JP7044995B2 - Fluid roasting furnace - Google Patents

Description

The present invention relates to a fluidized roasting furnace. More specifically, the present invention relates to a fluidized roasting furnace capable of roasting an object to be roasted, which requires high quality.

In general, a fluidized roasting furnace creates a mixed state with a medium by suspending the granular raw material to be roasted as if it were a fluid while supplying gas with the raw material alone or using a fluid medium, and is efficient. It is a device for roasting. By roasting in a state where the raw material to be roasted and the fluidized medium are mixed, roasting proceeds while the raw material and the fluidized medium collide with each other, and the raw material can stay in the fluidized bed for a relatively long time. It can be roasted efficiently.

In order to reliably roast the raw material supplied using such a fluidized roasting furnace, the flow velocity of the gas is changed to the raw material (hereinafter, may be referred to as “roasted object” in the present specification) and the flow rate. The superficial velocity of the mixture with the medium must be precisely controlled to be in the range above the minimum fluidization velocity and below the terminal velocity.

Here, the "superficial velocity" is the actual velocity obtained by the gas flow rate / the cross-sectional area in the furnace. Here, the "in-furnace cross-sectional area" refers to the area inside the furnace in a plane perpendicular to the axis of the furnace core. The "minimum fluidization rate" is the minimum rate at which the powder (mixture of the material to be roasted and the fluid medium) begins to flow. The "terminal velocity" is the speed at which the powder rises from the fluidized bed and begins to pop out.

The reason why the speed control needs to be performed accurately as described above is as follows. That is, if the flow velocity of the supplied gas is less than the "minimum fluidization rate" of the mixture of the raw material and the flow medium, roasting does not proceed uniformly because the raw material does not fluidize, and the raw materials aggregate. Problem arises.

On the other hand, if the flow rate of the gas is equal to or higher than the "terminal velocity" of the mixture, the flow rate is too high and the raw material or the fluid medium is flown together with the gas, and roasting cannot be performed effectively. There is a problem that the recovery rate is greatly reduced.

That is, in fluidized roasting, it is necessary to control the gas flow rate within an appropriate range and fluidize the raw material in the fluidized bed for a time sufficient for roasting.

Patent Documents 1 and 2 disclose the configuration of the fluidized roasting furnace described above. These fluid roasting furnaces have some problems in order to carry out industrial production. The four listed below are considered to be important.

The first problem is that continuous processing is difficult. From the viewpoint of efficiency, raw materials are continuously added during continuous processing. At this time, if the raw material being roasted and the raw material not roasted are mixed and roasting cannot be performed efficiently, the quality of the product to be roasted is deteriorated, which is not preferable.

In order to solve the above problem, it is conceivable to separate the raw material input port and the raw material recovery port so that the raw material goes from the input port to the recovery port, but in the case of liquid roasting, the granular raw material is used. Since it is fluidized like a fluid, the raw materials that have not been roasted immediately after being put in and the raw materials that have been floating in the furnace for a while and have been roasted are immediately mixed, and only the raw materials that have been roasted are collected. It is not possible to do so, and raw materials that are inadequately roasted are also recovered in a mixed state. For this reason, low quality products are collected, and the roasting efficiency is also deteriorated.

In Patent Document 1, old sand dust is supplied into a roasting chamber of a fluidized roasting furnace, placed in the roasting chamber for fluidized roasting, and overflows at an upper position of a fluidized bed formed in the roasting chamber. A technique for overflowing from a flow port and collecting it as recycled dust is disclosed. Here, the old sand dust is obtained by collecting dust generated by a pipe-drying remanufacturing machine for regenerating old cast sand. In addition, silica sand is housed as base sand in the bottom of the fluidized roasting furnace.

In addition, it is also disclosed that the compressed air blowing pipe provided at the inlet of the chute allows compressed air to be blown toward the outlet of the chute from a nozzle formed at the tip thereof. That is, the old sand dust is supplied into the furnace while compressed air is blown toward the chute, and the old sand dust is overflowed and collected from the overflow port.

In the fluidized roasting furnace disclosed in Patent Document 1, since the supply height position of the old sand dust and the height position of the overflow port (collection port) are almost the same, the old sand dust is fluidized. As for, only the roasted ones are not surely overflowed from the overflow port and collected.

That is, since the old sand dust before roasting is supplied one after another to the old sand dust that has been fluidized and roasted, the old sand dust collected from the overflow port is insufficiently roasted. Sand dust is mixed. Therefore, continuous processing is difficult at this point.

