US3337312A - Solid fuel coatings - Google Patents

Description

United States Patent Office 3,337,312 Patented Aug. 22, 1967 3,337,312 SOLID FUEL COATINGS Tibor George Perlus, Toronto, Ontario, Canada, assignor to Douglas Louis Breithaupt No Drawing. Filed Dec. 9, 1963, Ser. No. 329,261 2 Claims. (Cl. 44--6) This application is a continuation-in-part of my application Ser. No. 75,936 filed Dec. 15, 1960, now abandoned.

This invention relates to a coating for solid carbonaceous fuels and more particularly to a readily ignitable coating which on burning ignites the coated fuel. The coating is especially suitable for solid carbonaceous fuels in small pieces or lumps such as charcoal or charcoal briquettes which are employed for cooking foods over an open fire such as with barbecue equipment.

The use of solid carbonaceous fuels for general heating or cooking purposes is well known and more recently charcoal briquettes and the like have been used for cooking foods, such as meats, either indoors or outdoors. The principal difliculty encountered in using charcoal and other solid carbonaceous fuels in lump or briquette form is that they are not easily ignited and require a more readily combustible material to ignite them. Liquid starting fuels such as, for example, the so-called lighter fluids, are currently in common usage for igniting solid fuels. But, the lighting technique is both laborious and inconvenient and the fluids are dangerous when used without great care, owing to their highly flammable and flame producing characteristics, especially in view of the large quantities that are required to ignite the solid fuel. Moreover, such fluids generally are expensive and usually burn with an unsavory smell or taste which is often imparted to the foods being cooked.

Various means have been proposed to kindle solid fuels to overcome the disadvantages of using lighter starter fuels.

U.S. Patent No. 741,728, Oct. 30, 1903 to Shimper teaches the use of an oxidizing agent, potassium nitrate, and other additives which are mixed intimately with a large proportion of ground charcoal and then pressed into briquettes. However, the fuel does not provide desirable burning characteristics. The oxidizing agent in the proportion taught, being dispersed throughout the body of the fuel, does not reduce the igniting point of the fuel enough to provide easy kindling. Also the presence of the oxidizing agent throughout the body of the fuel results in rapid burning after ignition providing higher temperatures than desired for cooking and reduced burning time for the fuel. The presence of the potassium nitrate throughout the fuel body during burning results in unpleasant nitrous fumes being evolved and also contamination of the food.

U.S. Patent No. 1,983,560, Dec. 11, 1934 to Palmer discloses the use of fire kindling briquettes to ignite a solid fuel. Such briquettes are designed for use with conventional fuels such as coal or coke for starting an ordinary furnace or grate fire. However, these briquettes do not provide the advantage of igniting the fuel evenly and fully over the entire surface of the fuel to provide the even heating desirable for cooking.

It may be suggested that the briquettes of the Palmer patent be used as the fuel per so. However, as these briquettes contain the oxidizing agent, sodium nitrate, dispersed throughout the fuel body in a large proportion they would burn rapidly and provide high temperatures which are undesirable for cooking. The ingredients of rosin, pitch and light fuel oil in the fuel body will also make the fuel unsatisfactory for cooking because of the odorifer-ous fumes produced which would be picked up by the food.

As an alternative other proposals involve solid fuels which have been coated or impregnated with another material.

U.S. Patent No. 2,822,251, Feb. 4, 1958 to Swinehart et a1. relates to a charcoal briquette coated with a pigmented and plasticized water soluble cellulose ether composition in order to provide a clean, dustless, and n0nsmudging fuel. However, although the burning characteristics may be improved, the coating will not provide a very readily ignitable fuel. In order to provide enough heat to raise the temperature of the briquette to its ignition point a very thick coating of cellulose ether would be required. Thus, the expense of using this coating is relatively great.

U.S. Patent No. 2,916,364 to Grimes describes a combustible coating in partially gelled form of a petroleum fraction and an aluminum soap. Such a coating is highly inflammable and is thus very dangerous and in this respect does not overcome the disadvantages of using the liquid starting fuels as described above.

