Q&A

(2013) Question 59: How does improper control of desalter washwater and brine affect crude unit overhead pH?

Guidelines around the addition of desalter washwater were historically 3 to 5% on volume based on crude charge. Some years back, with a shift towards heavy Venezuelan and unconventional crudes, the trend pushed up towards the 7 to 10% range or higher.

(2013) Question 60: What has been done to address corrosion problems either inside your desalter or in the brine handling circuit?

Some refiners have used acids in the desalter washwater as a means to assist in emulsion resolution. We always look for other solutions as this practice may present other challenges including operator exposure, corrosion to the desalter internals/water circuit, and additional acid load to the atmospheric tower.

(2013) Question 61: What are some of the potential strategies to mitigate iron carryover from the desalter?

High iron content on desalted crude manifests itself in two main areas. These are inability to make anode-grade coke and as a FCC catalyst poison. The iron can be in many forms. Three of the most common forms of iron we see are iron oxide, which is rust; iron sulfide, which is corrosion; and, siderite, which is essentially crystalline iron carbonate that we are seeing more and more of in certain tight oils.

(2013) Question 62: What criteria are used to evaluate the performance of crude pre-heat train exchangers to support a decision to clean any portion?

It is essential to keep crude pre-heat exchangers clean. Cleaning benefits are hard to justify if they negatively affect crude rate. The criteria we use are crude hydraulic throughput, heater firing limits, fuel gas savings, desalter temperature efficiency, or crude or vacuum tower heat balance if you have needs in that area to remove heat.

(2013) Question 63: How are refiners monitoring and controlling the efficiency of fired heaters? Are adjustments made to fuel gas composition to improve heater performance?

At CITGO, we utilize both daily monitoring tools and weekly programs to rank the heaters based on performance and missed opportunity. Optimization targets get set based upon best efficiency points, and the consoles are expected to be at these optimization points.

(2013) Question 64: How do you select the proper metallurgy for crude overhead (OVHD) to increase reliability?

Our belief is that a proper design includes a good waterwash system and less expensive metallurgy. Our tower tops are typically carbon steel with Monel overlay.

(2013) Question 65: Please share experiences in crude tower fouling from organic and/or phosphorous-containing deposits.

We have experience with two types of organic tower fouling. The first was an organic fouling in the top portion of the tower due to rerunning cracked slop oil, coker naphtha, and kerosene material. Typically, we do not want to do that. Since then, we have stopped processing those materials or limited the amount that we are rerunning so it does not happen anymore.

(2013) Question 16: What is the typical carbon monoxide (CO) concentration in the reformer net gas? How is the CO content measured? What are the potential effects to downstream units from the CO?

Carbon monoxide can form in reformer units as the hydrocarbon reacts with moisture under very low-unit pressure conditions. Typically, semi-regeneration reformer net gas would have nil CO and only a minimal amount in a CCR-type unit. I expect it to probably be on the order of 5 ppm (parts per million), though some units report routine measurements of 10 to 20 ppm CO in their net hydrogen off gas.

(2013) Question 17: How many continuous reforming operators have completed a catalyst change while the unit continues to operate? What variables should be taken into account when planning such a change?

HollyFrontier has two CCRs: one at Tulsa that was converted from a semi-regeneration reformer and one at Artesia. We have not done a catalyst change at the Tulsa refinery CCR, but we have done an online catalyst change at Artesia.

(2013) Question 18: What are some typical causes for high pressure drop across regenerator dust collectors in continuous reforming units? Is anyone using continuous blowback on the bags?

The obvious answer to the high-pressure drop would seem to be that you have too many fines on the bags. But realistically, why do you get too many fines? The causes could be that you waited too long to do the reverse jet blowing or, a less common cause, that you are getting hydrocarbon carryover which is causing the fines to clump together on the bags.

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