Characterization of Dust Particles Emitted Through Pulse-Jet Fabric Filters During Industrial Pollution Control

The present investigation elucidates the role of pulse-cleaning parameters and filter media designs on the extent of dust emission and emitted particle characteristics during industrial pollution control using the pulse-jet filtration process. The study is followed by statistical analysis based on L₈ (2⁷) orthogonal design methodology. The experimental study shows that the dust concentration in clean gas increases with an increase in pulse pressure and pulse duration, whereas it decreases with an increase in pulse cycle. However, the contribution of pulse pressure and pulse duration is much higher than the impact of pulse cycle. In regard to the impact of filter media design, a higher level of bag height (which also implies lower air-to-cloth ratio) and lower level of seamline spacing can lead to higher outlet emissions at the transitory stage. The role of pulse pressure, bag height, and seamline spacing are found to be very significant in regulating fine particles in the emission (PM_2.5) and, consequently, the aforesaid factors affect all volume particles diameters (D₁₀, D₅₀, and D₉₇) and weight mean particles diameter D (4, 3) of particles in bulk.     

Observation of dust release behavior from ceramic filter elements

The dust-releasing behavior from a ceramic candle filter, which is a key technology of the hot gas cleaning system in advanced coal power generation processes such as pressurized fluidized bed combustion and integrated gasification combined cycle, is discussed based on the observation of the dust-releasing process using a high-speed video camera and the measurement of time change of pressure inside the filter. Time changes of dust-released area and geometrical characteristics and motion of released dust cake fragments were investigated by analyzing photo images from the video camera, compared with the time change and distribution of pressure inside the filter. In order to discuss the influence of porosity of the dust layer, a consolidated dust layer was prepared by clean air filtration at an elevated filtration velocity after the dust filtration. The dust-releasing process was found to be a multi-mode process, i.e. release occurred in a short time after the injection of cleaning air, followed by one or two intermittent releases afterwards. The amount of dust released by the first strike increased with tank pressure. The dust-releasing behavior was sensitive to the cake porosity: the mean size and perimeter of cake fragments increased with porosity and tank pressure for the consolidated dust layer. The initial radial velocity of cake fragment released just after the first strike increased with tank pressure and was almost independent of the filter location.     

Friction effect on contact pressure during indentation and scratch into amorphous polymers

Using finite element analysis (FEA), for monotonic loadings, variations of the true contact geometry and of the mean contact pressure p_m, defined by the ratio of the applied normal load to the true projected contact area, are described as a function of the testing conditions, the geometrical strain a/R and the local friction coefficient μ_loc, during indentation and scratch experiments with spherical indenter. The estimation of an equivalent plastic strain is also proposed and shown to be a complex function of a/R and μ_loc, especially during scratch experiments. The normalized contact pressure p_m/σ_y, with σ_y, the initial yield stress of the tested material, determined during indentation and scratch tests is compared to an expanding cavity model, recently developed for indentation of elastic-strain hardening plastic materials.     

Slip Effects in Vibrating Wire Experiments on 3He-4He Mixtures

We report enormous slip effects in viscosity measurements on the concentrated and the dilute phase of saturated ³He-⁴He mixtures, using vibrating wires in the temperature range 10-250 mK. The concentrated phase data show that the liquid almost does not stick to the wires. There is striking agreement between the data and the solution of the Navier–Stokes equation with the non-sticking boundary condition of zero transverse momentum between the liquid and the surface of the wire. If the slip is taken into account, we obtain good agreement between the viscosity of concentrated and pure ³He. The dilute phase shows slip of a different nature. The analysis based on Eq. (112) of Højgaard Jensen et al. ¹ resugts in the kinematic viscosity and a parameter β relating the slip length, ζ, to the radius of the wire, a. Instead of the expression for β given in the literature, we propose β=ζ/(2ζ+a), because (1) in the limit of ζ→∞ our expression agrees with the non-sticking boundary condition and (2) only our expression fits under the constraint that ζ∝l _η, where l _η is the viscous mean free path. As long as ζ>2a, our expression fits the data very well with ζ/l _η in the range 50–150, depending on the wire.     

