EP0023455A1 - Process and installation for drying and/or preheating coal to be coked - Google Patents

Abstract

The invention relates to a method and an installation for drying and / or preheating by entrainment and / or fluidization of coking coal. An installation for preheating by fluidization with grinding in an enclosure (2) is combined, by means of an exchanger (13) interposed on the circuit for recycling the heat-carrying gas, with an installation for dry extinguishing of hot coke in a chamber. extinction (30). The flow rate through the exchanger (13) of the recycled coke quenching fumes is regulated as a function of the rate of introduction of the coal into the enclosure (2) by the screw (11). An additional combustion chamber (4) allows fine adjustment of the temperature, measured at (24), in the enclosure (2). The invention applies to the drying and / or preheating of coal combined with the dry quenching of coke.

Description

Process and installation for drying and / or preheating charcoal for coking.

The invention relates to a process for drying and / or preheating by entrainment and / or fluidization of carbon to be coked by means of a neutral coolant or reducing gas partially recycled and maintained at an appropriate temperature of the order of 250 to 65 ° C. , in which the coal to be dried and / or preheated is introduced into a drying and / or preheating chamber by means of an introduction device with known and / or adjustable flow rate. The invention also relates to an installation for implementing the method.

Almost all of the steel coke is produced in traditional coke ovens where the load is brought to around 1000 ° C. The cooling of the coke at diversion is very generally carried out by massive sprinkling of water in an extinguishing tower. The sensible heat of the coke thus lost represents from 40 to 45% of the heat used to heat the coke ovens, which is 550 to 600 therms per tonne of dry coal put in the oven. This is the most important heat loss item in the heat balance of coking. Consideration has long been given to recovering the sensible heat of coke by means of dry extinction, the principle of which is as follows. The hot coke is cooled by circulation of inert gases in a closed cycle, by direct contact. The sensible heat recovered by the gases is used to make steam.

However, dry extinguishing processes are generally criticized for providing steam which is generally not used. The use of this heat in the coking plant itself would obviously be much preferable to the installation of turbines allowing the production of electricity. Coal preheating could be an application, as has already been described in patent DE 453,464, and more recently in patent FR 2,173,997 and its equivalents DE 2,304,541 and US 3,843,458 and 3,728,230 which propose to use for the drying of coal a gas heated in a heat exchanger by extinguishing gas, when the latter has already supplied part of its heat to a generator steam.

In patent DE 453 464, the heat exchange is only imperfect. In the other aforementioned process, an attempt has been made to isolate the two extinction and heat-transfer gas circuits by a set of complex gas-gas and gas-liquid exchangers, by supplying heat to the coal at two distinct stages of drying and heating and introducing water vapor condensers. But then, if we put already dried coal in contact with gases at more than 350 ° C, we will degrade it.

The object of the invention is to avoid these drawbacks and to propose a new process and an installation for its implementation which make it possible to obtain good regulation of the temperature of the heat-transfer gas and good use of the sensible heat of the fumes. dry extinguishing of the coke, while avoiding the introduction into the extinguishing fumes of water vapor capable of gasifying the coke. Another object of the invention is to guarantee in all circumstances the supply of heat in the quantity necessary for the heat-transfer gas, that is to say the coal to be dried and / or preheated, while having the possibility of using the heat in excess of this necessary quantity, in particular if the latter is low or zero as a result of voluntary or accidental shutdown of the dryer and / or preheater. Another aim is, again, to be able, at any time, to separate the two extinguishing and drying and / or preheating installations in order to free them from each of the failures occurring at the other.

These aims are achieved, according to the invention, in a method of the type mentioned at the beginning, by the fact that, for the heating of the heat-carrying gas, at least a fraction not yet cooled of the dry extinguishing fumes of hot coke is used. furnace and one proceeds to the heat exchange between heat transfer gas and dry extinction fumes of hot coke through a heat exchange wall of heat exchanger.

It is advantageous for the flow rate of extinguishing smoke which is introduced into the heat exchanger to be controlled by the flow rate of the device for introducing the coal to be dried and / or preheated in the drying and / or preheating chamber.

According to other advantageous characteristics of the invention, the fraction of the extinguishing fumes used for heating the heat transfer gas and the unused fraction are used for the production of heat by heat exchange, and part of the heat necessary for drying and / or preheating of the coal is provided in addition by a combustion chamber whose caloric flow is controlled by the temperature measured in the drying and / or preheating chamber.

By the above means, which are very simple, it can be seen that the fitting of complicated apparatuses is avoided and that the problems of water condensation are freed, because it is not bothersome, only at the limit , the coolant is nothing more than water vapor, whereas it would be damaging if it were the recycled extinguishing fumes that contained it.

