US2616858A - Method for reactivating bone-char and the like - Google Patents

Description

1952 E. D. GILLETTE ET AL 2,616,858

METHOD FOR REACTIVATING BONE-CHAR AND THE LIKE Filed March a, 1946 Z6 12 10 SPENT g/ 51" w .32 v CHAR INLET 712; I I -Jif y;

JPEN CHAR 570F465 J0 7 5 URNER l Y FURNACE 60015 FRESH c/Mfi V I SPENT 01ml? Z9 10 INLET 31/ 2 was r: FINES sue/m 83 r--,---- 4/01/01? PERCOLAT/O/V AND 4 WASH TAN/(s,

ACTIVATED V565 mam cARao/v 111i 5 MIX TANK 2d cum F/L 75R CAKE INVENTORS EARL DWIGHT GILLETTE THOMAS M. BROWN ATTORNEYS V COOZER fiatentecl Nov. 1952 UNITED STATES PATENT OFFICE EarlDjwight Gillette, Hastings-ori-Hudson, and Thomas M; Brown, Bronxville, N. Y., assignors to Refined Syrups & Sugars, 71nd, Yonkers; N. Y., a corporation of New York Application March 6, 1944;, Serial No, 652,460

1 Claim.

This inventionrelates to methods and apparatus-for reactiv'atin-g filtering material and the like such, for enampl'e, as spent moist bonehar which has been used for decolorizing or otherwise refining sugar liquors or other mat'erials;

In the refining of sugar liquors, syrups; and the lili'epit has ulna been the practiceto treat the sa e in percolation tanks or otherwise, with bone char for decoloriz'in'g purposes or the removalof other undesired ingredients. Such bonechar as customarilyused comprises aporous tricalciu iri 5 phosphate material in 'finely dividedcondition, the orous surfaces'being covered with a thi n layerofc'arbon (surface char is usually 14-60 mesh). Usually the bone-char as commercially available for these purposes comprises in the neighborhood of from 8 to 10% carbon. After each use of the bone-char for this purpose i'thas'for many years been the custom to reactivate the char by allowing it to fallthrough tubes which are heated externally to a temperaturesuch that the decolorizing properties of the char are more or less restored, However, repeated treatment of the char in this way results in theaccuniulation therein of higher and higher percentages of carbon. Yet when the carbon content'ireache's even as high or higher than 11% the material hasbeen found to be definitely unsatisfactory for'tre'ating sugar liquors. As such unsatisfactory condition progresses with the reuse "ofthe' char,-it becomes necessary to use larger" and larger amounts ofchar in order to maintain thedes'ired color in the char filtered liquor. The" mixture becomes sorelatively ineffectivethat in commercial practice heretofore it has been found necessary to use anamount of bone-char ranging'from' about 3 5 up to as high as 160% of the amount of sugar being treated (by dry weight). Since such bone-char and the reactivating thereof is'costly, the use of it in such large proportions, with the necessity of constantly adding considerable fresh quantities, results in aheavy expense' which has not'heretofore been avoidabledespite various efforts which have been made to try to do' so. For example, in some cases it is the practice after the char has been reactivated a number oftimes to subject it to a kiln treatment for burning off a subsantial propor-ti'on of theexcess carbon. However, this practice-as usually carried out has the disadvantage that during intermediate periods the char is relatively inelficient; also the percentage of re,- mainingcarbon cannot be properly controlled and in some'parts of the char nearly all of the carbon may be burned outso that thesep'ortions are thereafter inactive; Furthermore, despite these reactivating and decarbonizin'g steps as heretofore practicedthe char masses havea very objectionable odor, generally noticeable throughout the plant, and this" results in imparting an odor orp o s'sibly other undesirable'qualities to the sugar liquor. It-appears' thatin a conventional char kiln" where the bone -char passes through elongated tubes and where the char has'probably a'thic'kness' in these tubesrangingfr'om l" to 2" that only theparticle's -of charin contact with the inside of th'e tubes becomes reactivated; the bulk of the charpas'sing through the entire kiln wit-h out sufli'cient heat treatment to either reactivate the carbon on the char'or'to dispel the impurities from the char.

