JP4606651B2 - Smoke removal device for SO3 - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides SO_ThreeIn particular, a SOFC in flue gas from a furnace using sulfur-containing fuel._ThreeSO to remove minute (sulfur trioxide)_ThreeThe present invention relates to a minute removing device.
[0002]
[Prior art]
In furnaces such as boilers that use sulfur-containing fuels such as heavy oil, sulfur dioxide (SO₂) Is generated. For this reason, in furnaces that use heavy oil, the flue gas is treated with a desulfurizer before the flue gas is released into the atmosphere, and SO₂To be removed.
[0003]
However, SO in the flue gas₂Part of this is further oxidized in the boiler and denitration equipment to form sulfur trioxide (SO_Three). SO_ThreePasses through an air preheater or the like, and the smoke emission temperature decreases. For example, when the temperature falls below about 300 ° C., it reacts with the moisture in the smoke and SO2_Three+ H₂O → H₂SO_FourH₂SO_FourGenerate gas. This H₂SO_FourThe gas produces fine sulfuric acid mist when the flue gas temperature falls below the dew point of sulfuric acid. When using a desulfurization device, especially a wet desulfurization device, the flue gas temperature drops below the sulfuric acid dew point temperature when passing through the desulfurization device.₂SO_FourAll the gas becomes sulfuric acid mist, but since the removal rate of sulfuric acid mist in the wet desulfurization apparatus is low, the flue gas at the outlet of the desulfurization apparatus contains a relatively large amount of sulfuric acid mist in a heavy oil-fired boiler or the like. When sulfuric acid mist is discharged into the atmosphere, it produces purple smoke and causes air pollution as an acid drop.
[0004]
Generally, a wet electrostatic precipitator (hereinafter referred to as “wet EP”) is used to remove sulfuric acid mist in the flue gas. In the wet EP, a water film is formed on an electrode by spraying water or an alkaline liquid onto a dust collection electrode of an electric dust collector, and the collected sulfuric acid mist is washed and removed from the electrode.
In addition, SO is used for flue gas without using wet EP._ThreeAn apparatus that prevents the formation of sulfuric acid mist by introducing a neutralizing agent has been devised.
[0005]
An example of this type of apparatus is described in Japanese Patent Application Laid-Open No. 2000-317260. The apparatus of the publication discloses SO in the flue gas at a location where the flue gas temperature is relatively high on the upstream side of the desulfurizer._ThreeBy introducing alkali powder such as calcium carbonate as a neutralizing agent, SO_ThreeHas been removed. That is, calcium carbonate (CaCO) introduced into the flue gas._Three) Is SO in flue gas_ThreeOr H₂SO_FourReacts with CaSO_FourEven if the smoke emission temperature subsequently decreases,₂SO_FourMist is not generated. Calcium carbonate and SO_ThreeCaCO produced by reaction with_ThreeSince is not corrosive, it can be easily collected by an ordinary electrostatic precipitator without using wet EP. As a result, the apparatus disclosed in this publication prevents the release of sulfuric acid mist to the atmosphere without using wet EP.
[0006]
[Problems to be solved by the invention]
However, in boilers, etc., the SO in exhaust fumes is affected by load fluctuations, sulfur concentration in the fuel used, and boiler contamination._ThreeThe amount varies greatly. For this reason, when removing sulfuric acid mist using wet EP, the maximum processing capacity (collection capacity) of wet EP is the maximum SO after considering various conditions._ThreeIt is necessary to set a large value with a margin for the generation amount. In addition, since wet EP usually requires a large installation area, if the processing capacity of wet EP is increased, the apparatus cost and construction cost are greatly increased, and there is a problem that the cost of the entire boiler plant increases.
[0007]
Further, as in the apparatus of the above-mentioned JP 2000-317260 A, SO such as alkali powder is disposed upstream of the desulfurization apparatus._ThreeAlthough the method of adding a neutralizing agent does not cause an increase in construction cost due to an increase in the processing capacity of wet EP, it will eventually be SO._ThreeCaSO after neutralization_FourIn order to remove such particles, a dust collector is required. Furthermore, in the apparatus of the publication, it is necessary to always add the neutralizing agent to the flue gas during the plant operation, and there is a problem that the consumption of the relatively expensive neutralizing agent becomes large and the plant operating cost increases.
[0008]
In view of the above problems, the present invention provides SO in flue gas flowing into wet EP without using a neutralizing agent or the like._ThreeBy removing a certain amount of NO in advance, the load of wet EP can be greatly reduced, and the increase in equipment cost and construction cost due to increased processing capacity of wet EP can be prevented._ThreeAn object is to provide a minute removal device.
