Chemical solid dust drying process risk assessment and control method

Abstract

The invention discloses a chemical solid dust drying process risk assessment and control method, and belongs to the technical field of chemical safety technology and engineering, and the method comprises the following steps: S10, assessing the thermal hazard of solid dust; s20, evaluating the electrostatic hazard of the solid dust; s30, evaluating the explosion hazard of the solid dust; and S40, evaluating the explosion severity of the solid dust. The risk assessment and control problem of the dust drying process can be solved, the production safety is guaranteed, and a scientific basis is provided for how to carry out assessment of the chemical solid dust drying process.

Description

Technical Field

[0001] This invention belongs to the field of chemical safety technology and engineering technology, and more specifically, it relates to a risk assessment and control method for the drying process of chemical solid dust. Background Technology

[0002] Solid dust drying is an important unit operation in the chemical industry. Its purpose is to remove moisture or volatile solvents from substances through drying, thereby meeting the requirements of product quality specifications, storage, and subsequent processing.

[0003] The main risks inherent in the drying process include dust thermal hazards, electrostatic hazards, and explosion hazards. If these risks are not effectively identified, assessed, and controlled, they can easily lead to safety accidents, harm the environment and human health, and cause significant economic losses. However, there is currently very little research, both domestically and internationally, on risk assessment and control methods for chemical solid dust drying processes, especially regarding risk assessment methods, for which no relevant reports have been published.

[0004] Therefore, there is an urgent need to develop a risk assessment and control method for the drying process of chemical solid dust, to solve the problem of risk assessment and control in the dust drying process, and to ensure the safe operation of the dust drying unit. Summary of the Invention

[0005] To solve the above problems, the present invention adopts the following technical solution: A method for risk assessment and control of a chemical solid dust drying process, comprising: S10. Assess the thermal hazards of solid dust. S11. Collect process information on the drying of solid dust and determine the upper limit temperature of the drying process. T p ; S12. Conduct thermal hazard tests on solid dust using a combined testing and research approach, obtain the temperature corresponding to the time when the maximum reaction rate is reached in 24 hours under adiabatic conditions, and further conduct decomposition kinetic analysis on the materials undergoing thermal decomposition to obtain... T D24 ; S13. Obtain the minimum ignition temperature (MIT) of the dust cloud. c Minimum Ignition Temperature (MIT) of Dust Layer L ; S14. Assess the thermal hazards of solid dust and select... T p and T D24 MIT c MIT L Compare the data and consider a certain safety margin; S20. Assess the electrostatic hazards of solid dust. Obtain the minimum ignition energy (MIE) of dust clouds to assess the electrostatic hazards of solid dust; S30. Assess the hazards of solid dust explosions. Obtain the limiting oxygen concentration (LOC) and lower explosive limit (MEC) of dust clouds to assess the hazards of solid dust explosions; S40. Assess the severity of solid dust explosions. Obtain the maximum explosion index K max To assess the severity of solid dust explosions.

[0006] Furthermore, in S12, for undecomposed materials, based on the adiabatic tracking time... t z and tracking temperature forecasts T D24 The expression is as follows: ; In the formula, T z This indicates the upper limit temperature for adiabatic tracking without decomposition.

[0007] Furthermore, in S14, the thermal hazard of solid dust is assessed. T D24 , T p MIT c and MIT L As evaluation criteria, the following are included: when T p <T D24 , T p <2 / 3 MIT c , T p <MIT> L When -75 is simultaneously satisfied, the thermal safety risk of the drying process is considered acceptable. when T p ≥T D24 , T p ≥2 / 3 MIT c , T p ≥MIT L -75, if any condition is met, the thermal safety risk of the drying process is considered unacceptable.

[0008] Furthermore, in S20, an assessment of the electrostatic hazards of solid dust is conducted, including: MIE>1000, the sample is almost insensitive to electrostatic sparks, and the grade is 1; 300 < MIE ≤ 1000, the sample is less sensitive to electrostatic sparks and the grade is 1; 100 < MIE ≤ 300, the sample is more sensitive to electrostatic sparks and the grade is 1; 30 < MIE ≤ 100, the sample is sensitive to electrostatic sparks and the grade is 2; 10 < MIE ≤ 30, the sample is very sensitive to electrostatic sparks and the grade is 2; 1 < MIE ≤ 10, the sample is extremely sensitive to electrostatic sparks and the grade is 3; MIE ≤ 1, the sample is extremely sensitive to electrostatic sparks and the grade is 3.

