Multi-stage countercurrent water washing method for incineration fly ash based on the calculation of optimal liquid-solid ratio based on the balance method

Abstract

The present invention relates to fly ash washing technology, and aims to provide a multi-stage countercurrent washing method for incineration fly ash that calculates the optimal liquid-solid ratio based on the balance method. The method is to use a multi-stage washing device to wash the original fly ash with a countercurrent washing process, add a salt-containing waste liquid for coordinated disposal to the washing device during the washing process, and add pure water in the last stage; the balance method means that after each stage of the washing device completes the solid-liquid mixing, the migration of chloride salts can approximately reach a balance state, and the calculation of the optimal liquid-solid ratio of the washing process aims to achieve this balance state. The present invention can quantitatively calculate the required liquid-solid ratio value based on the expected dechlorination effect and the properties of the fly ash raw materials, filling the gap in the existing waste incineration fly ash washing process parameter design; it can realize the liquid-solid ratio parameter design calculation under the complex conditions of coordinated disposal of salt solution and taking multiple stages; the calculated parameters are used for the specific implementation of the incineration fly ash multi-stage countercurrent washing process.

Description

Technical Field

[0001] The invention relates to the technical field of fly ash washing, and in particular to a multi-stage countercurrent washing method for incineration fly ash based on a balance method for calculating an optimal liquid-solid ratio. Background Art

[0002] The continuous development of waste incineration technology has brought about a large number of incineration fly ash disposal problems. The chloride salt content in fly ash usually accounts for more than 50%, which will cause equipment corrosion, form secondary fly ash or crusting and ringing, affect product quality and promote dioxin generation, and have a serious adverse effect on the fly ash disposal process, which needs to be removed in advance. The current common practice is to desalinate fly ash by water washing, and it is a multi-stage countercurrent water washing.

[0003] The current method for determining the liquid-to-solid ratio parameters of the water washing process is not accurate enough and lacks a design calculation method. For example, the Chinese patent application "Method and system for treating waste incineration fly ash by water washing, dechlorination and evaporation, fractionation and crystallization of washing liquid" (CN113105138) gives the preferred ratio of three-stage countercurrent water washing as 1:2-1:4L / kg, and the most preferred ratio is 1:3L / kg; although the document gives the preferred range and value, it does not give a calculation method for adjusting the liquid-to-solid ratio. If it is to be promoted and applied, it cannot be adjusted according to actual production conditions. In addition, due to the large fluctuations in the composition of fly ash raw materials, inaccurate liquid-to-solid ratio parameters can easily lead to insufficient dechlorination effect or high water volume problems, making it difficult to meet the expected results.

[0004] The fly ash washing process mainly includes the solid-liquid mixing process and the solid-liquid separation process. The former is used to dissolve the soluble salt, and the latter is used to separate the salt solution. Studies have shown that the soluble salt in fly ash dissolves quickly. If the single solid-liquid mixing time is guaranteed to reach more than 10 minutes, the desalination efficiency can be ignored by other factors such as mixing time and water temperature, and only the influence of the liquid-solid ratio is considered. Generally, increasing the liquid-solid ratio is conducive to improving the dechlorination efficiency. On the other hand, the high-salt water washing solution produced by water washing is usually disposed of by evaporation and crystallization, which consumes huge energy, and the larger the volume produced, the higher the energy consumption. Therefore, the liquid-solid ratio should be reduced as much as possible under the premise of meeting the residual chlorine content requirements.

[0005] The Technical Specifications for Pollution from Fly Ash from Incineration of Municipal Waste (Trial) (HJ 1134) stipulates that the soluble chlorine content of water-washed fly ash should be less than 2%, and it is recommended to be less than 1%, which puts forward requirements for the stability of the water washing effect. Since the raw material composition of fly ash is unstable and the chlorine content fluctuates greatly, it is necessary to frequently adjust the liquid-solid ratio of water washing. At present, technicians usually ignore the chloride ion adsorption effect of solid phase particles during the water washing process. However, due to the small particle size of fly ash particles and the presence of activated carbon with a high specific surface area, solid phase adsorption will be formed, increasing the residual amount of chloride ions in the solid-liquid separation residue, and the impact cannot be ignored. In addition, multi-stage countercurrent water washing is a commonly used water washing process, which divides the water washing into multiple stages, with low-concentration liquid used to wash low-salt ash and high-concentration brine used to wash high-salt ash, thereby reducing the liquid-solid ratio. The complex water washing process further increases the complexity of setting the liquid-solid ratio parameters based on the dechlorination efficiency, causing design difficulties.

