Slurry Solids Research Articles

CODISPOSAL OF FBC BY-PRODUCTS AND COAL SLURRY SOLIDS: CHARACTERIZATION OF MATERIALS

The preparation and combustion of high sulfur coal generates many waste products including cleaning and combustion wastes. Pyrite is associated with coal cleaning wastes and it makes them potentially acidic. Coal slurry solids (CSS), the finest textured cleaning wastes, are stored in large impoundments. After the impoundments are retired, they must be reclaimed with a 1.2 in soil cap. Reclamation of abandoned CSS impoundments by direct revegetation would avoid costs associated with the required soil cap. However, CSS have physical and chemical limitations for plant growth including undesirable pH, surface temperatures, and moisture holding capacity. Fluidized bed combustion is a coal combustion technique designed to reduce smoke stack emissions of SO{sub 2}. It results in a highly alkaline by-product (FBC). The combination of CSS and FBC may allow direct revegetation of CSS materials. This would possibly be a more cost effective method of reclaiming CSS materials than using a soil cap while creating an economic value for FBC by-products. This will also preclude the necessity of disturbing a borrow area for the soil cap. An experiment was designed to evaluate the potential for CSS/FBC mixtures to support direct revegetation. Three test blocks with 18 plots each were established on amore » temporarily inactive portion of an active coal slurry impoundment. The addition of FBC increased the pH of the potentially acidic CSS. Soil fertility analyses indicated Al, B, Ca, Mg, Zn, and soluble salts increased with additions of FBC, while Cu, Fe, K, P, and S remained relatively unchanged, and Mn and Na concentration decreased. Direct revegetation of CSS materials may be facilitated by the addition of FBC by-products. However, other treatments in addition to FBC amendments may be necessary to optimize conditions for plant growth.« less

High Speed Photographic Study of Wet Droplets and Solid Particles in the Inductively Coupled Plasma

Motion pictures of the ICP were taken at 4000 frames s–1 . An intact wet droplet containing yttrium causes the formation of a pale red cloud juxtaposed on the usual ambient emission structure of the plasma. Most of these droplet clouds are shaped like an oval or a comet. A few droplets produce small, bright spheres followed by faint, wispy streaks that point downstream. Such a spherical cloud is caused by some rapid event such as explosion of a droplet in the final stages of solvent evaporation. The faint streaks are some residue, perhaps small solid particles. In a particular frame, a number of these faint streaks protrude from the tip of the initial radiation zone (IRZ) into the normal analytical zone (NAZ). When wet droplets are introduced, that portion of the analyte that travels through the center of the plasma passes through three distinct regions (i.e., the IRZ, the streaks, then the NAZ), rather than directly from the IRZ to the NAZ. Groups of two or three droplets tend to appear together in the same time interval (≈0.12 ms) in the plasma. These droplet clouds are not seen, and the particle streaks are much less evident, when the solvent is removed before the aerosol is injected into the plasma. Aqueous slurries of Y2O3 in various particle sizes (0.1 or 3 µm mean diameter) produce white streaks along the center line of the plasma, which are attributed to individual solid particles. These observations also support the general precept that calibration of the response for slurries using aqueous solution standards is best accomplished by keeping the particle loading such that each wet droplet contains no more than one solid slurry particle.

Measurement of solids concentration in aqueous slurries using a microwave technique

Measurement of solids concentration in aqueous slurries is of practical importance in many industries. In this research work, a guided microwave total transmission technique was developed to measure the solids concentration of slurries. A novel approach was used to calculate the complex permittivity of slurries and to minimize the measurement errors. Experimental results were obtained for various differently concentrated kaolin-in-water slurries. Quantitative relations between the complex permittivity and volumetric fraction of the suspended solids in slurries were obtained. These data could be used to model the dielectric behavior of slurries in microwave frequency region and to provide definitive information about the solids concentration in slurries. The effect of ions on the complex permittivity of slurries at microwave frequency was also examined experimentally.