[0009] Furthermore, in S30, the hazard of solid dust explosion is evaluated, LOC is selected and compared with the oxygen content O c at the factory site, and a certain safety margin is considered; LOC and O c as the evaluation criteria include: When LOC (LOC ≥ 5%) - 2% > O c or LOC (LOC < 5%) · 60% > O c it is considered that the risk of solid dust explosion in the drying process is acceptable; When LOC (LOC ≥ 5%) - 2% ≤ O c or LOC (LOC < 5%) · 60% ≤ O c it is considered that the risk of solid dust explosion in the drying process is unacceptable.

[0010] Furthermore, MEC is selected and compared with the dust concentration FDC at the factory site. MEC and FDC as the evaluation criteria include: When MEC > FDC, it is considered that the risk of solid dust explosion in the drying process is acceptable; When MEC ≤ FDC, it is considered that the risk of solid dust explosion in the drying process is unacceptable.

[0011] Furthermore, in S40, the severity of solid dust explosion is evaluated. The specific criteria are: The grade is St0, K max = 0, and the explosion characteristic is no explosion; The grade is St1, 0 < K max < 20.0, and the explosion characteristic is weak; The grade is St2, 20.0 ≤ K max < 30.0, and the explosion characteristic is strong; The grade is St3, K max ≥ 30.0, and the explosion characteristic is severe.

[0012] Compared with the prior art, the present invention has the following beneficial effects: The method for risk assessment and control of chemical solid dust drying process provided by this invention can solve the problem of risk assessment and control of dust drying process, ensure production safety, and provide a scientific basis for how to carry out the assessment of chemical solid dust drying process. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0014] Figure 1 The present invention provides a flowchart of a risk assessment and control method for a chemical solid dust drying process.

[0015] Figure 2 The result is a differential scanning calorimetry (DSC) curve of the sealed sample.

[0016] Figure 3 The time-temperature-pressure curve of the calorimetric test is used for rapid screening of samples.

[0017] Figure 4 The sample's adiabatic thermal test time-temperature-pressure curve is shown.

[0018] Figure 5 The TMRad curve of the sample decomposition reaction is shown in Figure 1.

[0019] Figure 6 The TMRad curve for the sample decomposition reaction is shown in Figure 2. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1

[0022] refer to Figure 1 A method for risk assessment and control of chemical solid dust drying process, comprising: S10. Assess the thermal hazards of solid dust. S11. Collect process information on the drying of solid dust and determine the upper limit temperature of the drying process. Tp ; S12. Conduct thermal hazard tests on solid dust using a combined testing and research approach, obtain the temperature corresponding to the time when the maximum reaction rate is reached in 24 hours under adiabatic conditions, and further conduct decomposition kinetic analysis on the materials undergoing thermal decomposition to obtain... T D24 ; Specifically, for undecomposed materials, based on the adiabatic tracking time t z and tracking temperature forecasts T D24 The expression is as follows: ; In the formula, T z This indicates the upper limit temperature for adiabatic tracking without decomposition.

[0023] In this embodiment, the combined testing and research methods employed include differential scanning calorimetry, rapid screening calorimetry, adiabatic calorimetry, and microcalorimetry. The relevant testing methods refer to GB / T 42300 Standard for Safety Risk Assessment of Fine Chemical Reactions.

[0024] S13. Obtain the minimum ignition temperature (MIT) of the dust cloud. c Minimum Ignition Temperature (MIT) of Dust Layer L ; In this embodiment, the minimum ignition temperature (MIT) of the dust cloud is obtained using relevant standard methods. c Minimum Ignition Temperature (MIT) of Dust Layer L For example, GB / T 16429-1996 Determination of the minimum ignition temperature of dust clouds and GB / T 16430-2018 Determination of the minimum ignition temperature of dust layers.

[0025] S14. Assess the thermal hazards of solid dust and select... T p and T D24 MIT c MIT L Compare the data and consider a certain safety margin; Among these, the thermal hazards of solid dust were assessed. T D24 , T p MIT c and MIT L As evaluation criteria, the following are included: when T p <T D24 , T p<2 / 3 MIT c , T p <MIT L - 75 are both satisfied, the thermal safety risk during the drying process is considered acceptable; When T p ≥T D24 , T p ≥2 / 3 MIT c , T p ≥MIT L - 75, when any one of the conditions is met, the thermal safety risk during the drying process is considered unacceptable.

[0026] The following Table 1 is used to evaluate the thermal hazard of solid dust.

[0027] Table 1

[0028] S20. Evaluate the electrostatic hazard of solid dust

[0029] Obtain the minimum ignition energy MIE of the dust cloud to evaluate the electrostatic hazard of solid dust; Among them, the minimum ignition energy MIE of the dust cloud is obtained by using relevant standard methods, such as the method for determining the minimum ignition energy of dust cloud in GB / T 16428 - 1996.

