CN115448330B - System and process for recycling and separating chloride salt in flue gas after plasma melting of fly ash - Google Patents
System and process for recycling and separating chloride salt in flue gas after plasma melting of fly ash Download PDFInfo
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Abstract
The invention discloses a recovery and separation system and a process for chlorine salt in flue gas after fly ash plasma melting, wherein the system comprises a quenching tower, a molten salt storage tank A, a heat exchanger and a molten salt storage tank B which form a closed loop; the molten salt storage tank A is externally connected with a heavy metal recycling system, the molten salt storage tank B is externally connected with a cooling crystallizer, and the heat exchanger is externally connected with a superheated steam output device. Compared with the prior art, the invention has the advantages that: (1) The system and the process avoid the pollution risk of dioxin and the use of chemical agents caused by water washing; (2) The system and the process adopt molten salt circulation heat exchange to cool the flue gas, fully utilize the waste heat of the flue gas, and do not need to spray water into the flue gas for quenching, so that the water washing liquid does not need to be subjected to precipitation filtration and evaporative crystallization; (3) The system and the process avoid the problem that the mixed salt is difficult to go out after the chlorine salt is recovered, and can realize the separation of sodium chloride, potassium chloride and calcium chloride by fractional crystallization in the molten salt storage tank.
Description
Technical Field
The invention belongs to the technical field of environmental engineering, relates to a downstream treatment technology of household garbage incineration, and in particular relates to a system and a process for recovering and separating chloride salt in flue gas after plasma melting of fly ash.
Background
Fly ash generated by incineration of household garbage contains a large amount of toxic and harmful substances such as heavy metals, dioxin, chloride salts and the like, and belongs to dangerous waste HW18. At present, the fly ash is mainly treated in a landfill mode after solidification, and the method needs to occupy a large amount of land resources and has serious secondary pollution risk. Plasma melting technology is one of the most advanced fly ash disposal methods at present, and the method can decompose dioxin in the fly ash into CO and CO 2 、H 2 O, HCl, and heavy metals are wrapped in a tetrahedral network structure of the glass body and cannot be leached out. Through plasma melting technology, the problems of dioxin and heavy metal pollution in fly ash can be effectively solved. However, the problem of chloride pollution is not solved. The main components of the chloride salt in the fly ash comprise sodium chloride, potassium chloride and calcium chloride, and the main components account for about 20-45% of the total mass of the fly ash. After the fly ash is melted by plasma, most of sodium chloride and potassium chloride and a small amount of calcium chloride enter the flue gas. The melting point of the chlorine salt is 700-800 ℃, when the temperature of the flue gas in the pipeline is reduced, the chlorine salt is easily condensed in the pipeline to form a very hard salt shell, thereby blocking the pipeline and causing the equipment to stop the furnace.
Chinese patent application CN 113105138A discloses a method and system for treating waste incineration fly ash by water washing and dechlorination and evaporating water washing liquid for fractional crystallization. The method realizes the separation and recovery of chloride in the fly ash through the steps of three-stage washing, filtering and precipitating, evaporative crystallization, crystallization separation and the like. However, this method requires washing fly ash with water, drying the washed fly ash, precipitating and filtering the washing liquid, and evaporating and crystallizing, and thus requires a large amount of chemical agents and energy. In addition, the washing liquid contains a small amount of fine fly ash particles, and inevitably contains a small amount of dioxin, so that the risk of dioxin pollution still exists.
Chinese patent application CN 107008127a discloses a wet purification process of plasma fly ash molten tail gas. The technology rapidly cools the fly ash molten tail gas to below 100 ℃, then passes through a water washing tower and an alkali washing tower, and then carries out precipitation, flocculation, separation and drying to recycle chloride salt in the tail gas. However, the method needs to quench the flue gas, and wastes a large amount of flue gas waste heat. And the water washing liquid also needs to be subjected to precipitation filtration and evaporation crystallization after the water washing tower, so that a large amount of chemical agents and energy are consumed. In addition, the chlorine salt obtained by the method is a mixture of sodium chloride and potassium chloride, and cannot meet the standards of industrial salts.
