EP0064617A2 - Process and apparatus for operating a coke oven plant - Google Patents

Abstract

In this process, the coke ovens are charged with preheated or pre-dried coal and the coke produced becomes a so-called. Subjected to dry cooling by means of a gaseous cooling medium. The coal is preheated by indirect heat transfer in a cascade fluidized bed dryer which is heated with a partial stream of the circulating gas from the coke oven cooling and in which the coal is present in a coal-water vapor fluidized bed. The device relates to a special embodiment of the cascade fluidized bed dryer.

Description

The invention relates to a method for operating a coke oven plant, in which the coke ovens are periodically charged with preheated or predried coal and the coke produced is subjected to dry cooling by means of a gaseous cooling medium, the plant for coke drying cooling and for coal preheating being connected to one another by a common gas circuit through which the heat extracted from the hot coke during cooling is transferred to the preheated coal. Furthermore, the invention relates to a special cascade fluidized bed dryer which can advantageously be used for preheating coal when the method according to the invention is used.

A method of the type described above, in which the systems for coke dry cooling and coal preheating are connected to one another by a common gas circuit, has already been described in DE-OS 23 04 541, FIG. 8. It is provided that the hot gas emerging from the coke dry cooler is, after appropriate cooling and dedusting, introduced into the coal preheater from below in such a way that the wet coal introduced from above is in the form of a fluidized bed. The gas emerging from the coal preheater is then reintroduced into the lower part of the coke dryer cooler. In the procedure outlined above, in which the preheat de Coal comes into direct contact with the gas from the coke dryer cooler, there should be considerable difficulties in practice because the circulating gas stream with the entire water vapor content that the gas has taken up in the coal preheater gets back into the coke dryer cooler. Due to the high water vapor content of the circulated gas on the hot coke, a considerable amount of water gas should form in this. This water gas reaction, on the one hand, causes a not inconsiderable burning of the glowing coke and, on the other hand, the explosive water gas that arises naturally also brings about considerable problems for operational safety.

The invention is therefore based on the object of improving the method of the type described at the outset in such a way that on the one hand the disadvantages described above are avoided and on the other hand, of course, the operating conditions in general are improved both in the case of coal preheating and coke oven cooling.

• a) Die Vorerhitzung der Kohle erfolgt durch indirekte Wärmeübertragung in einem Kaskadenwirbelschichttrockner, in dem die Kohle in einer Kohle-Wasserdampf-Wirbelschicht vorliegt;
• b) die aus dem Kokstrockenkühler austretende Gasmenge wird in zwei Teilströme zerlegt, von denen nur der eine Teilstrom zur Kohlevorerhitzung genutzt und mit einer Temperatur zwischen 550 und 650 ° C in die erste (oberste) Kaskade des Kaskadenwirbelschichttrockners eingeleitet wird, wobei dieser Teilstrom nach dem Passieren des Kaskadenwirbelschichttrockners wieder mit dem Teilstrom vereinigt wird, der nicht zur Kohlevorerhitzung genutzt wird.
• c) die wieder vereinigten Teilströme der aus dem Kokstrockenkühler austretenden Gasmenge werden nach entsprechender Reinigung und Abkühlung in den Kokstrockenkühler wieder - eingeleitet, wobei die Wiedereinleitung gleichzeitig in den unteren und in den mittleren Teil des Kokstrockenkühlers erfolgt; und
• d) der für die Aufrechterhaltung der Kohle-Wasserdampf-Wirbelschicht im Kaskadenwirbelschichttrockner erforderliche Wasserdampf wird im Kreislauf geführt, wobei der aus dem Kaskadenwirbelschichttrockner austretende Wasserdampf vor seiner Wiedereinleitung in denselben einer Entstaubung, Teilkondensation und Wiederverdichtung unterworfen wird.

