US3483134A - Impact pulverization plus-additives in the production of activated carbon from coal - Google Patents

Description

Dec; 9, 1969 E. T. oLsoN 3,483,134

S ADDITIVES IN THE PRODUCTION OF IMPACT PULVERIZATION PLU ACTIVATED CARBON FROM COAL 2 Sheets-Sheet 1 Filed Aug. l5. 1966 shown-JOU .vmbo 20mm mm m mollo mz ,M m fd@ z W ruauum Dec. 9, 1969 E. 'r. oLsoN 3,483,134

IMPACT PULVERIZATION PLUS ADDITIVES IN THE PRODUCTION OF ACTIVATED CARBON FROM COAL Filed Aug. l5, 1966 2 Sheets-Sheet 2 EYS United States Patent O IMPACT PULVERIZATION PLUS-ADDITIVES lN THE PRODUCTION OF ACTIVATED CARBON FROM COAL Edgar T. Olson, Marmora, NJ., assignor to Kingsford Company, Louisville, Ky., a corporation of Illinois Filed Aug. 15, 1966, Ser. No. 572,363 Int. Cl. C01b 31/12 U.S. Cl. 252-421 15 Claims ABSTRACT OF THE DISCLOSURE To make activated carbon from bright banded bituminous coal, by pulverizing under impact of a particular size range, introducing a required quantity of an organic additive which will at least partially vaporize at a tempearture of between 200 F. and the tempearture of heat treating, regulating the moisture content to between 2.5 and 11% on the dry weight of the coal, molding into briquettes at a specified pressure, heat treating the briquettes at a temperature between 250 F. and 800 F. and not in excess of the temperature of agglomeration of the coal, breaking down the briquettes into granules and activating the carbon granules. The reaction may be exolthermic.

The present invention relates to processes and apparatus for making hard activated carbon black of the type which can be repeatedly reactivated and reused.

In summary, the raw material is bright banded bituminous coal, which in the preferred embodiment has an analysis by weight as follows:

Volatile Between 28 and 46% most desirably between 39 and 42%.

Fixed carbon Between 49 and 71%, most desirably between 54 and 58%.

Ash Between 1 and 15%, preferably between l and 5%, most desirably between 3 and 4%.

The bituminous coal is pulverized under impact to build up a reaction potential in the coal, and reduce it to the following size range:

At least 60% by weight through 200 mesh, and preferably at least 85% by weight through 200 mesh;

At least 25% by weight through 325 mesh, and preferably at least 60% by weight through 325 mesh.

The coal is mixed with between l and by Weight of the dry coal, and preferably 2 to 3%, ofk an organic additive which will vaporize at a temperature between 220 F. and the temperature of heat treating, say 800 F. The organic additive is most desirably of the type which will react with the coal exothermically, such as a cereal or seed, an aldehyde or an amino or ammonium compound. The additive may, however, be a compound which favors azeotropic distillation such as an alcohol, a ketone or an ester. The additive may be a halogenated hydrocarbon. The additive may also be a multi-ring cyclic hydrocarbon. The moisture content of the coal is adjusted to bring it within 2.5 and 11% on the dry Weight of the 3,483,134 Patented Dec. 9, 1969 "ice Where the volatile in the coal is below 38% by weight,

in excess of 10,000 p.s.i.

The molded coal is then heat treated at a temperature between 250 F. and 800 F. and not in excess of the temperature of agglomeration of the coal, for a time of at least four hours, preferably at least five hours. Prior to or after heat treating the briquettes are broken down into granules, then the carbon granules are activated.

A purpose of the invention is to produce superior activation of carbon as evidenced by the fact that the carbon shows activation properties even before activation.

A further purpose is to control the size of pores in activated carbon in order to give the carbon special properties.

A further purpose is to control the surface chemistry of activated carbon and particularly the extent of cross linkage and the extent of free valences.

A further purpose is to produce an activated carbon of higher density, having greater adsorption capacity per cubic foot and thus more efficiently using the space requirements in adsorption towers and the like.

A further purpose is to provide an activated carbon which will undergo regeneration more times, With less abrasion loss than comparable products now available, by reason of greater hardness and greater density.

A further purpose is to produce a superior activated carbon from a readily available low cost raw material, that is, bituminous coal, sub-bituminous coal, or semibituminous coal, the latter being included in the term bituminous coal when used herein.

