阅读说明：本技术 气体净化处理和/或燃烧灰中和处理的装置及方法 (Device and method for gas purification treatment and/or combustion ash neutralization treatment ) 是由 大峰成人 吉川博文 今田典幸 于 2020-03-31 设计创作，主要内容包括：一种对燃烧废气进行净化处理的方法,其包括如下步骤：使燃烧废气通过湿式烟气脱硫装置而从所述燃烧废气去除硫氧化物,从而得到含有二氧化碳的气体；以及使所得到的含有二氧化碳的气体与含有燃烧灰的水浆料接触,从而从该气体去除二氧化碳,以及一种对燃烧灰进行中和处理的方法,其包括如下步骤：使燃烧灰在水、或者含有钙的水浆料或水溶液中悬浮,从而得到含有燃烧灰的水浆料；使从湿式烟气脱硫装置排出的含有二氧化碳的气体与所得到的含有燃烧灰的水浆料接触,从而得到含有碳酸处理灰的水浆料；以及从含有碳酸处理灰的水浆料分离并取出固体成分。(A method for purifying combustion waste gas comprises the following steps: passing a combustion flue gas through a wet flue gas desulfurization device to remove sulfur oxides from the combustion flue gas, thereby obtaining a gas containing carbon dioxide; and contacting the resulting carbon dioxide containing gas with a combustion ash containing water slurry to remove carbon dioxide from the gas, and a method of neutralizing combustion ash comprising the steps of: suspending the combustion ash in water, or an aqueous slurry or solution containing calcium, thereby obtaining an aqueous slurry containing combustion ash; bringing a gas containing carbon dioxide discharged from a wet flue gas desulfurization device into contact with the obtained aqueous slurry containing combustion ash, thereby obtaining an aqueous slurry containing carbonated treated ash; and separating and removing a solid component from the aqueous slurry containing the carbonated treated ash.)

1. A method for purifying combustion exhaust gas, wherein,

the method for purifying the combustion waste gas comprises the following steps:

passing a combustion flue gas through a wet flue gas desulfurization device to remove sulfur oxides from the combustion flue gas, thereby obtaining a gas containing carbon dioxide; and

the resulting carbon dioxide-containing gas is contacted with an aqueous slurry containing combustion ash, thereby removing carbon dioxide from the gas.

2. The method of purifying a combustion exhaust gas according to claim 1,

the aqueous slurry containing combustion ash is obtained by adding combustion ash to an aqueous slurry or aqueous solution containing calcium discharged from a wet flue gas desulfurization apparatus and suspending the combustion ash.

3. The method for purifying combustion exhaust gas according to claim 1 or 2, wherein the combustion ash is coal ash, biomass ash, or a mixture of coal ash and biomass ash.

4. The method of subjecting combustion exhaust gas to purification treatment according to any one of claims 1 to 3,

the wet flue gas desulfurization apparatus includes a gas absorption device capable of bringing combustion exhaust gas into contact with an aqueous slurry containing limestone, slaked lime or quick lime.

5. The method of subjecting combustion exhaust gas to purification treatment according to claim 4,

the wet flue gas desulfurization device comprises a device for separating and removing gypsum.

6. A method for neutralizing combustion ash, wherein,

the method for neutralizing the combustion ash comprises the following steps:

suspending the combustion ash in water, or an aqueous slurry or solution containing calcium, thereby obtaining an aqueous slurry containing combustion ash;

bringing a gas containing carbon dioxide discharged from a wet flue gas desulfurization device into contact with the obtained aqueous slurry containing combustion ash, thereby obtaining an aqueous slurry containing carbonated treated ash; and

the solid component is separated and taken out from the aqueous slurry containing the carbonated treated ash.

7. The method of neutralizing combustion ash of claim 6 wherein,

the combustion ash comprises biomass ash.

8. The method for neutralizing treatment of combustion ash as claimed in claim 6 or 7, wherein,

the wet flue gas desulfurization apparatus includes a gas absorption device capable of bringing combustion exhaust gas into contact with an aqueous slurry containing limestone, slaked lime or quick lime.

9. The method of neutralizing combustion ash of claim 8 wherein,

the method for neutralizing the combustion ash comprises the following steps:

the liquid obtained by separating the solid component from the aqueous slurry containing the carbonated treated ash is added to the aqueous slurry or aqueous solution containing calcium discharged from the wet flue gas desulfurization apparatus.

10. An apparatus for purifying combustion exhaust gas, wherein,

the device for purifying the combustion waste gas comprises a hearth, a wet flue gas desulfurization device, a carbon dioxide removal device, a flue for guiding the combustion waste gas discharged from the hearth to the wet flue gas desulfurization device, and a flue for guiding the gas containing carbon dioxide discharged from the wet flue gas desulfurization device to the carbon dioxide removal device,

the carbon dioxide removal device is provided with an aqueous slurry containing combustion ash, and facilitates removal of carbon dioxide from a gas containing carbon dioxide by bringing the gas into contact with the aqueous slurry containing combustion ash.

