Hidden Secrets of the Flash Tank

[@abirbasu4073]

Good information Ben. I attended some of your F2F courses as a part of Amine Experts training at McMahon plant in norther British Columbia (Fort St John). During the 3 year turnaround we used to clean the garbage out of the flash tank. Need to be careful about the present of iron sulfide while cleaning any part of the amine network. Based on my experience, residence time can be difficult to specify, but 25-30 min is reasonably good depending upon the quality of the incoming HC gas. More the better if there are some free HC liquid coming with the gas, but the design concept varies. Best practice - clean the sludge during the turnaround. Thanks for the table of residence time vs HC particle size.

[@aliamirov28]

Another great video! Just a lessons learned, lowering the operating pressure below the normal operating point will lead to more flashing d/s of absorber LCV that can cause erosion-corrosion of rich amine inlet line and nozzle of the flash drum.

[@benspooner8690]

Ali, this true, but usually is also associated with excessive amine circulation rate. You shouldn't have so much hydrocarbon entrained in the rich amine that flashing across the absorber LCV causes erosion, no matter how much the pressure drop. Check that the amine is not being overcirculated and picking up more hydrocarbon than it should be!

[@govindsoni3782]

awesome channel....all the practical aspects of Amine and Sulfur are covered with actual plant examples...great..

[@7184ppl]

Helpful information

[@m.dellil2587]

Thanks Ben for the amazing information, just an idea: Is there a simple why to make residance time calculation and it will be updated from real plant values? If I see that residence time getting reduced than 20 min then a troubleshooting is required? Thanks again

[@bryansutphen1884]

You can calculate the normal liquid volume of the tank/drum, which should be a fixed value (minus solids accumulation). Then, residence time = liquid volume/circulation rate.

[@benspooner8690]

I normally calculate the total volume of the tank then use 50% of that as the liquid volume. If your plant operates with a liquid level greatly different than 50% you will have to adjust your calculation, but 50% is generally pretty close. Once you have the liquid volume its easy to figure out how many minutes the amine will be in and out of the tank based on your circulation rate. You'd be surprised how many plants we come across where the residence time turns out to be less than 10 minutes. Its no wonder skimming doesn't do anything in these situations!

[@playstore4297]

Superb sir

[@beautifulbirds455]

kindly upload more videos related to gas processing and equipments

[@mohammadsalman5297]

Thank you for your so much useful information! Can you please upload a video on "How to set-up Lean Amine Circulate Rate?" Thanks.

[@aldenhagel5082]

Alden from Estevan Sask here. You ran us through the course a few years back. We have been pulling out buckets and buckets of a gray gel out of our flash tank. Any ideas what it could be?

[@benspooner8690]

Alden, its probably antifoam!! Antifoam quickly floats to the surface of amine when it is stagnant, like in a flash tank. Because it is so viscous it picks up a lot of hydrocarbon and suspended solids, and eventually turns into what we call "black shoe polish". Pretty much any antifoam you inject into an amine absorber winds up floating in the flash tank.

[@1981phatty]

@@benspooner8690 Its definitely not black show polish it is a grey gel, almost like silly putty kids make. Its not heavy but does stick together and we use a alcohol based anti-foam. It almost looked like brains coming out of the skim, chunky and did not break down with anything other than methanol. Thanks for all the videos we have been watching and rewatching them at work all week!

[@aliamirov28]

I am curious about sight glass. Is it possible to visually define the hc interface? Usually rich amine is black or opaque.

[@benspooner8690]

Ali, rich amine should not be black! If it is, determine what's causing the colour change and fix it. And yes, if the sight glass is properly located, when you purge it and allow it to refill it should accurately reflect the location of the interface.

[@ashishps3790]

​@@benspooner8690Rich amine will be dark green colour only, right?

[@julianharis3364]

Hi Ben, thanks for this great video.. If over-circulation is indeed found, then we need to reduce the circulation in such a way that the remaining time for the rich amine in the flash tank is> = 20 minutes. In parallel, we also have to pay attention to the impact on the on spec condition of the resulting sweet gas (treated gas). Can it be off spec? do we need to increase his amine strength? Are there any negative effects that need to be considered when increasing the existing amine strength? I am really triggered to recheck this via simulation.. looking forward to your response...

[@benspooner8690]

Julian, you are right you cannot simply reduce the amine circulation rate without checking several parameters first. Make sure to control the rich loading of the amine (which is a function of both amine circulation rate AND concentration), calculate the expected temperature bulge in the absorber, and double check the hydraulic limitations of your pumps, absorber internals and heat exchangers. Yes there are negatives to increasing amine strength. Depending on the amine, too high of strength may lead to corrosion! As well as high viscosity which as all sorts of potential problems associated with it. If there is a liquid-liquid treater in your system, high amine strength can result in high amine losses with the treated hydrocarbon stream.

[@Ikazmn]

Increasing the strength of amine you can’t control the temperature due less water

[@troym.campbell9535]

How often should I drain my reflux accumulator

[@benspooner8690]

Troy, in a gas plant you'd drain or purge whenever you had foaming in the regenerator (or whenever a reflux water foam test shows that it's foamy). Some plants dump their reflux once a week, some once a year. It depends on how much contamination is entering with the feed gas to the absorbers. In a refinery the same rule applies but also add in the concentration of ammonium salts. Most refiners constantly purge 5-10% of their reflux water to the sour water stripper.

[@troym.campbell9535]

@@benspooner8690 good deal Mr. Ben, very much appreciate you taking the time to do these troubleshooting videos.

[@mrladeuce397]

WHY ARE YOU YELLING? YOU DON'T HAVE TO YELL TO BRING OUT YOUR ENTHUSIASM