Q&A

(2011) Question 14: Have you successfully dumped, screened and reloaded spent hydrotreating or hydrocracking catalyst without regeneration during a turnaround? Can you share any best practices during this operation to avoid problems on restart?

Providers of onsite screening services are typically limited in available equipment compared to offsite specialized companies. It is important to have adequate equipment to determine the particle size distribution of the screened catalyst.

(2011) Question 15: In treating kerosene, what factors play into the decision to use hydrotreating versus sweetening processes such as caustic treating?

Hydrotreating, by contrast, affects several key properties of the kerosene including smoke point, aromatic, sulfur, and nitrogen content and other properties such as oxidation stability.

(2011) Question 16: What LCO 95% distillation point do you target for optimizing ULSD production? Do you see a significant catalyst life penalty with an increased LCO cut point?

The purpose of adding more LCO is to improve the refinery’s financial performance by upgrading low value LCO to ULSD products.

(2011) Question 17: What sets the volume gain in ULSD units? How much does lowering the space velocity increase the volume gain? How much volume gain can be expected for each feed component?

Volume gain requires hydrogen consumption. Aromatic saturation reactions consume the most hydrogen, followed by olefin saturation. For same feed qualities and same LHSV, the units that make higher cetane product will have higher volume gain due to more aromatic saturation.

(2011) Question 18: What considerations are being given to include mild hydrocracking in your high pressure ULSD unit?

Due to the increasing global demand for diesel, the ability to reduce product density (increase volume gain) and blend a significant amount of heavy diesel and/or light vacuum gasoil in the ultra-low sulfur diesel pool represents a large economic advantage. These economic gains could potentially include margin increases of tens of millions of dollars per year for a refinery.

(2011) Question 19: With limited hydrogen availability for desulfurization of diesel, what criteria influence the optimization of hydrogen consumption between the FCC Pretreat and ULSD units? What catalytic options exist to achieve the desired balance of consumption?

Hydrogen supply and compression constraints are becoming more common for refineries in the US as more and more bitumen-based crude is brought in from Canada.

(2011) Question 20: Pre-hydrotreated feeds and crudes look easy to process on paper. Why is it more difficult than expected to process pre-hydrotreated feeds in a hydroprocessing unit?

Pre-hydrotreated feeds are often the most difficult feeds to process in hydrotreaters primarily because the remaining molecules to be treated are the most refractory. Low sulfur feeds are not automatically the easiest to process; the sulfur species determines the difficulty of processing, not the total sulfur.

(2011) Question 21: What needs to be considered when processing LCO or increasing the amount of cracked feed in a hydrocracker?

It is important to ensure that sufficient H2 is available to satisfy the minimum required H2/oil ratio because hydrogen consumption will increase significantly.

(2011) Question 22: Which is the impact of feed asphaltenes content on hydrocracker cycle length?

The asphaltenes are high boiling, high molecular weight and hydrogen deficient materials that are the least reactive in a hydrocracking environment.

(2011) Question 23: What is the impact of HPNA (Heavy PolyNuclear Aromatics) on hydrocracking catalyst activity, stability. and yield selectivity?

The impact on hydrocracking catalyst deactivation and yield selectivity due to precipitation of Heavy PolyNuclear Aromatics (HPNA) is typically based on several criteria.

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