US1458106A - Method of making fuel - Google Patents

Description

June 5, 1%23.

W. L. M LAUGHLIN METHOD OF MAKING FUEL Filed March 26 1919 l'rn/en or TIES Patented June 5, i923.

UNHTED STATES WILSON L. MCLAUGHLIN, OF DECATUR, ILLINOIS.

METHOD OF MAKING FUEL.

Application filed March 26, 1919. Serial No. 285,324.

To all whom it my concern:

Be it known that I, WILSON L. Mo- LAUGHLIN, a citizen of the United States, residing at Decatur, in the county of Macon and-State of Illinois, have invented certain new and useful Improvements in Methods of Making Fuel, of which the following is a specification.

My invention relates to a novel method of making fuel,-made from coal, peat, sludge, culm, or other like carbonaceous substances, in a state suitable for burning in suspension in air.

The ordinary powdered coal of commerce can be burned only in an air blast. It is injected into the combustion space with air under considerable pressure. This is essential because the particles of coal being relatively large, a blast of considerable force is necessary in order to keep the fuel in suspension until it has time to be consumed. As a result, ordinary powdered coal is not practical for a low temperature or small furnace since, unless the heat of combustion is to be wasted, fuel must be supplied in proportion to the large volumes of air necessary to maintain it in suspension during the combustion period, and for high temperature furnaces, that is, for a furnace maintaining a temperature in the combustion chamber above the slagging point of the ash in the coal, the use of ordinary powdered coal encounters the difliculty that the ash in the coal will melt and will be carried by the air blast against boiler pipes, flue walls, and the like, to which it will adhere. The slagging of furnaces fed with fine fuel burned in suspension in a large measure accounts for the lack of success which has attended the efl'orts to utilize generally this method of combustion. Moreover, as the air performs a double function, namely, the physical function of imparting to the coal particles a force which tends to hold 4 them suspended against the action of the force of gravity, as well as the chemical function of supplying the amount of oxygen requisite for combustion, it is obvious that it is difficult, really impossible in practice,

to properly proportion the volume of air to fuel especially where, in a given installation, the temperature has to be varied from time to time and the proper amount of air for keeping the particles in suspension is therefore likely to be altogether in excess of the amount needed for supplying the correct proportion of oxygen.

My invention overcomes all of these difliculties by reducing the fuel by the novel method, to be hereinafter described, to a very dry, impalpable powder of which the particles are so small and light as to require no air blast to suspend them during the process of combustion. In other words, the fuel, when merely introduced into the combustion space in any suitable way, will remain suspended in the air against the force of gravity long enough to be completely burned. The fuel in fact will float in the zone of combustion in contradistinction to being impelled through the same and its subsidence will be so gradual that combustion is complete before the fuel particles escape from the high temperature. The fuel therefore can be burned at the mouth of the fuel nozzle, or substantially so, like a gas, and, as in the case of a gas flame, the flame produced by this combustion may be regulated down to a small volume and low temperature, which has never been possible heretofore with solid fuel burned in suspension. The fuel is, therefore, consequently adapted to small plants, such as domestic heating plants. On the other hand, since combustion is complete it is possible to obtain economically a very high temperature when a high temperature is desired. My invention also obviates the difficulty of slagging. Combustion can be maintained at a sub-slagging temperature, that is, at a temperature below that at which the ash and the coal will melt, and even with combustion above the slagging temperature, if the flame is not confined the fact that the minute subdivision of the fuel produces a physical separation of the ash particles from the carbon particles, and the further circumstance that when so minutely subdivided the fuel will be consumed very rapidly, a precipitation of the ash from the flame before the ash particles have time to melt results, provided that the flame is not confined or reverberated but is allowed to pass unobstructedly through the flue. Incidentally it may be said the ash so recovered has some value as a pigment.

The difficulty in reducing fuel such as coal, culm, sludge, peat, and the like, to impalpability, grows out of the presence in ghe fuel of a considerable amount of moisture. This has to be removed before it is possible to grind the material to the fineness required. It is impossible to dry pieces of coal of substantial size because if subjected to a high temperature distillation will result or, at least, a searing of the outside of the pieces which checks the extraction of the moisture.

I have found that fuel in a state as above described can be produced by first comminuting the material to a rather fine, granular state, substantially as fine as the ordinary fine feed fuel of commerce, then drying the material by showering the same through a rising current of gases which are heated but below the distillation point of the material, and then grinding the dried material in .a certain manner, as will be hereinafter described, and removing the extremely minute particles from the. grinding apparatus by suspending them by means of air jets and applying the light suction to the particles in suspension.

