Cyclone Type Research Articles

タワーミル粉砕機（ＫＤ−３型機）における微粒子実収率を高めるための捕集部と分級部の改良

In the previous studies on pulverization of limestone by a Tower Mill Pulverizer, a product containing particles finer than 10μm could be obtained using a newly developed Tower Mill KD-3. From now, the Tower Mill KD-3 needs a higher level of efficiency for its further development, that achieves a high recovery of fine particles from the pulverized products. With this purpose, a series of investigations have been carried out on different types of cyclones and classifiers to clarify the factors which could affect the recovery of pulverized particles: Single Cyclone with Spiral Ribbons (SCSR), Twin Cyclone (TC), Twin Cyclone with Spiral Ribbons (TCSR), Simple Classifying Part (SCP), Classifying Part with Inclined Sieves (CPIS).The results of these investigations can be summarized as follows:(1) An increase in the recovery of fine particles was recorded using a TCSR and a CPIS. In both cases the achieved performances are certainly due to the high air flow rate in the cyclone.(2) The relationships between the maximum particle diameters and the 50 % particle diameters of the products were approximately straight lines whatever cyclones and classifiers were used.

Effect of different spray chambers on the determination of organotin compounds by high-performance liquid chromatography–inductively coupled plasma mass spectrometry

One of the potential problems to overcome when coupling liquid chromatography with atomic spectrometry is the low sample transport efficiency. Often this is a consequence of the interface design, and in particular the nebulizer and spray chamber configuration. The present study reports on a comparison of several spray chambers (single-pass, double-pass and cyclone types) with respect to both design and performance characteristics. In order to evaluate performance for speciation studies, different configurations have been evaluated utilizing HPLC–ICP-MS. Various organotin compounds (monobutyltin, dibutyltin, tributyltin and triphenyltin chlorides) were coinjected and the effects on resolution, sensitivity and SNR assessed. Of the spray chambers evaluated, a cyclone spray chamber (internal volume 22 ml) with cooling jacket was found to offer the best performance and gave a transport efficiency of 7.5% without loss of chromatographic resolution and sensitivity.

Design Methodology for Multiple Inlet Cyclones

Correlations were developed to model the performance of two types of multi-inlet aerosol sampling cyclones. The body of one cyclone had the Lapple conventional geometry and the other had a shorter ...

In vitro starch disappearance procedure modifications

Four in vitro experiments evaluated the effects of ruminal fluid inoculum:artificial saliva ratios, grinder type, grind size, and diet of ruminal fluid donor on in vitro starch disappearance. Experiment 1 examined rates of starch disappearance and coefficients of determination obtained by linear regression of starch disappearance using five grain sorghum (Sorghum bicolor (L.) Moench) lines, a corn (Zea mays L.) control, and a wheat (Triticum aestivum L.) control. Grains were incubated for 4, 8, 12, 16, and 20 h with inoculum varying in proportion of ruminal fluid and artificial saliva (1:1, 1:2, 1:3, and 1:4). In vitro rates of starch disappearance and coefficients of determination were similar for the 1:2, 1:3, and 1:4 inoculum dilutions and were higher (quadratic, P < 0.01) than the 1:1 dilution. As the proportion of artificial saliva in the inoculum increased, in vitro pH increased (linear, P < 0.01). In Experiment 2, six grain sorghum lines and a corn control were ground through a 1-mm screen in a Udy (cyclone type) or Wiley mill. Starch disappearance for samples ground using a Udy mill were higher (P < 0.01) than for samples ground in a Wiley mill and approached 90% digestion in 8 h. Experiment 3 compared six grain sorghum lines and a corn control ground through a Wiley mill equipped with either a 1-mm or 2-mm screen. Starch disappearance of samples ground through a 1-mm screen were lower (P < 0.10) when compared with samples ground through a 2-mm screen. In Experiment 4, the effect of grain type (corn, sorghum, or 50:50 corn:sorghum) in 92.5% concentrate diets of ruminal fluid donors was compared in a replicated 3 ⇔mes; 3 Latin square design. Six grain sorghum lines and five corn hybrids were evaluated with in vitro digestion. Ranking by in vitro rate of starch digestion was not affected (P > 0.10) by grain type fed; however, absolute rates of digestion varied among inoculate sources. Grinder, grind size, and ruminal fluid inoculum:artificial saliva ratios affected rate of starch disappearance in samples digested in vitro. Diet of ruminal fluid donor affected the rate of starch digestion, but not the relative ranking of the grains. If rates are to be compared across in vitro runs for different grains, these processing and dietary factors must be kept constant.

