Energy-saving steel rolling annealing furnace shielding gas resource recovery and cyclic utilization system

Abstract

The invention discloses an energy-saving steel rolling annealing furnace shielding gas resource recovery and cyclic utilization system. A first purification subsystem receives shielding gas from an annealing furnace and removes dust and oil stains. And the heat recovery subsystem is used for exchanging heat for the protective gas subjected to dust and oil stain removal. And the second purification subsystem is used for pressurizing, deoxidizing and drying the shielding gas subjected to heat exchange and then inputting the shielding gas into the gas circulation subsystem. The gas circulation subsystem and the gas circulation subsystem are matched with each other, the nitrogen and hydrogen component proportion of the recycled protective gas is adjusted according to needs, and the recycled protective gas is fed into the annealing furnace after heat exchange is completed. The annealing furnace is optimized from two angles of nitrogen and hydrogen resource recovery and heat recovery, so that the problem of heat waste caused by direct emptying can be solved, the difficulty of incomplete recovery of resources caused by nitrogen and hydrogen separation can be overcome, and the problems that the nitrogen consumption of the furnace is increased and the load of an oxygen production system of an enterprise is not matched can be solved; energy conservation and carbon reduction of the annealing furnace unit are realized to the greatest extent.

Description

Technical Field

[0001] The invention belongs to the field of industrial annealing furnace process waste heat recovery and gas resource recycling, and in particular relates to an energy-saving steel rolling annealing furnace protective gas resource recovery and recycling system. Background Art

[0002] The steel rolling unit is an indispensable part of the production process of steel industry products. During the annealing process of the steel rolling continuous and bell-type annealing furnace equipment, the radiation tube heating process is adopted to control the flue gas temperature and protective gas in the furnace to meet the quality requirements of steel products. During the working process, the protective gas usually uses high-purity nitrogen, high-purity hydrogen, nitrogen-hydrogen mixed gas and ammonia decomposition gas. Specifically, in the process of heating and cooling the annealing furnace, nitrogen, as a neutral gas, can effectively prevent the oxidation of components; hydrogen can effectively reduce the oxidized elements and some metal oxides in the steel when the temperature is too high by using its reducing property, thereby protecting the quality of the workpiece; because hydrogen has strong permeability and high thermal conductivity, it can significantly improve the heat transfer efficiency and make the mechanical properties of the product more uniform.

[0003] According to the process requirements and product characteristics of the cold rolling annealing furnace, the common nitrogen-hydrogen mixed gas ratios include 25% N2 + 75% H2, 75% N2 + 25% H2, 95% N2 + 5% H2, etc. During the operation of the annealing furnace, the protective gas has only a small amount of hydrogen loss, and the furnace temperature is about 400-700 ° C. The protective gas after the furnace is almost directly emptied, resulting in a double waste of nitrogen and hydrogen protective gas resources and waste heat energy. The amount of oxygen and nitrogen used in steel mills varies with the rhythm of the steel production process. It is necessary to rely on production scheduling to maintain the balance of oxygen and nitrogen production and consumption between oxygen production and metallurgical processes. The practice of recycling nitrogen in the furnace can also solve the problem of nitrogen and oxygen load mismatch to a certain extent.

[0004] At present, in the prior art, a protective gas recycling device is designed, which purifies the protective gas discharged from the furnace body and returns it to the furnace body for recycling. The protective gas inlet of the protective gas recycling device is connected to the protective gas outlet of the furnace body, and the protective gas outlet of the protective gas recycling device is connected to the protective gas inlet of the furnace body. Although this prior art can recycle the protective gas for the continuous annealing furnace, it does not recycle its heat, resulting in most of the heat being wasted.

[0005] In addition, in another prior art, a heat energy recycling device is designed, and the protective gas in the hood annealing furnace is sent to the heat exchanger through a gas circulation pump. The protective gas undergoes heat exchange and is cooled in the heat exchanger. The cooled protective gas flows back from the heat exchanger to the hood annealing furnace to achieve efficient annealing or cooling. This approach saves energy to a certain extent and is more suitable for hood annealing furnaces. For continuous annealing furnaces, the waste heat of flue gas can meet the preheating of coal gas and air. This application further improves the energy utilization efficiency of the furnace through the self-compensation of the protective gas heat.

