US3336122A - Briquets made of char and method for the production thereof - Google Patents

Description

AUZ- 155.1957 w. C, SMITH 3,336,122

BRIQUETS MADE OF CHAR AND METHOD FOR THE PRODUCTION THEREOF Filed April 28, 1964 INVENTOR. fav/f# United States Patent C) 17 Claims. (Cl. 44--17) This invention relates to briquets made of char and method for the production thereof. The present application is a continuation-in-part of, and a substitute for, my application 225,093, tiled Sept. 20, 1962 and now abandoned as a substitute for abandoned application Ser. No. 187,042, led Apr. 12, 1962.

Most of the briquets presently available are bonded with cornstarch and corn ilour and other relatively expensive materials. Unless specially coated, they are dirty to handle and they disintegrate readily in the presence of moisture. The briquet of the present invention is so clean that it can be handled without soiling the users hands and it is substantially non-absorbent of moisture and does not disintegrate in the presence of moisture. These results are achieved by the use as a binder of a reaction product of sulphite liquor and an oxidizing agent such as sodium nitrate, the latter being incorporated in quantities very greatly in excess of those employed when the oxidizing agent is used solely to facilitate combustion. The composition and method of manufacture of my improved briquet make it practicable to use these materials without offensive odor or other problems.

The improved briquet can be ignited readily despite Y the fact that if the binder is carbonized the briquet surface is so hard that it does not soil the hands of the user and will not disintegrate in water. If the binder is un-carbonized, the briquet is still superior even though it may be no different from standard charcoal as to dusting or disintegration when soaked.

Spent sulphite liquor is a by-product of the paper in-` dustry. Although the product itself is well-known, its precise chemical composition is not fully understood even by researchers in paper chemistry. It normally has a strong odor on burning which would make it unacceptable as a component ofva briquet used in cooking. However, I have diScovered'hoW to eliminate the odor substantially completely. Disposition of the spent sulphite liquor in paper mill waste has long been a major problem because this material, if dumped into streams, chemically combines with the oxygen in the water with the resulting death of marine life dependent on oxygen. Currently, much of the spent sulphite liquor is being burned to get rid of it. The present invention gives value to this Waste product.

As will hereinafter be explained, one embodiment of the invention contemplates the use of a special form of char which is also a by-product of the paper industry, being collected in the form of fly ash from the burning of bark and other waste wood products. Other forms of char are lignite char and coal char and wood char.

Also used in my improved briquet is a nitrate such as sodium nitrate. Other nitrates which are strong oxidizing agents can be substituted with due allowance for nitrate mol equivalence. All examples herein use sodium nitrate but contemplate substitution of known oxidizing nitrate equivalents in proper chemical proportions.

3,336,122 Patented Aug. 15, 1967 Sodium nitrate has previously been employed in briquets in small quantities to promote ignition. The quantities have had to be very limited because sodium nitrate is such a powerful oxidizing agent that if the quantities used in conventional briquets are very substantial, the briquets burn fiercely, emitting copious quantities of sparks. Even the small amounts of nitrate commonly used require the drying temperatures to be sharply limited lest the briquets burst into llame.

The present invention is based on my discovery that if enough nitrate is used to react chemically with the sulphite liquor, very high temperatures required to drive olf odorous components of the liquor may be used without experiencing spontaneous combustion of charcoal which has heretofore been experienced when attempts have been made to accelerate the drying of charcoal briquets or the carbonizing of sulphite liquor without using inert atmospheres. Such combustion has heretofore been experienced in attempts to dry 4charcoal or to carbonize sulphite liquors at temperatures in excess of 300 F. Thus, whereas oxidizing nitrates have heretofore been used to promote ignition, and the quantities had to be severely limited, I use such nitrates in relatively large quantities to oxidize theisulphite liquor. The anomalous result is that instead of the fierce ignition heretofore experienced with much lower percentages of nitrate, I am able to dry the briquets very quickly and at very high temperatures, thereby driving off odors, and without spontaneous combustion. The result is that I am able to produce superior char briquets which ignite as readily as conventional charcoal or more so and without the grave hazard experienced in igniting briquets -containing free or unreacted oxidant.