A further purpose is to produce, from a low grade raw material such as bituminous coal, an activated carbon having properties similar to cocoanut shell activated carbon. f

A further purpose is to convert mechanical energy used in pulverizing bituminous coal to chemical energy which is capable of assisting and promoting the reaction between the coal and the additives.

Further purposes appear in the specification and in the claims.

In the drawings I have chosen to illustrate one only of the numerous embodiments of equipment which may be used to carry out the process of the invention, the forms shown being illustrated diagrammatically.

FIGURE 1 is a diagrammatic iloW sheet of the first portion of the process of the invention, illustrating apparatus which may be employed.

FIGURE 2 is a diagrammatic flow sheet of the latter part of the process according to the invention, illustrating suitable apparatus.

In the prior art a wide variety of raw materials are used to produce activated carbon for the purposes of making adsorbants for use in liquid phase and in gaseous phase systems. While in many cases relatively expensive raw materials such as cocoanut shell carbon and fruit pit carbon have been used, limited success has also been achieved in making activated carbons from more available materials such as bituminous coal.

atsaist and mixed with a binder'such as tar, compressed into briquettes and then heat treated to produce activated carbon. See Morrell U.S. Patents 1,968,846 and 1,968,847; 2,008,144, 2,008,145, and 2,088,146; and Barrett U.S. Patent 3,021,287.

The present invention is concerned with an improved process and apparatus for manufacture of activated carbon from bituminous coal.

One of the important effects achieved is that the activated carbon of the invention has superior activation and even shows activation properties before it is activated. In accordance with the invention the size and character of the pores in the activated carbon are subject to control, and also the surface chemistry of the carbon is controlled, particularly in respect to cross linkage and free valences.

One of the unusual features is that the carbon of the invention has greater density for a given adsorption capacity, thus more effectively utilizing the space in adsorption towers and the like, and being harder and denser, is capable of undergoing many regenerations without serious loss.

A further feature of the invention which is of great importance is that the pulverizing converts mechanical energy into chemical energy by impacting the particles and this energy is partially or wholly liberated during the heat treatment. In fact, with certain additives the reaction is exothermic, once it is started at a suitable temperature range.

In making activated carbon according to the invention it is important to start with a bright banded bituminous coal. It Will be remembered that bituminous coals are characterized by several different petrographic substituents. Vitrain is the constituent of lowest ash content. When it is nearly pure it may have less than 0.5% ash. It behaves as a plastic.

Fusain in bituminous coal is essentially mineral charcoal. It has a woody structure and its ash content may be in the range of 15 to 20% by weight.

Clarain is a translucent material made up of such ingredients as spores, algae, and exines (outer shells of spores and the like). It is somewhat similar to vitrain but has higher contents of nitrogen and sulphur and is also relatively low in ash (1 to 2% by Weight).

Durain is a constituent formed from organic matter such as twigs, bark, leaves and moss, and forms the bulk constituent of dull coal. It has an ash content in the range of to 15% by weight.

Bituminous coals, as well known in the art, are classified into bright banded coals which consist mainly of vitrain and clarain and are of low ash content and dull coals which consist mainly of durain and fusain and are of high ash content.

In general the bituminous coal after removal of slate which has the lowest ash content has the highest content of vitrain and clarain.

A large part of the high ash bituminous coals consists of so-called slate. This is a deposit laid down by water including clay, mineral fragments, iron-bearing materials, bark and the like.

The ash in fusain is primarily lime and sulphates. The ash in vitrain and clarain is primarily alkali, alumina and sulphates. The ash in durain is chiey alumina and silica.

A good bright banded bituminous coal as mined may contain up to of ash by weight. This material is beneficiated by any well known means to remove slate, rock and part of the clay. The coal is rst crushed to a nominal size of 1A inch. One mechanism for accomplishing this is a shaking table, of which a well known acceptable type is made Iby Sutton, Steele and Steele. The beneiiciation reduces the ash content to less than 15% and preferably less than 5%, and separates debris which will often contain 40% of ash and will be suitable for burning under the boiler to generate steam for the activator.

The beneiated bright banded pituniinous coal which is used as a raw material in the invention will have an analysisV asfollows on a`moisture-f`ree or dry basis by weight:

Volatile 28 to 46%, and most desirably Fixed carbon 49 to 71%, and most desirably Ash 1 to 15%, preferably l to 5%,

and most desirably 3 to 4%.

