A urea catalytic hydrolyzer online pollutant detection device and method

Abstract

The present invention relates to an online pollutant detection device and method for a urea catalytic hydrolyzer, comprising: a medium detection valve and a sewage detection valve, wherein the medium detection valve and the sewage detection valve are connected to a sampling valve, and a monitoring valve is sequentially connected to a pipeline booster pump, a main channel check valve, a filtering device, a liquid flow metering module, a pretreatment module, a detection module, and a detection discharge port; the detection module includes: a pH detector, a phosphate detector, a chloride ion detector, an iron ion detector, and a conductivity detector. The present invention connects a device capable of monitoring conductivity, pH value, phosphate, chloride ion, and iron ion to the medium inlet and sewage discharge port of the urea catalytic hydrolyzer, and performs time-sharing detection on the medium entering the urea catalytic hydrolyzer and the discharge. When it is detected that the quality of the medium entering the urea catalytic hydrolyzer is unstable, corresponding measures are taken to reduce the impact. When it is detected that harmful components in the discharge increase, corresponding measures are taken to avoid damage to the hydrolyzer.

Description

Technical Field

[0001] The present invention relates to an online pollutant detection device and method for a urea catalytic hydrolyzer, which is an auxiliary device and method for chemical equipment and a monitoring device and method for emissions from a urea catalytic hydrolyzer. Background Art

[0002] Existing urea catalytic hydrolyzers commonly suffer from internal corrosion. Research indicates that this type of corrosion is generally caused by the presence of chloride ions in the urea solution. The small amount of chloride ions present during the urea solution preparation accumulates during the evaporation process in the urea catalytic hydrolyzer, causing severe corrosion. The introduction of chloride ions is primarily related to the quality of the purchased urea granules and the quality of the water used to prepare the urea solution.

[0003] Another issue with existing urea catalytic hydrolyzers is the uncertainty surrounding clean wastewater discharge. Urea catalytic hydrolyzers primarily discharge a urea solution containing impurities. To prevent urea solution volatilization from impacting the production environment, the solution is typically piped directly to a closed wastewater tank. Under these conditions, it's often impossible to visually determine whether the discharged urea solution contains solid contaminants. Insufficient wastewater discharge can lead to equipment failure or reduced production efficiency.

[0004] Another problem with existing urea catalytic hydrolyzers is that blowdown removes the reaction catalyst. Since blowdown is discharged directly into the urea solution within the reactor, it carries away not only harmful salts and insoluble pollutants, but also the active ingredient urea and the dissolved polyacid phosphates in the solution. The current solution replenishes the catalyst once a year, but during the initial replenishment phase, the catalyst content in the reactor decreases, potentially reducing urea conversion or increasing steam consumption during critical load adjustments.

[0005] Therefore, how to accurately determine the chloride ion content in the urea catalytic hydrolyzer and whether the content of various substances in the emissions meets the requirements is a problem that needs to be solved. Summary of the Invention

[0006] To overcome the problems of the prior art, the present invention proposes an online pollutant detection device and method for a urea catalytic hydrolyzer. The device and method detect the medium inlet and waste outlet of the urea catalytic hydrolyzer, monitoring the medium entering the urea catalytic hydrolyzer and the wastewater on a time-sharing basis, analyzing their composition, thereby eliminating potential corrosive raw materials, monitoring wastewater discharge integrity, and preventing excessive emissions.

[0007] The objective of the present invention is achieved as follows: an online pollutant detection device for a urea catalytic hydrolyzer comprises: a medium detection valve connected to a medium inlet of the urea catalytic hydrolyzer and a sewage discharge detection valve connected to a sewage discharge outlet of the urea catalytic hydrolyzer, wherein the medium detection valve and the sewage discharge detection valve are connected to a sampling valve, and the monitoring valve is sequentially connected to a pipeline booster pump, a main channel check valve, a filtering device, a liquid flow metering module, a pretreatment module, a detection module, and a detection object discharge outlet; and the detection module comprises: a pH detector, a phosphate detector, a chloride ion detector, an iron ion detector, and a conductivity detector.

[0008] Furthermore, the monitoring valve, medium detection valve, and sewage detection valve are ball valves.

[0009] Furthermore, the monitoring valve, medium detection valve, and sewage detection valve are pneumatic ball valves.

[0010] Furthermore, the filtering device is a duplex filter.

[0011] Furthermore, pressure sensors are provided before and after the duplex filter.

[0012] Furthermore, the liquid flow metering module is provided with a flow regulating valve connected to the filtering device, the flow regulating valve is connected to the flow meter, and the flow meter is connected to the pre-processing module.

[0013] Furthermore, the flow meter is an electromagnetic flow meter or an ultrasonic flow meter.

