Filtration method and filtration apparatus

Abstract

To provide a filtration method and a filtration apparatus for filtering a liquid containing suspended matter resulting from cutting a resin composition, thereby enabling an increased removal rate of the suspended matter.SOLUTION: Provided is a filtration method comprising using an apparatus that filters a liquid containing suspended matter resulting from cutting a resin composition by means of a screen filter, wherein the screen filter has a filtration surface having an arcuately curved shape to allow the liquid containing suspended matter to be retained and filtered, and wherein, when the liquid containing suspended matter is sprayed onto the screen filter, an average spray velocity at a spray nozzle is 9 to 25 m / sec.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a filtering method and a filtering device for filtering a liquid containing suspended solids produced by cutting a resin composition. [Background technology]

[0002] While plastics are used in a variety of fields, they are also considered to be a cause of marine pollution, such as microplastics. Conventionally, devices have been disclosed that increase the efficiency of solid-liquid separation using a screen filter that is curved in an arc shape when viewed from the side in order to separate solids and liquids (for example, Patent Document 1).

[0003] Additionally, a technique for separating algae from a culture solution has been disclosed (Patent Document 2).

[0004] Patent Document 3 relates to a device for collecting chips generated when pellets are cut in the process of manufacturing plastic pellets, and discloses a separation technique using a mesh filter. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-198715 A [Patent Document 2] JP 2016-214151 A [Patent Document 3] JP 2004-106402 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, although the arc-shaped curved screen filter increases the efficiency of solid-liquid separation, the ease of separation of solids and liquid depends on the angle at which the liquid is sprayed, so there is an issue that the solid-liquid separation efficiency, or the rate at which suspended solids are removed, is not stable.

[0007] The present invention provides a method and apparatus for recovering suspended matter, which is short fibrous particles generated by cutting a resin composition during a pelletizing process, from a liquid containing the suspended matter, with a high removal rate. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention has the following configuration.

[0009] (1) A filtration method using a screen filter to filter a liquid containing suspended solids, wherein the filtering surface of the screen filter is curved in an arc so as to retain and filter the liquid containing suspended solids, and when the liquid containing suspended solids is sprayed onto the screen filter, the average spray velocity at a spray nozzle is 9 to 25 m / sec.

[0010] (2) The filtration method according to (1), wherein the screen filter is made of wedge wires, and the spacing between the wedge wires (hereinafter, slit width) is 10 to 150 μm.

[0011] (3) The filtration method according to (1), wherein the angle of the liquid containing the suspended solids is, when viewed from the right side with the filtration surface of the screen filter facing forward, between a straight line in the direction of the spray and a tangent to the filtration surface at the landing point of the liquid, is 2 to 20°.

[0012] (4) The filtration method according to (1), wherein the angle of the spray nozzle is such that, when viewed from the right side with the filtration surface of the screen filter facing forward, an angle between a horizontal line passing through the upper end of the screen filter and a line in the spray direction is 70 to 90°.

[0013] (5) The filtration method according to (1), wherein the spray nozzle is provided above the filtering surface of the screen filter, and the shape of the spray nozzle is any one of a perfect circle, an ellipse, and a slit.

[0014] (6) The amount of spray per one of the spray nozzles is 6 to 15 m 3 Filtration method (1) at 100 / h.

[0015] (7) The filtration amount per 1 mm of width in the direction perpendicular to the direction of the arc of the filtration surface of the screen filter is 0.030 to 0.075 m 3 The filtration method according to (1), wherein the filtration rate is 1 / h.

[0016] (8) The filtration method according to (1), wherein the spray nozzle is provided above the filtering surface of the screen filter, and the height of the spray nozzle is 0 to 400 mm from the upper end of the screen filter.

[0017] (9) The method for filtering according to (1), wherein the residual chlorine concentration in the liquid before filtering through the filter is 0.1 to 5.0 ppm.

[0018] (10) A method for filtering a liquid containing suspended solids with the filter according to (1), wherein the suspended solids content (SS) of the filtered liquid is less than 2.0 mg / L.

[0019] (11) A filtration device using a screen filter for filtering a liquid containing suspended solids, wherein the filtering surface of the screen filter is curved in an arc so as to retain and filter the liquid containing suspended solids, and when the liquid containing suspended solids is sprayed onto the screen filter, the average spray velocity at a spray nozzle is 9 to 25 m / sec.

