JPS61217694A - Composite type gas preheater - Google Patents

Abstract

PURPOSE:To facilitate a soot blowing and washing with water to be performed by a method wherein a single pipe type heat pipe heat exchanger having thermal conduction substance of organic thermal medium is arranged at a hot temperature part and a separate type heat pipe exchanger having water naturally circulated therein is arranged at a low and medium part and then a preheating temperature of the preheated gas is increased efficiently. CONSTITUTION:In an air preheater device, a hot temperature part is constructed by a single pipe type heat pipe heat exchanger 2 having organic thermal medium therein and a medium and low temperature part is constructed by a separate type heat pipe heat exchanger 3 is which the water is naturally circulated. Hot discharged gas 4 from the boiler is flowed from the upper part to the lower part, changed to a low temperature discharging gas 5, resulting in that the gas is discharged to a disulfurizer or directly into the smoke discharging device. The air 6 fed by a forced aeration device is flowed from the lower part toward the upper part, made as a preheated air of hot temperature under a heat exchanging operation and then fed to a combustion chamber in the boiler. In the single pipe type heat pipe heat exchanger 2, an operating point of the heat pipe is automatically determined in response to an air temperature level as well as the discharged gas G.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a composite gas preheater for a boiler air heater, a fuel gas heating device, etc. used for recovering exhaust heat from dust-containing gas such as coal-fired boiler exhaust gas.

[Conventional technology]

FIG. 4 is a side view of a conventional gas preheating device.

Conventionally, a gas preheater in which a plurality of heat exchangers 01 and 02 are arranged with a partition wall in between and exchanges heat by circulating a heat transfer medium 03 between the heat exchangers 01 and 02, uses high-temperature exhaust gas 04.
It is used to mix heated gas and heated gas 05, or to avoid leakage of gas from one duct 06 to the other duct 07. In the gas preheater 08, water is used as the heat transfer medium 03, and the heat exchanger 01,
02 as an evaporator 09 and the other as a condenser O1O,
Generally, a method is adopted in which the heat transfer medium is circulated through natural circulation that utilizes the density difference between steam and water. However, in the above method, as the temperature range for heat exchange increases,
Since the saturation pressure of water, which is the heat transfer medium 03, also increases, the density difference between water and steam decreases, and the natural circulation force decreases. Therefore, the above gas preheater 0 using water as the heat transfer medium 03
8, there is a practical upper limit temperature level, and it is difficult to increase the temperature of the heated gas 05 to 350°C or higher.

Further, the conventional gas preheater employs a vertical arrangement of heat exchanger tubes, which is advantageous for natural circulation. Heat transfer tubes are usually constructed of circular finned tubes, but if the exhaust gas contains dust such as ash, the dust tends to accumulate on the surface of the fins, and cleaning with water etc. is difficult to achieve a sufficient effect. This is a heat tube arrangement.

[Problem that the invention seeks to solve]

Depending on the type of coal used as fuel for coal-fired power plants, the air preheating temperature may be approximately 3.
Even if a temperature of 50° C. or higher is required, when only water is used as a heat transfer medium, natural circulation is not established, and the exhaust gas temperature of about 400° C. cannot be effectively exchanged. In addition, dust contained in the exhaust gas adheres to heat transfer surfaces such as fins of heat transfer tubes constituting the heat exchanger and blocks the heat transfer surfaces, resulting in a reduction in heat transfer efficiency.

[Means for Solving the Problems] The present invention is characterized in that high-temperature exhaust gas flows downward from the top through one of two vertical ducts adjacent to each other with a partition wall in between, and the heated gas Flows upward from the bottom and between the above ducts! (c) Composite gas preheating using a gas rectification method, in which heat is transported by a heat transfer medium circulating in a heat exchanger installed across the partition wall, and heat is exchanged between the high-temperature exhaust gas and the heated body. The high-temperature section is equipped with a single-tube heat pipe heat exchanger that uses an organic heating medium as the heat transfer medium, and the medium-low temperature section is equipped with a separate heat pipe heat exchanger that naturally circulates water. The present invention provides a composite gas preheater characterized in that the gas preheater is installed substantially horizontally.

