Device and method for quickly and automatically adding concentrated sulfuric acid according to Bernoulli principle

Abstract

The invention relates to the technical field of chemical analysis, in particular to a device and a method for quickly and automatically adding concentrated sulfuric acid according to a Bernoulli principle. The rapid and automatic concentrated sulfuric acid liquid adding device comprises a storage device for containing concentrated sulfuric acid; the liquid adding device is used for conveying the concentrated sulfuric acid stored in the storage device into a target container and comprises a flow control device for monitoring and adjusting the flow of the concentrated sulfuric acid and a liquid adding assembly with adjustable height; the flow control device comprises a liquid adding pump and a flow sensor, and the liquid adding pump and the flow sensor are located on the same horizontal plane. The liquid level of the concentrated sulfuric acid in the storage device is higher than the outlet of the liquid adding assembly, so that a height difference exists between the concentrated sulfuric acid and the liquid adding assembly. According to the invention, a flow path for adding the concentrated sulfuric acid is designed through the Bernoulli equation, so that rapid and automatic liquid adding of the concentrated sulfuric acid is realized, and the efficiency and accuracy of chemical analysis such as chemical oxygen demand and soil organic matter test can be remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical analysis, and in particular to a concentrated sulfuric acid rapid automatic liquid adding device and a liquid adding method based on the Bernoulli principle. Background Art

[0002] Concentrated sulfuric acid is widely used in the field of chemical analysis, especially in the test experiments of chemical oxygen demand and soil organic matter. In the above experiments, concentrated sulfuric acid mainly plays the role of digesting organic matter in the sample, and concentrated sulfuric acid dissolution provides a high temperature and high acid environment. Accurately adding an appropriate amount of concentrated sulfuric acid is the basis for ensuring the accuracy of the test. Insufficient addition of concentrated sulfuric acid may cause incomplete digestion of organic matter in the sample to be tested, and excessive addition of concentrated sulfuric acid may interfere with other oxidant reactions. At the same time, the speed of adding concentrated sulfuric acid should not be too slow. First, it will prolong the entire digestion time and affect the detection efficiency. Second, adding concentrated sulfuric acid too slowly may cause uneven reaction temperature and incomplete digestion. At present, most laboratories use manual methods to test chemical oxygen demand and soil organic matter. Concentrated sulfuric acid is added by manual pouring, which is easy to cause it to splash everywhere. Concentrated sulfuric acid is highly corrosive and can easily cause harm to people.

[0003] In order to improve the detection efficiency, manufacturers have developed automated chemical oxygen demand and soil organic matter testers, such as a fully automatic COD analysis device disclosed in patent 201921060194.9, in which multiple flasks containing mercuric sulfate solution, potassium dichromate solution, and sulfuric acid-silver sulfate solution are connected to precision syringes through connecting tubes and reversing valves. The device uses precision syringes to simultaneously connect multiple oxidant flasks, first selects the required oxidant through the reversing valve, and then forms negative pressure through the precision syringe to lift the required reagent to the position of the liquid adding tube. However, it can be found that when the device extracts sulfuric acid-silver sulfate reagent, the viscosity of the reagent is very different from other reagents. The extraction method through negative pressure not only has low extraction efficiency, but also easily generates a large number of bubbles during the extraction process, making the amount of sulfuric acid-silver sulfate reagent added less than the set amount.

[0004] In order to overcome the problems of slow liquid addition speed and inaccurate liquid addition amount caused by concentrated sulfuric acid and other high-viscosity reagents in automatic liquid addition, patent 202123199299.2 discloses an automatic acid addition mechanism for a digestion instrument, which designs a rotating belt, and an acid addition box is fixedly connected to the surface of the belt. The concentrated sulfuric acid pre-added in the acid addition box is sequentially added to the sample to be tested through the belt transmission, and the coordination between the motor, the main turntable, the belt, the secondary turntable and the acid addition box effectively speeds up the acid addition work speed. However, this technical solution is limited by the volume of the device and the limited number of acid addition boxes, which makes it difficult to meet multi-frequency detection, and it is necessary to add concentrated sulfuric acid to the acid addition box in advance, which is also prone to errors.

