EP0153254B1 - Molten metal bath furnace for coal gasification - Google Patents

Abstract

This reactor for the gasification of solid fuels in the powdered form, of the type employing a bath of liquid metal (5) comprises: a substantially cylindrical vessel (1) which has a substantially oblong section and lateral walls (2) and a bottom wall (3) which are lined with a refractory lining (4), this vessel further comprising an orifice (37) for discharging the bath of liquid metal, and an orifice (36) for discharging slag supernatant on the bath of liquid metal (5), a dome (11) positioned in a sealed manner on the vessel (1) and having in its upper part in the vicinity of one of the ends of the vessel a sealed box (16) for introducing an injecting branch (17) and, also in its upper part, but at the opposite end of the vessel, an orifice (21) of large section for exhausting the gases produced, and a roughly central orifice (29) for introducing addition elements; and means (8, 9, 10a-e, 6, 13, 14, 15) for cooling the lateral walls and the bottom wall of the vessel and the dome.

Description

The present invention relates to a coal gasification reactor of the liquid metal bath type.

Coal gasification reactors are already known in which pulverized coal is injected through a bath of liquid metal using nozzles placed in the bottom of a reactor whose inner walls are coated with a refractory lining intended to withstand the stresses generated by the liquid metal.

These reactors are of a construction similar to that of steelworks converters and they are provided with journals allowing a tilting around a horizontal axis in particular for reasons of regular access essential for the maintenance of the nozzles and the repair of the coating. refractory.

A first drawback of this type of reactor resides precisely in the tilting design which is necessary and which does not allow the construction of large diameter tanks lined with a thick refractory lining and suitably cooled, due to the weight inherent in these characteristics.

The lack of cooling combined with the relatively small thickness of the refractory lining of the tilting reactors, leads to rapid wear of the latter which requires frequent repairs detrimental to the availability of operation of the device and its operating cost.

It is, moreover, difficult to ensure a good seal of the tilting reactors so that there can occur air inlets or gas losses and that the increase in the operating pressure, which would be favorable to the operation. of the device and its economy, is limited.

In addition, the gasification capacity of a nozzle being limited, the installation of numerous nozzles for an industrial unit complicates the technological realization of the distribution of coal and gases between the nozzles.

The bottom nozzles cause excellent mixing of the various reactants, but on the other hand cause rapid wear of the refractory lining which, in particular on the bottom, in the nozzle area, cannot be very thick due to the tilting design of the assembly and which does not comprise effective cooling as indicated previously.

Finally, the nozzles themselves must be effectively cooled, in general by a liquid or gaseous hydrocarbon or even by a liquid gas (C0 ₂ ), the cost of this cooling agent very significantly increasing the cost price of the gas produced from coal.

Reactors for the gasification of coal on a liquid metal bath are also known, into which pulverized coal is injected by means of a lance, the jet of which is projected onto the surface of the bath, but these reactors also remain of the tilting type and have the same drawbacks as those indicated above which limit profitability and efficiency; in particular their too small internal volume does not allow the gas to reach the equilibrium of the reactions and moreover harms the good behavior of the refractories in the belly.

In addition, the too small surface of the interface between the bath of liquid metal and the slag produced by the melting of the ashes, does not allow a good decantation of the metal balls in the slag and causes a costly and harmful loss of liquid metal. to the good valorization of this same milkman.

Document FR 2 445 364 describes a coal gasification reactor on a liquid metal bath of the blowing lance type in which the slag is kept at a constant level. The reactor has a weir through which the slag floating on the surface of the bath can overflow continuously, but this implies a uniform bath depth as well as a constant bath mass. Although the efficiency of the use of coal has thus been partly improved, this reactor presents problems of wear resistance and cooling.

The object of the present invention is to remedy these drawbacks by providing a reactor whose availability for operation is greater, the operation simpler and more continuous and which produces a high quality gas as well as a slag from the ash, which can be recovered. .

