Spontaneous combustion detector for high-viscosity powder

Abstract

The invention discloses a spontaneous combustion detector for high-viscosity powder. The spontaneous combustion detector comprises a test bin, a bubble generation module, a direct-current high-voltage electrode, a spectral analysis module and a data acquisition and control system, an anti-sticking and anti-static coating is arranged on the inner wall of the test bin, and a microporous ceramic disc is arranged at the bottom of the test bin and used for introducing gas to generate bubbles; the direct-current high-voltage electrode comprises a main electrode and an auxiliary electrode, and a segmented electric field is formed in the powder through independent adjustment of a multi-channel high-voltage power supply so as to damage agglomeration and promote release of combustible components; the spectroscopic analysis module is used for detecting spectral information of bubble rupture volatile matters; the data acquisition and control system cooperatively controls gas flow, electric field voltage and spectrum scanning according to PID and an interval judgment algorithm, and rapid and accurate detection is achieved. According to the method, heating or mechanical stirring is not needed, detection can be completed within 60-120 seconds at the normal temperature, the sensitivity reaches 10-100 ppm, and the method is suitable for spontaneous combustion risk screening of high-viscosity powder in the fields of coal, metallurgy, chemical engineering and the like.

Description

Technical Field

[0001] This invention relates to a high-viscosity powder self-ignition tester, which belongs to a safety monitoring device. Background Technology

[0002] High-viscosity powders pose safety hazards in the production and storage of coal, power, metallurgy and chemical industries. This is mainly because such powders are prone to forming large agglomerates, which hinders the timely dissipation of flammable substances or low flash point components contained within them.

[0003] Common detection methods include mechanical stirring, vibrating sieving, and thermal volatilization analysis. However, these methods are prone to problems such as localized overheating, uneven stirring, and large detection errors in high-viscosity powders. Incomplete agglomeration caused by mechanical stirring can prevent the full release of some combustible components. Vibrating sieving has strict limitations on particle size and moisture content, while thermal volatilization analysis can easily damage the original properties of some sensitive components, ultimately leading to low stability and accuracy of the detection results. Some powders require a room temperature environment during detection, and current technologies lack more effective methods to simultaneously achieve agglomeration and accurate detection, failing to meet the industrial safety regulatory requirements for rapid and highly sensitive analysis of high-viscosity powders. Summary of the Invention

[0004] To address the aforementioned shortcomings, a high-viscosity powder auto-ignition detector is proposed to enable rapid screening and detection of high-viscosity powders.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a high viscosity powder self-ignition tester, including a test chamber, a bubble generating module, a DC high voltage electrode, a spectrophotometric analysis module, and a data acquisition and control system; The test chamber is a cylindrical stainless steel shell with an epoxy fluorocarbon resin anti-stick coating on the outer surface, with a coating thickness of 0.20 mm. The inner wall of the chamber is sprayed with a graphene-modified epoxy resin antistatic coating with a thickness of 0.05 mm. The volume resistivity of this coating is less than 10^9 ohm·cm. The bottom of the chamber is equipped with a flow control valve. A ring-shaped high-voltage main electrode bracket is set at the top of the chamber 10 mm from the top cover for mounting DC high-voltage electrode plates. An exhaust pipe is provided at the top of the test chamber, and the spectrophotometric analysis module is connected to the exhaust pipe. The spectrophotometric module has a built-in one-way microvalve. The bubble generating module includes a microporous ceramic disc, a stainless steel tube, and an external gas cylinder. The microporous ceramic disc is installed at the center of the bottom of the test chamber. It is hollow inside and has micropores with a diameter of 1 micrometer on the outside. The microporous ceramic disc is connected to the stainless steel tube. A flow control valve is installed on the microporous ceramic disc. The other end of the stainless steel tube is connected to the external gas cylinder. The data acquisition and control system (DCS) consists of an industrial-grade microprocessor, analog input units, digital output units, and control algorithm software. The analog input units are connected to the electrical signals of the flow control valve, pressure sensor, and spectrophotometer. The digital output channels are used to send voltage regulation commands to the multi-channel high-voltage power supply and valve opening regulation commands to the flow control valve. The multi-channel high-voltage power supply is connected to the DC high-voltage electrode plate.

[0006] According to the high viscosity powder self-ignition tester, the test chamber has a wall thickness of 5 mm, can withstand a positive pressure of 20 kPa, and can hold 200 g to 1000 g of powder sample.