In vitro starch disappearance procedure modifications

Four in vitro experiments evaluated the effects of ruminal fluid inoculum:artificial saliva ratios, grinder type, grind size, and diet of ruminal fluid donor on in vitro starch disappearance. Experiment 1 examined rates of starch disappearance and coefficients of determination obtained by linear regression of starch disappearance using five grain sorghum ( Sorghum bicolor (L.) Moench) lines, a corn ( Zea mays L.) control, and a wheat ( Triticum aestivum L.) control. Grains were incubated for 4, 8, 12, 16, and 20 h with inoculum varying in proportion of ruminal fluid and artificial saliva (1:1, 1:2, 1:3, and 1:4). In vitro rates of starch disappearance and coefficients of determination were similar for the 1:2, 1:3, and 1:4 inoculum dilutions and were higher (quadratic, P < 0.01) than the 1:1 dilution. As the proportion of artificial saliva in the inoculum increased, in vitro pH increased (linear, P < 0.01). In Experiment 2, six grain sorghum lines and a corn control were ground through a 1-mm screen in a Udy (cyclone type) or Wiley mill. Starch disappearance for samples ground using a Udy mill were higher ( P < 0.01) than for samples ground in a Wiley mill and approached 90% digestion in 8 h. Experiment 3 compared six grain sorghum lines and a corn control ground through a Wiley mill equipped with either a 1-mm or 2-mm screen. Starch disappearance of samples ground through a 1-mm screen were lower ( P < 0.10) when compared with samples ground through a 2-mm screen. In Experiment 4, the effect of grain type (corn, sorghum, or 50:50 corn:sorghum) in 92.5% concentrate diets of ruminal fluid donors was compared in a replicated 3 ⇔mes; 3 Latin square design. Six grain sorghum lines and five corn hybrids were evaluated with in vitro digestion. Ranking by in vitro rate of starch digestion was not affected ( P > 0.10) by grain type fed; however, absolute rates of digestion varied among inoculate sources. Grinder, grind size, and ruminal fluid inoculum:artificial saliva ratios affected rate of starch disappearance in samples digested in vitro. Diet of ruminal fluid donor affected the rate of starch digestion, but not the relative ranking of the grains. If rates are to be compared across in vitro runs for different grains, these processing and dietary factors must be kept constant.

An Analysis of NMC's Nested Grid Model Forecasts of Alberta Clippers

Abstract Forecasts of Alberta Clipper–type cyclones defined as cyclones that move southeastward from regions of western Canada into south-central Canada or the north-central United States before moving eastward to the coast of North America, were studied using the National Meteorological Center's Nested Grid Model (NGM). All available NGM forecasts between 1 January 1988 and 31 December 1992, excluding the months of June, July, and August, were analyzed. The 5-yr sample included 59 Alberta Clippers. For each cast, the cyclone center position and central pressure were recorded for the NGM's initialization (0 h) and for 12-, 24-, 36-, and 48-h forecasts for each available run. Average cyclone position errors ranged from 140 km, with a standard deviation of 183 km at 12 h, to 339 km, with a standard deviation of 407 km at 48 h. Average central pressure errors ranged from 0.0 hPa, with a standard deviation of 2.5 hPa at 12 h, to 1.0 hPa, with a standard deviation of 5.7 hPa at 48 h. East of 84.0°W, cyclones v...

Performance assessment of three personal cyclone models, using an Aerodynamic Particle Sizer

The sampling efficiency of three types of personal cyclone has been experimentally measured at a sampling flow rate of 2.11 min −1. All samplers were based on the original Higgins and Dewell-type cyclone. Samplers were characterised using a polydisperse glass microsphere aerosol contained in a calm air chamber. A modified Aerodynamic Particle Sizer was used to determine the particle size distribution of the aerosol entering and leaving the cyclones. Two of the cyclone types were shown to be statistically identical within experimental errors, when characterised in terms of their d 50 points. However, the third type showed a significant deviation in sampling characteristics from the others. It was possible to trace this to a manufacturing error, which has since been rectified. Comparison with previously measured cyclone efficiency curves using similar techniques was good, indicating that characterising aerosols samplers using the APS and polydisperse aerosols is at a stage where experimental errors are not dominated by the instrument, or the aerosol type.

The cyclone separators performances under high temperature in PFBC unit

A high temperature gas cleanup system, which consisted of three cyclone separators in series, has operated satisfactorily through 500 hours in a 1 Mwt PFBC pilot test unit. The total collection efficiency of this system was 99–99.3%. The fly ash concentration in cleaned gas stream reduced to values below 2×10 −4 kg/m 3 (N) and there are no particles larger than 10μm. The second stage cyclone is the newly developed Φ 240mm PV type cyclone separator with dimensions optimized. Its measured cut size is 1.2μm and the resistance coefficient considering pressure drop about 12. The third stage multicyclone separator consists of three Φ100 EPVC — I type cyclone tubes and its collection efficiency of 8μm particle is about 99.5%.