[0006] In addition, the prior art also designs a nitrogen-hydrogen protective gas separation system for steel rolling annealing furnaces, which separates nitrogen and hydrogen protective gas by using membrane separation technology after cooling, deoxidizing and drying the nitrogen and hydrogen protective gas, and obtains hydrogen-rich mixed gas for recycling. This practice only recycles hydrogen, wastes a large amount of separated nitrogen, increases the load of the oxygen production system of steel enterprises, and even worse, increases the economic cost of the steel rolling process. Summary of the invention

[0007] The technical purpose of the present invention is to provide an energy-saving steel rolling annealing furnace protective gas resource recovery and recycling system to solve the technical problems of energy and resource waste caused by the direct discharge of nitrogen-hydrogen mixed protective gas in the existing steel rolling annealing furnace and the mismatch between the increased nitrogen consumption of the furnace and the load of the enterprise's oxygen production system.

[0008] To solve the above problems, the technical solution of the present invention is: An energy-saving steel rolling annealing furnace protection gas resource recovery and recycling system is connected to the annealing furnace to achieve a circulation pipeline, including: a first purification subsystem, a heat recovery subsystem, a second purification subsystem, a gas circulation subsystem, a gas supply subsystem and a smoke exhaust device; The annealing furnace is provided with two outlets, which are respectively connected to a smoke exhaust pipe and a circulation pipe; the smoke exhaust device is connected to the annealing furnace pipeline via the smoke exhaust pipe, and is configured to receive the smoke from the annealing furnace and release it to the atmosphere; the first purification subsystem is connected to the annealing furnace pipeline via the circulation pipe, and the first purification subsystem is configured to receive the protective gas from the annealing furnace and remove dust and oil; The heat recovery subsystem is connected to the first purification subsystem pipeline and is configured to perform heat exchange between the protection gas output from the first purification subsystem and the protection gas in the gas supply subsystem; The second purification subsystem is connected to the heat recovery subsystem pipeline, and is configured to receive the protective gas after heat exchange and perform gas pressurization, catalytic deoxidation and drying treatment before inputting it into the gas circulation subsystem; The gas circulation subsystem is configured to receive the processed shielding gas and monitor the flow rates of nitrogen and hydrogen shielding gases in the shielding gas; The gas supply subsystem is connected to the gas circulation subsystem pipeline and is configured to cooperate with the gas circulation subsystem to receive the protective gas from the gas circulation subsystem and adjust the nitrogen-hydrogen composition ratio as needed, and then send the adjusted protective gas into the annealing furnace after heat exchange through the heat recovery subsystem.

[0009] The first purification subsystem includes an adjusting baffle, an air induction device, an ash removal tower and an oil removal tower which are sequentially connected by pipelines; The regulating baffle is arranged at the front end of the first purification subsystem and is configured to regulate the suction flow rate of the protective gas; The induced draft device is an induced draft fan arranged in parallel and is configured to draw the protective gas into the first purification subsystem; A dust removal tower is configured to remove dust from the protective gas passing therethrough; The de-oiling tower is configured to de-oil the protective gas after dust removal.

[0010] Specifically, a protective gas bypass channel is connected to the front end of the ash removal tower and the rear end of the oil removal tower. The protective gas bypass channel is provided with a first plug valve and a check valve, which are configured so that when the ash removal tower or the oil removal tower is in a fault or maintenance state, it will not affect the normal production of the steel rolling annealing furnace.

[0011] Wherein, the heat recovery subsystem includes a heat exchanger and a blast device which are sequentially connected by pipelines; The air blowing device uses air blowers arranged in parallel and is configured to pass the protective gas of the air supply subsystem into the heat exchanger; The heat exchanger is configured to exchange heat between the shielding gas from the first purification subsystem and the shielding gas from the air supply subsystem. The shielding gas from the first purification subsystem enters the second purification subsystem after heat exchange, and the shielding gas from the air supply subsystem returns to the air supply subsystem after heat exchange.

