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Dewatering of Rolling Mill Sludge From A Tin Mill HANS W. FORSTER, Product Manager Solids Disposal Division Beloit-Passavant Corporation Birmingham, Alabama 35201 The chemical composition and relatively low solid concentration of sludges generated from Tin Mills have historically been difficult to dewater to any reasonable degree. The greatest single constituent contributing to the difficult dewatering job are the ever- present oils and greases. These stem from hydraulic systems as well as lubricating systems and coating systems. The remainder of solids in the sludge are ferrous compounds, chromium, phosphate, sulphur, etc. Dewatering of these sludges has been attempted by the well known devices, as vacuum filters and centrifuges. A very large plant in the Middle West has employed centrifuges for several years but was unable to concentrate the sludge to more than 18-20 percent solids, hardly a product which can be readily handled. Vacuum filters, likewise, will tend to dewater this material up to a point; however, in no case was the degree of solid concentration in the resulting cake high enough to permit recycling of the resulting cake through the roasting process. In addition, conditioning cost of vacuum filtration and centrifuging in particular, have been high. Polymers appear to be the only conditioning agent suitable for this dewatering technique and the required admixture high. Changes in solid concentration of the incoming feed present still another obstacle to successful dewatering of this sludge. Although solid concentrations may run as high as 8 percent, they can go down to well under 4 percent. The limitation in pressure differential and solids concentration on the vacuum filter rules thistype of machine out; the relatively short retention time in the machine proper of a centrifuge and the limited "G" forces produced no greater solid concentration than those mentioned above. Pressure filters were then investigated because of their ability to accept great changes in sludge characteristics as well as sludge concentrations. In addition, the sludge accumulated in the pressure filter is "captive", thus it cannot slough off. Furthermore, the pressure differential of 225 psig results in filter cake concentrations anywhere from 50-60 percent solids. As in other systems, the sludge feed for a pressure filter must, likewise, be conditioned in order to render it filterable. In this particular case, it was found that the addition of hydrated lime at a rate of 8 percent of dry solids in the sludge produced acceptable filtration rates and reasonable filter cycles. It is to be noted that the treatment plant for which the dewatering system was planned, did not even exist at the time of testing, thus — all test work was conducted at another plant site and was assumed that sludge conditions would be similar at the new plant site. This assumption proved to be correct with the exception that the oil and grease content of the sludge was somewhat higher than anticipated. This, however, did not influence — in any way, the actual operation. After all test data had been analyzed, design parameters determined and the plant actually designed, the client suggested another series of tests, however, this time to use 323
Object Description
Purdue Identification Number | ETRIWC197330 |
Title | Dewatering of rolling mill sludge from a tin mill |
Author | Forster, Hans W. |
Date of Original | 1973 |
Conference Title | Proceedings of the 28th Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://earchives.lib.purdue.edu/u?/engext,23197 |
Extent of Original | p. 323-328 |
Series | Engineering extension series no. 142 |
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 | 2009-06-02 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page 323 |
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 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Transcript | Dewatering of Rolling Mill Sludge From A Tin Mill HANS W. FORSTER, Product Manager Solids Disposal Division Beloit-Passavant Corporation Birmingham, Alabama 35201 The chemical composition and relatively low solid concentration of sludges generated from Tin Mills have historically been difficult to dewater to any reasonable degree. The greatest single constituent contributing to the difficult dewatering job are the ever- present oils and greases. These stem from hydraulic systems as well as lubricating systems and coating systems. The remainder of solids in the sludge are ferrous compounds, chromium, phosphate, sulphur, etc. Dewatering of these sludges has been attempted by the well known devices, as vacuum filters and centrifuges. A very large plant in the Middle West has employed centrifuges for several years but was unable to concentrate the sludge to more than 18-20 percent solids, hardly a product which can be readily handled. Vacuum filters, likewise, will tend to dewater this material up to a point; however, in no case was the degree of solid concentration in the resulting cake high enough to permit recycling of the resulting cake through the roasting process. In addition, conditioning cost of vacuum filtration and centrifuging in particular, have been high. Polymers appear to be the only conditioning agent suitable for this dewatering technique and the required admixture high. Changes in solid concentration of the incoming feed present still another obstacle to successful dewatering of this sludge. Although solid concentrations may run as high as 8 percent, they can go down to well under 4 percent. The limitation in pressure differential and solids concentration on the vacuum filter rules thistype of machine out; the relatively short retention time in the machine proper of a centrifuge and the limited "G" forces produced no greater solid concentration than those mentioned above. Pressure filters were then investigated because of their ability to accept great changes in sludge characteristics as well as sludge concentrations. In addition, the sludge accumulated in the pressure filter is "captive", thus it cannot slough off. Furthermore, the pressure differential of 225 psig results in filter cake concentrations anywhere from 50-60 percent solids. As in other systems, the sludge feed for a pressure filter must, likewise, be conditioned in order to render it filterable. In this particular case, it was found that the addition of hydrated lime at a rate of 8 percent of dry solids in the sludge produced acceptable filtration rates and reasonable filter cycles. It is to be noted that the treatment plant for which the dewatering system was planned, did not even exist at the time of testing, thus — all test work was conducted at another plant site and was assumed that sludge conditions would be similar at the new plant site. This assumption proved to be correct with the exception that the oil and grease content of the sludge was somewhat higher than anticipated. This, however, did not influence — in any way, the actual operation. After all test data had been analyzed, design parameters determined and the plant actually designed, the client suggested another series of tests, however, this time to use 323 |
Resolution | 300 ppi |
Color Depth | 8 bit |
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