Employing a strong de-emulsifier to the oily sludge emulsions from many industries, including oil re-refining, collection points for disposable waste oils, petrochemical plants, crude oil storage, process operations, deballasting, tank cleaning services, and oil spills at sea, will augment the reclamation of saleable oil while preventing water pollution.
Recovery makes it possible to reuse valuable oil for reprocessing, reformulating, or recovery of energy through burning. The application of ALKEN® 860 reduces the amount of emulsified, oily sludge which must be trucked out, landfilled, or disposed of in other ways (all of which are costly).
The heavier hydrocarbon fractions accumulate as bottom muck to kill plant and bottom dwelling animal life when released to surface waters. Dissolved or emulsified fractions act as toxic agents depleting the oxygen content of waterbodies. Floating fractions create fire hazards, and coat banks and boat hulls. They also contaminate the water, interfering with fishing and recreation.
In municipal waste treatment systems, excessive oily wastes interrupt treatment processes, interfere with disposal plant operations, and clog sewer lines. Excess oily wastes will inhibit natural biological activities in the treatment plant, requiring the plant to re-seed their bacterial colonies with a selected, specially adapted product, such as ALKEN CLEAR-FLO® 7036, to re-activate the system. It is therefore desirable and necessary to reduce the amount of oily wastes entering the waste treatment facility.
In the case of a crude oil spill, the primary concern is with heavy hydrocarbon emulsions. This includes asphaltenes, paraffins, and tar. Usually, the higher the temperature of the oily waste, the easier it is to separate the oil from the water.
Seawater acts as a natural emulsifier, increasing the viscosity of the oil-water waste which makes it difficult to pump the waste from the barges to shore tanks for processing. Reclaimed oil, refinery crudes, and slops often contain chemical emulsions which have been stabilized by inorganic impurities, viscosity stabilizers, etc.
Tank cleaning services often obtain fuel with a high saltwater content caused by damage to the ship's hull or tanks, by the practice of a ship taking on excessive sea water as ballast without sufficiently removing it prior to refueling, or when inferior fuel is taken on. The tank cleaning operation also results in an oil-water emulsion.
An emulsion is the intimate two-phase mixture of oil and water, with one phase dispersed, as minute globules, inside the other. These minute globules are stabilized by the interfacial film, so that the globules cannot coalesce, and do not respond to gravity settling. Dual emulsions, where oil globules surrounded by water (oil-in-water) and water globules surrounded by oil (water-in-oil) coexist, may be encountered. These dual combinations are sometimes referred to as onion skin emulsions. Improper treatment of either type may invert the emulsion to the opposite type.
An interfacial film exists as a complex mixture of dissolved and colloidal matter, together with suspended solids and may be highly viscous, gelatinous and/or may possess an electrical charge. The stability of an emulsion is a function of the stabilizing agents and properties of the interfacial film, such as film viscosity and electrical charge, not of the degree of dispersion. The relative magnitude of surface tension, on each side of the interfacial film, determines the type of emulsion formed, whether oil-in-water or water-in-oil. Stability of the emulsion is also affected by the nature, and quantity, of emulsifying agents added. The interfacial film bends in the direction of the higher interface-to-liquid surface tension, enveloping the liquid on that side.
When water cannot be satisfactorily removed from the oil, the expense of disposing of this oil/water emulsion is very expensive. Decreasing the amount of oil entering the system is most economically accomplished at the source of the contamination. When the initial treatment of an oil desalination spill at sea includes mechanically skimming the water's surface, a mixture of floating oil, emulsified oil, tar balls, etc. will be taken onto the recovery barge and delivered for reclamation.
A large percentage of the water will settle out by gravity. Other processes include centrifuging, desalination, and chemical separation. The presence of solids (especially when they are finely divided), soaps, wetting or emulsifying agents, and certain solvents, can also increase the difficulty of treating oil wastes.
