WO1993020245A1

WO1993020245A1 - Combined process for generating metallurgical coke and sponge iron

Info

Publication number: WO1993020245A1
Application number: PCT/EP1993/000735
Authority: WO
Inventors: Gerd Nashan; Klaus Wessiepe; Heinrich Wilhelm Gudenau; Georg Lange
Original assignee: Still Otto Gmbh
Priority date: 1992-03-27
Filing date: 1993-03-25
Publication date: 1993-10-14
Also published as: DE4210003A1; AU4260793A

Abstract

A combined process is disclosed for generating metallurgical coke and sponge iron or liquid iron. The coal used is at first coked and the crude gas thus obtained is processed at a high temperature. The crude hydrogen and carbon monoxyde thus obtained are used for the direct reduction of iron ore to sponge iron.

Description

Combined process for the production of metallurgical coke and sponge iron

description

The invention relates to a method for producing metallurgical coke and sponge iron. The connecting link is raw hydrogen, which is preferably supplied to the direct reduction system in a direct thermal combination, that is to say hot. The hot iron sponge can be used to produce crude steel in a thermal bond, either directly or by way of pig iron.

Conventional coking of hard coal produces metallurgical coke and a raw gas which, in addition to approx. 60% H ₂ and approx. 25% CH _4, also have higher aliphatic hydrocarbons (C ₂ H ₆ , C ₃ H ₈ etc.), aromatic hydrocarbons such as benzene, naphthalene and tar as well as ammonia and sulfur compound. These by-products are summarized under the term "carbohydrates" because they have been highly valued in the past.

In the meantime, however, the profit situation has deteriorated so much that it only slightly reduces the production costs of the main product coke. Another important aspect is the avoidance of environmental / occupational health and safety problems associated with the extraction and handling of the carbon materials.

The aim of the present invention is therefore a coking process or a process structure associated therewith, in which as much as possible the entire carbon introduced with the insert coal is converted into metallurgical coke. In addition to this increased coke output compared to conventional mode of operation, a largely uniform gas is to be generated at the same time, which, compared to previous uses of coke oven gas, is of higher quality or can be used universally, also as a raw material. Such a gas, referred to here as "raw hydrogen ^M , is produced by post-treatment of the raw gas and should contain, for example, 80% H ₂ .

The economic higher valuation of raw hydrogen compared to its calorific value results from the fact that it can be fed, for example, to a direct reduction system for producing sponge iron. Such direct reduction plants have so far not been able to establish themselves in industrialized countries because they have to be preceded by complex catalytic reformers in which methane has to be converted with steam or carbon dioxide to form a reducing gas consisting of hydrogen and carbon monoxide. When using raw hydrogen, the reformer is replaced by a much cheaper and thermally cheaper gas heater of known type.

The solution to the problem is that feed coal is first coked in a conventional coke chamber, but preferably in a jumbo coking reactor, and the raw gas obtained is subjected to a high-temperature treatment in a subsequent process stage in such a way that the carbohydrates, such as tar, Benzene, naphthalene, ammonia, etc., are either converted to ﬁ xed carbon and hydrogen or else to kohiene monoxide and hydrogen, and the raw hydrogen obtained is fed to the direct reduction of iron ore to sponge iron.

In the process according to the invention, the aftertreatment is preferably carried out at a temperature in the range from 1,000 to 1,500 ° C., in particular 1,100 to 1,300 ° C. At this temperature, an extensive conversion of the raw gas into hydrogen is guaranteed, especially when the raw gas is oxygen or oxygen-containing gases are metered in, which promote the decomposition of the hydrocarbons in CO and H ₂ . The tendency towards hydrogen formation is also promoted by the use of large-scale coking chambers, so-called jumbo reactors with a chamber width of approx. 85 cm. This is presumably due to the fact that in such coking chambers there is a particularly intensive and long contact of the raw gas with the hot coke, which supports the decomposition of the carbohydrates into carbon monoxide and hydrogen. The combination of such a jumbo reactor with the high-temperature treatment according to the invention makes it possible, in particular, to obtain raw hydrogen with a methane content of significantly less than 8%.

