other information
drafter:Xu Guangwen, Yue Junrong, Wang Fang, Shang Weili, Li Zhaojun, Zhou Lan, Yang Jiebin, Wang Shaonan, Han Zhennan, Zeng Xi, Fang Zheng, Yu Jian, Liu Xuejing, Yao Hong, Sun Shaozeng, Han Yizhuo, Zhu Qingkai, Shen Lu, Guo Zhancheng, Cui Xiangzhong, Dong Yuping, Sun Guogang, Zheng Zhong, Yin Xiang
Drafting unit:Institute of Process Engineering, Chinese Academy of Sciences, Shenyang University of Chemical Technology, Shenzhen Defang Nanotechnology Co., Ltd., China Testing Technology Research Institute, Southwest Chemical Research and Design Institute Co., Lt
Focal point unit:National Technical Committee for Particle Characterization and Sorting and Sieve Standardization (SAC/TC 168)
Proposing unit:National Technical Committee for Particle Characterization and Sorting and Sieve Standardization (SAC/TC 168)
Publishing department:State Administration for Market Regulation National Standardization Administration
competent authority:National Technical Committee for Particle Characterization and Sorting and Sieve Standardization (SAC/TC 168)
Some standard content:
ICS19.120
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National Standard of the People's Republic of China
GB/T38432—2019
Gas-solid reaction measurement
Micro fluidized bed method
ParticleGas-solid reaction measurementMicro fluidized bed method2019-12-31 Issued
State Administration for Market Regulation
National Standardization Administration
2020-03-01 Implementation
Terms and definitions
Composition of test device
Reagents or materials
Test method
Test report
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Appendix A (Informative Appendix)
Appendix B (Informative Appendix)
References
Gas flow characteristics in microfluidized bed
Test case of microfluidized bed method
Graphite combustion
GB/T38432—2019
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This standard was drafted in accordance with the rules given in GB/T1.1—2009. GB/T38432—2019
This standard is proposed and managed by the National Technical Committee for Particle Characterization and Sorting and Screen Standardization (SAC/TC168). Drafting units of this standard: Institute of Process Engineering, Chinese Academy of Sciences, Shenyang University of Chemical Technology, Shenzhen Defang Nanotechnology Co., Ltd., China Testing Technology Research Institute, Southwest Chemical Research and Design Institute Co., Ltd., Institute of Chemistry, China Testing Technology Research Institute, Huazhong University of Science and Technology, Harbin Institute of Technology, Shanxi Coal Chemistry Research Institute, Chinese Academy of Sciences, Zhangjiagang Jiushun Energy Technology Co., Ltd., Shanghai Diren Vacuum Technology Co., Ltd., University of Science and Technology Beijing, China Aviation Manufacturing Technology Research Institute, Shandong Tianxue, China University of Petroleum (Beijing), Chongqing University, Beijing Zhongke Jiechuang Energy Technology Co., Ltd.
The main drafters of this standard: Xu Guangwen, Yue Junrong, Wang Fang, Shang Weili, Li Zhaojun, Zhou Lan, Yang Jiebin, Wang Shaonan, Han Zhennan, Zeng Xi, Fang Zheng, Yu Jian, Liu Xuejing, Yao Hong, Sun Shaozeng, Han Yizhuo, Zhu Qingkai, Shen Lu, Guo Zhancheng, Cui Xiangzhong, Dong Yuping, Sun Guogang, Zheng Zhong, Yin Xiang, m
GB/T38432—2019
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Gas-solid reaction is a type of reaction widely used in process industry, and its process is jointly affected by chemical reaction and transfer. Studying reaction characteristics, reaction mechanisms, and calculating reaction kinetic parameters are the foundation of process industry science and technology, and are also important contents of testing science and technology. Therefore, this standard adopts the microfluidized bed method to test gas-solid reactions involving particle reactants or catalysts. The concentration curve of gas components released or generated by chemical reactions under constant temperature reaction conditions is obtained through real-time online monitoring. It can not only calculate the time required to complete the reaction, the conversion rate and reaction rate at any reaction time, and the reaction activation energy of gas components, but also study the reaction characteristics, analyze the product law, and infer the reaction mechanism. IV
1 Scope
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Particle gas-solid reaction determination
Microfluidized bed method
GB/T38432—2019
This standard specifies the test method for the characteristics of gas phase products in gas-solid reactions involving particle reactants or catalysts using a microfluidized bed reactor, including principles, test device composition, reagents or materials, test methods and test reports. This standard applies to gas-solid reactions involving or generating gas phase substances. Note: This standard method provides a test method for obtaining raw data for studying gas-solid reactions, analyzing reaction mechanisms, calculating reaction kinetic parameters, etc. using a micro fluidized bed reactor.
