Dehazers

Water can contaminate fuel through several different routes. Examples include  

Under normal circumstances, refined fuels do not form emulsions with water. The fuel and water readily separate into two distinct phases, a lower water phase and an upper fuel or oil phase. However, when emulsifying agents mix with fuel, emulsification can result. Examples of common fuel emulsifying agents include any of the following  

Tanks used to store fuel are usually emptied and filled on a continuous basis. Although most fuel refiners and marketers maintain some type of routine tank maintenance schedule, water and debris still accumulate. 

Products of microbial metabolism, rust, salts of calcium, sodium, magnesium, 

Distillate fuel fractions can contain naphthenic acids, sulfonic acids, and other hydrophilic compounds. If these hydrophilic compounds are present as sodium salts due to caustic washing of fuel, they become powerful emulsifying agents. Also, heavy resinous compounds in fuel can act to stabilize existing emulsions. 

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Inject a Dehazer Additive into the High Pressure Separator (HPS)... 

The terms demulsifier and dehazer are often used interchangeably to describe compounds which break fuel emulsions or remove water-initiated haze from fuel. The terms can be distinguished as follows ... 

Dehazing refers to removal of water which has been dispersed throughout a fuel matrix. Haze created by water droplets can be removed by coalescence or by further dispersion through the action of a chemical dehazer. 

Two basic mechanisms have been proposed to explain the performance of demulsifiers and dehazers in finished fuels. These two mechanisms are defined as coalescence and adsorption. Both processes rely on the fact that the demulsifier contains both hydrophobic and hydrophilic sites. The mechanisms can be defined as follows ... 

Given time, water which exists as discrete droplets in finished fuel may coalesce into larger drops and settle by gravity from the fuel. Demulsifiers or dehazers can accelerate this process by functioning as a site for attraction of dispersed water. 

To break through this oil or surfactant layer and free the retained water, it is necessary to chemically disrupt the stability of this layer. Demulsifiers and dehazers can adsorb onto the protective film and subsequently interfere with the electrochemical forces which hold this outer layer together. 

Upon adsorption, demulsifier/dehazer compounds function to break the oil or surfactant layer thus releasing the contained water. Once free, the water can then coalesce into larger drops and be removed from the fuel. 

Quaternary ammonium salts and salts of alkyl naphthalene sulfonic acid were some of the first compounds to be used effectively as fuel demulsifiers and dehazers. Today, a wide range of monomeric and polymeric demulsifiers and dehazers exist. 

Sorbitol and glycerine are commonly used as monomers for oxide addition. Various alkyl phenol-formaldehyde compounds are examples of polymeric acceptor compounds having a large number of unreacted hydroxyl groups. The extent of oxide polymerization can have a significant impact on performance and solubility of the dehazer or demulsifier in fuel and oil systems. 

As a general rule, the addition of ethylene oxide to a resin backbone will tend to increase the water solubility of the compound. The addition of propylene oxide or butylene oxide to the resin will tend to increase the hydrocarbon solubility of the compound. Often, the dehazer or demulsifier can be made to perform selectively in oil-water systems by adding both ethylene oxide and propylene oxide to the same molecule. Performance and solubility of the alkoxylated compound can then be finely tuned by closely controlling the amount and order of epoxide addition. A random EO-PO based fuel demulsifier is shown in FIGURE 6-6. 

To remove water haze from cloudy fuel, refiners will sometimes use fuel dehazers. Some dehazers disperse water into fine droplets so that the water haze cannot be seen. The fuel, thus, appears bright and clear. However, if fuel treated with a dehazer is transported through a pipeline system, the dispersed water can sometimes cling to the pipeline wall and remain as water droplets. 

If high concentrations of dehazing compounds are added to fuel, >1000 ppm for example, a possibility exists for the dehazer to interact with deposits held within a fuel transfer line or fuel tank. The surfactant-like character of the dehazer may enable it to function in removal and dispersion of existing deposits. 

For this reason, extreme care should be taken when using high concentrations of dehazers to clear fuel of water haze. The excess dehazer may also act to solubilize deposits which are present within a fuel system. The deposits may then be carried with the fuel throughout the distribution system. 

The terms dehazing and demulsification are often used synonymously to describe... 

The addition of a fuel dehazer may provide some performance at clearing the fuel of water haze. If not, the fuel may require filtering or reprocessing to eliminate the haze. 

Buggs, Ralph N. 1992. (Internal report) Dehazer for gasoline package. 92/496. Sugar Land, Tex. Nalco/Exxon Energy Chemicals, L.P. 

In addition to dehazing, the Sonnebom white oil plant also reduced pour point from 4°C to 18°C and cloud point from +4°C to 10°C by removing 3 to 4% wax. This plant was unique in being a batch operation and being the first commercial use of this technology. Here, methanol was used as a promoter for adduct formation. 

L. Sonnebom Sons Petrolia, Pennsylvania 1950 Dehazing to produce very low cloud point white oil 17, 41... 

In spite of the fact that Chevron chose not to use their dewaxing catalyst for their heavy stream, in an interesting application they did employ the same (or very similar) catalyst to dehaze the heavy dewaxed oil when pinholes or tears in the filter fabric caused leakage of wax into the solvent dewaxed oil. The refinery s... 

Source J. A. Zakarian and J. N. Ziemer, Catalytic Dehazing of Heavy Lube Oil A Case History, Energy Progress 8 109-112 (1988). With permission. 

Deacidification of drinks Chitosan salts that carry a strong positive charge have been shown to be effective as dehazing agents. They may be nsed to control acidity in fruit juices or coffee drinks. 

Dehazer Coalesce suspended water droplets Ethoxylated/propoxylated surfactants... 

Dehazers are used to diminish haze in organic liquids. Here siloxanes functionalized in a,co position with polyethers (Fig. 6) can be mixed with copolymers of ethylene and unsaturated esters such as vinyl acetate, methylacrylate, etc. [57]. Because free acid groups tend to promote haze if moisture is present, completely esterified groups are preferred. 

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