Scrubbing Effect Research Articles

Improving Fine Particle Removal Using a Single-Channel Slit Bubbling Device in Wet Flue Gas Desulfurization System.

To improve the cleanliness of coal-fired power plants' particulate matter emissions, a novel device (single-channel slit bubbling particle removal device (SCSB-PRD)) is proposed to improve the wet flue gas desulfurization system's (WFGDs) collaborative particle removal effect. Actual coal-fired flue gas was used to test the particle removal performance. The results showed that the flue gas temperature had no obvious effect on the scrubbing effect of the SCSB-PRD. The scrubbing space, scrubbing liquid volume, and flue gas flow rate effectively changed the gas-liquid flow state, and the bubbling state was the key factor in particle removal. The jet-bubbling contact state was more conducive to removing particles than the foam bubbling state. The jet-bubbling state improved the removal efficiency of fine particles by approximately 30% compared to the foam bubbling state. The device operated in a single stage, and the removal performance of the particulate matter reached more than 60%. Even the submicron particles had a satisfactory removal performance of greater than 50%. The particulate matter concentration at the outlet of the WFGDs was reduced to less than 10 mg/m3, which provides a feasible transformation path for ultraultra-low emissions of particulate matter from coal-fired power plants.

A pilot scale test study with theoretical justification of reaction mechanism for the recovery of chromium(VI) based on solvent extraction using novel centrifugal extractors

As a strategic resource and hazardous substance, the purification and recovery of chromium(VI) from the aqueous phase have attracted attention. In this study, the centrifugal extractor was used to treat the leach liquor of sodium roasting chromite on a pilot scale. The extraction performance and equilibrium distribution of chromium in countercurrent extraction were investigated. Meanwhile, the scrubbing effect of impurities was carefully studied, and the stripping and regeneration effects of the organic phase were tested. Under the selected process parameters, the pilot scale test results, including extraction efficiency of chromium, scrubbing efficiency of impurities, and regeneration performance of the organic phase, were excellent. The qualified (NH4)2Cr2O7 and Cr2O3 products were prepared using the strip liquor, and several physical properties of the products were tested. In addition, the molecular electrostatic potential surface maps, HOMO-LUMO orbitals, Fukui functions, and single point energy of the molecules involved were calculated by Quantum Chemistry. The molecular electrostatic potential analysis, frontiers molecular orbital analysis, Fukui function analysis and interaction energy analysis were applied to investigate the mechanism of separation of chromic acid from impurities in the extraction system.

Lid scrubbing with a gel combining natural extracts for dry eye treatment.

To evaluate the effect of lid scrubbing using a gel combining different natural extracts on ocular signs and symptoms of dry eye patients. A retrospective study was performed on 19 dry eye patients (51.1±16.0y). Non-invasive tear break-up time, tear meniscus height, meibomian gland loss, lipid layer thickness, conjunctival redness, corneal staining, ocular surface disease index (OSDI), and ocular pain intensity were measured before (baseline), 1wk, and 2mo after lid scrubbing with a gel containing different natural extracts (okra extract, aloe vera leaf juice, hydrolysed soy protein, caffeine, citrus unshiu peel extract, and raspberry seed oil). Compared with the baseline, there was a statistically significant improvement in both first (P=0.048) and average (P=0.026) non-invasive tear break-up time 2mo after treatment, as well as in corneal staining (P=0.043, 0.012), OSDI (P<0.001), and ocular pain intensity (P<0.001) after 1wk and 2mo. In addition, there was no correlation between ocular signs and symptoms. The lid scrubbing with a gel combining different natural extracts show beneficial effects on tear film stability, corneal damage, and ocular symptoms, which is the reason why this therapeutic procedure is proposed as an alternative for dry eye management. However, it is not possible to attribute this beneficial effect solely to the presence of the natural extracts in the gel, primarily due to the absence of a negative control group.

