JPS63216912A - Fluidized reduction method for granular ore - Google Patents

Abstract

PURPOSE:To improve thermal efficiency by making heating zone of whole height in fluidized bed, by dividing inner part of a fluidized reduction furnace into a reducing zone and the heating zone so as to communicate at the prescribed position, fluidizing them separately and shifting ore mutually between both zones. CONSTITUTION:The inner part of the fluidized reduction furnace 1 is partitioned into the reducing zone 11 and the heating zone 12 by a partition wall 10 and the also both zones 11, 12 are communicated at the prescribed position, to form opening zones 15, 16. Fluidized gas 2 is separately supplied into both above zones 11, 12, to develop difference of flow rate of the gas. And, the ore is shifted mutually between both zones 11, 12. Thus, by supplying the heat to the heating zone 12, the heat is compensated over whole zone in the inner part of the furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a fluid reduction method for reducing powdery ores such as iron ore and chromium ore.

[Prior Art] One of the methods for reducing ores such as iron ore and chromium ore is a fluid reduction method.

In the fluidized reduction method, granular ore and carbonaceous material, which is a reducing agent, are charged into a furnace, and a fluidizing gas such as hydrogen gas H2 and -carbon oxide gas CO is supplied from the bottom of the furnace to separate the ore and carbonaceous material. The purpose is to form a mixed fluidized bed for reduction.

When the object to be reduced by this method is iron ore, it can be reduced at a high temperature of 900°C or higher without sintering problems, and if reduced with a fluidizing gas such as H2 or Co, 90% or more of the metal can be reduced in 20 to 30 minutes. The conversion rate can be obtained.

When fluidizing and reducing granular ores such as iron ore and chromium ore, there is heat loss due to heat absorption by the ore due to reduction and heat radiation from the fluidized fluidized reduction furnace, and it is necessary to maintain the inside of the furnace at the optimal temperature for reduction. It is necessary to thermally compensate for the reduction heat absorption and heat radiation outside the furnace, or to raise the temperature as necessary.

Conventionally, one method of supplying heat is to maintain a reducing atmosphere in the furnace by increasing the supply temperature of the fluidizing gas. According to this method, the fluidizing gas is supplied at a temperature raised by about 50 to 200°C.

Furthermore, when chromium ore is reduced with H2 or hydrocarbon gas, the reducing atmosphere is even higher, at 1100°C or higher, and the temperature of the supplied fluidizing gas needs to be about 1150 to 1300°C.

Further, as another method of heat supply, there is a partial oxidation method in which reducing gas is partially oxidized (combusted) in a furnace.

The partial oxidation method will be explained with reference to FIG. 6. The fluidized reducing gas 2 is supplied into the fluidized reduction furnace l through the supply pipe 3 and the aeration pipe 4, and the ore charging port 5 The granular ore 6 is fluidized and reduced, and the exhaust gas is discharged from the exhaust gas discharge line 7. Oxygen or oxygen-containing gas is supplied from the oxidizing gas inlet 9 provided at the upper part of the fluidized bed 8 within the height h of the furnace to combust the reducing gas in the upper part of the fluidized bed, and the heat of combustion causes powder to float in the upper part. Heat the grain ore.

As the powder ore moves up and down in the fluidized bed, the heated ore in the upper part acts as a heat medium in the lower part and heats the gas, and as this is repeated, the temperature of the entire fluidized bed increases.

Regarding the partial oxidation method explained above,
9 is described in detail.

[Problems to be solved by the invention] However, in the former method, a heat exchanger (recuperator) is used as a method to maintain the reducing property of the reducing gas and raise the temperature, but there are limitations due to the material of the heat exchange tube or thermal efficiency. According to the current state of the art, the maximum temperature is about 800°C.

Such a problem is particularly important in the reduction of chromium ore where the reducing atmosphere temperature is high.

Further, although the latter partial oxidation method solves the problems of the above method, in the conventional partial oxidation method, partial oxidation is carried out in the upper part of the fluidized bed, which causes the following problems.