Regarding the first problem above, in order to recover the old sand dust that has been roasted as much as possible by the method disclosed in Patent Document 1, it is necessary to slow down the supply speed of the old sand dust as much as possible. Conceivable. However, in this case, the treatment by the fluidized roasting furnace is very inefficient, and continuous treatment is still difficult.

The second problem is that it is difficult to separate the gas used for roasting after roasting and the object to be roasted after roasting.

Patent Document 2 describes a step of oxidatively roasting a metallic iron source in a fluidized roasting furnace, a step of peeling an oxide layer of coarse particles discharged from an overflow port of the roasting furnace, and a step of peeling iron oxide after the peeling step. A method for producing high-grade iron oxide is disclosed, which comprises a step of circulating metallic iron powder in a fluidized roasting furnace and a step of flowing out the produced fine iron oxide together with the roasting gas and capturing and recovering it from the roasting gas. ing.

However, although Patent Document 2 describes that fine iron oxide is discharged together with roasting gas and captured and recovered from the roasting gas, specifically how fine iron oxide is discharged together with roasting gas is described. Is not clearly shown. That is, it is completely unknown how to efficiently separate the fine iron oxide and the roasting gas and capture and recover the fine iron oxide.

Further, Patent Document 2 also discloses that the exfoliated oxide film is accompanied by the exhaust gas of the fluidized roasting furnace and discharged to the outside of the furnace. It is also unclear whether it will be discharged.

The third problem is that the purity of the product required for the product to be roasted differs depending on the product to be roasted. A specific example of the raw material of the fluidized roasting furnace will be described. Nickel oxide (NiO), which is often used as a raw material for a secondary battery, for example, is a very strict product to be roasted in terms of purity and the like. Nickel oxide is produced by adding an alkali to an aqueous solution containing nickel sulfate (NiSO ₄ ), neutralizing it to obtain nickel hydroxide (Ni (OH) ₂ ), and roasting the nickel hydroxide. ..

With respect to this nickel oxide, the sulfur grade of the impurities contained in the obtained nickel oxide is high, and if it exceeds 100 ppm, for example, the characteristics of the battery manufactured from nickel oxide are deteriorated, which is not preferable. Therefore, it is indispensable to remove sulfur adhering by pretreatment such as washing and to reduce sulfur by roasting uniformly and surely. That is, the configuration of the fluidized roasting furnace disclosed in Patent Document 1 and the like has a problem that the uniformity of roasting cannot be sufficiently improved with respect to a predetermined raw material.

The fourth problem is related to the characteristics of the object to be roasted. In the above-mentioned liquid roasting of nickel hydroxide, it is also necessary to consider the influence of the generated gas. That is, at the same time that nickel hydroxide is roasted to generate nickel oxide, water ( _H2O ), that is, steam gas, is also generated along with the decomposition of nickel hydroxide. Due to the volume of the generated steam gas, the flow velocity in the fluidized roasting furnace rapidly increases, and as a result, the object to be roasted is discharged with incomplete roasting, which causes a problem that the quality and the recovery rate are deteriorated.

The influence of the gas generated by the above roasting occurs not only in the case of nickel hydroxide or the like, but also in the case of roasting copper concentrate, for example, to separate arsenic. That is, when the copper concentrate is roasted in an inert gas, arsenic sulfide is generated as a gas, and the copper concentrate is flushed out of the furnace.

Regarding this fourth problem, when gas is generated by roasting, in order to prevent the discharge of unreacted raw materials from the fluidized roasting furnace, the amount of generated gas is predicted in advance and the amount of generated gas is used. It is necessary to reduce the amount of gas sent to a considerable amount of fluidization. However, the above-mentioned water vapor gas and the like are generated in the fluidized bed in association with the roasting reaction, and if the amount of gas supplied for fluidization is uniformly reduced, fluidization does not occur and the reaction does not proceed or is excessive. There arises a problem that the desired roasting does not proceed smoothly due to the flow rate.

In response to this fourth problem, in Patent Document 1, a portion having an enlarged in-furnace cross-sectional area is installed on the outlet side of the core body of the fluidized roasting furnace, and the gas flowing in the furnace of the fluidized roasting furnace is provided. In addition, the flow velocity of the object to be roasted is reduced by expanding the cross-sectional area to prevent the discharge of raw materials that are insufficiently roasted.