The nitrate may be incorporated in the mix either dry or in solution in the water which is added. Assuming the nitrate is present in adequate quantities and the temperatures are adequate for substantially complete chemical combination, the nitrate reacts in situ with the sulphite liquor on the surfaces of the particles of char to make a better binder than the sulphite liquor used alone. In practice this result is achieved whether the nitrate is added Wet or dry.

The desired results are not achieved if the sulphite liquor and the nitrate are pre-mixed. lf desired, it is possible to carbonize the sulphite liquor to make the briquets water resistant. In any event, practically all of the objectionable odor of the sulphite liquor is destroyed during drying, the remainder disappearing during the ignition stages so that when the briquet is burning in the combustion required for use in cooking, there is no odor left.

Some of the proportions involved are highly critical. It is even necessary to take into account the nature of the product from which the char is made. Even more important is the porosity and the content of volatile matter of the char.

The procedures involved can be performed entirely by hand or can be controlled in part or in whole by hand even though the mixing is done mechanically. The entire operation is preferably controlled automatically but the accompanying drawings show flow diagrams in which both batch mixing and continuous mixing are illustrated.

In the drawings:

FIG. 1 is a liow diagram for a method of manufacture using a batch mixing process manually controlled.

FIG. 2 is a ow diagram for a method of manufacture using a continuous and automatically controlled mixing process.

FIG. 3 is a fragmentary detail view on an enlarged scale of the extruding portion of a preferred plasticizer in axial section.

FIG. 4 is a detail view in elevation of the delivery end of the plasticizer.

The char used is in particles desirably averaging no more than one-eighth or one-quarter inch in accordance with conventional practice. The resulting particles of char are porous and different chars have different porosities based on their mode of being produced and the original products from which they are made. This has a bearing on the procedure as will be noted hereinafter.

One embodiment of the invention contemplates the use of so-called y ash charcoal. This charcoal is already of small particle size. It is -produced in the combustion of bark and other waste. It is most often found as a by-product in the operation of a pulp mill. Some mills feed bark and other waste into their `regular boilers while others use special boilers to dispose of the waste. In either case, the waste is used as fuel to generate steam used in the mill but there is an air pollution problem due to the large quantity of charcoal given off in the form of smoke and fly ash. In the past, this material has been collected and is commonly re-injected into the boiler. For the purposes of the present invention, the collected material is screened to remove particles of sand and ash and the resulting ily ash charcoal is used in the manufacture of briquets.

Another embodiment contemplates use of ychar made from lignite or coal by drying and carbonizing to reduce water content and volatile matter. Carbonizing processes for making fuel chars as performed in standard multiple hearth furnaces, properly controlled, are appropriate. Typical carbonizing retorts which are widely known and have been used commercially are the Badger-Stafford and Lurgi retorts.

Low porosity high density chars referred to herein are those weighing twenty to thirty pounds per cubic foot. These include chars of coal and lignite. High porosity low density chars are those weighing ten to twenty pounds per cubic foot and include those made from wood, y ash of sawdust and bark, peat and other vegetable matter.

To the particulate char, the nitrate is added. In the case of sodium nitrate, the amount added is approximately twenty to thirty percent of the weight of the sulphite solids used as the binder. Twenty-five percent is ideal. If other nitrates are substituted, the amounts will be varied in accordance with their mol value. The ingredients are mixed together. The nitrate may, if desired, be pre-mixed with the water. Otherwise the nitrate is mixed in dry form with the char and water is then added in sufficient quantity to ll the voids or capillary openings in the surfaces of the char particles. The amount of water should be such that the total water ultimately present in the wet mix should be about fourteen percent of the total wet weight for low por-osity chars and twenty percent of the total wet weight for high porosity chars. The respective ranges are preferably about twelve to sixteen percent and eighteen to twenty-two percent. The term total water includes not only the amount added at this time but the water present in the concentrated sulphite liquor (about fifty percent of the weight of the liquor used) and the water present in the char itself (from about two to about ten percent).

