Online pollutant detection device and method for urea catalytic hydrolyzer

Abstract

The invention relates to an online pollutant detection device and method for a urea catalytic hydrolyzer, and the device comprises a medium detection valve and a pollution discharge detection valve which are connected with a sampling valve. The monitoring valve is sequentially connected with 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 port; the detection module comprises a PH value detector, a phosphate detector, a chloride ion detector, an iron ion detector and a conductivity detector. A device capable of monitoring the conductivity, the PH value, phosphate, chloride ions and iron ions is connected to a medium inlet and a drain outlet of the urea catalytic hydrolyzer, a medium and discharged substances entering the urea catalytic hydrolyzer are detected in a time-sharing mode, and when it is detected that the quality of the medium entering the urea catalytic hydrolyzer is unstable, corresponding measures are taken, so that the quality of the medium entering the urea catalytic hydrolyzer is not stable. The influence is reduced. And when it is detected that harmful components in the discharged substances are increased, corresponding measures are taken to avoid damage to the hydrolyzer.

Description

Technical Field

[0001] The 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 generally have internal corrosion problems. 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 when preparing the urea solution is continuously enriched during the evaporation process of the urea catalytic hydrolyzer, causing serious corrosion of the equipment. The introduction of chloride ions is mainly related to the quality of the purchased urea granules and the water quality of the urea solution.

[0003] Another problem with existing urea catalytic hydrolyzers is that it is impossible to determine whether the sewage is clean: the sewage discharged by the urea catalytic hydrolyzer is mainly urea solution containing impurities. In order to avoid the volatilization of urea solution during the sewage discharge process and affect the working environment of the production site, the solution is generally transported directly to the wastewater pool through a pipeline, and the wastewater pool is generally closed. Under such conditions, it is generally impossible to intuitively observe whether the discharged urea solution still contains solid pollutants. Insufficient sewage discharge may cause equipment failure or reduced production efficiency.

[0004] Another problem with existing urea catalytic hydrolyzers is that the discharge of wastewater will take away the reaction catalyst. Since the urea catalytic hydrolyzer discharges wastewater directly into the urea solution in the reactor, it will not only take away harmful salts and insoluble pollutants, but also take away 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 coordinating unit load adjustment.

[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] In order 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 the sewage outlet of the urea catalytic hydrolyzer, monitor the medium and the discharge entering the urea catalytic hydrolyzer in time, analyze their components, thereby eliminating raw materials that may cause corrosion and monitoring whether the sewage is discharged cleanly and avoiding excessive discharge.

[0007] The object 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 a urea catalytic hydrolyzer and a sewage discharge detection valve connected to a sewage discharge port of the urea catalytic hydrolyzer, the medium detection valve and the sewage discharge detection valve are connected to a sampling valve, 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 port; the detection module comprises: a pH value 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, the flow regulating valve, the flow meter and the 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 of a urea catalytic hydrolyzer and anti-corrosion protection of a urea catalytic hydrolyzer using the above device, the steps of the method are as follows: Step 1, selecting a detection working condition: when the urea catalytic hydrolyzer is in a medium loading working condition, the medium detection valve is opened, the sewage detection valve is closed, and the medium input into the urea catalytic hydrolyzer is in a sampling state; when the urea catalytic hydrolyzer is in a sewage discharge working condition, the sewage detection valve is opened, the medium detection valve is closed, and the discharge from the urea catalytic hydrolyzer is in a sampling state; Step 2, sampling: during the period between the input medium working condition or the sewage 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: start 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: filtering the liquid sample to remove solid particles in the liquid sample, and judging 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 samples with inconsistent temperature and pressure, and configure dilution and pre-drug treatment for the liquid samples according to the needs of the back-end detection module; Step 7, detection: detecting 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; Step 8, analysis: by analyzing the test data, suggestions are made on adjusting the frequency of adding medium and discharging pollutants according to different working conditions, so as to effectively control the internal corrosion and catalyst shortage of the catalytic hydrolyzer, so as to ensure the normal operation of the urea catalytic hydrolyzer to the greatest extent.

