A method for detecting flue gas in a fire resistance test of a fire resistance member

Abstract

This invention discloses a method for detecting flue gas during fire resistance testing of fire-resistant components. The method includes flue gas collection and detection steps: a flue gas collection device comprising a sampling head fixedly installed inside the test furnace, an outlet valve of the sampling head directly connected to a dust filter using a polytetrafluoroethylene (PTFE) filter element, an outlet of the dust filter directly connected to a drying device, and an outlet of the drying device connected to a secondary filtration device. The gas is then detected online using a Fourier transform infrared (FTIR) analysis system. This method provides data support for assessing the concentration limits of major toxic indicators in the flue gas. Based on these concentration limits, it provides criteria for additional classification of different categories of fire doors, facilitating an understanding of the degree of harm to the environment and human health posed by toxic components in the flue gas produced by different levels of fire doors after a fire.

Description

Technical Field

[0001] This invention relates to the field of exhaust gas detection technology, specifically a method for detecting flue gas during fire resistance testing of fire-resistant components. Background Technology

[0002] With the continuous development of the construction industry and various new building materials, the fire resistance performance of building components has become increasingly important. Currently, the fire resistance performance testing of building components is usually carried out in a fire resistance testing furnace. The fire resistance test of building components must be conducted in a fire resistance testing furnace in accordance with the temperature and pressure requirements in the national standard GB / T 9978.1-2008 "Fire Resistance Test Method for Building Components" to simulate a fire environment. The fire resistance performance of the specimen is determined by analyzing indicators such as integrity and thermal insulation.

[0003] The core material of fire doors needs to possess high fire resistance, fireproofing, and heat insulation properties to ensure that the door leaf can effectively isolate the fire source and slow the spread of fire in the event of a fire. Common materials include aluminum silicate wool, glass fiber, magnesium oxide, expanded perlite, and fluorocarbon polymer foam, which are widely used in the field of building fire protection. However, when exposed to high temperatures, the organic matter in the fire door core material undergoes incomplete combustion, producing carbon monoxide, which easily generates irritating and corrosive sulfides (such as H2S), nitrogen oxides (NOx), and toxic hydrogen cyanide and its salts, causing serious damage to the human nervous and cardiovascular systems. If the core material contains additives such as sodium alkylbenzene sulfonate, it will release carcinogens after being exposed to high temperatures. The amount of toxic gases produced is related to the type and category of the core material, and is also affected by the environment and conditions during a fire. If the content of harmful gases is too high, it will directly affect people's health during a fire. Therefore, the detection of harmful gases in smoke is imperative. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for detecting flue gas during fire resistance testing of fire-resistant components.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for detecting flue gas during fire resistance testing of fire-resistant components, characterized by including flue gas collection and detection steps:

[0006] The system includes a flue gas collection device, which includes a sampling head fixedly installed inside the test furnace. The outlet valve of the sampling head is directly connected to a dust filter, which uses a polytetrafluoroethylene filter element. The outlet of the dust filter is directly connected to a drying device, and the outlet of the drying device is connected to a secondary filtration device. The flue gas then enters a Fourier transform infrared spectroscopy (FTIR) analysis system for online detection.

[0007] Alternatively, the outlet of the drying device can be connected to a cooling device via a pipe. The cooling device is connected to a gas bag via a sampling assembly, which includes a sampling pump, a sampling valve, and a timer for recording the sampling time. The gas in the sampling bag then passes through a secondary filtration device before entering a Fourier transform infrared spectroscopy (FTIR) analysis system for detection. The filter material of the secondary filtration device is quartz wool or glass wool.

[0008] In the above scheme: the sampling bags need to be aged before each sampling. The aging procedure is to fill the sampling bags with nitrogen gas to about 50% of the bag volume, place them in a constant temperature chamber at 100°C or above for 2 days, change the air 3 times a day, and the air change interval is not less than 10 hours. The sampling tubes are placed in an oven at 65°C or above for at least 1 day. After aging, the bags and sampling tubes should be sealed and stored in a clean room.

[0009] In the above scheme: the drying device includes a drying tower, with a gas inlet at the bottom and a gas outlet at the top. The drying tower is filled with anhydrous calcium chloride desiccant. Calcium chloride is a neutral desiccant that only absorbs moisture and does not absorb other acidic gases in the gas.