[0006] In summary, due to the lack of a quantitative relationship calculation method between the original characteristics of fly ash, liquid-to-solid ratio parameters and expected dechlorination efficiency, technicians are unable to accurately set the liquid-to-solid ratio parameters, resulting in the adverse effects of substandard chloride ion content in water-washed fly ash or excessive production of water-washing liquid. Therefore, it is urgent to propose a new calculation method for the optimal liquid-to-solid ratio of water washing to realize the design calculation of liquid-to-solid ratio process parameters. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a multi-stage countercurrent water washing method for incineration fly ash based on the balance method to calculate the optimal liquid-solid ratio.

[0008] To solve the technical problem, the solution of the present invention is:

[0009] Provided is a multi-stage countercurrent water washing method for incineration fly ash for calculating the optimal liquid-solid ratio based on the balance method. The method uses a multi-stage water washing device to wash the original fly ash with a countercurrent water washing process, adds salt-containing waste liquid for coordinated disposal to the water washing device during the water washing process, and supplements pure water in the last stage. The balance method means that after each stage of the water washing device completes the solid-liquid mixing, the migration of chloride salts can approximately reach a balance state, and the calculation of the optimal liquid-solid ratio of the water washing process aims to achieve the balance state.

[0010] The multi-stage countercurrent washing method specifically comprises the following steps:

[0011] (1) The waste incineration fly ash to be washed is stored in batches, and the activated carbon injection mass M during the ash production period is obtained based on the operating status monitoring data of the fly ash source incinerator during the ash production period. AC And the fly ash mass M FA , unit kg; based on this, calculate the mass fraction of activated carbon contained in the fly ash m AC , and the average specific surface area data of activated carbon contained in fly ash AAC , unit m 2 / g; then record and create files;

[0012] (2) Take samples of each batch of fly ash in advance and determine the contents of Cl, Na, and K in the fly ash; calculate the mass fractions of Cl, Na, and K in the fly ash, which are recorded as m Cl 、m Na 、m K ;

[0013] (3) Establish the concentration relationship equation, volume relationship equation, adsorption relationship equation and desalination efficiency equation, and expand the equation group according to the number of stages of the water washing device, as follows:

[0014] The concentration relationship equation is:

[0015]

[0016] Among them, C n is the total salt concentration of the liquid phase after the nth stage of solid-liquid separation, kg / m 3 ;M n M is the dry weight of fly ash or residue entering the nth stage of water washing, kg; N+1 is the dry weight of washed fly ash; M1 is the mass of dry ash initially added, kg, and is set to 1 kg for ease of calculation; C add,n Total salt concentration of the salt solution added for co-treatment at the nth stage, kg / m 3 ; V add,n is the volume of salt solution added for co-processing at the nth stage, m 3 ; V n is the volume of liquid phase after the nth stage solid-liquid separation, m 3 ; V N+1 is the volume of water initially added; N+1 represents the concentration of water initially added, which is taken as zero;

[0017] The volume relationship equation is:

[0018]

[0019]

[0020] V N+1 =RM1

[0021] Among them, R wc is the water content of the solid-liquid separation residue that can be achieved by the solid-liquid separation device, kg (water) / kg (total mass); R is the liquid-solid ratio adopted in the water washing process, m 3 / kg;

[0022] The adsorption relationship equation is:

[0023]

[0024]

[0025]

[0026] k A =6×10 -5 A * AC +0.91

[0027] m ad,n =k A (-4.82x 1,n x 2,n 2 +120.92x 1,n x 2,n -88.36x 1,n +1.78x 2,n -1.97)×10 -3 ,n=1,2,......,N

[0028] k n =m ad,n / [m Cl,st C n R wc / (1-R wc )]+1,n=1,2,......,N

[0029]

[0030] Among them, m Cl,st is the proportion of chlorine in soluble salt; x 1,n and x 2,n is the intermediate variable in the calculation process; k A is the specific surface area correction factor; m ad,n k is the amount of salt adsorbed on the solid phase of the residue from the nth stage of water washing separation; n m is the salt content coefficient of the residue of the nth stage solid-liquid separation; RCl is the target value of soluble chlorine content in water-washed fly ash, which should be lower than 90% of the soluble chlorine content of the product required by the downstream disposal unit and less than or equal to 2%; the physical quantity with * means that the value of the physical quantity is taken as a dimensionless parameter;

