Method for determining the characteristic temperature and the decomposition rate of cement raw meal under co2 / o2 atmosphere

Abstract

The application discloses a method for determining the characteristic temperature and decomposition rate of cement raw materials under CO2 / O2 atmosphere, comprising the following steps: 1) obtaining the characteristic temperature and reaction kinetics parameters of cement raw materials under different CO2 / O2 atmosphere; constructing and correcting the calculation model between the characteristic temperature and CO2 concentration; constructing the prediction model between the reaction kinetics parameters and CO2 and O2 concentration; 2) obtaining the CO2 and O2 concentration in the actual cement production process, and calculating the characteristic temperature and reaction kinetics parameters of raw material decomposition according to the model obtained in step 1); 3) obtaining the conversion rate alpha at different temperatures according to the decomposition rate model and the parameters obtained in step 2), and then obtaining the decomposition rate according to the decomposition rate calculation model. The method can simply and quickly obtain the decomposition characteristics of cement raw materials, is beneficial to the targeted adjustment of production process parameters, improves the cement raw material production efficiency, reduces the pollutant emission and the like, and is suitable for application.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of analysis, and particularly relates to a method for determining the decomposition characteristic temperature and decomposition rate of cement raw materials under a CO2 / O2 atmosphere. BACKGROUND

[0002] A large amount of mineral fuels and carbonate raw materials are used in the cement production process, and a large amount of CO2 is generated by fuel combustion and carbonate decomposition, thereby causing huge carbon emissions. According to statistics, about 0.7-1.1 tons of CO2 are emitted per ton of cement produced, and reducing carbon emissions is an important direction for the development of the cement industry.

[0003] At present, the methods for reducing carbon emissions in the cement industry mainly include replacing raw materials, using alternative fuels, and capturing and purifying CO2 in flue gas. The flue gas back blending technology is to send flue gas into the rotary kiln and the decomposition furnace instead of air to achieve the enrichment of CO2 in the flue gas, which will be beneficial to the capture, purification and compression of CO2. Studies have shown that when the CO2 concentration in the flue gas is greater than 70%, the capture of CO2 is relatively easy. Therefore, the flue gas back blending technology is one of the important directions for reducing the capture and emission of CO2 in the cement industry.

[0004] The flue gas back blending technology will lead to the enrichment of CO2, which will greatly increase the CO2 concentration in the decomposition furnace in the cement production process, and further affect the decomposition characteristics of the cement raw materials, so it is necessary to adjust the production process parameters accordingly. It is of great research and application significance to further explore and optimize the determination method of the decomposition characteristics of the cement raw materials under the condition of atmosphere change. SUMMARY

[0005] The main purpose of the present application is to provide a method for determining the decomposition characteristic temperature and decomposition rate of cement raw materials under a CO2 / O2 atmosphere, to calculate the decomposition characteristic temperature and reaction speed of the cement raw materials under different gas concentration conditions, to obtain the decomposition characteristics of the cement raw materials under the corresponding conditions, and to adjust and optimize the actual production parameters.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A method for determining the decomposition characteristic temperature and decomposition rate of cement raw materials under a CO2 / O2 atmosphere, comprising the following steps:

[0008] 1) Obtain the decomposition characteristic temperature and reaction kinetic parameter values of the cement raw materials under different CO2 / O2 atmospheres; use the stoichiometric method to construct a prediction model between the decomposition characteristic temperature and the CO2 concentration V CO2 , and then further construct a correction model between the decomposition characteristic temperature and the O2 concentration V O2 ; use the stoichiometric method to construct a reaction kinetic parameter and CO2 concentration V CO2and O2 concentration V O2 ; wherein the decomposition characteristic temperature comprises reaction starting temperature T i , reaction ending temperature T f , and temperature T max corresponding to the maximum reaction rate; and the reaction kinetic parameter comprises reaction activation energy E and reaction pre-exponential factor A.

[0009] 2) obtaining CO2 concentration V CO2 and O2 concentration V O2 in actual cement production process, and calculating the decomposition characteristic temperature and the reaction kinetic parameter of raw meal decomposition according to the model (the modified model between the decomposition characteristic temperature and O2 concentration V O2 and the prediction model between the reaction kinetic parameter and CO2 concentration V CO2 and O2 concentration V O2 obtained in step 1);

[0010] 3) according to the mechanism function integral model of raw meal decomposition, integrating with the reaction kinetic parameter E and A obtained in step 2) and different reaction temperatures T, wherein the integral starting point corresponding to each reaction temperature T to be detected is T i , the ending point is reaction temperature T, and the maximum value of reaction temperature T is T f , the mechanism function integral parameter g(α) under different reaction temperatures T is obtained, the conversion rate α under different reaction temperatures T is calculated according to the formula , and the decomposition rate corresponding to different reaction temperatures T in the raw meal decomposition process is obtained according to the decomposition rate calculation model of the derivative of conversion rate α with respect to time.

