JPH0341760B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a powder preheating device.

BACKGROUND ART Conventionally, in furnaces for heating and firing powder and granular materials such as cement, cyclone-type suspension preheaters have often been employed as powder and granular material preheating devices for the purpose of saving thermal energy. The reason for this is that it has many advantages compared to other preheaters, such as its simple structure and easy scale-up.

The above-mentioned cyclone type suspension preheater has a part that performs heat exchange between gas and powder and a cyclone part that separates gas and powder as one unit, and is constructed by combining one or more units. has been done.

Heat exchange performance can be improved by increasing the number of heat exchanges. In other words, it is possible to improve the heat exchange performance by arranging the units in multiple stages. However, cyclones have a large pressure loss, so it is necessary to consider both the advantage of reducing fuel costs by having multiple stages and the disadvantage of increasing power energy due to increased pressure loss. Due to the balance between these two factors, cement firing kilns usually use 4
I am using a stepped type.

On the other hand, recently, research has been conducted to reduce the pressure loss of cyclones, and axial flow cyclones, horizontal cyclones, etc. have been developed and are being put into practical use. However, although these cyclones have reduced pressure loss compared to conventional cyclones, their structures are more complex and there is a strong possibility that problems will arise in terms of stable operation. In addition, it had many drawbacks, such as the fact that its pressure loss reduction effect was not significant.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and includes a small-diameter gas inlet at the bottom, a powder inlet at the side, and a discharge port at the top. The area up to the bottom end is an enlarged inclined part facing upward, and the inclination of the enlarged inclined part is relative to the horizontal plane.
55° or less, and the cross-sectional area of the upper part of the enlarged inclined part and the gas so that the gas velocity at the upper part of the enlarged inclined part is 1/2 or less of the gas velocity of the gas inlet. A heat exchanger that constitutes the cross-sectional area of the inlet, an inlet that is directly connected to the outlet at the top without a duct, a gas outlet that is provided on the opposite side of the inlet or on the ceiling, and a gas outlet that extends downward from the above. The present invention provides a powder preheating device characterized in that it is equipped with a unit consisting of a separator adjacent to the heat exchanger, which is provided with a reduced slope portion toward the heat exchanger and a discharge port provided at the lower part.

The invention will now be described with reference to embodiments illustrated in the accompanying drawings.

Figure 1 shows one unit consisting of a heat exchanger and a separator used in the powder preheating device of the present invention, where 1 is a heat exchanger, 2 is a separator, 3 is a gas inlet, and 4 is a powder and granule material. 5 is a gas transfer port, 6 is a gas discharge port, and 7 is a powder discharge port. The heat exchanger 1 is provided with an enlarged inclined part 8' formed by an inclined side wall 8, and is configured such that the inclination α of the side wall 8 is not less than 55 degrees, and the enlarged inclined part 8'
The gas velocity at the upper part of the gas inlet 3 is configured to be 1/2 or less of the gas velocity at the gas inlet 3. The gas introduction port 3 forms a constricted portion, and the one shown has a throat shape. The powder inlet 4 is provided at a predetermined location on the side wall 8. The gas transfer port 5 is a gas delivery port for the heat exchanger 1 and also serves as a gas introduction port for the separator 2. The gas discharge port 6 is provided in the ceiling portion 9 of the hopper-shaped separator 2.
The cross-sectional area of the upper part of this separator 2 is larger than that of the gas transfer port 5.

In the above embodiment, the granular material entering from the granular material inlet 4 (arrow A in the figure) merges with the upward gas from the gas inlet 3 (arrow B in the figure). Gas B is 15
It passes through the throat section at a speed of ~40 m/s, merges with the powder and granular material A, and forms a spouted bed C within the enlarged slope section 8'. Preferably, the speed of the throat gas flow is adjusted to prevent the liquid powder from falling below the throat.

In the spouted bed C, the powder and granules are moved up and down by the upward jet of gas, and the powder and granules are accelerated many times by the gas flow. Heat exchange between the gas B and the powder fluid A is particularly intense when the powder material is accelerated by the gas flow, so that efficient heat exchange is performed in the spouted bed. Note that even with the conventional method, if the powder and granules can be uniformly dispersed in the gas, heat exchange should be performed with the same efficiency as the present invention. Dispersion was extremely difficult and efficient heat exchange was impossible.