According to the invention, the method used to achieve this object is characterized by the following measures:

• a) The coal is preheated by indirect heat transfer in a cascade fluidized bed dryer in which the coal is present in a coal-water vapor fluidized bed;
• b) the gas quantity emerging from the coke dryer cooler is broken down into two partial flows, of which only one partial flow is used for preheating coal and is introduced into the first (top) cascade of the cascade fluidized bed dryer at a temperature between 550 and 650 ° C, this partial flow being after the Passing the cascade fluidized bed dryer is combined again with the partial stream that is not used for coal preheating.
• c) the reunited partial flows of the gas emerging from the coke dryer cooler are reintroduced into the coke dryer cooler after appropriate cleaning and cooling, the reintroduction simultaneously taking place in the lower and middle parts of the coke dryer cooler; and
• d) the water vapor required for maintaining the coal-water vapor fluidized bed in the cascade fluidized bed dryer is circulated, the water vapor emerging from the cascade fluidized bed dryer being subjected to dedusting, partial condensation and recompression before being reintroduced into it.

Further design options and details of the method according to the invention and of the cascade fluidized bed dryer preferably used result from the present subclaims and the figures.

• Fig. 1 ein Fliess-Schema des erfindungsgemässen Verfahrens ;
• Fig. 2 die Darstellung einer Kaskade des Kaskadenwirbelschichttrockners, die sich als besonders geeignete Ausführungsform zur Durchführung des erfindungsgemässen Verfahrens erwiesen hat;
• Fig. 3 eine Draufsicht auf die Kaskade gem. Fig. 2 und
• Fig. 4 eine schematische Darstellung einer besonders geeigneten und einfachen Ausführungsform eines Anströmbodens im Kaskadenwirbelschichttrockner .

They show:

• 1 shows a flow diagram of the method according to the invention;
• 2 shows the representation of a cascade of the cascade fluidized bed dryer, which has proven to be a particularly suitable embodiment for carrying out the method according to the invention;
• Fig. 3 is a plan view of the cascade acc. Fig. 2 and
• Fig. 4 is a schematic representation of a particularly suitable and simple embodiment of an inflow floor in the cascade fluidized bed dryer.

In the Fli.ess diagram in FIG. 1, which serves to further explain the method according to the invention using an example, only the system parts that are absolutely necessary for the explanation of the method are of course shown, while other auxiliary devices and the system parts of the actual coking plant are not shown.

The coal to be coked in an amount of approx. 100 t / h from the feed bunker 1, which is provided with a cellular wheel sluice 2 at its outlet, from above onto the cascade fluidized bed. dryer 3 abandoned. In the present case, this consists of three cascades arranged one above the other, which are separated from one another by the gas-permeable inflow trays 4. Of course, the number of cascades depends on the moisture content and the desired degree of drying or preheating of the coal used. In the present case, the coal used has a water content of 9%. In the first (upper most) cascade, the coal is heated to approx. 80 ° C and dried to a water content of approx. 1.5%. The partially dried coal is then transferred via line 5, which is provided with a rotary valve 6, into the second cascade below. In this cascade, the coal reaches a temperature of approx. 150 ° C and a water content of approx. 0.5%. The coal then passes via line 7, which in turn is provided with a cellular wheel sluice 8, into the third [bottom] casa practical, in which it is dried / to a residual water content of ~ 0% and to a temperature of approx. 200 ° C. is heated. At this temperature, the dried coal is drawn off from the cascade fluidized bed dryer 3 and transported via a screw conveyor 9 and a chain conveyor 10 to the coal tower of the coking plant, not shown in the flow diagram. Both the screw conveyor 9 and the chain conveyor 10 can be electrically heated in order to prevent heat losses. The entire conveyor system is rendered inert in order to avoid the penetration of water vapor from the cascade fluidized bed dryer 3.

