1. Ethylene Furnace PGC Applications

2. Ethylene Plant Cracking Furnace
Takes the feedstock and cracks the molecules in the presence of a catalyst at high temperatures
Typically 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

3. 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

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

5. 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

6. 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

7. 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

8. GC #1 Example

9. GC #1 Chromatogram

10. GC #2 Example

11. GC #2 Chromatogram – TCD 1

12. GC #2 Chromatogram – TCD 2