The extraction of species from slurries of insoluble solids with ion-exchange resins

Insoluble solids which slightly dissociate to give traces of ions in solution can be dissolved with ion-exchangers to recover valuable species. A dissociation equilibrium exists between the dissolved ions in solution and the solid. If the dissolved ions are removed from the solution by ion-exchange, the equilibrium concentration is restored by the further dissociation of the solid. It is possible to recover metals from insoluble solids by contacting a slurry of the solid with an ion-exchange resin which adsorbs the cation, thereby continually displacing the solid/liquid dissociation equilibrium. Complete dissolution of the solid, hence complete liberation of the valuable metal species, can be achieved provided that a sufficient amount of ion exchanger is used. The selective adsorption of calcium and magnesium in dolomite was tested. Various interactions that take place in the slurry during adsorption as well as the effects of various variables, i.e. pH, size of adsorbing species, leaching rates, resins, etc. were determined. A mathematical model for the equilibrium extraction of calcium ions from dolomite was formulated and can be used for possible other applications (rare earths) in the mineral processing industry.

Effect of Varying the Rate of Partitioning of Phenanthrene in Nonaqueous-Phase Liquids on Biodegradation in Soil Slurries

A study was conducted to determine the influence of varying the rates of partitioning of phenanthrene from nonaqueous-phase liquids to water on its biodegradation. Partitioning rates from dibutyl phthalate and 2,2,4,4,6,8,8-heptamethylnonane were rapid in slurries of soil or aquifer solids that were shaken and were affected by the identity and volume of the nonaqueous-phase liquid. Concentrations of the surfactant Alfonic 810-60 that increased partitioning inhibited biodegradation. The rates of mass transfer from the phthalate to water were not influenced by the identity of the environmental sample. Although the rate of mass transfer of phenanthrene did not limit its mineralization by microorganisms in the soil or aquifer solids, treatments that increased the rate of partitioning enhanced biodegradation, presumably because the treatment overcame some other factor that limited degradation of the hydrocarbon.

Negative effects of winter‐ and spring‐applied cattle slurry on the yield of herbage at simulated early grazing and first‐cut silage

AbstractExperiments were earned out on seven UK sites during 1985–1988 to evaluate the importance of negative effects (smoethering and scorch) of winter and spring‐applied cattle slurry on grass yield, assessed at the time of early grazing or first‐cut silage. Slurry application has both positive and negative effects on herbage growth. Positive effects, usually associated with herbage yield increases, derive from the nutrient value of the slurry. Negative effects, often resulting in herbage yield decreases, are caused by smothering and/or scorch. The net effect on herbage depends on the balance between these positive and negative effects. These experiments were designed to isolate the negative effects of slurry whilst attempting to minimize the positive effects. Yield reductions of up to 20% for early grazing and 5% for first‐cut silage were recorded, following applications of cattle slurry in February and March. Earlier applications smaller yield reductions. The threshold for the occurrence of yield reduction was estimated at 3–4 t ha−1 of slurry solids applied, at 6% solids content. In practice this would mean an application of 50–65 m3 ha−1 at 6% dry matter, which would supply 150–200 kg ha−1 total nitrogen, based on typical slurry analyses. Within the limits of application rates tested in these experiments, yield depression tended to increase with increasing rate of slurry applied above this threshold. Although the results suggest that the effects are more likely to occur following spring applications of slurry, earlier (autumn or winter) applications would increase the risk of losses of slurry nitrogen by leaching and denitrification. These results, therefore, confirm current advice in the UK that, where possible, cattle slurry is best applied to grassland in early spring according to the fertilizer needs of the crop. High rates of application should be avoided after early March for cutting areas and, more especially, for early grazing.

