US3843458A

US3843458A - Coal treating method and apparatus for coke plants

Info

Publication number: US3843458A
Application number: US00350961A
Authority: US
Inventors: R Kemmetmueller
Original assignee: WAAGNER BIRO AMERICAN
Current assignee: AMERICAN WAAGNER BIRO CO INC US; WAAGNER BIRO AMERICAN
Priority date: 1972-02-07
Filing date: 1973-04-13
Publication date: 1974-10-22
Anticipated expiration: 1991-10-22

Abstract

1. IN A METHOD OF OPERATING A COKE PLANT, FEEDING PULVERIZED COAL INTO A COAL DRYER, DIRECTING A HOT DRYING GAS AT A FIRST GIVEN TEMPERATUE UPWARDLY THROUGH THE COAL DRYER AND SUSPENDING THE PULVERIZED COAL IN THE UPWARDLY FLOWING DRYING GAS TO FORM A FLUIDIZED BED, CIRCULATING A DRYING FLUID THROUGH COAL BY CONTACT WITH THE COILS, HEATING THE DRYING THE COAL BY CONTACT WITH THE COIL, HEATING THE DRYING FLUID CIRCULATED THROUGH THE COILS AT LEAST INDIRECTLY WITH HEAT EXTRACTED FROM HOT COKE SHORTLY AFTER THE COKE IS DISCHARGED FROM A COKE OVEN, TRANSPORTING DRY COAL AT A SECOND GIVEN TEMPERATURE FROM THE COAL DRYER INTO A HEATER, EXPOSING THE DRY COAL IN THE HEATER TO A HEATING GAS AT A TEMPERATURE SUBSTANTIALLY HIGHER THAT SAID FIRST AND SECOND GIVEN TEMPERATURES AFTER PRELIMINARILY HEATING THE LATTER GAS WITH HEAT EXTRACTED FROM THE HOT COKE, AND

DELIVERING THE DRY, HEATED COAL TO A COKE OVEN SO THAT THE COAL IS RECEIVED AT THE OVEN IN A DRY, PREHEATED CONDITION.

Description

O 1974 R. KEMMETMUELLER 3,843,458 COAL TREATING METHOD AND APPARATUS FOR COKE PLANTS 3 Sheets-Sheet 1 Filed April 13, 1973 com. TREATING METHOD AND APPARATUS FOR com: PLANTS Filed April 13, 1973 Oct. 22, 1974. R. KEMMETMUELLER 5 Sheets-Sheet 2 COAL TREATING METHOD AND APPARATUS FOR COKE PLANTS Filed April 15; 1973 Oct. 22, 1974 R. KEMMETMUELLER 3 Sheets-Sheet 3 'III United States Patent O 3,843,458 COAL TREATING METHOD AND APPARATUS FOR COKE PLANTS Roland Kemrnetmueller, Pittsburgh, Pa., assignor to American Waagner-Biro Company, Inc., Pittsburgh, Pa.

Continuation-impart of application Ser. No. 224,154, Feb. 7, 1972, now Patent No. 3,728,230. This application Apr. 13, 1973, Ser. No. 350,961

Int. Cl. Cb 39/02 US. Cl. 20139 Claims ABSTRACT OF THE DISCLOSURE A coal treating method and apparatus for coke plants, according to which coal is delivered to coke ovens in a dry, preheated condition. Pulverized coal is fed to a coal dryer in which the coal is suspended in a fluidized bed of heated gaseous material while in the coal dryer the coal is free to move into contact with coils through which a drying fiuid is circulated. A dry-quenching gas is circulated through a body of hot coke shortly after pushing of the latter from a coke oven, so that the dry-quenching gas extracts heat from the hot coke, and it is this heat which is used to heat the drying fluid. From the coal dryer, the coal in a fully dry condition is delivered to a heater which also receives its heat from the heat energy extracted from the body of hot coke by the dry-quenching gas, and in this heater the temperature of the dry coal is raised, so that coal in a dry heated condition issues from the heater. From the latter the coal is transported to the coke ovens so that in this way the coke ovens are charged with dry, preheated coal, with the energy which is used for this purpose being taken from the hot coke which is discharged from the coke ovens.

CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of copending application Ser. No. 224,154, filed Feb. 7, 1972 and entitled Coke Plant and Method for Operating Same.

BACKGROUND OF THE INVENTION The present invention relates to coke plants.

In particular, the present invention relates to the treatment of coal which is to be converted into coke in the coke plant.

As is well known, the treatment of the coal in preparation for converting the latter into coke is an extremely important phase of the operation of a coke plant. The output of any given coke plant will of course be determined by the operating cycles at the coke batteries. The shorter the time required for converting the coal into coke at the coke ovens, the greater the output. Moreover, it is known that a higher quality coke can be achieved from coal which is in a given condition prior to distillation in the coke ovens.

A further factor which is of great importance is the necessity of reducing pollution of the surrounding atmosv phere to the greatest possible extent. One of the greatest sources of pollution at the present time in the operation of coke plants is the result of the handling of the coke as it is discharged from the coke ovens and the handling of the coal during transportation and treatment thereof in reparation for charging the coke ovens.

While it is possible to improve the above factors, at the present time the available expedients for this purpose involve considerable costs so that if steps are taken to reduce pollution and to treat the coal so as to achieve coke of superior quality with a high output, the result is an undesirably high operating cost.

Patented Oct. 22, 1974 It is accordingly a primary object of the present invention to provide a method and apparatus which will avoid the above drawbacks.

Eln particular, it is an object of the present invention to provide a method and apparatus which make it possible to achieve coke of high quality at relatively low cost.

Also it is an object of the present invention to provide a method and apparatus capable of achieving a high output of coke, also at relatively low cost.

Furthermore, it is an object of the present invention to provide a method and apparatus which will protect the atmosphere against pollution without involving any extremely high cost.

In particular, it is an object of the present invention to take advantage of energy which is present in the form of heat in coke which is discharged from the coke ovens, and making use of this energy for the purpose of achieving the above objects at a relatively low cost.

According to the present invention pulverized coal is fed to a coal dryer in which the pulverized coal is suspended in an upwardly directed hot drying gas so as to form a fluidized bed. A drying fluid is circulated through coils in the fluidized bed in order to further dry the coal by contact with these coils. The drying fluid which is circulated through the coils is heated at least indirectly with heat which is extracted from hot coke shortly after the latter is discharged from a coke oven. The dry coal is transported from the coal dryer to a heater where the dry coal is exposed to a heating gas which has been preliminarily heated with heat from the hot coke, so that in this way a dry, preheated coal is achieved to be delivered in this dry, preheated condition to the coke battery.

The coke plant of the invention includes a coal-drying means for drying pulverized coal. A heating means communicates with the coal-drying means for receiving the dry coal therefrom and for heating the dry coal. A bunker is provided to receive hot coke from a coke oven. A heattransfer means communicates with this bunker, with the coal-drying means, and with the heating means for extracting heat from the coke in the bunker and for delivering the extracted heat in part to the coal dryingmeans and in part to the heating means for drying the coal at least in part with heat extracted from the hot coke in the bunker and for heating the coal at the heating means with heat extracted from the coke in the bunker. A transporting means communicates with the heating means to transport the coal in hot, dry condition from the heating means to a coke battery, so that the coal is received at the coke battery in dry, preheated condition.

BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way of example in the accompanying drawings which form part of this application and in which:

FIG. 1 is a schematic illustration of one possible method and apparatus according to the present invention;

FIG. 2 is a schematic illustration of a variation of the method and apparatus illustrated in FIG. 1; and

FIG. 3 is a schematic illustration of a third embodiment of a method and apparatus according to the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring first to FIG. 1, there is schematically illusstrated therein, at the upper right part of FIG. 1, a bunker 10 which receives in a known way hot coke immediately subsequent to pushing of the coke from a coke oven. The hot coke in the bunker 10 is cooled therein prior to being discharged in a known way by way of the

valves

12 and 14 so that the relatively cool coke will be received on a conveyer means 16 to be conveyed to suitable bins where the coke is maintained in readiness to be used for such purposes as blast furnace operations, for example.

