JPS5928805B2 - Coke combustion method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coke and soot combustion device, and more particularly to a combustion method and device for burning coke in a deposited layer.

When coke is loaded and deposited in an upright cylindrical furnace and is combusted by flowing combustion air from below to above the deposited layer, the supplied combustion air is combusted with the coke at the bottom of the deposited layer. Consumed in reaction.

Therefore, a combustion reaction occurs only in the lower part of the deposited layer, resulting in a high temperature, and in the upper part of the deposited layer, coke is thermally decomposed by the combustion exhaust gas from the lower part of the deposited layer, and carbon monoxide is generated. As a result, unburned matter is wasted and released.
Combustion efficiency is poor. Further, as described above, since combustion occurs only in the lower part of the deposited layer, the temperature in the lower part of the deposited layer becomes high. For example, when the temperature exceeds 1200° C., the ash after coke combustion melts and becomes clinker. When this clinker is generated, a so-called shelf hanging phenomenon occurs in the deposited layer, making stable combustion difficult, and the clinker may adhere to the furnace wall and damage the furnace wall. Furthermore, due to the above-mentioned shelf hanging phenomenon and adhesion of clinker to the furnace wall, ash after coke combustion cannot be smoothly discharged.
Therefore, it becomes difficult to continuously and stably burn coke. J An object of the present invention is to solve the above-mentioned technical problems and provide a coke combustion method and apparatus that can efficiently and stably burn solid fuel.

The present invention provides a coke combustion method in which combustion air is supplied from the lower part of a grate for combustion, in which the combustion temperature of the coke is lower than the melting point of the ash after combustion of the coke, and This coke combustion method is characterized in that a part of the combustion exhaust gas discharged from the coke is mixed into the combustion air so as to prevent the coke from being locally combusted.

The present invention provides a grate in the middle of a combustion tube, connects an exhaust gas main pipe that guides combustion exhaust gas to the top of the combustion tube, connects an air supply pipe that supplies combustion air to the bottom of the combustion tube, and connects the exhaust gas main pipe to the bottom of the combustion tube. This coke combustion apparatus is characterized in that a part of the combustion exhaust gas in the main exhaust gas pipe is mixed into the lower part of the grate through the exhaust gas circulation pipe from the middle of the main pipe.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a simplified system diagram of one embodiment of the present invention.
A grate 21 is provided in the middle of the combustion tube 16. On this grate 21, coke is loaded and a deposited layer 36
is formed. An exhaust gas main pipe 61 that guides combustion exhaust gas is connected to the upper part of the combustion tube 16 . Air supply pipe 41 that supplies combustion air to a lower part of the combustion tube 16 than the grate 21
is connected. A part of the combustion exhaust gas in the main exhaust gas pipe 61 is mixed into the air supply pipe 41 via the exhaust gas circulation pipe 43 from the middle of the main exhaust gas pipe 61 . The deposited layer 36 includes:
Combustion air is supplied through the air supply pipe 41, and this combustion air flows upward within the deposition layer 36. The combustion exhaust gas generated by the combustion reaction between the coke and the combustion air in the deposited layer 36 is induced by the induced blower 33 and discharged, but the heat exchanger 15
The sensible heat of the combustion exhaust gas is radiated through the smell. Induced blower 33
A part of the combustion exhaust gas discharged from the air supply pipe 41 is circulated through the pipe line 43 to the air supply pipe 41 . The circulating amount of the combustion exhaust gas is controlled by the control means 45 controlling the opening of the damper 46 in the middle of the pipe 43 according to the temperature detection value of the temperature detector 44 which detects the internal temperature of the deposited layer 36. adjusted. In this way, by mixing a portion of the combustion exhaust gas into the combustion air, the coke is combusted throughout from the bottom to the top of the deposited layer 36, preventing the generation of unburned gas and reducing the amount of coke deposited. Clinker formation within layer 36 is prevented. It will now be detailed that coke combustion according to the present invention is different from coal combustion, and the present invention solves problems unique to coke combustion.

The combustible content of coal consists of (A) volatile matter, (B) nol, pitch, and C) carbon, and its ignition temperature is 225-5
It is 00℃. On the other hand, the only combustible component of coke is carbon, and its ignition temperature is approximately 600°C.
more expensive than coal. Therefore, in coal combustion, gasification of volatiles occurs at 225-500°C and ignition is easy, similar to ignition of gaseous fuels.

