Combustion control system of fluidized bed roasting furnace and control method of combustion control system

Abstract

The invention belongs to the field of industrial furnace combustion control, and relates to a combustion control system of a fluidized bed roasting furnace and a control method thereof. The combustion control system comprises a fuel gas pipeline and an air pipeline which are connected to the hearth, and the fuel gas pipeline is provided with an air-fuel proportional valve used for adjusting the fuel gas flow to change the ratio of fuel gas to air. One end of the pressure guide branch is connected to the air-fuel proportional valve, and the other end is connected to the air pipeline; a throttling orifice plate is arranged on the pressure guide branch to reduce the impact of high-temperature air on the air-fuel proportional valve; one end of the adjusting branch is connected to the pressure guiding branch, and the other end of the adjusting branch is completely opened to allow high-temperature air in the pressure guiding branch to be discharged into the external environment, so that adjusting proportion fluctuation, caused by air temperature rising, of the air-fuel proportional valve is compensated. Based on the combustion control system and the control method provided by the invention, under the condition that the back pressure of the hearth continuously changes, the high-temperature combustion-supporting air and the fuel gas can always keep a stable proportion in the combustion process, so that the stability and the timeliness of temperature regulation are enhanced.

Description

Technical Field

[0001] The invention belongs to the field of industrial furnace combustion control and relates to a combustion control system of a fluidized bed roasting furnace and a control method thereof. Background Art

[0002] As an efficient and flexible heating equipment, fluidized bed roaster plays a vital role in many important industrial fields such as non-ferrous metallurgy, casting and solid waste treatment. However, traditional fluidized bed roaster has many shortcomings in combustion control and temperature regulation, which has become a key factor restricting its further development and application.

[0003] Specifically, the fluidized bed roasting furnaces currently on the market generally use a relatively rough combustion control system, which makes it difficult to achieve precise temperature and combustion efficiency control. This extensive control method not only leads to a large waste of energy, but also seriously affects the operating stability and economy of the roasting furnace. Taking a casting sand hot regeneration fluidized bed roasting furnace as an example, the furnace needs to maintain a high temperature environment of about 600°C or more during normal operation. However, in the actual operation process, due to the continuous fluctuation of the furnace pressure, especially the huge difference in furnace pressure between the empty furnace and the full load state, the traditional combustion control system is difficult to cope with.

[0004] In order to meet the stable operation requirements of the equipment at full load, the existing combustion control system usually sets the gas supply pressure at a higher level. However, when the furnace back pressure is low, this setting will cause the gas consumption to far exceed the theoretical value, resulting in unnecessary energy waste. In addition, most of the existing combustion control systems rely on the change of furnace temperature to adjust the flow of combustion air through PID, and adjust the gas flow proportionally according to the feedback value of the air flow to control the furnace temperature. However, this control method has obvious hysteresis. When the combustion air flow changes instantaneously, the adjustment of the gas flow often cannot keep up in time, resulting in a significant reduction in the temperature control accuracy. For example, when it is necessary to increase the combustion air flow to increase the furnace temperature, due to the lag in the change of gas supply, the low-temperature combustion air will enter the furnace and cause the furnace temperature to drop. At the same time, the increase in gas supply will also cause the furnace back pressure to rise, further reducing the gas supply, thereby exacerbating the problem of control accuracy.

[0005] In summary, in view of the influence of furnace back pressure fluctuation, temperature control stability and timeliness problems existing in the combustion control system of the fluidized bed roasting furnace, it is urgent to develop a new type of combustion control system and combustion control method to improve the operation economy and stability of the roasting furnace. Summary of the invention

[0006] In view of this, the object of the present invention is to provide a combustion control system and a control method for a fluidized bed roasting furnace, which can achieve a stable ratio of high-temperature combustion air and fuel gas during the combustion process when the furnace back pressure continuously changes, thereby enhancing the stability and timeliness of temperature regulation.

[0007] To achieve the above-mentioned purpose, the present invention provides a combustion control system for a fluidized bed roasting furnace, comprising a gas pipeline and an air pipeline respectively connected to a furnace, an air-fuel ratio valve being arranged on the gas pipeline; one end of a pressure-conducting branch is connected to the air-fuel ratio valve, and the other end is connected to the air pipeline; a throttling orifice is arranged on the pressure-conducting branch to reduce the impact of high-temperature air in the air pipeline on the air-fuel ratio valve; one end of a regulating branch is connected to the pressure-conducting branch, and the other end is connected to the external environment to allow the high-temperature air in the pressure-conducting branch to be discharged into the external environment, thereby compensating for the fluctuation of the regulating ratio of the air-fuel ratio valve caused by the increase in air temperature.

