Combustion optimization method and system for coal-fired boiler coupled with biomass gas

Abstract

The invention discloses a combustion optimization method and system for a coal-fired boiler coupled with biomass gas. The combustion optimization system comprises a coal quantity calculation unit, a biomass gas quantity calculation unit, a primary air quantity calculation unit, a secondary air quantity calculation unit, a reburning air quantity calculation unit, a burnout air quantity calculation unit, a coal quantity adjustment unit, a primary air quantity adjustment unit and a secondary air quantity adjustment unit. And a reburning air volume adjusting unit and a burnout air volume adjusting unit. Under the full load of the coal-fired boiler, by adjusting the coal amount, the biomass gas amount, the primary air amount, the secondary air amount, the re-combustion air amount and the after-combustion air amount, the coal amount can be reduced, the biomass gas using amount can be increased, and meanwhile the NOX content of flue gas at an outlet of a hearth can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of power station boilers, and in particular relates to a combustion optimization method and system for a coal-fired boiler coupled with biomass gas. Background Art

[0002] As a renewable, zero-carbon fuel, biomass has unique advantages in carbon reduction. How to significantly reduce carbon emissions by utilizing the high efficiency and environmental protection advantages of existing large-scale coal-fired units through biomass-coupled power generation is currently a hot topic.

[0003] With the development of biomass gasification technology, pulverized coal coupled with biomass gas power generation technology has gradually been applied. As a zero-carbon energy source, the effective and reasonable use of biomass gas can reduce the amount of coal burned by coal-fired boilers, thereby reducing carbon emissions. At the same time, biomass gas is a mixed gas with reducing properties, which has a great impact on NO at the outlet of the coal-fired boiler furnace. X Emissions have a certain inhibitory effect. Summary of the invention

[0004] In view of this, the present invention provides a combustion optimization method and system for a coal-fired boiler coupled with biomass gas, which takes a tangentially fired boiler as the research object, and reduces the amount of coal as much as possible, increases the amount of biomass gas used, and reduces the NO of the flue gas at the furnace outlet while ensuring the stable operation of the coal-fired boiler. X content.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for optimizing combustion of a coal-fired boiler coupled with biomass gas, comprising:

[0006] The coal of the tangentially fired boiler is injected into the furnace in layers for combustion;

[0007] According to the target biomass gas blending ratio, the target biomass gas blending amount and the target coal amount of each burner layer in operation are calculated;

[0008] Control the coal feeding amount of each operating coal feeder to keep the coal amount of each operating burner layer the same;

[0009] According to the coal quantity and air-coal ratio curve of each operating burner layer, calculate the target primary air volume of each operating burner layer;

[0010] Calculate the target secondary air volume of each burner layer in operation according to the target excess air coefficient of the main combustion zone;

[0011] Control the primary air volume regulating damper and the secondary air volume regulating damper of each operating burner layer so that the primary air volume and the secondary air volume of each operating burner layer reach the target primary air volume and the secondary air volume respectively;

[0012] Calculate the target reburning air volume based on the coal volume, biomass gas blending volume and target reburning zone excess air coefficient;

[0013] Control the reburning air volume and adjust the damper to make the reburning air volume reach the target reburning air volume;

[0014] Calculate the target burnout air volume based on the amount of coal, the amount of biomass gas blended combustion, and the excess air coefficient of the target burnout zone;

[0015] Control the burnout air volume and adjust the damper to make the burnout air volume reach the target burnout air volume.

[0016] Furthermore, the target biomass gas blending amount C s The calculation formula is: C s =C r ×α; where C r is the total fuel quantity of coal-fired boiler, t / h; α is the target biomass gas blending ratio.

[0017] Furthermore, the target coal quantity C of the nth burner layer is mn The calculation formula is: C mn =C r ×(1-α) / n.

[0018] Furthermore, the target secondary air volume F of the nth burner layer is en The calculation formula is: en =C mn ×T m ×β-F yn ; Among them, T m is the theoretical air volume of coal, t / t; β is the target main combustion zone excess air coefficient, F yn The primary air volume of the nth operating burner layer, t / h.

