JP2000107541A - Venturi scrubber installed in waste gas treatment route - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent formation of break holes due to the pushing up of layered metal nets of a circular demister in the case dust adheres locally to the metal nets and the pressure loss is increased. SOLUTION: In a waste gas flow route in the vertical direction surrounding the outer circumference of a lower end part of a venturi tube 9 installed in a venturi scrubber 5, an expanded metal 21 having grating with not wider than 100 cm2 surface area of each grating aperture and a sufficient strength standing the pressure loss of a waste gas flow is put on the upper face of an annular demister 10 produced by layering metal nets. Even in the case that a part of the annular demister is clogged with dust due to insufficient washing and that waste gas flow concentrates on the other part which is not clogged, since the expanded metal 21 put on the upper face of the metal nets of the annular demister 10 can suppress the metal nets from being pushed up, local break hole formation in the metal nets can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a water-cleaning venturi pipe installed on an exhaust gas treatment path, and a demister comprising a laminated metal mesh through which blast furnace exhaust gas passes downstream of the venturi pipe. The venturi scrubber installed in the exhaust gas treatment path.

[0002]

BACKGROUND OF THE INVENTION In general blast furnace, a temperature 200 ° C. from the furnace top of the blast furnace 1 as shown in FIG. 12, the pressure 2 kg / cm blast furnace exhaust gas is released at about ² (hereinafter, referred to as exhaust gas) 2 was collected and gas fuel When used as a waste gas, coarse particles in the exhaust gas are removed by a dust catcher 4 installed in a blast furnace exhaust gas treatment path passing through an exhaust gas duct 3, then wet-type dust is removed by a venturi scrubber 5, and a septum valve 6 for controlling furnace top pressure is used. The dust content is further reduced sufficiently by an electric precipitator 8 installed downstream of the steelworks, and is used as fuel gas or the like in a steelworks.

In order to effectively utilize the pressure of the exhaust gas, the exhaust gas is guided to a power generation turbine 7 disposed in parallel with the septum valve 6 after wet dedusting with a venturi scrubber 5 and used for power generation. . At this time, when the dust-containing water droplets generated by the venturi scrubber 5 reach the power generation turbine 7, they adhere to the turbine blades, and significantly lower the power generation efficiency. Therefore, as shown in FIG. 13, the venturi tube 9 is provided inside the venturi scrubber 5 having the water-cleaning type venturi tube 9 connected to the exhaust gas duct 3 on the entrance side.
A demister 10 is arranged on the downstream side.

[0004] The venturi tube 9 has a variable throat 11 provided at the upper minimum constriction portion, penetrates a central portion of the venturi scrubber 5 and is vertically extended downward, and has a lower end open. A plurality of water supply headers 12 are arranged so as to surround the vicinity of the upstream side of the variable throat 11 formed by the venturi tube 9, and a large number of cleaning nozzles 13 branched from each water supply header 12 and taken out are provided by the variable throat 11. Is disposed in the vicinity of the upstream side. An annular demister 10 is disposed in a vertical exhaust gas passage surrounding the outer periphery of the lower end of the venturi tube 9 which faces downward on the downstream side of the venturi scrubber 5, that is, inside the venturi scrubber 5. Above, a plurality of demister cleaning nozzles 14 are arranged.

The high-pressure exhaust gas 2 guided from the exhaust gas duct 3 on the upstream side to the Venturi pipe 9 is removed and cleaned by atomizing and spraying water from a number of cleaning nozzles 13 disposed near the throat 11 to remove dust. Water accumulates as sewage at the bottom of the venturi scrubber 5. The exhaust gas 2 that has passed through the venturi pipe 9 is supplied to the power generation turbine 7 after dust-containing water droplets are removed while passing through the annular demister 10 on the downstream side, so that dust adhesion to turbine blades can be prevented, and power generation efficiency can be reduced. Is achieved. Further, dust adhering to the annular demister 10 is washed by water spraying from the demister washing nozzle 14 constantly, thereby preventing clogging. The washed dust-containing water accumulates as dirty water at the bottom of the venturi scrubber 5 in the same manner as the dust-containing water in the Venturi tube 9. The sewage collected at the bottom of the venturi scrubber 5 is taken out by opening and closing the valve 17 as needed.

