An in-situ automatic detection device and method for sludge settling ratio

Abstract

The invention discloses an in-situ automatic detection device and method for sludge settling ratio, comprising: a rotary gate, arranged at the bottom opening of a settling pipe; a motor, arranged at the upper end of the settling pipe, connected to the rotary gate via a connecting shaft; an air pipe, arranged at the top of the settling pipe, connected to the inside of the settling pipe, a first electromagnetic valve is arranged on the air pipe, and can be connected to an external air source; an exhaust pipe, arranged at the top of the settling pipe, connected to the inside of the settling pipe, a second electromagnetic valve is arranged on the exhaust pipe; a first and a second photometer are arranged at different height positions outside the lower part of the settling pipe, and the optical paths of the two adjacent photometers are reversely parallel; a control device, respectively electrically connected to the motor, the first electromagnetic valve, the second electromagnetic valve, and each photometer, can receive signals from each photometer, and control the actions of the motor, the first and the second electromagnetic valves according to set program instructions. The device can overcome human errors, automatically sample, and automatically analyze the settling characteristics of activated sludge.

Description

Technical Field

[0001] The invention relates to the field of detection equipment for sewage treatment, and in particular to an in-situ automatic detection device and method for sludge settling ratio. Background Art

[0002] In sewage treatment plants that use the traditional activated sludge process, the sludge settling ratio (SV) is a conventional indicator used to monitor sludge concentration and warn of sludge bulking. It usually requires manual timing, fixed-point sampling, waiting for sludge to stand, and calculation and analysis, which is time-consuming and has large errors. The conventional method for determining SV is to take the mixed liquid at the outlet of the aeration tank and place it in a 1L measuring cylinder. After standing for a period of time (such as 30 minutes), the ratio of the volume occupied by the settled sludge to the volume of the mixed liquid (1L) is the SV.

[0003] The existing measurement of sludge settling ratio mostly adopts online automatic monitoring devices, such as China invention patent 201810624803.2 discloses an online automatic monitoring device for sludge settling ratio, which is a plug that cooperates with each other in the metering tube, the upper end of the plug is connected to the motor through a spiral rod, a sampling tube connected to it is provided at the lower end of the metering tube, a sampling control valve is provided on the sampling tube, a sample discharge tube connected to it is provided on one side of the lower end of the metering tube, a sample discharge control valve is provided on the sample discharge tube, an internal photometer is provided on the outer side of the metering tube, and an external photometer is provided on the outer side of the internal photometer, the motor, the sampling control valve, the sample discharge control valve, the internal photometer and the external photometer are respectively connected to the control device, and a liquid crystal display is provided on the control device. However, this type of online automatic monitoring device for sludge settling ratio has a high failure rate due to too many mechanical structures; the sludge is easy to accumulate and difficult to clean; the pump peristalsis and the narrow inlet pipeline are easy to cause some flocs to break, affecting the test results. Another Chinese invention patent 201911416167.5 discloses a device for online monitoring of sludge settling performance, which connects the control pump outlet to the first valve, the first valve to the transparent standard metering container, the infrared photoelectric switch transmitter is fixedly mounted on the mounting bracket, the linear guide is fixedly mounted on the column, the slider is mounted on the linear guide, the slide is fixedly mounted on the slider, the infrared photoelectric switch transmitter is mounted on the slide and a nut is mounted on the slide, the stepper motor is fixedly mounted on the motor mounting seat, the column is mounted with a ball screw and both ends of the ball screw are mounted on the column through a bearing seat, the stepper motor is connected to the ball screw on the column through a coupling and the ball screw is mounted on the nut, and the water outlet at the bottom of the transparent standard metering container is connected to the vent valve through a pipeline. However, due to the complex pipeline, the flocs are easily blocked and difficult to clean in this device for online monitoring of sludge settling performance; the pump peristalsis and the narrow inlet pipeline are easy to cause some flocs to break, affecting the test results.

