US2347140A - Method of predetermining and controlling the clinkering characteristics of coal - Google Patents

Description

S. WEIMR Filed Jan. l1, 1943 THE CLINKERING CHARACTERISTICS OF COAL METHOD 'OF PREDETERMINING AND CONTROLLING April 1s, 1 944.

Patented Apr. 18, 1944 METHOD F PREDETERMINING AND CON- TROLLING THE CLINKERING CHARAC- TERISTICS OF COAL Raymond S. Weimer, Morris, Ill.; Mabel Weimer adminstratrix of Raymond S. Weimer, de-

ceased Application January 11, 1943, Serial No. 472,008'

21 Claims.

This invention relates to a method of predetermining and controlling the clinkering characteristics of coal.

In the burning of coal, especially in furnaces of industrial plants, the adherence of clinkers to the gratos, with the resultant obstructions to the passage of air through the grates and other disadvantages, has long been an annoying problem. The immediate reason for the formation of such troublesome grate adhering clinkers is that they migrate from the zone of fusion or of maximum temperature to the relatively cool grates before they have solidified or frozen and this result may be due to one or more of several causes or oonditions prevailing in a particular furnace, as well as to the inherent qualities of the particular coal ash. A molten clinker of a particular grade or type of coal may be so dense and be of such low viscosity that its passage through the fuel bed to the grate of a particular furnace occurs before the clinker solidifies, whereas clinkers formed from coal having different constituents, or where the firing conditions are different, may be trouble free, due to the fact that they solidify before reaching the grates of such furnaces. Clinkers that solidify before they reach a grate will not adhere to the grate and will not deform into a flat sheet, and may be designated, generally, as non-fouling or non-obstructing or trouble free clinkers, yet they should not solidify at too great a distance above the grate since, in that case, the depth of the fuel -bed may be increased beyond the desired maximum, or the percentage of weight or volume of ash compared to burning fuel may become so great as to retard the combustion.

Numerous factors, including, of course, the constituents of the coal and the coal ash materials, the freezing temperature and flow properties thereof, the maximum temperatures of the furnace, the temperature gradient between the maximum temperature of the fuel bed and the temperature of the grate, the depth and char'- acter of the fuel bed and other conditions, have bearing on whether a particular gra-de, kind, or type of coal can be burned without clinker trouble in a particular furnace.

Efforts have heretofore been made to control or modify the clinkering action of coal by the addition of substancesto the coal to avoid or lessen some of the diiculties encountered in pari ticular furnaces when burning certain types of coal, but insofar as I am aware, no method has been known for determining whether a particular batch of coal will burn without clinlrer trouble in a particular furnace at known maximum temperature, or whether, if such a batch gives an experimental indication of being troublesome, what minimum treatment can be utilized to so modify the clinkering action of the coal as to avoid the indicated diiiiculty.

iii)

Different coals, that is, coals from diierent mines, frequently so vary in their clinkering characteristics that while a particular coal may be satisfactory in a particular furnace, it may cause considerable trouble when burned in another furnace, or even in the same furnace when said furnace is operated in a different manner. Not only do coals from different mines vary in their clinkering characteristics, as stated, but coal from different seams or the same seam or locations in a single mine may so vary that portions of a days production will give results varying in clinkering characteristics when burned in the same furnace under similar conditions.

An object of the present invention is to provide a method of determining and controlling or modifying the clinkering action of coal whereby not only may such portions or batches of coal produced at a mine that are best suited for producing satisfactory results in particular furnaces be selected or supplied for use in such furnaces (if any such portions are found to be suitable), but whereby such portions not found to be suitable for use in a particular furnace may be treated for modifying the clinkering characteristics thereof as may be desirable for conditioning the coal for more sastifactory results under the known furnace conditions. 4

While as stated above, numerous factors inuence the formation and behavior of clinkers, it has been found that there is a relationship between the maximum temperature at which a particular coal is burned and the density of the olinkers formed which provides a criterion or index or indicator whereby a determination can be made as to the suitability (insofar as freedom from clinker trouble and more satisfactory burning are concerned) of a particular batch of coal for use in a furnace of known firing character istics. For example, if, from a given batch or quantity of coal of substantially uniform characteristics, a sample 0f such coal is burned at a given maximum temperature and the density of its resulting olinkers is determined, that density value constitutes a reliable indicator or index or criterion as to whether that batch of coal, if burned in a furnace wherein the firing condi tions, particularly the average maximum temperature of the fire bed are known, ,will produce troublesome or trouble-free clinkers or ash residue.

