Heating furnace hearth pressure adjusting method and system

Abstract

The invention discloses a heating furnace hearth pressure adjusting method and system, and relates to the technical field of industrial furnaces. The method comprises the steps that a smoke exhaust pipe is arranged at the tail of a heating furnace, smoke in a hearth is led out of the furnace, the temperature of discharged smoke is reduced to be lower than the target temperature through an air heat exchanger, an air mixing cooler is arranged in front of the air heat exchanger to provide protection, and the air mixing cooler is interlocked with the temperature of the smoke in front of the heat exchanger; a pneumatic furnace pressure adjusting valve is arranged on a smoke outlet pipe of the heat exchanger, the smoke outlet end of the furnace pressure adjusting valve is connected with an induced draft fan capable of adjusting the smoke exhaust air volume, a furnace pressure detecting element is arranged on the furnace top of the soaking section of the heating furnace, and the smoke exhaust air volume of the induced draft fan and the opening degree of the furnace pressure adjusting valve are adjusted according to the furnace pressure value. A cold mixing branch pipe is further connected to the pipeline between the furnace pressure regulating valve and the induced draft fan, a cold mixing air valve is arranged on the branch pipe, and the opening degree of the cold mixing air valve is interlocked with the flue gas temperature in front of the induced draft fan; the method is simple, reasonable, easy to implement, sensitive in adjustment, high in precision, wide in application range and capable of achieving wide-range precise adjustment of the hearth pressure.

Description

Technical Field

[0001] The invention relates to the technical field of industrial furnaces, and in particular to a method and system for regulating the furnace pressure of a heating furnace. Background Art

[0002] With the development of steel rolling technology, the technical indicators of heating furnaces are becoming more and more demanding, such as higher requirements for billet heating quality, energy saving and consumption reduction, environmental protection, etc. These high requirements have led to the iterative update of heating furnace combustion systems and their control methods, such as applying pulse control to conventional combustion systems. In actual application, pulse control has played a positive role in improving thermal efficiency and improving the uniformity of temperature field in the furnace. However, due to the discontinuity of pulse combustion, the furnace pressure will be unstable. For heating furnaces that use regenerative combustion, due to the regenerative reversing combustion method, each reversal has a very obvious impact on the furnace pressure of the heating furnace, resulting in a large range of furnace pressure fluctuations. Under this background, improving the furnace pressure control accuracy of the heating furnace has become a difficult problem.

[0003] The utility model patent with announcement number CN211645345U and name of Dynamic Optimization Control System of Furnace Pressure of Heating Furnace Based on Furnace Gas Volume discloses a scheme for adjusting the inlet valve of the induced draft fan and the speed change of the induced draft fan according to the furnace gas volume and furnace pressure. However, the inlet valve is the valve of the induced draft fan itself, and its purpose is to match the furnace gas volume. There is no actual improvement in the adjustment of the speed change of the induced draft fan. When facing a wide range of furnace pressure changes, the adjustment is stretched to its limits. In recent years, with the development of the domestic economy, the demand for special steel in various industries has increased significantly, and the special steel industry has become an important industrial foundation for the development of my country's manufacturing industry. For the heating furnace configured in the special steel production line, because the output range of the special steel heating furnace is large, the furnace pressure changes with the change of output, and the adjustment range becomes larger, which also puts forward high requirements for realizing wide-range and precise adjustment of the furnace pressure. Therefore, a method and system for adjusting the furnace pressure of a heating furnace are urgently needed to solve this problem. Summary of the invention

[0004] The object of the present invention is to provide a method and system for regulating furnace pressure of a heating furnace, so as to solve the problem that a smoke exhaust system needs to be improved in order to achieve wide range of furnace pressure regulation.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a method for regulating the furnace pressure of a heating furnace, comprising the following contents: a smoke exhaust pipe is arranged at the tail of the heating furnace to lead the smoke in the furnace out of the furnace, and the temperature of the smoke out of the furnace is reduced to below the target temperature through an air heat exchanger, and a cold air fan is arranged in front of the air heat exchanger to provide protection, and the cold air fan is interlocked with the smoke temperature in front of the heat exchanger; a pneumatic furnace pressure regulating valve is arranged on the smoke outlet pipe of the heat exchanger, and the smoke outlet end of the furnace pressure regulating valve is connected to an induced draft fan that can adjust the smoke exhaust air volume, and a furnace pressure detection element is arranged on the top of the heating furnace equalizing section, and the exhaust air volume of the induced draft fan and the opening of the furnace pressure regulating valve are adjusted according to the furnace pressure value; a cold air branch pipe is also connected to the pipeline between the furnace pressure regulating valve and the induced draft fan, and a cold air valve is provided on the branch pipe, and its opening is interlocked with the smoke temperature in front of the induced draft fan.

