US1786714A - Method of sintering clay - Google Patents

Description

Dec. 30, 1930. J] E REENAWALT. 1,786,714

METHOD OF SINTERING CLAY Filed Feb. 16, 1929 hvwavraa; JOHM f. GREEN/4 WA L I Hrroe/m'r UNITED STATES PATENT OFFICE JOHN E. GBEENAWALT, on NEW YORK, N. Y.

METHOD OI SINTERING CLAY Application filed February 16, 1929. sem No. 340,643.

My invention relates to an. improved process of sintering argillaceous material to produce an artificial concrete or mortar material in place of crushed stone, gravel and sand.

' Heretofore, clay, slate, shale and other argillaceous materials have been calcined in kilns or furnaces heated in the usual manner to produce a light weight aggregate. It has also been proposed to heat treat a finely crushed charge of mixed clay and fuel on a sintering apparatus in the same manner that ores are sintered.

However, owing to the plasticity of the clay and the tendency of the particles to adhere, 5 the free passage of air through the charge is obstructed, rendering it impossible to maintain, the sintering action throughout the charge, unless special precautions are taken to preserve the voids in the charge. I have found that these voids, so essential to either downdraft or updraft sintering, may be preserved by treatmg the material with a view {:0 improving its physical condition as folows:

The clay, or similar material, is first crushed by any suitable device to a fineness, that on mixing the material with water will produce a slurry. I' do not wish to be restricted to a process in which the water is added to the material after the same is crushed, as my invention may be practised with equal facilit by adding the water either before or during the crushin operation. The slurry is then subjected to ead while being mechanically a 'tated so that it will dry in the condition 0 small bodies approximately the size of a pea. These small bodies may then be stored (if desired) until it is convenient to charge them into a sintering appara- 40 tus. This drying operation need not be continued until all moisture is expelled, but merely to the point where the balls will not stick to ether. 1 V

n treating some clays '-1t may notbe necessary to produce a slurry, but the formation of the small bodies, or balls, may be effected by forcing the clay, in the. condition of soft mud throu h a suitable screening'device. However, t e balls should be dried, pref- V so, erably by the application of 'heat beforethey' are stored. If the sintering of the clay is to be eifected immediately as a part of a continuous operation, the moist balls ma be dusted with pulverized fuel, which will orm a coating about them. The fuel coated clay balls, in a moist condition, may now be charged into a sintering pan and the sintering operation performed in the usual way; that is, by passing a blast of air through the charge and igniting the fuel constituent thereof at its surface.

In the drawing-I show a Greenawalt apparatus, comprismg asintering pan 1 and connected through its'hollow trunnions 2, 2 and conduits 4, 4 to a dust chamber 3, through which air is drawn by means of an exhauster 5, having its outlet 6 connected to a stack 7. The usual charge car 8 is provided for feeding the material constituting the charge onto the grate 9 of the sintering pan 1, after which the igniter 10 is brought into position over the charge for the purpose of effecting ignition at its surface. After ignition of the charge the igniter is either removed or the flame extinguished as combustion is continued internally of the charge under the influence of the air blast. The small bodies, or balls, that are formed by the above described operation obviously will not be of a uniform size and they may be separated, if desired, so into two or more components m and m; the larger balls m being fed directly onto the grate 9, and the smaller balls m being charged on top of the'larger ones. However, the manner of .arrangingthe charge is optional with the operator who will perform the operation as experience teaches him, with the view of obtaining the most satisfactory results.

The physical condition of the charge, made up as it is of a mass of small bodies, insures the presence of voids throughout, so that the air may pass freel through it to sustain combustion of the uel. As the combustion of the fuel propagates itself throu h the charge, the small clay bodies are su jected to intense heat and are burnt hard. The escape of occluded gases in the bodies is readily accomplished because of their small mass, so that'the burnt clay bodies become highly porous. At the same time fusion occurs at the surfaces of the bodies causing them to be cemented together into a hard, lightweight porous mass of clay sinter. This mass or cake of clay sinter may then be pressed to any size required by the ultimate use that is to be made of it. In making concrete blocks, both the finely and the coarsely crushed particles of sinter are mixed with the desired amount of Portland cement and water, and molded to shape. If the clay sinter is to be used merely as a mortar material it may be mixed with cement or lime in any proportion selected by the builder, according to his purpose.

