Waste heat recycling system of continuous cast pipe annealing furnace

Abstract

The utility model provides a waste heat recycling system of a continuous cast pipe annealing furnace. The waste heat recycling system comprises an annealing furnace, a waste heat recycling system, a sand core drying furnace, a spraying preheating furnace and a spraying drying furnace, the annealing furnace comprises a quenching section and a slow cooling section; the annealing furnace slow cooling section is respectively communicated with the sand core drying furnace, the spraying preheating furnace and the spraying drying furnace through waste heat insulation pipelines; an electric adjusting butterfly valve, a pipeline valve, a manual adjusting butterfly valve, a cold air mixing valve and a slow cooling section induced draft fan are sequentially arranged on the waste heat insulation pipeline in the fluid direction. A pipeline reducer is arranged in the waste heat insulation pipeline behind the slow cooling section induced draft fan; and the quenching section of the annealing furnace is communicated with the pipeline through a second waste heat insulation pipeline in a reducing manner. According to the system, the heat exhausted from the quenching section of the annealing furnace can be brought to the sand core drying furnace, the spraying preheating furnace and the spraying drying furnace behind through the induced draft fan, so that the energy consumed by combustion is saved, and the emission of harmful substances generated by fuel combustion is also reduced; not only is the cost reduced, but also the purposes of energy conservation and emission reduction can be achieved.

Description

Technical Field

[0001] The utility model relates to a waste heat recovery technology for a spheroidal mill cast iron pipe production line, in particular to a waste heat recovery and utilization system for a continuous cast pipe annealing furnace. Background Art

[0002] The production process of ductile iron pipe includes molten iron preparation, sand core preparation, centrifugal casting, annealing, zinc spraying, water pressure test, cement lining, asphalt spraying and packaging.

[0003] The spheroidizing annealing of ductile iron pipe is to anneal the pipe by heating, heat preservation, rapid cooling and slow cooling to eliminate the cementite and pearlite generated in the casting process and transform the matrix into the ductile iron pipe matrix structure of ferrite.

[0004] In the annealing furnace rapid cooling section, the cold air indirect cooling method is used to complete the cast pipe rapid cooling process. The cold air sent by the fan passes through the cold air duct installed above the rapid cooling section, absorbs the heat of the rapid cooling section furnace, and then reduces the temperature of the cast pipe, and directly discharges the high-temperature hot air after absorbing heat, so as to achieve the purpose of rapid cooling of the cast pipe.

[0005] In the sand core preparation process, in order to increase the strength of the sand core, it needs to be heated and baked in a sand core drying furnace; in the asphalt spraying process, in order to increase the corrosion resistance of the pipe, the surface of the cast pipe needs to be heated in a spray preheating furnace, then spray asphalt, and then use a spray drying furnace to dry the surface of the cast pipe with asphalt attached; the above three furnaces (sand core drying furnace, spray preheating furnace, spray drying furnace) all require energy consumption when working. However, the waste heat recovery and utilization of the existing ductile iron pipe production line is unreasonable and cannot achieve effective energy utilization. Utility Model Content

[0006] The purpose of the utility model is to propose a waste heat recovery system for a continuous cast pipe annealing furnace in response to the problem of unreasonable waste heat recovery and utilization of a ductile iron pipe production line. The system can bring the heat exhausted from the rapid cooling section of the annealing furnace to the sand core drying furnace, spray preheating furnace and spray drying furnace behind it through an induced draft fan, thereby saving energy consumed by combustion and also reducing harmful emissions generated by fuel combustion; it not only reduces costs but also achieves the purpose of energy conservation and emission reduction.