Japanese Unexamined Patent Publication No. 2000-42515 Japanese Unexamined Patent Publication No. 61-236616

In response to the third and fourth problems, when a portion having an expanded cross-sectional area in the furnace is installed on the outlet side of the core body of the fluidized bed described in Patent Document 1, that is, fluidized roasting is performed. If a part with an expanded in-furnace cross-sectional area is installed above the fluidized bed, the in-furnace cross-sectional area does not change up and down in the part where the fluidized bed where fluidized roasting is performed is formed. Due to the straight cylinder shape, the generated gas tends to make the speed of the fluidized bed non-uniform inside the fluidized bed, and as a result, the object to be roasted is often not completely roasted and tends toward the outlet side of the core body. There is a problem that quality and recovery rate are reduced.

In view of the above circumstances, it is an object of the present invention to provide a fluidized roasting furnace capable of increasing the quality and recovery rate after roasting even for a roasted product for which gas is generated by roasting.

The fluidized roasting furnace of the first invention has a tubular core portion in which the object to be roasted is roasted using gas flowing from the lower side to the upper side, and an electric heater provided on the outer periphery of the tubular core portion. The tubular core portion has a plurality of inner vertical portions having different cross-sectional areas in the furnace in the region in the height direction in which the electric heater is provided , and the inner surface is located on the upper side. It is characterized in that the in-core cross-sectional area of the vertical portion is larger than the in-core cross-sectional area of the inner vertical portion located on the lower side.
The fluidized roasting furnace of the second invention is characterized in that, in the first invention, the tubular core portion has three or more vertical inner surface portions.
In the fluidized roasting furnace of the third invention, in the first invention or the second invention, the roasting temperature of two of the inner vertical portions having different cross-sectional areas in the furnace is set . It is characterized in that it can be made different by the electric heater .

According to the first invention, the tubular core portion forming the fluidized roasting furnace has a plurality of inner vertical portions having different cross-sectional areas in the furnace in the region in the height direction in which the electric heater is provided. Since the upper side has a larger cross-sectional area in the furnace than the lower side, even if gas is generated by roasting the object to be roasted, the volume increase of the generated gas is absorbed by the vertical part of the inner surface of the upper side, so that the fluidized bed The velocity of the fluidized gas is kept uniform inside. Therefore, the quality and recovery rate of the roasted product after roasting are improved.
According to the second invention, since the tubular core portion has three or more vertical inner surface portions, the cross-sectional area inside the furnace can be gradually increased from the bottom to the top, so that the flow occurs inside the fluidized bed. The velocity of the gas is maintained more uniform.
According to the third invention, since the roasting temperature of the two inner vertical portions can be set differently, the roasting can be progressed step by step, and the speed of the fluidized gas inside the fluidized bed is further increased. It is kept uniform.

It is sectional drawing from the front direction of the fluid roasting furnace which concerns on 1st Embodiment of this invention. It is sectional drawing from the front direction of the fluid roasting furnace which concerns on 2nd Embodiment of this invention.

Next, an embodiment of the present invention will be described with reference to the drawings. However, the embodiments shown below exemplify the flow roasting furnace and its operation method for embodying the technical idea of the present invention, and the present invention describes the flow roasting furnace and its operation method as follows. Not specific to the one. The size or positional relationship of the members shown in each drawing may be exaggerated for the sake of clarity.

(First Embodiment)
FIG. 1 shows a cross-sectional view of the fluidized roasting furnace 10 according to the first embodiment of the present invention from the front direction. In FIG. 1, the thick black arrow indicates the flow direction of the flowing gas. The fluidized roasting furnace 10 of the present embodiment is provided with a tubular core portion 11 in a state where the axis is vertical. A fixed layer 15 is provided at the lower part of the tubular core portion 11. As the fixed layer 15, for example, one filled with ceramics such as spherical alumina can be used, and the ceramics may be porous or may have a high filling factor. Then, the fixed layer 15 may be composed of several layers so that the object to be roasted does not fall under the fixed layer 15. For example, spherical alumina may be used on the lower side of the fixed layer 15, and smaller spherical alumina may be used on the upper side of the fixed layer 15. On the lower surface of the fixed layer 15, a flow gas introduction pipe 12 for introducing the flow gas from the lower part of the tubular core portion 11 is provided. When the fluidized gas is supplied from the fluidized gas introduction pipe 12 in the direction indicated by the thick arrow, the fluidized medium 31 and the raw material 32 located on the fixed layer 15 are fluidized to form a fluidized bed. Roasting is performed with the raw material 32 floating in the fluidized bed.

