SE446880B - Method and device for reduction of pulverised, iron oxide-containing material in a fluid bed - Google Patents

Abstract

The invention is a method for reduction of pulverised, iron oxide-containing material in a mixture of carbonaceous material in a circulating fluid bed, to which the flow of iron oxide-containing material and gas is directed, and solid, powder material consisting of wholly or partly reduced iron oxide is fed out, while there is a certain overpressure in the fluid bed. The method of this invention is unique in that the reduced material is fed into at least a single rising pipe (7), extending from the fluid bed's (1) lower part, and the fluidising gas is blown in from the bottom (A) through the same pipe, whereby the outgoing material, because of thinning through the fluidising gas, rises to a higher level than would occur solely through overpressure in the fluid bed and under any influence of fluidising gas, and output occurs through this higher level (C) to a further treatment (11) of the reduced material.<IMAGE>

Description

The present invention constitutes a solution to. these and other related problems. The method according to the invention is characterized in that the undraduced material is discharged into at least one riser, starting from the lower part of the floating bed, and fluidizing gas is blown in from below into the same pipe, the discharged material being on. due to the depletion by the fluidizing gas rises to a higher level than would have occurred alone. due to the overpressure in the fluidized bed and under the influence of basic fluidizing gas, and discharge takes place e from this. higher level for further processing of the undreduced material.

In this way, a reduced material can be discharged in a well-controlled manner at a pressure at or near atmospheric pressure, and a continuous reduction process can be obtained, comprising both pre- and final reduction.

Freshly cut valve wear is also avoided.

The invention is further exemplified in the accompanying figure.

The device according to the figure comprises a reactor 1 and one or more cyclones 2 for separating powder grains from the gas. Fluidization and reduction data, eåeem co, co, H2 een / or Ng, inblëeee in the bottom ev the fm- bäaa (at 5), which is achieved in the reactor 1. Jäz-nexiahaltigc material mixed with finely divided, solid, carbonaceous material may meet in the floating bed 1 in countercurrent and in this case the hot material is reduced in whole or in part to iron, which is discharged into container 4, 5 in the bottom of the reactor.

Ascending gas is liberated in cyclone gas from ptllverformy material, which is recycled to a fluidized bed. known manner. See the above-mentioned Swedish patent document.

Containers 4, 5 are provided. with valves 6,6 ', which. must be closed after the containers have been filled, when the pressure in the floating bed is an overpressure, for example 5 bar, and the pressure in the following treatment station, final reduction in an arc-DC suction, is atmospheric pressure. It is possible to alternately fill these containers 4, 5 and alternately use their contents for further reduction, but the valve wear becomes significant, and the process is not continuous.

According to the invention, one or more risers 7, drawn from the lower part of the floating bed, for example above its conically tapered part 10, are connected to the reactor surface bed 7.

At A, a basic fluidizing gas is introduced into the riser, which at gas flow _ I's - o (at B) gives a powder column in the riser 1 belene with the reemertry pressure P (in the fluidized bed 1). The powder column reaches, under the influence of these factors, up to a level in the riser '1 below the level C, where discharge means 9 for reduced powder material 11 for a subsequent process are arranged, 10 446 880 at 1a are arranged means for additional gas flow (liquefied gas) and if this is increased 8 (the proportion of voids in a powder) will increase in the riser part BC. The pressure A-B is AP1 and through the gas injection comes the pressure B-C ..

= APZ to drop, and P> A P1 + AP. The powder rises to C, and the gas flow at B can be regulated so that the desired material supply from the reactor (flow baaaer) to the receiver via c (9) is obtained.

Normal pressure in the reactor is 5 bar overpressure and the gas velocity at A 0.2 m / s and at IB 0.5 m / s.

Suitable gas for blowing at A and B can be mentioned N2 or process gas (from 1), such as co, CO2 or H2.

The grain size of the powder in the riser 7 can be less than 1 mn ø (0.3 m ß average diameter). Larger grains or agglomerates go to containers 4, 5, for example with a diameter larger than 10 mm.

You can also arrange. lower withdrawal levels for powder at riser 7 at pressures lower than 5 bar in the reactor, but above atmospheric pressure. It is also possible to provide additional supply points (B) for fluidizing gas to the riser.

The method according to the invention is available:. as follows: Iron oxide in powder form plus carbonaceous material in powder form is fed into the reactor 1, in which fluidizing gas of reducing kind is blown. A fluidized bed is obtained in the reactor, in which a certain overpressure is maintained.

In a riser pipe 7, the reduced powder rises to by means of a blown fluidizing gas blown in at A. a level between LB and C. In B, additional fluidizing gas is blown in, and the powder between B and C is thinned and the pressure between these points drops, the column rising to C, where it is discharged (at 11).

The method and device according to the above can be varied in many ways within the scope of the following claims.

Claims (5)

446 880 r PATENTKIRAV A method of reducing finely divided iron oxide-containing material in admixture with carbonaceous material in a circulating fluidized bed, to which flows of atomized iron oxide-containing material and gas are fed, and solid, powdery material consisting of wholly or partially reduced iron oxide is discharged and a certain overpressure is present in the fluidized bed, characterized therefrom, one of the investigated neterielet utnetee in at least one etihre (7), starting from the lower part of the fluidized bed (1), and fluidizing gas is blown from below (A) into the same tube, whereby discharged material on. due to the thinning by the fluidizing gas rises to a higher level. than would only occur due to the overpressure in the floating bed and under the influence of the basic fluidization, s, and discharge takes place from this higher level (C) to further processing (11) of the undreduced material. 2. A method according to claim 1, characterized in that fluidizing gas is blown into the lower part (A) of the riser and at a higher level (B) in the riser, the blowing pressure of the latter gas being adjusted so that powder is discharged at a level (C), lying higher than the level to which the powder in the riser would rise solely due to the overpressure in the fluidized bed and the influence of the lower fluidizing gas. Device according to claim 2, intended for the reduction of atomized iron oxide-containing material in a mixture with carbonaceous material in a circulating fluidized bed, to which streams of atomized iron oxide-containing material and gas are arranged to be carried, and solid pulverulent material, consist »Completely of partially or partially reduced iron oxide, is arranged to be fed, le enneteekned dar-ev, one from the lower baths (1) lower part is drawn at least one riser (7), in the lower part the lower part is an inflated fluidizing gas (A ), and that at a higher level. (B) is arranged to blow in additional fluidizing gas under variable pressure, and to at a higher level. (C) at the riser than the one to which the powder would have risen solely due to the pressure in the fluidized bed and the influence of the lower fluidizing gas, the eerdnede netting gene (9) for the powder is for further treatment (11). Device according to Claim 3, characterized in that at least one valve-provided container (4, 5) for green pieces or agglomerates of reduced material is connected to the bottom of the floating bed. 446 880 Device according to: claim 3, characterized in that more extraction means for powder and / or more inhalation points for fluidizing gas to the riser are arranged, for example at other pressures in the floating bed.