• - une enceinte de séchage et/ou préchauffage par entraînement et/ou fluidisation,
• - des moyens d'introduction dans ladite enceinte d'un gaz caloporteur à débit sensiblement constant servant également de fluide d'entraînement et/ou fluidisation du charbon à sécher et d'entraînement du charbon séché et/ou préchauffé,
• - des moyens de recyclage d'une partie au moins du gaz caloporteur,
• - des moyens d'introduction dans l'enceinte à débit connu et/ou réglable du charbon à y sécher et/ou préchauffer,
• - une chambre d'extinction à sec de coke avec un circuit d'utilisation thermique et de recyclage des gaz d'extinction, par le fait qu'elle comporte :
• - un échangeur thermique dans lequel le gaz caloporteur est chauffé à travers une paroi d'échange thermique par les fumées d'extincticn directement amenées d'une chambre d'extinction à sec de coke chaud défourné par une canalisation d'entrée et récupérées par une canalisation de sortie.

The aims of the invention are also achieved by a combined coking coal drying and / or preheating installation, in a single installation, with a diverted hot coke dry quenching installation comprising:

• - a drying and / or preheating chamber by entrainment and / or fluidization,
• means for introducing into said enclosure a heat transfer gas at a substantially constant flow rate also serving as a fluid for driving and / or fluidizing the coal to be dried and for driving the dried and / or preheated coal,
• means for recycling at least part of the heat transfer gas,
• means for introducing into the enclosure at a known and / or adjustable flow rate the coal to be dried and / or preheated therein,
• - a dry coke extinguishing chamber with a circuit for thermal use and recycling of extinguishing gases, by the fact that it comprises:
• - a heat exchanger in which the heat transfer gas is heated through a heat exchange wall by the extinguishing fumes directly brought from a dry coking chamber for hot coke discharged through an inlet pipe and recovered by a outlet pipe.

• - les canalisations d'entrée et de sortie des fumées de l'échangeur thermique soient réunies par une dérivation
• - un jeu de vannes permette de régler la répartition du débit des fumées d'extinction en deux fractions respectivement entre l'échangeur et la dérivation
• - des moyens soient prévus pour asservir le débit de la fracticn de fumées d'extinction traversant l'échangeur au débit du dispositif d'introduction du charbon dans l'enceinte.

It is in accordance with the invention that:

• - the smoke inlet and outlet pipes of the heat exchanger are joined by a bypass
• - a set of valves makes it possible to adjust the distribution of the flow rate of the extinguishing smoke into two fractions respectively between the exchanger and the bypass
• - Means are provided for controlling the flow rate of the fraction of extinguishing fumes passing through the exchanger to the flow rate of the device for introducing coal into the enclosure.

According to other characteristics, the common pipe bringing together the pipe for the outlet of the fumes from the exchanger and the bypass brings the fumes to another device for thermal use, the means for introducing the heat-transfer gas into the drying enclosure and / or preheating further comprises a combustion chamber interposed between the outlet pipe of the heat transfer gas from the exchanger and the means for introducing the heat transfer gas into the drying and / or preheating chamber.

In an installation _' in which the drying and / or preheating enclosure comprises means for measuring the temperature, it is advantageous for the combustion chamber to include means for regulating the caloric flow controlled by the means for measuring the temperature in the 'drying and / or preheating enclosure, or at its outlet, as is known per se.

Other features and benefits A description will emerge from the description, which will be given below by way of example only, of an embodiment of the invention. For this purpose, reference is made to the single appended drawing which represents the diagram of an installation in accordance with the invention.

An installation for the pretreatment of coking coal comprises a preheater mill 1 for grinding and preheating in a fluidized bed. This grinder-preheater 1 comprises a fluidization enclosure 2 inside which rotates a hammer mill 3. The fluidizing and heating gas for the fluidization and preheating of the coal is produced in part in a combustion chamber 4 by combustion of gas brought to its burner 5 by a pipe 6 with air forced by a fan 7. In addition, the fumes from the pretreatment of the coal are recycled, through a heat exchanger 13 and a pipe 14, into the chamber combustion by a fan 8. The exchanger 13 is of a heat exchange type through a partition wall, for example tubes or a coil, avoiding any communication between the two gas circuits which must exchange heat. The hot gases coming from the heat exchanger 13 and from the combustion chamber 4 are brought, through a venturi 10, to a vertical pipe 9 for pneumatic transport and for pre-drying, in the lacquer-opening, of a conveyor screw 11 , the coal stored in a hopper 12. The vertical pipe 9 opens out as is known per se, into the enclosure 2 for fluidization and grinding and preheating. From the top of the enclosure 2 leaves a pipe 15 for pneumatic transport of the ground coal and preheated by the fluidization gas again acting as a gaseous transport vector. Line 15 brings the carrier gas and the coal transported to a battery of cyclones 16 to the vortex 17 of the last or the last group of which is connected a pipe 18 serving to collect the gases which are then distributed between an extraction pipe 19 and a recycling pipe 20, having a flow measurement throttle 28 and connected to the fan 8. In the paintings 21 of the cyclones 16, the preheated coal is collected ready to be put in a coke oven, for which it is brought by a conveyor assembly 22 to a hot coal hopper 23.

