Method for decalcification and carbon sequestration of fly ash water washing liquid

Abstract

The invention relates to a method for decalcification and carbon sequestration of fly ash water washing liquid. According to the method, the extraction effect of insoluble organic amine on acid is utilized to improve the pH value of a water washing liquid system, CO2 is continuously absorbed, and calcium in the fly ash water washing liquid is completely removed; the amine in the organic phase is regenerated through alkali, and meanwhile, a small amount of organic diluent mixed in the water washing liquid is separated from low-boiling-point azeotrope containing the organic diluent at the tower top through azeotropic distillation, so that recycling is realized. The prepared calcium carbonate product is small in particle and high in purity, is a high-quality vaterite type calcium carbonate particle, can be used as a very good adsorbent and additive material, and has wide application in multiple fields.

Description

Technical Field

[0001] The invention belongs to the technical field of fly ash resource processing, and specifically relates to a method for strengthening fly ash water washing liquid decalcification and carbon fixation by using organic amine as a medium. Background Art

[0002] The coordinated disposal technology of cement kiln fly ash is currently an important treatment path for waste incineration fly ash. However, there are also a large number of chlorides in the fly ash, which affect the quality of cement products and also cause corrosion to cement kilns. Therefore, waste incineration fly ash needs to be pre-treated by water washing and dechlorination before it is put into cement kiln production. The fly ash washing liquid can be concentrated, evaporated, crystallized and other treatment processes to obtain chloride salt products, realizing resource recycling, and the desalted water can also be reused.

[0003] However, the water wash liquid has a high calcium ion concentration (0.5-2%), which will cause scaling in the evaporation system and affect the stable operation of the equipment. Moreover, the presence of calcium will affect the subsequent salt separation and crystallization of sodium chloride and potassium chloride, resulting in the destruction of the entire system cycle. Therefore, it is necessary to decalcify it. The currently commonly used soda ash decalcification method consumes about 120kg of soda ash per ton of water wash liquid. On the other hand, the water wash liquid has a certain alkalinity, with a pH of about 11.8, and has strong buffering properties. It takes about 30-40kg of hydrochloric acid to neutralize each ton of water wash liquid.

[0004] Mineralization carbon fixation is a process that converts CO2 into stable mineral carbonates through chemical reactions. It is one of the important methods of carbon capture and storage (CCS) technology. This technology uses alkaline minerals or solutions rich in calcium and magnesium ions to react with CO2 to generate minerals such as calcium carbonate or magnesium carbonate, which can achieve long-term CO2 storage and reduce its concentration in the atmosphere. In this process, alkalinity is consumed to convert dissolved CO2 into carbonate ions. The reaction formula is:

[0005]

[0006] When the solution pH>10,

[0007]

[0008] When the solution pH is <10,

[0009]

[0010] The alkali content in the washing liquid is consumed by the CO2 absorption method, which can save the use of hydrochloric acid for neutralization (such as patent CN118754344A, a method for carbon fixation and calcium removal of waste incineration fly ash washing liquid), but only 10-15% of the calcium in the washing liquid can be removed. Further decalcification requires additional alkali, and the selection of alkali source is directly related to the cost of fly ash resource processing. Invention patent CN117303425A proposes a method for indirectly preparing calcium carbonate from fly ash mediated by an organic phase, using an acid solution to leach calcium from fly ash, and adding an organic amine phase to the leachate to promote the absorption of CO2 to prepare calcium carbonate; but it does not consider that the organic diluent will partially dissolve into the decalcification purification liquid when the two phases are in contact for carbonation reaction, resulting in the loss of organic matter, and the influence of the presence of organic matter on the evaporation and crystallization process. In recent years, the utilization of alkali from wastes such as carbide slag has received widespread attention, but its composition is mainly calcium hydroxide. When it is directly used in the process of absorbing CO2 to generate calcium carbonate, an equal amount of new calcium will be introduced at the same time, which cannot play a role in decalcification. Summary of the invention

[0011] The purpose of the present invention is to provide a method for decalcification and carbon fixation of fly ash water washing liquid in view of the limitations of the current technology. The method utilizes the extraction effect of insoluble (or slightly soluble) organic amine on acid to increase the pH value of the water washing liquid system, continuously absorbs CO2, and achieves complete removal of calcium in the fly ash water washing liquid; and regenerates the amine in the organic phase by alkali, and at the same time, uses azeotropic distillation to separate the low-boiling azeotrope containing the organic diluent mixed in the water washing liquid by distilling it at the top of the tower, so as to achieve reuse. The present invention adjusts the characteristics of calcium carbonate produced as a byproduct of decalcification by using organic amines to obtain high-quality vaterite-type calcium carbonate particles, which are good adsorbents and additives and have wide applications in many fields; and can simultaneously regulate the prepared calcium carbonate crystal form, and the obtained calcium carbonate product has small particles and high purity.

