Methods for controlling chlorine induced superheater corrosion

Transcription

1 Metso solutions for tackling the effects of corrosion and optimizing the fuel blend Methods for controlling chlorine induced superheater corrosion Juha Roppo, Metso Power

2 Megatrends Targets CO 2 reduction 20% by 2020 Renewables 20% by 2020 Towards recycled and renewable fuels Fuels more diverse in quality 2 Metso

3 Megatrends Market interest for low cost fuels 0.01% Fuel Cl- content 0.05% 0.1% 1.0% Market need Market interest Fossil Hard coal Wood biomass Northern wood Pulp&Paper sludges Wood pellets Fast growing wood Willow Eucalyptus Agro biomass Straw Sunflower hulls Corn Stover Miscanthus Recycled fuels Packaging waste Recycled wood Challenge 3 Metso

4 The role of chemistry in power production Chemistry impact on corrosion and boiler design Temperature Gas atmosphere Power Ash plant = Chemical reactor Fuel mixture Air K 2 SO 4, PbCl 2, Na 2 SO 4 ZnCl 2 K 2 CO 3, Na 2 CO 3 Furnace reactions Deposit KCl Corrosion Corrosion product layer Primary emissions Slagging /Fouling HCl Additives Final steam SO 2 Change of temperature K 2 SO material and pressure 4 PbCl 2, Na 2 SO 4 ZnCl Fuel 2 mixture K 2 Si 4 O 9 C, H, Na 2 Si 4 O 9 N, S, Cl Sintering HHV Fuel mixture H 2 O CO 2 N 2 O 2 H 2 SO Superheater 4 placement HCl Corrosion Additives CaCl 2 H 2 O Flue gas cleaning Emissions CaSO 4 Ash quality NO X HCl SO 2 LHV Pb, Zn, As, Cr, Cu, Ti,, Ba. 4 Metso

5 Tools to mitigate corrosion Prediction methods & tools Novel boiler design - Steam parameters & efficiency - Superheater arrangement - Material grades low alloyed / high alloyed Corrosion Control Management - Measurement of environment corrosivity - Fuel blend optimisation - Additives - Control system and application - On-line corrosion rate calculation - Superheater lifetime prediction - Help to plan preventive maintenance and replacement operations 5 Metso

6 Metso Corrosion Management Facing the fire Corrosion is natural phenomenon and it occurs everywhere around us. Only the corrosion rate varies. Utilisation of biomass and recycled fuels speeds up the corrosion. We can measure the corrosion rate and control it to a sustainable level. Corrosion significantly reduces the lifetime of superheaters Fear of corrosion limits utilisation of inexpensive fuels Unmanaged corrosion leads to risk of failure and unplanned shutdown Dealing with corrosion is a cost Corrosion significantly reduces the lifetime of superheater 6 Metso

7 Calculated corrosivity of the environment 1,E The relative corrosivity of the fuel /fuel mixture 1,E ,E ,E-061 1,E-07 0,1 1,E-08 0, RDF 50% Stem wood + 50% RDF Bark (spruce) Stem wood Flue gas temperature [C] Composition of the gas phase and Condensed phases Detailed temperature and flow model of the critical area 7 Metso

8 The corrosivity of the environment at different locations in the boiler High Moderate Low Negligible 8 Metso

9 Corrosion calculation tools Corrosion risk index verified based on empirical data Corrosion No corrosion Fuel S/Cl (molar ratio) Variation due to material and temperature HYBEX Empirical knowledge to verify results Corrosion index Corrosivity of environment and Corrosion index as base values for corrosion rate calculation Continuos verification in existing boilers 9 Metso

10 Metso Corrosion Management Corrored Analyzer The solution consists of the online analyzer unit and the sampling device. Hot flue gas sampling is followed by analyzer using titration technology. Total chlorine & sulphur concentration Calculates the flue gas S/Cl molar ratio ON-LINE Providing Flue gas S/Cl molar ratio for corrosion risk and rate evaluation Fuel Cl content for fuel quality determination Information for fuel blend and additive control Sampling Operating inside hot furnace up to 1000 C Classifies particles > 10 um back to boiler Dissolves sample to sample water for analysis Metso Corrored 10 Metso

11 Metso Corrosion Management CorroStop Additives Metso CorroStop The Metso CorroStop consists of two fuel additives (liquid and solid) and an injection system that feeds the additive directly into the boiler. Alkali chloride reacts with sulfur trioxide or dioxide 2MCl (g,c) + SO 3(g) + H 2 O (g) => M 2 SO 4 (g,c) + 2 HCl (g) CorroStop liquid solution - Aluminiumsulfate Al 2 (SO 4 ) 3 or Ferric sulfate Fe 2 (SO 4 ) % liquid solutions - Spraying through nozzles before superheaters CorroStop+ elementary sulphur - 0,5 3,2 mm granulates - Addition to fuel feeding screws Controlling of alkalichloride induced high temperature corrosion 11 Metso

12 Metso Corrosion Management Measurement results of reference cases Case: Co-combustion of solid recovered fuel and biomass Corrosion rate with and without CorroStop TM. Tertiary superheater, made of high alloyed material, steam out 500 C Fuel chlorine content 12 Metso

13 Future development High temperature superheater corrosion risk KCl concentration realtime on-line (TUT Optics; T. Sorvajävi, J. Toivonen) Superheater material & steam temperature Corrosion rate approximation Empirical verification with references Verification with calculation tools Online additive & process control Online condition monitoring Results: M. Hedman et. al. Measurement and control of corrosive environment in combustion of solid recovered fuels in BFB boiler. Impacts of Fuel Quality on Power Production and the Environment, Metso

14 Metso Corrosion Management A solution that creates real savings Case, 90 MW th CHP power plant Steam: 34 kg/s, 90 bar, 510 C Fuels: recycled fuel and biomass, 720 GWh per year 8,000 operation hours per year Scope: Corrored analyzer, CorroStop - additive injection system, Metso DNA control and reporting system Investment: EUR 300, ,000 (scope) Annual operation, maintenance and chemical costs: EUR 250,000 Earnings increase Increased lifetime of superheaters from 3 to 10 years Optimizing fuel diet creates EUR 1.4M annual savings. Average fuel cost lower from 18 EUR/MWh to 16 EUR/MWh Earnings increase of EUR 90,000 by steam temperature rise from 485 to 510 C. Electricity price: 45 EUR/MWh Payback of investment in 4-6 month. 14 Metso

15 Research Partners In the development of Corrosion control management Metso Automation Tampere University of Technology: Optics Laboratory Aerosol Physics Laboratory Flow Research Laboratory Power Plant and Combustion Technology VTT Technical Research Centre of Finland Åbo Akademi Laboratory of Inorganic Chemistry 15 Metso

16 Thank You! 16 Metso