Furnace burden preheating heat treatment process

Abstract

The invention discloses a furnace charge preheating heat treatment process. The heat treatment method comprises the following steps that S1, furnace charge is added into a feeding trolley on an intermediate frequency furnace platform, and the feeding trolley vibrates to enable the furnace charge to be in a tiled shape; s2, the feeding trolley is transferred to an oxygen-enriched combustion preheating device through a vibration conveying device on an intermediate frequency furnace platform, so that the oxygen-enriched combustion preheating device preheats the tiled furnace charge; and S3, the feeding trolley is transferred to a discharging port through a vibration conveying device on an intermediate frequency furnace platform, and the furnace burden is placed in the intermediate frequency furnace for smelting. Before furnace charge is fed into the intermediate frequency furnace, the furnace charge is brought to the oxygen-enriched combustion preheating device for preheating through cooperation of the feeding trolley and the vibration conveying device, the oxygen-enriched combustion preheating efficiency is high, the smelting time is shortened, and energy consumption is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment, in particular to a furnace charge preheating heat treatment process. Background Art

[0002] A medium frequency furnace is a power supply device that converts industrial frequency 50HZ alternating current into medium frequency. It rectifies three-phase industrial frequency alternating current into direct current, and then converts direct current into adjustable medium frequency current to supply medium frequency alternating current flowing through capacitors and induction coils, generating high-density magnetic lines in the induction coil, cutting the metal material contained in the induction coil, and generating large eddy currents in the metal material.

[0003] In the prior art, the smelting of scrap steel is usually carried out by directly placing it into a medium frequency furnace through a conveying pipeline. The scrap steel needs to be heated to 800° C. in the medium frequency furnace first. The energy consumption is relatively high during the entire smelting process, for which reason this application is proposed. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a charge preheating heat treatment process, in which an oxygen-enriched combustion preheating device is added in front of a medium frequency furnace to reduce energy consumption.

[0005] In order to solve the above technical problems, the present invention is solved by the following technical solutions: A charge preheating heat treatment process, comprising a charge preheating heat treatment device, which comprises an intermediate frequency furnace, an intermediate frequency furnace platform, and a vibration conveying device and an oxygen-enriched combustion preheating device arranged on the intermediate frequency furnace platform, wherein the vibration conveying device is provided with a feeding trolley that can be moved transversely thereon, the feeding trolley comprises a vehicle body with an upper opening and a vibration motor arranged on the vehicle body, the vehicle body comprises a trough body for accommodating charge, and the intermediate frequency furnace is arranged at the discharge port of the vibration conveying device; The heat treatment steps are as follows: S1. Add the charge to the feeding trolley on the medium frequency furnace platform. The feeding trolley uses vibration to make the charge flat; S2. The feeding trolley is transferred to the oxygen-enriched combustion preheating device through the vibrating conveying device on the medium frequency furnace platform so as to preheat the flat-laid furnace charge; S3. The feeding trolley is transferred to the discharge port through the vibrating conveying device on the medium frequency furnace platform, and the charge is placed into the medium frequency furnace for smelting.

[0006] In the above technical solution, preferably, the oxygen-enriched combustion preheating device is composed of a frame, a thermal insulation cover, a burner, a natural gas pipeline and a valve group, a combustion-supporting air system, an oxygen pipeline and a valve group, an electronic control system and a number of instruments.

[0007] In the above technical solution, preferably, a dust collecting hood is provided on the thermal insulation cover, and the workshop dust removal duct is arranged on the side of the dust collecting hood or connected to the dust collecting hood.

[0008] In the above technical solution, preferably, the material of the trough body is heat-resistant stainless steel.

[0009] In the above technical solution, preferably, the outer side of the trough body is provided with fire-resistant fiber wool and / or an outer protective plate.

[0010] In the above technical solution, preferably, the charge in step S1 is scrap steel.

[0011] In the above technical solution, preferably, in step S1, the furnace charge is loaded in a hopper, and the hopper is lifted to the charging point on the top of the feeding trolley by a crane, and the furnace charge is added to the feeding trolley.

[0012] In the above technical solution, preferably, in step S1, the charge is added to the feed trolley by an electric suction cup in the charge feeding span.

[0013] In the above technical solution, preferably, in step S2, the oxygen-enriched combustion preheating device preheats the charge through the upper opening of the feeding trolley.

