JP2003200021A - Method for injecting fine powder and injection nozzle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for injecting fine powder to be used when a combustion exhaust gas discharged from a waste incinerator, or the like, is treated in the combustion exhaust gas and to provide an injection nozzle which is suitable for implementing this method and through which the fine powder can be injected continuously over a long period of time. <P>SOLUTION: When the fine powder is injected into the exhaust gas, the fine powder and a dry gas are jetted so that a current of the dry gas surrounds the periphery of a current of the fine powder. A concentric circle-shaped double tube nozzle 100 is used as the injection nozzle. An inside tube 2 is used for jetting the fine powder and an outside tube 1 is used for jetting the dry gas. A tapering part 3 expanding to the end on the outlet side of the nozzle 100 is formed in the vicinity of the outlet part of the tube 2. A scraper extending from the vicinity of the beginning position of the part 3 to the vicinity of the end on the outlet side of the nozzle 100 can be arranged. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for injecting fine powder used in the treatment of combustion exhaust gas generated from a waste incinerator or the like into the exhaust gas stream, and a method suitable for carrying out this method. Regarding the injection nozzle. In particular, a method capable of continuously injecting a fine powder suitable for adsorbing and treating various substances such as dioxins in the exhaust gas that may adversely affect the environment over a long period of time, and this method An injection nozzle suitable for implementation.

[0002]

Exhaust gas generated from waste incinerators, etc.
In addition to soot dust such as unburned matter and ash, it contains acid gases such as hydrochloric acid, sulfur oxides, nitrogen oxides, etc., so generally after cooling with a heat exchanger, etc., use a dust collector such as an electric dust collector or a bag filter. Soot and dust are captured, and then acid gas components are neutralized with a caustic soda solution or the like in an exhaust gas cleaning device, and then discharged from the chimney to the atmosphere.

Further, in the case of a small-scale waste incinerator, solid fine powder such as slaked lime is injected into the exhaust gas in place of the above-mentioned neutralization treatment by the wet method, and after neutralization treatment by the so-called dry method, Techniques for collecting dust have also been developed (for example, Japanese Patent Laid-Open No. 20
00-51658 and 2000-61252).

Further, in any of the above-mentioned wet method and dry method, the activated carbon is injected into an appropriate portion of the flue so that the dioxins in the exhaust gas are adsorbed by the activated carbon and removed by dust collection. The technology to do so has also been developed and put to practical use.

[0005]

The activated carbon injected to adsorb and remove the dioxins and the solid fine powder such as slaked lime injected to neutralize the acidic gas component by the dry method are Due to the water present in the exhaust gas, it adheres to the inlet of the solid fine powder, generally the nozzle outlet, and gradually accumulates, finally closing the nozzle,
As a result, a situation may occur in which continuous injection of fine powder cannot be performed for a long period of time.

As a countermeasure against this, conventionally, the above fine powder has been used with a blower or a compressor so as to be entrained in a compressed air flow and injected from a nozzle, or this nozzle is bent toward the downstream of an exhaust gas flow in a flue. The tip of the nozzle is tapered so that the nozzle can be tapered.

However, even by these measures, fine powder adheres to the end of the nozzle outlet side in a short time when the atmosphere is in a high-humidity state, and this fine powder gradually becomes a core and gradually accumulates, resulting in clogging. It does not provide a fundamental solution, as it only slightly extends the time.

The present invention solves such problems and provides a method capable of continuously injecting a predetermined amount of fine powder over a long period of time, and an injection nozzle suitable for carrying out this method. The purpose is to do.

[0009]

In order to achieve the above object, the method for injecting fine powder of the present invention is such that, when injecting fine powder into exhaust gas, the fine powder is surrounded by a dry gas flow. It is characterized by injecting a body and a dry gas. Further, the fine powder injection method of the present invention is such that the fine powder has a gas-solid ratio of 0.1 to 10 g / m ^{3 in} the flue where the temperature of the exhaust gas is 50 to 350 ° C. and the humidity is 50 to 100%. To spray.

