GB2150159A - Cooling heated surfaces - Google Patents

Abstract

Heated surfaces, particularly surfaces such as hot worked sheet steel plate, but also steel structures such as drilling rigs, are rapidly cooled by spraying thereon an aqueous surfactant solution containing upto 0.2% by volume of one or more non-ionic surfactants having a cloud point or combined cloud point in the range 20 DEG C-100 DEG C.

Description

SPECIFICATION Cooling heated metal surfaces This invention relates to methods for rapidly cooling heated metal surfaces.

In many fields there is a need for rapidly cooling metal surfaces that may have been heated to extremely high temperatures. For instance, in the production of steel, most of it is cast in the form of ingots and then mechanically treated. Ingots are typically at the temperature range of 1090"-1430"C according to the steel composition and then subjected to a hot working which usually includes one or more rolling, hammering or pressing operations.

This hot working is important to achieve for the steel an improvement in the mechaical properties such as the yield and tensile strength and particularly the ductility, provided that the temperature of the steel is above the thermal critical range of the steel.

This high temperature requirement then necessitates a cooling operation which has been in the past ineffective and inefficient to effect a rapid cooling.

In the past, the heated metal surfaces have been cooled with water. Unfortunately, the volume of water required is great, and at times creates the problem of availability as well as the costlines of transporting such a great volume of water to the hot working site.

In addition, the water obviously be converted to steam with a lower heat conductivity resulting in lowered heat absorbing capacity, and therefore a longer cooling cycle.

In accordance with the present invention, an improved method has been found for the rapid cooling of heated surfaces, particularly, but not exclusively metals such as sheet steel.

Also the invention is applicable to the rapid cooling of metal structures, especially steel structures, such as drilling rigs which may have become overheated as the result of fire or for any other reason.

This method comprises spraying on to the hot surface an aqueous cooling composition comprising an aqueous non-ionic surfactant solution containing one or more non-ionic surfactants in a total amount not greater than 0.2% by volume and having a combined cloud point in the range 69 F-21 2 F (20"C-100"C). In this way metal surfaces that have been heated by various means are rapidly cooled by using a low volume substantially foam free liquid stream which not only conserves the volume of liquid used, but cools the heated metal far more quickly as compared with a conventional water cooling systems.

Preferably the composition is used in the form of a concentrate comprising one or more non-ionic surfactants having a combined cloud point of 68"F-212"F (20"C-100"C) and sufficient water to form a concentrate solution of not greater than 30% by weight of the surfactant. The ultimate heated surface cooling composition is then formed virtually in situ by passing the concentrate through a conventional pump wherein it is admixed with additional water sufficient to reduce the surfactant concentration to 0.2% by volume or less which is then sprayed onto the hot surfaces which are to be cooled. By keeping the surfactant concentration below 0.2% by volume undesirable foaming of the solution and cavitation of the pump can be avoided.

The surfactants useable for the present invention include those non-ionic surfactants having a cloud point between 68"F-212"F (20'-100'C) or which when combined produce a composite cloud point in that range. A cloud point below 68 F (20"C) for the sole or combination of surfactants would render them not sufficiently soluble to be useful, also a surfactant with a cloud point above 21 2 F (100"C) loses its cooling capability. However, it is possible that combinations of more than one non-ionic surfactant, each of which having a cloud point outside the specified range, could together produce a composite cloud point within the specified range and be sufficiently soluble and effective for the purposes of this invention.

In general it has been found that the surfactants useful to perform functions of the present invention are primarily, although not exclusively, those obtained through the condensation of ethylene oxide or propylene oxide with various substances and particularly with phenolic compounds having a side chain.

Among the substances are the following: fatty acids such as stearic, lauric, palmitic, etc.; fatty alcohols such as mannitol, sorbitol, etc.; primary, secondary or tertiary alcohols such as ethanol, isopropyl or isobutyl alcohols, etc.; fatty amines or amides; alkylolamines and block copolymers with ethylene and propylene oxides with M.W. of 1100-1 5,500, block copolymers of oxypropylene oxyethylene polyols derived from ethylene diamine. Of particular usefulness are those surfactants produced by the condensation of ethylene oxide with alkylphenols. The alkyl group may have from 1 to 1 2 or more carbon atoms though particularly 6 to 9 carbons atoms is preferred such as octyi-, nonyl-, etc.

