JPS629372B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a heat treatment method such as drying, calcination, etc. of a material having a particle size distribution such as coal, limestone, etc., and an apparatus therefor. When a fluidized bed apparatus is used to perform heat treatments such as drying and calcining of natural products such as coal and limestone, the treatment is generally performed on particles with a narrow particle size distribution. Recently, there has been a growing demand for continuous heat treatment of materials with a large particle size distribution using a fluidized bed method, and especially for coal, there has been a strong demand for continuously and uniformly drying materials with a large particle size distribution (0 to 50 mm). Ta. However, conventional fluidized bed apparatuses have the disadvantage that the residence time and gas superficial velocity cannot be adjusted appropriately depending on the particle size. Furthermore, conventional kiln-type and grade-type heat treatment apparatuses not only have the disadvantage of poor thermal efficiency and require a large floor area, but also have difficulty uniformly drying coal particles with a large particle size distribution. In order to establish a technology that meets the above requirements, the present inventors have conducted intensive research and found that it is possible to operate materials with a large particle size distribution so that the residence time and gas superficial velocity are in accordance with the particle size. Eventually, they invented a method and apparatus that can perform heat treatment continuously and uniformly in a fluidized bed. That is, the present invention provides (1) a method of heat treating a material with a particle size distribution using a high temperature gas fluidized bed method, in which a fluidized bed is formed in which the superficial velocity of the high temperature gas increases in the lower stages in multiple stages; The above-mentioned material is supplied into a fluidized bed at each stage, and the part of the material with a particle size that cannot be fluidized in the fluidized bed at each stage is sequentially dropped into the fluidized bed at the lower stage to form a fluidized bed and then heat-treated with high-temperature gas. (2) A method for heat treating a material with a particle size distribution, and (2) a column apparatus for heat treating a material with a particle size distribution in a fluidized bed type with high-temperature gas, in which the diameter of the column is reduced in multiple stages toward the bottom. , the gist is a heat treatment apparatus for materials with a particle size distribution, which is characterized in that a high-temperature gas distribution plate inclined at a portion where the column diameter changes stepwise is provided such that the lower side thereof maintains a constant distance from the column wall. It is something to do. Hereinafter, the present invention will be described in detail with reference to FIG. 1, with reference to FIG. 1, in which it is applied to coal drying as an example. FIG. 1 shows an embodiment of the apparatus of the present invention, in which 1 is a coal supply line, 2 is a high-temperature gas supply line, 3 is a heat-treated gas discharge line, 4 is a cyclone, 5 is a gas discharge line, and 6 is a fine particle Coal discharge line, F ₁ , F ₂ and F ₃ are column diameter D ₁ ,
This is a fluidized bed section having D ₂ and D ₃ (D ₁ >D ₂ >D ₃ ). 7, 8 and 9 are fluidized bed sections F ₁ to _{F 2} , respectively.
A gas distribution plate installed between F ₂ to F ₃ and F ₃ to the high temperature gas line 2. The gas distribution plates 7 and 8 are inclined as shown in the figure, and have a certain gap α,
It is provided with β open. 10 and 11 are valves that move large coal particles from the fluidized bed section F ₁ to F _{2 ;}
In order to further classify the gas into _F3 , it is provided in association with each gas distribution plate 7,8. Reference numerals 12, 13 and 14 are discharge lines for coal particles that have been subjected to fluidized bed treatment from each fluidized bed section F ₁ , F ₂ and F ₃ . Coal with a particle size distribution is supplied from the coal supply line 1 to the fluidized bed section F ₁ with a column diameter D ₁ at the top stage, and only the coal with a particle size corresponding to the superficial velocity of the high-temperature gas is fluidized. After remaining for a certain period of time, discharge line 1
However, coal with a larger particle size is not fluidized and falls onto the gas distribution plate 7. Since this gas distribution plate 7 is inclined, the coal that falls there moves downward on the gas distribution plate 7, and the coal falls on the valve 1.
0 and falls into the fluidized bed section _F2 . Fluidized bed section F ₁
The high-temperature gas that dried the coal passes through a derivation line 3 and reaches a cyclone 4, where it is separated into exhaust gas and fine coal, which are discharged through a gas discharge line 5 and a fine coal discharge line 6, respectively. In the fluidized bed section F ₂ , the column diameter is D ₂ and D ₂ <D ₁ , so the superficial velocity of the high temperature gas rising there is higher than that of F ₁ , so in the fluidized bed F ₂ , Coal larger than the particle size in the fluidized bed section _F1 is fluidized, and since the high temperature gas temperature is also high, coal with a large particle size is sufficiently dried while staying in the fluidized bed and is discharged from the discharge line 13. be done. The large particle size coal that is not fluidized in the fluidized bed section _F2 also falls onto the gas distribution plate 8 below the fluidized bed section _F2 , moves the gas distribution plate 8 by the same action as described above, and moves to the valve 11. The coal then falls into the lower fluidized bed section _F3 , where all of the large particle size coal is fluidized and is discharged from the discharge line 14 after staying there for a certain period of time. By doing this, the larger the particle size of the coal, the longer it takes to pass through and stay in the entire fluidized bed, and the more it comes into contact with the higher temperature gas, so even the larger particle size can be sufficiently dried. I can do it. It should be noted that the gas distribution plate 9 of the fluidized bed section _F3 does not need to be inclined, nor does it need to have a certain interval between it and the tower wall. It will be easily understood that the fluidized bed section may be provided in two or more arbitrary stages depending on the width of the distribution. Further, the gas superficial velocity of each fluidized bed section is determined by the following method. In other words, coal etc. are treated as Rosin-