[0007] To achieve the above-mentioned purpose, the technical scheme adopted by the utility model is: a waste heat recovery and utilization system of a continuous cast pipe annealing furnace, including an annealing furnace, a waste heat recovery system, a sand core drying furnace, a spray preheating furnace and a spray drying furnace; the annealing furnace includes a rapid cooling section and a slow cooling section; the waste heat recovery system includes: a first waste heat insulation pipeline, a second waste heat insulation pipeline, a pipeline valve, a manual adjustment butterfly valve, an electric adjustment butterfly valve, a slow cooling section induced draft fan, a cold air valve, a high-temperature pneumatic switch butterfly valve and a high-temperature electric switch butterfly valve; the slow cooling section of the annealing furnace is connected with the sand core drying furnace, the spray preheating furnace and the spray drying furnace respectively through the first waste heat insulation pipeline; the first waste heat insulation pipeline is sequentially provided with an electric adjustment butterfly valve, a pipeline valve, a manual adjustment butterfly valve, a cold air valve and a slow cooling section induced draft fan along the fluid direction; a pipeline reducer is provided in the first waste heat insulation pipeline after the slow cooling section induced draft fan 5;

[0008] The annealing furnace rapid cooling section is connected to the pipeline reducer through a second waste heat insulation pipeline, a high-temperature pneumatic switch butterfly valve is provided at the outlet of the second waste heat insulation pipeline, and a high-temperature electric switch butterfly valve is provided on the second waste heat insulation pipeline.

[0009] The utility model sends the hot air discharged from the rapid cooling section to the sand core drying furnace and the spraying line (spraying preheating furnace and spraying drying furnace) through the second waste heat insulation pipeline. The cooling air of the rapid cooling section provides sufficient air volume and air pressure. The second waste heat insulation pipeline is connected to the rear line. According to calculation, the hot air generated by the rapid cooling section cannot reach the sum of the maximum heat loads designed for the preheating furnace and the drying furnace. Therefore, a part of the flue gas is introduced from the heat exchanger of the slow cooling section of the annealing furnace through the first waste heat insulation pipeline as a supplement;

[0010] Furthermore, the first waste heat insulation pipe is connected to the spray preheating furnace and the spray drying furnace respectively through the pipe welding tee, and a spray line induced draft fan is arranged between the first waste heat insulation pipe and the pipe welding tee. Since the annealing furnace station is far away from the paint line station, a high-power induced draft fan - the spray line induced draft fan is installed near the spray preheating and spray drying furnaces. The hot air discharged from the annealing furnace rapid cooling section and slow cooling section is drawn by the spray line induced draft fan to supply the spray preheating furnace and the spray drying furnace. The spray preheating furnace and the spray drying furnace retain the original burner heating and hot air circulation functions. When the waste heat of the annealing furnace cannot meet the requirements of the paint heating process, the burner is automatically started through the thermocouple monitoring installed on the furnace, and the ignition process is executed to complete the heating process.

[0011] Furthermore, the first waste heat insulation pipe is connected to the sand core drying furnace through the sand core drying induced draft fan. The sand core drying furnace is located between the annealing furnace and the paint spraying line (spray preheating furnace and spray drying furnace). Considering that the suction force of the induced draft fan of the spraying line may cause the hot air to be unable to be smoothly delivered to the sand core drying furnace, an induced draft fan is added here - the sand core drying induced draft fan. The sand core drying induced draft fan extracts a part of the hot air for the sand core drying furnace. The sand core drying furnace also retains the original burner heating and hot air circulation functions. When the waste heat of the annealing furnace cannot meet the drying process requirements, the burner is automatically started through the thermocouple monitoring installed on the furnace, and the ignition process is executed to complete the heating process.

[0012] Furthermore, a stainless steel expansion joint is provided in the first waste heat insulation pipeline. There are multiple stainless steel expansion joints. The pipeline is filled with high-temperature furnace gas extracted from the rapid cooling section or slow cooling section of the annealing furnace. Under long-term high-temperature environment, the pipeline will expand due to heat. In particular, the waste heat recovery pipeline is generally long, and this heat deformation will be more serious. Therefore, appropriately arranging expansion joints in the pipeline can effectively offset this thermal expansion and contraction of the pipeline.

[0013] Furthermore, a pipe elbow is provided in the first waste heat insulation pipe.

[0014] Furthermore, the waste heat recovery system of the continuous cast pipe annealing furnace also includes a control system, which is electrically connected to the slow cooling section induced draft fan, the cold air valve, the electric regulating valve, the rapid cooling section electric switch butterfly valve, the pneumatic switch butterfly valve, the sand core drying induced draft fan and the spray line induced draft fan.