[0031] The desalination efficiency equation is:

[0032]

[0033]

[0034] Among them, m st is the chloride mass fraction of the original fly ash;

[0035] After solving the above equations, the value of the liquid-to-solid ratio R is the optimal liquid-to-solid ratio of the water washing process;

[0036] (4) The single feed amount M of the original fly ash determined by the design capacity of the water washing device s (kg) and the liquid-to-solid ratio R (m 3 / kg), and the amount of pure water added in the washing process V is calculated N+1 (m 3 ):

[0037] V N+1 =R×M s

[0038] According to the calculation results, pure water is added to the last stage of the water washing device, and then the original fly ash is washed with water according to the operating procedures of the countercurrent water washing process.

[0039] As a preferred embodiment of the present invention, the salt-containing waste liquid is used to reduce the water-solid ratio of the washing liquid and reduce the total energy consumption, and its main components include Cl-, and Na + , K + , Ca 2+ One or more of the .

[0040] As a preferred embodiment of the present invention, the salt-containing waste liquid is a hazardous waste, containing heavy metals, inorganic fluorides or other harmful substances that can be rendered harmless in the fly ash washing and subsequent disposal.

[0041] As a preferred embodiment of the present invention, in step (1), the mass fraction of activated carbon in the fly ash is calculated by the following formula: AC :

[0042]

[0043] Among them, M AC and M FA are the activated carbon injection mass and fly ash generation mass (kg) during the monitoring period, respectively.

[0044] As a preferred embodiment of the present invention, in step (1), the average specific surface area data A of the activated carbon contained in the fly ash is calculated by the following formula: AC (m 2 / g):

[0045]

[0046] Among them, M AC,j Indicates the mass of the jth activated carbon, kg; AAC,j is the specific surface area of ​​the jth activated carbon, m 2 / g; Z is the number of activated carbon types contained in the fly ash.

[0047] As a preferred embodiment of the present invention, in the step (2), the contents of Cl, Na and K in the waste incineration fly ash are determined by X-ray fluorescence spectrometry (XRF).

[0048] As a preferred embodiment of the present invention, in step (3), the concentration and volume of the co-disposal salt-containing waste liquid added at the nth stage are determined in the following manner:

[0049] (1) Detect the concentration of the salt-containing wastewater to be disposed of, according to C add,n =0, V add,n = 0, n = 1~N, the C under pure water conditions is calculated n and V n , n = 1 to N;

[0050] (2) According to C add,n <0.5C n and V add,n <V n The judgment principle is used to determine the timing and amount of adding salt-containing waste liquid for co-treatment.

[0051] As a preferred embodiment of the present invention, when adding the salt-containing waste liquid for co-treatment, it is added in any one or more stages of the multi-stage countercurrent washing device; if the salt-containing waste liquid is not added, when calculating the liquid-solid ratio R of the washing process, the total salt concentration C of the salt solution in the corresponding equation is add,n and the volume of the salt solution V add,n Just set both parameters to 0.

[0052] Description of the invention principle:

[0053] After each solid-liquid mixing is completed, the migration of chloride salts approximately reaches a balanced state. If the mass balance calculation of chloride salts can be performed, the design calculation of liquid-solid ratio can be realized. The present invention analyzes the migration law of chloride salts in the multi-stage countercurrent water washing process of fly ash and the process, obtains the main parameters, constructs multiple sets of equilibrium equations, and solves them through mathematical methods. According to the calculation results of the optimal liquid-solid ratio, a water washing method using the optimized process parameters is realized. Among them, the technical principles involved are as follows:

[0054] (1) Chloride salt migration characteristics in multi-stage countercurrent washing process: Almost all existing fly ash washing production lines adopt multi-stage countercurrent washing process. The process flow is as follows: Figure 1As shown. The chlorine element in fly ash almost all exists in the form of soluble chloride ions, which can be quickly dissolved into the liquid phase when the solid and liquid are mixed. At the same time, the fly ash particles are small in size and contain highly adsorbable activated carbon, which will form solid phase adsorption. The solid-liquid mixing process of the water washing process needs to continue for a sufficient time to stabilize the concentration of liquid phase chloride ions. During this process, dissolution and adsorption reach a state of equilibrium or near equilibrium. In summary, in the multi-stage countercurrent water washing process, there are mass balance, volume balance and adsorption balance processes between each stage, and the process parameter design calculation can be achieved by establishing a group of equilibrium equations.

