Dynamic Fouling and Slagging Trend Prediction Method for Biomass Ash Based on Changes in Ashing Temperature

Abstract

The present invention discloses a method for predicting the dynamic fouling and slagging tendency of biomass ash based on the change of ashing temperature, which relates to the technical field of predicting biomass ash fouling and slagging, and includes: determining the sintering rate and sintering characteristic index of biomass ash at different temperatures; determining the melting characteristic temperature and melting characteristic index of biomass ash at different temperatures; determining the fixed-phase fouling and slagging index and volatile-phase fouling and slagging index during the ashing process of biomass ash at different temperatures; and determining the comprehensive fouling and slagging tendency of biomass ash. The beneficial effect of the present invention is that, based on the change rules of the melting characteristic index and ash sintering rate of biomass ash at different ashing temperatures, and simultaneously considering the distribution and allocation rules of alkali metal components in the fixed phase and volatile phase during the fouling and slagging process of biomass ash, it makes up for the deficiency of ignoring the melting characteristics and sintering characteristics of biomass ash in the prior art, and improves the accuracy and reliability of the prediction results of the dynamic fouling and slagging tendency of biomass ash at different ashing temperatures.

Description

Technical Field

[0001] The present invention relates to the technical field of biomass fouling and slagging prediction, and particularly to a method for predicting the dynamic fouling and slagging trend of biomass ash based on the change of ashing temperature. Background Technique

[0002] As an efficient biomass energy utilization approach, biomass thermochemical conversion technology has received increasing attention worldwide. However, biomass contains a large amount of alkali metal elements such as potassium and sodium. During the thermochemical conversion process, the coexistence of a large amount of alkali metal elements, together with alkaline earth metal elements such as calcium and magnesium, and non-metal elements such as chlorine and sulfur, will lead to the formation of a large number of alkali metal compounds. These alkali metal components reduce the ash melting point and are the main reasons for biomass ash fouling and slagging. From the current situation of biomass thermochemical conversion applications, hazards such as ash deposition and slagging caused by alkali metal problems severely restrict the development of this technology. Effectively reducing the fouling and slagging hazards of biomass ash is a practical problem that must be solved during the biomass thermochemical conversion process.

[0003] During the process of biomass ash fouling and slagging, the melting and sintering of ash occur concomitantly. Sintering refers to the process in which ash particles expel pores and shrink in volume to form dense particles with a certain strength at a temperature lower than their melting temperature. In terms of the ash melting characteristics, biomass ash is a mixture composed of various mineral components, so it has no fixed melting point and only melts within a certain temperature range. The melting characteristics of biomass ash are usually characterized by four characteristic temperatures: deformation temperature (DT), softening temperature (ST), hemisphere temperature (HT), and flow temperature (FT). Essentially, the melting and sintering characteristics of ash are not only closely related to the ash composition but also related to factors such as ashing temperature and atmosphere, and to a large extent affect the fouling and slagging characteristics of ash. Among them, ashing temperature, as the research basis for biomass ash characteristics, there is no unified standard globally: ASTM / E870-82 in the United States stipulates that the ashing temperature is 600 °C, and the SS-ISO540 standard in the European Union stipulates it as 550 °C. There is currently no relevant standard in China, and existing research still refers to the 815 ± 10 °C stipulated in the coal quality analysis standard (GB / T212-2008).

[0004] During the utilization of biomass energy, if the fouling and slagging characteristics of the biomass ash produced can be accurately recognized before fuel use, a series of measures can be taken for this type of biomass to reduce its slagging risk. Therefore, whether it is possible to accurately predict the fouling and slagging trend of biomass ash is crucial for taking measures to inhibit slagging. There are many indicators for judging the fouling and slagging of coal ash at home and abroad, and the commonly used ones include the ash melting point, ash composition, and ash viscosity of coal, etc. For biomass ash, there is currently no specific standard for evaluating its fouling and slagging. The existing evaluation of the fouling and slagging of biomass ash generally directly uses or modifies the fouling and slagging discrimination indicators of coal ash, such as the base-acid ratio, silicon ratio, silicon-aluminum ratio, basicity index, iron-calcium ratio, etc. Although the types of components in biomass ash and coal ash are similar, due to the large difference in the content of each component in the two, simply using the slagging index of coal ash to judge the slagging tendency of biomass ash will cause a large deviation in the judgment result, with serious limitations and inadaptability.

[0005] Therefore, some scholars have proposed multi-index discrimination methods on this basis, such as the comprehensive discrimination index method, fuzzy mathematics method, pattern recognition method, and artificial neural network method. These discrimination methods have improved the accuracy of the results to a certain extent, but still difficult to meet the actual needs, with a large deviation. The main reason is that these methods usually only consider the influence of the solid residue or molten components after the thermal conversion of the fuel on fouling and slagging, while ignoring the influence of the melting and sintering characteristics of the ash, such as the melting temperature and sintering rate, on fouling and slagging, and ignoring the alkali metal components that are released into the flue gas in the form of gas during the thermal conversion process of biomass and then deposited into the fouling due to various physical or chemical effects, and ignoring the influence of the dynamic change relationship between the volatility of such components and temperature on fouling and slagging. This leads to the lack of pertinence of the existing discrimination methods for predicting the fouling and slagging of biomass ash at different temperatures. Therefore, the ash characteristics of biomass ash at different temperatures and the melting and sintering characteristics of the ash should be comprehensively considered to explore a more reliable discrimination method for predicting the fouling and slagging of biomass ash at different ashing temperatures.

