A control system for precisely controlling the concentration of sodium hypochlorite in a falling film process

Abstract

This invention relates to a control system for precisely controlling the concentration of sodium hypochlorite produced by a falling film process. The system comprises: a fresh alkali solution input component, a chlorine gas input component, a synthesis component, a detection component, a product buffer and conveying component, a qualified product output component, a non-qualified product circulation component, and a control component. When the product concentration is under normal production conditions, the control component is connected to both the fresh alkali solution input component and the chlorine gas input component to form a ratio control system. When the product concentration is under unqualified conditions, the control component is connected to both the detection component and the chlorine gas input component to form a cascade control system. This invention can reduce overchlorination and precisely control the concentration of sodium hypochlorite. Furthermore, this invention can reduce the frequency of sodium hypochlorite salt buildup and blockage in the detection component, ensuring long-term stable operation of the device.

Description

Technical Field

[0001] This invention relates to the field of sodium hypochlorite production technology, and in particular to a control system for precisely controlling the concentration of sodium hypochlorite produced by the falling film method. Background Technology

[0002] Tubular falling film absorbers are used to absorb chlorine gas from sodium hydroxide solution (hereinafter referred to as alkali) to prepare sodium hypochlorite solution. They offer advantages such as timely heat transfer, minimizing the decomposition of sodium hypochlorite due to reaction heat, and ensuring a complete reaction. The production process of preparing sodium hypochlorite solution from chlorine gas using alkali can be divided into two stages: a normal production condition and a substandard production condition. The normal production condition refers to the alkali absorbing chlorine gas to produce a sodium hypochlorite solution of the target concentration. The substandard production condition refers to situations where the concentration of sodium hypochlorite produced is lower than the target concentration due to factors such as excessively rapid chlorine gas introduction causing localized overchlorination or thermal decomposition of the sodium hypochlorite solution.

[0003] Currently, the product control system of this process cannot control the appropriate chlorine flow rate. If the chlorine flow is excessive, a superchlorination reaction will occur, causing all the generated sodium hypochlorite to decompose instantly, reducing the economic efficiency and safety of the equipment. Chinese patent CN116474704A controls the chlorine feed flow rate based on the results of an online oxidation-reduction potentiometer (ORP) to achieve the product concentration target. However, when this control method is used in the initial stage of the reaction, it is very easy for the ORP to fully open the chlorine flow regulating valve to increase the sodium hypochlorite concentration because there is no sodium hypochlorite in the fresh alkaline solution. This can easily lead to localized superchlorination. Summary of the Invention

[0004] In view of this, the present invention provides a control system for precisely controlling the concentration of sodium hypochlorite in the falling film method.

[0005] Specifically, the present invention is achieved through the following technical solution:

[0006] According to a first aspect of the present invention, a control system for precisely controlling the concentration of sodium hypochlorite using a falling film method is provided, comprising:

[0007] Fresh lye solution input component, used for inputting fresh lye solution;

[0008] Chlorine gas input component, used for inputting chlorine gas;

[0009] Synthesis component, used to receive fresh alkali solution / substandard product and chlorine gas and generate sodium hypochlorite;

[0010] A detection component for detecting the concentration of the sodium hypochlorite;

[0011] Product buffering and conveying components are used to buffer and convey products;

[0012] Qualified product output component, used to output qualified products;

[0013] A defective product recycling component is used to recycle defective products back to the synthesis component;

[0014] A control component is used to precisely control the concentration of sodium hypochlorite; the synthesis component is connected to the fresh alkali solution input component, the defective product circulation component, the chlorine gas input component, the detection component, and the product buffer and conveying component; the product buffer and conveying component is connected to the qualified product output component and the defective product circulation component.

[0015] Specifically, when the product concentration is under normal production conditions, the control component is connected to the fresh alkali input component and the chlorine input component to form a ratio control system; when the product concentration is under unqualified conditions, the control component is connected to the detection component and the chlorine input component to form a cascade control system.

[0016] Optionally, the fresh lye input component includes: a fresh lye storage tank, a fresh lye feed pump, a fresh lye flow meter, a fresh lye flow regulating valve, and a fresh lye on / off valve. The fresh lye feed pump is connected to the output end of the fresh lye storage tank and the input end of the fresh lye flow meter via pipelines. The fresh lye flow regulating valve is connected to the output end of the fresh lye flow meter and the input end of the fresh lye on / off valve via pipelines. The output end of the fresh lye on / off valve is connected to the synthesis component via a pipeline.