In accordance with the present invention, if the density of particular experimentally formed clinkers indicates that clinkers from such coal will be troublesome if the coal is burned in a particular furnace of known maximum re bed temperature, the coal can be so treated as to decrease the density of the resulting clinkers and thus increase the time required for the migration of the molten clinkers from the zones of highest temperature or the zone of fusion of the fuel bed to the furnace grate and thereby enable them to solidify before reaching the grate. On the other hand, if the density o f the sample, or experimental or test clinkers indicate that such clinkers will migrate too slowly through the fuel bed and thus unduly increase the depth of the fuel bed or unduly increase the ratio of clinkers to burning fuel, the coal can be treated to increase the density of the clinkers and thus hasten the migration thereof to the grate, or the coal can be allocated for use in a particular furnace in which the normal firing conditions are such that the coal will produce suitable results,

As stated above, numerous. factors have effect on the clinkerability of coal, but it has been found that all of them need not be taken into consideration in utilizing the present improvements commercially, since improved results in the burning of coal at certain known maximum temperatures can be obtained by making use of the discovery that the density measurements of clinkers of particular coals indicates whether such coals, if burned in a particular furnace under conditions normal to said furnace, will be troublesome or trouble free. It is true that many clinker effecting factors are known as well as the character of their effects on clinkering, but are unknown as to the magnitude of their result. It has been discovered that the density of clinkers is related to or is a function of said factors and expresses the collective magnitude of their results in burning operations.

The density of ash residues, such as clinkers or loose ash of a particular coal appears to be a function of or at least related to the temperature at `which the coal is burned since the density of clinkers and the bulk density of fine ash increases with the burning temperatures, and in making use .of the present improvements the density determinations of tested ash residues may be expressed in terms of density, vtrue specific gravity, apparent specific gravity or in terms of related values such as the specific volumes of the samples, or in terms of bulk density (weight per unit loose volume) or as the reciprocal of bulk density which is loose volume per unit weight. For the sake of brevity in the specification apparent specific gravity determinations (the weight of the clinkers or ash residues of the samples in grams, divided by the volume of Water in c. c. displaced oroccupied by the samples) have been found convenient to make with sufficient accuracy and are preferred as the basis for expressing density values of the samples and in this specification apparent specic gravity values of the ash residues of the samples will be used principally as the selected basis for expressing density values. As will be more particularly pointed out later, the apparent specific gravity of clinkers of a coal increases or decreases at a predictable rate with increase or decrease of the burning temperatures. Likewise, the bulk density of nne ash increases or decreases with increase or decrease of the burning temperatures which may be below the fusion temperature of the ash. The variations in bulk density of fine ash are of lesser magnitude than the variations effected in the apparent specific gravity of clinkers for similar variations in temperature, and clinker density determinations are therefore preferred in utilizing the present improvements Where clinkers are available or can be made available for testing purposes.