In the formation of the surfactant the quantity of the molecules of ethylene oxide may be varied from below 3 up to 40 although preferably from 1.5 to 9.

In the practice of the present invention the concentrate solution is formed with not more than 30% by weight of the non-ionic surfactant and preferably 20-29% by weight of the surfactant. If greater amounts of the surfactant are used such that the concentration is greater than 30% by weight of the surfactant in water, the surfactant forms a gel rendering it less useable if at all. It is therefore important to maintain the concentration of the nonionic surfactant at a maximum of 30% by weight.

It is this concentrate solution that is placed in a storage or supply tank and provided for use. This solution concentrate when maintained in the storage tank at a maximum concentration of 30% by weight can be stored for ready use to form the heated surfaces cooling solution. It is from this storage tank that the concentrate may be educted into the intake side of a conventional pump with its discharge spraying one or more liquid streams onto the heated surfaces. Of course the concentrate solution can be premixed to form the cooling solution and taken into the pump at the intake side for spraying out through the discharge lines.

The concentrate solution has the unique characteristics of being able to be educted into the intake side of the pump rather than having to be educted into the nozzle of the discharge line. Such capability provides for the mixing and forming of the cooling solution at the intake side of the pump so that the discharge is capable of dispensing the liquid stream without excessive foam or cavitation that would overheat and disable the pump.

The need as in the prior art for individual eduction and metering means at each discharge site is negated with consequent economy.

To use the concentrate solution a conventional eductor or metering means may be provided to the intake side of the conventional pump. If the usual pumper trucks are used to cool metal structural rigs, the pump capacities are in the range of 250 gpm, 500 gpm, 750 gpm, 1000 gpm, 1250 gpm and 1500 gpm (950, 1900, 2850, 3800, 4750, 5700 I/m respectively). In the 1 500 gpm (5700 I/m) pumper, usually six 2-1 /2 inch (6.4 cms) lines each rated at a capacity of 250 gpm (950 I/m) may be provided. Before this invention when eductor equipment was used to feed prior compositions into the discharge line, the pipe size was reduced to 1-1/2 inch (3.8 cms) having only a 100 gpm (380 I/m) capacity.

In use for cooling sheet metal surfaces in a hot rolling mill, for instance, the cooling solution being formed from the concentrate can be pumped into any form of discharge system currently in use to spray the heated metal surfaces. When an oil rig, for instance, is to be cooled, the structural elements are sprayed with the cooling liquid preferably from a pumper as discussed above.

The cooling solution is formed from the concentrate solution in an amount such that the solution contains between 0.02% to 0.2% by volume of the surfactant. Preferably, the solution would have the surfactant in the concentration of between 0.03% to 0. 1% by volume. When premixed from the concentrate to the specified concentration, the pump draws in the premixed cooling solution.

Concentration of this surfactant in the cooling solution is important in enabling the heat to be absorbed very rapidly from the metal surfaces. It has been found that the low concentration enables the heat to be absorbed by a cloud generated from the cooling solution so as to more rapidly cool the metal surfaces compared to any other liquid composition.

The low concentration of the non-ionic surfactant in the cooling solution is also desirable because it enables the pump to pump the solution without excessive foam or cavitation that would damage the pump or limit the distance to which the water stream would be directed. To demonstrate the importance of the concentration not being greater than 0.2% by volume of the surfactant a surfactant concentration of 0.5% by volume such as disclosed in Nieneker. et al., U.S. Patent 3,578,590 was used in a truck having a 500 gallon (1900 1) capacity. The particular nonionic was a nonylphenol ethyoxylate with 9 moles of ethylene oxide. This provided 0.3% of the non-ionic surfactant to the water stream and the mixture was pumped through a standard nozzle set at 60 gallons per minute (228 I/m).The mixture when added to the intake side of the pump and sprayed at a maximum distance of 55-60 feet (16.8-18.2 m) as compared to a distance of 82 feet (25 m) either with piain water or with the formulation of the present invention utilizing a maximum of 0.2% non-ionic surfactant in the water.

This illustrates that there was some foaming in the use of the prior art composition that caused a loss of pressure sufficient to reduce the spray distance.

