US3762886A - Formed carbon fuel briquets - Google Patents

Abstract

Formed fuel briquets of reduced reactivity are prepared with the use of a binder contributing little, if any, green strength. The fuel is suitable for such purposes as industrial and metallurgical applications and for domestic heating. Briquets possessing high green strength, and high shatter and compressive strength in the cured state, are produced even while employing a rapid compacting operation, such as roll briquetting. Carbon aggregate, of controlled particle sizing, and preferably of a specified type, is an essential ingredient employed in the making of the formed fuel. The use of a hydraulic setting cement binder, such as Portland cement, which reduces the reactivity of the formed briquets, is also an integral part of the process, as are also a compacting step and a curing step, and the employment of closely controlled conditions particularly with respect to the use of water in each of these steps.

Description

[ 1 Oct. 2, 1973 1 1 FORMED CARBON FUEL BRIQUETS [75] inventor: Alfred A. Triska, New York, N.Y.

[73] Assignee: Great Lakes Carbon Corporation, New York, N.Y.

22 Filed: June 14,1971

21 Appl.No.: 152,605

[52] US. Cl. 44/10 E, 44/16 A [51] Int. Cl. C101 5/00, C101 5/12 [58] Field of Search 44/10 E, 10 R, 10 0, 44/1 R, 16 A; 75/42 [56] References Cited UNITED STATES PATENTS 776,373 11/1904 Andes 44/16 A 2,017,402 10/1935 Komarek et al.. 44/16 A 3,093,463 6/1963 Madley 44/10 R FOREIGN PATENTS OR APPLICATIONS 414,361 7/1934 Great Britain 44/16 B Primary Examiner-C. F. Dees Attorney-Wallace F. Neyerlin [57] ABSTRACT Formed fuel briquets of reduced reactivity are prepared with the use ofa binder contributing little, if any, green strength. The fuel is suitable for such purposes as industrial and metallurgical applications and for domestic heating. Briquets possessing high green strength, and high shatter and compressive strength in the cured state, are produced even while employing a rapid compacting operation, such as roll briquetting. Carbon aggregate, of controlled particle sizing, and preferably of a specified type, is an essential ingredient employed in the making of the formed fuel. The use of a hydraulic setting cement binder, such as Portland cement, which reduces the reactivity of the formed briquets, is also an integral part of the process, as are also a compacting step and a curing step, and the employment of closely controlled conditions particularly with respect to the use of water in each of these steps.

32 Claims, 1 Drawing Figure PATENTEUUBI 2197a lillllLlllll- II PS5 FORMED CARBON FUEL BRIQUE'IS BACKGROUND OF THE INVENTION l. Field of the Invention The present invention relates to the field of formed fuel, such as briquets suitable for industrial and metallurgical applications and domestic heating purposes. The briquets produced herein possess high shatter and compressive strength, high hot strength, and reduced reactivity, are water resistant, are readily ignited under the conditions of, their intended use and burn evenly and relatively slowly. Upon burning they also leave a controlled amount of ash which is below the acceptable limits in the particular field of use involved and typically evolve low quantities of smoke.

In general it may be stated that the process utilizes low cost binder and also employs low cost processing steps to prepare the final product. In many respects the formed fuel and/or the process(es) of the present invention are superior to, or advantageous over, formed fuels prepared by using different binders and/or by using different processing techniques, because of differences in one or more of the foregoing described product properties, and/or because of beneficial differences in the processing conditions employed in preparing the respective formed fuels.

2. Description of the Prior Art The prior art, considering both commercial practices and literature references relating to formed fuel, is extensive. Such elements as the particular aggregate being bonded and/or its sizedistribution, the particular binder system employed, processing techniques used in preparing the aggregate for forming, and/or in forming the fuel, and subsequent treatment steps such as heating which are necessary and/or which are carried out upon the formed fuel after the forming operation, are key factors for consideration in determining the pertinency of the prior art or lack of same. Prior art briquets are typically made employing forming pressures equivalent to no more than I to 1.2 metric tons force per centimeter of roll face in roll briquetting, and correspondingly low pressures such as less than 0.18 metric tons per square centimeter in other types of compacting operations. Pressures higher than these are not typically employed because this causes breakage of grains of the carbon material being bonded. This is avoided because it leads to carbon particle surfaces inadequately covered with binder, thus producing weak briquets. Heating of the mixture prior to and/or during pressing is also often required in preparing such prior art briquets, as is also heating of the briquets after they have been formed.

Also a key factor in the evaluation of pertinency is an appraisal of the goals sought to be achieved in the present invention, such as reduced reactivity, and the simic. The use of cement as a binder for a carbonaceous material, as described in U. 8. Pat. Nos. 2,017,402, 2,540,l73 and 3,442,670; and in theliterature reference "Burn Waste Coke in Cupola" by W. A. Engelhart and H. W. Arterburn, pages 59-60 of American Foundryman Nov. 1948); and

d. The use of miscellaneous types of other binders for a carbonaceous material and/or other materials, such as ores, as described in U. S. Pat. Nos. 71,1 19; 2,844,457; 2,907,645; 2,996,372; 3,215,520; Belgian Pat. 712,285; and British Pats. 770,898, 877,932 and 1,081,349.

Summary of the Invention An object of the present invention is to produce a formed fuel which is very suitable for industrial and metallurgical applications and/or domestic heating purposes because ofits possessing the following properties:

a. Good burning properties characterized by: possessing reduced reactivity; being readily ignitable; demonstrating uniform and prolonged burning; leaving controlled amount of ash residue; and liberating low quantities of smoke upon burning;

b. High shatter and compressive strength;

0. High hot strength; and

d. Capability of withstanding adverse and open weather conditions in storage and shipment by virtue of being resistant to damage from water and having high strength.

Another object of the present invention is to produce a competitive formed fuel for industrial and metallurgical applications and/or for domestic purposes, employing low cost binder material, i.ie., hydraulic cement which, on reacting with water, hydrates forming a stone-like mass, and the achievement of a process which entails a minimum of expense.

Another object of the present invention is to provide a commercially attractive outlet for conventional solid carbon materials, such as delayed coker and fluid coker petroleum cokes, (raw and/or partially devolatilized and/or calcined), coal tar pitch coke, anthracite, charcoal, bituminous coal as such, or partially devolatilized (char), or calcined and/or mixtures of these materials, particularly the fractions of said solid carbon materials which are of a relatively fine particle size and have low economic value.

Another object of the present invention is to produce a formed fuel, industrial, metallurgical or domestic, having competitive properties by means of a highvolume, low cost, efficient process which includes a compacting operation which may be rapid and wherein sufficient pressure is used during forming to fracture the grains in the mix.

Another object is the attainment of an optimum forming and curing technique whenever hydraulic cement is employed as a binder for a carbon aggregate to prepare a formed fuel.

DESCRIPTION OF THE DRAWING The invention will be better understood by reference to the block drawing presented herewith.