[0005] The automatic liquid addition method for conventional reagents is to place the reagent kit on the operating table, and use a syringe pump, plunger pump or peristaltic pump to lift the concentrated sulfuric acid from the low-level operating table to the high-level liquid addition arm, and then add it to the reagent cup or sample cup. However, for high-viscosity fluids such as concentrated sulfuric acid, increasing the pump speed has limited effect on the flow rate. A higher pump speed not only has low pumping efficiency, but also produces bubbles in the fluid, affecting accurate liquid addition. Generally speaking, in order to improve the efficiency of pumping high-viscosity fluids such as concentrated sulfuric acid, two methods are usually used. One is to slow down the speed of the pump and keep the pump speed at a low value; the other is to reduce the viscosity of the fluid by other means besides dilution. In practice, the viscosity of viscous fluids is often reduced by preheating the fluid, but heating concentrated sulfuric acid is prone to produce harmful gases. Therefore, it is difficult to achieve rapid automatic liquid addition of concentrated sulfuric acid in precision chemical analysis using the above methods. Summary of the invention

[0006] The present invention aims to overcome the defects of low efficiency and large error in adding concentrated sulfuric acid in conventional automated chemical analysis devices in the prior art, and provides a concentrated sulfuric acid fast automatic adding device and a adding method based on the Bernoulli principle to overcome the above defects.

[0007] In order to achieve the purpose of the above invention, the present invention is implemented by the following technical solutions: A concentrated sulfuric acid fast automatic liquid adding device based on Bernoulli principle, comprising: A storage device for concentrated sulfuric acid; A liquid adding device for delivering concentrated sulfuric acid stored in the storage device to a target container, the liquid adding device comprising a flow control device for monitoring and adjusting the flow of concentrated sulfuric acid and a highly adjustable liquid adding component; The flow control device includes a liquid adding pump and a flow sensor, and the liquid adding pump and the flow sensor are located at the same horizontal plane; the liquid level of concentrated sulfuric acid inside the storage device is higher than the outlet of the liquid adding component, so that there is a height difference between the two.

[0008] The common automated analysis device on the market is to place the reagent storage device at a lower position, and then use the lifting device that extends into the storage device to lift the reagent from the low position to the high position liquid adding arm, and then use the high position liquid adding arm to perform the liquid adding operation. The reason for doing this is that when the lifting device is paused, the liquid addition can be automatically stopped, which will not cause excessive addition or overflow of the reagent; secondly, when lifting the reagent from a low position to a high position, the lifting device does not need to consider the amount of remaining reagent, which is convenient for both the simplicity of automated calculation and precision control. However, for the automated liquid addition of concentrated sulfuric acid, the pump speed of the lifting pump needs to be adjusted as slow as possible in the process from a low position to a high position to ensure a high lifting efficiency, and after one liquid addition, it is necessary to wait for a period of time, otherwise it is easy to inhale a large number of bubbles, resulting in a low amount of liquid addition. In general, it causes the time for adding concentrated sulfuric acid to be too long, especially affecting the efficiency and accuracy of chemical analysis such as chemical oxygen demand and soil organic matter testing.

[0009] Furthermore, the height difference between the liquid level of concentrated sulfuric acid inside the storage device and the outlet of the liquid adding component is calculated by the following formula: in: In the above formula, z is the height difference between the sulfuric acid liquid surface and the outlet of the liquid adding component, and u is the flow rate of concentrated sulfuric acid, which can be calculated by the predetermined flow rate V s The cross-sectional area A at the outlet of the liquid adding component s Determine,∑h f is the head loss along the concentrated sulfuric acid, W e is the power of the liquid adding pump, λ is the friction coefficient of concentrated sulfuric acid in the tube, d is the inner diameter of the flow path between the sulfuric acid liquid surface and the outlet of the liquid adding component, and l is the length of the flow path from the sulfuric acid liquid surface to the outlet of the liquid adding component.

