JPH09126387A - Internal heat insulation type gas pipe device and its corrosion prevention method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a convenient and inexpensive device without using an anticorrosive material by connecting a purge gas pipe which removes gas containing corrosive component which remains in a heat insulation material layer section of a pipe at least at one section on an outer face of the pipe. SOLUTION: Air pipes 5, 9 for purge are arranged from an air source 3 for control which has higher pressure than pressure of exhaust gas at a temperature below dew point of corrosive oxide in an exhaust gas pipe system having high temperature and high pressure. Purge gas 12 flows into a heat insulation material 10 of an external pipe 7 (exhaust gas pipe) from the air pipe 9 for purge from the time before corrosive oxide in exhaust gas when boiler load drops becomes dew point temperature till the time when exhaust gas does not flow after a boiler stops. Consequently, the corrosive oxide which remains in the heat insulation material 10 flows into exhaust gas flow passage, the corrosive oxide in the heat insulation material 10 part is purged, and a problem of corrosion of the external pipe 7 is eliminated. Accordingly, it is unnecessary to use an expensive anticorrosive external pipe, and it is possible to realize an inexpensive internal heat insulation type gas pipe device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-temperature, high-pressure internal adiabatic gas pipe apparatus having a structure in which a heat insulating material layer is provided on the inner surface of the pipe and a method for preventing the corrosion thereof, and particularly to a corrosive gas contained in exhaust gas. The present invention relates to a gas pipe apparatus having a structure suitable for preventing corrosion of an inner surface of a pipe due to an oxide and a method for preventing the corrosion.

[0002]

2. Description of the Related Art When the internal fluid gas of a pipe has a high temperature and a high pressure, the pipe structure adopts a closed double pipe system or an internal heat insulation system. In particular, if the internal fluid is at a high temperature of more than 800 ° C and the temperature cannot be lowered due to the conditions of the piping system, an example of adopting a method in which the inner surface of the pipe is covered with an internal heat insulating material using a liner is recommended. Many. The feature of this system is that the heat quantity of the high temperature gas is blocked by the internal heat insulating material, so that the temperature of the high temperature gas itself is prevented from lowering, and the temperature of the pipe outside the inner heat insulating material with respect to the internal gas temperature, Can be quite low. This brings about the effect of reducing the material or the thickness of the pipe (referred to as an outer pipe) and is preferable from the viewpoint of cost. However, in the case of this internal heat insulation structure with liner, unlike the closed double pipe system, the liner or internal heat insulating material does not support the pressure of the hot gas, but the outer pipe supports the pressure. The high temperature gas is made to flow toward the inner surface of the outer tube through the gap with the heat insulating material. When the high temperature gas flowing in the pipe contains a sulfuric acid component and the like, the problem of corrosion of the outer pipe occurs. Therefore, the thickness of the heat insulating material layer is set so that the corrosive component in the high temperature gas does not reach the dew point, or the outer tube made of a material considering corrosion resistance is required. However, this leads to the upgrade of the external pipe, and there is a problem that the cost of the piping device is unavoidably increased.

[0003]

In the prior art,
For the corrosive components in the high temperature gas that enter the inner surface of the outer pipe,
Measures have been taken in terms of the gas dew point temperature and the materials that are resistant to corrosion, but the removal of the corrosive components themselves (purging) in the gas
However, the problem of corrosion of the outer pipe is still unavoidable, and there is a problem that the cost of the piping device becomes high due to the use of a corrosion resistant material.

An object of the present invention is to solve the above-mentioned problems of the prior art, that is, an inexpensive internal adiabatic gas using a simple purging mechanism of corrosive gas without using an expensive corrosion resistant material. (EN) Provided is a piping device and a corrosion prevention method therefor.

