EP0025400B1 - Process for treating coal for coking and apparatus for carrying out the process - Google Patents

Description

The invention relates to a process for the treatment by drying and / or preheating of carbon to be coked by entrainment and / or fluidization in an enclosure by means of a heat transfer gas also serving to pneumatically transport the coal out of the enclosure through a pipe which brings it to a loading station through a separating device, process in which a hydrocarbon binder is injected in the liquid state into the coal during treatment, as well as an installation for the implementation of the process .

It has already been proposed, by French patent n ° 1 265 397 to increase the quality of the steel coke obtained from a dried coal by adding to the coal, before or after its drying, a hydrocarbon binder, consisting of a coal pitch, an artificial pitch or bitumen, or an extract or extraction residue, said hydrocarbon binder being added so that it takes a pasty or liquid consistency. Another known advantage of the introduction of a hydrocarbon binder is to reduce the quantity of dust flights when the coal is loaded into the coke oven.

More recently, it has been proposed in FR-A-2326464, to add the hydrocarbon binder by sprinkling and / or kneading the carbon, the binder being previously melted or put into an aqueous emulsion.

It has also been proposed, in FR-A-252 306 252 to add the hydrocarbon binder in one of the transporters of coal already preheated and this just before it is placed in the oven to reduce the flight of dust during loading in the coke oven.

However, in the case of a preheating process of the type described at the start, all of these known processes have drawbacks.

In fact, if the binder is introduced into the cold coal, and therefore before it is introduced into the dryer and / or preheater, the coal grains more or less impregnated with the hydrocarbon binder are suddenly subjected to the high temperature of the drying fumes and / or preheating which are sometimes at 600 or 800 ° C. This thermal shock has the effect of vaporizing a part of the hydrocarbon binder which therefore passes into the vapor phase not stopped by the electrostatic precipitators and causes the effectiveness of the process to lose against flight. In addition, the applicant has observed that large deposits are formed in the dryer and / or preheater, to the point of stopping the installation if it is of the internal shredder type.

As for the process for introducing a hydrocarbon binder into one of the already dried and / or preheated coal transporters, it loses the advantage of the previous processes, of improving the efficiency of capture of the separation cyclones.

The aim of the invention is to propose a new process and a new installation which avoid the above drawbacks, that is to say which allow both an improvement in the quality of the coke, a reduction in takeoffs during loading, good performance of dust cyclones and therefore the reduction in their size.

Another object of the invention is to allow the reduction of the consumption of hydrocarbon binder each time the quality of the charcoal to be placed will allow it. That is to say that it will be necessary to be able to reduce the consumption of hydrocarbon binder to the quantity strictly necessary both for a good yield of the separating cyclones according to the dryer and / or preheater by entrainment and / or fluidization and subsequently to the reduction or elimination of dust flows when loading into the oven.

These aims are achieved, according to the invention, in a method of the type described at the start, thanks to the fact that the hydrocarbon binder is injected into the pneumatic transport zone of the coal from the enclosure to the separating device.

According to an advantageous characteristic, the hydrocarbon binder is a molten product such as pitch or softening point bitumen, determined according to French standard NF - T 66 008, between 30 and 100 ° C, molten, preferably, at a temperature between 150 and 260 ° C.

According to a variant, also advantageous, the hydrocarbon binder is in the form of a liquid aqueous bitumen emulsion preferably containing approximately 40 to 60% of bitumen of the type of those which are known for the cold coating of materials, such as road aggregates.

• - une enceinte de séchage et/ou préchauffage par échange thermique en régime d'entraînement et/ou fluidisation se continuant par une canalisation de transport pneumatique,
• - un dispositif d'introduction dans ladite enceinte du charbon à y sécher et/ou préchauffer,
• - des moyens d'introduction dans ladite enceinte d'un gaz caloporteur à débit sensiblement constant servant également de fluide gazeux d'entraînement et/ou fluidisation du charbon à sécher et d'entraînement du charbon séché et/ou de préchauffé dans la canalisation de transport pneumatique,
• - un dispositif séparateur charbon/gaz dans lequel débouche ladite canalisation de transport pneumatique, caractérisée par le fait que, pour la mise en oeuvre du procédé, elle comporte, en outre, un dispositif d'introduction de liant hydrocarboné débouchant dans ladite canalisation de transport pneumatique.

