CN114888056A - Method for synchronously solidifying carbon dioxide and deeply dechlorinating waste incineration fly ash - Google Patents

Abstract

The invention discloses a method for synchronously solidifying carbon dioxide and deeply dechlorinating waste incineration fly ash. The method performs three-stage countercurrent water washing on waste incineration fly ash. The carbon dioxide-containing gas is introduced into the slurry formed by fly ash and water for reaction. The method uses the carbonation of waste incineration fly ash to couple the process of chlorine eluting with countercurrent water. In the case of low, the dechlorination rate of waste incineration fly ash can be improved, and carbon dioxide can be effectively solidified simultaneously.

Description

A method for simultaneous solidification of carbon dioxide and deep dechlorination of waste incineration fly ash

technical field

The invention relates to a water washing treatment method for waste incineration fly ash, in particular to a method for synchronously solidifying carbon dioxide and deep dechlorination of waste incineration fly ash, and belongs to the field of fly ash solid waste recycling treatment.

Background technique

Domestic waste treatment in my country has entered the stage of incineration and is in the mature stage of the industry. In the process of waste incineration, the organic matter is converted into gas and discharged into the atmosphere, while the inorganic matter forms solid particles, and the finer particles pass from the incinerator along the flue gas to the next system, and finally these particles react with the added purifying agent and react. The products together constitute the waste incineration fly ash.

China produces a large amount of waste incineration fly ash every year, and the fly ash contains high CaO content, which is easy to form CaCO ₃ precipitation with CO ₂ . Fly ash used for carbonization has great potential to sequester carbon dioxide, and carbonized fly ash can also be reused as building aggregate after carbonation.

Based on the characteristics of waste incineration fly ash, there is currently no process that can perform carbon sequestration and deep dechlorination at the same time. The treatment methods for waste incineration fly ash include water washing, sintering, and stabilization technology. As an economical and feasible method, water washing is easy to operate and low in cost, and can dissolve most of the soluble chloride salts in the fly ash of waste incineration. In the application of the existing waste incineration fly ash washing technology, most of them focus on the technical improvement of ordinary washing, adding various leaching agents on the basis of washing, which is expensive, consumes huge amounts of water, and most of them are difficult to apply to specific engineering applications. However, the dechlorination degree of current waste incineration fly ash is not high, and deep dechlorination cannot be carried out, which also limits the resource utilization of waste incineration fly ash.

SUMMARY OF THE INVENTION

Aiming at the technical problem that conventional water washing is difficult to achieve deep dechlorination of waste incineration fly ash in the prior art, resulting in limited resource utilization of waste incineration fly ash, the purpose of the present invention is to provide a kind of waste incineration fly ash synchronously solidifying carbon dioxide and deep The method of dechlorination, this method introduces carbon dioxide-containing gas in the process of dechlorination of waste incineration fly ash water, utilizes the characteristics of high specific surface area, high porosity and active calcium oxide of waste incineration fly ash to realize the fixation of carbon dioxide, and at the same time utilizes Carbon dioxide is used to promote the dissolution of chlorides in the process of washing chlorine with water, which greatly improves the dechlorination efficiency of waste incineration fly ash. Compared with the traditional water washing method of waste incineration fly ash, it can improve the dechlorination rate at lower solid-liquid conditions , and can effectively synchronize carbon dioxide fixation, and carbon dioxide can be derived from industrial flue gas, in line with the development concept of "carbon neutrality".

In order to achieve the above-mentioned technical purpose, the present invention provides a method for the simultaneous solidification of carbon dioxide and deep dechlorination of waste incineration fly ash. During the water washing process, a gas containing carbon dioxide is introduced into the slurry formed by the waste incineration fly ash and water for reaction.