[0012] Specifically, the second purification subsystem includes a pressurizing device, a catalytic deoxidation tower and an adsorption dryer which are sequentially connected by pipelines; The boosting device uses a gas boosting pump arranged in parallel and is configured to boost the pressure of the protective gas after heat exchange; The catalytic deoxidation tower is configured to deoxidize the protective gas after the pressurization treatment; The adsorption dryer is configured to dry the protective gas after deoxygenation treatment.

[0013] Wherein, the gas circulation subsystem includes a gas storage device, a first flow detection device and a workstation; The gas storage device uses a plurality of gas storage tanks arranged in parallel and is configured to store the protective gas output from the second purification subsystem; The first flow detection device adopts a thermal flow meter, which is installed at the outlet of the gas storage tank and is configured to measure the nitrogen and hydrogen flow of the protective gas in the corresponding gas storage tank; The workstation is connected to the first flow detection device by signal, and receives the thermal flow meter signal collected by the thermal flow meter.

[0014] Specifically, the gas supply subsystem includes: a first gas intake pipeline, a second gas intake pipeline, a gas mixing device, a pressure detection device, a pressure reducing device, a gas buffer device, and a second flow detection device; The first air inlet pipeline and the second air inlet pipeline are respectively connected to the gas mixing device and are configured to respectively introduce nitrogen and hydrogen into the gas mixing device; The gas mixing device is a gas mixing tank, which is also connected to the gas storage tank pipeline and is configured to receive the protective gas from the gas storage tank. Based on the control of the workstation, nitrogen or hydrogen is introduced into the received protective gas to achieve nitrogen-hydrogen ratio readjustment; The pressure reducing device adopts a pressure reducer or a pressure reducing valve, which is respectively installed on the first air intake pipeline and the second air intake pipeline and is arranged close to the gas mixing tank, and is configured to reduce the pressure of the gas introduced into the first air intake pipeline and the second air intake pipeline; The pressure detection device adopts a pressure gauge, which is configured to detect the pressure of the gas introduced into the first air intake line and the second air intake line; The gas buffer device is a plurality of gas buffer tanks arranged in parallel, one end of the gas buffer tank is connected to the gas mixing tank pipeline, and the other end of the gas buffer tank is connected to the annealing furnace pipeline, and is configured to buffer the protective gas to be input into the annealing furnace; The second flow detection device adopts a thermal flow meter, which is installed at the outlet of the gas buffer tank and is configured to measure the nitrogen and hydrogen flow rates of the protective gas in the corresponding gas buffer tank. The second flow detection device is also connected to the workstation signal to transmit the thermal flow meter signal collected by the thermal flow meter to the workstation.

[0015] Further preferably, the gas supply subsystem also includes a second stopcock, a control valve and a heat circulation pipeline. The second stopcock is arranged on the pipeline between the gas buffer tank and the gas mixing tank, the control valve is arranged on the pipeline between the gas buffer tank and the annealing furnace, one end of the heat circulation pipeline is connected to the pipeline between the second stopcock and the gas mixing tank, and the other end of the heat circulation pipeline is connected to the pipeline between the heat recovery system and the second stopcock and the gas buffer tank.

[0016] Among them, the air supply subsystem and the air supply subsystem are both controlled by the workstation, which is configured to receive the thermal flow meter signals from the air supply subsystem and the air supply subsystem respectively, and issue instructions to the sensors corresponding to the first air intake pipeline and the second air intake pipeline according to the gas ratio set by the unit, so as to adjust the nitrogen and hydrogen intake flow rates.

[0017] The circulation pipeline is also provided with a venting pipeline connected thereto, and the venting pipeline is configured to release the protective gas.