[0010] In the above scheme: the sampling head is a single-hole sampling head or a multi-hole sampling head, and the sampling head is provided with sampling holes, the diameter of which is greater than 3mm. The refractory component testing furnace is divided into small, medium, and large-sized model furnaces. Small-sized testing furnaces use single-hole sampling heads, while medium and large-sized testing furnaces use multi-hole sampling heads. The sampling port should be drilled according to the size of the testing furnace to fix the sampling head. The diameter of the sampling head should not be less than 3mm. The sampling head should be made of a material that is corrosion-resistant, pollution-resistant, high-temperature resistant, and does not chemically react with flue gas. The sampling head should be placed in a location where the flue gas is uniformly mixed and there is no turbulence.

[0011] Calculation of acid gas concentration correction values:

[0012] C = Va / Vs × 10 6

[0013] Vs=Sf×St

[0014] Va = (Q / M) × 22.4

[0015] Where: C is the correction value for acid gas concentration (ppm)

[0016] Vs Total volume of gas passing through the filter during gas sampling (L)

[0017] Sf is the gas sampling flow rate (L / min).

[0018] St is the gas sampling time (in minutes).

[0019] Va is the relative volume of the gas.

[0020] 22.4 is the molar volume (L / mol) under standard conditions.

[0021] M is the molar mass of the gas (g / mol).

[0022] Q is the total amount of acidic gas remaining on the filter material (g).

[0023] In the above scheme: the cooling device is a heat exchanger, and the cooling medium is water or air.

[0024] In the above scheme: the sampling bag is made of polytetrafluoroethylene.

[0025] In the above scheme: the Fourier transform infrared spectroscopy (FTIR) analysis system uses an MCT or DTGS detector; the optical path length of the gas cell is greater than 4m; and the spectral range is 4500-650cm². -1 (MCT); The wavelength resolution of the spectrometer should be 4 cm⁻¹. -1 .

[0026] The high-temperature flue gas collected by the sampling head first passes through a dust filter to remove large solid particles. The outlet valve of the sampling head is directly connected to the dust filter, reducing pipeline transport and preventing temperature drops and condensation of water vapor. Water also dissolves acidic gases such as HCN, H2S, and SO2, thus minimizing the loss of acidic gases during drying and filtration. The dust filter outlet is then directly connected to a drying device, with a distance of less than 2 cm between the filter and the drying device to avoid excessive cooling. The drying device primarily absorbs H2O from the flue gas. Because the high-temperature flue gas contains acidic substances such as HCN, H2S, and SO2, these substances readily combine with H2O and adsorb onto the sampling device and sampling pipeline after temperature reduction; therefore, H2O must be removed first. The flue gas after drying is then cooled by a cooling device before passing through the sampling assembly and being drawn into the gas bag. The sampling pump in the sampling assembly provides the sampling power, a timer records the sampling time, and a flow meter records the flow rate. The sampling bag is made of polytetrafluoroethylene (PTFE), which does not adsorb substances from the flue gas. The collected gas should be analyzed as soon as possible (generally within 8 hours). The collected gas is then analyzed using a Fourier transform infrared spectroscopy (FTIR) system.

[0027] The flue gas from the sampling bag is filtered through a filter (quartz wool or glass wool) to remove impurities that cannot be vaporized. After secondary filtration, the flue gas is heated through a heating transmission line (heated to about 180℃-190℃) and enters the front-end filter of the Fourier transform infrared gas cell. Then it is analyzed in the gas cell, and the analyzed gas is discharged through the tail gas port.

[0028] The gas collection device of this invention has the following beneficial effects: after the flue gas is filtered and dusted, it is first dried and then cooled. This avoids water vapor condensing into water after the gas cools down, thus preventing the carry-over of acidic gases and minimizing the loss of acidic gases. It provides data support for assessing the concentration limits of major toxic indicators in flue gas. Based on the concentration limits of major toxic indicators, it provides a criterion for additional classification of different types of fire doors, which is beneficial for understanding the degree of harm to the environment and human health from the toxic components in the flue gas produced by different levels of fire doors after a fire. Attached Figure Description

[0029] Figure 1 This is a flowchart of the flue gas collection device for fire resistance testing of fire-resistant components according to the present invention.

