Method for real-time component monitoring of manheim potash production tail gas

Abstract

The present application belongs to the technical field of component analysis, and relates to a real-time component monitoring method for tail gas of a Mannheim potassium fertilizer production process, comprising the following steps: a light source end emits a test light beam containing a target absorption wavelength and a non-absorption reference wavelength to penetrate a to-be-measured flow field; a transient heating unit applies a periodic heating pulse to a measurement area, so that sulfuric acid mist droplets are gasified to form a transient gas phase environment; a receiving end collects time sequence data of transmitted light intensity, extracts reference light intensity and transient light intensity before and after the application of the heating pulse; a gasification compensation factor is determined according to the light intensity change of the non-absorption reference wavelength, the transient light intensity is corrected, and the concentration of hydrogen chloride is calculated. The present application uses a thermodynamic mechanism to eliminate scattering interference caused by liquid phase droplets in situ, solves the problem of response lag caused by physical filtration and equipment corrosion, ensures the fidelity of component detection under strong corrosion and multiphase flow conditions, and improves monitoring efficiency.

Description

Technical Field

[0001] This invention belongs to the field of component analysis technology, and in particular relates to a method for real-time component monitoring of exhaust gas from Mannheim potash fertilizer production. Background Technology

[0002] The current Mannheim process for producing potassium sulfate produces hydrogen chloride as a byproduct. To adjust the feed ratio to the reactor, it is necessary to monitor the concentration of hydrogen chloride in the exhaust pipe in real time. Tunable semiconductor laser absorption spectroscopy has the physical characteristics of high selectivity and non-contact measurement, and is a commonly used method for gas concentration analysis in this field. The exhaust gas from the Mannheim reactor is a high-temperature and highly corrosive multiphase flow environment, containing gaseous hydrogen chloride and liquid sulfuric acid aerosol. Mie scattering generated by liquid particles interferes with the narrow-band absorption characteristics of gaseous molecules. Conventional solutions use multi-stage corrosion-resistant filter elements and high-temperature heat tracing pipelines to construct an extraction pretreatment system to physically separate sulfuric acid aerosol.

[0003] Sulfuric acid aerosols cause capillary condensation at the pores of the physical filter element, leading to filter blockage and salt accumulation. The heated pipeline and filter interface form a gas concentration buffer space. Hydrogen chloride molecules undergo adsorption and desorption on the filter fibers and inner walls of the pipeline. The dynamic equilibrium process generated by this adsorption and desorption offsets the transient fluctuations in exhaust gas concentration, resulting in a lag in the measurement signal response. Simply increasing the purging pressure or raising the heating temperature accelerates the equipment corrosion rate and cannot eliminate the inherent transmission delay caused by the physical sampling path. At the hardware level, limitations exist due to the physical filtration architecture, and the software control methods also have shortcomings. For example, the authorization announcement number CN10551026... The Chinese invention patent 0B discloses a differential absorption lidar CO2 detection method based on aerosol perturbation correction. It corrects the perturbation of the detection results by establishing a linear empirical relationship of aerosol characteristics between different wavelengths. Under the conditions of Mannheim production exhaust gas, the mass load of sulfuric acid mist droplets is far greater than that of the atmospheric environment and the phase distribution is unstable. Simply relying on cross-wavelength linear fitting or statistical correction is difficult to eliminate the deep obscuring of narrowband absorption characteristics by Mie scattering generated by high-concentration liquid particles. It lacks phase transition support at the physical mechanism level. When the lightweight correction model for open atmosphere is used to process industrial-grade high-concentration acid mist, the inversion results produce nonlinear distortion and cannot guarantee the fidelity of monitoring data.

[0004] Therefore, the technical problem to be solved by this invention is how to drive the phase change of the medium through a transient thermal excitation field in order to strip away the scattering interference generated by sulfuric acid aerosol without changing the physical configuration of the flow field. Summary of the Invention

[0005] The present invention aims to solve the problems of delayed response of measurement signals generated by physical filtering in existing technologies and high maintenance frequency in corrosive environments.

[0006] In this technical solution, a method for real-time component monitoring of exhaust gas from Mannheim potash fertilizer production is implemented through a light source, a receiver, and a transient heating unit, and includes the following steps:

[0007] Step S101: A test beam containing the target absorption wavelength and the non-absorption reference wavelength is synchronously emitted from the light source end into the flow field to be tested inside the pipe; the flow field to be tested contains hydrogen chloride gas and sulfuric acid droplets.

[0008] Step S102: The transient heating unit applies periodic transient heating pulses to the measurement area covered by the test beam to vaporize the sulfuric acid droplets in the measurement area, wherein the pulse width of the transient heating pulse is 10ms to 50ms.

[0009] Step S103: The receiver collects the transmission light intensity time series data of the test beam under the action of the transient heating pulse; Step S104: Extract the first reference light intensity before the application of the transient heating pulse and the second transient light intensity under the sulfuric acid droplet vaporization state from the transmission light intensity time series data.

