Q&A

(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.

(2016) Question 56: What mechanical/design alterations to the "standard" crude furnace design do you require to prevent fouling when processing LTOs (light tight oils)?

From the various articles and presentations on this subject, plus our own experience, we have found that LTO, in itself, is not an issue. Rather, LTO mixed with crudes containing asphaltenes is the issue. Industry seems to agree that precipitation of asphaltenes is one of the main fouling mechanisms.

(2016) Question 57: Please discuss desalter level control equipment and its effectiveness at detecting and controlling rag layer, oil undercarry and water carryover.

There are many types of level controllers for desalters, so an exhaustive response is not possible here. Generally, each type has comparative merits based on how robust it is with regard to the various contaminants in desalters, resolution, or cost. Traditional capacitance probes, and also float-type level controllers, have a broad application in desalters and have been used for many years in the industry.

(2016) Question 58: What techniques do you use to rapidly detect fouling in the top section of the crude tower besides top section differential pressure?

Besides the use of flow-normalized pressure drop, another observable parameter that can be used is the distillation overlap of the overhead distillation curves.

(2016) Question 59: What is the contribution to salting in crude fractionators and overhead systems due to steam condensate amines, and what are your mitigation strategies?

Amines have been used in refinery steam systems for decades. When properly applied, the amount of amine that may make it to the crude fractionator towers should be very small; the partial pressure contribution should be so low that the steam condensate amines should not contribute to salt formation.

(2016) Question 60: When is your return on investment (ROI)adequate to justify installing a desalter to treat purchased FCC feeds? What other factors besides FCC catalyst impact and unit corrosion are used to determine ROI? How do these desalters differ, mechanically and operationally, from a conventional crude oil desalter?

This is a three-part question. The first question is: When is the return on investment (ROI)adequate to justify installing a desalter to treat purchased FCC feeds? The capital and operating costs of an FCC feed desalter are supported by improvements in performance, operating costs, and reliability.

(2016) Question 61: How many inside/outside operators staff your FCC plant? What other processes are included in their scope of responsibility?

[United Refining Company (URC)] Our FCC unit has five operators per shift. Typically, two people are inside running the DCS (distributed control system) and board-mounted controls while the other three are doing rounds in the unit.

(2016) Question 62: We have run a full-burn FCCU for many years. We are considering processing more resid and operating in a partial CO combustion mode. What is a carbon runaway, and how can it be addressed?

A carbon runaway or “snowball” occurs in an FCC that is operating in partial CO combustion mode and very high CO levels. In the runaway situation, the carbon on regenerated catalyst (CRC) rises to levels such that additional coke that is laid down on the catalyst cannot be burned from the catalyst in the regenerator, causing the CRC to continue rising like a snowball that gets bigger and bigger as it rolls down a hill.

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