JPH10141602A - Corrosion preventing apparatus for waste gas remaining heat-recovering apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the utility cost such as vapor outside a system and prevent an air preheater from being corroded with acid by providing a heater on a gas inlet side of a residual heat gas recovery apparatus for recovering residual heat of waste gas with the aid of gas, and heating the gas with part of the gas heated with the waste gas in the waste gas residual heat apparatus. SOLUTION: A branch pipe 12 is branched from a piping 11 on an outlet side, partial air 13 of air 9 exhausted from an air preheater 1 flows therethrough, and the branch pipe 12 joins the piping 11 on the downstream outlet side. An air heater 2 is provided on the branch pipe 12 for heat exchanging with air 7 in a piping 10 on an inlet side for heating of the air 7. Combustion exhaust gas 5 is heat exchanged with the air in the air preheater 1. Thereupon, an iron surface of the air preheater 1 is lowered to an acid dew point or lower owing to temperature of the inlet air 8 so that part of the air 9 heated with the combustion waste gas in the air preheater 1 is flowed to the branch pipe 12 to heat the inlet air 8 to the air preheater 1. Hereby, acid erosion of the air preheater 1 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corrosion prevention device for an exhaust gas residual heat recovery device such as an air preheater that recovers residual heat of exhaust gas by air.

[0002]

2. Description of the Related Art As shown in FIG. 2, a conventional air preheater for recovering residual heat of exhaust gas by air is an air preheater.
Is heated by the steam-type air preheater 4 and
The gas is introduced into the air preheater 1, and the temperature of the exhaust gas contact iron surface in the air preheater 1 is maintained at an acid dew point or higher to prevent corrosion of the air preheater 1. 2, reference numeral 5 denotes combustion exhaust gas supplied to the air preheater 1, reference numeral 6 denotes combustion exhaust gas discharged from the air preheater 1, and reference numeral 7 denotes air supplied to the steam-type air preheater 4.

[0003]

In the prior art shown in FIG. 2 described above, steam for heating the inlet air of the air preheater as a utility was required, and thus utility costs were incurred.

An object of the present invention is to provide an apparatus for preventing corrosion of an exhaust gas residual heat recovery device, which can reduce utility costs such as out-of-system steam by using the heated self-gas of the exhaust gas residual heat recovery device.

[0005]

According to the present invention, there is provided a corrosion prevention device for an exhaust gas residual heat recovery device, which is heated by the exhaust gas residual heat recovery device to the gas inlet side of the exhaust gas residual heat recovery device for recovering the residual heat of the exhaust gas by gas. A heater for heating a gas by a part of the gas is provided.

In the present invention, the gas entering the exhaust gas preheat recovery device is heated in the heater by a part of the gas heated by the exhaust gas preheat recovery device. Therefore, a heating source for gas such as steam from outside the system is not required for preventing corrosion of the exhaust gas residual heat recovery device, and a decrease in plant efficiency can be prevented.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. Reference numeral 1 denotes an air preheater for heating air by combustion exhaust gas, and air 7 is introduced into the air preheater 1 from a pipe 10 on the upper inlet side through an air heater 2 described later, and exchanges heat with the combustion exhaust gas. The heated air 9 is discharged from a pipe 11 on the outlet side. Reference numeral 5 denotes a combustion exhaust gas introduced into the air preheater 1, and reference numeral 6 denotes a combustion exhaust gas discharged from the air preheater 1.

[0008] A branch pipe 12 branches from the outlet pipe 11 and a part of the air 9 discharged from the air preheater 9 flows. The branch pipe 12 is a downstream pipe 1 on the outlet side.
It merges into one. The branch pipe 12 is provided with an air heater 2 for exchanging heat with the air 7 in the pipe 10 on the inlet side to heat the air 7. Reference numeral 8 denotes inlet air heated by the air heater 2 and introduced into the air preheater 1. Reference numeral 3 denotes a damper provided between the branch point of the branch pipe 12 of the pipe 11 and the junction.

In the present embodiment, the flue gas 5 exchanges heat with air in the air preheater 1. At this time, since the temperature of the inlet air 8 lowers the iron surface of the air preheater 1 to below the acid dew point, a part of the air 9 heated by the combustion exhaust gas 5 in the air preheater 1 is caused to flow to the branch pipe 12, The inlet air 8 to the preheater 1 is heated. Thereby, acid corrosion of the air preheater 1 can be prevented.

Further, the amount of air to the air heater 2 is adjusted by using the damper 3 so that the temperature of the inlet air 8 to the air preheater 1 becomes the optimum temperature.

As described above, in the present embodiment, acid corrosion of the air preheater 1 can be effectively prevented without using a utility such as steam outside the system.

Although the present embodiment relates to a corrosion prevention device of an exhaust gas preheating recovery device that heats air with combustion exhaust gas, the present invention is widely applied to other devices that recover the preheating of exhaust gas by gas. be able to.

[0013]

As described above, according to the present invention, the gas on the inlet side of the exhaust gas residual heat recovery device for recovering the residual heat of the exhaust gas by the gas is heated by a part of the gas heated by the exhaust gas in the exhaust gas residual heat recovery device. By doing so, the corrosion of the exhaust gas residual heat recovery device can be reliably prevented without using a utility such as steam outside the system.

[Brief description of the drawings]

FIG. 1 is a system diagram of an embodiment of the present invention.

FIG. 2 is a system diagram of a conventional corrosion prevention device for an air preheater.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 air preheater 2 air heater 3 damper 4 steam type air heater 5,6 flue gas 7 air 8 inlet air to air preheater 9 air 10,11 pipe 12 branch pipe

Claims (1)

[Claims] 1. A heater for heating a gas by a part of the gas heated by the exhaust gas in the exhaust gas residual heat recovery device is provided on the gas inlet side of the exhaust gas residual heat recovery device for recovering the residual heat of the exhaust gas by the gas. Corrosion prevention equipment for exhaust gas residual heat recovery equipment.