11. The apparatus for purifying combustion exhaust gas according to claim 10,

the apparatus for purifying the combustion exhaust gas further comprises a device for adding combustion ash to the aqueous slurry or aqueous solution containing calcium discharged from the wet flue gas desulfurization device and suspending the combustion ash to obtain an aqueous slurry containing combustion ash.

12. The apparatus for purification treatment of combustion exhaust gas according to claim 10 or 11, wherein,

the combustion ash is coal ash, biomass ash, or a mixture of coal ash and biomass ash.

13. The apparatus for purifying a combustion exhaust gas according to any one of claims 10 to 12,

the wet flue gas desulfurization apparatus includes a gas absorption device capable of bringing combustion exhaust gas into contact with an aqueous slurry containing limestone, slaked lime or quick lime.

14. The apparatus for purifying combustion exhaust gas according to claim 13,

the wet flue gas desulfurization device comprises a device for separating and removing gypsum.

15. An apparatus for neutralization treatment of combustion ash, wherein,

the device for neutralizing combustion ash comprises a wet flue gas desulfurization device, a combustion ash carbonic acid treatment device, a carbonic acid treatment ash separation device and a flue for guiding gas containing carbon dioxide discharged from the wet flue gas desulfurization device to the combustion ash carbonic acid treatment device,

a combustion ash carbonation treatment apparatus comprising a preparation apparatus for a combustion ash-containing aqueous slurry, wherein a gas containing carbon dioxide is brought into contact with the combustion ash-containing aqueous slurry obtained by the preparation apparatus to promote conversion from the combustion ash-containing aqueous slurry to a carbonated ash-containing slurry,

the carbonated treated ash separation device facilitates the separation of solids components from the aqueous slurry containing the carbonated treated ash.

16. The apparatus for neutralization treatment of combustion ash according to claim 15,

the combustion ash comprises biomass ash.

17. The apparatus for neutralization treatment of combustion ash according to claim 15 or 16, wherein,

the wet flue gas desulfurization apparatus includes a gas absorption device capable of bringing combustion exhaust gas into contact with an aqueous slurry containing limestone, slaked lime or quick lime.

18. The apparatus for neutralization treatment of combustion ash according to claim 17,

the apparatus for neutralizing combustion ash further comprises a pipe for adding a liquid obtained by separating a solid component from a water slurry containing carbonated treated ash to a water slurry or an aqueous solution containing calcium discharged from the wet flue gas desulfurization apparatus.

Technical Field

The present invention relates to a gas purification treatment for removing carbon dioxide and the like contained in combustion exhaust gas and/or a combustion ash neutralization treatment for utilizing or discarding combustion ash.

Background

In recent years, with the economic development of developing countries, the influence of global human activities has increased, and there is an increasing concern that this will cause environmental changes on the earth scale, such as global warming and the like. In this case, it is desired to reduce the emission of carbon dioxide, which is considered to be one of the causes of global warming. On the other hand, since ash generated by burning biomass, coal, or the like is strongly alkaline, it is desired to safely treat the ash.

Patent document 1 discloses a wastewater treatment method for a flue gas desulfurization apparatus by a wet limestone-gypsum method, which is characterized in that wastewater from a flue gas desulfurization apparatus by a wet limestone-gypsum method suitable for combustion exhaust gas treatment is concentrated, recovered moisture is returned to the flue gas desulfurization apparatus, coal ash is added to the concentrated water to form slurry, then moisture in the slurry is evaporated to generate a sediment containing a hydration reaction product of a dissolved component in the wastewater and the coal ash, and thereby the wastewater is not discharged to the outside of the flue gas desulfurization apparatus system.

Patent document 2 discloses a wet flue gas desulfurization method in which a combustion exhaust gas is guided to an absorption tower and sulfur oxides in the exhaust gas are absorbed and removed by an absorbent slurry, wherein a part of the absorbent slurry is extracted from the absorption tower, and coal ash and slaked lime are added and mixed, followed by heating to obtain a pollution-free solid.

Patent document 3 discloses a wet flue gas desulfurization method for absorbing and removing sulfur oxides in combustion exhaust gas by a desulfurizing agent containing an alkaline substance, which is characterized in that exhaust gas containing coal combustion ash is cooled to 40 ℃ or lower, the coal combustion ash is mixed into condensate water thereof, and a desulfurization absorbing liquid in which a desulfurizing agent is added to a slurry of the coal combustion ash and the condensate water is used to separate and remove the sulfur oxides in the exhaust gas.

Patent document 4 discloses a method for treating desulfurization waste water in which desulfurization waste water is discharged from an absorption tower of a desulfurization apparatus by a wet limestone-gypsum method installed in an exhaust gas line to the outside of the system, the method comprising a two-stage chlorine concentration step of: detecting the concentration of chloride ions in the absorption liquid circulating in the absorption tower, and concentrating the concentration of chloride ions in the absorption liquid to a predetermined concentration by adjusting the extraction amount of the absorption liquid extracted from the absorption tower and the amount of make-up water from the outside of the system; the absorbent extracted from the absorption tower to the outside of the system is conveyed to a gypsum recovery device, the residual absorbent after separating and recovering gypsum is conveyed to a concentration tower provided in an exhaust gas line and brought into contact with combustion exhaust gas, thereby concentrating the chloride ion concentration in the circulating liquid in the concentration tower to a set concentration, and at least one or more substances selected from coal ash, lime and cement are added to the liquid extracted from the concentration tower, followed by drying.

