Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Hybrid DCMD and SWRO desalination using a small PWR of 75 MW(th) for cogeneration of water and electricity
Submission Author:
Paulo Augusto Berquo de Sampaio , RJ , Brazil
Co-Authors:
Paulo Augusto Berquo de Sampaio, LUIZ FLAVIO ALVES, Maria de Lourdes Moreira
Presenter: Paulo Augusto Berquo de Sampaio
doi://10.26678/ABCM.COBEM2023.COB2023-0725
Abstract
Nuclear cogeneration systems of electricity and water can make relevant contributions towards the United Nations sustainable development goals such as “Clean Water and Sanitation”, “Affordable and Clean Energy” and “Climate Action”. Here we investigate a hybrid desalination strategy, using both Direct Contact Membrane Distillation (DCMD) and Sea Water Reverse Osmosis (SWRO), for cogeneration of water and electricity using a small PWR of 75 MW(th). The simplest hybrid desalination solution is considered, where the DCMD and the SWRO desalination plants operate independently. The small PWR provides the heat and the electrical power required by both desalination plants, besides generating electricity for either the grid or local use. Blending the water produced by SWRO with that produced by DCMD has two main advantages. One is the improvement of the quality of the water produced, as compared to that obtained with the SWRO plant. The other is the reduction of the cost of water production, as compared to that attained by the DCMD plant alone. The SWRO plant uses the electricity generated on site by the small PWR. In our computations, the water production of the SWRO plant is determined using the reference specific electricity consumption of 4 kW(e)h per cubic meter, which is a value typical of a real-scale SWRO plant. On the other hand, to provide heat to the DCMD plant, we divide the steam produced in the steam generator into two parallel Rankine cycles. The first of those cycles operates at pressures and temperatures that are typical of a Rankine cycle optimized for electricity generation. In the second cycle, though, steam expansion in the turbine is shortened to a pressure just below the atmospheric pressure. Thus, steam condensation occurs at a temperature just below 100 oC, which allows heating the seawater in the second Rankine cycle condenser up to 92 oC. The external heating required for the DCMD desalination process comes exclusively from cooling the two Rankine cycle condensers. Using this arrangement, a specific electricity consumption of 8.47 kW(e)h per cubic meter has been obtained for the DCMD process. These computations were performed using the DE-TOP program, developed by the International Atomic Energy Agency (IAEA), which simulates the Rankine cycles of PWRs, and the DESAL-PLANT program, developed at IEN/CNEN, which models a DCMD desalination plant with heat recovery. Finally, estimates of water and electricity production are presented, considering the mean seawater temperature of the Brazilian northeast.
Keywords
Small PWR, cogeneration, nuclear desalination
