GB2076794A

GB2076794A - Apparatus for Use in Adsorbing Gaseous Fluorine on Particles of Alumina

Info

Publication number: GB2076794A
Application number: GB8116349A
Authority: GB
Original assignee: Tilghman Wheelabrator Ltd
Current assignee: Tilghman Wheelabrator Ltd
Priority date: 1980-05-30
Filing date: 1981-05-28
Publication date: 1981-12-09
Also published as: GB2076794B

Abstract

The apparatus comprises means for preventing the alumina particles suspended in the adsorption column from moving by gravity in counter- current to the gaseous fluoride beyond a predetermined threshold is a rectilinear duct (16) at the bottom of the adsorption column mounting internally an orifice plate (17), and an alumina delivery arrangement (18, 19) for delivering alumina particles into the column above the orifice plate. The orifice of the orifice plate may be variable in size (e.g. a motorised iris diaphragm), or there may be a number of orifice plates with differently-sized orifices. <IMAGE>

Description

SPECIFICATION Apparatus for Use in Adsorbing Gaseous Fluorine on Particles of Alumina This invention relates to apparatus for use in adsorbing gaseous fluorine on particles of alumina.

Such an apparatus is known and includes an adsorption column through which gaseous fluorine is passed upwardly and which has at its bottom a means for preventing alumina particles suspended in the column from moving by gravity in counter-current to the gaseous fluoride beyond a predetermined threshold. Such means are a convergent-divergent duct (i.e. a Venturi) into the divergent part of which the alumina particles are downwardly introduced into contact with the upwardly-flowing gaseous fluorine.

The present invention is particularly concerned with such means and provides an alternative solution, which tests have shown to provide a better distribution of the adsorbing alumina particles than is obtained in the known apparatus.

According to the present invention there is provided apparatus for use in adsorbing gaseous fluorine on particles of alumina in which the means for preventing the alumina particles suspended in the adsorption column from moving by gravity in counter-current to the gaseous fluoride beyond a predetermined threshold is a rectilinear duct at the bottom of the adsorption column mounting internally an orifice plate, and an alumina delivery arrangement for delivering alumina particles into the column above the orifice plate.

Preferably the delivery arrangement feeds the alumina particles horizontally into the column, although downward in-feed is also visualised.

The orifice of the orifice plate is preferably of variable diameter or cross-sectional area.

Alternatively, a plurality of orifice plates having differently sized orifices are provided so that an operator can select and fit the correctly-sized orifice plate to suit plant requirements.

There is preferably a second delivery arrangement for feeding recycled activated alumina particles into the adsorption column preferably at a level above the feed-in point of the raw alumina particles and preferably horizontally.

Here again, downward feed-in is visualised. Such recycled activated alumina particles are preferably recovered for filter means. The filter means may be one or more filter bag units.

An embodiment of the present invention will now be described by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic part sectional view of apparatus according to the invention; Figs. 2 and 3 are diagrammatic side and front views of the apparatus of Fig. 1; and Figs. 4 and 5 are diagrammatic views of modifications.

In general terms, the apparatus for use in adsorbing gaseous flurine on particles of alumina comprises an adsorption column 10 connected by a transition unit 1 1 to a branched duct 12, each branch of which is connected to a filter bag unit 13 or other separator from which gas egresses through a chimney indicated by an arrow 14.

Alumina partly charged with fluorine is delivered to a storage hopper (not shown) from where it is recycled to the adsorption column 10 as described below.

Gaseous fluorine is delivered to the adsorption column along a horizontal duct 15 which is tapered to maintain velocity of the gas.

As previously stated, the adsorption column 10 has at its bottom a means for preventing alumina particles suspended in the column 10 from moving by gravity in counter-flow to the gaseous fluorine beyond a predetermined threshold. Such means is housed between the column 10 and the duct 15 in a vertical rectilinear duct 16 within which is mounted an orifice plate 17 which determines the aforesaid threshold.

