In this post I want to share how to estimate total capital cost of flare system. Since the post is quite long, I will divide it into 3 posts:
- Part 1 will explain how to estimate equipment cost
- Part 2 will explain how to estimate installation cost
- Part 3 will explain total capital cost
In the last part, I will also post a free spreadsheet on how to estimate capital cost of flare system described in every post.
For disclaimer, the accuracy of this cost estimation is ±30% (study estimate). Apply for tip flare tip diameter ranging from 1-60 in and stack heights ranging from 30-500 ft. Standard construction material is carbon steel.
The cost is based on 2017$ basis.
Flare Cost (CF)
Flare costs area based on 2017 basis and function of support type as follows:
where:
CF = flare cost (2017 $)
D = flare tip diameter (in), ranging from 1-60 in
H = flare stack height (ft), ranging from 30-500 ft
The equations above are for estimation only. To obtain more accurate value, it is necessary to ask vendor quotation.
The scope of the above estimate is as follow.
Material of construction: carbon steel, except for upper 4 ft and burner tip which are based on 310SS.
Figure below shows capital cost of each type of flare.
Flare Monitoring System Cost (CM)
The cost of flare monitoring system may include flame monitoring system, flare vent gas flow rate meter, and net heat value monitor.
The presence of flame is commonly detected by thermocouples or ultraviolet (UV) monitor.
The flare vent gas rate meter is commonly monitored by ultrasonic flow meter due to wide flow range and ability to measure flow without additional pressure drop in the flare vent line.
Net heat content is generally determined either by using a calorimeter or by calculating it from the composition of flare gas.
Monitoring system costs usually do not vary with flare size, so the following flare monitoring system costs apply to most applications. The price is based on 2017$ basis.
For example, for one flare vent gas monitoring location is needed for a given flare, and only a pilot flare monitoring, flow monitor, and calorimeter needed, the flare monitoring equipment cost will be $4,100 + 58,000 + 77,300 = $139,400 per flare.
Knock-Out Drum Cost (CK)
The cost of knock-out drum is estimated using equation below. The basis is 2017$.
where:
CK = knock-out drum cost (2017 $)
d = drum diameter (in)
t = vessel thickness (in), based on drum diameter
h = height (in)
Piping Cost (CP)
The flare gas header and transfer line piping are dependent on the site location on the process facility where the emission is generated and where the flare is located. For capital cost estimation purposes, it is assumed that the transfer line will have the same diameter as the flare tip and a minimum length of 100 feet.
Equations below used to estimate piping cost of flare header. Piping costs cover only straight, schedule 40 carbon steel pipes, and 2017$.
where:
CP = vent stream piping cost (based on 2017$)
L = length of pipe run (ft), 100 ft minimum
D = diameter of pipe/flare tip (in)
Seal Cost (Cs)
Liquid seal costs are included in the flare cost. For flares with routine flow, a flame arrestor may be needed instead of a liquid seal. The cost for a flame arrestor (for flares with D < 24 in) is provided below.
where:
CS = flame arrestor cost (2017$)
D = diameter of pipe/flare tip (in)
Flare Gas Recovery Cost (CFGR)
Flare gas recovery system costs are estimated using the system’s design capacity, which is determined by either the maximum flow to be collected or the routine flare flow and a utilization factor—typically 70% to 80%.
Equation below is used to estimate flare gas recovery system cost.
where:
CFGR = flare gas recovery system costs (2017$)
Qcap = design flare gas recovery capacity of system (scfm)
Utility Cost (Cu)
The costs for necessary utilities to supply the flare with steam, auxiliary fuel, and electricity to power the monitoring equipment should be considered as on a case-by-case basis.
Conclusion
The total equipment cost (EC) of flare is again presented below.
Purchase Equipment Cost (PEC) is equal to Equipment Cost (EC) plus factors for ancillary instrumentation, such as control room instruments (10%), sales taxes (3%), and freight (5%).
I hope you find this post useful!
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