Primary air powder feeding pipeline throttle element calculation and adjustment method

Abstract

The present application relates to a kind of primary air powder conveying pipe throttle element calculation and adjustment method, including the primary air, coal powder concentration calculation method based on DCS control system;Based on the frictional resistance of primary air powder conveying pipe, local resistance, equipment and component resistance, the loss of primary air coal powder lifting pressure head and the pressure head loss of primary air coal powder acceleration resistance evaluation method of primary air powder conveying pipe based on theoretical calculation;Throttle element resistance deviation and adjustment calculation method.Finally, the resistance of each powder conveying pipe is balanced, and the primary air velocity is uniform.This method can be adjusted to different types of powder conveying pipe throttle element, effectively improve the uniformity of powder conveying pipe resistance, and ensure the economic and stable operation of unit.

Description

Technical Field

[0001] This invention relates to a method for calculating and adjusting the throttling element of a primary air-powder conveying pipeline. Background Technology

[0002] Flexible retrofitting is an important way to achieve energy conservation and emission reduction in thermal power units and a crucial means to fully tap the energy-saving potential of coal-fired power units.

[0003] Refined operational adjustments to coal-fired power units can improve the operating efficiency of the boiler combustion system and tap into the boiler's stable combustion capacity under existing coal quality and equipment conditions. Engineering practice has proven that by adjusting the throttling components of the boiler's primary air pulverized coal conveying pipeline and reducing the primary air velocity deviation in each pulverized coal pipe, uniform pulverized coal distribution within the furnace can be ensured, thereby enhancing the unit's stable combustion capacity under ultra-low loads. Against this backdrop, higher requirements are placed on the uniformity of the primary air pulverized coal conveying pipeline velocity. How to achieve refined adjustment of the throttling components through calculation and adjustment methods, ultimately improving the uniformity of the primary air pulverized coal conveying pipeline velocity, has become a concern for those skilled in the art. Summary of the Invention

[0004] In view of the above situation and to overcome the shortcomings of the existing technology, the purpose of this invention is to provide a method for calculating and adjusting the throttling element of a primary air conveying powder pipeline, which can effectively solve the problems of inaccurate adjustment of the throttling element and uniform air velocity in the primary air conveying powder pipeline.

[0005] A method for calculating and adjusting a throttling element in a primary air powder conveying pipeline includes the following steps:

[0006] Step 1: Collect equipment operating status information and parameters through the DCS control system, and use them as boundary conditions for the calculation and adjustment of the throttling element of the primary air conveying powder pipeline;

[0007] Step 2: Calculate the primary air velocity and pulverized coal concentration in each primary air conveying pipeline by measuring the primary air volume entering the primary air conveying pipeline and the coal feed rate of the coal mill.

[0008] Step 3: Calculate the frictional resistance, local resistance, equipment and component resistance, primary air pulverized coal lifting head loss, and primary air pulverized coal acceleration head loss of each primary air pulverized coal conveying pipeline based on the primary air velocity and pulverized coal concentration.

[0009] Step 4: Calculate the resistance of the throttling element under the current state;

[0010] Step 5: Calculate the total resistance of each primary air powder conveying duct;

[0011] Step Six: Determine whether the total resistance deviation of each primary air conveying pulverized coal pipeline is less than 1%. If it is less than 1%, complete the adjustment of the throttling element; otherwise, proceed to Step Seven.

[0012] Step 7: Calculate the average value of the deviation between the total resistance of each primary air duct and the minimum total resistance of the primary air powder conveying duct;

[0013] Step 8: Calculate the required increase (or decrease) in resistance for each primary air duct;

[0014] Step 9: Adjust the throttling element according to the required increase (or decrease) resistance of each primary air duct, and repeat steps 4 to 10 until the total resistance of each primary air powder conveying duct is the same.

[0015] Coal-fired power units typically employ a primary air pulverized coal feeding system. This type of system generally requires a uniform distribution of primary air velocity and consistent pipeline resistance among the pulverized coal feeding pipes on the same burner level. Due to factors such as length and routing, the resistance of each pulverized coal feeding pipe varies. To address this uneven resistance, the throttling elements of each pulverized coal feeding pipe on the same level are usually adjusted to ensure uniform resistance. However, currently, there is a widespread problem of inadequate adjustment of the throttling elements, leading to inconsistent primary air velocities in different pulverized coal pipes within the same coal mill. This ultimately causes flame deflection in the furnace, and in severe cases, water-cooled wall erosion, coking, and corrosion of the pipe walls, affecting the stable operation of the unit.

