JPS58221382A - Method and device for retrieving heat of exhaust gas - Google Patents

Abstract

PURPOSE:To prevent a duct from being corroded by corrosive substances, contained in the waste gas and dewing on the wall surface of the duct, by a method wherein fluid, forming a multi-layered flow by the waste gas and a multitude of fluid layers, is heated in a multitude of stages. CONSTITUTION:Bulkheads 4, 5 are provided at the front and rear parts of the axial direction of the duct 1 and the exhaust gas ducts 6 are bridged between the bulkheads 4, 5 while a space is provided at the inside of the bulkhead 4 and a partitioning plate 15 is provided to form the space S3. The duct 17 is communicated with the space S3 in such a manner that it is surrounding around the exhaust gas duct 6 while the air duct 19 is constituted by the space S1, which is the space in the duct 1 excluding the spaces of the exhaust duct 6 and the duct 17, the space S2, formed by the duct 17 and the exhaust duct 6, and the space S3. Air passes through a fluid inlet port 20, the spaces S1, S2, S3 and a fluid outlet port 21 sequentially while the heat is transmitted from the exhaust gas to the air in the spaces S2, S1 sequentially.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas heat recovery method and apparatus, in which a multilayer flow is formed by the exhaust gas and a plurality of fluid layers to be heated that communicate with each other, and the flow is heated in multiple stages. In particular, it relates to a method and apparatus for preventing corrosive substances such as sulfur oxides contained in exhaust gas from condensing on duct walls and causing equipment corrosion.

Ru. Conventionally, attempts have been made to recover some of this thermal energy and use it for other useful purposes, but generally this thermal energy is recovered by using a heat exchanger to recover a portion of this thermal energy. This was done by applying heat directly to a fluid such as water or air.

However, the exhaust gas discharged from boilers, deodorizing furnaces, incinerators, etc. contains corrosive substances such as sulfur oxides and hydrogen chloride, albeit in small amounts, and this exhaust gas is directly transferred to the heat exchanger. For example, when heat is exchanged with outside air in the winter, the outside air is at a low temperature, so the wall temperature of the exhaust gas pipe through which the exhaust male flows through the heat exchanger decreases, and the exhaust gas comes into contact with the wall and locally reaches a dew point. The sulfur oxides and the like in the exhaust gas were then supercooled and condensed on the tube wall surface, causing corrosion of the equipment.

Further, when the fluid to be heated is a liquid such as cold water, the film coefficient of the liquid is large and the wall surface of the exhaust gas pipe is cooled, and sulfur oxides and the like condense on the core portion for the same reason as described above. As a result of intensive research in view of the above-mentioned current state of heat energy recovery from exhaust gas, the inventor of the present invention has discovered that exhaust gas and multiple heated fluid layers form a multi-layer flow, and these fluid layers are communicated with exhaust gas. The present application was completed based on the knowledge that the above-mentioned drawbacks can be overcome by sequentially exchanging heat between a fluid layer that is directly exchanging heat with another fluid layer.

That is, the present application is an exhaust gas heat recovery method characterized in that the exhaust gas and at least two heated fluid layers communicating with each other form a multilayer flow to recover heat from the exhaust gas.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings, with reference to FIGS. 1 to 7, in which the fluid to be heated is gas, particularly air.

First of all, in Figures 1 to 3, / is a rectangular duct, and at the axial front (left side in Figure 1) and rear (right side in Figure 1) end of the duct / is a connecting piping lunar Francis, 3. It is provided. Also, there are rectangular partition plates at the front and rear of the duct in the axial direction! are installed perpendicular to the axis and parallel to each other, and between these partition plates ≠, there is a total of nine exhaust gas ducts in which exhaust gas flows through three stages in the vertical direction and three rows in the width direction. They are constructed at equal pitches and removable. Each duct B has a circular tube shape, and a fixed flange 7 is provided at the front end of the duct B.
On the other hand, a screw thread is engraved on the other end as shown in FIG. Thus, each exhaust gas duct) J is fixed to the partition plate as follows.

That is, the exhaust gas duct B is inserted between the oval holes 9 and 70 formed so as to face each other on the partition plate B, as shown in FIG. 1, and the movable flange/ / is screwed on as shown in Figure 2. 7.2 is a spring,
It serves to press the fixed flange 7 against the partition plate t to maintain a seal at the core. By providing a sealing material in the seal portion, more reliable airtightness can be maintained.