[0017] The advantages and beneficial effects of the present invention are as follows: the present invention connects a device capable of monitoring conductivity, pH value, phosphate, chloride ion and iron ion to the medium inlet and sewage outlet of the urea catalytic hydrolyzer, and detects the medium and discharge entering the urea catalytic hydrolyzer in different time periods. 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 the harmful components in the discharge increase, corresponding measures are taken to avoid damage to the urea catalytic hydrolyzer. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0019] Figure 1 It is a connection diagram and a structural diagram of the device described in Example 1 of the present invention and a urea catalytic hydrolyzer; Figure 2 It is a flow chart of the method described in Embodiment 10 of the present invention. DETAILED DESCRIPTION

[0020] Embodiment 1: This embodiment is an online pollutant detection device for a urea catalytic hydrolyzer. Figure 1As shown. 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 the sewage detection valve are connected to the sampling valve 4, and the sampling valve is sequentially connected to the pipeline booster pump 5, the main channel check valve 6, the filtering device 7, the liquid flow metering module 8, the pretreatment module 9, the detection module 10, and the detection object discharge port 11; the detection module includes: a pH value 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.

[0021] The working principle of the urea catalytic hydrolyzer is to transport the prepared urea solution into the urea catalytic hydrolyzer through a pump. The urea solution is heated by a steam coil and the hydrolysis endothermic reaction in the hydrolyzer generates 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. By changing the urea decomposition reaction path, the reaction activation energy is reduced and the reaction is accelerated.

[0022] In actual operation, urea particles contain a certain degree of pollutants, including low-concentration metal ions, harmful salt components, calcium ions and other soluble salts accidentally introduced into the deionized water / hydrophobic water used to prepare the urea solution, and insoluble particles. As the equipment is put into operation for a longer period of time, the urea catalytic hydrolyzer needs to be regularly discharged.

[0023] The 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, and is mainly used to discharge the pollutants floating on the upper part or the 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, and 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.

[0024] At present, the frequency of sewage discharge from equipment is generally determined by 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 mode of operation also creates some hidden dangers to the stability of system operation.

[0025] The input medium and sewage discharge of the existing urea catalytic hydrolyzer have the following problems: 1) Corrosion problem inside the hydrolyzer: Through material corrosion tests on urea catalytic hydrolyzers by many manufacturers, it is found that the safe temperature for 316L material to withstand corrosion of ammonium carbamate is below 165°C, and the annual corrosion rate is below 0.08mm. The operating temperature of the urea catalytic hydrolyzer is not higher than 160°C, and generally serious corrosion should not occur. However, in many cases, the urea catalytic hydrolyzer has been operating for 1 to 2 years and has to replace the hydrolyzer coil. After sampling and research, this type of corrosion is generally caused by the presence of chloride ions in the urea solution. The small amount of chloride ions present when the urea solution is prepared is continuously enriched during the evaporation process of the urea catalytic hydrolyzer, causing serious corrosion of the equipment.

[0026] The introduction of chloride ions is mainly related to the quality of purchased urea granules and the water quality of urea solution. Therefore, the situation in each plant is different. 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.

[0027] 2) Unable to determine whether the sewage is clean: The sewage discharged by the urea catalytic hydrolyzer is mainly urea solution containing impurities. In order to avoid the volatilization of urea solution during the sewage discharge process and affect the working environment of the production site, the solution is generally transported directly to the wastewater pool through a pipeline, and the wastewater pool is generally closed. Under such conditions, it is generally impossible to visually observe whether the discharged urea solution still contains solid pollutants. Under the operating conditions of different plant areas, the sewage concentration of 400L / time may be sufficient for good operating conditions, but for enterprises with poor water quality and urea quality, insufficient sewage discharge may cause other equipment problems.

[0028] 3) Wastewater discharge will take 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 take away harmful salts and insoluble pollutants, but also the effective ingredient urea and reaction catalyst in the solution - 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 is reduced, which may cause a decrease in urea conversion rate, or increase steam consumption in the process of urgent unit load adjustment.

[0029] The device of this embodiment solves the above problem by connecting 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, so as to solve the corrosion protection problem of the urea catalytic hydrolyzer, whether the discharge is clean, and whether the catalyst is wasted.

[0030] In this embodiment, the medium input port and the sewage outlet of the urea catalytic hydrolyzer are connected to the detection facilities through the pipeline medium detection valve and the sewage detection valve. According to the working conditions of the urea catalytic hydrolyzer when inputting medium or discharging sewage, the medium input or sewage detection is selected by opening and closing the medium detection valve and the sewage detection valve.

[0031] The detection equipment consists of pipelines, multiple valves, aisle booster pumps, filtration equipment, pretreatment modules, detection modules and other parts, each of which has a corresponding function: The function of the sampling valve is to isolate the urea catalytic hydrolyzer and the detection facilities. The sampling valve is opened at the middle time of the input medium condition or the sewage condition, and the medium entering the urea catalytic hydrolyzer or the sewage of the urea catalytic hydrolyzer is sampled through the branch pipe entering the detection facility and sent to the subsequent detection facilities.