The hot coke which is received in the bunker contains a tremendous amount of energy. In many conven tional coke plants this energy is wasted, particularly in the case where the coke is cooled by wet-quenching procedures. Thus, it is known to cool the hot coke immediately subsequent to discharge thereof from a coke oven with liquid which creates great clouds of steam, creating undesirable pollution of the surrounding atmosphere and wasting the energy which is contained in the heat of the hot coke.

Therefore, dry-quenching of the hot coke is far more preferable, and in the method and apparatus shown in FIG. 1 dry-quenching is provided with a dry-quenching gas. The dry-quenching gas, which may if desired be a suitable inert gas, is directed along a closed circuit indicated by the dot-dash line in FIG. 1, as explained by the code at the lower right portion of FIG. 1. The dryquenching gas is circulated through the closed path by a suitable blower 18 or the like. This lower 18 delivers the dry-quenching gas through a conduit 20 to a cyclone 22 in which any particles of coke entrained in the gas are separated, these particles of coke being delivered to a collecting bin 24 from which they are transported by a suitable screw conveyer 26 or the like to any desired location where the fine particles of coke will be used.

From the cyclone 22 the dry-quenching gas continues to travel through a pipe 28 to a supply header 30 in the form of a ring having suitable valves and communicating through pipes 32 with an inlet 34 in the interior of the bunker 10. The inlet 34 in a known way has the baflles 36 between which the dry-quenching gas escapes with these baffles preventing the travel of the dry-quenching gas into the body of coke from being obstructed.

The dry-quenching gas enters the bunker 10 at a temperature of approximately 150 C, as indicated in FIG. 1, and after travelling upwardly through the hot coke, the dry-quenching gas discharges from the bunker 10 into the discharge pipe 38 at a temperature of approximately 800 C., for example. At this latter temperature the dryquenching gas will reach the top of an elongated vertical housing 40 down which the dry-quenching gas flows to discharge out of the housing 40 into an inlet pipe 42 which returns the dry-quenching gas to the blower 18. Thus, the dry-quenching gas has been cooled from 800 C. to a temperature of 150 C. in the illustrated example before being returned to the bunker 10. As the dryquenching gas travels down the housing 40, it gives up its heat to various heat exchangers, economizers, and the like, which are distributed along the interior of the housing 40 in a manner described in greater detail below.

As the hot dry-quenching gas flows downwardly along the interior of the tubular housing 40, it first flows across a heat exchanger 44, then across additional heat exchangers or economizers 46 and 48, and so on across additional heat exchangers or

economizers

50, 52, and 54. Before discharging out of the housing 40 into the pipe 42 in order to be returned back to the blower 18, the dry-quenching gas flows also across an additional heat exchanger 56. All of the above heat-exchanger units in the housing 40 successively cool the dry-quenching gas so that it is returned to the bunker 10 at a temperature of approximately 150 C. while issuing from the bunker 10 at a temperature of approximately 800 C., in the illustrated example, as pointed out above. Through this series of heat exchangers energy is extracted from thp dry-quenching gas, and thus through the latter from the hot coke in the bunker 10, so that further use may be made of this energy.

