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The standpipe has become a standard element of most circulation loops. In the past, standpipes have been thought of as a device to only allow solids to transfer from a low to a higher‐pressure region. However, it also has another function in a solids circulation loop. It is also the device that adjusts its operation to balance the pressure around the solids circulation loop. An overflow standpipe adjusts the pressure drop across it by raising or lowering the solids level in the standpipe. However, the operation of the underflow standpipe is more complex. This self‐adjusting function can cause underflow standpipe pressure drops to be negative, which seems counter‐intuitive. How an underflow standpipe operating with a negative pressure build can occur in a circulation loop is described below using two commercial unit examples as illustrations of this phenomenon. [ABSTRACT FROM AUTHOR]

Water infrastructure development is key to attaining sustainable development, especially for water supply, sanitation and health, agricultural development, and energy production. However, sub-Saharan African countries face specific challenges around infrastructure financing, systemic and repeated malfunctioning, and decentralised infrastructure types. Using Nigeria as a case, this article aims to analyse historical water infrastructure development in Nigeria with a specific focus on dams and standpipes. Seven themes are discussed: infrastructure divisions; deprioritising water supply; political infrastructures; infrastructure failure and sustainability; infrastructure classification and typologies; optimal use of water resources and infrastructure; and a commentary on the future of water infrastructure development. The article concludes with policy and research suggestions for policymakers and other relevant stakeholders.

Highlights • The CPFD method was used to simulate the gas-solid flow in a cyclone and standpipe. • Gas leakage reduced the swirling intensity in the cyclone. • Gas leakage made the downward vortex turn upward in advance. • Gas leakage increased the pressure in the standpipe and the cyclone cone. • The particle circulations in the cyclone might be enhanced by gas leakage. Abstract This paper, the second part of a two-paper series, discusses the computational particle fluid dynamics (CPFD) simulation results to clarify the effects of gas leakage on the separation performance of a cyclone. Compared with the experimental results in Part 1 of this two-paper series, the CPFD simulation results showed good agreements on the pressure drop, the overall separation efficiency, and the grade efficiency. Gas leakage would reduce the swirling intensity in the cyclone, make the downward vortex turn upward in advance, and increase the pressure in the standpipe and the cyclone cone. The particle circulations in the cyclone might be enhanced by gas leakage. [ABSTRACT FROM AUTHOR]

Highlights • Experiments were carried out in a cold model of a cyclone. • Gas leakage fraction less than 8% did not affect the pressure drop over a cyclone. • Gas leakage fraction above 4% decreased the separation efficiency of a cyclone. • Gas leakage worsened the separation efficiency on fine particles of diameter less than 200 μm. Abstract This paper, first of a two-paper series, analyzes the experimental results to clarify the effects of gas leakage on the separation performance of a cyclone. Experiments were carried out in a cold model of a cyclone. Varied parameters were inlet gas velocity, inlet solid concentration, and gas leakage velocity. In the experimental range, the pressure drops over a cyclone showed small variation with the increase in gas leakage velocity. When the gas leakage fraction exceeded 4%, experiments showed that the separation performance deteriorated significantly. Gas leakage re-entrained separated fine particles in the standpipe into the cyclone, indicated by a significant decrease of the separation efficiency for fine particles. [ABSTRACT FROM AUTHOR]

In pumped storage power stations, according to whether diameter of the standpipe and the throttled orifice is same or not, the tailrace surge chamber can be divided into two types. The mathematical models of boundary conditions in the throttled surge chamber with two different types of long standpipe were established. Based on the method of characteristic and combined with the engineering example, transient process of several combination programs of different diameters of the standpipe and throttled orifice were simulated numerically and head loss coefficient of throttled orifice in combination programs was calculated. And the difference of combination programs’ head loss coefficient and its influence on upsurge and draft tube pressure were analyzed. The results show that increasing the diameter of the standpipe or throttled orifice can make minimum pressure at draft tube inlet and the maximum upsurge rise. The combination program that diameter of the standpipe and the throttled orifice is same compared with the combination program that diameter of the standpipe is slightly larger than that of throttled orifice, the difference of minimum draft tube pressure is small but the latter can more significantly reduce the maximum upsurge. The conclusion can provide references for the selection of diameter of the standpipe and throttled orifice in engineering. [ABSTRACT FROM AUTHOR]