[0006] At present, there is no complete unified standard for predicting the fouling and slagging of biomass ash at home and abroad. Simply using the slagging index of coal ash has serious inadaptability, and the existing slagging prediction methods usually only consider the influence of the residual ash components after the thermal conversion of the fuel on ash slagging, while ignoring the influence of the melting and sintering processes such as the melting temperature and sintering rate on the fouling and slagging characteristics of biomass ash, and at the same time ignoring the influence of the relationship between the volatility of elements such as alkali metals, chlorine, and sulfur and temperature changes. Therefore, it is urgent to explore a fouling and slagging prediction model suitable for biomass ash at different temperatures on the basis of previous research, combined with the ash characteristics of biomass ash and the ash melting and sintering characteristics under different thermal conversion conditions, to make it more accurate and effective. Summary of the Invention

[0007] To solve the above technical problems, the present invention discloses a method for predicting the dynamic fouling and slagging tendency of biomass ash based on the change of ashing temperature. This method is based on the change rules of the melting characteristic index and ash sintering rate of biomass ash at different ashing temperatures, and comprehensively considers the distribution and allocation rules of alkali metal components in the fixed phase and volatile phase during the fouling and slagging process of biomass ash. It is applicable to the method for predicting the dynamic fouling and slagging of biomass ash based on the gas-solid two-phase distribution rule at different ashing temperatures.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] The method for predicting the dynamic fouling and slagging tendency of biomass ash based on the change of ashing temperature specifically includes the following steps:

[0010] Step 1, determine the sintering rate and sintering characteristic index of biomass ash at different temperatures;

[0011] Step 2, determine the melting characteristic temperature and melting characteristic index of biomass ash at different temperatures;

[0012] Step 3, determine the fixed-phase fouling and slagging index and volatile-phase fouling and slagging index during the ashing process of biomass ash at different temperatures;

[0013] Step 4, determine the comprehensive fouling and slagging tendency of biomass ash.

[0014] Further, the specific process of Step 1 is as follows:

[0015] (1.1) Crush and grind the biomass raw materials air-dried under natural conditions, sieve to obtain the required biomass particle samples as biomass powder samples, and put them into a sealed bag for standby;

[0016] (1.2) Weigh an appropriate amount of the prepared biomass powder sample and evenly spread it in a crucible, and place it in a muffle furnace;

[0017] (1.3) Take 600 °C as the reference ashing temperature, denoted as T 600 , raise the muffle furnace to 600 °C or the specified temperature and keep it warm for 2 h to prepare the reference ash or the biomass ash at the specified temperature;

[0018] (1.4) After the ash preparation is completed, wait for the furnace temperature to drop below 200 °C, take out the crucible and cool it to room temperature, and then weigh it;

[0019] (1.5) The residual ash obtained at a certain ashing temperature is the fixed phase, and the lost part is the volatile phase. Use the following formula to calculate the yield of the fixed phase at this ashing temperature, denoted as Ash%, and the calculation formula is:

[0020] Ash% = (M2 - M1) / M0 × 100% (1)

[0021] Wherein, M0 is the mass of the biomass sample, M1 is the mass of the crucible; M2 is the total mass of the crucible and the biomass ash;

[0022] (1.6) According to the law of conservation of mass, calculate the yield of the volatile phase at this specific ashing temperature, denoted as Gas%, and the calculation formula is:

[0023] Gas% = 100% - Ash% (2)

[0024] (1.7) Invert the crucible on the sieve, gently tap the bottom of the crucible to vibrate all the biomass ash samples in the crucible onto the sieve, continue vibrating for 1 min, and finally weigh the net weight of the ash sample on the sieve with an electronic balance;

[0025] (1.8) Calculate the sintering rate of the biomass ash sample at the reference temperature of 600 °C, denoted as ASI a,600 , and the calculation formula is:

[0026] ASI a,600 = M3 / (M2 - M1) (3)

[0027] Wherein, M3 is the net weight of the ash sample;

[0028] (1.9) Take ASI a,600 as the reference ash sintering rate, and the percentage of ASI a,T obtained at a certain ashing temperature relative to the reference ash sintering rate ASI a,600 is the relative sintering degree or sintering characteristic index of the biomass ash at this temperature, denoted as D ASI,T , and the calculation formula is:

[0029] D ASI,T = ASI a,T / ASI a,600 (4)

[0030] Wherein, ASI a,T is the sintering rate of the biomass ash at a certain ashing temperature above 600 °C.

