GB2244326A - Controlling the speed of gases discharged from a chimney - Google Patents

Abstract

A device (2) for controlling the speed of gases discharged from a chimney (4) comprises a tubular member (6) fixed by means (14) in a bore (8) of the chimney (4) so that gases passing up the chimney (4) can pass between the tubular member (6) and the inside (10) of the chimney (4) and obturator means (18) in the tubular member (6), movable from a closed position to an open position by the gases passing up the chimney (4) when the speed of the gases exceeds a predetermined value, and movable back to its closed position when the speed of the gases passing up the chimney (4) falls below the predetermined value. <IMAGE>

Description

APPARATUS FOR CONTROLLING THE SPEED OF GASES DISCHARGED FROM A CHIMNEY This invention relates to apparatus for controlling the speed of gases discharged from a chimney.

A problem inherent in both natural and forced draught chimneys is that when the gases are being discharged at a rate which is lower than the maximum capacity, then the exit speed of the gases is so low that relatively cold air surrounding the chimney is allowed to enter into the top of the chimney as a down draught. Down draughts are particularly prevalent around the inner perimeter of the chimney where, due to surface friction, gases rising up the chimney are rising slower than at the centre of the chimney.

The low exit speed of the gases and the attendant down draught may have the following detrimental effects.

1. The top of the chimney may be not sufficiently warm throughout, causing the formation of condensation which combines with combustion deposits to form an acid solution, which then encourages corrosion.

2. If local eddies caused by the wind are sufficiently strong at the top of the chimney and they have more energy than the exiting gases, then moisture laiden air may form a down draught into the chimney, again causing condensation to occur with resulting increased corrosion rates.

3. When the speed of the exiting gases is low, and winds and eddies around the chimney are high, then the plume of the gases emerging from the chimney is soon broken up after leaving the chimney so that the gas is dispersed at a much lower height than is desirable.

It is an aim of the present invention to reduce the above mentioned problems.

Accordingly, in one non-limiting aspect of the present invention, there is provided apparatus for controlling the speed of gases discharged from a chimney, which apparatus comprises a tubular member which is for fitting in a bore of the chimney and which is of a smaller cross sectional size than the bore of the chimney so that gases passing up the chimney can pass between the tubular member and the inside of the chimney, fixing means for fixing the tubular member in position in the bore of the chimney, a bore in the tubular member, and obturator means for opening and closing the bore in the tubular member, the obturator means being such that it is movable from a closed position to an open position by the gases passing up the chimney when the speed of the gases exceeds a predetermined value, and the obturator means being such that it is movable back to its closed position when the speed of the gases passing up the chimney falls below the predetermined value.

Usually, the tubular member will be centrally positioned in the bore of the chimney so that there is an annular space between the tubular member and the inside of the chimney. If desired however the tubular member may be off-set from the longitudinal axis of the bore of the chimney.

Usually, the obturator means will open by an amount which is proportional to the speed of the gases when they exceed the predetermined value.

Preferably, the obturator means moves under gravity to its closed position when the speed of the gases passing up the chimney falls below the predetermined value. If desired, the obturator means may be spring biased to its closed position.

Preferably, the obturator means is a pivotally mounted obturator means. The obturator means may be pivotally mounted at one side. Alternatively, the obturator means may be pivotally mounted at its centre.

Preferably, the obturator means is pivotally mounted by a hinge arrangement. The hinge arrangements may comprise one or more hinges.

Preferably, the obturator means is in the form of at least one plate. Other types of obturator means may however be employed.

If desired, the obturator means may have two plates which open and shut about a centre line across the bore of the tubular member. The obturator means may alternatively comprise a single plate or three or more plates.

Preferably, the obturator means includes stop means for limiting the degree of opening of the obturator means. The stop means may thus ensure that the obturator means does not open so far that it will not automatically move back to its closed position when the speed of the gases in the chimney bore falls below the predetermined value.

Preferably, the stop means is positioned on the obturator means. If desired however the stop means may be positioned on the inside of the chimney.

Preferably, the stop means is at least one stop member which upstands from a top surface of the obturator means.

The fixing means may be brackets for fixing to the bore of the chimney, and arms which extend outwardly from the tubular member and which locate in the brackets. Other types of fixing means may be employed. Where the fixing means comprises brackets and arms, then there will preferably be three or four of the brackets and three or four of the arms.

Usually, the tubular member will be of circular cross section. If desired however the tubular member may be of another cross sectional shape such for example as a square, rectangular or octanganal cross sectional shape. Usually, the cross sectional shape of the tubular member will be the same as the cross sectional shape of the bore of the chimney.