[0018] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art: The present application provides an energy-saving steel rolling annealing furnace protective gas resource recovery and recycling system, which optimizes the annealing furnace from the two perspectives of nitrogen and hydrogen resource recovery and heat recovery, so that the system can not only solve the problem of heat waste caused by direct emptying, but also overcome the difficulty of incomplete resource recovery caused by nitrogen and hydrogen separation, and can also solve the problem of increased furnace nitrogen consumption and mismatch with the load of the enterprise's oxygen production system, thereby realizing energy saving and carbon reduction of the annealing furnace unit to the greatest extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the following detailed description of the preferred embodiment.The drawings are only for the purpose of illustrating the preferred embodiments and are not to be construed as limiting the invention.

[0020] Figure 1 This is a structural block diagram of an energy-saving steel rolling annealing furnace protection gas resource recovery and recycling system provided by the present invention; Figure 2 This is a schematic diagram of the structure of the first purification subsystem provided by the present invention; Figure 3 This is a schematic diagram of the structure of the heat recovery subsystem provided by the present invention; Figure 4 This is a schematic diagram of the structure of the second purification subsystem provided by the present invention; Figure 5 This is a schematic diagram of the structure of the gas circulation subsystem and the gas supply subsystem provided by the present invention.

[0021] Description of Reference Numerals 1: annealing furnace; 2: smoke exhaust device; 3: first purification subsystem; 301: adjusting baffle; 302: induced draft fan; 303: ash removal tower; 304: oil removal tower; 4: heat recovery subsystem; 401: blower; 402: heat exchanger; 5: second purification subsystem; 501: gas booster pump; 502: catalytic deoxidation tower; 503: adsorption dryer; 6: gas circulation subsystem; 601: gas storage device; 602: first flow detection device; 7: gas supply subsystem; 701: first air inlet pipeline; 702: second air inlet pipeline; 703: pressure reducing device; 704: gas mixing device; 705: gas buffer device; 706: second flow detection device; 8: workstation. DETAILED DESCRIPTION

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings and other implementation methods can be obtained based on these drawings without creative work.

[0023] In order to simplify the drawings, only the parts related to the present invention are schematically shown in each figure, and they do not represent the actual structure of the product. In addition, in order to simplify the drawings and facilitate understanding, in some figures, only one of the parts with the same structure or function is schematically drawn or marked. In this article, "one" not only means "only one", but also means "more than one".

[0024] The following is a further detailed description of an energy-saving steel rolling annealing furnace 1 protective gas resource recovery and recycling system proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims.

[0025] Example See also Figure 1 This embodiment provides an energy-saving steel rolling annealing furnace shielding gas resource recovery and recycling system. The system is constructed around the annealing furnace 1 so that the shielding gas can be recycled between the system and the annealing furnace 1. It is specifically composed of a first purification subsystem 3, a heat recovery subsystem 4, a second purification subsystem 5, a gas circulation subsystem 6, a gas supply subsystem 7 and a smoke exhaust device 2.

[0026] From the overall structure, the annealing furnace 1 is provided with two outlets, which are respectively connected to the exhaust pipe and the circulation pipe. Among them, the end of the exhaust pipe away from the annealing furnace 1 is connected to the pipeline, and the smoke from the annealing furnace 1 enters the exhaust device 2 after passing through the exhaust pipe, and then released into the atmosphere. The end of the circulation pipe away from the annealing furnace 1 is connected to the first purification subsystem 3 pipeline, and the first purification subsystem 3 receives the protective gas from the annealing furnace 1 and removes its dust and oil. Among them, the circulation pipeline is also provided with a control valve for controlling the discharge of the protective gas out of the furnace. The heat recovery subsystem 4 is connected to the first purification subsystem 3 pipeline, which is used to receive the protective gas output from the first purification subsystem 3 and exchange heat with the protective gas in the gas supply subsystem 7. The second purification subsystem 5 is connected to the heat recovery subsystem 4 pipeline, which is used to receive the protective gas after heat exchange and perform gas pressurization, catalytic deoxidation and drying treatment before inputting it into the gas circulation subsystem 6. The gas circulation subsystem 6 can receive the protective gas after the treatment, and monitor the flow rate of nitrogen and hydrogen protective gases in the protective gas. The gas supply subsystem 7 is respectively connected to the gas circulation subsystem 6 and the gas inlet pipeline of the annealing furnace 1. It cooperates with the gas circulation subsystem 6 to receive the protective gas from the gas circulation subsystem 6 and adjust the nitrogen and hydrogen composition ratio as needed, and then sends the adjusted protective gas into the annealing furnace 1 after heat exchange through the heat recovery subsystem 4.

