Calculation method of effective calcium content in household garbage incineration fly ash

Abstract

The present application relates to the technical field of waste incineration fly ash, and particularly relates to a method for calculating the content of effective calcium in household waste incineration fly ash. The method comprises the following steps: obtaining a mixed solution after water washing and chlorine removal of household waste incineration fly ash; introducing a target gas containing carbon dioxide into the mixed solution; collecting the carbon dioxide concentration of the gas discharged from the mixed solution, and generating a curve of the carbon dioxide concentration changing with time; and calculating the content of effective calcium in the household waste incineration fly ash based on the changing curve, wherein the effective calcium includes basic calcium chloride and calcium hydroxide. The above technical solution can realize the calculation of the content of effective calcium in household waste incineration fly ash.

Description

Technical Field

[0001] This invention relates to the field of waste incineration fly ash technology, and in particular to a method for calculating the effective calcium content in municipal solid waste incineration fly ash. Background Technology

[0002] With the rapid development of the municipal solid waste incineration industry, its incineration capacity has increased year by year. This has also generated a large amount of fly ash enriched with heavy metals and dioxins, necessitating its harmless treatment. With the introduction of the zero-landfill policy for hazardous waste, the resource utilization of fly ash is gradually becoming a trend, and water washing and dechlorination is a crucial step in this process. However, because the high calcium content in fly ash accumulates in the washing solution during the washing process, the subsequent salt separation, salt extraction, and dehardening treatment of the washing solution becomes excessively costly.

[0003] Fly ash carbonation refers to the addition of carbon dioxide during fly ash treatment to simulate the natural weathering process. In this process, carbon dioxide, an acidic gas, reacts with alkaline elements (such as calcium and magnesium) in the fly ash to form thermodynamically stable carbonates. While fixing carbon dioxide, it also has a certain effect on fixing heavy metals, thus achieving the goal of "treating waste with waste." The absorption of carbon dioxide by fly ash is highly dependent on its calcium content, but calcium in fly ash exists in various forms, such as basic calcium chloride, calcium hydroxide, calcium sulfate, and calcium carbonate. Not all calcium-containing substances can react with calcium dioxide. Therefore, to quantify the total amount of calcium in municipal solid waste incineration fly ash that can be fixed through reaction with carbon dioxide, and to demonstrate the potential of fly ash in utilizing carbon dioxide for calcium fixation, the calcium in municipal solid waste incineration fly ash that can react with carbon dioxide can be defined as "effective calcium" (i.e., effective calcium can be considered to include basic calcium chloride and calcium hydroxide).

[0004] Therefore, there is an urgent need for a method to calculate the effective calcium content in fly ash from municipal solid waste incineration to solve the above-mentioned technical problems. Summary of the Invention

[0005] This invention provides a method for calculating the effective calcium content in fly ash from municipal solid waste incineration, which enables the calculation of the effective calcium content in fly ash from municipal solid waste incineration.

[0006] This invention provides a method for calculating the effective calcium content in fly ash from municipal solid waste incineration, comprising:

[0007] Obtain a mixture of fly ash from municipal solid waste incineration after water washing and dechlorination;

[0008] The target gas containing carbon dioxide is introduced into the mixture;

[0009] The carbon dioxide concentration of the gas discharged from the mixture is collected, and a curve of the carbon dioxide concentration changing over time is generated;

[0010] Based on the changing curve, the content of available calcium in the fly ash from the municipal solid waste incineration is calculated; wherein, the available calcium includes basic calcium chloride and calcium hydroxide.

[0011] As described above, the method for calculating the effective calcium content in municipal solid waste incineration fly ash provided by this invention involves passing a target gas containing carbon dioxide into a mixture of municipal solid waste incineration fly ash after water washing and dechlorination. The carbon dioxide concentration of the gas discharged from the mixture is then collected, and a curve showing the change in carbon dioxide concentration over time is generated. Finally, the effective calcium content in the municipal solid waste incineration fly ash can be calculated based on this curve. Therefore, the above technical solution can achieve the calculation of the effective calcium content in municipal solid waste incineration fly ash. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 A flowchart illustrating the method for calculating the effective calcium content in fly ash from municipal solid waste incineration, as provided in this embodiment of the invention.