[0011] In the above scheme, the prediction model in step 1) uses response surface method to analyze experimental data, and constructs the prediction model for calculating the characteristic temperature and the reaction kinetic parameter.

[0012] In the above scheme, the prediction model between the decomposition characteristic temperature and CO2 concentration V CO2 comprises formula (1)-(3):

[0013]

[0014]

[0015]

[0016] In the formula, T i初始 (reaction starting temperature T i in the prediction model), T f初始 (reaction ending temperature T f in the prediction model), and T max初始(Temperature T corresponding to the maximum reaction rate in the prediction model) max The unit is ℃; V O2 V CO2 The unit is %.

[0017] Further corrections were made to obtain the decomposition characteristic temperature and O2 concentration V. O2 The corrected model includes equations (4) to (6):

[0018]

[0019]

[0020]

[0021] In the above scheme, the reaction kinetic parameters are related to the CO2 concentration V. CO2 and O2 concentration V O2 The prediction model between them includes equations (7) to (8):

[0022]

[0023]

[0024] In the formula, E is in kJ / mol and A is a dimensionless quantity.

[0025] In the above scheme, the decomposition characteristic temperature and reaction kinetic parameters mentioned in step 1) are obtained by thermogravimetric analysis under a CO2 / O2 atmosphere with known N2, O2, and CO2 concentrations.

[0026] In the above scheme, the mechanistic function integral model used in step 3) is: Where β is the heating rate, ℃ / min, and takes a value of 1-30℃ / min (in specific cement raw material decomposition experiments, the heating rate is controlled and kept constant).

[0027] In the above scheme, the decomposition rate calculation model used in step 3) is shown in equation (9):

[0028]

[0029] In the formula, α is the decomposition rate, % / min; α is the reaction conversion rate, %; R is the gas constant, 8.314 J / (mol·K); T is the reaction temperature, K.

[0030] In the above scheme, the decomposition of cement raw meal conforms to the mechanism of random nucleation and subsequent growth. The mechanism function used to calculate the decomposition rate is:

[0031] Further, the conversion rate α obtained in step 3) is normalized without temperature.

[0032] In the above scheme, the CO2 / O2 atmosphere comprises O2, CO2 and N2, wherein the concentration of CO2 is 0-100%, and the concentration of O2 is 0-50%.

[0033] Compared with the prior art, the present application has the following beneficial effects:

[0034] 1) The method of the present application can be used to simply and quickly obtain the cement raw material decomposition characteristics, and can accurately and timely obtain the characteristic temperature and kinetic parameters of cement raw material decomposition under different atmospheres, which is beneficial to save the instrument cost under actual production conditions and greatly shorten the data obtaining period.

[0035] 2) The present application can use the obtained kinetic parameters and decomposition characteristic temperatures to obtain the decomposition reaction conversion rate and decomposition rate of cement raw material under different CO2 / O2 atmospheres and temperatures, which is beneficial to adjust the production process parameters, improve the cement raw material production efficiency, reduce pollutant emissions, etc. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 Figure 4 is a comparison chart of the decomposition rate prediction curve obtained in application example 1 and the actual reaction rate curve;

[0037] Figure 2 Figure 5 is a comparison chart of the decomposition rate prediction curve obtained in application example 2 and the actual reaction rate curve;

[0038] Figure 3 Figure 6 is a comparison chart of the decomposition rate prediction curve obtained in application example 3 and the actual reaction rate curve;

[0039] Figure 4 Figure 7 is a comparison chart of the decomposition rate prediction curve obtained in application example 4 and the actual reaction rate curve;

[0040] Figure 5 Figure 8 is a comparison chart of the decomposition rate prediction curve obtained in application example 5 and the actual reaction rate curve;

[0041] Figure 6 Figure 9 is a comparison chart of the decomposition rate prediction curve obtained in comparative example 1 and the actual reaction rate curve. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0043] Example 1

[0044] A method for determining the characteristic temperature and decomposition rate of cement raw meal under CO2 / O2 atmosphere, comprising the following steps:

[0045] 1) Obtain the characteristic temperature and reaction kinetic parameter values of cement raw meal under different CO2 / O2 atmospheres, analyze the experimental data by response surface method, construct a prediction model between the characteristic temperature and CO2 concentration V CO2 , then construct a correction model between the characteristic temperature and O2 concentration V O2 ; construct a prediction model between the reaction kinetic parameter and CO2 concentration V CO2 and O2 concentration V O2 by stoichiometric method; see specific formulas (1)-(8):

[0046]

[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054] 2) According to Coats-Redfern integral method β is the heating rate, which is uniformly controlled at 10℃ / min in the examples, and the reaction kinetic parameters E and A obtained in step 1) and different reaction temperatures T are used for integration, wherein the integral starting point corresponding to each reaction temperature T to be detected is T i , the terminal point is the reaction temperature T, the maximum value of the reaction temperature T is T f , and the mechanism function integral parameter g(α) under different reaction temperatures T is obtained; then the conversion rate α under different reaction temperatures is calculated according to the formula , and the data obtained is normalized; and the decomposition rate calculation model of time derivative according to the determined mechanism function and conversion rate α is shown in formula (9), and the decomposition rate corresponding to different reaction temperatures T in the raw meal decomposition process is obtained;

[0055]

[0056] In the formula, decomposition rate, % / min; a is the reaction conversion, %, a = (w0-w t ) / (w0-w f ), wherein w0is the initial raw material mass, w t is the mass of raw material at a certain reaction time t, w f is the mass of the remaining solid at the end of the reaction, mg; R is the gas constant, 8.314 J / (mol·K); T is the reaction temperature, K;

[0057] 3) Obtain the CO2concentration V CO2 and O2concentration V O2 in the actual production process of cement, calculate the characteristic temperature and reaction kinetics parameters of raw material decomposition according to the model obtained in step 1), and calculate the decomposition rate of cement raw material at different temperatures under the effect of the corresponding atmosphere by using the decomposition rate calculation model obtained in step 2).

[0058] Application Example 1

[0059] A method for determining the characteristic temperature and decomposition rate of cement raw material under CO2 / O2atmosphere, comprising the following steps:

[0060] 1) Obtain the gas concentration in the decomposition furnace, the concentrations of N2, O2, and CO2are 10%, 20%, and 70%, respectively;

[0061] 2) Calculate the initial value of the reaction starting temperature T i , the initial value of the reaction termination temperature T f , the initial value of the temperature T max corresponding to the maximum reaction rate, the reaction activation energy E, and the reaction pre-exponential factor A according to the models described in equations (1)-(5):

[0062]

[0063]

[0064]

[0065]

[0066]

[0067] 3) According to the models described in equations (6)-(8), correct the reaction starting temperature T i , the reaction termination temperature T f , and the temperature T max corresponding to the maximum reaction rate:

[0068]

[0069]

[0070]

[0071] 4) Using a thermal gravimetric analyzer, the actual values T i = 915.10, T f = 989.24 and T max = 955.15 are measured respectively, the obtained calculated values are compared with the actual values, and the results show that the errors of T i , T f , T max obtained by using the method are 1.01%, 1.09% and 1.07% respectively.

[0072] 5) According to the calculated E, A, T i , T f , the change relationship of the decomposition rate with different reaction temperatures T is obtained (see FIG. 2, R is 0.97). Figure 1

[0073] By comparing the fitting curve (prediction) obtained in the example with the actual reaction rate curve (actual, obtained by thermal gravimetric experiment), it can be seen that the method can achieve good fitting effect.

[0074] Application Example 2

[0075] A method for determining the characteristic temperature and decomposition rate of cement raw meal under CO2 / O2 atmosphere, comprising the following steps:

[0076] 1) Obtain the gas concentration in the decomposition furnace, the concentrations of N2, O2 and CO2 are 10%, 30% and 60% respectively;

[0077] 2) According to the model described in equations (1)-(5), the initial value of the reaction starting temperature T i , the initial value of the reaction termination temperature T f , the initial value of the temperature T max corresponding to the maximum reaction rate, the reaction activation energy E and the reaction pre-exponential factor A are calculated:

[0078]

[0079]

[0080]

[0081]

[0082]

[0083] ​3) According to the model of formula (6)-(8), the reaction starting temperature T i , the reaction termination temperature T f , and the temperature T max corresponding to the maximum reaction rate are corrected:

[0084]

[0085]

[0086]

[0087] 4) The actual values T i 901.56, T f 979.66 and T max 942.25 are measured by a thermal gravimetric analyzer, and the calculated values are compared with the actual values, and the results show that the errors of T i , T f and T max obtained by the method are 1.42%, 1.41% and 0.72%, respectively.