A heater 13 for holding the flow medium 31 and the like at a constant temperature is provided in the lower part of the tubular core portion 11. The heater 13 may not be provided depending on the raw material 32. When the heater 13 is not used, for example, a high-temperature flow gas may be flowed to perform flow roasting.

The raw material 32 to be supplied to the tubular core portion 11 is appropriately charged by the raw material input pipe 14 provided on the side portion of the tubular core portion 11. Then, after the raw material is charged, the raw material input pipe 14 is closed with a lid or a valve.

The tubular core portion 11 of the fluidized roasting furnace 10 of the present embodiment has a plurality of inner vertical portions 17 having different cross-sectional areas in the furnace. In the present embodiment, the cross section of the inner vertical portion 17 is circular. These inner vertical portions 17 are connected to each other by the enlarged portion 16 and integrated to form a tubular core portion 11. In the present embodiment, two inner vertical portions 17 are provided, and the in-core cross-sectional area of the inner vertical portion 17b located on the upper side is larger than the in-furnace cross-sectional area of the inner vertical portion 17a located on the lower side. There is. The fluidized bed in which the object to be roasted is roasted is formed over the two inner vertical portions 17. That is, in the present embodiment, the fluidized bed is formed over a part of a region in the height direction of the lower inner surface vertical portion 17 and a part of a region in the height direction of the upper inner surface vertical portion 17. .. However, the fluidized bed may be formed over the entire height direction of any of the inner vertical portions 17. In the present specification, reference numeral 17 is used to mean all of the vertical inner surface portions, and reference numerals 17a and 17b are used to mean the vertical vertical portions of the inner surface having different cross-sectional areas.

The tubular core portion 11 forming the fluidized roasting furnace 10 has a plurality of inner vertical portions 17 having different cross-sectional areas in the furnace in the region in the height direction in which the fluidized bed is formed, and the upper side is higher than the lower side. Since the cross-sectional area inside the furnace is large, even if gas is generated by roasting the object to be roasted, the increased volume of the generated gas is absorbed by the upper vertical part of the inner surface, so that the fluidized gas is absorbed inside the fluidized bed. The speed is kept uniform. Therefore, the quality and recovery rate of the roasted product after roasting are improved.

The in-core cross-sectional area of the upper vertical inner surface portion 17b shall be in the range of 1.2 times or more and 10 times or less of the in-core cross-sectional area of the lower inner surface vertical portion 17a, which is the lowermost stage. In terms of continuing stable fluid roasting, the in-core cross-sectional area of the upper inner vertical portion 17b is 1.5 times or more and 5 times or less of the in-core cross-sectional area of the lower inner vertical portion 17a, which is the lowermost stage. It is preferable to use the cross-sectional area of. When the cross-sectional area in the furnace is less than 1.2 times, the change in the flow velocity is small and it is difficult to maintain the stability, while when it exceeds 10 times, the difference in the effect is small and the equipment cost or the volume is not preferable.

The enlarged portion 16 which is a portion connecting the portions where the difference in cross-sectional area occurs may be horizontal, but as shown in FIG. 1, the structure is provided with an inclination so as to be lowered toward the furnace core side. Is preferable. This is because such a structure can prevent the formation of a blank portion where the flow gas does not flow, and can prevent the object to be roasted from accumulating on the enlarged portion 16.

Further, by providing a device for generating vibration such as a knocker, a vibrator, or an ultrasonic vibrator on the outside of the furnace of the enlarged portion 16, or a device for blowing gas from the outside, the deposited material to be roasted is placed inside the furnace core. It is also possible to provide a mechanism that can be wiped off.

Nickel hydroxide (Ni (OH) ₂ ) greatly changes the properties of the object to be roasted depending on the roasting temperature, and gas with different properties is generated. In the case of such raw materials, if the roasting temperature is located in one temperature range, gas may be generated at once, or the properties of the object to be roasted may change at once, and uniform flow may not be possible. Then, the generated gas may bring out the object to be roasted in an incompletely roasted state.

Specifically, in nickel hydroxide, the water content is first volatilized at 100 ° C, then the hydroxyl groups (OH groups) are decomposed at around 300 ° C to generate water vapor, and the sulfur contained at around 700 ° C begins to fly. ..

In the fluidized roasting furnace 10 of the present embodiment, the tubular core portion 11 of the fluidized roasting furnace 10 has a plurality of inner vertical portions 17, and the temperature is changed for each of the inner vertical portions 17. It can also be roasted.