[0055] (2) Concentration relationship and volume relationship equations: Figure 1 As shown, the liquid concentration obtained at a certain stage of solid-liquid separation is the dry mass difference between the solid and washed fly ash entering this stage, plus the mass of salt brought in by the co-treatment liquid added in all stages after this stage, and the ratio of the sum to the liquid volume of this stage; the liquid volume obtained at a certain stage of solid-liquid separation is the difference between the initial liquid volume, the co-treatment liquid volume added in all stages before this stage, the liquid brought in by the solid-liquid separation residue entering this stage, and the liquid volume brought out by the solid-liquid separation residue of the last stage.

[0056] (3) Adsorption relationship equations: Studies have shown that the apparent liquid concentration in the residue obtained from a certain level of solid-liquid separation, that is, the ratio of the total salt content of the residue to the water content, is much higher than the concentration of the liquid obtained from solid-liquid separation; this ratio is defined as the salt content coefficient k n , n is the number of orders currently calculated. Studies have shown that the main reason for the solid phase adsorption of chloride ions is that the adsorption effect is formed on the surface of calcium carbonate under the high specific surface area of ​​activated carbon. The adsorption amount is mainly affected by the liquid concentration, activated carbon content and the specific surface area of ​​activated carbon. By fitting the experimental data, further calculation can obtain k n The relationship between the above variables is thus n The definition of is used to establish the adsorption relationship equation group.

[0057] Based on the above principle, the present invention constructs a set of equilibrium equations for the fly ash washing process, fully describes the migration law of chloride salts in the fly ash washing process, and thus realizes the quantitative calculation of the liquid-solid ratio parameter. In this process, calculation preparation is first required to obtain the mass fractions of Cl, Na, and K in the waste incineration fly ash, the mass fraction of activated carbon, the average specific surface area of ​​activated carbon, and the target value of the soluble chlorine content of the washed fly ash; then, the concentration relationship, volume relationship, and adsorption relationship equations are established; finally, the equations are solved by mathematical means to obtain the liquid-solid ratio parameter value.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] 1. The present invention can quantitatively calculate the required liquid-to-solid ratio according to the expected dechlorination effect and the properties of the fly ash raw materials, filling the gap in the existing waste incineration fly ash washing process parameter design;

[0060] 2. The present invention can realize the design and calculation of liquid-to-solid ratio parameters under the complex conditions of coordinated disposal of salt solution and adoption of multiple stages; and the calculated parameters are used for the specific implementation of the multi-stage countercurrent water washing process for incineration fly ash. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 The present invention is a schematic diagram of the process of countercurrent water washing fly ash.

[0062] Figure 2 This is a graph of the soluble chloride salt content of the three-stage countercurrent water washing residue with variable liquid-to-solid ratio of the fly ash described in Example 1. DETAILED DESCRIPTION

[0063] First of all, it should be noted that the present invention relates to a method for calculating the liquid-to-solid ratio of multi-stage countercurrent washing of fly ash from garbage incineration, which is an application based on the material balance research of the fly ash washing process. In the process of implementing the present invention, it involves the acquisition of multiple basic data, the calculation of equilibrium equations and the application of washing processes. The applicant believes that after carefully reading the application documents and accurately understanding the implementation principle and purpose of the present invention, in combination with the existing known technology, those skilled in the art can fully use the mathematical and technical means they have mastered to implement the present invention.

[0064] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described below in conjunction with specific embodiments. Obviously, the embodiments are only the most basic embodiments of the present invention, rather than all embodiments. Other embodiments based on the present invention belong to the scope of protection of the present invention.

[0065] In the present invention, the salt-containing waste liquid for coordinated treatment can be added to any one or more stages in the multi-stage countercurrent washing device according to actual production needs. Theoretically, as long as the concentration of the salt solution to be added is lower than the liquid phase concentration of the current stage, it can be added. The liquid-to-solid ratio R only calculates the water-cement ratio added initially, and the salt water added in the middle is not included in R. Adding salt solution according to the principle that the concentration of the added salt solution is lower than the liquid phase concentration of the current stage can increase the amount of dissolved salt, that is, it can reduce the R value. If it is not added, when calculating the liquid-to-solid ratio R of the washing process, the total salt concentration C of the salt solution in the corresponding equation is used. add,n and the volume of the salt solution V add,n Just set both parameters to 0.