Composition andin saccoDegradability of Variously Treated Pig Slurry Solids before and after Anaerobic Digestion

Abstract Flachowsky, G., Richter, G. H. and Löhnert, H.J. 1995. Composition and in sacco degradability of variously treated pig slurry solids before and after anaerobic digestion. J. AppL Anim. Res., 7: 161–168. The fresh and digested pig slurry was separated into a solid and liquid phase by centrifugation. The solids of the slurry (fresh and digested) were treated with urea and I or NaOH and used for the estimation of chemical composition and dry matter degradability (DMD). Anaerobic digestion did not significantly influence chemical composition except iron content. The DMD of anaerobically—digested solids was significantly lower (34.8%) than that of the influent material (48%). Chemical treatment of solids from the influent increased DMD from 48.0 to 54.5 (2% urea), 60.2 (2% NaOH) and 62.0% (2% urea and NaOH each); DMD of effluent was increased from 34.8 to 46.4, 49.4 and 51.3%, respectively. Pig slurry solids from the effluent of anaerobic digesters contain low energy for ruminants and should primarily be used as manure.

Flue Gas Desulfurization Scheme To Recover Elemental Sulfur

A sodium-based flue gas desulfurization process, employing reductive burning and a Claus recovery system, has the advantage of producing elemental sulfur as a byproduct. This study optimized the process conditions for two steps in the proposed reaction scheme: (1) removing approximately one-sixth of the sulfur in the spent scrubbing liquor by a combination of acidification and evaporation and (2) precipitation of 50% of the remaining Na{sub 2}SO{sub 3}(s) by the addition of NaHCO{sub 3}/Na{sub 2}CO{sub 3} slurry. Several combinations of process conditions can be used to produce favorable results, but the optimum from a technical perspective is to add concentrated H{sub 2}SO{sub 4} to the spent liquor to 1.5% v/v, concentrate the mixture to 70% by weight, and then treat it with a >70% solids slurry of NaHCO{sub 3}/Na{sub 2}CO{sub 3}. The optimum from an economic perspective is dependent on the relative costs of H{sub 2}SO{sub 4} and the steam needed to concentrate the spent liquor.

Enhanced mineralization of organic compounds in nonaqueous‐phase liquids

AbstractBiodegradation of phenanthrene, biphenyl, or di(2 ethylhexyl) phthalate initially present in a variety of nonaqueous phase liquids (NAPLs) was slow in samples of soil and aquifer solids The NAPLs were hexadecane, dibutyl phthalate, 2,2,4,4,6,8,8‐heptamethylnonane, cyclohexane, commercial oils, crude oil, creosote, and kerosene Slurrying the soil or aquifer solids markedly enhanced the rate and extent of mineralization of the test compounds initially in many of the NAPLs Both the low rate and the extent of mineralization of the three compounds initially in dibutyl phthalate in soil slurries and of di(2 ethylhexyl) phthalate in heptamethylnonane present in slurries of aquifer solids were increased by inoculation of acclimated microbial cultures Increasing the NAPL volume decreased phenanthrene biodegradation in soil, but the effect of larger NAPL volume could be alleviated by slurrying and inoculation The rate or extent of mineralization in aquifer slurries of di(2‐ethylhexyl) phthalate initially in some NAPLs was increased by addition of N and P, and inoculation further enhanced the degradation

Hydrodynamic Behavior of Graphite Powder Slurries in Journal Bearings

The increasingly severe requirements imposed on rotating machinery in terms of speeds, loads, and temperature impose severe operating conditions on journal bearings. An approach of using solid lubricant slurry would advance the capabilities of the existing rotating machinery related to gas turbine engines. In this study, the behavior of graphite-ethylene glycol slurry is evaluated in a hydrodynamic journal bearing operating at ambient temperatures. The evaluation is based on laboratory testing and provides some insight on the lubrication capabilities of the non-Newtonian slurry. A laboratory lest rig was designed and fabricated and the effects evaluated in terms of the difference in fluid film pressure between the pure carrier fluid and the powder slurry. It is observed that the addition of graphite increases the effective viscosity of the carrier fluid, causing not only an increase in pressure, but also an increase in fluid temperature. Presented at the 48th Annual Meeting in Calgary, Alberta, Canada May...