The basic process comprises: The preparation of a mixture comprised of parts by weight (dry basis) of carbon aggregate of controlled sizing, (such as is achieved by mechanically crushing the aggregate in an impact mill to at least 92 percent minus A inch and no more than 35 percent minus 200 Mesh), about 3 to 15 parts by weight of hydraulic setting cement binder per 100 parts of dry carbon aggregate and about 3 to about 14 parts by weight of water per 100 parts of dry carbon aggregate, the parts of water being inclusive of any water or moisture derived from one or more of the ingredients making up said mixture, but being inadequate to fully satisfy the water sorption of the carbon aggregate and the water required for the hydraulic setting of the cement (in the body to be formed from this mixture); forming this mixture into a firm mass of adequate green compressive strength for post-forming handling and curing operations and of desired size and shape in a compacting operation, while simultaneously fracturing the carbon aggregate, employing a pressing force of at least 1.4 metric ton per centimeter of face contact in case of roll briquetting or the equivalent of at least about 0.18 metric ton per square centimeter in case of other methods of compacting; and then curing the formed mixture by adding within 120 minutes after forming the required additional water to satisfy the water sorption of the carbon aggregate and also that required to permit the hydraulic setting of the cement; to yield a high strength formed fuel product suitable for industrial and/or metallurgical applications and/or domestic heating purposes. Preferably the compaction method employed is a rapid one requiring a pressing time of no more than 2 seconds and is also preferably carried out at ambient temperatures.

The carbon aggregate employed is selected from the group of carbon materials previously specified. it must also possess a size distribution pattern characteristic of a carbon material such as has been mechanically crushed in an impact mill to at least 92 percent minus A inch and no more than 35 percent minus 200 mesh. If the carbon material is soft, i.e., is easily fractured in the compaction step, and possesses the necessary size, that is, is already at least 92 percent minus A inch, and also if its moisture content is not too high, then it may be used directly in the mixture to be compacted. However, if the carbon material is hard and does not fracture easily in compaction, it will be necessary to size it, such as by crushing and selective screening, to obtain the desired size distribution necessary to produce a firm green mass upon compaction. It is typically also desirable to initially dry the carbon aggregate before sizing or mixing it with the other ingredients. The sizing will typically be carried out by means of conventional grinding and/or milling operations in conjunction with selective screening, although it may sometimes also be advantageous and possible to accomplish this by means of compacting the aggregate, such as in a briquetting press in order to crush the larger particles. lf initially of the desired moisture content, then sizing alone may be necessary; or, if initially of the desired sizing, then drying alone may be necessary; however, as aforesaid, typically it will be both dried and sized. (These various procedures and possible alternatives for mix preparation are indicated in the drawing, the typical procedures by the solid lines and blocks and the possible alternatives by dotted lines). After mixing, the prepared mix is compacted in commercially available roll, static or extrusion presses (referred to more fully hereinafter) producing a green formed fuel body of the desired strength, size and shape. The hydraulic cement in the green formed fuel body is then hydrated to a stone-like mass in the curing step. Curing is always accomplished by adding water in some form to the green bodies within 120 minutes after forming and may be carried out by techniques such as by spraying the bodies with water, keeping them damp or wet, or submerging them in water, typically at room or ambient temperature. The water for curing may be provided in other ways, such as by using steam or hot water, provided that in all cases of curing adequate amounts of water are used so as to make water available for proper cement hydration to permit satisfactory hydraulic setting of the cement. Optionally the water used in the curing step may contain some lime.

DETAILED DESCRlPTlON In the preferred practice of the present invention, the carbon aggregate employed in the forming step must be such that after pressing it will possess a uniform particle size distribution so that it will result in firm compacts containing minimum voids. The particle size distribution of the aggregate after pressing must meet certain specifications such that in a screen analysis in which the screens are arranged so that the maximum size openings of the top screen in the screens employed is in the range of 3 to 6 millimeters, and the screen with the smallest size openings possesses openings of no less than 0.074 millimeter, (200 mesh) and in which each successive screen after the top screen has openings one-half the size of the preceding screen, substantially all of the aggregate or to parts would pass through the screen having the maximum size openings and substantially equal amounts of about 13 parts by weight of the aggregate, varying by no more than about 4 parts, would be retained on each successive screen having openings one-half the size of the immediately preceding screen. For example, and to further illustrate the foregoing described size distribution requirements, the following table shows their application to an aggregate of maximum size of either 3 millimeter of 6 millimeter (which are approximately the same as A; and V4 inch, respectively).

Typical Size Distribution of Carbon Aggregate in Briquets 3 Millimeter Maximum Size Screen Opening, mm Percent Percent Retained Cumulative 3 0 0 L5 l3 l3 0.75 i5 28 0.375 l5 43 0.188 14 57 0.094 I2 69 0.074 (200 Mesh) 6 75 6 Millimeter Maximum Size Screen Opening, mm Percent Percent Retained Cumulative 6 0 0 3 l3 [3 L5 l5 28 0.75 I5 43 0.375 14 57 0.]88 ll 69 0.094 9 78 0.074 (200 Mesh) 6 84 The particle size distribution of the aggregate in the green formed coke or briquets made according to the present invention can be determined as follows. Immediately on discharge of the formed coke from the press, a moisture determination of the briquets is made at C and 5 to l0 briquets are weighed and placed in a bucket and covered with cold tap water containing 1 gram of Dow Separan 2610 per 2.25 liters (a very effective flocculating agent). The material in the bucket is immediately stirred to disintegrate and slurry the briquets. The slurry is strained over a 200 mesh screen. The plus 200 mesh carbon aggregate is retained on the screen and should be thoroughly washed with cold tap water. The retained carbon aggregate is then dried and a screen analysis is made. The material passing through the 200 mesh screen and wash water containing cement and minus 200 mesh aggregate is placed in a beaker or cylinder and allowed to stand until the solids are well settled to the bottom (about one-half hour). The supernatant water is then siphoned off or decanted carefully, avoiding loss of solid material. The small amount of material floating or suspended in the water is negligible. The solids are then evaporated to dryness at 130 C and weighed. The residue consists of cement and minus 200 mesh carbon aggregate. As the percent cement used and moisture content of the briquets were previously determined, the amount of cement in the weighed residue can be calculated. The balance of the weight of the residue represents the minus 200 mesh carbon aggregate which generally is to 30 percent of the total carbon aggregate. The weight of the aggregate retained on each screen from the screen analysis along with the weight of the calculated minus 200 mesh is then expressed in cumulative weight percent and plotted on a graph such as The Tyler Standard Screen Scale Form No. L6. From this graph the percent retained on each successive screen having one-half sized screen openings is obtained.

In the event a promoter, such as is referred to hereinafter, is used, then the necessary weight adjustments to the screen fractions are made as the size, affinity for carbonation, solubility, and amounts used are known.

The presence of a very small percentage (such as up to 5 percent or 5 parts) of carbon particles coarser than the maximum aggregate particle size in the finished briquet, is also to be considered within the scope of the in vention so long as the balance of the carbon particles possesses the foregoing described uniform particle size distribution.

