Modelling continuous foam fractionation with reflux

An equilibrium stage approach is taken to modelling the performance of a continuous foam fractionation column with reflux. Such an approach has been facilitated by recent developments in the understanding of pneumatic columns of foam that allow liquid rates within the rising column of foam to be predicted with confidence. It is shown that the recovery of surfactant into the product stream increases monotonically with increasing reflux ratio but this is at the expense of reduced product rate.     

Experimental investigation of foam performance in the presence of crude oil

The foam performance in the presence of oil plays an important role in foam application in enhancing oil recovery. The present study systematically investigated the effect of oil type, oil content, surfactant type, surfactant concentration, alkane chain length, salinity, and polymer concentration on foam performance in both the absence and presence of oil. The results showed that oil viscosity and oil density as well as oil component all contributed to foam performance in the presence of oil. Within a certain oil content, both light oil and heavy oil had a positive effect on foam, but heavy oil had a higher tendency to stabilize the foam. The order of foam performance by different surfactants was changed by the oil. It is noteworthy that heavy oil is detrimental to sodium dibutyl naphthalene sulfonate (BM) foam. Light oil can improve foam performance while heavy oil can harm foam in some specific cases. Lower salinity, longer alkane chain length, higher surfactant concentration and the presence of a polymer all benefited foam in the presence of crude oil.     

Process intensification of foam fractionation by successive contraction and expansion

Enrichment in foam fractionation is enhanced by reducing the liquid flux while maintaining the flux of bubble surfaces. We show that it is possible to do so in a continuous foam fractionation column by inserting a plate into the foam layer and forcing the foam through a narrower tube (foam riser) mounted at the centre of the plate. A 35% reduction in liquid flux was observed by using a single plate-foam riser assembly in a foam stabilised by 0.52 g/L sodium dodecyl sulphate solution, and the liquid rejected from the foam due to the presence of the foam riser had the same concentration as the feed solution. However, due to the nature of the adsorption isotherm of SDS, the enrichment enhancement measured in the experiments hererin was modest. The mechanism of the foam riser plate was explained by invoking recent theoretical studies on pneumatic foam. It was demonstrated that the reduction in liquid flux was affected by sudden expansion of the flow area causing a rejection of interstitial liquid to the top of the plate and extracted, whence it was recycled back to the feed. Preliminary experiments on the effect of liquid pool depth and foam height on interfacial adsorption were also carried out to demonstrate that the insertion of the plate does not affect the adsorption of the target substance to the bubble surface in the current system. It was found that equilibrium could be achieved within 0.2 m of liquid pool depth or foam height, however the equilibrium surface excess on a rising bubble in the liquid pool is roughly 51% of the equilibrium value on a quiescent interface, while that in the foam layer is roughly 73% of the equilibrium value on a quiescent interface.     

Removal of trace Cu from aqueous solution by foam fractionation

A system for removal of Cu²⁺ from aqueous solution by foam fractionation is proposed. The effects of pH, gas flow rate, surfactant concentration and froth/solution ratio on the removal rate and the enrichment ratio were studied to optimize the conditions. The results show that the removal rate increased with gas flow rate decreased, surfactant concentration increased and the froth/solution ratio increased, and was higher at pH4.0-5.0 than at other pH value. The optimum separation conditions were pH5.0, 200 mL/min of gas flow rate, 0.15 g/L of surfactant concentration and 1.1 of froth/solution ratio. Under the optimum conditions, the removal rate was 97.2% and the enrichment was 53.0.     

Development of bubble column for foam separation

The foam separation of metal in model wastewater is performed by using two different bubble columns in a continuous operation mode. The equipment and operation conditions are changed, and the foam flow rate and metal concentration in foam flow are measured. The foam flow ratio (the ratio of foam flow rate to the inlet one) increases with increasing gas velocity, with decreasing liquid velocity, with decreasing foam layer height and with decreasing metal concentration in model wastewater. Metal enrichment (the ratio of metal concentration in foam flow to that in inlet flow) shows the reverse tendencies. When a draft tube is inserted in the bubbling layer, the foam flow rate decreases. The enrichment is strongly governed by the foam flow ratio. Since the foam flow ratio is adjusted by means of the equipment and operation conditions, the metal concentration in foam flow is controlled to be a desired value. This paper was presented at The 5th International Symposium on Separation Technology-Korea and Japan held at Seoul between August 19 and 21, 1999.     

