Mechanical Foam Breaker Research Articles

Description of the Preliminary Proposals and Modeling for Applying the Mechanical Foam Breakers Techniques in the Processing Trays Columns

A preliminary proposal and some novel ideas have been described and theoretically analyzed in the present study for applying the mechanical and physical foam control methods in the trays column, that some common methods have been modeled and new configurations are created. study has tried to satisfy the much promising capability to utilize the Revolving Paddles and Ultrasonic methods. flow driven foam breaker demonstrates a self-driven mechanism while it is running continuously, turbo driven and liquid sprays foam breaker models are using the same process fluids and providing a clean fast correction action, Stethoscope and magnetostriction Ultrasonic models are utilizing the Ultrasonic waves for defoaming action. the recognized designs supposed applicable and reliable to be installed and functioned in the trays columns and the similar applications in different industries with no more chemical agents' consumption, accordance with the operation criteria and the technical standards and the safety precautions. CFD simulation and numerical analysis have been initiated for two models as an example that include flow driven foam breaker and the Ultrasonic Stethoscope model, while the study pointed to illustrate the basic ideas of the listed models and explored the main components and avoid going through deep details.

Modeling of Non-Newtonian Flow in an Inverted Cone Foam Breaker

Abstract Foam formation is a widespread phenomenon and often a serious problem in fermentation processes. Inverted cones used as mechanical foam breakers are rotating devices that pump the fluid up and pulverize it at the edge. The shearing and centrifugal actions of such geometries can help to control foaming. In this study, a model was developed using Computational Fluid Dynamics (CFD), based on the non-Newtonian properties of foam, to describe and explain the action of inverted cones as foam breakers.

Numerical and experimental study of a novel aerodynamic foam breaker for foam drilling fluid

AbstractDefoaming is a key technology for increasing the efficiency of foam drilling in petroleum engineering. To enhance the performance of a mechanical foam breaker in foam drilling, a novel aerodynamic foam breaker with two annular slits was investigated in this study. The computational fluid dynamics code of ANSYS Fluent was used to simulate the velocity and pressure distribution inside the foam breaker, and the optimum distance between the two annular slits was determined based on the simulation methods. Meanwhile, a series of experiments were conducted to test the actual performance of the foam breaker. The results demonstrate that various factors may affect the efficiency of the foam breaker, including the foam gas‐liquid ratio, basic liquid viscosity, and air supply method. A higher gas‐liquid ratio of the foam and air supply pressure result in a superior foam breaker performance. The viscosity of the foam liquid phase exhibits exactly the opposite behavior, meaning that the foam breaker more effectively destroys foam from a lower‐viscosity liquid. This study verifies the practicability of this novel aerodynamic foam breaker and discusses the effects of different parameters on the defoaming percentage, and this study can act as a reference and guidance for subsequent defoaming research.

Novel mechanical foam breaker based on self-oscillation for promoting the application of foam drilling technology

Defoaming of foam drilling fluid on the ground is the key to its cyclic utilization. This paper proposes a novel mechanical foam breaker based on self-oscillation to promote the application of foam drilling technology. Simulation results showed that the combined effects of the negative pressure, collision, extrusion, and shear generated in the cavity cause the foam to fracture. A prototype was developed, and the effects of the structural parameters, components of the foam drilling fluid, cuttings, and temperature on the defoaming percentage were investigated in experiments. The experimental results showed that the diameter of the upper nozzle was the major structural factor influencing the defoaming. A smaller diameter for the upper nozzle resulted in a higher defoaming percentage. The defoaming percentage first increased and then decreased with increases in the lower nozzle diameter, cavity length, and diameter, which indicated that there is an optimum structure for the foam breaker. The cutting concentration and temperature could improve the defoaming percentage to some extent, and the salts had a minor influence on the defoaming percentage. The results verified the feasibility and advantages of using the mechanical foam breaker and laid a solid theoretical foundation for its application in petroleum and natural gas drilling.

