CN107117672A - Choosing method is matched somebody with somebody in filtrate optimization in a kind of filtering particulate material - Google Patents

Abstract

The invention provides a method for optimizing and matching filter materials in granular material filtration, which belongs to the field of industrial sewage treatment. This method first sets up a sewage water sampling point at the water inlet of each suspended solids removal equipment, obtains the sewage water sample and performs a slow filtration, and then measures the average particle size of the sewage water sample; according to the average particle size and unequal diameter The relationship between the throats of the most closely packed porous media of spherical particles determines the type of filter material, as well as the quality and throat of each filter material; finally, according to the relationship between the throat and the diameter of spherical particles, the corresponding value of each filter material is obtained. The particle size, and then determine the filter material combination composed of filter materials of different quality and particle size. The present invention combines the particle size characteristics of suspended matter in industrial sewage to screen out suitable particle size filter materials in a targeted manner, thereby obtaining a higher removal effect of suspended matter and greatly improving the treatment efficiency of suspended matter in industrial sewage.

Description

A method for optimizing the selection of filter media in the filtration of granular materials

technical field

The invention relates to a method for optimizing and matching filter materials in granular material filtration, which belongs to the field of industrial sewage treatment and mainly focuses on oilfield sewage treatment.

Background technique

In the process of industrial sewage treatment, the filtering link has become an essential link, and the main purpose of the filtering link is to remove suspended solids (particle size is 0.1-100 μm) in the sewage. Filtration can be divided into granular material filtration and porous media material filtration. The principle is to use the filter material (referred to as filter material) throat to intercept and block the suspended matter and the surface of the filter material to absorb and adhere to the suspended matter.

Water treatment technology that removes suspended solids in sewage by passing sewage through a porous medium composed of a variety of spherical granular materials (quartz sand, iron ore, fiber balls, etc.) with different particle sizes and different mass ratios (thickness ratios). Filter for particulate material. For the filtration of granular materials, it mainly removes suspended solids in sewage by intercepting and blocking the suspended solids in sewage through the throats between granular filter materials, so that the throats between granular filter materials match the particle size of suspended solids in sewage The relationship plays a decisive role in the filtration effect of the filter material. When the particle size of the suspended solids is much smaller than the throat between the granular filter materials, the granular filter material will not be able to fully exert its interception and blocking effect on the suspended solids in the sewage, and the filtering effect of the granular filter material will be greatly reduced. The particle size of suspended solids in sewage is determined by the characteristics of the source sewage, while the throat between particle filter materials is mainly determined by the mass ratio (thickness ratio) of particles, particle size and accumulation form of particles.

The accumulation form of particles has a direct effect on the throat size of porous media, which in turn affects the removal effect of suspended solids in sewage. When the spherical particles are packed in the most compact form, the throats of the porous media formed are smaller, and the filtering effect on the suspended solids in the sewage is better. In the closest-packed porous medium of equal-diameter spherical particles, each sphere has the same diameter and is tightly packed. Fig. 1 is a schematic diagram of the packing form of the first layer of the most closely packed porous medium of equal-diameter spherical particles. The most closely packed is the mutual contact between each equal-diameter spherical particles with the greatest capacity; at the same time, mark the second layer (above the third layer) Similar) There are only three types of positions where spherical particles can accumulate, and no other positions are possible. Position A is the position of the first layer of balls, position B is the gap where the triangular tip is upward, and position C is the gap where the triangular tip is downward; The second layer (similar to the third layer and above) is the most compact only if the repeated stacking is on the B-site or C-site of the void, thus forming only two combinations of ABC and ABA; The geometric structure of the smallest unit of the model is composed of 4 spheres, as shown in Figure 2. Normally, in order to achieve the best suspended solids removal effect, the accumulation of the filter material is presented in the form of the most compact accumulation of spherical particles with unequal diameters. Under the premise that the filter materials in the filtration of granular materials are all packed in the most compact way, the throat between the granular filter materials is mainly determined by the mass ratio (thickness ratio) and particle size of the particles. The treatment process of industrial sewage is mainly based on the water quality characteristics of its source sewage, and when it comes to the removal of suspended solids in sewage, the filter tank process filled with granular materials that is cheap, stable in nature, and reusable for repeated washing is preferred. For example, the oilfield sewage treatment station currently mainly uses the four-stage treatment process of "first-stage settling tank→secondary settling tank→first-stage quartz sand filter tank→secondary quartz sand filter tank". Among them, the two-stage quartz sand filter tank is mainly used to remove suspended solids in oilfield sewage.