It thus relates to a gasification reactor for solid fuels in pulverized form, of the type comprising an enclosure containing a bath of liquid metal and a fuel injection lance situated at the upper part of the enclosure, comprising a substantially cylindrical tank the section of which by a plane perpendicular to the generators has an oblong shape, comprising side walls and a bottom coated with a refractory lining, and delimiting an orifice for discharging the slag supernatant on the surface of the metal and an orifice for discharging the metal; a dome resting with a tight seal on the tank and delimiting at least one orifice for introducing at least one vertical lance through a sealed casing, an orifice of large section for the evacuation of the gases produced in the reactor, these two orifices being arranged respectively in the vicinity of the opposite ends of the reactor, as well as an orifice for the introduction of addition elements; means being provided for cooling the side walls and the bottom of the tank as well as the dome, characterized in that the tank has at least a bottom portion in the form of an inclined plane, so that the depth of the metal bath is maximum in the area below the lance and minimum in the area below the gas exhaust port.

The invention will be described below using the appended drawing which represents only one embodiment.

The single Figure is a perspective view with partial section of the reactor according to the present invention.

The gasification reactor shown in FIG. Unique consists of a tank (1) of substantially cylindrical steel with an oblong section, the side wall (2) and the bottom (3) of which are provided with a refractory lining (4) on their inner surface.

This refractory lining is double thick at the lower level of the tank, that is to say at least in the zone in contact with the liquid metal bath (5), constituting the crucible.

The bottom (3) of the tank is cooled using a network cooling fluid circulation tubes (6) which are embedded in a layer of refractory lining, such as refractory concrete, located between the refractory lining (4) and the bottom wall (3).

The side wall (2) of the tank is lined along its outer surface by an envelope (8) of corrugated shape delimiting with the shielding of the tank channels (9) for circulation of a cooling fluid, which communicate with an external cooling circuit through the orifices 10a, 10b, 10c, 10d, 10e, etc. This circuit is put into forced circulation and pressurized by means not shown.

The tank (1) is surmounted by a dome (11) also provided on its internal face with a refractory lining (12), the connection between the dome (11) and the upper edge of the tank (1) being ensured by waterproof way. A channel (13) forming a gutter circulates along the outer wall of the reactor at the dome (11) - tank (1) junction to recover the cooling fluid sent by runoff from spraying ramps (14, 15) placed at the top of the dome

The dome (11) has at its upper part, vertically above the large cross-sectional diameter of the tank, an orifice 16a surmounted by a sealed box (16) for introducing a lance (17), in a position in projection, close to the side wall, that is to say of an end of the large diameter.

This box (16) is received on a seat (18), the seal between the seat (18) and the box (16) being ensured by a mechanical seal. The seat (18) is internally cooled by a circular network of tubes (19) for the circulation of a cooling fluid embedded in a refractory lining (20) placed along the internal wall of the seat.

Furthermore, to ensure sealing at the level of the introduction opening of the lance (17), movable in vertical translation by means not shown, the box (16) is pressurized by blowing an inert gas such as water vapor or carbon dioxide.

The dome (11) also has at its upper part, an orifice (21) for discharging the produced gases, of large diameter, this orifice being centered, in projection on the large diameter of the tank, in a relative position close to the end opposite to that where the lance is located (17). The orifice (21) is sealed in a sealed manner by an exhaust duct (22), which in the embodiment shown is a high pressure boiler with direct radiation of frustoconical shape. This boiler (22) is received on a seat (23) provided at the upper part of the dome which is cooled, like the seat (18), by a network of circular tubes (24) embedded in a refractory lining (25).

This boiler 22 consists of tubes (26) joined and welded connected to their lower inlet to a circular (27) supply of superheated water under pressure at 40-60 bars.

The dome (11) also has at its upper part a chute (28) for introducing addition elements which opens out through an orifice (29) formed through the refractory lining in the interior volume of the tank. The chute (28) is located between the box (16) and the boiler (22) and is inclined so that the addition elements reach the liquid metal bath (5) in the impact zone of the jet from the lance (17).