In a fluidized bed, the gas flow rate is fast, so the contact time between the gas heated up by combustion and the powder ore is short, and most of the combustion heat escapes upward, resulting in large heat loss.

Alternatively, the amount of partial oxidation must be sufficiently larger than the heat-compensating bone from the viewpoint of thermal efficiency because the heat to maintain the reduction temperature in the furnace is carried out through the granular ore, and as a result (1) oxygen or The consumption of oxygen-containing gas increases, α) The oxidation rate of reducing gas increases, so the added value of exhaust gas decreases (lower latent heat, gas reformation when exhaust gas is recycled, e.g. removal of H2O, CO2) (2) The combustion temperature becomes high and there is a risk of sintering. (2) A part of the furnace becomes an oxidizing atmosphere, so the reduction rate of the ore decreases. In addition, the increased amount of oxygen increases the reoxidation of the ore, causing a reduction in the reduction rate.

For reference, if oxygen or oxygen-containing gas is supplied from the middle to the lower part of the fluidized bed to burn the reducing gas and compensate for heat, it is more advantageous from the point of view of heat compensation than supplying from the upper part.
This is not preferable because the oxidation of the reducing gas throughout the fluidized bed progresses, making it difficult to achieve the target reduction rate.

Means for Solving Problem E] The present invention has been made to solve the above-mentioned problems, and it further develops the partial oxidation method to efficiently compensate for heat while causing a reduction in the reduction rate. The interior of the fluidized reduction furnace is divided into a reduction zone and a heating zone, and both zones are communicated at the required positions so that fluidizing gas can be supplied separately and also supplied to both zones. This is characterized in that a difference is caused in the flow rate of the fluidizing gas.

[Function] Since a difference is created in the flow rate of the fluidizing gas, there is mutual movement of the fluidized bed between the reduction zone and the heating zone, and if heat is supplied to the heating zone, heat compensation can be achieved over the area inside the furnace.

[Example] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIGS. 1 and 2, a partition wall 10
The ore is divided into a reduction zone 11 and a heating zone 12, and the partition wall 1
The height of the partition wall 0 is set to be a predetermined level lower than the height h of the fluidized bed, and the lower part of the partition wall 0 is cut out, so that the reduction zone and the heating zone are in communication between the upper and lower parts.

Further, an ore discharge port 13 is provided at the lower part of the reduction zone 11. Diffusion pipes 4a are provided at the bottom of the reduction zone 11 and the heating zone 12, respectively.
, 4b are arranged, and the fluidized reducing gas supply pipes 3a, 3b are connected to the respective diffuser pipes 4a, 4b, and both the supply pipes 3a, 3b are connected.
are individually connected to a gas supply (not shown).

An oxidizing gas supply port 14 is provided in the middle position of the furnace wall of the heating zone 12 of the fluidized fluidized furnace 1, and the supply port 14 is connected to the oxidizing gas supply source (
(not shown). The position of the supply port 14 is preferably an intermediate position of the height of the partition wall 10 above the diffuser pipes 4a, 4b.

Ore 6 crushed to a predetermined particle size is charged through the ore charging port 5, and reducing gas is supplied through the supply pipes 3a and 3b, and the reducing gas is ejected through the aeration pipes 4a and 4b.

The ejected reducing gas fluidizes the ore 6 and creates a reduction zone 11,
A fluidized bed is formed in each of the heating zones 12. Further, oxygen or an oxygen-containing oxidizing gas is supplied from the oxidizing gas supply port 14 of the heating zone 12 . By supplying this oxidizing gas, a part of the reducing gas is combusted, and the temperature of the fluidizing gas increases. The floating ore is heated by increasing the temperature of the fluidizing gas in this heating zone. Further, since partial combustion of the reducing gas is performed inside the heating zone 12, combustion is effectively used to heat the ore, and heat loss to the exhaust gas is reduced.

Next, the fluidizing gas flow rate supplied from the aeration pipes 4a and 4b is set to a constant fluidizing gas flow rate on the reduction zone 11 side, and the heating zone 1
Change the fluidizing gas flow rate on the second side.

