US2280611A - Process for producing activated carbon - Google Patents

Description

April 21, 1942. R. ADLER PROCESS FOR PRODUCING ACTIVATED CARBON Filed March 15, 1940 INVENTOR: Rudolf Adler BYa/LM AGENT.

Patented Apr. 21, 1942 PROCESS roa raonoomo. ACTIVATED CARBON Rudolf Adler, London, England Application March 15, 1940, Serial No. 324,071 In Czechoslovakia October 7, 1937 3 Claims.

My present invention relates to a process for producing activated carbon in the residue of producer gas generators without'detri'ment to the production of power gas.

The normal operation of a producer gas generator tends to convert the carbon content of the fuel completely into so-called producer gas or mixed producer gas, so that a slag and ash residue is obtained which is substantially free of carbon or has a negligibly small carbon content amounting to 2-10% as a maximum. In the case of normal operation conditions of said generator the resulting ashes therefore consist practically of the mineral substances of the fuel. When operating a generator in this usual way addition of steam and air in a certain proportion to the quantity of carbon in the fuel is required, the ratio between carbon, air (oxygen) and steam (H20) and also the quantity of gas resulting from the respective reactions being determined by well-known equations. Such calculation shows that 1 kilogram carbon contained in the fuel requires for complete gasification about 2.19 cubic meters air and 0.777 kilogram steam and result in 4.53 cubic metres gas of the composition: 41.0 per cent CO, 20.6 per cent H, and 38.4 per cent N, on the assumption that the water is added in form of steam of 100 C. (see Ullmann, Encycl. d. techn. Chemie, 1930, vol. 6, pages 786-791). These standard figures are known to the'expert, but vary with different factors (composition of fuel, construction of the generator, velocity of the passage, quality of the gas re-v quired, outside temperature, etc.)

In general air and steam are added mixed with each other, the appropriate ratio between air and steam being efiected by just saturating the air with steam at a certain temperature of the mixture, since the quantity of steam required for saturation of a given quantity of air varies with the temperature of the air-steam-mixture. (Ullmann, l. c., p. 792; Rambush, The Modern Gas Producers, p. 269). Each degree of the mixture thus corresponding to a certain ratio between air and steam, it is possible and usual in practice, to use the temperature of the saturated air-steamcubic metres air contains 0.777 kilogram steam. The saturation degree of 60 C. is in fact the standard figure employed for gasification of dry fuel (coke, dry pit-coal), as may be seen from N. Latta, American Producer Gas Practice,

, New York, 1910, p. 36; there this schedule is It appears here, that 60 is the optimum, with regard to the caloric value of the gas. But in special circumstances, f. 1. high water content of the fuel, construction of the producer certain changes may be necessary.

This saturation degree is only a means to determine the desired ratio between air and steam, not being identical with the temperature at .which the mixture is added to the fuel; the

mixture as means to determine the amount of steam in a given amount of air. Employing saturated blast of a certain degree, therefore, means the use of a certain ratio between air and steam. The figures for air and steam given above for the gasification of 1 kilogram carbon (2.19 cubic metres air and 0.777 kilogram steam) correspond to a saturation degree of about 60 0., i. e. a

figures given above (4.53 cubic meters gas for 1 kilogram carbon) suppose that the mixture-of 2.19 cubic meters air and 0.777 kilogram steam, although mixed at a temperature of C. are added at a degree of C.

-A properly adapted air-steam supply will create a temperature of about 1200-1600.C. in the incandescent zone of the generator. Various disadvantages appear if the air-steam ratio or the quantity supplied are not appropriate. If the amount of air and steam is below the quantity required for complete gasification the result is a poorer yield of gas with the result that the carbon not gasified appears in the ashes. II the amount of air or steam is higher than required, other disadvantages appear (carbondioxide and too much hydrogen in the gas, clinker formation, thermal losses).

When operating in the usual way under optimal-conditions as described above practically no carbon is contained in the ash residue. This residue can not be used in any technical way and must be regarded as worthless. This is also true,. if the residue contains a higher percentage of carbon on account of a non-optimal operation of the producer, particularly an insufficient supply of air and steam.

saturated blast of that degree containing 2.19 55 The main obj of y present invention con sists in conducting the operating or producer gas generators in such a way that while producing gas of substantially standard quality and composition the residue is enriched with carbon in activated form, thus rendering useful the otherwise useless generator slags and ashes.

A further object of my invention is to maintain during this operation substantially equal production of producer gas, 1. e., to produce activated carbon in the residue without decreasing the gas production.