[0006] Preferably, the target temperature is 350°C, and the cold air fan and the cold air valve are opened when the flue gas temperature before the heat exchanger and the flue gas temperature before the induced draft fan are respectively higher than the target temperature, and the air volume of the cold air fan and the opening of the cold air valve are adjusted according to the degree of overtemperature.

[0007] Another technical solution provided by the present invention: a system for implementing the above method is arranged at the tail of the heating furnace, including a cooling air fan, a heat exchanger, a furnace pressure regulating valve, a cooling air valve and an induced draft fan; the tail of the heating furnace is connected to the flue gas inlet of the heat exchanger through a furnace tail exhaust pipe, and a branch pipe is provided on the furnace tail exhaust pipe for connecting the cooling air fan, and the flue gas outlet of the heat exchanger is connected to the induced draft fan through a rear exhaust pipe, and the furnace pressure regulating valve is installed on the pipeline of the rear exhaust pipe, and a cooling branch pipe is connected to the cooling air valve on the pipeline between the furnace pressure regulating valve and the induced draft fan; a front temperature measuring element is provided on the furnace tail exhaust pipe at the front end of the heat exchanger, and an induced draft fan temperature measuring element is provided on the pipeline between the furnace pressure regulating valve and the induced draft fan.

[0008] Preferably, a rear temperature measuring element is provided on the rear exhaust pipe at the rear end of the heat exchanger, and an induced draft fan pressure measuring element is also provided on the pipeline between the furnace pressure regulating valve and the induced draft fan; the induced draft fan outlet pipeline is connected to a steel chimney.

[0009] Preferably, the outer periphery of the rear smoke exhaust duct is wrapped with an insulating environmentally friendly blanket.

[0010] Preferably, the furnace pressure regulating valve is a rotary plate valve without an insulating lining, which includes a steel pipe and flanges at both ends for connecting to pipelines. A support is fixedly provided on the outside of the steel pipe, and the support is rotatably connected to a rotating shaft perpendicular to the steel pipe. The rotating shaft passes through the outer wall of the steel pipe and is fixedly connected to a valve plate inside the steel pipe. Semicircular ring blocks are fixedly provided on both sides of the rotating shaft on the inner wall of the steel pipe, and the ring blocks are perpendicular to the steel pipe, and the two ring blocks are respectively located on both sides of the valve plate; the diameter of the valve plate is smaller than the inner diameter of the steel pipe, and the sum of the width of the ring block and the diameter of the valve plate is greater than the inner diameter of the steel pipe.

[0011] Preferably, a plurality of ribs are fixedly provided on both sides of the ring baffle for reinforcement, and the ribs are fixedly connected to the inner wall of the steel pipe.

[0012] Preferably, the inner diameter of the furnace pressure regulating valve is smaller than the inner diameter of the rear smoke exhaust pipe.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. The method and system for regulating the furnace pressure of a heating furnace are simple, reasonable, easy to implement, sensitive to regulation, high in precision, and have a wide range of applications. They can adapt to larger changes in furnace pressure and can be used for heating furnaces on steel rolling production lines with different combustion systems, such as heating furnaces with a regenerative combustion system that burns low-calorific value coal gas, and heating furnaces with a conventional combustion system that burns higher-calorific value coal gas; they can be used for heating furnaces with a combustion system that uses double cross-limiting control, and they can also be used for heating furnaces with a combustion system that uses pulse control. They are especially suitable for heating furnaces that heat grade steel, because the output of grade steel heating furnaces varies widely, the furnace pressure varies with the output, and the regulation range becomes larger. The application of this regulation method can achieve wide-range and precise regulation.