The annular demister 10 is, for example, shown in FIGS.
As shown in FIG. 15, a highly flexible laminated metal mesh formed by laminating small-meshed metal meshes 15 to a thickness of 100 to 200 mm is usually a square having a very coarse mesh (height 250 × width 250 mm).
A structure is used in which the support lattice frame 16 made of the above-mentioned steel material is used, and is integrally fixed so as to be sandwiched from above and below.

[0007]

However, when the annular demister 10 is washed, the washing water supplied to the demister washing nozzle 14 generally has poor water quality because it is circulated through a thickener and often has poor water quality. Blockage of the water supply pipe and a decrease in the amount of water may occur.
May be clogged by dust-containing mist. If a part of the annular demister 10 is clogged, the pressure of the exhaust gas passing through the wire mesh 15 of the annular demister 10 gradually increases because the permeated exhaust gas flow concentrates on the unclogged portion, and the wire mesh 15 is pushed up. However, the wire mesh 15 cannot be held by the coarse support lattice frame 16. The wire mesh 15 is a braided thin stainless wire, and deterioration due to long-term use is inevitable. As a result, as shown in FIG. 16, the annular demister 10 is locally broken and a broken hole 20 is generated.

[0008] The broken hole 20 formed locally has a small gas flow velocity due to its narrowness, so that the annular demister 10
The dust-containing mist 18 passing through the mist increases rapidly, and the flow rate of the exhaust gas after passing through the damaged hole 20 decreases, so that the coarse-grained dust-containing mist 19 drops on the upper surface of the annular demister 10 to promote clogging. At the same time, the relatively small dust mist is entrained by the exhaust gas flow and reaches the power generation turbine 7 and adheres to the turbine blades. As a result, a significant reduction in power generation efficiency is observed. As described above, when the support of the wire mesh 15 by the support lattice frame 16 is insufficient, if the wire mesh 15 is poorly cleaned, the wire mesh 15 is easily broken, and the damage is enormous.

In order to solve such a problem, the present invention provides:
An object of the present invention is to provide a venturi scrubber that is installed in a blast furnace exhaust gas treatment path that can prevent the wire mesh from breaking even when dust mist locally adheres to a stacked wire mesh forming an annular demister. Is what you do.

[0010]

Means for Solving the Problems The present inventors first increased the size of a support grid frame conventionally used in order to increase the size of a grid arranged on the upper surface of an annular demister 10 formed by laminating a wire mesh. Tried to plan. However, it has been found that it is not easy to retrofit the existing support grid frame using the blast furnace downtime because the blast furnace downtime is usually a short period of around 24 hours. Since the support grid frame is divided into many parts, and each of the divided grid frames is fixed with bolts, it takes a lot of time to attach and detach it, and the individual grid frames are additionally attached by welding This is because it takes time. Therefore, as a result of trying to strengthen by disposing a grid-like member finer than the grid of the support grid frame on the upper surface of the annular demister 10 formed by laminating the wire mesh, it can be easily implemented using the downtime of the blast furnace. And completed the present invention.

According to a first aspect of the present invention, there is provided an exhaust gas treatment path, wherein a water-cleaning venturi pipe is provided downward on an entrance side and surrounds an outer periphery of a lower end of the venturi pipe. In a venturi scrubber in which an annular demister formed by laminating a wire mesh in a vertical exhaust gas passage is horizontally disposed, a grid having a strength capable of withstanding a passage pressure loss of blast furnace exhaust gas is formed on an upper surface of the annular demister. A fine lattice-shaped member having a lattice opening area of less than 100 cm ² and a support lattice frame for forming a coarse lattice on the lower surface of the annular demister are disposed. It is ba.

According to a second aspect of the present invention, the individual lattice opening area formed by the lattice of the fine lattice member is larger than the individual hole opening area of the wire mesh. A venturi scrubber installed in the exhaust gas treatment path. According to a third aspect of the present invention, there is provided the venturi scrubber installed in the exhaust gas treatment path according to the first aspect, wherein the fine lattice member is an expanded metal.