[0015] Working principle of the waste heat recovery system of the utility model continuous cast pipe annealing furnace:

[0016] 1. Hot air extraction system

[0017] 1.1 The start-up of the spray line induced draft fan 13 is interlocked with the electric control valve on the exhaust chimney of the quenching section of the annealing furnace and the cooling air temperature. The spray line induced draft fan 13 can be started only when the quenching fan is started and the cooling air temperature reaches the standard.

[0018] 1.2 The slow cooling section induced draft fan 5 is only allowed to start when the slow cooling section cooling fan is working. At the same time, in order to protect the slow cooling section induced draft fan 5, a cold air valve 6 is set, which is interlocked with the waste hot air temperature in front of the slow cooling section induced draft fan 5. When the temperature exceeds the set value, cold air is automatically added to protect the slow cooling section induced draft fan 5.

[0019] 2. Temperature control system

[0020] 2.1 When the extracted hot air volume can meet the process requirements, the circulating air temperature is sent to the PLC detection channel. After PID calculation, the control signal is output to adjust the opening of the hot air valve 6, thereby controlling the circulating air temperature.

[0021] 2.2 When the amount of hot air extracted cannot meet the process requirements and the circulating air temperature cannot meet the production requirements, the PLC will give a burner start signal, and the original system will start the burner, and the circulating air system will be mixed with the burner power as a heat source. When the burner is working, the cold air valve maintains the maximum opening. When the circulating air temperature reaches the production requirements, the burner is closed, and the cold air valve 6 is put back into control, which can reduce the burner workload and avoid energy waste. The temperature points for starting and closing the burner are set with a return difference to prevent the system from oscillating and the burner from starting and stopping frequently.

[0022] 2.3 When the induced draft fan of the spraying line stops working and cannot extract the residual heat of the annealing furnace, it will be controlled by the original system.

[0023] Compared with the prior art, the waste heat recovery and utilization system of the continuous cast pipe annealing furnace of the utility model has the following advantages:

[0024] 1) The front section of the waste heat recovery system of the continuous cast pipe annealing furnace of the utility model is divided into: waste heat recovery in the rapid cooling section and waste heat recovery in the slow cooling section, and the back section of the system is divided into: waste heat utilization in the sand core drying furnace, waste heat utilization in the spray preheating furnace, and waste heat utilization in the spray drying furnace;

[0025] 2) The utility model brings the heat exhausted from the rapid cooling section of the annealing furnace to the sand core drying furnace, spray preheating furnace and spray drying furnace behind through the induced draft fan, saving the energy consumed by combustion and also reducing the harmful emissions generated by fuel combustion; not only reducing costs but also achieving the purpose of energy conservation and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of the waste heat recovery system of the continuous cast pipe annealing furnace;

[0027] Figure 2 It is a structural schematic diagram of an annealing furnace;

[0028] Figure 3 This is a schematic diagram of the structure of the spray preheating furnace and the spray drying furnace. DETAILED DESCRIPTION

[0029] The present invention is further described below with reference to the embodiments:

[0030] Example 1

[0031] The present embodiment discloses a waste heat recovery and utilization system of a continuous cast pipe annealing furnace, comprising an annealing furnace, a waste heat recovery system, a sand core drying furnace, a spray preheating furnace and a spray drying furnace; the annealing furnace comprises a rapid cooling section and a slow cooling section; the waste heat recovery system comprises: a first waste heat insulation pipeline 1, a second waste heat insulation pipeline, a pipeline valve 2, a manual adjustment butterfly valve 3, an electric adjustment butterfly valve 4, a slow cooling section induced draft fan 5, a cold air valve 6, a high-temperature pneumatic switch butterfly valve 8 and a high-temperature electric switch butterfly valve 9.