The means of securing the desired size distribution in the formed fuel depends on the hardness of the carbon aggregate and the amount of crushing occurring in the sizing, mixing and pressing steps. (One of the features of the present invention is the use of higher pressures during pressing to promote fracturing of the carbon aggregate grains during pressing. in processes of the prior art, which typically use non-cement type binders, fracturing of grains during pressing is avoided as these binders do not have the expansion and growth characteristics of hydraulic cements. As a result of this, fractured grains when using other binders are not properly covered with the binder and this results in poor strength briquets. 1n the case of hydraulic cement, on proper hydration the specific volume expands about 2.5 times and the specific surface area increases about 1,000 fold during hydration to cement gel. The growth on hydration of cement to cement gel is similar to that of crystal growth and of a thin fingery nature. Therefore, significant amounts of new surfaces due to grain fracturing during pressing are subsequently coated by the produced cement gel during curing and strong bri quets are obtained with hydraulic cements). For example in an operation using a mix muller for mixing, and a roll briquetting press, and employing a mixture of 100 parts of carbon aggregate, 7 parts cement and 8 parts of water, the carbon aggregate consisting of raw petroleum coke of 104 Hardgrove hardness (ASTM Method D 409-51) ground in an impact mill to minus 3 millimeter, the aggregate as charged to the press and after forming at 3.9 metric tons per centimeter of roll face possessed the following particle sizings:

Screen Opening Percent Retained Percent Cumulative mm As After As After Charged forming Charged forming 3 4.9 1.2 4.9 1.2 1.5 12.1 12.0 17.0 13.2 0.75 22.5 15.1 39.5 28.3 0.375 19.2 16.9 58.7 45.2 0.188 18.5 15.6 77.2 60.8 0.094 9.8 12.0 87.0 72.8

and resulted in briquets having a green strength of 30 pounds as the coke grains were soft and during pressing fractured to the desired uniform particle size distribution specified previously. On curing less than 3 days by immersion in water at 60F (ambient temperature) the briquets withstood a six-foot drop to a concrete floor. However, petroleum coke of 64 Hardgrove hardness when ground in an impact mill to minus 3 millimeter, when mixed with the same amount of cement and water and formed under the same pressure as the petroleum colte of 104 l-llardgrove hardness resulted in particles 20 percent of which were retained on a 1.5 miliizneter screen and a cumulative retention of 89 percent on a screen of 0.094 millimeter (determined in the same manner as the preceding aggregate). The size distribution necessary for optimum, or preferred results was not obtained during the pressing operation and resulted in briquets which were relatively firm but which possessed a green compressive strength of only 12 pounds, as inadequate fracturing of grains occurred for achieving higher strength. However, with selective grinding and screening of the same initial aggregate, or by prepressing the aggregate, it was found possible to secure the preferred size distribution (previously described) in the pressed briquets, and green compressive strengths of 28 to 32 pounds were obtained, resulting in sound, high-strength briquets on curing. As previously mentioned, hydration of cement results in a crystal growth of a thin fingery nature. These growths clog some of the carbon aggregate pores as a result of which reactivity to carbon dioxide is inhibited. This characteristic of low reactivity is particularly desirable in blast furnace and cupola operations and in other industrial applications where increased carbon dioxide concentrations are desirable such as in carbon dioxide generators.

The forming step, after mixing the components in high intensity mixers known in the art such as mixrnullers, can be and preferably is carried out in a rapid compacting operation employing a pressing time of no more than 2 seconds, such as by means of a roll briquetting operation using a briquetting machine in which the feed (mixture) is subjected to high pressure between two rolls rotating counter to each other. The outer surfaces (faces) of these rolls possess recesses which define the desired shape and volume of the briquets to be produced. The pressure applied by the rolls forces the grains of the feed together thus making it possible to obtain a coherent and dense formed coke. The roll faces may possess any given or desired number of opposing rows of pockets which shape the'briquets, such as 4 rows or 8 rows: etc., depending upon the design of the machine and/or the desired production capacity. In contrast to typical pressing conditions of the prior art, in the present invention a pressing force of at least about 1.4 and preferably between about 2.0 and 5.0 metric tons, and generally no higher than 6 metric tons, per centimeter of roll face is employed in the forming step. The particular amount of higher pressure selected and used in the process and type of carbon aggregate employed, with reference to its hardness, are regulated to assure that the weaker grains of the carbon aggregate are crushed or fractured making for grain interlocking thus bringing the grains into very close contact and using the forces of adhesion, compaction and cohesion more efficiently to contribute to green strength and final product strength. However the amount of fracturing necessary, of the carbon particles in the forming step, is a variable, depending upon a number of factors, such as the initial sizing of the particles, green strength required or desired, etc.

The formed fuel can also be produced by means of static pressure with a plunger pressing on the carbon aggregate-cement-water mixture inside of a mold. When using 8 to 12 parts of water in the mixture, during the first 250 PS static pressure there is typically a volume reduction of slightly over 16; of the original volume after initially compacting at 1 P816 pressure. The formed fuel thus produced has insufficient physical strength and can not be further processed (cured). On increasing the static pressure to 2,500 PSlG (0.18 metric tons per square centimeter) the total volume reduction is typically about 45 percent and firm green formed fuel is produced which on 3-day moist curing will typically possess a compressive strength of about 500 PS16 when using 7 parts of cement. On further increasing the static pressure to 6,000 PSlG the volume contraction is typically about 1 percent for each 1,000 PSlG static pressure increase above 2,500 PSlG resulting in even firmer green formed fuel which on 3-day moist curing typically shows an increase in compressive strength of 50 PSlG for each 1,000 PSIG increase in static pressure. (The moist curing procedure used consisted of placing the green formed fuel on a grate above water at 70F). From the foregoing it can be concluded that pressures equivalent to at least about 0.18 metric ton per square centimeter static pressure should be used in methods of compacting other than roll briquetting that might be employed in carrying out the present invention, (such as by compacting in tableting machines or by compacting in extrusion devices).

The compressive strength of the green, formed fuel directly affects the final cured strength. This is so since green compressive strength measures the degree of compaction as a result of pressure, sorption forces, grain packing and grain interlocking. In the case of roll briquetting, for each particular type of carbon aggregate mix there is a maximum roll face pressure which, if exceeded, produces split briquets. The maximum permissible roll face pressure is a function of the amount of moisture in the mix and the hardness, sorption characteristics and particle size distribution of the carbon aggregate used.

The following Example illustrates the effect of the amount of water in a mix on permissible roll face briquetting pressure used in the forming step and the resulting green compressive strengths of briquets, when using a petroleum coke carbon aggregate screened to essentially minus V4 inch (8 percent above V4 inch) having a Hardgrove hardness of 104. (The green compressive strengths of the formed fuel were determined by means of a Rimac L860 Spring Tester which measures the pressure exerted between two parallel plates on a dial scale which is also equipped with a pointer for reading the maximum pressure exerted. The formed fuel, typically of a pillow shape, is placed horizontally between the plates and pressure evenly applied until a sudden reduction of pressure occurs. No further pressure is then applied and the maximum pressure recorded by the pointer is reported as compressive strength).

