GB1600025A - Nozzle - Google Patents

Description

(54) NOZZLE (71) We, THE BRITISH PETROLEUM COMPANY LIMITED, of Britannic House, Moor Lane, London, EC2Y 9BU, a British Company, do hereby declare the invention for which we pray thata patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: The present invention relates to nozzles and distributor plates containing such nozzles for fluidised bed combustors.

A fluidised bed combustor is operated by blowing air through a bed of inert particulate material to maintain the bed in a fluidised state and injecting fuel into the bed so as to achieve optimum combustion conditions. The fuel, which may be solid, liquid or gaseous, or a mixture, burns within the bed which is maintained at a temperature which may be typically in the range 7000l 000 "C by controlled extraction of heat. The use of the term 'fluidised bed combustor' is also intended to cover the use of a fluidised bed as a gasifier whereby partial reaction of a fuel and oxygen containing gas produces a combustible mixture which may be stored or burned at a point remote from the fluidised bed.

Fluidised bed combustors are capable of very high heat outputs per unit volume capacity and high rates of heat transfer to cooling surfaces immersed in the bed.

In large scale fluidised bed combustors particularly using liquid fuels, it is desirable to periodically check the state of the fuel injection nozzles, for example, for maintenance purposes so as to enable prolonged bed operation under optimum conditions.

The present invention is directed towards this problem and envisages the use of injection nozzles which are removable during fluidised bed operation.

Thus, according to the invention, there is provided a nozzle comprising an outer portion in loose sealing contact with an external sleeve and a removable inner portion, there being an inlet for a pressurised gas to the space between the sleeve and the nozzle, the outer portion having a projection lying outside the sleeve and being movable to cause the projection to abut with the sleeve, the sleeve also closing the outlet of the nozzle.

By the term 'in loose sealing contact' is meant close enough to substantially prevent bed particles from falling into the surrounding sleeve.

One or more of the nozzles are preferably incorporated into a distributor plate. Thus in a liquid fuel fired fluidised bed, a distributor plate may have one or more removable nozzles being supplied with fuel and air and a number of non-removable nozzles for supply of air to the fluidised bed. If and when the fuel nozzles require inspection or servicing they may be removed preferably one at a time from the bed while still maintaining fluidisation and increasing fuel flow to the remaining nozzles so as to substantially maintain the bed temperature.

The nozzles are preferably moved by sliding through the surrounding sleeve, which acts as a concentric air nozzle to fluidise the bed below the point of oil injection.

For a liquid fuel fired fluidised bed combustor, the distributor plate preferably has an air plenum chamber, and may also have a fuel gas chamber for use during start up of the fluidised bed.

Preferably the outer portion of the nozzle has a peripheral projection which is adapted to engage with the upper part of the sleeve to form a substantially gas tight seal when the nozzle is lowered prior to removal.

The outer portion of the nozzle preferably is partly screw threaded at its base so that its up and down movement through the distributor plate may be achieved by rotation of a nut or similar device. Further, the inner portion of the nozzle may be connected, at the top, by a screw thread or locking peg arrangement to the outer portion so that withdrawal of the inner from the outer portion may be achieved simply by rotation. The inner portion of the nozzle may be withdrawn from the outer portion and from its sleeve through a sealing ring or the like which would be incorporated into the outer nozzle portion. While the inner nozzle is removed some air may escape but this loss only represents a small proportion of the total amount required for fluidisation and combustion. The sealing ring preferably comprises an annular polymeric seal in a surrounding seat through which the nozzle is drawn.

Alternatively, a nut and olive may secure the inner nozzle portion to its outer portion.

The invention will now be described by way of example with reference to the accompanying drawing.

The distributor plate assembly comprises an air plenum chamber 1, a liquid fuel supply entry 2, and an assembly of three co-axial tubes, the outer sleeve 3, the outer nozzle 4, and the inner nozzle 5. The annulus between outer sleeve 3 and the outer nozzle 4 communicates with the air plenum chamber 1, to a fuel gas chamber 6, and also to the fluidised bed 7. Air bleed holes 8 communicate between the air plenum chamber 1 and the annular clearance between the inner and outer nozzles 4,5.