As mentioned above, the height of the partition wall 10 is lower than the height h of the fluidized bed by a predetermined level, and the lower part of the partition wall lO is cut out, so that the reduction zone can be passed through both the upper and lower open zones 15 and 16. 11 and the heating zone 12, there is mutual movement due to the difference in gas flow rate in the fluidized bed due to the difference in the fluidizing gas flow rate.

That is, the ore heated in the heating zone 12 is transferred to the upper open zone 15.
The ore in the lower part of the reduction zone 11 passes through the lower open zone 16 and moves to the heating zone 12, and the fluidized ore circulates between the reduction zone 11 and the heating zone 12. Note that the amount of ore circulation is determined by the magnitude of the difference in flow rate (ie, the difference in flow velocity) of the fluidizing gas supplied to both zones. When the ore moves within the reduction zone 12, it is reduced and also moves into the heating zone 11.
A part of the heat obtained therein is released to raise the atmospheric temperature in the reduction zone 12. On the other hand, the ore that has moved from the reduction zone to the heating zone has a reduced temperature due to the endothermic reaction of reduction in the reduction zone 11, but is reheated in the heating zone.

As described above, heat is exchanged between the reduction zone 12 and the heating zone U through the upper and lower open zones 15 and 16, and heat compensation from the heating zone 12 to the reduction zone 11 can be performed.

Incidentally, since the partial combustion is carried out only in the heating zone 12 partitioned by the partition wall IO, no oxygen is mixed into the reduction zone 11, and an extremely favorable atmosphere is created for the reduction of the ore, resulting in a high reduction rate. Further, the difference in flow rate of fluidized gas between both zones may be continuous or intermittent, and the flow rate side may be a heating zone.

An example of the results obtained when chromium ore was specifically reduced in the above example will be shown.

Reduction rate 60% Reduction temperature 1150℃ Reduction time 2 hours Reduction gas Coke oven gas (H2: 57%, CH
4: 33%, CO near%, etc.) Reducing gas flow rate 120ONm"/1 Reducing gas Ore reducing gas temperature 800°C Oxygen for partial combustion 26ON+"bar Reducing ore exhaust residue component H2: 54% 1H20: 27%, coats%,
CO2: 3% Exhaust gas temperature 1200°C In the case of chromium ore, the fluidizing reducing gas is preferably a mixture of the above gas and a hydrocarbon gas, but in the case of iron ore, H2 or CO containing H2 as the main component is preferable. Mixed gas with etc. is preferable.

The gas used for reduction may be reformed by removing H20, etc., and then used for circulation as a fluidized reducing gas.

FIG. 3 shows another embodiment, in which a heating zone 12 is formed in the center of the partition wall 10, and reducing zones 11 are formed on both sides. It goes without saying that a similar furnace structure may be used, with the center section serving as the reduction zone and the both sides serving as the heating zone.

The embodiment shown in FIG. 4 shows an example in which a diffuser plate 17 is used in place of the diffuser pipes 4a and 4b, and a chamber below the diffuser plate 17 is partitioned by a partition plate 18 to create a defined room. Supply pipes 3a and 3b are connected to each compartment.

FIG. 5 shows an embodiment in which the lower part of the partition wall 10 is not cut out, and in this embodiment as well, the flow rate of the fluidizing gas supplied to the reduction zone I and the flow rate of the fluidized gas supplied to the heating zone 12 are By changing the flow rate of the oxidizing gas, heat can be effectively transferred through the open zone 15 at the top. In the case shown in FIG. 5, the oxidizing gas supply port 14 is preferably provided above the diffuser pipe 4b and as close to the bottom of the heating zone 11 as possible.

Further, the communication position between the reducing zone 11 and the heating zone 12 is not limited to the upper and lower parts, but may be an intermediate position of the partition wall.

In the above example, oxidizing gas was supplied for heating and reducing gas was combusted, but a dedicated combustor was provided outside the fluidized bed reduction furnace, and the combustion gas produced by combustion in the combustor was sent to the heating zone. It may be fed through the supply port 15 or may be fed as a fluidizing gas.

