Coal mill air passage flow field adaptive adjustment method

Abstract

The invention discloses a coal mill air passage flow field adaptive adjustment method. A traditional throttle plate structure adopted by current equipment is not subjected to special adaptive design according to primary air parameters in the Xinjiang area and the size of a grinding area of a ZGM95N-II type coal mill. The method comprises the following steps: on the basis of the actual operation primary air parameters of the coal mill, constructing a technical path of parameter actual measurement-molded line design-field verification; the machining process of the inner wall of the air channel is optimized, the surface roughness Ra is controlled to be smaller than or equal to 1.6 microns, and the attachment area and adhesive force of pulverized coal on the wall face are reduced; a detachable scraper is arranged in the powder accumulation area and is made of a wear-resistant material the same as that of the efficiency improving device, so that accumulated powder can be quickly cleaned during shutdown; the flow resistance change rule of the throttle plate under different pulverization loads is obtained through field testing, and the matching relation of the primary air volume, the air pressure and the loads is defined. The device is used for adaptive adjustment of the coal mill air passage flow field.

Description

TECHNICAL FIELD

[0001] The application relates to a method for adjusting a flow field of a coal mill air duct. BACKGROUND

[0002] Xinjiang is an important energy base in China, and its power production plays a key supporting role in regional economic development and people's livelihood protection. As a core power enterprise in Aksu region of Xinjiang, Huadian Kuche Power Generation Co., Ltd. undertakes the winter heating task of 12 million square meters in Kuche City and the industrial and residential power supply guarantee function in the southern region of Xinjiang. In 2023, it is expected to complete 2.8 billion kilowatt-hours of power generation, and the No. 4 unit under its jurisdiction has won the title of "2022 Annual National Power Generation Unit Reliability Benchmark Unit" awarded by China Electricity Enterprise Association, representing the top level of regional thermal power operation. However, the company's ZGM95N-Ⅱ medium-speed roller disc type coal mill in service has gradually exposed a series of technical bottlenecks in long-term operation due to the influence of coal quality characteristics in Xinjiang region and the operation condition of the pulverizing system. Not only does it restrict the operation efficiency and reliability of the coal mill, but also leads to rising energy consumption and increasing maintenance costs, posing challenges to the overall economy and safe and stable operation of the unit, and urgent technical research and development is needed to achieve a breakthrough.

[0003] From the perspective of the flow field and resistance characteristics of the coal mill air duct, the traditional throttle plate structure currently used by the equipment is not specially designed for the primary air parameters in Xinjiang region and the grinding area size of ZGM95N-Ⅱ type coal mill. Field operation data shows that local vortex and airflow deflection phenomena are prone to occur when primary air passes through the air duct, resulting in serious uneven airflow distribution in the grinding area - the primary air speed is too high in some areas, and the coal powder is not fully ground before being taken out, causing a decrease in pulverizing efficiency; the wind speed is too low in some areas, and the coal powder accumulates, causing the risk of mill roller jamming. At the same time, the unreasonable air duct structure also leads to a difference pressure fluctuation range of 1.2-1.5 kPa between the inlet and outlet of the coal mill, significantly increasing the ventilation resistance, directly causing an additional increase of 4%-6% in the power consumption of the primary air fan, which is inconsistent with the company's development goal of energy saving and green power generation. To solve this problem, optimization research on the air duct profile needs to be carried out based on the actual operation parameters of the coal mill, and the curvature radius of the air duct, the inlet / outlet cross-sectional size and the primary air characteristics need to be accurately matched to achieve the dual goals of improving airflow uniformity and reducing resistance.

[0004] The problem of powder accumulation also threatens the operation of the coal mill. The coal powder carried by the primary air is prone to deposit at the turning of the air duct. Field inspection shows that when the thickness of the accumulated powder reaches 5-8 mm, the ventilation area of the air duct is reduced by 15%-20%, and in severe cases, the air duct may be blocked, causing the forced shutdown of the coal pulverizing system for cleaning. At present, there is a lack of effective means for preventing powder accumulation and cleaning, and the accumulated powder not only further increases the airflow deviation and resistance, but also may cause spontaneous combustion risk due to long-term accumulation, posing a potential threat to the safe operation of the equipment. To solve this problem, an efficient powder accumulation prevention structure needs to be designed in combination with the airflow trajectory in the air duct, and the inner wall characteristics or cleaning device needs to be optimized to avoid the impact of powder accumulation on the operation efficiency and safety of the coal mill.

