t TNO Environment, Energy and Process Innovation Jaap Koppejan Reducing corrosion and ash deposition in Dutch WtE plants ACERC conference, Feb, Salt Lake City

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators2 Content General info on Dutch waste incineration sector Corrosion processes Corrosion reduction measures

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators3 Waste to Energy plants in the Netherlands 11 installations, total capacity approx. 5.5 Mton Existing WtE plants were retrofitted in 90’s Very low emissions

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators4 Emission limits (dry m 3, 11% O 2 ) ComponentEmission limit total dust5 mg/m 3 HCl10 mg/m 3 HF1 mg/m 3 CO50 mg/m 3 VOC10 mg/m 3 SO 2 40 mg/m 3 NO x 70 mg/m 3 Sum of heavy metals1 mg/m 3 Cd0,05 mg/m 3 Hg0,05 mg/m 3 PCDD's + PCDF's0,1 ng I-TEQ/m 3

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators5 WtE plants in the Netherlands Processing capacity E-Power output Heat output Number of lines Date of operation kton/yrMWeMWth Alkmaar Amsterdam Rotterdam Rijnmond (distilled water) (6 lines) 1995 (1 line) Roosendaal6714 MWth21972 Dordrecht / 1992 Moerdijk Steam to CHP31997 Nijmegen /1995 Arnhem (district Heating)31985/1990/1991 Hengelo Wijster

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators6 Need for increased availability Typical: steam conditions 40 Bar/400°C, efficiency 22% Availability in hours/year: 90% 1 day production loss equals about 125,000 $  corrosion in first pass and boiler is major reason for production loss. Higher steam conditions needed for higher efficiencies (e.g. 100 Bar/500°C)  Corrosion and deposition problems

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators7 Overview of corrosion processes in WtE- boilers Boiler water wall Ceramic Lining Grate ~700°C Boiler: 400°C/ 40 Bar °C Generation of Volatile chlorides Super heaters chlorides +CO chlorides +H 2 O gas NaCl ZnCl 2 Sulphates of NaCl and ZnCl 2 NaCl(g) > NaCl(s) Cl-gas corrosion NaCl+ SO 2 + O 2 = Na 2 SO 4 + Cl 2 Fe + Cl 2 = FeCl 2 FeCl 2 + O 2 = Fe 3 O 4 + Cl 2 Ev SSEc

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators8 Typical temperatures in boilers of WtE- plants BoilerpartSteamT metal °CT gas °C Waterwall, evaporator 265 °C~ 300°C~ °C Evaporator tubes 265 °C~ 300 °C~ °C Superheater400 °C~ 450 °C~ °C

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators9 Typical corrosion in Dutch WtE plants EvaporatorSuperheater Metal temperature~ °C~ °C ConstructionMembrane wallTube bundles MaterialC-steel (St.35.8)Alloy (15Mo3) Typical corrosion velocities 0,15-0,30 mm/y0,20-0,40 mm/y

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators10 Corrosion on water walls 1.CO corrosion at locations with reducing conditions

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators11 CO corrosion on furnace walls Carbon steel corrosion at 450 °C

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators12 Corrosion on water walls 1.CO corrosion at locations with reducing conditions 2.Corrosion by metal chloride deposits 3.Erosion due to high dust loads and high local velocities 4.Missing refractory tiles

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators13 Corrosion on superheater tubes

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators14 Corrosion on superheater tubes 1.Corrosion by Cl 2 or HCl containing gas (active oxidation) 2.Corrosion by metal chloride deposits 3.Erosion due to high dust loads and local high velocities 4. Sulphate corrosion (less influence)

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators15 Active oxidation from Cl in gas at 500 C, no SO 2 1.2NaCl + Fe 2 O 3 + ½ O 2 = Na 2 Fe 2 O 4 + Cl 2 2. Fe + Cl 2 = FeCl 2, attaching Fe 3 O 4 layer Metal chlorideT 4 (°C) FeCl FeCl CrCl CrCl NiCl 2 607

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators16 Corrosion reduction measures 1.Combustion conditions 2.Boiler cleaning mechanisms 3.Materials used 4.Boiler design

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators17 1. Combustion conditions Improvement of air distribution Optimisation of combustion behaviour Better flue gas temperature control

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators18 2. Improved boiler cleaning mechanism Removal/adaptation of soot blowers Optimisation of boiler tube cleaning system Cleaning with dynamite/gas explosions Water jet cleaning

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators19 Cleaning with explosives

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators20 Effect of cleaning with explosives jan-01feb-01apr-01jun-01jul-01sep-01nov-01dec-01feb-02apr-02mei-02jul-02sep-02 date Flue gas temperature

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators21 3. More advanced materials Cladding Alloy 625

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators22 steel 15Mo3 tube corrosion

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators23 Alloy 625 tube corrosion

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators24 Composite tubes for super heaters Advanced refractory on membrane walls, e.g. SiC tiles or better fixation 3. More advanced materials Cladding, e.g. Alloy 625

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators25 4. Adaptations of design: Super heater configuration

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators26 Changing configuration of super heater bundles Temperatures and corrosion of 15Mo3/St Flue gas temperature °C Steam temperature °C Much corrosion Little corrosion

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators27 4. Adaptations of design: Super heater bundle configuration Water injection in steam system Increasing refractory area or cladding in first pass Water cooled grate (if sufficient heating value)

t Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators28 Summary: Good experiences exist in the Netherlands with Optimization of combustion process (case specific) Improved boiler tube cleaning Improved materials and constructions (cladding, superheater configuration)