Pollutant emissions from circulating atmospheric fluidised beds burning low-grade coal

More than 70% of the total electricity production in Greece is based on the utilisation of soft brown coal of medium ash content ( 15%), high moisture ( 58%) and low calorific value (4.5-5 MJ kg −1 ). The increasing demand (twice the EC average) for electrical power imposes the need for the best exploitation of the existing brown-coal surface mines, together with new ones producing solid fuel of the same or even lower quality. This fact, combined with the high cost of the DeNO x /DeSO 2 facilities required when the conventional pulverised-fuel combustion technology is applied, implies a need for investigating the applicability to the particular coal quality of alternative coal-combustion technologies such as fluidised-bed combustion. This paper presents the results of combustion tests on Greek lignite in two CFBC (circulating fluidised bed combustor) facilities. The first, a laboratory-scale facility of approximately 100 kW thermal power, is at NTUA (the National Technical University of Athens); the second, which is of semi-industrial scale (1.2 MW thermal power), is at RWE's power station at Niederaussem in Germany. The two installations are of different size and different design, and the concepts represent the major CFBC construction trends: the Niederaussem facility operates with a thermally insulated («hot») cyclone, whereas the CFBC in Athens features a non-insulated («cold») cyclone. The results reported in this paper include determination of the operating conditions to achieve proper fuel burnout, examination of the influence of air-staging on the temperature distribution inside the reactor, and investigation of the combustion behaviour of the particular fuel type in relation to the size of fuel particles. As regards pollutant emissions, the CO, SO 2 , NO x and N 2 O emissions are recorded during various test cases for both facilities. Particular interest applies to the examination of additives of various types in order to obtain the maximum SO 2 retention inside the reactor, because the fuel that was used has a high sulphur content (1.5%). Several conclusions are drawn concerning the necessary modifications and requirements of the plant layout when a large-scale CFBC installation is designed to burn low-grade brown coal. The air-staging, furnace cooling, reactor height and cyclone type are considered the critical parameters for proper ignition and burnout conditions. Note, however, that the results in this paper are not exclusively of industrial interest: they also include documented experimental data from various test cases, which can be used for the evaluation of computational models aiming to simulate the combustion of coal in CFBCs

North Atlantic ultra high frequency variability: An introductory survey

This study attempts to depict east Atlantic cyclones specificity using ECMWF 1984–1994 cold season analyses. Due to the strong low frequency variability in this area, a climatology of transient events has to take the “background” weather regime into account. North Atlantic weather regimes have therefore been recovered through cluster analysis techniques. An objective criterion defining the occurrence of subsynoptic cyclones is then designed. It uses the high frequency signature of vorticity. The events thus retained include frontal waves, cold air cyclogenesis and other small scale developments. The preferred location of these events is found to be quite distinct from the classical storm-tracks. They appear downstream and slightly south of them, reaching the north-western part of Europe during Zonal weather regimes, and a zone centred some 500 km north of the Azores during Greenland Anticyclone regimes. In order to gain some idea of the various types of subsynoptic cyclones captured by the criterion, a one-point selection of cases was performed and the resulting vorticity fields were partitioned by a cluster analysis. Two types of waves out of three clusters are documented. A Type 1 is shown to be a modified baroclinic development, with reduced scale and features well accounted for by recent theoretical work on frontal waves. A Type 2 composite, with its typical warm front, is more difficult to set into an existing theoretical framework. It seems connected to the presence of an actively diffluent background flow. DOI: 10.1034/j.1600-0870.1995.00112.x

Synoptic typing and its application to the investigation of weather air pollution relationships, Birmingham, United Kingdom

Principal components analysis and cluster analysis are used to derive airmass types based on surface meteorological data for the Birmingham area. UK. Airmass types are analysed in terms of their climatological, meteorological and air pollution characteristics. Continental anticyclonic airmass types are identified as producing high pollution concentration events, whereas, maritime cyclonic types, characterised by strong westerly flows are associated with low levels of atmospheric pollutants.