Effects of air volume ratio parameters on air curtain dust suppression in a rock tunnel’s fully-mechanized working face

To investigate the effects of the air volume ratio parameters (axial-to-radial flow ratio of the wall-attached air cylinder “δ” and the forced-to-exhaust ratio of the ventilation system “β”) on the air curtain dust suppression in a rock tunnel’s fully-mechanized working face, the eastern belt fully-mechanized working face in Huipodi mining company (Shanxi Mineral Group Co., Ltd., China) was numerically simulated by CFD software in this study. First, a mathematical model for describing the airflow-dust migration in a fully-mechanized working face was established using the Euler-Lagrange method. A full-scale geometrical model of the tunnel was also developed. The effectiveness of the established models and the related parameter settings were then verified by making comparisons between the field measured values and the numerical simulation results. Finally, the airflow migration and dust dispersion rules under different ventilation conditions (δ?=?5:5–1:9 and β?=?0.5–1.5) were simulated. According to the simulation results, a decrease in δ and β contributed to the formation of an effective axial dust-suppression air curtain in the fully-mechanized excavating region. For eastern belt fully-mechanized working face and those under similar production conditions, an effective axial dust-suppression air curtain can be formed when δ?=?1:9–2:8 and β?=?0.5–0.75. When δ?=?1:9 and β?=?0.5–0.75, the high-concentration dust were blocked in the space in front of the driver of heading machine (i.e., within 7?m from the head-on section), which achieved a better dust suppression effect.     

DEM study and machine learning model of particle percolation under vibration

This paper aims to understand model the effect of vibration on particle percolation. The percolation of small particles in a vibrated bed of big particles is studied by DEM. It is found the percolation velocity (V_p) decreases with increasing vibration amplitude (A) and frequency (f) when the size ratio of small to large particles (d/D) is smaller than the spontaneous percolation threshold of 0.154. Vibration can enable percolation when the size ratio is larger than 0.154, while V_p increases with increasing A and f first and then decreases. V_p can be correlated to the vibration velocity amplitude under a given size ratio. Previous radial dispersion model can still be applied while the dispersion coefficient is affected by vibration conditions and size ratio. Furthermore, a machine learning model is trained to predict V_p as a function of A, f and d/D, and is then used to obtain the percolation threshold size ratio as a function of vibration conditions.     

Effect of nozzle type on pulse-jet cleaning performance of ceramic filter tube

The dust-cleaning efficiency of the ceramic filter tube is the key factor to determine the long-term stable operation of the dust removal system, and the type of nozzle significantly influences the performance. In this study, four types of nozzles (injection hole, sudden enlargement nozzle, tubular nozzle, and induction nozzle) are used to conduct comparative experimental study on the dust-cleaning effect of the ceramic filter tube. Using the schlieren technique find that the tubular and induction nozzles can improve the deviation angle of pulse-jet airflow. The injection parameters were set as an injection pressure of 200 kPa, an injection distance of 120 mm and a pulse width of 80 ms in the experiment. Using the sidewall pressure measurement system indicates that the integrated pressure of the sudden enlargement nozzle is the largest, but the uniformity is poor. The comprehensive pressure of the sudden enlargement nozzle is increased by 64.86 %, and the non-uniformity is reduced by 28.62 % compared with those of the induction nozzle. Using the visualization filtration cycle test system implies that the degree of damage and stripping state of the dust layer are directly proportional to the sidewall pressure. Moreover, it is found that the residual pressure drop changes exponentially with the dust removal quality under different nozzle types. These conclusions can help explain the mechanism of dust stripping and provide a basis for the selection of nozzles.     

Investigation to rectangular flat pleated filter for collecting corn straw particles during pulse cleaning

This work investigated the amounts of dust residual of a rectangular flat pleated filter for collecting corn straw particles during pulse cleaning and attempted to explore the causes of incomplete cleaning. In this study, dust residual, filter’s pressure drops and static peak pressures were obtained across flat pleated filter during the pulse cleaning. The optimum parameters were obtained that the pulse electromagnetic valve size was one inch, the pulse pressure was 0.2–0.3?MPa, and the filtration velocity was 0.6?m/min for the nozzle type with 7 holes with a diameter of 7?mm (7?×?Ф7?mm). Under this condition, the experimental results show that the dust residuals were 198.4 (64%), 52.7 (17%), 58.9 (19%)?g for initial collected dust residual 310?g at top, middle and bottom areas of the filter panel, respectively. The dust residuals were major on the top area of the filter panel, especially on the gap locations between the two-adjacent pulse airflows. Meanwhile, the more pulse interval or dust concentration was increased the dust residuals of the filter panel and the pressure drops of the filter were increased. Moreover, the static peak pressure distribution can give guidance to the dust residual distribution.     

