Method for purifying high-calcium mother liquor of fly ash water washing liquid

Abstract

The invention belongs to the field of resource utilization of fly ash water washing liquid, and discloses a high-calcium mother liquid purification method of fly ash water washing liquid, which comprises the following steps: purifying heavy metal ions of the fly ash water washing liquid, and then evaporating and concentrating filtrate after heavy metal purification to separate sodium chloride and potassium chloride; finally, in the process of removing the potassium salt in the mother liquor, original sulfate ions in the solution are utilized, a small amount of ferric salt is added to achieve the purposes of purifying and removing potassium and purifying the calcium chloride concentrated solution, then evaporative crystallization is conducted, and an industrial calcium chloride product meeting the GB / T26520-2021 requirement is produced. The method is simple in process and low in cost, and green and efficient resource utilization of the fly ash washing liquid is achieved.

Description

Technical Field

[0001] The invention belongs to the field of resource utilization of fly ash water washing liquid, and particularly relates to a method for purifying high-calcium mother liquor of fly ash water washing liquid. Background Art

[0002] The chloride ion content of fly ash after incineration of domestic waste in my country can reach about 12-30%. If the fly ash is not treated with chlorine removal, it will not only seriously pollute the land and water sources, causing great impact on the environment and human body, but also cause troubles in the treatment and resource disposal of fly ash.

[0003] Although fly ash is a hazardous waste, it still has a large amount of resources. Potassium salt is one of the scarce mineral resources in my country. The chloride salt in fly ash can be purified to recover a large amount of sodium salt and potassium salt for industrial use. At the same time, the elements such as Ca, K, Na contained in it are similar to the composition of cement, and can partially replace cement as a building material, realizing sustainable development of resources and harmless treatment of fly ash.

[0004] In the prior art, Chinese patent CN117798179A discloses a method for resource utilization of fly ash from incineration of domestic waste, wherein the washing liquid after three-stage countercurrent washing is added with Na 2 CO 3 After solid-liquid separation, a mother liquor containing Na salt and K salt is obtained; Na salt product and K salt product are finally obtained by evaporation crystallization hot filtration and cooling crystallization filtration. 2 CO 3 The dosage of the agent is large, the disposal cost is high, and the calcium salt is not fully utilized.

[0005] Chinese patent CN106185989A discloses a method for recovering inorganic salts from fly ash from the incineration of domestic waste. The method first separates potassium chloride, sodium chloride and calcium chloride by multiple leaching of fly ash, but the system is complex, and multiple heating and cooling result in high energy consumption. In addition, the product purity is not high and does not meet industrial standards, and the comprehensive utilization of inorganic salts cannot be achieved.

[0006] Therefore, it is necessary to develop a high-calcium mother liquor purification method for fly ash water washing liquid with low cost, simple process and high product purity. Summary of the invention

[0007] In order to overcome the deficiencies of the prior art, the present invention provides a method for purifying high-calcium mother liquor of fly ash washing liquid, which can effectively remove sodium and potassium salts in the calcium-containing mother liquor of fly ash washing, thereby solving the problem that the currently recovered calcium chloride products do not meet the requirements of industrial-grade quality standards. The present invention also converts the calcium-containing waste salt in the fly ash washing liquid into an economically profitable calcium chloride chemical product, and the product quality meets the product quality requirements of industrial calcium chloride GB / T26520-2021. A new resource utilization method is proposed in three aspects: solving fly ash pollution, reducing treatment costs, and generating economic benefits.

[0008] The technical solution adopted by the present invention to solve the technical problem is:

[0009] A method for purifying high-calcium mother liquor of fly ash water washing liquid comprises the following steps:

[0010] (1) purifying heavy metal ions in the fly ash washing liquid M to obtain a heavy metal-purified material P;

[0011] (2) evaporating and crystallizing material P, filtering out sodium chloride to obtain mother liquor Q, and continuously cooling and crystallizing mother liquor Q, continuously stirring, and filtering to obtain potassium chloride and material R;

[0012] (3) adjusting the pH of the material R obtained in step (2) to 0.5-3.0 to obtain a mother liquor S;

[0013] (4) The mother liquor S is heated to 100-110° C., and iron salt is added to react to generate a yellow precipitate of potassium ferric sulfate containing hydroxyl group, and the precipitate is filtered out by heat preservation. After complete filtration, the pH of the filtrate is adjusted to 6.0-7.0 to obtain a calcium chloride mother liquor, which is completely evaporated to obtain a calcium chloride product. The dry content of calcium chloride is greater than 95%.

