Q&A

(2016) Question 32: What are your current practices and experiences of performing online cleaning of heat exchangers versus offline cleaning?

To achieve a good online cleaning (with the exchanger bypassed by not pulled), it is imperative to have nozzles on the inlet and outlets that are large enough to facilitate the circulation of a heat cleaning solution or steam with a cleaner.

(2016) Question 33: Can you share your experience with chemical additives to prevent fouling in the naphtha hydrotreater feed side of the feed/effluent heat exchangers or resolve reactor pressure drop issues?

The answer is partially the same as the one given to Question 28. First, the root cause needs to be determined. If the dP is caused by corrosion products due to corrosion in the upstream refinery units, the corrosion in these units can be reduced by applying the proper corrosion control program.

(2016) Question 34: The cycle life of a high-pressure ULSD unit operating for maximum aromatic saturation and liquid yield is limited by aromatics equilibrium at elevated temperatures. What strategies or solutions do you employ to extend operation with maximum liquid yield?

This question is more related to EOR conditions when you have employed all of the operational techniques but wish to further optimize the EOR performance without yield decline. If you are already maximizing H2 pp (partial pressure), achieving full catalyst utilization with state-of-the art reactor internals, and adjusting bed profiles at MOR/EOR (middle-of-run/end-of-run) to remain in region of optimum aromatic saturation, the following example illustrates the benefits of optimizing the nickel-molybdenum catalyst for your application.

(2016) Question 44: What issues do you consider to establishing a purchased crude oil custody transfer Best Practices from various sources?

Custody transfer requirements and regulations can differ by world area, by modality, and even by company. Most companies follow API (American Petroleum Institute) standards for the measurement sampling and custody transfer. Generally, there is a pay meter and a check meter. The contract specifies what happens when there is too large of a discrepancy between those two meters.

(2016) Question 45: What criteria and requirements that you use to determine mixing equipment for crude tankage? How do you map the sludge level? What methods do you use for sludge removal to shorten time to clean the tank?

Question 45 is actually a combination of three questions. The central issue here is the sludge. There are many purposes of using crude tank mixtures, many of which are listed on the slide. The purpose of the crude tank mixer might be for homogenization–in terms of density, viscosity, or temperature–or its purpose may be to control BS&W to reduce or eliminate sludge or the blending of crudes.

(2016) Question 46: What measurement methods (i.e., analytical, and/or online analyzers) do you use in crude and coker units, and product quality management? How do you use the information to improve unit reliability and profitability?

instrumentation was used in crude unit feed management in one project to ensure that the correct crude blends were being used for various crude units.

(2016) Question 47: Given the increased volatility of crude and product prices, what additional steps do you take to adjust your crude unit cutpoints to maximize profitability?

In order to have the flexibility to operate with a wide range of crude APIs and the ability to vary product draws to maximize revenue, a complete study has to be carried out to analyze crude unit operation between the bracketed crudes, including the effect on preheat train, furnace, and column operation

(2016) Question 48: What are important considerations for evaluating the methods used for fouling detection and mitigation in preheat exchangers and furnaces in crude and coker units?

Methods for fouling detection and quantification need to be capable of normalization to minimize ‘noise’ from system variables. Complex heat transfer rating programs can be used for this purpose. These programs must be capable of looking at heat exchanger networks as systems, as well as individual exchangers.

(2016) Question 49: What criteria for materials of construction do you use for structured packing at the different sections of the crude, vacuum, and coker towers? What criteria do you use to replace packing during turnaround?

316SS works well against naphthenic acid corrosion attack. Inconel 625 is another alternative for extreme service conditions, but it is generally not required.

(2016) Question 50: In the absence of individual dipleg sample points, how do you manage corrosion in the vacuum overhead system?

Although it is not fully a Best Practice, the monitoring of the combined stream coming off of the overhead accumulator has historically been used successfully.

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

Q&A