GB2058128A

GB2058128A - A process and aq. graphite suspension for treating steel parts

Info

Publication number: GB2058128A
Application number: GB8022900A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-07-23
Filing date: 1980-07-14
Publication date: 1981-04-08
Also published as: GB2058128B

Abstract

A smooth lubricating coating is applied to steel parts to prevent those parts in an electrical precipitation apparatus becoming covered by the accumulation of particulate matter thereon, by cleaning the parts and then penetrating the parts with a liquid suspension comprising between 5% and 25% sub micron sized (e.g. 2 Angstrom units or less) particles of graphite by weight, between 2% to 10% by weight concentrated hydrochloric acid, between 15% to 20% by weight water, and at least one of the following: (a) 34%-75% by weight of a solution of water and sodium silicate, with the sodium silicate present at about 40% of the solution, (b) 33%-75% by weight of a solution of water and a water soluble resin (e.g. a carboxy vinyl polymer), the resin being present in amounts between 1% to 10% of the solution, and (c) 33%-75% by weight of a solution of water and xanthan gum wherein the gum is present in amounts between 1% to 10% of the solution. s

Description

SPECIFICATION A process and suspension for treating steel parts This invention relates to a process and suspension for treating the steel parts of electrical precipitators such as are used in cleaning flue gases in power plants, blast furnaces, coke ovens in order to prevent the accumulation of particulate matter therein and thereby avoid restrictions arising in the gas circulation.

Fossil fuelled power plants, such as used in electrical and steam generating installations, blast furnaces and coke ovens, have heretofore been provided with various flue gas scrubbers and electrical precipitators for removing particulate material which would otherwise be discharged with the flue gases and pollute the atmosphere.

The electrical precipitators collect solid or liquid particles suspended in a gas by means of a unidirectional electric field, the precipitated particles being attracted to and collected on the positive electrode of the precipitator. In order that the solid or liquid particles may reach the positive electrode of the precipitator, the communicating passageways must be kept open and the prior art installations have provided no means of assuring the non-blocking accumulation of particles in such passageways.

In electrical power or steam generating plants, considerable fly ash and other objectionable particulate matter is encounted. In blast furnaces coke, limestone and iron ore dusts are produced and in coke ovens coal tar and other by-products build up deposits which are difficult to remove and which like the other particular matter accumulate and block the passageways through the precipitators.

The present invention relates to a process of building up a penetrating coating on the inner walls and fan blades or blower parts in the electrical precipitation devices with a material that is not affected by the heat of the operation and to which tar and other solid or liquid particles suspended in a gas will not adhere with the result that the passageways, fan blades and/or blower parts remain clean and free of solid or liquid particle build up.

The material used in the process forms a penetrating and lubricating adhesive coating on the fan blades and/or blower parts in electrical precipitation installations.

According to the present invention there is provided a process of treating the inner steel walls and fluid handling and moving devices in electrical precipitation installations comprising the steps of: cleaning said steel walls and devices, penetrating a liquid suspension of sub micron sized particles of graphite into said cleaned steel walls and devices so as to build up a smooth adhering and lubricating coating on said steel walls and devices to form a slick smooth surface, wherein said suspension comprises substantially between 5% and 25% sub micron sized particles of graphite by weight, between about 2% to 10% by weight concentrated hydrochloric acid, between about 1 5% to 20% by weight water, and at least one of the following (a) between about 34 and 75% by weight of a solution of water and sodium silicate, with the sodium silicate present at about 40% of the solution, (b) between about 33% and 75% by weight of a solution of water and a water soluble resin, the resin being present in amounts between 1% to 10% of the solution, and (c) between about 33% and 75% by weight of a solution of water and xanthan gum wherein the gum is present in amounts between about 1% to 10% of the solution.

According to a second aspect of the invention there is provided a liquid suspension of sub micron sized particles of graphite for use in treating steel walls comprising substantially between 5% and 25% sub micron sized particles of graphite by weight, between about 2% to 10% by weight concentrated hydrochloric acid, between about 15% to 20% by weight water, and at least one of the following: (a) between about 34% and 75% by weight of a solution of water and sodium silicate, with the sodium silicate present at about 40% of the solution, (b) between about 33% and 75% by weight of a solution of water and a water soluble resin, the resin being present in amounts between 1% to 10% of the solution, and (c) between about 33% and 75% by weight of a solution of water and xanthan gum wherein the gum is present in amounts between 1% to 10% of the solution.