[0008] Optionally, along the gas flow direction, a first pressure regulating valve and a second pressure regulating valve are provided on the gas pipeline, the first pressure regulating valve and the second pressure regulating valve are located before the air-fuel ratio valve, one end of the ignition branch is connected between the first pressure regulating valve and the second pressure regulating valve, and the other end is connected after the air-fuel ratio valve.

[0009] Optionally, a third pressure regulating valve is provided on the ignition branch, and one end of the furnace pressure feedback branch is connected to the furnace, and the other end is connected to the second pressure regulating valve and the third pressure regulating valve respectively, so as to feedback the furnace pressure to the gas pipeline and the ignition branch, and dynamically adjust the gas supply pressure through the first pressure regulating valve.

[0010] Optionally, a first solenoid valve and a second solenoid valve are provided between the second pressure regulating valve and the air-fuel ratio valve, and an opening speed of the second solenoid valve is lower than an opening speed of the first solenoid valve.

[0011] Optionally, along the gas flow direction, a third solenoid valve, a fourth solenoid valve and a first manual fine adjustment valve are sequentially arranged after the third pressure regulating valve of the ignition branch, and an opening speed of the fourth solenoid valve is lower than an opening speed of the third solenoid valve.

[0012] Optionally, a fifth solenoid valve and a second manual fine adjustment valve are provided on the regulating branch.

[0013] Optionally, a combustion-supporting fan, a heat exchanger and an electric regulating valve are provided on the air pipeline.

[0014] Optionally, along the gas flow direction, the gas pipeline is provided with a manual ball valve, a filter, a pressure gauge and a flow meter in sequence before the first pressure regulating valve.

[0015] Optionally, the pressure-conducting branch is a capillary copper tube with a diameter not exceeding 8 mm, and a part of the capillary copper tube has a spiral coil.

[0016] Based on the above-mentioned combustion control system of the fluidized bed roasting furnace, the present invention also provides a control method of the combustion control system of the fluidized bed roasting furnace, comprising the following steps:

[0017] Ignition start: Close the gas pipeline after the first pressure regulating valve, open the air pipeline and ignition branch to ignite the burner in the furnace.

[0018] Successful start-up and normal operation: When the burner is burning stably, close the ignition branch, open the entire gas pipeline, and supply gas and air to the furnace;

[0019] When the air temperature in the air pipeline exceeds the rated operating temperature of the air-fuel ratio valve, the regulating branch is opened to discharge part of the high-temperature air to compensate for the fluctuation of the regulating ratio of the air-fuel ratio valve caused by the increase in air temperature.

[0020] The beneficial effects of the present invention are:

[0021] First, the present invention effectively solves the temperature control hysteresis and inaccuracy problems existing in the PID adjustment method by introducing an air-fuel ratio valve and an improved pressure-conducting branch. Compared with the traditional PID method of adjusting the combustion air flow, the introduction of the air-fuel ratio valve enables the gas flow to match the combustion air flow in real time, which greatly reduces the hysteresis effect in the temperature adjustment process, improves the accuracy of temperature control, and reduces the consumption of gas. When it is necessary to increase the combustion air flow to increase the furnace temperature, the air-fuel ratio valve can respond quickly and increase the gas flow synchronously to prevent the temperature drop caused by the delay in the gas supply, thereby avoiding the instability of the furnace temperature caused by the lag in the gas supply change.

[0022] In addition, since the pressure of the air pipeline changes significantly under high temperature conditions, the present invention stabilizes the pressure in the pressure pipe by adding a throttling orifice plate at the connection between the pressure pipe and the air pipeline, further reducing the pressure impact of high-temperature air on the proportional valve and ensuring the stability of the combustion process. At the same time, the present invention also adds a regulating branch with a solenoid valve and a manual fine-adjustment valve to the pressure pipe. This design allows the solenoid valve to be opened and part of the gas to be discharged using the manual fine-adjustment valve when the temperature of the combustion air exceeds the normal operating temperature, thereby compensating for the problem of proportional valve adjustment misalignment caused by temperature increase. This method not only achieves constant proportional control of the outlet pressure of the air-fuel proportional valve and the air control pressure under the condition of preheating the combustion air, but also, compared with the traditional flow feedback control method, each air branch can reduce an air flow meter with temperature and pressure compensation, thereby reducing equipment costs and simplifying the control system.

