A method for determining a high furnace gas blending ratio of a coal-fired power plant boiler

Abstract

The application discloses a method for determining a blast furnace gas blending ratio of a coal-fired power plant boiler, which comprises the following steps: firstly, assuming a mass ratio z of the blast furnace gas entering the boiler to the actual burned coal; secondly, performing CO2 balance calculation by using the input coal quality characteristic parameters, the blast furnace gas characteristic data, the fly ash carbon content, the slag carbon content, the existing operation flue gas dry basis oxygen content, the dry basis CO2 volume fraction and the dry basis CO volume fraction; thirdly, obtaining the real mass ratio z of the blast furnace gas entering the boiler to the actual burned coal by iterative calculation of the CO2 balance; and finally, determining the final blast furnace gas blending ratio by combining the unburned combustible material with the supplied fuel mass ratio l u The application can determine the blast furnace gas blending ratio of the coal-fired power plant boiler, so as to meet the thermal state operation requirements of the coal-fired power plant, improve the economic operation level of the unit, and also can strengthen the accurate supervision on the blast furnace gas blending ratio.

Description

Technical fields:

[0001] This invention belongs to the field of coal-fired power generation technology, specifically relating to a method for determining the blending ratio of blast furnace gas in a coal-fired power plant boiler. This method involves performing CO2 balance calculations on the coal-fired boiler, considering the CO2 content in the air, and using existing thermal parameters, coal quality and blast furnace gas characteristic data, as well as the carbon content of fly ash and slag, to obtain the blending ratio of blast furnace gas in the mixed fuel online. Background technology:

[0002] For coal-fired power plants, profit margins are shrinking due to high coal prices, leading to increasingly stringent cost control measures. To reduce costs, more and more coal-fired power plants are engaging in comprehensive resource utilization and blending with lower-grade fuels. Steel mills' self-owned power plants are also facing operational pressure from rising fuel costs. Steel mills generate large amounts of blast furnace gas during production, which many companies directly discharge without utilizing it. However, directly discharging blast furnace gas, which has some thermal value, as waste gas is a waste of resources. Therefore, some steel mills' self-owned power plants are recovering and utilizing this low-grade resource through blast furnace gas blending. The blending ratio of lower-grade fuels is often difficult to determine, affecting the economic operation of the unit. Therefore, accurately determining the blending ratio of lower-grade fuels, including blast furnace gas, is crucial during operation. Summary of the Invention:

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for determining the blending ratio of blast furnace gas in coal-fired power plant boilers, thereby improving the utilization rate of blast furnace gas and enhancing the regulatory effectiveness of blast furnace gas usage.

[0004] The present invention adopts the following technical solution:

[0005] This invention provides a method for determining the blending ratio of blast furnace gas in a coal-fired power plant boiler, comprising the following steps:

[0006] S1. Let z be the mass ratio of blast furnace gas fed into the furnace to the actual mass of coal burned.

[0007] S2. Calculate the theoretical dry flue gas volume V generated per unit mass of coal combustion. God1 Dry flue gas volume V Gd1 ; Calculate the theoretical dry flue gas volume V generated per unit mass of blast furnace gas combustion. God2 Dry flue gas volume V Gd2 ;

[0008] S3. Based on the z-value, calculate the volume of dry flue gas V generated by the combustion of a coal-blast furnace gas mixture per unit mass of coal. Gd (The coal and blast furnace gas mixed fuel corresponding to a unit mass of coal = unit mass of coal + corresponding mass of blast furnace gas calculated according to z);

[0009] S4. Calculate the theoretical CO2 mass generated per unit mass of coal combustion. Compared with actual CO2 mass Calculate the theoretical CO2 mass generated per unit mass of blast furnace gas combustion Compared with actual CO2 mass

[0010] S5. Based on the z-value, calculate the actual CO2 mass generated per unit mass of coal by combustion of the coal and blast furnace gas mixture.

[0011] S6, according to V Gd and Calculate the volume fraction of CO2 in the dry flue gas generated from the combustion of a mixture of coal and blast furnace gas.

[0012] S7. Measure and obtain the actual dry basis CO2 volume fraction in the flue gas. Volume ratio of CO on dry basis y COd ;

[0013] S8, will y COd sum and Compare the two values; if the deviation is too large, reset z until the difference between the two values ​​is reduced to the target value.