While most of the raw material for the present invention would be described as bituminous coal, it is intended also to include in this designation semi-bituminous and subbituminous coals which can be used and have the above properties.

PULVERIZING An important aspect of the present invention is the incorporating into the coal prior to reaction under heat of potential chemical energy capability by shattering the macro molecules, and forming free valences. In order to do this, it is not enough merely to grind by' any one of the accepted methods which will produce nely divided coal particles. It is necessary to shatter the particles by impact.

The most effective way of accomplishing this is by passing the particles through a vertical or horizontal Raymond mill, of well known character in the art, which subjects the particles of bituminous coal to impact and reduces them to very fine size.

A Raymond mill useful in pulverizing the bituminous coal according to the invention is illustrated in Crites U.S. Patent No. 2,561,564, granted July 24, 1951, for Pulverizing Mill Separator, Having Whizzer and Directional Blades and Combustion Engineering, Inc., Raymond Division, Bulletin 78 (1955). In this mechanism as well shown in the drawings of this patent, bituminous coal enters near the bottom and encounters pivoted hammers 27 which impact against it. Finely divided particles are then accelerated by whizzer blades 11 and finely divided material is withdrawn from the mill by suction applied by fan 12 at the top.

It will be evident that in the Raymond mill air is circulated through the mill and it cools the particles notwithstanding that much heat is generated by the impact and keeps the particles from compacting into a mass and also lblows the ground products out of the mill.

The neness of the etiluent from the impact grinding should be at least 60% by weight through 200 mesh per linear inch and at least 25% yby weight through 325 mesh per linear inch, preferably at least by weight through 200 mesh per linear inch, and at least 60% by weight through 325 mesh per linear inch.

Bright banded bituminous coai reduced to this fineness under impact pulverizing has the macromolecules disrupted, has a large amount of free valence and will ow like a plastic under molding as later described.

Screen analysis of two products which have been used in an experimental program in accordance with the present invention are as follows:

Screen size Product A Product B Nothing on Nothing on 5% on Nothing on 5% 0n 4% on 9% on 7% on 55% on 20% on 325 mesh 30% through 69% through ADDITIVES An important aspect of the invention is the creation of controllable pores in activated carbon before it is first activated. In the process of the invention, it will, of course, be evident that moisture is evolved by the coal during heat treatment both because as later explained moisture is deliberately retained or added to the coal, and also because in the pyrolitic decomposition which the coal undergoes during heat treatment, considerable moisture is evolved from hydrogen and oxygen or hydroxyl present in the coal and in some cases in the additive. The evolution of the moisture present as such is not helpful in producing pores, but the evolution of the water formed by pyrolitic decomposition of the coal and particularly the formation of free valences by its evolution is helpful in producing pores which are useful in the activated carbon.

Also, in the pyrolytic decomposition of bituminous coal many volatile components are given off and others similar are evolved when tar is incorporated as a binder. However I find that this also is not desirable in producing an effective pore structure in the final activated carbon.

It appears that the most desirable activated carbon is the result of special additives which have a combination of the following features:

(1) Size of molecule which apparently controls the minimum space vacated by the additive in pyrolytically decomposing or distilling.

(2) Volatiles of the additive which may be expressed in terms of its vapor pressure and boiling point.

(3) Ability of the additive to combine with the coal, especially with its free valences, and form a surface chemistry condition adjoining the pore which is favorable to adsorption.

(4) Capability of the additive to cooperate with the products evolved by the coal in promoting azeotropic boiling which is favorable to flush out the pores.

(5) Critical size of the pore influenced by all these factors which determines whether it is in effect a micropore, a submicropore or a macropore. It will be evident that the size of the pore not only controls the ratio of weight to surface area of the activated carbon but also influences the ability of the activated carbon to adsorb components from either a liquid or a gaseous phase.