[0012] The technical solution adopted by the present invention is:

[0013] A method for decalcifying and fixing carbon in fly ash water washing liquid, the method comprising the following steps:

[0014] (1) mixing an organic amine and a diluent in a volume ratio of 1:1 to 3 to obtain an organic amine phase, and mixing the organic amine phase and a water washing liquid in a volume ratio of 1 to 3:1, and continuously stirring to obtain an oil-water mixed system;

[0015] The organic amine is a secondary amine or a tertiary amine, preferably a tertiary amine, more preferably trioctylamine; the diluent is a saturated monohydric fatty alcohol, kerosene or solvent oil having a carbon number of not less than 3, preferably a saturated monohydric fatty alcohol, further preferably n-butanol;

[0016] (2) introducing CO2 gas into the continuously stirred oil-water mixture system until the pH value reaches 7.5 to 9.0, thereby obtaining an organic phase containing organic amine hydrochloride and an aqueous phase mixed with calcium carbonate;

[0017] (3) separating the liquids after standing, filtering the aqueous phase to obtain calcium carbonate and decalcified water washing liquid, and washing and drying the calcium carbonate to obtain a calcium carbonate product;

[0018] In addition, a base is added to the organic phase containing the organic amine hydrochloride and stirred for 10 to 90 minutes to achieve regeneration of the organic amine; after regeneration, the organic amine is mixed with a diluent and used as the organic amine phase in the next cycle step (1);

[0019] Wherein, the molar amount of the base is 2 to 5 times the molar amount of the organic amine;

[0020] The alkali is sodium hydroxide, ammonia water or alkaline solid waste (the amount of alkali is expressed as OH - mole of );

[0021] Solid waste residue is industrial waste alkali residue or carbide residue;

[0022] (4) the decalcified water washing liquid containing a small amount of diluent is introduced into a distillation tower for azeotropic distillation, the diluent and water are evaporated at the top of the tower in the form of a low-boiling azeotrope, the water phase is refluxed to the distillation tower after phase separation, the oil phase is the regenerated diluent, and the refined decalcified water washing liquid is obtained in the bottom of the distillation tower; the recovered diluent is mixed with the regenerated organic amine and then enters step (1) for recycling; the refined decalcified water washing liquid in the bottom of the tower is transported to the MVR system for salt separation and crystallization to obtain sodium chloride and potassium chloride;

[0023] The distillation tower is a plate tower with a jet-type plate installed inside; the number of plates is 10 to 15, the feed position is the 1st to 3rd plate, the reflux ratio is 0.8 to 1.2, the tower top operating temperature is 92 to 94°C, the tower bottom operating temperature is 103 to 105°C, and the operating pressure is 102 to 113 kPa; the feed liquid is preheated with MVR evaporation condensate (88 to 92°C);

[0024] The main components and mass percentages of the fly ash washing liquid are: Ca 2+ :0.5~2%,Cl - :4~9%,K + :1~3%,Na + :1~5%.

[0025] The CO2 introduced in step (2) of the above method can be pure CO2 gas or a mixed gas containing CO2 such as purified kiln gas; the purpose of continuously stirring the mixed system of the organic amine phase and the fly ash water washing liquid during the ventilation process is to fully mix the two, which is beneficial to maintaining the alkalinity of the water phase and absorbing CO2.

[0026] The calcium carbonate washing process obtained in step (3) of the above method includes water washing and ethanol washing, and the purpose of the alcohol washing is to remove the organic phase adsorbed by the calcium carbonate product.

[0027] The essential features of the present invention are:

[0028] The present invention uses an organic amine phase composed of an organic amine and a diluent to mix with a fly ash water washing liquid, continuously absorbs the acid produced by the reaction during the process of CO2 decalcification and carbon fixation, and regenerates the produced organic amine salt with alkali, and distills and recovers the organic diluent dissolved in the water washing liquid, thereby realizing the closed-loop use of insoluble organic amine and its diluent in the entire treatment system; using the insoluble organic amine as an intermediary, industrial waste alkali, such as Ca(OH)2 in carbide slag, can be used as an alkali source for regeneration without introducing calcium ions, thereby saving the cost of alkali reagents.