Inverted Troughs and Cyclogenesis over Interior North America: A Limited Regional Climatology and Case Studies

Abstract A limited regional climatology of cyclones with and without inverted troughs that form in the Colorado region is presented along with case study results from two major cyclone events in which an inverted trough plays a prominent role in the life cycle of the storm. Typically, the inverted trough separates a polar or arctic air mass dammed up along the eastern foothills of the Rockies from an older modified polar air mass over the plains. Inverted troughs are favored when anticyclonic conditions prevail at the surface across south-central Canada and the northern plains states beneath a confluent flow aloft. Although both types of cyclones form in response to a progressive trough crossing the Rockies, a composite analysis shows that an inverted trough is most likely when a band of meridionally oriented ascent in the lower and middle troposphere persists along the eastern slopes of the Rockies beneath confluent flow aloft. Cyclones without an inverted trough tend to occur when the synoptic-scale asc...

Computation of Turbulent Flow in a Cyclone Chamber with a Reynolds Stress Model. 2nd Report. Numerical Prediction of Cyclone Performance.

The Reynolds stress model and the standard k-ε eddy viscosity model were applied to highly swirl-confined flows in six types of cyclones, which are widely used as centrifugal separators in industrial applications, in order to numerically predict the collection efficiency of dust particles and the pressure loss across the cyclone. The Reynolds stress model can capture the feature of the highly swirling turbulence field accurately, while the standard k-ε model misrepresents the flow characteristics due to the error in its eddy viscosity hypothesis. Prediction of the collection efficiency is, therefore, improved by the Reynolds stress model over the standard k -ε model. In addition, the pressure losses obtained by the Reynolds stress model calculation are in good agreement with experimental data.

Stable Combustion in Sludge Melting Furnace by Fuzzy Logic Control

This paper discusses combustion control using fuzzy logic for a sewage sludge melting furnace. The sewage sludge melting process is gaining attention as an effective method for reducing sludge volume. The slag from molten sludge is stable, causes no pollution, and can be used as a by-product. However, the operation of a sludge melting plant requires expert operators who have to deal with complex phenomena that take place in a melting furnace. In an effort to facilitate the operation, the authors have employed a control system which features the use of fuzzy logic for automatic combustion control in a cyclone type sewage sludge melting furnace. Confirmation was made that this fuzzy logic combustion control system functioned effectively for controlling the furnace temperature, O2 concentration in the furnace outlet flue gas, and concentration of NOx.

Validation of GCM control simulations using indices of daily airflow types over the British Isles

In this study, the control simulations of two general circulation model (GCM) experiments are assessed in terms of their ability to reproduce realistic ‘real world’ weather. The models examined are the UK Meteorological Office high-resolution atmospheric model (UKHI) and a coupled ocean/atmosphere model of the Max Planck Institut fur Meteorologic, Hamburg (MPI). An objective classification of daily airflow patterns over the British Isles is used as a basis for comparing the frequencies of model-generated weather types with the frequencies derived from 110 years of observed mean-sea-level pressure (MSLP) fields. The weather-type frequencies generated by the GCMs, and their relationships with simulated monthly mean temperatures and total precipitation over the UK, are compared, season by season, with similar results derived using the observational data. An index of gale frequencies over the British Isles, derived from a similar objective analysis of daily MSLP fields, is used to evaluate the ability of the GCMs to simulate the observed frequency of storm events. One advantage of using 110 years of observational data is that the observed decadal-scale variability of climate can be introduced into this type of validation exercise. Both the GCMs assessed here are too cyclonic in winter. The seasonality of both anticyclonic and cyclonic types is much too strong in MPI and summer precipitation in this model is greatly underestimated. MPI simulates the annual cycle of temperature well, while UKHI successfully reproduces the annual cycle of precipitation. The analysis also indicates that the summer temperature variability of the two models is not driven by circulation changes.

Radiotracer Evaluation of Laterite and Coal-Ash Dust Discharged into Environment

Abstract In Elbasan steel plant a large quantity of dust is discharged into the environment by laterite fluidized bed calciner and the coal boiler for steam production. By means of radiotracers the erosion of the laterite in the fluidized bed calciner was estimated experimentally. Based on the experimental data a mathematical model has been constructed for the erosion, which permits calculation of the mass of the dust deriving from erosion when the granulometric composition of the mineral on entry to the calciner is known. The efficiency of two types of cyclones in laterite calciner and coal boiler, for three granulometric classes of laterite dust and coal-ash was studied. Ways for reducing the quantity of dust discharged into environment are proposed.

