Foam-enhanced product recovery

The use of foams to remove heavy immiscible fluids such as DNAPL from soil was developed by the petroleum industry for crude oil production. Subsequently, The Gas Research Institute developed the use of foams to release and mobilized DNAPL contaminants in the subsurface. Coupled with in situ or ex situ bioremediation, foam-enhanced product recovery can, potentially, transport CHC contaminants upward in the groundwater, flius reducing the potential for driving the contamination to previously non-impacted areas. 

In addition to chemical synthesis and enhanced oil recovery, gaseous carbon dioxide is used in the carbonated beverage industry. Carbon dioxide gas under pressure is introduced into mbber and plastic mixes, and on pressure release a foamed product is produced. Carbon dioxide and inert gas mixtures rich in carbon dioxide are used to purge and fiH industrial equipment to prevent the formation of explosive gas mixtures. 

Recent research and field tests have focused on the use of relatively low concentrations or volumes of chemicals as additives to other oil recovery processes. Of particular interest is the use of surfactants as CO (184) and steam mobility control agents (foam). Also combinations of older EOR processes such as surfactant enhanced alkaline flooding and alkaline-surfactant-polymer flooding have been the subjects of recent interest. Older technologies polymer flooding (185,186) and micellar flooding (187-189) have been the subject of recent reviews. In 1988 84 commercial products polymers, surfactants, and other additives, were listed as being marketed by 19 companies for various enhanced oil recovery applications (190). 

Foams, in the form of froths, are intimately involved and critical to the success of many mineral-separation processes (Chapter 10). Foams may also be applied or encountered at all stages in the petroleum recovery and processing industry (oil-well drilling, reservoir injection, oil-well production and process-plant foams). A class of enhanced oil recovery process involves injecting a gas in the form of a foam. Suitable foams can be formulated for injection with air/nitrogen, natural gas, carbon dioxide, or steam [3,5]. In a thermal process, when a steam foam contacts residual crude oil, there is a tendency to condense and create W/O emulsions. Or, in a non-thermal process, the foam may emulsify the oil itself (now as an O/W emulsion) which is then drawn up into the foam structure the oil droplets eventually penetrate the lamella surfaces, destroying the foam [3], See Chapter 11. 

Any kind of dispersion that was useful in the reservoir may be, or may become, an undesirable dispersion when produced at a well-head. This could include used drilling fluid that has returned to the surface, conventional oil production that occurs in the form of a W/O emulsion, or foam from an enhanced oil-recovery process. These can present some immediate handling, process control, and storage problems. In addition, pipeline and refinery specifications place severe limitations on the water, solids, and salt contents of oil they will accept in order to avoid corrosion, catalyst poisoning, and process-upset problems. For pipeline transportation, an oil must usually contain less than 0.5% basic sediment and water (BS W). 

Foam exhibits higher apparent viscosity and lower mobility within permeable media than do its separate constituents.(1-3) This lower mobility can be attained by the presence of less than 0.1% surfactant in the aqueous fluid being injected.(4) The foaming properties of surfactants and other properties relevant to surfactant performance in enhanced oil recovery (EOR) processes are dependent upon surfactant chemical structure. Alcohol ethoxylates and alcohol ethoxylate derivatives were chosen to study techniques of relating surfactant performance parameters to chemical structure. These classes of surfactants have been evaluated as mobility control agents in laboratory studies (see references 5 and 6 and references therein). One member of this class of surfactants has been used in three field trials.(7-9) These particular surfactants have well defined structures and chemical structure variables can be assigned numerical values. Commercial products can be manufactured in relatively high purity. 

Since surfactin causes foaming during fermentation process, foam fractionation can be used for the recovery of surfactants. A bioprocess for the enhanced production of surfactin from a medium containing glucose and metal cations along with continuous removal of product by foam fractionation has been established by Cooper et al. which is shown in Figure 14.9. 

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