JP2711822B2 - Exhaust gas cooling system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a newly developed exhaust gas cooling system.

[0002]

2. Description of the Related Art For example, a boiler 1 using petroleum, coal, LNG, or the like as a fuel in a plant such as a power plant facility.
As shown in FIG. 10, the exhaust gas is subjected to denitration 2, desulfurization 3, dust collection 4, and discharged from a chimney 5. In the meantime, the exhaust heat is collected by the air preheater 6 etc.
Even a power plant with high energy use efficiency has a chimney 5
The temperature of exhaust gas discharged from is as high as 95 to 120 ° C. In the figure, reference numeral 7 denotes a blower fan. As described above, the high-temperature exhaust gas discharged from the chimney 5 contains water while being unsaturated, and when this is discharged into the atmosphere, it condenses to generate a large amount of white smoke. This large amount of white smoke is a cause of local residents' complaints such as environmental destruction.
The height is made higher than necessary, such as ~ 200 m, so that high-temperature exhaust gas is discharged to high places. On the other hand, increasing the height of the chimney 5 impairs the scenery of the area, and in recent years there are many cases where the chimney is surrounded by a highly designed structure as a measure against the scenery, but in any case, the cost is high and extra costs are unnecessarily increased. Design and economic inconvenience.

As a solution to the above-mentioned problem, for example, an exhaust gas energy recovery apparatus has been proposed as disclosed in Japanese Patent Application Laid-Open No. 54-76716. As shown in FIG. 11, a heat exchanger 1 for recovering exhaust gas energy provided in a pump 11 and an exhaust pipe 13 of a diesel engine 12 as shown in FIG.
4, a simple closed loop including a heat exchanger 15 for extracting thermal energy is provided to remove the energy from the exhaust gas and cool the exhaust gas. Therefore, the exhaust gas temperature is considerably higher than normal temperature, and the water removal is not sufficient.

It is an object of the present invention to provide a flue gas cooling system capable of preventing the generation of white smoke when exhaust gas is discharged by condensing and separating water in the flue gas and achieving a low or no chimney stack.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide an exhaust gas flue through a closed cooling loop consisting of a liquid pressurization step, a gasification step, a gas expansion step, a heating and heating step, a gas compression step, and a cooling and liquefaction step. The cooling and liquefaction step and the gasification step receive heat from each other, receive heat from the exhaust gas in the heating and heating step, and release heat to the external low-temperature heat sink in the cooling and liquefaction step. Is done. The above object is achieved by the exhaust gas cooling system according to claim 1, wherein the gasification step is performed by obtaining additional high-temperature heat outside the cooling closed loop to promote gasification. The above purpose is
The exhaust gas cooling system according to claim 1 or 2, wherein the gas expansion step is performed by a gas expansion turbine, and the gas compression step is performed by a gas compressor. The above object is achieved by an exhaust gas cooling system according to claim 3, which connects the gas expansion turbine and a gas compressor. The above object is achieved by supplementarily applying power to the gas compressor. The above object is achieved by an exhaust gas cooling system according to claim 1 or 2, wherein the gas expansion step is performed by a diffuser, and the gas compression step is performed by a diffuser.

[0006]

Embodiments of the present invention will be described in detail with reference to the drawings. 1 is a cross-sectional view showing a flue of exhaust gas from a dust collection, denitration, and desulfurization coal, FIG. 2 is an explanatory diagram of an exhaust gas cooling system in which a cooling closed loop is provided in the flue, FIG. FIG. 5 is an explanatory view of an exhaust gas cooling system which obtains separate high-temperature heat outside the cooling closed loop to promote gasification, FIG. 5 is an explanatory view of an exhaust gas cooling system showing another embodiment of FIG. 4, and FIG. FIG. 7 is an explanatory diagram of an exhaust gas cooling system in which a turbine and a gas compressor are connected, FIG. 7 is an explanatory diagram of an exhaust gas cooling system in which auxiliary power is applied to the gas compressor, and FIG. FIG. 9 is an explanatory diagram of an exhaust gas cooling system in which an exhaust gas expansion step is performed by a diffuser and a gas compression step is performed by a diffuser.

As an example of conventional exhaust gas conditions, referring to exhaust gas from a power plant, a flue 2 such as a duct or pipe shown in FIG.
Exhaust gas passing through the exhaust gas in the direction of the arrow and discharged into the atmosphere from a chimney (not shown) has already been subjected to dust collection, denitration, and desulfurization as described above.
The temperature is still high at ~ 120 ° C and the amount of water vapor is quite high. That is, water vapor is saturated at 40 ° C. and 50 ° C. even if the relative humidity is not high at the exhaust gas temperature.
Water vapor condenses into large amounts of white smoke when released to the atmosphere from a 150-200 m-high stack above the ground in winter. In the present invention, as shown in FIG. 2, a cooling closed loop A using seawater or the like as a heat radiation heat sink is interposed in the flue 21 to cool, for example, 100 ° C. exhaust gas to about 10 ° C. to reduce water vapor in the exhaust gas. Even if this exhaust gas is released into the atmosphere by condensation, it does not produce white smoke, or the amount of white smoke can be reduced and the height of the chimney can be reduced. It makes it possible to use it. As described above, the technical advance of the cooling closed loop A in the present invention is to use a normal-temperature heat sink such as seawater to generate cold heat at a lower temperature than seawater. Instead of using a gas compressor that requires a large amount of mechanical energy at the time of increasing the pressure as in the case of the Rankine cycle method, that is, a gas compressor with low energy efficiency, a liquid pressurizing pump is used.