The technical scheme of the invention cleverly introduces carbon dioxide gas into the waste incineration fly ash, makes full use of the mutually beneficial relationship between the two in the water washing process, fixes the carbon dioxide through the waste incineration fly ash, and uses carbon dioxide to promote chlorine in the waste incineration fly ash at the same time. Dissolution of salt. Waste incineration fly ash has a large specific surface area, high porosity, and contains active components that can react with _CO , such as alkali metals (Ca, Mg, Na, K) and their oxides (CaO, MgO), etc. These alkali metals When the oxide is in contact with the _CO2 in the flue gas, it will be converted into carbonate, so that the _CO2 is mineralized and the _CO2 is sequestered. At the same time, the carbon dioxide can promote the deep dechlorination of the waste incineration fly ash, and the waste The insoluble chloride salt in incineration fly ash is mainly Friedel Salt, and the following reaction will occur after carbon dioxide is introduced: 3CaO·Al ₂ O ₃ ·CaCl ₂ ·10H ₂ O+3CO ₂ →3CaCO ₃ +Al ₂ O ₃ ·xH ₂ O+CaCl ₂ +(10-x)H ₂ O, which can promote the conversion of this part of insoluble chloride salts into soluble salts by introducing carbon dioxide, and with the introduction of carbon dioxide, the pH of the entire system can be controlled from the original strong The alkalinity is adjusted to weak acidity, which is beneficial to promote the conversion and dissolution of some insoluble chloride salts, thereby improving the removal rate of fly ash chloride salts.

As a preferred solution, in the three-stage countercurrent washing process, the waste incineration fly ash and water are all formed into a slurry according to a liquid-solid ratio of 3mL:1g to 4mL:1g. Compared with no introduction of carbon dioxide, the liquid-solid ratio of water washing is greatly reduced, water consumption is saved, and waste water generation is reduced. The washing water used is not particularly limited, and can be tap water or purified water of industrial wastewater.

As a preferred solution, during the first-stage countercurrent water washing process, gas containing carbon dioxide is introduced into the slurry at a flow rate of 100-200 L/min per kilogram of waste incineration fly ash.

As a preferred solution, during the first-stage countercurrent washing process, the pH of the slurry is controlled within the range of 6.0-6.5.

As a preferred solution, during the second-stage countercurrent water washing process, gas containing carbon dioxide is introduced into the slurry at a flow rate of 60-100 L/min per kilogram of waste incineration fly ash.

As a preferred solution, during the second-stage countercurrent washing process, the pH of the slurry is controlled within the range of 5.5-6.0.

In the process of the first-stage countercurrent water washing and the second-stage countercurrent water washing process, the introduction of carbon dioxide gas can promote the dissolution of some insoluble chlorine salts, and at the same time, the weakly acidic carbon dioxide continuously consumes the alkaline substances to make the pH value It is also beneficial to promote the conversion and dissolution of some insoluble chloride salts, thereby improving the removal rate of fly ash chloride salts. The flow of CO ₂ in the first-stage countercurrent washing process is greater than that in the second-stage countercurrent washing process, mainly because the chlorine content of the waste incineration fly ash is relatively higher in the first-stage countercurrent washing process, which requires a larger flow rate of carbon dioxide to achieve In the second-stage countercurrent washing process, the chlorine content in the waste incineration fly ash is relatively reduced, and the required carbon dioxide flow is relatively small, but maintaining the carbon dioxide inflow flow within a certain range can ensure the deep removal of chlorine.

As a preferred solution, the volume percent content of carbon dioxide in the carbon dioxide-containing gas is 5% to 30%. Carbon dioxide-containing gas comes from a wide range of sources and can be industrial flue gas. Specifically, such as iron and steel industry flue gas, waste incineration flue gas, power plant flue gas, etc.

As a preferred solution, in the process of passing the carbon dioxide-containing gas into the slurry, air stone is used to achieve uniform bubbling. By using air stone, carbon dioxide can be stably dispersed into water, and the contact reaction efficiency of carbon dioxide and waste incineration fly ash can be increased.