According to the present invention a method and apparatus is provided for so reactivating the bone-char that its carboncontent may be'maintained at the desired optimum value and at the same time'eliminatingall objectionable or noticeableodors, With this invention it has been found that the" amount of bone-char us'ed'for decolorizing sugar, for example, may be reduced to a quantity amounting to about 1'1 to 12% of the amount of sugar. At the same time, the amount of char lost with each"reactivat'ion thereof is no more than from A to /2 of one percent so that the corresponding percentage of make-up char required to be added to the reactivated char represents a very minor expense as compared with the prior practice. Furthermore, the resuiting sugar liquor astreated with the char: reactivated in accordance with the invention is' free of odor so that so far as concerns removal'of odors no subsequent vegetable carbon treatment would be required although for final clear ole colorizationsub's'equent treatment with a smaller quantity of activated vegetable carbon is desirable.

When: organic matter, of the type which the I Various further and more specific objects, features and advantages of the invention will appear from the detailed description given below taken in connection with the accompanying drawings which form a part of this specification and illustrate merely by way of example, preferred form of apparatus for the practice of the invention. The invention consists in such novel features, arrangements and combinations of parts and features as may be shown and described herein.

In the drawings:

Figure l is an elevational view showing somewhat schematically an arrangement of furnace apparatus for carrying out the invention;

Fig. 2 is a similar view of a modified form of the apparatus; and

Fig. 3 is a flow sheet schematically indicatin the manner in which the bone-char may be utilized and reactivated in a plant for treating sugar liquor in accordance with the invention.

With the apparatus shown a substantially continuous supply of spent moist bone-char may be introduced through an inlet I0, at the top of a furnace H, as from a conveyor l2. The furnace may comprise a plurality of superposed hearths as at I2-l9 inclusive, contained within a surrounding cylindrical furnace wall as at 20. The furnace may be of the well-known Herreschoff type having a central rotatable shaft as at 2|, carrying rabble-arms as at 22 extending out over each hearth and all carrying rabble-teeth as at 23, for periodically agitating and gradually advancing the material over each hearth. Alternate hearths are formed, respectively, with central and peripheral discharge openings as at 24, 25, so that the material may be rabbled inwardly and outwardly, respectively, on alternate hearths and allowed to fall from hearth-to-hearth through said discharge ports.

The rabbling structure may be rotated in the usual way as by motor driven gearing 26. Also cooling air cavities may be provided through the rabbling structure in the usual way, the air being admitted as through a conduit 21 connected to the base of the shaft. The air after passing through the cooling conduits may be withdrawn through a conduit 28 from the top of the shaft, as by a suction blower 29.

For purposes of explaining the operation of the apparatus in accordance with the invention,

the furnace may be considered as being divided into four zones, as indicated in Figure 1, two hearths being shown for each zone, although it will be understood that depending upon the diameter and desired capacity of the furnace and other factors, each zone if desired might comprise only one hearth or might comprise more than two hearths. Also the functions of each of these zones to a certain extent may overlap. The first or upper zone will be referred to as a drying zone. Ordinarily the material on the two hearths I2, [3 of this zone, respectively, may be subjected to gas temperatures in the neighborhood of 300 and 460 F. When subjected to these temperatures, as the bone-char is being rabbled over these two top hearths, substantial quantities of moisture and generally the greater part of the moisture thereof will be evaporated and may be drawn off through an outlet conduit 30 connected into the conduit 28 and thus to the suction blower 29. A damper as at 3| may be provided accompanied by a manometer as at 32 for the conduit 30. The damper, for example, may be adjusted so as to provide 4 a gas pressure at the furnace outlet for example of .45" H2O.

The next or second zone will be referredto as a heating zone. On hearths I4 and i5 therein the bone-char may be subjected to gas temperatures for example in the neighborhood of 460 and 690 F., respectively.

At this zone outlet conduits as at 33, 34 are provided having dampers as at 35 so that adjustable amounts of the relatively drier atmosphere of gases may be withdrawn from this zone and passed through a dust separator or classifier as at 3B. In this classifier the excessively fine particles of bone-char and carbon are removed and passed to a storage container as at 32', whereas the withdrawn gases will pass through a conduit 38, drawn by blower 39 which discharges the same through a conduit 40 into a combustion chamber 4! in a manner hereinafter described.

