CA1104819A - Briquetting plant - Google Patents
Briquetting plantInfo
- Publication number
- CA1104819A CA1104819A CA360,689A CA360689A CA1104819A CA 1104819 A CA1104819 A CA 1104819A CA 360689 A CA360689 A CA 360689A CA 1104819 A CA1104819 A CA 1104819A
- Authority
- CA
- Canada
- Prior art keywords
- heat exchanger
- furnace
- feed material
- briquettes
- tumbler
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Abstract
ABSTRACT OF THE DISCLOSURE
A briquetting plant for hot briquetting particulate matter, such as mill waste containing a material that softens when heated, such as iron oxide, which includes a low tempera-ture tumbler type heat exchanger, an intermediate temperature tumbler type heat exchanger, a fluid bed furnace and a compactor, with the feed material being fed therethrough in succession.
The briquettes produced by the compactor are first fed from the outlet of the compactor into the intermediate temperature heat exchanger, for liberation of heat therein, separated from the feed material by a screen at the outlet of the intermediate temperature heat exchanger and from such screen transported into the low temperature heat exchanger for further imparting of heat to the feed material. A-second screen is provided at the outlet of the low temperature heat exchanger for separating and discharging the briquettes in relatively cooled form. The tumbler type heat exchangers are in-the form of a hollow cone having a wide included angle enclosed by a cover and slowly rotated about an inclined axis to provide intimate mixing of the components and uniform withdrawal of the mixture. The heat exchangers are mounted at a low level and the screens are mounted at a high level with bucket type elevators in between and with the furnace and compactor being located at successive intermediate levels so that, except for the two bucket elevators, all of the flow in the plant takes place under action of gravity. Wet and dry feed materials are separately handled, with means being provided for conveying the dry feed directly to the second heat exchanger.
A briquetting plant for hot briquetting particulate matter, such as mill waste containing a material that softens when heated, such as iron oxide, which includes a low tempera-ture tumbler type heat exchanger, an intermediate temperature tumbler type heat exchanger, a fluid bed furnace and a compactor, with the feed material being fed therethrough in succession.
The briquettes produced by the compactor are first fed from the outlet of the compactor into the intermediate temperature heat exchanger, for liberation of heat therein, separated from the feed material by a screen at the outlet of the intermediate temperature heat exchanger and from such screen transported into the low temperature heat exchanger for further imparting of heat to the feed material. A-second screen is provided at the outlet of the low temperature heat exchanger for separating and discharging the briquettes in relatively cooled form. The tumbler type heat exchangers are in-the form of a hollow cone having a wide included angle enclosed by a cover and slowly rotated about an inclined axis to provide intimate mixing of the components and uniform withdrawal of the mixture. The heat exchangers are mounted at a low level and the screens are mounted at a high level with bucket type elevators in between and with the furnace and compactor being located at successive intermediate levels so that, except for the two bucket elevators, all of the flow in the plant takes place under action of gravity. Wet and dry feed materials are separately handled, with means being provided for conveying the dry feed directly to the second heat exchanger.
Description
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BACKGROUND OF TEIE INVF,NTIO~I
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In -the operation of skeel mill and similar pro-duction facilities large tonnages of rejected screenings and waste are produced in the form of ore fines, furnace dusts, water treatment plant sludges, grindings, borings, scarfings, coke fines, mill scale, slags, and other materials containing valuable constituents, such as iron oxide and combustible elements, which range in size from sub-micron to as læge as three-eighths inch but which are too finely divided to feed into a melting furnace. The feeding of such fine materials causes them to be blown out of the combustion zone beore melting or chemical conversion can take place.
Thus it has been recognized for many years that if such screenings and wastes are to be utilized to recover their constituents including any fuel value which they contain, it is necessary to form the materials into agglomerated form.
In the past agglomeration of ores~ concentrates, screenings and wastes has been accomplished by one or more of three procedures: pelletizing, sintering and briquetting.
Both pelle~izing and sintering require a high ; plant investment and have high operating costs. Because of the lar~e scale on which such processes must be carried out and the large quantities of air and other gases which must ` ~ be handled, pelletizing and sintering are not well suited to `~ utilization of the more limited quantities of waste and rejected screenings available at many plant locations. The pelletiæing and sintering plants now in use require large ' ~ ' ', ;~ - :
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amounts o~ ~uel, sin-teriny plants being particularly inefficient in the use of fuel. Also, both processes require complete combustion of non volatile combustible matter in the material being processed. Objectionable volatile matter, such as the oil frequently present in mill scale and water plant sludges, can present serious pollution problems due to its presence in the gases evolved from pelletizing and sintering plants.
With respect to briquetting, the proces 6 has received only limited acceptance. Agglomeration at low temperature by compaction without binders produces a fragile briquette and the use of binders is too expensive ~or most applications. Cold~bonded briquettes usually are not acceptable as a furnace feed material because they tend to disintegrate within the furnace prior to melting. Hot briquetting, on the other hand, has not reached a mature state of development or gained acceptance because large quantities of ore fines have been generally available at the steel mills for mixing with ~he wastes, so that large sintering plan~s using well-known processing techniques could be built and operated economically. With the advent ; of pelletizing plants located at the mine sites to process the ore fines and concentrates, and with the increased cost o~ energy and pollution controls for sintering plants, it is no longer economical to construct sintering plants at most mill sites, and many existing sintering plants have been shut down for these reasons.
It is, accordingly, an object of the present invention to prov;.de a plant, or system, capable of accepting a wide variety of feed materials, such as rejected screenings, :
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.nill wa~tes, ore f:ines~ ore concentrates alld other materials having heat-softerlahle const-ltuents, and capable oE reliably forming such materials into highly durable briquettes, by hot briquettes which will hold together during the handling, feeding and smelting process as, for examp:Le, in a blast furnace, for melting and chemical conversion and without reverting to fines or flue dust.
In one particular aspect the present application, a division of copending Canadian Appl.ication No. 301,3~7, filed April 18, 1978, is concerned with the provision of a system for hot briquetting particulate feed material containing heat-softenable matter and for cooling the resultl.ng briquettes which comprises a fluid bed furnace having an inlet at the top and an outlet at the bottom for utilizing the heat of combustion to raise the temperature of the residue to the point of incipient fusion, a compactor coupled to the outlet of the furnace for compacting the residue into briquettes, an enclosed cone type tumbler-heat exchanger having an inclined axis and with an axial inlet at the top and an axial outlet at the bottom together with means for slowly rotating the same, the inlet being coupled to the compactor for receiving hot briquettes therefrom, means for conveying feed material to the inlet of the heat exchanger for mixing ~ith the briquettes so that the briquettes are cooled and :: the feed material is heated, a screen assembly for separating ;~ the cooled briquettes from the heated feed material, a ~ conveyor for coupling the outlet of the heat exchanger to : the screen for conveying briquettes and feed material thereto, means for cDnveying the briquettes from the top of the screen and means for conveying the heated feed material from the bottom of the screen to the inlet of the furnace.
In anotheF particular aspect the present application, ~ 3-~, . .. .
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- division of copend-lng (`anadain Appl:ication No. 301~3~79 filed April 18, 1978, i6 concerned with the provis:ion of a system for ~ot briquetting of particulate feed material containing heat-softenable matter which comprises a vertical frame, a furnace in the central region of the vertical frame, the furnace being of the Eluid bed type having an inlet at the top and an outlet at the bottom for heatin8 the feed material to form a residue raised to a temperature of incipient fusion, a roll type compactor arranged below the outlet of the furnace for receiving the resldue and for compacting it under high pressure to form brlquettes, a cone type heat exchanger-tumbler located below the outlet of the compactor for receiving the briquettes, the heat exchanger-tumbler having an inclined axis with an axia]. inlet at the top and an axial outlet at the bottom as well as drive means for slowly rotating the same, means for conveying feed material to the inlet of the heat exchanger-tumbler so that the feed material is heated and so that the briquettes are cooled, a vertically arranged bucket elevator extending substantially f~om the bottom to the top of the frame, the elevator being coupled at its lower end to the outlet of the : heat exchanger-tumbler so that each bucket receives a uniform mixture of briquettes and feed material, means for driving the elevator so that the process of heat exchange continues in the buckets as the buckets are elevated to the top of the frame, a screen assembly at the top of the frame for separating the briquettes Erom the heated feed material, means for :~ dumping the buckets into the screen assembly so that the :.s .
-~ briquettes are discharged in a relatively cooled state and so that the heated feed material falls through the screen, means for feeding the material from the underside of the ~ screen to the inlet of the furnace, ancl a feed/gas heat .~ :
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- -dxchanger interposed at the inlet of the Eurnace for bringing the off gas Erom the Eurnace into contact with the heated feed material for further heating of the Eeed material to a temperature more nearly approaching the temperature of the Eurnace, and for cooling the oEE gas to a temperature more nearly approaching the temperature of the feed material, and means for subsequently purifying the off gases from the furnace and the heat exchanger-tumbler for discharge into the atmosphere.
10Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:
Figures la and lb comprise an elevational view, in partial section, of a briquetting plant construction in accordance with the present invention.
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Fig. 2 is a view simllar -to Fig. 1 but with super-imposi-tion of flow lines indicating ~he paths taken by the materials flowing within the plant.
Fig. 3 is a block type flow diagram correspondiny to Figs. 1 and 2.
Fig. 4 is an elevational view of a simplified installation employing elements of the present invention.
Fig. 5 is a flow diagram corresponding to Fig. 4.
Fig. 6 is a view similar to Fig. 4 but with ~;10 modified features.
Fig. 7 is a view similar to Fig. 6 but with still further modifications.
While the invention has been described in connection with certain preferred embodiments, it will be understood that I do no~ intend to be limited by the disclosed embodiments but intend to cover, on the contrary, the various alternative and equivalent constructions included within the spirit and scope of the appended claims.
Turning now to Figure 1 a preferred form of briquetting plant designed to process a variety of steel mill was~es and screenings is shown, of which the components will be understood to be mounted upon a supporting framework which, for the sake of simplicity, has been omltted from the drawings. At the right-hand side of the plant is a wet feed conveyor belt 10 having a drive 11 for bringing into the,plant feed material containing iron, primarily in the form o iron oxide, and combustible elements, the latter predominantly car~on. The materials are referred to as "wet" since they contain filter ; ~ cake or mill scale or have been taken from outside storage . ~ .