Experimental research on aerosol scrubbing characteristics under steam-air mixture submerged jet condition

The occurrence of severe accidents in nuclear power plants may lead to the leakage of radioactive aerosol. And the scrubbing efficiency of aerosol contained in the air-steam mixture submerged jet is important for assessing the radioactivity in the containment during a severe accident. Several experiments were carried out to analyze the effect of inlet pressure, aerosol diameter, submergence, and steam fraction on the scrubbing efficiency of aerosol in the jet regime. Then, the scrubbing effects of steam and different flow regimes under submerged jet conditions were investigated by comparing the experimental results. The scrubbing efficiency increased with the increase of the aerosol diameter in the air jet regime while the most penetrating region of the aerosol in the steam-air mixture jet regime is 0.2–0.4 μm. When the gas flow characteristic is subcritical flow, as the inlet pressure increases, the scrubbing efficiency increases rapidly. When the critical flow is reached, the inertial effect was the dominant factor in aerosol scrubbing due to the sufficient gas velocity, the scrubbing efficiency under different steam fractions is close to 100%. The scrubbing efficiency increases with the increase of the steam fraction, which may be caused by the increase of the temperature gradient field under subcritical flow conditions. Additionally, the increase the submergence can increase the residence time and improve the scrubbing efficiency. However, due to the decrease of the gas velocity during the gas floating, the scrubbing efficiency in the flow region of the same height is gradually decreasing.

Pool scrubbing in unit 1 of fukushima daiichi

Under the frame of OECD/BSAF and ARC-F projects, CIEMAT estimated that around 40% of the Cesium initial inventory in the reactor core and nearly 60% of the Iodine one of the Unit 1 of Fukushima Daiichi, got absorbed in the suppression pool. CIEMAT has critically reviewed the bases of the MELCOR pool scrubbing module, including the major assumptions and approximations underneath, under the prevailing conditions in Unit 1 of Fukushima Daiichi during fission product scrubbing. The results have shown that most fission product mass is retained in the water nearby the injection point as a consequence of diffusiophoresis and inertial mechanisms. However, some of the approximations underneath the corresponding models have been found to be questionable and some new formulations have been considered and implemented within the stand-alone SPARC-90 code, which is the basis of the MELCOR models for pool scrubbing. In particular, a model capable of describing the scrubbing effect of jet injection has been implemented. This work presents better-fitted models for the scenario and, after implementing them into the SPARC-90 code, the resulting moderate quantitative impact on the accident scenario of Unit1 in Fukushima Daiichi, has been discussed to be well within the uncertainty range associated to the original code estimates. However, updating of MELCOR concerned models for fission products trapping in pools is highly recommended for physical consistency.

Physics linkages between arterial stiffness, cerebrovascular flow and cognitive impairment

Background. Reduced cerebrovascular flow and localized hypoperfusion have been widely associated with various forms of cognitive impairment. Vascular cognitive impairment has also been associated with arterial stiffening and arteriosclerotic development. The linkages between cerebrovascular arteriosclerosis and localized cerebral ischemia, as dictated by the physics of fluid flow, while relatively unaddressed, are vascular contributions to cognitive impairment.&#x0D; Methods. The physics of fluid dynamics, particularly that of wave propagation in compliant vessels, was applied to the analysis of blood flow in a complex cerebrovascular tree, consisting of hundreds of thousands of arterial junctions. Each of these arterial junctions or bifurcations may partially reflect antegrade pulsatile flow into retrograde flow, resulting in reduced peripheral cerebral pulsatile flow.&#x0D; Results. The physics of fluid dynamics predicts1 that, at each bifurcation in the complex cerebrovascular maze, the percentage of antegrade flow which is reflected in retrograde flow is determined by the quotient of the arterial stiffnesses ratio and cross-sectional areas ratio on each side of each bifurcation. Physics predicts that, if the arterial stiffness/area ratios quotient is equal to unity then, ideally, there is no pulsatile retrograde flow. A ten percent pulsatile reflection would result from an arterial mismatch (in the quotation of trunk to branch artery stiffnesses to areas ratios) of about twenty percent. In other words, if a trunk artery at a bifurcation stiffens with aging by twenty percent relative to the bifurcations branch arteries, and the dimensions are unchanged, then the pulsatile antegrade flow reduces by about ten percent. In progressing from the extracranial arteries into the cerebral capillaries this pulsatile flow reduction process may be repeated at each bifurcation tier, causing an accumulating reduction in pulsatile flow into the capillaries. If the amplitude of the pulsatile retrograde flow is sufficiently large, the collision of the retrograde and antegrade pulsatile flows may result in transient flow reversal at select locations in the vascular bed. Such flow reversals may occur where a maximum in the retrograde flow pattern coincides with a minimum in the antegrade flow pattern, resulting in localized diastolic flow reversal. Persistent blood cell flow reversal, with its “scrubbing effect” on endothelial cells, combined with the flow’s associated pulse pressure amplification, may cause lifting of endothelial cells, thereby exposing the underlying intima and media to deposition of foreign materials, such as lipids and calcium. Hence, localized retrograde flow may induce arteriosclerotic development, which in turn, may increase bifurcation arterial stiffness ratios, which may further increase pulsatile flow reversals, increase arteriosclerotic development, decrease peripheral flow and increase arteriole ischemia at select cerebral locations.&#x0D; Conclusions. The physics of fluid dynamics predicts quantifiable cross-linkages between macro and microcirculation, as shown in Figure 1, which include age-related increases of localized arterial stiffness, cerebral ischemia and ultimately, parenchymal hypoxia.2,3 The specific cerebral locations of such hypoxia would be dependent on localized vascular and physiological conditions. The manifestation and nature of any cognitive impairment associated with localized hypoxia, would, therefore, also be dependent on localized vascular and physiological conditions.