[0020] (12) The filtration device according to (11), wherein the screen filter is made of wedge wires, and the spacing between the wedge wires (hereinafter, slit width) is 10 to 150 μm.

[0021] (13) The filtration device according to (11), wherein the angle of the liquid containing the suspended solids is, when viewed from the right side with the filtration surface of the screen filter facing forward, between a straight line in the direction of the spray and a tangent to the filtration surface at the landing point of the liquid, is 2 to 20°.

[0022] (14) The filtration device according to (11), wherein the angle of the spray nozzle is such that, when viewed from the right side with the filtration surface of the screen filter facing forward, an angle between a horizontal line passing through the upper end of the screen filter and a line in the spray direction is 70 to 90°. Effect of the Invention

[0023] According to the present invention, it is possible to provide a filtering method and a filtering device that filter a liquid containing suspended solids generated by cutting a resin composition and that has a high rate of removing suspended solids. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The present invention will be described in detail below. However, the present invention is not limited to the embodiments described below.

[0025] According to one embodiment, the present invention relates to a method and a filtering device for filtering, with a screen filter, a liquid containing particles produced by cutting a resin composition in a process of pelletizing the resin composition.

[0026] A representative resin composition is a polyester resin composition, and among these, a polyethylene terephthalate composition can be mentioned.

[0027] An example of a method for producing polyethylene terephthalate is as follows. For example, an esterification reaction is initiated with terephthalic acid and ethylene glycol, and after completion of the reaction, the mixture is transferred to a polymerization tank, an antimony compound, a magnesium compound, and a phosphorus compound are added, and the mixture is depressurized to a high vacuum and heated to about 290°C to carry out a polycondensation reaction until the target intrinsic viscosity is reached. The resulting polyester composition is then discharged in the form of strands from the nozzle of the polymerization tank, cooled with water, and pelletized with a cutter to produce pellets of polyethylene terephthalate.

[0028] Examples of antimony compounds include antimony trioxide, antimony pentoxide, antimony acetate, and antimony salts of aliphatic carboxylic acids. Among these, antimony trioxide is preferably used in view of its polycondensation reactivity, the color tone of the resulting polymer, and its inexpensive availability.

[0029] The magnesium compound includes magnesium acetate, magnesium hydroxide, etc., with magnesium acetate being particularly preferred.

[0030] Examples of phosphorus compounds include trimethyl phosphate, phosphoric acid, sodium dihydrogen phosphate, phosphorous acid, and phosphonic acid, with trimethyl phosphate being preferred. The present invention relates to a method for filtering wastewater containing particles generated by cutting polyethylene terephthalate in the pelletizing process, and it is preferred that the particles contained in the wastewater before filtration are short fiber-like and have a major axis size of 50 to 5000 μm. In addition, the suspended solids (SS 0 ) is preferably 2 to 1000 mg / L.

[0031] The present invention relates to a filtration method that uses a screen filter to filter a liquid containing suspended solids, wherein the filtering surface of the screen filter is curved in an arc shape so that the liquid containing suspended solids can be retained and filtered, and when the liquid containing suspended solids is sprayed onto the screen filter, the average spray velocity from a spray nozzle is 9 to 25 m / sec.

[0032] Here, "curved in an arc" refers to a shape obtained by cutting out a part of a circle or an ellipse. It is necessary that the filtering surface (side surface) of the screen filter is in an arc shape when viewed from the side with the filtering surface facing forward.

[0033] In the present invention, when a liquid containing suspended solids is sprayed onto a screen filter, the average spray speed from the spray nozzle must be 9 to 25 m / sec. If the average spray speed is lower than 9 m / sec, the water drainage is poor, and if the average spray speed exceeds 25 m / sec, the removal rate of suspended solids is poor.

[0034] The screen filter used for filtration is composed of wedge wires, and the spacing between the wedge wires (hereinafter, slit width) is preferably 10 to 150 μm, more preferably 10 to 100 μm, and even more preferably 10 to 50 μm. If it is less than 10 μm, the screen is easily clogged with suspended solids, and if it exceeds 150 μm, the removal rate of suspended solids decreases.