The fine powder injection nozzle of the present invention is a nozzle composed of concentric double pipes, wherein the inner pipe is for outflow of fine powder and the outer pipe is for outflow of dry gas, and the vicinity of the nozzle outlet portion of the inner pipe. Is characterized in that a taper portion that spreads to the outlet side end is provided. At this time, a scraper may be provided from the vicinity of the start portion of the tapered portion of the inner pipe to the vicinity of the end on the nozzle outlet side, and the scraper may have a string shape or a sheet shape.

In the injection method of the present invention, when the fine powder is injected into the exhaust gas, the injection flow of the fine powder is surrounded by the flow of the dry gas, so that the injection portion of the fine powder is mainly used (for example, the present invention. (In the outlet of the injection nozzle), the probability of contact between the fine powder and the water in the exhaust gas is reduced, and the water in the exhaust gas wets the injection part of the fine powder and prevents the fine powder from adhering thereto. Suppress and even
Even if the fine powder adheres to the fine powder injection portion, it is removed by the dry gas flow before being deposited.
As a result, the fine powder injecting portion can be prevented from being blocked for a long period of time and a predetermined amount of fine powder can be stably injected. Moreover, in the injection method of the present invention, since the fine powder is uniformly and widely dispersed by the dry gas flow in the part slightly away from the fine powder injection part (nozzle outlet part), the fine powder and the exhaust gas are The contact efficiency is improved, and the exhaust gas purification efficiency can be improved.

The injection nozzle of the present invention utilizes the principle of a two-fluid nozzle and is suitable for carrying out the injection method of the present invention. The inner tube and the outer tube are provided in a concentric shape, By injecting the fine powder from the pipe and injecting the dry gas from the outer pipe, a state in which the periphery of the fine powder flow is surrounded by the dry gas flow appears. Moreover, since the injection nozzle of the present invention is provided with the tapered portion that spreads to the outlet side end in the vicinity of the nozzle outlet portion of the inner pipe, the dry gas flow is injected into the exhaust gas by increasing the pressure and flow velocity at this tapered portion. , Effectively exhibiting the above-mentioned actions (1) to (3). Further, in the injection nozzle of the present invention, if a scraper is provided in the above-mentioned inner tube, even if the fine powder adheres, it can be easily scraped off before being deposited. Therefore, when the injection nozzle of the present invention is used when carrying out the injection method of the present invention, blockage of the fine powder injection portion is prevented for a long period of time, and a predetermined amount of fine powder can be stably and continuously injected. .

The injection method of the present invention is applied to an exhaust gas flue system generated from incinerators for general waste, industrial waste, etc., combustion furnaces of various boilers, etc., and has an exhaust gas temperature of 50 to 350 ° C.
Especially 60 ~ 250 ℃, humidity 50 ~ 100%, especially 60
When applied to a flue gas of up to 100%, clogging of the injection nozzle can be prevented for a long period of time, and dioxin, dioxin precursor, chlorine-containing compound, etc. can be effectively adsorbed and removed.

The fine powder to be injected into the above-mentioned exhaust gas is not limited to the above-mentioned activated carbon and slaked lime, but active coke, magnesium carbonate, heavy metal fixing agent (phosphoric acid, sodium phosphate, potassium phosphate, calcium phosphate, phosphoric acid). Ammonium, phosphates such as aluminum phosphate, dithiocarbamic acid derivatives such as dithiocarbamate),
Inorganic oxides (silicic acid, aluminum silicate, acid clay, activated clay, porous materials such as kaolin, bentonite, allophane, clay minerals such as diatomaceous earth), amorphous aluminum hydroxide, and other incinerators and combustion furnaces Examples include various fine powders that are usually used in a dry purification method of exhaust gas generated in a flue. These fine powders may be individually injected, or two or more kinds may be appropriately combined and injected.

The particle size of these fine powders is not particularly limited, and may be the particle size of the fine powder usually used in the above-mentioned flue dry purification method, but the purification efficiency (dioxin or its precursor, or Considering together the removal efficiency of various acidic gas components, heavy metals, etc.) and continuous injection that is stable for a long period of time, those of about 1 to 100 μm are preferable.

The injection amount of the fine powder is such that the gas-solid ratio is 0.1 to 10.
The amount is set to g / m ³ . If the injection amount of the fine powder is less than this range, the treatment efficiency decreases and it becomes difficult to discharge the exhaust gas to the atmosphere as it is. If the amount is more than this range, the treatment efficiency will not be significantly improved and it will be uneconomical. The fine powder is injected by a blower or a compressor.