This water vapor is responsible for maintaining the coal-water vapor fluidized bed in the cascade fluidized bed dryer 3 and is at a pressure of about 2 bar and a temperature of about 200 ° C via the line 11 and the inflow floor 4 from below into the third (bottom ) Cascade initiated. The water vapor then flows through the individual cascades from bottom to top and emerges from the first (top) cascade at a temperature of approx. 140 ° C. He then passes through line 12 to the dust collector (cyclone) 13, in which the mitge cracked coal dust is separated. This separated coal dust is fed via line 14, which is provided with cellular wheel locks 15 and 16, to the screw conveyor 9 and mixed there with the dried and preheated coal. The dedusted water vapor is withdrawn from the dust separator 13 via the line 17. Since the steam flow has additionally absorbed water vapor separated from the moist coal when it passes through the individual cascades of the cascade fluidized bed dryer 3, this excess water vapor must be removed from the circuit by partial condensation. For this purpose, a partial flow of the water vapor is branched off from the line 17 via the line 18, which is provided with the control / 19, and is condensed in the circuit washer 20. The majority of the water vapor, however, gets into the blower 21, in which the required recompression takes place to approx. 2 bar, the water vapor also being heated up again to approx nothing stands in the way. The water vapor cycle is now closed. If necessary, inert gas can be fed into the water vapor circuit via line 32.

The partial stream of water vapor drawn off through line 18 is introduced into the circuit washer 20, in which, in addition to condensation, impurities are also washed out. The liquid running out of the circuit washer 20 is fed via the line 22 and the pump 23 to the cooling tower 24, in which it cools down to 40 ° C. The GE Cooled liquid is then introduced into the cooling water distributor 26 via the line 25. From here, the required circuit water is fed back to the circuit washer 20 at different heights via lines 27, 28 and 29. Excess water, however, is withdrawn via line 30 and introduced into the sewer 31. If necessary, a wastewater treatment device, not shown in the flow diagram, can also be provided in the line 22 leading from the circuit washer 20 to the cooling tower 24. The solids separated from the wastewater, which have a high proportion of fine coal, can either be deposited in a landfill or incinerated.

The hot gas stream emerging from the upper part of the coke dry cooler 33 at a temperature of approximately 800 ° C. is withdrawn via line 34, from which branches off the gas inlet line 35, through which the partial stream of the gas is withdrawn, which is used for indirect heat transfer in the cascade fluidized bed dryer 3 becomes. This partial stream, which contains about 50% by volume of the total gas quantity, reaches the heating tubes 36 of the first (top) cascade of the cascade fluidized bed dryer 3 at a temperature of about 600 ° C. After passing through the heating tubes 36, the gas stream still has a temperature from approx. 400 ° C. The gas stream is now further divided, one partial stream entering the heating tubes 37 of the second (middle) cascade and the other partial stream entering the heating tubes 38 of the third (lowest) cascade. The gas stream emerging from this cascade at a temperature of approximately 288 ° C. is withdrawn through the gas outlet line 39. The line 40 opens into this, through which the gas stream emerging from the heating pipes 37 at a temperature of approximately 266 ° C. mixes with the gas stream in the gas outlet line 39 becomes. Through this line, the gas is conveyed back to line 34 via blower 41. The line 42 branches off from the gas outlet line 39, through which, with the corresponding position of the control flaps 44 and 45, a partial flow of the gas can be discharged into the atmosphere via the chimney 43. In addition, a bypass line 46 is provided behind the blower 41, through which the gas outlet line 39 is connected to the gas inlet line 35. This bypass line 46 allows cold gas from the gas outlet line 39 to be mixed into the hot gas in the gas inlet line 35 for the purpose of temperature control. For this purpose, the temperature measuring point 47 is provided in the gas inlet line 35, the value determined there being transmitted via the interrupted pulse line 48 to the control device 49, which in turn actuates the motor-driven control flap 50 in the gas outlet line 39 as a function of a predetermined target value. If the gas temperature determined at the temperature measuring point 47 falls below the predetermined target value, the control flap 50 is correspondingly opened further, so that the gas supply to the line 34 and thus to the coke dry cooler 33 is increased. Of course, this also causes an increase in the hot gas flow which emerges from the coke dry cooler 33 and can enter the gas inlet line 35, while at the same time the amount of cold gas which can enter the gas inlet line 35 via the bypass line 46 is correspondingly reduced. As a result, an overall increase in the gas temperature in the gas inlet line 35 is achieved. Conversely, if the gas temperature determined at the temperature measuring point 47 rises above the specified target value, the motor becomes driven control valve 50 throttled accordingly, which of course leads to a reduction in the gas supply to the coke dry cooler 33 and at the same time to an increase in the cold gas supply via the bypass line 46. This in turn results in the desired drop in the gas temperature in the gas inlet line 35. To further regulate the gas flow in this line, the motor-driven control flap 51 is also provided.