Next, the spring 12 is covered with a heat-resistant expansion joint /≠ which is fixed with screws /3 between the inner end face of the movable flange // and the outer end face of the partition plate j and formed into a cylindrical shape from Teflon, asbestos, etc., and the partition plate Maintain the airtightness of the contact area of exhaust gas duct) 4. This mechanism can deal with thermal expansion of the exhaust duct B.

A partition plate /j is installed inside the partition plate≠ with a predetermined distance from the partition plate≠, and a space S3 is formed between the partition plate and the partition plate. Further, in this partition plate /j, a circular hole /B is concentrically bored in correspondence with the circular hole 9, and a cylindrical duct /7 is an exhaust duct in the circular hole /B). The exhaust duct Ft communicates with the space S3 so as to surround the exhaust duct B, and the right end portion is provided with a distance S between it and the partition wall j, forming a double structure with the exhaust duct B.

/ is a flat plate-shaped lip that is fixed to either exhaust duct O or duct /7, and the other has a sliding structure.

In particular, the rectangular duct/inside the exhaust duct) J
and the space S excluded by the duct /7, the space SX formed by the duct /7 and the exhaust duct J, and the space S3 constitute an air duct) /9.

A fluid population λθ is installed in communication with the space S/ of the fluid duct /9, and a fluid outlet 21 is installed in communication with the space S3.

Thus, air has fluid population θ, space S/, Sλ.

S3, the fluid exit λ/ flows in this order, and from the exhaust gas to the space S
Since heat is transferred in two stages to the air in space a and from this air to the air in space S/, the exhaust gas does not directly exchange heat with the low-temperature air.

Next, the operation of the present invention will be explained based on FIGS. 1, 3, and 7.

FIG. 7 is a block diagram showing an example of application of this device, and the device shown in FIG. Vessel 2
A blower 2 is arranged on the downstream side of the blower 2.

Fuel 2 and combustion air 27 are supplied to the boiler 23,
Fuel JJ burns inside, and high-temperature exhaust gas 2δ' generated by this combustion is sucked into the blower 2 and sent to the heat exchanger 2.
It passes through the exhaust duct ≦ (see Figure 1) in the chimney 2, performs heat exchange as described below and is cooled, and then moves into the chimney 2 by the action of the blower 23.
Released into the atmosphere from ≠.

Further, the air 29 to be heated is forced to be sent to the heat exchanger 2 by the blower 3/ through the flow rate control valve 3θ. This air 29 flows into the fluid duct/9 from the fluid population 2θ of the heat exchanger 22, exchanges heat with the exhaust gas 2 via the exhaust gas duct B, and the exhaust gas 2! It is heated by receiving heat from the At this time, it is the air flowing through the space SJ that directly exchanges heat with the exhaust gas 2.
Since the air in 2 has already been heated to a certain degree of high temperature, the exhaust gas 2 near the wall of the exhaust gas duct 4 is not locally supercooled, and therefore the air in the exhaust gas 2 is There will be no situation where corrosive substances such as sulfur oxides contained in the exhaust gas duct condense on the wall of the exhaust gas duct and corrode it.

In addition, the exhaust gas discharged from boilers, deodorizing furnaces, incinerators, etc. is often at a high temperature of about 230°C - 0°C, and in such cases, side-to-side heat transfer from the exhaust gas to the air is not negligible. In particular, in the dual structure of the exhaust gas duct) 4 and duct 7 shown in Fig. 3, if the outer circumferential surface of the exhaust gas duct 4 is colored white and the inner circumferential surface of the duct 7 is colored black, side-to-side transmission can be achieved. Heat is applied effectively.

The heated air 29 receives heat from the high-temperature exhaust gas 2 and flows out from the fluid 0.2/, and its thermal energy is used for other useful purposes or a part is used as supply air for the boiler. used for. In addition, in FIG. 7, 32 is a flow control valve.

If the exhaust gas 2 changes, the flow rate control valve 3o is adjusted according to the fluctuation, and the heat transfer rate is controlled to effectively prevent condensation between the exhaust gas 2 and the corrosive substances contained therein. can do.

On the other hand, since the exhaust gas duct 4 is configured to be detachable, attached dust and the like can be easily removed.

Other embodiments are shown in Figures ≠ and 5.

First, the embodiment shown in Figure 1 corresponds to a water tube boiler, and is an example in which a large number of fluid ducts are arranged in an exhaust gas duct.

