Method for chloridion elution and dioxin degradation in household garbage incineration fly ash

Abstract

The invention relates to the technical field of household garbage incineration fly ash treatment, and discloses a method for chloridion elution and dioxin degradation in household garbage incineration fly ash, which comprises the following steps: washing and filter-pressing the household garbage incineration fly ash by using a garbage percolation concentrated solution, so that organic matters in the garbage percolation concentrated solution are adsorbed on the household garbage incineration fly ash; the household garbage incineration fly ash is subjected to three-stage countercurrent washing and filter pressing; the household garbage incineration fly ash is subjected to drying and low-temperature pyrolysis under the condition that nitrogen is not introduced, so that dioxin is degraded; the chemical oxygen demand of organic matters in the leachate adsorbed on the household garbage incineration fly ash is not less than 500mg / L, and oxygen in the low-temperature pyrolysis atmosphere can be consumed, so that the volume concentration of the oxygen in the low-temperature pyrolysis atmosphere does not exceed 1%. According to the method, chloride ions in the household garbage incineration fly ash can be effectively eluted, dioxin in the household garbage incineration fly ash can be degraded without depending on nitrogen oxygen control, and the method has good dechlorination and detoxification effects on the household garbage incineration fly ash.

Description

Technical Field

[0001] The invention relates to the technical field of disposal of fly ash from incineration of domestic waste, and in particular to a method for eluting chloride ions in fly ash from incineration of domestic waste and coordinating the degradation of dioxins. Background Art

[0002] With the rapid development of urbanization in recent years, the population growth and the demand for production capacity have inevitably brought about a large increase in solid waste, which has now put tremendous pressure on the environment. Incineration technology has become the main way to treat and dispose of solid waste in countries such as Europe, Japan and Singapore, especially the typical domestic waste and medical waste in urban life, and has shown significant advantages in reducing the amount of waste. Solid waste incineration includes the incineration of domestic waste, medical waste and industrial hazardous waste, which usually produces 3-5% of the total amount of incineration fly ash. These solid waste incineration fly ashes are rich in pollutants such as dioxins, heavy metals and chloride salts, which may potentially threaten the surrounding environment and human health, and are therefore classified as hazardous waste.

[0003] In 2023, more than 70% of domestic waste will be incinerated, and the proportion is on the rise. In order to cope with the adverse effects of persistent organic pollutants represented by dioxin compounds on humans and the environment, my country passed and implemented the "Technical Specifications for Pollution Control of Fly Ash from Incineration of Domestic Waste" (HJ 1134-2020) in 2020, which clearly stated that fly ash can be treated by technologies other than cement kiln co-disposal (low-temperature thermal decomposition, high-temperature sintering and high-temperature melting, etc.), and the dioxin content in the fly ash can be reduced to below 50ng-TEQ / kg, and then further resource utilization can be carried out. As a recommended process for degrading dioxins, the low-temperature pyrolysis process has shown unique advantages in energy consumption and degradation efficiency, and has the potential to become the next generation of industrial disposal methods for degrading dioxins in fly ash.

[0004] However, since the development of low-temperature pyrolysis dioxin technology, a strict inert atmosphere has been a necessary condition for the efficient degradation of dioxins. Therefore, the inevitable leakage of oxygen has become the main reason restricting the promotion of low-temperature pyrolysis dioxin technology in fly ash. Subject to this, existing means usually reduce the impact of leakage oxygen on dioxin degradation by increasing the reaction temperature, increasing the nitrogen supply during the reaction, adding active ingredients or inhibitors, etc. However, in this way, the advantage of low-temperature pyrolysis of dioxins in terms of low energy and high efficiency will no longer exist. Therefore, it is very necessary and urgent to develop a method that can make low-temperature pyrolysis dioxin technology free from atmosphere dependence while further improving the efficiency of dioxin degradation. Summary of the invention

