EP0156676A1 - Apparatus for the gasification of coal - Google Patents

Abstract

The installation comprises mainly a reactor (1) for the gasification of powdered coal on a bath (2) of liquid iron, a cooling flue (9) constituting a boiler connecting the outlet of the reactor (1) to a vapor superheater (11) fed with vapor (26) issuing from the boiler, a dust-removing cyclone (13) connected to the outlet of the superheater (11), a thermal exchanger (14) connected to the outlet of the cyclone (13) in which a drying fluid (31, 32)is heated by thermal exchange with the combustible gas, a conditioning tower (16) connected to the outlet of the thermal exchanger, the conditioning tower being connected to a dry electrofilter (17) which feeds a storage gasometer (20) through a three-way valve (21). The heated drying fluid (32) and the vapor (28,30) issuing from the superheater (11) are employed in the installation for preparing and conveying the fuel and the comburent fed to the reactor.

Description

The present invention relates to a coal gasification installation and more particularly using a gasification technique on a liquid metal bath.

The technique of gasifying coal on a liquid iron bath is already known and makes it possible to produce a gas rich in CO and H ₂ with low contents of C0 ₂ . However, the gas contains residual S contents which should be limited as much as possible for the various applications envisaged and in particular for the use of the gas as a chemical synthesis raw material, in particular for the production of methanol and ammonia.

The present invention aims to provide an installation for the production of high-quality syngas, with good efficiency in the use of coal.

It thus relates to a gasification plant of pulverized solid fuel of the type comprising a gasification reactor with a liquid metal bath, provided with at least one lance for introducing therein the pulverized solid fuel and an oxidizing gas, and an orifice for evacuating the gases produced, characterized in that it comprises, arranged in series from the outlet of the reactor and traversed in series by the gases leaving the reactor, a chimney forming a boiler, a steam superheater supplied with from said boiler, a dust collector, a heat exchanger intended to heat a drying fluid, a conditioning tower, a filtering device and a device for storing the gas, the steam supplied by the superheater and the drying fluid leaving the heater being used in the installation, in particular for the preparation and supply of the fuel and of the oxidant supplied to the reactor.

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

The single figure is a schematic representation of the gasification installation according to the present invention.

This installation includes a coal gasification reactor 1 which is the subject of another patent application filed today. This reactor 1 shown diagrammatically in section is of the bath type (2) of liquid iron, this bath being surmounted by a layer of slag (3). The pulverized coal is injected with a flux containing lime and desulphurizing additives into the iron bath by means of a lance (4) from a conduit (5). This same lance (4), thanks to a structure with cooled multiple envelopes (not shown) also serves for the injection of oxygen added with steam which is supplied by a conduit (6). The reactor (1) is also provided at its upper part with a pipe (7) for introducing rock addition elements.

The reactor (1) is of the non-tilting type, but translatable and of large dimensions. Indeed, thanks to slides on which the reactor is mounted, it is possible to replace a new reactor with a used reactor, thus reducing to a minimum the shutdown of the gasification installation for repairing the reactor. The reactor (1) is also provided with draining means making it possible to renew the metal which would have been polluted by non-volatile alloy metals, that is to drain it before translation.

The gases produced in the reactor (1) are discharged through an orifice (8) opening into a gas cooling chimney (9) described below according to the direction of flow of the gases. This chimney (9) firstly comprises a direct pressure high-pressure boiler (9 A) of conical shape forming a hood, covering the orifice (8), then an ascending duct (10 A) and a descending duct (10 B), with double jacket which connects the boiler (9 A) to a steam superheater (11). The gases from the reactor (1) therefore pass through the chimney (9) consisting of the three sections defined above in which they are cooled before entering the steam superheater. The sections (10 A) and (10 B) of the chimney also function as a boiler thanks to a circulation of water in the double jacket. The water circulating in the boiler (9 A) and the double envelopes of the conduits (10 A) and (10 B), is sent into a conventional separator tank not shown.

After passing through the superheater (11), the combustible gases are sent via a line (12) into one (or more) cyclone (s) for dust collector (13). The dusted gases from the cyclone (s) (13) pass through a heat exchanger (14), then are sent via a pipe (15) to a conditioning tower (16) into which a water mist is injected. In this conditioning tower, the gases are humidified and co-cooled with a descending water mist and extracted at the base of the tower to be sent to a dry electrostatic precipitator (17) by a pipe (18). The dust collected in the cyclone (13), the conditioning tower (16) and the dry electrostatic precipitator (17) are stored in an evacuation hopper (19). The purified combustible gases coming from the electrostatic precipitator (17) are sent, after saturation by spraying with water, not shown in a sheath arranged at the outlet of the electrostatic precipitator, into a gasometer (20) via a three-way valve (21) which ensures the possibility of rapidly sending gases to a flare (22).

