NL8103451A - PROCESS FOR THE PREPARATION OF GAS. - Google Patents

Description

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Process for the preparation of gas.

The invention relates to a process for the production of gas in an iron melting reactor, in which a liquid iron melt is present, to which carbonaceous, solid or liquid fuels are supplied and on the surface of which at least a part of an oxygen gas jet is blown , whereby the fuels gasify, accumulate in the gas space above the surface of the melt and are discharged from there.

The continuous gasification of coal or other carbonaceous fuels in an iron-melting reactor or steel-melting reactor with a slag layer into a gas consisting mainly of CO and Hg has been known for a long time. In the method according to DE-A-29 52, oxygen is blown onto the surface of the melt via a blow lance present above the surface of the iron melt, thereby creating an inflation site with a high temperature.

At this high temperature inflation site, a solid carbonaceous powder is inflated together with a carrier gas.

DE-B-25 20 883 also discloses a method in which coal or a carbon-containing fuel are blown into the iron melt below the surface. The at least partly oxygen jet of gas is also blown below the surface into the iron melt, a casing with hydrocarbons serving to protect the associated blowing nozzles.

Finally, DE-C-25 20 868 discloses a method in which, in addition to the coal to be gasified and optionally independently of the coal to be gasified, energy-rich coal, unbound carbon, aluminum, silicon, calcium carbide or mixtures thereof be fed. Thereby heat is supplied to the coal gasification process.

A drawback with these known processes is that the gasification of bad fuels, in particular of coal types with a low incineration value, has hitherto not been economically unfriendly, because they require the addition of high-energy fuels in order to be able to maintain the temperature of the iron melt with such fuels Finally, it is not possible in the known processes to use cheap, available oxidizing gases, such as, for example, air.

The object of the invention is now to avoid the drawbacks of the known processes and to provide a process with which a flammable gas can be economically prepared from an carbon melting reactor in solid, ground or liquid form from carbon and / or hydrocarbon-containing fuels of low-energy fuels and using inexpensive oxidizing gases, in particular the addition of energy-rich fuels to balance the heat balance of the gasification process can be omitted.

This objective is achieved in that the gas jet is blown through the gas space onto the surface of the melt and, as it passes through the gas space, aspirates the gases prepared, burns in part and drags them to the surface of the melt in such a manner, that the heat generated during the combustion of the prepared gases is transferred to the iron melt.

The gas jet travels through the gas space above the surface of the melt for the greatest possible distance. As a result of the jet effect, the gas present in the gas space, which has been developed by gasification of the fuels, is sucked in and entrained. This effect also occurs, for example, with a water jet pump. Since the gas jet directed to the surface of the melt contains oxygen, part of the generated flammable gas is burned. The resulting heat is supplied to the iron melt, because the gas jet deflects the hot combustion products to the surface of the melt, so that the hot combustion products contact the surface of the melt and can release their heat.

By blowing a jet of gas from an oxidizing working gas (oxygen, air or the like 8103451 - - 3 -) onto the surface of the melt, it becomes possible to heat the importantly improve the balance in an iron melting reactor.

The method according to the invention makes it possible to use air for the welding beam. It is therefore not necessary to use technically pure oxygen, as in the known processes. Air is normally available at a favorable cost price and can be compressed to the required working pressure by simple means. It is then particularly advantageous to preheat the air, so as not to extract the heat required for heating the air from the gasification process. In practice, a preheating temperature of 300 U00 ° C has proved effective. Conventional pipeline systems and shut-off devices can be used up to this temperature, while the heat insulation of the supply system can also be carried out economically.

In addition, however, it is possible to use technically pure oxygen for the gas jet. This is particularly advantageous with fuels with a very low calorific value. The oxygen content in the gas jet is therefore mainly determined by economic considerations and by the quality of the fuel used.

Preferably, the solid or liquid fuels are blown into the iron melt below the surface. Carrier gases such as, for example, air, nitrogen, carbon monoxide, an inert gas or the like are used for transport. However, it is also possible to feed the fuel above the surface of the melt.

The oxygen in the jet of gas blown in through the gas space and above the surface of the melt serves, in particular, for the combustion of part of the gas produced from the fuel. The actual oxygen supply for the gasification process, on the other hand, takes place favorably via blowing nozzles present under the surface of the melt. These may consist, for example, of a number of concentric tubes; a hydrocarbon is used on the outside in known manner in 8103451 4 · - · 5 __ - U manner, in order to protect the blowing nozzles.