[0066] Unless otherwise specified, the contents in the following examples are all in mass percentage.

[0067] Example 1

[0068] The waste incineration fly ash is washed with three-stage countercurrent water, and the salt-containing wastewater is not treated in coordination; therefore, n = 1 to 3, C add,n and V add,n The value is 0.

[0069] (1) A batch of waste incineration fly ash to be washed is stored according to the M in the ash production period. AC and M FA , calculate the mass fraction of activated carbon contained in fly ash m AC , the type of injected activated carbon is unique, and its surface area is A AC , the above data are recorded in Table 1;

[0070] (2) Sampling test to obtain m Cl 、m Na 、m K , the results are listed in Table 1;

[0071] (3) Establish and expand the concentration relationship equation as shown below

[0072]

[0073]

[0074] C3=(M3-M4+C add,3 V add,3 ) / V3

[0075] Set up and expand the volume relationship equation as shown below

[0076]

[0077]

[0078] V3=V4+V add,3 -(M4-M3)R wc / (1-R wc )

[0079] V4=RM1

[0080] Establish and expand the adsorption relationship equation as shown below

[0081]

[0082]

[0083]

[0084]

[0085]

[0086]

[0087]

[0088] k A =6×10 -5 A * AC +0.91

[0089] m ad,1 =k A (-4.82x 1,1 x 2,1 2 +120.92x 1,1 x 2,1 -88.36x 1,1 +1.78x 2,1 -1.97)×10 -3

[0090] m ad,2 =k A (-4.82x 1,2 x 2,2 2 +120.92x 1,2 x 2,2 -88.36x 1,2 +1.78x 2,2 -1.97)×10 -3

[0091] m ad,3 =k A (-4.82x 1,3 x 2,3 2 +120.92x 1,3 x 2,3 -88.36x 1,3 +1.78x 2,3 -1.97)×10 -3

[0092] k1=m ad,1 / [m Cl,st C1R wc / (1-R wc )]+1

[0093] k2=m ad,2 / [m Cl,st C2R wc / (1-R wc )]+1

[0094] k3=m ad,3 / [m Cl,stC3R wc / (1-R wc )]+1

[0095]

[0096]

[0097] k3M4C3R wc / (1-R wc )-M4m RCl / m Cl,st =C4V4-C add,3 V add,3

[0098] The desalination efficiency equation is established as follows

[0099] M1m st -M4m RCl / m Cl,st =C1V1

[0100] Among them, R wc See Table 1. Washed fly ash is used to produce cement. The receiving unit requires a soluble chlorine content of 1.2 wt.%. RCl Set to 1.0wt.%. Simultaneously establish the above equations, substitute the data and solve, the results of R are listed in Table 1.

[0101] (4) The original fly ash feed volume of the equipment is 0.8t, and the amount of pure water added is calculated to be 2.31m 3 , According to the operating procedures of the three-stage countercurrent water washing process, the original fly ash was washed with water, and the desalination efficiency data are listed in Table 1.

[0102] Example 2

[0103] The fly ash from garbage incineration is washed with secondary countercurrent water, and the salty wastewater is not treated in coordination; therefore, n = 1~2, C add,n and V add,n are all 0 and therefore are not reflected in the equations.

[0104] Steps (1) and (2) are the same as in Example 1;

[0105] (3) Establish and expand the concentration relationship equation as shown below

[0106] C1=(M1-M3) / V1

[0107] C2=(M2-M3) / V2

[0108] Set up and expand the volume relationship equation as shown below

[0109] V1=V3-M3R wc / (1-R wc )

[0110] V2=V3-(M3-M2)R wc / (1-R wc )

[0111] V3=RM1

[0112] Establish and expand the adsorption relationship equation as shown below

[0113]

[0114]

[0115]

[0116]

[0117]

[0118] k A =6×10 -5 A * AC +0.91

[0119] m ad,1 =k A (-4.82x 1,1 x 2,1 2 +120.92x 1,1 x 2,1 -88.36x 1,1 +1.78x 2,1 -1.97)×10 -3

[0120] m ad,2 =k A (-4.82x 1,2 x 2,2 2 +120.92x 1,2 x 2,2 -88.36x 1,2 +1.78x 2,2 -1.97)×10 -3

[0121] k1=m ad,1 / [m Cl,st C1R wc / (1-R wc )]+1

[0122] k2=m ad,2 / [m Cl,stC2R wc / (1-R wc )]+1

[0123] The desalination efficiency equation is established as follows

[0124] M1m st -M3m RCl / m Cl,st =C1V1

[0125] Among them, R wc See Table 1. Washed fly ash is used to produce cement. The receiving unit requires a soluble chlorine content of 1.8 wt.%. RCl Set to 1.5wt.%. The above equations were combined, the data were substituted and solved, and the results of R are listed in Table 1.