[0030] Figure 2 Chart showing the trend of total acid gas volume. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] Example 1

[0033] like Figure 1 As shown, the refractory component refractory test flue gas collection device includes a sampling head 1 fixedly installed inside the test furnace. The sampling head 1 can be a single-hole sampling head or a multi-hole sampling head, with sampling holes 101 on it. The diameter of the sampling holes is greater than 3mm. The figure shows a multi-hole sampling head. Refractory component test furnaces are divided into small, medium, and large-sized model furnaces. Small-sized test furnaces use single-hole sampling heads, while medium and large-sized test furnaces use multi-hole sampling heads. The sampling port should be drilled according to the size of the test furnace. The sampling head should be fixedly installed and made of a material that is corrosion-resistant, pollution-resistant, high-temperature resistant, and does not chemically react with the flue gas. The sampling head should be placed in a location where the flue gas is uniformly mixed and there is no turbulence. An outlet valve 2 is provided at the outlet end of the sampling head 1. The outlet valve 2 of the sampling head 1 is directly connected to a dust filter 3, which uses a polytetrafluoroethylene (PTFE) filter element. The structure of the dust filter 3 is existing technology, designed to intercept large dust particles. The outlet of dust filter 3 is directly connected to drying device 4. Drying device 4 includes a drying tower with a gas inlet 401 at the bottom and a gas outlet 402 at the top. The drying tower is filled with anhydrous calcium chloride desiccant. Gas inlet 401 is directly connected to dust filter 3, and the distance between dust filter 3 and drying device 4 is less than 2 cm.

[0034] The outlet of the drying device 4 is connected to a secondary filtration device, and then enters a Fourier transform infrared spectroscopy (FTIR) analysis system for online detection.

[0035] The outlet of the drying device 4 is connected to the cooling device 5 via a sampling tube. The cooling device is a heat exchanger, and the cooling medium is water or air; this is existing technology. The cooling device 5 is connected to the gas bag 6 via a sampling assembly. The sampling bag is made of polytetrafluoroethylene (PTFE). The assembly includes a sampling pump 7, a sampling valve 8, and a timer 9 for recording the sampling time. The gas in the sampling bag then passes through a secondary filtration device before entering the Fourier Transform Infrared Spectroscopy (FTIR) analysis system for detection. The filter material of the secondary filtration device is quartz wool or glass wool.

[0036] Sampling bags must undergo aging treatment before each sampling. The aging treatment procedure is as follows: fill the sampling bag with nitrogen gas to about 50% of the bag's volume, place it in a constant temperature chamber at 100°C or above for aging for 2 days, with air exchanged 3 times a day and an interval of not less than 10 hours between air exchanges. Place the sampling tube in an oven at 65°C or above for aging for at least 1 day. After aging, the bags and sampling tubes should be sealed and stored in a clean room.

[0037] The Fourier Transform Infrared (FTIR) spectroscopy analysis system employs an MCT or DTGS detector; gas cell optical path length: 5m; spectral range: 4500-650cm². -1 (MCT); The wavelength resolution of the spectrometer should be 4 cm⁻¹. -1 The gas cell volume was 250 mL, and the scanning frequency was 0.2 s. The detection limits for each gas component within the characteristic absorption peak range are shown in Table 1.

[0038] Table 1. Detection limits for each gas component within the characteristic absorption peak range.

[0039]

[0040]

[0041] The core material of fire doors needs to possess high fire resistance, fireproofing, and heat insulation properties to ensure that the door leaf can effectively isolate the fire source and slow the spread of fire in the event of a fire. Common materials include aluminum silicate wool, glass fiber, magnesium oxide, expanded perlite, and fluorocarbon polymer foam, which are widely used in the field of building fire protection. However, when exposed to high temperatures, the organic matter in the fire door core material undergoes incomplete combustion, producing carbon monoxide, which easily generates irritating and corrosive sulfides (such as H2S), nitrogen oxides (NOx), and toxic hydrogen cyanide and its salts, causing serious damage to the human nervous and cardiovascular systems. If the core material contains additives such as sodium alkylbenzene sulfonate, it will release carcinogens after being exposed to high temperatures. The amount of toxic gases produced is related to the type and category of the core material, and is also affected by the environment and conditions during a fire. Based on the above testing methods, the maximum concentration volume of gaseous components such as carbon monoxide (CO), carbon dioxide (CO2), hydrogen cyanide (HCN), hydrogen chloride (HCl), hydrogen bromide (HBr), hydrogen fluoride (HF), nitrogen oxides (NOx), sulfur dioxide (SO2), and formaldehyde (HCHO) in the smoke produced during fire resistance tests of fire doors with different core materials and types was analyzed and statistically determined.

[0042] Because acidic gases tend to adhere to the core material, correction is necessary.

[0043] Calculation of acid gas concentration correction values:

[0044] C = Va / Vs × 10 6

[0045] Vs=Sf×St

[0046] Va = (Q / M) × 22.4

[0047] Where: C is the correction value for acid gas concentration (ppm)

[0048] Vs Total volume of gas passing through the filter during gas sampling (L)

[0049] Sf is the gas sampling flow rate (L / min).

