A method of detecting properties of sludge

Abstract

The present application relates to a kind of methods for detecting sludge properties, comprising the following steps: providing a sludge mixture, the sludge mixture is filtered by applying pressure;The sludge mixture is separated into filtrate and cake by filtration, the mass of filtrate and the corresponding filtration time are recorded, until the mass of filtrate no longer increases, then stop recording, and the data of the mass of filtrate and filtration time are obtained;Using the relationship model formula m=D-G / (1+H×t F ) of the mass of filtrate and filtration time is fitted, and the values of constants D, G, H and F are obtained, wherein m is the mass of filtrate, t is filtration time;The values of invariants D and G are calculated to obtain the values of saturation S ∞ , cake porosity ε, capillary number N cap , cake particle size x, critical pressure P b And cake permeability K.The present application has the advantages of simple operation, accurate results and reduced detection cost.

Description

Technical Field

[0001] The present invention relates to the field of sludge treatment, and in particular to a method for detecting sludge properties. Background Art

[0002] With the development of the economy, sewage treatment capacity has been further strengthened, but the output of sludge as a by-product of sewage treatment has also increased day by day. Sludge will waste land resources and even cause secondary environmental pollution during the treatment and disposal process, thereby affecting the stable and sustainable development of my country's society and economy. Dehydration can reduce the volume of sludge, which is beneficial to its subsequent transportation, digestion and comprehensive treatment and disposal. The optimal conditioning method for dehydration depends on the characteristics of the sludge itself. Due to the influence of factors such as sewage type and treatment process, the characteristics of sludge dehydration are also different. The irreducible saturation S of sludge cake during filtration dehydration is ∞ , porosity ε, capillary number N cap , particle size x, critical pressure P b Parameters such as sludge cake permeability (K) can effectively reflect the difficulty of dewatering and demonstrate the spatial structural characteristics of the sludge cake. Therefore, understanding the characteristics of sludge cake can provide guidance for actual sludge dewatering operations. However, traditional testing methods are complex and cannot obtain all parameters at once. Obtaining these parameters undoubtedly increases usage costs and hinders water plants' control over sludge dewatering. Summary of the Invention

[0003] In view of this, it is indeed necessary to provide a method for detecting sludge properties that is easy to operate and can obtain multiple parameters at one time, thereby reducing the detection cost.

[0004] A method for detecting sludge properties, comprising the following steps: providing a sludge mixture, applying pressure to the sludge mixture for filtering; filtering the sludge mixture to separate it into a filtrate and a mud cake, recording the mass of the filtrate and the corresponding filtration time until the mass of the filtrate no longer increases, and stopping the recording to obtain data on the mass of the filtrate and the filtration time; using a relationship model formula m=D–G / (1+H×t F ) is fitted to obtain the values ​​of constants D, G, H and F, where m is the mass of the filtrate and t is the filtration time; the irreducible saturation S is calculated based on the constants D and G. ∞ , mud cake porosity ε, capillary number N cap , mud cake particle size x, critical pressure P b And mud cake permeability K.

[0005] Compared with the prior art, the present invention has the following advantages: by establishing a model of filtration time and filtrate mass, multiple property parameters of sludge cake can be calculated at one time, such as irreducible saturation S ∞, porosity ε, capillary number N cap , particle size x, critical pressure P b and mud cake permeability K, etc.; this detection method is easy to operate, has accurate results, and reduces detection costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 This is a structural diagram of a sludge detection system provided by an embodiment of the present invention.

[0007] Figure 2 This is a graph showing the relationship between filtrate quality and filtration time provided in an embodiment of the present invention.

[0008] Description of main component symbols

[0009] Sludge detection system 10

[0010] Pressurizing device 1

[0011] Sludge mixed liquid storage tank 2

[0012] Filter device 3

[0013] Electronic scale 4

[0014] Data Processor 5

[0015] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0016] The method for detecting sludge properties provided by the present invention will be further described in detail below with reference to the accompanying drawings.