Some parts of the rural areas of South Africa are receiving water services below the legislative standards stipulated in the Water Services Act (1997) of South Africa. This is because small-scale water infrastructures (SWI), including standpipes, handpumps and windmills, are failing to supply adequate water in rural communities for various activities that enhance their livelihoods. This is due to technical, community, institutional, and environmental factors. Literature indicates that these factors are complex in nature. However, research on their complex interactions has been limited. Therefore, the complex interactions of the factors causing SWI failure were investigated and analysed in this study. A qualitative research approach was employed to investigate the factors that cause failure of SWI. The network approach combined with graph theory and the community structure method were used to generate a theme and domain network that allowed for a systematic analysis and interpretation of the causes of SWI failure in the study area. The major causes of failure identified include: (i) the use of a top-down approach to implement water projects in rural communities without consultation, (ii) sharing of SWI in high numbers due to the limited number of SWI available/functional, resulting in overloading and increased breakdowns, and (iii) drying up of water sources due to poor siting leading to vandalism of SWI. Overall, the causes of SWI failure are as a result of the complex interactions of different categories of factors. The theme and domain network is a powerful tool that can be used represent and analyse the complex interactions. It is therefore imperative for interventions aiming to improve rural water supply to analyse the complex interactions of the causes of SWI failure to understand the underlying problems at a level of a system, in order to propose suitable solutions. [ABSTRACT FROM AUTHOR]

Background & objectives: Despite the increasing number of reported autochthonous malaria cases in Nouakchott and the identification of Anopheles arabiensis as the major malaria vector in this Saharan city, anopheline larval habitats have never been identified so far. The objective of this study was to identify and characterize anopheline larval habitats in Nouakchott. Methods: During September and October 2012, samples from pools of rainwater, water discharged from standpipes and household drinking water tanks in the districts of Dar Naim, Teyarett and Arafat were analyzed for the presence/absence of anopheline larvae and physicochemical characterization of breeding habitats. Results: Of the 51 prospected water bodies, eight consisting of seven water discharged from standpipes and one household drinking water tank were productive for Anopheles sp. All emerged anopheline mosquitoes from the positive dipping were morphologically identified as members of the An. gambiae complex. Multivariate regression analyses showed that a salinity up to 0.1 g/l and a shaded situation were respectively protective factors against high larval density in breeding sites (adjusted odds ratio = 0.62, 95% CI [0.44-0.87], p = 0.0052 and adjusted odds ratio = 0.56, 95% CI [0.44-0.71, p p = 0.0001). Interpretation & conclusion: The study demonstrated in Nouakchott that despite an arid and dry climate, human practices have contributed to the establishment of favourable environmental conditions for the development of anopheline mosquitoes and, therefore, maintaining malaria transmission in this Saharan city. The core malaria vector control intervention as the use of long-lasting insecicidal nets (LLINs) could be complemented in Nouakchott by larval source control. In this area, appropriate larval control measures may be recommended in line with an integrated vector management (IVM) approach.

