Apparatus and method for control of air relative humidity with reduced energy usage in the treatment of tobacco

Claim 3

The method of claim 1 in which the dew point temperature of the conditioned air is sensed in the said remainder portion thereof subsequent to the heating of same but prior to passing said remainder portion through the tobacco.

Claim 4

The method of claim 1 in which the relatively dry tobacco has a moisture content of up to about 2%, the first portion of said conditioned air being flowed through said tobacco at a rate and relative humidity such as to raise the moisture content of the tobacco from about 2% up to about 8.5%, the remainder portion of said conditioned air being flowed through said tobacco at a rate and relative humidity such as to raise the moisture content of the tobacco from about 8.5% up to about 11%.

Claim 5

The method of claim 3 in which the first portion and the remainder portion of conditioned air are flowed through said tobacco for substantially equal periods of time.

Claim 6

The method of claim 4 in which said time periods are substantially 15 minutes each.

Claim 7

The method of claim 3 in which the relative humidity of the first portion of said conditioned air is in the range of about 60% to about 62%, the remainder portion of said conditioned air being heated to reduce its relative humidity to about 58%.

Claim 8

The method of claim 3 in which the relatively dry tobacco is one which has been subjected to a tobacco expansion operation.

Claim 11

The method of claim 8 in which the relatively dry tobacco has a moisture content of up to about 2%, the first stream of conditioned air being flowed through said tobacco at a rate and relative humidity such as to raise the moisture content of the tobacco from about 2% up to about 8.5%, the second stream of conditioned air being flowed through said tobacco at a rate and relative humidity such as to raise the moisture content of the tobacco from about 8.5% up to about 11%.

Claim 12

The method of claim 9 in which the first and second streams of conditioned air are flowed through said tobacco for substantially equal periods of time.

Claim 13

The method of claim 10 in which said time periods are substantially 15 minutes each.

Claim 14

The method of claim 11 in which the relative humidity of the first stream of conditioned air is in the range of about 60% to about 62%, the second conditioned stream being at a relative humidity of about 58%.

Claim 15

The method of claim 12 in which the relatively dry tobacco is one which has been subjected to a tobacco expansion operation.

Claim 16

The method of claim 8 in which the first air stream is passed through said tobacco in a first treatment zone, the tobacco thereafter being conveyed to a second separate treatment zone wherein the second air stream is passed therethrough.

Claim 17

Apparatus for moistening relatively dry tobacco to provide same with a desired predetermined moisture content with a conditioned air stream having desired predetermined dry bulb temperature and relative humidity values, which apparatus comprises means for establishing and maintaining a water spray curtain, means for passing the air through said water spray curtain to condition it, said water spray curtain being disposed transversely of the direction of the air flow and presenting a variable area of heat exchange confrontation to said flow, means for conveying a first portion of said conditioned air through the tobacco to add moisture thereto up to a certain content less than said predetermined moisture content, means for heating the remainder portion of said conditioned air to reduce the relative humidity thereof by a predetermined level and means for passing said remainder portion of said conditioned air through the tobacco to add sufficient additional moisture thereto to raise the tobacco moisture content to said desired predetermined content, means for sensing the dry bulb temperature of the conditioned air downstream of the spray curtain and varying the spray curtain area responsive to variations of the sensed dry bulb temperature from said desired predetermined value to correspondingly control the quantity of heat exchange effected to the air stream in said spray curtain, and means for sensing the dew point temperature of the conditioned air stream downstream of the spray curtain and controlling the temperature of the water supplied to said spray curtain responsive to variations of the sensed dew point temperature from a predetermined value thereby to control the dew point temperature of said conditioned air at said predetermined value whereby the air leaving said spray curtain is at said desired relative humidity value.