[0007] According to the high viscosity powder self-ignition tester, the DC high voltage electrode plate is a ring-shaped aluminum alloy plate with chamfered edges, an outer radius of 40 mm, and a thickness of 2 mm. It is fixed 2 mm above the ring-shaped high voltage main electrode support. The main electrode support is made of PA or equivalent high temperature resistant insulating plastic. The diameter of the central opening of the DC high voltage electrode plate is 20 mm. The high voltage power supply cable connected to the DC high voltage electrode plate passes through and is connected to a multi-channel high voltage power supply. When the maximum output voltage of the multi-channel high voltage power supply is 5 kV, it can be adjusted in 0.1 kV steps. It is equipped with a 5 mA current limiting protection device. The DC high voltage electrode plate maintains positive polarity during the test, and the test chamber shell is kept grounded. Four auxiliary electrodes, each measuring 20 mm × 10 mm × 1 mm, are arranged around the DC high-voltage electrode plate and are evenly distributed on the same horizontal plane around the main electrode. The auxiliary electrodes are connected to the multi-channel high-voltage power supply through independent high-voltage output channels. The auxiliary electrodes are isolated from the test chamber shell by polytetrafluoroethylene (PTFE) insulating columns. The polyethylene columns are hollow and used to lay independent channel cables for connecting the auxiliary electrodes. An annular insulating gasket is placed directly below the DC high-voltage electrode plate. The thickness of the insulating gasket should be controlled below 0.5 mm.

[0008] According to the high-viscosity powder self-ignition detector, the multi-channel high-voltage power supply is equipped with a corresponding current limiter in the hardware circuit. Each output channel can be adjusted independently within the range of 1 kV to 5 kV, with a voltage step accuracy of 0.1 kV. When it is necessary to form a segmented electric field, the main electrode and the auxiliary electrode can apply different potential differences together, and the voltage values ​​of each output channel can be adjusted step by step. Each auxiliary electrode is equipped with an independent ground detection circuit. If a breakdown occurs in a certain channel or the abnormal current value exceeds 5 mA, the multi-channel high-voltage power supply will cut off the channel within 0.5 seconds and reduce the voltage of the other channels to a safe level to prevent electric field overload or unstable discharge.

[0009] According to the high-viscosity powder spontaneous combustion detector, the microporous ceramic disc has a diameter of 80 mm and a thickness of 5 mm. The flow control valve connected to the microporous ceramic disc adjusts the air intake accuracy to 0.02 L / min, with a minimum stable flow rate of 0.01 L / min and a maximum flow rate of 0.15 L / min. The gas in the external gas cylinder enters the flow control valve after passing through the gas purity monitor and the one-way valve. The gas in the external gas cylinder is filled with inert gas or air according to the properties of the powder. When multiple external gas cylinders are connected in parallel, the channel is switched by a hardware lever. The gas purity monitor is installed 5 cm upstream of the flow control valve to detect the residual oxygen content.

[0010] According to the high-viscosity powder spontaneous combustion detector, the spectroscopic analysis module comprises three parts: a grating spectrometer, a tunable light source, and a photodetector. The grating spectrometer has a grating line density of 1200 lines / mm, covering a wavelength range of 0.4 μm to 5 μm, with a spectral resolution better than 0.5 nm. The tunable light source is a combination of a xenon lamp and an infrared excitation unit, with a tuning range of 0.4 μm to 5 μm. A specific detection band can be selected by choosing a filter. The photodetector uses a high-sensitivity indium gallium arsenide array, with a measurement range covering 0.9 μm to 1.7 μm, and is equipped with a silicon detector module at the visible end to meet wide-band scanning requirements. The optical fiber is connected to the grating spectrometer via an SMA interface, and the optical fiber is connected to the tunable light source.

[0011] According to the high viscosity powder self-ignition tester, the microprocessor has a main frequency of 1 GHz, a built-in 512 megabytes of storage space, and the digital output channel has a step accuracy of 0.1 kV for sending voltage regulation commands to the multi-channel high voltage power supply and a step accuracy of 0.01 L / min for sending valve opening regulation commands to the flow control valve.

[0012] According to the high-viscosity powder self-ignition tester, the control algorithm is based on a logic structure combining PID and interval judgment, specifically including three major modules: low-pressure stabilization stage, pressurization stage, and enrichment stabilization stage. Each stage runs an independent valve-voltage coupling control subroutine, maintaining flow synchronization when switching voltage to ensure that the powder is not excessively impacted. The data acquisition and control system (DCS) is connected to the host computer software via a wired network, and the host computer displays pressure, flow, voltage, and spectral peak data in real time.

[0013] The high-viscosity powder spontaneous combustion detector also includes a safety management and alarm device. This device includes a current-limiting module in the multi-channel high-voltage power supply configuration, a check valve in the external gas cylinder, a pressure sensor on the upper part of the test chamber, and an overload protection unit built into the spectrophotometric analysis module. When the current-limiting module detects that the current in the circuit exceeds 5 mA, the multi-channel high-voltage power supply is de-energized within 0.5 seconds. The check valve is installed 10 cm from the outlet of the external gas cylinder and is activated to close when there is insufficient positive pressure in the downstream pipeline. The pressure sensor has a range of 0 to 50 kPa (gauge pressure) and a sampling frequency of 100 Hz. When the pressure (gauge pressure) inside the chamber exceeds the upper limit of 20 kPa, the data acquisition and control system (DCS) immediately issues an audible and visual alarm and executes a valve closure and pressure reduction command. When the overload protection unit in the spectrophotometric analysis module detects that the absorption peak intensity is greater than 80% of the full scale, the analyzer reduces the light source power within 10 milliseconds to prevent detector oversaturation.