Three-dimensional full-loop simulation of a high-density circulating fluidized bed (HDCFB) is conducted using the multiphase particle-in-cell (MP-PIC) method. The computational results are in good agreement with the experimental data of pressure distribution and solids circulation rate under different aeration conditions of the standpipe. The main feature of gas-solid flow in the riser is qualitatively predicted, with coexistence of the developed flow in the upper region and the acceleration flow in the lower region. The flow regime in the standpipe is mainly concurrent downward gas-solid flow in the close packing region. Due to the influence of the aeration gas, the pressure gradient presents a wave variation along the height of standpipe. The predicted solids residence time distribution in the standpipe exhibits a feature of early peak with an extended tail, indicating that the solids flow is not uniform in the standpipe. [ABSTRACT FROM AUTHOR]

In this paper, computational particle fluid dynamic (CPFD) modelling approach was used to describe the discharge of a fine glass beads powder from different hopper-standpipe geometries. The comparison between the CPFD predictions and the experimental results in terms of solid discharge rates, surface cone shape during discharge and pressure drops in the standpipe. The comparison allowed to assess on the possibility to use the CPFD modelling approach to simulate the powder flow in the hopper-standpipe system even accounting for the rather complex interactions between the interstitial gas and the particles occurring in the presence of a standpipe. Furthermore, the effect of hopper geometry on powder discharge was investigated with the CPFD model and verified experimentally in some purposely built hoppers. Finally, the relationships between the hopper geometry parameters (hopper outlet diameter and hopper half angle) and the flow parameters (solid discharge rate, height of characteristic surface, particle volume fraction, particle velocity, gas pressure and flow pattern) were obtained. [ABSTRACT FROM AUTHOR]

Pyrite-rich sediments would, invariably, undergo redox reactions which would lead to acidic aqueous environment containing solubilized toxic metal species. When such sediments are subjected to preload, a technique employed by geotechnical engineers to improve the load-bearing capacity of highly compressible formation, transient flow of pore water, accompanied by acidity transfer, would occur as a response. Despite the concomitant environmental and socio-economic significance, to date, there has been limited interdisciplinary research on the underpinning geotechnical engineering and geo-environmental science issues for pyrite-rich sediments under preload. In this study, we investigate the effect of pyrite-rich sediment pore water transfer under preload surcharge on the receiving environment and the impact on the groundwater speciation and quality. Sediment samples were obtained at close depth intervals from boreholes established within pristine areas and those subjected to the preload application. Soil and pore water samples were subjected to solid/solution speciation, moisture contents, soil pH and the Atterberg Limits' analyses using standard analytical techniques and methods. Standpipes were also installed in the boreholes for groundwater sampling and in situ monitoring of water quality parameters. It is shown that the imposition of preload surcharge over pyritic sediment created a reducing environment rich in SO , iron oxide minerals and organic matter. This reducing environment fostered organic carbon catabolism to generate excess pyrite and bicarbonate alkalinity, which would invariably impact adversely on soil quality and plant growth. These were accompanied by increase in pH, dissolved Al, Ca, Mg and K species beneath the surcharge. [ABSTRACT FROM AUTHOR]

The well-known Hvorslev (1951) formula was developed to estimate soil permeability using single-well slug tests and has been widely applied to determine riverbed hydraulic conductivity using in situ standpipe permeameter tests. Here, we further develop a general solution of the Hvorslev (1951) formula that accounts for flow in a bounded medium and assumes that the bottom of the river is a prescribed head boundary. The superposition of real and imaginary disk sources is used to obtain a semi-analytical expression of the total hydraulic resistance of the flow in and out of the pipe. As a result, we obtained a simple semi-analytical expression for the resistance, which represents a generalization of the Hvorslev (1951). The obtained expression is benchmarked against a finite-element numerical model of 2-D flow (in r - z coordinates) in an anisotropic medium. The results exhibit good agreement between the simulated and estimated riverbed hydraulic conductivity values. Furthermore, a set of simulations for layered, stochastically heterogeneous riverbed sediments was conducted and processed using the proposed expression to demonstrate the potential associated with measuring vertical heterogeneity in bottom sediments using a series of standpipe permeameter tests with different lengths of pipe inserted into the riverbed sediments. [ABSTRACT FROM AUTHOR]