[0027] See also Figure 2, the first purification subsystem 3 of the present embodiment is now described, which includes an adjustment baffle 301, an induced draft device, a dust removal tower 303 and an oil removal tower 304 connected in sequence by pipelines. The adjustment baffle 301 is arranged at the front end of the first purification subsystem 3, and is used to adjust the suction flow of the protective gas. The induced draft device is a pair of induced draft fans 302 arranged in parallel, which suck the protective gas into the first purification subsystem 3. When one of the induced draft fans 302 fails or is under maintenance, the other parallel fan can be enabled. The dust removal tower 303 and the oil removal tower 304 perform dust removal and oil removal on the inhaled protective gas. Preferably, a protective gas bypass channel is connected to the front end of the dust removal tower 303 and the rear end of the oil removal tower 304, and the protective gas bypass channel is provided with a first plug valve and a check valve, so that when the dust removal tower 303 or the oil removal tower 304 is in a state of failure or maintenance, it does not affect the normal production of the steel rolling annealing furnace 1.

[0028] See also Figure 3 The heat recovery subsystem 4 of this embodiment is now described, including a heat exchanger 402 and a blower connected in sequence by pipelines. The protective gas from the de-oiling tower 304 enters the heat exchanger 402 and is blown by the blower 401 to heat exchange with the protective gas from the air supply system, and then connected to the inlet of the booster device of the second purification subsystem 5. The protective gas from the air supply system returns to the air supply system after heat exchange. The blower device uses a blower 401 arranged in parallel to realize the main and standby settings. When one of the gas booster pumps 501 fails or is under maintenance, the other parallel pump can be activated.

[0029] See also Figure 4 The second purification subsystem 5 includes a booster device, a catalytic deoxidation tower 502 and an adsorption dryer 503 connected in sequence by pipelines. The booster device uses two gas booster pumps 501 arranged in parallel to boost the shielding gas after heat exchange. The catalytic deoxidation tower 502 deoxidizes the shielding gas after the boosting treatment, and the adsorption dryer 503 dries the shielding gas after the deoxidation treatment.

[0030] For details, see Figure 5 In this embodiment, the gas circulation subsystem 6 includes a gas storage device 601, a first flow detection device 602 and a workstation 8. The gas storage device 601 uses a plurality of gas storage tanks arranged in parallel to receive and store the protective gas output from the second purification subsystem 5. The first flow detection device 602 uses a thermal flow meter, which is installed at the outlet of the gas storage tank to measure the nitrogen and hydrogen flow of the protective gas in the corresponding gas storage tank, and transmits the thermal flow meter signal to the workstation 8 through the sensor.