[0005] One of the purposes of the embodiments of the present invention is to provide a method for eluting chloride ions and synergizing dioxin degradation in fly ash from domestic waste incineration, which can effectively elute chloride ions in fly ash from domestic waste incineration and degrade dioxins in fly ash from domestic waste incineration without relying on nitrogen atmosphere, and has a good dechlorination and detoxification effect on fly ash from domestic waste incineration.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for eluting chloride ions from fly ash from the incineration of domestic waste and coordinating the degradation of dioxins is provided, comprising the following steps:

[0008] Step 1: using landfill leachate concentrate to wash and filter press the fly ash from the incineration of domestic waste, so that the organic matter in the landfill leachate concentrate is adsorbed on the fly ash from the incineration of domestic waste;

[0009] Step 2, performing three-stage countercurrent water washing on the domestic waste incineration fly ash after washing and filter pressing with the landfill leachate concentrate;

[0010] Step 3, filter pressing the domestic waste incineration fly ash after the three-stage countercurrent washing;

[0011] Step 4, drying and low-temperature pyrolysis of the household waste incineration fly ash after the filter pressing without nitrogen, so as to degrade dioxins in the household waste incineration fly ash;

[0012] Among them, the chemical oxygen demand of organic matter in the leachate adsorbed on the fly ash of domestic waste incineration is not less than 500 mg / L, which can consume the oxygen in the low-temperature pyrolysis atmosphere so that the volume concentration of oxygen in the low-temperature pyrolysis atmosphere does not exceed 1%.

[0013] As a further solution of the method for eluting chloride ions and synergizing dioxin degradation in fly ash from incineration of domestic waste, the landfill leachate concentrate is the landfill leachate of a domestic waste incineration power plant treated by ultrafiltration, nanofiltration and reverse osmosis system, or the landfill leachate of a domestic waste incineration power plant treated by ultrafiltration and reverse osmosis system. This process is a conventional technology in the art and will not be described in detail.

[0014] In the present invention, the organic matter in the landfill leachate concentrate comprises aromatic hydrocarbons, organic sulfur components, nitriles and phenols, which are used to provide chemical oxygen demand. The landfill leachate concentrate also comprises chlorine, heavy metals and inorganic sulfur components.

[0015] As a further solution of the method for eluting chloride ions and coordinating dioxin degradation in fly ash from incineration of domestic waste, the fly ash from incineration of domestic waste comes from a bag filter in a municipal domestic waste incineration plant.

[0016] In the present invention, the domestic waste incineration fly ash contains calcium sulfate, calcium carbonate, basic calcium chloride, calcium hydroxide, sodium chloride and potassium chloride.

[0017] As a further scheme of the method for eluting chloride ions in domestic waste incineration fly ash and coordinating dioxin degradation, in step 1, the mass ratio of landfill leachate concentrate to domestic waste incineration fly ash is 1 to 5:1.

[0018] As a further scheme of the method for eluting chloride ions from municipal solid waste incineration fly ash and synergizing dioxin degradation, step 1 refers to mixing and stirring the landfill leachate and municipal solid waste incineration fly ash for 20-90 minutes, and then filtering them to allow the organic matter in the landfill leachate to be adsorbed on the municipal solid waste incineration fly ash after filtering.

[0019] As a further solution of the method for eluting chloride ions from domestic waste incineration fly ash and coordinating dioxin degradation, in step 2, the water-ash mass ratio of the three-stage countercurrent washing is 1 to 2: 1. It should be noted that the "ash" in the water-ash mass ratio refers to the domestic waste incineration fly ash without water, and the mass of the dry ash can be calculated by detecting the water content of the domestic waste incineration fly ash containing water after filter pressing.

[0020] As a further solution of the method for eluting chloride ions from domestic waste incineration fly ash and coordinating dioxin degradation, in step 3, the washed domestic waste incineration fly ash is filtered by plate and frame filter pressing, and the pressure of the plate and frame filter pressing is 0.4 to 1.5 MPa.