Therefore, if the coal combustion area is maintained within this temperature range, the process of gasification of the combustible content of coal → combustion of its volatile content → generation of radiant heat → generation of volatile content of coal, or gasification →... will be repeated continuously. The volatile content of the coal is burned while maintaining a constant combustion. The radiant heat simultaneously burns the tar, pitch, and carbon content of the coal. Since the combustion of coal is accompanied by the combustion of gas, combustion can be easily maintained and the amount of unburned carbon monoxide generated can be reduced. On the other hand, coke combustion presents the following unique combustion conditions. As mentioned above, coke has an ignition temperature of about 600° C., so the reaction will not occur unless the coke itself is maintained above that temperature.

In order to cause combustion to occur continuously, it is necessary to ensure that the temperature of the coke itself is maintained above about 600° C. by the heat generated. In the case of coke combustion, if part of the combustion exhaust gas is not mixed into the combustion air, that is, if the exhaust gas circulation pipe 43 is omitted, oxygen will be locally consumed by combustion and the reaction of equation 1 will not occur. Moreover, since the temperature is locally high, oxygen is reduced, and the reaction becomes more likely to occur.

Therefore, if part of the combustion exhaust gas is not circulated, carbon monoxide will inevitably be generated in an increased amount. Moreover, since local high temperature areas occur, the coke ash content is 1200
If the temperature exceeds ℃, clinker will occur. When a part of the combustion exhaust gas is recycled through the exhaust gas circulation line 43 according to the present invention as shown in FIG. 1 during coke combustion, the oxygen concentration in the lower part of the deposited layer 36 is reduced.

Therefore, the reaction represented by the first equation becomes slow. This also slows the consumption of oxygen. Therefore, oxygen is distributed even to the upper part of the deposited layer 36. Therefore, it is possible to cause combustion of coke also in the upper part of the deposited layer 36, and furthermore, it is possible to transfer the combustion heat in the lower part of the deposited layer 36 to the upper part of the deposited layer 36 by passing the gas. , it becomes possible to raise the upper part of the deposited layer 36 to the ignition temperature of about 600° C. or higher. Continuous combustion is thus also possible in the upper part of the deposited layer 36. As a result, it becomes possible to perform combustion slowly and over a long period of time in the remaining portion of the deposited layer 36 other than the vicinity of the grate 21.

In addition, no local temperature rise occurs, and therefore the ash after coke combustion can be combusted without becoming clinker. In addition, as mentioned above, coke burns slowly and does not cause localized high temperatures.
The reaction of the second formula following the reaction of the first formula is suppressed.

This makes the amount of carbon monoxide generated extremely small, and low-temperature combustion suppresses the generation of NOx. For reference, if a part of the combustion exhaust gas is mixed with the combustion air and circulated in a non-storage type combustion equipment where the thickness of the coke layer on the grate is small, the following problems will occur. occurs.

In this combustion device, the oxygen concentration is low and the flow rate supplied to the coke deposit layer increases by the amount of combustion exhaust gas mixed in, so the coke is excessively cooled. For these reasons, it becomes difficult to burn coke near the grate. Moreover, since the coke deposit layer is thin, the mixed gas of combustion air and combustion exhaust gas from below the grate tends to form a so-called short bath. This creates the possibility of local combustion of coke. In the present invention, the coke deposit layer 3
6 is thickened, so to speak, it is a storage type combustion device, and in such a configuration, a part of the combustion exhaust gas is mixed with the combustion air and circulated, thereby solving the above-mentioned problem. In another embodiment of the present invention, instead of connecting the exhaust gas circulation line 43 to the air supply pipe 41 and introducing it into the lower part of the grate 21, the exhaust gas circulation line 43 is connected to the grate 21 of the combustion tube 16.
The combustion exhaust gas and the combustion air are introduced directly into the lower part of the air supply pipe 41 together with the combustion air from the air supply pipe 41, and the combustion exhaust gas and the combustion air are caused to collide with each other at the lower part of the grate 21 of the combustion tube 16 to achieve sufficient mixing of the two. and such embodiments are also to be construed as falling within the scope of the following claims.

FIG. 2 is a cross-sectional view showing an apparatus configured according to the system diagram of FIG. 1, and FIG. 3 is a right side view thereof.