[0126] (4) The original fly ash feed volume of the equipment is 1.0 t, and the amount of pure water added is calculated to be 1.92 m 3 , According to the operating procedures of the two-stage countercurrent water washing process, the original fly ash was washed with water, and the desalination efficiency data are listed in Table 1.

[0127] Example 3

[0128] The waste incineration fly ash is washed with four-stage countercurrent water, and the salt-containing wastewater is not treated in coordination; therefore, n = 1 to 4, C add,n and V add,n are all 0 and therefore are not reflected in the equations.

[0129] Steps (1) and (2) are the same as in Example 1;

[0130] (3) Establish and expand the concentration relationship equation as shown below

[0131] C1=(M1-M5) / V1

[0132] C2=(M2-M5) / V2

[0133] C3=(M3-M5) / V3

[0134] C4=(M4-M5) / V4

[0135] Set up and expand the volume relationship equation as shown below

[0136] V1=V5-M5R wc / (1-R wc )

[0137] V2=V5-(M5-M2)R wc / (1-R wc )

[0138] V3=V5-(M5-M2)Rwc / (1-R wc )

[0139] V4=V5-(M5-M2)R wc / (1-R wc )

[0140] V5=RM1

[0141] Establish and expand the adsorption relationship equation as shown below

[0142]

[0143]

[0144]

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151] k A =6×10 -5 A * AC +0.91

[0152] m ad,1 =k A (-4.82x 1,1 x 2,1 2 +120.92x 1,1 x 2,1 -88.36x 1,1 +1.78x 2,1 -1.97)×10 -3

[0153] m ad,2 =k A (-4.82x 1,2 x 2,2 2 +120.92x 1,2 x 2,2 -88.36x 1,2 +1.78x 2,2 -1.97)×10-3

[0154] m ad ,3=k A (-4.82x 1,3 x 2,3 2 +120.92x 1,3 x 2,3 -88.36x 1,3 +1.78x 2,3 -1.97)×10 -3

[0155] m ad,4 =k A (-4.82x 1,4 x 2,4 2 +120.92x 1,4 x 2,4 -88.36x 1,4 +1.78x 2,4 -1.97)×10 -3

[0156] k1=m ad,1 / [m Cl,st C1R wc / (1-R wc )]+1

[0157] k2=m ad,2 / [m Cl,st C2R wc / (1-R wc )]+1

[0158] k3=m ad,3 / [m Cl,st C3R wc / (1-R wc )]+1

[0159] k4=m ad,4 / [m Cl,st C4R wc / (1-R wc )]+1

[0160] k1M2C1R wc / (1-R wc )-M4m RCl / m Cl,st =C2V2

[0161] k2M3C2R wc / (1-R wc )-M4m RCl / m Cl,st =C3V3

[0162] k3M4C3R wc / (1-R wc )-M4m RCl / m Cl,st =C4V4

[0163] k4M5C4R wc / (1-R wc )-M4m RCl / m Cl,st =C5V5

[0164] The desalination efficiency equation is established as follows

[0165] M1m st -M5m RCl / m Cl,st =C1V1

[0166] Among them, R wc See Table 1. Washed fly ash is used to produce cement. The receiving unit requires a soluble chlorine content of 1.8 wt.%. RCl Set to 1.5wt.%. The above equations were combined, the data were substituted and solved, and the results of R are listed in Table 1.

[0167] (4) The original fly ash feed volume of the equipment is 2.0 t, and the amount of pure water added is calculated to be 4.48 m 3 , According to the operating procedures of the four-stage countercurrent water washing process, the original fly ash was washed with water, and the desalination efficiency data are listed in Table 1.

[0168] Example 4

[0169] In this embodiment, the incineration fly ash is the same as that in Example 1, and there is a salt-containing wastewater to be treated, containing Na + , Ca 2+ , K + and Cl - , total salt concentration 25kg / m 3 .

