JP2661730B2 - Pyrolysis apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention thermally decomposes fluid harmful substances contained in a gas such as exhaust gas, in particular, dioxins and furans. This device introduces a substantially cylindrical main combustion chamber, a sub-combustion chamber disposed above the main combustion chamber, and a flow of gas containing harmful substances into the main combustion chamber with angular momentum. Therefore, an introduction opening communicating with the main combustion chamber at an angle to a tangent plane and a burner arranged to direct a flame toward the main combustion chamber to burn gas containing harmful substances. Have. An annular gas flow retention device is disposed above the burner;
The gas flow retention device is provided with a central opening that directs the gas flow from the main combustion chamber to the sub-combustion chamber. The central opening has a smaller diameter than that of the cylindrical main combustion chamber, and the gas flow retention device has nozzle means directed obliquely downward.

[Problems to be Solved by the Prior Art and the Invention] Substances having a very harmful composition such as dioxin and furan are economically obtained only by thermally decomposing them at high temperatures into less problematic compounds. Can be disposed of. For example, the West German Patent Application Publication (Publishe
German Patent Application No. 2357804 discloses a combustion apparatus provided with a burner using a fuel such as natural gas for the thermal decomposition of such harmful substances. A large volume combustion chamber is required to ensure a sufficient residence time for the harmful substances to burn in the high temperature region. Such furnaces are correspondingly expensive and, furthermore, the gas flow in the combustion chamber is turbulent and difficult to mix properly in order to ensure the desired pyrolysis. If the volume of the combustion chamber is reduced, the time during which the harmful substance stays in the high-temperature region is too short, and the decomposition reaction is not completed.

Accordingly, it is a primary object of the present invention to eliminate these problems and to provide a device for thermally decomposing flowable harmful substances contained in a gas, which is compact, but the gas containing the harmful substance is used in a combustion chamber. To ensure that the thermal decomposition reaction proceeds completely, and to provide a device that allows the pyrolysis reaction to proceed completely.

SUMMARY OF THE INVENTION In an apparatus of the type initially set forth, according to one aspect of the invention, a burner is provided with nozzle means directed diagonally downward to provide secondary air to the main combustion chamber. The above-mentioned object is achieved by arranging the flame so as to be directed to the main combustion chamber above the introduction opening, and the annular stagnation device partitions the circulation means arranged around the central opening. Is done.

In such a device, the gas containing the harmful substances to be decomposed is introduced into the bottom of the main combustion chamber through the introduction opening and becomes the primary gas for the burner. The first of combustion
The steps are performed stoichiometrically or slightly less than stoichiometrically. 800 ° C or 1400 ° C caused by this combustion
High temperatures are suitable for the thermal decomposition of complex organic molecules such as dioxins and furans. The stagnation device prevents gas from escaping too early from the main combustion chamber, and a downwardly directed nozzle in the stagnation device supplies secondary air to the main combustion chamber. This has the main purpose of keeping the combustion gases longer in the main combustion chamber. Furthermore, 2
By supplying the secondary air to the main combustion chamber, it is placed in a sufficiently air-rich condition to ensure that all combustible constituents are completely burned, thereby reducing hydrocarbons and
CO emissions are extremely low. In order to discharge exhaust gas from the main combustion chamber to the chimney, not only is a central opening provided in the retaining device, but also another flow path for exhaust gas surrounding this central opening in the region of the wall of the combustion chamber. It has been found by long-term tests that it is preferable to provide Given the angular momentum imparted to the gas flow, the heavier constituent molecules tend to remain in the region near the combustion chamber wall, whereas the lighter gas constituent molecules tend to remain near the combustion chamber axis. Try to get together. By providing a central opening in the dwelling device together with the surrounding channel means, the undesirable situation in which the lighter gas constituent molecules are selectively removed is avoided. Preferably, the annular retention device has a bar between the central opening and the channel means, the bar having an annular fan shape and coaxially surrounding the axis of the cylindrical main combustion chamber. In. These piers are 2
It is connected to the outer part of the annular retaining device by more than one support bar. The entire flow path constituting the flow path means has an annular fan shape.

According to another embodiment of the present invention, there is provided a furnace for pyrolyzing flowable harmful substances contained in a gas, the furnace comprising:
The furnace includes a furnace wall that is formed by stacking annular pieces and modularly assembled. The furnace wall defines a substantially cylindrical main combustion chamber and a sub-combustion chamber disposed thereon. Arranged between these combustion chambers is an annular gas flow retention device, which defines a central opening having a smaller diameter than the cylindrical main combustion chamber, and has an annular furnace wall section. One of them is the outer part of the dwelling device.