The inner nozzle 5, which is the removable portion, is surrounded by the outer nozzle 4.

The outside of the outer nozzle 4 is screw threaded and is engaged by a nut 9 located on the underside of the air plenum chamber 1. The head 10 of the inner nozzle 5 engages with the interior of the head 11 of the outer nozzle 4 and is held in position by a nut and olive fitting 12. The heads 10, 11 of the inner and outer nozzles 4, 5 have corresponding outlets 13 for supply of fuel oil to the fluidised bed 7.

During start up of the fluidised bed by underbed gas feeding, the outer sleeve 3 supplies a mixture of combustion air and fuel gas to the fluidised bed 7. The apertures 14 allow the fuel gas from fuel gas chamber 6 to be entrained into the space between sleeve 3 and outer nozzle 4 before passing into the fluidised bed 7. After the fluidised bed working temperature has been attained, liquid fuel from the entry 2 is supplied to the interior walls of the nozzle 5 and vertically transported by an upward current of air previously supplied at the mouth 15 of nozzle 5. The fuel is thus caused to pass along the inner nozzle 5 in the form of a climbing film eventually passing through heads 10, 11 of the nozzle and thence to be burned in the fluidised bed 7. The air from plenum chamber 1 passes through air bleed holes 8 to pressurise the space between the inner and outer nozzles 4, 5 so that fuel passing through the outlets of the heads 10, 11 of the nozzle does not trickle down into the space. Bleedholes 8 are located so that nut 9 prevents the passage of air from the plenum chamber 1 when nozzle 5 is withdrawn from its outer portion 4.

To remove a nozzle 5 from the distributor plate during operation of the fluidised bed the following procedure is adopted. Fuel supply to the nozzle is initially shut off and compensation made to the fuel flow of remaining nozzles so as to maintain steady bed operation. On turning the nut 9 in the appropriate direction, outer nozzle 4 and inner nozzle 5 are gradually moved downwards until the nozzle shield 11 mates with the upper part of the outer sleeve 3 and the outlets 13 are closed off by the outer sleeve 3. Air supply 15 is turned off and the inner nozzle 5 is then separated from the nozzle shield 11 by rotating nut 12 and withdrawn for inspection. (The inner nozzle 5 and outer nozzle 4 are alternatively internally connected by screw threading or the like.) The inset shows that the holes 13 in the nozzle shield 11 are much greater in size than the fuel outlet holes of the inner nozzle 5. The holes 13 take, for example, the form of pillar box holes as in the inset or the form of a cage.

The nozzle replacement procedure is substantially a reversal of the removal procedure.

WHAT WE CLAIM IS: 1. A nozzle comprising an outer portion in loose sealing contact with an external sleeve and a removable inner portion, there being an inlet for a pressurised gas to the space between the sleeve and the nozzle, the outer portion having a projection lying outside the sleeve and being movable to cause the projection to abut with the sleeve and to substantially seal the space between the sleeve and nozzle, the sleeve also closing the outlet of the nozzle.

2. A nozzle according to claim 1 in which the outer portion carries a portion of screw threading which allows movement of the outer portion up and down relative to the sleeve.

3. A nozzle according to claim 1 or claim 2 in which the inner portion of the nozzle is connected to the top of the outer portion by a screw thread, a locking peg or a nut and olive.

4. A nozzle according to any of claims 1 to 3 in which the inner portion of the nozzle is adapted to be withdrawn from the outer portion through a sealing ring or the like.

5. A nozzle according to claim 4 in which the sealing ring is an annular polymeric seal.

6. A distributor plate for a fluidised bed comprising a nozzle arrangement according to any of the preceding claims and a chamber for supply of pressurised fluidising gas to the bed.

