Production of a fine fraction using micro-perforated screens

2020 ◽  
Vol 35 (4) ◽  
pp. 611-620
Author(s):  
Elisabeth Björk ◽  
Mikael Bouveng ◽  
Hannes Vomhoff
Keyword(s):  
Separation Efficiency ◽  
Fibre Length ◽  
Fine Fraction ◽  
High Concentration ◽  
Feed Concentration ◽  
Chemical Pulp ◽  
High Feed ◽  
The Difference ◽  
Hardwood Pulp ◽  
Fraction I

AbstractThe objective for this work was to investigate the possibility to use a pressure screen equipped with a micro-perforated screen basket to produce a fine fraction from bleached chemical pulp. Trials were performed with unrefined bleached chemical hardwood pulp, and with unrefined and refined bleached chemical softwood pulp. The effect of feed concentration, feed flow, and volumetric fine fraction flow was evaluated. The difference between the fine fraction (i. e. the particles passing the screen) and the feed was analysed by studying the fibre morphology. The results showed that high feed concentration was positive for both the fine fraction concentration and the separation efficiency. A higher fine fraction concentration was also obtained when using hardwood pulp, which was explained by the shorter fibre length. Refining of the pulp prior to the fractionation proved beneficial, as a larger share of the refined pulp passed the screen, resulting in a twice as high concentration of the fine fraction when compared to unrefined pulp.

Production of fines from refined kraft pulp by fractionation with micro-perforated screens

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Elisabeth Björk ◽  
Hannes Vomhoff ◽  
Per Engstrand
Keyword(s):  
Kraft Pulp ◽  
Fibre Length ◽  
Fine Fraction ◽  
Pilot Scale ◽  
Hole Size ◽  
High Concentration ◽  
Feed Concentration ◽  
Screening Process ◽  
Perforated Screen ◽  
In Series

Abstract The objective in this work was to obtain a fine fraction of kraft pulp, with as high concentration as possible, in a pilot-scale fractionation with micro-perforated screen baskets. The influence of screen basket surface, hole size, feed concentration, pulp type and refining segment design was investigated. The results showed that a smooth screen basket surface improved the fractionation efficiency of the unrefined pulp compared to a profiled screen basket, despite a larger hole size. A significantly higher fine fraction concentration was obtained when using refined hardwood pulp compared to when using softwood pulp, which was explained with its lower average fibre length and narrower and thus more flexible fibre fragments. The pilot trials also showed that the screening process could be operated at feed concentrations similar to those directly after a refiner, 30–40 g/l. This was demonstrated in a process layout with partial recirculation where a refiner and a micro-perforated screen basket were operated in series in pilot scale.

Removal of hazardous trace elements from green liquor dregs by mechanical separation methods

2018 ◽  
Vol 33 (3) ◽  
pp. 420-429 ◽  
Author(s):  
Teemu Kinnarinen ◽  
Mohammad Golmaei ◽  
Eeva Jernström ◽  
Antti Häkkinen
Keyword(s):  
Trace Elements ◽  
Separation Efficiency ◽  
Solid Phase ◽  
Pulp Mills ◽  
High Concentration ◽  
Green Liquor ◽  
Chemical Pulp ◽  
Green Liquor Dregs ◽  
Hazardous Trace Elements ◽  
Mechanical Separation

Abstract Green liquor dregs represent the most important inorganic residue of chemical pulp mills. The dregs are usually settled in thickeners, washed and deliquored with lime mud precoat filters, and transported to the landfill. The utilization of dregs is challenging, due to the high concentration of hazardous trace elements (HTE) in their solid phase. There are basically two potential strategies for the reduction of the HTE content of dregs: mechanical classification according to differences in the size and density of particles, and removal of HTE by various chemical treatments. The objective of this study was to evaluate the applicability of straightforward mechanical separation methods for the purification of dregs from HTE. The evaluated separation methods included particle size–based classification by sieving, and classification on the basis of differences in the settling properties of particles in gravitational and centrifugal separation. It can be concluded that all the evaluated separation methods could be used to reduce the HTE content of dregs, although the separation efficiency was not very high in most cases. Centrifugation had clearly the best performance of the investigated techniques. The fractions consisting of large particles contained consistently lower concentrations of HTE, compared to fractions containing a lot of fines.

Tem analysis of multiple-energy arsenic implanted and Rta'd silicon

1987 ◽  
Vol 45 ◽  
pp. 246-247
Author(s):  
R.A. Herring
Keyword(s):  
Device Fabrication ◽  
High Concentration ◽  
Tem Analysis ◽  
Defect Clusters ◽  
High Fluences ◽  
Small Defect ◽  
Before And After ◽  
The Matrix ◽  
The Difference ◽  
Factor Type

Rapid thermal annealing (RTA) of ion-implanted Si is important for device fabrication. The defect structures of 2.5, 4.0, and 6.0 MeV As-implanted silicon irradiated to fluences of 2E14, 4E14, and 6E14, respectively, have been analyzed by electron diffraction both before and after RTA at 1100°C for 10 seconds. At such high fluences and energies the implanted As ions change the Si from crystalline to amorphous. Three distinct amorphous regions emerge due to the three implantation energies used (Fig. 1). The amorphous regions are separated from each other by crystalline Si (marked L1, L2, and L3 in Fig. 1) which contains a high concentration of small defect clusters. The small defect clusters were similar to what had been determined earlier as being amorphous zones since their contrast was principally of the structure-factor type that arises due to the difference in extinction distance between the matrix and damage regions.

Applicability of electrodialysis to the separation of sodium acetate from synthetic alkaline hardwood extract

TAPPI Journal ◽  
2015 ◽  
Vol 14 (11) ◽  
pp. 695-708 ◽  
Author(s):  
RAVIKANT PATIL ◽  
CHI TRUONG ◽  
JOSEPH GENCO ◽  
HEMANT PENDSE ◽  
ADRIAAN VAN HEININGEN
Keyword(s):  
Current Density ◽  
Sodium Sulfate ◽  
Sodium Acetate ◽  
Separation Efficiency ◽  
Feed Concentration ◽  
Initial Concentration ◽  
White Liquor ◽  
Complete Extraction ◽  
Electro Osmosis ◽  
Preliminary Separation

Our objective was to develop a process for recovering acetyl groups from industrial northeast hardwood chips. Extraction experiments showed that the white liquor charge of 6% effective alkali at 50°C and liquor-to-wood ratio of 4:1 leads to the complete extraction of acetyl groups from industrial hardwood chips. Electrodialysis was assessed as a technique for separating and concentrating sodium acetate from synthetic hardwood extract. Preliminary separation experiments using dilute sodium acetate showed that the sodium acetate can be concentrated up to approximately 24% by weight from an initial concentration of about 2% by weight. The effects of current density, feed concentration, electro-osmosis, and osmosis on the separation of sodium acetate were evaluated. Finally, selectivity experiments were performed to study the effect of various components of the white liquor on the separation of sodium acetate. Fully oxidized synthetic white liquor was used in selectivity experiments to avoid deleterious effects of Na2S. Selectivity experiments using synthetic oxidized white liquor showed a significant decrease in the separation efficiency due to the presence of sodium hydroxide, sodium carbonate, and sodium sulfate in the synthetic extract.