The amount of oxygen supplied below the surface of the melt relative to the amount of oxygen supplied in the gas jet above the surface of the melt can be varied within arbitrary limits. For example, it is possible to supply B0% of the total oxygen with the gas jet from above and enter only 20% below the surface of the melt, or alternatively exactly 80% of the total amount of oxygen supplied to the iron melting reactor below 10 blowing the surface of the melt and feeding only 20% from above with the gas jet. However, it has been found that at least 10% of the total amount of oxygen supplied to the iron melt reactor must be blown with the gas jet on top of the surface of the melt in order to utilize the advantages of the invention in terms of the heat economy of the process . This amount can be increased to 100%. It has surprisingly been found that this oxygen from the gas jet serves for oxidation of the fuel in the iron melt. In the conventional operation with the iron melting reactor, about 90% of the total amount of oxygen is fed into the gas jet. The fraction fed from above is already kept as high as possible for economic reasons, because this fraction of the total quantity is generally under a lower pressure compared to the pressure required for the blowing nozzles present under the melting surface, is blown in.

Preferably, a number of gas jets are directed to the surface of the melt. Inflation takes place from a relatively great distance from the surface of the melt and the place where the gas jets strike the surface of the melt is approximately in the center of the surface of the melt. Decisive is a sufficiently large length (path) for the gas jets in the gas space above the surface of the melt. Normally, a distance between the nozzles of the gas jet and the surface of the melt should be maintained, at least approximately 2 meters. The blow nozzles are placed in the refractory lining in the top. n 8103451 <? * - 5 - th part of the iron melting reactor mounted. They can consist mainly of a single tube or, as for example when using technically pure oxygen, of two concentric tubes, mainly when air is blown. In the latter embodiment, the oxygen flows through the central tube and nitrogen, carbon monoxide, an inert gas, a hydrocarbon or the like is calculated in a small amount (0.1-5 $ based on the oxidizing agent) to protect the blowing nozzle through the annular space. gas).

The method according to the invention is preferably used in the preparation in an iron melt reactor of a substantially sulfur-free gas for combustion in boiler and heating installations, for example for the production of steam, starting from sulfur-containing fuels. The sulfur is taken up by a slag containing CaO in the iron melting reactor. The required slag formers, especially CaO, are preferably fed in powder form with the oxygen-containing gases introduced into the iron melt below the surface of the melt.

Mixing the slag formers with the fuels or separately introducing CaO with a carrier gas is also possible according to the invention. The slag formed with the ash constituents from the fuels accumulated therein can be removed protagonistically from the iron melting reactor or, in order to improve the heat balance, desulfurized in the liquid state according to German patent specification 25 20 5fik and substantially again in the form of a liquid form. iron melting reactor are added.

Application of the method according to the invention has produced, for example, depending on the fuel used, production gases with the following composition. For the gasification of 1 t coke with about 10 $ ash and a sulfur content of 1 $, about 2,000 ml air, which had been preheated at a temperature of 300 ° C, were melted under the surface in an iron melt.

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while simultaneously blowing 2H00 nr of air preheated at the same temperature on top of the melt. The iron melt had a temperature of about 100 ° C and a carbon \

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\ 8103451. 5-6 / 3 content of about 2%. Per ton of coke 5500 m gas consisting of about 25% CO, about 6% 00 ^, about 69%, about 0.002% sulfur with a temperature of 1X00 ° C were formed. The gas contained about 2 g / m 2 of dust and could readily be used in a steam boiler for firing.

When gasification of gas flame coals with J8% C, 5% Η, T% 0.5% ash, a gas was formed with the following composition: 19.0% CO, M% Hg, bt6% COg, 66.5% N2.

Low-energy, dried brown coal with 6.0 wt.% 10 C, h, 9 wt.% H, 23.6 wt.% 0.5, 5.9 wt.% Ash, .0 wt.% Sulfur and ... .. with a combustion value H of 5680 kcal (23780 kJ), which were gasified with air of 300 ° C in an iron melting reactor according to the method according to the invention, gave a gas with 21, b vol.% CO, 6.2 vol. .% Hg, 5 Λ vol · ·. # COg, 6.2 vol. # H ^ O, 60, T 15 vol. # Hg, 20 ppm sulfur and a calorific value of 806 kcal / nf * (3375 kJ / v? ). Approximately 9 kg of CaO / t coal were fed to the iron melting reactor for desulfurization.

The use of oxygen according to the invention has always proved to be favorable when the requirement is to prepare an energy-rich gas with a low Hg content or if particularly energy-poor fuels are used for the gasification in the iron melting reactor. Which carrier gases are used for the oxygen or whether pure oxygen may be used in the gasification in the iron melting reactor, is primarily determined on the basis of economic considerations and taking into account the use of the prepared gases. There are no technical problems in gasification and in balancing the energy balance of the process due to the partial combustion of the prepared gases in the gas space of the reactor 30 when using different oxygen-containing media when operating according to the invention is gone.

