JPH10122534A - Furnace wall structure of circulating fluidized bed combustion furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid wear of a refractory furnace material caused by flowing sand and enable a stable operation to be carried out for a long period of time by a method wherein anti- wearing block members are arranged at the top surface of the refractory furnace material, the block materials are removably fixed to a water-cooled wall and then a step caused by a thickness of the refractory furnace material is eliminated by the block members. SOLUTION: In a circulating fluidized bed combustion furnace, a furnace main body is constructed at first of water-cooled walls 2 for forming furnace walls 1. Then, they are covered with refractory furnace materials 3 at a lower section of the water-cooled walls 2 forming a combustion chamber, i.e., a predetermined height from the furnace bottom part. Then, some engaging protrusions are buried and fixed in a predetermined pitch from the top surfaces of the refractory furnace materials 3. After this operation, the engaging protrusions at both sides are inserted into fitting recesses 6a at both sides while the block members 4 are being lifted up and the block members 4 are lowered and placed onto the top surface of the refractory furnace materials 3. With such an arrangement as above, the block members 4 are fitted and fixed while being closely contacted with the water-cooled walls 2. This operation is repeated to cause the protection wall of the anti-wear refractory block material to be formed on the upper part of the refractory furnace materials 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a circulating fluidized bed combustion furnace using coal, wood chips, biomass other than wood chips, sewage sludge, municipal solid waste, industrial waste, etc. as a fuel. TECHNICAL FIELD The present invention relates to a furnace wall structure of a fluidized-bed combustion furnace with improved properties.

[0002]

2. Description of the Related Art Fluidized bed combustion furnaces include coal, wood chips, biomass other than wood chips, sewage sludge, municipal solid waste, industrial waste, and RDF.
, Etc., can be efficiently burned and has been widely used for a long time. Among them, the so-called circulating fluidized bed combustion in which the fluidized medium (sand) blown up to the upper part of the fluidized bed furnace body is introduced into the cyclone, and the fluidized medium collected here is returned to the furnace bottom of the fluidized bed body. Furnace technology has been remarkably developed in recent years, and the number of furnaces has increased significantly (Japanese Utility Model Laid-Open No. 4-122927).

[0003] In a circulating fluidized bed combustion furnace, since the flow velocity difference between the combustion gas rising in the furnace body and the fluidized medium (sand) is considerably large, the mixing and agitation of the fuel and the fluidized medium throughout the furnace body are performed. The combustion reaction proceeds very rapidly. As a result, the fuel A with a relatively low excess air ratio
Can be burned almost completely, the unburned loss can be reduced and the boiler efficiency can be increased, and low NOx combustion can be achieved by using two-stage combustion under a low excess air ratio. Because.

FIG. 7 shows an example of a conventional circulating fluidized bed combustion apparatus of this type, in which reference numeral 20 denotes a fuel silo,
21 is a fuel feeder, 22 is a tank for a fluid medium (sand),
23 is a limestone tank, 24 is a circulating fluidized bed furnace main body, 25 is a fuel supply port, 26 is a primary air supply port, 27 is a secondary air supply port, 28 is a fluid medium outlet, 29 is a fluid medium return port,
30 is a starter burner, 31 is an ash outlet, 32 is a cyclone, 33 is a steam header, 34 is a economizer, 35 is a steam superheater, 36 is a push blower, 37 is a boiler feed pump,
38 is a steam turbine power generation device, 39 is a waste gas treatment device,
40 is an induction ventilator, 41 is a chimney, 42 is an ash silo, 43
Is an exhaust gas recirculation fan, 44 is a slaked lime tank, A is fuel, B is a fluid medium, C is primary combustion air, D is secondary combustion air, E is ash, and F is combustion gas.

Fuel A is supplied from a fuel silo 20 to a furnace bottom of a circulating fluidized bed furnace body 24 through a fuel supply port 25 by a fuel feeder 21. On the other hand, the primary combustion air C is supplied to a furnace bottom from a primary air supply nozzle (not shown) provided at the furnace bottom through a primary air supply port 26, and the secondary combustion air D is supplied to a furnace wall below an intermediate portion of the furnace main body 1. From the secondary air supply nozzle (not shown) provided in the furnace. In the fluidized bed furnace main body 24, a so-called fluidized bed is formed by the primary combustion air C supplied from the furnace bottom, and the fuel A in the fluidized bed burns violently by the supply of the primary combustion air C and the secondary combustion air D. The combustion gas F in the circulating fluidized bed furnace main body 24 and the fluidized medium B in the rising fluidized bed rise while being stirred in the furnace main body 24, and the unburned matter accompanying the combustion is completely burned. . The fluid medium B and the like that flew up with the combustion gas F are led out of the fluid medium outlet 28 into the cyclone 32, where they are separated into the combustion gas F and the like and the fluid medium B.
Further, the collected fluid medium B is returned from the fluid medium return port 29 to the bottom of the furnace main body 24.