[0017] Optionally, the chlorine input component includes: a liquid chlorine storage tank, a liquid chlorine storage tank pressure gauge, a steam feed regulating valve, a weighing instrument, and a chlorine flow regulating valve. The chlorine flow regulating valve is connected to the liquid chlorine storage tank and the synthesis component via pipelines. The liquid chlorine storage tank pressure gauge and the weighing instrument are installed on the liquid chlorine storage tank, and the weighing instrument is connected to the fresh alkali input component or the detection component. The steam feed regulating valve is located on the steam feed pipeline of the internal coil for vaporization of the liquid chlorine storage tank.

[0018] Optionally, the synthesis component includes: a tubular falling film absorber, which is connected to the fresh alkali inlet valve of the fresh alkali inlet component, the chlorine flow regulating valve of the chlorine inlet component, the detection component, the product buffer and conveying component, and the non-conforming product circulation component.

[0019] Optionally, the detection component includes an online detector, which is connected via pipelines to the inlet pipe of the fresh alkali feed pump in the fresh alkali input component and the outlet pipe of the tubular falling film absorber in the synthesis component.

[0020] Optionally, the product buffer and conveying assembly includes a sodium hypochlorite buffer tank and a sodium hypochlorite conveying pump, wherein the sodium hypochlorite buffer tank is connected to the output end of the tubular falling film absorber in the synthesis assembly and the input end of the sodium hypochlorite conveying pump via pipelines, and the output end of the sodium hypochlorite conveying pump is connected to the qualified product output assembly and the unqualified product output assembly.

[0021] Optionally, the qualified product output component includes: a qualified product switch valve, a qualified product flow meter, and a qualified product flow regulating valve, wherein the qualified product switch valve is connected to the output end of the sodium hypochlorite delivery pump in the product buffer and delivery component and the input end of the qualified product flow meter via pipelines, and the output end of the qualified product flow meter is connected to the input end of the qualified product flow regulating valve via a pipeline.

[0022] Optionally, the non-conforming product circulation assembly includes: a non-conforming product switching valve, a non-conforming product flow meter, and a non-conforming product flow regulating valve. The non-conforming product switching valve is connected to the output end of the sodium hypochlorite delivery pump in the product buffer and delivery assembly and the input end of the non-conforming product flow meter via pipelines. The non-conforming product flow regulating valve is connected to the output end of the non-conforming product flow meter and the input end of the tubular falling film absorber in the synthesis assembly via pipelines.

[0023] Optionally, the control component includes: a controller, which is connected to the fresh alkali flow meter in the fresh alkali input component and the weighing instrument in the chlorine input component when the product concentration is under normal production conditions, and is connected to the online detector in the detection component and the weighing instrument in the chlorine input component when the product concentration is under unqualified conditions.

[0024] The technical solution provided by this invention brings at least the following beneficial effects:

[0025] This invention provides a control system for precisely controlling the concentration of sodium hypochlorite produced using the falling film method. This system overcomes the shortcomings of current falling film sodium hypochlorite production methods, reducing the occurrence of overchlorination and thus achieving precise control of the sodium hypochlorite concentration. Furthermore, this invention also reduces the frequency of sodium hypochlorite salt buildup and blockage within the detection components, ensuring long-term stable operation of the device. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0028] Figure 1 A schematic diagram of a control system for precisely controlling the concentration of sodium hypochlorite using a falling film method, provided in an embodiment of the present invention;

[0029] Figure 2 A partial structural schematic diagram of a control system for precisely controlling the concentration of sodium hypochlorite using a falling film method, provided in an embodiment of the present invention;

[0030] Figure 3 This is a partial structural diagram of a control system for precisely controlling the concentration of sodium hypochlorite using a falling film method, provided in an embodiment of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Figure 1 The illustration schematically depicts a control system for precisely controlling the concentration of sodium hypochlorite using a falling film method, applicable to embodiments of the present invention.

[0033] Reference Figure 1-3 As shown, this application provides a control system for precisely controlling the concentration of sodium hypochlorite using a falling film method, comprising:

[0034] Fresh lye solution input component, used for inputting fresh lye solution;

[0035] Chlorine gas input component, used for inputting chlorine gas;

[0036] Synthesis component, used to receive fresh alkali solution / substandard product and chlorine gas and generate sodium hypochlorite;

[0037] A detection component for detecting the concentration of the sodium hypochlorite;

[0038] Product buffering and conveying components are used to buffer and convey products;

[0039] Qualified product output component, used to output qualified products;

[0040] A defective product recycling component is used to recycle defective products back to the synthesis component;

[0041] A control component is used to precisely control the concentration of sodium hypochlorite; the synthesis component is connected to the fresh alkali solution input component, the defective product circulation component, the chlorine gas input component, the detection component, and the product buffer and conveying component; the product buffer and conveying component is connected to the qualified product output component and the defective product circulation component.

