DE2431537A1 - Direct redn of iron ore to sponge iron in shaft furnace - with redn. gas obtd from high-pressure gasification of coal - Google Patents

Abstract

Process is for direct redn. of lumps or agglomerate contg. iron oxide in a shaft furnace using a counter-current of hot gas contg. CO and H2 obtd. by the gasification of solids contg. carbon with gases contg. O2 and steam at high pressure. The gases contg. O2 and steam are fed at 10-100 atmos. in counter-current to the solids contg. carbon, and steam is removed from the resulting gases by indirect cooling, so the steam condenses, a gases contg. O2 are added to the cooled gases to cause further cracking; and scrubbing is then used to remove CO2 and H2S; the reducing gas thus obtd. is heated to 700-1000 degrees C., esp. 800-900 degrees C. and fed to the shaft-furnace. The gases contg. O2 pref. consist of technically pure oxygen. The reducing gas obtd. has a high H2 content and is free from sulphur and soot; the cost of the sponge-iron produced is reduced by this process.

Description

Method of direct reaction with reduced gases The invention relates to a process for the direct reduction of lumpy or agglomerated iron oxide alloys Materials in a reduction shaft furnace using reducing agents containing CO and 112 hot gases in countercurrent between the gas and the feed to generate the reducing Gases by gasifying solid carbon carriers with gases containing oxygen and water vapor under increased pressure.

It is known to use lumpy or agglomerated iron ores in a shaft furnace with the help of reducing gases to reduce sponge iron, the reducing Gases by gasifying solid carbon carriers with technically pure oxygen and steam can be produced by direct current gasification (DT-PS 872 952, DD-OS 1 911 Q52).

These processes are based on the fact that the gasification in countercurrent as a result undesirable tar constituents in the reducing gas is unsuitable and that only one Gasification operated in cocurrent results in a gas suitable for direct reduction. The cocurrent gasification, however, has the disadvantages that only fine-grained carbon carriers can be used, the gases generated with a high temperature and require a lot of oxygen, and the ash is in liquid form and therefore carries and destroys a lot of thermal energy. The gases also contain an undesirably high proportion of CO, so that for setting a high Proportion of H2 in the gasification gaseous hydrocarbons have to be added.

The gases contain sulfur, so the sponge iron produced either desulfurized or a desulfurizing agent added during the reduction process got to.

The invention is based on the object of avoiding these disadvantages and to generate a reducing gas that is high in H2 free from Sulfur and soot is and reduce the cost of the sponge iron produced.

This object is achieved according to the invention in that the Gasification in countercurrent between the direction of movement of lumpy or agglomerated solid carbon carriers and the direction of flow of the oxygen-containing gases and the water vapor takes place under a pressure of 10-100 atmospheres, from the generated Gases of the water vapor is largely condensed out by indirect cooling, the Subsequent cleavage of cooled gases with the addition of oxygen-containing gases the gases escaping from the subsequent cleavage are largely in a scrubbing stage are freed of C02 and H2S, the reducing gases to a temperature of 700 - 100,000, preferably 800-900 ° C, heated and fed into the reduction shaft furnace will.

The solid carbon supports can be in lump form or in agglomerated form Form, such as in the form of briquettes or pellets, can be used. As oxygenated Gases can be air, oxygen-enriched fragrance or technically pure oxygen used will.

The cooling for condensation of the water vapor takes place at a temperature which is below the dew point at the present pressure. The afterburning takes place at temperatures of about 9000C. The leaching of C02 and 2S takes place conveniently together in a hot potash wash. It can, however other suitable cleaning methods can also be used.

A preferred embodiment is that as oxygen-containing Gases technically pure oxygen is used. This makes the gas volume considerable reduced, there is little fiber carried and treated, and the Apparatus dimensions can be kept smaller. The content of oxidizing Components (C ° 2 + 1120) and neutral components (N2 + CH4) in the reducing Gases is less than 10, with the oxidizing components being less than 6%.

Another preferred embodiment is that the washed reducing gases with a partial flow of emerging from the reduction shaft furnace and cleaned exhaust gases are mixed. The admixture takes place in particular, when the technically pure oxygen has a high oxygen content. To avoid the enrichment of the nitrogen content in the circuit is a corresponding partial flow of the exhaust gas from the P-reduction shaft furnace is not mixed in and can be used as fuel, for example used.