The circulating fluidized bed furnace main body 24, cyclone 3
2 and a flue are provided with a group of water tubes constituting a boiler device, and absorb heat of the combustion gas F. The steam extracted from the steam header 33 is supplied to a steam turbine generator 38 through a steam superheater 35. Further, the combustion gas F whose waste heat has been recovered by the economizer 34 or the like is drawn out by the induction ventilator 40 through the waste gas treatment device 39,
Released from the chimney 41 into the atmosphere. Further, the combustion residue (ash E) formed in the fluidized bed is led out of the furnace body 24 from an ash outlet 31 formed in the furnace bottom of the furnace body 24,
After being separated from the fluid medium B by a separation device (not shown), it is carried out to the ash silo 42.

[0007]

In a circulating fluidized-bed combustion furnace, most of the fluid medium (sand) B rising above the furnace body is led out into the cyclone 32 as described above. However, the part of the soaking fluid medium B and the fluid medium B that did not soar to the vicinity of the furnace top flow down along the inner surface of the water cooling wall, and the so-called fluid medium (sand) B Downflow will occur.

On the other hand, in the conventional circulating fluidized bed combustion furnace, the lower inner surface of the combustion chamber 46 is generally lined with a refractory furnace material 47 as shown in FIGS.
A step 48 corresponding to the thickness of the refractory furnace material 47 is formed at a boundary between a portion where the refractory furnace material 47 is exposed and a portion lined with the refractory furnace material 47. Therefore, the water cooling wall 45
The downflow of the fluid medium B flowing down along the step collides with the step 48 to disturb the flow, and the fluid medium B is scattered, so that the water cooling wall near the upper portion of the step 48 is worn. It will be.

In order to prevent abrasion of the water cooling wall 45 due to the disturbance of the downflow of the fluid medium B, the outer surface of the water cooling wall 45 having a height of about 300 mm above the step 48 is subjected to abrasion resistance by metal spraying. A method of forming a protective film having a property is adopted. However, it has been proved that the wear of the water cooling wall 45 when the circulating fluidized bed combustion furnace is operated for a long time cannot be completely suppressed only by forming the protective coating by the metal spraying. The problem of wear of the water cooling wall 45 due to the downflow of B is still left unsolved.

The present invention has the above-mentioned problem in the conventional circulating fluidized bed combustion furnace, namely, the problem that the downflow of the fluidized medium B causes abrasion of the water cooling wall immediately above the step of the refractory material 47. The furnace wall of a circulating fluidized bed combustion furnace that enables stable operation of a circulating fluidized bed combustion furnace for a long period of time without causing abrasion due to downflow of fluidized sand on a water cooling wall. Provides structure.

[0011]

According to the first aspect of the present invention, a furnace wall forming a combustion chamber of a circulating fluidized bed combustion furnace is provided with a water cooling wall; a refractory furnace material covering a lower portion of the water cooling wall; The basic structure of the present invention comprises a wear-resistant block body which is disposed above the furnace material and is detachably disposed on the inner side surface of the water-cooling wall and eliminates a step between the water-cooling wall and the refractory furnace material. It is assumed that.

The invention described in claim 2 is the first invention.
In the invention according to the invention, the block body is a cast iron block body having a semi-cylindrical fitting concave portion on the back surface into which the water pipe of the water pipe wall is fitted, and having engaging concave portions of the engaging projections on both side surfaces. The basic structure of the present invention is to provide a block body which is detachably fixed to the inner surface of the water cooling wall by engaging the engaging projections projecting from the fins of the water pipe wall into the engaging recesses. Things.

Further, the invention according to claim 3 is the invention according to claim 1.
Or, in the invention according to claim 2, the block body, the side surfaces and the bottom surface have a rectangular flat shape, the upper end surface has a narrow semicircular flat shape, and the front side is from the upper end. A basic configuration of the present invention is to provide a block formed on a curved surface of a skirt shape facing downward.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a perspective view showing a part of a furnace wall according to the present invention, FIG. 2 is a front view showing a part of the furnace wall according to the present invention, FIG. 3 is a sectional view taken along the line II in FIG. 2, and FIG. FIG. 5 is a front view of the block body,
FIG. 6 is a side view of the block body. Referring to FIGS. 1 to 3, 1 is a furnace wall, 2 is a water cooling wall, 2a is a water pipe, 2b is a fin, 3 is a refractory furnace material, and 4 is a block body.

