JPS58184422A - Treating device for exhaust gas - Google Patents

Abstract

PURPOSE:To prevent the low temperature corrosion of a heat pipe or its related devices, by a method wherein, in a treating device for exhaust gas employing a separating type heat pipe system gas heater, a heater is mounted to a lower header adapted to gather together heat pipes at an evaporating side. CONSTITUTION:A gas-gas heater installed at a rear stage of a wet type desulfurizer in a treating device for exhaust gas is constituted such that heat pipes 24A and 24B, respectively installed in an evaporating part 11 located in a flue duct at high temperature side and a condensing part 12 situated in a flue duct at a low temperature side, are connected together through a rise pipe 17 and a fall pipe 18, but it differs from a conventional device that an electric heating type sheath heater 30 is mounted to a lower header 27 adapted to collect together the heat pipes 24A and the evaporating part 11. In this constitution, if a boiler is brought to suspend operation and the temperature in a flue duct 21 is lowered, water stored in the header 27 and supplied to the heat pipes 24A at the evaporating side 11 is heated by the sheath heater 30 to heat the heat pipes 24A and 24B at the evaporating side and the condensation side, and this permits the prevention of the occurrence of a low temperature corrosion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flue gas treatment device, and more particularly to a flue gas treatment device that prevents low-temperature corrosion of a gas/gas heater attached to a flue gas desulfurization device of a combustion device such as a boiler.

Combustion devices such as large boilers for commercial thermal power plants are equipped with flue gas desulfurization equipment, but in such desulfurization equipment,
Reheating of exhaust gas is performed as a measure to prevent white smoke when dissipating exhaust gas from a chimney. This exhaust gas reheating is
Initially, this was done by raising the temperature in the afterbar (1), but recently, from the standpoint of energy conservation, it has been done by exchanging heat with the boiler combustion exhaust gas. As a heater used for such exhaust gas reheating, a rotary regenerative heat exchanger, a so-called Jungstrom type heater, which is conventionally used in an air heater such as a boiler, has been used.

FIG. 1 is a system diagram of an exhaust gas treatment apparatus using such a gas reheating heater. In the figure, exhaust gas 2 generated from a boiler 1 is first dedusted in a Cottrell 10, then enters a gas/gas heater 3 and becomes a heat source.
Furthermore, air is blown to the exhaust gas desulfurization device 5 by the induced blower number. As the flue gas desulfurization device 5, one based on a wet method such as a limestone-gypsum method is used. The processing gas exiting the desulfurization device 5 is cleaned by spraying a cleaning water in a water washing device 6 as necessary, and enters the gas-gas heater 3 as a cleaning gas.
Here, it is heated by exchanging heat with the heated waste gas from the Cottrell 10, and reaches a temperature at which white smoke can be prevented, and is discharged from the chimney 8 into the atmosphere.

However, recently, regulations on the amount of medium (2) dust in the flue gas discharged from the chimney have become even stricter, and a rotary regeneration type gas/gas heater 3, as shown in Figure 1, moves the dust from the high-temperature side to the low-temperature side flue. However, there is a problem in that it becomes leak dust 9 and gets mixed into the stack gas, making it impossible to satisfy the pollution regulation value.

In order to solve the above problem, the present applicant has proposed a separate heat pipe type gas/gas heater as the heater 3, in which the heat exchange section is completely separated into a high temperature side and a low temperature side. Figure 2 shows a model diagram of such a heater. The heat pipe 24A of the evaporating part 11 and the heat pipe 24B of the condensing part 12 are as follows:
A closed circuit is formed by the riser pipe 1B which transfers the vapor of the working medium (for example, water) of the heat pipe and the downcomer pipe 1B which returns the water. The structure of the evaporation section 11 and the condensation section 12 consists of heat exchanger tubes 24A and 24B with a fin 26 provided in the exhaust gas flue 21 in a direction perpendicular to the gas 13.15, and a row of these heat exchanger tubes arranged above and below. Header 2'7.2B, 29.3 to be collected at
0, the lower header 2F, 29 has a downcomer pipe 18,
Further, rising pipes 1'7 are connected to the upper headers 2B and 30, respectively. The heat exchanger tubes in each row form one heat exchanger tube screen, which is housed in the main body (flue) 21 in a number of different stages.

However, in such a device, there is a problem that when the device is stopped (boiler banking), the wet gas containing SOx in the flue 21 condenses as it cools, causing low-temperature corrosion in the heat pipe.

An object of the present invention is to provide a flue gas treatment device that prevents low-temperature corrosion of a gas heater using the conventional separated heat pipe.

