MXPA99003745A - Process for returning finely dispersed solids discharged with a carrier gas from a reactor vessel - Google Patents

Abstract

In a process for returning finely dispersed solids discharged from a reactor vessel (1) with a carrier gas through a discharge point (2) of the reactor vessel (1) to a return point (15) of the reactor vessel (1), the solids are separated in a solid separator (4), in particular a cyclone separator, then returned with a carrier gas to the reactor vessel (1) while a differential pressure is maintained between the solid separator (4) and the return point (15). When the solids enter the reactor vessel (1), they are at least partially gasified and/or burned with oxygen supplied for that purpose. To enable the solids to be returned without moving parts which would be exposed to abrasion, in a continuous and controlled manner, the separated solids are directly and continuously aspirated by the solid separator (4) by means of a propellant gas and by an injector effect, accelerated and supplied to the reactor vessel (1).

Description

PROCESS FOR SOLID RECYCLING BN FINAL PARTICLES DOWNLOADED FROM THE DN REACTOR TANK BY MEANS OF A CARRIER GAS DESCRIPTION OF THE INVENTION The invention relates to a process for recycling a solid into fine particles, such as fine particles of coal and iron, discharged from the tank. of a reactor, in particular a melt gasifier by means of a carrier gas at a point of discharge from the tank of a reactor, at a point of recycling of the reaction tank, where the solid is separated in a separator of solids in particularly a cyclone and subsequently recycled to the reactor tank by means of a carrier gas maintaining a pressure difference between the solids separator and the point of recycling, and at least partially gasified and / or burned after entry to the reactor tank under the oxygen supply as well as an arrangement to carry out the process. A process of the type mentioned above is known from EP-A-0 493 752. In this process the hot powders of a melt gasifier are separated in a hot cyclone and recycled in a melting gasifier by means of a burner. To solve the difference in pressure between the hot cyclone and the melting gasifier, the recycling is carried out by means of a system of locks with several tanks provided between each two locks. The reducing gas extracted from the melting gasifier REF .: 29826 It has a temperature of approximately 1050 ° C and carries considerable amounts of powdered solids. The powder charge is approximately 150 g / m2 of reducing gas. Immediately after leaving, the temperature of the reducing gas is adjusted to approximately 850 ° C when adding refrigerant gas, mainly gas of the same type. The solid, which consists mainly of a mixture of carbon and iron particles, is continuously separated in the hot cyclone. Since this solid is highly abrasive the known locks system not only requires a specific design but also undergoes a high degree of wear. The solid is transported discontinuously to the injector, for example in batches, in such a way that a continuous mode of operation of the dust burner is not ensured and the effectiveness of the powder burner is reduced. The solid can settle when filling a tank and the dust flow can be blocked. A process for recycling a solid of fine particles discharged from a reactor tank by means of a carrier gas is known from EP-B-0 278 287. In this process, the solid that accumulates in the solids separator is transported to a collector tank and accumulates there. The collector tank serves as a compensation tank in this chaos, from which the solid is extracted by means of a hot reactor gas extracted directly from the reactor tank and recycled directly in the reactor tank by means of an injector. In the tank collector the solid can settle and block the flow of solids, in particular because the hot carrier gas extracted directly from the reactor tank, which can cause the hardening and partial melting of the solid. In the known process, the injector opens the reactor directly in the tank. The object of the invention is to prevent these disadvantages and difficulties and solve the technical problem of creating a process as well as an arrangement to carry out the process, which allows the recycling of the solid without moving parts, which would be thus subjected to a high degree of abrasion and alternating thermal stress, wherein the particular recycling has to be carried out in a continuous and controlled manner and the pressure difference between the outlet of the solids separator and the reactor vessel is overcome without problems. In addition, a continuous flow of solids must be ensured without problems with a high degree of certainty. In a process of the aforementioned type, this problem is solved by direct and continuous ejection of the separated solids by means of a propellent gas under the action of an injector, by accelerating it and transporting it to the reactor tank. According to the invention, a completely open line is provided between the solids separator and the reactor tank under normal operating conditions, without retention zones and deflectors. The propellant gas sucks the solids directly from the solids separator together with a small part of the gas carrier in which they are dispersed in the solids separator. This assures that the solids are in constant motion and are not allowed to settle. thus reliably reverting the danger of adhering particles and consequently blocking the flow of dust. The flow velocity of the propellant gas should preferably be equal to or greater than the speed of sound (in a supercritical pressure ratio) in order to ensure a highly operational stability of the solid recycle. It is advantageous to use nitrogen and / or cold or clean process gas as the propellant gas. According to a preferred embodiment, the cold and clean process gas is formed by a reducing gas containing CO and H ,. An arrangement for carrying out the process according to the invention with a reactor tank, in particular a melt gasifier, a gas discharge pipe that leaves the reactor tank and leads to a solids separator, in particular a cyclone from the reactor. a solids discharge duct that carries the separated solid to an injector, and with a solid recycle duct going from the injector to the reactor tank and opening at the last by means of a dust burner, is characterized in that the solid separator is connected to a solids recycle duct and thus the powder burner by means of the injector by means of a continuous line. The simple Assembly of the arrangement according to the invention ensures a very low maintenance expense and high availability and performance of the arrangement. To separate the large particles, for example coarse coal or coke parts, a coarse filter advantageously connected downstream of the solids separator.

