US1913341A - Means for activating carbon - Google Patents

Description

June 6, 1933. T, SANDERS 1,913,341

MEANS FOR ACTIVATING CARBON Original Filed Feb. 3, 1931 2 Sheets-Sheet 1 Illllllll 690x024 June 6, 1933. M, T SANDERS 1,913,341

MEANS FOR ACTIVATING CARBON Original Filed Feb. 3, 1931 2 Sheets-Sheet 2 Patented June 6, 1933 UNITED ISTATES PATENT OFFICE 'IION, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE MEANS FOR ACTIVATING CARBON MARSHALL 'r. SANDERS, or vvILnmGron, DELAWARE, ASSIGNOR 'i'o DAROO coaroaA- Original application. filed li'ebruary 3, 1931, Serial No. 513,217. Divided and this application filed larch 2,

- 1832. Serial No. 596,356. 7

This invention relates to means for activating carbon; and it comprises an apparatus for activating carbon including a heat insulated vertical reaction chamber of rela- 5 tively large cross-sectional area provided with a tangential lateral extension of small diameter inclined at a small angle to the horizontal, with means for introducing into said extension air as a current and With means in the extension for suspending and dispersing finely divided carbonaceous material in the introduced air current, said reaction chamher having a gas outlet at the top and means for removing activated carbon at the bottom and being advantageously provided'with-a steam inlet adapted 0 effect in the chamber treatment with steam of the carbonaceous material after its ignitiorxvdvith air and after its separation from the g ses formed in said 0 ignition; all as more fully hereinafter set forth and as claimed.

Activation of carbonaceous materials to increase their power of adsorption is accomplished by heat treatment in various ways, one of the commonest being the subjecting of raw material or of spent material during the heat treatment to an atmosphere of CO or steam or products of combustion containing both. As a rule the temperatures maintalned during such treatmenthave ranged well 7 v above 800 C. and in some cases have been above 1,300 C. It has also been proposed to use air as an activating agent during the heat treatment with a view to applying the oxidizing action of the air oxygen to prevent charring of the material and consequent clogging of its pores. When air has been thus used it has usually been found necessary to keep the temperature below 500 C. to prevent overburning and it has been found impossible under these conditions to obtain a satisfactory degree of uniformity in the operation and product. The action of air at low temper-' atures is slow and hence the capacity of the apparatus is limited. Temperature control is diificult.

Various a paratus arrangements have been used-in activating carbon. Sometimes the material is treated in horizontal rotating cylinders, sometimes in stationary vertical chambers. The reactionchambers have been in some cases externally heated and in others they have been adapted to internal heating by superheated activating gases; Combinations of both internal and external heating have been proposed.

In the patent to Davis No. 1,873,998,-where on the present invention in some of its aspects 1s an improvement, a method of carbon acti vation, particularly adapted to revivification of spent carbons, is described and claimed 1 wherein activation is effected by the action of air at temperatures ranging around and above 800 C. in an externally heated tube, the amount of air being definitely proportioned to the amount of volatile'matter in the material undergoing activation and a selecrial being activated. .So doing, I find it ad vantageous tocontrol the temperature by conserving the heat of reaction through adequate insulation of the reaction chamber and by introducing a controlled quantity of steam into the reaction chamber. It is also advantageous to adapt the reaction chamber to effect therein a separation of the carbon material from the gaseous products produced by the air and to introduce steam into the reaction chamber at such a location that steam reacts-with the carbon material after its separation from the air reaction gases. The steam acts both to complete the carbon activation and to moderate the temperature by endothermic action as well as by taking up sensible heat.

