GB1565198A

GB1565198A - Systems for heating fluids

Info

Publication number: GB1565198A
Application number: GB4857475A
Authority: GB
Original assignee: British Gas Corp
Current assignee: British Gas Corp
Priority date: 1975-11-26
Filing date: 1975-11-26
Publication date: 1980-04-16

Description

(54) IMPROVEMENTS IN OR RELATING TO SYSTEMS FOR HEATING FLUIDS (71) We, BRITISH GAS CORPORATION, of 59 Bryanston Street, London, WIA 2AZ, a British Body Corporate, do hereby declare the invention, for which we pray that a 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 statements: This invention relates to systems for heating fluids, particularly, although not exclusively, liquids in vats or tanks, and is an improvement in or modification of the invention disclosed in our British Patent Specification No. 1,473,320.

Claim 1 of said Patent '.pecification is directed to a system for heating fluid including in combination a fluid container, a burner having a burner head to which air and a gaseous fuel can be separately but forceable supplied and mixed at the burner head, means for igniting the combustible gas/air mixture, a combustion chamber disposed downstream of the burner but external to the container and in which chamber the gas/air mixture can be combusted, and a continuous length of tube of small bore diameter (therein defined as meaning up to 4 inches diameter) communicating the combustion chamber and an outlet for exhaust gases, the whole length of which tube between the chamber and the exhaust outlet being adapted in use of the system to be immersed in the fluid to be heated whereby the heat from the combested gases passing through the tube can be transferred to the fluid.

The preferred embodiment of said Patent Specification has a burner head comprising a gas supply tube at its inner end, which inner end is provided with a plurality of gas outlet ports, an air tube of greater diameter than the gas tube and disposed concentrically about it, and a conical perforate member disposed substantially across the annular space defined between the outlet ends of the gas and air tubes with its inner peripheral edge located behind the gas outlet ports.

The perforations in the conical member supply a flow of primary combustion air, while secondary combustion air passes through the annular gap between the outer edge of the conical member and a burner back plate. The position of the conical member with respect to the back plate therefore determines the ratio of secondary to primary air.

It has been found in practice that this ratio is important in attaining the required combustion performance and flame stability. Hence, the conical member must be precisely positioned for optimum performance and it is difficult to do so reproducibly with the construction of the preferred embodiment of said Patent Specification.

The present invention therefore seeks to provide a burner arrangement which is simpler and capable of greater accuracy in manufacture.

The invention accordingly provides a system according to Claim 1 of our British Patent Specification No. 1,473,320 in which the burner head comprises a gas supply tube closed at its downstream end except for a plurality of gas-outlet ports formed adjacent said end, an air tube of greater diameter than the gas tube and disposed concentrically about it, the downstream end of the air tube being spaced rearwardly from said gas-outlet ports, and an annular member secured at its inner periphery to the gas tube rearwardly of its gas-outlet ports and its outer periphery to said downstream end of the air tube. the annular member being perforated to provide primary air outlet pots adjacent said gas outlet ports and secondary air outlet ports spaced from the primary air ports and remote from said gas outlet ports.

Preferably, the gas-outlet ports are directed radially around the end region of the gas tube.

Preferably also, the annular member is generally planar with its primary air outlet ports being directed axially of the tubes and on one or more circles concentric with the tubes, and its secondary air outlet ports directed radially of the tubes in a shoulder provided at the outer periphery of said annular member.

An embodiment of the present will now be described, by way of example, referring to the single figure of the accompanying drawing which is a cross-sectional elevation of a modified form of burner head designed to replace the burner used in the system described and illustrated in Figures 1 to 6 of our said Patent Specification.

The modified burner, generally indicated at 10. supplies gaseous fuel (referred to herein simply as "gas") and air to support combustion in a refractory tunnel 11, the combustion products from the tunnel 11 then passing through an immersion tube 3 as seen in the aforesaid Figures 1 and 2.

The burner 10 comprises an air tube 14 secured as by welding in a back plate 16. A gas tube 18 passes concentrically through the air tube 14 and projects beyojnd the inner end of the air tube 14. The end of the gas tube 18 is closed at 20.

An annular member 22 is welded at its inner periphery to the external surface of the gas tube 18 and at its outer periphery to the end of the air tube 14.

The annular member 22 is of generally planar form but has an outer peripheral shoulder.

Gas ports 24 and provided in the gas tube 18 adjacent and externally of the annular member 22. The annular member 22 is provided with primary combustion air ports 26 arranged in three concentric circular rows about the gas tube 18, and with radial secondary combustion air ports 28 through its peripheral shoulder.

In use, gas and air are supplied foreceably. preferably by pressurising the gas and air supplies, or alternatively by means of suction at the outlet from the immersion tube. The major portion of the air passes through the primary air ports 26 at right angles to the gas flow and the remainder through the surrounding secondary air ports 28. wherebv collectlvely to ensure that the air flow is broken up into small turbulent streams at regions of gas flow so as to create regions of gas-rich and gas-weak combustible mixtures which encourage flame stability.

The gas ports are suitably sized to such that a part of this available supply pressure is dropped across them at the rated burner input to ensure maximum momentum for mixing.

In a specific example, the gas tube 18 was of 21 - inch outside diameter; the gas ports comprise eight 1.8mm diameter ports; the primary air pots 26 comprised three rows, namely eigth 1/16th-inch ports ona 17/32-inch pitch circle radius, eight 1.8mm ports on a 21)32-inch pitch circle radius, and eight 3/32-inch ports ona 25/32 inch pitch circle radius: and the secondary air ports 28 comprised twelve 9/64-inch diameter ports.