The high-temperature aftertreatment according to the invention takes place in particular at a temperature in the range from 1,000 to 1,300 ° C., the aftertreatment chamber, for example, with a. Coke fill, ceramic packing or a lattice can be equipped. In these cases, it is expedient to provide two parallel chambers, one of which is charged with the raw gas at the set temperature while the parallel chamber is being regenerated, ie. H. freed of separated carbon by passing oxygen-containing gases and thereby brought back to the working temperature.

Alternatively, it is possible to provide the high-temperature treatment chamber as a pebble-bed reactor with rotating ceramic heat carriers through which the raw gas flows and which convert it. Balls loaded with carbon are drawn off, regenerated and used again at the required working temperature.

A further possibility is the partial combustion of the raw gas with oxygen or gases containing oxygen in a continuous process with retention of H ₂ and CO. The partial combustion provides the energy required for the thermal cracking process.

REPLACEMENTB The raw hydrogen produced can be cooled or heated to the temperatures required for the subsequent steps in each process stage. Thus it can be expedient to lower the gas temperature to such an extent that the raw water material can be conveyed in a suction device / compressor.

Desulfurization can e.g. B. by passing over an iron oxide or dolomite fill. Desulfurization in other process stages, as also described below, is also possible.

The raw hydrogen which is optionally generated and desulfurized is expediently fed to the direct reduction system at the process temperature in order to use the energy contained therein for the reduction process. However, it can be expedient - especially if a longer distance has to be covered to the direct reduction system - to cool the raw hydrogen first in order to use the heat contained therein on the other hand and then to use the cold raw hydrogen before or when it is introduced into to heat up the direct reduction system again.

The raw hydrogen used in the direct reduction of iron ore is generally used only very incompletely, so that the residual gas emerging from the reduction still contains considerable amounts of usable gases (h ₂ , CO, CH ₄ ). Here it makes sense to add this residual gas to the raw hydrogen after appropriate treatment (separation of water and possibly CO ₂ , enrichment of H ₂ and CO at a cost of CH ₄ ) and recycle it to direct reduction.

The direct reduction of the iron ores used is carried out in a known manner in shaft furnaces, static or circulating fluidized bed furnaces of known construction. As a rule, sponge iron is produced, which can easily be converted into high-quality steel either directly or by pig iron. The processing of the iron sponges in cold or hot condition corresponds to the state of the art.

According to FIG. 1, the raw gas stream (2) generated in the coking chamber (1) is fed to a high-temperature aftertreatment system (3). The high-temperature aftertreatment system (3) consists of two alternating reactors (thermal crackers). While in the reactor (3a) the carbohydrates from the coking chamber (1) and the raw gas stream (2) are broken down into hydrogen and fixed carbon, the reactor (3b) is heated to a temperature between 1,100 and 1,300 ° C, preferably about 1,200 ° C. Coke or ceramic fillers, for example, serve as heat transfer media for the cyclically operating reactors.

The cyclically operating reactors can be replaced by a continuous reactor which operates on the principle of the pebble bed reactor with ceramic heat transfer media which are circulated at the aforementioned temperatures.

Another alternative is not shown in Figure 1 partial combustion of the coal by-products with oxygen or 0 ₂ -enriched air.

In the coke-filled treatment chambers (3) the combustion can only take place up to the CO. The exhaust gases (6) are suitable as heating gases for consumers at various points in the overall process. In Figure 1, use as an additional fuel for gas heating (101) is provided.

Caused by the cyclical operation of the aftertreatment chambers (3a) and (3b), the temperature of the raw hydrogen (5) fluctuates. In order to be able to convey the raw hydrogen to the direct reduction system (100) and to compress it to the pressure of approximately 5 bar, for which the heating gas compressor (8) is provided, the temperature of the raw hydrogen must be reduced, in particular peaks must be reduced. This is done in a heat exchanger (7), the heat being given off to a partial stream of the recycle gases (117) of the direct reduction system.

The hot compressed raw hydrogen still contains all the sulfur that was contained in the raw gas (2).

It is indeed possible to leave the sulfur compounds in the raw hydrogen and thus to transfer a part of the sulfur into the sponge iron and out of it into the liquid pig iron or into the liquid raw steel and then to desulfurize the liquid phase, for example with magnesium and / or calcium carbide. However, desulphurization in the gas phase in the desulphurization tower (10) filled with iron oxide or dolomite appears to be more advantageous according to known processes.