[0016] This invention provides a method for calculating and adjusting primary air throttling components, including a method for calculating primary air and pulverized coal concentrations based on a DCS control system; a method for evaluating the frictional resistance, local resistance, equipment and component resistance, primary air pulverized coal lifting head loss, and primary air pulverized coal acceleration head loss of the pulverized coal conveying pipeline based on theoretical calculations; and a method for calculating and adjusting the resistance deviation of the throttling component. Ultimately, this achieves balanced resistance in each pulverized coal conveying pipeline and uniform primary air velocity.

[0017] The calculation of the inherent resistance of the primary air conveying pulverized coal pipeline starts from the primary air volume and the coal feed rate of the pulverizer. Through theoretical calculations, the frictional resistance, local resistance, equipment and component resistance, pressure head loss during primary air pulverized coal lifting, and pressure head loss during primary air pulverized coal acceleration are calculated, serving as the starting point for adjustment. Based on the calculation of the inherent resistance of the conveying pipeline, the resistance of the throttling element is calculated as the initial operating condition. By analyzing the resistance deviation of each conveying pipeline, the throttling ratio of the throttling element is calculated as the basis for adjustment. The throttling ratio of the throttling element is adjusted, and the resistance of each conveying pipeline is repeatedly calculated until the resistance of each pipeline is balanced.

[0018] This invention provides an effective solution to the problem of improper adjustment of throttling elements in coal feeding pipelines. This method is adaptable to different types of throttling element adjustments in coal feeding pipelines, effectively improving the uniformity of resistance in the coal feeding pipeline and ensuring the economical and stable operation of the unit. Compared with existing technologies, this invention has the following advantages:

[0019] (1) Based on aerodynamic theory and combined with the design principles of pulverizing system, this invention provides a method for calculating and adjusting the primary air throttling element. This method can quickly obtain the adjustment amount of the throttling element by relying only on conventional parameters such as pipeline layout, primary air volume, and coal mill feed rate, which is convenient and fast.

[0020] (2) When adjusting conventional throttling components, it is necessary to conduct a wind leveling test to obtain wind speed data. The method of the present invention can adjust the throttling components while the unit is in operation. The entire adjustment process does not require a test to measure wind speed data, which greatly reduces the workload of the test.

[0021] (3) Based on conventional primary air leveling, this invention adds the influence of primary air pulverized coal concentration on the resistance of the pulverized coal conveying pipeline, and the resistance calculation is highly accurate;

[0022] (4) This invention takes into account various types of powder feeding pipe resistance and can be applied to the resistance adjustment of throttling components in different types of powder making systems, making it highly applicable. Attached Figure Description

[0023] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0024] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0025] like Figure 1 As shown, the present invention provides a method for calculating and adjusting a throttling element in a primary air powder conveying pipeline, comprising the following steps:

[0026] Step 1: Collect equipment operating status information and parameters through the DCS control system, and use them as boundary conditions for the calculation and adjustment of the throttling element of the primary air conveying powder pipeline;

[0027] Specifically, the DCS control system collects equipment operating status information and obtains the following parameters: coal mill feed rate B. M 1. Coal mill inlet air volume Qi;

[0028] Step 2: Calculate the primary air velocity and pulverized coal concentration in each primary air conveying pipeline by measuring the primary air volume entering the primary air conveying pipeline and the coal feed rate of the coal mill.

[0029] Specifically, the primary air velocity ω and pulverized coal concentration μ in each primary air conveying duct are calculated based on the primary air volume entering the pulverized coal conveying duct and the coal feed rate of the pulverizer.

[0030]

[0031] In the formula: A is the cross-sectional area of ​​the powder delivery pipe, in meters. 2 ;

[0032] Q i The inlet air volume of the coal mill is m. 3 / s;

[0033]

[0034] In the formula: B M The coal feed rate of the coal mill is kg / s;

[0035] ρ f Primary air density, kg / m 3 .

[0036] Step 3: Calculate the frictional resistance, local resistance, equipment and component resistance, primary air pulverized coal lifting head loss, and primary air pulverized coal acceleration head loss of each primary air pulverized coal conveying pipeline based on the primary air velocity and pulverized coal concentration.

