JPS63315801A - Heat exchanger - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a heat exchanger that utilizes the heat possessed by fluidized and heated particles.

A more preferred application example is to supply coal as a solid fuel onto a fluidized bed (dense head) formed of relatively large particles such as gravel, and further supply coal as a heat transfer object with particles smaller than the particles such as sand. Regarding a heat exchanger that is mainly applied to a circulating fluidized bed boiler that improves thermal efficiency by circulating particles (fine particles) and recovering heat using the heat possessed by the circulating particles, the peripheral wall of this heat exchanger is This proposes a lightweight structure.

[Prior art]

As a boiler that can burn solid fuel efficiently while meeting exhaust gas emission standards, it uses fine particles such as ash and limestone on a fluidized bed, or dense bed, made of relatively large particles such as gravel. A circulating fluidized bed boiler with a recirculating bed has been proposed.

An overview of this circulating fluidized bed boiler will be explained with reference to FIG. 2. This boiler consists of a comparator 1 which is a combustor, an external heat exchanger 2 installed adjacent to this comparator 1, and an external heat exchanger 2 provided adjacent to this comparator 1. The heat exchanger 2E has a fluid supply port connected to the top of the comparator 1 via a connecting duct 3, and is composed of a cyclone 4 and the like. The inside of the external heat exchanger 2 is divided into two parts by a partition wall 5, and a hot well 6 is formed on one side and a heat exchange section 7 is formed on the other side. A flowing air supply pipe 12 is provided. Further, a heat transfer section 22 is provided within the heat exchange section 7, and the water supplied thereto is heated to generate water vapor.

Further, the comparator 1 is composed of a rewiring region B of a large diameter portion of the upper part of the comparator 1, which connects to the fluidized bed region of the lower part.

In the fluidized bed region A, a dense bed 9 is formed in which a dense head material 8 made of gravel or the like is accommodated. Further, coal 10 and limestone as solid fuel are supplied to this dense head 9 through a supply pipe 11. Further, at the lowest part of the fluidized bed region A, a fluidizing air system constituted by a supply pipe 13 and the like is provided, and fluidizing air a for fluidizing the dense bed 9 is supplied into the comparator l.

This fluidized air a is transferred to the dense bed 9 by a dispersion plate or the like.
It plays the role of fluidizing the dense bed material 8 as a whole.

A combustion air system consisting of a supply pipe 14 and the like is provided at a location corresponding to the upper edge of the fluidized bed region A, and the supply amount of the combustion air system is automatically adjusted by a flow rate adjustment section 15. It is fed into the comparator l.

On the other hand, the circulation area B formed in the enlarged upper part of the comparator l has a circulation layer 16 in which carbon, ash, or finely divided limestone generated by combustion floats and circulates in the fluidized bed area and in the lower part of this circulation area B. is forming. Secondary air C is supplied to this circulation layer 16 from a secondary air system 17, and final combustion takes place.

As mentioned above, solid fuel such as coal 10 is burned in the comparator 1, but the circulating bed material made of carbon and ash generated in the fluidized bed region A and the circulation region B, or finely divided limestone, etc. Gas g containing r is supplied into the cyclone 4 via the connecting duct 3, where the gas is separated into circulating bed materials r, and the gas g is supplied to a convection boiler (not shown) and used as an energy source for steam generation. be done.

and circulating head material made of limestone, ash, carbon, etc.
falls into the real well 6 of the external heat exchanger 2 from the extraction pipe 20 extending to the lower part of the cyclone 4,
Supplied. Air is supplied into this external heat exchanger 2 from the fluidizing air supply pipe 21, so the circulating bed material r
is liquidized.

The circulation bed material supplied into the hot well 6 is
It overflows from the upper end of the partition wall 5 and flows into the heat exchange section 7 containing the heat exchanger tubes 22, where the heat is recovered and steam S is generated.

The lower part of the hot well 6 and the lower part of the comparator 1 are connected by a hot recycle pipe 24, and the lower part of the heat exchange section 7 and the lower part of the comparator 1 are connected by a cold recycle pipe 25.