[0030] Specifically, evaluating the electrostatic hazard of solid dust includes: MIE > 1000, the sample is almost insensitive to electrostatic sparks, and the grade is 1; 300 < MIE ≤ 1000, the sample is less insensitive to electrostatic sparks, and the grade is 1; 100 < MIE ≤ 300, the sample is relatively sensitive to electrostatic sparks, and the grade is 1; 30 < MIE ≤ 100, the sample is sensitive to electrostatic sparks, and the grade is 2; 10 < MIE ≤ 30, the sample is very sensitive to electrostatic sparks, and the grade is 2; 1 < MIE ≤ 10, the sample is extremely sensitive to electrostatic sparks, and the grade is 3; MIE ≤ 1, the sample is extremely sensitive to electrostatic sparks, and the grade is 3.

[0031] The following Table 2 is used to evaluate the electrostatic hazard of solid dust.

[0032] Table 2

[0033] S30. Assess the hazards of solid dust explosions.

[0034] Obtain the limiting oxygen concentration (LOC) and lower explosive limit (MEC) of dust clouds to assess the hazards of solid dust explosions; Among them, the limiting oxygen concentration (LOC) of dust cloud and the lower explosive limit (MEC) of dust cloud are obtained by relevant standard methods (e.g., ASTM E2931-13(2019) Determination of Limiting Oxygen Concentration of Dust Cloud).

[0035] In this embodiment, the explosion hazard of solid dust is assessed, and the LOC (Local Oxygen Content) and the controlled oxygen content (O2) at the factory site are selected. c Compare and consider a certain safety margin; LOC, O c The evaluation criteria include: When LOC (LOC≥5%)-2%>O c Or LOC (LOC < 5%) · 60% > 0 c At that time, the risk of solid dust explosion during the drying process was considered acceptable; When LOC (LOC≥5%)-2%≤O c Or LOC (LOC < 5%) · 60% ≤ O c At that time, it was considered that the risk of solid dust explosion during the drying process was unacceptable.

[0036] The MEC (Medium-to-Concentration) and the FDC (Factory Direct Dust Concentration) at the factory site were selected for comparison. MEC and FDC were used as evaluation benchmarks, including: When MEC > FDC, the risk of solid dust explosion during the drying process is considered acceptable. When MEC≤FDC, the risk of solid dust explosion during the drying process is considered unacceptable.

[0037] MEC and FDC at the factory site were selected for comparison, as shown in Table 3, with MEC and FDC serving as evaluation benchmarks.

[0038] Table 3

[0039] S40. Assess the severity of solid dust explosions.

[0040] Obtain the maximum explosion index Kmax to assess the severity of solid dust explosions.

[0041] The maximum explosion index was obtained using relevant standard methods, such as GB / T 16426-1996, "Method for Determining the Maximum Explosion Pressure and Maximum Pressure Rise Rate of Dust Clouds". K max .

[0042] The assessment of the severity of solid dust explosions is based on the following criteria: The level is St0, K max =0, the explosion characteristic is non-explosive; The level is St1, 0 <K max <20.0, the explosion characteristics are weak; The grade is St2, and 20.0 ≤ K. max <30.0, the explosion characteristic is strong; Level St3, K max ≥30.0, the explosion characteristics are severe.

[0043] The severity of solid dust explosions was assessed using the following tables-Table 4.

[0044] Table 4

[0045] Example 2

[0046] This embodiment is based on Embodiment 1, and uses a certain chemical product as an example for illustration.

[0047] The drying conditions for a certain chemical product are as follows: A chemical product is placed in a drying tower for air drying. The highest temperature of the material during the drying process is 90~110℃, the drying time for a single batch is 6 hours, the drying capacity is 150 kg / h, and the hot air volume is 10000 m³ / h. 3 / h, the on-site oxygen content is controlled to not exceed 8%.

[0048] A risk assessment of the product drying process needs to be conducted based on existing conditions, and risk control measures should be established for high-risk stages.

[0049] First, a combined testing approach (including differential scanning calorimetry, rapid screening calorimetry, adiabatic calorimetry, and microcalorimetry) was used to conduct thermal stability tests on the solid dust. Further decomposition kinetics studies were carried out to obtain the temperature at which the maximum reaction rate was reached in 24 hours under adiabatic conditions. T D24 .

[0050] The thermal stability test information is summarized in Tables 5 below: Table 5 Material Stability Information

[0051] Note: The data in the table are the results of adiabatic thermal tests.