[0023] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0025] Figure 1 A schematic structural diagram of a combustion control system for a fluidized bed roasting furnace provided by the present invention.

[0026] Figure markings: 1-gas pipeline; 11-filter; 12-flow meter; 13-first pressure regulating valve; 14-second pressure regulating valve; 15-first solenoid valve; 16-second solenoid valve; 17-air-fuel ratio valve; 2-air pipeline; 21-combustion-supporting fan; 22-heat exchanger; 23-electric regulating valve; 3-ignition branch 31-third pressure regulating valve; 32-third solenoid valve; 33-fourth solenoid valve; 34-first manual fine-adjusting valve; 4-pressure branch; 41-throttling orifice; 5-adjusting branch; 51-fifth solenoid valve; 52-second manual fine-adjusting valve; 6-furnace pressure feedback branch; 7-furnace; 71-burner; 8-manual ball valve; 9-pressure gauge; 10-pressure switch. DETAILED DESCRIPTION

[0027] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0028] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0029] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0030] The present invention aims to provide a combustion control system and a control method for a fluidized bed roasting furnace, so as to solve the problems of unstable combustion control, high energy consumption and delayed temperature regulation caused by back pressure fluctuation of the furnace 7 in the prior art.

[0031] like Figure 1 As shown, the combustion control system of the fluidized bed roasting furnace provided by the present invention includes a gas pipeline 1 and an air pipeline 2, which are respectively connected to the burner 71 of the furnace 7. An air-fuel ratio valve 17 for adjusting the gas flow to change the ratio of gas and air is provided on the gas pipeline 1. By introducing the air-fuel ratio valve 17, the real-time matching of the gas flow and the combustion-supporting air flow is achieved, thereby greatly reducing the lag effect in the temperature adjustment process and improving the accuracy of temperature control. When it is necessary to increase the combustion-supporting air flow to increase the furnace temperature, the air-fuel ratio valve 17 can respond quickly and increase the gas flow synchronously to prevent the temperature drop caused by the delay in gas supply, thereby avoiding the instability of the furnace temperature.

[0032] One end of the pressure-conducting branch 4 is connected to the air-fuel ratio valve 17, and the other end is connected to the air pipeline 2. In order to further optimize the working performance of the combustion control system, a throttling orifice 41 is provided on the pressure-conducting branch 4 to reduce the impact of the high-temperature air in the air pipeline 2 on the air-fuel ratio valve 17. The throttling orifice 41 is used to stabilize the pressure in the pressure-conducting pipe, further reducing the pressure impact of the high-temperature air on the ratio valve, and ensuring the stability of the combustion process. Further, an adjustment branch 5 is provided on the pressure-conducting branch 4, one end of the adjustment branch 5 is connected to the pressure-conducting branch 4, and the other end is connected to the external environment, so as to allow the high-temperature air in the pressure-conducting branch 4 to be discharged to the external environment, thereby compensating for the fluctuation of the adjustment ratio of the air-fuel ratio valve 17 caused by the increase in air temperature. When the temperature of the combustion-supporting air exceeds the rated operating temperature of the air-fuel ratio valve 17, the adjustment branch 5 can discharge part of the high-temperature air, so as to realize the constant ratio control of the outlet pressure of the air-fuel ratio valve 17 and the air control pressure under the condition of preheating the combustion-supporting air, thereby further improving the combustion efficiency and the stability of temperature control.

[0033] Furthermore, the first pressure regulating valve 13 and the second pressure regulating valve 14 are sequentially arranged on the gas pipeline 1 along the gas flow direction, and the first pressure regulating valve 13 and the second pressure regulating valve 14 are arranged before the air-fuel ratio valve 17. One end of the ignition branch 3 is connected between the first pressure regulating valve 13 and the second pressure regulating valve 14, and the other end is connected to the back of the air-fuel ratio valve 17. The third pressure regulating valve 31 is arranged on the ignition branch 3, and one end of the furnace pressure feedback branch 6 is connected to the furnace 7, and the other end is connected to the second pressure regulating valve 14 and the third pressure regulating valve 31, so as to feedback the furnace 7 pressure to the gas pipeline 1 and the ignition branch 3. When the back pressure of the furnace 7 fluctuates, the gas supply pressure of the gas is dynamically adjusted by the first pressure regulating valve 13 to ensure that the pressure of the burner 71 during the ignition stage or normal operation is within a stable and economic pressure range, thereby reducing the gas consumption during the empty furnace heating stage.