[0031] Furthermore, the specific process of step two is as follows:

[0032] (2.1) Use an intelligent ash melting point tester to directly measure the deformation temperature and hemisphere temperature of the biomass ash prepared at different temperatures;

[0033] (2.2) Use the ash melting characteristic index to characterize the melting characteristic of the biomass ash, denoted as AFI, and the calculation formula is:

[0034] AFI = (4DT + HT) / 5 (5)

[0035] In the formula, DT is the deformation temperature of biomass ash, and DT is the DT of biomass ash;

[0036] (2.3) Calculate the ash fusion characteristic index of the reference ash at 600 °C;

[0037] (2.4) Calculate the ash fusion characteristic index of the biomass ash obtained at a certain ashing temperature T;

[0038] (2.5) Calculate the dimensionless percentage of the biomass ash fusion characteristic index at a certain temperature relative to the standard ash fusion characteristic index, denoted as D AFI,T , and the calculation formula is:

[0039] D AFI,T = AFI a,T / AFI a,600 (6)

[0040] In the formula, AFI a,600 is the ash fusion characteristic index of the reference ash at 600 °C, and AFI a,600 is the ash fusion characteristic index of the biomass ash at a certain ashing temperature higher than 600 °C.

[0041] Furthermore, the specific process of step three:

[0042] (3.1) Use an X-ray fluorescence spectrometer to measure the chemical composition of the biomass ash prepared at a certain ashing temperature, denoted as W x , where X represents different oxides, including K2O, Na2O, CaO, MgO, SO3, Fe2O3, SiO2, Al2O3, TiO2; use an ion chromatograph to measure the chlorine element content in the ash, denoted as W Cl ;

[0043] (3.2) At a certain temperature, the fouling slagging index of the fixed phase obtained during the ashing process of biomass is denoted as R b / a,s,T , and the calculation formula is:

[0044] R b / a,s,T =[(W K2O +W Na2O +W CaO +W MgO +W Fe2O3 +W SO3 +W Cl ) / (W SiO2 +W Al2O3 +W TiO2 )] s,T ×(T / T 600 )

[0045] In the formula, T 600 represents the ashing temperature of 600 °C for preparing the reference ash, and T represents a certain set ashing temperature;

[0046] (3.3) Calculate the fouling and slagging index R of the volatile phase b / a,g,T , and the calculation formula is:

[0047] R b / a,g,T = R b / a,s,T ×(Gas% / Ash%) (7)

[0048] In the above formula, R b / a,s,T is the fouling and slagging index of the fixed phase;

[0049] (3.4) Calculate the comprehensive fouling and slagging index of biomass ash based on the change of ashing temperature, denoted as R b / a,T , and the calculation formula is:

[0050] R b / a,T = D ASI,T ×D AFI,T ×R b / a,s,T ×R b / a,g,T (8).

[0051] Furthermore, the specific process of step four is as follows:

[0052] (4.1) For a certain biomass, taking the ash prepared at an ashing temperature of 600 °C as the reference ash, calculate the fouling and slagging index of the fixed phase and the fouling and slagging index of the volatile phase of the reference ash, denoted as R b / a,s,600 and R b / a,g,600 respectively, and then calculate the comprehensive fouling and slagging index of the reference ash, denoted as R b / a,600 ;

[0053] (4.2) Calculate D ASI,T , D AFI,T , R b / a,s,T and R b / a,g,T of biomass ash at a certain temperature, and calculate the comprehensive fouling and slagging index R b / a,T of biomass ash at this temperature from this;

[0054] (4.3) According to the magnitude of the calculation result of R b / a,T at a certain temperature, combined with the calculation result of the comprehensive fouling and slagging index of the reference ash, divide the fouling and slagging tendency of biomass ash at this temperature into three levels: slight, moderate and severe, and the discrimination boundaries are as follows:

[0055] When R b / a,T ≤1 / 2R b / a,600 , it is slight fouling and slagging;

[0056] When 1 / 2R b / a,600 <R b / a,T ≤2R b / a,600 , it is moderate fouling and slagging;

[0057] When R b / a,T >2R b / a,600 it is severe fouling and slagging.

[0058] The beneficial effects of the present invention are as follows:

[0059] 1) Based on the variation laws of the melting and sintering characteristics of biomass ash at different temperatures, and fully considering the distribution laws of sulfur, chlorine, and alkali metal components in the fixed phase and volatile phase during the fouling and slagging process, the present invention proposes calculation methods for the fixed-phase fouling and slagging index and the volatile-phase fouling and slagging index during the biomass ashification process at different temperatures, and based on this, proposes a dynamic fouling and slagging prediction method for biomass ash based on the gas-solid two-phase distribution law applicable to different ashification temperatures.