[0004] In summary, the existing automatic detection devices for sludge sedimentation mostly have problems such as complex mechanical structure, narrow sampling pipeline, and pump peristaltic squeezing and destroying flocs, which affect the accuracy of the measurement results. Summary of the invention

[0005] Based on the problems existing in the prior art, the purpose of the present invention is to provide an in-situ automatic detection device for sludge settling ratio, which can solve the problems of complex mechanical structure, narrow sampling pipeline and pump peristaltic squeezing and destroying flocs in the existing online automatic monitoring device for detecting sludge settling ratio, thereby affecting the accuracy of the measurement results.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] The embodiment of the present invention provides an in-situ automatic detection device for sludge settling ratio, comprising:

[0008] A settling pipe, a rotating gate, a motor, a connecting shaft, an air pipe, a first electromagnetic valve, an exhaust pipe, a second electromagnetic valve, at least two photometers and a control device; wherein,

[0009] The rotating gate is arranged at the bottom opening of the settling pipe and can open or close the bottom opening of the settling pipe;

[0010] The motor is arranged at the upper end of the settling tube, and the motor is connected to the rotating gate through the connecting shaft, and can open or close the rotating gate;

[0011] The air pipe is arranged at the top of the settling pipe and communicated with the inside of the settling pipe. The first electromagnetic valve is arranged on the air pipe, and the air pipe can be connected to an external air source;

[0012] The exhaust pipe is arranged at the top of the settling pipe and is connected with the inside of the settling pipe. The exhaust pipe is provided with the second electromagnetic valve;

[0013] Each photometer is respectively arranged at different height positions outside the lower part of the settling tube, and the optical paths of two adjacent photometers are anti-parallel;

[0014] The control device is electrically connected to the motor, the first electromagnetic valve, the second electromagnetic valve and the photometer respectively, can receive signals from each photometer, and control the actions of the motor, the first electromagnetic valve and the second electromagnetic valve according to set program instructions.

[0015] The embodiment of the present invention further provides an in-situ automatic detection method for sludge settling ratio, which uses the in-situ automatic detection device for sludge settling ratio of the present invention, and pre-sets the opening and closing rules and operation time of the electromagnetic valve through the control device of the in-situ automatic detection device for sludge settling ratio, including the following steps:

[0016] Step 1) The control device controls the closing of the first electromagnetic valve, opens the second electromagnetic valve, controls the motor to open the rotary gate through the connecting shaft, and the mixed liquid fills the sedimentation tube under the action of water pressure;

[0017] Step 2) The control device controls the motor to close the rotating gate through the connecting shaft, and waits for the sludge to settle for a predetermined time;

[0018] Step 3) The control device controls the closing of the second electromagnetic valve and the opening of the first electromagnetic valve. The motor opens the rotary gate through the connecting shaft. Air enters the sedimentation tube through the air pipe to press the liquid in the sedimentation tube out of the rotary gate. Each photometer measures the photometric signal of the change of the liquid in the sedimentation tube and sends it to the control device. The control device calculates the mud level according to the photometric signal of each photometer to obtain the sludge settling ratio.

[0019] Step 4) When the photometric signal measured by the photometer at the bottom is an air signal, the control device confirms that the sedimentation tube has been emptied and flushed, controls the closing of the first electromagnetic valve and the second electromagnetic valve, and controls the motor to close the rotating gate through the connecting shaft to complete a detection.

[0020] It can be seen from the technical solutions provided by the present invention that the in-situ automatic detection device and method of sludge settling ratio provided by the embodiments of the present invention have the following beneficial effects:

[0021] By setting a rotating gate controlled by a motor, in conjunction with an air pipe and an exhaust pipe, the mixed liquid can be driven in situ by the liquid level pressure to complete the liquid inlet. Since there is no pump and fine branch pipeline, the flocs will not be destroyed and the sedimentation result determination will not be affected; there is only one straight sedimentation pipe in the liquid pipeline, which has no complex structure, is not easy to be blocked, and can operate stably for a long time; after each measurement, the inside of the sedimentation pipe is alternately flushed with water and air, which is easy to clean and not easy to sludge and scale; the equipment has no complex mechanical structure, is easy to maintain, and the cost of replacing the original parts is low; the control device can realize the automatic determination of the sludge sedimentation property at a fixed time and continuously. The device has a simple structure, is easy to install, maintain, and clean, can realize the long-term stable operation of the equipment, can overcome human errors during measurement, and automatically take samples and automatically analyze the sedimentation characteristics of activated sludge. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0023] Figure 1 A schematic diagram of an in-situ automatic detection device for sludge settling ratio provided by an embodiment of the present invention;