[0005]

The above object of the present invention is to provide a structure as described in the claims of the present invention. That is, according to the present invention, as described in claim 1, in a high-temperature, high-pressure internal adiabatic gas piping device having a structure in which a heat insulating material layer is provided on the inner surface of the piping, the gas stays in the heat insulating material layer portion of the piping. The purge gas pipe for removing the gas containing a corrosive component is an internal adiabatic gas pipe device connected to at least one location on the outer surface of the pipe. By simply providing a simple purge gas pipe in this way, it is possible to effectively purge the gas containing corrosive components that accumulates in the heat insulating material layer of the pipe at a temperature above the dew point temperature, and to effectively corrode the inner surface of the pipe. Therefore, there is an effect that an inexpensive internal adiabatic gas piping device can be realized without using expensive corrosion resistant piping. Further, the present invention is a method for preventing corrosion of a high-temperature, high-pressure internal adiabatic gas pipe apparatus having a structure in which a heat insulating material layer is provided on the inner surface of the pipe as described in claim 2, At a temperature equal to or higher than the dew point temperature of a gas containing a corrosive gas flowing inside, a purge gas for removing the exhaust gas staying in the heat insulating material layer portion of the inner surface of the pipe is sent from the outer surface of the pipe at a predetermined pressure. This is a method for preventing corrosion of the gas pipe of the internal adiabatic type that is introduced to prevent condensation of the exhaust gas. Thus, before the corrosive gas staying in the portion of the heat insulating material layer on the inner surface of the pipe is below the dew point temperature, purge gas can be fed into the heat insulating material layer to suppress dew condensation. Similar to the effect of 1,
An inexpensive internally insulated gas piping system can be obtained. Further, as described in claim 3, the present invention provides the method of preventing corrosion of an internal adiabatic gas pipe according to claim 2, wherein the purge gas is dry air, nitrogen or an inert gas. By doing so, for example, a purge gas can be obtained from a control air source, and nitrogen or an inert gas having a low reactivity can be used, and the common effect of the above-mentioned claim 1 or claim 2 can be obtained. In addition to this, a simple and inexpensive purge gas pipe can be provided. The corrosion prevention method in the internal heat insulation type gas piping device of the present invention is to provide a mechanism for purging the corrosive gas accumulated in the heat insulating material layer provided on the inner surface of the gas piping system. This mechanism uses a purge gas such as dry air, nitrogen, or an inert gas that purges corrosive gas, supplies the corrosive gas that remains in the heat insulating material layer inside the pipe at a pressure that allows it to be purged, and then remains in the pipe. It is for purging the corrosive gas. Structurally, dry air from a purge gas source,
Nitrogen or an inert gas pipe is connected to an external pipe, and the purge gas is introduced by this mechanism before the dew point temperature of the corrosive gas accumulated in the heat insulating material layer is reached. That is, the corrosive components in the gas accumulated in the heat insulating material layer inside the pipe exist in a gas state until the dew point temperature is reached, and there is not much problem for the corrosion of the pipe. The problem arises when the corrosive gas contained in the exhaust gas reaches the dew point temperature and combines with the water in the exhaust gas to liquefy. This problem can be solved by purging in the gas state before the corrosive components in the gas are liquefied. The pressure of the purge gas at this time is set higher than the gas pressure at the time before the corrosive component in the gas reaches the dew point temperature under the operating conditions of the piping system and the like. By purging the corrosive gas inside the pipe before the dew point temperature, the pressure of the purge gas is higher than the pressure of the exhaust gas. Extruded into the flow path. As a result, the corrosive components in the gas do not flow into the heat insulating material layer, and the outer pipe is not exposed to the corrosive environment.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION When supplying high-temperature, high-pressure exhaust gas containing corrosive oxides from a pressurized fluidized bed boiler furnace to a gas turbine, the above exhaust gas piping system has The pressure cannot be reduced. Therefore, conventionally, as shown in FIG. 3, in many cases, a piping structure having a heat insulating material 10 made of a ceramic fiber layer having a liner 8 mounted therein is adopted. This structure is a heat insulating material 10
Although the liner 8 is attached to prevent the scattering of the liner to increase the airtightness of the heat insulating material portion, the slide gap 11 is provided to absorb the thermal expansion of the liner 8. Further, since the ceramic fiber layer, which is the heat insulating material 10, has a large amount of space inside, there is a high temperature in the direction of the heat insulating material 10 from the slide gap 11.
High-pressure exhaust gas 13 flows in. On the other hand, the temperature of the exhaust gas flowing through the piping changes with the load change of the boiler, and the temperature change from the low temperature to the high temperature range occurs by interposing the dew point temperature of the corrosive oxides in the exhaust gas. Since the temperature is lower than the dew point temperature of the corrosive oxide, dew condensation occurs and the corrosive oxide corrodes the inner surface of the outer pipe 7. On the other hand, the internal adiabatic gas piping device of the present invention, as shown in FIG. 1, has a corrosive oxide in the exhaust gas piping system at a dew point temperature or less,
For example, a control air source 3 having a pressure higher than the exhaust gas pressure
The air pipe 5 for purging which is divided from the above is arranged. The structure of the exhaust gas pipe in which the purging air pipe 5 is arranged is shown in FIG. In the operation of the boiler, the exhaust gas temperature rises when the load rises, so there is no problem of dew condensation due to the temperature decrease of corrosive oxides in the exhaust gas. Since there is a temperature range below the dew point temperature of the corrosive oxide, the problem of dew condensation occurs. Therefore, from the time before the corrosive oxides in the exhaust gas when the boiler load drops to the dew point temperature to the time when the exhaust gas stops flowing after the boiler is stopped, the high temperature, high pressure exhaust gas pipe 9 provided in the purge air pipe 9 If it flows in the heat insulating material 10 of the pipe 7 (high temperature, high pressure exhaust gas pipe 4), as shown in FIG. 2, the corrosive oxides stagnating in the heat insulating material 10 inside the pipe flow to the exhaust gas passage inside the pipe. Therefore, the corrosive oxide in the portion of the heat insulating material 10 is purged, so that the problem of corrosiveness of the outer pipe 7 is solved. Further, in a piping structure in which the internal fluid contains a corrosive component and a heat insulating material with many gaps inside is pressed by a liner material, the present invention can be applied to a piping or duct in which corrosion of the inner surface of the outer tube becomes a problem. Is possible.

