JPS642649B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a fluidized roasting method that uses metal sulfides, metal sulfide concentrates, or concentrates as raw materials and roasts them to produce low-sulfur metal oxides. In recent years, oligopoly and depletion of energy resources have become increasingly serious, and even in the field of smelting and refining of metals, there is a strong desire for ways to utilize limited energy rationally and effectively. It's beyond debate. Conventionally, from this point of view, the Japanese Patent Publication No. 36-16401 was developed as a typical method for producing low-sulfur metal oxides from raw materials containing metal sulfides as main components, such as sulfide concentrates and concentrates, while saving energy. A fluidized roasting method is known, which is an improvement on the method described in the publication. A process diagram of this conventional method is shown in FIG. 1st
In the figure, 1 is the flotation concentrate raw material (composed of more than 90% of the 200-mesh Tyra sieve)
There is also a head tank for storing recovered powder. The pulp supplied from the head tank 1 is adjusted to have an appropriate moisture content in a disk filter 2, and the filter cake obtained here is supplied to a boring desk 4 via a rotary bin 3. The filter cake, which is turned into pellets with a diameter of about 1/4 inch (6.35 mm) at the boring desk 4, is charged into a primary fluidized fluidized furnace 6 through a double lock type feeder 5. Then, the dust carried over from the primary fluidized furnace as transport layer dust is struck against the impingement plate 7 together with the carrier gas. At this time, large particle size dust is separated and collected from the gas whose direction has suddenly changed. The small particle size dust that cannot be recovered here is separated and recovered from the gas in the cyclone 8, and 99% of the finer dust is recovered in the next electrostatic precipitator 9. Water is added to the dust collected by the electrostatic precipitator 9 in a repulping tank 10, and the pulp is made into pulp and stored in the head tank 1 together with the flotation concentrate raw material. Further, 11 in FIG. 1 is an air lifter for transferring overflow cinder from the primary and secondary fluidized furnaces to the next process, and 12 is a secondary fluidized fluidized furnace. 2
The exhaust gas from the secondary fluidized fluidized furnace 12 is injected into the primary fluidized fluidized furnace 6 through a gas passage connected to the primary fluidized fluidized furnace 6. Overflow cinder (for example, low sulfur nickel oxide) from the secondary fluidized fluidized furnace 12 is led to a cooler 13 and cooled to near room temperature to become a product. This cooler 13 is of a fluidized bed type that blows atmospheric air from a wind box at the bottom of the furnace, and can also be cooled rapidly by injecting water from the furnace ceiling. The oxidized low-sulfur metals are sent to recovery equipment and recycled as dust. However, even in the above-mentioned fluidized roasting method, which was developed based on the idea of saving resources and energy, (a) the raw material is one that has been separated from the copper and Ni components by flotation; More than 90% of the raw material, nickel pine, has a particle size of -200 mesh, and therefore, in order to prevent most of the charge from becoming dry dust in the transport layer, 0.208 m2 containing about 7.5% moisture is used.
(b) A portion of the transport layer dry dust recovered from the primary fluidized fluidized furnace shall be charged to the primary fluidized fluidized furnace as pellets with a particle size between ~6.35 mm; (c) The remaining pellets must be mixed with nickel pine powder and charged to the primary fluidized fluidized furnace as pellets for the same reason as shown in item (a) above; (c) Since the raw material charged to the reactor is formed into pellets with a size of approximately 0.208 to 6.35 mm, a large amount of airflow is required to maintain a stable flow state, but when operated at such an airflow,
Pellet-like molded products are not roasted in the same size as when they were put into the fluidized fluidized furnace, and the strong wind pressure causes them to collide with each other, causing extensive wear and collapse, making it difficult to produce according to the amount of air blown. It becomes impossible. For this reason, it is often necessary to carry out operations where the concentration of sulfur dioxide gas in the exhaust gas is as low as 3.2 to 4.5%, making exhaust gas treatment equipment expensive; (d) Use of combustion improver oil; In an attempt to reduce the amount, the torrefaction temperature in the primary fluidized fluidized furnace is set to a high temperature of approximately 1204℃, and the average reaction residence time of the raw materials in the furnace is set to approximately 5 hours, ensuring the necessary internal volume. (e) Roasting temperature in the secondary fluidized flow furnace requires a large furnace, and requires a wind box pressure of about 7730 mm of water column, resulting in high power consumption. Therefore, in order to desulfurize the 0.15% S content in the calcined material that overflowed from the primary fluidized fluidized furnace and flowed into the secondary fluidized fluidized furnace, the average reaction residence time in the secondary fluidized fluidized furnace was approximately There were many problems, such as the need for a long time of 2 hours, which necessitated an increase in the internal volume of the reactor. From the above-mentioned viewpoints, the present inventors conducted research to find a metal sulfide fluidized roasting method that reduces the amount of combustion improver and reduces energy costs without increasing the size of the main equipment or adding additional auxiliary equipment. As a result of repeated efforts, the following findings were obtained. If, for example, crushed massive sulfide produced by removing impurities from garnierite is used as a raw material, flotation is not required since it is not metal matte from sulfide ore.
