CA2302108A1 - Method for inhibiting oil adsorption onto steel mill scale - Google Patents
Method for inhibiting oil adsorption onto steel mill scale Download PDFInfo
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- CA2302108A1 CA2302108A1 CA 2302108 CA2302108A CA2302108A1 CA 2302108 A1 CA2302108 A1 CA 2302108A1 CA 2302108 CA2302108 CA 2302108 CA 2302108 A CA2302108 A CA 2302108A CA 2302108 A1 CA2302108 A1 CA 2302108A1
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- Prior art keywords
- oil
- mill scale
- scale
- nonionic surfactant
- steel mill
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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Abstract
A method of inhibiting the deposition of oil on steel mill scale particles is disclosed. The method comprises adding a nonionic surfactant such as an alkylphenolethoxylate to the mill flume water.
Description
METHOD FOR INHIBITING OIL ADSORPTION
ONTO STEEL MILL SCALE
FIELD OF THE INVENTION
The present invention relates to a method of inhibiting oil adsorption onto steel mill scale particles. More particularly, the present invention relates to a method of inhibiting oil adsorption onto steel mill scale by treatment of steel mill flume water.
BACKGROUND OF THE INVENTION
Oily mill scale presents a significant waste handling problem for the steel industry due to the large amount of mill scale produced at a hot rolling mill. Incineration processes to remove the oil, while effective, can be prohibited by environmental regulations or concerns. A method to inhibit oil adsorption onto steel mill scale will allow more efficient reuse of the scale.
In a typical hot rolling mill, the steel ingots are rolled for shaping and thinning. Water is sprayed onto the steel to cool it and to knock off the iron oxide scale that forms as oxygen reacts with the steel surface.
This mill scale falls through a grating below the steel stands and into a scale pit. A variety of oils, greases and hydraulic fluids (hereinafter called oil) utilized for lubrication of mechanical equipment also collect in the scale pit. In the scale pit, oil, scale and water are separated. However, the mill scale becomes oil-wet due to contact with the oil present in the scale pit. The oil content of the scale can be as high as 10%.
Steel mills would like to recycle this scale since the scale has a high iron content. However, oil-fouled scale can cause problems. In typical operations, iron ore and other particulate iron sources such as mill scale are agglomerated in a sintering process to reduce particulate emissions. Agglomeration is accomplished in a sintering plant by exposing the iron-containing particulate to elevated temperatures to fuse the particles into agglomerate. Exposure of oily mill scale to such elevated temperatures results in some vaporization of the oil and release to the off gases. The release of such hydrocarbon emissions is a concern. In addition, the hydrocarbon emission can foul the air filters in the ubag house" of the sinter plant.
Therefore, there is a limit on the amount of oil that can be tolerated in a mill scale sintering operation. The limit for oil on mill scale can vary depending on local regulations, on other hydrocarbon emissions from within the mill, and on the amount of oily mill scale that is processed in the sinter operation. In some mills, oil content of the mill scale must be less than 1 %, while other mills may utilize mill scale with 2% or more oil.
In general, however, reduced oil content of mill scale may allow higher mill scale recycle and reduce emissions. A cost-effective treatment is needed to allow higher mill scale recycle rates without increasing environmental discharges.
SUMMARY OF THE INVENTION
The present invention relates to a method of inhibiting the adsorption of oil on steel mill scale particles comprising adding nonionic surfactants to the scale pit water. The addition of nonionic surfactants to the scale pit water inhibit the deposition of oil onto the scale while not emulsifying the oil and water so that the oil and water can easily be separated via skimming.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A method of inhibiting deposition of oil on steel mill scale particles is disclosed. The method comprises adding nonionic surfactants to steel mill scale pit water. Preferably, the nonionic surfactant is added to the scale pit water, ahead of the scale pit. Oil present in the scale pit in the absence of the nonionic surfactant treatment quickly adsorbs onto the mill scale. Addition of the treatment of the present invention to the scale pit water prior to water contact with the mill scale will inhibit adsorption of the oil onto the mill scale.
Preferably, the scale pit water is treated in the flume, ahead of the scale pit. Typical scale pit water has a pH of from about 3.0 to about 9Ø
Typical temperature for mill scale water ranges from about 20° C
to about 50° C.
ONTO STEEL MILL SCALE
FIELD OF THE INVENTION
The present invention relates to a method of inhibiting oil adsorption onto steel mill scale particles. More particularly, the present invention relates to a method of inhibiting oil adsorption onto steel mill scale by treatment of steel mill flume water.
BACKGROUND OF THE INVENTION
Oily mill scale presents a significant waste handling problem for the steel industry due to the large amount of mill scale produced at a hot rolling mill. Incineration processes to remove the oil, while effective, can be prohibited by environmental regulations or concerns. A method to inhibit oil adsorption onto steel mill scale will allow more efficient reuse of the scale.