The main body of the circulating fluidized bed combustion furnace is formed of a furnace wall having a structure mainly composed of a water cooling wall, and a lower portion of the furnace wall forming a combustion chamber inside the furnace body is as shown in FIG. The furnace wall 1 is formed of a combination of a water cooling wall 2, a refractory furnace material 3 and a block body 4. That is, the furnace wall 1 according to the present invention includes a water-cooling wall 2, a refractory furnace material 3 having a predetermined thickness covering the inner surface of the water-cooling wall 2, and a water-cooling wall mounted on the top surface of the refractory furnace material 3. The furnace wall 1 forms a lower portion of the combustion chamber.

The water cooling wall 2 is formed of a known finned water pipe, and is formed by connecting a water pipe 2a via a plate-like fin 2b. A well-known refractory brick is used for the refractory furnace material 3 covering the inner surface of the water-cooled wall 2. In the present embodiment, the refractory brick having a thickness of about 80 to 300 mm has a height of about 3000 to 7000 mm from the furnace bottom. The inner surface of the water cooling wall 2 in the range is covered. In addition, water cooling wall 2
As the refractory furnace material 3 covering the inner surface of the above, wear-resistant castables or wear-resistant blocks can be used in addition to the refractory bricks.

The block body 4 is made of wear-resistant cast iron, and has an upper half on the front side of a quadrangular prism formed in a half-conical column shape as shown in FIGS. That is, the back side of the block body 4 which is in close contact with the water cooling wall 2 is shown in FIG.
As shown in FIG. 2, the cross-sectional shape is a substantially semicircular concave curved surface 4a, which forms a semi-cylindrical fitting concave portion 4b into which the water pipe 2a of the water cooling wall 2 is fitted. Further, both end portions 4c on the back surface of the block body 4 are formed in a narrow plane, and the narrow plane portion 4c comes into close contact with the inner surface of the fin 2b of the water cooling wall 2.

As shown in FIGS. 5 and 6, the front side of the block body 4 has an upper part 4 corresponding to about ／ of its height.
d is formed in the shape of the surface of a substantially half-conical cone,
The downflow of the fluidized bed medium B flowing down from above is
It flows down along the front surface. Further, both side surfaces 4e and the bottom surface 4f of the block body 4 are formed in a rectangular plane, and the upper end surface 4g of the block body 4 is a narrow plane of about 10 mm or less along the concave curved surface 4a of the inner surface. .
That is, the front side of the block body is formed in a skirt-like curved surface from the upper end to the lower part.

On both side surfaces 4e, 4e of the block body 4, engagement recesses 6a are formed facing each other near the inner surface at the lower part thereof. That is, as shown by a dotted line in FIG. 4, the engaging concave portion 6a has a cross-sectional shape formed by halving the bolt, and the concave portion 6a is formed on the lower surface of the block body 4 as shown in FIG. It is provided over a height of about 1/3 from the side. Therefore, two blocks 4
When the blocks are closely contacted in parallel, the engaging recesses 6a, 6a of the two block bodies 4 form a fitting recess 6 having an outer shape of a bolt in cross section. By fitting an engagement projection 5 described below into the interior, the block body 4 is detachably fixed in a state where the block body 4 is prevented from falling off to the water cooling wall 2 side.

In the present embodiment, the refractory furnace material 3 is a refractory brick, a wear-resistant castable or a wear-resistant block, but any material may be used.
Further, in the present embodiment, the block body 4 is a block body in which the front side shown in FIGS. 4 to 6 has a skirt-shaped curved surface, but the boundary between the refractory furnace material 3 and the water-cooling wall 2 is formed. Of course, any form may be used as long as it can smoothly flow downward without disturbing the downflow of the fluid medium B without steps. Further, in the present embodiment, the block body 4 is made of cast iron, but the material may be other wear-resistant steel or wear-resistant ceramic. In addition, in the present embodiment, the engaging recess 6a is formed as a so-called bolt-shaped recess, but the shape of the engaging recess 6a can be appropriately selected according to the shape of the engaging projection 5 described later. it can.

A well-known steel bolt is used for the engaging projection 5, and its tip is fixed to the water cooling wall fin 2b at a predetermined height by welding or screwing. In this embodiment, a so-called stud bolt is used as the engaging projection 5 and is protruded from the water cooling wall fin 2b directly above the refractory furnace material 3 toward the inside of the combustion chamber. It goes without saying that the shape of the projection 5 may be any shape as long as it can be locked to the engagement recess 6 of the block 4.

In forming the furnace wall 1 according to the present invention, first, a circulating fluidized bed furnace main body is constructed by the water cooling wall 2, and then,
The lower part of the water cooling wall 2 forming the combustion chamber in the furnace main body, that is, a range of a predetermined height from the furnace bottom is covered with the refractory furnace material 3 and a predetermined position above the top surface of the refractory furnace material 3 is provided. The engaging projections 5 are implanted and fixed at a pitch. Thereafter, with the block body 4 slightly lifted upward, the heads of the engagement protrusions 5 on both sides are inserted into the fitting recesses 6a on both sides, and the block body 4 is continuously lowered to remove the refractory furnace material 3. The block body 4 is placed on the top surface. Thereby, the block body 4 is attached and fixed to the water cooling wall 2 in a state of being in close contact therewith. In this way, by repeatedly performing the mounting work of the block body, a protective wall of a wear-resistant block body having a predetermined height is formed above the refractory furnace material 3 as shown in FIG.