[0015] 2. The heating furnace chamber pressure regulating method and system adopt a special non-insulated lining furnace pressure regulating valve, and replace the original insulating valve seat with a ring baffle. Compared with the traditional flue valve structure, it is simpler, lighter than the traditional flue rotating gate valve with internal insulation, has a short manufacturing cycle, is easy to inspect and maintain, and has low maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A system schematic diagram of the furnace pressure regulating method of the present invention;

[0017] Figure 2 It is a schematic diagram of the main structure of the furnace pressure regulating valve in the present invention;

[0018] Figure 3 for Figure 2 The top view cross-sectional structure diagram of the furnace pressure regulating valve is shown.

[0019] In the figure: 100, heating furnace; 101, furnace tail exhaust pipe; 102, cold air fan; 103, heat exchanger; 104, rear exhaust pipe; 105, furnace pressure regulating valve; 106, cold air valve; 107, induced draft fan; 108, steel chimney; 109, front temperature measuring element; 110, rear temperature measuring element; 111, induced draft fan temperature measuring element; 112, induced draft fan pressure measuring element;

[0020] 1. Rotating shaft; 2. Valve plate; 3. Support; 4. Flange 1; 5. Flange 2; 6. Bolted connector; 7. Steel pipe; 8. Ring stop; 9. Rib plate. DETAILED DESCRIPTION

[0021] The method provided by the present invention can be used for heating furnaces on steel rolling production lines with different combustion systems, such as heating furnaces with regenerative combustion systems that burn low-calorific value coal gas, and heating furnaces with conventional combustion systems that burn higher-calorific value coal gas; it can be used for heating furnaces whose combustion systems adopt double cross-limiting control, and it can also be used for heating furnaces whose combustion systems adopt pulse control; specifically, a method for regulating the furnace pressure of a heating furnace of the present invention comprises the following contents: a smoke exhaust pipe is arranged at the tail of the heating furnace to lead the smoke in the furnace out of the furnace, and the temperature of the smoke out of the furnace is reduced to below the target temperature through an air heat exchanger, and a cooling fan is arranged in front of the air heat exchanger to provide protection, and the cooling fan is interlocked with the smoke temperature in front of the heat exchanger. The efficiency of the air heat exchanger is sufficient to reduce the smoke temperature to the target temperature under normal working conditions. The target temperature is below the standard temperature. The air heat exchanger can be used to recover as much waste heat of the flue gas as possible to preheat the air. At the same time, the flue gas temperature after the heat exchanger can be reduced to below the target temperature, which can reduce heat loss. A pneumatic furnace pressure regulating valve is arranged on the flue gas outlet pipe of the heat exchanger. The flue gas outlet end of the furnace pressure regulating valve is connected to an induced draft fan that can adjust the exhaust air volume. A furnace pressure detection element is arranged on the top of the heating furnace in the equalizing section. The exhaust air volume of the induced draft fan and the opening of the furnace pressure regulating valve are adjusted according to the furnace pressure value. For reference only, the furnace pressure is roughly adjusted by adjusting the air volume of the induced draft fan, and then the furnace pressure is finely adjusted by the opening of the furnace pressure regulating valve. This method is sensitive to adjustment and has high accuracy. A cold air branch pipe is also connected to the pipeline between the furnace pressure regulating valve and the induced draft fan. A cold air valve is arranged on the branch pipe, and its opening is interlocked with the flue gas temperature before the induced draft fan.

[0022] The flue gas is led out from the tail of the heating furnace and can be used to preheat the billet in the tail of the heating furnace; the use of induced draft fans for mechanical smoke exhaust can avoid the problem of large chimney footprint caused by natural smoke exhaust.

[0023] For reference, for example, if the above target temperature is 350℃, the cold air fan and the cold air valve will be opened when the flue gas temperature before the heat exchanger and the flue gas temperature before the induced draft fan are respectively higher than 350℃, and the air volume of the cold air fan and the opening of the cold air valve can be adjusted according to the degree of over-temperature; among them, the induced draft fan and the cold air fan can adjust the air volume by frequency conversion.