The circulating bed material r, which has a higher temperature than the hot recycling 6, is returned to the fluidized bed area A via the hot recycling pipe 24, and is heat exchanged in the heat exchange section 7, and the circulating head material r whose temperature has decreased is transferred to the cold recycling pipe. 25 into the fluidized bed jlA. The high temperature circulating bed material r flowing back through the hot recycle pipe 24 is used to maintain the fluidized bed regions A and B at a predetermined concentration. The low-temperature circulation bed material r that is recirculated in the cold recycle pipe 25 controls the combustion temperature.

Note that one end of the gas vent pipe 27 is connected to the top of the external heat exchanger 2, and the other end is connected to the large diameter part forming the recirculation area B of the comparator 1, so that the gas in the external heat exchanger 2 is configured to return into the circulation area B of the comparator 1.

As mentioned above, the circulating fluidized bed boiler is configured as follows:
It has the following ground-breaking effects.

(1) Since solid fuel is supplied into the fluidized dense bed material 8, the lump coal that has been brought in can be burned.

Therefore, it is capable of burning not only coal but also low-quality, incombustible fuels such as fluid coke. Furthermore, since the combustion efficiency is good, the cross-sectional area of the comparator is small, and the construction cost of the device is reduced.

(2) In the external heat exchanger 2, the heat exchanger tubes 19 (boiler tubes) have little wear because they are operated at a low flow rate.

(3) Since the comparator and the external heat exchanger have a separate structure, it is adaptable to various operating conditions.

[Problems to be solved by the present invention]

Although the circulating fluidized bed boiler constructed as described above has various effects, the external heat exchanger constituting this boiler has the following problems.

That is, the circulation bed material r captured by the cyclone 4 is at a high temperature, and the walls of the heat exchange section 7 and the real well 6 that receive the heat of q are naturally heated to a high temperature, for example, 500 to 900°C. Become.

Therefore, in order to protect the structure of the above-mentioned portion, it is necessary to cover the peripheral wall surface with a heat-resistant heat insulating material.

For example, the dimensions of the heat exchange section 7 of the external heat exchanger attached to a circulating fluidized bed boiler with an output of 100T/11 are rectangular in cross section, length 4 m, width 3 m, and height 3 m. As the heat insulating material forming the peripheral wall surface of the heat exchange section 7, firebrick or castable is used, and the surface of the structure is coated with a thickness of 30 cm or more.

Therefore, the volume of the firebrick or castable is
It is a heavy object of 10 tons or more, requires a strong structure, increases cost, and has maintenance problems.

[Object of the present invention]

In the heat exchanger using W4 ring particles as a heat medium as described above, the present invention uses no insulation material at all, or even if it is used, uses a thin insulation material to reduce weight and efficiently heat the heat exchanger. To provide a heat exchanger that can be replaced and is easy to maintain.

[Summary of the invention]

To achieve the above object, the present invention is a heat exchanger that uses heated particles as a heat medium and circulates the particles, comprising:
Part or all of the peripheral wall of the main body is formed by a water-cooled wall, and a fluidizing air supply section formed at the lower part of the main body is formed with a part that does not supply air near the peripheral wall, thereby preventing the non-flowing of the particles. It is characterized by forming a curved part.

That is, the present invention forms a heat insulating layer by using the particles themselves, which are heat carriers, and the particles in the center of the heat exchanger are sufficiently fluidized to the extent necessary for heat exchange. In particular, a non-fluidized state or a state close to non-fluidized state is actively created in the vicinity of the peripheral wall.

Inside the heat exchanger, particles move to become fluidized, but near the peripheral wall, there is no air flow to float the particles, so there is a gentle downward flow of particles due to the thickness. This downward flow acts as a heat insulating layer.

The length of the fluidized part and non-fluidized part of the particles that are the heat medium is 4.
In the case of a rectangular heat exchanger with a width of 3 m, a width of 3 m, and a height of 3 m, the fluidizing air should not be ejected within a range of 5 to 10 cm from the peripheral wall surface, and should be ejected only from the center.

〔Example〕

Next, the present invention will be explained in detail with reference to FIG.