Still a further important object of my invention is to achieve an activated carbon content in the residue of more than weight of the residue.

It is still a further object of my invention to increase the throughput of the fuel and the supply of air and steam in such a way that only a partial gasiflcation of the fuel is obtained, whereas the carbon content of the rest of the fuel is retained in an activated condition in the residue, the quantity of activated carbon amounting to more than 25 per cent of the per cent of the weight of this residue. This activated residue, in

spite of its high mineral content, is particularly suitable for bleaching and deodorizing liquids and for other adsorptive purposes.

It should be especially emphasized that the products thus obtained are by no means a coarse agglomeration of mineral ash, slag, and degasifled fuel, but that they are a very intimate mix- 7 ture, wherein the carbon enters the finest interstices of the mineral substances, so that the designation carbon containing slag and ash characterises quite properly the nature of the product.

In order to carry out my invention I propose in a process for producing activated carbon in must be accordingly increased, so that the ratio between air and steam is maintained, care being taken that it shall be supplied at such a rate as not only to convert most, if not all, of the carbon ulated according to the results of these tests.

The expert who has to operate the generator under the invention has to increase the passage of the fuel according to the amount of carbon desired in the ashes,'and to increase the supply of air and steam, until the analysis and measure of the gas shows that this air and steam increase is appropriate to compensate for the additional the residue of gas generators to combine the steps of constantly maintaining in said generator temperature conditions adapted for gasiflcation of the fuel passing, through said generator, or activation of the carbon contained therein, and of maintaining a throughput of fuel being larger than a throughput which could be completely gasified under the air and steam conditions prevailing in said generator, thereby obtaining partial gasification of the fuel passing through the generator and obtaining activation of the carbon in the residue having passed through the generator without having been gasified.

This process may be carried out by increasing the throughput of the fuel through the generator, and increasing the supply of air and steam to the generatoronly to an extent being sufllcient to establish temperature conditions adapted for gasiflcation of the fuel passing the generator, or activation of the carbon contained therein, but being insufficient for complete gasification of the passing fuel during the time of its passage.

The increase in the speed of the fuel passage is definitely determined by the amount of additional carbon desired in the ashes on the one hand and the carbon content of the fuel on the other. -As the amount of carbon to be consumed for the production of gas remains the same in spite of the larger input, this input has to be increased within a' given period of time, so that the carbon content of this additional input is equal to the additional amount of carbon desired to appear in th ashes; but these reactions requiring a certain mperature the supply ofair must be increased, as the larger amount of fuel,

which on account of the quicker passage has to be heated up requires a greater quantity of heat. With the increase of air the'supply of steam heat required by the increased input. As a result of the additional supply of air and steam there is also a certain'increase in the quantity of the gas produced; but this amount is so small that it can practically be'disregarded.

If the tests show that quantity and composition of the gas have remained substantially the same, in spite of the increased throughput, the carbon content of the additional throughput must appear in the ashes and must be-activated, having been treated with steam in the usual way of steam activation, as steam and fuel employed at the temperature which represents the optimum conditions under which steam activation takes place. a

The test for ascertaining whether the method has been correctly employed, in so far as theproduction of the carbon is concerned, is carried out by means of the methylene blue titre and determining the carbon content of the residue.

For carrying the invention into eflect any kind of coal, for example pitcoal, charcoal or lignite (brown) coal, may be used. In order to facilitate the combustion the fuels may also be used in the form of brickettes obtained by the addition of a binder (for example tar) or by subjecting finely-ground fuel to a high pressure.

Asan explanation of the technical and economic improvement provided by the invention an example, taken from a producer operated on brown coal, will now be set forth, but variations according to the requirements of the particular case have to be made within the scope of the invention.

r A gas generator having a daily input of 25,000 kilograms of Bohemian brown coal (of an average content of 41.4 per cent C, 3 per cent H, 0.6 per cent N, 0.3 per cent S, 11.7 per cent 0, 3 per cent ash, and 40 per cent H20) and consuming 5000 kilograms steam gives in normal operation about 1000 kilograms of slag and ash residue containing 0 to 3 per cent C and having no noticeable adsorptive properties. The necessary quantity of air and steam is introduced into the producer, the ratio between air and steam being so regulated that the saturation temperature of the steam-air mixture amounts to 45-50% C; the low saturation temperature follows from the high water. content of the brown coal employed.