[0024] To implement the above method, see Figure 1A heating furnace furnace pressure regulating system of the present invention is arranged at the furnace tail of the heating furnace 100, and includes a cold air fan 102, a heat exchanger 103, a furnace pressure regulating valve 105, a cold air valve 106 and an induced draft fan 107; the furnace tail of the heating furnace 100 is connected to the smoke inlet of the heat exchanger 103 through a furnace tail exhaust pipe 101, and a branch pipe is provided on the furnace tail exhaust pipe 101 for connecting the cold air fan 102, and the smoke outlet of the heat exchanger 103 is connected to the induced draft fan 107 through a rear exhaust pipe 104, and the furnace pressure regulating valve 105 is installed on the pipeline of the rear exhaust pipe 104, and a cold air branch pipe is connected to the cold air valve 106 on the pipeline between the furnace pressure regulating valve 105 and the induced draft fan 107; a front temperature measuring element 109 is provided on the pipeline of the furnace tail exhaust pipe 101 at the front end of the heat exchanger 103, and an induced draft fan temperature measuring element 111 is provided on the pipeline between the furnace pressure regulating valve 105 and the induced draft fan 107.

[0025] In addition, a rear temperature measuring element 110 may be provided on the rear smoke exhaust duct 104 at the rear end of the heat exchanger 103 to observe whether the heat exchange effect reaches the expected effect. An induced draft fan pressure measuring element 112 may also be provided on the pipeline between the furnace pressure regulating valve 105 and the induced draft fan 107, and the pressure information at this position can be used to reflect whether the operation is stable; the outlet pipeline of the induced draft fan 107 is connected to a steel chimney 108; the outer periphery of the rear smoke exhaust duct 104 is wrapped with an insulating environmentally friendly blanket.

[0026] The temperature measuring elements and pressure measuring elements mentioned above can generally be realized by conventional online thermometers and pressure gauges. It is well known that the interlocking method is to transmit data to a controller, such as a PLC, through the temperature measuring elements and pressure measuring elements, and then the controller makes judgments and issues instructions according to the set program to control the induced draft fan, furnace pressure regulating valve, cold air valve, and the actuating mechanism of the cold air valve.

[0027] See also Figure 2 and 3 In a preferred embodiment, the furnace pressure regulating valve 105 of the present invention adopts a specially designed structure, which is generally similar to a rotary plate valve, but does not require an insulating lining, has a simple structure, is lighter than a traditional flue rotary gate valve with internal insulation, has a short manufacturing cycle, is easy to inspect and maintain, and has a low maintenance cost. Specifically, it includes a steel pipe 7 and flanges at both ends of the steel pipe 7 for connecting pipelines. A support 3 is fixedly provided on the outside of the steel pipe 7. The support 3 is rotatably connected to a rotating shaft 1 perpendicular to the steel pipe 7. The rotating shaft 1 passes through the outer wall of the steel pipe 7 and is fixedly connected to a valve plate 2 in the steel pipe 7. Semicircular ring blocks 8 are fixedly provided on both sides of the inner wall of the steel pipe 7 on the rotating shaft 1. The ring blocks 8 are perpendicular to the steel pipe 7, and the two ring blocks 8 are respectively located on both sides of the valve plate 2; the diameter of the valve plate 2 is smaller than the inner diameter of the steel pipe 7, and the sum of the width of the ring block 8 and the diameter of the valve plate 2 is greater than the inner diameter of the steel pipe 7.

[0028] To strengthen the connection, further optionally, a plurality of ribs 9 are fixedly provided on both sides of the ring baffle 8 , and the ribs 9 are fixedly connected to the inner wall of the steel pipe 7 .

[0029] Usually, the inner diameter of the furnace pressure regulating valve 105 can be made equal to the inner diameter of the rear exhaust pipe 104 . However, in order to increase the regulation sensitivity, the inner diameter of the furnace pressure regulating valve 105 can be made smaller than the inner diameter of the rear exhaust pipe 104 .

[0030] The above-mentioned furnace pressure regulation method and system were applied to a heating furnace for heating grade steel for long-term testing. Since the output variation range of the grade steel heating furnace is large and the furnace pressure varies widely with the output, the furnace pressure needs to be adjusted by a large range. Under this relatively harsh test condition, the furnace pressure is basically maintained within the variation range of ±10Pa, which well realizes the requirements of sensitive and high-precision furnace pressure regulation.

[0031] The above are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined by the claims.

[0032] The matters not described in detail in the present invention are all known technologies to those skilled in the art.