EXAMPLE 1 Green Compressive Strength, pounds Parts Water in Mix at Forming Briquetting Pressure, metric tons per Example 1 illustrates that the maximum green strength, which indicates the optimum balance of sorption forces, grain fracture, particle packing, grain interlocking and compaction, occurs at a pressure of 4.3 metric tons per centimeter of roll face and at 6 parts of water in the mix, when using an aggregate of 104 Hard grove hardness. However, in the case of an aggregate having a Hardgrove hardness of 64 and the same original size distribution before pressing, it was not possible to obtain green compressive strengths as high as 15 pounds, irrespective of the number of parts water used in the mix. In this case, excessive pressures were required for grain fracture and interpenetration due to the hardness of the aggregate and split briquets were produced. However, when another portion of this aggregate was presized before mixing, on compaction with 5.6 parts of water and a briquetting pressure of 2.5 metric tons per centimeter of roll face, briquets were produced having a green compressive strength of 32 pounds.

The final bonding after curing is of a matrix type which depends for its effectiveness on imbedding the carbon aggregate in a more or less continuous matrix of cement.

The required moisture or water for proper curing must be supplied to the formed briquets promptly after pressing to prevent crusting and sponginess. By promptly is meant within minutes of completion of the forming step and preferably within 30 minutes. On pressing there is normally a sudden temperature rise of 20 to 50F due to friction, depending on the pressure used, which accelerates drying resulting in improper hydration of cement leading to crusting and sponginess. Also, diminishing moisture in the capillaries of the fresh briquets causes the development of significant capillary forces which, aside from producing undesirable internal stresses, causes migration of moisture along with the calcium hydroxide produced in the initial hydraulic setting of cement, and produces an undesirable layered system within the briquet which is of greater density at the surface, with crumbly aggregate internally. On the other hand, some limited period, preferably of at least 3 minutes and not exceeding 30 minutes, for setting" of the green briquets before adding the water required for curing is beneficial.

EXAMPLE ll Elapsed Minutes on Pressing before wetting with 70F water Percent Increase in cured compressieve strength over green strength after 2 ays water treatment As has been indicated, the forming step may be carried out using several types of compacting devices. Typical devices that might be employed are described in an Article entitled Agglomeration by Jon E. Browning in the Dec. 4, 1967 edition of Chemical Engineering", pages 147-170, and in addition to roll briquetting machines particularly include Tableting and Extrusion Devices as are described in that Article.

A substantially ambient forming temperature is also typicallyand preferably employed in this step. By this is meant the customary temperature during any particular season of the year at the site of the forming apparatus, be it in a heated or non-heated building or enclosure. In other words, the process does not depend upon preheating the mixture to be formed or upon a heated forming device. (However, the forming temperature of the mixture is affected somewhat by heat generated in the pressing and mixing steps). This results in cost advantages over other processes which require heating of the binder or external heating prior to or during pressing.

it is typical in the present invention that the carbon aggregate employed will contain some water or moisture. The source of this water or moisture may be traceable to the fact that the carbon aggregate has been exposed to rainy or snowy weather, etc. Even in dry weather the carbon aggregate contains water or moisture due to sorption from the atmosphere. As previously indicated, this carbon material is typically dried, which facilitates obtaining the desired particle sizing of the aggregate by grinding and selective screening operations. Selective screening may sometimes be dispensed with simply by employing a predetermined proper mill or grinder setting and/or by precompacting the aggregate before the mixing step. If the particular carbon material to be employed in the process possesses the desired particle size distribution as received so that it will give the necessary particle size distribution after pressing to formed fuel (which particle sizing can also be possessed by some carbon aggregate fines of low economic value), then such steps as drying, grinding, compacting and/or selective screening may be unnecessary. in either case, undried or dried, the carbon material will generally not have sufficient water as is required to achieve the desired results in the forming step, i.e., sufficient to produce a firm mass having a green compressive strength adequate for postforming and curing operations and preferably of at least 15 pounds. Without being bound by the correctness of the following explanation or discussion of theo- 6 gregate, to provide and/or facilitate hydrophilic attraction, as well as compaction and grain interlocking between the carbon particles. Without water or with too little water there is insufficient hydrophilic attraction and the bodies formed are dry and crumbly. When water fills part of the voids or capillaries of the compacted carbon aggregate, solid-water-gas interaction causes strong liquid bridges to be formed which constitutes hydrophilic attraction. As water is increased, capillary-like bonding forces act until water envelops the particles, at which point surface tension or loss of same comes into play and mushy, soggy briquets of weak green strength are produced. in addition water acts as a lubricant in the forming step. To obtain desired or optimum compaction :and grain interpenetration the required pressure must be developed and this can only be developed when there is not too much water present. Example I is demonstrative of these as pects of the invention, it being realized that the absolute number of parts of water foroptimun results will vary depending upon a number of factors such as the particular type of carbon aggregate, its hardness and porosity and particle sizing, etc.

As has been indicated, the mixture prepared for forming contains from about 3 to about 14 parts by weight of water per 100 parts of carbon aggregate. More typically the mixture will contain between about 4 and about 12 parts of water. If an amount of water in these ranges fails tp provide adequate green strength in the briquetting step, then this typically will be an indication that the carbon aggregate possesses inadequate porosity to provide adequate hydrophilic attraction by means of adsorption between the carbon particles. If this occurs, then an agent to promote or increase the green strength of the formed fuel may be added to the mixture before it is formed. Such an agent or promoter, if employed, will typically be used in amounts varying between about l0 percent and about percent by weight, based upon the weight of the hydraulic cement employed in the process, and will preferably be selected from the group consisting of hydrated lime, bentonite, sodium silicate, non-swelling clays, molasses, tar, starch and sugar. Higher percentages of agent or promoter such as up to about 200 percent by weight of the cement may also be employed but it is generally disadvantageous to do so because of cost factors and marginal improvement in strength over that obtained by using much lower quantities. (An exception to the foregoing economic considerations would be at locations where spent lime is produced such as where acetylene is produced from calcium carbide, and in beet sugar production where spent lime is a waste product. In these cases, up to 10 to 20 percent of spent lime, based on the weight of the carbon aggregate, can be used for producing formed fuel for recycling in the operations and thus also utilizes what is normally a waste product in these operations. in such cases, the amount of cement used would be kept at a low level and the spent lime used could be as high as four times the amount of cement used). Agents(s) may also be employed in order to accelerate the rate of hydration of the cement.

in some instances for particular metallurgical usage an agent or promoter of the inorganic type may be added, even if not necessary for the purpose of increasing the green strength, in order to modify the ash chemistry of the formed fuel and of the resultant slag. For instance, in a blast furnace, generally a high percentage of CaO is desired in the slag while in grey iron cupolas the reverse, i.e., an acidic slag is desired. Factors such as these which, for example, indicate a choice between hydrated lime or active silica would control the particular inorganic promoter employed if any.

It should be noted that the aforesaid 3 to 14 or 4 to 12 parts by weight of water per 100 parts of carbon aggregate is the amount of water which is always used before the briquetting step to provide for the aforesaid hydrophilic attraction, albeit that a green strength promoter may sometimes also desirably be employed in conjunction with the water in order to develop the desired amount of green strength upon forming and/or improve upon same. However, as previously indicated, the particular amount of water which is employed in the briquetting step should never be sufficient to fully satisfy the water sorption of the carbon aggregate. This sorption by the carbon aggregate is inclusive of moisture or water taken up an held by the carbon aggregate by both adsorption and absorption.