Next, a cooling closed loop A will be described with reference to FIGS.
To explain in detail, the cooling closed loop A has a pressurized state.
Heat is radiated to the heat sink 22 at room temperature such as seawater to liquefy,
A refrigerant 23 gasified at the temperature of the exhaust gas is flowing. cold
The medium 23 is, for example, 30 ° C. and 12 kg / cm.^TwoLiquefy in
Propane or a similar fluid may be used. (A) Liquid pressurization step Refrigerant 23 is liquid in state a and also serves as a buffer tank.
(Ta, Pa), pressurized
Pump (liquid pressure pump) P ₁The pressure is increased by Pb
It is. (B) Gasification step Next, the refrigerant 23 is led to the heat exchanger (evaporator) 25,
Heat energy (Tc) is obtained from heat medium x and heat medium y.
Is changed to C. Here, the heat medium x, y is a heat exchanger (condensation)
Around the condenser 26 in a loop, and the heat energy of the condenser 26
Lugie (Tf) is transported to the evaporator 25. Heat medium x, y
May be the same or different, and depending on the design, the same heat transfer
A transmission loop may be used. The shape of the heat exchangers 25 and 26
It doesn't matter. Also, energy compensation for gasification c
Is required, a heat source is obtained from outside the closed cooling loop A.
Supply of thermal energy (Tc) to the evaporator 25
Can also. When this design example is shown, as shown in FIG.
Thermal energy was supplied from an external heat source (not shown)
As shown in Fig. 5, a part of the heat energy of the exhaust gas is divided
Supply. (C) Gas expansion step The gasified refrigerant 23 (Pb, Tc) is converted into a gas expansion target.
The output (Hc−Hd) is led to the bin 27 and is used as external work.
And reaches state d. The refrigerant 23 has an output (Hc-H
The work of d) lowers the temperature to Td, and the flue 21
Exhaust gas (T ° C.) can be sufficiently cooled. (D) Heating / heating step Tb is lower in temperature than the external heat sink 22 in the natural world.
100 ° C exhaust gas at room temperature or below room temperature
For example, it can be cooled sufficiently to about 10 ° C. That is, state d
Refrigerant (mainly gas, part of liquid) 23 is led into flue 21
Then, the exhaust gas is cooled by heat exchange 28 with the exhaust gas (for example, 10
0 ° C. → 10 ° C.), while the temperature of the low-temperature Td refrigerant 23 is 100 ° C.
Temperature rises to a high temperature of, for example, Te = 90 ° C.
It is. (E) Gas compression step As shown by Pe and Te, the refrigerant 23 in the state e
It is led to the compressor 29 and is equal to the state f (Pf, Tf).
It is tropically compressed to obtain a high temperature Tf. The gas inflator described above
If the output (Hc−Hd) of the bin 27 is used, the compression work
(Hf-He)
Can be. Here, Te is, for example, an exhaust gas temperature of 100 ° C.
It can be higher than T ° C. As shown in Fig. 6 depending on the design
, A gas expansion turbine 27 and a gas compressor 29 are connected,
Mechanical energy loss can be minimized. pressure
Pf is radiated to the external low-temperature heat sink 22 in a later process (state
g → state a), and there is no hindrance for the refrigerant 23 to liquefy.
Is set. For example, using seawater as heat sink
If it is, the temperature Ta from the state g to the state a is small.
At least at 30 ° C. and if the refrigerant 23 is propane
Pf ≧ 11.5Kg / cm^TwoSet to. In this case, P
The compression work up to f is greater than the expansion output (Hc-Hd)
If it becomes larger, the auxiliary power 30 is supplied to the gas compressor 29.
It can also be provided. (FIG. 7) (f) Cooling and liquefaction step The refrigerant 23 whose pressure has been increased and its temperature has been increased is transferred to a heat exchanger (condenser) 26.
And the heat medium x, y for heat transport to the evaporator 25 described above.
And cool to the state g while radiating heat.
Liquid in state a while radiating heat to low temperature heat sink 22
And flows into the original vessel 24.

The gas expansion and gas compression in the present invention are
As shown in FIG. 9, it can be performed by the fuser 32 and the diffuser 33. By setting the gas flow velocity in the constricted portion to a subsonic speed (Mach 1 or less), the pressure in the constricted portion decreases and drops to Pd ', thereby obtaining an intended low temperature Td'. After that, the temperature is raised and raised by the diffuser 33 to obtain Pe 'and Te'. The effect as a process is the same. PdPe, TdTe and Pd'Pe ', Td'Te' can have different values.

