TITANIUM FOR POWER PLANTS
Power Plant Condensers:
Titanium has been proven by the power industry to be the most reliable of all surface condenser tubing materials. Several hundred million metres of thin wall welded titanium tube are now in service worldwide. Titanium is immune to all of the processes of corrosion which occur in condenser operation, and which continue to cause damage or threaten operational efficiency for units tubed with less corrosion resistant metals and alloys. Design to optimise the engineering properties of titanium is possible for new condensing equipment. The retubing of existing units may require modifications to the condenser to compensate for the lower modulus and density of titanium as well as its possible influence as a cathode in a mixed metal system. Experience gathered from hundreds of condenser units operating in widely varying conditions has progressively exposed practices which are prejudicial to the normal long life expectation of titanium tubes. Condenser performance is a significant factor in the overall operational efficiency of power plant. The widespread use of low cost titanium welded tube which is immune to corrosion has virtually eliminated condenser problems from power station economics.
Flue Gas Desulphurisation:
More than 20 years operational experience with wet FGD scrubbers, ductwork and stacks, has shown that titanium can resist the highly corrosive conditions encountered continuously or intermittently in the FGD process. The aggressive conditions experienced include wet/dry interfaces, acidic condensates and flyash laden deposits enriched in chloride and fluoride species.
The largest single FGD plant installation in Europe is the Drax plant of National Power PLC in North Yorkshire, England. The three 260 metre (850ft) high concrete flues of the stack are lined with a total of over 24,000 square metres (258,000ft¬≤) of Grade 2 commercially pure titanium sheet. One flue per year was lined in 1992, ’93 and ’94 respectively. A recent inspection (1999) revealed no significant corrosive attack on the titanium after seven years exposure to a full range of operating conditions.
Steam Turbine Blading:
Titanium alloys are used for advanced steam turbine blades. The advantages are weight reduction, (56% the density of 12 Cr steel), and corrosion resistance. Titanium resists attack by reducing acid chlorides in condensate which forms at the Wilson line.
Titanium is additionally resistant to corrosion fatigue and stress corrosion cracking. Hydrogen absorption is not a concern at the temperatures in the L-1 and L region of turbines. As with other blading alloys, titanium requires a leading edge shield to improve the resistance to water droplet erosion.