Upon being formed, the formed fuel or briquet possesses good green strength, amply suitable for handling and transfer operations which precede the curing step. Green strength refers to the compressive strength of the formed fuel immediately after forming but before completion of the curing step. After fon'ning, the formed body, possessing green strength, is rendered permanently strong and water-resistant by a curing step wherein water is provided after a limited time to the formed body in an amount sufficient to prevent evaporation of water from its surface and thus inhibit water migration due to the capillary action of the carbon aggregate and also in an amount necessary to permit the hydraulic setting of the cement.

Carbonaceous aggregates absorb l to over 20 percent by weight of water depending on type and conditions, i.e., porosity, capillary action and the manner in which moisture is provided. For instance with petroleum coke spread out in a thin bed the moisture content may be 1 to 3 percent; if stored in an open pile in dry weather, 5-8 percent; and if soaked in water may be over 16 percent.

Typically, the amount of water employed within the 3 to 14 parts of water range in preparing the mixture for forming is selected so as to satisfy only so much of the water sorption characteristics of the aggregate as to provide strong hydrophilic attraction. For example, the use of 14 parts of water might exceed the water sorption characteristics of some particular carbon aggregate (A) but not of another particular type of carbon aggregate (B). In such cases less than 14 parts of water would be used with aggregate (A) while as much as 14 parts of water might be employed with aggregate (B). These same factors apply also, of course, to a lesser number of parts of water than 14 parts, so as to insure that the particular amount of water employed in the forming step is never sufficient to completely fulfill the water sorption requirements of the particular aggregate being bonded. As water evaporates from the surface of the formed fuel, additional water must always be added after the forming step in order to prevent this evaporation which causes undesirable water migration. The additional water must also be added to satisfy the water sorption of the carbon aggregate and also to supply the additional water, (over and above the carbon aggregate water sorption requirements), necessary to permit the hydraulic setting of the cement. It is a finding of the present invention that the necessary amount of water required to fulfill all of the foregoing requirements should not be mixed with the carbon aggregate and the cement binder before the forming step because as has been previously indicated, if this is done, the fuel after the forming step will not possess optimum green compressive strength (i.e., of at least l5 pounds) and generally will not even be a firm mass or possess sufficient green compressive strength for the necessary further handling and transfer operations, even if a green strength promoter is used and/or an extraordinary amount of care is exercised in such operations.

Many techniques may be resorted to in carrying out the curing step, that selected generally being chosen which offers the highest strength in the shortest period of time. But they all depend upon adding, within minutes of completion of the forming step, sufficient water to satisfy water sorption of the carbon aggregate and also to permit the hydraulic setting of the cement. Preferably the formed fuel is maintained or set under ambient room conditions, i.e., normal humidity and temperaturefor no more than 45 minutes and preferably no more than 30 minutes followed by maintaining a water wet surface either by spraying the formed fuel with water or submerging it in water for several hours up to seven days and then air drying. One or more of the following additional curing methods may also be employed:

1. Curing at ambient temperature or up to F while keeping the surface of the formed fuel wet by spraying or submerging in water;

2. curing at room temperature in an atmosphere containing substantially 100 percent humidity;

3. curing at a temperature of l00l40F in an atmosphere containing substantially l00 percent humidy;

4. curing with wet low pressure steam in an atmosphere containing 100 percent humidity; and

5. curing with high pressure steam in an atmosphere containing substantially 100 percent humidity.

In all of the foregoing methods of curing sufficient water to satisfy water sorption of the carbon aggregate and also to permit the hydraulic setting of the cement is available within l20 minutes of completion of the forming step.

The use of warm water or steam will generally accelerate the rate of curing. Also if a green strength promoter such as hydrated lime has previously been employed in preparing the formed fuel, a gas such as carbon dioxide can be provided in the curing step to accelerate the cure of the formed fuel and to also improve the strength of the cured product. If the formed fuel is for a metallurgical process in which an acidic slag is desired, such as in cupolas, then pozzolanic cements, with possible additions of sand or active silica such as sodium silicate or fly ash may be used in bonding; and the curing might best be carried out using technique 5, i.e., high pressure steam to obtain a cured product of high strength and other desired properties.

The total amount of water employed in fulfilling the requirements of both the initial preparation for forming step, and the final curing step, will generally vary between about 4 and about 16 parts and more typically between about 5 and about 14 parts per 100 parts of carbon aggregate. The optimum total amount and individual amounts of water employed in any given case will, of course, vary depending upon a number of factors especially the particular carbon aggregate being processed and its hardness, porosity, sorption characteristics and particle size, the amount and type of cement binder being employed and its hydraulic (or water of hydration) requirements for setting, the use or non-use of a green strength promoter, and the amount of pressing force employed in the forming or roll briquetting operation.

The foregoing aspects of the present invention are all inter-related and of importance in achieving a commercially practical process and in producing a commercially acceptable carbonaceous fuel.

The delayed coker and fluid coker petroleum cokes may be raw and/or calcined and/or partially devolatilized and/or mixtures of these materials. Delayed coker raw petroleum coke will generally possess a volatile matter (VM) content between about 8 percent and about 20 percent, with -13 percent being typical; fluid coker raw petroleum coke will generally possess a volatile matter content between about 4 percent and about 8 percent with 5 percent being typical. The pitch coke employed may also be either calcined or uncalcined or both. Uncalcined pitch coke will generally possess a volatile matter content between about 8 percent and about percent with 12 percent being typical. The VM of charcoal will generally be between about 18 percent and about 26 percent with 23 percent being typical of charcoal fines. The VM of anthracite is generally between about 2 percent and about 8 percent, with 6 percent being typical. Semi-anthracite intended herein to be included under the term anthracite will generally have a VM between about 8 percent and about 14 percent with 12 percent being typical. The bituminous coal employed includes coals of the low volatile, mid-volatile and high volatile matter types, possessing VM contents typical for these types. In addition, chars from these coals are included. By .char. is meant to connote a material which has been partially devolatilized, i.e., subjected to a postproduction heating step such that its VM content has been reduced, for example, to below 10 percent from a substantially higher initial VM content, e.g., of from 16 to percent. The carbon aggregate employed may sometimes also consist of a mixture of coals as described, including anthracite coal, and petroleum coke or a mixture of charcoal and petroleum coke. The pe-- troleum coke in these instances designates either delayed coker petroleum coke or fluid petroleum coke, either of these being raw and/or calcined. By calcined is meant to connote a material which has been subjected to a post-production heating step such that its VM content has been substantially reduced, for example, to below 3 percent from a substantially higher initial VM content, (e.g., from about 8-20 percent as in the cases of pitch coke and raw, delayed coker petroleum coke, or from a VM content of about 4-8 percent as in the case of raw fluid petroleum coke).

. For certain applications for the final product it may be desirable that the carbon aggregate employed possess an average VM content between about 4 percent and about 23 percent. For example, in domestic heating applications a VM content less than 4 percent leads to a product which is more difficult to ignite and more difficult to maintain burning whereas a VM content above 23 percent can lead to excessive evolution of smoke and/or tarry material on combustion.