[0009]
[Means for Solving the Problems]
  According to the first aspect of the present invention, the flue gas passage for guiding the flue gas from the furnace that burns fuel containing sulfur to the chimney, and the SO disposed in the flue gas are disposed on the flue gas passage.₂A wet desulfurization apparatus for removing the components, and an upstream side of the wet desulfurization apparatus on the flue gas passage to cool the flue gas and remove SO_ThreeThe component is liquid sulfuric acid (H₂SO_Four) To condense and separate and remove from the flue gas_ThreeAnd a separation deviceAnd the SO _Three The separator includes a heat exchanger that cools the flue gas by exchanging heat between the cooling water and the flue gas through the heat transfer surface, and a liquid H that condenses on the flue gas side surface of the heat transfer surface during the passage of the flue gas. ₂ SO _Four And a washing device for washing with waterSO of flue gas_ThreeA minute removal device is provided.
[0010]
  That is, according to the first aspect of the present invention, the flue gas is cooled to the upstream side of the wet desulfurization apparatus and the flue gas is discharged from the flue gas._ThreeSO to separate and remove components_ThreeA separation device is provided. As mentioned above, SO in flue gas_ThreeReacts with moisture in the flue gas when the temperature drops below a certain level (for example, about 300 ° C.).₂SO_FourIs generated. This H₂SO_FourAs for the gas, smoke temperature decreases further and H₂SO_FourWhen the dew point is below the gas, it condenses and becomes liquid H₂SO_Fourbecome. In the present invention, SO_ThreeBy forcibly cooling the flue gas containing_ThreeLiquid H₂SO_FourSeparated from flue gas by condensation. As a result, the SO in the flue gas_ThreeA significant part of SO_ThreeH with separator₂SO_FourIt can be removed in the form of a liquid, and the amount of sulfuric acid mist remaining in the flue gas at the outlet of the wet desulfurization apparatus is greatly reduced. For this reason, it is possible to prevent the release of sulfuric acid mist to the atmosphere without providing a wet EP at the outlet of the wet desulfurization apparatus, and without using a neutralizing agent or the like that causes an increase in plant operating costs. An increase in apparatus cost due to the installation of EP can be prevented.
  Also, SO _Three The separator uses a heat exchanger that uses cooling water to lower the smoke emission temperature. By reducing the flue gas temperature using a heat exchanger, ₂ SO _Four Condensation occurs on the heat transfer surface in contact with the flue gas, and the generated liquid H ₂ SO _Four Will adhere to the heat transfer surface. Liquid H adhering to the heat transfer surface ₂ SO _Four Can be easily removed by washing the heat transfer surface during operation using washing water. Thereby, in the present invention, the SO in the flue gas is simply and inexpensively. _Three H ₂ SO _Four It can be removed in the form of an aqueous solution.
[0011]
According to invention of Claim 2, it is arrange | positioned further in the said wet desulfurization apparatus downstream on the said flue gas passage, and the sulfuric acid (H₂SO_Four2) The flue gas SO of claim 1 comprising a wet electrostatic precipitator that removes mist._ThreeA minute removal device is provided.
[0012]
That is, in the invention of claim 2, wet EP is further arranged at the outlet of the wet desulfurization apparatus. Thereby, the sulfuric acid mist remaining in the flue gas at the outlet of the wet desulfurization apparatus is removed by the wet EP, and the amount of sulfuric acid mist released to the atmosphere can be greatly reduced. In addition, the SO in the flue gas flowing into the wet desulfurizer_ThreeMinute is SO_ThreeSince a considerable amount is removed by the separation device, the concentration of sulfuric acid mist in the flue gas at the outlet of the wet desulfurizer is greatly reduced. Thus, the exhaust gas downstream of the wet desulfurizer using wet EP is used. Even when removing residual sulfuric acid mist, SO in wet EP_ThreeThe removal efficiency can be greatly reduced. Thereby, it becomes possible to set the processing capacity of wet EP low and to reduce apparatus cost, without using the neutralizing agent etc. which cause the increase in plant operation cost.
[0015]
  Claim3According to the invention described in the above, the wet desulfurization apparatus includes an absorption tower through which flue gas passes, and an SO in the absorption tower.₂SO in the flue gas by spraying the absorbent solution₂And an absorbent circulation device that absorbs and recovers the water in the aqueous solution, and the cleaning device is configured to clean the heat transfer surface after cleaning the H₂SO_FourThe waste water containing is supplied as make-up water to the absorbent circulation device.1Exhaust SO_ThreeA minute removal device is provided.
[0016]
  That is, the claim3In the present invention, H after the heat transfer surface of the heat exchanger of claim 2 is washed₂SO_FourThe wash water containing is supplied to the absorbent circulation device of the wet desulfurization device and used as makeup water. In the absorption tower of wet desulfurization equipment, SO is used for flue gas.₂The SO in the flue gas is sprayed with an aqueous solution of the absorbent.₂In this process, the flue gas is saturated with water vapor, and a considerable amount of water is carried away from the absorption tower along with the flue gas. Therefore, it is necessary to constantly supply water to the circulation device. Therefore, the consumption of makeup water can be reduced by supplying cleaning water for the heat transfer surface to the absorbent circulation device. H contained in the wash water₂SO_FourIs SO₂Since it neutralizes by reacting with the absorbent, the present invention has an advantage that it is not necessary to provide a separate water treatment device for treating the washing water.