IN THE LATE 1800s IN ST. LOUIS, MO., THREE MASSIVE STANDPIPES AND TOWERS WERE ERECTED TO PREVENT PUMP DAMAGE AND REDUCE MAIN BREAKS. THESE TOWERS BECAME CHERISHED MONUMENTS OF THE COMMUNITY AND REPRESENT THE EVER‐PRESENT STRUGGLES OF WATER PROFESSIONALS THROUGHOUT TIME. [ABSTRACT FROM AUTHOR]

The article examines occupational noise in a production fish hatchery and noise reduction techniques. Topics mentioned include the noise levels in the hatchery tank room with and without flowing water and the reduction of the noise through covering the open standpipes, placing partial tank covers over the tank's top above the water inlet, and covering both the tanks and standpipes.

The kick and loss accident is the critical risks of drilling engineering, and that will seriously affect the speed of drilling, quality of well construction and efficiency of exploration. To this end, this work is based on the characteristics of the pressure transmission speed is faster and the correlation between kick & loss and change trend of Standpipe Pressure (SPP) and Casing Pressure (CP), the change trend is used for monitoring the kick and loss accident. In this research, the value of neighbor well accident prior probability is combined with the SPP and CP of neighbor well whose block, horizon and drilling way is similar to target well, then extracting the pressure variation characteristics value vector, using the multidimensional variable normal density function for conditional probability Density Function (DF) and obtaining discriminant function based on Bayesian statistics method, finally using the DF to monitor the Drilling Status (DS) of target well. The actual field application showed that the Monitoring System is timely, accurate, and able to meet the needs of field applications and provide effective technical support for field kick and loss accident monitoring, it can be used as a new monitoring method of DS. [ABSTRACT FROM AUTHOR]

The vertical hydraulic conductivity ( Kv) of a stream or lake sediment is often determined in the field using standpipe tests. Calculation of Kv is based on the assumption that the hydraulic head in the pipe is equal to that of the stream or lake stage. In this work, a modified equation for Kv is developed for the standpipe test which is applicable when this assumption is not valid. The equation involves not only the hydraulic head at different times but also the difference in the hydraulic head ( a) between the groundwater level and river stage. The effects of certain factors on Kv, such as the ratio of the hydraulic head at different times ( h1/ h2), the difference a, and the initial water table height ( h0), are also discussed. The results show that when h1/ h2 is constant, the relative error ( Er) in Kv increases with the ratio a/ h2. Furthermore, if a/ h2 < 0.05, then for any value of h1/ h2, Er is less than 5% using the modified equation. Also, if a/ h2 is large, hydraulic head readings with larger h1/ h2 ratios must be used to avoid large Er values. The results of a field test also indicate that the error in Kv decreases as the value of h0 increases. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new N-valve was demonstrated to eliminate the stagnant particle layers in the solid recycling valve of CFB system. [•] The stagnant particle layer of N-valve can eliminate completely when the angled standpipe is θ ⩾45°. [•] High particle circulation rate G s could be realized by using the new N-valve with side aeration in angled standpipe. [•] G s increased with raising the side aeration flow rate U sa/U mf and the bottom aeration rate U ba/U mf. [ABSTRACT FROM AUTHOR]

Abstract: Loop-seal is one of the most common valves used in circulating fluidized bed (CFB) system. In the present work, a hydrodynamic model is developed for the operation that the particles in the recycle chamber are fluidized by the air, while the particles in the standpipe are in moving bed condition. Through hydrodynamic analysis, a hydrodynamic model including three equations has been established, whose solution results in the actual gas velocity, particle velocity and bed voidage in the recycle chamber. The model also predicts the solids flow rate, gas flow rate and pressure drop in both standpipe and recycle chamber. Experiments were conducted in a circulating fluidized bed with silica gel particles (Geldart group A). The model predictions showed good agreement with experimental data. [Copyright &y& Elsevier]

