JPH0577924B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a heat recovery device for burning municipal waste, industrial waste, coal, and other combustible materials in a fluidized bed and simultaneously recovering heat from the fluidized bed. , particularly regarding the heat transfer surface of the heat recovery device.

(Prior art and problems to be solved by the invention) In a fluidized bed heat recovery device, a heat transfer surface is provided in a portion of the fluidized medium through which fluidizing gas passes, that is, in the fluidized bed. Extremely efficient heat transfer can be obtained between the two. In order to heat this fluidized medium, municipal garbage, industrial waste, coal, or other combustible materials are burned in the fluidized medium. Particularly when burning combustible materials that contain non-combustible materials such as municipal waste, providing a heat transfer surface with a large number of heat transfer tubes in a fluidized bed can cause heat transfer between heat transfer tubes or heat transfer tubes as the case may be. In the end, the non-combustible material gets stuck in the gap between the heat transfer surface and the wall surface, impeding the movement of the fluid medium, resulting in a decrease in heat transfer efficiency, and furthermore, there is a possibility that the flow of the fluid medium may be blocked. For this reason, regarding the arrangement of heat transfer tubes, the width of the gap around the heat transfer surface such as the heat transfer tube and the heat transfer tube and the wall surface should be determined so that the width of the gap around the heat transfer surface such as the heat transfer tube and the heat transfer tube and the wall surface should be set to In addition, in order to secure the necessary heat transfer area, a large volume of heat recovery section is required, or the amount of heat recovery is insufficient due to the inability to secure a sufficient heat transfer surface. It was limited.

In recent years, fluidized bed incinerators that use municipal waste as a combustible material without crushing it have been developed and put into practical use. When a surface is installed, the volume of the heat recovery section becomes extremely large. Also,
If the combustion material is shredded into pieces smaller than the width of the gap between the heat transfer tubes by using more power than necessary for combustion and handling, and at the risk of abrasion of the crushing teeth, or conversely, if shredding cannot be carried out, large amounts of waste may be produced. Even materials that could be used as combustible materials were treated as non-combustible and disposed of separately.

Furthermore, regarding the arrangement of heat transfer tubes, it is effective to arrange them in a checkerboard pattern or perpendicular arrangement in the vertical direction in order to prevent non-combustible materials from getting caught.
On the other hand, since the gas tends to rise vertically, the fluidized medium in the area vertically sandwiched between the tubes becomes a fixed layer, and the contact surface between the flowing or moving fluidized medium and the heat transfer tube is small. The drawback was that the amount of heat transfer was limited to the vertical portions of the sides.
Furthermore, when heat exchanger tubes are arranged in a staggered manner to increase heat recovery efficiency, the heat exchanger tube pitch must be intentionally increased to prevent congestion, which also means that the heat recovery section becomes large in volume. It was a contributing factor.

Therefore, when heat is recovered from a fluidized bed, it is common to reduce the size of the combustible material to a size equal to or smaller than the width around the heat transfer surface. In reality, there have been few attempts to recover heat from a fluidized bed.

(Means for Solving the Problems) In order to solve the problems of the prior art described above, the present invention aims to solve the problems of the prior art described above. Adjacent to the combustion part where things are put in and burned,
A heat recovery section that recovers heat from the fluidized medium is installed in a moving bed that changes the fluidized medium from a fixed bed to a weakly fluidized bed by gas blown upward from the bottom, and these heat recovery sections and combustion sections are connected. The combustion section is divided by a partition wall with the upper and lower parts communicating with each other, and the flow rate of the fluidizing gas per unit area of the combustion section is higher than the flow rate of the gas blowing per unit area of the heat recovery section. By increasing the size, the fluidized medium in the combustion section is allowed to flow into the heat recovery section over the partition wall, and the fluidized medium settles in the heat recovery section and flows back to the combustion section from the lower part of the partition wall, Fluidized bed heat using a fluidized bed in which a heat transfer surface for heat recovery into which a heat-receiving fluid is guided is provided in the moving bed of the heat recovery section, and a supply device is provided for supplying the material to be combusted to the combustion section. In the recovery device, a sieve is provided in the fluidized medium passage area above the partition wall, and the gap around the heat recovery heat transfer surface installed in the fluidized medium of the heat recovery section is set to have a width equal to or larger than the sieve opening diameter. It is characterized by

