WO2000044942A1 - Method and device for granulating and fragmenting liquid slags - Google Patents

Abstract

The invention relates to a method for granulating and fragmenting liquid slags, whereby the slag jet is expelled into a cooling reactor and is cooled in the cooling reactor by adding hydrocarbons. The slag jet is expelled into the cooling reactor with hot combustion gases, especially the gases resulting from a complete combustion, wherein conversion to CO and H2 is effected. Burners (4) are disposed above the slag bath in the device for implementing the method, which device comprises a slag tundish (1) and a slag outlet (5), to which a cooling reactor (6) is connected. The slag tundish (1) can be closed pressure-proof. Lines (14) for the hydrocarbons are connected to the cooling reactor. Alternatively, the hot combustion gases of a combustion engine are blown to the liquid slags using a lance (7).

Description

Method and device for granulating and crushing liquid slags

The invention relates to a method for granulating and crushing liquid slags such. B. blast furnace slag or smelting chamber ash from coal-fired thermal power plants, in which the slag jet is ejected into a cooling reactor and is cooled in the cooling reactor with the addition of hydrocarbons, and to a device for carrying out this process with a slag tundish and a slag outlet opening to which a cooling reactor is connected is.

For granulating and comminuting liquid slags, the applicant has already proposed in older proposals to inject coal, hydrocarbons and / or coal water mixtures or coal slurries into the slags or the slag jet, whereupon the liquid slag is expelled into an expansion or granulation chamber and into one Mill was transferred. In such a procedure, hydrocarbons, for example in the form of a jet of heavy oils, diesel oils or old solvents under pressures of about 30 to 250 bar, had to be used, cracking reactions and thus rapid cooling being triggered immediately by contacting such hydrocarbons with the hot liquid slag. With such hydrocarbons, the process was relatively complex to control and maintain the desired solidification conditions, and in particular it had to be prevented that the outlet opening through which the liquid slag was discharged into the cooling reactor or expansion or granulation chamber froze. In addition to thermal problems in the area of the hot liquid slag and the slag outlet, for the further cooling in the known proposals, water vapor was always largely injected coaxially to the mouth of the slag outlet. In particular, if hydraulically active materials are to be obtained from appropriate starting slags such as blast furnace slags, However, the use of water or water vapor poses a serious danger to the hydraulic properties of the end product. Due to the relatively high pressure, which is desired for subsequent jet mills, for example, water vapor or water can be trapped, which can lead to an undesirable, at least ' partial hydration of the end product leads, which can affect the hydraulic properties of the end product.

In order to be able to better control the thermal problems in the area of the slag outlet, it has already been proposed to insert a burner into the slag outlet, the slag being introduced into the pelletizing space as a coaxial jet with the hot combustion exhaust gases or the flame jet. In this known proposal, too, water and / or wet steam was subsequently applied to the particle stream, for example following a first radiation cooling, as a result of which the problems described at the outset cannot be ruled out. In addition, burners which open into the slag outlet cannot be regulated in the desired manner in a simple manner, so that the extent of the combustion and thus the formation of further water vapor in the granulation room cannot be easily controlled. Due to the mostly incomplete combustion when using such burners, in which the flame jet is directed together with the hot slag into the granulation chamber, large amounts of carbon monoxide are formed, as a result of which effective cooling, for example by blowing hydrocarbon into the cooling reactor or granulation chamber is difficult.

Overall, in the known processes for granulating and comminuting liquid slags, blowing water or water vapor was generally not dispensed with, to make matters worse, further water vapor was formed in the course of the combustion and cracking reactions in the course of the selected procedure. The invention now aims to provide a method of the type mentioned at the beginning in which the use of water or water vapor for cooling can be avoided entirely and it can also be ensured that water or water vapor is not formed in the course of the combustion processes becomes. Furthermore, the invention aims to control and regulate the process in a comparatively simple manner in order to ensure reproducible conditions irrespective of the choice of the slag to be granulated or comminuted. Finally, the invention aims to maintain a correspondingly high temperature in the slag inlet or the slag tundish, in which the liquid slag is kept in stock, which reliably prevents freezing or clogging of the outlet opening.

