Application of the most efficient regenerative lad

The application of high-efficiency regenerative ladle roaster in Taigang

Abstract: the energy-saving technical transformation of the original conventional ladle roaster was carried out by using regenerative combustion technology. Practice has proved that the regenerative ladle roaster has the characteristics of less investment, quick effect, safety, stability and reliability, and has extensive promotion value

key words: regenerative combustion technology ladle roaster

1 preface

regenerative combustion technology is an advanced combustion technology gradually popularized and applied in China after the 1990s. It has the dual effects of energy conservation and environmental protection. At present, it has been widely used in various fuel industrial furnaces in industrial departments such as steel, metallurgy, machinery, building materials, etc. Adopting regenerative combustion technology has become one of the important ways for iron and steel enterprises to save energy, reduce consumption and improve economic benefits

there is one set of ladle roaster device and three sets of off-line ladle roaster devices in the steelmaking plant of Taigang, all of which are baked by conventional combustion. In order to save gas and improve the baking effect, in September, 2002, Taigang Co., Ltd. cooperated with Beijing Shenwu company to carry out a thermal energy-saving technical transformation on one of the offline devices. At present, the equipment operates normally and has remarkable economic benefits

2 transformation scheme

this transformation adopts swx-i (vertical) regenerative ladle roaster, and the combustion system adopts the air single thermal storage mode, that is, a pair of regenerative burners are installed on the fixed position of the ladle cover, working alternately with each other, so that the preheating temperature of combustion supporting air reaches above 1000 ° C, and the exhaust gas temperature in overseas markets falls below 150 ° C

2.1 burner

the burner adopts wdhxr type regenerative high-efficiency energy-saving burner, the heating load is 3.3gj/h, and the burner capacity is 200nm3/h. The honeycomb heat accumulator developed by Shenwu company is used as the heat accumulator, which has self-cleaning, dust prevention and slagging prevention, and the heat storage efficiency is as high as 85 ~ 95%, with a normal service life of more than 1 year

2.2 the reversing device

adopts the air four-way reversing valve developed by Shenwu company, its specification is DN200, and the switching time is 1min/time. It has the functions of timing and forced commutation, as well as the function of all pass in the middle position (at this time, the smoke exhaust system stops working, and the smoke is discharged from the package edge)

2.3 smoke exhaust system

the smoke exhaust system is composed of air four-way valve, smoke exhaust pipe and high-temperature induced draft fan. The air volume of induced draft fan is 2000m3/h, the total pressure is 2000Pa, and the temperature resistance is 200 ℃

2.4 air supply system

use the existing blower, fan model 9-19 5.6A, air volume: 3317m3/h, air pressure 7375pa

2.5 control system

try to use the original instruments and equipment, expand appropriately, and add PLC input and output points and analog input and output points acquisition points. The action of reversing valve and gas shut-off valve is controlled by PLC. The reversing system, gas regulating valve, air regulating valve and induced draft inlet regulating valve have the functions of regular reversing, constant temperature forced reversing and smoke exhaust over temperature alarm. Alarm, gas cut-off, etc. in case of emergency. At the same time, it realizes the display, alarm and interlocking of temperature, pressure, flow and smoke exhaust temperature. Realize manual control of furnace temperature and air-fuel ratio. Combustion control, reversing control, and the start and stop of blower and induced draft fan are all centralized in one control cabinet

the ladle barbecue adopts PLC and supporting instruments to control the heating process of ladle barbecue. So as to ensure that the temperature always follows the pre selected control curve during the ladle barbecue process, and the lowest air-fuel ratio can be maintained in the steady-state and transition process of combustion, so as to fully burn the fuel and further reduce energy consumption and environmental pollution

when the system is put into operation, the heating process of ladle baking can be controlled manually. Qingdao bioenergy and process research institute has recently successfully developed a new polyurethane material to realize manual control. In order to facilitate the adjustment and maintenance of the system, the manual operation mode and necessary parameter display instruments are considered in this scheme

2.5.1 main detection and control parameters

(1) ladle baking temperature control, display

(2) exhaust gas temperature detection, display, participation in forced commutation

(3) air temperature detection into combustion chamber, display

(4) gas flow control, display and accumulation

(5) air flow control, display

(6) gas pressure detection, display

(7) air pressure detection, display

(8) air pressure Low gas pressure alarm, indication and cut-off gas

(9) directional valve directional in place indication and not in place alarm

(10) blower, induced draft fan shutdown, gas quick cut valve interlock function

2.5.2 control principle

when the system determines to receive the "open shut-off valve" and "start the system" instructions, it enters the operation preparation state. After confirming that the ignition works normally and selecting the temperature control curve, The system starts automatic temperature control by manually pressing the set temperature curve

during operation, if the air pressure or gas pressure is lower than the set value, the system will automatically cut off the gas and send an alarm signal, so as to ensure the safe operation of the toaster. After the air and gas pressure returns to normal, it will be unlocked manually

the control of air and gas reversing valves is switched synchronously by PLC according to the given time interval, and any travel switch still has no signal in place after 5 ~ 6 seconds of valve action, and the alarm signal is output and displayed. At the same time, the whole system is stopped, and it can not be put into operation until the fault is eliminated

