Method of producing a refractory lining in a cylinder or tube

#This invention relates in general to refractory-lined tubes, pipes or cylinders, and more particularly to a method for producing a refractory-lined cylinder by an exothermic reduction reaction, such as aluminothermic reduction.

#Tubes, pipes, cylinders, and tanks lined with acid-resistant, corrosion-resistant or abrasion-resistant materials intimately bonded to the metal shell are required in many industrial applications. The shells of some tanks used in the oil industry, for example, are protected by a cured mixture of furnace cement and sand containing short asbestos fibers. The interiors of steel pipes and tanks exposed to corrosive water, salt solutions, or oils containing sulfur compounds are also often coated with cement to inhibit the attack on the steel. In cases where tanks are not subjected to high abrasive wear, but still require protection from an agressive environment, expensive stainless steels are often used in place of carbon steel.

#In other applications, glass lined vessels and pipes are used despite their obvious disadvantages and limitations. Thin impervious linings for steel vessels are also obtained through the use of vitreous enamels. This material is essentially a borosilicate glass containing fluorides which is finely ground, suspended in water or an organic solvent, and applied to the surface of the steel by dipping or spraying. The assembly is then dried by warming and finally heated in a furnace to near 1600.degree. F to melt the enamel so that the particles flow together to form a continuous coat. The operation is often repeated to obtain a sufficiently thick coat. In addition to the complicated and tedious procedure, the substrate steel must be carefully cleaned by degreasing and pickling to assure satisfactory bonding. These treatments are costly and time consuming.

#These and other objects of our invention will become apparent from the following detailed specification and the appended drawing in which:

#FIG. 1 is a cross-section of the apparatus required for coating large diameter metal tanks or cylinders in accordance with our invention.

#FIG. 2 is a cross-section of the apparatus required to produce an interior refractory coating on small diameter tanks, tubes, tuyeres, or pipes.

#The preferred embodiment of this invention consists of filling a metal tube with an exothermic reduction reaction mixture such as an aluminothermic reduction (ATR) mixture rapidly rotating the filled tube about its longitudinal axis, initiating the ATR reaction, and continuing to rotate the tube until the reaction products have solidified. The centrifugal forces developed effect a separation of a metal phase from a slag phase, propelling the heavier metal phase toward the tube wall where it bonds metallurgically to the metal. The lighter molten slag layer, being displaced toward the center of the pipe by the metal phase, subsequently solidifies to form a continuous layer of refractory. Upon cooling, the metal pipe walls will contract to a greater extent than the ceramic liner, thereby locking the liner into the pipe. The chemical reaction involved in this method includes the very energetic reduction of oxides by such metals as aluminum, magnesium, silicon, and calcium-silicon alloys and mixtures thereof and can be generally represented by:

#2Al + 3MeO .fwdarw.Al.sub.2 O.sub.3 + 3Me + .DELTA.H

#where .DELTA.H represents the evolution of a large quantity of heat per mole of reductant (Al). The metal oxide (MeO) should be low in cost, readily available in a dry form and easily reduced by the reductant (Al, Mg, Si, or SiCa) to generate a substantial heat of reaction. Common iron ores, containing magnetite (Fe.sub.3 O.sub.4) or preferably hematite (Fe.sub.2 O.sub.3) are well suited for the process, and a stoichiometric mixture of iron ore fines and aluminum is preferred for most applications. In some applications, particularly where the pipe wall is rather thin and in danger of being burned through by the ATR reaction, it is preferable to include a small amount of alumina, typically up to about 20%, to retard the ATR reaction, and thus minimize the risk of burn-through.