It is important that the free water added at this time must be in the char before the sulphite liquor is added. Yet it is related to the amount of water in the sulphite liquor in such proportion that after the sulphite liquor has been introduced the total water will not besmaller than twelve or eighteen percent respectively, or greater than sixteen or twenty-two percent respectively, of the wet mix.

It will be noted hereinafter that low porosity chars also require that substantially less sulphite liquor be used to effect binding. In practice, I use about half as much sulphite in low porosity chars as in high porosity chars.

While it is important that sufficient water be added in advance of the sulphite liquor to fill the voids or capillary openings, nevertheless it is important, particularly on high porosity chars, that extra water not be present or the mix will be unable to assimilate suicient quantities of liquor to acquire bond strength. Also, too little Water present allows the sulphite liquor to penetrate the char particle pores causing the briquets to crack either during molding or drying. Proper water content allows the right amount of liquor t-o be utilized to effect good surface bonding without undue penetration of the char particles.

The fly ash charcoal above referred to is a high porosity char. In practice, my briquet mix contains about twenty percent total water when made with fly ash charcoal. About one-fifth of this represents free water. The nitrate is preferably dissolved in the free water, although, particularly if the ultimate product is to be carbonized, the nitrate may be used dry.

The sulphite liquor as produced originally by a paper mill contains more than fifty percent water. To assure that enough free water is present to fill the voids of the char before the sulphite liquor is added, While still maintaining total water within the range indicated, the sulphite liquor used in this process should be dried to about fifty percent water before being added. The percentage is not highly critical since adjustment of the amount of free water may be made to compensate.

Before the sulphite liquor is introduced, the wet mix is stirred well to disperse the free water. The sulphite liquor comprising about fifty percent water is then added in an amount such that in a normal product the sulphite liquor solids represent from eight to twenty percent of the total mix weight on a dry basis. This is a critical relationship, being dependent upon the porosity of the char and its volatile matter content. In practice, I prefer to use sulphite liquor solids in the proportion of about nine percent by weight with lignite char and about seventeen percent with fly ash char.

In either case, the nitrate solids used amount to approximately twenty-five percent by weight of the solids of the sulphite liquor.

If there is too little sulphite liquor used, the briquet will lack wet and dry strength and will readily ignite spontaneously during the drying process. If there is too much, the mix will be too sticky to handle conveniently during mixing or briquetting. Even with the proportions of sulphite liquor specified as desirable, spontaneous combustion can be expected to occur during high temperature drying unless the amount of nitrate present is adequate to assure the desired chemical reaction.

Briquets made with two much sulphite liquor have poor appearance and tend to crack open during drying. However, even briquets requiring high sulphite liquor percentage for bonding (because of high porosity char) do not ordinarily exhibit cracking when burned. In the case of the y ash or lignite char, no cracking whatever has been experienced. Even if they crack open, the briquets will not break in two and the portions of the briquet separated slightly by the crack tend to retain their firmness if full advantage has been taken of the principles herein disclosed.

After the sulphite liquor is introduced, the mix is stirred lightly. It is subjected to moderate densication by compaction or plasticizing, maintaining uniform densityvwhile avoiding any such compaction as would reduce particle size needed for briquet strength. The plasticizing operation can be performed manually but is desirably performed in a special extruder automatically controlled as hereinafter described. The properly plasticized mix has a dry appearance as its leaves the `dual heads in short, chip-like, tlat extrusions. In these extrusions, the mix is densilied and the components well distributed.