A study on the dust control effect of the dust extraction system in TBM construction tunnels based on CFD computer simulation technology

In order to control dust in a tunnel boring machine (TBM) construction tunnels, this paper, in combination with field measurements, applies CFD computer simulation technology to study the dust control effect of TBM construction tunnels under different dust extraction flow rates. Firstly, the dust extraction system is closed, and the result of the simulation show that the dust diffuses to the entire TBM working area within 181 s, indicating the necessity of having a dust extraction system in the tunnel. Secondly, the dust extraction system is open and under the original dust extraction flow rate of Q_e = 8 m³/s, the overall dust diffuses to the entire working area L_o = 130 m, and the full-face dust diffusion distance is L_f = 47.54 m. Then the study was carried out with the setting of 2 m³/s ≤ Q_e ≤ 14 m³/s. The results show that: when Q_e ≤ 8 m³/s, the full-face dust diffuses to 47.54–71.84 m; when Q_e > 8 m³/s, the full-face dust can be controlled at 42.81–46.34 m; and when Q_e = 8 m³/s, the full-face dust control effect is better, and the average dust concentration in the tunnel is as low as 12.25 mg/m³, indicating that the original dust extraction system has a better design. The field measurement results verify that the CFD computer simulation results are accurate.     

Effect of filtration velocity and dust concentration on cake formation and filter operation in a pilot scale jet pulsed bag filter

Bag filters are used for the removal of fine solid particles from process gases. Thus, understanding the filter cake build up and its properties is a subject of interest. The filter cakes properties may depend on many factors like, for example, filtration velocity and dust concentration. The effect of dust concentration and filtration velocity on filtration time, specific cake resistance and mean cake density is investigated in a pilot scale jet pulsed bag filter. An in situ optical system is used to measure cake thickness distributions on the filter surface. Additionally, the operation is simulated using a one-dimensional model and results are compared with experiments. The experimental results indicate that cake density and specific resistance increase with increasing velocity at constant dust concentration. The effect of dust concentration on filter cake density and specific resistance is small.     

Chemomechanical control of sliding friction behaviour in non-metals

Recent work has shown that surface active environments can be used to significantly and predictably influence the near-surface flow behaviour (i.e. hardness) of such solids as magnesium oxide, calcite, alumina, quartz and soda-lime (s.l.) glass. Specifically, these solids are hardest in environments in which theirζ-potential is approximately zero. The results of the present study demonstrate that such chemomechanical effects can, under certain conditions, also be used to affect and control sliding friction behaviour. In particular, it is shown that for magnesium oxide and s.l. glass in various environments the coefficient of frictionμ _f is a minimum when ζ ? 0. This and other results are described, and some mechanistic and practical implications discussed.     

Structural aspects of alpha-omega transformation in group IV transition metals and alloys

The three most common crystal structures encountered in group IV transition metals Ti, Zr, and Hf and alloys based on them, under different temperature, pressure and alloy concentration conditions, are hcp(α), bcc (β) and simple hexagonal (ω). Although the structural relations of α?β andβ?ω transformations are well understood, the same is not true for α→ω phase change, which occurs at high pressures. We have done high pressure experiments on Ti-V alloys, followed by electron diffraction to study this. These patterns from pressure treated foils of alloys Ti₉₅ V₅ and Ti₉₁ V₉ showed the presence ofβ-phase with fourω variants. Some of them showed the existence of all three phases, α,β andω, with the number of variants given by the lattice correspondence matrix, derived through the orientation relations of α →β andβ →ω. This is a clear evidence that the α →ω transformation proceedsvia theβ-phase. The atomic rearrangements required forα →ω are found to be much smaller if the path is via theβ-phase, rather than the earlier model of Silcock.     