In addition, in implementation, the heat transfer tube groups constituting the heat recovery heat transfer surface are arranged horizontally and arranged in a staggered manner on a cross section perpendicular to the tube axis direction, or in addition, It is desirable that the heat exchanger tube group is arranged so as to extend substantially parallel to a plane including the opening of the partition wall communication section.

(Function) The present invention provides a fluidized bed heat recovery device in which a fluidized medium circulates between the heat recovery section and the combustion section as described above, in which a sieve is provided at the inlet of the heat recovery section, so that a sieve is provided at the inlet of the heat recovery section. The size of the solids is limited. Thereby, the pitch of the heat exchanger tubes in the heat recovery section can be reduced. That is, if there is no sieve,
The area around the heat transfer surface through which the fluid medium passes should be However, by attaching a sieve as in the present invention, the size of noncombustibles that may enter the heat recovery section is limited, so the size of the incombustibles that can pass through is limited. If the gap around the hot surface is larger than the gap between the sieves, there is no fear that incombustibles will get trapped, and if the sieve opening width is made small to a certain extent, the pitch of the heat exchanger tubes can be reduced accordingly.

The sieve itself should be placed at least 1m from the vicinity of the top surface of the fluidized bed through which most of the fluidic medium passes, preferably 1.5m, to prevent incombustible materials blocked from passing through the sieve from clogging the sieve itself. For the part of about m, it is made vertical or inclined towards the combustion part side so that the non-combustibles fall along the sieve and are scattered again into the fluidized bed by the flow of the fluidized bed, and the openings are made vertically. It is desirable to have a slit-like structure that does not get caught in the sieve openings. Furthermore, if the sieve forming the slit is alternately shifted in a zigzag pattern between the combustion section side and the heat recovery section side, the fluidic medium colliding with the sieve will also flow from the side of the sieve to the heat recovery section. This makes it easier to jump into the slit, and prevents the slit from colliding with the slit, thereby preventing incombustible materials from getting caught in the slit. Note that if the slit is constructed of a group of tubes through which a heat-receiving fluid is passed, the tube group is cooled, thereby preventing deterioration due to heat during operation, and making manufacturing easier.

Next, the effect of the flow around the heat exchanger tube will be explained.

In general, there are two types of arrangement of heat exchanger tubes: a staggered arrangement shown in FIG. 3 with respect to a cross section perpendicular to the tube axis direction, and an orthogonal arrangement shown in FIG. 4. The gas introduced into the fluid medium flows from bottom to top, as shown by arrows A in Figure 3 and arrow B in Figure 4, respectively, and the fluid medium is stirred as the gas passes through. .

In the staggered arrangement shown in Fig. 3 above, the heat transfer tubes 1 are arranged so as to prevent the gas from rising vertically, so the effect of stirring the fluid medium is large, and the part where there is almost no movement of the fluid medium is is the shaded area 1 in the figure.
In the orthogonal arrangement shown in FIG.
As a result, the fluid medium around the heat transfer tubes 2 is not sufficiently stirred, and there is almost no movement of the fluid medium in the shaded area 2a in the figure where the tubes 2 are vertically sandwiched, and the fluid medium on both sides of the tubes is It has been observed experimentally that only a small portion of the near-vertical surface is exposed to the flowing or moving fluid medium. This tendency is particularly noticeable as the width in the vertical direction indicated by dimension b in FIG. 6 is smaller. However, as the amount of gas flowing from the bottom to the top increases and the flow becomes more intense,
The portion 2a where there is almost no movement of the fluid medium narrows as it moves away from the upper surface of the tube, and further reduces from a trapezoid to the shape shown in FIG. 3, 1a. It progresses rapidly when the gas amount is around 3 to 5 times the minimum fluidizing gas amount.

