WO1993022064A1

WO1993022064A1 - Nozzle assembly

Info

Publication number: WO1993022064A1
Application number: PCT/GB1993/000924
Authority: WO
Inventors: Thomas Henry White
Original assignee: W.H. Dickinson Engineering Limited
Priority date: 1992-05-06
Filing date: 1993-05-05
Publication date: 1993-11-11
Also published as: GB9209728D0

Abstract

A nozzle assembly (7) for spraying gas or steam containing liquid additive into a chamber (2), particularly adapted for the treatment of particulate material such as tobacco. The assembly (7) is mounted at an entrance to the chamber in a housing which is pressurised with gas or steam so as to produce a gas shroud surrounding the nozzle outlet, preventing the treated product from attaching itself to the nozzle (7) and clogging it.

Description

"Nozzle Assembly"

This invention relates to a nozzle assembly for supplying liquid additive in gas or steam under pressure.

In the processing of certain types of tobacco and other products, such as foodstuffs, detergents and fertilisers, it is common practice to apply liquid additives, such as flavourings, by means of a spray nozzle directed on to the product as it tumbles through a revolvin dru .

Frequently, the additive is a sticky liquid and, to minimise accumulations of both product and additive on the walls of the drum, the spray must be arranged so as to minimise impingement of droplets on to the walls of the drum. This requires selection of a nozzle whose spray pattern is appropriate to the geometry of the chamber defined by the drum, and which can be positioned so that th spray is effectively directed on to ,the tumbling product.

The scope for optimal positioning of the spray nozzle is restricted by the need to prevent stray particles of product from attaching themselves to the nozzle or masking it or otherwise interfering with its spray pattern.

Another constraint upon the positioning of the spray nozzle results from the use of an airstream within th chamber defined by the drum to perform conditioning or heating of the product. If the spray nozzle is positioned too close to the point at which the airstream is exhausted from the chamber, there is a strong possibility that droplets of the additive will be entrained in the exhaust, thus reducing the efficiency of application and necessitating additional cleaning of the exhaust system.

Accordingly, the present invention resides in a nozzle assembly for spraying a liquid additive into a

SUBSTITUTE SHEET chamber in which the outlet of the nozzle is spaced from an entrance to the chamber; means are provided for supplying gas or steam under pressure and the additive to the nozzle to produce a jet of gas or steam containing the additive which is directed into the chamber through the entrance thereof; and means for shrouding the outlet of the nozzle with gas or steam flowing in the direction towards the entrance of the chamber.

The gas or steam which is arranged to shroud the outlet of the nozzle serves to ensure that particles of product from the chamber are propelled away from the spray ^•nozzle. In this way, the spray nozzle is not blocked or otherwise affected by the product in the chamber at any time.

In order that the invention may be more readily understood, it will now be described, by way of example only, with reference to the accompanying drawings, in which:-

Figure 1 is a diagrammatic side elevation of apparatus including a nozzle assembly in accordance with the present invention;

Figure 2 is a section on the line A-A of Figure 1;

Figure 3 is a sectional side elevation to a larger scale of the part of the apparatus indicated by reference III of Figure 1; and

Figure 4 is plan view of an alternative form of the invention.

The nozzle assembly of the present invention is particularly suitable in the processing of particulate product, such as certain types of tobacco. This application of the invention is illustrated in the figures.

Referring to Figures 1 and 2 in particular, a cylindrical drum 1 is arranged with its longitudinal axis inclined slightly with respect to the horizontal axis and is

SUB rotatable about this axis by means (not shown) . The drum defines, a chamber 2 and lifting pins or ribs 3 project inwardly into the chamber from the side walls thereof so that, as the drum is rotated, particulate product in the drum is tumbled and makes its way to the lower end of the drum. The lower end of the drum 4 is open, and serves as a entrance to the chamber located within a stationary housing 5 and there is a pod 6 on the outside wall of the housing.

The nozzle assembly 7 is located within the pod and the outlet of the nozzle is close to an opening 8 in th outside wall of the housing which connects the interior of the pod with the interior of the housing.

