WO2018121517A1 - 测量锅炉灰渣可燃碳含量的方法 - Google Patents

测量锅炉灰渣可燃碳含量的方法 Download PDF

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WO2018121517A1
WO2018121517A1 PCT/CN2017/118572 CN2017118572W WO2018121517A1 WO 2018121517 A1 WO2018121517 A1 WO 2018121517A1 CN 2017118572 W CN2017118572 W CN 2017118572W WO 2018121517 A1 WO2018121517 A1 WO 2018121517A1
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gas
ash
flow rate
combustible carbon
carbon content
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PCT/CN2017/118572
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French (fr)
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夏红德
魏凯
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中国科学院工程热物理研究所
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
    • G01N27/622—Ion mobility spectrometry
    • G01N27/623—Ion mobility spectrometry combined with mass spectrometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
    • G01N5/04—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by removing a component, e.g. by evaporation, and weighing the remainder

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  • the invention relates to the measurement of combustible carbon content of boiler ash, in particular to a method for accurately measuring residual combustible carbon content in boiler ash by using thermogravimetry combined with mass spectrometry.
  • the combustible carbon content in boiler ash is not only an important indicator reflecting the quality of combustion, but also determines its application in building materials. Since the boiler ash is formed in a complex dynamic combustion process, its composition is relatively complicated.
  • ash usually includes water, carbonates, sulfates and oxides.
  • the water mainly consists of water adsorbed between particles and particles, crystal water (such as CaSO 4 ⁇ 2H 2 O), and possibly The potential water (such as Ca(OH) 2 ) is formed by chemical reaction.
  • the carbonate includes the unresolved, secondary reaction, and the coal itself is carried in the furnace.
  • the sulfate is mainly from the desulfurization process.
  • LOI Loss-On-Ignition
  • fly ash in fluidized bed boilers, the deviation is even greater than two orders of magnitude, even with a measurement error of more than 40% for pulverized coal furnaces [Reference 1].
  • the reason why the above measurement error is very large is mainly because the existing measurement means cannot distinguish the distribution of the true amount of different escape components during the loss and loss process.
  • the second stage is a constant temperature at 725 ° C and the nitrogen is switched to air.
  • the weight loss measured in this section is considered to be the content of combustible carbon. Comparing the flammable carbon content obtained by the above measurement method with the data of the traditional direct burning loss method, it can be seen that the error of the burning loss method reaches 75% for the pulverized coal furnace ash, and the error for the fluidized bed boiler exceeds 100%, even reaching 2780. % [Reference 1].
  • the flammable carbon content of boiler ash is measured by the power industry standard DL/L567.6-95.
  • Two methods are specified in the fly ash and slag combustibles determination method.
  • the first method is the routine of coal-fired boiler ash flammables.
  • DL-A Supervised method
  • DL-B Supervised method
  • the method needs to determine the moisture and ash content of the ash and slag air drying base according to the GB212 air drying method, and determine the carbonate in the ash and slag according to GB/T218.
  • the carbon dioxide content, the total loss on ignition minus the ash, the moisture in the slag and the carbon dioxide content in the carbonate are the flammable content in the ash and slag.
  • the first method is the traditional loss-of-fire method.
  • the combustible carbon content in the second method is obtained by subtraction, and the measurement is not completed in the same process, and the measurement error is difficult to control.
  • thermogravimetric measurement with infrared qualitative analysis hereinafter referred to as TGA-FT method.
  • the method is to put the fly ash sample into the thermobalance tray, firstly introducing inert gas and heating from room temperature to 725 °C. Maintain this temperature until the mass is constant, then pass the air and continue to maintain this temperature until the mass is constant; the carbon content of the fly ash in the circulating fluidized bed boiler is defined as the ratio of the sample weight loss to the initial mass of the sample after passing air [Reference 3] ].
  • the working principle is mainly to use the temperature rising process of the sample in different gas atmospheres to distinguish the burning loss temperature range of the combustible carbon as much as possible.
  • the ash itself and its reaction with the surrounding atmosphere are very complicated.
  • the weight loss mechanism of carbonate and sulfate contained therein cannot be deduced from the weight loss mechanism under air conditions, because the change of atmosphere has already produced the weight loss mechanism of carbonate and sulfate.
  • the oxidation process of combustible carbon often overlaps with the decomposition process of carbonate.
  • Figure 1 is a graph showing a typical evolution gas profile of a fly ash pyrolysis of a circulating fluidized bed boiler in an argon atmosphere as measured by the method of the present invention. It shows the process of pyrolysis of fly ash in Ar atmosphere after desulfurization of circulating fluidized bed boiler.
  • the mass flow rate of main escape gases H 2 O, CO 2 and SO 2 has been given, and the escape of CO 2 can be found. It is spread over 400-1000 ° C, and it is very unscientific to infer that the total gas escape mass in a partial temperature range is or is not a certain gas.
  • the primary technical drawback of the traditional method of measuring flammable carbon in boiler ash is the distortion of the test principle, which attempts to directly distinguish and confirm the “carbon” itself, so it can be understood that these methods pay more attention to the “carbon” in the “combustible carbon” measurement.
  • the "flammable” characteristics of "combustible carbon” have not been clearly resolved from the mechanism, and this difference in nature directly leads to large deviations and even wrong judgments.
  • the existing methods are not able to explain the reaction mechanism of the various components of the test process.
  • changes in measurement conditions can cause large errors, making it difficult to perform accurate measurements.
  • the traditional method of multi-step the measurement process takes longer.
  • the present invention proposes a measurement method having a basic principle different from the above-mentioned prior art method, and based on the "combustible" characteristic of combustible carbon in boiler ash, oxygen consumption is obtained by aerobic combustion. The amount, thereby accurately obtaining the content of combustible carbon.
  • the present invention provides a method of measuring the combustible carbon content of a boiler ash, the method comprising: measuring the oxygen consumption of the ash ash combustion of the boiler, and calculating the total oxygen consumption from burning all combustible carbon The absolute value of the ash flammable carbon content, wherein the total oxygen consumption is obtained by burning and pyrolyzing the boiler ash in the thermogravimetric-mass spectrometer, and subtracting the weight loss rate from the sum of the mass flow of the escaping gas And the value obtained.
  • the evolved gas mass flow rate and the weight loss rate are summed in the interval from normal temperature to 950 ° C or from normal temperature to 1000 ° C or from normal temperature to 1250 ° C.
  • the evolved gas comprising CO.'S 2, and SO 2, H 2 O, O 2, one or more of.
  • the mass flow of the evolved gas k at time i Calculated by:
  • ⁇ k is the density of the evolved gas k at normal temperature, It is the volume flow rate of the evolved gas k at normal temperature.
  • this method is suitable for substances having phase change characteristics such as H 2 O.
  • the volumetric flow rate of the evolved gas k at normal temperature is obtained from the mass spectrogram obtained by combustion and pyrolysis of the boiler ash in the thermogravimetric mass spectrometer according to the characteristic map and relative sensitivity of the evolved gas.