This pyrolysis furnace has a very simple configuration. More specifically, it is possible to use pre-built modules for assembling the furnace, greatly reducing the time it takes to build the furnace on site. A proper seal is provided between the modular components by fitting and connecting them with projections and grooves. Another advantage of such a configuration is that the same set of modules can be used to build combustion chambers of different capacities, and that ideal furnaces are built for each of the common operating conditions. Is what you can do.

[Example] An apparatus for thermally decomposing harmful substances contained in a gas will be described with reference to the drawings. The figure shows a furnace with a main combustion chamber of a schematic diagram, the main combustion chamber being delimited by an outer wall part consisting of an annular piece 2 forming the wall of the furnace. The partial piece serving as the wall of the furnace has a substantially annular shape and is composed of a plurality of layers.
The figure shows an inner layer 17 of the refractory brick and two layers 18, 19 surrounding the inner layer of the refractory brick. Due to the multilayer structure of the pieces of the furnace wall, the optimum material can be used for all areas of the combustion chamber wall. As is known, a piece of rocker wool and a steel jacket can surround a piece of the furnace wall. The steel jacket is able to absorb the stresses caused by the thermal expansion of the refractory brick, and the stress acting on the refractory brick is the primary stress on the combustion chamber.
Provide a seal. The steel jacket itself constitutes another seal, so that it is not necessary to operate the device under negative pressure.
This avoids the use of expensive suction ventilation equipment.

As shown in FIG. 1, the contact end surface 21 of the piece 2 of the furnace wall
Has an annular projection, that is, a protruding piece 22, which has a protruding piece 22 that defines an annular groove between the protruding pieces 22. To ensure proper sealing between these pieces. The pieces of the furnace wall have the same shape,
Thus, the connections can be made in any manner that is compatible and forms combustion chambers of the same diameter but of different volumes.

The device shown comprises a sub-combustion chamber 15 arranged above the circular main combustion chamber 1 and an inlet opening 3 leading to the main combustion chamber for introducing a gas stream containing harmful substances into the main fuel chamber. It also has. This gas is, for example, exhaust gas from a refuse incineration plant. Such equipment is usually operated with excess air, and the exhaust gas contains oxygen and functions as a combustion gas. If such a gas stream introduced into the main combustion chamber 1 contains no or insufficient oxygen, it may be mixed with the surrounding air. The axis 3a of the introduction opening 3 may be oriented with respect to the axis 1a of the main combustion chamber, that is, may extend in the radial direction. It is preferred to impart angular momentum to the gas flow introduced into the main combustion chamber towards. This angular momentum ensures that the gas flow becomes turbulent and the gas components are well mixed in the main combustion chamber, optimizing operating efficiency.

In the example shown, three schematically illustrated burners 4 are arranged so as to direct a flame 4b above the inlet opening 3 towards the main combustion chamber 1 for burning harmful substances. . Although these three burners are equally spaced around the periphery of the main combustion chamber, it should be understood that one or more than three burners may be used. The axis 4a of the burner 4 is oriented slightly upward and also extends at an acute angle to the tangent plane, increasing the angular momentum imparted to the gas flow. Arranging the burner above the inlet opening ensures that all of the gas flow flows through the flame 4b and thus all of the gas is in a state of combustion.

As shown in FIG. 1, the annular gas flow stagnation device 20 is disposed above the burner 4 between the main combustion chamber 1 and the sub-combustion chamber 15, and is connected to the main combustion chamber 1 and the sub-combustion chamber 15. Are separated from each other. The stagnation device 20 has a central opening 7 having a diameter smaller than the diameter of the cylindrical main combustion chamber 1 and passing a gas flow from the main combustion chamber to the sub-combustion chamber, and a flow arranged around the central opening 7. A flow path means composed of the road 9 is defined. In the furnace shown, the annular furnace wall piece 5 constitutes the outer part of the dwelling device, the inner part of which is composed of webs 6 each having the shape of a sharp fan and is combined. The crosspiece 6 between the central opening 7 and the flow path 9 surrounding the central opening 7 is a substantially trapezoidal cross section having a side that converges downward. (See FIG. 3). This shape is optimal as a housing for accommodating the secondary air nozzles 10a, 10b, since the angle between the downwardly directed nozzle and the side of the bar is avoided from becoming too flat. In the staying device, the channel means is arranged around the central opening, and in the illustrated example,
And a flow path 9 between the inner wall 8 of the combustion chamber.

