Contact Compartment for Removing Noxious Gaseous Components From a Gas Stream

The present invention relates generally to devices for exchange of materials, and in particular to a materials contact compartment of the kind including a turbulent or fluidized bed or layer.

It is well known that, in order to induce chemical reactions or absorption bonding between a solid substance and a gas containing noxious components, the solid substance be placed in the fluidized state by means of the gas containing noxious components. By intermixing the solid substance and the gas in a turbulent manner, the former combines or forms absorptive bonds (absorption compounds) with the noxious gas components.

In practice, however, it was discovered that such turbulent intermixing of a solid substance acting as a turbulence material and a gas acting as a turbulence agent or carrier, does not always form a homogeneous fluidized or turbulent bed. A conventional fluidized bed may have vertical passages, rising gas bubbles, or gas layers devoided of turbulence material. Such effects are highly undesirable. It results, for example, in a substantial portion of the noxious gas components not combining or chemically reacting with the solid substance, and the latter not being utilized as a turbulence material or only partially or inadequately so. It is also apparent that, since the solid substance particles vary considerably in grain size, it is primarily and practically only the smaller particles (having a relatively large surface as compared to their weight) which react or combine with the noxious gas components.

It is an object of the invention to minimize or prevent gas passages, gas bubbles or gas layers, from being formed without admixture of turbulence material in a fluidized or turbulent layer of an upright fluid bed compartment, and to utilize the turbulence material to the optimum degree notwithstanding different particle sizes.

To fulfill this and other objects in a device of the kind hereinabove referred to, an upright fluid bed compartment of rectangular cross-section having a lower and upper portion, into which lower portion the turbulence carrier and the turbulence material are fed and from which top portion the carrier and turbulence material are drawn off contains at least one sieve drum which occupies the cross-section, revolves and is charged with regular (e.g., spheroids), or irregular objects.

The volume of the fluid bed compartment or chamber is thus interrupted at least once by one sieve drum but advantageously several or many times by sieve drums so that the forming of gas passages, gas bubbles or the like without admixture of turbulence material is prevented in the turbulence or fluid bed chamber. This causes immediate mixing of turbulence material and turbulence carrier in the turbulence chamber and thereafter repeated mixing of the same in each subsequent spheroid charged revolving drum or rotor, and an homogenous fluidized bed which promotes the collision of solid particles and noxious gases is subsequently produced by means of fluidized displaced turbulence material particles above the lowest sieve drum or above every sieve drum as the case may be. The solid material particles are broken up increasingly from sieve drum to sieve drum, so that new surfaces of the solid particles are produced after each sieve drum for reaction with the noxious gases. It is thus possible to utilize to the optimum degree the solid particles or additives, which are to be added, for the chemical reaction.

The absorption compounds produced may also be partially separated from the gas flow outside the fluid bed compartment and fed into the compartment again together with fresh solid particles, if the compounds separated were still to contain solid particles which had not as yet formed any compound with the noxious gases.

In order for the invention to be clearer and better understood, reference will now be made to the accompanying single FIGURE of the drawings, which illustrates one embodiment of a fluid bed compartment in vertical diagrammatical cross-section and by way of example only.

Referring now to the drawing, the fluid bed compartment, in accordance with the invention comprises an upright casing 1 of rectangular horizontal cross-section, within which spaced-apart sieve drums 2, 3, 4 are caused to revolve, matching the horizontal cross-section of the compartment 1 and the periphery of which has the casing sides or side walls 1a, 1b, tangent to it. The drums are journalled horizontally. The casing 1 is provided with an inlet opening at the lower portion thereof and an outlet opening at the top portion thereof.

These sieve drums 2, 3, 4 are partially filled with heavy spheroids 5 or other heavy objects which may be of regular or irregular shape, and are entrained by the rotation of the drums and then drop down again in the drum. In order that a useful entrainment of these objects 5 occurs, the internal surface of the peripheral side of the drum may be provided with axially parallel entraining bars 6.

The diameter of the lowest sieve drum 2 is a little smaller than that of the upper sieve drums 3, 4 which may, if desired, be increased in number, and this lower drum 2 is provided on its external periphery with axially parallel scraper bars 7 which sweep over and scrape the cylindrical compartment base 1c and thereby prevent accumulation of material below the drum 2.

The turbulence material and the turbulence carrier, in particular a gas originating from optional combustion plants or the like and in particular containing solids or additives and a noxious gas, are fed to the sieve drum 2, via the inlet opening and the cylindrical compartment base 1c, in the lower section of the fluid bed compartment, so that the turbulence material drawn from a store 8 and the turbulence carrier come into contact in the sieve drum 2. The turbulence material, in the form of solids or additives is such as to react with molecules of noxious gases, such as HC1, H.sub.2 F.sub.2, SO.sub.3, SO.sub.2, or the like of the turbulence carrier to form and produce absorption compounds which are subsequently separated in conventional manner from the fluid layer carrier, that is from the gas flow.

Direct contact between the gas and the solids is already obtained in the drum 2 by means of the moving or rolling spheroids or tumbling objects co-operating with the solids or additives fed into it, whereupon a turbulent fluidized layer consisting of gas and solids is then formed above the lowest sieve drum 2 in which solid-free gas passages, gas bubbles or the like cannot occur because the turbulent layer is interrupted by the next sieve drum 3 which is again traversed by flow from the bottom towards the top insert portion and outlet opening of the casing, by-passing of the drum 3 being prevented by the fact that it is partially screened along the lower periphery by flanking surfaces 9 projecting from the tangential contact surfaces 1a and 1b, which are also incorporated for the topmost drum 4. Scrapers 10 projecting from the surfaces 1a and 1b and which prevent spheroids 11 or the like which lie loose on the sieve drums 3 and 4 from being jammed between the drum and the wall, are situated at the upper side of each upper drum 3, 4. These spheroids 11 serve the purpose of keeping the perforations of the sieve drums 3 and 4 clear and free of solid particles. As will be understood, a free turbulence or fluid layer is again formed above the drum 3, in which the noxious gases in turbulent motion come into contact with the solid substances and undergo reactions, just as inside the sieve drums themselves, in which connection it is pertinent to point out that the solids undergo continuing break-up or grinding in the drum 3 by the action of the continuously rotarily entrained and dropping objects 5, so that new surfaces of the solids are available to the noxious gases for absorption compound forming.

The number of sieve drums may be increased if desired. The solids or additives which are to be added may on the whole be largely used up.

The gas containing a combination of noxious gases and solid particles or additives, in compound form as well as unused particles or additives and flowing out from the casing 1 at the top portion thereof via the outlet opening and the pipe 12, may for example be ducted to a separator 13, from which the compounds and additives are separated and are fed to the gas duct together with fresh additives via a bucket wheel 14, a proportion of the solids and compounds being withdrawable from the gas duct, e.g. at 15. The additives not used at that time may then be brought again into direct contact with the noxious components of a gas in the vortexial layer compartment 1, so that an extensive utilization of the additives may also be assured in a case of this kind. It should be noted, however, that this procedure may not be applicable in certain exceptional cases.