GB1591242A

GB1591242A - Device for the removal of constituents in a gas

Info

Publication number: GB1591242A
Application number: GB42270/77A
Authority: GB
Original assignee: Carl Munters AB
Current assignee: Carl Munters AB
Priority date: 1976-10-26
Filing date: 1977-10-11
Publication date: 1981-06-17
Also published as: FR2369017A1; SE7611889L; SE417911B; DE2746977A1; JPS5353582A

Description

(54) A DEVICE FOR THE REMOVAL OF CONSTITUENTS IN A GAS (71) We, AKTIEBOLAGET CARL MUNTERS, a Swedish Company of Industrivagen 2, S-191 47 Sollentuna, Sweden, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a device for the removal of constituents in a gas (air) utilizing a body or bed of activated carbon.

One example of the area where similar bodies are used is the removal of solvents or the purification of air from substances which are environmentally undersirable such as foul-smelling gases e.g. in industries manufacturing fishmeal or cellulose pulp, mainly using the sulphate method or something similar. Up to the present the body of activated carbon has consisted of relatively large granules which are used to fill a container provided with an inlet and an outlet for the air which is to be purified. The granules in the container form a body with irregular passages between them through which the air is passed. This results in the resistance to the body of air being high and different parts of the body of activated carbon participating in the adsorption process with varying intensity. Moreover, there is a risk, due specifically to the high resistance and the irregular passages, that the granules will shift position in relation to each other causing an abrasive action which will result in them eroding each other.

The form of the granules is an intrinsic disadvantage due to the resistance which occurs when the constituent which is to be removed becomes diffused in the granules.

Diffusion resistance can be reduced if small granules are selected, shortening the diffusion path; but on the other hand the use of small granules increases resistance to the air when it passes through the bed with the result that the thickness of the bed has to be reduced thereby diminishing its contact capacity. The diffusion resistance resulting from the use of granules of a practical size means for its part that a limit is placed on the time during which the activated carbon can be utilized.

Therefore, in a device of this nature compensation must be made for a large drop in pressure which makes operating costs relatively high and moreover the degree to which the body of activated carbon can be utilized is not fully exploited.

This invention is intended to eliminate these inconveniences by providing a device which gives a high degree of absorption efficiency with a low resistance to the gas, such as air, which is flowing through it.

According to the present invention there is provided a method of producing a body for the removal of constituents contained in a gas comprising the steps of forming a cellular structure of alternate plane and corrugated sheets of inorganic material by internally supporting the sheets on each other at separate points to form a plurality of parallel channels extending from end to end of the body and applying a layer of activated carbon in finely powdered form on said sheets by applying a fluid substance to said sheets containing carbon in a chemically bound state and freeing the carbon and activating the carbon in conjunction with the application of heat. The invention also includes a gas purification device made in accordance with the above method. In this invention the structural body is constructed incorporating pre-determined channels; in other words they are not dependent on the size of the granules of activated carbon. The activated carbon can therfore take the form of sheets of small particles of any size which are then exposed to the gas passing through the channels thereby making the entire volume of the activated carbon available to absorb the constituent that is to be removed. The separate, pre-determined passages for the current of contaminated gas result in the resistance to the current being low even if the channel section is small. Moreover, the structural body according to this invention is particularly suitable for the implementation of a reactivation process involving one section of the body having the gas which is to be purified passing through it while another distinctly separate section has the heated reactivating gas passed through it. This means that the structural body can be advantageously designed in the form of a rotor encased in a housing with the channels arranged to have both currents of gas passing alternately through them during rotation.

The body can advantageously be made of paper-thin sheets of fibre material such as cellulose, asbestos or another inorganic material. Every other sheet can be made corrugated and every other flat allowing the sheets to contact and support each other along the ridges of the corrugations so that the body becomes filled with intemal transectional parallel channels which discharge through both of its flat sides. The distance between the flat sheets should preferably not exceed 3 mm and should optimally be around 1.5 mm. The body can be executed in the form of a cylindrical rotor moving in a closed path between two passages in an enclosed casing, the rotor having two currents of gas passing through it at separate points, i.e. the current of gas to be purified and the heated reactivating gas.

It is possible to produce a coating of activated carbon from an organic substance such as melamine, phenol or dextrin which is dissolved in e.g. water, the solution being absorbed by the sheets after they have been made into a structural body as described above. Alternatively the organic substance can be applied to the sheets in the form of a melt. The sheets are subsequently heated to 800" in the absence of air, i.e. pyrolysis, which carbonizes the organic substance thereby forming a fine deposit or coating of free carbon on the sheets. The carbon obtains the required adsorption properties by subsequently activating the carbon by e.g. using high-temperature steam in the well-known manner. This treatment opens the pores in the carbon.