Next, the gas-particle mixture flows into the separator 2 from the gas transfer port 5 (arrow D).

In general, in gas-powder mixtures, when the solid-gas ratio is increased, particles that behaved as single particles when the solid-gas ratio was low become more likely to behave as a group of particles, causing the appearance of coarse particles. It will work the same way.

In the above embodiment, the heat exchanger 1 is a heat exchanger with an upwardly enlarged slope extending from the gas inlet to the lower end of the gas outlet.
A spouted bed C is formed within the heat exchanger. In the spouted bed C, the powder becomes dense on the side walls of the heat exchanger and thinner in the center. The dense portion of the side wall behaves as a group of particles, so it appears to have the same function as coarse particles. The powder and granules separated and transferred from the heat exchanger as apparently coarse particles can be separated without applying centrifugal force. That is,
Since there is no need to use a cyclone, this can be sent to the separator 2 immediately, reducing pressure loss.

Most of the powder discharged from the spouted bed C is in the form of particle groups, and the amount of individual particles dispersed in the gas is relatively small. Therefore, since the amount of powder and granules discharged together with gas from the "separator 2 that does not rely on centrifugal force" is relatively small, the separation efficiency of this separator is also good.

In addition, the granular mixed gas is directly sent to the separator 2 without going through a duct, and the longitudinal cross-sectional area of the separator 2 is larger than the area of the gas transfer port 5 of the heat exchanger 1 along its slope. (In FIG. 1, the longitudinal length of the separator 2 increases along the inclined surface of the separator 2, so the cross-sectional area perpendicular to the flow direction increases.) Therefore, the flow rate of the powder mixed gas decreases rapidly. As a result, the gas and the granular material are rapidly separated due to the agglomeration effect of the granular material.

Furthermore, since at least the lower part of the separator is formed into a hopper shape, the powder and granules are smoothly discharged from the powder and granule discharge port 7 at the lower part. Further, it is preferable that the exhaust chute connected to the exhaust port 7 is provided with an aerodynamic device such as a flap damper for the purpose of preventing powder particles from being re-scattering due to gas backflow. On the other hand, gas is discharged from the gas discharge port 6 (arrow E).

In order to increase the separation efficiency of the conventional cyclone, it is necessary to increase the inlet wind speed of the cyclone, and the pressure drop increases significantly. Therefore, the separation efficiency of the final stage cyclone was set at around 95% to facilitate exhaust gas treatment and dust treatment, and the separation efficiency of the other stage cyclones had to be kept at 60 to 90%. Conventional cyclones apply centrifugal force to particle groups to break them up and transport them to the wall, slowing down the gas velocity and causing the particles to settle. On the other hand, according to the separator of the present invention, there is no need to increase the gas velocity, so the pressure loss is extremely small.

In the above example, cement raw material (88 μ sieve remaining 10 to 20%) was introduced as powder at a rate of 160 t/h, and the solid-air ratio was maintained at 0.5 or higher.
The above cement raw materials apparently act as a coarse flow,
Efficient separation was performed. The pressure drop was 100 to 300 mmAg using a conventional cyclone, but was only 40 to 70 mmAg according to the present invention.

Figures 2a-e show other embodiments of heat exchangers that can be used in the present invention.

10 is a type in which the gas inlet 3 is shaped like an orifice and the ceiling is circular; 11 is a type in which the gas inlet 3 is shaped like an orifice;
A type with a throat shape and a circular ceiling.
12 is a type with a flat ceiling and an orifice-shaped gas inlet, 13 is a two-stage type, and 14 is the same as type 13 with a circular ceiling.

Figures 3a-f show other embodiments of separators that can be used in the present invention.

17 is a base type type, 18 is a type in which the transfer port side of the gas exhaust port is extended inward, 19 is a type in which the entire circumference of the gas exhaust port is extended inward, and 20 is a type with a gas exhaust port on the upper side opposite to the gas transfer port. Type 21 is the type with an exit, Type 21 is the type with a barrier in the center of Type 20, and Type 22 is the type with an inclined ceiling.

