GB2073041A

GB2073041A - Fluidised bed distributor plates

Info

Publication number: GB2073041A
Application number: GB8011241A
Authority: GB
Original assignee: Coal Industry Patents Ltd
Current assignee: Coal Industry Patents Ltd
Priority date: 1980-04-03
Filing date: 1980-04-03
Publication date: 1981-10-14
Also published as: GB2073041B

Abstract

A distributor plate (1) for fluidised bed apparatus has one or more cooling passages (6) for heat exchange fluid flow and a plurality of nozzles (10) upstanding from the plate, suitably from a lower skin (2) of the plate. A well (16) is defined around each nozzle (10) to enable the nozzle (10) to be insulated, in use, from the cooling space (6) by bed material. A layer (20) of heat insulative material may be attched to the lower side of the lower skin (2). <IMAGE>

Description

SPECIFICATION Water cooled distributor plate This invention concerns improvements in or relating to fluidised bed apparatus.

In particular, the present invention has reference to an improved distributor plate for use in such apparatus especially when employed for reactions conducted at eievated temperatures.

The combustion of fuel in a fluidised bed has been known for many years and various designs of apparatus have been proposed. An important element in the design of a fluidised bed com us or is the distributor plate which is subjected to a hot environment. In general, when a fluidising gas at ambient temperature is employed, a flat distributor plate is quite satisfactory in operation.

However, when a fluidising gas at elevated temperature is used, for example when starting up the bed or for other purposes, such a plate tends to be unsatisfactory. Temperature gradients tend to be generated giving use to differential thermal expansion and concomitant stressing resulting in damage to the plate which is usually constructed of metal. It is known to construct a distributor plate of a double skin defining a cooling space for the passage of a coolant medium thereby to reduce the degree of stressing and to obviate the likelihood of distortion.

An object of the present invention is to provide an improved distributor plate.

Accordingly the invention provides a distributor plate for fluidised bed apparatus, the plate having at least one cooling passage defined therein, and a plurality of nozzles upstanding from the plate, each nozzle being spaced from the at least one cooling passage.

The distributor plate is conveniently of doubleskin construction, the cooling passage being defined between the two skins which are advantageously of metal. The nozzles are preferably secured in appropriate apertures in the lower skin, a well being formed around the lower part of each nozzle whereby that part is spaced from the cooling passage and is not, in use, subjected to the effect of a coolant passing through the plate. This advantageously insulates the nozzle and thus the hot gas passing throughthrough from a cooling effect. The well also fills up with bed material which enhances the insulation of the nozzle. In addition in use a static layer of bed material also extends up to the nozzle outlets thus insulting the top skin from the hot bed material.

In order further to assist in the insulation of the distributor plate, a layer of insulating material is advantageously provided on the lower surface of the lower skin, that is the surface normally subjected to radiative and conductive heating by fluidising gas passing through the plenum chamber of the fluidised bed apparatus.

There may be one cooling passage or more than one and one or more coolant medium inlets and outlets may be provided.

The coolant employed is preferably water but may be air.

In an alternative form of construction the distributor plate of the present invention may be formed in like manner to a membrane wall, that is a plurality of cooling tubes joined together by fins, the nozzle being mounted in apertures provided in the fins.

By way of example only, one embodiment of distributor plate according to the invention is described below with reference to the accompanying drawings in which: Figure 1 is a plan view of a part of a distributor plate; and Figure 2 is a sectional view on the line Il-Il of Figure 1.

Referring to the drawings, a distributor plate is depicted generally at 1 and comprises a lower skin 2 and a relativeiy upper skin 4 spaced apart in a vertical direction to define a cooling passage 6 for the flow therethrough in use of a coolant, e.g.

water shown at 8.

A plurality of nozzles 10 in the form of stub pipes are secured in apertures provided in the lower skin 2. The nozzles 10 have laterally disposed outlet holes 14 located in the walls of the nozzles 10 at the ends remote from skin 2.

The plate 1 is so formed adjacent each nozzle 10 as to define a well 1 6 surrounding the lower part of the nozzle 1-0, this part thereby being spaced from the surrounding cooling passage 6 in the plate.

A layer 20 of insulting material is secured to the underside of the lower skin 2 of the plate, the layer 20 being suitably apertured to allow the flow of gas therethrough into the nozzles 10.

In use, a fluidised bed of particulate material is supported by the plate, a static layer of bed material 30 being created below the level of the holes 14 down to the upper skin 4 and into the wells 1 6 as shown in Figure 2. High temperature fluidising gases pass through a plenurn (not shown) into the nozzles 10 and thence into the bed to fluidise it above the level of the holes 14 in nozzle 10. It is important that there should be as little loss of heat from the gases during their passage through the plate 1 and the insulation provided by the bed material around the lower part of the nozzles 10 and there above minimises heat loss. At the same time, the plate 1 is cooled by the flow of water through the passage 6 and is insulated by layer 20 from convective and radiative heat transfer from the high temperature gases to which it is subject. The hot fluidised bed is also insulated from the plate 1 by the static layer 30.

The distributor plate of the present invention is thus of cheaper construction than a comparable stainless steel plate and lighter in weight than a refractory design.