For example, by providing the heater 13 for each of the inner vertical portions 17, it is possible to control the temperature to a different temperature. The heater 13 is preferably an electric type. This is because it is possible to control with high accuracy if it is an electric type. Further, it is preferable that the installation density of the heater 13 is different between the upper and lower parts of the inner vertical portion 17. In this case, the temperature can be gently changed in the vertical direction.

By setting the roasting temperature of the two inner vertical portions 17, the roasting can proceed step by step, and the speed of the fluidized gas is more uniformly maintained inside the fluidized bed. Therefore, it is possible to suppress the popping out of the roasted product due to fluctuations such as gas generation, and as a result, it is possible to obtain a high quality roasted product with a high recovery rate.

(Operation method of the fluidized roasting furnace 10 according to the first embodiment)
As shown in FIG. 1, the fluidized roasting furnace 10 is charged with a fluidized medium 31 for forming a fluidized bed together with the raw material 32. The flow gas is introduced into the flow roasting furnace 10 from the flow gas introduction pipe 12, and the raw material 32 is charged in a predetermined amount. The flow velocity of the fluidizing gas is adjusted so that the "superficial velocity" of the mixture of the raw material 32 and the fluidizing medium 31 is equal to or higher than the "minimum fluidization velocity" and less than the "terminal velocity".

It is preferable that the fluidized roasting furnace 10 is kept heated by the heater 13 and the raw material 32 is charged and roasted. This is because if the raw material is heated after being charged, it takes time and the efficiency deteriorates. It is preferable that the heater 13 is an electric type because it is easy to control. Further, although not shown, a gas burner or the like is preferable because it is cheap in terms of cost.

(Second Embodiment)
FIG. 2 shows a cross-sectional view of the fluidized roasting furnace 10 according to the second embodiment from the front direction. The difference from the fluidized roasting furnace 10 of the first embodiment is that the tubular core portion 11 has three inner vertical portions 17. In this embodiment, the number of vertical portions 17 on the inner surface is three, but there is no problem even if there are four or more.

In the present embodiment, the cross section of the inner vertical portion 17 is circular. The three inner vertical portions 17 are connected to each other by the two enlarged portions 16 existing between them to form a tubular core portion 11. In the present embodiment, the in-core cross-sectional area of the two inner vertical portions 17b and 17c located on the upper side is larger than the in-furnace cross-sectional area of the inner vertical portions 17a located in the lowermost stage. Further, the in-core cross-sectional area of the inner vertical portion 17c located at the uppermost stage is larger than the in-furnace cross-sectional area of the inner vertical portion 17b located at the middle stage. The fluidized bed in which the object to be roasted is roasted is formed over three vertical portions 17 on the inner surface. That is, in the present embodiment, the fluidized bed is formed from a part of the lowermost inner surface vertical portion 17a in the height direction to a part of the uppermost inner surface vertical portion 17c in the height direction. .. However, the fluidized bed may be formed over the entire height-wise region of the inner vertical portion 17 of the uppermost stage or the lowermost stage.

The in-furnace cross-sectional area of the inner vertical portions 17b and 17c located above the lowermost stage shall be in the range of 1.2 times or more and 10 times or less of the in-furnace cross-sectional area of the lowermost inner surface vertical portions 17a. In terms of continuing stable fluid roasting, the in-core cross-sectional area of the inner vertical portions 17b and 17c located above the bottom is 1 of the in-core cross-sectional area of the lower inner vertical portion 17a, which is the lowest. It is preferable that the cross-sectional area is 5 times or more and 5 times or less. When the cross-sectional area in the furnace is less than 1.2 times, the change in the flow velocity is small and it is difficult to maintain the stability, while when it exceeds 10 times, the difference in the effect is small and the equipment cost or the volume is not preferable.

Since the tubular core portion 11 has three or more inner vertical portions 17, the cross-sectional area inside the furnace can be gradually increased from the bottom to the top, so that the velocity of the fluidized gas increases inside the fluidized bed. It is maintained more evenly. The operation method of the fluidized roasting furnace 10 is the same as that of the first embodiment.

Hereinafter, experiments related to the present invention will be conducted, and examples of each embodiment of the present invention will be shown and described. The present invention is not limited to the following examples.

