GB2138558A

GB2138558A - Method and apparatus for the ignition of fuel

Info

Publication number: GB2138558A
Application number: GB08405375A
Authority: GB
Inventors: Joachim Secker
Original assignee: Deutsche Babcock Werke AG
Current assignee: Deutsche Babcock Werke AG
Priority date: 1983-04-22
Filing date: 1984-03-01
Publication date: 1984-10-24
Also published as: GB2138558B; DE3314675A1; SE454910B; SE8400941D0; GB8405375D0; SE8400941L

Abstract

For the ignition of fuel in a combustion space (1) which is dust- laden or accessible with difficulty, an easily ignitable medium, e.g. carbon disulphide, is blown into the combustion space via line 6. The medium is mixed with air from line 5 in a ratio which lies within the ignition range of the mixture. The air is heated by a heater 17 before the intermixing to such a temperature, e.g. 124 DEG C, that after the intermixing self ignition takes place. <IMAGE>

Description

SPECIFICATION Method and apparatus for the ignition of fuel The present invention relates to a method of igniting fuel in a combustion space especially a space which is dust-laden or of difficult accessibility, and to apparatus for carrying out the method.

Known electrical igniters arranged in combustion spaces of that kind wear out relatively rapidly or become functionally inoperable and must be exchanged. Exchanging of the igniter presents appreciable difficulties when access to the combustion space is difficult.

There is therefore a need for a method and apparatus which are independent of the dust loading in the combustion space and which require no electrical or mechanical parts at the ignition place.

According to a first aspect of the present invention there is provided a method of igniting fuel in a combustion space, comprising the steps of feeding a readily ignitable liquid or gaseous medium into the combustion space and mixing the fed medium with preheated air in a ratio within the range of ignition of such an air and medium mixture, the air being preheated to such a temperature that the temperature of the air and medium mixture is above the ignition point thereof.

According to a second aspect of the invention there is provided apparatus for carrying out the method of the first aspect of the invention, the apparatus comprising means defining a combustion space, means defining a mixing chamber within the combustion space, and a respective duct communicating with the mixing chamber to conduct thereto each of heated air and a readily ignitable liquid or gaseous medium, the ducts extending to the mixing chamber from externally of the combustion space.

In a method exemplifying the present invention, the easily ignitable medium is introduced into the combustion space under such conditions that it ignites and thus initiates ignition of the fuel. Parts sensitive to wear are not needed for the introduction of the medium into the combustion space. The process of ignition manifests itself by a temperature rise at the exit of the mixing chamber.

The ignition can be monitored in simple manner by temperature measuring means. The easily ignitable medium is preferably carbon disulfide (CS2), which is self-igniting at a temperature of above 1240C in a mixture of 1 to 55% by volume with air.

An example of the method and an embodiment of the apparatus of the present invention will now be more particularly described with reference to the accompanying drawings, in which: Fig. 1 is a diagram of the layout of apparatus embodying the invention; and Fig. 2 is a sectional view of part of the apparatus, showing the detail Z of Fig. 1.

Referring now to the drawings, there is shown a combustion space 1 to which fuel is fed in a known manner and which can be the firing space of a furnace operated with oil or gas. The combustion space 1 can, however, aiso be the reaction space of a coal gasifier or the fluidised bed zone of a fluidised bed, particularly a pressurecharged bed.

A mixing chamber 2 is provided within the combustion space 1 and is connected to the outlet end portion 3 of a feed duct 5 for air and to an outlet end portion 4 of a feed duct 6 for an easily ignitable medium. The main parts of the ducts 5 and 6 are disposed externally of the combustion space 1.

The duct end portion 4 defines a central channel 7, which is surrounded by an annular channel 8 defined by the duct end portion 3. The two channels 7 and 8 are closed off at their outlet ends by a plate 9, in which outlet openings 10 and 11 are arranged. In the case of the embodiment illustrated in Fig. 2, the axes of the outlet openings 10 of the central channel 7 are arranged to be divergent. The outlet openings 11 of the annular channel 8 are aligned to be partially convergent and partially parallel to the axis of the mixing chamber 2. The direction of the issuing jets caused by this alignment of the axes of the outlet openings 10 and 11 effects an intermixing of medium and air.

A temperature measuring device 12 is arranged in the region of the exit of the mixing chamber 2.

A respective regulating device 13 and a respective non-return valve 14 are provided in each of the feed ducts 5 and 6. A pump 1 5 is arranged in the feed duct 6, since it is assumed that the easily ignitable medium is liquid at room temperature. The feed duct 5 for air is equipped with a blower 16 and is conducted through a heating device 17, for example an electrical wall heater. The heating device 1 7 can be dispensed with when compressed air is conveyed into a pressure-charged combustion space 1. In this case, the air will be brought to a sufficiently high temperature through the compression.

The described apparatus operates in the following manner: By means of the blower 1 6, air is blown through the feed duct 5 to the annular channel 8, the air being heated by means of the heating device 1 7. The easily ignitable medium, for example carbon disulfide, is now conveyed by the pump 15 through the feed duct 6 to the central channel 7. In that case, the quantity ratio of medium to air is so set that a self-igniting mixture results in the mixing chamber 2. In the case of carbon disulfide, the proportion by volume of the medium in the mixture must be between 1 and 55%. In that case, the mixture heated up by the air must have a temperature of at least 1240C.

Under these conditions, self-ignition of the mixture of medium and air takes place, which initiates ignition of the fuel in the combustion space 1. The temperature level necessary for the self-ignition and for the temperature rise that takes place through the completed ignition, can be monitored by the temperature measuring device 12.

Apart from carbon disulfide, any other liquid or gaseous medium, which itself or the vapour of which together with air forms a self-ignitable mixture at relatively low temperatures, can be used as the easily ignitable medium.

Claims

1. A method of igniting fuel in a combustion space, comprising the steps of feeding a readily ignitable liquid or gaseous medium into the combustion space and mixing the fed medium with preheated air in'a ratio within the range of ignition of such an air and medium mixture, the air being preheated to such a temperature that the temperature of the air and medium mixture is above the ignition point thereof.

2. A method as claimed in claim 1, comprising the step of monitoring the temperature of the mixture downstream of a zone of inter-mixing of the air and medium.

3. A method substantially as hereinbefore described with reference to the accompanying drawings.

4. Apparatus for carrying out the method claimed in claim 1, the apparatus comprising means defining a combustion space, means defining a mixing chamber within the combustion space, and a respective duct communicating with the mixing chamber to contact thereto each of heated air and a readily ignitable liquid or gaseous medium the ducts extending to the mixing chamber from externally of the combustion space.

5. Apparatus as claimed in claim 4, comprising temperature measuring means arranged to measure the temperature of air and medium mixture in the mixing chamber, the measuring means being arranged downstream of a zone of intermixing of the air and medium.

6. Apparatus as claimed in either claim 4 or claim 5, wherein the duct for the air is provided with heating means for heating the air.

7. Apparatus as claimed in any one of claims 4 to 6, wherein the duct for the air comprises an annular outlet end portion surrounding an outlet end portion of the duct for the medium, the outlet end portion of each of the ducts communicating with the mixing chamber by way of a plurality of feed bores.

8. Apparatus as claimed in claim 7, wherein at least some of the feed bores communicating with the outlet end portion of the duct for the medium extend divergently in direction towards the mixing chamber and at least some of the feed bores communicating with the outlet end portion of the duct for the air extend convergently in direction towards the mixing chamber

9. Apparatus substantially as hereinbefore described with reference to the accompanying drawings.