In addition, since it is a crushed lump of raw material, it has a larger particle size than the flotation concentrate, so it is roasted at a temperature of 900 to 1000°C, entangled with transport layer dry dust, and granulated in the furnace. Because of this trend, there is no need to pelletize it in advance, and furthermore, the recovered transport bed dry dust from the primary fluidized fluidized furnace can be mixed with crushed mats, which are the raw materials, in a pug mill and charged into the primary fluidized fluidized furnace. , There is a tendency for the transport layer dry dust to be entangled and granulated in the furnace at a roasting temperature of 900 to 1000℃, and as mentioned above, the raw material input to the primary fluidized fluidized furnace is not pellets but matte powder. If it is made into a mixture of itself and the transport layer dry dust, it will be densely fused in the furnace and become granular, so it will not crumble like pellet raw materials, but rather it will remain in the furnace to the extent that it will not adversely affect the fluidization state. It is granulated and roasted, the air ratio only needs to be around 1.2, the sulfur dioxide concentration in the exhaust gas is about 6-8%, the exhaust gas treatment equipment is compact, and the entire equipment is inexpensive. If the temperature is about 900 to 1000℃, the dry mixture of crushed mat and transport layer dry dust can maintain a stable fluidized state in the fluidized bed furnace, and at this temperature, the average reaction retention of the raw mat in the primary fluidized bed furnace If the time is about 3 hours, then
The residual sulfur of the torrefied calcined product from the secondary fluidized fluidized furnace can be set to an optimal value that can be used as a fuel in the secondary fluidized fluidized furnace, and the residence time in the primary fluidized fluidized furnace can be reduced, so the internal volume of the furnace can be reduced. It can be small, and the wind box pressure is about 3500 mm water column, which reduces power consumption. Even if the particles of the calcined material have been desulfurized to the extent that the sulfur content in the calcined material flowing into the fluidized fluidized furnace is less than about 1.0%, the average reaction residence time in the secondary fluidized fluidized furnace may be about 1 hour.
The internal volume of the furnace is relatively small, and the wind box pressure is also small, reducing the construction and operating costs of the furnace. Since it does not have a chemical composition that causes a desulfurization reaction, it is necessary to use a combustion improver such as oil to raise the roasting temperature. Fine powder (particle size
When bag filter mat powder (approximately 100μm) is injected into the lower part of the fluidized bed of a secondary fluidized furnace with hot air,
It instantly melts and adheres to cover the surface of the roasted and calcined material flowing in the furnace, and then rapidly reacts with oxygen to perform desulfurization. And this result is
Even without the aid of the exothermic reaction of the combustion improver oil,
The roasting temperature can be maintained at 1300-1400℃ mainly by the combustion heat of dry fine powder of raw material powder, and low-sulfur metal oxides can be produced even if the average reaction residence time in the secondary fluidized fluidized furnace is about 1 hour. Depending on the chemical composition of the raw material powder whose main component is metal sulfide, the operating conditions for torrefaction in the primary fluidized fluidized furnace may change; A part of the roasted and calcined material that overflows from the secondary fluidized fluidized furnace is mixed with the raw material powder in a pug mill without being sent to the secondary fluidized fluidized furnace, and is recycled and used to perform the function of a refrigerant while at the same time causing poor flow. By achieving the effect of suppressing the extreme granulation phenomenon that occurs in a fluidized bed furnace, smooth operation can be continued for a long period of time. Therefore, the present invention has been made based on the above knowledge, and provides a primary and secondary fluidized bed furnace equipped with a single hearth and an overflow port to process a raw material powder containing metal sulfide as a main component. In the method of fluidized fluidized roasting using an oxygen-containing gas, the raw material powder is the raw material powder that has been crushed, and this is charged in a dry state from the top of the primary fluidized fluidized furnace together with the transport layer dry dust. 2, and the particles of the roasted and calcined product are discharged from the overflow port.
