Home › Forums › Coking › Maintenance › On-line Spalling › Using BFW
This topic contains 3 replies, has 3 voices, and was last updated by Mike Kimbrell 6 years, 1 month ago.
February 8, 2008 at 7:45 pm #3800
Actually we are running our OLS with high pressure steam (the same velocity steam during normal operation). There is known that some coker heaters can run the OLS using BFW. Which are the main differences (advantages and deadvantages) of using this two services?. If there is an incentive of using BFW instead of Steam, There is a way for modifying a furnace from the HPS to BFW?. Thanks in advance for your answer.
September 16, 2015 at 2:54 pm #18721
Paul R OrlowskiKeymaster
I assume this injection is for velocity protection / emergency purging of the tubes. If that is the case, you may want to consider using HP steam instead of water altogether – it is much more functional. There are no safety issues related to pump failure, and far less headache trying to balance flows to multiple furnace passes. Is your BFW produced through a demineralizing or softening process? If softened, you may have higher levels of chlorides in the BFW, which will adversely impact furnace tube fouling. Hope this helps.
-posted in Kansas
September 16, 2015 at 2:55 pm #18722
Paul R OrlowskiKeymaster
Injecting BFW vs steam can present two problems I know of: 1) the latent heat of vaporization is energy wasting in a very heat intensive furnace. One should always make steam at a boiler instead of a process furnace if possible. If your unit is furnace limited then this could cause rate cuts. 2) if your bfw is of poor quality you can get inorganic deposits on your tubes as bfw is vaporized which are catalysts to coking thus reducing furnace run length.
-posted in behalf of pkpb
February 22, 2017 at 10:50 pm #24881
There is a significant safety risk in using liquid water for velocity media. With a blocked heater outlet, liquid water will generate its vapor pressure at the process temperature at the water injection point. This typically results in pressures much higher than the heater feed pump shut off pressure.
Depending on the location of the BFW injection, the bottom shock tube temperature will be low due to the vaporization of the BFW. In that case, the tube temperature will not increase enough to cause any coke to spall off and no decrease in tube metal temperature will be experienced during the spall. Use of steam will result in higher tube metal temperatures during the spall as the water will not have to be vaporized. Managing the convection section temperature during the spall is more difficult with steam and the tube supports in the convection section can experience excessive temperatures.
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