GB2198658A

GB2198658A - Fluidised bed furnaces and nozzle means for the introduction of fluent material into fluidised bed furnaces

Info

Publication number: GB2198658A
Application number: GB08728380A
Authority: GB
Inventors: Trevor James Keirle
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-12-04
Filing date: 1987-12-04
Publication date: 1988-06-22
Anticipated expiration: 2007-12-04
Also published as: GB8629055D0; GB8728380D0; GB2198658B

Abstract

A fluidised bed furnace includes a base plate (10) provided with an array of nozzles 12d,12c which are substantially uniformly distributed throughout at least one zone of the base plate. Each nozzle comprises a body 30d,30c which affords an inlet passageway (31d,31c) leading to a distribution chamber with at least one laterally directed outlet (33d,33c), and at least some of said nozzles are provided with a regulating member (34d,34c) arranged to adjust the rate of flow of a fluent medium through the nozzle. The nozzles are associated with plenum chambers (13,25,29) beneath the base plate (10). <IMAGE>

Description

Title: "Fluidised bed furnaces and nozzle means for the introduction of II fluent material into fluidised bed furnaces Description of the Invention This invention relates to fluidised bed furnaces wherein a bed of particulate materials is maintained in a fluidised condition within a housing by the passage of a fluidising medium, the bed being maintained at a temperature appropriate to the operation to be carried out.

The material which makes up the fluidised bed may at least in part be constituted by the material which is to be treated within the furnace, or it may be inert, or take part in the treatment to be carried out in the furnace and/or take part in the heating of the bed. Likewise, the fluidising medium may be inert, or take part in the treatment to be carried out in the furnace, and/or take part in the heating of the bed.

These diverse possibilities have previously meant that fluidised bed furnaces have normally been designed for specific types of operation rather than general purpose use, with consequential high design and construction costs.

It is one object of the present invention to provide a design of fluidised bed furnace which is adapted for a wide range of different operations with a minimum of alteration.

According to the invention the base plate of the housing of a fluidised bed furnace is provided will an array of nozzles which are substantially uniformly distributed throughout at least one defined zone of the base plate, a each nozzle comprises a body which affords an inlet passageway leading to a distribution chamber with at least one laterally directed outlet, and at least some of said nozzles are provided with a regulating member which is arranged to adjust the rate of flow of a fluent medium through the nozzle from the inlet passageway to the outlet.

Preferably the regulating member comprises a plug having a noze portion which projects into the distribution chamber towards the inlet passageway, the plug being movable towards and away from said inlet passageway, typically by being threadedly received in the nozzle body. The nose portion of the plug may terminate in a tapered section which is so dimensioned as to enter into the inlet passageway.

By providing such a regulating member on some or all of the nozzles it becomes possible to adapt the operation of the furnace to suit a wide range of differing requirements without changing the basic design, whereas previously it has generally been the practice to design fluidised bed furnaces to meet specific requirements.

The housing may also afford a plenum chamber beneath the base plate and at least some of the nozzles may be arranged with their inlet passageways in direct communication with the interior of the plenum chamber to receive the fluent medium from the plenum chamber. However, the nozzles may be divided into at least two different groups, and the housing may afford a separate plenum chamber in communication with each group of nozzles, whereby each group of nozzles can be supplied with a different medium. The plenum chambers may be disposed one above another, and each extend over substantially the whole area of the base plate, one group of nozzles being connected to tubes which extend through the first plenum chamber adjacent to the base plate and into communication with a second plenum chamber below the first.

Alternatively or additionally, the nozzles, or at least one group of nozzles, may be associated with two or more plenum chambers so that each such nozzle receives two or more different fluent media which are mixed within the distribution chamber. In this way, for example, a combustible gas may be supplied to one group of nozzles from one plenum chamber and air or other combustian supporting medium may be supplied to the same group of nozzles from a further plenum chamber so that the two combustion components mix only within the distribution chambers of the nozzles. Where required, a further group of nozzles may be supplied with a separate fluidising medium or with a medium taking part in the operation being carried out in the bed, for example a material which is to be incinerated within the bed.

Different groups of nozzles may be arranged at different levels above the base plate and/or in different zones of the base plate.

It will therefore be seen that by providing the base plate with an array of nozzles and appropriate plenum chambers it becomes possible, without changing the basic design of the housing, to connect differing groups of nozzles with different plenum chambers so as to enable a wide variety of operations to be carried out with a minimum of adaptation of the basic design.

The invention also resides in- a distribution nozzle for use in a fluidised bed furnace and comprising a body which forms an inlet passageway leading to a distribution chamber with at least one laterally directed outlet.

The invention will now be described by way of example with reference to the accompanying drawings wherein Figures I and 2 show respectively two typical arrangements of nozzles in accordance with the invention in association with a base plate and plenum chambers for the supply of respective media to a fluidised bed.