Next, while adjusting the amount overflowing to the fluidized fluidized furnace,
Either low-temperature roasting is performed at a temperature of 1000℃ and then sent to the secondary fluidized fluidized furnace, or a portion of the overflowed roasted and calcined material is taken out and recycled as raw material powder without being sent to the secondary fluidized fluidized furnace. In addition, in the secondary fluidized flow furnace,
The dry crushed material of the raw material powder containing metal sulfide as a main component is blown into the fluidized bed, and the temperature range is 1300 to 1400℃ while adjusting the overflow amount of the low sulfur metal oxide powder product from the overflow port. It is characterized by producing low-sulfur metal oxides from metal sulfides at low cost by roasting them at high temperatures. In addition, in the fluidized roasting method of this invention, the raw material powder is charged into the primary fluidized fluidized furnace in a dry state because if the raw material contains more than a predetermined amount of moisture, the raw material loading of the fluidized fluidized furnace is The raw material becomes soft and lumpy at the entrance.
This is because there is a risk of blocking the ore supply chute. For example, if the raw material contains about 1% by weight of water, the ore feed chute will become clogged after about one hour of operation. In addition, the roasting temperature in the primary fluidized furnace is set to 900~
The reason why we set the temperature to 1000℃ is because if the roasting temperature is below 900℃, the residence time of the calcined material in the furnace will have to be extremely long, leading to a decrease in operational efficiency or an increase in the size of the fluidized roasting furnace equipment. On the other hand, if the roasting temperature exceeds 1000°C, the calcined materials in the fluidized bed furnace will exhibit a phenomenon in which they fuse together, leading to deterioration of fluidity and eventually rendering it impossible to operate. Furthermore, the roasting temperature in the secondary fluidized furnace was increased to 1300~
The reason for setting it at 1400℃ is that if the temperature is lower than 1300℃, the time required to reduce the residual sulfur in the roasted product to the desired value, that is, the residence time in the furnace, becomes longer, making efficient operation impossible. On the other hand, if the temperature exceeds 1,400°C, the calcined materials in the fluidized fluidized furnace will fuse together, and there is a risk that the refractories in the furnace will be melted and damaged. The roasting temperature in this secondary fluidized fluidized furnace also changes depending on the average particle size of the roasted product and the average reaction residence time. In the fluidized roasting method of the present invention, adjusting the amount of roasted and calcined material and roasted products overflowing from the overflow ports of the primary fluidized fluidized furnace and the secondary fluidized fluidized furnace is important in order to obtain high-quality products. It's important. This is because, in fluidized torrefaction, there is a large variation in the desulfurization rate due to short circuit overflow of the roasted calcined material, and the variation in the amount of overflowed roasted and calcined material, which is correlated with this, has traditionally been surprisingly important. They were not being looked at. However, this variation in desulfurization rate also
If the desulfurization rate is acceptable at a level of a few percent, it may not affect the quality of the product, but in the end it reaches 99.9%.
When aiming for a higher desulfurization rate, this cannot be ignored. Therefore, in the fluidized roasting method of the present invention, it is essential to adjust the overflow amount from the overflow port in order to stably obtain a high-quality product with no variation in desulfurization rate. be. Next, the fluidized roasting method of the present invention will be explained in more detail based on process diagrams. FIG. 2 is a schematic diagram showing the fluidized roasting process of the present invention. In Fig. 2, 21 is a raw material powder bin, and 22 is a container for collecting dry dust from the transport layer from the primary fluidized fluidized furnace using various dust collectors, and storing the dust transported by a chain conveyor with a water-cooled jacket. This is a dustbin that repeatedly collects powder. The raw material powder and the repeated dust are conveyed while being uniformly mixed by a pug mill 23, and charged into a primary fluidized fluidized furnace 24 by a rotary feeder with a gas seal. Reference numeral 25 is a gas cooler, in which the larger particle size of the rotating bed dry dust from the primary fluidized fluidized furnace is separated and recovered from the gas. The small-diameter dry dust in the transport layer that was not separated by the gas cooler 25 is transferred to the cyclone 2.