[0042] Specifically, when the product concentration is under normal production conditions, the control component is connected to the fresh alkali input component and the chlorine input component to form a ratio control system; when the product concentration is under unqualified conditions, the control component is connected to the detection component and the chlorine input component to form a cascade control system.

[0043] In this embodiment, the fresh alkali solution input component is used to input fresh alkali solution; it is responsible for introducing fresh alkali solution into the system, which is one of the raw materials for producing sodium hypochlorite. The fresh alkali solution input component may include an alkali solution storage tank, pump, valve, flow meter, and regulating valve, etc., to ensure a stable supply and accurate measurement of alkali solution.

[0044] In this embodiment, the chlorine input component is used to input chlorine gas; it is responsible for introducing chlorine gas into the system, which is another raw material for reacting with alkali solution to produce sodium hypochlorite. The chlorine input component may include a chlorine storage tank, a pressure regulating device, a weighing instrument, and a regulating valve, etc., to ensure a safe, stable supply and accurate measurement of chlorine gas. When the product concentration is at normal production conditions, the chlorine flow rate is controlled by the alkali solution flow rate. The two constitute a ratio control system, that is, the fresh alkali solution flow meter in the fresh alkali solution input component sends a signal to the controller. After calculation, the controller output value is used as the input value of the weighing instrument in the chlorine input component. The input value of the weighing instrument controls the opening degree of the chlorine flow regulating valve.

[0045] In this embodiment, the synthesis component receives fresh alkali solution / substandard product and chlorine gas and generates sodium hypochlorite. This synthesis component is connected to the fresh alkali solution input component's fresh alkali solution switch valve, the chlorine gas input component's chlorine gas flow regulating valve, the detection component, the product buffer and conveying component, and the substandard product circulation component. It is the core of the system, responsible for receiving fresh alkali solution and chlorine gas when the product concentration is under normal production conditions. When the product concentration is under substandard conditions, the synthesis component receives substandard product and chlorine gas, generating sodium hypochlorite through a chemical reaction. The synthesis component can employ high-efficiency reaction equipment such as a tubular falling film absorber to improve reaction efficiency and product quality.

[0046] In this embodiment, the detection component is used to detect the concentration of sodium hypochlorite. The detection component is connected via pipelines to the inlet pipe of the fresh alkali feed pump in the fresh alkali input component and the outlet pipe of the tubular falling film absorber in the synthesis component; it is responsible for real-time monitoring of the sodium hypochlorite solution concentration. The detection component may include an online analyzer, sensors, and a data processing system to ensure the stability of the production process and product quality.

[0047] In this embodiment, the product buffering and conveying component is used to buffer and convey products, and may include a sodium hypochlorite buffer tank, a sodium hypochlorite conveying pump, etc., to ensure product buffering and conveying.

[0048] In this embodiment, the qualified product output component is used to output qualified products and may include a switching valve, a flow meter, a flow regulating valve, etc.

[0049] In this embodiment, the non-conforming product recycling component is used to recycle non-conforming products back into the synthesis component, and may include a switching valve, a flow meter, a flow regulating valve, etc.

[0050] In this embodiment, the control component is used to precisely control the concentration of sodium hypochlorite: when the product concentration is under normal production conditions, the control component is connected to the fresh alkali flow meter in the fresh alkali input component and the weighing instrument in the chlorine input component via software or DCS, controlling the chlorine flow rate based on the fresh alkali flow rate, thus forming a ratio control system. When the product concentration is under substandard conditions, the control component is connected to the online detector in the detection component and the weighing instrument in the chlorine input component via software or DCS, controlling the chlorine flow rate based on the online detector, thus forming a cascade control system. The control component is the intelligent brain of the system, responsible for adjusting the chlorine flow rate in real time according to the input values ​​of the control component. Advanced control algorithms and automated control systems may be employed to achieve precise control and optimized production.

