Cotton dust particle size distribution in oil mills

Analytical procedures have been developed for characterizing the size and shape of cotton dust particulates collected by the vertical elutriator (VE) sampler. Data are reported for dust distributions on VE filters collected from different processing areas (cleaning, delintering, hulling, and baling) in cottonseed oil mills. Results of particle volume distributions obtained with a Coulter counter are compared with data obtained from an image-analysis system designed to classify cotton dust into fibrous and nonfibrous (particulate) components. The image-analysis data include distributions of the lengths and widths of fibers and the areas and diameters of particles present on the VE filters. In many of the locations studied, a considerable amount of the total dust sampled can be attributed to lint, lint fragments, and also to particles significantly larger than 15 μm diameter. Southern Region, SEA, USDA.     

Chemical composition of dusts from cottonseed oil mills

The proximate chemical composition of total dust samples from five Texas cottonseed oil mills was determined. Dust compositions were highly variable and were affected more by the processing step than by differences among mills. Composition of cleaning room dusts reflected differences in soil minerals. Typical inorganic values were: silicon (12%), aluminum (0.5%), and iron (0.7%). Delintering dust was highest in cellulosic materials (40%), whereas the 23% protein composition of the hulling dust showed the influence of kernel fragments. Baling, dust contained large amounts of cellulose (38%) and noncellulosic organic constituents (36%).     

Evaluation of occupational dust control technology in cottonseed oil mills

Occupational cotton dust control technology was evaluated in 10 oil mills throughout the cotton belt of the U.S. This evaluation was restricted to mechanical portions of each mill: seed cleaning, delintering, hulling and separating, and linter baling. Based on the process machinery observed in these mills, a 500 ton/day model cottonseed oil mill was designed. The occupational dust control systems for this mill were based on current state-of-the-art technology observed during this project. Further improvements based on readily available air pollution control devices have been incorporated. In order to achieve minimal respirable dust concentrations in the mill, all dust emission points have been enclosed to the maximal extent consistent with efficient plant operations. The various processing areas in the mill were designed with negative pressure dust control systems separate from the general ventilation system. The dust control system includes coarse dust removal by high-efficiency cyclones whose effluent discharges into pulse-jet fabric filter bag-houses operated at an air-to-cloth ratio of 20:1. The emission control system for saw-type delinter systems were divided into small units to reduce the deleterious effects of fires. In order to conserve space, Figures 4, 5, 9, 10, 11, 12, 13, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 28, 29 and 30 are not shown, even though they are referenced in the text. Readers desiring copies of these may obtain them at reproduction costs from the authors.     

Liquid Explosive Evaporative Removal of Submicron Particles from Hydrophilic Oxidized Silicon Surfaces

A pulsed CO₂ laser-based system, operating at a wavelength of 10.6 μm, was used as a cleaning tool to remove particles as small as 0.1 μm from hydrophilic, oxidized silicon surfaces. The laser beam served as a fast heating source to induce the explosive evaporation of a water film deposited on the particle-contaminated surface. The resulting explosive forces were high enough to expel particles from the surface efficiently. The contaminant particles used were 0.1 μm alumina, 0.1–0.2 μm silica, and 0.1 μm polystyrene latex.

For each of these, the cleaning efficiency was monitored as a function of the laser fluence, the thickness of the deposited water film and the number of cleaning cycles. Whatever the nature of the particles, the cleaning efficiency was characterized by an upper limit of the energy density, determined to be 1.5 J/cm², at which substrate damage occurred. At all lower laser fluences, the removal efficiency was particle-dependent.

The thickness of the deposited water film was varied by changing the time of exposure of the surface to water vapor, the vapor flow being fixed at 4700 ml/min. An exposure time of 1.5 s was found to be the most effective. Increasing the number of cleaning cycles permitted the evaluation of the effect of the zeta potentials of the particles with respect to that of the surface.     