Separation of Heavy Metal Ions from the Solution Obtained by Leaching Low-Grade Pyrolusite with Pyrite and H2SO4

2013 ◽  
Vol 773 ◽  
pp. 283-288
Author(s):  
Xing Zou ◽  
Xiang Quan Chen ◽  
Hai Chao Xie ◽  
Xiao Dan Qiu
Keyword(s):  
Heavy Metal ◽  
Metal Ions ◽  
Heavy Metal Ions ◽  
Separation Efficiency ◽  
Ph Value ◽  
Sulfate Solution ◽  
Ion Concentration ◽  
Manganese Sulfate ◽  
Low Grade ◽  
High Concentration

The manganese sulfate solution leached from low-grade pyrolusite with pyrite and H2SO4 contains heavy metal ions of high concentration, influencing the quality of the final products of manganese compounds and causing manganese ions not to be electrolyzed. The present study was focused on the separation of Co, Ni and Zn ions from the leached solution with BaS. By controlling the pH value at 5.0-6.5, temperature at 50-60°C, reaction time at 15 min and mixing velocity at 78 rpm, the heavy metal ions could be separated effectively. Under the above optimized conditions, the ion concentration of Co, Ni, and Zn in the solution was reduced to 0.06 mg.L-1, 0.27mg.L-1 and 0.01mg.L-1, and the separation efficiency was 99.72%, 99.18% and 99.9% respectively. The obtained pure solution meets the demands of manganese electrowinning.

The centriolar complex isolated from starfish spermatozoa

1981 ◽  
Vol 49 (1) ◽  
pp. 33-49 ◽  
Author(s):  
R. Kuriyama ◽  
H. Kanatani
Keyword(s):  
Gradient Centrifugation ◽  
Sucrose Density Gradient ◽  
Microtubule Assembly ◽  
High Concentration ◽  
Microtubule Organization ◽  
Sucrose Density Gradient Centrifugation ◽  
The Difference ◽  
Distal Centriole

Centrioles from spermatozoa of the starfish, Asterina pectinifera, were isolated and partially purified by solubilization of chromatin followed by sucrose density-gradient centrifugation. The ultrastructure of the isolated centriolar complex was investigated in whole mount preparations by electron microscopy. The complex unit was composed of a pair of centrioles and a pericentriolar structure, which associated with the distal end of the distal centriole by 9 spoke-like satellites extending radially to a marginal ring. Each satellite bifurcated at a dense node forming 2 fan-like shapes with a periodic striated pattern. The tubular structure of the centrioles easily disintegrated, leaving the pericentriolar structure or axonemal microtubules intact. The distal centriole in a spermatozoon served as an initiating site for flagellar microtubule assembly; that is, a number of “9 + 2′ axonemal tubules were observed adhering just beneath the distal end of the basal body. In experiments in vitro, polymerization of microtubule proteins purified from porcine brain was initiated by the structure at the ends of both proximal and distal centrioles, but not from the satellites or the marginal ring. Also, few if any microtubules were formed from the sides of each centriole, even in the presence of a high concentration of exogenous tubulin. On the other hand, centrioles of spermatozoa, when they were in mature ooplasm, could initiate the formation of sperm asters by microtubules. Therefore, centrioles in spermatozoa seem to be able to initiate microtubules in a 2 ways. A possible explanation of the difference between the 2 types of microtubule organization in vivo, i.e. in the sperm cell itself and in the ooplasm, it discussed.

scholarly journals hydrocyclone Performance Comparison between Recycled Single Stage and Double Stage Hydrocyclones

2020 ◽  
Vol 21 (3) ◽  
pp. 51-55
Author(s):  
Mohannad A. Raheem ◽  
Raghad F. Qassim
Keyword(s):  
Flow Rate ◽  
Separation Efficiency ◽  
Performance Comparison ◽  
Single Stage ◽  
Feed Concentration ◽  
Modes Of Operation ◽  
Split Ratio ◽  
Inlet Flow Rate ◽  
Water Feed ◽  
The Cost

   This research presents a comparison of performance between recycled single stage and double stage hydrocyclones in separating water from water/kerosene emulsion. The comparison included several factors such as: inlet flow rate (3,5,7,9, and 11 L/min), water feed concentration (5% and 15% by volume), and split ratio (0.1 and 0.9). The comparison extended to include the recycle operation; once and twice recycles. The results showed that increasing flow rate as well as the split ratio enhancing the separation efficiency for the two modes of operation. On the contrary, reducing the feed concentration gave high efficiencies for the modes. The operation with two cycles was more efficient than one cycle. The maximum obtained efficiencies were 97% and 97.5% at 5% concentration, 11 L/min, and 0.9 split ratio for twice recycled single stage and double stage hydrocyclones, respectively. The pressure drop was the same for the two modes of operation. It was concluded that using recycled single stage hydrocyclone was more economical since it reduced the cost of additional hydrocyclone.

