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CLARIFICATION OF BLACKWATER WASTES BY FLOTATION AND BY COAGULATION .Alan J. Rubin, Professor Paul R. Schroeder, Research Associate Ralph J. Kramer, III, Research Associate Water Resources Center The Ohio State University Columbus, Ohio 43210 INTRODUCTION Virtually all of the coals cleaned in the United States are wet cleaned. Consequently, bUlions of gallons of black wash waters are discharged annually to the nation's streams [ 1 ]. The fine coal particles carried away by wash waters represent a waste of energy and a significant source of pollution. The successful recovery of this waste coal could provide the economic incentive needed to resolve many present environmental problems associated with coal preparation. Waters laden with suspended coal particles are generated in increasing amounts as a result of modern methods of mechanized mining, the expansion of the coal mining industry and the greatly increased demand for ash-free coal with a minimum sulfur content. Because, frequently, very little more than plain settling is applied, especially in older preparation plants, much -48 mesh coal is lost [2]. Clarification should be employed in order to recover the coal and to meet the suspended solids effluent discharge limit of 0.07 g/1 imposed on the industry [3]. There has been little research reported in the literature which deals specifically with the removal or recovery of colloidal coal. Since it is the most difficult to remove by standard coal beneficiation methods, this ultrafine coal ends up as a major constituent of plant blackwaters. Accordingly, this study was initiated to investigate the feasibility of coal recovery by flotation and by coagulation under laboratory conditions. The major parameters controlling both processes were also examined in the study. EXPERIMENTAL METHODS AND MATERIALS Coal Suspensions Coal suspensions were prepared from a highly volatile, low sulfur, low ash bituminous coal from the Elkhorn seam in Kentucky. In order to prepare stable and reproducible suspensions a lengthy procedure was developed which is described in detail elsewhere [4]. In summary, the coal was ground, ball mUled and passed through a 400-mesh standard U.S. Series sieve. Batches were oxidized with dilute hydrogen peroxide at 80 C for several hours. The resultant slurry was washed, filtered and resuspended in distilled water. Typically, the pH ranged between 5.5 and 6.0; any suspensions having an unusually low pH were discarded. The surface areas of the coal particles were measured with a Quantasorb BET multipoint analyzer manufactured by Quantachrome Corporation. The ground, sieved coal had a surface area of 7.2 m2/g prior to oxidation and 9.3 m2/g afterward. Suspension turbidities were estimated by absorbance measurements taken with a Coleman model 14 spectrophotometer at a wavelength of 400 nm. Absorbance was linear with suspension concentration. A suspension absorbance of 0.6 corresponded to approximately 28 mg/l of coal. A Sargent-Welch model LS or model NX pH meter and combination electrode were used to measure pH. Suspension mobilities were measured using a Zeta-Meter microelectrophoresis apparatus. 316
Object Description
Purdue Identification Number | ETRIWC198030 |
Title | Clarification of blackwater wastes by flotation and by coagulation |
Author |
Rubin, Alan J. Schroeder, Paul R. Kramer, Ralph J. |
Date of Original | 1980 |
Conference Title | Proceedings of the 35th Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://e-archives.lib.purdue.edu/u?/engext,31542 |
Extent of Original | p. 316-324 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital object copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Date Digitized | 2009-10-22 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page 316 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Transcript | CLARIFICATION OF BLACKWATER WASTES BY FLOTATION AND BY COAGULATION .Alan J. Rubin, Professor Paul R. Schroeder, Research Associate Ralph J. Kramer, III, Research Associate Water Resources Center The Ohio State University Columbus, Ohio 43210 INTRODUCTION Virtually all of the coals cleaned in the United States are wet cleaned. Consequently, bUlions of gallons of black wash waters are discharged annually to the nation's streams [ 1 ]. The fine coal particles carried away by wash waters represent a waste of energy and a significant source of pollution. The successful recovery of this waste coal could provide the economic incentive needed to resolve many present environmental problems associated with coal preparation. Waters laden with suspended coal particles are generated in increasing amounts as a result of modern methods of mechanized mining, the expansion of the coal mining industry and the greatly increased demand for ash-free coal with a minimum sulfur content. Because, frequently, very little more than plain settling is applied, especially in older preparation plants, much -48 mesh coal is lost [2]. Clarification should be employed in order to recover the coal and to meet the suspended solids effluent discharge limit of 0.07 g/1 imposed on the industry [3]. There has been little research reported in the literature which deals specifically with the removal or recovery of colloidal coal. Since it is the most difficult to remove by standard coal beneficiation methods, this ultrafine coal ends up as a major constituent of plant blackwaters. Accordingly, this study was initiated to investigate the feasibility of coal recovery by flotation and by coagulation under laboratory conditions. The major parameters controlling both processes were also examined in the study. EXPERIMENTAL METHODS AND MATERIALS Coal Suspensions Coal suspensions were prepared from a highly volatile, low sulfur, low ash bituminous coal from the Elkhorn seam in Kentucky. In order to prepare stable and reproducible suspensions a lengthy procedure was developed which is described in detail elsewhere [4]. In summary, the coal was ground, ball mUled and passed through a 400-mesh standard U.S. Series sieve. Batches were oxidized with dilute hydrogen peroxide at 80 C for several hours. The resultant slurry was washed, filtered and resuspended in distilled water. Typically, the pH ranged between 5.5 and 6.0; any suspensions having an unusually low pH were discarded. The surface areas of the coal particles were measured with a Quantasorb BET multipoint analyzer manufactured by Quantachrome Corporation. The ground, sieved coal had a surface area of 7.2 m2/g prior to oxidation and 9.3 m2/g afterward. Suspension turbidities were estimated by absorbance measurements taken with a Coleman model 14 spectrophotometer at a wavelength of 400 nm. Absorbance was linear with suspension concentration. A suspension absorbance of 0.6 corresponded to approximately 28 mg/l of coal. A Sargent-Welch model LS or model NX pH meter and combination electrode were used to measure pH. Suspension mobilities were measured using a Zeta-Meter microelectrophoresis apparatus. 316 |
Resolution | 300 ppi |
Color Depth | 8 bit |
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