It has been found that in the conventional fur- 7n nace which commonly maintains a maximum temperature of approximately 2.700 degrees Fahrenheit, if the clinkers formed from the coal employed have an apparent specic gravity of approximately 2.4, the clinkers will be trouble free, that is, their rate of migration through the fuel bed of average depth will be such that upon reaching the grate they will have solidified sufficiently as to be non-deforming, non-welding or non-adherent to the grate. Thus, for a maxi-- mum temperature of 2700 degrees Fahrenheit, the ideal or critical apparent specific gravity of clinkers has been determined to be 2.4. This gravity of clinkers gives the smallest volume of ash or clinker possible without the clinkers reaching the grate in a molten condition or so as to be deforming or adherent. Such determination has -been made by burning coal of the character found in northern Illinois and Indiana, and it will be ap` parent that a different apparent specific gravity of clinkers may possibly be found ideal forcoal of substantially different inherent constituents. it has been found also that if the maximum teniperatures of the fire bed of furnaces are, for example, 2500 F., 2600c F., 2800 F., 2900 F., or 3000 F. the ideal apparent specific gravity for clinkers is also approximately 2.4 and that coals which, when burned at 2700 degrees Fahrenheit, produce clinkers having apparent specific gravities of 2.3, 2.6, 2.2, 2.0 and 1.8 will produce clinkers having a. critical or ideal apparent specific gravity of 2.4 when burned at the above mentioned temperatures respectively. A coal which, when burned at a temperature of 2700 degrees Fahrenheit, produces clinkers having a specic gravity of 2.4 will, when burned at temperatures of 2500 F., 2600 F., 2800o F., 2900o F. and 3000 F. produce clinkers having apparent specific gravities respectively as follows: 2.0, 2.2., 2.6, 2.8 and 3.0. It Will be observed that with each increase or decrease in temperature of degrees Fahrenheit from 27 00 F. as a base or reference standard, the apparent specific gravity is increased or decrease respectively -by approximately 0.2. Conversely. the apparent specific gravity of va clinker formed from a coal which, when burned at 2700 degrees Fahrenheit gives an apparent specific gravity of 2.4, gives an indication of the temperature at which the coal Was burned. The apparent specific gravity of 2.4 is ideal for the temperatures stated and any gravity greater will be likely to be productive of clinker trouble at the correlative temperatures, although lighter clinkers, when formed at such temperatures, while they will not perform in the most satisfactory manner, will not be particularly objectionable if their apparent specific gravities are not below 1.25 or the approximate gravity of the fuel bed particles. Below an apparent specific gravity of approximately 1.25 clinkers will not migrate or sink through the fuel beds readily.

The above illustrations are based on temperatures of conventional power plants operated under what may be termed conventional practices as to depth of fuel bed, and the usual temperature gradient between the maximum temperature and the temperature at the grates. It will be obvious that if in a particular furnace the grate temperature is relatively high, a coal producing clinkers having a lower specific gravity should be employed (or the coal treated in accordance with vsubsequent disclosures) whereby the clinkers will have time to solidify before reaching the grates. It will be apparent that compensation Will have to be made also Where non-conventional firing practices are maintained, as, for example, with respectl to the depth of the fuel bed since, if the fuel bed is of less than usual thickness, less resistance will be offered and less time will elapse during the downward movement of the molten clinkers and they might thus reach the grate in molten form and be troublesome. Other conditions, such as the size of the pieces of the coal and the compactness of the fuel bed, will, of course, have some influence on the rate of descent o the molten clinkers, but with an understanding of the principles of the present invention such variations can be compensated for by those skilled in the art, and hence the present disclosures for illustrative purposes are based upon the use of the improvements with conventional or standard or typical present day furnace practices.

It will be apparent from the foregoing that the time required for the movement of the clinkers from the Zone of maximum temperature, or of fusion of the ash, to the grate or walls should be no less than the time required for the temperature at which the clinkers solidify or so approach the solid state that they will not adhere to the grate or wall or flatten out on the grate.

The rate of travel of a clinker may be said to be a function of, or at least dependent upon, its apparent specific gravity, which is dependent on not only the inherent constituents of the clinker but is a function of the rate of cooling of a cllnker and the range of temperature through which it is cooled, that is, from the maximum temperature to the freezing temperature. Stated differently, the rate of travel of molten ash residue is dependent on the flow properties of the ash as is also the apparent density, and hence a measurement of the apparent specific gravity gives a relative measurement of the flow properties of the ash.

For the purpose of illustrating the use of gravity altering materials, assume that a known furnace operates at a maximum temperature of 2700 degrees Fahrenheit and that a sample of a particular batch of coal when burned at that temperature gives a clinker having a natural apparent specic gravity of 3.0 and that the ash content of the coal is 6 per cent. Since, as stated above, under such firing conditions, molten elinkers having an apparent specific gravity in excessv of 2.4 will move through the average fuel bed to the grate before the clinkers will have time to solidify and will thus be in a molten condition when they reach the grate, it is desirable to lower the density of the clinkers of such coal to reduce the rate of travel thereof through the fuel bed an extent whereby they will be in a non-molten, or at least a non-Welding, state as they reach the grate. By adding certain substances to the coal it has been found that the density of the resultant clinkers will be altered. Several substances may be employed which, when added in certain proportions to the coal, will effect a determinable reduction in the density of the resultant clinkers. The substances now known by me to effect a reduction in the density of clinkers or ash residue are as follows: silica, alumina, bauxite, clay (silica-alumina) (reclay).