[0017] An embodiment of the present invention provides a method for detecting sludge properties, comprising the following steps:

[0018] Step S1, providing a sludge mixture, and applying pressure to the sludge mixture for filtering;

[0019] Step S2, filtering the sludge mixture to separate it into a filtrate and a mud cake, recording the mass of the filtrate and the corresponding filtration time, and stopping the recording until the filtrate no longer increases, thereby obtaining data on the mass of the filtrate and the filtration time;

[0020] Step S3, using the relationship model formula of filtrate mass and filtration time m=D–G / (1+H×t F ) were fitted to obtain the values ​​of constants D, G, H and F, where m is the mass of the filtrate and t is the filtration time;

[0021] Step S4, calculate the irreducible saturation S according to the constants D and G ∞ , mud cake porosity ε, capillary number N cap, mud cake particle size x, critical pressure P b And mud cake permeability K, where S ∞ =(V–m0–D) / (V–m0–D+G), ε=ρ s G / (ρ l m s (1–S ∞ )+ρ s G), N cap 0.49 =0.031×0.155 / (S ∞ –0.155), x 2 =N cap σm s (1–ε) 2 / (ρ l gm s ε 3 +ρ s AP(1–ε)ε 3 ), P b =4.6(1–ε)σ / (εx), K=1 / (αρ s (1–ε)), V is the total mass of the sludge mixture (kg), m0 is the mass of the filtrate at the initial moment of mud cake dehydration (kg), m s (kg) is the mass of the mud cake after drying, ρ l (kg / m 3 ) is the density of the filtrate, ρ s (kg / m 3 ) is the density of mud cake, A(m 2 ) is the effective filtration area, P (Pa) is the filtration pressure, μ (Pa·s) is the filtrate viscosity, α (m / kg) is the filtration resistance of the sludge mixture, g (m 2 / s) is the gravity constant, and σ (N / m) is the surface tension of the filtrate.

[0022] In step S1, the nature of the sludge mixture is not limited, and can be sludge produced by domestic sewage, sludge produced by factory sewage, etc. In this embodiment, the sludge mixture is mixed sludge from a municipal sewage treatment plant, and the filtration resistance is 6.03×10 10 m / kg.

[0023] The filtration and subsequent detection of the sludge mixture can be completed by a sludge detection system 10. Figure 1The sludge detection system 10 includes a pressurizing device 1, a sludge mixture storage tank 2, a filtering device 3, an electronic scale 4 and a data processor 5. The pressurizing device 1 is used to provide a fixed pressure during the filtration of the sludge mixture, so that the sludge mixture is discharged from the sludge mixture storage tank 2 to the filtering device 3. The sludge mixture storage tank 2 is used to store the sludge mixture. The filtering device 3 is used to filter and separate the sludge mixture. The electronic scale 4 can record time and quality data at the same time, and is used to record the quality and time of the filtrate, and at the same time transmit the recorded quality and time data to the data processor 5. The data processor 5 can be a computer or a mobile terminal device, which is used to process and fit the data. In this embodiment, the pressure provided by the pressurizing device is 10kPa, and the sludge mixture is discharged from the sludge mixture storage tank to the filtering device.

[0024] The specific process of using the sludge detection system 1 to detect the properties of sludge is as follows: the sludge mixture is placed in the sludge mixture storage tank 2, the pressurizing device 1 applies pressure to discharge the sludge mixture from the sludge mixture storage tank 2 to the filtering device 3, the filtering device 3 filters and processes the sludge mixture under pressure, and the filtrate obtained by filtration flows into the electronic scale 4, the electronic scale 4 records the mass of the filtrate and the filtration time, and transmits the data to the data processor 5, and the data processor 5 processes and fits the data.