In any of the above embodiments, efficient heat exchange and separation can be performed. Note that the use of a two-stage heat exchanger improves mixing, allows heat exchange to be performed with a small amount of auxiliary fuel, and is also effective in denitration.

As described above, in the present invention, the heat exchanger has a jet function, and the powder and granules are repeatedly accelerated by the gas flow to perform heat exchange, so that the heat exchange performance is superior to the conventional air flow method. In addition, since the separator utilizes the agglomeration effect (particle clustering) of the powder and granular material without using the separation effect of gas powder and granular material by centrifugation, high separation efficiency can be obtained with low pressure loss. . Furthermore, both the heat exchanger and the separator have simple structures.

In addition, despite having such a simple structure, after sufficient heat exchange is performed in the heat exchanger, the mixture is transported to the separator, where the gas and powder are separated for the first time. It also has the characteristic of being efficient.

A multistage preheater to which the powder preheating device of the present invention is applied is shown in FIGS. 4 and 5.

In Fig. 4, 1 ₁ to 1 4 are heat exchangers, 2 1 to _{1 4} are heat exchangers, and 2 ₁ to 1 4 are heat exchangers.
2 ₄ is a separator, 23 is a rotary kiln, and 24 is a connecting duct. In the figure, solid line arrows indicate the behavior of the powder and granular material, and dotted line arrows indicate the gas flow.

Further, in FIG. 5, the same reference numerals as in FIG. 4 indicate the same parts, 25 is a calciner, 26 is a fuel burner, and 27 is a secondary air introduction pipe. Calcining furnace 25
For example, those disclosed in Japanese Patent Application No. 51-81344 can be used.

In addition, in the above embodiment, the uppermost separator 2
₄ may be attached with an electrostatic precipitator (not shown).

The device of the above embodiment has various advantages over conventional cyclone suspension preheaters, such as higher thermal efficiency, extremely small pressure loss, and relatively simple structure.

According to the present invention, it is possible to provide a powder preheating device that has extremely low pressure loss and is excellent in thermoeconomics.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of a powder preheating device according to the present invention taken along a plane including the central axes of a heat exchanger and a separator; FIGS. 2 a to e are longitudinal sectional views of an embodiment of the heat exchanger; 3a to 3f are longitudinal sectional views of an embodiment of the separator. FIG. 4 is an elevational view when the present invention is applied to a multistage preheater, and FIG. 5 is an elevational view when the present invention is applied to a multistage preheater with a calciner. 1,10~14...Heat exchanger, 2,17~22
...Separator, 3...Gas inlet, 4...Powder inlet, 5...Gas transfer port, 6...Gas discharge port, 7
...Powder discharge port, 8...Side wall.

Claims (1)

[Scope of Claims] 1. A small-diameter gas inlet at the bottom, a granular material inlet at the side, and a discharge port at the top, with an enlarged slope extending upward from the gas inlet to the lower end of the gas discharge port; The expansion slope section is configured such that the slope thereof is not less than 55 degrees with respect to the horizontal plane, and the gas velocity at the upper part of the expansion slope section is 1/2 or less of the gas velocity at the gas inlet. A heat exchanger comprising the cross-sectional area of the upper part of the enlarged slope and the cross-sectional area of the gas inlet, an inlet directly connected to the discharge port at the upper part without a duct, and a side opposite to the inlet or the ceiling. A granular material characterized by comprising a unit consisting of a gas discharge port provided at the heat exchanger, a separator adjacent to the heat exchanger, which has a reducing slope downward from the above and a discharge port provided at the bottom. Preheating device. 2 Connect the gas outlet of the separator to the lower gas inlet of the upper heat exchanger, and connect the lower outlet of the upper separator to the powder inlet of the lower heat exchanger to form the unit in multiple stages. A granular material preheating device according to claim 1, which is connected. 3. The powder preheating device according to claim 1, wherein the lowermost unit is connected to a calcining furnace and/or a firing furnace. 4. The powder preheating device according to any one of claims 1 to 3, wherein two stages of spouted beds are formed in the heat exchanger.