PTQ Q1 2023 Issue

allow the emulsion to be withdrawn and externally pro- cessed. As with the issue of injecting emulsion breaker into the rag layer, these options have intellectual property com- plications. There is a new option, in-situ resolution of the rag layer emulsion. In-situ resolution of rag layer emulsion The demulsifier or emulsion breaker (EB) is the core of the desalter chemistry programme. EB is added to the crude to accelerate the oil-water separation in the desalter. Adjunct chemistry refers to the use of secondary chemistry to sup- plement the primary EB. Traditionally, the classes of adjunct chemistries used are 1) solids wetting agent, 2) reverse emulsion breaker, and 3) acid. Dorf Ketal has invented a new fourth class of adjunct chemistry called ‘reactive adjunct’. Reactive adjunct (RAC)

Levels of filterable solids in crude and organic calcium



76.20 ppm



Organic calcium Total calcium Wax in crude Filterable solids

10.30 ppm 11.00 ppm

2.44 %

180.00 (514.80) ptb (ppm)

Table 1

Figure 5





is a patented discovery based on aldehyde chemistry (see Figure 4 ). Aldehydes are non- acidic, nitrogen-free compounds containing a reactive C=O carbonyl bond. It has been discov -


FS: 85,100

FS: 111,100

FS: 116,000 FS: 153,500





5% O&G


ered that there is synergy between the EB and RAC. A low dosage of RAC in combination with EB increases the speed of emulsion breaking more than the equivalent increase in EB dosage. Substitution of the greener RAC formulation for nonylphenol-containing EBs improves overall sustainabil - ity. The polar nature of the carbonyl bond makes it highly water soluble. The reactive nature of the carbonyl bond reacts with a variety of crude contaminants that impede emulsion breaking, including organo-metallics and amines. RAC can be added to the raw crude or wash water. In addition to increasing the speed of emulsion breaking, the combination offers in-situ resolution of the rag layer emulsion. Field data case history 1 An Asian refiner faced frequent upsets in its desalter, reported whenever processing Dulang crude. The upsets included rag layer accumulation, desalter trips, and high levels of oil under-carry. Levels of filterable solids in the crude and organic calcium (see Table 1 ) are the root cause of the increase in rag. Toward the end of a Dulang run, Dorf Ketal conducted a five-day demonstration of the ability of RAC to deliver in-situ resolution of the rag layer emulsion. Figure 5 shows the qualitative and quantitative measure- ments of the rag layer prior to starting the feed of RAC. The water level had been reduced to increase the oil layer residence time to maximise dehydration in the presence of rag. There is no clear oil-water interface. Solids are floating in both the oil and water layers at levels as high as 70 times theoretical. Oil and grease are 5% of the brine. RAC feed was started to demonstrate in-situ resolution of the rag layer emulsion. Figure 6 shows the results after five days of feeding RAC to the wash water. We can see in Figure 5 that the oil-water interface is evident at tryline 1. Comparing Figures 5 and 6, solids floating in the oil layer are reduced by >97% due to RAC. Oil and grease in the brine are reduced by >99%. The level of solids floating at the oil-water interface was reduced by about 40% when the feed of Dulang was stopped. We

Figure 6




FS: 85 ppm O&G

FS: 69,000 ppm

FS: 3,230

Improvements in desalting & filterable solids removal


Dorf Ketal





Desalting efficiency Crude outlet FS, ppm



13.3 30.7 15.4



FS removal efficiency, % 27.5


Table 2

know from other experiences that this emulsion could have been further resolved if more time had been avail- able. This extreme example is noteworthy for demonstrat- ing the power of the chemistry to resolve existing rag layer emulsions that are not addressable by the conventional EB approach. Field data case history 2 A refinery in South Asia faced frequent upsets in its single- stage desalter combined with reduced preheat tempera- ture due to fouling. The audit and baseline study indicated the presence of a rag layer that inhibited filterable solids removal and aggravated asphaltene deposition in the pre- heat train. With the EB and RAC programme, the rag layer in the desalter was reduced. This allowed for faster mass transfer across the oil-water interface, improving desalting and fil - terable solids removal efficiency, as shown in Table 2 . Figure 7 shows the furnace inlet temperature versus


PTQ Q1 2023

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