When the flash point of the emulsified oil is high enough that it is unlikely to create a fire hazard, steam heat, in a temperature range of 150° F to 200° F, may be injected to the emulsified oil to increase the speed of the emulsion break-up.
Heating the oil-water emulsion is not generally recommended when light fuels such as gasoline, jet fuel, kerosene, and other solvents are present and could present a fire hazard, especially aboard ship.
The major disadvantages of employing only heat and gravity for separation are:
- Poor oily sludge resolution which results in poor oil recovery.
- Oily sludge is slow to resolve. Several weeks of settling may be required.
- Storage space is tied up because more oily sludge and slop oil is on hand than can be heat treated and resolved or recovered.
- Recovered oil quality is usually poor and unsuitable for recycling to crude units or desalters.
Centrifuging can handle comparatively stable mixtures with heat. However, many emulsions, such as those occurring when an oil spill mixes with seawater, fail to yield to physical methods alone. Chemical de-emulsifiers are required.
Chemicals are effective in breaking emulsions when the interface surface tension on each side of the interface is balanced or reversed, stabilizing electrical charges are neutralized, and/or emulsifying agents are precipitated. The resulting clarification, or emulsion breaking, is believed to result from the destruction of the emulsifying agents by neutralizing or reversing interfacial film electrical charges, and in turn, by agglomeration of the precipitated floc, and adsorption of the suspended oily matter on the floc surface.
When the recovered oily hydrocarbons (gasoline, jet fuel, miscellaneous solvents, heavy fuels and tars) are especially valuable, complete separation of water and oil is essential. ALKEN® 860 De-emulsifier, added to the emulsified oil aboard the barge, aids in off-pumping operations, by de-stabilizing the dispersed water droplets, or destroying the emulsifying agents present. Alken® 860 is oil miscible, remaining with the oil while effectively releasing water and solids.
ALKEN® 860 destabilizes the oil-water interface surrounding each water particle in the emulsion, replacing the emulsifier molecules (if any), which allows the water to coalesce. The process is assisted by moderate heat, which speeds the destabilization, and, by reducing the viscosity of the oil, promotes the rapid separation of the water by gravity or centrifugation. Treatment will resolve the emulsified oily sludge into free oil, water, and settleable solids.
ALKEN® 860 is recommended for breaking emulsions in oil spill clean-up, tank-cleaning slop operations, separator skimmings, and for other difficult water oil emulsion breaking requirements. Alken® 860 is effective, consistently successful and inexpensive. The effectiveness should be considered from an overall point of view and the water layer can be cleaned up and remediated, following the emulsion breaking step, with Alken Clear-Flo® 5100 prior to its release into a natural water stream or municipal sewer system.
Although highly efficient mechanical methods are available to separate seawater from oil, ALKEN® 860 De-emulsifier is recommended to aid breaking the more difficult water-in-oil emulsions.
General Application Procedure:
A typical waste oil treatment program, utilizing ALKEN® 860 De-emulsifier, to separate water from oil, includes application of heat, and quiescent settling in large treatment tanks. The separation of the oil, water, and solids fractions occurs during the quiescent period. The general process is as follows:
- Waste oils are received, segregated by type and/or degree of treatment required, and pumped into storage tanks.
- Waste is transferred from storage tanks to treatment tanks with a centrifugal pump. ALKEN® 860 De-emulsifier is injected, in a ratio of 1 gallon to 1,000 gallons of oil (pending laboratory bench test evaluation to the contrary) with a proportioning pump (or it may be added directly to the tank) into the injection side of the centrifugal pump.
- The waste may then be passed through a steam heat exchanger, to preheat it, or the contents of the treatment tank may be heated directly, by means of steam coils. The optimum temperature range is 180° F to 200°F.
- When the waste oil has reached optimum temperature, heat should be maintained, and tank contents should be allowed to settle from 2 to 24 hours. The separated fractions of water, solids, and oil can then be drained off. (Convection currents caused by the heat may disrupt the separation during the settling period.
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