JP2006255530A - Separation method for foreign matter particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for improving the fact that a separation efficiency is extremely insufficient and does not reach to a practical level regarding many particles in separation of particles by an electrostatic separator and a magnetic separator conventionally. <P>SOLUTION: In the electrostatic separator and the magnetic separator, before the particles are charged with a charge or magnetism in order to separate a mixed powder of particles having different characteristics, aggregate existing in the mixed powder of particles is dispersed. Specifically, the dispersion is performed at the high dispersing condition by an ejector, a pipe or the like. Thereafter, the particles having different characteristics are separated by the electrostatic separator or the magnetic separator. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is economical when separating and recovering target substances or separating and removing unnecessary components from various minerals in powder form, powdered intermediate products or wastes in various industries using static electricity or magnetism. The present invention relates to a method for providing a desired separation / recovery efficiency or removal efficiency, and a target component concentration rate that can withstand practical use.

  The method of separating and recovering the target substance from the powder containing particles of different components and substances, removing unnecessary substances, or concentrating the target substance, the specific gravity of these particles, magnetic properties (magnetism), Conventionally, there are various methods such as specific gravity separation, magnetic separation, and electrostatic separation utilizing differences in physical or physicochemical properties such as electrical properties (dielectric constant, electrical conductivity, chargeability). In selecting these methods, the target substance to be separated and recovered or concentrated is determined by the difference in characteristics from the remaining unnecessary substances. However, in many cases, these methods conventionally have a low separation / recovery efficiency and concentration rate of the target substance, and have been limited in practical use in industry.

  On the other hand, in recent years, the separation and recovery or concentration of residual useful substances for recycling and utilization of resources, especially useful minerals, and by-products and waste from various industries has become extremely important, and the target substance has become practical. It is strongly desired to establish technology for separation and recovery efficiency and concentration rate that can withstand sufficiently, as well as low equipment costs and running costs.

Under such circumstances, the method using electrostatic separation and the method using magnetic separation are both promising in recent years because both the construction cost and running cost of equipment are low, and they may be applicable in a wide range of fields. However, most of the conventional techniques have low separation and recovery efficiency and concentration rate of the target substance and have not been practically used.
For example, in the method using electrostatic separation, techniques as disclosed in Patent Document 1 and Patent Document 2 are known.
JP 2004-243154 A International Publication 2002/76620 Pamphlet

  The present invention has discovered that the major cause of the impediment to practical use by adversely affecting the separation efficiency such as the separation and recovery efficiency and concentration of the target substance is something other than what was conventionally known and common sense, In order to greatly improve the separation efficiency enough for practical use, a specific method for overcoming the cause of the inhibition has been devised.

In electrostatic separation, the moisture on the particle surface that affects the surface conductivity and contact resistance of the particle, or the humidity in the air that affects it affects the separation efficiency such as the separation recovery efficiency and concentration of the target substance. It is well known that it is an important factor and needs to be done in a dry state.
However, when the experiment is actually performed in a dry state, some particles exhibit a relatively high separation efficiency, but many particles have an extremely insufficient separation efficiency, and can reach a practical level at all. There wasn't.

  Therefore, in order to find out factors that have a significant effect other than moisture and humidity, the inventor must supply the gas type and temperature, gas flow rate, applied voltage, electric field strength, magnetic strength, magnetic gradient, and fluidized state of the powder layer. In addition to the operating conditions, we investigated and investigated the effects of particle size distribution, particle surface chemical composition, and adsorbents. As a result, in both electrostatic separation and magnetic separation, it was discovered that the separation efficiency is greatly reduced if a mixture of particles with different characteristics contains a lot of fine powder with a sphere equivalent diameter of 10 μm or less. . It can be considered that the agglomeration of particles becomes remarkable when the amount of such fine powder is large, and the separation efficiency deteriorates due to aggregation in a state where particles having different properties to be separated, that is, a target substance and a non-target substance are mixed. According to further investigation and investigation by the inventor, even if the fine powder of 10 μm or less is only one of the target substance and the non-target substance, the fine powder is a fine powder. It has also been found that it adheres to the surface of large particles and cannot effectively perform electrostatic separation, greatly reducing the separation efficiency.