The aims of the invention are also achieved in an installation for drying and / or preheating charcoal comprising:

• - a drying and / or preheating chamber by heat exchange in the drive and / or fluidization regime continued by a pneumatic transport pipe,
• a device for introducing coal into said enclosure to be dried and / or preheated therein,
• means for introducing into said enclosure a heat transfer gas with a substantially constant flow rate also serving as a gaseous fluid for driving and / or fluidizing the coal to be dried and for driving the dried and / or preheated coal in the pipe of pneumatic transport,
• - a coal / gas separator device into which opens said pneumatic transport pipe, characterized in that, for implementing the method, it further comprises a device for introducing hydrocarbon binder opening into said transport pipe pneumatic.

It is advantageous that the device for introducing a hydrocarbon binder is a device with adjustable flow rate.

If the device for introducing carbon into the drying and / or preheating chamber by entrainment and / or fluidization is at a known and / or adjustable flow rate, it is in accordance with the invention that the flow rate of the device for introducing hydrocarbon binder is controlled by the flow rate of the flow rate device introduction of coal into the drying and / or preheating chamber, whether the device for introducing the hydrocarbon binder is a device for introducing the binder in the molten state or in the state of a liquid emulsion and whether this device is a spray device.

Other characteristics and advantages 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 appended single figure which represents the diagram of an installation according to the invention.

As a whole, the invention is described in its application to an installation of the same technical field as that of FR-A-2378081.

An installation for the pretreatment of coking coal comprises a grinder-preheater 1 for grinding preheating in a fluidized bed. This grinder-preheater 1 comprises a fluidization enclosure 2 inside which rotates a hammer mill 3. The fluidization and heating gas for the fluidization and preheating of the coal is produced 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 into the combustion chamber by a fans. The hot gases coming from the combustion chamber 4 are brought through a venturi 10 to a vertical pipe 9 for pneumatic transport and for pre-drying, into which opens, with a conveyor screw 11, the coal stored in a hopper 12 where it was brought by a conveyor 13 of recovery on park 14. The vertical pipe 9 opens, as is known per se, in the enclosure 2 of 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 cyclone battery 16, to the vortex 17 of the last or the last group of which is connected a line 18 serving to collect the gases which are then distributed in an extraction line 19 and a recycling line 20 by the fan 8. At the points 21 of the cyclones 16, the preheated coal is collected ready to be placed in a coke oven, which is why it is brought by a conveyor assembly 22 to a hot coal hopper 23.

According to the methods mentioned above, it is known to introduce 0.5 to 3% by weight of hydrocarbon binder, such as coal tar in the conveyor assembly 22, at E for example. However, if this effectively reduces the flight of dust in the oven, this does not prevent the entrainment of too much dust in the gases collected at the vortex of the last cyclone or. last group of cyclones, hence loss of carbon by entrainment or by degradation in the combustion chamber 4. It is also known to introduce 5 to 10% of molten hydrocarbon binder in the cold coal, ie stored on park 14, in A for example, either in a mixing device, such as the screw conveyor 11, that is to say at B. All the drawbacks of these known methods have been shown at the beginning of the present application.

According to the invention, a molten hydrocarbon binder or liquid emulsion of the type for cold coating is injected into the pneumatic transport pipe 15, for example at one or more points D, by means of a nozzle or several spray nozzles supplied by the supply line 24, the flow rate of which is adjustable by means of a valve 25. The adjustable flow rate is controlled by a circuit 30 at the speed of rotation, and therefore at the flow rate of coal, of the conveyor screw 11 of introduction of the coal into the line 9, that is to say into the enclosure 2, so that the mass percentage of binder introduced relative to the treated coal is 0.5 to 3%, and preferably l 'order of 1%.