[0029] The beneficial effects of the present invention are:

[0030] (1) Insoluble organic amines are used to extract acid to continuously carry out carbon fixation and decalcification, thereby achieving decalcification of the fly ash water wash liquid, with a decalcification rate of more than 99%, and obtaining a high-purity calcium carbonate product (with a purity of more than 95%). Compared with the process of decalcification with soda ash and then neutralization with hydrochloric acid, this method can save more than 2 million yuan in annual reagent costs for a factory with an annual fly ash processing capacity of 50,000 tons.

[0031] (2) Insoluble amines can be regenerated using a variety of alkali sources including waste alkali, using OH in the waste alkali - Without the additional introduction of calcium, the regenerated organic amine can be recycled after mixing with the recovered diluent, and the recovery rate of the organic phase can reach more than 98%; using calcium carbide slag and industrial waste alkali slag as regeneration agents for organic amines can save the cost of alkali used in the system.

[0032] (3) The small amount of organic diluent dissolved in the distillation separation water wash liquid is used to achieve the recovery and recycling of organic matter, effectively ensuring the smooth progress of the subsequent MVR evaporation and crystallization process, and can minimize the loss of organic matter, thereby improving the economic efficiency of the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic flow diagram of the method for decalcifying and fixing carbon in fly ash water washing liquid by using organic amines in the present invention;

[0034] Figure 2 is the XRD pattern of the calcium carbonate product obtained in Example 1;

[0035] Figure 3 It is a scanning electron microscope image of the calcium carbonate product obtained in Example 1. DETAILED DESCRIPTION

[0036] The present invention is further described below with reference to the embodiments.

[0037] The fly ash washing liquid in the present invention comes from the washing liquid in the process of washing and dechlorinating fly ash from domestic waste incineration, and can also be other calcium-rich industrial wastewater. The fly ash washing liquid in the following examples comes from Wuhu Conch Environmental Protection Co., Ltd., and the main components and concentrations include a calcium ion concentration of 0.9%, a potassium ion content of 2.2%, a sodium ion content of 2.6%, a chloride ion content of 6.46%, and a pH value of 11.8. But it is not limited to this.

[0038] Example 1

[0039] A method for decalcifying and carbonizing fly ash water washing liquid by organic amine enhancement comprises the following steps:

[0040] (1) trioctylamine and n-butanol are mixed uniformly in a volume ratio of 1:2 to form an organic amine phase, and the organic amine phase is mixed uniformly with fly ash water washing liquid in a volume ratio of 2:1, and pure CO2 gas is introduced to carry out a mineralization reaction, and the reaction is terminated when the pH value reaches 8.8 to obtain a mixed solution;

[0041] (2) allowing the mixed solution obtained in step (1) to stand for phase separation, filtering the aqueous phase to obtain a decalcified water washing solution and solid calcium carbonate, and washing the calcium carbonate with water, washing with alcohol, and drying to obtain a calcium carbonate product;

[0042] (3) The organic phase containing the organic amine hydrochloride obtained in step (2) is mixed with the carbide slag slurry (according to the OH content in the carbide slag) - The organic phase is regenerated by stirring for 60 minutes, and the regenerated organic phase is mixed with the recovered diluent and continuously used for the mineralization reaction in step (1), thereby realizing the recycling of the organic phase;

[0043] The process achieved a calcium ion removal rate of 98.2% in the fly ash water wash, a CO2 fixation rate of 51.5%, an organic amine regeneration rate of 97.7%, and an organic phase total recovery rate of 98.5%.