  As a countermeasure for these, the inventor has devised the following method. In other words, the mixed powder of particles to be supplied to the electrostatic separation device or magnetic separation device is dispersed in advance (disaggregating the particles into unitary particles of the target substance or non-target substance). This is a method of promptly supplying the separation device before re-aggregation. Specifically, as a means for dispersion, the mixed powder is supplied into an ejector having a gas supply pressure of 100 kPa to 600 kPa in gauge pressure or a jet behind the ejector (Claim 1), and the Reynolds number is Supplying the mixed powder into a pipe having a gas flow of 12000 or more (Claim 2), and the mixed powder in a container in which a protrusion attached to a rotating shaft rotates at a peripheral speed of 5 m / s or more. Supplying the body (Claim 3), supplying the mixed powder into a container having a rotating body in which a protrusion attached to each of two or more rotating shafts on the same line rotates. The particle separation method for dispersing the particle aggregates in the mixed powder is a relative circumference by rotation of the projections at the portion where the projections attached to the two rotating shafts are closest to each other. Speed is at its maximum The mixed powder is supplied to a container filled with a ball having a sphere equivalent diameter of 1 mm to 60 mm or a solid that does not limit the shape as a dispersion medium. The dispersion medium may be moved by rotating or rotating a rotating shaft installed inside the container and a stirring blade or a stirring rod joined to the rotating shaft (Claim 5).

  The present invention makes it possible to recover only the target substance from the mixed powder of the target substance particles and the non-target substance particles with high purity (high concentration) and high yield. The target substances can be used effectively, and from the viewpoint of effective use of resources and by-products / industrial waste, it can greatly contribute to the future effective use of resources on a global scale and environmental measures.

Hereinafter, a specific method of the present invention will be described.
In the first method of dispersing in advance (Claim 1), the mixed powder (raw material powder) in which the target substance particles and the non-target substance particles having properties to be separated are mixed is separated by being charged or magnetized. Before, a gas such as air is supplied to an ejector whose example is shown in FIGS. 1 and 2 at a supply pressure of 100 kPa to 600 kPa, more preferably 200 kPa to 400 kPa as a gauge pressure, and the negative pressure portion in the ejector Alternatively, supply raw material powder into the jet behind the ejector to sufficiently disperse the target substance and non-target substance, that is, particle aggregates with different electrical characteristics (dielectric constant, conductivity, etc.) or magnetic characteristics. It is. If the supply pressure is too low, the dispersion becomes insufficient. If the supply pressure is too high, pulverization occurs partially at the same time and fine powder increases, both of which are undesirable in terms of separation efficiency. In addition, if the supply pressure is excessive, a large compressor is required, which is not economical in terms of equipment and energy consumption.

  The second method of dispersing in advance (Claim 2) is to provide a Reynolds number before separating the raw material powder in which the target substance particles and the non-target substance particles to be separated are charged or magnetized. Supply raw material powder into a pipe with a gas flow of Re 12000 or more, more preferably 40000 or more, and target and non-target materials, that is, different electrical characteristics (dielectric constant, conductivity, etc.) or magnetic It is to disperse particle aggregates having characteristics.

Here, the Reynolds number Re is a dimensionless number defined by the following equation, which indicates a turbulent state in the pipe, and means that the larger the value, the stronger the turbulent flow. The units of D, U, ρ, and μ are arbitrary, and the calculated Re may be dimensionless.
Re = D Uρ / μ
D: Inner diameter of pipe
U: Gas velocity in the pipe
ρ: Gas density
μ: Gas viscosity coefficient

  The supplied raw material powder has a strong turbulent flow as shown by the Reynolds number (turbulent flow when the Reynolds number is 3000 or more) in the pipe as schematically shown in FIG. A strong collision occurs between the walls and the agglomerated particles are dispersed. At that time, a plurality of pipes may be provided in parallel. Moreover, the cross-sectional shape of the pipe is not limited, and may be circular or rectangular. Furthermore, the length of the pipe may be designed so that the residence time of the gas passing through the pipe is 0.005 seconds or longer.

