US3328187A

US3328187A - Manufacture of expanded shale

Info

Publication number: US3328187A
Application number: US407172A
Authority: US
Inventors: Thomas E Ban
Original assignee: Mcdowell Wellman Engineering Co
Current assignee: Mcdowell Wellman Engineering Co
Priority date: 1964-10-28
Filing date: 1964-10-28
Publication date: 1967-06-27
Anticipated expiration: 1984-06-27

Description

June 27, BAN

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ATTORNEYS.

3,328,187 MANUFACTURE OF EXPANDED SHALE Thomas E. Ban, Cleveland Heights, Ohio, assignor to Mc- DoWcll-Wellman Engineering Company, a corporation of Ohio Filed Oct. 28, 1964, Ser. No. 407,172 5 Claims. (Cl. 106-288) The present invention relates to an improved process for the manufacture of expanded shale, More particularly, the process of this invention is carried out in a traveling grate sintering machine having a plurality of carefully controlled heating stages whereby naturally occurring shales may be continuously converted to expanded shales.

Expanded shale is very useful in the building material industry as a lightweight aggregate in reinforced concrete compositions. It is superior to other lightweight aggregates such as expanded vermiculite, perlite, slag, fly ash, pumice, slate, and clay in that it is characterized by an extremely low water adsorption property and extremely high crushing strength. Normally, expanded shale will absorb water to the extent of about seven percent of its weight, and it will exhibit a crushing strength of about 16,500 measured in a two inch compaction test.

Although it is well known to those skilled in this art that shale may be expanded by the application of heat, it has heretofore been exceedingly diflicult to produce it continuously on a commercial basis in a manner which will provide a consistently uniform product. If insufiicient heat is applied to the shale, it will not expand while on the other hand, if too much heat is applied the shale will fuse into a solid mass and, consequently, temperature control is of critical importance.

Accordingly, it is the object of this invention to provide a process for the continuous production of expanded shale which will insure a product of uniform high quality.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the appended claims, the following description and annexed drawings setting forth in detail certain illustrative embodiments of the invention, such disclosed means constituting, however, but a few of the various forms in which the principle of this invention may be employed.

In the annexed drawings:

The figure is a schematic drawing of an embodiment of this invention.

In brief, the process of this invention comprises the steps of preparing a feed of controlled composition and size and comprising shale and a solid carbonaceous material, and subjecting this feed to a carefully controlled program of gradually increasing temperature conditions.

The source of the shale which is employed in the process of this invention is not in any way critical and any naturally occurring shale may be employed in the process. It is important, however, that the shale be of fairly uniform size. In general, the best results are obtained when the size of the shale is reduced to a value in the range of about 1 /2 inches to about /2 inch, Such a feed may be prepared with facility from the crude shale by means of conventional size reduction and classification techniques.

Referring to the figure, the other ingredient of the feed to the process is a solid carbonaceous material, preferably anthracite coal, and once again size is an important consideration. The preferred size range is from about /2 inch to about 50 mesh.

Another important factor in the preparation of the feed to the process is the relative proportion of shale and the carbonaceous material. In general, the feed should States Pate comprise at least 90% by weight of shale and not more than 99% by weight with the remainder being the solid carbonaceous material. It is important that the feed be substantially uniform in composition and any convenient mixing technique may be employed in order to obtain a homogeneous dispersion of the carbonaceous material and the shale.

As mentioned above, the process may be conveniently carried out in a conventional traveling grate sintering machine, e.g. the traveling grate sintering machine hearing the name Dwight-Lloyd, manufactured by the Mo- Dowell-Wellman Engineering Company. Such machines are equipped with windboxes and fans so that the flow of gases through the bed may be controlled in the desired manner. A traveling grate sintering machine utilizing downdraft is preferable as temperatures are more easily controlled. For the purposes of the instant process, the machine is divided into at least three substantially distinct sections, each of which is independently regulated so as to maintain a relatively uniform temperature therein. Temperature regulation is accomplished primarily by a plurality of burners adapted to burn either oil or gas which are disposed adjacent to the moving bed in each section. Alternatively and in addition to the burners, means may be provided for the recovery and recirculation of the hot exhaust gases from the sintering machine in order to utilize the heat values contained in such gases in the process.

In order to protect the grates of the sintering machine from exposure to excessively high temperatures, it is customary in the operation of such machines to cover the metal grates to a depth of about 1 to 2 inches with an insulating material before depositing the feed material thereon. A very convenient source of insulating material for this so-called hearth layer is the product of the instant process, ie, expanded shale. Once the hearth layer has been deposited on the grates, the mixture of coal and crude shale which forms the feed for the instant process is laid on top of it in a generally uniform horizontal layer to a depth in the range of about 2 to 6 inches and, preferably, about 4 inches.

In the operation of the process the first section of the sintering machine is employed to preheat the feed materials. In this section, the gas temperature is maintained within the range of 1500" F. to 1850 F. and the residence time of the moving bed within this section should be at least 6 minutes. In the second section of the sintering machine, the temperature of the gas is maintained in the range of 2050 F. to 2250 F. and the residence time of the moving bed in this section should be at least 2 minutes. It is in this section of the sintering machine that the combustion of the carbonaceous material in the feed is initiated and the shale begins to expand.

As the bed proceeds into the third section of the sintering machine, the temperature of the gas passing through the bed is raised to a value within the range of 2300 F. to 2500 F. and the residence time in this section of the sintering machine should be at least two minutes so that the combustion of the coal in the feed will be substantially completed.

Although not essential to the operation of the process, additional sections can be provided in the sintering machine by the use of additional windboxes for the purpose of cooling the expanded shale. When such a cooling section is provided, outside air at the ambient temperature makes a very convenient cooling medium.