  • the characteristic map and relative sensitivity of the evolved gas are through a gas corresponding to the evolved gas at a fixed flow rate, or a gas and a carrier gas corresponding to the evolved gas at a fixed flow rate, or a pure compound and a fixed amount.
  • the carrier gas is obtained by calibration of the thermogravimetric mass spectrometer.
  • the characteristic map and relative sensitivity of the evolved gas are calibrated using an equivalent feature map method.
  • the equivalent feature mapping method uses a carrier gas as a reference gas.
  • the carrier gas comprises at least one of an inert gas (eg, Ar or the like) and N 2 ; and/or the pure compound includes at least one of a carbonate, a sulfate, and H 2 O.
  • an inert gas eg, Ar or the like
  • the pure compound includes at least one of a carbonate, a sulfate, and H 2 O.
  • the calibration of the thermogravimetric-mass spectrometer is off-line calibration.
  • the invention accurately measures the combustible carbon content by accurately measuring the mass flow rate of the gas and combining the dynamic data of the weight loss.
  • This measurement method is applicable to all boiler ash, and the measurement results of different types of ash can be compared.
  • Figure 1 is a typical escape gas distribution diagram of fly ash pyrolysis of a circulating fluidized bed boiler in an argon atmosphere.
  • FIG. 2 is a schematic diagram showing the principle division of the combustible carbon content measurement of the present invention.
  • Figure 3 is a flow chart showing the measurement of combustible carbon content of boiler ash according to the present invention.
  • Fig. 4 is a graph showing the mass flow rate of the evolved gas of the ash content of the ash of the circulating fluidized bed boiler according to Example 1 of the present invention.
  • Fig. 5 is a diagram showing a stacked area converted from the mass flow rate diagram of Fig. 4.
  • Figure 6 is a graph showing the mass flow rate of evolved gas of a calcium-based model compound according to Example 2 of the present invention.
  • Fig. 7 is a diagram showing a stacked area converted from the mass flow rate diagram of Fig. 6.
  • Figure 8 is a graph showing the mass flow rate of the evolved gas of the pulverized coal content of the pulverized coal furnace ash according to Example 3 of the present invention.
  • Figure 9 is a plot of the stacked area converted from the mass flow rate diagram of Figure 8.
  • Figure 10 is a graph showing the mass flow rate of the evolved gas of the coal-like combustible carbon content after low temperature ashing according to Example 4 of the present invention.
  • Fig. 11 is a view showing a stacked area converted from the mass flow rate chart of Fig. 10.
  • the present invention proposes a measurement method whose basic principle is different from the prior art.
  • the carbon content of boiler ash measurement produced CO 2 2 comprises carbon produced by combustion of combustible CO 2, also comprising a thermal boiler ash component produced by decomposition of carbonate CO 2.
  • the traditional method of trying to directly distinguish and confirm the “carbon” itself pays more attention to the “carbon” in the “combustible carbon” measurement, and does not clearly solve the “flammable” characteristic in “combustible carbon”. This difference in nature directly leads to Huge deviations, even wrong judgments.
  • the measurement of combustible carbon in boiler ash by the present invention is based on its "flammable" characteristics.
  • the direct method can be used to measure the form of oxygen or the indirect method.
  • the present invention uses a more accurate, stable and reliable indirect method to calculate the oxygen consumption.
  • the present invention provides a method for measuring a combustible carbon content of a boiler ash, the method comprising: measuring an oxygen consumption of a ash ash combustion of a boiler, and calculating a boiler ash by a total oxygen consumption of burning all combustible carbon The absolute value of the combustible carbon content, wherein the total oxygen consumption is obtained by subtracting the weight loss rate from the sum of the mass flow of the evolved gas by burning and pyrolyzing the boiler ash in the thermogravimetric-mass spectrometer. And got it.
  • the sum of the mass flow rate of the evolved gas and the rate of weight loss can be achieved in a one-step temperature increase process.
  • the summation of the mass flow of the evolved gas and the sum of the rate of weight loss are performed in the same temperature interval, the temperature interval including at least the temperature interval in which the combustible carbon burnout process occurs.
  • the temperature interval may be from normal temperature to 1000 ° C, or to 950 ° C, or to 900 ° C, or to 850 ° C, or to 800 ° C. If you need to measure the sulfur content of the ash, the temperature can reach 1250 ° C, or 1200 ° C. The upper limit of the temperature range can be determined by the specific sample.
  • the evolved gas refers to a gas generated during combustion and pyrolysis of the boiler ash.
  • the evolved gas includes at least CO 2 .
  • the evolved gas may also include one or more of SO 2 , H 2 O, and O 2 .
  • the mass flow rate of the evolved gas may be obtained by multiplying the density of the evolved gas at normal temperature by the volume flow rate of the gas at normal temperature, or by multiplying the molar flow rate of the evolved gas by the molecular weight, and second.
  • the method is suitable for gases having phase change characteristics, such as H 2 O.
  • the volume flow rate of the evolved gas at normal temperature can be obtained by analyzing the mass spectrum of the combustion ash and the pyrolysis of the boiler ash in the thermogravimetric mass spectrometer according to the characteristic map and relative sensitivity of the evolved gas.
  • the characteristic map and relative sensitivity of the evolved gas are obtained by calibration of the thermogravimetric-mass spectrometer.
  • the calibration of the thermogravimetric-mass spectrometer apparatus can be performed by injecting a fixed flow of gas and/or carrier gas corresponding to the evolved gas into the thermogravimetric-mass spectrometer, measuring the mass spectrometry data, and then utilizing Equivalent Characteristic Spectrum Analysis (ECSA), which is based on the conversion of different types of gases into their equivalent relative parameters, ie, the characteristic map and relative sensitivity, based on a specific amount of reference.
  • ECSA Equivalent Characteristic Spectrum Analysis
  • the gas can obtain the physical parameters of various gases, so it is called the equivalent feature map method.
  • thermogravimetric-mass spectrometer calibrate the characteristic map and relative sensitivity of the corresponding gas (relative to the carrier gas); or to the thermogravimetric-mass spectrometer
  • the medium-purity compound is injected with a fixed amount of carrier gas.
  • the thermogravimetric and mass spectrometry data are measured after the temperature of the device is raised, and then the characteristics of the gas released by the pure compound (corresponding to the gas product after ash combustion) are calibrated by the equivalent characteristic mapping method (ECSA). Map and relative sensitivity.
  • the carrier gas used for calibration is the same as the carrier gas used in the actual boiler ash measurement.
  • an inert gas such as argon (Ar) or the like
  • a gas which does not participate in and does not interfere with the release and detection of the evolved gas such as nitrogen (N 2 ) or the like
  • N 2 nitrogen
  • the pure compound used for calibration corresponds to the components contained in the boiler ash, such as carbonate, sulfate, H 2 O, and the like. Specific compounds include calcium carbonate, calcium sulfate, water, and the like.
  • the flow rate of the corresponding gas and/or carrier gas may be from 5 to 100 ml/min.
  • thermogravimetric-mass spectrometer device of the present invention is preferably off-line calibration and can typically be calibrated once during a certain period of time.
  • Figure 3 shows a flow chart for measuring the combustible carbon content of boiler ash according to the present invention.