As a result of the above, heat recovery is performed more efficiently in a staggered arrangement, as can be seen from the area exposed to the flowing or moving fluid medium and the degree of agitation of the flowing or moving fluid medium. This means that
This is particularly noticeable when the gas amount is small, and the difference from the orthogonal arrangement is also large. However, as described above, when the gas amount is increased to create a strong flow, the diagonal lined portion 2a, which is difficult to move, also tends to start flowing, and the mixing of the fluidized media increases, resulting in a staggered arrangement of heat recovery efficiency as a whole. The difference from the orthogonal arrangement becomes smaller.

Furthermore, the pitch of the heat transfer tubes is limited by the size of the incombustibles contained in the fluidized medium and the stirring state of the fluidized medium. That is, in the case of a staggered arrangement, since the fluidized medium is well stirred as described above, the gap a or b between the heat exchanger tubes 2 shown in FIG. The bigger the better. Conventionally, the above dimension a is at least
100mm or more was realistic. On the other hand, in the case of an orthogonal arrangement, as shown in Figure 6, the gap a between the heat transfer tubes in the lateral direction needs to be larger than its maximum size in order to avoid clogging with incombustibles contained in the fluidizing medium. However, there is a gap b between the heat exchanger tubes 2 in the vertical direction.
As can be seen from the explanation of FIG. 4, there is no concern that the fluid medium will get stuck, so it is possible to make the size of the gap a considerably smaller than that of the gap a. For this reason, in conventional fluidized bed heat recovery equipment, by making the longitudinal gap b of the heat transfer tubes in the orthogonal arrangement smaller than the horizontal gap a, the heat transfer in the heat recovery section is better than using the orthogonal arrangement in a staggered arrangement. The area can be made quite large within the same volume. As a result, the volume of the heat recovery section is reduced and a large amount of gas is passed through, that is, 3 to 5 times or more of the minimum fluidization gas amount to create intense flow and obtain the specified amount of heat transfer. 2 to 3 times, we face the inevitable problem of short heat transfer surface life. However, the present inventors conducted experiments to reduce the amount of gas in consideration of heat transfer surface wear, and at a blowing gas amount of around 1.5 times the minimum fluidizing gas amount (Gmf), which is said to maximize the heat transfer coefficient. In operating conditions where there is only weak flow or movement, the staggered arrangement may have a smaller total heat transfer area, but as explained in Figures 3 and 4, the retained heat transfer surface is utilized. It has been found that a large amount of heat transfer can be obtained in the same volume due to the strong agitation of the fluid medium.

That is, according to the present invention, the maximum size of the noncombustibles that enter the heat recovery section is the gap size of the sieve, which can be easily reduced to about 40 mm depending on the structure of the sieve. Also, for this reason, if the heat transfer tubes are arranged in a staggered manner, the amount of blown gas will be 1.5 of the minimum fluidizing gas amount.
If the heat recovery section is about twice the size, usually less than twice the size, and three times or less if it is devised, the volume of the heat recovery section can be made smaller than when arranged orthogonally. In addition, there is a limit on the size of non-combustibles that can enter the heat recovery section, so even in equipment that burns combustible materials such as municipal waste without crushing them, unexpectedly large non-combustibles may get stuck in the heat transfer tubes, causing problems in the past. There is no risk of it happening.

Furthermore, even if the exit of the heat recovery section is provided with a member that supports the partition wall or a diffuser pipe in the heat recovery section so as to pass through the exit, the hole diameter of this portion should be determined by the gap around the heat transfer surface. If you take it even larger than
There is no risk of non-combustible materials being caught.

