The invention relates to an inductive radial-discharge tunnel-shaped nozzle compris¬ ing, in series, a socket to supply a fluid and a spreading cone, whose tip resides in tront ot a discharge mouth ot the said socket, as well as a tunnel-shaped housing en¬ casing them.

Nozzles ot the type as set torth above serve tor dividing, distributing, dispensing and/or dispersing a gas in a fluid e.g. in flotation plants.

A nozzle ot the above type is known trom EP 0 035 243. The known nozzle is charac¬ terized by a convergent-divergent mixing chamber having a constant hydraulic diameter so that by increasing the circumterence a dittuser is created. It is charac¬ teristic ot the known nozzle that by means thereot no such quantity of gas can be in¬ duced that the ratio of the flows ot the fluid and ot the induced gas would be 1 nor is it possible to produce bubbles ot a relatively small magnitude (about 150 microns). In practice, all these features ot the known nozzle together limit the possibilities ot in¬ stalling the nozzle.

It is an object ot the present invention to modify the above-mentioned comparable design ot a nozzle so that its inducing characteristics will be altered to result in a sig¬ nificantly broader field ot use.

When searching tor a solution to improve the characteristics of the tunnel-shaped nozzle it was surprisingly tound that the inducing ettect ot the nozzle was markedly higher it an annulus between a cone-shaped spreading element and a housing was continuously reduced towards the exit. The reduction of the said annulus was such that the annular flow area along the cone was maintained constant.

Herematter, the invention is disclosed m more detail by means of an embodiment shown in the drawing. In the drawing:

Fig 1 is partly an elevational axial section and partly an elevational view ot the in¬ ventive nozzle,

Fig. 2 is a graph ot inducing characteristics, and

Fig. 3 is a graph of nozzle capacities.

Basically, the nozzle is composed of three mutually coaxial/equiaxial component members: a spreading cone 1 having a tip angle of 90°, a socket 2 of an inner diameter d for supplying a liquid, and a shaped housing 3 common to both first- mentioned members. A part of the housing 3 residing at the socket 2 together with the latter forms an annulus for supplying a gas, and a part of the housing 3 residing at the cone 1 together with the mantle surface of the latter forms an annulus for dis¬ charging the fluid/gas dispersion.

The fundamental feature of the invention i.e. that the flow area of the annulus be¬ tween the cone 1 and the housing 3 is constant in axial direction, can be carried out according to the invention by a plurality of approaches. In the embodiment shown the cone 1 is an elementary geometrical body so that a spacing of an inner mantle surface of the funnel-shaped part of the housing 3 is defined depending on the mantle surface of the said cone. In the arrangement as shown the said spacing equals D _h at the location where it is smallest i.e. prior to entering a radial gap of the nozzle.

Added to the cone 1 and the housing 3, respectively, are D-diameter flanges that mutually define a radial discharge gap of the nozzle.

Pressurized water is supplied through the socket 2 onto the tip of the cone 1. A vacuum is established in a hole existing between the socket 2, the cone 1 and the housing 3, which results in an induction of gas through the housing 3 into the spread flow of the fluid. From here on the fluid and the gas flow in the form of a fluid/gas dispersion.

Fig. 2 shows the inducing characteristics of funnel-shaped nozzles. Line A indicates the characteristics of an embodiment having a constant hydraulic diameter (prior art) and lines B and C indicate the characteristics of a nozzle having a constant flow area of an annulus according to the invention. Evidently, the ratio of the gas flow vs. liquid flow according to the invention is not only increased to 1, but increased for a factor of about 4.

Tests (Fig. 3) made by using several funnel-type nozzles (D = 100 mm, 200 mm. 300 mm) of the respective design confirmed the proposition that beyond a certain critical value all funnel-type nozzles having a constant flow area operate equally well.