[0017]
  Claim4According to the invention described in the above, the heat exchanger includes a shell-and-tube heat exchange provided with a casing through which flue gas passes and a tube disposed inside the casing and through which cooling water passes. The inner surface of the casing and the outer surface of the tube are made of a corrosion-resistant material or coated with a corrosion-resistant material.3Exhaust SO_ThreeA minute removal device is provided.
[0018]
  That is, the claim4In the invention of SO_ThreeThe heat exchanger used in the separation device is a shell-and-tube heat exchanger with a simple configuration. Further, the inner surface of the casing in contact with the flue gas and the outer surface of the tube as the heat transfer surface are made of a corrosion-resistant material having chemical resistance, such as stainless steel, or PTFE (polytetrafluoroethylene) or PFA, for example. It is coated with a corrosion resistant material having chemical resistance such as (tetrafluoroethylene perchloroalkyl vinyl ether copolymer). As a result, H on the outer surface of the tube and the inner surface of the casing₂SO_FourCorrosion due to corrosion is prevented and the reliability of the device is improved.
[0019]
  Claim5According to the invention described in the above, the wet desulfurization apparatus further includes a cooling tower that sprays water during flue gas to lower the flue gas temperature flowing into the absorption tower, and the SO_ThreeThe separation device is disposed at the smoke exhaust inlet portion at the upper part of the cooling tower, and the cleaning device supplies the waste water after the heat transfer surface cleaning into the cooling tower and absorbs the absorption tower together with the water sprayed in the cooling tower. Supplying as replenishment water to the agent circulation device3Or4SOx for flue gas as described in any one of_ThreeA minute removal device is provided.
[0020]
  That is, the claim5In this invention, the temperature of the flue gas flowing into the absorption tower of the desulfurization apparatus is lowered to reduce the SO₂A cooling tower is provided to improve the absorption efficiency. In the cooling tower, the flue gas flows into the tower from the flue gas inlet at the upper part of the cooling tower, and the temperature decreases due to evaporation of water sprayed into the flue gas while flowing downward in the tower. At this time, since a considerable amount of sprayed water evaporates and is removed from the cooling tower along with smoke, it is necessary to replenish the cooling tower with water corresponding to the amount of evaporation. In the present invention, SO is provided at the flue gas inlet at the top of the cooling tower._ThreeSince the separation device is provided, the temperature of the flue gas flowing into the cooling tower is lowered, and the amount of water evaporated in the cooling tower is reduced. Also, SO_ThreeSince the separation device is arranged in the upper part of the cooling tower, the water after the heat transfer surface cleaning falls into the cooling tower by gravity, and the sprayed water and the SO tower of the absorption tower from the lower part of the cooling tower.₂The absorbent circulation device is replenished. For this reason, it is not necessary to separately provide a transfer pump or the like for supplying cleaning water to the absorbent circulation device.
[0021]
  Claim6According to the invention described in claim 3, boiler feed water is used as cooling water for the heat exchanger, and the heat of the flue gas is recovered in the boiler feed water.1, 3, 4, or 5SOx for flue gas as described in any one of_ThreeA minute removal device is provided.
[0022]
  That is, the claim6In the invention of SO_ThreeBoiler feed water is used as cooling water for the heat exchanger of the separator. As a result, SO_ThreeIt is possible to use the heat taken from the flue gas to separate the boiler as the remaining heat of the boiler feed water, and the fuel consumption of the boiler furnace is greatly reduced.
[0023]
  Claim7According to the invention described in the above, the SO_ThreeThe gas / gas heater which heat-exchanges the flue gas after passing the said wet-type electrostatic precipitator and the flue gas discharged | emitted from a furnace is provided in the flue gas passage of the upstream side of a separator.6SOx for flue gas as described in any one of_ThreeA minute removal device is provided.
[0024]
  That is, the claim7In the invention of SO_ThreeA gas / gas heater for exchanging heat between the flue gas and the flue gas after passing through the wet electrostatic precipitator is provided on the upstream side of the separator. It is possible to prevent the generation of white smoke by raising the temperature of the flue gas emitted from the chimney by exchanging heat between the flue gas at the outlet of the wet electrostatic precipitator and the flue gas discharged from the furnace using a gas heater. it can.
[0025]
  Claim8According to the invention described in claim 1, in the upstream side flue gas passage of the existing wet desulfurization apparatus,7The SO described in any one of_ThreeBy installing a new separator, SO_ThreeSmoke exhaust SO that constitutes a minute removal device_ThreeA method of making a minute removal device is provided.
[0026]
  That is, the claim8In the present invention, by modifying an existing boiler plant having only a wet desulfurization apparatus or a wet desulfurization apparatus and a wet electrostatic precipitator, SO_ThreeProduces a minute removal device. From claim 17SO_ThreeThe separation apparatus can be applied to any type of apparatus as long as it is a wet desulfurization apparatus. Therefore, as in the present invention, the existing wet desulfurization apparatus is used to perform SO_ThreeBy manufacturing a minute removal device, SO_ThreeIt is possible to manufacture a minute removing device. In boiler plants that have only wet desulfurization equipment, SO_ThreeIt is also possible to newly install a wet electrostatic precipitator together with the separator.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
In the following, embodiments of the present invention will be described._ThreeA case where the flue gas treatment is performed using only the wet desulfurization apparatus without providing the separation apparatus or the wet EP will be described.