2.6 ladle cover

the ladle cover can adopt the original structure and material. The opening position of the two burners on the ladle cover and the flame length and stiffness control during combustion are the technical know-how carefully developed by Shenwu company, which can ensure the uniform baking of the ladle and the best matching of the two regenerative burners

3 technical indicators and technical parameters

3.1 main indicators

baking temperature ≥ 1200 ° C, which can be appropriately increased as needed

temperature difference at the mouth and bottom of the bag: 1100 ° C, about 30h

cold bag:>1100 ° C, about 16h

turnover bag: 750 ~ 1100 ° C, about 10min

3.2 ignition mode: automatic

3.3 temperature regulation: automatic control; Manual

3.4 air fuel ratio adjustment: manual or automatic control

3.5 maximum heating load: 3.3gj/hour

3.6 regenerative burner capacity: 200nm3/h

3.7 fuel: coke oven gas, calorific value: 4000 4.18kj/nm3

3.8 air preheating temperature: ≈ 1000 ° c

3.9 flue gas emission temperature: ≤ 150 ° c

3.10 average fuel saving rate: more than 40%

4 application effect

the regenerative ladle roaster of 1# converter at Taigang was successfully ignited and put into operation on September 5, 2002. At present, the equipment operates stably and reliably, and the main economic and technical indicators have been significantly improved (as shown in Table 1). Compared with that before the transformation, its remarkable characteristics are as follows: Table 1: comparison of main indicators before and after the transformation

4.1 gas consumption is significantly reduced: the gas consumption of new ladle is reduced from the original 7425m3 to 3865m3, 3560m3 gas is saved for each ladle, and the energy saving rate is 47.95%

4.2 ladle baking time is significantly shortened: the baking time of new ladle is shortened from the original 72 hours to 62 hours. The shortening of ladle turnover time will make steelmaking production more orderly

4.3 ladle baking effect is significantly improved, cracks and other defects are significantly reduced

4.4 the reduction of smoke exhaust temperature improves the workshop environment to a certain extent, is conducive to the physical and mental health of workers, and objectively promotes the improvement of labor productivity

5 benefit analysis

5.1 direct benefit

5.1.1 gas consumption is significantly reduced

according to the test data on September 26th, 2002 after the transformation, compared with the average data from November 1999 to August 2002 before the transformation, the coke oven gas consumption of the existing regenerative ladle roaster for baking a new ladle is about 3865m3, and the gas consumption of the conventional ladle roaster for baking a new ladle is 7425m3, saving 3560 m3 of gas per ladle

if 15 new bags are baked every month, gas can be saved every year: 15 × three thousand five hundred and sixty × 12 = 640800m3

coke oven gas is calculated according to the transfer price in the plant of 0.398 yuan/m3, and the annual gas saving benefit is 0.398 × 640800 = 255000 yuan, the investment for the regenerative transformation of a set of offline conventional ladle roaster is about 150000 yuan, and the investment payback period is about 15/25 = 0.6 years, that is, 7.2 months

based on the market price of coke oven gas of 1.0 yuan/m3, the annual gas saving benefit is 1.0 × 640800 = 640800 yuan, and the investment payback period is about 15/64.08 = 0.23 years, that is, 2.8 months

5.2 indirect benefits

5.2.1 the ladle baking time is significantly shortened

the new ladle baking time is shortened from the original 72 hours to 62 hours. If the pressure is stable, it can be further shortened to 48 hours, and the ladle turnover time is further shortened

5.2.2 the ladle baking effect is significantly improved

due to the high and uniform baking temperature, the service life of the ladle lining is extended. If the power consumption caused by increasing the molten steel discharge temperature due to the low traditional ladle baking temperature is considered, the investment payback period will be shorter and the economic benefit will be more considerable

6 conclusion

the economic benefits of the ladle roaster in the steelmaking plant of Taigang are extremely significant through the transformation of regenerative energy-saving technology. At present, the equipment operates safely and reliably, and the production is normal and stable. Practice has proved that the application of regenerative ladle roaster in Taigang is successful. The regenerative ladle roaster has the characteristics of less investment and effective greening of plastic additives, that is, the additives synthesized are non-toxic, efficient, fast, safe, stable and reliable, and has a wide range of promotion value

about the author: Gao Zhenmin, male, born in 1952 in Qingdao, Shandong Province, is a senior engineer, mainly engaged in the design and research of metallurgical industrial furnaces

contact address: Shandong Laiwu Taishan Iron and Steel Co., Ltd