Formulation and Evaluation of a Laterite Soil Based Scrubbing Effect Herbal Cleansing Bar

Cosmetics play a dynamic role for every person to have a glad and confident life. In the current scenario, herbal cosmeceuticals have more demand because they have no side effects. People often suffer from acne, whiteheads, and blackheads, so scrubbing becomes essential. The main objective of the present study was to prepare a herbal-mineral facial scrubbing effect cleansing bar. Majorly facial skin comes in direct contact with dirt, pollution, dust particles, and many dead cells. Some facial preparations are required to remove the dead cells and make the skin in fine fettle, cleaned, and nourished. The present study formulated a laterite soil-based herbal scrubbing effect cleansing bar for all typed skin using laterite soil powder. In contrast, glycerin soap base, virgin coconut oil, olive oil, bee honey, aloe vera, lime juice, turmeric, and lavender essential oil are used and evaluated by using various parameters such as physical appearance, color, odor, pH, washability, irritants, stability studies, microbial tests, heavy metals, and total fatty matter. It was given fruitful results with all the tests. The herbal formulation had characteristic pleasant order, reddish-brown in color having, light, non-irritant to the skin and quite an elegant, microbial and heavy metal safe product. Thus, the formulated scrubbing effect facial cleansing bar can be utilized efficaciously without a side effect that exfoliates makes healthy, clean, and glowing skin.&#x0D; Keywords: Facial scrub, Cosmetic, Herbal, Mineral, Laterite soil

Effect of vaginal scrubbing on post-C-section infection

Aims: The aim was to study the effect of vaginal scrubbing on post-C-section infection. Settings and Design: This was a randomised controlled trial. Subjects and Methods: This study was carried out from January 2019 to January 2021 on 434 patients who were divided into two groups: Group 0 which received abdominal and vulval scrubbing with povidone-iodine and Group 1 which also received vaginal scrubbing. Patients were monitored for any infection from the time of C-section to 30-day post-operative. Results: The mean ages of patients in Groups 0 and 1 were 27.15 ± 8.11 and 28.27 ± 8.14 years, respectively. Pyrexia was noted in 45 (10.4%) patients of Group 0 and 22 (5.1%) patients of the second group, respectively, with P = 0.01. Surgical site infection was noted in 22 (5.1%) patients of Group 0 and 21 (4.8%) patients of Group 1, P = 0.8. Endometritis occurred in 27 (6.2%) patients of Group 0 and 12 (2.8%) patients of Group 1; P = 0.01. Conclusions: Vaginal scrubbing reduces post-C-section infection.