In a typical hot rolling mill, the steel ingots are rolled for shaping and thinning. Water is sprayed onto the steel to cool it and to knock off the iron oxide scale that forms as oxygen reacts with the steel surface.
This mill scale falls through a grating below the steel stands and into a scale pit. A variety of oils, greases and hydraulic fluids (hereinafter called oil) utilized for lubrication of mechanical equipment also collect in the scale pit. In the scale pit, oil, scale and water are separated. However, the mill scale becomes oil-wet due to contact with the oil present in the scale pit. The oil content of the scale can be as high as 10%.
Steel mills would like to recycle this scale since the scale has a high iron content. However, oil-fouled scale can cause problems. In typical operations, iron ore and other particulate iron sources such as mill scale are agglomerated in a sintering process to reduce particulate emissions. Agglomeration is accomplished in a sintering plant by exposing the iron-containing particulate to elevated temperatures to fuse the particles into agglomerate. Exposure of oily mill scale to such elevated temperatures results in some vaporization of the oil and release to the off gases. The release of such hydrocarbon emissions is a concern. In addition, the hydrocarbon emission can foul the air filters in the ubag house" of the sinter plant.
Therefore, there is a limit on the amount of oil that can be tolerated in a mill scale sintering operation. The limit for oil on mill scale can vary depending on local regulations, on other hydrocarbon emissions from within the mill, and on the amount of oily mill scale that is processed in the sinter operation. In some mills, oil content of the mill scale must be less than 1 %, while other mills may utilize mill scale with 2% or more oil.
In general, however, reduced oil content of mill scale may allow higher mill scale recycle and reduce emissions. A cost-effective treatment is needed to allow higher mill scale recycle rates without increasing environmental discharges.
SUMMARY OF THE INVENTION
The present invention relates to a method of inhibiting the adsorption of oil on steel mill scale particles comprising adding nonionic surfactants to the scale pit water. The addition of nonionic surfactants to the scale pit water inhibit the deposition of oil onto the scale while not emulsifying the oil and water so that the oil and water can easily be separated via skimming.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A method of inhibiting deposition of oil on steel mill scale particles is disclosed. The method comprises adding nonionic surfactants to steel mill scale pit water. Preferably, the nonionic surfactant is added to the scale pit water, ahead of the scale pit. Oil present in the scale pit in the absence of the nonionic surfactant treatment quickly adsorbs onto the mill scale. Addition of the treatment of the present invention to the scale pit water prior to water contact with the mill scale will inhibit adsorption of the oil onto the mill scale.
Preferably, the scale pit water is treated in the flume, ahead of the scale pit. Typical scale pit water has a pH of from about 3.0 to about 9Ø
Typical temperature for mill scale water ranges from about 20° C
to about 50° C.
The treatment of the present invention comprises a nonionic surfactant. The nonionic surfactant can be selected from:
polyoxyethylenated alkylphenols, alcoholethoxylates, polyoxyethylenated mercaptans, long chain carboxylic acid esters, polyoxyethylenated polyoxypropylene glycols, polyoxyethylenated sorbitol esters, polyoxyethylene glycol ester and fatty acids, alkanol amine - fatty acid condensates, tertiary acetylenic glycols and mixtures thereof. Preferred nonionic surfactants are alkylphenol ethoxylates where the alkyl group is C8 - C9, and the moles of ethoxylation range from N=5 to N=25. The most preferred nonionic surfactants are Ca alkyl phenol ethoxylates having from 8 to 12 moles of ethoxylation.
The treatment of the present invention is added to the scale pit water in an amount sufficient to inhibit deposition of oil on the mill scale particles. The limits of acceptable oil on the mill scale can vary from site to site. Typically the oil content of the mill scale is preferred to be 2% by weight or lower. Typical treatments in accordance with the present invention comprise adding from about 2 to 10,000 ppm and preferably from about 2 to 250 ppm nonionic surfactant to the scale pit water.
The present invention will now be further described with reference to a number of specific examples which are to be regarded solely as illustrative and not as restricting the scope of the present invention.
Examples A laboratory protocol was developed to clean oil fouled sinter, determine the level of fouling present, and to evaluate the inhibitory effects of selected treatments. Oil fouled mill scale samples were obtained from a Midwestern steel mill. The extent of fouling was determined by placing a 50 gram sample of oil fouled scale on a fluted filter cloth and washing the sample with 60 ml of Freon~ (Freon is a trademark of E.I. DuPont de Nemours Co.). The filtrate was analyzed 5 with a Horiba Oil and Grease Analyzer to determine the oil content.
