Method for detecting biomass heat share in fire coal coupled biomass combustion

Abstract

The invention relates to the technical field of steam production through fire coal coupling biomass, in particular to a method for detecting biomass heat share in fire coal coupling biomass combustion, which comprises the following steps of: performing fire coal and biomass combustion experiments in a boiler; measuring the oxygen content and the carbon dioxide content in the tail flue gas of the boiler in the fire coal and biomass combustion experiment, obtaining the carbon dioxide content based on the standard oxygen content according to the measured oxygen content and the carbon dioxide content in the flue gas, and calculating the content of the carbon dioxide based on the standard oxygen content according to the carbon dioxide content based on the standard oxygen content. And calculating to obtain the biomass heat share in fire coal coupled biomass combustion. According to the method, the heat share of the biomass input into the boiler during coupling combustion of the fire coal and the biomass is calculated according to the carbon dioxide content based on the standard oxygen content under the three conditions, and rapid and accurate metering and statistics of the heat share of the biomass in the coupling combustion of the fire coal and the biomass are achieved.

Description

Technical Field

[0001] This invention relates to the field of coal-fired co-firing biomass steam generation technology, and is a method for detecting the heat share of biomass in coal-fired co-firing biomass combustion. Background Technology

[0002] my country's energy structure is characterized by abundant coal, scarce oil, and limited natural gas; therefore, coal is the primary source of primary energy consumption. Biomass, as one of the oldest energy sources used by humankind, currently ranks fourth in total utilization after coal, oil, and natural gas. As a renewable, zero-carbon emission fuel, biomass possesses natural advantages in carbon reduction and substitution. Increasing the proportion of biomass utilization and reducing coal combustion consumption can effectively reduce carbon dioxide emissions. Therefore, co-firing biomass with coal combustion and utilizing existing coal-fired boilers for steam production is an effective way to reduce carbon emissions.

[0003] There are two main approaches to steam production using biomass coupled with coal-fired boilers. ① Direct co-combustion: This refers to the combustion of biomass and coal in the same boiler. This is mainly divided into two categories: using a common fuel preparation / combustion system for both biomass and coal, and setting up a separate biomass processing / combustion system. However, due to the significant differences in biomass fuel characteristics, it is impossible to directly calculate the heat utilized from the biomass mass of the combustion. ② Indirect co-combustion: This involves first gasifying or burning the biomass, and then using the resulting gas or flue gas in the boiler to utilize its heat. The heat calculation for this method primarily uses C14 detection technology.

[0004] Chinese patent document CN115342333A discloses a biomass-coal boiler coupled power generation system and its power generation calculation method. By setting up a separate furnace for burning biomass, the biomass fuel is burned to generate high-temperature flue gas. After dust removal, the clean high-temperature flue gas is metered and analyzed for composition before being sent into the furnace of the coal-fired boiler. It is burned together with pulverized coal in the pulverized coal furnace. By measuring the flow rate, temperature, and composition of the flue gas sent into the pulverized coal furnace, as well as the flue gas temperature at the air preheater outlet, the heat of the biomass sent into the pulverized coal furnace can be calculated in real time. Chinese patent document CN108387569A discloses a method for co-firing biomass power generation with measurable biomass blending. The method involves sampling and analyzing the raw coal and biomass entering the plant to obtain key coal quality data and trace element data. The mixture is then uniformly mixed according to the power plant's required proportions and fed into the boiler via a conveyor belt for combustion. A belt scale and online coal quality monitoring system on the conveyor belt are used to monitor the weight, coal quality data, and trace element data of the raw coal and biomass mixture in real time. These data are then used to calculate the biomass content in the mixture. However, this method remains complex to operate and, due to limitations in detection conditions, cannot accurately measure the heat contribution of biomass during the steam generation process in a co-firing coal-fired boiler. Summary of the Invention

[0005] This invention provides a method for detecting the heat contribution of biomass in coal-fired coupled biomass combustion, overcoming the shortcomings of the prior art. It can effectively solve the problem that in the use of biomass coupled with coal-fired boilers, due to the large differences in biomass fuels, it is impossible to accurately measure the heat contribution of biomass during the steam generation process of biomass coupled with coal-fired boilers.

[0006] The technical solution of this invention is achieved through the following measures: a method for detecting the heat share of biomass in coal-coated biomass combustion, comprising the following steps:

[0007] Step 1: Conduct coal and biomass combustion experiments in a boiler. The coal and biomass combustion experiments include coal-only combustion experiments, biomass-only combustion experiments, and combustion coupled with coal and biomass combustion experiments.

