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DIRECT FILTRATION OF STEEL MILL SCALE AND METAL FINISHING RINSEWATERS WITH A CONTINUOUS FILTER Ingolf V. Janerus, Technical Manager Ray M. Shimokubo, Engingeer Parkson Corporation Fort Lauderdale, Florida 33334 Conventional granular media filters are used as polishing filters for many applications, e.g., wastewaters containing mill scale from hot finishing of steel and metal finishing rinse- waters. These fdters have to be taken off stream to be backwashed periodically. The associated equipment (pumps, valves, holding tanks, etc) and controls are expensive and complicated. At higher feed suspended solids concentrations the filters have to be backwashed excessively, which is impractical. The DynaSand Filter is a unique granular media fdtration system developed by The Axel Johnson Institute for Industrial Research in Sweden. The media is continuously cleaned while the filter is in operation. The dirtiest media is transported to the top of the filter through an internal air lift and washed before being returned onto the bed. A smad continuous stream of dirty reject water is produced. The filter wdl therefore be in continuous operation and can fdter suspensions with high suspended solids concentrations at a low pressure drop. This paper describes the filtration process and summarizes the results from several demonstration projects and commercial installations to highlight the advantages of the new concept. CONTINUOUS SAND FILTRATION Figure 1 depicts one module of a DynaSand Filter. This is an upflow gravity fdter. The feed enters the filter through a number of riser tubes which discharge under a distribution hood (A). The feed is introduced into the sand bed from the open bottom of the distribution hood. There is as much cross sectional fdter area outside the hood as there is inside it. Water flows upward through the sand bed (B) which is moving downward. The clear fdtrate exits the sand bed, overflows a weir (C) and is discharged from the filter (D). The used sand is transported to the top of the fdter (I) by an air lift (E) which extends through the sand bed. The air is injected at the bottom end of the air lift. The flow of air, water and sand in the air lift is very turbulent and the impurities are scoured loose from the sand so that when the mixture exits the air lift (F) it consists of clean sand and very dirty water. The sand is returned to the sand bed through a gravity washer/separator (G) which allows the fast-settling sand to penetrate but not the dirty liquid. The washer/separator is placed concentrically around the upper part of the air lift and consists of several stages to eliminate any risk of short-circuiting. In each stage, the sand is changing direction at least two to three times. A liquid barrier ascertains that no dirty liquid accompanies the clean sand into the fdtrate compartment. The liquid barrier consists of a small amount of filtrate which is forced upwards through the washer/separator counter-current to the sand. The driving force for this transportation is the level difference between the fdtrate weir (C) and the reject weir (J), which is adjustable. The clean sand is returned to the top of the sand bed by means of a cone shaped distributor (H). The dirty reject water leaves the filter as a continuous stream so there is no need for holding tanks for backwash water, etc. The filtration is only taking place in the part of the sand bed above the distribution hood (A). This part is generally about 40 in. deep to ensure deep bed fdtration. The sand is slowly 733
Object Description
Purdue Identification Number | ETRIWC198073 |
Title | Direct filtration of steel mill scale and metal finishing rinsewaters with a continuous filter |
Author |
Janerus, Ingolf V. Shimokubo, Ray M. |
Date of Original | 1980 |
Conference Title | Proceedings of the 35th Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://earchives.lib.purdue.edu/u?/engext,31542 |
Extent of Original | p. 733-745 |
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 733 |
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 | DIRECT FILTRATION OF STEEL MILL SCALE AND METAL FINISHING RINSEWATERS WITH A CONTINUOUS FILTER Ingolf V. Janerus, Technical Manager Ray M. Shimokubo, Engingeer Parkson Corporation Fort Lauderdale, Florida 33334 Conventional granular media filters are used as polishing filters for many applications, e.g., wastewaters containing mill scale from hot finishing of steel and metal finishing rinse- waters. These fdters have to be taken off stream to be backwashed periodically. The associated equipment (pumps, valves, holding tanks, etc) and controls are expensive and complicated. At higher feed suspended solids concentrations the filters have to be backwashed excessively, which is impractical. The DynaSand Filter is a unique granular media fdtration system developed by The Axel Johnson Institute for Industrial Research in Sweden. The media is continuously cleaned while the filter is in operation. The dirtiest media is transported to the top of the filter through an internal air lift and washed before being returned onto the bed. A smad continuous stream of dirty reject water is produced. The filter wdl therefore be in continuous operation and can fdter suspensions with high suspended solids concentrations at a low pressure drop. This paper describes the filtration process and summarizes the results from several demonstration projects and commercial installations to highlight the advantages of the new concept. CONTINUOUS SAND FILTRATION Figure 1 depicts one module of a DynaSand Filter. This is an upflow gravity fdter. The feed enters the filter through a number of riser tubes which discharge under a distribution hood (A). The feed is introduced into the sand bed from the open bottom of the distribution hood. There is as much cross sectional fdter area outside the hood as there is inside it. Water flows upward through the sand bed (B) which is moving downward. The clear fdtrate exits the sand bed, overflows a weir (C) and is discharged from the filter (D). The used sand is transported to the top of the fdter (I) by an air lift (E) which extends through the sand bed. The air is injected at the bottom end of the air lift. The flow of air, water and sand in the air lift is very turbulent and the impurities are scoured loose from the sand so that when the mixture exits the air lift (F) it consists of clean sand and very dirty water. The sand is returned to the sand bed through a gravity washer/separator (G) which allows the fast-settling sand to penetrate but not the dirty liquid. The washer/separator is placed concentrically around the upper part of the air lift and consists of several stages to eliminate any risk of short-circuiting. In each stage, the sand is changing direction at least two to three times. A liquid barrier ascertains that no dirty liquid accompanies the clean sand into the fdtrate compartment. The liquid barrier consists of a small amount of filtrate which is forced upwards through the washer/separator counter-current to the sand. The driving force for this transportation is the level difference between the fdtrate weir (C) and the reject weir (J), which is adjustable. The clean sand is returned to the top of the sand bed by means of a cone shaped distributor (H). The dirty reject water leaves the filter as a continuous stream so there is no need for holding tanks for backwash water, etc. The filtration is only taking place in the part of the sand bed above the distribution hood (A). This part is generally about 40 in. deep to ensure deep bed fdtration. The sand is slowly 733 |
Resolution | 300 ppi |
Color Depth | 8 bit |
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