US1919048A - Protective lining for a furnace - Google Patents

Description

July 18, 1933. TscHmKy 1,919,048

PROTECTIVE LINING FOR A FURNACE I Filed May 5, 1932 TEMPE/F94 7095 Z Z60 00/0 Ecirfi] lPatented July 18, 1933 LEOIOLD TSCHIRKY, OF ROSEMONT, PJEJNNEJYIIVALTIA PROTECTIVE LINING FOR A FURNACE Application fi1ed May 5,

An object of my invention is to provide a protective coating to the refractory lining or parts thereof of furnaces of any type, such as open hearthsteel furnaces, non-ferrous furnaces, gas manufacturing apparatus and the like, as well as to the refractory lining of such auxiliary parts of and connections to the furnaces and apparatus which are also subjected to high heat. The purpose of this coating is to permit the furnaces to be more rapidly brought to their operating temperature. At the present time as much as three weeks may berequired to properly heat the refractory lining of a furnace before it can be used. Ifthe refractory lining is heated too rapidly the unequal expansion of the lining causes it to crack or spall and thereby lose its efficiency. Instances have been known where the buck stays which hold the furnace together have snapped due to unequal expansion caused by too rapid heating.

Thus an object of my invention is'to pro vide on those surfaces or parts of those surfaces of the refractory lining which are exposed to the heat of the furnace, a protective coating of a heat insulating material which may have a greater resistance to heat flow than the material of which the lining is made and which may be less refractory than the lining itself. lVhen a furnace is provided with such a lining the heat may be applied thereto at the full rate because the protective coating shields the refractory surface behind it from too rapid temperature rise through the critical range and from consequent too rapid expansion and subsequent cracking and spalling.

The protective coating may be applied to the refractory lining, the auxiliary parts and connections, in any convenient manner as by applying it to the surfaces or parts of the surfaces of the bricks, when they are made, or by spraying, plastering, coating or otherwise applying the protective coating to the refractory lining or parts of the lining, the auxiliary parts and connections, when the latter is in place.

For a further exposition of my invention reference may be had to the annexed drawtory material I have provided a coating 3 1932. Serial No. 609,423.

ing and the following description at the end whereof my invention will be specificall pointed out andclaimed.

In the drawing,

Figure 1 is a'vertical cross section through a portion of a furnace to whlch my invention has been applied. I

Figure 2 is a View in elevation of a brick to which my invention has been applied.

Figure 3 is a curve showing the action of my invention.

The protective coating" of my invention is preferably made of a mixture of any heat insulating or partially heat insulating material, such as magnesia, asbestos, rock or lead wool, granulated slag, diatomaceous earth, kieselguhr, etc., which may be bonded together with any suitable binder, such as clay, oils, glues, molasses, etc. The mixture slag is applied in a wet condition, water being preferably used or other liquids where water is injurious to the brick work.

As an example of such a coating I have found the following mixtures to be useful to granulated slag wool. 20% to 25% kaolin clay. v The slag wool in the above mixture is a low conductor and serves to protect the re fractory behind it from heat.- The kaolin acts as a binder for the mixture. This mixture may be less refractory than the material to which it is applied and hasa lower thermal conductivity. When the heat. is applied to the furnace the protective coating disappears at a slow rate as it fuses,

fluxes, volatilizes or disappears from the refractory surface to whiohit is applied.

Another mixture which I have found suitable for forming a protective coating is the following 70% to 75% granulated slag wool,

10% asbestos,

15% to20% kaolin clay.

In the drawing 1 have shown a furnace generally indicated'at 1 having a gas inlet port generally indicated at 2 therein. On the interior walls of the furnace, which are formed of refractory bricks or other refracwhich is of a material less refractory than the refractory lining of the furnace.

In Figure 2 I have shown another embodiment which my invention may take consisting of a brick e having a layer or coating 5 of a less refractory material, such as one of the mixtures referred to above, applied to one or more of its surfaces.

Figure 3 shows a curve showing the ratio of temperature of the furnace to time. Curve A shows the time which wasformerly neces sary to heat the furnace to the final temperature without danger of cracking or spelling the refractory lining. Curve B shows the ratio which it is possible to now obtain due to the use of my protective coating and shows that the furnace may be brought to operating temperature in considerably less time than heretofore used.

It is quite common practice to lay up refractory brick work with the brick to allow for expansion while coming up to heat, as in the case of laying up furnace walls made of silica brick or magnesite brick, etc. l/Vhen heating up a new furnace, wood is generally employed for the initial heating after which the temperature is raised higher with the application of gas or oil but with a minimum of air or by other heating means. This naturally leads, both from the wood and subsequent as, or oil, or other heating medium, to a deposit of carbon or other detrimental product, such as alkalies, sulphur, etc., in between the bricks, being carried up into the joints between the brick and into the pores of the brick before they are either completely expanded or later glazed over. These substances will later, when the temperature of the brick reaches 2500 F. or higher, react with the silica or magnesia, the carbon, for example, reducing the silica to silicon and releasing CO gas. The other deteriorating materials act differently from the carbon and react directly with the silica or magnesia, whichever is present in the brick. Therefore an additional purpose of importance in applying the protective coating is to absorb or stop the passage of unburned carbon in fine form or of any other detrimental substances from the furnace into the between the bricks.

open joints between pores ofthe brick or the joints In this description and claims, the term insulating material includes protective coatings or protections of lower thermal conductivity than the refractory lining being protected.

I do not intend to be limited in the prac tice of my invention save as the scope of the prior art and of the attached claims may require.

I claim:

' 1. A process of so conditioning and heating up of a furnace having a refractory lining as safely to eifect an abridgement of the period thereof, which process consists in providing said lining with a temporarily insulating and protective coating of less refractory material than said lining, and applying heat at full rate to said furnace thereby causing said protective coating to disappear.

2. A process of so conditioning and heat in up of a furnace having a refractory lin ing as safely to effect an abridgni-ent of the period thereof, which process consists in providing said lining with an insulating protection, and applying heat-at full rate to said furnace thereby causing said protection to disappear.

3. A process of so conditioning and blowing in a furnacehaving a refractory lining as safely to effect an abridgment of the period thereof, which process consists in providing said lining with an insulating protection, and applying heat at full rate to said furnace.

4:. A process of protecting a refractorv lining of a furnace from too rapid heating during the heating of the furnace, which process consists in applying to that surface of the lining, which is ordinarily exposed to the heat of the furnace, a protective coating of less refractory material and having a lower c'oeificient of thermal conductivity than the material of said lining.

5. A process of protecting a furnace having heating means and a refractory lining during heating up, which process consists in interposing a barrier to the flow of heat between the heating means and the refractory lining, and then applying heat to the furnace by means of the heating means at full rate.

' LEOPOLD TSCHIRKY.

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