Fired Heater Energy efficeincy/combusiton control

[ebonydegaris9]

Dear Fellow refiners,
we are looking at improving energy efficiency of fired heaters and looking at various options. currently we use volumetric flow meter to feed the refinery fuel gas (off gases) to the fired heater. we have high o2 percentage. the composition of fuel gas is not very constant. we are looking to control the fuel gas feed on the basis of energy content ? what all types of measurement instrumentation is required. we already have one mass flow meter as spare ?what else should we go for and how to control using energy ?
thanks

[calvin gao]

In order to help you, please clarify the following:
1. Is your heater efficiency low due to high O2, and the reason for unable to run at lower O2 is FG variability of the FG heating value?

You may install a fuel gas density analyzer at the fuel gas main header. Using that as a feed back to blend fuel gases.

[Anonymous]

Hi calvin, yes there is high variability in the FG . can you elaborate a sgood solution. sorry i am also new and doing internship

[evan]

Hi. I agree with Calvin, there are lots of things to be understood to help you with this issue.

Some initial thoughts,
– If XSO2 is high due to damper control, you may be successful. If it is high due to tramp air, controlling at the burner itself will be hard.
– Corriolis is a good measurement, you get mass and volume and density flow real time. This is the best practice but rare.
– Most refiners now have real time analyzers on the refinery fuel gas network to get composition and heating value. This can be central to the FG ring. But you should also do some QC testing at the DCU to be sure the quality is the same there. Most DCU are at the end of the header and quality changes over the run.
– Generally DCUs like higher XSO2 to prevent heater fouling. If you run too low for heater efficiency, your decoking frequency is likely to increase.

[Anonymous]

Hi Evan, our refinery has energy efficiency program and we are operating at high %O2 levels around 4-5% , we are also having orifice plate flow measurement on the fuel gas line. the emissions are still within the limits of local regulations but we want to operate the heaters at low %O2 may be 2-3% , having a analyzer which means are you referring to Gas chromatograph which would give the Composition and heating value ? the GC has high maintenance and also it isn’t fast enough to give real time data which can be used to control. so hence we were looking at the other ways. the reason why we can operated at low O2 is high variability of fuel gases.

[calvin gao]

Hi there,

To know the heating value of a fuel gas online, a GC is not required. You may use an online density analyzer to measure the fuel gas density and then correlate it to the gas heating value.

Hopefully this helps.

[Author]

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