  The third method of dispersing in advance (Claim 3) is to rotate the rotating shaft before separating the raw material powder in which the target substance particles having properties to be separated and the non-target substance particles are mixed with electric charge or magnetism. The raw material powder is supplied continuously or batchwise into a container in which protrusions such as blades and pins attached to the blade rotate at a speed of 5 m / s or more, preferably 15 to 50 m / s. Dispersing substances and non-target substances, that is, particle aggregates having different electrical characteristics (such as dielectric constant and conductivity) or magnetic characteristics.

  FIGS. 4 and 5 show examples of structures in which the blade and the pin rotate in the container, respectively. Many variations are conceivable for these structures and shapes, but the shape is not limited as long as the supplied raw material powder has a structure in which an impact force or a shear force is applied by a rotating blade or pin. For example, a high-speed rotational impact pulverizer such as a pin mill or a blade mill can be applied to the dispersion of the present invention. If the speed of the blade or pin is too slow, the dispersion will be insufficient, and if the speed is too fast, pulverization will occur simultaneously and fine powder will increase, both of which are undesirable in terms of separation efficiency. Further, when the rotational speed is excessive, it is not economical in terms of equipment cost and energy consumption.

  Further, in the container, at least two rotation shafts are provided on the same line, the protrusions attached to the respective rotation shafts are rotated, and the protrusions in the portions where the protrusions are closest to each other are rotated. The relative peripheral speed by rotation may be set to 5 m / s or more at the position where the maximum speed is attained (claim 4). FIG. 6 shows an example of a pin mill provided with two rotating shafts. In FIG. 6, shafts 11a and 11b are provided on the same line. Pins 10a and 10c are attached to shaft 11a, and pin 10b is attached to shaft 11b. “The position where the respective protrusions are closest to each other” refers to the position between the pins 10a and 10b in the case of FIG. 6 and thus the relative position of the pins 10a and 10b. The shafts 11a and 11b are rotated so that the peripheral speed becomes 5 m / s or more. In this case, the relative peripheral speed of the pins 10b and 10c is smaller than the relative peripheral speed of the pins 10a and 10b, but the position where the relative peripheral speed is maximum, that is, the portion where the projections are closest to each other, The radial position may be the outermost side, and the relative peripheral speed between the pins 10a and 10b may be 5 m / s or more in FIG. The shafts 11a and 11b may rotate in opposite directions, or may rotate in the same direction. Further, the form of the dispersing device is not limited to the pin system as shown in FIG. It suffices that at least two rotating shafts that rotate separately and protrusions are attached to the respective rotating shafts, and that each protrusion can rotate at a relative peripheral speed of 5 m / s or more. By introducing the raw material powder into such a container, the same dispersion effect as described above can be obtained.

  In the fourth method of dispersing in advance (Claim 5), before the raw material powder in which the target substance particles having properties to be separated and the non-target substance particles are mixed is separated by charging or magnetizing, FIG. For example, in a container filled with balls having a sphere equivalent diameter (the diameter of the sphere assuming a sphere with the same volume) of 1 mm to 60 mm, preferably 5 mm to 40 mm as a dispersion medium, By rotating or rotating a rotating shaft and a stirring blade or a stirring rod joined to the rotating shaft inside the container, the ball as the dispersion medium is moved, and the raw material powder is supplied continuously or batchwise to the container, The target substance and the non-target substance, that is, particle aggregates having different electrical characteristics (such as dielectric constant and conductivity) or magnetic characteristics are sufficiently dispersed. There is no limitation on the shape of the container and the direction of the rotation axis, and the rotation axis may be horizontal or vertical. For example, a ball mill or a medium stirring mill can be applied to the dispersion of the present invention. If the diameter of the ball is too small, the passage resistance of the raw material powder becomes large and continuous supply becomes difficult, and in the batch type, powder discharge after dispersion (separation from the ball) is not easy. On the other hand, if the balls are too large, the gap between the balls becomes large, so the ratio of the raw material powder passing through without being dispersed becomes high, and the impact force of the balls becomes large, and the function of agglomerating fine powders also appears. Not desirable. When the ball becomes larger, the torque applied to the shaft becomes excessive, and the shaft may not rotate. Here, the shape of the dispersion medium filled in the container is not limited as long as the balls have the same sphere equivalent diameter. Further, the material is selected from wood, cork, rubber, plastics, ceramics, metal, and the like depending on the strength of aggregation of the raw material powder. Note that the average residence time of the raw material powder in the container is preferably within 10 minutes because it is necessary to prevent the fine powder from being excessively generated as the pulverization proceeds.

