Demulsification of crude oils

The published literature on demulsification of crude oil emulsions is often based on studies of samples derived from the author s main research sponsors and so the sources... 

Figure 26 Schematic summarizrug factors that affect demulsification of crude oil and hitumen emulsions as discussed in this chapter...

Highly ethoxylated amines and diamines have been recommended for demulsification of crude oil. Combinations of quaternary ammonium salts and amines oxides are useful for foaming and silt suspension. Coco alkyltrimethylammonium chloride and bis(2-hydroxy-ethyljcoco alkylamine oxide comprise the preferred combinations. Quaternary ammonium salts, including coco alkyltrimethylammonium chloride, are useful for preparing foamed oil-in-water emulsions, which can dissolve paraffins and asphaltenes without formation damage. The pyrolized amine salts of humic acid have been used in filtrate control additives. 

Block copolymers have been reported for many years as surfactants for the demulsification of crude oil and tars [32 36]. 

Effect of salinity, temperature, water content, and pH on the microwave demulsification of crude oil emulsions. Energy Fuels, 21,1358-1364, ISSN 0887-0624. 

Further details of interfaeial rheology of crude-oil emulsion films are diseussed extensively by Menon et al. (174), Neustadter et al. (166), Mohammed et al. (175), Tambe et al. (176), and Mukherjee and Kushnick (167). They discussed the effects of demulsi-fiers on the interfaeial properties governing the crude-oil demulsification. 

Aveyard et al. systematically studied phase behavior of the specific nonionics with varied HLBs to illustrate demulsification (202). They emphasized that changing the HLBof the system and not the HLBnumber of the surfactant can promote the demulsification of crude or model emulsions. The HLBof the system of Forties crude oil emulsion with ethoxylated phenol-formaldehyde resins was... 

For these reasons the basic understanding of crude oil and bitumen emulsions and demulsification has received considerable attention. Advances in the knowledge of the physicochemical-mechanical structure of the stable emulsions and their films are being made in our laboratory and elsewhere. The films response to demulsifiers are studied in order to understand the detailed mechanisms of demulsification. This knowledge will provide a more scientific basis for formulating products. The knowledge of surfactant chemistry, the behavior in solutions, the behavior at interfaces, and interactions with the crude-oil solvent base involve a wide interplay of complex processes in designing formulations. 

If the crude is to be transported either by pipeline or tanker, chemicals such as wax inhibitors for highly paraffinic crudes, corrosion inhibitors, and lubricants are added. The excess of fluids produced in extraction of crude oils are also transported for further treatment to remove solids, water, and impurities before disposal. Demulsification treatment can also be complicated by crudes that have already been subjected to many other chemicals. 

Most chemical agents used for demulsification are preferentially oil-soluble blends consisting of HMW polymers. These blends commonly consist of (1) floc-culants (large, slow acting polymers) (2) coalescers (LMW polyethers) (3) wetting agents and (4) sol-vents/cosolvents. Some chemical structures of demulsifiers used for breaking crude oil emulsions have been listed by Jones et al. (42). Much work has been carried out in order to identify and understand the mechanisms behind chemical demulsification. Fiocco (43) concluded that the inter facial viscosity was kept at a low level when demulsifiers were present. Later on it was realized that the interfacial shear viscosity of crude oil emulsions does not have to be very low in order to ensure accelerated water separation (44). 

An understanding of such phenomena is of crucial importance in many fields. For example, a study of crude oil demulsification revealed that a critical... 

Thompson et al. [109] studied emulsification and demulsification related to cmde oil production, in particular the role of temperature. The stability of crude oil emulsions was strongly temperature-dependent and in fact demanded the presence of wax crystals. Fat crystals ranged in size from submicrometer to 50 (Am needles. In the temperature range 30-50°C, emulsion instability substan-... 

At the refinery, before distillation, the salt content is often further reduced by a second emulsification with freshwater, followed by demulsification. Crude oils with high salt contents could lead to breakdowns and corrosion at the refinery. The object of using an emulsion breaker, or demulsifier, is to break the emulsion at the lowest possible concentration and, with little or no additional consumption of heat, to bring about a complete separation of the water and reduce the salt content to a minimum. 

S. Mukherjee and A. P. Kushnick. Effect of demulsifiers on interfacial properties governing crude oil demulsification. In Proceedings Volume. Annu AICHE Mtg (New York, 11/15-11/20), 1987. 

Effect of Demulsifiers on Interfacial Properties Governing Crude Oil Demulsification... 

The demulsification data with four different demulsifiers for a crude oil-water system (Table I) support this conclusion. Structurally, the demulsifier PI and R0 are of moderate (MW 2,000-5,000) molecular weights, whereas PI and P2 are large (MW >50,000) three dimensional structures. 

The importance of rapid relaxation in demulsification effectiveness can be seen with the crude oil-water dynamic tension results with P2 (Figure 3) and 0P1 (Figure 4). As can be seen, it takes only about 60 seconds for the interface to reach its equilibrium state with the effective demulsifier P2, whereas with less effective demulsifier 0P1, the equilibrium is reached only after 800 seconds. 

DEMULSIFICATION TESTS. Demulsification tests were conducted using standard bottle test procedures to evaluate the relative performance of Thin Film Spreading Agents in coalescing emulsions of formation brine in crude oil under reservoir conditions. 

Mukherjee, S. Kushnick, A.P. Effects of Demulsifiers on Interfacial Properties Governing Crude Oil Demulsification in Oil-Field Chemistry, Enhanced Recovery and Production Stimulation, Borchardt, J.K. Yen, T.F. (Eds.), American Chemical Society Washington,... 

Demulsification. The final part of the emulsion transportation system is demulsification or breaking of the oil-in-water emulsion to recover dry crude oil. The equipment and process conditions required for this operation are the same or similar to those used for a conventional crude-oil dewatering process. 

The techniques used for demulsification of a transport emulsion may include raising the temperature of the emulsion, addition of emulsionbreaking additives, addition of diluents to reduce the viscosity of the heavy crude oil, and the use of equipment designed to promote coalescence of the crude-oil droplets. Raising the temperature of the emulsion increases the... 

The basic procedure for demulsification of a heavy-crude-oil transport emulsion then consists of the following steps ... 

In some cases it may be desirable to perform the demulsification process in two stages. In the first stage the bulk of the water may be removed at a minimum process severity, as already described. A second process stage at a higher temperature and possibly at elevated pressure may then be used for final dry crude-oil recovery. 

---