When it is necessary to replace the blocks 4, each block 4 is slightly lifted in order and then pulled forward. By repeating such operations, each block body 4 can be easily removed from the water cooling wall 2. In the present embodiment, the block body 4 is detachably fixed to the water cooling wall 2 by locking the engagement projection 5 to the engagement recess 6, but the block body 4 may be fixed in any manner. It may be a method.

By disposing and fixing the block body 4 having the predetermined height on the top surface of the refractory furnace material 3, the step at the boundary between the water cooling wall 2 and the refractory furnace material 3 is eliminated. . As a result, the flowing medium B flowing down along the inner surface of the water cooling wall 2
In the downflow, the water flows smoothly to the bottom without disturbing and scattering on the way, and the water cooling wall just above the refractory furnace material, as in the case of the conventional circulating fluidized bed combustion furnace, There is almost no damage to the wear.

As shown in FIG. 3, a protective coating 7 may be formed on the water cooling wall 2 by metal spraying over a height range of 300 to 500 mm above the block body 4. By forming the protective coating 7 by the metal spraying, the wear of the water cooling wall 2 can be more completely prevented in combination with the use of the block body 4, and the life of the furnace wall is greatly extended.

[0026]

According to the present invention, a wear-resistant block body is provided on the top surface of a refractory furnace material, and the block body is detachably fixed to a water-cooling wall. The block body eliminates a step due to the thickness of the refractory furnace material. Configuration. As a result, the down flow of the fluid medium B descending along the inner surface of the water cooling wall smoothly flows down to the bottom of the furnace without being disturbed and scattered on the way, as in the conventional furnace wall structure. In addition, the wear of the water cooling wall near the top surface of the refractory furnace material is greatly reduced, and the service life of the furnace wall can be extended.

According to the second aspect of the present invention, the mounting and dismounting of the block body can be performed very easily, and the fluid medium B
The downflow of the furnace also flows down smoothly to the furnace bottom, so that the cost of forming and repairing the furnace wall can be significantly reduced. The present invention has excellent practical utility as described above.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a part of a furnace wall according to the present invention.

FIG. 2 is a front view showing a part of a furnace wall according to the present invention.

FIG. 3 is a cross-sectional view taken along the line E in FIG. 2;

FIG. 4 is a plan view of a block body.

FIG. 5 is a front view of a block body.

FIG. 6 is a side view of the block body.

FIG. 7 is an explanatory diagram of a conventional circulating fluidized bed combustion device.

FIG. 8 is a longitudinal sectional view showing a part of a furnace wall structure of a conventional circulating fluidized bed combustion furnace.

FIG. 9 is a cross-sectional view taken along a roll in FIG. 8;

[Brief description of reference numerals]

1 is a furnace wall, 2 is a water-cooled wall, 2a is a water pipe, 2b is a fin, 3 is a refractory furnace material, 4 is a block body, 4a is a concave curved surface on the back, 4b
Is a semi-cylindrical fitting recess, 4c is a rear end portion, 4d is a front upper portion, 4e is a side surface, 4f is a bottom surface, 4g is an upper end surface,
5 is an engaging projection (bolt), 6a is an engaging concave portion, 6 is an engaging concave portion, and 7 is a protective coating formed by metal spraying.

Claims (3)

[Claims] A furnace wall forming a combustion chamber of the circulating fluidized bed combustion furnace; a water cooling wall; a refractory furnace material covering a lower portion of the water cooling wall; and an inner surface of the water cooling wall located above the refractory furnace material. A furnace wall structure for a circulating fluidized bed combustion furnace, comprising a wear-resistant block body which is detachably disposed and eliminates a step between a water cooling wall and a refractory furnace material. 2. The block body is a cast iron block body having a semi-cylindrical fitting concave portion on the back surface into which a water pipe of a water cooling wall is fitted, and having engaging concave portions of engaging projections on both side surfaces, and The circulating fluidized bed combustion according to claim 1, wherein a block body is detachably fixed to an inner surface of the water cooling wall by engaging an engaging protrusion protruding from a fin of a water pipe wall with the engaging recess. Furnace wall structure of the furnace. 3. A skirt-shaped curved surface, wherein the block body has a rectangular flat surface on both sides and a bottom surface, a semicircular flat surface on an upper end surface, and a front side facing downward from an upper end portion. The furnace wall structure of a circulating fluidized bed combustion furnace according to claim 1 or 2, wherein the block body is formed as described above.