Why is it necessary to open the furnace lid and ignite the fixed-bed gas generator during temporary shutdown?

Prevent explosions at the furnace opening when the lid is opened to add coal while driving again. To enhance steam suction, one needs to open the steam suction valve of the chimney, thereby increasing the suction power of the chimney and drawing away as much combustible gas as possible from inside the furnace, so as to prevent the accumulation of combustible gases within the system (especially at the furnace outlet).

During normal operation, the cycle of the gas furnace follows several steps: blowing air in, upper blowing, lower blowing, secondary upper blowing, and final cleaning. During the upper blowing and secondary upper blowing steps, combustible gases are present in the top part of the furnace. And when parking temporarily, to prevent explosions, we need to burn off the flammable gases on top of the furnace; therefore, it is necessary to open the furnace lid to ignite them.

Prevent the accumulation of gas above the furnace from causing an explosion.

After opening the furnace lid, ignition should be carried out to allow air and flames to enter the furnace slowly, where they can burn slowly with any remaining gas in the furnace. This prevents explosions that may occur if a large amount of air enters suddenly due to rapid opening of the lid. Once flames appear at the furnace outlet, the steam suction valve should be opened.

Ignition is primarily done to prevent explosions. Under normal circumstances, ignition is not required when the furnace is shut down for a short period of time during operation; however, this is unsafe, as neither the valves nor the furnace itself can be completely leak-proof. As a result, when the furnace is shut down, mixed gases may enter the furnace and mix with the gas produced there, leading to an explosion. This has happened in our plant as well – a stopped furnace caused the upper cover and the waste heat recovery valve to be damaged. Since then, we have established that ignition must be performed whenever the furnace is shut down. As for the main function of steam suction, it is to use high-speed fluid to drive low-speed fluid, thereby increasing the power of the flue and accelerating the release of residual gas in the furnace. It is important to note that if the upward bend in the suction pipe breaks, this mechanism will no longer work; on the contrary, it can have negative effects, sometimes even extinguishing the fire in the furnace. Therefore, after lighting the fire and activating the suction system, it is necessary to check whether the suction force has increased; otherwise, it is safer to turn off the suction system.

During temporary shutdowns, a fixed-bed gas generator generally does not require the furnace lid to be opened for ignition; it is sufficient to displace the air with steam. However, ignition is safer but more troublesome

The gas generation furnace we use now is equipped with an automatic coal feeding mechanism; when shutting down the furnace, air is blown in for 8 seconds after cleaning it, and then the furnace is shut down. During shutdown, simply open the blowdown valve (chimney valve) to exhaust the combustible gases from the furnace through the chimney; it is prohibited to open any holes or covers on the furnace to prevent explosions caused by the entry of air. In fact, lighting the fire by opening the lid is an outdated and unsafe method; it also raises the temperature of the furnace surface, increases the temperature of the gas flowing upward, and accelerates the crushing of the coal in the furnace surface – it has only disadvantages and no advantages at all. Therefore, under normal circumstances, do not open the furnace lid (or flame viewing port) to light the fire.