The purging steps and precautions of gas shutdown shall be collected and integrated by the refractory manufacturer.
- Close all burner valves in turn. After the manual butterfly valve of blast furnace gas burner is closed, close the supporting manual butterfly valve of combustion air, and use coal smoke induced draft fan and air smoke induced draft fan to maintain negative pressure in the furnace.
Precautions: it is strictly forbidden to close the combustion air first and then the burner gas valve.
- After the butterfly valve of the gas main pipe is closed, inject nitrogen in front of the quick cut valve of the gas main pipe for pressure maintaining and purging in the furnace. The internal pressure of the gas pipeline shall not be greater than 20KPa;
- After the butterfly valve of the gas main pipe is closed, close the eye valve of the gas main pipe, open the vent valves of each section of the gas successively from the far end, and inject nitrogen into each section of the gas pipeline to purge the residual gas;
matters needing attention:
(1) First, confirm that there is no fire source and personnel retention within 40m, and there is no electric welding wire tied to the pipeline. Generally, at least two people are required to hold a carbon monoxide alarm and operate it with the control button of remote control appliance. After the operation, confirm whether there is gas leakage. If gas leakage is found, handle it in time in strict accordance with the safety operation procedures.
(2) It is strictly forbidden to stop the combustion supporting blower without turning off the gas;
- Operation method of purging residual gas with nitrogen:
First close the electric control valves of heating section I and section II, open the electric control valve of soaking section, and purge the gas pipeline of soaking section with nitrogen for 20 minutes. When the gas / flue gas three-way valve is opened to the gas side, the flue gas side is closed. Start from the far end, open the gas butterfly valve of heat storage burner in turn, and then close it after one minute. Then use this operation to purge the first and second heating sections respectively with nitrogen.
- After all gas and flue gas pipelines are purged (the nitric oxide concentration at the end of the pipeline is detected to be less than 160ppm), shut down the nitrogen. Purge the gas pipeline with compressed air to remove nitrogen. The purging time is more than 30 minutes. After detecting that the carbon monoxide concentration at the end of the pipeline is 24ppm, shut down the air purging. Shut down the induced draft fan of coal smoke and air smoke when the process conditions of the heating furnace are allowed;
- After all purging is completed, open the furnace door, flue gate and manhole for natural ventilation, so that the oxygen content in the furnace is not less than 19.5% and the temperature drops below 60 ℃, meet the operation conditions in the furnace, and enter the furnace for operation after obtaining the "furnace operation permit";
- Safety requirements for operation process:
(1) After the boiler is shut down, the cooling of the heating furnace is slow, and the measures of spraying water in the heating furnace or blowing excessive cold air into the furnace shall not be used for cooling; When the furnace temperature drops below 800 ℃, increase the air volume appropriately and control the gradual cooling by adjusting the furnace pressure; When the furnace temperature drops to 50 ℃ ~ 400 ℃, the blower and fan can be shut down; Maintain a certain water level in the steam drum of the heating furnace and gradually cool down with cooling equipment;
(2) When the furnace temperature drops to 200 ℃, the manhole and furnace door can be opened for natural ventilation until the furnace temperature drops to normal temperature.
- When entering the heating furnace for operation, the "work permit in limited space" must be handled in advance. When all safety measures are in place, the inspector can enter the furnace for operation only after sampling and analysis are qualified and signing the permit on the work permit. All safety measures adopted in the work permit shall be strictly implemented in the process of operation.