In order not to directly prevent the separation of eolidoe in the case of disturbances in the powder recycling line, a solids tank is connected downstream of the solder separator according to a preferred embodiment, which is provided with an element of fluidization in transition with a solid discharge duct. The tank for solids does not work during normal operation, this is the solid is freely dispersed in this tank by means of free fall. In order to be able to discharge large particles originating, for example, from a refractory lining of the solid discharge duct without impeding the flow of solids, the injector consists of a tank of solids designed in the form of a bag, which is provided with a drain hole that can be closed with a blocking element, the solids collecting tank being advantageously provided with a fluidization element in the bottom area. In the following the invention will be explained in greater detail by means of the modalities shown in the drawing, Figure 1 shows a general distribution of a system of recycled solids of the state of the art, and Figure 2 is a schematic representation of the recycling of solids according to the invention. According to the state of the art illustrated in FIG. 1, the waste gas generated by the gasification of the coal and subsequently used as the reducing gas is discharged from a reactor tank designed as a melting gasifier 1, which serves for the fusion of sponge iron and the simultaneous generation of a reducing gas of carbon-containing material, by means of a gas discharge pipe 2 opening in the melt gasifier 1 in an upper region of the latter. As the fine-grained solid until powdered is entrained by the waste gas, the latter, which serves as the carrier gas for this solid, is fed to the solids separator 4, which is advantageously designed as a hot cyclone. Immediately after the reducing gas has left the melt gasifier 1, a cooling gas at the same time is fed to the reducing gas by means of the refrigerant gas pipe 5 in such a way that the reducing gas has a favorable temperature for the subsequent reduction of the gas. iron ore and an excessive temperature load is prevented in the hot cyclone 4. The solids separated in the hot cyclone 4 fall and are collected in a de-cyclone tank 6 integrated in the hot cyclone. The solids are transported in batches by means of of a deposit system connected downstream. For this purpose, gate valves 10 are placed between the tanks 6, 7 and 8 in the solid discharge pipe 9 that connects the tanks 6, 7 and 8. Finally the solids are dosed to the injector 12 in the most uniform manner possible by means of a metering element 11, for example a metering valve or according to another embodiment a rotary valve (not shown here). The injector 12, which is operated, for example, with N2 as a propellant gas, which is fed by means of the tube 13, transports the solid in the melt gasifier 1 via the solid recycle duct 14 that opens in a powder burner 15. The oxygen is fed to a pole burner 15 by means of the oxygen feed pipe 16., As the C fraction of the powder ee. burns / gasifies, the remaining inert parts of the solid (Fe, coal ash, CaO, Si02, etc.) agglomerate. the agglomeration of the solid particles prevents them from being discharged by the gas leaving the reactor tank. These fall to the bottom of the reactor tank and either melt or extract as slag. This type of solid recycling requires a high maintenance expense. The particular problems in the recycling of solids are represented by the deposit system 6 to 10, that is the transportation of dust in the form of lots, and by the dosage of solid. Another disadvantage of the solid recycling system illustrated in Figure 1 is that individual solids deposits 6 to 10 have to be closed each time with gate valves to isolate them from the gaseous process system that takes place in the reactor tank l. Since the pressure of the seventh, this is the pressure itself in the melt gasifier 1, and also in the following reduction vessel (not shown), in which the reducing gas generated in the melt gasifier is fed, is subject to variations, they have large pressure differences which, in combination with the gas flow, lead to high wear of the gate valves 10. In order to maintain these pressure differences limited, pressure compensation pipes not shown in greater detail are required, in the known arrangement between the solids deposits 6, 7 and 8, on the one hand and between the gas system of the melting gasifier l and the reduction vessel on the other hand. Figure 2 shows the powder recycle system according to the invention. The solids separated in the hot cyclone 4 are transported to the container 18 integrated in the outlet of the cyclone 17. In this container 18 which is provided with a refractory lining, an inclined grate 19 is installed which serves to separate large talee particles as coal pieces. and of coke, which are extracted from the container 19 by means of an extraction opening 20 in case of necessary. From the hot cyclone 4, the solid is dispersed in free fall in the container 18, which during normal operation has no function, is extracted by an injector 12 through a discharge tube 9 which is shaped as a down tube. This down tube 9 is cylindrical or advantageously conical, expanding downwards in order to avoid obstructions. Advantageously, it is also provided with a refractory coating. From the injector 12, the solid recycle duct 14 leads to a powder burner 15. The injector 12 is preferably operated at a supercritical pressure ratio, ie the velocity of the propellant gas fed by means of the injector via the pipe l3 is equal to or greater than the speed of sound. For example, nitrogen or refrigerant gas, such as cold reducing gas, can be used as the propellant gas. Beneath the propellant nozzle 22 itself, the injector housing 21 changes to the collection tank 23, in which the coarse-grained particles, such as flakes or pieces of the coating which can lead to obstructions, are trapped. To be able to discharge the coarse-grained particles, the bottom 24 of the collecting tank 23 is provided with an outlet with a closing element 25 or a pressure lock (not shown here). To facilitate the extraction of the particles, 24 fluidizing elements 26, such as ring nozzles, purging elements made of refractory material, can be provided in the bottom of the container, Sintered material elements, nozzles in the form of self-closing valves, etc. The fluidizing gas can simultaneously act as a secondary gas for the injector 12. The fluidization is adjusted in such a way that the fine particles can be sucked by the injector and ejected and only coarse particles accumulate. In the arrangement according to the invention, the closure elements 27 at the inlet of the down tube 9 and upstream of the powder burner 15 are only provided for repair and maintenance purposes. In the event that problems occur during operation, the container 19 connected downstream of the hot cyclone 4 can also serve as an accumulator tank, when the closure element 28 is closed. To prevent the solids from settling in this emergency case, fluidization elements 26 are provided at the outlet of the tank 28, that is at the transition to the down tube 9. The invention is not limited to the described mode but can be modified in several respects. Not only can it be applied to foundry gasifiers but particularly to reactor tanks of any type in which solids are discharged by means of a waste gas.