Washing and analysis was continued until > 95% of the oil had been removed from the fouled sinter. This sinter was then used to conduct experiments designed to ascertain the ability of the nonionic surfactant treatment to prevent oil from re-adsorbing. In order to accurately model the plant conditions, samples of the various rolling oils and cutting fluids used were submitted. Monthly usage rates for each of the oils were obtained, and a synthetic blend of the oils prepared with the various oils at the appropriate percentages.
The level of oil (100 - 2000 ppms) determined in the washing of a sample was used for the preliminary screening studies. Studies were conducted using a Phipps and Bird Jar Testing Apparatus, immersed in a Precision Scientific Water Bath, so that the treatment could be applied at 120° F, a temperature typical of the flume water. Initial screening studies were conducted as follows: 2.5g of cleaned sinter added to a 600 ml beaker which contained 250 ml tap water. The beaker was immersed in the water bath. The sinterlwater mix was agitated at high speed (100 rpm), and the nonionic surfactant treatment added and mixed at high speed for 1 minute. Oil was added at a dosage of 2000 ppm, and the surfactantlsinter/oil/water system mixed vigorously (100 rpm) for 4 minutes, followed by 10 minutes of slow (30 rpm) mixing. The system was then allowed to settle for 10 minutes. Qualitative observations were made of the presence of oil floating on the water surface, and the fluidity of the sinter. After 10 minutes, the water was decanted off, the remaining sinter/water poured through a filter and the sinter aid-dried for 30 minutes.
The sinter was then extracted with Freon, and the oil extracted measured using the Horiba Oil and Grease Analyser. The percent inhibition was calculated as the amount of oil extracted from the sinter after contact with the copolymer treatment and oil divided by the amount of oil initially added X 100.
The most promising treatments gave an oil skim layer, and produced sinter that visually remained as discrete particles. For the most promising products, a modified procedure was used to better simulate the actual flume conditions. For these experiments, the fast mix time was reduced to 30 seconds. Tables I and II summarize the results.
Table I
Fouling Studies (4 minute fast mix, 10 minute slow mix) Dosage Oil Extracted Treatment (ppm) (ppm~ % Inhibition Blank ------ 2400 _--.
A 250 200 g2 Treatment A is a nonyl phenol ethoxylate with 10 moles of ethoxylation lil Table II
Fouling Studies (30 second fast mix, 10 minute slow mix) Dosage Oil Extracted Treatment ~ppm) jppm) % Inhibition B la n k _______ 1200 ______ The results in Tables I and II show that the Treatment A, a nonyl phenol ethoxylate with 10 moles of ethoxylation was an effective means for inhibiting oil adsorption onto steel mill scale.
While the present invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of this invention will be obvious to those skilled in the art. The appended claims and this invention should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention.
polyoxyethylenated alkylphenols, alcoholethoxylates, polyoxyethylenated mercaptans, long chain carboxylic acid esters, polyoxyethylenated polyoxypropylene glycols, polyoxyethylenated sorbitol esters, polyoxyethylene glycol ester and fatty acids, alkanol amine - fatty acid condensates, tertiary acetylenic glycols and mixtures thereof. Preferred nonionic surfactants are alkylphenol ethoxylates where the alkyl group is C8 - C9, and the moles of ethoxylation range from N=5 to N=25. The most preferred nonionic surfactants are Ca alkyl phenol ethoxylates having from 8 to 12 moles of ethoxylation.
The treatment of the present invention is added to the scale pit water in an amount sufficient to inhibit deposition of oil on the mill scale particles. The limits of acceptable oil on the mill scale can vary from site to site. Typically the oil content of the mill scale is preferred to be 2% by weight or lower. Typical treatments in accordance with the present invention comprise adding from about 2 to 10,000 ppm and preferably from about 2 to 250 ppm nonionic surfactant to the scale pit water.
The present invention will now be further described with reference to a number of specific examples which are to be regarded solely as illustrative and not as restricting the scope of the present invention.
Examples A laboratory protocol was developed to clean oil fouled sinter, determine the level of fouling present, and to evaluate the inhibitory effects of selected treatments. Oil fouled mill scale samples were obtained from a Midwestern steel mill. The extent of fouling was determined by placing a 50 gram sample of oil fouled scale on a fluted filter cloth and washing the sample with 60 ml of Freon~ (Freon is a trademark of E.I. DuPont de Nemours Co.). The filtrate was analyzed 5 with a Horiba Oil and Grease Analyzer to determine the oil content.