Observation on the Effect of Toothbrush Brushing and Cotton Ball Scrubbing in Oral Nursing of Patients with Intubation through Endotracheal Tube

Observation on the Effect of Toothbrush Brushing and Cotton Ball Scrubbing in Oral Nursing of Patients with Intubation through Endotracheal Tube

Ekman Layer Scrubbing and Shroud Heat Transfer in Centrifugal Buoyancy-Driven Convection

Abstract This paper presents large-eddy and direct numerical simulations of buoyancy-driven convection in sealed and open rapidly rotating cavities for Rayleigh numbers in the range 107–109, and axial throughflow Reynolds numbers 2000 and 5600. Viscous heating due to the Ekman layer scrubbing effect, which has previously been found responsible for the difference in sealed cavity shroud Nusselt number predictions between a compressible N–S solver and an incompressible counterpart using the Boussinesq approximation, is discussed and scaled up to engine conditions. For the open cavity with an axial throughflow, laminar Ekman layer behavior of the mean flow statistics is confirmed up to the highest condition in this paper. The Buoyancy number Bo is found useful to indicate the influence of an axial throughflow. For the conditions studied the mean velocities are subject to Ra, while the velocity fluctuations are affected by Bo. A correlation, Nu′=0.169(Ra′)0.318, obtained with both the sealed and open cavity shroud heat transfer solutions, agrees with that for free gravitational convection between horizontal plates within 16% for the range of Ra′ considered.

Effects of pressure on soot formation in laminar coflow methane/air diffusion flames doped with n-heptane and toluene between 2 and 8 atm

There is currently a lack of adequate understanding of soot formation in flames fueled with liquid hydrocarbons at elevated pressures. In this study, laminar coflow n-heptane and toluene doped CH4/air diffusion flames were numerically investigated under a constant carbon mass flow rate at pressures between 2 and 8 atm to understand how pressure affects the sooting propensity of these two main components of surrogate fuels mimicking gasoline. Numerical simulations were performed using a detailed reaction mechanism containing 175 species and 1175 reactions and a sectional soot model. Soot inception is modeled by collisions among pyrene, BAPYR and BGHIF. Soot surface growth and oxidation are modeled using the hydrogen abstraction acetylene addition (HACA) mechanism as well as PAH surface condensation. The predicted sensitivity of soot production to pressure is in better agreement with the measurements of Daca and Gülder (2017) when the soot aging effect is considered in HACA surface growth. The predicted soot concentrations are in overall good agreement with measurements. Propargyl recombination and propargyl reaction with propyne are important pathways for the formation of benzene. In methane+toluene flames, attack of toluene by H radical is an effective benzene formation pathway low in the flame, but the relative importance of benzene formation from toluene is reduced with increasing pressure. Although all the soot formation processes are enhanced with increasing pressure, PAH condensation is enhanced the most, followed by HACA and inception. At 6 and 8 atm, PAH condensation becomes comparable to HACA. The pressure dependence of the sooting propensity follows the order of methane+toluene < methane+n-heptane < methane, consistent with measurements. This result can be explained by the pressure dependence of benzene formation pathways, the kinetic effect of pressure, and the scrubbing effect of soot production on the gas-phase species involved in soot formation.

A catalytic composite membrane reactor system for hydrogen production from ammonia using steam as a sweep gas

For catalytic reactions involving H2 extraction, the membrane reactor is an attractive option for enhancing the equilibrium and kinetics while eliminating excessive purification steps. In this study, a steam carrier adopted composite membrane reactor system is developed to produce pure H2 (>99.99%) from ammonia with high H2 productivity (>0.35 mol-H2 gcat−1 h−1) and ammonia conversion (>99%) at a significantly reduced operating temperature (<723 K). Coupling of a custom developed palladium/tantalum composite metallic membrane and ruthenium on lanthanum-doped alumina catalysts allowed stable operation of the membrane system with significant mass transfer enhancement. Various reactor assemblies involving as-fabricated membranes and catalysts are experimentally compared to suggest the optimal configuration and operating conditions for future applications. Steam is adopted as a sweep gas, presenting efficient H2 recovery (>91%) while replacing conventionally utilized noble carrier gases that require additional gas separation processes. The steam carrier presents similar membrane reactor performance to that of noble gases, and the water reservoir used for steam generation acts as an ammonia buffer via scrubbing effects. Finally, electricity generation is demonstrated using a commercial fuel cell along with process simulation, substantiating potential of the proposed membrane system in practical applications for H2 production from ammonia and on-site power generation.