There is, on the other hand, a dry extinguishing installation of the hot coke discharged, the main apparatus of which is a dry extinguishing chamber 30, of known type, which comprises a prechamber 31, constituting an introductory airlock. coke to be extinguished and which is introduced through an opening 32. From the prechamber 31, the coke descends into the cooling chamber 33 which constitutes a heat exchanger between the hot solid constituted by the coke and neutral or reducing fumes brought to the chamber cooling 33 by a fan 34 and a pipe 35 and evacuated to the thermal use of their sensible heat by a pipe 36. The gases and the vapor released, by the coke in the prechamber 31, are extracted by an extraction pipe 37. The cooled coke is extracted at 38. The neutral or reducing fumes are used in a closed circuit from the pipe 36 to the fan 34. At the outlet of a dust separator 39, a pipe 40 conducts these fumes to the exhaust chiller 13 through a pipe 41, 42 whose flow is controlled by a valve 43 or a set of valves. Upstream of the valve 43, the pipe 41, 42 is closed by a bypass pipe 44 which may include a valve 45 contributing with the valve 43 to regulate the distribution of the hot smoke flow rates between the exchanger 13 and the pipe 44. At their junction, the pipes 42 and 44 open into a pipe 45 supplying a boiler 46, at the outlet of which the extinguishing fumes, now cold, are brought back to the fan 34 through a dust collector 47 and the pipe 48. We see the great simplicity of the combined installation, the exclusion of any risk of disturbance by one of the two basic installations, the simplicity of their uncoupling by simply closing the valve 43.

The installation of the invention also includes regulation devices.

It comprises, as is known per se, a regulation circuit R2 ensuring stoichiometric combustion at the burner 5.

The installation also has a regulation circuit R ₁ of the gas flow to the pipe 6 to control the additional caloric flow to the temperature measured in the enclosure 2, or to its setting, by a thermometric probe 24. The flow of recycled heat transfer gas is regulated at the outlet of the exchanger 13 by valves 25 and / or 26 controlled by pressure at the vortex 17 by a regulation circuit R ₃ .

Finally, and in accordance with a preferred feature of the invention, the distribution of the flow of hot extinguishing fumes between the exchanger 41 and the bypass 44 is ensured by the valve 43 whose adjustable flow control is controlled by a circuit regulation valve R ₄ , at the rate of the coal supply screw 11 for the dryer and / or preheater 1.

For a quenching unit 30 of 56 t / h of coke cooled from 1000 ° C to 220 ° C, the quantity of vapor produced is 26.1 t / h having the following characteristics: 440 ° C, 40 kg / cm ² . The amount of heat recovered is around 325 therms per tonne of coke, or 240 therms per tonne of dry coal. For a preheating unit at 200 ° C, it is estimated that 210 to 240 th / t of coke is required. At 260 ° C it takes about 300 th / t of cokeo The thermal balance is therefore favorable to the process according to the invention. For a 56 t / h dry extinguisher unit, the smoke flow is 90,000 m ³ N / h at a temperature of 750 to 800 ° C. We can therefore combine an extinguishing installation of 56 t / h of coke and a preheater of 80 t / h of wet coal.

In the installation described, the temperature of 250 ° C can be taken as the set temperature at the temperature probe 24.

The preheating temperature will therefore be maintained at 260 ° C. with good finesse by automatic action on the gas flow rate to the burner 5 of the combustion chamber 4. The regulation circuit R ₂ will accordingly adjust the air flow rate so that the combustion remains stoichiometric. The speed of the gases in the preheating chamber 2 will be kept constant by acting on the flow of neutral smoke recycled in the combustion chamber, by the circuit R ₃ , which keeps the pressure drop of the secondary cyclones constant by varying the flow recycled smoke.