Suitable apparatus for carrying out the method as outlined above is shown somewhat diagrammatically in the drawing, wherein J Fig. 1 is a side elevation of the apparatus with certain parts in section, and

Fig. 2 is a cross sectional view on line 2-2 of Fig. 1, illustrating the step of grinding the material to impalpability and removing it from the grindin apparatus.

Referring to the rawing, A is a crusher of any suitable type by which the material,

coal, peat, sludge, culm, or thellike, is reduced to a rather finely granulated state. I have found it desirable to reduce the material so that 80% will pass a screen having sixty meshes to the linear inch. From the crusher A the material is carried by an elevator B to the top of a drying tower G into the bottom of which air, or other gases, are introduced from the furnace D at a subdistillation temperature, preferably ata temperature of approximately 360 Fahrenheit,

although this temperature may be varied with fuels of different character. The material falls through the drying tower against the risin current of the heated gases, its travel being preferably impeded by providing the tower with a number of staggered bafiies E. The material discharged from the bottom of tower C is carried by an elevator F and chute G to the pulverizing device H, the latter consisting of a revoluble drum containing a number of crushing rollers or rods J of different diameter which roll and tumble freely over each other. The drum rotates around an axially arranged feed tube K in which is a screw conveyor L, the tube being formed with a feeding slotM proportioned so that the fuel is evenly distributed lengthwise of the drum. Particles in suspension in the drum are removed therefrom accompanying by suction fan N in a pipe 0 which leads from a stationary housing I at the delivery 'Vide in the drum an air pipe R having a number of nozzles S playing on the crushing rollers J. Very little air enters the drum with the fuel. A balanced pressure just slightly below atmospheric pressure is maintained in the drum b control of the air entering through pipe and nozzle S in correspondence with the volumes of air and fuel withdrawn through pipe 0. The moisture and hot gases are withdrawn from the top of the drying tower C through a pipe T having a suction fan U. This draft will carry wit-h it the finest of the particles which, however, are in a very moist condition. They are carried to a dust collector B and then to a drier W in which they .are

about 10% of the material ground in the crusher is carried off in this way.

With the drying and pulverizing operations carried on as above described there is no danger of explosion or spontaneous combustion either in the drying tower or in the pulverizer H or elsewhere 1n the apparatus, and this is an important consideration when dried. As the process is now practiced,

one considers the dangers which are frequently encountered in the handling of an extremely dry, impalpable powder composed of highly combustible matter. Y

I have found it possible to produce from a low grade bituminous coal, and also from sludge, peat, culm, and the like, a fuel which will burn practically as a gas and the combustion of which may be regulated as a gas flame can be regulated. It is quite possible to burn the fuel while it floats in the air, that is, without any substantial air blast. A temperature can be maintained in an ordinary fire pot at least as low as 1250 Fahrenheit, and under advantageous conditions I have obtained a considerably lower temperature. material makes the measuring of it difficult but it has been found possible to reduce it so that 90% will pass through a 400 mesh screen and through a346 mesh screen, the meshes calculated to the linear inch. The p'ulverization should certainly be carried far enough so that at least 90% should The extreme fineness of the moisture content may be somewhat higher than this but it is my'belief that it should not be substantially above three per cent.

When the temperature obtained in the fur,- nace is below the sla ging point of the ash, wh1ch,of course, will vary for differentv coals, the possibility of slagging is, of course, eliminated. As far as I know, there has been no commercial production of coal which will burn in suspension in the air at a subslagging temperature. The fuel made in accordance with my invention may be burned, if proper precaution be taken, at temperatures above the slagging pointwithout the formation of slag by the melting of the ash by allowing the high temperature flame to pass unobstructedly and without reverberation through the flue. In such case the ash is deposited as ash for the reasons above stated.

It will be understood that while the fuel is capable of burning while floating upon, in contradistinction to being forced by an air blast through the combustion space, it is, of course, possible to burn the fuel in an air blast. This will depend entirely upon the size of the nozzle orifice in comparison with the volumes of fuel and air passing therethrough. The fuel may be introduced into the combustion space by means of an strong enough to project the particles to any extent through the combustion space'though, obviously, this will take place provided a small nozzle is used for the handling of relatively large volumes of air and fuel.

This application is filed as a continuation of and in substitution for application Serial No. 272,072, filed Jan. 20, 1919, for comminuted fuel and process of producing the same.

I claim:

The method of commercially reducing fuel to impalpability which consists in comminuting the fuel, then removing substantially all the moisture therefrom, then pulverizing the material to an impalpable powder, then removing the impalpable powder from the crusher by carrying the material in a slow moving body of air and then separating the fuel from the air.

WILSON L. MoLAUGHLIN.

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