[0050] St is the gas sampling time (in minutes).

[0051] Va is the relative volume of the gas.

[0052] 22.4 is the molar volume (L / mol) under standard conditions.

[0053] M is the molar mass of the gas (g / mol).

[0054] Q represents the total amount of acidic gas remaining on the filter material (g).

[0055] Q is calculated as follows: After each sampling test, remove the filter cartridges from the dust filter and secondary filtration device, place them in a minimum amount of analytical pure water sufficient to submerge the filter cartridges, sonicate the solution in an ultrasonic cleaner for at least 10 minutes, bring the solution to a known volume, and quantitatively analyze the amount of each acidic gaseous substance. Analytical method reference:

[0056] Analysis of HCN in Filter Material Solution

[0057] The spectrophotometric method (picrate method) is suitable for HCN content greater than 0.3 mg; the dimethyl ketone method is suitable for HCN content less than 0.3 mg. The detection limit for both methods is 0.0004 mg.

[0058] All substances on the filter material were dissolved in H2O and diluted to a total volume V. A certain volume of solution V1 was taken, and 30 mL of titrant (titer: 3 g / L picric acid aqueous solution and 50 g / L sodium carbonate aqueous solution) was added. The solution was heated in a 90°C water bath for 10 min to carry out a colorimetric reaction. After the solution cooled to room temperature, quantitative analysis was performed using a spectrophotometer, and blank calibration of the sample (i.e., a solution containing only the reagent) was performed simultaneously. A calibration curve was plotted using a series of KCN solutions containing a certain concentration (range 1 g / L to 10 g / L). The HCN content in the mixed solution could be obtained by analyzing the absorbance of the sample against the standard curve, with the unit being milligrams (mg). The calculation of the HCN content in the filter material solution is given by formula (1).

[0059]

[0060] V1: Solution used for analysis

[0061] V: Total volume of the filter material after dissolution

[0062] X: HCN content obtained from analyzing the solution.

[0063] e: Collection efficiency (Note: Part of the target substance in the flue gas is adsorbed, and the other part is directly detected by Fourier transform infrared spectroscopy. The e value of this filter material solution is 1; if the unadsorbed flue gas is not subsequently detected, the e value needs to be calculated, which can be verified by testing with two collectors) In this practical application, it is taken as 1. Analysis of halogen acid gas and SO2 content in filter material solution Halogen acid gas can be directly detected by establishing a standard series of halide ion concentrations using ion chromatography to detect the concentration of halide ions in the solution. Sulfur dioxide is absorbed by alkaline absorption liquid to form sulfite, and sulfite is oxidized by peroxide to sulfate. The sulfate content is also analyzed by ion chromatography, and the concentration of sulfur dioxide in the filter material solution can be calculated. The content of halogen acid gas in the filter material solution is calculated according to formula (2); the content of SO2 in the filter material solution is calculated according to formula (3). The standard series for halide and sulfate ion concentrations are 0.00 mg / L, 1.00 mg / L, 2.00 mg / L, 10.0 mg / L, and 20.0 mg / L. A standard curve is plotted with peak height or peak area as the ordinate. Optimize measurement conditions or parameters according to the instrument's instruction manual.

[0064] Calculate the concentration of halogenated acid gases according to formula (2), and calculate the concentration of SO2 according to formula (3):

[0065]

[0066]

[0067] In the formula:

[0068] C HX Hydrogen halide concentration (ppm)

[0069] C X Concentration of halide ions in the filter material solution (mg / L)

[0070] C SO4 Sulfate ion concentration (mg / L) in the filter material solution

[0071] V2, V3: Solutions used for analysis (L)

[0072] V: Total volume of the filter material after dissolution (L)

[0073] e: Collection efficiency (Note: Part of the target in the flue gas is adsorbed, and the other part is directly detected by Fourier transform infrared spectroscopy. The e value of this filter material solution is taken as 1; if the unadsorbed flue gas is not subsequently detected, the e value needs to be calculated, which can be verified by testing with two collectors.) This experiment is taken as 1.

[0074] M HX Molar mass of hydrogen halides (g / mol)

[0075] M X Molar mass of halide ions (g / mol)

[0076] Table 2. Correction values ​​for acid gas concentrations.