Effects of three concentrations of mixed fatty acids on dechlorination of tetrachloroethene in aquifer microcosms

AbstractChloroethenes are among the most common organic contaminants of ground water. The biotransformation of these compounds by reductive dechlorination is a promising technology for in situ treatment. The effects of three concentrations of a fatty acids mixture on the reductive dehalogenation of tetrachloroethene (PCE) were studied in methanogenic microcosms. These microcosms were constructed with slurries of aquifer solids collected from an area impacted both by aviation gasoline and chlorinated ethenes at Traverse City, Michigan. The microcosms were amended with approximately 30 μM PCE and one of three concentrations (0.1, 1, or 10 mM total acids) of a mixture of low‐molecular‐weight organic acids, or were part of a control set that received no amendment. The observed lag or adaptation times before the onset of PCE dehalogenation were 51 d (10 mM acids), 65 d (1 mM acids), 86 d (0.1 mM acids), and >233 d (no acids). After 233 d of incubation, no PCE was detectable in any of the fatty‐acid‐supplemented microcosms, but 23 to 27 μM of combined tri‐ and dichloroethenes (TCEs, DCEs) was detected. PCE was not dechlonnated in microcosms without a fatty acid supplement. Although there were observed differences in the length of the lag time, the amount of ultimately dechlorinated PCE was similar. A zero‐order rate constant of 0.3 μM d−1 was calculated for PCE dechlorination and for TCE dechlorination for the two series of microcosms receiving 0.1 and 1.0 mM fatty acid supplements. Of the fatty acids tested in the mixture, butyrate oxidation appeared to be the most probable link to PCE dechlorination.

EFFECT of PROCESSING TEMPERATURES ON MICROBIOLOGICAL and CHEMICAL QUALITY of SOY MILK PRODUCED BY RAPID HYDRATION HYDROTHERMAL COOKING

Soy milk samples produced from 11% soybean slurry cooked by the rapid hydration hydrothermal cooking (RHHTC) process at temperatures from 105-157C for 24-90 s were studied for their sterility, microbiological quality, flatulent sugar reduction, and physical characteristics. Soy milk produced at the temperature of 132C, or higher, for 29 s or longer was sterile. All of the bacteria (Pseudomonas aeruginosa, Serratia lequefaciens, S. rubidaea, and Enterobacter cloacae including the bacilli cells and spores) were destroyed completely. At lower temperatures, 105-127C, the Gram negative bacteria were destroyed; however, the spores of Bacillus licheniformis and B. cereus, Gram positive bacteria survived the heat. Temperatures of 143-157C with a retention time of soy slurry solids in the holding tube of 30 s or longer are recommended to sterilize the product. the mean residence time of soy solids processed by the RHHTC unit was 30 s.

Apparatus and technique to measure settling velocity and holdup of solids in water slurries

A technique based on conductivity is described which is shown to be capable of accurately determining settling front velocity and solids holdup simultaneously

家畜汚水浄化用凝集・限外ろ過自動連続処理装置の試作

For the purpose of clarifying animal wastewater, an automatic administration with inorganic cohesion and ultrafiltration was tried. As an inorganic agglutinant, 0.385g Ferric Trichloride was added to 1g total suspended solids of slurry. The ultrafiltration module, which had the membrane made of vacant string tubes of poly sulfon, had an effective membrane area 1.0m2. Maximum tolerable pressure of the module was 3kg/cm2. For an automatic operation of the unit, a programmable controller PL 40-III was used. The administration procedure was as follows; Pumping up of the wastewater and addition of agglutinant solution-Agitation (circulation) of the slurry in the tank-Pumping out to the sedimentation tank-Sedimenting administration-Drainage of the muddy slurry-Ultrafiltration of the supernatant-Reverse cleansing of the filter. The unit worked according to the program. During the experimental operation, original sewage, supernatant after inorganic cohesion, and filtrate after ultrafiltration were sampled, and the loads of organic matters were analyzed. Indices of the filtrate compared with those of the original slurry changed as follows; pH 7.5 to 3.0, T-S 290mg/l to 450mg/l, T-SS 150mg/l to 0mg/l, COD 120mg/l to 26mg/l, BOD 210mg 30mg/l, and transparence 2.6cm to more than 30cm.