(Experiment 1) (Verification of multiple vertical parts on the inner surface, raw material: nickel hydroxide)
<Raw materials>
Nickel hydroxide (Ni (OH) ₂ ) was prepared as the raw material (to be roasted) 32 to be roasted. Nickel hydroxide had an average particle size of 22.3 to 24.3 μm, and was subjected to vacuum heat treatment at 175 ° C. for 3 hours in advance in a vacuum to substantially remove the water content. Analysis revealed that the sulfur content was 2.1 to 2.3% by weight. Other impurity components were virtually negligible.

In each of the following experiments, batch processing was performed. That is, each raw material 32 is charged into the fluidized roasting furnace 10 in a predetermined amount, and then air is sent from the lower part of the furnace as a fluidizing gas to be fluidized, and the temperature is raised to a predetermined temperature to maintain the fluidized roasting. The flow gas after roasting was discharged from the upper part.

<Fluid roasting process>
In Experiment 1, the flow roasting furnace 10 according to the first embodiment shown in FIG. 1, the flow roasting furnace 10 according to the second embodiment shown in FIG. 2, and the inner surface vertical portion 17 are one type of roasting of a straight cylinder. With a furnace was used. Nickel hydroxide as a raw material was roasted in these roasting furnaces, and nickel oxide (NiO), which was a roasted product, was recovered.

Specifically, the fluidized roasting furnace 10 of the first embodiment was used by changing the ratio of the upper furnace cross-sectional area to the lowermost furnace cross-sectional area as shown in Table 1. Further, in the fluidized roasting furnace 10 of the second embodiment, the ratio of the in-furnace cross-sectional area of the middle stage to the in-furnace cross-sectional area of the lowest stage is 1.6, and the in-furnace cross-sectional area of the uppermost stage with respect to the in-furnace cross-sectional area of the lowest stage. The ratio of was changed as shown in Table 1 and used. Examples 1 to 5 are roasted in the fluidized roasting furnace 10 of the first embodiment, and Examples 6 to 10 are roasted in the fluidized roasting furnace of the second embodiment. The one roasted in the furnace is Comparative Example 1.

In the table, the inner surface vertical portion 17a at the bottom is the first stage, the inner surface vertical portion 17b located on the upper side next to the inner surface vertical portion 17a of the first stage is the second stage, and the inner surface vertical portion 17b at the second stage is next to the inner surface vertical portion 17b. The inner vertical portion 17c located on the upper side is displayed as the third stage.

The weights of the input raw materials were all the same, and the roasting conditions were all the same. Specifically, the roasting temperature was 900 ° C., the roasting time was 20 minutes, and air was used as the flowing gas. After the predetermined roasting, the furnace was cooled and the roasted material in the furnace was recovered.

<Evaluation>
In each of the treatments of Examples 1 to 10 and Comparative Example 1, the recovery rate (that is, the actual yield) of the sample obtained by roasting, the content of nickel oxide in the recovered sample, and the sulfur in the recovered sample. Content was evaluated. Table 1 shows the measurement results. The evaluation method is as follows.

[Recovery rate of samples obtained by roasting]
The recovery rate of the sample obtained by roasting was calculated by the following equation 1.

[Number 1]
R = W ₁ / (W2 _- S) x 100

R: Recovery rate [%]
W ₁ : Weight of the recovered sample W ₂ : Weight when all the charged raw material 32 (this time Ni (OH) ₂ ) is roasted (this time NiO) S: Sulfur contained in the charged raw material 32 Weight

[Ratio of nickel oxide content in the recovered sample]
For the ratio of the nickel oxide content in the recovered sample, the contents of nickel oxide (NiO) and nickel hydroxide (Ni (OH) ₂ ) contained in the recovered sample were calculated, respectively, and the respective contents were calculated. It was calculated as the ratio (% by weight) of the NiO content to the total value.

[Sulfur content in the recovered sample]
The sulfur content in the recovered sample was measured using a sulfur analyzer (manufactured by Mitsubishi Chemical Corporation, model: TOX-100).

As shown in Table 1, good results were obtained in Examples 1 to 10 using the fluidized roasting furnace 10 of the first embodiment or the second embodiment. That is, the recovery rates (actual yields) all showed high values of 99% or more, and the content ratio of nickel oxide in the recovered products was 99% or more, and NiO could be roasted. In addition, the sulfur grade in the recovered product, which is mostly nickel oxide, was low, and high-quality nickel oxide could be obtained.

On the other hand, in Comparative Example 1 in which a straight-cylinder roasting furnace was used, the recovery rate was low and the sulfur grade in the recovered product was high as compared with Examples.