[0010] Only directly changing the liquid adding process of concentrated sulfuric acid from high position to bottom position, the practical effect is equally poor. First, unlike common viscous fluid transportation, the effect of viscous fluid shear force on flow velocity can be reduced by expanding the pipe diameter. In the analytical experiments such as chemical oxygen demand and soil organic matter test, the single concentrated sulfuric acid addition is small and has high accuracy requirements, so the liquid adding pipe diameter is preferably designed to be below 2mm, and concentrated sulfuric acid is prone to embolism in a capillary at this time. And, at this time, the liquid adding pump power is improved, and too many bubbles are easily sucked, and cavitation occurs. Therefore, the present invention realizes the fast and accurate liquid adding of concentrated sulfuric acid by limiting the height difference between the devices, and the pipeline design. By setting the height difference between the concentrated sulfuric acid liquid level and the liquid outlet when the concentrated sulfuric acid is stably flowing in advance, then by the liquid adding port that can be lifted and lowered, the stability of the height difference in the liquid adding process is kept at all times, so that the liquid adding of the concentrated sulfuric acid is stable when the liquid adding pump power is fixed. And by fixing the dosing pump and the flow sensor at the same horizontal plane, a stable laminar flow area can be provided during the descent of concentrated sulfuric acid. The dosing pump and the flow sensor are successively arranged in this area to improve the accuracy of flow monitoring as much as possible, and the local head loss can be ignored as much as possible in the formula calculation, so that the calculation of the height difference is more accurate, and finally the stability of concentrated sulfuric acid transportation can be achieved at a flow rate of more than 4 ml / s.

[0011] Preferably, the storage device comprises a test kit for storing concentrated sulfuric acid, and a clamping device for fixing the test kit. During the addition of concentrated sulfuric acid, the operation of the liquid adding pump will cause vibration to the entire device, and the shaking of the storage device will affect the stability of the entire flow path and affect the accurate addition of liquid. Therefore, in practice, at least two clamping devices are provided to fix the upper end and the lower end of the storage device respectively, and due to the high corrosiveness of concentrated sulfuric acid, the replacement of the storage device is also facilitated by the clamping device.

[0012] As a further preferred embodiment, the reagent box is provided with a replenishing port and a liquid outlet. The replenishing port is provided on the top of the reagent box, which is convenient for maintaining the stability of the concentrated sulfuric acid liquid surface pressure in the device and for replenishing concentrated sulfuric acid when the flow sensor detects that the concentrated sulfuric acid is insufficient. The liquid outlet can be provided with an external thread.

[0013] As a further preferred embodiment, the storage device further comprises a liquid outlet valve disposed at the lower end of the liquid outlet. When it is necessary to stop adding concentrated sulfuric acid, after the liquid adding pump is stopped, a small amount of concentrated sulfuric acid will still flow out from the liquid adding pipe due to gravity. Therefore, the liquid outlet valve can be connected to an automatic control system. When the liquid addition is stopped, the liquid outlet valve is closed to prevent the additional concentrated sulfuric acid from flowing out under the action of atmospheric pressure. The liquid outlet valve can be a two-way valve, and the valve body is preferably made of polytetrafluoroethylene.

[0014] As a further preferred embodiment, the storage device further comprises an adapter connecting the liquid outlet and the liquid outlet valve. Since the concentrated sulfuric acid in the device has a relatively fast flow rate, in order to ensure the safety of the experiment, a larger adapter can be installed between the liquid outlet and the liquid outlet valve. The adapter is preferably made of polytetrafluoroethylene, with an internal thread interface at one end and an external thread interface at the other end; the external thread interface is screwed together with the liquid inlet of the liquid outlet valve.

[0015] As a further preference, the replenishing port is in a cone shape that is larger at the top and smaller at the bottom, and a detachable dust cover is provided at the upper end of the replenishing port, and a ventilation hole is provided on the dust cover.

[0016] Furthermore, the liquid adding assembly includes a liquid adding pipe and a liquid adding arm which fixes the liquid adding pipe and can move in a vertical direction.