At present, the selection of particles in the filtration technology of granular materials is mostly based on empirical methods, and it is not possible to screen the filter materials of granular materials according to the particle size characteristics of suspended solids in sewage. Therefore, in the current industrial sewage treatment process, it is very common that the effect of removing suspended solids in the original design scheme cannot be achieved due to improper screening of particulate filter materials. In the process of industrial sewage treatment, improving the filtration effect of granular filter materials has become an urgent problem to be solved in the current industrial sewage treatment process.

Contents of the invention

The purpose of the present invention is to overcome the disadvantages in the prior art that the granular material filter material cannot be screened according to the particle size characteristics of the suspended solids in sewage, and propose a method for optimal matching of the filter material in the granular material filtration. The present invention combines the particle size characteristics of suspended matter in industrial sewage to screen out suitable particle size filter materials in a targeted manner, thereby obtaining a higher removal effect of suspended matter and greatly improving the treatment efficiency of suspended matter in industrial sewage.

A method for optimizing the matching of filter materials in the filtration of granular materials proposed by the present invention, specifically comprises the following steps:

1) Determine the sewage sampling points;

Determine the suspended solids removal equipment at the sewage treatment point that needs to filter particulate materials, and set up a sewage water sampling point at the water inlet of each suspended solids removal equipment;

2) Measure the particle size of the suspended matter; Concrete steps are as follows:

2-1) Take a sewage water sample whose volume is V at any sewage water sampling point determined in step 1);

2-2) Use several filter membranes with a pore size of 0.1mm to slowly filter the sewage water sample collected in step 2-1); the sewage water sample filtered by each filter membrane is less than or equal to 50ml, and save the filtered sewage water sample. The total volume of the filtered sewage water sample is still V;

2-3) Repeat steps 2-1) to 2-2) to obtain sewage water samples from each sewage sampling point and perform a slow filtration;

2-4) Take 5-10ml from any sewage water sample that has been filtered once in step 2-3), and use a laser particle size analyzer to measure the particle size distribution curve of the suspended matter in the sewage water sample obtained in step 2-3) And the average particle size D _average ;

3) Optimizing the matching of the filter material; the specific steps are as follows:

3-1) The average particle size D _average of the suspended matter in the sewage water sample and the throat D _average of the most closely packed porous medium of spherical particles with different diameters satisfy the expression shown in formula (2):

D _{throat mean} ≈ D _mean (2)

According to formula (2), the mean particle diameter D of suspended solids in the sewage water sample that D _{throat average} value is step 2) obtains is _average ;

3-2) According to formula (3), for the determined D _{throat average} , first determine the type of filter material, and then determine the quality of each filter material and the corresponding throat according to the type of filter material; the expression is as follows:

In the formula, n is the number of types of filter materials, m ₁ , m ₂ , m ₃ , ..., m _n are the quality of each filter material; D _{throat 1} , D _{throat 2} , D _{throat 3} , ... , D _{throat n} is the throat of each filter material;

3-3) The throat D _throat of the filter material has the following relational expression with the spherical particle diameter D _P , and the expression is as shown in formula (4):

According to formula (4), combined with the throats _{Dthroat 1} , _Dthroat , _{Dthroat 3} , ..., _{Dthroat n} of each filter material obtained in step 3), calculate the corresponding Particle diameters D _P1 , D _P2 , D _P3 , ..., D _Pn ; thus, it is determined that the optimal filter material selection plan for the equipment for removing suspended solids corresponding to the sewage water sample is: mass m ₁ , particle size D _P1 ; mass m ₂ , particle size D _P2 ; mass m ₃ , particle size D _P3 ; ... ; mass m _n , particle size D _Pn constituted filter material combination.

Features and beneficial effects of the present invention are:

In the present invention, a method for optimizing the selection of filter materials in the filtration of granular materials, the spherical particle accumulation porous medium throat algorithm is proposed for the first time, and according to the spherical particle accumulation porous medium throat formula, the quality and particle size of the required filter material are reasonably matched, It provides a basis for the targeted screening of particulate filter materials suitable for removing suspended solids in industrial sewage. According to the characteristics of suspended solids in industrial sewage, this algorithm screens out suitable granular filter materials, and improves the removal effect of granular filter materials on suspended solids in industrial sewage. This method overcomes the deficiency that the filter material selected only by manual experience may not be able to achieve the ideal effect in the previous filtering technology, and the selected filter material can remove suspended matter in water in a targeted manner, and has strong application value.

