Q&A

(2014) Question 60: How does the mercury in crude distribute in your refinery (e.g., what units are affected)? What operating procedures or technology are you using to mitigate this issue?

How does the mercury in crude distribute in your refinery (e.g., what units are affected)? What operating procedures or technology are you using to mitigate this issue?

(2014) Question 61: What measurement and/or predictive methods are you using to determine crude oil blend compatibility?

Various methods exist to determine blend compatibility; one method would be a comparative asphaltene instability point determination via an anti-solvent titration, or another method used is the Wiehe insolubility number to solubility blend number method.

(2014) Question 62: What are the advantages and disadvantages to constructing “modular" refining process units versus traditional "stick built" units? What are the issues with each construction approach?

What are the advantages and disadvantages to constructing “modular" refining process units versus traditional "stick built" units? What are the issues with each construction approach?

(2014) Question 63: For the operating company, what are your crude unit typical run lengths between shutdowns? What factors do you consider when setting this run cycle?

For the operating company, what are your crude unit typical run lengths between shutdowns? What factors do you consider when setting this run cycle?

(2014) Question 64: Some crudes appear to have chlorides that are not readily removed in the desalter. What are sources for these un-desalted chlorides? How are the various un-desalted chlorides detected and mitigated?

The main source seems to be crystalline salt. A relatively new method to determine total chlorides is the Chlora instrument, desaltable chlorides can be determined by the extraction method, and the difference is taken as un-desaltable chlorides.

(2014) Question 65: What are the advantages and issues with different desalter wash water sources in a refinery? What issues do you experience by combining wash water from multiple sources?

The advantage is a reduction of freshwater use and sometimes a reduction in the load of contaminants(phenols) to the WTP. We have developed desalter washwater specs to prevent negative effects on desalter performance, fouling and corrosion. Oxygen, Ammonia, Hardness, TDS and Filterable are solids, the most obvious ones.

(2014) Question 66: What desalter instrumentation issues do you experience when switching from a light gravity feed to a heavy gravity feed?

The main influence is on level controllers, the most sensitive are the float type controllers but other instruments are also somewhat influenced by the crude Sulphur content.

(2013) Question 66: What strategies should be considered to adjust for phosphorous in crude oil to protect downstream catalyst and processing units?

Extensive work was done with Western Canadian refineries in the late 2000s to investigate and solve this problem, including adjusting desalter pH to extract phosphorous in the desalter brine, adding a phosphorous removal chemistry, changing the trays in the crude tower to reduce fouling susceptibility, solvent-washing the deposit to avoid long cleanouts and shutdowns, and adjusting process temperatures.

(2013) Question 67: When heat input is limited at the vacuum heater, what are the issues with bypassing crude tower over-flash around this heater?

For this answer, I am going to define crude tower over-flash as liquid collected on a collector tray above the flash zone at the atmospheric crude column. This may be either a total collector tray or some form of active tray. This liquid contains a mixture of entrainment from the flash zone and distillate from the wash section. The normal disposition is to send the liquid inside the tower down to the stripping section.

(2013) Question 68: For those refiners seeing an increase in vacuum overhead chloride concentration at constant desalted crude salt content, what are the consequences and how can they be controlled?

First, verify the chlorides found in the hot well water. Could the chlorides be from leaks from the vacuum system condenser cooling water? A hardness test will quickly identify water system leaks. Essentially, getting a high chloride concentration in the vacuum overhead at a constant salt content in the desalted crude implies either a change in the chloride type or in the operating conditions leading to more chloride hydrolysis.

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