  • the main measurement links include: calibration, testing, and analysis.
  • the specific implementation steps of each link are as follows:
  • Mass spectrometry data was measured by using a flow meter of a thermogravimetric mass spectrometer to inject a fixed steady flow of gas such as CO 2 , O 2 , and a carrier gas.
  • the characteristic map and relative sensitivity of the gas corresponding to the gas products (CO 2 , O 2 ) after ash combustion are respectively calibrated by the equivalent characteristic map method (ECSA); or the balance of the device using the thermogravimetric mass spectrometer is placed Appropriate pure compounds, such as CaSO 4 , H 2 O, etc., are injected into the carrier gas at a fixed flow rate, and the thermogravimetric and mass spectrometry data are measured after the temperature of the device is raised.
  • the characteristic map and relative sensitivity of the evolved gases corresponding to some gaseous products (SO 2 , H 2 O) after ash combustion were calibrated by equivalent feature mapping method (ECSA).
  • the intensity of the mixed ion current measured at m/z j, Represents the characteristic ion current intensity of gas k.
  • the relative sensitivity is calculated as equation (2), and ⁇ r,k is the sensitivity of gas k relative to the reference gas r (eg, carrier). Represents the volume flow of the gases r, k, respectively.
  • thermogravimetric and mass spectrometry system the ash test sample is placed, a fixed flow of carrier gas and oxygen are introduced, and the sample is burned and pyrolyzed by a temperature rising program.
  • the temperature rise can reach 950 ° C. If the sulphur content of the ash is also measured, the temperature rise should reach 1250 ° C.
  • the weight loss data of the balance was measured, and the mass spectrum (m/z) of the mass spectrum was a total scan spectrum H j of 2-64 (ie, mixed ion current intensity H j ).
  • a r,k - is the relative sensitivity vector of the gas, capitalized here because it is a multi-gas for the actual situation, it must be represented by a vector, representing a group of gases.
  • I r,k + is the equivalent ion current intensity of the gas and is also a vector representing the value of a group of gases.
  • the mass flow rate of the evolved gas and the weight loss rate are summed from the normal temperature to the range of 950 ° C, and the sum of the mass flow rate of the evolved gas minus the weight loss rate is obtained, and the combustion of all combustible carbon is obtained.
  • Total oxygen consumption As shown in formula (5).
  • Z C They are the molecular weights of carbon and oxygen, respectively.
  • the relative value of the amount is obtained by dividing m Carbon by the amount of sample.
  • the measurement process clearly explains and utilizes various reaction mechanisms.
  • H 2 O, CO 2 , SO 2 , O 2 and the like are escaping, and the present invention can give a clear explanation, and at the same time, the carbonic acid can be performed by using these reaction processes.
  • Estimation of salt, sulfate, water of crystallization, combined water, and adsorbed water content may not be limited to combustible carbon content, and the measurement of more parameters facilitates parameter adjustment of the boiler.
  • Measurement process error is small, data stability and reliability are high. For repeated measurements of the same sample, even if the test conditions, such as heating rate, oxygen concentration, sample volume, carrier gas flow rate, etc., change the combustible carbon content measurement value is very good, the relative error is very small, and the anti-interference ability is strong. .
  • the measurement process is realized in one step, and the time for sample measurement is shortened.
  • the measuring method of the invention adopts one-step temperature rising, and the burning and losing process of the combustible carbon occurs synchronously with the decomposition and dehydration of the carbonate and the sulfate, and does not need to utilize different heating processes to distinguish the decomposition and dehydration of the carbonate and the sulfate, and the reduction is reduced. Test time for a single sample.
  • the measuring method of the present invention is applicable to the measurement of the carbon content of the ash in the gasification process.
  • thermogravimetric-mass spectrometer used in the examples was a synchronous thermal analyzer (model 449F3) and a quadrupole mass spectrometer (model QMS403C) from Germany's NETZSCH.
  • thermogravimetric-mass spectrometry equipment Calibration of thermogravimetric-mass spectrometry equipment is carried out according to the following procedure:
  • Ar was used as the carrier gas, and the carrier gas flow rate was 60 ml/min.
  • the CO 2 and O 2 were separately injected at a flow rate of 10 ml/min, and the mass spectrometry data was measured at a heating rate of 10 K/min.
  • the characteristic maps and relative sensitivities of gas CO 2 and O 2 were respectively calibrated by equivalent feature mapping method (ECSA).
  • thermogravimetric mass spectrometer 5-10 mg of CaSO 4 and H 2 O were weighed and placed in a balance of a thermogravimetric mass spectrometer.
  • the carrier gas Ar was injected at a volume flow rate of 60 ml/min.
  • the temperature was raised at a heating rate of 10 K/min, and the temperature was raised to 1,250 ° C, and the thermogravimetric and mass spectrometry data were measured.
  • the characteristic maps and relative sensitivities of gaseous products SO 2 and H 2 O were respectively calibrated by equivalent feature mapping method (ECSA).
  • the relative sensitivities measured with respect to the Ar carrier gas are as follows.
  • CO 2 can also be calibrated by CaCO 3 heating and pyrolysis, and the characteristic map and relative sensitivity at this time are completely consistent with the use of gas CO 2 .
  • Example 1 Measurement of combustible carbon content of fly ash in a typical circulating fluidized bed boiler
  • the fly ash of the circulating fluidized bed boiler of Ningbo Coal-fired Power Plant in Zhejiangzhou is selected as the test sample.
  • the measurement conditions are: the gas atmosphere composed of Ar and O 2 , the Ar flow rate is 65ml/min, the O 2 flow rate is 5ml/min, and the thermogravi The heating rate of the furnace body was 10 ° C / min, and the sample amount was 127.4 mg.
  • Figure 4 shows the gas evolution process of the sample in this measurement method.
  • the emission of H 2 O, CO 2 and SO 2 can be seen.
  • the mass flow rate of the evolved gas is determined by mass spectrometry data. The result is very accurate. stable.
  • the escape of CO 2 is concentrated at 400-700 ° C, two distinct peaks appear, and the escape of H 2 O is concentrated at 100-400 ° C, and a prominent peak appears in front of 400 ° C.
  • the mass flow curve of the evolved gas in Fig. 4 is converted into a stacked area map. As shown in Fig. 5, it can be clearly seen that the weight loss curve and the gas escape mass flow rate agree well under most temperature conditions, at 400-700.
  • the test sample obtained by the above analysis can obtain a combustible carbon content of 2.32% in the fly ash, and a carbon content of 3.72% in the sample.
  • the main compounds in the fly ash of the three calcium-based compound models were selected as experimental samples, and the measurement accuracy when the combustible carbon content was 0 was demonstrated to demonstrate the reliability of the measuring method of the present invention.
  • the three selected compounds were Ca(OH) 2 (national medicine reagent, analytical grade), CaCO 3 (national medicine reagent, excellent grade pure), CaSO 4 ⁇ 2H 2 O (national medicine reagent, analytical grade), and the three reagent contents were respectively 50 mg
  • the measurement conditions were: a gas atmosphere composed of Ar and O 2 , an Ar flow rate of 65 ml/min, an O 2 flow rate of 5 ml/min, and a heating rate of the hot heavy furnace body of 10 ° C/min.
