Energy Optimization Of Low Temperature Seawater Multi-effect Desalination System

Now, with the rapid development of human society and the economy, especially the fast increase of the population of the world, the consumption of water for life is becoming more and more, and the pollution and the waster is becoming more serious and more serious, causing the fresh water resources more shortage, so the development of seawater desalination technology has become a world consensus. In seawater desalination field, MSF, LT-MED and RO are three mainstream technologies. The technology of LT-MED is easily large-scale implemented and its costs lower, thus it is the main direction of the research.At the same time, saving energy has become the hot topic of the world, too. The consumption of energy is the key to measure the level of project operation, in particular the use of software simulation to guide the production. While, Aspen Plus is the first choice, because of its comprehensive physical property database and the unit operation model library.In this thesis, the simulation models of operation unit of LT-MED seawater distillation are built with Aspen Plus software, and then LT-MED system was simulated and analyzed. Finally, the four-effect LT-MED seawater desalination system of SIDEM Corporation France is used as an example for evaluating dependability basing on the simulation model. Contents of the study include:1. Establishing system model. The model of Heater, Flash2and Mixer of Aspen Plus are used to simulation the system of LT-MED.2. The influence of the system simulation parameters on the simulated results and the process is optimized. By establishing system model, which with the BPE and flash tank or without to studying the influence of them, the results show that the BPE causes the energy losing of the system, while the flash tank improves energy efficiency. By establishing system model which has different number of evaporators, the simulation results show that with the increase of the number of evaporators, the energy efficiency is improved.3. The study of system of LT-MED of northern power plant. The data obtained from the northern power plant as the basic data of simulation to establishing system model withl4multi-effect evaporators. According to Northern power plant-Hangu salt plant cycle economic model’s requirements, when the export of system is determinate and the different evaporator’s secondary steam backflow to mix with the waste steam to be the heating steam of the first evaporator, with the place of secondary steam backflow to back, system also improve energy utilization ratio.