This is the first application filed for the present invention.
The present invention relates generally to burning and combusting of hydrocarbons and, in particular, to burners or combustors for heaters.
Burning hydrocarbons in air produces NOx (mono-nitrogen oxides such as nitrogen oxide and nitrogen dioxide). NOx emissions are known to be deleterious for the ozone in the stratosphere. Atmospheric NOx also forms nitric acid, which contributes to acid rain. Because of these significant environmental concerns, it is highly desirable to reduce NOx emissions in the burning or combustion of hydrocarbon fuels. Furthermore, in some jurisdictions, environmental regulations limit the amount of NOx emissions that a burner may emit.
In general, the present invention provides a low NOx burner, i.e. a burner that emits reduced NOx.
Accordingly, one aspect of the present invention is a burner having a housing that includes a burner head defining a gas manifold including an upstream wall, a downstream wall, and a sidewall and a primary flame zone downstream of the burner head, a gas inlet in the burner head for connecting to and receiving gas from a gas line, a plurality of flow-through air vents disposed around a center of the burner head and extending as continuous passageways through the gas manifold of the the burner head thereby enabling cold core air to flow from an annular core space upstream of the burner head to the primary flame zone downstream of the burner head, a plurality of premix air vents in fluid communication with the manifold for premixing air and gas within the manifold and for emitting premixed air and gas into the primary flame zone, a plurality of staging pipes extending in fluid communication with and from the manifold into the primary flame zone for conveying gas into the primary flame zone, and an ignition device extending into the primary flame zone.
Another aspect of the present invention is a heater including a burner that has a blower and a burner. The burner has a housing that includes a burner head defining a gas manifold including an upstream wall, a downstream wall, and a sidewall and a primary flame zone downstream of the burner head, a gas inlet in the burner head for connecting to and receiving gas from a gas line, a plurality of flow-through air vents disposed around a center of the burner head and extending as continuous passageways through the gas manifold of the burner head thereby enabling cold core air to flow from an annular core space upstream of the burner head to the primary flame zone downstream of the burner head, a plurality of premix air vents in fluid communication with the manifold for premixing air and gas within the manifold and for emitting premixed air and gas into the primary flame zone, a plurality of staging pipes extending in fluid communication with and from the manifold into the primary flame zone for conveying gas into the primary flame zone, and an ignition device extending into the primary flame zone.
Yet another aspect of the present invention is a method of burning a combustible hydrocarbon gas in air while minimizing the emission of NOx. The method entails supplying the combustible hydrocarbon gas through a gas inlet to a burner head defining a gas manifold including an upstream wall, a downstream wall, and a sidewall through which the gas flows into a primary flame zone downstream of the burner head through a plurality of staging pipes extending in fluid communication with and from the manifold into the primary flame zone, flowing air through a plurality of flow-through air vents disposed in the burner head around a center of the burner head enabling cold core air to flow from an annular core space upstream of the burner head through continuous passageways in the gas manifold of the burner head to the primary flame zone downstream of the burner head, premixing a portion of the gas entering the manifold with air and emitting premixed air and gas into the primary flame zone, and igniting the gas and air in the primary flame zone.
The details and particulars of these aspects of the invention will now be described below, by way of example, with reference to the attached drawings.
Further features and advantages of the present technology will become apparent from the following detailed description, taken in combination with the appended drawings, in which:
It will be noted that throughout the appended drawings, like features are identified by like reference numerals.
A burner, generally designated by reference numeral 10, is illustrated by way of example in
For the purposes of this specification, the expression “combustible hydrocarbon gas” (herein referred to simply as “gas”) is meant to include any flammable vapour state hydrocarbon gas or combustible petroleum product such as propane, natural gas, butane, methane, or any other petroleum gas, or alcohol-based fuels such as ethanol, etc.
In the embodiment illustrated by way of example in
As further illustrated by way of example in
Although
To promote turbulent mixing, outlets 31 of each respective staging pipe 30 may be bevelled at an angle β of 30-90 degrees from a transverse plane through the pipe. As well, the bevelled outlets are oriented at an angle θ of 25-60 degrees relative to a radial line extending from the respective staging pipe to the center of the burner head. The outlets 31 are so oriented in order to swirl the gas emitted by the staging pipes 30. In the specific embodiment illustrated in
In one embodiment, the outlets 31 are bevelled at an angle β of 40-50 degrees as illustrated in
This burner may operate vertically, horizontally or in any other spatial orientation.
The burner may be constructed of stainless steel or any other equivalent or suitable material. The surfaces of the burner exposed to extreme heat (i.e. the primary flame zone and bottom face of the burner head) may furthermore be coated with a heat-resistant coating to prolong service life.
The burner may be used, or adapted for use, in a heater equipped with a blower 50 such as the one depicted by way of example in
The burner also enables a method of burning a combustible hydrocarbon gas in air while producing reduced NOx emissions. The method entails supplying the combustible hydrocarbon gas through a gas inlet to a burner head defining a gas manifold through which the gas flows into a primary flame zone downstream of the burner head through a plurality of staging pipes extending from the manifold into the primary flame zone, flowing air through a plurality of flow-through air vents disposed in the burner head around a center of the burner head enabling cold core air to flow from an annular core space upstream of the burner head to the primary flame zone downstream of the burner head, premixing a portion of the gas entering the manifold with air and emitting premixed air and gas into the primary flame zone, and igniting the gas and air in the primary flame zone.
In one embodiment of the method, supplying the gas involves swirling the gas exiting the outlets of each respective staging pipe by orienting the outlets at 25-60 degrees, more particularly 25-35 degrees relative to a radial line extending from the respective staging pipe to a center of the burner head. Supplying the gas may also entail directing the gas exiting the outlets of each respective staging pipe in the burner at an angle by beveling the outlets at 30-90 degrees or more particularly at 40-50 degrees. In one specific embodiment, the method may be performed by swirling the gas using staging pipes that have outlets oriented at 30 degrees to the radial line and being beveled at 45 degrees. Premixing may be performed, in one embodiment, by using premix air vents that are disposed radially outwardly of the flow-through air vents so that the supplying of the gas is performed by the staging pipes that are disposed radially outwardly of the premix air vents.
The burner produces low NOx emissions in a compact design. The shorter length of the burner provides for a more compact heater with a superior power density relative to axially staged burners. The injection of air via the flow-through air vents 24 has the effect of cooling the core of the flame, thereby reducing the amount of NOx being produced in the primary flame zone. Tests have demonstrated emissions in the range of 9-19 ppm NOx for a burner embodying the invention whereas a conventional comparable burner would produce approximately 100 ppm NOx.
This invention has been described in terms of specific examples, embodiments, implementations and configurations which are intended to be exemplary only. Persons of ordinary skill in the art will appreciate that obvious variations, modifications and refinements may be made without departing from the scope of the present invention. The scope of the exclusive right sought by the Applicant is therefore intended to be limited solely by the appended claims.
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Number | Date | Country | |
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20150050605 A1 | Feb 2015 | US |