JP2010089980A - Exhaust heat recovery power generation plant in lime firing plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To contrive a mechanism structure of an exhaust heat recovery boiler reducing its installation cost as much as possible and stably maintaining a high exhaust heat recovery rate by efficiently removing dust adhering to heat transfer pipes so as to install an exhaust heat recovery power generation plant for a lime firing plant at a low cost and in a small space. <P>SOLUTION: As to a grate preheater exhaust heat recovery power generation plant of a lime firing plant, vertical type exhaust heat boilers by respective coiled-tube type heat transfer pipes are installed at the right and left lower parts of a grate preheater, exhaust gas collecting chambers of the grate preheater are connected to the upper ends of the vertical type exhaust heat boilers and collecting ducts are connected to the lower parts, superheaters are arranged at the upper parts of the vertical type exhaust heat boilers, evaporators and fuel economizers are arranged under the superheaters, and a steam turbine is connected to the superheaters. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a waste heat recovery power plant that recovers waste heat of a lime firing plant, and is capable of stably generating power with high efficiency using waste heat of a great preheater of the lime firing plant. .

  A lime baking plant equipped with a great preheater is conventionally known (Japanese Patent Laid-Open No. 2001-342044), and its gas flow is as shown in FIG. The exhaust gas from the rotary kiln 1 for firing lime is introduced into a great preheater 2 for preheating limestone w. Then, the exhaust gas flows into the left and right stabilizers (those that reduce the exhaust gas temperature to a predetermined temperature) 4, 4 through the exhaust gas collecting chamber 3 of the great preheater 2, and the collecting duct 5, gas cooler 7, bag filter 8, It is discharged from the chimney 100 through the blower 9. The outlet temperature of the great preheater 2 is 300 to 500 ° C., and is lowered to a predetermined temperature by water spraying with a stabilizer. Further, after passing through a gas cooler 7, dust is removed by a bag filter and blown to a chimney 100 through a blower 9. . The exhaust gas temperature when discharged from the chimney 100 is about 200 ° C.

Conventionally, the waste heat from the great pre-heater 2 is discarded without being recovered, or only a part of the boiler is used to generate saturated steam. This is because the temperature of the exhaust gas from the great preheater of the lime burning plant is not so high, and the amount of exhaust gas is not large (in the usual case, 50,000 to 100,000 Nm ³ / H), and the exhaust gas is also finely divided. A large amount of dust is contained (approximately 30 gr / Nm ³ ), which adheres to the heat transfer tube and significantly reduces the heat transfer rate (heat transfer efficiency). For this reason, the waste heat of the above great preheater is used. This is because it is not easy to generate power stably with high efficiency.
However, in recent years, since the need to reduce energy costs has become stronger, it has been demanded that waste heat from the above-mentioned great preheater can be used to efficiently generate power.

  On the other hand, in order to construct a waste heat recovery power generation system by installing a waste heat boiler in a great preheater, the installation cost can be reduced as much as possible, and the waste heat recovery efficiency can be increased to stably generate power. Must do so. In addition, it is most preferable to install a waste heat boiler in the installation space of the stabilizers on both sides of the great preheater, but for that purpose, there is nothing but to use a vertical waste heat boiler. However, for that purpose, it is necessary to make it easy to install the waste heat boiler in the above space, and to efficiently remove the fine dust adhering to the heat transfer tube, thereby improving the heat transfer efficiency of the heat transfer tube. In order to achieve this, specially devised a fine dust removal device suitable for vertical waste heat boilers with a vertical gas flow (hereinafter simply referred to as “vertical waste heat boilers”) There is a need to.