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~ where large amounts of water, resulting from preclpi-tation, are normally absorbed. ~eans are provided, also, for bringing "dry" waste into the plant, such as dust which has not been stored out of doors but which arrives directly from current steel mill operations. For transporting this material into the plant a dry feed conveyor 15 is used having a drive 16. Discussion of the flow of the dry feed component will be reserved to a later point.
The discharge from the wet feed conveyor belt 10 is conducted by an inlet chute 17 into a first, or low temperature, heat exchanger 20 which is of the constantly rotating tumbler type. The heat exchanger has an axial inlet 21 at the top and an axial outlet 22 at the bottom, the inlet and outlet being provided with seals to make the unit as nearly as possible gas tight. The heat exchanger in its preferred form is of double conical shape having a lower hollow conical container 23 and which is enclosed by a cover 24 which may also be of conical shape. For the details of such a conical heat exchanger-tumbler reference may be made to my U.S. Patent No. 4,106~114, issued August 8, 1978. It will suffice, for the present, to say that the heat exchanger has a refractory lining 24 and is supported for rotation about its axis by a single large annular bearing 30 wi~hin which the lower cone section is mounted, the axis defined by the bearing being inclined at an angle of approximately 45 bot which may vary between about 35 and 55. As a result of rotation and inclination materials entering at the inlet are constantly cascaded, and thus evenly distrlbuted, over the surface 26 of the .
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::, ' contained load. A further advantage of the lnclination is that mater:ials are drawn from the outlet 22 from over a wide range of positions within the exchanger. The operation may be contrasted with that of an hour glass in which the grains are fed primarily along a fixed line which extends vertically upwardly from the constriction. In the present heat exchanger-tumbler the vertical line extending through the mass of material within the device constantly orbits so that the material drawn from the exit is not drawn from any one particular location so that a mixing occurs which not only equalizes the composition flowing through the outlet but in addition greatly impxoves the efficiency of the heat exchange. The unit is preferably driven by means of teeth formed into the outer ring of the bearing 33 which are engaged by the teeth of a pinion 34 connected to a drive 35 having a control 36 which is capable of adjusting the speed from a portion of a r~volution to several revolutions per minute, for example, from 0.2 to 2.0 rpm. In carrying out the invention the heat exchanger 20, in addition to receiving flow of feed material also receives a flow of hot, freshly made briquettes, the purpose of the heat exchanger being to pre-hjeat the feed material and, at the same time, to cool the briquettes to a safe discharge t~mperature. However, a discussion of briquette production and path of flow will be temporarily deferred.
The mixture of briquettes and feed which is fed ;; ~ from the outlet 22 of the heat exchanger 20 passes in~o a screw type feeder 40 having a drive 41, the feeder serving `~ ~ to load an elevator 50 having chain supported buckets 51 driven by a drive 52. While the drive is shown for convenience at the lower end, it is desirable, in fact, to have the drive . . .
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at the upper end. At the upper end of the elevator the buckets are emptied into a to-tally~enclosed screen assembly 60, which is preferably of the vibratory type having a frame 61 mounting a screen 62 and supported on resilient mounts 63. An electric motor- driven vibrator 64~ which is preferably of the eccentric type, causes the frame, and the screen 62 which it contains, to vibrate resulting in efficient separation of the briquettes which flow along a path 65 on the upper side of the screen, from which they are discharged from the plant, and the heated feed material which flows through the screen along a path 66.
The heated feed material is conducted downwardly through a first feed tube 70 having an upper end 71 and a lower end 72 which feeds into the second, or lntermediate : . temperature, heat exchanger 80 to be discussed.
The heat exchanger-tumbler 80 is similar to the heat exchanger 20 previously described having a sealed inlet 81 and a sealed outlet 82, with the vessel being formed by a hollow conical receptacle 83 enclosed by a cover 84.
The receptacle has a refractory lining 85. The heat exchanger is supported upon a bearing 93 having teeth driven by a pini~h 94 which has a drive connection with the heat exchanger drive 95 having a controller 96.
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At the outlet of the heat exchanger 80 is a screw feeding device 100 powered by a drive 101 for the feeaing ~ of material at a controlled ra~e into an elevator 110 having : a series of chain supported buckets 112 driven by a dxive 113.
; The elevator buckets are dumped into a screen assembly 120 having a gas-tight housing 121 and a stationary screen 122 of ` :
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the inclined "grizzly" type, with the briquettes flowing over the top oE the screen along path 125 and the heated Eeed materials falling to a position 126 below the screen which feeds a hopper 130. At -the hottom of the hopper is a screw type feeding device 131 having a drive 132.
From the hopper 130 the heated feed material is discharged into a furnace 140 of the ~luid bed type, the furnace having an inlet 141 at its upper end and outlet 142 at its lower end. The furnace, in its preferred form, 10 has an upper cylindrical portion 143 and a lower conical portion 144 lined wi~h a layer 145 of refractory material (Fig. la~.
The bottom of the fuxnace has multiple air inlets 146 and an air plenum 147 underlying the inlets. The plenum receives pressurized air through a line l48 leading from a blower 149 driven by a motor M~ The bed of material, indicated at 151, at the bottom of the furnace is fluidized by the air which flows upwardly through the inlets, as is characteristic of a fluid bed, resulting in efficient burning of combustible elements in the feed.
In accordance wi-th one of the more detailed aspects of the present invention the off gases resulting from the combustion are conducted upwardly through the inlet opening 141 and past the point of discharge of the feeder 131 which feeds material into the furnace to provide a feed/gas heat exchanger 150. Moreovery the inlet 141 is sufficiently restricted so that the of gases have a sufficient velocity as they pass the point of feeder discharge so a substantial portion of the discharged material is conducted upwardly and maintained in contact with the high kemperature off gases thereby recover mg wast~ heat, which raises the temperature .~ :
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of ~he waste to more nearly that of the furnace. The remaining coarser and more abrasive material discharged by feeder 131 falls into -the furnace, counter current to the gas, also aiding in heat recovery ~rom the gas. The off gases and the entrained particles are conducted into a vertical stack 152 and into a known cyclone type separator 153 having an upper discharge 154 i-or the gases and a down-wardly extending convergent discharge 155 containing a trickle valve (not shown) for returning the entrained particles o waste back into the furnace. In addition to recovering heat, the feed/gas heat exchanger causes a reduction in the internal temperature of the cyclone separator which tends to become plugged when operated at furnace bed temperature. If desired, air may be injected into the upper outlet port of the separator, as indicated at 156 for the purpose of completing the oxidation of carbon monoxide and any unburned hydrocarbons. The off gas then flows through a duct 157 downwardly into a scrubber assembly 160 having an upper, or manifold, section 161 and a lower section 162.
The manifold is positioned over the inlet opening 21 of the - first heat exchanger 20 so as to receive, also, the off gases from the heat exchanger. Water is sprayed into the gaseous stream as indicated at 163 to purify the gases and to remove any entrained particles, following which the stream of gas is sucked into a blower 164 which discharges into an upstanding flue or stack 165~ The solid particles, in ~he form of a slurry, are drawn from a dLischarge port 166 at the lower end of the scrubber assembly.
With regard to the off gases from the second, or intermediate temperature, heat exchanger 80, these pass through : .
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a manifold 170 and a small scrubber 171, supplied with water 172. The effluent yases, oil, water and solids are conducted by means of a duct 173 for injection, at 174, in the lower portion 162 of the aforementioned scrubber. Scrubber 171 may be in the form of a jet-type venturi eductor, using water 172 at high pressure to provide the efficiency necessary to remove the oil vapors ~rom the gas. Preferably interposed in the duct 173 is an oil separator 175 which removes the oil condensed from the off gas and which is desirable in the case of particularly oily feed materials. The duct 173 also includes a divertor 176 so that the off gas from the second heat exchanger, instead of being sent to the scrubber, may be directed back into the furnace via a line 177.
Turning attention to the furnace, the combustible elements in the material 151 at the bottom of the furnace are largely burned away to leave a residue o~ iron oxide-containing material at a temperature of incipient ~usion which may be on ~he order o~ 1800 F., such materials passing through the outlet 142 of the furnace to engage a feeder 180 having a drive 181 which controls the rate of flow into a roll type compactor 190. The latter has a pair of pocketed rolls 191, 192 rotating in opposition to one another and driven by a drive motor 193. The compactor has an inner housing 194 enclosing the high temperature zone between the feed inlet 1~7 and the product outlet 199 and an outer housing 195 with a source of water 196 which is sprayed onto the rolls, between the housings, and at other strategic points, to maintain the temperature at a safe level for the machine.
The exiting briquettes, interconnected by "flash", are broken apart by a breaker 138 located at the output nip.
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A second compactor is employed in parallel with the first and carries the same reference numerals followed by suffix a. The two compactors discharge through outlets 199 and l99a into the manifold 170 ~rom which the briquettes flow into the inlet opening 81 of t:he second heat exchanger 80.
In this second heat exchcLnger the briquettes mix with the partially pre~heated feed material flowing thr~ugh the feed tube 70 from the underside of the first screen assembly 60.
Thus the bxiquettes, in the second heat exchanger, lose a portion of their high furnace heat to the eed material. The heat exchange is continued to the point of near-equalization as the mix is transported upwardly in the ; buckets of the second elevator 110.
Following separation in the second screen assembly 120, the briquettes, flowing along the upper side o~ the screen, pass into a downwardly angled feed tube 200 having a feed gate 201 at the lower end thereof which is driven by a drive motor 202. In accordance with one of the more detailed aspects of the invention the feed tube 200 is kept substantially full ~f briquet~es so that they are lowered gently to the point of discharge rather than falling freely through the tube. This is accomplished by providing a level detector 202 at the upper end of the tube which produces an output ~ignal feeding a controller 203 so that the drive 202 is actuated, causing discharge at the gate 201, only when the level of the briquettes in the tube is above the level of the detector. As will appear, level detectors, and associated : ~
controllers are utilized for control purposes at a numbe~
of points in the plant and it will suffice to say that while the invention is not limited to use of any particular type of detector, it is preferred to employ a detector which utilizes gamma rays and which may thus be mounted externally of the device with which it is used. Such level detectors and associated control equipmen-t are commonly used and are available as standard equipment from a number of suppliers.