Effect of ionic strength on the foam fractionation of BSA with existence of antifoaming agent

Foam fractionation is an economical and effective technology for protein concentration and separation. However, the presence of antifoaming agent in the fermentation broth restricts the application of this technology. In this paper surfactant-assisted foam process was conducted with a mimic system using bovine serum albumin (BSA) as target protein, polyoxypropylene polyoxyethylene glylerin ether (PGE) as antifoaming agent and cetyltrimethyl ammonium bromide (CTAB) as surfactant, putting emphasis on study of the effect of ionic strength on the separation process. The experimental results showed that with ionic strength increasing, the mixed-system foaming ability gradually increased. Under the conditions of C_BSA 100 mg/L, C_CTAB 20 mg/L, C_PGE 8 mg/L and pH 7.4, feed liquid 250 mL, air flow rate 100 mL/min at 25 °C, the maximum enrichment ratio of BSA reached 27 when the ionic strength was 0.0500 mol/kg and the maximum recovery of BSA reached 80.5% when the ionic strength was 0.1696 mol/kg. Furthermore, K⁺ had better separate efficiency than Na⁺ under the same ionic strength.     

Separation of aromatic components from light cycle oil by solvent extraction

To improve the versatility of light cycle oil (LCO), separation of aromatic compounds from LCO by solvent extraction was investigated. LCO was analyzed to identify 35 components: 19 aromatics and 16 alkanes. The batch liquid–liquid equilibrium extraction of LCO was performed using furfural, sulfolane, and methanol as extraction solvents. In each solvent, the aromatics present in LCO were selectively extracted relative to the alkanes. The separation selectivities of aromatics relative to alkanes were larger in sulfolane than in the other solvents. Among the aromatic components, di- and tricyclic compounds were selectively extracted relative to the monocyclic ones.     

Milk fat fractionation by solid-layer melt crystallization

The layer crystallization process has the potential to produce the same milk fat fractions as can be obtained by the suspension crystallization process. That is, milk fat fractions with solid fat content melting profiles similar to those obtained by suspension fractionation can be produced with this technique. The fatty acid profiles as well as the melting enthalpies of the different fractions confirm the separation of milk fat by the layer technique. Furthermore, there is potential to improve the results of separation presented in the first part of this paper. The two sources of improvement, temperature control of the process and controlled nucleation, lead to (i) a smooth crystalline layer with a low amount of entrapped mother liquor, contrary to the layers composed of agglomerated needles, and (ii) a good quality of attachment of the crystalline layer to the cooled surface. Moreover, the product quality can be increased using sweating as a postcrystallization step. “Sweating by warm gas” seems to have a better outlook concerning handling and controlling the process than “sweating by warm tube” because sloughing of the crystal layers can be avoided. Further investigations of the mass ratio of sweating fraction and amount of product as well as the aspect of energy consumption will determine the technical feasibility of solid-layer crystallization for fractionation of milk fat.     

Improving the cold flow properties of biodiesel from waste cooking oil by surfactants and detergent fractionation

The use of surfactants and detergent fractionation to improve the cold flow properties of biodiesel from waste cooking oil (BWCO) was investigated. The effect of five types of surfactants, including sugar esters (S270 and S1570), silicone oil (TSA 750S), polyglycerol ester (LOP-120DP) and diesel conditioner (DDA) on the reduction of the cold filter plugging point (CFPP) of the BWCO, was evaluated, with the greatest reduction to the CFPP of the BWCO (from −10 °C to −16 °C) being was achieved by the addition of 0.02 wt% of polyglycerol ester (LOP-120P). Detergent fractionation of the BWCO was performed by first mixing partially crystallized biodiesel with a chilled detergent (sodium dodecylsulfate) solution accompanied by an electrolyte (magnesium sulfate), and then separating the mixture by centrifugation to obtain the BWCO liquid. An orthogonal experimental design was utilized to investigate the effects of the various parameters on detergent fractionation. The optimal parameters, as obtained by range analysis, were as follows: detergent loading 0.3 wt%, electrolyte loading 1.0 wt%, and water loading 150 wt%. The CFFP of the liquid biodiesel from waste cooking oil (LBWCO) was −17 °C with a yield of 73.1% when the detergent fractionation was performed under these conditions. A limited number of biodiesel physical and chemical properties were analyzed before and after the addition of surfactants and detergent fractionation.     

Separation of reaction mixture after ethanolysis of rapeseed oil

Various effects on the separation of a raw reaction mixture after the ethanolysis of rapeseed oil were investigated. Water addition, initial temperature of separation, centrifugation, ionic compound addition and time effects affecting the concentrations of potassium and free glycerol and the yield of the ester phase were revealed. Centrifugation has the most positive effect. Finally, a correlation between the concentrations of potassium and free glycerol was found.     