In an apparatus embodiment of my invention, involving operation of the described method, the carbonaceous material to .be activated is after fine grinding suspended and dispersed in a current of air passing through a somewhat inclined chamber'which' delivers into a vertical chamber of substantially larger area than the inclined chamber and the steam is introduced into the vertical chamher advantageously at a point well below the point of entry of the carbon-air dispersion; the vertical chamber being provided with gas outlet at the top and with carbon outlet means at-Ithe bottom; the cross-sectional area of the vertical chamber being such that the activated carbon settles out of the gases to the bottom of the chamber. I

In-a modified form of my apparatusthe vertical reaction chamber is divided into an 16 external and an internal portion, the'air reaction taking place in the external chamber and thereb heating the internal chamber and the car on, after separation from the air gases, being transferred from the bottom of so the external chamber to the top of the internal chamber to be dropped through an upward current of steam introduced near the bottom of the internal chamber.

I In the process embodiment of my invention as the oxidation by air oxygen of the material being activated is relied upon to maintain the temperature proper for speedy activation, which I have found to be from 800 to 1,050 0., a part of the heat of the exothermic oxida- .tion being utilized in supplying the heat absorbed in the endothermic oxidation of the carbon material with steam. In some cases it is desirable to preheat the steam and for this the gases formed in the activation reacbe preheated.)

Regulation of the operation of the present invention, usingv air. alone as the activating agent, may bemerely by dissipating the heat formed in the activating reaction as by externally coolingv the reaction chamber. But in most cases I find it better to conserve the heat of reaction by carrying it on in a heat insulated chamber and introducing steam .into the chamber in an'amoufit so proportioned to that of the air that the temperature is moderated and controlled within the desired range. In' all cases the quantity of air in which the starting material is dispersed is carefully regulated. in proportion to the volatile matter in the material. The quantity'of air varies with different materials and usual- 1y ranges between 70 and 130 cubic feet (measured at F. and atmospheric pressure) per pound of volatile combustible matter in the raw material. In a properly insulated reaction chamber the necessary activating temperature can in most cases be main-" tained with a proportion 'of air to carbonaceous material such that CO is formed with but little 00 the heat being largely pro- ,vided by selective oxidation of contained volatile combustible matter to CO'and H2O, but little of the solid carbon of the raw ma- 0' terial being consumed. With greater air tions'may be used as fuel. The air also may material carried by the air current ratios more CO may be formed and some of the solid carbon ma be gasified. When using a raw materia such for example as lignite, the conditions of temperature, time or rate of reaction and air ratio can be so adjusted that high yields of finished activated carbon areobtained and the gases produced in activation have a good fuel value.

It is of course possible to use oxygen-enriched air in the present process and when oxygen for enrichment is cheaply available, this may have advantage in increasing apparatus capacities.

In the accompanying drawings I have shown more or less diagrammatically apparatus within my invention.

In this showing,

Fig. 1 is a view in vertical section of an activating apparatus;

Fig. 2 is a horizontal section along the line A'-A of Fig. 1;

Fig. 3 shows a view in vertical section partly in elevation of an activating apparatus similar to that shown in Figs. 1 and 2 but having additional means for eflectin the activation in two stages; a portion 0 the showing of Fig. 1 being omitted from Fig. 3.

Referring first to Figs. 1 and 2, the vertical activating chamber 10 is provided with a refractory lining 11 backed by heat insulat-' ing material 12 and has an external metal shell 13. The activating chamber has a'tangential projection 14 inclined at a small angle to the horizontal, which is adapted to receive through afunnel 15' the finely powdered materiahto be activated. Funnel 15 is provided with avstar valve 16 and receives the ground material from hopper 17. A worm and tube may be used instead of the funnel and valve for introducing carbon material 'into 14. Into the outer end of the lateral chamber 14 a current of air is blown (by suitable means not shown) through air conduit 18 rovided with a meter 19. As shown, the inc inedprojection 14 joins with vertir the vertical chamber has a cross-sectional being thereby adapted to cause separation from the gases in the chamber of susflpended rough Vertical the inclined lateral chamber.

