Oxygen-enriched combustion heat treatment process

Abstract

The invention discloses an oxygen-enriched combustion heat treatment process. Comprising the following steps that S1, ignition is conducted, specifically, a PLC system sends an operation signal to a combustion controller BCU, the combustion controller BCU opens a gas electromagnetic valve and an air valve and switches on an ignition transformer power source, and ignition is started; and S2, when ignition succeeds and the heating furnace is in a high-temperature period, combustion enters an oxygen-enriched combustion mode, and the temperature in the high-temperature period is larger than or equal to 850 DEG C. The oxygen-enriched combustion mode in the high-temperature period is adopted and matched with the molecular sieve and the compressed air injection mode, the natural gas consumption is reduced, the higher gas energy saving amount is achieved, the peroxide coefficient is low, and therefore the production cost is reduced, and the product quality is improved.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment, in particular to an oxygen-enriched combustion heat treatment process. Background Art

[0002] Oxygen-enriched combustion refers to combustion when the volume fraction of oxygen in the gas supplied for combustion is greater than 21%. At present, conventional air is generally used as the combustion air for combustion systems of heating furnaces and heat treatment furnaces at home and abroad. Usually, the oxygen content in the air is 21% and the nitrogen content is 78%. During the combustion process, only about 21% of the oxygen in the total air participates in the combustion, while the nitrogen and other inert gases that account for 78% of the total air not only do not support combustion, but will be discharged into the atmosphere with the flue gas, taking away a large amount of heat, resulting in high energy consumption, large product loss and serious pollution in the existing heating furnaces. For the long-term high-quality development of the enterprise and to comply with the technological innovation and development of equipment and technology, it is necessary to upgrade and transform the existing equipment. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides an oxygen-enriched combustion heat treatment process, replaces the combustion system with a self-preheating heat storage burner with high adjustment accuracy, adds a molecular sieve, abolishes the blower / induced draft fan, replaces it with a compressed air injection method, and adopts an oxygen-enriched combustion method during a high temperature period, thereby reducing the use of natural gas, achieving higher gas energy saving, and a low excess oxygen coefficient, thereby achieving the goals of reducing production costs and improving product quality.

[0004] In order to solve the above technical problems, the present invention is solved by the following technical solutions: The oxygen-enriched combustion heat treatment process comprises the following steps: S1, ignition: The PLC system sends an operation signal to the combustion controller BCU, and the combustion controller BCU opens the gas solenoid valve, air valve and connects the ignition transformer power supply to start ignition; S2. When the ignition is successful and the furnace is in the high temperature period, the combustion enters the oxygen-rich combustion mode, and the temperature in the high temperature period is ≥850°C.

[0005] In the above technical solution, preferably, in step S1, if a flame signal is detected within a specified time of the combustion controller BCU, a contact signal indicating successful ignition is issued to maintain the opening of the gas solenoid valve and the air valve; If no flame signal is detected within the specified time of the combustion controller BCU, the gas solenoid valve will be immediately cut off to interrupt the gas supply and a contact signal of ignition failure will be issued.

[0006] In the above technical solution, preferably, a fire monitoring mode is implemented after the ignition is completed: After the system is successfully ignited and operates normally, the flame detector continues to detect the burner flame, and its detection signal is sent to the combustion controller BCU. Once the flame signal disappears, the combustion controller BCU immediately cuts off the gas solenoid valve, interrupts the gas supply, and sends a flame fault alarm contact signal.

[0007] In the above technical solution, preferably, the flame detector is an ultraviolet detector UVS or an electrode.

[0008] In the above technical solution, preferably, after the ignition is completed, the control mode is switched: After the burner is successfully ignited and enters the normal operating state, the switching timer in the PLC starts running. When the timer is up, a switching control signal is sent to control the switching of the corresponding burner's combustion-supporting gas and fuel gas as well as the smoke exhaust control valve.

[0009] In the above technical solution, preferably, after the ignition is completed, the combustion power control mode is implemented: Duty cycle power regulation: The system uses on / off fire pulse control to control the furnace temperature. The PLC temperature control system receives the furnace temperature sensor signal and compares it with the set value. The difference is calculated through PID operation to send a burner duty cycle switch signal to the combustion controller BCU. The combustion controller BCU executes the burner switch accordingly.

[0010] In the above technical solution, preferably, the combustion power control mode also includes: Air / heat ratio control: This task is automatically completed by the pneumatic proportional valve, which automatically controls the burner gas inlet pressure according to the combustion-supporting gas pressure.