The lance (17) consists of a quadruple envelope tube delimiting four concentric annular spaces.

A jet (30) of pulverized coal possibly containing additives and transported by steam, is sent to the surface of the liquid metal bath (5) by the central cylindrical duct of the lance. Oxygen and water vapor are sent through the annular space immediately adjacent to the central duct, these gases being projected into the vacuum region of the bath created by the impact of the jet (30), through orifices (31 the outermost annular spaces of the lance (17) being intended for circulation of the cooling fluid of the lance.

According to an essential characteristic of the present invention, the bottom of the tank comprises an area (32) in the form of an inclined plane in the part not exposed to the vacuum created on the surface of the liquid metal bath (5) by the jet (30 ) of pulverized coal from the lance.

This inclined bottom delimits two distinct zones of the liquid metal bath (5), a first zone with a greater depth for the chemical reactions of gasification of coal with intense mixing, and a second zone (32) with gradually reducing depth having a function balancing of reactions and settling between metal and slag.

It is also possible to accommodate under the part (32) of the bottom in the form of an inclined plane a device (33) for electromagnetic stirring promoting the settling of the bath (5) by circulation along the path of the arrow (34).

A layer of slag (35) floats above the metal bath (5), and is periodically, and in an adjustable manner, evacuated by a tap hole (36) situated at the end of the zone of the shallow bath at the level of the slag layer.

A tap hole (37) of the bath metal is formed at the opposite end of the slag tap hole (36) in the zone of great depth and at the bottom of the crucible.

The bath consists of a metal in which the carbon can exist in the dissolved state and is, for example, cast iron, the physicochemical characteristics of which are adjusted by addition elements as a function of the operating temperature.

The non-tilting reactor vessel (1) is mounted on a metal frame (38). The assembly can be moved in horizontal translation by means not shown.

The operation of the reactor is as follows:

Solid iron and / or scrap metal, as well as ferro-silicon and coke are introduced, then oxygen and pulverized coal are blown out with the lance.

At the start-up stage, the gases produced are worthless oxidized gases which are eliminated. The liquid iron bath is formed and is added by the chute, in addition to the powdered lime admitted into the jet of pulverized coal, elements of addition in rocks such as fluxes and fluxes, possibly lime, dolomite, scrap and ferro-alloys.

When the bath is established at a determined composition and temperature, the injection is increased of pulverized coal and the height of the lance is adjusted to its optimal position, neither too high not to obtain a gas oxidized by the escaping oxygen, nor too low not to be degraded by the molten metal. Coal gasification is then carried out in a continuous regime taking into account thermodynamic and chemical equilibria.

An important characteristic of the reactor of the present invention resides in the large free volume situated above the bath of liquid metal, favorable to the establishment of the reaction gas equilibria for obtaining a good quality gas.

Thus the reactor according to the present invention, thanks to its fixed position, that is to say non-tilting, can be provided with better quality cooling and a greater thickness of refractory lining which condition the longevity and therefore the availability of the installation, which can produce gas almost continuously.

Given the large dimensions of the reactor, the quantity of liquid metal contained in the reactor is greater and therefore makes it possible to obtain a higher unit gasification capacity without causing excessive wear of the refractories.

Furthermore, the large free surface of the liquid metal bath allows a longer slag residence time and therefore better obtaining of the chemical reaction equilibria, and better settling of the metal balls entrained by the slag.

The variation in the depth of the bath also makes it possible to install a zone with strong mechanical mixing due to the impact of the jet of lance, where the reactions are faster, and a relatively calm zone of settling above the inclined plane (32 ).

It may be noted that the reduction in the depth of the bath, in addition to the favorable effect exerted on the settling, makes it possible to reduce the weight of the liquid metal present in the reactor for a given depth necessary at the location of the impact of the jet and therefore to lighten the load-bearing structures.