After flowing downwardly past the first heat exchanger 44, the temperature of the dry-quenching gas is reduced in the above example to approximately 250. The heat ex changer 46 forms part of a closed path for a drying fluid which in the illustrated example is steam, this drying fluid flowing through coils 58 situated in a coal dryer 60. The coal dryer 60 is in the form of a suitable container to which pulverized coal is fed by way of a feeding means 62 part of which is illustrated schematically in FIG. 1. Thus, coal in pulverized condition is conveyed in any suitable way to the inlet 62 from which the pulverized coal drops down into the interior of the closed vessel 60. The coils 58 are distributed through the container 60 so that the particles of pulverized coal will engage the coils 58. The bottom of the container 60 communicates with a pipe 62 by which a hot drying gas is directed upwardly through the interior of the container 60. This hot drying gas is taken from any suitable source such as a source of waste gas, this gas arriving at a temperature of approximately 150 C., for example, to a blower 64 which delivers the drying gas to the heat exchanger 50 so that in the latter the temperature of the gas will be elevated to a range of 250450 C., in the illustrated example, before reaching the container 60. The blower 64 assures that the gas has a suflicient pressure to be able to suspend the pulverized coal particles to form a fluidized bed therefrom. As is well known the gas may be delivered to a lower plenum defined at its upper end by a perforated plate through which streams of drying gas issue upwardly to form the fluidized bed in a well known manner. The particles of coal move about in the fluidized bed so as to contact the coils 58 a number of times, and in this way the coal is dried not only by the drying gas which forms the fluidized bed but also by contact with the coils 58.

The fluid in the coils 58 also flows in accordance with the invention along a closed path, this path being desig nated by the dash-dot-dot line, as is apparent from the code at the lower right of FIG. 1. Thus upon discharging from the coal dryer 60 the drying fluid will flow along a pipe 68 to a condensate tank 70 from where the condensed liquid flows to a pump 72 in order to be pumped thereby along the pipe 7 4 into the heat exchanger 54 from which the pumped fluid flows to a second heat exchanger 52 and then along a pipe 74 to the steam drum 76. From the steam drum 76, from which steam may be taken for other purposes also, the fluid circulates through the heat exchanger 48 by way of a pair of pipes 78 and 80. A branch from the pipe 78 directs some of this fluid through the heat exchanger 46 from which the heated fluid at a temperature of 250, for example, flows along the pipe 82 to the coils S8 to progress along these coils to the pipe 68, in this way completing the closed path for the drying fluid.

The drying gas from the fluidized bed flows out through an outlet 84 at approximately a temperature of 100 C. This gas then flows through a Venturi scrubber 86 from which moisture with particles of coal is discharged by a pipe 88, and a desmister 90 condenses further liquid out of the discharging gas to flow also along the pipe 88 to any suitable receptacle. A heater 92 is provided to raise the temperature of the gas before it is vented at 94 to the outer atmosphere. In this way this gas has been cleaned before being released to the outer atmosphere.

From the coal-dryer 60, the pulverized coal in dry condition flows through a supply conduit 96 at a temperature of approximately 100 C. to the inlet of an elongated heating means 98 which may be a flash heater, for example. The pipe 96 is in the form of a pneumatic conveyor for the pulverized dry coal particles. Thus, the coal is completely dry by the time it reaches the heating means 98. This heating means 98 is in the form of an elongated hollow container having the inlet end to which the dry coal is delivered by the conveyer 96.

The heating gas which flows along the interior of the heating means 98 is preferably an inert gas such as nitrogen or a mixture of nitrogen and carbon dioxide. This heating gas reaches the inlet of the heating means 98 at a temperature of approximately 650 C., in the illustrated example. The heating gas is heated by the first heat exchanger 44 to an extremely high temperature on the order of 650 in the illustrated example. Thus, from the heat exchanger 44 the heating gas flows through the pipe 100 to the inlet of the heating means 98. This gas flows through the heating means 98 at a speed of approximately 60 meters per second, so that the pulverized coal is conveyed along the interior of the heating means 98 to issue at the outlet thereof into a cyclone 102. The pipe 104 connects the discharge end of the heating means 98 with the cyclone 102, and at this pipe 104, which may be provided with a suitable valve 106, the coal has a temperature of approximately 250 C.