[0014] S9. Calculate the mass ratio of unburned combustible material to supplied fuel. u , through l u The value of z is used to calculate the blast furnace gas blending ratio x. gas The ratio of calories to q gas .

[0015] Furthermore, in S2,

[0016] V God1 =0.01(8.893C) ar +20.9724H ar +3.319S ar -2.6424O ar +0.7997N ar );

[0017]

[0018]

[0019]

[0020] Among them, C ar H arO ar N ar and S ar These are the raw coal's carbon content, hydrogen content, oxygen content, nitrogen content, and sulfur content as received; x CO , and These represent the mass fractions of CO, CO2, N2, H2, CH4, O2, and H2S in blast furnace gas, respectively. This refers to the dry basis oxygen content of the exhaust gas.

[0021] Furthermore, in S3, V Gd =V Gd1 +z·V Gd2 .

[0022] Furthermore, in S4,

[0023]

[0024]

[0025]

[0026]

[0027] in, The CO2 content per unit mass of dry air.

[0028] Furthermore, in S5,

[0029] Furthermore, in S6,

[0030] Furthermore, in S8, the z value satisfies:

[0031] Furthermore, in S9,

[0032]

[0033]

[0034]

[0035] Among them, u FA u SL η represents the carbon content of fly ash and slag. FA η SL For fly ash rate and slag rate; A ar and W ar These represent the ash content and total moisture content of the raw coal as received, respectively; ν represents the volatile matter content in the ash as received; Q coal,net,arQ represents the lower calorific value of the coal fed into the furnace, in kJ / kg; gas,net,ar The lower heating value of blast furnace gas is kJ / kg.

[0036] The beneficial effects of this invention are:

[0037] This invention performs CO2 balance calculations on coal-fired boilers, taking into account the CO2 content in the air. It utilizes existing thermal parameters, coal quality and blast furnace gas characteristic data, as well as fly ash carbon content and slag carbon content to obtain the blending ratio of blast furnace gas in mixed fuels online. This ensures accurate and reliable monitoring of the blending ratio of blast furnace gas and improves the safe and economical operation of coal-fired boilers. Attached image description:

[0038] Figure 1 This is an overall flowchart of the present invention;

[0039] Figure 2 This is a flowchart for calculating the blending ratio of blast furnace gas in this invention. Detailed implementation method:

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1

[0042] This invention provides a method for determining the blending ratio of blast furnace gas in a coal-fired power plant boiler, comprising the following steps:

[0043] 1. Let z be the mass ratio of blast furnace gas fed into the furnace to the actual mass of coal burned.

[0044] II. Calculate the theoretical dry flue gas volume V generated per unit mass of coal combustion. God1 Dry flue gas volume V Gd1 ; Calculate the theoretical dry flue gas volume V generated per unit mass of blast furnace gas combustion. God2 Dry flue gas volume V Gd2 Specifically:

[0045] (1) Determine the density ρ of blast furnace gas n :

[0046]

[0047] In the formula, ρ n Density of blast furnace gas, kg / m³ 3;y CO , Volume fractions (%) of each component of blast furnace gas: CO, CO2, N2, H2, CH4, O2, H2O, and H2S; ρ as.g The ash concentration of blast furnace gas is expressed in g / m³. 3 .

[0048] (2) Calculate the mass fraction and calorific value of each component of blast furnace gas:

[0049] CO mass fraction in blast furnace gas, %;

[0050] CO2 mass fraction in blast furnace gas, %;

[0051] N2 mass fraction in blast furnace gas, %;

[0052] H2 mass fraction in blast furnace gas, %;

[0053] CH4 mass fraction in blast furnace gas, %;

[0054] O2 mass fraction in blast furnace gas, %;

[0055] Mass fraction of H2O in blast furnace gas, %;

[0056] H2S mass fraction in blast furnace gas, %;

[0057] Blast furnace gas ash mass fraction, %;

[0058] Q gas,net,ar The lower heating value of blast furnace gas, kJ / kg;

[0059]

[0060] (3) Calculate the theoretical dry flue gas volume generated by the combustion of coal and blast furnace gas:

[0061] Theoretical dry flue gas volume V generated per unit mass of coal combustion God1 Nm 3 / kg:

[0062] V God1 =0.01(8.893C) ar +20.9724H ar +3.319S ar -2.6424O ar +0.7997N ar )

[0063] In the formula, C ar H ar O ar N ar S ar These are the raw coal's carbon content, hydrogen content, oxygen content, nitrogen content, and sulfur content as received, respectively, in percentages.

