A low nitrogen emission submerged combustion gasifier system

Abstract

The present invention relates to a low-nitrogen emission submerged combustion gasifier system, belonging to the technical fields of liquefied natural gas gasification and environmental protection. A burner system is designed in which the primary and secondary intake air are rotated in advance by a baffle, a uniform vortex is formed by the main swirl blades and the secondary guide vanes, a water spray device is added to increase the moisture concentration in the flame zone, a blending system and a hydrogen production system are utilized, and hydrogen-blended natural gas is used as fuel, thereby effectively reducing NOx and CO emissions.

Description

Technical Field

[0001] The invention relates to a low-nitrogen emission submerged combustion gasifier system, belonging to the technical fields of liquefied natural gas gasification and environmental protection. Background Art

[0002] Demand for natural gas, a fossil fuel with a lower environmental impact, is growing globally. Countries with limited natural gas resources, including China, rely heavily on imports via pipelines or LNG tankers, essentially relying on imports to meet their gas consumption gap. By 2025, global demand for liquefied natural gas (LNG) trade is projected to double due to rising demand in developing countries.

[0003] The submerged combustion gasifier can gasify LNG into natural gas (NG). The flue gas produced during the combustion process contains air pollutants, including nitric oxide and nitrogen dioxide, commonly known as nitrogen oxides (NO x ), the submerged combustion gasifier has a special operating environment as a burner and cannot easily control NO x and CO emissions.

[0004] In order to solve the above problems, the present invention installs a water spray device in the burner, designs a vortex structure and uses hydrogen-mixed natural gas as fuel to reduce NO x and CO production. Summary of the Invention

[0005] The purpose of the present invention is to provide a low nitrogen emission submerged combustion gasifier system, thereby reducing the NO x Based on the design of baffles, partitions, main swirl blades and secondary guide blades, the burner with mixed hydrogen and natural gas as fuel and equipped with a water spray device can achieve NO x and low CO emissions.

[0006] The present invention mainly solves the following problems:

[0007] (1) Design a water spray device. The water droplets in the jet flow evaporate quickly on the vaporization plane close to the diffusion flame. The evaporation of water in the spray helps to increase the water concentration in the flame zone. Adding a water spray device can effectively reduce NO x and CO emissions.

[0008] (2) Using a blending system and a hydrogen production system, using hydrogen-mixed natural gas as fuel, changing the fuel composition to reduce NO x and CO emissions.

[0009] (3) The baffle is designed to make the primary and secondary air intakes form swirls in advance.

[0010] (4) The main swirl blades and secondary guide blades are designed to form a uniform vortex. The vortex structure weakens the airflow, stabilizes the local excess air ratio, forms an exhaust gas recirculation area, and promotes mild combustion.

[0011] In order to achieve the above objectives, the technical solutions of the present invention are as follows.

[0012] A low nitrogen emission submerged combustion gasification system is characterized by comprising a burner system 20 and a blending system 24;

[0013] Furthermore, the burner system 20 includes a diverter valve 201, a water spray nozzle 202, a baffle 203, a primary swirl vane 204, a secondary guide vane 205, a fuel nozzle 206, a fuel pipeline 207, a fuel tank 208, a water pipeline 209, a baffle 210, an inner cylinder 211 and an outer cylinder 212;

[0014] The diverter valve 201 is placed at the center of the inlet of the burner system 20 and can be shaken up and down to control the primary and secondary air intake volumes; the water nozzle 202 is located at the bottom of the water supply pipe 209, with a spray speed of 20L / h, spraying water downward; the baffle 203 is horizontally arranged in the middle of the burner system 20 and surrounds the outside of the inner cylinder 211 to isolate the primary and secondary air intakes, the main swirl blades 204 are located at the bottom of the inner cylinder 211 and above the secondary guide blades 205, the fuel nozzles 206 are located at the bottom of the fuel tank 208 and are evenly distributed, the fuel pipe 207 is connected to the middle position of the fuel tank 208, the water supply pipe 209 runs through the fuel tank 208, the baffle 210 is vertically placed on the outside of the inner cylinder 211 and intersects vertically with the baffle 203. By arranging the baffle 210, the primary and secondary air rotate in advance and form a uniform vortex through the main swirl blades 204 and the secondary guide blades 205.

