Combustion gas extraction probe and combustion gas treatment method

Abstract

[Problems] A combustion gas extraction probe that is capable of preventing burnout of a head metal portion of a probe, capable of rapidly cooling a high-temperature gas in a uniform manner in a probe, and whose outer diameter can be kept small. [Means for Solving Problems] A combustion gas extraction probe (4) having a hollow-cylindrical inner tube (4a) in which a high-temperature combustion gas flows, a hollow-cylindrical outer tube (4b) surrounding the inner tube (4a), a low-temperature gas discharge hole (4c) provided in the inner tube (4a), and a low-temperature gas supply means (9) for supplying a low-temperature gas between the inner tube (4a) and the outer tube (4b) and discharging the low-temperature gas from the discharge hole (4c) into the direction that is substantially perpendicular to the sucking direction of the high-temperature combustion gas and is toward the center of the flow of said high-temperature combustion gas. Alternatively, plural discharge holes (4c) may be provided, where the individual discharge holes (4c) are arranged at substantially the same positions from the head of the probe in the high-temperature combustion gas sucking direction, or alternatively, the discharge holes (4c) may be arranged in stages in the high-temperature combustion gas sucking direction. The flow speeds of the low-temperature gas and the high-temperature combustion gas are preferably not less than 40 m/s and not more than 100 m/s.

Claims

1. A combustion gas extraction probe for extracting a high-temperature combustion gas while cooling said high-temperature combustion gas with a low-temperature gas characterized by: an outer tube; and a metal inner tube positioned within the outer tube to define a cooling fluid passage therebetween, the metal inner tube being of unitary construction and having an inner diameter defining a flow path area substantially along the entire tube and through which extracted high-temperature combustion gas flows, the metal inner tube configured to emit low-temperature gas into the flow path area only in a single transverse plane generally perpendicular to a sucking direction of the high-temperature combustion gas, the inner tube having a plurality of low-temperature discharge holes in direct fluid communication with the cooling fluid passage and the flow path area and spaced from a sucking end of the inner tube and disposed about respective axes aligned within a single plane for emitting said low-temperature gas so as to flow in a direction that is substantially perpendicular to the sucking direction of the high-temperature combustion gas and is toward a center of a flow of said high-temperature combustion gas such that said low-temperature gas reaches the centermost portion of said high-temperature combustion gas to create a single transverse sheet of low-temperature gas for mixed cooling and that all vector components of said low-temperature gas emitted into the high-temperature gas and parallel to the flow direction of said high-temperature gas are in a downstream direction of the high-temperature combustion gas; and a plurality of collars coupled to the inner tube and disposed about respective ones of the plurality of low-temperature discharge holes, each collar being disposed about a respective axis which is perpendicular to the sucking direction of the high-temperature combustion gas; the inner tube being independent of a discharge hole disposed about an axis spaced from the single plane and arranged perpendicular to the inner tube.

2. The combustion gas extraction probe as claimed in claim 1 comprising: a low-temperature gas supply means for supplying the low-temperature gas between the inner tube and the outer tube, and discharging the low-temperature gas from the discharge hole into the inner tube; the inner tube being connected to the outer tube such that all of the low-temperature gas flowing in the inner tube passes through the plurality of low-temperature gas discharge holes.

3. The combustion gas extraction probe as claimed in claim 2, wherein individual discharge holes are rotationally symmetrically arranged at substantially the same positions from a head of the probe in the high-temperature combustion gas sucking direction.

4. The combustion gas extraction probe as claimed in claim 2, wherein the outer tube defines a closed end.

5. The combustion gas extraction probe as claimed in claim 4, wherein the inner tube defines an open end through which the high-temperature combustion gas enters the inner tube.

6. The combustion gas extraction probe as claimed in claim 5, wherein the closed end of the outer tube circumnavigates the open end of the inner tube.

7. The combustion gas extraction probe as claimed in claim 2, wherein: the inner tube terminates to define an inner entrance end through which the high-temperature gas enters the inner tube, the inner entrance end defining an inner entrance plane; and the inner and outer tubes are configured such that the low-temperature gas does not traverse the inner entrance plane.