[0025] In step S2, during the filtration process of the sludge mixture, the filtrate is gradually filtered out, and the unfiltered sludge is gradually deposited to form a solid initial mud cake, and the solid initial mud cake continues to be dehydrated until the filtrate no longer increases. Here, the water content of the mud cake changes continuously during the filtration process, and the initial mud cake formed at the beginning has a higher water content. During the filtration process, the initial mud cake continues to be dehydrated until a mud cake is formed in which the filtrate no longer increases. Therefore, the "initial mud cake" described herein refers to the form of the mud cake when it has just formed a solid, and the various parameter values ​​of the mud cake calculated in the last step of the present invention refer to the parameters of the mud cake when the filtrate no longer increases. The electronic scale 4 can be used to record the mass change of the filtrate and the corresponding filtration time during the entire filtration process, thereby obtaining data on the filtrate mass m and the corresponding filtration time t. The filtration time t is calculated from the start of the filtration process and stops recording after the filtrate mass no longer increases.

[0026] In step S3, the recorded filtrate mass m and filtration time t are substituted into the model formula m = D – G / (1 + H × t F) are fitted in order to obtain the values ​​of the constants D, G, H and F. The data of the filtrate mass m and the filtration time t can be fitted by the data processor 5. Furthermore, the data processor 5 will perform a pre-processing step on the data. Specifically, the data processor 5 can intercept the data after the initial mud cake is formed, that is, the data after the mud cake begins to be dehydrated, and then reset the initial filtrate mass m and the filtration time data formed by the mud cake to zero before fitting. This is because the time when the initial mud cake is formed is unknown, so the data processing program will cyclically adopt an exhaustive method to intercept the data, and after fitting respectively, select the set of data with the highest goodness of fit as the final fitting result.

[0027] In step S4, since the constants D and G are related to the properties of the mud cake, such as irreducible saturation, mud cake porosity, capillary number, sludge particle size, critical pressure and mud cake permeability, the properties of the mud cake can be calculated based on the constants D and G. Constant D = V – m0 – GS ∞ / (1–S ∞ ), constant G = m s ρ l ε(1–S ∞ ) / (ρ s –ερ s ), according to the above formula, the irreducible saturation S can be derived ∞ =(V–m0–D) / (V–m0–D+G), mud cake porosity ε = ρ s G / (ρ l m s (1–S ∞ )+ρ s G), and according to the relationship formula S between the parameters ∞ =0.155(1+0.031N cap –0.49 ), K=1 / (αρ s (1–ε)), N cap =ε 3 x 2 (ρ l gL+P) / ((1–ε) 2 Lσ), P b =4.6(1–ε)σ / (εx), thus N cap 0.49 =0.031×0.155 / (S ∞ –0.155) to obtain the capillary number N cap , x 2 =N cap σm s (1–ε) 2 / (ρ l gms ε 3 +ρ s AP(1–ε)ε 3 ) to obtain the sludge particle size x, critical pressure P b =4.6(1–ε)σ / (εx), mud cake permeability K=1 / (αρ s (1–ε)). Where V is the total mass of the sludge mixture (kg), m0 is the mass of the filtrate at the initial moment of mud cake dehydration (kg), m s (kg) is the mass of the mud cake after drying, ρ l (kg / m 3 ) is the density of the filtrate, ρ s (kg / m 3 ) is the density of mud cake, A(m 2 ) is the effective filtration area, P (Pa) is the filtration pressure, μ (Pa·s) is the filtrate viscosity, α (m / kg) is the filtration resistance of the sludge mixture, g (m 2 / s) is the gravity constant, and σ (N / m) is the surface tension of the filtrate.

[0028] In order to further elaborate on the method for detecting sludge properties, a specific example will be described below.

[0029] Example 1

[0030] See also Figure 1 The present invention adopts the sludge detection system 10 to obtain and detect sludge cake. The sludge detection system 10 includes a pressurizing device 1, a sludge mixture storage tank 2, a filtering device 3, an electronic scale 4 and a data processor 5.

[0031] The method for detecting the properties of sludge cake using the sludge detection system 10 comprises the following specific steps:

[0032] (1) The pressure device 1 is used to apply a pressure P of 10 kPa to filter 0.1 kg of sludge mixed liquid. The mass of the filtrate is recorded by the electronic scale 4 and then transmitted to the data processor 5. The sludge mixed liquid is municipal mixed sludge. The effective filtration area A of the filtering device 3 is 0.0044 m 2 The filtrate mass was recorded every 1s. The original data recorded can be found in Table 1 and Figure 2 shown.