The stagnation device 20 further comprises obliquely downwardly directed nozzle means 10a, 10b for sending secondary air to the main combustion chamber 1, preferably at an angle α of 15 °. In the example shown (see FIG. 3), the nozzle 10a is directed tangentially inward, whereas the nozzle 10b is directed tangentially outward, through which it is fed to the main combustion chamber. The secondary air angular momentum is increased so that these nozzles are substantially oriented at the angled orientation of the gas flow in the main combustion chamber. These nozzles are oriented away from, rather than toward, the axis 1a of the combustion chamber. This will not only create an optimal residence time for the combustion of the gas in the combustion chamber, but will also produce a desirable downward stirring flow for the gas to be agitated in the combustion chamber. By directing the secondary air supply diagonally downward, a rapid flow of gas towards the chimney is avoided. The outwardly directed secondary air supply nozzle 10b extends substantially tangentially to the center circle inscribed in the crosspiece 6 and delays the flow of gas through the flow path 9; A similarly extending inwardly directed nozzle 10 a retards gas flow through the central opening 7. All these nozzles are the axis of the combustion chamber
The direction is the same as that of the burner 4 clockwise or counterclockwise with respect to 1a. This further increases the angular momentum in the combustion chamber, increasing the mixing action and correspondingly better combustion.

The annular retaining device 20 further includes a support bar 13 for supporting the bar 6 (FIG. 2). The support bar 13 separates the flow channel 9 from each other, and the arch-shaped bar 6 defines a secondary air passage between the central opening 7 and the flow channel 9 surrounding the central opening 7. . The support bar 13 defines a conductive path 12 for supplying secondary air to the conductive path 11 of the bar 6. In this configuration, the secondary air supply nozzle may be arranged along the entire circumference of the crosspiece.

If desired, the secondary air may contain other substances of concern for environmental pollution, in the form of liquid or solid particles. This may be particularly advantageous where a gas containing a higher concentration of harmful substances than the exhaust gas is to be detoxified, for example. At this time, it is also possible to send the ash together with the secondary air to the main combustion chamber, where after it has passed, the ash is removed from the bottom of the combustion chamber as an inert glassy medium. . The vitrified ash contains no water-soluble substances and can be discarded without any problem.
Thus, the device is used not only to treat exhaust gases but also to treat ash.

The annular retaining device 20 is advantageously designed such that it reduces the cross-sectional area of the gas flow path by 20% to 50%, preferably 30% to 35%. In other words, in the plan view, the bars of the dwelling device 20 cover this recommended percentage for area. The flow path cross-sectional area of this gas flow is determined by the central opening 7 and the flow path 9 surrounding it. In the design of the staying device 20,
It is important to consider as long as possible the residence time of the gas stream containing harmful substances in the main combustion chamber, which, among other factors, must prevent the flow of the gas stream by the retention device as much as possible. Means that. On the one hand, the pressure drop in the main combustion chamber should be kept to a minimum, so that the gas stream can be expelled appropriately by its own conveying power or at least by the smallest possible ventilation system. Tests have shown that such a situation fits within the above percentage ranges, and it is optimal to reduce the cross-sectional area of the gas stream by 1/3.

The sub-combustion chamber 15 is located above the gas flow retention device 20 in the furnace to complete the combustion process. The third gas supply nozzle 16 is connected to the upper end (first
Elbow joint 24 which increases the supercharging of the combustion air and deflects the gas flow to cool the gas discharged through a chimney (not shown) attached to the furnace. ing. The gas supply nozzle 16 is also directed slightly downward to the sub-combustion chamber 15 to increase the residence time in this combustion chamber. By cooling the gas and burning the gas with an additional supply of third air, the exhaust gas exiting the furnace will be more purified.

As shown in FIG. 1, a manhole 23 is provided on the wall of the sub-combustion chamber 15. A suction fan is not usually required to generate the transport force required to move the gas flow from the inlet opening 3 to the chimney, but may be provided if desired. During operation, gas containing harmful substances sent from, for example, a garbage incineration plant is introduced into the main combustion chamber 1 through the introduction opening 3, and flows upward in a spiral shape to remove the flame from the burner 4. pass. The secondary air flowing downward through the nozzles 10a, 10b of the gas flow stagnation device suppresses the upward flow of the gas and increases the residence time of the gas flow in the main combustion chamber. Finally, the gas stream flows through the central opening 7 and the flow path 9 into the sub-combustion chamber 15, where the thermal decomposition reaction of the harmful substances is completed. And
Purified gas exits the device through the elbow joint 24 and the chimney attached thereto.

[Effect of the Invention] With respect to a gas handled under all practical operating conditions including a state where the device is only partially charged, almost all harmful substances are substantially completely removed from this gas by the device having the above-described configuration. This is achieved by a furnace which can be built with a relatively simple construction and at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view in the axial direction of a furnace according to the present invention,
FIG. 2 is a horizontal sectional view taken along the line II-II of FIG. 1, FIG. 3 is an enlarged partial detailed view of a stay device, and FIG. 4 is an enlarged partial view showing another detail of the stay device. . 1 ... main combustion chamber, 3 ... introduction opening, 4 ... burner,
6 ... Bar, 7 ... Central opening, 10a, 10b ... Nozzle, 13 ...
... support beam, 15 ... combustion chamber, 20 ... gas flow retention device.