[0008] Step 2: Measure the oxygen and carbon dioxide content in the flue gas at the tail end of the boiler for the coal and biomass combustion experiments.

[0009] Step 3: Based on the measured oxygen and carbon dioxide content in the flue gas, obtain the carbon dioxide content based on the standard oxygen level.

[0010] Step four: Calculate the biomass heat share in coal-coupling biomass combustion based on the carbon dioxide content at standard oxygen levels.

[0011] The following are further optimizations and / or improvements to the above-mentioned technical solution:

[0012] In step two above, the oxygen content in the flue gas at the tail end of the boiler is measured using an oxygen sensor.

[0013] In step two above, the carbon dioxide content in the flue gas at the boiler tail end is measured using an infrared gas analyzer.

[0014] Step three above includes the following steps:

[0015] Based on the oxygen and carbon dioxide content in the flue gas measured in the combustion experiment, the nitrogen content in the combustion experiment flue gas is calculated.

[0016] Based on the oxygen, carbon dioxide, and nitrogen contents measured in the flue gas from coal and biomass combustion experiments, the carbon dioxide content based on standard oxygen levels was calculated for coal combustion only, biomass combustion only, and combustion of a combination of coal and biomass.

[0017] The nitrogen content in the flue gas from the above combustion experiment is the total amount of flue gas after deducting the oxygen and carbon dioxide content.

[0018] The carbon dioxide content based on standard oxygen levels is calculated using the following formula:

[0019]

[0020] Among them, CO 2_corrected CO2 content is based on standard oxygen levels. 2_measured The carbon dioxide content measured in the combustion experiment, CO 2_std The carbon dioxide content under standard conditions, O 2_measured The oxygen content is measured in a combustion experiment, η is the combustion efficiency (i.e., the proportion of fuel converted into heat in actual combustion), and N is the oxygen content. 2_measured The nitrogen content in the flue gas from the combustion experiment, N 2_std This represents the nitrogen content under standard conditions.

[0021] In step four above, the heat share of biomass input into the boiler during the coupled combustion of coal and biomass is calculated using the following formula:

[0022]

[0023] Where R represents the heat share of biomass in coal-coated biomass combustion, and CO... 2-corrected-coupled The CO2 content based on standard oxygen levels when combustion couples coal and biomass. 2_corrected_coal CO is the carbon dioxide content based on standard oxygen levels when only coal is burned. 2_corrected_biomass This represents the carbon dioxide content based on standard oxygen levels when only biomass is burned.

[0024] This invention achieves rapid and accurate measurement and statistical analysis of the biomass heat share in coal-biomass coupled combustion by measuring the oxygen and carbon dioxide content in the flue gas at the boiler tail end under three conditions: burning only coal, burning only biomass, and co-firing coal and biomass. Based on the carbon dioxide content with standard oxygen levels under these three conditions, the heat share of biomass input into the boiler during coal-biomass coupled combustion is calculated. Attached Figure Description

[0025] Appendix Figure 1 This is a flowchart of Embodiment 8 of the present invention. Detailed Implementation

[0026] The present invention is not limited to the following embodiments, and the specific implementation can be determined according to the technical solution of the present invention and the actual situation.

[0027] The present invention will be further described below with reference to embodiments:

[0028] Example 1: The method for detecting the biomass heat share in coal-coated biomass combustion includes the following steps:

[0029] Step 1: Conduct coal and biomass combustion experiments in a boiler. The coal and biomass combustion experiments include coal-only combustion experiments, biomass-only combustion experiments, and combustion coupled with coal and biomass combustion experiments.

[0030] Step 2: Measure the oxygen and carbon dioxide content in the flue gas at the tail end of the boiler for the coal and biomass combustion experiments.

[0031] Step 3: Based on the measured oxygen and carbon dioxide content in the flue gas, obtain the carbon dioxide content based on the standard oxygen level.

[0032] Step four: Calculate the biomass heat share in coal-coupling biomass combustion based on the carbon dioxide content at standard oxygen levels.

[0033] Example 2: As an optimization of the above example, in step two, the oxygen content in the flue gas at the tail end of the boiler is measured using an oxygen sensor.

[0034] Example 3: As an optimization of the above example, in step two, the carbon dioxide content in the flue gas at the tail end of the boiler is measured using an infrared gas analyzer.

[0035] Example 4: As an optimization of the above embodiment, step three includes the following steps:

[0036] Based on the oxygen and carbon dioxide content in the flue gas measured in the combustion experiment, the nitrogen content in the combustion experiment flue gas is calculated.