Description of drawings

Figure 1 is a schematic diagram of the packing form of equidiametric spherical particles in porous media.

Fig. 2 is a schematic diagram of the minimum unit body of the equidiameter spherical particle porous medium model.

Fig. 3 is a flowchart of the method of the present invention.

Fig. 4 is a simplified geometric structure diagram of the smallest unit body of the equidiameter spherical particle porous medium model.

Fig. 5 is a curve diagram of the concentration of suspended solids in the incoming water and the outgoing water of the secondary quartz sand filter tank in an embodiment of the present invention.

Fig. 6 is a curve diagram of the removal rate of suspended solids by the secondary quartz sand filter tank in the embodiment of the present invention.

Fig. 7 is a graph showing particle size distribution of suspended matter in sewage in an embodiment of the present invention.

detailed description

The present invention proposes a method for optimizing the selection of filter materials in the filtration of granular materials. The present invention will be further described in detail below in conjunction with the accompanying drawings and specific examples.

The present invention proposes a method for optimizing the matching of filter materials in the filtration of granular materials. The overall process is shown in Figure 3, including the following steps:

1) Determine the sewage sampling points;

According to the current situation of sewage treatment process at the sewage treatment point that needs to filter particulate materials, determine the equipment for removing suspended solids in the sewage treatment process, and set up a sewage water sampling point at the water inlet and outlet of each equipment for removing suspended solids. For example: set up a sewage water sampling point at the water inlet of the removal of suspended matter equipment 1 and record it as 1-1, set up a sewage water sampling point at the water outlet of the removal of suspended matter equipment 1 and record it as 1-2, and set up a sewage water sampling point at the water outlet of the removal of suspended matter Set up sewage water sampling points at the water inlet of 2-1, and set sewage water sampling points at the outlet of suspended solids removal equipment 2, which is recorded as 2-2.

Taking the oilfield sewage treatment process "first-level settling tank → second-level settling tank → first-level quartz sand filter tank → second-level quartz sand filter tank" as an example, set up at the water inlet of the first-level quartz sand filter tank Sewage water sampling point 1-1, set up sewage water sampling point 1-2 at the water outlet; set up sewage water sampling point 2-1 at the water inlet of the secondary quartz sand filter tank, set up sewage water sampling point at the water outlet Point 2-2.

2) Analyze the characteristics of suspended solids in sewage; the specific steps are as follows:

2-1) Determination of suspended matter concentration; specific steps are as follows:

Filtration of granular materials is mainly to remove suspended solids (particle size between 0.1 μm and 100 μm) in sewage, while solid phase particles with a particle size greater than 100 μm in sewage are not removed in this link.

2-1-1) Take a sewage water sample with a volume V at any sewage sampling point determined in step 1), where V is generally 500ml to 1000ml;

2-1-2) Use several filter membranes with a pore size of 0.1mm to slowly filter the sewage water samples collected in step 2-1-1); each filter membrane filters sewage water samples less than or equal to 50ml to prevent During the process, a dense filter layer is formed on the surface of the filter membrane with a pore size of 0.1mm, resulting in the loss of suspended solids (with a particle size of 0.1 μm to 100 μm) in the sewage; the filtered sewage water sample is saved, and the volume of solid particles with a particle size > 100 μm is ignored. The total volume of the filtered sewage water sample is still V.

Remarks: In order to remove solid particles with a particle size > 100 μm as much as possible and prevent the loss of suspended solids in sewage water samples as much as possible, the volume of filtered sewage corresponding to each filter membrane should be as small as possible, preferably ≤ 50ml.

2-1-3) Put a filter membrane with a pore size of 0.1 μm into a watch glass, bake the filter membrane and the watch glass together in an oven at 40°C for 8 hours, weigh the filter membrane and the watch glass as a whole, and record it as G ₁ ( In this implementation, Mettler Toledo MS205DU electronic balance is used for weighing, with a range of 0-82g and an accuracy of 0.01mg).

2-1-4) Take out the dried filter membrane with a pore size of 0.1 μm from the watch glass, and use the filter membrane with a pore size of 0.1 μm after drying to filter the volume of V sewage water after the first filtration in step 2-1-2) The sample is slowly filtered twice;

2-1-5) Put the filter membrane with a pore size of 0.1 μm after secondary filtration (at this time, on the filter membrane with a pore size of 0.1 μm, the particle size in the sewage water sample with an attachment volume of V is between 0.1 μm and 100 μm) into the In the original watch glass, and then bake the filter membrane and watch glass together in an oven at 40°C for 12 hours, then weigh the filter membrane and watch glass as a whole and record it as G ₂ .