Chinese patent No. CN 113441536B discloses a fly ash treatment system and a fly ash treatment method. The method comprises the steps of firstly removing dust from flue gas after the fly ash is melted, then cooling the flue gas, condensing chlorine salt on the inner wall, and then starting a heater to melt the chlorine salt and discharging and collecting the chlorine salt. The method needs a high-temperature dust remover, has higher technical requirements and cost, and can easily condense chloride in a pipeline and the dust remover. In addition, the chlorine salts condense on the inner wall, forming a very hard salt shell, which is difficult to melt by heating. And the method consumes a great deal of energy, and the obtained mixture is also a mixture of sodium chloride and potassium chloride.
In summary, the existing separation and recovery method of chloride salt in flue gas after the plasma melting of fly ash has the following defects: (1) the residual heat of the flue gas cannot be utilized; (2) evaporating water consumes a large amount of energy; (3) mixed salts are obtained instead of technical salts.
Disclosure of Invention
The technical problems to be solved are as follows: in order to overcome the defects in the prior art, the molten salt circulation heat exchange is adopted to cool the flue gas, so that on one hand, the risk of dioxin pollution caused by water washing is avoided, on the other hand, the waste heat of the flue gas is fully utilized, and the water washing liquid is not required to be subjected to precipitation filtration and evaporative crystallization; in addition, the process of the invention realizes the separation of sodium chloride, potassium chloride and calcium chloride, and meets the standards of industrial salts. In view of this, the invention provides a system and a process for recovering and separating chloride salt from flue gas after the plasma melting of fly ash.
The technical scheme is as follows: the system comprises a quenching tower, a molten salt storage tank A, a heat exchanger and a molten salt storage tank B which form a closed loop, wherein a molten salt pump A is arranged between the molten salt storage tank A and the heat exchanger, a molten salt pump B is arranged between the heat exchanger and the molten salt storage tank B, and a molten salt pump C is arranged between the molten salt storage tank B and the quenching tower; the molten salt storage tank A is externally connected with a heavy metal recycling system, the molten salt storage tank B is externally connected with a cooling crystallizer, and the heat exchanger is externally connected with a superheated steam output device.
Preferably, a longitudinal baffle is arranged in the middle of the interior of the molten salt storage tank A.
The process for recycling and separating chloride from the flue gas after the plasma melting of the fly ash by using the system comprises the following steps:
s1, conveying high-temperature flue gas obtained after the plasma melting of fly ash to a quenching tower, and simultaneously spraying low-temperature molten salt into the quenching tower to enable the high-temperature flue gas and the low-temperature molten salt to exchange heat in a countercurrent mode to form high-temperature molten salt and treated flue gas, and discharging the treated flue gas through a flue gas outlet and purifying the flue gas;
s2, enabling the high-temperature molten salt generated in the S1 to enter a molten salt storage tank A, standing, precipitating and separating, discharging heavy metal precipitates to a heavy metal recycling system, and sending the treated high-temperature molten salt into a heat exchanger through a molten salt pump A;
s3, indirectly exchanging heat between the high-temperature molten salt and water in the heat exchanger, heating the water into superheated steam, and then enabling the superheated steam to enter superheated steam output equipment, and simultaneously enabling the high-temperature molten salt to be cooled to be low-temperature molten salt;
s4, the low-temperature molten salt enters a molten salt storage tank B through a molten salt pump B, a part of the molten salt enters a cooling crystallizer, and a part of the molten salt circulates back to the quenching tower; in a cooling crystallizer, sodium chloride, calcium chloride and potassium chloride are obtained by sectional cooling crystallization separation.
Preferably, the high-temperature flue gas in the S1 enters from the lower part of the quenching tower and is discharged from the upper part of the quenching tower, and the low-temperature molten salt is sprayed downwards from the top of the quenching tower.
Preferably, the low-temperature molten salt sprayed in the S1 comprises sodium chloride, potassium chloride, calcium chloride=40-60:30-40:10-20, and the use temperature of the molten salt is 500-900 ℃.
Preferably, the droplet size of the molten salt injection at low temperature in S1 is 100-200 μm.
Preferably, in S2, the high-temperature molten salt generated in S1 enters into a side of a baffle of the molten salt storage tank a, which is far away from the molten salt pump a.
Preferably, in S2, after standing, precipitation and separation, high-temperature molten salt containing heavy metal is deposited at the bottom of one side of the baffle, and supernatant fluid flows to the other side of the baffle and is sent to the heat exchanger through the molten salt pump A.