[0014] Furthermore, the flow regulating valve is connected to the filtering device through the first inspection valve, the flow meter is connected to the pretreatment module through the second inspection valve, and a third inspection valve is bypassed in parallel on the main channel connected by the first inspection valve, flow regulating valve, flow meter and second inspection valve.

[0015] Furthermore, the pretreatment module includes: a temperature regulator, a pressure regulator, a dilution regulator, and a pre-dosing controller.

[0016] A method for online pollutant detection and corrosion protection of a urea catalytic hydrolyzer using the above-mentioned device, the steps of the method are as follows:

[0017] Step 1: Select the detection working condition: when the urea catalytic hydrolyzer is in the medium loading working condition, open the medium detection valve, close the sewage detection valve, and the medium input to the urea catalytic hydrolyzer is in the sampling state; when the urea catalytic hydrolyzer is in the sewage discharge working condition, open the sewage detection valve, close the medium detection valve, and the discharge from the urea catalytic hydrolyzer is in the sampling state;

[0018] Step 2, sampling: during the period between the input medium working condition or the sewage discharge working condition, the sampling valve is opened to sample the input medium or sewage to obtain a liquid sample;

[0019] Step 3, pressurization and check valve: Turn on the booster pump to pressurize the liquid sample in the pipeline to meet the detection requirements, and use the check valve to maintain the pipeline pressure of the pressurized liquid sample;

[0020] Step 4, filtration: Filter the liquid sample to remove solid particles in the liquid sample, and determine the degree of solid particle contamination in the liquid sample based on the pressure difference before and after the filter;

[0021] Step 5, flow measurement: measuring the flow of the liquid sample;

[0022] Step 6, pretreatment: adjust the liquid sample with inconsistent temperature and pressure, and configure, dilute and pre-dose the liquid sample according to the needs of the back-end detection module;

[0023] Step 7, testing: testing the three ions that most significantly affect the operation of the urea catalytic hydrolyzer, including chloride ion, iron ion and phosphate content, as well as the pH value and conductivity of the liquid sample;

[0024] Step 8, Analysis: By analyzing the test data, suggestions are made on adjusting the frequency of adding media and discharging pollutants according to different working conditions, so as to effectively control the internal corrosion and catalyst shortage of the catalytic hydrolyzer and ensure the normal operation of the urea catalytic hydrolyzer to the greatest extent.

[0025] The advantages and beneficial effects of the present invention are as follows: A device capable of monitoring conductivity, pH, phosphate, chloride ion, and iron ion is connected to the medium inlet and sewage outlet of the urea catalytic hydrolyzer. The device monitors the medium entering the urea catalytic hydrolyzer and the sewage outlet in a time-sharing manner. If unstable quality of the medium entering the urea catalytic hydrolyzer is detected, appropriate measures are taken to reduce the impact. If an increase in harmful components in the sewage is detected, appropriate measures are taken to prevent damage to the urea catalytic hydrolyzer. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described below with reference to the accompanying drawings and examples.

[0027] Figure 1 1 is a schematic diagram of the connection and structure of the device described in Example 1 of the present invention and a urea catalytic hydrolyzer;

[0028] Figure 2 This is a flowchart of the method described in Example 10 of the present invention. DETAILED DESCRIPTION

[0029] Example 1:

[0030] This embodiment is an online pollutant detection device for a urea catalytic hydrolyzer. Figure 1 This embodiment includes: a medium detection valve 2 connected to the medium inlet 101 of the urea catalytic hydrolyzer 1 and a sewage detection valve 3 connected to the sewage outlet 102 of the urea catalytic hydrolyzer. The medium detection valve and sewage detection valve are connected to a sampling valve 4, which is sequentially connected to a pipeline booster pump 5, a main channel check valve 6, a filtering device 7, a liquid flow metering module 8, a pretreatment module 9, a detection module 10, and a test object discharge outlet 11; the detection module includes: a pH detector 10.1, a phosphate detector 10.2, a chloride ion detector 1.3, an iron ion detector 1.4, and a conductivity detector 10.5.

[0031] The working principle of the urea catalytic hydrolyzer is to pump the prepared urea solution into the urea catalytic hydrolyzer through a pump. The urea solution is heated by a steam coil and undergoes an endothermic hydrolysis reaction in the hydrolyzer to produce NH3, H2O and CO2. The "catalysis" refers to the reaction catalyst added once before the urea catalytic hydrolyzer is put into operation. Its main component is polyacid phosphate, which reduces the reaction activation energy and accelerates the reaction by changing the urea decomposition reaction path.

