Foaming Solution Research Articles

Quantitative Evaluation of Imbibition Damage Characteristics of Foaming Agent Solutions in Shale Reservoir

Shale reservoirs are characterized by extremely low porosity and permeability, poor connectivity, and high content of clay minerals. This leads to the reservoir being vulnerable to imbibition damage caused by foaming agent solutions during foam drainage gas recovery. It results in the decrease of reservoir permeability and the reduction of gas well production and ultimate recovery. Therefore, as the most commonly used foam drainage gas production, it is particularly important. This study is structured as follows. First, we analyze and evaluate the characteristics of shale reservoirs within the target area, and that of mineral composition and microscopic pore throat structures. Second, we study foaming agent types and two types are selected to be applied in subsequent sensitivity tests. Simultaneously, the nuclear magnetic resonance (NMR) method was used to study the microscopic characteristics of reservoir damage and imbibition damage of shale, caused by the impact of foaming agent solutions during the foam drainage and gas recovery processes. Finally, it is concluded that the degree of damage to the core permeability is minimized when the concentration of foaming agents is 0.4–0.6%. A trend has been established for increased damage to the cores with increasing exposure time. Additionally, this study provides technical guidance for damage evaluation and reservoir protection in shale reservoir exploitation.

Spreading behavior of firefighting foam solutions on typical liquid fuel surfaces

AbstractA series of experiments was performed to investigate the spreading behavior of firefighting foam solutions on liquid fuel surfaces. The spreading coefficients of six kinds of aqueous film‐forming foam solutions and one fluorine‐free foam solution on the surface of four liquid fuels, namely, cyclohexane, diesel, n‐heptane, and ethanol, were calculated on the basis of surface and interfacial tension. Spreading behavior was studied systematically using a high‐speed camera, and then the relationship between spreading behavior and spreading coefficient was analyzed. Furthermore, the spreading area and spreading rate of different foam solution droplets on liquid fuel surfaces were studied in depth. The spreading amount of the foam solution droplets on the liquid fuel surfaces was measured. Four typical spreading phenomena, namely, spreading, suspension, dissolution, and sinking, of AFFF solutions on liquid fuel surfaces were identified. Moreover, a positive spreading coefficient did not necessarily lead to the formation of an aqueous film. The spreading area, spreading rate, and spreading amount were not proportional to the spreading coefficient. During the evaluation of the spreading property of firefighting foam, the spreading coefficient, spreading rate, and spreading amount must be focused on instead of only the spreading coefficient.

Preparation and transdermal effect of a tip-loaded bubble-soluble microneedle

As a new transdermal drug delivery technology, bubble microneedle could achieve painless and precise drug delivery, which has attracted great attention from researchers. In order to improve the utilization rate of the drug carried by microneedle, we proposed a method for preparing a tip-loaded bubble-soluble microneedle. During the molding process of the microneedle, air bubbles were formed in the needle body, and the drug was concentrated on the needle tip. The preparation process of the bubble microneedle was optimized. The effects of foaming agent concentration, drying temperature, and solution viscosity on the forming of bubble microneedles were explored. Furthermore, the transdermal effect of the product was analyzed. The experimental results showed that the bubble microneedle forming process was stable, with the forming rate above 90% and the forming cycle shortened to about 4 h. The drug was mainly concentrated on the tip of the microneedle, with a length of 180 μm, and the length of the bubble was 250 μm. Moreover, the microneedle array can create microchannels on the mouse skin, and the needle bodies can be rapidly dissolved within 5 min. The bubble microneedle could rapidly release about 48% of the drug within 1 min and about 91% of the drug within 5 min. The bubble microstructure of the microneedle array hindered the diffusion of the drug to the substrate, which improves the utilization rate of the drug. This study provides a technical basis for the practical application of microneedle for transdermal drug delivery.