[0010] Step S105: Determine the vaporization compensation factor based on the transmittance jump ratio before and after the transient heating pulse at the non-absorption reference wavelength.

[0011] Step S106: The second transient light intensity is corrected using a vaporization compensation factor, and the real-time concentration of hydrogen chloride is calculated based on the ratio of the corrected second transient light intensity to the first reference light intensity; the negative natural logarithm of the ratio is positively correlated with the real-time concentration of hydrogen chloride.

[0012] Preferably, step S102 further includes the following sub-steps: step S1021, setting the trigger frequency of the transient heating pulse according to the flow rate in the pipe; step S1022, adjusting the angle between the emission axis of the transient heating pulse and the propagation axis of the test beam to 5° to 15°, so that the thermal effect area covers the measurement area.

[0013] Preferably, in step S102, the peak energy density of the transient heating pulse is greater than the latent heat of vaporization of the sulfuric acid droplets, so that the sulfuric acid droplets are converted into a gaseous state within the pulse width period of the transient heating pulse.

[0014] Preferably, step S101 further includes the following sub-steps: step S1011, setting a protective air curtain inside the light source end and the receiver end; step S1012, spraying dry nitrogen gas into the pipe from the protective air curtain to form a laminar flow protective layer on the surface of the optical window.

[0015] Preferably, step S1012 further includes the following sub-steps: step S10121, extracting the falling edge signal of the transient heating pulse; step S10122, increasing the gas supply pressure of the protective air curtain to the purging pressure within a preset time after the falling edge signal is generated; wherein, the duration of the purging pressure avoids the sulfuric acid droplet vaporization state in step S104.

[0016] Preferably, in step S105, the gasification compensation factor The light intensity value of the non-absorption reference wavelength after the sulfuric acid droplets are vaporized is calculated by dividing the light intensity value of the sulfuric acid droplets before vaporization.

[0017] Preferably, in step S106, the absorption spectral intensity of hydrogen chloride molecules is corrected based on the real-time temperature within the measurement area to determine the real-time concentration of hydrogen chloride.

[0018] Preferably, in step S101, the target absorption wavelength is 1742 nm; the non-absorption reference wavelength is selected between 1730 nm and 1735 nm.

[0019] Preferably, after step S106, a self-calibration step is also included: monitoring the fluctuation frequency of the real-time concentration of hydrogen chloride; when the fluctuation frequency exceeds a preset threshold, increasing the electrical power of the transient heating pulse in step S102.

[0020] Compared with existing technologies, the real-time component monitoring method for Mannheim potash fertilizer production tail gas of the present invention has the following advantages:

[0021] 1. In real-time component monitoring of exhaust gas from Mannheim potash fertilizer production, the transient thermal pulse-induced medium phase change mechanism is used to eliminate signal hysteresis caused by physical sampling. Traditional technology relies on physical filters to intercept acid mist, resulting in significant adsorption and desorption effects of hydrogen chloride molecules in the filter pores and sampling pipelines, forming a concentration signal buffer that is difficult to eliminate. This invention injects millisecond-level thermal excitation into the in-situ test optical path, causing the sulfuric acid aerosol in the optical path to undergo in-situ instantaneous vaporization. This state modulation logic driven by thermodynamic phase change shifts the testing process from physical separation in the spatial dimension to signal differential decoupling in the temporal dimension, avoiding the dynamic response delay caused by complex pre-processing flow paths, and enabling the real fluctuations of exhaust gas components to be reflected in the temporal changes of transmitted light intensity in real time.

[0022] 2. Based on the time-domain linkage of the signal wavelength and the reference wavelength, adaptive stripping of multiphase interference signals is achieved. This invention does not passively filter acid mist, but constructs a physical counterbalancing closed loop for aerosol Mie scattering through real-time transmission feedback of dual-wavelength coaxial beams. The jump slope of the reference wavelength transmittance measures the physical degree of liquid-phase particle to gas phase conversion in real time and participates in the concentration inversion process of the signal wavelength as a normalization factor. This cross-signal dimension collaborative calculation logic isolates the superposition interference of scattering background on molecular absorption spectrum from the physical mechanism level without destroying the in-situ coexistence state of the flow field, ensuring the objectivity and fidelity of concentration analysis results under non-ideal conditions such as strong acid and high aerosol.