In order to obtain a slag and ash residue in 2,2so,e11 I about 2,400 kilograms, that is to say, to a total of 27,400 kilograms. Then, in order to obtain the necessary temperature in the incandescent zone, the quantity of air and steam must be increased empirically only to such an extent as to maintainthe required temperature in spite of the larger throughput, i. e. to about 5300 kilograms. The result of this procedure is the production of gas in quantity and quality as before, with however about 2,000 kilograms of slag and ash residue containing 40-50% C, which residue, after having been ground, shows a remarkable adsorptive capacity (methylene blue titre 2-3.5).

I have further found that the process in accordance with my invention gives particularly good results by dividing the fuel within the generator, after its passing into the incandescent zone, into two portions, admitting into the one the major part or even the whole quantity of the air supply and no steam or only a small quantity of it, and to the other portion the major part or even the whole quantity of the steam supply and no air or only a small quantity of it. This permits a complete combustion of the fuel in the air-fed part, so as to create appropriate temperature conditions throughout the incandescent zone, whereas the exclusive or prevailing admission of steam to the other part creates here temperature and steam condition sufficient only to a partial gasification of the fuel and appropriate to activation of the non-gasified carbon.

By properly regulating the admission of air and steam to the two portions the required temperature conditions throughout the generator and the desired' carbon content of the residue" from the steam-fed part may be obtained; the appropriate regulation of air and steam for both portions will also' yield gases, which after their mixing in the upper part of the generator form power gas of normal or desired composition.

The volume of the air-fed part need not be more than a quarter to a third of the volume of mg to the special conditions of the said method. 1

Referring to the accompanying drawing, the fuel is introduced in the normal manner, through the hopper A provided with a suitable feeding mechanism, not shown, and travels downwardly within the generator B.

Within the incandescent zone a central tube C is provided, which forms an inner cylindrical compartment D, and around the outer surface of which tube an annular compartment is formed, so as to divide the fuel into an inner core and an outer annular portion.

Below the central tube C, the grate is arranged which may be of any known or other suitable construction.

Through the grate, for example at G, air or an air-steam mixture is introduced by a tube H.

The annular outer portion of the fuel is carried by the tray 1, which is provided with a device for assisting the discharge of'the carbon containing slag and ash, which is removed at J, "remote from the inner core of the fuel.

Through the steam tube K, steam is' introduced into the outer portion of the incandescent fuel. For breaking up the fuel and forpreventing the same from baking together an agitator L is provided.

The producer gas obtained is discharged at M.

Although the disclosure of the above is that of the preferred embodiments, it will be readily.

prehends other details and procedures without departing from the spirit of the invention defined in the following claims.

This application is a continuation-in-part of application Ser. No. 217,621, filed July 5, 1938.

What I claim as my invention is:

1. A method for simultaneously producing an activated carbonaceous residue and producer gas which comprises supplying solid carbonaceous fuel through a gas producer at a rate materially in excess of that normally required to produce a fixed amount of gas by substantially complete asification of said solid carbonaceous fuel under optimal conditions of producer operation, and adjusting the air and steam supply with respect to said increased rate of fuel passage to (1) effect only a partial gasification of the total charged fuel, (2) maintain in the incandescent zone of the producer, in spite of said increase offuel' passage, that optimal temperature range which results when there are normal conditions of fuel and air and steam supply and which would ordinarily effect substantially complete gasification of said normal fuel supply and which would normally produce said fixed amount of gas from said normal fuel supply, (3) produce a gas which in quality and quantity corresponds substantially to that which would be produced under said optimal conditions of normal fuel passage and air and steam supply, and (4) yield a residue containing at least 25% of activated carbon.

2. A method for simultaneously producing an activated carbonaceous residue and producer gas which comprises supplying solid carbonaceous fuel through a gas producer at a rate materially in excess of that normally required to produce a fixed amount of gas by substantially complete asification of said solid carbonaceous fuel under optimal conditions of producer operation, and adjusting the air and steam supply with respect to said increased rate of fuel passage to (1) effect only a partial gasification of the total charged fuel, (2) maintain in the incandescent zone of the producer an optimal temperature range of about 1200-1600" C., (3) produce a gas which in amount of gas by substantially complete gasification of said solid carbonaceous fuel under. optimal conditions of producer operation, and adjusting the air and steam supply with respect to said increased rate of fuel passage to (1) effect only a partial gasification of the total charged fuel, (2) maintain in the incandescent zon of the promal fuel supply, (3) produce a gas which in quality and quantity corresponds substantially to that which would be produced under said optimal conditions of normal fuel passage and air and steam supply, and (4) yield a residue containing about 40-50% of activated carbon.

RUDOLF ADLER.

Images