[0034] In order to ensure the safety and reliability of the combustion system, a first solenoid valve 15 and a second solenoid valve 16 are arranged between the second pressure regulating valve 14 and the air-fuel ratio valve 17, and the opening speed of the second solenoid valve 16 is lower than the opening speed of the first solenoid valve 15. Further preferably, the first solenoid valve 15 is a fast-opening solenoid valve with an opening time of less than 1s and a closing time of less than 1s, and the second solenoid valve 16 is a slow-opening solenoid valve with an opening time of less than 15s and a closing time of less than 1s, so as to ensure that when the gas pipeline 1 system is opened, the gas can be slowly supplied into the furnace 7, so as to avoid a large amount of gas being instantly supplied into the furnace 7 and causing excessive furnace pressure fluctuations, so that the burner 71 can be smoothly ignited and transition to a stable combustion stage.

[0035] In some possible implementations, along the gas flow direction, a manual ball valve 8, a filter 11, a pressure gauge 9 and a flow meter 12 are sequentially arranged on the gas pipeline 1 before the first pressure regulating valve 13; a third solenoid valve 32, a fourth solenoid valve 33 and a first manual fine adjustment valve 34 are sequentially arranged on the ignition branch 3 after the third pressure regulating valve 31, and a combustion-supporting fan 21, a heat exchanger 22 and an electric regulating valve 23 are arranged on the air pipeline 2. A fifth solenoid valve 51 and a second manual fine adjustment valve 52 are arranged on the regulating branch 5 to control the on-off of the regulating branch 5. The opening speed of the fourth solenoid valve 33 is less than the opening speed of the third solenoid valve 32. It is further preferred that the third solenoid valve 32 is a fast-opening solenoid valve with an opening time of less than 1s and a closing time of less than 1s, and the fourth solenoid valve 33 is a slow-opening solenoid valve with an opening time of less than 15s and a closing time of less than 1s.

[0036] In some possible implementations, the pressure-conducting branch 4 is a capillary copper tube with a diameter not exceeding 8 mm, which has a spiral coil in part to cooperate with the throttling orifice plate 41 to alleviate the flow impact of high-temperature air and reduce the air temperature to a certain extent.

[0037] In some possible implementations, a pressure gauge 9 is arranged between the filter 11 and the flow meter 12 of the gas pipeline 1; a pressure gauge 9 and a pressure switch 10 are arranged between the second pressure regulating valve 14 and the first solenoid valve 15 of the gas pipeline 1; a pressure switch 10 is arranged between the first solenoid valve 15 and the second solenoid valve 16 of the gas pipeline 1; a pressure gauge 9 and a pressure switch 10 are arranged on the pipeline of the gas pipeline 1 after the air-fuel ratio valve 17; a pressure gauge 9 and a pressure switch 10 are arranged between the combustion-supporting fan 21 and the heat exchanger 22 of the air pipeline 2.

[0038] In some possible implementations, a manual ball valve 8 is provided between the first pressure regulating valve 13 and the second pressure regulating valve 14 of the gas pipeline 1 , and a manual ball valve 8 is provided before the third pressure regulating valve 31 of the ignition branch 3 .

[0039] Based on the above-mentioned combustion control system of the fluidized bed roasting furnace, the present invention also provides a control method of the combustion control system of the fluidized bed roasting furnace, comprising the following steps:

[0040] Step S1, ignition start: close the portion of the gas pipeline 1 after the first pressure regulating valve 13, open the air pipeline 2 and the ignition branch 3 to ignite the burner 71 of the furnace 7;

[0041] Step S2: Successful startup and normal operation: When a stable flame signal appears at the burner 71 , the ignition branch 3 is closed, the entire gas pipeline 1 is opened, and gas and air are supplied to the furnace 7 .

[0042] Specifically, in step S1, the combustion-supporting blower 21 is first turned on to purge all pipelines, and then the gas pipeline 1 is safely leak-checked. After the gas pipeline 1 is safely leak-checked, the manual ball valve 8 at the front end of the gas pipeline 1 and the manual ball valve 8 of the ignition branch 3 are opened, and the manual ball valve 8 between the first pressure regulating valve 13 and the second pressure regulating valve 14 is closed, and at the same time, the electric regulating valve 23 of the air pipeline 2 is opened to the opening required in the ignition stage to ignite the furnace burner 71.

[0043] In step S2, a flame detector (not shown in the figure) is provided at the burner 71. When the flame detector detects a stable flame signal, it indicates that the roasting furnace has been successfully ignited and started. At this time, the ignition branch 3 is closed, and the manual ball valve 8 between the first pressure regulating valve 13 and the second pressure regulating valve 14 is opened to make the gas pipeline 1 unobstructed. The air pipeline 2 remains open to supply gas and air to the furnace 7.