[0014] In this invention, the test chamber uses a low-flow-rate aeration (bubbles) at the bottom of the powder, outputting gas through a microporous ceramic disc or multi-hole nozzle, causing the bubbles to form longitudinal channels within the viscous powder. A DC high-voltage electrode at the top applies an electric field to the powder particles, overcoming powder agglomeration limitations and improving the enrichment efficiency of combustible components. A spectrophotometric analysis module performs multi-band rapid scanning of the volatiles released after bubble bursting, and sensors and a control microprocessor execute data acquisition, identification, and alarm logic. Through a series of clearly defined operating steps and specific technical parameters, the system ensures that the entire scheme can complete a rapid, stable, and accurate enrichment and detection process across different viscosity grades and particle sizes.

[0015] This invention, without applying high temperatures, mechanical stirring, or large amounts of chemical reagents, utilizes a programmable mass flow controller and high-voltage power supply to complete the detection of a single batch of powder within a timeframe of 60 to 120 seconds. Compared to traditional pyrolysis and stirring dispersion methods, this invention reduces equipment energy consumption by approximately 15% to 30% and achieves a detection sensitivity of 10 to 100 ppm at room temperature. Through these features, this invention provides a new solution for detecting the spontaneous combustion risk of mine dust, metal powders, pharmaceutical solids, and other types of powders. It significantly surpasses traditional single-detection methods and possesses high value for widespread application. Attached Figure Description

[0016] Figure 1 This is a structural diagram of the present invention.

[0017] Figure 2 This is a schematic diagram of the circuit structure of the present invention.

[0018] Figure reference numerals: 1 Test chamber, 11 Flow control valve, 12 Exhaust pipe, 13 Pressure sensor, 2 Bubble generating module, 21 Microporous ceramic disc, 22 Stainless steel pipe, 23 External gas cylinder, 24 Check valve, 3 DC high voltage electrode, 31 Ring high voltage main electrode support, 32 High voltage power supply main cable, 33 Auxiliary electrode, 34 PTFE insulating column, 4 Spectrophotometric analysis module. Detailed Implementation

[0019] The specific structure of the present invention will be further described below: The present invention relates to a high-viscosity powder self-ignition tester, comprising a test chamber 1, a bubble generating module 2, a DC high-voltage electrode 3, a spectrophotometric analysis module 4, and a data acquisition and control system.

[0020] Among them, test chamber 1 is a columnar stainless steel shell with an opening at the top. It is 300 mm high, 140 mm in inner diameter, and 5 mm thick. It can withstand a positive pressure of 20 kPa, meeting industrial-grade safety requirements. The chamber can hold 200 g to 1000 g of powder samples of conventional density.

[0021] The outer surface is coated with an epoxy-based fluorocarbon resin anti-stick coating with a thickness of 0.20 mm. This anti-stick material is in a dense, cured state at room temperature and has a coefficient of friction of less than 0.1. The inner wall of the chamber is sprayed with a graphene-modified epoxy resin antistatic coating with a thickness of 0.05 mm. The volume resistivity of this coating should be less than 10^9 ohm·cm to prevent localized arcing in high-voltage environments.

[0022] The bottom of the chamber is equipped with a flow control valve 11. A ring-shaped high-voltage main electrode bracket 31 is set at the top of the test chamber 1 10 mm away from the top cover for installing DC high-voltage electrode plates. An exhaust pipe 12 is provided at the top of the test chamber 1. The spectrophotometric analysis module 4 is connected to the exhaust pipe 12. An optical fiber coupler and a one-way micro valve are installed in the middle section of the exhaust pipe 12.

[0023] The DC high-voltage electrode plate of this device is a ring-shaped aluminum alloy plate with an outer radius of 40 mm and a thickness of 2 mm. It is fixed 2 mm above the ring-shaped high-voltage main electrode bracket 31. The diameter of the opening in the center of the DC high-voltage electrode plate is 20 mm. The high-voltage power supply cable connected to the DC high-voltage electrode plate passes through and is connected to the multi-channel high-voltage power supply. When the maximum output voltage of the multi-channel high-voltage power supply is 5 kV, it can be adjusted in 0.1 kV steps. It is equipped with a 5 mA current limiting protection device. The DC high-voltage electrode plate maintains positive polarity during the test, and the outer shell of the test chamber 1 is grounded to maintain zero potential.

[0024] Four auxiliary electrodes, each measuring 20 mm × 10 mm × 1 mm, are arranged around the main electrode at equal intervals on the same horizontal plane. Each auxiliary electrode is connected to a multi-channel high-voltage power supply via a high-voltage auxiliary cable, and a corresponding current limiter is incorporated into the hardware circuitry. Each output channel can be individually adjusted within the range of 1 kV to 5 kV, with a voltage step accuracy of 0.1 kV. When a segmented electric field is required, the main electrode and auxiliary electrodes can jointly apply different potential differences.