Silica/mullite fiber composite membrane with double-layer structure for efficient sub-micrometer dust removal

Here, we developed silica/mullite fiber composite membranes with double-layer structure by a simple vacuum procedure for the removal of sub-micrometer dust. The support with three-dimensional skeleton structure exhibited high porosity (higher than 90%), low density (lower than 0.25?g/cm³) and high compressive strength (higher than 0.55?MPa) at 1000?°C. By controlling the mass ratio of silica sol to mullite fiber, we can obtain uniform and complete filtering layers with different thicknesses. The composite membranes exhibited high PM filtration efficiency with 99% for 1–10?µm, 97% for 0.5?µm and 90% for 0.3?µm. These samples had high air flow with very low pressure drop (lower than 600?Pa when airflow velocity reached 1?m/s). These results indicated that the silica/mullite fiber composite membranes were very promising for PM pollution control in the field of hot gas filtration.     

A simple synthesis of nitrate cancrinite from natural bentonite

A nearly pure, pale brown, spherical, nitrate cancrinite zeolite was successfully synthesized from natural bentonite as starting material with acidic activation treatment via hydrothermal method at 368 K for 24 h. The effect of different NaOH concentrations (pH at around 12) was investigated without addition of silica and aluminum sources. The effect of different NaOH concentrations (pH at around 12) was investigated without addition of silica and aluminum sources. The final products were characterized by powder X-ray diffraction, scanning electron microscopy, elemental and thermal analyses, infrared (IR) spectroscopy, and Brunauer–Emmett–Teller (BET) surface area measurements. While the Si/Al ratio of ideal cancrinite is 1.0, the Si/Al ratio of the product framework is approximately 1.76, apart from trace components. Unique single nitrate band was observed in both IR and thermogravimetric measurements, indicating that pure cancrinite was synthesized. This study showed that pure nitrate cancrinite was obtained with NaOH concentrations from 8 to 12 M, independent of NaOH contents on crystallization. Through this study, we proposed a simple synthesis method for pure nitrate cancrinite from bentonite for the purpose of recycling natural clay minerals.     

Preparation of Cu(II)-Immobilized Chitosan (CIC) and Preliminary Urea Uptake Study

The effect of filler loading and size on commercially available silica (Vulcasil C) and value added silica (ultrafine) as filler in SMR L grade natural rubber were studied. Vulcasil C with particle size ranged from 10 µm–20 µm whilst ultrafine (1 µm–3 µm) was loaded in SMR L compound at 4 different loadings. The curing characteristics, tensile properties and swelling behavior were studied. At similar filler loading, ultrafine-filled vulcanizates exhibited shorter scorch time and cure time. It also shows higher tensile strength and elongation at break up to 20 phr filler loading and exhibit lower swelling ratio compared to Vulcasil C-filled vulcanizates.     

Crack healing in liquid-phase-pressureless-sintered silicon carbide–aluminum nitride composites

Crack healing in liquid-phase-pressureless-sintered SiC–AlN composites was investigated by introducing cracks into specimens and subsequently heat-treating the specimens. It was observed that cracks were healed and the strength was recovered. Cracks were filled with silica or mullite produced by the oxidation of the composites. It was shown that the healing temperature could be fixed in the range 1100–1300 °C and that large cracks up to about 300 μm could be healed completely. Our results imply that a simple oxidation heat-treatment can improve the reliability of silicon carbide–aluminum nitride components.     

Liquid Explosive Evaporative Removal of Submicron Particles from Hydrophilic Oxidized Silicon Surfaces

A pulsed CO₂ laser-based system, operating at a wavelength of 10.6 μm, was used as a cleaning tool to remove particles as small as 0.1 μm from hydrophilic, oxidized silicon surfaces. The laser beam served as a fast heating source to induce the explosive evaporation of a water film deposited on the particle-contaminated surface. The resulting explosive forces were high enough to expel particles from the surface efficiently. The contaminant particles used were 0.1 μm alumina, 0.1-0.2 μm silica, and 0.1 μm polystyrene latex.