Patent document 5 discloses a method for absorbing and immobilizing carbon dioxide, which is characterized in that a combustion exhaust gas is brought into gas-liquid contact with a coal ash water slurry or a coal ash water solution, and is reacted with and absorbed by carbon dioxide in the combustion exhaust gas to immobilize the carbon dioxide as carbonate.

Patent document 6 discloses a method for immobilizing carbon dioxide, characterized in that at least one of fuel, garbage and biomass containing ash is introduced into a combustion furnace and combusted, sensible heat of combustion exhaust gas is recovered, and the heat-recovered combustion exhaust gas is introduced into CO₂Immobilizing the reactor and passing the fuel from the furnaceCombustion ash is introduced into the CO₂Immobilization reactor in CO₂The combustion exhaust gas is brought into contact with combustion ash in the immobilization reactor, carbon dioxide in the combustion exhaust gas is oxidized by a metal oxide in the combustion ash to be immobilized as carbonate, and reaction heat generated during the oxidation of carbon is recovered and the recovered heat is used for power generation.

Patent document 7 discloses a biomass-fired boiler system including a coal vertical mill for milling coal, a biomass vertical mill for milling solid fuel containing biomass, a boiler for combusting the milled coal and the solid fuel, and a dust collecting device for removing ash in combustion exhaust gas discharged from the boiler, wherein an exhaust gas feed line for extracting a part of the combustion exhaust gas from a downstream side of a combustion exhaust gas flow of the dust collecting device and guiding the extracted part to the biomass vertical mill is provided, a slurry manufacturing device for manufacturing a desulfurization slurry containing coal ash collected by the dust collecting device and alkali salt as a desulfurization portion is provided, and a slurry supply line for guiding the desulfurization slurry to the biomass vertical mill is provided.

Prior art documents

Patent document

Patent document 1: japanese laid-open patent publication No. 3-8411

Patent document 2: japanese laid-open patent publication No. 4-141216

Patent document 3: japanese laid-open patent publication No. 6-126127

Patent document 4: japanese patent laid-open publication No. 9-29058

Patent document 5: japanese patent laid-open publication No. 2004-261658

Patent document 6: japanese laid-open patent publication No. 11-192416

Patent document 7: japanese laid-open patent publication No. 2012-137250

Disclosure of Invention

Problems to be solved by the invention

The present invention addresses the problem of providing a combustion gas purification treatment for removing carbon dioxide and the like contained in a combustion gas, and/or a combustion ash neutralization treatment for utilizing or disposing of combustion ash, and a method therefor.

Means for solving the problems

The present invention including the following aspects has been accomplished to solve the above problems.

[ 1 ] A method for purifying combustion exhaust gas, wherein,

the method for purifying the combustion waste gas comprises the following steps:

passing a combustion flue gas through a wet flue gas desulfurization device to remove sulfur oxides from the combustion flue gas, thereby obtaining a gas containing carbon dioxide; and

the resulting carbon dioxide-containing gas is contacted with an aqueous slurry containing combustion ash, thereby removing carbon dioxide from the gas.

[ 2 ] the method for purifying a combustion exhaust gas according to [ 1 ], wherein,

the aqueous slurry containing combustion ash is obtained by adding combustion ash to an aqueous slurry or aqueous solution containing calcium discharged from a wet flue gas desulfurization apparatus and suspending the combustion ash.

[ 3 ] the method for purifying a combustion exhaust gas according to [ 1 ] or [ 2 ], wherein,

the combustion ash is coal ash, biomass ash, or a mixture of coal ash and biomass ash.

[ 4 ] the method for purifying a combustion exhaust gas according to any one of [ 1 ] to [ 3 ], wherein,

the wet flue gas desulfurization apparatus includes a gas absorption device capable of bringing combustion exhaust gas into contact with an aqueous slurry containing limestone, slaked lime or quick lime.

[ 5 ] the method for purifying a combustion exhaust gas according to [ 4 ], wherein,

the wet flue gas desulfurization device comprises a device for separating and removing gypsum.

[ 6 ] A method for neutralizing combustion ash, wherein,

the method for neutralizing the combustion ash comprises the following steps:

suspending the combustion ash in water, or an aqueous slurry or solution containing calcium, thereby obtaining an aqueous slurry containing combustion ash;

bringing a gas containing carbon dioxide discharged from a wet flue gas desulfurization device into contact with the obtained aqueous slurry containing combustion ash, thereby obtaining an aqueous slurry containing carbonated treated ash; and

the solid component is separated and taken out from the aqueous slurry containing the carbonated treated ash.

[ 7 ] the method for neutralizing combustion ash according to [ 6 ], wherein,

the combustion ash comprises biomass ash.