[0023] 3. By using the phase interlocking logic of the thermal excitation pulse and the protective air curtain, the continuous cleanliness and zero dilution interference of the optical detection interface are ensured. This invention establishes a purging control strategy that is highly coupled with the thermophysical process. The system extracts the falling edge signal of the thermal pulse as the trigger origin. At a specific phase point when the vaporized medium enters the initial stage of the cooling phase change, a millisecond-level high-pressure pulse purging is initiated. This coordinated action chain ensures that the maintenance action completely avoids the effective window period of signal acquisition. The fluid dynamic pressure difference is used to achieve physical stripping of the window attachments, while avoiding the dilution and contamination of the intrinsic concentration of the local flow field by the purging gas. This deep cohesion between the monitoring mechanism and the protective structure maintains the long-term steady state of the optical components in extreme corrosive environments. Attached Figure Description

[0024] Figure 1 This is a flowchart of the steps of the real-time monitoring method for hydrogen chloride in Mannheim exhaust gas according to the present invention;

[0025] Figure 2 This is a functional architecture and signal interaction diagram of the real-time monitoring system of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0027] It should be noted that all directional and positional terms used in this invention, such as: up, down, left, right, front, back, vertical, horizontal, inner, outer, top, bottom, transverse, longitudinal, center, etc., are only used to explain the relative positional relationship and connection between components in a specific state (as shown in the accompanying drawings). They are only for the convenience of describing this invention and do not require that this invention be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention. In addition, the descriptions of "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0028] In the description of this invention, unless otherwise explicitly specified and limited, the terms installation, connection, and linking should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal connection of two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0029] In the description of this specification, references to the terms "an embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example, and the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0030] A real-time component monitoring method for exhaust gas from Mannheim potash fertilizer production comprises a light source, a receiver, and a transient heating unit operating in concert. The light source emits a coaxial dual-wavelength test beam containing a target absorption wavelength and a non-absorption reference wavelength into the test flow field within the exhaust gas pipeline. The test flow field consists of hydrogen chloride gas and sulfuric acid droplets. The transient heating unit applies periodic transient heating pulses to the measurement area covered by the test beam, driving the sulfuric acid droplets within the measurement area to undergo phase change vaporization. The receiver collects the time-series data of the transmitted light intensity after the test beam penetrates the measurement area, extracts the first reference light intensity before the application of the transient heating pulse and the second transient light intensity under the sulfuric acid droplet vaporization state, and determines the vaporization compensation factor based on the transmittance change of the non-absorption reference wavelength before and after the transient heating pulse. The vaporization compensation factor is used to correct the second transient light intensity, and the real-time concentration of hydrogen chloride gas is calculated.

[0031] The light source uses a tunable semiconductor laser with a target absorption wavelength of 1742nm and a non-absorption reference wavelength selected in the range of 1730nm to 1735nm. The sulfuric acid droplets in the flow field under test produce Mie scattering loss on the test beams of the above two wavelengths, while only hydrogen chloride gas molecules produce characteristic spectral absorption at the target absorption wavelength of 1742nm. The light source couples the lasers of the two wavelengths to a coaxial collimator through an optical fiber combiner to generate a test beam with a single propagation axis.

[0032] The transient heating unit is located on the side wall of the exhaust gas duct, with its emission axis intersecting the propagation axis of the test beam at an angle of 5° to 15°. This ensures that the core area of ​​the thermal effect covers the detection field of view of the receiving end. The transient heating unit uses a high-power infrared semiconductor laser array as the heat source, with its output wavelength selected in the strong absorption band of sulfuric acid molecules (such as 9.6μm or 10.6μm) to achieve efficient coupling of thermal energy to liquid droplets. The unit integrates a high-energy capacitor array and an IGBT high-speed switching circuit. By receiving the drive level signal sent by the remote computing decision node, it controls the capacitor array to discharge to the laser array within milliseconds, thereby generating a transient thermal radiation pulse with a peak power reaching the kilowatt level. The defocused beam emitted by the laser array, after being collimated and focused by a lens group, forms a thermal excitation field covering the radial cross-section of the test beam, ensuring that the fluid microparticles in the measurement area can acquire enough energy to overcome the latent heat of vaporization in a very short time. The transient heating pulse generated by the transient heating unit has a pulse width of 10ms to 50ms, and the pulse frequency is synchronized with the sampling frequency of the receiving end. The peak power of the pulse is determined by the latent heat of vaporization of sulfuric acid and the preset mass concentration of sulfuric acid droplets in the flow field under test. When the transient heating pulse acts on the measurement area, the sulfuric acid droplets are heated and change from liquid to gas. In terms of physical mechanism, the peak energy density of the transient heating pulse is set to enable the droplet group with the highest volume in the measurement area to reach the boiling point within milliseconds. Since the transient thermal excitation field only acts on the local micro-area (usually 10mm to 30mm in diameter) through which the test beam passes, the required absolute energy value is limited to the rated output range of the thermal excitation unit. When the thermal pulse is injected into the flow field, the surface of the liquid sulfuric acid droplets rapidly absorbs photon energy and generates a superheating effect. Through thermal conduction, explosive vaporization is triggered from the surface to the inside. Since the pulse width is controlled between 10ms and 50ms, this time scale is much smaller than the characteristic time for the fluid micro-particles to pass through the measurement area. Therefore, it can be ensured that the phase change is completed before the droplets migrate out of the detection field of view with the airflow, thus forming a pure gas phase optical observation window in the time domain. This supports the feasibility of eliminating Mie scattering in situ using thermodynamic mechanisms from a physical perspective.