[0024] Figure 2 A schematic diagram of state changes in a settling tube in an in-situ automatic detection method for sludge settling ratio provided by an embodiment of the present invention, wherein FIG1 is a schematic diagram of a settling tube filled with a mixed liquid, FIG2 is a schematic diagram of a settling tube in a static state, FIG3 is a schematic diagram of a state of measuring the sludge settling ratio, FIG4 is a schematic diagram of a state of emptying the settling tube, and FIG5 is a schematic diagram of a state of measuring the settling ratio of the settling tube again;

[0025] Figure 3 A schematic diagram of the time difference state of photometric signals of two photometers in the in-situ automatic detection device for sludge settling ratio provided by an embodiment of the present invention;

[0026] Figure 4 A schematic diagram of the mud-water interface state of the photometric signals of two photometers in the in-situ automatic detection device for sludge settling ratio provided by an embodiment of the present invention;

[0027] The components corresponding to the marks in the figure are: 1-sedimentation tube; 2-rotating gate; 3-connecting shaft; 4-motor; 5-air pipe; 6-air source; 7-first electromagnetic valve; 8-exhaust pipe; 9-second electromagnetic valve; 10-first photometer; 11-second photometer; 12-control device; 13-liquid crystal display. DETAILED DESCRIPTION

[0028] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in combination with the specific content of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention. The contents not described in detail in the embodiments of the present invention belong to the prior art known to professional and technical personnel in this field.

[0029] like Figure 1 As shown, an embodiment of the present invention provides an in-situ automatic detection device for sludge settling ratio, comprising:

[0030] Sedimentation pipe 1, rotary gate 2, motor 4, connecting shaft 3, air pipe 5, first electromagnetic valve 7, exhaust pipe 8, second electromagnetic valve 9, at least two photometers and control device 12; wherein,

[0031] The rotating gate 2 is arranged at the bottom opening of the settling tube 1 and can open or close the bottom opening of the settling tube 1;

[0032] The motor 4 is arranged at the upper end of the settling tube 1, and the motor 4 is connected to the rotating gate 2 through the connecting shaft 3, and can open or close the rotating gate 2;

[0033] The air pipe 5 is arranged at the top of the settling pipe 1 and communicated with the inside of the settling pipe 1. The air pipe 5 is provided with the first electromagnetic valve 7. The air pipe 5 can be connected to an external air source 6.

[0034] The exhaust pipe 8 is arranged at the top of the settling pipe 1 and is connected to the inside of the settling pipe 1. The exhaust pipe 8 is provided with the second electromagnetic valve 9;

[0035] Each photometer 11 is respectively arranged at different height positions outside the lower part of the settling tube 1, and the optical paths of two adjacent photometers are anti-parallel;

[0036] The control device is electrically connected to the motor 4, the first electromagnetic valve 7, the second electromagnetic valve 9, and each photometer, respectively, can receive signals from each photometer, and control the actions of the motor 4, the first electromagnetic valve 7, and the second electromagnetic valve 9 according to set program instructions.

[0037] In the above automatic detection device, the control device is a control device with a liquid crystal display screen 13.

[0038] In the above automatic detection device, the sedimentation tube adopts a long straight tube body. The sedimentation tube of this shape has a simpler structure and is more convenient for sampling and cleaning.

[0039] The automatic detection device further comprises: an air source or a vacuum pump connected to the air pipe 5. Preferably, the air source can also be an aeration branch pipe of the aeration tank. When a vacuum pump is used, the sedimentation tube is raised but the bottom is still below the liquid level. Through the connected vacuum pump, negative pressure is formed inside the sedimentation tube, forcing the liquid on the pool surface to rise to the sedimentation tube.

