult due to the limited resources such as maintenance budget and personnel. In such cases, cleaning activities are shifted towards suboptimal schedules resulting in higher costs. Therefore, it is necessary to consider the constraints of available maintenance resources. To our knowledge, the resource limitations have not been previously considered in HEN fouling mitigation studies.
This work addresses this gap by modeling maintenance activities with resource limitations. Further, the concept of grouped maintenance, wherein the initial preparatory costs shared across all units within a group, is incorporated (Do et al., 2015). Heat exchangers can be grouped based on the similarity of the type of cleaning activities (mechanical or cleaning methods) or according to their locations. In the present work, we first propose a MINLP formulation for simultaneous optimization of flow distribution and grouped cleaning schedules of the heat exchangers in HENs. Grouping of cleaning activities is modeled through linear constraints based on the type of cleaning required for the heat exchangers. The period for the cleaning of all heat exchangers is assumed to be two weeks. Optimization can be performed using stochastic optimization techniques such as genetic algorithm. The proposed methodology has been evaluated on two HEN case studies with three and six heat exchangers, respectively. Our results demonstrate that the grouping of the maintenance activities results in significant savings. The proposed methodology and the results from the two case studies will be presented in this paper.
- Assis, B. C. G., Lemos, J. C., Liporace, F. S., Oliveira, S. G., Queiroz, E. M., Pessoa, F. L. P., & Costa, A. L. H. (2015). Dynamic Optimization of the Flow Rate Distribution in Heat Exchanger Networks for Fouling Mitigation. Industrial and Engineering Chemistry Research, 54(25), 6497â6507.
- da Silva, R. L., Costa, A. L. H., & Queiroz, E. M. (2015). Stream flow rate optimization for fouling mitigation in the presence of thermohydraulic channeling. Heat Exchanger Fouling and Cleaning - 2015, 2015, 384â391.
- Diaby, A. L., Miklavcic, S. J., & Addai-Mensah, J. (2016). Optimization of scheduled cleaning of fouled heat exchanger network under ageing using genetic algorithm. Chemical Engineering Research and Design, 113, 223â240.
- Do, P., Vu, H. C., Barros, A., & BÃ©renguer, C. (2015). Maintenance grouping for multi-component systems with availability constraints and limited maintenance teams. Reliability Engineering and System Safety, 142, 56â67.
- Georgiadis, M. C., & Papageorgiou, L. G. (2000). Optimal energy and cleaning management in heat exchanger networks under fouling. Chemical Engineering Research and Design, 78(2), 168â179.
- Georgiadis, Michael C., Lazaros G. Papageorgiou, and Sandro Macchietto. "Optimal cleaning policies in heat exchanger networks under rapid fouling." Industrial & engineering chemistry research 39.2 (2000): 441-454.
- Ishiyama, E. M., Heins, A. V., Paterson, W. R., Spinelli, L., & Wilson, D. I. (2010). Scheduling cleaning in a crude oil preheat train subject to fouling: Incorporating desalter control. Applied Thermal Engineering, 30(13), 1852â1862.
- Ishiyama, E. M., Paterson, W. R., & Ian Wilson, D. (2011). Optimum cleaning cycles for heat transfer equipment undergoing fouling and ageing. Chemical Engineering Science, 66(4), 604â612.
- Macchietto, S., Hewitt, G. F., Coletti, F., Crittenden, B. D., Dugwell, D. R., Galindo, A., Wilson, D. I. (2011). Fouling in crude oil preheat trains: A systematic solution to an old problem. Heat Transfer Engineering, 32(3â4), 197â215.
- MÃ¼ller-Steinhagen, H., Malayeri, M. R., & Watkinson, A. P. (2005). Fouling of heat exchangers-new approaches to solve an old problem. Heat Transfer Engineering, 26(1), 1â4.
- Rodriguez, C., & Smith, R. (2007). Optimization of Operating Conditions for Mitigating Fouling in Heat Exchanger Networks. Chemical Engineering Research and Design, 85(6), 839â851.
- Santamaria, F. L., & Macchietto, S. (2020). Online Integration of Optimal Cleaning Scheduling and Control of Heat Exchanger Networks under Fouling. Industrial and Engineering Chemistry Research, 59(6), 2471â2490.
- SmaÃ¯li, F., Vassiliadis, V. S., & Wilson, D. I. (2002). Optimization of cleaning schedules in heat exchanger networks subject to fouling. Chemical Engineering Communications, 189(11), 1517â1549.
This paper has an Extended Abstract file available; you must purchase the conference proceedings to access it.
Do you already own this?
Log In for instructions on accessing this content.
|AIChE Pro Members||$150.00|
|AIChE Emeritus Members||$105.00|
|AIChE Graduate Student Members||Free|
|AIChE Undergraduate Student Members||Free|
|AIChE Explorer Members||$225.00|