Slurry Solids Research Articles

Combined chemical (ozone) and biological treatment of polychlorinated biphenyls (PCBs) adsorbed to sediments

AbstractLaboratory experiments were conducted to test the feasibility of ozone sparging to oxidize PCBs in sediments, and to determine the organic acid content and biodegradability of the oxidation products. Two PCBs were tested; 2‐,2′‐dichlorobiphenyl (DCB) and 2‐,3‐,4‐,2′‐,3′‐,4′‐hexachlorobiphenyl (HCB). DCB and HCB were allowed to adsorb onto solids in slurries of pure kaolinite and river sediments containing 2% native organic matter (NOM). Ozone was sparged through the slurries while concentrations of PCBs and Cl−, and chemical oxygen demand (COD) were measured with time. Gas chromatography/mass spectrometry (GC/MS) was used to identify the organic acids produced from the reaction of ozone with DCB and HCB. After sparging, the liquid was placed in bioreactors with inoculum from a domestic wastewater treatment plant and nutrients. Ozone sparging in the kaolinite slurries removed 94% of HCB and 97% of DCB in 30 days. In contrast, 55 days were required to achieve the same PCB removal in river sediment slurries. Ozone doses per g of DCB and HCB in kaolinite were 19 g and 30 g, respectively. Doses were 13–14 times greater in river sediments. Formic and oxalic acids were ozonation products of both PCBs. Specific ozonation products of DCB and HCB were 2‐hydroxybenzoic acid and 2,3,4‐trihydroxybenzoic acid, respectively. The results show that ozone caused ring cleavage of PCBs and stoichiometric replacement of Cl with OH groups. Over 93% of the soluble COD from ozone sparging was biodegraded within 20–26 days in the bioreactors.© 2002 Society of Chemical Industry

Materials for Freeform Fabrication of GHz Tunable Dielectric Photonic Crystals

ABSTRACTPhotonic crystals are of interest for GHz transmission applications, including rapid switching, GHz filters, and phased-array technology. 3D fabrication by Robocasting enables moldless printing of high solid loading slurries into structures such as the “woodpile” structures used to fabricate dielectric photonic band gap crystals. In this work, tunable dielectric materials were developed and printed into woodpile structures via solid freefrom fabrication (SFF) toward demonstration of tunable photonic crystals. Barium strontium titanate ceramics possess interesting electrical properties including high permittivity, low loss, and high tunability. This paper discusses the processing route and dielectric characterization of (BaxSr1-XTiO3):MgO ceramic composites, toward fabrication of tunable dielectric photonic band gap crystals.

Appropriate Processing And Food Functional Properties Of Maize Flour

The physicochemical properties of whole maize flour (nDF) and dehulled-degermed maize flour (DF) were studied to be able to predict the functional properties of products derived from them. Whole milled grains produced 92% yield of flour; whilst (DF) yielded 65% net from grains.In the production of flour,degerming and dehulling effected reductions in crude protein (8.2- 7.5 %), fat (6.0-1.4 %), crude fibre (1.8-0.5 %), ash (1.5-0.2 %) ; whilst an increase in carbohydrates (74-80 %) was effected. DF showed higher water absorption capacity (197 %) than nDF (154 %) ; thus the swelling capacity of DF was about 1.5 times that of nDF. Brabender hot-paste viscometry showed that 10% total solids slurry (DF) was adequate to produce about 500 BU consistency.The mean peak hot-paste viscosity for DF and nDF were 505 BU and 370 BU respectively.Starch, fat and fibre contents were the major contributing factors in the differences in functional properties exhibited by the two types of flours. DF products would produce more sticky and pasty products than those of nDF. (Af. J. of Science and Technology: 2002 3(1): 126-131)

A high-pressure, continuous-operation cyclone separator using a water-generated flow restriction

A novel high-pressure, continuous-operation separator for moderately laden, gas–solid flows was designed, built, and tested. The novelty of this device was its use of supplemental water to produce a virtual flow restriction that acted to maintain high-pressure and to prevent gas from escaping with the separated solids. The water–solid slurry thus produced may be pumped, and can be continuously and easily conveyed away. Over a range of practical operating points, the separator showed very high collection efficiencies (>90%), low-pressure drop, and robust operation. A minimum supplemental water requirement was determined to prevent gas loss with the separated solids stream.