Figure I shows part of the base plate 10 of the housing of a fluidised bed furnace not otherwise shown. The plate 10 is formed with a regular array of circular apertures II and 21 distributed uniformly throughout the area of the base plate. In this particular embodiment the apertures II and 21 are associated with respective different nozzle assemblies 12 and 22 so that there are two sets of nozzles. The nozzle assemblies 12 comprise nozzles 12a located directly in the apertures 11 so as to communicate with the interior of a plenum chamber 13 which is arranged immediately beneath the base plate 10 and is defined by a plate 14 and an annular wall 15. A fluidising medium, such as air or an inert gas, may thus be supplied to the plenum chamber 13 and injected into the fluidised bed above the base plate 10 through the nozzles 12a.

By contrast, the nozzle assemblies 22 include similar nozzles 12b which are carried by a short tube 26 which carries the nozzle 12b at a predetermined spacing above the base plate 10. The assemblies 22 are associated with tubes 23 which extend downwardly through the apertures 2 1 in the base plate 10 and into similar apertures 24 in the plate 14. A further plenum chamber 25 is defined beneath the first plenum chamber 13 so that fluent material supplied to the plenum chamber 25 is delivered through tubes 23 to nozzles 22.

In the Figure I embodiment, it is intended that the fluidised bed should be heated by means of external electric heaters. As mentioned previously, a fluidising medium is injected into the bed through the first group of nozzles 12a, and the second group of nozzles 12b is disposed at a higher level so as to be within the fluidised zone of the bed. The nozzles 12b may be used to introduce into the bed, for example, a liquid which is required to be incinerated within the bed. It will be appreciated that where incineration of the liquid involves a sufficiently exothermic reaction, this may generate sufficient heat to maintain the fluidised bed at the required working temperature so that the external electric heaters may be de-energised once the bed has attained its working temperature.

The nozzles 12a and 12b are in this case both of the same design. Each comprises a body 30 having an inlet bore 31 leading to a widened end portion or chamber 32 with a plurality of radially arranged outlet ports 33. The chamber 32 is closed at its upper end by means of a plug 34 which is preferably threadedly received within the chamber 32. The plug 34 includes a tapered nose portion 35 which is adapted to co-operate with the end of the inlet bore 31 at the shoulder defined by the lower end of the chamber 32 in order to afford a variable throttle.In this way, each nozzle may be adjusted to provide a wide range of different flow rates thereby enabling it to be used for the injection of gases, low viscosity liquids, and high viscosity liquids or pastes, at a range of delivery rates which can be determined in combination by the supply pressure established in the associated plenum chamber and the setting of the plug 34.

However, where the fluidised bed is to be heated internally by the combustion of fluid fuel, such fuel and a combustion-supporting gas can be supplied separately to a further tuype of mixing nozzle through concentric tubes leading to respective plenum chambers. Such an arrangement is shown in Figure 2, wherein the same reference numerals as used in relation to Figure I are used to denote similar components.

The nozzle asseblies 12 may use nozzles identical with the nozzles 12a of the Figure I embodiment, but Figure 2 illustrates a simplified nozzle 12c which may also be substituted for the nozzles 12a and 12b of the Figure I embodiment.

The modified nozzle 12c comprises a body 30c formed as a length of tube which is secured into the aperture II by any appropriate means, for example by welding or by threaded engagement. The body has outlet ports 33c at a position intermediate its ends and the bore 31e of the tube serves both as an inlet and a distribution chamber. The body 30e is closed at its upper end by means of a plug in the form of a bolt 34c which is threadedly engaged within the bore 31c. As shown a lock-nut is provided.

Axial adjustment of the bolt 34c serves to regulate flow through the nozzle according to the extent to which the bolt blocks the outlet parts 33e Thus, nozzles 12c are mounted like nozzles 12a in one set of apertures II associated with plenum chamber 13 for the supply of fluidising air.

However, instead of nozzles 12b, the other set of apertures 21 is associated with burner nozzle assemblies 42.

Each burner nozzle assembly 42 comprises a mixing nozzle 12d carried by a short tube 26a. The mixing nozzle 12d comprises a body 30d which includes in addition to the centrally disposed inlet bore 31 a plurality of further parallel bores 37 leading to lateral outlet ports 33d. The body 30d of the nozzle 12d also carries a threadedly mounted cap 36 which is adjustable relative to a flange 38 formed on the body below the outlet ports 33d thereby to form a variable width annular gap which forms a burner orifice.

An adjustable plug 34d is carried by the cop 36 as shown.

Combustion air is supplied to the nozzle 12d from plenum chamber 25 through tube 23, and concentrically within the latter is a pipe 27 which is screwed into the inlet bore 31d and leads through plenum chamber 25 to a further plenum chamber 29 defined by between plates 16 and 17. A combustible gas is supplied to this plenum chamber and through pipe 27 to the burner nozzle 12d, the combustion gases mixing only in the outlet bores 33d of the burner nozzle 12d.

The plate 16 dividing plenum chambers 25 and 29 may serve as a thermal barrier, for example, by being made from a thermally insulating material or by carrying layers of thermal insulation. However, in a preferred arrangement (not shown) the two plenum chambers 25 and 29 are separated by a ventilated cooled air space. This enables the combustion air supplied to plenum chamber 25 and the fluidisation gas supplied to plenum chamber 13 to be pre-heated safely.