Numerical Simulation of the Laval Annular Mechanical Foam Breaker for Foam Drilling

Numerical Simulation of the Laval Annular Mechanical Foam Breaker for Foam Drilling

Numerical Simulation and Optimization Design of the Annular Mechanical Foam Breaker

The annular foam breaker is one which uses the vacuum and shear force generated by the Coanda effect to break foam. The pressure distribution directly affects its performance. So an investigation on the flow characteristics inside the annular foam breaker is important to optimize its structure. In this paper, the computational fluid dynamics (CFD) code, FLUENT, is employed to simulate the flow phenomena. The effect of various geometric parameters on the pressure distribution inside the annular foam breaker has been evaluated, including the width of the annular slot, the Coanda surface radius and the diffuser dimensions, etc. The numerical results show that the optimum value of the annular slot d = 0.5mm, the Coanda surface radius r = 20mm, the diffuser angle θ=6°, and the ratio of the diffuser length to radius is more than 14. Based on these analyses, an optimum structure of the annular foam breaker was designed and tested in the well bore flow simulation loop laboratory equipment. Compared with the old ones, the foam-breaking efficiency of the optimized annular foam breaker is improved from 71.16% to 86.58%, which increases by some 22.61%.

Foam Breaking Characteristics of a Mechanical Foam-Breaker Using Shear Force Fitted to a Stirred-Tank Reactor

This study examined foam breaking characteristics of a mechanical foam-breaker using shear force (MFUS) between a fixed orifice plate and a rotating disk fitted to a stirred-tank reactor (STR). The effects of operating conditions on the liquid holdup in foam φL and the volumetric rate of foam flow Qa, which reflect the foaming behavior of the STR, were revealed. The foam-breaking behavior of the MFUS was investigated from changes in the foam density after foam breaking (ρf)c, which remained constant at a disk rotational speed N, transitional disk rotational speed Nt, and shearing power Ps. The value of (ρf)c decreased concomitant with the increase in the mass flow rate of liquid in the foam flowing into the orifice, wL. The Nt became larger concomitant with the lower average ascending velocity of the foam Ua and higher φL. The magnitude of Ps was related to that of wL. Empirical equations for predicting (ρf)c, Nt and Ps were obtained based on those results.

Batch production of biosurfactant with foam fractionation

AbstractMethods of producing the biosurfactant surfactin from cultures of Bacillus subtilis (BBK006) have been investigated. A reactor with integrated foam fractionation was designed and used in batch mode, and the performance compared with that of the same culture in shaken flasks. In the batch reactor, significant foaming occurred between 12.5 h and 14.5 h of culture time. During this period, the foam was routed through the foam fractionation column to a mechanical foam breaker, and a biosurfactant‐enriched foamate was collected. Concentration of surfactin in the foamate product was around 50 times greater than that in the culture medium. Using the integrated reactor, 136 mg L−1 of surfactin was produced, significantly more than was achieved in shaken flasks (92 mg L−1). The foam fractionation method allowed a real‐time measurement of the rate of surfactin production during growth. This showed that the maximum rate of production occurred at the interphase between log and stationary modes of growth, in contrast to previous work showing that surfactin is exclusively a secondary metabolite. The high value of surfactin yield in relation to biomass (YP/x = 0.262) indicated that surfactin was produced very efficiently by Bacillus subtilis (BBK006) in this integrated bioreactor. Copyright © 2006 Society of Chemical Industry

Hydromechanics of separation of gas?liquid systems with foam structure

The operation of mechanical foam breakers (filtering, centrifugal, nozzle, disk, paddle, drum, and jet foam breakers) is modeled, and their main characteristics are calculated. This will allow development of a rational and optimal design of equipment for foam breaking in technological processes.

Treatment of strongflow wool scouring effluent by biological emulsion destabilisation

The stable oil-in-water emulsion contained in wool scouring effluent was destabilised by aerobic biological treatment as the basis of a potential new effluent treatment process. The de-emulsified wool wax, which is recalcitrant to biodegradation, can then be readily removed by centrifugation. In 12-day batch experiments, 97% of wool wax and 87% of COD were removed after gentle centrifuging at 200× g, compared to only 6% and 8%, respectively, for sterile controls. Steady-state chemostat experiments under optimum conditions gave essentially complete removal of wool wax and 90% removal of COD at less than 40 h retention time, and demonstrated that the mechanism of pollutant removal was by bioflocculation rather than aerobic degradation. At 100 L pilot scale, 95% of wool wax and 82% of COD were consistently removed over a period of 116 days of continuous operation at 38 h retention time and 30°C, producing a spadable sludge of 5.7 mL/g. Variable influent concentration or filamentous bacteria did not disrupt this process and foaming was readily controlled using a mechanical foam breaker. After a shutdown period of 15 days the process could be restarted easily, achieving normal performance within one retention time. The successful operation of the pilot reactor suggests this process could be developed to full scale and incorporated into an overall treatment package.