[0044] During normal operation, when the air temperature in the air pipeline 2 exceeds the rated operating temperature of the air-fuel ratio valve 17 (usually 60°C), the regulating branch 5 is opened to discharge part of the high-temperature air to compensate for the fluctuation of the regulating ratio of the air-fuel ratio valve 17 caused by the increase in air temperature.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A combustion control system for a fluidized bed roasting furnace, characterized in that: It comprises a gas pipeline (1) and an air pipeline (2) respectively connected to a furnace (7), wherein an air-fuel ratio valve (17) is arranged on the gas pipeline (1); one end of a pressure-conducting branch (4) is connected to the air-fuel ratio valve (17), and the other end is connected to the air pipeline (2); One end of the regulating branch (5) is connected to the pressure-conducting branch (4), and the other end is connected to the external environment, so as to allow the high-temperature air in the pressure-conducting branch (4) to be discharged to the external environment, thereby compensating for the fluctuation of the regulating ratio of the air-fuel ratio valve (17) caused by the increase in air temperature.

2. The combustion control system according to claim 1, characterized in that: Along the gas flow direction, the gas pipeline (1) is provided with a first pressure regulating valve (13) and a second pressure regulating valve (14) in sequence, wherein the first pressure regulating valve (13) and the second pressure regulating valve (14) are arranged before the air-fuel ratio valve (17), and one end of the ignition branch (3) is connected between the first pressure regulating valve (13) and the second pressure regulating valve (14), and the other end is connected after the air-fuel ratio valve (17).

3. The combustion control system according to claim 2, characterized in that: The ignition branch (3) is provided with a third pressure regulating valve (31); one end of the furnace pressure feedback branch (6) is connected to the furnace (7), and the other end is connected to the second pressure regulating valve (14) and the third pressure regulating valve (31) respectively, so as to feed back the furnace (7) pressure to the gas pipeline (1) and the ignition branch (3), and dynamically adjust the gas supply pressure through the first pressure regulating valve (13).

4. The combustion control system according to claim 1, characterized in that: A first solenoid valve (15) and a second solenoid valve (16) are arranged between the second pressure regulating valve (14) and the air-fuel ratio valve (17); an opening speed of the second solenoid valve (16) is lower than an opening speed of the first solenoid valve (15).

5. The combustion control system according to claim 3, characterized in that: Along the gas flow direction, a third solenoid valve (32), a fourth solenoid valve (33) and a first manual fine adjustment valve (34) are sequentially arranged behind the third pressure regulating valve (31) of the ignition branch (3), and the opening speed of the fourth solenoid valve (33) is lower than the opening speed of the third pressure regulating valve (31).

6. The combustion control system according to any one of claims 1 to 5, characterized in that: The regulating branch (5) is provided with a fifth solenoid valve (51) and a second manual fine-adjusting valve (52).

7. The combustion control system according to any one of claims 1 to 5, characterized in that: The air pipeline (2) is provided with a combustion-supporting fan (21), a heat exchanger (22) and an electric regulating valve (23).

8. The combustion control system according to any one of claims 2 to 5, characterized in that: Along the gas flow direction, the gas pipeline (1) is provided with a manual ball valve (8), a filter (11), a pressure gauge (9) and a flow meter (12) in sequence before the first pressure regulating valve (13).

9. The combustion control system according to any one of claims 1 to 5, characterized in that: The pressure-conducting branch (4) is a capillary copper tube with a diameter not exceeding 8 mm, and a part of the capillary copper tube has a spiral coil.

10. A control method for a combustion control system of a fluidized bed roasting furnace, based on the combustion control system of the fluidized bed roasting furnace according to claim 1, characterized in that: The following steps are involved: Ignition start: closing the portion of the gas pipeline (1) after the first pressure regulating valve (13), opening the air pipeline (2) and the ignition branch (3) to ignite the burner (71) of the furnace (7), Successful startup and normal operation: when the burner (71) burns stably, the ignition branch (3) is closed, the entire gas pipeline (1) is opened, and gas and air are supplied to the furnace (7); wherein, During operation, when the air temperature in the air pipeline (2) exceeds the rated operating temperature of the air-fuel ratio valve (17), the regulating branch (5) is opened to discharge part of the high-temperature air in the air pipeline (2) to compensate for the fluctuation of the regulating ratio of the air-fuel ratio valve (17) caused by the increase in air temperature.

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