Air flow control in shaft furnaces

Claim 2

In a method of indurating pellet like material which comprises flowing the material downwardly in a shaft furnace and causing heat exchange gas to flow upwardly through the furnace relative to said material, the improvement comprising heating a portion of said heat exchange gas introduced to said furnace, introducing a predetermined volume of said heated gas to said furnace over a predetermined period of time, introducing said heated gas to at least two separate locations at a given level in said furnace, said heated gas being introduced at one of said locations being varied in volume during said predetermined period of time between a minImum and a maximum.

Claim 3

The method according to claim 1 wherein said heated gas is introduced to locations at opposite sides of said furnace.

Claim 4

The method according to claim 1 wherein said heated gas introduced at said one of said locations is distributed to one-half of the perimeter of said furnace.

Claim 5

In a method of indurating pellet like material which comprises flowing the material downwardly in a vertical shaft furnace and causing heat exchange gas to flow upwardly through said furnace relative to said material, the improvement comprising heating a predetermined percentage of said heat exchange gas prior to introduction into said furnace, introducing a part of said fixed percentage of heated gas at an intermediate vertical level and at one side of said furnace, introducing the remaining part of said fixed percentage of heated gas at the opposite side of said furnace, said first mentioned part of said heated gas being varied from a minimum to a maximum amount over a predetermined period of time, and simultaneously varying said remaining part of said heated air from a maximum to a minimum amount during said predetermined period of time.

Claim 6

In a method of indurating pellet like material which comprises flowing the material downwardly in a vertical shaft furnace and causing heat exchange gas to flow upwardly through said furnace relative to said material, the improvement comprising heating a predetermined percentage of said heat exchange gas prior to introduction into said furnace, introducing a part of said fixed percentage of heated gas at an intermediate vertical level and at one side of said furnace, introducing the remaining part of said fixed percentage of heated gas at the opposite side of said furnace, said first mentioned part of said heated gas being varied from a minimum to a maximum amount over a predetermined period of time, and simultaneously varying said remaining part of said heated air from a maximum to a minimum amount during said predetermined period of time.

Claim 7

The method according to claim 4 wherein said heated gas is maintained at a predetermined, uniform temperature during the said predetermined period of time that said parts of said fixed percentage of heated gas are introduced to said furnace.

Claim 8

The method according to claim 4 wherein said first mentioned part of said heated gas introduced to one side of said furnace is distributed to one-half of the perimeter of said furnace and said remaining part of said heated gas is distributed to the remaining perimeter of said furnace at the other side of said furnace.

Claim 9

In a method of indurating pellet like material in a shaft type furnace comprising establishing a gravitationally descending mass of pellet like material in initially unheated form, removing indurated pellets from the bottom of said mass and replacing pellets in unheated form at the top of said mass to maintain the height of the latter, continuously introducing heat exchanged gas in an unheated state to the bottom portion of said mass of pellets, simultaneously introducing heat exchanged gas in a heated state to an intermediate level and at opposite sides of said mass, said heated and unheated heat exchange gas being maintained at a predetermined substantially constant volume for a given period of time, a portion of said heated heat exchange gas being introduced at one side of said mass and being varied in volume from a predetermined minimum up to a maximum and back to a minimum during said given period of time and the remaining portion of said heated heat exchange gas being introduced at the other side of said mass and being varied in volume from a predetermined maximum down to a minimum and back to a maximum during said given period of time.

Claim 10

In a method of indurating pellet like material in a shaft type furnace comprising establishing a gravitationally descending mass of pellet like material in initially unheated form, removing indurated pellets from the bottom of said mass and replacing pellets in unheated form at the top of said mass to maintain the height of the latter, continuously introducing heat exchanged gas in an unheated state to the bottom portion of said mass of pellets, simultaneously introducing heat exchanged gas in a heated state to an intermediate level and at opposite sides of said mass, said heated and unheated heat exchange gas being maintained at a predetermined substantially constant volume for a given period of time, a portion of said heated heat exchange gas being introduced at one side of said mass and being varied in volume from a predetermined minimum up to a maximum and back to a minimum during said given period of time and the remaining portion of said heated heat exchange gas being introduced at the other side of said mass and being varied in volume from a predetermined maximum down to a minimum and back to a maximum during said given period of time.

Claim 11

The method of claim 7 in which the volume of said heated heat exchange gas introduced during said given period of time is substantially lower than the volume of said unheated heat exchange gas.

Claim 12

The combination set forth in claim 8 in which said heated heat exchange gas is between 20 and 35 percent of said predetermined substantially constant volume of heat exchange gas.

Claim 13

Apparatus for distributing heat exchange gas to a bed of pellet like material in a shaft furnace comprising, in combination, a shaft type indurating furnace comprising an upper heating stove and a lower cooling stove, first and second sources of heated gas, first and second manifold means operatively connecting said first and second sources of heated gas with separate portions of said furnace intermediate said upper and said lower stoves, respectively, control means operatively associated with said first manifold means and operative to vary the quantity of heated gas between a minimum and a maximum quantity, second control means operatively associated with said second manifold means and operative to vary the quantity of heated Gas between a maximum and a minimum in inverse proportion to the quantity of heated gas introduced through said first manifold means, said first and second control means being operatively associated with each other to maintain the quantity of said heated gas delivered through said first and second manifold means constant.

Claim 14

Apparatus for distributing heat exchange gas to a bed of pellet like material in a shaft furnace comprising, in combination, a shaft type indurating furnace comprising an upper heating stove and a lower cooling stove, first and second sources of heated gas, first and second manifold means operatively connecting said first and second sources of heated gas with separate portions of said furnace intermediate said upper and said lower stoves, respectively, control means operatively associated with said first manifold means and operative to vary the quantity of heated gas between a minimum and a maximum quantity, second control means operatively associated with said second manifold means and operative to vary the quantity of heated Gas between a maximum and a minimum in inverse proportion to the quantity of heated gas introduced through said first manifold means, said first and second control means being operatively associated with each other to maintain the quantity of said heated gas delivered through said first and second manifold means constant.

Claim 15

The combination set forth in claim 10 in which said heated gas is introduced at super atmospheric pressure.