If the activated carbon is to be applied on the sheets it is best that they be made of inorganic fibres or wires e.g. of asbestos, mineral wool or metal gauze respectively. If the fibre material consists of asbestos it is converted at high temperatures so that the fibres take on a sort of powdered form. In order to provide the structural body with sufficient mechanical strength, the fibres can be impregnated with one or more inorganic substance, e.g. sodium silicate or calcium chloride, which forms a layer of stiffening precipitation which can tolerate high temperatures. A similar treatment using substances which form a load-bearing or ceramic skeleton can also be used when the activated carbon is to be introduced into the sheets in an already pulverised form.

The finely-powdered form referred to in this patent is defined as the maximum dimension of the activated carbon particles being from 1 mm down to colloidal size.

The sheets can also be made of metal foil to which the finely-powdered activated carbon is applied.

WHAT WE CLAIM IS: 1 A method of producing a body for the removal of constituents contained in a gas comprising the steps of forming a cellular structure of alternate plane and corrugated sheets of inorganic material by internally supporting the sheets on each other at separate points to form a plurality of parrallel channels extending from end to end of the body and applying a layer of activated carbon in finely powdered form on said sheets by applying a fluid substance to said sheets containing carbon in a chemically bound state and freeing the carbon and activating the carbon in conjunction with the application of heat.

2. A method according to claim 1 wherein the step of applying the fluid substance containing carbon comprises applying said fluid substance containing carbon to the sheet in a solution.

3. A method according to claim 1 wherein the step of applying the fluid substance containing carbon comprises applying said fluid substance containing carbon to the sheet in the form of a melt.

4. A method of producing a body for the removal of constituents contained in a gas according to claim 1 and substantially as hereinbefore described.

5. A gas purification device made in accordance with the method of any one of the preceding claims.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

reactivating gas passed through it. This means that the structural body can be advantageously designed in the form of a rotor encased in a housing with the channels arranged to have both currents of gas passing alternately through them during rotation.

The body can advantageously be made of paper-thin sheets of fibre material such as cellulose, asbestos or another inorganic material. Every other sheet can be made corrugated and every other flat allowing the sheets to contact and support each other along the ridges of the corrugations so that the body becomes filled with intemal transectional parallel channels which discharge through both of its flat sides. The distance between the flat sheets should preferably not exceed 3 mm and should optimally be around 1.5 mm. The body can be executed in the form of a cylindrical rotor moving in a closed path between two passages in an enclosed casing, the rotor having two currents of gas passing through it at separate points, i.e. the current of gas to be purified and the heated reactivating gas.

It is possible to produce a coating of activated carbon from an organic substance such as melamine, phenol or dextrin which is dissolved in e.g. water, the solution being absorbed by the sheets after they have been made into a structural body as described above. Alternatively the organic substance can be applied to the sheets in the form of a melt. The sheets are subsequently heated to 800" in the absence of air, i.e. pyrolysis, which carbonizes the organic substance thereby forming a fine deposit or coating of free carbon on the sheets. The carbon obtains the required adsorption properties by subsequently activating the carbon by e.g. using high-temperature steam in the well-known manner. This treatment opens the pores in the carbon.

If the activated carbon is to be applied on the sheets it is best that they be made of inorganic fibres or wires e.g. of asbestos, mineral wool or metal gauze respectively. If the fibre material consists of asbestos it is converted at high temperatures so that the fibres take on a sort of powdered form. In order to provide the structural body with sufficient mechanical strength, the fibres can be impregnated with one or more inorganic substance, e.g. sodium silicate or calcium chloride, which forms a layer of stiffening precipitation which can tolerate high temperatures. A similar treatment using substances which form a load-bearing or ceramic skeleton can also be used when the activated carbon is to be introduced into the sheets in an already pulverised form.

The finely-powdered form referred to in this patent is defined as the maximum dimension of the activated carbon particles being from 1 mm down to colloidal size.

The sheets can also be made of metal foil to which the finely-powdered activated carbon is applied.

WHAT WE CLAIM IS: 1 A method of producing a body for the removal of constituents contained in a gas comprising the steps of forming a cellular structure of alternate plane and corrugated sheets of inorganic material by internally supporting the sheets on each other at separate points to form a plurality of parrallel channels extending from end to end of the body and applying a layer of activated carbon in finely powdered form on said sheets by applying a fluid substance to said sheets containing carbon in a chemically bound state and freeing the carbon and activating the carbon in conjunction with the application of heat.
2. A method according to claim 1 wherein the step of applying the fluid substance containing carbon comprises applying said fluid substance containing carbon to the sheet in a solution.
3. A method according to claim 1 wherein the step of applying the fluid substance containing carbon comprises applying said fluid substance containing carbon to the sheet in the form of a melt.
4. A method of producing a body for the removal of constituents contained in a gas according to claim 1 and substantially as hereinbefore described.
5. A gas purification device made in accordance with the method of any one of the preceding claims.