Referring particularly to Figure 3, the nozzle assembly 7 includes a mixing head 9 to which a pipe 10 is connected through which gas or steam under pressure is applied to the mixing head. A further pipe 11 enables liquid additive, such as flavouring, to be supplied to the mixing head. The mixing head is connected to the nozzle outlet 9A. A further pipe 12 leads into the pod to enable the pod to be pressurised with a gas or steam, preferably this being the same as the medium applied to the nozzle assembly. To allow precise angular positioning of the nozzle assembly, ,a ball joint 13 is incorporated into the mounting of the spray nozzle and the pipes 10, 11 are flexible to allow movement of the spray nozzle.

When steam is used as the gas applied to the pod, the pod is insulated to minimise condensation and heat loss A drain hole 14 is provided adjacent the base of the pod to allow condensate to be removed.

In use, the gas or steam under pressure is supplied via pipe 10 to the mixing head of the nozzle and small quantities of the additive liquid are also supplied via the pipe 11. This additive liquid is atomised by, and introduced into, the gas or steam to produce a jet 15 of an

SUBSTITUTE SHEET appropriate shape issuing from the outlet of the nozzle. The jet passes through the opening 8 in the wall of the pod and through the fixed housing 5 and into the chamber 2 through the entrance 4. The shape of the jet is arranged so that the spray contacts the cascading curtain of product within the chamber 2 with the minimum of overspray on to the walls of the chamber. By arranging for the pod to be under pressure, a shroud 16 of gas or steam flows from the pod around the outlet of the nozzle and through the opening into the housing 5 and serves to keep particles of product and debris away from the outlet of the nozzle. The shroud of gas lows from the pod through the opening 8 in the direction towards the entrance to the chamber. The shroud effectively prevents product particles from approaching the nozzle due to the locally high velocity present in the shroud. Experience indicates that, for tobacco, shroud velocities of 0.5 - 1.5 /sec are necessary to prevent product from contacting the nozzle. The shroud velocity is related to the terminal velocity of the product particles and will be higher for products with high terminal velocities.

To obtain full benefits from the shrouded nozzle system, control means should be provided to ensure that the shroud gas flow is established before product is present in the vicinity of the nozzle and that it remains established until all product has left the cylinder. Similarly, control means should be provided to ensure that the liquid to be sprayed into the chamber is only supplied to the nozzle when product is present in the vicinity of the nozzle to avoid spray impingement on to the walls of an empty chamber.

By mounting the nozzle assembly on a ball joint, appropriate selection of the spray geometry relative to the chamber can be obtained to maximise contact between the spray and the product in the chamber minimising impingement

SUBSTITUTE SHEET of the spray on to the chamber walls.

In the arrangement shown in Figure 4, the spray i directed along a line which is slightly oblique to the longitudinal axis of the chamber in plan view and coinciden with the chamber axis when viewed from the side.

The product enters the upper end of the drum 1 by way of a conveyor and leaves the lower end of the drum by another conveyor 18.

SUBSTITUTE SHEET

Claims

1. A nozzle assembly for spraying a liquid additive into a chamber in which the nozzle assembly is mounted at an entrance to the chamber, means are provided for supplying gas or steam under pressure and the additive to the nozzle so as to produce a jet of gas or steam containing the additive directed into the chamber; and means are provided for shrouding the outlet of the nozzle with gas or steam flowing into the chamber.

2. A nozzle assembly according to claim 1 in which the nozzle assembly is mounted in a housing external to the chamber which encloses the entrance means being provided to supply the shrouding gas or steam under pressure to the housing.

3. A nozzle assembly according to claim l or claim 2 further comprising a swivel mounting for the_.nozzle to allow adjustment of the spraying direction.

4. A nozzle assembly according to any preceding claim further comprising control means arranged to detect the presence of product to be treated in the chamber, and so arranged so that the shroud gas is supplied when the product is present, and that additive flow is stopped when the product is absent.

SUBSTITUTE SHEE