The heating gas is also directed along a completely closed path designated by the dash-dot-dot-dot line, as shown by the code at the lower right of FIG. 1. From the cyclone 102 the heating gas flows with any additional smaller coal particles to an additional cyclone assembly 108, and from the latter the heating gas flows into the lower end of a bag filter assembly 110 or the like where cleaning of the gas takes place. A part of the gas may be vented to the atmosphere through a vent 112. However, the greatest part of the gas flows from the filter 110 along a pipe 114 back to a blower 116 from which the gas is delivered to the heat exchanger 44 in order to again be raised to the elevated temperature on the order of 650 C. in the illustrated example before again reaching the heating means 98. In this way the heating gas is also directed along a closed path.

The above method and apparatus of the invention are completed by a number of added features. Thus, make-up water is added to the pump 73 through an inlet 118.

Also, part of the inert gas with fine coal dust suspended therein is delivered by a pipe 120 from the filter 110 to an auxiliary burner 122 which may be operated to regulate the temperature of the dry-quenching gas before it reaches the heat exchanger 40. For example, toward the end of a cooling cycle it may happen that the temperature of the dry-quenching gas falls below a desired value. At this time the auxiliary burner 122 may be used to increase the temperature of the gas so that the heat exchanger 44 will receive a sufiicient amount of heat to provide the desired temperature in the heating gas.

Of course, the coal dust is suspended in the pipe 120 in an inert atmosphere. Combustion air for the burner 122 is derived by way of a blower 124 which conveys air from an inlet 126 through a pipe 128 into the heat exchanger 56 in which the air is preheated before flowing along a pipe 130 to the burner 122 in order to provide at the burner 122 combustion air to regulate the temperature of the dryquenching gas.

Also, part of this preheated combustion air may be branched through a pipe 132 to an additional burner 134 which also receives coal dust suspended in the inert gas by way of a conduit 136, and thus by way of the auxiliary burner 134 it is also possible to regulate the temperature of the heating gas before it reaches the heating means 98.

In addition, those fairly large coal particles which are too heavy to be carried along with the heating gas flow automatically to a crusher 138 which further pulverizes these particles and directs them back through a recirculating pipe 140 to the inlet of the heating means 98.

The dry, preheated coal is delivered from the

cyclones

102, 108 to a conveyer 142, such as a suitable screw conveyer, which delivers the coal to a bin 144 in which the coal is temporarily stored for a relatively short time before being delivered by the larry car units 146 to an oven of the coke battery 148.

According to a further feature of the invention part of the inert gas discharging from the heating means 98 is diverted by a branch pipe 150 to the bin 144 so that this inert gas which is at a temperature approximately 250 C. in the illustrated example serves on the one hand to contribute toward maintaining the coal at its eleveated temperature and on the other hand to prevention of any explosions. For the purpose of maintaining the coal at the bin 144 at the desired temperature, the bin 144 may be surrounded by a jacket 152 to which steam is supplied through an inlet 154, from any suitable source, this steam discharging through the outlet 156 and being again heated in any way before returning to the inlet 154. Thus maintenance of the dry coal at the elevated temperature is assured with the method and apparatus of the invention so that perfectly dry pulverized coal at an elevated temperature on the order of 250 C. reaches each coke oven of the coke battery.

It has been found from experience that with the above method and apparatus of the invention fully 50% of the heat energy available in the hot coke in the bunker 10 is utilized for the various drying and heating operations referred to above. Furthermore, it has been found that the operating time required at each of the coke ovens can be reduced by 40% because of the treatment of the coal according to the method and apparatus of the present invention, so that in this way the output of a given coke battery will be greatly increased with the present invention. Furthermore it will be noted that no Where is there any escape of pollutants to the outer atmosphere, so that the method and apparatus of the invention have the additional advantage of enhancing the quality of the atmosphere.

Of course, it is possible to achieve still additional use from the available energy as by utilizing steam issuing fgom the steam drum 76 for other purposes, as pointed out a ove.