FIG. 5A is a diagram for explaining a schematic configuration of the apparatus when performing the flue gas treatment using only the wet desulfurization apparatus.
[0028]
In FIG. 5 (A), 1 is a furnace such as a boiler, 3 is a flue through which combustion exhaust gas of the boiler 1 flows, and 7 is SO in exhaust gas.₂This is a desulfurization device that removes water. The desulfurization apparatus 7 is a generally known type of wet desulfurization apparatus (for example, SO such as calcium hydroxide and calcium carbonate).₂An aqueous solution of absorbent and flue gas are brought into contact with CaSO_FourSO in flue gas in the form of₂That removes SO2 in flue gas using magnesium hydroxide or sodium hydroxide₂MgSO_FourOr Na₂SO_FourTo be removed). SO in the desulfurizer 7₂The flue gas from which the gas is removed passes through the downstream flue 9 and is emitted from the chimney 11 to the atmosphere.
[0029]
The combustion gas (smoke) generated by the combustion of heavy oil in the boiler 1 passes through the air preheater 5 provided in the flue 3 and exchanges heat with the combustion air supplied to the boiler. (Not shown) flows through the flue 3 and is supplied to the desulfurizer 7.
If cheap heavy oil containing a relatively high sulfur content (for example, about 2% or more) is used as the fuel, a large amount of SO₂And a part of it is further oxidized to form SO._Threebecome. SO_ThreeWhen the smoke emission temperature decreases due to passage of the air preheater 5 or the like, for example, a part of the smoke reacts with the moisture in the smoke to produce gaseous or fine mist sulfuric acid (H₂SO_Four) Is generated.
[0030]
Therefore, SO in the flue gas supplied to the wet desulfurization apparatus 7 is₂Not only sulfuric acid gas and mist are included. Since the flue gas temperature drops below the sulfuric acid dew point temperature when passing through the wet desulfurization apparatus, all sulfuric acid gas in the flue gas becomes sulfuric acid mist. In the wet desulfurization unit 7, SO₂Is removed with high efficiency, but since the removal rate of sulfuric acid mist in the wet desulfurization apparatus is low, the concentration of sulfuric acid mist in the flue gas at the outlet of the wet desulfurization apparatus 7 is usually a relatively high value.
[0031]
FIG. 5 (B) shows the smoke emission temperature and SO in the smoke emission at the locations indicated by I to III in FIG. 5 (A).₂Concentration and SO_ThreeThe concentration is shown. In FIG. 5 (B), the SO in the smoke is exhausted._ThreeAnd gas and mist H₂SO_FourThe total concentration of SO_ThreeExpressed as concentration.
As shown in FIG. 5 (B), at the outlet (II) of the air preheater 5 (that is, the inlet of the wet desulfurization device 7), the SO in the exhaust gas is exhausted._ThreeConcentration is about 60ppm, SO₂The concentration is as high as about 2000 ppm.
[0032]
At the outlet (III) of the wet desulfurization unit 7, SO₂Most of the water is removed by the desulfurization unit, and SO₂The concentration drops to about 40 ppm, but SO_ThreeThe concentration does not decrease so much, and is a relatively high value of 48 ppm in the example of FIG.
When flue gas containing a relatively high concentration of sulfuric acid mist is directly discharged from the chimney 11 to the atmosphere, fine sulfuric acid mist forms purple smoke at the smoke outlet, and a so-called “purple smoke flickering” phenomenon occurs. In addition, when sulfuric acid mist is released to the atmosphere, there is a problem that it becomes an acid fallout and falls to the surroundings.
[0033]
Therefore, in general, when the wet desulfurization apparatus 7 is used, it is common to collect sulfuric acid mist in the flue gas using the wet EP before releasing the flue gas into the atmosphere.
6A shows the configuration of the apparatus when wet EP indicated by reference numeral 8 is added to the apparatus of FIG. 5A, and FIG. 6B shows the exhaust at points I to IV in FIG. 6A. Smoke temperature, SO₂Concentration and SO_ThreeThe concentration is shown. In FIG. 6 (B), the numerical values from I to III are the same as those in FIG. 5 (B).
[0034]
In general, in order to prevent the generation of purple smoke from the chimney, the SO in the flue gas at the inlet of the chimney 11_ThreeIt is necessary to reduce the concentration to about 2 ppm. Thus, in the example of FIG. 6, the SO at the wet EP8 outlet (IV)._ThreeThe concentration (in this case, sulfuric acid mist concentration) needs to be 2 ppm. That is, SO in the flue gas by wet EP8_ThreeIt is necessary to reduce the concentration from 48 ppm to 2 ppm, and SO required for wet EP8_ThreeThe removal efficiency η is η = (48−2) / 48≈96%.