[0064] Theoretical dry flue gas volume V generated per unit mass of blast furnace gas combustion God2 Nm 3 / kg:

[0065]

[0066] (4) Calculate the volume of dry flue gas generated by the combustion of coal and blast furnace gas:

[0067] V is the volume of dry flue gas generated per unit mass of coal combustion. Gd1 Nm 3 / kg:

[0068]

[0069] V is the volume of dry flue gas generated per unit mass of blast furnace gas combustion. Gd2 Nm 3 / kg:

[0070]

[0071] In the formula, The percentage is the dry basis oxygen content in the flue gas.

[0072] III. Calculate the volume of dry flue gas V generated by the combustion of a coal-blast furnace gas mixture per unit mass of coal, based on the z-value. Gd Nm 3 / kg, specifically:

[0073] V Gd =V Gd1 +z·V Gd2 ;

[0074] In the formula, z is the mass ratio of blast furnace gas fed into the furnace to the actual mass of coal burned, which is dimensionless.

[0075] IV. Calculating the theoretical CO2 mass generated per unit mass of coal combustion Compared with actual CO2 mass Calculate the theoretical CO2 mass generated per unit mass of blast furnace gas combustion Compared with actual CO2 mass Specifically:

[0076] Theoretical CO2 mass produced per unit mass of coal combustion kg / kg:

[0077]

[0078] Theoretical CO2 mass generated per unit mass of blast furnace gas combustion kg / kg:

[0079]

[0080] The actual CO2 mass generated per unit mass of coal combustion kg / kg:

[0081]

[0082] Actual CO2 mass generated per unit mass of blast furnace gas combustion kg / kg:

[0083]

[0084] in, The value is the CO2 content per unit mass of dry air, in kg / kg, and is taken as 0.000505 kg / kg.

[0085] V. Based on the z-value, calculate the theoretical CO2 mass generated per unit mass of coal by combustion of the coal and blast furnace gas mixture. and actual CO2 mass Specifically:

[0086] The theoretical CO2 mass generated per unit mass of coal by combustion of a coal-blast furnace gas mixture kg / kg:

[0087]

[0088] The actual CO2 mass generated per unit mass of coal corresponding to the combustion of the coal and blast furnace gas mixture. kg / kg:

[0089]

[0090] VI. According to V Gd and Calculate the volume fraction of CO2 in the dry flue gas generated from the combustion of a mixture of coal and blast furnace gas. %:

[0091]

[0092] VII. Determine the final mass ratio z of blast furnace gas fed into the furnace to the actual mass of coal burned:

[0093] First, assuming a mass ratio z between the blast furnace gas fed into the furnace and the actual coal burned, calculate the volume fraction of CO2 in the dry flue gas. Then, the dry basis CO2 volume fraction in the flue gas was measured. Volume ratio of CO on dry basis y COd If the difference between the two is too large, a new assumption of z is made until the difference is reduced to the level that satisfies the objective. until.

[0094] 8. Calculate the mass ratio of unburned combustible material to supplied fuel. u , through l u The value of z is used to calculate the blending ratio x of blast furnace gas, which is the z-value set in step seven. gas The ratio of calories to q gas :

[0095] (1) Calculate the mass ratio of unburned combustible material to supplied fuel l u :

[0096]

[0097] In the formula, l u The ratio of unburned combustible material to supplied fuel is dimensionless; u FA u SL Carbon content of fly ash and slag, % η FA η SL For fly ash rate and slag rate, %; A ar and W ar The ash content and total moisture content of raw coal as received, respectively, are %.

[0098] (2) Calculate the mass ratio of blast furnace gas to mixed fuel x gas The ratio of calories to q gas ,%.

[0099]

[0100]

[0101] In the formula, Q coal,net,ar The lower heating value of the coal received for furnace feeding is kJ / kg.

[0102] The calculation results for Example 1 are shown in Appendix Table 1.

