Induced Air Flotation Research Articles

Polymer flotation and activated carbon adsorption treatment for in situ tar sand process water

AbstractProcess waters collected during a Department of Energy's in situ tar sand extraction experiment near Vernal, Utah were treated by polymer assisted induced air flotation and activated carbon adsorption. The flotation process removed over 99 percent of the organic load as emulsified bitumen but did little to reduce residual toxicity in the effluents. Activated carbon adsorption was needed to remove the toxic materials from the waste stream.GC/MS analysis, using a modification of the EPA Method 625, yielded an estimated 2000 compounds in the untreated process water. Internal and recovery standards present at 10 ppm were totally obscured in the chromatogram. Flotation effluents contained 39 identified organic compounds; none of which was listed on EPA's hazardous chemicals list. Internal and recovery standards were immediately visible in the chromatogram. The GC/MS analysis was unable to determine the chemical basis for the toxic properties present.

The effect of air distribution on the induced air flotation of fine oil in water emulsions

AbstractThe induced air flotation (IAF) of a highly stabilized oil in water (o/w) emulsion has been studied experimentally in a batch column 10 cm in diameter and 150 cm in height. Column performance was strongly affected by the method of air distribution. The main variables investigated were the type of air distributor (either porous plate, single hole plate, or multi‐hole plate), initial oil concentraton (30‐600 mg/L), oil drop size distribution of feed (1.0‐30 μm), surfactant type, and gas superficial velocity. Results were successfully analyzed in terms of a first order kinetic rate model which yielded a removal rate constant (K1) that varied from 2.0 to 60.0 h−1. Corresponding total organic carbon (TOC) removal efficiencies went from 20 to 99.9 percent, illustrating the wide performance range for the flotation cell.

The Continuous Induced Air Flotation of Highly Stabilized Oil in Water Emulsions

Abstract The performance of a 12 L induced air flotation (IAF) cell has been evaluated for the continuous separation of highly stabilized oil in water (o/w) emulsions. Emulsions created for test purposes had stability rate constants (Ks) less than 0.06 h-1 and narrow droplet size distributions with mean diameters less than 20 um. Removal efficiences were expressed in terms of both total organic carbon (TOC) and oil removed. In addition, a solvent extraction/spectrophometric analysis enabled residual surfactant concentrations in the cell effluent to be determined. The main variables that affected the flotation cell operation were the following: air superficial velocity (O.5-4.O cm/s), liquid residence time (3-15 min), de-emulsifier concentration (0-160 mg solution/L), and gas distributor design. Under the best continuous operating conditions, the flotation cell removed oil droplets above 2.0 um giving oil removal rates greater than 95 percent. On the other hand, improper control of the independent variables resulted in poor cell performance with separations as low as 20 percent.

An Experimental Investigation into the Induced Air Floatation of Fine Oil in Water Emulsions

Abstract The induced air flotation (IAF) of a highly stabilized oil in water (o/w) emulsion has been studied experimentally in a batch column 10 cm in diameter and 150 cm in height. The main variables investigated were initial oil concentration (50 - 600 mg/L), oil droplet size distribution of feed (1.0 - 30 um), type of surfactant, gas superficial velocity, volume of liquid feed, and type of air distributor. Results were successfully analyzed in terms of a first order kinetic rate model which yielded a removal rate constant (K1) that varied from 2.0 to 60.0 h-1. Corresponding total organic carbon (TOC) removal efficiencies went from 20 to 99.9 percent illustrating the wide performance range for the flotation cell. In addition, an important contribution of this work was the development and recommendation of a standard method to create and quantitatively characterize test emulsions for use in experimental flotation equipment. Emulsion stabilities were determined experimentally from a static test and quantified in terms of a stability rate constant. This constant was less than 0.001 h-1 for highly stable emulsions and greater than 0.20 h-1 for unstable emulsions. For the values of K1 between these two extremes, emulsions were only moderately stable.

Oil/Water Separation by Induced-Air Flotation

Abstract The separation of oil, stabilized with an oil-soluble petroleum sulfonate, from brine solutions by induced-air flotation was studied in a continuous-flow pilot unit. The effects of inlet oil concentration, vessel residence time, air flow rate, bubble diameter, oil drop diameter, temperature, NaCl concentration, and cationic polyelectrolyte concentration were investigated. Oil drop and air bubble diameters, liquid residence time, and concentration of cationic polyelectrolyte were the most significant variables affecting overall flotation performance. Only drops larger than 2μm showed significant removal, while smaller drops were generated by the air-inducing rotor. The cationic polyelectrolyte improved flotation performance by increasing the number of large oil drops. The removal rate for each oil drop size was first order with respect to oil drop concentration, and an experimental procedure permitting determination of the first-order rate constants for removal only due to bubble/drop interactions was developed. The oil drop and air bubble diameters were the only variables which affected these rate constants. Inceasing oil drop diameter and decreasing bubble diameter increased the rate constants. Comparison of the experimental and theoretically predicted rate constants showed that the mechanism of oil-droplet removal by bubbles from 0.2- to 0.7-mm is one of hydrodynamic capture in the wake behind the rising bubbles.