[0033] In the transmitted light intensity time-series data collected by the receiver, the first reference light intensity is the light intensity value before the application of the transient heating pulse, including droplet scattering loss; the second transient light intensity is the light intensity value after the pulse reaches its peak power and the sulfuric acid droplets in the measurement area are completely vaporized. The receiver simultaneously extracts the light intensity change of the non-absorption reference wavelength before and after the pulse and calculates the vaporization compensation factor. The calculation formula for the vaporization compensation factor is as follows: ,in, As a gasification compensation factor, The transmitted light intensity at the non-absorption reference wavelength before the application of the transient heating pulse. The transmitted light intensity is the non-absorption reference wavelength in the vaporized state of sulfuric acid droplets.

[0034] The real-time concentration of hydrogen chloride gas is obtained by converting absorbance, and the vaporization compensation factor is then obtained. Then, the liquid phase scattering component is stripped away by modifying the second transient light intensity. The formula for calculating the absorbance is as follows: ,in, The intrinsic absorbance of hydrogen chloride gas is given. The first reference light intensity at the target absorption wavelength before the application of the transient heating pulse. The second transient light intensity at the target absorption wavelength during the sulfuric acid droplet vaporization state. The system's inherent background absorbance is used as the basis for determining the real-time concentration, which is determined by the Lambert-Beer law. The gas absorption cross section and effective optical path length are calculated.

[0035] Both the light source and receiver detection windows are equipped with protective air curtains. These air curtains continuously inject dry nitrogen gas into the exhaust pipe, forming a laminar protective layer on the window surface with a pressure greater than that of the pipe. The receiver monitors a steady-state reference for the transmitted light intensity time-series data. When the first reference light intensity... When the attenuation exceeds the preset threshold, the system triggers the high-pressure purging mode, instantly increasing the nitrogen flow rate to remove acidic deposits from the viewing window surface.

[0036] Reference value for purge pressure of protective air curtain and purging delay time Based on fluid dynamics parameters, the processing unit obtains the inner diameter of the exhaust pipe. With real-time flow rate And use sensors to read the total pressure inside the pipeline. With exhaust gas density The local static pressure at the detection window was calculated based on Bernoulli's equation. The system sets the purging pressure baseline value. Constantly greater than local static pressure Preset differential pressure value, purging delay time According to the formula Calculate, where, To protect the flow distance from the air curtain nozzle to the propagation axis of the test beam, For real-time flow rate, this delay time ensures that pressure fluctuations generated by the purge airflow are expelled from the detection field of view before the vaporization sampling action begins.

[0037] The transient heating unit has a power adaptive adjustment function, and the receiver monitors the vaporization compensation factor in real time. The fluctuation, if during the transient heating pulse, the vaporization compensation factor The absence of a flat segment in the timing waveform indicates that the current heat is insufficient to completely vaporize the sulfuric acid droplets in the measurement area. At this point, the system automatically increases the driving voltage of the transient heating unit, causing the peak energy density of the transient heating pulse to increase until the vaporization compensation factor... The system is restored to a preset saturated and stable state to ensure measurement accuracy under different acid mist load conditions.

[0038] Example 1: When the system faces a multiphase flow condition where fluctuations in the feed to the Mannheim reactor cause a rapid increase in the concentration of sulfuric acid droplets in the tail gas pipeline, the measurement path based on extraction filtration fails due to droplets adhering to the filter element. Furthermore, the high-density liquid aerosol in the pipeline induces Mie scattering, causing broadband attenuation of the optical signal penetrating the flow field and masking the absorption characteristics of the target gas. To address the technical contradiction between liquid-phase scattering interference and concentration analysis, the monitoring system abandons physical flow-blocking components. Instead, it simultaneously emits a coaxial test beam from the light source end into the flow field under test within the pipeline, consisting of a target absorption wavelength of 1742 nm and a non-absorption reference wavelength in the range of 1730 nm to 1735 nm. This beam is simultaneously positioned within the pipeline... The transient heating unit on the sidewall applies transient heating pulses with a pulse width between 10ms and 50ms to the measurement area covered by the test beam in a rhythm synchronized with the sampling frequency of the receiver. The peak energy density of the transient heating pulse is output according to the preset sulfuric acid droplet mass concentration calibration value, causing the liquid sulfuric acid droplets in the radiation area to absorb heat and cross the latent heat of vaporization threshold, thus inducing a brief gas phase optical channel in situ within the local space of the test optical path. Under the condition of maintaining the physical topology of the global flow field, the optical detection boundary is reconstructed. According to the spatial displacement law of fluid particles in fluid mechanics, in order to ensure that the fluid particles are completely updated in adjacent measurement cycles, the processing unit obtains the diameter of the detection spot of the test beam. Real-time flow rate inside the pipe The processing unit sets the transient heating pulse trigger frequency. Satisfying the relation ,in, To set the spatial dispersion constant, the controller receives frequency commands and outputs underlying drive level signals to synchronously control the pulse emission rhythm of the transient heating unit.