EXOTHERMIC REACTIONS WITH ADDITIVES An unusual feature of the present invention is that after pulverizing the coal under impact to cause formation of free valences, certain of the additives incorporated with the finely divided coal, preferably prior to but permissi- 'bly after pulverizing (assuming the additives are about as nely divided as the coal) will under heat treatment producey exothermic reactions which are remarkably effective in producing a superior activated carbon at low cost.

vOne' class of very desirable additives is cereals, seeds or beans, hereinafter called cereals, including lbran, white corn meal, yellow corn meal, or soyabean flour (low fat). These cereals contain a substantial quantity of phosphorus. For example, the phosphorus contents of these materials in milligrams per hundred grams are as follows:

Bran 1215 Corn meal 248 Soyabean flour (low fat) 623 ously been used in activated carbon, for example, magnesium oxide, magnesite, dolomite, calcite, or tricalcium phosphate.

The concentration of cereal such as bran or the like is 1 to 10% on the dry weight of the coal, preferably 2 to 7%, and most desirably 2 to 3%. The concentration of the magnesium oxide or other basic component is also in the range of 1 to 10%, and preferably 2 to 7%, on the dry weight of the coal, and most desirably about 2 to 3%.

Experience indicates that fiber and carbohydrate in these cereals have the property of associating themselves with very small (micron size) coal particles which are likely to contain the greatest number of free Valences per unit of weight. When subjected to high pressure as later discussed, they produce macromolecules with a high density of cross linking, whereas the coal itself originally had a rather low density of cross linking. After high pressure molding there is a tendency to form a material which is like a plastic from the standpoint of strength and other properties.

Activated carbon when made from one of these cereal components, particularly when incorporating an alkaline material such as magnesia, is very suitable as a brightening and buffering agent in treating sugar refining solutions, dextrose, Syrups and vegetable oils. The magnesia or the like after activating of the carbon tends to prevent the inversion of can sugar. Activated carbon of this type is also very useful for purifying citric acid, malic acid, pharmaceutical materials and water, especially for use in power plants. It is also incorporated in side wall tires to prevent bleeding.

It has a pore diameter between 2 and 45| A. units.

The property of reacting exothermically wih coal is also possessed by aldehydes which have boiling points in the range between 220 and 800 F. The preferred aldehydes for this purpose are furfural, benzaldehyde and paraldehyde.

The concentration of aldehyde used is 1 to 10% on the dry weight of the coal and preferably 2 to 7%, most desirably 2 to 3%.

My tests indicate that 2% furfural on the dry weight of the coal produces after heat treatment pores of about 6 A. units. The aldehyde condenses with hydroxyl groups in the coal during heat treatment when the temperature rises to about 300 F. and produces a high density network of macromolecules.

Activated carbon of this type is very good for catalyst carriers, for example, employing platinum black, and for adsorbing toxic gases in gas masks and in mines, for solvent recovery, for air conditioning filters, and for purifying tobacco.

A third group of additives which react exothermically with coal during heat treatment are the amines and ammonium salts which boil or decompose between 220 and 800 F. Suitable amines are urea, ammonium oxalate, monoethanol amine, diethanol amine and triethanol amine. Suitable ammonium compounds are ammonium chloride, ammonium fluoride and ammonium bifluoride. These activated carbons are especially good for gas adsorption, particularly of acid gases such as carbon dioxide, sulphur dioxide and hydrogen sulphide. They are very effective for air conditioning filters and for purifying electroplating solutions.

The activated carbon produced using amonium chloride evolves products of decomposition during heat treatment at temperatures above about 550 F. It produces an activated carbon having a very large number of micro and submicropores in the range of 3 to 4 A. units. This activated carbon is slightly acid and is especially suitable for adsorbing alkaloids, amino acids, such as glutomic acid, for purifying glycerine and for purifying electroplating solutions.

Activated carbon which incorporated 2% of urea on the dry weight of the coal added in aqueous solution was found to give a superior gas adsorbing activated carbon.

7 SWELLING AND AZEOTROPIC BOILING All of these additives now to be referred to are employed in concentrations of 1 to 10%, preferably 2 to 7%, and most desirably 2 to 3%, on the dry weight of the coal.

There are a number of different additives which attack the humins in the coal and tend to promote swelling of the coal.

Alcohols (and phenols) having boiling points in the range from 220 to 800 F. tend to exert swelling action on the coal, thus promoting formation of pores, and are very effective in producing a flushing action which clears out the pores very effectively and makes an unusually active carbon. The preferred alcohols are glycerol, propylene glycol, and normal hexanol. The preferred phenols are phenol, cresol, catechol and resorcinol.