[0052] Depend on Figure 2As shown, the differential scanning calorimetry results indicate that the sample exhibits a segment of exothermic signal within the test range. An exothermic signal is generated at 311.6℃, indicating exothermic decomposition of the sample. Within the test range of 311.6℃ to 355.6℃, the exothermic heat generated by the sample is 100.1 J / g (based on sample mass, the same below). Subsequently, when the temperature is raised to 400℃, no significant exothermic signal is observed.

[0053] Depend on Figure 3 As shown, the rapid screening calorimetric test results indicate that the sample exhibits a segment of exothermic signal within the test range. When the system temperature is raised to approximately 300℃, a significant exothermic signal is generated, indicating exothermic decomposition of the sample accompanied by gas generation. After cooling, the pressure does not return to normal, further demonstrating that the sample decomposes during the test, generating irreversible gas.

[0054] Depend on Figure 4 As shown, the adiabatic thermal test results indicate that the sample began to release gas at 149.7℃. Upon further heating to 268.7℃, the system began to show a significant exothermic signal, indicating exothermic decomposition of the sample. The system temperature and pressure rose slowly. Within the test range of 268.7℃ to 293.3℃, ​​the exothermic heat was 100 J / g, and the temperature increased by 24.6℃. The maximum temperature rise rate reached 1.0℃ / min at 288.6℃, and the maximum pressure rise rate reached 0.01 MPa / min at 279.1℃.

[0055] Based on the results of the thermal stability study, further decomposition kinetics studies were conducted on the sample to obtain the time to reach the maximum reaction rate under adiabatic conditions. The results are as follows: Figure 5 and Figure 6 As shown.

[0056] Based on thermodynamic studies, the temperature at which the maximum reaction rate of the sample is reached in 2 hours under adiabatic conditions is... T D2 For 260℃, T D4 247℃ T D8 234℃ T D24 216℃ T D168 The temperature was 187℃ (the system Phi was 1.05).

[0057] The samples were tested using GB / T 16429-1996 Determination of Minimum Ignition Temperature of Dust Cloud and GB / T 16430-2018 Determination of Minimum Ignition Temperature of Dust Layer. The test results showed that the minimum ignition temperature of the dust cloud was 560℃ and the minimum ignition temperature of the dust layer was 400℃. The above test data were used to assess the thermal hazard of solid dust.

[0058] The thermal hazard parameters of solid dust are shown in Tables 6-6 below: Table 6

[0059] The results of the thermal hazard assessment of solid dust are shown in Tables 7-7 below: Table 7

[0060] Based on the assessment results, under the existing dry conditions, the thermal hazard assessment of the dust is an acceptable risk, and the probability of an accident caused by thermal runaway of the solid dust is low.

[0061] The sample was tested using GB / T 16428-1996, the method for determining the minimum ignition energy of dust clouds. The test results showed that the minimum ignition energy of the sample dust cloud was greater than 1000 mJ. The electrostatic hazards of solid dust were assessed using the above test data, as shown in Tables 8-8 below: Table 8

[0062] Based on the assessment results, under the existing drying conditions, the electrostatic hazard level of this solid dust is Level 1, and it is recommended to take routine measures to ground the drying equipment.

[0063] The samples were tested using ASTM E2931-13(2019) Determination of Limiting Oxygen Concentration in Dust Clouds and GB / T 16425-2018 Determination of Lower Explosive Limit Concentration in Dust Clouds. The test results showed that the lower explosive limit concentration of dust clouds was 160~200 g / m³. 3 The limiting oxygen concentration of the dust cloud is 15.5%. The above test data are used to assess the hazards of solid dust explosions.

[0064] Table 9

[0065] The thermal hazard parameters of solid dust are shown in Tables 1-10 below: Table 10

[0066] Based on the assessment results, under the existing dry conditions, the risk of dust explosion is acceptable, and the probability of a dust explosion accident caused by this solid dust is low.

[0067] (9) The sample was tested using the method for determining the maximum explosion pressure and maximum pressure rise rate of dust clouds in GB / T 16426-1996. The test results showed that the maximum explosion pressure of the dust cloud was 0.65 MPa, the maximum pressure rise rate was 16.4 MPa / s, and the maximum explosion index was 4.4 MPa. m s -1 The severity of solid dust explosions was assessed using the above test data, as shown in Tables 1-11 below: Table 11

[0068] According to the assessment results, the severity level of the solid dust explosion is St1, which is considered a weak explosion.

[0069] The technical solutions of the present invention have been fully described above. It should be noted that the specific embodiments of the present invention are not limited to the above description. All technical solutions formed by those skilled in the art based on the spirit and essence of the present invention by adopting equivalent transformations or equivalent transformations in terms of structure, method or function fall within the protection scope of the present invention.