[0021] Among them, the filter pressing in step 2 is the same as the plate and frame filter pressing process in step 3, and the details are not repeated here.

[0022] As a further solution of the method for eluting chloride ions and coordinating dioxin degradation in fly ash from the incineration of domestic waste, in step 4, the temperature of low-temperature pyrolysis is 300-600°C, and the residence time of the low-temperature pyrolysis reaction is 20-120 minutes.

[0023] As a further scheme of the method for eluting chloride ions and coordinating dioxin degradation in municipal solid waste incineration fly ash, in step 4, the dioxin content in the municipal solid waste incineration fly ash after low-temperature pyrolysis treatment is less than 50 ng-TEQ / kg, and the chloride ion content is less than 2%.

[0024] Beneficial effects:

[0025] The present invention utilizes landfill leachate concentrate to wash domestic waste incineration fly ash to elute chloride ions in the domestic waste incineration fly ash. Based on the relationship between the components of the domestic waste incineration fly ash and the components of the landfill leachate concentrate, and the characteristic that the domestic waste incineration fly ash has developed multi-pores, organic matter in the landfill leachate concentrate can be adsorbed on the domestic waste incineration fly ash during the chlorine elution process. When the washed domestic waste incineration fly ash is dried and low-temperature pyrolyzed after filter pressing, the chemical oxygen demand of the organic matter in the leachate adsorbed on the domestic waste incineration fly ash is not less than 500 mg / L, which consumes oxygen in the low-temperature pyrolysis atmosphere and can control the oxygen volume content in the low-temperature pyrolysis atmosphere to no more than 1%, so that the atmosphere meets the conditions required for the degradation of dioxins. Nitrogen does not need to be introduced into the entire low-temperature pyrolysis process, effectively saving resources.

[0026] The present invention uses landfill leachate concentrate to wash the fly ash from the incineration of domestic waste and then performs three-stage countercurrent washing. The water-ash mass ratio in the three-stage countercurrent washing process is 1-2:1 to achieve the effect of eluting chlorine, while the conventional three-stage countercurrent washing of the fly ash from the incineration of domestic waste requires a water-ash mass ratio of 3:1 to achieve the effect of eluting chlorine. Compared with the prior art, the present invention can save water for washing the fly ash from the incineration of domestic waste.

[0027] The present invention has a good dechlorination and detoxification effect on fly ash from the incineration of domestic waste. After the fly ash is washed, the chloride salts and metals in the ash washing water are both resources. The process can be coupled with chemical precipitation, crystallization evaporation and other processes to achieve the recovery and reuse of chloride salts and metal resources in the ash. The process flow is simple and the operation is convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention is further described in detail below based on the accompanying drawings and embodiments.

[0029] Figure 1 is a comparison chart of the changes of domestic waste incineration fly ash before and after washing with landfill leachate concentrate in an embodiment of the present invention;

[0030] Figure 2 is a comparison chart of changes in the landfill leachate concentrate after washing the fly ash from the incineration of domestic waste with the landfill leachate concentrate in the embodiment of the present invention;

[0031] Figure 3 Schematic diagram of the distribution of residual dioxin homologues after low-temperature pyrolysis of domestic waste incineration fly ash washed with landfill leachate concentrate in an embodiment of the present invention;

[0032] Figure 4 It is a schematic diagram of the toxicity distribution of residual dioxin homologues after low-temperature pyrolysis of domestic waste incineration fly ash after washing with landfill leachate concentrate in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the technical problems solved by the present invention, the technical solutions adopted and the technical effects achieved clearer, the technical solutions of the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0034] Example 1