[0032] The main function of the pipeline booster pump is to increase the pressure of liquid samples with insufficient pressure. In the urea catalytic hydrolyzer, urea solution and hydrolysis catalyst have dedicated delivery pumps, and their medium pressure meets the requirements of delivery to the detection facilities, so there is no need for boosting. During the sewage discharge process of the urea catalytic hydrolyzer, the pressure inside the urea catalytic hydrolyzer is between 0.4 and 0.55 MPa, which also meets the requirements of the detection facilities. However, desalted water is generally transported by the owner's pipeline for use, and the pressure reaching the urea catalytic hydrolyzer may not meet the detection needs. Therefore, a booster pump is set to increase the pressure of desalted water or other media that may be underpressured.

[0033] The main function of the main channel check valve is to prevent accidental backflow of the rear-end liquid sample and interfere with the detection effect.

[0034] The main function of the filtration equipment is to filter solid impurities from the liquid samples extracted during the sewage discharge process to avoid damage to the precision testing instruments. The filtration equipment can adopt a double filter type, and the filter element can be replaced online. The replacement of the filter element does not affect the continuous operation of the equipment. The inlet and outlet of the filtration equipment are respectively equipped with pressure detection devices, which can effectively observe the solid impurities in the sewage discharge. Once the pressure at the rear end of the filter is reduced, it means that the filter is blocked by solid impurities, indicating that the sewage discharge needs to be enhanced.

[0035] The main function of the liquid flow metering module is to measure and adjust the flow of the extracted test liquid sample. Generally, a high-precision electromagnetic flowmeter or ultrasonic flowmeter can be used to control the flow of the liquid sample sent to the back-end pretreatment module, and to verify the pollutant concentration. At the same time, the flow of a single sewage discharge from the urea catalytic hydrolyzer is measured, and the actual sewage discharge volume is determined in combination with the sewage discharge time. Since the detection process requires the precise knowledge of the volume and mass of the solution sent to the back-end detection instrument, the combination of the regulating valve + flowmeter is used to quantify the liquid sample sent to the detection module, so that the concentration of the pollutant can be calculated after the pollutant content is determined.

[0036] The main function of the pretreatment module is to adjust the liquid samples with inconsistent temperature and pressure, and configure dilution and pre-dosing according to the needs of the back-end detection module. Since the detection module contains multiple detection items and each detection item has different temperature and concentration requirements, some detection instruments or detection items also need to add reagents according to various different operating requirements. The pretreatment module can complete these adjustments to the solution samples.

[0037] The main function of the detection module is to detect the composition of the liquid sample. The three ions that have the most significant impact on the operation of the urea catalytic hydrolyzer are detected, including chloride ions, iron ions and phosphates, as well as liquid characteristic parameters such as the pH value and conductivity of the liquid sample. By detecting the presence of different ions and the characteristic parameters of the liquid sample, problems such as internal corrosion and catalyst shortage in the catalytic hydrolyzer can be effectively controlled.

[0038] The liquid sample that has passed through the testing facility can be returned to the urea catalytic hydrolyzer if it is in the medium adding condition; if it is in the sewage discharge condition, the liquid sample can continue to be discharged into the wastewater pool for unified decontamination and then discharged without pollution.

[0039] This embodiment may also include a module specifically used 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 situations, and makes suggestions for sewage discharge.

[0040] Embodiment 2: This embodiment is an improvement of the first embodiment, and is a refinement of the first embodiment regarding the monitoring valve, the medium detection valve, and the sewage detection valve. The monitoring valve, the medium detection valve, and the sewage detection valve described in this embodiment are ball valves.

[0041] The ball valve has a tight seal, which is beneficial for sampling in situations where precise control is required.

[0042] Embodiment three: 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.

[0043] 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.

[0044] Embodiment 4: This embodiment is an improvement of the above embodiment, and is a refinement of the filtering device in the above embodiment. The filtering device described in this embodiment is a double filter.

[0045] 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.

[0046] Pressure sensors can be installed at the inlet and outlet of the filter to measure the pressure difference before and after the filter.

[0047] Embodiment five: This embodiment is an improvement of the above embodiment, and is a refinement of the above embodiment regarding the double filter. Pressure sensors are arranged before and after the double filter described in this embodiment.

[0048] The pressure sensor can be a pressure gauge or other electronic pressure sensing element. The pressure sensor is used to observe the solid impurities in the sewage. The increase in the pressure difference between the front and rear ends of the filter indicates that the filter is blocked by solid impurities. Based on this pressure difference, it can be used to judge the quality of the input medium and the sewage discharge volume as a basis for increasing the number of discharges.