The activated carbon made with these alcohols and phenols as additives is rather similar to that obtained from bran, corn meal or soyabean our.

Hydrocarbons having, 2 or 3 fused rings, such as naphthalene, anthracene and 1,2,3,4-tetrahydronaphthalene when used as additives produce activated carbon having micropores, which is especialy effective in a-dsorbing polymers of high molecular Weight from solution.

Esters of straight fatty chain acids, boiling between 220 and 800 F., such as butyl acetate and amyl acetate, produce activated carbons having intermediate pore sizes between 6 and 7 A. units, which are very effective in adsorbing materials of this size range from liquids and gases.

Ketones boiling between 220 F. and 800 F. such as methylethylketone and methylisobutylketone produce activated carbon having properties similar to the alcohols and having the azeotropic boiling tendency.

For adsorbing halides from liquids and gases, an especially effective activated carbon can be made by incorporating as an additive a chlorinated hydrocarbon boiling between 220 and 800 F., such as tetrachloroethylene or perchloroethylene. These produce pores having a particle size of about 1l A. units.

Activated car-bon made in this way is especially effective for adsorbing halide solvent vapors, and gases containing halides such as arsenic trichloride and phosphorus pentachloride.

Another Very effective additive is oxalic acid in concentrations of 1 to 10% on the dry weight of the coal, preferably 2 to 7%, and most desirably about 2 to 3%. Oxalic acid produces a very effective acidic activated carbon having pore size of about 4.25 A. units.

In all of the above additives the concentration will be between about 1 and 10% on the dry weight of the coal, preferably 2 to 7%, and most desirably about 2 to 3%. All of the above additives can be put in prior to pulverizing and in the case of the dry additives, are preferably added at this time. The liquid additives, however, are preferably incorporated after pulverizing.

In general the invention permits an activated carbon having a selected pore size and selected surface chemistry capable of adsorbing materials whose particle size and whose properties are known.

ADJUSTMENT OF MOISTURE Regardless of the character of the additive or the question of whether it is a liquid or solid, it is important to regulate the moisture content of the coal to bring it within a range of 2.5% to 11% on the dry weight of the coal, preferably A moisture content of 21/2% is enough lfor best results in the case of the coarser coals, but for best results with the finer coals, the moisture content prior to molding should be in the range from 7 to 11%.

The moisture performs three different functions. It acts as a lubricant to make the coal particles flow plastically under the molding pressure. It tends to hold the very ne coal particles in uniform distribution throughout the briquette. It seals the mold against tendency to extrude coal particles between the punch and the die in the closed mold. The moisture adjustment is preferably made in a blender.

8 MOLDING Molding must be carried out in a closed chamber mold. An auger press should not be used.

While molding may be carried on in a closed chamber brick molding press, it is preferred to use a tableting press such as a Stokes DD2 Press (15 tons), having a die size of 1%6 inches X 1/2 inch. When molding at 10,000 p.s.i., the tablets obtained in the present invention have a density of about 1.05 grams per cubic centimeter. Under 11,000 p.s.i., the density of the tablets is 1.10 grams per cubic centimeter. When molding at 13,000 p.s.i., the density is 1.15 grams per cubic centimeter. When molding at 20,000 p.s.i, the density is grams per cubic centimeter In general, the density increases with the molding pressure.

When molding high volatile coals having a volatile content of 38% by Weight or higher, the molding pressure can be as low as 5000 p.s.i., or when molding coals having lower volatility (below 38% by weight), vthe molding pressure should be at least 10,000 p.s.i., and preferably at least 11,000 p.s.i. Pressures up to 30,000 p.s.i. are desirable, and higher pressures can be used but are not regarded as beneficial.

The briquette or tablet after molding resembles many plastic moldings. It has a brittle fracture like chinaware.

GRANULATION The tablets or briquettes are preferably next broken down to a size in the range between A inch and 1;/18 inch'. While this granulation can be accomplished before heat treatment, it can be done after heat treatment. The preferred mechanism for granulation is a Crusher which will produce brittle fractures, for example, a Cumberland Crusher, in which the granulation is accomplished by saw blades.

HEAT TREATMENT The coal after molding and before or after granulation is heat treated at a temperature between 250 and 800 F. and not in excess of the temperature of agglomeration for a time of at least four hours and preferably -four and one-quarter hours.