The outside of the chimney may be provided with a cladding material. The cladding material may be, for example, aluminium or mineral wool insulating cladding material.

An embodiment of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 is a longitudinal section through a top part of a chimney; and Figure 2 is a top plan view of the chimney shown in Figure 1.

Referring to the drawings, there is shown apparatus 2 for controlling the speed of gases discharged from a chimney 4. The apparatus 2 comprises a tubular member 6 which is for fitting in a bore 8 of the chimney 4 and which is of a smaller cross sectional size than the bore 8 of the chimney 4 so that gases passing up the chimney 4 can pass between the tubular member 6 and the inside 10 of the chimney 4. As can be seen from Figures 1 and 2, the tubular member 6 is centrally positioned in the bore 8 so that there is an annular space 12 between the tubular member 6 and the inside 10 of the chimney 4.

The apparatus 2 further comprises fixing means 14 for fixing the tubular member 6 in position in the bore 8 of the chimney 4.

The apparatus 2 further comprises a bore 16 in the tubular member 6, and obturator means 18 for closing the bore 16. The obturator means 18 is such that it is movable from a closed position as shown in Figures 1 and 2 to an open position (not shown). The obturator means is so movable by the gases passing up the chimney 4 when the speed of the gases exceeds a predetermined value. The obturator means 18 is movable back to its closed position when the speed of the gases passing up the chimney 4 falls below the predetermined value. The obturator means 18 opens by an amount which is proportional to the speed of the gases when they exceed the predetermined value.

The obturator means 18 moves under gravity to its closed position when the speed of the gases passing up the chimney 4 falls below the predetermined value.

As shown most clearly in Figure 2, the obturator means 18 comprises a pair of plates 20, 22 which are each pivotally mounted at one side by a hinge arrangement comprising a pair of hinges 24,26.The plates 20,22 open and shut about a centre line 28 across the bore 16 of the tubular member 6.

The plates 20, 22 are each provided with stop means in the form of a pair of stop members 30, 32 which upstand from a top surface 34 of the plates 20, 22.

The obturator means limits the degree of opening of the plates 20, 22 by engaging the inside 10 of the chimney 4 as shown in chain lines in Figure 1.

As can be seen from Figure 2, there are four of the fixing means 14. Each fixing means 14 comprises a U-shaped bracket 36 which is secured to the inside 10 of the bore 8 of the chimney 4. Each fixing means 14 also comprises an arm 38 which extends radially outwardly from the tubular member 6 and which locates in the bracket 36.

The arm 38 may be secured to a bracket 36 by a bolt (not shown) if desired.

As can also be seen from Figure 2, the tubular member 6 is of circular cross section and it is of the same cross sectional shape as the chimney 4.

The outside of the chimney 4 is provided with a cladding material 40. The cladding material will usually be an insulating cladding material such for example as aluminium or mineral wool.

The apparatus 2 operates such that when there is no gas flowing up the chimney 4, the plates 20, 22 remain in their closed position. When gases are to be produced in small volumes they will pass up the bore 8 of the chimney 4 and they will pass through the annular space 12 and out of the top of the chimney 4. By causing these gases to pass through the annular space 12, the temperature of the surfaces in contact with the gases will be increased.

As the volume of gases passing up the chimney 4 increases, their velocity will also increase and it will eventually reach a predetermined value. This predetermined value will be determined by design and commissioning. At this predetermined value, the plates 20, 22 will start to open as a result of the increased energy from the gases overcoming the resistance and the weight of the plates 20, 22. The plates 20, 22 will be appropriately balanced and mounted about the hinges 24, 26. As the plates 20, 22 start to open, then some of the waste gases passing up the chimney 4 will flow through the bore 16 of the tubular members 6, resulting in a steadying of the acceleration of the velocities of the exiting gas through the annular space 12.As the volume of the gas passing up the chimney 4 increases still further, the plates 20, 22 will eventually open to their maximum amount so that substantially the entire full bore 8 of the chimney 4 will be available for receiving the exiting gases.

When the exiting gases reduce from a maximum value, the reverse of the above described process will occur so that the plates 20, 22 will gravitate to their closed position and the gases will then exit only through the annular space 12. The gases will close under their own weight due to gravity.

The ratio between the diameter of the bore 8 of the chimney, the bore 16 of the tubular member 6, and the energy required of the gases to open the plates 20, 22 will be appropriately calculated and may be tested on site, usually with a view to maintaining a minimum exiting gas velocity through the annular space 12 under minimum gas volume conditions, and a maximum exiting gas velocity through both the annular space 12 and the bore 16 under maximum waste gas emission conditions. The size, weight and location of the hinges 24, 26 can easily be varied and, if desired, adjustable weight means may be employed to appropriately balance the plates 20, 22.

