Diesel corrosion

[bugbuster]

Pat:

When 2,500 ppm was added to ULSD, how much actually remained in solution? Most ULSD water solubility v. temperature tables indicate water solubility at 65 F to 75 F to be <1,000 ppm.

I agree with you about KF being the only reliable method for determining the concentration of dissolved and dispersed water. Recognizing that microbes can't used dissolved water, KF's limitation - as far as I know - does not differentiate between dissolved and dispersed water. For that, one needs ultra-centrifugation (i.e., centrifugation with sufficient gravitational force for a sufficient interval to separate the dispersed water from fuel - leaving dissolved water behind).

I also agree that as biodiesel absorbs water, it will become heavier than ULSD and settle, with the consequences you described. I often marvel at diesel generator fuel tank design. As you noted, fuel is typically drawn from (too) close to the tank bottom - great for using all of the fuel in the tank; not so much for protecting the engines and filters from fouling, and so-called bottom drains typically penetrate tank bottoms by 1/4 to 1/5 in (or more) so that they cannot actually drain the bottoms-water and sludge from the tank bottom. Such fittings are easier for the folks constructing the tanks, but create conditions that make it more challenging to maintain fuel quality during long tern storage.

There are those who have argued that high dispersed-water concentrations might decrease soot, NOx, and SOx emissions. I haven't seen compelling data one way or the other. Personally, as a microbiologist, I'm all for fuel-emulsified water. I can't see who such a product would not enhance bug growth and related biodeterioration issues.

[PatSmyth]

Hi Fred,

Best I first direct you to the SAE J1488 Test Procedure for details on the test setup. https://www.sae.org/standards/content/j1488_201010/. Cost $85.

There are two phases to the test, phase one uses 100% pure ULSD; phase two uses a B20 equivalent sample

From the procedure “ A 3500-rpm centrifugal pump is used to disperse water in the fuel”.

Pure ULSD cannot hold 2500 ppm amount of water, but for the J1488 test the fuel/water mixture is immediately sent through the filter being tested, and then retested after filtration. In this way, SAE ascertained that most filters have close to 100% efficiency in removing most water from pure ULSD (as diesel was before the into of biodiesel in 2006).

The test is then run again using a B20 equivalent sample. The water is much harder to remove, as water has formed a hydrogen bond with the biodiesel molecule. Most traditional filters have low efficiency at removing this water. A 92% efficiency is needed to keep water below 200 ppm. ((1 - .92) * 2500 = 200)).

I have only found two filter manufacturers that have test results higher than 92%. One company is called DieselPure. I reference them because I have seen their test results duplicated in the field. SAE J1488 test results at https://dieselpure.com/dieselpure/

The use of SAE J1488 2010_10 filtration on both terminal storage tanks and delivery trucks will deliver dry diesel blends to a storage tank. If the storage tank is turned over in a short timeframe and again refilled with dry diesel, the fuel should remain dry other than water leaking into tank.

If diesel is stored long term (backup generators) then permanent filtration should be installed, using filters tested against SAE J1488 filtration.

Pat

[ZMiller]

It should be noted that the PEI Forum has who I consider two of the foremost experts discussing the diesel fuel issues of major concern. I put my two cents in every once in a while. The issue seems to be keeping moisture out of the tank to ensure long term storage of and the perseveration of fuel quality. I'm always interested in ways to monitor and keep moisture out of a storage tank.

Initially we just studied methods commonly used to inert tank empty spaces. In the process of study using NEA and DA as a blanketing atmosphere in diesel tanks bio diesel and its affinity to bond with water, the molecular bond was found to be a road block seemly unsurmountable.
Quite unexpectedly as with the Comstock Load initially mining for gold and the silver stuff kept getting in the way. With further redirected study to address specifically breaking the bio water hydrogen bond it was found possible to do. Simply changing the temperature of the inerting or blanketing gas seems to work quite well in monitoring moisture and preserving fuel within acceptable specifications. I often wonder why simple solutions and basic laws of physics regarding fuel stability are so often overlooked.

I'm sure we can all agree that regular filtration and biocide treatment to preserve quality of stored fuel in diesel and critical care standby generator fuel storage tanks. Not addressing moisture and oxidization problem as well seems to be effecting a storage tanks integrity at now alarming rates.

[bugbuster]

Thanks for the explanation, Pat.

It appears that J1488 intentionally includes dispersed and dissolved water to assess a filter medium's ability to strip both from the test fuel.

That certainly makes sense.

Cheers,
Fred

[ZMiller]

Pat and Bug,
I'm asking if you see any bio activity in the actual fuel column above the water fuel interfaces?

[PatSmyth]

With biodiesel blends there is no longer a discrete water fuel interface, rather as the water absorbs into the biodiesel, the combined water/biodiesel molecule becomes heavier than diesel, and settles towards the bottom as a hazy section at most 6 inches thick. This is where I think the increased microbial growth will occur.

I have tested for microbial growth at bottom and mid tank, via a HunBug test, and found fungal growth in every sample.

I also tested 3 levels for water, TAN and particulate. Water was excessive on the bottom (but no visible free water), though the fuel was dry at 6 inches and mid tank. TAN levels exceeded limits all levels, as you would expect with excessive microbial growth. Particulate was also above limits at all levels. The Humbug test referenced above shows fungal growth at bottom and midtank.

[PatSmyth]

I agree with Zanes comments on using NEA and DA as a blanketing atmosphere in diesel tanks. I can see this as the ultimate solution for terminal tanks storing biodiesel blends, these tanks have a large surface areas that give a huge footprint for the bonding of water molecules to biodiesel molecules, which then will settle towards the bottom of the terminal tank to enhance microbial growth, diesel acidification, and corrosion. The nitrogen blanket in the terminal tank ullage will control/prevent this absorption. Next, the introduction of heated nitrogen from the blanketing system bubbling into the stored fuel can break these bonds, and dry the fuel.

In the interim, a SAE J1488 filtration system between the terminal tank and delivery trucks can, in a single pass, break the hydrogen bond holding the water molecule to the biodiesel molecule, providing dry fuel to be delivered to the end user.

Pat

[rgarza]

Zane Miller,
Do you happen to know what percent of tanks had high acid numbers in that study?

[ZMiller]

Fuel labs 40% of diesel nation wide. May be due to higher percentages of bio fuel refiners pushing out sub standard fuel in efforts to meet contracted supply agreements.

There seems to be a shortage of bio feed stock. Often leading to less ripe product being blended. Seeing more unscrubbed catalysts in the end product these days. Interesting reports on dio diesel product out of federal engine lad in Colorado. I'll post reports shortly.

[ZMiller]

Tulsa Letter link to latest report....

A new Coordinating Research Council (CRC) study on corrosion in diesel underground storage tank (UST) systems provides some, but not all, of the answers for which the industry has been waiting.