In sintering some clays it may be desirable to mix powdered fuel with the clay before it is balled. Then again certain conditions may require that the clay balls and the fuel be independently charged into the slntering pan in such a manner that the voids between the balls be filled with fuel. In fact, I do not wish to be restricted in any respect as concerns the fuel, as the essence of this invention is the treatment of the clay to produce small bodies, or balls, which are massed in a holder to constitute a charge to be sintered.

The invention may be modified to the extent that only suflEicient clay be used in the charge to render it plastic. The balance of the charge (aside from the fuel) may be nonplastic argillaceous matter, such as slate or shale, or even other substances such as ashes, crushed brick, or any mixture of substances provided plastic clay is present in suflicient amount to render the mixture susceptible to the balling operation. From 10% to 15% of plastic clay is sufficient fonthis purpose.

Aside. from the excellence of the sintered clay product, there are two other very important advantages in sintering argillaceous material. One of them is the speed of the operation (but a few minutes being required to sinter a charge weighing several tons), and the other is the economy of the use of the fuel, the amount of which can be quite accurately determined for the best results. With combustion taking place within the charge very little heat is wasted.

Having described my invention, I claim:

1. The process of manufacturing an aggregate for mortars or concretes, which comprises reducing argillaceous material to a finely divided condition, adding water thereto to form an agglutinated mixture, converting said mixture into a homogeneous mass of small bodies, and arranging said bodies on a permeable hearth to form a charge, effecting a distribution of fuel throughout said charge, igniting the fuel at one surface of the charge,

causin asupporter of combustion to pass throng the charge away from said ignited surface, whereupon combustion of the fuel will proceed through the charge and produce a hard, porous, burnt product.

2. The process of manufacturing an aggregate for mortars or concretes, which comprises reclucing argillaceous material to a finely divided state, adding water to the finely divided material to form a slurry, subjecting the slurry to mechanical action and heat to form small bodies, arranging a mass of said bodies and finely divided fuel on a suitable support to constitute a charge, maintaining the particles of the charge in a quiescent condition and subjecting said mass to heat and a blast of air to form a hard, porous product.

3. The process of manufacturing an aggregate for mortars and concretes, which comprises reducing argillaceous material to a finely divided condition, mixing finely divided fuel therewith, adding water to said mixture to agglutinate the same, converting said mixture into a homogeneous mass of small bodies, arranging said bodies in a layer, igniting the exposed surface of said layer, passing air through the layer away from said surface to cause combustion of the fuel throughout the layer to form a hard porous product.

4. The process of manufacturing an aggregate for mortars or concretes, which comprises reducing argillaceous material to a finely divided condition, converting said mixture into a homogeneous mass of small bodies, and arranging said bodies on a permeable hearth to form a charge, effecting a distribution of fuel throughout said charge, igniting the fuel at one surface of the charge, causing a supporter of combustion to pass through the charge away from said ignited surface, whereupon combustion of the fuel will proceed through the charge and convert the same into a hard, porous product.

5. The process of manufacturing an aggregate for mortars or concretes which comprises reducing argillaceous material to a homogeneous mass of small bodies, arranging said bodies on a permeable hearth to form a charge, subjecting said charge to heat and simultaneously therewith causing a sup orter of combustion to pass through said 0 arge, whereupon the said bodies become fused and agglomerated to form a hard, porous cake.

6. The process of manufacturing an aggregate for mortars or concretes which comprises mixing finely divided ar illaceous material with fuel, converting sai mixture into an ag lutinated mass, forming a multitude of small odies from said mass, arranging said bodies in a layer to form a charge, igniting said charge at one'surface and causing a supporter of combustion to traverse the charge to propagate combustion throughout the mass to form a hard,porous, agglomerated product.

7 The process of manufacturing an aggreate for mortars or concretes which comprises orming a multitude of small bodies from finely divided argillaeeous material, arrangingamixture ofsaidsmallbodies and fuel in a layer to form a charge, igniting the charge at its exposed surface, passing air through the charge away from the ignited surface to propagate combustion throughout the charge and produce a hard, porous agglomerated product.

In testimony whereof I hereunto afiix my signature.

- JOHN E. GREENAWALT.

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