Washing and analysis was continued until > 95% of the oil had been removed from the fouled sinter. This sinter was then used to conduct experiments designed to ascertain the ability of the nonionic surfactant treatment to prevent oil from re-adsorbing. In order to accurately model the plant conditions, samples of the various rolling oils and cutting fluids used were submitted. Monthly usage rates for each of the oils were obtained, and a synthetic blend of the oils prepared with the various oils at the appropriate percentages.
The level of oil (100 - 2000 ppms) determined in the washing of a sample was used for the preliminary screening studies. Studies were conducted using a Phipps and Bird Jar Testing Apparatus, immersed in a Precision Scientific Water Bath, so that the treatment could be applied at 120° F, a temperature typical of the flume water. Initial screening studies were conducted as follows: 2.5g of cleaned sinter added to a 600 ml beaker which contained 250 ml tap water. The beaker was immersed in the water bath. The sinterlwater mix was agitated at high speed (100 rpm), and the nonionic surfactant treatment added and mixed at high speed for 1 minute. Oil was added at a dosage of 2000 ppm, and the surfactantlsinter/oil/water system mixed vigorously (100 rpm) for 4 minutes, followed by 10 minutes of slow (30 rpm) mixing. The system was then allowed to settle for 10 minutes. Qualitative observations were made of the presence of oil floating on the water surface, and the fluidity of the sinter. After 10 minutes, the water was decanted off, the remaining sinter/water poured through a filter and the sinter aid-dried for 30 minutes.
The sinter was then extracted with Freon, and the oil extracted measured using the Horiba Oil and Grease Analyser. The percent inhibition was calculated as the amount of oil extracted from the sinter after contact with the copolymer treatment and oil divided by the amount of oil initially added X 100.
The most promising treatments gave an oil skim layer, and produced sinter that visually remained as discrete particles. For the most promising products, a modified procedure was used to better simulate the actual flume conditions. For these experiments, the fast mix time was reduced to 30 seconds. Tables I and II summarize the results.
Table I
Fouling Studies (4 minute fast mix, 10 minute slow mix) Dosage Oil Extracted Treatment (ppm) (ppm~ % Inhibition Blank ------ 2400 _--.
A 250 200 g2 Treatment A is a nonyl phenol ethoxylate with 10 moles of ethoxylation lil Table II
Fouling Studies (30 second fast mix, 10 minute slow mix) Dosage Oil Extracted Treatment ~ppm) jppm) % Inhibition B la n k _______ 1200 ______ The results in Tables I and II show that the Treatment A, a nonyl phenol ethoxylate with 10 moles of ethoxylation was an effective means for inhibiting oil adsorption onto steel mill scale.
While the present invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of this invention will be obvious to those skilled in the art. The appended claims and this invention should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention.
Claims (4)
1. A method of inhibiting deposition of oil on steel mill scale particles comprising:
adding to mill scale pit water a nonionic surfactant;
contacting steel mill scale particles fouled with oil with said mill scale pit water containing said nonionic surfactant in a scale pit; and separating the scale particles from the mill scale pit water.
adding to mill scale pit water a nonionic surfactant;
contacting steel mill scale particles fouled with oil with said mill scale pit water containing said nonionic surfactant in a scale pit; and separating the scale particles from the mill scale pit water.
2. The method of claim 1 wherein said nonionic surfactant is selected from the group consisting of polyoxyethylenated alkylphenols, alcoholethoxylates, polyoxyethylenated mercaptans, long chain carboxylic acid esters, polyoxyethylenated polyoxy propylene glycols, polyoxyethylenated sorbitol esters, polyoxyethylene glycol esters, polyoxyethylene glycol fatty acids, alkanolamine fatty acid condensates, tertiary acetylenic glycols and mixtures thereof.
3. The method of claim 1 wherein said nonionic surfactant is an alkylphenolethoxylate having a C8-C9 alkyl group and from about 5 to 25 moles of ethoxylation.
4. The method of claim 1 wherein said nonionic surfactant is a C9 alkylphenolethoxylate having 10 moles of ethoxylation.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US52005600A | 2000-03-07 | 2000-03-07 | |
| US09/520,056 | 2000-03-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2302108A1 true CA2302108A1 (en) | 2001-09-07 |
Family
ID=24071018
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2302108 Abandoned CA2302108A1 (en) | 2000-03-07 | 2000-03-24 | Method for inhibiting oil adsorption onto steel mill scale |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2302108A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102009072A (en) * | 2010-10-27 | 2011-04-13 | 宝钢工程技术集团有限公司 | System for preventing oil and water separation of emulsified liquid in magnetic filters |
-
2000
- 2000-03-24 CA CA 2302108 patent/CA2302108A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102009072A (en) * | 2010-10-27 | 2011-04-13 | 宝钢工程技术集团有限公司 | System for preventing oil and water separation of emulsified liquid in magnetic filters |
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| FZDE | Dead |