GB2094971A

GB2094971A - Method of igniting a coal-dust annular burner flame

Info

Publication number: GB2094971A
Application number: GB8206864A
Authority: GB
Original assignee: L&C Steinmueller GmbH
Current assignee: Hitachi Zosen Inova Steinmueller GmbH
Priority date: 1981-03-17
Filing date: 1982-03-09
Publication date: 1982-09-22
Also published as: GB2094971B; ZA821405B; JPS57166422A; FR2502302A2; AU550115B2; AU8159782A; FR2502302B2; DE3110284A1

Abstract

A method of igniting a coal-dust annular burner flame with an internal return flow region, wherein the ignition energy is introduced centrally into the internal return flow region of the coal-dust annular burner flame, the dust-laden air-dust weight ratio for the dust igniting flame amounting to 0.2-0.5, the dust-laden air-dust weight ratio for the main burner flame amounting to 1.5-2.0 and the dust igniting flame being operated with an air number of lambda =0.4-0.8 and drawing the additional stream of air necessary for the complete combustion from the leakage air of the main burner.

Description

SPECIFICATION Method of igniting a coal-dust annular burner flame This invention relates to a method of igniting a coal-dust annular burner flame with an internal return flow region, wherein the ignition energy is introduced centrally into the internal return flow region of the coal-dust annular burner flame.

In order to ignite a burner flame, ignition energy is generally supplied to the combustible mixture of fuel and air. In coal-dust annular burners, the preparation and supply of the ignition energy is usually effected by so-called igniting burners which are operated with oil or gas. In this case, the oil or the gas is ignited by means of an electrical ignition spark. The use of oil or gas as an ignition energy carrier is effected in view of its readiness to ignite and combustion stability, which is particularly necessary with cold combustion-chamber influences.

For reasons of cost and of the available reserves it is becoming ever more desirable to use coal or an other solid fuel as ignition fuel instead of natural gas or petroleum as an ignition energy carrier, particularly with coal-dust firing.

In our co-pending British patent application No.

8025034 there is described and claimed a method of igniting a coal-dust annular burner flame with an internal return-flow region, in which the ignition energy is introduced centrally into the internal return-flow region of the coal-dust annular burner flame, wherein the ignition energy for the annular burner flame is applied by a dust igniting flame obtained by combustion of a fuel dust which differs from the main fusel in grain size and/or in consistency. A coal-dust annular burner of known construction with an igniting burner disposed in the burner axis and using the principle of the method of Application 8025034 is described and illustrated in the specification and drawing of that application to which reference may be made for details of its construction.

In the preferred method of carrying out the invention of application No. 8025034 as described in the specification thereof, the dustladen airdust weight ratio for the dust igniting flame is lower (0.5-1.0) than that of the main burner flame (1.5-2.0), and the dust igniting flame is operated with a lower air number (:1=0.8-1.1) than the main burner flame (:1=1.1-1.3).

It has now been discovered that the method as described in our British patent application 8025034 can also be carried out with lower values than those given in the specification thereof.

Thus according to the present invention there is provided a method of igniting a coal-dust annular burner flame with an internal return flow region, in which the ignition energy is introduced centrally into the internal return-flow region of the coal-dust annular burner flame and in which the ignition energy for the annular burner flame is applied by a dust igniting flame obtained by combustion of a fuel dust which differs from the main fuel in grain size and/or in consistency characterised in that the dust-laden air-dust weight ratio for the dust igniting flame amounts to 0.2-0.5, the dust-laden air-dust weight ratio for the main burner flame amounting to 1.5-2.0.

The dust igniting flame is preferabiy operated with an air number of :1=0.4.8 and draws the additional stream of air necessary for the complete combustion from the leakage air of the main burner.

Claims

1. A method of igniting a coal-dust annular burner flame with an internal return flow region, in which the ignition energy is introduced centrally into the internal return-flow region of the coal-dust annular burner flame and in which the ignition energy for the annular burner flame is applied by a dust igniting flame obtained by combustion of a fuel dust which differs from the main fuel in grain size and/or in consistency, characterised tn that the dust-laden airdust weight ratio for the.dust igniting flame amounts to 0.2-0.5, the dust-laden airdust weight ratio for the main burner flame amounting to 1.52.0.

2. A method as claimed in claim 1, characterised in that the dust igniting flame is operated with an air number of A=0.8i 0.8 and draws the additional stream of air necessary for the complete combustion from the ieakage air of the main burner.

3. A method as claimed in claim 1 or 2, characterised in that the axial combustion air component for the dust igniting flame is smaller than that of the main burner flame.

4. A method as claimed in any of claims 1-3, characterised in that the tangential combustion air component for the dust igniting flame is greater than that of the main burner flame.

5. A method as claimed in any of claims 1 4, characterised in that the combustion air is supplied to the igniting burner flame through the core air passage of the main burner.

6. A method as claimed in any of claims 1-5, characterised in that igniting burner flame is operated with the main fuel.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Method of igniting a coal-dust annular burner flame This invention relates to a method of igniting a coal-dust annular burner flame with an internal return flow region, wherein the ignition energy is introduced centrally into the internal return flow region of the coal-dust annular burner flame. In order to ignite a burner flame, ignition energy is generally supplied to the combustible mixture of fuel and air. In coal-dust annular burners, the preparation and supply of the ignition energy is usually effected by so-called igniting burners which are operated with oil or gas. In this case, the oil or the gas is ignited by means of an electrical ignition spark. The use of oil or gas as an ignition energy carrier is effected in view of its readiness to ignite and combustion stability, which is particularly necessary with cold combustion-chamber influences. For reasons of cost and of the available reserves it is becoming ever more desirable to use coal or an other solid fuel as ignition fuel instead of natural gas or petroleum as an ignition energy carrier, particularly with coal-dust firing. In our co-pending British patent application No. 8025034 there is described and claimed a method of igniting a coal-dust annular burner flame with an internal return-flow region, in which the ignition energy is introduced centrally into the internal return-flow region of the coal-dust annular burner flame, wherein the ignition energy for the annular burner flame is applied by a dust igniting flame obtained by combustion of a fuel dust which differs from the main fusel in grain size and/or in consistency. A coal-dust annular burner of known construction with an igniting burner disposed in the burner axis and using the principle of the method of Application 8025034 is described and illustrated in the specification and drawing of that application to which reference may be made for details of its construction. In the preferred method of carrying out the invention of application No. 8025034 as described in the specification thereof, the dustladen airdust weight ratio for the dust igniting flame is lower (0.5-1.0) than that of the main burner flame (1.5-2.0), and the dust igniting flame is operated with a lower air number (:1=0.8-1.1) than the main burner flame (:1=1.1-1.3). It has now been discovered that the method as described in our British patent application 8025034 can also be carried out with lower values than those given in the specification thereof. Thus according to the present invention there is provided a method of igniting a coal-dust annular burner flame with an internal return flow region, in which the ignition energy is introduced centrally into the internal return-flow region of the coal-dust annular burner flame and in which the ignition energy for the annular burner flame is applied by a dust igniting flame obtained by combustion of a fuel dust which differs from the main fuel in grain size and/or in consistency characterised in that the dust-laden air-dust weight ratio for the dust igniting flame amounts to 0.2-0.5, the dust-laden air-dust weight ratio for the main burner flame amounting to 1.5-2.0. The dust igniting flame is preferabiy operated with an air number of :1=0.4.8 and draws the additional stream of air necessary for the complete combustion from the leakage air of the main burner. Claims