Shenyang Chuangsida Technology Co., LTD   billow

 

Abstract: As one of the by-products of steelmaking, the recycling and utilization of converter gas can help iron and steel enterprises to save energy and reduce emissions, reduce costs and reduce environmental pollution. It is of great significance to realize the goal of "negative energy steelmaking". On the other hand, converter gas is flammable, explosive and highly toxic gas, which is easy to cause casualties. Therefore, the safety problem is the most troublesome and worrying problem in the process of gas dust removal and recovery in steel converter. It is also the key to ensure the normal operation of the converter.

Key words: smelting, dust removal, safety, anti-virus operation
The flue gas of steel converter is composed of CO, CO2, N2 and a small amount of H2, O2, etc., which is high temperature, high dust, inflammable, explosive and highly toxic, and is easy to cause casualties. When the converter gas was released through the chimney, there were cases of poisoning birds passing through the air and falling down, which shows how toxic it is. Therefore, only through good design, operation, manufacturing, control and safety protection measures as a guarantee, and strive to reduce accidents.

Converter gas is one of metallurgical gas, metallurgical gas mainly include: blast furnace gas, coke oven gas, ferroalloy gas, converter gas and producer gas. Gas is a mixture, because the composition is not the same, the risk of gas is not the same. From a safety point of view, the most concerned are carbon monoxide, hydrogen, methane three components, they are both dangerous ingredients, but also useful ingredients, with a high calorific value. The toxicity of gas is mainly carbon monoxide poisoning. The hydrogen and methane in the gas are explosive, and the lower the explosion limit, the stronger the explosion of the gas. The properties of common metallurgical gas are shown in Table 1

Table 1 Metallurgical gas composition and explosion range

ingredient Type of gas	CO	H2	CH4	Explosion range
Coke oven gas	6-9	58-60	22-25	4.5-35.8
Blast furnace gas	26-29	2.0-3.0	0.1-0.4	35.0-72.0
Converter gas	63-66	2.0-3.0		12.5-74.0
Ferroalloy furnace gas	60-63	13-15	0.5-0.8	7.8-75.07
Producer gas	27-31	7-10	16-18	21.5-67.5

 

It can be seen from Table 1 that the CO content in coke oven gas is relatively low, the toxicity is the least, but the explosive limit is the lowest and the explosive is the strongest; Converter gas CO is the highest, the content accounts for 60-70%, the most toxic. Blast furnace gas is both toxic and explosive, but there are differences.

1, converter gas dust recovery system main gas protection area

1.1 Converter smoke hood, oxygen gun, auxiliary gun insertion hole, manhole, transfer charging hole, etc.;

1.2 There is a danger of gas poisoning in all the platforms above the vaporizing cooling flue of the converter, the inlet and outlet of the evaporative cooler, and the furnace mouth of the converter;

1.3 In the dust removal system, the rear devices such as: electric precipitator, air room, switching station, gas cooling tower, gas tank, gas pipeline and release tower, etc.;

1.4 The distribution area of the gas pipe network is wide and the danger point is many, and the gas pipe should take measures to eliminate static electricity and lightning protection.

2. Prevention of gas and nitrogen poisoning accidents

Three procedures for poisoning prevention:

2.1 One person is not allowed to work, only more than 2 people can work;

2.2 Two people can not work at the same time, one person to work and one person to monitor;

2.3 Wait for the gas alarm.

3, dust recovery system safety operation specifications

3.1 Operators must master the knowledge of gas safety and gas poisoning first aid, master the use of gas tester, air breathing apparatus and other gas protective appliances;

3.2 Gas tester and air breathing apparatus and other gas protective appliances must always be in good condition, every day shift must be carefully checked;

3.3 In the gas inspection and maintenance and replacement, more than two people must do a good job of monitoring, and wear a gas tester, air breathing apparatus, hanging pigeons, while trying to be in the limelight;

3.4 In addition to the staff of the Department, the outside idle personnel shall not enter the gas area without permission;

