US 2552014 A
Description (OCR text may contain errors)
y 8, 1951 F. PUENING v 2,552,014
PROCESS FOR PREHEATING com, FOR coxmc Filed July 25, 1946 1o Sheets-Sheet 1 May 8, 1951 F. PUENING 2,552,014
PROCESS FOR PREHEATING COAL FOR COKING Filed July 25, 1946 10 Sheets-Sheet 2 lnventa l0 Sheets-Sheet 3 -i-l. -llwhlrnT U, I 1 J, 9, I
F. PUENING PROCESS FOR PREHEATING COAL FOR COKING May 8,1951
Filed July 25, 1946 y 8, 1951 F. PUENING 2,552,014
PROCESS FOR PREHEATING COAL FOR COKING Filed July 25, 1946 10 Sheets-Sheet 4 May 8, 1951 F. PUENING PROCESS FOR PREHEATING COAL FOR COKING l0 Sheets-Sheet 6 Filed July 25, 1946 May 8, 1951 F. PUENlNG PROCESS FOR PREHEATING com. FOR coxmc 10 Sheets-Sheet '7 Filed July 25, 1946 May 8, 1951 F. PUENING PROCESS FOR PREHEAT ING COAL FOR COKING 1 0 Sheets-Sheet 8 Filed July 25, 1946 May 8, 1951 F. PUENiNG PROCESS FOR PREHEATING COAL FOR CQKING 1O Sheets-Sheet 10 Filed July 25, 1946 Patented May 8, 1951 PROCESS FOR PREHEATING COAL FOR COKING Franz Puening, Riegelsville, Pa.
Application July 25, 1946, Serial No. 686,084
2 Claims. (Cl. 263-52) The present invention relates to the preheating of coking-coal in preheaters in which the coal travels through externally heated vertical tubes or conduits.
It is an object of this invention to provide means whereby repeated and excessive overheating of the outer layers of the coal to a temperature above its intended highest preheating temperature is avoided, and thus to protect the coal against damage to its coking power.
It is another object to provide a tubular preheater of high heat economy by providing counter current heat exchange between the raw coal and the heating gases and by reducing the heating gases to a lower temperature, before leaving the preheater and by reducing heat losses into the atmosphere.
It is a further object to provide means which guarantee the destruction of tenacious agg10merations of wet fine coal and their complete drying and preheating. Further improvements will become apparent hereinafter in the specification and claims.
In order that the nature of the invention may be more clearly appreciated, particular embodi ments are shown in the accompanying drawings, in which:
Figure l is a vertical section of the new preheater.
Fig. 2 is a horizontal section, taken on lines 2--2 of Fig. 1;
Fig. 3 is a sectional elevation, taken on lines Fig. 4 is an enlarged vertical section of the bottom portion, already shown in Fig. 1;
Fig. 5 is an enlarged section view of the bottom portion of Fig. 3;
Fig. 6 is a horizontal section, taken on lines 5-45 of Fig. 5;
Fig. 7 shows an alternative to that shown in Fig. 5, also taken on lines 55 of Fig. 2;
Fig. 8 is a horizontal section, taken on lines 8-8 of Fig. '7;
Fig. 9 is an enlarged vertical view of the top agitating device shown in Fig. 3;
Fig. 10 is an enlarged vertical section of the same agitating device as shown in Figs l and 9;
Fig. 11 is a sectional elevation of an alternative for Fig. 1, the tubes in Fig. 11 occupying a slopewise position, while those in Fig. l are vertical.
Fig. 12 is a vertical section of an alternative for Fig. 3, the chain and bucket conveyor in Fig. 3 having been replaced by a skip hoist.