According to a fourth aspect of the present invention, there is provided an exhaust gas treatment apparatus according to the first aspect, wherein a support lattice frame for forming a coarse lattice is disposed on the upper surface of the fine lattice member disposed on the upper surface of the annular demister. It is a venturi scrubber installed on the route. According to a fifth aspect of the present invention, in the exhaust gas treatment path according to the first aspect, a fine lattice member is interposed between the lower surface of the annular demister and the support lattice frame forming the coarse lattice. Venturi scrubber to be set up.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. In the present invention, as shown in FIG. 1 and FIG. 2, each of the annular demisters 10 formed by laminating wire meshes 15 to have a thickness of about 100 to 200 mm has a grid having a strength capable of withstanding the passage pressure loss of the blast furnace exhaust gas. The expanded metal 21 is arranged as a fine lattice member having a lattice opening area of less than 100 cm ^2, and a support lattice frame 16 for forming, for example, a square coarse lattice (250 mm long × 250 mm wide) is arranged on the lower surface of the annular demister 10. Then, the annular demister 10 is sandwiched from both upper and lower surfaces.

The expanded metal 21 is disposed on the upper surface of the annular demister 10 and the support lattice frame 16 for forming a square coarse lattice is disposed on the lower surface, as shown in FIG. Therefore, the venturi pipe 9 is disposed horizontally in the vertical exhaust gas passage surrounding the lower end outer periphery of the venturi tube 9 facing downward in the venturi scrubber 5 installed in the blast furnace exhaust gas treatment path. In FIG. 3, the same components as those shown in FIG. 13 are denoted by the same reference numerals, and the description thereof will not be repeated.

Here, the size of the expanded metal 21
In other words, wire mesh 15 in actual operation when the area in the grid is changed
The annular demister 10 is divided into three equal parts every 120 ° in the circumferential direction on a plane in order to investigate the damage state of the expander, and the expanders having different areas in the grid as shown in FIG. Fabricate a grid member equivalent to Metal 21,
This was placed at a predetermined position and a test was performed. Testing is performed 3 times, the area of the grid of the grid-shaped member used in the test, the test 1 (50, 100, 200 cm ^2), the test 2 (100, 200, 400 cm ^2), the test 3 (200 , 400,
500 cm ² ) was used. The reason why such a lattice-shaped member was manufactured and used for the test was that an expanded metal having an area within a large lattice exceeding 150 cm ² was not commercially available.

For the grid members of different sizes arranged in each area at the time of repair about every 3 to 4 months from the start of the test, the area (cm ² ) in the grid and the number of broken holes generated in the wire mesh are determined. FIG. 4 shows the relationship. As shown in FIG. 4, when the area of the lattice of the lattice-shaped member in the lattice is less than 100 cm ^2, there is no breakage hole in the wire mesh, whereas when the area is greater than 100 cm ² , the area in the lattice is It can be seen that as the number increases, the number of broken holes in the wire net 15 increases.

In addition, three tests were performed to determine what would happen if the area of the lattice-like member arranged on the upper surface of the annular demister 10 was reduced to less than 100 cm ² . In this case, as shown in FIG. 5, since the wire mesh 15 forming the annular demister 10 becomes clogged with dust as the continuous operation period of the blast furnace elapses, the differential pressure before and after the annular demister 10 gradually increases. . However, when the area of the lattice member in the lattice was less than 100 cm ^2, it was found that the wire mesh 15 would not be damaged even if the differential pressure across the annular demister 10 increased. Based on this test result, in the present invention, and less than 100 cm ² the individual grid opening area grating having a strength to withstand the passage pressure loss of the blast furnace exhaust gas to the upper surface of the annular demister 10 formed by laminating a wire mesh 15 is formed The basis for doing so.

Commercially available expanded metals include:
There are three types of meshes, grating, standard and flat, depending on the shape of the mesh. In the present invention, any commercially available expanded metal can be used. FIG.
7 and FIG. 7 show the shapes and dimensional relationships of the expanded metal 21 of the grating type and the standard type, and Table 1 shows the dimensions and aperture ratio (%) of each part of the expanded metal of the grating type and the standard type. I have.

[0020]

[Table 1]

The expanded metal 21 of each of the grating type and the standard type shown in Table 1 satisfies the condition that the area in the lattice is less than 100 cm ² . The steel material used for expanded metal 21 is JI
Manufactured mainly from steel sheets based on SG 3131 (hot-rolled mild steel sheet) or JIS G 3141 (cold-rolled steel sheet), the expanded metal shown in Table 1 has the strength to withstand the passage pressure loss of blast furnace exhaust gas. All can be used in the present invention. Note that the lower limit of the individual lattice opening area formed by the lattice of the expanded metal 21 is larger than the individual hole opening area of the laminated wire mesh 15 forming the annular demister 10 and has a strength enough to withstand the passage pressure loss of the blast furnace exhaust gas. What should I do,
In Table 1, the smallest area of the expanded metal 21 in the lattice is 1 cm ² , and it is practically preferable that the area in the lattice is 1 cm ² or more.