The gamma ray source,level detector and associa-ted electronic equipment may, for example, be of catalog types 7063, 7002 and 7311, respectively, manufactured by Kay Ray, Inc. o~
Arlington ~Ieights, Illinois and the controller may be of catalog type GS 2A4A manufactured by The Foxboro Company of Foxboro, ~assachusetts.
The partially cooled briquettes are fed from the lower end of the feed tube 200 into the inlet 21 of the first heat exchanger 20 where they are mixed with the incoming wet feed material which is fed into the plant on conveyor lO.
In the firs~ heat exchanger 20 the intimate mixing which occurs as the heat exchanger revolves, and as the material cascades upon the surface of the charge, brings about an apprdximate equalization of temperature, which is continued as the mix of briquettes and feed material is fed, by feeder 40, into the buckets of the first elevator 50. Separation and discharge of the briquettes occurs in the screen assembly 60, with the briquettes passing along the top of the screen and with the now pre-heated feed material being discharged into the first feed tube 70 which leads to the second, or intermediate temperature, heat exchanger as previously discussed.
In orde:r to insure that the temperature in the first heat exchanger is kept below the temperature at which any oil containecl in the feed will vaporize, a ~ater spray head 210 is provided in the first heat exchanger coupled to a source oE water 211 which is under the control of a temperature detector 212. In short, whenever the detector reaches a temperature greater than a set value, water is sprayed in automatically to reduce the temperature to a safe level. Thus most of the oil contained in the feed remains in the feed until vaporized at the higher temperature existing in the second heat exchanger 80 and following which the oil is preferably removed from the system by the oil separator 175.
The above discussion has traced a charge of wet feed material through the plant. I desired, all of the feed, either wet or dry, may be caused to follow -~he same paths but, in accordance with one of the aspects of the present invention, the dry feed material entering on collveyor 15 powered by drive 16, is fed directly to the second heat exchanger 800 Preferably there is provided at the output of the drive feed conveyor a shiftable director 220 having a normal position 221, an alternate position 222 and a third position 223 which may, or example, be used on start-up. In the normal position the dry f~ed material passes through a conduit 225 which leads to the second heat exchanger. In the alternate position 222, in which the dry feed i5 combined with the wet, the dry feed is led through a conduit 226 to the first heat exchanger. In the third position 223 the director directs the dry feed intake directly to the furnace by means of a conduit (not shown).
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Under conditions of star-t-up an auxiliary burner 230 for the furnace 140 is used which may, for example, receive gas or oil ~rom an auxiliary source 231 and air from a line 232 leading from the b]ower 149. In addition, an inlet tube 233 having a three-way valve 284 is provided for injecting fuel, water or purge air directly into the fluidized bed when needed to control the bed temperature, automatically, by temperature sensor 235 and controller 236.
In a plant having little or no fuel in its feed supply, coke fines may be added to the feed, powdered coal may be fed into the bed by a screw conveyor (not shown) or oil or gas may be injected directly into the bed through one or more fuel inlet tubes, of the type shown, in accordance with standard techniques.
With the construction of the plant in mind, reference may be made to Figs. 2 and 3 for a more detailed understanding of the operation. In Fig. ~ the paths of flow of the feed materials, the hot briqu~ttes, the recycled fines and the off gases have been superimposed, in coded form, upon the drawing, whereas in Fig. 3 the flow of such materials has been set forth in a flow diagram. The flow of the wet feed material 12 takes place vertically down the center of the sheet to the compactor at the bottom. Thus the material rom the wet feed conve~or 10 flows successively through the low temperature heat exchanger 20, the feeder 40, the shaker screen 60 into the intermediate temperature heat exchange~ 80.
From the latter, flow continues through the feeder 100, screen -120, hopper 130, feeder 131, the heat exchanger 150 into the furnace 140. From the furnace the residue, heated to incipient ~ -:
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fusion, is fed via feeder 180 lnto the compactor 190 where the briquettes are formed.
The hot briquettes, after compaction, are caused to ~low in a hea~ exchange path which ls counter to the f]ow of the waste material. That is to say the briquettes are conducted from the compactor 190 along path 170 into the intermediate heat exchanger. In this heat exchanger the briquettes, at an entering temperature of approximately 1800 F., encounter the feed which has been pre-heated, in the first heat exchanger, to a temperature of approximately 300 F. The resulting mix, which is conveyed through feeder 100 anA up elevator 110 to ~he screen 120 achieves a near-equilibrium temperature which is on the order of 1000 F.
The briquettes flowing along the top of the screen in the screen assembly 120 are lowered through the feed tu~e 200 to enter the low temperature heat exchanger at a temperature of 1000F. Here the briquettes are joined by the wet feed from conveyor 10 which is at an assumed temperature of 0 F.
The mix exiting from the low temperatu~e heat exchanger 20 and elevated by the elevator 50 reaches an equilibrium temperature of approximately 300 F. which is then the temperature of the briquettes at the point of discharge 65v - The out gas from the low temperature heat exchanger, because of the spraying of water from the spray head 210, is at a somewhat lower temperature, namely,212 F.as it is fed into scrubber 160. Furnace off gas passes through feed/sas heat exchanger 150, cyclone 153 to scrubber 160 by way of conduits 152 and 157. Fines from the cyclone flow through tube 155 to the furnace . Gas rom the intermediate temperature heat ~' ' ' ~-, , ~
e~changer 80 ~lows into scrubber 171 and then into scrubher 160 dir~ctly or by way of oil separa-tor 175. Alternatively, the gases from scrubber 171 may be piped into the furnace for combustion of any fuel content.
AUTOMATIC FLOW CONTROL
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In the above description it has been assumed that the various feeding devices have each been adjusted to produce equalized rates of feed so that there will be no tendency toward material accumulation at any point in the system. However, it is one of the features of the present invention that manual intervention is not required to equalize flow rates under changing conditions. Briefly stated, the output rate of the plant is determined by the speed of rotation of the compactor rollers and the degree of compaction which is maintained. Working upwardly through the syste~, back to the point of feed of the wet raw material, each vessel is provided with a level detector which actuates a controller which correctively controls a feeder located upstream in the path of material flow to keep the level in the vessel automatically at its working level. In other words, each vessel has a level detector which "calls" for material from an upstream point in the flow as needed to keep the material in the vessel at its desired, and most efficient, working level.
Attention will first be gi~en to the means for controlling flow of the material, heated to incipient fusion, to the compactor. For this purpose the compactor 190 has a pressure sensor 240 which determines the force applied between the two rolls and produces a signal to activate a controller 241.
The controller tends to maintain constant brique~te density by ~ -17-.~
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b~inging a~out a correctlve increase or decrease in the speed of the drive ]81 for the feeder 180. A sui-table pressure sensing cell 240 and controller 241, which completes a servo loop, are available commercially from several suppliers.
When the pressure between the rolls drops, indicating that insufficient material is being fed, a signal is produced which actuates the controller in a direction to speed up the drive 181, and vice versa.
Assuming that the rate of feed at the feeder 180 increases, this will tend to produce a drop in the body of material contained in the furnace. In carrying ouk the invention such drop in level is sensed by a level detector 242 which actuates a controller 243, causing a speed-up in the drive 101 which drives the feeder 100 at the outlet of the second heat exchanger 80. This causes loadiny of material onto the second elevator 110 at a higher rate thereby increasing the xate of replenishment of the furnace 140. Feeder controller 243 also controls the speed of elevator 110 by changing the speed of its motor 133 in proportion to the rate of feed.
; The hopper 130 which is positioned between the elevator 110 and the furnace has its own control loop including a level detector 244 which actuates a controllex 245 to correctively adjust the drive 132 associated with the feeder 131. This sexvo loop tends to maintain a constant leveI of material in the hopper so that when additional material is deposited by the elevator 110, raising the hopper level, this is immediately sensed by the level detector 244 so that material is immediately fed from the hopper to the furnace at a greater rate.
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The above mentioned increase in feed from the second heat e~chanyer to satisfy -the requirements oE the furnace, results in a drop in level of the material i.n the second heat exchanger 80 which is sensed by the level detector 246, producing an output signal which activa-tes an associated controller 247 to increase the rate of feed of the feeder 40, at the lower end oE the elevator 50 and the speed of the elevator. This produces a higher rate of feed from th.e elevator so that feed material passes at a greater rate through the screen 60 fox replenishment of the second heat exchanger via the feed tube 70.
The greater rate of withdrawal from the first heat exchanger 20, in turn, tends to cause a drop in level in that heat exchanger which is sensed by a level detector 248 which transmits a signal to controller 249 which produces a corrective adjustment in ~he speed of the drive 11 which drives the wet feed conveyor 10, with the result that the wet feed material is fed at a greater rate for immediate replenishment of the first heat exchanger.
In the above discussion of the progressive : automatic control by a series of servo loops, it has been assumed that an increased rate of feed at the compactor has occurred calling for replenishment at successive points in the upstream path of flow. It will, however, be under~
stood by one skllled in the art that the reverse will take place when the needs of the compa~tor tend to decrease~
with an over-pressure condition at the compactor resulting in a cutting down of the flow successively in the upstream position. In a practical case this replenishment, or cutting down, does not take place in a step-by-step fashion as ~19~
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described but, instead, each ser~o loop tends to establish and maintain an equilibrium condition until the equilibrium tends to be upset in one direction or the other, whereupon corrective action automatically occurs.