The heating gases enter tube enclosure I, Figure 1. through inlet flue 2 and leave through exit flue 3 into the atmosphere, being preferably drawn by a motor driven exhaust fan, not shown. The heating gases may be hot waste gases from coke ovens of various types or they may be produced specially for the purpose or they may be a mixture of both. If the temperature of the heating gases coming from the coke ovens is too high for the purpose it may be reduced, by recirculation of some of the cooled waste gases from exit flue 3, or by passing the heating gases first through some other cooling device, such as an air preheater used by the coke ovens; Tube enclosure I is sub-divided by bafile walls 4 in order to lengthen the travel of the heating gases and. provide for their better, exploitation. Said tube enclosure I is preferably made of iron and of airtight construction in order to avoid infiltration of steam or dust. A portion of the inside surfaces of the iron-walls forming the tube enclosure, i. e., the portion nearest heating gas in-- let 2 is preferably heat insulated; however, the iron walls near the heating gas exit 3 are left bare or are thinly insulated so that some heat is supplied into elevator enclosure 5 surrounding tube enclosure I.
The travel of the coal through the preheater is as follows: Raw coal, sufficiently pulverized and screened to eliminate undesirable tramp bodies enters through inlet 6 into the lower part of elevator enclosure 5 and slides into left hand corner of the first floor trough I from which it is scooped up by the first set of elevator buckets 8 attached to elevator chains 9 and hoisted to high position a above tube enclosure I and discharged onto coal pile I I accumulated above the tube enclosure. From coal pile II the coal is caused to descend through the" first row of tubes I2, its speed being governed by extracting mechanism I5 described later. This mechanism extracts the coal and forces it to fall down again into first floor trough I, but during its fall the coal is deflected by means of deflector I6, best seen in Figs. 4, 5 and '7, which have the effect of defiecting the coal from its vertical fall, so that it now enters the right hand corner of the first floor trough, the amount of deflection being adjustable as will be described later. Having arrived in the right hand corner of the first floor trough l the coal is scooped up again by buckets 8 of the first elevator and hoisted and dropped again onto coal pile I I. However, its new location on this pile is now to the right of its first location, with the result that the coal now descends through the second row of tubes I1 and after being extracted.
from them, the coal is again deflected to the right and so forth. Finally the fully preheated coal, after having been advanced through all tube rows is hoisted to its end position [8 above the tube enclosure from which it slides down through chute l8 into insulated collecting hopper from which in turn it is discharged, at the proper time, into a hot coal collecting car 2 I or an equivalent conveyor. Thus the coal is advanced through a sequence of vertical tubes substantially horizontally and in sequence and in counter current to the general flow of the heating gases.
Preferably a plurality of chain and bucket elevators are employed, Figure 1 showing five. Preferably only one upper common drive shaft 24 is used, being equipped with 10 large sprocket wheels 25 while 10 small sprocket wheels 26 are connected to each of the two lower idler shafts 21. The top sprockets, being large, permit the chains and buckets to go up on one side of the heating enclosure i and down the other side, see Figure 3. The usual provision (not shown) is made to enable the raising or lowering of the upper or lower shafts to allow for wear and tear and fine adjustment. The upper shaft 24 and its sprockets can be removed after removing roof 28 of the elevator enclosure. Panels 29 (Figure 5), are also removable, permitting removal of the elevator chains and buckets and of shafts 2? with their sprockets 26 and of floor troughs l and fenders 30.
The floor of the elevator housing is made up of the floor plate 32 fastened to floor beams 33. For the collection of the coal, special floor troughs l are provided permitting elevator buckets 8 to scoop up the coal. Floor troughs l are firmly fixed upon vertical ribs 34 by bolts 35, so that their permanent location is assured. The gaps between adjoining floor troughs are shielded by fenders which are supported by the floor troughs by means of posts 3%. These fenders are shaped with sloping top surfaces for shedding of the coal into the floor troughs. Insulating material is placed between the fioor troughs E and the floor plate 32.