8. The combustion gas extraction probe as claimed in one of claims 1-2 and 3, wherein flow speeds of the low-temperature gas and the high-temperature combustion gas are not less than 40 m/s and not more than 100 m/s.

9. The combustion gas extraction probe as claimed in one of claims 1 and 3, characterized by having a blaster injecting compressed air in an opposite direction to the sucking direction of the high-temperature combustion gas at a head of the probe.

10. The combustion gas extraction probe as claimed in claim 1, wherein the low-temperature gas is emitted along at least two intersecting axes.

11. The combustion gas extraction probe as claimed in claim 10, wherein the low-temperature gas is emitted along at least two perpendicular axes.

12. The combustion gas extraction probe as claimed in claim 1, wherein the low-temperature gas is emitted into the high-temperature combustion gas to cool a peripheral portion of the high-temperature combustion gas as well as a central portion of the high-temperature combustion gas.

Description

THE BEST MODE TO CARRY OUT THE INVENTION

(1) Next, embodiments of the present invention will be explained with reference to drawings. In the following explanation, the combustion gas extraction probe (hereafter referred to as probe for short) and the combustion gas treatment method according to the present invention will be explained in case that they are exemplarily applied to the chlorine bypass system of a cement kiln.

(2) As shown in FIG. 1, a rising portion 3 which constitutes a part of a flow passage of exhaust gas from a cement kiln 2 is connected near an entrance hood of the cement kiln 2 of cement burning equipment, and a probe 4 for attracting high-temperature combustion gas to this rising portion 3 protrudes on it. In the rear stage of this probe 4, a secondary mixing chamber 5, a cyclone 6, a heat exchanger 7, a bag filter 8 and so on are arranged to constitute a chlorine bypass system 1.

(3) FIG. 2 shows the first embodiment of the combustion gas extraction probe according to this invention, and the probe 4 comprises: a hollow-cylindrical inner tube 4a through which high-temperature combustion gas flows in the direction of arrow A; a hollow-cylindrical outer tube 4b which surrounds the inner tube 4a; plurality (four in this figure) of low-temperature gas injection holes 4c; a cooling air passage 4g formed between the inner tube 4a and the outer tube 4b; and a cooling air supply portion 4d for feeding low-temperature gas from a fan 9 (shown in FIG. 1) as a low-temperature gas supply means to the cooling air passage 4g.

(4) The inner tube 4a is formed cylindrical and is provided with an inlet portion 4e of the high-temperature combustion gas, and an outlet portion 4f. The inlet portion 4e of the combustion gas is inserted in the rising portion 3 of the cement kiln 2, and the outlet portion 4f is connected to the gas disposal equipment in the rear stage.

(5) The outer tube 4b is formed cylindrical with a section of a concentric circle so that the outer tube 4b may surround the inner tube 4a. The outer tube 4b is provided with the cooling air supply portion 4d for drawing the cooling air from the cooling fan 9 into the probe 4, and the space between the outer tube 4b and the inner tube 4a serves as the cooling air passage 4g, which is closed at the head portion of the probe 4. On the peripheral portion of the outer tube 4b is installed fire-resistant material not shown. In the above-mentioned embodiment, although the inner tube 4a and the outer tube 4b are formed cylindrical, it is not limited circularly but section shapes of the inner tube 4a and the outer tube 4b can also be the shape of a rectangle, or a polygon.

(6) Plurality of discharge holes 4c are provided, and individual discharge holes 4c are arranged at substantially the same positions from the inlet portion 4c of the inner tube 4a in the direction that the high-temperature combustion gas flows (the direction of arrow A), that is, the axial direction of the inner tube 4a, from these low-temperature gas injection holes 4c, cooling air introduced by the cooling fan 9 is breathed out in the direction that is substantially perpendicular to the sucking direction of the high-temperature combustion gas and is toward the center of the flow of the high-temperature combustion gas (the direction of arrow C). As is apparent from FIG. 2, the discharge holes 4c are each disposed about respective axes aligned within a common plane for emitting low temperature gas in a single plane, thereby creating a single plane, i.e., sheet or curtain, of low-temperature gas. Although the number of discharge holes 4c is four in FIG. 2, it is preferred to provide two to six.