Unit weight of expanded metal = (unit weight of steel sheet) / (elongation ratio), unit weight of steel sheet = 7.85 × T
(Kg / m ² ). Therefore, expanded metal 1
The weight of a sheet is obtained by multiplying the unit weight by the area. Elongation rate = (SW / 2W) T: Plate thickness (mm) SW: Distance between centers in the shorter direction of the mesh (mm) w: Step width (mm) Opening ratio = [[SWO x (LWO + B)] / (SW x LW) )]｝ × 100 SWO = SW−T′−2W ′, LWO = LW−B−2d Surface area of two sides of expanded metal = {[8W (B + c) + 4T (B + 2c−d)]} / (SW × LW) SWO: Mesh short direction opening distance LWO: Mesh long direction opening distance B: Bond distance LW: Mesh long direction center-to-center distance (mm) FIG. Grating type expanded metal (mesh size: SW = 3.4 cm,
LW = 13.5cm, aperture ratio = 59.4%, aperture area in grid = about 14
cm ² ), an annular demister 10 formed by laminating a wire mesh 15
On the lower surface of the annular demister 10
The support grid frame 16 forming a coarse grid of cm × 25 cm = 625 cm ² is placed horizontally in a vertical exhaust gas passage surrounding the lower end outer periphery of the Venturi tube 9 facing downward in the Venturi scrubber 5. FIG. 15 shows an annular demister shown in FIG. 15 showing a temporal decrease in furnace top pressure power generation by the power generation turbine during a continuous operation period when the present invention is set.
This is shown in comparison with a conventional case in which a support lattice frame 16 having a coarse mesh is simply sandwiched from above and below 10.

In FIG. 8, the power generation amount at startup after completely removing the deposits on the power generation turbine is set to 100 (dimensionless index). As shown in FIG. 8, according to the present invention, as a result of preventing the wire mesh 15 forming the annular demister 10 from being damaged, dust adhesion to the power generation turbine blades is suppressed as compared with the related art, and the power generation amount is reduced. It became clear that it could be greatly reduced. In FIG. 8, the reason why the power generation index recovers during the continuous operation is that dust adhering to the turbine is removed by partially cleaning it when the blast furnace is shut down.

According to the present invention, as shown in FIGS. 9 and 10, an expanded metal 21 having a lattice opening area of less than 100 cm ² is arranged on the upper surface of an annular demister 10 formed by laminating a wire netting 15, and an expanded metal 21 is further provided. A support grid frame 16 (250m long) that forms a coarse grid used conventionally
m × 250 mm) and the support lattice frame 16 on the lower surface of the annular demister 10 is preferable. Thereby, the holding force from above when the wire mesh 15 is clogged with dust can be further enhanced. In some cases, as shown in FIG. 11, the expanded metal 21 is disposed on the upper surface and the lower surface of the annular demister 10 formed by laminating the wire mesh 15, and the support lattice frame 16 is disposed and clamped on the upper and lower surfaces. A structure is also possible.

In the above embodiment of the present invention, the venturi scrubber annular demister installed in the blast furnace exhaust gas treatment path has been described. However, the present invention is not limited to the blast furnace exhaust gas treatment, but the venturis installed in various exhaust gas treatment paths. Applicable to scrubbers. In addition, the case where expanded metal manufactured from a steel plate is used as the fine lattice-shaped member arranged on the upper surface of the annular demister has been described.However, the present invention is not limited to this, and ordinary steel and various steel materials such as special steel are used. ^What is necessary is just to manufacture a lattice-like member having an opening area in the lattice of less than ² with a required strength, and an opening in the lattice can be selected in an appropriate shape. The fine lattice member is not limited to a steel material, and metal materials such as a copper alloy and an aluminum alloy, plastics, and even wood can be used in consideration of properties of exhaust gas to be treated, cost conditions, and the like.