[0015] Furthermore, the blending system 24 includes a temperature, pressure and flow sensor A241 and a temperature, pressure and flow sensor B242, an adjustment control device A243, an adjustment control device B244, a PLC control system 245, a mixing system 246, a static mixer 247, a rectifier 248, and a delivery pipeline 249;

[0016] The static mixer 247 adopts SK type static mixers 701, the number of which is 3, the rotation angle is 120 degrees, and they are arranged continuously; the rectifier 248 is composed of small regular hexagonal thin tubes 801.

[0017] Furthermore, the water spray nozzle 202 is an atomizing nozzle.

[0018] Furthermore, the main swirl blades 204 have a total of 16 main swirl blades with an inclination angle of 45°.

[0019] Furthermore, the secondary guide blades 205 have a total of 18 secondary guide blades with an inclination angle of 45°.

[0020] Furthermore, the fuel nozzles 206 include fuel nozzle A901, fuel nozzle B902, fuel nozzle C903, fuel nozzle D904, fuel nozzle E905, and fuel nozzle F906;

[0021] The fuel nozzle A901, fuel nozzle B902, fuel nozzle C903, fuel nozzle D904, fuel nozzle E905, and fuel nozzle F906 are all burner nozzles;

[0022] Furthermore, the fuel pipeline 207 includes a fuel pipeline A907 , a fuel pipeline B908 , a fuel pipeline C909 , a fuel pipeline D910 , an annular pipe 911 , and a fuel intake manifold 912 .

[0023] A low nitrogen emission submerged combustion gasification system comprises the following steps:

[0024] S1: The burner system 20 is connected to the axial flow fan 11. The axial flow fan 11 supplies air to the inlet of the burner system 20. The primary and secondary air intakes are distributed through the diverter valve 201. The primary and secondary air intakes are rotated in advance by the arrangement of the baffle 210. The air inflow temperature is determined by the compression effect of the axial flow fan 11.

[0025] S2: The water spray nozzle 202 is located at the bottom of the water delivery pipe 209 and sprays water downward at a spray rate of 20L / h. The hydrogen-blended natural gas is transported to the fuel tank 208 through the fuel inlet manifold 912, the annular pipe 911, the fuel pipe A907, the fuel pipe B908, the fuel pipe C909, and the fuel pipe D910. The fuel is then sprayed out from the fuel nozzles A901, B902, C903, D904, E905, and F906 at the bottom of the fuel tank 208 at a spray rate of 10m 3 / h, the primary intake air flows downward and mixes with the sprayed fuel and the water mist sprayed from the water nozzle 202, and forms a uniform vortex through the main swirl blades 204. The secondary intake air is rectified by the secondary guide blades 205 and then sent into the furnace 13;

[0026] S3: The hydrogen production system 25 produces H2 and part of the NG at the outlet of the submerged combustion gasifier is transported to the mixing system 24. The temperature, pressure and flow sensor A241 and the temperature, pressure and flow sensor B242 collect signals and send them to the PLC control system 245. The regulating control device A243 and the regulating control device B244 adjust the opening degree. The mixed gas is evenly mixed under the action of the static mixer 247 and the rectifier 248, and is transported to the fuel intake manifold 912. After the S2 step, it is burned in the furnace 13. The center of the furnace 13 presents a negative pressure due to the swirling flow, forming an upward countercurrent area. The burned gas dilutes the unburned fuel and air and promotes mild combustion, suppressing NO x The production of

[0027] S4: Flue gas from the furnace 13 is discharged through the circular holes in the flue gas distribution pipe 14. The gas-liquid two-phase flow surges upward and sweeps across the initially semi-submerged horizontally arranged serpentine heat exchange cluster 17, completely immersing it. The LNG in the heat exchange cluster is heated and vaporized. After heat, mass, and kinetic energy are transferred between the flue gas and water, they overflow and separate above the overflow weir 16. The water falls back into the water bath header 15 due to gravity, forming a reflux, while the flue gas is discharged through the upper exhaust pipe 19.

[0028] S5: The circulating water pump 12 supplies cold water from the bottom of the water bath header 15 to the water jacket 21 to cool the furnace wall that is not immersed in the water bath. Since the cooling water in the water jacket 21 flows at a high speed, it can take away a large amount of heat and also cool the furnace 13;

[0029] S6: Set up the pH meter 22. When it is found that the pH value in the water bath header is low, the alkali solution storage tank 18 needs to be opened to adjust the pH value in the water bath header.