3.5 In the gas area, turn off the mobile phone and other communication tools, and do not allow anyone to carry fire;

3.6 The oxygen gun holes and feeding ports on the flue shall be provided with reliable nitrogen seals. Gas detection and alarm devices should be installed on the platform of each layer above the crossing of the converter furnace. The above platforms, personnel should not stay for a long time to prevent gas poisoning; If it is necessary to stay for a long time, it should coordinate with relevant parties and take reliable safety measures;

3.7 The equipment of the converter gas recovery system, the air room, the gas tank and other equipment that may leak gas should be located on the upwind side of the workshop with the minimum frequency wind direction throughout the year. When the converter gas is recovered, the air room shall be a Class B production workshop and a second-class dangerous place. Fire prevention and explosion prevention measures shall be taken in its design, and fire fighting equipment, fire alarm signals, communication and ventilation facilities shall be equipped. Normal ventilation should be no less than 7 times per hour, and emergency ventilation should be no less than 20 times per hour.

3.8 For the converter gas dust removal and recovery system, facilities such as unloading, dispersing and purging should be set reasonably;

3.9 When overhauling the evaporative cooling tower, it must be overhauled in the case of furnace shutdown, and the furnace opening must be placed horizontally, and the "no operation" can be hung before operation.

3.10 When opening the manhole doors of gas equipment and pipelines, the body should be opened sideways to prevent gas poisoning and nitrogen asphyxiation;

3.11 When cleaning ash inside the evaporative cooling tower ash bin, all N2 purging must be turned off and detected with O2 meter to prevent N2 from choking people;

3.12 When the evaporative cooling tower nozzle, the fan is best to run at a low speed, and the speed is controlled at about 500-700r/min;

3.13 Fan, must be equipped with CO testing instrument, first test CO concentration is less than 50ppm, confirm the safety before entering the fan internal maintenance;

3.14 When working inside the fan and in the fan pipeline, the recovery cup valve and outlet glasses valve must be closed before operation;

3.15 enter all nitrogen valve must be closed before the electric field, to prevent internal high nitrogen concentration caused by maintenance personnel

Suffocation;

3.16 The furnace must be shut down for more than 6 hours after entering the electric field, and the inlet temperature should be controlled below 40 degrees;

3.17 The recovery cup valve and outlet glasses valve must be closed during the internal maintenance of electric dust removal and pipeline;

3.18 Inform the gas tank to close the water seal valve, butterfly valve, and close the recovery cup valve rear lens valve;

3.19 Spot inspection should prevent the sudden explosion of the explosion valve from hurting people, and it is not allowed to stay near the explosion valve for a long time. The spot inspection of the explosion valve must be carried out in the state of non-blowing oxygen (O2);

3.20 Before resuming power supply after electric field maintenance, it is necessary to confirm whether there is anyone inside and whether all maintenance tools and materials are cleared out. Otherwise, no one is allowed to seal the manhole door and electric field voltage boost. When the electric field rises to high pressure, all manhole doors must be closed. If you want to check the electric field discharge situation must be checked by an electric field, and the electric field entering must be reliably grounded, do not allow to stand in the electric field to be checked inside to prevent high voltage electric shock;

3.21 When checking and handling the scraping of the aircraft, more than two people must contact each other with the walkie-talkie to confirm the error before commissioning;

3.22 After electric field maintenance, all manhole doors must be sealed to prevent air from entering the electric field and causing plate deformation;

3.22 Do not open any manhole door during the operation of the gas cooler to check the hole.

3.23 When the gas cooler is repaired, do the following work:

1) The gas recovery operating system is switched to the shutdown state;

2) Ensure normal use of air breathing apparatus;

3) carbon monoxide tester to ensure good operation;

3.24 The order of replacing the gas inside the gas cooler is as follows:

1) First notify the dispatching system to fill the gas tank U-shaped water seal and close the butterfly valve;

2) After confirming that the U-type water seal is filled with water and the butterfly valve is closed, close the gas cooler outlet blind valve first, and then close the gas cooler inlet blind valve;

3) Wear breathing apparatus to open gas cooling release valve, inlet blind valve outlet pipe release valve;

4) Wear a respirator to open the gas cooler inlet blind valve, outlet pipe nitrogen (N2) valve, gas cooler nitrogen valve (nitrogen pressure shall not exceed 0.05mPa) to purge the gas;