[0044] (4) The calcium carbonate product obtained in step (2) is characterized by an X-ray diffractometer and a scanning electron microscope; the X-ray diffraction result is as follows: Figure 2 As shown by Figure 2 It can be seen that the calcium carbonate products obtained are all in the form of vaterite; the scanning electron microscope image is as follows Figure 3 As shown by Figure 3 It can be seen that the particle size of the obtained calcium carbonate product is about 3 microns; the purity test result of calcium carbonate is 96.2%;

[0045] (5) The decalcified water washing liquid containing a small amount of diluent is introduced into a distillation tower for azeotropic distillation at room temperature, and the diluent and water are evaporated at the top of the tower in the form of a low-boiling point azeotrope. After phase separation, the water phase is refluxed to the distillation tower, and the oil phase is the regenerated diluent. The distillation tower kettle obtains the refined decalcified water washing liquid; the recovered diluent is mixed with the regenerated organic amine and then enters step (1) for recycling; the refined decalcified water washing liquid in the tower kettle is transported to the MVR system for salt separation and crystallization to obtain sodium chloride and potassium chloride;

[0046] The distillation tower is a plate tower with jet-type plates installed inside; the number of plates is 12, the feed position is the third plate, the reflux ratio is 0.8, the tower top operating temperature is 93°C, the tower bottom operating temperature is 104°C, and the operating pressure is 102kPa; the 90°C MVR evaporation condensate is used as the heat source for preheating;

[0047] The azeotropic distillation device also includes a reboiler, a tower body, a tower top condenser and a phase separator.

[0048] During the process, n-butanol and water are evaporated at the top of the tower in the form of an azeotrope (92.7° C., 57.5% n-butanol), and the recovered n-butanol is returned to step (1) for reuse after phase separation in a phase separator. The aqueous phase after phase separation is refluxed to the distillation tower, and a refined decalcified water wash liquid with an n-butanol content of <50 ppm is obtained in the bottom of the tower.

[0049] The role of distillation is, on the one hand, to recover the diluent, reduce the loss of diluent and realize recycling; on the other hand, it is to prevent the diluent from entering the water vapor in the MVR and affecting the compressor and steam temperature.

[0050] Example 2

[0051] A method for decalcifying and carbonizing fly ash water washing liquid by organic amine enhancement comprises the following steps:

[0052] (1) Diisobutylamine and n-butanol are mixed uniformly in a volume ratio of 1:2 to form an organic phase, and the organic phase is mixed uniformly with fly ash water washing liquid in a volume ratio of 1:1, and pure CO2 gas is introduced to carry out a mineralization reaction, and the reaction is terminated when the pH value reaches 8.5 to obtain a mixed solution;

[0053] (2) allowing the mixed solution obtained in step (1) to stand for phase separation, filtering the aqueous phase to obtain a decalcified water washing solution and solid calcium carbonate, and washing the calcium carbonate with water, washing with alcohol, and drying to obtain a calcium carbonate product;

[0054] (3) The organic phase containing the organic amine hydrochloride obtained in step (2) is mixed with aqueous ammonia (OH - The organic phase is regenerated by mixing with the organic amine hydrochloride (the molar ratio of the content to the acid content in the organic amine hydrochloride is 3.0) for 30 minutes, and the regenerated organic phase is mixed with the recovered diluent and continuously used for the mineralization reaction in step (1) to achieve the recycling of the organic phase;

[0055] The process achieved a calcium ion removal rate of 86.6% in the fly ash washing liquid, a CO2 fixation rate of 63.8%, and an organic amine regeneration rate of 90.6%.

[0056] (4) The calcium carbonate product obtained in step (2) is characterized by an X-ray diffractometer and a scanning electron microscope. From the X-ray diffraction results and the scanning electron microscope images, it can be seen that the obtained calcium carbonate product is mainly composed of vaterite and a small amount of calcite. The purity test result of the calcium carbonate is 97.5%.

[0057] The organic matter distillation recovery process of the decalcified water washing liquid is the same as that in Example 1; the refined decalcified water washing liquid directly enters the MVR evaporation crystallization salt separation to obtain potassium chloride and sodium chloride products.

[0058] Example 3

[0059] A method for decalcifying and carbonizing fly ash water washing liquid by organic amine enhancement comprises the following steps:

[0060] (1) trioctylamine and n-butanol are mixed uniformly in a volume ratio of 1:1 to form an organic phase, and the organic phase is mixed uniformly with fly ash water washing liquid in a volume ratio of 1.5:1, and pure CO2 gas is introduced to carry out a mineralization reaction, and the reaction is terminated when the pH value reaches 9 to obtain a mixed solution;

[0061] (2) allowing the mixed solution obtained in step (1) to stand for phase separation, filtering the aqueous phase to obtain a decalcified water washing solution and solid calcium carbonate, and washing the calcium carbonate with water, washing with alcohol, and drying to obtain a calcium carbonate product;

[0062] (3) The organic phase containing the organic amine hydrochloride obtained in step (2) is mixed with the industrial waste alkali slurry (according to the OH content in the waste alkali) - The organic phase is regenerated by mixing with the organic phase (the molar ratio of the concentration to the acid concentration in the organic amine hydrochloride is greater than 3) for 60 minutes, and the regenerated organic phase is mixed with the recovered diluent and continuously used for the mineralization reaction in step (1) to achieve the recycling of the organic phase;

[0063] The process achieved a calcium ion removal rate of 80.5% in the fly ash water wash, a CO2 fixation rate of 36.5%, and an organic amine regeneration rate of 95.6%.