Impacts of oil components on the stability of aqueous bulk CO2 foams: An experimental study

Study of foam stability in the presence of oil components is mainly devoted to the impacts of aliphatic components like short- and long-chained alkanes. In this study, several experiments, including critical micelle concentration (CMC) determination, IFT measurement, high pressure bulk foam stability as well as foam texture visualization and analysis have been designed and performed in the presence of various oil solution samples to explore the impacts of aromatic components and compare them with the impacts of aliphatic components on CO2 foam stability. Alpha-Olefin-Sulfonate (AOS) surfactant solutions with different concentrations of surfactant in the presence of various synthetic oil solutions comprising toluene and n-heptane were prepared to compare the interfacial behavior and performance of the surfactant solutions containing aromatic and aliphatic components with regards to foam stability. The results revealed that, due to higher micellar solubilization of the n-heptane as the aliphatic component compared to toluene, surfactant surface activity would be more detrimentally impacted by the presence n-heptane. Employing electrical conductivity measurements, it was observed that the CMC of surfactant solutions with addition of 1 vol% of toluene and n-heptane to the surfactant solution, increased by 15 and 19 times, respectively. Increase in surfactant concentration in solutions above CMC with no oil compound, did not show any promising improvement on foam stability. However, in the presence of different oil additives, increase in surfactant concentration from 0.1 wt% to 0.5 wt% resulted in the increase in foam stability by 45% on average measured by foam half-life time where the foam was generated by aeration method. This observation was further validated by the decrease in IFT, measured by spinning drop method, from the average range of 1.4 mN/m for different oil solutions to 0.6 mN/m by increasing surfactant concentration from 0.1 wt% to 0.5 wt%. IFT measurements between surfactant solutions and different oleic samples with oil components suggested that the presence of higher n-heptane in oil solutions resulted in higher IFT. Similar behavior was observed in foam stability measurements. Generally, addition of oil components to the foam solution resulted in lower foam stability. That is, higher oil content concentration would result in lower foam stability. Also, the presence of n-heptane had more detrimental impacts on foam stability compared to the presence of toluene. The texture of the resulted foam in the presence of toluene and n-heptane was visualized. It was observed that the texture of the foam generated in the presence of toluene had smaller bubble size compared to that in the presence of n-heptane. Also, it was observed that as time passes, oil droplets migrate from lamellae to the plateau borders, resulting in lamellae thinning and foam bubble coarsening and rupture.

Determination of factors effecting the properties of water-air microdispersion

The article presents the results of laboratory studies on the effect of the liquid-gas ratio and the foaming agent type on the average water-air micro dispersion size obtained from the foaming agent solution. The size of microbubbles significantly effects the efficiency of flotation and depends on the type and concentration of foaming agent used for their production. A generator was used to obtain water-air micro dispersion. The works were performed to work out the water-air micro dispersion parameters of at different liquid-gas ratio and different performance of the generator. The following foaming agents were used as objects of research: sodium butyl aero flot (BTF), flotanol C-7, butyl triethylenetetramine (B-TETA) at a concentration of 0.5 g/dm3. It has been established, that the optimal phase liquid-gas ratio was 1:1, the optimal capacity of the generator was 6-7.2 dm3/h with an average particle size of air-water micro dispersion- 33-41 mm for BTF solution, 103-107 mm for C-7 solution, 90-93 mm for B-TETA solution. The type of foaming agent used in flotation effects the size and stability of microbubbles. It is established that the flotation agents can be arranged in the following line with respect to their ability to create micro dispersion: IIBK→Senfroth 580→B-TETA→OPSB→Flotanol C-7→T-92→BTF. The best results are shown by BTF that creates micro dispersion of 43-58 μm (t 20-40 °С) and stability of 80 sec with concentration of 0.5 g/dm3.