[0051] In this embodiment, when the detection component detects that the sodium hypochlorite concentration is within acceptable limits, the control component opens the qualified product switch valve in the qualified product output component and closes the unqualified product switch valve in the unqualified product circulation component, sending the qualified product out of the system. When the detection component detects that the sodium hypochlorite concentration is unacceptable, the control component opens the unqualified product switch valve in the unqualified product circulation component, closes the qualified product switch valve in the qualified product output component, and closes the fresh alkali solution switch valve in the fresh alkali solution input component, circulating the unqualified product back to the synthesis component. Simultaneously, when the product concentration is unacceptable, the chlorine flow rate is controlled by the detection component. The two constitute a cascade control system: the detection component sends a signal to the controller, and after calculation, the controller output value serves as the input value of the weighing instrument in the chlorine input component. The input value of the weighing instrument controls the opening of the chlorine flow regulating valve.

[0052] In this embodiment, the synthesis component receives fresh alkali solution of concentration A from the fresh alkali solution input component and chlorine gas of concentration B from the chlorine gas input component. The control component is connected to both the fresh alkali solution input component and the chlorine gas input component to form a ratio control system. The detection component can detect the concentration C of sodium hypochlorite produced by the synthesis component. If the theoretical concentration D of the sodium hypochlorite solution corresponding to A and B, calculated based on chemical knowledge (e.g., through chemical formula calculation methods), matches the actual concentration C, then the sodium hypochlorite solution is a qualified product, and it is output through the qualified product output component. If the actual concentration C is lower than the theoretical concentration D due to factors such as excessively rapid chlorine gas flow causing local overchlorination or thermal decomposition of the sodium hypochlorite solution, then the sodium hypochlorite solution is a substandard product, and it is recycled back to the synthesis component. Simultaneously, the control component is connected to the detection component and the chlorine gas input component to form a cascade control system. Based on the continuous changes in the detection value of the detection component, the opening of the chlorine gas flow regulating valve is continuously adjusted.

[0053] For example, the fresh lye input component includes: a fresh lye storage tank 1, a fresh lye feed pump 2, a fresh lye flow meter 3, a fresh lye flow regulating valve 4, and a fresh lye switch valve 5. The fresh lye feed pump 2 is connected to the output end of the fresh lye storage tank 1 and the input end of the fresh lye flow meter 3 via pipelines. The fresh lye flow regulating valve 4 is connected to the output end of the fresh lye flow meter 3 and the input end of the fresh lye switch valve 5 via pipelines. The output end of the fresh lye switch valve 5 is connected to the synthesis component via a pipeline.

[0054] In this embodiment, the fresh alkali feed pump 2 draws fresh alkali stored in the fresh alkali storage tank 1 and transports it to the synthesis component through a pipeline. The fresh alkali flow meter 3 is used to detect the flow rate of the liquid flowing through the pipeline. The fresh alkali flow regulating valve 4 is used to control the flow rate of the liquid flowing through the pipeline. The fresh alkali switch valve 5 is used to control the on / off state of the pipeline.

[0055] For example, the chlorine input component includes: a liquid chlorine storage tank 6, a liquid chlorine storage tank pressure gauge 7, a steam feed regulating valve 8, a weighing instrument 9, and a chlorine flow regulating valve 10. The chlorine flow regulating valve 10 is connected to the liquid chlorine storage tank 6 and the synthesis component via pipelines. The liquid chlorine storage tank pressure gauge 7 and the weighing instrument 9 are installed on the liquid chlorine storage tank 6, and the weighing instrument 9 is connected to the fresh alkali input component / the detection component via software or DCS. The steam feed regulating valve 8 is located on the steam feed pipeline of the internal coil for vaporization of the liquid chlorine storage tank.

[0056] In this embodiment, chlorine stored in the liquid chlorine storage tank 6 is transported to the synthesis assembly via pipeline. A weighing instrument 9 can detect the weight of the liquid chlorine storage tank 6. A fixed time difference is set for the weighing instrument (assuming t2 - t1 = 1 second). By calculating the difference between the weighing instrument readings at time t2 and t1 and then comparing it to the time difference, the measured weight can be indirectly converted into flow rate. Since the accuracy of the weighing instrument is much higher than that of the flow meter, this invention uses a weighing instrument installed on the liquid chlorine storage tank to indirectly measure the chlorine flow rate. The chlorine flow regulating valve 10 is used to control the chlorine flow rate through the pipeline. The liquid chlorine storage tank pressure gauge 7 and the steam feed regulating valve 8 form a simple loop to control the pressure stability of the liquid chlorine storage tank 6.

