Q&A

(2017) Question 16: HCl concentration in the reformer net off-gas is being actively measured using hand-held detector tubes. Despite routinely measuring near-zero ppm (parts per million), chloride corrosion occurs downstream. What is the source of this corrosion, and what can be done to better measure and manage the source?

Organic chlorides can be invisible to simple HCl- detecting tubes. There are alternative measuring devices from which to choose to detect organic chlorides. It is well known that organic chlorides can be created from an alumina guard bed and cause green oil, chloride salt formation, and corrosion downstream.

(2017) Question 17: What is the importance of water content in reformer feed and recycle gas on the performance of the catalyst? What are your desired water concentrations in each of these streams?

Managing the water content in the reactive environment is critical for the overall performance of the reformer unit and catalyst. The content of water (H2O) must be controlled to allow for a sufficient quantity of hydroxyl [AlOH (aluminum hydroxide)] sites while simultaneously controlling the hydrogen chloride (HCl) levels to have the right balance of H2O/HCl to set the catalyst HCl content (Al-Cl).

(2017) Question 18: In a fixed-bed reformer regeneration, caustic is used to neutralize the combustion and chlorination gasses. How do you dispose of caustic after the regeneration is complete?

During the regeneration step of fixed-bed reformers, caustic is typically used to neutralize the regeneration effluent. Additional use of sodium bicarbonate to maintain the pH of the neutralization solution has also been utilized and is included for disposal.

(2017) Question 19: What are your Best Practices for recovering from high coke on spent catalyst in continuously regenerating reforming units?

The Honeywell UOP Platforming™ CCR regenerator is designed to burn 5 wt% (weight percent) carbon off catalyst circulating at 100% of the design rate. Most units can successfully burn off significantly more coke than design at normal operating conditions when the screens are clean and regeneration gas flow is uniform. Note that if there is screen fouling or some other condition leading to non-uniform or reduced flow, the coke-burning capacity would be reduced.

(2010) Question 26: What are the best practices for entering the vapor space above an internal floating roof in a gasoline tank

Entering the vapor space above an internal floating roof tank creates a set of somewhat unique safety concerns that must be addressed in a facility’s safe work procedures. The primary hazard is entry into an air atmosphere with some level of hydrocarbon vapor or toxics, and liquid hydrocarbon (gasoline for this discussion) beneath the floor, with wiper seals, pontoons, etc. creating a barrier to prevent conditions within the confined space from changing.

(2010) Question 27: It has become increasingly common to chemically neutralize / passivate refinery towers and vessels prior to entry. What are the recommended practices for implementing these tasks? In your experience, what conditions trigger the need for chemical treatment?

Although this list is not “all-inclusive”, here are some general recommended practices when chemical cleaning and/or neutralizing towers and vessels. First, there needs to be a single point of contact for the chemical cleaning vendor. This person is responsible for the planning, preparation and execution of the chemical cleaning process. Prior to cleaning, P&ID’s need to be marked up to identify all injection points, steam and chemical flows and even line ups for the chemical cleaning.

(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.

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