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Fouling mitigation on the Preheat, Furnace Convection Section and
GE Power & Water Water & Process Technologies Fouling mitigation on the Preheat, Furnace Convection Section and vaporizer Patrick Lucas Global Product and Technical Director, Petrochemical GE Water & Process Technologies (GE W&PT) VINYL INDIA - 2013 3rd International PVC & Chlor - Alkali Conference 11 - 12 April 2013, Hotel Grand Hyatt, Mumbai, India Copyright 2013 the General Electric Company. Presentation Outline • Potential problems affecting plant efficiency • VCM and Coke Reaction Mechanisms • Factors influencing the Fouling • How to mitigate the fouling on the preheat, furnace convection section and vaporizer • Case Histories Copyright 2013 the General Electric Company. EDC/VCM Flowsheet Copyright 2013 the General Electric Company. Presentation Outline • Potential problems affecting plant efficiency • VCM and Coke Reaction Mechanisms • Factors influencing the Fouling • How to mitigate the fouling on the preheat, furnace convection section and vaporizer • Case Histories Copyright 2013 the General Electric Company. EDC/VCM Plant Process EDC Manufacture 1. CH2=CH2 (g) + Cl2(g) FeCl3 H<0 2. CH2=CH2 (g) + 2 HCl + 1/2 O2 VCM Manufacture ClCH2CH2Cl (g) heat 500°C ClCH2CH2Cl (l) CuCl2 H<0 ClCH2CH2Cl (g) + H2O CH2=CHCl (g) + HCl Copyright 2013 the General Electric Company. VCM Reaction Mechanisms Mechanism 1: Radical Chain Reactions : 3 steps Cl. catalyzed reaction mechanism • Initiation: Cl. Radical generation CH2ClCH2Cl CCl4 • Propagation: Abstraction of H by Cl. CH2ClCH2Cl + Cl. • CH2ClCH2. + Cl. CCl3. + Cl. CH2ClCHCl. + HCl Termination: Decomposition to VCM CH2ClCHCl. C2H3Cl + Cl. Copyright 2013 the General Electric Company. VCM Reaction Mechanisms Mechanism 2: CH2ClCH2Cl Thermal Decomposition C2H3Cl + HCl By-Products 1,1,2-trichloroethane CHCl2-CH2Cl 1,2-dichloroethylenes CHCl=CHCl chloral (trichloroacetaldehyde) CCl3-CHO 1,1,-dichloroethane CH2Cl-CH2Cl ethyl chloride C2H5Cl Methyl chloride CH3Cl Dichloromethane CH2Cl2 Chloroform CHCl3 Carbon tetrachloride CCl4 Chlorinated tars Contaminants precursor of coke - Acetylene (major) -1,1,2-trichloroethane - Butadienes - Chloroprene - Vinylacetylene - Methylchloride C2H2 CHCl2-CH2Cl C4H6 C4H5Cl C4H4 CH3Cl Copyright 2013 the General Electric Company. VCM Reaction Mechanisms • CCl4 is a promotor CCl4 Increase in Cl. radical formation CCl3 + Cl. C2H3Cl conversion Coke formation Coking increase in the heat transfert resistance and pressure drop decrease in process efficiency and VCM selectivity • EDC Conversion at the range 54 to 58+% • CCl4 around 200 to 600ppm Copyright 2013 the General Electric Company. Organic Fouling • Cracking of EDC and other chlorinated organics due to heat and catalyzed by iron promoting polymerization • Precipitation or loss of solubility of high molecular weight organics (Heavies T4/T4+) • Coke from upstream Typical deposit analysis: Loss on Ignition (550C) MeCl2 Solubles MeCl2 Insolubles % Carbon % Hydrogen % Chlorine % Nitrogen 98% 20% 80% 40-80% 1-2% 10-37% <0.5% Copyright 2013 the General Electric Company. Presentation Outline • Potential problems affecting plant efficiency • VCM and Coke Reaction Mechanisms • Factors influencing the Fouling • How to mitigate the fouling on the preheat, furnace convection section and vaporizer • Case Histories Copyright 2013 the General Electric Company. Factors influencing Fouling • Heat Flux and high TMT (tube metal temperature) • High amount of water and contaminants (acetylene, butadiene, chloroprene, vinylacetylene, methylchloride, chloral, Tri 1,1,2…) • Iron Concentration (FeCl3/FeCl2) Catalyst of Cracking Increases Fouling • Purge Flow Rate Low Flow High Flow Increased Fouling Decreased Fouling • Liquid level Too Low Too High Fouling on Liquid/Vapor Interface Longer Residence Time Copyright 2013 the General Electric Company. Factors influencing Fouling Impact of Iron Test Method: Iron added to 1,2 EDC, heated to 120°C under nitrogen purge 2 hours, evaporated to dryness Run Sample Fe form ppm Fe mg Deposit 1 10 ml EDC None None 15.4 2 10 ml EDC FeCl3 5000 700 Copyright 2013 the General Electric