〔Example〕

1 and 2 conceptually show one embodiment of the gas rectification type hybrid heat pipe type air preheater according to the present invention, and its construction and operation will be explained. In the air preheater 1 of this embodiment, the high temperature section is composed of a single tube heat pipe type heat exchanger 2 using an organic heat medium, and the medium and low temperature section is composed of a separate type heat pipe type heat exchanger 2 in which water naturally circulates. It consists of 3. Therefore, high-temperature boiler exhaust gas 4 flows downward from the top, becomes low-temperature exhaust gas 5 through heat exchange, and is discharged to a desulfurization device (not shown) or directly to a smoke exhaust device (not shown).

On the other hand, air 6 sent from a forced draft fan (not shown) flows upward from the bottom, and the high-performance separated heat pipe type heat exchanger 3 is divided into multiple modules according to the temperature levels of the exhaust gas 5 and air 6 through heat exchange. need to be divided. Further, in order to ensure natural circulation force, it is necessary to place the evaporator section 3a on the exhaust gas 5 side at a lower position than the condensation section 3b on the air side. On the other hand, in the single-tube heat pipe type heat exchanger 2, the operating point (heating medium pressure and temperature) of the heat pipe is automatically determined according to the temperature levels of the exhaust gas G and the air 6. FIG. 3 is an example of a temperature diagram showing the operating state of the entire hybrid heat pipe type air preheater. In this example, the exhaust gas temperature range is from 400°C to 350°C, and the usage range of the single tube heat pipe 2 is from 350°C to 1°C.
The usage range of the separate heat pipe 3 is up to 40℃.
The separate type range is further divided into six modules depending on temperature level.

〔Effect of the invention〕

The gas preheater is a vertical type heat exchanger that uses an organic heat medium as a heat transfer medium and has a single-tube heat pipe heat exchanger in the high-temperature section and a separate heat pipe heat exchanger that naturally circulates water in the middle and lower parts. This is a composite type gas preheater.In the duct where each of the above heat exchangers is stacked in multiple stages, the high temperature exhaust gas and the heated gas are completely separated by a partition wall, so the preheating temperature of the heated gas can be efficiently adjusted. The temperature can be raised to 350°C or higher if necessary.

In addition, since the multiple heat transfer tubes that make up each heat exchanger are arranged horizontally, the heat transfer surface of the heat transfer section is prevented from being clogged by dust-containing gas, and suit blowing and water washing are easy to prevent dust adhesion. It becomes possible to adopt a heat transfer surface arrangement.

[Brief explanation of the drawing]

FIG. 1 is a side view conceptually showing an embodiment of a gas rectification type composite air preheater according to the present invention, FIG. 2 is a side view taken along arrow A-A in FIG. The figure is an example of a temperature chart showing the operating state of the entire hybrid heat pipe type air preheater, and FIG. 4 is a side view of the device showing a conventional example. 1... Composite gas preheater, 2... Single tube heat pipe heat exchanger, 3... Separate heat pipe heat exchanger, 4... High temperature boiler exhaust gas, 5... Low-temperature exhaust gas, 6... Air for heating, 3a... Evaporator part on the exhaust gas side, 3b... Condensing part on the air side.

Claims (1)

[Claims] High-temperature exhaust gas flows downward from the top through one of the two vertical ducts adjacent to each other across the partition wall, and the heated gas flows upward through the other duct from the bottom, straddling the space between the ducts. A vertical gas flow type composite gas preheater that transports heat by a heat transfer medium that circulates in a heat exchanger that penetrates the partition wall and exchanges heat between the high-temperature exhaust gas and the heated gas. In the high temperature section, a single tube heat pipe type heat exchanger using an organic heat medium as the heat transfer medium is used, and in the medium and low temperature section, a separate type heat pipe type heat exchanger with natural circulation of water is used. A composite gas preheater characterized by being installed substantially horizontally.