[0033] Table 1 Original data of filtrate quality and filtration time

[0034]

[0035] (2) The data processor 5 performs pre-processing on the original data and then performs fitting. The data processor 5 intercepts the data after the mud cake starts to be dehydrated, and then resets the filtrate mass and filtration time data to zero before fitting. In order to find the turning point between the sludge mixture filtration and mud cake dehydration, the data processing program adopts an exhaustive method to intercept the data, and after fitting, selects a set of data with the highest goodness of fit as the final fitting result. The interception points and the goodness of fit are shown in Table 2. From the data in the table, it can be seen that the 39th second is the initial moment (t0) when the mud cake is formed and dehydration begins. At this time, the goodness of fit is the highest, R 2 and adjusted R 2 They are 0.99908 and 0.99904 respectively.

[0036] Table 2 Data goodness of fit table

[0037]

[0038] The best fitting results obtained according to the best fitting goodness of fit given by the data processor are shown in Table 3, and the corresponding best fitting curve is shown in Figure 2 shown.

[0039] Table 3 Best fitting results

[0040] project Fitting results D coefficient (95% confidence interval) 0.01283(0.01277,0.01289) F coefficient (95% confidence interval) 1.294(1.254,1.334) G coefficient (95% confidence interval) 0.01463(0.01429,0.01498) H coefficient (95% confidence interval) 0.1283(0.1147,0.1419) SSE 4.4368E-07 <![CDATA[R 2 ]]> 0.99908 <![CDATA[Adjusted R 2 > 0.99904 RMSE 7.6914E-05

[0041] (3) According to the obtained constants D and F values, the mud cake property parameters (irreducible saturation S ∞ , porosity ε, capillary number N cap , particle size x, critical pressure P b In this embodiment, the total mass V of the sludge mixture used is 0.1 kg, and the density of the filtrate is 1000 kg / m 3 The filtrate viscosity μ is about 0.001003 Pa·s, the filtrate surface tension σ is about 0.072 N / m, and the sludge mixed liquid filtration resistance α is 6.03×10 10 m / kg, density of the mud cake after filtration ρ s 1500kg / m 3 , the mass of dried mud cake after filtration m s It is 0.00105kg, and the mass of the filtrate m0 at the initial moment of mud cake dehydration is 0.077kg.

[0042] By formula S ∞ =(V–m0–D) / (V–m0–D+G) to obtain the irreducible saturation S ∞ is 0.4101; according to ε=ρ s G / (ρ l m s (1–S ∞ )+ρs G) The mud cake porosity ε is 0.9725; according to N cap 0.49 =0.031×0.155 / (S ∞ –0.155) to obtain the capillary number N cap 3.02×10 –4 ; According to x 2 =N cap σm s (1–ε) 2 / (ρ l gm s ε 3 +ρ s AP(1–ε)ε 3 ) The average particle size x is 1.01×10 –7 m; According to P b =4.6(1–ε)σ / (εx) to obtain the critical pressure P b is 92493.84Pa; according to K=1 / (αρ s (1–ε)) gives the permeability K as 4.02×10 –13 m –2 The properties of the mud cake obtained are shown in Table 4.

[0043] Table 4 Properties of mud cake

[0044]

[0045] In order to verify the rationality of the mud cake property parameters obtained by this method, the product Z of dimensionless dehydration time and dimensionless pressure is further used for verification, Z = PKt d / (μεL 2 (1–S ∞ )), when Z is in the range of [0.096,204], m and t meet the formula m=D–G / (1+H×t F ), indicating that the detection method is applicable. d is the dehydration time of the mud cake, that is, from the initial dehydration of the mud cake (t0) to the end of dehydration. In this embodiment, t d =113s-39s=74s, and thus the Z value is calculated to be 15.52. Therefore, the mud cake parameters calculated by the detection method provided by the present invention are reasonable.