By the way, although it is technically quite different from the lime burning plant, there is a cement plant as a plant that discharges a large amount of high-temperature exhaust gas containing a large amount of fine dust, and the waste heat of the suspension preheater of this cement plant is discarded. It is well known to generate electricity by collecting with a thermal boiler. Since the amount of exhaust gas from the cement plant is large and the amount of waste heat is large, the waste heat recovery power plant is extremely large, and the waste heat boiler is a horizontal waste heat boiler. Incidentally, this horizontal waste heat boiler is a type of waste heat boiler having a serpentine heat transfer tube meandering vertically in a vertical plane and in which exhaust gas flows in a horizontal direction (lateral direction).
The amount of exhaust gas from the suspension preheater of a cement plant is large (generally 200,000 to 500,000 Nm ³ / H). This exhaust gas contains a large amount of finer fine dust (usually about 100 gr / Nm ³ ), which adheres to the serpentine heat transfer tube of the waste heat boiler and has a high heat transmissivity ( Heat transfer efficiency). For this reason, a dust removing device is provided in the horizontal waste heat boiler in order to remove fine dust and prevent a decrease in heat transfer efficiency. This dust removal device is equipped with a hammering device, which applies a strong blow to the individual straight pipe sections of the suspended serpentine type heat transfer tubes to vibrate them vigorously, thereby removing the adhering dust. Shake off.
Since the waste heat boiler of the cement plant is a horizontal boiler, fine dust can be efficiently removed using the hammering device (see Japanese Patent Laid-Open No. 5-106408).

  The hammering device includes a hammering connecting shaft that is hit by the hammering hammer at the outer end, and the hammering connecting shaft (hereinafter simply referred to as “connecting shaft”) is connected to the straight pipe portion of the heat transfer tube meandering in the vertical direction. Is fixed, and a large number of connecting shafts are sequentially hit with a hammer to sequentially apply a strong impact to the straight pipe portion. This sufficiently prevents the heat transfer rate of the heat transfer tube from being reduced due to adhesion of fine dust (Japanese Patent Publication No. 59-28813).

A vertical waste heat boiler is advantageous as a waste heat recovery power generation boiler for a great preheater of a lime firing plant because of the installation space and layout. However, in the case of a vertical boiler, the straight tube portion is arranged in a vertical plane with the horizontal tube portion arranged in a vertical plane, and the straight tube portion of the heat transfer tube is located on the upper side. The structure of the heat transfer tube and the support structure are completely different from the horizontal boiler, such as being supported by a hanging rod extending from the bottom to the bottom. It cannot be applied to.
In addition, in order to make it possible to efficiently remove fine dust from a vertical waste heat boiler, there is no other way than using the basic technology of the hammering device described above. The structure related to the hammering device must be specially devised.
JP 2001-342044 A JP-A-5-106408 Japanese Patent Publication No.59-28813

  The invention of the present application aims to enable a waste heat recovery power plant for a lime firing plant to be installed at a low cost and in a small space, and can suppress the installation cost as much as possible and adhere to a heat transfer tube. The problem is to devise the mechanism structure of the waste heat recovery boiler so that dust is efficiently removed and a high waste heat recovery rate is stably maintained.

[Means 1]
Means 1 for solving the above-mentioned problems are the following (a) to (c) for the great preheater waste heat recovery power plant of the lime firing plant.
(A) Vertical waste heat boilers are installed on the left and right of the great preheater,
(B) The exhaust gas collecting chamber of the great preheater is connected to the upper end of the vertical waste heat boiler, and the collecting duct is connected to the lower part,
(C) A superheater is disposed above the vertical waste heat boiler, an evaporator and a economizer are disposed below the superheater, and a steam turbine is connected to the superheater.

[Means 2]
Means 2 for solving the above-mentioned problem is based on the following (d) to (h) in addition to the means 1 described above.
(D) The vertical pipe heat transfer tube of the vertical waste heat boiler is in a vertical plane and the straight pipe portion is horizontal and perpendicular to the gas flow;
(E) a large number of straight pipe portions of the serpentine type heat transfer tube are lowered at both ends by the first suspension means and the second suspension means;
(F) the first suspension means includes a bent portion in which the link member is connected by a hinge pin;
(G) the connecting shaft of the hammering device is connected to the link member of the bent portion via a hinge pin;
(H) The bent portion can be bent in the impact direction of the connecting shaft.

[Action]
According to the above means 1, the vertical waste heat boiler in which the serpentine type heat transfer tube having the straight pipe portion in the horizontal direction is arranged in the vertical plane is a type in which exhaust gas flows downward from above, and is vertically long. Therefore, it has the same external shape as the left and right stabilizers in the prior art, so it can be replaced without any problem, and the upper gas inlet is connected to the exhaust gas collecting pipe of the great preheater, and the lower gas exhaust is connected. Since the outlet can be connected to the collecting duct, a vertical waste heat boiler can be easily installed in place of the stabilizer, and there is almost no structural change required for that purpose.