Claims

1. A method for risk assessment and control in the drying process of chemical solid dust, characterized in that, Including: S10. Evaluate the thermal hazard of solid dust S11. Collect process information on the drying of solid dust and determine the upper limit temperature of the drying process. T p ; S12. Conduct thermal hazard tests on solid dust using a combined testing and research approach, obtain the temperature corresponding to the time when the maximum reaction rate is reached in 24 hours under adiabatic conditions, and further conduct decomposition kinetic analysis on the materials undergoing thermal decomposition to obtain... T D24 ; S13. Obtain the minimum ignition temperature (MIT) of the dust cloud. c Minimum Ignition Temperature (MIT) of Dust Layer L ; S14. Assess the thermal hazards of solid dust and select... T p and T D24 MIT c MIT L Compare the data and consider a certain safety margin; S20. Evaluate the electrostatic hazard of solid dust Obtain the minimum ignition energy MIE of the dust cloud and evaluate the electrostatic hazard of solid dust; S30. Evaluate the explosion hazard of solid dust Obtain the limiting oxygen concentration LOC and the lower explosive limit concentration MEC of the dust cloud and evaluate the explosion hazard of solid dust; S40. Evaluate the severity of solid dust explosion Obtain the maximum explosion index K max To assess the severity of solid dust explosions.

2. The method for risk assessment and control of chemical solid dust drying process according to claim 1, characterized in that, In S12, for undecomposed materials, based on the adiabatic tracking time... t z and tracking temperature forecasts T D24 The expression is as follows: ； In the formula, T z This indicates the upper limit temperature for adiabatic tracking without decomposition.

3. The method for risk assessment and control of chemical solid dust drying process according to claim 2, characterized in that, In S14, the thermal hazards of solid dust are assessed. T D24 , T p MIT c and MIT L As evaluation criteria, the following are included: when T p <T D24 , T p <2 / 3 MIT c , T p <MIT> L When -75 is simultaneously satisfied, the thermal safety risk of the drying process is considered acceptable. when T p ≥T D24 , T p ≥2 / 3 MIT c , T p ≥MIT L -75, if any condition is met, the thermal safety risk of the drying process is considered unacceptable.

4. The method for risk assessment and control of chemical solid dust drying process according to claim 1, characterized in that, In S20, when evaluating the electrostatic hazard of solid dust, it includes: If MIE > 1000, the sample is almost insensitive to electrostatic sparks and the grade is 1; If 300 < MIE ≤ 1000, the sample is less insensitive to electrostatic sparks and the grade is 1; If 100 < MIE ≤ 300, the sample is relatively sensitive to electrostatic sparks and the grade is 1; If 3 < MIE ≤ 100, the sample is sensitive to electrostatic sparks and the grade is 2; If 10 < MIE ≤ 30, the sample is very sensitive to electrostatic sparks and the grade is 2; If 1 < MIE ≤ 10, the sample is extremely sensitive to electrostatic sparks and the grade is 3; If MIE ≤ 1, the sample is extremely sensitive to electrostatic sparks and the grade is 3.

5. The method for risk assessment and control of chemical solid dust drying process according to claim 1, characterized in that, In S30, the explosion hazard of solid dust is assessed, and the LOC (Local Oxygen Content) and the controlled oxygen content (O2) at the factory site are selected. c Compare and consider a certain safety margin; LOC, O c The evaluation criteria include: When LOC (LOC≥5%)-2%>O c Or LOC (LOC < 5%) · 60% > 0 c At that time, the risk of solid dust explosion during the drying process was considered acceptable; When LOC (LOC≥5%)-2%≤O c Or LOC (LOC < 5%) · 60% ≤ O c At that time, it was considered that the risk of solid dust explosion during the drying process was unacceptable.

6. The method for risk assessment and control of chemical solid dust drying process according to claim 5, characterized in that, Select MEC to compare with the dust concentration FDC at the factory site. The evaluation benchmarks for MEC and FDC include: When MEC > FDC is satisfied, it is considered that the explosion risk of solid dust in the drying process is acceptable; When MEC ≤ FDC is satisfied, it is considered that the explosion risk of solid dust in the drying process is unacceptable.

7. The method for risk assessment and control of chemical solid dust drying process according to claim 1, characterized in that, In S40, when evaluating the severity of solid dust explosion, the specific benchmark is: The level is St0, K max =0, the explosion characteristic is non-explosive; The level is St1, 0 <K max <20.0, the explosion characteristics are weak; The grade is St2, and 20.0 ≤ K. max <30.0, the explosion characteristic is strong; Level St3, K max ≥30.0, the explosion characteristics are severe.

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