Waste incineration fly ash washing liquid calcium chloride extraction system and process method

Abstract

The invention discloses a waste incineration fly ash washing liquid calcium chloride extraction system which comprises an air stripping tower, a pH adjusting tank, a filter press, a second-effect forced circulation evaporator, a first-effect forced circulation evaporator, a DTB crystallizer, a drying machine, a single-effect forced circulation evaporator, a fluidized bed, an electrostatic separator, a heating furnace and three groups of centrifugal machines, the three groups of centrifugal machines are respectively a first centrifugal machine, a second centrifugal machine and a third centrifugal machine. The method has the advantages that interference of impurity ions on follow-up salt separation is reduced through deamination pretreatment, particle characteristics are improved through high-temperature drying, surface charges are optimized through low-temperature complexing, accurate separation of potassium, sodium and calcium salts is achieved through electrostatic separation, and carbon emission is reduced by combining an ammonia gas recycling technology.

Description

Technical Field

[0001] This invention relates to the field of resource recycling and chemical separation technology, and in particular to a calcium chloride extraction system and process for waste incineration fly ash washing liquid. Background Technology

[0002] The existing technology has the following technical problems: 1. Lack of ammonia removal process: Existing technologies, such as the Chinese patent application number CN202221223021 "A pretreatment device for fly ash washing liquid", do not remove ammonia from the fly ash washing liquid and directly evaporate it. On the one hand, this leads to the emission of ammonia into the atmosphere and causes pollution. On the other hand, the presence of ammonium salts (NH4Cl / NH4NO3) in the original solution will greatly affect the purity of calcium chloride products.

[0003] 2. Limitations of mixed salt separation technology: When potassium chloride (KCl), sodium chloride (NaCl), and calcium chloride (CaCl2) coexist in a solution, the calcium chloride product obtained by directly evaporating and cooling crystallizing generally contains impurities such as potassium and sodium salts that exceed the standard requirements (calcium chloride purity is less than 90%). Summary of the Invention

[0004] The purpose of this invention is to provide a calcium chloride extraction system and process for waste incineration fly ash washing liquid. The system reduces the interference of impurity ions on subsequent salt separation through ammonia removal pretreatment, improves particle characteristics through high-temperature drying, optimizes surface charge through low-temperature complexation, achieves precise separation of potassium, sodium and calcium salts through electrostatic separation, and reduces carbon emissions by combining ammonia recycling technology.

[0005] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A calcium chloride extraction system for fly ash washing liquid from waste incineration is characterized by comprising an air stripping tower, a pH adjustment tank, a filter press, a double-effect forced circulation evaporator, a single-effect forced circulation evaporator, a DTB crystallizer, a dryer, a single-effect forced circulation evaporator, a fluidized bed, an electrostatic separator, a heating furnace, and three sets of centrifuges, namely a first centrifuge, a second centrifuge, and a third centrifuge. The air stripping tower is provided with a fly ash washing liquid inlet, and the liquid outlet of the air stripping tower is connected to the pH adjustment tank, which is connected to the filter press. The filter press has a clear liquid outlet connected to a double-effect forced circulation evaporator. The double-effect forced circulation evaporator, the first centrifuge, the first-effect forced circulation evaporator, the second centrifuge, the DTB crystallizer, the third centrifuge, and the single-effect forced circulation evaporator are connected in sequence. The salt outlets of the second and third centrifuges are connected to a dryer. The outlet of the dryer and the ammonia outlet of the air stripping tower are both connected to a fluidized bed. The fluidized bed is also connected to an electrostatic separator. The electrostatic separator is connected to a heating furnace. The ammonia outlet of the heating furnace is connected to the fluidized bed.

[0006] Preferably, an ammonia storage tank is also connected between the air stripping tower and the fluidized bed, and the ammonia gas from the air stripping tower enters the fluidized bed after passing through the ammonia storage tank.

[0007] Preferably, a buffer tank is also connected between the filter press and the double-effect forced circulation evaporator, and the filter press is provided with a heavy metal sludge outlet.

[0008] Preferably, the first centrifuge is provided with a sodium chloride outlet, the electrostatic separator is provided with potassium chloride and sodium chloride outlets, and the heating furnace is provided with an anhydrous calcium chloride outlet.