Further to demonstrate the distinction between the present invention and prior art compositions, the hose nozzle was shut off to allow the non-ionic solution to circulate through the conventional bypass valve back into the water supply tank. In three minutes the pump began to overheat due to foam generated in the pump. The resulting cavitation in the pump would have damaged the pump and rendered it useless. When the nozzle was again open to the 60 gallon per minute (228 I/m) flow rate a stream of 25-40 feet (2.6-12.2 m) resulted. The water stream was not continuous but tended to spurt. After all the water was pumped out of the tank the tank gauge still registered full but inspection of the tank indicated that it was full of dense foam which gave the false indication of the quantity of the content of the tank. The foam so impeded the operation that even the refill of the tank was ineffective.

The following examples illustrate the effectiveness of this invention. It is understood that these examples are not intended to limit the scope of the invention.

Examples 1 and 2 were conducted with the cooling composition of the present invention which was formed from a concentrate composed by weight of 74% water, 21.0% nonylphenoxy polyethoxy ethanol, with 9 moles of ethylene oxides, 4.0% block polymer a nonylphenoxy polyehoxy ethanol having a mixture of condensation product with 3 and 9 moles of ethylene oxide, molecular weight 2900, cloud point 136'F (58'C) and 0.8% corrosion inhibitors, such as sodium nitrate and boramide (boric acid and monoethanol amine) and optional 0.2% biocidal inhibitors such as sodium 1-hydroxy pyridine-2-thione. The corrosion inhibitors may be conventional however a 2:1 to 1:2 ratio by weight of sodium nitrate and boramide from .1% to 3% by weight is adequate.The biocide may be present between 0.001%-1% by weight and may also include one or more of the following: sodium omadine-Olin Corp. (1-hydroxy pyridine-2thione sodium salt); proxel CRL-ICI America (1,2 benzisothianoline 3-one); Kathon 886 Microbiocide, Rohm 8 Haas (8.6% 5-chloro2-methyl-4-isothiazoline-3-one) and (2.6% 2methyl-4-isothioazoline-3-one). This mixture had a cloud point of 137 F (58 C). One gallon (3.8 I) of this concentrate was premixed with 500 gallons (1900 í) of water and drawn into the intake side of a pumper. This provides .2% of the concentrate solution or .05% by volume of the non-ionic ingredients in the cooling solution.

EXAMPLE 1 A slab from the slabbing mill at a temperature of over 1100 C is hot rolled to a plate or sheet. The liquid cooling composition is to be sprayed onto the heated surface of the plate of sheet and in a few minutes, the plate is at a temperature of below 80"C and usually below 60"C.

EXAMPLE 2 An oil rig when set ablaze with an oil fire heats to a very high temperature all the structural elements of the rig. The liquid cooling composition would then be sprayed onto the structural steel elements of the rig to cool it in a few minutes. The metal surfaces are then comfortable to the touch.

Claims (9)

1. A method of cooling heated surfaces which comprises spraying onto the surface an aqueous surfactant solution containing one or more non-ionic surfactants having a cloud point or a combined cloud point as the case may be in the range 68"F-212"F (20"C-100"C) and present in said solution in an amount not greater than 0.2% by volume.

2. A method according to Claim 1 wherein said surface is of metal.

3. A method according to Claim 2 wherein said surface is the surface of a steel structure.

4. A method according to Claim 2 wherein said surface is the surface of a hot worked steel sheet.

5. A method according to any one of Claims 1-4 wherein said surfactant comprises one or more alkylphenoxy polyoxyethylene ethanols.

6. A method according to Claim 5 wherein the surfactant comprises a condensate of nonylphenol with from 1.5-40 moles of ethylene oxide.

7. A method according to any one of Claims 1-6 wherein said solution additionally contains a biocide and a corrosion inhibitor.

8. A method according to any one of Claims 1-7 wherein said solution contains from 0.02 to 0.2% by volume of said surfactant or surfactant mixture.

9. A method according to Claim 8 wherein said solution contains from 0.03% to 0.1% by volume of said surfactant or surfactant mixture.

1 0. A method according to any one of Claims 1-9 wherein said solution is sprayed onto said surface from a pump and wherein said solution is formed in situ in the pump by feeding thereto in separate streams an aqueous concentrate comprising one or more nonionic surfactants having a cloud point or combined cloud point as the case may be of 68 F-212 F (20'C-100 C) in an amount up to 30% by weight and additional water in an amount sufficient to dilute the concentrate in said pump to a surfactant concentration not greater than 0.2% by volume prior to spraying.