. chamber 10 has a conical bottom 20 which-is shown as un-insulated, and from the bottom leads a conduit 21 provided with a valve or worm 22, the arrangement adapted for continuous removal of activated material from the activating chamber after its separation from the gases ilfthe chamber. Gases.

leave the vertical chamber 10 through .the

stack 23 and removal of the gases may be assisted by 'a suitable suction device (not shown). Into the vertical chamber 10 at a level wcllbelow that of the lateral chamber 14 steam can be admitted through a steam no cal chamber 10 near its middle portion. and

I -line 24' provided with a meter 25. The steam activating carbon, etc. is admitted through funnel 15 and suspended and dispersed in a current of air introduced through air conduit 18 and is blown through chamber 14 into the vertical chamber 10 where the mixture becomes ignited. I have found that the air volume required for satisfactory working may be varied between 70 and 130 cubic feet (measured at 60 F. and atmospheric pressure) per pound of volatile matter in the carbonaceous material. The best air ratio varies according to the nature of the material being activated, and tothe temperature and the rate of carbon-air feed. The air ratio can be readily determined by trial. I have obtained a highly activated carbon from a lignite with an air ratio of about 70 cubic feet per pound of volatile combustible matterin the lignite as determined by the usual proximate analysis. The tangential relation of chamber 14 to chamber 10 is advantageous and with a suitably regulated air draft the burning off of the volatile matter from the carbonaceous material proceeds rapidly and regularly in chamber 10 and the chamber is held by the heat of the reaction itself at between 800 and 1100 C. In this temperature range many carbonaceous materials have been found to be well activated in the short time during which they are treated in the vertical chamber and the activated material separates from the products of the air combustion in the vertical chamber to settle in the conical bottom 20 and to be removed by means of the conduit 21 through the valve 22, the arrangement being such as to prevent gas from passing out of the chamber with the activated product. The reaction temperature in chamber 10 is controlled by the introduction of steam through pipe 24 and the steam aids in the activation. This pipe advantageously delivers tangentially into chamber 10 and the material separating from the gases in the upper part of chamber 10 is treated with steam in'the lower part.

The steam is introduced in the quantity necessary to hold the temperature inside chamber 10 at the desired point. H O contained in ,the raw material tempers the heat developed by the air. If desired, a cooling chamber may be inserted between chamber 10 and outlet valve 22. Sometimes the flame produced by the ignited mixture in chamber 10 strikes back into projection 14 and ignition may occur as the air and carbon mix. This usually does no harm and in some cases is of advantage in increasing the time of treatment but as a rule it is better to maintain a rate of air flow in 14 suflicient to prevent the flame striking back. It is found advantageous to have chamber 14 considerably inclined with respect to the vertical chamber, without the inclined chamber being actually horizontal. Ordinarily the pressure in chamber 10 is kept slightly above atmospheric, a positive pressure around 0.1 inch Water being in most cases satisfactory. Higher pressures or subatmospheric. pressures can be applied if desired.

Certain materials require a more extended treatment with steam to effect a high degree of activity, and in such cases the apparatus shown in'Fig. 3 may be used. In this apparatus an inner un-insulated metal tube 30 is placed in chamber 10, into which is intro duced through side chamber 14 a current of air and dispersed carbon as in the apparatus of Fig. 1, the means for doing this being omitted from the showing of Fig. 3. The steam. is admitted near the bottom of tube 30 through valved pipe 31 provided with meter 32.

Tube 30 is heated externally by the air activation reaction taking place in chamber 10 and the air treated material is withdrawn from chamber 10 through conduit 33 and valve 34 and is conveyed by conveyor 35 to the hopper 36, from which it is delivered through valve 37 into the top of tube 30.

Activation of the material begun in chamber I the top. The tube temperature is observed by means of a pyrometer inserted at 40. In the steam treatment the fine particles of material delivered into tube 30 by valve 37 are retarded in their fall by the upward current of steam and gaseous reaction products and the time of treatment is thereby extended.

In treating various materials to produce activated carbon some variations of method and means is sometimes desirable. For example, when working with a readily activatable material such as some of the spent activated carbons produced in decolorizing processes, it may be desirable to increase the rate of throughput and it may thenbe advantageous, as stated ante, to use an uninsulated chamber 10 and sometimes even to externally cool this chamber as by a water spray. So doing, a high rate of throughput with a concomitant high rate of heat development and dissipation becomes possible without sacrifice of the degree of activityimparted to the product.