[0009] A process for extracting calcium chloride from waste incineration fly ash washing liquid includes the following steps: The fly ash washing liquid enters the air stripping tower for ammonia removal, then enters the pH adjustment tank to adjust the pH, and finally enters the filter press to filter out insoluble matter to obtain a clear liquid. The clear liquid enters the double-effect forced circulation evaporator for evaporation and crystallization. After reaching the preset density, it enters the first centrifuge to obtain the first crystalline salt and the first centrifugal mother liquor. The first crystalline salt is packaged as a de-icing agent. The first centrifugal mother liquor enters a single-effect forced circulation evaporator for further evaporation. After reaching the preset density, it enters a second centrifuge to obtain the second crystalline salt and the second centrifugal mother liquor, respectively. The second centrifugal mother liquor enters the DTB crystallizer for cooling and crystallization. The third crystalline salt and the third centrifugal mother liquor are obtained by centrifugation of the second centrifuge. The third centrifugal mother liquor is concentrated by evaporation in a single-effect forced circulation evaporator and then spray-dried to obtain anhydrous calcium chloride with a purity of over 95%. The second and third crystallized salts are mixed and fed into a dryer for drying and dehydration. After being cooled by dehumidified cold air, they are fully contacted with the ammonia gas produced by the deammoniation of the air stripping tower in a fluidized bed at room temperature to generate octaammonia calcium chloride. The powder is then separated in an electrostatic separator to obtain a high-purity mixture of octaammonia calcium chloride, potassium chloride, and sodium chloride. High-purity octaammonium calcium chloride is heated and decomposed in a furnace to obtain high-purity anhydrous calcium chloride and ammonia gas. The ammonia gas is then refluxed back into the fluidized bed.

[0010] Preferably, a 32% hydrochloric acid solution is added to the pH adjustment tank to adjust the pH to 9.

[0011] Preferably, the boiling point in the double-effect forced circulation evaporator is controlled at 115~122℃, the density range is 1.18~1.25g / ml, and the sodium chloride mass fraction in the first crystalline salt is >94%.

[0012] Preferably, the boiling point in the first-effect forced circulation evaporator is controlled at 122~130℃, the density range is 1.22~1.29g / ml, and the total mass fraction of potassium chloride and calcium chloride in the second crystalline salt is 10~20%.

[0013] Preferably, the cooling crystallization temperature of the DTB crystallizer is 33~39°C, and the mass fraction of potassium chloride in the third crystallized salt is 50~60%.

[0014] Preferably, the drying temperature of the dryer is 300℃, and the voltage range of the electrostatic separator is 10~15kV.

[0015] In summary, the present invention has the following beneficial effects: 1. This invention improves the purity of calcium chloride products by adding an ammonia removal process and using an air stripping tower to separate precipitates containing heavy metals and ammonium salts. The ammonium salt removal rate is ≥99.3%.

[0016] 2. This invention uses an electrostatic separation process to input powder into a high-voltage electric field. KCl, NaCl (positively charged) and octaammonium chloride (negatively charged) are collected on both sides of the electrode, effectively separating the solid mixed salts. The final calcium chloride obtained has a purity of ≥98%.

[0017] 3. This invention recycles the ammonia gas generated by the air stripping tower and the heating furnace, thereby effectively reducing carbon emissions. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall process of a calcium chloride extraction system and process for fly ash washing liquid from waste incineration according to the present invention. Detailed Implementation

[0019] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. These embodiments do not constitute a limitation on the present invention.

[0020] like Figure 1The system shown is a calcium chloride extraction system for fly ash washing liquid from waste incineration, comprising an air stripping tower, a pH adjustment tank, a filter press, a double-effect forced circulation evaporator, a single-effect forced circulation evaporator, a DTB crystallizer, a dryer, a single-effect forced circulation evaporator, a fluidized bed, an electrostatic separator, a heater, and three centrifuges. The three centrifuges are designated as a first centrifuge, a second centrifuge, and a third centrifuge. The air stripping tower has a fly ash washing liquid inlet, and its liquid outlet is connected to the pH adjustment tank. The pH adjustment tank is connected to the filter press. The filter press is connected to the double-effect forced circulation evaporator. The double-effect forced circulation evaporator, the first centrifuge, the first-effect forced circulation evaporator, the second centrifuge, the DTB crystallizer, the third centrifuge, and the single-effect forced circulation evaporator are connected in sequence. The salt outlets of the second and third centrifuges are connected to the dryer. The outlet of the dryer and the ammonia outlet of the air stripping tower are both connected to the fluidized bed. The fluidized bed is also connected to an electrostatic separator. The electrostatic separator is connected to the heating furnace. The ammonia outlet of the heating furnace is connected to the fluidized bed.