Pressure-drop balance and L-valve performance in a circulating fluidized bed (CFB) were investigated for variation in gas superficial velocity (Ug), secondary air fraction (SA), total solids inventory (Is), and external aeration flow rate (QA), at ambient temperature. The study shows that the solids discharge rate of an L-valve (Gs) changes with the system control variables. Apparently, a wider range of Gsis achieved at increasing Ug, decreasing SA, increasing Is, and increasing QA. The pressure-drop analysis indicates that these characteristics are directly governed by the loop pressure balance. Standpipe bottom pressure is found to be an important indicator of the operating status of the riser, standpipe, and L-valve. The experimental results confirm that an L-valve can be operated effectively by regulating the standpipe bottom pressure. The knowledge obtained from this study is essential for maintaining the performance of a CFB system for combustion operation, as well as for operating circulating fluidized beds on a practical scale. [ABSTRACT FROM AUTHOR]

Abstract: Two models for a Circulating Fluidized Bed (CFB) standpipe were formulated, implemented and validated to estimate critical CFB operational parameters. The first model continuously estimates standpipe bed height using incremental pressure measurements within the standpipe. The second model estimates variations in the void fraction along the standpipe using the Ergun equation in conjunction with the overall pressure drop across the bed, solids circulation rate and the standpipe aeration flows introduced at different locations of the pipe. The importance of different standpipe parameters obtained from these models is discussed in terms of successful operation of the overall CFB system. Finally, the applications of these models are shown in improving the solids circulation rate measurement and in calculating riser inventory. [Copyright &y& Elsevier]

Site-specific information about local water sources is an important part of a community-driven effort to improve environmental conditions. The purpose of this assessment was to gather this information for residents of rural villages in Ghana. Sanitary surveys and bacteriological testing for total coliforms and Escherichia coli (EC) using Colilert(®) were conducted at nearly 80 water sources serving eight villages. A focus group was carried out to assess the desirability and perceived quality of water sources. Standpipes accounted for almost half of the available water sources; however, a third of them were not functioning at the time of the survey. EC bacteria were found in the majority of shallow wells (80%), rivers (67%), and standpipes (61%), as well as 28% of dug wells. Boreholes were free of EC. Residents felt that the standpipes and boreholes produced safe drinking water. Intermittent service and poor water quality from the piped supply has led to limited access to drinking water. The perception of residents, that the water from standpipes is clean and does not need to be treated at home, is particularly troubling in light of the poor bacteriological quality of water from the standpipes. [ABSTRACT FROM AUTHOR]

Copyright of Revista Fuentes, El Reventón Energético is the property of Universidad Industrial de Santander and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Water quality surveillance can help to reduce waterborne diseases. Despite better access to safe drinking water in Sierra Leone, about a third of the population (3 million people) drink water from unimproved sources. In this cross-sectional study, we collected water samples from 15 standpipes and 5 wells and measured the physicochemical and bacteriological water quality, and the antimicrobial sensitivity of Escherichia coli (E. coli) in two communities in Freetown, Sierra Leone in the dry and wet seasons in 2021. All water sources were contaminated with E. coli, and all five wells and 25% of standpipes had at least an intermediate risk level of E. coli. There was no antimicrobial resistance detected in the E. coli tested. The nitrate level exceeded the WHO’s recommended standard (>10 parts per million) in 60% of the wells and in less than 20% of the standpipes. The proportion of samples from standpipes with high levels of total dissolved solids (>10 Nephelometric Turbidity Units) was much higher in the rainy season (73% vs. 7%). The level of water contamination is concerning. We suggest options to reduce E. coli contamination. Further research is required to identify where contamination of the water in standpipes is occurring.