The embodiment of the method and apparatus which is illustrated in FIG. 2 of the drawings is identical with that of FIG. 1 except for the drying fluid which is circulated through the coils 58 in the coal dryer 60 and the manner in which this drying fluid is heated. In the embodiment of FIG. 2, the drying fluid is in the form of a suitable liquid such as oil or glycerine. The coils 58 communicate with a pa1r of

pipes

160 and 162 which in turn communicate with a suitable heat exchanging coil 164. A pump 166 is connected for example to the pipe 162 for continuously circulating the drying liquid through the coils 58 and through the heat exchanging coil 164 which is schematically represented in FIG. 2. The heat exchanging coil 164 is in heat exchanging relationship with a vessel 168 in which circulates another heat-exchanging fluid such as a suitable liq- 111d, steam, or the like, this latter fluid being heated by way of a heat exchanger 170 in the housing 40. Thus, this heat exchanger 170 may be in the form of a simple set of coils across which the dry-quenching gas flows to heat the fluid in these coils, this fluid being, for example, water which is converted into steam and then condenses before flowing back to the lower end of the coils 170, so that in this way there rs a natural circulation of the heating fluid in vessel 168 which transfers its heat to the liquid in the coil 164 WhlCh 1S continuously pumped through the coils 58. Of course, with the embodiment of FIG. 2 the drying fluid circuit does not require the series of economizers or

heat exchangers

46, 48, 52, 54, or the condensate tank 70 and the pump 72. Thus, a simpler arrangement is provided for heating a drying liquid which continuously circulates through the coils 58, but in this case also it is to be noted that the heat is derived, although indirectly, from the dryquenching gas which extracts the heat from the hot coke 1n the bunker 10.

Except for these differences the embodiment of FIG 2 15 the same as that of FIG. 1.

As Was indicated above in connection with FIG. 1, the dry-quenching gas is preferably an inert gas, such as car bon dioxide or a mixture of the latter with nitrogenTand according to the embodiment of FIG. 3 the dry-quenching gas tself serves as the heating gas for heating the pulverized dry coal in the heating means 98. Thus, referring to FIG. 3 it will be seen that the housing 40 is replaced by an upper housing section 172 communicating with a lower housing section 174 by way of a connecting pipe 176 through which the dry-quenching gas flows downwardly after giving up some heat to a heat exchanger 178 which may be used as a source of steam for any desired purpose with this embodiment. From the pipe 176 some of the dry-quenching gas is branched along a pipe 180 to flow therethrough into the heating means 98 where the gas also enters at a temperature of approximately 650 C. in the illustrated example, and from the heating means 98 the heating gas in this embodiment also conveys the heated dry coal to the

cyclones

102 and 108 from which the coal is delivered to the bin 144 in the same way as described above. Part of the heating gas is also diverted to the bin 144 for the purposes referred to above, and of course the bin 144 may also be further heated by way of a steam jacket 152 as described above. While part of the gas may be cleaned at the filter 110 and vented to the outer atmosphere, most of the heating gas flows from the filter 110 through the pipe 182 back to the blower 18 with this part of the dry-quenching gas also reaching the blower 18 at a temperature of approximately 150 C. as is the case with the dry-quenching gas returned through the pipe 42 in the manner described above. Thus the heating gas is recircullated together with the remainder of the dry-quenching gas through the bunker in the embodiment of FIG. 3. In this way it becomes unnecessary to provide an additional heating gas which is separate from the dry-quench mg gas.

Also, with the embodiment of FIG. 3, the drying fluid which circulates through the coils 58 in the dryer 60 is delivered to the coils 58 through a supply conduit 184 while flowing out of the coils 58 through a discharge conduit 186 which delivers the drying fluid to a circulating pump 188. Through this circulating pump the drying fluid is circulated through a heat exchanger 190 to return in heated condition to the supply pipe 184. In this case the drying fluid may also be steam which is heated at the heat exchanger 190 with heat taken from the dry-quenching fluid which flows through the lower housing portion 174 in the example of FIG. 3. In this case also the steam which flows through the coils 58 can be delivered to the latter at a temperature on the order of 250 C.

With the embodiments of FIGS. 2 and 3 it is also possible to achieve the advantages set forth above in connection with FIG. 1, with respect to the economy of the operation, utilizing approximately 50% of the available heat in the hot coke and reducing the operating time at the coke ovens by approximately Also with the embodiments of FIGS. 2 and 3 there is no discharge of pol lutants to the outer atmosphere.