[0035] The suspended solids (SS) after filtration through a screen filter is less than 2.0 mg / L, and more preferably less than 0.5 mg / L, which reduces the particles contained in the liquid to a level that cannot be seen with the naked eye.

[0036] When the liquid containing suspended solids is sprayed, as viewed from the right side with the filtration surface of the screen filter facing forward, the angle between the straight line of the spray direction and the tangent to the filtration surface at the landing point of the liquid is preferably 2 to 20°, more preferably 7 to 15°. If the tangent direction of the screen is less than 2°, drainage will be poor, and if the tangent direction of the screen is more than 20°, separation of suspended solids will be difficult.

[0037] When viewed from the right side with the filtration surface of the screen filter facing forward, the angle of the jet nozzle between a horizontal line passing through the upper end of the screen filter and a line in the jet direction is preferably 70 to 90°, more preferably 80 to 85°. If the jet nozzle angle exceeds 90°, drainage will be poor, and if it is less than 70°, the liquid will hit the filtration surface of the screen filter too hard, resulting in a poor removal rate of suspended solids.

[0038] The spray nozzle is preferably provided above the filtering surface of the screen filter, and the shape of the spray nozzle is preferably a perfect circle, an ellipse, or a slit, more preferably an ellipse. The slit is preferable as a means for effectively using the filtering area of ​​the screen filter.

[0039] The amount of spray per nozzle is 6 to 15 m 3 / h, and more preferably 7 to 10 m 3 / h. The injection volume per injection nozzle is 6m 3 If it is lower than 15m / h, drainage will be poor. 3 If the rate exceeds 1 / h, the rate of suspended solids removal may decrease.

[0040] The filtration amount per 1 mm of width in the direction perpendicular to the direction of the arc of the filtering surface of the screen filter is 0.030 to 0.075 m 3 / h, and more preferably 0.045 to 0.065 m 3 / h. 0.030m 3 If the filter is lower than 0.075 m / h, the amount of liquid filtered is small. 3 If it exceeds this rate, the rate of suspended solid removal will decrease.

[0041] The spray nozzle is provided above the filtering surface of the screen filter, and the height of the spray nozzle from the upper end of the screen filter is preferably 0 to 400 mm, more preferably 100 to 300 mm. If the height of the spray nozzle exceeds 400 mm, drainage becomes poor.

[0042] The residual chlorine concentration in the liquid before filtration is preferably 0.1 to 5.0 ppm by mass, more preferably 0.1 to 3.0 ppm by mass, and even more preferably 0.2 to 2.0 ppm by mass. If the residual chlorine concentration is less than 0.1 ppm by mass, microorganisms such as bacteria will grow and become entangled with suspended matter in the liquid, and the viscosity of the suspended matter captured in the slits on the screen filter surface will increase, making the screen filter prone to clogging and making it difficult to efficiently collect the chlorine. In addition, if the residual chlorine concentration exceeds 5.0 ppm by mass, it is not preferable because it places a burden on the environment and increases the economic burden, such as increasing costs.

[0043] There is no particular limitation on the means for incorporating chlorine into the liquid, but simple methods include injecting chlorine gas, immersing a tablet that slowly releases chlorine, such as a tablet containing a chloroisocyanurate, in cooling water, immersing a tablet containing a hypochlorite in cooling water, and electrolyzing magnesium chloride, sodium chloride, or the like.

[0044] Among these, from the viewpoints of ease of handling and durability of effect, it is desirable to use chlorine gas, hypochlorous acid compounds (more preferably sodium hypochlorite, potassium hypochlorite, or calcium hypochlorite), isocyanuric acid or isocyanuric acid salts or compounds thereof (more preferably sodium dichloroisocyanurate, trichloroisocyanuric acid), and chlorides of hydantoin derivatives (more preferably dichlorodimethylhydantoin, bromochlorodimethylhydantoin).

[0045] When a liquid containing suspended solids is filtered through a screen filter, the suspended solids (SS) of the filtered liquid is preferably less than 2.0 mg / L, more preferably less than 1.0 mg / L, and even more preferably less than 0.5 mg / L, which reduces the particles contained in the liquid to a level that cannot be visually confirmed. EXAMPLES

[0046] The present invention will be described in detail below with reference to examples. The methods for measuring physical properties and evaluating effects are as follows.