5) 1 hour after nitrogen replacement, test the gas content with carbon monoxide tester at the sampling point of the release pipe (the gas content is less than 3%);

6) After qualified nitrogen replacement, close the nitrogen valve, open the compressed air for air replacement, and close the compressed air valve after 30 minutes of replacement;

7) The above work can be repaired only after completion;

8) After the maintenance is completed, the special person in charge will carry out various checks and confirm that the replacement gas can be carried out;

        

3.25 The order of replacement gas is as follows:

1) Open the nitrogen valve of the inlet pipe and the nitrogen valve of the gas cooler (nitrogen pressure shall not exceed 0.05MPa).

2) 30 minutes after nitrogen replacement, monitor whether the oxygen content is qualified. After nitrogen replacement is qualified, close the N2 valve.

3) When the gas replaces N2, the two release valves are in the release state. First open the blind valve at the entrance of the gas cooler, and then open the blind valve at the exit of the gas cooler.

4) The special person in charge shall notify the dispatch to contact the gas tank U-shaped water seal to release water and open the butterfly valve.

5) After the gas cooler meets the requirements, wear a respirator to close the two release valves.

6) After the above work is completed, the gas recovery operating system can be converted to the recovery state.

3.26 Normal shutdown for maintenance

1) After the converter is stopped, the dust removal fan must run for more than 20 minutes before it can be stopped;

2) The CO content must be detected before the equipment maintenance work (the CO detector should not exceed 500mm on the ground during the detection), before entering the construction;

3) Maintenance equipment and pipeline purging work must be comprehensive, leaving no dead corners;

3.27 Abnormal Shutdown

1) If the fan jumps, the dust collector operator should immediately notify the main control room of the converter to stop blowing, and the production can be resumed only after the fan runs normally;

2) CO testing must be carried out before maintenance, and the construction can only be completed after passing the purge;

3) Inspection of the dust removal system should be strengthened during the production process, especially inspection of equipment along the pipeline, manhole, hand hole, test point, etc.

3.28 During the gas release process, 20m on the windward side and 40m on the downwind side of the gas release are prohibited, and warning lines are set up to prevent accidental contact.

3.29 When the concentration of carbon monoxide in the air is less than 160PPm, the operator shall strictly implement the national regulations on the working time of carbon monoxide concentration:

1) CO concentration of 160PPm can work for 15-20 minutes;

2) The CO concentration reaches 80PPm and can work for 30 minutes;

3) CO concentration of 40PPm can work for 60 minutes;

4) The CO concentration can be continuously operated below 24PPm;

3.30 In the production, operation and construction, such as  carbon monoxide concentration more than 160PPm, ventilation or wear gas masks should be taken;

3.31 When gas leakage occurs in gas equipment (pipe network), it is strictly prohibited to rescue or enter the leakage area at risk;

3.32 The gas cutting method of V-type water seal and partition device is used, and the V-type water seal is not allowed to be used as a cutting device alone. When using V-type water seal, the water supply should be sufficient, the high water level overflow must be maintained, the drainage pipe is not allowed to discharge water, and the water seal should be inspected and monitored by a special person to prevent the water seal from losing water.

3.33 The outlet of the release pipe must be 4m higher than the gas pipeline, equipment and platform, and not less than 10m from the ground. The height of the outlet of the pressure regulating gas release pipe should be higher than the surrounding buildings, generally not less than 30m from the ground. The released gas must be ignited and there are fire extinguishing facilities;

3.34 When sending gas, carefully check the manhole doors for gas leakage, do not pull the welding wire on the gas facilities, and do not allow fire sources and pedestrians within 40 meters around the gas facilities;

3.35 Gas pressurization station and mixing station

Coke oven gas blower - pressurized machine room is regarded as the heart, is an explosive place, lighting fixtures, switches, wiring must be explosion-proof, doors and Windows to open outwardly, doors and Windows area can not be less than one tenth of the volume, usually and accident conditions should have ventilation.

4. Estimation of gas diffusion poisoning range

The range of gas diffusion poisoning can be calculated according to the relationship between atmospheric harmful matter propagation and concentration attenuation, that is, the normal Gaussian distribution model.