[0017] In another aspect, the present invention discloses a method for rapid automatic liquid addition of concentrated sulfuric acid based on the Bernoulli principle, comprising the following steps: S1. According to the predetermined flow rate, the height difference between the liquid level of concentrated sulfuric acid and the outlet of the liquid adding component is determined by the above formula; S2, installing the storage device and the liquid adding assembly so that the outlet of the liquid adding assembly and the concentrated sulfuric acid liquid level inside the storage device reach the target height difference; S3, the liquid adding pump transports the concentrated sulfuric acid to the outlet of the liquid adding assembly. During the liquid adding process, the height difference between the liquid level of the concentrated sulfuric acid and the outlet of the liquid adding assembly is maintained through the height-adjustable liquid adding assembly.

[0018] Furthermore, in the above step S3, when the liquid adding component descends to the set lowest point and the flow sensor does not detect that the flow rate has been restored to the set flow rate, a signal is fed back to the storage device to replenish the concentrated sulfuric acid.

[0019] Therefore, the present invention has the following beneficial effects: (1) The present invention effectively reduces the influence of the concentrated sulfuric acid concentration on the liquid addition speed by redesigning the concentrated sulfuric acid flow path. Under the premise of ensuring the pumping efficiency, the pumping speed of the concentrated sulfuric acid is increased, thereby achieving rapid liquid addition of concentrated sulfuric acid and improving the detection efficiency. (2) The present invention can not only realize stable automatic transportation of concentrated sulfuric acid by limiting the height difference between the concentrated sulfuric acid liquid surface and the liquid outlet, but also determine the change of the height difference through the flow change detected by the flow sensor, thereby realizing dynamic automatic adjustment of the device. (3) The present invention achieves stable flow during the addition of concentrated sulfuric acid through the design of the flow path, effectively avoiding the inhalation of bubbles by the addition device, and improving the accuracy of chemical analysis such as chemical oxygen demand and soil organic matter testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1The present invention is a schematic diagram of the installation of a concentrated sulfuric acid fast automatic liquid adding device based on the Bernoulli principle.

[0021] Figure 2 This is a schematic diagram of a storage device in a concentrated sulfuric acid fast automatic liquid adding device based on the Bernoulli principle shown in Example 1 of the present invention.

[0022] Figure 3 This is a connection diagram of a flow control device in a concentrated sulfuric acid fast automatic liquid adding device based on the Bernoulli principle shown in Example 1 of the present invention.

[0023] Figure 4 This is a schematic diagram of a liquid adding component in a concentrated sulfuric acid fast automatic liquid adding device based on the Bernoulli principle shown in Example 1 of the present invention.

[0024] Figure 5 This is a schematic diagram of a reagent box in a concentrated sulfuric acid rapid automatic liquid adding device based on the Bernoulli principle shown in Example 2 of the present invention.

[0025] In the figure: a storage device 1; a reagent kit 2; a clamping device 3; a replenishing port 4; a liquid outlet 5; an adapter 6; a liquid outlet valve 7; a liquid adding device 10; a flow control device 11; a liquid adding component 12; a liquid adding pump 13; a flow sensor 14; a liquid adding tube 15; and a liquid adding arm 16. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all of the embodiments. Therefore, based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work should fall within the scope of protection of the present invention. It should be noted that the words "front", "back", "left", "right", "up" and "down" used in the above description refer to the directions in the accompanying drawings, and the words "inside" and "outside" refer to the directions toward or away from the geometric center of a specific component, respectively.

[0027] Embodiment 1: like Figure 1-4As shown, this embodiment includes a storage device 1 for containing concentrated sulfuric acid, the main body of the storage device is a reagent box 2 specially used for containing concentrated sulfuric acid, the upper end of the reagent box 2 is a conical replenishing port 4, the upper end of the replenishing port 4 is detachably provided with a dust cover, the dust cover is provided with a plurality of air holes, the lower end of the reagent box 2 is a liquid outlet 5, which is connected to a liquid outlet valve 7 through an adapter 6, the liquid outlet valve 7 is a two-way valve, and the other end is connected to a flow control device 11 through a pipeline, the flow control device 11 is composed of a liquid adding pump 13 and a flow sensor 14, the flow control device 11 is generally horizontal with the pipelines at both ends, the end of the flow sensor 14 is connected to a liquid adding pipe 15, the inner diameter of the liquid adding pipe is 1.6 mm, the liquid adding pipe 15 is installed on a liquid adding arm 16 that can rotate freely and can be raised and lowered, and the friction coefficient of concentrated sulfuric acid in the overall selected pipeline is 0.025.