FIG. 1 shows an external heat exchanger 2 applied to the circulating fluidized bed boiler shown in FIG.
A heat transfer section 22 is provided within the heat exchange section 7.

The peripheral wall of the heat exchange section 7 is constituted by a water-cooled wall 2a.

Therefore, the peripheral wall of the heat exchange section 7 is formed by a water-cooled wall.

A fluid ejection bed 30 is formed in the lower part of the heat exchange section 7, a fluidization region M is provided with a fluid ejection port 31 in the central portion, and a fluidization region M is provided with a fluid ejection port 31 in the peripheral wall portion, or Even if provided, a non-fluidized region N is formed in which a small amount of fluid is ejected.

Although the ceiling surface of the external heat exchanger 2 and the peripheral wall surface of the hot well 6 are protected by a heat insulating material 32, the water cooling partition wall 5
No heat insulating material is provided on the inner surfaces of the water cooling wall 2a and the surrounding wall.

The operation of the external heat exchanger 2 is carried out together with the operation of the boiler shown in FIG. is supplied into the heat exchange section 7 overflowing from the water cooling partition wall 5a.

In the heat exchange section 7, air, which is a fluidizing fluid, is supplied to the lower part of the fluid ejection bed 30 from the fluidized air supply pipe 21, and is ejected from the ejection port 31 to the part where the heat transfer section 22 is accommodated. The circulating bed material r is fluidized to promote heat exchange.

On the other hand, no spout 31 is provided in the peripheral wall, and the non-fluidized region N
Since the retention bed material R forms the water cooling walls 2a, 5
It covers the surface of a.

As mentioned above, by forming the retention bed material R on the surface of the water cooling wall, this will act as a heat insulating material.

〔Effect of the invention〕

The heat exchanger according to the present invention is a heat exchanger that uses heated particles as a heat medium, and is characterized in that a fluidizing fluid jet port is arranged near the peripheral wall so that the particles stagnate. The following effects can be achieved.

That is, since the circulating bed material can be used as a heat insulating layer, the peripheral wall of the heat exchanger can be constructed of a water-cooled wall.

Therefore, unlike conventional devices, there is no need to use a large amount of heat insulating material such as refractory bricks, and the main body of the heat exchanger can be formed from a steel water cooling wall, resulting in a reduction in weight.

Insulating materials such as refractory bricks and castables are extremely difficult to support within the main body, and if they fall off, the boiler must be stopped for a long time to be repaired, but such repairs are no longer necessary.

In addition, because castables require the use of anchors, they must be designed to ensure that one side does not become hot, and the structure of the heat exchanger is also subject to major constraints. However, according to the present invention, this It becomes possible to design without being constrained.

As described above, since the heat-insulating structure is simplified, the structure of the heat exchanger body is simplified, manufacturing costs are reduced, and maintenance is also facilitated.

In particular, when the heat exchanger becomes larger as the boiler becomes larger, the heat exchanger has to be heavy and large due to its insulation structure, but according to the present invention, it can be made smaller and larger. Greater freedom in design.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a heat exchanger according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of a circulating fluidized bed boiler to which the heat exchanger of the present invention can be applied. 1...Compaster, 2...External heat exchanger, 3...
Connecting duct, 4... cyclone, 5... partition wall, 6
... Hot well, 7... Heat exchange section, 8... Dense bed material, 9... Dense bed, 16... Circulation layer, 17... Secondary air, 21... Fluidized air Supply pipe, 2
2...Heat transfer part, 24...Hot recycling pipe, 25
...Cold recycling pipe, 27...Gas vent pipe, 3
0...Fluid ejection bed, 31...Ejection port, 32...Insulating material. A...Fluidized bed area, B...Circulation area, M...Fluidization area, N...Non-fluidization area, a...Air for fluidized bed formation, b...Air for combustion, C...Secondary air, d...
・Ash, g...gas.

Claims (1)

[Claims] 1. A heat exchanger using heated particles as a heat medium, characterized in that fluidizing fluid jet ports are arranged near a peripheral wall so that the particles stagnate.