Q&A

(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.

(2016) Question 51: What key parameters of coker furnace tube design and metallurgy do you experience that can impact run-length? What metallurgy do you use specifically to increase run-length and tube life?

For many years, our standard has been 9 Cr-1 Mo tubes. We also have numerous Amec Foster Wheeler delayed coker heaters that have been retubed with347SS.

(2016) Question 52: What are your Best Practices for a waterwash system to control corrosion in delayed coking fractionator overhead and light-ends systems?

The overhead waterwash for a delayed coker main fractionator system is the same as for an FCCU main fractionator overhead. The volume of water required is calculated based on what is needed to condense the water present with an added excess; typically, this is 25%. In some cases, the site, instead, bases the washwater requirement on the feed to the tower.

(2016) Question 53: What operational improvements do you make to reduce silicone from antifoam agents in coker products?

Ensure that the following scenarios or standards are met.

(2016) Question 54: When using coker LPG (liquefied petroleum gas) for propylene production, what contaminants are a concern for you and how do you mitigate them?

Coker LPG contains various species of mercaptans and other organo-sulfur compounds, besides other contaminants. Depending on capacity and impurity levels, coker LPG treatment in a coker may include amine treating for CO2and H2S, as well as a coker LPG mercaptan removal unit.

(2016) Question 55: What are your effective ways of measuring vacuum overflash flow in a gravity seal loop (not pumped)? Please comment on overflash measurement for controlling wash oil flow.

Fluor's standard design to measure overflash that is not pumped uses a simple loop and an orifice plate. Having adequate elevation difference to route the overflash return to the top stripping tray is needed. It is easy to do on a new unit, and sometimes more difficult to do on a revamp.

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