Optimization method for combustion fan system of heating furnace

Abstract

The invention relates to the technical field of combustion fan systems, in particular to an optimization method of a heating furnace combustion fan system. Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects that according to an existing header pipe air supply mode, an air supply header pipe is replaced by a column pipe, two combustion fans are connected in parallel and then directly enter the hot blast stove through a header pipe, and the two fans operate at variable frequencies at the same time; the problem of flow field interference during parallel operation of a plurality of fans is effectively reduced, a heating furnace combustion fan system is reasonably optimized, and energy consumption is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of combustion-supporting fan systems, and in particular to an optimization method for a combustion-supporting fan system of a heating furnace. Background Art

[0002] At present, hot rolling mills and thick plate mills in the steel industry are generally equipped with 2 to 4 walking beam heating furnaces. The original design equipped each heating furnace with two combustion-supporting fans, one for use and one for standby, for 24-hour continuous operation. However, considering the continuity of hot rolling production, if a single heating furnace adopts the operation mode of one combustion-supporting fan for use and one for standby, when the combustion-supporting fan in service fails and stops, it will take about 15 to 20 seconds for the other combustion-supporting fan to start up and reach the air volume and air pressure required for the production and operation of the heating furnace. The furnace head will lose pressure, which may cause the heating furnace to stall, and have a serious impact on the smooth operation of the furnace. Therefore, the current design of the combustion-supporting fan system of the heating furnace adopts the method of mother pipe control to centrally supply air to the heating furnace.

[0003] According to the production situation of the heating furnace, the number of fans in the parallel system is turned on and off to match the combustion-supporting air volume and furnace head pressure required by the system. However, due to the flow field interference phenomenon in the main pipe, the difference in the fan flow in the parallel system, and the relatively steep resistance characteristics of the heating furnace combustion-supporting air system, the air supply capacity of the main pipe in the parallel system will be significantly less than the sum of the air supply capacities of the single fan equipment in the parallel system, causing the operation mode of the heating furnace combustion-supporting fan equipment to deviate from the preset equipment operation mode, especially when the production rhythm of the heating furnace fluctuates, the impact is more obvious, thereby affecting the overall energy consumption of the fan unit.

[0004] The mutual interference of flow fields in the combustion-supporting fan parallel system is a prominent problem affecting the energy consumption and reliability of the combustion-supporting fan operation. Summary of the invention

[0005] The purpose of the present invention is to solve the deficiencies of the prior art and provide an optimization method for adopting pipe-line control to supply air, wherein two combustion-supporting fans are connected in parallel and directly enter the hot blast furnace through a main pipe, and the two fans are operated at variable frequency at the same time.

[0006] To achieve the above object, the present invention provides a method for optimizing a combustion-supporting fan system of a heating furnace, and the specific steps are as follows:

[0007] S1. Simulate the combustion air system in the main pipe and obtain data;

[0008] S2. Summarize and analyze the data in step S1 and organize the data;

[0009] S3. Simulate the combustion air system in the column control and obtain data;

[0010] S4. Re-determine the appropriate operating parameters of the combustion-supporting fan equipment according to the process parameter requirements of the heating furnace system for the combustion-supporting air in the column control;

[0011] S5. Determine the variable frequency constant pressure control scheme for the combustion-supporting fan system.

[0012] Preferably, the step S1 further comprises the following steps:

[0013] S11. Conduct three-dimensional modeling of the actual situation of the ventilation system pipes in the existing main pipe system;

[0014] S12. Meshing the three-dimensional model in S11, and then setting boundaries in the meshed geometric model.

[0015] Preferably, the boundaries described in step S12 include a fluid inlet boundary, a fluid outlet boundary and a given pressure boundary.

[0016] Preferably, the step S2 further includes a step S21, and the step S21 is specifically as follows:

[0017] S21. Perform iterative calculations on the meshed geometric model according to the boundary conditions to obtain the corresponding pressure distribution diagram.

[0018] Preferably, the step S3 specifically comprises adopting the methods in steps S1 and S2 to obtain the corresponding pressure distribution diagram under column control.

[0019] Preferably, the step S5 is specifically as follows: the air supply volume of a single combustion-supporting fan is defined as 85% to 92% of the total combustion-supporting air volume required by a single heating furnace; and the pressure value of a single combustion-supporting fan is 9 to 11 kPa.