On the other hand, as the gas to be injected so as to surround the fine powder flow, dry air is preferable, and it is suitable to use compressed air having a pressure near the injection nozzle of 0.05 to 0.15 MPa. . When the pressure is less than the above dry air, it becomes difficult to surround the periphery of the fine powder injected at the gas-solid ratio, and when the pressure is higher than the above,
Contact between the fine powder injected into the exhaust gas and various components in the exhaust gas is hindered, and the cleaning efficiency of the fine powder is reduced.

Although the flow rate of the dry air varies depending on the temperature and humidity conditions of the exhaust gas to which the injection method of the present invention is applied,
Exhaust gas temperature (50 to 350 ° C) and humidity (50
〜100%) condition, 0.1-10 m ³ / min
The optimum flow rate for the temperature and humidity conditions of the exhaust gas is selected from this range. At the exhaust gas temperature and humidity conditions described above, if the flow rate is less than this, it is difficult to prevent adhesion and deposition of fine powder for a long period of time,
Even if the amount is larger than the above, it takes a long time for the fine powder injected into the exhaust gas to come into contact with various components in the exhaust gas, and the treatment efficiency of the fine powder is reduced.

An example of one embodiment of the injection nozzle of the present invention suitable for carrying out the injection method of the present invention as described above is shown in the half sectional view of FIG. In FIG. 1, 100 is an injection nozzle body composed of concentric double tubes, and an inner tube 2 for outflowing fine powder is concentrically provided inside an outer tube 1 for outflowing dry air. The outlet side end 21 near the outlet of 2
The taper part 3 which spreads to is provided. In the example of FIG.
The tapered portion 3 has a flange 32 provided at the base of the tapered portion 3 and a flange 22 provided at the tip of the inner pipe 2.
In the present invention, the inner pipe 2 is connected by bolts and nuts.
The vicinity of the tip of itself may be spread out like a trumpet to the outlet side end 21 to form a tapered portion. In the example shown in FIG. 1, the gap at the dry air outlet side end 11 is preferably about 0.5 to 2 mm, and more preferably about 0.8 to 1.2 mm.

In FIG. 1, 101 is a flange of the outer tube 1, 103 is a flange of the inner tube 2, and an introduction for introducing dry air into the outer tube 1 is provided between these flanges 101 and 103. A mouth 102 is provided. Although two dry air inlets 102 are shown in FIG.
The number may be one or two or more. Further, several stays 104 are provided at appropriate places on the inner pipe 2 to prevent the inner pipe 2 itself from swinging due to the fine powder flow.
The ferrule 1 at the root of the dry air inlet 102
05 is provided. In the case of the injection nozzle 1 shown in FIG. 1, the flange 101 of the outer tube 1 is attached to a wall of a flue (not shown) for use.

As the material of the injection nozzle 100, for both the outer pipe 1 and the inner pipe 2, various metals such as stainless steel, aluminum alloy and iron, as well as heat resistant engineering plastics and heat resistant plastics can be used. The outer pipe 1, the inner pipe 2, and the tapered portion 3 may be made of the same material or different materials. In particular, when the outer tube 1 is attached to the wall of the flue with the flange 101 as described above, the portion from the flange 101 to the outlet side end 11 of the dry air flow is exposed to the exhaust gas in the flue. Therefore, it is preferable to use a material that can withstand the acidic gas component in the exhaust gas or a material that covers the outer wall surface with such a material. The inner tube 2 and the taper portion 3 may be left as they are if the material of the inner tube 2 and the taper portion 3 itself is such that fine powder or other substance is hard to adhere thereto. It is preferable that the wall surface is polished so as not to adhere to them, or is coated with a fluororesin or the like.

