Process of producing a mixture of iron ore and low-temperature coke

Abstract

Granular coal and preheated granular iron ore are charged into a low-temperature carbonization reactor, in which temperatures in the range from 800 to 1050 ° C. are produced by supplying gas containing oxygen and by partial oxidation of the components of the coal. In the low-temperature carbonization reactor, the granular solids are maintained in a turbulent movement. From the upper region of the reactor, hot exhaust gas is supplied to a solids separator. The granular iron ore is preheated by means of the hot exhaust gas and hot, granular mixture of iron ore and low-temperature coke is withdrawn as product from the reactor and/or from the separator. The low-temperature carbonization reactor may be designed as fluidized-bed reactor or as pneumatic conveyor section. The granular mixture of iron ore and low-temperature coke is suitable e.g. for a melt reduction process.

Description

[0001] This invention relates to a process of producing a hot, granular mixture of iron ore and low-temperature coke.

[0002] It is the object underlying the invention to produce the above-mentioned mixture in an inexpensive way. The ore-coke mixture should be suitable in particular for use in a subsequent melt reduction process.

[0003] In accordance with the invention, this object is solved in that granular coal and preheated granular iron ore is charged into a low-temperature carbonization reactor, in which temperatures in the range from 800 to 1050° C. are produced by supplying gas containing oxygen and by partial oxidation of the components of the coal, the granular solids being maintained in a turbulent movement and being supplied from the upper region of the reactor to a solids separator, from which a hot exhaust gas is withdrawn, that the granular iron ore is preheated by means of the hot exhaust gas, and that a hot granular mixture of iron ore and low-temperature coke is withdrawn as product from the reactor and/or from the separator.

[0004] The low-temperature carbonization reactor may be designed e.g. as fluidized-bed reactor or as pneumatic conveyor section. Usually, the pressure in the low-temperature carbonization reactor lies in the range from 1 to 10 bar and preferably 2 to 7 bar.

[0005] Expediently, highly volatile coal, also lignite, is supplied to the low-temperature carbonization reactor. The coal may also contain water. The coal supplied to the low-temperature carbonization reactor has grain sizes up to about 10 mm and preferably up to not more than about 6 mm; the grain sizes of the iron ore lie in the range up to 10 mm and preferably up to 6 mm. In the product of iron ore and low-temperature coke, the weight ratio Fe:C usually lies in the range from 1:1 to 2:1.

[0006] Embodiments of the process will be explained with reference to the drawing. The drawing shows a flow diagram of the process.

[0007] To a low-temperature carbonization reactor (1) granular coal is supplied through line (2) and preheated granular iron ore is supplied through line (3). Air for the partial oxidation in the reactor (1) and for the fluidization and transport of the solids is supplied via line (5) and enters the reactor (1) through a distributor (6). Secondary air is supplied via line (4). In the reactor, temperatures in the range from 800 to 1050° C. and mostly 850 to 1000° C. are provided. The dwell times for the solids in the reactor (1) lie in the range from about 2 to 20 sec.

[0008] Entrained by hot exhaust gas, the solids are supplied from the upper region of the reactor (1) through the passage (8) to a separator (9) designed as cyclone. The hot exhaust gases largely free of solids flow upwards in a suspension heat exchanger (10), to which granular iron ore is supplied from the outside through line (11). This iron ore is preheated in direct contact with the hot exhaust gas and supplied through line (12) to a cyclone separator (13), from where the preheated iron ore is recirculated to the reactor (1) through line (3). Exhaust gas is withdrawn via line (14) and is supplied to a gas cleaning not represented.

[0009] Ore-coke mixture produced is withdrawn on the one hand from the cyclone separator (9) through line (15) and on the other hand from the lower region of the reactor (1) through line (16). Usually, line (16) contains coarser-grained mixture than line (15). A syphon (15a) expediently serves as pressure barrier. Via line (16a), the solids mixture can be supplied to the further use, e.g. in a melt reduction process. Such melt reduction process is described e.g. in the U.S. Pat. Nos. 6,083,296 and 6,143,054. The iron ore in lines (15) and (16) is already partly reduced as compared to the ore of line (11), where usually 10 to 40% of the oxygen contained in the original iron ore have already been removed.

EXAMPLE

[0010] In a plant corresponding to the drawing, 170 t/h granular iron ore are supplied through line (11), and 142 t/h granular coal with 25.4 wt-% volatile components and 17 wt-% humidity are supplied through line (2). Through lines (4) and (5) a total of 114000 Nm3/h air enter the low-temperature carbonization reactor (1), by means of which the temperature is maintained at 950° C. Through line (16a), 210 t/h mixture of ore and low-temperature coke are withdrawn, which mixture comprises 16 wt-% Fe2O3, 49 wt-% FeO, 28 wt-% carbon and 7 wt-% ash. The process gas withdrawn via line (14) has a temperature of 518° C. and the composition

CO  11 vol-%
CO2 11 vol-%
H2O 22 vol-%
H2  15 vol-%
CH4 1 vol-%
N2  40 vol-%

Claims

1. A process of producing a hot, granular mixture of iron ore and low-temperature coke, characterized in that granular coal and preheated granular iron ore are charged into a low-temperature carbonization reactor, in which temperatures in the range from 800 to 1050° C. are produced by supplying gas containing oxygen and by partial oxidation of the components of the coal, the granular solids being maintained in a turbulent movement and being supplied from the upper region of the reactor to a solids separator from which a hot exhaust gas is withdrawn, that the granular iron ore is preheated by means of the hot exhaust gas, and that a hot, granular mixture of iron ore and low-temperature coke is withdrawn as product from the reactor and/or from the separator.

2. The process as claimed in claim 1, characterized in that the low-temperature carbonization reactor is designed as fluidized-bed reactor or as pneumatic conveyor section.

3. The process as claimed in claim 1 or 2, characterized in that the pressure in the low-temperature carbonization reactor lies in the range from 1 to 10 bar.

4. The process as claimed in claim 1 or any of the preceding claims, characterized in that highly volatile coal is supplied to the low-temperature carbonization reactor.

5. The process as claimed in claim 1 or any of the preceding claims, characterized in that the product of iron ore and low-temperature coke has a weight ratio Fe:C of 1:1 to 2:1.

6. The process as claimed in claim 1 or any of the preceding claims, characterized in that the granular mixture of iron ore and low-temperature coke is introduced into a melt reduction process.