Preferably, in the step S4, the low-temperature molten salt components in the molten salt storage tank B are controlled to be sodium chloride, potassium chloride and calcium chloride=40-60:30-40:10-20 according to weight percentage; the specific method comprises the following steps: and (3) periodically sampling and detecting the molten salt in the molten salt storage tank B, and when the weight percentage of the molten salt exceeds the weight percentage range, discharging all the molten salt in the molten salt storage tank B into a cooling crystallizer for salt separation, and re-proportioning the molten salt in the weight percentage range.
Preferably, in S4, the first stage is the crystallization temperature of 490-500 ℃ of sodium chloride, the second stage is the crystallization temperature of 470-480 ℃ of calcium chloride, and the third stage is the crystallization temperature of 450-460 ℃ of potassium chloride during the stage cooling crystallization.
The beneficial effects are that: (1) The system and the process avoid the pollution risk of dioxin and the use of chemical agents caused by water washing; (2) The system and the process adopt molten salt circulation heat exchange to cool the flue gas, fully utilize the waste heat of the flue gas, and do not need to spray water into the flue gas for quenching, so that the water washing liquid does not need to be subjected to precipitation filtration and evaporative crystallization; (3) The system and the process avoid the problem that the mixed salt is difficult to go out after the chlorine salt is recovered, and can realize the separation of sodium chloride, potassium chloride and calcium chloride by fractional crystallization in the molten salt storage tank.
Drawings
FIG. 1 is a schematic flow chart of the process of the present invention;
FIG. 2 is a schematic diagram of the system of the present invention;
wherein, 1 is the quench tower, 2 is fused salt holding vessel A,3 is fused salt pump A,4 is the heat exchanger, 5 is fused salt pump B,6 is fused salt holding vessel B,7 is fused salt pump C,8 is cooling crystallizer, 9 is superheated steam output device.
Detailed Description
The following examples further illustrate the invention but are not to be construed as limiting the invention. Modifications and substitutions to the method, steps or conditions of the invention without departing from the spirit and nature of the invention are intended to be within the scope of the invention. The technical means used in the examples are conventional means well known to those skilled in the art unless otherwise indicated.
Example 1
1-2, a system for recovering and separating chloride from flue gas after plasma melting of fly ash is characterized by comprising a quenching tower 1, a molten salt storage tank A2, a heat exchanger 4 and a molten salt storage tank B6 which form a closed loop, wherein a molten salt pump A3 is arranged between the molten salt storage tank A2 and the heat exchanger 4, a molten salt pump B5 is arranged between the heat exchanger 4 and the molten salt storage tank B6, and a molten salt pump C7 is arranged between the molten salt storage tank B6 and the quenching tower 1; the molten salt storage tank A2 is externally connected with a heavy metal recycling system, the molten salt storage tank B6 is externally connected with the cooling crystallizer 8, and the heat exchanger 4 is externally connected with the superheated steam output device 9.
A longitudinal baffle plate is arranged in the middle of the inside of the molten salt storage tank A2.
The process for recycling and separating chloride from the flue gas after the plasma melting of the fly ash by using the system comprises the following steps:
s1, conveying high-temperature flue gas obtained after the plasma melting of fly ash to a quenching tower 1, and simultaneously spraying low-temperature molten salt into the quenching tower 1 to enable the high-temperature flue gas and the low-temperature molten salt to exchange heat in a countercurrent mode to form high-temperature molten salt and treated flue gas, and discharging the treated flue gas through a flue gas outlet and purifying the flue gas;
s2, enabling the high-temperature molten salt generated in the S1 to enter a molten salt storage tank A2, standing, precipitating and separating, discharging heavy metal precipitates to a heavy metal recycling system, and sending the treated high-temperature molten salt into a heat exchanger 4 through a molten salt pump A3;
s3, indirectly exchanging heat between the high-temperature molten salt and water in the heat exchanger 4, heating the water into superheated steam, and then enabling the superheated steam to enter the superheated steam output equipment 9, and simultaneously enabling the high-temperature molten salt to be cooled to be low-temperature molten salt;
s4, enabling the low-temperature molten salt to enter a molten salt storage tank B6 through a molten salt pump B5, enabling a part of the molten salt to enter a cooling crystallizer 8, and enabling a part of the molten salt to circulate back to the quenching tower 1; in the cooling crystallizer 8, sodium chloride, calcium chloride and potassium chloride are obtained by fractional cooling crystallization separation.