[0037] Based on the oxygen, carbon dioxide, and nitrogen contents measured in the flue gas from coal and biomass combustion experiments, the carbon dioxide content based on standard oxygen levels was calculated for coal combustion only, biomass combustion only, and combustion of a combination of coal and biomass.

[0038] Example 5: As an optimization of the above example, the nitrogen content in the combustion test flue gas is the total amount of combustion test flue gas minus the oxygen and carbon dioxide content in the flue gas, that is, nitrogen content = 100% - oxygen content - carbon dioxide content.

[0039] Example 6: As an optimization of the above examples, the carbon dioxide content based on standard oxygen levels is calculated using the following formula:

[0040]

[0041] Among them, CO 2_corrected CO2 content is based on standard oxygen levels. 2_measured The carbon dioxide content measured in the combustion experiment, CO 2_std The carbon dioxide content under standard conditions, O 2_measuredThe oxygen content is measured in a combustion experiment, η is the combustion efficiency (i.e., the proportion of fuel converted into heat in actual combustion), and N is the oxygen content. 2_measured The nitrogen content in the flue gas from the combustion experiment, N 2_std This represents the nitrogen content under standard conditions.

[0042] Based on the data obtained from experiments involving only coal combustion, only biomass combustion, and combined coal and biomass combustion, the carbon dioxide content (CO2) based on standard oxygen levels during coal combustion can be calculated using Equation 1 above. 2_corrected_coal ), the carbon dioxide content based on standard oxygen levels when burning biomass alone (CO2). 2_corrected_biomass The carbon dioxide content based on standard oxygen content when combustion is coupled with coal and biomass combustion. 2-corrected-coupled ).

[0043] In Equation 1, 20.9 and 3.76 are derived from the concentrations of oxygen and carbon dioxide in the air under standard conditions (i.e., 25°C and standard atmospheric pressure). 20.9 is the volume fraction of oxygen in the air under standard conditions, and 3.76 is the molar ratio of carbon dioxide to oxygen in the air under standard conditions. These two parameters are used to calculate a correction factor to adjust for the carbon dioxide content produced during actual combustion, ensuring it matches the value under standard conditions. In the formula, 20.9 and 3.76 are used in the denominator of the correction factor to account for the influence of oxygen content on carbon dioxide content. During the calculation, the values ​​of these two parameters are fixed and do not require measurement or estimation.

[0044] Example 7: As an optimization of the above embodiment, in step four, the heat share of biomass input into the boiler during the coupled combustion of coal and biomass is calculated by the following formula:

[0045]

[0046] Where R represents the heat share of biomass in coal-coated biomass combustion, and CO... 2-corrected-coupled The CO2 content based on standard oxygen levels when combustion couples coal and biomass. 2_corrected_coal CO is the carbon dioxide content based on standard oxygen levels when only coal is burned. 2_corrected_biomass This represents the carbon dioxide content based on standard oxygen levels when only biomass is burned.

[0047] For biomass-co-fired boilers with direct co-firing, the significant differences in biomass fuels make them susceptible to interference from factors such as detection technology and experimental conditions. Therefore, it is not possible to directly distinguish the heat contribution of biomass during the steam production process. This invention addresses this issue by separately detecting the oxygen and carbon dioxide content in the boiler flue gas when only coal is burned, only biomass is burned, and when both coal and biomass are burned in a combined manner. Using a formula, the proportion of biomass heat input into the boiler during the coal-co-fired biomass combustion process is calculated, enabling the measurement and statistical analysis of biomass heat during steam production in biomass-co-fired boilers with direct co-firing.

[0048] Example 8: The specific process of this method for detecting the biomass heat share in coal-coated biomass combustion is as follows:

[0049] Step one involves conducting combustion experiments in the boiler under three conditions: combustion of coal only, combustion of biomass only, and combustion coupled with both coal and biomass.