[0021] An ammonia storage tank is also connected between the air stripping tower and the fluidized bed. The ammonia gas from the air stripping tower enters the fluidized bed through the ammonia storage tank.

[0022] A buffer tank is also connected between the filter press and the double-effect forced circulation evaporator, and the filter press is equipped with a heavy metal sludge outlet.

[0023] The first centrifuge is equipped with a sodium chloride outlet, the electrostatic separator is equipped with potassium chloride and sodium chloride outlets, and the heating furnace is equipped with an anhydrous calcium chloride outlet.

[0024] A process for extracting calcium chloride from waste incineration fly ash washing liquid includes the following steps: The fly ash washing liquid enters the air stripping tower for ammonia removal, then enters the pH adjustment tank to adjust the pH, and finally enters the filter press to filter out insoluble matter to obtain a clear liquid. The clear liquid enters the double-effect forced circulation evaporator for evaporation and crystallization. After reaching the preset density, it enters the first centrifuge to obtain the first crystalline salt and the first centrifugal mother liquor. The first crystalline salt is packaged as a de-icing agent. The first centrifugal mother liquor enters a single-effect forced circulation evaporator for further evaporation. After reaching the preset density, it enters a second centrifuge to obtain the second crystalline salt and the second centrifugal mother liquor, respectively. The second centrifugal mother liquor enters the DTB crystallizer for cooling and crystallization. The third crystalline salt and the third centrifugal mother liquor are obtained by centrifugation of the second centrifuge. The third centrifugal mother liquor is concentrated by evaporation in a single-effect forced circulation evaporator and then spray-dried to obtain anhydrous calcium chloride with a purity of over 95%. The second and third crystallized salts are mixed and fed into a dryer for drying and dehydration. After being cooled by dehumidified cold air, they are fully contacted with the ammonia gas produced by the deammoniation of the air stripping tower in a fluidized bed at room temperature to generate octaammonia calcium chloride. The powder is then separated in an electrostatic separator to obtain a high-purity mixture of octaammonia calcium chloride, potassium chloride, and sodium chloride. High-purity octaammonium calcium chloride is heated and decomposed in a furnace to obtain high-purity anhydrous calcium chloride and ammonia gas. The ammonia gas is then refluxed back into the fluidized bed.

[0025] Add a 32% hydrochloric acid solution to the pH adjustment tank to adjust the pH to 9.

[0026] The boiling point in the double-effect forced circulation evaporator is controlled at 115~122℃, the density range is 1.18~1.25g / ml, and the sodium chloride mass fraction in the first crystallized salt is >94%.

[0027] The boiling point in the single-effect forced circulation evaporator is controlled at 122~130℃, the density range is 1.22~1.29g / ml, and the total mass fraction of potassium chloride and calcium chloride in the second crystallized salt is 10~20%.

[0028] The cooling crystallization temperature of the DTB crystallizer is 33~39℃, and the mass fraction of potassium chloride in the third crystallized salt is 50~60%.

[0029] The drying temperature of the dryer is 300℃, and the voltage range of the electrostatic separator is 10~15kV.

[0030] Example Deammoniation and heavy metal removal processes Raw material: Fly ash washing solution, density 1.045 g / ml, pH 14, containing NH4+. + .

[0031] Equipment: Adjustment tank (pH meter, stirrer), centrifuge, sedimentation tank.

[0032] Operating steps: Ammonia removal in air stripping tower; pH adjustment: add hydrochloric acid (32%) to lower the pH to 9, stir for 30 min to generate Mg(OH)2 and Fe(OH)3 precipitates; centrifuge to obtain clear liquid (calcium chloride concentration 2.63%) and precipitate (containing heavy metals and ammonium salts).

[0033] Double-effect counter-current forced circulation evaporation process Raw material: the supernatant after ammonia and heavy metal removal, pH 9.