[0060] 2) The present invention makes up for the deficiencies of previous research on predicting the fouling and slagging trend of biomass ash that ignored the melting characteristics and sintering characteristics of biomass ash, and at the same time fully considers the influence of the dynamic change relationship between the volatile phase and temperature on fouling and slagging, improving the accuracy and reliability of the prediction results of the dynamic fouling and slagging trend of biomass ash applicable to different ashification temperatures. Specific Embodiments

[0061] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0062] Based on the variation laws of the melting and sintering characteristics of biomass ash at different ashification temperatures, and comprehensively considering the aggregation and distribution laws of sulfur, chlorine, and alkali metal components in the fixed phase and volatile phase during the fouling and slagging process of biomass ash, the present invention proposes a dynamic fouling and slagging prediction method for biomass ash based on the gas-solid two-phase distribution law applicable to different ashification temperatures, which can provide scientific guidance for accurately predicting the fouling and slagging trend of biomass ash at different ashification temperatures, and is of great significance for taking reasonable and effective measures to inhibit the fouling and slagging of biomass ash in the actual production process.

[0063] A method for predicting the dynamic fouling and slagging trend of biomass ash based on the change of ashification temperature includes the following specific processes:

[0064] (1) Determine the sintering rate and sintering characteristic index of biomass ash at different temperatures. Specifically:

[0065] (1.1) Crush and grind the biomass raw materials air-dried under natural conditions, and sieve the required biomass particle samples with a 100-mesh sieve (particle size ≤ 0.154 mm) as biomass powder samples, and put them into a sealed bag for standby;

[0066] (1.2) Weigh an appropriate amount of the prepared biomass powder sample using an electronic balance and evenly spread it in the crucible. Record the mass of the biomass sample as M0 and the mass of the crucible as M1, and place them in the muffle furnace.

[0067] (1.3) According to the standard of ASTM-E1755-01 "Industrial Analysis Method for Biomass" in the United States, take 600 °C as the reference ashing temperature, denoted as T 600 , heat the muffle furnace to 600 °C or the specified temperature and keep it for 2 h to prepare the reference ash or the biomass ash at the specified temperature.

[0068] (1.4) After ash preparation, wait until the furnace temperature drops below 200 °C, take out the crucible and cool it to room temperature, then weigh it, and record the total mass of the crucible and the biomass ash as M2.

[0069] (1.5) The residual ash obtained at a certain ashing temperature is the fixed phase, and the lost part is the volatile phase. Use the following formula to calculate the yield of the fixed phase at this ashing temperature, denoted as Ash%:

[0070] Ash% = (M2 - M1) / M0 × 100% (1)

[0071] In the formula, M0 is the mass of the biomass sample, M1 is the mass of the crucible; M2 is the total mass of the crucible and the biomass ash;

[0072] (1.6) According to the law of conservation of mass, calculate the yield of the volatile phase at this specific ashing temperature, denoted as Gas%:

[0073] Gas% = 100% - Ash% (2)

[0074] (1.7) Invert the crucible on a 100-mesh sieve, gently tap the bottom of the crucible to vibrate all the biomass ash samples in the crucible onto the sieve, continue vibrating for 1 min, and finally weigh the net weight of the ash sample on the sieve using an electronic balance, denoted as M3.

[0075] (1.8) Finally, use the following formula to calculate the sintering rate of the biomass ash sample at the reference temperature of 600 °C, denoted as ASI a,600 :

[0076] ASI a,600 = M3 / (M2 - M1) (3)

[0077] In the formula, M3 is the net weight of the ash sample;

[0078] (1.9) Take ASI a,600 as the reference ash sintering rate, and the ASI a,T obtained at a certain ashing temperature relative to the reference ash sintering rate ASI a,600The percentage is the relative sintering degree of biomass ash at this temperature, or the sintering characteristic index, denoted as D ASI,T :

[0079] D ASI,T = ASI a,T / ASI a,600 (4)

[0080] In the formula, ASI a,T is the sintering rate of biomass ash at an ashing temperature above 600 °C

[0081] (2) Determine the melting characteristic temperature and melting characteristic index of biomass ash at different temperatures. Specifically,

[0082] (2.1) Use an intelligent ash melting point tester to directly measure the deformation temperature and hemispherical temperature of biomass ash prepared at different temperatures

[0083] (2.2) Use the ash melting characteristic index to characterize the melting characteristics of biomass ash, denoted as AFI, and the calculation formula is

[0084] AFI = (4DT + HT) / 5 (5)

[0085] In the formula, DT is the deformation temperature of biomass ash, and DT is the DT of biomass ash

[0086] (2.3) Calculate the ash melting characteristic index of the 600 °C reference ash, denoted as AFI a,600 ;

[0087] (2.4) Calculate the ash melting characteristic index of biomass ash obtained at a certain ashing temperature T, denoted as AFI a,T ;

[0088] (2.5) Calculate the dimensionless percentage of the ash melting characteristic index of biomass ash at a certain temperature relative to the standard ash melting characteristic index, denoted as D AFI,T , and the calculation formula is

[0089] D AFI,T = AFI a,T / AFI a,600 (6)

[0090] In the formula, AFI a,600 is the ash melting characteristic index of the 600 °C reference ash, and AFI a,600 is the ash melting characteristic index of biomass ash at an ashing temperature above 600 °C