In the figure, the upper and lower duct walls of the rectangular exhaust duct lA/ have corresponding circular holes l1-2°4L3.
is drilled in the hole, and the outer duct l/of the double pipe is inserted into the hole.
Ll/L is inserted and the exhaust duct l/L/
Fixed.

Further, a box-shaped duct 4'J- is attached to the upper part of the exhaust duct lI-/, and a circular hole is bored concentrically in the duct≠j corresponding to the circular hole≠2. A partition plate≠0 having ≠B is provided parallel to the axial direction of the exhaust duct≠/, forming spaces S/ and SJ. A double-pipe inner duct≠7 is installed in the hole 4Lg, communicating with the space S/ and passing through the outer duct lI-≠.

Note that the lower part of the inner duct≠ means that it is desirable to extend the exhaust duct to the vicinity of the lower end of the exhaust duct≠l from the viewpoint of efficiency of the heat exchanger. This is a reply. And j≠゛ is installed with a cover that covers the lower part of the exhaust duct to isolate it from the outside.

The inner duct IA7 is formed to communicate with the space Sj via the spaces S and z surrounded by the outer duct≠≠ and the inner duct≠7, and the fluid duct is connected to the space S7, the inner duct ll-7, and the space 84°SJ. Configure jO. The fluid inlet j/ is communicated with the space SJ, and the fluid outlet 5 is communicated with the space S3.
．． 2 are provided respectively.

Air is thus delivered for use in the fluid volume kl, the space S/, the inner dash, and other strokes.

FIG. 5 shows an example in which a large number of baffle plates 3 are provided in the air duct 9 of the embodiment shown in FIG. 1 in a direction perpendicular to the axial direction of the duct IO. Buckle plate j as in this example
3, the flow rate of air is increased by the constriction effect, and the air flow is further disturbed to improve the heat passing rate, thereby increasing the heat recovery efficiency.

Next, the case where the fluid to be heated is a liquid, particularly cold water, will be described.

Basically, it is the same as in the case of gas, but in order to maintain the liquid tightness of the fluid duct/9 in Fig. 1, as shown in Fig. A heat-resistant O-ring, such as Teflon or glass fiber-containing Teflon, is interposed in between. Also, as shown in Figure 9, bellows/≠ is a seal! A flange member tough may be installed on the exhaust gas duct B to seal the screw portion with the screw part B, and a seal J may be provided between the movable flange and the movable flange. Although air and cold water have been described as the fluids to be heated in the above description, the present invention is not limited thereto, and can be applied to other fluids in general such as nitrogen gas, carbon dioxide gas, argon gas, and liquids.

Further, in the present application, the device may be constructed by forming a large number of layers as shown in the figure.

As is clear from the above description, according to the present invention, the exhaust gas and multiple fluid layers form a multilayer flow and the fluid is heated in multiple stages, so that the exhaust gas is not locally supercooled. Corrosive substances contained in the exhaust gas condense on the duct wall and corrode the duct, which is irreversible.

Furthermore, more heat can be received from the exhaust gas than by heating the fluid in multiple stages.

[Brief Description of the Drawings] Figure 1 is a longitudinal cross-sectional view of a heat exchanger constituting the device of the present invention, Figure 2 is an enlarged view of section A in Figure 1, and Figure 3 is a cross-sectional view taken along line 3-3 in Figure 1. Figures ≠ to g are longitudinal sectional views showing other embodiments, Figure 7 is a block diagram showing an example of application of the device of the present invention, and Figures ♂ to 9 show still other embodiments. Each is shown below. In the figure, B is the exhaust gas duct, /9 is the air duct, Kθ is the air inlet, 2/ is the air outlet, 22 is the heat exchanger,
23 represents a boiler, and 30 represents a flow control valve.
・Patent applicant: Kikkoman Corporation

Claims (4)

[Claims] (1) An exhaust gas heat recovery method characterized in that the exhaust gas and at least two heated fluid layers communicating with each other form a multilayer flow to recover heat from the exhaust gas. (2) Claim No. (1), wherein the fluid layer is a gas.
Exhaust gas heat recovery method described in section. (3) Claim No. (1), wherein the fluid layer is a liquid.
Exhaust gas heat recovery method described in section. (4) A multilayer structure is formed by an exhaust gas duct and at least a double-structured fluid duct that communicates with each other, and the exhaust gas and fluid layer flowing through these ducts are unitized to form a multilayer flow. Exhaust gas heat recovery equipment.