The decantation zone thus created makes it possible to obtain, by simple pouring, a well decanted slag whose evacuation rate can be adjusted and authorizes a treatment by granulation with a view to the preparation of recoverable clinkers in cement works.

The reactor according to the invention can operate, thanks to its tightness, in pressurized form and therefore increase its unit yield and its profitability.

Claims (10)

1. A reactor for the gasification of solid fuels in the powdered form, of the type comprising an enclosure containing a bath of liquid metal and a fuel injection nozzle located in the upper part of the enclosure, comprising a substantially cylindrical vessel (1) having a section in a plane perpendicular to the generatrices of oblong shape, having lateral walls (2) and a bottom (3) covered with a refractory lining (4) and defining an orifice (36) for discharging slag supernatant on the surface of the metal and an orifice (37) for discharging the metal; a dome (11) bearing on the vessel with a sealed joint and defining at least one orifice (16a) for introducing at least one vertical nozzle (17) through a sealed box (16), an orifice (21) of large section for exhausting gases produced in the reactor, these two orifices being disposed respectively in the vicinity of opposite ends of the reactor, and an orifice (29) for introducing addition elements; means (8, 9 10a-10e, 6, 13, 14, 15) being provided for cooling the lateral walls (2) and the bottom (3) of the vessel and the dome (11), characterized in that the vessel (1) comprises at least a bottom part (3) in the shape of an inclined plane so that the depth of the bath of liquid metal is maximum in the zone located below the nozzle (17) and minimum in the zone located below the orifice (21) for exhausting the gases.

2. A reactor according to claim 1, characterised in that an electromagnetic strirring device (33) is placed under the part (32) having the shape of an inclined plane of the bottom (3) of the vessel (1).

3. A reactor according to any one of the preceding claims, characterised in that the bottom of the vessel (1) is cooled by means of a network of tubes (6) for circulating a cooling fluid embedded in a layer (7) of refractory covering located between the refractory lining (4) and the bottom (3).

4. A reactor according to any one of the preceding claims, characterised in that the lateral wall (2) of the vessel has along its outer side a jacket (8) of corrugated shape defining passageways (9) for the circulation of a cooling fluid in a forced and pressurized form.

5. A reactor according to any one of the preceding claims, characterised in that the dome is cooled by the running of a fluid distributed by spraying systems (14, 15), the fluid being collected by a gutter (13) encircling the outer wall of the reactor at the level of the joint between the dome and the vessel.

6. A reactor according to any one of the preceding claims, characterised in that the sealed box (16) is received on a seat (18) with a sealed joint, said seat being internally cooled by a network of tubes (19) for circulating a cooling fluid embedded in a refractory lining (20) placed along the inner wall of the seat (18).

7. A reactor according to anyone of the preceding claims, characterised in that the orifice (21) for exhausting the gases produced is surmounted in a sealed manner by a high-pressure direct-radiation boiler (22).

8. A reactor according to claim 7, characterised in that the boiler (22) is constitued by adjoining tubes (26) defining a frustoconical inner radiation volume, these tubes (26) being connected at their lower inlet to a circular manifold (27) supplying superheated water, the boiler (22) being received with a sealed joint on a seat (23) internally cooled by a network of tubes (24) for circulating a cooling fluid embedded in a refractory lining (25) placed along the inner wall of the seat (23).

9. A reactor according to any one of the preceding claims, characterised in that an inclined spout (28) opens onto an orifice (29) for introducing addition elements so that the latter reach the bath (5) of liquid metal in the zone of impact of the jet (30) issuing from the nozzle (17).

10. A reactor according to any one of the preceding claims, characterised in that the injection nozzle (17) is constitued by a tube having a quadruple casing defining four separate concentric spaces, the central space serving to inject powdered coal conveyed by a neutral gas, the immediately adjacent space serving to inject oxygen and steam and the outer spaces serving to circulate a cooling fluid.

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