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Ethylene

MOGAS valves handle the complications from massive cracking operations in ethylene production

A colorless flammable gas with a faint sweet and musky odor when pure, ethylene is widely used in the chemical industry. More ethylene is produced than any other organic compound, mostly to make polyethylene for plastic bags and pipes.

The ethylene production process includes four main steps: cracking, quenching, compression and processing. Reliable shut-off valves are essential to maximize ethylene quality and yield, and to minimize emissions, equipment damage and shutdowns.

The primary heat exchanger valve is the first valve in the system that sees the full range of products of the massive cracking operation that just occurred upstream, from the lightest (methane) to the heaviest (coke). Valves in this main transfer line need to absolutely isolate during the de-coking cycle, typically monthly, until a unit-wide shutdown is necessary for maintenance, cleaning and refurbishment.

Process hazards include:

  • fugitive emissions of feedstock
  • toxic and corrosive gases, e.g, hydrogen sulfide
  • corrosive materials (iron oxide, iron sulfide) that causes stress cracking
  • high temperature swings from 850 to 350° F from furnace to quench towers that causes leaks and valve damage
  • high pressure steam up to 1500° F
  • coke buildup, where de-coking presents a fire hazard should the valve not provide reliable air-tight isolation

MOGAS valves protect equipment from the harsh conditions of ethylene production through design features:

  • bi-directional sealing for backflow protection to restrict coke build-up and leaks into lines
  • durable disc spring design is particle tolerant (vs multiple coil springs)
  • wide seats and sharp leading seat edges wipe ball clean of harsh naphtha feedstock and coke build-up
  • fire safe graphite packing and spiral-wound body gasket
  • Class V shut-off due to risk of fire and cavitation
  • process and customer-specific coatings
  • high cycles
  • tight shutoff

 

Typical Operating Conditions:
  • Temperature: -50 – 850° F (-45 – 454° C)
  • Pressure: 50 – 600 psig (3.4 – 41.4 bar g)

Ethylene Process Flow Diagram
  1. Feed
  2. Steam
  3. Recycle Feed
  4. Primary Heat Exchanger
  5. Fuel Oil
  6. Primary Fractionator Overhead
  7. Cooling Distillation Tower Ethylene Cut
  8. Cooling Distillation Tower Recycle
  9. Cooling Distillation Tower Water
  10. Cooling Distillation Tower Overhead
  11. Cracked Gas Compressor
  12. Pre-Fractionator
  13. Caustic Wash Column
  14. Pre-Fractionator Overhead
  15. Caustic Wash Column Overhead
  16. Drying Column
  17. Main Cooler
  18. Main Cooler Overhead
  19. Hydrogen Separator Methane
  20. Hydrogen Separator Hydrogen
  21. De-methanizer
  22. De-methanizer Overhead
  23. De-ethanizer
  24. De-ethanizer Overhead
  25. Acetylene Hydrogenator
  26. Hydrogen
  27. Ethylene Separator
  28. Ethylene Overhead
  29. Ethylene Separator Bottoms
  30. De-propanizer
  31. De-propanizer Overhead
  32. Methylacetylene Hydrogenation
  33. Hydrogen
  34. Propylene Splitter
  35. Propylene Splitter Overhead
  36. De-butanizer
  37. De-butanizer C4 Overhead Fraction
  38. De-penthanizer
  39. De-penthanizer C5 Overhead Fraction
  40. Gasoline Splitter
  41. Gasoline Splitter C6-C9 Overhead
 
  • Heat Exchanger (not shown)
  • General Ball Valves (not shown)