Where it is required additionally to inject, for example, a liquid to be incinerated, a further group of nozzles may be connected to a further plenum chamber through which such liquid is supplied, in a manner similar to the nozzle assembly 22 as illustrated in Figure 1. Where no separate fluidising medium is required, the nozzle assemblies 12 may be replaced by assemblies of nozzles mounted in a manner similar to nozzle 12b for the supply of the liquid to be incinerated, and in that case the burner nozzles may, if desired, be disposed immediately adjacent to the base plate 10.

It can be seen that by providing the nozzles with regulating members it is possible to set up a wide range of operating conditions within the same design of furnace so as to enable it to carry out a wide range of different operations, such as heat treatment of various, incineration of waste materials, reclamation process etc. Similarly by providing the base plate 10 with a plurality of nozzles divided into groups associated with respective plenum chambers, it is possible to construct a range of different fluidised bed housings for a specific type of operation, for example with or without combustion, using only essentially the same components and by varying the numbers of groups of nozzles and associated plenum chambers.

Whilst in both of the embodiments described there are only two groups of nozzles and these are both dktributed uniformly over the entire area of the base plate 10, it will be appreciated that in some cases it may be appropriate for there to be more than two groups of nozzles, or for different groups of nozzles to be associated with different zones of the base plate.

This can be achieved most simply by arranging the respective plenum chambers one above the other as illustrated, but alternatively in some cases some of the plenum chambers could be arranged, for example concentrically, at the same level. Alternatively, in some cases the nozzles may not be divided into groups, but all may be identically arranged and supply the same medium to the bed.

The features disclosed in the foregoing description, or the accompanying drawing, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, may, separately or in any combination of such features, be utilised by realising the invention in diverse forms thereof.

Claims

CLAIMS:

I. A fluidised bed furnace having a housing which encloses the fluidised bed and includes a base plate provided with an array of nozzles which are substantially uniformly distributed throughout at least one defined zone of the base plate, wherein each nozzle comprises a body which affords an inlet passageway leading to at least one laterally directed outlet, and at least some of said nozzles are provided with a regulating member which is arranged to adjust the rate of flow of a fluent medium through the nozzle from the inlet passageway to the outlet.
2. A fluidised bed furnace according to the Claim I wherein said regulating member comprises a plug movable towards and away from said inlet passageway.
3. A fluidised bed furnace according to Claim 2 wherein said plug is threadedly received in said nozzle body.
4. A fluidised bed furnace according to Claim 2 or Claim 3 wherein said plug co-operates with said outlets to regulate flow through the nozzle.
5. A fluidised bed furnace according to Claim 4 wherein said nozzle comprises a tubular body and said outlets extend through the wall of the body.
6. A fluidised bed furnace according to Claim 2 or Claim 3 wherein said plug bas a nose portion which terminates in a tapered section which is so dimensioned as to enter into said inlet passageway so as to regulate flow through the nozzle.
7. A fluidised bed furnace according to any one of the preceding claims wherein the bodies of at least some of said nozzles are mounted directly in respective apertures in said base plate.
8. A fluidised bed furnace according to any one of the preceding claims wherein at least some of said nozzles are spaced above the bose plate and are carried by respective tubes associated with apertures in the base plate.
9. A fluidised bed furnace according to any one of the preceding claims wherein at least some of said nozzles are mixing nozzles which are arranged to be supplied with two different fluid media which are mixed in said nozzles.
10. A fluidised bed furnace according to Claim 9 wherein in said mixing no.zles said inlet passageway which is associated with said regulating member is connected to an inlet pipe for one fluent medium and the body is formed with one or more further inlet passageways connected to a duct for a second fluent medium.
II. A fluidised bed furnace according to Claim 10 wherein said further inlet passageways communicate respectively with said outlets of the nozzle.
12. A fluidised bed furnace according to any one of the preceeding claims wherein the housing also affords a plenum chamber beneath the base plate and at least some of the nozzles are arranged with their inlet passageways in direct communication with the interior of the plenum chamber to receive a fluent medium from the plenum chamber.
13. A fluidised bed furnace according to Claim 12 wherein the nozzles are divided into at least two different groups, and the housing affords respective plenum chambers in communication with each group of nozzles, whereby each group of nozzles can be supplied with a different medium.
14. A fluidised bed furnace according to Claim 13 wherein the plenum chambers are disposed one above another, each extending over substantially the whole area of the base plate, one group of nozzles being connected to tubes which extend through a first one of said plenum chambers which is immediate adjacent to the base plate and into communication with a second one of said plenum chambers disposed below the first.
15. A fluidised bed furnace according to Claim 14 as appendent to Claim 9 wherein the mixing nozzles are each associated with two or more of said plenum chambers so that each such nozzle receives two or more different fluent media which are mixed in the distrubution chamber of the nozzle.
16. A fluidised bed furnace according to Claim 15 wherein a further group of nozzles is supplied with a further medium through a further plenum chamber.
17. A fluidised bed furnace according to any one of Claims 13 to 16 wherein different groups of nozzles are provided at different levels above the base plate.
18. A fluidised bed furnace incorporating nozzle assemblies substantially as hereinbefore described and as shown in Figures I or 2 of the accompanying drawings.