  Coal ash (fly ash) generated from power stations nationwide is about 10 million tons per year. From the viewpoint of effective use of resources, the use of low-grade coal with high ash content will increase. Further increase is expected. Of this, about 60% is used as part of the raw material in cement production, and the usable amount has already reached its limit due to the chemical composition of cement. Most of the rest is disposed of in landfills. It goes without saying that this landfill disposal is not desirable for environmental measures.

  In order to further increase the amount of fly ash used in the cement field, it is necessary to add and mix not only as a raw material but with the finished cement within the range specified by JIS. At present, however, unburned carbon remaining in fly ash (more than a few percent of the carbon component that did not burn when coal is burned at a thermal power plant) adversely affects the quality of cement and concrete. Then, the addition mixing is not completed.

Therefore, if unburned carbon is efficiently separated and removed from such fly ash, and the unburned carbon content in the fly ash can be reduced to about 0.5% or less, it can be added to the cement.
Against this background, electrostatic classification using the difference in electrical characteristics between ash and carbon has attracted attention. However, the concentration rate of the target substance (concentration rate of the ash content, that is, the unburned carbon content in fly ash) Both the separation and recovery efficiency (fly ash yield) have not reached practical levels.

Therefore, the results of experimental investigation of the effect of the present invention are shown below.
In this example, before supplying fly ash having an unburned carbon content of 3.2 mass% to the electrostatic separator, the fly ash was dispersed with air using an ejector as shown in FIG. After the dispersion, separation was performed using an electrostatic separation device with an electrode interval of 65 mm, an applied voltage of 30 kV, and dry air (temperature 70 ° C., relative humidity 10%) as a gas. FIG. 8 shows a part of the result. In this figure, data where the supply pressure is 0 is the case where this dispersing device is not used, that is, the conventional case. As can be seen from the figure, by using the ejector, the unburned carbon content is significantly reduced and the yield is also greatly improved. It can also be seen that the supply pressure has an appropriate range.

  As a result, the unburned carbon content on the separated low carbon content side (ash concentration side) has reached a value that can be added to and mixed with cement, but on the other hand, the yield has been greatly improved and discarded. The amount of ash on the high carbon content side (carbon enrichment side), which is the target, is drastically reduced and the carbon content is increased, suggesting that it may be used as a fuel substitute in some cases.

In this example, the same fly ash as in Example 1 was used, and dispersion was performed using a pipe as shown in FIG. 3 as a dispersing device, and a similar experiment was performed. A part of the result is shown in FIG.
In this figure, the data with a Reynolds number of 1000 is almost the same value as when this dispersing device is not used. As can be seen from the figure, the use of pipes significantly reduces the unburned carbon content and significantly improves the yield.

In this example, the same experiment was performed by making a prototype of a high-speed rotating dispersion device for pins as shown in FIG. 5 using the same fly ash as in Example 1. A part of the result is shown in FIG.
In this figure, the data where the rotational speed of the pin is 0 is the case where this dispersing device is not used, that is, the conventional case. As can be seen from the figure, the use of this dispersing device significantly reduces the unburned carbon content and significantly improves the yield. It can also be seen that there is an appropriate range for the rotational speed of the pin.

In this example, the same experiment was performed using the same fly ash as in Example 1 to produce a ball motion type dispersion apparatus as shown in FIG. 7D. The ball material was rubber. A part of the result is shown in FIG.
Although not shown in this figure, the data in the case where this dispersing device is not used, that is, in the conventional case, is the same as that in the case where the supply pressure in Example 1 is 0. As can be seen from the figure, the use of this dispersing device significantly reduces the unburned carbon content and significantly improves the yield. It can also be seen that the ball has an appropriate range.