  • the evolution process of the model compound in Figs. 6 and 7 basically also verified the gas evolution process of the fly ash of the circulating fluidized bed boiler in Example 1, in which the escape of CO 2 was concentrated at 600-850 ° C, which is CaCO. 3
  • the evolution of H 2 O forms a prominent peak in the temperature range of 100-200 ° C and 400-450 ° C, reflecting the release of moisture in CaSO 4 ⁇ 2H 2 O and Ca(OH) 2 . Since the temperature required for the decomposition of CaSO 4 is high and the time is long, a large release does not occur in Figs.
  • the masses of H 2 O and CO 2 can be obtained as 22.08 mg and 23.86 mg, respectively. According to the weight loss of the thermogravimetric balance, the masses of H 2 O and CO 2 can be calculated to be 21.30 mg and 23.76 mg, respectively. The relative error is low.
  • the data can be calculated to have a combustible carbon content of 0.21%. It can be confirmed that the sample does not contain combustible carbon, and the carbon content in the sample can be 4.31%.
  • Example 3 Measurement of combustible carbon content of a typical pulverized coal fired furnace
  • the coal ash furnace fly ash of Hunan coal-fired power plant was selected as the test sample.
  • the measurement conditions were as follows: a gas atmosphere in which Ar and O 2 were combined, an Ar flow rate of 65 ml/min, an O 2 flow rate of 5 ml/min, a heating rate of the hot heavy furnace body of 10 ° C/min, and a sample amount of 52.4 mg.
  • the ash in the boiler is basically subjected to high-temperature combustion process.
  • Xinjiang Zhundong coal rich in alkali metal is selected, and the coal sample is ashed by means of plasma low-temperature ashing.
  • the equipment is the K1056X plasma ashing instrument of Quorum Company of the United Kingdom.
  • the gas is pure oxygen. After ashing, the sample has low impurity content and complex composition, and the measurement of combustible carbon is very difficult.
  • the measurement conditions of the coal sample are: a gas atmosphere composed of Ar and O 2 , an Ar flow rate of 65 ml/min, an O 2 flow rate of 5 ml/min, and a heating rate of the hot heavy furnace body of 10 ° C/min. 14.5mg.
  • Example 5 Measurement of combustible carbon content under different measurement conditions
  • the measurement sample is the fly ash of the circulating fluidized bed boiler of Linyi coal-fired power plant in Shandong province.
  • the four measurement conditions are shown in Table 2, which are the reference conditions, the change sample amount, the variable heating rate, the varying oxygen injection amount, etc., and the latter three measurements.
  • the condition changes only one item based on the baseline condition. It can be seen from the contents of Table 2 that although the measurement conditions have undergone a large change, the measurement results are stable, which fully demonstrates that the test method is not affected by the test conditions.
  • the weight loss in Table 2 represents the result of the national standard test method.