It has been found that the different materials above mentioned, when added to coal (by mixing the same with the coal that has been washed and while it is still wet to cause the materials to adhere to the coal) do not effect precisely the same alteration in the density of the clinkers formed upon burning the coal, each having an alteration pattern specific to itself, and in this application the use of silica (sand) preferably with fractured surfaces will be assumed to be the additive product referred to for reducing or lowering the density of the clinkers, although, as stated, silica-alumina clay or other economically suitable substances may be employed in proper proportions if desired.

In the illustration referred to in the preceding paragraph the reduction of the natural apparent specific gravity of the clinkers from 3.0 to 2.4, where the coal is to be burned at 2700 degrees Fahrenheit, is effected by adding to the coal a certain percentage by weight of the additive material. It has been found that by adding to such coal silica in the amount of 2 per cent of the weight of the coal (which amounts to the addition of a fixed percentage of the weight of ash) the apparent specific gravity of the clinkers subsequently formed when the coal is burned at 2700 degrees Fahrenheit will be 2.4 and hence will require such time to pass through the fuel bed to the grate as to be cooled to a non-welding or non-adhering temperature when they arrive at the grate and hence will be trouble free. The ash per cent of such coal will have been increased to approximately 8 per cent by such treatment,

but such increase in the percentage of ash is less objectionable generally than the annoyance incurred with the troublesome clinkering of the coal.

The accompanying drawing graphically illustrates the above described example of coal treatment, as well as others with coal ranging from r 4 to l2 per cent ash content. In the drawing the curved full lines are ash percentage lines of coal; the horizontal lines indicate the eiect of adding silica to the coal and thus indicate the amount in percentage of silica, based on the weight of the coal, to be added to the coal to effect the reduction of the natural specific gravity of clinkers to a modified or ideal apparent specific gravity which gives freedom from clinker trouble when the coal is burned at a selected maximum temperature or at a lower temperature.

In the drawing, line A, for example, passes through the point of the intersection of the 6 per cent ash line and the 3.0 specific gravity line and intersects the 2.4 apparent specific gravity line at approximately the 8 per cent ash percentage line which thus indicates that to reduce the apparent specific gravity of the clinkers from 3.0 to 2.4, silica amounting to 2 per cent approximately of the weight of the coal must be added to the coal, that is, the silica added, being noncombustible, constitutes an addition to the ash content of the coal.

As another example, assume it is desirable to reduce the apparent specic gravity of clinkers of coal having 10 per cent ash from 3.0 to 2.6 apparent specific gravity. Dotted line B extends through the point of intersection of the 3.0` specific gravity line and 10 per cent ash line and intersects the 2.6 specific gravity line to the right of the l2 per cent ash line and thus indicates that to effect such reduction in the specific gravity the addition of 2 plus per cent silica to the coal is required.

If it is desired to know the amount of silica to add to coal to reduce the natural or inherent specific gravity of clinkers of coal of 8 per cent ash content from 2.8 to 2.2, find the point of intersection of the 8 per cent ash line with the 2.8 specific gravity line and follow the dotted line C through that point downwardly and to the right to the point of intersection of the dotted line C with the 2.2 specific gravity line, which point will be found to .be to the left of the point oi lintersection of the 2.2 specific gravity 'line with the l11 per cent ash percentage line. Such point indicates that approximately 3 per cent of silica must be added for achieving the result sought.

From the above examples, it will be seen that the determination of other percentages of the gravity reducing material to be added to coal for effecting the desired reduction in the apparent specific gravity of the clinkers may be made by drawing, if desired, additional lines through the points of intersection of the pertinent apparent specific gravity lines and the ash percentage lines and extending such drawn lines parallel with the dotted line system through the lines of the desired apparent specic gravities. subtracting the known ash percentage of a coal from the total ash percentage indicated by the position of the point of intersection of such a drawn line with the last mentioned apparent specic gravity line gives the percentages of the silica to be added to the coal.

From the foregoing description it will be seen that if a batch of coal is to be burned, for example, in a furnace which normally maintains an average maximum temperature in the re bed of 2700 degrees Fahrenheit, the ideal apparent specific gravity of the clinkers is 2.4. If a burned sample of such coal gives an apparent specic gravity above 2.4, the amount of silica to be added can readily be determined by reference to the drawing .as described above.