Processing of Al2O3/SiC nanocomposites—part 2: green body formation and sintering

Pressure filtration was used to form green compacts from aqueous slurries of alumina with 5 vol.% silicon carbide. Green densities of 64%TD were achieved for slurries containing a 50 vol.% solids loading. Lower green densities were obtained for a very fine alumina due to the practical limits on maximum slurry solids loading when using finer powders. The samples were dried in a purposely built humidity cabinet to limit sample cracking. It was found that a higher consolidated layer permeability gave a higher initial drying rate. Near fully dense (99% TD) nanocomposites were produced, via pressureless sintering at 1900 °C. Poor sintered densities were obtained in the case of the fine alumina because of localised sintering of these low green density compacts. The required intra/inter-granular nanocomposite microstructures have been obtained for several different systems, with an average grain size of approximately 5 μm. Abnormal grain growth was noted for samples containing the larger particle size silicon carbide. This shows that a maximum particle size limit exists when selecting the powders for a 5 vol.% nanocomposite.

Determination and Control of Metallic Impurities in Alumina Deposits Obtained by Aqueous Electrophoretic Deposition

Electrophoretic deposition (EPD) is a suitable manufacturing method for depositing thin and thick films onto conducting materials. Usually, EPD is performed in organic vehicles, where handling difficulties and health hazards are important problems. These difficulties can be solved using aqueous suspensions; however, the high voltages that develop during EPD increase the rate of hydrolysis and galvanic reactions. As a result, pores or metallic contamination can be retained in the ceramic deposit. The deposition of Al2O3 onto zinc electrodes in water is described in this work. The formation and characteristics of Al2O3 deposits and the effect of Zn2+ contamination have been studied as a function of the processing conditions (current density and deposition time) and the slurry properties (dispersing state and solids content). A neodymium:yttrium aluminum garnet (Nd:YAG) laser, coupled to an inductively coupled plasma spectrometer, has been used to determine the contamination profile in the ceramic coatings. By controlling the intensity of the electric field applied to the slurry, as well as the slurry conductivity and solids content, the contaminating effect of the electrode can be reduced significantly.

Optimization of the rheological properties of alumina slurries for ceramic processing applications Part I: Slip-casting

Aqueous powder slurries are widely employed in ceramic manufacturing processes like slip-casting and spray-drying. The aim of the present work was to identify the conditions for the preparation of stable alumina slurries with high solids content for the production of slip-cast objects with improved properties, as well as to correlate the slurry properties to the final object properties. For slurry stabilization, three commercial dispersants were compared. It was found that for each dispersant there exists an optimum concentration range within which low viscosity is achieved for a slurry of high solids content. In addition to the slurry solids content, the choice of a particular dispersant also affects the slurry viscosity and through that the casting rate. The combination of high slurry solids content and slower casting rate results in objects with higher densities both in the green and fired state.

New Dispersing Turbines for the Preparation of Concentrated Suspensions.

The performance of two new dispersing tools (Deflo and Sevin turbines) were tested for the preparation of highly pigmented solids slurries. Their power consumption and dispersing efficiency are compared against the performance of the classical Cowles sawtooth turbine. The experiments are carried out with kaolin clays at solid concentration up to 72 wt.%. The influence of powder feeding rate on the slurry preparation is also investigated. Although the classical Cowles disperser is able to promote good slurry dispersion, the power consumption is significant due to the high rotational speed required to maintain a sufficient circulation in the tank. The Deflo and Sevin turbines give the same results for the dispersion quality, but the power consumption is greater with the Deflo turbine, which makes the Sevin impeller a very promising technology for high solids slurry preparation.