[0011] In the above technical solution, preferably, the heating furnace also includes a cut-off module, which is executed by two solenoid valves to cut off the gas emergency when an emergency occurs such as gas pressure, air pressure, or over-temperature. The cut-off signal is taken from the corresponding pressure switch, temperature alarm contact, and emergency cut-off switch.

[0012] In the above technical solution, preferably, the heating furnace also includes a main solenoid valve air tightness detection: This is automatically completed by the air tightness detector. When the PLC control system starts, it sends a command to the air tightness detector. The air tightness detector automatically runs the built-in detection program to detect the air tightness of the cut-off solenoid valve. By sending out an OK contact signal, the PLC system runs the next process accordingly. If it fails, it sends out an alarm contact signal, and the PLC terminates the system operation accordingly.

[0013] In the above technical solution, preferably, two burners are arranged at the bottom of the north and south sides of the heating furnace, and at least one burner is connected to the molecular sieve and injected by compressed air; Several temperature sensor measuring points are arranged on the heating furnace, including one measuring point each near the furnace door on the upper south and north sides, one measuring point each at the upper center of the south and north sides, three measuring points evenly distributed from west to east along the east-west central axis on the top, one measuring point each near the south and north on the upper east side, and one measuring point at the north-center of the east side.

[0014] The beneficial effects of the present invention are: The present invention adopts oxygen-enriched combustion in high temperature period, cooperates with molecular sieve and compressed air injection, reduces natural gas consumption, has higher gas energy saving, and low excess oxygen coefficient, thereby reducing production costs and improving product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the present invention.

[0016] Figure 2 This is a schematic diagram of the layout of the temperature sensor measurement points of the present invention. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments: See also Figure 1 and Figure 2 , the oxygen-enriched combustion heat treatment process comprises the following steps: S1. Ignition: This task is performed by the combustion controller BCU. The PLC system sends an operation signal to the combustion controller BCU. The combustion controller BCU opens the gas solenoid valve, air valve and connects the power supply of the ignition transformer to start ignition.

[0018] If the flame signal is detected within the specified time of the combustion controller BCU, a contact signal of successful ignition will be issued to maintain the opening of the gas solenoid valve and the air valve; If no flame signal is detected within the specified time of the combustion controller BCU, the gas solenoid valve will be immediately cut off to interrupt the gas supply and a contact signal of ignition failure will be issued.

[0019] S2. When the ignition is successful and the furnace is in a high temperature period (temperature ≥ 850°C), the combustion enters the oxygen-rich combustion mode, which is flameless combustion. At this time, the combustion efficiency reaches its peak and the oxygen content is lower.

[0020] In this embodiment, the fire monitoring mode is implemented after the ignition is completed: After the system is successfully ignited and operates normally, the flame detector (ultraviolet detector UVS or electrode) continues to detect the burner flame, and its detection signal is sent to the combustion controller BCU. Once the flame signal disappears (the flame is extinguished), the combustion controller BCU immediately cuts off the gas solenoid valve, interrupts the gas supply, and sends a flame fault alarm contact signal.

[0021] In this embodiment, the control mode is switched after the ignition is completed: After the burner is successfully ignited and enters the normal operating state, the switching timer in the PLC starts running. When the timer is up, a switching control signal is sent to control the switching of the corresponding burner's combustion-supporting gas and fuel gas as well as the smoke exhaust control valve.

[0022] In this embodiment, after ignition is completed, the combustion power control mode is implemented: Duty cycle power regulation: The system uses on / off fire pulse control to control the furnace temperature. The PLC temperature control system receives the furnace temperature sensor signal and compares it with the set value. The difference is calculated by PID to send the burner duty cycle switch signal to the combustion controller BCU. The combustion controller BCU executes the switch of the burner accordingly. Air / heat ratio control: This task is automatically completed by the pneumatic proportional valve, which automatically controls the burner gas inlet pressure according to the combustion-supporting gas pressure.

[0023] For gas main control, it includes gas pressure regulation, emergency cut-off and main solenoid valve air tightness detection, among which gas pressure regulation is automatically performed by the pressure regulating valve.

[0024] The emergency cut-off is performed by the cut-off module, which specifically includes two solenoid valves. It cuts off the gas in an emergency when gas pressure, air pressure, or over-temperature occurs. The cut-off signal is taken from the corresponding pressure switch, temperature alarm contact, and emergency cut-off switch.