7. A distributor plate according to claim 6 having an air plenum chamber.

8. A distributor plate according to claim 6 or claim 7 having a fuel gas chamber for supplying fuel gas during start up.

9. A distributor plate or nozzles as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

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

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. of example with reference to the accompanying drawing. The distributor plate assembly comprises an air plenum chamber 1, a liquid fuel supply entry 2, and an assembly of three co-axial tubes, the outer sleeve 3, the outer nozzle 4, and the inner nozzle 5. The annulus between outer sleeve 3 and the outer nozzle 4 communicates with the air plenum chamber 1, to a fuel gas chamber 6, and also to the fluidised bed 7. Air bleed holes 8 communicate between the air plenum chamber 1 and the annular clearance between the inner and outer nozzles 4,5. The inner nozzle 5, which is the removable portion, is surrounded by the outer nozzle 4. The outside of the outer nozzle 4 is screw threaded and is engaged by a nut 9 located on the underside of the air plenum chamber 1. The head 10 of the inner nozzle 5 engages with the interior of the head 11 of the outer nozzle 4 and is held in position by a nut and olive fitting 12. The heads 10, 11 of the inner and outer nozzles 4, 5 have corresponding outlets 13 for supply of fuel oil to the fluidised bed 7. During start up of the fluidised bed by underbed gas feeding, the outer sleeve 3 supplies a mixture of combustion air and fuel gas to the fluidised bed 7. The apertures 14 allow the fuel gas from fuel gas chamber 6 to be entrained into the space between sleeve 3 and outer nozzle 4 before passing into the fluidised bed 7. After the fluidised bed working temperature has been attained, liquid fuel from the entry 2 is supplied to the interior walls of the nozzle 5 and vertically transported by an upward current of air previously supplied at the mouth 15 of nozzle 5. The fuel is thus caused to pass along the inner nozzle 5 in the form of a climbing film eventually passing through heads 10, 11 of the nozzle and thence to be burned in the fluidised bed 7. The air from plenum chamber 1 passes through air bleed holes 8 to pressurise the space between the inner and outer nozzles 4, 5 so that fuel passing through the outlets of the heads 10, 11 of the nozzle does not trickle down into the space. Bleedholes 8 are located so that nut 9 prevents the passage of air from the plenum chamber 1 when nozzle 5 is withdrawn from its outer portion 4. To remove a nozzle 5 from the distributor plate during operation of the fluidised bed the following procedure is adopted. Fuel supply to the nozzle is initially shut off and compensation made to the fuel flow of remaining nozzles so as to maintain steady bed operation. On turning the nut 9 in the appropriate direction, outer nozzle 4 and inner nozzle 5 are gradually moved downwards until the nozzle shield 11 mates with the upper part of the outer sleeve 3 and the outlets 13 are closed off by the outer sleeve 3. Air supply 15 is turned off and the inner nozzle 5 is then separated from the nozzle shield 11 by rotating nut 12 and withdrawn for inspection. (The inner nozzle 5 and outer nozzle 4 are alternatively internally connected by screw threading or the like.) The inset shows that the holes 13 in the nozzle shield 11 are much greater in size than the fuel outlet holes of the inner nozzle 5. The holes 13 take, for example, the form of pillar box holes as in the inset or the form of a cage. The nozzle replacement procedure is substantially a reversal of the removal procedure. WHAT WE CLAIM IS:

1. A nozzle comprising an outer portion in loose sealing contact with an external sleeve and a removable inner portion, there being an inlet for a pressurised gas to the space between the sleeve and the nozzle, the outer portion having a projection lying outside the sleeve and being movable to cause the projection to abut with the sleeve and to substantially seal the space between the sleeve and nozzle, the sleeve also closing the outlet of the nozzle.

2. A nozzle according to claim 1 in which the outer portion carries a portion of screw threading which allows movement of the outer portion up and down relative to the sleeve.

3. A nozzle according to claim 1 or claim 2 in which the inner portion of the nozzle is connected to the top of the outer portion by a screw thread, a locking peg or a nut and olive.

4. A nozzle according to any of claims 1 to 3 in which the inner portion of the nozzle is adapted to be withdrawn from the outer portion through a sealing ring or the like.

5. A nozzle according to claim 4 in which the sealing ring is an annular polymeric seal.

6. A distributor plate for a fluidised bed comprising a nozzle arrangement according to any of the preceding claims and a chamber for supply of pressurised fluidising gas to the bed.

7. A distributor plate according to claim 6 having an air plenum chamber.

8. A distributor plate according to claim 6 or claim 7 having a fuel gas chamber for supplying fuel gas during start up.

9. A distributor plate or nozzles as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.