Oligolayered Co@MXene with a Co···SO3 cation-π bridge for ultra-rapid catalytic oxidation of a novel “forever chemical” OBS

Sodium p-perfluorous nonenoxybenzene sulfonate (OBS) as a novel alternative to perfluorooctane sulfonate (PFOS), belongs to the family of per- and polyfluoroalkyl substances (PFASs). We demonstrated that Co-based oligolayered MXene (Co@o-MXene) achieved the complete oxidation of OBS during catalytic ozonation with peroxymonosulfate (PMS). The optimized catalyst exhibited 78.5% OBS oxidation in only 2 min, and the oxidation route was thoroughly investigated by Fukui function calculations and QTOF-MS/MS analysis. However, within the fluoroprotein (FP) foam solution, high TOC removal was performed via the newly designed two-stage ozonation process. Systematic studies indicated that OBS can donate electrons through a Co···SO3 cation-π bridge on the surface of o-MXene/PMS accompanied by the generation of reactive oxygen species (ROS), the strong adsorption energy (Eads) value of PMS, enhanced total density of states (TDOS) and uneven electron density in this reaction system. This work extended the potential of newly developed MXene family materials to decompose PFAS.

Evaluating the effect of different foam mat drying methods on the properties of orange beverage powder

Foam mat drying is a simple method used for food preservation. The purpose of this study was to evaluate the effect of different foam mat drying methods on the properties of permeate-based orange beverage powder. In order to prepare the beverage foam, egg white and basil gum solution were used according to the experimental design and were mixed in an electric mixer at the highest speed for 6 min. The samples with 3 and 5 mm thickness were dried at different oven temperatures (45, 65, and 80°C) and at different microwave power (360, 600, and 900 W). Various properties of the beverage powder including moisture content, water activity, solubility, water binding capacity, rehydrating the powder, hygroscopy, flowability, pH, color, differential scanning calorimetry, and Fourier transform infrared spectroscopy characteristics were investigated. Almost all the properties indicate an increasing trend with increase in the drying temperature. Samples with 3 mm thickness showed higher solubility. Novelty impact statement Different drying temperatures had a significant effect on the properties of the beverage powder at the statistical level of 5%. Increasing the drying temperature showed a significant effect on the properties of the beverage powder. Foam thickness showed a significant effect on the properties of the beverage powder.

Influence of admixtures on the characteristics of aqueous foam produced using a synthetic surfactant

Foam characteristics, including density, stability, and texture, influence the properties of end products like foamed concrete. The present work investigates the individual and combined influence of xanthan gum and low-cost sodium-based admixtures (NaOH, NaCl, and Na2CO3) on the viscosity of sodium lauryl sulfate (SLS) foaming solution and the foam characteristics. Where xanthan gum induced its characteristic pseudo-plastic behavior to the foaming solution, the addition of sodium-based admixtures did not affect the Newtonian behavior of the SLS solution. The addition of sodium-based admixtures elevated the critical turbidity and Krafft temperature of the surfactant solution. Xanthan gum substantially reduced the liquid drainage and improved stability to a great extent. However, the increment in foam density was more gradual with increasing xanthan gum dosage, following an increase in lamella thickness. Sodium-based admixtures significantly increased the density of foam while reducing the bubble sizes. Further, the SLS solution admixed with xanthan gum and sodium-based admixture resulted in foam with properties intermediate to the foams stabilized with individual admixtures. The resulting foam had a higher density and a smaller mean bubble size than unstabilized or xanthan gum stabilized foam. In contrast, the stability was more increased compared to unstabilized or sodium-based admixture stabilized foam.

Insights into the flow behaviour of the pre-generated polymer enhanced foam in heterogeneous porous media during tertiary oil recovery: Effect of gravitational forces

Over the past few decades, foam flooding has emerged as a decent option for diverting flow from high permeable layers toward dense layers. Here, a visualization study of the conventional foam and polymer enhanced foam (PEF) behavior in the heterogeneous porous media is presented and the PEF performance in horizontal and vertical injection modes is evaluated. A heterogeneous porous medium made of transparent plexiglass packed with two different layers of glass beads to attain a heterogeneity ratio of 4:1 was used in various flooding experiments. The results of dynamic tests in the absence of oil showed that the presence of polymer in the foaming solution increases the flow resistance of foam in the porous medium and prevents foam fingering in the low-permeable layers. Horizontal oil displacement experiments showed that PEF flooding has an excellent plugging capacity and oil recovery increased by 72.5% of water flooded residual oil (S*or), which was 19.1% more than that of conventional foam injection. Comparison between vertical and horizontal PEF flooding proved that due to the positive gravity effect, the performance of PEF in vertical mode was better than that in horizontal mode, and the recovery factor increased to 78.3% water-flooded residual oil.