While no servo control has been shown for the drive 16 for the dry feed conveyor 15, it will be understood that where a dry feed is fed simultaneously, as will normally be the case, the dry feed conveyor may be equipped with a servo loop under the control of the level detector 246 10 in the second heat exchanger, so that a drop in the level ; of such heat exchanger simultaneously increases the rate of feed from the first heat exchanger and the rate of input of the dry feed from outside of the system. Alternatively, where the director 220 is in its position 222, in which the dry and wet feeds are combinedr the dry feed drive 16 may be coupled to the wet feed drive 11 for simultaneous control~
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PHYSICA~ LAYOUT OF _LANT
While the invention as described by a ~low diagram in Fig. 3 is not limited to any par~icular physical arrange-ment, it is nevertheless one of the important features ofthe invention that the plant is constructed in a framework in which the two heat exchangers 20, 80 occupy the lowermost positions and the two screens, which are fed by respective elevators from the heat exchangers, occupy the topmost positions, with the furnace occupying an intermediate position, and with the compactors interposed between the furnace and the inter-mediate temperature heat exchanger. The wet ~eed conveyor 10 is preferably located at a level above the first heat exchanger and the dry feed conveyor is preferably located at a level ;
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,, . - : .. . .. . : . ~ , ~ , above the bot-tom o~ the furnace. In this way all of the transport, except that which occurs in the two elevators, is vertically downward under the action of gravity. This greatly simplifies the system since the only -transport drives which are required, aside from the input conveyors, are those which are used to drive the elevators.
Preferably the openings in the intermediate temperature screen assembly 120, which is just ahead of the furnace, are larger than the openings in the screen assembly 60, thereby insuring that any materials which pass the low temperature screen 60, and which are smaller than briquette size, are certain to be passed by the intermediate temperature screen for treatment in the furnace, including undersized portions of the briquet~es which may break off as a result of physical handling.
While it is one of the features of the present invention that the materials fed into the plant on the inlet conveyors 10, 15, are well mixed within the plant as a result of the mixing actions, of the tumbler type heat exchangers, the furnace, screens and conveying devices, the invention, in one of its aspects, extends beyond the physical plant to encom~ass the manner in which the raw materials are stored.
~s stated above, the waste materials from a steel making operation vary widely in type, source, size and composition including metallic iron, oxides of iron, other compounds of iron, coke and other carbonaceous materials. In accordance with one aspect o~ the present process, these raw materials are not necessarily stored in separate piles but are, instead, deposited on a sin~le pile or reservoir in relatively thin layers. When the materials are scoop~d for the loading of , ~
, ~'L~4~3~9 the input conveyors 10, 15 it is contemplated that the scooping, ~y a power shovel, front end loader, or the like~
will ta~e place in passes acxoss the layers so that each scoop contains a por-tion of many layers from the pile. This produces an automatic mixing of the available iron and carbon containing components to bring them within the range of tolerance of the present plant and without requiring the provision of a separate, costly, or cumbersome pre-mi~ing plant. This further adds to the economy of the present system.
A.LTERNATE EMBODIMENT
While the present invention has been described in connection with Figs. 1-3 which show a preferred embodiment employing a two-stage heat exchange cycle in which the briquettes flow counter to the raw material, the invention in its broader aspects is not limited to use of two heat exchangers and a plant may be constructed in simplified form as set forth in Figs. 4 and 5 without departing from the invention. In this plant, in which similar elements are denoted by similar reference numerals with addition of subscript a, it will be noted that the intermediate temperature heat exchanger 80, with its associated feeder 100, elevator 110 and screen 120, has been omitted. Instead, only one heat exchanger 20a of the tumbling type is employed wh~ch takes raw material directly from the wet feed conveyor --lOa and which takes the briquettes direc~ly from the compactor l90a. It will be understood that the features of automatic control are the same. This plant design may be preferable to that of the more complex plant in the following cases~
when the material fed contains so much water that the briquettes ` ~ :
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are su~ficiently coolecl in one heat ex.changer, (2) when -the feed material softens and is briquetted at such a low temperature that 2-stage heat exchange is not ~ustified and (3) when the tonnage to be processed is too low to justify the more expensive plant, even though the fuel consumption might be greater.
While the embodiments of the present invention illustrated were designed primarily to operate using as raw material the waste and screenings in the form of iron oxide together with combustible elements in the form of carbon and hydrocarbons produced in the normal operation of a steel plant, the invention may be employed in the briquetting of particulate materials from a number of different sources. Indeed, the present invention may be utilized in hot briquetting many materials, including iron ore fines and concentrates,chrome ore fines, ferro- ~.
manganese screenings, metal chips, phosphate rock, mixtures of raw materials for glass and portland cement manufacture, and other materials and mixtures that soften at temperatures at least as high as 2000 F. In many such applications, the plants illustrated in Figures 1-5 could be used with ~: little or no alteration. Also while the texm "briquette"
has been used to designate the end product, and while such term is intended primarily to describe dense, pillow shaped pellets of consistent size, it will be.understood that the term "briquette" is by no means limited to production of pellets of equal size and consequently it shall be interpreted ~ to cover irregular of broken pieces or granules of material : produced by compaction in continuous strip form and then broken or crushed and screened to the desired size.
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ALTERNATE ANTI-POI,LUTION EMBODIMENTS
While khe anti-pollution means described in connection with the embodiments set forth in Figures :L-5 are adequate for many materials and will meet ~he pollution standards for a number of plant locations, even more elaborate anti-pollution equipment may be required for processing some materials and for locations having unusually stringent pollution limitations.
Two equipment arrangements involving more extensi-ve means for pollution control are shown in Figures 6 and 7, which are modifications of the arrangement set forth in Figure 4~
In both arrangements, all off gases are passed through a combustion zone for removal of combustible contaminants, such as oil vapors and carbon monoxide, prior to being scrubbed and discharged to atmosphere. ~oth arrangements include optional condensers for removing moist~re from the gases prior to entering the combustion chamber, so as to reduce the consumptionO~ fuel and the size of combustion and scrubbing equipment when economically justified.
The arrangement illustrated in Fig. 6 is intended for applicatlons in which ~he feed to the plant contains a relatively low percentage of objectionable hydrocarbons having a low boiling point or in which the feed contains an - excess oE solid fuels that would provide a low-cost source of the additional heat required. In the arrangement of Figure 6 (in which corresponding reference numerals are employed with addition of subscript b) the scrubber 160b has been mo~red from its previous location (Fig. 4) a~ the gas outlet of the heat exchange tumbler 80b to a pssition near the outlet oE the cyclone separator 153b, and a condenser ' - ~
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~ ' ' ', ' : : . ' 253 has been added at the outlet o~ the tumbler 80b. In this arrangemen-t, the off gases from the tumbler 80b, compactor 190b and miscellaneous sources (no-t shown) are collected by hood 250 into which water 251 is optionally sprayed to minimize dust entering t:he condenser 253 by way of inlet header 252. The condenser may be cooled with air or water, as desired. The ~ases exit the condenser by way of outlet header 254 and duct 255 and are injected into the bottom of the fluid bed reactor 140b, by means of a blower 256 and duct 257~ together with fluidizing air from blower 149b and duct 148b. The gases from the furnace 140b flow through optional gas/feed heat exchanger 150b, then duct l51b and cyclone separator 153b. ~ir 156b is optionally introduced into the off-gases at the gas outlet 154b of the cyclone to burn any small amounts of carbon monaxide or hydrocarbons in the gas, which flow through duct 157b into scrubber 160b, which is supplied with water 163b.
The effluent gases are then exhausted to atmosphere by blower 164b through stack 165b. Slurry and condensate are drained from ~he scrubber 160b and condenser 253 through connections 166b and 258.
; The arrangement shown in Figure 7 is applicable to feed materials having a relatively large amount of volatile fuel difficult to remove by scrubbing in standard equipment.
In this arrangement, ~he gases from the tumbler 80c, ~compactor l90c and miscellaneous sources are processed in an optional condenser 253c having features similar to those described for the condenser 253 of Fig. 6. The gases from condenser 235c pass through a head 254c which discharges into the top of an afterburner 270. The off gases from ,, : ' ~ 25 :
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the furnace 140c also enter the top of the afterburner, after passing throuyh the feed/gas heat exchanyer 150c, cyclone separator 153c and duct 157c. The afterburner is equipped with a burner 271 at the top to preheat the unit and to supply heat as required to cause complete combustion of all combustible matter in the gases. The burner has suitable sources of fuel 272 and air 273, and secondary air is supplled to the afterburner at inlet 274.
The burner and secondary air supply are conkrolled by standard regulating devices to maintain the afterburner ; at the proper temperature. The afterburner is refractory lined and insulated. The effluent gases pass from the afterburner to the scrubber 160c, which is supplied with water 163c for removing entrained par~iculate matter, and then through exhauster 164c and stack 165c to the atmosphere.
Although the simplified plant design of Fig. 4 has been used to illustrate these anti-pollution means, such means are equally applicable to other plant designs that employ the present invention, including the design shown in Fig. 1.
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BACKGROUND OF TEIE INVF,NTIO~I
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In -the operation of skeel mill and similar pro-duction facilities large tonnages of rejected screenings and waste are produced in the form of ore fines, furnace dusts, water treatment plant sludges, grindings, borings, scarfings, coke fines, mill scale, slags, and other materials containing valuable constituents, such as iron oxide and combustible elements, which range in size from sub-micron to as læge as three-eighths inch but which are too finely divided to feed into a melting furnace. The feeding of such fine materials causes them to be blown out of the combustion zone beore melting or chemical conversion can take place.
Thus it has been recognized for many years that if such screenings and wastes are to be utilized to recover their constituents including any fuel value which they contain, it is necessary to form the materials into agglomerated form.
In the past agglomeration of ores~ concentrates, screenings and wastes has been accomplished by one or more of three procedures: pelletizing, sintering and briquetting.
Both pelle~izing and sintering require a high ; plant investment and have high operating costs. Because of the lar~e scale on which such processes must be carried out and the large quantities of air and other gases which must ` ~ be handled, pelletizing and sintering are not well suited to `~ utilization of the more limited quantities of waste and rejected screenings available at many plant locations. The pelletiæing and sintering plants now in use require large ' ~ ' ', ;~ - :
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amounts o~ ~uel, sin-teriny plants being particularly inefficient in the use of fuel. Also, both processes require complete combustion of non volatile combustible matter in the material being processed. Objectionable volatile matter, such as the oil frequently present in mill scale and water plant sludges, can present serious pollution problems due to its presence in the gases evolved from pelletizing and sintering plants.