[ 8 ] the method for neutralizing combustion ash according to [ 6 ] or [ 7 ], wherein,

the wet flue gas desulfurization apparatus includes a gas absorption device capable of bringing combustion exhaust gas into contact with an aqueous slurry containing limestone, slaked lime or quick lime.

[ 9 ] the method for neutralizing combustion ash according to [ 8 ], wherein,

the method for neutralizing the combustion ash comprises the following steps: the liquid obtained by separating the solid component from the aqueous slurry containing the carbonated treated ash is added to the aqueous slurry or aqueous solution containing calcium discharged from the wet flue gas desulfurization apparatus.

An apparatus for purifying combustion exhaust gas, wherein,

the device for purifying the combustion waste gas comprises a hearth, a wet flue gas desulfurization device, a carbon dioxide removal device, a flue for guiding the combustion waste gas discharged from the hearth to the wet flue gas desulfurization device, and a flue for guiding the gas containing carbon dioxide discharged from the wet flue gas desulfurization device to the carbon dioxide removal device,

the carbon dioxide removal device is provided with an aqueous slurry containing combustion ash, and facilitates removal of carbon dioxide from a gas containing carbon dioxide by bringing the gas into contact with the aqueous slurry containing combustion ash.

[ 11 ] the apparatus for purifying combustion exhaust gas according to [ 10 ], wherein,

the apparatus for purifying the combustion exhaust gas further comprises a device for adding combustion ash to the aqueous slurry or aqueous solution containing calcium discharged from the wet flue gas desulfurization device and suspending the combustion ash to obtain an aqueous slurry containing combustion ash.

[ 12 ] the apparatus for purifying combustion exhaust gas according to [ 10 ] or [ 11 ], wherein,

the combustion ash is coal ash, biomass ash, or a mixture of coal ash and biomass ash.

[ 13 ] an apparatus for purifying combustion exhaust gas according to any one of [ 10 ] to [ 12 ], wherein,

the wet flue gas desulfurization apparatus includes a gas absorption device capable of bringing combustion exhaust gas into contact with an aqueous slurry containing limestone, slaked lime or quick lime.

[ 14 ] the apparatus for purifying combustion exhaust gas according to [ 13 ], wherein,

the wet flue gas desulfurization device comprises a device for separating and removing gypsum.

[ 15 ] an apparatus for performing neutralization treatment of combustion ash, wherein,

the device for neutralizing combustion ash comprises a wet flue gas desulfurization device, a combustion ash carbonic acid treatment device, a carbonic acid treatment ash separation device and a flue for guiding gas containing carbon dioxide discharged from the wet flue gas desulfurization device to the combustion ash carbonic acid treatment device,

a combustion ash carbonation treatment apparatus comprising a preparation apparatus for a combustion ash-containing aqueous slurry, wherein a gas containing carbon dioxide is brought into contact with the combustion ash-containing aqueous slurry obtained by the preparation apparatus to promote conversion from the combustion ash-containing aqueous slurry to a carbonated ash-containing slurry,

the carbonated treated ash separation device facilitates the separation of solids components from the aqueous slurry containing the carbonated treated ash.

[ 16 ] the apparatus for neutralizing combustion ash according to [ 15 ], wherein,

the combustion ash comprises biomass ash.

[ 17 ] the apparatus for neutralization treatment of combustion ash according to [ 15 ] or [ 16 ], wherein,

the wet flue gas desulfurization apparatus includes a gas absorption device capable of bringing combustion exhaust gas into contact with an aqueous slurry containing limestone, slaked lime or quick lime.

[ 18 ] the apparatus for neutralizing combustion ash according to [ 17 ], wherein,

the apparatus for neutralizing combustion ash further comprises a pipe for adding a liquid obtained by separating a solid component from a water slurry containing carbonated treated ash to a water slurry or an aqueous solution containing calcium discharged from the wet flue gas desulfurization apparatus.

Effects of the invention

According to the combustion exhaust gas purification treatment method and apparatus of the present invention, carbon dioxide can be efficiently removed by using combustion ash, which is by-produced by combustion of coal or biomass fuel, and, if necessary, an aqueous slurry or aqueous solution containing calcium, which is by-produced in the process of removing sulfur oxides contained in the combustion exhaust gas.

According to the combustion ash neutralization treatment method and apparatus of the present invention, alkaline combustion ash can be efficiently neutralized by a gas containing carbon dioxide obtained by removing sulfur oxides contained in combustion exhaust gas and an aqueous slurry or aqueous solution containing calcium, which is by-produced in the process of removing sulfur oxides contained in combustion exhaust gas.

Drawings

Fig. 1 is a diagram showing an example of a boiler system.

Fig. 2 is a diagram showing an example of an apparatus for purifying combustion exhaust gas according to the present invention.

Fig. 3 is a diagram showing an example of an apparatus for purifying combustion exhaust gas according to the present invention.

Fig. 4 is a diagram showing an example of an apparatus for purifying combustion exhaust gas according to the present invention.

Fig. 5 is a diagram showing an example of an apparatus for purifying combustion exhaust gas according to the present invention.