[0032] In actual operation, urea particles contain a certain amount of contaminants, including low-concentration metal ions, harmful salt components, calcium ions and other soluble salts accidentally introduced into the demineralized water / hydrophobic water used to prepare the urea solution, and insoluble particulate matter. As the equipment continues to operate, the urea catalytic hydrolyzer requires regular drainage.

[0033] Regular sewage discharge of urea catalytic hydrolyzer includes surface sewage discharge and bottom sewage discharge. The top sewage discharge is located 400mm below the operating liquid level, mainly discharging pollutants floating on the upper part or oily substances that may be brought in by the solution; the bottom sewage discharge is located at the lowest point of the bottom centerline of the reactor. Its main purpose is to discharge the deposited impurities at the bottom and effectively reduce the harmful salt concentration of the liquid in the hydrolyzer by discharging the solution.

[0034] At present, the frequency of sewage discharge of equipment is generally determined by the equipment operation experience, usually once a month. The discharge volume is also determined based on the reference volume provided by the equipment manufacturer and the actual operation of the equipment, usually 400L / time. This operation mode also creates some hidden dangers to the stability of the system operation.

[0035] The input medium and sewage discharge of existing urea catalytic hydrolyzers have the following problems:

[0036] 1) Corrosion within the hydrolyzer: Material corrosion testing conducted by numerous manufacturers on urea-catalyzed hydrolyzers indicates that the safe temperature for 316L material to withstand ammonium carbamate corrosion is below 165°C, with an annual corrosion rate below 0.08mm. Urea-catalyzed hydrolyzers operate at temperatures below 160°C, so severe corrosion is generally not expected. However, in many cases, severe corrosion has occurred within one to two years of operation in urea-catalyzed hydrolyzers, necessitating replacement of the hydrolyzer coils. Sampling studies have shown that this type of corrosion is generally caused by the presence of chloride ions in the urea solution. The small amount of chloride ions present during the urea solution preparation accumulates during the evaporation process in the urea-catalyzed hydrolyzer, causing severe corrosion.

[0037] The introduction of chloride ions is mainly related to the quality of purchased urea granules and the quality of water used to prepare the urea solution. Therefore, the situation in each plant is different. For example, if more corrosion-resistant materials are consistently used to make urea catalytic hydrolyzers, the investment cost will increase dramatically; if the frequency of sewage discharge is consistently increased, it will cause a waste of operating costs for some manufacturers.

[0038] 2) Unable to determine whether the wastewater is clean: The wastewater discharged from the urea catalytic hydrolyzer is mainly urea solution containing impurities. To prevent the volatilization of the urea solution during the wastewater discharge process and affecting the working environment at the production site, the solution is generally transported directly to the wastewater pool through pipes, and the wastewater pool is generally closed. Under such conditions, it is generally impossible to visually observe whether the discharged urea solution also contains solid pollutants. Under the operating conditions of different plant areas, a wastewater concentration of 400L / time may be sufficient for good operating conditions. However, for enterprises with poor water quality and urea quality, insufficient wastewater discharge may cause other equipment problems.

[0039] 3) Wastewater discharge will carry away the reaction catalyst: Since the wastewater from the urea catalytic hydrolyzer is directly discharged into the urea solution in the reactor, it will not only carry away harmful salts and insoluble pollutants, but also the effective ingredient urea in the solution and the reaction catalyst - dissolved polyacid phosphate. The existing solution is to replenish the catalyst once a year, but in the early stage of catalyst replenishment, the catalyst content in the reactor decreases, which may cause a decrease in urea conversion rate, or increase steam consumption in the process of urgently needing to cooperate with unit load adjustment.

[0040] The solution of the device described in this embodiment to solve the above problem is: a set of detection facilities ( Figure 1In the double-dotted line frame), two working conditions, input medium and sewage discharge, are selected to perform real-time online detection on the medium input to the urea catalytic hydrolyzer and the sewage discharged from the urea catalytic hydrolyzer. The frequency of sewage discharge and whether the sewage discharge volume meets the requirements are inferred based on the input medium and the composition of the sewage discharge. In this way, the corrosion protection problem of the urea catalytic hydrolyzer, whether the sewage discharge is clean, and whether the catalyst is wasted are solved.

[0041] In this embodiment, the medium input port and the sewage discharge port of the urea catalytic hydrolyzer are connected to the detection facilities through a pipeline medium detection valve and a sewage discharge detection valve. According to the working conditions of the urea catalytic hydrolyzer when inputting medium or discharging sewage, the medium input or sewage discharge is selected by opening and closing the medium detection valve and the sewage discharge detection valve.