Terms and Definitions
The following terms and definitions apply to this document. 2.1
Fluidized bed reactor
fluidizedbedreactor
A reactor that uses gas or liquid to pass through a granular solid layer to place solid particles in a suspended motion state and conduct a gas-solid phase reaction process or a liquid-solid phase reaction process.
micro fluidized bed reactor
Micro fluidized bed reactor
Fluidized bed reactor with an inner diameter of no more than 20 mm and loaded with an appropriate amount of fluidizing medium Note: For the gas flow characteristics in the micro fluidized bed, see Appendix A, 2.3
Pulse-injection feed of particles The method of using gas to spray a small amount of fine particles at high speed and instantly feed them into the micro fluidized bed reactor under preset conditions.
Note 1: The amount of injected particles is about 10 mg. The particle size is between 5μm and 500μm. Note 2: The injection process takes about 10ms.
isothermal reaction in microfluidized bed
isothermal reaction in microfluidized bed is a gas-solid reaction induced by a pulsed trace sample in a microfluidized bed at a constant temperature. Note: It takes about 0.1s for the particles with a diameter of less than 100um in the microfluidized bed to heat up, which is much shorter than the reaction time required to complete most reactions. 3 Principle
3.1 Overview
The microfluidized bed is used as the reactor, inert (silica sand) or catalyst particles are used as the fluidizing medium, and the reactor is heated to the preset temperature by a heating furnace. After the reactor reaches the preset conditions, the microfluidized bed is supplied with a trace amount of fine particle samples by particle pulse sampling. Through the rapid heat and mass transfer of the fluidized bed, the sample is instantly heated to the set temperature, inducing an isothermal reaction in the microfluidized bed; the concentration of the target component of the gas phase product in the gas phase product is monitored online as the reaction time changes, providing raw data for calculating the time required to complete the reaction, the conversion rate and reaction rate at any reaction time, and the reaction activation energy generated by the gas component. Figure 1 is a schematic diagram of the principle of the micro fluidized bed method. 1
GB/T38432—2019
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Note: The fluidized medium particles are much larger than the mass of the sample, and the minimum mass ratio of the two should be about 100. Reactor
Fluidizing gas
Online monitoring
Pulse sample connector
Particle domain pulse example fat
Green external gas
Schematic diagram of the principle of the micro fluidized bed method
3.2 Reaction time calculation
Figure 2 is a schematic diagram of the concentration of a gas phase product component obtained by testing a certain reaction in the gas phase product versus reaction time. The baseline of the gas online test instrument is the horizontal line marked by the red line in the figure, which is a relatively stable straight line area of the concentration data collected before sampling or before reaction. The reaction start time is the starting point indicated by the vertical black line in Figure 2, which is also the starting time of the test reaction, corresponding to the moment when the concentration of a certain two-gas product component begins to increase rapidly from the baseline. For a certain gas-phase reactant, it should be the moment when the concentration curve of the reactant component begins to drop rapidly. The moment when the concentration curve of the target gas under test evolves to the same concentration as the baseline again is taken as the end time of the reaction, that is, the end point of the test reaction. The time difference between the determined end point and the starting point is the time required to complete the reaction: that is, the complete reaction time.