Thus, with all of the embodiments of the invention the heat energy available from the hot coke is used to a very large degree, so that waste of this valuable source of energy is reduced to a great extent. In addition, experience has shown that perfectly dry pulverized coal at the above temperature on the order of 250 C. is capable of producing the highest quality coke, enhancing operations such as those which are encountered in a blast furnace, so that a very superior quality of coke is achieved with the method and apparatus of the invention.

What is claimed is:

1. In a method of operating a coke plant, feeding pulverized coal into a coal dryer, directing a hot drying gas :at a first given temperature upwardly through the coal dryer and suspending the pulverized coal in the upwardly flowing drying gas to form a fluidized bed, circulating a drying fluid through coils in the fluidized bed for further drying the coal by contact with the coils, heating the drying fluid circulated through the coils at least indirectly with heat extracted from hot coke shortly after the coke is discharged from a coke oven, transporting dry coal at a second given temperature from the coal dryer into a heater, exposing the dry coal in the heater to a heating gas at a temperature substantially higher than said first and second given temperatures after preliminarily heating the latter gas with heat extracted from the hot coke, and

delivering the dry, heated coal to a coke oven so that the coal is received at the oven in a dry, preheated condition.

2. In a method as recited in claim 1, circulating a dryquenching gas along a closed path through the hot coke, and utilizing heat in the dry-quenching gas as a source of heat for the drying fluid which is circulated through the coils in the coal dryer and for the heating gas to which the dry coal is exposed in the heater.

3. In a method as recited in claim 2, circulating the heating gas along a closed path which intersects the closed path along which the dry-quenching gas is circulated while placing the gases in heat-exchanging relation at the place where said paths intersect.

4. In a method as recited in claim 3 and wherein the heating gas is an inert gas.

5. In a method as recited in claim 4 and wherein the heating gas is selected from the group consisting of nitrogen and mixtures of nitrogen and carbon dioxide.

6. In a method as recited in claim 2, branching part of the dry-quenching gas from said closed path and utilizing the branched dry-quenching gas as the heating gas.

7. In a method as recited in claim 6, returning the branched dry-quenching gas after exposing the dry coal thereto at the heater back to the closed path for recirculation with the remainder of the dry-quenching gas through the hot coke.

8. In a method as recited in claim 2, circulating the drying fluid along a closed path and heating the drying fluid at the latter closed path with heat extracted from the dry-quenching gas.

9. In a method as recited in claim 8, wherein the drying fluid is steam and is circulated along a closed path which intersects the closed path along which the dry-quenching gas is circulated and which is in heat-exchanging relation with the dry-quenching gas at the location where said paths intersect.

10. In a method as recited in claim 8 and wherein the drying fluid is a liquid.

11. In a method as recited in claim 10 and wherein said liquid is placed in heat-exchanging relation with a further fluid which is heated directly by the dry-quenching gas.

12. In a coke plant, coal-drying means for drying pulverized coal While raising the temperature thereof to a given value, heating means communicating with said coaldrying means for receiving dry coal therefrom and for heating the dry coal to a temperature substantially higher than said given value, a bunker for receiving hot coke from a coke oven, heat-transfer means communicating with said bunker, with said coal-drying means, and with said heating means for extracting heat from coke in the bunker and for delivering the extracted heat in part to said coal-drying means and in part to said heating means for drying the coal at least in part with heat extracted from the hot coke in the bunker and for heating the coal at said heating means with heat extracted from the coke in the bunker, and transporting means communicating with said heating means for transporting coal in hot, dry condition from said heating means to a coke oven battery, so that the coal is received at the coke oven battery in dry, preheated condition.