[0037] Specifically, the resistance generated by the primary air as it passes through the powder delivery pipeline on the pipeline wall and at bends and diameter changes mainly includes the following components: pipeline friction resistance Δp fμ，i When a gaseous or powder-containing gas flows through a straight pipe, the resistance is generated due to the viscosity of the gas and friction with the pipe wall; the local resistance Δp of the pipe components. ζμ，i Resistance refers to the resistance caused by changes in cross-sectional size or direction when airflow or airflow containing powder flows, such as the resistance caused by various pipe components like bends, fittings, and tees; and the resistance Δp of equipment and components. ξ，i The resistance generated when airflow or powder-containing airflow passes through various equipment and components of the pulverizing system, such as coal mills, dryers, coarse and fine powder separators, pulverized coal distributors, and primary air boxes; the pulverized coal lifting head loss Δp t，i This refers to the energy consumed in the lifting of pulverized coal during the upward motion of the pulverized coal airflow, as well as the pressure head loss Δp due to the acceleration of coal and pulverized coal. r，i .

[0038] (1) Pipe friction resistance Δp fμ，i

[0039]

[0040] In the formula: Δp fμ，i Frictional resistance during powder-containing airflow, Pa;

[0041] λ μ The coefficient of frictional resistance during the flow of gas containing powder;

[0042] L i Calculation length of pipe friction resistance, in meters;

[0043] D e Equivalent pipe diameter, in meters;

[0044] ρ0 is the primary air density, kg / m³3 ;

[0045] (2) Local resistance Δp of pipeline components ζμ，i

[0046]

[0047] In the formula: Δp ζμ，i The local resistance of the gas containing powder flowing through the pipeline component, in Pa;

[0048] ζ μ The local resistance coefficient of gas containing powder flowing through pipeline components.

[0049] (3) Equipment and component resistance Δp ξ，i

[0050]

[0051] Where: ζ0 is the drag coefficient of equipment and components under pure gas conditions;

[0052] Correction factor for K-flow containing powder;

[0053] μ concentration of pulverized coal in equipment or components, kg / kg;

[0054] ω is the airflow velocity at the cross-section of the primary air pulverized coal pipeline, in m / s;

[0055] ρ g Airflow density inside equipment or components, kg / m³ 3 .

[0056] (4) Coal powder lifting head loss Δp t，i

[0057] Δp t，i =∑ΔZ j μ j ρ g g

[0058] In the formula: ΔZ j The elevation of the section, in meters (m).

[0059] μ j The concentration of pulverized coal in the section, kg / kg;

[0060] ρ g Gas density, kg / m³ 3 ;

[0061] g-force acceleration, m / s² 2 ;

[0062] (5) Head loss Δp due to acceleration of coal and pulverized coal r，i

[0063] Δpr，i =μ i ρ g ω 2

[0064] Where: μ i The concentration of pulverized coal in the i-th pulverized coal feeding pipe is kg / kg;

[0065] Step 4: Calculate the resistance of the throttling element under the current state;

[0066] Specifically, the resistance of the throttling element under the current state is calculated using the following formula:

[0067]

[0068] In the formula: Δp jμ0，i The resistance of the throttling element under the current condition is expressed in Pa.

[0069] ζ jμ，0 The local resistance coefficient of the throttling element in the pipeline for gas containing powder;

[0070] Local drag coefficient ζ of throttling element jμ，0 The calculation method is as follows:

[0071] When m < 0.73:

[0072] ζ jμ，0 =(0.3827m) -3.408 -0.6)(1-0.638μ+0.4μ 2 )

[0073] When 0.73 ≤ m < 0.81:

[0074] ζ jμ，0 =(0.5873m) -1.6965 -0.6)(1+(1-0.3638μ+0.5662μ)μ)

[0075] When m ≥ 0.81:

[0076] ζ jμ，0 =(0.5873m) -1.6165 -0.6)(1+(1-0.6910μ+8μ 2 )μ)

[0077] Where m is the throttling ratio of the throttling element, and μ is the coal powder concentration, kg / kg.

[0078] Step 5: Calculate the total resistance of each primary air powder conveying duct;

[0079] Specifically, the total resistance of each primary air powder conveying duct is calculated using the following formula:

[0080] Δp i =Δp fμ，i +Δp ζμ，i +Δp ξ，i +Δp t，i +Δp r，i

[0081] Step Six: Determine whether the total resistance deviation of each primary air conveying pulverized coal pipeline is less than 1%. If it is less than 1%, complete the adjustment of the throttling element; otherwise, proceed to Step Seven.