2-1-6) Use formula (1) to calculate the suspended matter concentration C in the sewage water sample, the expression is as follows:

2-1-7) Repeat steps 2-1-1) to 2-1-6), obtain the sewage water samples of all sewage water sampling points and calculate the corresponding suspended matter concentration;

2-2) Measure the particle size of the suspended matter; the specific steps are as follows:

2-2-1) Repeat steps 2-1-1) to 2-1-2) to obtain a sewage water sample from any sewage water sampling point and perform a slow filtration;

2-2-2) Take 5-10ml from the sewage water sample retained after the primary filtration in step 2-2-1), and use a laser particle size analyzer (the higher the model and accuracy of the laser particle size analyzer, the better the effect; this implementation For example, Winner2000ZD laser particle size analyzer)) is used to measure the particle size distribution curve and _average particle size Daverage of the suspended matter in the sewage water sample obtained in step 2-2-1).

3) Optimizing the matching of the filter material; the specific steps are as follows:

3-1) In order to remove the suspended matter in the sewage by using the throat between the particle filter materials to intercept and block the suspended matter in the sewage, the _average particle size D of the suspended matter in the sewage and the spherical particles with different diameters are the most tightly packed porous media The throat of D _{throat on average} satisfies the expression shown in formula (2):

D _{throat mean} ≈ D _mean (2)

According to formula (2), _{the average value of D throat} is the average particle size D _average of the suspended matter in the sewage water sample obtained in step 2).

3-2) The filter material in granular material filtration is composed of a variety of spherical particles with different particle sizes and different mass ratios (thickness ratios) in the most closely packed form.

According to the formula (3), for the filter material composed of unequal diameter spherical particles with different masses and particle sizes, the filter material consists of mass m ₁ , particle size D _P1 ; mass m ₂ , particle size D _P2 ; mass m ₃ , Particle size D _P3 ;...; Spherical particles with different diameters such as mass m _n and particle size D _Pn are most closely packed.

Change the porous medium from the closest packing of unequal-diameter spherical particles to the closest packing of equal-diameter spherical particles, that is, the throat diameter of the porous medium formed after the particles of each particle size are packed according to the closest packing of spherical particles of equal diameter and equal diameter is the D _-throat , for example, the particle size D _Pn corresponds to the D _{-throat n} .

For the determined D _{throat average} , first determine the type of filter material (the type of particle size), that is, determine the specific value of n; according to the value of n, determine the quality of n kinds of filter materials and the corresponding throat; select The process of filter material is completed manually, and there are two specific implementation methods:

3-2-1) Firstly determine the quality of n kinds of filter materials respectively, that is, mass m ₁ , mass m ₂ , mass m ₃ , ..., mass m _n ; The corresponding throats are throat D _{throat 1} , throat D _{throat 2} , throat D _{throat 3} , ... , throat D _{throat n} .

3-2-2) First determine the throats corresponding to the closest accumulation of n kinds of filter materials according to the closest accumulation of equal-diameter spherical particles, that is, throat D _{throat 1} , throat D _{throat 2} , throat D _{throat 3} , ... , throat D _{throat n} ; then determine the mass m ₁ , mass m ₂ , mass m ₃ , ..., mass m _n corresponding to n kinds of filter materials.

3-3) The smallest unit body of the closest-packed porous medium with equal-diameter spherical particles is formed by dividing two layers of closest-packed spheres, as shown in FIG. 2 . The smallest unit body is further simplified into a triangular pyramid composed of four spherical centers connected to form a regular tetrahedron, as shown in Figure 4(a), and one face of the regular tetrahedron is further taken, as shown in Figure 4(b) . In Fig. 4(b), the diameter of the prototype in the blank space in the middle is the throat corresponding to the most closely packed porous medium of equal-diameter spherical particles.

From Fig. 4(b), it can be deduced that the _throat D corresponding to the most closely packed porous medium of equal-diameter spherical particles and the diameter D _P of spherical particles have the following relationship, and the expression is shown in formula (4):

According to the formula (4), each filter material obtained in combination with step 3) corresponds to the throat D _{throat 1} , the throat D _{throat 2} , the throat D _{throat 3} , ... , throat D _{throat n} , respectively calculate the particle size D _P1 , particle size D _P2 , particle size D _P3 , ..., particle size D _Pn corresponding to each filter material.