To achieve this object, the method according to the invention consists in that the slag jet with hot combustion exhaust gases, in particular complete combustion, is expelled into the cooling reactor. Because the slag jet is ejected into the cooling reactor with hot combustion exhaust gases, in particular complete combustion, a relatively high temperature level can be specified on the one hand without uncontrolled combustion occurring in the area of the outlet opening of a slag tundish. The hot combustion gases, particularly when they are combustion gases from a complete combustion, can be described as largely inert and therefore do not trigger any chemical reactions in the area of the outlet of the slag jet. Such hot combustion gases consist primarily of carbon dioxide and nitrogen, the combustion gases being largely free of oxygen, so that with such a procedure the addition of hydrocarbons for cooling results particularly advantageously in an efficient cooling effect and at the same time prevents one such addition of hydrocarbon water vapor or water is formed. In principle, by using carbon dioxide as the propellant or transport gas for the liquid slag, a reaction with Hydrocarbons to carbon monoxide and hydrogen can be achieved, the formation of water vapor or water can be excluded with certainty if no increased oxygen supply is available and consequently no water or water vapor is injected for further cooling. At the same time, a valuable product gas, namely carbon monoxide and hydrogen, is formed, which can subsequently be used thermally or chemically, so that overall the energy efficiency is significantly improved.

The process according to the invention is advantageously carried out in such a way that the combustion gases are blown into the liquid slag at temperatures of 1000 to 1500 ° and the liquid slag, in particular as a jacket of the gas stream, is pushed into the cooling reactor with the hot combustion gases via a tubular opening or nozzle and that the hydrocarbons are gasified with the CO 2 of the hot combustion exhaust gases and converted to CO and H2. Due to the high supply of CO 2 in the form of the hot combustion exhaust gases and due to the gasification or cracking reactions used in the cooling reactor, the following chemical reactions can be observed primarily, which contribute significantly to efficient cooling. I. C + C02 -> 2 CO, ΔH = + 3784 KJ / Nm ³ CO

II. CH4 + C02 -> 2 CO + 2 H2, ΔH = + 2767 KJ / Nm ³ (2 CO + 2 H2)

the specified enthalpies are based on the production of a standard cubic meter of CO + H2. The gasification reaction in the cooling reactor leads to a corresponding increase in the amount of gas and thus the pressure and to an acceleration of the slag granules, the conversion taking place directly to synthesis gas or water gas. The overall process can be controlled much more easily in this way, with only a corresponding stoichiometry being provided in order to optimize the energetic use. It is therefore advantageous to proceed in such a way that the amount of CO2 in the hot combustion exhaust gas is selected stoichiometrically according to the amount of hydrocarbon blown.

For a subsequent further comminution, a large amount of propellant gas is made available due to the gasification reaction taking place in the cooling reactor, which allows, as in a preferred embodiment of the method according to the invention, to proceed in such a way that the solidified and cooled slag drops at temperatures above 500 ° and below 800 ° C are discharged together with the CO and H2 formed into a mill, in particular a jet mill, and that the CO and H2 are drawn off.

The device according to the invention for carrying out the method requires a slag tundish with a slag outlet opening to which a cooling reactor is connected. The device can be designed according to the invention such that burners are arranged above the slag bath, that the slag tundish can be closed in a pressure-tight manner and that lines for the hydrocarbons are connected to the cooling reactor.

Alternatively, the device can be designed in such a way that a combustion chamber or an internal combustion engine, in particular a turbine combustion chamber, is arranged outside the slag tundish and that the hot combustion exhaust gases are fed to a lance directed towards the liquid slag bath or immersed in the liquid slag bath.

When using burners arranged above the slag bath, it is only necessary to ensure that the slag tundish can be appropriately pressure-tightly closed in order to ensure the pressure required for the safe discharge of the liquid slag into the cooling reactor. At the same time, the slag bath is heated accordingly by such burners, so that the slag can be safely kept in the liquid phase. When using separate combustion chambers or internal combustion engines, in particular turbine combustion chambers, the combustion can in each case be carried out optimally in order to achieve a largely complete combustion, which also ensures a better energetic use of the fuels used. In particular, the use of a turbine combustion chamber leads directly to the required pressure level of about 2 to 5 bar, so that the use of a simple lance immersed in the slag bath for the safe discharge of the liquid slag into the cooling reactor becomes possible without the risk that the outlet openings of the slag tundish subsequently move.