[0032] The slow cooling section of the annealing furnace is connected to the sand core drying furnace, the spray preheating furnace and the spray drying furnace respectively through the first waste heat insulation pipeline 1; the first waste heat insulation pipeline 1 is sequentially provided with an electric regulating butterfly valve 4, a pipeline valve 2, a manual regulating butterfly valve 3, a cold air valve 6 and a slow cooling section induced draft fan 5 along the fluid direction; a pipeline reducer 11 is provided in the first waste heat insulation pipeline 1 after the slow cooling section induced draft fan 5; a pipeline stainless steel expansion joint 7 is provided in the first waste heat insulation pipeline 1. The number of the pipeline stainless steel expansion joints 7 is multiple. A pipeline elbow 10 is provided in the first waste heat insulation pipeline 1.

[0033] The first waste heat insulation pipe 1 is connected to the spray preheating furnace and the spray drying furnace respectively through the pipe welding tee 14, and a spray line induced draft fan 13 is arranged between the first waste heat insulation pipe 1 and the pipe welding tee 14. Since the annealing furnace station is far away from the paint line station, a high-power induced draft fan, the spray line induced draft fan 13, is installed near the spray preheating and spray drying furnaces. The hot air discharged from the annealing furnace rapid cooling section and the slow cooling section is drawn by the spray line induced draft fan 13 to supply the spray preheating furnace and the spray drying furnace. The spray preheating furnace and the spray drying furnace retain the original burner heating and hot air circulation functions. When the waste heat of the annealing furnace cannot meet the requirements of the paint heating process, the burner is automatically started through the thermocouple monitoring installed on the furnace, and the ignition process is executed to complete the heating process.

[0034] The first waste heat insulation pipe 1 is connected to the sand core drying furnace through the sand core drying induced draft fan 12. The sand core drying furnace is located between the annealing furnace and the paint spraying line (spray preheating furnace and spray drying furnace). Considering that the suction force of the spray line induced draft fan 13 may cause the hot air to be unable to be smoothly delivered to the sand core drying furnace, an induced draft fan - the sand core drying induced draft fan 12 is added here. The sand core drying induced draft fan 12 extracts a part of the hot air for the sand core drying furnace. The sand core drying furnace also retains the original burner heating and hot air circulation functions. When the waste heat of the annealing furnace cannot meet the drying process requirements, the burner is automatically started through the thermocouple monitoring installed on the furnace, and the ignition process is executed to complete the heating process.

[0035] The annealing furnace rapid cooling section is connected to the pipe reducer 11 through a second waste heat insulation pipe, a high-temperature pneumatic switch butterfly valve 8 is provided at the outlet of the second waste heat insulation pipe, and a high-temperature electric switch butterfly valve 9 is provided on the second waste heat insulation pipe.

[0036] The system sends the hot air discharged from the rapid cooling section to the sand core drying furnace and the spraying line (spraying preheating furnace and spraying drying furnace) through the second waste heat insulation pipe. The cooling air of the rapid cooling section provides sufficient air volume and air pressure. The second waste heat insulation pipe is connected to the rear line. After calculation, the hot air generated by the rapid cooling section cannot reach the sum of the maximum heat loads designed for the preheating furnace and the drying furnace. Therefore, a part of the flue gas is introduced from the heat exchanger of the slow cooling section of the annealing furnace through the first waste heat insulation pipe as a supplement.

[0037] The waste heat recovery system of the continuous cast pipe annealing furnace also includes a control system, which is electrically connected to the slow cooling section induced draft fan 5, the cold air valve 6, the sand core drying induced draft fan 12 and the spraying line induced draft fan 13 respectively.

[0038] Working principle of the waste heat recovery system of the utility model continuous cast pipe annealing furnace:

[0039] Hot air extraction system

[0040] 1.1 The start-up of the spray line induced draft fan 13 is interlocked with the electric control valve on the exhaust chimney of the quenching section of the annealing furnace and the cooling air temperature. The spray line induced draft fan 13 can be started only when the quenching fan is started and the cooling air temperature reaches the standard.

[0041] 1.2 The slow cooling section induced draft fan 5 is only allowed to start when the slow cooling section cooling fan is working. At the same time, in order to protect the slow cooling section induced draft fan 5, a cold air valve 6 is set, which is interlocked with the waste hot air temperature in front of the slow cooling section induced draft fan 5. When the temperature exceeds the set value, cold air is automatically added to protect the slow cooling section induced draft fan 5.