Therefore, it is determined that the optimal filter material selection plan for the suspended solids removal equipment corresponding to the sewage water sample is: mass m ₁ , particle size D _P1 ; mass m ₂ , particle size D _P2 ; mass m ₃ , particle size D _P3 ;...; The filter material combination composed of mass m _n and particle size D _Pn .

Remarks: In the project, for the same filter tank, its cross-sectional area is certain, and the laying thickness of the filter material of the same material can represent the quality. At the same time, according to the formula (3) to calculate the particle size D _Pn , without knowing the corresponding exact mass m _n , the throat D _{throat n} can be calculated under the condition of mass percentage, and then the particle size D _Pn can be calculated.

4) Evaluate the effect of filter material optimization matching;

In order to measure the removal effect of suspended solids in sewage, the suspended solids removal rate α is defined, and the expression is shown in formula (5):

In formula (5), C _{incoming water} is the suspended matter concentration of the water inlet sewage water sample of any suspended matter removal equipment obtained in step (2), unit mg/L; C _effluent is the water outlet sewage of the suspended matter removal equipment The concentration of suspended solids in water samples, in mg/L; the larger the α value, the better the removal effect of suspended solids in this link, indicating that the combination of granular filter materials selected according to this method is more suitable for removing suspended solids in this type of sewage.

For the particle size distribution curve of the suspended matter in the sewage at the outlet before improvement, the closed area (the closed area enclosed by the particle size curve and the axis of abscissa) is 2/3, and the main suspended matter in the sewage before improvement is determined. Concentrated area, that is, the main area of particle size [a b].

For the particle size distribution curve of suspended solids in the sewage at the outlet after improvement, the main concentration area of suspended solids in the improved sewage, that is, the main area of particle size [c d], is determined with 2/3 of the closed area as the boundary.

Comparative analysis of the changes in the area of particle size before and after improvement, when c<a and d<b, it shows that the improved filter material has a better effect on removing suspended solids in sewage, and the larger the difference, it means the removal The better the effect.

Example

In a specific embodiment of the present invention, a method for optimal matching of filter materials in granular material filtration proposed by the present invention is applied to sewage filtration of oilfield produced water.

The current status of the treatment process and granular filter material of the produced water sewage treatment station in an oilfield is as follows:

The sewage treatment process of the oilfield sewage treatment station is "first-level settling tank → second-level settling tank → first-level quartz sand filter tank → second-level quartz sand filter tank"; in the process "first-level quartz sand filter tank " and "secondary quartz sand filter material filter tank" are typical particulate material filtration links, and their main function is to remove suspended solids in oilfield production water.

In this process, the original filter material parameters of the secondary quartz sand filter tank are shown in Table 1.

Table 1 Parameters of the original filter material of the secondary quartz sand filter tank

Types of quartz sand 1 2 3 4 Particle size/μm 300 500 600 800 Thickness/mm 150 150 250 250 mass percentage/% 18.75 18.75 31.25 31.25

In this embodiment, before the process improvement, two kinds of sewage water samples of the secondary quartz sand filter tank, the incoming water and the outgoing water, were collected for 7 months from November 2015 to May 2016, on the 10th and 20th of each month and No. 30 were detected 21 times in total. The schematic diagram of the concentration of suspended solids in the incoming and outgoing water of the secondary quartz sand filter tank is shown in Figure 5. In the figure, the connection line corresponding to the triangle data points is the suspended solids concentration curve of the incoming water, and the connection line corresponding to the square data points is the suspended solids concentration curve of the effluent water. There are 21 data points on each curve corresponding to 21 detections Seen from Figure 5: the fall between the curves of the incoming water and the outgoing water of the secondary quartz sand filter tank is relatively small, taking the 21st detection result as an example, the concentration of suspended solids in the incoming water is 150.64mg/L, and the concentration of suspended solids in the outgoing water It was 127.69mg/L, and the concentration of suspended solids only dropped by 22.95mg/L. Figure 6 is a curve diagram of the removal rate of suspended solids by the secondary quartz sand filter tank. It can be seen from Figure 6 that the removal rate of suspended solids in the secondary quartz sand filter tank is 10.44% to 18.87%, and the removal rate is relatively small, with the 21st time Taking the test results as an example, the removal rate of suspended solids is only 15.23%. Figure 7 is a curve diagram of the particle size distribution of suspended solids in sewage. It can be seen from Figure 7: For "incoming water from the secondary quartz sand filter tank - the 21st time" and "outlet water before the improvement of the secondary quartz sand filter tank - the 21st time" The particle size distribution curves of the suspended solids in the medium are basically similar; with 2/3 of the closed area (enclosed area enclosed by the particle size curve and the abscissa axis) as the boundary, the main areas of the suspended solids particle size of the two water samples are both within 35 ~80μm; relative to the incoming water curve, the outlet water curve is only slightly shifted to the left; the average particle size of the incoming water is 61.09μm; the average particle size of the outlet water is 56.33μm. Based on the above, it can be concluded that the secondary quartz sand filter tank has a poor removal effect on suspended solids, and the filter material is basically in an invalid state.

