LU86217A1 - PROCESS FOR THE TREATMENT AND PACKAGING OF A HETEROGENEOUS MIXTURE OF SOLID MATERIALS AND PLANT FOR IMPLEMENTING SAME - Google Patents

Description

The invention relates to a process for the treatment and conditioning of a heterogeneous wet mixture of solid materials with a view to their transport by pneumatic route.

The heterogeneous mixture of solid materials treated according to this application is generally heterogeneous both from the particle size point of view and from the composition point of view and is generally available with a water content of 5 to 25% by weight, often around 8 to 15 % in weight. These solid materials are for example mineral materials, more particularly dusty coal residues, often from 0 to 6 mm in thickness, which it has not been possible to separate from non-combustible materials, such as shales, clays and silicas. .

A treatment and conditioning process has proved necessary to allow regular transport without blocking the transport pipes and a regular distribution of the mixture in an enclosure.

In fact, when the mixture is transported as it is, without appreciable reduction in its water content, using a helical screw device, it quickly compacts inside this device, which causes the blocking of that -this.

We have tried to remedy this drawback by supplying the untreated mixture with an alveolar metering device in an air or carrier gas line.

The discontinuous flow resulting from the cellular metering device is eminently unfavorable for the smooth running of the transport which is done in spurts with very rapid wear of the pipe and regular blockages.

In addition, it has proved impossible to distribute the mixture of solid materials regularly in an enclosure or a reactor, for example through a series of nozzles distributed in a plane or in a determined volume of * - 3 - so that the expected effect is maximum.

If there is heat action inside the enclosure or the reactor, the mixture is transformed into a kind of cement which obstructs the pipe.

To avoid these drawbacks, a treatment and conditioning method of the type to which this application relates has been applied.

In a known method of this kind, the mixture of solids is first dried according to well-known techniques, for example in a rotary drying oven and the dried mixture is stored in heated hoppers.

The quantity of mixture required is continuously extracted pneumatically from these hoppers to introduce it through a heated pipe into the enclosure or the reactor.

The installation for the implementation of this known process is relatively large and the process involves a significant consumption of fuel, first for the complete drying of the mixture and then to avoid reabsorption of moisture during storage and transport.

The object of the invention is to remedy these drawbacks and to provide a simple and economical method which involves only a relatively small energy consumption and which requires only a simple installation, but which nevertheless allows problem-free transport and distribution. uniform in an enclosure or reactor of the heterogeneous mixture of solid materials.

For this purpose, the mixture is suspended in an enclosure using hot gases introduced into the lower part of the enclosure, these moisture-laden gases coming from the mixture are evacuated to the upper part of the enclosure. above the upper level of the suspension mixture and the at least partially dried solids are discharged in the form of granules through at least one discharge tube, the open end of which is below the above-mentioned upper level. suspended solids, using gas which is injected, under a pressure higher than the pressure in the enclosure, into this evacuation tube from a place located opposite the open end of this tube.

In a particular embodiment of the invention, the volume of the suspension of the solid materials is chosen so that the residence time of the solid materials in suspension in the enclosure required to obtain the desired reduction in humidity of these material is between 10 and 60 sec.

In an effective embodiment of the invention, the humidity of the mixture in the enclosure is reduced to 3 to 8% by weight.

In an advantageous embodiment of the invention, the temperature of the hot gases is adjusted between 75 and 200 ° C.

Preferably, the hot gases are produced in a combustion chamber and the temperature of the hot gases is adjusted by controlling the amount of fuel burned in the combustion chamber.

The invention also relates to a particularly suitable installation for implementing the method mentioned above.

The invention thus relates to an installation characterized in that it comprises a closed enclosure, an inlet for the wet mixing of solid materials, at the upper part of this enclosure, a device for injecting hot gases into the lower part of the enclosure, an opening for evacuation of hot gases charged with humidity coming from the wet mixture at the upper part of the enclosure, at least one tube for evacuating solid materials in the form of aggregate, the end open upper part of this tube being situated above the hot gas injection device at a distance from the bottom of the enclosure, at least one gas injector at a pressure higher than the pressure in the enclosure, mounted above above the open end of the tube and directed towards the inside of this tube, the hot gas injection device being a device capable of injecting gas at a rate such that the solids are suspended until a level above d e the open upper end of the tube but below the inlet of the mixture and the discharge opening of the hot gases laden with moisture.