[0039] Within the time-domain window of the transient heating pulse reconstructing the measurement boundary, the dual-wavelength beam emitted from the light source forms a multi-field coupling response with the thermal excitation mechanism. The receiver continuously acquires the time-series data of the transmitted light intensity penetrating the measurement area, from which the first reference light intensity, including droplet scattering loss, is extracted before the transient heating pulse is applied. And the second transient light intensity when the pulse reaches its peak and the sulfuric acid droplets are in a vaporized state. The processing unit synchronously extracts the first reference light intensity of the non-absorption reference wavelength before and after the pulse is applied. With the second reference light intensity According to the formula Determine the gasification compensation factor The non-absorption reference wavelength avoids the absorption peak of hydrogen chloride molecules, and its transmittance jump is directly reflected by the liquid phase scattering cross-section elimination ratio induced by the thermal pulse. The processing unit will use the vaporization compensation factor. Importing the attenuation calculation logic into the target wavelength, according to the formula Calculate the intrinsic absorbance of hydrogen chloride gas after removing the gasification ratio error. ,in, The system's intrinsic background absorbance is determined by the Lambert-Beer law. By combining the gas absorption cross-section and effective optical path length to convert into the real-time concentration of hydrogen chloride gas, and utilizing thermodynamic phase transitions and the temporal evolution of dual-wavelength differential optics to eliminate multiple interference errors in the liquid phase, the computational processor separates the attenuation amount based on the Lambert-Beer law and Mie scattering theory for complex multiphase flow backgrounds. The computational processor then reads the initial non-absorption reference light intensity pre-stored in the storage medium. Extract the first reference light intensity containing the overall attenuation of the target absorption wavelength before pulse application. Extract the first reference light intensity of the non-absorption reference wavelength before and after the application of the transient heating pulse. With the second reference light intensity The processing unit is based on the formula Perform cross-decoupling calculations and output the pure gas phase intrinsic absorbance after stripping away scattering interference. In practical calculations, the formula reflects the use of the transmittance jump at the non-absorbing reference wavelength to compensate in real time for the Mie scattering effect on the target absorption wavelength. This is the initial emitted light intensity reference value pre-calibrated by the system under conditions of no test medium and no droplet interference. Since the scattering cross-sections of liquid sulfuric acid droplets at the target wavelength (1742nm) and the reference wavelength (1730-1735nm) are very similar, the ratio... (i.e., the vaporization compensation factor C) can accurately reflect the proportion of transmittance increase brought about by droplet vaporization. By substituting this proportion factor into the light intensity comparison of the target wavelength, the algorithm can... The portion of the transient light intensity (in the vaporized state) increased due to liquid phase elimination is normalized to match the normalized value. (Reference intensity) Differentiation is performed under the same scattering background reference to cancel out the complex Mie scattering background within the pipe, extracting the narrowband absorption contribution purely generated by hydrogen chloride molecules. To determine the system's inherent background absorbance, and based on the nonlinear dependence of molecular spectral absorption line shapes on thermodynamic states, the computational processor calibrates the spectral line intensity according to the Boltzmann distribution law. Simultaneously, the processor acquires real-time flow field temperature data from the temperature sensor. Set up reference temperature Subscript line strength According to the formula Calculate transient linear intensity ,in, The energy level for the low-level transition of the target molecule. The system uses the intrinsic absorbance constant, which is the Boltzmann constant. With transient line strength Algebraic conversion is performed to output the final real-time concentration of hydrogen chloride.

[0040] To address the boundary state where drastic fluctuations in the flow velocity within the pipeline result in insufficient transient heat flux to maintain adequate vaporization, the receiving end continuously monitors the vaporization compensation factor. Assess the effectiveness of thermal intervention by analyzing the temporal evolution characteristics, when gasification compensation factors are identified. If a flat saturation waveform is not reached and maintained within the transient heating pulse's effective range, the current phase change volume is determined to be substandard. The processing unit then outputs a control signal to increase the driving voltage of the transient heating unit, thereby gradually raising the peak energy density of subsequent transient heating pulses. Simultaneously, the protective air curtain distributed inside the detection window adjusts according to the first reference light intensity. The continuous attenuation slope instantaneously increases the supply pressure of dry nitrogen, establishing a laminar purging barrier inside the exhaust pipe to resist the cooling and condensation of acidic vapors. Under the condition of offsetting the risk of physical adhesion and dynamically calibrating the liquid phase scattering background, the system continuously outputs the transient concentration curve of hydrogen chloride reflecting the evolution of the combustion ratio in the reactor.

[0041] Example 2: In this example, a multiphase flow gas chamber simulating the high-temperature and high-corrosion conditions of the Mannheim method is constructed as a verification platform. The main body of the gas chamber is made of acid-resistant Teflon-coated quartz tube with a diameter of 200mm. The gas chamber is equipped with a high-frequency ultrasonic atomizer to introduce sulfuric acid aerosol of a set concentration. At the same time, hydrogen chloride standard gas is injected in a gradient through a mass flow meter. Sapphire optical windows are installed at both ends of the gas chamber to connect to the test light source and photoelectric receiver with a target absorption wavelength of 1742nm and a non-absorption reference wavelength between 1730nm and 1735nm. A transient heating unit is integrated on the side wall of the gas chamber at a 10° angle with the beam propagation axis.

