Air-Gas Pilot Burner that can Operate with Oxygen

Abstract

A system includes at least one pilot burner and one more powerful main burner. The pilot burner includes at least a first tube open at an end and including at least a first feedline capable of injecting a combustible gas into the first tube. The pilot burner further includes at least a second tube open at an end and including at least a third feedline capable of injecting an oxygen-rich gas into the second tube. The pilot burner further includes at least a second feedline capable of feeding the first tube with air.

Description

[0001]This application claims the benefit of priority under 35 U.S.C. §119 (a) and (b) to French Application No. 0950256, filed Jan. 16, 2009, the entire contents of which are incorporated herein by reference.BACKGROUND[0002]1. Field of the Invention[0003]The present invention relates to a pilot burner for igniting or maintaining a flame of a main burner, to an installation comprising a boiler or furnace capable of implementing the technology referred to as “oxy-fuel combustion” and such a pilot burner, and to a process for employing said installation, especially for making it easier to capture the carbon dioxide, or CO2, in the flue gases exiting the boiler or furnace.[0004]2. Related Art[0005]A pilot burner is a device capable of generating what is called a “pilot” flame intended to ignite or maintain the flame of at least one more powerful main burner. Typically, a main burner releases 5 to 1000 times more energy than a pilot burner. In one particular configuration, the pilot bur...

AI Technical Summary

Benefits of technology

[0013]The object of the present invention is to alleviate some or all of the drawbacks of the prior art mentioned above, i.e. in particular to obtain a high-quality pilot flame having the required stability and safety, while operating both with air and with an oxygen-rich gas as oxidizer for the pilot burner.

[0041]Other principles for detecting the presence of a flame may be used, for example by measuring the ultraviolet (UV) radiation. This is because combustion of the hydrogen present in the fuel for the pilot burner emits substantial radiation in the UV spectrum. Another principle is based on detecting the infrared (IR) radiation emitted by the combustion. These methods may be employed without distinction. The principle of this pilot burner makes it possible to use the same flame detector for the oxy-fuel combustion operating mode and for the operating mode using air. Different flame detection means specific to each of these modes may also be chosen. The detection means are positioned according to the prior art, in general relative to the position of the flame root in order to allow reliable detection.

[0046]Independently of their general shape, one or both of the tubes may have a convergent terminal portion, i.e. the flow bores narrow down in the flow direction before the gas outlet. The tubes may also have a constriction near their outlet. The expression “near the outlet” means the terminal portion of the tube that goes from its outlet back to 5 times the hydraulic diameter of the outlet cross section of the tube. This constriction allows the gas ejection velocity to be increased and prevents flash-back.

[0048]To enhance the flame properties, one or both tubes may have a convergent portion that converges in the flow direction near its outlet.

[0076]When the boiler or furnace is made to operate in air mode, for example during a start-up phase, it may be very advantageous and without any risk for the pilot burner also to be operated in air mode (step a)). This avoids consuming oxygen-rich gas and avoids having to start up the air separation unit just for the pilot burner.

Problems solved by technology

This pilot burner does not provide a very stable flame under all operating conditions.

However, in this configuration it is not possible to operate in oxy-fuel combustion mode, i.e. with an oxygen-rich gas as oxidizer.

In fact, such a pilot burner cannot operate correctly with any type of oxidizer.

In particular, although it operates correctly with an oxygen-rich oxidizer, which is its purpose, it will not operate well with air as oxidizer.

It is difficult for such a change in oxidizer to be compatible with the reliability required of a pilot flame, which reliability determines the safety of the boiler or furnace.

However, it may prove to be very troublesome to have to feed the pilot burner or burners for these main burners with oxygen-rich gas as it may require an air separation unit to be started up or maintained in operation.

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