By adding a partial flow, the reducing constituents are removed used again. When the technically pure oxygen has a higher nitrogen content contains, it makes more sense to use the exhaust gas as fuel. The limit of the The nitrogen content depends largely on the cost of the oxygen and for the Cleaning the exhaust gases.

A preferred embodiment is that the gasification under a pressure of 20-30 atm. Good gasification occurs at these pressures and the effort in terms of printing technology is relatively low.

A preferred embodiment is that from the condensation exiting cooled gases before entering the secondary cleavage by indirect Heat exchange to a temperature of 200 - 6000C. This will be favorable conditions for the subsequent cleavage are achieved and part of the exhaust gas can be used of the reduction shaft furnace can be used as fuel in the system.

A preferred embodiment is that the subsequent cleavage oxygen-containing gases used before entry through indirect heat exchange This means that the same advantages occur as with the heating the condensation escaping gases.

A preferred embodiment consists in the fact that the and H2S cal escaping gases by indirect cooling largely from water vapor to be freed. Here, too, the cooling takes place below the dew point of the water vapor at the present pressure. The water content is lowered below 1 ?:.

If the reduction is carried out under normal pressure or with lower pressure ^ than the pressure under which the reducing gases are present, there is an embodiment in that the washed reducing gases are expanded in a de-steaming turbine will. This allows electrical energy to be obtained. A preferred embodiment is that a partial flow of the washed reducing gases at the bottom of the reduction shaft furnace as cooling gas for the reduced sponge iron will. If the reducing gases are part of the exhaust gas from the reduction shaft furnace is admixed, part of this mixture is used as a cooling gas. This takes place a simple cooling of the sponge iron and its heat content is in a simple manner used for the system.

Another preferred embodiment is that at least a partial flow of the exhaust gas emerging from the reduction shaft furnace with combustion is used as a heating medium in the system. Either the unpurified substream is used or all exhaust gas is used.

As a result, its heat content can be used in the system.

The invention is based on the flow chart in more detail and example explained.

In #### pressure gasifier 1, over 2 21.4 t / h of lumpy coal are added 10% ash and 5% water are charged. Via line 3, 9800 Nm5 / h are technical pure oxygen and water vapor introduced via line 4. The pressure in the pressure carburetor 1 is 22 atm. The gases generated enter the via line 5 at about 6000C Cooler 6. The table is delivered in solid form.

Xer t The gases largely freed from water vapor are heated in the heat exchanger 7 to about 3500C and in the Nachspaltwng 8 headed. 4000 Nm3 / k of technically pure oxygen are used in the heat exchanger 10 heated and passed at about 250 ° C via line 9 into the post-cleavage 8. The gases exit the secondary cleavage 8 at around 20 atmospheres and 90,000 are in the cooler 11 largely freed of water vapor, go through the caustic cooker 12, where the sensible heat can be used to heat the washing liquor and are washed in the washing stage 13 with hot potash liquor, whereby C02 and H2S can be largely removed. The cleaned gases enter the at about 115 ° designed as a Sconomizer cooler 14, in which the water vapor largely condenses out will. The water vapor content is below 1% 0.

The reducing gases can either be in the energy saving turbine 30 desn> 2nt if the reduction is carried out under low pressure, or can be passed without relaxation when the reduction is high pressure is carried out.

The reducing gases are cleaned with a partial flow of the Exhaust gases from the reduction shaft furnace 17 are mixed.

A partial flow of about 56,000 Nm³ / h is in the heat exchanger 15 heated to about 85,000 and via line 18 into the reduction zone of the reduction shaft furnace 17 initiated.

A partial flow of about 20,000 Nm³ / h is used as cooling gas via line 16 initiated at the bottom of the shaft furnace. In the shaft furnace 17 are at 19 62.5 t / h iron ore pellets used and drawn off at 20 41.25 t / h sponge iron.

The exhaust gas is drawn off at about 365 ° C. via line 21.

A partial flow is washed with water in a direct cooler 22, whereby the water vapor and dust content are largely removed. In the washer 23 is the C02 e.g. by washing hot potatoes or washing with ethanol amines to a large extent removed. The cleaned exhaust gas is compressed in the cycle compressor 24 and admixed to the reducing gases via line 25. The remaining partial flow of the Exhaust gases from line 21 are passed into the heat exchanger 15 via line 25 and there ##### burned with additional fuel and burner air. The exhaust gases from the heat exchanger 15 are fed into the steam boiler 27 and used to generate steam.