This orifice plate 17 may have a variable sized orifice. For example, the orifice plate 17 may be in the form of a motorised iris diaphragm.

Alternatively, a number of orifice plates 17 having different orifice sizes are provided for the adsorption column 10, the appropriately-sized orifice plate 17 being selected and slotted into an appropriate gap in the duct 16.

Such adjustability or substitution allows the operator to take account of, for example, the volume of gaseous fluorine being delivered to the column 10 and/or the amount of unsaturated powdered alumina being introduced.

Unsaturated powdered alumina is delivered into the stream of gaseous fluorine above the orifice plate 17 by a screw feed arrangement 18 which horizontally inputs the alumina into the gas stream through horizontal duct 19.

Recycled alumina partially charged with fluorine is recycled to the adsorption column 10 by a horizontal delivery duct 20 fed from the storage hopper (not shown) or even directly from the bag filter units 13 as indicated by lines 21.

The introduction of alumina particles into the adsorption column 10 at the horizontal ducts 19 and 20 may be improved or assisted by allowing air or gas to be drawn in and/or by introducing air or gas under pressure and indicated by the arrows 22. Alternatively, air or gas is drawn in or introduced under pressure at both alumina particle delivery ducts 19 and 20.

In Fig. 4, the orifice plate 17 is immediately adjacent the duct 15 as it is in Fig. 5 but in the latter the length of rectilinear duct 1 6 is reduced to reduce the overall height of the adsorption column 10.

Claims

1. Apparatus for use in adsorbing gaseous fluorine on particles of alumina in which the means for preventing the alumina particles suspended in the adsorption column from moving by gravity in counter-current to the gaseous fluoride beyond a predetermined threshold is a

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Apparatus for Use in Adsorbing Gaseous Fluorine on Particles of Alumina This invention relates to apparatus for use in adsorbing gaseous fluorine on particles of alumina. Such an apparatus is known and includes an adsorption column through which gaseous fluorine is passed upwardly and which has at its bottom a means for preventing alumina particles suspended in the column from moving by gravity in counter-current to the gaseous fluoride beyond a predetermined threshold. Such means are a convergent-divergent duct (i.e. a Venturi) into the divergent part of which the alumina particles are downwardly introduced into contact with the upwardly-flowing gaseous fluorine. The present invention is particularly concerned with such means and provides an alternative solution, which tests have shown to provide a better distribution of the adsorbing alumina particles than is obtained in the known apparatus. According to the present invention there is provided apparatus for use in adsorbing gaseous fluorine on particles of alumina in which the means for preventing the alumina particles suspended in the adsorption column from moving by gravity in counter-current to the gaseous fluoride beyond a predetermined threshold is a rectilinear duct at the bottom of the adsorption column mounting internally an orifice plate, and an alumina delivery arrangement for delivering alumina particles into the column above the orifice plate. Preferably the delivery arrangement feeds the alumina particles horizontally into the column, although downward in-feed is also visualised. The orifice of the orifice plate is preferably of variable diameter or cross-sectional area. Alternatively, a plurality of orifice plates having differently sized orifices are provided so that an operator can select and fit the correctly-sized orifice plate to suit plant requirements. There is preferably a second delivery arrangement for feeding recycled activated alumina particles into the adsorption column preferably at a level above the feed-in point of the raw alumina particles and preferably horizontally. Here again, downward feed-in is visualised. Such recycled activated alumina particles are preferably recovered for filter means. The filter means may be one or more filter bag units. An embodiment of the present invention will now be described by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic part sectional view of apparatus according to the invention; Figs. 2 and 3 are diagrammatic side and front views of the apparatus of Fig. 1; and Figs. 4 and 5 are diagrammatic views of modifications. In general terms, the apparatus for use in adsorbing gaseous flurine on particles of alumina comprises an adsorption column 10 connected by a transition unit 1 1 to a branched duct 12, each branch of which is connected to a filter bag unit 13 or other separator from which gas egresses through a chimney indicated by an arrow 14. Alumina partly charged with fluorine is delivered to a storage hopper (not shown) from where it is recycled to the adsorption column 10 as described below. Gaseous fluorine is delivered to the adsorption column along a horizontal duct 15 which is tapered to maintain velocity of the gas. As previously stated, the adsorption column 10 has at its bottom a means for preventing alumina particles suspended in the column 10 from moving by gravity in counter-flow to the gaseous fluorine beyond a predetermined threshold. Such means is housed between the column 10 and the duct 15 in a vertical rectilinear duct 16 within which is mounted an orifice plate 17 which determines the aforesaid threshold. This orifice plate 17 may have a variable sized orifice. For example, the orifice plate 17 may be in the form of a motorised iris diaphragm. Alternatively, a number of orifice plates 17 having different orifice sizes are provided for the adsorption column 10, the appropriately-sized orifice plate 17 being selected and slotted into an appropriate gap in the duct 16. Such adjustability or substitution allows the operator to take account of, for example, the volume of gaseous fluorine being delivered to the column 10 and/or the amount of unsaturated powdered alumina being introduced. Unsaturated powdered alumina is delivered into the stream of gaseous fluorine above the orifice plate 17 by a screw feed arrangement 18 which horizontally inputs the alumina into the gas stream through horizontal duct 19. Recycled alumina partially charged with fluorine is recycled to the adsorption column 10 by a horizontal delivery duct 20 fed from the storage hopper (not shown) or even directly from the bag filter units 13 as indicated by lines 21. The introduction of alumina particles into the adsorption column 10 at the horizontal ducts 19 and 20 may be improved or assisted by allowing air or gas to be drawn in and/or by introducing air or gas under pressure and indicated by the arrows 22. Alternatively, air or gas is drawn in or introduced under pressure at both alumina particle delivery ducts 19 and 20. In Fig. 4, the orifice plate 17 is immediately adjacent the duct 15 as it is in Fig. 5 but in the latter the length of rectilinear duct 1 6 is reduced to reduce the overall height of the adsorption column 10. Claims

