EP0153254A2 - 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 may be air inlets or gas losses and that the increase of 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 technical 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 at the level of 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.

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 provides a solid fuels gasification reactor in powder form, the ty- ^pe comprising an enclosure containing a bath of liquid metal and a fuel injection lance located in the upper part of the enclosure, characterized in that it comprises a substantially cylindrical tank whose section 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 metal and a metal discharge port; 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, the tank comprising at least one bottom portion in the form of an inclined plane, so that the depth of the metal bath is maximum in the area located below the lance and minimum in the area below the gas exhaust port.

The invention will be described below with the aid of the appended drawing which represents only one embodiment.

Fig. Unique 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 oblong section, the side wall (2) and the bottom (3) are provided on their inner face with a refractory lining (4).

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

The bottom (3) of the tank is cooled using a network of cooling fluid circulation tubes (6) which are embedded in a layer (7) 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 external 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 ^w rojec- tion, close to the side wall, that is to say, one 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. We send by the annular space immediately adjacent to the central duct, oxygen and water vapor, these gases being projected into the vacuum zone 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 lance coolant.

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 provided 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 carbon can exist in the dissolved state and is, e.g., cast iron of which is adjusted ^p hysico- chemical characteristics by addition elements according to 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.

• On introduit de la fonte solide et/ou des ferrailles, ainsi que du ferro-silicium et du coke, puis on souffle par la lance de l'oxygène et du charbon pulvérisé qui est enflammé.

The operation of the reactor is as follows:

• Solid cast iron and / or scrap metal, as well as ferro-silicon and coke are introduced, then oxygen and pulverized coal are blown which is ignited.

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 of pulverized carbon is increased and the height of the lance is adjusted to its optimal position, or too high not to obtain a gas oxidized by oxygen which s 'escapes, 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 reac tor, 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. Gasification reactor for solid fuels in spray 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, characterized in that it comprises: substantially cylindrical tank (1) whose section through a plane perpendicular to the generators has an oblong shape, comprising side walls (2) and a bottom (3) coated with a refractory lining (4), and delimiting an orifice (36) evacuating the slag supernatant on the surface of the metal and an orifice (37) for evacuating the metal; a dome (11) resting with a tight seal on the tank and delimiting at least one orifice (16a) for introducing at least one vertical lance (17) through a watertight box (16), a large orifice (21) section for the evacuation of the gases produced in the reactor, these two orifices being disposed respectively in the vicinity of the opposite ends of the reactor as well as an orifice (29) for the introduction of addition elements; means (8, 9, 10a-10e, 6, 13, 14, 15) being provided for cooling the side walls (2) and the bottom (3) of the tank as well as the dome (11), the tank (1 ) comprising at least a bottom part (3) in the form of an inclined plane, so that the depth of the liquid metal bath is maximum in the zone situated below the lance (17) and minimum in the zone situated below below the orifice (21) for evacuating gases. 2. Reactor according to claim 1, characterized in that an electromagnetic stirring device (33) is placed under the part (32) in the form of an inclined plane of the bottom (3) of the tank (1). 3. Reactor according to any one of the preceding claims, characterized in that the bottom of the tank (1) is cooled using a network of tubes (6) for circulation of a cooling fluid which are embedded in a layer (7) of refractory lining situated between the refractory lining (4) and the bottom ( 3). 4. Reactor according to any one of the preceding claims, characterized in that the side wall (2) of the tank comprises, along its external face, a double envelope (8) of corrugated shape delimiting channels (9) for circulation of a coolant in a forced and pressurized form. 5. Reactor according to any one of the preceding claims, characterized in that the cooling of the dome is ensured by the flow of a fluid distributed from spraying ramps (14, 15), the fluid being collected by a gutter (13 ) circulating along the external wall of the reactor at the dome-tank junction. 6. Reactor according to any one of the preceding claims, characterized in that the sealed box (16) is received with a sealed seal on a seat (18) internally cooled by a network of tubes (19) for circulation of a cooling embedded in a refractory lining (20) placed along the internal wall of the seat (18). 7. Reactor according to any one of the preceding claims, characterized in that the orifice (21) for discharging the gases produced is sealed in a sealed manner by a direct pressure high pressure boiler (22). 8. Reactor according to claim 7, characterized in that the boiler (22) is made up of joined tubes (26) defining a tapered interior radiation volume, these tubes (26) being connected at their lower inlet to a supply circular (27 ) in superheated water, the boiler (22) being received with gasket sealed on a seat (23) internally cooled by a network of tubes (24) for circulation of a cooling fluid embedded in a refractory lining (25) placed along the internal wall of the seat (23). 9. Reactor according to any one of the preceding claims, characterized in that an inclined chute (28) opens into an orifice (29) for introducing the addition elements so that the latter reach the bath (5) of liquid metal in the impact zone of the jet (30) from the lance (17). 10. Reactor according to any one of the preceding claims, characterized in that the injection lance (17) consists of a quadruple envelope tube delimiting four separate concentric spaces, the central space serving for the injection of coal sprayed transported by a neutral gas, the immediately adjacent space used for the injection of oxygen and steam and the spaces outside for the circulation of a cooling fluid.

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