With respect to briquetting, the proces 6 has received only limited acceptance. Agglomeration at low temperature by compaction without binders produces a fragile briquette and the use of binders is too expensive ~or most applications. Cold~bonded briquettes usually are not acceptable as a furnace feed material because they tend to disintegrate within the furnace prior to melting. Hot briquetting, on the other hand, has not reached a mature state of development or gained acceptance because large quantities of ore fines have been generally available at the steel mills for mixing with ~he wastes, so that large sintering plan~s using well-known processing techniques could be built and operated economically. With the advent ; of pelletizing plants located at the mine sites to process the ore fines and concentrates, and with the increased cost o~ energy and pollution controls for sintering plants, it is no longer economical to construct sintering plants at most mill sites, and many existing sintering plants have been shut down for these reasons.
It is, accordingly, an object of the present invention to prov;.de a plant, or system, capable of accepting a wide variety of feed materials, such as rejected screenings, :
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.nill wa~tes, ore f:ines~ ore concentrates alld other materials having heat-softerlahle const-ltuents, and capable oE reliably forming such materials into highly durable briquettes, by hot briquettes which will hold together during the handling, feeding and smelting process as, for examp:Le, in a blast furnace, for melting and chemical conversion and without reverting to fines or flue dust.
In one particular aspect the present application, a division of copending Canadian Appl.ication No. 301,3~7, filed April 18, 1978, is concerned with the provision of a system for hot briquetting particulate feed material containing heat-softenable matter and for cooling the resultl.ng briquettes which comprises a fluid bed furnace having an inlet at the top and an outlet at the bottom for utilizing the heat of combustion to raise the temperature of the residue to the point of incipient fusion, a compactor coupled to the outlet of the furnace for compacting the residue into briquettes, an enclosed cone type tumbler-heat exchanger having an inclined axis and with an axial inlet at the top and an axial outlet at the bottom together with means for slowly rotating the same, the inlet being coupled to the compactor for receiving hot briquettes therefrom, means for conveying feed material to the inlet of the heat exchanger for mixing ~ith the briquettes so that the briquettes are cooled and :: the feed material is heated, a screen assembly for separating ;~ the cooled briquettes from the heated feed material, a ~ conveyor for coupling the outlet of the heat exchanger to : the screen for conveying briquettes and feed material thereto, means for cDnveying the briquettes from the top of the screen and means for conveying the heated feed material from the bottom of the screen to the inlet of the furnace.
In anotheF particular aspect the present application, ~ 3-~, . .. .
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- division of copend-lng (`anadain Appl:ication No. 301~3~79 filed April 18, 1978, i6 concerned with the provis:ion of a system for ~ot briquetting of particulate feed material containing heat-softenable matter which comprises a vertical frame, a furnace in the central region of the vertical frame, the furnace being of the Eluid bed type having an inlet at the top and an outlet at the bottom for heatin8 the feed material to form a residue raised to a temperature of incipient fusion, a roll type compactor arranged below the outlet of the furnace for receiving the resldue and for compacting it under high pressure to form brlquettes, a cone type heat exchanger-tumbler located below the outlet of the compactor for receiving the briquettes, the heat exchanger-tumbler having an inclined axis with an axia]. inlet at the top and an axial outlet at the bottom as well as drive means for slowly rotating the same, means for conveying feed material to the inlet of the heat exchanger-tumbler so that the feed material is heated and so that the briquettes are cooled, a vertically arranged bucket elevator extending substantially f~om the bottom to the top of the frame, the elevator being coupled at its lower end to the outlet of the : heat exchanger-tumbler so that each bucket receives a uniform mixture of briquettes and feed material, means for driving the elevator so that the process of heat exchange continues in the buckets as the buckets are elevated to the top of the frame, a screen assembly at the top of the frame for separating the briquettes Erom the heated feed material, means for :~ dumping the buckets into the screen assembly so that the :.s .
-~ briquettes are discharged in a relatively cooled state and so that the heated feed material falls through the screen, means for feeding the material from the underside of the ~ screen to the inlet of the furnace, ancl a feed/gas heat .~ :
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- -dxchanger interposed at the inlet of the Eurnace for bringing the off gas Erom the Eurnace into contact with the heated feed material for further heating of the Eeed material to a temperature more nearly approaching the temperature of the Eurnace, and for cooling the oEE gas to a temperature more nearly approaching the temperature of the feed material, and means for subsequently purifying the off gases from the furnace and the heat exchanger-tumbler for discharge into the atmosphere.
10Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:
Figures la and lb comprise an elevational view, in partial section, of a briquetting plant construction in accordance with the present invention.
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Fig. 2 is a view simllar -to Fig. 1 but with super-imposi-tion of flow lines indicating ~he paths taken by the materials flowing within the plant.
Fig. 3 is a block type flow diagram correspondiny to Figs. 1 and 2.
Fig. 4 is an elevational view of a simplified installation employing elements of the present invention.
Fig. 5 is a flow diagram corresponding to Fig. 4.
Fig. 6 is a view similar to Fig. 4 but with ~;10 modified features.
Fig. 7 is a view similar to Fig. 6 but with still further modifications.
While the invention has been described in connection with certain preferred embodiments, it will be understood that I do no~ intend to be limited by the disclosed embodiments but intend to cover, on the contrary, the various alternative and equivalent constructions included within the spirit and scope of the appended claims.
Turning now to Figure 1 a preferred form of briquetting plant designed to process a variety of steel mill was~es and screenings is shown, of which the components will be understood to be mounted upon a supporting framework which, for the sake of simplicity, has been omltted from the drawings. At the right-hand side of the plant is a wet feed conveyor belt 10 having a drive 11 for bringing into the,plant feed material containing iron, primarily in the form o iron oxide, and combustible elements, the latter predominantly car~on. The materials are referred to as "wet" since they contain filter ; ~ cake or mill scale or have been taken from outside storage . ~ .
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~ where large amounts of water, resulting from preclpi-tation, are normally absorbed. ~eans are provided, also, for bringing "dry" waste into the plant, such as dust which has not been stored out of doors but which arrives directly from current steel mill operations. For transporting this material into the plant a dry feed conveyor 15 is used having a drive 16. Discussion of the flow of the dry feed component will be reserved to a later point.
The discharge from the wet feed conveyor belt 10 is conducted by an inlet chute 17 into a first, or low temperature, heat exchanger 20 which is of the constantly rotating tumbler type. The heat exchanger has an axial inlet 21 at the top and an axial outlet 22 at the bottom, the inlet and outlet being provided with seals to make the unit as nearly as possible gas tight. The heat exchanger in its preferred form is of double conical shape having a lower hollow conical container 23 and which is enclosed by a cover 24 which may also be of conical shape. For the details of such a conical heat exchanger-tumbler reference may be made to my U.S. Patent No. 4,106~114, issued August 8, 1978. It will suffice, for the present, to say that the heat exchanger has a refractory lining 24 and is supported for rotation about its axis by a single large annular bearing 30 wi~hin which the lower cone section is mounted, the axis defined by the bearing being inclined at an angle of approximately 45 bot which may vary between about 35 and 55. As a result of rotation and inclination materials entering at the inlet are constantly cascaded, and thus evenly distrlbuted, over the surface 26 of the .
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::, ' contained load. A further advantage of the lnclination is that mater:ials are drawn from the outlet 22 from over a wide range of positions within the exchanger. The operation may be contrasted with that of an hour glass in which the grains are fed primarily along a fixed line which extends vertically upwardly from the constriction. In the present heat exchanger-tumbler the vertical line extending through the mass of material within the device constantly orbits so that the material drawn from the exit is not drawn from any one particular location so that a mixing occurs which not only equalizes the composition flowing through the outlet but in addition greatly impxoves the efficiency of the heat exchange. The unit is preferably driven by means of teeth formed into the outer ring of the bearing 33 which are engaged by the teeth of a pinion 34 connected to a drive 35 having a control 36 which is capable of adjusting the speed from a portion of a r~volution to several revolutions per minute, for example, from 0.2 to 2.0 rpm. In carrying out the invention the heat exchanger 20, in addition to receiving flow of feed material also receives a flow of hot, freshly made briquettes, the purpose of the heat exchanger being to pre-hjeat the feed material and, at the same time, to cool the briquettes to a safe discharge t~mperature. However, a discussion of briquette production and path of flow will be temporarily deferred.
The mixture of briquettes and feed which is fed ;; ~ from the outlet 22 of the heat exchanger 20 passes in~o a screw type feeder 40 having a drive 41, the feeder serving `~ ~ to load an elevator 50 having chain supported buckets 51 driven by a drive 52. While the drive is shown for convenience at the lower end, it is desirable, in fact, to have the drive . . .
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at the upper end. At the upper end of the elevator the buckets are emptied into a to-tally~enclosed screen assembly 60, which is preferably of the vibratory type having a frame 61 mounting a screen 62 and supported on resilient mounts 63. An electric motor- driven vibrator 64~ which is preferably of the eccentric type, causes the frame, and the screen 62 which it contains, to vibrate resulting in efficient separation of the briquettes which flow along a path 65 on the upper side of the screen, from which they are discharged from the plant, and the heated feed material which flows through the screen along a path 66.
The heated feed material is conducted downwardly through a first feed tube 70 having an upper end 71 and a lower end 72 which feeds into the second, or lntermediate : . temperature, heat exchanger 80 to be discussed.
The heat exchanger-tumbler 80 is similar to the heat exchanger 20 previously described having a sealed inlet 81 and a sealed outlet 82, with the vessel being formed by a hollow conical receptacle 83 enclosed by a cover 84.
The receptacle has a refractory lining 85. The heat exchanger is supported upon a bearing 93 having teeth driven by a pini~h 94 which has a drive connection with the heat exchanger drive 95 having a controller 96.
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At the outlet of the heat exchanger 80 is a screw feeding device 100 powered by a drive 101 for the feeaing ~ of material at a controlled ra~e into an elevator 110 having : a series of chain supported buckets 112 driven by a dxive 113.
; The elevator buckets are dumped into a screen assembly 120 having a gas-tight housing 121 and a stationary screen 122 of ` :
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the inclined "grizzly" type, with the briquettes flowing over the top oE the screen along path 125 and the heated Eeed materials falling to a position 126 below the screen which feeds a hopper 130. At -the hottom of the hopper is a screw type feeding device 131 having a drive 132.