[0170] Steps (1) and (2) are the same as in Example 1;

[0171] (3) Under pure water conditions, according to the method of Example 1, C1, C2 and C3 are calculated to be 149.0, 36.1 and 8.7 kg / m 3 , V1, V2 and V3 are 2.47, 2.97 and 2.91 respectively (10 -3 m 3 ). Wastewater is added to the first stage of co-treatment, C add,1 =25kg / m 3 , V add,1 =0.002m3 . Establish the equation system, R wc 、m RCl The form of the equation group is the same as that of Example 1, and the calculation results are listed in Table 1.

[0172] (4) The original fly ash feed volume of the equipment is 0.8t, and the amount of pure water added is calculated to be 1.93m 3 , According to the operating procedures of the three-stage countercurrent water washing process, the original fly ash was washed with water, and the desalination efficiency data are listed in Table 1.

[0173] Example 5

[0174] In this embodiment, the incineration fly ash is the same as that in Example 1, and there are three types of salt-containing wastewater to be treated, including Na + and Cl - The total salt concentrations were 63.5, 12.7 and 3.4 kg / m 3 .

[0175] Steps (1) and (2) are the same as in Example 1;

[0176] (3) Under pure water conditions, the calculation was performed according to the method of Example 1, and the results were the same as those of Example 4. Wastewater was added to each stage of coordinated treatment, C add,1 , C add,2 and C add,3 63.5, 12.7 and 3.4 kg / m respectively 3 , V add,1 、V add,2 and V add,3 Both are 10 -3 m 3 . Establish the equation system, R wc 、m RCl The form of the equation group is the same as that of Example 1, and the calculation results are listed in Table 1.

[0177] (4) The original fly ash feed volume of the equipment is 0.8t, and the amount of pure water added is calculated to be 1.17m 3 , According to the operating procedures of the three-stage countercurrent water washing process, the original fly ash was washed with water, and the desalination efficiency data are listed in Table 1.

[0178] Table 1 Parameters of the embodiment

[0179]

[0180] Combined with the optimal liquid-to-solid ratio data of Example 1 in Table 1 and Figure 2 The results show that the use of this liquid-to-solid ratio meets the requirements for the soluble salt content of the water-washed fly ash and reduces the liquid-to-solid ratio to the minimum. Therefore, it can be confirmed that the value of the water-washing process liquid-to-solid ratio R obtained by the calculation method of the present invention is indeed the optimal liquid-to-solid ratio R.

[0181] Obviously, those skilled in the art may make various subsequent applications, supplements, modifications and variations to the present invention without departing from the spirit and scope of the present invention. If various applications, supplements, modifications and variations based on the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such applications, supplements, modifications and variations.

