Cyclone Burner
A description is given of a cyclone burner for converting solid fuel comprising a substantially rotationally-symmetric whirling chamber (1), means for introducing gas and fuel into the whirling chamber (1), means for bringing the gas and fuel into rotation in the whirling chamber (1) and an outlet (4) for the gas and the converted fuel where the outlet (4) is centrally positioned in the outlet end (3) of the whirling chamber (1). The cyclone burner is characterized in that the whirling chamber (1) comprises a conical shaped portion (2) having the smaller diameter furthest from the outlet end (3) and in that the means (5) for introducing gas are connected to the whirling chamber (1) along the length of the conical shaped portion (2).
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The present invention relates to a cyclone burner for converting solid fuel comprising a substantially rotationally-symmetric whirling chamber, means for introducing gas and fuel into the whirling chamber, means for bringing the gas and fuel into rotation in the whirling chamber and an outlet for the gas and the converted fuel where the outlet is centrally positioned in the outlet end of the whirling chamber.
Cyclone burners of the above-mentioned type are well known in the industry, being used inter alia in power plants. From U.S. Pat. No. 7,261,047 BB, for example, is known a horizontally positioned cyclone burner where the fuel is introduced at the back end of a cyclone chamber, whereafter it flows along with the gas stream towards a conical outlet end where particle separation takes place. In this type of cyclone burner, the fuel must be substantially converted before it reaches the outlet end, otherwise the result would be build-up of fuel at this location, eventually leading to complete interruption of the fuel flow and/or its discharge by entrainment out of the chamber. The associated disadvantage is that the particles must be so finely divided as to ensure almost complete conversion of the particles before they reach the outlet end of the burner. As a result, the total amount of retained fuel in the compartment will be at a comparatively modest level, therefore necessitating an unnecessary degree of comminution of the fuel in order to ensure an acceptable degree of conversion for a given chamber volume. Another consequence of the design is that the fuel will not be substantially distributed along the length of the compartment, but instead it will accumulate at one of the ends of the chamber, entailing poor control of the temperature distribution in the chamber and leading to undesirable formation of slags.
It is an objective of the present invention to provide a cyclone burner whereby the aforementioned disadvantages are eliminated or significantly reduced.
This is achieved by a cyclone burner of the kind mentioned in the introduction and being characterized in that the whirling chamber comprises a conical shaped portion having the smaller diameter furthest from the outlet end and in that the means for introducing gas are connected to the whirling chamber along the length of the conical shaped portion.
Hereby it is obtained that the gas and fuel are forcibly led along the wall of the conical shaped portion of the whirling chamber back towards the back end of the whirling chamber at which location they will subsequently be led towards the eddy flow centrally in the whirling chamber and then led to and discharged through the outlet. Hence a significant amount of fuel can be retained, thereby reducing the need for comminuting the fuel to a very small particle size. The angle of the conical shaped portion of the whirling chamber relative to the centre axis of the whirling chamber will influence the effect of the centrifugal counter force acting on the rotating fuel in the whirling chamber. At a given gas stream and gas velocity, a large angle will allow a greater amount of fuel to be retained than achievable if a smaller angle is applied for the same gas stream and gas velocity. However, if the angle is too big the whirling chamber may lose its self-discharging capability if excessively filled, potentially giving rise to an undesirable accumulation of the fuel. Therefore, the angle is also important in terms of preventing accumulation of fuel. It is preferred that the angle of the conical shaped portion is kept within the range of 5 to 20 degrees. The angle for optimization of operating characteristics varies in dependence of quality, size and type of fuel.
Converted fuel is taken to mean fuel which has been introduced to the whirling chamber, where the fuel has undergone combustion, pyrolysis, gasification and/or mechanical comminution due to forces of collision and friction.
It is preferred that the predominant portion or the entire whirling chamber is conically and that the means for introducing gas are arranged over the whole conical shaped portion in the longitudinal direction of the cyclone burner. The cyclone burner may be arranged inclined, however, it is preferred that the cyclone burner is arranged horizontally.
The means for bringing the gas and the fuel into rotation in the whirling chamber may in principle comprise any suitable means as long as they are capable of bringing the gases and fuel into rotation. For example, the means may comprise a number of fixed devices in the whirling chamber which are formed and positioned so that they will impart rotation to the gas and the fuel. However, it is preferred that the means for introducing gas (for example air, O2, H2O or CO2, mixed or pure) are connected substantially tangentially to the conical shaped portion. The means for introducing fuel may also comprise a tangentially arranged fuel inlet. Generally a tangential inlet, which is a common feature of cyclone separators, will cause an introduced medium to be brought into rotation in the cyclone chamber when being fed hereto at sufficient velocity.