Experimental Study on Application Performance of Foamed Concrete Prepared Based on a New Composite Foaming Agent

The performance of foaming agent plays a key role in the forming quality of foamed concrete. In order to overcome the limitation of single composition of traditional foaming agent, this paper adopts the research method of multicomponent composite combined with the foaming theory and preparation technology of foaming agent, a new protein composite foaming agent was prepared using a mixture of anionic surfactant (SCA), nonionic surfactant (APG), and foam stabilizer (AR), and then, the effects of different surfactant mass ratios and foam stabilizer concentrations on the properties of composite foaming agent were studied by a series of tests. The results show that the optimal mass ratio of surfactants is mAPG: mSCA = 2 : 1, and the optimal concentration of foam stabilizer is 0.5 g/L, which verified that the self-made composite foaming agent system in this paper has the advantages of strong foaming ability, excellent foam stability, and low cost. In addition, foamed concrete was prepared on the basis of the optimized composite foaming agent system, and the influence rules of different foaming agent solution volumes, water-cement ratios, and diatomite dosages on the performance of foamed concrete were revealed through laboratory tests and SEM images. At the same time, the optimal ratio of each component required for the preparation of high-quality foamed concrete was further obtained by using the response surface analysis of compressive strength. The research results provide an important reference for the preparation of high-performance foamed concrete and corresponding foaming agent, which is beneficial for solving the disadvantages of poor foam stability in the existing foaming agents and improving the application level of foamed concrete in engineering construction.

Fire Test Performance of Eleven PFAS-Free Class B Firefighting Foams Varying Fuels, Admixture, Water Types and Foam Generation Techniques

The firefighting performance of eleven PFAS-free firefighting foams was evaluated using different fuels (Jet A1, commercial heptane and diesel) and types of water (freshwater and synthetic sea water). Moreover, different firefighting foam generation techniques and application methods were evaluated. The firefighting foams were generated as aspirated foams or as compressed air foams (CAFs). The results for CAF showed a higher performance, with respect to extinction time and burn-back resistance, compared to the foam generated using a UNI 86 nozzle. The CAF was not optimised, indicating a further potential of this foam generation technique. The results indicate that the time to fire knockdown decreases with decreasing foam viscosity. The heat flux was shown to be small, although the entire fuel surface was involved in the fire. The tests showed a dependence on fuel type; different products performed differently depending on the fuel. Tests using sea water showed that addition of salt to the foam solution generally prolonged the extinction time, although for one of the firefighting foams a shorter extinction time was observed. Out of the eleven evaluated PFAS-free products there was no product that outperformed the rest. None of the products in the study met the fire test performance requirements in all the referenced standards. Instead, the products seem to have different niches where they perform best e.g., with different types of fuel or water.

Доминирующая роль самоэмульгирования в процессе контактного взаимодействия пены с углеводородами