Normal perforation of reinforced concrete target by rigid projectile

An analytical model on the normal perforation of reinforced concrete slabs is constructed in the present paper. The effect of reinforcing bars is further hybridized in a general three-stage model consisting of initial crater, tunnelling and shear plugging. Besides three dimensionless numbers, i.e., the impact function I, the geometry function of projectile N and the dimensionless thickness of concrete target χ, which are employed to predict the ballistic performance of perforation of concrete slabs, the reinforcement ratio ρ_s of concrete (or area density) and the tensile strength f_s of reinforcing bars are considered as the other main factors influencing the perforation process. Simpler solutions of ballistic performances of normal perforation of reinforced concrete slabs are formulated in the present paper. Theoretical predictions agree well with individual published experimental data and have a higher degree of accuracy than the model suggested by Dancygier [Effect of reinforcement ratio on the resistance of reinforced concrete to hard projectile impact. Nucl Eng Des 1997;172:233–45].     

PRELIMINARY PERFORMANCE TESTS OF A PULSED JET PLEATED PAPER CARTRIDGE FILTER SYSTEM

ABSTRACT

A pulsed jet pleated paper cartridge filter system was tested for particle removal efficiency and operating stability using agricultural limestone as the test dust. The test system consisted of 6 pleated paper filter units arranged in parallel, each unit having an effective filtration area of 18.1 square meters. The system was operated at constant pressure drops of 6.25, 7.50 and 8.75 kPa (2.5, 3.0 and 3.5 inches of water), with face velocities of 0.78 to 1.04 m/ min (2.5 to 3.4 feet per minute) and dust loadings ranging from 0.5 g/ m to 2.5 g/ m³. Penetration through the media appeared to be relatively independent of dust loading, and efficiencies were in the 99.95 + % range. Slightly lower efficiencies were found for particles having diameters of 0.3 to 1.0 micrometers. A measure of the redeposition of dust pulsed from the filter was required to describe the effects on the pulse rate caused by changes in system flow and pulsing set point. Increased redeposition was found to occur with increasing flow rate, causing an increase in the pulse rate required to maintain operation of the system at a pulsing set point. Overall, the reverse pulse jet pleated paper cartridge filter system displayed extremely high particle removal efficiency in a compact unit that operated with low differential pressure.     

Comparison of fatigue failure criterion in flexural fatigue test

This study compares traditional stiffness and energy based fatigue failure criteria with the fatigue failure criterion based on the viscoelastic continuum damage (VECD) approach. In traditional approach, fatigue failure is defined as the number of cycles at which the stiffness of a material reduces by 50% (N_f50). In energy based approach, fatigue failure is defined by the number of cycles at the maximum energy ratio or Rowe’s maximum stiffness defined by stiffness multiplied by the corresponding number of the cycle (E * N). In VECD approach, fatigue failure is defined by the number of loading cycles at the inflection point of the normalized pseudostiffness (C) versus damage variable (S) curve. It is shown that a correlation exits between traditional criteria and VECD criteria. It is shown that maximum energy ratio or Rowe’s maximum stiffness based fatigue life is higher than the traditional fatigue life (N_f50). This indicates the traditional approach is conservative. A strong correlation of fatigue was observed between the VECD fatigue criterion and energy ratio based fatigue criteria. However, the fatigue life by VECD approach is always less than the fatigue life by energy ratio or Rowe’s maximum stiffness.     

Influence of Nano-Ag Addition on the Mechanical Properties of (Cu0.5Tl0.5)-1223 Superconducting Phase

Superconducting samples of type (nano-Ag) _x Cu_0.5Tl_0.5Ba₂Ca₂Cu₃O_10?δ , x=0.0,0.5,1.0,1.5,2.0, and 3.0 wt.% of the total sample’s mass were prepared by a single step solid-state reaction technique. The prepared samples were characterized using X-ray powder diffraction (XRD) and a scanning electron microscope (SEM). The electrical properties of the prepared samples were investigated using the electrical resistivity and I–V measurements. The Vickers microhardness (H _v ) was measured at different applied loads (0.25–3.0 N) for studying the mechanical performance of the prepared samples. All prepared samples exhibited normal indentation size effect (normal ISE) and the H _v number was load dependent. H _v number increases as nano-Ag addition increased. The experimental data of H _v was analyzed using different models; Mayer’s law, Hays–Kendall (H–K) approach, elastic/plastic deformation (EPD) model, proportional specimen resistance (PSR) model, and indentation induced cracking (IIC) model. In addition, the true microhardness (H _o ) values were evaluated through different models. The obtained data has good agreement with the PSR model. Also, Young’s modulus (E), yield strength (Y), fracture toughness (K _f ), and brittle index (B _i ) were calculated.     