The high-temperature flue gas in S1 enters from the lower part of the quenching tower 1, is discharged from the upper part of the quenching tower 1, and the low-temperature molten salt is sprayed downwards from the top of the quenching tower 1.
The low-temperature molten salt sprayed in the S1 comprises the components of sodium chloride, potassium chloride, calcium chloride=40-60:30-40:10-20, and the use temperature of the molten salt is 500-900 ℃.
The particle size of the liquid drops sprayed by the low-temperature molten salt in the step S1 is 100-200 mu m.
In S2, the high-temperature molten salt generated in S1 enters one side of a baffle of the molten salt storage tank A2, which is far away from the molten salt pump A3.
In S2, after standing, precipitation and separation, high-temperature molten salt containing heavy metal is deposited at the bottom of one side of the baffle, and supernatant fluid flows to the other side of the baffle and is sent to the heat exchanger 4 through the molten salt pump A3.
In S4, the low-temperature molten salt components in the molten salt storage tank B6 are controlled to be sodium chloride, potassium chloride and calcium chloride=40-60:30-40:10-20 according to weight percentage; the specific method comprises the following steps: and (3) periodically sampling and detecting the molten salt in the molten salt storage tank B6, and when the weight percentage of the molten salt exceeds the weight percentage range, discharging all the molten salt in the molten salt storage tank B6 into the cooling crystallizer 8 for salt separation, and re-proportioning the molten salt in the weight percentage range.
In S4, the first stage is the crystallization temperature of 490-500 ℃ of sodium chloride, the second stage is the crystallization temperature of 470-480 ℃ of calcium chloride, and the third stage is the crystallization temperature of 450-460 ℃ of potassium chloride during the sectional cooling crystallization.
Example 2
The system and the process described in the embodiment 1 are adopted to recycle and separate the chloride salt in the flue gas after the plasma melting of the fly ash, and the specific steps are as follows:
s1, conveying high-temperature flue gas obtained after the plasma melting of fly ash to a quenching tower 1, and simultaneously spraying low-temperature molten salt into the quenching tower 1 to enable the high-temperature flue gas and the low-temperature molten salt to exchange heat in a countercurrent mode to form high-temperature molten salt and treated flue gas, and discharging the treated flue gas through a flue gas outlet; wherein, high temperature flue gas enters from the lower part of the quenching tower 1, and is discharged from the upper part, and low temperature molten salt is sprayed downwards from the top of the quenching tower 1. The inlet temperature of the high-temperature flue gas is 910 ℃, and the outlet temperature is 590 ℃; the inlet temperature of the low-temperature molten salt is 550 ℃, and the outlet temperature is 840 ℃. In the process, chloride salt in the high-temperature flue gas becomes liquid particles, heavy metals are condensed into solid small particles, and the solid small particles are separated from gas phase and enter the high-temperature molten salt. The particle size of the liquid drops sprayed by the low-temperature molten salt is 170 mu m, so that the full mixing and heat transfer of the molten salt and the high-temperature flue gas are ensured, and the chlorine salt and heavy metal in the high-temperature flue gas are completely dissolved into the molten salt as much as possible.
And S2, enabling the high-temperature molten salt generated in the S1 to enter a molten salt storage tank A2, standing, precipitating and separating, discharging heavy metal precipitates to a heavy metal recycling system, and sending the treated high-temperature molten salt into a heat exchanger 4 through a molten salt pump A3. Wherein, high temperature fused salt gets into fused salt holding vessel A2 baffle and keeps away from the left side of fused salt pump A3, and heavy metal in the high temperature fused salt is because of the density is great, separates with high temperature fused salt, deposits the bottom of fused salt holding vessel A2. And discharging heavy metals from the bottom of the molten salt storage tank A2 at regular intervals, and recycling resources. The temperature of the high-temperature molten salt at the outlet of the molten salt storage tank A2 is 830 ℃.
S3, indirectly exchanging heat between the high-temperature molten salt and water in the heat exchanger 4, heating the water into superheated steam and enabling the superheated steam to enter the superheated steam output equipment 9, and simultaneously enabling the high-temperature molten salt to be cooled to be low-temperature molten salt. The water is heated to be superheated steam at 400 ℃ from room temperature, and can be sold for heat supply, power generation and the like. The temperature of the low-temperature molten salt after heat exchange is 570 ℃.