[0030] The beneficial effects of the invention are:

[0031] (1) Design a water spray device. The water droplets in the jet flow evaporate quickly on the vaporization plane close to the diffusion flame. The evaporation of water in the spray helps to increase the water concentration in the flame zone. Adding a water spray device can effectively reduce NO x and CO emissions.

[0032] (2) Using a blending system and a hydrogen production system, using hydrogen-mixed natural gas as fuel, changing the fuel composition to reduce NO x and CO emissions.

[0033] (3) The baffle is designed to make the primary and secondary air intakes form swirls in advance.

[0034] (4) The main swirl blades and secondary guide blades are designed to form a uniform vortex. The vortex structure weakens the airflow, stabilizes the local excess air ratio, forms an exhaust gas recirculation area, and promotes mild combustion. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the structure of the submerged combustion gasification system in an embodiment of the present invention.

[0036] Figure 2 It is a schematic structural diagram of a burner of a submerged combustion gasification system in an embodiment of the present invention.

[0037] Figure 3 It is a front view of the internal structure of the burner of the submerged combustion gasification system in an embodiment of the present invention.

[0038] Figure 4 It is a bottom view of the internal structure of the burner of the submerged combustion gasification system in an embodiment of the present invention.

[0039] Figure 5 Schematic diagram of the nozzle and fuel pipe in an embodiment of the present invention.

[0040] Figure 6 Schematic diagram of a hydrogen doping system in an embodiment of the present invention.

[0041] Figure 7 Schematic diagram of an SK type static mixer in an embodiment of the present invention.

[0042] Figure 8 Schematic diagram of a rectifier in an embodiment of the present invention.

[0043] Figure 9 Schematic diagram of a hydrogen production system in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] The specific embodiments of the present invention are described below in conjunction with the accompanying drawings to facilitate a better understanding of the present invention.

[0045] Example

[0046] In this embodiment, Figure 1 Schematic diagram of the submerged combustion gasification system structure. The submerged combustion gasification system includes an axial flow fan 11, a circulating water pump 12, a furnace 13, a flue gas distribution pipe 14, a water bath header 15, an overflow weir 16, a heat exchange bundle 17, an alkali liquid storage tank 18, an exhaust pipe 19, a burner system 20, a water jacket 21, a pH meter 22, a thermometer 23, a mixing system 24, a hydrogen production system 25, a water pump 26, and a water tank 27.

[0047] The axial flow fan 11 is connected to the air inlet of the burner, the circulating water pump 12 connects the bottom of the water bath header 15 to the water jacket 21 of the burner, the flue gas distribution pipe 14 is connected to the burner system 20 and is located on the right side of the burner system 20, the ratio between the initial water level height of the water bath header 15 and the height of the overflow weir 16 is between 0.6 and 0.8, the heat exchange cluster 17 is located above the flue gas distribution pipe 14 and between the overflow weir 16, the heat exchange cluster 17 is a serpentine heat exchange cluster, the alkali solution storage tank 18 is located Outside the gasifier, it is connected to the water bath header through a pipeline; the smoke exhaust pipe 19 is located in the middle of the top of the gasifier, the burner system 20 is connected to the axial flow fan 11 and the flue gas distribution pipe 14, and is placed on the left side of the box, the water jacket 21 is located outside the furnace 13, the pH meter 22 and the thermometer 23 are both located in the lower right corner of the water bath header 15, the mixing system 24 is connected to the hydrogen production system 25, the burner system 20 and the NG outlet of the submerged combustion gasifier, and the water pool 27 provides a water source for the burner system 20.

[0048] Figure 2 This is a schematic diagram of the burner structure of the submerged combustion gasification system. Figure 3 This is a front view of the internal structure of the submerged combustion gasification system burner in the embodiment of the present invention. Figure 4 2 is a bottom view of the internal structure of a submerged combustion gasification system burner according to an embodiment of the present invention. The submerged combustion gasification system burner includes a diverter valve 201, a water spray nozzle 202, a baffle 203, a primary swirl vane 204, a secondary guide vane 205, a fuel nozzle 206, a fuel pipeline 207, a fuel tank 208, a water pipeline 209, a baffle 210, an inner cylinder 211, and an outer cylinder 212.