[0042] The detection equipment consists of multiple parts, including pipelines, multiple valves, aisle booster pumps, filtration equipment, pretreatment modules, and detection modules. Each part has a corresponding function:

[0043] The function of the sampling valve is to isolate the urea catalytic hydrolyzer and the detection facilities. The sampling valve is opened at an intermediate time in the input medium working condition or the sewage working condition. The medium entering the urea catalytic hydrolyzer or the sewage from the urea catalytic hydrolyzer is sampled through the branch pipe entering the detection facility and sent to the subsequent detection facilities.

[0044] The primary function of a pipeline booster pump is to increase the pressure of liquid samples with insufficient pressure. In a urea catalytic hydrolyzer, both the urea solution and the hydrolysis catalyst have dedicated delivery pumps, and their media pressures meet the requirements for delivery to testing facilities, thus eliminating the need for boosting. During the urea catalytic hydrolyzer's discharge process, the pressure within the urea catalytic hydrolyzer is between 0.4 and 0.55 MPa, which also meets the requirements of testing facilities. However, desalted water is typically delivered by the owner through pipelines for use, and the pressure reaching the urea catalytic hydrolyzer may not meet testing requirements. Therefore, a booster pump is installed to increase the pressure of desalted water or other media that may be underpressured.

[0045] The main function of the main channel check valve is to prevent the accidental backflow of the rear-end liquid sample and interfere with the detection effect.

[0046] The primary function of filtration equipment is to filter solid impurities from liquid samples extracted during the sewage discharge process to prevent damage to precision testing instruments. Filters can be duplex filters with replaceable filter elements, which do not affect continuous operation. Pressure detection devices are installed at the inlet and outlet of the filtration equipment to effectively monitor the presence of solid impurities in the sewage discharge. A drop in pressure at the rear end of the filter indicates blockage by solid impurities, indicating the need for enhanced sewage discharge.

[0047] The liquid flow metering module primarily measures and adjusts the flow of the extracted test liquid sample. Typically, a high-precision electromagnetic flowmeter or ultrasonic flowmeter is used to control the flow of the liquid sample entering the back-end pretreatment module, verifying pollutant concentrations. It also measures the flow of a single blowdown from the urea catalytic hydrolyzer, determining the actual discharge volume based on the discharge time. Because the testing process requires precise knowledge of the volume and mass of the solution entering the back-end testing instrument, the control valve and flowmeter are used to quantify the amount of liquid sample entering the testing module, allowing the concentration of the pollutant to be calculated after the pollutant content is determined.

[0048] The pretreatment module's primary function is to adjust liquid samples for inconsistent temperatures and pressures. It also configures dilution and pre-dosing according to the needs of the back-end detection module. Because the detection module contains multiple test items, each with varying temperature and concentration requirements, and some testing instruments or test items require the addition of reagents based on varying operational requirements, the pretreatment module facilitates these adjustments for solution samples.

[0049] The detection module primarily tests the composition of liquid samples. It detects the three ions that most significantly impact urea catalytic hydrolyzer operation: chloride, iron, and phosphate. It also measures characteristic liquid parameters such as pH and conductivity. By monitoring the presence of different ions and the characteristic parameters of the liquid sample, it can effectively control problems such as internal corrosion and catalyst deficiency in the catalytic hydrolyzer.

[0050] The liquid samples that have passed through the testing facilities can be returned to the urea catalytic hydrolyzer if the medium is added; if it is a sewage discharge condition, the liquid samples can be continued to be discharged into the wastewater pool for unified decontamination and then discharged without pollution.

[0051] This embodiment may also include a module specifically for display and analysis, which comprehensively analyzes the various indicators detected by the detection module and the various parameters received by the pressure sensors before and after the filter, anticipates possible corrosion conditions, and proposes drainage recommendations.

[0052] Example 2:

[0053] This embodiment is an improvement of the first embodiment, and is a refinement of the first embodiment regarding the monitoring valve, medium detection valve, and sewage detection valve. The monitoring valve, medium detection valve, and sewage detection valve described in this embodiment are ball valves.

[0054] The ball valve has a tight seal, which is beneficial for sampling in situations where precise control is required.

[0055] Example 3:

[0056] This embodiment is an improvement of the above embodiment, and is a refinement of the above embodiment regarding the monitoring valve, medium detection valve, and sewage detection valve. The monitoring valve, medium detection valve, and sewage detection valve described in this embodiment are pneumatic ball valves.

[0057] Pneumatic valves open and close quickly, facilitate data collection, and are safe and reliable. However, their disadvantage is that they require an air source, and their control requires compressed air as a medium for electrical control, which is relatively troublesome.

[0058] Example 4:

[0059] This embodiment is an improvement of the above embodiment and a refinement of the filtering device in the above embodiment. The filtering device described in this embodiment is a double filter.

[0060] The filter element of the duplex filter can be replaced online, and the replacement of the filter element does not affect the continuous operation of the equipment.