[0034] Equipment: Forced circulation heat exchanger, crystallizer, forced circulation pump, discharge pump, thickener, centrifuge, mother liquor tank, mother liquor tank agitator, vacuum pump.

[0035] Operating steps: The raw material is evaporated and crystallized in the second effect until the density is 1.22 g / ml, then discharged and centrifuged. The mother liquor is pumped into the first effect for further evaporation and crystallization until the density is 1.26 g / ml, then centrifuged to remove the salt.

[0036] DTB Cooling Crystallization Process Raw material: thermal crystallization mother liquor, density 1.26 g / ml.

[0037] Equipment: DTB crystallizer, shell and tube heat exchanger, circulating pump, discharge pump, thickener, thickener agitator, centrifuge.

[0038] Operating steps: The hot crystallization mother liquor is pumped into the DTB crystallizer and cooled to 37°C for crystallization. The residence time is 8 hours. The crystals are discharged by the discharge pump to the thickener and then centrifuged by the centrifuge.

[0039] High-temperature drying and low-temperature complexing process Raw materials: single-effect crystallizing salt and DTB cold crystallizing salt.

[0040] Equipment: Fluidized bed dryer (drying temperature 300℃), dehumidifier.

[0041] Operating steps: The mixed salt enters the fluidized bed dryer and is dried and dehydrated at 300℃. After being cooled by dehumidified cold air, it comes into full contact with the ammonia gas produced by the ammonia removal process at room temperature in the fluidized bed to generate octaammoniacalcium chloride.

[0042] Electrostatic separation and ammonia circulation process Raw material: octaammoniacalcium chloride powder (particle size 150~200μm).

[0043] Equipment: Electrostatic separator (voltage range 10~15kV).

[0044] Operating steps: Electrostatic separation: Powder is input into a high-voltage electric field (12kV), and KCl, NaCl (positively charged) and octaammonium chloride (negatively charged) are collected on the two electrodes respectively.

[0045] Calcium chloride purification process Raw material: octaammoniacalcium chloride powder (purity 98%).

[0046] Equipment: heating furnace, cyclone separator.

[0047] Operating steps: Heating decomposition: The powder is kept at 80℃ for 2 hours to completely decompose into calcium chloride (≥95%) and ammonia (recycling rate ≥90%).

[0048] Product separation: Ammonia is recovered by a cyclone separator, and calcium chloride is packaged after being cooled to room temperature.

[0049] Mother liquor concentrated and then spray dried Raw material: cold crystallization mother liquor.

[0050] Equipment: Forced circulation heat exchanger, crystallizer separator, spray dryer (temperature 300℃, inlet air velocity 0.8m / s).

[0051] Operating steps: The cold crystallization mother liquor is evaporated and concentrated to a density of 1.37 g / ml by a single-effect forced circulation evaporator; spray drying: the concentrated liquid is sprayed into the drying tower through an atomizer (particle size 5~10 μm) to form amorphous calcium chloride particles (moisture content <0.5%).

[0052] This invention improves the purity of calcium chloride products by adding an ammonia removal process and using an air stripping tower to separate precipitates containing heavy metals and ammonium salts. The ammonium salt removal rate is ≥99.3%.

[0053] This invention uses an electrostatic separation process to input powder into a high-voltage electric field. KCl, NaCl (positively charged), and octaammonium chloride (negatively charged) are collected on two electrodes respectively, effectively separating the solid mixed salts. The final calcium chloride obtained has a purity of ≥98%.

[0054] This invention recycles the ammonia gas generated by the air stripping tower and the heating furnace, thereby effectively reducing carbon emissions.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within the scope of its essence and protection. Such modifications or equivalent substitutions should also be considered to fall within the protection scope of the present invention.

Claims

1. A calcium chloride extraction system for waste incineration fly ash washing liquid, characterized in that, The air stripping tower is provided with a fly ash water washing liquid inlet, a liquid outlet of the air stripping tower is communicated with a pH adjusting tank, the pH adjusting tank is communicated with a filter press, a clear liquid outlet of the filter press is communicated with a two-effect forced circulation evaporator, the two-effect forced circulation evaporator, a first centrifugal machine, a one-effect forced circulation evaporator, a second centrifugal machine, a DTB crystallizer, a third centrifugal machine and a single-effect forced circulation evaporator are sequentially communicated, salt outlets of the second centrifugal machine and the third centrifugal machine are communicated with a dryer, an outlet of the dryer and an ammonia gas outlet of the air stripping tower are both communicated with a fluidized bed, the fluidized bed is further communicated with an electrostatic separator, the electrostatic separator is communicated with a heating furnace, and an ammonia gas outlet of the heating furnace is communicated with the fluidized bed.