(7) Next, operation of the probe 4 with the above-mentioned construction will be explained with reference to FIGS. 1 and 2.

(8) A part of kiln exhaust gas of approximately 1000 C. that is generated in the cement kiln 2 is extracted with the probe 4. In this case, the cooling air from the cooling fan 9 is supplied to the probe 4 through the cooling air supply portion 4d, and the cooling air is introduced in the inner tube 4a from the discharge holes 4c through the cooling air passage 4g, and is mixed with the combustion gas by the probe 4. This rapidly cools the high-temperature combustion gas so that the outlet gas temperature T1 of the probe 4 may become approximately 450 C. Here, the outlet gas temperature T1 is set to be approximately 450 because KCl and the like becomes to have adhesion when it exceeds approximately 450. Further, the extracted gas cooled with the probe 4 is cooled again in the secondary mixing chamber 5 by a secondary cooling fan 12, which is controlled so that the entrance temperature T2 of a heat exchanger 7 becomes approximately 350 C.

(9) When cooling the high-temperature combustion gas from the above-mentioned cement kiln 2, with the probe 4 according to the present invention, the cooling air that flows in the inner tube 4a from the discharge holes 4c flows in the direction that is substantially perpendicular to the sucking direction of the high-temperature combustion gas and is toward the center of the flow of the high-temperature combustion gas with a certain amount of momentum, so that the low-temperature gas reaches to the central portion of the flow of the high-temperature combustion gas, and is mixed with the high-temperature combustion gas, which rapidly cools the high-temperature combustion gas. In addition, the low-temperature gas has no velocity vector ingredient in a direction opposite to the flow of the combustion gas, so that exhaust gas from the cement kiln 2 that is not extracted is not cooled by the cooling air, which allows the low-temperature gas to be made high-speed and allows the velocity of the cooling air between the inner and outer tubes to be raised to a permissible limit of the pressure loss accompanying the increase in the flow velocities. As a result, the outer diameter of the probe can be held small.

(10) Then, the extracted gas containing dust from the secondary mixing chamber 5 is classified by the cyclone 6. And, coarse powder is returned to a rotary kiln system, and fine powder and combustion gas are supplied to the heat exchanger 7 and heat exchange is carried out by the cooling air from the fan 10, and then the dust is collected with the bag filter 8, and they are returned to an exhaust gas processor through the fan 11. Here, the gas volume induced by the fan 10 is controlled so that the entrance temperature T3 of the bag filter becomes approximately 150 C. Further, the dust with high chlorine content that is collected with the heat exchanger 7 and the bag filter 8 may be added to a cement mill system, or processed out of the system. It is also possible by introducing cooling air by the secondary cooling fan 12 so that the outlet gas temperature of the secondary mixing chamber 5 may become approximately 150 C. to make the heat exchanger 7 unnecessary.

(11) Next, the second embodiment of the combustion gas extraction probe according to this invention will be explained with reference to FIG. 3.

(12) This probe 14 comprises: a hollow-cylindrical inner tube 14a in which high-temperature gas flows in the direction of arrow D; an outer tube 14b surrounds the inner tube 14a, and is provided with, at a head portion, a folded portion 14h covering a head portion of the inner tube 14a; plurality of low-temperature gas discharge holes 14c provided on the folded portion 14h facing the high-temperature combustion gas; and a cooling air passage 14g formed between the inner tube 14a and the outer tube 14b; and a cooling air supply portion 14d for supplying the low-temperature gas from the cooling fan 9 (illustrated in FIG. 1) as a low-temperature gas supply means to the cooling air passage 14g.

(13) Since the main structural elements of this probe 14 are the same as those of the probe 4 shown in the above FIG. 2, detailed explanation for the elements will be omitted. In this embodiment, the head portion of the inner tube 14a is covered by the folded portion 14h of the outer tube 14b, so that the cooling air passing the cooling air passage 14g may turn around the inside of the head portion of the outer tube 14b, which allows the head portion of the outer tube 14b exposed to high temperature to be protected, and lengthens the life of the probe.