[0049] The diverter valve 201 is placed at the center of the inlet of the burner system 20 and can be adjusted up and down to control the primary and secondary air intake volumes; the water nozzle 202 is located at the bottom of the water supply pipe 209, with a spray speed of 20L / h, spraying water downward, and the water nozzle 202 is an atomizing nozzle; the baffle 203 is horizontally arranged in the middle of the burner system 20 and surrounds the outside of the inner cylinder 211 to isolate the primary and secondary air intakes, the main swirl blades 204 are located at the bottom of the inner cylinder 211 and above the secondary guide blades 205, the fuel nozzles 206 are located at the bottom of the fuel tank 208 and are evenly distributed, the fuel pipe 207 is connected to the middle position of the fuel tank 208, the water supply pipe 209 runs through the fuel tank 208, the baffle 210 is vertically placed on the outside of the inner cylinder 211 and intersects perpendicularly with the baffle 203. By arranging the baffle 210, the primary and secondary air rotate in advance and form a uniform vortex through the main swirl blades 204 and the secondary guide blades 205.

[0050] Figure 5Schematic diagram of the nozzles and fuel pipes, including fuel nozzle A901, fuel nozzle B902, fuel nozzle C903, fuel nozzle D904, fuel nozzle E905, fuel nozzle F906, fuel pipeline A907, fuel pipeline B908, fuel pipeline C909, fuel pipeline D910, annular pipe 911, and fuel intake manifold 912;

[0051] The fuel nozzle A901, fuel nozzle B902, fuel nozzle C903, fuel nozzle D904, fuel nozzle E905, and fuel nozzle F906 all use burner nozzles; the fuel enters the annular pipe 911 from the fuel intake manifold 912 and then enters the fuel tank 208 through the fuel pipe A907, fuel pipe B908, fuel pipe C909, and fuel pipe D910, and then is sprayed out through the fuel nozzle A901, fuel nozzle B902, fuel nozzle C903, and fuel nozzle D904.

[0052] Figure 6 This is a schematic diagram of the hydrogen doping system. Figure 7 This is a schematic diagram of an SK type static mixer. Figure 8 Schematic diagram of a rectifier. The hydrogen blending system includes temperature, pressure and flow sensors A241 and B242, a regulating control device A243, a regulating control device B244, a PLC control system 245, a mixing system 246, a static mixer 247, a rectifier 248, and a delivery pipeline 249.

[0053] The PLC control system 245 is connected to the temperature, pressure and flow sensor A241 and the temperature, pressure and flow sensor B242, the regulating control device A243, and the regulating control device B244. The mixing system 246 is connected to the regulating control device A243, the regulating control device B244 and the conveying pipeline 249. The PLC control system 245 receives signal input from the temperature, pressure and flow sensor B242, the regulating control device A243, and the regulating control device B244, and controls the regulating control device A243 and the regulating control device B244. The static mixer 247 adopts SK type static mixer 701, the number of which is 3, the rotation angle is 120°, and they are arranged continuously. The rectifier 248 is composed of small regular hexagonal thin tubes 801. The mixed gas is evenly mixed after passing through the static mixer 247 and the rectifier 248.

[0054] Figure 9 is a schematic diagram of a hydrogen production system, which includes seawater electrolysis 251, seawater photocatalysis 252, photoelectrochemical seawater decomposition 253, and a hydrogen storage system 254;

[0055] The three hydrogen production methods of electrolysis of seawater 251, photocatalytic seawater 252, and photoelectrochemical seawater decomposition 253 should be selected according to local conditions to complete hydrogen production by one or more methods, and the hydrogen storage system 254 can complete the storage of the produced hydrogen.

[0056] A low nitrogen emission submerged combustion gasifier system comprises the following steps:

[0057] S1: The burner system 20 is connected to the axial flow fan 11. The axial flow fan 11 supplies air to the inlet of the burner system 20. The primary and secondary air intakes are distributed through the diverter valve 201. The primary and secondary air intakes are rotated in advance by the arrangement of the baffle 210. The air inflow temperature is determined by the compression effect of the axial flow fan 11.

