Top seal chamber pressurized. Coal jet can pressurize. Blast furnace gas bag dust removal, function: 1, clean ash. 2: Some valve power needs. There are also a lot of places where valves need nitrogen. Oh, you just spray coal. So be specific: After putting pulverized coal into the blast tank, open the boiling valve or charging valve to pressurize the blast tank. Because the pressure inside the blast furnace is 300KPa, you need more than 500KPa (400KPa before the distributor, mainly depending on the pressure before the distributor must be more than 50KPa higher than the blast furnace pressure) to inject into the blast furnace, otherwise the gas inside the blast furnace will be injected back. So called tempering. And then the valve we don't use nitrogen here, we just use the electric one. And then the fire valve might use nitrogen.