1. Apparatus for use in adsorbing gaseous fluorine on particles of alumina in which the means for preventing the alumina particles suspended in the adsorption column from moving by gravity in counter-current to the gaseous fluoride beyond a predetermined threshold is a rectilinear duct at the bottom of the adsorption column mounting internally an orifice plate, and an alumina delivery arrangement for delivering alumina particles into the column above the orifice plate.

2. Apparatus as claimed in claim 1, in which the orifice of the orifice plate is of variable size.

3. Apparatus as claimed in claim 2 in which the orifice plate is in the form of a motorised iris disphragm.

4. Apparatus as claimed in claim 1 comprising a plurality of orifice plates each having a differently sized orifice so that an operator can select that orifice plate best suited to operational requirements.

5. Apparatus as claimed in any one of claims 1 to 4, in which the delivery arrangement feeds the alumina particles horizontally into the adsorption column.

6. Apparatus as claimed in any one of claims 1 to 5 comprising a second delivery arrangement for feeding recycled activated alumina particles into the adsorption column.

7. Apparatus as claimed in claim 6 in which the second delivery mean delivers the recycled activated alumina particles horizontally into the adsorption column.

8. Apparatus as claimed in claim 7 in which one or both delivery arrangements feeds the alumina particles downwards into the adsorption column.

9. Apparatus as claimed in claims 7 or 8, in which the introduction of alumina particles in the adsorption column is assisted by entrainment of, or pressure feed-in of air and/or gas at the delivery arrangements.

10. Apparatus as claimed in any one of claims 1 to 9, in which the adsorption column at its top is connected to a separator, such for example as a filter bag unit.

1 Apparatus for use in adsorbing gaseous fluorine on particles of alumina, substantially as hereinbefore described with reference to the accompanying drawings.