[0040] Preferably, in the above-mentioned automatic detection device, the number of photometers is two, such as a first photometer 10 and a second photometer 11, the first photometer 10 and the second photometer 11 are installed at different heights on the outside of the lower part of the sedimentation tube 1, and the optical paths of the two are reversely parallel, so that the first photometer 10 and the second photometer 11 measure the photometric signal, transmit it to the control device 12 and record it, and the control device 12 calculates the sludge settling ratio according to the jump time difference of the photometric signal measured by the first photometer 10 and the second photometer 11 and the position and distance between the first photometer 10 and the second photometer 11;

[0041] Furthermore, more than two photometers may be provided to increase the number or number of photometers, and the mud level after settlement may be determined by the signal jump time difference of photometers greater than two in number and the position and distance of the photometers.

[0042] See also Figure 2The embodiment of the present invention provides an in-situ automatic detection method for sludge settling ratio, which uses the above-mentioned in-situ automatic detection device for sludge settling ratio, and pre-sets the opening and closing rules and operation time of the electromagnetic valve through the control device 12 of the in-situ automatic detection device for sludge settling ratio, including the following steps:

[0043] Step 1) The control device 12 controls the closing of the first electromagnetic valve 7, opens the second electromagnetic valve 9, controls the motor 4 to open the rotary gate 2 through the connecting shaft 3, and the mixed liquid fills the sedimentation tube 1 under the action of water pressure;

[0044] Step 2) the control device 12 controls the motor 4 to close the rotary gate 2 via the connecting shaft 3, and waits for the sludge to settle for a predetermined time;

[0045] Step 3) The control device 12 controls the closing of the second electromagnetic valve 9 and the opening of the first electromagnetic valve 7. The motor 4 opens the rotary gate 2 through the connecting shaft 3. The air enters the sedimentation tube 1 through the air pipe 5 (constant flow) to press the liquid in the sedimentation tube 1 out of the rotary gate 2. The first photometer 10 and the second photometer 11 measure the photometric signal of the change of the liquid in the sedimentation tube 1 and send it to the control device 12. The control device 12 calculates the mud level according to the photometric signal of each photometer to obtain the sludge settling ratio;

[0046] Step 4) When the photometric signal measured by the photometer at the bottom is an air signal, the control device 12 confirms that the sedimentation tube 1 has been emptied and flushing has been completed, controls the closing of the first electromagnetic valve 7 and the second electromagnetic valve 9, and controls the motor 4 to close the rotating gate 2 through the connecting shaft 3 to complete a detection.

[0047] In step 3 of the above method, the control device 12 calculates the mud level according to the photometric signals of each photometer 11 to obtain the sludge settling ratio:

[0048] According to the two jumps of the photometric signals of adjacent photometers (i.e., two adjacent photometers), the mud-water interface and the gas-liquid interface in the sedimentation tube 1 are determined, and the mixed liquid level falling speed is calculated by the time difference of the jumps of adjacent photometers (i.e., two adjacent photometers) and the installation height difference, and the mud level is calculated according to the mixed liquid level falling speed to obtain the sludge settling ratio.

[0049] In step 2 of the above method, the predetermined standing time is: greater than or equal to 30 minutes.

[0050] The embodiments of the present invention are described in further detail below.

[0051] like Figure 1As shown, an embodiment of the present invention provides an in-situ automatic detection device for sludge settling ratio, comprising: a settling pipe 1, a rotary gate 2 that is expected to cooperate with each other is arranged at the bottom end of the settling pipe 1, the rotary gate is connected to a motor 4 arranged at the upper end of the settling pipe 1) through a connecting shaft 3, an air pipe 5 is arranged at the top of the settling pipe 1 to connect with an air source 6 and an aeration tank air branch pipe, a first electromagnetic valve 7 is arranged between the air pipe 5 and the air source 6, an exhaust pipe 8 is arranged at the top of the settling pipe 1 to communicate with the atmosphere, a first electromagnetic valve 19 is arranged at the place where the exhaust pipe 8 is connected with the atmosphere, a first photometer 10 and a second photometer 11 are installed at different heights on the outer side of the lower part of the settling pipe 1, and the optical paths are reversely parallel (this embodiment is described by taking the arrangement of two photometers as an example, and more than two photometers can also be arranged), the motor 4, the first electromagnetic valve 7, the second electromagnetic valve 9, the first photometer 10, and the second photometer 11 are connected to a control device 12, and a liquid crystal display screen 13 is arranged on the control device 12.

