Process for providing ethanol

1. A process for providing ethanol comprising:

a) flashing carbon dioxide from a beer stream ( 100 ) to provide a carbon dioxide gas stream ( 104 ) and a degassed beer feed ( 106 );

b) boiling the degassed beer feed ( 106 ) in a pre-boiler ( 110 ) to provide a vapor by-pass fraction ( 112 ) and a beer column feed stream ( 114 );

c) distilling the beer column feed stream ( 114 ) in a beer column to provide an overhead vapor fraction ( 118 ) and a spent beer fraction ( 122 );

d) distilling in a rectifier column ( 124 ), a combination comprising the vapor by-pass fraction ( 112 ) and the overhead vapor fraction ( 118 ) to provide an ethanol-rich rectifier overhead vapor stream ( 126 ) and a water-rich rectifier bottoms stream ( 128 ).

2. The process of claim 1 , further comprising:

e) cooling the carbon dioxide gas stream ( 104 ) with a first condenser ( 105 ) to provide a degasser condensate stream ( 108 );

wherein in step (d) distilling, said combination further comprises the degasser condensate stream ( 108 ).

3. The process of claim 2 further comprising:

f) condensing the vapor by-pass fraction to provide a vapor by-pass condensate fraction ( 302 ) and a remaining vapor by-pass stream ( 304 );

wherein in step (d) distilling, said combination further comprises the vapor by-pass condensate fraction and the remaining vapor by-pass stream.

4. The process of claim 3 further comprising:

g) condensing a portion of the overhead vapor fraction to provide an overhead vapor condensate fraction ( 402 ) and a remaining vapor overhead fraction ( 404 );

wherein in step (d) distilling, said combination further comprises the overhead vapor condensate fraction ( 402 ) and the remaining vapor overhead fraction ( 404 ).

5. The process of claims 1 , 3 or 4 , further comprising:

(i) dehydrating said rectifier overhead vapor stream ( 126 ) by passing the stream through one or more active molecular sieve beds ( 200 ) to provide an anhydrous ethanol vapor stream ( 202 ) and one or more water-rich molecular sieve beds;

(ii) dehydrating the water-rich molecular sieve bed ( 204 ) to provide an active molecular sieve bed and a regenerate ethanol-water stream ( 130 ); and

(iii) providing to the rectifier column the regenerate ethanol-water stream ( 130 );

wherein in step (d) distilling, said combination further comprises the regenerate ethanol-water stream ( 130 ).

6. The process of claim 5 , wherein the rectifier column further comprises:

a first feed point ( 124 a ) for the degasser condensate stream ( 108 );

a second feed point ( 124 b ) for the vapor by-pass fraction ( 112 );

a third feed point ( 124 c ) for the overhead vapor fraction ( 118 );

a fourth feed point ( 124 d ) for the regenerate ethanol-water stream ( 130 );

a fifth feed point ( 124 e ) for the vapor by-pass condensate fraction ( 302 );

a sixth feed point ( 124 f ) for the remaining vapor by-pass stream ( 304 ); and further comprises:

optimizing the first, second, third, fourth, fifth and sixth feed points, the vapor by-pass fraction and the vapor by-pass condensate fraction to provide an optimal throughput and energy use.

7. The process of claims 1 , 3 or 4 , further comprising:

(i) dehydrating said rectifier overhead vapor stream ( 126 ) by passing the stream through one or more active molecular sieve beds ( 200 ) to provide an anhydrous ethanol vapor stream ( 202 ) and one or more water-rich molecular sieve beds;

(ii) dehydrating the water-rich molecular sieve bed ( 204 ) to provide an active molecular sieve bed and a regenerate ethanol-water stream ( 130 ); and

(iii) providing to the rectifier column the regenerate ethanol-water stream ( 130 );

wherein in step (d) distilling, said combination further comprises the regenerate ethanol-water stream ( 130 ); and

wherein said step (ii) dehydrating the water-rich molecular sieve bed ( 204 ) comprises:

1. off-line, passing a dry non-condensable gas stream through the water-rich molecular sieve bed to provide a wet gas stream communicating with a condenser, and an active molecular sieve bed;

2. condensing the wet gas stream to provide said regenerate ethanol-water stream ( 130 ).

8. The process of claims 1 , 3 or 4 , further comprising:

(i) dehydrating said rectifier overhead vapor stream ( 126 ) by passing the stream through one or more active molecular sieve beds ( 200 ) to provide an anhydrous ethanol vapor stream ( 202 ) and one or more water-rich molecular sieve beds;

(ii) dehydrating the water-rich molecular sieve bed ( 204 ) to provide an active molecular sieve bed and a regenerate ethanol-water stream ( 130 ); and

(iii) providing to the rectifier column the regenerate ethanol-water stream ( 130 );

wherein in step (d) distilling, said combination further comprises the regenerate ethanol-water stream ( 130 ); and

wherein said step (ii) dehydrating the water-rich molecular sieve bed ( 204 ) comprises:

1. off-line, applying a vacuum through the molecular sieve bed to provide a wet vacuum stream communicating with a condenser, and an active molecular sieve bed;

2. condensing the wet vacuum stream to provide said regenerate ethanol-water stream ( 130 ).

9. The process of claim 1 wherein the vapor by-pass fraction ( 112 ) comprises 2 to 14 wt % of said degassed beer feed ( 106 ).

10. A process for providing ethanol, comprising:

a) flashing and boiling from a beer stream comprising a liquid-solids fraction, carbon dioxide and about 2 to about 14 wt % of the liquid-solids fraction to provide a beer column feed stream ( 514 ) and a carbon dioxide-ethanol-water vapor fraction ( 500 );

b) condensing the carbon dioxide-ethanol-water stream to provide a ethanol-water liquid stream ( 502 ) and a carbon dioxide gas stream;

c) distilling the beer column feed stream in a beer column to provide an overhead vapor fraction ( 518 ) and a spent beer fraction ( 522 ); and

d) distilling, in a rectifier column ( 124 ) a combination of the ethanol-water liquid stream ( 502 ) and the overhead vapor fraction ( 518 ) to provide an ethanol-rich rectifier overhead vapor stream ( 126 ) and a water-rich rectifier bottoms stream ( 128 ).

11. The process of claim 10 wherein said ethanol-water liquid stream ( 502 ) communicates with the rectifier column ( 124 ) at a first feed point ( 524 a ) and said overhead vapor fraction ( 518 ) communicates with the rectifier column at a second feed point ( 524 b ).

12. The process of claim 11 further comprising:

e) dehydrating said rectifier overhead vapor stream ( 126 ) by passing the stream through a series of one or more active molecular sieve beds ( 200 ) to provide an anhydrous ethanol vapor stream ( 202 ) and one or more water-rich molecular sieve beds; and

f) dehydrating the water-rich molecular sieve bed ( 204 ) to provide an active molecular sieve bed and a regenerate ethanol-water stream ( 130 ).

13. The process of claim 12 further comprising:

g) providing, to the rectifier column, the regenerate ethanol-water stream ( 130 );

wherein in step (d) distilling, said combination further comprises the regenerate ethanol-water stream ( 130 ).