GB2128573A

GB2128573A - Non-mechanical valve for particulate material

Info

Publication number: GB2128573A
Application number: GB08327970A
Authority: GB
Inventors: Gordon William Sutton
Original assignee: BP PLC
Current assignee: BP PLC
Priority date: 1982-10-22
Filing date: 1983-10-19
Publication date: 1984-05-02
Also published as: GB8327970D0

Abstract

A non-mechanical valve suitable for particulate solids having a chamber 4 with one or more lateral outlets 8 and a tube 1 passing into the upper part of the chamber to the same or a lower level than the outlets of the chamber, the lateral outlets leading to a further downstream tube 7. The lower part of the chamber has an aerator 5 capable of causing slumped particulate solid in the chamber to pass through the lateral outlets and into the further tube. One form of aerator has an aeration chamber having lateral outlets and having an upper conical portion projecting into the mouth of the inlet tube. <IMAGE>

Description

SPECIFICATION Non-mechanical valve This invention relates to valves and more particularly relates to non-mechanical valves for controlling the flow rate of particulate solids, A non-mechanical valve is a device used to control the flow rate of particulate solids through it by virtue of its geometrical shape and the use of an aeration gas. Such valves have certain advantages over mechanical valves in that they have no moving parts subject to wear or seizure and are usually simple and inexpensive to construct.

A specific form of non-mechanical valve is the L-valve which is aerated and has a right angled shape. A typical application for the L-valve is as part of a particulate solid control system for a fluidised bed.

Thus, according to the present invention there is provided a non-mechanical valve suitable for particulate solids comprising a chamber having one or more lateral outlets, a tube passing into the upper part of the chamber, the outlet of the tube being at the same or a lower level than the outlets of the chamber, the lateral outlets leading to a further tube, the lower part of the chamber having a means for aeration capable of causing slumped particulate solid in the chamber to pass through the lateral outlets and into the further tube.

The means for aeration preferably takes the form of one or more outlet nozzles at or near the base of the chamber. The preferred embodiment comprises an aeration chamber having one or more lateral outlets, the chamber most preferably having an upper conical portion projecting into the mouth of the inlet tube. The aeration chamber is supplied from an external air supply.

The non-mechanical valve can be used in a variety of systems for control of particulate solids such as when changing the bed material in a fluidised bed system, varying of bed height in a fluidised bed combustor for load control purposes, for sampling of bed material for analysis of, say metal content and for use in drying systems.

The non-mechanical valve is suitably constructed from a metal such as stainless steel and is preferably of a circular cross section. The outlets from the chamber are preferably in the form of a plurality of equally spaced holes in the walls of the chamber but may also comprise a single continuous slot. The holes may be at right angles to the plane of the chamber walls or may be inclined.

The internal geometry of the valve is arranged so that, during aeration, the flow of particulate solids is directed towards the outlets of the aeration chamber and components of solid flow back along the upper inlet tube are discouraged. In one embodiment of the invention this is achieved by contouring the outlet of the down tube to the aeration chamber and the upper portion of the aeration chamber.

The invention also includes a fluidised bed reactor or combustor having a non-mechanical valve as hereinbefore described.

The invention will now be described by way of example only and with reference to Figures 1 and 2 of the accompanying drawings.

Figure 1 shows a vertical cross section through a non-mechanical valve according to the invention and Figure 2 shows a schematic diagram of a fluidised bed combustor incorporating a nonmechanical valve for solids discharge.

A down tube 1 constructed from metal passes through a collar 2 into a cup or main chamber 4.

The chamber 4 has a number of lateral outlets 8 around its periphery, the outlets 8 connecting with an annulus 9 between the chamber 4 and a surrouding housing 3. The annulus 9 connects via a reducer or adapter 6 to a discharge tube 7.

In the base of the chamber 4 there is an air discharge nozzle 5 or aerator. This aerator 5 comprises an aeration chamber 10 having a conical top 11 pointing into the outlet of the down tube 1. The combination of the conical top 11 of the aeration chamber 10 and the contoured end of the down tube 1 tends to encourage particulate solid flow towards the outlets 8 of the chamber 4 rather than cause back flow along down tube 1.

The aeration chamber 10 has outlets 12 in its periphery at a level below the lateral outlets 8 of the main chamber 4. The aeration chamber 10 is supplied by an air tube 13 passing into its base, the air tube 13 being co-axial with the discharge tube 7.

During use of the valve, particulate solid passes into the down tube 1 and into the main chamber 4 where its flow is arrested. In order to open the valve and enable transport of particulate solid to the discharge tube 7, compressed air is supplied through tube 1 3 to the aeration chamber 10, the air passing through the outlets 12. The flow of air through outlets 12 promotes the passage of particulate solids through lateral outlets 8 of the main chamber 4 and thence to the discharge tube 7.

Figure 2 shows a vertical section through a fluidised bed combustor incorporating a nonmechanical valve according to the invention.

A vessel 14 contains a bed 1 5 of solid particulate material such as sand, the bed being supported by a distributor plate 16. The distributor plate 16 has a number of air nozzles 1 7 connected to a chamber 1 8 linked to a source of compressed air. Two vertical oil nozzles 1 9 pass through the air chamber 1 8 and have their outlets in the bed of particulate solids 1 5. The oil nozzles 1 9 are connected to a supply of fuel oil. The bed of particulate solids 1 5 is linked to a non-mechanicai solids flow valve 20 located beneath the distributor plate 1 6 by means of a downcomer tube 21. The valve 20 has an aerator 22 supplied with compressed air.The outlet of the valve passes to discharge 23.

During use of the fluidised bed combustor, the bed 1 5 is preheated and fluidising air supplied from chamber 18 to the air nozzles 1 7 which causes the bed 1 5 to become fluidised. Fuel oil is supplied to the oil nozzles 1 9 and the bed warmed up by means of an overbed burner (not shown).

The detailed procedure for oil fired combustion in a fluidised bed is described in GB Patent Numbers 1368352 and 1487391. The exhaust products of the combustion pass through the outlet 24 at the top of the vessel 14.

When the bed material is required to be removed from the bed for load control or sampling purposes, compressed air is supplied to the nonmechanical valve 20 from the aerator 22 so as to disturb the slumped particulate solid in the valve 20 below the downcomer tube 21 and to allow solids discharge under gravity. The discharge solids are then collected for analysis, disposal or subsequent use.

Claims

1. A non-mechanical valve comprising a chamber having one or more lateral outlets, a tube passing into the upper part of the chamber, the outlet of the tube being at the same or a lower level than the outlets of the chamber, the lateral outlets leading to a further tube, the lower part of the chamber having a means for aeration capable of causing slumped particulate solid in the chamber to pass through the lateral outlets and into the further tube.

2. A valve according to claim 1 in which the means for aeration comprises one or more outlet nozzles at or near the base of the chamber.

3. A valve according to claim 1 in which the means for aeration comprises an aeration chamber having one or more lateral outlets.

4. A valve according to claim 3 in which the aeration chamber has an upper conical portion projecting into the mouth of the inlet tube.

5. A valve according to any of the preceding claims having a circular cross section and being fabricated from metal.

6. A valve according to any of the preceding claims in which the outlets from the chamber are in the form of a plurality of equally spaced holes around the periphery of the chamber.

7. A valve according to claim 6 in which outlet holes are inclined to the plane of the chamber walls.

8. A non mechanical valve as hereinbefore described and with reference to Figure 1 of the accompanying drawings.

9. A fluidised bed reactor or combustor having a non mechanical valve according to any of claims 1 to 8.