[0057] For example, the synthesis component includes: a tubular falling film absorber 11, which is connected to the fresh alkali switch valve 5 in the fresh alkali input component, the chlorine flow regulating valve 10 in the chlorine input component, the detection component, the product buffer and conveying component, and the non-conforming product circulation component.

[0058] In this embodiment, when the product concentration is under normal production conditions, the tubular falling film absorber 11 receives fresh alkaline solution and chlorine gas, and reacts to obtain a sodium hypochlorite solution. When the product concentration is under unqualified conditions, the tubular falling film absorber 11 receives unqualified product and chlorine gas, and reacts to obtain a sodium hypochlorite solution.

[0059] For example, the detection component includes an online detector 12, which is connected to the inlet pipe of the fresh alkali feed pump 2 in the fresh alkali input component and the outlet pipe of the tubular falling film absorber 11 in the synthesis component via pipelines.

[0060] In this embodiment, the inlet pipe of the online detector 12 is connected to the outlet pipe of the tubular falling film absorber 11, and the outlet pipe of the online detector 12 is connected to the inlet pipe of the fresh alkali feed pump 2. Compared with the traditional method of introducing the outlet pipe of the online detector 12 into the sodium hypochlorite buffer tank 13, this solution increases the pressure difference between the inlet and outlet of the online detector, thereby reducing the frequency of salt blockage in the online detector pipe, i.e., reducing the frequency of abnormal readings from the online detector 12. This is crucial for accurately controlling the concentration of sodium hypochlorite. The online detector 12 can detect the actual concentration of the sodium hypochlorite solution produced in the tubular falling film absorber 11. At the same time, the flow rate of the alkali solution transported by the fresh alkali solution storage tank 1 is detected by the fresh alkali solution flow meter 3, and the concentration is known to be constant. The chlorine flow rate is indirectly detected by the weighing instrument 9. Therefore, the theoretical concentration of the sodium hypochlorite solution can be calculated by chemical formula calculation method and compared with the actual concentration.

[0061] For example, the product buffer and delivery assembly includes: a sodium hypochlorite buffer tank 13 and a sodium hypochlorite delivery pump 14, wherein the sodium hypochlorite buffer tank 13 is connected to the output end of the tubular falling film absorber 11 in the synthesis assembly and the input end of the sodium hypochlorite delivery pump 14 through pipelines, and the output end of the sodium hypochlorite delivery pump 14 is connected to the qualified product output assembly / unqualified product output assembly.

[0062] In this embodiment, the sodium hypochlorite buffer tank 13 is used to receive the sodium hypochlorite solution discharged from the tubular falling film absorber 11 and output it through the sodium hypochlorite delivery pump 14.

[0063] For example, the qualified product output component includes: a qualified product switching valve 15, a qualified product flow meter 16, and a qualified product flow regulating valve 17. The qualified product switching valve 15 is connected to the output end of the sodium hypochlorite delivery pump 14 in the product buffer and delivery component and the input end of the qualified product flow meter 16 through pipelines. The output end of the qualified product flow meter 16 is connected to the input end of the qualified product flow regulating valve 17 through a pipeline.

[0064] In this embodiment, the qualified product switching valve 15 is used to switch the qualified product output component out of / into the system, and the qualified product flow meter 16 and the qualified product flow regulating valve 17 are used to control the stability of the qualified product flow.

[0065] For example, the non-conforming product circulation assembly includes: a non-conforming product switching valve 18, a non-conforming product flow meter 19, and a non-conforming product flow regulating valve 20. The non-conforming product switching valve 18 is connected to the output end of the sodium hypochlorite transfer pump 14 in the product buffer and conveying assembly and the input end of the non-conforming product flow meter 19 through pipelines. The non-conforming product flow regulating valve 20 is connected to the output end of the non-conforming product flow meter 19 and the input end of the tubular falling film absorber 11 in the synthesis assembly through pipelines.

[0066] In this embodiment, the non-conforming product switching valve 18 is used to disconnect / connect the non-conforming product circulation component from the system, and the non-conforming product flow meter 19 and the non-conforming product flow regulating valve 20 are used to control the stability of the non-conforming product flow.