[0014] The beneficial effects of the present invention are: Before the charge is put into the medium frequency furnace, the charge is brought to the oxygen-enriched combustion preheating device for preheating through the cooperation of the feeding trolley and the vibrating conveying device. The oxygen-enriched combustion preheating efficiency is high, the smelting time is shortened, and energy consumption is saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the charge preheating heat treatment device of the present invention.

[0016] Figure 2 It is a schematic diagram of the coordination state between the feeding trolley and the oxygen-enriched combustion preheating device 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 charge preheating heat treatment process includes a charge preheating heat treatment device, which includes an intermediate frequency furnace 1, an intermediate frequency furnace platform 2, a vibration conveying device 3 and an oxygen-enriched combustion preheating device 4 arranged on the intermediate frequency furnace platform 2.

[0018] like Figure 1 As shown, the medium frequency furnace 1 can be placed on one side of the medium frequency furnace platform 2, the vibration conveying device 3 and the oxygen-enriched combustion preheating device 4 are arranged above the medium frequency furnace platform 2, the discharge port of the vibration conveying device 3 is located above the medium frequency furnace 1, and the charge can be added into the medium frequency furnace 1 from the discharge port for smelting.

[0019] The vibrating conveyor 3 is provided with a feeding trolley 5 which can move horizontally thereon. The feeding trolley 5 is used as a placement position for the charge in the preheating stage. The feeding trolley 5 includes a vehicle body with an upper opening and a vibration motor arranged on the vehicle body. The vehicle body includes a trough body 51 for accommodating the charge, so that after the vibration motor is started, the charge can be vibrated in the trough body 51 to make it flat, so as to improve the preheating efficiency.

[0020] The heat treatment steps are as follows: S1. Add the charge to the feeding trolley on the medium frequency furnace platform. The feeding trolley uses vibration to make the charge flat. The thickness of the charge flattening is selected according to actual needs. S2. The feeding trolley is transferred to the oxygen-enriched combustion preheating device through the vibrating conveying device on the medium frequency furnace platform, and the flat-laid charge is preheated through the upper opening of the feeding trolley; S3. The feeding trolley is transferred to the discharge port through the vibrating conveying device on the medium frequency furnace platform, and the charge is placed into the medium frequency furnace for smelting. In this step, the charge can be added to the furnace in multiple times according to the actual loading capacity of the medium frequency furnace, such as a single addition of about 1.5-2 tons.

[0021] For the feeding method in step S1, there are at least two of the following: First, the furnace charge is loaded in a hopper, which is lifted to the top of the feeding trolley by a crane, and the furnace charge is added to the feeding trolley; Secondly, the charge is added to the feeding trolley by an electric suction cup at the charge feeding span.

[0022] Compared with the existing trolley, the upper baffle of the existing trolley is removed to make the upper part of the trolley open for easy feeding.

[0023] For the tank body on the vehicle body, a wide tank body may be used, such as Figure 2 As shown, the material of the trough body is heat-resistant stainless steel to avoid premature deformation caused by high temperature. Furthermore, refractory fiber cotton and an outer protective plate can be laid on the outside of the trough body.

[0024] The oxygen-enriched combustion preheating device is composed of a frame, a thermal insulation cover, a burner, a natural gas pipeline and a valve group, a combustion-supporting air system, an oxygen pipeline and a valve group, an electronic control system and several instruments.

[0025] The performance characteristics of oxygen-enriched combustion: accelerate the combustion speed, promote complete combustion, and increase the combustion temperature of the flame; reduce NOx emissions and reduce heat loss; reduce the ignition temperature of the fuel, which can increase the flame intensity and increase the heat release; reduce the excess air coefficient, reduce fuel consumption, and thus save energy; increase the heat utilization rate, oxygen-enriched combustion technology has improved the heat utilization rate.

[0026] The oxygen-enriched combustion preheating device is divided into a mechanical system, a valve station system, an instrumentation system and an electrical control system.

[0027] For the mechanical system, its oxygen-enriched combustion system includes high-efficiency energy-saving burners, long-fire ignition burners, and distribution pipelines for combustion-supporting air, gas, oxygen, etc., which can ensure that the scrap steel is quickly preheated after passing through the preheating section; its steel frame structure includes high insulation, dust removal docking protective cover, combustion system, pipelines, structural frame and connecting parts; it has a long-fire function, and each ignition burner is equipped with an electronic igniter.