[0042] The pulse width of the transient heating pulse determines the degree of sulfuric acid droplet vaporization. When the pulse width is below the set lower limit, the core temperature of the sulfuric acid droplets does not reach the boiling point, leaving micro-droplets in the optical path and generating Mie scattering. When the pulse width is above the set upper limit, the heat flux exceeds the latent heat limit required for droplet vaporization, increasing system energy consumption and prolonging the phase recovery period, thus reducing the detection time resolution. In the experiment, the sulfuric acid droplet loading was set to... The standard hydrogen chloride gas injection concentration was maintained at Three test sample groups with gradient pulse width differences were set up, including a first control sample group with a pulse width of 5ms, the present invention sample group with a pulse width of 30ms, and a second control sample group with a pulse width of 80ms.

[0043] After the multiphase flow chamber stabilizes, the transient heating unit outputs periodic thermal pulses. The receiver records the time-series data of dual-wavelength transmitted light intensity. The light intensity recovery waveform of the first comparative sample group exhibits sawtooth oscillations, and the extracted vaporization compensation factor... The value is 0.45, and the hydrogen chloride concentration obtained from the analysis is within the range of... to Between them, the maximum relative error reached 31.6%, and the gasification compensation factor extracted from the second control group... Reaching 0.98, the concentration data update frequency decreased to 0.2Hz due to the thermal relaxation effect. The sample group of this invention completed the vaporization phase transition within 12.4ms after the thermal pulse, and the extracted vaporization compensation factor... Maintaining a flat state at 0.96, the processing processor operates according to the formula... Calculate the intrinsic absorbance of hydrogen chloride gas, where, For intrinsic absorbance, The second transient light intensity at the target absorption wavelength during the sulfuric acid droplet vaporization state. The first reference light intensity at the target absorption wavelength before the application of the transient heating pulse. As a gasification compensation factor, The background absorbance was determined by background gaseous residues, and the final calculated hydrogen chloride concentration stabilized at [value missing]. to Between these values, the maximum relative error decreased to 1.8%. The specific experimental test results of the component analysis index under different transient heating pulse widths are shown in Table 1.

[0044] Table 1: Comparison of component analysis indices for different transient heating pulse widths

[0045]

[0046] When the pulse width of the transient heating pulse is limited to the range of 10ms to 50ms, the thermal radiation flux is higher than the latent heat threshold of droplet vaporization, the liquid phase Mie scattering background is eliminated, and the phase recovery period is shorter than 500ms, which meets the response frequency requirements for real-time component monitoring.

[0047] To verify the completeness of the phase transition of sulfuric acid droplets within the measurement area, the sample group of this invention continuously monitored the vaporization compensation factor during the application of transient heating pulses. The rate of change of vaporization compensation factor over time, when the driving voltage of the transient heating unit increases from 24V to 48V. It exhibits a non-linear upward trend, and its numerical increment enters the preset steady-state envelope range after the driving voltage reaches 36V. This phenomenon indicates that the liquid aerosol in the measurement area has completely absorbed the latent heat of vaporization and transformed into a gaseous medium. At this time, the extracted second transient light intensity... With gasification compensation factor The product reaches a saturated and stable state, eliminating measurement deviations caused by local liquid phase residue. The optimal driving energy point for the current operating condition is established through this dynamic derivative determination logic. The system executes parallel feedforward control based on concentration fluctuations. According to the law of conservation of mass in chemical kinetics, the hydrogen chloride concentration in the reactor experiences drastic high-frequency fluctuations accompanied by a transient surge in the mass concentration of the byproduct sulfuric acid droplets. The processing unit extracts the real-time hydrogen chloride concentration sequence over several consecutive sampling periods and uses a fast Fourier transform algorithm to calculate the dominant frequency component of the sequence as the fluctuation frequency. The system will fluctuate frequency With the steady-state frequency threshold pre-stored in the register Compare the differences, when At that time, the processing unit follows the formula Calculate the target output power ,in, The derivative determination logic locks in the optimal driving energy reference power. To set the feedforward gain factor, the processing unit calculates the target output electrical power. The power control motherboard of the heating unit is directly written to increase the latent heat of vaporization input in subsequent pulse cycles, and physically smooth out the spatiotemporal lag interference caused by high-density aerosol load on the optical field of view.

[0048] Example 3: Under long-term continuous operation, the current real-time composition monitoring system for the Mannheim reactor exhaust gas accumulates incompletely vaporized residual sulfuric acid droplets and solid particles on the surface of the optical detection window, causing the first reference light intensity to rise. To mitigate baseline drift, the processing unit continuously acquires the first reference light intensity for 100 sampling cycles when the system is initially operational and the optical window is clean. The average value was then set as the initial cleaning baseline value. The system initiates a sliding time window monitoring algorithm, and the processing unit calculates the first reference light intensity within the current sliding time window in 5-minute increments. moving average When the moving average Reduced to initial cleaning baseline value When the output reaches 80%, the processor issues a cleanup command.