It is definitely not desired to have the coal agglomerate or fuse during heat treatment and, therefore, while the coal still is plastic, it must not be heated high enough to agglomerate. The test used is to heat treat at a succession of different temperatures and then transfer the heat treated coal samples to a muiile furnace heated at 1742 F. (950 C.) and leave it there for seven minutes. If a fused mass forms under this test, it means that the heat treatment had previously caused the coal to agglomerate, and the heat treating temperature was too high.

The heat treatment is preferably carried out in a multiple hearth furnace such as Herreshoff Furnace (Nichols Engineering and Research Corporation, New York City) in which initially gas flames'heat the different hearths, and where the reaction is exothermic, in the case of bran, corn meal, soyabean flour, aldehyde, amine or ammonium compounds as the additive, the flames can be cut off once the exothermic reaction starts. Suitable temperatures forheating the various hearths in a particular case are as follows:

It should be mentioned that the additive yperforms a very important lfunction in accelerating the operation as well as producing a much better product. For example, to heat treat the coal even much less effectively without an additive would require at least nine hours.

F. Corn meal 800 Furfural 600 Urea 700 Ammonium chloride 700 Tetrachloroethylene 700 Heat treatment in accordance with the invention drives olf a great deal of water vapor, which evidently comes from hydrogen combined with the coal long after any uncombined moisture has ceased to come off, and there is very little loss of carbon in the heat treatment of the coal.

ACTIVATION Activation of the coal according to the present invention and reactivation follow well-accepted present practice, that is, heating to an elevated temperature in the presence of steam to form water gas. The activation and reactivation temperatures will be between 11l2 F. (600 C.) and 1832 F. (1000 C.), and preferably between 1742 F. (950 C.) and 1778 F. (970 C.). Temperatures for activation higher than 1832 F. are not recommended, and if submicropores are to be retained, activation should be carried on at lower ternperatures. Reactivation at higher temperatures is likely to form more macropores.

The activated carbon of the invention weighs about 35 pounds per cubic foot at a density of 1.20 grams per cubic centimeter and 34 pounds per cubic foot at a density of 1.15 grams per cubic centimeter.

Example 1 Following the general technique described above, bright banded bituminous coal having the following analysis by weight was used:

Two different products were pulverized in the Raymond Single-Pass Vertical Mill, one having the particle size of Product A described and the other having the particle size of Product B above described. Prior to pulverizing, of bran and 5% of magnesium oxide, both on the dry weight of the coal, were incorporated. The products were molded at 10,000 p.s.i., 11,000 p.s.i., 13,000 p.s.i. and 20,000 p.s.i., obtaining densities as above set forth, and the product was heat treated for four hours at a maximum temperature of 800 F. Very superior sugar carbons were obtained, as above set forth.

The products molded using the ner grain size distribution (product B) had lower molecular weights and more reactive free valences than the products using the coarser particle size (product A).

The activated carbon produced in Example 1 was compared for adsorbence of coloring material in molasses with a standard commercial activated carbon, using the well known absorbence test. Forty milliliters of molasses (Brer Rabbit) was dissolved in 1000 cc. of distilled water, suitably bulered. To cc. samples of this molasses solution was added in one case 100 mg. of the control commercial activated carbon and in another case 100 mg. of the activated carbon of Example 1, and each sample was boiled for seconds. The samples were ltered hot through Whatman lter paper and tested comparatively in the same colorimeter. The molasses solution alone gave a light transmittance of 48.5. The sample treated with commercial activated carbon gave a light transmittance of 67.5, the increase being 19.0. The molasses sample treated with the activated carbon of the invention gave a light transmittance of 89.0, or an increase of 40.5, or was more than twice as eiective as the control.

Example 2 The procedure of Example 1 was repeated except that 5% of yellow corn meal on the weight of the dry coal was used instead of 5% of bran. Comparable products were obtained.

Example 3 The procedure of Example 1 was repeated, using 5% of soyabean our (low fat) on the weight of the dry coal rather than bran. The results were comparable.

Example 4 The procedure of Example 1 was repeated, using 2% of furfural on the weight of the dry coal rather than bran and magnesia. The heat treatment was carried on at a maximum temperature of 600 F. The activated carbon has micropores of about 6 A. units in diameter and was very eiective for adsorbing toxic gases and solvents.