(14) Next, the third embodiment of the combustion gas extraction probe according to this invention will be explained with reference to FIG. 4.

(15) This probe 24 is characterized by adding a blaster 21 to remove blocks at a suction opening of the probe 14 through compressed air to the probe 14 in the second embodiment. The probes 4 and 14 according to the present invention shown in FIGS. 2 and 3 are characterized in that the outer diameters of the probes 4 and 14 are held small as a feature. In connection with this, there is a possibility that the inlet portion of probes 4 and 14 may blockade by the blocks adhering to the surface of a wall of the kiln exhaust gas passage in which probes 4 and 14 are installed, so that the blaster 21 is installed. In FIG. 4, about the same structural elements as the probe 14 shown in FIG. 3, the same reference numbers are attached and detailed explanation is omitted.

(16) The blaster 21 is introduced in the kiln exhaust gas passage through a vertical wall 23 of the rising portion 3 (refer to FIG. 1) from the upper portion of the outer tube 14b. When removing the block 22 at the probe suction opening 25, after shutting the extracted gas suction damper not shown (a damper being provided in the rear stage of the combustion gas exit portion 14f and making the high-temperature combustion gas flow in the direction of arrow D), and decreasing the quantity of cooling air automatically by temperature control of the extracted gas, compressed air is blown from the blaster 21 to remove the block 22. After removing the block 22, the extracted gas suction damper is opened and it returns to usual operation.

(17) The timing performing the block removal using the above blaster 21 is judged by the fall of the pressure at the outlet of the probe 24, the fall of the current of the fan (refer to FIG. 1) and so on. In case that the discharge mouth 14c blocked by the blocks removed by the blaster 21, a lattice can be installed at the low-temperature gas discharge holes 14c.

(18) In the above-mentioned embodiment, although two or more discharge holes 4c and 14c have been arranged in the sucking direction of the high-temperature combustion gas from the head of the probes 4, 14, and 24 at substantially the same positions, it may be made to arrange these plurality of discharge holes 4c and 14c over two or more stages from the head of the probes 4, 14, and 24 in the suction direction of the high-temperature combustion gas.

(19) Further, it is also possible to add exhaust gas that contains bad smell generated by processing of sludge and the like to the air as gas for cooling, and to perform simultaneously cooling of the high-temperature combustion gas and bad smell processing.

(20) Still further, in the above-mentioned embodiment, although the combustion gas extraction probe and the combustion gas treatment method according to the present invention are explained taking the case where applied to the chlorine bypass system of a cement kiln, the probe and the method of this invention are applicable to not only the chlorine bypass but the alkali bypass of a cement kiln or the like and combustion furnaces other than a cement kiln etc.

BRIEF EXPLANATION OF DRAWINGS

(21) FIG. 1 A flowchart showing a chlorine bypass system using the combustion gas extraction probe according to this invention.

(22) FIG. 2 A sectional view showing the first embodiment of the combustion gas extraction probe of this invention.

(23) FIG. 3 A sectional view showing the second embodiment of the combustion gas extraction probe of this invention.

(24) FIG. 4 A sectional view showing the third embodiment of the combustion gas extraction probe of this invention.

EXPLANATION OF SIGNALS

(25) 1 chlorine bypass system 2 cement kiln 3 rising portion 4 probe 4a inner tube 4b outer tube 4c discharge hole 4d cooling air inlet portion 4e combustion gas inlet portion 4f combustion gas exit portion 4g cooling air passage 5 secondary mixing chamber 6 cyclone 7 heat exchanger 8 bag filter 9 cooling fan 10 fan 11 fan 12 secondary cooling fan 14 probe 14a inner tube 14b outer tube 14c discharge hole 14d cooling air inlet portion 14e combustion gas inlet portion 14f combustion gas exit portion 14g cooling air passage 14h folded portion 21 blaster 22 block 23 vertical wall 24 probe 25 probe suction opening