[0005] The special characteristics of coal quality in Xinjiang region and the operating conditions of the coal mill determine that the traditional technical solutions cannot meet the current demand for efficient, reliable and low-consumption operation of the equipment. The development of "coal mill air duct flow field adaptation and dynamic and static ring compensation technology" is not only an urgent need to solve the technical bottleneck of the coal mill of Huadongkuache Power Generation Co., Ltd., but also an important measure to improve the ability of thermal power equipment in Xinjiang region to adapt to local coal quality and promote energy saving and consumption reduction and technological upgrading of the thermal power industry. Through key technology researches such as air duct profile optimization, dynamic and static ring sealing and material coupling improvement, efficiency improvement device material upgrading and powder accumulation prevention structure design, the project can achieve the goals of reducing the inlet and outlet differential pressure of the coal mill by 3%-8%, controlling the primary air leakage rate at ≤5%, prolonging the service life of the efficiency improvement device to ≥5 years and reducing the unit consumption of the coal mill by 3%-7%, which is of great significance to improving the economy and reliability of the unit, ensuring the energy security and livelihood supply in Xinjiang region. SUMMARY

[0006] The purpose of the present application is to provide a coal mill air duct flow field adaptation adjustment method to solve the above technical problems.

[0007] The above purpose is achieved by the following technical solutions: A coal mill air duct flow field adaptation adjustment method, which comprises the following steps: Step 1: Based on the actual operating primary air parameters of the coal mill, a technical path of parameter measurement-profile design-site verification is established; Step 2: Optimize the processing technology of the inner wall of the air duct to control the surface roughness Ra≤1.6 μm, reduce the adhesion area and adhesion force of the coal powder on the wall; Step 3: A detachable scraper is arranged in the powder accumulation area, and the scraper is made of the same wear-resistant material as the efficiency improvement device, which facilitates quick cleaning of the accumulated powder during shutdown; Step 4: Obtain the flow resistance variation law of the throttle plate under different pulverizing loads through field test to determine the matching relationship among the primary air volume, air pressure and load.

[0008] The specific process of step one of the coal mill air duct flow field adaptive adjustment method is: first, obtain the pressure loss and flow velocity distribution data of the primary air in the existing air duct under the 50%-100% pulverizing load condition through field test, and determine the key influence law of air duct curvature radius and inlet / outlet cross section size on air flow characteristics, and then design two types of air duct profile schemes of variable curvature and gradually changing cross section, process the physical devices, and then carry out comparative test on the No. 4 furnace D and E coal mills, verify the optimization effect of different profiles on air flow uniformity and resistance characteristics by monitoring the core parameters such as coal powder carrying amount distribution in the grinding area, inlet and outlet differential pressure of the coal mill, and primary air pressure loss, and finally determine the air duct structure that can minimize the primary air pressure loss and cover the whole area of the grinding table, so as to realize the reduction of 3%-8% of the inlet and outlet differential pressure of the coal mill, and the differential pressure fluctuation is controlled within 0.5 kPa.

[0009] The specific process of step three of the coal mill air duct flow field adaptive adjustment method is: a detachable scraper is arranged in the powder accumulation area, the scraper is made of the same wear-resistant material as the efficiency improving device, which facilitates quick cleaning of the accumulated powder during shutdown, and the air duct components of the two types of schemes are processed and compared in the field, the powder accumulation thickness at the turning part of the air duct is checked regularly, the ventilation area change rate and the ventilation resistance of the inlet and outlet of the coal mill are monitored, and other parameters are monitored to evaluate the anti-powder accumulation effect, determine the optimal structure scheme, ensure that the powder accumulation thickness is ≤1 mm and the ventilation area reduction is ≤3%, and avoid air duct blockage and ventilation efficiency reduction caused by powder accumulation.

[0010] The specific process of step four of the coal mill air duct flow field adaptive adjustment method is: when the pulverizing load increases from 50% to 100% and the primary air pressure increases from 4.5 kPa to 6.8 kPa, adjust the structure parameters of the throttle plate to make the flow resistance change linearly and smoothly, monitor the inlet and outlet differential pressure fluctuation of the coal mill through field test, ensure that the differential pressure fluctuation is controlled within 0.5 kPa under different loads, realize the collaborative optimization of primary air energy consumption and pulverizing efficiency, and reduce the additional increase of primary air fan power consumption. Advantages