A method for optimizing the matching of filter materials in the filtration of granular materials proposed by the present invention comprises the following steps:

1) Determine the sewage sampling points;

In this embodiment, a sewage sampling point is respectively set up for the water inlet and the water outlet of the secondary quartz sand filter tank in the sewage treatment process.

2) Analyze the characteristics of suspended solids in sewage; the specific steps are as follows:

2-1) Determination of suspended matter concentration; specific steps are as follows:

2-1-1) Take a sewage water sample with a volume of V at any sewage water sampling point determined in step 1) (in this embodiment, the water inlet and water outlet of the secondary quartz sand filter tank). V is 500ml;

2-1-2) Use 10 filter membranes with a pore size of 0.1mm to slowly filter the sewage water samples collected in step 2-1-1); each filter membrane only filters 50ml of sewage water samples to prevent the In the process, a dense filter layer is formed on the surface of the filter membrane with a pore size of 0.1 mm, which causes the loss of suspended solids (particle size between 0.1 μm and 100 μm) in the sewage; the filtered sewage is saved, and the volume of solid particles with a particle size > 100 μm is ignored. The total volume of the sewage water sample is still V.

2-1-3) Put a filter membrane with a pore size of 0.1 μm into a watch glass, bake the filter membrane and the watch glass together in an oven at 40°C for 8 hours, weigh the filter membrane and the watch glass as a whole, and record it as G ₁ ( In this implementation, Mettler Toledo MS205DU electronic balance is used for weighing, with a range of 0-82g and an accuracy of 0.01mg).

2-1-4) Take out the dried filter membrane with a pore size of 0.1 μm from the watch glass, and use the filter membrane with a pore size of 0.1 μm after drying to filter the volume of V sewage water after the first filtration in step 2-1-2) The sample is slowly filtered twice;

2-1-5) Put the filter membrane with a pore size of 0.1 μm after secondary filtration (at this time, on the filter membrane with a pore size of 0.1 μm, the particle size in the sewage water sample with an attachment volume of V is between 0.1 μm and 100 μm) into the In the original watch glass, and then bake the filter membrane and watch glass together in an oven at 40°C for 12 hours, then weigh the filter membrane and watch glass as a whole and record it as G ₂ .

2-1-6) Use the formula (1) to calculate the suspended solids concentration C in the sewage water sample, the expression is as follows:

2-1-7) Repeat steps 2-1-1) to 2-1-6), obtain the sewage water samples of all sewage water sampling points and calculate the corresponding suspended matter concentration;

2-2) Measure the particle size of the suspended matter; the specific steps are as follows:

2-2-1) Repeat steps 2-1-1) to 2-1-2) to obtain a sewage water sample from any sewage water sampling point and perform a slow filtration;

2-2-2) Take 5-10ml from the sewage water sample retained after primary filtration, and use a laser particle size analyzer (the higher the model and accuracy of the laser particle size analyzer, the better the effect; this embodiment uses Winner2000ZD laser particle size analyzer)) The particle size distribution curve and the _average particle size Daverage of the suspended matter in the sewage water sample obtained in the determination step 2-2-1).

In this embodiment, taking the data of the 21st test as an example, the average particle diameters of the incoming water and the effluent (21st time) of the secondary quartz sand filter tank are obtained, as shown in FIG. 7 .

3) Optimizing the matching of the filter material; the specific steps are as follows:

3-1) In order to remove the suspended matter in the sewage by using the throat between the particle filter materials to intercept and block the suspended matter in the sewage, the _average particle size D of the suspended matter in the sewage and the spherical particles with different diameters are the most tightly packed porous media The throat of D _{throat on average} satisfies the expression shown in formula (2):

D _{throat mean} ≈ D _mean (2)

According to formula (2), _{the average value of D throat} is the average particle size D _average of the suspended matter in the sewage water sample obtained in step 2).