A heating device 2 for burning coke to obtain hot air according to the present invention is provided in the horticultural greenhouse 1 at a position close to the door 3. The warm air obtained by this heating device 2 is blown out from the blow-off holes (not shown) of the blow-off pipe 4 laid along the inner surface of the side wall of the greenhouse 1, thereby warming the inside of the greenhouse 1. . FIG. 4 is a longitudinal sectional view of the heating device 2, and FIG.
It is a sectional view taken along the cutting plane line V-V in the figure, and FIG. 6 is a perspective view showing the inside of the heating device 2 with a part thereof cut away. The casing 6 of the heating device 2 has a horizontally long box shape and is installed on the ground by legs 7a and 7b. Inside the casing 6, from one longitudinal end to the other end (
A heating chamber 8, a heat exchange section 9, and an air introduction chamber 10 are formed in this order (from left to right in FIGS. 4 and 5). The heat exchange section 9 includes an upper gas chamber 12 defined by side walls 11a, 11b and the casing 6, and side walls 13a,
13b and a lower gas chamber 14 defined by the casing 6
A heat exchanger 15 is interposed between them. This heat exchanger 15 allows air to flow from the air introduction chamber 10 to the heating chamber 8 as shown by the solid line arrow, and is arranged in an upper gas chamber in a direction perpendicular to the air circulation direction as shown by the broken line arrow. 12
The combustion exhaust gas is allowed to flow from the exhaust gas chamber 14 to the lower gas chamber 14, and the two do not mix with each other. A plurality of, for example, five upright combustion tubes 16 are arranged in the heating chamber 8 . These combustion tubes 16 may be arranged in a straight line as shown, or may be arranged in a staggered manner. An outlet pipe 17 is connected to the upper part of each combustion cylinder 16,
Each outlet pipe 17 is commonly connected to a collecting pipe 18. One end of the collecting pipe 18 is closed, and the other end is connected to the upper gas chamber 12. Air supply pipes 41 are connected to the lower part of each combustion cylinder 16, and these air supply pipes 41 are commonly connected to a pipe line 47, and the pipe line 47 is opened to the atmosphere. A blow-off pipe 4 communicating with the heating chamber 8 is connected to one end side wall 6c of the casing 6. Figure 7 shows the combustion tube 16.
FIG.

The combustion tube 16 has an upright cylindrical shape made of metal, and its upper end passes through the top plate 6a of the casing 6 in an airtight manner. Combustion tube 1
The lower end of the casing 6 passes through the bottom plate 6b of the casing 6 in an airtight manner and is installed on the ground. A charging cylinder 42 that protrudes concentrically into the combustion cylinder 16 is fixed to the upper end of the combustion cylinder 16, and a lid 50 is removably inserted into the charging cylinder 42. In the vicinity of the bottom plate 6b of the casing 6, a conical perforated plate 19 is fixed to the inner wall of the combustion tube 16, which is located below. A support frame 20 is suspended from the lower surface of the perforated plate 19, and a grate 21 that closes the opening of the perforated plate 19 is supported by the support frame 20 so as to be movable in the horizontal direction. The air supply pipe 41 is connected to the combustion tube 16 below the perforated plate 19. FIG. 8 is a sectional view taken along the section line ■--■ in FIG. 7, and FIG. 9 is a sectional view taken along the section line ■--■ in FIG.

In the lower part of the combustion tube 16, an opening 22 for discharging incinerated ash is formed on a side perpendicular to the moving direction of the fire grate 21. A cover 23 is provided to cover the opening 22, and the cover 23 is supported by upper and lower guide members 24a and 24b fixed to the side of the combustion tube 16. Moreover, the cover 23 is guided by guide members 24a and 24b,
It is movable along the outer peripheral surface of the combustion tube 16. FIG. 10 is a perspective view showing the heat exchanger 15.

This heat exchanger 15 includes a gas passage 26 that communicates the upper gas chamber 12 and the lower gas chamber 14, and an air introduction chamber 1.
0 and heating chambers 8 are formed adjacent to each other and alternately via plate-shaped heat transfer walls 28. Therefore, combustion exhaust gas flows through the gas passage 26 from above to below, as shown by the dashed arrow, and air flows laterally through the air passage 27 in a direction intersecting the combustion exhaust gas, as shown by the solid arrow. do. Gas passage 26 and air passage 2
7 is charged with corrugated wire meshes 29 and 30,
The gap between the wire meshes 29 and 30 is filled with a filler such as a Raschig ring 31.

By filling the Raschig ring 31 in this way,
The flow of combustion exhaust gas and air flowing through the gas passage 26 and the air passage 27 is disturbed, and the heat transfer area is increased, so that the heat transfer efficiency is improved. One end of a discharge pipe 32 is connected to the lower gas chamber 14 .