[0061] Pressure sensors can be installed at the inlet and outlet of the filter to measure the pressure difference before and after the filter.

[0062] Embodiment 5:

[0063] This embodiment is an improvement of the above embodiment and a refinement of the above embodiment regarding the duplex filter. Pressure sensors are provided before and after the duplex filter described in this embodiment.

[0064] The pressure sensor can be a pressure gauge or other electronic pressure sensing element. It is used to monitor the presence of solid impurities in the wastewater. An increase in the pressure differential between the filter and its ends indicates increased filter blockage by solid impurities. This pressure differential can be used to assess the quality of the input medium and the amount of wastewater discharged, serving as a basis for increasing the number of discharges.

[0065] Example 6:

[0066] This embodiment is an improvement of the above embodiment and is a refinement of the above embodiment regarding the liquid flow metering module. The liquid flow metering module described in this embodiment is provided with a flow regulating valve 8.1 connected to the filtering device, the flow regulating valve is connected to the flow meter, and the flow meter is connected to the pre-processing module. Figure 1 shown.

[0067] The flow regulating valve is used to adjust the flow of the liquid sample according to the indication of the flow meter for subsequent measurement.

[0068] Embodiment seven:

[0069] This embodiment is an improvement of the above embodiment and a refinement of the flowmeter in the above embodiment. The flowmeter described in this embodiment is an electromagnetic flowmeter or an ultrasonic flowmeter.

[0070] Electromagnetic flowmeters or ultrasonic flowmeters are high-precision flowmeters, which are mainly used to measure the flow of liquid samples with high precision, so as to subsequently accurately detect the liquid samples and calculate the concentration.

[0071] Embodiment 8:

[0072] This embodiment is an improvement of the above embodiment and is a refinement of the flow meter in the above embodiment. The flow regulating valve in this embodiment is connected to the filtering device through the first inspection valve 8.3, and the flow meter is connected to the pre-processing module through the second inspection valve 8.4. A third inspection valve 8.5 is connected in parallel to bypass the main channel connecting the first inspection valve, flow regulating valve, flow meter, and second inspection valve. Figure 1 shown.

[0073] The three inspection valves are mainly used for the inspection of high-precision flow meters. The first and second inspection valves are used to cut off the liquid sample entering the flow meter, and the third inspection valve is used to bypass the liquid sample.

[0074] Embodiment 9:

[0075] This embodiment is an improvement of the above embodiment and a refinement of the pre-processing module of the above embodiment. The pre-processing module described in this embodiment includes: a temperature regulator, a pressure regulator, a dilution regulator, and a pre-dosing controller.

[0076] The temperature regulator is used to adjust the temperature of the liquid sample, that is, to heat or cool the liquid sample. The temperature change caused by heating or cooling the liquid sample will cause a change in volume, and the flow rate may also change. Therefore, the flow rate of the liquid sample needs to be fine-tuned to ensure the accuracy of the measurement. A dilution regulator is configured to adjust the concentration of the liquid sample. Since the measurements in this embodiment are all high-precision measurements, the measurement range of high-precision instruments is controlled within a smaller range. Therefore, the concentration of the liquid sample needs to be adjusted before measurement to adapt to the measuring instrument. The function of the pre-dosing controller is to add the reagents required for measurement to the liquid sample.

[0077] Embodiment 10:

[0078] This embodiment is a method for online pollutant detection and corrosion protection of a urea catalytic hydrolyzer using the device described in the above embodiment. The steps of the method are as follows: Figure 2 As shown:

[0079] Step 1, select the detection working condition: when the urea catalytic hydrolyzer is in the medium adding working condition, open the medium detection valve, close the sewage detection valve, and the medium input to the urea catalytic hydrolyzer is in the sampling state; when the urea catalytic hydrolyzer is in the sewage discharge working condition, open the sewage detection valve, close the medium detection valve, and the discharge from the urea catalytic hydrolyzer is in the sampling state.

[0080] In this step, the valve is opened or closed according to the working conditions of the urea catalytic hydrolyzer to sample the input medium or the wastewater.

[0081] Step 2, sampling: During the period between the input medium working condition or the sewage discharge working condition, open the sampling valve, sample the input medium or sewage, and obtain a liquid sample.

[0082] Sampling in this step is continuous sampling, that is, the sampling valve is opened for a period of time after the input medium condition or the sewage condition is started to sample the input medium or sewage. Sampling continues uninterrupted during the working condition until the medium input condition reaches the end, that is, sampling and online measurement are terminated before the input medium ends. In the sewage condition, sampling also begins after sewage discharge begins and stops when the detection shows that the sewage has dropped to a certain level.

[0083] Step 3, pressurization and check valve: Turn on the booster pump to pressurize the liquid sample in the pipeline to meet the detection requirements, and use the check valve to maintain the pipeline pressure of the pressurized liquid sample.