In any case, the previously used steam or pressurized water can be completely dispensed with in the device according to the invention, so that hydration reactions can be excluded. Simultaneously with the desired comminution, a high-quality product gas, namely carbon monoxide and hydrogen, can be formed, so that the energy balance of the method and the device according to the invention is significantly improved.

The invention is explained in more detail below on the basis of an exemplary embodiment shown schematically in the drawing. In the drawing, 1 denotes a slag tundish in which a bath of liquid slag, for example liquid blast furnace slag, is contained. The liquid level is designated 2 here. The tundish 1 can, as indicated by the dash-dotted line 3, be sealed off. When the tundish 1 is sealed off, burners, indicated schematically by 4, can be arranged above the liquid level, which can be fixed in the lid, for example. With such burners, the energy required to maintain the liquid phase and the pressure required to expel the slag through the tubular one Opening 5 are constructed, to which a cooling reactor 6 is connected.

In the illustration according to the drawing, 7 denotes a lance for hot combustion exhaust gases, which dips into the slag bath and is used as a jacket for such a hot exhaust gas flow through the opening 5 for the discharge of the liquid slag. The slag inflow can be regulated accordingly by a height-adjustable, tubular weir 8.

After the passage of the hot slag droplets as a jacket of the gas stream or due to the pressure generated by the burner 4 through the opening 5, the liquid slag droplets with diameters between 10 and 60 μ and temperatures of about 1200 to 1400 ° enter the cooling reactor and are essentially over radially inwardly directed nozzles 9 acted upon by hydrocarbons. In the cooling reactor, in which a gasification and a cracking reaction takes place, the CO 2 injected via the lance 7 converts with the hydrocarbons to CO and H2, with the corresponding increase in volume also resulting in a corresponding pressure build-up, which largely discharges the material solidified particles via a passage 10 in a jet mill 11 allows. With a corresponding geometric arrangement, the flow energy can be converted directly in the jet mill. Fission gas is withdrawn from the jet mill 11 as a product gas via the line 12, the granules obtained in each case being able to be discharged via cellular wheel locks 13 at temperatures of approximately 600 ° C.

Hydrocarbon, and in particular Ci-io hydrocarbons, are introduced by introducing such hydrocarbons into a ring line 14 to which the nozzles 9 are connected.

The outlet opening 5 can be heated or cooled in a conventional manner in order to optimize the wear accordingly. In the illustration in the drawing, a ring insert 15 through which a fluid can flow can be seen.

Claims

Claims: 1. Process for granulating and crushing liquid slags such. B. blast furnace slag or smelting chamber ash from coal-fired thermal power plants, in which the slag jet is ejected into a cooling reactor and is cooled in the cooling reactor with the addition of hydrocarbons, characterized in that the slag jet is discharged into the cooling reactor with hot combustion exhaust gases, in particular complete combustion becomes. 2. Process according to claim 1, characterized in that the combustion gases are blown into the liquid slag at temperatures of 1000 to 1500 ° and the liquid slag, in particular as a jacket of the gas stream, with the hot combustion gases via a tubular opening or nozzle in the Cooling reactor is injected and that the hydrocarbons are gasified with the CO 2 of the hot combustion gases and converted to CO and H2. 3. The method according to claim 1 or 2, characterized in that the solidified and cooled slag drops at temperatures above 500 ° and below 800 ° C together with the CO and H2 formed in a mill, in particular a jet mill, and that the CO and H2 is subtracted. 4. The method according to claim 1, 2 or 3, characterized in that the CO 2 amount of the hot combustion exhaust gas is selected stoichiometrically in accordance with the amount of the injected hydrocarbon. 5. Device for performing the method according to one of claims 1 to 4 with a slag tundish (1) and a slag outlet opening (5) to which a cooling reactor (6) is connected, characterized in that burners (4) are arranged above the slag bath that the slag tundish (1) can be closed pressure-tight and that the cooling gate (6) lines (14) for the hydrocarbons are connected. 6. Device for performing the method according to one of claims 1 to 4 with a slag tundish (1) and a slag outlet opening (5) to which a cooling reactor (6) is connected, characterized in that outside the slag tundish (1) a combustion chamber or an internal combustion engine, in particular a turbine combustion chamber, is arranged and that the hot combustion exhaust gases are fed to a lance (7) directed towards the liquid slag bath or immersed in the liquid slag bath.