Performance Characteristics of a Stirred-Tank Reactor with a Mechanical Foam-Breaker Utilizing Shear Force

A new mechanical foam-breaker was developed. It uses the shear force between a fixed orifice plate and a rotating disk (MFUS). Foam-breaking performance of the MFUS fitted to a stirred-tank reactor (STR) was evaluated from changes in foam density and shearing power. The maximum value of the ratio of foam density (after foam breaking) to liquid density was 0.90. Change in foam densities before and after foam breaking in the MFUS was considerably larger than that in existing mechanical foam-breakers with rotating parts at the same level of power for foam breaking. The volumetric liquid-phase oxygen transfer coefficient was measured in the bubble-dispersing and foam-ascending sections of the STR with the MFUS. Comparison of the volumetric liquid-phase oxygen transfer coefficient between the STR with the MFUS and the STR or the foam column in terms of the specific power input demonstrated higher oxygen transfer performance and saving power requirements for the STR with the MFUS.

Foam Rupture by Mechanical and Vibrational Methods

The need to destabilize foams and control their formation arises in many industrial processes. Mechanical foam breakers, mechanical vibration and ultrasonic vibration are examples of physical destructive techniques which do not suffer from the drawbacks associated with the use of chemical antifoams and defoamers. This paper reports on recent studies in this area. Two novel designs of mechanical foam breaker are presented which are superior to traditional foam breakers in controlling unwanted foaming in both bubble columns and stirred vessels. The effectiveness of mechanical and ultrasonic vibrations in destabilizing foams is shown to be governed by vibrational amplitude and frequency, and foam structure. A fundamental understanding of foam destabilization by these physical techniques is crucial to further advancement in the design of efficient and robust foam breakers and the development of enhanced non-invasive vibrational destructive techniques.

Biological treatment of highly foaming pharmaceutical wastewater by modified bubble-column under mechanical foam control

Activated sludge treatment of highly foaming pharmaceutical wastewater was carried out with modified bubble columns equipped with a mechanical foam-breaker (MFRD). The geometry of the bubble column was modified based on the foam breaking mechanism of the MRFD in order to improve the foam breaking capacity and hence to enhance the treatment capacity. Four types of modifications were examined. The activated sludge treatment of the wastewater with the modified columns was successfully carried out with COD removal efficiency about 90% at BOD loading of 4 g/Ld. Little effect of the mechanical foam control on the sludge settling characteristics was observed. The column modification significantly reduced the power required for foam control. The maximum power decrement of 75% was attained. Furthermore, oxygen transfer was found to be facilitated in the modified bubble columns. The results are expected to be helpful for economic and effective treatment of highly foaming organic wastewater.

Mechanical suppression of the dynamic foam head in bubble column reactors

The necessity of suppressing foam formation arises in many industrial operations and in sewage treatment plants. Mechanical foam breakers are used for such a purpose when the use of chemical antifoams and defoaming agents is prohibited by the process. Two new foam breakers were used to control a dynamic foam head generated in a bubble column containing foamable liquid: a comb-type two-blade paddle with three slits, and a brush-type two-blade paddle with 168 needles. In comparison with more conventional foam breakers, both foam breaker designs gave significantly reduced critical speeds for foam control. Their performance was characterised under various experimental conditions including different foam-base liquid properties, gas sparger types, surfactant concentrations, and foam breaker clearances above the liquid surface level. The control of dynamic foams generated continuously in a bubble column was found to depend on the foam characteristics such as bubble size and liquid holdup, and the foamability of the base liquid. Foams generated in stirred tank reactors were found to be have different characteristics and hence different control requirements.