It has a particle size distribution that is almost a straight line 1 on the Rammler diagram. Now, if we assume that the number of fluidized bed sections is three stages F ₁ , F ₂ , and F ₃ as shown in Figure 1, each fluidized bed section F ₁ , F ₂ , and F ₃ will each account for 33.3% of the cumulative weight. Ideally, each particle should be fluidized. On the other hand, the gas superficial velocity in each fluidized bed section F ₁ , F ₂ , F ₃ is determined by the representative particle size of the particles in that fluidized bed section (the ideal average particle size is between the maximum particle size and the minimum particle size). is determined based on the minimum fluidization speed U of Fluidization occurs, but the amount of fragmentation and scattering of small particles increases, and conversely, if the minimum fluidization speed U is set based on the minimum particle size, large particles will not be fluidized and will stagnate. In order to fluidize the particles uniformly and without carrying over, the minimum fluidization speed U is determined by using the average particle size ((arithmetic mean particle size of maximum particle size and minimum particle size)) as the representative particle size. (preferably). In Figure 2, the average particle size of fluidized bed section _F1 is 83.3
% (=100+66.6/2), that is, 1.9 mm, and similarly, the average particle size of the fluidized bed section _F2 is at a position of 50% of the cumulative weight (=66.6+33.3/2). The particle size is 7.8 mm, and the average particle size in fluidized bed section _F3 is 16.7% of the cumulative weight (=
The grain size is 19.9 mm at the position of 33.3/2). Therefore, the gas superficial velocity in each fluidized bed section F ₁ , F ₂ , F ₃ is the minimum velocity U ₁ , U ₂ , U ₃ that can fluidize particles with particle diameters of 1.9 mm, 7.8 mm, and 19.9 mm, respectively. determined based on. Specifically, in the fluidized bed section _F1 , the minimum fluidization speed for particles with a particle size of 1.9 mm is 0.5 m/
sec, and the gas superficial velocity is 1 to 2 times this, that is, 0.5 to 1.0 m/sec, similarly, in the fluidized bed section _F2 , it is 7.5 to 15 m/sec, and in the fluidized bed section _F3 , it is 20 to 1.0 m/sec.
It is preferable to set it as 40m/sec. By the way, in the above example, the fluidized bed section is divided into three parts: F ₁ , F ₂ , and F ₃ .
Regarding the case where the fluidized bed section is
In the case of n stages of F ₁ , F ₂ , ......Fm, ......Fn,
The cumulative weight on the Rosin-Rammler line in each fluidized bed section is determined from the formula 1/2n (2n-2m+1) x 100%, and the average particle diameter is determined on the Rosin-Rammler line from this cumulative weight. The gas superficial velocity of is determined. Note that the minimum fluidization speed of particles is calculated by the following formula. U _nf = (D _p φ _s ) ² /180 (ρ _s − ρ _F )/
M _F gε ³ _nf /1−ε _nf U _nf : Minimum fluidization speed (cm/sec) D _p : Particle diameter (cm) φ _s : Shape factor (-) ρ _s : Solid density (g/cm ³ ) ρ _F : Fluid density (g/cm ³ ) M _F : Fluid viscosity (g/cm・sec) g: Gravitational acceleration = 980 cm/sec ² ε _nf : Coarsest porosity (-) Furthermore, as described above, each fluidized bed In order to change the superficial gas velocity of each fluidized bed section, it is necessary to change the cross-sectional area of each fluidized bed section since the inlet gas amount is constant. This cross-sectional area is determined such that the cross-sectional area x gas superficial velocity is constant in each fluidized bed section. The method and apparatus of the present invention described above have the following advantages over other drying apparatuses and ordinary fluidized bed drying apparatuses. (1) Compared to common drying equipment such as kilns and grade drying equipment, it has a larger processing capacity and is more efficient. (2) It is difficult to uniformly dry solids with a particle size distribution using a normal fluidized bed dryer, but according to the present invention, solids of all particle sizes flow at a gas superficial velocity corresponding to the particle size. Furthermore, larger particles have a longer residence time and come into contact with a higher temperature gas, so uniform drying can be achieved. (3) As stated in (2) above, the larger the particles, the longer the residence time and the contact with the high temperature gas, which causes the particles to be crushed and the particle size distribution of the product particles to be uniform. Next, the effects of the present invention will be specifically illustrated by giving Examples. Example (i) Properties of coal used Moisture 8.8% Ash 11.8% Volatile content 35.6% Fixed carbon 43.8% Calorific value 5700 Kcal/Kg (ii) Experimental apparatus An apparatus according to the present invention shown in the flowchart of Fig. 3,
For comparison, a conventional fluidized drying apparatus shown in the flowchart of FIG. 4 was used. In FIG. 3, the same symbols as in FIG. 1 indicate the same functional parts as in FIG. 1, 31 is an air introduction line, 32 is a propane introduction line, 33 is a furnace, 34 is a scrubber, The same reference numerals as in FIGS. 1 and 3 indicate the same functional parts as in FIGS. 1 and 3, 41 is a fluidized bed, and 42 ₁ and 42 ₂ are treated coal discharge lines. (iii) Experimental conditions

