JPH0325692B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Background of the Invention The present invention relates to a fuel conduit for feeding pulverized coal of a steam generator, and in particular a fuel conduit for modifying the distribution amount of pulverized coal flow between a plurality of fuel conduits arranged in parallel. The present invention relates to an orifice device for a conduit.

In a steam generator, pulverized coal is typically aerated in a coal pulverizer and then pumped through a fuel conduit to the steam generator. A plurality of fuel conduits arranged in parallel flow relationship are then used to transport this pulverized coal. Uneven distribution of the pulverized coal flow through these fuel conduits has deleterious consequences on the flammability of the furnace. This uneven distribution of pulverized coal flow also results in significantly less flow in certain conduits;
This causes the airborne pulverized coal to fall out of the air stream and clog the fuel conduit. If such a reduction in flow occurs in any one fuel conduit, excessive flow will occur in the other fuel conduits.

Therefore, because each fuel conduit has to be routed at different routes and distances from the pulverizer to the inlet at a particular location in the furnace, an uneven distribution of pulverized coal flow is inherent. be.
For this reason, it has been common practice in the past to modify the distribution of the pulverized coal flow to obtain an even flow by inserting an orifice into the fuel conduit.

However, conventional methods have had the following problems. Pulverized coal is clearly a highly erosive material. Therefore, the orifice, to which the fuel conduit is initially installed to obtain proper distribution of the pulverized coal flow, gradually becomes eroded by the pulverized coal as the operation progresses. Therefore, when the combustibility of the furnace deteriorates or the fuel conduit becomes clogged, the orifice must be replaced.

In order to solve these problems, according to other conventional techniques, an orifice made of a highly hard material such as hard nickel, or an orifice plate whose surface is hardened. are using. Although this allows the life of such orifices to be longer than orifices made of cast iron or common steel, it is still necessary to replace the orifices frequently.

Therefore, instead of using these materials such as steel, it has been considered to use an orifice made directly from ceramic, but it is not easy to implement this at present. This is because, as a manufacturing problem, it is technically difficult to form an annular member made of ceramic material that is dense enough to be used as an orifice, and the manufacturing cost for forming it is expensive. Another problem in use is that there is a risk that the ceramic material will suddenly crack due to physical bending or thermal changes in the fuel conduit during operation.

Summary of the Invention The present invention has been made to solve these conventional problems.

The orifice device according to the invention includes a metal support ring whose inner periphery is coated with ceramic. The support ring is formed from a hollow cylinder having an inwardly extending flange at one end. A number of ceramic bull nose inserts are placed inside this cylindrical support ring.
It is supported by its inwardly extending flanges. Each insert has a truncated pie shape.
shape) and a sufficient number of inserts to occupy the entire circumference of the support ring are inserted into the inside of the support ring, immobilized radially relative to each other by their truncated pie-like shape. It is located. A metal fixing plate is also secured to the other end of the support ring to hold down the ceramic insert. The orifice device thus assembled is then secured to a fuel conduit to modify the distribution of pulverized coal flow through the fuel conduit.

Since each of the inserts described above is a small piece, it can be formed densely and inexpensively of ceramic. And by presetting the air gap between adjacent inserts to a predetermined value, any thermal or structural stresses are absorbed by the slight movement between these inserts, which allows the ceramic pieces to form a single molded piece. It is possible to eliminate the sudden occurrence of cracks that may occur in the case of Each of the independent inserts is then sized small enough to withstand forces such as thermal stresses that occur.

DESCRIPTION OF A PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in FIG. 1, a pulverizer 1 is connected to a furnace 2 to supply pulverized coal to the furnace. This furnace is provided with a wind box 3, through which combustion air is supplied to the furnace 2 and is used for combustion of fuel. The fuel conduit 4 carries pulverized coal in the air, and the air-
The pulverized coal mixture is transported from the pulverizer 1 to the fuel nozzle 5 of the wind box 3. The lengths of these fuel conduits 4 are different from each other, as is clear from FIG. 1, which is schematically shown. The amount of coal flowing will also be different.

An orifice device 6 is then placed in the middle of each fuel conduit 4 to modify the distribution of the pulverized coal flow so as to generally equalize the flow of pulverized coal through each fuel conduit 4.

As shown in detail in FIG. 2, each orifice device 6 is affixed to an associated particular fuel conduit 4. Although a flange connection using bolts 10 is shown as an example of this fixing means in FIG. 2, the present invention is not limited to this, and other suitable well-known fixing means can be applied.