AKW Equipment + Process Design Smart Hydrosizer (AKA-SIZER) and Smart Attrition Cells (AKA-TRIT)

For more than 50 years AKW Equipment + Process Design has been successfully active in the international mining sector as engineering provider, equipment supplier and EPC player. Focusing on the ‘separation step’ in the overall mining value chain, we offer a wide range of proprietary and state-of-the-art equipment that enable processing in the most efficient and economical way. Some of the recent developments in the phosphate industry, which call for sharper cuts and better particle cleanliness, motivated AKW Equipment + Process Design to introduce smart solutions that have already found acceptance in several other mineral processing industries. Taking into consideration the particular environment of a mining operation, relevant smart features that are robust enough and provide the needed controls constitute critical parts of the concepts developed by AKW Equipment + Process Design. In smart attrition cells, the control and monitoring of a given and specific high solid concentration is compulsory in order to achieve the required scrubbing effect within a specific timeframe. To determine this suspension concentration, the agitator shaft torque will be measured indirectly via consumed motor current and used as basis for control. Therefore with an adjustable intensity range for the torque, a dosing valve will be controlled to ensure that the working concentration is continuously adjusted in the wanted level, hence delivering a steady and optimum scrubbing performances. In smart hydrosizers, a continuous control and adjustment of the teeter bed is compulsory in order to ensure a constant and uninterrupted classification effect. By the mean of an automatic hydrostatic measurement, the specific conditions of the teeter bed are determined, and thereafter are kept stable through a unique control system of the discharge valves. This allows a steady cut size and prevent interruptions that might be caused by discontinuous batch discharge and sudden variation of the hydrosizer feed conditions.

An Eco-friendly Alternative to Polyethylene Microbeads in Personal Healthcare Products

Recently a huge chunk of the population has shifted towards shower gels. The biggest reason might be the fact that shower gels can provide a better care for the skin. They were made with the motive of providing gentle cleansing and moisturizing qualities contrary to that of a regular soap, so that the people can enjoy a better skin care experience. Shower gels generally use chemicals especially sodium lauryl sulfate and betaines. These are believed to cause skin irritation and may not be washed off properly especially in hard water. The recent shower gels have a combined scrubbing effect included along with the scented or flavored body wash. For the scrubbing activity microbeads are employed. These microbeads used as a scrubber are polymers, e.g. being polyethylene or nylon etc. We know how plastics are harmful to us and the environment. And this is a cause of major concern. And since it is small in size it makes it relatively dangerous. Microbeads, because of their small size, have a large surface area by volume which allows them to accumulate highly toxic materials which are toxic to the person and the environment. To overcome the menace of microbeads we propose an alternative

Experience of Using Manganese-Containing Materials in Blast-Furnace Charge

The paper discusses the experience gathered at the Yenakievo metallurgical plant and Dnepr metallurgical complex with respect to using manganese-containing materials in the blast-furnace charge, which results in one of the greatest scrubbing effects when rationally formed in the feed charging cycle and contributes to maintaining the stability of the blast furnace operation at low and unstable quality of the charge material and pulverized coal injection (PCI). As an alternative to manganese-containing scrubbing materials, it is proposed to use the roller-pressed briquettes of ferroalloy production waste characterized by high quality parameters consistent with the iron source requirements.

