High wax content heavy oil remover

Details High wax content heavy oil remover High wax content heavy oil remover

1999-10-13

2001-03-06

Gupta, Yogendra (Department: 1751)

Cleaning compositions for solid surfaces, auxiliary compositions

Cleaning compositions or processes of preparing

For cleaning a specific substrate or removing a specific...

C510S213000, C510S215000, C510S365000, C510S371000, C510S407000, C510S413000, C510S414000, C510S432000, C510S463000, C510S506000, C510S484000

Reexamination Certificate

active

06197734

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to a high wax content heavy oil remover formulation. More particularly, the invention is directed to a composition useful for removing high wax content heavy oil and oily sludges from process equipment such as storage tanks, transfer piping, and pumping facilities.
BACKGROUND OF THE INVENTION
Conventional heavy oil degreaser compositions contain so-called “alkaline builders.” Moreover, many heavy oil remover compositions include halogens which are undesirable for steel process equipment degreasers, because the halogens may contribute to stress cracking of the metal. Many heavy oil degreasers only work at full strength, and are ineffective when diluted by residual liquids contained within the process equipment being cleaned. Some heavy oil degreasers are ineffective at ambient temperatures and must be heated along with the process equipment in order to remove the heavy oil sludge. Conventional heavy oil removers generally are incapable of absorbing and/or neutralizing the toxic gases and vapors which have accumulated within fouled process equipment. Finally, many of the heavy oil remover compositions of the prior art are toxic and not biodegradable.
Moreover, conventional heavy oil remover compositions are not useful for dissolving and removing heavy oils that have a high wax content. When conventional heavy oil remover formulations are used to clean process equipment containing high wax content heavy oil sludges, it is observed that such formulations are incapable of dissolving many of the waxes in the sludge. Also, those materials which are dissolved do not easily self-demulsify when mixed petroleum waxes are present. This is particularly inconvenient since demulsification is essential to the recovery of useful petroleum products from a sludge cleaning process. Finally, high wax content petroleum sludges typically invert, changing from a liquid phase at ambient temperatures to a solid at conventional sludge cleaning temperatures in the range of 80 degrees Celsius and higher. Since these higher cleaning temperatures are required in conventional cleaning processes in order to dissolve and emulsify the largest carbon chain length and highest melting point waxes, this phenomenon of congealing at higher temperatures tends to diminish the ability of conventional heavy oil remover formulations to extract and recover the oils and waxes from high wax content heavy oil sludges.
Waxes are defined as substances that are plastic solids at ambient temperatures and, on being subjected to moderately elevated temperatures, become low viscosity liquids. One type of wax “Paraffin Wax” is a petroleum wax which occurs naturally in many types of crude oil around the world. Chemically, paraffins, and by extension paraffin waxes occurring naturally in petroleum, are usually mixtures of straight carbon chain alkanes. The physical properties of the paraffin waxes, including melting point, congealing point, and plastic flow properties, vary with the “carbon chain length” of the wax or waxes present in the petroleum. When combined with the presence of other types of petroleum hydrocarbons found in natural petroleum sources, the physical properties exhibited by wax impurities in natural petroleum can produce difficulties with storage tanks and other process equipment, leading to a buildup of difficult to remove sludges with a mixed wax and petroleum impurities content. These waxes eventually cause a reduction in tank storage and equipment processing capacity as they build up, and also present a difficult cleanup problem as they are by their chemistry not soluble in most solvents.
U.S. Pat. No. 5,085,710 to Goss discloses a composition for removing oil sludges utilizing an alkylphenol adduct and a castor oil etholylate. U.S. Pat. No. 5,389,156 to Mehta et al discloses a heavy oil degreaser including a terpene and a second nonionic co-surfactant from the family of ethylene oxide/propylene oxide polyol adducts. These disclosed formulations are not effective for dissolving high wax content heavy oils, and additionally suffer from a number of the undesirable characteristics listed above.
It would be desirable to prepare a high wax content heavy oil remover composition that is effective for dissolving and emulsifying high wax content heavy oil sludges, and which is additionally free from alkaline builders and halogens, capable of absorbing toxic gases and vapors such as hydrogen sulfide and benzene, nontoxic, and biodegradable.
SUMMARY OF THE INVENTION
Accordant with the present invention, there surprisingly has been discovered a high wax content heavy oil remover, comprising: from about 1 to about 80 weight percent dipropylene glycol mono n-butyl ether; from about 0.5 to about 50 weight percent ethoxylated alkyl mercaptan; from about 0.5 to about 90 weight percent salt of an aromatic sulfonic acid; from about 0.5 to about 50 weight percent branched alcohol ethoxylate; from about 1 to about 90 weight percent d-limonene; and from about 1 to about 90 weight percent white oil.
The high wax content heavy oil remover according to the present invention is particularly useful for dissolving and emulsifying high wax content heavy oil sludges from fouled process equipment and storage tanks.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The high wax content heavy oil remover formulation according to the present invention comprises a dipropylene glycol mono n-butyl ether, ethoxylated alkyl mercaptan, salt of an alkyl aromatic sulfonic acid, branched alcohol ethoxylate, d-limonene, and white oil.
The design of a high quality high wax content heavy oil remover requires attention to the chemical characteristics related to the performance enhancements required to achieve removal of high wax content heavy oils. Specifically, the most important chemical characteristics are solvency and detergency (or ability to emulsify). These factors affect the high wax content heavy oil remover's ability to clean and degrease metal surfaces, its impact on corrosion of the metal surfaces, its ability to be safely handled, and its environmental acceptability.
The high wax content heavy oil remover according to the present invention exhibits the desired characteristics of solvency and detergency. Moreover, halogens are absent from the formulation, thus reducing the potential for stress cracking of the metal process equipment. The inventive formulation is effective over a range of process temperatures, even when substantially diluted with water or residual process fluids. Finally, the inventive composition can absorb toxic vapors such as hydrogen sulfide and benzene, yet is itself non-toxic and biodegradable.
The inventive formulation's ability to dissolve and emulsify waxes contained in the heavy oil sludges is best understood by examining the mechanism by which the petroleum waxes are carried by the crude oil and subsequently congeal over time to become insoluble and settle in the crude oil sludge in the first place. The waxes at first are dissolved in the crude oil often under the tremendous pressures existing in natural petroleum formulations, possibly sometimes above the “saturation point,” i.e., the point at which the liquid crude oil can under standard atmospheric pressure and ambient temperatures dissolve no more waxes without those waxes precipitating as sludges from the crude oil. Under conditions existing in the oil bearing formations in the earth, however, it is possible to “supersaturate” crude oil with petroleum (paraffinic) wax to the point above the saturation point. The wax then needs only a nucleus or seed wax crystal to rapidly solidify in a manner not unlike inorganic crystal growth in salts, which eventually causes the excess paraffin waxes to precipitate as sludge. The sludge then becomes a concentrated source of paraffin waxes.
The key to returning the paraffin wax in the heavy oil sludge to the dissolved liquid state in petroleum therefore is to provide a solvent into which the paraffin wax can dissolve. This is achieved by adding the inventive high wa

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