The orifice device 6 now includes a support ring 12 in the form of a hollow cylinder, which has an inwardly extending flange 14 at one end thereof. The inner diameter of the flange 14 extending in this direction is preferably larger than the inner diameter of the fuel conduit 4, thereby avoiding wear and also eliminating flow restriction in parts of the fuel conduit where no throttling is required. That's what I do.

A number of ceramic bullnose inserts 20 are supported by flanges 14 and are disposed inside the cylindrical support ring 12. Each of these inserts is shaped like a truncated pie, and a sufficient number of inserts are attached to the support ring 12 to occupy the entire inner circumference of the support ring 12.
placed on the inner periphery of the Due to their frusto-pie shape, these inserts are immovably interlocked in the radial direction. That is, a suitable number of these inserts 20 are once inserted into the support ring 1.
2, their truncated pie-shaped shape allows adjacent inserts to interact with each other and impede their respective movement, so that the inserts 20 do not move radially inwardly into the fuel conduit 4. cannot be moved to. In this way, after all of the inserts 20 have been installed, there will be some acceptable clearance and play between the inserts.

Further, a shim material 22 is disposed between the inner peripheral surface of the support ring 12 and the outer peripheral surface of each insert 20. The thickness of this shim material is sufficient to force a number of inserts 20 inwardly together and to securely hold each of these inserts in its position. After installing this shim material 22, the metal fixing plate 24 is
For example, a built-in bolt 2 is attached to the support ring 12.
6 to firmly fix the insert 20 so as not to move in the axial direction of the fuel conduit 4. The orifice device 6 thus assembled is then attached to the fuel conduit 4 with bolts 10 as described above.

The ceramic insert 20 described above is
Specifically, it is made of alumina ceramic, preferably 90% alumina ceramic, sintered under high pressure. In addition, the density of ceramic is required to be 3.5 or higher in consideration of its high wear resistance. Although it is difficult to form products with complex shapes using such ceramic materials,
The bullnose-shaped insert 20 of the present invention described above can be easily and inexpensively formed. Further, when a ceramic orifice plate is exposed to a flow of highly corrosive pulverized coal, wear often occurs only on a portion of the inner peripheral surface of the orifice plate. Therefore, by using multiple inserts 20 in such areas as in the present invention, only those inserts that have become unacceptably worn need be replaced. Furthermore, normally preheated air is used to dry and preheat the coal in the coal pulverizer 1, so that the fuel conduit 4 is heated to about 95°C.
It is used by being exposed to temperatures of (200〓). As a result, thermal expansion occurs in the fuel conduit, and thermal stress is generated in the fuel conduit accordingly. and,
Since ceramic has brittle properties, when such stress is applied, the ceramic suddenly cracks.

However, according to the present invention, a large number of inserts 20 are used, and the gaps formed between adjacent inserts can be viewed as pre-formed cracks, and therefore stress is not exerted on the inserts. However, this stress does not cause any cracks in the ceramic that makes up the insert, and the insert only moves slightly due to this stress.

Similarly, an insert 20 made of ceramic
Even if localized stresses occur due to the differential expansion between the inserts and the support ring 12 surrounding these inserts, these stresses can be absorbed by slight movements between adjacent inserts. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example in which a pulverizer and a steam generator are connected by a plurality of fuel conduits to which orifice devices according to the present invention are attached, and FIG.
The figure is a vertical sectional view showing in detail the orifice device for a fuel conduit according to the present invention by enlarging a part of FIG.
The figure is a cross-sectional view taken along the - line in FIG. 2. 1... Pulverizer, 2... Furnace, 3... Wind box, 4
... Fuel conduit, 5 ... Fuel nozzle, 6 ... Orifice device, 10 ... Bolt, 12 ... Support ring, 14 ... Flange, 20 ... Insert,
22...Shim material, 24...fixing plate, 26...bolt.

Claims (1)

[Claims] 1. In a fuel conduit orifice device that is installed in each of a plurality of fuel conduits that conveys pulverized coal in air to a plurality of fuel nozzles to modify the distribution amount of pulverized coal flow, the orifice device is not smaller than the inner diameter of the fuel conduit. a metal support ring consisting of a hollow cylinder having an inner diameter and an inwardly extending flange at one end; a plurality of ceramic bullnose inserts, each having a truncated pie shape and being immovable radially inward relative to each other; , at the other end of the support ring opposite to the inwardly extending flange, a metal fixing plate that extends inwardly and is fixed to the support ring to suppress axial movement of the insert; and an orifice device for a fuel conduit, comprising means for securing the fuel conduit to the fuel conduit.