As the plates 20, 22 open, they will usually be stopped just short of their vertical position by the stop members 30, 32 engaging the inside 10 of the chimney 4.

This enables the plates 20, 22 to drop back under gravity as mentioned above.

The apparatus 2 may be made from any desired and appropriate material. Usually, the material will be a metal. Preferably, the metal will be a a non-corrosive metal. The chimney 4 may also be made of any desired and appropriate material such for example as metal, brick, concrete, or a plastics material.

The chimney 4 may be any desired and suitable chimney and it may vary in size from household chimneys, to factory chimneys to industrial waste plant chimneys.

The chimney 4 can be used to discharge a wide variety of waste or surplus gases.

It will be appreciated that the apparatus 2 is such that it is able to automatically operate in a mechanical manner without the need to employ electrical or hydraulic control means. Furthermore, the apparatus 2 provides little or no resistance to the gases passing up the chimney 4. The apparatus 2 enables the exit speed of gases at the top of the chimney to be set within minimum and maximum limits, for example as may be set by present and future legislation. Because the gases are directed through the annular space 12 at low volume/low speed gas conditions, the temperature of the inside 10 of the chimney 4 is maintained relatively high, thereby reducing the likelihood of condensation being formed within the chimney 4, and also decreasing the likelihood of down draughts, and cold air inversion.Thus, in addition to improving corrosion resistance, the apparatus 2 may increase the plume height of the exiting gases, thereby increasing the height of the waste gas dispersal after leaving the top of the chimney 4.

The apparatus 2 may be fitted to new chimneys at a manufacturing stage or it may be installed in existing chimneys. The apparatus 2 can be sized to cater for any range of chimney sizes. The apparatus 2 can also be made to be removable or replaceable so that if there is any change in the volume of gases being produced, or if there is a change in the turn down ratio resulting from an operational change in the gas producing apparatus, then the apparatus 2 can appropriately be modified as may be required.

It is to be appreciated that the embodiment of the invention described above with reference to the accompanying drawings has been given by way of example only. Thus, for example, different types of fixing means 14 may be employed.

Also, a single obturator balance plate could be employed instead of the two plates 20, 22.

Claims (17)

1. Apparatus for controlling the speed of gases discharged from a chimney, which apparatus comprises a tubular member which is for fitting in a bore of the chimney and which is of a smaller cross sectional size than the bore of the chimney so that gases passing up the chimney can pass between the tubular member and the inside of the chimney, fixing means for fixing the tubular member in position in the bore of the chimney, a bore in the tubular member, and obturator means for opening and closing the bore in the tubular member, the obturator means being such that it is movable from a closed position to an open position by the gases passing up the chimney when the speed of the gases exceeds a predetermined value, and the obturator means being such that it is movable back to its closed position when the speed of the gases passing up the chimney falls below the predetermined value.

2. Apparatus according to claim 1 in which the tubular member is centrally positioned in the bore of the chimney so that there is an annular space between the tubular member and the inside of the chimney.

3. Apparatus according to claim 1 or claim 2 in which the obturator means opens by an amount which is proportional to the speed of the gases when they exceed the predetermined value.

4. Apparatus according to any one of the preceding claims in which the obturator means moves under gravity to its closed position when the speed of the gases passing up the chimney falls below the predetermined value.

5. Apparatus according to any one of the preceding claims in which the obturator means is a pivotally mounted obturator means.

6. Apparatus according to claim 5 in which the obturator means is pivotally mounted at one side.

7. Apparatus according to claim 5 or claim 6 in which the obturator means is pivotally mounted by a hinge arrangement.

8. Apparatus according to any one of the preceding claims in which the obturator means is in the form of at least one plate.

9. Apparatus according to claim 8 in which the obturator means has two plates which open and shut about a centre line across the bore of the tubular member.

10. Apparatus according to any one of the preceding claims in which the obturator means includes stop means for limiting the degree of opening of the obturator means.

11. Apparatus according to claim 10 in which the stop means is positioned on the obturator means.

12. Apparatus according to claim 11 in which the stop means is at least one stop member which upstands from a top surface of the obturator means.

13. Apparatus according to any one of the preceding claims in which the fixing means are brackets for fixing to the bore of the chimney, and arms which extend outwardly from the tubular member and which locate in the brackets.

14. Apparatus according to any one of the preceding claims in which the tubular member is of circular cross section.

15. Apparatus for controlling the speed of gases discharged from a chimney, substantially as herein described with reference to the accompanying drawings.

16. A chimney when provided with apparatus as claimed in any one of the preceding claims.

17. A chimney according to claim 16 in which the outside of the chimney is provided with a cladding material.