US1277707A - Calcining coal at high temperatures. - Google Patents

Description

W. DYRSSEN.

CALCINING COAL AT HIGH TEMPERATURES.

APPLICATION FILED MAY 27, I918.

1 ,27 7,707 Patented Sept. 3, 1918.

' process.

WALDEMAR DYBSSEH, OF NEW YORK, N. Y.

CALCINING COAL AT'HIGH TEMPERATURES.

Specification of Letters Patent.

Patented Sept. 3, 1918.

Application filed May 27, 1918. Serial No. 236,866.

To all whom it may concern:

Be it known that I, WALDEMAR DYRSSEN, a subject of the king of Sweden, residing in the city, county, and State of New York, have invented certain new and useful Improvements in Calcining Coal at High Tem- 1riieratures, of which the following is a specication. v

The pur ose of the invention is to facilitate the ca cinin of coal by an electric furnace especially designed for such work and by a method which protects the charge from the air, involves hlgh efficiency and small radiation losses, may be worked continuously and economically and operates with 'changes of voltage within only narrow limits, or with practically constant voltage and power.

H The accompanying drawings illustrate the furnace built according to the invention and arranged to carry out the improved Figure 1 is a vertical section;

Ffig. 2 is a horizontal section above the rec 3 is a vertical section of a modified detail.

7 Referring now to the furnace illustrated,

- through which water is passe it is provided with a brick wall A on the outside of which are coolin troughs B (i and with a roof C also of brick with a charging opening lined with a water. cooling r1n D. Around the charge opening are electro es E which penetrate the roof, these openings in the roof also being surrounded by water cooling rings F. The bottom G of the furnace is also of brick and water cooled and has a discharge opening preferably in line with the charging, opening above. and formed at the lower end with a water cooled chute or cone H and a cylindrical extension J at the upper and lower end of which are located slide valves K and L. At the top is a charging chute M which is maintained approximately full of crushed coal fed to it by a screw conveyer or similar device. From the bottom of the chute M the charge will spread out to the walls as shown with a roughly conical upper surface leaving a space below the roof which will save the roof and the openings through which the electrodes pass from excessive heat.

The current is conveyed to the electrodes usually from a transformer, at suitable voltages, by means of cables N and electrode holders. 0. The upper ends of the electrodes carry screws P passing throu h hand operated nuts Q bearing on fixed By turning the nuts the electrodes may be raised or lowered.

The product is discharged practically continuously by alternately operating the valves K and L. Or a continuously operating screw S, Fig. 3, driven by a motor T may be used for removing the product from the bottom of the discharge chute H.

The electric furnaces heretofore used for the calcining of coal have been rather crude and usually of the open-top style with electrodes in vertical position entering from above and with no provision or no adequate provision for protecting the charge from air. In such furnaces the regulation of the electric power consumed has required a considerable range of adjustment of the voltage. At the start, when the charge has been cold and the electric resistance correspondingly high, a high voltage has been required.

And as the temperature in the charge has increased and the resistance has been correspondingly lowered, the voltage had also to be lowered.

These difficulties are largely eliminated by the present invention. Where air has been allowed to enter it has burned the charge and the electrodes and the resulting combustion gases have escaped at a high temperature andwith a considerable loss of heat. The present process admits little or no air to the charge and to the electrodes supports R.

and for this reason effects a considerable economy. With my improved process the operation is easier and the output is increased by reason of the practically or approximately constant voltage and power consumption. The angular arrangement of the electrodes permits their lower ends to be brought together or separated and thus to take care of the variations in resistance in the charge. At the start the ends of the electrodes can be put so close to each other that the electric energy will be consumed entirely or greatly by arcs between the ends of the electrodes and an ordinary voltage can be used. As the charge and the gases in the arc become hotter the resistance will become less and the current taken will tend to increase, but the resistance can be increased to normal by withdrawing the elec tively high resistance.

it is possible to regulate the input of electricpower without change of voltage.