S4, enabling the low-temperature molten salt to enter a molten salt storage tank B6 through a molten salt pump B5, enabling a part of the molten salt to enter a cooling crystallizer 8, and enabling a part of the molten salt to circulate back to the quenching tower 1; in the cooling crystallizer 8, sodium chloride, calcium chloride and potassium chloride are obtained through sectional cooling crystallization separation, wherein the crystallization temperature of the sodium chloride is 495 ℃, the crystallization temperature of the calcium chloride is 475 ℃, and the crystallization temperature of the potassium chloride is 455 ℃. The low-temperature molten salt temperature at the outlet of the molten salt storage tank B6 is 550 ℃.
In addition, in the embodiment, the low-temperature molten salt component in the molten salt storage tank B6 still needs to be controlled to be sodium chloride, potassium chloride and calcium chloride=40-60:30-40:10-20, and the concrete method is that the molten salt in the tank is periodically sampled and detected, if the molten salt component deviates from the range, the molten salt in the tank is required to be completely discharged into a cooling crystallizer for salt separation, and new molten salt is re-proportioned, so that the molten salt can be prevented from being decomposed due to too low use temperature or blocked due to too high use temperature.
In the embodiment, the low-temperature molten salt and the high-temperature flue gas are directly mixed and heat-transferred in the practical application process. On one hand, the waste heat of the flue gas is fully utilized and converted into sensible heat of molten salt, and then superheated steam is generated to supply heat and generate power; on the other hand, the chlorine salt and heavy metal in the flue gas are dissolved into molten salt, and then the recycling of the chlorine salt and the heavy metal is realized through precipitation and cooling, so that the defect that a large amount of medicaments and energy are needed in a water washing method is avoided.
The components of the chlorine salt in the low-temperature molten salt are strictly controlled to be sodium chloride, potassium chloride and calcium chloride, and the components of the molten salt are also sodium chloride, potassium chloride and calcium chloride. Sodium chloride: potassium chloride: calcium chloride=40 to 60: 30-40: 10-20, the use temperature of the fused salt of the component is about 500-900 ℃. On the one hand, the chlorine salt in the flue gas is dissolved into the fused salt to the greatest extent by utilizing the similar compatibility principle; on the other hand, the fluctuation of the components of the molten salt is small so as to prolong the recycling time.
In the embodiment, according to different crystallization separation temperatures of sodium chloride, calcium chloride and potassium chloride, the molten salt is subjected to distributed cooling crystallization, so that the efficient separation of sodium chloride, calcium chloride and potassium chloride is realized. The method can obtain purer industrial salt, and solves the problem that the conventional method is difficult to obtain mixed salt.
The proportions and purities of sodium chloride, calcium chloride and potassium chloride obtained by the chlorine salt recovery and separation system in this example are shown in the following table.
| Component (A) | Proportion (%) | Purity (%) |
| Sodium chloride | 67 | 98.3 |
| Calcium chloride | 12 | 97.5 |
| Potassium chloride | 21 | 95.6 |
Example 3
The system and the process described in the embodiment 1 are adopted to recycle and separate the chloride salt in the flue gas after the plasma melting of the fly ash, and the specific steps are as follows:
s1, conveying high-temperature flue gas obtained after the plasma melting of fly ash to a quenching tower 1, and simultaneously spraying low-temperature molten salt into the quenching tower 1 to enable the high-temperature flue gas and the low-temperature molten salt to exchange heat in a countercurrent mode to form high-temperature molten salt and treated flue gas, and discharging the treated flue gas through a flue gas outlet; wherein, high temperature flue gas enters from the lower part of the quenching tower 1, and is discharged from the upper part, and low temperature molten salt is sprayed downwards from the top of the quenching tower 1. The inlet temperature of the high-temperature flue gas is 890 ℃, and the outlet temperature is 570 ℃; the inlet temperature of the low-temperature molten salt is 550 ℃, and the outlet temperature is 820 ℃. In the process, chloride salt in the high-temperature flue gas becomes liquid particles, heavy metals are condensed into solid small particles, and the solid small particles are separated from gas phase and enter the high-temperature molten salt. The particle size of the liquid drops sprayed by the low-temperature molten salt is 140 mu m, so that the full mixing and heat transfer of the molten salt and the high-temperature flue gas are ensured, and the chlorine salt and heavy metal in the high-temperature flue gas are completely dissolved into the molten salt as much as possible.