In this embodiment, in order to separate and remove the wear iron powder mixed in the silicon nitride powder pulverized by a ball mill using an iron pulverizing medium, the high-speed rotating dispersing device for pins according to claim 3 This is an experiment of magnetic separation using ceramics. A part of the result is shown in FIG. Here, separation was performed using a drum-type magnetic separation device having a magnetic field strength of 500 Oe as the magnetic separation device.
In this figure, the data where the rotational speed of the pin is 0 is the case where this dispersing device is not used, that is, the conventional case. As can be seen from the figure, the Fe content is significantly reduced by using this dispersing device. It can also be seen that there is an appropriate range for the rotational speed of the pin.

It is a figure which illustrates the schematic of the structure of an ejector. It is a figure which illustrates the schematic of the structure of an ejector. It is a figure which illustrates the schematic of the structure of a pipe. It is a figure which illustrates the schematic of a blade-type disperser. It is a figure which illustrates the schematic of a pin type | mold disperser. It is a figure which illustrates the schematic of a 2-axis type pin type disperser. It is a figure which illustrates the schematic of a ball filling type disperser. It is a figure which shows the unburnt carbon content rate and concentrated fly ash yield when fly ash is processed by the electrostatic separator after being dispersed by the ejector. It is a figure which shows the unburned carbon content rate and concentrated fly ash yield when fly ash is processed by the electrostatic separator after being dispersed by the dispersion pipe. It is a figure which shows the unburned carbon content rate and concentrated fly ash yield when fly ash is processed by the electrostatic separator after being dispersed by the pin type disperser. It is a figure which shows the unburned carbon content rate and concentrated fly ash yield when disperse | distributing with a ball filling type disperser and processing fly ash with an electrostatic separator. It is a figure which shows Fe content when a silicon nitride powder is processed with a magnetic separation apparatus after disperse | distributing with a pin type disperser.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pressure gauge 2 Compressed gas 3 Raw material powder 4 Gas 5 Flowmeter 6 Blade 7 Rotating plate 8 Projection 9 Motor 10 Pin 10a Pin 10b Pin 10c Pin 11a Rotating shaft 11b Rotating shaft

Claims (5)

  In an electrostatic separation operation or magnetic separation operation in which particles having different characteristics are separated from a mixed powder of particles having different characteristics, the gas supply pressure is reduced to a gauge pressure before the mixed powder is separated by being charged or magnetized. A method for separating particles, characterized in that particle aggregates in the mixed powder are dispersed by supplying the mixed powder into an ejector of 100 kPa to 600 kPa or a jet behind the ejector.   In an electrostatic separation operation or magnetic separation operation that separates particles with different characteristics from a mixed powder of particles having different characteristics, a gas having a Reynolds number of 12000 or more is separated before the mixed powder is charged or magnetized. A method for separating particles, comprising supplying the mixed powder into a pipe having a flow to disperse particle aggregates in the mixed powder.   In an electrostatic separation operation or magnetic separation operation for separating particles having different characteristics from a mixed powder of particles having different characteristics, a protrusion attached to the rotating shaft before the mixed powder is separated by being charged or magnetized. Particles characterized by dispersing particle aggregates in the mixed powder by supplying the mixed powder into a container having a rotating body whose outermost part rotates at a peripheral speed of 5 m / s or more Separation method.   In electrostatic separation operation or magnetic separation operation that separates particles with different characteristics from a mixed powder of particles with different characteristics, before the powder mixture is charged or magnetized and separated, A method for separating particles in which the mixed powder is supplied to a container having a rotating body that rotates a projection attached to each of two or more rotating shafts to disperse particle aggregates in the mixed powder. The relative peripheral speed by the rotation of the projections at the portion where the projections attached to the two rotating shafts are closest to each other is 5 m / s or more at the maximum position. A method for separating particles.   In an electrostatic separation operation or a magnetic separation operation in which particles having different characteristics are separated from a mixed powder of particles having different characteristics, a sphere equivalent diameter is used as a dispersion medium before the mixed powder is separated by being charged or magnetized. The mixed powder is supplied to a container filled with 1 mm to 60 mm balls or solids not limited in shape, and the container is rotated or a rotating shaft installed inside the container and a stirring blade or a stirring rod joined thereto are provided. A method for separating particles, characterized by dispersing particle aggregates in the mixed powder by rotating and moving the dispersion medium.

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