Insteadof starting by bringing the ends of the electrodes close enough together to strike an are directly between them, another,

and preferable, method. is to start the charge with coke between the electrodes and to gradually displace this by coal, which has a higher resistance; using the adjustment of the electrodes for varying the resistance after the operation shall have been well started and the coke passed below the calcining zone. j

The first small part ofthe product discharged will be coal which has not been well calcined or will be coke. After this coal will be fed continuously into the chute M as it is withdrawn from the discharging opening. The operation will thus be continuous or practically so. This will result in increased output. Also the operation will be more regular and the electric resistance will be so nearly constant as to avoid any substantial movement of electrodes or changes in the voltage, and a more uniform product can be obtained.

The diverging arrangement of the electrodes, besides providing an easy means of regulating the resistance, has also an equalizing effect on the power input even after the charge has become hot and the desired equilibrium is reached by withdrawing the electrodes to proper position. The resistance in the charge at the lower ends of the electrodes is considerably less than that of the buried portions of the electrodes above their ends. The current will tend to go to the ends and to create there a heat zone of practically constant resistance so that the power consumption is nearly steady and can be kept absolutely so with only small changes in voltage. As the charge is withdrawn at the bottom and introduced at the top practically no change in resistance will occur. The heat zone between the ends of the electrodes can be maintained at a substantially constant temperature and the colder portion above will have a compara- On the other hand, where parallel electrodes have been used the conditions are less favorable because the current seeks to go through the charge at every point in the buried portion of the electrodes and, since the distance between them is the same at any point, there is no tendency to create a distinct heat zone such as is produced by my arrangement. With my arrangement, therefore, a transformer andother electric equipment may be used without 2. volt changer or with a simple one having only a few. taps working within narrow l1mits, which is much chca er than a transformer with a wide range 0 voltage.

Radiation losses are reduced to a minimum with my arrangement. Most of. the heat is developed around the ends of the electrodes and these are buried in the-charge and located at or near the center of the furnace. The surrounding portion of the charge protects the furnace walls and roof from the heat. The air space between the top of the charge and the roof and water cooling rings therein further protects these parts and insures their durability in good condition. The passing of the electrodes 80 through portions of the roof which are above the natural level of the charge, where there is no coal to heat the furnace roof to a conductive degree, saves any escape of current from the electrodes to the roof at these points. The gases or other volatile matter dried out .of the charge take the shortest path to the outlet through the charging chute M and thus preheat the charge passing down through this chute. The discharge outlet is so arranged that little or no air can pass therethrough into the furnace.

Though I have described with great par- 'ticularity a certain furnace and mode of operation, yet it is not to be understood therefrom that the invention is restricted to the particular furnace and method described. Separate features of the furnace and separate steps, of the process may be used in other connectionsand the invention may be utilized not only 'for calcining but also for graphitizing or otherwise treating coal and other materials without departing from the invention as defined in the following claims.

What I claim is: a

1. An electric furnace for calcining coal having a roof through which is a charging opening and a bottom through which is a discharging opening for the calcined coal and which is adapted to exclude air and having electrodes arranged to extend into the chargeand to produce a heating zone in the path between said openings. I

2. An electric furnace for calcining coal having a roof, electrodes extending through 115 said roof and converging toward each other at their ends, said furnace having a charging opening. for raw coal through the roof and a discharging. opening for calcined coal through the bottom so that the furnace may 120 be operated continuously.

3. The method of calcining coal which consists in embedding therein electrodes arranged at an angle with each other so as to be nearest to,each' other at their ends, 1215 4.-The method of calcining coal which 1&6.

consists in embedding therein electrodes ar-' gitudinally to vary the distance between ranged -'at. an angle with each other so as their ends so as to require a substantially or to be nearest to each other at their ends, approximately constant voltage for varying 10 and passing a suitable current through said conditions of the charge.

5 electrodes and feeding coal continuously In Witness whereof I have hereunto signed through the zone aboutthe ends of the my name. electrodesand adjusting said electrodes lon- WALDEMAR DYRSSEN.

copies of this patent may be obtained tor five cents each, by addressing the Commissioner of ratentl.

Washington, D. 0.

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