Application of mechanical similarity laws to the collection efficiencies of geometrically types of uni-flow cyclone dust collectors

From the mechanical similarity point of view, the centrifugal effect, Λr, and the Stokes number,St, as well as the Reynolds number,Rec for the motion of solid particles in the cyclone are the relevant parameters. In order to apply these similarity laws for the prediction of the characteristics of the collection efficiency,ηc, geometrically similar types of uni-flow cyclones were used. The body diameters of the cyclones wereD1=30,50,69 and 99 mm, respectively. The feed particle concentration of the fly-ash particles was up toCo=60 g/m3. From the experimental results: (1) the pressure drop, Δpc, in the cyclones was a function of not only the Reynods number,Rec, but also the body diameter,D1; (2) the collection efficiency,ηc, did not always increase with decreasing body diameter but there existed an optimal body size; (3) application of the mechanical similarity laws to the collection efficiency was not always sufficient for estimating the collection efficiency, since the feed particle concentration was an additional important factor; (4) a new parameter which was the ratio,Epf, of the apparent separation energy,Wp, of the solid particles to the energy loss,Ec, of the gas flow in the cyclone was introduced for discussing the collection efficiency; (5) Fuchs theory, used to estimate the collection efficiency, was examined. Fuchs theory may be applied for high feed particle concentration.

異形サイクロンの集塵性能

Free vortex cyclones are used in various industrial fields because of their simple structure, low equipment investment, easy maintenance and low running cost. Recent studies have improved their performances. A broad range of applications of free vortex cyclones are expected for industrial and especially high temparature dust collections. However, there are still many phenomena that need to be made clearly.In this study, the performances of free vortex cyclones as dust collectors have been experimentally studied under various operating conditions using several types of cyclones and with several kinds of wall surface roughness. It was found that the addition of a little friction resistance to a cyclone's cylindrical wall is desirable to reduce pressure loss without reducing collection efficiency. On the other hand, a special type of cyclone is capable of better performance than that of the normal type. Its pressure loss is lower, and its collection efficiency is slightly higher than the normal type. A cylindrical type has a performace similar to a normal one, but a conical type is inferior. A slightly eccentric exit pipe does not have much effect on the cyclone's performance.

Statistical evaluation of Lower Flammability Distance (LFD) using four hazardous release models

AbstractUsing four hazardous dispersion models, the ability to predict Lower Flammability Distance (LFD), the distance from a release through which the released gas is present in concentration below flammable range, has been evaluated using a set of large‐scale propane release field experiment data. The four models evaluated were the DEGADIS model, the SLAB model, the OME Simple Gas model and the OME Heavy Gas model (1983). The observed LFDs were compared with the predicted LFDs for three atmospheric conditions. The complete data set was broken into two parts: (1) the cyclone type releases (representing instantaneous release situations) and (2) the nozzle type releases (representing horizontal jet releases). A procedure based on the USEPA guidelines on air quality models was followed to evaluate the models.The complex models (DEGADIS and SLAB models) appear unreasonably weak in predicting LFD's compared with the relatively simple Gaussian model used in the OME Simple Gas model for instantaneous releases. The OME simple gas model is significantly better than the DEGADIS and SLAB models for cyclone type (instantaneous) releases under unstable and neutral atmospheric conditions; and the DEGASIS model is significantly better than the SLAB model for nozzle type (horizontal jet) releases under stable atmospheric conditions. Since the size of the data set is not large enough (n = 20 for cyclone type release and n = 18 for nozzle type release), it is difficult to show 95% significant differences between models.

Simulation of barotropic wind-driven circulation in the upper layers of Bay of Bengal and Andaman Sea during the southwest and northeast monsoon seasons using observed winds

A two-dimensional, nonlinear, vertically integrated model was used to simulate depth-mean wind-driven circulation in the upper Ekman layers of the Bay of Bengal and Andaman Sea. The model resolution was one third of a degree in the latitude and longitude directions. Monthly mean wind stress components used to drive the model were obtained from the climatic monthly mean wind data compiled by Hastenrath and Lamb. A steady-state solution was obtained after numerical integration of the model for 15 days. The sensitivity of the model to two types of open boundary conditions, namely, a radiation type and clamped type, was tested. A comparison of simulated results for January with available ship drift data showed that the application of the latter along the open boundary could reproduce all the observed features near the boundary and the interior of the model domain. The model was integrated for 365 days to study the circulation during the southwest and northeast monsoon seasons. The model was successful in simulating the broad features of circulation including gyres and eddies observed during both the seasons, the development of north equatorial current during the northeast monsoon period and eastward moving monsoon drift current up to 90°E during the southwest monsoon season. During the latter season, two anticyclonic gyres were observed in the central and the southern parts of the Bay. A cyclonic type of circulation was prevalent in the central and western parts of the Bay of Bengal during the northeast monsoon months of November and December. The simulated western boundary current along the east coast of India, flows northward and southward during the southwest and northeast monsoon seasons respectively. It is presumed that this western boundary current, simulated during both the seasons, is locally wind-driven.