[0035]
The wet EP is an electrostatic precipitator of a type in which the collected sulfuric acid mist is washed away from the electrode by spraying alkaline liquid or water onto the dust collecting electrode. The sulfuric acid mist in the flue gas is a submicron particle with a very small particle size. In order to increase the removal efficiency of sulfuric acid mist in wet EP to about 96 percent, wet EP is divided into two or more sections in series. Need to be placed. For this reason, in the structure which removes sulfuric acid mist using wet EP like FIG. 6, there exists a problem which the construction cost of the whole plant increases by the enlargement of wet EP, the increase in installation area, etc.
[0036]
The present invention relates to SO described below._ThreeUsing the separation device, the SO in the flue gas upstream of the wet desulfurization device 7_ThreeBy removing a substantial part of the above, an increase in cost due to the increase in the size of wet EP is prevented.
[0037]
FIG. 1 is a view similar to FIGS. 5 and 6 showing a configuration of an embodiment of the present invention, and the same reference numerals as those in FIGS. 5 and 6 denote similar elements.
As shown in FIG. 1 (A), in the embodiment, the SOFC is connected to the flue 3 upstream of the wet desulfurization apparatus 7 (downstream of the air preheater 5)._ThreeThe point where the separation device 10 is provided is different from the case of FIGS. 5 and 6. Also in this embodiment, wet EP8 is installed in the flue 9 on the downstream side of the wet desulfurization apparatus 7 as in the case of FIG.
[0038]
SO of this embodiment_ThreeThe structure of the separation device 10 will be described later, but the SO_ThreeSeparator 10 uses a heat exchanger to set the flue gas temperature to H₂SO_FourBy cooling to the gas dew point temperature or lower, the SO_ThreeLiquid H₂SO_FourIt is condensed in the form of Since the temperature of exhaust gas decreases due to contact with the heat transfer surface of the heat exchanger, H₂SO_FourCondensation (condensation) first occurs on the heat transfer surface, and the condensed liquid H₂SO_FourMost of the water adheres to the heat transfer surface. For this reason, H adhering to the heat transfer surface₂SO_FourBy removing it in the form of drainage by rinsing it with water._ThreeAre separated and removed.
[0039]
FIG. 1B shows the smoke emission temperature and SO at each location shown in FIG.₂Concentration and SO_ThreeThe concentration is shown. In this embodiment, as shown in FIG._ThreeThe temperature of the flue gas at the inlet of the separator 10 (point II) and the SO₂, SO_ThreeThe concentration is the same as in FIG. 5 and FIG._ThreeAt the outlet of the separation device 10 (point II ′), the smoke emission temperature is reduced from 160 ° C. to 100 ° C. H₂SO_FourThe dew point of the gas is about 110 ° C, SO_ThreeSO in the flue gas in the separator 10_ThreeIs almost all liquid H₂SO_FourCondenses in the form of In addition, this condensation is SO_ThreeSince it occurs at the heat transfer surface of the heat exchanger in the separation device 10, the condensed H₂SO_FourMost of the water adheres to the heat transfer surface and is separated and removed from the flue gas.
[0040]
For this reason, SO_ThreeAt the separator outlet, SO_ThreeThe concentration drops from 60 ppm at the inlet to 40 ppm.
As a result, at the outlet of the wet desulfurization apparatus 7, SO_ThreeThe concentration is 32 ppm.
Therefore, the SO in the flue gas emitted from the chimney 11_ThreeWet EP8 SO required to reduce concentration to 2 ppm_ThreeThe removal efficiency η is η = (32−2) / 32≈94%.
[0041]
That is, the removal efficiency required for the wet EP8 is reduced by about 2% compared to the case of FIG. Thus, the difference in the required removal efficiency of 2% in the region of relatively high removal efficiency has a great influence on the size of the wet EP8 apparatus. By reducing the removal efficiency from 96% to 94%, the wet EP8 is reduced. The size and cost of the device is reduced by about 20 to 30%. Thus, in the present embodiment, the SO cost that increases the operating cost without increasing the apparatus cost of the wet EP8 is obtained._ThreeSO without exhausting neutralizer etc._ThreeMinute (SO_ThreeAnd gaseous and mist-like H₂SO_Four) Can be removed.
[0042]
In the example of FIG._ThreeAn air heater 5 for preheating the combustion air by exchanging heat between the smoke and the boiler combustion air is provided upstream of the separation device. In addition to the air heater 5, the smoke and SO at the wet EP8 outlet (or the chimney 11 inlet) are provided._ThreeA gas / gas heater that prevents the generation of white smoke due to water vapor in the chimney by heating the flue gas emitted from the chimney by exchanging heat with the flue gas on the upstream side of the separation device may be provided.
[0043]
Next, the SO of this embodiment_ThreeThe configuration of the separation device 10 will be described with reference to FIG.