If the material were unduly compacted at this stage, the briquets would crack in the Wet or dry state, as the compressed char particles try to return to their original shape. In the case of briquets made from fly ash char, cracking is not a problem but undue compaction is to be avoided because of the difficulty of ignition. Ignition is facilitated if compaction is very light. Disintegration during handling can be avoided by adding minute quantities of lime in any form. I have used one-half of one percent of slaked lime added with the free water.

Also this plasticizing aligns and Orients, most advantageously, the size range of char particles to get maximum green, dry and burning strength.

The material is then briquetted in a conventional roll press having a vertical screw or paddle stuler which forces the proper amount of mix into each cavity of the press to mold a briquet with a tight surface for appearance and prevention of spontaneous ignition in the drier. Finally, the wet briquets are dried in a standard tunnel air drier under operational conditions which may advantageously diler markedly from present practice.

The practice of my invention differs somewhat according to whether the briquets are to be carbonized or not. Particularly in the case of barbecue briquets made from fly ash charcoal, it may be desirable to leave the briquet uncarbonized.

It is an important factor of the present invention that the desirable carbonization of the binder which protects the briquet from disintegration in the presence of moisture is achieved, according to the present invention, without excluding oxygen and at temperatures so elevated and for such lengths of time that the binder is carbonized.

Heretofore, experimentally, at least, carbonization of briquets has been performed previously but has required exclusion of oxygen if the briquets were held at temperatures as high as 300 F. for any appreciable time.

Conventionally, starch or our bound wet briquets enter a drier with a low inlet temperature, about 250 F. and are gradually raised to a maximum temperature of about 300 F. to 325 F. in one hour. These briquets are then maintained at such temperatures for one-half hour and then cooled to an exit temperature of less than 200 F. in another hour. Total elapsed time in the drier is thus about two and one-half hours with gradual heating and cooling and maximum time at high heat of onehalf an hour. These conventional briquets must be heated slowly to prevent surface sealing and accompanying cracking during moisture release. They cannot be raised to temperatures much in excess of those specified and ,can be held for only a short period of time or the briquets will spontaneously ignite. These briquets must also be cooled slowly to prevent cracking and the finished product may not leave the drier with a temperature over 4200" F. for safety. Such drying as described above requires a proportionally longer time and often the briquets leave the drier with moisture content considerably greater than the accepted standard of four percent. This standard is recognized as the maximum moisture limit allowable to preclude shipment of wet product to customers.

According to the present invention, there is no slow rise of temperature and no limitation to 325 F. Charcoal briquets properly bound with sulphite liquor and nitrate as herein disclosed may enter such an air drier at any temperature up to about 450 F. In fact, the preferred temperature of the entire drier, even at the inlet, is 450 F. Drying and reacting takes about seventeen to twenty minutes. No surface sealing and cracking of the product occurs, as the briquet surface, although becoming hard, maintains its porosity. Y

Assuming that the briquets are to be carbonized, they are then maintained at this temperature for about twenty minutes more to effect carbonization. With high porosity char, forty minutes total exposure is about the maximum. Within this period (or a much longer time with low porosity char) there is no apparent tendency to ignite spontaneously. Total time in the drier thus averages from a minimum of about fifteen minutes to a maximum of about forty minutes or less.

To cool the briquets rapidly from 450 F., they are sprayed with a iine mist of water which reduces their temperature to F. in ten minutes. While the briquets of the present invention may be cooled conventionally by subjecting them to a blast of cold air for about a half hour, it is a great advantage to be able to cool them rapidly. The carbonized product is fully water lresistant and the uncarbonized product is not. However, if the water is used in the form of spray, it is possible to water cool both products because they are so effectively bound that they resist cracking when rapidly cooled.

Prior to water cooling, the briquets have zero per cent moisture and due to their high temperature, they absorb only about one to two per cent moisture on spray cooling. Further humidilication in moist atmosphere to three per cent moisture may be done if desired.