[0026]

According to the present invention as described above,
An annular demister formed by laminating a wire mesh in a vertical exhaust gas passage surrounding the lower end outer periphery of a water-cleaning type venturi tube provided on the entrance side of the venturi scrubber, which is installed in the exhaust gas treatment path, is arranged. On the upper surface of the demister, there is arranged a fine grid-like member having a grid opening area smaller than 100 cm ² formed by a grid having a strength capable of withstanding the passage pressure loss of exhaust gas. When cleaning the annular demister, a part of the annular demister 10 is clogged with dust due to poor cleaning, and even if the permeated exhaust gas flow concentrates on a non-clogged portion, the wire mesh of the demister is meshed by the lattice member on the upper surface. Since pushing up can be suppressed, it is possible to prevent the occurrence of locally damaged holes in the wire mesh, and stable operation is achieved.

[Brief description of the drawings]

FIG. 1 is a partial plan view showing a structure of an annular demister according to the present invention.

FIG. 2 is a side view of FIG.

FIG. 3 is a cross-sectional view showing a state where an annular demister according to the present invention is disposed in a venturi scrubber.

FIG. 4 shows the area (cm ² ) in the grid formed by the grid members of different sizes arranged in each area at the time of repair approximately every 3 to 4 months from the start of the test, and the broken hole of the wire mesh forming the demister. 6 is a graph showing a relationship between the number of the holograms and the number of holograms.

FIG. 5 is a graph showing a time change of a pressure drop of a demister portion during a continuous operation period of a blast furnace when an area of a grid member in the grid is less than 100 cm ² .

FIG. 6 is a partial plan view showing a grating type and a standard type expanded metal.

FIG. 7 is a cross-sectional view showing the direction of arrow AA in FIG. 6;

FIG. 8 is a graph showing a temporal decrease in furnace top pressure power generation by a power generation turbine during a continuous operation period when the present invention is implemented, in comparison with a conventional case.

FIG. 9 is a partial plan view showing the structure of a conventional annular demister.

FIG. 10 is a side view of FIG. 9;

FIG. 11 is a partial side view showing the structure of another conventional annular demister.

FIG. 12 is a flow sheet of a conventional blast furnace exhaust gas energy recovery facility.

FIG. 13 is a cross-sectional view showing a state in which a conventional annular demister is disposed in a venturi scrubber.

FIG. 14 is a partial plan view showing a structure of a conventional annular demister.

FIG. 15 is a side view of FIG. 14;

FIG. 16 is an explanatory diagram showing a situation in which pressure loss increases due to partial clogging of a conventional annular demister, and a broken hole is locally generated by pushing up a wire mesh.

[Explanation of symbols]

 Reference Signs List 1 Blast furnace 2 Blast furnace exhaust gas 3 Exhaust gas duct 4 Dust catcher 5 Venturi scrubber 6 Septum valve 7 Power generation turbine 8 Electric precipitator 9 Venturi tube 10 Annular demister 11 Variable throat 12 Water supply header 13 Washing nozzle 14 Demister washing nozzle 15 Wire mesh 16 Support grid frame 17 Valve 18 Dust-containing mist 19 Coarse-grained dust-containing mist 20 Breakage hole 21 Fine grid-like member (expanded metal)

Continued on the front page F term (reference) 4D032 AD01 AD02 AD04 BA03 BA05 BA06 BB05 4K015 HA06 4K056 AA01 CA02 DB14 EA01

Claims (5)

[Claims] 1. A water-cleaning venturi pipe is provided on an entrance side of the exhaust gas treatment path, and is formed by laminating a wire net in a vertical exhaust gas passage surrounding the outer periphery of a lower end portion of the venturi pipe. In a venturi scrubber in which an annular demister is horizontally arranged, a fine lattice member having an individual lattice opening area of less than 100 cm ² formed by a lattice having a strength capable of withstanding a passage pressure loss of blast furnace exhaust gas on the upper surface of the annular demister. And a support lattice frame for forming a coarse lattice on the lower surface of the annular demister is disposed. 2. The exhaust gas treatment path according to claim 1, wherein each grid opening area formed by the grids of the fine grid members is larger than each hole opening area of the wire mesh. Venturi scrubber. 3. The venturi scrubber installed in an exhaust gas treatment path according to claim 1, wherein the fine lattice member is an expanded metal. 4. A venturi crack installed in an exhaust gas treatment path according to claim 1, wherein a support lattice frame for forming a coarse lattice is disposed on an upper surface of the fine lattice member disposed on an upper surface of the annular demister. Ba. 5. A venturi installed in an exhaust gas treatment path according to claim 1, wherein a fine lattice member is interposed between a lower surface of said annular demister and a support lattice frame forming said coarse lattice. Scrubber.