[0028] The usage process of this embodiment is as follows: The output flow rate of concentrated sulfuric acid is preset to be 240 ml / min, the power of the liquid adding pump 13 is 20 w, the flow path length from the sulfuric acid liquid surface to the outlet of the liquid adding pipe 15 is 0.73 m, and the resistance of the pipe joint is negligible. Substitute the above data into the height difference equation: The height difference Z from the sulfuric acid liquid level to the outlet of the liquid adding pipe 15 is calculated to be 0.49m. The storage device 1 equipped with concentrated sulfuric acid is set at a high position, and each component is connected. The outlet height of the liquid adding pipe 15 is adjusted to meet the height difference with the liquid level. The target container is placed below the liquid adding pipe 15, and the liquid addition is turned on. During the liquid addition process, the flow control device 11 monitors the flow state at all times to ensure that the flow is constant. When the flow sensor 14 detects that the flow rate drops, the liquid adding arm 16 controls the liquid adding pipe 15 to drop, so that the flow rate returns to the predetermined value. When the liquid adding arm 16 continues to drop, and the flow rate does not return to the predetermined value, it indicates that there is insufficient concentrated sulfuric acid in the test kit 2. At this time, the flow sensor 14 feeds back the signal to the storage device or other reminder devices.

[0029] Embodiment 2: like Figure 1 , 5As shown, this embodiment includes a storage device 1 for containing concentrated sulfuric acid, the main body of the storage device is a reagent box 2 specially used for containing concentrated sulfuric acid, the reagent box 2 is a prefabricated component, and the whole is made of polytetrafluoro material, the upper end of the reagent box 2 is a conical replenishing port 4, the upper end of the replenishing port 4 is detachably provided with a dust cover, and the dust cover is provided with a plurality of air holes, the lower end of the reagent box 2 is a liquid outlet 5, the lower end liquid outlet 5 is provided with an external thread, and is connected to the liquid outlet valve 7 through an adapter 6, and the adapter 6 is an internal thread. The liquid outlet valve 7 is a two-way valve, one end of which is connected to the adapter 6 with an external thread, and the other end is connected to the flow control device 11 through a pipeline. The flow control device 11 is composed of a liquid adding pump 13 and a flow sensor 14. The flow control device 11 is horizontal with the pipelines at both ends as a whole. The end of the flow sensor 14 is connected to a liquid adding pipe 15 with an inner diameter of 1.8 mm. The liquid adding pipe 15 is installed on a liquid adding arm 16 that can rotate freely and can be raised and lowered. The friction coefficient of concentrated sulfuric acid in the overall selected pipeline is 0.025.

[0030] The usage process of this embodiment is as follows: The outlet flow rate of concentrated sulfuric acid is preset to be 270 ml / min, the power of the liquid adding pump 13 is 15 w, the flow path length from the sulfuric acid liquid surface to the outlet of the liquid adding pipe 15 is 0.73 m, and the resistance of the pipe joint is negligible. Substitute the above data into the height difference equation: The height difference between the sulfuric acid liquid level and the outlet of the liquid adding pipe 15 is calculated to be 0.25m. The storage device 1 containing concentrated sulfuric acid is set at a high position, and each component is connected. The outlet height of the liquid adding pipe 15 is adjusted to meet the height difference with the liquid level. The target container is placed under the liquid adding pipe 15, and the liquid addition is turned on. During the liquid addition process, the flow control device 11 monitors the flow state at all times to ensure that the flow is constant. When the flow sensor 14 detects that the flow rate drops, the liquid adding arm 16 controls the liquid adding pipe 15 to drop, so that the flow rate returns to the predetermined value. When the liquid adding arm 16 continues to drop, and the flow rate does not return to the predetermined value, it indicates that there is insufficient concentrated sulfuric acid in the test kit 2. At this time, the flow sensor 14 feeds back the signal to the storage device or other reminder devices.

[0031] The above embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the scope of protection of the claims of the present invention.