[0019] Furthermore, the target reburning air volume F z The calculation formula is: z =(C m ×T m +C s ×T s )×γ-F y -F e Among them, C m is the total coal quantity of coal-fired boiler, t / h; F y is the total primary air volume of the coal-fired boiler, t / h; F e is the total secondary air volume of coal-fired boiler, t / h; T s is the theoretical air volume of biomass gas, t / t; γ is the excess air coefficient in the target reburning zone.

[0020] Furthermore, the target burnout air volume F r The calculation formula is: r =(C m ×Tm +C s ×T s )×θ-F y -F e -F z ; Wherein, θ is the excess air coefficient in the target burnout zone.

[0021] The present invention also provides another technical solution: a biomass gas-coupled coal-fired boiler combustion optimization system, which includes a coal quantity calculation unit, a biomass gas quantity calculation unit, a primary air quantity calculation unit, a secondary air quantity calculation unit, a reburn air quantity calculation unit, a burnout air quantity calculation unit, a coal quantity adjustment unit, a primary air quantity adjustment unit, a secondary air quantity adjustment unit, a reburn air quantity adjustment unit, and a burnout air quantity adjustment unit;

[0022] The coal quantity calculation unit calculates the target coal quantity of each operating burner layer according to the target biomass gas blending ratio;

[0023] The biomass gas amount calculation unit calculates the target biomass gas blending amount according to the target biomass gas blending ratio;

[0024] The primary air volume calculation unit calculates the target primary air volume of each operating burner layer according to the coal volume of each operating burner layer and the air-coal ratio curve;

[0025] The secondary air volume calculation unit is used to calculate the target secondary air volume of each operating burner layer according to the target excess air coefficient of the main combustion zone;

[0026] The reburning air volume calculation unit calculates the target reburning air volume according to the coal volume, the biomass gas blending volume and the target reburning zone excess air coefficient;

[0027] The burnout air volume calculation unit calculates the target burnout air volume according to the coal volume, the biomass gas blending volume and the target burnout zone excess air coefficient;

[0028] The coal quantity regulating unit controls the coal quantity of each operating coal feeder to keep the coal quantity of each operating burner layer the same;

[0029] The primary air volume regulating unit controls the primary air volume regulating damper of each operating burner layer so that the primary air volume of each operating burner layer reaches the target primary air volume;

[0030] The secondary air volume regulating unit controls the secondary air volume regulating damper of each operating burner layer so that the secondary air volume of each operating burner layer reaches the target secondary air volume;

[0031] The reburning air volume regulating unit controls the reburning air volume regulating damper to make the reburning air volume reach the target reburning air volume.

[0032] The burnout air volume regulating unit controls the burnout air volume regulating damper to make the burnout air volume reach the target burnout air volume.

[0033] Compared with the prior art, the present invention can reduce the amount of coal, increase the amount of biomass gas, and reduce the NO in the flue gas at the furnace outlet by adjusting the amount of coal, biomass gas, primary air, secondary air, reburning air, and burnout air under full load of the coal-fired boiler while ensuring the stable operation of the coal-fired boiler. X content. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flow chart of a method for optimizing combustion of a coal-fired boiler coupled with biomass gas according to the present invention;

[0035] Figure 2 This is a schematic diagram of a combustion optimization system for a coal-fired boiler coupled with biomass gas according to the present invention;

[0036] Figure 3 This is a schematic diagram of the air staging and fuel staging principles of a coal-fired boiler coupled with biomass gas in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0037] The following will further describe the specific implementation of the present invention in combination with the accompanying drawings of the embodiments of the present invention, so that the technical solution of the present invention is easier to understand and grasp. It should be understood that the specific embodiments described here are only used to explain part of the embodiments of the invention, rather than all the embodiments. Other embodiments obtained by ordinary technicians in this field without making creative work are all within the scope of protection of the present invention.

[0038] Example 1

[0039] This embodiment provides a combustion optimization method for a coal-fired boiler coupled with biomass gas. A common tangentially fired boiler is used as a research object. Under full load of the coal-fired boiler, the amount of coal, the amount of biomass gas, the primary air volume, the secondary air volume, the reburning air volume and the burnout air volume are adjusted to reduce the amount of coal as much as possible, increase the amount of biomass gas used, and reduce the NO in the flue gas at the furnace outlet while ensuring the stable operation of the coal-fired boiler. X content.