It is pointed out that the dotted line system shown in the drawing is based upon experiments wherein batches of sample coals Were burned at 2700 degrees Fahrenheit and silica was the additive material. It will be obvious that a different system of such lines can be plotted by burning coal samples at a different temperature, such as 2800 degrees Fahrenheit, for example, or by using a different specific gravity altering material. The temperature of 2700 degrees Fahrenheit has been selected as a standard for the reason that it is the maximum temperature frequently maintained in many furnaces, while silica has been employed as the additive material in plotting the line system of the drawing merely because of its general availability.

The discovery that the density of clinkers formed from coal burned under known furnace conditions gives a clue to the clinkering difficulty to be expected from coal burned under like conditions results in decided advantages. For example, coals forming clinkers of different densities sometimes can be mixed or blended in proportions based on the densities of their clinkers to provide a fuel which will be satisfactory under known furnace conditions without the use of the density altering materials which, as will be appreciated, being substantially or wholly non-combustible, increase the ash content of the fuel. In other words, the percentage of ash and the apparent specific gravities of the ash residues of different coals modify each other. It will be obvious also that the present invention enables a coal producer to determine whether coal from any mine or from any portion thereof will be free from clinker trouble if delivered to a customer whose furnace conditions are known or ascertainable. Hence, by making use of the principles of this invention, the selective distribution of coal can be practiced, that is, coals best suited to the heating equipment of particular customers can be supplied to them when available Without-the addition of the density reducing materials, but when burning tests indicate that treatment of a coal is desirable to avoid subsequent .clinkering trouble, by means of the present improvements the proper quantity or quantities of such materials to be added can be determined, and only that quantity need be added, and hence undue increase in the ash content of the coal can be avoided.

It may be pointed out that during the numerous tests that have been made in evolving the principles of the present improvements it has been found that the addition to coal of the density altering materials above mentioned does alter the true specic gravity of the clinkers but the effect of the materials on the true specific gravity of the clinkers is substantially less than the effect that the same percentage of the material has on the apparent specific gravity of the clinkers of such coal, and it therefore is preferred to use the apparent specific gravity of the clinkers as the gage or criterion for determining what percentage of the material, if any, is to be added, since thereby more precise results can be obtained and the use of an excess of such materials can be avoided. The avoidance of the use of an excess of such materials, as stated above, is desirable since any addition increases the percentage of the noncombustibles and it has been found that addition of the material beyond certain limits appears to result in proportionately less alteration in the apparent specific gravity of the resulting clinkers. Excess ash by Weight reduces B. t. u. values (heat content) and excess ash by weight or volume reduces the rate of heat release which is usually a valuable characteristic of coal.

It will thus be seen that where the equipment or duty of a furnace is such as to forbid the use of coal having an ash content in excess of a given maximum, certain coals having such maximum ash content could not be burned satisfactorily in such furnaces if the density of the clinkers or ash residues indicates that addition of the density reducing material is required. However, such coal may be blended in proper proportions with Sodium chloride Calcium oxide Each of the above has a distinctive pattern or system of modifying additive curves or lines unique unto itself.

In the drawing the lines D-H indicate the eect of adding limestone to various coals producing clinkers having relatively low natural apparent specific gravities. Line D indicates that the clinkers of coal (burned at 2700 degrees Pyrites (iron sulphide) Fahrenheit) had anapparent specific gravity of 1.7 and that the addition of approximately l per cent of powdered limestone based on the weight of the coal increased the apparent specific gravity of the resulting clinkers to approximately 1.9. Lines B to H, inclusive, indicate the results of other tests. To make similar determinations as to other coals giving clinkers of 'apparent specic gravities different from the natural apparent specific gravities of the samples exemplifiedby the lines D to H proceed as follows: Determine the apparent specific gravity of the clinkers of coal and its percentage of ash, locate the point on the drawing corresponding to the apparent specific gravity of clinkers formed by burning the raw or untreated coal and project a line from that point parallel with the system of the lines D to H. The location of the` point where the projected line intersects the line of the desired specific gravity gives an indication as to the percentage of limestone to be added to the coal. With a knowledge of the method employed in treating with limestone coals producing low density clinkers, anyone skilled in the art can plot the lines, similar to lines D to H of the drawing, which will indicate the percentage of other additive material to be used. As stated above the density reducing materials that have been found to be effective do not have like effects, nor do the materials which increase the density of light weight clinkers, and those additive materials obviously may be selected for use by reason of their availability to a particular coal producer,` the cost or other economic reasons.

