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We are having 3 nos. of identical SRU trains (2 nos. of Claus & 2 nos. of CBA reactors) with each having a capacity of 65T/day of Sulphur production. We are frequently facing a problem of second condenser tubes leaks problem and plugging of rundowns due to catalyst dust carry over. Operating temperatures are being maintained above dew point in all three trains. However, tubes leaks problems are coming in only one train very frequently. Can anyone suggest the cause for frequent failure of condenser tubes leaks?
C2 outlet temperature is being maintained >150 degC against the design of 168 degC. 1st claus reactor (R1) outlet temperature was being maintained >340 degC. C2 outlet temperatures observed >150 degC even for R1 o/l temperature of 310-320 degC.
In spite of maintaining C2 o/l temperature >150 degC, sudden decrease in C2 o/l temperature and increase in system back pressure is being observed due to tubes leaks.
 
Answers
27/05/2014 A: Rajesh Nandanwar, Bharat Oman Refineries Limited, Bina, rajesh.nandanwar@borl.co.in
Do you have frequent start up shutdown of unit, turn down operation or prolong fuel gas mode operation of unit. All three would cause for problem majority of times. For avoiding choking and leakages in condenser, make sure following is strictly followed.
1. Sweeping of sulfur from converters till the time liquid coming out from seal pots,
2. Purging of train at least 4-5 times system volume using N2 to remove moisture in the system.
During start up, you should ensure that
1. Sparger steam is opened in condensers to keep the water at high temperature to avoid moisture condensation from flue gas.
2. Heating of train using combustion air initially so that dew point is not achieved. (normally temp above 60 deg C with system back pressure of 0.15 kg/cm2g would be sufficient)
3. Stoichiometric combustion if catalyst bed allows without sharp rise in temperature- so as to avoid soot generation.
4. Operation of Condenser outlet temperature to design value 168 deg C at least during turn down operation and then can be brought down as desired to >150 deg C.
In next turn around ensure following.
1. Check converter for refractory damage.
2. Screen catalyst and reload with some fresh catalyst make up at top.
3. Plug the leaky tubes of condenser with specialized welding procedures so as not to have thinning to tube ends and tube sheet damages.
Hope this should solve your problem.
26/05/2014 A: Rajesh Nandanwar, Bharat Oman Refineries Limited, Bina, rajesh.nandanwar@borl.co.in
Do you have frequent start up shutdown of unit, turn down operation or prolong fuel gas mode operation of unit. All three would cause for problem majority of times. For avoiding choking and leakages in condenser, make sure following is strictly followed.
1. Sweeping of sulfur from converters till the time liquid coming out from seal pots,
2. Purging of train at least 4-5 times system volume using N2 to remove moisture in the system.
During start up, you should ensure that
1. Sparger steam is opened in condensers to keep the water at high temperature to avoid moisture condensation from flue gas.
2. Heating of train using combustion air initially so that dew point is not achieved. (normally temp above 60 deg C with system back pressure of 0.15 kg/cm2g would be sufficient)
3. Stichiometric combustion if catalyst bed allows without sharp rise in temperature- so as to avoid soot generation.
4. Operation of Condenser outlet temperature to design value 168 deg C at least during turn down operation and then can be brought down as desired to >150 deg C.
In next turn around ensure following.
1. Check converter for refractory damage.
2. Screen catalyst and reload with some fresh catalyst make up at top.
3. Plug the leaky tubes of condenser with specialized welding procedures so as not to have thinning to tube ends and tube sheet damages.
Hope this should solve your problem.
03/05/2014 A: Sandeep Sutar, Saudi Aramco, sandeep.sutar@aramco.com
Please make sure that SRU startup procedure are followed correctly. Make sure before lit up Reaction Furnace burner you should achieve the 100 deg C by air preheater. This will avoid the FG condensation which may cause corrosion problem. Also catalyst bed must be above 200 deg C before introduction of Acid Gas. Moreover please check maintenace procedure to attend the leak heat exchanger. SRU exchanger are typical and require special procdure to attend its leak.