On the other hand, the heat recovery section in the present invention is under the great influence of the flow of the fluid medium centered on the partition wall,
The flow of the fluid medium and the amount of heat recovered in the heat recovery section vary greatly depending on the positional relationship with the partition wall. In other words, it can be said that different behaviors are exhibited depending on the distance between the heat recovery section and the partition wall. Therefore, when setting various quantities in the heat recovery section design, it is necessary to consider the plane along the flow of the fluidized medium (the plane shown in the example shown in Figure 1).
The flow in the flow is made to repeat the same shape or a simple shape, and for this purpose, scale-up is carried out in a direction perpendicular to the flow of the fluid medium (in the example shown in Fig. 1, a direction perpendicular to the plane of the paper). It is preferable to do this, and thereby the design quantities can be obtained with good reproducibility. For this reason, it is desirable that the heat exchanger tubes and the like extend in the direction of scale-up, that is, it is desirable to arrange the heat exchanger tubes so that they extend substantially parallel to the plane containing the opening of the partition wall communication portion.

When deployed as described above, the shape of the heat recovery section will be
Compared to the width between the partition wall and the outer wall in the diagram shown in the figure, the width in the direction of scale-up, that is, in the direction in which they are stretched in a shape close to similar shapes perpendicular to the plane of the paper, is much larger!? Therefore, the number of bent portions of the heat exchanger tube can be reduced, and the number of entrances and exits at the outer wall of the heat exchanger tube is also reduced, so it can be made compact without creating wasted space. Furthermore, since the flow of the fluid medium is always arranged in the same manner in the scale-up width direction (direction perpendicular to the plane of the paper in Figure 1), the flow of the fluid medium is made uniform, and heat exchange between the heat transfer tube and the fluid medium is improved. is also improved and heat transfer is enhanced.

(Example) Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of a heat recovery device which is a preferred steam boiler to which the present invention is applied. In the figure, an air diffuser 14 for fluidizing gas introduced from a blower 12 through a fluidizing gas introduction pipe 13 is provided at the inner bottom of the heat recovery device 11, and the air diffuser 14 has air blowing positions on both sides. The edges are lower than the center and are formed into a chevron-shaped cross section (roof-like) that is approximately symmetrical with respect to the center line of the furnace 11. The fluidizing gas sent from the blower 12 passes through air chambers 15, 16, and 17 and is ejected upward from the air diffuser 14. The mass velocity of the gas is sufficient to form a fluidized bed of the fluidized medium in the furnace 11, but the mass velocity of the fluidizing gas ejected from the air chamber 16 in the center is
is chosen to be smaller than.

The upper portions of the air chambers 15, 17 on both side edges block the upward flow path of the fluidizing gas.
It functions as a reflecting wall that reflects and diverts the fluidized gas ejected from the heat recovery device 11 toward the center of the fluidized bed, and also connects the layer formed by the fluidized medium of the heat recovery device 11 with the combustion section. A partition wall 18 is provided that separates the recovery section from the recovery section, and the difference between the partition wall 18 and the mass velocity of the jetted fluidizing gas causes a swirling flow in the direction shown by the arrow in the drawing. The outer wall of the heat recovery device 11 is configured as a membrane outer wall in which wall heat exchanger tubes are arranged side by side and connected to each other by fins, and the water pipes 21 are connected to the headers 19 and 20 provided above and below the membrane outer wall. A partition wall 18 is constructed in which a membrane wall partition is provided at an inclined lower part of each branch and the combustion part side has a fireproof structure.

On the other hand, a heat recovery chamber (section) 22 is formed on the back surface of the partition wall 18 and the furnace wall surface, and is configured such that a part of the fluidized medium passes over the top of the partition wall 18 and enters the heat recovery chamber 22 during operation. has been done. In addition, an aeration device 25 such as an aeration pipe that introduces gas through an introduction pipe 24 from a blower 23 is provided at a level higher than the bottom of the furnace at the lower part of the heat recovery chamber 22.
There is an opening 26 near where the air diffuser 25 of No. 2 is installed.
is provided, and the fluidized medium that has entered the heat recovery chamber 22 settles while forming a weak fluidized bed or a moving bed close to a fixed bed continuously or continuously depending on the operating condition, and burns through the opening 26. The process returns to section 10 and circulates.