The mechanism for extracting the the tubes is as follows:
The coal, emerging from one of the heating tubes enters into a rectangular hopper ill each having substantially the same horizontal cross sectional area as the tubes above the hopper. The hopper is formed between long beams 4i and short beams 42, forming a strong grid, which is used also for supporting tube enclosure l and its tubes. tudinal beams 43 which are part of the elevator enclosure 5 and are connected to outside columns 44. Long common longitudinal coal supporting tables 45 and 3B are supported below hoppers 40 by means of pipes il. Tables 15 are supported at an elevation below tables 46. These different elevations make it possible to give each table a width greater than the distance between the tubes thus preventing the coal from spilling over the table edge unless desired without however requiring an excessive distance between the heating tubes. Pipes 4? pass slidably through elevator enclosure 5 and are supported by connecting hangers 48, rotatable around fulcrum 49. Motor is provided, which by means of crank 5| and connecting rod 52 serves to reciprocate pipes 41 and tables 45 and d6, thereby extracting the coal from the tubes.
Figures 7 and 8 show an alternative scheme in which the coal supporting tables 45 and .6 are coal from Long beams 41 are connected to longisuspended by bolts 55 from grid beams M and 12. A diamond shaped push-block 55 is placed beneath each heating tube, resting upon the tables. The push-blocks 56 located beneath one longitudinal row of tubes are connected together by means of a long continuous bar 57 to which the push-blocks 5'3 are fastened. This bar is guided in slots cut into the lower edges of long beams H. Bar 51 extends into the open through the endw-all of the elevator housing, and is reciprocated by crank and motor as described before with the result that the coal resting upon tables 45 and 45 is pushed over the longitudinal edges of the tables and falls down into the floor troughs 1. The edges of the push-blocks 56 are at an angle of, for instance, 45 to the long axis of the supporting tables. The recirculation of the coal through the tubes can be stepped up by increasing the number of reciprocations of the tables in Fig. 5 or of he push-blocks 55 in Fig. '7, thereby filling more coal into the elevator buckets, which preferably are of ample hoisting ca pacity.
The coal pushed down from the tables by the reciprocating means is advanced to the right in countercurrent motion to the heating gases by deflectors [8, installed beneath the supporting tables. The deflectors are fastened to shafts 22 and rotatably hung in bearings 64 and all deflectors are rotatably connected to common connecting rod 65, passing through the elevator enclosure 5, the rod being adjustable in the direction of its length by crank 66 and screw 6?. Thus the angle of the deflectors can be changed, thereby increasing or retarding the rate at which the coal is advanced through the preheater. Thus with a steep position of the deflectors a sensitive coal can be recirculated through the tubes at high speed without however being pushed out of the preheater more quickly than desired. On the other hand if a coal is already fairly dry, so that its heat requirements are relatively low, the coal deflectors can be fixed at a flatter angle so that the coal is promoted toward the exit more quickly.
Provision has been made for dealing with high moisture coals coming from wet washing plants. Vertical agitating bars 10 are provided, adapted to prevent arching of the wet coal over the first groups of heating tubes and to cause it to enter the tubes. The bars extend a short distance into the tubes. The agitation of the bars is accomplished by eccentric rings ll fastened upon sprocket shaft 2% and roller 12 which roll upon the eccentric rings, thereby imparting up and down motion to cross connecting bar 13 to which bars it! are fastened. The frame containing the rollers is made up of roof l5 and side pieces 16 which jointly prevent the coal from falling onto the rollers and the eccentric rings. The frame is composed of 2 parts bolted together by bolts TI to enable the agitating bars to be removed. Metal funnels 86 are provided to rest on the top plate of tube enclosure I each funnel being so constructed as to surround one of the tubes and to guide the coal into the tube.
