Combustion of fuels

Patented Sept. 17, 1935

2,014,686

UNITED STATES PATENT OFFICE

2,014,686 COMBUSTION OF FUELS Eugene Lubovitch and Jean Midor Fiescbi, Paris, France; said Fiescbi assignor to said Lubovitch No Drawing. Application August 18, 1932, Serial No. 629,308. In France August 27, 1931

Claims.

Our invention relates to the combustion of carbonaceous fuels in furnaces and hearths of all kinds for industrial or home use. In order to make such combustion as complete as possible 5 a more or less large excess of air had to be supplied up to now. This leads to the disadvantage that the temperature of the hearth or furnace is lowered and that unburnt volatile substances escape, On the other hand it is known that part 10 of the fuel is lost unburnt during the formation of ashes and slag.

In order to overcome these drawbacks it has been proposed to add to the fuel mixtures of different substances such as metal nitrates or 15 chlorates or the oxides of manganese, iron, chromium. It has been found, however, that these substances when employed singly or in the mixtures known so far have only a comparatively small influence on the combustion. Besides these 20 were mixed quite unsystematically as the effect of the different substances was not recognized and consequently there have been proposed some mixtures, which contained up to ten different components. It is also unknown up to now that 25 mixtures of this kind were employed in shaft furnaces where the fuel is brought in direct contact with the material to be treated, undoubtedly because some of the chemicals commonly used for enhancing the combustion, like the sul30 phides or phosphates, would have, a detrimental influence upon the ore to be melted.

We have found that the combustion process may be considerably improved by adding mixtures of substances belonging to certain groups 35 of substances which partly act as oxidizing catalysts, (i. e. substances which, without apparently losing their own oxide content to the fuel, nevertheless promote the absorption of the atmospheric oxygen by the fuel); partly as promotors 40 of the catalysts, (i. e. substances which, without containing themselves any oxygen, nevertheless seem to increase the catalytic action of any oxidizing catalysts present); partly as immediate oxidizing agents or igniters (i. e. substances which 45 at the oven temperature yield their own oxygen to the fuel or the available atmospheric oxygen and by doing so directly accelerate the combustion of the fuel). The action of these combined mixtures exceeds by far the effects which could 50 have been expected from the known action of some of the individual components. The new compositions comprise as their main constituents:

(1) Oxides or salts of the rare earth metals or of metals having properties similar to those 55 of the rare earths, such as the oxides or salts of (Cl. 44—4) cerium or thorium, in a form occurring in nature, e. g. in the form of monazite, which is a phosphate containing rare earths, or as an artificial product. Besides these substances the oxides of barium must be mentioned as especially potent 5 oxidizing catalysts, whose use is equivalent to that of the oxides of rare earth metals;

(2) An alkali chloride, such as potassium or sodium chloride, which presumably acts as a promoter. 10 (3) Furthermore, salts having an oxidizing action. These salts in being decomposed transfer their oxygen wholly or in part to the fuel and act as promoters of the catalytical substances or as igniters or as both promoters and igniters. 15 For instance, the nitrates or permanganates or chlorates of the alkali or alkaline earth metals may be used for such purpose. Different salts of this kind may be used simultaneously. Some of these substances may be regarded both as imme- 20 diate oxidizing agents and as oxidizing catalysts, e. g. the alkali or alkaline earth permanganates. . To these main constituents of the new composition of matter, which represent the three abovementioned classes of substances, in the order 25 named, other substances may, or may not be added, namely:

(4) Compounds of metals which can form different degrees of oxidation, for instance the oxides or other derivatives of manganese, iron, 30 •lead, copper, or mixtures thereof. All metal salts or oxides mentioned under 1 and 4 occur in different reversible degrees of oxidation. Their action which resembles that of strong catalysts, may be.explained in such a manner that the lower 35 oxides are temporarily oxidized higher by the oxygen of the air conducted over or through the . hearth or furnace, whereupon the oxygen set free again is transferred to the fuel in the nascent form, e. g. in an especially active form. In this 40 way the metal compounds are retransformed into the lower oxidized state (or into the metallic state), and the whole process repeats itself continuously, associations and dissociations occurring simultaneously. ⁴⁵

Instead of the compounds described above under (1) and (4), such compounds may be used, which at the temperature of the hearth or furnace form the oxides described and required.

The addition of merely a small amount of the 50 new composition is sufficient for a considerable amount of fuel, because part of the reaction with the fuel to be consumed is not so much a chemical one in the ordinary sense, but a catalytic action, where a small amount of ingredients exerts 55

2,014,686 an Indefinite effect, without appreciably lessening the amount or changing the composition of the agents.

The presence of such a mixture facilitates the 5 oxidation of the fuel. In consequence thereof the amount of air which up to now had to be supplied in excess to the hearth or furnace may be greatly diminished. The incandescent mass is no longer cooled by the stream of superfluous 10 air and the losses of calories in the waste gases are diminished.

On the other hand the oxygen, taken up by the added composition from the air is given off to the fuel in the nascent form. In that way the burn16 ing process is highly intensified and a higher temperature is reached in the glowing mass. For instance, the pressure in a steam boiler is raised more rapidly by using coal with an addition according to our invention than with ordinary coal. 00 Gaseous hydrocarbons are by this method burnt within the hearth or furnace instead of being drawn off uhignlted by the waste gases.

From the foregoing it becomes evident that a better localized, easier and more complete com26 bustion is obtained with a minimum excess of air. It is observed that the amount of unburnt particles in the ashes and' slag of the hearths and furnaces is decreased. It becomes, therefore, possible to use inferior fuels by raising the efficiency 36 of the hearths and furnaces.

The mixture described here before is prepared as a powder. For its, use it may be brought into aqueous solution or suspension and sprinkled onto the fuel in order to be distributed .evenly 35 in this latter. The powder; may be added also in a suitable way in the preparation of briquettes, agglomerates and the like.

Example

As an example, the mixture according to our invention may be composed as follows:

Percent

Cerium oxide_______.__________________10 to 20

Barium nitrate______________________30 to 40

Sodium chloride______________________40 to 60

One to two kilograms of this mixture per ton of the fuel are sufficient in order to obtain a far more complete combustion with a minimum ex_M cess of air and to have the other advantages described above.

The present invention Is of special importance for use In shaft furnaces in which the materials to be treated are mixed with the fuel and in „ which the disadvantage of the coal being incompletely oxidized is especially great. The presence of the new composition has no detrimental Influence whatever on the product of the furnace work since it does not contain any In_m jurious components such as sulfur, phosphorus, and the like.

The scope of applicability of our invention is large and extends over hearths for Industrial and home use and different kinds of furnaces (rotary „ furnaces, so called Hoffmann furnaces, (annular furnaces for roasting limestone and the like) metallurgical furnaces, etc.). It is furthermore suitable for every kind of natural or artificial solid, liquid or gaseous fuel.