US1882916A - Manufacture of decolorizing carbon and the like - Google Patents

Description

Patented Oct. 18, 1932 ROBERT N. RIDDLE, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOB, '10 RIDDLE P300388 OOIPANY, O1 PHILADELPHIA,

NEW YORK PENNSYLVANIA, A CORPORATION 01? IANUI'ACTURE OF DECOLORIZING CARBON AND THE LIKE Io Drawing.

M invention relates to the manufacture of ecolorizing carbon and the like, being concerned with the production of a form of carbon (hereinafter referred to as activated carbon) that has valuable decolorizing, clarifying, and deodorizing properties, and is also useful for various other purposes. The invention affords an expeditious, convenient, and economical method or process of manufacture. 7

In producing my carbon from forms of carbon such as coal, I employ another material of the character hereinafter indicated, with which I associate the particles of coal in a pulverized state of fine division, in such wise that the coal particles are invested, coated or embedded in the other material. I heat the thus prepared fine coal sufliciently to liberate much or all of its volatile matter, and even subject it to a suflicient tem perature to cause some combustion of its residual fixed carbon, on exposure to the air,- all, however, without permitting free and total combustion and consumption of the fixed carbon, and without sintering or coking together the original fine carbonaceous particles, such sintering or coalescence, (as well as free or rapid combustion of the coal) being prevented by the presence or action of the other material. After the heating operations are completed, the carbon product may be freed of the other material or its residue.

As the other material in my process as above outlined, I may make use of a substance such as sodium carbonate, which is soluble, so that it can be brought into intimate relations with the coal particles by solution and evaporation; affords the coal particles an investure sufiiciently refractory not to burn away, fuse, or coalesce at the temperatures required in my process to distil away those 1 hydrocarbons which might fuse and cement the carbonaceous Earticles together; does not chemically alter t e fixed carbon of the coal;

- and is inexpensive. But many other materials are known which possess similar pro erties in greater or less degree, and may used for the purposes of my invention: especially the various alkali metal salts and compounds, and the alkali metal carbonates Application fled February 24, 1980. Serial No. 431,051.

in particular,though I believe that few such substances are so cheap as sodium carbonate. V

In associating the sodium carbonate or the like with the coal by solution and evaporation, I find it of great advantage to make use'of a wetting agent for the coal,-i. e., some reagent that will cause better contact of the water with the coal, like a fatty acid or some substance containing or yielding a fatty acid, and particularly a fatty acid of the open chain series. Water-soluble soa is a fatty acid reagent of this sort; and may also instance stearates and commercial fats of various kinds. I have found that the use of such a wetting agent greatly abbreviates the time required to complete the preparatory treatment of the coal with the so dium carbonate, and produces variousother beneficial effects.

In particular, the use of such an agent tends toward better contact of the ultimately deposited soda with the coal; makes the dried mass of coal and soda break up easily into a. soft and perfect powder; and results in a smooth escape of the gases when the powder is heated. 1 also believe that during the heating the fatty acid slowly decomposes and produces beneficial catalytic or other effects, particularly as regardsthe decomposition of the saturated and unsaturated components of the coal: i. e., it results in a larger proportion of gaseous and liquid products. For exemple, a soft gas coal having fixed carbon may yield carbon when treated as hereinafter described. Apparently this additional carbon (resulting from decomposition of the volatile constituents of the coal) considerably improves the absorptive power of the final product for gums, albumenoids, pectins, allurones, etc., and gives the product the power of concurrently filtering, clarifying and purifying.

Commercial soft coal of any good quahty 'may be used, but I prefer the kind known as high volatile, and particularly gas coking coal: e. g. Pittsburgh gas coal with 40% volatiles, or Westmoreland coal of similar character. This should be pulverized to a fineness of about 200 mesh (or finer) as for Parts Beef tallow 100 Caustic soda (NaOH) 30 Water--- 60 A small addition of aqueous ammonia greatly facilitates the mixing, but is not essential: if it is used, an amount whose ammonia (NIL) content is 10% of the rest of the mixture will give ood results. Or a corresponding amount 0 ammonium carbonate may be used. This keeps the mass mealy when subsequently heated.

The amount of the soap used should be about 1% of the amount of coal, by welght. The sodium carbonate used should be about 30-40% of the coal, also by weight.

The soap having been prepare the SOdlllIIl carbonate, in 15% aqueous solution, is stirred andmixed in with the soap. This ma be done at a temperature of about 80 C. 1s mixture is placed in a steam 1acketed kettle also e uip ed with agitators or scrapers, an then the ried pulverized coal is added and thoroughly mixed in without stirring, at a temperature of about 100 C.