[0020] Compared with the prior art, the technical solution proposed in this application has the following beneficial effects: the existing main pipe air supply method is replaced by a series pipe system instead of a main pipe system, in which two combustion-supporting fans are connected in parallel and directly enter the hot blast furnace through a main pipe. The two fans are operated at variable frequency at the same time, which effectively reduces the flow field interference problem when multiple fans are operated in parallel, and reasonably optimizes the combustion-supporting fan system of the heating furnace, thereby reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0022] Figure 1 This is the outlet pipeline diagram of the mother pipe fan in the present invention;

[0023] Figure 2 This is the mother tube pressure distribution diagram of the present invention;

[0024] Figure 3The present invention lists and controls the fan outlet pipeline diagram;

[0025] Figure 4 The following is a pressure distribution diagram of the control system of the present invention. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe and discuss the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings of the present invention. Obviously, what is described here is only a part of the examples of the present invention, not all the examples. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may also be a component centered. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may also be a component centered. When a component is considered to be "set on" another component, it may be directly set on the other component or there may also be a component centered. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0029] A practical and feasible optimization method for the combustion-supporting fan system of a heating furnace involves the following four points: 1. First, simulate and analyze the pressure distribution and flow field of the combustion-supporting air system in the mother pipe to understand the mutual interference problem of the flow field in the mother pipe; 2. Secondly, simulate and analyze the pressure distribution and flow field of the combustion-supporting air system in the column pipe to understand the situation after the flow field in the column pipe is optimized and clarify the data range after the pressure of the pipe network is reduced; 3. According to the process parameter requirements of the heating furnace system for combustion-supporting air in the column pipe, redefine the appropriate design parameters of the combustion-supporting fan equipment and the capacity configuration of the prime mover; 4. Determine the variable frequency constant pressure control scheme of the combustion-supporting fan system, and compare the operating energy consumption of the combustion-supporting fan unit on the premise of ensuring the stable and reliable operation of the heating furnace.

[0030] 1. Simulate and analyze the pressure distribution and flow field of the combustion air system in the mother pipe to understand the mutual interference problem of the flow field in the mother pipe.

[0031] For the actual situation of the ventilation system pipes in the existing main pipe, firstly, an accurate geometric model is established in the SOLIDWORKS 3D coordinate system according to the actual size. Figure 1 ; Secondly, mesh the established geometric model; then set the boundaries of the meshed geometric model in FLUENT, including the fluid inlet boundary, fluid outlet boundary and given pressure boundary; finally, iterate the meshed geometric model according to the boundary conditions, and obtain the following Figure 2 The pressure distribution diagram of the main pipe is shown. It can be seen that there is obvious airflow interference in the main pipe system, and the kinetic energy loss is large, resulting in the flow rate from the main pipe to the combustion-supporting air ducts of the two heating furnaces only reaching 9-11m / s, which is significantly lower than the required airflow speed of 13-15m / s.

[0032] 2. Simulate and analyze the pressure distribution and flow field in the combustion-supporting air system in the pipe train control system to understand the situation after the flow field in the pipe train control system is optimized and to clarify the data range after the pressure of the pipe network is reduced.

[0033] Repeat the steps in point 1 to model the column-mounted airflow system (see Figure 3 ), gridding and flow field analysis, and finally the following is obtained: Figure 4 The pressure distribution diagram of the row pipe is shown. It can be seen that the pressure distribution field in the row pipe is relatively uniform, and the flow rate sent to the combustion-supporting air ducts of the two heating furnaces reaches 13-15m / s, which is more than 35% higher than that of the main pipe system. This is mainly because the pipe network resistance in the row pipe is reduced by 800-1200Pa compared with the main pipe, and the air supply capacity is effectively improved.

[0034] 3. Based on the process parameter requirements of the heating furnace system for combustion-supporting air in the column control, redetermine the appropriate design parameters of the combustion-supporting fan equipment and the prime mover capacity configuration.

[0035] The series-pipe-controlled combustion-supporting air system in the present invention is composed of two combustion-supporting fans connected in parallel and directly entering the hot blast furnace through a main pipe. The two fans are operated at variable frequency at the same time, which not only reduces the flow field interference problem when multiple fans are operated in parallel, but also solves the problem of possible decompression and flameout of the heating furnace when a single fan equipment fails and stops because the two fans are operated in parallel.

[0036] Selection of air supply volume for a single combustion-supporting fan:

[0037] It is designed according to 85% to 92% of the total combustion-supporting air volume required for a single heating furnace.

[0038] Selection of pressure value for a single combustion-supporting fan:

[0039] Since the resistance of the combustion-supporting air duct drops by 800-1200Pa, the furnace head pressure of the heating furnace is generally required to reach 8-10kPa. As a result, the resistance of the combustion-supporting air outlet total pipe drops from the previous 10-12kPa to 9-11kPa.

[0040] 4. Determine the variable frequency constant pressure control scheme for the combustion-supporting fan system, and compare the operating energy consumption of the combustion-supporting fan unit while ensuring the stable and reliable operation of the heating furnace.