Introduction. The results of a series of experiments on the interaction of fire extinguishing foam with various hydrocarbons are described, which make it possible to understand the processes that affect the extinguishing efficiency. Goals and objectives. The purpose of this work was to explain self-emulsification during mass transfer as a possible dominant factor in the process of contact destruction of fire-extinguishing foam by hydrocarbons. For this, the following tasks were set: - to experimentally establish the possibility of self-emulsification during mass transfer in contact of foaming agent solutions with hydrocarbons; - to show the relationship between the stability of the foam and the stability of the emulsion formed in the foam films; - to establish the effect of foam parameters (multiplicity) on the possibility of stabilization (or destruction) of foams under the action of the resulting emulsion. Research methods. The main research method in this work was to observe the stability of the foam on the surface of hydrocarbons at different temperatures. Results and discussion. The paper presents the results of experimental studies showing that the contact of solutions of the investigated foaming agents with hydrocarbons leads to the spontaneous appearance of an emulsion. In the case of using aromatic hydrocarbons, this process is more intensive than for saturated ones. For solutions of a foaming agent in the form of a thin film, the process of self-emulsification during mass transfer is significantly accelerated and can take place at room temperature. A stable emulsion, introduced into the foam, stabilizes it, and an unstable one destroys it. Low expansion foam is usually stabilized in contact with hydrocarbon. Medium expansion foam is destroyed even under the condition of thermodynamic stability of foam films. Conclusion. The experimental data obtained made it possible to propose a mechanism for the contact interaction of foam with a hydrocarbon, according to which a more stable foam on the surface of a hydrocarbon can be obtained by a foaming agent, which, in addition to foaming properties, is a good emulsifier. Keywords: fire extinguishing foam, hydrocarbon, oil product, contact destruction, self-emulsification during mass transfer.

Non linear elasticity of foam films made of SDS/dodecanol mixtures.

Foam film elasticity plays a significant role in film drainage and film stability and is thus expected to influence foam dynamical properties. It strongly depends on the foaming solution composition and differs from the interface elasticity measured in unconfined geometries. We use a deformable frame to deform an assembly of five films and we measure the tension and extension of each film. This provides a simple and accurate determination of the film elasticity, in the linear and non-linear regimes, for a set of SDS/dodecanol mixtures, at various concentrations. We show that the non-linear elastic behavior is well reproduced by Mysel's model coupled with a Langmuir coadsorption isotherm for a large range of chemical compositions.

Induction of foaming in vacuum drying by needle stimulation and the impact of solution viscosity, vapor pressure, and the type of solute and solvent

Reliable induction of foaming is indispensable for vacuum foam drying. We previously showed that, adequate partial drying followed by puncturing a solution with a needle (needle stimulation) resulted in the induction of the foaming, even under insufficient vacuum where foaming is minimal. Herein, characteristics of needle-stimulation-induced foaming was investigated, focusing on the impact of solution viscosity and vapor pressure. Different combinations of solutes (disaccharides, polyvinylpyrrolidones, polyacrylic acid, Eudragit) and solvents (methanol, ethanol, isopropanol, water) were used. Needle stimulation was conducted after different periods of initial vacuum drying, and the probability of foaming induction during the restart of vacuum drying was determined. Each series of solutes (polymers and disaccharides) respectively indicate solvent-independent correlations between foaming induction probability and solution viscosity. The existence of a lower limit for the solution vapor pressure required for foaming induction was also implied. A possible mechanism for needle-stimulation-induced foaming under reduced pressure is proposed.

Type-Ⅰ hetero-junction of BiOI-BiO2-x anchored on Ni foam accelerating charge separation and transfer for efficiently purifying hazardous wastewater

About 70 mg of BiOI-BiO2-x powder was attached to Ni foam. Compared to BiOI/Ni foam and BiO2-x/Ni foam, the BiOI-BiO2-x/Ni foam exhibited distinctly enhanced photocatalytic activity for removing RhB from water. Among them, the BiOI-BiO2-x = 1:3/Ni foam demonstrated the optimal photocatalytic activity. Around 97% of RhB was decomposed over BiOI-BiO2-x = 1:3/Ni foam under 7 h irradiation of a 300 W xenon lamp, which was 47.5 times that over BiOI/Ni foam and 1.3 times that over BiO2-x/Ni foam, respectively. The degradation rate constant (k) of RhB over BiOI-BiO2-x = 1:3/Ni foam was 71.8 times that over BiOI/Ni foam and 2.6 times that over BiO2-x/Ni foam, respectively. The removal rates of TOC and TON in the BiOI-BiO2-x = 1:3/Ni foam solution were approximately 50% and 29%, respectively. Photo-induced electrons and holes flowed from BiOI to BiO2-x and then photo-generated electrons of BiO2-x further transferred to Ni foam. The separation efficiency of carriers in BiOI-BiO2-x = 1:3/Ni foam was greatly improved, thereby enhancing its photocatalytic activity. In addition, the improved photocatalytic activity of BiOI-BiO2-x = 1:3/Ni foam was ascribed to its strong adsorption capacity. The mainly active species for RhB degradation were holes (h+) and superoxide radicals (·O2–).