Evaluation of separation plus acidification with nitric acid and separation plus dilution to make cattle slurry a balanced, efficient fertilizer for grass and silage

SUMMARYCombinations of treatments of cattle slurry, which have previously been shown to have lowered ammonia volatilization by 75% of that from whole slurry, were compared in a field experiment with perennial ryegrass at the Agricultural Research Institute, Hillsborough in 1990. Whole slurry and slurries obtained by separation through screens with mesh sizes of 5·0, 3·0, 1·1 and 0·4mm were acidified with 1·4% by volume of 10M nitric acid. Slurries separated through 5·0 and 0·4 mm meshes were diluted 100% and 50% respectively by volume with water and amended with calcium nitrate to supply the same amount of nitrogen as the nitric acid. All slurry combinations were surface-applied at 100 kg (NH4+-N + NO3−-N)/ha to different plots on three occasions during the growing season. Volatilization of ammonia was measured on adjacent plots using ventilated enclosures. By comparison with inorganic fertilizer treatments, assessments were made of the efficiency of slurry nitrogen for herbage production, the fertilizer value of phosphorus, potassium and sulphur in the slurry, and the effects of slurry on silage quality.The mean ammonia volatilization over all applications of acidified slurries was 17% of that from whole slurry. The two separation plus dilution treatments, however, only lowered volatilization to about half of that from whole slurry. Within separation plus acidification treatments, the trend was for dry matter yield and nitrogen offtake to increase as mesh size decreased down to 1.1 mm. For slurries separated through 5·0 and 0·4 mm meshes, the effect of the additional dilution treatment on dry matter yield and nitrogen offtake was similar to the effect of acidification. Efficiency of nitrogen offtake over all three cuts, relative to inorganic fertilizer nitrogen, was 54% for acidified whole slurry and 88% for slurry separated through a 1·1 mm mesh and acidified. Denitrification in nitric-acid amended slurries and sward contamination from slurry solids may have been responsible for lowering nitrogen efficiency.Chemical analyses of herbage showed that the concentrations of phosphorus, potassium and sulphur from the slurry treatments were comparable to those in herbage receiving the recommended rates of inorganic fertilizers and were sufficient for optimum yield. Slurry application had a detrimental effect on the fermentation quality of the ensiled herbage. Chemical analyses indicated that fermentations from two slurry treatments at the first cut and all slurry treatments at the third cut were poorer than those on treatments receiving the equivalent rate of inorganic fertilizer nitrogen.

Effects of separation, dilution, washing and acidification on ammonia volatilization from surface-applied cattle slurry

SUMMARYTreatments which lowered the rate of ammonia volatilization from surface-applied cattle slurry were evaluated in three field experiments during 1989/90 at the Agricultural Research Institute of Northern Ireland. The relative effects of separation, dilution with water before application and washing with a water spray after application, on ammonia volatilization rates were compared over 4 days using ventilated enclosures. As the loss rate of ammonia during the first 4 days after application was highly correlated with the loss rate over the first 4 hours after application, the loss rate in the first 4 hours was used as a rapid method to assess the efficacy of various combinations of separation, dilution and acidification. Ammonia volatilization loss rates from treatment combinations were compared to the loss rate from whole slurry.A 50% decrease in ammonia volatilization was achieved by separation through a 0·4 mm mesh, separation through a 10·0 mm mesh plus dilution with 86% by volume of water, or separation through a 2·0 mm mesh plus washing with 53% by volume of water.A 75% decrease in ammonia volatilization was achieved by acidification to pH 6·5, or combinations of separation and dilution, namely separation through a 0·4 mm mesh plus 50% dilution or separation through a 5·0 mm mesh plus 100% dilution.A 90% decrease in ammonia volatilization was achieved by acidification to pH 6·0, dilution by 50% plus acidification to pH 6·5, or separation through a 0·4 mm mesh plus acidification to pH 6·5.The effects of separation and acidification on ammonia volatilization were cumulative. There was a highly significant inverse linear relationship between ammonia volatilization rate and volume of nitric acid used. Adding 10 M nitric acid at 1·4% by volume lowered volatilization by 75% of that from whole slurry and increased the nitrogen content of the slurry by 2 g N/l, making it a more balanced NPK fertilizer for cut swards. Because the variable value of cattle slurry is due to loss of nitrogen as ammonia and smothering of the sward with slurry solids, a combination of separation or dilution to lower sward contamination and acidification with nitric acid to lower volatilization may be the best practical option for improving cattle slurry as a fertilizer for cut grass.