[0014] Figure 2 The curve showing the change of carbon dioxide concentration over time when introduced into the mixed solution is provided in an embodiment of the present invention;

[0015] Figure 3 The curve showing the change of carbon dioxide concentration over time when introduced into pure water, provided in an embodiment of the present invention;

[0016] Figure 4 The XRD patterns of three different fly ash samples provided in this embodiment of the invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see Figure 1 This invention provides a method for calculating the effective calcium content in fly ash from municipal solid waste incineration, the method comprising:

[0019] Step S1: Obtain the mixture after washing and dechlorinating the fly ash from municipal solid waste incineration;

[0020] Step S2: Pass the target gas containing carbon dioxide into the mixture;

[0021] Step S3: Collect the carbon dioxide concentration of the gas discharged from the mixture and generate a curve showing the change of carbon dioxide concentration over time.

[0022] Step S4: Based on the changing curve, calculate the content of available calcium in the fly ash from municipal solid waste incineration; where available calcium includes basic calcium chloride and calcium hydroxide.

[0023] In this embodiment, a target gas containing carbon dioxide is introduced into the mixture after the municipal solid waste incineration fly ash has been washed and dechlorinated. The carbon dioxide concentration of the gas discharged from the mixture is then collected, and a curve showing the change in carbon dioxide concentration over time is generated. Finally, based on this curve, the effective calcium content in the municipal solid waste incineration fly ash can be calculated. Therefore, the above technical solution can achieve the calculation of the effective calcium content in municipal solid waste incineration fly ash.

[0024] It should be noted that some calcium-containing substances in fly ash can react with carbon dioxide to form calcium carbonate, achieving the dual effect of fixing calcium and storing carbon dioxide. However, calcium in fly ash exists in various forms, and not all calcium-containing substances, such as calcium sulfate, can react with carbon dioxide. Therefore, the calcium in fly ash that can react with carbon dioxide is defined as "effective calcium" to quantify the ability of fly ash to absorb carbon dioxide and its potential to fix calcium in fly ash through carbon dioxide.

[0025] In the high-calcium fly ash produced during the incineration of municipal solid waste, calcium mainly exists in divalent forms, such as CaClOH (basic calcium chloride), Ca(OH)2, CaSO4, and CaCO3. The equations for the reaction of basic calcium chloride and calcium hydroxide with carbon dioxide are shown below:

[0026] 2CaClOH(s)+nH2O→Ca(OH)2+CaCl2gnH2O

[0027] Ca(OH)₂(s) + CO₂ → CaCO₃(s) + H₂O

[0028] As can be seen from the above formula, if calcium and carbon dioxide in fly ash combine, their molar ratio is 1:1.

[0029] In one embodiment of the present invention, the target gas contains carbon dioxide and nitrogen.

[0030] In some implementations, the target gas may contain only carbon dioxide.

[0031] In one embodiment of the present invention, the target gas is the flue gas emitted from a waste-to-energy power plant. Thus, the method provided in this embodiment can be applied to waste-to-energy power plants, demonstrating significant practical engineering value.

[0032] In one embodiment of the present invention, step S2 may specifically include:

[0033] The flue gas emitted from the waste-to-energy plant is introduced into the bottom of the mixture.

[0034] This setup allows the carbon dioxide in the flue gas and the effective calcium in the mixture to react more effectively without the need for external power.

[0035] In one embodiment of the present invention, step S2 may specifically include:

[0036] The flue gas emitted from the waste incineration power plant is introduced into the mixed liquid, and the mixed liquid is stirred.

[0037] This setup allows for better reaction between carbon dioxide in the flue gas and effective calcium in the mixture, but it requires external power (e.g., an agitator) compared to the above embodiments.

[0038] like Figure 2 and Figure 3 As shown, in one embodiment of the present invention, step S4 may specifically include:

[0039] Based on the changing curves, the start and end times of carbon dioxide absorption by the mixture are determined.

[0040] Based on the carbon dioxide concentrations at the start, end, and end times, and the total flow rate of the target gas introduced into the mixed liquid, the effective calcium content in the fly ash from municipal solid waste incineration is calculated.

