System for recovering pressure and sensible heat from blast furnace gas with use of dry-type dust collector

In a system for recovering as power, pressure and sensible heat from a gas discharged from the top of a blast furnace, including a gas channel which conducts the gas from the blast furnace to a dust collector means for the removal of dust while maintaining the gas at furnace top pressure and which feeds the gas from the dust collector means into a turbine for expansion, the improvement wherein:

• said dust collector means comprises a dry-type bag filter or electric precipitator installed in said gas channel for cleaning the gas without substantial cooling of the gas from a normal high temperature of 130.degree. to 150.degree. C.;
• supply means for supplying a cooling fluid to said gas channel between the blast furnace and said dust collector means, said supply means including pipes connecting said supply means with first, second and subsequent injectors arranged along and exposed to the interior of said gas channel at suitable spacing, each injector being provided with an electrically operable valve, the valves differing from one another in the maximum rate of flow therethrough with the valve of smaller maximum flow rate being provided on said first injector, and said first injector being positioned closer to the downstream side with respect to the flow of the gas;
• sensor means for detecting the temperature of the gas is disposed in the gas channel close to the gas outlet of said dust collector means;
• and
• control means connected to said sensor means and to said injector valves for opening at least one of said injector valves in response to the gas temperature detected by said sensor means exceeding a specified value set above said normal high temperature and below the maximum temperature said dust collector means can endure, the control means being adapted to feed opening signals to the injector valves starting with the valve provided on the first injector on the downstram side and from valve to valve toward the upstream side, and the control means being adapted to calculate a desired degree of opening of the first injector valve from the magnitude of a signal representing the difference between the detected temperature signal from said sensor means and the set temperature signal and feed the resulting signal to the first injector valve, to further calculate a desired degree of opening of the second injector valve and feed the resulting signal to the second injector valve when the difference signal can result even when the first injector valve is fully opened, and to further calculate a desired degree of opening of each subsequent injector valve in succession and feed the resulting signal to the corresponding injector valve when the difference signal can result even when each preceding injector valve is fully opened.