[0049] Embodiment six: 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.

[0050] 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.

[0051] Embodiment seven: This embodiment is an improvement of the above embodiment, and is a refinement of the above embodiment regarding the flow meter. The flow meter described in this embodiment is an electromagnetic flow meter or an ultrasonic flow meter.

[0052] 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.

[0053] Embodiment eight: This embodiment is an improvement of the above embodiment and a refinement of the above embodiment regarding the flow meter. The flow regulating valve in this embodiment is connected to the filtering device through the first inspection valve 8.3, the flow meter is connected to the pre-processing module through the second inspection valve 8.4, and the third inspection valve 8.5 is bypassed and connected in parallel on the main channel connected with the first inspection valve, the flow regulating valve, the flow meter and the second inspection valve. Figure 1 shown.

[0054] 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.

[0055] Embodiment nine: This embodiment is an improvement of the above embodiment, and is a refinement of the pretreatment module of the above embodiment. The pretreatment module described in this embodiment includes: a temperature regulator, a pressure regulator, a dilution regulator, and a pre-dosing controller.

[0056] 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, so it is necessary to fine-tune the flow rate of the liquid sample to ensure the accuracy of the measurement. The 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 in 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.

[0057] Embodiment ten: 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: Step 1, select the detection working condition: when the urea catalytic hydrolyzer is in the working condition of adding medium, open the medium detection valve, close the sewage detection valve, and the medium input into the urea catalytic hydrolyzer is in a sampling state; when the urea catalytic hydrolyzer is in the sewage condition, open the sewage detection valve, close the medium detection valve, and the discharge of the urea catalytic hydrolyzer is in a sampling state.

[0058] 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.

[0059] Step 2, sampling: During the period between the input medium working condition or the sewage working condition, open the sampling valve, sample the input medium or sewage, and obtain a liquid sample.

[0060] The 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 opened to sample the input medium or sewage, and the sampling is carried out uninterruptedly during the working condition until the medium input condition comes to an end, that is, the sampling and online measurement are ended before the input medium ends. In the sewage condition, sampling is also started after the sewage starts, and sampling is stopped when it is found that the dirt has been reduced to a certain level.

[0061] 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.

[0062] The function of pipeline pressurization is to pressurize the medium with insufficient pressure. In the urea catalytic hydrolyzer, urea solution and hydrolysis catalyst have dedicated delivery pumps, and their medium pressure meets the delivery requirements, so there is no need for pressurization. During the sewage discharge process of the urea catalytic hydrolyzer, the pressure in the hydrolyzer is between 0.4 and 0.55 MPa, and the sewage liquid can be fully discharged for testing; but desalted water is generally transported by the owner's pipeline for use, and the pressure reaching the urea catalytic hydrolyzer may not meet the detection needs. Therefore, a booster pump is set to pressurize the desalted water or other media that may be underpressured. After pressurization, prevent the liquid sample from flowing back.

[0063] 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.

[0064] This step is an important part of testing the quality of the input medium in the working condition of the input medium. In the working condition of the medium input, 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.

[0065] Step 5, flow measurement: perform flow measurement on the liquid sample.

[0066] 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.

[0067] Step 6, pretreatment: adjust the liquid samples with inconsistent temperature and pressure, and configure dilution and pre-drug treatment for the liquid samples according to the needs of the back-end detection module.

[0068] This step is to adjust the liquid sample with inconsistent temperature and pressure before measuring the liquid sample, and configure dilution and pre-dosing treatment according to the needs of the back-end detection module.

[0069] 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.

[0070] The detection of three ions in liquid samples and the detection of pH value and conductivity can be carried out by special detection instruments. Since it is an online detection, the detection process of various instruments must be very fast and quick.

[0071] The object of pH and conductivity (no flow metering required) detection is the discharge drain of the urea catalytic hydrolysis system (the drain discharged after steam heat exchange). Since the drain only flows inside the heat exchange tube of the urea catalytic hydrolysis system and does not directly contact the urea solution, the drain should be neutral with a pH value between 5 and 7 under normal conditions, and the conductivity (the sample needs to be cooled to 25°C) should be between 0.01 and 1.0 mS / m. However, once the pH value of the drain is detected to increase to alkaline and the conductivity increases, it means that pitting corrosion may occur in the heat exchange tube, and urea solution enters the drain in the heat exchange tube, which means that the heat exchange tube needs to be maintained.