Best-estimate severe accident and source term analysis for an ISLOCA scenario of a CANDU-6 plant using the MAAP-ISAAC code

An interfacing system LOCA (ISLOCA) is a bypass accident that results in the release of reactor coolant directly to the outside of a reactor building through a break in part of the low-pressure boundary of the reactor coolant system. Though the core damage frequency resulting from an ISLOCA scenario in the CANDU-6 type Wolsong nuclear power plant is very low, a direct release of radioactive nuclides to the environment could lead to severe radiation exposure among residents near the plant, and cannot be overlooked. For this reason, a quantitative evaluation of the amount of radioactive nuclides to be released to the environment was carried out by applying a best-estimate methodology to the MAAP-ISAAC code11MAAP-ISAAC is a CANDU version of MAAP owned by the Electric Power Research Institute, and a relevant accident management strategy for it was investigated in terms of a deterministic analysis. As part of this, an auxiliary building was additionally modeled to simulate deposition effects in the auxiliary building as well as pool scrubbing effects at the submerged break location following an ISLOCA. The decontamination effect by deposition and so on within the piping following an ISLOCA was evaluated. The analysis results showed that the decontamination factor for other nuclide groups excluding inert gas, Sb and Te2 nuclide groups was about 2.5. The analysis with consideration of all these decontamination effects was identified to yield a 78.4% reduction of Cs released to the environment compared with previous conservative analysis, which did not consider the decontamination effect within the ISLOCA piping and in the auxiliary building. In the case of the Wolsong CANDU plant, prior to external cooling water injection to the reactor vault (which is considered to be a Severe Accident Management Guidance (SAMG) accident management strategy), the amount of Cs-137 released to the environment exceeds the domestic regulatory requirement (100 TBq). In contrast, a sensitivity analysis in which an operator closes the test valve installed in a medium-pressure emergency core cooling system piping path and relieves the pressure of a reactor building using a containment filtered venting system (CFVS), met the aforementioned limitation for the amount of Cs-137 when an operator closes the test valve within 1 h following the accident and operates the CFVS properly (i.e., according to its operating procedure). This means that the appropriate accident management strategy for an ISLOCA scenario in the Wolsong CANDU plant can sufficiently prevent severe radiation exposure around the plant. Moreover, it is expected that these best-estimate methodologies developed from this study can be applied to all CANDU-6 plants.

Numerical investigation of buoyancy-induced flow in a sealed rapidly rotating disc cavity

This paper presents buoyancy-induced flow for a sealed rotating cavity with rotational Rayleigh number Ra in the range 107–109. DNS for an incompressible model with the Boussinesq approximation is compared with LES for a compressible gas flow model. The compressible solver’s solutions show the shroud Nusselt number Nu scales with Ra0.286, in close agreement with the corrected experimental correlation and the Ra2/7 scaling for gravitational heat convection between horizontal plates, but differs from the Nu∝Ra1/3 scaling given by the incompressible solver. The shroud thermal boundary layer thickness, based on the root mean square of the temperature fluctuation, can be estimated with λ∗=0.5Nu-1. Velocities scale approximately with ΩaβΔT. Disc laminar Ekman layer behaviour is confirmed up to Ra=109. An Ekman layer scrubbing effect, associated with the viscous energy dissipation, is considered to be mainly responsible for the difference in Nu between the two solvers at Ra=109, in spite of rather small Eckert number. The analysis of the turbulent kinetic energy budget shows a dominant constant buoyancy production in the core. The use of the incompressible formulation for the considered problem is restricted by the applicable range of the Boussinesq approximation characterised by the buoyancy parameter βΔT and neglect of viscous heating and compressibility effects characterised by the Eckert number Ec=Ω2rm2/(CpΔT).

Meeting future emission regulation at sea by combining low-pressure EGR and seawater scrubbing

In the current study, the environmental performance of the first full-scale combined low-pressure exhaust gas recirculation (EGR) and seawater scrubbing system was investigated thoroughly onboard an LPG carrier operated on high-sulfur HFO. Results clearly show that the chosen approach allows around 70% $$\hbox {NO}_x$$ reduction and simultaneous elimination (98% reduction) of $$\hbox {SO}_x$$ emissions. This would allow compliance both with $$\hbox {NO}_x$$ Tier III and future ECA sulfur regulations, although it would result in minor fuel penalty due to slightly deteriorated combustion (effect of EGR) and increased backpressure (effect of scrubber). The performed chemical analysis of the water samples revealed a fairly good performance of the wash water treatment plant with water samples identified as a good-quality water almost against all measured compounds. The values for pH, turbidity and nitrates were also far below the IMO requirements. However, in terms of certain metals (vanadium, nickel and zinc) and PAHs (fluoranthene and pyrene), the quality of discharge water was somewhat poorer. These compounds also appear to be the main drivers of risk of the environmental damage as was determined by the PEC/PNEC analysis. Here, the sufficient dilution with ambient seawater is essential to bring down the corresponding concentrations to the acceptable levels, although the measured excessive pollution of ambient water in terms of arsenic, copper and molybdenum should be kept in mind. Finally, different sampling procedures (IMO MARPOL and US EPA VGP rules) were practically evaluated providing some ideas for their further improvement, as with wrong sampling the obtained results can be very misleading.