The amount of sedimentation mentioned above is controlled by the amount of diffused air in the heat recovery chamber and the amount of fluidized gas in the combustion section.

The combustible material F is introduced into the combustion section 10 from the combustible material inlet 28 provided in the ceiling of the heat recovery device 11.
burns while flowing together with the fluidized medium which is swirled by the fluidizing gas. At this time, air chamber 1
6, the fluidized medium near the upper central part does not move violently up and down because the amount of air blown is small, and forms a descending moving layer in a weak fluid state. The width of this moving layer is narrow at the top, but it becomes slightly wider at the bottom due to the effect of the slope of the dispersion plate 14, and a part of the bottom reaches above the air chambers 15, 17 on both side edges. Therefore, the fluidizing gas is blown up at a high mass velocity from both air chambers. Then, the fluidized medium at the tip of the hem is removed, and the fluidized medium from the fluidized bed above the air chambers 15 and 17 is replenished and deposited directly above the air chamber 16. The layer descends and repeats this process so that the flowing medium above the air chamber 16 quickly forms a continuously descending moving layer.

The fluidized medium that has moved onto the air chambers 15 and 17 is blown upward, but when it hits the partition wall 18, it is reflected and turned, turning toward the center of the furnace 11, falling onto the top of the moving bed in the center, and being blown up again. While being circulated as described above, a portion of the fluidized medium passes over the top of the partition wall 18 and into the heat recovery chamber 22 . When the sedimentation speed of the fluidized medium deposited in the heat recovery chamber 22 is slow, an angle of repose is formed in the upper part of the heat recovery chamber 22, and the excess fluidized medium flows from the upper part of the partition wall 18 to the combustion section 1.
Fall to 0.

The fluidized medium that has entered the heat recovery chamber 22 is gradually transformed into a completely fixed bed, a slow flowing state, or a state close to a fixed state, depending on the amount of gas blown in from the blowholes 25a of the air diffuser 25. After a changing layer is formed in the descending descending layer, and heat exchange with the built-in heat transfer tube 29 is extremely suppressed, extremely promoted, or controlled, the combustion section 10 is transferred from the opening 26 to the combustion section 10. It is refluxed to. The mass velocity of the diffused gas introduced from the diffuser 25 into the heat recovery chamber 22 is adjusted according to the required amount of heat recovery within the range of 0 to 3 Gmf, preferably 0.5 to 2 Gmf or completely stopped. .

If there is a non-combustible material with a larger diameter than the fluidized medium in the combustion material, the combustion residue will be mixed with some of the fluidized media.
It is discharged from the screen bearer 31 at the bottom of the furnace through the incombustible material outlet 30.

In this embodiment, the water pipe 21 supports the partition wall 18 and the fluidized medium is connected to the heat recovery chamber 2.
It acts as a sieve at the entrance when entering 2. In the figure, 32 indicates an exhaust gas outlet, and 33 indicates a brackish water drum.

FIG. 2 is a sectional view of a main part showing details of the vicinity of the heat recovery chamber in FIG. 1, and in the figure, the same reference numerals as those shown in FIG. 1 indicate the same or similar parts.

In the figure, the inlet sieve (screen) by the water pipe 21 is the sieve 2a, which is the sectional view taken along the line A-A in FIG.
As shown in the figure, every other wire is arranged in a zigzag pattern, which prevents incombustible materials from getting caught. The size of particles that can pass through the sieve and enter the heat recovery chamber 22 from the combustion section 10 is equal to or smaller than the gap between the water tubes 21 constituting the sieve.

Therefore, if the gap between the heat transfer tubes 29 shown in FIG. The pitch can be made smaller,
Even with a staggered arrangement, which has good heat recovery efficiency, there is no problem as it can be stored compactly without worrying about catching incombustibles. In addition, as shown in this embodiment, when the water pipe 21 is also present in the opening 26 for returning the fluidized medium from the heat recovery chamber 22 to the combustion section 10, As shown in the figure, the gap between the water tubes 21 may be made larger than the gap between the heat transfer tubes 29 or more.