SO of this embodiment_ThreeSeparation apparatus 10 includes a shell and a casing 10a in which flue gas passes from above to below, and a tube 10b that is disposed in casing 10a at a right angle to the flow of flue gas and through which cooling water passes. -It has the tube-type heat exchanger 100 and the washing | cleaning apparatus 101 arrange | positioned at the upper part of the tube 10b group.
[0044]
The cleaning device 101 is, for example, arranged in parallel to the tube 10b, a header pipe 101a to which industrial water is supplied, and a plurality of branch pipes (5 in the example of FIG. 2) 101b extending horizontally from the header to the upper portion of the tube 10b group. And a nozzle 101c for injecting water from each branch pipe toward the tube 10b group, and an on-off valve 101d provided in each branch pipe and controlling the supply of water from the header pipe 101a to each branch pipe.
[0045]
In this embodiment, a total of ten nozzles 101c, two for each branch pipe 101b, are provided, and each nozzle sprays water in a range indicated by a circle centered on each nozzle in FIG. The spray circle 101e from each nozzle sufficiently overlaps with the adjacent spray circle, and the ten nozzles can be cleaned without leaving the outer periphery of all the tubes 10b of the heat exchanger 100.
SO in FIG._ThreeIn the separation device 10, the flue gas flowing in from the upper part of the casing 10a comes into contact with the tube 10b in the casing 10a, and the SO in the flue gas is placed on the outer periphery of the low temperature tube 10b._ThreeThe component is liquid H₂SO_FourAs it condenses and adheres. H around tube 10b₂SO_FourThe amount of adhesion increases with time and forms a scale together with the dust in the smoke, but in this embodiment, the cleaning device 101 periodically cleans the outer periphery of the tube with water, thereby depositing the scale on the outer periphery of the tube 10b. This prevents the heat exchange efficiency of the tube from decreasing due to the₂SO_FourIs removed from the flue gas.
[0046]
The tube 10b is washed by, for example, opening the on-off valves 101d of the branch pipes 101c one by one in order for a certain period of time and spraying water from the nozzles 101c during passage of smoke. As a result, the tube 10b is washed by 1/5 of the entire surface by water spray from the two nozzles 101c at a time. For example, in this embodiment, the branch pipe is changed at an interval of 1 hour and water injection is repeated for about 2 minutes per time, so that 5 hours 10 minutes is one cycle, and SO_ThreeWashing of the entire surface of the tube 10c is repeated while continuing the separation.
[0047]
The surface of the tube 10b and the inner surface of the casing 10a are H₂SO_FourSince it comes in contact with mist, it becomes a strong corrosive environment. For this reason, in this embodiment, the tube 10b surface and the casing 10a inner surface are all coated with PTFE (polytetrafluoroethylene) or PFA (tetrafluoroethylene perchloroalkyl vinyl ether copolymer), which has high chemical resistance. The corrosion of the casing is prevented. Thus, the corrosion of the heat exchanger 100 is almost completely prevented by using the PTFE coating or the PFA coating in combination with the water cleaning. The casing 10a and the tube 10b may be made of a corrosion-resistant material such as stainless steel having high chemical resistance.
[0048]
Furthermore, in this embodiment, boiler water supply is used as the cooling water supplied to the tube 10b. As shown in FIG._ThreeSince the temperature drop of the flue gas is relatively large in the heat exchanger 100 of the separation apparatus 10, the fuel consumption of the boiler is greatly reduced by using this waste heat to heat the boiler feed water in the heat exchanger 100. It becomes possible to do. Further, the cooling water after the flue gas is cooled by the heat exchanger 100 can be used to prevent the generation of white smoke by heating the gas at the chimney inlet, for example, in addition to the boiler feed water. (In this case, a heat exchanger for exchanging heat again between the cooling water and the smoke is installed.)
[0049]
That is, in this embodiment, as shown in FIG._ThreeBy providing the separation device 10, the SO in the flue gas is not produced without increasing the device cost of the wet EP8._ThreeIt is possible to reduce the operating cost of the boiler by using inexpensive heavy oil with a relatively high sulfur content (for example, 2% or more)._ThreeBy using the heat exchanger 100 of the separator 10 as an economizer for heating boiler feed water, fuel consumption can be greatly reduced in addition to the above.
[0050]
Next, SO_ThreeThe waste water treatment used for cleaning the surface of the tube 10b by the cleaning device 101 of the separation device 10 will be described. The waste water after cleaning the surface of the tube 10b contains sulfuric acid adhering to the tube. For this reason, the waste water after washing cannot be discharged as it is, and a neutralization treatment of sulfuric acid is necessary.
[0051]
In the present embodiment, the waste water after washing the tube 10b is supplied to the absorption tower of the wet desulfurization apparatus 7, so that the washing waste water is neutralized without separately providing waste water treatment equipment, and the SO of the absorption tower.₂By using it as makeup water for the absorbent aqueous solution, it is possible to reduce the water consumption of the wet desulfurization apparatus 7.
[0052]
Figure 3 shows SO_ThreeSO in the case of using the washing waste water of the separation device 10 as makeup water for the absorption tower_ThreeIt is a figure which shows arrangement | positioning of a separation apparatus typically.
