Intelligent blowdown system and method for urea hydrolysis process based on chloride ion monitoring

Abstract

The invention discloses an intelligent sewage discharge system and method for a urea hydrolysis process based on chloride ion monitoring. The intelligent sewage discharge system comprises a urea hydrolyzer, a plate heat exchanger, a sewage discharge barrel, a dilution unit and chloride ion automatic online monitoring equipment, an outlet of the urea hydrolyzer is communicated with a shell side inlet of the plate heat exchanger through the sewage sampling valve, a shell side outlet of the plate heat exchanger is communicated with an inlet of the sewage barrel, and an outlet of the sewage barrel is communicated with an inlet of the dilution unit sequentially through the variable frequency injection pump, the filter and the resin exchange column. An outlet of the dilution unit is communicated with an inlet of the chloride ion automatic on-line monitoring equipment through a variable-frequency injection pump and a water inlet pipeline, an outlet of the chloride ion automatic on-line monitoring equipment is communicated with an inlet of the pollution discharge barrel through a water return pipeline, and a pollution discharge opening of the pollution discharge barrel is connected with a pollution discharge valve. The corrosion condition of the urea hydrolyzer body in the urea hydrolysis process is relieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical analysis and industrial online monitoring of denitration systems in thermal power plants, and relates to an intelligent sewage discharge system and method for a urea hydrolysis process based on chloride ion monitoring. Background Art

[0002] When thermal power plants use the urea hydrolysis process to produce ammonia for flue gas denitrification, chloride ions are an "invisible killer" of corrosion in the urea hydrolyzer itself. Chloride ion control runs through the entire process of "raw material purification - material selection - process design - real-time monitoring." In urea hydrolysis systems, the presence of chloride ions has a significant impact on the corrosion behavior of the equipment itself (especially metal structures). Chloride ions can originate from impurities in the raw urea, process water (such as steam condensate), or equipment cleaning residues. Most thermal power plants discharge urea hydrolyzer wastewater based on empirical cycles. Statistics show that at 150°C and a chloride ion concentration of 50 mg / L, the annual corrosion rate of 316L stainless steel can reach 0.3-0.5 mm / a. Furthermore, the presence of chloride ions can easily cause pitting corrosion and stress corrosion cracking. Therefore, controlling chloride ions within the hydrolyzer is crucial to the safe operation of the denitrification system, as severe conditions can lead to system shutdown or even accidents. Existing chloride ion monitoring mainly relies on manual titration methods (such as the molar method and potentiometric titration). However, ammonia and ammonium ions in the hydrolyzate react with silver nitrate to form silver-ammonium complexes. If tested using traditional testing methods, excessive consumption of the titrant (silver nitrate) will result, which cannot truly reflect the chloride ion level in the hydrolyzer, resulting in uncontrolled discharge cycles and increased equipment corrosion risks. Based on the above problems, it is now necessary to develop a chloride ion monitoring method with strong anti-interference, accurate and fast performance to effectively guide the intelligent discharge of urea hydrolyzers in denitrification systems, thereby alleviating the corrosion of the urea hydrolyzer itself during the urea hydrolysis process. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide an intelligent sewage discharge system and method for the urea hydrolysis process based on chloride ion monitoring. The system and method can guide the intelligent sewage discharge of the urea hydrolyzer and alleviate the corrosion of the urea hydrolyzer body caused by the urea hydrolysis process.

[0004] To achieve the above-mentioned object, the present invention discloses an intelligent sewage discharge system for a urea hydrolysis process based on chloride ion monitoring, comprising a urea hydrolyzer, a plate heat exchanger, a sewage discharge barrel, a dilution unit and an automatic online chloride ion monitoring device;

[0005] The outlet of the urea hydrolyzer is connected to the inlet of the shell side of the plate heat exchanger through a blowdown sampling valve. The outlet of the shell side of the plate heat exchanger is connected to the inlet of the blowdown bucket. The outlet of the blowdown bucket is successively connected to the inlet of the dilution unit through a variable-frequency injection pump, a filter, and a resin exchange column. The outlet of the dilution unit is connected to the inlet of the automatic on-line chloride ion monitoring device through a variable-frequency injection pump and a water inlet pipe. The outlet of the automatic on-line chloride ion monitoring device is connected to the inlet of the blowdown bucket through a return water pipe. A blowdown valve is connected to the blowdown port of the blowdown bucket.