[0042] Temperature control system

[0043] 2.1 When the extracted hot air volume can meet the process requirements, the circulating air temperature is sent to the PLC detection channel. After PID calculation, the control signal is output to adjust the opening of the hot air valve 6, thereby controlling the circulating air temperature.

[0044] 2.2 When the amount of hot air extracted cannot meet the process requirements and the circulating air temperature cannot meet the production requirements, the PLC will give a burner start signal, and the original system will start the burner, and the circulating air system will be mixed with the burner power as a heat source. When the burner is working, the cold air valve maintains the maximum opening. When the circulating air temperature reaches the production requirements, the burner is closed, and the cold air valve 6 is put back into control, which can reduce the burner working compliance and avoid energy waste. The temperature points of the burner start and close are set with a return difference to prevent the system from shaking and the burner from starting and stopping frequently.

[0045] 2.3 When the induced draft fan stops working and cannot extract air from the annealing furnace for preheating, it will be controlled by the original system.

[0046] The waste heat recovery and utilization system of the continuous cast pipe annealing furnace of the present invention can be used in the sand core drying furnace, the spray preheating furnace and the spray drying furnace because the high-temperature hot air discharged from the quenching section is dry and clean and contains a large amount of heat, which can greatly save costs and reduce energy consumption.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the utility model.

Claims

1. A waste heat recovery system for a continuous cast pipe annealing furnace, characterized in that: The invention comprises an annealing furnace, a waste heat recovery system, a sand core drying furnace, a spray preheating furnace and a spray drying furnace; the annealing furnace comprises a rapid cooling section and a slow cooling section; the waste heat recovery system comprises: a first waste heat insulation pipeline (1), a second waste heat insulation pipeline, a pipeline valve (2), a manually adjustable butterfly valve (3), an electric adjustable butterfly valve (4), a slow cooling section induced draft fan (5), a cold air valve (6), a high temperature pneumatic switch butterfly valve (8) and a high temperature electric switch butterfly valve (9); the slow cooling section of the annealing furnace is connected to the sand core drying furnace, the spray preheating furnace and the spray drying furnace respectively through the first waste heat insulation pipeline (1); the first waste heat insulation pipeline (1) is provided with an electric adjustable butterfly valve (4), a pipeline valve (2), a manually adjustable butterfly valve (3), a cold air valve (6) and a slow cooling section induced draft fan (5) in sequence along the fluid direction; a pipeline reducer (11) is provided in the first waste heat insulation pipeline (1) after the slow cooling section induced draft fan (5); The annealing furnace rapid cooling section is connected to the pipe reducer (11) via a second waste heat insulation pipe, a high-temperature pneumatic switch butterfly valve (8) is provided at the outlet of the second waste heat insulation pipe, and a high-temperature electric switch butterfly valve (9) is provided on the second waste heat insulation pipe.

2. The waste heat recovery system of the continuous cast pipe annealing furnace according to claim 1 is characterized in that: The first waste heat insulation pipeline (1) is connected to the spray preheating furnace and the spray drying furnace respectively through the pipeline welding tee (14), and a spray line induced draft fan (13) is arranged between the first waste heat insulation pipeline (1) and the pipeline welding tee (14).

3. The waste heat recovery system of the continuous cast pipe annealing furnace according to claim 1 is characterized in that: The first waste heat insulation pipeline (1) is connected to the sand core drying furnace via a sand core drying induced draft fan (12).

4. The waste heat recovery system of the continuous cast pipe annealing furnace according to claim 1 is characterized in that: The first waste heat insulation pipeline (1) is provided with a pipeline stainless steel expansion joint (7).

5. The waste heat recovery system of the continuous cast pipe annealing furnace according to claim 1 is characterized in that: A pipeline elbow (10) is provided in the first waste heat insulation pipeline (1).

6. The waste heat recovery system of the continuous cast pipe annealing furnace according to claim 1 is characterized in that: The waste heat recovery system of the continuous cast pipe annealing furnace also includes a control system, which is electrically connected to the slow cooling section induced draft fan (5), the cold air valve (6), the sand core drying induced draft fan (12) and the spraying line induced draft fan (13).

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