[0091] (3) Determine the fixed-phase fouling slagging index and volatile-phase fouling slagging index during the biomass ashing process at different temperatures. Specifically,

[0092] (3.1) The chemical composition of the biomass ash prepared at a certain ashing temperature was determined using an X-ray fluorescence spectrometer (XRF), and the content of the oxide was denoted as W x , where X represents different oxides, including K2O, Na2O, CaO, MgO, SO3, Fe2O3, SiO2, Al2O3, TiO2, etc.; the content of chlorine element in the ash was determined using an ion chromatograph (IC) and denoted as W Cl ;

[0093] (3.2) Drawing on the slagging prediction index of base-acid ratio commonly used to judge the slagging and fouling tendency of coal ash, and fully considering the synergistic effect of components such as sulfur and chlorine during the slagging and fouling process of biomass ash, the fouling and slagging index of the fixed phase obtained during the ashing process of biomass at a certain temperature was proposed and denoted as R b / a,s,T , and the calculation formula is:

[0094] R b / a,s,T = [(W K2O + W Na2O + W CaO + W MgO + W Fe2O3 + W SO3 + W Cl ) / (W SiO2 + W Al2O3 + W TiO2 )] s,T × (T / T 600 )

[0095] In the formula, R b / a,s,T represents the fouling and slagging index of the fixed phase of biomass ash at a certain ashing temperature, and its subscript s represents the fixed phase., T 600 represents the ashing temperature of 600 °C when preparing the reference ash, and T represents a certain set ashing temperature;

[0096] (3.3) The ratio of the volatile phase yield to the fixed phase yield was used as the volatile phase action factor to calculate the fouling and slagging index R b / a,g,T , and the calculation formula is:

[0097] R b / a,g,T = R b / a,s,T × (Gas% / Ash%) (7)

[0098] In the above formula,, R b / a,g,T represents the fouling and slagging index of the volatile phase of biomass ash at a certain ashing temperature, and its subscript g represents the volatile phase, R b / a,s,T is the fouling and slagging index of the fixed phase, T 600 represents the ashing temperature of 600 °C when preparing the reference ash, and T represents a certain set ashing temperature;

[0099] (3.4) Considering the sintering characteristic index, melting characteristic index, fixed-phase fouling and slagging index, and volatile-phase fouling and slagging index of the biomass ash described above, calculate the comprehensive fouling and slagging index of the biomass ash based on the change in ashing temperature, denoted as R. b / a,T , and the calculation formula is:

[0100] R b / a,T = D ASI,T ×D AFI,T ×R b / a,s,T ×R b / a,g,T (8).

[0101] (4) Determine the comprehensive fouling and slagging trend of the biomass ash. Specifically,

[0102] (4.1) For a certain biomass, take the ash prepared at an ashing temperature of 600 °C as the reference ash, and calculate the fixed-phase fouling and slagging index and the volatile-phase fouling and slagging index of the reference ash, denoted as R b / a,s,600 and R b / a,g,600 , respectively, and then calculate the comprehensive fouling and slagging index of the reference ash, denoted as R b / a,600 ;

[0103] (4.2) According to the above calculation formula, calculate D ASI,T , D AFI,T , R b / a,s,T and R b / a,g,T of the biomass ash at a certain temperature, and calculate the comprehensive fouling and slagging index R b / a,T of the biomass ash at this temperature;

[0104] (4.3) According to the magnitude of the calculation result of R b / a,T at a certain temperature, combined with the calculation result of the comprehensive fouling and slagging index of the reference ash, divide the fouling and slagging tendency of the biomass ash at this temperature into three grades: slight, moderate, and severe. The discrimination boundaries are as follows:

[0105] When R b / a,T ≤ 1 / 2R b / a,600 , it is slight fouling and slagging;

[0106] When 1 / 2R b / a,600 < R b / a,T ≤ 2R b / a,600 , it is moderate fouling and slagging;

[0107] When R b / a,T > 2R b / a,600 , it is severe fouling and slagging.

[0108] Example

[0109] Taking the corn stalk biomass that exists in large quantities in the Northeast region as an example, the fouling and slagging trends of corn stalks at ashing temperatures of 400°C and 800°C are predicted and analyzed as follows:

[0110] ① Grind the air-dried corn stalks, sieve the required powder samples through a 100-mesh sieve (particle size ≤ 0.154 mm), and prepare corn stalk ash at ashing temperatures of 400°C, 600°C, and 800°C respectively;

[0111] ② According to the above method, calculate the yields of the fixed phase and volatile phase during the ashing process of corn stalks at different temperatures, represented by Ash% and Gas% respectively. The calculation results are shown in Table 1;

[0112] Table 1 Yields of the fixed phase and volatile phase during the ashing process of corn stalks at different temperatures

[0113] Ashing Temperature Ash% Gas% 400℃ 17.9％ 82.1％ 600℃ 15.9％ 84.1％ 800℃ 13.7％ 86.3％

[0114] ③ According to the above method, measure the sintering rate and sintering characteristic index of the prepared corn stalk powder samples at 400°C, 600°C, and 800°C. The sintering rate test results at 400°C, 600°C, and 800°C are represented by ASI a,400 , ASI a,600 and ASI a,800 respectively. The calculation results of the sintering characteristic index of the ash samples prepared at 400°C and 800°C relative to the reference ash ASI a,600 are represented by D ASI,400 and D ASI,800 respectively.

