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1. US20090308757 - Electrochemical reactor

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

[ EN ]

Claims

1. An electrochemical reactor comprising:
at least one liquid compartment, each having side walls, a top and a bottom, and an interior volume of said at least one compartment defining an inlet region and an outlet region;
a multitude of freely suspended conductive granules enclosed within said at least one liquid compartment, and
at least one pump unit for pumping liquids with an upstream flow,
wherein at least one of the side walls of the compartment is an electrode and an opposite side wall is formed by a separator element,
wherein there is provided a bottom inlet and a top outlet of the compartment for a liquid catholyte or a liquid anolyte,
wherein the inlet region as well as the outlet region of the at least one compartment are provided with an upper grid and a lower grid, the width of each grid's mesh and the positioning of each grid is chosen such as to allow the liquid catholyte or the liquid anolyte to pass through from bottom to top but to prevent the granules from passing through the grids to leave the compartment,
wherein an upstream flow of the liquid catholyte or of the liquid anolyte in operation causes the multitude of granules in a compartment to be dragged against the upper grid while the lower grid is substantially not in contact with the granules, thereby forming a dragged bed,
wherein the granules have a size distribution full width at half height which is in the range of 50-100 micrometer,
wherein there are no granules below or equal 50 micrometer in size,
wherein the granules have a sphericity in the range of 0.6-0.8,
wherein the upper and the lower grid both have a mesh width in the range of 50-150 micrometer,
and wherein the dragged bed has a porosity in the range of 0.5-0.6.
2. The reactor according to claim 1, wherein the granules are selected from the group of:
activated carbon, coke, metal particles, particles of a conducting polymer, graphite granules, or
mixtures thereof, with or without a surface treatment.
3. The reactor according to claim 1, wherein the volume between the two grids is at least
10% larger than the volume of the total of the multitude of granules enclosed by the two grids in dense packing.
4. The reactor according to claim 1, wherein the separator element is membrane or a grid,
and wherein the distance between the electrode wall and the membrane wall of the compartment is in the range of 0.5-5 centimeter.
5. The reactor according to claim 1, wherein the compartment has a height of in the range of 10-100 cm.
6. The reactor according to claim 1, wherein both grids are electrically neutral.
7. The reactor according to claim 1, wherein the compartment is a cathodic or anodic
compartment, and wherein one of the side walls is a cathode plate or an anode plate, respectively
and the opposite side wall is a membrane to an adjacent anodic compartment or cathodic compartment, respectively.
8. An electrochemical reactor comprising
at least two reactors according to claim 7 which are located adjacent to each other with alternating polarity such that adjacent side walls of adjacent units comprising a cathodic compartment and an anodic compartment are forming common electrode plates for adjacent units.
9. The reactor according to claim 1, wherein the granules have an average particle size diameter of more than 50 micrometer and less than or equal to 0.5 mm.
10. The reactor according to claim 1, wherein the granules have an average particle size diameter in the range of 200-500 micrometer.
11. The reactor according to claim 1, wherein the volume between the two grids is at least 40% larger than the volume of the total of the multitude of granules enclosed by the two grids in dense packing.
12. The reactor according to claim 1, wherein the separator element is membrane or a grid, and wherein the distance between the electrode wall and the membrane wall of the compartment is in the range of 0.5-1.5 centimeter.
13. The reactor according to claim 1, wherein the dragged bed has a porosity in the range of 0.50-0.55.
14. The electrochemical reactor as recited in claim 1,
wherein the upstream velocity of the liquid catholyte or the liquid anolyte carrying the component is larger than a minimum fluid velocity (ν m) determined by the following equation:

          ν m=[(ρ s−ρ f) gd p 2]/μ,
wherein ν m=minimum flow velocity, ρ s=density of the granulate, ρ f=density of the fluid, g=acceleration due to gravity, d p=mean particle diameter, μ=fluid viscosity.
15. The electrochemical reactor as recited in claim 1, wherein, said at least one pump unit is operative such that in a first step a fluid velocity of the electrolyte is increased up above the minimum flow in accordance with the Stokes equation but not more than twice the minimum of the Stokes equation at least until the freely suspended conductive granules are dragged against the upper grid, in a second step the flow velocity is increased to a minimum value of in the range of

          ν m=[(ρ 2−ρ f) gd p 2]/μ,
and not up to a value of

          ν m<500 μP/S*(ρ f)[10(1−ε)/ε 3]
wherein to this end the flow ν mc given as

          ν mc=[ε 8 3/{10(1−ε)}]*ν m
is increased by 0.001-0.05 cm/s per second; and
after the actual electrolytic process is started, in a third step the variation in the flow velocity is kept low, such as to avoid a rearrangement of the dragged bed leading to a compacting of the dragged bed.
16. A method for the reduction or oxidation of a component in a reactor according to claim 1 in a continuous or quasi continuous process, wherein the upstream velocity of the liquid catholyte or the liquid anolyte carrying the component is chosen to be larger than a minimum fluid velocity (ν m) determined by the following equation:

          ν m=[(ρ s−ρ f) gd p 2]/μ,
wherein ν m=minimum flow velocity, ρ s=density of the granulate, ρ f=density of the fluid, g=acceleration due to gravity, d p=mean particle diameter, μ=fluid viscosity.
17. The method according to claim 16, wherein the component is a vat dye and/or a sulphur dye in aqueous solution, a bleaching component or a mediator for oxidation.
18. The method according to claim 16, wherein the fluid velocity (ν m) is adjusted such as to have laminar flow at least in the region of the dragged bed.
19. The method according to claim 16, wherein the fluid velocity (ν m) is adjusted such as to have laminar flow at least in the region of the dragged bed, wherein this is achieved by choosing the fluid velocity to be

          ν m<500 μP/S*(ρ f)[10(1−ε)/ε 3].
20. A method for the production of a dragged bed in an electrochemical reactor according to claim 1 comprising at least one liquid compartment in which a multitude of freely suspended conductive granules is enclosed, wherein at least one of the side walls of the compartment is an electrode and an opposite side wall is formed by a separator element, wherein there is provided a bottom inlet and a top outlet of the compartment for a liquid catholyte or a liquid anolyte, wherein the inlet region as well as the outlet region of the compartment are provided with an upper grid and a lower grid, the width of the mesh and the positioning of which is chosen such as to allow the liquid catholyte or the liquid anolyte to pass through from bottom to top but to prevent the granules to pass through the grids to leave the compartment, and wherein the upstream flow of the liquid catholyte or of the liquid anolyte can be adjusted so that in operation the multitude of granules is dragged against the upper grid while the lower grid is substantially not in contact with the granules, wherein
in a first step the fluid velocity of the electrolyte is increased up above the minimum flow in accordance with the Stokes equation but not more than twice the minimum of the Stokes equation at least until the freely suspended conductive granules are dragged against the upper grid;
in a second step the flow velocity is increased to a minimum value of in the range of

          ν m=[(ρ s−ρ f) gd p 2]/μ,
and not up to a value of

          ν m<500 μP/S*(ρ f)[10(1−ε)/ε 3]
wherein to this end the flow ν mc given as

          ν mc=[ε 3/{10(1−ε)}]*ν m
is increased by 0.001-0.05 cm/s per second;
in a third step the actual electrolytic process is started, wherein the variation in the flow velocity is kept low, such as to avoid a rearrangement of the dragged bed leading to a compacting of the dragged bed.
21. A method for operating a reactor according to claim 1 for vat and/or sulphur dye dyeing of fibres, yarns and/or textiles wherein the reactor is used for the reduction of the dye and/or for the preparation of a bleaching agent and/or for oxidation of the dye after its application to the fibres, yarns and/or textiles.
22. A method for the production of a dragged bed in an electrochemical reactor according to claim 1 comprising at least one liquid compartment in which a multitude of freely suspended conductive granules is enclosed, wherein at least one of the side walls of the compartment is an electrode and an opposite side wall is formed by a separator element, wherein there is provided a bottom inlet and a top outlet of the compartment for a liquid catholyte or a liquid anolyte, wherein the inlet region as well as the outlet region of the compartment are provided with an upper grid and a lower grid, the width of the mesh and the positioning of which is chosen such as to allow the liquid catholyte or the liquid anolyte to pass through from bottom to top but to prevent the granules to pass through the grids to leave the compartment, and wherein the upstream flow of the liquid catholyte or of the liquid anolyte can be adjusted so that in operation the multitude of granules is dragged against the upper grid while the lower grid is substantially not in contact with the granules, wherein
in a first step the fluid velocity of the electrolyte is increased up above the minimum flow in accordance with the Stokes equation but not more than twice the minimum of the Stokes equation at least until the freely suspended conductive granules are dragged against the upper grid;
in a second step the flow velocity is increased to a minimum value of in the range of

          ν m=[(ρ s−ρ f) gd p 2]/μ,
and not up to a value of

          ν m<500 μP/S*(ρ f)[10(1−ε)/ε 3]
wherein to this end the flow ν mc given as

          ν mc=[ε 3/{10(1−ε)}]*ν m
is increased by 0.005-0.02 cm/s per second;
in a third step the actual electrolytic process is started, wherein the variation in the flow velocity is kept low, such as to avoid a rearrangement of the dragged bed leading to a compacting of the dragged bed.
23. A method for operating a reactor according to claim 1 for vat and/or sulphur dye dyeing of fibres, yarns and/or textiles wherein the reactor is used for the reduction of the dye and/or for the preparation of a bleaching agent and/or for oxidation of the dye after its application to the fibres, yarns and/or textiles, wherein two distinct reactors are used, one for the preparation of a bleaching agent and for the oxidation of the dye after its application to the fibres, and a second one for the reduction of the dye.