[0084] Pipeline boosting increases the pressure of insufficiently pressurized media. In a urea catalytic hydrolyzer, dedicated pumps deliver both the urea solution and the hydrolysis catalyst, ensuring sufficient pressure for delivery, thus eliminating the need for boosting. During the urea catalytic hydrolyzer's blowdown process, the pressure within the hydrolyzer is between 0.4 and 0.55 MPa, sufficient for discharging the wastewater for testing. However, demineralized water is typically delivered by the client's pipelines for use, and the pressure reaching the urea catalytic hydrolyzer may not meet testing requirements. Therefore, a booster pump is installed to boost the pressure of demineralized water or other potentially insufficiently pressurized media. This boosting prevents backflow of liquid samples.

[0085] Step 4, filtration: Filter the liquid sample to remove solid particles in the liquid sample, and determine the degree of solid particle contamination in the liquid sample based on the pressure difference before and after the filter.

[0086] This step is an important step in detecting the quality of the input medium. In the medium input working condition, if the pressure difference before and after the filter increases rapidly, it means that the content of solid particles in the input medium is large, indicating that there may be problems with the quality of the input medium.

[0087] Step 5, flow measurement: perform flow measurement on the liquid sample.

[0088] During the detection process, it is necessary to accurately measure the solution volume and mass of the liquid sample sent to the back-end detection instrument, so that the concentration of the pollutant can be calculated after knowing the pollutant content. Therefore, the flow rate detected in this step is a high-precision flow measurement.

[0089] Step 6, pretreatment: adjust the liquid samples with inconsistent temperature and pressure, and configure, dilute and pre-drug the liquid samples according to the needs of the back-end detection module.

[0090] This step is to adjust the liquid sample with inconsistent temperature and pressure before measuring the liquid sample. At the same time, according to the needs of the back-end detection module, dilution and pre-dosing treatment are configured.

[0091] Step 7, detection: Detect the three ions that have the most significant impact on the operation of the urea catalytic hydrolyzer, including chloride ion, iron ion and phosphate content, as well as the pH value and conductivity of the liquid sample.

[0092] The detection of the three ions, pH value, and conductivity in liquid samples can be performed using specialized testing instruments. Since this is an online test, the testing process of various instruments must be extremely fast and efficient.

[0093] The pH and conductivity tests (no flow metering required) are conducted on the drain water from the urea catalytic hydrolysis system (the drain water discharged after steam heat exchange). Since the drain water only flows through the heat exchange tubes of the urea catalytic hydrolysis system and does not come into direct contact with the urea solution, the drain water should normally have a neutral pH value between 5 and 7 and a conductivity (the sample must be cooled to 25°C) between 0.01 and 1.0 mS / m. However, if the pH value of the drain water increases to alkaline and the conductivity increases, it indicates that the heat exchange tubes may have pitting corrosion and leakage, and urea solution has entered the drain water inside the heat exchange tubes, indicating that the heat exchange tubes need maintenance.

[0094] The objects of chloride ion detection include:

[0095] (1) Regular sewage discharge from the urea catalytic hydrolyzer. The sewage discharge of the urea catalytic hydrolysis system is currently based on the habits of the user. The discharge pattern and discharge volume are different. Some discharge once a year, and some discharge once a month. The discharge volume ranges from 300L to 600L. Generally, the color and impurity concentration of the discharged liquid are observed by sampling. If the color is dark or the impurity content is high, the sewage discharge time should be extended. This is actually a very unscientific sewage discharge method. Since the media in the urea solution that can cause corrosion to the catalytic hydrolysis reactor include chloride ions and the intermediate product ammonium carbamate, but the corrosion degree of ammonium carbamate is very small under the operating conditions of 140°C, which is within the range of the wall panel corrosion allowance, so there is basically no need to worry. Then the main corrosive medium is chloride ions (at the same time, in engineering applications, the corrosion of equipment is mainly pitting, which also indirectly confirms that it is caused by chloride ions). Therefore, we need to strictly control the chloride ion concentration of the reactor in the urea catalytic hydrolysis system. Therefore, when discharging sewage, by sampling and testing the sewage, when the chloride ion concentration is too high (there is no data here, and experience will be accumulated in later operations), the sewage discharge time should be increased. When the chloride ion concentration is not high (and there is no blockage in the front-end filter), it actually proves that the reaction environment in the catalytic hydrolyzer is within a reasonable range, and the frequency and amount of sewage discharge can be reduced (because sewage discharge will take away the catalyst, and sewage treatment also needs to be considered).