Abstract: The mass and heat balances in circulating fluidized bed systems strongly depend on the overall solids flux recirculated, making it necessary to estimate or measure this flux. Many methods have been reported in literature to continuously monitor the solids flux, with the curve solids flux G s vs. pressure drop in the riser ΔP riser as one of the most used approaches. In this work, we show that in a circulating fluidized bed equipped with an inclined standpipe the whole mass flux is well correlated with the standard deviation of the pressure fluctuations in the standpipe. Contrary to the correlation G s vs. ΔP riser, our correlation results to be virtually independent of the superficial gas velocity in the riser in the range 3.1–7.5m/s. This makes it applicable for the on-line monitoring of the solids flux in a broad range of superficial gas velocities. Moreover, it has been shown that from the data G s vs. standard deviation it is possible to estimate the maximum solids flux achievable by the unit. From this information, we can know at which fraction of the maximum mass flux the circulating fluidized bed is operating. [Copyright &y& Elsevier]

A WHO and UNICEF joint report states that in 2008, 884 million people lacked access to potable drinking water. A life-cycle approach to develop potable water systems may improve the sustainability for such systems, however, a review of the literature shows that such an approach has primarily been used for urban systems located in resourced countries. Although urbanization is increasing globally, over 40 percent of the world's population is currently rural with many considered poor. In this paper, we present a first step towards using life-cycle assessment to develop sustainable rural water systems in resource-limited countries while pointing out the needs. For example, while there are few differences in costs and environmental impacts for many improved rural water system options, a system that uses groundwater with community standpipes is substantially lower in cost that other alternatives with a somewhat lower environmental inventory. However, a LCA approach shows that from institutional as well as community and managerial perspectives, sustainability includes many other factors besides cost and environment that are a function of the interdependent decision process used across the life cycle of a water system by aid organizations, water user committees, and household users. These factors often present the biggest challenge to designing sustainable rural water systems for resource-limited countries. [ABSTRACT FROM AUTHOR]

Uncontrollable blowout is a great drilling accident. For gas kick during drilling, in order to prevent uncontrollble blowout, the gas-liquild two-phase flow model is established, considering the kick characteristics in well kick and well killing process, and it is solved with finite difference method, given initial values in different periods. The results indicated that a one-to-one correspondence was established between standpipe pressure and kick rate and height while drilling, and another one-to-one correspondence was also established between casing pressure and kick rate and height while well killing. Based on the findings above, the standpipe pressure method and casing pressure method were proposed to detect kick, and the related coefficient method was used to judge the kick rate and height during drilling and killing. Meanwhile, a computer system was developed to judge kick velocity and height automatically, which provided a theoretical basis for kick parameter judgement. [ABSTRACT FROM AUTHOR]

Abstract: Control of solid flow rate is an essential parameter in various fluidized bed processes involving circulation of particles. L-valve is a common non-mechanical valve used to control solid flow rate pneumatically. Gas flow around the elbow of an L-valve together with particles properties determines the amount of solids transported through the L-valve of known geometry. The L-valve operation in an interconnected fluidized bed system is presented in this work. Helium was used to trace gas flow rate across the standpipe of an L-valve with 0.017 m i.d. Ilmenite and sand particles were used with corresponding density of 4750kg/m3 and 2650kg/m3 and average diameters of 128 and 368μm. 0.3vol.% of Helium in the fluidization air was used to trace gas flow rate across the standpipe of the L-valve. The average voidage of the non-fluidized solid flow across the standpipe was measured for packed bed and transitional packed bed flow. Moreover, the L-valve was operated alternatively with Helium and air to investigate gas properties effect on the L-valve operation. Accordingly, gas density had a minimum effect on the solid flow rate in the L-valve. Finally, the limiting operation of the L-valve was investigated in batch and continuous solid circulation operations. The overall pressure balance was found to play an important role in stability of the solid flow rate in the standpipe by imposing gas flow rate across this section. [Copyright &y& Elsevier]