Nutrient losses by surface run-off following the application of organic manures to arable land. 1. Nitrogen

Research was conducted on nitrogen (N) surface run-off losses following organic manure applications to land, utilising a purpose-built facility on a sloping site in Herefordshire under arable tillage. Different rates and timing of cattle slurry, farmyard manure and inorganic N and phosphorus (P) fertiliser were compared, over a 4-year period (1993–97). P losses from the same studies are reported in a separate paper. The application of cattle slurries to the silty clay loam soil increased the loss of solids and NH 4 +-N in surface water flow compared to control plots receiving inorganic fertiliser only, or no treatment, but had little effect on NO 3 −-N losses by this route. Results were consistent with other observations that rainfall events immediately after manure applications are particularly likely to be associated with nutrient run-off losses. Losses via subsurface flow (30 cm interflow) were consistently much lower than via surface water movement and were generally unaffected by treatment. Increasing slurry application rate and, in particular, slurry solids loading, increased solids and NH 4 +-N losses via surface run-off. The threshold, above which the risk of losses via surface run-off appeared to be greatly increased, was ca. 2.5–3.0 t/ha slurry solids, which approximates to the 50 m 3/ha limit suggested for slurry within UK ‘good agricultural practice’. Sealing of the soil surface by slurry solids appears to be a possible mechanism by which polluting surface run-off may occur following slurry application on susceptible soils. Total losses of NH 4 +-N and NO 3 −-N during the 4-year monitoring period were insignificant in agronomic terms, but average soluble N concentrations (NH 4 +-N+NO 3 −-N) in run-off, ranging from ca. 2.0 mg/l, up to 14.0 mg/l for the higher rate slurry treatments. Peak concentrations of NH 4 +-N>30 mg/l, are such as to be of concern in sensitive catchments, in terms of the potential for contribution to accelerated eutrophication and adverse effects on freshwater biota.

Nutrient losses by surface run-off following the application of organic manures to arable land. 2. Phosphorus

Phosphorus (P) surface run-off losses were studied following organic manure applications to land, utilising a purpose-built facility on a sloping site in Herefordshire under arable tillage. Different rates and timing of cattle slurry, farm yard manure (FYM) and inorganic nitrogen (N) and P fertiliser were compared, over a 4-year period (1993–97). N losses from the same studies are reported in a separate paper. The application of cattle FYM and, especially slurry, to the silty clay loam soil increased both particulate and soluble P loss in surface water flow. Losses via subsurface flow (30 cm interflow) were consistently much lower than via surface water movement and were generally unaffected by treatment. Increased application of slurry solids increased all forms of P loss via surface run-off; the results suggested that a threshold for greatly increased risk of P losses via this route, as for N, occurred at ca. 2.5–3.0 t/ha solids loading. This approximates to the 50 m 3/ha application rate limit suggested for slurry within UK ‘good agricultural practice’. The studies also provided circumstantial evidence of the sealing of the soil surface by slurry solids as the major mechanism by which polluting surface run-off may occur following slurry application on susceptible soils. Losses of total and soluble P, recorded for each of the 4 years of experiments, reached a maximum of only up to 2 kg/ha total P (TP), even after slurry applications initiating run-off. Whilst these losses are insignificant in agronomic terms, peak concentrations of P (up to 30,000 μg/l TP) in surface water during a run-off event, could be of considerable concern in sensitive catchments. Losses of slurry P via surface run-off could make a significant contribution to accelerated eutrophication on entry to enclosed waters, particularly when combined with high concentrations of NO 3 −-N. Restricting slurry application rates to those consistent with good agronomic practice, and within the limits specified in existing guidelines on good agricultural practice, offers the simplest and most effective control measure against this potentially important source of diffuse pollution.

Mechanisms of wear on a Co-base alloy in liquid–solid slurries

The efficient performance of drilling tools in aqueous environments requires materials to be used, which can effectively resist excessive material loss due to the combined effects of erosion and corrosion. In this paper, the interactions between electrochemical corrosion and mechanical erosion have been assessed in liquid–solid slurries on a Co-base material (Stellite X40), which is currently used in the manufacture of oil tools. The material degradation is assessed as a function of aqueous environment and sand loading. Corrosion has been shown to represent an important factor in the degradation of this material even though it essentially exhibits passivity in static saline conditions. The relative importance of corrosion and its synergistic effect when combined with erosion are quantified and the implications in terms of material performance and of potential methods of reducing oil tool degradation are discussed.