[0025] The auxiliary electrodes are isolated from the outer shell of the test chamber 1 by PTFE insulating pillars 34. An annular insulating gasket is installed directly below the DC high-voltage electrode plate to further prevent high voltage penetration or creepage into the chamber. Each auxiliary electrode is equipped with an independent grounding detection circuit. If a breakdown occurs in one circuit or the abnormal current value exceeds 5 mA, the main control system will disconnect that channel within 0.5 seconds and reduce the voltage of other channels to a safe level to prevent electric field overload or unstable discharge.

[0026] The bubble generating module 2 includes a microporous ceramic disc 21, a stainless steel tube 22, and an external gas cylinder 23. The microporous ceramic disc 21 is installed at the center of the bottom of the test chamber 1. It is hollow inside and has micropores with a diameter of 1 micrometer on the outside. The lower part of the microporous ceramic disc 21 is connected to the stainless steel tube 22, which passes through the bottom of the test chamber 1. The stainless steel tube 22 is equipped with a flow control valve 11 outside the test chamber 1, and the other end of the stainless steel tube 22 is connected to the external gas cylinder 23.

[0027] The microporous ceramic disc 21 of this device has a diameter of 80 mm and a thickness of 5 mm. The flow control valve 11 connected to the microporous ceramic disc 21 adjusts the air intake accuracy to 0.02 L / min, with a minimum stable flow rate of 0.01 L / min and a maximum flow rate of 0.15 L / min. The gas in the external gas cylinder 23 enters the flow control valve 11 after passing through the gas purity monitor and the one-way valve. The gas in the external gas cylinder 23 is filled with inert gas or air according to the properties of the powder. When multiple external gas cylinders 23 are connected in parallel, the channel is switched by a hardware lever. The gas purity monitor is installed 5 cm upstream of the flow control valve 11 to detect the residual oxygen content to meet the inert requirements.

[0028] The spectroscopic analysis module 4 in this device comprises three parts: a grating spectrometer, a tunable light source, and a photodetector. The grating spectrometer has a grating line density of 1200 lines / mm, covering a wavelength range of 0.4 μm to 5 μm, with a spectral resolution better than 0.5 nm. The tunable light source is a combination of a xenon lamp and an infrared excitation unit, with a tuning range of 0.4 μm to 5 μm. A specific detection band can be selected by choosing a filter. The photodetector uses a high-sensitivity indium gallium arsenide array, with a measurement range covering 0.9 μm to 1.7 μm, and is equipped with a silicon detector module at the visible end to meet wide-band scanning requirements. The optical fiber is connected to the grating spectrometer via an SMA interface, and the optical fiber is connected to the tunable light source.

[0029] The data acquisition and control system (DCS) of this device consists of an industrial-grade microprocessor, an analog input unit, a digital output unit, and control algorithm software. The analog input unit is electrically connected to the flow control valve 11, the pressure sensor, and the spectrophotometer module 4. The digital output channel is used to send voltage regulation commands to the multi-channel high-voltage power supply and valve opening regulation commands to the flow control valve 11. The multi-channel high-voltage power supply is connected to the DC high-voltage electrode plate.

[0030] The microprocessor has a main frequency of 1 GHz and a built-in 512 megabytes of storage space. The digital output channel sends voltage regulation commands to the multi-channel high-voltage power supply with a step accuracy of 0.1 kV and sends valve opening adjustment commands to the flow control valve 11 with a step accuracy of 0.01 L / min.

[0031] The control algorithm of the data acquisition and control system (DCS) is based on a logic structure that combines PID and interval judgment. Specifically, it includes three major modules: low-pressure stabilization stage, pressurization stage, and enrichment stabilization stage. Each stage runs an independent valve-voltage coupling control subroutine to maintain flow synchronization when switching voltage, ensuring that the powder is not excessively impacted. The DCS is connected to the host computer software via a wired network, and the host computer displays pressure, flow, voltage, and spectral peak data in real time.

[0032] To enhance the safety of this device's operation, a safety management and alarm device is built into the data acquisition and control system (DCS). This device includes a current limiting module in the multi-channel high-voltage power supply configuration, a check valve 24 in the external gas cylinder 23, a pressure sensor on the upper part of the test chamber 1, and an overload protection unit built into the spectrophotometer analysis module. When the current limiting module detects that the current in the circuit exceeds 5 mA, the multi-channel high-voltage power supply is de-energized within 0.5 seconds. The check valve 24 is installed 10 cm from the outlet of the external gas cylinder 23 and is activated to close when there is insufficient positive pressure in the downstream pipeline. The pressure sensor has a range of 0 to 50 kPa (gauge pressure) and a sampling frequency of 100 Hz. When the pressure (gauge pressure) in the chamber exceeds the upper limit of 20 kPa, the DCS immediately issues an audible and visual alarm and executes a valve closure and pressure reduction command. When the overload protection unit in the spectrophotometer analysis module detects that the absorption peak intensity is greater than 80% of the full scale, the analyzer reduces the light source power within 10 milliseconds to prevent the detector from oversaturating.