[0041] In the column pipe control system of the present invention, the combustion-supporting blower of the heating furnace adopts two parallel arrangements to supply air to the heating furnace. Due to the change of the production load of the heating furnace, and considering various situations such as hot loading and cold loading of slabs, roll replacement and rolling line failure, and heating furnace insulation, the demand of the heating furnace for the combustion-supporting air volume will change, and the pressure of the combustion-supporting air pipeline and the furnace head pressure will also change accordingly. According to the needs of the heating furnace control parameters, the furnace head pressure needs to be maintained in the pressure range of 8 to 10 kPa, and the pressure of the combustion-supporting air outlet pipeline is in the range of 9 to 11 kPa, and it is controlled to operate near the lower limit of 9 kPa as much as possible. When the inlet regulating door is used to adjust the air volume of the combustion-supporting blower, it will cause the inlet regulating door of the combustion-supporting blower to be adjusted to a smaller opening when the heating furnace is under low load. Even so, it will still cause excess air, and the air volume is greater than the hot air volume required by the heating furnace and must be released. Since the position of the air release pipe is behind the heat exchanger, it can only release hot air, resulting in a certain heat loss, increasing the gas unit consumption of the heating furnace, and wasting energy. In view of this situation, the controlled object of the combustion-supporting fan is changed from the inlet regulating gate to the variable frequency regulating fan motor speed, so as to realize the variable frequency constant pressure control of the combustion-supporting fan and save the valve throttling loss when the fan is originally adjusted by valve.

[0042] Variable frequency constant pressure control process: When the heating furnace's demand for combustion air volume changes, the pressure in the cold air duct changes accordingly, and the output signal of the pressure sensor installed on the cold air duct also changes accordingly, which is used as feedback to be compared with the given value. If it is negative, the output frequency of the inverter will increase after automatic processing by the PID unit in the inverter, and the motor speed will also increase until the wind pressure is balanced with the set wind pressure and the motor speed remains constant. If the comparison signal value is positive, on the contrary, the motor speed slows down, and after the pipeline pressure is reduced to the set wind pressure, the motor speed drops to a certain value and no longer changes. In this way, a closed-loop constant pressure variable frequency speed regulation system is formed, which realizes constant pressure air supply for combustion air and ensures that the automatic optimization furnace burning system works at the optimal working point. Specific implementation example:

[0043] 1. Situation analysis under parent control conditions

[0044] A steel enterprise has two walking beam heating furnaces and four combustion-supporting fans. The design air volume of each combustion-supporting fan is Q=62100m 3 / h, design full pressure P t=12480Pa, medium temperature t=20℃, medium density ρ=1.2kg / m 3 , design speed n = 1450rpm. Motor YXKK4503-4 10kV 4P 400kW I e =28.7A.

[0045] Using offline testing technology, the actual operating data of the combustion-supporting fan under mother pipe control conditions are as follows:

[0046] The maximum gas consumption of the two heating furnaces in actual production is 55,000 Nm 3 / h, the air consumption needs to reach 110000m 3 / h, and the air-fuel ratio is 2:1.

[0047] During normal production, a three-in-one standby mode is required. At this time, the inlet regulating door opening of each combustion-supporting fan is between 30% and 45%, the average operating current of a single motor is about 14A, and the combustion-supporting air outlet pipe resistance is maintained at around 10 to 12 kPa to ensure the furnace heating temperature and pressure requirements.

[0048] The energy consumption data of the combustion-supporting fan unit under the mother control condition are as follows:

[0049] Under the mother control condition, three combustion-supporting fans are running at the same time. The average operating current of a single combustion-supporting fan is about 14A, and the motor operating power factor is 0.82. The actual power consumption of a single fan during operation can be obtained as:

[0050]

[0051] Calculated based on 8,500 operating hours per year, the annual operating power consumption of a single combustion-supporting fan is approximately 1.7 million kWh of electricity, and the total annual operating power consumption of the combustion-supporting fan unit (three combustion-supporting fans) is 5.1 million kWh of electricity.

[0052] 2. Situation analysis under the listed control conditions

[0053] Under the control conditions, four combustion-supporting fans are still configured, and two combustion-supporting fans supply air to one heating furnace. The design air volume of a single combustion-supporting fan is Q = 50000m 3 / h (Based on the total combustion air volume required for a single heating furnace of 55000m 3 / h 85% ~ 92%), design total pressure P t =11000Pa, medium temperature t=20℃, medium density ρ=1.2kg / m 3 , design speed n = 1450rpm. Motor YXKK355-4 10kV 4P 220kW I e =16.5A.