[0047] (Evaluation method) (1) Suspended solids amount (SS) The method for measuring SS is specified as suspended solids in JIS K 0102. 1 L of wastewater sample is filtered through filter paper with a pore size of 1 μm and a diameter of 47 mm, and then dried in an oven at 105°C for 90 minutes. The dry weight of the material remaining on the filter paper is calculated from the weight of the filter paper before and after drying, and this value is divided by the amount of filtered wastewater to obtain a value (mg / L).

[0048] (2) Suspended solids removal rate (SS 0): Amount of suspended solids before filtration (SS): Suspended solids after filtration Suspended solids removal rate (wt%) = (SS 0 )-(SS)) / (SS 0 ) x 100.

[0049] (3) Residual chlorine concentration in wastewater One packet of DPD reagent and one spoonful of potassium iodide were added to 10 ml of the sample, and the residual chlorine concentration was calculated by measuring it using a residual chlorine meter (DPD method) manufactured by Shibata Scientific Co., Ltd.

[0050] Example 1 Terephthalic acid and ethylene glycol were subjected to an esterification reaction at 250°C. After the esterification reaction was completed, antimony trioxide, magnesium acetate, and trimethyl phosphate were added, the reaction system was gradually lowered to 100 Pa, and the temperature was raised to 290°C to complete the polycondensation reaction. The mixture was discharged by leaking with nitrogen and pelletized with a strand cutter. The wastewater from the pelletization had a residual chlorine concentration of 0.3 ppm and suspended solids (SS 0 ) was 16.3 mg / L, and the liquid was filtered through an arc screen manufactured by Toyo Screen Kogyo Co., Ltd. The conditions of the arc screen were as follows: when viewed from the right side with the filtration surface of the screen filter facing forward, the shape of the screen filter was arc-shaped, the screen filter width was 600 mm, the slit width was 10 μm, the average liquid injection speed was 15 m / sec, the liquid injection angle was 10°, the injection nozzle angle was 85°, the injection nozzle shape was elliptical with a major axis of 15 mm and a minor axis of 13 mm, and the injection amount per injection nozzle was 10 m. 3 / h, filtration volume per 1 mm of screen width: 0.050 m 3 / h, the nozzle height was 200 mm, and the number of nozzles was 3. The liquid processing capacity was 30 m 3 The suspended solids removal rate after filtration was high at 99.4% by weight. The results are shown in Table 1.

[0051] (Examples 2 to 4) Except for changing the slit width, filtration was performed in the same manner as in Example 1. The suspended solids (SS) after filtration was less than 1.4 mg / L. The results are shown in Table 1.

[0052] (Examples 5 to 8) Filtration was carried out in the same manner as in Example 1, except that the average jet speed, the jet amount per jet nozzle, and the filtration amount per 1 mm of screen width were changed. The liquid processing amount was 18 to 45 m 3 / h, and the amount of suspended solids after filtration was less than 0.5 mg / L. The results are shown in Table 1.

[0053] (Examples 9 to 12) Except for changing the liquid injection angle, filtration was carried out in the same manner as in Example 1. The amount of suspended solids after filtration was less than 0.3 mg / L. The results are shown in Table 1.

[0054] (Examples 13 to 15) Except for changing the angle of the spray nozzle, filtration was performed in the same manner as in Example 1. The amount of suspended solids after filtration was 0.1 mg / L. The results are shown in Table 1.

[0055] (Example 16) Filtration was performed in the same manner as in Example 1, except that the spray nozzle shape was changed to a perfect circle, the spray nozzle diameter was changed to 15 mm, the spray amount per spray nozzle, and the filtration amount per 1 mm of screen width were changed as shown in Table 1. The amount of suspended solids after filtration was 0.1 mg / L. The results are shown in Table 1.

[0056] (Example 17) Filtration was carried out in the same manner as in Example 1, except that the shape of the spray nozzle was changed to a slit, there were three spray nozzles with a width of 200 mm, and the spray amount per spray nozzle and the filtration amount per 1 mm of squeen width were changed as shown in Table 1. The amount of suspended solids after filtration was 0.1 mg / L. The results are shown in Table 1.

[0057] (Examples 18 to 21) Except for changing the height of the spray nozzle, filtration was carried out in the same manner as in Example 1. The amount of suspended solids after filtration was less than 0.8 mg / L. The results are shown in Table 1.

