Ethylene Furnace PGC Applications

Ethylene Plant Cracking Furnace Takes the feedstock and cracks the molecules in the presence of a catalyst at high temperatures Typically 12 -15 furnaces are used in a single ethylene plant The feedstock is typically naphtha (outside U.S.) and ethane / propane mix (within U.S.) The stream is also run through a caustic wash system to remove H2S and CO2 between compression stages

Improving Furnace Performance with PGC’s Advanced control of the cracking furnace is critical to the ethylene plant's entire efficiency “Over-cracking” leads to a premature furnace shutdown Excessive coke formation on catalyst “Under-cracking” is a direct reduction in overall production ABB PGC’s provide the data to the plant's control system to help optimize the right balance for cracking severity

Typical Cracking Furnace in a Ethylene Plant GC #1 GC #2 GC #3

Analytical Instruments – PGC and DRS The primary analysis point for this measurement is the exit from the transfer line exchangers Before either analyzer can extract a sample, a specialized sample probe called a "pyrolysis" or "reflux“ probe must first condition it – DRS GC #1 Fast analysis, limited measurements, quick update on cracking severity One PGC per furnace Possibly backups in case of failures, this is critical data

Analytical Instruments – PGC and DRS (cont.) More through analysis on furnace effluent Used by the plant control system to optimize the furnace cracking model More than one stream from multiple furnaces could be measured on a single GC GC #3 For the plants with the ethane / propane feedstocks Monitor variations in feed compositions Naphtha feeds take too long to be analyzed by a GC, but there has been some success with FT-NIR analyzers

PGC Analysis Summary GC # Stream Components Measured Measurement Objective 1 Furnace effluent (one per furnace) C1, C2, C2=,C3, C3= Used to calculate conversion severity 2 (shared between furnaces) H2 - C5+ Provide mass balance information to furnace control model updating 3 Furnace feed (if E/P mix) C1, C2, C2=, C3, C3=, C4+ Compensate for variations in product feed composition

GC #1 Example

GC #1 Chromatogram

GC #2 Example

GC #2 Chromatogram – TCD 1

GC #2 Chromatogram – TCD 2