[0115] It should be noted here that taking the 600°C ash as the reference, the sintering characteristic index of the ash is calculated by the formula D ASI,T = ASI a,T / ASI a,600 . Therefore, the sintering characteristic index of the 600°C reference ash is equal to 1. If ASI a,T > 1, it means that the sintering degree of the ash sample at this temperature is weak; if ASI a,T < 1, it means that the sintering degree of the ash sample at this temperature is strong. Under normal circumstances, when other conditions such as ashing time and atmosphere are the same, the higher the ashing temperature, the stronger the sintering degree for the same kind of biomass. The measurement results of the sintering rate and sintering characteristic index of the corn stalk ash prepared at 400°C, 600°C, and 800°C are shown in Table 2.

[0116] Table 2 Measurement results of the sintering rate and sintering characteristic index of corn stalk ash at different temperatures

[0117] Ashing Temperature <![CDATA[Sintering rate ASI a,T > <![CDATA[Sintering characteristic index D ASI,T > 400℃ 25.63％ 0.68 600℃ 37.79％ 1.00 800℃ 53.50％ 1.42

[0118] ④ Use an intelligent ash fusion point tester to measure the deformation temperature (DT) and hemisphere temperature (HT) of corn stalk ash at 400 °C, 600 °C, and 800 °C, and calculate the fusion characteristic index of ash at different temperatures, represented by AFI a,400 , AFI a,600 , and AFI a,800 respectively. At the same time, calculate the dimensionless index D AFI,T of the fusion characteristic index of corn stalk ash at 400 °C and 800 °C relative to the 600 °C standard ash, represented by D AFI,400 and D AFI,T respectively.

[0119] It should be noted here that based on the 600 °C ash, the dimensionless index of ash fusion characteristics is calculated by the formula D AFI,T = AFI a,T / AFI a,600 . Therefore, the D AFI,600 of the 600 °C reference ash is equal to 1. If D AFI,T > 1, it indicates a higher degree of fusion of the ash sample prepared at this temperature; if D AFI,T < 1, it indicates a lower degree of fusion of the ash sample at this temperature. Under normal circumstances, when other conditions such as ashing time and atmosphere are the same, the higher the ashing temperature, for the same kind of biomass, the stronger the degree of fusion of the biomass ash obtained. The measurement results of the fusion characteristic index and the dimensionless index D AFI,T of corn stalk ash prepared at 400 °C, 600 °C, and 800 °C are shown in Table 3.

[0120] Table 3 Measurement results of the sintering rate and sintering characteristic index of corn stalk ash prepared at 400 °C, 600 °C, and 800 °C

[0121] Ashing Temperature Deformation Temperature DT Hemisphere Temperature HT <![CDATA[Melt Flow Index AFI a,T > <![CDATA[Dimensionless index D AFI,T > 400℃ 936℃ 1284℃ 1005.6 0.97 600℃ 966℃ 1298℃ 1032.4 1.00 800℃ 1188℃ 1342℃ 1218.8 1.18

[0122] ⑤ Use an X-ray fluorescence spectrometer (XRF) to measure the chemical composition of corn stalk ash prepared at 400 °C, 600 °C, and 800 °C respectively, and use an ion chromatograph (IC) to measure the chlorine element content in each ash sample. The test results are shown in Table 4.

[0123] Table 4 Test results of the chemical composition of corn stalk ash prepared at 400 °C, 600 °C, and 800 °C (%)

[0124] Ashing Temperature <![CDATA[SiO2]]> <![CDATA[Na2O]]> MgO <![CDATA[Al2O3]]> <![CDATA[SO3]]> <![CDATA[K2O]]> CaO <![CDATA[Fe2O3]]> <![CDATA[TiO2]]> Cl 400℃ 24.64 12.16 3.29 1.83 1.23 31.67 6.42 0.51 0.12 8.39 600℃ 29.65 5.75 4.23 2.66 4.92 26.11 5.29 0.67 0.05 7.26 800℃ 32.31 4.06 6.64 2.12 5.43 24.24 6.87 0.46 0.09 5.15

[0125] ⑥ Calculate the fixed-phase fouling slagging index R b / a,s,T .

[0126] According to the test results of the chemical composition of the ash sample, calculate the fixed-phase fouling slagging index during the ashing process of corn stalk ash at 400 °C, 600 °C, and 800 °C according to the formula described above, represented by Rb / a,s,400 , R b / a,s,600 and R b / a,s,800 indicates that the calculation results are shown in Table 5.