(Experiment 2) (Verification of multiple vertical parts on the inner surface, raw material: copper concentrate)
<Raw materials>
As the raw material (to be roasted) 32 to be roasted, the arsenic and sulfur grade copper concentrates shown in Table 2 were used.

<Fluid roasting process>
In Experiment 2, as in Experiment 1, the fluid roasting furnace 10 according to the first embodiment shown in FIG. 1, the fluidized roasting furnace 10 according to the second embodiment shown in FIG. 2, and the inner vertical portion 17 are one type. , A straight-cylinder roasting furnace, was used. The raw material copper concentrate was roasted in these roasting furnaces.

Specifically, the fluidized roasting furnace 10 of the first embodiment was used by changing the ratio of the upper furnace cross-sectional area to the lowermost furnace cross-sectional area as shown in Table 3. Further, in the fluidized roasting furnace 10 of the second embodiment, the ratio of the in-furnace cross-sectional area of the middle stage to the in-furnace cross-sectional area of the lowest stage is 1.6, and the in-furnace cross-sectional area of the uppermost stage with respect to the in-furnace cross-sectional area of the lowest stage. The ratio of was changed as shown in Table 3 and used. Examples 11 to 15 were roasted in the fluidized roasting furnace 10 of the first embodiment, and Examples 16 to 20 were roasted in the fluidized roasting furnace of the second embodiment. The one roasted in the furnace is Comparative Example 2. The notation of the inner vertical portion 17 in the table is the same as in Experiment 1.

The weights of the input raw materials were all the same, and the roasting conditions were all the same. Specifically, the roasting temperature was 900 ° C., the roasting time was 4.0 hours, and nitrogen was used as the fluid gas. After the predetermined roasting, the furnace was cooled and the roasted material in the furnace was recovered.

<Evaluation>
In each of the treatments of Examples 11 to 20 and Comparative Example 2, the recovery rate (scattering rate) of the sample by the filter and the arsenic content in the copper concentrate were evaluated by the following methods. Table 3 shows the measurement results. The evaluation method is as follows.

[Sample recovery rate with filter]
After roasting, the sample discharged together with the exhaust gas was collected with a bag filter, and the recovery rate (scattering rate) was calculated from the recovered amount by the following formula. It is not preferable that the copper concentrate is originally collected by the filter because it is a loss, and it is preferable that the recovery rate (scattering rate) is low.

[Number 2]
R ₂ = W ₃ / W ₄ x 100

R ₂ : Recovery rate with filter [%]
W ₃ : Weight of recovered sample W ₄ : Weight of input raw material (copper concentrate this time)

[Arsenic content in the sample before and after the experiment]
For the samples before and after the experiment, arsenic and sulfur were analyzed using an ICP emission spectrophotometer.

As shown in Table 3, good results were obtained in Examples 11 to 20 using the fluidized roasting furnace 10 of the first embodiment or the second embodiment. That is, in the examples, the amount of arsenic was less than 0.1% by weight, and the contents of arsenic and sulfur in the concentrate were greatly reduced. Since the amount of arsenic and sulfur in the copper concentrate decreased, the copper content in the copper concentrate increased by 10% or more by fluid roasting, and copper could be concentrated.

On the other hand, Comparative Example 2 in which a straight-cylinder roasting furnace was used gave unfavorable results. That is, the arsenic grade was 0.2% by weight, and the amount recovered by the filter was 10% or more, which greatly increased the loss.

(Experiment 3) (Verification of multiple roasting temperature settings, raw material: nickel hydroxide)
<Raw materials>
Nickel hydroxide (Ni (OH) ₂ ) was prepared as the raw material (to be roasted) 32 to be roasted. Nickel hydroxide had an average particle size of 22.5 to 24.5 μm, and was subjected to vacuum heat treatment at 175 ° C. for 3 hours in advance in a vacuum to substantially remove the water content. When analyzed, the sulfur grade of nickel hydroxide was 2.0 to 2.2% by weight. Other impurity components were virtually negligible.

<Fluid roasting process>
In Experiment 3, the fluidized roasting furnace 10 according to the first embodiment shown in FIG. 1 was used. The raw material nickel hydroxide was roasted in this roasting furnace, and nickel oxide (NiO), which was a roasted product, was recovered.