1. A distributor plate for fluidised bed apparatus, the plate having at least one cooling passage defined therein, and a plurality of nozzles upstanding from the plate, each nozzle being

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Water cooled distributor plate This invention concerns improvements in or relating to fluidised bed apparatus. In particular, the present invention has reference to an improved distributor plate for use in such apparatus especially when employed for reactions conducted at eievated temperatures. The combustion of fuel in a fluidised bed has been known for many years and various designs of apparatus have been proposed. An important element in the design of a fluidised bed com us or is the distributor plate which is subjected to a hot environment. In general, when a fluidising gas at ambient temperature is employed, a flat distributor plate is quite satisfactory in operation. However, when a fluidising gas at elevated temperature is used, for example when starting up the bed or for other purposes, such a plate tends to be unsatisfactory. Temperature gradients tend to be generated giving use to differential thermal expansion and concomitant stressing resulting in damage to the plate which is usually constructed of metal. It is known to construct a distributor plate of a double skin defining a cooling space for the passage of a coolant medium thereby to reduce the degree of stressing and to obviate the likelihood of distortion. An object of the present invention is to provide an improved distributor plate. Accordingly the invention provides a distributor plate for fluidised bed apparatus, the plate having at least one cooling passage defined therein, and a plurality of nozzles upstanding from the plate, each nozzle being spaced from the at least one cooling passage. The distributor plate is conveniently of doubleskin construction, the cooling passage being defined between the two skins which are advantageously of metal. The nozzles are preferably secured in appropriate apertures in the lower skin, a well being formed around the lower part of each nozzle whereby that part is spaced from the cooling passage and is not, in use, subjected to the effect of a coolant passing through the plate. This advantageously insulates the nozzle and thus the hot gas passing throughthrough from a cooling effect. The well also fills up with bed material which enhances the insulation of the nozzle. In addition in use a static layer of bed material also extends up to the nozzle outlets thus insulting the top skin from the hot bed material. In order further to assist in the insulation of the distributor plate, a layer of insulating material is advantageously provided on the lower surface of the lower skin, that is the surface normally subjected to radiative and conductive heating by fluidising gas passing through the plenum chamber of the fluidised bed apparatus. There may be one cooling passage or more than one and one or more coolant medium inlets and outlets may be provided. The coolant employed is preferably water but may be air. In an alternative form of construction the distributor plate of the present invention may be formed in like manner to a membrane wall, that is a plurality of cooling tubes joined together by fins, the nozzle being mounted in apertures provided in the fins. By way of example only, one embodiment of distributor plate according to the invention is described below with reference to the accompanying drawings in which: Figure 1 is a plan view of a part of a distributor plate; and Figure 2 is a sectional view on the line Il-Il of Figure 1. Referring to the drawings, a distributor plate is depicted generally at 1 and comprises a lower skin 2 and a relativeiy upper skin 4 spaced apart in a vertical direction to define a cooling passage 6 for the flow therethrough in use of a coolant, e.g. water shown at 8. A plurality of nozzles 10 in the form of stub pipes are secured in apertures provided in the lower skin 2. The nozzles 10 have laterally disposed outlet holes 14 located in the walls of the nozzles 10 at the ends remote from skin 2. The plate 1 is so formed adjacent each nozzle 10 as to define a well 1 6 surrounding the lower part of the nozzle 1-0, this part thereby being spaced from the surrounding cooling passage 6 in the plate. A layer 20 of insulting material is secured to the underside of the lower skin 2 of the plate, the layer 20 being suitably apertured to allow the flow of gas therethrough into the nozzles 10. In use, a fluidised bed of particulate material is supported by the plate, a static layer of bed material 30 being created below the level of the holes 14 down to the upper skin 4 and into the wells 1 6 as shown in Figure 2. High temperature fluidising gases pass through a plenurn (not shown) into the nozzles 10 and thence into the bed to fluidise it above the level of the holes 14 in nozzle 10. It is important that there should be as little loss of heat from the gases during their passage through the plate 1 and the insulation provided by the bed material around the lower part of the nozzles 10 and there above minimises heat loss. At the same time, the plate 1 is cooled by the flow of water through the passage 6 and is insulated by layer 20 from convective and radiative heat transfer from the high temperature gases to which it is subject.The hot fluidised bed is also insulated from the plate 1 by the static layer 30. The distributor plate of the present invention is thus of cheaper construction than a comparable stainless steel plate and lighter in weight than a refractory design. CLAIMS

1. A distributor plate for fluidised bed apparatus, the plate having at least one cooling passage defined therein, and a plurality of nozzles upstanding from the plate, each nozzle being spaced from the at least one cooling passage.

2. A plate according to claim 1 in which an upper skin and a lower skin are provided, the cooling passage being defined between the skins.

3. A plate according to claim 2 in which the nozzles are secured in apertures in the lower skin.

4. A plate according to claim 3 in which a well is formed around the lower part of each nozzle adjacent the lower skin whereby that part is spaced from the cooling passage.

5. A plate according to any one of the preceding claims 2 to 4 in which a layer of insulating material is secured to the lower surface of the lower skin.

6. A plate according to claim 1 in which more than one cooling passage is provided and inlets and outlets for a coolant medium to the passages are provided.

7. A distributor plate substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

7. A plate according to claim 1 in which each cooling passage is in the form of a pipe connected in parallel to an adjacent pipe by heat exchange fins, the nozzles being secured in apertures in the fins.

8. A distributor plate substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

New claims or amendments to claims filed on 13Jan1981 Superseded claims 1-8 New or amended claims:

1. A distributor plate for fluidised bed apparatus, the plate having at least one cooling passage defined therein, a plurality of nozzles upstanding from the plate, and a well formed around the lower part of each nozzle whereby that part is spaced from the cooling passage.

4. A plate according to any one of the preceding claims 2 or 3 in which a layer of insulting material is secured to the lower surface of the lower skin.

5. A plate according to claim 1 in which more than one cooling passage is provided and inlets and outlets for a coolant medium to the passages are provided.

6. A plate according to claim 1 in which each cooling passage is in the form of a pipe connected in parallel to an adjacent pipe by heat exchange fins, the nozzles being secured in the fins.