On the Superfluid Fraction and the Hydrodynamics of Supersolids

This review largely considers the author’s extensions of two foundation works in supersolids: Andreev and Lifshitz’s hydrodynamics, and Leggett’s Non-Classical Rotational Inertia (NCRI) with estimates of the T=0 upper limit. Relative to the case of a perfect lattice, the Andreev and Lifshitz equations contain an additional degree of freedom, which permits a liquid-like internal pressure P that is distinct from the lattice stress (or ‘solid-like pressure’). This is particularly relevant to ⁴He, which requires an applied pressure P _a to solidify; use of a Maxwell relation relating P and strain yields that $P\sim P_{a}^{2}$ ; we estimate that near the melting pressure the liquid-like pressure in equilibrium is about 1/4 of the solid-like pressure. This new freedom also permits vacancy diffusion, which we have studied for both ordinary solids and supersolids. In both cases, for the vacancy diffusion mode the liquid-like pressure and the lattice stress cancel. Further, since at T=0 the supersolid fraction f _s is less than unity and the excitation part of the normal fraction is zero, we argue that there must be an additional source of “normal” mass, to which we attribute a velocity that in principle is distinct from the lattice velocity associated with elasticity. Relative to NCRI we have made numerous estimates of the upper limit for the superfluid fraction f _s ; we find f _s values on the order of 0.2 for realistic models of the atomic density. Correlation effects in the solid cause the superfluid velocity $\vec{v}_{s}$ of one particle to depend on correlations with the positions of other particles, and this leads to a more complex theory for the flow pattern and for the upper limit on f _s .     

Modified shear lag theory based fatigue crack growth life prediction model for short-fiber reinforced metal matrix composites

Closed form expressions for the low cycle and high cycle fatigue crack growth lives have been derived for the randomly-planar oriented short-fiber reinforced metal matrix composites under the total strain-controlled conditions. The modeling was based on fatigue-fracture mechanics theory under both the small scale and the large scale yielding conditions. The modified shear lag theory was considered to describe the effect of yielding strength. The present model is essentially a crack growth model because crack initiation period in short fiber reinforced metal matrix composite is much shorter; hence, not assumed to play a dominant role in the calculation of fatigue crack growth life. The effects of short-fiber volume fraction (V_f), cyclic strain hardening exponent (n′) and cyclic strain hardening coefficient (K′) on the fatigue crack propagation life are analyzed for aluminum based SFMMCs at different levels of cyclic plastic strain values. It is observed that the influence of fatigue crack growth resistance increases with increase in cyclic strain hardening exponent (n′) and decreases when volume fraction (V_f) or cyclic strain hardening coefficient (K′) increases. The present MSL theory based fatigue crack growth life prediction model is an alternative of modified rule of mixture and strengthening factor models. The predicted fatigue life for SFMMC shows good agreement with the experimental data for the low cycle and high cycle fatigue applications.     

Observation of the process of dust accumulation on a rigid ceramic filter surface and the mechanism of cleaning dust from the filter surface

The accumulation process of captured particles on the surface of a rigid filter element is experimentally studied by measuring the pressure drop. It is then related to the packing density of the dust layer. The process of the release of dust from filter surface is also studied through the changes in the pressure difference across the filter and the movement of the released dust after clean air is injected. As a result, for a given filtration condition, dust forms the densest layer at the initial and the loosest at the middle stage of the filtration, and forms a uniform layer at the final stage. The cleaning efficiency of the dust layer is found to depend upon the layer structure, i.e, it decreases as dust forms a denser layer, even if the accumulated mass per unit filter surface area is the same. The release velocity of dust from the surface is also found to become slower as the porosity of the layer decreases.