The means for introducing gas, which are connected to the whirling chamber along the length the conical shaped portion, may in principle comprise any suitable means as long as they are capable of introducing the gas along the conical shaped portion. The means are preferably arranged tangentially over at least the major part of the conical shaped portion in the longitudinal direction of the cyclone burner. For example the means may comprise a gas inlet with a single opening extending over the major part of the length of the conical shaped portion. However, it is preferred that the means for introducing gas comprise a number of gas inlets, at least two, arranged one after another along the length of the conical shaped portion, preferably along the major part of the conical shaped portion. Such tangentially inlets arranged at the conical shaped portion in the longitudinal direction of the cyclone burner combined with a fuel inlet connected to the half of the whirling chamber which is closest to the outlet end, will force the fuel and gas along the wall of the conical shaped portion of the whirling chamber back towards the back end of the whirling chamber. During this movement the fuel will be converted and subsequently led towards the eddy flow centrally in the whirling chamber for being transported to and discharged through the outlet.
It is further preferred that the end faces at each end of the whirling chamber are plane. One or several gas nozzles may advantageously be fitted to the back end face for co-firing with other fuels, such as oil, gas, coal or sawdust.
It is preferred that the outlet comprises an outlet duct which protrudes into the whirling chamber in order to stabilize the eddy flow in the whirling chamber.
In one embodiment the means for introducing fuel is connected to that half of the whirling chamber which is closest to the outlet end.
The cyclone burner may in principle be used for all types of industrial processes which require a source of heat like rotary kilns or power plant boilers. For example it may be used for manufacturing cement clinker where cement raw materials are introduced to a cement or mineral processing plant where raw materials are supplied with thermal energy and converted into cement clinker or other mineral products, e.g. burned lime. Here a cyclone burner may at least provide some of the thermal energy. If the cyclone burner is used for processing materials in a rotary kiln, its outlet may be fitted to a burner lance extending into the rotary kiln, thereby allowing the converted fuel to be fed and ignited at a distance further inside the rotary kiln. With this type of arrangement, it will be possible to use heated process gases, e.g. from a clinker cooler, for the gas inlets connected to the whirling chamber.
The invention will now be explained in further details with reference to the drawing, being diagrammatical, and where
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Claims
1. A cyclone burner for converting solid fuel comprising a substantially rotationally-symmetric whirling chamber (1), means (5, 6) for introducing gas and fuel into the whirling chamber (1), means for bringing the gas and fuel into rotation in the whirling chamber (1) and an outlet (4) for the gas and the converted fuel where the outlet (4) is centrally positioned in the outlet end (3) of the whirling chamber (1) characterized in that the whirling chamber (1) comprises a conical shaped portion (2) having the smaller diameter furthest from the outlet end (3) and in that the means (5) for introducing gas are connected to the whirling chamber (1) along the length of the conical shaped portion (2).
2. A cyclone burner according to claim 1 characterized in that the means (5) for introducing gas are connected tangentially to the conical shaped portion (2).
3. A cyclone burner according to claim 1 or 2 characterized in that the means for introducing gas comprise a number of gas inlets (5a) arranged one after another along the length of the conical shaped portion (2).
4. A cyclone burner according to claim 1 or 2 characterized in that the means for introducing gas comprise a gas inlet (5c) with a single opening extending over the major part of the length of the conical shaped portion (2).
5. A cyclone burner according to any preceding claim characterized in that the means for introducing fuel comprise a tangentially arranged fuel inlet (6).
6. A cyclone burner according to any preceding claim characterized in that the angle of the conical shaped portion (2) relative to the centre axis (8) of the whirling chamber (1) is between of 5 and 20 degrees.
7. A cyclone burner according to any preceding claim characterized in that the predominant portion or the entire whirling chamber (1) is conically.
8. A cyclone burner according to any preceding claim characterized in that the cyclone burner is arranged horizontally.
9. A cyclone burner according to any preceding claim characterized in that the outlet (4) comprises an outlet duct which protrudes into the whirling chamber (1).
10. A cyclone burner according to any preceding claim characterized in that the means (6) for introducing fuel is connected to that half of the whirling chamber (1) which is closest to the outlet end (3).
Type: Application
Filed: Nov 25, 2011
Publication Date: May 14, 2015
Applicant: FLSMIDTH A/S (Valby)
Inventors: Mads Nielsen (Gadstrup), Mads Peter Rasmussen (Farup), Karl Emil Andreas Strömberg (Sodra Sandby), Mads Kristian Ullitz (Aalborg), Jagannath Pandian Manohar (Chennai)
Application Number: 14/359,360
International Classification: F23D 1/02 (20060101); F23D 1/00 (20060101); F23M 20/00 (20060101);