Further, the injection nozzle 100 may be provided with a scraper for peeling off the deposits.
When a scraper is provided, for example, as shown in FIG. 2 (for convenience of explanation, FIG. 2 shows the injection nozzle 100 in the vertical direction), the mounting flange 2 of the taper portion 3 is attached.
Attach using 2,32. FIG. 2A shows a case where the cord-shaped scraper 4 is provided, in which one end of the cord-shaped scraper 4 is attached to the flanges 22 and 32 (for example, fixed with bolts and nuts) and the other end is in a free state. Figure 2
(B) is a case where the sheet-shaped scraper 5 is provided, in which one side of the sheet-shaped scraper 5 is sandwiched between the mounting flanges 22 and 32 of the tapered portion 3 and the other side is free.

The string-shaped scraper 4 and the sheet-shaped scraper 5 shown in FIGS. 2 (A) and 2 (B) oscillate as a whole due to the fine powder flow and collide with the inner wall surface of the inner tube 2, particularly the taper portion 3, A scraping action appears. It should be noted that the scrapers 4 and 5 shown in FIGS. 2A and 2B are detachably attached, and it is easy to remove only the scrapers 4 and 5 for cleaning, or to replace them with new scrapers 4 and 5 easily. It can also be made possible. 2A and 2B, the scrapers 4 and 5 may be attached by welding, heat-resistant adhesive, screws, etc. It may be fixedly attached to. The material of the scraper is not particularly limited, and swingable heat-resistant engineering plastic, heat-resistant plastic, or the like can be used.

In the case of FIG. 2A, one end of the cord-shaped scraper 4 is attached to the flanges 22 and 23, and the other end is long enough to reach the outlet side end 21 of the taper portion 3. However, the thickness differs depending on the number of the cord-shaped scrapers 4 to be provided and cannot be decided unconditionally. However, when a plurality of these are provided, even if all of them are provided, it does not hinder the fine powder flow. is important. The string-shaped scraper 4
May be a cord formed by twisting a plurality of threads together, or may be a single filament, and the shape of these cords is not limited to a circular cross section, but an oval shape. It may be a rhombus, a star, a triangle, a quadrangle, or more polygons. Further, in FIG. 2 (A), the string-shaped scrapers 4 are shown in a state in which a plurality of the string-shaped scrapers 4 are collectively attached to one place.

The sheet-shaped scraper 5 has a length similar to that of the string-shaped scraper 4 and a width which does not hinder the flow of fine powder, and is sufficient to bring about a sufficient scraping action in contact with the inner wall surface. In consideration of practical strength, when the material is made of the above-mentioned material, about 1 to 2 mm is suitable. Only one sheet-shaped scraper 5 may be provided, or a plurality of sheet-shaped scrapers 5 may be provided to such an extent as to impede the flow of fine powder.

One or a plurality of the injection nozzles of the present invention may be set on the wall surface of the flue in the downstream direction of the exhaust gas, or may be set in a direction orthogonal to the flow direction of the exhaust gas. Good. Further, when a plurality of surfaces are set, they may be set so that they are all fit around one surface crossing the flow direction of the exhaust gas, or one may be set around each of the plurality of crossing surfaces. You may set multiple pieces one by one.

[0027]

Example 1 The temperature of exhaust gas is 200 in the flue of an industrial waste incinerator.
One injection nozzle 100 of the embodiment shown in FIG. 1 was set on the wall surface of the flue where the temperature was 60 ° C. and the humidity was 60% in a direction orthogonal to the flow direction of the exhaust gas.

The specifications of the injection nozzle 100 were as follows. Outer diameter (outer diameter of outer tube 1): 80 mm Gap between dry air outlet side end 11: 1 mm Material (outer / inner tube 1, 2, taper part 3, other attached parts):
SUS304

Compressed dry air of 0.1 megapascal as a pressure near the injection point was introduced into the outer tube 1 at a flow rate of 3.5 m ^3.
/ Min, and activated carbon having an average particle size of 20 μm was flown into the inner tube 2 so that the gas-solid ratio was 3.2 g / m ³ .
As a result, when the solid adhesion state of the inner wall surface of the outer tube 1 and the inner wall surface of the inner tube 2 was observed after continuous injection for one month, the adhesion area was found to be the whole (the entire inner wall surface of the outer and inner tubes 1, 2 1% or less of the total area) and the height of adhesion from the wall surface is 1
It was less than mm. Further, when the components of the exhaust gas at the flue outlet were continuously analyzed over a period of one month, the dioxin content was 1 mgTEQ / Nm ³ or less.