If the raw hydrogen is to be sent to the direct reduction system over a longer distance, a raw hydrogen cooler (11) can be provided. The raw hydrogen, if not already desulfurized, could be subjected to a particularly environmentally friendly desulfurization to obtain elemental sulfur.

There is also the possibility of desulfurization elsewhere. Since the iron sponge produced during the reduction is discharged at approx. 800 ° C, its sulfur content is relatively low. The sulfur then leaves the direct reduction shaft (102) via the residual gas (112). If the raw hydrogen has not already been desulphurized, desulphurization of the pure gas (114) after washing (103) would be advantageous. If a chemical wash with KHC0 _{3 is} used, C0 ₂ would also be washed out, which may be desirable.

If you accept sulfur enrichment in the reducing gas, desulfurization is also possible in the area of the heating gas flow (118) or via the exhaust gases of the gas heater (101), here via S0 ₂ . The direct reduction system (100) essentially consists of the gas heater (101), the direct reduction shaft (102) when using piece or a fluidized bed reactor (not shown) when using fine ore, the washer cooler (103) and the recycling compressor (104).

In the following example, the raw water flow comes from a jumbo coking reactor with a chamber width of 85 cm. After the raw gas has been treated by one of the abovementioned methods, the compressed raw hydrogen (12) has, for example, the composition:

100

with a calorific value of Hu = 12.1 MJ / Nm ³ . In the event that the raw water stream has not been desulfurized, the sums of H ₂ + H ₂ S = 82% and CO + COS = 6%.

A lumpy or fine-grained hematite is used as ore (105)

62.2% total Fe and 2.5% gait.

From this, lumpy or fine-grained sponge iron (106) is produced with a metallization of 90% and the composition:

93.33% Fe total thereof 84.00% Fe metallic

0.5% C, mainly as Fe ₃ C 2.67% residual oxygen 3.50% gait. 1,369 kg lump or fine ore of the abovementioned composition are used per ton of iron sludge of the specified composition. The use of raw hydrogen (12) is 700 Nm ³ / t sponge iron (ES), corresponding to 8.47 GJ / tES.

All quantities for the gas circuit shown below relate to 1,000 kg of sponge iron of the above composition.

700 Nm ^{3 of} raw hydrogen (12) are mixed with 1,529 Nm ^{3 of} recycling gas (109) of the composition:

56.9% H ₂ 14.2% CO

5.5 -s CH ₄ 10.7% C0 ₂

3.0% H ₂ 0

9.7% N ₂

100.0%

mixed and give 2,229 Nm ^{3 of} cold reducing gas (110), which after heating in the gas heater (101) has a temperature of 950 ° C and a composition of:

61.6% H ₂ 18.4% CO

4.3% CH ₄

1.8% C0 ₂

6.2% H ₂ 0

7.7% N ₂

having. The amount (111) of hot reducing gas is 2,296 Nm ³ / tES. The increase in the amount of cold reducing gas (110) to hot reducing gas (111) of 67 Nm ³ results from the conversion of methane to hydrogen and carbon monoxide when the gas was heated in the gas heater (101).

543 Nm ³ CO + H _{2 are} consumed for the reduction of the hematite to sponge iron with 90% metallization and 0.5% carbon in the sponge iron

The residual gas (112) leaving the reduction vessel (102) has the following composition:

The amount is 2,287 Nm ³ / tES. The equilibrium value:

C0 ₂ x H ₂

Kw = = 1.50

H ₂ 0 x CO

corresponds to a temperature of 706 ° C.

The residual gas is subsequently removed in the washer cooler (103). known methods dedusted. The water vapor content of the blast furnace gas is reduced to 3% by separating 374 kg of condensate (113) by injecting wash water. The clean gas (114) then has the following composition:

100.0%

The amount is 1,820 Nm ³ / tES. Of this, 84% = 1,529 Nm ³ / tES are compressed as recycle gas (116) in the compressor (104) and mixed with the raw hydrogen (12), as already described above.

Part of the recycle gas (116) serves as cooling gas (117) for the raw hydrogen cooler (7). This gas stream (117) is combined with the larger part of the recycle gas (115) to form the recycling gas stream (109).

The remaining 16% of the clean gas (114) serve as heating gas (118). A branch is always required to limit the nitrogen content in the system. The branch of 16% has been selected in the example so that the system does not require heating agents from external sources.

