DE2620454A1 - Gasification of fuels in molten metal bath - with cooling of the reducing gas by mixing with blast furnace gas - Google Patents

Abstract

Sulphur-free reducing a gas mixts., made by known processes of gasification of solid, liquid or gaseous carbonaceous fuels with an oxidising medium below the surface of a basic slag-covered molten metal bath, are cooled to temps. suitable for metallurgical reduction processes by mixing the purified blast furnace or similar waste gases. For use as partial replacement for coke in blast furnaces for reduction of iron ores, and for production of spongy iron by direct reduction. The reaction gas is cooled from 1300-1450 degrees C. to the optimum value for blast furnace use (110-1200 degrees C.) or for direct reduction (800-1000 degrees C). Since the waste gases contain substantial amounts of unreacted CO and H2, the partial pressure of these components, and hence the reduction rate, is not significantly reduced.

Description

Annex to the patent application by

Klöckner-Humboldt-Deutz Aktiengesellschaft of April 28, 1976 Proceedings for gasifying carbonaceous fuels to produce a reducing gas The invention relates to a method for gasifying solid, liquid or gaseous Carbon carriers for the production of a reducing gas by means of a molten metal bath, the one below the molten bath surface of the carbon carrier and an oxidizing one Gasification medium are supplied and optionally on the melt bath surface a sulfur-absorbing slag is maintained, with a largely sulfur-free, Reaction gas consisting essentially of CO and H2 leaves the molten bath.

In a known method, the molten metal bath consists of one Iron melt, the fine-grained coal over a water-cooled lance below the Bath surface is fed continuously. At the same time is about a second Lance air or oxygen (German Offenlegungsschrift 1 915 248) or a Mixture of oxygen and water vapor (German Offenlegungsschrift 1 955 115) as a gasification medium continuously in the iron bath below the bath surface a ¢ initiates.

Lime is added to the iron bath to create an alkaline slag to generate the iron bath. The fine-grained coal is from the gasification medium underneath the iron bath surface converted into a reaction gas, which essentially consists of a mixture of carbon monoxide and hydrogen.

The sulfur present in the coal is taken from the basic slag recorded. The sulfur-containing slag is withdrawn from the gasification reactor, desulfurized and returned to the gasification reactor.

The reaction gas leaving the iron bath reactor has practical no shares of carbon dioxide and water vapor and it is therefore used as a reducing gas very suitable for metallurgical reduction processes. Due to the temperature of the liquid iron bath and the heat tones caused by the underneath If chemical reactions occur on the surface of the iron bath, the reaction gas has a temperature of approx. 13000 to 14500 C. This means that the reaction gas has when it leaves of the iron bath reactor a higher temperature than the temperature, required for a reducing gas for most metallurgical reduction processes is.

Does the metallurgical reduction process affect the reduction of ores in a blast furnace, in which part of the coke is introduced by introducing reducing gas is to be replaced, the reducing gas should be fed to the blast furnace at a temperature from about 11,000 C - 12,000 C. Concerns the metallurgical reduction process the so-called direct reduction process for the production of sponge iron, so should the temperature of the reducing gas is between 8000 and 10000 C. That the Reaction gas leaving the iron bath reactor must therefore be used as a reducing gas be cooled down for metallurgical reduction processes.

The invention is based on the object of a method for gasifying of solid, liquid or gaseous carbon carriers to produce a To create reducing gas at which the temperature and gas composition values as they are required for the optimal operation of a metallurgical reduction process required are.

This task is performed in a method of the type mentioned at the beginning solved according to the invention in that the reaction gas when used as a reducing gas for metallurgical reduction processes by adding purified furnace gas or Similar exhaust gas from the metallurgical reduction process to that for the reduction process required temperature is cooled.

According to the invention are used to cool the in the molten bath reactor generated reducing gas with advantage without additional manufacturing costs furnace gases or similar exhaust gases used in conventional metallurgical reduction processes incurred anyway. Contain furnace gases or exhaust gases from metallurgical reduction processes always in addition to C02 and H20 not yet converted or used proportions of reducing Gases (CO, H2) i, for example, the top gas of an iron blast furnace contains approx. 25 up to 30, CO approx. 0.5 to 4 X H2 approx. 10 to 16 s C02 approx. 52 to 60 s N2 Mixes one such furnace gas, which has a temperature of about 1500 to 4000 C the Blast furnace leaves, after its cleaning, the reducing gas generated in the molten metal bath to, so is in the resulting reducing gas mixture, which has been cooled to the optimum reduction temperature the partial pressure of the reducing gases CO and H2 is practically not reduced.

