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We have SR Catalytic Reforming (Pt-Rh) Unit for 90.0 RONC production. It is our third cycle and the delta T of SR Reactors is decreasing rapidly day by day, but RONC is decreasing slightly or almost constant. However, stablizer overhead gases has also increased extensively. Some opinions arises that there may be the leakage in Combined feed exchangers of Platforming section. But, we are unable to detect this leakage during plant operation. Please mention, how we can detect this leakage (during plant operation) and secondly, please also describe that what may be the other reasons of such decreasing trend of delta T (i.e; from 125 deg c to 88 deg C in 7-8 months), keeping in view that we are running plant at 110% load and our design H2 / HC ratio is 4.5 in first cycle. Is there any need of revision of H2/HC ration in third cycle, if yes then how?

Additional info: Its again me who put up the questions. 1-- Yes, it was text fault,, its Platinum - Rhenium. 2-- Please tell, what we have to check in feed and product regarding MCH? means which thing will proof us leakage in F/E? 3-- Their is only excessive increase in OVHD gases of stablizer. 4-- Hydrogen purity decreased from 90 to 85%. 5-- YES, H2 / HC ratio is easy to calculate, but i want to ask that during third cycle or as the cycles progress, is it necessary to revised this H2 /HC? if yes, then on what basis? 6-- We have increased RITs from 4-5 deg C but RON did not increase. 7-- We have decreased H2 / HC to about 3000 NM3/ hr and delta T improves from 89 deg C to 90 deg C. but a slight yellowish appearance of reformate was detected. ( what will be the reason?) But, RONC did not change
08/10/2011 A: Kavirayani R Murthy, K R Murthy Consultants, krmurthy_ipcl@yahoo.com
The above symptoms clearly show slow poisoning of catalyst by various factors like high coke, high sulphur or excessive chlorination which we generally add to compensate excess moisture in the recycle gas and many other unknown factors. Each factor is to be closely monitored and eliminated. Usually in practice we look for big causes and overlook some times small causes which may create havoc. For example
If lubricating oil of either the feed pump or the recycle pump gets in to the feed naphtha due to a pump seal rupture we may not monitor because some body else tops up the lube oil when the lube level comes down in the equipment. This lube with additives may poison the active metal of the catalyst. Since we can not find out this thief we may increase the chloride content in naphtha to compensate the activity loss and to meet the pressing production schedules, Thus becoming a victim of this vicious cycle.
In the present case reformate fluorescence color indicate excessive cracking and possible hydrogen starvation by way of decreased hydrocarbon mole ratios in the reactor. The fluorescence color may be due the formation of poly nuclear aromatic compounds like caronene which can be analyzed by GC-MS .Once the hydrogen starvation is rectified we may notice color free clear reformate
I have come across the lube oil problem in one of the refineries where in the lube oil has leaked in to the system killing the newly charged all platinum monometallic catalyst with in 40 days of its charging. The delta T has come down drastically. We have identified the problem. Fortunately the catalyst was not permanently damaged by the additives of lube as verified by Electronic Spectra of Chemical Analyzer. (ESCA).
Some of these problems can be identified by doing the PNA (paraffin naphthenes aromatic) analysis of the feed and reformate for calculating and closely monitoring the extent of dehydrogenation activity to convert naphthenes to aromatics a function of metal activity and also by monitoring the dehydrocyclization activity by monitoring extent of conversion of paraffins to naphthenes an acidic support function activity followed by formation of aromatics on active metal . Alternatively by monitoring the C3/C1 mole ratios in the recycle gas to know the extent of hydrogenolysis a function of metal and hydrocracking a function of acidic alumina support.

09/12/2010 A: Satyalal Chakravorty, Sr Consultant, satya1354@yahoo.co.in
Reduction of Delta Tee and other symptoms mentioned are the indication of following:
1) Feed quality change w.r.t Napthene content. Any olefin ingress?
2) Sulphur poison (temporary)
3) More chloride additions
Increase in temperature at this juncture will result in further deterioration.
Thus following actions are needed;
1) Reduce temp( RIT) & throughput to bring up recycle ratio & H2 partial pressure if you want to continue with the current cycle
2) Adjust chloriding based on gas analysis & chloride levels
3) Sulphur level in feed to be analyzed & improved
Is it possible to reduce differential pressure across the feed vs effluent exchange to minimise sleepage /leakage if any? Please try to improve reactor effluent cooling?
Thru above actions, Reformate colour will improve, RON will be sustained.
07/12/2010 A: SImone Robinson, Tube Tech International Ltd, simone@tubetech.com
What are your ROT (reactor outlet temperatures) and HIT (heater inlet temperatures) readings?
02/12/2010 A: Wim Bond, Licence to consult bv, wim.bond@zeggis.com
I would like to respond to your request for leak detection. This can easily be done by tracer injection in the feed (tube side) and by monitoring the tube outlet and effluent (shell side). This technique will give you an indication of the amount of leakage if at all present. Please contact me so that I can send more details on this technique and the expert company for leak detection.
01/12/2010 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
1- MCH is methyl cyclohexane. It gets converted to about or more than 99.5% in reactor. Presnce in product may have some symptom of leakage or decativation too
3 Excessive hydrocracking and no ON increase means deactivation
4 No need to revise H2/ HC ratio in cycle
5 Five degree increase in RIt means about two number increase in ON for normal catalyst
6 Yellowish appearance is due to excessive cracking, deactivation and coroneene type compounds in product
30/11/2010 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
No, increasing H2/H.C. ratio during successive cycles is not normally practiced. Yellowish product is another indication of substituting hydrocracking for naphthene conversion, as is increased light ends yield. Again, increasing RIT at constant RON is also an indication of the increased hydrocracking. It apparently is increasing at the same rate of decrease of the conversion to aromatics. I don’t think you have a leak, just deactivated catalyst.
27/11/2010 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
Firstly Rh is the symbol for rhodium. Your catalyst may have rhenium (Re) as promoter not rhodium.
1- There are various tests for leakage in F/E exchanger. One of the simple test is to check for MCH in feed and product.
2-As a thumb rule Delta T from start of run to end of run is about 60 %. If you have 120 at SOR, at EOR it will be about 75
3-Sharp Delta fall may be due to deactivation of metal function by poisons like sulfur or metal in worse case. Coke deposition also lead to delta T fall. Shifting in delta T to successive reactor is also an symptom to be observed for deriving inferences.
4 An imbalance and high chloride content leads to high stabilizer OVHD. Yield of C1 - C4 Hydrocarbons at be about 2 to 3 % higher at EOR than at SOR. Change in feed stock also causes higher OVHD at Stabilizer What is change in hydrogen yield?
5- Higher H2/ HC ratio with all other parameters same cause lower delta T due to heat carried by recycle gas and can be easily calculated.
6- When the catalyst deactivates ON falls, so temperature has to be increased to get right ON. What is change in hydrogen purity of separator gas?
26/11/2010 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
It sounds like accelerated catalyst deactivation. To maintain RON, increased hydrocracking is replacing conversion of naphthenes to aromatics, as evidenced by the changing delta T’s, hydrocracking being exothermic and naphthene conversion being endothermic. The deactivation can be either excessive coking, temporary sulfur poisoning, or metals poisoning. Also, excessive chloride on catalyst can cause excessive hydrocracking. If you are reducing heater outlet temperatures to maintain RON, excessive chlorides cold be the cause.