Pilot-scale supercritical carbon dioxide extraction and fractionation of wheat germ oil

There is a need for the development of new processing techniques to facilitate vegetable oil extraction and refining while sustaining the nutritional components naturally present in edible oils and reducing the adverse impact of oil processing on the environment. In this study supercritical carbon dioxide (SC−CO₂) extraction and fractionation techniques were examined as alternative methods to obtain wheat germ oil (WGO) of high quality and purity. It was shown that the SC−CO₂ extraction technique is effective in extraction of WGO. There was no significant difference in the FA composition of SC−CO₂- and hexane-extracted WGO. Both hexane-and SC−CO₂-extracted WGO were rich in α-tocopherol. Moisture content of the SC−CO₂-extracted oil was higher than that of the hexane-extracted oil. Solvent/feed ratio had a significant effect on the SC−CO₂ extraction yields. This study demonstrated that supercritical fluid fractionation was a viable process to remove FFA efficiently from both hexane-and SC−CO₂-extracted WGO while retaining bioactive oil components in the final product.     

Characterization of foam flow in horizontal pipes by using two-flow-regime concept

Foam has been widely used in numerous scientific and engineering applications. Although foam has relatively low fluid density because of high gas content, it can exhibit a viscosity value enormously higher – often several orders of magnitude higher – than that of bulk gas or liquid phase. Since foam typically exists as a complex fluid system with internal gas bubbles and external liquid phase, understanding and characterizing its flow behavior is very challenging.The objective of this study is to investigate the characteristics of foam rheology in horizontal pipes in a wide range of experimental conditions—two different pipe materials (stainless steel and nylon pipes with about 0.5 in in outer diameter and 12 ft in length), three surfactant formulations (Cedepal FA-406, Stepanform-1050, and Aquet-944), and three surfactant concentrations (0.1, 0.5, and 5 wt%). The experimental data can be collected in terms of (i) pressure measurements at several positions along the pipes and (ii) visual analysis of bubble size and bubble-size distribution during the shear flow. The concept of “two foam-flow regimes” consisting of high-quality regime and low-quality regime is at the heart of interpreting the experimental outcome.The experimental results showed that there were two distinct high-quality and low-quality foam flow regimes which could be identified by both pressure responses and direct visual observations. The results further showed that the high-quality regime was characterized by unstable and oscillating pressure responses represented by the repetition of fine-textured foam and free gas (i.e., slug flow), while the low-quality regime was characterized by stable pressure responses represented by either the flow of fine-textured foams (i.e., plug flow) or the flow of upper-layer foams and lower-layer liquid (i.e., segregated flow). These two regimes, separated by a locus of f_g^? in the contour plot, were shown to have different sensitivities to the change in gas and liquid velocities: (1) foam rheology in the high-quality regime was dependent upon both gas and liquid velocities because the lengths of fine-textured-foam and free-gas sections were altered to adjust to the new flow conditions, and (2) foam rheology in the low-quality regime was primarily dependent upon gas velocity because of the development of fine-textured foams with increase in shear rates, and was relatively independent of liquid velocity because of lubricating effect and drainage effect.The implication of these experimental findings is discussed for applications such as foam-assisted underbalanced drilling processes and foam fracturing treatments in the petroleum industry.     

Separation and determination of cadmium in water by foam column prior to inductively coupled plasma optical emission spectrometry

The sorption profile of cadmium (II) ions from aqueous iodide media onto procaine hydrochloride (PQ⁺·Cl⁻) treated polyurethane foams (PUFs) solid sorbent was studied. PQ⁺·Cl⁻ treated PUFs solid sorbent was found suitable and fast for Cd²⁺ uptake as [CdI4]_aq²⁻. Thus, removal of Cd²⁺ at trace levels by the sorbent packed columns was achieved. The sorbed Cd²⁺ species onto packed column were recovered with HNO₃ (10.0 mL, 1.0 mol L⁻¹) prior determination by inductively coupled plasma-optical emission spectrometry (ICP-OES). Plot of Cd²⁺ ions concentration was linear in the range 0.05–15 μg L⁻¹. The limits of detection and quantification of Cd²⁺ were found 0.01 μg L⁻¹ and 0.033 μg L⁻¹, respectively. Such limits could be improved to lower values by retention of Cd²⁺ species from large sample volumes of the aqueous phase at the optimized conditions. The relative standard deviation of the packed column for the extraction and recovery of standard aqueous solutions (0.1 L) containing 1.0 and 5.0 μg L⁻¹ (n = 3) of Cd²⁺ ions at flow rate of 5.0 mL min⁻¹ were 1.98 and 2.9%, respectively. The method was validated by analysis of Cd in certified reference materials (CRMs) IAEA-Soil-7 and TMDW water and wastewater samples.     