Fig. 6 is a diagram showing an example of an apparatus for performing neutralization treatment of combustion ash according to the present invention.

Fig. 7 is a diagram showing an example of an apparatus for performing neutralization treatment of combustion ash according to the present invention.

Fig. 8 is a diagram showing an example of an apparatus for performing neutralization treatment of combustion ash according to the present invention.

Detailed Description

[ method for purifying combustion exhaust gas ]

The combustion exhaust gas purification treatment method of the present invention includes the steps of: sulfur oxides are removed from the combustion exhaust gas (flue gas desulfurization), followed by carbon dioxide removal (flue gas decarbonation).

Combustion exhaust gas is gas discharged when the following substances are combusted: fossil fuels such as coal, liquefied natural gas, petroleum and the like; biomass fuels such as wood chips, straws, wooden waste, animal wastes, kitchen wastes and the like; mixtures of fossil fuels with biomass fuels, and the like. Such combustion exhaust gas contains acidic substances such as nitrogen oxides, sulfur oxides, and carbon dioxide, which are considered to have an influence on the environment. The present invention is particularly preferably directed to gas discharged by combustion in a furnace provided in a boiler or the like. Combustion ash (slag ash) can be obtained from the bottom of the furnace. In addition, the combustion ash (fly ash) can be obtained from the bottom of the economizer or air preheater.

The combustion exhaust gas purification treatment method of the present invention preferably further includes a step of removing nitrogen oxides from the combustion exhaust gas, i.e., flue gas denitration.

The flue gas denitration can be performed by, for example, bringing the combustion exhaust gas into contact with a denitration catalyst in the presence of a reducing agent such as ammonia. The denitration catalyst used is not particularly limited, and examples thereof include a titanium oxide-based denitration catalyst, a zeolite-based denitration catalyst, and a mixed denitration catalyst thereof. The flue gas denitration is preferably performed before flue gas dust collection and flue gas desulfurization described later.

The combustion exhaust gas purification treatment method of the present invention preferably further comprises a step of removing combustion ash from the combustion exhaust gas, i.e., flue gas dust collection.

The flue gas dust collection can be performed by passing the combustion exhaust gas through a dust collecting device such as a cyclone, an electric dust collector, or a bag filter. By collecting dust in the flue gas, combustion ash (fly ash) can be removed from the combustion exhaust gas. The combustion ash (fly ash) is collected appropriately and can be used for removing carbon dioxide described later.

The flue gas desulfurization is performed by passing the combustion exhaust gas through a wet flue gas desulfurization device 5. Typical examples of wet flue gas desulfurization include lime-gypsum method, magnesium hydroxide method, and caustic soda method. The wet flue gas desulfurization apparatus used in the present invention preferably comprises a system for mixing the combustion exhaust gas with limestone (CaCO)₃) Slaked lime (Ca (OH)₂) Or a gas absorption device which the aqueous slurry of quicklime (CaO) contacts. By this gas absorption device, sulfur oxides in the combustion exhaust gas react with limestone, slaked lime, or quick lime in the water slurry to become calcium sulfite, and this calcium sulfite is oxidized to become calcium sulfate (gypsum). In the apparatus for separating and removing gypsum, as for the gypsum slurry (water slurry containing calcium) discharged from the gas absorption apparatus, gypsum is separated and removed therefrom. The gypsum was removed by separation to obtain a gypsum dehydration filtrate (aqueous solution containing calcium). On the other hand, a gas containing carbon dioxide is discharged from the wet flue gas desulfurization device.

The flue gas decarbonation is performed by bringing the gas containing carbon dioxide obtained by the wet flue gas desulfurization described above into contact with an aqueous slurry containing combustion ash.

The combustion ash may be bottom ash obtained from the bottom of a furnace, fly ash obtained from the bottom of an economizer or an air preheater, fly ash obtained by collecting flue gas, or combustion ash obtained from other incinerators, thermal power stations, factories, or the like. Among them, fly ash is preferably used from the viewpoint of easy preparation of the aqueous slurry. In addition, the combustion ash is preferably coal ash, biomass ash, or a mixture of coal ash and biomass ash. The amount of the combustion ash contained in the aqueous slurry is not particularly limited, but is preferably 3 to 30% by mass, and more preferably 5 to 15% by mass.

The water used for preparing the aqueous slurry containing the combustion ash is not particularly limited, and examples thereof include industrial water, water of rivers, ponds and lakes, sea water, aqueous slurry or aqueous solution containing calcium, and the like. The water used for preparing the aqueous slurry containing the combustion ash is preferably hard water, or an aqueous slurry or aqueous solution containing calcium from the viewpoint of the carbon dioxide absorption power, and is preferably an aqueous slurry or aqueous solution containing calcium discharged from the wet flue gas desulfurization apparatus (for example, a gypsum dehydrated filtrate) from the viewpoint of the carbon dioxide absorption power and the running cost.