The present invention provides a separate heat pipe type gas heating device having an evaporating section and a condensing section in the exit flue gas flue of a combustion device and a wet type pipe attached thereto, and the exit flue of a smoke desulfurization device, respectively. The device is characterized in that a medium heating device (4) is provided at the lower header of the heat pipe on the evaporation side of the device.

Hereinafter, the present invention will be explained in more detail with reference to embodiments shown in the drawings.

FIG. 3 shows one embodiment of the present invention, and is a schematic diagram of a gas-gas heater provided after the wet desulfurization device of the flue gas treatment equipment. As in the case of FIG. 2, this equipment W has a heat pipe of 24A% for each of the evaporator section 11 disposed in the high temperature side flue and the condensation section 12 disposed in the low temperature side flue.
24B are connected through the riser pipe 1 and the downcomer pipe 1, but the main point is that an electric sheathed heater 30 is provided in the lower header 2'2, which is the header of the heat pipe 24A of the evaporator 11. This is different from Figure 2.

In such a configuration, the operation of the boiler etc. is stopped,
When the exhaust gas flows in the flue 21 and i<h, the temperature decreases, and as mentioned above, the gas containing acidic components condenses and there is a risk of low-temperature corrosion. The water stored in the heat pipe 11 and the ladder 27 is heated to a temperature that does not cause low-temperature corrosion, e.g.
70-0 or higher (5) Heat pipes 24A and 24B on the evaporation side and condensation side
By heating, low-temperature corrosion can be prevented. In addition, when the operation is stopped, the heat pipes on the evaporation side (heating side) and condensation side (cooling side) are heated by repeating evaporation and condensation of a small amount of the working medium in the heat pipe [7]. This will also speed up the startup time.

In addition, compared to a normal heat exchanger that heats by forced circulation of a heat medium, heat pipes do not require any power means, making maintenance easier. Furthermore, when the heat medium is water, In cold regions, there is a risk that the water stored in the heat pipe 24A on the evaporation side may freeze when the operation is stopped in winter, but in the above embodiment, such troubles can be prevented by providing the sheathed heater 30. can do.

FIG. 4 shows another embodiment of the present invention, in which the lower header of the heat pipe of the evaporation section 11 of the separate heat pipe heater is configured as a multi-tube heat exchanger 32, and steam 3 is placed inside the tube. It is like sending a number. In this way, even when formula (6) is used by steam heating, the same effects as in the above embodiment can be obtained.

In all of the above embodiments, a heating means is provided in the lower header of the heat pipe of the evaporating section 11 of the separated heat pipe type heater. It can also be provided in the lower header 29 of the pipe. However, since the working medium is generally stored in the lower part of the heat pipe of the evaporator 11 when the operation is stopped, it is sufficient to simply provide a heater in the lower header of the heat pipe 24A.

As described above, according to the present invention, in an exhaust gas treatment device using a separate heat pipe type gas heater, when the temperature drops when the boiler or the like stops operating due to the heating device being provided in the lower header for the heat pipe on the evaporation side, It can prevent low-temperature corrosion of heat pipes and related equipment, and when the working medium is water, it can prevent freezing inside vinyl pipes in cold weather and facilitate maintenance. Excellent effects such as:

(7)

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a wet desulfurization and gas reheating system for boiler exhaust gas, Fig. 2 is an explanatory diagram of a separated heat pipe type gas heating device, and Fig. 3 is a diagram showing a separated type heat pipe type gas heating device used in the present invention. FIG. 4 is a diagram showing an embodiment of the gas heating device.
It is an explanatory view showing an evaporation side heat pipe of the gas heating device showing another example of the present invention. 3...Gas-gas heater, 5...Wet flue gas desulfurization equipment, 6...Cleaning device, 8...
Chimney, 11... Evaporation section (heater), 12...
... Condensing section (heat receiving heater), 13 ... High temperature exhaust gas, 15 ... Low temperature exhaust gas, 17 - ... Rising pipe, 18 ... Down pipe, 2+A, 24B...
... Heat pipe, 27 ... Lower header, 3
0...Sheathed heater, 32...Multi-tube heat exchanger that also serves as header, No. 3...Steam. Agent Patent Attorney □, Takeshi Shikawa Kita (8) Figure 1 Figure 2 Figure 31i

Claims (1)

[Claims] (1) A separate heat pipe type gas heating device having an evaporating section and a condensing section is provided in the exit flue of the combustion device and the exit flue of the wet flue gas desulfurization device attached thereto, and An exhaust gas treatment device characterized in that a medium heating device is provided in a lower header of an evaporation side heat pipe.