An automatic bench‐scale unit for clarification of animal wastewater by dual means of cohesion and ultrafiltration

Abstract For the purpose of clarifying animal wastewater, an automatic administration with inorganic cohesion and ultrafiltration was tried. As an inorganic agglutinant, 0.385g Ferric Trichloride was added to 1g total suspended solids of slurry. The ultrafiltration module, which had the membrane made of vacant string tubes of poly sulfon, had an effective membrane area 1.0m2 . Maximum tolerable pressure of the module was 3kg/cm . For an automatic operation of the unit, a programmable controller PL 40‐III was used. The administration procedure was as follows; Pumping up of the wastewater ———‐Addition of agglutinant solution —‐ Agitation (circulation) of the slurry in the tank —‐ Pumping out to the sedimentation tank —‐ Sedimenting administration —‐ Drainage of the muddy slurry —‐ Ultrafiltration of the supernatant —‐ Reverse cleansing of the filter. The unit worked according to the program. During the experimental operation, original sewage(diluted 125 fold), supernatant and sediment after inorganic cohesi...

Capillary filtration at Outokumpu Mintec

Outokumpu Mintec has introduced a different approach to dewatering and filtration to many of the centuries-old technologies — ‘capillary filtration’. Capillary filtration uses the molecular-scale effects of surface and liquid adhesion to extract water from solid slurries, just as tree roots pull water from the ground. This new technique yields a drier filter cake, with only 10% of the energy cost of conventional vacuum- or pressure-driven filtration equipment.

Measurement of slurry solids content by electrical conductivity

Electrodes positioned within a sedimenting and flowing suspension have been used to measure the conductivity of a dispersion and the supporting liquid. Variation in the ratio between these conductivities with solid concentration has been investigated and shown to conform to known equations for isotropic solids. Anisotropic and conducting materials had to be correlated using an empirically determined parameter. This was used to deduce solid concentration during solid/liquid separations, in situ, under carefully controlled experimental conditions, and in a system where temperature and electrolyte concentration were allowed to vary at random. Using this correlation solid concentrations up to 56% by volume were measured, during ballotini sedimentation. Sedimentation of minerals other than ballotini did not exhibit simple zone settling alone. The particle size distribution of the suspended non-conducting solids did not influence the correlation.

Slurry transport in horizontal rotary drums with an end-constriction

Transport of sand—water slurries through horizontal rotating drums with an end-constriction was studied. The effects of the slurry feed solids concentration, feed flow rate, drum rotational speed, fluid surface tension, and the presence of lifters on the slurry hold-up, solids concentration and the flow pattern inside the drum were examined. For a drum without lifters, the slurry bed within the drum was found to oscillate. The bed frequency of oscillation was found to be a function of the drum rotational speed. A mathematical model was developed to predict bed frequency of oscillation. Model predictions were in good agreement with the experimental measurements. For a drum with lifters, no slurry bed oscillation was observed. In general, the drum slurry hold-up and solids concentration were dependent on the drum rotational speed. Mean solids concentration in the drum was found to be higher than that in the feed, especially at low feed solids concentrations. The slurry hold-up was found to increase as the slurry feed flow rate was increased. Mean residence time measurements for the solid and fluid phases for both drums showed that the commonly used assumption that the residence times of the two phases are equal is only valid for the sand particles examined at slurry feed concentrations ≥45 vol.%.