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Materials Technologies for performance improvement of Cooling Systems in Power Plants

Periodic Reporting for period 3 - MATChING (Materials Technologies for performance improvement of Cooling Systems in Power Plants)

Reporting period: 2019-03-01 to 2019-08-31

Power generation is a sector requiring great amounts of water primarily for cooling purposes. At European level, while water is in general abundant, water scarcity still affects some regions in particular during summer. In the Mediterranean area water demand for energy production compete with the demand from agriculture and tourism generating situation of water stress. An improved approach for a sustainable management of water resources is therefore crucial The goal of MATChING is to reduce the cooling water demand in the energy sector through the implementation of innovative technological solutions.
The project target include: a) Reduction of geothermal steam emitted into the atmosphere up to 15% and extension of production wells life up to 10%; b) Overall plant efficiency increase up to 0.5%; c) Overall reduction of fresh water abstraction in power plants of 30%. To reach these target a broad set of technologies are investigated, as indicated in Figure 1, where their application to a typical open recirculating cooling system is shown.
"The project is organized in 8 work packages as indicated in figure 2. WP1 holds the management and coordination actions. WP2 provides the criteria for the evaluation of the technologies developed in WP3-WP6 and supports their economical analysis (WP7). WP3-WP6 are the ""technological WPs"" and are dedicated to the demonstration of the technologies.

WP3 deals with the exploitation of low temperature geothermal source for electricity generation in bynary cycle configuration. The first application case is the geothermal site of Balmatt, in Belgium, where, currently, geothermal brine is used for district heating. To maximize the electricity production from the process, without consuming water for cooling, a hybrid configuration based on the use of Ground Water Cooling (GWC) and Air Cooler Condenser (ACC) is investigated through a simulation tool. In addition, as the geothermal brine is a high salinity fluid, to reduce the installation costs, the application of coatings for upgrading the corrosion resistance of cheap materials is experimentally evaluated. The simulation tool showed that the yearly potential gain in electricity production of a CHP low-enthalpy binary plant by using groundwater as heat sink in place of air coolers ranges between 20% and 45%. On the coatings side, a total of 12 coatings for AISI 316L and 9 coatings for P265G have been tested in laboratory. Five of them have been selected for the testing at Balmatt site where they worked with the real geothermal brine. The demonstration tests showed that coatings are a promising option for metal surface protection but careful selection for a specific geothermal site is required and wrong selection can result in fatal consequences.

WP4 deals with the application of hybrid Cooling Towers to high temperature geothermal plants. The application case was in Nuova San Martino plant in Italy. Within the Project one of the 6 cells was retrofitted to host a hybrid cell. A total of 8 coatings on two different base materials (Aluminium 6060T, Carbon Steel ASTM A179) were characterized in laboratory before and after their exposure in by-pass configuration in Nuova San Martino. The best 3 combinations have been chosen for 3 of the 4 exchanger tube bundles. The fourth one was in AISI 316 L. Two different filling media have been tested in the SPIG facility. One of them has been chosen for the demo. The erection and commissioning of DEMO module was in April 2018. The hybrid demonstration began at November 2018 after the restoring works due to fire accident. Demonstration tests lasted for more than 1 year comparing performances of wet and hybrid configurations. Results clearly showed an average reduction of the evaporated water of about 10% of hybrid operation with respect to the wet one with a small energy penalty. The assessment of new coatings and base materials did not confirm expected reliability and stainless steel (SOA) remained the acceptable design material for the HEXs even though deep investigation on deposition procedure is recommended in the coated aluminum and carbon steel pipes.

WP5 aims at improving steam condenser performances, increasing, at the same time, heat transfer rate and condenser robustness. Different material solutions were investigated, acting on the steam side, to promote drop-wise condensation, and on the cooling water side, to contrast biofouling phenomenon. All the thermal and nuclear power plants are potential application cases for the technologies developed in WP5. For drop-wise condensation five solutions have been selected and tested at THRYCO pilot with promising results for DTI and MateriaNova coatings. Pilot condenser design and installation was completed in As Pontes. Due to problems in the commissioning phase and also due to the lack of production of the commercial group where the facility is installed, the starting of the tests has been delayed. On the cooling water side, many coatings and materials have been investigated by the Consortium and have been tested in laboratory and on field for quick and dirty test. The selected coatings and materials were tested in Pericles. The materials showed very low biocide effect compared to standard material with similar matter deposition. Poor results obtained also for the coatings, only a commercial coating, silicon-based used in ships, showed antifouling properties in conformity with certain success indicators on stainless steel.

WP6 aims to demonstrate a series of technologies, mainly based on the use of membranes, for cooling water conditioning and/or for process water recovery.The five technologies selected for water treatment are: Membrane capacitive deionization (MCDI); Industrial Vortex Generator (IVG); Membrane distillation (MD); a combination of pressure driven membranes; Membrane Condensers (MC). All these technologies have been tested at lab scale; IVG, MD, UF/RO and CDI membranes have been tested at higher scale (pilot CT, As Pontes CT, Torrevaldaliga). MC pilot tests at Pericles are still ongoing. Application cases for these technologies are all the power plants equipped with cooling towers as well as power plants with issues in managing their wastewater process streams. Technologies (CDI, MD and IVG) are available to reduce the water intake for wet cooling for thermal power plants with 30 % or more, compared to current practice or optimized reference (CC-gasfired). Reductions are site specific, depending on climate and water quality."
The technologies developed in the project represent an innovation with respect to the market situation or with respect to the current practice in Industry: hybrid towers are normally applied to thermal sector but not to the geothermal one due to the aggressiveness of the fluid. On the water treatment side, despite of the great amount of technologies present in the market, their application in the power industry is still moderate due to sector specific constraints or technical/economic barriers. Now, thanks also to the increasing awareness in Europe on the importance to safeguard water, this situation is going to change. Each of the described technologies contributes to water saving at a different extent but as they are applicable in a synergic way and in all the sectors of electricity production (from renewable to fossil and nuclear) a huge impact is expected from their exploitation.
Figure 2 - Workplan
Figure 1 - Technologies