[0006] A further improvement of the intelligent blowdown system for the urea hydrolysis process based on chloride ion monitoring according to the present invention lies in:

[0007] Further, the dilution unit includes a container, a nitric acid automatic adding device, a silver nitrate automatic adding device, and a demineralized water automatic adding device. The outlet of the resin exchange column is connected to the inlet of the container. A stirrer is arranged in the container. The outlets of the nitric acid automatic adding device, the silver nitrate automatic adding device, and the demineralized water automatic adding device are connected to the inlet of the container.

[0008] Further, it also includes an automated intelligent control module panel. The automated intelligent control module panel is connected to the blowdown sampling valve, the blowdown valve, the variable-frequency injection pump, the stirrer, the nitric acid automatic adding device, the silver nitrate automatic adding device, the demineralized water automatic adding device, and the automatic on-line chloride ion monitoring device through connecting wires.

[0009] Further, it also includes a cooling water inlet pipe and a cooling water outlet pipe. The cooling water inlet pipe is connected to the inlet of the tube side of the plate heat exchanger. The cooling water outlet pipe is connected to the outlet of the tube side of the plate heat exchanger.

[0010] Further, the filter uses a 0.45μm filter element for filtration.

[0011] Further, the resin exchange column uses hydrogen-type cation resin to remove cations.

[0012] Further, the dilution ratio of the dilution unit is controlled by the automated intelligent control module panel.

[0013] Further, a scale is arranged on the container.

[0014] Further, the automated intelligent control module panel has the function of transmitting data to the cloud in real time and supporting remote monitoring and alarm.

[0015] The present invention discloses an intelligent blowdown method for the urea hydrolysis process based on chloride ion monitoring, including the following steps:

[0016] Open the blowdown sampling valve. The blowdown liquid of the urea hydrolyzer is cooled by a plate heat exchanger and then stored in a blowdown bucket. The blowdown liquid in the blowdown bucket enters a filter through a variable-frequency injection pump to remove suspended solids, and then enters a resin exchange column to remove cations in the blowdown liquid. It then enters a dilution unit for dilution, and then nitric acid and silver nitrate are added respectively to remove ammonia and react to form silver chloride precipitation. After the reaction is complete, the sample enters an automatic online chlorine ion monitoring device through a variable-frequency injection pump for monitoring. When the measured chlorine ion concentration is within the standard curve range, it is determined whether the measured chlorine ion concentration is greater than or equal to the set threshold. When the measured chlorine ion concentration ≥ the set threshold, control the blowdown sampling valve and the blowdown valve to conduct blowdown; when the measured chlorine ion concentration < the set threshold, keep the blowdown sampling valve in the closed state and maintain the continuous operation of the urea hydrolyzer; when the measured chlorine ion concentration continues to exceed the standard curve range, control the dilution unit to continue diluting until the measured chlorine ion concentration meets the standard curve range.

[0017] The present invention has the following beneficial effects:

[0018] When the intelligent blowdown system and method for the urea hydrolysis process based on chlorine ion monitoring according to the present invention are specifically operated, continuous sampling is carried out from the bottom of the urea hydrolyzer, and after cooling and pretreatment, the chlorine ion content is monitored online. By comparing the measured chlorine ion content with the preset value, the blowdown frequency and blowdown volume of the urea hydrolyzer are automatically adjusted, and the chlorine ion concentration of the blowdown liquid of the urea hydrolyzer is controlled within the standard curve range. The chlorine ion content of the urea solution is used to guide the intelligent blowdown in the urea hydrolysis process, thereby effectively alleviating the corrosion of the urea hydrolyzer body during the urea hydrolysis process; compared with the traditional testing and blowdown methods, this system can intelligently control the blowdown of the urea hydrolyzer and has simple operation, and at the same time provides a strong guarantee for the safe operation of the flue gas denitration process in thermal power plants.

[0019] Furthermore, the automation intelligent control module panel integrates functions of filtration, dilution, and masking. By adding an acidic medium (nitric acid), the decomposition of urea is inhibited, the interference of NH3 is reduced, and at the same time, the interference of metal cations is selectively removed by pretreatment with hydrogen-type cation resin. Finally, the chlorine ion content is monitored in real time by an online spectrophotometer, and the data is transmitted to the cloud in real time, supporting remote monitoring and alarm functions to avoid manual operation errors. Description of the Drawings

[0020] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0021] Figure 1 is the structural diagram of the present invention.