[0127] Table 5 Calculation Results of Fixed Phase Contamination and Slagging Index during Corn Stalk Ashing at Different Temperatures

[0128] Ashing Temperature <![CDATA[Fixed-phase contamination slagging index R b / a,s,T > 400℃ 1.60 600℃ 1.68 800℃ 2.04

[0129] ⑦ Calculate the volatile phase contamination and slagging index R b / a,g,T .

[0130] According to the formula R b / a,g,T = R b / a,s,T ×(Gas% / Ash%), calculate the volatile phase contamination and slagging index during corn stalk ashing at 400 °C, 600 °C and 800 °C, which are represented by R b / a,g,400 , R b / a,g,600 and R b / a,g,800 respectively, and the calculation results are shown in Table 6.

[0131] Table 6 Calculation Results of Volatile Phase Contamination and Slagging Index during Corn Stalk Ashing at Different Temperatures

[0132] Ashing Temperature <![CDATA[R b / a,s,T > Ash% Gas% <![CDATA[Volatile phase contamination slagging index R b / a,g,T > 400℃ 1.60 17.9％ 82.1％ 7.34 600℃ 1.68 15.9％ 84.1％ 8.89 800℃ 2.04 13.7％ 86.3％ 12.85

[0133] ⑧ According to the calculated D ASI,T , D AFI,T and R b / a,s,T of the biomass ash, calculate the comprehensive contamination and slagging index of corn stalk ash at 400 °C, 600 °C and 800 °C, which are represented by R b / a,400 , R b / a,600 and R b / a,800 respectively, and the calculation results are summarized in Table 7.

[0134] Table 7 Summary of Calculation Results of D ASI,T , D AFI,T , R b / a,s,T and R b / a,T for Corn Stalk Ash Prepared at Different Temperatures

[0135] Ashing Temperature <![CDATA[D ASI,T > <![CDATA[D AFI,T > <![CDATA[R b / a,s,T > <![CDATA[R b / a,g,T > <![CDATA[Comprehensive fouling and slagging index R b / a,T > 400℃ 0.68 0.97 1.60 7.34 7.75 600℃ 1.00 1.00 1.68 8.89 14.94 800℃ 1.42 1.18 2.04 12.85 43.92

[0136] ⑨ Prediction of Comprehensive Contamination and Slagging Tendency of Corn Stalk Ash:

[0137] Taking the corn stalk ash prepared at an ashing temperature of 600 °C as the reference ash, the comprehensive contamination and slagging index R b / a,600 = 14.94; when the ashing temperature is 400 °C, the comprehensive contamination and slagging index R b / a,400 = 7.75, which is located in 1 / 2R b / a,600 < R b / a,T ≤ 2R b / a,600In the range, it can be predicted that the comprehensive fouling and slagging tendency of corn stalk ash at 400 °C is moderate; when the ashing temperature is 800 °C, its comprehensive fouling and slagging index R b / a,800 = 43.92, which is in the range of R b / a,T > 2R b / a,600 In the range, so it can be predicted that the comprehensive fouling and slagging tendency of corn stalk ash at 800 °C is serious. This prediction result is consistent with the relevant experimental results, verifying the reliability and accuracy of this prediction method.