[0035] 20kg of dried domestic waste incineration fly ash (water content <3%, referred to as raw ash) collected from the bag filter in the municipal domestic waste incineration plant and 40kg of landfill leachate concentrate from the water system of the domestic waste incineration power plant were placed in a 100L mechanical stirring reactor and stirred for 20 minutes. The sample was then filtered at a pressure of 0.6MPa using a plate and frame filter press to reduce its water content. Figure 1 The household waste incineration fly ash and the Figure 2 The landfill leachate concentrate before and after washing the fly ash from the incineration of domestic waste is shown in Figure 1 and Figure 2 The leachate concentrate in the above all refers to the landfill leachate concentrate. The municipal solid waste incineration fly ash after filter pressing was washed by three-stage countercurrent water washing (water-ash mass ratio was 2:1), and then the sample was filtered by a plate and frame filter press at a pressure of 0.6 MPa to obtain the washed municipal solid waste incineration fly ash (referred to as washed ash).

[0036] Chemical oxygen demand (COD) can only detect solution samples, so the COD before and after leachate washing fly ash was detected using the national standard method GB11914-89, which was 1792 mg / L and 1292 mg / L respectively. Therefore, it can be inferred that during the leachate washing process, the fly ash adsorbed organic matter in the leachate concentrate and the COD was 500 mg / L, that is, the COD of the washed ash was 500 mg / L.

[0037] The washed ash is dried in a low-temperature pyrolysis device until the moisture content does not exceed 1%, and then the dried washed ash is subjected to low-temperature pyrolysis treatment, wherein the low-temperature pyrolysis process parameters are pyrolysis at 450°C for 60 minutes. After detection, the volume concentration of oxygen in the pyrolysis atmosphere is less than 1%; the fly ash after pyrolysis is referred to as pyrolysis ash.

[0038] X-ray fluorescence spectrometry (XRF, EDX-8000, Shimadzu, Japan) was used to detect the soluble chlorine content in the raw ash and the washed ash. The soluble chlorine content in the raw ash was 25.2%, and the soluble chlorine content in the washed ash was 1.5%.

[0039] The dioxin concentrations in the washed ash and pyrolysis ash were detected by high-resolution gas chromatography-high-resolution mass spectrometry (HRGC-HRMS, AutoSpec Premier, Waters, USA), which were 3783.4 ng / kg and 22.7 ng / kg, respectively, and the dioxin degradation efficiency reached 99.4%. The concentration distribution and toxicity distribution of dioxin homologues in pyrolysis ash are shown in Figure 2. Figure 3 and Figure 4 As shown, the residual toxicity of dioxins in pyrolysis ash is 1.22ng-TEQ / kg.

[0040] Example 2

[0041] 20kg of dried domestic waste incineration fly ash (water content <3%, referred to as raw ash) collected from the bag filter in the municipal domestic waste incineration plant and 40kg of landfill leachate concentrate in the water system of the domestic waste incineration power plant were placed in a 100L mechanical stirring reactor and stirred for 60 minutes. The sample was then filtered at a pressure of 0.6MPa through a plate and frame filter press to reduce its moisture content. The filtered domestic waste incineration fly ash was washed with three-stage countercurrent water washing (water-ash mass ratio of 2:1), and then filtered at a pressure of 0.6MPa through a plate and frame filter press to obtain washed domestic waste incineration fly ash (referred to as washed ash).

[0042] The same method as in Example 1 was used to detect the COD before and after the fly ash was washed with leachate, which were 1792 mg / L and 56 mg / L, respectively. Therefore, it can be inferred that the fly ash adsorbed the organic matter in the leachate during the leachate washing process, and the COD was 1736 mg / L, that is, the COD of the washed ash was 1736 mg / L.

[0043] The washed ash is dried in a low-temperature pyrolysis device until the moisture content does not exceed 1%, and then the dried washed ash is subjected to low-temperature pyrolysis treatment, wherein the low-temperature pyrolysis process parameters are 400°C for 60 minutes. After testing, the volume concentration of oxygen in the pyrolysis atmosphere is less than 1%; the fly ash after pyrolysis is referred to as pyrolysis ash.