[0025] For the main solenoid valve air tightness test: This is automatically completed by the air tightness detector. When the PLC control system starts, it sends a command to the air tightness detector. The air tightness detector automatically runs the built-in detection program to detect the air tightness of the cut-off solenoid valve. By sending out an OK contact signal, the PLC system runs the next process accordingly. If it fails, it sends out an alarm contact signal, and the PLC terminates the system operation accordingly.

[0026] As for the burner installation position, in this embodiment, two burners are arranged at the bottom of the north and south sides of the heating furnace, and at least one burner is connected to the molecular sieve, which is injected by compressed air. Figure 1 shown.

[0027] As one of the implementation methods, two burners are arranged at the bottom of the north and south sides of the heating furnace, below 440mm, with a horizontal stagger of 750mm in the north-south relative depth direction, and the positions of the four flame nozzles correspond to the center of the pier column gap; the burner can use a self-preheating heat storage burner with high adjustment accuracy, and all high-temperature flue gases in the furnace are discharged through the burner. Through the internal heat exchange / heat storage of the burner, the heat is fully recovered to ensure that the exhaust temperature is ≤130℃ (when the furnace temperature is 1100℃). The first-level heat exchange uses a heat exchanger made of high-temperature resistant materials to ensure that it is not damaged at the highest furnace temperature of 1100℃; the front end of the burner is a semi-premixed structure design, and the air / fuel is fully mixed, which can obtain lower CO emissions and excess oxygen content, and higher accuracy.

[0028] The four burners are arranged opposite to each other in pairs with their horizontal centers staggered, ensuring turbulence during combustion, which is beneficial to the uniform distribution of the temperature field in the furnace; the four burners are arranged opposite to each other in pairs with staggered spray flames, forming a horizontal heat flow disturbance. At the same time, the stacking method of materials above the flame maintains a gap for the upward movement of flue gas, and the flue gas in the furnace forms natural convection up and down. The burner's own reflux exhaust gas refluxes from the gap between the material bracket and the furnace wall, further strengthening the up and down reflux disturbance of the flue gas.

[0029] As one of the implementation methods, each burner is equipped with a set of molecular sieves, which automatically switch between two to operate; the molecular sieve technology is combined to make the high-temperature combustion period oxygen-rich combustion, stripping away 79% of the nitrogen in the air that does not participate in the combustion, greatly reducing the smoke exhaust volume, thereby reducing heat loss and improving energy saving rate.

[0030] Through later debugging, the furnace pressure can be lowered as much as possible; the furnace pressure is regulated by the smoke exhaust system; when the flue and chimney are at low temperature in the furnace, condensed water will precipitate, so the flue and chimney need to be drained and collected; the smoke exhaust port on the rear wall of the kiln is closed to prevent the emission of uncontrollable high-temperature flue gas and avoid heat loss.

[0031] The total gas consumption of the four burners is 100Nm3 / h, which is the same as the maximum output load of the original regenerative burner. The maximum load is not changed and the heat load required by the furnace can still be met.

[0032] The burner and important parts of the combustion system are all imported high-end components to ensure reliable operation and long life cycle of the system; The original indoor emission chimney was abolished, and the outdoor emission chimney flue was used to avoid the impact of flue gas on the workshop environment; during debugging, the 10 temperature measurement points on the original furnace were screened, and the most reasonable measurement point was selected as the combustion load control point; during debugging, the furnace back pressure control parameters were finally set according to the actual working conditions to make it controllable and easy to control; during debugging, the flue gas was analyzed to adjust the combustion operation state to the best.

[0033] When the PLC program is compiled, a communication interface is reserved to facilitate future intelligent upgrades; the open part of the PLC program can set the parameter interface, and according to the actual production, the temperature rise for each time period or hour, as well as the product batch input, can be input to automatically generate production reports for easy production management.

[0034] In order to keep the control cabinets in the workshop control room unified, the original cabinet body can be used. After the control is integrated, only the installation plate inside the cabinet is provided; the original exhaust chimney is partially modified to avoid smoke cross-flow, and a smoke detection port that meets the specifications is opened to carry out drainage and water collection modifications; all air ducts are made of seamless steel pipes to ensure sealing, and the smoke ducts are separately insulated to avoid burns.

[0035] In this embodiment, several temperature sensor measuring points are arranged on the heating furnace, and their positions are arranged as follows: Figure 2 As shown, as one of the implementation methods, the upper south and north sides near the furnace door are measuring points 7# and 1#, the upper center positions of the south and north sides are measuring points T2 and T1, the top is evenly distributed along the east-west central axis from west to east at three measuring points 2#, 8#, and 6#, the upper east side near the south and north are measuring points 5# and 3# respectively, and the north-center position of the east side is measuring point 4#, totaling 10 measuring points.