[0058] (Examples 22 to 24) Except for changing the residual chlorine concentration of the liquid before filtration, filtration was performed in the same manner as in Example 1. The amount of suspended solids after filtration was 0.1 mg / L. The results are shown in Table 1.

[0059] Comparative Example 1 The liquid injection angle, injection nozzle shape, and injection nozzle diameter were set to a perfect circle and 7 mm, respectively, and filtration was performed under the conditions shown in Table 1, which are similar to the conditions in Patent Document 1. The liquid processing volume was 15 m 3 The results are shown in Table 1.

[0060] Comparative Example 2 The slit width was changed to 200 μm, and otherwise filtration was performed under the same conditions as in Comparative Example 1. The amount of suspended solids after filtration was large, and the suspended solids removal rate was poor at 89.6% by weight. The results are shown in Table 1.

[0061] Comparative Example 3 The filter used was a screen mesh type #150 (109μm mesh), with a flat filter shape that was linear when viewed from the right side, and filtration was performed under the other conditions shown in Table 1. The suspended solids (SS) after filtration was high at 9.3mg / L, and the suspended solids removal rate was poor at 42.9% by weight. The results are shown in Table 1.

[0062] [Table 1]

[0063] [Table 2]

Claims

1. A filtration method using a screen filter to filter a liquid containing suspended solids, the filtration surface of the screen filter has an arc-shaped curved shape so that the liquid containing suspended solids can be retained and filtered, and when the liquid containing suspended solids is sprayed onto the screen filter, an average spray speed from a spray nozzle is 9 to 25 m / sec.

2. 2. The filtering method according to claim 1, wherein the screen filter is made of wedge wires, and the spacing between the wedge wires (hereinafter, slit width) is 10 to 150 μm.

3. 2. The filtering method according to claim 1, wherein the angle of the liquid containing suspended solids between a straight line in the direction of the spray and a tangent to the filtering surface at the landing point of the liquid is 2 to 20° when viewed from the right side of the screen filter with the filtering surface facing forward.

4. 2. The filtering method according to claim 1, wherein the angle of the spray nozzle is such that, when viewed from the right side with the filtration surface of the screen filter facing forward, an angle between a horizontal line passing through an upper end of the screen filter and a line in the spray direction is 70 to 90°.

5. 2. The filtering method according to claim 1, wherein the spray nozzle is provided above the filtering surface of the screen filter, and the shape of the spray nozzle is any one of a perfect circle, an ellipse, and a slit.

6. The amount of spray per nozzle is 6 to 15 m ３ 2. The method according to claim 1, wherein the filtration rate is 1 / h.

7. The filtration amount per 1 mm of width in the direction perpendicular to the direction of the arc of the filtering surface of the screen filter is 0.030 to 0.075 m ３ 2. The method according to claim 1, wherein the filtration rate is 1 / h.

8. 2. The filtering method according to claim 1, wherein the spray nozzle is provided above the filtering surface of the screen filter, and the height of the spray nozzle is 0 to 400 mm from the upper end of the screen filter.

9. 2. The method according to claim 1, wherein the residual chlorine concentration in the liquid before filtration is 0.1 to 5.0 ppm.

10. 2. The method of claim 1, wherein the suspended solids (SS) of the filtered liquid is less than 2.0 mg / L.

11. A filtration device using a screen filter for filtering a liquid containing suspended solids, the filtering surface of the screen filter having an arc-shaped curve so as to retain and filter the liquid containing suspended solids, and when the liquid containing suspended solids is sprayed onto the screen filter, the average spray speed at a spray nozzle is 9 to 25 m / sec.

12. 12. The filtering device according to claim 11, wherein the screen filter is made of wedge wires, and the interval between the wedge wires (hereinafter, slit width) is 10 to 150 μm.

13. 12. The filtration device according to claim 11, wherein the angle of the liquid containing suspended solids between a straight line in the spray direction and a tangent to the filtration surface at the landing point of the liquid is 2 to 20° when viewed from the right side with the filtration surface of the screen filter facing forward.

14. 12. The filtration device according to claim 11, wherein the angle of the spray nozzle is such that, when viewed from the right side with the filtration surface of the screen filter facing forward, an angle between a horizontal line passing through the upper end of the screen filter and a line in the spray direction is 70 to 90 degrees.

Images