LPG / Natural Gas Spilt Control system

[Ahmed Elzawawi]

Dear Group
In our plant we already use LPG for complex flare system to ethylene plant, polyethylene and polypropylene plant, since we have a shortage of LPG we decide to use in parallel N.G ( size 16") to feed flare-pilots by design new pipeline connected to all F. pilots data of the N.G are :
proposed Pipeline Size: 2"
pressure : 16 kg/cm2
flow : 43 nm/hr3
temp: 20 C

Q1.Is it necessary to attached a flow meter for Flare-pilot pipeline? API537 dose not illustrated whether or not ?
2. another issue to connect the N.G line to ethylene plant to feed fuel for furnaces, where already there is a control loop controlling LPG fuel flow by using foxboro pneumatic pressure controller with ( 2-output)to control valve feeding LPG.
Q2. can I use the second foxboro controller output to control the new loop for N.G flow to furnaces, or i have to use another controller?

 

[mk3223]

IMO, the requirement of the flow meter on the fuel gas line is the operation and process safety issue. Consider to conduct a PHA/HAZOP with the right people involved to determine the flow meter requirement for both questions you have.

 

[georgeverghese]

Q1. In many oil and gas companies, it is customary practice to keep track of and report CO2 and other greenhouse gas emissions. If this practice is active in your plant, then it is likely that Operations staff would insist on a pilot gas flow meter here.
Q2. Process controls for fuel gas feed to furnaces can be complicated, there may be controllers to control air /fuel ratio, another for max set PC and yet another for min set control. Talk to the controls engineers responsible for these control loops at these furnaces before you scavenge any PC here for flare pilot gas pressure control.