U.S. Patent No. 2,948,594, Dec. 10, 1957, to Doyle deals with a felted fibrous pulp coating to provide a selfstarting and clean briquette. However, a very large quantity of fibrous pulp would be required to provide a high enough temperature to ignite the fuel core. It is thus expensive to provide such a heavy coating. Such a coating will also produce undesirable flames when ignited. It has been found experimentally that four times the theoretical quantity of priming fuel, such as proposed by Doyle and Swinehart, is needed to provide enouglr heat to ignite the briquette. For example, if calculation shows that 1,000 B.t.u.s are needed to raise the temperature of the surface of the briquette to its ignition point, enough coating will be needed, in practice, to supply 4,000 B.t.u.s.

U.S. Patent No. 2,816,013, Dec. 10', 1957 to Powell discloses a coated and impregnated charcoal fuel body obtained by impregnating a charcoal briquette with an ordorless mineral spirit and coating the impregnated briquette with an organic polymerized material such as cellulose nitrate. In essence, Powell is coating a commonly used lighter fluid (mineral spirit) so that the fluid will not be exposed to atmosphere prior to use. The coating could be considered as a retainer for the lighter fluid. Lighter fluids, as described above, have mny disadvantages whether they are sprayed on before ignition or impregnated as taught by Powell. Such fluids are highly flammable and are thus very dangerous. Large quantities of fluid are required to provide enough heat to ignite the fuel. Also there would be a fire hazard during storing or handling as the mineral spirits would evaporate into the atmosphere if the retainer'or coating is broken.

An object of the present invention is to provide a fuel coating which is capable of being ignited by a burning match, lighter or other common means and which ignites the solid fuel.

A further object is to provide a relatively inexpensive coating which may be simply and readily prepared and applied to a solid carbonaceous fuel.

A still further object is to provide a coating characterized by being non-toxic, dustless and substantially nonvolatile thereby permitting clean and safe handling, storing and packaging of the fuel.

A still further object of this invention is to provide a solid fuel coating which will not produce any objectionable odours or appreciable flame or smoke. The coating will also not appreciably affect the cooking or heating qualities of the solid fuel as the solid fuel core will not burn more rapidly or at higher temperatures than normal and the coating will not impart any unsavory smell or taste to foods being cooked.

A still further object is to provide a solid fuel coating which ignites the solid fuel evenly and fully so that initial combustion takes place over substantially the entire uppermost layer of the fuel to provide the even heating desirable for cooking.

The foregoing features and others which will become apparent from a reading of this specification, are obtained by a coating prepared in accordance with my invention which essentially comprises a mixture of a combustible film-forming material and a combustion-supporting oxidizing agent. Although the coating is suitable for solid fuels in either lump or briquette form, the following description will be directed to charcoal briquettes for the purpose of explaining the same but not limiting the scope of the invention thereto.

The coating is simply prepared by adding the film-forming material and the oxidizing agent to a volatile vehicle in which the oxidizing agent is soluble to form a liquid composition which may be applied to the fuel by any desired manner. Dipping the charcoal briquettes in the liquid composition or spraying the briquettes with the composition are examples of two methods of application which may be employed. Of course, in the case of the coating ingredients being insoluble in the vehicle, it is necessary that the composition be agitated during the application to the briquette to maintain the coating particles in dispersed and suspended form. Alternately, the solution of oxidizing agent may be applied in one step and the filmforming material in a second step. After the briquette has been coated it is dried, usually by heating, to solidify the coating thereon.

The volatile vehicle may be any liquid which will permit application of the coating. Water is especially suitable for this purpose.

The film-forming material to be used for the coating may be any material which is film-forming, combustible, and has the necessary properties to provide the desired coating. Such materials may be methyl cellulose, starch, or etherified polymeric carbohydrate. It is desirable that the film-forming material possess a strengthening and binding-like quality so that the coating will not be susceptible to crumbling or chalking thereby preventing the formation of dust.