[0049] The processing unit according to the formula Calculate the target purging pressure, where, Blow away the pressure to achieve the goal. Based on purging pressure, Let be the pipeline dynamic pressure constant. As the initial cleaning baseline value, It is a moving average. The cumulative operating time of the system since its initial commissioning, and the pipeline dynamic pressure constant. This empirical coefficient was derived by calibrating the jet coverage capability of the protective air curtain nozzles at different flow rates using a Pitot tube anemometer and a standard pressure sensor, simulating a standard flue environment in the laboratory beforehand. This constant reflects the unit power pressure increment required for the purging airflow to form a stable laminar protective film on the window surface after overcoming the intrinsic dynamic pressure of the duct. This ensures that even when long-term operation leads to a decrease in window transmittance, the system can calculate an accurate pressure feedback value sufficient to peel off physical deposits through algebraic compensation. The air circuit controller receives the target purging pressure. Adjust the opening of the corresponding valve to drive the protective air curtain to the target purging pressure. Dry nitrogen gas is injected into the exhaust pipe, and the duration of this injection is set to [duration to be specified]. Furthermore, the injection start time is anchored within the resting interval between two adjacent transient heating pulses. After the injection action ends, the processing unit recalculates the moving average value. If the moving average Restore to initial cleaning baseline More than 95% of the system has been restored to the normalized test beam emission and transmission intensity timing data acquisition steps.

[0050] Example 4: In scenarios involving the commissioning of a Mannheim reactor or replacement of an optical window, the computational processor measures the initial attenuation reference of the test beam in an interference-free flow field. The gas path controller injects pure nitrogen into the exhaust pipe until the residual mixed gas is discharged. The light source emits the target absorption wavelength, and the receiver collects the basic transmitted light intensity within a preset time period. The computational processor then calculates the intensity according to the formula... Calculate and store the system's inherent background absorbance, where, Absorb brightness from the system's inherent background. The baseline transmitted light intensity is measured at the receiving end. Given the initial emitted light intensity from the light source, the system's inherent background absorbance is... It is stored in the storage medium of the processing processor as a compensation reference for the inherent loss of the stripped optical path.

[0051] After storing the compensation reference, the gas path controller introduces standard sulfuric acid aerosol of a preset mass concentration into the exhaust pipe. The transient heating unit emits transient heating pulses to the measurement area according to the voltage gradient sequence. The receiver records the first and second reference light intensities of the non-absorption reference wavelength before and after the transient heating pulse at each driving voltage. The arithmetic processor calculates the vaporization compensation factor based on the ratio of the second reference light intensity to the first reference light intensity. When the rate of change of the vaporization compensation factor with increasing voltage enters the preset convergence range, the arithmetic processor extracts the driving voltage corresponding to the inflection point of the rate of change and records it as the initial threshold voltage. The arithmetic processor constructs a mapping feature pair between the initial threshold voltage and the preset mass concentration and writes it into the underlying control matrix. The gas path controller repeatedly introduces standard sulfuric acid aerosol according to the concentration gradient law and cycles through the above data entry. The transient heating unit outputs the pulse energy density matching the current droplet load according to the underlying control matrix, so that the system forms a thermodynamic control benchmark with quantitative data support before flow field monitoring.

[0052] Example 5: In the initial commissioning scenario of different batches of Mannheim reactors, due to installation tolerances, the energy deposition range of the transient heating pulse deviates from the theoretical optical path. The system initiates the reconstruction calibration procedure of the optical detection boundary. The light source emits a non-absorption reference wavelength, and the transient heating unit adjusts the emission axis in steps within an angle range of 5° to 15° through a piezoelectric deflection mechanism, with the step size set to 0.5°. At each discrete angle node, the transient heating unit emits a thermal pulse with a pulse width between 10ms and 50ms. The processing unit extracts the first reference light intensity before and after the pulse of the non-absorption reference wavelength through the receiving end. With the second reference light intensity And according to the formula Iteratively calculate the gasification compensation factor at the current angle. When the gasification compensation factor When the maximum value is reached, the processing unit locks the current deflection angle and establishes the core area of ​​intersection between the transient heating pulse and the test beam.