When using the prepared by the method according to the invention Reducing gas becomes the rate of reduction of the metallurgical reduction process so not reduced.

On the other hand, the reducing gas generated in the molten metal bath would through Admixture of inert gas, e.g. B. nitrogen, are cooled, this would im metallurgical reduction process of the partial pressure of the reducing gases CO and H2 be reduced. Among other things, this has the disadvantage of a reduced rate of reduction result.

Example When adding 25% purified furnace gas to the melt bath reactor The reducing gas generated is a partial pressure of reducing gases in the cooled reducing gas mixture of 0.84, while cooling with the same amount of nitrogen only 0.78 can be achieved.

The furnace gas or similar exhaust gas mixed with the reducing gas can taken from any metallurgical reduction process. With advantage originates the furnace gas or a similar exhaust gas from that metallurgical reduction process, to which the reaction gas leaving the molten metal bath is fed as a reducing gas will.

The original slag of the molten metal bath, e.g. iron bath, can optionally after complete or partial desulphurization, various uses be fed, for example processing to cement raw meal.

For this purpose, the metal content, e.g. iron content, must be separated necessary. This can preferably be done by means of magnetic separation. This is done as a Another feature of the invention proposed that the liquid slag from the molten metal bath withdrawn, rapidly cooled in a stream of water, granulated and possibly further comminuted will. Iron components separated out by magnetic separation may become Molten metal bath or returned to the metallurgical reduction process, to cover the iron losses when the slag is withdrawn from the gasification reactor.

Is there the slag former abandoned on the molten metal bath from limestone, the sulfur content of the carbon carrier to be gasified is e.g. coal, preferably in the form of calcium sulfide during the gasification process Slag added. Both for a slag recirculation and for a It is necessary to remove the sulfur from the slag or put it in a landfill to convert a harmless form. To this end, as a further feature of the invention proposed the water-soluble sulfide sulfur of the slag by a sulfating To convert roasting in water-insoluble sulphate sulfur, e.g. CaS04. So that is Slag can be dumped. The oxidation of sulphide sulfur to sulphate sulfur can in the immediate vicinity of the gasification reactor or at the site of the landfill, for example be carried out in a rotary kiln, deck oven, inclined grate or the like. If necessary, this conversion only needs to be carried out in part to convert only that portion of the sulphide sulfur of the slag into sulphate which with regard to the use of the slag material in the cement industry exceeds critical limit.

The sulphide sulfur of the slag is rendered harmless by means of a transformation to SO2 and / or H2S is not only complex in terms of equipment and therefore expensive, but also the subsequent procedural steps, for example the CLAUS process, capital - and operating costs - intensive. In contrast, the sulfide sulfur can be converted then realize the slag in a metal sulfide if this one is so low Has boiling point that the equilibrium of this through the transition into the gas phase Desulfurization reaction is influenced in a positive way. This is for example Lead sulfide (boiling point 12900 C) or antimony sulfide (boiling point 8700 C) are suitable.

Therefore, it is proposed according to a further feature of the invention, that for processing the sulfur-containing slag of the sulfide sulfur in one with Metal sulphide which is volatile under the reaction conditions, e.g. in lead sulphide or antimony sulphide, is transferred, e.g. according to the reaction: CaS + Pbo - CaO + PbS Such The generated metal sulfides are input materials for non-ferrous metal smelters and can therefore be sold for a profit. The following advantages are achieved with these procedures: Regeneration of the sulphide-containing slag by recycling the calcium oxide as Slag former for gasification reactor; elegant removal of sulphide sulfur from the slag; and recovery of valuable metal sulfides as feedstock for non-ferrous metal huts.

In the gasification of gas-rich coal, such as lignite, gas flame coal, e.g. by means of steam, an endothermic warming occurs. About the gassing process To keep it going in such cases, heat must enter the gasification reactor from outside be introduced.

This disadvantage of the gasification process is after another feature the invention thereby avoided that the metal bath during the gasification process such elements or

the compounds of which are added during the chemical reaction exhibit an exothermic heat release in the reactor.

To set the temperature of the molten metal bath, exothermic reactants are used Metals or metal compounds, e.g.

Calcium, magnesium, titanium, chromium, manganese or pyrite are added to their Oxidation products, e.g. CaO, are at least partially absorbed by the slag will. These metals or metal compounds are blown through the Molten metal is oxidized with the oxygen-containing gasification medium, with heat in the order of magnitude between 120 and 220 Kcal per mole of oxygen. Through this, that the generated oxidation products, e.g. CaO, are immediately absorbed into the slag and serve there to set the basicity, the desulphurisation capacity can be used the slag can be specifically influenced and, if necessary, a separate one Addition of lime to the slag will no longer be necessary.

