Q&A

(2018) Question 25: Coke drum integrity can be compromised due to the use of feed side entry devices. What is your experience with drum roundness upon inspection?

Coke drum integrity is typically dominated by low cycle fatigue. Imposed stresses due to thermal gradients during drum warming, water quenching and the contraction of the drum while full of coke can result in stresses higher than the yield stress of the coke drum metal.

(2018) Question 26: How do you monitor furnace convection section fouling? What mitigation steps do you implement?

Monitoring the flue gas temperature leaving the process convection section is a simple method of tracking the heat transfer in the convection section. The excess air needs to be taken into consideration as a higher O2 concentration will shift heat transfer into the convection section and causes the total quantity of flue gas to increase.

(2018) Question 27: What is your experience with chemical treatment to reduce furnace coking?

For conventional fouling, which is the result of asphaltene destabilization due to temperature, chemical treatment programs have not been effective for Coker heaters. For premature asphaltene precipitation due to resid compatibility concerns, chemical treatment programs have been effective in reducing or eliminating fouling.

(2018) Question 28: What are your best practices around initial crude oil qualifications? Upon receipt, what are your best practices for continuous inspection/receiving crude oil at a plant?

Once they have located these crudes, our economic/planning group will utilize the assay of the crude to evaluate this crude using our linear program (LP). This will generate the possible net back for processing the crude.

(2018) Question 30: When injecting wash water upstream of the cold train in a 2-stage system, do you use fresh wash water or brine water from the 2nd stage desalter?

For two stage desalting, injecting all the fresh wash water upstream of the second stage desalter provides the opportunity to use the lowest salt water on partially desalted crude which should result in the lowest level of salt in the desalted crude oil. Water from the second stage desalter is then used to provide wash water for the first stage. This water is typically split between being injected upstream of the exchanger train and upstream of the mix valve for the first stage desalter.

(2018) Question 31: How does emulsion breaker performance compare when injected in the crude or wash water? What is your method to inject emulsion breaker for 2 stage desalters?

For the desalter system as a whole, the typical emulsion breaker is injected into the crude stream as far upstream as possible in order to provide intimate contact. In this case, the emulsion breaker is one that has a hydrocarbon solvent and so is hydrophilic which wants to stay in the oil phase. There are cases where injecting this emulsion breaker into the water phase can help reduce the impact of surfactants that surround the water droplets.

(2018) Question 32: Have you developed processes to successfully extract the emulsion layer from the desalter, so the emulsion can be treated separately? Please describe your chemical treatment programs and equipment that have been implemented successfully to treat this extracted emulsion.

Emulsion extraction headers, sometimes called cuff headers, have been an option and have been installed in desalters for decades. The removal of the emulsion layer solves one problem and creates another as this emulsion layer can be very difficult to treat.

(2018) Question 53: In the Third Stage Separator (TSS), what is the expected life of swirl tubes or cyclones assuming good performing regenerator cyclones? Of these two types, which handle upsets/ variable particulate loadings better?

The performance of swirl tubes is comparable with cyclones in terms of separation efficiency. Swirl tubes have distinct advantages over cyclones in being more compact, much easier to construct and have high mechanical integrity.

(2018) Question 54: What are your best practices for soot blowing or scouring waste heat boiler tubes that ensure minimal impact to process variables, environmental limits are met, and spurious trips of safety instrumented functions on the ESP are avoided?

Automated systems are employed at Refineries that inject some type of abrasive (e.g., sand, walnut/pecan shells) on a scheduled interval basis. Injection duration must be controlled to ensure opacity limits are not exceeded. Manual injection of abrasives is also utilized.

(2018) Question 55: With new challenges presented by the Refinery Sector and Maintenance Venting Rules oil circuits are taking longer to prepare for maintenance; what successes and challenges have you had in staging shutdown operations to allow for safe entry to the FCC reactor/regenerator section prior to clearing other sections of the unit?

With new challenges presented by the Refinery Sector and Maintenance Venting Rules oil circuits are taking longer to prepare for maintenance; what successes and challenges have you had in staging shutdown operations to allow for safe entry to the FCC reactor/regenerator section prior to clearing other sections of the unit?

Find the answer to your technical question in AFPM's extensive Q&A database.

Q&A