The Basics of Refinery Slop – Part 1 | RefinerLink

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The Basics of Refinery Slop – Part 1

By Steve Pagani

Feb 20, 2017

Understanding slop creation and management can improve refinery profitability.


Slop is the ugly 4 letter S-Word that refiners don’t like to hear. The very mention of slop means that something un-ideal has occurred in your refinery process. Well, for the most part. 


While all refineries strive to minimize slop generation, we should accept that slop is a necessary part of the oil refining business. There are many different types of slop and many different ways to create slop. 


This article introduces the role of slop in the refinery business, and seeks to create awareness on how to minimize slop generation. Every barrel of slop prevented is a mega bucks saved for a refinery. 



Slop Creation


Slop is essentially any product stream or volume of liquid that does not meet specification for downstream sales or processing. Slop can be created at any point in a refinery or supply distribution process. Sometimes slop can be created as the result of unplanned activity, but sometimes it occurs from planned activity.


Unplanned Slop


Off-Spec Production:

The most commonly known slop is created when streams fail refinery product specifications


This can occur for any type of product, whether it is gasoline, jet, diesel, chemicals, or LPG. If the product spec failure is minimal, refiners can often save the production and re-blend it back onto spec. 


However, this article focuses on slop, so this means that the product stream is beyond saving. Off-test slop can occur from a variety of reasons, such as:


  • Improper blend planning / execution
  • Inadequate fractionation / stabilization
  • Insufficient reaction completion
  • Equipment failure (i.e. heat exchanger leak, equipment corrosion)
  • Operator field error
  • Inadequate heating or cooling

Off-spec slop is not limited to finished product specifications, but can also apply to intermediate streams.  If Reformer Unit or Diesel Hydrotreater Unit feed does not meet feed specifications the stream can be sent to slop for reprocessing. 


Depending on the extent of contamination, or the type of spec failure, management of slop stream will differ. We will discuss slop management in a section below.


Transportation and Storage Contamination:

Since finished product is often handled through multiple transportation and storage modes before reaching the end customer, additional contamination risks exist downstream of the refinery.


Every aspect of the refining supply chain introduces a failure point.  Product contamination and slop creation commonly occurs through any of the following:




Planned Slop


Startup and Shutdown Activity:


As units come online or are taken offline, a significant amount of slop is generated during transition periods where unit operating temperatures or pressures do not meet steady-state conditions. While this is one of the few times where slop generation is acceptable, refiners should still aim to minimize slop production by properly planning this activity. 


Transportation Flushing Activity:


Refining and Supply systems often do not have dedicated piping and equipment to manage finished product storage and transportation. Since pipes, tanks, and vessel compartments may often change service from managing one product to another, planned flushes are often required to maintain product integrity.


Planned flushes commonly use a small volume of a finished product to “rinse” the equipment free of contaminants. Depending on the severity of product service change, varying volume of flush material is required. For example, less flush material is required to change the compartment service of a barge from Diesel to Jet than from Gasoil to Jet. 



Stay tuned for the next article where we will discuss how to manage and minimize costs once slop is produced.

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  • Eric Vetters :   You seemed to have left out one of the most challenging sources of slop to manage - oil undercarry from the desalter and other miscellaneous hydrocarbons that make it into the waste water treatment plant. This hydrocarbon is typically badly emulsified and laden with solids. It recycles back to the desalter where it causes yet more oil undercarry/slop. If the refiner does not manage this operation well the slop can build to crisis levels where slop is controlling the whole refinery operation.

    Oct 20, 2014

  • M.J.Sast ry :   This is a very good article, this is a loss of product at any stage, This sholud be reverted to very immidiste step to reprocess For cru start up, naptha. is fed to unit, till the products becomes spec, rundown streams are routed to slop Similarly For wax planr. Slack wax is fed to plant. Till rundown wax is spec both foots oil and wax routed to slop.??? here iit was going to furnace oil tank I have suggeated 1.recirculate both wax&foots oil streams be put back to feed tank, this help conservation feed stock, but since both rundown proprties are different care to mix. and feed back to unit is nessary The foots oil is a by prodct it wad designated as slop and routed to furnce oil,??? I have suggested to market as product, it was marketred as SOFO OIL, the consumer. used to reprocess fot further recovery of wax and the remaining oil is sold out CASTROL There is nothing wrong in utilising or upgrading than the valuble oil then downgrading. Solp at each stage to be analysed and utilised. as it is,upgrade, reprocess,get higher priced by discyssing with intellectals,than down grading and total reprocessing as crude. Feed unless no othet option. is available Presenly the foots oil is also being used as feed to FCCU and also Hdrocracker units Anyway it is economics and technical ability tto minimise slop and prevention of losses Product wax splilages were reprocessed along with feed, I have suggested to blend to product wax. of lower grade. This to avoid process operation cost It is ulmately the boss decides .....but I feel economics than boss, Some times lack of tankage a factor, again decide well to which tank to recover back Plant operations a more skill thank mere seniority. Of favoritism This is not to blame, but cautioning to run profitably and wisely to next juniors,to be called by them we worked under wisemen

    Oct 22, 2014

  • Ajay Sharma :   Now Slop oil recovery for reprocessing is possible , We are already helping refineries do the same. Sureflo Techcon is leading name in floating oil recovery and Slop oil recovery for more details contact +919833505111

    Mar 11, 2020

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