As a preferred solution, the conditions for each level of countercurrent washing in the three-stage countercurrent washing process are as follows: the temperature is 40°C to 60°C, the time is 40min to 60min, and the stirring rate is 500 to 800r/min. Under the optimal temperature conditions, the waste incineration fly ash can achieve the maximum dechlorination efficiency. If the temperature is too low, the effect of deep dechlorination will not be achieved. The processing cost increases, and the solubility of _CO2 will also decrease at high temperature, which is not conducive to carbon fixation. If the temperature is too low, the reaction efficiency will decrease. Proper stirring is beneficial to improve the gas-liquid-solid three-phase contact reaction efficiency.

As a preferred solution, the third-stage countercurrent water washing adopts a conventional water washing process.

As a preferred solution, solid-liquid separation is achieved by centrifugation after the three-stage countercurrent washing is completed, and the solid moisture content is lower than 35%. By dehydrating the solids to a lower moisture content, residual chlorine levels can be reduced.

Relative to the prior art, the beneficial technical effects brought by the technical solution of the present invention are:

(1) The method for the simultaneous solidification of carbon dioxide and deep dechlorination of fly ash provided by the present invention saves water consumption, the solid-liquid ratio is only 3:1 to 4:1, and the water is recycled through a three-stage countercurrent process.

(2) adopting the method for synchronously solidifying carbon dioxide and deep dechlorination of fly ash provided by the present invention, not only can utilize waste incineration fly ash to realize carbon dioxide fixation, but also utilize carbon dioxide to promote the deep dechlorination of waste incineration fly ash. Waste incineration fly ash has a large specific surface area, high porosity, and is rich in CaO and other active substances that can react with carbon dioxide. It forms CaCO ₃ precipitation with CO ₂ . The waste incineration fly ash is used to store carbon dioxide, and the carbonized fly ash can also be used as building aggregates. Reuse and realize resource utilization. At the same time, the insoluble chlorine salt in the waste incineration fly ash is mainly Friedel Salt. XRD was used to detect the water washed fly ash before and after carbonation, and it was found that the insoluble salt Friedel Salt peak disappeared in the fly ash after the flue gas was introduced. It is because the following reaction occurs after the introduction of carbon dioxide: 3CaO·Al ₂ O ₃ ·CaCl _{2 ·} 10H ₂ O+3CO ₂ →3CaCO ₃ +Al ₂ O ₃ ·xH ₂ O+CaCl ₂ +(10-x)H ₂ O . The pH of the entire system is controlled from strong basicity to weak acidity, which directly promotes the conversion and dissolution of some insoluble chloride salts, thereby improving the removal rate of fly ash chloride salts.

(3) the method for the simultaneous solidification of carbon dioxide and deep dechlorination of the fly ash provided by the invention can also fix heavy metals in the fly ash, and the heavy metals in the solution exist in the form of unstable hydroxides under alkaline conditions, and CO After ₂ , it reacts with it to generate insoluble carbonate.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings that are used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort.

Fig. 1 is the flow chart of the method for the simultaneous solidification of carbon dioxide and deep dechlorination of waste incineration fly ash.

Figure 2 shows the XRD comparison of the waste incineration fly ash after carbonated water washing and ordinary water washing.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