[0138] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the essence of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for predicting the dynamic fouling and slagging trend of biomass ash based on the change of ashing temperature, characterized in that, Specifically, it includes the following steps: Step 1: Determine the sintering rate and sintering characteristic index of biomass ash at different temperatures; Step 2: Determine the melting characteristic temperature and melting characteristic index of biomass ash at different temperatures; Step 3: Determine the fixed-phase fouling slagging index and volatile-phase fouling slagging index during the ashing process of biomass ash at different temperatures; Step 4: Judge the comprehensive fouling and slagging trend of biomass ash; The specific process of Step 2 is as follows: (2.1) Use an intelligent ash melting point tester to directly measure the deformation temperature and hemisphere temperature of biomass ash prepared at different temperatures; (2.2) The ash fusion characteristics of biomass ash are characterized by the ash fusion characteristic index, denoted as AFI , and the calculation formula is as follows: AFI =(4 DT + HT ) / 5 In the formula, DT is the deformation temperature of biomass ash, HT is the hemisphere temperature of biomass ash; (2.3) Calculate the ash melting characteristic index of the reference ash at 600 °C; (2.4) Calculate the ash fusion characteristic index of the biomass ash obtained at a certain ashing temperature T under which; (2.5) Calculate the dimensionless percentage of the biomass ash fusion characteristic index relative to the standard ash fusion characteristic index at a certain temperature, denoted as D AFI,T , and the calculation formula is: D AFI,T = AFI a,T / AFI a,600 In the formula, AFI a,600 is the ash fusion characteristic index of the reference ash at 600°C, AFI a,T is the ash fusion characteristic index of the biomass ash at an ashing temperature higher than 600°C; The specific process of Step 3: (3.1)Determine the chemical composition of the biomass ash prepared at a certain ashing temperature using an X-ray fluorescence spectrometer, denoted as W x , where X represents different oxides, including K2O, Na2O, CaO, MgO, SO3, Fe2O3, SiO2, Al2O3, TiO2; determine the chlorine content in the ash using an ion chromatograph, denoted as W Cl ; (3.2) At a certain temperature, the fouling and slagging index of the fixed phase obtained during the ashing process of biomass is denoted as R b / a,s,T , where b / a is the base-to-acid ratio, and the calculation formula is: R b / a,s,T =[( W K2O + W Na2O + W CaO + W MgO + W Fe2O3 + W SO3 + W Cl ) / ( W SiO2 + W Al2O3 + W TiO2 )] s,T ×( T / T 600 ) In the formula, T 600 represents the ashing temperature of 600 °C when preparing the reference ash, T represents a set ashing temperature; (3.3) Calculate the fouling and slagging index of the volatile phase R b / a,g,T , and the calculation formula is as follows: R b / a,g,T = R b / a,s,T × (Gas% / Ash%) In the above formula, R b / a,s,T is the fouling and slagging index of the stationary phase; Gas% is the yield of the volatile phase; Ash% is the yield of the stationary phase; (3.4) Calculate the comprehensive fouling and slagging index of biomass ash finally based on the change of ashing temperature, denoted as R b / a,T , and the calculation formula is: R b / a,T = D ASI,T × D AFI,T × R b / a,s,T×Rb / a,g,T In the above formula, D ASI,T is the sintering characteristic index at temperature T; D AFI,T is the ash fusion characteristic index at temperature T; The specific process of Step 4 is as follows: (4.1)For a certain biomass, taking the ash prepared at an ashing temperature of 600 °C as the reference ash, calculate the fixed-phase fouling and slagging index and the volatile-phase fouling and slagging index of the reference ash, denoted as R b / a,s,600 and R b / a,g,600 respectively, and then calculate the comprehensive fouling and slagging index of the reference ash, denoted as R b / a,600 ; (4.2) Calculate the D ASI,T , D AFI,T , R b / a,s,T and R b / a,g,T at a certain temperature, and calculate the comprehensive fouling and slagging index R b / a,T of biomass ash at this temperature; (4.3) According to the magnitude of the calculation result at a certain temperature R b / a,T Combined with the calculation result of the comprehensive fouling and slagging index of the reference ash, the fouling and slagging tendencies of the biomass ash at this temperature are divided into three levels: slight, moderate, and severe. The discrimination boundaries are as follows: When R b / a,T ≤ 1 / 2 R b / a,600 it is slight fouling and slagging; When 1 / 2 R b / a,600 < R b / a,T ≤2 R b / a,600 it is moderate fouling and slagging; When R b / a,T > 2 R b / a,600 it is severe fouling and slagging.

2. The method for predicting the dynamic fouling and slagging trend of biomass ash based on the change of ashing temperature according to claim 1, characterized in that The specific process of Step 1 is as follows: (1.1) Crush and grind the biomass raw materials air-dried under natural conditions, sieve to obtain the required biomass particle samples as biomass powder samples, and put them into a sealed bag for standby; (1.2) Weigh an appropriate amount of the prepared biomass powder sample, spread it evenly in the crucible, and place it in the muffle furnace; (1.3)Taking 600 °C as the reference ashing temperature, denoted as T 600 , raise the muffle furnace to 600 °C or the specified temperature and keep it warm for 2 h to prepare the reference ash or the biomass ash at the specified temperature; (1.4) After the ash is prepared, wait for the furnace temperature to drop below 200 °C, take out the crucible, cool it to room temperature, and then weigh it; (1.5)The residual ash obtained at a certain ashing temperature is used as the stationary phase, and the lost part is the volatile phase. The yield of the stationary phase at this ashing temperature is calculated using the following formula, denoted as Ash %, and the calculation formula is: Ash %=( M 2- M 1) / M 0×100% Wherein, M 0 is the mass of the biomass sample, M 1 is the mass of the crucible; M 2 is the total mass of the crucible and the biomass ash; (1.6) Calculate the yield of the volatile phase at this specific ashing temperature according to the law of conservation of mass, denoted as Gas %, and the calculation formula is: Gas % = 100% - Ash% (1.7) Invert the crucible on the sieve, gently tap the bottom of the crucible to vibrate all the biomass ash samples in the crucible onto the sieve, continue vibrating for 1 min, and finally weigh the net weight of the ash sample on the sieve with an electronic balance; (1.8) Calculate the sintering rate of the biomass ash sample at the reference temperature of 600 °C, denoted as ASI a,600 , and the calculation formula is: ASI a,600 = M 3 / ( M 2- M 1) In the formula, M 3 is the net weight of the grey sample; (1.9) Taking ASI a,600 as the reference ash sintering rate, the ASI a,T percentage relative to the reference ash sintering rate ASI a,600 is the relative sintering degree, or sintering characteristic index, of the biomass ash at this temperature, denoted as D ASI,T , and the calculation formula is: D ASI,T = ASI a,T / ASI a,600 In the formula, ASI a,T is the sintering rate of biomass ash at an ashing temperature higher than 600 °C.