[0088] 5) According to the calculated E, A, T i and T f , the change relationship of the decomposition rate with different reaction temperatures T is obtained (see Figure 2 , and R is 0.98).

[0089] Comparing the fitting curve obtained in the example with the actual reaction rate curve, it can be seen that the method can achieve good fitting effect.

[0090] Application Example 3

[0091] A method for determining the characteristic temperature and decomposition rate of cement raw material under CO2 / O2 atmosphere, comprising the following steps:

[0092] 1) Obtain the gas concentration in the decomposition furnace, and the concentrations of N2, O2 and CO2 are 10%, 40% and 50%, respectively;

[0093] 2) According to the model of formula (1)-(5), the initial value of the reaction starting temperature T i , the initial value of the reaction termination temperature T f , the initial value of the temperature T max corresponding to the maximum reaction rate, the reaction activation energy E and the reaction pre-exponential factor A are calculated:

[0094]

[0095]

[0096]

[0097]

[0098]

[0099] 3) According to the model of formula (6)-(8), the reaction starting temperature T i , the reaction termination temperature T f , and the temperature T max corresponding to the maximum reaction rate are corrected:

[0100]

[0101]

[0102]

[0103] 4) The actual values T i =895.53, T f =962.45, and T max =920.13 are measured by a thermal gravimetric analyzer, and the calculated values are compared with the actual values, and the results show that the errors of T i , T f , and T max obtained by the method are 0.66%, 2.33%, and 0.33%, respectively.

[0104] 5) According to the calculated E, A, T i , and T f , the relationship between the decomposition rate and different reaction temperatures T is obtained (see FIG. 2, R is 0.98). Figure 3

[0105] By comparing the fitting curve obtained in the example with the actual reaction rate curve, it can be seen that the method can achieve good fitting effect.

[0106] Application Example 4

[0107] A method for determining the characteristic temperature and decomposition rate of cement raw material under CO2 / O2 atmosphere, comprising the following steps:

[0108] 1) Obtain the gas concentration in the decomposition furnace, and the concentrations of N2, O2, and CO2 are 50%, 0%, and 50%, respectively;

[0109] 2) According to the model of formula (1)-(5), the initial value of the reaction starting temperature T i , the initial value of the reaction termination temperature T f , and the temperature T max ​Initial value, reaction activation energy E, reaction pre-exponential factor A:

[0110]

[0111]

[0112]

[0113]

[0114]

[0115] 3) According to the model of formula (6)-(8), the reaction starting temperature T i , the reaction termination temperature T f , and the temperature T max corresponding to the maximum reaction rate are corrected:

[0116]

[0117]

[0118]

[0119] 4) The actual values T i =892.4, T f =982.20 and T max =911.50 are measured by using a thermal gravimetric analyzer, and the obtained calculated values are compared with the actual values, and the results show that the errors of T i , T f and T max obtained by using the method are 3.30%, 1.77% and 2.91% respectively.

[0120] 5) According to the calculated E, A, T i and T f , the relationship between the decomposition rate and the temperature is obtained, and the relationship between the decomposition rate and different reaction temperatures T is obtained (see Figure 4 , and R is 0.99).

[0121] By comparing the fitting curve obtained in the embodiment with the actual reaction rate curve, it can be seen that the method can achieve good fitting effect.

[0122] Application Example 5

[0123] A method for determining the decomposition characteristic temperature and the decomposition rate of cement raw materials under CO2 / O2 atmosphere, comprising the following steps:

[0124] 1) Obtain the gas concentrations in the decomposition furnace, with N2, O2, and CO2 concentrations of 40%, 0%, and 60%, respectively;

[0125] 2) Based on the model described in equations (1) to (5), the initial reaction temperature T is calculated. i Initial value, reaction termination temperature T f Initial value, temperature T corresponding to the maximum reaction rate max Initial values, activation energy E, pre-exponential factor A:

[0126]

[0127]

[0128]

[0129]

[0130]

[0131] 3) Based on the model described in equations (6) to (8), the reaction initiation temperature T is corrected. i The reaction termination temperature T f The temperature T corresponding to the maximum reaction rate max :

[0132]

[0133]

[0134]

[0135] 4) The actual values ​​T were measured using a thermogravimetric analyzer. i =921.30, T f =981.30 and T max =950.30. Comparing the calculated value with the actual value, the results show that T obtained using the method described in this invention is... i T f T max The errors were 0.91%, 2.37%, and 0.04%, respectively.