From the hopper 130 the heated feed material is discharged into a furnace 140 of the ~luid bed type, the furnace having an inlet 141 at its upper end and outlet 142 at its lower end. The furnace, in its preferred form, 10 has an upper cylindrical portion 143 and a lower conical portion 144 lined wi~h a layer 145 of refractory material (Fig. la~.
The bottom of the fuxnace has multiple air inlets 146 and an air plenum 147 underlying the inlets. The plenum receives pressurized air through a line l48 leading from a blower 149 driven by a motor M~ The bed of material, indicated at 151, at the bottom of the furnace is fluidized by the air which flows upwardly through the inlets, as is characteristic of a fluid bed, resulting in efficient burning of combustible elements in the feed.
In accordance wi-th one of the more detailed aspects of the present invention the off gases resulting from the combustion are conducted upwardly through the inlet opening 141 and past the point of discharge of the feeder 131 which feeds material into the furnace to provide a feed/gas heat exchanger 150. Moreovery the inlet 141 is sufficiently restricted so that the of gases have a sufficient velocity as they pass the point of feeder discharge so a substantial portion of the discharged material is conducted upwardly and maintained in contact with the high kemperature off gases thereby recover mg wast~ heat, which raises the temperature .~ :
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of ~he waste to more nearly that of the furnace. The remaining coarser and more abrasive material discharged by feeder 131 falls into -the furnace, counter current to the gas, also aiding in heat recovery ~rom the gas. The off gases and the entrained particles are conducted into a vertical stack 152 and into a known cyclone type separator 153 having an upper discharge 154 i-or the gases and a down-wardly extending convergent discharge 155 containing a trickle valve (not shown) for returning the entrained particles o waste back into the furnace. In addition to recovering heat, the feed/gas heat exchanger causes a reduction in the internal temperature of the cyclone separator which tends to become plugged when operated at furnace bed temperature. If desired, air may be injected into the upper outlet port of the separator, as indicated at 156 for the purpose of completing the oxidation of carbon monoxide and any unburned hydrocarbons. The off gas then flows through a duct 157 downwardly into a scrubber assembly 160 having an upper, or manifold, section 161 and a lower section 162.
The manifold is positioned over the inlet opening 21 of the - first heat exchanger 20 so as to receive, also, the off gases from the heat exchanger. Water is sprayed into the gaseous stream as indicated at 163 to purify the gases and to remove any entrained particles, following which the stream of gas is sucked into a blower 164 which discharges into an upstanding flue or stack 165~ The solid particles, in ~he form of a slurry, are drawn from a dLischarge port 166 at the lower end of the scrubber assembly.
With regard to the off gases from the second, or intermediate temperature, heat exchanger 80, these pass through : .
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a manifold 170 and a small scrubber 171, supplied with water 172. The effluent yases, oil, water and solids are conducted by means of a duct 173 for injection, at 174, in the lower portion 162 of the aforementioned scrubber. Scrubber 171 may be in the form of a jet-type venturi eductor, using water 172 at high pressure to provide the efficiency necessary to remove the oil vapors ~rom the gas. Preferably interposed in the duct 173 is an oil separator 175 which removes the oil condensed from the off gas and which is desirable in the case of particularly oily feed materials. The duct 173 also includes a divertor 176 so that the off gas from the second heat exchanger, instead of being sent to the scrubber, may be directed back into the furnace via a line 177.
Turning attention to the furnace, the combustible elements in the material 151 at the bottom of the furnace are largely burned away to leave a residue o~ iron oxide-containing material at a temperature of incipient ~usion which may be on ~he order o~ 1800 F., such materials passing through the outlet 142 of the furnace to engage a feeder 180 having a drive 181 which controls the rate of flow into a roll type compactor 190. The latter has a pair of pocketed rolls 191, 192 rotating in opposition to one another and driven by a drive motor 193. The compactor has an inner housing 194 enclosing the high temperature zone between the feed inlet 1~7 and the product outlet 199 and an outer housing 195 with a source of water 196 which is sprayed onto the rolls, between the housings, and at other strategic points, to maintain the temperature at a safe level for the machine.
The exiting briquettes, interconnected by "flash", are broken apart by a breaker 138 located at the output nip.
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A second compactor is employed in parallel with the first and carries the same reference numerals followed by suffix a. The two compactors discharge through outlets 199 and l99a into the manifold 170 ~rom which the briquettes flow into the inlet opening 81 of t:he second heat exchanger 80.
In this second heat exchcLnger the briquettes mix with the partially pre~heated feed material flowing thr~ugh the feed tube 70 from the underside of the first screen assembly 60.
Thus the bxiquettes, in the second heat exchanger, lose a portion of their high furnace heat to the eed material. The heat exchange is continued to the point of near-equalization as the mix is transported upwardly in the ; buckets of the second elevator 110.
Following separation in the second screen assembly 120, the briquettes, flowing along the upper side o~ the screen, pass into a downwardly angled feed tube 200 having a feed gate 201 at the lower end thereof which is driven by a drive motor 202. In accordance with one of the more detailed aspects of the invention the feed tube 200 is kept substantially full ~f briquet~es so that they are lowered gently to the point of discharge rather than falling freely through the tube. This is accomplished by providing a level detector 202 at the upper end of the tube which produces an output ~ignal feeding a controller 203 so that the drive 202 is actuated, causing discharge at the gate 201, only when the level of the briquettes in the tube is above the level of the detector. As will appear, level detectors, and associated : ~
controllers are utilized for control purposes at a numbe~
of points in the plant and it will suffice to say that while the invention is not limited to use of any particular type of detector, it is preferred to employ a detector which utilizes gamma rays and which may thus be mounted externally of the device with which it is used. Such level detectors and associated control equipmen-t are commonly used and are available as standard equipment from a number of suppliers.
The gamma ray source,level detector and associa-ted electronic equipment may, for example, be of catalog types 7063, 7002 and 7311, respectively, manufactured by Kay Ray, Inc. o~
Arlington ~Ieights, Illinois and the controller may be of catalog type GS 2A4A manufactured by The Foxboro Company of Foxboro, ~assachusetts.
The partially cooled briquettes are fed from the lower end of the feed tube 200 into the inlet 21 of the first heat exchanger 20 where they are mixed with the incoming wet feed material which is fed into the plant on conveyor lO.
In the firs~ heat exchanger 20 the intimate mixing which occurs as the heat exchanger revolves, and as the material cascades upon the surface of the charge, brings about an apprdximate equalization of temperature, which is continued as the mix of briquettes and feed material is fed, by feeder 40, into the buckets of the first elevator 50. Separation and discharge of the briquettes occurs in the screen assembly 60, with the briquettes passing along the top of the screen and with the now pre-heated feed material being discharged into the first feed tube 70 which leads to the second, or intermediate temperature, heat exchanger as previously discussed.
In orde:r to insure that the temperature in the first heat exchanger is kept below the temperature at which any oil containecl in the feed will vaporize, a ~ater spray head 210 is provided in the first heat exchanger coupled to a source oE water 211 which is under the control of a temperature detector 212. In short, whenever the detector reaches a temperature greater than a set value, water is sprayed in automatically to reduce the temperature to a safe level. Thus most of the oil contained in the feed remains in the feed until vaporized at the higher temperature existing in the second heat exchanger 80 and following which the oil is preferably removed from the system by the oil separator 175.
The above discussion has traced a charge of wet feed material through the plant. I desired, all of the feed, either wet or dry, may be caused to follow -~he same paths but, in accordance with one of the aspects of the present invention, the dry feed material entering on collveyor 15 powered by drive 16, is fed directly to the second heat exchanger 800 Preferably there is provided at the output of the drive feed conveyor a shiftable director 220 having a normal position 221, an alternate position 222 and a third position 223 which may, or example, be used on start-up. In the normal position the dry f~ed material passes through a conduit 225 which leads to the second heat exchanger. In the alternate position 222, in which the dry feed i5 combined with the wet, the dry feed is led through a conduit 226 to the first heat exchanger. In the third position 223 the director directs the dry feed intake directly to the furnace by means of a conduit (not shown).
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. - . , ~: ,' .' , ~ . '' ' ' ' ':
'4~3 I..L~
Under conditions of star-t-up an auxiliary burner 230 for the furnace 140 is used which may, for example, receive gas or oil ~rom an auxiliary source 231 and air from a line 232 leading from the b]ower 149. In addition, an inlet tube 233 having a three-way valve 284 is provided for injecting fuel, water or purge air directly into the fluidized bed when needed to control the bed temperature, automatically, by temperature sensor 235 and controller 236.
In a plant having little or no fuel in its feed supply, coke fines may be added to the feed, powdered coal may be fed into the bed by a screw conveyor (not shown) or oil or gas may be injected directly into the bed through one or more fuel inlet tubes, of the type shown, in accordance with standard techniques.
With the construction of the plant in mind, reference may be made to Figs. 2 and 3 for a more detailed understanding of the operation. In Fig. ~ the paths of flow of the feed materials, the hot briqu~ttes, the recycled fines and the off gases have been superimposed, in coded form, upon the drawing, whereas in Fig. 3 the flow of such materials has been set forth in a flow diagram. The flow of the wet feed material 12 takes place vertically down the center of the sheet to the compactor at the bottom. Thus the material rom the wet feed conve~or 10 flows successively through the low temperature heat exchanger 20, the feeder 40, the shaker screen 60 into the intermediate temperature heat exchange~ 80.
From the latter, flow continues through the feeder 100, screen -120, hopper 130, feeder 131, the heat exchanger 150 into the furnace 140. From the furnace the residue, heated to incipient ~ -:
: `
.
: ~ --15-- :
fusion, is fed via feeder 180 lnto the compactor 190 where the briquettes are formed.
The hot briquettes, after compaction, are caused to ~low in a hea~ exchange path which ls counter to the f]ow of the waste material. That is to say the briquettes are conducted from the compactor 190 along path 170 into the intermediate heat exchanger. In this heat exchanger the briquettes, at an entering temperature of approximately 1800 F., encounter the feed which has been pre-heated, in the first heat exchanger, to a temperature of approximately 300 F. The resulting mix, which is conveyed through feeder 100 anA up elevator 110 to ~he screen 120 achieves a near-equilibrium temperature which is on the order of 1000 F.