As has been indicated, the process of the present invention is dependent to some extent upon the porosity of the particles of the carbon aggregate being bonded as well as their particle size distribution and also their shape. in cases where the carbon aggregate, on pressing, possesses inadequate porosity to provide adequate hydrophilic attraction, or there is inadequate grain interlocking and cohesion, adequate and/or optimum compressive green strengths will not be achieved. in such cases a suitable agent added to the mixture before the mixture is formed will frequently be capable of increasing the green strength of the formed fuel to the desired level(s).

Also, as has been indicated, in the preferred practice of the present invention, it is necessary that the carbon aggregate have a relatively specific particle size distribution after forming. Such particle sizing of the carbon aggregate after forming will generally be realized ifbefore forming it has an average particle size distribution such that no more than about 20 percent of same would be retained on a l.5 millimeter screen, at least about 25 percent and no more than about percent would be retained on a 0.5 millimeter screen, and at least about 40 percent and no more than about percent would be retained on a 0.2 millimeter screen. If the particle size distribution of the carbon aggregate before forming is coarser or finer than the foregoing then typically the particle size distribution after forming, desired for optimum strengths, is not obtained, the green compressive strength on pressing is substantially below 15 pounds, and the green formed coke may not even 1possess adequate strength for subsequent handling and curing. Under these conditions the cured formed coke has a low compression and shatter index.

The amount of hydraulic setting cement binder employed in the process must be between about ,3 and about 15 parts by weight per parts of carbon aggregate. Less than 3 parts of cement binder provide inadequate amounts to provide sufficient matrix and asa re suit the cured formed colce has low compressive strength and low shatter index. More than 15 parts of cement binder contributes to higher strength butalso results in excessive ash which is undesirable for both metallurgical and domestic fuel and generally also for industrial purposes.

The term hydraulic cement" or hydraulic setting cement" employed in the present invention is intended to include any cement which has the characteristic of hydrating with water to a stone-like mass. Hyraulic cement includes Portland cement, blends of Portland cement and natural cement, air-entraining Portland ,cement, hydraulic limes, grappier cements, pozzolan .cements, natural cements, aluminous cement, oil wellcement, white Portland cement, anti-bacteria cement, masonry cement, blends of Portland cement and blast furnace cement, and like materials. Pozzolan cements include slag cements made from slalted lime and granulated blast furnace slag. These cements typically are mixtures of lime, silica, and alumina, or of lime and magnesia, silica and alumina and iron oxide (magnesia for example may replace part of the lime, and .iron oxide a part of the alumina).

Because of its superior strength Portland cementis preferred among the hydraulic cements. Howevenbecause the art of cements recognizes hydraulic cements as a definite class, and because results of value maybe obtained with any member'of that class, it is desiredto include all hydraulic cements which harden, i.e., hydrate to a stone-like mass, upon the addition of water. In addition to the ordinary construction grades of Portland cement or other hydraulic cements, modified hydraulic cements and Portland cements designated as high-early-strength cement, heat-resistant cement, and slow-setting cement may also be used in the present invention.

More detailed information relating-to specific compositions and properties of different Portland cements which may be used herein is contained in several standard texts or handbooks including, for example, the Fourth Edition of Civil Engineering Handbook (pages 7-1 to 7-100), edited by LC. Urquhart, and published in 1959 (New York, Toronto, and London) by McGraw-Hill Book Company, Inc.

The invention is illustrated in more detail by the additional examples that follow:

EXAMPLE III One hundred parts by weight of petroleum coke calculated on a dry basis, 7 parts by weight Type III Portland Cement and water (added in such an amount that the total water of the mix before forming was 5.6 parts per I parts by weight of petroleum coke) were mixed for 10 minutes in a Simpson Mix-Muller. The mixture was pressed on a one meter diameter briquetting press at a pressure of 3.2 tons per centimeter of roll face. The compressive strength of the green briquets was 32 pounds and the briquets after curing, had a compressive strength of 250 pounds and withstood four six-foot drops on a steel plate before shattering. The petroleum coke employed had a VM content of l 1.2 percent and a particle size distribution before and after forming as follows:

1: Cumulative Before Fonning After Forming Size Retained Cumula- Retained Cumulative tive 3mm 0 0 0 0 [.5 l4 14 l l l l 0.75 12 36 I7 28 0.38 20 56 17 45 0.19 15 71 I 60 0.094 12 83 i3 73 It will be noted that on forming the aggregate size distribution was found to be in the preferred range previously described, showing that fracturing of the particles occurred in the compaction step.

Curing was carried out by permitting the green formed bodies to remain in air for 15 minutes and then immersing them in 60 F water for 1 minute and storing the wet briquets under soaking wet kitchen paper towels for 3 days in a closed 5 gallon can. The final water content of the cured briquets was 7.0 percent.

Upon heating and partially combusting the briquets over a forced air meeker burner no reduction in compressive strength at a temperature of l,700 F was found.

EXAMPLE IV One hundred parts by weight of dry carbon aggregate consisting of 75 percent of petroleum coke (VM 9.2 percent) and 25 percent charcoal (VM l9.l percent) were hammer milled to minus 3 millimeters containing 5.3 percent oversize and placed in a mix muller. 10 parts by weight of Type Ill Portland Cement and 7.5 parts by weight of water were added and the mixture was mixed for l5 minutes. The mixture was pressed on a one meter diameter briquetting press at a pressure of 2.8 tons per centimeter of roll face, which pressure also was sufficient to cause fracturing of the carbon aggregate to within the preferred size distribution range. On l0 minutes in air the briquets were moistened and stored for three days. The compressive strength was pounds and the briquets withstood a 6-f0ot drop to a steel plate.

EXAM PLE V One hundred parts by weight of dry petroleum coke (VM 12.8 percent) minus 6 millimeters from a screening operation were placed in a Simpson Mix Muller. 7 percent Type 1 Portland cement and 8 parts by weight of water were added and the mixture was mixed for 25 minutes. The mixture was then pressed on a 28 inch diameter briquetting press at a pressure of 2.4 tons per centimeter of roll face and sufficient to fracture the petroleum coke particles to the preferred size distribution. The green briquets had a green strength of 34 pounds. On 15 minutes in air the briquets were moistened and stored under water for 3 days. Their final water content was 14.7 percent. The compressive strength was pounds and the briquets withstood several 6-foot drops on to a steel plate.

Similar examples as the foregoing were carried out employing different types of carbon aggregate and different types of cements as described herein and with varying proportions of cement and water withinthe ranges previously specified. Generally satisfactory green and cured compressive strengths were obtained in all cases, with the strengths achieved varying, however, depending upon the specific materials and formulations employed. Before carrying out these examples, as well as Examples l-V previously set forth, the amount of water necessary to fully satisfy the water sorption of a particular carbon aggregate being processed was determined by preparing preliminary test samples utilizing different amounts of water within the broad 3 to l4 parts range previously specified. Typically the test samples were prepared using gradually increasing amounts of water such as 4, 6, 8, 10, etc. up to 14 parts of water if an amount this high seemed at all warranted. If a fairly high green strength was achieved by using 4 parts and the best green strength obtained in such tests was that obtained with 6 parts of water and the strength decreased substantially when using 8 parts, then this usually meant that with 12 parts of water little or no green strength could be achieved. It was thus known that the water sorption capability of the aggregate was exceeded by 12 parts, that a maximum of about 8 parts of water could be employed without completely filling the water sorption characteristics of the carbon aggregate, that the optimum amount of water was 6 parts and that 4 parts of water was operative for this particular system. in Example I the strength decreased substantially when employing 12 parts and the best results were obtained using 6-8 parts. The data of this example, therefore, indicated that approximately 3-12 parts of water were operative with 6-8 parts preferred. For any given aggregate and mix formulation the results obtained on test samples can be graphed and interpolations made to achieve optimum results. It will be noted that these optimum results are achieved when the mixture charged to the forming apparatus or roll briquetting press contains at least 50 percent of the water required for the water sorption characteristics of the carbon aggregate.