The material of this embodiment is particularly suitable for building up penetrating and lubricating adhesive smooth surface coatings on the inner steels walls of electrical precipitation installations including fan steel blades and blower parts therein and comprises substantially between about 5% to 25% by weight'sub micron sized particles of graphite, between about 34% to 75% by weight of a solution of water and sodium silicate (NaSiO) wherein the water is present at about 60% of the solution, between about 2% to 10% concentrated hydrochloric acid of a 90% purity weight, between about 33% to 75% of a solution of water acid carboxy vinyl polymer resin wherein the resin is present in amounts between 1% to 10% of the solution by weight and between 1 5% to 20% water by weight.The particle size of the sub micron sized graphite is substantially smaller than that of a micron sized particle, which is between 0.2 and 10 millionths of a metre. The particle size of the sub micron sized graphite may be of the order of 2 Angstrom units or less.

The carboxy vinyl resin powder has a specific gravity of 1.41 and a bulk density 13 Ibs per cubic foot. It is available commercially under the trade name "CARBOPOL" and low concentrations mixed with water as herein disclosed produce a thin gel-like liquid with penetrating and adhesive qualities.

Those skilled in the art will observe that the liquid carrier as set forth hereinbefore comprises an effective wetting agent which contributes to the ability of the sub micron sized particles of graphite to penetrate the metal comprising the inner walls, fan blades and/or blower parts of the electrical precipitation installations, and form a smooth dry lubricating adhesive coating.

Those skilled in the art will also observe that the percentages of the sub micron sized particles of graphite in the liquid carrier may be varied depending upon the number of applications of the material to the metal parts being treated and it has been determined that some metals used in the duct work walls, fan blades and blower parts in electrical precipitation installations are advantageously treated by preheating said metal surfaces and/or parts immediately prior to the application of the material in the process herein disclosed.

For example small percentages of the sub micron sized particles of graphite in the liquid carrier perform effectively when a number of applications of the material are applied and when only one or a few applications of the material are applied to the metal surfaces then the higher percentages of the sub micron sized particles of graphite are desirable. In either case the material penetrates the metal surfaces being treated and builds up an extremely smooth slick surface coating to which fly ash and other particulate matter including solid or liquid particles suspended in the flue gases will not adhere or if some adherence occurs the adhering material may be easily removed from the treated surfaces by air jets or the like.

In using the material disclosed herein, the process involves mixing the material to form a liquid suspension of the sub micron sized particles of graphite and then spraying the same by any suitable spraying equipment on cleaned metal surfaces of the inner steel walls, fan blades and/or blower parts of the electrical precipitation installations being treated. One or more coatings are applied as necessary to build up a smooth unbroken surface of the material on the metal surfaces being treated and the material may be applied to the metal surfaces while they are either hot or cold as aforesaid. The ability of the material to be applied to and remain on hot steel surfaces is particularly advantageous in power plants, blast furnace and coke oven installations as the flue gases being handled are of a high temperature.

Those skilled in the art will observe that the heretofore necessary manual cleaning of the inner steel wall surfaces, fan blades and/or blower parts required considerable down time of the particular electrical precipitation installation being cleaned and that this down time is now largely eliminated through the use of the material and process disclosed herein.

it will be observed that the operation of an electrical precipitator is improved and stabilized by providing for the effective coating of the inner walls and passageways, fan blades and blower parts thereof to prevent the accumulation of materials thereon and that as customary the normal dual installations can be alternated with the cleaning of the collecting electrodes performed rapidly as the passageways, inner walls, and other parts of the circulatory systems remain clean and free of circulation interfering build ups of particular matter and the like.

The following specific examples of the material have been found satisfactory.

A. Substantially 8% by weight sub micron sized particles of high purity synthetic graphite, substantially 7% by weight concentrated hydrochloric acid of substantially 90% purity, substantially 18% by weight water (H2O), substantially 34% by weight aqueous sodium silicate solution wherein the NaSiO is present at about 40% by weight of the solution and substantially 33% by weight water soluble carboxy vinyl polymer resin as a powder wherein the resin is present at substantially 8% by weight of the solution.

B. Substantially 8% by weight sub micron sized particles of high purity synthetic graphite substantially 7% by weight concentrated hydrochloric acid of substantially 90% purity substantially 18% by weight water (H2O), substantially 67% by weight aqueous sodium silicate solution wherein the Na2Si3O7 is present at about 40% by weight of the solution.