[0040] Attached Figure 1 This is a flow chart of a method for optimizing combustion of a coal-fired boiler coupled with biomass gas in this embodiment. The specific steps of the method are:

[0041] Step 1, injecting coal from a tangentially fired boiler into a furnace in layers for combustion;

[0042] Step 2, according to the target biomass gas blending ratio, calculate the target biomass gas blending amount and the target coal amount of each operating burner layer;

[0043] Step 3, controlling the coal feeding amount of each operating coal feeder to keep the coal amount of each operating burner layer the same;

[0044] Step 4, calculating the target primary air volume of each operating burner layer according to the coal volume of each operating burner layer and the air-coal ratio curve;

[0045] Step 5, calculating the target secondary air volume of each operating burner layer according to the target excess air coefficient of the main combustion zone;

[0046] Step 6, controlling the primary air volume regulating damper and the secondary air volume regulating damper of each operating burner layer so that the primary air volume and the secondary air volume of each operating burner layer reach the target primary air volume and the secondary air volume respectively;

[0047] Step 7, calculating the target reburning air volume according to the coal volume, biomass gas blending volume and target reburning zone excess air coefficient;

[0048] Step 8, controlling the reburning air volume regulating damper so that the reburning air volume reaches the target reburning air volume;

[0049] Step 9, calculating the target burnout air volume according to the amount of coal, the amount of biomass gas blended combustion and the excess air coefficient of the target burnout zone;

[0050] Step 10, controlling the burnout air volume regulating damper so that the burnout air volume reaches the target burnout air volume.

[0051] After the above steps are taken, if the flue gas temperature in the main combustion zone drops too much, it means that the amount of biomass gas blended is too large, and it can be adjusted by reducing the amount of biomass gas blended.

[0052] If the CO volume fraction of the flue gas at the furnace outlet rises too much, it means that the excess air coefficient of the main combustion zone and the reburning zone is too low, and it can be adjusted by increasing the excess air coefficient of the main combustion zone and the reburning zone.

[0053] If the furnace outlet flue gas NO X If the volume fraction increases too much, it means that the excess air coefficient of the main combustion zone and the reburning zone is too high, which can be adjusted by reducing the excess air coefficient of the main combustion zone and the reburning zone.

[0054] The calculation formulas involved in the above steps are as follows:

[0055] Target biomass gas blending amount C s The calculation formula is: C s =C r ×α; where C r is the total fuel quantity of coal-fired boiler, t / h; α is the target biomass gas blending ratio.

[0056] The target coal quantity C of the nth layer of burners in operation mn The calculation formula is: C mn =Cr ×(1-α) / n.

[0057] The target secondary air volume F of the burner layer in operation on the nth layer en The calculation formula is: en =C mn ×T m ×β-F yn ; Among them, T m is the theoretical air volume of coal, t / t; β is the target main combustion zone excess air coefficient, F yn The primary air volume of the nth operating burner layer, t / h.

[0058] Target reburning air volume F z The calculation formula is: z =(C m ×T m +C s ×T s )×γ-F y -F e Among them, C m is the total coal quantity of coal-fired boiler, t / h; F y is the total primary air volume of the coal-fired boiler, t / h; F e is the total secondary air volume of coal-fired boiler, t / h; T s is the theoretical air volume of biomass gas, t / t; γ is the excess air coefficient in the target reburning zone.

[0059] Target reburning air volume F r The calculation formula is: r =(C m ×T m +C s ×T s )×θ-F y -F e -F z ; Wherein, θ is the excess air coefficient in the target burnout zone.

[0060] The principles of air staging and fuel staging in coal-fired boilers coupled with biomass gas are as follows Figure 3 shown.

