Fouling mitigation on the Preheat, Furnace. Convection Section and vaporizer

Transcription

1 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 rd International PVC & Chlor - Alkali Conference April 2013, Hotel Grand Hyatt, Mumbai, India

2 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

3 EDC/VCM Flowsheet

4 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

5 EDC Manufacture EDC/VCM Plant Process FeCl 3 H<0 1. CH 2 =CH 2 (g) + Cl 2(g) ClCH 2 CH 2 Cl (l) CuCl 2 2. CH 2 =CH 2 (g) + 2 HCl + 1/2 O 2 ClCH 2 CH 2 Cl (g) + H 2 O H<0 VCM Manufacture heat ClCH 2 CH 2 Cl (g) 500 C CH 2 =CHCl (g) + HCl

6 Mechanism 1: VCM Reaction Mechanisms Cl. catalyzed reaction mechanism Initiation: Cl. Radical generation Radical Chain Reactions : 3 steps CH 2 ClCH 2 Cl CH 2 ClCH 2. + Cl. CCl 4 CCl 3. + Cl. Propagation: Abstraction of H by Cl. CH 2 ClCH 2 Cl + Cl. CH 2 ClCHCl. + HCl Termination: Decomposition to VCM CH 2 ClCHCl. C 2 H 3 Cl + Cl.

7 Mechanism 2: VCM Reaction Mechanisms Thermal Decomposition CH 2 ClCH 2 Cl By-Products C 2 H 3 Cl + HCl 1,1,2-trichloroethane CHCl 2 -CH 2 Cl 1,2-dichloroethylenes CHCl=CHCl chloral (trichloroacetaldehyde) CCl 3 -CHO 1,1,-dichloroethane CH 2 Cl-CH 2 Cl ethyl chloride C 2 H 5 Cl Contaminants precursor of coke - Acetylene (major) C 2 H 2-1,1,2-trichloroethane CHCl 2 -CH 2 Cl - Butadienes C 4 H 6 - Chloroprene C 4 H 5 Cl - Vinylacetylene C 4 H 4 - Methylchloride CH 3 Cl Methyl chloride CH 3 Cl Dichloromethane CH 2 Cl 2 Chloroform CHCl 3 Carbon tetrachloride CCl 4 Chlorinated tars

8 VCM Reaction Mechanisms CCl 4 is a promotor CCl 4 CCl 3 + Cl. Increase in Cl. radical formation C 2 H 3 Cl 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+% CCl 4 around 200 to 600ppm

9 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 T 4 /T 4 +) Coke from upstream Typical deposit analysis: Loss on Ignition (550 C) 98% MeCl 2 Solubles 20% MeCl 2 Insolubles 80% % Carbon 40-80% % Hydrogen 1-2% % Chlorine 10-37% % Nitrogen <0.5%

10 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

11 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 (FeCl 3 /FeCl 2 ) Catalyst of Cracking Purge Flow Rate Low Flow High Flow Liquid level Too Low Too High Factors influencing Fouling Increases Fouling Increased Fouling Decreased Fouling Fouling on Liquid/Vapor Interface Longer Residence Time

12 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 ml EDC FeCl

13 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

14 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

15 Features Dispersant functionality: GE Petroflo Benefits Highly surface active chemistry Inorganic and Organic dispersant functionality Prevents agglomeration of solids Cleanup capability at high dosages Process compatibility Low water content Used in all the designs Prevents deposition of solids Effective fouling control of both salt deposition and entrapped HC Protection for downstream equipment Provides ability to respond to upsets Eliminates concerns for downstream contamination Eliminates corrosion concern Proven technology

16 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

17 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

18 Preheat, Furnace Convection Section and Vaporizer Dispersant VCM Furnace Hot Quench Tower EDC 100 C 220 C bottleneck to distillation 250 C Dispersant EDC Vaporizer 500 C Blowdown to Heavy ends

19 EDC/VCM Cracking Furnace Convection Section 200 Delta T trend ( C) Un Un Un Un Un Un Un Nov Jun Dec Jul Jan Aug Mar Sep Apr Oct-05

20 Preheat, Furnace Convection Section and Vaporizer Dispersant VCM Furnace Hot Quench Tower EDC 100 C 220 C to distillation 235 C EDC Vaporizer bottleneck Blowdown 500 C to Heavy ends

21 EDC/VCM Cracking Furnace Convection Section 200 Delta T trend ( C) Un Un Un Un Un Un Un Nov Jun Dec Jul Jan Aug Mar Sep Apr Oct-05

22 Results Preheat, Furnace Convection Section and Vaporizer - 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 : t/y VCM

23 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 rd International PVC & Chlor - Alkali Conference April 2013, Hotel Grand Hyatt, Mumbai, India