  • the combustible carbon content of various types of boiler ash can be determined by the method of the invention, and is suitable for different measurement conditions, such as different sample amounts, gas atmosphere and the like. Since the technical features and the interpretation algorithm of the method can reduce the error by itself and the anti-interference ability is strong, the measurement condition can be appropriately adjusted according to the performance of the device, and is not limited to the measurement conditions mentioned in the embodiment.

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Abstract

本发明提供一种测量锅炉灰渣可燃碳含量的方法，包括：测量锅炉灰渣有氧燃烧时的氧气消耗量，由燃烧全部可燃碳的总氧气消耗量计算锅炉灰渣可燃碳的含量绝对值，其中所述总氧气消耗量是通过将锅炉灰渣在热重-质谱联用设备中燃烧与热解，由逸出气体质量流量求和值减去失重速率的求和值而获得的。本发明是通过准确测量气体的质量流量，结合失重的动态数据，精准测量可燃碳含量。该测量方法适用于所有锅炉灰渣，且不同种类灰渣的测量结果可以比对。

Description

测量锅炉灰渣可燃碳含量的方法 技术领域
本发明涉及锅炉灰渣可燃碳含量的测量，尤其涉及利用热重与质谱联用准确测量锅炉灰渣中残余可燃碳含量的方法。
背景技术
锅炉灰渣中的可燃碳含量不仅是反映燃烧状况好坏的重要指标，也决定了其在建材方面的应用范围。由于锅炉灰渣是在复杂动态的燃烧过程中形成的，其成分比较复杂。除过可燃碳以外，灰渣通常还包括水分、碳酸盐、硫酸盐及氧化物等，水分主要有颗粒间与颗粒内吸附的水、结晶水(如CaSO 4·2H 2O)、以及可能通过化学反应生成水的潜在水(如Ca(OH) 2)，碳酸盐包括投入炉内且未分解的、二次反应生成的、煤种自身携带的，硫酸盐主要来自脱硫过程。在可燃碳的测量过程中，目前通常采用烧失量(LOI:Loss-On-Ignition)来表征粉煤灰中可燃碳含量的大小，而灰渣中的水分、碳酸盐、硫酸盐的存在，往往造成烧失量与可燃碳含量之间存在非常大的差异。例如，对于流化床锅炉的飞灰，其偏差甚至大于两个数量级，即使对煤粉炉也存在大于40％的测量误差[参考文献1]。造成上述测量误差非常大的原因主要在于现有的测量手段无法分辨烧失过程中不同逸出组分的真实量的分布情况。例如，在煤粉炉飞灰的可燃碳测量中，飞灰内有以Ca(OH) 2形式存在的大量潜在水，其在400-500℃之间分解释放，因此这部分的质量损失往往被计入烧失量，但其并不完全是可燃碳的含量。Robert C.Brown利用热重研究不同飞灰可燃碳含量(以下简称TGA法)，该方法采用两段加热形式，第一段是样品在氮气氛围以固定升温速率升至725℃，根据热天平的失重量测定水分及碳酸盐中二氧化碳逸出量，第二段是在725℃恒温并将氮气切换为空气，此段测定的失重量认为是可燃碳的含量。以上述测量方法得到的可燃碳含量对比传统直接烧失法的数据，可以看到烧失法的误差对煤粉炉灰渣达到75％，对于流化床锅炉的误差超过100％，甚至达到2780％[参考文献1]。
在我国锅炉灰渣可燃碳含量的测量采用电力行业标准DL/L567.6-95， 飞灰和炉渣可燃物测定方法中规定了两种方法，方法一是燃煤锅炉灰渣可燃物的例行监督方法(以下简称DL-A)，该方法为称取一定质量的飞灰或者渣样品，使其在815±10℃下缓慢灰化，根据其减少的质量计算其可燃物含量；方法二应用于锅炉机组性能考核及精确的热力计算(以下简称DL-B)，该方法则需按照GB212空气干燥法测定灰、渣空气干燥基水分和灰分，按照GB/T218测定灰、渣中碳酸盐的二氧化碳含量，总烧失量减去灰、渣中水分和碳酸盐内二氧化碳含量即为灰、渣中可燃物含量。方法一为传统的烧失量法，方法二中的可燃碳含量是利用减法求得，且并不是在同一过程完成测量，测量的误差难以控制。
为了更加清楚地测定循环流化床中灰渣的可燃碳含量，国内的学者也从两方面探索了测量方法。东北电力学院的吕太将烧失法分解成两步，首先利用工业分析中灰分测定，在815℃灼烧样品得到灰渣中挥发分与水分含量，其次通过在960℃灼烧样品，得到灰渣的烧失量，对于循环流化床锅炉飞灰的可燃碳含量用上述的烧失量扣除工业分析中水分及挥发分来计算(以下简称C-LOI法)[参考文献2]。清华大学的王启民通过将热重测量与红外定性分析结合(以下简称TGA-FT法)，该方法是将飞灰样品放入热天平托盘，首先通入惰性气体，从室温开始加热到725℃，保持这一温度至质量恒定，而后通入空气，继续保持这一温度，直至质量恒定；定义循环流化床锅炉飞灰碳含量就是通入空气后样品失重与样品初始质量的比值[参考文献3]。
上述五种灰渣可燃碳含量测量方法的流程与特点比较如表1，各种方法虽然各有特点，但是它们共同的问题是测量过程中各种气体成分的逸出的真实情况并未得到，也未明确灰渣各种成分在不同气氛下相互反应的机理，所测的过程基本依靠推理确认某部分失重为可燃碳的烧失量。
表1灰渣可燃碳含量测量方法的流程与特点对比表
Figure PCTCN2017118572-appb-000001
Figure PCTCN2017118572-appb-000002
发明内容
如上所述，现有的各类测量灰渣可燃碳含量的方法的共同缺点是：反应原理都是建立在主观推理的基础上，没有真实的观察到反应过程。由于各种气体逸出的动态质量流量难以测量，因此造成这种以烧失量表征可燃碳的方法误差极大，其根本原因在于测试原理性的失真。
归纳上述各种测量方法，其工作原理主要是利用样品在不同气体氛围中的升温过程，尽可能的区分出可燃碳的烧失温度区间。其实，不论有氧气氛还是无氧惰性气氛，灰渣自身及其与周围气氛的反应都是非常复杂。即使在惰性气体氛围中加热飞灰样品，其中所含碳酸盐、硫酸盐的失重机理并不能由空气条件下的失重机理推导，因为气氛的改变已经对碳酸盐、硫酸盐的失重机理产生了关键的影响。而在有氧的气氛中，可燃碳的氧化过程往往与碳酸盐的分解过程重叠出现，依靠反应过程的失重难以区分可 燃碳与碳酸盐中二氧化碳的质量，况且二氧化碳的分子量远大于碳，在同等反应失重的情况下，如果将碳酸盐中二氧化碳的失重当作可燃碳，由此所造成的测量误差极大。
图1示出了根据本发明的方法测量的氩气氛围中循环流化床锅炉飞灰热解的一个典型的逸出气体分布图。其显示了循环流化床锅炉脱硫后飞灰在Ar氛围中热解的过程，其中主要的逸出气体H 2O、CO 2、SO 2的质量流量已经给出，可以发现CO 2的逸出遍布400-1000℃，而简单的以部分温度区间的总气体逸出质量推断是或不是某种气体，这种方法非常不科学。
另外，各类锅炉灰渣的成分差异非常大。对于循环流化床锅炉脱硫与否也会影响其灰渣组成，对于不同的灰渣采用不同工作原理的测量方式，往往造成数据结果不可比对，甚至造成很多错误的判断。
总之，锅炉灰渣可燃碳测量的传统方法首要技术缺陷在于测试原理的失真，其试图直接区分并确认“碳”本身，因此可以理解为这些方法更注重“可燃碳”测量中的“碳”，而未从机理上明确解决“可燃碳”中的“可燃”特性，这种性质上的差别直接导致巨大偏差，甚至是错误的判断。其次，现有的各类方法不可能解释测试过程的各类组分的反应机理。再者，对于不同的锅炉、不同运行状况、不同燃料等条件变化，难以形成统一合适的对比。另外，测量条件的变化也会造成很大的误差，难以实施精确测量。最后，对于多步的传统方法，测量过程需要更长的时间。