For each of these, the cleaning efficiency was monitored as a function of the laser fluence, the thickness of the deposited water film and the number of cleaning cycles. Whatever the nature of the particles, the cleaning efficiency was characterized by an upper limit of the energy density, determined to be 1.5 J/cm², at which substrate damage occurred. At all lower laser fluences, the removal efficiency was particle-dependent.

The thickness of the deposited water film was varied by changing the time of exposure of the surface to water vapor, the vapor flow being fixed at 4700 ml/min. An exposure time of 1.5 s was found to be the most effective. Increasing the number of cleaning cycles permitted the evaluation of the effect of the zeta potentials of the particles with respect to that of the surface.     

碱化度对聚合氯化铝混凝除硅的影响

通过对实验室现有工业级聚合氯化铝进行碱化度分析,向多个化学试剂厂调研得出,现场常用聚合氯化铝的碱化度在1.5～2.7之间。通过合成不同碱化度(2.0～2.4)的聚合氯化铝,对模拟成垢水进行系统的混凝实验,考察碱化度对聚合氯化铝混凝除硅的影响。研究表明,碱化度会决定铝形态的分布,进而影响混凝除硅的效果。随着碱化度的升高,Al_a含量逐渐降低,Al_b含量先增大后减小,Al_c含量逐渐增加。对模拟污水处理后,残余硅酸形态有很大差异,用聚合氯化铝(2.0)除硅后Si_a含量变为32.1mg/L,Si_c含量变为15.3mg/L;聚合氯化铝(2.2)除硅后Si_a含量变为28.71mg/L,Si_c含量变为30.5mg/L;聚合氯化铝(2.4)除硅后Si_a含量变为22.4mg/L,Si_c含量变为41.2mg/L。聚合氯化铝(2.0)除硅后Si_a降低的比例最大,聚合氯化铝(2.4)除硅后Si_c降低的比例最大。随着碱化度的升高,全硅剩余含量依次为47.4mg/L、59.5mg/L、63.6mg/L,表明碱化度越低,除硅效果越好。     

Status of efforts by oil mill machinery manufacturers to control fugitive dust emissions

Machinery manufacturers who serve the cottonseed crushing industry are fully aware of the existing fugitive dust problems. The main problem lies in the unique characteristic of cottonseed as being a non-free-flowing material until after lint removal. This characteristic is compounded by varying degrees of moisture. Therefore, a totally enclosed cottonseed cleaner in a dust-tight shroud is not practical due to periodic choke-ups, tail-over from the top trays and the frequent necessity to manually clean the screens. Delintering equipment has been successfully equipped with canvas drapes connecting the feeder to the top of the roll box front as well as hinged doors that connect the black seed chutes to the bottom of the roll box. Dust and noise levels have been reduced, but not eliminated. Rock and shale traps between the white seed tank and cleaning rooms, as well as within the lint rooms and separating rooms, help reduce free-fly lint within the processing streams. Rock and shale traps that operate under positive pressure can be another potential dust source which can be eliminated by a dual fan arrangement. After delintering, cottonseed becomes more predictable with regard to flowing ability and more conventional methods of dust control can be applied. Separators can be enclosed as long as maintenance accessibility and operator control visibility are not hindered. The operating air requirements for the machine can be used to maintain an air flow into the enclosure, thus greatly reducing dusty emissions.     