1) Leakage and diffusion mode of ground gas equipment

In general, the relative height of gas equipment from the ground is low, we can calculate according to the continuous point source diffusion model on the ground, and establish a mathematical model. To wit:

C_(x.y.0：0)==exp[-()]         (1)

 

Shizhong：

C_(x.y.0：0) ：Pollutant concentrations at downwind spatial locations  (mg/m³)

σ_y:  Y Standard deviation of direction (horizontal diffusion parameter)

σ_z：Z Standard deviation of direction (vertical diffusion parameter)

    υ：  Mean wind speed   (m/s)

    Q：   Source intensity       (mg/s )

2) Gas tank leakage and diffusion mode

When the gas tank leaks (or is released by the release pipe), the diffusion mode can be connected by elevated

Continuous point source diffusion model calculation. To wit:

     C_(x.y.0：0) ==exp[-()]      (2)

Shizhong：

H：Gas tank        (m)

Z： Height of gas tank leak point (or release pipe)  (m)

From the above two formulas, we can see that the diffusion parameter σ_y、σ_{z Is the second calculation of air pollutants}

An important parameter. It is closely related to the properties of atmospheric turbulence, and its laws are generally obtained through theoretical studies and experiments of atmospheric diffusion. At present, the national standard GB3840-91/T "Technical methods for Formulating local air pollutant emission standards", Pasquill diffusion parameters, Briggs diffusion parameters are mainly used for calculation.

5, rescue measures for gas poisoning

5.1 After the occurrence of gas poisoning, immediately move the poisoned person to the fresh air on the upwind side outside the danger zone;

5.2 Clear warning signs should be set up in the area where gas poisoning occurs to prevent others from straying into the gas area;

5.3 After the occurrence of gas poisoning, call the plant control room, gas protection station and medical department immediately, and report the number, time, place and degree of poisoning clearly;

5.4 Before the arrival of the personnel at the gas checkpoint, the oxygen cylinder of the oxygen respirator used for the post should be removed, and the switch of the gas cylinder should be slowly turned on in the mouth and nostrils of the poisoned person to allow the poisoned person to inhale oxygen. The on-site wind source can be used under oxygen-free conditions.

5.5 When rescuing the victim, the shoulder pads should be 15cm high, the limbs should be extended, the head should be tilted back as far as possible, and the face should be turned to one side to facilitate smooth breathing;

5.6 During rescue, the buckle, belt and shoe buckle that hinder the victim's breathing should be loosened to relax the victim, which can relieve the victim;

5.7 In winter, to maintain the body temperature of the poisoned, properly cover the quilt, can be performed mouth-to-mouth artificial respiration or chest compression method;

5.8 When the victim is breathing on his own, use the resuscitation device to adjust the intake volume and observe the oxygen absorption of the victim; For those who are not breathing on their own, forced breathing is used. Adults should be sent to the hospital with oxygen infusion 12-16 times per minute.

5.9 Severe poisoning: immediately give artificial respiration, do not move the victim into the car before returning to consciousness;

5.10 Do not stop rescue without the permission of medical personnel.

6. Summary

From Table 1, we can see that the converter gas is the most toxic of all metallurgical gas, and is flammable, explosive, highly toxic dangerous substances, in the dust removal (recovery), transmission and distribution, storage and use of all links, there is the possibility of leakage, once the leak is very easy to cause a major malignant accident of death and injury. There have been many accidents of gas poisoning of converter in domestic metallurgical enterprises, especially in the production and maintenance stage, which have caused great economic losses and bad social effects.

Gas plays a very important role in metallurgical enterprises and is the key to energy saving and consumption reduction. We must do a good job in the prevention and control of gas accidents, reduce or even eliminate the occurrence of similar accidents gas accidents. It has become a long-term and arduous task for metallurgical enterprises.

              

reference

1 Oxygen converter gas purification and recovery design reference [M] Metallurgical Industry Press, December 1975

2 steelmaking converter flue gas recycling technology [M] China environmental science press in March 1991

3 Wang Xinyu Huang Bin, "Analysis of leakage Source and Poisoning Accident Prediction consequences of dry gas tank [J] 2008(6) 32-36.