Cooling water is fed to the pressure gasifier 1 via line 28 is withdrawn as steam via line 29.

The composition of the gases by volume is as follows: A B C D E F G H J C02 29.0 29.0 24.7 0.1 0.1 0.1 14.1 17.0 0.1 CO 21.0 21.0 30.6 40.9 40.5 32.0 18.2 22.0 26.5 H2 38.0 38.0 42.1 56.2 55.6 57.9 40.5 49.0 59.0 CH4 10.0 10.0 1.6 2.1 2.1 4.4 4.0 4.9 5.8 2 / C3 1.0 1.0 -112S 0.5 0.5 0.5 - - - - - -N2 0.5 0, 5 0.5 0.7 0.7 2.7 2.7 3.3 4.0.

total 100 100 100 100 99 97.1 79, 96.2 95.9 dry 1120 65.0 10.0 19.8 10.6 1.0 2.9 20.5 3.8 4.6 Total wet 165 110 119.8 110.6 100 100 100 100 100 Sm) / h 36280 36280 39588 29638 - - - - -dry Nm³ / h wet 59860 39900 47435 32782 29640 76600 68413 56541 46960 BLlrch the invention The following advantages are achieved: Due to the pressure gasification in countercurrent, ### die Ash and the generated gas with lower temperatures from the gas generator, and the consumption of oxygen for gasification is lower. The ashes are in solid form so that the heat of fusion of the laundry does not cool down must be destroyed and lost. The thermal efficiency of the gas generator is better. The reducing gas is free from soot and others after the post-treatment solid components, it is also free from H2S, COS and other sulfur carriers, which can cause sulphurisation of the sponge iron. Despite the post-split, in which the carbon particles contained in the gas and the lt; ethane with the Oxygen CO, C02 H2 and H20 form is the oxygen requirement for the generation of one Nm3 of CO and H2 less than with the known methods of co-current gasification. The condensation of the water vapor takes place at higher temperatures and can therefore can be used thermally for the process. Fluctuations in moisture content the coal or coal quality can through the downstream gas treatment steps be balanced so that the reducing gas produced always has a constant composition Has. The reduction can be done under normal pressure or without additional expenses be carried out under increased pressure.

Claims (10)

Claims 1)) Process for the direct reduction of lumpy or agglomerated materials containing iron oxide in a reduction shaft furnace using CO and H2 containing reducing hot gases in countercurrent between gas and feed with generation of the reducing gases by gasification of solid carbon carriers with oxygen-containing gases and water vapor under increased pressure, characterized in that that ws the gasification in countercurrent between the direction of movement of lumpy or agglomerated solid carbon carriers and the direction of flow of the oxygen-containing Gases and water vapor under a pressure of 10-100 atü takes place from the generated Gases of the water vapor is largely condensed out by indirect cooling, the Subsequent cleavage of cooled gases with the addition of oxygen-containing gases the gases exiting from the post-splitting are largely in a slash step are freed from C ° 2 and 2, the reducing gases to a temperature of 700-1000 0, preferably 800-900 0C, and fed into the reduction shaft furnace will. 2) Method according to claim 1, characterized in that the oxygen-containing Gases, technically pure oxygen is used. 3) Method according to claims 1 and 2, characterized in that that the washed reducing gases with a partial flow of from the reduction shaft furnace emerging and cleaned exhaust gases are mixed. 4) Method according to claims 1-3, characterized in that the gasification takes place under a pressure of 20 - 30 atmospheres. 5) Method according to claims 1-4, characterized in that the cooled gases emerging from the condensation before entering the Subsequent cleavage through indirect heat exchange to a temperature of 200 to 6000C be heated. 6) Method according to claims 1-5, characterized in that the oxygen-containing gases used in the post-splitting before entering through indirect heat exchange. 7) Method according to claims 1-6, characterized in that the gases emitted from the CO2 and H2S scrubbing are largely due to indirect cooling earth freed of water vapor. 8) Method according to claims 1-7, characterized in that the washed reducing gases are expanded in an expansion turbine. 9) Method according to claims 1-8, characterized in that a partial flow of the washed reducing gases at the bottom of the reduction shaft furnace is introduced as cooling gas for the reduced sponge iron. 10) Method according to claims 1-9, characterized in that at least a partial flow of the exhaust gas emerging from the reduction shaft furnace is used under combustion as a heating medium in the system.