Q & A > Question Details
Why at low plant load S/C ratio is to be kept high?
21/04/2016 A: ARUN RS, INDIAN OIL CORPORATION LTD, arunrskmr@gmail.com
to maintain the space velocity in the reformer
14/11/2015 A: Rajesh Nandanwar, Bharat Oman Refineries Limited, Bina, rajesh.nandanwar@borl.co.in
At lower plant throughput, S/C ratio and excess air are adjusted higher to avoid channeling effect. Hydrogen plant reformer tubes are hydralically design for the certain throughput level (say 100% throughput) At lower plant throughput, distribution through the tubes is lower and there are chances of localized overheating and coking.
Typically at throughput level below 50%, Steam flow equivalent to 50% throughput is maintained constant to avoid such conditions. This results in higher s/c ratio and lower chances of coking and overheating in the tubes by maintaining required flow through the tubes.
Similarly excess air which at normal throughput with naphtha firing is at 10% increased to 15% at 50-60% throughput and upto 30-40% excess at throughput level of 30-50%.
11/11/2015 A: NS Murthy, Suez, murthy.ns.ext@suez.com
As Hydrogen producing reforming unit operate at elevated temp, low plant load implies higher residence time which would lead to coking on catalyst. Hence, higher stream to carbon mole ratio helps to minimize coking and retain the catalyst activity.