In an advantageous embodiment of the invention, the installation comprises a combustion chamber connected to the hot gas injection device and a combustion device in this chamber supplying at least part of the hot gases.

Other advantages and particularities of the invention will emerge from the description of a process for the treatment and conditioning of a heterogeneous wet mixture of solid materials and of an installation for its implementation, according to the invention; this description is given below only by way of nonlimiting example and with reference to the accompanying drawings.

FIG. 1 schematically represents a vertical section of an installation for treating and packaging a heterogeneous wet mixture of solid materials according to the invention.

Figure 2 schematically shows a horizontal section of the installation of Figure 1, taken at the height of line II-II of Figure 1 and viewed in the direction indicated.

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In the two figures, the same reference numbers refer to identical elements.

The installation according to the figures comprises a vertical cylindrical enclosure 1 made of metal which is divided into a lower space 2 and an upper space 3 by a grid 4.

The upper space 3 is supplied with solids essentially by gravity through an inlet hopper 5 mounted in the middle in the upper wall of the enclosure 1.

A sealing device of known construction and not shown in the figures is mounted on this hopper preventing the gases from escaping through the inlet 5.

The heterogeneous wet mixture of solid materials introduced into space 3 is suspended using hot gases which is introduced into the lower space 2 using an injection device composed of a tube horizontal 6 provided with nozzles 7 inside the space 2. These hot gases rising through the grid 4 cause the transformation of the solid materials into granulate.

These hot gases are combustion gases optionally mixed with a portion of excess hot air.

The injection device 6,7 is connected for this purpose to a combustion chamber 8 in which is mounted a gas burner 9. In the supply line 10 of this burner 9 is mounted a flow regulator 11 controlled in function the temperature in the suspension of solid materials in space 3 using a thermal probe 12 mounted in space 3 and connected by an electrical line 13 to the regulator.

Excess combustion air is introduced into the combustion chamber through a line 14 using a fan 15 mounted therein.

The flow of hot gases is adjusted in such a way that the solids are suspended up to a well-determined level 16. The necessary speed of the hot gases depends on the nature of the solid matter and more particularly on the weight and the dimensions of the aggregate which is formed in the upper space 3.

A device for locating the upper level 16 of the dense suspension of solid matter makes it possible to identify the critical level not to be exceeded and makes it possible to avoid exceeding this critical level, for example by stopping the introduction of the mixture. This locating device is of known construction and is not described below or shown in the drawings for reasons of simplification.

The volume of the suspension of solid materials is determined by the residence time of these materials in enclosure 1, required for the reduction of the desired humidity of the mixture of solid materials and more particularly so that the humidity of the mixture is reduced. from 8 - 20% by weight to 3-8% by weight. This residence time is ideally between 10 and 60 sec. This residence time is also proportional to the solids content of 3 the suspension, which content is between 300 and 800 kg / m, and inversely proportional to the nominal flow of solids through the enclosure 1. Taking into account of these constraints, a suspension volume is chosen with, however, a horizontal section which gives an ascending speed of the hot gases rising through the grid 4 of between 0.5 and 3.5 m / sec.

The temperature of the hot gases is adjusted between 75 and 200 ° C by adjusting the supply to the burner 9 using the flow regulator 11 controlled by the thermal probe 12 which measures the temperature in the enclosure 1. A temperature set point is chosen in this interval as a function of the flow of solid matter through the enclosure 1 and the reduction in humidity which proves to be necessary.

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To ensure sufficient drying time for the mixture before it leaves the enclosure 1 and adjust its suspension, a vertical cylindrical wall 17 is mounted on the grid 4 around the place where the mixture falls. The granulate formed suspended inside this wall passes over the upper edge of this wall and fills the volume between this wall and the enclosure 1 where it is also kept in suspension by the hot gases. The upper edge of the wall 17 is located below the level 16 of the suspended solids.

