Abstract: The aim of this work is to build a model of a heated brine spray system in order to predict its behaviour through dynamic simulation and thus optimize its performance. Concentrated brine solutions with initial temperatures from 65 to 85 degrees C are sprayed into the surrounding ambient air, in windy conditions. This spray system will be used in the NaCl salt recrystallization ponds that are integrated with a cogeneration unit, in order to increase the global process efficiency. This industrial platform is located in Pombal, Portugal, as already referred in a previous work [Moita, R. D., Matos, H. A., Fernandes, C., Nunes, C. P., & Prior, J. M. (2005). Dynamic modelling and simulation of a cogeneration system integrated with a salt recrystallization process. Computers and Chemical Engineering, 29, 1491-1505]. A global three-dimensional mathematical dynamic model was built, which includes two models. The single drop model, which is based on the ballistics theory and includes material and energy balances, allows calculating each drop trajectory and velocity as it exits the nozzle, as well as its temperature, salt concentration and volume. The spray system model accounts for the full-cone spray-nozzle by considering a set of random defined drops. The spray system model was implemented and simulated in gPROMS 2.3.7. Asensitivity analysis of some model parameters and choices was performed. Model predictions, obtained through dynamic simulation, were compared with retrieved literature data, referring to water drops, in terms of drop trajectories and of evaporation rates. The model validation was also carried out using the experimental data obtained in the herein above mentioned NaCl recrystallization industrial ponds, referring to the respective heated brine spray system. It must be stressed that the simulated results are in reasonable agreement with the literature Values and also with the experimentally measured ones. Although the model developed in this work allows predicting the behaviour of the mentioned heated brine scheme, it can be easily adapted to account for other types of systems and sprays. (C) 2009 Elsevier Ltd. All rights reserved.
Abstract: The aim of this study is to optimise a Portuguese industrial three integrated process system, by studying the effect of some operational and atmospheric conditions on the system. For this main goal it was built a dynamic model, which includes the cogeneration system, the plate heat exchangers and the salt production unit. The cogeneration system was modelled and analysed in GateCycle 5.34.0.r. and the interface variables were used as input of the dynamic model of the remaining integrated process. This model was developed and exploited through gPROMS 2.3. Some particular issues (start-up, scheduling and atmospheric conditions) were investigated to forecast the performance of the integrated system. The best start-up conditions were established. Several atmospheric conditions were studied and the minimum number of ponds required for each situation was calculated. The scheduling of the evaporation ponds in operation was also investigated to enhance the salt production and to optimise the salt harvesting. The process simulation indicated that it is better to work with the corresponding minimum number of ponds, having a "turbo" pond that receives a larger quantity of heated brine. The efficiency of the cogeneration system (thermal plus electric power divided by natural gas consumption) was approximately 92%. However, the global process efficiency (accounting for energy losses in the evaporation step of the salt production process) was in the range of 70-80%, depending on the atmospheric and operational conditions considered. (c) 2005 Elsevier Ltd. All rights reserved.
Abstract: Process Integration has been applied in several industrial processes mainly using standard shell and tube heat exchangers (1-1 or 1-2). The flow arrangement in 1-2 multiple shell and tube heat exchangers involves part counter-current flow and part co-current flow. This fact is accounted for in the design by introducing a FT correction factor into the I-I heat exchanger design equation. To avoid some steep regions in the feasible space of heat exchangers design some authors introduce other parameters like X-P or G. Until now it was not possible to have an overall map to give some guidelines of how to choose between the several X-P approaches established in the literature. This paper summarizes the current existing criteria in a general design algorithm (DeAl(12)) to show a path for the calculations of the main design variables of the heat exchanger Also a new strategy design algorithm (StratDeAl(12)) is introduced in this paper to allow the best choice between the existing X-P approaches based on the heat exchanger cost minimisation. Several examples illustrate the advantage of using the developed algorithm and the deviations obtained in the heat exchanger cost if a wrong approach was chosen.
Abstract: A distributed dynamic model was built using gPROMS 2.3.7 language for an integrated Process including a cogeneration system, a plate heat exchangers set and a salt recrystallization process. It was analyzed the effect of a simulated spray system model on the integrated process, by comparing the global performance of the system with and without sprays. Due to air drift issues, quasi-random time daily profiles for the allowed operation of the spray system (on-off working time periods) were created. Using three distinctive atmospheric scenarios, several ponds spray distributions schemes were analysed. A sensibility analysis of the salt production was considered by changing the brine flow rate fraction entering in the ponds through taps and by sprays.
Abstract: The aim of this study is to obtain a dynamic modelling and simulation of a Portuguese se industrial integrated system composed of three different processes. This work includes the analysis of the optimal integration of the different units, and the study of the effect of some operational and atmospheric conditions on the system to maximize its global thermal efficiency. The cogeneration system was modelled and analysed using the GateCycle 5.34.0.r software. It was concluded that the electric and the thermal power obtained strongly depend on air and economizer cooling water temperatures. The whole integrated process (cogeneration, plate exchangers and salt production unit) is simulated and exploited through gPROMS 2. 1. 1. The best start-up conditions were established. The minimum number of ponds required strongly depends on atmospheric conditions, but it can never be less than three in order to obey the operational defined temperature intervals. The scheduling of the evaporation ponds to be put into operation is also investigated in order to enhance the salt production and to optimise the salt harvesting. The simulation indicates that it is better to have the minimum number of ponds working (higher temperatures inside the ponds) and to have a "turbo" pond that receives a larger quantity of heated brine than the others. It was also studied the effect of different atmospheric conditions, and the number of ponds in service required to overcome the more adverse atmospheric conditions. The global process efficiency (thermal and electric power over natural gas consumption) is approximately 92%. However, the effective global thermal efficiency of the whole integrated site (accounting for the existing losses into the open air of the evaporation process) is in the range of 75-80%, depending on the atmospheric and operational conditions considered.