[0067] In this embodiment, when the concentration of sodium hypochlorite in the detection component is within acceptable limits, the qualified product switch valve 15 in the qualified product output component is opened, and the unqualified product switch valve 18 in the unqualified product circulation component is closed, thus sending the qualified product out of the system. When the concentration of sodium hypochlorite in the detection component is outside acceptable limits, the unqualified product switch valve 18 in the unqualified product circulation component is opened, the qualified product switch valve 15 in the qualified product output component is closed, and the fresh alkali solution switch valve 5 is closed, thus circulating the unqualified product back to the synthesis component, and then absorbing a small amount of chlorine gas until the concentration of sodium hypochlorite is within acceptable limits.

[0068] For example, the control component includes: a controller 21, which is connected to the fresh alkali flow meter 3 in the fresh alkali input component and the weighing instrument 9 in the chlorine input component via software or DCS when the product concentration is under normal production conditions; and the controller is connected to the online detector 12 in the detection component and the weighing instrument 9 in the chlorine input component via software or DCS when the product concentration is under unqualified conditions.

[0069] In this embodiment, the controller 21 is used to precisely control the concentration of sodium hypochlorite: When the product concentration is under normal production conditions, the controller 21 is connected to the fresh alkali flow meter 3 in the fresh alkali input component and the weighing instrument 9 in the chlorine input component via software or DCS, and controls the chlorine flow rate by controlling the flow rate of the fresh alkali, thus forming a ratio control system. When the product concentration is under unqualified conditions, the controller 21 is connected to the online detector 12 in the detection component and the weighing instrument 9 in the chlorine input component via software or DCS, and controls the chlorine flow rate by controlling the chlorine flow rate by the online detector 12, thus forming a cascade control system.

[0070] In this embodiment, fresh alkali solution (sodium hydroxide concentration range of 10-25 wt%) in fresh alkali solution storage tank 1 is pressurized by fresh alkali solution feed pump 2 and enters the falling film tube from the top of the tubular falling film absorber 11, forming a continuous liquid film on the inner surface of the falling film tube. Liquid chlorine in liquid chlorine storage tank 6 is vaporized into chlorine gas and enters the falling film tube from the top of the tubular falling film absorber 11 to fully contact and react with the liquid film. The generated sodium hypochlorite solution flows out from the bottom of the tubular falling film absorber 11 and enters the sodium hypochlorite buffer tank 13 by gravity. The outlet pipe of the tubular falling film absorber 11 is equipped with an online detector 12. When the actual value of sodium hypochlorite concentration detected by the online detector 12 meets the theoretical value, it is a qualified product. At this time, the qualified product switch valve 15 is opened and the unqualified product switch valve 18 is closed, and the qualified product is sent out of the system. When the actual value of sodium hypochlorite concentration detected by the online detector 12 does not meet the theoretical value, it is a non-conforming product. At this time, the non-conforming product switch valve 18 is opened, the qualified product switch valve 15 is closed, the fresh alkali solution switch valve 5 is closed, and the non-conforming product is recycled back to the synthesis component.

[0071] In this embodiment, two control methods are employed for normal production conditions and for conditions where the product concentration is substandard: For normal production conditions, the fresh alkali flow rate is set to a constant value, and the alkali flow rate is controlled by a ratio control system to regulate the chlorine flow rate entering the tubular falling film absorber. A weighing instrument 9 is installed on the liquid chlorine storage tank 6 to indirectly measure the chlorine flow rate. Specifically, during configuration, a fixed time difference is set for the weighing instrument 9 (assuming t2 - t1 = 1 second). By calculating the difference between the weighing instrument 9 at time t2 and time t1 and comparing it with the time difference, the measured weight of the liquid chlorine storage tank 6 can be indirectly converted into the chlorine flow rate. The actual concentration of sodium hypochlorite is detected by an online detector 12 installed on the outlet pipe of the tubular falling film absorber 11. When the product concentration is substandard, the substandard product flow rate is set to a constant value, the supply of fresh alkali to the fresh alkali input component is suspended, and the control system switches to the online detector controlling the chlorine flow rate through a cascade control system. The combination of the two control methods can effectively prevent overchlorination and achieve precise control of the sodium hypochlorite solution concentration.

[0072] When the product concentration is under normal production conditions, the above method has the following advantages: The flow rate of the alkali solution in the above method is controlled by the ratio control system. The flow rate of chlorine entering the tubular falling film absorber is mainly obtained by calculating the molar ratio of sodium hydroxide in the alkali solution to the raw material chlorine gas based on the reaction equation, which can control the concentration of sodium hypochlorite more accurately.