If, for example, liquid iron is used as a metal bath for coal gasification, the following disadvantages occur: high melting point, which means that the temperature is too high of the product gas; Dependence of the possible working range on the carbon content of iron, since iron only absorbs about 4% carbon at working temperatures can; limited specific carburettor output due to the speed of the carburizing process.

In contrast, these disadvantages are according to a further feature of Invention when using non-ferrous metals, for example lead, aluminum, copper, as well as liquid salts, salt mixtures and slag as a melt pool. In the case of a lead bath reactor, it can be coupled to a lead shaft furnace by using the gasifier's product gas to reduce lead. It is also possible to use two different liquid phases (metal and slag) to work with only one melting phase.

The injection of the reactants using lances from above into the Molten metal bath leads to practically insoluble thermotechnical and mechanical Problems. A lateral inflation of the reactants onto the surface of the melt pool leads to significant carbon combustion, that is to say contains the product gas considerable amounts of C02 and H20 and is therefore used as a reducing gas for metallurgical Reduction processes cannot be used. Will the reactants from below by means of Nozzles blown through the molten metal bath, the nozzles are subject to one high wear.

In addition, there is a risk of the liquid Metal into the nozzles if the nozzle pressure should drop. When blowing through vertically only short residence times of the reactants in the metal bath can be achieved, which can reduce the specific carburetor performance.

There is also a risk of metal and slag being ejected from it the reactor.

In contrast, it is proposed according to a further feature of the invention, that the reactants laterally and obliquely downwards through nozzles into the molten metal bath are blown in, the nozzles if necessary from the horizontal axis downwards and are pivotable at the top. The nozzles are below the surface of the melt pool on the side wall of the gasification reactor arranged and adjustable in their inclination.

The reactants blown in obliquely downwards are then inside of the molten metal bath is deflected in the upward direction, reducing the dwell time extended and the reaction yield increased.

Patent claims

Claims (8)

Claims 1. A method for gasifying solid, liquid or gaseous carbon carriers for the production of a reducing gas, by means of a Molten metal bath, the carbon carrier below the surface of the molten bath and an oxidizing gasification medium are supplied and optionally on the Melt bath surface a sulfur-absorbing slag is maintained, wherein a largely sulfur-free reaction gas consisting essentially of CO and H2 the molten bath leaves that the reaction gas when used as a reducing gas for metallurgical reduction processes by admixing of purified furnace gas or similar waste gas from the metallurgical reduction process is cooled to the temperature required for the reduction process. 2. The method according to claim 1, characterized in that the furnace gas or similar exhaust gas is taken from that metallurgical reduction process, to which the reaction gas leaving the molten metal bath is fed as a reducing gas will. 3. The method according to claim 1, characterized in that the liquid Slag is continuously withdrawn from the molten metal bath, cooled in the water bath, granulated and possibly further crushed and optionally partially or completely desulfurized is preferably carried out and especially when processing into cement raw meal Magnetic separation is freed from entrained metallic particles, if necessary returned to the molten metal bath or to the metallurgical reduction process will. 4. The method according to any one of claims 1 to 3, characterized in that that for processing the slag withdrawn from the molten metal bath surface the sulphide sulfur (for example water-soluble CaS) by a sulphating Roasting is implemented in water-insoluble sulphate sulfur (for example CaSO4). 5. The method according to any one of claims 1 to 3, characterized in, that for the work-up of the sulphide-containing slag, the sulphide sulfur in one at metal sulfide volatile under the reaction conditions, for example in lead sulfide or Antimony sulfide, transferred by introducing the gas into a liquid metal bath ufi approx. 6. The method according to any one of claims 1 to 5, characterized in that that to adjust the temperature of the molten metal bath reacting exothermically to this Metals or metal compounds, for example calcium, magnesium, titanium, chromium, Manganese or pyrite are added, their oxidation products, e.g. CaO, at least to be partially absorbed by the slag and at the same time to adjust the Slag basicity and can be used for desulfurization of the reaction gas. 7. The method according to any one of claims 1 to 6, characterized in that that the molten metal bath is made of liquid iron, liquid non-ferrous metals, salts, Mixtures of salts, slags or mixtures thereof. 8. The method according to any one of claims 1 to 7, characterized in that that the reacton partners laterally and preferably obliquely downwards into the molten metal bath are blown in through nozzles, which are below the melt pool surface on the side wall of the gasification reactor are arranged and optionally adjustable in their inclination.