Shale core wettability alteration, foam and emulsion stabilization by surfactant: Impact of surfactant concentration, rock surface roughness and nanoparticles

Hexadecyltrimethyl ammonium bromide (HCTAB) and sodium dodecyl sulfate (SDS) are popular conventional surfactants with versatile industrial and oilfield applications. Knowledge of the optimum conditions for their applications for shale rock wettability modification, as well as foam and emulsion stabilization is relevant for hydrocarbon recovery process optimization. Influence of surfactant concentration, rock surface roughness and presence of nanoparticles in surfactant solutions on contact angles, oil-water interfacial tension (IFT), as well as foam and emulsion stabilization by HCTAB and SDS was investigated in this study. The interfacial properties measurements were conducted with Drop Shape Analyser (DSA 25), whereas the foam generation and stability properties were investigated via dynamic foam analyzer (DFA100). The emulsion stabilization and demulsification processes were investigated in Formulaction Turbiscan. Results showed an existence of optimum concentration of surfactant for obtaining the lowest contact angles, oil-water IFT reduction, as well as attaining maximum foam stability. The contact angle measured on rough core surfaces were smaller than the contact angle measured on smooth surfaces. Contact angles increased with increasing salnity concentration, but decreased with the increasing rock saturation time. Oil was more detrimental to foam stability when the generated foam was brought into contact with the resident oil, compared to when oil was added to the foaming solutions before foam generation. Lower contact angles, durable foam, and stable emulsion were produced in presence of oil and at high temperature via the synergy of nanoparticles and surfactants. Almost 66% decreased in contact angle was achieved with carbon nanotubes-SDS solutions, whereas Al 2 O 3 nanoparticles-HCTAB foam attained a viscosity of 99 mPa-s at 60 °C. The foam demonstrated shear thinning Newtonian fluids behaviors but attained a plateau after sometimes. The study suggests the conditions for optimization of conventional surfactants applications in conventional and unconventional reservoir. • Synergy of nanoparticles and surfactants on shale core wettability was studied. • Foams are less stable when they suddenly contacts the resident oil. • There is optimum surfactant concentration for maximizing interfacial activities. • Contact angle decreased by 66% in presence of carbon nanotubes-SDS solutions. • Al 2 O 3 -HCTAB foam attained a viscosity of 99 mPa-s at 60 °C.

Effect of polysaccharide polymers on the surface and foam properties of aqueous film-forming foam

Three kinds of polysaccharide polymers were used as the proposed foam stabilizers in aqueous film-forming foam (AFFF). The effect of polysaccharide polymers on viscosity, surface tension, foaming ability and foam stability of AFFF was discussed by various analytical methods. The results shows that the addition of polysaccharide polymers slightly increases the surface tension of foam solution, while the combination of xanthan gum and gelatin presents the least negative influence on the surface tension of foam solution. Especially, the addition of gelatin improves the foaming ability of AFFF while both xanthan gum and sodium alginate decrease the foaming ability of AFFF. The combination of xanthan gum and gelatin can effectively balance the foaming ability and foam stability of AFFF, which is ascribed to the increases of viscosity that enhances the surface strength of foam liquid film and decreases the diffusion of water in the liquid film, thus effectively slowing down the drainage rate and bubbles coarsening of foam.

