Device and method for gas dispersion

1. A device for dispersing gas in a liquid comprising a number n of successive zones Z 1 , Z 2 , . . . , Z n comprising static mixing elements having channels, each zone Z i having a length L i , the mixing elements in zone Z i having an effective diameter D i , wherein the individual zones Z i are constructed such that a mechanical energy input E i normalized to the respective ratio L i /D i increases from zone to zone in a direction of flow through the device, wherein n is an integer greater than or equal to 3 and i is an index which runs through integers from 1 to the number of zones n, and the mixing elements present in the zones Z 1 to Z n have a same ratio d i /D i and an effective diameter D i which becomes increasingly smaller from zone to zone in the direction of flow, wherein:

d i is an effective channel diameter averaged arithmetically over all of the channels of the mixing elements in zone Z i ,

the effective diameter D i is calculated as

D

i

=

4

⁢

⁢

A

i

π

,

the effective channel diameter d i is calculated as

d

i

=

4

⁢

⁢

a

i

π

,

A i is the cross-sectional area of the mixing elements in each zone Z i , and

a i is the sum of projected free cross-sectional areas of the channels of the mixing elements in each zone Z i .

2. The device as claimed in claim 1 , wherein the zones Z 1 to Z n comprise mixing elements of different types, which at the same ratio L i /D i cause an increasing pressure drop from zone to zone in the direction of flow.

3. The device as claimed in claim 1 , wherein there is a first zone Z 0 , which achieves a higher specific energy input E 0 than the next zone Z 1 in the direction of flow.

4. The device as claimed in claim 1 , further comprising a tube or a thin capillary for feeding gas into the device, wherein the tube or the thin capillary is mounted upstream of the mixing elements.

5. The device as claimed in claim 1 , further comprising a porous or screen-like body for feeding gas into the device wherein the body is mounted upstream of the arrangement of mixing elements.

6. A method for dispersing gas in a liquid comprising flowing a mixture of the gas and liquid through a number n of successive zones Z 1 , Z 2 , . . . , Z n comprising static mixing elements, each zone Z i having a length L i , the mixing elements having channels, in zone Z i having an effective diameter D i , wherein a mechanical energy input E i acting on the gas and liquid mixture and normalized to the respective ratio L i /D i increases from zone to zone in the direction of flow, wherein n is an integer greater than or equal to 3 and i is an index which runs through integers from 1 to the number of zones n, and the mixing elements present in the zones Z 1 to Z n have a same ratio d i /D i and an effective diameter D i which becomes increasingly smaller from zone to zone in the direction of flow, wherein:

d i is an effective channel diameter averaged arithmetically over all of the channels of the mixing elements in zone Z i ,

the effective diameter D i is calculated as

D

i

=

4

⁢

⁢

A

i

π

,

the effective channel diameter d i is calculated as

d

i

=

4

⁢

⁢

a

i

π

,

A i is the cross-sectional area of the mixing elements in each zone Z i , and

a i is the sum of projected free cross-sectional areas of the channels of the mixing elements in each zone Z i .

7. The method according to claim 6 , wherein the liquid has a viscosity of between 2 mPa·s and 10,000,000 mPa·s.

8. The method according to claim 7 , wherein the liquid has a viscosity of between 1,000 mPa·s and 1,000,000 mPa·s.