Claims (12)

1. CLAIMS 1.- Process for recycling solids of fine particles, such as coal or iron particles, discharged from a reactor tank, in particular a melt gauge, by means of a carrier gas at a discharge point of the reactor tank in a point of recycling of the reactor tank, in which the solids are separated in a separator of solids, in particular a cyclone and subsequently recycled in the reactor tank by means of a carrier gas, maintaining a difference in preherence between the separator of solids and the point of recycling and at least gasified and / or burned upon entering the reactor tank under the supply of oxygen, the process is characterized in that the separated solids are expelled directly and continuously from the solids separator by means of a propellant gas under the action of an injector, they are accelerated and transported to the reactor tank.
2. 2. A process according to claim 1, characterized in that the speed of the flow of propellant gas is equal to or greater than the speed of sound when coming into contact with the solid.
3. 3. - A process according to claim 1 or 2, characterized in that the solid is filtered after separation.
4. 4. - A process according to one or more of claims 1 to 3, characterized in that the solid ee fluidizes after leaving the solids separator.
5. 5. A process according to one or more of claims 1 to 4, characterized in that nitrogen and / or cold and clean process gas are used as the propellant gas.
6. 6. A process according to claim 5, characterized in that the cold and clean process gas is formed by reducing a reducing gas containing CO and H2.
7. 7. An arrangement for carrying out the process in accordance with one or several of claims 1 to 6, with a reactor tank, in particular a melt gasifier, a gas discharge pipe that leaves the reactor tank and leads to a solids separator, in particular a cyclone, from the which is a solids discharge duct that carries the separated solids to an injector, and is a solids recycling duct that leads from the injector to the reactor tank and that opens in the latter by means of a dust burner, the arrangement is characterized in that the solder separator is connected to the solids recycle duct and thus to the powder burner through the injector by means of a continuous line
8. 8. An arrangement according to claim 7, characterized in that a filt for coarse is connected downstream of the solids separator.
9. 9. - An arrangement according to claim 7 or 8, characterized in that the tank for solids is connected downstream of the solids separator, the tank for solids it is provided with a fluidizing element during a transition to the solid discharge duct.
10. 10. - An arrangement according to one or more of claims 7 to 9, characterized in that the injector consists of a solidoe collecting tank designed in the form of a bag, which is provided with a drainage orifice that can be closed with an element of blocking.
11. 11. An arrangement according to claim 10, characterized in that the solids collector tank is provided with a fluidization element in the bottom region.
12. 12. - An arrangement according to one or more of claims 7 to 11, characterized in that the solids discharge duct is constantly expanded from the solids tank to the injector.