Having thus described the nature of my invention and the uses for same, but being limited only by the .appended claims with respect to the scope of the invention.

I claim:

1. A process for the production of a formed and cured carbonaceous fuel which comprises the following steps:

a. Preparing a mixture of at least three ingredients comprising 100 parts by weight of carbon aggregate of controlled sizing such as is achieved by mechanically crushing the aggregate in an impact mill to at least 92 percent minus A inch and no more than 35 percent minus 200 mesh, about 3 to about parts by weight ofhydraulic setting cement binder per 100 parts of carbon aggregate, and about 3 to about 14 parts by weight of water per 100 parts of carbon aggregate, the parts of water being inclusive of any water derived from one or more of the ingredients making up said mixture;

b. forming the fuel by compacting its ingredients,

while simultaneously fracturing some of the carbon aggregate, utilizing sufficient water in the forming step to produce a firm mass but less water than is necessary to fully satisfy the water sorption of the carbon aggregate and the hydraulic setting of the cement, a pressing force of at least L4 metric ton per centimeter of face contact in case of roll briquetting, or the equivalent of at least about 0.18 metric ton per square centimeter in case of other methods of compacting, also being employed in this forming step; and

c. curing the formed mixture by adding, within 120 minutes of completion of the forming step, sufficient water to satisfy water sorption of the carbon aggregate and also to pen'nit the hydraulic setting of the cement, thereby producing a strong briquet.

2. A process according to claim 1 wherein the forming step is carried out employing a pressing time ofno more than 2 seconds. i

3. A process according to claim 2 wherein the forming step is carried out by means of a roll briquetting press.

4. A process according to claim 1 wherein the formed fuel from step b is permitted to set for a limited period before the addition of water in the curing step.

5. A process according to claim 3 wherein the mixture charged to the roll briquetting press contains at least 4 parts of water and wherein the mixture also contains at least 50 percent of the water required for the water sorption characteristics of the carbon aggregate.

6. A process according to claim 1 wherein the addition of water in the curing step is carried out within 30 minutes after the forming step.

7. A process according to claim 3 wherein the pressing force employed in the forming step is between about 1.4 and about 6.0 metric tonsper centimeter of face contact.

8. A process according to claim 7 wherein the pressing force employed in the forming step is between about 2.0 and about 5.0 metric tons per centimeter of face contact.

9. A process according to claim 1 wherein the carbon aggregate possesses inadequate porosity to provide adequate hydrophilic attraction by means of absorption to produce a firm mass of the desired green strength and wherein an effective amount of an agent selected from the group consisting of hydrated lime, bentonite, sodium silicate, non swelling clays, molasses, tar, starch and sugar to increase the green strength of the formed fuel is added to the mixture before it is formed.

10. A process according to claim 1 wherein forming step b is carried out at a substantially ambient forming temperature.

ll. A formed fuel prepared by the process of claim 1.

12. A process for the production of a formed and cured carbonaceous fuel which comprises the following steps:

0. Preparing a mixture of at least three ingredients comprising 100 parts by weight of carbon aggregate, about 3 to about 15 parts by weight of hydraulic setting cement binder per 100 parts of car bon aggregate, and about 3 to about 14 parts by weight of water per 100 parts of carbon aggregate, the parts of water being inclusive of any water derived from one or more of the ingredients making up said mixture;

b. forming the fuel by compacting its ingredients, while simultaneously fracturing some of the carbon aggregate, utilizing sufficient water in the forming step to produce a firm mass having a green compressive strength of at least 15 pounds but less water than is necessary to fully satisfy the water sorption of the carbon aggregate and the hydraulic setting of the cement, a pressing force of at least 1.4 metric ton per centimeter of face contact in case of roll briquetting, or the equivalent of at least about 0.18 metric ton per square centimeter in case of other methods of compacting also being employed in this forming step; and

c. curing the formed mixture by adding, within 120 minutes of completion of the forming step, sufficient water to satisfy water s-orption of the carbon aggregate and also to permit the hydraulic setting of the cement, thereby producing a strong briquet;

said carbon aggregate being selected from the group consisting of delayed coker petroleum coke, fluid coker petroleum coke, pitch coke, anthracite, charcoal, bituminous coal and mixtures thereof;

the carbon aggregate after the forming step b also having an average particle size distribution such that when subjected to a screen analysis in which the screens are arranged so that the maximum size openings of the top screen in the screens employed is in the range of 3 too millimeters, and the screen with the smallest size openings possesses openings of no less than 0.074 millimeter, and in which each successive screen after the top screen has openings one-half the size of the preceding screen, substantially all of the aggregate or to parts would pass through the screen having the maximum size openings and substantially equal amounts of about 13 parts by weight of the aggregate, varying by no more than about 4 parts, would be retained on each successive screen having openings one-half the size of the immediately preceding screen. 13. A process according to claim 12 wherein the forming step is carried out employing a pressing time of no more than 2 seconds.

14. A process according to claim 13 wherein the forming step is carried out by means of a roll briquetting press.

15. A process according to claim 12 wherein the formed fuel from step b is permitted to set for a limited period before the addition of water in the curing step.

16. A process according to claim 14 wherein the mixture charged to the roll briquetting press contains at least 4 parts of water and wherein the mixture also contains at least 50 percent of the water required for the water sorption characteristics of the carbon aggregate.

17. A process according to claim 12 wherein the addition of water in the curing step is carried out within 30 minutes after the forming step.

18. A process according to claim 14 wherein the pressing force employed in the forming step is between about 1.4 and about 6.0 metric tons per centimeter of face contact.

19. A process according to claim 18 wherein the pressing force employed in the forming step is between about 2.0 and about 5.0 metric tons per centimeter of face contact.

20. A process according to claim 12 wherein the carbon aggregate possesses inadequate porosity to provide adequate hydrophilic attraction by means of adsorption to produce a firm mass of the desired green strength and wherein an effective amount of an agent selected from the group consisting .of hydrated lime, bentonite, sodium silicate, non-swelling clays, molasses, tar, starch and sugar to increase the green strength of the formed fuel is added to the mixture before it is formed.

21. A process according to claim 12 wherein forming step b is carried out at a substantially ambient forming temperature.

22. A process according to claim 12 wherein the average volatile matter content of the carbon aggregate is between about 4 percent and about 23 percent.