[0033] The steps for using this device are as follows: 1) During the powder sample loading and preparation stage, the powder to be tested is weighed and loaded into the test chamber, with a loading amount between 250 grams and 500 grams. The microprocessor matches the bubble flow rate (initial value 0.03 liters / minute) and the voltage (initial value 1 kV) according to the powder properties (viscosity grade, moisture content, and types of combustible components) input from the host computer, and records the current sample number and test date.

[0034] 2) During the low-pressure stabilization phase, the DCS (Distributed Control System) outputs an opening command of 0.03 L / min to the flow control valve and a voltage command of 1 kV to the high-voltage power supply. Gas enters the powder through the ceramic disc at a rate of 0.03 L / min, with bubble diameters of approximately 0.5 mm, and the pressure at the bottom of the silo stabilizes below 5 kPa. At this time, channels begin to appear inside the powder, causing fluctuations in the pressure signal of approximately 3 Hz. When the microprocessor detects that the fluctuation frequency is below 5 Hz, it determines that the channels have initially formed, ending the low-pressure stabilization phase and entering the pressurization phase.

[0035] 3) During the pressurization phase, the microprocessor sends a signal to increase the high-voltage power supply to 3 kV and the valve flow rate to 0.05 L / min. At this point, the bubble diameter increases to 1 mm, and powder agglomeration begins to break up over a large area; the pressure sensor reading is approximately 8 kPa. During this phase, the microprocessor monitors the flow rate and pressure at 1-second intervals. If the pressure suddenly rises above 15 kPa, it immediately reduces the valve opening to 0.04 L / min and maintains this position for 5 seconds to prevent excessive impact within the chamber. Once the internal channels of the powder have fully expanded, the system pressure fluctuation range decreases to within 2 kPa, and the spectral module begins scanning for absorption peaks of oily or hydrocarbon volatile components. The pressurization phase typically lasts 20 to 30 seconds, with the exact duration determined by the DCS based on pressure stability.

[0036] 4) During the enrichment and stabilization phase, the microprocessor maintains the high-voltage power supply at 3 kV and the valve flow rate at 0.05 L / min, executing constant-state operation within the database based on the powder properties. At this stage, the combustible components carried by the bubbles are concentrated and output. The spectrophotometer module acquires spectral data at a frequency of 1 Hz and transmits the absorption peak intensity back to the microprocessor. The microprocessor compares the absorption peak intensity with a standard threshold. If the value corresponding to the C-H near-infrared absorption band in the 1.65–1.75 μm range exceeds the safety limit, an alarm is immediately triggered. If the spectral amplitude is below 5% of full scale, the system continues to maintain this state until acquisition is complete.

[0037] 5) Result Determination and Data Output At the end of the enrichment and stabilization phase, the microprocessor records key data such as spectral peaks, valve flow rate, chamber pressure, and electrode voltage, and stores these parameters in an internal database. The system sends the results to the host computer to generate a test report, which includes a timestamp, powder number, main spectral peaks, and safety assessment results. If the safety assessment result is higher than the threshold, the DCS closes the valve and reduces the voltage to below 1 kV within 0.5 seconds, while simultaneously issuing an audible and visual warning to prompt operators to isolate or handle the powder.

[0038] Precautions for using this device: For specific flammable or easily oxidized metal powders, detection must be performed in a low-oxygen or oxygen-free atmosphere. By adding an inert gas switching valve assembly at the interface 10 cm from the gas cylinder outlet, the microprocessor can switch to the inert gas pipeline after receiving the powder oxygen-sensitive command on the main interface, and check that the oxygen sensor reading remains below 1%. If detection under ultra-low oxygen conditions is required, inert gas purging and extraction circuits can be configured at both ends of the inlet and outlet pipelines. First, purge with high-purity argon or nitrogen for 3-5 minutes to reduce the oxygen volume fraction in the chamber to below 0.05%. The flow control valve and microporous ceramic disc maintain their original accuracy under low-oxygen conditions, and the spectrophotometric analysis module's spectral curve calibration module will correct according to the oxygen-free line to ensure that the peak identification accuracy is not less than 90%.

[0039] For powders with large particle size and high internal oil content, a single voltage increase may trigger a transient localized electric arc. This invention employs four auxiliary electrodes (20 mm × 10 mm × 1 mm) outside the main electrode, with the voltage output channel independently controlled by a microprocessor. Different voltages are applied based on the powder's loosening and enrichment stages. For the first 10 seconds, the auxiliary electrode voltage is set to 2 kV and the main electrode to 1 kV. After initial loosening of the powder, all electrodes are uniformly increased to 3.5 kV and maintained for 20 seconds. Upon reaching a stable state, the voltage is switched back to 2.5 kV, with the current limited to no more than 3 mA. Experiments have shown that this method reduces the risk of partial discharge in the detection of powders with high moisture or high oil content and prevents excessively strong electric fields from damaging bubble penetration.