[0082] Specifically, the calculation should determine that the total resistance deviation of each primary air powder conveying pipeline is less than 1%.

[0083]

[0084] Where: Δp i The total resistance of the i-th powder feeding pipe, Pa;

[0085] Δp min The minimum total resistance of all primary air-powder conveying pipelines, in Pa.

[0086] Step 7: Calculate the average value of the deviation between the total resistance of each primary air duct and the minimum total resistance of the primary air powder conveying duct;

[0087] Specifically, the average deviation between the total resistance of each primary air duct and the minimum total resistance of the primary air powder conveying duct is calculated using the following formula:

[0088]

[0089] Step 8: Calculate the required increase (or decrease) in resistance for each primary air duct;

[0090] Specifically, the required increase or decrease in resistance for each primary air duct is calculated using the following formula:

[0091] Δp en，i =Δp i -Δp avg .

[0092] Step 9: Adjust the throttling element according to the required increase (or decrease) resistance of each primary air duct, and repeat steps 4 to 10 until the total resistance of each primary air powder conveying duct is the same.

[0093] Specifically, by adjusting the throttling ratio of the throttling element according to the required increase or decrease in resistance of each primary air duct, and repeating steps four through ten until the total resistance deviation of each primary air duct is less than 1%, thus completing the adjustment of the throttling element of the primary air duct.

[0094] Throttling ratio adjustment Δm i The following formula is used to calculate:

[0095]

[0096] Where: m i The throttling ratio of the throttling element in its original state.

[0097] This invention has achieved good technical results through practical application, and the application examples are as follows:

[0098] This application example demonstrates the adjustment of the throttling element in the primary air-powder conveying pipeline of a four-corner tangential positive pressure direct-fired boiler.

[0099] Step 1: Obtain the coal feed rate B of the coal mill through the DCS control system. M Qi, the inlet air volume of the coal mill;

[0100] B M =40t / h Q i =64t / h

[0101] Step 2: Calculate the primary air velocity ω and pulverized coal concentration μ in the primary air conveying duct;

[0102]

[0103]

[0104] Step 3: Calculate the pipe friction resistance Δp fμ，i Local resistance Δp ζμ，i Equipment and component resistance Δp ξ，i The head loss Δp of pulverized coal hoisting t，i and the head loss Δp due to the acceleration of coal and pulverized coal r，i .

[0105] (1) Pipe friction resistance Δp fμ，i

[0106] Serial Number Horizontal pipe length (m) Vertical pipe length (m) 1 10 10 2 10 10 3 15 10 4 15 10

[0107]

[0108]

[0109]

[0110]

[0111] (2) Local resistance Δp of pipeline components ζμ，i

[0112] Serial Number Number of elbows 1 5 2 5 3 7 4 7

[0113]

[0114]

[0115]

[0116]

[0117] (3) Resistance Δp of equipment and components ξ，i

[0118]

[0119] (4) Coal powder lifting head loss Δp t，i

[0120] Δp t，i =∑ΔZ j μ j ρ g g = 62 (Pa)

[0121] (5) Accelerated loss of coal or pulverized coal Δp r，i

[0122] Δp r，i =μ i ρ g ω 2 =319 (Pa)

[0123] Step 4: Calculate the resistance of the throttling element under the current state.

[0124] Serial Number Throttling ratio m 1 0.431 2 0.420 3 0.419 4 0.448

[0125]

[0126]

[0127]

[0128]

[0129] ζ 1μ，0 =(0.3827m) -3.408 -0.6)(1-0.638μ+0.4μ 2 )

[0130] =(0.3827×(0.431) -3.408 )-0.6)×(1-0.638×0.667+0.4*0.667*0.667)

[0131] =4.62

[0132] ζ 2μ，0=(0.3827m) -3.408 -0.6)(1-0.638μ+0.4μ 2 )

[0133] =(0.3827×(0.420)) -3.408 )-0.6)×(1-0.638×0.667+0.4*0.667*0.667)

[0134] =5.09

[0135] ζ 3μ，0 =(0.3827m) -3.408 -0.6)(1-0.638μ+0.4μ 2 )

[0136] =(0.3827×(0.419)) -3.408 )-0.6)×(1-0.638×0.667+0.4*0.667*0.667)