6, and further, the finest particles are separated and recovered from the gas in an electrostatic precipitator 27. dust content
The roasted gas whose concentration is less than 0.2 g/Nm ³ is sent to a sulfuric acid factory for sulfur dioxide gas recovery. Further, 28 is a secondary fluidized fluidized furnace, and the primary fluidized fluidized furnace 2
The roasted and calcined material overflowing from flow rate regulator 3
It flows in through 0. The low sulfur metal oxide produced by roasting in the secondary fluidized fluidized furnace 28 is passed from the overflow port of the secondary fluidized fluidized furnace to the product cooler 31 via a flow rate regulator 30'.
After cooling, it is packaged after passing the prescribed inspection.
The product will be shipped after the actual weight has been confirmed. In addition, 29 is a secondary fluidized fluidized furnace 28 in which dry fine powder, which is a raw material powder, is suspended in hot air and used as a transport layer dry fine powder.
It is a fluidized bed pot for stable pressure feeding to 3
2 is a burner for preheating the secondary fluidized furnace 28 together with the seed cinder at the start of operation. this is,
It can also be used in the unlikely event that an abnormal temperature drop occurs in the secondary fluidized flow furnace 28. Furthermore, Fig. 3 shows that a part of the roasted and calcined material overflowing from the primary fluidized fluidized furnace is not sent to the secondary fluidized fluidized furnace.
FIG. 2 is a schematic diagram showing a process for stabilizing the operation by mixing with the raw material charged in the primary fluidized bed furnace and recirculating it.
In addition, in FIG. 3, the same symbols are used for devices having the same functions as those in the fluidized roasting equipment shown in FIG. 2. The fluidized roasting process shown in FIG.
When the transport layer dry dust from No. 4 is granulated and roasted too much in the primary fluidized fluidized furnace and there is insufficient refrigerant to the primary fluidized fluidized furnace 24, the roasted dust that cannot become the transport layer dry dust in the primary fluidized fluidized furnace is A part of the calcined product is transferred to the primary fluidized furnace 24.
From the flow rate regulator 30″ to the roasted and calcined product cooler 3
3, and instead of sending it to the secondary fluidized fluidized furnace 28, it is mixed with the raw material powder in the pug mill 23 and used for circulation, so that it can function as a refrigerant, but at the same time, it can be used in extreme cases such as causing poor flow. The effect of suppressing the granulation phenomenon in the fluidized fluidized furnace is achieved, and smooth operation can be continued for a long period of time. Next, the present invention will be explained using examples and comparing with comparative examples. First, raw materials for examples of the present invention and raw materials for comparative examples as shown in Table 1 were prepared. In the examples of the present invention, the raw material was dry powder itself, and in the comparative example, it was pellets containing 7.5% moisture. In addition, the example of the present invention used the apparatus shown in the process diagram of FIG. 3, and the comparative example used the apparatus shown in the process diagram of FIG. 1 to carry out actual operation. It is something. The operating conditions at this time and the results obtained are also shown in Table 1. Both the method of the present invention and the comparative method are two-stage roasting methods, guaranteeing that the residual sulfur in the product is 0.02 weight or less, both can be operated using only air oxygen, and the product is roasted in a fluidized fluidized furnace. Since there is only overflowing cinder, they are similar in that there is almost no flow below 65 mesh, but the hearth sky velocity is

【table】

Compared to the 21.9 cm/sec in [Table], the comparative method has to use a much larger value of 46.8 cm/sec because the raw material is in the form of pellets and the particle size is large. Moreover, in comparative law,
Since the pellets cannot be kept in their original shape in the fluidized fluidized furnace, the production volume per unit floor area is slightly lower. In addition, in the comparative method, the roasting temperature of the primary fluidized furnace is
The temperature is as high as 1204℃, and the average reaction residence time is 5.24℃.