And S2, enabling the high-temperature molten salt generated in the S1 to enter a molten salt storage tank A2, standing, precipitating and separating, discharging heavy metal precipitates to a heavy metal recycling system, and sending the treated high-temperature molten salt into a heat exchanger 4 through a molten salt pump A3. Wherein, high temperature fused salt gets into fused salt holding vessel A2 baffle and keeps away from the left side of fused salt pump A3, and heavy metal in the high temperature fused salt is because of the density is great, separates with high temperature fused salt, deposits the bottom of fused salt holding vessel A2. And discharging heavy metals from the bottom of the molten salt storage tank A2 at regular intervals, and recycling resources. The temperature of the high-temperature molten salt at the outlet of the molten salt storage tank A2 is 810 ℃.
S3, indirectly exchanging heat between the high-temperature molten salt and water in the heat exchanger 4, heating the water into superheated steam and enabling the superheated steam to enter the superheated steam output equipment 9, and simultaneously enabling the high-temperature molten salt to be cooled to be low-temperature molten salt. The water is heated to be superheated steam at 400 ℃ from room temperature, and can be sold for heat supply, power generation and the like. The temperature of the low-temperature molten salt after heat exchange is 550 ℃.
S4, enabling the low-temperature molten salt to enter a molten salt storage tank B6 through a molten salt pump B5, enabling a part of the molten salt to enter a cooling crystallizer 8, and enabling a part of the molten salt to circulate back to the quenching tower 1; in the cooling crystallizer 8, sodium chloride, calcium chloride and potassium chloride are obtained through sectional cooling crystallization separation, wherein the crystallization temperature of the sodium chloride is 492 ℃, the crystallization temperature of the calcium chloride is 472 ℃, and the crystallization temperature of the potassium chloride is 452 ℃. The low-temperature molten salt temperature at the outlet of the molten salt storage tank B6 is 530 ℃.
In addition, in the embodiment, the low-temperature molten salt component in the molten salt storage tank B6 still needs to be controlled to be sodium chloride, potassium chloride and calcium chloride=40-60:30-40:10-20, and the concrete method is that the molten salt in the tank is periodically sampled and detected, if the molten salt component deviates from the range, the molten salt in the tank is required to be completely discharged into a cooling crystallizer for salt separation, and new molten salt is re-proportioned, so that the molten salt can be prevented from being decomposed due to too low use temperature or blocked due to too high use temperature.
In the embodiment, the low-temperature molten salt and the high-temperature flue gas are directly mixed and heat-transferred in the practical application process. On one hand, the waste heat of the flue gas is fully utilized and converted into sensible heat of molten salt, and then superheated steam is generated to supply heat and generate power; on the other hand, the chlorine salt and heavy metal in the flue gas are dissolved into molten salt, and then the recycling of the chlorine salt and the heavy metal is realized through precipitation and cooling, so that the defect that a large amount of medicaments and energy are needed in a water washing method is avoided.
The components of the chlorine salt in the low-temperature molten salt are strictly controlled to be sodium chloride, potassium chloride and calcium chloride, and the components of the molten salt are also sodium chloride, potassium chloride and calcium chloride. Sodium chloride: potassium chloride: calcium chloride=40 to 60: 30-40: 10-20, the use temperature of the fused salt of the component is about 500-900 ℃. On the one hand, the chlorine salt in the flue gas is dissolved into the fused salt to the greatest extent by utilizing the similar compatibility principle; on the other hand, the fluctuation of the components of the molten salt is small so as to prolong the recycling time.
In the embodiment, according to different crystallization separation temperatures of sodium chloride, calcium chloride and potassium chloride, the molten salt is subjected to distributed cooling crystallization, so that the efficient separation of sodium chloride, calcium chloride and potassium chloride is realized. The method can obtain purer industrial salt, and solves the problem that the conventional method is difficult to obtain mixed salt.
