Compositions: coating or plastic – Coating or plastic compositions – Wax containing
Reexamination Certificate
1999-05-24
2001-11-27
Brunsman, David (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Wax containing
C271S272000
Reexamination Certificate
active
06322621
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to converting crystalline wax, as, for example, exists in slop oil, to an amorphous form of wax, causing it to be dissolvable in, for example, crude oil at, for example, ambient temperature and maintained in a dissolved state for a prolonged period of time at ambient temperature, and more particularly, in its preferred, exemplary embodiment, to the use preferably of a chemical composition of surfactants, polymeric dispersants and corrosion & scale formation inhibitors that can, for example, recover waste hydrocarbon products (paraffin waxes, asphaltenes, and coke) from both naturally-occurring and synthetic sources, and more particularly to recover these waste hydrocarbon products for use as energy sources and to reduce environmental pollution. A number of other applications is also disclosed and claimed.
BACKGROUND ART
Waxy materials present in crude oils and in the high boiling fractions are considered to be crystalline throughout but under certain conditions may behave like a colloid. Certain wax solutions of refined products such as petrolatum, when agitated or mixed for long periods near or at the crystallizing temperature, will form a completely transparent jelly. But the same solution, when chilled rapidly with moderate agitation will precipitate a wax that can be centrifuged.
It was observed many years ago in the sweating of solid paraffins at the petroleum refinery that three crystalline forms (manifestations) of hydrocarbons are involved. These are known as “plate”, “malcrystal”, and “needle”[note, for example,
The Chemistry and Technology of Waxes
bu Albin H. Warth, published by Reinhold Publishing Corp. (New York, 1947) p. 239]. It was recognized that the relative proportion of these types of crystals not only has a relationship to the source of the crude but also to the process of handling the wax.
The members of each series crystallize similarly as either plates, malcrystals, or needles. If one type is present (plate, mal, or needle), the crystal form remains the same regardless of such factors as the amount and kind of solvent.
When crude oil is pumped from the ground and transported through pipelines, transported by ocean tankers, or stored in storage tanks on land or offshore, a large amount of heavy material separates and comes out of solution. The main component of this residue is high molecular weight paraffin waxes. In some cases the wax represents as much as 90 percent of the deposited residues.
The amounts of wax present in crude oil are to a large extent an indicator of its origin, whether the crude originated in Venezuela, Mexico, or Malaysia.
This mixture of wax, oil, sand, and water is referred to as “slop oil”, or “slop”, in the petroleum industry. The percentage of slop oil varies according to the type of crude and the conditions under which it has been transported. Usually the amount of slop oil ranges from a low of 0.5% to a high of 10%; normally, it is in the range of 2% to 5%.
For the last century and until today the only way to keep slop oil from separating from crude oil is to heat the slop oil while it is being transferred into mixing tanks with crude oil. The cost of keeping slop oil mixed with crude oil is a function of many variables such as temperature, solvent diluents, and residence time of the crude in a tank or pipeline.
The petroleum industry is plagued with the problem of having to deliver crude oil to refineries in a timely and economic manner. If a pipeline becomes plugged up or clogged because of paraffin wax precipitating out during the pumping operation, a crisis can arise. Numerous pipelines worldwide are clogged daily or monthly due to wax precipitating out of the crude oil. Daily, 50,000,000 barrels of crude oil are pumped from the ground worldwide (as of May, 1999). If 5% of the heavy residues come out of the crude oil being transported, whether by pipeline or tanker, the amount of slop oil or crude residue is 2,500,000 barrels per day. This amounts to 912,000,000 barrels per year. If 70% of this slop oil is useable crude which can be processed to refine production, then the amount of recoverable hydrocarbon equals over 640,000,000 barrels per year. At a cost of $10.00/barrel of crude oil this amounts to the recovery of $6.4 billion per year of useable hydrocarbon as either energy or petrochemical feedstock.
Another important factor in the transportation of crude oil is the corrosion of pipelines, storage tanks, and marine tankers. One of the main sites of corrosion in pipelines and storage tanks is at the point of buildup of the paraffin wax. At this site corrosion-causing chemicals become embedded in the wax and migrate to the metal surfaces. Pipelines with intrinsically large wax buildup or settling have many more corrosion problems than pipelines where the oil moves swiftly without deposition occurring. This results in increased maintenance cost and in some cases pipelines have to be shut down and crude must be rerouted to new lines as a result of both the clogged lines and corrosion. One of the main maintenance tools used to unclog crude oil pipelines is pigging the line. In this process a small device shaped like a pig with a series of scrapers on its sides is shot through the line to remove all the wax. This wax is then collected at traps located along the line and shipped to pipeline pumping stations for storage.
In storage tanks the problems associated with wax settling out are tremendous and present an extremely challenging task to refiners and terminal operators.
When crude oil remains idle and cold in a storage tank, a heavy residue forms that, over time, accumulates at the bottom of the tank and reduces useable tank volume. This residue, known as slop oil (or, slop), consists of heavy paraffinic waxes and asphaltenes which solidify in crystalline form. Slop oil is extremely difficult to remove from tanks and presents a very costly disposal problem for the refinery and terminal operator.
Traditional tank cleaning methods use a combination of heat (e.g., 60 to 75 degrees C. or greater) and mechanical agitation to force the slop oil back into solution with crude oil, so the mixture can be pumped out of the tank. In order to keep the waxes and asphaltenes in solution with the crude oil, the mixture must be kept at, for example, 75 degrees C. or greater and, in most cases, continuously circulated. The tremendous amounts of energy required to heat and circulate large volumes of dense crude oil to these elevated temperatures over long periods of time increase handling costs dramatically.
After pumping out the slop oil containing paraffin waxes and asphaltenes, the slop oil mixture must be kept hot or the wax will separate from solution, and the problems associated with slop oil will recur.
This need to use heat results in great energy cost and losses.
The preferred, exemplary chemical compound mixture described herein will perform, inter alia, the following functions:
1. Converts the wax in, for example, the slop oil from a crystalline to an amorphous material;
2. Disperses the amorphous material into a diluent solvent;
3. Acts as a demulsifier which separates any water present in the slop oil;
4. Acts as a degreaser and works at a very low activity, e.g., 0.025%; and
5. Acts as a pour point depressant.
Since it acts as a wax liquefier and converts the wax to a less crystalline and more amorphous form, the slop oil waxes are readily dispersible into the crude oil medium. Thus a colloid is formed consisting of heavy paraffin wax and asphaltene compounds dispersed in crude oil. Since the preferred, exemplary composition of matter described herein also acts as a demulsifier, all water present in the slop oil mixture separates out, as well as the sand or grit present. The heavy paraffin wax and asphaltenes are dispersed as hydrocarbon into the crude oil and can be, for example, transported to the refinery for processing or to a marine tanker or other transport for shipment, for example, at ambient temperature.
The use of the preferred, exemplary composi
Brunsman David
Nuritchem, LLC (LA)
Pugh C. Emmett
Pugh/Associates, Patent & Trademark Attys,
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