[0031] Further, the gas supply subsystem 7 includes: a first air inlet pipeline 701, a second air inlet pipeline 702, a gas mixing device 704, a pressure detection device, a pressure reducing device 703, a gas buffer device 705 and a second flow detection device 706. The first air inlet pipeline 701 and the second air inlet pipeline 702 are respectively connected to the gas mixing device 704, and are used to respectively introduce nitrogen and hydrogen into the gas mixing device 704. The gas mixing device 704 is a gas mixing tank, and the gas mixing tank is also connected to the gas storage tank pipeline, and is used to receive the protective gas from the gas storage tank. According to the control of the workstation 8, nitrogen or hydrogen is introduced into the received protective gas to achieve the nitrogen-hydrogen ratio readjustment. The pressure reducing device 703 adopts a pressure reducer or a pressure reducing valve, and the pressure reducing device 703 is respectively installed on the first air inlet pipeline 701 and the second air inlet pipeline 702, and is arranged close to the gas mixing tank, and is used to reduce the pressure of the gas introduced through the first air inlet pipeline 701 and the second air inlet pipeline 702. The pressure detection device uses a pressure gauge to detect the pressure of the gas introduced into the first air inlet pipeline 701 and the second air inlet pipeline 702. The gas buffer device 705 is a plurality of gas buffer tanks arranged in parallel, one end of the gas buffer tank is connected to the gas mixing tank pipeline, and the other end of the gas buffer tank is connected to the annealing furnace 1 pipeline, which is used to buffer the protective gas to be input into the annealing furnace 1. The above-mentioned second flow detection device 706 also uses a thermal flow meter, which is installed at the outlet of the gas buffer tank to measure the nitrogen and hydrogen flow of the protective gas in the corresponding gas buffer tank. The second flow detection device 706 is also connected to the workstation 8 signal, and then the thermal flow meter signal collected by the thermal flow meter is transmitted to the workstation 8.

[0032] Further preferably, the gas supply subsystem 7 also includes a second stopcock, a control valve and a heat circulation pipeline. The second stopcock is arranged on the pipeline between the gas buffer tank and the gas mixing tank, the control valve is arranged on the pipeline between the gas buffer tank and the annealing furnace 1, one end of the heat circulation pipeline is connected to the pipeline between the second stopcock and the gas mixing tank, and the other end of the heat circulation pipeline is connected to the pipeline between the heat recovery system and the second stopcock and the gas buffer tank.

[0033] Both the air supply subsystem 7 and the air supply subsystem 7 are controlled by the workstation 8, which receives the thermal flow meter signals from the air supply subsystem 7 and the air supply subsystem 7 respectively, and issues instructions to the sensors corresponding to the first air intake pipeline 701 and the second air intake pipeline 702 according to the gas ratio set by the unit, so as to adjust the nitrogen and hydrogen intake flow rates.

[0034] The workflow of this embodiment is now described: When the annealing furnace 1 just starts production, the workstation 8 will first issue instructions to the two air inlet pipelines according to the gas ratio set by the unit to adjust the nitrogen and hydrogen intake amounts.

[0035] When the annealing furnace 1 is in normal production, smoke and protective gas will be discharged. The smoke is released into the atmosphere through the smoke exhaust device 2, and the protective gas enters the first purification system, the heat recovery system, the second purification system, the gas circulation system and the gas supply system in sequence through the bypass pipe connected to the circulation pipe, and then returns to the annealing furnace 1 to continue production.

[0036] The protective gas first enters the first purification system, and the flow rate of the protective gas is adjusted by adjusting the baffle 301. The induced draft fan 302 extracts the protective gas, and the protective gas enters the dust removal tower 303 and the oil removal tower 304 in turn to remove dust and oil. Then, the protective gas enters the heat recovery system, and after completing the heat exchange with the protective gas in the gas supply system in the heat exchanger 402, it enters the second purification system. The protective gas is pressurized by the gas booster pump 501, the impurity oxygen is removed in the catalytic deoxidation tower 502, and the excess water is removed by the adsorption dryer 503, and then enters the gas circulation system. The protective gas will be stored in multiple gas storage devices 601 and flow to the gas mixing device 704 of the gas supply system. Nitrogen and hydrogen are supplemented by the first and second air inlet pipelines 702 in front of the gas mixing device 704 to perform the ratio of gas content. When the gas is mixed, it is sent to multiple parallel gas buffer devices 705 for buffering, and then returned to the annealing furnace 1 through the corresponding valve control. Among them, the protective gas at the outlet of the gas mixing device 704 will complete heat exchange with the protective gas from the first purification system through the blower 401 and the heat exchanger 402 of the heat recovery system, and then return to the pipeline before the inlet of the gas buffer device 705 in the gas supply system. A second stopcock valve is provided between the pipelines of the gas mixing device 704 outlet and the gas buffer device 705 inlet.