[0103] Appendix 1: Example of Calculating the Blending Ratio of Blast Furnace Gas

[0104]

[0105]

[0106]

[0107] This invention discloses a method for determining the blending ratio of blast furnace gas in a coal-fired power plant boiler. The hardware components mainly include a data acquisition module, a calculation module, and an output module. The data acquisition module collects parameters of the coal entering the boiler, blast furnace gas characteristics, fly ash carbon content, slag carbon content, and existing operating flue gas dry-basis oxygen content, dry-basis CO2 volume fraction, and dry-basis CO volume fraction. The calculation module calculates the amount of dry flue gas generated by fuel combustion and the dry-basis CO2 volume fraction generated in the flue gas through CO2 balance calculations, and determines the blast furnace gas blending ratio. The output module outputs the real-time blast furnace gas blending ratio. This invention first assumes a mass ratio z of blast furnace gas fed into the furnace to the actual coal burned. Using input parameters of the coal's quality characteristics, blast furnace gas characteristics, fly ash carbon content, slag carbon content, and existing operating flue gas dry-basis oxygen content, dry-basis CO2 volume fraction, and dry-basis CO volume fraction, a CO2 balance calculation is performed. Through iterative CO2 balance calculations, the actual mass ratio z of blast furnace gas fed into the furnace to the actual coal burned is obtained. This is then combined with the mass ratio l of unburned combustibles to supplied fuel. u This invention determines the final blending ratio of blast furnace gas in coal-fired power plant boilers to meet the hot operation requirements of coal-fired power plants, improve the economic operation level of the units, and strengthen the accurate monitoring of the blending ratio of blast furnace gas.

[0108] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions that fall within the scope of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for determining the blending ratio of blast furnace gas in a coal-fired power plant boiler, characterized in that, Includes the following steps: S1. Let z be the mass ratio of blast furnace gas fed into the furnace to the actual mass of coal burned. S2. Calculate the theoretical dry flue gas volume generated per unit mass of coal combustion. V God1 Dry flue gas volume V Gd1 ; Calculate the theoretical dry flue gas volume generated per unit mass of blast furnace gas combustion V God2 Dry flue gas volume V Gd2 ; S3. Based on the z-value, calculate the volume of dry flue gas generated by the combustion of a coal-blast furnace gas mixture per unit mass of coal. V Gd ; ; S4. Calculate the theoretical CO2 mass generated per unit mass of coal combustion. Compared with actual CO2 mass Calculate the theoretical CO2 mass generated per unit mass of blast furnace gas combustion. Compared with actual CO2 mass ; S5. Based on the z-value, calculate the actual CO2 mass generated per unit mass of coal by combustion of the coal and blast furnace gas mixture. ; S6, according to V Gd and Calculate the volume fraction of CO2 in the dry flue gas generated from the combustion of a mixture of coal and blast furnace gas. ; S7. Measure and obtain the dry basis CO2 volume fraction in the flue gas actually generated by the combustion of coal and blast furnace gas mixture. Volume fraction of CO on dry basis ; S8, will , sum and Compare the two values; if the deviation is too large, reset z until the difference between the two values ​​is reduced to the target value. S9. Calculate the mass ratio of unburned combustible material to supplied fuel. ,pass The value and the z value set in S8 are used to calculate the mass ratio of blast furnace gas co-firing. And the ratio of calories .

2. The method for determining the blending ratio of blast furnace gas in a coal-fired power plant boiler according to claim 1, characterized in that, In S2, ； ； ； in, , , , and These are the carbon content, hydrogen content, oxygen content, nitrogen content, and sulfur content of the raw coal as received; 、 、 、 、 、 and These represent the mass fractions of CO, CO2, N2, H2, CH4, O2, and H2S in blast furnace gas, respectively. This refers to the dry basis oxygen content of the exhaust gas.

3. The method for determining the blending ratio of blast furnace gas in a coal-fired power plant boiler according to claim 1, characterized in that, In S4, ； ； ； in, The value represents the mass of CO2 per unit mass of dry air.

4. The method for determining the blending ratio of blast furnace gas in a coal-fired power plant boiler according to claim 1, characterized in that, In S5, 。 5. The method for determining the blending ratio of blast furnace gas in a coal-fired power plant boiler according to claim 1, characterized in that, In S6, 。 6. The method for determining the blending ratio of blast furnace gas in a coal-fired power plant boiler according to claim 5, characterized in that, In S8, the z value satisfies: 。 7. The method for determining the blending ratio of blast furnace gas in a coal-fired power plant boiler according to claim 1, characterized in that, In S9 ； ； in, , The carbon content of fly ash and slag. , For fly ash rate and slag rate; A ar and W ar These represent the ash content and total moisture content of the raw coal as received, respectively; ν represents the volatile matter content in the ash as received. The lower calorific value of the coal fed into the furnace, It is the lower heating value of blast furnace gas.

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