A further, particularly favorable embodiment of the invention consists in adding, for example, ore, to the melt in the reactor vessel, materials containing iron in bound or unbound form, in order to produce liquid iron (pig iron). -1 ... '8103451 «ί _3> - 7 - and prepare a gas at the same time. Accordingly, in this embodiment of the process according to the invention, the heat generated during the partial afterburning of the gases formed in the iron-melting reactor is at least partly used for the reduction of the iron-containing substances, in particular ore. In addition to the carbonaceous, solid or liquid fuels, as well as oxygen and slag formers, the iron melt in the reactor vessel is supplied with additional substances which contain iron at least partly in oxynisebic form, such as, for example, 10 ore. The essential economic advantage of this embodiment of the method according to the invention is that with a small technical effort ore is directly reduced by a relatively small amount of coal and at the same time produces a gas which can be used in many ways.

15 For the formation of 1 ton of iron by reduction of iron ore there are about 1.1 t of coal (composition about 78% 0.5% H, 3% H-0.5% ash, 5% 0 1% S, calorific value Hu 7500 kcal / m = 3 ^ 31 ^ -00 kJ / m). At the same time, an industrially applicable gas is produced with approximately a composition of 75% CO, I% CO ^, 20 1¼% Η ^, I% H ^ O with a calorific value of approximately 2100 kcal / m3 = 8790 kJ / m3.

The process according to the invention thus makes it possible to economically optimize the iron preparation in combination with the preparation of the gas in an iron melting reactor.

If, for example, such a process step is carried out without, as prescribed according to the invention, the transfer of energy from the partial afterburning of the gas formed in the iron melt, then using the same coal for the preparation of 1 t iron from iron ore, approximately 3 t coal would be 30 are required. The waste gas would then have a composition of approximately 70% CO, 1 $ C0, 27% H, 1% HO and a combustion heat Hu

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have about 2700 kcal / m-3 = 11305 kJ / m.

The further known multistage processes for the reaction

The production of iron ore and for the preparation of liquid iron, for example according to DE-A 2 01909, have the drawback that the

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. Gases generated due to their low combustion heat without cost-effective blending of energy-rich gases can only be used for purposes of minor importance.

Approximately 5 650 kg of coal is required in this process for the preparation of 1 ton of iron. This produces a gas with approximately 1 * 1% CO, 30% CCL, 18 HO, 10% H and an analysis <3 d.

heat Hu of 1100 kcal / m = 1 * 605 k <J / m.

In the process according to the invention the ore in the iron melt can be blown directly onto the melt via nozzles in the bottom or also from above. In a favorable embodiment of the invention, the supply of the ore takes place at least partly together with the oxygen blown to the melt. This is how it works. dusty ore already preheated and pre-reduced in the gas atmosphere, thereby increasing the thermal efficiency of the process. In order to further improve these effects, it may be expedient to use provisions in the nozzles for inflation which contribute to a mixing of the jet with the ore particles, for example by the jet emerging from the nozzle in a swirling motion.

As the materials to be used which contain iron at least partly in oxidic form, in addition to ore of all kinds, especially "pellets" and briquettes from incompletely reduced ore are suitable.

The method according to the invention can be special.

are advantageously applied in those places where it is possible to use the formed gas in the immediate vicinity as a fuel gas, for instance as a replacement for natural gas. The gas which has arisen in the process according to the invention and partly afterburned has, mainly because of the relatively high C0 content is about the same flame temperature as natural gas and can therefore be used without significant changes to the furnaces as a replacement for natural gas. are used.

The following example describes the application of the method according to the invention in a converter.

1h 0 3 4 5 1 e - 9 -shaped reaction vessel with 6o when melting. In the bottom of the converter are placed 10 nozzles with an internal diameter of 28 mm. Carbon is blown through 2 of the nozzles at a rate of 350 kg / min, whereby the carrier gas is nitrogen, 5 carbon dioxide or reduction gas from the converter itself can be used 3. Oxygen is blown in together with ore through 3 nozzles, while oxygen is supplied to the other 5 nozzles, in part together with slag formers, such as lime, through a side, in the upper conical part 10 of the converter applied nozzle, about 50% of the oxygen is melt-fed. With coal of the aforementioned composition and with an ore containing 85% Fe 2, 20 tons of iron with a carbon content of about 3% are prepared per hour. The oxygen consumption for the gasification of a ton of coal with the simultaneous melting of 1Λ50 kg of ore is 580 m. A coal gas or fuel gas with the aforementioned composition is produced (approximately 75% CO, I% CO2, \ b% ^ 1 ° 2g0 and with a calorific value Hu of approximately 8790 kJ m3 (2100 kcal / m3)).