[0052] See also Figure 2 The embodiment of the present invention further provides an in-situ automatic detection method for sludge settling ratio, using the above-mentioned in-situ automatic detection device for sludge settling ratio, comprising the following steps:

[0053] Step 1) The control device controls the first electromagnetic valve 7 to close, the second electromagnetic valve 9 to open, and the motor 4 drives the connecting shaft 3 to open the rotary gate 2, so that the mixed liquid fills the sedimentation tube 1 under the action of water pressure;

[0054] Step 2) The control device controls the motor 4 to drive the connecting shaft 3 to close the rotary gate 2, and waits for a period of time, such as 30 minutes, for the sludge to settle;

[0055] Step 3) the control device controls the second electromagnetic valve 9 to close, the first electromagnetic valve 7 to open, the motor 4 drives the connecting shaft 3 to open the rotary gate 2, and the air enters the settling tube 1 from the air source 6 to press the liquid out of the rotary gate 2; the first photometer 10 and the second photometer 11 measure the photometric signal, transmit it to the control device 12 and record it, and the control device 12 calculates the sludge settling ratio according to the jump time difference of the photometric signal measured by the first photometer 10 and the second photometer 11 and the position and distance between the first photometer 10 and the second photometer 11;

[0056] In step 3), the photometric signal changes as follows Figure 3 , 4 As shown, based on two sudden jumps in the absorbance value, the mud-water interface is distinguished, and the control device 12 calculates the falling speed of the mixed liquid level through the time difference of the photometer sudden jump and the installation height difference, and calculates the mud level to obtain the sludge settling ratio.

[0057] Step 4) After receiving the air signal measured by the second photometer 11, the control device confirms that the sedimentation tube 1 has been emptied and flushed, controls the closing of the first electromagnetic valve 7, closes the second electromagnetic valve 9, and controls the motor 4 to drive the connecting shaft 3 to close the rotating gate 2, thus completing this measurement and being ready to enter the next measurement.

[0058] In the next measurement, the control device controls the opening of the first electromagnetic valve 7, the motor 4 drives the connecting shaft 3 to open the rotary gate 2, and the mixed liquid enters the sedimentation tube under the water pressure to enter the next measurement cycle.

[0059] Preferably, in the above method, the valve opening and closing rules and the operation time are programmed in the control device 12 and interactively set through the liquid crystal display 13. The valve opening and closing rules and the operation time programming may be preset in the control device 12.

[0060] The sludge settling ratio in-situ automatic detection device of the embodiment of the present invention can be driven by the liquid level pressure to complete the mixed liquid in-situ. Since there is no pump and fine branch pipeline, the flocs will not be destroyed and the sedimentation result determination will not be affected; there is only one straight sedimentation pipe in the liquid pipeline, which has no complex structure, is not easy to be blocked, and can operate stably for a long time; after each measurement, the inside of the sedimentation pipe is alternately flushed with water and air, which is easy to clean and not easy to sludge scale; the equipment has no complex mechanical structure, is easy to maintain, and has a low cost for replacing the original parts; the control device can realize the automatic determination of the sludge settling property at a fixed time and uninterruptedly. The device has a simple structure, is easy to install, maintain, and clean, can automatically take samples, and automatically analyze the sedimentation characteristics of activated sludge, can overcome human errors, and realize the long-term stable operation of the equipment. The device can well solve the problems of the existing sludge settling property determination system with complex mechanical structure and poor operation stability; the water inlet system interferes with the flocs, and the measurement accuracy is poor; the pipeline is easy to scale and sludge, and it is inconvenient to clean.