[0011] 1. The invention breaks through the traditional throttle plate structure "generalized design" limitations, taking the actual operation of the coal mill primary air parameters as the benchmark, establishing a "parameter measurement - profile customization - field verification" technical path. Through field testing, the primary air pressure loss and flow velocity distribution data under the working condition of 50%-100% pulverizing load are obtained, the key influence law of air duct curvature radius, inlet / outlet cross section size on air flow characteristics is clarified, and two types of air duct profile schemes of variable curvature and gradually changing section are designed. Compared with the traditional structure which is prone to local vortex and air flow deflection, this innovation can minimize the pressure loss of primary air along the air duct, and can evenly cover the entire mill after entering the grinding area. Field test verification shows that the inlet and outlet differential pressure of the coal mill can be reduced by 3%-8%, the differential pressure fluctuation can be controlled within 0.5kPa, and the problem of excessive coal powder carrying or accumulation caused by uneven wind speed in the grinding area is solved.

[0012] 2. The invention proposes two types of targeted anti-powder deposition schemes based on the measured air flow trajectory in the air duct. Scheme one optimizes the processing technology of the inner wall of the air duct to control the surface roughness to Ra≤1.6μm, reducing the adhesion area and adhesion force of coal powder on the wall; Scheme two sets a detachable scraper in the area prone to powder deposition, which is made of the same high-temperature and wear-resistant material as the efficiency improvement device, facilitating quick cleaning during shutdown. Compared with the traditional air duct blockage and ventilation efficiency reduction caused by the lack of anti-powder deposition measures, this innovation can control the powder deposition thickness to ≤1mm, reduce the ventilation area by ≤3%, ensure the long-term smoothness of the air duct, and avoid the risk of spontaneous combustion and air flow deflection caused by powder deposition.

[0013] 3. The invention breaks through the limitation of the present primary air parameters being adjusted only according to the outlet coal powder concentration without linkage with the flow resistance characteristics of the throttle plate. By field testing, the flow resistance variation of the throttle plate under different pulverizing loads is obtained, and the matching relationship between primary air volume, pressure and load is clarified. When the pulverizing load increases from 50% to 100% and the primary air pressure increases from 4.5kPa to 6.8kPa, the throttle plate structure parameters are adjusted in combination with the air duct profile optimization results to make the flow resistance change linearly and smoothly. This innovation can reduce the inlet and outlet differential pressure fluctuation of the coal mill from the traditional 1.2-1.5kPa to within 0.5kPa, realize the coordinated optimization of primary air energy consumption and pulverizing efficiency, reduce the additional power consumption of the primary air fan, and adapt to the stable operation demand of the coal mill under different loads. DETAILED DESCRIPTION

[0014] A coal mill air duct flow field adaptation and adjustment method, the method comprising the following steps: Step one: taking the actual operation of the coal mill primary air parameters as the basis, constructing a parameter measurement - profile design - field verification technical path; Step two: optimize the airway inner wall processing technology, control the surface roughness Ra≤1.6μm, reduce the adhesion area and adhesion force of coal powder on the wall; Step three: set a detachable scraper in the powder accumulation area, the scraper is made of the same wear-resistant material as the efficiency improving device, which facilitates quick cleaning of the accumulated powder during shutdown; Step four: obtain the variation law of the throttle plate flow resistance under different pulverizing loads through on-site testing, and determine the matching relationship between the primary air flow, air pressure and load.

[0015] The specific process of step one of the coal mill air duct flow field adaptive adjustment method is as follows: first, obtain the pressure loss and flow velocity distribution data of the primary air in the existing air duct under the condition of a pulverizing load of 50%-100% through on-site testing, determine the key influence law of the air duct curvature radius and the inlet / outlet cross-sectional size on the air flow characteristics, design two types of air duct profile schemes with variable curvature and gradually changing cross-section, process the physical devices, and then carry out comparative tests on the No.4 furnace D and E coal mills. Through monitoring the core parameters such as the coal powder carrying amount distribution in the grinding area, the inlet and outlet differential pressure of the coal mill, and the primary air pressure loss, the optimization effect of different profiles on the air flow uniformity and resistance characteristics is verified, and finally the air duct structure that can minimize the primary air pressure loss and cover the entire mill disc is determined, realizing a reduction of 3%-8% in the inlet and outlet differential pressure of the coal mill, and controlling the differential pressure fluctuation within 0.5kPa.

