US1435540A

US1435540A - Comminuted fuel

Info

Publication number: US1435540A
Authority: US
Publication date: 1922-11-14
Anticipated expiration: 1939-11-14

Description

W. L. McLAUGHLIN. \COMMINUTED FUEL- APPLICATION men JAN. 20, m9.

@WM' KZW M' Patented Nov. 14, 1922.

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

COMMI NUTED FUEL.

Original application filed September 25, 1918, Serial No. 255,618.

nary 20, 1919.

'1 0 all whom it may concern:

Be it known that I, VVILson L. MCLAUGH- LIN, 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 Comminu-ted Fuel, of which the followin is aspecifica tion. a

My invention relates to fuel in the form of an 'impalpable powder and-has for its primary object to provide a novel and improved form of powdered fuel which will burn readily and efficiently. The invention was first fully disclosed in myco-pend-ing application; Serial No, 255,618, filed September 25, 1918, of which this application is a division.

By practicing the method herein disclosed I am able to commercially reduce fuel to a degree of fineness which may be technically termed impalpability that is, as fine as i our, and which when a quantity thereof is blown into the surrounding air has the ap pearance of smoke, remains suspended and finally disappears. When in such condition it is as nearly in its molecular relation. as itis possible to get it bythe use of any known apparatus. $uch material when properly carbu'retted-burns vith the ease of a gas or hydrocarbon and is as readily controlled.

It is well known that fuel is consumed with the highest efliciency when reduced to a. powder and combined with the correct proportion of air. This has been demonstrated in laboratory experiments but the dii'liculties encountered in reducing the fuel to the necessary degree of fineness has precluded the general adoption of the practice. Producing expense cannot be ascertained by computing the cost of such mec'l'ianica'l operations or such power expenditures as are necessary to reduce the material to impalpability as that cost is very low. In arriving at a figure representing the total cost of production it must be taken into Consideration that all fuels of this character contain, in mechanical mixture, a consiz lerable amount of water which. must be eliminated before they can be sufficiently finely divided for most efficient combustion. 7 It is also well known that the coal commonly in use contains a substantial proportion of volatile matter which constitutes one of the important heat producingelements. In the bitu- Divided and this application filed Jan- Serial No. 272,072.

minous coal, which is most adaptable for use in powdered form, the volatile matter is lightly held and is readily released and diffused at an oxidizing temperature. The difiiculty heretofore encountered in producmg coal in a sufiiciently finely divided condition for successful combustion has been to eliminate the uncombinedwater without at the same time losing considerable quantities of the volatile matter in the coal.

I have demonstrated in practice that the desired object may be attained by dividing the pulverizing operation into two stages and effecting the drying by an intermediate operation. According to my method the fuel is reduced to a certain degree of fineness and is then subjected for a relatively very short period of time to a rather high degree of heat, effective drying being secured by allowing the finely divided material to freely fall in a closed space in opposition to an ascending current .of hot dry non-oxidizing In this manner the particles are separated and each thereof is able to quickly dispose of its burden of water; the drying action is rapid and the material is subjected to the reducing temperature for but a very short time.

However, in the practice of the described method a serious difiiculty was encountered, that is, in determining how finely the material should be sub-divided in the first operation. If too coarse, it would be insuificiently dried in its passage through a drying tower of practical height and if too fine the particles would not have sufficient mass to overcome the velocity of the ascending current of sufficiently heated gas and would be carried along with it. If carried out with the gas the moisture taken up by the gas would immediately condense on the fuel particles when the gas expanded in a cooler space.

I have found that by crushing the ma terial in the first operation to a point at which substantially all thereof will pass through a screen having 200 openings per square inch and less than 25 0 thereof will pass through a 400 mesh screen the desired result is secured. Of course, under those conditions a certain portion of the material is so finely divided that it is carried off by the current of heated gas, but this is separated and subsequently dried in .a suitable device.

The drying operation is continuous and very economically carried out. The product at the end of the drying step should contain less than of water in which condition it may be subjected to the second pulverizing operation. This is carried out in a tube or ball mill and the final product is removed therefrom by inducing a very slowly moving current of air therethrough. The current will remove only such particles as are sufficiently light to remain suspended in the air. The final product is so finely divided that substantially 50% thereof will pass througl'i a screen having 200 openings per linear inch and substantially 20% through a screen having 300 openings per linear inch.

Fuel in this condition may be burned with a high degree of efficiency and may be produced at such. low cost as to warrant its general adoption. Tests serve to. determine that there is no substantial reduction of the quantity of volatile matter or of the number of heat units which conclusively prove that the theory heretofore advanced is correct.

Different forms of apparatus may be employed for carrying out the process. A suitablearrangement is illustrated in the accompanying drawing, in which the figure is a diagrammatic view thereof, partly in section.

'Referring to the drawing it will be seen that the first important step in the manufacture of the novel product, that is, the preliminary comminuting of the material, is

carried out in a crusher 10. In this device the material is reduced to such a degree of fineness that substantially all thereof will pass through a screen of 200 meshes per square inch and substantially 25% thereof will pass through a screen of 400 meshes per square inch.' WVhen properly comminuted as described the material passes into a conveyor 11 by means ofwhich it is elevated to. the top of a tower 12. Suitable means such as a transverse conveyor 13 are provided for distributing the material across the width of the tower and discharging the same thereinto. Bafiles or deflectors 14 arranged transversely of the tower serve to break the fallof the material, insure a thorough separation of the particles and so hamper or slow up the velocity thereof that the required effect is secured without necessitating the construction of a tower of impractical'height. f course. the desired effect can be secured without employing baffles in the tower but the tower would of necessity be much higher than with the present arrangement, with consequent increase of heat loss and greater initial cost.