2. The system for extracting calcium chloride from a waste incineration fly ash water wash solution of claim 1, wherein: An ammonia water storage tank is further arranged and communicated between the air stripping tower and the fluidized bed, and the ammonia gas outlet of the air stripping tower enters the fluidized bed through the ammonia water storage tank.

3. The system for extracting calcium chloride from a waste incineration fly ash water wash solution of claim 1, wherein: A buffer tank is further arranged and communicated between the filter press and the two-effect forced circulation evaporator, and the filter press is provided with a heavy metal sludge outlet.

4. The system for extracting calcium chloride from a waste incineration fly ash water wash solution of claim 1, wherein: The first centrifugal machine is provided with a sodium chloride outlet, the electrostatic separator is provided with potassium chloride and sodium chloride outlets, and the heating furnace is provided with an anhydrous calcium chloride outlet.

5. The process for extracting calcium chloride from a waste incineration fly ash water wash solution according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: The fly ash water washing liquid enters the air stripping tower for ammonia removal, then enters the pH adjusting tank for pH adjustment, and then enters the filter press to filter out insoluble substances to obtain clear liquid; The clear liquid enters the two-effect forced circulation evaporator for evaporation crystallization, and then enters the first centrifugal machine when reaching a preset density, to obtain first crystalline salt and first centrifugal mother liquor, and the first crystalline salt is packaged and treated as a snow melting agent; The first centrifugal mother liquor enters the one-effect forced circulation evaporator for continuous evaporation, and then enters the second centrifugal machine when reaching a preset density, to obtain second crystalline salt and second centrifugal mother liquor; The second centrifugal mother liquor enters the DTB crystallizer for cooling crystallization, and then is centrifugally separated by the second centrifugal machine to obtain third crystalline salt and third centrifugal mother liquor, and the third centrifugal mother liquor is evaporated and concentrated by the single-effect forced circulation evaporator, and then is spray dried to obtain anhydrous calcium chloride with a purity of more than 95%; The second crystalline salt and the third crystalline salt are mixed and sent into the dryer for drying and dehydration, and the dehumidified cold air is used for cooling, and the ammonia gas generated by the ammonia removal of the air stripping tower is fully contacted with the cold air in the fluidized bed to generate calcium chloride octoammine, and the subsequent powder is separated in the electrostatic separator to obtain high-purity calcium chloride octoammine and a mixture of potassium chloride and sodium chloride; The high-purity calcium chloride octoammine is heated in the heating furnace to obtain high-purity anhydrous calcium chloride and ammonia gas, and the ammonia gas is reflowed into the fluidized bed.

6. A process for the extraction of calcium chloride from a waste incineration fly ash water wash liquor according to claim 5, characterised in that: A hydrochloric acid solution with a mass fraction of 32% is added to the pH adjusting tank to adjust the pH to 9.

7. A process for the extraction of calcium chloride from a waste incineration fly ash water wash liquor according to claim 5 characterised in that: The boiling point in the double-effect forced circulation evaporator is controlled at 115-122 ℃, the density range is 1.18-1.25 g / ml, and the mass fraction of sodium chloride in the first crystallized salt is > 94%.

8. A process for the extraction of calcium chloride from a waste incineration fly ash water wash liquor according to claim 5 characterised in that: The boiling point in the single-effect forced circulation evaporator is controlled at 122-130 ℃, the density range is 1.22-1.29 g / ml, and the total mass fraction of potassium chloride and calcium chloride in the second crystallized salt is 10-20%.

9. A process for the extraction of calcium chloride from a waste incineration fly ash water wash liquor according to claim 5 characterised in that: The cooling crystallization temperature of the DTB crystallizer is 33-39 ℃, and the mass fraction of potassium chloride in the third crystallized salt is 50-60%.

10. A process for extracting calcium chloride from a waste incineration fly ash water wash solution according to claim 5, characterized in that: The drying temperature of the dryer is 300 ℃, and the voltage range of the electrostatic separator is 10-15 kV.

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