[0014] The present invention is to utilize fly ash water washing liquid in a green and environmentally friendly way to obtain sodium chloride, potassium chloride and calcium chloride products. The first step is to purify the heavy metal ions in the fly ash water washing liquid, and use sodium sulfide solution or sodium phosphate to remove heavy metal ions in the water washing liquid; the second step is high-temperature evaporation crystallization and heat preservation filtration to separate sodium chloride and potassium chloride. After that, it is a high-concentration calcium chloride mother liquor. Considering the salting-out effect of high-concentration calcium chloride, the mother liquor after filtration is a high-content calcium chloride and a small amount of potassium ions, which leads to the problem that potassium ions in the production of calcium chloride products are prone to exceed the standard. In the process of removing potassium salts from the mother liquor, the original sulfate ions in the solution are used, and a small amount of iron salt is added to purify and remove potassium, so as to achieve the purpose of purifying the calcium chloride concentrate, and then evaporate and crystallize to produce industrial calcium chloride products that meet the requirements of GB / T26520-2021.

[0015] Preferably, in step (1), heavy metal ion purification uses a 5% by mass sodium sulfide solution or a 5% by mass sodium phosphate solution, and the volume ratio of the fly ash water wash to the sodium sulfide solution or the sodium phosphate solution is 100:1-2.

[0016] Preferably, the evaporation and crystallization temperature in step (2) is 95-115° C., and the filtration is performed by heat preservation.

[0017] Preferably, in step (2), the stirring rate is 150-200 rpm, and the stirring time is 0.5-4 h.

[0018] Preferably, in step (3), hydrochloric acid is used to adjust the pH of material R to 0.5-3.0.

[0019] Preferably, in step (4), the iron salt is one or both of ferric chloride and ferric sulfate.

[0020] Preferably, in step (4), the mass of iron salt added per liter of the mother liquor S is 12 to 18 g.

[0021] Preferably, in step (4), the iron salt is added to react for 3.0 to 6.0 hours, and the temperature of this process is controlled at 90 to 105°C.

[0022] Preferably, in step (4), one or more of calcium carbonate, calcium hydroxide and calcium oxide are used to adjust the pH.

[0023] The advantages and beneficial effects of the present invention are:

[0024] (1) The method of the present invention adopts a precipitation and impurity removal process, utilizes the original sulfate ions in the mother liquor S, adds a small amount of iron salt to generate a yellow precipitate containing potassium hydroxyferric sulfate, removes the calcium-containing waste salt in the fly ash washing liquid, and converts it into an economically profitable calcium chloride chemical product. The product quality meets the product quality requirements of industrial calcium chloride GB / T26520-2021.

[0025] (2) The method of the present invention does not require the addition of sodium carbonate to remove calcium, greatly reduces the consumption of reagents, has low cost and low energy consumption, and realizes the green and efficient resource utilization of fly ash water washing liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is a flow chart of the method for purifying high calcium mother liquor of fly ash water wash liquid. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0028] The composition of the fly ash water wash liquid M used in the following examples is: 2wt~3wt% of calcium, 1wt~2wt% of potassium, 1wt~2wt% of sodium, 5wt~10wt% of chlorine, 0.1wt~0.2wt% of sulfate, 0~0.1wt% of lead, 0~0.1wt% of chromium, 0~0.1wt% of cadmium, 0~0.1wt% of zinc, 0~0.1wt% of magnesium, 0~0.1wt% of strontium, 0~0.1wt% of iron, 0~0.1wt% of cobalt, 0~0.1wt% of nickel, and the balance is water.

[0029] Example 1

[0030] A method for purifying high-calcium mother liquor of fly ash water washing liquid comprises the following steps:

[0031] (1) Take 250 mL of fly ash water washing liquid M, add 5 mL of 5% sodium sulfide solution, stir at room temperature for 30 minutes and then filter to obtain material P after purification of heavy metals.

[0032] (2) Material P was transferred to a stainless steel reactor and the temperature was raised to 100°C. The amount of water evaporated was 178 mL, and the mass of sodium chloride filtered out here was 6.73 g.

[0033] (3) The filtered mother liquor Q is continuously cooled and crystallized. When the solid phase wet salt w(Ca 2+ )>0.2%, the precipitated salt was filtered, and the mass of potassium chloride filtered out here was 4.85g.

[0034] (4) The stainless steel reactor was cooled to 25°C and stirred for 0.5 h at a stirring rate of 150 rpm. 2.32 g of potassium chloride was filtered out.

[0035] (5) Hydrochloric acid was added to the material R in the stainless steel reactor to adjust the pH to 1.5 to obtain a mother solution S. The temperature was raised to 100° C. and 20 mL of a 1 mol / L ferric chloride solution was added dropwise to react to generate a yellow precipitate of potassium ferric sulfate containing hydroxyl groups and the precipitate was filtered.

[0036] (6) After filtration is complete, calcium oxide is added to adjust the pH to 6.0 to obtain calcium chloride mother liquor.

[0037] (7) The calcium chloride mother liquor in the stainless steel reaction kettle was evaporated to dryness to obtain 16.83 g of industrial-grade calcium chloride with a dry basis content of 97.8%.

[0038] Table 1 Chemical composition of calcium-containing mother liquor before and after precipitation

[0039]

[0040] Example 2

[0041] A method for purifying high-calcium mother liquor of fly ash water washing liquid comprises the following steps:

[0042] (1) Take 5L of fly ash water washing liquid M, add 50mL of 5% sodium phosphate solution, stir at room temperature for 60min and filter to obtain material P after purification of heavy metals.