13. The combination of claim 12 and wherein said heat-transfer means includes a quenching gas circulating means for circulating a dry-quenching gas along a closed path through said bunker to extract heat from hot coke therein, a drying fluid circulating means including coils situated in said coal-drying means for at least partly drying coal by contact between the latter and said coils, said drying fluid circulating means providing a closed path for a coal-drying fluid, and heating-gas circulating means for circulating a heating gas through said heating means to heat coal therein, said heat-transfer means further including a pair of heat exchanger means one of which provides transfer of heat from said quenching gas circulating means to said drying fluid circulating means and the other of which provides transfer of heat from said quenching gas circulating means to said heating gas circulating means.

14. The combination of claim 13 and wherein said one heat exchanger means is situated subsequent to said other heat exchanger means in the path of fiow of the dryquenching gas from said bunker out of the latter and back to said bunker so that said other heat exchanging means cools the dry-quenching gas before said one-heat exchanging means extracts heat therefrom.

15. The combination of claim 14 and wherein said coaldrying means includes a container and means for directing upwardly through the latter a hot gas which will maintain pulverized coal suspended therein to form a fluidized bed in which the coal particles will be dried not only by the fluidizing gas but also by contact with said coils.

16. The combination of claim 15 and wherein said means for directing the hot fiuidizing gas upwardly into said coal-drying means includes an additional heat exchanger situated along the closed path of the dry-quenching gas for extracting further heat from the latter to be used to achieve drying from the fluidizing gas.

17. The combination of claim 16 and wherein said additional heat exchanger is situated in the path of flow of the quenching gas out of the bunker and back to the latter subsequent to the other heat exchangers for extracting heat from the quenching gas only after heat has been extracted therefrom for the heating gas and drying fluid.

18. The combination of claim 13 and wherein said transporting means includes a bin in which the dry, preheated coke is temporarily stored for a relatively short time just prior to being charged into the coke ovens of a coke battery, and a branch conduit communicating with said bin and said heating-gas circulating means for directing a part of the latter gas to said bin.

19. The combination of claim 18 and wherein the heating gas is an inert gas such as nitrogen, to prevent explosions at said bin and to reduce the rate of cooling of coal in said bin.

20. In a method as recited in claim 4 and wherein just prior to delivery of the dry, heated coal to a coke oven, the latter coal is temporarily stored for a short time in a bin, and delivering part of the inert heating gas to the latter bin for preventing explosions at the bin and for maintaining the coal at the bin at an elevated temperature.

References Cited UNITED STATES PATENTS 2,658,862 11/1953 Horner 202 X 1,854,407 4/1932 Janeway 202150 FOREIGN PATENTS 1,086,670 8/1960 Germany 202-228 NORMAN YUDKOFF, Primary Examiner D. EDWARDS, Assistant Examiner US. Cl. X.R.

Claims

1. IN A METHOD OF OPERATING A COKE PLANT, FEEDING PULVERIZED COAL INTO A COAL DRYER, DIRECTING A HOT DRYING GAS AT A FIRST GIVEN TEMPERATUE UPWARDLY THROUGH THE COAL DRYER AND SUSPENDING THE PULVERIZED COAL IN THE UPWARDLY FLOWING DRYING GAS TO FORM A FLUIDIZED BED, CIRCULATING A DRYING FLUID THROUGH COAL BY CONTACT WITH THE COILS, HEATING THE DRYING THE COAL BY CONTACT WITH THE COIL, HEATING THE DRYING FLUID CIRCULATED THROUGH THE COILS AT LEAST INDIRECTLY WITH HEAT EXTRACTED FROM HOT COKE SHORTLY AFTER THE COKE IS DISCHARGED FROM A COKE OVEN, TRANSPORTING DRY COAL AT A SECOND GIVEN TEMPERATURE FROM THE COAL DRYER INTO A HEATER, EXPOSING THE DRY COAL IN THE HEATER TO A HEATING GAS AT A TEMPERATURE SUBSTANTIALLY HIGHER THAT SAID FIRST AND SECOND GIVEN TEMPERATURES AFTER PRELIMINARILY HEATING THE LATTER GAS WITH HEAT EXTRACTED FROM THE HOT COKE, AND