Claims

1. A concentrated sulfuric acid rapid automatic liquid adding device based on Bernoulli's principle, comprising: A storage device (1) for containing concentrated sulfuric acid; A liquid adding device (10) for conveying concentrated sulfuric acid in a storage device (1) to a target container, the liquid adding device (10) comprising a flow control device (11) for monitoring and adjusting the flow of concentrated sulfuric acid and a height-adjustable liquid adding component (12); the flow control device (11) comprises a liquid adding pump (13) and a flow sensor (14), the liquid adding pump (13) and the flow sensor (14) being located on the same horizontal plane; The liquid level of concentrated sulfuric acid inside the storage device (1) is higher than the outlet of the liquid adding component (12), so that there is a height difference between the two.

2. A concentrated sulfuric acid fast automatic liquid adding device based on Bernoulli's principle according to claim 1, characterized in that: The height difference is calculated by the following formula: in: In the above formula, z is the height difference between the sulfuric acid liquid surface and the outlet of the liquid adding component (12), and u is the flow rate of concentrated sulfuric acid, which can be determined by the predetermined flow rate V s The cross-sectional area A at the outlet of the liquid adding component (12) s Determine,∑h f is the head loss along the concentrated sulfuric acid, W e is the power of the liquid adding pump, λ is the friction coefficient of concentrated sulfuric acid in the tube, d is the inner diameter of the flow path between the sulfuric acid liquid surface and the outlet of the liquid adding component (12), and l is the length of the flow path from the sulfuric acid liquid surface to the outlet of the liquid adding component (12).

3. A concentrated sulfuric acid fast automatic liquid adding device based on Bernoulli's principle according to claim 1, characterized in that: The storage device (1) comprises a reagent box (2) for storing concentrated sulfuric acid and a clamping device (3) for fixing the reagent box (2).

4. A concentrated sulfuric acid fast automatic liquid adding device based on Bernoulli's principle according to claim 3, characterized in that: The reagent box (2) is provided with a replenishing port (4) at the top and a liquid outlet (5) at the bottom.

5. A concentrated sulfuric acid fast automatic liquid adding device based on Bernoulli's principle according to claim 4, characterized in that: The storage device (1) further comprises a liquid outlet valve (7) arranged at the lower end of the liquid outlet (5).

6. A concentrated sulfuric acid fast automatic liquid adding device based on Bernoulli principle according to claim 5, characterized in that: The storage device (1) further comprises an adapter (6) connecting the liquid outlet (5) and the liquid outlet valve (7).

7. A concentrated sulfuric acid fast automatic liquid adding device based on Bernoulli principle according to claim 4, characterized in that: The replenishing port (4) is in the shape of a cone that is larger at the top and smaller at the bottom, and a detachable dust cover is provided at the upper end of the replenishing port (4), and a vent hole is provided on the dust cover.

8. The concentrated sulfuric acid fast automatic liquid adding device based on Bernoulli principle according to claim 1, characterized in that: The liquid adding assembly (12) comprises a liquid adding pipe (15) and a liquid adding arm (16) which fixes the liquid adding pipe (15) and can move in a vertical direction.

9. A method for rapid automatic liquid addition of concentrated sulfuric acid based on the Bernoulli principle, which is based on the rapid automatic liquid addition device for concentrated sulfuric acid according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Determine the height difference between the liquid level of concentrated sulfuric acid and the outlet of the liquid adding component (12) according to a predetermined flow rate; S2, installing the storage device (1) and the liquid adding assembly (12) so that the outlet of the liquid adding assembly (12) and the concentrated sulfuric acid liquid level inside the storage device (1) reach a target height difference; S3, the liquid adding pump (13) transports the concentrated sulfuric acid to the outlet of the liquid adding assembly (12). During the liquid adding process, the height difference between the liquid level of the concentrated sulfuric acid and the outlet of the liquid adding assembly (12) is maintained through the height-adjustable liquid adding assembly (12).

10. A method for rapid automatic liquid addition of concentrated sulfuric acid based on Bernoulli's principle according to claim 9, characterized in that: In step S3, when the liquid adding component (12) drops to the set lowest point and the flow sensor (14) does not detect that the flow rate has returned to the set flow rate, a signal is fed back to the storage device (1) to replenish concentrated sulfuric acid.

Images