[0058] S2: The water spray nozzle 202 is located at the bottom of the water delivery pipe 209 and sprays water downward at a spray rate of 20L / h. The hydrogen-blended natural gas is transported to the fuel tank 208 through the fuel inlet manifold 912, the annular pipe 911, the fuel pipe A907, the fuel pipe B908, the fuel pipe C909, and the fuel pipe D910. The fuel is then sprayed out from the fuel nozzles A901, B902, C903, D904, E905, and F906 at the bottom of the fuel tank 208 at a spray rate of 10m 3 / h, the primary intake air flows downward and mixes with the sprayed fuel and the water mist sprayed from the water nozzle 202, and forms a uniform vortex through the main swirl blades 204. The secondary intake air is rectified by the secondary guide blades 205 and then sent into the furnace 13;

[0059] S3: The hydrogen production system 25 produces H2 and part of the NG at the outlet of the submerged combustion gasifier is transported to the mixing system 24. The temperature, pressure and flow sensor A241 and the temperature, pressure and flow sensor B242 collect signals and send them to the PLC control system 245. The regulating control device A243 and the regulating control device B244 adjust the opening degree. The mixed gas is evenly mixed under the action of the static mixer 247 and the rectifier 248, and is transported to the fuel intake manifold 912. After the S2 step, it is burned in the furnace 13. The center of the furnace 13 presents a negative pressure due to the swirling flow, forming an upward countercurrent area. The burned gas dilutes the unburned fuel and air and promotes mild combustion, suppressing NO x The production of

[0060] S4: Flue gas from the furnace 13 is discharged through the circular holes in the flue gas distribution pipe 14. The gas-liquid two-phase flow surges upward and sweeps across the initially semi-submerged horizontally arranged serpentine heat exchange cluster 17, completely immersing it. The LNG in the heat exchange cluster is heated and vaporized. After heat, mass, and kinetic energy are transferred between the flue gas and water, they overflow and separate above the overflow weir 16. The water falls back into the water bath header 15 due to gravity, forming a reflux, while the flue gas is discharged through the upper exhaust pipe 19.

[0061] S5: The circulating water pump 12 supplies cold water from the bottom of the water bath header 15 to the water jacket 21 to cool the furnace wall that is not immersed in the water bath. Since the cooling water in the water jacket 21 flows at a high speed, it can take away a large amount of heat and also cool the furnace 13;

[0062] S6: Set up the pH meter 22. When it is found that the pH value in the water bath header is low, the alkali solution storage tank 18 needs to be opened to adjust the pH value in the water bath header.

[0063] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A low nitrogen emission submerged combustion gasifier system, characterized by: Burner system (20), mixing system (24); The burner system (20) comprises: a diverter valve (201), a water spray nozzle (202), a partition (203), a primary swirl blade (204), a secondary guide vane (205), a fuel nozzle (206), a fuel pipeline (207), a fuel tank (208), a water pipeline (209), a baffle (210), an inner cylinder (211), and an outer cylinder (212); The mixing system (24) includes: a temperature, pressure and flow sensor A (241) and a temperature, pressure and flow sensor B (242), an adjustment control device A (243), an adjustment control device B (244), a PLC control system (245), a mixing system (246), a static mixer (247), a rectifier (248), and a conveying pipeline (249); the static mixers (247) are SK-type static mixers (701), three in number, with a rotation angle of 120°, and arranged in series; the rectifier (248) is composed of a combination of small regular hexagonal thin tubes (801); The diverter valve (201) is placed at the center of the burner system (20) inlet and can be adjusted up and down to control the primary and secondary air intake volumes; The water spray nozzle (202) is located at the bottom of the water supply pipe (209), has a spray speed of 20L / h, and sprays water downward. The baffle (203) is horizontally arranged in the middle of the burner system (20) and surrounds the outside of the inner cylinder (211) to isolate the primary and secondary air intakes. The main swirl blades (204) are located at the bottom of the inner cylinder (211) and above the secondary guide blades (205). The fuel nozzles (206) are located at the bottom of the fuel tank (208) and are evenly distributed. The fuel pipe (207) is connected to the middle position of the fuel tank (208). The water supply pipe (209) runs through the fuel tank (208). The baffle (210) is vertically placed outside the inner cylinder (211) and vertically intersects with the baffle (203). By arranging the baffle (210), the primary and secondary air intakes rotate in advance and form a uniform vortex through the main swirl blades (204) and the secondary guide blades (205).