[0022] Among them, 1 is a sewage sampling valve, 2 is a plate heat exchanger, 3 is a cooling water inlet pipe, 4 is a cooling water outlet pipe, 5 is a sewage bucket, 6 is a sewage valve, 7 is a variable frequency injection pump, 8 is a filter, 9 is a resin exchange column, 10 is a dilution unit, 11 is a container, 12 is a stirrer, 13 is a nitric acid automatic addition device, 14 is a silver nitrate automatic addition device, 15 is a demineralized water automatic addition device, 16 is a chloride ion automatic on-line monitoring device, 17 is a raw water pipeline, 18 is a return water pipeline, 19 is an automated intelligent control module panel, and 20 is a connecting line. Specific implementation manners

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0024] In the description of the present invention, it should be understood that the terms "including" and "comprising" indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the existence or addition of one or more other features, wholes, steps, operations, elements, components and / or their combinations.

[0025] It should also be understood that the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0026] It should be further understood that the term " / and" used in the specification of the present invention and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations. For example, A and / or B can represent: the sole existence of A, the simultaneous existence of A and B, and the sole existence of B. In addition, the character " / " in the present invention generally represents an "or" relationship between the front and rear associated objects.

[0027] It should be understood that although the terms first, second, third, etc. may be used in the embodiments of the present invention to describe preset ranges, etc., these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0028] Depending on the context, as used herein, the word "if" can be interpreted as "when" or "while" or "in response to determining" or "in response to detecting". Similarly, depending on the context, the phrase "if determined" or "if detecting (stated condition or event)" can be interpreted as "when determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)".

[0029] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. Generally, the components described and shown in the accompanying drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0030] Schematic diagrams of various structures according to the disclosed embodiments of the present invention are shown in the drawings. These figures are not drawn to scale, where for the purpose of clear expression, some details are enlarged and some details may be omitted. The shapes of various regions and layers shown in the figures and their relative sizes and positional relationships are merely exemplary. In practice, there may be deviations due to manufacturing tolerances or technical limitations, and those skilled in the art can design regions / layers with different shapes, sizes and relative positions according to actual needs.

[0031] Embodiment 1

[0032] Reference Figure 1 , the intelligent sewage discharge system for urea hydrolysis process based on chloride ion monitoring according to the present invention includes a sewage sampling valve 1, a plate heat exchanger 2, a cooling water inlet pipe 3, a cooling water outlet pipe 4, a sewage bucket 5, a sewage valve 6, a variable frequency injection pump 7, a filter 8, a resin exchange column 9, a dilution unit 10, a container 11, a stirrer 12, a nitric acid automatic addition device 13, a silver nitrate automatic addition device 14, a demineralized water automatic addition device 15, a chloride ion automatic on-line monitoring device 16, a water inlet pipe 17, a return water pipe 18, an automated intelligent control module panel 19 and a connecting line 20;

[0033] The outlet of the urea hydrolyzer is connected to the inlet of the shell side of the plate heat exchanger 2 through the blowdown sampling valve 1. The outlet of the shell side of the plate heat exchanger 2 is connected to the inlet of the blowdown bucket 5. The outlet of the blowdown bucket 5 is successively connected to the inlet of the dilution unit 10 through the variable-frequency injection pump 7, the filter 8, and the resin exchange column 9. The outlet of the dilution unit 10 is connected to the inlet of the automatic online chloride ion monitoring device 16 through the variable-frequency injection pump 7 and the incoming water pipeline 17. The outlet of the automatic online chloride ion monitoring device 16 is connected to the inlet of the blowdown bucket 5 through the return water pipeline 18. A blowdown valve 6 is connected to the blowdown port of the blowdown bucket 5.

[0034] The dilution unit 10 includes a container 11, a nitric acid automatic addition device 13, a silver nitrate automatic addition device 14, and a demineralized water automatic addition device 15. The outlet of the resin exchange column 9 is connected to the inlet of the container 11. A stirrer 12 is arranged in the container 11. The outlets of the nitric acid automatic addition device 13, the silver nitrate automatic addition device 14, and the demineralized water automatic addition device 15 are connected to the inlet of the container 11.

[0035] The automatic intelligent control module panel 19 is connected to the blowdown sampling valve 1, the blowdown valve 6, the variable-frequency injection pump 7, the stirrer 12, the nitric acid automatic addition device 13, the silver nitrate automatic addition device 14, the demineralized water automatic addition device 15, and the automatic online chloride ion monitoring device 16 through the connecting line 20.

[0036] In addition, the cooling water inlet pipe 3 is connected to the inlet of the tube side of the plate heat exchanger 2, and the cooling water outlet pipe 4 is connected to the outlet of the tube side of the plate heat exchanger 2.

[0037] The filter 8 is filtered with a 0.45μm filter element.

[0038] The resin exchange column 9 uses hydrogen-type cation resin to remove cations.