The briquettes flowing along the top of the screen in the screen assembly 120 are lowered through the feed tu~e 200 to enter the low temperature heat exchanger at a temperature of 1000F. Here the briquettes are joined by the wet feed from conveyor 10 which is at an assumed temperature of 0 F.
The mix exiting from the low temperatu~e heat exchanger 20 and elevated by the elevator 50 reaches an equilibrium temperature of approximately 300 F. which is then the temperature of the briquettes at the point of discharge 65v - The out gas from the low temperature heat exchanger, because of the spraying of water from the spray head 210, is at a somewhat lower temperature, namely,212 F.as it is fed into scrubber 160. Furnace off gas passes through feed/sas heat exchanger 150, cyclone 153 to scrubber 160 by way of conduits 152 and 157. Fines from the cyclone flow through tube 155 to the furnace . Gas rom the intermediate temperature heat ~' ' ' ~-, , ~
e~changer 80 ~lows into scrubber 171 and then into scrubher 160 dir~ctly or by way of oil separa-tor 175. Alternatively, the gases from scrubber 171 may be piped into the furnace for combustion of any fuel content.
AUTOMATIC FLOW CONTROL
.
In the above description it has been assumed that the various feeding devices have each been adjusted to produce equalized rates of feed so that there will be no tendency toward material accumulation at any point in the system. However, it is one of the features of the present invention that manual intervention is not required to equalize flow rates under changing conditions. Briefly stated, the output rate of the plant is determined by the speed of rotation of the compactor rollers and the degree of compaction which is maintained. Working upwardly through the syste~, back to the point of feed of the wet raw material, each vessel is provided with a level detector which actuates a controller which correctively controls a feeder located upstream in the path of material flow to keep the level in the vessel automatically at its working level. In other words, each vessel has a level detector which "calls" for material from an upstream point in the flow as needed to keep the material in the vessel at its desired, and most efficient, working level.
Attention will first be gi~en to the means for controlling flow of the material, heated to incipient fusion, to the compactor. For this purpose the compactor 190 has a pressure sensor 240 which determines the force applied between the two rolls and produces a signal to activate a controller 241.
The controller tends to maintain constant brique~te density by ~ -17-.~
;' ~ ''' :
~.g~
b~inging a~out a correctlve increase or decrease in the speed of the drive ]81 for the feeder 180. A sui-table pressure sensing cell 240 and controller 241, which completes a servo loop, are available commercially from several suppliers.
When the pressure between the rolls drops, indicating that insufficient material is being fed, a signal is produced which actuates the controller in a direction to speed up the drive 181, and vice versa.
Assuming that the rate of feed at the feeder 180 increases, this will tend to produce a drop in the body of material contained in the furnace. In carrying ouk the invention such drop in level is sensed by a level detector 242 which actuates a controller 243, causing a speed-up in the drive 101 which drives the feeder 100 at the outlet of the second heat exchanger 80. This causes loadiny of material onto the second elevator 110 at a higher rate thereby increasing the xate of replenishment of the furnace 140. Feeder controller 243 also controls the speed of elevator 110 by changing the speed of its motor 133 in proportion to the rate of feed.
; The hopper 130 which is positioned between the elevator 110 and the furnace has its own control loop including a level detector 244 which actuates a controllex 245 to correctively adjust the drive 132 associated with the feeder 131. This sexvo loop tends to maintain a constant leveI of material in the hopper so that when additional material is deposited by the elevator 110, raising the hopper level, this is immediately sensed by the level detector 244 so that material is immediately fed from the hopper to the furnace at a greater rate.
.
~ -18-, ~ , .
p~
The above mentioned increase in feed from the second heat e~chanyer to satisfy -the requirements oE the furnace, results in a drop in level of the material i.n the second heat exchanger 80 which is sensed by the level detector 246, producing an output signal which activa-tes an associated controller 247 to increase the rate of feed of the feeder 40, at the lower end oE the elevator 50 and the speed of the elevator. This produces a higher rate of feed from th.e elevator so that feed material passes at a greater rate through the screen 60 fox replenishment of the second heat exchanger via the feed tube 70.
The greater rate of withdrawal from the first heat exchanger 20, in turn, tends to cause a drop in level in that heat exchanger which is sensed by a level detector 248 which transmits a signal to controller 249 which produces a corrective adjustment in ~he speed of the drive 11 which drives the wet feed conveyor 10, with the result that the wet feed material is fed at a greater rate for immediate replenishment of the first heat exchanger.
In the above discussion of the progressive : automatic control by a series of servo loops, it has been assumed that an increased rate of feed at the compactor has occurred calling for replenishment at successive points in the upstream path of flow. It will, however, be under~
stood by one skllled in the art that the reverse will take place when the needs of the compa~tor tend to decrease~
with an over-pressure condition at the compactor resulting in a cutting down of the flow successively in the upstream position. In a practical case this replenishment, or cutting down, does not take place in a step-by-step fashion as ~19~
,. .
.
described but, instead, each ser~o loop tends to establish and maintain an equilibrium condition until the equilibrium tends to be upset in one direction or the other, whereupon corrective action automatically occurs.
While no servo control has been shown for the drive 16 for the dry feed conveyor 15, it will be understood that where a dry feed is fed simultaneously, as will normally be the case, the dry feed conveyor may be equipped with a servo loop under the control of the level detector 246 10 in the second heat exchanger, so that a drop in the level ; of such heat exchanger simultaneously increases the rate of feed from the first heat exchanger and the rate of input of the dry feed from outside of the system. Alternatively, where the director 220 is in its position 222, in which the dry and wet feeds are combinedr the dry feed drive 16 may be coupled to the wet feed drive 11 for simultaneous control~
::
PHYSICA~ LAYOUT OF _LANT
While the invention as described by a ~low diagram in Fig. 3 is not limited to any par~icular physical arrange-ment, it is nevertheless one of the important features ofthe invention that the plant is constructed in a framework in which the two heat exchangers 20, 80 occupy the lowermost positions and the two screens, which are fed by respective elevators from the heat exchangers, occupy the topmost positions, with the furnace occupying an intermediate position, and with the compactors interposed between the furnace and the inter-mediate temperature heat exchanger. The wet ~eed conveyor 10 is preferably located at a level above the first heat exchanger and the dry feed conveyor is preferably located at a level ;
. ~
,, . - : .. . .. . : . ~ , ~ , above the bot-tom o~ the furnace. In this way all of the transport, except that which occurs in the two elevators, is vertically downward under the action of gravity. This greatly simplifies the system since the only -transport drives which are required, aside from the input conveyors, are those which are used to drive the elevators.
Preferably the openings in the intermediate temperature screen assembly 120, which is just ahead of the furnace, are larger than the openings in the screen assembly 60, thereby insuring that any materials which pass the low temperature screen 60, and which are smaller than briquette size, are certain to be passed by the intermediate temperature screen for treatment in the furnace, including undersized portions of the briquet~es which may break off as a result of physical handling.
While it is one of the features of the present invention that the materials fed into the plant on the inlet conveyors 10, 15, are well mixed within the plant as a result of the mixing actions, of the tumbler type heat exchangers, the furnace, screens and conveying devices, the invention, in one of its aspects, extends beyond the physical plant to encom~ass the manner in which the raw materials are stored.
~s stated above, the waste materials from a steel making operation vary widely in type, source, size and composition including metallic iron, oxides of iron, other compounds of iron, coke and other carbonaceous materials. In accordance with one aspect o~ the present process, these raw materials are not necessarily stored in separate piles but are, instead, deposited on a sin~le pile or reservoir in relatively thin layers. When the materials are scoop~d for the loading of , ~
, ~'L~4~3~9 the input conveyors 10, 15 it is contemplated that the scooping, ~y a power shovel, front end loader, or the like~
will ta~e place in passes acxoss the layers so that each scoop contains a por-tion of many layers from the pile. This produces an automatic mixing of the available iron and carbon containing components to bring them within the range of tolerance of the present plant and without requiring the provision of a separate, costly, or cumbersome pre-mi~ing plant. This further adds to the economy of the present system.
A.LTERNATE EMBODIMENT
While the present invention has been described in connection with Figs. 1-3 which show a preferred embodiment employing a two-stage heat exchange cycle in which the briquettes flow counter to the raw material, the invention in its broader aspects is not limited to use of two heat exchangers and a plant may be constructed in simplified form as set forth in Figs. 4 and 5 without departing from the invention. In this plant, in which similar elements are denoted by similar reference numerals with addition of subscript a, it will be noted that the intermediate temperature heat exchanger 80, with its associated feeder 100, elevator 110 and screen 120, has been omitted. Instead, only one heat exchanger 20a of the tumbling type is employed wh~ch takes raw material directly from the wet feed conveyor --lOa and which takes the briquettes direc~ly from the compactor l90a. It will be understood that the features of automatic control are the same. This plant design may be preferable to that of the more complex plant in the following cases~
when the material fed contains so much water that the briquettes ` ~ :
.
., , , : , ... . , ~, . , , , . .: ... .
are su~ficiently coolecl in one heat ex.changer, (2) when -the feed material softens and is briquetted at such a low temperature that 2-stage heat exchange is not ~ustified and (3) when the tonnage to be processed is too low to justify the more expensive plant, even though the fuel consumption might be greater.
While the embodiments of the present invention illustrated were designed primarily to operate using as raw material the waste and screenings in the form of iron oxide together with combustible elements in the form of carbon and hydrocarbons produced in the normal operation of a steel plant, the invention may be employed in the briquetting of particulate materials from a number of different sources. Indeed, the present invention may be utilized in hot briquetting many materials, including iron ore fines and concentrates,chrome ore fines, ferro- ~.
manganese screenings, metal chips, phosphate rock, mixtures of raw materials for glass and portland cement manufacture, and other materials and mixtures that soften at temperatures at least as high as 2000 F. In many such applications, the plants illustrated in Figures 1-5 could be used with ~: little or no alteration. Also while the texm "briquette"
has been used to designate the end product, and while such term is intended primarily to describe dense, pillow shaped pellets of consistent size, it will be.understood that the term "briquette" is by no means limited to production of pellets of equal size and consequently it shall be interpreted ~ to cover irregular of broken pieces or granules of material : produced by compaction in continuous strip form and then broken or crushed and screened to the desired size.