Performance characteristics of novel mechanical foam breakers in a stirred tank reactor

Unlimited foam formation and insufficient foam collapse can have serious effects in an aerated system such as a fermentation process. Mechanical foam breakers are used in foam control to avoid the drawbacks associated with the use of chemical antifoams and defoaming agents. In this paper, two new foam breakers consisting of a two-blade paddle with three slits, and a two-blade paddle with 168 thin needles have been tested. They gave significantly reduced critical speeds and power consumption for foam control in a stirred vessel, compared with some conventional foam breakers. The effects of various parameters, namely the physical properties of the foaming solution, type of gas sparger, surfactant concentration, and foam-breaker clearance above liquid level, have been investigated. The degree of difficulty of controlling dynamic foams generated continuously in a stirred vessel is found to be a function of the nature of the foam, ie its bubble size, its liquid holdup, and the degree of foamability of the system. © 1999 Society of Chemical Industry

Bubble growth in secondary foams

AbstractWhen mechanical foambreakers are used in chemical engineering processes to control an undesired primary foam, a secondary foam is often produced. Secondary foams consist of small bubbles, have a high liquid hold‐up, and cannot be condensed further by mechanical foambreakers. Secondary foams can be converted into liquid and gas in a coalescence column by drainage, diffusion, and breakage of the lamellas. This paper presents a new model to determine the velocity of bubble growth and the time of coalescence of secondary foams. The experimental investigations have been carried out with surfactants in aqueous solutions.

Mechanical foam breaking – a physical model for impact effects with high speed rotors

AbstractDuring recent years in chemical engineering processes for instance with aerated stirred tanks containing surface‐active components foams and their mechanical control have become very important. However, there are still no rules for calculating mechanical foam breakers. As a contribution to foam control the present paper discusses the fundamentals of foam breaking by means of foam densities and gives a physical model for the mechanisms of a mechanical foam breaker when the main breaking effect is based on impact. The mechanisms were proved by measuring pressures in a foam breaker box. Diameters of secondary foam bubbles produced by foam breakers are calculated and discussed. Experimental investigations were made with different surfactants in aqueous solutions. The paper points out their influence on the process of foam breaking.

Performance Characteristics of Mechanical Foam-Breakers with Rotating Parts Fitted to Bubble Column

The characteristics of four mechanical foam-breakers (a six-blade turbine (F-B), a six-blade vaned disk (V-D), a two-blade paddle (T-P) and a conical rotor (C-R) having six-blades fixed internally) with rotating parts fitted to a bubble column (BC) treating various foaming liquids were examined. In the BC with different foam-breakers, the average liquid hold-up in foam, ϕL, was both a typical parameter reflecting the foaming intensity of the BC, and a parameter related to the difficulty or ease of foam-breaking. The value of power consumption, Pkc, for foam-breaking in the C-R was the largest amongst the foam-breakers. Furthermore, it was demonstrated that in the four foam-breakers with rotating parts a considerable amount of very small liquid droplets was entrained with the exhaust air. © 1997 SCI.

Effect of Gas Sparger Type on Operational Characteristics of a Bubble Column under Mechanical Foam Control

The effects of gas sparger types on the operational characteristics of a bubble column (BC) with a rotating-disk mechanical foam-breaker (MFRD), such as foam-breaking, foaming, flow and mass transfer characteristics, were studied. The required critical disk rotational speed, N c , and liquid hold-up in the foam, Φ L , reflected the foam-breaking behaviour of the MFRD and the foaming behaviour of the BC respectively, which changed depending on the gas sparger type. The dependence of the gas sparger type on the gas hold-up, e g , was similar to that observed for the volumetric mass transfer coefficient, k L a. A comparative investigation of k L a with various gas spargers, in terms of the specific power input, also demonstrated the usefulness of the porous sintered glass bead filter as a gas sparger.

Relation between critical disk speed for foam-breaking of rotating-disk mechanical foam-breakers and foaming characteristics of solutions

For tower fermentors, i.e., bubble columns (BCs), treating various foaming liquids, the critical disk rotational speed N c required for foam-breaking of rotating-disk mechanical foam-breakers (MFRDs) fitted to BCs was studied in relation to the foaming characteristics of the liquids. An empirical equation was presented for predicting N c in foam-breaking regions. With this equation, it was found that prediction of N c of MFRDs fitted to BCs treating various liquids was possible regardless of the type of foaming liquid or its concentration.