Photodosimeter Badge System

PEDIATRICS ◽  
1985 ◽  
Vol 75 (2) ◽  
pp. 437-441
Author(s):  
Peter C. Scheidt ◽  
Phyllis M. Sternthal ◽  
Robert Anderson ◽  
Robert Studholme ◽  
Dolores A. Bryla ◽  
...  
Keyword(s):  
Child Health ◽  
Human Development ◽  
Optical Density ◽  
Action Spectrum ◽  
Radiant Energy ◽  
National Academy Of Sciences ◽  
High Concentration ◽  
Film Badge ◽  
The Difference ◽  
Academy Of Sciences

The Committee on Phototherapy in the Newborn of the National Academy of Sciences has recommended10 development of a compact system to continuously measure radiant energy exposure of infants treated with phototherapy. A small bilirubinimpregnated photodosimeter film badge was developed by the Beckman Instrument Company for this purpose and was used during the National Institute of Child Health and Human Development (NICHD) phototherapy study. This report summarizes the results of data obtained with this measurement device and briefly describes the performance of this system. METHODS The film badge dosimeter system consists of a 5.2x2.6-cm plastic badge composed of an imbedded disk of bilirubin cast in a polymeric substrate and sandwiched between two layers of clear plastic. Before exposure to light, the badge exhibits a high optical density at 460 nm due to a relatively high concentration of bilirubin. The optical density of the badge at 400 to 500 nm decreases as a function of the total dose of light within the action spectrum for the photodecomposition of bilirubin to which the badge has been exposed. Initial optical density at 460 nm is measured by a densitometer designed and dedicated specifically for this purpose. After exposure, the optical density is again measured by insertion into the densitometer; the total dosage, which is the time-integrated irradiance received by the badge during the photodecomposition process, is derived from the difference in optical density between the two readings. (A description of the calibration of the badge is available on request from Biometry Branch, Epidemiology and Biometry Research Program, National Institute of Child Health and Human Development, Bethesda, Maryland.)

scholarly journals Occurrence and correlation between the numbers of Black-headed Gull Chroicocephalus ridibundus and Yellow-legged Gull Larus michahellis on Kolut fish ponds (Serbia)

2015 ◽  
Vol 84 (1) ◽  
pp. 37
Author(s):  
Marko Tucakov ◽  
Milan Vogrin
Keyword(s):  
Food Availability ◽  
Fish Ponds ◽  
Early Winter ◽  
High Food ◽  
High Concentration ◽  
Aquatic Animals ◽  
Autumn Period ◽  
Larus Michahellis ◽  
The Difference ◽  
Fish Harvest

Presence and correlation between the numbers of Black-headed and Yellow-legged Gull was studies between 1998 and 2004 on Kolut fishponds in NW Serbia. Both species occurred there from February to December. Spring migration culminated in late February and early March. The period of the most intensive autumn concentration was from October to December. The difference between the numbers in all months as well as between the numbers in spring and in autumn was statistically significant. The period of the most intensive autumn passage of Yellow-legged Gull was from late October to early December. The difference between the numbers between the months was not statistically significant. A high concentration of both species in autumn and early winter was explained by high food availability during fish harvest when ponds were empty. Positive correlation between the numbers of two species thru the year indicated attractiveness of large flocks of Black-headed Gulls for Yellow-legged Gulls. This is especially true for the autumn period, when feeding niches and food is easily accessible. Correlation between the numbers of two species was negative in spring, when accesibility of aquatic animals is lower and large flocks of Black-headed Gulls are lacking.

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