[0137] =5.13

[0138] ζ 4μ，0 =(0.3827m) -3.408 -0.6)(1-0.638μ+0.4μ 2 )

[0139] =(0.3827×(0.448)) -3.408 )-0.6)×(1-0.638×0.667+0.4*0.667*0.667)

[0140] =3.99

[0141] Step 5: Calculate the total resistance of each primary air powder conveying duct;

[0142] Δp i =Δp fμ，i +Δp ζμ，i +Δp ξ，i +Δp t，i +Δp r，i

[0143] Serial Number <![CDATA[Total resistance ΔP of the primary air powder conveying pipeline i > 1 2511 2 2623 3 3092 4 2819

[0144] Step Six: Calculate the total resistance deviation of each primary air powder conveying duct.

[0145]

[0146] Serial Number Total resistance deviation of each primary air powder conveying duct 1 0.00％ 2 4.26％ 3 18.78％ 4 10.94％

[0147] Step 7: Calculate the average value of the deviation between the total resistance of each primary air duct and the minimum total resistance of the primary air powder conveying duct;

[0148]

[0149] Step 8: Calculate the required increase in resistance for each primary air duct;

[0150] Δp en，i =Δp i -Δp avg

[0151] Serial Number The required increase in resistance for each primary air duct 1 -250 2 -138 3 331 4 58

[0152] Step 9: Adjust the throttling ratio of the throttling element, and repeat steps 4 to 10 until the total resistance of each primary air powder conveying pipeline is the same, thus completing the adjustment of the throttling element of the primary air powder conveying pipeline.

[0153] Throttling ratio adjustment amount:

[0154]

[0155]

[0156] After adjustment, the total resistance deviation of each calculation and each primary air conveying pulverized coal pipeline is less than 1%, and the adjustment is complete.

[0157] Serial Number Total resistance deviation of each primary air powder conveying duct 1 0.00％ 2 0.88％ 3 0.55％ 4 0.55％

[0158] After adjustment, the air velocity in the primary air pulverized coal pipeline was measured. The air velocities in each pipeline were similar, which proves that the resistance of each pipeline is basically the same. The measurement results are as follows:

[0159] Serial Number Primary air pulverized coal pipeline air velocity (m / s) Relative deviation (%) 1 21.70 -1.36 2 22.10 0.45 3 21.90 -0.45 4 22.50 1.36

Claims

1. A method for calculating and adjusting a throttling element in a primary air powder conveying pipeline, comprising the following steps: Step 1: Collect equipment operating status information and parameters through the DCS control system, and use them as boundary conditions for the calculation and adjustment of the throttling element of the primary air conveying powder pipeline; Step 2: Calculate the primary air velocity and pulverized coal concentration in each primary air conveying pipeline by measuring the primary air volume entering the primary air conveying pipeline and the coal feed rate of the coal mill. Step 3: Calculate the frictional resistance, local resistance, equipment and component resistance, primary air pulverized coal lifting head loss, and primary air pulverized coal acceleration head loss of each primary air pulverized coal conveying pipeline based on the primary air velocity and pulverized coal concentration. Step 4: Calculate the resistance of the throttling element under the current state; Step 5: Calculate the total resistance of each primary air powder conveying duct; Step Six: Determine whether the total resistance deviation of each primary air powder conveying pipeline is less than 1%. If it is less than 1%, complete the adjustment of the throttling element; otherwise, proceed to Step Seven. Step 7: Calculate the average value of the deviation between the total resistance of each primary air duct and the minimum total resistance of the primary air powder conveying duct; Step 8: Calculate the resistance that needs to be increased or decreased for each primary air duct; Step 9: Adjust the throttling element according to the required increase or decrease in resistance of each primary air duct, and repeat steps 4 to 10 until the total resistance of each primary air powder conveying duct is the same. Step three specifically involves the following: Primary air encounters resistance on the pipe wall and at bends and diameter changes as it passes through the powder delivery pipe. This resistance mainly includes the following components: pipe friction resistance. When a gaseous or powder-containing gas flows through a straight pipe, the resistance is generated due to the viscosity of the gas and friction with the pipe wall; local resistance of pipe components. Resistance refers to the resistance caused by changes in cross-sectional size or direction when airflow or airflow containing powder flows; resistance of equipment and components. The resistance generated when airflow or airflow containing powder flows through various equipment and components of the pulverizing system; the pressure head loss during pulverized coal lifting. This refers to the energy consumed in the lifting of pulverized coal during the upward motion of the pulverized coal airflow, as well as the pressure head loss due to the acceleration of coal and pulverized coal. ; (1) Pipeline friction resistance In the formula: Frictional resistance during powder-containing airflow, Pa; The coefficient of frictional resistance during the flow of gas containing powder; L i Calculation length of pipe friction resistance, in meters; D e Equivalent pipe diameter, in meters; ρ 0 Primary air density, kg / m³ 3 ; (2) Local resistance of pipeline components In the formula: The local resistance of the gas containing powder flowing through the pipeline component, in Pa; The local resistance coefficient of the gas containing powder flowing through the pipeline components; (3) Resistance of equipment and components In the formula: The drag coefficient of equipment and components under pure gas conditions; K Correction factor for airflow containing powder; μ The concentration of pulverized coal in the equipment or component, in kg / kg; The airflow velocity at the cross-section of the primary air pulverized coal pipeline, in m / s; ρ g Airflow density inside equipment or components, kg / m³ 3 ; (4) Coal powder lifting head loss In the formula: The elevation of the section, in meters (m). The concentration of pulverized coal in the section, kg / kg; ρ g Gas density, kg / m³ 3 ; g-force acceleration, m / s² 2 ; (5) Head loss due to accelerated coal and pulverized coal In the formula: μ i Let be the pulverized coal concentration in the i-th pulverized coal feeding pipe, in kg / kg.

