US2191592A - Process of reactivating bauxite - Google Patents

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YIELD IN GALLONS PER TON TO SASTM SOLUTION COLOR Feb. 27, 1940.

o. Frrz SIMONS 2,191,592

PROCESS OF REACTIVATING BAUXITE' Filed Sept. 6, 1938 T|ME(HouRs) OF BURNING ()yden Lon/J;

zawzz Patented Feb. 27, 1940 UNITED STATES PROCESS OF REACTIVATING BAUXITE Ogden Fitz Simons, Warren, Pa., assignor to Floridin Company, Warren, Pa., a corporation of Delaware Application September 6, 1938, Serial No. 228,717

9 Claims.

This invention relates to improved methods for reactivating bauxite which has been used-as an adsorbent in the decolorization of hydrocarbons.

. Bauxite has heretofore been used, as a substitute for fullers earth in the decolorization of oils, and it possesses certain advantages, the most significant of which is the capacity for reactivation and reuse. monly effected by heating to a temperature of 1200 F. or higher for a period of time sumcient to burn out all of the adsorbed substances.

0 It has been the practice to reactivate fullers earth at temperatures as close to 1200 F. as possible, but extremely careful control and expensive equipment was necessary to prevent a higher temperature, since the fullers. earth suffers a marked loss in efficiency if subjected to temperatures above 1200 F., regardless of the time of exposure. v

Even with the utmost care, it has been found that the fullers earth in the top half inch layer in the furnace often reached a temperature approximately 200 in excess of the temperature of the main body of the clay. This is due to the a fact that the spent fullers earth contains from one 1%) to three (3%) per cent of adsorbed carbonaceous matter, which is heated to ignition temperatures in the upper portion of the clay bed, with the result that a very rapid oxidation and rise in temperature occurs. For this reason, re-

gardless of the care used in burning, after ten (10) to twenty (20) burns, it is found that the efficiency of the fullers earth has decreased to about fifty per cent (50%) of the efliciency of new fullers earth, and must be discarded for economical operation.

Bauxite, on,the other hand, may be reactivated in a similar manner and, after fifteen (15) or twenty (20) burns, it will suffer only a loss of f about ten per cent (10%) in efiiciency. This is apparently due to the ability of the bauxite to but it has been recently found that the bauxite reactivates much more quickly at higher temperatures, the time of reactivation being inverse-' lyproportional to approximately thefourth power of the absolute temperature.

'With a view to more economical 'operation,

the reactivation has, therefore, been carried out at temperatures in the neighborhood of 1500 F.

This reactivation is com- In spite of the fact that previous knowledge indicated that a temperature of 1500" F. was not injurious to the bauxite, it was found that after the material had been reactivated at this temperature,,a considerable number of times, a very 5 marked loss in eiilciency occurred. The loss in efliciency, after a plurality of reactivations at 1500 F. was much greater than the loss of efficiency after the same number of burns at lower temperatures, and it has been found that an even greater loss in efliciency occurs at higher temperatures. Y

As the result of research which has been conducted in an endeavor to devise a process whereby bauxite can be used most emciently, I have =15 ascertained that for any given temperature, the time during which the bauxite is burned has a very important effect on the efliciency. The effect of burning time at various burning temperatures on yields of Pennsylvania steam refined solution percolated through bauxite is illustrated in the graph shown in the drawing.

I have also ascertained that the effect of the burning time is arithmetically cumulative. That is to say, the same change in efiiciency occurs where the bauxite is burned intermittently for short periods of time, as occurs where the bauxite is burned continuously for a length of time equal to the total time during which the bauxite is sub- -jected to intermittent "burning. For example, if a fifteen per cent (15%) loss in efficiency occurs after the bauxite has been burned continuously for thirty-five (35) hours, the same loss in efliciency will occur if the bauxite is burned thirtyfive (35) times at the same temperature, each burn continuing from one (1) hour, and the same loss in efficiency willoccur if the duration of each burn is one-half (V2) hour and the material is burned seventy ('10) times. It will now be apparent that while the tem- 40 perature of burning has an effect on the emciency of the bauxite, the time of burning is a much more important factor, and this has not been realized heretofore. It will also be apparent that in order to utilize the bauxite most efficiently, it is desirable to reduce the length of time during which the bauxite is burned for each reactivation, since the number -of reactivations which can'be carried out for any given loss in -emciency may be increased in direct inverse ratio to the time of burning. In other words, if the time of burning is cut in half, twice as many reactivationscan be carried out for a given loss in efliciency, and if the time of burning is deci- 55 mated, ten times as many reactivations can be carried out.