A comparison of light transmittance was made according to the test referred to in Example 1. The light transmittance of the molasses treated with this activated carbon was 78.5 with an improvement of 30, as compared with an improvement of 19 for the activated carbon control, or a benet of about 50%.

Example 5 The procedure of Example 1 was carried out, using 2% of urea on the dry weight of the coal instead of bran and magnesia.

The heat treatment was carried out at a maximum temperature of 700 F. A very effective gas adsorbent activated carbon was obtained.

Example 6 The procedure of Example 1 was carried out, omitting the bran and magnesia and using 2% of ammonium chloride on the weight of the dry coal, the ammonium chloride being added as an aqueous solution after the coal was pulverized. The heat treatment was carried out at a maximum temperature of 700 F. The coal began to gasify at 550 F. A very large volume of micro and submicropores of about 3 to 4 A. unit diameter was produced. The activated carbon was superior for adsorbing alkaline material such as amino acids.

Example 7 The procedure of Example 1 was carried out, substif tuting 2% of tetrachloroethylene on the dry weight of the coal for the bran and magnesia. The pores produced were of a diameter of 11 A. units and larger. The activated carbon was very elfective for adsorbing chlorinated or other halogenated solvents.

Example 8 The procedure of Example 1 was carried out, substituting 2% of oxalic acid on the dry weight of the coal and omitting the bran and magnesia. The activated carbon produced was acidic and had a pore size of about 4.25 A. units.

APPARATUS The apparatus shown in FIGURE 1 takes coal from a storage bin 20 and passes it through a bar screen 21, where it is picked up by a `feeder 22 and passed through a crusher 23 to a scalping screen 24 from which the coal is passed by a feeder 25 to an elevator 26 which discharges to a storage bin 27 and a feeder 28. The feeder 28 empties into a single pass vertical Raymond impact pulverizer 30 having air circulation provided at 31 and feeding to an air classifier 32. Excessively large particles are recirculated at 32', and particles of suitable neness are carried in an air stream 33, which communicates with a classifier 34, which feeds the main stream of effluent in a feeder 35 and consolidates coal particles recovered by a rotary precipitator 36, returning coal to the feeder at 37 and discharging air to the atmosphere at 38. Finely divided coal is carried by an elevator 40 to a storage bin 41, which also receives coal returned in a stream 42 from a dust collector. A feeder 43 progresses the coal and mixes with it an additive 44 (assuming that the additive is to be put in after the impact pulverizing), and any required moisture. The feeder empties the mixture of coal and additive or additives into a briquetting press 45 having a closed mold. Briquettes are discharged into a feeder 46, which conveys them to a crusher 47, which may if desired be supplemented by a grinder 48. The particles are picked up by an elevator S and discharged into a storage bin S1 and then to a feeder 52 and a classifying screen 53. Oversize particles are returned by a ow line 54 to the grinder, and fine particles that should be recycled are recycled by means not shown. Particles of coal leave this operation at 55.

FIGURE 2, which shows the heat treatment, receives molded coal particles at 56 to enter an elevator 57 to discharge to a storage bin S and then by a weighing scale feeder 60 to enter a heat treating furnace 61 suitably of the multiple hearth type. The heat treating furnace 61 discharges heat-treated coal granules through a cooler 61 to an elevator 62 and then to storage bin 63. At the top of the heat treating furnace 61 there is a dust collector 64 discharging gas and vapor to atmosphere at 65 and discharging particles to a storage bin at 66. The heat treating furnace has internal gas burners on each hearth, which may be cut off once the reaction is started if the reaction is exothermic. Means for introducing steam at 67 is shown for emergency use if necessary to cool the heat treating furnace.

The heat-treated carbon from the storage bin 63 passes through a weight scale feeder 68 to a multihearth activating furnace 70, from which the product discharges to a cooler 71. Steam for the activation reaction is introduced at 72, and vapor and dust passes through dust collector 73, discharging the vapor to atmosphere at 74 and returning any particles collected by the dust collector through a line 75 to a storage bin. The activation furnace has internal gas burners not shown. The activation temperature will be between 600 C. and 1000 C., as previously mentioned. In some cases the activation can be carried on without introducing steam since the presence of controlled amounts of carbon dioxide and carbon monoxide in the combustion gases will accomplish activation without requiring introduction of steam, as well known in the art.