[0073] When the product concentration is below standard, the above method has the following advantages: When the product concentration is below standard, the circulating liquid only needs to absorb a small amount of chlorine to bring the product concentration up to standard. The control system in the above method is switched to an online detector that controls the chlorine flow rate through a cascade control system to obtain the product concentration in real time and flexibly adjust the actual required chlorine flow rate, which greatly reduces the probability of overchlorination.

[0074] The present invention provides a control system for precisely controlling the concentration of sodium hypochlorite in the falling film process. By precisely controlling the input amount of chlorine, the system avoids overchlorination caused by excessive chlorine, thereby improving the quality and stability of the product.

[0075] The present invention provides a control system for precisely controlling the concentration of sodium hypochlorite using the falling film method. Through real-time monitoring and feedback adjustment, the system can precisely control the concentration of sodium hypochlorite to meet the needs of different application scenarios.

[0076] The present invention provides an automated control system and a high-efficiency reaction equipment in a control system for precisely controlling the concentration of sodium hypochlorite in a falling film process, which improves production efficiency and product quality while reducing production costs.

[0077] The control system for precisely controlling the concentration of sodium hypochlorite using the falling film method provided by this invention has broad application prospects in chemical, water treatment, and disinfection fields. In particular, it will play an important role in situations requiring high-quality sodium hypochlorite solutions, such as medical, food processing, and environmental protection.

[0078] The present invention will be further described in detail below with reference to the embodiments.

[0079] Example 1:

[0080] In a sodium hypochlorite solution production unit with an annual capacity of 1000 tons and an effective chlorine content of approximately 12%, under normal production conditions, fresh alkali solution (sodium hydroxide concentration of 16.15 wt%) is pressurized by fresh alkali solution feed pump 2 and enters the falling film tube from the top of the tubular falling film absorber 11, forming a continuous and stable liquid film. The flow rate of the fresh alkali solution is maintained at the set value of 110.0 kg / h of the alkali solution flow meter 3 through a simple loop consisting of the fresh alkali solution flow meter 3 and the fresh alkali solution flow regulating valve 4. Chlorine gas enters the falling film tube from the top of the tubular falling film absorber 11 and is absorbed by the liquid film formed by the alkali solution, thereby generating sodium hypochlorite solution. The flow rate of chlorine gas is controlled by the flow rate of the alkali solution, and the ratio between the two is controlled (the mass ratio of chlorine gas to sodium hydroxide solution feed is 0.1364:1, and the chlorine gas feed flow rate is 15.0 kg / h). The outlet pipe of the tubular falling film absorber 11 is equipped with an online ORP detector 12. When the oxidation-reduction potential value is about 575±5mV, the effective chlorine content in the sodium hypochlorite solution is qualified. The product is buffered by the sodium hypochlorite buffer tank 13 and pressurized by the sodium hypochlorite transfer pump 14. The qualified product switch valve 15 is opened and the unqualified product switch valve 18 is closed, and the qualified product is sent out of the system.

[0081] When the oxidation-reduction potential value is lower than the set value of 575±5mV, which means that the product concentration is unqualified, the feed flow rate of chlorine is controlled by the online detector 12. At the same time, the unqualified product switch valve 18 is opened, the qualified product switch valve 15 is closed, and the fresh alkali solution switch valve 5 is closed. The unqualified product is sent back to the tubular falling film absorber 11 for re-reaction through the sodium hypochlorite transfer pump 14 until the online detector 12 index is qualified.

[0082] The present invention provides a control system for precisely controlling the concentration of sodium hypochlorite produced by the falling film method, which overcomes the shortcomings of the current falling film method for sodium hypochlorite production, and can prevent overchlorination, thereby achieving precise control of the concentration of sodium hypochlorite.

[0083] It should be noted that in this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are mainly for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0084] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0085] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0086] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, elements, or components (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, elements, or components. Unless otherwise stated, "a plurality of" means two or more.

[0087] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A control system for precisely controlling the concentration of sodium hypochlorite using a falling film method, characterized in that, include: Fresh lye solution input component, used for inputting fresh lye solution; Chlorine gas input component, used for inputting chlorine gas; Synthesis component, used to receive fresh alkali solution / substandard product and chlorine gas and generate sodium hypochlorite; A detection component for detecting the concentration of the sodium hypochlorite; Product buffering and conveying components are used to buffer and convey products; Qualified product output component, used to output qualified products; A defective product recycling component is used to recycle defective products back to the synthesis component; A control component is used to precisely control the concentration of sodium hypochlorite; the synthesis component is connected to the fresh alkali solution input component, the defective product circulation component, the chlorine gas input component, the detection component, and the product buffer and conveying component; the product buffer and conveying component is connected to the qualified product output component and the defective product circulation component. Specifically, when the product concentration is under normal production conditions, the control component is connected to the fresh alkali input component and the chlorine input component to form a ratio control system; when the product concentration is under unqualified conditions, the control component is connected to the detection component and the chlorine input component to form a cascade control system.

