[Hedewandro Lucredi]

Which naphtha is better to inject in the compressor ? Heavy or light naphtha ? Why ?

[Hedewandro Lucredi]

It was confirmed that the fractionator top temperature is around 10 degree C above the estimated water dew point. Additionally, there are no salting problems at this region.

The severe corrosion is found around packing bed #2 (heavy naphtha). The salt point was estimated, based on chloride and ammonia concentrations, and it was confirmed that NH4Cl deposition can be occurring at this region. That is why we are interested to know about the use of corrosion inhibitors in intermediate tower sections…
The refinery is trying to solve some known desalting problems in order to reduce the chloride content in the DCU feed.

[Hedewandro Lucredi]

The temperature is around 150 Celsius. The corrosion products are from chlorides of our poor desalter

[Hedewandro Lucredi]

Mike. We analysed the residue and the relation C and H2 was CH2. So it seems that was produced by polymerization. How can I reduce this polymerization ? How can I reduce the corrosion inside the tower ?Is it possible to inject anti corrosion chemicals inside the main tower in the heavy naphtha pan or other main tower section ? Or inject in the heavy naphtha circuit ?

[Hedewandro Lucredi]

We observe corrosion products mainly. It seems that when we have any flow variation some corrosion products are carry over from the system (tower, pipes, etc) and goes to the filter.

[Hedewandro Lucredi]

We do the analysis of the deposit in the slurry heat exchanger and it seems to be catalyst (Al and Si we found) a lot. It seems that the chemical that we are adding is not solving the problem (keeping the catalyst in suspension).

[Hedewandro Lucredi]

Thanks Mike. I will check

[Hedewandro Lucredi]

Yes. We add some FeCl3 in the paper with sour water and observe if change the colour to blue. How long does it take to change the colour ? In our case is +/- 12 h. We try to keep the wash water +/- 8 % related with the feed. The water is from the SWS (retified sou water). We add 60 % wash water in the interestage gás compressor. We observe that the wash water limit is 6 %. If the spot test show a “positive” we increase the water from 6 to 8 %. How is it the water wash limit ? What Kind of water do you use ?

[Hedewandro Lucredi]

The filter screen size of the slurry pump is 9 mm. In fact the problem is the plugging of the equipments (heat exchangers) after the slurry pump because coke fine and catalyst deposition. It has a “huge filter” in the bottom of the main Fractionator in order to avoid to send “coke” to the slurry pump. We are using a slurry dispersant in the suction of the pump but it still plugging the pipe and heat exchanger. How can I check the dispersant yield ?

[Hedewandro Lucredi]

We checked our PSV’s and PV with ultrasom and we observed that some PV’s had leakage to the flare. We are fixing these valves. In the field and in the DCS these valves were closed but they had some leakages. Also we found one PSV with some leakage.

[Hedewandro Lucredi]

During the start up we have some cavitation but after above a determined temperature the cavitation stopped.

[Hedewandro Lucredi]

We checked and there is no fine carryover (huge space in drum top). No foaming problem. We use anti foaming 100000 cST. We think the problem was from any coke fines from packing beds, trays that the steam removed part of it.

[Hedewandro Lucredi]

Thanks for your answer. Which condition can I run the heaters without velocity media? In our case is water and because we are in the end of campaign for decoking we cut the water in one heater path. We measured by infrared the coil temperature and there is no huge change. Is it possible to operate a campaign with no water ? Do you have any experience or know any DCU which operate in this conditions (no velocity media) ?

[Hedewandro Lucredi]

In order to improve the decoking water quality we are doing purges in the cutting water tank more often and clean more the pit. What we can do to remove more coke fines in the cutting water tank ? Anything in the DCU process ? Is it common to use hydrociclone in the water to the tank ? Centrifuge ?

[Hedewandro Lucredi]

Our tipicaly data for Chloride is 50 – 70 ppm, pH = 9, NH3 = 2, RSH = 2 and now we have a huge problem with coke fines. This coke fines are plugging the decoking valve in our pump decoking. Also, the Rotary joint are leaking due this fines.

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