In this example, the concentration of suspended solids in the incoming water from the secondary quartz sand filter tank—the 21st time” is 150.64 mg/L, and the average particle diameter D is 61.09 μm on _average .

3-2) According to formula (3), for the determined D _{throat average} , first determine the type of filter material (the type of particle size), that is, determine the specific value of n; according to the value of n, determine n kinds of filter materials respectively. The quality of the material and the corresponding throat;

In this embodiment, four kinds of quartz sand particle filter materials with different particle sizes are firstly determined, that is, n=4.

Then determine the quality of the four different particle sizes of quartz sand. First, determine that the laying thickness of the four different particle sizes of quartz sand is 160mm, 160mm, 240mm, and 240mm. The percentage of quartz sand with different particle sizes in the overall thickness of quartz sand is the mass percentage. From this, it is determined that the mass percentages of the four kinds of quartz sands with different particle sizes are 20%, 20%, 30%, and 30%, respectively.

Finally, determine the corresponding throats of the four kinds of quartz sands with different particle sizes according to the closest accumulation of equal-diameter spherical particles, that is, throat D _{throat 1} = 46.40 μm, throat D _{throat 2} = 54.13 μm, throat D _{throat 3} = 61.87 μm, throat D _{throat 4} = 77.33 μm.

3-3) The _throat D corresponding to the most densely packed porous medium of equidiameter spherical particles and the diameter D _P of spherical particles has the following relational expression, and the expression is shown in formula (4):

According to the formula (4), each filter material obtained in combination with step 3) corresponds to the throat D _{throat 1} , the throat D _{throat 2} , the throat D _{throat 3} , ... , throat D _{throat n} , respectively calculate the particle size D _P1 , particle size D _P2 , particle size D _P3 , ..., particle size D _Pn corresponding to each filter material.

Therefore, it is determined that the optimal filter material selection plan for the suspended solids removal equipment corresponding to the sewage water sample is: mass m ₁ , particle size D _P1 ; mass m ₂ , particle size D _P2 ; mass m ₃ , particle size D _P3 ;...; The filter material combination composed of mass m _n and particle size D _Pn .

_{In this embodiment} , the _{corresponding} The particle diameter D _P1 =300 μm, the particle diameter D _P2 =350 μm, the particle diameter D _P3 =400 μm, and the particle diameter D _P4 =500 μm.

As a result, the optimal matching scheme of the filter material was determined, which is shown in Table 2.

Table 2 Parameters of the improved filter material of the secondary quartz sand filter tank

Types of quartz sand 1 2 3 4 Particle size/μm 300 350 400 500 Thickness/mm 160 160 240 240 mass percentage/% 20 20 30 30

4) Evaluate the effect of filter material optimization matching;

In order to measure the removal effect of suspended solids in sewage, the suspended solids removal rate α is defined, and the expression is shown in formula (5):

In formula (5): C _{incoming water} is the suspended matter concentration of the water inlet sewage water sample of any suspended matter removal equipment obtained in step (2), unit mg/L; C _{outlet water} is the water outlet sewage of this suspended matter removal equipment The concentration of suspended solids in water samples, in mg/L; the larger the α value, the better the removal effect of suspended solids in this link, indicating that the combination of granular filter materials selected according to this method is more suitable for removing suspended solids in this type of sewage.

4-2) Use a laser particle size analyzer ((the higher the model and precision of the laser particle size analyzer, the better the effect; this embodiment uses the Winner2000ZD laser particle size analyzer) to measure the particle size distribution of the suspended matter in the sewage at the water outlet before and after improvement curve.

For the particle size distribution curve of suspended matter in the sewage at the outlet before improvement, the closed area (the closed area enclosed by the particle size curve and the axis of abscissa) is 2/3, and the main concentration of suspended matter in the sewage before improvement is determined Area, that is, the main area of particle size [a b].

For the particle size distribution curve of suspended solids in the sewage at the outlet after improvement, the main concentration area of suspended solids in the improved sewage, that is, the main area of particle size [c d], is determined with 2/3 of the closed area as the boundary.

Comparative analysis of the changes in the particle size area before and after improvement, when c<a and d<b, it shows that the improved filter material has a better effect on removing suspended solids in sewage, and the larger the difference, it means that the removal The better the effect.