[0028] For the valve station system, its gas valve group includes quick shut-off valves, cut-off valves, pneumatic regulating valves and manual valves; its oxygen valve group includes quick shut-off valves, pressure reducing valves, regulating valves, manual valves and flame arresters; in addition, it also includes nitrogen solenoid valves, ball valves, pilot flame solenoid valves, combustion-supporting air electric regulating valves and manual regulating valves.

[0029] For the instrumentation system, it includes oxygen pressure gauge, flow meter, pressure transmitter and fuel gas pressure gauge.

[0030] For the electrical control system, the power supply capacity is reasonably selected according to the electricity consumption of electrical, instrumentation and machinery, and the line classification is protected against short circuit and overload; the power supply required by the instrument is configured to ensure the normal operation of the electrical, instrumentation and machinery: through the collection and feedback of the primary instrument on site, the electric control cabinet implements different controls on the baking status and mechanical equipment to achieve the expected purpose of preheating.

[0031] Siemens PLC is used to facilitate network communication and reserve sufficient I / O points. The PLC system will provide logical control and closed-loop control of the preheating equipment, and provide accident handling procedures. In the event of an accident, the operator only needs to press the emergency stop button to run each component of the equipment to a safe state, reducing misoperation caused by human tension. At the same time, the system can also be manually operated by humans based on experience.

[0032] The electrical automation part has a safety interlock function; it has a flammable gas leakage alarm: if the concentration of natural gas leakage exceeds the standard, an audible and visual alarm will be issued; it has a gas cut-off, power cut-off, and low gas pressure quick cut-off function: when the natural gas pressure is too low or too high, the cut-off valve and oxygen valve will be quickly closed, and an audible and visual alarm signal will be issued. When the power grid is powered off, the control system will automatically lock, the gas and oxygen cut-off valves will automatically close, and the natural gas and oxygen pipelines will be quickly cut off. The line classification implements short circuit, overload protection, and power off protection; it has a flame detection and flameout alarm device. When the flame detector cannot detect a flame, an audible and visual alarm will be issued and the gas and oxygen quick-cut valves will be cut off; it has a long-lasting open flame function. A nitrogen purge branch is set on the gas pipeline, and a control valve group is installed. The gas pipeline is purged before each startup and after baking to take away the gas remaining in the pipeline, which plays a safety protection role.

[0033] The preheating equipment is arranged on the medium frequency furnace platform. After the charging cart adds the charge, the vibration conveying mechanism transports the charge to the preheating area for rapid preheating. After the preheating is completed, when the medium frequency furnace needs to be charged, the charging cart is driven to the charging position, and the high-temperature scrap steel is added to the furnace through vibration conveying.

[0034] By adding oxygen-rich fuel to the combustion, the flame with oxygen as the core is strong and powerful, which can quickly heat up the scrap steel in the trough and ensure uniform preheating of the scrap steel.

[0035] In the preheating stage, the scrap steel (charge) is preheated in the vibration tank, and the charge is preheated by mixed combustion of natural gas, air and oxygen. The flame temperature is high and the penetration is extremely strong. 1.5-2 tons of charge can be preheated to 800-900℃ in 15-20 minutes, and the charge is preheated evenly. After preheating, it can directly enter the medium frequency furnace for smelting. It saves about 40% of electricity and shortens the smelting time of the furnace by 20 minutes during continuous smelting.

[0036] In addition to preheating scrap steel outside the furnace, a medium frequency furnace baker can be installed to heat the refractory materials and charge materials in the furnace before the first furnace opening, increase the temperature in the furnace, further reduce the first furnace smelting time and energy consumption, speed up the production rhythm, and reduce smelting costs.

[0037] The flue gas collection system is equipped with a dust hood on the insulation cover of each preheating device. The dust removal pipeline in the workshop is led to the side of the dust hood or connected to the dust hood. The waste flue gas generated after preheating is collected through the dust removal pipeline and then centrally treated.

[0038] In the above technical solution, preferably, in step S2, the oxygen-enriched combustion preheating device preheats the charge through the upper opening of the feeding trolley.

[0039] Benefit Analysis: 1. Existing economic data: Power consumption per ton of molten steel: 580KW.h; Electricity price: 0.33 yuan / KW.h; Water and electricity cost per ton of steel: 580*0.33=191.4 yuan; The induction energy generated by 580 degrees of electricity is: 448920Kcal; The theoretical energy required to heat a ton of scrap steel from room temperature to 1480℃ liquid: 328014Kcal; Actual energy conversion rate: 73%.