[0007]

According to the gas pipe apparatus of the internal heat insulation type and the method of preventing corrosion thereof according to the first and second aspects of the present invention, the heat insulating material layer having a large gap is pressed into the inside of the outer tube by the liner material. In the internal insulation type piping structure, high temperature,
When the high-pressure internal fluid contains a corrosive component, it is possible to prevent the corrosive component from entering and staying in the heat insulating material layer on the inner surface of the outer pipe, and to effectively prevent the above-mentioned corrosive component from falling below the dew point temperature to form dew condensation. Therefore, it is not necessary to consider an expensive corrosion-resistant outer pipe, an inexpensive internally adiabatic gas piping device can be realized, and the reliability against corrosion is improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of an internal adiabatic gas piping device exemplified in an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a cross-sectional structure of an internal adiabatic gas pipe illustrated in an embodiment of the present invention.

FIG. 3 is a schematic diagram showing a cross-sectional structure of a conventional internal adiabatic gas pipe.

[Explanation of symbols]

 1 ... Boiler 2 ... Gas Turbine 3 ... Control Air Source 4 ... High Temperature / High Pressure Exhaust Gas Pipe 5 ... Purge Air Pipe 6 ... Stop Valve (Stop Valve) 7 ... External Pipe 8 ... Liner 9 ... Purge Air Pipe 10 ... Insulation Material (ceramic fiber layer) 11 ... Liner sliding gap 12 ... Purge gas 13 ... Exhaust gas

Claims (3)

[Claims] 1. A high-temperature, high-pressure internal adiabatic gas pipe apparatus having a structure in which a heat insulating material layer is provided on the inner surface of the pipe, wherein a gas containing a corrosive component accumulated in the heat insulating material layer of the pipe is removed. An internal adiabatic exhaust gas piping device, characterized in that at least one purge gas pipe is connected to the outer surface of the pipe. 2. A method for preventing corrosion of a high-temperature, high-pressure internal adiabatic gas piping device having a structure in which a heat insulating material layer is provided on the inner surface of a pipe, the gas containing a corrosive gas flowing inside the pipe. At a temperature equal to or higher than the dew point temperature of the pipe, a purge gas for removing the exhaust gas staying in the portion of the heat insulating material layer on the inner surface of the pipe is fed at a predetermined pressure from the outer surface of the pipe to prevent dew condensation of the exhaust gas. Internal insulation type gas pipe corrosion prevention method characterized by 3. The method for preventing corrosion of an internal adiabatic gas pipe according to claim 2, wherein the purge gas is dry air, nitrogen or an inert gas.