This discharge pipe 32 extends upward in the air introduction chamber 10 and passes through the top plate 6a of the casing 6, and the other end is connected to a suction port of an induced blower 33 installed in the upper part of the casing 6. A discharge port of the induced blower 33 is connected to the chimney 5 via a discharge pipe 48. One end of an introduction pipe 34 is connected to the other end side wall 6d of the casing 6 so as to communicate with the air introduction chamber 10. The other end of the introduction pipe 34 is connected to a discharge port of a blower 35 installed on the ground within the greenhouse 1 . Discharge pipe 48
A pipe line 43 branches off from the middle of the pipe line 4.
Connected to 7. Therefore, a portion of the combustion exhaust gas is mixed into the air sucked into each combustion tube 16 via the air supply pipe 41. A damper 46 is provided in the middle of the pipe line 43, and the opening degree of this damper 46 is controlled by a control means 45 (see FIG. 1). Deposition layer 36 of each combustion tube 16
A temperature detector 44 (see FIG. 1) is provided inside the interior to detect the internal temperature of the highest temperature part, and the temperature detected by this temperature detector 44 is set to a predetermined value, for example, 1.
The opening degree of the damper 46 is controlled so that the temperature does not exceed 200°C. When heating the inside of the greenhouse 1, enough coke is loaded into each combustion tube 16 to be consumed within the heating time, and the coke deposit layer 36 in each combustion tube 16 is At the same time, the blowers 33 and 35 are driven.

This initiates combustion of the coke. When this coke is burned, the combustion air is mixed with combustion exhaust gas, so the oxygen concentration is low. Therefore, the combustion reaction rate of coke is reduced, and the combustion reaction progresses from the lower part of the deposited layer 36 to the upper part without causing the combustion reaction only in the lower part of the deposited layer 36. Accordingly, the deposited layer 3
The amount of carbon monoxide generated from the upper part of the combustion chamber 6 is reduced, and therefore wasteful release of unburned matter is suppressed to the utmost, and combustion efficiency is improved. According to experiments conducted by the present inventors, the composition of the exhaust gas discharged from the upper part of the deposited layer 36 is the first when a part of the exhaust gas is circulated and when the exhaust gas is not circulated.
It was found that there were differences as shown in the table.

In Table 1, the amount of recycled exhaust gas is selected to be 1:1 with respect to the amount of combustion air. As is clear from Table 1, carbon monoxide in the exhaust gas can be reduced by circulating a portion of the exhaust gas and mixing it into the combustion air.

Further, the internal temperature of the deposited layer 36 is controlled by the damper 4 as described above.
By adjusting the combustion gas circulation amount by controlling the opening degree in step 6, the temperature does not exceed, for example, 1200° C., so clinker does not occur.

Therefore, the shelf-hanging phenomenon caused by clinker and the adhesion of clinker to the furnace wall are prevented, and stable combustion can be maintained. The combustion exhaust gas generated in the combustion tube 16 is transferred to the outlet pipe 17.
, the collecting pipe 18 , the upper gas chamber 12 , the heat exchanger 15 , the lower gas chamber 14 , and the exhaust pipe 32 to reach the induced blower 33 , and a part of the combustion exhaust gas is mixed into the combustion air through the pipe 43 . , the remaining combustion exhaust gas is discharged from the chimney 5.

On the other hand, the air introduced into the air introduction chamber 10 is transferred to the heat exchanger 1
It is heated by heat exchange with combustion exhaust gas at step 5, and then heated by heat radiation from the furnace wall of each combustion tube 16 in heating chamber 8, and then blown into greenhouse 1 from blow-off pipe 4.
Heating within the greenhouse 1 is thereby achieved. Note that when the height of the deposited layer 36 is high, a plurality of temperature detectors 44 may be provided in the vertical direction and the temperature of the highest temperature part may be controlled so as not to exceed a set value.

Furthermore, when there are no large fluctuations in the quality of fuel coke and the melting point of the ash content after combustion is almost constant, experiments have shown that the appropriate combustion exhaust gas should be used so that the combustion temperature is below the melting point of the coke after combustion. The automatic control by the temperature detector 44 and the control means 45 can be omitted by fixing the damper opening at a position that provides an appropriate circulation amount, or by inserting a limiting orifice that provides an appropriate circulation amount of combustion exhaust gas.

In addition, the arrangement of the blower is not limited to that shown in Figs. 1 and 4, as it is sufficient to provide a prescribed flow to the combustion air and combustion exhaust gas, but may be arranged as shown in Figs. 11, 12, or 13. It may also be provided with blowers 33a to 33e.