[0053] After establishing the intersecting core region, the system triggers the calibration procedure for the mass concentration baseline. The transient heating unit emits pulse sequences with different peak energy densities into the measurement area, and the processing unit records the second transient light intensity at the target wavelength. Restored to the first reference light intensity The required phase recovery time is determined by nonlinearly fitting the phase recovery time under different heat fluxes to generate a thermodynamic relaxation curve describing the current droplet characteristics. The processor then converts this thermodynamic relaxation curve into a discrete parameter mapping matrix and stores it in the processor's storage medium. The thermodynamic relaxation curve is constructed using a double exponential decay model to describe the permeability change trend of the medium in the measurement area as it re-condenses from the gas phase back to the aerosol phase after the heat pulse ends. The mapping matrix is ​​a lookup table composed of experimental calibration data under different flow rates and acid mist loads. Its row vectors correspond to the steady-state value of the vaporization compensation factor C, and its column vectors correspond to the flow field velocity. When the phase recovery characteristics extracted by the system in real time deviate from the preset curve, the processor retrieves the corresponding drive correction coefficient in the mapping matrix using an interpolation algorithm, thereby achieving closed-loop control of the drive voltage. This ensures that the system can obtain the optimal signal-to-noise ratio under different loads, enabling the system to monitor the flow field based on the current vaporization compensation factor. The fluctuation amplitude is adaptively increased by adjusting the driving voltage, and the increased driving voltage makes the vaporization compensation factor... It remains in a saturated and stable state.

[0054] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit of this application and the scope of protection of this invention, and all of these forms are within the protection scope of this application.

Claims

1. A method for real-time component monitoring of exhaust gas from Mannheim potash fertilizer production, comprising a light source, a receiver, and a transient heating unit, characterized in that, Includes the following steps: Step S101: A test beam containing the target absorption wavelength and the non-absorption reference wavelength is synchronously emitted from the light source end into the flow field to be tested inside the pipe. The flow field to be measured contains hydrogen chloride gas and sulfuric acid droplets; Step S102: The transient heating unit applies periodic transient heating pulses to the measurement area covered by the test beam to vaporize the sulfuric acid droplets in the measurement area, wherein the pulse width of the transient heating pulse is 10ms to 50ms. Step S103: The receiver collects the transmission light intensity time series data of the test beam under the action of the transient heating pulse; Step S104: Extract the first reference light intensity before the application of the transient heating pulse and the second transient light intensity under the sulfuric acid droplet vaporization state from the transmission light intensity time series data. Step S105: Determine the vaporization compensation factor based on the transmittance jump ratio before and after the transient heating pulse at the non-absorption reference wavelength. Step S106: The second transient light intensity is corrected using a vaporization compensation factor, and the real-time concentration of hydrogen chloride is calculated based on the ratio of the corrected second transient light intensity to the first reference light intensity; the negative natural logarithm of the ratio is positively correlated with the real-time concentration of hydrogen chloride.

2. The method for real-time component monitoring of exhaust gas from Mannheim potash fertilizer production according to claim 1, characterized in that, Step S102 further includes the following sub-steps: Step S1021, setting the trigger frequency of the transient heating pulse according to the flow rate in the pipe; Step S1022, adjusting the angle between the emission axis of the transient heating pulse and the propagation axis of the test beam to 5° to 15°, so that the thermal effect area covers the measurement area.

3. The method for real-time component monitoring of exhaust gas from Mannheim potash fertilizer production according to claim 1, characterized in that, In step S102, the peak energy density of the transient heating pulse is greater than the latent heat of vaporization of the sulfuric acid droplets, so that the sulfuric acid droplets are converted into a gaseous state within the pulse width period of the transient heating pulse.

4. The method for real-time component monitoring of exhaust gas from Mannheim potash fertilizer production according to claim 1, characterized in that, Step S101 further includes the following sub-steps: Step S1011, setting a protective air curtain inside the light source end and the receiver end; Step S1012, spraying dry nitrogen gas into the inside of the pipe from the protective air curtain to form a laminar flow protective layer on the surface of the optical window.

5. The method for real-time component monitoring of Mannheim potash fertilizer production tail gas according to claim 4, characterized in that, Step S1012 further includes the following sub-steps: Step S10121, extracting the falling edge signal of the transient heating pulse; Step S10122, within a preset time after the falling edge signal is generated, increasing the gas supply pressure of the protective air curtain to the purging pressure; wherein, the duration of the purging pressure avoids the sulfuric acid droplet vaporization state in step S104.

6. The method for real-time component monitoring of exhaust gas from Mannheim potash fertilizer production according to claim 1, characterized in that, In step S105, the gasification compensation factor The light intensity value of the non-absorption reference wavelength after the sulfuric acid droplets are vaporized is calculated by dividing the light intensity value of the sulfuric acid droplets before vaporization.

7. The method for real-time component monitoring of exhaust gas from Mannheim potash fertilizer production according to claim 1, characterized in that, In step S106, the absorption spectral intensity of hydrogen chloride molecules is corrected based on the real-time temperature within the measurement area to determine the real-time concentration of hydrogen chloride.

8. The method for real-time component monitoring of exhaust gas from Mannheim potash fertilizer production according to claim 1, characterized in that, In step S101, the target absorption wavelength is 1742 nm; the non-absorption reference wavelength is selected between 1730 nm and 1735 nm.

9. The method for real-time component monitoring of exhaust gas from Mannheim potash fertilizer production according to claim 1, characterized in that, Step S106 is followed by a self-calibration step: monitoring the fluctuation frequency of the real-time concentration of hydrogen chloride; when the fluctuation frequency exceeds a preset threshold, increasing the electrical power of the transient heating pulse in step S102.

Images