[0040] 2. Improved data: To heat a ton of scrap steel to 800°C, 15 Nm³ of natural gas, 1.7 KW.h of electricity and 10 N m³ of oxygen are required.

[0041] The cost of preheating scrap steel with natural gas + oxygen is: Oxygen cost: 10Nm2 / ton scrap steel x 1 yuan / Nm³=10 yuan; Natural gas cost: 15Nm2 / ton scrap steel x 4.5 yuan / Nm³=67.5 yuan.

[0042] Electricity cost: 10,000 tons of fuel / ton of scrap steel x 0.33 yuan / KW.h = 0.561 yuan; The total preheating cost per ton of scrap steel is: 78 yuan.

[0043] The theoretical energy required to heat scrap steel from 850°C to 1480°C liquid is 113615 Kcal, and the theoretical amount of electricity is 136 degrees.

[0044] According to the actual on-site energy conversion rate: 73%, the required energy is 155637Kcal, which is converted into electricity consumption: 201 degrees.

[0045] Later electricity fee: 201 / ton scrap steel x 0.33 yuan / KW.h = 66.33 yuan; The total cost is: 78+66.33=144.33 yuan; Balance cost: 191.4-144.33=47 yuan.

[0046] According to the data, the energy conversion of natural gas power generation units is 7-8 kWh of electricity per 1N m³ natural gas. Taking the middle value of 7.5 kWh, 15 cubic meters of natural gas consumed by natural gas to heat scrap steel is approximately equal to 112.5 kWh of electricity. The electricity consumption of 1N m³ of oxygen production is 0.33 kWh, and 10 cubic meters of oxygen consumed to heat scrap steel is approximately equal to 3.3 kWh of electricity. The total electricity consumption of natural gas heating a ton of scrap steel is 115.8 kWh of electricity.

[0047] 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. Charge preheating heat treatment process, characterized by: It comprises a charge preheating heat treatment device, which comprises an intermediate frequency furnace, an intermediate frequency furnace platform, and a vibration conveying device and an oxygen-enriched combustion preheating device arranged on the intermediate frequency furnace platform. The vibration conveying device is provided with a feeding trolley that can move transversely thereon, the feeding trolley comprises a vehicle body with an upper opening and a vibration motor arranged on the vehicle body, the vehicle body comprises a trough body for accommodating charge, and the intermediate frequency furnace is arranged at the discharge port of the vibration conveying device; The heat treatment steps are as follows: S1. Add the charge to the feeding trolley on the medium frequency furnace platform. The feeding trolley uses vibration to make the charge flat; S2. The feeding trolley is transferred to the oxygen-enriched combustion preheating device through the vibrating conveying device on the medium frequency furnace platform so as to preheat the flat-laid furnace charge; S3. The feeding trolley is transferred to the discharge port through the vibrating conveying device on the medium frequency furnace platform, and the charge is placed into the medium frequency furnace for smelting.

2. The charge preheating heat treatment process according to claim 1, characterized in that: The oxygen-enriched combustion preheating device is composed of a frame, a heat-insulating cover, a burner, a natural gas pipeline and a valve group, a combustion-supporting air system, an oxygen pipeline and a valve group, an electric control system and a plurality of instruments.

3. The charge preheating heat treatment process according to claim 2 is characterized in that: The heat-insulating cover is provided with a dust collecting hood, and the workshop dust removal pipeline is arranged on the side of the dust collecting hood or connected with the dust collecting hood.

4. The charge preheating heat treatment process according to claim 1, characterized in that: The material of the tank body is heat-resistant stainless steel.

5. The charge preheating heat treatment process according to claim 1 or 4, characterized in that: The outer side of the tank body is provided with fire-resistant fiber wool and / or an outer protective plate.

6. The charge preheating heat treatment process according to claim 1, characterized in that: The charge in step S1 is scrap steel.

7. The charge preheating heat treatment process according to claim 1, characterized in that: In step S1, the furnace charge is loaded into a hopper, and the hopper is lifted to the charging position on the top of the feeding trolley by a crane, and the furnace charge is added into the feeding trolley.

8. The charge preheating heat treatment process according to claim 1, characterized in that: In step S1, the charge is added to the feed trolley by an electric suction cup at the charge feeding span.

9. The charge preheating heat treatment process according to claim 1, characterized in that: In step S2, the oxygen-enriched combustion preheating device preheats the charge through the upper opening of the feeding trolley.

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