2. The method for calculating and adjusting the throttling element of a primary air-powder conveying pipeline according to claim 1, characterized in that, Step one specifically involves: collecting equipment operating status information through the DCS control system and obtaining the following parameters: coal mill feed rate. B M Coal mill inlet air volume Qi .

3. The method for calculating and adjusting the throttling element of a primary air-powder conveying pipeline according to claim 2, characterized in that, Step two specifically involves calculating the primary air velocity within each primary air conveying duct based on the primary air volume entering the primary air conveying duct and the coal feed rate of the coal mill. ω and coal powder concentration μ : In the formula: A is the cross-sectional area of ​​the powder delivery pipe, in meters. 2 ; Q i The inlet air volume of the coal mill is m. 3 / s; In the formula: B M The coal feed rate of the coal mill is kg / s; ρ f Primary air density, kg / m 3 .

4. The method for calculating and adjusting the throttling element of a primary air-powder conveying pipeline according to claim 3, characterized in that, Step four specifically involves calculating the resistance of the throttling element under the current state: In the formula: The resistance of the throttling element under the current condition is expressed in Pa. The local resistance coefficient of the throttling element in the pipeline for gas containing powder; Local drag coefficient of throttling element The calculation method is as follows: When m < 0.73: When 0.73≤ m When <0.81: when m When ≥0.81: in, m For the throttling element, the throttling ratio, μ The concentration of pulverized coal is expressed in kg / kg.

5. The method for calculating and adjusting the throttling element of a primary air-powder conveying pipeline according to claim 4, characterized in that, Step five specifically involves calculating the total resistance of each primary air powder conveying duct using the following formula: 。 6. The method for calculating and adjusting the throttling element of a primary air-powder conveying pipeline according to claim 5, characterized in that, Step six specifically involves determining that the deviation of the total resistance of each primary air powder conveying pipeline is less than 1%. in: The total resistance of the i-th powder feeding pipe, Pa; The minimum total resistance of all primary air-powder conveying pipelines, in Pa.

7. The method for calculating and adjusting the throttling element of a primary air-powder conveying pipeline according to claim 6, characterized in that, Step seven specifically involves calculating the average deviation between the total resistance of each primary air duct and the minimum total resistance of the primary air powder conveying duct using the following formula: 。 8. The method for calculating and adjusting the throttling element of a primary air-powder conveying pipeline according to claim 7, characterized in that, Step eight specifically involves calculating the required increase or decrease in resistance for each primary air duct using the following formula: 。 9. The method for calculating and adjusting the throttling element of a primary air-powder conveying pipeline according to claim 8, characterized in that, Step nine specifically involves: gradually adjusting the throttling ratio of the throttling element by increasing or decreasing the resistance of each primary air duct, and repeating steps four through ten until the total resistance deviation of each primary air duct is less than 1%, thus completing the adjustment of the throttling element of the primary air duct. The throttling ratio adjustment amount is calculated using the following formula: In the formula: m i The throttling ratio of the throttling element in its original state.

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