Heretofore, it was thought necessary to burn the bauxite for a period which might range in the neighborhood of onehalf /g) hour to one (1) hour or more, depending on the size of the charge. A very large charge of bauxite could be reactivated during this period of time in a furnace and the loss in eiiiciency of the bauxite which occurred after a number of burns, was thought to be inevitable and apparently due to the temperature employed. It will now be seen that a great saving may be effected by reducing the burning time to a minimum, and by a minimum is meant a period of not more than fifteen (15) minutes and preferably of the order of one (1) to five (5) minutes.

The importance of this invention will be appreciated when it is observed that heretofore if a fifteen percent (15%) loss in efliciency resulted after burning a batch of bauxite thirty-five (35) times, each burn being carried out for a period of one (1) hour, the same loss in efliciency will not occur until after twenty-one hundred (2100) reactivations, if each reactivation is accomplished within a period of one (1) minute.

The period of time in which complete reactivation can be 'carried out may be shortened somewhat by increasing the temperature. It will be noted from the graph of the drawing that as the temperature is increased beyond 1200 F. a loss in efllciency results, but this loss in efficiency, at least with respect to temperatures up to 1500 F., is more than compensated for by the decrease in the burning time, and hence in the increase in the number of reactivations, which is made possible.

The bauxite which is reactivated at temperatures lower than 1200 F. or higher than 1800 F.

has such a low efficiency that I prefer to utilize the temperatures within this range.

Another method which may be availed of to effect a complete reactivation of the bauxite in a minimum period of time is the use of relatively thin layers of bauxite in the reactivating furnace.

Heretofore, the bauxite has been treated in furnaces,,such as the Herreshoff multiple hearth, or the rotary kiln, and the material was charged in layers of at least six (6) inches in depth. Under such conditions, a complete reactivation could not be effected in aminimum period of time. It hasnow been found that the layer should not be more than three (3) inches in depth, and preferably from one-eighth to one (1) inch in depth. It has been found that the time during which complete reactivation can be brought about, and the depth of the layer of material in the furnace, decrease in approximately direct proportion. While the ratio is subject to variations, it is generally true that where a three (3) inch layer can be completely reactivated in fifteen (15) minutes, a two (2) inch layer can be completely reactivated in ten (10) minutes; a one (1) inch layer in five (5) minutes; a'one-half /2) inch layer in two and one-half (2%) 'minutes,

moisture would existand this would have a very deleterious eifect upon the bleaching act-ion. It is only necessary to cool below 900 F. since prolonged heating at a temperature below 900 F. has no harmful effects.

I claim:

1. The process of reactivating adsorbent bauxite contaminated with organic deposits by heating a layer of the material less than three inches in depth in an oxidizing atmosphere at a temperature above 1200 F. and below 1800 F. for a period of time less than fifteen minutes.

2. The process of reactivating adsorbent bauxite contaminated with organic deposits by heating a layer of the material less than three inches in depth in an oxidizing atmosphere at a temperature above 1200 F. and below 1800 F. for a period of time less than fifteen minutes, and then rapidly cooling the material.

3. The process of reactivating adsorbent bauxite contaminated with organic deposits by heating a layer of the material less than three inches in depth in an oxidizing atmosphere at a temperature above 1200 F. and below 1800 F. for a period of time less than six minutes.

4. The method of prolonging the useful life of adsorbent bauxite which is alternatively used to decolorize hydrocarbons and reactivated by burning in an oxidizing atmosphere, which consists in carrying out each of the said burnings by heating a layer of the material less than three inches in depth at a temperature above 1200 F. and below 1800 F. for a period of time less than fifteen minutes.

5. The method of prolonging the useful life of adsorbent bauxite which is alternatively used to decolorize hydrocarbons and reactivated by burning in an oxidizing atmosphere, which consists in carrying out each of the said burnings by heating a layer of the material less than three inches in depth at a temperature above 1200 F. and below 1800 F. for a period of time less than six minutes.

6. The process of reactivating adsorbent bauxite contaminated with organic deposits by passing the same through a furnace in an oxidizing atmosphere at'a temperature of approximately 1500 F. in a layer having a depth of from oneeighth to one inch, the period of burning bein less than fifteen minutes.

7. The process of reactivating adsorbent bauxite contaminated with organic deposits by passing the same through a furnace in an oxidizing atmosphere at a temperature of approximately 1500 F. in a layer having a depth of from oneeighth to one inch, the period of burning being less than six minutes.

8. The process, of reactivating adsorbent baux ite contaminated with organic deposits by moving the same across a hearth in an oxidizing at- .60

mosphere, in a layer less than one inch deep, in

contact with hot gases at 1200 F. to 1800 F. for a period of time less than fifteen minutes, and cooling the adsorbent rapidly to a temperature below 900 F.

OGDEN FITZ SIMONS.

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