[0096] (2) The urea solution input to the urea catalytic hydrolyzer. Considering that the water used to prepare the urea solution and flush the catalytic hydrolysis system is generally demineralized water and does not contain chloride ions, it has been verified through experiments that most of the chloride ions in the system are introduced by urea granules. The chloride ions in the urea granules enter the system after being prepared into a solution. Therefore, the urea catalytic hydrolyzer samples the medium input pipeline. Once the chloride ion concentration of the input urea solution is found to be high, the following measures can be taken:

[0097] i. Replace urea granules. However, this requires time and cycles and may not be possible immediately.

[0098] ii. Increase the frequency of sewage discharge and strictly monitor the concentration of discharged chloride ions. This can avoid serious chloride ion accumulation and thus corrosion of equipment.

[0099] The object of phosphate + flow detection is the regular sewage discharge of the urea catalytic hydrolysis system. The sewage discharge is to discharge chloride ions, accumulated solid impurities, biuret by-products generated by the reaction, etc., but at the same time, the useful medium - catalyst phosphate will be discharged. Therefore, the discharge flow and concentration of phosphate are tested, and the flow * concentration = the amount of phosphate discharged. Then the control system can automatically open the catalyst skid module to replenish this part of the catalyst to ensure the catalyst concentration in the reaction environment (currently in industrial applications, the catalyst is generally replenished once a year, and the amount of phosphate is 500~2000kg / times depending on the size of the equipment. It is a very rough management method).

[0100] The object of iron ion detection is the regular sewage from the urea catalytic hydrolysis system. This is actually to assist in detecting whether serious corrosion has occurred, because the pH value and conductivity detection verify the occurrence of corrosion, which means that the heat exchange tube has been corroded and penetrated. However, under non-extreme working conditions, it generally does not reach this level. Therefore, the detection of the concentration of iron ions in the sewage means that once the iron ion concentration has increased significantly compared with the initial operation stage, it means that corrosion has occurred. Through long-term monitoring of the iron ion concentration, once abnormal fluctuations occur, it means that serious corrosion has occurred, and it is necessary to consider inspection and maintenance of the equipment in the urea catalytic hydrolysis system.

[0101] Step 8, Analysis: By analyzing the test data, suggestions are made on adjusting the frequency of adding media and discharging pollutants according to different working conditions, so as to effectively control the internal corrosion and catalyst shortage of the catalytic hydrolyzer and ensure the normal operation of the urea catalytic hydrolyzer to the greatest extent.

[0102] The analysis is performed for two working conditions:

[0103] 1. Working conditions for adding medium:

[0104] During the process of adding the medium, the main function of this embodiment is to detect the pollutants that may be carried by the added medium, mainly monitoring the chloride ions and solid particles that may be brought in.

[0105] When adding urea solution, if the quality of the urea granules purchased by the enterprise is unstable and the chloride concentration exceeds the standard at a certain stage, this device can be used to detect it in time. The discharge frequency can be adjusted in time according to the urea filling amount to avoid corrosion of stainless steel equipment caused by chloride ions.

[0106] When adding desalted water, since the desalted water in general plant areas comes from the owner's integrated desalted water pipeline, its water quality is treated by mixed bed ion exchange and should not contain salt ions. However, if the owner uses recycled water or other water sources, the salt ion content of this water source will affect the stable operation of the urea catalytic hydrolysis device, and it is necessary to monitor the chloride ions that may cause corrosion.

[0107] When adding catalyst solution, the catalyst concentration and emission volume in the wastewater are detected through the urea catalytic hydrolyzer, and the catalyst content reduced due to wastewater discharge is automatically calculated, so as to carry out quantitative addition of catalyst.

[0108] 2. System sewage discharge conditions:

[0109] The system's sewage discharge is mainly related to the pollutants in the installed medium. When the concentration of pollutants in the installed medium does not exceed the standard, the sewage can be discharged once a month with reference to the existing operating rules. During the sewage discharge stage, the pollutants discharged in the median time period are connected to this system, and the flow rate, chloride ion concentration, phosphate concentration, and iron ion concentration of the pollutants are tested. The solid particulate matter content in the sewage is judged based on the differential pressure measuring points before and after the filter device.

[0110] The purpose of phosphate detection is to calculate the amount of catalyst carried away in the sewage discharge. The phosphate content carried by the sewage discharge is calculated based on the sewage discharge volume and phosphate concentration. After the sewage discharge is completed, the catalyst skid is intelligently linked to replenish the amount of catalyst lost in the sewage discharge.

[0111] The detection of chloride ion concentration can directly reflect the chloride ion concentration in the urea catalytic hydrolyzer. High concentration of chloride ions will accelerate the corrosion of stainless steel materials. The frequency and amount of sewage discharge should be increased, and the chloride ions added to the medium should be strictly controlled.