[0061] Application Examples

[0062] Taking the operation of a supercritical 600MW four-corner tangential combustion boiler as an example, the primary and secondary air of the boiler are arranged at intervals, with a total of 13 layers, including 6 layers of primary air nozzles and 7 layers of secondary air nozzles. Two layers of burnout air nozzles are arranged 6m above the uppermost secondary air nozzles in the main combustion zone. According to the principle of fuel grading, a biomass gas reburning zone is set between the main combustion zone and the burnout zone of the furnace, and one layer of biomass gas nozzles and one layer of reburning air nozzles are arranged. A combustion optimization method for a coal-fired boiler coupled with biomass gas of the present invention is adopted. Taking full load as an example, the boiler is mixed with pine wood gas, and the calorific value mixing ratio is 10%. Its total coal volume, pine wood gas volume, primary air volume, secondary air volume, reburning air volume and burnout air volume are shown in Table 1.

[0063] Table 1 Full load operation status of the coal-fired boiler of the present invention

[0064]

[0065] In order to ensure stable combustion of pulverized coal in the main combustion zone, the flue gas temperature in the main combustion zone should not be too low and should be maintained at at least 900°C. The total coal amount in Table 1 should not be too low. If the flue gas temperature in the main combustion zone is insufficient, the amount of biomass gas blended is too large and can be adjusted by reducing the amount of biomass gas blended.

[0066] If the CO volume fraction of the flue gas at the furnace outlet rises too much, it means that the excess air coefficients of the main combustion zone and the reburning zone in Table 1 are too low, and can be adjusted by increasing the excess air coefficients of the main combustion zone and the reburning zone.

[0067] If the furnace outlet flue gas NO X The excessive increase in volume fraction indicates that the excess air coefficients in the main combustion zone and the reburning zone in Table 1 are too high, and can be adjusted by reducing the excess air coefficients in the main combustion zone and the reburning zone.

[0068] Example 2

[0069] Please refer to the attached Figure 2 , which is a schematic diagram of a combustion optimization system of a coal-fired boiler coupled with biomass gas of the present invention. A combustion optimization system of a coal-fired boiler coupled with biomass gas of the present invention takes a tangential combustion boiler of a power station as a research object, and the system comprises a coal quantity calculation unit, a biomass gas quantity calculation unit, a primary air quantity calculation unit, a secondary air quantity calculation unit, a reburn air quantity calculation unit, a burnout air quantity calculation unit, a coal quantity adjustment unit, a primary air quantity adjustment unit, a secondary air quantity adjustment unit, a reburn air quantity adjustment unit and a burnout air quantity adjustment unit.

[0070] The coal quantity calculation unit calculates the target coal quantity of each operating burner layer according to the target biomass gas blending ratio;

[0071] The biomass gas amount calculation unit calculates the target biomass gas blending amount according to the target biomass gas blending ratio;

[0072] The primary air volume calculation unit calculates the target primary air volume of each operating burner layer according to the coal volume of each operating burner layer and the air-coal ratio curve;

[0073] The secondary air volume calculation unit is used to calculate the target secondary air volume of each operating burner layer according to the target excess air coefficient of the main combustion zone;

[0074] The reburning air volume calculation unit calculates the target reburning air volume according to the coal volume, the biomass gas blending volume and the target reburning zone excess air coefficient;

[0075] The burnout air volume calculation unit calculates the target burnout air volume according to the coal volume, the biomass gas blending volume and the target burnout zone excess air coefficient;

[0076] The coal quantity regulating unit controls the coal quantity of each operating coal feeder to keep the coal quantity of each operating burner layer the same;

[0077] The primary air volume regulating unit controls the primary air volume regulating damper of each operating burner layer so that the primary air volume of each operating burner layer reaches the target primary air volume;

[0078] The secondary air volume regulating unit controls the secondary air volume regulating damper of each operating burner layer so that the secondary air volume of each operating burner layer reaches the target secondary air volume;

[0079] The reburning air volume regulating unit controls the reburning air volume regulating damper to make the reburning air volume reach the target reburning air volume.

[0080] The burnout air volume regulating unit controls the burnout air volume regulating damper to make the burnout air volume reach the target burnout air volume.

[0081] In the biomass gas amount calculation unit, the target biomass gas blending amount C s The calculation formula is: C s =C r ×α; where C r is the total fuel quantity of coal-fired boiler, t / h; α is the target biomass gas blending ratio.

[0082] In the coal quantity calculation unit, the target coal quantity C of the nth operating burner layer is mn The calculation formula is: C mn =C r ×(1-α) / n.