The original chloride ion content of the used incineration fly ash is 20.75%, and the introduced carbon dioxide comes from flue gas, and its volume content is 13%. The fly ash was added to the water washing reactor, the liquid-solid ratio was controlled to be 3:1, the flow rate of the gas containing carbon dioxide was 100 L/min per kilogram of fly ash, and air stone was used to disperse it. Use an electric stirrer to stir for 1 h at a speed of 500 r/min, control the stirring temperature to be 40 °C, and the pH value to be 6.5 to carry out the first-stage water washing process. After solid-liquid separation, water washing liquid and water washing residue are obtained. The washing residue enters the second-stage washing process, and the flow rate of the gas containing carbon dioxide is 60L/min per kilogram of fly ash, and air stone is used to disperse it. Use an electric stirrer to stir for 1 h at a speed of 500 r/min, and control the stirring temperature to be 40 °C and the pH value to be 6.0. After solid-liquid separation, water washing liquid and water washing residue are obtained. The washed slag is subjected to the third-stage water washing process, using an electric stirrer to stir at a speed of 500 r/min for 1 h, and the stirring temperature is controlled to be 40 °C. The first-stage washing liquid is derived from the second-stage washing filtrate, the second-stage washing liquid is derived from the third-stage washing filtrate, and the third-stage washing liquid is the additional tap water added. The water is removed to below 35%. The chlorine content of the final washing residue is 0.86%, which meets the requirements of Article 6.3-c of "HJ-1134-2020": the soluble chlorine content in the treated product should not exceed 2%, preferably not higher than 1%.

Example 2

The original chloride ion content of the used incineration fly ash is 19.25%, and the introduced carbon dioxide comes from flue gas, and its volume content is 30%. The fly ash was placed in the reactor. The liquid-solid ratio was controlled to be 4:1, the flow rate of the gas containing carbon dioxide was 200L/min per kilogram of fly ash, and air stone was used to disperse it. Use an electric stirrer to stir for 1 h at a speed of 800 r/min, control the stirring temperature to be 60 °C, and the pH value to be 6.0 to carry out the first-stage water washing process. After solid-liquid separation, water washing liquid and water washing residue are obtained. The water-washed slag enters the second-stage water-washing process, and the flow rate of the gas containing carbon dioxide is 100L/min per kilogram of fly ash, and air stone is used to disperse it. Use an electric stirrer to stir at a speed of 800 r/min for 1 h, and control the stirring temperature to be 60 °C and the pH value to be 5.5. After solid-liquid separation, water washing liquid and water washing residue are obtained. The washed slag is subjected to the third-stage water washing process, using an electric stirrer to stir at a speed of 800 r/min for 1 hour, and the stirring temperature is controlled to be 60 °C. The first-stage washing liquid is derived from the second-stage washing filtrate, the second-stage washing liquid is derived from the third-stage washing filtrate, and the third-stage washing liquid is additionally added tap water. The solid-liquid separation of each stage must ensure the washing residue The water is removed to below 35%. The chlorine content of the final washing residue is 0.70%, which meets the requirements of Article 6.3-c of "HJ-1134-2020": the soluble chlorine content in the treated product should not exceed 2%, preferably not higher than 1%.

Comparative Example 1

The original chloride ion content of the used incineration fly ash was 20.75%, and the fly ash was placed in the reactor. Control the liquid-solid ratio to 3:1, use an electric stirrer to stir at a speed of 500 r/min for 1 h, control the stirring temperature to 40 °C, and carry out the first-stage water washing process. After solid-liquid separation, water washing liquid and water washing residue are obtained. The washed slag enters the second-stage water washing process, and uses an electric stirrer to stir at a speed of 500 r/min for 1 hour, and the stirring temperature is controlled to be 40 °C. After solid-liquid separation, water washing liquid and water washing residue are obtained. The washed slag was subjected to the third-stage water washing process, using an electric stirrer to stir at a speed of 500 r/min for 1 h, and the stirring temperature was controlled to be 40 °C. The first-stage washing liquid is derived from the second-stage washing filtrate, the second-stage washing liquid is derived from the third-stage washing filtrate, and the third-stage washing liquid is additionally added tap water. The solid-liquid separation of each stage must ensure the washing residue The water is removed to below 35%. The chlorine content of the final washed residue was 2.85%.