[0036] As one of the implementation methods, the furnace back pressure measurement point is located in the north-central part of the east side.

[0037] Through a series of transformation work, the original 60Nm 3 Natural gas consumption dropped to 34Nm / ton 3 / ton of natural gas consumption, or even higher gas energy saving, and low excess oxygen coefficient, to achieve the goal of reducing production costs and improving product quality (reducing product oxide scale formation).

[0038] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. Oxygen-enriched combustion heat treatment process, characterized in that: The following steps are involved: S1, ignition: The PLC system sends an operation signal to the combustion controller BCU, and the combustion controller BCU opens the gas solenoid valve, air valve and connects the ignition transformer power supply to start ignition; S2. When the ignition is successful and the furnace is in the high temperature period, the combustion enters the oxygen-rich combustion mode, and the temperature in the high temperature period is ≥850°C.

2. The oxygen-enriched combustion heat treatment process according to claim 1, characterized in that: In step S1, if the flame signal is detected within the specified time of the combustion controller BCU, a contact signal of successful ignition is issued to maintain the opening of the gas solenoid valve and the air valve; If no flame signal is detected within the specified time of the combustion controller BCU, the gas solenoid valve will be immediately cut off to interrupt the gas supply and a contact signal of ignition failure will be issued.

3. The oxygen-enriched combustion heat treatment process according to claim 1, characterized in that: After ignition is completed, the fire monitoring mode is implemented: After the system is successfully ignited and operates normally, the flame detector continues to detect the burner flame, and its detection signal is sent to the combustion controller BCU. Once the flame signal disappears, the combustion controller BCU immediately cuts off the gas solenoid valve, interrupts the gas supply, and sends a flame fault alarm contact signal.

4. The oxygen-enriched combustion heat treatment process according to claim 3, characterized in that: The flame detector is an ultraviolet detector UVS or an electrode.

5. The oxygen-enriched combustion heat treatment process according to claim 1, characterized in that: After ignition is completed, switch the control mode: After the burner is successfully ignited and enters the normal operating state, the switching timer in the PLC starts running. When the timer is up, a switching control signal is sent to control the switching of the corresponding burner's combustion-supporting gas and fuel gas as well as the smoke exhaust control valve.

6. The oxygen-enriched combustion heat treatment process according to claim 1, 3 or 5, characterized in that: After ignition is completed, the combustion power control mode is implemented: Duty cycle power regulation: The system uses on / off fire pulse control to control the furnace temperature. The PLC temperature control system receives the furnace temperature sensor signal and compares it with the set value. The difference is calculated through PID operation to send a burner duty cycle switch signal to the combustion controller BCU. The combustion controller BCU executes the burner switch accordingly.

7. The oxygen-enriched combustion heat treatment process according to claim 6, characterized in that: Combustion power control modes also include: Air / heat ratio control: This task is automatically completed by the pneumatic proportional valve, which automatically controls the burner gas inlet pressure according to the combustion-supporting gas pressure.

8. The oxygen-enriched combustion heat treatment process according to claim 1, characterized in that: The heating furnace also includes a cut-off module, which is executed by two solenoid valves to cut off the gas in case of emergency situations such as gas pressure, air pressure, and over-temperature. The cut-off signal is taken from the corresponding pressure switch, temperature alarm contact, and emergency cut-off switch.

9. The oxygen-enriched combustion heat treatment process according to claim 1, characterized in that: The heating furnace also includes the main solenoid valve air tightness test: This is automatically completed by the air tightness detector. When the PLC control system starts, it sends a command to the air tightness detector. The air tightness detector automatically runs the built-in detection program to detect the air tightness of the cut-off solenoid valve. By sending out an OK contact signal, the PLC system runs the next process accordingly. If it fails, it sends out an alarm contact signal, and the PLC terminates the system operation accordingly.

10. The oxygen-enriched combustion heat treatment process according to claim 1, characterized in that: Two burners are arranged at the bottom of the north and south sides of the heating furnace, and at least one burner is connected to the molecular sieve and injected by compressed air; Several temperature sensor measuring points are arranged on the heating furnace, including one measuring point each near the furnace door on the upper south and north sides, one measuring point each at the upper center of the south and north sides, three measuring points evenly distributed from west to east along the east-west central axis on the top, one measuring point each near the south and north on the upper east side, and one measuring point at the north-center of the east side.

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