[0077]

[0078]

[0079]

[0080]

[0081]

[0082]

[0083] The maximum volume concentration data of each toxic component in the flue gas are shown in Table 3 below:

[0084] Table 3 Maximum volume concentrations of various toxic components in flue gas

[0085]

[0086]

[0087]

[0088]

[0089]

[0090] The data in the table clearly shows that the composition and content of toxic gases released during fire resistance tests differ among different types and grades of fire doors. Under almost identical combustion conditions (such as temperature, gas flow rate, and oxygen concentration), test methods, and equipment, the test data are reliable and representative. By comparing statistical data from different types and grades of fire doors, the influence of various factors on the monitoring results is understood, and the trend of changes in the key parameter, total acid gas content, is analyzed, revealing patterns and correlations. Figure 2 As shown:

[0091] It can be seen that during the fire resistance test, the acidic gas produced by steel doors ranged from 300-520 ppm, with an average of approximately 400 ppm; the acidic gas produced by steel-wood doors ranged from 150-270 ppm, with an average of approximately 190 ppm; and the acidic gas produced by wooden doors ranged from 70-110 ppm, with an average of approximately 85 ppm. According to Table 3, the CO2 produced by the combustion of steel doors, steel-wood doors, and wooden doors were between 30000-50000 ppm, 13000-29000 ppm, and 10000-16000 ppm, respectively; CO was between 900-1500 ppm, 500-1000 ppm, and 150-480 ppm, respectively; and HCHO was approximately between 15-30 ppm, 10-20 ppm, and 0-10 ppm, respectively. Comprehensive analysis shows that the dispersion is small. It can be used for risk assessment. For example, risk assessment can be conducted using the "risk matrix method" recommended in GB / T22760-2020 "Guidelines for Risk Assessment of Consumer Product Safety".

[0092] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for detecting flue gas during fire resistance testing of fire-resistant components, characterized in that: Including the steps for collecting and detecting flue gas: The system includes a flue gas collection device, which comprises a sampling head fixedly installed inside the test furnace. The outlet valve of the sampling head is directly connected to a dust filter, which uses a polytetrafluoroethylene (PTFE) filter element. The outlet of the dust filter is directly connected to a drying device. The outlet of the drying device is connected to a cooling device via a pipe. The cooling device is connected to a sampling bag via a sampling assembly, which includes a sampling pump, a sampling valve, and a timer for recording the sampling time. The gas in the sampling bag then passes through a secondary filtration device before entering a Fourier transform infrared spectroscopy (FTIR) analysis system for detection. The filter material of the secondary filtration device is quartz wool or glass wool. Calculation of acid gas concentration correction values: C = Va / Vs × 10 6 Vs = Sf × St Va = (Q / M) × 22.4 In the formula: C is the correction value for acid gas concentration (ppm). Vs is the total volume (L) of gas passing through the filter during gas sampling. Sf is the gas sampling flow rate (L / min). St is the gas sampling time (min). Va is the relative volume of the gas. 22.4 is the molar volume (L / mol) under standard conditions. M is the molar mass of the gas (g / mol). Q is the total amount of acidic gas remaining on the filter material (g); Sampling bags must undergo aging treatment before each sampling. The aging procedure is as follows: fill the sampling bag with nitrogen gas to 50% of its volume, place it in a constant temperature chamber at 100℃ or above for 2 days, changing the air 3 times a day with an interval of no less than 10 hours. Place the sampling tubes in an oven at above 65℃ for at least 1 day. After aging, the bags should be sealed and stored in a clean room along with the sampling tubes. The Fourier Transform Infrared (FTIR) spectroscopy analysis system uses an MCT or DTGS detector; the gas cell optical path length is 4m or more; the spectral range is 4500-650 cm⁻¹. -1 (MCT); The wavelength resolution of the spectrometer should be 4 cm⁻¹. -1 .

2. The method for detecting flue gas during fire resistance testing of fire-resistant components according to claim 1, characterized in that: The drying device includes a drying tower with a gas inlet at the bottom and a gas outlet at the top. The drying tower is filled with anhydrous calcium chloride desiccant.

3. The method for detecting flue gas during fire resistance testing of fire-resistant components according to claim 2, characterized in that: The sampling head is a single-hole sampling head or a multi-hole sampling head, and the sampling head is provided with sampling holes, the diameter of which is greater than 3mm.

4. The method for detecting flue gas during fire resistance testing of fire-resistant components according to claim 3, characterized in that: The cooling device is a heat exchanger, and the cooling medium is water or air.

5. The method for detecting flue gas during fire resistance testing of fire-resistant components according to claim 4, characterized in that: The sampling bag is made of polytetrafluoroethylene.

Images