The contact of the carbon dioxide-containing gas with the aqueous slurry containing the combustion ash can be performed, for example, by blowing the gas into the aqueous slurry in a bubble column, a bubble tank, a bubble column, or the like, flowing the aqueous slurry in a packed column, a wetted-wall column, or the like and flowing the gas thereinto, and flowing the gas in a spray column, or the like and spraying the aqueous slurry thereto. The temperature at the time of contact is preferably low from the viewpoint of easy dissolution of carbon dioxide, and specifically, preferably 10 to 80 ℃, and more preferably 30 to 60 ℃.

The carbon dioxide-removed gas may be accompanied by droplets, and therefore, it is preferable to pass through a demister or the like as necessary. Subsequently, the exhaust gas can be discharged from the chimney to the atmosphere.

[ method of neutralizing Combustion Ash ]

The combustion ash neutralization treatment method of the present invention comprises the steps of: the method comprises adding combustion ash to water or a calcium-containing aqueous slurry or an aqueous solution to suspend the combustion ash to obtain a combustion ash-containing aqueous slurry, bringing a gas containing carbon dioxide into contact with the obtained combustion ash-containing aqueous slurry to obtain a carbonated ash-containing aqueous slurry, and separating and removing a solid component from the obtained carbonated ash-containing aqueous slurry.

The water used in the combustion ash neutralization treatment method of the present invention may be either hard water or soft water, but hard water is preferred. The calcium-containing aqueous slurry or aqueous solution used in the combustion ash neutralization treatment method of the present invention is preferably an aqueous slurry or aqueous solution (for example, gypsum dehydration filtrate) discharged from a wet flue gas desulfurization apparatus. The wet flue gas desulfurization apparatus preferably includes a gas absorption device capable of bringing the combustion exhaust gas into contact with an aqueous slurry containing limestone, slaked lime or quick lime.

The combustion ash to which the combustion ash neutralization treatment method of the present invention can be applied is not particularly limited, and preferably contains biomass ash. Biomass ash is more alkaline than coal ash and the like, and is not suitable for reuse as cement or the like, and the treatment cost is increased. The combustion ash neutralization method of the present invention can neutralize combustion ash at low cost to make it a material suitable for reuse. The biomass ash may be any one of bottom ash and fly ash. In addition, the combustion ash may also be a mixture of biomass ash and coal ash. The amount of the combustion ash that can be contained in the aqueous slurry is preferably 3 to 30 mass%, more preferably 5 to 15 mass%.

Neutralization is carried out by contacting the gas containing carbon dioxide with an aqueous slurry containing combustion ash. The carbon dioxide containing gas is preferably the gas discharged from a wet flue gas desulfurization unit. The contacting of the aqueous slurry containing the combustion ash with the gas containing carbon dioxide can be performed in a bubble column, a bubble tank, a bubble column, or the like. The temperature at the time of neutralization is not particularly limited, but a low temperature is preferred, specifically, 10 to 80 ℃ is preferred, and 30 to 60 ℃ is more preferred. This neutralization can yield an aqueous slurry containing the carbonated treated ash.

The solid component is separated and taken out from the resulting aqueous slurry containing the carbonated treated ash. The solid component can be separated by a normal solid-liquid separation operation. The solid component (mainly composed of the carbonated ash) thus extracted has a pH of about 7, and can be reused for cement and the like.

The liquid obtained by separating the solid component from the aqueous slurry containing the carbonated treated ash can be used for preparing an aqueous slurry containing limestone, slaked lime or quick lime used in a wet flue gas desulfurization apparatus, or can be used for preparing an aqueous slurry containing combustion ash, or can be added to an aqueous slurry or aqueous solution (e.g., desulfurization waste water or the like) containing calcium discharged from a wet flue gas desulfurization apparatus.

[ device for purifying combustion exhaust gas ]

The apparatus for purifying combustion exhaust gas of the present invention includes a furnace 1, a wet flue gas desulfurization device 5, a carbon dioxide removal device 11, a flue 7 for guiding combustion exhaust gas discharged from the furnace to the wet flue gas desulfurization device, and a flue 14 for guiding gas containing carbon dioxide discharged from the wet flue gas desulfurization device to the carbon dioxide removal device. The flue 7 for guiding the combustion exhaust gas discharged from the furnace to the wet flue gas desulfurization device is preferably provided with the flue gas denitration device 2 and/or the dust collector 4.

The carbon dioxide removal device 11 is provided with an aqueous slurry containing combustion ash, and facilitates removal of carbon dioxide from a gas containing carbon dioxide by bringing the gas into contact with the aqueous slurry containing combustion ash. As the carbon dioxide removal device, a bubble column, a bubble tank, a bubble column, or the like can be used. The apparatus for purifying combustion exhaust gas of the present invention preferably further comprises means for adding combustion ash to the aqueous slurry or aqueous solution (for example, gypsum dewatering filtrate) containing calcium discharged from the wet flue gas desulfurization apparatus and suspending the mixture to obtain an aqueous slurry containing combustion ash.

The wet flue gas desulfurization apparatus 5 preferably includes a gas absorption device capable of bringing the combustion exhaust gas into contact with an aqueous slurry containing limestone, slaked lime or quick lime, and further includes a device for separating and removing gypsum. The gas absorption unit may be a packed tower, a wetted wall tower, a spray tower, or the like. The device for separating and removing the gypsum may be a well-known water treatment device. In the water treatment apparatus, coagulation, dehydration and the like are performed.