Provision is made for accelerating the drying and giving the coal a higher mobility at an earlier time, thus improving the working of the preheater. This is done by draining a portion of the hot dry coal through port-hole 82 and return pipe 83 and reentering it through entrance opening 84 into the preheater. The reentered coal is thoroughly mixed with the coal emerging from tubes above Opening 8 by virtue of the recirculation performed by the elevator, the extractors and the deflectors. This recirculation of some of the hot coal through the tubes located between openings 82 and 84 increases the speed of travel through these tubes and shortens the time during which the coal is exposed to heat in each of these tubes. The coal passing through the tubes located between openings 82 and 84 is therefore more frequently re-mixed, which is desirable since the outer layers of the coal in these tubes reach a temperature sufficient to form steam, which steam promptly condenses into the colder central core of the coal, imparting to this core an excessive humidity which tends to interfere with the free flow of the coal. The proportion of hot coal reentered for mixture can be adjusted by valve 85. The addition of the reentered volume only increases that particular volume of mixed coal passing through the tubes located between openings 82 and 84, so that the action of the extracting mechanism below these tubes is correspondingly accelerated, for instance by increasing the number of reciprocations of a portion of the coal supporting tables. For this purpose these tables may be cut into independent pieces as indicated by cuts 86 and 8'! in Figure 4, the cuts permitting the center portion 88 of the tables to be reciprocated at a higher speed or a longer stroke. For this purpose the three independent table-pieces created by cuts 86 and B1 are independently supported by independently movable tubes 41, hung on individual bars 48 (Fig. 5) and operable by individual drives 50, 5| and 52, of which only one is shown.
Loaded valve 92 is provided for releasing steam from enclosure 5.
In the new preheater the coal is passed in sequence through successive rows of tubes, the time required by a particle of coal, to complete one trip through one of the tubes is greatly shortened thus protecting the coal against local overheating.
Every time when emerging from a tube the coal is mixed thoroughly so that its hot outer annular layer is intermingled with its colder center core thus protecting the outer layers against injury. The mixing operation i performed by the action of the extracting mechanism, the deflectors and the action of the elevator buckets, in scooping up and subsequently dumping the coal. This frequent mixing lowers the temperature of the coal in contact with the tubes and increases heat transfer from the heating gases into the coal.
At each emergence from the tubes air, steam and later on some CO2 are vented from the coal, their presence being injurious to the agglutinating power of the coal. The frequent venting also releases steam pressure from the tubes which support the coal and interferes with its descent.
The coal which is passed through the initial rows of tubes, is raw coal in undiluted form and preheated hot coal is mixed with it only later on. Thus the heating gases, just before leaving the tube enclosure, encounter the coldestand wettest coal, so that their temperature is reduced to their lowest permissible degree. ,Furthermore', due to the heat imparted to the raw coal in the coldest tubes the weight of the hot coal which is returned for admixture is reduced to a minimum. The temperature of the returned hot coal is not very high, so that danger of damage to the hot coal by repeated over exposure to high heat is eliminated.
In this manner the coal passes through what may be considered as three distinct zones or phases of preheat. In the initial zone of partial preheat, the cold and wet raw coal travels through the first group of tubes I2 and I7, wherein it absorbs heat until it emerges at about 200 F. In the second or intermediate preheat zone, in the tubes between the openings 82 and 84, the coal is heated to a temperature about 350, or between the intermediate and final preheat temperatures. A portion of this hotter (350 F.) coal is constantly being recirculated and admixed with incoming coal from the initial preheat zone by means of the top opening 82, return pipe 83, and bottom opening 84. In the third or final preheat zone, the coal is raised to the full'desired preheating temperature, dependent upon the fusing point of the particular coal less a reasonable safety margin, or approximately 500 F. The path of the heating gases is essentially the reverse of that of the coal, for economy of heat transfer.
The heat passing through the walls of the tube enclosure enters the elevator enclosure, which is heat insulated. Thus the temperature inside the elevator enclosure is kept above 212 F., so that the steam given off by the coal is protected against condensation. The steam in the elevator enclosure by means of valve 92 is kept under sufiicient pressure to preclude infiltration of air.