Performance Evaluation of Induced Gas Flotation Machine Through Mathematical Modeling

Oil removal from produced water was studied in an induced gas flotation machine to (1) determine influential parameters in oil removal efficiency, (2) develop efficiency models, and (3) predict machine settings for optimal performance. Chemical concentration and flow rate were found to be the performance. Chemical concentration and flow rate were found to be the most important variables affecting oil removal efficiency. Introduction Standards have been promulgated recently by the U.S. Environmental Protection Agency for oil and grease content of offshore produced-water discharges. Other instances where water quality requirements must be met are (1) steam generator feedwater in thermal recovery operations, (2) flood water for low-permeability oil reservoirs, and (3) underground disposal of waste waters containing viscous oils and/or excessive suspended solids.Dissolved gas flotation cells have been used extensively as the final step in oil removal from produced water. Shell Oil Co. has used induced produced water. Shell Oil Co. has used induced gas flotation (IGF) machines in produced-water service since 1970. Degner reviewed the application of induced air flotation technology to industrial wastewater contaminant removal. He discussed the operational parameters and flotation cell design and their relation to removal efficiency. These cells now are used principally in minerals beneficiation. However, no published information was available on full-scale IGF machine processing of actual produced water. As such, it was felt that a systematic study could lead to improved design for oil/water separation. Optimal design and operation of these machines could help meet offshore discharge regulations and would result in lower operating costs for treating produced water. A program was initiated to study a full-scale four-cell experimental IGF machine. This machine was purchased from WEMCO Div. of Envirotech Corp. It was installed in Shell's Coalings, CA, oil field to (1) determine the parameters that influence oil removal efficiency in parameters that influence oil removal efficiency in IGF machines, (2) develop performance models and curves based on these parameters, (3) predict machine parameter settings for optimal performance, (4) develop a mathematical model for performance, (4) develop a mathematical model for power usage, and (5) develop economical methods of power usage, and (5) develop economical methods of operation.The study was conducted in two phases. The initial-phase test results determined parameters that significantly influence oil removal efficiency. These parameters were studied in more detail in the final parameters were studied in more detail in the final phase. This allowed regression models to be built for phase. This allowed regression models to be built for predicting oil removal percentage at each stage. predicting oil removal percentage at each stage. These models were used to generate several plots of oil removal efficiency as a function of important parameters. Optimization runs at various flow rates parameters. Optimization runs at various flow rates indicated machine settings for maximum oil removal efficiency. A total cost expression was developed by combining the total rotor horsepower model with chemical costs derived from the oil removal efficiency model for the overall machine. JPT P. 48

Biological Oxidation of Dissolved Compounds in Oilfield-Produced Water by a Pilot Aerated Lagoon

JPT Forum Articles are limited to 1,500 words including 250 words for each table and figure, or a maximum of two pages in JPT. A Forum article may present preliminary results or conclusions of an investigation that the present preliminary results or conclusions of an investigation that the author wishes to publish before completing a full study; it may impart general technical information that does not warrant publication as a full-length paper. All Forum articles are subject to approval by an editorial committee. Letters to the editor are published under Dialogue, and may cover technical or nontechnical topics. SPE-AIME reserves the right to edit letters for style and content. Introduction Despite the lack of documented adverse effects, environmental protection regulations severely restrict the offshore discharge of oilfield-produced waters. The California Ocean Plan (COP), adopted in 1972, regulates all domestic and industrial wastewaters discharged within California's 3-mile (4.8-km) zone. The 1972 COP includes strict limits on oil and grease, dissolved phenols and ammonium compounds, and toxicity to phenols and ammonium compounds, and toxicity to marine life. Federal guidelines proposed in 1975 for the offshore petroleum industry by the U.S. Environmental Protection Agency would require "zero pollutant Protection Agency would require "zero pollutant discharge" inside the 3-mile (4.8-km) zone by 1983.Besides small amounts of suspended oil, oilfield produced waters can contain dissolved organics (e.g., produced waters can contain dissolved organics (e.g., organic acids and phenols) and ammonium compounds that conventional oilfield gravity-separation and flotation processes are not designed to remove. Other processes are not designed to remove. Other water-treatment processes may be needed to remove such dissolved compounds and to allow ocean discharge of produced water to continue as an alternative to produced water to continue as an alternative to underground injection. Biological oxidation processes appear suitable for this application.The aerated lagoon is one of the most common biological oxidation processes. It is used widely for treating municipal wastewater and process water from oil refineries and chemical plants. The process is cost-competitive when sufficient land is available and is fairly resistant to sudden changes in feedwater characteristics. Water-retention times range from a few days to more than a month, and water depths range from 6 to 15 ft (2 to 5 m)Aerators are used to supply oxygen to the bacteria and may induce enough mixing in the lagoon to keep a significant portion of the bacteria in suspension. These bacteria then are carried out of the lagoon and contribute to suspended solids in the effluent. Therefore, clarification of lagoon effluent may be required to comply with suspended-solids limits.This paper describes a 19-month field pilot study conducted in southern California that demonstrated for the first time the feasibility of the aerated lagoon for biotreating oilfield-produced water. Description of Pilot Plant The two-stage pilot lagoon (Fig. 1) consisted of two 500-bbl (80-m3), plastic-lined steel tanks in series, each filled with 375 bbl (60 m3) fluid. Stage 1 was primarily for oxidizing suspended oil and dissolved organic compounds; Stage 2 was for oxidizing dissolved ammonium compounds. Each stage was aerated by a variable-speed, "egg-beater" type of mixer. Feedwater flowed continuously to the pilot plant, with each stage independently controlling the water-retention time.Feedwater to the lagoon was a mixture of produced waters from the Carpinteria and Summerland state leases after oil removal by induced-air flotation. The total dissolved solids (TDS) content of the mixture was 20,000 g/m3 . About 10 g of Na3PO4 (as P) was added per cubic meter of feedwater, to ensure adequate (though per cubic meter of feedwater, to ensure adequate (though not necessarily optimum) phosphorus for microbial growth. JPT P. 241