针对现有技术中存在的问题，本发明提出了一种基本原理与上述现有方法不同的测量方法，基于锅炉灰渣中可燃碳的“可燃”特性，采用有氧燃烧的方式得到氧气的消耗量，由此准确获得可燃碳的含量。
简而言之，本发明提供一种测量锅炉灰渣可燃碳含量的方法，所述方法包括：测量锅炉灰渣有氧燃烧时的氧气消耗量，由燃烧全部可燃碳的总氧气消耗量计算锅炉灰渣可燃碳的含量绝对值，其中所述总氧气消耗量是通过将锅炉灰渣在热重-质谱联用设备中燃烧与热解，由逸出气体质量流量求和值减去失重速率求和值而获得的。
根据一些实施方案，将逸出气体质量流量与失重速率在常温至950℃区间或者常温至1000℃区间或者常温至1250℃区间求和。
根据一些实施方案，逸出气体包括CO 2，以及SO 2、H 2O、O 2中的一 种或多种。
根据一些实施方案，逸出气体k在时间i的质量流量
Figure PCTCN2017118572-appb-000003
由下式计算：
Figure PCTCN2017118572-appb-000004
其中ρ k为逸出气体k常温下的密度，
Figure PCTCN2017118572-appb-000005
为逸出气体k常温下的体积流量。
或者，逸出气体k在时间i的质量流量
Figure PCTCN2017118572-appb-000006
由逸出气体的摩尔流量乘以分子量获得，此方法适合于具有相变特性的物质，如H 2O。
根据一些实施方案，逸出气体k常温下的体积流量根据逸出气体的特征图谱与相对灵敏度，由锅炉灰渣在热重质谱联用设备中燃烧与热解所得的质谱图谱解析而得。
根据一些实施方案，逸出气体的特征图谱与相对灵敏度通过用固定流量的与逸出气体对应的气体，或者固定流量的与逸出气体对应的气体和载气，或用纯化合物和固定量的载气标定所述热重质谱联用设备获得。
根据一些实施方案，利用等效特征图谱法标定逸出气体的特征图谱与相对灵敏度。
根据一些实施方案，等效特征图谱法采用载气作为参比气体。
根据一些实施方案，载气包括惰性气体(例如Ar等)和N 2中的至少一种；和/或，纯化合物包括碳酸盐、硫酸盐、H 2O中的至少一种。
根据一些实施方案，热重-质谱联用设备的标定为离线标定。
本发明通过准确测量气体的质量流量，结合失重的动态数据，精准测量可燃碳含量。该测量方法适用于所有锅炉灰渣，且不同种类灰渣的测量结果可以比对。
附图说明
图1为氩气氛围中循环流化床锅炉飞灰热解的一个典型的逸出气体分布图。
图2为本发明的可燃碳含量测量的原理区分示意图。
图3为根据本发明的锅炉灰渣可燃碳含量测量的一个流程图。
图4为根据本发明实施例1的循环流化床锅炉灰渣可燃碳含量测量的 逸出气体质量流量曲线图。
图5为由图4的质量流量曲线图转换而得的堆积面积图。
图6为根据本发明实施例2的钙基模型化合物的逸出气体质量流量曲线图。
图7为由图6的质量流量曲线图转换而得的堆积面积图。
图8为根据本发明实施例3的煤粉炉灰渣可燃碳含量测量的逸出气体质量流量曲线图。
图9为由图8的质量流量曲线图转换而得的堆积面积图。
图10为根据本发明实施例4的低温灰化后煤样可燃碳含量测量的逸出气体质量流量曲线图。
图11为由图10的质量流量曲线图转换而得的堆积面积图。
具体实施方式
本发明提出了一种基本原理与现有技术不同的测量方法。如图2所示，锅炉灰渣碳含量测量中产生的CO 2包括可燃碳燃烧产生的CO 2，也包括锅炉灰渣中碳酸盐等成分的热分解产生的CO 2。试图直接区分并确认“碳”本身的传统方法更注重“可燃碳”测量中的“碳”，未从机理上明确解决“可燃碳”中的“可燃”特性，这种性质上的差别直接导致巨大偏差，甚至是错误的判断。而本发明对于锅炉灰渣中可燃碳的测量，基于其“可燃”的特性。既然是“可燃碳”，那么它就需要利用氧气来进行氧化反应；而不能进行氧化反应的“碳”，如碳酸盐、难燃碳化物等，都不能将其所含碳列入测量的范畴。对于锅炉灰渣，其本身已经历过燃烧过程，不含挥发分，因此在可燃碳的测量过程中，如果采用有氧燃烧的方式，且能得到氧气的消耗量，那么可燃碳的含量即可准确获得。而对于氧气消耗量的测量，可以采用直接法测量氧气的形式，也可以采用间接的方式测量，本发明采用了更加准确、稳定且可靠的间接方式计算氧的消耗量。
具体地，本发明提供一种测量锅炉灰渣可燃碳含量的方法，所述方法包括：测量锅炉灰渣有氧燃烧时的氧气消耗量，由燃烧全部可燃碳的总氧气消耗量计算锅炉灰渣可燃碳的含量绝对值，其中所述总氧气消耗量是通过将锅炉灰渣在热重-质谱联用设备中燃烧与热解，由逸出气体质量流量求 和值减去失重速率求和值而获得的。
根据本发明，可以在一步升温过程中实现逸出气体质量流量和失重速率的求和。逸出气体质量流量的求和和失重速率的求和在相同的温度区间进行，所述的温度区间至少包括发生可燃碳烧失过程的温度区间。根据一个实施方案，该温度区间可以为从常温升温至1000℃，或者升温至950℃，或者升温至900℃，或者升温至850℃，或者升温至800℃。如还需测量灰渣含硫量，升温可以到达1250℃，或1200℃。温度区间的上限可视具体样品情况而定。
本发明的测量锅炉灰渣可燃碳含量的方法中，逸出气体是指在锅炉灰渣燃烧与热解过程中产生的气体。对于可燃碳含量测量而言，逸出气体至少包括CO 2。逸出气体还可以包括SO 2、H 2O、O 2中的一种或多种。
根据本发明的一些实施方案，逸出气体的质量流量可以由逸出气体常温下的密度乘以该气体常温下的体积流量获得，也可以由逸出气体的摩尔流量乘以分子量获得，第二种方法适合于具有相变特性的气体，如H 2O。逸出气体常温下的体积流量可根据逸出气体的特征图谱与相对灵敏度，由锅炉灰渣在热重质谱联用设备中燃烧与热解所得的质谱图谱解析而得。而逸出气体的特征图谱与相对灵敏度则通过标定热重-质谱联用设备获得。
本发明中，热重-质谱联用设备的标定可以如下进行：向热重-质谱联用设备中注入固定流量的与逸出气体对应的气体和/或载气，测得质谱数据，然后利用等效特征图谱法(Equivalent Characteristic Spectrum Analysis(ECSA),该方法主要是将不同种类气体通过各自的相对特征参数，即特征图谱与相对灵敏度，换算为等效的参比气体，基于特定量的参比气体可得到各类气体的物理参数，故称为等效特征图谱法)[参考文献4]标定相应气体的特征图谱及相对灵敏度(相对于载气)；或者向热重-质谱联用设备中纯化合物并且注入固定量的载气，设备升温后测得热重与质谱数据，然后利用等效特征图谱法(ECSA)标定纯化合物释放的气体(对应灰渣燃烧后的气体产物)的特征图谱及相对灵敏度。
此处，标定使用的载气与实际锅炉灰渣测量时使用的载气相同。作为载气的实例，可以列举惰性气体如氩气(Ar)等，以及不参与且不干扰逸出气体的释放与检测的气体，如氮气(N 2)等。标定使用的纯化合物对应 于锅炉灰渣中所含的组分，例如碳酸盐、硫酸盐、H 2O等。具体的化合物包括碳酸钙、硫酸钙、水等。
标定时相应气体和/或载气的流量可以为5-100ml/min。
本发明的热重-质谱联用设备的标定优选为离线标定，通常可以在某一期间内标定一次。
图3显示了根据本发明的锅炉灰渣可燃碳含量测量的一个流程图。如图3所示，主要测量环节包含：标定、测试、分析三个环节。每个环节的具体实施步骤如下：
1.标定环节