The use of an oxidizing agent on the surface of the solid fuel is the remarkable aspect of my invention. No one has previously proposed the use of an oxidizing agent in this way. The Shimper and Palmer patents, discussed earlier, show the use of oxidizing agents dispersed throughout the solid fuel body and have the accompanying disadvantages. The Powell patent discloses the use of cellulose nitrate in a coating and indicates that this renders the coating more flammable. However, this is not an oxidizing agent and is not taught to be such by Powell. A calculation will show that cellulose nitrate C H O (NO does not contain enough oxygen for its own combustion therefore cannot cause the oxidation of another substance and is not an oxidizing agent. If cellulose nitrate is mixed with another combustible material and is ignited, the combustion of the combustible material will not be furthered because of any oxidation action of the cellulose nitrate but, due to the heat evolved, by the auto-oxidation of the cellulose nitrate the temperature is raised to a high enough level allowing the combustible compound to combine with the oxygen of the ambient air.

Examples of suitable oxidizing agents for use in the present invention are potassium nitrate and sodium nitrate but it should be evident that many oxidizing agents, that is chemical compounds containing excess oxygen which is available for reaction with a combustible compound during combustion and having the desired properties would be suitable. The oxidizing agent supports and promotes the combustion of the coating and the uppermost layer of the briquette. The agent together with the oxygen of the ambient air permits the easy ignition and complete com bustion of the film-forming material.

Enough heat is evolved during the combustion of the film-forming material to raise the temperature of the outer layer of the briquette to the ignition-point, which has been lowered significantly by the high proportion of oxidizing agent absorbed into the surface. The combustion of the oxidizing agent impregnated outer layer will in turn ignite the fuel core which will provide the slow, even and substantially odorless heating desirable for cooking and normally obtained from untreated fuels. The high proportion of oxidizing agent contained in the coating and the outer layer of the solid fuel will substantially reduce the quantity of igniting fuel required by the previously proposed treated fuels. As these igniting fuels are generally expensive the cost is considerably reduced by the present invention. Also, as the oxidizing agent of this invention is applied only at or near the surface of the fuel the total quantity required to lower the ignition point of the solid fuel is much less than would be needed if the oxidizing agent were dispersed throughout the entire fuel body as previously proposed. The quantity of oxidizing agent to be used will depend on the amount required to supplement the ambient air for complete combustion. However, care must be exercised in practicing this invention, to avoid using an amount of oxidizing agent which approaches that required to produce combustion of the coating and the uppermost layer of the briquette without the oxygen of the ambient air. The use of too much oxidizing agent will result in an explosive mixture.

A powdered combustible material which will provide texture and additional heating value to the coating may also be incorporated in the coating. Carbon black or charcoal in a finely divided state are examples of such materials, the use of which will reduce the quantity of filmforming material since the heating value of such substances materially assists in raising the briquette to its ignition temperature.

Combustible fibrous materials may also be employed beneficially in the coating since such materials reinforce the coating and impart porosity thereto which allows permeation of ambient air. Such materials include cellulosic fibers, wood particles, e.g. sawdust, or like materials.

An important feature of the coating of this invention is that it has a greater speed of combustion than untreated charcoal thereby producing a glowing zone which will propagate faster on the surface of the charcoal than on untreated charcoal. The coating provides a full covering of the solid fuel so that the briquette is ignited evenly and throughout its surface layer whereby a more even and faster distribution of heat is produced than in the case of kindlings, or coating or impregnating materials used heretofore.

Another feature of the coating of this invention is that it is non-toxic and therefore can be safely handled by persons. This is particularly important when the fuels are accessible to children.