The high drying temperature employed in this process not only reduces the time in the drier (which is important commercially) without danger of spontaneous ignition but almost completely drives out any sulfurous odors remaining in the reacted binder. Such odors have heretofore made it impractical to use sulphite liquor as a binder for briquets of the type used in cooking. The product of the present invention may give off some slight odor during ignition but before it reaches the full combustion required for cooking, it has no remaining odor whatever.

Briquets previously known could not lbe dried and heated in the manner contemplated by the present invention without igniting. Even at the temperatures conventionally used in drying charcoal briquets, a briquet containing one per cent of nitrate by dry weight is extremely hazardous. When ignited, it will burn ercely and may spin like a pinwheel.

In the formula herein disclosed, almost all of the nitrate appears to -be used in oxidizing the sulphite liquor to improve its binder characteristics. Thus no excess of nitrate remains to cause re hazard. The oxidation of the sulphite liquor by means of the nitrate is a very important factor in eliminating objectionable odor. If the nitrate is below twenty to twenty-tive per cent of the weight of the solids in the spent sulphite liquor, the briquets smell strongly. In fact, at least twenty-tive per cent is a desirable amount of nitrate.

If the product is fully carbonized, ignition is aided by having a slight excess of nitrate uncombined in the briquet in dry form. If the binder in the product is to be uncarbonized it is not only unnecessary that the nitrate be added dry but it may even be undesirable because the dry particles at the surface of the briquet tend to glow to a degree that they do not do if the nitrate has been completely dissolved in water and reacted with the sulphite liquor.

The fact that my improved briquets can be dried at high temperature'is a very important consideration in eliminating odor. The high temperature treatment, even in the case of the briquet with binder not fully carbonized, is adequate to drive olf most of the objectionable odors. By this I mean that the sulfur compounds are converted to products such as sulfur dioxide which is given off as a vapor or to sulphates or other precipitates which do not burn or give olf odor at the temperatures at which briquets are burned in barbecuing. However, excessive carbonization will burn out the bonding material with the result that the briquet loses Weight-and strength. Experience shows that the briquet with uncarbonized binder has higher strength than as if the binder is carbonized, although its water resistance may be somewhat less.

If full advantage of the disclosures herein is taken, my improved briquets are clean since they do not dust or leave marks. They are very water resistant if the binder is carbonized, being capable of maintaining their integrity even when immersed in water over long periods. They are smokeless, this being a very desirable factor in briquets made for barbecue usage. Finally, they are very strong when burning as compared with previously known commercial briquets.

If the amount of nitrate solids present exceed thirty per cent of the sulphite solids, this will preset the sulphite liquor with the result that the sulphite liquor cannot be properly dispersed in the mix, and unreacted nitrate is present in the product.

The preliminary addition of free water in advance of adding the sulphite liquor is to ll the voids of the char particles so that the binder which is the reaction product of the sulphite liquor and the nitrate will be as much as possible limited to the surfaces of the char particles instead of being adsorbed deeply into the pores or capillary openings thereof. Whether the nitrate is used dry or dissolved in water, the desired reaction-product binder is quite largely on or close to the surfaces.

The entire operation as above described can be performed either as a batch or a continuous process according to the iow sheets shown in the drawings.

The batch mixing process A batch of char is placed in the container 6 and to it is then added the dry nitrate carefully weighed to maintain the proportions indicated. After the char and nitrate have been mixed by means of mixer `8, a carefully measured batch of water is introduced in the proportions above speciiied and the mixing continued until the wet pre-mix is thoroughly homogeneous. In the alternative procedure discussed above, the nitrate, proportioned by weight to the char, is incorporated in the water prior to the admixture of the water with the char. Only at that point is the metered sulphite liquor added. The well-mixed batch is then dumped as indicated by the arrow 10 into the hopper 12 which feeds the paddle conveyor 14 driven by motor 16 under manual control of rheostat 18.