[0039] The dilution unit 10 controls the dilution ratio by the automatic intelligent control module panel 19, and the dilution unit 10 has the function of accurately adding demineralized water, nitric acid (volume fraction 25%), and silver nitrate solution (17g / L) through scales. At the same time, it has an online temperature control function.

[0040] The automatic online chloride ion monitoring device 16 uses the combined method of spectrophotometry and turbidimetry for multi-channel automatic sampling, monitoring, and flushing. The spectrophotometry measures the absorbance at a wavelength of 420nm using a 300mm colorimetric cell, and monitors the precipitation generation amount in real time. The chloride ion concentration is automatically calculated by combining with the standard curve (0 - 5mg / L).

[0041] The automatic intelligent control module panel 19 has the function of transmitting data to the cloud in real time and supports remote monitoring and alarm.

[0042] Example 2

[0043] This embodiment discloses an intelligent sewage discharge method for the urea hydrolysis process based on chloride ion monitoring. The intelligent sewage discharge method for the urea hydrolysis process based on chloride ion monitoring is realized based on the intelligent sewage discharge system for the urea hydrolysis process based on chloride ion monitoring. The intelligent sewage discharge system for the urea hydrolysis process based on chloride ion monitoring includes a sewage sampling valve 1, a plate heat exchanger 2, a cooling water inlet pipe 3, a cooling water outlet pipe 4, a sewage bucket 5, a sewage discharge valve 6, a variable-frequency injection pump 7, a filter 8, a resin exchange column 9, a dilution unit 10, a container 11, a stirrer 12, a nitric acid automatic adding device 13, a silver nitrate automatic adding device 14, a demineralized water automatic adding device 15, a chloride ion automatic on-line monitoring device 16, a raw water pipe 17, a return water pipe 18, an automated intelligent control module panel 19 and a connecting wire 20. The specific connection relationship is as shown in Example 1.

[0044] Specifically, the intelligent sewage discharge method for the urea hydrolysis process based on chloride ion monitoring includes the following steps:

[0045] Open the sewage sampling valve 1. The sewage discharge liquid of the urea hydrolyzer is cooled by the plate heat exchanger 2 and then stored in the sewage bucket 5. The sewage discharge liquid in the sewage bucket 5 enters the filter 8 through the variable-frequency injection pump 7 to remove suspended solids, and then enters the resin exchange column 9 to remove cations such as ammonium, iron, and calcium in the sewage discharge liquid. Then it enters the dilution unit 10 for dilution, and then nitric acid and silver nitrate are added respectively for ammonia removal and reaction to generate silver chloride precipitate. During the reaction, the temperature control systems of the stirrer 12 and the container 11 are always in the open state. After the reaction is complete, the sample enters the chloride ion automatic on-line monitoring device 16 through the variable-frequency injection pump 7 for monitoring. When the chloride ion concentration obtained by the monitoring is in the standard curve range of 0.1 - 5 ppm, it is judged whether the monitored chloride ion concentration is greater than or equal to the set threshold. When the monitored chloride ion concentration ≥ the set threshold, control the sewage sampling valve 1 and the sewage discharge valve 6 to discharge sewage; when the monitored chloride ion concentration < the set threshold, keep the sewage sampling valve 1 in the closed state and maintain the continuous operation of the urea hydrolyzer. When the monitored chloride ion concentration exceeds the maximum upper limit of the standard curve range, control the opening of the variable-frequency injection pump 7 to reduce the amount of sewage discharge liquid entering the dilution unit 10, increase the dilution multiple and then conduct monitoring; when the monitored chloride ion concentration continues to exceed the standard curve range, control the dilution unit 10 to continue diluting until the monitored chloride ion concentration meets the standard curve range.

[0046] Other embodiments of the present invention will be readily contemplated by those skilled in the art in view of the specification and disclosure of the invention. This application is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the present invention and include known common general knowledge or conventional technical means in the technical field not disclosed in the present invention. The specification and examples are only illustrative, and the true scope and spirit of the present invention are pointed out by the following claims.

[0047] It should be understood that the present invention is not limited to the exact structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.