When the flue gas is circulated, the oxygen concentration in the combustion air decreases, so the oxidation reaction of coke, that is, combustion, is less likely to occur near the grate, and the amount of air flowing into the combustion chamber from the bottom of the grate increases the amount of flue gas mixed in. For a corresponding increase, the flow rate must be increased.

Therefore, the coke near the grate 21 is cooled more strongly than when no combustion exhaust gas is mixed. Therefore, as mentioned above, when the coke deposit layer on the grate is thin, the inventor's experiments have confirmed that even if the coke near the grate ignites and starts burning, it extinguishes after a while. Ta.

In other words, the ignition temperature of coal is 225 to 500°C, whereas the ignition temperature of coke is as high as about 600°C, making it easier to extinguish. Therefore, when coke is burned by mixing combustion exhaust gas into combustion air, unlike in the case of coal, the coke layer on the grate 21 needs to be sufficiently thick, and the coke layer on the grate 21 must be thick enough to In the case of a relatively small-sized combustion apparatus, a storage tank type, in which a sufficient amount of coke is charged in batches, as shown in FIGS. 1, 7, and 11 to 13, is simple and preferable. In this case, since the coke near the grate 21 is affected by the heat of the combustion coke above it, it is more likely to burn than when the coke layer is thin. Note that the required minimum thickness of the coke deposit layer 36 cannot be uniformly determined because it varies depending on the quality of coke, the amount of combustion air, the amount of combustion exhaust gas mixed in, and the like.

In normal operation, a sufficient amount of coke is added, so it is not necessary to determine this minimum required thickness, but if it is determined, it must be determined based on individual experiments. In one example in which a certain amount of combustion exhaust gas is mixed, the fire will naturally extinguish when the thickness of the coke layer on the grate 21 becomes less than about 300 mm, and a coke layer of about 300 mm or more is required for continued combustion. It was hot. However,
The minimum required thickness of this coke is shown in Figures 1, 7, and 11.
In the storage type combustion apparatus as shown in FIGS. Non-storage type combustion equipment that automatically feeds coal generally has a complicated structure and is expensive, so it is preferable to provide means for detecting the amount of accumulated coke and supplying coke to always ensure the minimum required thickness of coke because it is even more expensive. do not have.
As described above, according to the present invention, since combustion air mixed with combustion exhaust gas is supplied to the coke deposit layer, the entire deposit layer is combusted, and therefore unburned components are not released wastefully. combustion efficiency is improved. Furthermore, since the temperature of the deposited layer does not become locally high, the ash is prevented from melting into clinker, and stable combustion can be achieved. In the above-described embodiments, the combustion tube is elongated and vertically extending, for example, a cylindrical body, but in other embodiments of the present invention, the combustion tube may have a shape other than circular in horizontal cross section, such as a rectangular shape. The height is sufficient as long as it has a volume that allows coke to be deposited on the grate at least in an amount that allows continued combustion.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of an embodiment of the present invention, Fig. 2 is a cross-sectional view showing a device configured according to the system diagram in Fig. 1, Fig. 3 is a right side view thereof, and Fig. 4 is a system diagram of an embodiment of the present invention. Vertical sectional view of heating device 2, fifth
The figure is a sectional view taken from the section line V-V in FIG. 4, FIG. 6 is a perspective view showing the inside of the heating device 2 with a part cut away, and FIG. 7 is a longitudinal sectional view of the combustion tube 16. Figure 8 is the cutting plane line of Figure 7■
A cross-sectional view seen from 1■, Figure 9 is the section line of Figure 8 ■1■
10 is a perspective view showing the heat exchanger 15, and FIGS. 11 to 13 are system diagrams of other embodiments. 21...Grate, 36...Deposition layer, 44...Temperature detector, 45...Control means, 61...Exhaust gas main pipe. (2) Figure 1 is corrected as shown in the attached sheet. (2) Add Figures 11 to 13.

Claims (1)

[Claims] 1. In a coke combustion method in which combustion air is supplied from the lower part of a grate for combustion, the combustion temperature of coke is set to be below the melting point of ash after combustion of the coke. and a method for burning coke, characterized in that part of the combustion exhaust gas discharged from the coke is mixed into the combustion air so as to prevent the coke from burning locally. 2 An air supply pipe that provides a grate in the middle of the combustion tube, connects the exhaust gas main pipe that leads the combustion exhaust gas above the grate of the combustion tube, and supplies combustion air to the area below the grate of the combustion tube. A coke combustion device characterized in that a part of the combustion exhaust gas in the exhaust gas main pipe is mixed into the lower part of the grate through the exhaust gas circulation pipe from the middle of the exhaust gas main pipe.