In this embodiment, the comparison table of water outlet conditions before and after the improvement of the secondary quartz sand filter tank is shown in Table 3:

Table 3: Comparison table of the water output before and after the improvement of the secondary quartz sand filter tank

Find out by table 3: after the secondary quartz sand filter tank filter material is improved according to the method of the present invention, the concentration of suspended solids in the effluent water has dropped to 18.65mg/L by 127.69mg/L; %. It can be seen from Figure 6 that the main area of suspended matter particle size in the effluent water is reduced from 35-80 μm to 10-45 μm; the average particle size of suspended matter is reduced from 56.23 micron to 19.29 micron.

Analysis of the reasons for the improvement of suspended solids removal effect after improvement:

Calculated from formula (3) and formula (4), the average throat of the secondary quartz sand filter tank filter material after improvement is 61.87 μm, which is 28.99 μm lower than the average throat of 90.86 μm before improvement, and Compared with the average suspended particle size of 61.09 in the incoming water, the difference is only 0.78 μm. The improved filter material can remove the suspended solids in the water with a particle size of 61.87-90.86 μm. The throat of the porous medium composed of the improved filter material is closer to the particle size of the suspended solids in the incoming water, and the matching degree is greater. The interception and blocking effect of the improved filter material on the suspended solids is more significant, thereby improving the suspended solids in the entire process. Removal.

This proves that: according to the method of the present invention, the optimization of matching of the granular filter material can realize the purpose of improving the removal rate of suspended solids by the filtering mode of the granular material.

Claims (1)

1. choosing method is matched somebody with somebody in filtrate optimization in a kind of filtering particulate material, it is characterised in that comprised the following steps：

1) sewage intake sampling point is determined；

It is determined that needing the sewage disposal point for carrying out filtering particulate material to go oil removal equipment, each oil removal equipment is gone The mouth of a river of coming set up a sewage intake sampling point；

2) suspension particle diameter is determined；Comprise the following steps that：

2-1) in step 1) determine any sewage intake sampling point at take volume be V Wastewater Sample；

2-2) using several apertures 0.1mm filter membrane to step 2-1) collection Wastewater Sample carry out slowly once filter；Often The Wastewater Sample for opening membrane filtration is less than or equal to 50ml, preserves the Wastewater Sample after filtering, the Wastewater Sample cumulative volume after filtering Still it is V；

2-3) repeat step 2-1) to 2-2), obtain each sewage intake sampling point Wastewater Sample and simultaneously carry out slowly once filtering；

2-4) from by step 2-3) once filter after any Wastewater Sample in take 5~10ml, determined using laser particle analyzer Step 2-3) obtain the Wastewater Sample in suspension grading curve and average grain diameter D_{It is average}；

3) to filtrate optimization with choosing；Comprise the following steps that：

3-1) suspension average grain diameter D in Wastewater Sample_{It is average}The venturi of not isometrical spherical particle closestpacking porous media D_{Venturi is averaged}Meet the expression formula as shown in formula (2)：

D_{Venturi is averaged}≈D_{It is average} (2)

According to formula (2), D_{Venturi is averaged}Value is step 2) the average grain diameter D of suspension in obtained Wastewater Sample_{It is average}；

3-2) according to formula (3), for the D of determination_{Venturi is averaged}, it is first determined the species of filtrate, it is true respectively further according to the species of filtrate The quality and corresponding venturi of fixed every kind of filtrate；Expression formula is as follows：

In formula, n is the species number of filtrate, m₁、m₂、m₃、……、m_nFor the quality of every kind of filtrate；D_{Venturi 1}、D_{Venturi 2}、D_{Venturi 3}、……、 D_{Venturi n}For the venturi of every kind of filtrate；

3-3) the venturi D of filtrate_VenturiWith spherical particle diameter D_PIn the presence of following relational expression, shown in expression formula such as formula (4)：

According to formula (4), with reference to step 3) the obtained venturi D of every kind of filtrate_{Venturi 1}、D_Venturi、D_{Venturi 3}、……、D_{Venturi n}, calculate respectively The corresponding particle diameter D of every kind of filtrate_P1、D_P2、D_P3、……、D_Pn；Thereby determine that and go oil removal equipment corresponding to the Wastewater Sample Optimization filtrate with selecting the scheme to be：Quality m₁, particle diameter D_P1；Quality m₂, particle diameter D_P2；Quality m₃, particle diameter D_P3；……；Quality m_n、 Particle diameter D_PnThe filtrate combination constituted.