In the above-described embodiment, it is desirable to attach a protector (not shown) around the water pipe 21 in the upper part of the partition wall 18 through which the fluid medium passes to protect it from wear and the like. In addition, the heat recovery device 11
In the above description, the furnace wall is composed of a membrane outer wall, but it goes without saying that other wall water tube cooling structures or fireproof wall structures may be used.

(Effects of the Invention) As explained above, according to the present invention, in a fluidized bed heat recovery device in which a fluidized medium circulates between a heat recovery section and a combustion section that are separated by a partition wall, By installing a sieve in the medium passage area and making the gap around the heat recovery heat transfer surface in the heat recovery section equal to or larger than the gap in the sieve hole diameter, the size of solids that enter the heat recovery section is limited. Therefore, there is no trouble such as clogging of non-combustible materials in the heat transfer tubes in the heat recovery section, and therefore, it is possible to accept combustion materials including even large lumps and recover heat without crushing or crushing them. In addition, since the pitch of the heat exchanger tubes in the heat recovery section can be reduced, it can be made compact and the heat recovery rate can be improved.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment to which the present invention is applied, Fig. 2 is an enlarged sectional view of the main part of Fig. 1, Fig. 2a is a sectional view taken along line A-A in Fig. 2, and Fig. 2b is a sectional view showing an embodiment of the present invention. Figure 2 is a sectional view of the main part of the heat transfer tube, Figure 2c is C-C in Figure 2.
The line sectional views and FIGS. 3 to 6 are explanatory diagrams regarding the heat exchanger tube group. 10... Combustion section, 11... Heat recovery device, 14...
...Air diffuser, 15, 16, 17...Air chamber, 18
... Partition wall, 21 ... Water pipe, 22 ... Heat recovery room,
25...Air diffuser pipe, 29...Heat transfer tube.

Claims (1)

[Scope of Claims] 1. Adjacent to the combustion section where the material to be combusted is charged and combusted in a fluidized bed in which a fluidized medium is fluidized by fluidizing gas blown upward from the bottom, upward from the bottom. A heat recovery section is installed to recover heat from the fluidized medium in a moving bed that changes the fluidized medium from a fixed bed to a weakly fluidized bed state by blowing gas, and these heat recovery sections and the combustion section are connected at the top and bottom. The combustion section is divided by a partition wall, and the fluidizing gas blowing air volume per unit area of the combustion section is set to be larger than the gas blowing air flow per unit area of the heat recovery section, The fluidized medium of the combustion section is caused to flow into the heat recovery section over the partition wall, and the fluidized medium settles in the heat recovery section and flows back to the combustion section from the lower part of the partition wall,
Fluidized bed heat using a fluidized bed in which a heat transfer surface for heat recovery into which a heat-receiving fluid is guided is provided in the moving bed of the heat recovery section, and a supply device is provided for supplying the material to be combusted to the combustion section. In the recovery device, a sieve is provided in the fluidized medium passage area above the partition wall, and the gap around the heat recovery heat transfer surface installed in the fluidized medium of the heat recovery section has a width equal to or larger than the sieve opening diameter. A heat transfer surface of a heat recovery device characterized by: 2. The heat transfer surface of the heat recovery device according to claim 1, wherein the opening diameter of the communicating portion below the partition wall is equal to or larger than the gap around the heat recovery heat transfer surface. 3. According to claim 1 or 2, the heat transfer tube group constituting the heat recovery heat transfer surface is arranged substantially horizontally and arranged in a staggered manner on a cross section perpendicular to the tube axis. heat transfer surface of a heat recovery device. 4. Claim 1, wherein the heat transfer tubes constituting the heat recovery heat transfer surface are arranged so as to extend substantially parallel to a surface including the opening of the partition wall communication section.
The heat transfer surface of the heat recovery device according to any one of Items 1, 2, and 3.