Delayed Coking Valve Applications

Coking Market Dynamics

The rising price of and the ever increasing shortage of sweet, light and easily refinable crudes has forced many refineries to process heavier cheaper crudes. This is in addition to converting low value residues to high value fuels with moderate capital investment budgets.

 Typical two drum delayed coking plant 

Coking Process Challenges

Despite being an established process for over 50 years Delayed Coking presents several challenges. It is one of the most hostile environments in the refinery. Process temperatures can reach 1000 Degrees F, and the by product Coke is very abrasive and erosive. Fully solidified coke is harder than concrete. As a result of these environmental factors valves are cycled more frequently than in other parts of the refinery.

Valve failure can lead to the complete shut down of a refinery unit, and this down time is a large process and financial cost.

Definition

Delayed coking is a cyclic process that thermally cracks vacuum residue or other residue feedstocks into gas, light products and petroleum coke. The typical process steps are outlined below:

Delayed Coking Process Steps

• heat residue to about 930° F in coker furnace
• transfer the hot residue to coke drum before it has formed coke
• fill the drum and allow the tars to coke
• switch the drums on timed cycle (12 to 24 hours)
• decoke the full drum hydraulically
• recover the cut, crush and prepare for shipment
• recycle water to eliminate waste
• fractionate cracked products into gas, coker naphtha, light coker gasoil and heavy coker gasoil
• further process fractionated products in downstream units

Valves for Delayed Coking

SchuF has designed a range of valves for use in Delayed Coking operations. These include the key switch, isolation, bypass, backpressure and overhead vapour valves. The valves are based on an original SchuF patented (received in 1914) invention – the lift plug Model 12 and Model 14

20 inch lift plug isolation valve

SchuF can also provide valves for all other required functions in and around the delayed coking process from its extensive range of valves (e.g. for drain, warm or quench functionality the SchuF  Model 30 valves can be used.)

Lift Plug Valves Advantages

The simple and rugged design delivers many benefits:

• Protected Valve Seat (PVS) – Valve life is increased as seat or body faces do not come in contact with the flow media
• Total Sealing between body and plug ensures clean cavities and reduces maintenance significantly
• Trunnion spindle guiding can be used for high pressure applications or to prevent vibration
• Flushing and/or Purging is only required during operation from open to close or vice versa. This leads to significant cost savings in comparison with other valve designs
• Efficient Lift, Turn and Reseat (LTS) operator mechanism
• Automated Control Panel (ACP) can be used to control single or multiple valves, actuators and sensors
• Top or bottom entry design for ease of maintenance