In sub-Saharan Africa only 35% of the urban population has access to a piped water connection on their premises. The majority of households obtain water from public standpipes or from neighbors who are connected to the municipal network. Water resale is often prohibited, however, because of concerns about affordability and risks to public health. Using data collected from 1,377 households in Maputo, Mozambique, we compare the microbiological quality, as well as the time and money costs of water supply from individual house connections, public standpipes, and water obtained from neighbors. Households with their own water connections have better service across virtually all indicators measured, and express greater satisfaction with their service, as compared with those using other water sources. Households purchasing water from their neighbors pay lower time and money costs per liter of water, on average, as compared with those using standpipes. Resale competes favorably with standpipes along a number of service quality dimensions; however, after controlling for water supply characteristics, households purchasing water from neighbors are significantly less likely to be satisfied with their water service as compared with those using standpipes. [ABSTRACT FROM AUTHOR]

Abstract: In China, the vertical lifting method is typically applied when building the water intakes of hydraulic tunnels in the seabed in China. In this work, a 3D finite element method was employed to investigate the dislocations of joints, the stress distribution of segments and the bolt inner force during the lifting of the standpipe. Because the loading conditions of the tunnel during different construction phases vary greatly, a numerical model with three loading phases corresponding to different construction phases was established. The radial and circumferential bolts and the interactions between segments and standpipes were investigated. The critical issues associated with the design and construction of hydraulic tunnel, including the inner force of liners, the inner force of bolts and joint dislocations were vigorously analyzed. The results indicated that due to the jacking up of ceiling segments and the imposition of the lifting force, the maximum dislocation, which occurred at the crown between the open ring and the adjacent ring, increased with the lifting force. Although the maximum dislocation was within the allowable range, the maximum inner force of bolts caused by dislocations was close to the ultimate strength. As a result, it was concluded that special attention should be given to controlling of the lifting force, and protection measures should be adopted to reduce dislocations. [Copyright &y& Elsevier]

Circulating fluidized beds (CFB) have been widely applied to many area of industry such as chemical processing, petroleum refining, catalytic cracker processing, power generation and waste treatment. The application of CFBs provides several advantages, such as improving gas-solid contact, reducing the cross-sectional area because of high superficial velocities, and having a higher solids flux trough the reactor. A cold flow circulating fluidized (CFCB) has been built at the National Energy Technology Laboratory (NETL) in Morgantown recently, a mathematical model of the CFCFB standpipe was successfully developed and tested using an extended Kalman filter EKF and an H∞ estimator algorithm. The H∞ estimator and EKF algorithms have been used to estimate states such as the void fraction and the bed-height of the standpipe using pressure drop measurements. Using this standpipe mathematical model requires a solid circulation rate(SCR) to be a measurable variable offered from a spiral installed in the standpipe of CFCFB the spiral device at the standpipe of the NETL CFCFB test bed is impractical when a CFB system is operating in order to estimate the solids circulation, using a least squares estimator and a subspace algorithm. In this model, the measured aeration flow rates and pressure drop are used as inputs and outputs in the from of a time series in order to build the state space dynamic model. After this model has been obtained, the Kalman filter and H∞ algorithms is applied in order to estimate the solids circulation rate with the measured pressure drop profiles. [ABSTRACT FROM AUTHOR]

According to the filed frost damage investigation, frost heaving test and moisture migration simulation test, this paper describes results from filed and experimental data that investigated the reason and factors affecting freeway subgrade frost damage in seasonally frozen ground region. The results of field observation and the test series are compared to discuss the relationship of frost damage and water content, the origin of water on frost damage, the characteristic of water translocation and the road frost boiling caused by the lime-ash-soil deterioration of the subbase. Furthermore, by virtue of comprehensive study of this project, the distribution data of capillary water along the height by standpipe method are combined with the change law of frost heaving radio and water content, then the effective frost damage height can be obtained. Experimental results show that the values in specification are lower than those in test in some cases, which is unfavorable for the design of the subgrade prevention frostbite and anti-freeze. These results are significant for the design of the least height of road embankment and the depth of prevention frostbite at the site of excavation. [ABSTRACT FROM AUTHOR]