In FIG. 3, 71 is an absorption tower of the wet desulfurization apparatus 7, and 75 is SO.₂Absorbent (for example, SO such as calcium hydroxide)₂An absorbent aqueous solution circulation pump 73 is a cooling tower disposed upstream of the absorption tower 71. The cooling tower 73 reduces the temperature of the flue gas flowing into the absorption tower 71 to reduce the SO₂It is for improving the absorption efficiency. In the cooling tower 73, the flue gas enters the cooling tower from the inlet provided at the upper part of the cooling tower, flows downward in the tower, and flows into the absorption tower 71 from the flue gas passage 77 provided at the lower part of the cooling tower 73. To do.
[0053]
In the cooling tower 73, the industrial water supplied from the outside is sprayed into the flue gas from the cooling nozzle 73a, and a part thereof evaporates to lower the flue gas temperature. The water sprayed from the cooling nozzle 73a is temporarily stored in the water tank 73b below the cooling tower 73, overflows the smoke passage 77 due to the rise of the water level, and flows into the circulating water tank 71b of the absorbent aqueous solution in the absorption tower. The absorbent aqueous solution in the circulating water tank 71b is sprayed into the flue gas from the nozzle 71a at the upper part of the absorption tower by the circulation pump 75, and the sprayed absorbent comes into contact with the flue gas flowing upward in the absorption tower 71, for example, CaSO_FourSO in flue gas in the form of₂And is collected in the circulating water tank 71b.
In addition, SO₂The flue gas from which the gas is removed flows out from the upper part of the absorption tower 71 to the flue.
[0054]
As shown in FIG. 3, in this embodiment, SO_ThreeThe separation device 10 is disposed at the smoke exhaust inlet at the top of the cooling tower 73. For this reason, SO_ThreeH after washing the tube of the separation device 10₂SO_FourThe wastewater containing the water descends in the cooling tower 73 and enters the lower water tank 73b, and further overflows and is supplied to the circulating water tank 71b of the absorption tower 71. As a result, H in the cleaning wastewater₂SO_FourIs SO₂While reacting with an absorbent (for example, calcium hydroxide) and neutralized, the amount of makeup water to the circulating water tank 71b is reduced.
[0055]
Further, in this embodiment, the smoke emission temperature flowing into the cooling tower 73 is SO._ThreeSince it passed through the separation device 10, it is considerably lowered (see FIG. 1B). For this reason, the amount of water that evaporates when the flue gas is cooled in the cooling tower 73 is reduced, and the water consumption itself in the cooling tower is reduced. Therefore, in the present embodiment, it is possible to greatly reduce the consumption of industrial water in the wet desulfurization apparatus 7 together with the above-described reduction of makeup water.
[0056]
In addition, as shown in FIG. 4, an independent cooling tower is not provided, and in the configuration in which the flue gas is cooled by injecting water by providing a cooling nozzle 73 a in the flue gas passage 77 at the inlet of the absorption tower 71, SO at the top of the flue passage 77_ThreeBy arranging the separation device 10, it is possible to obtain the same industrial water reduction effect as in FIG.
[0057]
In the embodiment of FIG. 1, a wet EP is used in which an alkaline liquid or water is sprayed onto the dust collecting electrode to form a water film on the electrode, and the collected sulfuric acid mist is washed away from the electrode. However, the wet EP usable in the present invention is not limited to this type.
[0058]
For example, particles such as sulfuric acid mist in the flue gas are charged, and a dielectric such as water is sprayed on the charged particles, and the dielectric is dielectrically polarized by applying a DC electric field to the sprayed dielectric. It is also possible to use a wet EP of a type that captures fine particles such as charged sulfuric acid mist on a dielectric having a large target particle size. As described above, by substituting relatively large dielectric particles with submicron sulfuric acid mist particles and collecting them together with the dielectric particles, it becomes possible to greatly improve the collection efficiency of the submicron particles. Can be miniaturized.
[0059]
In the above-described embodiment, the case where wet EP is provided on the downstream side of the wet desulfurization apparatus has been described as an example._ThreeWhen the generation amount is low, SO is not provided without wet EP._ThreeIt is also possible to remove sulfuric acid mist sufficiently with only the separation device and the wet desulfurization device.
In addition, the SO of this embodiment_ThreeRegardless of the type of wet desulfurization apparatus, the separation apparatus can be installed on the wet desulfurization apparatus as shown in FIGS. For this reason, for example, even in an existing flue gas treatment device that performs flue gas treatment using only the desulfurization device as shown in FIG. SO_ThreeAdditional installation of only separation device or SO_ThreeAdditional installation of separation device and wet EP (or in the existing device as shown in FIG._ThreeAdditional installation of only the separation device) can be performed. For this reason, the SO of the present invention is modified by remodeling work using an existing wet desulfurization apparatus._ThreeAccording to the method for manufacturing the minute removal device, the SO_ThreeIt is possible to configure a minute removing device.