Fig. 2 to 5 show an example of an apparatus for purifying combustion exhaust gas according to the present invention.

In the combustion exhaust gas purification processing apparatus shown in fig. 2, the combustion ash (fly ash) collected by the electrostatic precipitator 4 and then supplied by a combustion ash supply device such as a belt conveyor or a screw feeder is suspended in the industrial water supplied through the industrial water supply pipe 13 to obtain an aqueous slurry, a part of the gas having passed through the wet flue gas desulfurization device 5 is passed through the carbon dioxide removal device 11 provided with the aqueous slurry to remove carbon dioxide, and the gas from which carbon dioxide has been removed is released to the atmosphere through the chimney 6.

The combustion exhaust gas purification apparatus shown in fig. 3 is the same as the apparatus shown in fig. 2 except that gypsum dewatering filtrate supplied through the gypsum dewatering filtrate supply pipe 20 is used instead of industrial water. The gypsum dehydration filtrate is a liquid obtained when gypsum is removed by filtration or the like from a gypsum-containing aqueous slurry obtained by contacting a sulfur oxide-containing gas with an aqueous slurry containing limestone, quicklime or slaked lime in a gas absorption apparatus of a wet flue gas desulfurization apparatus. The liquid is obtained as an aqueous slurry or solution containing calcium.

The combustion exhaust gas purification treatment apparatus shown in fig. 4 is the same as the apparatus shown in fig. 3 except that the biomass ash supplied via the biomass ash supply device 21 is used in preparing the water slurry containing the combustion ash. The biomass ash can be obtained and transported by a device for burning biomass fuel located at another place.

The combustion exhaust gas purification treatment apparatus shown in fig. 5 is the same as the apparatus shown in fig. 4 except that water obtained by clarifying the gypsum dewatering filtrate by the water treatment means 22 is used for preparing a water slurry containing combustion ash. The water treatment apparatus has a pH adjusting tank for adding and stirring the alkali agent, a flocculation tank for adding the flocculant to generate flocs, and a settling tank 25 for settling the flocs.

[ means for neutralising combustion ashes ]

The device for neutralizing combustion ash of the present invention comprises a wet flue gas desulfurization device 5, a combustion ash carbonic acid treatment device 10, a carbonic acid treatment ash separation device 9, and a flue 14 for guiding a gas containing carbon dioxide discharged from the wet flue gas desulfurization device to the combustion ash carbonic acid treatment device.

The combustion ash carbonation treatment device is provided with a preparation device for a combustion ash-containing aqueous slurry, and promotes conversion from the combustion ash-containing aqueous slurry to a carbonation treated ash-containing slurry by bringing a gas containing carbon dioxide into contact with the combustion ash-containing aqueous slurry obtained by the preparation device. In the combustion ash carbonic acid treatment apparatus, a bubble column, a bubble tank, a bubble column, or the like may be used in order to bring the water slurry containing the combustion ash into contact with the gas containing carbon dioxide.

The carbonated treated ash separation device facilitates the separation of solids components from the aqueous slurry containing the carbonated treated ash. The wet flue gas desulfurization apparatus preferably includes a gas absorption device capable of bringing the combustion exhaust gas into contact with an aqueous slurry containing limestone, slaked lime or quick lime. The carbonated treated ash separation apparatus preferably further comprises: piping for transporting a liquid obtained by separating a solid component from a water slurry containing a carbonated treated ash for preparing a water slurry containing limestone, slaked lime or quick lime; or piping for transporting a liquid obtained by separating a solid component from a water slurry containing carbonated treated ash for preparing a water slurry containing combustion ash; or a pipe for adding a liquid obtained by separating a solid component from a water slurry containing carbonated ash to a water slurry or an aqueous solution containing calcium discharged from a wet flue gas desulfurization apparatus.

Fig. 6 to 8 show an example of an apparatus for neutralizing combustion ash according to the present invention.

The combustion ash neutralization treatment apparatus shown in fig. 6 is capable of storing biomass ash obtained and conveyed by an apparatus for combusting biomass fuel in a hopper 21a, suspending the biomass ash in a gypsum dehydration filtrate to obtain an aqueous slurry, and neutralizing the biomass ash by passing the gas passed through the wet flue gas desulfurization apparatus 5 through the aqueous slurry. The carbonated treated ash 8 is withdrawn from the neutralized aqueous slurry by means of a carbonated treated ash separation device 9. The carbonated ash has low alkalinity and can be used as a secondary material in the production of cement or the like. The liquid separated by the carbonic acid treatment ash separation device 9 is returned to the desulfurization waste water tank 18 and can be used for wet flue gas desulfurization or combustion ash carbonic acid treatment.

The combustion ash neutralization treatment apparatus shown in fig. 7 is the same as the apparatus shown in fig. 6 except that the combustion ash recovered by the electrostatic precipitator 4 is used instead of the biomass ash.