[0050] Combustion experiments under three scenarios—coal combustion only, biomass combustion only, and a combination of coal and biomass combustion—not only provide the data needed to determine the heat share of biomass in coal-biomass coupled combustion, but also offer the following advantages: 1) By conducting separate combustion experiments, the combustion characteristics and performance of coal and biomass in the boiler can be evaluated, including combustion stability, combustion rate, combustion temperature, and ash characteristics. This helps determine the suitability and combustion effect of different fuels in the boiler, providing a basis for optimizing the combustion process. 2) By analyzing the flue gas produced by different fuel combustion, the combustion characteristics and emission composition of different fuels can be understood, including carbon dioxide, nitrogen oxides, and sulfides. This helps assess the environmental impact of different fuels, providing a reference for reducing pollutant emissions. 3) Through experimental measurement and analysis, the energy conversion efficiency of different fuels can be calculated, i.e., the efficiency of converting input fuel energy into steam or hot water produced by the boiler. This helps compare the energy utilization efficiency of different fuels, providing a basis for selecting the optimal fuel and optimizing energy utilization. 4) By analyzing the experimental results, combustion parameters and control strategies can be optimized to achieve the best combustion effect and energy utilization efficiency. This helps improve boiler performance, reduce energy consumption, and decrease environmental pollution. Therefore, conducting combustion experiments under three conditions—burning only coal, burning only biomass, and a combination of burning both coal and biomass—helps to understand the characteristics of different fuels and optimize the combustion process to achieve efficient and environmentally friendly energy utilization.

[0051] Step two: Measure the oxygen and carbon dioxide content in the flue gas from the boiler tail section of the coal and biomass combustion experiments. The specific operation is as follows:

[0052] Instrument calibration and standardization: Before conducting combustion experiments, the gas analysis instruments are rigorously calibrated and standardized to ensure the accuracy and stability of the measurement results.

[0053] When conducting combustion experiments, control experimental conditions such as temperature, pressure, and combustion process stability to reduce the impact of the experimental environment on the measurements.

[0054] Infrared gas analyzers are used to measure the carbon dioxide content in the flue gas at the tail end of boilers. Infrared gas analyzers can accurately and quickly measure the carbon dioxide content in flue gas, avoiding the measurement errors and interference that may exist in traditional methods.

[0055] Oxygen sensors are used to measure the oxygen content in the flue gas at the tail end of the boiler. The oxygen sensor can measure the oxygen content in the flue gas in real time and accurately, avoiding the estimation and calculation of oxygen content in traditional methods and improving the accuracy of the measurement.

[0056] The measurement results in this embodiment are as follows:

[0057] In the flue gas from the tail section of the experimental coal-fired boiler: O 2-measured =5%, CO 2-measured =12%.

[0058] In the flue gas from the tail section of the biomass-burning experimental boiler only: O 2-measured =3%, CO 2-measured =20%.

[0059] In the tail flue gas of the experimental boiler combining coal and biomass combustion: O 2-measured =4%, CO 2-measured =15%.

[0060] By using gas analysis instruments and rigorous calibration procedures, the accuracy of measuring oxygen and carbon dioxide content in flue gas can be improved, thereby increasing the accuracy of measuring the biomass heat share in coal-co-biomass combustion.

[0061] Step 3: Based on the measured oxygen and carbon dioxide content in the flue gas, obtain the carbon dioxide content based on the standard oxygen level. The specific operation is as follows:

[0062] The nitrogen content in the flue gas was calculated based on the oxygen and carbon dioxide content. The calculated nitrogen content in the flue gas from the coal-fired experimental boiler was 83%, while that from the biomass-fired experimental boiler was 77%. The nitrogen content in the flue gas from the combined coal-fired and biomass-fired experimental boiler was 81%.

[0063] Based on the oxygen, carbon dioxide, and nitrogen contents measured in the flue gas from coal and biomass combustion experiments, the carbon dioxide content (CO2) based on standard oxygen levels for coal combustion alone was calculated using the formula. 2_corrected_coal ), the carbon dioxide content based on standard oxygen levels when burning biomass alone (CO2). 2_corrected_biomass The carbon dioxide content based on standard oxygen content when combustion is coupled with coal and biomass combustion. 2-corrected-coupled ).

[0064] In this embodiment, the combustion efficiency η = 0.85, and the nitrogen content N under standard conditions is... 2_std =79%, carbon dioxide content under standard conditions (CO) 2_std It is 0.04%.

[0065] For the three combustion experiments, the carbon dioxide content, corrected for standard oxygen content and calculated according to Equation 1, is as follows:

[0066] When only coal is burned: CO 2_corrected_coal =12%*(20.9+3.76*(12%-0.04%) / (20.9-5%))*(1+(1-0.85)*(1-(83% / 79%))).

[0067] When only biomass is burned: CO 2_corrected_biomass =20%*(20.9+3.76*(20%-0.04%) / (20.9-3%))*(1+(1-0.85)*(1-(77% / 79%))).