Furthermore, as the fluidizing reducing gas, it is necessary to use a hydrocarbon gas with a good reducing effect or an expensive gas such as H2, but the gas supplied to the heating zone becomes high temperature due to combustion for that purpose. Since the purpose is to fluidize, it is possible to reduce costs by burning an inexpensive CO-based gas, carbonaceous material, heavy oil, or a combination thereof in the heating zone. In addition, the sensible heat of the exhaust gas after being used for reduction
If latent heat is used to preheat and supply the ore outside the fluidized reduction furnace, partial combustion can be reduced, and if the fluidized reducing gas is preheated using the heat of this exhaust gas, the overall reduction equipment heat consumption can be further reduced.

Furthermore, a mixed fluidized bed of ore and carbonaceous material may be obtained by mixing coal, char, coke, or other carbonaceous material as a reducing agent or for preventing sintering in the fluidized bed.

In each of the above embodiments, the operation may be such that the ore is continuously supplied and the reduced ore is continuously discharged, or it may be a batch type operation. Further, it is preferable to supply the ore from the vicinity of the heating zone, and a system in which the ore is supplied from the upper part of the fluidized bed and discharged from the lower part is convenient for continuous operation.

[Effects of the Invention] As described above, according to the present invention, the following excellent effects can be exhibited.

(i) Whereas in the conventional system, the heating zone is located above the middle of the height of the fluidized bed, in the present invention, it is located throughout the entire height of the fluidized bed.

Therefore, the contact time between the combusted high-temperature gas and the ore becomes longer, the combustion heat of the gas is effectively transferred to heat the ore, and the thermal efficiency is improved.

■ Improving thermal efficiency reduces the amount of combustion gas, and the space for the heating zone can be reduced, making equipment more compact.

0 Since inexpensive gas can be supplied to the heating zone as a gas for heating and combustion, running costs can be reduced.

(f) The combustion gas subjected to heating is mixed with the gas that has passed through the reduction zone and discharged from the fluidized bed furnace as exhaust gas, but the ratio of combustion gases such as H2O and CO2 in this mixed gas can be lowered. , gas reforming (H20 removal, etc.) costs can be reduced when exhaust gas is recycled as a reducing gas.

(V) In addition, since the H2 and CO concentrations in the exhaust gas can be kept high, the gas value is high when used for other purposes, and even when this gas is burned and used for preheating ores or supply gas, the calorie content is low. is high.

(D As mentioned above, the heating efficiency of the ore is good and the amount of combustion gas can be reduced, so the combustion temperature can be lowered, and the amount of combustion generated gas is also reduced, so the temperature of the mixed exhaust gas can be lowered. As a result, the refractory material in the furnace can be It can be made inexpensive and is also effective in preventing sintering of ore.

Special features: When preheated in a recubator, the supply temperature of the fluidizing reducing gas is limited to about 800°C, but the temperature of the reducing atmosphere can be easily raised because of its large thermal compensation ability. Therefore, it can also be used in cases where high temperature reduction (1100 to 1200°C) is required, such as with chromium ore.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the first embodiment of the present invention, and FIG. 2 is an explanatory diagram of the first embodiment of the present invention.
3 is an explanatory diagram of the second embodiment; FIG. 4 is a partial explanatory diagram of the third embodiment; FIG. 5 is an explanatory diagram of the fourth embodiment; FIG. 6 is an explanatory diagram of a conventional example. 2 is a fluidized reduction furnace, 2 is a fluidized reducing gas, 4a and 4b are diffuser pipes, 8 is a fluidized bed, 10 is a partition wall, 11 is a reduction zone, 12
15.16 indicates the heating zone, and 15.16 indicates the open zone.

Claims (1)

[Claims] 1) The inside of the fluidized reduction furnace is divided into a reduction zone and a heating zone, and both zones are communicated at the required positions, so that fluidizing gas can be supplied individually, and a difference is created in the flow rate of fluidizing gas supplied to both zones. A fluid reduction method for powdery ore, characterized in that the method is characterized in that: