GB2159266A - Fluid fuel fired burner - Google Patents

Abstract

The burner has a fuel supply pipe (12) and at least one tube 14 surrounding the fuel pipe and into which air can be introduced through a first air opening from a main fan (not shown) or a second air opening from an auxiliary fan (21). Each opening has an associated closure (19, 22). There may be two air passages (17, 18) one in communication with both air inlets and the other in communication with only the first air inlet. Several burners may be mounted in a common windbox communicating with the main fan. However, not all of these burners necessarily have a second air inlet fed from an auxiliary fan. Under high load conditions all burners can be used in conjunction with the main fan and under low load conditions some (possibly only one) can be used in conjunction with an auxiliary fan or fans. <IMAGE>

Description

SPECIFICATION Fluid fuel fired burner This invention relates to a fluid fuel fired burner e.g. an oil or gas fired burner.

Oil and gas fired burners have for many years been able to operate with wide turn down characteristics enabling boiler load fluctuations to meet varying steam demands.

However, the reduced efficiency when burners are under low load conditions is only acceptable if the low load requirements are for a small percentage of steaming time.

The invention seeks to provide a fluid fuel fired burner which can operate efficiently under low and high load conditions.

According to one aspect of the invention there is provided a fluid fuel fired burner having first and second air inlets each of which has an openable closure associated therewith, the first air inlet being for receiving air from a main fan and the second air inlet being for receiving air from an auxiliary fan.

According to another aspect of the invention, there is provided a method of operating a fluid fuel fired burner wherein air is supplied to the burner from a main fan when the burner is operating under high load conditions and from an auxiliary fan when the burner is operating under low load conditions.

Several burners may be mounted in a common windbox communicating with the main fan. However, not all of these burners will necessarily have a second air inlet fed from an auxiliary fan or fans. Hence, under high load conditions all burners can be used in conjunction with the main fan, and under low load conditions some (possibly only one) can be used in conjunction with an auxiliary fan or fans.

The invention will now be more particularly described, by way of example, with reference to the accompanying drawings, which are schematic views of two embodiments of a burner according to the invention, the upper half of each figure showing the main air inlet closed and the auxiliary air inlet open and the lower half of each figure showing the main air inlet open and the auxiliary air inlet closed.

Refering firstly to Figure 1, the burner 10 shown therein is mounted in a windbox 11 which receives air from a main or high load fan (not shown).

The burner has a fuel supply pipe 1 2 with a fuel outlet or nozzle 1 3 (designed to operate either on gas or oil) at one end, and inner and outer concentric air supply tubes 1 4 and 1 5 respectively, surrounding the fuel supply pipe 12. The tubes 14 and 15 each have an annular radially outwardly extending flange at an end remote from the nozzle 1 3 and together with a burner closing plate 1 6 define two concentric air passages 1 7 and 1 8.

A slidable sleeve valve 1 9 is provided to open and close an air inlet from the windbox 11 to the passages 1 7 and 18.

Attached to the burner closing plate 1 6 at the end of the burner remote from the nozzle 1 3 is a chamber 20 which is connected to an auxiliary or low load fan 21.

A slidable plate valve 22 is provided to open and close an air inlet from the chamber 20 to the inner air passage 1 7. The valve 22 seals on two concentric sealing strips and when closed, with the sleeve valve 1 9 open, is urged against these sealing strips by air from the main fan.

The air supply tubes 14 and 1 5 are connected to the closing plate 1 6 by a plurality of angularly spaced bolts (not shown) which extend parallel to the longitudinal extent of the fuel supply pipe 1 2.

The sleeve valve 1 9 and plate valve 22 may be operated manually or automatically from the exterior of the windbox.

The fuel supply pipe 1 2 is contained in a tube 23 supported by a burner front plate and an interlock safety block arrangement 24.

Swirlers 25 and 26 impart directional flow to part or all of the air exiting from the passages 1 7 and 1 8 to give combustion stability. The directional flow imparted by the two swirlers 25 and 26 may or may not match each other as combustion configuration design dictates.

Moreover swirl vanes could be fitted in the air passages 1 7 and 1 8 if it is desired to impart radial flow to the air in these passages to suit flame and combustion configurations.

As shown, the burner has only one fuel supply pipe 12 and one nozzle 13. However, it could have two fuel supply pipes contained in tube 23, each with its own nozzle, designed as individual low load range and high load range nozzles.

The burner can be ignited by any appropriate fixed or portable igniter such as a spark or hot rod type electric igniter.

A common flame surveillance device can be employed for when the burner is in either the low load or high load mode.

The main and auxiliarly fans may or may not be fitted with associated air heaters.

In accordance with the burner configuration, i.e. whether it is designed for axial or swirl air flow, the burner firing block 27 can vary from a divergent form to a convergent form.

For operation under high load modulating conditions, the sleeve valve 1 9 is opened and the plate valve 22 is closed. Air flows from the main fan via the windbox 11 and through both air passages 1 7 and 1 8.

For operation under low load modulating conditions, the sleeve valve 1 9 is closed and the plate valve 22 is opened. Air flows from the auxiliary fan 21 via chamber 20 and through only the inner air passage 1 7.

The burner may have a single combustion and sequence control system, or two such systems, one for operating the burner under high load conditions and the other for operating the burner under low load conditions.

Often, in practice, a number of burners will be mounted in a single windbox. In many cases only some (possibly even one) of these will be designed to operate on auxiliary fans as well as the main fan. In this case all burners will be used under high load conditions but only those designed to operate on auxiliary fans will be used under low load conditions.

The above described burner can be operated efficiently under both high and low loads. For example, the auxiliary fan, with separate air control, will operate at much lower power consumption than the main fan and because the main fan is not working under low load conditions there will be no air leakage through non operating burners. Moreover, the burner can be operated under low load conditions at high combustion efficiencies and low 02.

Referring now to Figure 2, the burner 10' shown therein differs from the burner shown in Figure 1 only in that the inner air supply tube 14 is omitted. Hence, air supplied by either the main or auxiliary fan flows along the single air passage 17'.

In this case, when mounted in a common windbox with other burners designed only for operation with the main fan, the burner 10' may be designed to work at the same load as the other burners when operating with the main fan or at a lower load, e.g. half that of the other burners. In the latter case at least it could be designed to operate at the same load with the main fan and auxiliary fan.

Claims (9)

1. A fluid fuel fired burner having first and second air inlets each of which has an opena ble closure associated therewith, the first air inlet being for receiving air from a main fan and the second air inlet being for receiving air from an auxiliary fan.

2. The burner of claim 1, further comprising a fluid fuel supply pipe having a fuel outlet at one end and at least one tube surrounding the fuel supply pipe to define an air passage into which air can be introduced through either of the air inlets.

3. The burner of claim 2, comprising two concentric tubes surrounding the fuel pipe to define two air passages, one of which is in communication with both air inlets and the other of which is in communication with only the first air inlet.

4. The burner of claim 2 or claim 3, wherein the first air inlet is in the side of the burner and its associated closure is in the form of a slidable sleeve.

5. The burner of anyone of the preceding claims, wherein the second air inlet is at the end of the burner remote from the fuel outlet and its associated closure is in the form of a slidable plate valve.

6. A burner assembly domprising a burner as claimed in anyone of the preceding claims, the burner being mounted in a wind box communicating with the main fan, and there being provided an auxiliary fan communicating with the second inlet of the burner.

7. The burner assembly of claim 6, wherein one or more further burners are mounted in the windbox.

8. A fluid fuel fired burner substantially as hereinbefore described with reference to and as shown in Figure 1 or Figure 2 of the accompanying drawings.

9. A method of operating a fluid fuel fired burner wherein air is supplied to the burner from a main fan when the burner is operating under high load conditions and from an auxiliary fan when the burner is operating under low load conditions.

9. A method of operating a fluid fuel fired burner wherein air is supplied to the burner from a main fan when the burner is operating under high load conditions and from an auxiliary fan when the burner is operating under low load conditions.

CLAIMS Amendments to the claims have been filed, and have the following effect: New or textually amended claims have been filed as follows:

1. A fluid fuel fired burner having first and second air inlets each of which has an openable closure associated therewith, the first air inlet being for receiving air from a main fan and the second air inlet being for receiving air from an auxiliary fan, whereby air is supplied to the burner from a main fan with the second air inlet closed when the burner is operating under high-load conditions and from an auxiliary fan with the first air inlet closed when the burner is operating under low-load conditions.

2. The burner of claim 1, further comprising a fluid fuel supply pipe having a fuel outlet at one end and at least one tube surrounding the fuel supply pipe to define an air passage into which air can be introduced through either of the air inlets.

3. The burner of claim 2, comprising two concentric tubes surrounding the fuel pipe to define two air passages, one of which is in communication with both air inlets and the other of which is in communication with only the first air inlet.

4. The burner of claim 2 or claim 3, wherein the first air inlet is in the side of the burner and its associated closure is in the form of a slidable sleeve.

5. The burner of anyone of the preceding claims, wherein the second air inlet is at the end of the burner remote from the fuel outlet and its associated closure is in the form of a slidable plate valve.

6. A burner assembly comprising a burner as claimed in anyone of the preceding claims, the burner being mounted in a windbox com municating with the main fan, and there being provided an auxiliary fan communicating with the second inlet of the burner.

7. The burner assembly of claim 6, wherein one or more further burners are mounted in the windbox.

8. A fluid fuel fired burner substantially as hereinbefore described with reference to and as shown in Figure 1 or Figure 2 of the accompanying drawings.