The line 34 is used to recycle the gaseous cooling medium which is used in the coke dry cooler 33 to cool the hot coke coming from the coke oven battery, not shown. The hot coke is fed in via line 69 in the upper part of the dry coke cooler 33, while the cooled coke is withdrawn from the lower part thereof via line 70. In line 34, in addition to devices for the dedusting of the gas stream, which are not shown in the flow diagram, the provided heat boilers 52 and 54 / in which the hot gas emerging from the coke dryer cooler 33 is cooled again to a temperature of approximately 150.degree. The two waste heat boilers 52 and 54 are connected to one another by the line (pipe system) 53, which is used for the feed water supply and steam discharge. The reintroduction of the gas flow from the gas outlet line 39 into the line 34 takes place between the two waste heat boilers 52 and 54, so that the partial streams of the gas which have been reunited pass the waste heat boiler 54 together. The gas, which has cooled to approximately 150 ° C., is then compressed again in the blower 55 to the operating pressure of the coke dryer cooler 33.

After the blower 55, the line 71 branches off from the line 34, through which a partial flow of the gas is introduced into the central part of the coke dry cooler 33, in which the coke to be cooled still has a temperature of approximately 400-600 ° C. The remaining part of the gas is simultaneously introduced into the lower part of the coke oven cooler 33 in a manner known per se. The control flap 72 and the control flap 73 are provided in line 34 for the necessary regulation of the two partial flows. This procedure on the one hand reduces the pressure loss of the gas in the coke dryer cooler 33. On the other hand, this results in a favorable influence on the temperature differences between the gas and the coke to be cooled and, moreover, is associated with improved controllability both with regard to the gas supply and with regard to the heat removal from the coke to be cooled.

So that the coal preheating in the cascade fluidized bed dryer 3 in the event of a failure. a malfunction of the coke dry cooler 33 is not impaired, a combustion chamber 56 is additionally provided, to which a gaseous, liquid or solid fuel is fed via line 57 and the required oxygen (air) is fed via line 58. Since the hot flue gases produced during the combustion are too high at approx. 1400 ° C., water vapor is supplied via line 59, which was branched off from line 18. By adding water vapor, the flue gas temperature can be reduced to the desired value of, for example, 600 ° C., and at this temperature the gas is then fed via line 60 into the gas supply line 35. The control flap 61 is provided in the line 60, so that the amount of gas released can also be throttled accordingly, if appropriate, and the combustion Chamber 56 can also be used as an additional heater if necessary.

The structural details of a special cascade fluidized bed dryer which can advantageously be used when carrying out the process according to the invention are to be explained below. However, this does not rule out the possibility that other types of cascade fluidized bed dryers can also be used.

Fig. 2 shows the representation of a cascade with horizontally installed heating pipes. The gas supplied via the gas inlet line, not shown, passes through the opening 62 into the distribution box 63, in which the baffle plates 64 can be arranged. The arrangement of these baffle plates 64 can be seen in FIG. 3, which shows a top view of the cascade shown in FIG. 2. The baffle plates 64 have the task of distributing the gas evenly as it enters the cascade and partially separating the dust in the gas. This separated dust collects in the tapered lower part of the distribution box 63 and can be removed there from time to time. The gas passes from the distribution box 63 into the horizontal heating pipes, which in the present case bear the reference symbol 36, which indicates that the cascade shown should be the first (top) cascade.