  And about a vertical waste heat boiler, it is possible to arrange | position the superheater and evaporator by a serpentine type heat exchanger tube up and down, and to comprise by the magnitude | size about the stabilizer of the conventional great preheater. Therefore, the vertical waste heat boiler according to the present invention can be easily and easily installed using the installation space of the existing lime firing plant by removing the stabilizer.

According to the above means 2, one end of the left and right ends of a large number of straight pipe portions of the serpentine type heat transfer tube arranged in the vertical plane is suspended by the first suspension means, and the bent portion formed by the link member and the hinge pin is The connecting shaft of the hammering device (the impact shaft that receives the impact of the air knocker or hammer and transmits the impact to the heat transfer tube and vibrates it) is connected by hinge pins, so many connecting shafts are vertically spaced at predetermined intervals. It is supported, and each straight pipe part is connected to this.
A large number of connecting shafts arranged at predetermined intervals above and below can freely vibrate (or move) with respect to each other in the direction of impact, and these are sequentially hit by an air knocker or the like, so that they do not interfere with each other. Vibrates freely.

Therefore, when the connecting shaft is hit with an air knocker, only the straight pipe part connected to it is subjected to a strong impact, and the impact force by the air knocker is intensively transmitted to the individual straight pipe parts, making these powerful. Since it vibrates, the adhering fine dust is efficiently removed.
Then, by hitting a large number of connecting shafts in sequence, all the straight pipe portions are vibrated strongly, so that the fine dust adhering thereto is sequentially removed. Therefore, the heat transfer efficiency of the serpentine heat transfer tube does not decrease. Therefore, it is possible to prevent the waste heat recovery performance of the waste heat boiler from being deteriorated.
As described above, the impact of each connecting shaft is transmitted only to the straight pipe portion connected thereto, and is not transmitted to the other straight pipe portions, so that the impact force by the plurality of connecting shafts is a serpentine type heat transfer tube or its supporting mechanism. Do not interfere with each other. Therefore, an excessive load is not applied to the heat transfer tube and its support mechanism due to this powerful impact, and the heat transfer tube and its support mechanism are not damaged by the excessive load.

  As described above, the present invention devised the structure of the vertical boiler for installing the waste heat boiler for power generation in the lime firing plant, and the support mechanism for the serpentine heat transfer tube of the vertical boiler, and the support mechanism By devising the structure related to the hammering device, the waste heat recovery power plant of the lime firing plant can be easily and easily installed at low cost, and it prevents the power generation capacity from being reduced due to the attachment of fine dust from the exhaust gas. However, it is possible to stably generate power with high efficiency.

  The vertical waste heat boiler can be made the same size as the left and right stabilizers of the great preheater, and a hammering device can be provided on this, so the performance of the stabilizers of the existing lime firing plant is good. It can be easily and easily replaced with a stable and stable waste heat boiler. In this case, since there is almost no need to change the structure of the great preheater, the waste heat recovery power plant can be easily and easily installed at low cost.

Next, embodiments of the present invention will be described with reference to the drawings.
The overall system of this embodiment (FIG. 2) is not different from the conventional example of FIG. 1, and vertical waste heat boilers 10 are respectively provided below the left and right exhaust gas collecting chambers 3 of the great preheater 2 of the conventional lime burning plant. It is an arranged configuration. The upper exhaust gas inlet 11 a is connected to the exhaust gas collecting chamber 3, and the lower exhaust gas outlet 11 b is connected to the collecting duct 5.

  The vertical waste heat boiler 10 includes a vertically long boiler body 10A having the same size as that of the stabilizer 4 (FIG. 1), and heat exchangers using a serpentine heat transfer tube arranged in three stages. The exchanger is the superheater 51, and the middle heat exchanger and the lower heat exchanger are the evaporator 52 and the economizer 53.

The evaporator 52 and the economizer 53 are connected to a brackish water drum 55, and the superheater 51 is connected to a steam turbine 57. Other than that, there is no difference from a normal power generation system.
The condensate from the condenser 59 downstream of the steam turbine 57 flows into the economizer 53 through the condenser pump 60 and the deaerator 61 through the boiler feed pump 62, and is heated by the economizer 53 before the steam cylinder. Then, it returns to the brackish water drum 55 again through the second evaporator 52, then flows into the superheater 51, and is heated by the superheater 51 before being supplied to the turbine 57. The steam turbine 57 is driven by the superheated steam from the superheater 51 and the generator G is driven.