This paper presents an in situ falling-head method for measuring hydraulic conductivity of beach sediments in tidal environment. A polyvinyl chloride (PVC) standpipe was vertically pushed into the submerged beach sediments so that its lower part was filled by a sediment column. During the experiment, the sediments were submerged by sea water and the standpipe top was higher than the sea level. The pipe was fully filled with sea water at the beginning of the experiment. Then the water level time series inside and outside the standpipe were recorded. Analytical solutions were derived to describe the relation among the sediment's hydraulic conductivity and the water levels inside and outside the standpipe and used to analyze the experiment data obtained from the intertidal zone of Puqian Bay, Haikou, Hainan Province, China. The water levels predicted by the analytical solution agreed very well with all the experiment data. Experiments for horizontal hydraulic conductivity estimation were also conducted using L-shaped standpipe which bends from vertical to horizontal in the beach sediments. The averaged hydraulic conductivity anisotropy ratio at the study area is about 2.9. After each in situ experiment, the sediments in the standpipe were stored in a plastic box and transported to university laboratory to measure the hydraulic conductivity using falling-head method. It is found that the in situ hydraulic conductivity averages one order of magnitude greater than the laboratory one, indicating that the original beach surface sediments were loose due to tidal and wave actions and that the samples were significantly compacted during the transportation to laboratory. [ABSTRACT FROM AUTHOR]

Abstract: Loop-seal, considered heart of a circulating fluidized bed (CFB), returns solids captured by cyclone to the base of the riser while preventing direct flow of gas from high pressure riser to the low-pressure cyclone. This non-mechanical valve is used in thousands of CFB systems yet only a limited information is available on its working. Present research studies the flow of solids through a loop-seal and the effect of several design and operating parameters on it. This experimental study was conducted in a loop-seal 110mm×448mm×400mm high connected to a riser 152mm diameter and 5180mm high. Majority of the experiments was done with 171μm sand though several other size and type of solids were studied for their flowability. It was found that for the solids to flow through the loop-seal a minimum level of aeration, in excess of that required for minimum fluidization was required. The length of the horizontal passage connecting the supply and recycle chambers of the loop-seal had an important effect on the solids flow. For example, the minimum aeration for the onset of solids flow increases with increase in this length. The pressure drop per unit length across the passage also increased with the passage length. The air fed into the supply chamber is split such that the superficial air velocity in the supply chamber (or the standpipe) remained below the minimum fluidization velocity of the particles while the remaining air conveys solids through the horizontal passage. Present study showed that the solids flowing through the horizontal passage are neither fully fluidized nor moving packed or suspended solids. It moves as a segregated flow of solids driven by hydrostatic pressure and fluid drag. [Copyright &y& Elsevier]

Abstract: Standpipes are commonly used in circulating fluidised beds (CFB) to gravitationally transport solids from a region of lower pressure at the apex of the cyclone to the higher pressure region of the riser. Positron Emission Particle Tracking (PEPT) is applied to observe and study the real-time particle motion in standpipes of 2.5 cm and 4.5 cm ID respectively. Experiments use a hopper connected to the top of the standpipe while the base is connected to a free-discharging L-valve. PEPT results confirm that the solids velocity profile is asymmetrical along the vertical axis of the standpipe at any given height. The average voidage of the standpipe, ε a and solids flow rate, Q s are dependent upon the discharge rate of the L-valve, expressed by its fractional opening, f. An empirical equation to predict ε a has been derived: . The drag force on an individual solid particle can then be calculated and determines the actual motion of solids. Upward solids motion will be detected when the drag force exceeds the particle weight, whereas the motion will be downward with some degree of particle acceleration if the particle weight exceeds the drag force. The use of the design equations is finally illustrated in assessing the operation of standpipes of different diameter. [Copyright &y& Elsevier]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)