[0054] When two combustion-supporting fans are connected in parallel and run at variable frequency at the same time, the air volume of the parallel main pipe is generally not less than 1.1 of the air volume of a single combustion-supporting fan. The combustion-supporting air volume after the parallel main pipe is 50000×1.1=55000m 3 / h, and the maximum combustion-supporting air volume required for a single heating furnace is 55000m 3 / h matches.

[0055] Using offline testing technology, the actual operating data of the combustion-supporting fan under the following control conditions are obtained:

[0056] In normal production, four combustion-supporting fans are operated at the same time with variable frequency, supplying air to two heating furnaces independently. At this time, the inlet regulating door of each combustion-supporting fan is fully open, and the motor operating frequency is adjusted between 39 and 47 Hz. The average operating current of a single motor is about 7.5A, and the resistance of the combustion-supporting air outlet pipe is maintained at about 9 to 11 kPa, which can ensure the furnace heating temperature and pressure requirements.

[0057] The energy consumption data of the combustion-supporting fan unit under the following control conditions are as follows:

[0058] Under the mother control condition, four combustion-supporting fans are operated at the same time with variable frequency speed regulation. The average operating current of a single combustion-supporting fan is about 7.5A, and the motor operating power factor is 0.97 (after inverter compensation). The actual power consumption of a single fan during operation can be obtained as:

[0059]

[0060] Calculated based on 8,500 operating hours per year, the annual operating power consumption of a single combustion-supporting fan is approximately 1.07 million kWh of electricity, and the total annual operating power consumption of the combustion-supporting fan unit (four combustion-supporting fans) is 4.28 million kWh of electricity.

[0061] 3. Analysis of energy consumption under column control conditions relative to parent control conditions

[0062] Under the column control condition, two optimized combustion-supporting fans are used to operate with variable frequency to supply air to one heating furnace at the same time, and a total of four combustion-supporting fans are operated with variable frequency for the two heating furnaces; under the mother control condition, four fans are configured, and three fans are operated simultaneously to supply air to the two heating furnaces. The annual total power consumption under the column control condition is reduced by 820,000 kWh compared with the annual total power consumption under the mother control condition, and the power saving rate is greater than 15%.

[0063] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and one or more of the above embodiments are combined into one embodiment. Those skilled in the art can make various changes or modifications or combinations within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other at will.

Claims

1. A method for optimizing a combustion-supporting fan system of a heating furnace, characterized in that: Eliminate the main pipe air supply method in the combustion-supporting air supply system of the heating furnace; The existing main pipe air supply mode is replaced by a tube-and-tube air supply mode to reduce the obvious mutual interference of airflow when multiple fans are running at the same time in the main pipe mode. The tube-and-tube mode consists of two combustion-supporting fans running in parallel to supply air to the heating furnace through a main pipe. The two combustion-supporting fans are operated at variable frequency at the same time, and the combustion-supporting air volume is adjusted according to changes in system demand to achieve variable frequency constant pressure control of the combustion-supporting fans. The specific steps are as follows: S1. Simulate the combustion air system in the main pipe and obtain data; S2. Summarize and analyze the data in step S1 and organize the data; S3. Simulate the combustion air system in the column control and obtain data; S4. Re-determine the appropriate operating parameters of the combustion-supporting fan equipment according to the process parameter requirements of the heating furnace system for the combustion-supporting air in the column control; S5. Determine the variable frequency constant pressure control scheme for the combustion-supporting fan system.

2. The optimization method of a heating furnace combustion-supporting fan system according to claim 1, characterized in that: The step S1 further comprises the following steps: S11. Conduct three-dimensional modeling of the actual situation of the ventilation system pipes in the existing main pipe system; S12. Meshing the three-dimensional model in S11, and then setting boundaries in the meshed geometric model.

3. The optimization method of a heating furnace combustion-supporting fan system according to claim 2, characterized in that: The boundaries described in step S12 include a fluid inlet boundary, a fluid outlet boundary and a given pressure boundary.

4. The optimization method of a heating furnace combustion-supporting fan system according to claim 3, characterized in that: The step S2 also includes a step S21, and the step S21 is specifically as follows: S21. Perform iterative calculations on the meshed geometric model according to the boundary conditions to obtain the corresponding pressure distribution diagram.

5. The method for optimizing a heating furnace combustion-supporting fan system according to claim 4, characterized in that: Specifically, the step S3 adopts the method in steps S1 and S2 to obtain the corresponding pressure distribution diagram under the column control.

6. The optimization method of a heating furnace combustion-supporting fan system according to claim 1, characterized in that: The step S5 is specifically as follows: the air supply volume of a single combustion-supporting fan is defined as 85% to 92% of the total combustion-supporting air volume required by a single heating furnace; and the pressure value of a single combustion-supporting fan is 9 to 11 kPa.

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