【table】

[Table] (iv) Experimental results The water content in the product charcoal by particle size is as shown in the table below, and the particle size distribution of the product charcoal is as shown in Figure 2. In Figure 2, line 2 is In the present invention example, line 3 is the particle size distribution of the product charcoal according to the comparative example.

[Table] From the above table, it can be seen that in the present invention, a product having almost uniform moisture content throughout the grain size can be obtained, but in the ordinary fluidized bed treatment, large grain size coal is not dehydrated very much. In addition, from the data in Figure 2, in the present invention, the slope of the line for particle size distribution 2 of product coal is considerably larger than that of particle size distribution 1 for coking coal, indicating that large particle size coal is crushed during processing and the particle size distribution is changed. It can be seen that the particle size has become narrower (that is, the particle size has become more uniform).

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the basic flow and configuration of the method and apparatus of the present invention, and Fig. 2 is a diagram showing the particle size distribution of coking coal and each product coal obtained in Examples on the Rosin-Rammler diagram. , 3 and 4 are diagrams showing the flow of the apparatus used in the examples, where FIG. 3 is the one according to the present invention and FIG. 4 is the one using a normal fluidized bed.

Claims (1)

[Claims] 1. In a column device that heat-treats materials with a particle size distribution in a fluidized bed type with high-temperature gas, the column diameter of the column is made smaller in multiple stages toward the bottom, and the high-temperature gas is heated at the portion where the column diameter changes in stages. A heat treatment apparatus for materials having a particle size distribution, characterized in that a distribution plate is provided such that its lower side maintains a constant distance from the column wall.