It is also within the scope of the invention to design the reaction vessel in such a way that it simultaneously serves as a converter for preparing direct steel therein. For this purpose, the carbon content of about 2 to 3%, as it arises during normal operation of the iron melting reactor, is always lowered to about 0.05% before parting off, and a part-portion of about 20 tons is cut off. An amount of about 50 t remains in the converter, which is then slowly recovered with a small excess of coal with the simultaneous blowing in of oxygen and coal, until the carbon content of 2 to 3% desired for continuous operation. In this mode of operation, it has further been found to be effective to remove the slag from the iron melt before the carbon is completely removed by freshening, ie approximately at a residual coal cool content between 0.5 and 2 fa. slag that is in equilibrium with the repelled steel melt then remains in the converter.

The method according to the invention is hereinafter described

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-10- explained in more detail on the basis of an exemplary embodiment on the basis of the drawing.

The drawing shows a longitudinal section through an iron melting reactor spring. A pear-shaped, gas-tight sealed reactor vessel 20 is approximately half filled with a liquid iron melt 21; the surface of the melt 22 is therefore approximately half the height of the reactor vessel 20. In the bottom of the reactor vessel there is a hay nozzle 23 for introducing finely divided coal 2h. Furthermore, in the bottom of the reactor 10 of 20 an oxygen oxygen nozzle 25, through which nozzle, separated from the nozzle 23, oxygen is introduced into the liquid iron melt 21. In the practical embodiment, this oxygen blowing nozzle 25 is surrounded by an annular gap for the supply of hydrocarbon or the like, so as to protect the blowing nozzle 15.

In the upper part of the converter there are two blowing nozzles 26 and 27, which are inserted through the wall of the reactor vessel 20. Air 28 is supplied to these blowing nozzles, which are blown in the form of jets which are directed approximately 20 to the center of the surface of the melt 22. The outlet openings of the nozzles 26 and 27 are located approximately 2 meters above the surface of the melt 22.

The gas jets 29 pass through the gas space above the surface 25 of the melt 22 and, by their jet action, entrain part of the gas 31 already formed by gasification of the coal 2k. Part of this gas 31 is burned by the oxygen content of the gas jets 29. The combustion heat e is controlled via. the surface of the melt 22 fed to the iron-melt 21.

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Claims (12)

1. Process for the preparation of. gas in an iron melting reactor, in which there is a liquid iron melt, to which carbonaceous, solid or liquid fuels are fed and on the surface of which a pass jet consisting of at least partly oxygen, where the fuels gasify, is blown in the gas space above collect the surface of the melt and be discharged therefrom, characterized in that the gas jet is blown through the gas space above the surface of the melt and sucks in gas formed as it passes through the gas space, partially burns and thus entrains to the surface of the melt, that the heat generated by the combustion of the formed gas is transferred to the iron melt. Method according to claim 1, characterized in that the gas jet directed at the surface of the melt consists of technically pure oxygen. 3. A method according to claim 1, characterized in that the gas jet blown through the gas space and on the surface of the melt 20 consists of air. 1 *. Method according to any one of the preceding claims, characterized in that in addition to the gas jet blown through the gas space and on the surface of the melt below the surface of the melt, an at least partly oxygen-containing gas is introduced into the iron melt *. Process according to claim U, characterized in that the amount of oxygen blown onto the surface of the melt is at least 10% of the total amount of oxygen supplied to the iron melt reactor. A method according to any one of claims 1 to 5, characterized in that the gas jet directed through the gas space and on the surface of the melt is preheated. 7. A method according to any one of the preceding claims, characterized in that the gas introduced below the surface of the melt is preheated. 8103451-12- "V 8. A method according to any one of the preceding claims, characterized in that the fuel is introduced into the iron melt below the surface. A method according to any one of the preceding claims, characterized in that the length of the gas jet in the gas space is greater than 2 meters. 10. A method according to any one of the preceding claims, characterized in that in the iron melting reactor gas and liquid iron are simultaneously formed from substances containing iron, at least partly in oxidic form. 11. Process according to any one of the preceding claims, characterized in that as substances containing iron at least partly in oxidic form, in particular ore, partly for reduced ore, such as pellets and / or briquettes, are fed to the iron melt reactor. 12. Process according to any one of claims 1-11, characterized in that the substances containing iron in at least partly oxidic form, in particular ore, are melt-blown together with the oxidizing gas, mainly oxygen. Process according to any one of the preceding claims, characterized in that the carbon-containing iron formed into steel is freshened in the reactor vessel. 25 0 3 4 5 1. 0