On the other hand, in the flue 21 in which the exhaust gas flows, (a) in order to compensate for the pressure loss due to the heat exchange equipment 31 when the exhaust gas is cooled and the reduction of the draft due to the lower stratification of the chimney, Blower fan 34 as shown
May be added as appropriate. (B) The flue 2
It is desirable to provide a water collecting pit 35 at the lower part of 1. In principle, the water collecting pit 35 is provided below the heat exchange facility 31 or slightly downstream of the blower fan 34. (C) It is desirable to provide a cover plate (not shown) having a porous structure in the water collecting pit 35 so that the water collecting pit 35 does not become a flow resistance of the exhaust gas. (D) A demister 36 may be provided downstream of the flue. (E) The cross section of the heat exchange facility portion of the flue may be changed. (F) The flue provided with the water collecting pit 35 may be bent downward to facilitate water collecting. (G) The water collecting pit 35 may be partitioned into a plurality of pits along the flow of exhaust gas so that water can be collected at each water temperature. (H) The collected water is discharged by a pump and adjusted for water quality and discharged according to environmental regulations, or adjusted for water quality and used for industrial water. (I) The exhaust gas that has been cooled and dewatered is appropriately pressurized with a draft fan or the like and released into the atmosphere from a conventional chimney, or released into the atmosphere from a lower stack, or sealed with a water seal as shown in FIG. Release it.

[0011]

According to the configuration of the present invention as described above,
An effect like a joint is obtained. (A) By interposing an exhaust gas cooling system that radiates heat to a low-temperature heat sink below normal temperature, the exhaust gas temperature is sufficiently reduced to condense and remove moisture in the exhaust gas, and white smoke is generated when the exhaust gas is released into the atmosphere. Can be prevented. This makes it possible to reduce the height of the chimney or to reduce the height of the chimney close to the ground level, so that plant equipment can be installed without damaging the landscape. (B) Condensed water can be recovered and used for industrial water and boiler water.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a flue of exhaust gas from a dust collection, denitration, and desulfurization coal.

FIG. 2 is an explanatory diagram of an exhaust gas cooling system in which a cooling closed loop is interposed in a flue.

FIG. 3 is a diagram illustrating the principle of a closed cooling loop.

FIG. 4 is an explanatory diagram of an exhaust gas cooling system configured to obtain additional high-temperature heat outside a cooling closed loop to promote gasification.

FIG. 5 is an explanatory view of an exhaust gas cooling system showing another embodiment of FIG. 4;

FIG. 6 is an explanatory diagram of an exhaust gas cooling system in which a gas expansion turbine and a gas compressor are connected.

FIG. 7 is an explanatory diagram of an exhaust gas cooling system in which auxiliary power is applied to a gas compressor.

FIG. 8 is an explanatory diagram of an exhaust gas cooling system in which an exhaust gas discharge end of a flue is sealed with water.

FIG. 9 is an explanatory diagram of an exhaust gas cooling system in which an exhaust gas expansion step is performed by a diffuser and a gas compression step is performed by a diffuser.

FIG. 10 is an explanatory diagram of a conventional boiler exhaust gas treatment plant.

FIG. 11 is an explanatory view of a conventional exhaust gas energy recovery device.

[Explanation of symbols]

 A Cooling closed loop a State b Pressure c Gasification d State e State f State g State x Heat medium y Heat medium 21 Flue 22 Heat sink 23 Refrigerant 24 Vessel 25 Heat exchanger (evaporator) 26 Heat exchanger (Condenser) 27 Gas expansion turbine 28 Heat exchanger 29 Gas compressor 30 Auxiliary power 31 Heat exchange equipment 32 Efuser 33 Diffuser 34 Blower fan 35 Water collecting pit 36 Demister

Claims (6)

(57) [Claims] 1. A cooling closed loop comprising a liquid pressurization step, a gasification step, a gas expansion step, a heating and heating step, a gas compression step, and a cooling and liquefaction step is interposed in the flue of the exhaust gas. An exhaust gas cooling system characterized in that heat is mutually transferred in a gasification step, heat is received from exhaust gas in a heating and heating step, and heat is released to an external low-temperature heat sink in a cooling and liquefaction step. 2. The exhaust gas cooling system according to claim 1, wherein in the gasification step, separate high-temperature heat outside the cooling closed loop is obtained to promote gasification. 3. The exhaust gas cooling system according to claim 1, wherein the gas expansion step is performed by a gas expansion turbine, and the gas compression step is performed by a gas compressor. 4. The exhaust gas cooling system according to claim 3, wherein the gas expansion turbine and a gas compressor are connected. 5. The exhaust gas cooling system according to claim 3, wherein power is additionally applied to the gas compressor. 6. The exhaust gas cooling system according to claim 1, wherein the gas expansion step is performed by a diffuser, and the gas compression step is performed by a diffuser.