.
ALTERNATE ANTI-POI,LUTION EMBODIMENTS
While khe anti-pollution means described in connection with the embodiments set forth in Figures :L-5 are adequate for many materials and will meet ~he pollution standards for a number of plant locations, even more elaborate anti-pollution equipment may be required for processing some materials and for locations having unusually stringent pollution limitations.
Two equipment arrangements involving more extensi-ve means for pollution control are shown in Figures 6 and 7, which are modifications of the arrangement set forth in Figure 4~
In both arrangements, all off gases are passed through a combustion zone for removal of combustible contaminants, such as oil vapors and carbon monoxide, prior to being scrubbed and discharged to atmosphere. ~oth arrangements include optional condensers for removing moist~re from the gases prior to entering the combustion chamber, so as to reduce the consumptionO~ fuel and the size of combustion and scrubbing equipment when economically justified.
The arrangement illustrated in Fig. 6 is intended for applicatlons in which ~he feed to the plant contains a relatively low percentage of objectionable hydrocarbons having a low boiling point or in which the feed contains an - excess oE solid fuels that would provide a low-cost source of the additional heat required. In the arrangement of Figure 6 (in which corresponding reference numerals are employed with addition of subscript b) the scrubber 160b has been mo~red from its previous location (Fig. 4) a~ the gas outlet of the heat exchange tumbler 80b to a pssition near the outlet oE the cyclone separator 153b, and a condenser ' - ~
` . ! ' ' ' ' : ' ' ' ' ' ' :
~ ' ' ', ' : : . ' 253 has been added at the outlet o~ the tumbler 80b. In this arrangemen-t, the off gases from the tumbler 80b, compactor 190b and miscellaneous sources (no-t shown) are collected by hood 250 into which water 251 is optionally sprayed to minimize dust entering t:he condenser 253 by way of inlet header 252. The condenser may be cooled with air or water, as desired. The ~ases exit the condenser by way of outlet header 254 and duct 255 and are injected into the bottom of the fluid bed reactor 140b, by means of a blower 256 and duct 257~ together with fluidizing air from blower 149b and duct 148b. The gases from the furnace 140b flow through optional gas/feed heat exchanger 150b, then duct l51b and cyclone separator 153b. ~ir 156b is optionally introduced into the off-gases at the gas outlet 154b of the cyclone to burn any small amounts of carbon monaxide or hydrocarbons in the gas, which flow through duct 157b into scrubber 160b, which is supplied with water 163b.
The effluent gases are then exhausted to atmosphere by blower 164b through stack 165b. Slurry and condensate are drained from ~he scrubber 160b and condenser 253 through connections 166b and 258.
; The arrangement shown in Figure 7 is applicable to feed materials having a relatively large amount of volatile fuel difficult to remove by scrubbing in standard equipment.
In this arrangement, ~he gases from the tumbler 80c, ~compactor l90c and miscellaneous sources are processed in an optional condenser 253c having features similar to those described for the condenser 253 of Fig. 6. The gases from condenser 235c pass through a head 254c which discharges into the top of an afterburner 270. The off gases from ,, : ' ~ 25 :
, ~::
the furnace 140c also enter the top of the afterburner, after passing throuyh the feed/gas heat exchanyer 150c, cyclone separator 153c and duct 157c. The afterburner is equipped with a burner 271 at the top to preheat the unit and to supply heat as required to cause complete combustion of all combustible matter in the gases. The burner has suitable sources of fuel 272 and air 273, and secondary air is supplled to the afterburner at inlet 274.
The burner and secondary air supply are conkrolled by standard regulating devices to maintain the afterburner ; at the proper temperature. The afterburner is refractory lined and insulated. The effluent gases pass from the afterburner to the scrubber 160c, which is supplied with water 163c for removing entrained par~iculate matter, and then through exhauster 164c and stack 165c to the atmosphere.
Although the simplified plant design of Fig. 4 has been used to illustrate these anti-pollution means, such means are equally applicable to other plant designs that employ the present invention, including the design shown in Fig. 1.
' ~, ~ ' .
., .
.
. .
. .
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A system for hot briquetting particulate feed material containing heat-softenable matter and for cooling the resulting briquettes which comprises a fluid bed furnace having an inlet at the top and an outlet at the bottom for utilizing the heat of combustion to raise the temperature of the residue to the point of incipient fusion, a compactor coupled to the outlet of the furnace for compacting the residue into briquettes, an enclosed cone type tumbler-heat exchanger having an inclined axis and with an axial inlet at the top and an axial outlet at the bottom together with means for slowly rotating the same, the inlet being coupled to the compactor for receiving hot briquettes therefrom, means for conveying feed material to the inlet of the heat exchanger for mixing with the briquettes so that the briquettes are cooled and the feed material is heated, a screen assembly for separating the cooled briquettes from the heated feed material, a conveyor for coupling the outlet of the heat exchanger to the screen for conveying briquettes and feed material thereto, means for conveying the briquettes from the top of the screen and means for conveying the heated feed material from the bottom of the screen to the inlet of the furnace.
2. A system for hot briquetting of particulate feed material containing heat-softenable matter which comprises a vertical frame, a furnace in the central region of the vertical frame, the furnace being of the fluid bed type having an inlet at the top and an outlet at the bottom for heating the feed material to form a residue raised to a temperature of incipient fusion, a roll type compactor arranged below the outlet of the furnace for receiving the residue and for compacting it under high pressure to form briquettes, a cone type heat exchanger-tumbler located below the outlet of the compactor for receiving the briquettes, the heat exchanger-tumbler having an inclined axis with an axial inlet at the top and an axial outlet at the bottom as well as drive means for slowly rotating the same, means for conveying feed material to the inlet of the heat exchanger-tumbler so that the feed material is heated and so that the briquettes are cooled, a vertically arranged bucket elevator extending substantially from the bottom to the top of the frame, the elevator being coupled at its lower end to the outlet of the heat exchanger-tumbler so that each bucket receives a uniform mixture of briquettes and feed material, means for driving the elevator so that the process of heat exchange continues in the buckets as the buckets are elevated to the top of the frame, a screen assembly at the top of the frame for separating the briquettes from the heated feed material, means for dumping the buckets into the screen assembly so that the briquettes are discharged in a relatively cooled state and so that the heated feed material falls through the screen, means for feeding the material from the underside of the screen to the inlet of the furnace, and a feed/gas heat exchanger interposed at the inlet of the furnace for bringing the off gas from the furnace into contact with the heated feed material for further heating of the feed material to a temperature more nearly approaching the temperature of the furnace, and for cooling the off gas to a temperature more nearly approaching the temperature of the feed material, and means for subsequently purifying the off gases from the furnace and the heat exchanger-tumbler for discharge into the atmosphere.
3. The combination as claimed in Claim 2 in which the feed/gas heat exchanger is a vertical stack of frustoconical shape so proportioned that the velocity of the off gas increases as it rises sufficient to entrain at least the finer particles of the incoming feed material while the coarser and heavier particles fall into the furnace counter current to the flow of off gas, a cyclone type separator having its upper end coupled to the top of the stack and having its lower end connected to the top of the furnace so that the entrained particles of feed material are deposited by gravity and at an augmented temperature back into the furnace.
4. The combination as claimed in Claim 2 in which a variable feeding device is interposed between the furnace and the compactor, means coupled to the feeding device for constantly determining compaction force and for making a corrective change in the rate of feed, a second variable feeding means interposed between the heat exchanger tumbler and the furnace, level measuring means coupled to the second feeding means for constantly measuring the level of the material in the furnace for making a corrective change in the rate at which feed material is fed to the inlet of the furnace for maintaining a substantially constant level therein, and third variable feeding means interposed between the feed material conveyor and the heat exchanger means, and level measuring means coupled to the third feeding means for measuring the level of material in the heat exchanger-tumbler and for making a corrective change in the rate at which feed material is fed to the heat exchanger-tumbler for maintaining a substantially constant level therein.
5. The combination as claimed in Claim 1 in which the tumbler is formed of a hollow conical bottom portion and a totally enclosed top, the tumbler having an angle of inclination, with respect to the horizontal, on the order of 35-55° and conical included angle of at least 90°, with the driving means rotating the heat exchanger-tumbler at a rate of between 0.2 and 2.0 rpm.
6. The combination as claimed in Claim 2 in which an afterburner having a heating means is provided and in which the off gas from the cyclone and the heat exchanger-tumbler is passed first through the afterburner for oxidation of combustible matter and then through the scrubber for removal of residual pollutants before discharge.
7. The combination as claimed in Claim 6 in which a condenser having a cooling means is provided and in which the off gas from the heat exchanger-tumbler passes through the condenser for removal of water vapor as condensate before entering the afterburner.
8. The combination as claimed in Claim 2 in which !
the off gas from the heat exchanger-tumbler is injected into the fluid bed for oxidation of combustible matter in the off gas.
the off gas from the heat exchanger-tumbler is injected into the fluid bed for oxidation of combustible matter in the off gas.
9. The combination as claimed in Claim 8 in which a condenser having a cooling means is provided and in which the off gas from the heat exchanger-tumbler passes through the condenser for removal of water vapor as condensate before entering the furnace.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA360,689A CA1104819A (en) | 1977-04-18 | 1980-09-18 | Briquetting plant |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US788,639 | 1977-04-18 | ||
| US05/788,639 US4123209A (en) | 1977-04-18 | 1977-04-18 | Briquetting plant |
| CA301,347A CA1103923A (en) | 1977-04-18 | 1978-04-18 | Briquetting plant |
| CA360,689A CA1104819A (en) | 1977-04-18 | 1980-09-18 | Briquetting plant |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1104819A true CA1104819A (en) | 1981-07-14 |
Family
ID=27165618
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA360,689A Expired CA1104819A (en) | 1977-04-18 | 1980-09-18 | Briquetting plant |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1104819A (en) |
-
1980
- 1980-09-18 CA CA360,689A patent/CA1104819A/en not_active Expired
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