Froth flotation: preparation of a laboratory standard

In evaluating the separation of coal from slurries of fine solids by froth flotation, it is necessary to work to a standard method to ensure that the procedure, on the same sample, can be repeated by others and the same results obtained. In a number of countries the standard procedure is produced and distributed by the International Standards Organisation (ISO) working through its member countries. In the preparation of a froth flotation standard, two different techniques from two countries (Australia and Great Britain) have been proposed. These procedures, known as the ‘tree’ and ‘release’ analyses respectively, differ in the laboratory technique and presentation of results. In order to assist in the debate of which of the procedures should be adopted as the basis for the International Standard, a short programme of comparative work was undertaken to evaluate the different methods. Samples of coal slurries from Australia, Great Britain and South Africa were evaluated using the Australian and British procedures. The work undertaken is described detailing the preparation of the samples, test procedures and differences between the two techniques. The results showed that the two techniques produced similar results with the ‘Release Analysis’ giving more detail at the cleaner (low ash) end of the curve and the ‘Tree Analysis’ more data for the middle (medium ash-higher yield) part of the curve. The results indicated that the technique chosen would be dependent upon the information required from the flotation analysis, i.e. the British ‘Release Analysis’ for the cleaner coal data and the Australian ‘Tree Analysis’ for higher ash fractions.

Influence of Slurry Parameters on the Characteristics of Spray‐Dried Granules

A systematic study has been performed to determine how the characteristics of granules prepared by spray drying aqueous alumina slurries are influenced by processing parameters: binder type (PEG Compound 20M or PEG‐8000), solids loading (30 or 40 vol%), ammonium polyacrylate deflocculant level (0.35‐1.00 wt%), and spray‐dryer type. Correlations between slurry rheology and granule characteristics have been made, and a model for granule formation is presented. The packing density of the primary particles within the granules is lower for slurries with higher yield stress and is dependent on the slurry solids loading. Granules prepared using 0.35 wt% deflocculant (0.14 mg/m2), which correspond to high slurry yield stress, are of solid morphology, whereas higher deflocculant levels result in hollow granules that contain a single large open pore or crater. The degree to which particles are able to rearrange during drying influences the final granule density and is determined by the strength of the floc structure, as indicated by the slurry yield stress. When the yield stress is low, a crater may form from the inward collapse of the surface of a forming granule when the particle packing density in a droplet continues to increase after the droplet size becomes fixed by the formation of a rigid shell, leaving an internal void with internal pressure lower than that of the surrounding atmosphere.

Optical fibres: atomic spectroscopic methods for the determination of fluoride glasses composition

Three different methods for the evaluation of the composition of optical fibres employed in long distance telecommunications have been developed. Such fibres are obtained from fluoride glasses containing very low impurity levels. The developed methods are based on inductively coupled plasma atomic emission spectrometry coupled with: 1. wet chemical dissolution; 2. alkali fusion; 3. direct solid slurry sampling. The procedures are compared with reference to the optimization of sample preparation, loss of components after sublimation, normalization with standards, accuracy, precision.

Direct Ground Injection of livestock waste slurry to avoid ammonia emission

The aim of the project was to improve the slurry injection techniques for injecting animal waste slurries into the soil under Norwegian conditions. A new slurry application technique for grassland was therefore developed, by adapting well known methods of injecting a fluid into a solid or porous material. The injection nozzles had a diameter of 13 mm, and the liquid pressure in the nozzles was between five and eight bar, which was sufficient for the slurry to be injected 5 to 10 cm into the ground. The depth of the injection depended on the soil type and on the slurry pressure. Ammonia emission was reduced as compared with application through ordinary broadcasting, and with band spreading. The emission was also reduced if water was added to the slurry, or if the slurry solids were separated from the liquid before application.

Coal slurry solids/coal fluidized bed combustion by-product mixtures as plant growth media

Fine-textured, pyritic waste produced by coal cleaning is stored in slurry settling ponds that eventually require reclamation. Conventionally, reclamation involves covering the dewatered coal slurry solids (CSS) with 1.3 m of soil to allow plant growth and prevent acid generation by pyrite oxidation. This study was conducted to determine the feasibility of a less costly reclamation approach that would eliminate the soil cover and allow direct seeding of plants into amended CSS materials. Potential acidity of the CSS would be neutralized by additions of fluidized-bed combustion by-product (FBCB), an alkaline by-product of coal combustion. The experiment involved two sources of CSS and FBCB materials from Illinois. Birdsfoot trefoil (Lotus corniculatus L.), tall fescue (Festuca arundinacea Schreb.), and sweet clover (Melilotus officinalis (L.) Lam.) were seeded in the greenhouse into pots containing mixtures of the materials. CSS-1 had a high CaCO3FeS2 ratio and needed no FBCB added to compensate for its potential acidity. CSS-2 was mixed with the FBCB materials to neutralize potential acidity (labeled Mix A and B). Initial pH was 5.6, 8.8, and 9.2 for the CSS-1, Mix A, and Mix B materials, respectively. At the end of the 70-day experiment, pH was 5.9 for all the mixtures. Tall fescue and sweet clover grew well in all the treatments, but birdsfoot trefoil had poor emergence and survival. Elevated tissue levels of B, Cd, and Se were found in some plants. Salinity, low moisture holding capacity, and potentially phytotoxic B may limit the efficacy of this reclamation method.