[0060]
【The invention's effect】
According to the invention described in each claim, since it is possible to significantly reduce the load of wet EP without using a neutralizing agent, etc., an increase in apparatus cost and construction cost due to an increase in processing capacity of wet EP There is a common effect that can be prevented.
Furthermore, in the invention according to claim 9, in addition to the above-mentioned common effect, the SOFC can be easily obtained by remodeling a flue gas treatment apparatus having an existing wet desulfurization apparatus._ThreeSince the minute removing device can be configured, the device cost can be further reduced.
[Brief description of the drawings]
FIG. 1 (A) shows SO of the present invention._ThreeThe figure which shows typically the whole structure of one Embodiment of a part removal apparatus, FIG.1 (B) is SO in the flue gas in each part of FIG. 1 (A)_ThreeIt is a figure explaining a density | concentration.
FIG. 2 shows SO in FIG._ThreeSO used in fraction remover_ThreeIt is a figure explaining the structure of one Embodiment of a separator.
FIG. 3 SO_ThreeIt is a figure which shows the example of arrangement | positioning of a separation apparatus.
FIG. 4 SO_ThreeIt is a figure which shows another example of arrangement | positioning of a separation apparatus.
FIG. 5 (A) is a diagram showing a device configuration when performing a flue gas treatment using only a wet desulfurization device, and FIG._ThreeIt is a figure explaining a density | concentration.
6A is a diagram showing a device configuration in the case of performing flue gas treatment using only a wet desulfurization device, and FIG. 6B is a diagram showing SO in fumes in each part of FIG. 6A._ThreeIt is a figure explaining a density | concentration.
[Explanation of symbols]
1 ... Boiler
3 ... Flue
5 ... Air preheater
7 ... Wet desulfurization equipment
8 ... Wet EP
10 ... SO_ThreeSeparation device
11 ... Chimney

Claims (8)

A flue gas passage for guiding flue gas from a furnace that burns fuel containing sulfur to a chimney, a wet desulfurization device that is disposed on the flue gas passage and removes SO _{2 in} the flue gas, and the flue gas passage The SO ₃ separation device which is arranged upstream of the above wet desulfurization device, cools the flue gas, condenses the SO ₃ component in the flue gas in the form of liquid sulfuric acid (H ₂ SO ₄ ), and separates and removes it from the flue gas If, Ete together become Bei a,
The SO ₃ separation device heat-cools the cooling water and the smoke through the heat transfer surface to cool the smoke, and condenses on the smoke side surface of the heat transfer surface during the passage of the smoke. flue gas SO ₃ minutes removing apparatus the liquid H ₂ SO _4, characterized in that it comprises a cleaning device for water washing, the for. _2. The smoke exhaust according to claim 1, further comprising a wet electrostatic precipitator disposed downstream of the wet desulfurization device on the smoke exhaust passage and removing sulfuric acid (H ₂ SO ₄ ) mist in the smoke. SO ₃ min remover. The wet desulfurization apparatus includes an absorption tower through which flue gas passes, and an absorbent circulation apparatus that sprays an SO ₂ absorbent aqueous solution into the absorption tower to absorb and recover SO ₂ in the flue gas in the aqueous solution. , the cleaning device supplies the effluent containing H ₂ SO ₄ after washing as makeup water to the absorbent circulating device the heat transfer surface, flue gas SO ₃ minutes removing apparatus according to claim 1. The heat exchanger is a shell-and-tube heat exchanger including a casing through which exhaust gas passes, and a tube disposed in the casing and through which cooling water passes, and the casing inner surface; The apparatus for removing flue gas from SO _{3 according} to claim 3 , wherein the outer surface of the tube is made of a corrosion-resistant material or coated with a corrosion-resistant material. The wet desulfurization apparatus further includes a cooling tower for spraying water into the flue gas to lower the temperature of the flue gas flowing into the absorption tower, and the SO ₃ separation device is disposed at the flue gas inlet portion at the upper part of the cooling tower. is, the cleaning device supplies the waste water after cleaning the heat transfer surfaces into the cooling tower is supplied as makeup water to the absorbent circulation system of the absorption tower together with the sprayed water in the cooling tower, according to claim 3 or 5. The apparatus for removing SO _{3 from} smoke as described in any one of 4 above. The removal of SO _{3 in} flue gas according to any one of claims 1, 3, 4, or 5 , wherein boiler feed water is used as cooling water for the heat exchanger, and the heat of the flue gas is recovered in the boiler feed water. apparatus. The flue gas passage of the SO ₃ separation device upstream, said the flue of the wet electrostatic precipitator after passing through, with a gas / gas heater to a flue gas heat exchanger to be discharged from the furnace, of claims 1-6 The exhaust gas SO ₃ minute removal device according to any one of the above. An additional SO ₃ separation device according to any one of claims 1 to 7 is additionally installed in the upstream smoke exhaust passage of an existing wet desulfurization device to constitute a SO ₃ component removal device for flue gas. Manufacturing method of SO ₃ minute removal device for flue gas.

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