The proportions and purities of sodium chloride, calcium chloride and potassium chloride obtained by the chlorine salt recovery and separation system in this example are shown in the following table.
| Component (A) | Proportion (%) | Purity (%) |
| Sodium chloride | 63 | 99.1 |
| Calcium chloride | 14 | 97.9 |
| Potassium chloride | 23 | 96.1 |
Claims (8)
1. The recovery and separation process of chloride in the flue gas after the plasma melting of the fly ash is characterized by comprising the following steps of:
s1, conveying high-temperature flue gas obtained after the plasma melting of fly ash to a quenching tower (1), simultaneously spraying low-temperature molten salt into the quenching tower (1) to enable the high-temperature flue gas and the low-temperature molten salt to exchange heat in a countercurrent manner to form high-temperature molten salt and treated flue gas, and discharging the treated flue gas through a flue gas outlet and then purifying the flue gas;
s2, enabling the high-temperature molten salt generated in the S1 to enter a molten salt storage tank A (2), standing, precipitating and separating, discharging heavy metal precipitates to a heavy metal recycling system, and sending the treated high-temperature molten salt into a heat exchanger (4) through a molten salt pump A (3);
s3, indirectly exchanging heat between the high-temperature molten salt and water in the heat exchanger (4), heating the water into superheated steam, and then enabling the superheated steam to enter the superheated steam output equipment (9), and simultaneously enabling the high-temperature molten salt to be cooled to be low-temperature molten salt;
s4, enabling the low-temperature molten salt to enter a molten salt storage tank B (6) through a molten salt pump B (5), enabling a part of the molten salt to enter a cooling crystallizer (8), and enabling a part of the molten salt to circulate back to the quenching tower (1); in a cooling crystallizer (8), sodium chloride, calcium chloride and potassium chloride are obtained by sectional cooling crystallization separation;
the recovery separation system adopted by the process comprises a quenching tower (1) forming a closed loop, a molten salt storage tank A (2), a heat exchanger (4) and a molten salt storage tank B (6), wherein a molten salt pump A (3) is arranged between the molten salt storage tank A (2) and the heat exchanger (4), a molten salt pump B (5) is arranged between the heat exchanger (4) and the molten salt storage tank B (6), and a molten salt pump C (7) is arranged between the molten salt storage tank B (6) and the quenching tower (1); the molten salt storage tank A (2) is externally connected with a heavy metal recycling system, the molten salt storage tank B (6) is externally connected with a cooling crystallizer (8), and the heat exchanger (4) is externally connected with a superheated steam output device (9);
a longitudinal baffle is arranged in the middle of the inside of the molten salt storage tank A (2).
2. The recovery and separation process of chloride in flue gas after plasma melting of fly ash according to claim 1, wherein the high temperature flue gas in S1 enters from the lower part of the quenching tower (1), and is discharged from the upper part, and the low temperature molten salt is sprayed downwards from the top of the quenching tower (1).
3. The recovery and separation process of chloride in flue gas after plasma melting of fly ash according to claim 1, wherein the low-temperature molten salt component sprayed in S1 is sodium chloride, potassium chloride, calcium chloride=40-60:30-40:10-20, and the use temperature of the molten salt is 500-900 ℃.
4. The recovery and separation process of chloride in flue gas after plasma melting of fly ash according to claim 1, wherein the particle size of droplets sprayed by low-temperature molten salt in S1 is 100-200 μm.
5. The recovery and separation process of chloride in flue gas after plasma melting of fly ash according to claim 1, wherein in S2, high-temperature molten salt generated by S1 enters into one side of a baffle of a molten salt storage tank a (2) far away from a molten salt pump a (3).
6. The process for recycling and separating chloride from flue gas after plasma melting of fly ash according to claim 1, wherein in S2, high-temperature molten salt containing heavy metal is deposited at the bottom of one side of the baffle plate after standing, precipitation and separation, and supernatant fluid flows to the other side of the baffle plate and is sent to the heat exchanger (4) through the molten salt pump a (3).
7. The recovery and separation process of chloride in flue gas after plasma melting of fly ash according to claim 1, wherein in S4, the low-temperature molten salt component in the molten salt storage tank B (6) needs to be controlled to be sodium chloride, potassium chloride, calcium chloride=40-60:30-40:10-20 in percentage by weight; the specific method comprises the following steps: and (3) periodically sampling and detecting the molten salt in the molten salt storage tank B (6), and when the weight percentage of the molten salt exceeds the weight percentage range, discharging all the molten salt in the molten salt storage tank B (6) into a cooling crystallizer (8) for salt separation, and re-proportioning the molten salt in the weight percentage range.
8. The process for recovering and separating chloride from flue gas after plasma melting of fly ash according to claim 1, wherein in S4, the crystallization temperature of sodium chloride is 490-500 ℃ in the first stage, 470-480 ℃ in the second stage and 450-460 ℃ in the third stage during the stage cooling crystallization.
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