[0083] In the secondary air volume calculation unit, the target secondary air volume F of the nth layer of burners in operation is en The calculation formula is: en =C mn ×T m ×β-F yn ; Among them, T mis the theoretical air volume of coal, t / t; β is the target main combustion zone excess air coefficient, F yn The primary air volume of the nth operating burner layer, t / h.

[0084] In the reburning air volume calculation unit, the target reburning air volume F z The calculation formula is: z =(C m ×T m +C s ×T s )×γ-F y -F e Among them, C m is the total coal quantity of coal-fired boiler, t / h; F y is the total primary air volume of the coal-fired boiler, t / h; F e is the total secondary air volume of coal-fired boiler, t / h; T s is the theoretical air volume of biomass gas, t / t; γ is the excess air coefficient in the target reburning zone.

[0085] In the burnout air volume adjustment unit, the target burnout air volume F r The calculation formula is: r =(C m ×T m +C s ×T s )×θ-F y -F e -F z ; Wherein, θ is the excess air coefficient in the target burnout zone.

[0086] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein.

Claims

1. A method for optimizing combustion of a coal-fired boiler coupled with biomass gas, characterized in that: include: The coal of the tangentially fired boiler is injected into the furnace in layers for combustion; According to the target biomass gas blending ratio, the target biomass gas blending amount and the target coal amount of each burner layer in operation are calculated; Control the coal feeding amount of each operating coal feeder to keep the coal amount of each operating burner layer the same; According to the coal quantity and air-coal ratio curve of each operating burner layer, calculate the target primary air volume of each operating burner layer; Calculate the target secondary air volume of each burner layer in operation according to the target excess air coefficient of the main combustion zone; Control the primary air volume regulating damper and the secondary air volume regulating damper of each operating burner layer so that the primary air volume and the secondary air volume of each operating burner layer reach the target primary air volume and the secondary air volume respectively; Calculate the target reburning air volume based on the coal volume, biomass gas blending volume and target reburning zone excess air coefficient; Control the reburning air volume and adjust the damper to make the reburning air volume reach the target reburning air volume; Calculate the target burnout air volume based on the amount of coal, the amount of biomass gas blended combustion, and the excess air coefficient of the target burnout zone; Control the burnout air volume and adjust the damper to make the burnout air volume reach the target burnout air volume.

2. The method for optimizing combustion of a coal-fired boiler coupled with biomass gas according to claim 1, characterized in that: Target biomass gas blending amount C s The calculation formula is: C s =C r ×α; where C r is the total fuel quantity of coal-fired boiler, t / h; α is the target biomass gas blending ratio.

3. The method for optimizing combustion of a coal-fired boiler coupled with biomass gas according to claim 1, characterized in that: The target coal quantity C of the nth layer of burners in operation mn The calculation formula is: C mn =C r ×(1-α) / n; C r is the total fuel quantity of coal-fired boiler, t / h; α is the target biomass gas blending ratio.

4. The method for optimizing combustion of a coal-fired boiler coupled with biomass gas according to claim 1, characterized in that: The target secondary air volume F of the nth layer of burner in operation en The calculation formula is: en =C mn ×T m ×β-F yn ; Among them, C mn is the target coal quantity of the nth burner layer; T m is the theoretical air volume of coal, t / t; β is the target main combustion zone excess air coefficient, F yn The primary air volume of the nth operating burner layer, t / h.

5. The method for optimizing combustion of a coal-fired boiler coupled with biomass gas according to claim 1, characterized in that: Target reburning air volume F z The calculation formula is: z =(C m ×T m +C s ×T s )×γ-F y -F e ; Among them, C m is the total coal quantity of coal-fired boiler, t / h; T m is the theoretical air volume of coal, t / t; C s is the target biomass gas blending amount; F y is the total primary air volume of the coal-fired boiler, t / h; F e is the total secondary air volume of coal-fired boiler, t / h; T s is the theoretical air volume of biomass gas, t / t; γ is the excess air coefficient in the target reburning zone.