2. The low nitrogen emission submerged combustion gasifier system according to claim 1, characterized in that: The main swirl blades (204) and the secondary guide blades (205) include: 16 main swirl blades with an inclination angle of 45 degrees, and 18 secondary guide blades with an inclination angle of 45 degrees; the water spray nozzle (202) is an atomizing nozzle; The fuel nozzle (206) includes a fuel nozzle A (901), a fuel nozzle B (902), a fuel nozzle C (903), a fuel nozzle D (904), a fuel nozzle E (905), and a fuel nozzle F (906); the fuel nozzle A (901), the fuel nozzle B (902), the fuel nozzle C (903), the fuel nozzle D (904), the fuel nozzle E (905), and the fuel nozzle F (906) are all burner nozzles; The fuel pipeline (207) includes a fuel pipeline A (907), a fuel pipeline B (908), a fuel pipeline C (909), a fuel pipeline D (910), an annular pipe (911), and a fuel intake manifold (912).

3. The working steps of a low nitrogen emission submerged combustion gasifier system according to claim 1: S1: The burner system (20) is connected to the axial flow fan (11). The axial flow fan (11) supplies air to the inlet of the burner system (20). The primary and secondary air intakes are distributed through the diverter valve (201). The primary and secondary air intakes are rotated in advance by arranging the baffle (210). The air inflow temperature is determined by the compression effect of the axial flow fan (11). S2: The water spray nozzle (202) is located at the bottom of the water delivery pipe (209) and sprays water downward at a spraying speed of 20L / h. The hydrogen-blended natural gas is transported to the fuel tank (208) through the fuel inlet main pipe (912) and the annular pipe (911) via the fuel pipe A (907), fuel pipe B (908), fuel pipe C (909), and fuel pipe D (910). The fuel is then sprayed from the fuel nozzles A (901), fuel nozzle B (902), fuel nozzle C (903), fuel nozzle D (904), fuel nozzle E (905), and fuel nozzle F (906) at the bottom of the fuel tank (208) at a spraying speed of 10m 3 / h, the primary intake air is mixed with the ejected fuel and the water mist sprayed from the water spray nozzle (202) when flowing downward, and forms a uniform vortex through the main swirl blade (204), and the secondary intake air is rectified by the secondary guide blade (205) and then sent into the furnace (13); S3: The hydrogen production system (25) produces H2 and part of the NG at the outlet of the submerged combustion gasifier is transported to the mixing system (24). The temperature, pressure and flow sensor A (241) and the temperature, pressure and flow sensor B (242) collect signals of the PLC control system (245). The regulating control device A (243) and the regulating control device B (244) adjust the opening degree. The mixed gas is evenly mixed under the action of the static mixer (247) and the rectifier (248) and transported to the fuel intake manifold (912). After the S2 step, it is burned in the furnace (13). The center of the furnace (13) presents a negative pressure due to the swirling flow, forming an upward countercurrent area. The burned gas dilutes the unburned fuel and air and promotes mild combustion, thereby suppressing the generation of NOx. S4: The flue gas from the furnace (13) is discharged through the circular hole opened on the flue gas distribution pipe (14). The gas-liquid two-phase flow surges upward and sweeps across the initially semi-submerged horizontally arranged serpentine heat exchange cluster (17) and completely immerses it, heating the LNG in the heat exchange tube bundle to increase its temperature and gasify it. After the heat, mass and kinetic energy are transferred, the flue gas and water overflow and separate above the overflow weir (16). The water falls back into the water bath header (15) due to gravity to form a reflux, and the flue gas is discharged from the upper exhaust pipe (19); S5: The circulating water pump (12) supplies cold water from the bottom of the water bath header (15) to the water jacket (21) to cool the furnace wall that is not immersed in the water bath. Since the cooling water in the water jacket (21) flows at a high speed, it can take away a large amount of heat and also play a cooling role on the furnace (13); S6: Set up a pH meter (22). When it is found that the pH value in the water bath tank is low, the alkali solution storage tank (18) needs to be opened to adjust the pH value in the water bath tank.

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