Device for recovering residual heat from exhaust gas

Abstract

A device for recovering residual heat from exhaust gas includes: a dry economizer which heats to-be-heated water by utilizing sensible heat of the exhaust gas, the dry economizer being provided in a duct extending to a funnel through which the exhaust gas is emitted to atmosphere; and a condensation economizer which heats to-be-heated water by utilizing latent heat of condensation of the exhaust gas, the condensation economizer being provided on a downstream side of the dry economizer. The duct includes an upstream duct in which the dry economizer is provided and a downstream duct connected to the upstream duct and directing the exhaust gas to flow upwardly. The condensation economizer is arranged in the downstream duct so that temperature of the exhaust gas amounts to condensation temperature at a vicinity of an upper part of the condensation economizer.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a device for recovering residual heat from exhaust gas. Particularly, the present invention relates to a device for recovering residual heat from exhaust gas that includes a dry economizer which heats to-be-heated water by utilizing sensible heat of the exhaust gas, the dry economizer being provided in a duct extending to a funnel through which the exhaust gas is emitted to atmosphere; and a condensation economizer which heats to-be-heated water by utilizing latent heat of condensation of the exhaust gas, the condensation economizer being provided on the downstream side of the dry economizer.[0003]2. Description of the Related Art[0004]In related art, in a duct through which the exhaust gas from a boiler is circulated, an economizer is provided which heats a boiler water supply (to-be-heated water) using residual heat of the exhaust gas. The economizer recovers the residual heat of the e...

AI Technical Summary

Benefits of technology

[0030]Thus, since the flow direction of the to-be-heated water flowing in the dry economizer and the condensation economizer is provided so as to face the flow direction of the exhaust gas, the heat recovery efficiency is able to be improved.

[0031]In the present invention, the condensation economizer is provided in a downstream duct that directs the exhaust gas to flow upward, and the device is configured so that temperature of the exhaust gas amounts to condensation temperature at a vicinity of the upper part of the condensation economizer. Thus, vapor in the exhaust gas is condensed in the vicinity of the upper part of the condensation economizer, and becomes a drain. The generated drain falls down from vicinity of the upper part of the condensation economizer and comes into contact with the water pipe group constituting the condensation economizer, and thus, the outer wall of the water pipe is kept in a wet state from the upper part to the lower part. For this reason, the drying and wetting cycle is able to be prevented in the water pipe group in the condensation economizer, which is able to prevent the stress corrosion cracking.

[0032]Furthermore, when falling down from the vicinity of the upper part of the condensation economizer, since the generated drain comes into contact with the water pipe group and falls down so as to face the exhaust gas of the upward flow, it is possible to increase partial pressure of the vapor in the exhaust gas flowing in the condensation economizer. For this reason, the condensation amount in the condensation economizer is increased, the condensation efficiency rises, and the residual heat recovery rate of the exhaust gas rises.

Problems solved by technology

In the middle part, the water pipe group repeats the cooling and the heating, and thus there is a possibility that stress corrosion cracking (SCC) may occur in the water pipe.

Furthermore, in Patent Document 2, since the sensible heat transfer area and the condensation heat transfer area are alternately provided, the structure is complicated and the apparatus increases in size.

In addition, since it is feared that the position of the condensation heat transfer area is changed due to a change in boiler load, similarly to Patent Document 1, a zone is generated where the drying and the wetting are repeated, whereby there is a possibility of the stress corrosion cracking being generated.

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