Claims

1. A method for regulating the furnace pressure of a heating furnace, characterized in that: The method includes the following contents: a smoke exhaust pipe is arranged at the tail of the heating furnace to lead the smoke in the furnace out of the furnace, and the temperature of the smoke out of the furnace is reduced to below the target temperature through an air heat exchanger, and a cooling fan is arranged in front of the air heat exchanger to provide protection, and the cooling fan is interlocked with the smoke temperature in front of the heat exchanger; a pneumatic furnace pressure regulating valve is arranged on the smoke outlet pipe of the heat exchanger, and the smoke outlet end of the furnace pressure regulating valve is connected to an induced draft fan that can adjust the smoke exhaust air volume; a furnace pressure detection element is arranged on the top of the heating furnace in the equalizing section, and the exhaust air volume of the induced draft fan and the opening of the furnace pressure regulating valve are adjusted according to the furnace pressure value; a cooling branch pipe is also connected to the pipeline between the furnace pressure regulating valve and the induced draft fan, and a cooling air valve is provided on the branch pipe, and its opening is interlocked with the smoke temperature in front of the induced draft fan.

2. The method according to claim 1, characterized in that: The target temperature is 350°C. The cold air fan and the cold air valve are opened when the flue gas temperature before the heat exchanger and the flue gas temperature before the induced draft fan are higher than the target temperature, and the air volume of the cold air fan and the opening of the cold air valve are adjusted according to the degree of overtemperature.

3. A system for implementing the method according to claim 1 or 2, arranged at the tail of a heating furnace (100), characterized in that: The heating furnace (100) comprises a cooling air blower (102), a heat exchanger (103), a furnace pressure regulating valve (105), a cooling air blower valve (106) and an induced draft fan (107); the furnace tail of the heating furnace (100) is connected to the flue gas inlet of the heat exchanger (103) through a furnace tail flue gas exhaust pipe (101); a branch pipe is provided on the furnace tail flue gas exhaust pipe (101) for connecting to the cooling air blower (102); the flue gas outlet of the heat exchanger (103) is connected to the induced draft fan (107) through a rear flue gas exhaust pipe (104) The furnace pressure regulating valve (105) is installed on the pipeline of the rear smoke exhaust duct (104); a cold air branch pipe is connected to the pipeline between the furnace pressure regulating valve (105) and the induced draft fan (107) for connecting the cold air valve (106); a front temperature measuring element (109) is provided at the front end of the heat exchanger (103) on the pipeline of the furnace tail smoke exhaust duct (101); and an induced draft fan temperature measuring element (111) is provided on the pipeline between the furnace pressure regulating valve (105) and the induced draft fan (107).

4. The system according to claim 3, characterized in that: The rear exhaust pipe (104) is provided with a rear temperature measuring element (110) at the rear end of the heat exchanger (103), and the pipeline between the furnace pressure regulating valve (105) and the induced draft fan (107) is also provided with an induced draft fan pressure measuring element (112); the outlet pipeline of the induced draft fan (107) is connected to a steel chimney (108).

5. The system according to claim 3, characterized in that: The outer periphery of the rear smoke exhaust duct (104) is wrapped with a heat-insulating environmentally friendly blanket.

6. The system according to claim 3, characterized in that: The furnace pressure regulating valve (105) is a rotary plate valve without an insulating lining, comprising a steel pipe (7) and flanges at both ends thereof for connecting to pipelines, a support (3) is fixedly arranged outside the steel pipe (7), the support (3) is rotatably connected to a rotating shaft (1) perpendicular to the steel pipe (7), the rotating shaft (1) passes through the outer wall of the steel pipe (7), and a valve plate (2) is fixedly connected inside the steel pipe (7), semi-circular ring blocks (8) are fixedly arranged on both sides of the rotating shaft (1) on the inner wall of the steel pipe (7), the ring blocks (8) are perpendicular to the steel pipe (7), and the two ring blocks (8) are respectively located on both sides of the valve plate (2); the diameter of the valve plate (2) is smaller than the inner diameter of the steel pipe (7), and the sum of the width of the ring block (8) and the diameter of the valve plate (2) is greater than the inner diameter of the steel pipe (7).

7. The system according to claim 6, characterized in that: A plurality of ribs (9) are fixedly provided on both sides of the ring baffle (8) for reinforcement, and the ribs (9) are fixedly connected to the inner wall of the steel pipe (7).

8. The system according to claim 6, characterized in that: The inner diameter of the furnace pressure regulating valve (105) is smaller than the inner diameter of the rear smoke exhaust pipe (104).

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