6. The method for optimizing combustion of a coal-fired boiler coupled with biomass gas according to claim 1, characterized in that: Target burnout air volume F r The calculation formula is: r =(C m ×T m +C s ×T s )×θ-F y -F e -F z ; Among them, C m is the total coal quantity of coal-fired boiler, t / h; T m is the theoretical air volume of coal, t / t; C s is the target biomass gas blending amount; T s is the theoretical air volume of biomass gas, t / t; θ is the excess air coefficient of the target burnout zone; F y is the total primary air volume of the coal-fired boiler, t / h; F e is the total secondary air volume of coal-fired boiler, t / h; F z is the target reburning air volume, t / h.

7. A biomass gas-coupled coal-fired boiler combustion optimization system, characterized in that: It includes a coal quantity calculation unit, a biomass gas quantity calculation unit, a primary air quantity calculation unit, a secondary air quantity calculation unit, a reburning air quantity calculation unit, a burnout air quantity calculation unit, a coal quantity adjustment unit, a primary air quantity adjustment unit, a secondary air quantity adjustment unit, a reburning air quantity adjustment unit and a burnout air quantity adjustment unit; The coal quantity calculation unit calculates the target coal quantity of each operating burner layer according to the target biomass gas blending ratio; The biomass gas amount calculation unit calculates the target biomass gas blending amount according to the target biomass gas blending ratio; The primary air volume calculation unit calculates the target primary air volume of each operating burner layer according to the coal volume of each operating burner layer and the air-coal ratio curve; The secondary air volume calculation unit is used to calculate the target secondary air volume of each operating burner layer according to the target excess air coefficient of the main combustion zone; The reburning air volume calculation unit calculates the target reburning air volume according to the coal volume, the biomass gas blending volume and the target reburning zone excess air coefficient; The burnout air volume calculation unit calculates the target burnout air volume according to the coal volume, the biomass gas blending volume and the excess air coefficient of the target burnout zone; The coal quantity regulating unit controls the coal quantity of each operating coal feeder to keep the coal quantity of each operating burner layer the same; The primary air volume regulating unit controls the primary air volume regulating damper of each operating burner layer so that the primary air volume of each operating burner layer reaches the target primary air volume; The secondary air volume regulating unit controls the secondary air volume regulating damper of each operating burner layer so that the secondary air volume of each operating burner layer reaches the target secondary air volume; The reburning air volume regulating unit controls the reburning air volume regulating damper to make the reburning air volume reach the target reburning air volume. The burnout air volume regulating unit controls the burnout air volume regulating damper to make the burnout air volume reach the target burnout air volume.

8. The biomass gas-coupled coal-fired boiler combustion optimization system according to claim 7, characterized in that: In the secondary air volume calculation unit, The target secondary air volume F of the nth layer of burner in operation en The calculation formula is: en =C mn ×T m ×β-F yn ; Among them, C mn is the target coal quantity of the nth burner layer; T m is the theoretical air volume of coal, t / t; β is the target main combustion zone excess air coefficient, F yn The primary air volume of the nth operating burner layer, t / h.

9. The biomass gas-coupled coal-fired boiler combustion optimization system according to claim 7, characterized in that: In the reburning air volume calculation unit, Target reburning air volume F z The calculation formula is: z =(C m ×T m +C s ×T s )×γ-F y -F e ; Among them, C m is the total coal quantity of coal-fired boiler, t / h; T m is the theoretical air volume of coal, t / t; C s is the target biomass gas blending amount; F y is the total primary air volume of the coal-fired boiler, t / h; F e is the total secondary air volume of coal-fired boiler, t / h; T s is the theoretical air volume of biomass gas, t / t; γ is the excess air coefficient in the target reburning zone.

10. The biomass gas-coupled coal-fired boiler combustion optimization system according to claim 7, characterized in that: In the burnout air volume adjustment unit, Target burnout air volume F r The calculation formula is: r =(C m ×T m +C s ×T s )×θ-F y -F e -F z ; Among them, C m is the total coal quantity of coal-fired boiler, t / h; T m is the theoretical air volume of coal, t / t; C s is the target biomass gas blending amount; T s is the theoretical air volume of biomass gas, t / t; θ is the excess air coefficient of the target burnout zone; F y is the total primary air volume of the coal-fired boiler, t / h; F e is the total secondary air volume of coal-fired boiler, t / h; F z is the target reburning air volume, t / h.

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