[0044] The soluble chlorine content in the raw ash and the washed ash was detected by the same method as in Example 1. The soluble chlorine content in the raw ash was 25.2%, and the soluble chlorine content in the washed ash was 1.2%.

[0045] The dioxin concentrations in the washed ash and pyrolysis ash were measured in the same manner as in Example 1, and the results were 3783.4 ng / kg and 18.5 ng / kg, respectively, and the dioxin degradation efficiency reached 99.5%. The residual toxicity of dioxins in the pyrolysis ash was 1.20 ng-TEQ / kg.

[0046] In the above embodiment of the present invention, the oxygen volume concentration in the low-temperature pyrolysis process can be kept at no more than 1% without introducing nitrogen. The low-temperature pyrolysis dioxin process under the low oxygen concentration condition exhibits extremely high dioxin degradation efficiency.

[0047] As a method for co-disposing two types of waste to improve dioxin degradation efficiency, the embodiments of the present invention show great potential for application.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for eluting chloride ions and coordinating dioxin degradation in fly ash from incineration of domestic waste, characterized in that: The following steps are involved: Step 1: using landfill leachate concentrate to wash and filter press the fly ash from the incineration of domestic waste, so that the organic matter in the landfill leachate concentrate is adsorbed on the fly ash from the incineration of domestic waste; Step 2, performing three-stage countercurrent water washing on the domestic waste incineration fly ash after washing and filter pressing with the landfill leachate concentrate; Step 3, filter pressing the domestic waste incineration fly ash after the three-stage countercurrent washing; Step 4: drying and low-temperature pyrolysis the household waste incineration fly ash after the filter pressing without introducing nitrogen to degrade dioxins in the household waste incineration fly ash; Among them, the chemical oxygen demand of organic matter in the leachate adsorbed on the fly ash of domestic waste incineration is not less than 500 mg / L, which can consume the oxygen in the low-temperature pyrolysis atmosphere so that the volume concentration of oxygen in the low-temperature pyrolysis atmosphere does not exceed 1%.

2. The method for eluting chloride ions and coordinating dioxin degradation in fly ash from incineration of domestic waste according to claim 1, characterized in that: The domestic waste incineration fly ash comes from the bag filter in the urban domestic waste incineration plant.

3. The method for eluting chloride ions and coordinating dioxin degradation in fly ash from incineration of domestic waste according to claim 1, characterized in that: In step 1, the mass ratio of landfill leachate concentrate to domestic waste incineration fly ash is 1 to 5:

1.

4. The method for eluting chloride ions and coordinating dioxin degradation in fly ash from incineration of domestic waste according to claim 1, characterized in that: Step 1 refers to mixing the landfill leachate concentrate and the domestic waste incineration fly ash for 20-90 minutes, and then performing filter pressing.

5. The method for eluting chloride ions and coordinating dioxin degradation in fly ash from incineration of domestic waste according to claim 1, characterized in that: In step 2, the water-to-ash mass ratio of the three-stage countercurrent washing is 1 to 2:

1.

6. The method for eluting chloride ions and coordinating dioxin degradation in fly ash from incineration of domestic waste according to claim 1, characterized in that: In step 3, the washed domestic waste incineration fly ash is filtered by plate and frame filter pressing, and the pressure of the plate and frame filter pressing is 0.4 to 1.5 MPa.

7. The method for eluting chloride ions and synergizing dioxin degradation in fly ash from incineration of domestic waste according to claim 1, wherein in step 4, the temperature of low-temperature pyrolysis is 300-600°C, and the residence time of the low-temperature pyrolysis reaction is 20-120 min.

8. The method for eluting chloride ions and synergizing dioxin degradation in fly ash from incineration of domestic waste according to claim 1, wherein in step 4, the dioxin content in the fly ash from incineration of domestic waste after low-temperature pyrolysis is less than 50 ng-TEQ / kg, and the chloride ion content is less than 2%.

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