Fuel Storage
Good quality stored fuel combusts properly without black smoke and adverse emissions and does not leave deposits inside of the engine.
If the fuel quality is not within specification, the vehicle or engine will probably not run properly if even at all. This fuel quality deficit is really caused by what ends up in the fuel that does not burn as well as the fuel itself.
There are chemical and mechanical solutions to help with fuel stability deficits. Fuel stability treatments are preventive treatments that keep these substances from forming thereby prolonging the usable life of the fuel. Fuel “polishing” (fuel filtration) is a reactive (but sometimes necessary) mechanical step that provides value by removing existing water, sludge, and asphaltene dropout from the fuel so that the fuel burns as it’s supposed to.
Water Accumulation In Diesel Storage Tanks
Water plays several roles in the destruction of stored fuel quality. The accumulated water builds up in fuel storage tanks that are vented to the outside. Temperature changes from day to night cause condensation to develop on the inside of the storage tanks; this condensed water rolls down the sides of the tank and sinks to the bottom of the diesel fuel, because water is heavier than diesel fuel.
This water enhances the possibility of microbial growth in that storage tank. Bacteria, fungi, and microbes only need a small layer of free water interfacing with a layer of diesel fuel in order to get all the things that they need to grow and thrive inside of a fuel storage tank.
Microbes that infest storage tanks produce acids and corrosive substances as a result of their biological processes. These biological by-products accelerate the breakdown of the quality of the diesel fuel and also contribute to corrosion damage to storage tanks.
There are water coalescers, filters, and centrifuges that can allow for the removal of significant amounts of water from tanks. There are also highly effective fuel treatment options that will absorb significant amounts of water and cause it to be locked into the diesel fuel for combustion. Alternatively, there are demulsifier treatments that can resolve fuel-water emulsions and enable more effective free water removal.
Water removal is also an essential element of a quality fuel & tank service program that typically involves the removal of excess water in storage tanks coupled with the addition of both water controllers and biocide treatments to stop microbial problems before they start.
Stability Breakdown In Stored Diesel Fuels
Today’s biodiesel blends and regular diesel fuels are prone to what is known as oxidative stability breakdown. They are less able to resist the chemical reactions that come from every day exposure to water, oxygen, light or heat, and bacterial byproducts – all of which are known to chemically deteriorate and break apart diesel fuel and biodiesel blends.
They all contribute to either providing the fundamental ingredients for the chemical reactions that cause a fuel’s break down, or the acceleration of the oxidative breakdown of the fuel quality over time.
Exposure to water and oxygen in the air provides oxygen that is the essential ingredient in oxidation and hydrolysis chemical reactions. These are the chemical reactions that attack diesel fuel molecules, break them apart and turn them from stable molecules to unstable molecules that want to form sludge and deposits in stored fuel.
Biological byproducts of bacteria and fungus in fuel tanks also lead to tank corrosion and the breakdown of stored fuel in the tank because of their acidic nature. Exposure to heat provides the energy catalyst needed to make sure that these harmful chemical reactions actually happen at a faster rate in the fuel.
Stored Ethanol Blends
Ethanol in petrol became common around 2005 and 2006 after the phaseout of MTBE (which used to be added as an oxygenate and an octane improver) because of fears of groundwater contamination. Ethanol alcohol became the new oxygenate of choice in certain countries. Oxygenates add more oxygen to a petrol mixture, helping the petrol to burn with fewer harmful emissions that affect urban air quality.
Ethanol blends have a much more compressed storage life than diesel fuels do, which makes them more difficult to store for backup use. They attract water quite easily, a big problem for ethanol fuel blends when stored for any significant length of time. This water accelerates oxidation and breakdown of ethanol fuels, contributes to the same type of microbial infestation problems in ethanol blends, and causes phase separation of the fuel.
Stored ethanol-petrol that has phase-separated is going to be useless – its octane rating and combustibility will be shot and there’s no way to put it back together again.
The only solution to protecting stored ethanol gasoline is to make sure the fuel doesn’t reach that point.
What Are The Best Practices For Protecting Stored Fuel?
When it comes to maintaining stored fuel and protecting its quality for the needed time, the best practices will fall into two camps – chemical and mechanical practices. Both camps have their value and also their limitations. It’s important to realize what these are.
A good mechanical process will involve the use of filters and water separators to mechanically remove particulates and water from the fuel and its storage tank.
Mechanical filtration is very useful for taking fuel that is out-of-spec and bringing it back into specification. Mechanical processes are also the best way to handle the sizable amounts of water that many fuel storage tanks accumulate over time if they are not diligently watched.
The biggest limitation that fuel filtration and similar processes have in protecting stored fuel quality are that they do nothing to keep fuel problems from coming back.
While Fuel polishing and filtration remove from the fuel what’s not supposed to be present there’s nothing to stop the fuel from darkening again or developing a repeat microbe problem within a couple of months. Mechanical fuel processing addresses current problems, it does not prevent them from re-occuring.
“Chemical practices” center on adding effective chemical treatments to the stored fuel to either fix an existing problem or prevent a possible future problem from developing. The important chemical treatments to consider are fuel stabilizers, water controllers, biocides, and sludge dispersants.
Fuel stabilizers are typically antioxidant packages that prevent the chemical reactions from starting that cause fuel quality to break down over time. Oxidative chemical reactions in diesel fuel are a chain reaction; this means that the process is started with a few chemical reactions that lead to more chemical reactions, eventually leading to a widespread breakdown of that diesel fuel.
Fuel stabilizers need to be added when the fuel is fresh before signs of instability become apparent. Once fuel sludge has developed in fuel and its storage tank, a stabilizer will not put it back together again.
Emulsifying or water-suspending formulations are the most common chemistries for helping get rid of free water in a tank. Water controllers can effectively control limited amounts of water but are not designed to make large amounts of water disappear.
If the fuel has an emulsion or haziness that cannot be resolved with a water dissolver chemistry, the solution is to use a demulsifier formulation. Demulsifiers are highly effective at breaking fuel-water emulsions to allow entrained or emulsified water to separate and drop out from diesel fuel and collect at the bottom of the tank as free water, where it can be more easily removed.
Fixing microbial contamination in stored fuels requires a biocide. Biocides and sludge dispersants need to be added and incorporated into the fuel through fuel circulation, to allow maximum contact between the chemical treatment and what it’s supposed to be remediating. It is rarely effective enough to add these types of treatments on top of the fuel and simply let them diffuse throughout the entire fuel body.
The meat of the matter is that fuel additives need to be added correctly.
Given the limitations of either side, the best practice recommendation for protecting stored fuel is to use a combination of both methods.
The best practice is to start with the use of periodic mechanical fuel and tank servicing to clean up and remove existing water, sludge, asphaltene dropout and microbial growth.
This is combined with the addition of quality chemical fuel treatments that both enhance the effectiveness of fuel polishing (water controllers to scavenge leftover water, sludge dispersants to remove hard-to-reach asphaltene collections) and prevent these problems from returning (biocides, fuel stabilizers) for long periods of time than would be possible without their use.