[0040] This device can be coupled with mass spectrometry / gas chromatography. The specific implementation of the expansion module involves installing an electromagnetic isolation valve 2 cm from the outlet of the spectrophotometer module, connected to a branch pipeline leading to the mass spectrometer ionization chamber or the gas chromatograph injection port. When the control system detects multiple overlapping peaks in the spectral data, the microprocessor sends a digital output command to open the electromagnetic isolation valve, introducing a portion of the gas into the mass spectrometer or chromatograph for secondary precise analysis. The inlet gas flow rate of the mass spectrometer ionization chamber is set at 2 mL / min, and the carrier gas flow rate of the gas chromatograph is maintained at 5 mL / min. The secondary detection takes approximately 40 seconds. This composite detection platform can separate and quantify complex components. Spectrophotometer detection only needs to provide early warning or routine screening functions, while mass spectrometry or chromatograph performs high-precision confirmation. This process is recorded in the DCS software and a comprehensive report is generated.

[0041] When continuous powder testing is required, a rotary valve is installed 3 cm from the side wall of the feeder. The rotary valve has a torque of 3 Nm and can complete a quantitative discharge within 3 seconds, with an error controlled within ±2 grams. An electric valve is installed 5 mm from the bottom of the feeder. The electric valve and the rotary valve are synchronized via digital signals, ensuring that the bottom electric valve is closed when the rotary valve is open, and vice versa. After each test, the microprocessor first disconnects the high-voltage power supply to stop the inflow of air bubbles, waits 5 seconds to complete the powder discharge, and then restarts the feeder to load the next batch of powder. This process avoids dust leakage and ensures operator safety.

[0042] The host computer software of this device includes a powder property database and a historical record management module. After each batch of powder is tested, the system generates a data file containing fields such as maximum pressure in the silo, average pressure, flow curve, electrode voltage timing, spectral peak value, and alarm status. Operators can set judgment thresholds, alarm delays, and data storage locations in the software. If an emergency power outage or forced pressure reduction occurs during a test, the system will highlight the record in red and retain it for one year for future review. Through the above management modules, detailed traceability of powder supply batches and storage locations can be achieved within the factory, realizing integrated risk control of "detection-warning-isolation".

[0043] This invention can be applied to high-viscosity powders with particle sizes ranging from 10 micrometers to 300 micrometers, and through multi-level bubble flow rate and voltage control strategies, it is suitable for samples with a moisture content of less than 15% and a viscosity index of 3 Pa·s to 30 Pa·s. For powders with higher viscosity or high moisture content, the efficiency of loose channel formation can be maintained under a segmented electrode and incremental flow rate strategy. Numerous experiments show that information such as the C-H peak value and O-H peak value of the main volatile components can be obtained within 120 seconds of a single detection, with a detection error of no more than 5%.

[0044] Energy consumption is reduced by about 20% to 30% compared with traditional pyrolysis detection methods, and the detection efficiency per unit time is increased by about 40%.

[0045] The built-in safety alarm module enables simultaneous monitoring of flow rate, pressure, and voltage. Segmented control of the auxiliary electrode reduces the risk of instantaneous discharge. The high-end version adds mass spectrometry or gas chromatography to the spectrophotometric analysis backend for more precise detection and can switch to nitrogen or argon in low-oxygen environments. All key parameters are uniformly maintained through DCS and database management, and the operating procedures can seamlessly interface with the host computer in the factory automation system, enabling batch application.

[0046] In summary, the specific embodiments of this invention, through close coordination of hardware, software, and safety management, provide a complete, specific, and operable technical path for the detection of flammable and volatile components in high-viscosity powders. Key steps fully disclose numerical values ​​and parameter limits, and the detailed step-by-step control method ensures that the detection process can be reproduced in actual industrial environments. The overall solution solves the problems of powder agglomeration and insufficient flammable component release efficiency that are difficult to overcome with traditional technologies, and achieves high-precision control in terms of gas source, pressure, and safety protection, demonstrating significant innovation and practical value.

Claims

1. A self-ignition tester for high-viscosity powder, characterized in that, It includes a test chamber (1), a bubble generation module (2), a DC high-voltage electrode (3), a spectrophotometric analysis module (4), and a data acquisition and control system; The test chamber (1) is a columnar stainless steel shell with an epoxy fluorocarbon resin anti-stick coating on the outer surface. The coating thickness is 0.20 mm. The inner wall of the chamber is sprayed with a graphene-modified epoxy resin antistatic coating with a thickness of 0.05 mm. The volume resistivity of the coating is less than 10^9 ohm·cm. The bottom of the chamber is equipped with a flow control valve (11). The top of the test chamber (1) is equipped with an annular high voltage main electrode bracket (31) 10 mm away from the top cover for installing DC high voltage electrode plates. The upper part of the test chamber (1) is equipped with an exhaust pipe (12). The spectrophotometric analysis module (4) is connected to the exhaust pipe (12). The middle section of the exhaust pipe (12) is equipped with an optical fiber coupler and a one-way micro valve. The bubble generating module (2) includes a microporous ceramic disc (21), a stainless steel tube (22), and an external gas cylinder (23). The microporous ceramic disc (21) is installed at the center of the bottom of the test chamber (1). It is hollow inside and has micropores with a diameter of 1 micrometer on the outside. The microporous ceramic disc (21) is connected to the stainless steel tube (22). The stainless steel tube (22) passes through the bottom of the test chamber (1). The stainless steel tube (22) is equipped with a flow control valve (11) outside the test chamber (1). The other end of the stainless steel tube (22) is connected to the external gas cylinder (23). The data acquisition and control system (DCS) consists of an industrial-grade microprocessor, an analog input unit, a digital output unit, and control algorithm software. The analog input unit is electrically connected to the flow control valve (11), the pressure sensor, and the spectrophotometer (4). The digital output channel is used to send voltage regulation commands to the multi-channel high-voltage power supply and valve opening regulation commands to the flow control valve (11). The multi-channel high-voltage power supply is connected to the DC high-voltage electrode plate.