[0043] (2) Material P was transferred to a stainless steel reactor and the temperature was raised to 95°C. The amount of water evaporated was 3550 mL, and the mass of sodium chloride filtered out here was 134.60 g.

[0044] (3) The filtered mother liquor Q is continuously cooled and crystallized. When the solid phase wet salt w(Ca 2+ )>0.2%, the precipitated salt was filtered, and the mass of potassium chloride filtered out here was 97.52g.

[0045] (4) The stainless steel reactor was cooled to 20°C and stirred for 2 h at a stirring rate of 170 rpm. 46.75 g of potassium chloride was filtered out.

[0046] (5) Hydrochloric acid was added to the material R in the stainless steel reactor to adjust the pH to 1.2 to obtain mother liquor S. The temperature was raised to 95° C. and 200 mL of 1 mol / L ferric sulfate solution was added dropwise to react to generate a yellow precipitate of potassium ferric sulfate containing hydroxyl groups and the precipitate was filtered.

[0047] (6) After filtration is complete, calcium carbonate is added to adjust the pH to 7.0 to obtain calcium chloride mother liquor.

[0048] (7) The calcium chloride mother liquor in the stainless steel reactor was evaporated to dryness to obtain 336.80 g of industrial-grade calcium chloride with a dry basis content of 96.3%.

[0049] Example 3

[0050] A method for purifying high-calcium mother liquor of fly ash water washing liquid comprises the following steps:

[0051] (1) Take 20L of fly ash washing liquid M, add 200mL of 5% sodium sulfide solution, stir at room temperature for 60min and filter to obtain material P after purification of heavy metals.

[0052] (2) Material P was transferred to a stainless steel reactor and the temperature was raised to 98°C. The amount of water evaporated was 14200 mL, and the mass of sodium chloride filtered out here was 538.40 g.

[0053] (3) The filtered mother liquor Q is continuously cooled and crystallized. When the solid phase wet salt w(Ca 2+ )>0.2%, the precipitated salt was filtered, and the mass of potassium chloride filtered out here was 388.20g.

[0054] (4) The stainless steel reactor was cooled to 24°C and stirred for 4 h at a stirring rate of 180 rpm. 188.40 g of potassium chloride was filtered out.

[0055] (5) Hydrochloric acid was added to the material R in the stainless steel reactor to adjust the pH to 2.0 to obtain mother liquor S. The temperature was raised to 98° C. and 800 mL of 2 mol / L ferric chloride solution was added dropwise to react to generate a yellow precipitate of potassium ferric sulfate containing hydroxyl groups and filtered.

[0056] (6) After filtration is complete, calcium hydroxide is added to adjust the pH to 7.0 to obtain calcium chloride mother liquor.

[0057] (7) Calcium chloride was evaporated to dryness in a stainless steel reactor to obtain 1347.32 g of industrial-grade calcium chloride with a dry basis content of 97.1%.

[0058] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept, which all belong to the protection scope of the present invention.

Claims

1. A method for purifying high calcium mother liquor of fly ash washing liquid, characterized in that: The following steps are involved: (1) purifying heavy metal ions in the fly ash washing liquid M to obtain a heavy metal-purified material P; (2) evaporating and crystallizing material P to separate sodium chloride to obtain mother liquor Q, cooling and crystallizing mother liquor Q, continuously stirring, and filtering to obtain potassium chloride and material R; (3) adjusting the pH of the material R obtained in step (2) to 0.5-3.0 to obtain a mother liquor S; (4) raising the temperature of the mother liquor S to 100-110° C., adding iron salt to react to generate a hydroxyl-containing potassium ferric sulfate precipitate, filtering out the precipitate while keeping warm, adjusting the pH of the filtrate to 6.0-7.0 after complete filtration to obtain a calcium chloride mother liquor, and completely evaporating to dryness to obtain a calcium chloride product having a dry basis content greater than 95%.

2. The purification method according to claim 1, characterized in that: In step (1), heavy metal ion purification uses a 5% by mass sodium sulfide solution or a 5% by mass sodium phosphate solution, and the volume ratio of the fly ash water washing liquid to the sodium sulfide solution or the sodium phosphate solution is 100:1-2.

3. The purification method according to claim 1, characterized in that: The evaporation and crystallization temperature of step (2) is 95-115° C., and the filtration is carried out by heat preservation.

4. The purification method according to claim 1, characterized in that: In step (4), the iron salt is one or both of ferric chloride and ferric sulfate.

5. The purification method according to claim 1, characterized in that: The mass of the iron salt added per liter of the mother liquor S is 12-18 g.

6. The purification method according to claim 1, characterized in that: In step (4), add iron salt and react for 3.0 to 6.0 hours, and control the temperature to 90 to 105°C.

7. The purification method according to claim 1, wherein in step (4), one or more of calcium carbonate, calcium hydroxide and calcium oxide are used to adjust the pH.

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