[0037] When the annealing furnace 1 stops production due to a fault or a plan, smoke and protective gas are exhausted, and the smoke is released into the atmosphere through the smoke exhaust device 2, and the protective gas is released into the atmosphere after passing through the circulation pipeline and the venting pipeline.

[0038] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they still fall within the protection scope of the present invention.

Claims

1. An energy-saving steel rolling annealing furnace protective gas resource recovery and recycling system, which is connected to the annealing furnace through a circulation pipeline, characterized in that: include: a first purification subsystem, a heat recovery subsystem, a second purification subsystem, a gas circulation subsystem, an air supply subsystem, and a smoke exhaust device; The annealing furnace is provided with two outlets, which are respectively connected to a smoke exhaust pipe and a circulation pipe; the smoke exhaust device is connected to the annealing furnace pipeline via the smoke exhaust pipe, and is configured to receive the smoke from the annealing furnace and release it to the atmosphere; the first purification subsystem is connected to the annealing furnace pipeline via the circulation pipe, and the first purification subsystem is configured to receive the protective gas from the annealing furnace and remove dust and oil; The heat recovery subsystem is connected to the first purification subsystem pipeline and is configured to perform heat exchange between the protective gas output from the first purification subsystem and the protective gas in the gas supply subsystem; The second purification subsystem is connected to the heat recovery subsystem pipeline, and is configured to receive the protective gas after heat exchange and perform gas pressurization, catalytic deoxidation and drying treatments before inputting it into the gas circulation subsystem; The gas circulation subsystem is configured to receive the processed shielding gas and monitor the flow rates of nitrogen and hydrogen shielding gases in the shielding gas; The gas supply subsystem is connected to the gas circulation subsystem pipeline and is configured to cooperate with the gas circulation subsystem to receive the protective gas from the gas circulation subsystem and adjust the nitrogen-hydrogen composition ratio as needed, and then send the adjusted protective gas into the annealing furnace after completing heat exchange through the heat recovery subsystem.

2. The energy-saving steel rolling annealing furnace protective gas resource recovery and recycling system according to claim 1 is characterized in that: The first purification subsystem includes an adjustment baffle, an air induction device, an ash removal tower and an oil removal tower connected in sequence by pipelines; The regulating baffle is disposed at the front end of the first purification subsystem and is configured to regulate the suction flow rate of the protective gas; The induced draft device is an induced draft fan arranged in parallel and configured to draw protective gas into the first purification subsystem; The dust removal tower is configured to remove dust from the protective gas passing through; The de-oiling tower is configured to de-oil the protective gas after dust removal.

3. The energy-saving steel rolling annealing furnace protective gas resource recovery and recycling system according to claim 2 is characterized in that: A protective gas bypass channel is connected to the front end of the ash removal tower and the rear end of the oil removal tower. The protective gas bypass channel is provided with a first plug valve and a check valve, and is configured so that when the ash removal tower or the oil removal tower is in a fault or maintenance state, it will not affect the normal production of the steel rolling annealing furnace.

4. The energy-saving steel rolling annealing furnace protective gas resource recovery and recycling system according to claim 1 is characterized in that: The heat recovery subsystem includes a heat exchanger and an air blowing device connected in sequence by pipelines; The blowing device adopts blowers arranged in parallel and is configured to pass the protective gas of the air supply subsystem into the heat exchanger; The heat exchanger is configured to exchange heat between the shielding gas from the first purification subsystem and the shielding gas from the gas supply subsystem. The shielding gas from the first purification subsystem enters the second purification subsystem after heat exchange, and the shielding gas from the gas supply subsystem returns to the gas supply subsystem after heat exchange.