[0068] When combustion is coupled with coal and biomass: CO 2-corrected-coupled =15%*(20.9+3.76*(15%-0.04%) / (20.9-4%))*(1+(1-0.85)*(1-(81% / 79%))).

[0069] Step four, calculate the carbon dioxide content (CO) based on standard oxygen levels when only coal is burned. 2_corrected_coal ), the carbon dioxide content based on standard oxygen levels when burning biomass alone (CO2). 2_corrected_biomass The carbon dioxide content based on standard oxygen content when combustion is coupled with coal and biomass combustion. 2-corrected-coupled Substituting into Equation 2, we obtain the biomass heat share in coal-coupling biomass combustion: R = (-0.091389 + 0.146186) / (0.121905 + 0.146186), R = 0.204, which is 20.4% in percentage terms.

[0070] In summary, the method for detecting the biomass heat share in coal-fired coupled biomass combustion of the present invention measures and statistically analyzes the oxygen and carbon dioxide content in the flue gas at the boiler tail end when only coal is burned, only biomass is burned, and when both coal and biomass are burned in a coupled manner. This method is unaffected by factors such as detection technology and experimental conditions, and can accurately obtain the biomass heat share in coal-fired coupled biomass combustion.

[0071] The above technical features constitute the preferred embodiment of the present invention, which has strong adaptability and optimal implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the requirements of different situations.

Claims

1. A method for detecting the heat share of biomass in coal-biomass co-combustion, characterized in that The method comprises the following steps: Step one, performing coal and biomass combustion experiments in a boiler, wherein the coal and biomass combustion experiments comprise a coal-only combustion experiment, a biomass-only combustion experiment, and a combustion experiment coupling coal and biomass; Step two, measuring oxygen content and carbon dioxide content in boiler tail flue gas of the coal and biomass combustion experiments; Step three, obtaining standard oxygen-based carbon dioxide content according to the measured oxygen content and carbon dioxide content in the flue gas; Step four, calculating the biomass heat share in the coal and biomass coupling combustion according to the standard oxygen-based carbon dioxide content.

2. The method of claim 1, wherein the method is used to detect the heat contribution of the biomass in a coal-biomass co-combustion process. In step two, the oxygen content in the boiler tail flue gas is measured by an oxygen sensor.

3. The method of detecting the heat contribution of biomass in a coal-biomass co- combustion according to claim 1 or 2, characterized in that In step two, the carbon dioxide content in the boiler tail flue gas is measured by an infrared gas analyzer.

4. The method of determining the heat contribution of biomass in a coal-biomass co- combustion according to claim 1 or 2 or 3, characterized in that Step three comprises the following steps: According to the measured oxygen content and carbon dioxide content in the flue gas of the combustion experiment, the nitrogen content in the flue gas of the combustion experiment is calculated; According to the measured oxygen content, carbon dioxide content, and nitrogen content in the flue gas of the coal and biomass combustion experiment, the standard oxygen-based carbon dioxide content of the coal-only combustion, the biomass-only combustion, and the combustion coupling coal and biomass is respectively calculated.

5. The method of claim 4, wherein the method is used to detect the heat contribution of biomass in a coal-biomass co-combustion system. The nitrogen content in the flue gas of the combustion experiment is the part of the total amount of the flue gas of the combustion experiment after deducting the oxygen content and the carbon dioxide content in the flue gas.

6. The method of detecting the heat contribution of biomass in a coal-biomass co- combustion according to claim 4 or 5, characterized in that The standard oxygen-based carbon dioxide content is calculated by the following formula: where CO 2_corrected is the carbon dioxide content based on the standard oxygen amount, CO 2_measured is the carbon dioxide content measured in the combustion experiment, CO 2_std is the carbon dioxide content under standard conditions, O 2_measured is the oxygen content measured in the combustion experiment, η is the combustion efficiency, N 2_measured is the nitrogen content in the flue gas of the combustion experiment, N 2_std is the nitrogen content under standard conditions.

7. The method of determining the heat contribution of biomass in a coal-biomass co- combustion according to any one of claims 1 to 6, characterized in that In step four, the heat share of the biomass input into the boiler in the coal and biomass coupling combustion is calculated by the following formula: where R is the share of biomass heat in the combustion of coal coupled with biomass, CO 2-corrected-coupled is the carbon dioxide content on the basis of standard oxygen quantity when combusting coal coupled with biomass, CO 2_corrected_coal is the carbon dioxide content on the basis of standard oxygen quantity when combusting coal only, CO 2_corrected_biomass is the carbon dioxide content on the basis of standard oxygen quantity when combusting biomass only.

Images