With a bitumen with a softening point between 30 and 100 ° C, melted between 150 and 260 ° C without however reaching its degradation temperature, and with an aqueous emulsion of bitumen, of the type for coating road aggregates, pumpable and sprayable at ambient temperature, used at ambient temperature, the applicant obtained a perfectly stable operation of the installation with a rate of dust in the fumes, sampled at the outlet 28 of a wet washer 27 disposed on the extraction pipe 19, of the order of 0.15 g / m ³ N of dry smoke. This result should be compared to that of approximately 1.0 g / m ³ N of dry smoke obtained without the introduction of a binder. This result is totally surprising, if we compare it to that resulting from the introduction of the usual 6% of bitumen introduced into the fleet (point A) and if we refer to the unstable operation of the dryer and / or preheater in the event of introduction of the hydrocarbon binder in B.

One could consider introducing the hydrocarbon binder into the enclosure itself, for example in C. But the applicant has observed that, if the binder is introduced into the action zone of the mill, that is to say in the zone where insufficiently ground grains fall back into the enclosure, an unstable operation is obtained linked to the fouling of the grinding mobile and of the walls. One could, however, remain in accordance with the lessons of the invention by introducing the binder from a point C ′ of the enclosure where the sufficiently ground coal has taken a drive regime in the: gas flow heading towards the pipe 15 drive. But the determination of the start of the training zone depends on too many parameters for an entry point C 'to be retained, unless this point C' is so close to the connection zone between the enclosure 2 and the drive line 15 that the gaseous fluid has already taken on a drive regime there and that this connection zone is already in the pneumatic transport zone to the point of constituting, as it were, the beginning of the pneumatic transport pipeline.

The invention has been described with regard to a fluidization drying and / or preheating installation. It also applies equally well to a drying and / or preheating installation by co-current drive by hot fumes.

Claims (12)

1. Process for the prior treatment of coking coal by entrainment and/or fluidisation in a chamber by means of a heat-transfer gas also serving to convey the coal pneumatically out of the chamber via a duct which brings it to a charging station via a separating device, in which process a hydrocarbon binder in the liquid state is injected in the coal during treatment, characterised in that said hydrocarbon binder is injected in the zone of pneumatic conveying of the coal from the chamber to the separator device.

2. Process according to Claim 1, characterised in that the rate of flow of hydrocarbon binder is controllable in dependence upon the rate of coal introduced into the entrainment and/or fluidisation .chamber.

3. Process according to Claim 1, characterised in that the hydrocarbon binder is a molten product such as pitch or bitumen, with a softening point of between 30 and 100 °C.

4. Process according to Claim 3, characterised in that the molten product is injected at a temperature of between 150 and 260 °C.

5. Process according to Claim 1, characterised in that the hydrocarbon binder is a liquid aqueous emulsion of bitumen.

6. Process according to Claim 2, characterised in that the hydrocarbon binder is added to the treated coal in a proportion by weight of 0.5 to 3%.

7. Process according to Claim 6, characterised in that said proportion by weight is of the order of 1 % of bitumen.

8. Installation for carrying out the process according to Claim 1, comprising

- a chamber (2) for drying and/or pre-heating by heat exchange in entrainment and/or fluidisation regime continuing through a pneumatic conveying duct (15),

­ a means (11) for introducing into said chamber (2) coal to be dried and/or pre-heated therein,

- means (9) for introducing into said chamber (2) a heat-transfer gas at approximately constant rate also serving as gaseous fluid for entrainment and/or fluidisation of the coal to be heated and/or pre-heated and for entrainment of the dried and/or pre-heated coal in the pneumatic conveying duct (15) ;

- a coal/gas separator device (16) into which opens said pneumatic conveying duct (15), characterised in that it comprises a device (24, 25) for introducing hydrocarbon binder into said pneumatic conveying duct (15).

9. Installation according to Claim 8, characterised in that the device for introducing hydrocarbon binder is a device (25) with adjustable rate.

10. Installation according to Claim 8, characterised in that the rate of the device (24, 25) for introducing hydrocarbon binder is controllable in dependence upon the rate of the device (11) for introducing coal into the drying and/or pre-heating chamber (2).

11. Installation according to Claim 8, characterised in that the device (24, 25) for introducing the hydrocarbon binder is a device for introduct- ing the binder in the molten state or in the state of liquid emulsion.

12. Installation according to Claim 11, characterised in that the device (24, 25) for introducing the binder in the molten state is a spraying device.

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