[0136] 5) Based on the calculated E, A, and T i T f The relationship between the decomposition rate and different reaction temperatures T was obtained (see...). Figure 5 (R = 0.98).

[0137] By comparing the fitted curve obtained in this embodiment with the actual reaction rate curve, it can be seen that the present invention can achieve a better fitting effect.

[0138] Comparative Example 1

[0139] A method for determining the characteristic temperature and decomposition rate of cement raw meal under CO2 / O2 atmosphere is substantially the same as that of Application Example 1, except that the correction process in step 3) is not performed to obtain the characteristic temperature and reaction kinetics parameters of raw meal decomposition. The specific fitting results are shown in Table 2. Figure 6 The fitting effect is poor.

[0140] The present application is not limited to the above-mentioned embodiments, and those skilled in the art can make several improvements and refinements without departing from the principles of the present application, which are also considered to be within the scope of protection of the present application. The contents not described in detail in the specification belong to the prior art known to those skilled in the art.

Claims

1. A method for determining the characteristic temperature and the rate of decomposition of cement raw meal under a CO2 / O2 atmosphere, characterized in that, The method comprises the following steps: 1) Obtain the decomposition characteristic temperature and reaction kinetics parameter values of cement raw materials under different CO2 / O2 atmospheres; construct a prediction model between the decomposition characteristic temperature and the CO2 concentration V CO2 , and then further construct a correction model between the decomposition characteristic temperature and the O2 concentration V O2 ; use stoichiometric method to construct a prediction model between the reaction kinetics parameter and the CO2 concentration V CO2 and the O2 concentration V O2 ; wherein the decomposition characteristic temperature includes the reaction starting temperature T i , the reaction termination temperature T f and the temperature T max corresponding to the maximum reaction rate, and the reaction kinetics parameter includes the reaction activation energy E and the reaction pre-exponential factor A; 2) obtaining the CO2 concentration V in the actual production process of cement CO2 and O2 concentration V O2 calculating the characteristic temperature and reaction kinetic parameters of raw meal decomposition from the model obtained in step 1) 3) According to the mechanism function integral model of raw material decomposition, the integral is carried out by using the reaction kinetic parameters E, A and different reaction temperatures T obtained in step 2), wherein the integral starting point corresponding to each reaction temperature T to be detected is T i , the termination point is the reaction temperature T, and the maximum value of the reaction temperature T is T f , the mechanism function integral parameters g (a) and conversion rate a under different reaction temperatures T are obtained; then according to the decomposition rate calculation model of the derivative of the conversion rate a with respect to time, the decomposition rate corresponding to different reaction temperatures T in the raw material decomposition process is obtained; The prediction model between the decomposition characteristic temperature and the CO2 concentration V CO2 includes formulas (1)-(3): （1）； （2）； （3）； wherein T i初始 , T f初始 , T max初始 in °C; V O2 , V CO2 in %; The correction model between the decomposition characteristic temperature and the O2 concentration V O2 includes equations (4) to (6): （4） （5） （6）； The predictive model between the reaction kinetic parameters and the CO2 concentration V CO2 and the O2 concentration V O2 includes equations (7)-(8): （7）； （8）； In the formula, E is in kJ / mol, and A is a dimensionless quantity. The mechanism function integral model in step 3) is where β is the temperature increase rate, ℃ / min; T is the reaction temperature, ℃. The conversion rate a is calculated by g(a) and the formula g(a) = 1 - a 2. The method of claim 1, wherein, In step 1), the prediction model is obtained by using a response surface method.

3. The method of claim 1, wherein, In step 1), the decomposition characteristic temperature and the reaction kinetic parameter value are obtained by using a thermal gravimetric experiment of cement raw meal under a CO2 / O2 atmosphere with known N2, O2 and CO2 concentrations.

4. The method of claim 1, wherein, The cement raw meal decomposition conforms to the random nucleation and subsequent growth mechanism, and a mechanism function used for calculating the decomposition rate is .

5. The method of claim 4, wherein, The decomposition rate calculation model of the cement raw meal is shown in formula (9): （9）； wherein is the decomposition rate, a is the reaction conversion rate, %, R is the gas constant, 8.314 J / (mol•K), and T is the reaction temperature, K.

6. The method of claim 1, wherein, The CO2 / O2 atmosphere comprises O2, CO2 and N2, wherein the concentration of CO2 is 0-100%, and the concentration of O2 is 0-50%.

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