Enhancement of smart water-based foam characteristics by SiO2 nanoparticles for EOR applications

Here, smart water assisted with synthesized SiO2 nanoparticles have been utilized to prepare the foam solution. Effect of SiO2 nanoparticles on foam stability and oil displacement efficiency in carbonated pattern of glass micromodel have been studied. Obtained results showed that foam solution with smart water assisted with silica nanoparticles has the highest stability in comparison to the distilled water and smart water free of nanoparticles. In the presence of the nanoparticles the stability of the foam solution has significantly increased. However, the highest stability of the smart water based-foam solution has been attained with SiO2 nanoparticles at concentration of 3000 ppm. In the foam solution of smart water without the nanoparticles, the values of R5 and half-life (t1/2) are 91.5 and 2813s, respectively. While, these values in the presence of the dispersed nanoparticles reach to about 99.2 and 3812s, respectively. During the injection experiments with foam solution prepared by the smart water mixed with SiO2 nanoparticles in micromodel, the breakthrough of the foam has been postponed and oil recovery factor has been improved. Due to the presence of the silica nanoparticles in foam solution high-thickness lamellae has been formed and snap-off and lamella division phenomena have occurred in porous network on microscopic scale.

Fluorocarbon Vapors Slow Down Coalescence in Foams

AbstractControlling the stability of liquid foams is of the utmost importance for a wide range of applications. For decades, fluorocarbon vapors have been added to the gas phase of foams to ensure long‐term stability against bubble coarsening. However, it is shown here for the first time that they also have an unexpected and pronounced effect on bubble coalescence. This effect is quantified in detail for foams stabilized by the nonionic surfactant hexaethylene glycol monododecyl ether (C12E6) at controlled fluorocarbon (perfluorohexane (C6F14)) concentrations, but it is observed for all investigated surfactants. Measuring surface tensions of the foaming solution with increasing fluorocarbon concentration, a synergy between the fluorocarbon and the surfactant is found which can be explained by a) the formation of mixed layers of both species at the gas/water interface at low fluorocarbon concentrations and b) the formation of a macroscopic fluorocarbon film if the gas phase is saturated with fluorocarbon vapor. The precise mechanism responsible for reducing coalescence, that is, film rupture, remains to be elucidated.

Increasing the stability of the fire extinguishing foam by replenishing the liquid phase during sprinkling

Introduction. The destruction of foam films occurs when they reach critical thickness and lose the liquid phase as a result of syneresis and evaporation, which are rather difficult to slow down. We have proposed a method for increasing the stability of the fire extinguishing foam by means of replenishing the liquid phase through sprinkling.Methods. Foam stability was measured by the time of destruction of 25 % of the initial foam volume. The concentration of the foaming agent in the sprinkled solution varied from 0.5 to 6 %. Carboxymethylcellulose sodium salt (Na CMC) was used as a stabilizing additive. Field studies were carried out by feeding foam and solution from two AT-3,2-40 (43253)001-MS tank cars.Results and discussion. It has been established that the foam stability is influenced by the sprinkling intensity and the foaming agent concentration. Foam sprinkling with the solutions having low concentration of thefoaming agent leads to the washout of surfactants from the films that reduces the foam stability. The sprinkling intensity reduction boosts the foam stability due to the replenishment of the moisture lost through evaporation. The foam stability was maximal in case of sprinkling with a 2 % solution of the foaming agent, while the sprinkling intensity had no influence. An increase in the concentration of the foaming agent in the sprinkled solution led to a decrease in the foam stability. It is found that a smaller amount of the foaming agent is consumed to maintain the amount of foam through sprinkling than to replenish the destroyed amount through additional foam generation. It is shown that various stabilizing additives can be added to the foam in the process of sprinkling. If Na CMC is added to the solution exposed to sprinkling, the time of foam destruction goes up 3–5 times even in case of a non-recurrent sprinkling session. Field tests have confirmed the feasibility of adding stabilizing additives to the foam by means of sprinkling.Conclusions. The results of the research have shown the feasibility of co-feeding the foam and surfactant solutions, containing various stabilizing additives, in order to extinguish fires and generate stable foams.