The next, or third zone, will be referred to as aburning zone. Here the bone-char which will previously have become substantially dry, is subjected to hot gaseous products of fuel combustion coming from the combustion chamber 4|. As will be hereinafter explained these hot gases contain a limited and controlled amount of oxygen and also preferably a small amount of water vapor in excess of such water vapor as may occur as a part of the products of combustion of the fuel. The temperature of the gases at hearths l6 and l! respectively may be maintained, for example, in the neighborhood of 1080 and 1170" F. On these hearths most of the organic material in the bone-char is burned away, together with a controlled amount of the carbon preferably so as to restore the carbon content to an amount comparable to or somewhat less than that present in fresh bone-char.

The combustion chamber 4| may comprise a housing preferably somewhat elongated in a horizontal direction as shown, and formed of or lined with suitable refractory material. This chamber may be supported by any suitable means with one end thereof against the external wall of th furnace, there being provided openings as at 42, 43 for bringing this end of the chamber into communication with the spaces over hearths l6 and H. An oil burner as at 44 may be mounted to extend through the outer end wall of the chamber to direct its flame toward the furnace opening 42, 43. Oil and air lines for the burner respectively are indicated at 45, 46, each provided with suitable valves for regulation of the oil and air mixture and the size of the flame. A plurality of conduits as at 48 may extend from th conduit 40 into and through the end of the combustion chamber 4| at spaced points as shown, surrounding the centrally positioned oil burner. Thus the flame in the chamber will be surrounded by jets of gases from the conduits 48 so that the walls of the chamber are protected against deterioration by the heat and at the same time the gases reintroduced through the conduits 48 become uniformly mixed with the gaseous products of fuel combustion as the mixture enters through the openings 42, 43 into the furnace.

After passing through the third zone, the treated bone-char may be passed over additional hearths l8 and [9 of the fourth zone at which the gas temperatures, for example, may be in the neighborhood of 875 and 850 F. respectively. If desired, this fourth zone may be omitted although it is believed that in some cases a further beneficial effect in activating thechar isjmade possible by reason of maintenance of the" relatively high temperature thereof during the: short additional period of passage through such a fourth zone.

From the bottom hearth IS the material may pass out through an exit opening as at 50 into a suitable cooling device as at El, which may be supplied with cooling fluid through conduits as at 52, 53. The specific construction of this cooling device forms no part of the present invention, various suitable devices for this purpose being commercially available. As the material passes through externally cooled tubes or cavities thereof, it will become cooled before dropping out, for example, onto a conveyor as at 54. In order toprevent any danger of ignition or injury of the carbon on the bone-char upon its discharge to the atmosphere from the furnace; it should be preferably first cooled to a temperature of 300 -F. or less.

Summarizing the operation of the above de scribed equipment, the spent moist bone char which may initially have a moisture content of about .22 to 25%, is subjected to a uniform and rapid drying action in the first zone with preferably the greater part of the moisture content being drawn off directly through the conduit 33. Because of the relatively slow rotation of the rabble arms over the hearths, the rabble teeth will periodically and gently advance each portion oI thetrelatively thin horizontal layer of material on each hearth so that the drying action in the first zone, as well as the treatment in subsequent zones, will be uniform for all of the material and insure that-all parts of it are repeatedly exposed to the atmosphere of gases over each hearth.

In the second zone, the bone-char will become rather thoroughly dried and heated up to a temperature ready for prompt burning action in the third zone. The gases as drawn off through conduits 33 and 34 from the second zone will include some of the moisture evaporated off in this zone, whereas the remainder will pass on up to the first zone. Hot gases from the burning zone will rise up into the second zone and act to maintain the desired temperatures therein and then partially travel up into the first zone for maintaining the drying temperatures therein, the remainder passing out through the conduits 33, 34 for eventual return to the combustion chamber M.