利用热重质谱联用设备的流量计，注入固定稳定流量的气体，如CO 2、O 2及载气等，测得质谱数据。利用等效特征图谱法(ECSA)分别标定与灰渣燃烧后的气体产物(CO 2、O 2)相对应的气体的特征图谱及相对灵敏度；或者利用热重质谱联用设备的天平，放入适当的纯化合物，如CaSO 4、H 2O等，注入固定流量的载气，设备升温后测得热重与质谱数据。利用等效特征图谱法(ECSA)分别标定对应灰渣燃烧后部分气体产物(SO 2、H 2O)的逸出气体的特征图谱及相对灵敏度。
特征图谱的计算公式如式(1)，β j,k为特定气体k的特征图谱，它是一组向量，表示气体在质谱质核比m/z＝j处的丰度，H j为质谱在m/z＝j处测得的混合离子流强度，
Figure PCTCN2017118572-appb-000007
代表气体k的特征离子流强度。
Figure PCTCN2017118572-appb-000008
相对灵敏度的计算公式如式(2)，α r,k为气体k相对于参考气体r(例如，载体)的灵敏度，
Figure PCTCN2017118572-appb-000009
分别代表气体r、k的体积流量。
Figure PCTCN2017118572-appb-000010
2.测试环节
在热重与质谱联用系统中，放入灰渣测试样品，通入固定流量的载气与氧气，通过升温程序将样品燃烧与热解。对于仅测 量可燃碳含量的工作模式，升温可以到达950℃，如还需测量灰渣含硫量，升温应到达1250℃。测得天平的失重数据，质谱质核比(m/z)为2-64的全部扫描图谱H j(即，混合离子流强度H j)。
3.分析环节
a.利用标定环节测得的CO 2、SO 2、H 2O、O 2等气体产物的特征图谱与相对灵敏度，解析测试环节中质谱图谱，得到各种逸出气体常温状态下体积流量。计算公式如式(3)，
Figure PCTCN2017118572-appb-000011
其中A r,k -为气体的相对灵敏度向量，此处大写因为对于实际情况是多种气体，必须使用向量表示，代表一组气体。同样，I r,k +为气体的等效离子流强度，也是向量，代表一组气体的值。根据(3)中所得体积流量，由质谱数据计算出气体k在不同时间i的质量流量
Figure PCTCN2017118572-appb-000012
如公式(4)，其中ρ k为气体k常温下的密度，
Figure PCTCN2017118572-appb-000013
为逸出气体k常温下的体积流量。
Figure PCTCN2017118572-appb-000014
b.对热天平的失重数据进行计算，得到样品在时间i失重速率
Figure PCTCN2017118572-appb-000015
c.对于测量可燃碳含量的计算，将逸出气体质量流量与失重速率在常温至950℃区间求和，逸出气体质量流量求和值减去失重速率的求和值，得到燃烧全部可燃碳的总氧气消耗量
Figure PCTCN2017118572-appb-000016
如公式(5)所示。
Figure PCTCN2017118572-appb-000017
d.通过总氧气消耗量计算出样品可燃碳的含量绝对值m Carbon，如公式(6)，
Figure PCTCN2017118572-appb-000018
其中，Z C、
Figure PCTCN2017118572-appb-000019
分别为碳与氧气的分子量。锅炉灰渣可燃碳含
量的相对值由m Carbon除以样品量可以得到。
相对于传统的锅炉灰渣可燃碳含量测量，本发明至少具有以下优点之 一：
1.真正实现了“可燃”碳含量的测量。由于采用氧气燃烧样品的方式，通过逸出气体与热重数据的对比，间接计算出可燃碳燃烧过程的氧气消耗量，以此测得可燃碳含量，从而合理、客观且准确地反映了可燃碳含量。
2.测量过程清楚地解释并利用各类反应机理。对于燃烧过程中锅炉灰渣测试样品，逸出的是H 2O、CO 2、SO 2、O 2等等，本发明都能给出明确的解释，同时利用这些反应过程，还能进行碳酸盐、硫酸盐、结晶水、化合水、吸附水含量的估算。因此本发明的测量参数可不限于可燃碳含量，更多参数的测量有利于锅炉的参数调节。
3.实现了不同锅炉、不同运行工况、不同燃料等情况下灰渣的可燃碳含量比对。由于本发明的方法基于真正的可燃碳含量测量，不受上述条件的改变而产生机理性误差，因此测试的数据便于统一比较。
4.测量过程误差很小、数据稳定性与可靠性高。对于同一种样品的重复测量，即使改变测试条件，如升温速率、氧气浓度、样品量、载气流量等等，可燃碳含量测量值的重复性很好，相对误差极小，抗干扰能力很强。
5.测量过程一步升温实现，缩短样品测量的时间。本发明的测量方法采用一步升温，可燃碳的烧失过程与碳酸盐、硫酸盐的分解与脱水同步发生，不需要利用不同的升温过程区分碳酸盐、硫酸盐的分解与脱水，减少了单一样品的测试时间。
6.本发明的测量方法可适用于气化过程灰渣的含碳量测量。
实施例
以下提供实施例以帮助理解本发明，但这些实施例不应理解为对本发明范围的限制。
实施例中使用的热重-质谱联用设备为德国耐驰公司的同步热分析仪 (型号为449F3)与四级杆质谱(型号为QMS403C)。
热重-质谱联用设备的标定按照以下程序进行：
选用Ar作为载气，载气流量为60ml//min。以10ml/min流量分别注入CO 2和O 2，在升温速率为10K/min的条件下测量质谱数据。利用等效特征图谱法(ECSA)分别标定气体CO 2、O 2的特征图谱及相对灵敏度。
另外，称取质量5-10mg的CaSO 4、H 2O，放入热重质谱联用设备的天平中。以60ml/min的体积流量注入载气Ar。以10K/min的升温速率进行升温，升温至1250℃，测量热重与质谱数据。利用等效特征图谱法(ECSA)分别标定气体产物SO 2、H 2O的特征图谱及相对灵敏度。
所测得的相对于Ar载气的相对灵敏度如下所示。
气体k O 2 CO 2 SO 2 H 2O Ar
α Ar,k 0.988 1.139 2.501 1.204 1.000
另外，CO 2也可以采用CaCO 3升温热解的方式标定，此时的特征图谱及相对灵敏度与采用气体CO 2时完全一致。
实施例1典型循环流化床锅炉飞灰可燃碳含量测量
由于循环流化床锅炉飞灰中含有较多的硫酸盐与碳酸盐，其中所含可燃碳非常容易与硫酸盐、碳酸盐的热解产物混淆，传统方法难以准确测量可燃碳含量。本实施例选择浙江宁波燃煤电厂循环流化床锅炉飞灰为测试样，测量条件为：Ar与O 2共同组成的气体氛围，Ar流量65ml/min，O 2流量为5ml/min，热重炉体的升温速率为10℃/min，样品量127.4mg。
图4给出了该样品在本测量方法中的气体逸出过程，其中可以看到H 2O、CO 2、SO 2的排放，逸出气体的质量流量依靠质谱数据解析得到，结果非常准确与稳定。其中CO 2的逸出集中在400-700℃，出现两个明显的峰值，H 2O的逸出集中在100-400℃，在400℃的前面还出现较突出的峰值。将图4中逸出气体的质量流量曲线转换为堆积面积图，如图5所示，可清楚地看到失重曲线与气体逸出质量流量在大部分温度情况下吻合很好，在400-700℃出现了偏差，此部分反映出参与反应的氧气量。图5中红色虚线 范围的可以采用公式(5)累积求和，避免了气体的吸附与脱附、质谱数据时间同步问题，确保了分析结果的稳定与可靠。本测试样品经上述分析可以得到飞灰中的可燃碳含量为2.32％，而样品中的碳含量3.72％。
实施例2钙基模型化合物的可燃碳含量测量