Under the conditions of hot gas flow rate and ascending speeds and by the possible presence in the heterogeneous mixture of a product agglomerating the fine particles, an aggregate with a particle size between 100 μm and 6 mm is obtained.

The hot gases charged with humidity coming from the wet mixture are evacuated from the upper space 3 by an evacuation pipe 18 opening into this space 3 through an opening 19 in the side wall of the enclosure 1, an opening located near the upper wall and above level 16 above.

Some fine dust can be entrained by hot gases, especially in the absence of agglomerating product. This dust is retained in a cyclone not shown in the figures, mounted in the discharge pipe 18.

In the evacuation pipe 18 is placed, between the enclosure 1 and the cyclone, an adjustable opening valve 30 which makes it possible to maintain the enclosure 1 at the overpressure necessary to assist the evacuation of the aggregate in the manner described above. after. The valve 30 is controlled as a function of the rate of introduction of the heterogeneous mixture into the enclosure 1, for example as a function of the speed of a honeycomb system of introduction. It is understood that the greater the flow, the greater the overpressure.

The aggregate formed from the solids is discharged through four vertical discharge tubes 20 arranged around the cylindrical wall 17.

The open upper end of these discharge tubes 20 is located below the upper edge of the cylindrical wall 17 and therefore below the upper level 16 of the suspended solids.

Each of the tubes 20 freely crosses the grid 4, moves in a displaceable manner a sealing ring 21 mounted in the bottom of the enclosure 1 and opens at its lower end in a discharge pipe 22 connecting it to a closed enclosure or a reactor not shown in the figures * The evacuation of the aggregate through these evacuation tubes 20 is controlled and controlled by a series of air injectors 23 under a pressure higher than the pressure prevailing in the upper space 3 .

Such injectors 23 are mounted above the upper end of each tube 20 and direct their air jet towards the interior of the tube.

The injectors 23 above the same tube 20 are connected to a supply line 24 in which a control valve 25 is mounted. This valve 25 is controlled by a pressure detector 26 mounted opposite the end of the tube 20. When the tube 20 or its discharge duct 22 is blocked, the pressure at the upper end of the tube 20 is higher, which causes the pressure detector 26 to control the closing of the valve 25 to which it is connected by an electrical pipe 27. Thus the tube is put out of use and can be unclogged without the installation having to be stopped.

All the supply lines 24 are connected to an annular line 28 supplied with air under pressure by a main line 29.

The pressurized air injected by the injectors 23 is injected into the tubes at a speed of the order of 20 m / sec and is preferably dry and hot, with a temperature of approximately 50 ° C.

The injectors locally create a depression at their end which entails the suspension 3 of solid materials in dense phase (300 to 800 kg / m) in the jet of the injectors and transforms it into suspension 3 in light phase (5 to 100 kg / m) in the evacuation tubes 20. This transformation depends on the flow rate of the pressurized air injected and on the relative position of the injectors 23 and the end of the corresponding tube 20.

The pressure and the flow rate of this air are adjusted by a valve 30 in the line 29 as a function of the output flow rate of the aggregate which is carried by the air outside the enclosure 1.

The position of the open ends of the discharge tubes 20 relative to the injectors 23 mounted above them can be individually adjusted by adjusting the corresponding tube 20 in height. This adjustment of the relative position makes it possible to control the distribution of the discharge flows of the aggregate through the discharge tubes 20.

The tubes 20 outside the enclosure 1 and the discharge pipes 22 are insulated so as to maintain them at a temperature above 100 ° C., in order to avoid condensation of the residual moisture of the discharged aggregate and the formation plugs.

The hot gases injected by the injection device 6,7 are obviously distributed so as to obtain a regular suspension around the tubes 20. The pressure of these hot gases is normally of the order of 2000 to 5000 mm 1 ^ 0.