[Structure of vertical waste heat boiler]
The boiler body 10A is a vertically long casing having a quadrangular cross section, and has an inlet 11a at the upper end and an outlet 11b at the lower end. The superheater 51, the evaporator 52, and the economizer 53 arranged in the boiler body 10A are formed by the heat transfer tube 14 meandering in the horizontal direction (left and right direction in FIG. 3) in the vertical plane, and this heat transfer tube ( (Also referred to as a serpentine heat transfer tube) 14 are arranged at a predetermined interval.
The boiler body 10A has an opening on the side wall, and both left and right ends 14e1 and 14e2 of the heat transfer tube 14 project outside the side wall through the opening (FIG. 3), and the protruding portion is an outer wall on the outside of the boiler body 10A. 10B.
The opening is large enough to allow the left and right ends of the heat transfer tube 14 to pass through with a margin.

The left end 14e1 and the right end 14e2 of the heat transfer tube 14 protrude outside the boiler body 10A, and on the other hand, the first suspension means H1 and the second suspension means H2 are provided outside the boiler body 10A. The left and right ends 14e1 and 14e2 are suspended by the first suspending means H1 and the second suspending means H2, whereby the heat transfer tubes of all the heat exchangers are suspended.
Both suspension means H1 and H2 are supported by a support structure F, and an outer wall 10B is provided outside the boiler body 10A.
Since the first suspending means H1 and the second suspending means H2 are outside the boiler body 10A, they are not exposed to high-temperature exhaust gas, and fine dust contained in the exhaust gas is not attached. Therefore, these suspension means H1 and H2 are protected from high-temperature exhaust gas and fine dust.

The main items of this example are 410 Kw (power generation end) for power generation, 0.7 MPa × 290 ° C. × 1.5 T / H for utility steam, and about 4,000 t-CO ₂ / year for CO ₂ reduction. The exhaust gas supplied to this embodiment contains about ³⁰ gr / Nm ³ of fine dust (60% is a particle size of 150 μm or less).

[Support structure and hammering device for heat transfer tube]
First, the second suspension means H2 at the right end will be described, and then the first suspension means H1 will be described.
The second suspending means H2 at the right end is made of a simple bar material, and is arranged every two of the closely arranged heat transfer tubes 14, and the long second suspending bar (steel having a diameter of 16 mm) 31 is used. The front and rear heat transfer tubes 14 and 14 are supported. A support plate 32 protrudes from the second suspension rod 31 in the front-rear direction (front-rear direction in FIG. 3, left-right direction in FIG. 5) (FIG. 5), and the straight plate portion 14 a of the heat transfer tube 14 is supported by the support plate 32. The other end 14e2 is slidably supported. In this embodiment, since the heat exchangers are provided in three stages, the second suspension rod 31 supports the heat transfer tubes of these heat exchangers.
The second suspension rod 31 is suspended from the frame of a vertical waste heat boiler.

The first suspending means H1 on the left side (left side in FIG. 3) has upper and lower suspenders (on a steel pipe member having a square cross section) 25 and upper and lower suspension bars (made of steel having a diameter of 21 mm) 21 and upper ends. 26, which is welded to the connecting shaft 25), and a hinge member 27 are sequentially connected by a hinge pin 28 (FIGS. 3 and 4).
The connecting shaft 25 is disposed between each tube group with four of the straight tube portions 14a of the heat transfer tubes 14 as one tube group (FIG. 4).
An air knocker 42 is fixed to the support structure of the vertical waste heat boiler. The air knocker 42 is a pneumatic hammer having a striking force of about 4 kg, and is repeatedly hit at appropriate intervals, for example, hitting is performed 2.5 times / minute. The operation control of the air knocker 42 is various, and may be empirically controlled while observing changes in the boiler output. For example, the air knocker 42 may be automatically controlled by a predetermined program based on the temperature distribution in the boiler. is there.

The air knocker 42 is a conventionally well-known and commonly used device for removing fine dust from a horizontal boiler. The air knocker 42 strikes the tip of the connecting shaft 25 and transmits the impact to the straight tube portion 14a of the heat transfer tube 14, Is vibrated shockingly.
A large number of arms 29 are welded to the connecting shaft 25 in addition to the above-described suspension metal 26 at predetermined intervals, and a straight pipe portion 14 a of a heat transfer tube is welded to each arm 29.