Company. Presentation Outline • Potential problems affecting plant efficiency • VCM and Coke Reaction Mechanisms • Factors influencing the Fouling • How to mitigate the fouling on the preheat, furnace convection section and vaporizer • Case Histories Copyright 2013 the General Electric Company. Methods to Reduce Fouling • Use saturated steam in reboilers • Maintain proper liquid level control • Minimize water contamination of crude EDC • Control corrosion on wash water and head column overheads and minimize steam leaks • Maintain proper control of ferric chloride feed to the reactor • Filtration • High molecular weigh Dispersant Copyright 2013 the General Electric Company. Dispersant functionality: GE Petroflo Features • Highly surface active chemistry Benefits • Prevents deposition of solids • Inorganic and Organic dispersant • Effective fouling control of both salt deposition and entrapped HC functionality • Prevents agglomeration of solids • Cleanup capability at high dosages • Process compatibility • Low water content • Protection for downstream equipment • Provides ability to respond to upsets • Eliminates concerns for downstream contamination • Eliminates corrosion concern • Proven technology • Used in all the designs Copyright 2013 the General Electric Company. Presentation Outline • Potential problems affecting plant efficiency • VCM and Coke Reaction Mechanisms • Factors influencing the Fouling • How to mitigate the fouling on the preheat, furnace convection section and vaporizer • Case Histories Copyright 2013 the General Electric Company. Application Case Preheat, Furnace Convection Section & Vaporizer - High Pressure design - Iron contamination in EDC going to the cracking furnaces - Fouling on the preheat exchangers, furnace convection section & Vaporizer - 1 cleaning of the convection section between 2 cleanings of the radiant section - Outlet temperature of the convection section limited to 220°C Economical impact - Unplanned shutdown - EDC feed reduction to furnace - Loss in production Copyright 2013 the General Electric Company. Preheat, Furnace Convection Section and Vaporizer Dispersant VCM Furnace Hot Quench Tower 100°C EDC to distillation 220°C bottleneck 250°C Dispersant EDC Vaporizer 500°C Blowdown to Heavy ends Copyright 2013 the General Electric Company. EDC/VCM Cracking Furnace Convection Section Delta T trend (°C) 200 treated 180 treated treated 160 Untreated 140 treated treated treated Untreated Untreated 120 treated Untreated 100 Untreated Untreated Untreated treated treated 80 60 40 20 0 20-Nov-00 08-Jun-01 25-Dec-01 13-Jul-02 29-Jan-03 17-Aug-03 04-Mar-04 20-Sep-04 08-Apr-05 25-Oct-05 Copyright 2013 the General Electric Company. Preheat, Furnace Convection Section and Vaporizer Dispersant VCM Furnace to distillation 100°C EDC Hot Quench Tower 220°C 235°C EDC Vaporizer Blowdown 500°C bottleneck to Heavy ends Copyright 2013 the General Electric Company. EDC/VCM Cracking Furnace Convection Section Delta T trend (°C) 200 treated 180 treated treated 160 Untreated 140 treated treated treated Untreated Untreated 120 treated Untreated 100 Untreated Untreated Untreated treated treated 80 60 40 20 0 20-Nov-00 08-Jun-01 25-Dec-01 13-Jul-02 29-Jan-03 17-Aug-03 04-Mar-04 20-Sep-04 08-Apr-05 25-Oct-05 Copyright 2013 the General Electric Company. Preheat, Furnace Convection Section and Vaporizer Results - No shutdown for cleaning before furnace radiant decoking (preheat/convection) - Increase in throughput due to rise in preheat outlet temperature (from 220 to 245 °C)----5% VCM production increase - Runlength 5 year on the vaporizers - Maintenance overcost reduction - Reduced Personnel Exposure to toxic deposits - Reduce hazardous waste disposal costs TOTAL SAVINGS : 27000+ t/y VCM Copyright 2013 the General Electric Company. GE Power & Water Water & Process Technologies Fouling mitigation on the Preheat, Furnace Convection Section and vaporizer Patrick Lucas Global Product and Technical Director, Petrochemical GE Water & Process Technologies (GE W&PT) VINYL INDIA - 2013 3rd International PVC & Chlor - Alkali Conference 11 - 12 April 2013, Hotel Grand Hyatt, Mumbai, India Copyright 2013 the General Electric Company.