23. A process according to claim 22 wherein the carbon aggregate employed is delayed coker raw petroleum coke.

24. A process according to claim 22 wherein the carbon aggregate employed is fluid coker raw petroleum coke.

25. A process according to claim 12 wherein the carbon aggregate employed is calcined petroleum coke.

26. A process according to claim 12 wherein the carbon aggregate employed consists of a mixture of calcined petroleum coke and raw petroleum coke.

27. A process according to claim 12 wherein the carbon aggregate employed is charcoal.

28. A process according to claim 12 wherein the carbon aggregate employed consists of a mixture of anthracite and petroleum coke.

29. A process according to claim 12 wherein the carbon aggregate employed consists of a mixture of charcoal and petroleum coke.

30. A process according to claim 12 wherein the carbon aggregate employed consists of a mixture of petroleum coke and bituminous coal.

31. A process according to claim 12 wherein the carbon aggregate employed is bituminous coal or partially devolatilized bituminous coal or a mixture of these materials.

32. A formed fuel prepared by the process of claim

Claims (31)

1. 2. A process according to claim 1 wherein the forming step is carried out employing a pressing time of no more than 2 seconds.
2. 3. A process according to claim 2 wherein the forming step is carried out by means of a roll briquetting press.
3. 4. A process according to claim 1 wherein the formed fuel from step b is permitted to set for a limited period before the addition of water in the curing step.
4. 5. A process according to claim 3 wherein the mixture charged to the roll briquetting press contains at least 4 parts of water and wherein the mixture also contains at least 50 percent of the water required for the water sorption characteristics of the carbon aggregate.
5. 6. A process according to claim 1 wherein the addition of water in the curing step is carried out within 30 minutes after the forming step.
6. 7. A process according to claim 3 wherein the pressing force employed in the forming step is between about 1.4 and about 6.0 metric tons per centimeter of face contact.
7. 8. A process according to claim 7 wherein the pressing force employed in the forming step is between about 2.0 and about 5.0 metric tons per centimeter of face contact.
8. 9. A process according to claim 1 wherein the carbon aggregate possesses inadequate porosity to provide adequate hydrophilic attraction by means of absorption to produce a firm mass of the desired green strength and wherein an effective amount of an agent selected from the group consisting of hydrated lime, bentonite, sodium silicate, non-swelling clays, molasses, tar, starch and sugar to increase the green strength of the formed fuel is added to the mixture before it is formed.
9. 10. A process according to claim 1 wherein forming step b is carried out at a substantially ambient forming temperature.
10. 11. A formed fuel prepared by the process of claim 1.
11. 12. A process for the production of a formed and cured carbonaceous fuel which comprises the following steps: a. Preparing a mixture of at least three ingredients comprising 100 parts by weight of carbon aggregate, about 3 to about 15 parts by weight of hydraulic setting cement binder per 100 parts of carbon aggregate, and about 3 to about 14 parts by weight of water per 100 parts of carbon aggregate, the parts of water being inclusive of any water derived from one or more of the ingredients making up said mixture; b. forming the fuel by compacting its ingredients, while simultaneously fracturing some of the carbon aggregate, utilizing sufficient water in the forming step to produce a firm mass having a green compressive strength of at least 15 pounds but less water than is necessary to fully satisfy the water sorption of the carbon aggregate and the hydraulic setting of the cement, a pressing force of at least 1.4 metric ton per centimeter of face contact in case of roll briquetting, or the equivalent of at least about 0.18 metric ton per square centimeter in case of other methods of compacting also being employed in this forming step; and c. curing the formed mixture by adding, within 120 minutes of completion of the forming step, sufficient water to satisfy water sorption of the carbon aggregate and also to permit the hydraulic setting of the cement, thereby producing a strong briquet; said carbon aggregate being selected from the group consisting of delayed coker petroleum coke, fluid coker petroleum coke, pitch coke, anthracite, charcoal, bituminous coal and mixtures thereof; the carbon aggregate after the forming step b also having an average particle size distribution such that when subjected to a screen analysis in which the screens are arranged so that the maximum size openings of the top screen in the screens employed is in the range of 3 to 6 millimeters, and the screen with the smallest size openings possesses openings of no less than 0.074 millimeter, and in which each successive screen after the top screen has openings one-half the size of the preceding screen, substantially all of the aggregate or 95 to 100 parts would pass through the screen having the maximum size openings and substantially equal amounts of about 13 parts by weight of the aggregate, varying by no more than about 4 parts, would be retained on each successive screen having openings one-half the size of the immediately preceding screen.
12. 13. A process according to claim 12 wherein the forming step is carried out employing a pressing time of no more than 2 seconds.
13. 14. A process according to claim 13 wherein the forming step is carried out by means of a roll briquetting press.
14. 15. A process according to claim 12 wherein the formed fuel from step b is permitted to set for a limited period before the addition of water in the curing step.
15. 16. A process according to claim 14 wherein the mixture charged to the roll briquetting press contains at least 4 parts of water and wherein the mixture also contains at least 50 percent of the water required for the water sorption characteristics of the carbon aggregate.
16. 17. A process according to claim 12 wherein the addition of water in the curing step is carried out within 30 minutes after the forming step.
17. 18. A process according to claim 14 wherein the pressing force employed in the forming step is between about 1.4 and about 6.0 metric tons per centimeter of face contact.
18. 19. A process according to claim 18 wherein the pressing force employed in the forming step is between about 2.0 and about 5.0 metric tons per centimeter of face contact.
19. 20. A process according to claim 12 wherein the carbon aggregate possesses inadequate porosity to provide adequate hydrophilic attraction by means of adsorption to produce a firm mass of the desired green strength and wherein an effective amount of an agent selected from the group consisting of hydrated lime, bentonite, sodium silicate, non-swelling clays, molasses, tar, starch and sugar to increase the green strength of the formed fuel is added to the mixture before it is formed.
20. 21. A process according to claim 12 wherein forming step b is carried out at a substantially ambient forming temperature.
21. 22. A process according to claim 12 wherein the average volatile matter content of the carbon aggregate is between about 4 percent and about 23 percent.
22. 23. A process according to claim 22 wherein the carbon aggregate employed is delayed coker raw petroleum coke.
23. 24. A process according to claim 22 wherein the carbon aggregate employed is fluid coker raw petroleum coke.
24. 25. A process according to claim 12 wherein the carbon aggregate employed is calcined petroleum coke.
25. 26. A process according to claim 12 wherein the carbon aggregate employed consists of a mixture of calcined petroleum coke and raw petroleum coke.
26. 27. A process according to claim 12 wherein the carbon aggregate employed is charcoal.
27. 28. A process according to claim 12 wherein the carbon aggregate employed consists of a mixture of anthracite and petroleum coke.
28. 29. A process according to claim 12 wherein the carbon aggregate employed consists of a mixture of charcoal and petroleum coke.
29. 30. A process according to claim 12 wherein the carbon aggregate employed consists of a mixture of petroleum coke and bituminous coal.
30. 31. A process according to claim 12 wherein the carbon aggregate employed is bituminous coal or partially devolatilized bituminous coal or a mixture of these materials.
31. 32. A formed fuel prepared by the proCess of claim 12.

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