[0046] The method for detecting sludge properties provided by the present invention has the following advantages: by establishing a model relationship between filtration time and filtrate quality, a constant value is obtained, and then the constant value is used to solve the property parameters of the mud cake, including the irreducible saturation S ∞ , porosity ε, capillary number N cap, particle size x, critical pressure P b and the sludge cake permeability K. This method is simple to operate and calculate, and can calculate the sludge cake property parameters at one time with accurate results, without the need to separately test the various property parameters of the sludge cake.

[0047] In addition, those skilled in the art may also make other changes within the spirit of the present invention. Of course, these changes made according to the spirit of the present invention should be included in the scope of protection required by the present invention.

Claims

1. A method for detecting sludge properties, characterized in that: The following steps are involved: Providing a sludge mixture, and applying pressure to the sludge mixture for filtering; The sludge mixture is filtered and separated into a filtrate and a mud cake, and the mass of the filtrate and the corresponding filtration time are recorded until the filtrate no longer increases, and the recording is stopped to obtain data on the mass of the filtrate and the filtration time; The relationship model formula between filtrate quality and filtration time is used m = D – G / (1+ H × t F ) is fitted to obtain the constant D, G, H and F The value of , where m is the mass of the filtrate, t is the filtering time; According to the constant D, G, H and F Irreducible saturation is calculated by S ∞ , mud cake porosity ε , capillary number N cap , mud cake particle size x , critical pressure P b and mud cake permeability K , wherein the irreducible saturation S ∞ pass S ∞ =( V – m 0– D ) / ( V – m 0– D + G ) is calculated; the mud cake porosity ε pass ε = ρ s G / ( ρ l m s (1– S ∞ )+ ρ s G ) is calculated; the capillary number N cap pass N cap 0.49 =0.031×0.155 / ( S ∞ -0.155) is calculated; the mud cake particle size x pass x 2 = N cap σm s (1– ε ) 2 / ( ρ l g m s ε 3 + ρ s AP (1– ε ) ε 3 ) is calculated; the critical pressure P b pass P b =4.6(1– ε ) σ / ( εx ) is calculated; the mud cake permeability K pass K =1 / ( αρ s (1– ε )) is calculated, where V is the total mass of the sludge mixture (kg), m 0 is the mass of filtrate at the initial moment of mud cake dehydration (kg), m s (kg) is the mass of the mud cake after drying, ρ l (kg / m 3 ) is the density of the filtrate, ρ s (kg / m 3 ) is the density of mud cake, A (m 2 ) is the effective filtration area, P (Pa) is the filtration pressure, μ (Pa·s) is the viscosity of the filtrate, α (m / kg) is the filtration resistance of the sludge mixture, g (m 2 / s) is the gravitational constant, σ (N / m) is the surface tension of the filtrate.

2. The method for detecting sludge properties according to claim 1, wherein: The process of detecting the properties of the sludge is based on the use of a sludge detection system, which includes a pressurizing device, a sludge mixed liquid storage tank, a filtering device, an electronic scale and a data processor.

3. The method for detecting sludge properties according to claim 2, wherein: The pressurizing device is used to apply pressure during the filtration of the sludge mixed liquid, so that the sludge mixed liquid is discharged from the sludge mixed liquid storage tank to the filtering device.

4. The method for detecting sludge properties according to claim 2, wherein: The filtering device is used to filter and separate the sludge mixed liquid into filtrate and mud cake.

5. The method for detecting sludge properties according to claim 2, wherein: The electronic scale is used to simultaneously record the filtration time and the mass of the filtrate, and transmit the data of the filtration time and the mass of the filtrate to the data processor.

6. The method for detecting sludge properties according to claim 2, wherein: The data processor is a computer or a mobile terminal device.

7. The method for detecting sludge properties according to claim 2, wherein: The data processor is used for preprocessing and fitting the data of filtration time and filtrate quality.

8. The method for detecting sludge properties according to claim 7, wherein: The pre-processing step of the data processor is to intercept the data after the mud cake starts to be dehydrated.

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