Comparative Example 1 Continuous injection of activated carbon was carried out in the same manner as in Example 1 except that a conventional single-tube injection nozzle having the following specifications was used and dry air was not injected. The injection nozzle was blocked and it became impossible to inject activated carbon. Outer diameter: 50 mm Material: SUS304

Example 2 As a result of carrying out the same processing as in Example 1 except that a scraper was attached to the injection nozzle in the following manner in Example 1, the solid adhesion state (both area and height) was obtained in Example 1. Was less than half of.

The sheet-shaped scraper 5 shown in FIG. 2B was attached. The specifications of this sheet-shaped scraper 5 were as follows. Material: Made of heat resistant plastic Length: 200mm Sheet width: 10mm Sheet thickness: 1mm Number of sheets used: 4 Places to be attached: 4 in the cross direction in the mode shown in FIG. 2 (B)
Place

[0033]

As described in detail above, according to the injection method and injection nozzle of the present invention, the following effects can be obtained. (1) Since the water in the exhaust gas is dried by the dry gas flow that is injected around the fine powder flow before it adheres to the inner wall surfaces of the outer and inner tubes of the injection nozzle and is condensed. , The fine powder flow comes in contact with condensed water and adheres.
It is possible to prevent the accumulation. (2) When a scraper is provided inside the inner pipe,
Even if the fine powder adheres to the inner wall surface of the inner tube of the injection nozzle, the scraper scrapes off the fine powder.
It is possible to prevent fine powder from accumulating on the inner wall surface of the inner tube. (3) With these, it is possible to effectively prevent the fine powder from adhering to and depositing on the inner wall surfaces of the outer and inner pipes of the injection nozzle, and continuously and stably maintaining the fine powder for a long period of time. Can be injected.

[Brief description of drawings]

FIG. 1 is a half sectional view for explaining an example of an embodiment of an injection nozzle of the present invention.

FIG. 2 is an explanatory view showing an embodiment of a scraper provided in the injection nozzle of the present invention, in which (A) is a string-shaped scraper and (B) is a sheet-shaped scraper.

[Explanation of symbols]

1 outer tube 2 inner tube 3 Tapered part 11 Outer end of outer tube 21 Outlet end of inner tube 22 Flange provided at the tip of the inner pipe 2 32 Flange provided at root of taper portion 3 100 injection nozzle 101 Outer pipe flange 102 Dry air injection inlet 103 Inner pipe flange 4 string scrapers 5 sheet scrapers

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hitoshi Okano             Kurita, 3-4-3 Nishi-Shinjuku, Shinjuku-ku, Tokyo             Industry Co., Ltd. F-term (reference) 3K070 DA01 DA24                 4D002 AA21 AC04 BA03 CA11 DA05                       DA06 DA08 DA12 DA16 DA18                       DA41 DA46 DA47 GA01 GB03                       GB08 GB12 GB20 HA06                 4F033 QA10 QB02X QB05 QB12X                       QB17 QD21 QD24 QH04                 4G068 AA02 AB01 AB22 AC01 AC13                       AD17 AD21 AF20

Claims (5)

[Claims] 1. A method for injecting fine powder, characterized in that, when injecting the fine powder into the exhaust gas, the fine powder and the dry gas are jetted so that the dry gas flow surrounds the fine powder flow. 2. A fine powder is injected at a gas-solid ratio of 0.1 to 10 g / m ³ in a flue where the temperature of exhaust gas is 50 to 350 ° C. and the humidity is 50 to 100%. The method for injecting fine powder according to claim 1, which is characterized in that. 3. A nozzle comprising a concentric double tube, wherein the inner tube is used for outflow of fine powder and the outer tube is used for outflow of dry gas, and a taper that spreads to the outlet end near the nozzle outlet of the inner tube. An injection nozzle for fine powder, characterized by being provided with a portion. 4. The injection nozzle for fine powder according to claim 3, wherein a scraper is provided from the vicinity of the starting portion of the tapered portion of the inner pipe to the vicinity of the end on the nozzle outlet side. 5. The fine powder injection nozzle according to claim 4, wherein the scraper has a cord shape or a sheet shape.