2. The high-viscosity powder auto-ignition tester according to claim 1, characterized in that, The test chamber (1) has a wall thickness of 5 mm and can withstand a positive pressure of 20 kPa. The chamber can hold 200 g to 1000 g of powder samples.

3. The high-viscosity powder spontaneous combustion detector according to claim 1, characterized in that it uses DC power. The high voltage electrode plate is an annular aluminum alloy plate with an outer radius of 40 mm and a thickness of 2 mm. It is fixed 2 mm above the annular high voltage main electrode bracket (31). The diameter of the central hole of the DC high voltage electrode plate is 20 mm. The high voltage power supply cable connected to the DC high voltage electrode plate passes through and is connected to the multi-channel high voltage power supply. When the maximum output voltage of the multi-channel high voltage power supply is 5 kV, it can be adjusted in 0.1 kV steps. It is equipped with a 5 mA current limiting protection device. The DC high voltage electrode plate maintains positive polarity during the test. The outer shell of the test chamber (1) is grounded. Four auxiliary electrodes are arranged around the DC high voltage electrode plate, each measuring 20 mm × 10 mm × 1 mm, and are distributed at equal intervals on the same horizontal plane around the main electrode. The auxiliary electrodes are connected to the multi-channel high voltage power supply through high voltage auxiliary cables. The auxiliary electrodes are isolated from the outer shell of the test chamber (1) by polytetrafluoroethylene insulating columns (34). An annular insulating gasket is set directly below the DC high voltage electrode plate.

4. The high-viscosity powder auto-ignition tester according to claim 3, characterized in that, The multi-channel high-voltage power supply has a corresponding current limiter in the hardware circuit. Each output channel can be adjusted independently in the range of 1 kV to 5 kV with a voltage step accuracy of 0.1 kV. When it is necessary to form a segmented electric field, the main electrode and the auxiliary electrode can apply different potential differences together, and the voltage value of each output channel can be adjusted step by step. Each auxiliary electrode is equipped with an independent ground detection circuit. If a breakdown occurs in one channel or the abnormal current value exceeds 5 mA, the multi-channel high-voltage power supply will cut off that channel within 0.5 seconds and reduce the voltage of the other channels to a safe level to prevent electric field overload or unstable discharge.

5. The high-viscosity powder auto-ignition tester according to claim 1, characterized in that it has micropores. The ceramic disc (21) has a diameter of 100 mm and a thickness of 5 mm. The flow control valve (11) connected to the microporous ceramic disc (21) adjusts the air intake accuracy to 0.02 L / min, the minimum stable flow rate to 0.01 L / min, and the maximum flow rate to 0.15 L / min. The gas in the external gas cylinder (23) enters the flow control valve (11) after passing through the gas purity monitor and the one-way valve. The gas in the external gas cylinder (23) is filled with inert gas or air according to the properties of the powder. When multiple external gas cylinders (23) are connected in parallel, the channel is switched by the hardware lever. The gas purity monitor is installed 5 cm upstream of the flow control valve (11) to detect the residual oxygen content.

6. The high-viscosity powder auto-ignition tester according to claim 1, characterized in that, The spectroscopic analysis module (4) consists of three parts: a grating spectrometer, a tunable light source, and a photodetector. The grating spectrometer has a grating line density of 1200 lines / mm, covering a wavelength range of 0.4 μm to 5 μm, and a spectral resolution better than 0.5 nm. The tunable light source is a combination of a xenon lamp and an infrared excitation unit, with a tuning range of 0.4 μm to 5 μm. The specified detection band can be selected by selecting a filter. The photodetector uses a high-sensitivity indium gallium arsenide array, with a range covering 0.9 μm to 1.7 μm, and is equipped with a silicon detector module at the visible end to meet the wide-band scanning requirements. The optical fiber is connected to the grating spectrometer via an SMA interface, and the optical fiber is connected to the tunable light source.

7. The high-viscosity powder auto-ignition tester according to claim 1, characterized in that, The microprocessor has a main frequency of 1 GHz and a built-in 512 megabytes of storage space. The digital output channel sends voltage regulation commands to the multi-channel high-voltage power supply with a step accuracy of 0.1 kV and sends valve opening adjustment commands to the flow control valve (11) with a step accuracy of 0.01 L / min.