Basically, of course, the cascades underneath also have the same construction. With regard to the diameter of the heating pipes, it has proven to be expedient if the diameter of the heating pipes in the first (top) cascade is larger than in the heating pipes of the cascades below. For example, the outer diameter of the heating pipes in the first cascade can be 60.3 mm and in the second and third th cascade be 48.3 mm. In any case, the pipe diameter should be selected so that an average gas velocity of approx. 20 m / s can be maintained in the heating pipes. It has been shown that, if this gas velocity is maintained, no significant dust deposits on the pipe walls are to be expected. To improve the heat exchange effect, the outside of the heating tubes can of course also be provided with a certain profile, for. B. the heating pipes as so-called. Fin tubes are designed. The coal to be heated flows, as can be seen from the statements made above, on the outside of the heating pipes from top to bottom.

After passing through the heating pipes, the gases enter the rear distribution box 65 and from there via the opening 66 into the line (not shown), which either leads to the cascade below or to the gas outlet line 39. With the construction according to the invention, if a heating tube 36 is torn off, the system can be quickly made operational again by closing the tube end in the distribution box 63. If an entire cascade fails, operation is not disrupted by the use of the other cascades. The cascades are made of wear-resistant steel and can be stiffened with profile iron on the outside. They are each located in a housing (not shown in FIG. 2), which normally consists of a steel frame construction with wall plates that are insulated from the outside. The individual cascades are connected to each other by compensators, which absorb the thermal expansion and prevent the transmission of vibrations. If necessary, the housing can also taper in the area of the inflow bases 4. This means that the inflow bases 4 then have a smaller diameter than the part of the housing above and below.

As has already been explained in connection with FIG. 1, the coal to be preheated or dried is fed onto the cascade fluidized bed dryer 3 from above, so that the coal flows through it and thus onto the individual cascades from top to bottom. The casings in which the cascades are accommodated are separated from one another by the gas-permeable inflow trays 4. These have the task of ensuring that the water vapor is distributed as evenly as possible at the entry into the coal-water vapor fluidized bed of the respective cascade. In order to ensure a uniform fluidization of the coal, it is necessary that the pressure loss of the inflow floor is only approx. 10-15% of the pressure loss of the coal-water vapor fluidized bed. This can be achieved in a simple manner by using a grating 68 as the inflow base, which has been loaded with coarse coal 67, the grain size of which is approximately> 40 mm. Fig. 4 shows a schematic representation of such an inflow floor. Another possibility is to use a so-called sandwich floor. This consists of two grids arranged one above the other and offset against each other, between which there is a gas-permeable packing layer.

• 1.) Schonende Trocknung und Vorerhitzung der Kohle in einer Wasserdampfatmosphäre, wodurch eine die Verkokungseigenschaften negativ beeinflussende Überhitzung der Kohlepartikel vermieden wird,
• 2.) grosse Temperaturdifferenz sowie hohe Wärmedurchgangszahlen zwischen dem Heiss-Gas und der Kohlewirbelschicht,
• 3.) eine günstige Kombination von Kontakttrocknung und konvektiver Trocknung,
• 4.) niedriger Flugstaubaustrag aus den einzelnen Kaskaden des Kaskadenwirbelschichttrockners,
• 5.) günstige Bedingungen bei der Kokstrockenkühlung mit geringem Druckverlust und guter Regelbarkeit,
• 6. ) grosse Flexibilität des Gesamtverfahrens sowie
• 7.) drucklose Apparatur mit niedrigen Investitions- und Betriebskosten und geringem Platzbedarf.