[0041] Based on the change curve of carbon dioxide concentration, the content of available calcium in fly ash from municipal solid waste incineration can be accurately calculated.

[0042] In one embodiment of the present invention, the starting time is the moment when the carbon dioxide concentration in the changing curve is at its minimum, and the ending time is the moment when the carbon dioxide concentration in the changing curve is at equilibrium.

[0043] In one embodiment of the present invention, the step of "calculating the effective calcium content in the fly ash of municipal solid waste incineration based on the carbon dioxide concentration at the start time, end time, and end time and the total flow rate of the target gas introduced into the mixed liquid" may specifically include:

[0044] Based on the carbon dioxide concentration at the start time, end time, and end time and the total flow rate of the target gas introduced into the mixture, calculate the first volume of carbon dioxide absorbed by the mixture.

[0045] Replace the mixture with pure water and repeat the above steps (i.e., steps S1 to S4) to calculate the second volume of carbon dioxide absorbed by the pure water.

[0046] Based on the mass of the first volume, the second volume, and the mass of the fly ash from municipal solid waste incineration in the mixed liquid, the content of available calcium in the fly ash from municipal solid waste incineration is calculated.

[0047] To eliminate the influence of pure water, a blank experiment needs to be set up, and the volume of carbon dioxide absorbed by the same amount of water needs to be calculated using the same method. That is, carbon dioxide not only reacts with available calcium, but is also absorbed by water in small amounts, so this factor also needs to be considered.

[0048] In one embodiment of the present invention, the first volume is calculated using the following formula:

[0049]

[0050] In the formula, V1 is the first volume, and t 12 t represents the end time when the mixture is introduced into the solution. 11 C represents the initial time when the mixture is introduced into it. 12 A1 is the carbon dioxide concentration at the end time when the mixture is introduced into the liquid, A1 is the integral of the curve of the change from the start time to the end time when the mixture is introduced into the liquid, and Q1 is the total flow rate of the target gas introduced into the mixture.

[0051] The second volume is calculated using the following formula:

[0052]

[0053] In the formula, V2 is the second volume, and t 22 t is the end time when pure water is introduced. 21 C represents the initial time when pure water is introduced. 22 A1 is the carbon dioxide concentration at the end of the flow into pure water, A2 is the integral of the curve showing the change from the start to the end of the flow into pure water, and Q2 is the total flow rate of the target gas flowed into pure water.

[0054] The content of available calcium in fly ash from municipal solid waste incineration is calculated using the following formula:

[0055]

[0056] In the formula, E represents the effective calcium content in the fly ash from municipal solid waste incineration, i.e., the mass of effective calcium contained in a unit mass of fly ash, and V represents the effective calcium content in the fly ash.m M represents the standard gas molar volume (L / mol), and m represents the mass of municipal solid waste incineration fly ash in the mixed liquid or the mass of municipal solid waste incineration fly ash in pure water. Ca Let be the molar mass of calcium; wherein, the mass of fly ash from municipal solid waste incineration in the mixed solution is equal to the mass of fly ash from municipal solid waste incineration in pure water.

[0057] In one embodiment of the present invention, after step S4, the above method may further include:

[0058] Determining the total calcium content in fly ash from municipal solid waste incineration using a digestion method;

[0059] The percentage of available calcium in municipal solid waste incineration fly ash relative to the total calcium in municipal solid waste incineration fly ash can be calculated using the following formula:

[0060]

[0061] In the formula, P is a percentage, m Ca The total calcium content in fly ash from municipal solid waste incineration.

[0062] The P-value provides a clear indication of the effective calcium content in fly ash that can be fixed by carbon dioxide.

[0063] like Figure 4 As shown in the XRD pattern, the CaClOH and Ca(OH)2 peaks of the fly ash treated by this method disappeared, and the main components became CaCO3 and CaSO4. This indicates that after the reaction, the calcium-containing substances in the fly ash that can absorb CO2, such as Ca(OH)2, were basically completely converted into CaCO3.