The time and wind box pressure are set to 7,730 mm water column to reduce the use of combustion improver in the secondary fluidized fluidized furnace. The dry fine powder is used as a substitute for oil as a combustion aid, and the roasting temperature in the primary fluidized fluidized furnace is as low as 940°C, the average reaction residence time is as short as around 3 hours, and the air flow rate is also low. It is clear that the wind box pressure can be lowered to 3500mm water column, which has a great effect on reducing power consumption. In addition, in the secondary fluidized fluidized furnace, the method of the present invention raises the roasting temperature, so the average residence time is 1.0 hours, which is much shorter than the 2.26 hours of the comparative method, and the internal volume of the furnace is Productivity per unit area has also improved. Furthermore, the concentration of sulfur dioxide gas in the exhaust gas is also very high in the method of the present invention, and it is clear from the above results that the exhaust gas recovery efficiency and recovery cost can be improved. Although this example describes the fluidized roasting method for nickel pine, good results can also be obtained by applying the method of the present invention to roasting other metal sulfides, such as zinc sulfide concentrate. Of course it is possible. As described above, according to the present invention, low-sulfur metal oxides can be efficiently produced from metal sulfides at low cost under stable operation, and sulfur from the by-product concentrate can be produced. The yield rate of sulfation is also significantly improved, and industrially useful effects such as greatly contributing to pollution prevention are brought about.

[Brief explanation of the drawing]

Figure 1 is a process diagram of the conventional metal sulfide fluidized roasting method, Figure 2 is a process diagram of the fluidized roasting method of the present invention, and Figure 3 is a process diagram of the fluidized roasting method of the present invention.
The figure is a drawing showing the steps of another fluidized roasting method of the present invention. In the drawings, 1...head tank, 2...desk filter, 3...rotary bin, 4...boring desk, 5...double lock type feeder, 6...primary flow furnace, 7...impingement plate, 8...cyclone, 9...electricity Dust collector, 10... Repulping dunk, 11... Air lifter, 12... Secondary fluidized furnace, 13... Cooler, 21... Raw material powder bin, 22...
Dust bin, 23... Pug mill, 24... Primary fluidized fluidized furnace, 25... Gas cooler, 26... Cyclone, 2
7... Electrostatic precipitator, 28... Secondary fluidized fluidized furnace, 29... Fluidized bed pot, 30, 30', 30''... Flow rate regulator, 3
1... Product cooler, 32... Preheating burner, 33... Roasting and calcined product cooler.

Claims (1)

[Claims] 1. A method of fluidized roasting of a raw material powder containing metal sulfide as a main component using an oxygen-containing gas using a primary and secondary fluidized fluidized furnace equipped with a single hearth and an overflow port. In this method, as the raw material powder, the raw material powder is used as it is, and it is charged in a dry state from the top of the primary fluidized fluidized furnace together with the transport layer dry dust, and the roasted and calcined product particles are passed through the overflow port. While adjusting the amount that overflows from the raw material to the secondary fluidized fluidized furnace, it is first roasted at a low temperature in a temperature range of 900 to 1000°C, and then in the secondary fluidized fluidized furnace, the raw material containing metal sulfides as the main component is transferred to the fluidized bed. While blowing in the dry pulverized powder and adjusting the overflow amount of the low sulfur metal oxide powder product from the overflow port,
A fluidized roasting method for producing low-sulfur metal oxides from metal sulfides, which is characterized by high-temperature roasting in a temperature range of 1300 to 1400°C. 2. In a method of fluidized roasting a raw material powder containing metal sulfide as a main component using an oxygen-containing gas using a primary and secondary fluidized fluidized furnace equipped with a single hearth and an overflow port, as the raw material powder The crushed raw material is used as it is, and it is charged in a dry state from the top of the primary fluidized fluidized furnace together with the transport layer dry dust, and the roasted and calcined material particles are transferred from the overflow port to the secondary fluidized fluidized furnace. While adjusting the amount of overflow, we first perform low-temperature roasting in a temperature range of 900 to 1000℃, and then take out a portion of the overflowed calcined material and use it as raw material powder without sending it to the secondary fluidized fluidized furnace. Furthermore, in the secondary fluidized bed furnace, the dried powdered powder containing metal sulfide as the main component is blown into the fluidized bed, and the amount of overflow of the low sulfur metal oxide powder product from the overflow port is increased. A fluidized roasting method for producing low-sulfur metal oxides from metal sulfides, which is characterized by high-temperature roasting in a temperature range of 1300 to 1400°C while adjusting the temperature.