[0112] The detection of iron ions is mainly used to detect whether serious corrosion actually occurs in the detection system. Since the urea catalytic hydrolyzer itself is a pressure vessel, its reactor as a whole adopts a steel structure and has no visual observation port; once the heat exchange tube corrodes, it is easy to cause steam leakage. Once the reactor shell is responsible, it is easy to cause the overall equipment to be damaged. At present, it is mainly through the use of a urea catalytic hydrolyzer that is replaced during maintenance and the internal situation of the standby hydrolyzer is repaired. The inspection frequency is low and requires large labor and time. Therefore, the iron ion concentration in the hydrolyzer can be detected by the method described in the present embodiment. If the iron ion concentration increases, it can be effectively predicted whether serious corrosion occurs in the reactor.

[0113] Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention and is not limiting. Although the present invention is described in detail with reference to the preferred arrangement scheme, it should be understood by those skilled in the art that the technical solution of the present invention (such as the form of the urea catalytic hydrolyzer, the treatment process of the hydrolyzer, the sequence of steps, etc.) can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. An online pollutant detection device for a urea catalytic hydrolyzer, characterized in that: include: A medium detection valve connected to the medium inlet of the urea catalytic hydrolyzer and a sewage detection valve connected to the sewage outlet of the urea catalytic hydrolyzer, the medium detection valve and the sewage detection valve are connected to the sampling valve, and the sampling valve is sequentially connected to the pipeline booster pump, the main channel check valve, the filtering equipment, the liquid flow metering module, the pretreatment module, the detection module, and the detection object discharge outlet; the detection module includes: a pH value detector, a phosphate detector, a chloride ion detector, an iron ion detector, and a conductivity detector.

2. The device according to claim 1, characterized in that The sampling valve, medium detection valve and sewage detection valve are ball valves.

3. The device according to claim 2, characterized in that The sampling valve, medium detection valve and sewage detection valve are pneumatic ball valves.

4. The device according to claim 3, characterized in that The filtering device is a duplex filter.

5. The device according to claim 4, characterized in that Pressure sensors are provided before and after the duplex filter.

6. The device according to claim 5, characterized in that The liquid flow metering module is provided with a flow regulating valve connected to the filtering device, the flow regulating valve is connected to the flow meter, and the flow meter is connected to the pre-processing module.

7. The device according to claim 6, characterized in that The flow meter is an electromagnetic flow meter or an ultrasonic flow meter.

8. The device according to claim 7, characterized in that The flow regulating valve is connected to the filtering device through the first inspection valve, the flow meter is connected to the pretreatment module through the second inspection valve, and a third inspection valve is bypassed and connected in parallel on the main channel connected by the first inspection valve, flow regulating valve, flow meter and second inspection valve.

9. The device according to claim 8, characterized in that The pretreatment module includes: a temperature regulator, a pressure regulator, a configuration dilution regulator, and a pre-dosing controller.

10. A method for online pollutant detection and corrosion protection of a urea catalytic hydrolyzer using the device according to claim 9, characterized in that: The steps of the method are as follows: Step 1, select the detection working condition: when the urea catalytic hydrolyzer is in the medium loading working condition, open the medium detection valve, close the sewage detection valve, and the medium input into the urea catalytic hydrolyzer is in the sampling state; When the urea catalytic hydrolyzer is in the sewage discharge working condition, the sewage discharge detection valve is opened, the medium detection valve is closed, and the discharge of the urea catalytic hydrolyzer is in the sampling state; Step 2, sampling: during the period between the input medium working condition or the sewage discharge working condition, the sampling valve is opened to sample the input medium or sewage to obtain a liquid sample; Step 3, pressurization and check valve: Turn on the booster pump to pressurize the liquid sample in the pipeline to meet the detection requirements, and use the check valve to maintain the pipeline pressure of the pressurized liquid sample; Step 4, filtration: Filter the liquid sample to remove solid particles in the liquid sample, and determine the degree of solid particle contamination in the liquid sample based on the pressure difference before and after the filter; Step 5, flow measurement: measuring the flow of the liquid sample; Step 6, pretreatment: adjust the liquid sample with inconsistent temperature and pressure, and configure, dilute and pre-dose the liquid sample according to the needs of the back-end detection module; Step 7, testing: testing the three ions that most significantly affect the operation of the urea catalytic hydrolyzer, including chloride ion, iron ion and phosphate content, as well as the pH value and conductivity of the liquid sample; Step 8, Analysis: By analyzing the test data, suggestions are made on adjusting the frequency of adding media and discharging pollutants according to different working conditions, so as to effectively control the internal corrosion and catalyst shortage of the catalytic hydrolyzer and ensure the normal operation of the urea catalytic hydrolyzer to the greatest extent.

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