[0016] The specific process of step three of the coal mill air duct flow field adaptive adjustment method is as follows: a detachable scraper is set in the powder accumulation area, which is made of the same wear-resistant material as the efficiency improving device, facilitating quick cleaning of the accumulated powder during shutdown. The air duct components of the two types of schemes are processed and comparative tests are carried out on site. Through regular inspection of the powder accumulation thickness at the air duct turning point, monitoring of the ventilation area change rate, and monitoring of the inlet and outlet ventilation resistance of the coal mill, the anti-powder accumulation effect is evaluated, the optimal structure scheme is determined, the powder accumulation thickness is ensured to be ≤1mm, the ventilation area reduction is ensured to be ≤3%, and the air duct blockage and ventilation efficiency reduction caused by powder accumulation are avoided.

[0017] The specific process of step four of the coal mill air duct flow field adaptive adjustment method is as follows: when the pulverizing load increases from 50% to 100% and the primary air pressure increases from 4.5kPa to 6.8kPa, the flow resistance is adjusted to change linearly and smoothly by adjusting the structure parameters of the throttle plate. Through on-site testing, the inlet and outlet differential pressure fluctuation of the coal mill is monitored to ensure that the differential pressure fluctuation is controlled within 0.5kPa under different loads, realizing the collaborative optimization of the primary air energy consumption and the pulverizing efficiency, and reducing the additional increase of the primary air fan power consumption.

Claims

1. A method for adapting and adjusting the airflow field in a coal mill duct, characterized in that: The method includes the following steps: Step 1: Based on the actual primary air parameters of the coal mill during operation, construct a technical path of parameter measurement - profile design - on-site verification; Step 2: Optimize the processing technology of the inner wall of the air passage, control the surface roughness Ra≤1.6μm, and reduce the adhesion area and adhesion of coal powder on the wall surface; Step 3: Install a detachable scraper in the powder accumulation area. The scraper is made of the same wear-resistant material as the efficiency improvement device, which facilitates quick cleaning of accumulated powder when the machine is stopped. Step 4: Obtain the variation law of the flow resistance of the throttling plate under different pulverizing loads through on-site testing, and clarify the matching relationship between primary air volume, air pressure and load.

2. The method for adapting and adjusting the airflow field in a coal mill according to claim 1, characterized in that: The specific process of step one is as follows: First, the pressure loss and velocity distribution data of primary air in the existing air duct under the pulverizing load of 50%-100% are obtained through on-site testing. The key influence laws of the air duct curvature radius and inlet / outlet cross-sectional dimensions on the airflow characteristics are clarified. Based on this, two types of air duct profile schemes, variable curvature and gradual cross-section, are designed. After the physical device is manufactured, comparative tests are carried out on the No. 4 boiler D and E coal mills. By monitoring the coal powder carrying capacity distribution in the grinding area, the differential pressure between the inlet and outlet of the coal mill, and the primary air pressure loss, the optimization effect of different profiles on the airflow uniformity and resistance characteristics is verified. Finally, the air duct structure that can minimize the primary air pressure loss and cover the entire grinding disc area is determined, achieving a reduction of 3% to 8% in the differential pressure between the inlet and outlet of the coal mill, and controlling the differential pressure fluctuation within 0.5 kPa.

3. The method for adapting and adjusting the airflow field of a coal mill according to claim 2, characterized in that: The specific process of step three is as follows: a detachable scraper is installed in the dust accumulation area. The scraper is made of the same wear-resistant material as the efficiency improvement device, which facilitates quick cleaning of dust accumulation when the machine is stopped. The air duct components of the two schemes are processed, and a comparative installation test is carried out on site. By regularly checking the dust accumulation thickness at the bend of the air duct, monitoring the change rate of ventilation area, and the ventilation resistance at the inlet and outlet of the coal mill, the dust accumulation prevention effect is evaluated, the optimal structural scheme is determined, and the dust accumulation thickness is ≤1mm, the ventilation area is reduced by ≤3%, and the air duct blockage and ventilation efficiency reduction caused by dust accumulation are avoided.

4. The method for adapting and adjusting the airflow field of a coal mill according to claim 3, characterized in that: The specific process of step four is as follows: when the pulverizing load increases from 50% to 100% and the primary air pressure increases from 4.5 kPa to 6.8 kPa, the flow resistance is made to change linearly and smoothly by adjusting the structural parameters of the throttling plate. The differential pressure fluctuation of the coal mill inlet and outlet is monitored by on-site test to ensure that the differential pressure fluctuation is controlled within 0.5 kPa under different loads, so as to achieve synergistic optimization of primary air energy consumption and pulverizing efficiency and reduce the additional increase in primary air fan power consumption.