C. Substantially 8% by weight sub micron sized particles of high purity synthetic graphite, substantially 7% by weight concentrated hydrochloric acid of substantially 90% purity, substantially 18% by weight water (H20), substantially 67% by weight aqueous solution of carboxy vinyl polymer resin as a powder wherein the resin is present at substantially 8% by weight of the aqueous solution.

An alternative liquid carrier has been found to produce a suitable suspension of the sub micron sized particles of graphite and substitutes xanthan gum, a natural high molecular weight linear polysaccharide, functioning as a hydrophilic colloid to maintain the sub micron sized particles of graphite in suspension and contribute to the penetrating lubricating adhesive coating as described hereinbefore.

A specific example of such an alternative material follows: D. Substantially 8% by weight sub micron sized particles of high purity synthetic graphite, substantially 7% by weight concentrated hydrochloric acid of substantially 90% purity, substantially 18% by weight water (H2O), substantially 67% by weight aqueous solution of xanthan gum as a powder wherein the gum is present at substantially 8% by weight of the aqueous solution.

Variations in the amounts of xanthan gum may be used as from 1% to 10% of the aqueous solution.

In the present process the material is preferably applied to the metal inner walls, pipes and duct work, fan blades, shafts and housing and/or blowers including the driving means therefor, all of which are preferably heated and the material applied by spraying the liquid suspension material disclosed herein. Under such conditions the sub micron sized particles of graphite aided the liquid carrier penetrates the metal surfaces which have been previously cleaned and the material builds up a smooth coating, which being largely graphite, is able to resist heat and wear and maintain its penetration and coating characteristics indefinitely. At such time as the smooth surface is eroded, it may be cleaned and recoated quickly and easily.

Claims

1. A process for treating the inner steel walls and fluid handling and moving devices in electrical precipitation installations comprising the steps of cleaning said steel walls and devices, penetrating a liquid suspension of sub micron sized particles of graphite into said cleaned steel walls and devices so as to build up a smooth adhering and lubricating coating on said steel walls and devices to form a slick smooth surface, wherein said suspension comprises substantially between 5% and 25% sub micron sized particles of graphite by weight, between about 2% to 10% by weight concentrated hydrochloric acid, between about 15% to 20% by weight water, and at least one of the following, (a) between about 34% and 75% by weight of a solution of water and sodium silicate, with the sodium silicate present at about 40% of the solution, (b) between about 33% and 75% by weight of a solution of water and a water soluble resin, the resin being present in amounts between 1% to 10% of the solution, and (c) between about 33% and 75% by weight of a solution of water and xanthan gum wherein the gum is present in amounts between about 1% to 10% of the solution.

2. A process according to Claim 1, wherein the water soluble resin is carboxy vinyl polymer.

3. A process according to either Claim 1 or Claim 2 wherein several penetrating coatings of said liquid suspension of sub micron sized particles of graphite are applied to said steel walls and devices successively.

4. A process according to either Claim 1 or Claim 2 wherein several penetrating coatings of said liquid suspension sub micron sized particles of graphite are sprayed on said steel walls and devices successively.

5. A process according to any one of Claims 1 to 4 wherein said steel walls and devices are heated prior to said application of said penetrating coating of said liquid suspension of sub micron sized particles of graphite, said walls and devices being heated to a temperature sufficient to facilitate the penetration of the said liquid suspension of sub micron sized particles of graphite and carrier into the steel due to the expanded grain structure of the steel by said heat.

6. A process of treating the inner steel walls and fluid handling and moving devices in electrical precipitation installations substantially as hereinbefore described with reference to the preferred embodiments.

7. A liquid suspension of sub micron sized particles of graphite for use in treating steel walls comprising substantially between 5% and 25% sub micron sized particles of graphite by weight, between about 2% to 10% by weight concentrated hydrochloric acid, between about 15% to 20% by weight water, and at least one of the following: (a) between about 34% and 75% by weight of a solution of water and sodium silicate, with the sodium silicate present at about 40% of the solution, (b) between about 33% and 75% by weight of a solution of water and water soluble resin, the resin being present in amounts between 1% to 10% of the solution, and (c) between about 33% and 75% by weight of a solution of water and xanthan gum wherein the gum is present in amounts between about 1% to 10% of the solution.

8. A suspension as claimed in Claim 1, wherein the water soluble resin is carboxy vinyl polymer.