Comparative Example 2

The original chloride ion content of the used incineration fly ash was 19.25%, and the fly ash was placed in the reactor. Control the liquid-solid ratio to be 4:1, use an electric stirrer to stir at a speed of 800 r/min for 1 hour, control the stirring temperature to be 60 °C, carry out the first-stage water washing process, and introduce the gas flow rate containing carbon dioxide to be 200L/kg of fly ash. min, use air stone to disperse it. After solid-liquid separation, water washing liquid and water washing residue are obtained. The washed slag enters the second-stage water washing process, and is stirred at a speed of 800 r/min for 1 h with an electric stirrer, and the stirring temperature is controlled to be 60 °C. After solid-liquid separation, water washing liquid and water washing residue are obtained. The washed slag is subjected to the third-stage water washing process, using an electric stirrer to stir at a speed of 800 r/min for 1 hour, and the stirring temperature is controlled to be 60 °C. The first-stage washing liquid is derived from the second-stage washing filtrate, the second-stage washing liquid is derived from the third-stage washing filtrate, and the third-stage washing liquid is additionally added tap water. The solid-liquid separation of each stage must ensure the washing residue The water is removed to below 35%. The chlorine content of the final washed residue was 1.64%.

Claims (10)

1. A method for synchronously solidifying carbon dioxide and deeply dechlorinating waste incineration fly ash is used for carrying out three-level countercurrent washing on the waste incineration fly ash and is characterized by comprising the following steps of: in the first stage countercurrent water washing and the second stage countercurrent water washing, gas containing carbon dioxide is introduced into slurry formed by the waste incineration fly ash and water to react.

2. The method for synchronously solidifying carbon dioxide and deeply dechlorinating the waste incineration fly ash according to the claim 1, characterized by comprising the following steps: in the three-stage countercurrent washing process, the waste incineration fly ash and water form slurry according to the liquid-solid ratio of 3mL to 1 g-4 mL to 1 g.

3. The method for synchronously solidifying carbon dioxide and deeply dechlorinating the waste incineration fly ash according to the claim 1, characterized by comprising the following steps: and in the first stage of counter-current water washing process, introducing gas containing carbon dioxide into the slurry at a flow rate of 100-200L/min per kilogram of waste incineration fly ash.

4. The method for synchronously solidifying carbon dioxide and deeply dechlorinating the waste incineration fly ash according to the claim 1 or the 3, characterized by comprising the following steps: and in the first stage of counter-current washing process, the pH of the slurry is controlled within the range of 6.0-6.5.

5. The method for synchronously solidifying carbon dioxide and deeply dechlorinating the waste incineration fly ash according to the claim 1, characterized by comprising the following steps: and in the second stage of counter-current water washing, introducing gas containing carbon dioxide into the slurry at a flow rate of 60-100L/min per kilogram of waste incineration fly ash.

6. The method for synchronously solidifying carbon dioxide and deeply dechlorinating the waste incineration fly ash according to the claim 1 or the 5, characterized by comprising the following steps: and in the second stage of counter-current washing process, the pH of the slurry is controlled within the range of 5.5-6.0.

7. The method for synchronously solidifying carbon dioxide and deeply dechlorinating the waste incineration fly ash according to the claim 1, 3 or 5, characterized by comprising the following steps: the volume percentage content of carbon dioxide in the carbon dioxide-containing gas is 5-30%.

8. The method for synchronously solidifying carbon dioxide and deeply dechlorinating the waste incineration fly ash according to the claim 1, 3 or 5, characterized by comprising the following steps: and the gas containing the carbon dioxide is uniformly bubbled by using a bubbled stone in the process of introducing the gas into the slurry.

9. The method for synchronously solidifying carbon dioxide and deeply dechlorinating the waste incineration fly ash according to the claim 1, is characterized in that: the conditions of all levels of countercurrent washing in the three levels of countercurrent washing processes are as follows: the temperature is 40-60 ℃, the time is 40-60 min, and the stirring speed is 500-800 r/min.

10. The method for synchronously solidifying carbon dioxide and deeply dechlorinating the waste incineration fly ash according to the claim 1, characterized by comprising the following steps: and after all levels of countercurrent washing of the three levels of countercurrent washing are finished, solid-liquid separation is realized by centrifugation, and the solid water content is lower than 35%.

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