[0064] It should be noted that, in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0065] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for calculating the effective calcium content in municipal solid waste incineration fly ash, characterized by, include: Obtain a mixture of fly ash from municipal solid waste incineration after water washing and dechlorination; The target gas containing carbon dioxide is introduced into the mixture; The carbon dioxide concentration of the gas discharged from the mixture is collected, and a curve showing the change of the carbon dioxide concentration over time is generated. Based on the changing curve, the content of available calcium in the fly ash from the municipal solid waste incineration is calculated; wherein, the available calcium includes basic calcium chloride and calcium hydroxide; The target gas contains carbon dioxide and nitrogen; The calculation of the available calcium content in the fly ash from municipal solid waste incineration based on the changing curve includes: Based on the changing curve, the start and end times of the carbon dioxide absorption by the mixture are determined. Based on the carbon dioxide concentration at the start time, the end time, and the end time, and the total flow rate of the target gas introduced into the mixture, calculate the effective calcium content in the fly ash from the municipal solid waste incineration. The starting time is the moment when the carbon dioxide concentration in the changing curve is at its minimum, and the ending time is the moment when the carbon dioxide concentration in the changing curve is at equilibrium. The calculation of the available calcium content in the fly ash from municipal solid waste incineration, based on the carbon dioxide concentration at the start time, the end time, and the total flow rate of the target gas introduced into the mixture, includes: Based on the start time, the end time, the carbon dioxide concentration at the end time, and the total flow rate of the target gas introduced into the mixture, calculate the first volume of carbon dioxide absorbed by the mixture; Replace the mixture with pure water and repeat the above steps to calculate the second volume of carbon dioxide absorbed by the pure water. Based on the first volume, the second volume, and the mass of the municipal solid waste incineration fly ash in the mixture, calculate the content of available calcium in the municipal solid waste incineration fly ash; The first volume is calculated using the following formula: In the formula, V 1 For the first volume, t 12 The end time when the mixture is introduced is [the time when it is introduced into the mixture]. t 11 The starting time when the mixture is introduced into the solution. C 12 The carbon dioxide concentration at the end of the flow into the mixture. A 1 The integral of the curve representing the change from the initial time to the final time when the mixture is introduced into it. Q 1 The total flow rate of the target gas introduced into the mixture; The second volume is calculated using the following formula: In the formula, V 2 For the second volume, t 22 The end time when the pure water is introduced. t 21 The starting time when the pure water is introduced. C 22 This represents the carbon dioxide concentration at the end of the process when the pure water is introduced. A 2 The integral of the curve representing the change from the initial time to the final time when the pure water is introduced. Q 2 The total flow rate of the target gas introduced into the pure water; The effective calcium content in the fly ash from municipal solid waste incineration is calculated using the following formula: In the formula, E The effective calcium content in the fly ash from municipal solid waste incineration is defined as the mass of effective calcium contained per unit mass of fly ash. V m The standard gas molar volume is expressed in L / mol. m The mass of the municipal solid waste incineration fly ash in the mixture or the mass of the municipal solid waste incineration fly ash in the pure water. M Ca The molar mass of calcium; wherein the mass of the municipal solid waste incineration fly ash in the mixture is equal to the mass of the municipal solid waste incineration fly ash in the pure water.

2. The method according to claim 1, characterized in that, The target gas is the flue gas emitted from a waste incineration power plant.

3. The method according to claim 2, characterized in that, The step of introducing the target gas containing carbon dioxide into the mixture includes: Flue gas from a waste-to-energy plant is introduced into the bottom of the mixture.

4. The method according to claim 2, characterized in that, The step of introducing the target gas containing carbon dioxide into the mixture includes: Flue gas from the waste incineration power plant is introduced into the mixture, and the mixture is stirred.

5. The method according to claim 1, characterized in that, After calculating the content of available calcium in the fly ash from the municipal solid waste incineration, the method further includes: The total calcium content in the fly ash from the municipal solid waste incineration was determined by digestion. The percentage of available calcium in the fly ash from municipal solid waste incineration to the total calcium in the fly ash is calculated using the following formula: In the formula, P For the percentage, m Ca The total calcium content in the fly ash from the incineration of the municipal solid waste.

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