It will be obvious that while different coals may be blended to produce a composite fuel which will produce clinkers having a density lower than the clinkers of one of the coals, as mentioned above, coals may also be `blended primarily to provide a fuel which will produce clinkers of higher density than one of the coals. The ratio of coals to be blended in either instance is determined by the relative densities of their respective clinkers. Thus two coals which at 2700 degrees Fahrenheit produce clinkers having apparent specific gravities of 2.0 and 3.0 Will, if blended in equal parts, produce a composite fuel whose clinkers will have an apparent specific gravity of approximately 2.5 when the fuel is burned at 2700 degrees Fahrenheit.

Inthe foregoing description and in the accompanying claims the use of the term coal is used generically t cover a fuel consisting of coal or fuel formed of or from coal and having at least somerofthe original ash content.

The term clinkers as used herein with reference to the clinkering or obstruction of furnace grates or walls refers to coagulant fused masses of ash residues. However, in making determinations of the densities of ash residues of burned coal'sainples in accordance with the present invention, it is not essential that such coal samples be burned at temperatures at or above the fusion temperatures of the residues. In fact samples of coals may be burned experimentally at temperatures below the fusion temperatures of the ash residues, and in such instances clinkers, as defined above, are not formed. However, the density determinations of such ash residues formed at the lower temperatures may be converted to the higher densities that would result from burning the respective samples at predetermined higher temperatures and hence density measurements of non-coagulant ash residues formed at temperatures below the fusion temperatures thereof may be employed as bases for predicting density values of clinkers formed from such coals when burned in industrial furnaces at clinker forming temperatures.

Where maximum temperatures `have been referred to above, that is, temperatures of` 2500 degrees Fahrenheit to 3000 degrees Fahrenheit, it will be understood that they refer to the average maximum temperatures at which the furnaces are operated and that there are instances in the operation of any furnace Where local temperatures may rise above or fall below the average maximum temperatures contemplated in this specification.

It will be seen that since the temperature at which coal is burned affects the density of the resulting clinkers, it is feasible in some instances to increase or decrease the rate of burning the fuel in a furnace and thus increase or reduce the maximum furnace temperatures for effecting a sufficient increase or` reduction, respectively, in the density of the clinkers to render the same trouble free.

From the foregoing description it will be seen that while 2700 degrees Fahrenheit was selected as a standard temperature for burning samples of coals for determining the apparent specific gravities of the resultant clinkers and the effects upon the natural apparent specific gravities of the clinkers by additions of the gravity altering materials, such selection was arbitrary inasmuch as another temperature, suchas 2600 degrees Fahrenheit or 2800 degreesFahrenheit, might have been selected.

Where gravity altering materials are employed which have a greater or less eect than the silica or the limestone above mentioned, the dotted line systems typied by the lines A to C and D to H will be different from those illustrated in the drawing, but a chart based on the use of such different materials can be prepared by burning samples of coals under a controlled temperature and employing different ratios of the selected additives.` The resulting apparent specific gravities or densities of the clinkers can be plotted to provide line systems similar to those above described for ready reference by one whose duty it is to treat coal or to allocate batches or vlots thereof to particular customers in accordance with the principles of the present improvements.

This application is a continuation in part of my application Serial No. 346,784, led Julyv22, 1940 for Method of predetermining and controlling the clinkering characteristics of coal.

I do not, therefore, wish to be restricted to the specific temperatures nor the specific materials referred to above since other temperatures and other materials may be employed Within the spirit of the invention.

I claim:

1. The method of preparing a batch of coal for burning at temperatures above the fusion temperature of the ash to form a desired non-fouling or non-obstructing clinker, comprising preburning a sample at the aforementioned temperatures, measuring the density of the clinker formed thereby, and finally treating the residual batch with such quantity of density altering materials for theclinkeras may be required by said measurement to produce said desired clinker.