[0064] (4) The calcium carbonate product obtained in step (2) is characterized by an X-ray diffractometer and a scanning electron microscope. It can be seen from the X-ray diffraction results and the scanning electron microscope images that the obtained calcium carbonate products are all in the form of vaterite. The purity test result of the calcium carbonate is 97.1%.

[0065] The organic matter distillation recovery process of the decalcified water washing liquid is the same as that in Example 1; the refined decalcified water washing liquid directly enters the MVR evaporation crystallization salt separation to obtain potassium chloride and sodium chloride products.

[0066] Example 4

[0067] A method for decalcifying and carbonizing fly ash water washing liquid by organic amine enhancement comprises the following steps:

[0068] (1) trioctylamine and n-butanol are mixed uniformly in a volume ratio of 1:2 to form an organic phase, and the organic phase is mixed uniformly with fly ash water washing liquid in a volume ratio of 2.5:1, and pure CO2 gas is introduced to carry out a mineralization reaction, and the reaction is terminated when the pH value reaches 7.8 to obtain a mixed solution;

[0069] (2) allowing the mixed solution obtained in step (1) to stand for phase separation, filtering the aqueous phase to obtain a decalcified water washing solution and solid calcium carbonate, and washing the calcium carbonate with water, washing with alcohol, and drying to obtain a calcium carbonate product;

[0070] (3) The organic phase containing the organic amine hydrochloride obtained in step (2) is mixed with a sodium hydroxide solution (pressed by OH - The organic phase is regenerated by mixing with the organic amine hydrochloride (the molar ratio of the content to the acid content in the organic amine hydrochloride is 3.0) for 30 minutes, and the regenerated organic phase is mixed with the recovered diluent and continuously used for the mineralization reaction in step (1) to achieve the recycling of the organic phase;

[0071] The process achieved a calcium ion removal rate of 69.5% in the fly ash washing liquid, a CO2 fixation rate of 32.2%, and an organic amine regeneration rate of 94.3%.

[0072] (4) The calcium carbonate product obtained in step (2) is characterized by an X-ray diffractometer and a scanning electron microscope. It can be seen from the X-ray diffraction results and the scanning electron microscope images that the obtained calcium carbonate products are all in the form of vaterite. The purity test result of the calcium carbonate is 96.6%.

[0073] The organic matter distillation recovery process of the decalcified water washing liquid is the same as that in Example 1; the refined decalcified water washing liquid directly enters the MVR evaporation crystallization salt separation to obtain potassium chloride and sodium chloride products.

[0074] Example 5

[0075] A method for decalcifying and carbonizing fly ash water washing liquid by organic amine enhancement comprises the following steps:

[0076] (1) Diisobutylamine and n-octanol are mixed uniformly in a volume ratio of 1:2 to form an organic phase, and the organic phase is mixed uniformly with fly ash water washing liquid in a volume ratio of 1:1, and pure CO2 gas is introduced to carry out a mineralization reaction, and the reaction is terminated when the pH value reaches 8.5 to obtain a mixed solution;

[0077] (2) allowing the mixed solution obtained in step (1) to stand for phase separation, filtering the aqueous phase to obtain a decalcified water washing solution and solid calcium carbonate, and washing the calcium carbonate with water, washing with alcohol, and drying to obtain a calcium carbonate product;

[0078] (3) The organic phase containing the organic amine hydrochloride obtained in step (2) is mixed with carbide slag slurry (according to the OH content in carbide slag) - The organic phase is regenerated by mixing with the organic phase (the molar ratio of the concentration to the acid concentration in the organic amine hydrochloride is greater than 3), and the regenerated organic phase is mixed with the recovered diluent and continuously used for the mineralization reaction in step (1), thereby realizing the recycling of the organic phase;

[0079] The process achieved a calcium ion removal rate of 99.8% in the fly ash washing liquid, a CO2 fixation rate of 71.3%, and an organic amine regeneration rate of 94.4%.