If the sponge iron is to be processed directly into crude steel, it is advantageous to discharge the sponge iron (106), which is approx. 800 ° C hot, and hot in a hot state using water-cooled screws (107) or in hot containers (108) under a protective gas atmosphere to be transported to the steelworks (109) and processed there to make crude steel. In the case of sponged iron sponges, processing into pig iron is recommended.

Hot briquetting (110) of the sponge iron is advisable for transport over long distances. Melting the sponge iron into a cupola or blast furnace is more energy-efficient, ecological and, depending on the location, also more economical.

In this case, cooling of the sponge iron is required, which takes place in the lower part of the direct reduction shaft. Since cooling gases (202) are blown into the appropriately designed shaft lower part (201), and the heated cooling gas

(203) below the entry level of the reducing gas. The heated cooling gases (203) are compressed

(204) compressed and cooled in a heat exchanger (205). The now cold cooling gases (202) are recycled in the manhole base.

Fewer base supports, and then mainly limestone instead of quicklime, and less primary energy are required for steel production via pig iron / LD and less steel energy than for steel production in the electric arc furnace.

The more gait the iron ore used contains, the more important the advantages of the pig iron route.

Claims

Combined process for the production of metallurgical coke and sponge iron

1. Combined process for the production of metallurgical coke and sponge iron, so that the charcoal is first coked and the raw gas obtained is subsequently subjected to a high-temperature treatment, and the raw hydrogen obtained is fed to the direct reduction of iron ore to sponge iron.

2. The method of claim 1, d a d u r c h g e k e n n ¬ z e i c h n e t that the high temperature treatment is carried out at a temperature of 1,000 to 1,500 ° C in a bed of material.

3. The method according to claim 1 or 2, dadurchge ¬ indicates that the coking in a jumbo reactor of at least about 85 cm in width and the raw gas leaving this reactor by the Hochtempera¬ treatment in raw hydrogen containing Kohienmo¬ oxide and Methane of less than 8% is converted.

4. The method according to any one of claims 1 to 3, characterized in that the raw gas for Hochtem¬ temperature treatment by a.hot coke bed, a lattice work or ceramic filler at a temperature of 1,100 to 1,300 ° C is performed.

5. The method of claim 4, d a d u r c h g e k e n n ¬ z e i c h n e t that the high temperature treatment is carried out in one of two parallel chambers, each of which one is regenerated by introducing oxygen-containing gases with combustion separated carbon.

6. The method according to any one of claims 1 to 3, so that the raw gas is passed through a pebble-bed reactor, the rotating ceramic balls of which are heated to a temperature in the range from 1,000 to 1,300 ° C.

7. The method according to any one of the preceding claims, since ¬ characterized in that the carbohydrates contained in the raw gas are continuously converted into CO and H ₂ by partial combustion with oxygen or oxygen-containing gases.

8. The method according to any one of the preceding claims, that the raw water after the high-temperature treatment is cooled to a temperature which permits conveyance in a suction device / compressor.

9. The method according to any one of the preceding claims, that the raw hydrogen is desulfurized, preferably by passing it over an iron oxide or dolomite bed.

10. The method according to any one of claims 1 to 9, characterized in that the raw hydrogen is fed to the direct reduction system with process temperature.

11. The method according to any one of claims 1 to 9, that the raw hydrogen is fed to the direct reduction plant in a cold state.

12. The method according to any one of claims 1 to 11, d a ¬ d u r c h g e k e n n z e i c h n e t that the Rohwasser¬ hydrogen is added to admixture of recycle gas and preferably heating to 950 ° C to reduce lumpy iron ores in shaft furnaces of a known type.

13. The method according to any one of claims 1 to 11, d a ¬ d u r c h g e k e n n z e i c h n e t that the raw hydrogen after admixing recycle gas and optionally heating to reduce fine ores in a reactor which works according to the static or cyclic fluidized bed process, is performed.

14. The method according to any one of the preceding claims, that the iron sponge is discharged hot, transported hot and processed to pig iron or crude steel using its physical heat.

15. The method according to any one of claims 1 to 13, d a ¬ d u r c h -g e k e n n z e i c h n e t that the Eisen¬ sponge is discharged hot and briquetted in the hot state.

16. The method according to any one of claims 1 to 13, so that the iron sponge is cooled in the lower part of the reduction unit.