After the coal has been stirred in, the temperature is gradually raised, and the liquid mass is kept boiling until all the water has been dried out,be1ng vigorously stirred all the while. The mass tends to froth during the heating, but does not stick together permanently.

An alternative mode of treatment is to keep the mass at the boiling point for about an hour, checking the evaporation by careful regulation of the heat, and then heating vigorously and drying out all the water. The mass will first become sticky and then break up into a fine, soft, velvety powder.

In either case, if the product is not a fine, loose powder, faulty stirring is indicated; then the mass should be screened through a ISO-mesh sieve.

The carbon product. in the form of a dry, loose powder, is put in a retort previously heated to a low red (about 300-400 C.) and is brought up to some 500-600 C.,--or even to 700 C.,-and held at the final heat for a period that depends on the temperature: i. e., for 500 0., three'hours may be required; for 600 (1., two hours may suffice; while for and then freed of the residue of the sodium carbonate by washing as hereinafter described. I

If it is to be further treated, however, it

may be taken out of the retort (with being allowed to cool appreciably) into a pan with a cover that can readily be raised and lowered to limit and control the access of air and the supply of oxygen. By raising and lowering the cover, the carbon is kept ust glowing,- being stirred vigorously all the time. This is continued till ammonia ceases to come off, when the cover is closed down on the pan and the material allowed to cool.

A test of the proper completion of this glowing operation is to heat u a portion of the material to substantially t e temperature at which the glowing was carried out, If no ammonia comes off when this is done, the process can be considered properly completed.

After cooling, the residue of the sodium carbonate can be removed from the product and recovered by washing the product with water, decanting or filterin off the solution, treatin the resldue with ilute acid (e. hydroc loric or sulphuric acid), and was ing it again with water. About 8090% of the original sodium carbonate can be recovered from the first wash water.

The carbon produced by this glowing step is equal to the best in the trade 1n decolorizing power, and is unique in its clarifying and decolorizing capacity, and especially in its power to absorb' ectins, gums, albumenoids, etc. The yie d of carbon is about -55% of the original coal by weight.

The yield from the retorting operation, if cooled and washed without glowing, is about -70% of the original coal; but the ualit is only about half as good as after t e g owing. Apparently the glowing operation purifies the decolorizing carbon by eliminating carbon of little or no decolorizing power. I

The recovery of soda on washing is greater after the glowing operation than without the glowing.

As an alternative to heat treatment in a retort and in a pan as above described, the dried mixture may be treated in an externally heated revolving drum, without access of air, but with provisions for venting it of the gases arising from the o eration. Heating under these conditions Wlll require about an hour, at a low red heat (about 600 to 700 (3.). After this, the material may be taken out and either lowed in a. pan as before, or assed throug a revolving drum externally eated to about 500 to 700 C., steam bein concurrently passed into or, through the rum. Under these conditions, the steam is decomposed and its oxygen reacts with the carbon or carbonaceous material of the coal; but the exothermic action is less pronounced or striking than in the open pan treatment, and the operation is slower.

Having thus described my invention, I claim 1. A process of preparing finely divided clarifying and decolorizing carbon, which process comprises forming a mixture of pulverized coal with a solution of an alkali metal salt and water soluble soap; boiling ofi the ,A

water and thereby investing the coal particles with a deposit of material from the solution; heatin the thus prepared coal to a temperature of redness, with exclusion of air and avoidance of fusion and sintering together of the carbonaceous particles; and then treating the latter at a glowing heat with a limited supply of oxidizing agent until ammonia has ceased to come off.

2. A process for preparing clarifyin and decolorizing carbon, which comprises eating pulverized coal having its particles invested with refractory material to a temperature of redness, with exclusion of air and avoidance of fusion and sintering together of the carbonaceous particles, and then treating the latter at a glowing heat with a limited supply of oxidizing agent until ammonia has ceased to come 3. A process for preparing clarifyin and decolorizin carbon, which comprises eating pulverized coal having its particles invested with an alkali metal salt to a temperature of redness, with exclusion of air and avoidance of fusion and sintering together decolorizing carbon, which process comprises formin a mixture of pulverized coal with a solution of an alkali metal compound, together with a fatty acid reagent, and boiling of! thewater. p

In testimony v whereof, I have hereunto signed my name at Philadelphia, Pennsylvania, thls 19th day of February, 1930. ROBERT N. RIDDLE.