Figure 2 Schematic diagram of the concentration change of a single component in the gas-phase product 3.3 Calculation of conversion rate
The conversion rate of the test material or the generation rate of the generated gas component is defined as formula (1). e
（1）
Where:
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Conversion rate (generation rate) corresponding to any time t: concentration signal intensity of gas component 1 at time t; a certain time in the reaction;
test reaction starting time;
test reaction end time. www.bzxz.net
GB/T38432—2019
The relative generation rate of gas phase products or relative conversion rate of conversion products is used to process the obtained raw data. Calculation. The definition of relative generation rate is: integrate the concentration signal intensity from the test reaction starting time to the reaction end time, and the integral value is used as the denominator. The relative conversion rate or generation rate corresponding to the end time of the reaction is 100%. The integral of the signal intensity from the test reaction starting time to any time in the reaction is used as the numerator, so that the reaction conversion rate or generation rate corresponding to any time can be obtained, as shown in Figure 3.
Figure 3 Schematic diagram of the change of conversion rate (generation rate) of a single component over time 3.4 Calculation of reaction rate
Based on the conversion rate (production rate) curve shown in Figure 3, the corresponding reaction rate is defined as formula (2). A schematic diagram of the change of single component reaction rate with conversion rate is shown in Figure 4.
Where:
R——t, the differential value with respect to t, is the reaction rate of component i at time t; Cir
Conversion rate (production rate) corresponding to any time t. Conversion rate
Figure 4 Schematic diagram of the change of single component reaction rate with conversion rate (2)
GB/T38432—2019
3.5 Calculation of activation energy
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The reaction rate curve shown in Figure 4 is obtained at different temperatures, and then the relationship curve between ln (dr/dt) [calculated according to formula (2)] and 1/T under different conversion rates (production rates) can be obtained, as shown in Figure 5. 0.100.240.3
V 0.40 0.50 0.6
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Fig. 5 Relationship between In(dx/dt) and 1/T for different conversion rates The Arrhenius formula (3) reflects the relationship between the chemical reaction rate constant and temperature: k(T)=A exp(-E/RT)
Wherein:
k—chemical reaction rate constant;
pre-exponential factor, in seconds (s1);
activation energy, in kJ/mol; R—molar gas constant, in kJ/(mol·K); T—thermodynamic temperature, in K. (3)
Since the tested reaction particles are pulsed into the micro fluidized bed reactor at a preset temperature, they are rapidly mixed with the fluidized particles and heated, but the overall temperature of the fluidized bed does not change much. Therefore, in principle, an isothermal reaction occurs in the micro fluidized bed reactor, and its kinetic treatment method adopts the isothermal kinetic equation. The kinetic equation describing the heterogeneous reaction under isothermal conditions is shown in formula (4): dx/dt=k(T)f(x)=Aexp(-E/RT)f(α)-Taking the logarithm of formula (4) yields:
In(dr/dt)=-E/RT+InA+Inf(r)
.(4)
··(5)
In the formula, I, A, E, R, T, and f() are respectively the reaction conversion rate (or gas component generation rate), pre-exponential factor, activation energy, molar gas constant, thermodynamic temperature, and model function of the reaction kinetic equation. According to formula (5), slope = -E/R, that is, the absolute value of the product of slope and R is the activation energy of the reaction, and the E value corresponding to different conversion rates such as = 0.1, 0.2, 0.3, 0.4... can be obtained. When the conversion rate is less than 0.2, the reaction is in a rapid temperature rise stage, and the activation energy at this time cannot represent the true value of the isothermal reaction. Usually, the average activation energy within the conversion rate of 0.2 to 0.9 is taken as the activation energy value of the test reaction.
4 Test device composition
Micro fluidized bed reactor
Load inert (silica sand) or catalyst particles, and the ratio of the particle layer height to the bed diameter in the bed is ≤2.4
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4.2 Pulse servo sample connector
Connection channel between micro fluidized bed reactor and pulse servo sampler. 4.3 Pulse sampler
GB/T38432—2019
It consists of a gas pulse component and a sampling branch pipe. The material loading end of the sampling branch pipe is connected to the gas pulse component, and the outlet end extends to the surface of the particle layer in the reaction zone of the microfluidized bed. Usually, the sampling branch pipe has an inclination angle of ≥15° to the horizontal direction, and the pulse gas sampling time is about 10ms. 4.4 Heating furnace
An electric heating furnace adapted to the microfluidized bed reactor to heat the fluidized medium particles in the reactor and the microfluidized bed reaction zone to the set reaction temperature.