2. The method of preparing a batch of coal for burning at a -temperature above the fusion temperature 4of the ash to form a desired non-fouling or non-obstructing clinker, comprising preyers formed upon burning burning a sampleat a temperature to form elinkers, measuring the density of the clinker formed thereby, and finally treating the residual batch With such quantity of apparent density altering materials for the clinker as may be required by said measurement to produce said desired clinker.

3. The method of preparing a batch of coal for burning at temperaturesl above the fusion temperature of the ash to'form a desired non-fouling or non-obstructing clinker, comprising pr burning a sample at a clinker forming temperature, measuring thel density of the vclinker formed thereby, and finally treating the residual batch with such quantity of density altering materials for the clinkers selected from the group consistingsoi",

Lime Calcium oxide Limestone Magnesium carbonate Fluorspar Chrome oxide Calcium chloride Silica Ironk oxide Silica-alumina Pyrites Alumina Sodium chloride Calcium carbonate Magnesium oxide as. may be required by said' measurement to produce said desired clinkers.

4. The method of burning a batch ofr coal at temperatures. above the fusion temperature of' the ash to form non-fouling.v or non-obstructing clinkers, comprising measuring the density of the clinker of a batch sample burned at said aforementioned temperatures, and thereafter treating the residual batch by the addition thereto of. material capable of altering the density of the clinker as determined by said. measurement to produce said desired clinker upon the burning of said batch of coal'.

The method of preparing a batch of coal for burning at a temperature above the fusion temperature of the ash to form non-fouling or nonobstructing clinkers, comprising measuring the density ofthe clinkers of a batch sample burned Clay (high in silica and/or alumina) Molybdenum oxide at a clinker forming temperature, and thereafter treating the residual batch by the addition thereto of material capable. of altering the density of the clinkers asv determined by said measurement togproduce clinkers having the desired density upon the burning ofl said batch of coal.

.6. The method of treating coal for improving the clinkeringI characteristics when burned in a furnace at knownr temperatures. which comprises determining the density of clinkers formed. by

said coal when burned at a predeterminedtemi perature and adding to the coal a density modifying agent in such quantity as to, effect a predetermined variation in the, density ofy the elinkthe coal in a furnace at said known temperatures.

7. The method of treating coal for altering the rate of migration. of molten clinkers in va furnace which comprises determining the density yof clinkers formed from such coal when burned at a given temperature and adding to the coal,- a density altering material in amount, to varythe density of the clinkers of the coal to a prede-` termined-value when burnedrat a given temperature.

8. The method of treating coal for effectingthe predetermined alteration in the apparent specic gravity of the clinkers formed upon burning the coal at predetermined temperatures which comprises determining the ash content of the coal and adding to the coal aquantity of specific-.gravthe sample the specic gravity of the clinkers of which approximates the specific gravity of such trouble free clinkers.

1-0. The method of preventing the formation of obstructing or fouling clinkers in a furnace which operates at clinker forming temperatures which comprises determining the density of trouble free clinkers formed from coal burned at said temperatures, separately burning samples of differentv batches of coal each at a temperature to form clinkers, determining the density of the ash residue so formed, and thereafter burning in said furnace the batch or batches corresponding to the sample the density of the ash residue of which approximates the density of such trouble free clinkers.

11. The method of preventing the formation of obstructing clinkers in a furnace which comprises determining the specific gravity of trouble free clinkers formed therein, burning samples of various coal batches each at temperatures to form clinkers, determining the specic gravity of the clinkers: so formed, and thereafter burning in said furnace the coal producing the clinkers the specic gravity of which approximates the said specific gravity of said trouble free clinkers.

l2. The method of preventing the formation of obstructing clinkers in a furnace which comprises determining the density of trouble free clinkers formed therein, burning samples of Various coal batches each at determinable temperatures, determining the density of the lash residue so farmed, and thereafter burning in said furnace the coal producing ash residue the density of which approximates the density of said trouble free clinkers.