[0048] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent structural changes made to the above embodiments according to the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. An intelligent sewage discharge system for urea hydrolysis process based on chloride ion monitoring, characterized in that, It includes a urea hydrolyzer, a plate heat exchanger (2), a sewage discharge bucket (5), a dilution unit (10), and an automatic on-line chloride ion monitoring device (16); The outlet of the urea hydrolyzer is connected to the shell side inlet of the plate heat exchanger (2) through a sewage sampling valve (1). The shell side outlet of the plate heat exchanger (2) is connected to the inlet of the sewage discharge bucket (5). The outlet of the sewage discharge bucket (5) is successively connected to the inlet of the dilution unit (10) through a variable frequency injection pump (7), a filter (8), and a resin exchange column (9). The outlet of the dilution unit (10) is connected to the inlet of the automatic on-line chloride ion monitoring device (16) through a variable frequency injection pump (7) and a raw water pipeline (17). The outlet of the automatic on-line chloride ion monitoring device (16) is connected to the inlet of the sewage discharge bucket (5) through a return water pipeline (18). A sewage discharge valve (6) is connected to the sewage discharge port of the sewage discharge bucket (5).

2. The intelligent sewage discharge system for urea hydrolysis process based on chloride ion monitoring according to claim 1, wherein, The dilution unit (10) includes a container (11), a nitric acid automatic adding device (13), a silver nitrate automatic adding device (14), and a demineralized water automatic adding device (15); The outlet of the resin exchange column (9) is connected to the inlet of the container (11). A stirrer (12) is arranged in the container (11). The outlets of the nitric acid automatic adding device (13), the silver nitrate automatic adding device (14), and the demineralized water automatic adding device (15) are connected to the inlet of the container (11).

3. The intelligent sewage discharge system for urea hydrolysis process based on chloride ion monitoring according to claim 2, wherein It further includes an automated intelligent control module panel (19). The automated intelligent control module panel (19) is connected to the sewage sampling valve (1), the sewage discharge valve (6), the variable frequency injection pump (7), the stirrer (12), the nitric acid automatic adding device (13), the silver nitrate automatic adding device (14), the demineralized water automatic adding device (15), and the automatic on-line chloride ion monitoring device (16) through a connecting wire (20).

4. The intelligent sewage discharge system for urea hydrolysis process based on chloride ion monitoring according to claim 3, wherein, It further includes a cooling water inlet pipe (3) and a cooling water outlet pipe (4). The cooling water inlet pipe (3) is connected to the tube side inlet of the plate heat exchanger (2). The cooling water outlet pipe (4) is connected to the tube side outlet of the plate heat exchanger (2).

5. The intelligent sewage discharge system for urea hydrolysis process based on chloride ion monitoring according to claim 3, wherein, The filter (8) is filtered with a 0.45μm filter element.

6. The intelligent sewage discharge system for urea hydrolysis process based on chloride ion monitoring according to claim 3, characterized in that, The resin exchange column (9) uses hydrogen-type cation resin to remove cations.

7. The intelligent sewage discharge system for urea hydrolysis process based on chloride ion monitoring according to claim 3, wherein The dilution unit (10) controls the dilution ratio by using the automated intelligent control module panel (19).

8. The intelligent sewage discharge system for urea hydrolysis process based on chloride ion monitoring according to claim 3, characterized in that, A scale is arranged on the container (11).

9. The intelligent sewage discharge system for urea hydrolysis process based on chloride ion monitoring according to claim 3, wherein, The automated intelligent control module panel (19) has the function of transmitting data to the cloud in real time and supporting remote monitoring and alarm.

10. An intelligent sewage discharge method for urea hydrolysis process based on chloride ion monitoring, characterized in that, The intelligent sewage discharge system for the urea hydrolysis process based on chloride ion monitoring according to claim 2 includes the following steps: Open the blowdown sampling valve (1). The blowdown liquid of the urea hydrolyzer is cooled by the plate heat exchanger (2) and then stored in the blowdown bucket (5). The blowdown liquid in the blowdown bucket (5) enters the filter (8) through the variable frequency injection pump (7) to remove suspended solids, and then enters the resin exchange column (9) to remove cations in the blowdown liquid. Then it enters the dilution unit (10) for dilution, and then nitric acid and silver nitrate are added respectively to remove ammonia and react to form silver chloride precipitate. After the reaction is complete, the sample enters the chloride ion automatic online monitoring device (16) through the variable frequency injection pump (7) for monitoring. When the chloride ion concentration obtained by monitoring is within the standard curve range, it is judged whether the chloride ion concentration obtained by monitoring is greater than or equal to the set threshold. When the chloride ion concentration obtained by monitoring ≥ the set threshold, control the blowdown sampling valve (1) and the blowdown valve (6) to conduct blowdown; when the chloride ion concentration obtained by monitoring < the set threshold, keep the blowdown sampling valve (1) in the closed state and maintain the continuous operation of the urea hydrolyzer; when the chloride ion concentration obtained by monitoring continues to exceed the standard curve range, control the dilution unit (10) to continue dilution until the chloride ion concentration obtained by monitoring meets the standard curve range.

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