4.5 Gas online detection instrument
A detection instrument that can detect the change of gas component concentration over time online or identify the generated gas phase products, generally using process mass spectrometry. 4.6 Reaction Condition Element Monitoring Components
Components for monitoring the temperature, pressure, and flow of the reaction system, including sensors, displays, etc., and the error of the reactor temperature, pressure, and flow needs to be controlled within 0.3%
4.7 System Control Software
Software that realizes various pre-inspection, operation, regulation, display, monitoring, data acquisition, data input and output, information storage, alarm and other functions of the test instrument and system, and supports and monitors the operation and use of the test instrument hardware. 4.8 Other Parts
A gas filter is installed at the gas outlet to remove dust and moisture from the product. 5 Reagents or Materials
5.1 Particle Sample
The sample loading range should be 5mg~50mg. The mass of the fluidized medium particles is much larger than the mass of the sample; the minimum mass ratio of the two should be about 100; the particle size range is 5μm~500μm.
5.2 Fluidizing gas
Set according to the test requirements, can be raw material reaction gas or inert gas, including water vapor, etc. The operating gas velocity should be 3 to 7 times the minimum fluidizing velocity of the fluidizing medium particles.
5.3 Pulse sample gas
Set according to the test requirements, can be inert gas such as argon, nitrogen or raw material gas, 5.4 Gas standard sample
Select according to the measured gas component and concentration, used for calibration of the indication of gas online monitoring instruments. SAG
GB/T38432—2019
6Test method
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Inert or catalytic fluidized medium particles are loaded into the microfluidized bed reactor, and the reactor is heated and adjusted to the set temperature, pressure and other reaction conditions. The chemical reaction of the reaction particles in the microfluidized bed is quickly stimulated by online instantaneous pulse sampling. 2Use a fast-response gas monitoring instrument to monitor the gas components generated by the gas curing reaction in the microfluidized bed online and their concentration changes with the reaction time to obtain the component concentration curve. At least three tests are carried out under the same conditions. 6.3
Note: See Appendix B for test cases.
7Test report
The test report should include but not be limited to the following: Manufacturer and model of the test device
Test conditions.
Test data:
1) Test repeatability verification data;
Reaction test data.
Data processing results:
Complete reaction time;
Component generation rate or reactant conversion rate curve; Reaction rate curve;
Arrhenius fitting curve corresponding to different conversion rates: 5) Calculation of activation energy.
Test conclusion.
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Appendix A
(Informative Appendix)
Gas Flow Characteristics in Microfluidized Bed
GB/T38432—2019
Using microfluidized bed for reaction test and analysis, it is hoped that the gas generated by the reaction will be affected by back mixing and diffusion in the reactor as little as possible. The ideal state is that the gas is as close to the plug flow as possible in the microfluidized bed to ensure that the gas generated by the reaction can flow out of the reactor in sequence according to the order of its generation and be detected by the gas online instrument, so that the reaction test is affected by time delay and gas back mixing to the minimum. This is the basic condition required for reaction testing and kinetic calculation using microfluidized bed method. Therefore, it is necessary to conduct in-depth research on the flow characteristics of gas in microfluidized bed and determine the necessary conditions for its close to plug flow. Note: The gas residence time distribution was measured experimentally based on the pulse method, and the contribution of the reactor inlet and outlet flow to the gas residence time was removed by deconvolution technology, so as to obtain the "real" gas residence time in the micro fluidized bed. The particle fluidization characteristics and gas backmixing characteristics in micro fluidized beds with different bed diameters and different operating conditions were studied, and it was found that the gas flow in the micro-sized fluidized bed is similar to the plug flow. The physical properties of different fluidized particles are shown in Table A.1. The RTD parameters of the gas residence time distribution in the micro fluidized bed calculated under different conditions are shown in Table A.2. Table A.1