At the discharge end of the paddle mixer 14, the material is delivered as shown by arrow 20 into a plasticizing conveyor 22, which is preferred to a hand plasticizing operation because the densification of the mix at this point is quite critical and it can be accurately controlled by the apparatus shown. Details of the discharge end of this conveyor are shown in FIGS. 3 and 4. A feed screw 24 driven by motor 26 `at speeds controlled by rheostat 28 discharges material through a pair of extruding dies 30 and 32 which have variably registrable openings 34 and 36, respectively. FIG. 4 shows these openings in partial registry. The die 32 is rotatable within the retaining ring 38 by means of a crank pin 40 and link 42. Clockwise rotation of the die disk 32, as viewed in FIG. 4, will decrease the registration of the openings 34 and 36 while counterclockwise rotation will increase the openings. By increasing or decreasing the composite openings, the density of the extruded mix may be decreased or increased.

The density is automatically controlled by means of an instrument 44 which has a pickup coil 46 associated with the line 48 to the motor 26. By means of this pickup coil, the instrument 44 senses the ampere load on the motor 26, such load increasing as the mixture in the plasticizing mixer22 becomes denser. If the mixture becomes less dense, the load on the motor decreases. Accordingly, the instrument 44, sensing the load on the motor, controls a regulating motor 50 which corrects for any change in density by rotating the disk 32 to increase or decrease the registration of ports 36 with ports 34.

The extrusions through the registering ports are kept in short chip-like form by a blade 54 connected with the shaft extension 56 of screw 24. As the screw rotates, the blade 54 wipes across the inner surface of the stationary extrusion disk 30 to sever the extrusions of material passing through the several ports 34.

An additional conveyor section S8 receives the short extrusions beyond the extruding die sets 30, 32 and remixes these into homogeneity before they are discharged as indicated by the .arrow 60 to be elevated by the elevating conveyor 62. The mix is delivered as indicated by `arrow 64 into the hopper 66 of a conventional briquetting press. The briquetting press rolls 68 and 70 are driven by motor 72, which may be controlled Ias to speed by a rheostat 74 subject to controller 76. The controller functions according to the response of low and high level probes 78 and 80 in the hopper to increase the speed of the briquetting rolls as the depth of rnix accumulating in the hopper is increased, and vice versa. The drive 82 from motor 72 operates the stuffer 84 which forces the mix into the briquetting rolls 68, 70. The briquets discharged from the briquetting rolls as indicated by arrow 86 are then taken to the tunnel drier above described.

The automatically controlled continuous process I can use either a vibratory or a volumetric feeder at 90 driven by motor 92, which feeder continuously delivers crushed char from the hopper 94 onto the scale platform conveyor 96 of a so-called weightometer. The weight of char on the Weightometer is continuously impressed as indicated diagrammatically by the line 98 upon an instru- -rnent 100 which integrates the weight with the moisture content of the char as lread by a moisture scanning instrument 102. The reading of instrument 102 is communicated to integrating instrument 100 as indicated by the dotted line 104. A reading representing the dry weight of the char is then communicated to the master controller as indicated diagrammatically by line 106.

The master controller 110 regulates the functioning of an instrument 112 to which it is connected as indicated diagrammatically by the line 114. The instrument 112 has a connection diagramm-atically indicated by line 116 with a controller 118 for rheostat 120 which varies the speed of motor 92, the net effect of this arrangement being to maintain char input feed at a constant dry rate.

The char fed at a uniform dry weight is discharged from the weightometer conveyor as diagrammatically indicated by arrow 122 to enter a pre-mix paddle type conveyor 124 in which nitrate is now added. The nitrate hopper is shown at 126 and the nitrate feeder at 128. The dotted line 130 from controller 132 indicates that the controller regulates the operation of the feeder. Such regulation is, in turn, controlled from another controller 136 as indicated by the broken line 138 and hereinafter described.

After the dry nitrate and the dry char have been mixed, water is added to the mix in the paddle conveyor as indicated by the arrow 140. The water feeder is diagrammatically shown at 142. It is regulated by a controller 144 as indicated diagrammatically by the broken line 146. The controller 144 responds to several factors including the amount of water already present in the char as read by moisture scanner 102. It will be remembered that the scanner affects the operation of the instrument 100 which debits the water flow controller 144 with the moisture already present in the char, the connection between instruments 100 and 144 being diagrammatically indicated by the broken line 148. The instrument 144 also responds to the flow of char on a dry weight basis as read by the master controller 110, the value being communicated to the instrument 144 as indicated diagrammatically by the broken line 150.

If the nitrate is to be added wet, the procedure varies from that above described in that the nitrate is simply 9 added from the feeder 128 to the water instead of being added dry to the char. The mixture of the water with the char, thereupon incorporates the nitrate in the char along with the water.

After the wet pre-mix is complete, the spent sulphite liquor is added as shown by `arrow 152. This is carefully proportioned by a rotary pump feeder 154 whose operation is regulated by the instrument 136 and indicated diagrammatically by the broken line 156. Instrument 136 is also responsive to the d ry weight of the char constantly fed from the weightometer into the mixer 124. The connection from the master controller 110 to the instrument 136 is diagrammatically illustrated by the broken line 158. If the nitrate is incorporated dry, it is this instrument that also proportions the dry nitrate feed as indicated by broken line 138. If the nitrate is incorporated wet, it will already have been mixed with the water.

The paddle mixer shaft 160 may be driven by motor 162 manually controlled by rheostat 164.

The operation from this point on is identical with that described in connection with FIGS. 1, 2, 3 and 4.

It will be understood thatthe instruments will be adjusted to maintain the proportions within the ranges indicated as critical and to produce uniformity of results.

'I'he product before drying has a moisture content approximating fourteen percent in the case of lignite char and twenty percent in the case of fly ash char as compared with twenty-eight to thirty-eight percent moisture in conventional briquets. The finished product, prior to water cooling has zero percent moisture and as discharged from the apparatus has a total of only about two percent moisture. This compares with prior practice in which the briquets leave the drier with a moisture content which may be greater than the accepted limit of four percent.

The final product of the present invention does not readily chip, and does not dust It can be handled without soil if the binder has been carbonized. It is readily ignited, burns uniformly, is without odor when in full combustion, `does not smoke, and with carbonized binder resists disintegration in the presence of moisture.

In View of the above noted fact that various components of the spent sulphite liquor including water and sulphur and other oxidizable elements are evaporated or consumed in processing, it will be understood that the reference to spent sulphite liquor as an ingreditent of the briquet defined in the accompanying claims is intended to refer to the essential fractions of the sulphite liquor which remain in the reaction product which serves as the binder component of the briquet.

I claim:

1. A briquet for barbecuing food and containing char and a binder which is a reaction product of an oxidizing nitrate and spent sulphite liquor, said briquet containing by weight eight to twenty percent of liquor solids and the equivalent of approximately twenty-five percent as much sodium nitrate solids as sulphite liquor solids.

2. A briquet containing char and a binder which is a reaction product of an oxidizing nitrate and spent sulphite liquor the char comprising discrete particles, the bonding material being primarily confined to the surfaces of such particles.

3. A briquet yaccording to claim 1 in which the sulphite liquor solids are present in the approximate amount of eight to ten percent yby weight of the dry weight of the briquet and the char is a low porosity char, the nitrate being the equivalent of sodium nitrate approximating twenty-five percent of the weight of the solids of the sulphite liquor.

4. A briquet according to claim 1 in which the sulphite liquor solids represent Iapproximately fifteen to twenty percent of the dry weight of the briquet and the char is a high porosity char, the nitrate solids being 10 equivalent to a percentage of sodium nitrate approximating twenty-five percent of the weight of the solids of sulphite liquor, the nitrate solids being used in general proportion to the density of the chars.

5. A briquet according to claim 1 which contains materially less than four percent moisture and has sulphite liquor solids proportioned to the density of the char and approximating at least about 8.5 percent of the dry weight of the briquet, and the nitrate is in proportions comparable in oxidizing value to sodium nitrate and in amounts which, in the case of sodium nitrate, approximate twenty to thirty percent of the weight of solid content of the sulphite liquor.

6. A briquet according to claim 5 in which the nitrate is sodium nitrate and the solids represent approximately twenty-five percent of the weight of the solid content of the sulphite liquor.

7. A briquet according to claim 5 which is substantially free lof sulfur compounds vaporizable in the combustion of the briquet, all components of the char and binder ybeing carbonized and the briquet being moisture-resistant, hard, free from dust, and free from odor when in full combustion.

I8. A method of making char briquets for barbecuing food which method comprises the steps of mixing 'with particular char free water sufiicient to fill voids and capillaries of char particles and thereafter adding spent sulphite liquor and reacting such liquor in situ with an oxidizing nitrate to form a binder precluded lby the water already in the particles from substantial entry into the voids and capillaries of the char particles, and thereafter mixing the char and binder, and subsequently briquetting the mix.

9. A method of making char briquets according to clai-m 8 in which the nitrate and char are pre-mixed dry before the Water is added.

10. A method according to claim 8 in which the nitrate is mixed with the Water before the Water is added to the char.

11. A method of making char briquets according to claim 8 in which the mixing after spent sulphite liquor is added lightly densiies the mix to a degree calculated to disperse component ingredients of the mix and to orient char particles without undue compaction thereof in the briquet.

12. A method according to claim 8 followed by ldrying for approximately twenty minutes in air at temperatures which materially exceed 400 F. to produce a product in which the Abinder is carbonized and from which odorous components are substantially eliminated.

13. A method according to claim 12 in which the drying is at a temperature at least approximately 450 F.

14. A method according to claim 12 followed by rapid cooling by spraying the briquets with water mist.

15. A method of making for food -barbecuing purposes char briquets from a wet briquet mix which method comprises making a pre-mix of particulate char and water, adding to the pre-mix an oxidizing nitrate in an amount equivalent in oxidizing value to sodium nitrate which comprises twenty percent to thirty percent by weight of the solid component of the spent sulphite liquor hereinafter mentioned, the water being in ya range of proportions of twelve to twenty-two percent of the total wet briquet mix weight; thereafter completing the briquet mix by adding spent sulphite liquor approximating fty percent water content in an amount such that the total solids in the spent sulphite liquor will be within a range of eight to twenty percent of the weight of the dry components of the briquet mix; plasticizing the briquet mix to .achieve moderate densiication short of undue reduction in the particle size of the char, and thereafter driving off water and reacting the sulphite 11 12 liquor with the nitrate on the surfaces of the char par- References Cited ticies to form a reaction product -binder by heating the FOREIGN PATENTS briquet m1x at temperatures materlally m excess of 400 F. to complete said reaction Without combustion. 470,477 1/1929 Germany- 16. A method according to claim 15 in which the ni- 5 OTHER REFERENCES trate is added to the water in advance of mixing with the Char. Handbook of Brquetting by Franke, v01. 1, Grin and 17. A method according to claim 1s in which the bri- CO-Ltd-Londom1917PP'45 and 46- quets are dried and heated While exposed to air .at teml. peratures approximating 450 F. to 460 F. until said 10 DANIEL E'WYMANPHmmy Exammer' binder is carbonized. C. F. DEES, Assistant Examiner.

Claims (1)

1. A BRIQUET FOR BARBECUING FOOD AND CONTAINING CHAR AND A BINDER WHICH IS A REACTION PRODUCT OF AN OXIDIZING NITRATE AND SPENT SULPHITE LIQUOR, SAID BRIQUET CONTAINING BY WEIGHT EIGHT TO TWENTY PERCENT OF LIQUOR SOLIDS AND THE EQUIVALENT OF APPROXIMATELY TWENTY-FIVE PERCENT AS MUCH SODIUM NITRATE SOLIDS AS SULPHITE LIQUOR SOLIDS.

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