The coating of the present invention may be readily ignited from the direct application of a single burning match and will burn with an insignificant amount of flame or obnoxious odor. Unlike the so-called lighter fluids and other flammable materials which burn with a flame, the coating minimizes the production of combustible gases and burns with substantially no flame and thus reduces fire hazards and the danger of burns to persons, especially children. This danger is particularly important when the fuel is ignited outdoors so that flames may be blown about by the wind. Moreover, complete burning of the coating results without appreciably affecting the cooking or heating characteristics or properties of the briquette and without imparting any unsavoury smell or taste to foods. The coating with the oxidizing agent is applied only at the surface where it is needed and having served the purpose of igniting the fuel is no longer present. All the igniting coatings, previously proposed, are combustible materials which heat up the surface of the solid fuel whereas this invention provides a material which forms a fast burning fuel on the surface comprising solid fuel and an oxidizing agent without changing the properties of the main fuel body.

The present invention is exemplified by the following examples which are not intended as limiting thereon.

Example 1 uninterrupted surface coating. Drainage of the excess composition was allowed and the briquettes were dried at 110 C.

Example 2 12 g. of laundry starch were cooked at 90-95 C. in 300 g. water until opalescence only was observed. A mixture of 12 g. of cellulose fibers, 6 g. carbon black and 7.5 g. KNO was then added while maintaining vigorous stirring. The resulting composition was allowed to cool and then applied and dried as in Example 1.

Example 3 12 g. of etherified polymeric carbohydrate were cooked at 90-95 C. in 300 g. water until opalescence only was observed. A mixture of 12 g. of cellulose fibers, 6 g. carbon black and 7.5 g. KNO was then added while maintaining vigorous stirring. The resulting composition was allowed to cool and then applied and dried as in Example 1.

Example 4 A mixture of 3 g. methyl cellulose, 25 cps. and 3 g.

methyl cellulose, 400 cps. was dissolved in water according to the procedure of Example 1, 20 g. of soft wood sawdust and 7.5 g. KNO were then added and dispersed in the aqueous solution. The mixture was applied as before.

What I claim as new and desire to protect by Letters Patent of the United States is:

1. A barbecue fuel comprising, in combination, a charcoal core having a member selected from the group consisting of potassium nitrate and sodium nitrate absorbed into its surface and a porous skin surrounding said surface consisting essentially of a mixture of combustible filmforming material selected from the: group consisting of methyl cellulose, starch and etherified polymeric carbohydrates, combustible cellulosic fibres and an oxidizing agent selected from the group consisting of potassium nitrate and sodium nitrate present in an amount sufficient on ignition of the coating to supplement ambient air to efiect ignition of the surface of the core.

2. A barbecue fuel according to claim 1 in which the mixture is formed of substantially equal portions of the film forming material and the fibres.

References Cited UNITED STATES PATENTS 741,728 10/ 1903 Shimper 44-17 1,983,560 12./1934 Palmer 44-41 2,816,013 12/1957 Powell 44-41 2,822,251 2/1958 Swinehart et a1. 44-41 2,916,364 12/1959 Grimes 44-41 X 2,948,594 8/1960 Doyle 44-6 DANIEL E. WYMAN, Primary Examiner. C. F. DEES, Assistan Examiner.

Claims (1)

1. A BARBECUE FUEL COMPRISING, IN COMBINATION, A CHARCOAL CORE HAVING A MEMBER SELECTED FROM THE GROUP CONSISTING OF POTASSIUM NITRATE AND SODIUM NITRATE ABSORBED INTO ITS SURFACE AND A POROUS SKIN SURROUNDING SAID SURFACE CONSISTING ESSENTIALLY OF A MIXTURE OF COMBUSTIBLE FILMFORMING MATERIAL SELECTED FROM THE GROUP CONSISTING OF METHYL CELLULOSE, STARCH AND ETHERIFIED POLYMERIC CARBOHYDRATES, COMBUSTIBLE CELLULOSIC FIBRES AND AN OXIDIZING AGENT SELECTED FROM THE GROUP CONSISTING OF POTASSIUM NITRATE AND SODIUM NITRATE PRESENT IN AN AMOUNT SUFFICIENT ON INGNITION OF THE COATING TO SUPPLEMENT AMBIENT AIR TO EFFECT IGNITION OF THE SURFACE OF THE CORE.

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