For example, the following working conditions can be chosen to effectively treat and condition a heterogeneous mixture at 11% by weight of humidity: - flow rate of the mixture of solid materials: 25 to 50 kg / min - hot gas pressure : 2000 to 5000 mm 1 ^ 0 - flow of hot gases to suspend the mixture in an enclosure 1 with an internal diameter of 400 mm and for a height of the suspended solids of 500 mm: 5 to 10 Nm / min - rate of rise of hot gases î 0.5 to 3.5 m / sec

- hot gas temperature: 75 to 200 ° C

- total dry air flow rate through the injectors 23: 3 5 to 10 Nm / min 2 - overpressure in front of the injectors: 2 kg / m - humidity of the evacuated aggregate: 3 to 5% by weight.

- granulometry of the evacuated aggregate: 100 jum to 6 mm.

The energy balance of the process described above is very favorable.

The risk of blocked pipes is minimal.

The transported aggregate can be distributed regularly in a reactor or an enclosure.

It should be understood that the invention is in no way limited to the embodiment described above and that in the context of the present application many modifications can be made to it, in particular as to the form, the layout, the composition and the number of elements involved in its realization.

In particular, the wall mounted above the grid in the upper space need not be cylindrical. This wall is also not absolutely necessary.

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The gas injected into the exhaust pipes does not have to be air.

The number of evacuation tubes does not necessarily have to be four and these tubes do not necessarily have to be height adjustable.

The installation does not necessarily have to include a gas burner inside the combustion chamber.

Another fuel can be used than gas.

The hot gases do not even have to include combustion gases. They can be produced in other ways, for example by heat exchange with fumes or with steam at a relatively low temperature (350 ° C.) which reduces the cost of using the assembly, in which case the The installation must not include a combustion chamber.

The hot gas injection device does not necessarily have to include nozzles.

Claims (26)