Specifically, the fluidized roasting furnace 10 of the first embodiment was used by changing the ratio of the upper furnace cross-sectional area to the lowermost furnace cross-sectional area as shown in Table 4. In Table 4, the inner vertical portion 17a at the bottom is shown as the first stage, and the inner vertical portion 17b located on the upper side next to the inner vertical portion 17a at the first stage is displayed as the second stage. In Examples 21 to 25, the roasting temperature at the inner vertical portion 17a of the first stage is 400 ° C., and the roasting temperature at the inner vertical portion 17b of the second stage is 900 ° C. In Examples 26 to 30, the roasting temperature at the inner vertical portions 17a and 17b of the first stage and the second stage are both 900 ° C.

The weights of the input raw materials were all the same, and the roasting conditions other than the roasting temperature were all the same. Specifically, the roasting time was 20 minutes, and air was used as the flowing gas. After the predetermined roasting, the furnace was cooled and the roasted material in the furnace was recovered.

<Evaluation>
In each of the treatments of Examples 21 to 30, the recovery rate (that is, the actual yield) of the sample obtained by roasting, the content of nickel oxide in the recovered sample, and the sulfur content in the recovered sample were determined. It was evaluated. Table 4 shows the measurement results. The evaluation method is the same as in Experiment 1.

As shown in Table 4, Good results were obtained in Examples 21 to 25 in which the roasting temperature of the first stage was lowered as compared with Examples 26 to 30 in which the roasting temperature was the same. That is, in Examples 21 to 25, when compared with Examples having the same cross-sectional area ratio, the recovery rates were all high, and the nickel oxide content in the recovery was also high. Further, when compared with the same cross-sectional area ratio, the sulfur grades of Examples 21 to 25 also showed low values.

(Experiment 4) (Verification of multiple roasting temperature settings, raw material: copper concentrate)
<Raw materials>
As the raw material (to be roasted) 32 to be roasted, the copper concentrate having the composition shown in Table 2 of the above experiment 2 was used as the raw material.

<Fluid roasting process>
In Experiment 4, the fluidized roasting furnace 10 according to the first embodiment shown in FIG. 1 was used. The raw material copper concentrate was roasted in this roasting furnace.

Specifically, the fluidized roasting furnace 10 of the first embodiment was used by changing the ratio of the upper furnace cross-sectional area to the lowermost furnace cross-sectional area as shown in Table 5. In Table 5, the inner vertical portion 17a at the bottom is shown as the first stage, and the inner vertical portion 17b located on the upper side next to the inner vertical portion 17a at the first stage is displayed as the second stage. In Examples 31 to 35, the roasting temperature at the inner vertical portion 17a of the first stage is 200 ° C., and the roasting temperature at the inner vertical portion 17b of the second stage is 900 ° C. In Examples 36 to 40, the roasting temperatures in the first-stage and second-stage inner vertical portions 17a and 17b are both 900 ° C.

The weights of the input raw materials were all the same, and the roasting conditions other than the roasting temperature were all the same. Specifically, the roasting time was 4.0 hours, and nitrogen was used as the fluid gas. After the roasting was completed, the furnace was cooled and the sample in the furnace was collected.

<Evaluation>
In each of the treatments of Examples 31 to 40, the recovery rate (scattering rate) of the sample collected by the filter and the arsenic content in the copper concentrate were evaluated. Table 5 shows the measurement results. The evaluation method is the same as in Experiment 2.

As shown in Table 5, Good results were obtained in Examples 31 to 36 in which the roasting temperature of the first stage was lowered as compared with Examples 36 to 40 in which the roasting temperature was the same. That is, in Examples 31 to 35, the recovery rate with the filter showed a low value when compared with Examples having the same cross-sectional area ratio.

10 Flow roasting furnace 11 Cylindrical core 17 Inner vertical part

Claims (3)

A cylindrical core in which the object to be roasted is roasted using gas flowing from the lower side to the upper side .
An electric heater provided on the outer periphery of the tubular core portion is provided.
The tubular core portion has a plurality of inner vertical portions having different cross-sectional areas in the furnace in a region in the height direction in which the electric heater is provided .
The in-combustion cross-sectional area of the inner vertical portion located on the upper side is larger than the in-core cross-sectional area of the inner vertical portion located on the lower side.
A fluid roasting furnace characterized by that. The tubular core portion has three or more vertical inner surface portions.
The fluidized roasting furnace according to claim 1. Of the plurality of vertical inner surface portions having different cross-sectional areas in the furnace, the roasting temperature settings of the two vertical inner surface portions can be set differently by the electric heater .
The fluidized roasting furnace according to claim 1 or 2 .

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