The number and arrangement of the baffies will be correlated with other factors which will be hereafter discussed. Heat is generated in a furnace 15 which maybe an ranged to utilize the material produced in accordance herewith but that is not essential. It is important, however, that heating means be employed which may be very accurately controlled as to the amount of heat and the volume of carbon dioxide discharged. Thefire should be so controlled that combustion is as nearly perfect as practically possible in order that there may be in the exhaust gases practically no oxygen. The desired resultcan only be securedwhen combustion is relatively perfect and this is possible by utilizing the fuel of my invention and burning the same in a properly constructed furnace. Similar results may be secured by burning a liquid hydrocarbon or carbon monoxide from a gas producer.

However, the important consideration is the product-ion of a highly heated current of substantially non-oxidizing gas which is admitted to the lower end of the tower and rises therein in opposition to the falling particles of comminuted fuel. It is well known that all fuels oxidize continuously when in contact with oxygen the rate of oxidation depending upon the temperature and, from a practical standpoint, upon the area of exposure. lVhen as finely divided as is necessary in order to carry out this invention there is a relatively great area exposed and as the temperature must be high in order to secure effective drying within such short space of time as to make the process commercially practical, serious reduction of heating value would occur in an oxidizing atmosphere. It is for this reasonthat the time element is important and the number and disposition of the baffles governs the time during which the material is under the action of the heat. Preferably the baffles will be in closely spaced relation in the upper end of the tower as at that point the gases have lost some of their heat while in the lower end. the baffles may be entirely omitted. At the lower end the gases are the hottest and the material is the driest; it should therefore. remain in that zone for but a short time.

It is also'apparent that a definite relation must be maintained between the velocity of the rising current of heated gas and the degree of fineness of subdivision of the fuel particles. The particles together with their associated water must have sufiicient mass to overcome the reduced velocity of the gas current at the upper end of the tower and must acquire suflicient inertia before reachingthe lower end to overcome the greater velocity of the current in the lower end. If the particles have insufficient mass or if the velocity of the gas current is too great they will be carried in suspension in the body of gas and escape therewith; if the particles are too large they will pass too rapidly through the heated zone and will have too little surface exposed to the moisture absorbing heat and the drying action will be incomplete. The initial subdivision heretofore specified has been found tobe most satisfactory as the material may be dried to within 5% of the uncombined moisture in a tower of practical height and without appreciable deterioration of volatile constituents or reduction of the available heat units. It will therefore be seen that the velocity of the gas in the tower must be accurately controlled in order to maintain the proper correlation with the size of the particles to be dried. This is accomplished by regulating the speed of the exhaust fan 12 and by suitable regulation of combustion in the furnace.

It is of course, impossible in practice to avoid crushing material so that a small por tion thereof will. not be carried off by the rising current of heated gas in the tower.

This material is conducted with thegas to a are conducted to the furnace which supplies the drying heat and there burned. This feature is, however, unimportant as far as this process is concerned.

The mate-rial which is under treatment in the drying tower falls onto the inclined floor 17 thereof and is delivered to a conveyor 18 which elevates and discharges it into a grav ity chute 19. By this means the material is delivered to the feed hopper of a pulverizer 20 which may be of the rod or ball type and in which the final pulverizing operation may be completed. A device should be selected which will rapidly reduce the material to impalpability, using the term in its strict sense. I have employed a pulverizer containin a large number of longitudinally 6X- tending rods of different diameters whereby I secure a grinding as well as a crushing action. However, the important feature in connection with this step is that of grinding and removing the particles when reduced to a proper degree of fineness. This I accomplish by gently agitating thematerial as it is carried to the surface of the rods and withdrawing it by removing the body of material in which it is suspended. Bymaintaining constant the velocity and volume of discharged air from the pulverizer I secure a uniform productand one which meets the strict requirements for a fuel of this character.

One of the most difficult problems in the entire operation arose in the final step-that is, that of separating the product in the form of dust particles of such insignificant mass as to tend toremain suspended in a quiet body of air from its carrier. The difiiculty will be appreciated when it is understood that substantially 50% of the product will pass through a screen having 200 meshes per lineal inch'that is, 40000 meshes per square 'inch.- The desired result was secured by permitting the air and its burden of fuel to progressively expand in a fabric enclosed space of such size withrelation to the incoming volume of air that there is no substantial increase over atmospheric pressure therein. In this manner the velocity of the air current is reduced to nearly zero and the dust particles are not projected against the fabric walls and therefore do not attempt to pass therethrough. This relatively still body of air finally becomes super-saturated with the dust and deposition on the floor of the space continuously occurs. 7

A device which I have found satisfactory for this purpose comprises a series of outer fabric walls 21, defining a spaceof the required size and a series of inner fabric walls 22, into which the air is delivered through, the conduit 23. In the smaller space defined by the walls 22,the air is first permitted to expand and its direction is changed. It

again expandsand tends to change its direction in the larger space and from this space the air escapes through the fabric walls al lowing the fuel to deposit in the subjoined hopper 24. It is then removed from the hopper and utilized as required.

Iclaim: l. As a new article of manufacture made from coal and the like, fuel in the form of a powder substantially 50% of which will pass a screen havingQOO meshes per linear inch and containing substantially 5% uncombined water.

2; As a new article of manufacture, coal in such finely divided condition that substantially 50% thereof will pass a screen having 200 meshes per linear inch and in which there is no substantial reduction in volatile matter over the coal from which it is prepared.

3. As a new article of manufacture, coal in such finely divided condition that substantially 50% thereof will pass a screen having 200 meshes per linear inch and in which there is no substantial reduction in volatile matter over the coal from which it is prepared, the product in its final condition containing no more than 5% of moisture.

WILSON L. McLAUGHLIN.