8. The high-viscosity powder auto-ignition tester according to claim 1, characterized in that, The control algorithm is based on a logical structure that combines PID and interval judgment. Specifically, it includes three major modules: low-pressure stabilization stage, pressurization stage, and enrichment stabilization stage. Each stage runs an independent valve-voltage coupling control subroutine to maintain flow synchronization when switching voltage, ensuring that the powder is not excessively impacted. The data acquisition and control system (DCS) is connected to the host computer software via a wired network, and the host computer displays pressure, flow, voltage, and spectral peak data in real time.

9. The high-viscosity powder auto-ignition tester according to claim 1 or 8, characterized in that, The data acquisition and control system (DCS) has a built-in safety management and alarm device, which includes a current limiting module in the multi-channel high-voltage power supply configuration, a check valve (24) in the external gas cylinder (23), a pressure sensor on the top of the test chamber (1), and an overload protection unit built into the spectrophotometric analysis module. When the current limiting module detects that the current in the line exceeds 5 mA, the multi-channel high-voltage power supply will cut off the power within 0.5 seconds. The check valve (24) is installed 10 cm from the outlet of the external gas cylinder (23). It will start to close when the positive pressure in the pipeline is insufficient. The pressure sensor has a range of 0 to 50 kPa (gauge pressure) and a sampling frequency of 100 Hz. When the pressure in the chamber (gauge pressure) exceeds the upper limit of 20 kPa, the data acquisition and control system (DCS) will immediately issue an audible and visual alarm and execute the valve closing and pressure reduction command. When the overload protection unit in the spectrophotometric analysis module detects that the absorption peak intensity is greater than 80% of the full scale, the analyzer will reduce the light source power within 10 milliseconds to prevent the detector from oversaturating.

10. A method of using the high-viscosity powder self-ignition tester according to claim 1, characterized in that, Includes the following steps, 1) During the powder sample loading and preparation stage, the powder to be tested is weighed and loaded into the test chamber, with a loading amount between 250g and 500g. The microprocessor matches the bubble flow rate (initial value 0.03L / min, initial voltage value 1kV) according to the powder properties (viscosity grade, moisture content, and types of combustible components) input by the host computer, and records the current sample number and test date. 2) During the low-pressure stabilization stage, the data acquisition and control system (DCS) outputs an opening command of 0.03 liters / minute to the flow control valve and a voltage command of 1 kV to the high-voltage power supply. The gas enters the powder through the ceramic disc at a rate of 0.03 liters / minute, with a bubble diameter of about 0.5 mm. The pressure at the bottom of the silo stabilizes below 5 kPa. At this time, channels begin to appear inside the powder, causing the pressure signal to fluctuate by about 3 Hz. When the microprocessor detects that the fluctuation frequency is below 5 Hz, it determines that the channel has been initially formed, ends the low-pressure stabilization stage, and enters the pressurization stage. 3) During the pressurization phase, the microprocessor sends a signal to increase the high-voltage power supply to 3 kV, and the valve flow rate to 0.05 L / min. At this time, the bubble diameter increases to 1 mm, and the powder agglomeration begins to break up over a large area. The pressure sensor reading is about 8 kPa. During this phase, the microprocessor detects the flow rate and pressure at a 1-second cycle. If the pressure suddenly rises above 15 kPa, the valve opening is immediately reduced to 0.04 L / min and maintained for 5 seconds to avoid excessive impact inside the chamber. When the internal channels of the powder are fully expanded, the system pressure fluctuation range is reduced to within 2 kPa. The spectral module begins to scan the absorption peaks of oily or hydrocarbon volatile components. The pressurization phase usually lasts 20 to 30 seconds, and the specific time is determined by the DCS based on the pressure stability. 4) During the enrichment and stabilization stage, the microprocessor maintains the high-voltage power supply voltage at 3 kV and the valve flow rate at 0.05 L / min. Based on the powder properties, it executes constant-state operation in the database. At this time, the combustible components carried by the bubbles are concentrated and output. The spectrophotometer module collects spectral data at a frequency of 1 Hz and transmits the absorption peak intensity back to the microprocessor. The microprocessor compares the absorption peak intensity with the standard threshold. If the value corresponding to the C-H near-infrared absorption band in the range of 1.65-1.75 micrometers exceeds the safety limit, an alarm is immediately triggered. If the spectral amplitude is less than 5% of the full scale, the system continues to maintain this state until the acquisition is completed. 5) Result Determination and Data Output At the end of the enrichment and stabilization phase, the microprocessor records key data such as spectral peaks, valve flow rate, chamber pressure, and electrode voltage, and stores these parameters in an internal database. The system then sends the results to the host computer to generate a test report, which includes a timestamp, powder number, main spectral peaks, and safety judgment results. If the safety judgment result is higher than the threshold, the DCS closes the valve and reduces the voltage to below 1 kV within 0.5 seconds, while simultaneously issuing an audible and visual warning to prompt the operator to isolate or handle the powder.

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