Claims

1. A multi-stage countercurrent water washing method for incineration fly ash based on the balance method to calculate the optimal liquid-solid ratio, characterized in that: The method is to use a multi-stage water washing device to wash the original fly ash in a countercurrent water washing process, add the salt-containing waste liquid for co-treatment to the water washing device during the water washing process, and add pure water in the last stage; the balance method means that after each stage of the water washing device completes the solid-liquid mixing, the migration of the chloride salt can approximately reach a balance state, and the calculation of the optimal liquid-solid ratio of the water washing process is aimed at achieving the balance state; The multi-stage countercurrent washing method specifically comprises the following steps: (1) The waste incineration fly ash to be washed is stored in batches, and the activated carbon injection mass M during the ash production period is obtained based on the operating status monitoring data of the fly ash source incinerator during the ash production period. AC And the fly ash mass M FA , unit kg; based on this, calculate the mass fraction of activated carbon contained in the fly ash m AC , and the average specific surface area data of activated carbon contained in fly ash A AC , unit m 2 / g; then record and create files; (2) Take samples of each batch of fly ash in advance and determine the contents of Cl, Na, and K in the fly ash; calculate the mass fractions of Cl, Na, and K in the fly ash, which are recorded as m Cl 、m Na 、m K ; (3) Establish the concentration relationship equation, volume relationship equation, adsorption relationship equation and desalination efficiency equation, and expand the equation group according to the number of stages of the water washing device, as follows: The concentration relationship equation is: Among them, C n is the total salt concentration of the liquid phase after the nth stage of solid-liquid separation, kg / m 3 ;M n M is the dry weight of fly ash or residue entering the nth stage of water washing, kg; N+1 is the dry weight of washed fly ash; M1 is the mass of dry ash initially added, kg, and is set to 1 kg for ease of calculation; C add,n Total salt concentration of the salt solution added for co-treatment at the nth stage, kg / m 3 ; V add,n is the volume of salt solution added for co-processing at the nth stage, m 3 ; V n is the volume of liquid phase after the nth stage solid-liquid separation, m 3 ; V N+1 is the volume of water initially added; C N+1 represents the concentration of water initially added, which is taken as zero; The volume relationship equation is: In N+1 =RM1 Among them, R wc is the water content of the solid-liquid separation residue that can be achieved by the solid-liquid separation device, kg (water) / kg (total mass); R is the liquid-solid ratio adopted in the water washing process, m 3 / kg; The adsorption relationship equation is: k A =6×10 -5 A * AC +0.91 m ad,n =k A (-4.82x 1,n x 2,n 2 +120.92x 1,n x 2,n -88.36x 1,n +1.78x 2,n -1.97)×10 -3 ,n=1,2,......,N k n =m ad,n / [m Cl,st C n R wc / (1-R wc )]+1,n=1,2,......,N Among them, m Cl,st is the proportion of chlorine in soluble salt; x 1,n and x 2,n is the intermediate variable in the calculation process; k A is the specific surface area correction factor; m ad,n k is the amount of salt adsorbed on the solid phase of the residue from the nth stage of water washing separation; n m is the salt content coefficient of the residue of the nth stage solid-liquid separation; RCl is the target value of soluble chlorine content in water-washed fly ash, which should be lower than 90% of the soluble chlorine content of the product required by the downstream disposal unit and less than or equal to 2%; the physical quantity with * means that the value of the physical quantity is taken as a dimensionless parameter; The desalination efficiency equation is: Among them, m st is the chloride mass fraction of the original fly ash; After solving the above equations, the value of the liquid-to-solid ratio R is the optimal liquid-to-solid ratio of the water washing process; (4) The single feed amount M of the original fly ash determined by the design capacity of the water washing device s The amount of pure water added in the washing process V is calculated by using the liquid-to-solid ratio R obtained in step (3). N+1 : In N+1 =R×M s According to the calculation results, pure water is added to the last stage of the water washing device, and then the original fly ash is washed with water according to the operating procedures of the countercurrent water washing process.

2. The method according to claim 1, characterized in that The salty waste liquid is used to reduce the water-solid ratio of the washing liquid and reduce the total energy consumption. Its main components include Cl - , and Na + , K + , Ca 2+ One or more of the .

3. The method according to claim 1, characterized in that The salt-containing waste liquid is a hazardous waste, containing heavy metals, inorganic fluorides or other harmful substances that can be rendered harmless through fly ash washing and subsequent disposal.

4. The method according to claim 1, characterized in that: In step (1), the activated carbon mass fraction m in the fly ash is calculated by the following formula: AC : Among them, M AC and M FA are the activated carbon injection mass and fly ash generation mass during the monitoring period, kg respectively.

5. The method according to claim 1, characterized in that In the step (1), the average specific surface area data A of the activated carbon contained in the fly ash is calculated by the following formula: AC : Among them, M AC,j Indicates the mass of the jth activated carbon, kg; A AC,j is the specific surface area of ​​the jth activated carbon, m 2 / g; Z is the number of activated carbon types contained in the fly ash.

6. The method according to claim 1, characterized in that In the step (2), the contents of Cl, Na and K in the waste incineration fly ash are determined by X-ray fluorescence spectrometry.

7. The method according to claim 1, characterized in that In step (3), the concentration and volume of the co-processed saline waste liquid added at the nth stage are determined in the following manner: (1) Detect the concentration of salt-containing wastewater to be disposed of, according to C add,n =0, V add,n = 0, n = 1~N, the C under pure water conditions is calculated n and V n , n = 1 to N; (2) According to C add,n <0.5C n and V add,n <V n The judgment principle is used to determine the timing and amount of adding salt-containing waste liquid for co-treatment.

8. The method according to claim 1, characterized in that: When adding the salty waste liquid for co-treatment, it is added in any one or more stages of the multi-stage countercurrent washing device; if the salty waste liquid is not added, when calculating the liquid-solid ratio R of the washing process, the total salt concentration C of the salt solution in the corresponding equation add,n and the volume of the salt solution V add,n Both parameters are set to 0.

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