Effect of scrubbing by NaClO backwashing on membrane fouling in anammox MBR

NaClO based chemically enhanced backwash (CEB) is often administered to maintain membrane permeability during the operation of MBR. However, the effect and working mechanism of NaClO concentrations in CEB were rarely investigated. The current investigation examined the changes in membrane resistance, permeate production and membrane morphology with or without CEB in an anammox MBR to reveal the scrubbing effect of different NaClO concentrations (0–596 mg/L). Good cleaning effect indicated by membrane fouling rate of 1.98–2.26 kPa/day and membrane permeate production of 80–88 L was observed when NaClO concentration of 149–596 mg/L was used. The best cleaning effect was observed when 298 mg/L of NaClO was used. To explore the mechanism of CEB action, backwashing foulants were also analyzed. Insoluble EPS transformed into soluble forms like S-EPS or SMP after the sludge was exposed to NaClO. The NaClO based CEB removed 112–675 mg of polysaccharide (PS)/m2 in foulants at NaClO concentration of 149–596 mg/L, which was significantly higher than the value obtained by pure water (35 mg PS/m2). The possible mechanisms behind the detachment of soluble PS seemed as oxidation and sterilization by NaClO. The current investigation provides useful guidelines on NaClO concentrations applied during CEB for anammox MBR.

EFFECT OF SUPPRESSION POOL CONDITIONS ON RISING BUBBLE PARAMETERS DURING WETWELL VENTING

The severe accident in Fukushima Daiichi NPP increased the need for better understanding of an accident progression. The events after the main earthquake followed by tsunami brought the attention to the flaws in the understanding and analysis of severe accident and made it clear which key points require more studies. One of the important factors became the containment thermal hydraulics and aerosol transport. In Fukushima Daiichi Unit 1 and 3 wetwell venting was utilized as a way to minimize the release of Fission Products (FPs) to the environment. However, the monitoring post radiation measurements showed that it was not the case. The retention of FPs in the Suppression Pool due to the pool scrubbing effect is affected by the changing conditions in the pool. Thermal stratification and depressurization may influence steam and non-condensable gas carrying FPs bubble hydrodynamics while bubbles are rising through the pool. The FPs transport from the bubbles to the water pool depends not only on the retention mechanisms inside the bubble, but also on the bubble hydrodynamics. Therefore, data base of bubble diameter and bubble rising velocity under thermal stratification and depressurization conditions is important for the improvement of Pool scrubbing code hydrodynamic models. Experimental data were collected in the test facility consisting of two pressure vessels – Drywell and Wetwell – connected via downcomer pipe, steam generator, and air compressor. The mixture of steam and non-condensable gas (air) was directed from Drywell to Wetwell, while the flow was governed by the pressure difference between the vessels slightly higher than the water head in the downcomer pipe. As the first step, experiments were conducted changing the conditions in suppression pool, varying the pool temperature (uniform and thermally stratified pool), air content, and downcomer submergence under atmospheric pressure. The rising bubble hydrodynamics was analysed adopting backlit shadowgraphy technique capturing the images with high speed camera. From the recorded data, influence of varied parameters was analysed on bubble size distribution represented by Sauter Mean Diameter (SMD) and average bubble rising velocity. Results show that bigger bubbles reached the pool surface with increasing downcomer submergence. Air content had small effect on SMD, while bubble rising velocity decreased with higher air content. With increasing suppression pool temperature both SMD and bubble rising velocity were decreasing. Thermal stratification did not have significant influence for both SMD and bubble rising velocity under constant pressure condition.