Claim 18

Apparatus for moistening relatively dry tobacco to provide same with a desired predetermined moisture content with a conditioned air stream having desired predetermined dry bulb temperature and relative humidity values, which apparatus comprises means for establishing and maintaining a water spray curtain, means for passing the air through said water spray curtain to condition it, said water spray curtain being disposed transversely of the direction of the air flow and presenting a variable area of heat exchange confrontation to said flow, means for conveying a first portion of said conditioned air through the tobacco to add moisture thereto up to a certain content less than said predetermined moisture content, means for heating the remainder portion of said conditioned air to reduce the relative humidity thereof by a predetermined level and means for passing said remainder portion of said conditioned air through the tobacco to add sufficient additional moisture thereto to raise the tobacco moisture content to said desired predetermined content, means for sensing the dry bulb temperature of the conditioned air downstream of the spray curtain and varying the spray curtain area responsive to variations of the sensed dry bulb temperature from said desired predetermined value to correspondingly control the quantity of heat exchange effected to the air stream in said spray curtain, and means for sensing the dew point temperature of the conditioned air stream downstream of the spray curtain and controlling the temperature of the water supplied to said spray curtain responsive to variations of the sensed dew point temperature from a predetermined value thereby to control the dew point temperature of said conditioned air at said predetermined value whereby the air leaving said spray curtain is at said desired relative humidity value.

Claim 19

The apparatus of claim 15 in which the dew point temperature sensing means is disposed to sense such value in the said remainder portion subsequent to the heating of same but prior to passing said remainder portion through the tobacco.

Claim 20

Apparatus for moistening relatively dry tobacco to provide same with a desired predetermined moisture content with first and second conditioned air streams having desired predetermined dry bulb temperature and relative humidity values, the relative humidity value of said first stream being higher than that of said second stream, which apparatus comprises means for establishing and maintaining first and second water spray curtains, means for passing the respective streams through the respective water spray curtains, said curtains being disposed transversely of the direction of the respective stream flow and presenting a variable area of heat exchange confrontation to said flow, means for conveying the first stream of conditioned air through the tobacco to add moisture thereto up to a certain content less than said predetermined moisture content, means for conveying said second stream of conditioned air through the tobacco to add sufficient additional moisture thereto to raise the tobacco moisture content to said desired predetermined content, means for sensing the dry bulb temperatures of each of said conditioned air streams downstream of their respective spray curtains and varying the respective spray curtain areas responsive to variations of the sensed dry bulb temperature from said desired predetermined value to correspondingly control the quantity of heat exchange effected to the air streams in said spray curtains, and means for sensing the dew point temperatures of said conditioned air streams downstream of the spray curtains and controlling the temperature of the water supplied to each said spray curtain responsive to variations of the second dew point temperatures from a predetermined value thereby to control the dew point temperatures of the respective conditioned air streams at said predetermined values whereby the air leaving each spray curtain is at the desired relative humidity value.

Claim 21

Apparatus for moistening relatively dry tobacco to provide same with a desired predetermined moisture content with first and second conditioned air streams having desired predetermined dry bulb temperature and relative humidity values, the relative humidity value of said first stream being higher than that of said second stream, which apparatus comprises means for establishing and maintaining first and second water spray curtains, means for passing the respective streams through the respective water spray curtains, said curtains being disposed transversely of the direction of the respective stream flow and presenting a variable area of heat exchange confrontation to said flow, means for conveying the first stream of conditioned air through the tobacco to add moisture thereto up to a certain content less than said predetermined moisture content, means for conveying said second stream of conditioned air through the tobacco to add sufficient additional moisture thereto to raise the tobacco moisture content to said desired predetermined content, means for sensing the dry bulb temperatures of each of said conditioned air streams downstream of their respective spray curtains and varying the respective spray curtain areas responsive to variations of the sensed dry bulb temperature from said desired predetermined value to correspondingly control the quantity of heat exchange effected to the air streams in said spray curtains, and means for sensing the dew point temperatures of said conditioned air streams downstream of the spray curtains and controlling the temperature of the water supplied to each said spray curtain responsive to variations of the second dew point temperatures from a predetermined value thereby to control the dew point temperatures of the respective conditioned air streams at said predetermined values whereby the air leaving each spray curtain is at the desired relative humidity value.