In order to provide a specific embodiment of the process of this invention the following test was carried out in a Dwight-Lloyd.

The test was conducted with feed consisting of a crushed Gold Hill shale having a size range of about 1% inches of inch and crushed anthracite coal having a size range of about /8 inch to about 10 mesh. The feed was made up of 95% by weight of shale and 5% by weight of coal. A hearth layer of expanded shale was deposited on the grates to a depth of 1.5 inches and then a 4-inch. layer of fresh feed was deposited on top of the hearth layer. The sintering machine was operated so that the gas temperature in the first section was maintained at about 1830 F. and the residence time in this section was about 6 minutes.

In the second section of the sintering machine, the gas temperature was maintained at about 2170 F. and the residence time was 2 minutes. The gas temperature in the third section was maintained at about 2310 F. and the residence time was 2 minutes. Examination of the resulting product revealed that it was a fully expanded shale of uniform high quality.

Other modes of applying the principle of this invention may be employed instead of those specifically set forth above, changes being made as regards the details herein disclosed, provided the elements set forth in any of the following claims, or the equivalent of such be employed.

It is, therefore, particularly pointed out and distinctly claimed as the invention:

1. A process for the manufacture of expanded shale comprising the steps of preparing a bed consisting essentially of from 90% to 99% by weight of a naturallyoccurring shale and from 1% to 10% by Weight of a carbonaceous material, moving said bed into a pre-heating zone maintained at a temperature in the range of 1500 F. to 1850 F. and maintaining said bed therein for a period of at least 6 minutes, next moving said bed into a second zone maintained at a temperature in the range of 2050 F. to 2250 F. and maintaining said bed therein for a period of at least two minutes, and, finally, moving said bed into a third zone maintained at a temperature of 2300 F. to 2500 F. and maintaining said bed therein for a period of at least two minutes.

2. A process for the manufacture of expanded shale comprising the steps of preparing a bed consisting essentially of from 90% to 99% by weight of a naturallyoccurring shale and from 1% to 10% by weight of a carbonaceous material, moving said bed into a pre-heating zone while passing a gas through said bed at a temperature in the range of 1500 F. to 1850 F. for a period of at lease 6 minutes, next moving said bed into a second zone while passing a gas through said bed at a temperature in the range of 2050 F. to 2250 F. for a period of at least two minutes, and, finally, moving said bed into a third zone while passing a gas through said bed at a temperature of 2300 F. to 2500 F. for a period of at least two minutes.

3. A process for the manufacture of expanded shale comprising the steps of preparing a bed consisting essentially of from 90% to 99% by weight of a naturallyoccurring crushed shale and from 1% to 10% by weight of a finely divided carbonaceous material, moving said bed into a preheating zone maintained at a temperature in the range of 1500 F. to 1850 F. and maintaining said bed therein for a period of at least 6 minutes, next moving said bed into a second zone maintained at a temperature in the range of 2050 F. to 2250 F. and maintaining said bed therein for a period of at least two minutes, and, finally, moving said bed into a third zone maintained at a temperature of 2300 F. to 2500 F. and maintaining said bed therein for a period of at least two minutes.

4. A process for the manufacture of expanded shale comprising the steps of depositing a bed consisting essentially of from to 99% by weight of a naturallyoccurring shale and from 1% to 10% by weight of a carbonaceous material on the grates of a traveling grate sintering machine, moving said bed into a pre-heating zone maintained at a temperature in the range of 1500 F. to 1850 F. and maintaining said bed therein for a period of at least 6 minutes, next moving said bed into a second zone maintained at a temperature in the range of 2050 F. to 2250 F. and maintaining said bed therein for a period of at least two minutes, and, finally, moving said bed into a third zone maintained at a temperature of 2300 F. to 2500 F. and maintaining said bed therein for a period of at least two minutes.

5. A process for the manufacture of expanded shale comprising the steps of depositing a bed consisting essentially of from 90% to 99% by weight of a naturallyoccurring crushed shale and from 1% to 10% by weight of a finely divided anthracite coal on the grates of a traveling grate sintering machine, moving said bed into a pre-heating zone maintained at a temperature in the range of 1500 F. to 1850 F. and maintaining said bed therein for a period of at least 6 minutes, next moving said bed into a second Zone maintained at a temperature in the range of 2050 F. to 2250 F. and maintaining said bed therein for a period of at least two minutes, and, finally, moving said bed into a third zone maintained at a temperature of 2300 F. to 2500 F. and maintaining said bed therein for a period of at least two minutes whereby said coal undergoes substantially complete combustion and said shale becomes fully expanded.

8/1960 Holm l0640

Claims

1. A PROCESS FOR THE MANUFACTURE OF EXPANDED SHALE COMPRISING THE STEPS OF PREPARING A BED CONSISTING ESSENTIALLY OF FROM 90% TO 99% BY WEIGHT OF A NATURALLYOCCURRING SHALE AND FROM 1% TO 10% BY WEIGHT OF A CARBONACEOUS MATERIAL, MOVING SAID BED INTO A PRE-HEATING ZONE MAINTAINED AT A TEMPERATURE IN THE RANGE OF 1500*F. TO 1850*F. AND MAINTAINING SAID BED THEREIN FOR A PERIOD OF AT LEAST 6 MINUTES, NEXT MOVING SAID BED INTO A SECOND ZONE MAINTAINED AT A TEMPERATURE IN THE RANGE OF 2050*F. TO 2250*F. AND MAINTAINING SAID BED THEREIN FOR A PERIOD OF AT LEAST TWO MINUTES, AND, FINALLY, MOVING SAID BED INTO A THIRD ZONE MAINTAINED AT A TEMPERATURE OF 2300*F. TO 2500*F. AND MAINTAINING SAID BED THEREIN FOR A PERIOD OF AT LEAST TWO MINUTES.