Liquid extraction on air cooled condensor steam ducts

Van der Westhuizen, J. J. (2015-12)

Thesis (MEng)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: Matimba Power Station in South Africa experiences erosion of its air-cooled condenser (ACC) bundle tubes, as stated in an ACC degradation report by Eskom. This erosion is caused by water droplets (wet steam) travelling at high velocities. Impurities due to demineralization system failures and corroded metal are carried via these water droplets to the ACC bundles. The impurities lower the pH level of the water droplets, promoting corrosion. If the impurities that are carried to the ACC bundles could be reduced through water/steam separation, the erosion of the ACC bundles would be reduced. An aerodynamic water/steam separator is designed to reduce the pressure loss caused by the separator and the best location for liquid extraction is identified in the ducting. To design such a separator certain sensitivities need to be evaluated like the shape of the separator and also the sensitivities on the shape itself. To find the best location for the separator in terms of the amount of liquid that can be extracted, it should be known where most of the droplets flow in the flow domain. There is no information regarding the droplet size distribution and certain assumptions need to make. Different models are used for different droplet sizes and these models are also investigated in this study and identified for the conditions on the power station. The shape and location for the separator is identified with an airfoil shape placed on one of the vanes in the bend of the ducting.

AFRIKAANSE OPSOMMING: Matimba Kragstasie in Suid-Afrika maak melding van erosie op die stasie se lugverkoelde kondensatorbuise in ʼn Eskom-verslag oor die degradasie van lugverkoelde kondensatorbuise. Hierdie erosie word veroorsaak deur waterdruppels (nat stoom) wat teen groot snelhede beweeg. Onsuiwerhede afkomstig van gedemineraliseerde sisteem probleme en verroesde metaal word in die druppels na die kondensatorbuise vervoer. Die onsuiwerhede in die waterdruppels verlaag die waterdruppels se pH, wat op sy beurt korrosie veroorsaak. Indien die druppels wat die onsuiwerhede bevat met behulp van water-/stoomskeiding onttrek kan word voordat hulle die kondensatorbuise bereik, kan die erosie op die kondensator verminder word. ‘n Aerodinamiese water/stoom skeier is ontwerp om die kleinste drukval wat deur die skeier veroorsaak word, te verminder, asook die beste plasing vir die skeier in die vloeikanaal. Om so ‘n skeier te ontwerp moet sekere sensitiwiteite getoets getoets word soos die vorm van die skeier asook die sensitiwiteite op die vorm self. Om die beste plasing vir die skeier te kry in terme van die plek waar die meeste vloeistof onttrek kan word, moet die plek bekend wees waar die meeste van die druppels vloei in die vloeikanaal. Daar is geen informasie aangaande die druppel grootte en verspreiding op die kragstasie nie en dus moet sekere aannames gemaak word. Verskillende modelle word gebruik vir verskillende druppel groottes en hierdie modelle word ondersoek en bepaal in hierdie studie vir die kondisies op die kragstasie. Die vorm en plasing van die skeier is bepaal met ‘n vlerkprofiel vorm op een van die gids wieke in die draai van die vloeikanaal.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/98024
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