Effect of siliconizing temperature on microstructure and phase constitution of Mo–MoSi2 functionally graded materials

Mo–MoSi₂ functionally graded materials were prepared by a liquid phase siliconizing method. The microstructure, phase constitution, cross-section elemental distribution, grains size, and coating thickness of these materials were investigated with scanning electron microscopy (SEM), back scattered electron (BSE), energy dispersive spectroscope (EDS), glow discharge spectrum (GDS) and X–ray diffraction (XRD). The results indicate that the Mo–MoSi₂ functionally graded materials have a dense multi-layer structure, mainly composed of surface layer (Si–MoSi₂ layer, 1–10?µm), intermediate layer (MoSi₂ layer, 22–40?µm), transitional layer (Mo₅Si₃ and Mo₃Si layer, 2–3?µm) and Mo substrate. Moreover, the silicon concentration, grains size, and coating thickness increase gradually with the increasing temperature. The surfaces silicon concentrations are about 68–75?wt%, the average grains sizes of MoSi₂ columnar crystals are about 7.1–9.4?µm, and the coating thicknesses are about 28–35?µm.     

Influence of the Grit size of Silicon Carbide Particles on the Mechanical and Electrical Properties of Stir Casting Aluminum Matrix Composite Material

This paper studies the influence of the grit size of silicon carbide particles on the mechanical and electrical properties of stir cast aluminum matrix composites. A two step-mixing method of stir casting technique at (500 rpm) has been adopted. Type 1170 Al with (99.66 % C.P) and silicon carbide (SiC) particulates of 240 grit size (45 µm), 320 grit size (29 µm), 600 grit size (9 µm) and 1200 grit size (3 µm) were used. The incorporation of weight fraction of SiC ranges from 2.5 %, 5 %, 7.5 % and 10 %. The microstructures of the produced composites were examined using a scanning electron microscope. Mechanical properties were determined by using a universal testing machine of 30 KN load. Microhardness was performed on the composite specimens by using a LECO 700 HT tester with a load of 492.3 N and with a dwell time of 10 seconds. The electrical properties were determined using a Keithley instrument Model 2400 point probe machine. The results show that the modulus, yield strength and hardness of the composite increase at lower grit sizes of silicon carbide of 3 micron. The maximum hardness of 26.1 HVN and maximum modulus elasticity of 1517.6 N/mm ^-2 was obtained at 7.5 % weight fraction of SiC. A boost in the mechanical and electrical properties of the produced alloys was gained by changing the grit size of the silicon carbide.     

Spatial distribution of silica fillers in phase-separated rubber blends investigated by three-dimensional elemental mapping

The distribution of nano-sized silica in binary rubber blends is characterized by scanning transmission electron microscopy (STEM) tomography combined with energy dispersive X-ray spectrometry (EDX). 3D distribution of silica is visualized by STEM-EDX tomography with the tilt-series of silicon elemental maps, while the phase-separated morphologies of polyisoprene rubber (IR) and styrene-butadiene rubber (SBR) are visualized by STEM-tomography in high-angle-annular-dark field (HAADF) mode. The combination of STEM-EDX and STEM-HAADF tomography enables us to determine the distribution of silica between the two rubber phases quantitatively even with high contents of silica up to 70 phr (weight parts per hundred rubber). It is found that silica is preferentially distributed in the SBR phase, but it is also distributed in the IR phase when the IR fraction in the total rubber components is higher than 40 wt%. The preferential distribution of silica in the SBR phase improves the dispersion of the IR domains. This is the first use of this technique for a multicomponent polymer system, showing the advantage to characterize the complicated multicomponent polymer composite morphologies.     

Experimental prediction of the agglomeration capability of waste vegetable oils (WVO) in relation to the recovery of coal from coal fines cleaning wastes (CFCW)

Coal fines cleaning wastes (CFCW) were agglomerated with samples of a vegetable oil heated at 150 °C for 1–15 days. An agglomeration efficiency index (AEI) which variation depends on the oil agglomeration capability was calculated. Good linear correlations were attained between the AEI values and the viscosity, and the unsaturation degree of the oil monitored by FT–IR and ¹H NMR. Based on the results achieved, the prediction of the agglomeration capability of the waste vegetable oils (WVO) from these properties in relation to the recovery of coal from coal fines cleaning wastes appears feasible.     