The separation of the dust or fines as by the classifier 36, from the gases withdrawn from the conduits 33, 34 is highly desirable, since otherwise such dust .Would tend to adhere to and ac-- cumulate to a prohibitive degree on the interior walls of the combustion chamber and of the furnace burning zone. In any event such fine material is generally of such a nature that it would be detrimental to the reactivated bone-char if returned to the furnace and mixed with the char therein. The classifier thus located in the gas recycling conduit provides a simple means for continuously eliminating much of the objectionable fines and dust from the product during its reactivation.

The oil burner, for example, may be operated in a. manner whereby its fiamewill be at a temperature in the neighborhood of 300 0 F. When the gaseous products of combustion therefrom become mixed with the recycled gas entering through conduits 48, the temperature of the resulting mixture upon entering the furnace openings 42 and 43 may, for example, be in the neighborhood of 1600 F., assuming that the gases overh'earths l6 and I1 are;to be maintained at about 1080 and 1 F. The recycled gases may for example comprise an amount by weight equal to about three times the amount oflthe gaseous products of combustion from the fuel burner. The oil and air supplies to the burner may, for example, be adjusted so as to provide about 2 of O2 in the combustiongases. This will provide the limited amount of oxygen required for burning away the organic material from the char and a portion only of the carbon thereon, in the burning zone.- A relatively small amount of this oxygen will be utilized inthe burning zoneso that the gases as withdrawn through the conduits 33, 34 before recyclingmay have an 02 content of nearly 2 The various temperatures and othernumerically specified factors giveri herein arefor a preferred example which has given unexpectedly satisfactory results, but itwill be appreciated that-these factors-may be varied considerablyin practice. For example, if a greater percentage of oxygen is made available in the burning zone, the temperature may be reduced somewhat or, if the temperatures are-increased, then in general the oxygen present in the burning zone should be reduced.

With a furnace as above described of 'a diameter of 13% feet, it was found that three tons per hour of spent bone-char could be readily reactivated, the speed of the rabbling structure being" adjusted at a rate to cause that amount of materlal'to be passed through the furnace per hour.

It is believed that the above described arrangement for recycling the gases from the furnace back into the combustion chamber is highly advantageous, not only because of its affording a ready means for carefully adjusting and controlling the temperatures and gas mixture at the burning hearths, but also because it provides a means for supplying a controlled and limited amount of moisture in the form of superheated steam in the presence of the bone-char while it is beingreactivated.

Due to the effect of the presence of superheated steam during the reactivation of the carbon on the bone-char, its properties as'a decolorizing agent appear to be substantially improved. Since the gases are preferably withdrawn through conduits 33 and 34 at intermediate hearths on which some moisture, but not an excess amount, is being evolved, it will be apparent that means is afforded for reintroducing with the combustion gases a continuous regulated and limited supply of steam. Such steam may for example constitute in the neighborhood of 15-20% of the gas mixture introduced at the burning hearths. This percentage may be varied by adjustment of the dampers 35. For example, if more moisture is desired in the recycled gases, the damper in conduit 33 may be'adjusted to a position relatively more open than thedamper in conduit 34. On the other hand, if drier recycled gases are desired, a greater percentage thereof may be withdrawn through conduit 34 by moving the damper in conduit 33 toward closed position.

A manometer tube as at 60 may be connected tothe combustion chamber to enable determination of the gas pressure therein. In a typical case, the manometer reading was .35" E20. This pressure may of course be adjusted by adjustment of the blowers 29, 39 and the various dampers.

' Extensive tests have shown, as hereinabove stated, that the carbon content of the bone-char should be reduced during the treatment to a figure below 11%. Considerably improved results are obtained if the carbon content is reduced to about 9%. Furthermore, it has been found that satisfactory results may be obtained within rather wide limits below 9%. It appears that best results for clear decolorization may be obtained with bone-char having from 3 to 7% of carbon, whereas from 2 to 9% may be stated as the outer limits for reasonably economical and practical purposes. 1 7

The above described equipment provides an efficient and economical arrangement to operate, in that the spent wet char may be fed in continuously and with the continuous delivery of cooled regenerated char. Also the time of treatment may be readily adjusted by adjusting the speed of the rabbling structure so that the conditions of time, temperature and concentration of gases at the burning zone may all be controlled, and by trial these factors may be adjusted to secure best results.

