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I am working in VGOHDT. We are facing flaring issue intermittently in Fractionator overhead drum. We are using split range controller for maintaining pressure using fuel gas and excess pressure will release in LP flare.
But we found that the overhead gas composition consist about 51% hydrogen ,23% methane and 14% nitrogen respectively which are non condensable gases. We increased HP steam in stripper column and reduce the pressure in Cold LP separator for removing it but problem persist. Kindly give suggestion to reduce H2 and methane to reduce flaring in Fractionator?
We are operating fractionator pressure at 1kg/cm2 and top temperature at 106 deg c.Overhead Finfan outlet temperature at 45 deg.
08/11/2018 A: keith bowers, B and B Consulting, kebowers47@gmail.com
You did not mention how the reactor effluent etc are cooled. As ambient temperatures drop, both cooling water and air coolers can cause H2S-hydrocarbon hydrates to form and restrict flows in the vent gas system, making pressure control difficult. The presence of hydrates can be easily confirmed by simply turning off the cooling for a few minutes and allowing any hydrates to melt and pressure control to resume working.
23/09/2018 A: Ganesh Maturu, Self, maturu.ganesh@gmail.com
It was mentioned that HHPS temperature maintained at 285 deg C and stripper bottom temperature at 275 deg C which is the way profile should look like and definitely no need to adjust feed temperature. Following can be done to avoid flaring issues in fractionator overhead condenser.
1. Since methane is available in flaring gas, reduce stripper pressure to the possible extent by checking stripper overhead vapor off gas control valve opening. This will ensure max stripping of methane. Did you analyze H2S also in flare gas? H2S might also be present if methane is present.
2. Check stripping steam flow to bottoms ratio. Maintain min of 3-5 lb/barrel. Do the water balance in stripper to ensure stripping steam flow meter is correct.
3. For fractionator push-pull system, you provide some dead band in split range controller i.e no action to be taken between 40-60% controller output.
4. Check the bottom section pressure drop of stripper i.e (Feed to bottom tray). If the pressure drop is very low compared to tray data sheet, there is a possibility of less vapors in bottom section which happens because of lower stripping steam flow, stripping steam inlet device malfunction or bottom tray damage.
11/09/2018 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
Confirm the stripping steam flow rate by making overall component balance and/or comparing with overhead water flow rate. If that is O.K, the stripping steam may not be dispersed across the cross-section of the column, or the liquid hydrocarbon may be channeling.
03/09/2018 A: Rajasekaran R, HMEL, Rajaskrn.89@gmail.com
We are maintaining H2/HC ratio as per licensor recommendation.There is no issue in Reactor.How Hydrogen slippage in Fractionator over head drum is related to reactor issue?
03/09/2018 A: Rajasekaran R, HMEL, Rajaskrn.89@gmail.com
we are maintaining HHPS inlet temp @ 285 deg C and stripper bottom temp @ 272 deg C.From where hydrogen and methane slippage was happening?
24/08/2018 A: Bhavesh Kanani, Kuwait National Petrolium Company, bhavesh.kanani@gmail.com
You may look into the reducing HHPS temperatures is feasible with is stripper feed.
As CLPS pressures is already reduced which will remove lighter to off gas. As stripping is done by HP steam, reduction of stripper bottom temperature to be checked.
24/08/2018 A: Bruce Carr, Suncor Inc, bcarr@suncor.com
That much slippage sounds more like a reactor issue.... have you tried adjusting your reactor temps.... recycle ratio?