Influence of surface treatments on topography and bond strength of densely-sintered zirconium-oxide ceramic

The aim of this study was to evaluate the effect of surface treatments on the roughness and bond strength of dental materials containing MDP to zirconium oxide ceramic. Forty square-shaped zirconium-oxide ceramic blocks (Lava Zirconia, 3M-ESPE) were treated as follows: (CT) polished only; (SB) sandblasting (110 µm aluminum oxide particles) or (SC) silica coating (110 µm particles). Roughness of treated surface was measured using a profilometer (Ra) and by atomic force microscope (AFM). Two resin luting agents were used after silane application: self-adhesive (Rely X U200, 3M-ESPE) and dual cure (Rely X Ultimate, 3M-ESPE). The samples were submitted to microshear bond strength test. The failure analysis was performed. Data were submitted to ANOVA and Tukey test (α=0.05). Bond strength results ranged from 20.44 (CT+Ultimate) to 34.37 MPa (SC+U200) after 24 h and from 12.03 (CT+Ultimate) to 27.44 MPa (SC+U200) after 12 months of storage with SC statistically superior to the other treatments. Mean values of roughness varied from 0.07 (CT) to 0.85 µm (SC). The both resin luting agents showed similar results to all surface treatment groups. Silica coating provided the best treatment of the ceramic surface.     

Microstructural evolution of a silicon oxide phase in a perfluorosulfonic acid ionomer by an in situ sol–gel reaction

Nanocomposites were produced via sol–gel reactions for tetraethylorthosilicate within the cluster morphology of perfluorosulfonic acid films. Small-angle x-ray scattering revealed that the polar/nonpolar nanophase-separated morphological template persists despite invasion by the silicon oxide phase. Scanning electron microscopy (ESEM–EDAX) studies have indicated that the greatest silicon oxide concentration occurs near the surface and decreases to a minimum in the middle. Optical and ESEM micrographs revealed a brittle, surface-attached silica layer at high silicon oxide contents. © 1995 John Wiley & Sons, Inc.     

Effect of hot-dip siliconizing time on phase composition and microstructure of Mo–MoSi2 high temperature structural materials

Mo–MoSi₂ high temperature structural materials were obtained by hot-dip siliconizing method. The results show that the silicon melt and molybdenum substrate have good wettability, molten silicon reacts with molybdenum substrate to form a molybdenum silicide phase with a columnar structure, and a strong MoSi₂ crystallographic preferred orientation (CPO) on the (110) crystal face is characterized. While, the Mo–MoSi₂ high temperature structural materials consist mainly of silicon rich layer, MoSi₂ layer, interface layer and molybdenum substrate. The coating surfaces contain a high silicon concentration (55–65?wt%) than the MoSi₂ layer (30–35?wt%). Moreover, the thicknesses and the average grain sizes of siliconized coatings increase sharply with increasing siliconizing time. The coatings thicknesses are 20, 25, 30, and 50?µm, respectively. And the average grain sizes are 6.9, 9.3, 11.7, and 11.8?µm, respectively.     

Comparison of sulphur in HNO3-extracted and physically cleaned coals

The sulphur contents of eight bituminous and subbituminous coals, after extraction with nitric acid, are compared with the sulphur contents of physically cleaned samples of the coals. Samples of −60 mesh (250 μm) coal were extracted with boiling 2 M HNO₃, which removes essentially all mineral sulphur. After washing and drying, the extracted samples were analysed for moisture, ash, and total sulphur. The dry, ash-free (daf) sulphur values for the eight coals obtained by this method show excellent agreement with the daf sulphur values for physically cleaned samples of the coals. The physically cleaned samples were prepared by float/sink separation of −60 mesh coal in 1.30 specific gravity media, followed by milling the float coal to particle sizes less than 10 μm and subsequent float/sink-centrifugation cleaning. The daf sulphur values determined in the HNO₃-extracted and physically cleaned samples were less than those obtained using ASTM Method D 2492 and differed by as much as 1.3%.