The coal flow rate is set to a constant value, chosen between 1/2 capacity and nominal capacity. If the coal flow rate is voluntarily changed, or if the humidity of the coal is variable, the preheating temperature and the speed of the gases are automatically maintained at their set value as just explained. The handling of the device is therefore extremely flexible.

Additional remarks may be made to show other advantages of the invention. The final dust removal of dewatering fumes will be greatly facilitated. In fact, the quantity of smoke discharged into the atmosphere will be roughly equivalent to the volume of water vapor coming from the humidity of the coal, i.e. 9,000 m ³ N / h for a unit of 80 t / h of capacity. In the classic version of the preheater, the volume of smoke released to the atmosphere is 25,000 m ³ N / h. It should also be noted that the coal preheating fumes, from the moment that equilibrium is reached, will essentially contain water vapor, coming from the humidity of the coal. The dewatering fumes could therefore possibly be condensed, which would make it possible to remove releases to the atmosphere. As for dry extinction fumes, they can still produce around 2 t / h of steam by yielding their residual sensible heat in the boiler 46.

Claims (10)

1) A method of drying and / or preheating by entrainment and / or fluidization of coking coal by means of a neutral coolant or reducing gas partially recycled and maintained at an appropriate temperature of the order of 250 to 650 ° C. in which introduces the coal to be dried and / or preheated into a drying and / or preheating chamber by means of an introduction device with a known and / or adjustable flow rate, characterized in that one uses, for the heating of the heat transfer gas at minus a not yet cooled fraction of the dry extinguishing fumes of the hot hot charged and the heat exchange is carried out between heat-exchange gas and dry extinguishing fumes of the hot coke through a heat exchanger heat exchange wall . 2) Method according to claim 1, characterized in that the flow of extinguishing smoke that is introduced into the heat exchanger is controlled by the flow rate of the device for introducing the coal to be dried and / or preheated in the enclosure of drying and / or preheating. 3) Method according to claim 1, characterized in that the fraction of the extinguishing fumes used for heating the heat transfer gas and the unused fraction are used for the production of heat by heat exchange. 4) Method according to claim 1, characterized in that part of the heat necessary for drying and / or preheating the coal is provided in addition by a combustion chamber whose caloric flow is controlled by the temperature measured in the drying chamber and / or preheating. 5) drying plant and / or ^p coal heating coking combined in a single installation, with a dry quenching facility unloaded hot coke comprising: - an enclosure (2) for drying and / or preheating by entrainment and / or fluidization, means of introduction (9) into said enclosure of a heat transfer gas with a substantially constant flow rate also serving as a driving and / or fluidizing fluid and of the coal to be dried and of entraining the dried and / or preheated coal, - recycling means (8) of at least part of the heat transfer gas, a device for introducing (11) into the enclosure (2) a known and / or adjustable flow rate of the coal to be dried and / or preheated, a chamber (30) for dry coking with coke with a circuit for thermal use and recycling (34) of the extinguishing gases,
characterized in that it comprises a heat exchanger (13) in which the heat transfer gas is heated through a heat exchange wall by the extinguishing fumes directly supplied from the dry coking chamber (30) for hot coke discharged by an inlet pipe (41) and recovered by an outlet pipe (42). 6) Installation according to claim 5, characterized in that: - the inlet (41) and outlet (42) pipes for the smoke from the heat exchanger (13) are joined by a bypass (44) a set of valves (43, 45) makes it possible to adjust the distribution of the flow rate of the extinguishing fumes into two fractions respectively between the exchanger (13) and the bypass (44), - Means (R2) are provided for controlling the flow rate of the fraction of extinguishing fumes passing through the exchanger (13) to the flow rate of the device for introducing coal (11) into the enclosure (2). 7) Installation according to claim 6, characterized in that the common pipe joining the outlet pipe of the fumes from the exchanger and the bypass brings the fumes to another appliance for thermal use. 8) Installation according to claim 6, characterized in that the means for introducing (9) the heat transfer gas into the enclosure (2) for drying and / or preheating further comprises a combustion chamber ( ₄ ) _. 9) Installation according to claim 8, characterized in that the combustion chamber (4) is interposed between the outlet pipe (14) of the heat transfer gas from the unloader (13) and the means for introducing the heat transfer gas into the '' drying and / or preheating enclosure. 10) Installation according to claim 8, wherein the enclosure (2) for drying and / or preheating comprises means for measuring (24) of the temperature, characterized in that the combustion chamber (4) comprises regulation means caloric flow (R ₁ ) controlled by the means for measuring (24) the temperature in the enclosure (2) for drying and / or preheating or at its outlet.

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