  A plurality (two in this example) of connecting shafts 25 are suspended vertically at a certain interval in the middle of the first suspension means H1, and the first suspension means H1 includes a hinge member 27 and a hinge pin 28. Can be freely bent in the axial direction of the connecting shaft 25 (the left-right direction in FIG. 4) at the bent portion, the plurality of connecting shafts 25 are relatively movable in the axial direction. A group of straight pipes fixed to the connecting shaft 25 (in this embodiment, two straight pipe portions in total, two on the upper and lower sides of the connecting shaft 25) move together. In this way, since the vertical pipe groups adjacent in the vertical direction can freely vibrate (or move) relative to each other in the same direction, when the adjacent connecting shafts 25, 25 are hit with a time difference, Due to the striking force, no excessive force is applied to the first suspension means H1. Therefore, an excessive load is not locally applied to the heat transfer tube 14 and its support mechanism.

  Further, when a strong impact is applied from the connecting shaft 25 to the one end portion 14e1 of the straight tube portion 14a, the impact is transmitted to the other end portion 14e2, and the entire straight tube portion 14a vibrates. When one connecting shaft 25 is hit, the hit is transmitted intensively only to a part of the straight pipe portion 14a fixed to the connecting shaft 25, and only this part of the straight pipe portion 14a is vibrated intensively. Therefore, the fine dust adhering to this is efficiently shaken off and removed. The other end portion 14e2 of the straight pipe portion 14a is slidably supported on the support plate 32 of the second suspension rod 31 (FIG. 5). An excessive load is not applied to the suspending means H2.

Fig. 1 is an overall view showing the gas flow of a conventional lime baking plant equipped with a great preheater. These are the whole figures which show the gas flow of the lime baking plant provided with the waste-heat recovery power plant of the Example of this invention. FIG. 2 is a partial sectional view of a vertical waste heat boiler according to the present invention. Is a left side view of FIG. Is a right side view of FIG. Is a top view of FIG.

Explanation of symbols

1: Rotary kiln 2: Great preheater 3: Exhaust gas collecting chamber 4: Stabilizer 5: Collecting duct 7: Gas cooler 8: Bag filter 10: Vertical waste heat boiler 10A: Boiler body 10B: Outer wall 11a: Exhaust gas inlet 11b: Exhaust gas Outlet 14: Heat transfer tube (conduit type heat transfer tube)
14a: Straight pipe portion 14e: Left and right end portions 21 of the heat transfer tube: First hanging rod 25: Connection shaft (connection shaft of hammering device)
26: Suspension lever 27: Hinge member 28: Hinge pin 29: Arm 31: Second suspension rod 32: Support plate 42: Air knocker 51: Superheater 52: Evaporator 53: Economy unit 55: Steam drum 57: Steam turbine 59 : Condenser 60: Condensate pump 61: Deaerator 62: Boiler feed pump 100: Chimney H1: First suspension means H2: Second suspension means F: Support structure for waste heat boiler

Claims (2)

A waste heat recovery power plant for a great preheater for a lime firing plant,
Vertical waste heat boilers are provided at the left and right lower parts of the Great Preheater,
An exhaust gas collecting chamber of a great preheater is connected to the upper end of the vertical waste heat boiler, and a collecting duct is connected to the lower part,
Waste heat recovery of a lime firing plant in which a superheater is arranged at the upper end of the vertical waste heat boiler, an evaporator and a economizer are arranged below the superheater, and a steam turbine is connected to the superheater Power plant. A waste heat recovery power plant of the lime firing plant according to claim 1,
The vertical pipe heat transfer tube of the vertical waste heat boiler is in a vertical plane, the straight pipe portion is horizontal and perpendicular to the gas flow,
A large number of straight pipe portions of the serpentine type heat transfer tube are suspended at both ends by the first hanging means and the second hanging means,
The first hanging means includes a bent portion by a link member and a hinge pin,
The connecting shaft of the hammering device is connected to the link member of the bent portion via a hinge pin,
A waste heat recovery power plant for a lime firing plant, wherein the bent portion can be bent in an impact direction of the connecting shaft.

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