The combustion ash neutralization treatment apparatus shown in fig. 8 is the same as the apparatus shown in fig. 7 except that water obtained by clarifying the gypsum dewatering filtrate by the water treatment facility 22 can be used for preparing a water slurry containing combustion ash and supplying biomass ash to the water slurry by the biomass ash supply apparatus 21.

Hereinafter, the effects of the apparatus and method of the present invention will be described by examples.

(pH of Combustion Ash)

0.1g of combustion ash was suspended in 100ml of pure water and boiled. It was allowed to return to room temperature and the pH of the suspension was measured.

(basicity of combustion ash)

Alkalinity was determined by neutralization titration.

(calcium concentration of Combustion Ash)

Calcium concentration was determined by chelate titration.

(example 1)

10 parts by mass of coal ash having a pH of 10.84, a basicity of 4.3 mol/kg and a Ca concentration of 2.5 mol/kg was suspended in 90 parts by mass of a gypsum dehydration filtrate having a chlorine concentration of 10g/L to obtain an aqueous slurry. 400g of the water slurry is put into a reactor, adjusted to the temperature of 20-25 ℃ and stirred. A mixed gas of 15 parts by volume of carbon dioxide and 85 parts by volume of air was blown into the aqueous slurry through a tourmaline at a rate of 2.0L/min, thereby carrying out the carbonation treatment. The aqueous slurry was sampled at predetermined time intervals, filtered, and dried at 40 ℃ for 2 hours to obtain a solid content, and the concentration of the carbonic acid component contained in the solid content was measured. When the concentration of the carbonic acid component contained in the solid component does not change any more, blowing of carbon dioxide is stopped. The pH of the aqueous slurry after the carbonic acid treatment was 6.7, and the fixed amount of carbon dioxide was 7kg-CO₂T-ash.

(example 2)

The carbonation treatment was performed in the same manner as in example 1, except that the gypsum dehydration filtrate was changed to industrial water. The pH of the aqueous slurry after the carbonic acid treatment was 7.3, and the fixed amount of carbon dioxide was 5.9kg-CO₂T-ash.

(example 3)

Except that 10 parts by mass of the coal ash was changed to 8 parts by mass of the coal ash containing pH10.84 and alkalinity of 4.3 molCarbonation treatment was carried out in the same manner as in example 2 except for 2 parts by mass of a mixed ash of coal ash having a Ca concentration of 2.5 mol/kg and rubber wood combustion ash having a pH of 11.74 and a basicity of 10.0 mol/kg and a Ca concentration of 5.2 mol/kg. The pH of the aqueous slurry after the carbonic acid treatment was 9.2, and the fixed amount of carbon dioxide was 37.9kg-CO₂T-ash.

(example 4)

Carbonation treatment was conducted in the same manner as in example 2 except that the coal ash was replaced with combustion ash having pH9.45, basicity 0.21 mol/kg and Ca concentration 0.15 mol/kg. The pH of the aqueous slurry after the carbonic acid treatment was 6.4, and the fixed amount of carbon dioxide was 0.2kg-CO₂T-ash.

(example 5)

Carbonation treatment was conducted in the same manner as in example 2 except that the coal ash was replaced with a rubber log combustion ash having a pH of 11.74, a basicity of 10.0 mol/kg and a Ca concentration of 5.2 mol/kg. The pH of the aqueous slurry after the carbonic acid treatment was 8.1, and the fixed amount of carbon dioxide was 155.7kg-CO₂T-ash.

(example 6)

Carbonation treatment was conducted in the same manner as in example 1 except that the coal ash was replaced with a rubber log combustion ash having a pH of 11.74, a basicity of 10.0 mol/kg and a Ca concentration of 5.2 mol/kg. The aqueous slurry before carbonation treatment was sampled, filtered and dried at 40 ℃ for 2 hours. The obtained combustion ash had a Na ion concentration of 2.8g/kg and a K ion concentration of 181 g/kg. The amount of alkali metal which causes alkali silica reaction that reduces the durability of concrete is greatly reduced. The pH of the aqueous slurry after the carbonic acid treatment was 7.9, and the fixed amount of carbon dioxide was 193.8kg-CO₂T-ash.

Description of reference numerals:

1 … hearth;

2 … flue gas denitration device;

3 … air preheater;

4 … electric dust collector;

5 … wet flue gas desulfurization device;

6 … chimney;

7 … flue;

8 … carbonic acid treated ash;

9 … carbonic acid treatment ash separating device;

10 … a combustion ash carbonic acid treatment plant;

11 … carbon dioxide removal means;

12 … combustion ash supply means;

13 … industrial water supply pipe;

14 … containing CO₂A flue for gas introduction;

15 … gypsum;

16 … gypsum separator (dehydrator);

17 … a gypsum dewatering filtrate tank;

18 … desulfurization waste water tank;

19 … limestone slurry preparation tank;

20 … gypsum dewatering filtrate supply line;

21 … biomass ash supply means;

21a … biomass ash hopper;

22 … water treatment facilities;

23 … supply of alkaline agent;

24 … coagulant supply;

25 … settling tank;

26 … supply pipe for water-treated waste water.