The following flow rates and supply pressures were observed when firing this burner at its rated throughout of one therm/hour: Gas rate 97 ft 3/hr (1 therm/hr) Gas pressure 12 ins water gauge Air 'ate 1070 ft 3/bur Air pressure 12 ins water gauge Gas pressure drop across burner head, 3.6 ins water gauge.

WHAT WE CLAIM IS: 1. A system according to Claim 1 of our British Patent Specification No. 1,473,320 in which the burner head comprises a gas supply tube closed at its downstream and except for a pluraliy of glas-outlet ports formed adjacent said end. an air tube of greater diameter than the gas tube and disposed concentrically about it. the downstream end of the air tube being spaced rearwardly from said gas-outlet ports, and an annular member secured at its inner periphery to the gas tube rearwardly of its gas-outlet ports and at its outer periphery to said downstream end of the air tube, the annular member being perforated to provide primary air outlet ports adjacent said gas-outlet ports and secondary air outlets ports spaced from the primary air ports and remote from said gas-outlet ports.

2. A system according to Claim 1. wherein the annular member is generally planar.

3. A system according to Claim 1 or Claim 2. wherein the primary air outlet ports of said annular member are directed axially of the tubes.

4. A system according to Claim 3 wherein the primary air outlet ports are arranged on one or more circles concentric with the tubes.

5. A system according to any preceding Claim, wherein the secondary air outlet ports

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. being perforated to provide primary air outlet pots adjacent said gas outlet ports and secondary air outlet ports spaced from the primary air ports and remote from said gas outlet ports. Preferably, the gas-outlet ports are directed radially around the end region of the gas tube. Preferably also, the annular member is generally planar with its primary air outlet ports being directed axially of the tubes and on one or more circles concentric with the tubes, and its secondary air outlet ports directed radially of the tubes in a shoulder provided at the outer periphery of said annular member. An embodiment of the present will now be described, by way of example, referring to the single figure of the accompanying drawing which is a cross-sectional elevation of a modified form of burner head designed to replace the burner used in the system described and illustrated in Figures 1 to 6 of our said Patent Specification. The modified burner, generally indicated at 10. supplies gaseous fuel (referred to herein simply as "gas") and air to support combustion in a refractory tunnel 11, the combustion products from the tunnel 11 then passing through an immersion tube 3 as seen in the aforesaid Figures 1 and 2. The burner 10 comprises an air tube 14 secured as by welding in a back plate 16. A gas tube 18 passes concentrically through the air tube 14 and projects beyojnd the inner end of the air tube 14. The end of the gas tube 18 is closed at 20. An annular member 22 is welded at its inner periphery to the external surface of the gas tube 18 and at its outer periphery to the end of the air tube 14. The annular member 22 is of generally planar form but has an outer peripheral shoulder. Gas ports 24 and provided in the gas tube 18 adjacent and externally of the annular member 22. The annular member 22 is provided with primary combustion air ports 26 arranged in three concentric circular rows about the gas tube 18, and with radial secondary combustion air ports 28 through its peripheral shoulder. In use, gas and air are supplied foreceably. preferably by pressurising the gas and air supplies, or alternatively by means of suction at the outlet from the immersion tube. The major portion of the air passes through the primary air ports 26 at right angles to the gas flow and the remainder through the surrounding secondary air ports 28. wherebv collectlvely to ensure that the air flow is broken up into small turbulent streams at regions of gas flow so as to create regions of gas-rich and gas-weak combustible mixtures which encourage flame stability. The gas ports are suitably sized to such that a part of this available supply pressure is dropped across them at the rated burner input to ensure maximum momentum for mixing. In a specific example, the gas tube 18 was of 21 - inch outside diameter; the gas ports comprise eight 1.8mm diameter ports; the primary air pots 26 comprised three rows, namely eigth 1/16th-inch ports ona 17/32-inch pitch circle radius, eight 1.8mm ports on a 21)32-inch pitch circle radius, and eight 3/32-inch ports ona 25/32 inch pitch circle radius: and the secondary air ports 28 comprised twelve 9/64-inch diameter ports. The following flow rates and supply pressures were observed when firing this burner at its rated throughout of one therm/hour: Gas rate 97 ft 3/hr (1 therm/hr) Gas pressure 12 ins water gauge Air 'ate 1070 ft 3/bur Air pressure 12 ins water gauge Gas pressure drop across burner head, 3.6 ins water gauge. WHAT WE CLAIM IS:

1. A system according to Claim 1 of our British Patent Specification No. 1,473,320 in which the burner head comprises a gas supply tube closed at its downstream and except for a pluraliy of glas-outlet ports formed adjacent said end. an air tube of greater diameter than the gas tube and disposed concentrically about it. the downstream end of the air tube being spaced rearwardly from said gas-outlet ports, and an annular member secured at its inner periphery to the gas tube rearwardly of its gas-outlet ports and at its outer periphery to said downstream end of the air tube, the annular member being perforated to provide primary air outlet ports adjacent said gas-outlet ports and secondary air outlets ports spaced from the primary air ports and remote from said gas-outlet ports.

are directed radially of the tubes in a shoulder provided at the outer periphery of said annular member.

6. A system according to any preceding Claim, wherein the gas-outlet pots are directed radially around the end region of the gas tube.

7. A liquid heating system according to Claim 10 of our British Patent Specification No.

1,473,320 modified by the substitution of said burner head by a burner head substantially as shown in and as hereinbefore described with reference to the accompanying drawing.