The advantages of using the method according to the invention can be summarized as follows:

• 1.) Gentle drying and preheating of the coal in a water vapor atmosphere, thereby avoiding overheating of the coal particles, which negatively affects the coking properties,
• 2.) large temperature difference and high heat transfer numbers between the hot gas and the carbon fluidized bed,
• 3.) a favorable combination of contact drying and convective drying,
• 4.) low flue dust discharge from the individual cascades of the cascade fluidized bed dryer,
• 5.) favorable conditions for dry coke cooling with low pressure loss and good controllability,
• 6.) great flexibility of the overall process as well
• 7.) unpressurized equipment with low investment and operating costs and small space requirements.

Claims (10)

1.) Method for operating a coke oven plant, in which the coke ovens are periodically charged with preheated or predried coal and the coke produced is subjected to dry cooling by means of a gaseous cooling medium, the plants for coke drying cooling and for coal preheating being connected to one another by a common gas circuit , by which heat extracted from the hot coke during cooling is transferred to the preheated coal, characterized by the following measures: a) The preheating of the coal is carried out by indirect heat transfer in a cascade fluidized bed dryer in which the coal is in a coal-water vapor fluidized bed; b) the gas quantity emerging from the coke dryer cooler is broken down into two partial streams, of which only one partial stream is used for coal preheating and is introduced into the first cascade of the cascade fluidized bed dryer at a temperature between 550 and 650 ° C, this partial stream being passed through the cascade fluidized bed dryer is reunited with the partial flow that is not used for coal preheating. c) the reunited partial flows of the gas emerging from the coke dry cooler are reintroduced into the coke dry cooler after appropriate cleaning and cooling, the re-introduction taking place simultaneously in the lower and the middle part of the coke dry cooler; d) the water vapor required for maintaining the coal-water vapor fluidized bed in the cascade fluidized bed dryer is circulated, the water vapor emerging from the cascade fluidized bed dryer being subjected to dust removal, partial condensation and recompression before it is reintroduced into it. 2.) Method according to claim 1, characterized in that a partial flow of 45 to 55 vol.% Is branched off from the total amount of gas emerging from the coke dryer cooler and is introduced into the first cascade of the cascade fluidized bed dryer. 3.) Process according to claims 1 and 2, characterized in that the partial stream of the gas introduced into the first cascade of the cascade fluidized bed dryer preferably has a temperature of approximately 600 ° C. 4.) Method according to claims 1 to 3, characterized in that the temperature of the partial flow of gas introduced into the first cascade of the cascade fluidized bed dryer is automatically regulated by the admixture of cold gas. which is introduced from the gas outlet line into the gas inlet line via a bypass line. 5.) Process according to claims 1 to 4, characterized in that the average gas velocity in the heating tubes of the cascade fluidized bed dryer is approximately 20 m / s. 6.) Process according to claims 1 to 5, characterized in that the water vapor required for maintaining the coal-water vapor fluidized bed with a temperature of about 200 ° C and a pressure of about 2 bar in the bottom cascade of the cascade fluidized bed dryer is initiated. 7.) Process according to claims 1 to 6, characterized in that, for the heating of the cascade fluidized bed dryer, flue gases are used or are also used which are generated by burning a solid, liquid or gaseous fuel in a separate combustion chamber, the gas temperature being controlled by Admixture of water vapor from the water vapor circuit of the cascade fluidized bed dryer is set to the desired value. 8.) cascade fluidized bed dryer for carrying out the method according to claims 1 to 7, characterized in that in each cascade the heating tubes (36; 37; 38) horizontally are arranged between two distribution boxes (63; 65), wherein vertical baffle plates (64) can be fitted in the distribution box (63) lying on the gas inlet side and the heating pipes (36) of the first (top) cascade can have a larger diameter than that Heating pipes (37; 38) of the cascades below. 9.) cascade fluidized bed dryer according to claim 8, characterized in that the heating tubes (36 or 37; 38) as so-called. Fin tubes are formed. 10.) Cascade fluidized bed dryer according to claims 8 and 9, that grids (68) are used as inflow bases (4) for the individual cascades, which have been loaded with coarse coal (67), the grain size of which is about> 40mm.

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