The combustible gases stored in the gasometer (20), of the wet type, can then undergo an additional treatment which consists of an additional purification of the gases in a wet electrostatic precipitator (23), then in a compression in a compressor (24) and possibly in a final treatment for complete desulfurization (25).

The vapor separated in the separator tank not shown, is sent by a line (26) into the superheater (11) from where it is extracted by a line (27). The vapor from this line (27) is sent on the one hand by a line (28) to a compressor (not shown) of the oxygen plant (29) which it drives, and on the other hand, by a line (30) to the line (5) where it serves as a transport fluid for the pulverized coal supplying the lance (4). The oxygen plant (29) supplies the lance with oxygen via the line (6) and also supplies nitrogen used as a drying fluid which is sent via a line (32) to a coal-mill-dryer ( 33).

This crusher-dryer is supplied with pulverized coal by a hopper (34) which is itself supplied from the homogenized stock of raw coal (35). The dry pulverized coal from the mill-dryer (33) is sent to the intermediate storage hoppers (36) via a cyclone (37).

Powdered lime is also stored in a hopper (38), as well as additives such as Mn ore, dolomite, and possibly kiln dust containing zinc in a hopper (39). The hoppers (36), (38), (39) constitute a supply battery for a mixer (40) which itself feeds intermediate silos (41) for weighing and adjusting the flow rate of pulverized coal which is sent into the pipe (5).

A battery (48) of hoppers containing various elements of addition of rock, flux and scrap coming from a corresponding stock (49), feeds weighing silos (44) which open into the pipe (7) for supplying elements addition in rocks.

The slag from the layer (3) surmounting the melt (2) is granulated in a granulator (45) and stored in (46) or discharged in (47) towards its final use, for example as a cement clinker.

One of the defining characteristics of the present invention resides in the design of the various members making it possible to obtain an appropriate thermal cycle. for cooling the combustible gases produced in the reactor (1) by gasification of coal.

In fact, in order to obtain a suitable desulfurization of the gases produced in the reactor (1), the gases should be kept at temperature levels and during determined residence times.

Desulphurization is carried out during the cooling of the gases in the chimney (9) and as far as the heat exchanger (14), before the elimination by coalescence of aerosols of sulphides and metal oxysulphides in the conditioning tower (16).

Desulfurization is carried out by action on the gas produced in particular by gasification of coal, vapors in the form of aerosols of iron and / or manganese and / or zinc and / or their oxides according to a process described in another application filed date by the plaintiff.

This desulfurization under the effect of iron vapors, coming from the iron bath as well as possibly manganese vapors introduced in the form of addition elements by the lance (4) or the pipe (7), takes place at the along the evolution of the temperature profile between the free internal volume of the reactor (1) and the gas conditioning tower (16).

Further desulphurization with zinc can be carried out by injecting Zn vapors in the form of aerosols in the gas produced, at a point preferably situated at the outlet of the superheater (11) to the cyclone (13). The devices for injecting Zn vapor in the form of aerosols have been schematically represented by the reference 70 in the single figure.

By way of nonlimiting example, the gases coming from the reactor leave the latter at a temperature of approximately 1500 ° C., are first of all cooled to approximately 1450 ° C. at the outlet of the boiler (9 A), then up to approximately 730-750 ° C at the inlet of the superheater (11). In this superheater, the steam from the separator tank is superheated to around 400 ° C and discharged through line (27).

At the outlet of the superheater (11), the gases are brought back to the temperature of approximately 620 ° C., then cooled to approximately 600 ° C., at the outlet of the cyclone (s) (13). The gases exit the exchanger (14) at the temperature of approximately 380 ° C. after having brought the drying fluid (which is nitrogen) withdrawn by the line (32) to a temperature of 355 ° C. to 360 ° C approx.

The gases are then treated in the conditioning tower (16) with a water mist and extracted at the base of the latter at approximately 150 ° C., then sent to this temperature in the dry electrostatic precipitator (17), at the outlet. from which they are cooled to around 55 ° C by water saturation before being sent to the gasometer (20).

• 1½ seconde à haute température (>1200° C) dans le réacteur, la chaudière (9 A) formant la hotte et le premier conduit (10 A) où se produit la désulfuration par les vapeurs de Mn ;
• seconde à moyenne température (>750° C) dans le deuxième conduit (10 B) où se produisent les désulfurations par les vapeurs de fer (en l'absence de Mn);
• 2 secondes à basse température (600 < t <750°C) dans le surchauffeur (11) et dans la (ou les) cyclone(s) (13) où se développe la désulfuration poussée au Mn et éventuellement au Zn (lorsque le Zn est introduit en aval du surchauffeur (11)) ;
• 1½ seconde à très basse température (350 < t < 600° C) dans l'échangeur à azote (14) où la désulfuration finale au Zinc permet d'obtenir un gaz relativement sec à très basse teneur en soufre, avant la tour de conditionnement où le gaz est humidifié, pendant 7 secondes environ, entre 350 et 150° C où se parachèvent la désulfuration et la coalescence des aérosols de sulfures et d'oxysulfures métalliques.