2. The control system for precisely controlling the concentration of sodium hypochlorite using the falling film method according to claim 1, characterized in that, The fresh lye input assembly includes: a fresh lye storage tank, a fresh lye feed pump, a fresh lye flow meter, a fresh lye flow regulating valve, and a fresh lye on / off valve. The fresh lye feed pump is connected to the output end of the fresh lye storage tank and the input end of the fresh lye flow meter via pipelines. The fresh lye flow regulating valve is connected to the output end of the fresh lye flow meter and the input end of the fresh lye on / off valve via pipelines. The output end of the fresh lye on / off valve is connected to the synthesis assembly via a pipeline.

3. The control system for precisely controlling the concentration of sodium hypochlorite using the falling film method according to claim 1, characterized in that, The chlorine input component includes: a liquid chlorine storage tank, a liquid chlorine storage tank pressure gauge, a steam feed regulating valve, a weighing instrument, and a chlorine flow regulating valve. The chlorine flow regulating valve is connected to the liquid chlorine storage tank and the synthesis component via pipelines. The liquid chlorine storage tank pressure gauge and the weighing instrument are installed on the liquid chlorine storage tank, and the weighing instrument is connected to the fresh alkali input component or the detection component. The steam feed regulating valve is located on the steam feed pipeline of the internal coil for vaporization of the liquid chlorine storage tank.

4. The control system for precisely controlling the concentration of sodium hypochlorite using the falling film method according to claim 1, characterized in that, The synthesis assembly includes: a tubular falling film absorber, which is connected to the fresh alkali inlet valve of the fresh alkali inlet assembly, the chlorine flow regulating valve of the chlorine inlet assembly, the detection assembly, the product buffer and conveying assembly, and the non-conforming product circulation assembly.

5. The control system for precisely controlling the concentration of sodium hypochlorite using the falling film method according to claim 1, characterized in that, The detection component includes an online detector, which is connected via pipelines to the inlet pipe of the fresh alkali feed pump in the fresh alkali input component and the outlet pipe of the tubular falling film absorber in the synthesis component.

6. The control system for precisely controlling the concentration of sodium hypochlorite using the falling film method according to claim 1, characterized in that, The product buffer and conveying assembly includes a sodium hypochlorite buffer tank and a sodium hypochlorite conveying pump. The sodium hypochlorite buffer tank is connected to the output end of the tubular falling film absorber and the input end of the sodium hypochlorite conveying pump in the synthesis assembly via pipelines. The output end of the sodium hypochlorite conveying pump is connected to the qualified product output assembly and the unqualified product output assembly.

7. The control system for precisely controlling the concentration of sodium hypochlorite using the falling film method according to claim 1, characterized in that, The qualified product output component includes: a qualified product switch valve, a qualified product flow meter, and a qualified product flow regulating valve. The qualified product switch valve is connected to the output end of the sodium hypochlorite delivery pump in the product buffer and delivery component and the input end of the qualified product flow meter via pipelines. The output end of the qualified product flow meter is connected to the input end of the qualified product flow regulating valve via a pipeline.

8. The control system for precisely controlling the concentration of sodium hypochlorite using the falling film method according to claim 1, characterized in that, The non-conforming product circulation assembly includes: a non-conforming product switching valve, a non-conforming product flow meter, and a non-conforming product flow regulating valve. The non-conforming product switching valve is connected to the output end of the sodium hypochlorite delivery pump in the product buffer and delivery assembly and the input end of the non-conforming product flow meter via pipelines. The non-conforming product flow regulating valve is connected to the output end of the non-conforming product flow meter and the input end of the tubular falling film absorber in the synthesis assembly via pipelines.

9. The control system for precisely controlling the concentration of sodium hypochlorite using the falling film method according to claim 1, characterized in that, The control component includes a controller, which is connected to the fresh alkali flow meter in the fresh alkali input component and the weighing instrument in the chlorine input component when the product concentration is under normal production conditions, and to the online detector in the detection component and the weighing instrument in the chlorine input component when the product concentration is under unqualified conditions.

Images