1. A method of treating and conditioning a heterogeneous wet mixture of solid materials with a view to their pneumatic transport, characterized in that the mixture is suspended in an enclosure (1) using hot gases introduced into the lower part of the enclosure (1), these moisture-laden gases from the mixture are evacuated to the upper part of the enclosure above the upper level (16) of the suspension mixture and the solids at least partially dried in aggregate form through at least one discharge tube (20), the open end of which is situated below the above level (16) above of the suspended solids, using gases that is injected, under a pressure greater than the pressure into the enclosure, into this evacuation tube (20) from a location located opposite the open end of this tube (20). 2. Method according to claim 2, characterized in that the volume of the suspension of solid materials is chosen so that the residence time of the solid materials in suspension in the enclosure (1) required to obtain the reduction d The desired humidity of these materials is between 10 and 60 sec. 3. Method according to either of Claims 1 and 2, characterized in that the horizontal section of the volume of the suspension of the solid materials is chosen so that with the flow of hot gases necessary to produce the desired reduction in humidity of the solid materials, gas velocities between 0.5 and 2.5 m / sec are obtained. 4. Method according to either of claims 1 to 3, characterized in that the humidity of the mixture in the enclosure (1) is reduced up to 3 to 8% by weight. 5. Method according to either of claims 1 to 4, characterized in that the temperature - 14 - of the hot gases is adjusted between 75 and 200 ° C. 6. Method according to Claim 5, characterized in that the hot gases are produced in a combustion chamber (8) and the temperature of the hot gases is adjusted by adjusting the quantity of fuel burned in the combustion chamber (8). 7. Method according to either of claims 1 to 6, characterized in that the granulate discharged outside the enclosure is maintained at a temperature above 100 ° C. 8. Method according to either of Claims 1 to 7, characterized in that an overpressure in the enclosure (1) is maintained. 9. Method according to claim 8, characterized in that this overpressure in the enclosure is adjusted as a function of the feed rate of solid matter. 10. Method according to either of claims 1 to 9, characterized in that gas is injected into the discharge tube (20) at a speed of the order of 20 m / sec. 11. Method according to either of Claims 1 to 10, characterized in that dry air is injected into the evacuation tube (20). 12. Method according to either of Claims 1 to 11, characterized in that the granulate of solid materials is evacuated by several evacuation tubes (20) whose open end is located below the upper level. (16) suspended solids, and a gas jet is directed into each tube (20) under a pressure higher than the pressure in the enclosure (1). 13. Method according to claim 12, characterized in that the pressure at the open ends -15- of the evacuation tubes (20) is measured and that an evacuation tube (20) is switched off to unblock it when the corresponding measured pressure exceeds a determined value. 14. Process for treating and conditioning a heterogeneous wet mixture of solid materials as described above. 15. Installation for the implementation of the method according to either of claims 1 to 14, characterized in that it comprises a closed enclosure (1), an inlet (5) for the wet mixing of solid materials , at the upper part of this enclosure (1), a device for injecting hot gases (6,7) into the lower part of the enclosure, a discharge opening (19) for hot gases charged with moisture in coming from the wet mixture at the upper part of the enclosure (1), at least one evacuation tube (20) for solid matter in the form of aggregate, the open upper end of this tube (20) being situated above the hot gas injection device (6,7) at a distance from the bottom of the enclosure (1), at least one injector (23) of gas under a pressure higher than the pressure in the enclosure (1) , mounted above the open end of the tube (20) and directed towards the inside of this tube, the hot gas injection device (6,7) being a device capable of i inject gas at a rate such that the solids are suspended up to a level (16) located above the open upper end of the tube (20) but below the inlet (5) of the mixture and the discharge opening (19) for hot gases charged with humidity. 16. Installation according to claim 15, characterized in that it comprises a combustion chamber (8) connected to the hot gas injection device (6,7) and a combustion device (9) in this chamber (8) providing at least some of the hot gases. - 16 - 17. Installation according to claim 16, characterized in that it comprises a fuel supply device (10,11) of the combustion chamber (8), comprising a fuel flow regulator (11) and a thermal probe (12) mounted in the enclosure (1) above the hot gas injection device (6,7) controlling the flow regulator (11). 18. Installation according to either of claims 15 to 17 "characterized in that it comprises a grid (4) sharing the enclosure (1) in a lower space (2) and an upper space (3) , the hot gas injection device (6,7) being mounted in the lower space (2) forming a wind chamber, the inlet (5) for solid materials, the discharge opening (19) hot gases and the evacuation tube (20) of the formed aggregate opening into the upper space (3). 19. Installation according to either of claims 15 to 18, characterized in that it comprises several discharge tubes for the aggregate (20), at least one injector (23) of gas under a pressure higher than the pressure in the enclosure (1) being mounted opposite the open end of each tube and directing its jet of gas in this tube. 20. Installation according to claim 19, characterized in that at least the end part of the evacuation tubes (20) located in the enclosure (1) extends from bottom to top and is adjustable in height so that the distance between the open upper ends of the tubes and the gas injectors mounted above these ends is adjustable. 21. Installation according to claim 20, characterized in that it comprises a device for measuring the pressure (26) around the open end of each discharge tube (20) and a setting device '- 17 - out of service (25) of the tube in question controlled by the corresponding pressure measuring device (26). 22. Installation according to claim 18 and either of claims 19 to 21, characterized in that it comprises a wall (17) mounted on the grill (4) and delimiting a space surrounding the place of fall solid materials introduced through the inlet (5), the evacuation tubes (20) being located outside this space. 23. Installation according to either of claims 18 to 22 "characterized in that it comprises a discharge pipe (18) mounted on the enclosure (1), pipe in which opens the opening of evacuation (19) of hot gases charged with humidity and a device (30) mounted in this pipe (18) and making it possible to maintain an overpressure in the enclosure (1). 24. Installation according to claim 23, characterized in that the device (30) mounted in the discharge pipe (18) is an adjustable valve controlled as a function of the rate of introduction of solid materials into the enclosure (1). 25. Installation according to either of claims 15 to 24, characterized in that the discharge tube (20) opens into a discharge pipe (22), and that inside the enclosure (1) the tube (20) and this pipe (22) are insulated. 26. Installation for treating and conditioning a heterogeneous wet mixture of solid materials as described above and shown in the accompanying drawings.