Claims (16)

(57) [Claims] An apparatus for thermally decomposing fluid harmful substances contained in a gas, comprising: (a) a main combustion chamber having a substantially cylindrical shape; (b) a sub-combustion chamber disposed above the main combustion chamber; c) an introduction opening communicating with the main combustion chamber for introducing a flow of gas containing harmful substances into the main combustion chamber; and (d) above the introduction opening for burning gas containing harmful substances, And (e) an annular gas flow stagnation device disposed above the burner, wherein (1) passing a gas flow from the main combustion chamber to the sub-combustion chamber. A central opening having a diameter smaller than the diameter of the cylindrical main combustion chamber, and (2) a gas flow passage means disposed around the central opening, and (3) a main combustion. Gas flow stagnation having obliquely downwardly directed nozzles for supplying secondary air to the chamber Pyrolysis apparatus and a location. 2. A pyrolysis apparatus as claimed in claim 1, wherein the inlet opening is directed at an acute angle to the tangent plane to the main combustion chamber and imparts angular momentum to the gas flow introduced into the main combustion chamber. . 3. The pyrolysis apparatus according to claim 1, wherein the nozzle means is directed downward at an angle to the main combustion chamber. 4. A pyrolysis apparatus according to claim 3, wherein said angle is about 15 °. 5. The nozzle means comprises tangentially outwardly directed nozzles as well as tangentially inwardly directed nozzles to increase the angular momentum of secondary air supplied therethrough. 2. A pyrolysis apparatus according to claim 1, wherein the nozzle means is substantially directed in the direction of the gas flow in the main combustion chamber. 6. The annular retaining device has a crosspiece having an arched fan shape between the central opening and the gas flow passage means, and the arcuate fan shape bar forms a ring. The pyrolysis apparatus according to claim 1. 7. The heat pipe according to claim 6, wherein the crosspiece of the annular staying device has a substantially trapezoidal cross section, and the crosspiece of the trapezoidal cross section has both side surfaces converging downward. Disassembly device. 8. The annular staying device further comprises a support bar for supporting a bar having an arcuate fan shape, wherein the bar having an arcuate fan shape has a central opening and flow path means surrounding the center opening. And a communication groove means for secondary air is provided therein, and the support bar is disposed between the respective flow paths of the flow path means, and the secondary air is formed in an arched shape. The thermal decomposition device according to claim 6, wherein a groove to be supplied to the communication groove of the fan-shaped bar is defined. 9. The apparatus according to claim 1, further comprising nozzle means for supplying tertiary air disposed at an upper end of the sub-combustion chamber.
The thermal decomposition apparatus according to Item. 10. The pyrolysis apparatus according to claim 1, wherein the annular retention device is configured to reduce the cross-sectional area of the gas flow therethrough by 20% to 50%. 11. The annular retention device reduces the cross-sectional area of the gas flow by 30%.
Or set to reduce by 35%
11. The thermal decomposition apparatus according to item 10. 12. A furnace for thermally decomposing flowable harmful substances contained in a gas, comprising: (a) a modularly assembled furnace wall comprising a plurality of annular partial pieces stacked; ) A substantially cylindrical main combustion chamber; (2) a furnace wall defining a sub-combustion chamber disposed above the main combustion chamber; and (c) a furnace wall disposed between the main combustion chamber and the sub-combustion chamber. (1) a central opening having a smaller diameter than the cylindrical main combustion chamber, and (2) one of the annular furnace wall partial pieces that are the outer part of the retention device. A pyrolysis furnace comprising a gas flow stagnation device that separates the two. 13. The furnace wall section piece is composed of a plurality of layers, wherein the inner one of the layers of the furnace wall section piece is made of refractory brick and the layer surrounding the inner layer. 13. The pyrolysis furnace according to claim 12, wherein at least one of the furnaces comprises a buffer brick. 14. The method according to claim 1, further comprising a cushioning material made of rock wool and a steel jacket surrounding a piece of the furnace wall.
13. The pyrolysis furnace according to item 12. 15. A method for pyrolyzing a flowable substance contained in a gas, comprising the steps of: a) introducing a gas stream containing harmful substances into a main combustion chamber; Directing to a combustion chamber; c) downwardly directed 2 exiting from an inlet provided in an annular gas flow retention device disposed above the burner.
D) passing through the central opening of said retention device and another opening surrounding said central opening in the region of the furnace wall of the combustion chamber, with the gas being retained in the main combustion chamber by the subsequent air. The exhaust gas passing through the sub-combustion chamber and further through the chimney. 16. The method according to claim 15, wherein the secondary air is mixed with another harmful substance before being sent to the combustion chamber.