This application is a division of my prior and copending application Serial No. 513, 217, filed February 3, 1931.

What I claim is 1. Apparatus adapted for activating carbon by an exothermic reaction with air oxygen, said apparatus comprising in combination a vertical chamber provided with a heat insulating lining adapted to maintain within the chamber an activating temperature developed solely by the heat set free in the activating reaction, a heat insulated tangential lateral inclined projection on said chamber, means at the outer upper end of said projection for introducing thereinto a regulated current of air, regulated positive feed means arranged in said projection .for dispersing pulverized carbon in said air current, a gas outlet near the top of the vertical chamber and positive means for continuous removal of activated carbon from the bottom of the chamber, said last-named means being sealed against passage of gas therethrou h.

2. Apparatus for activating car on comprising a vertical heat insulated chamber, an

inclined tangential lateral projection on said chamber, means at the outer upper end of saidv projection for introducing thereinto a current of air, positive feed means in said projection for dispersing pulverized carbon in said air current, a steam inlet pipe in the vertical chamber at a level below that of the Inclined projection, a gas: outlet near the top of the vertical chamber and positive means for continuous removal of activated carbon near the bottom, said last-named means being sealed against passage of gas therethrough. 3; Appar apus for activating carbon comprising an outer: heat-insulated vertical chamber, an inclined chamber in open communication with, and of less cross-sectional area than, the vertical chamber and projecting from the side of the vertical chamber at a v small angle to the horizontal, said inclined chamber comprising means for introducing outlet for gas at the-top a mixture or air and finely-divided carbonaceous material into the vertical chamber, an

of the vertical chamber, means for removing partially activated carbon from the bottom of the vertical cham- W her, a vertical inner chamber located inside in the outer chamber,

the outer vertical chamber and adapted to be heated by exothermic reactions taking placemeans for introducing partially activated carbon into the top of the inner chamber and means for removing activated carbon from. the bottom thereof, an inlet forsteam near the bottom of said inner chamber, and an outlet for gas near the top. 4. Apparatus for activating carbon by an exothermic oxidizing reaction, which com- 11888 three chambers: an inner chamber aving heat-conducting walls with an inlet and anoutlet for gases and an inlet and an' outlet for powdered carbon, an outer chamber surrounding the inner chamber but out of 'clined chamber near the outer direct communication therewith and having an outlet for gas and an outlet for powdered carbon, and a third chamber inclined to and opening directly into. the outer chamber tangentially and providing an inlet for carbon and oxygen-carrying gas into said outer chamber; and means for transferring carbon from the outer chamber to the inner chamber.

5'. Apparatus for activating carbon comprising a vertical refractory-lined chamber, a refractory-lined chamber of less cross-sectional area inclined at an angle to the vertical chamber, tangential to the chamber and inopencommunicationtherewithnear itsmiddle, positive gas-tight means for continuously introducing powdered carbon into the inupper end thereof, positive gas-tightmeans for continuous Withdrawal of carbon from the lower end of the vertical chamber, means for introducing air into the outer, upper end of the inclined chamber and means for introducing steam near the bottom of the vertical chamber, controlling means for each of said introducing means, and an outlet for gas at the top of the vertical chamber.

6. Apparatus for producing activated carbon comprising an outer heat insulated chamber provided with means for introduction therein of a current of air carrying admixed powdered carbonaceous material, said outer chamber having a gas outlet near the top and a gas-tight outlet for solid material at the bottom, an inner non-insulated chamber within said heat insulated chamber, out of communication therewith and adapted to be heated by heat transfer from the outer chamber, a gas inlet near the'bottom of the inner chamber, and conveying means for transferring the solid material from said gastight outlet to the topv of the inner chamber.

In testimony whereof, I have hereunto affixed my signature,

MARSHALL T. SANDERS.

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