[0061] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. An in-situ automatic detection device for sludge settling ratio, characterized in that: include: A sedimentation tube (1), a rotary gate (2), a motor (4), a connecting shaft (3), an air pipe (5), a first electromagnetic valve (7), an exhaust pipe (8), a second electromagnetic valve (9), at least two photometers and a control device (12); wherein: The rotating gate (2) is arranged at the bottom opening of the sedimentation tube (1) and can open or close the bottom opening of the sedimentation tube (1); The motor (4) is arranged at the upper end of the settling tube (1); the motor (4) is connected to the rotating gate (2) via the connecting shaft (3) and can open or close the rotating gate (2); The air pipe (5) is arranged at the top end of the sedimentation pipe (1) and is in communication with the interior of the sedimentation pipe (1). The air pipe (5) is provided with the first electromagnetic valve (7). The air pipe (5) can be connected to an external air source (6); The exhaust pipe (8) is arranged at the top end of the sedimentation pipe (1) and is in communication with the interior of the sedimentation pipe (1). The exhaust pipe (8) is provided with the second electromagnetic valve (9); Each photometer (11) is respectively arranged at different height positions on the outer side of the lower part of the sedimentation tube (1), and the light paths of two adjacent photometers are anti-parallel; The control device is electrically connected to the motor (4), the first electromagnetic valve (7), the second electromagnetic valve (9), and the photometers, respectively, and is capable of receiving signals from the photometers and controlling the actions of the motor (4), the first electromagnetic valve (7), and the second electromagnetic valve (9) according to set program instructions; The control device adopts a control device with a liquid crystal display (13); the control device (12) can calculate the mud level according to the photometric signals of each photometer (11) to obtain the sludge settling ratio, specifically: according to two sudden jumps of the photometric signals of adjacent photometers, the mud-water interface in the settling tube (1) is determined, and the falling speed of the mixed liquid level is calculated according to the time difference of the sudden jumps of adjacent photometers (11) and the height difference of the installation, and the mud level is calculated according to the falling speed of the mixed liquid level to obtain the sludge settling ratio; The settling pipe adopts a long straight pipe body; It also includes: an air source or a vacuum pump, connected to the air pipe (5).

2. A method for automatic in-situ detection of sludge settling ratio, characterized in that: The automatic in-situ detection device for sludge settling ratio according to claim 1 is used, and the opening and closing rules and operation time of the electromagnetic valve are pre-set through the control device (12) of the automatic in-situ detection device for sludge settling ratio, including the following steps: Step 1) The control device (12) controls the closing of the first electromagnetic valve (7), opens the second electromagnetic valve (9), controls the motor (4) to open the rotary gate (2) via the connecting shaft (3), and the mixed liquid fills the sedimentation tube (1) under the action of water pressure; Step 2) the control device (12) controls the motor (4) to close the rotary gate (2) via the connecting shaft (3), and allows the sludge to settle for a predetermined period of time; Step 3) The control device (12) controls the closing of the second electromagnetic valve (9) and the opening of the first electromagnetic valve (7); the motor (4) opens the rotary gate (2) through the connecting shaft (3); air enters the sedimentation tube (1) through the air pipe (5) to press the liquid in the sedimentation tube (1) out of the rotary gate (2); each photometer measures the photometric signal of the change of the liquid in the sedimentation tube (1) and sends it to the control device (12); the control device (12) calculates the mud level according to the photometric signal of each photometer to obtain the sludge settling ratio; Step 4) When the photometric signal measured by the photometer at the bottom is an air signal, the control device (12) then confirms that the sedimentation tube (1) has been emptied and flushing has been completed, controls the closing of the first electromagnetic valve (7) and the second electromagnetic valve (9), and controls the motor (4) to close the rotary gate (2) via the connecting shaft (3), thereby completing one detection.

3. The in-situ automatic detection method of sludge settling ratio according to claim 2 is characterized in that: In step 3) of the method, the control device (12) calculates the mud level according to the photometric signals of each photometer (11) to obtain the sludge settling ratio: The mud-water interface in the settling tube (1) is determined based on two sudden jumps of photometric signals of adjacent photometers, and the falling speed of the mixed liquid level is calculated based on the time difference of the sudden jumps of adjacent photometers (11) and the height difference of the installation. The mud level is calculated based on the falling speed of the mixed liquid level to obtain the sludge settling ratio.

4. The in-situ automatic detection method of sludge settling ratio according to claim 2 is characterized in that: In step 2) of the method, the predetermined standing time is: greater than or equal to 30 minutes.

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