5. The energy-saving steel rolling annealing furnace protective gas resource recovery and recycling system according to claim 1 is characterized in that: The second purification subsystem includes a pressurizing device, a catalytic deoxidation tower and an adsorption dryer connected in sequence by pipelines; The boosting device uses a gas boosting pump arranged in parallel, and is configured to boost the protective gas after heat exchange; The catalytic deoxidation tower is configured to deoxidize the protective gas after the pressurization treatment; The adsorption dryer is configured to dry the protective gas after deoxygenation.

6. The energy-saving steel rolling annealing furnace protective gas resource recovery and recycling system according to claim 1 is characterized in that: The gas circulation subsystem includes a gas storage device, a first flow detection device and a workstation; The gas storage device uses a plurality of gas storage tanks arranged in parallel and is configured to store the protective gas output from the second purification subsystem; The first flow detection device adopts a thermal flow meter, which is installed at the outlet of the gas storage tank and is configured to measure the nitrogen and hydrogen flow of the protective gas in the corresponding gas storage tank; The workstation is signal-connected to the first flow detection device and receives the thermal flow meter signal collected by the thermal flow meter.

7. The energy-saving steel rolling annealing furnace protective gas resource recovery and recycling system according to claim 6 is characterized in that: The gas supply subsystem comprises: a first gas inlet pipeline, a second gas inlet pipeline, a gas mixing device, a pressure detection device, a pressure reducing device, a gas buffer device and a second flow detection device; The first air intake pipeline and the second air intake pipeline are respectively connected to the gas mixing device and are configured to respectively introduce nitrogen and hydrogen into the gas mixing device; The gas mixing device is a gas mixing tank, which is also connected to the gas storage tank pipeline and is configured to receive the protective gas from the gas storage tank, and based on the control of the workstation, nitrogen or hydrogen is introduced into the received protective gas to achieve nitrogen-hydrogen ratio readjustment; The decompression device is a decompressor or a decompression valve, which is respectively installed on the first air intake pipeline and the second air intake pipeline and is arranged close to the gas mixing tank, and is configured to decompress the gas introduced into the first air intake pipeline and the second air intake pipeline; The pressure detection device adopts a pressure gauge, and is configured to detect the pressure of the gas introduced into the first air intake line and the second air intake line; The gas buffer device is a plurality of gas buffer tanks arranged in parallel, one end of the gas buffer tank is connected to the gas mixing tank pipeline, and the other end of the gas buffer tank is connected to the annealing furnace pipeline, and is configured to buffer the protective gas to be input into the annealing furnace; The second flow detection device adopts a thermal flow meter, which is installed at the outlet of the gas buffer tank and is configured to measure the nitrogen and hydrogen flow rates of the protective gas in the corresponding gas buffer tank. The second flow detection device is also connected to the workstation signal to transmit the thermal flow meter signal collected by the thermal flow meter to the workstation.

8. The energy-saving steel rolling annealing furnace protective gas resource recovery and recycling system according to claim 7 is characterized in that: The gas supply subsystem also includes a second stopcock, a control valve and a heat circulation pipeline. The second stopcock is arranged on the pipeline between the gas buffer tank and the gas mixing tank, and the control valve is arranged on the pipeline between the gas buffer tank and the annealing furnace. One end of the heat circulation pipeline is connected to the pipeline between the second stopcock and the gas mixing tank, and the other end of the heat circulation pipeline is connected through the heat recovery system and the pipeline between the second stopcock and the gas buffer tank.

9. The energy-saving steel rolling annealing furnace protective gas resource recovery and recycling system according to claim 8 is characterized in that: The air supply subsystem and the air supply subsystem are both controlled by the workstation, which is configured to receive thermal flow meter signals from the air supply subsystem and the air supply subsystem, respectively, and issue instructions to the sensors corresponding to the first air intake pipeline and the second air intake pipeline according to the gas ratio set by the unit, so as to adjust the nitrogen and hydrogen intake flow rates.

10. The energy-saving steel rolling annealing furnace protective gas resource recovery and recycling system according to claim 8, characterized in that: The circulation pipeline is also provided with a venting pipeline connected thereto, and the venting pipeline is configured to release the protective gas.

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