制备凝胶色谱在聚氨酯匀泡剂组成分析中的应用

用制备凝胶渗透色谱分离聚氨酯匀泡剂的混合组分,并对分离的组分进行了凝胶色谱、红外光谱等分析。对两个混合组分的聚氨酯匀泡剂的剖析结果进行了讨论。     

PS挤塑泡沫板综述

本文介绍了PS挤塑泡沫板作为保温材料的基本性能，加工工艺路线以及在我国的现状。     

Urea complexation for the rapid, ecologically responsible fractionation of fatty acids from seed oil

Urea complex formation is a classic method for fractionating fatty acids from seed and other oils. The method’s simplicity, ease of scaling, and ecological friendliness suggest its reevaluation in regard to modern fractionation challenges. In keeping with this, a simple, quick, inexpensive, robust, and environmentally friendly procedure was developed for reducing the saturated free fatty acid (FFA) content of saponified low-erucic acid rapeseed oil (LEAR). The process involves formation of a homogeneous 65°C solution of FFA and urea in 95% ethanol (5% water), followed by cooling of the resultant urea complex slurry to room temperature. The urea complex and liquid phases are separated by gravity filtration, and the urea isolated in each phase is removed by extraction with 60°C water. Saturated LEAR oil FFA preferentially formed urea complexes easily separated from the noncomplexed, mostly unsaturated FFA, the main product of interest. The effects of single- vs. double-stage fractionations and several other variables (component mass or volume ratios, temperature, ethanol solvent to water ratio) were preliminarily evaluated. Results demonstrated the robustness, reproducibility, and simplicity of the method.     

Quantitative NMRI studies of transient washwater addition to rising foam

For the first time, NMR Imaging has been used to provide non-invasive quantitative data for transient washwater addition to rising foam. Washwater is routinely added to flotation froths to aid rejection of unwanted gangue material from the concentrate stream. The results show that washwater added to a mature foam (i.e., one that has attained its equilibrium liquid fraction) travels down the column, whereas washwater added to an immature foam travels up the column. This observation has important implications for flotation plant practise; washwater added too early at start-up will not aid gangue rejection but will instead merely lead to a wetter concentrate stream. This is explained theoretically in the context of the Hydrodynamic Theory of Rising Foam.     

Separation and characterization of bitumen from Athabasca oil sand

Separation and chemical analysis was investigated using bitumen samples from Athabasca oil sand in Alberta. Fractionation according to solubility and polarity has been used to separate bitumen into its fractions. The solvent de-asphaltening was performed by n-pentane solvent (solubility fractionation), and the polarity fractionation using Fuller’s earth allows maltene to separate into SARA components (saturates, aromatics, resins and asphaltenes). The SARA components are analyzed comprehensively using elemental analysis (EA), Fourier-transformed infrared (FTIR), ultraviolet-visible spectroscopy (UV-vis), high performance chromatography (HPLC) and thermogravimetric analysis (TGA). EA (C, H, N, S), heavy metals (Ni, V) concentrations, FT-IR and UV-vis tests provided the explanation of chemical composition. From IR spectra, maltene and saturates/aromatics (sat/aro) contained more aliphatic compounds than resin or asphaltene. Also, IR spectrum of sat/aro was similar to crude oil and VGO (vacuum gas oil). Different UV signal data clearly indicates the contribution of aromatic constituents in the fractions. Using optimized analysis conditions of HPLC, we successfully separated the peaks for bitumen and its fractions. The characteristic peak pattern of SARA (saturates, aromatics, resins, asphaltenes) fractions was observed, and also the peak pattern of sat/aro was similar to that of crude oil and VGO. However, TGA results revealed that thermal behavior for sat/aro was similar to that of crude oil but different from that of VGO. Also, from the comparison between decomposition temperature of TGA and boiling point, their correspondence was found.     

小桐子油生物基多元醇的合成及其在硬质聚氨酯泡沫中的应用

通过对小桐子油双键进行环氧化、羟基化反应,成功制备出小桐子油生物基多元醇,并在硬质聚氨酯泡沫中进行了应用。小桐子油较佳环氧化工艺条件为：甲酸用量为理论用量的0．5倍、双氧水用量为理论用量的1．5倍、催化剂质量为小桐子油质量的2％,反应温度60℃,反应时间8h;较佳的羟基化条件为：n（二异丙醇胺）：n（环氧小桐子油）=1．3：1、反应温度155℃、反应时间6h;泡沫应用结果表明：在实现替代石化类聚醚多元醇不超过45份的情况下,制得的硬质聚氨酯泡沫与采用石化类聚醚多元醇制得的泡沫性能相当。     

Supercritical carbon dioxide fractionation of fish oil fatty acid ethyl esters

Fractionation of fish oil fatty acid ethyl esters was investigated with the aim of obtaining a lipid fraction enriched in ω-3 fatty acids and with a suitable EPA/DHA ratio. The results obtained highlight the possibility of modifying the original fatty acid ethyl esters concentration by optimizing the extraction conditions in terms of pressure, temperature, and supercritical carbon dioxide flow rate. Supercritical fluid fractionation (SFF) appears to be a useful processing technique for changing the composition of lipids in order to obtain high value functional products. The use of proper fractionation temperatures and pressures along the column influenced the solvent-to-feed ratio to obtain fractions with suitable composition for market requirements.