The finished product is suitably further pulverized if required, classified as to size and stored, preparing for shipment.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A process of making activated carbon, which comprises pulverizing bright banded bituminous coal under impact in the presence of a stream of air until the particles are of the following size range:

at least 60% by weight through 200 mesh, at least 25% by weight through 325 mesh,

introducing into the finely divided coal between I and by Weight of the dry coal of a cereal which will break down at a temperature between 220 F. and the temperature of heat treating, regulating the moisture content of the finely divided coal to between 2.5 and 11% on the dry Weight of the coal, molding the finely divided coal into briquettes in a closed mold under a pressure as follows: where the volatile in the coal is above 38% by weight,

in excess of 5 000 p.s.i., where the volatile in the coal is below 38% by weight,

in excess of 10,000 p.s.i., 4heat treating the coal in thus molded form at a temperature between 2509 F. and 800 F. and not in excess of the temperature of aglomeration of the coal for a time of at least four hours, the coal and the cereal reacting exothermically during heat treatment, breaking down the briquettes into granules, and activating the carbon granules.

2. A process of claim 1, in which the quantity of additive is between 2 and 3 3. A process of claim 1, in which the coal is pulverized in a Raymond mill.

4. A process of claim 1, in which the coal after pulverizing has the following size range:

atleast by weight through 200 mesh,

at least 60% by weight through 325 mesh.

5. A process of claim 1, in which the coal has the following analysis by weight:

volatile between 28 and 46%. fixed carbon between 49 and 71%. ash between 1 and 15%.

6. A process of claim 5, in which the coal has an ash content between 1 and 5% by weight.

7. A process of claim 5, in which the coal has the following analysis by weight:

volatile between 39 and 42%. fixed carbon between 54 and 58%. ash between 3 and 4%.

8. A process of claim 7, in which the moisture content is regulated to between 7 and 11% on the dry weight of the coal.

9. A process of making activated carbon, which comprises pulverizing bright banded bituminous coal under impact in the presence of a stream of air until the particles are of the following size range:

at least 60% by weight through 200 mesh,

at least 25% by weight through 325 mesh, introducing into the finely divided coal between l and 10% by weight of the dry coal of an organic additive of the class consisting of furfural, urea, oxalic acid, glycerol, propylene glycol, normal hexanol, phenol, cresol, resorcinol, butyl acetate, amyl acetate, methylethylketone and methylisobutylketone, regulating the moisture content of the tinely divided coal to between 2.5 and 11% on the dry weight of the coal, molding the finely divided coal into briquettes in a closed mold under a pressure as follows:

where the volatile in the coal is above 38% by weight,

in excess of 5000 p.s.i., where the volatile in the coal is below 38% by weight,

in excess of 10,000 p.s.i., heat treating the coal in the thus molded form at a temperature between 250 F. and an upper limit as follows:

furfural 600 oxalic acid 700 all other additives not in excess of the temperature of agglomeration of the coal for a time of at least four hours, breaking down the briquettes into granules, and activating the carbon granules.

10. A process of claim 9, in which the coal has the following analysis by weight:

volatile between 28 and 46% fixed carbon between 49 and 71% ash between 1 and 15% 11. A process of claim 10, in which the coal has an ash content of between 1 and 5% by weight.

12. A process of claim 9, in which the coal has the following analysis by weight:

volatile between 39 and 42% fixed carbon between 54 and 58% ash between 3 and 4% 13. A process of claim 12, in which the moisture content is regulated to between 7 and 11% on the dry welght of the coal.

13 14. The process of claim 9, in which the quantity of 1,768,963 additive is between 2 and 3% by Weight. 2,944,031 15. A process of claim 9, in which the coal after pul- 1,729,162 verizing has the following size range: 2,008,144 atleast 85% by weight through 200 mesh, 2,008,145

at least 60% by weight through 325 mesh. 5

References Cited UNITED STATES PATENTS 2,624,712 1/1953 Donegan 252-421 10 2,915,370 12/1959 Mitchell 23-209.1 2,304,351 12/1942 Goss 202-9 ODell 252-421 Mason 252-421 Coates l252-421 Morrell 252-421 Morrell 252-421 DANIEL E. WYMAN, Primary Examiner P. E. KONOPKA, Assistant Examiner U.S. C1. X.R.

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