[0072] The objects of chloride ion detection include: (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 patterns and discharge volumes 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 degree of corrosion of ammonium carbamate is very small under the operating condition of 140°C, which is within the consideration range of the wall corrosion margin, 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, which can reduce the frequency and amount of sewage discharge (because sewage discharge will take away the catalyst, and sewage treatment also needs to be considered).

[0073] (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. After the chloride ions in the urea granules are configured into a solution, they enter the system. 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: i. Replace urea granules. But this takes time and cycles, and may not be achieved immediately. ii. Increase the frequency of sewage discharge and strictly monitor the concentration of discharged chloride ions. This can avoid serious chloride ion enrichment, which can cause corrosion to equipment.

[0074] The object of phosphate + flow detection is the regular sewage discharge of urea catalytic hydrolysis system. The purpose of sewage discharge is to discharge chloride ions, accumulated solid impurities, biuret by-products generated by the reaction, etc., but at the same time, a 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-mounted 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).

[0075] 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, it means that the heat exchange tube has been corroded and penetrated, but under non-extreme 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 to the initial operation stage, it means that corrosion has occurred. Through long-term monitoring of the iron ion concentration, once an abnormal fluctuation occurs, it means that serious corrosion has occurred, and it is necessary to consider the inspection and maintenance of the equipment in the urea catalytic hydrolysis system.

[0076] Step 8, analysis: by analyzing the test data, suggestions are made on adjusting the frequency of adding medium and discharging pollutants according to different working conditions, so as to effectively control the internal corrosion and catalyst shortage of the catalytic hydrolyzer, so as to ensure the normal operation of the urea catalytic hydrolyzer to the greatest extent.

[0077] The analysis is performed for two operating conditions: 1. Working conditions for adding medium: During the process of adding the medium, the main function of this embodiment is to detect the pollutants that may be entrained by the added medium, mainly monitoring the chloride ions and solid particles that may be brought in.

[0078] When adding urea solution, if the quality of 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.

[0079] 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.

[0080] When adding catalyst solution, the catalyst concentration and emission in the wastewater are detected through the urea catalytic hydrolyzer, and the catalyst content reduced due to wastewater is automatically calculated, so as to carry out quantitative addition of catalyst.

[0081] 2. System sewage discharge conditions: The system sewage discharge is mainly related to the pollutants in the installed medium. When the pollutant concentration in the installed medium does not exceed the standard, the sewage discharge can be carried out 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 content in the sewage is judged by the differential pressure measuring points before and after the filter device.

[0082] The purpose of phosphate detection is to calculate the catalyst content carried away in the sewage discharge. The phosphate content carried by the sewage discharge is calculated through the sewage discharge volume and phosphate concentration. After the sewage discharge is completed, the catalyst skid is intelligently interlocked to replenish the catalyst loss in the sewage discharge. 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 added medium chloride ions should be strictly controlled. The detection of iron ions is mainly used to detect whether serious corrosion actually occurs in the 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 is corroded, it is easy to cause steam leakage, and once the reactor shell is responsible, it is easy to cause overall damage to the equipment. 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 inspected. The inspection frequency is low, and it requires a lot of manpower and time. Therefore, the method described in this embodiment can detect the iron ion concentration in the hydrolyzer, such as the increase of the iron ion concentration, and can effectively predict whether serious corrosion occurs in the reactor.

[0083] Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention is described in detail with reference to the preferred arrangement scheme, a person skilled in the art should understand that the technical solution of the present invention (such as the form of the urea catalytic hydrolyzer, the processing 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. A urea catalytic hydrolyzer online pollutant detection device, 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 monitoring 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 port; 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 monitoring valve, medium detection valve and sewage detection valve are ball valves.

3. The device according to claim 2, characterized in that The monitoring 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 double filter.

5. The device according to claim 4, characterized in that The double filter is provided with pressure sensors before and after.

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, the flow regulating valve, the flow meter and the second inspection valve.

9. The device according to claim 8, characterized in that The pretreatment module comprises: a temperature regulator, a pressure regulator, a 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 of 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 working condition of adding medium, 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 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 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: start 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: filtering the liquid sample to remove solid particles in the liquid sample, and judging 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 samples with inconsistent temperature and pressure, and configure dilution and pre-drug treatment for the liquid samples according to the needs of the back-end detection module; Step 7, detection: detecting 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; Step 8, analysis: by analyzing the test data, suggestions are made on adjusting the frequency of adding medium and discharging pollutants according to different working conditions, so as to effectively control the internal corrosion and catalyst shortage of the catalytic hydrolyzer, so as to ensure the normal operation of the urea catalytic hydrolyzer to the greatest extent.

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