Fig. 2 shows an alternative furnace arrangement in which certain of the parts corresponding to those of Fig. 1 are identified by the same ref erence numerals accompanied by prime marks. Except as to features hereinafter described, the arrangement of Fig. 2 may be the same as of Fig. 1. In Fig. 2 it will be noted that the lower two hearths have been omitted so that the burning zone is at the bottom of the furnace with the combustion chamber 4| correspondingly positioned. With this form of the invention, the

cooling conduits within the central shaft 2 I may be blocked off as by a plate 70 so that cooling air is not admitted to the rabbling structure at the relatively lower temperature hearths above this point. Instead of providing an independent source of cooling air, a part of the gases withdrawn through conduit 33 are conducted from conduit 40' through a connection 'Il into the base of the shaft 2|. This portion of the gases passes up through the central shaft and out through the hollow rabble arms as at 12 at the lower hearths. These rabble arms are thus kept at a safe temperature by these gases passing therethrough, the gases being discharged through suitable apertures or the open ends of the arms as at 13. It will be understood that various dampers may be provided in the conduits, as indicated, to regulate the amount of gas withdrawn by blower 39 and the proportion thereof which is returned to the combustion chamber 4 I as compared with the proportion which is returned in to the furnace by way of the cooling conduits of the lower rabble arms.

As indicated in Fig. 3, the reactivated bonechar, after passing from the furnace 20 through cooler 5!, may be allowed to fall on a suitable screen as at 80 for the discharge of waste fines into a hopper 8!. The desired reactivated char, together with such fresh make-up char as may be needed, may then be conducted into a char storage chamber 82. From this chamber the char may be discharged into alternatively used percolation and washing tanks as at 83, 84 containing the sugar liquor to be treated. From these tanks the treated liquor may be run into a tank as at 85 for mixing with a desired quantity of activated vegetable carbon for further clear-decolorizing treatment. After treatment in this tank the clear syrup and filter cake may be separated in a filter 86. The spent char in the percolation and washing tanks after removal of the sugar liquor, may be conveyed to a spent char storage chamber as at 81, where it is kept until fed into the reactivating furnace.

While the invention has been described in detail with respect to particular preferred examples, it will be understood by those skilled in the art after understanding the invention that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended therefore in the appended claims to cover all such changes and modifications.

What is claimed as new and desired to be secured by Letters Patent is:

Method for reactivating spent moist bone char which comprises passing a continuous supply thereof successively through drying, preheating and burning zones by periodically agitating and gradually advancing the char in generally horizontal layers through each zone and allowing same to fall from zone to zone.'continuously introducing into the burning zone a stream of hot gaseous products of fuel combustion together with steam, maintaining about 15-20% of steam, and a suflicient oxygen content, in the atmosphere in said burning zone to cause burning away of the organic material on the char but limiting such oxygen content to about 5% or less so that carbon will remain in and upon the char in amounts of about 2-9%, continuously conducting the gaseous products from such burning zone into the presence of the char in the preheating zone to provide suificient heat for causing steam to be there evolved from the char, continuously withdrawing from said preheating zone a substantial part of said gaseous products and steam and, after separating dust therefrom, reintroducing same into said burning zone along with said gaseous products of combustion in an amount and at a temperature such as to maintain a temperature of about 900-1170 F. in the burning zone.

EARL DWIGHT GILLETTE. THOMAS M. BROWN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 343,666 Lillie June 15, 1886 351,929 Lillie Nov. 2, 1886 1,114,371 Laist Oct. 14, 1914 1,440,194 Wijnberg Dec. 26, 1922 1,598,967 Hiller Sept. 7, 1926 1,806,020 Parker et al. May 19, 1931 1,833,590 Read Nov. 24, 1931 1,895,878 Bunce et al Jan. 31, 1933 2,064,813 Andrews Apr. 24, 1933 2,277,355 Roderick Mar. 24, 1942 2,333,111 Lykken Nov. 2, 1943 2,387,936 Nicholls et a1 Oct. 30, 1945 2,433,498 Whitford Dec. 30, 1947 2,457,837 Simpson et a1. 1 Jan. 4, 1949

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