Physical properties of different fluidized particles
Solid particles
Glass beads
Quartz sand 1
Quartz sand 2
Quartz sand 3
dp/μm
Note: d is the average particle size, P is the particle density. Um is the minimum fluidization velocity Table A.2
Solid particles
Glass beads
Quartz sand 1
Quartz sand 2
Quartz sand 3
Pp/(kg/m\)
Summary of parameters of gas RTD function in microfluidized bed under different conditions H./mm
Umr/(m/s)
E(t)n/st
Note: D is the bed diameter. H is the static bed height, U. is the superficial gas velocity, Um is the minimum fluidization velocity, t is the average residence time, a is the variance of the residence time distribution function, E(t) is the peak height of the residence time distribution curve, △t, is the relative time deviation. GB/T38432—2019
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Using the relationship between the peak height E(t) and the variance, 2 of the residence time distribution function curve, it is more suitable for characterizing the absolute gas backmixing characteristics in the micro fluidized bed than the Peclet number Pea obtained based on the one-dimensional gas axial model. As shown in Figure A, 1, the normalized correlation between the peak height E(t) and the variance o of the gas residence time distribution function curve is well consistent with the relevant experimental data obtained based on the axial diffusion model, including D. Boskovicetal. and JTAdeosunetal. From Figure A.1 and Table A.2, it can be concluded that when the absolute deviation of the absolute residence time of the gas flowing through the reactor from the ideal plug flow residence time is less than 10% (as shown in Table A.2), and the peak height E(t) of the gas residence time distribution function curve is greater than 1.0 or the variance is 6, less than 0.25 (calculated in time unit s), the gas flow in the reactor is basically close to the plug flow. When the variance of the gas residence time distribution function curve is greater than 5.0 or the peak height E(t) is less than 0.25, the gas flow in the bed is seriously affected by diffusion and is no longer a micro fluidized bed, but a conventional fluidized bed. 4
-20 mm
f-35 mm
H,-50 mm
Glass Corrosion Ball
H,20 mm
公右英莎
1i-20 mm
. i英秒2
H,-20 mum
Silica sand
H,-50 ramm
Silica sand
1)-20 mm
D.Boskovic
JTAdeosun
Figure A.1 Peak height E(t) of gas residence time distribution function curve in micro fluidized bed, normalized correlation with variance 62 The gas flow in the bed between the above two can be characterized as being in the transition zone, with both plug flow and full mixed flow characteristics. Among them, the associated data points are in the middle left and upper part of the figure, and the gas flow in the bed is closer to plug flow; on the contrary, the lower and to the right the data points are, the more the gas flow in the bed tends to full mixed flow. When using a microfluidized bed to conduct reaction tests and research, the gas flow in the bed is required to be as close to the plug flow as possible, so as to ensure that the gas products generated by the reaction are immediately and quickly transported to the reactor outlet with almost no backmixing, and are collected and analyzed by the online fast gas detector for their concentration and composition, so as to minimize the distortion of the product generation information. According to the criteria shown in Figure A.1, to achieve the maximum closeness of the gas flow in the bed to the plug flow requirements: the fluidized bed has a small diameter, few fluidized particles, and a high gas velocity. In addition, the study found that the bed material particles use Class B particles with a large specific gravity and a large diameter to increase the operating gas velocity, and the gas flow in the same microfluidized bed and at the same fluidization number is closer to the plug flow, which is more suitable for constructing the conditions for microfluidized bed reaction testing and analysis. Therefore, in the microfluidized bed method for gas-solid reaction testing, quartz sand particles with a particle size of 150um to 212um and a microfluidized bed with a bed diameter of 10mm to 20mm were selected. The above research results also put forward possible criteria for microfluidized beds. They not only put forward the requirements for reactors in microfluidized bed reaction analysis (ensuring that the back-mixing distortion of reaction information is minimized), but also the "near-flat plug flow" flow is very beneficial to improving conversion rate and selectivity, which essentially reveals the technical characteristics and advantages of microfluidized beds.
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