选用三种钙基化合物模型飞灰中的主要化合物作为实验样品，证明可燃碳含量为0时的测量准确度，以说明本发明的测量方法的可靠性。所选三种化合物分别为Ca(OH) 2(国药试剂，分析纯)、CaCO 3(国药试剂，优级纯)、CaSO 4·2H 2O(国药试剂，分析纯)，三种试剂含量各50mg，测量条件为：Ar与O 2共同组成的气体氛围，Ar流量65ml/min，O 2流量为5ml/min，热重炉体的升温速率为10℃/min。
图6、7中模型化合物的逸出过程基本上也验证了实施例1中循环流化床锅炉飞灰的气体逸出过程，其中CO 2的逸出集中在600-850℃，这正是CaCO 3分解的温度区间，H 2O的逸出在100-200℃、400-450℃两个温度区间形成突出的峰值，反映了CaSO 4·2H 2O、Ca(OH) 2中水分的释放。由于CaSO 4分解所需温度较高，且时间较长，因此未在图6、7中出现较大释放。
利用本测量方法可以得到H 2O、CO 2的逸出质量分别为22.08mg、23.86mg，根据热重的天平失重可以计算得到H 2O、CO 2的逸出质量分别为21.30mg、23.76mg，相对误差较低，以此数据可以计算得到可燃碳含量为0.21％，可以确认样品中肯定不含可燃碳，同时可以得到样品中碳元素含量为4.31％。
实施例3典型煤粉炉的可燃碳含量测量
选择了湖南燃煤电厂煤粉炉飞灰作为测试样品。测量条件为：Ar与O 2共同组成的气体氛围，Ar流量65ml/min，O 2流量为5ml/min，热重炉体的升温速率为10℃/min，样品量52.4mg。
在煤粉炉飞灰的测量过程中，清楚的看到CO 2的逸出，而H 2O及其它气体的逸出非常少，如图8、9所示。图中CO 2逸出气体的质量曲线与热重天平失重率的曲线在400-800℃之间近似保持稳定比例，说明此处失 重主要是被注入氧气燃烧掉的碳造成。通过数据解析可以得到测试样品的可燃碳含量为7.65％，而样品中碳元素含量的7.84％，两者之差低于0.2％，基本上说明样品中不含有碳酸盐。
实施例4低温灰化煤样的可燃碳含量测量
锅炉中灰渣基本上都经过高温的燃烧过程，为了考察更多煤中杂质对本方法的影响，选择了富含碱金属的新疆准东煤，采用等离子低温灰化的手段对煤样进行灰化，设备为英国Quorum公司的K1056X等离子灰化仪，气体采用纯氧，灰化后样品的杂质含量较低且成分复杂，可燃碳测量的难度非常大。低温灰化后煤样的测量条件为：Ar与O 2共同组成的气体氛围，Ar流量65ml/min，O 2流量为5ml/min，热重炉体的升温速率为10℃/min，样品量14.5mg。
通过图10可以清楚地看到H 2O、CO 2、SO 2的逸出，H 2O的逸出与测量的低温段失重吻合，而SO 2的逸出与高温段失重吻合。在图11中能够更加清晰地发现H 2O在400℃时，存在一个小的逸出峰，说明样品中存在含OH的盐分；而SO 2的逸出从600℃延伸至1200℃，其中出现多个峰值，说明样品内存在不同种类的硫酸盐。通过计算可以得到样品中的可燃碳含量为8.69％，而碳元素含量为12.34％，说明样品中存在部分碳酸盐。
实施例5不同测量条件下的可燃碳含量测量
为了验证测量条件变化对可燃碳含量测量的影响，采用同种锅炉飞灰样品在不同样品量、不同气体注入流量、不同升温速率下进行四组测试，测量结果具有高度的重复性。
测量样品为山东临沂燃煤电厂循环流化床锅炉的飞灰，四种测量条件如表2所示，分别为基准条件、变化样品量、变化升温速率、变化氧气注入量等，后三种测量条件仅在基准条件基础上变动一项。通过表2的内容可以看出，尽管测量条件发生了较大的变化，但是测量结果稳定性较好，充分说明本测试方法不受测试条件的影响。表2中的失重量代表了国标测试方法的结果，通过失重量与可燃碳含量的比较，可以看出传统国标测试方法的误差非常大，其相对误差接近200％；再者将碳元素含量与可燃碳 比较，前者总是大于后者，说明样品中含有易于热分解的碳酸盐，这点可以氧元素含量的分析得到证明。总之，锅炉灰渣中的可燃碳与碳元素、失重量存在本质差别，通过表2的数据可以证明本测试方法可以将这三者按照机理完全区分开，并给出各自的准确定量测试结果。
Figure PCTCN2017118572-appb-000020
利用本发明的方法可以测定各类锅炉灰渣的可燃碳含量，并且适用于不同的测量条件，如不同样品量、气体氛围等。由于本方法的技术特点及解释算法能自行消减误差，抗干扰能力强，因此测量条件可根据设备性能适当调整，并不局限于实施例中所提及的测量条件。
参考文献：
1.Robert C.Brown,Jeff Dykstra.Systematic errors in the use of loss-on-ignition to measure unburned carbon in fly ash,Fuel,1995,74:570-574
2.吕太，张默，毕春丽，等.循环流化床锅炉飞灰含碳的测定方法碳酸，粉煤灰综合利用，2004(1)：17-19
3.王启民，王玉召，吕俊复，等.烧失量法测量循环流化床锅炉飞灰碳的系统误差，热能动力工程，2006(21)：585-589
4.Hongde Xia,Kai Wei.Equivalent characteristic spectrum analysis in TG-MS system,ThermochimicaActa,2015,602:15-21

Claims (10)

  1. 一种测量锅炉灰渣可燃碳含量的方法，包括：测量锅炉灰渣有氧燃烧时的氧气消耗量，由燃烧全部可燃碳的总氧气消耗量计算锅炉灰渣可燃碳的含量绝对值，
    其中所述总氧气消耗量是通过将锅炉灰渣在热重-质谱联用设备中燃烧与热解，由逸出气体质量流量求和值减去失重速率求和值而获得的。
  2. 根据权利要求1所述的方法，其中将逸出气体质量流量与失重速率在常温至950℃区间求和，或者在常温至1000℃区间求和，或者在常温至1250℃区间求和。
  3. 根据权利要求1所述的方法，其中所述逸出气体包括CO 2，以及SO 2、H 2O、O 2中的一种或多种。
  4. 根据权利要求1所述的方法，其中逸出气体k在时间i的质量流量
    Figure PCTCN2017118572-appb-100001
    由下式计算：
    Figure PCTCN2017118572-appb-100002
    其中ρ k为逸出气体k常温下的密度，
    Figure PCTCN2017118572-appb-100003
    为逸出气体k常温下的体积流量，或者
    逸出气体k在时间i的质量流量
    Figure PCTCN2017118572-appb-100004
    由逸出气体的摩尔流量乘以分子量获得。
  5. 根据权利要求4所述的方法，其中所述逸出气体k常温下的体积流量根据逸出气体的特征图谱与相对灵敏度，由锅炉灰渣在热重质谱联用设备中燃烧与热解所得的质谱图谱解析而得。
  6. 根据权利要求5所述的方法，其中所述逸出气体的特征图谱与相对灵敏度通过用固定流量的与逸出气体对应的气体，或者固定流量的与逸出气体对应的气体和载气，或用纯化合物和固定量的载气标定所述热重质谱联用设备获得。
  7. 根据权利要求6所述的方法，其中利用等效特征图谱法标定逸出气体的特征图谱与相对灵敏度。
  8. 根据权利要求7所述的方法，其中等效特征图谱法采用载气作为参比气体。
  9. 根据权利要求6所述的方法，其中所述载气包括惰性气体和氮气中的至少一种，和/或所述纯化合物包括碳酸盐、硫酸盐、H 2O中的至少一种。
  10. 根据权利要求6所述的方法，其中所述标定为离线标定。
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