Q&A

(2010) Question 29: What technologies do you use for treating or recovering VOCs from small-scale truck loading terminals? Discuss the merits associated with each?

The three main VOC treating systems for small scale truck loading are vapor combustion system, flare gas recovery unit, and an adsorption/absorption vapor recovery system.

(2010) Question 30: What process parameters can affect alkylate T90? What are the critical variables you monitor in both sulfuric and HF units? Discuss processing schemes, feed impacts and operating variables.

The type of feed is very significant for T90. Amylenes make alkylate with higher T90 in both sulfuric and HF units. Propylene generally makes lower T90 than butylene in HF units. However, with sulfuric-catalyzed technologies, propylene can increase T90 as discussed below.

(2010) Question 31: In your experience, when sampling the HF Alky iso-recycle stream, how and where is the sample neutralized prior to analysis? Can this approach be used for online GC analysis as well?

The isobutane recycle sample can be neutralized at the sample location using a chamber filled with alumina or KOH pellets. If using a KOH chamber, it is best to add a filter downstream to filter out any fines.

(2010) Question 32: In your experience, what contributes to Monel denickelification in the HF Acid Regenerator circuit? What are the potential problems associated with this?

Oxygen is a major cause of monel denickelfication. Oxygen can enter the circuit during loading operations. Care should be taken to avoid pressuring air contained within loading pipes/hoses into the unit.

(2010) Question 33: How do refiners avoid De-isobutanizer (DIB) column/reboiler fouling in sulfuric acid alkylation? What process conditions on the column do you use to detect this fouling? What process modifications do you take to minimize the impact of this fouling?

Fouling in the DIB column is almost always caused by salt deposits. These salts are typically sodium sulfate and sodium sulfite but can also contain calcium or magnesium if the effluent treating water is not demineralized. If these water-soluble salts are present in the DIB feed, the water will evaporate once inside the column leaving the solids behind.

(2008) Question 1: What are your experiences taking reactor effluent samples? What safety issues do you consider when taking samples? What do you consider to be best practices?

Question 1: What are your experiences taking reactor effluent samples? What safety issues do you consider when taking samples? What do you consider to be best practices? Edwin Yuh (UOP) UOP has traditionally included sampling capability in our licensed units when there are multiple reactor systems. For example, a sample point is typically installed at the pretreat reactor outlet before the cracking reactor in hydrocracking units to measure nitrogen slip. Many UOP licensees collect reactor effluent samples routinely. Quite a few recently licensed units are designed as integrated hydroprocessing units processing different feeds with different catalyst systems.

(2008) Question 2: Do you re-evaluate your unit operating procedures at regular intervals? How often? What principles/standards are these procedures reviewed against?

Question 2: Do you re-evaluate your unit operating procedures at regular intervals? How often? What principles/standards are these procedures reviewed against? David Rapavi (HOVENSA) HOVENSA reviews and re-issues unit operating procedures in accordance with OSHA Standard 1910.119 paragraph (f)(3), which states “Operating procedures shall be reviewed as often as necessary to assure that they reflect current operating practice, including changes that result from changes in process chemicals, technology and equipment, and changes to facilities.

(2019) Question 15: What practices and modifications have you implemented in response to the new High Temperature Hydrogen Attack (HTHA) guidelines and updated Nelson curves?

JOE RYDBERG (CITGO)
The primary source document for dealing with High Temperature Hydrogen Attack (HTHA) is API Recommended Practice 941 – Steels for Hydrogen Service at Elevated Temperatures and Pressures in Petroleum Refineries and Petrochemical Plants. This document provides the basic guidelines

(2019) Question 16: What is required to achieve Safety Integrity Level 2 (SIL-2) rating on the hydrocracker depressuring system? For a hydrotreater that does not require SIL-2, what position should the depressurization valve fail to?

JOE RYDBERG (CITGO)
CITGO typically seeks process safety consultants to help with SIS design including SIL selection. Kenexis is such a company who has provided the following technical information regarding depressurization systems.

There are a multitude of different initiating events (loss of

(2019) Question 17: What testing frequency and additional feed characterization (apart from bulk properties) should be used to accurately monitor catalyst performance on heavy feeds?

FERNANDO MALDONADO (Shell Catalysts & Technologies)
The type and frequency of tests performed are unit and refinery specific. When creating or modifying a unit’s laboratory test schedule some factors to be considered include:

1.   Unit objectives
2.   Past and/or current operational issues
3.

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