13. The method of preventing the formation of obstructing clinkers in a furnace operated at predetermined temperatures which comprises determining the specific gravity of non-obstructing clinkers formed from a coal burned ,at the furnacey the clinkers so formed, and thereafter burningin said furnace coal producing the clinkers the specic gravity of which corresponds to the said sp-ecic gravity of non-obstructing clinkers formed from coal burned at such furnace temperatures.l

14. The method of preventing the formation of obstructing clinkers in a furnace operated at predetermined temperatures which comprises determining the density of non-obstructing clinkers formed from a coal burned at the furnace temperatures, burning samples of batches of different coals each at a definite temperature, determining the densities of the ash residues so formed, and thereafter burning in saidA furnace at said furnace temperatures the coal producing the ash residue of the density corresponding to the density of said non-obstructing clinkers.

15. The method of blending coals to provide a fuel that will produce clinkers that are non-adhering or non-obstructing in a furnace which comprises determining the specific gravity of nonadhering or non-obstructing clinkers formed from coal burned at the temperature at which the said furnace normally operates, burning samples of batches of different coals to form clinkers, measuring the specific gravity of the clinkers so formed and thereafter blending coal from all or some of said batches in such proportions that the specific gravity of the clinkers thereof, as indicated by the specific gravity of the respective samples, Will correspond approximately to the specific gravity of said non-adhering or nonobstructing clinkers.

16. The method of blending coals to provide a fuel that Will produce clinkers that are non-adhering or non-obstructing in a furnace which comprises determining the density of non-adhering or non-obstructing clinkers formed from coal burned at the temperature at which the said furnace normally operates, burning samples of batches of different coals at predetermined temperatures, measuring the density of the resulting ash residue so formed and thereafter blending coal from all or some of said batches in such proportions that the density of the clinkers thereof, as indicated by the density of the respective samples, will correspond approximately to the density of said non-adhering or non-obstructing clinkers.

17. The method of operating a furnace to prevent the formation of clinkers of troublesome density which comprises determining the density of troublesome clinkers formed therein, and thereafter increasing or decreasing the maximum temperatures of the furnace to a given extent for increasing or decreasing, respectively, to a given extent the density of the resulting clinkers.

18. The method of determining the suitability of coals from the standpoint of their clinkering characteristics for burning in a particular furnace Linder the normal ring conditions thereof which comprises determining the average maximum temperatures of the furnace when normally operated, determining the specific gravity of nongrate adhering clinkers formed under such conf ditions, burning samples of different coals experimentally at known temperatures to form clinkers, and measuring the specific gravity of the clinkers so formed to enable the selection for use in the furnace of the coal or coals the specific gravity of the clinkers of the samples of which indicate the formation of clinkers of the specific gravity of said non-adhering clinkers when such selected coal or coals are burned in the furnace under said normal conditions.

19. The method of determining the suitability of coals from the standpoint of their clinkering characteristics for burning in a particular furnace under the normal ring conditions thereof which comprises determining the average maximum temperatures of the furnace as operated, determining the density of non-grate adhering clinkers formed under such conditions, burning samples of different coals experimentally at known temperatures, and measuring the density of the ash residue of said burned samples to enable the selection for use in the furnace of the coal or coals the density of the ash residues of the samples of which indicate the formation of clinkers of the density of said non-adhering clinkers when such selected coal or coals are burned in the furnace under said normal conditions.

20. The method of determining the suitability with respect to the clinkering characteristics thereof of one or more batches of coals for consumption in a furnace which comprises determining the specific gravity of trouble free clinkers formed by burning a different coal at the temperature at which the furnace normally operates, burning samples of said batches of coals experimentally at predetermined temperatures, measuring the specific gravities of the ash residues of the samples, `and comparing the specific gravity measurements of said samples with the specific gravity measurement of said trouble-free clinkers to enable the selection of the batch or batches of coal which When burned in said furnace -will produce clinkers having a specic gravity corresponding to that of said trouble-free clinkers.

2l. The method of determining the suitability with respect to the clinkering characteristics thereof of one or more batches of coals for consumption in a furnace which comprises determining the density of trouble-free clinkers formed by burning a diierent coal at the ltemperature at which the furnace is operated, burning samples of said batch or batches of coals experimentally at predetermined temperatures, measuring the densities of the ash residues of the samples, and comparing the density measurements of said samples with the density measurement of said trouble-free clinkers to enable the selection of the batch or batches of coal which when burned in said furnace will produce clinkers having a density corresponding to that of said trouble-free clinkers.

RAYMOND S. WEIMER.

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