Once-through multistage flash desalination installation combined with thermal vapour compression MSF-OT/TVC

• Published in: Desalination and water treatment 2019-09, Vol.161, p.48-55
• Main Authors: Sellami, Ahlem, Ali, Mongi Ben, Lakhdar, Mouna, Kairouani, Lakdar
• Format: Article
• Language: English
• Subjects: Once-through multistage flashing; Performance indicators; Thermal vapour compression
• ISSN: 1944-3986
• DOI: 10.5004/dwt.2019.23893

Novel configurations for the once-through multistage flash desalination MSF-OT process are proposed to improve its performance indicators. In these configurations, steam jet ejectors are used to compress vapour entrained from stages of the installation, which is then used to produce heating steam for the heat input section. Three configurations of once-through multistage flash desalination installation combined with thermal vapour compression (MSF-OT/TCV) are investigated, which includes vapour entrainment and compression from different stages. The TVC unit uses one or two jet steam ejectors in series, in order not to exceed the limit value of the compression ratio. The study includes the development of mathematical models for the three configurations, followed by the description of the method used to solve the equation systems obtained. This method uses the solver fsolve of MATLAB software. The analysis of the configurations is based on comparison of the thermal performance ratio, and the specific feed seawater flow rate, as a function of the top brine temperature and location of vapour entrainment. The results obtained indicate that entrainment vapour and compression by the steam jet ejector from high temperature stages give higher thermal performance ratio, than for vapour entrainment from low temperature stages. Results show that the increase in thermal performance ratio of the best MSF-OT/TCV configuration over the conventional MSF-OT configuration varies between 42% and 57%. However, this improvement is accompanied by a slight degradation in the specific feed seawater flow rate, whose value varies from 0.26% to 2.1%.