The residence times of the gases produced in the reactor (1) in the various elements constituting the cooling circuit with a view to their desulfurization are as follows, by way of non-limiting indication:

• 1½ seconds at high temperature (> 1200 ° C) in the reactor, the boiler (9 A) forming the hood and the first conduit (10 A) where desulphurization takes place with Mn vapors;
• second at medium temperature (> 750 ° C) in the second conduit (10 B) where desulfurization by iron vapors occurs (in the absence of Mn);
• 2 seconds at low temperature (600 <t <750 ° C) in the superheater (11) and in the cyclone (s) (13) where the intense desulphurization develops at Mn and possibly at Zn (when Zn is introduced downstream of the superheater (11));
• 1½ seconds at very low temperature (350 <t <600 ° C) in the nitrogen exchanger (14) where the final desulfurization with Zinc makes it possible to obtain a relatively dry gas with very low sulfur content, before the conditioning tower where the gas is humidified, for about 7 seconds ron, between 350 and 150 ° C where complete the desulfurization and coalescence of aerosols of sulfides and metal oxysulfides.

Claims (13)

1. Gasification plant for pulverized solid fuel, of the type comprising a gasification reactor (1) in a liquid metal bath, provided with at least one lance (4) for introducing the pulverized solid fuel and an oxidizing gas therein, and d an orifice (8) for evacuating the gases produced, characterized in that it comprises, arranged in series starting from the orifice (8) leaving the reactor and traversed, in series, by the gases leaving the reactor: a chimney (9) forming a boiler, a steam superheater (11) supplied from said boiler, a dust collector (13), a heat exchanger (14) intended to heat a drying fluid, a conditioning tower (16), a filtering device (17) and a device (20) for storing the gas, the steam supplied by the superheater (11) and the drying fluid leaving the heater (14) being used, in the installation, in particular for the preparation and the supply of fuel and oxidant supplied to the reactor (1). 2. Installation according to revendi cation 1, characterized in that the chimney (9) comprises in the direction of flow of the gases, a boiler (9 A) with direct radiation of frustoconical shape forming hood, an ascending duct (10 A ) with double jacket and a down pipe (10 B) with double jacket. 3. Installation according to claim 2, characterized in that the ducts (10 A, 10 B) jacketed also constitute at least one boiler used to supply the superheater (11). 4. Installation according to one of claims 1 to 3, characterized in that it comprises at a point located between the outlet of the superheater (11) and the inlet of the dust collector (13) means (70) for injecting into the gases from the zinc vapor reactor or its oxides, in the form of aerosols. 5. Installation according to any one of the preceding claims, characterized in that the gas com the product is taken off at around 1500 ⁹ C in the reactor (1) and cooled to the temperature of around 7.450 ° C at the outlet of the boiler (9 A). 6. Installation according to any one of claims 2 to 5, characterized in that the combustible gas is cooled to the temperature of about 730 to 750 ° C in the conduits (10 A and 10 B) jacketed. 7. Installation according to any one of the preceding claims, characterized in that the combustible gas is cooled to the temperature of approximately 620 ^° C. in the superheater (11) while the steam is superheated to a temperature of 400 ° C. about. 8. Installation according to any one of the preceding claims, characterized in that the combustible gas is cooled to the temperature of approximately 600 ^° C. in the dust collector (13). 9. Installation according to any one of the preceding claims, characterized in that the combustible gas is cooled to the temperature of approximately 380 ° C in the exchanger (14) while the drying fluid is brought to the temperature of 355 to 360 ° C approximately. 10. Installation according to any one of the preceding claims, characterized in that the combustible gas is treated in the conditioning tower (16) at a temperature between approximately 350 and 150 ° C which is the sampling temperature at the base of tower. 11. Installation according to any one of the preceding claims, characterized in that the combustible gas is treated in the filtering device which is preferably a dry electrostatic precipitator, at a temperature of approximately 150 ° C. and cooled at the outlet of the latter. at around 55 ° C before being stored. 12. Installation according to any one of the preceding claims, characterized in that a three-way valve (21) is arranged between the filtering (17) and storage (20) devices. 13. Installation according to any one of the preceding claims, characterized in that the drying fluid (32) heated in the exchanger (14) is admitted into a grinder-dryer (33) which sprays the raw fuel intended for the supply to the lance (4), a fraction (30) of the steam coming from the superheater being used for transporting the pulverized fuel, the additional fraction of steam (28) coming from the superheater (11) driving at least one compressor of a central (29) which, on the one hand supplies the lance (4) with oxidizing oxygen (6) intended for the gasification of coal and, on the other hand, supplies the heat exchanger (14) with nitrogen (31) used as drying fluid.

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