[0080] (4) The calcium carbonate product obtained in step (2) is characterized by an X-ray diffractometer and a scanning electron microscope. From the X-ray diffraction results and the scanning electron microscope images, it can be seen that the obtained calcium carbonate product is mainly composed of vaterite and a small amount of calcite. The purity test result of the calcium carbonate is 94.6%.

[0081] The solubility of n-octanol in water is low, about 0.1% at room temperature, which has little impact on the subsequent process. The water washing liquid after decalcification directly enters the MVR system for evaporation, crystallization and salt separation.

[0082] Matters not covered by the present invention are known technologies.

Claims

1. A method for decalcifying and fixing carbon in fly ash water washing liquid, characterized in that the method comprises the following steps: (1) mixing an organic amine and a diluent in a volume ratio of 1:1 to 3 to obtain an organic amine phase, and mixing the organic amine phase and a water washing liquid in a volume ratio of 1 to 3:1, and continuously stirring to obtain an oil-water mixed system; in, The organic amine is a secondary amine or a tertiary amine; the diluent is a saturated monohydric fatty alcohol with a carbon number of not less than 3, kerosene or solvent oil; (2) introducing CO2 into the continuously stirred oil-water mixture system until the pH value reaches 7.5 to 9.0, thereby obtaining an organic phase containing an organic amine hydrochloride and an aqueous phase mixed with calcium carbonate; (3) separating the liquids after standing, filtering the aqueous phase to obtain calcium carbonate and decalcified water washing liquid, and washing and drying the calcium carbonate to obtain a calcium carbonate product; In addition, a base is added to the organic phase containing the organic amine hydrochloride and stirred for 10 to 90 minutes to achieve regeneration of the organic amine; after regeneration, the organic amine is mixed with a diluent and used as the organic amine phase in the next cycle step (1); Wherein, the molar amount of the base is 2 to 5 times the molar amount of the organic amine; The alkali is sodium hydroxide, ammonia water or alkaline solid waste (the amount of alkali is expressed as OH - mole of ); (4) The decalcified water washing liquid containing a small amount of diluent is fed into a distillation tower for azeotropic distillation. The diluent and water are evaporated at the top of the tower in the form of a low-boiling azeotrope. After phase separation, the water phase is refluxed to the distillation tower, and the oil phase is the regenerated diluent. The refined decalcified water washing liquid is obtained in the bottom of the distillation tower; the recovered diluent is mixed with the regenerated organic amine and then fed into step (1) for recycling; the refined decalcified water washing liquid in the bottom of the tower is transported to the MVR system for salt separation and crystallization to obtain sodium chloride and potassium chloride.

2. The method for decalcifying and fixing carbon in fly ash water washing liquid as claimed in claim 1, characterized in that: In step (1), the organic amine is trioctylamine and the diluent is n-butanol.

3. The method for decalcifying and fixing carbon in fly ash washing liquid according to claim 1, characterized in that: In step (3), the solid waste residue is industrial waste alkali residue or carbide slag.

4. The method for decalcifying and fixing carbon in fly ash water washing liquid as claimed in claim 1, characterized in that: In step (4), the distillation tower is a plate tower equipped with jet-type plates; the number of plates is 10 to 15, the feed position is the 1st to 3rd plate, the reflux ratio is 0.8 to 1.2, the top operating temperature is 92 to 94° C., the bottom operating temperature is 103 to 105° C., and the operating pressure is 102 to 113 kPa; the feed liquid is preheated with MVR evaporative condensate (88 to 92° C.).

5. The method for decalcifying and fixing carbon in fly ash washing liquid according to claim 1, wherein in step (1), The main components and mass percentages of the fly ash washing liquid are: Ca 2+ :0.5~2%,Cl - :4~9%,K + :1~3%,Na + :1~5%.

6. The method for decalcifying and fixing carbon in fly ash water washing liquid as claimed in claim 1, characterized in that: The CO2 introduced in step (2) is pure CO2 gas or purified kiln gas.

7. The method for decalcifying and fixing carbon in fly ash water washing liquid as claimed in claim 1, characterized in that: The calcium carbonate washing in step (3) includes water washing and ethanol washing.

Images