97/04469 Manufacture of solid fuels-water slurries for gasification: Sawada, M. et al. Jpn. Kokai Tokkyo Koho JP 09 03,464 [97 03,464 (Cl. C10L1/32), 7 Jan 1997, Appl. 95/153,029, 20 Jun 1995, 7 pp. (In Japanese)

97/04469 Manufacture of solid fuels-water slurries for gasification: Sawada, M. et al. Jpn. Kokai Tokkyo Koho JP 09 03,464 [97 03,464 (Cl. C10L1/32), 7 Jan 1997, Appl. 95/153,029, 20 Jun 1995, 7 pp. (In Japanese)

Oligomerization of Ethylene in a Slurry Reactor Using a Nickel/Sulfated Alumina Catalyst

During the oligomerization of ethylene over heterogeneous catalysts, the production of α-olefins may be lowered because of an accompanying deactivation of catalyst resulting from strong adsorption of products, by isomerization or by a tendency to copolymerize into branched products. The oligomerization of ethylene was studied using Ni(II)/sulfated alumina catalysts prepared with a nonporous fumed alumina (ALON) support. The influences of methods of catalyst preparation and activation upon oligomerization activity were screened using a gas−solid microreactor. On the basis of the test results obtained in the microreactor, a modified form of the superior catalyst was prepared and its performance was examined in more detail using a well-agitated gas−liquid−solid slurry reactor. This catalyst exhibited very good oligomerization activity with no apparent deactivation in the slurry reactor at temperatures at or below 298 K and at near-atmospheric pressure. Complete conversion of the ethylene with the production of mainly two oligomers, 1-butene and 1-hexene, was attained. After 34 h in the slurry, formation of a significant amount of two branched C6 isomers was observed.

Inductively Coupled Plasma–Atomic Emission Spectrometric Analysis of Aqueous Slurries of Solids

The direct injection of solids–water slurries into the torch of an inductively coupled plasma–atomic emission spectrometer offers a quick and easy method for the analysis of major and minor elements in various solids. In this project aqueous slurries of solids were prepared by wet milling with a stirred-ball slurry attritor mill and analyzed. Slurries of standard reference materials, prepared in the same way, were used as calibration standards. The best results were obtained with solids having a small particle size (2–5 μm) and a close distribution of particle sizes. The average percent relative error for slurry–ICP analysis of most major and minor elements was generally less than 5% for the solids studied.

Extraction and Precipitation Chemistry for Mercury Recovery from Aqueous Wastes

This paper describes an extraction-precipitation process to recover mercuric chloride from aqueous solutions. The process is a modification of a dicarboxylic acid recovery process that exploits the enhanced solubility of mercuric chloride in organic solvents loaded with water. Mercuric chloride in ethyl acetate has a solubility enhancement of 1.34 moles mercuric chloride per mole of water added to the solvent, consistent with previously reported phase behavior. Solubility enhancement is also reported for formates, in contrast to previously reported results. For example, propyl formate showed 2.91 moles mercuric chloride per mole water enhancement. The modified process described in this paper relies on (1) favorable liquid-liquid equilibrium (mercuric chloride distribution into ethyl acetate or into propyl formate), (2) favorable liquid-solid equilibrium with enhanced solute solubility on addition of a minor constituent (water), and (3) preferential vaporization of the minor constituent from the solid slurry (relative volatility of water in mercuric chloride loaded ethyl acetate is four). Enhanced solubilities for zinc(II) chloride(3.46) and mercury(II) iodide(1.10) in isopentyl acetate indicate a potential application of the process for the recovery of other metal halides from aqueous wastes.