The location of the elevator in the elevator enclosure which surrounds the tube enclosure reduces the length of way which the elevator has to travel and the coal while being hoisted does not lose heat into the atmosphere. While 5 sets of elevator chains and buckets are shown in Figs. 1 and 4, their number may be decreased by the use of longer buckets.
The new extracting means have hoppers of a cross sectional area substantially equal to that of the tubes, so that passage of the coal is not interfered with. The openings for coal extraction are large and permit coal of coarse size to be passed through the tubes. The extractor tables upon which the coal is supported are located above each other and are especially wide, i. e., wider than the distance between tube centers so that the dry coal in spite of its mobility cannot escape from the extractor tables, unless the extracting mechanism is operated.
The fall of the coal from the extractor tables down upon the deflectors and then upon the bucket-filling floor and finally upon the top coal pile destroys any dense lumps of fine, wet coal and produces good mixture.
In the case of a sensitive coal, danger of overheating of the outer annular ring of coal can further be reduced by increasing the speed of travel through the tubes. This is obtained by increasing the number of reciprocations of the extracting mechanism in conjunction with fixation of the rotatable deflectors in a steeper position so that promotion of the coal out of the preheater does not need be accelerated.
The details of the elevator arrangement may be varied. The rising as well as the descending chains of the elevator may be located on the same side of the heating enclosure. The diameter and number of the sprockets may be altered. Figure 12 shows that the chain and small bucket type of elevator may be replaced by a skip hoist type having one or two large reciprocating buckets 95.
As shown in Figs. 1 and 2, tubes of different diameters may be used in the same enclosure; and in the case of a very large enclosure, the enclosure may be subdivided into two or more smaller ones, surrounded by the same elevator enclosure.
The heated tubes need not be absolutely vertical but may have a slope in the direction counter current to the gas travel, as shown in Figure 11, thus making the work of the deflectors superfluous either completely or partially, the deflectors in the latter case merely serving the purpose of regulating the speed of promotion of the coal through the preheater.
Although I have shown and described my invention in considerable detail hereinabove, I do not wish to be limited narrowly to the exact structures so shown and described, but may use also such substitutions, modifications, or equivalents thereof as may be more broadly embraced within the wording of my claims.
1. A method of preheating raw coal in consecutive groups of vertical tubes by means of a current of heating gases which consists in subjecting the coal to consecutive preheating phases, to wit, in the first phase imparting to the cold raw coal a partial preheat, in the second phase admixing to the partially preheated raw coal a recirculated portion of coal heated to a temperature intermediate the partial and the desired final preheating temperature and thereafter heating the mixture to the temperature of said recirculated portion and thereafter dividing said mixture into two portions of which the one, namely, a portion equal in Volume to said recirculated portion is returned for readmixture to more of the partially preheated coal and in the third phase heating the remaining of the two portions to the desired final preheating temperature, and directing the current of heating gases to supply its heat first to the third phase then to the second and finally to the first phase.
2. A method of preheating coal, consisting in preheating the coal in undiluted condition to approximately 200 F., admixing to it hot dry coal of approximately 350 F., heating the mixture to about 350 F. dividing the mixture of 350 F. into two portions, and heating one of them to the desired final preheating temperature while returning the other of the two portions for admixture to more raw coal already heated to 200 F.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 219,599 Shaw Sept. 16, 1879 707,384 Burner Aug. 19, 1902 804,876 Noxon Nov. 21, 1905 940,190 Provost Nov. 16, 1909 1,139,610 Wegner May 18, 1915 1,161,834 Brantingham Nov. 30, 1915 1,262,842 Randolph Apr. 16, 1918 1,781,079 Puening Nov. 11, 1930 1,932,830 Puening Oct. 31, 1933 2,148,946 I-Iubmann et a1 Feb. 28, 1939 2,424,229 Erisman July 22, 1947 2,437,395 Magnusson et al. Mar. 9, 1948