CLIAMS:1. An improved pulverized coal combination fuel burner, having
at least one dummy nozzle (1) with at least one swirler, at least one convergent part (3) at its back, and at least one straight portion of at least one dummy pipe (4) having diameter;
at least one second pipe (5); and
at least one third pipe (6);
said improved pulverized coal combination fuel burner CHARACTERIZED BY COMPRISING:
said dummy nozzle (1) having said swirler made of one or more vanes (2) at a tip of said dummy nozzle (1);
said converging part (3) of said dummy nozzle (1) is associated with said straight portion of said dummy pipe (4);
said second pipe (5) encloses said dummy nozzle (1) such that it maintains a required primary air velocity through an annulus space, between said dummy nozzle (1) and said second concentric pipe (5), for carrying a pulverized coal along with primary air in mixture form to at least one burner;
said third pipe (6) encloses said second pipe (5) thereby sending secondary air to said burner, wherein said secondary air mixes with said mixture.

2. The improved pulverized coal combination fuel burner as claimed in claim 1, wherein said dummy pipe (4) is of higher diameter as compared to a tip of said dummy nozzle (1), wherein a diameter of said dummy pipe (4) is preferably selected from a range of 150 mm to 250 mm.

3. The improved pulverized coal combination fuel burner as claimed in claims 1 and 2, wherein said dummy nozzle (1) is configured to accommodate said swirler of a particular dimension.

4. The improved pulverized coal combination fuel burner as claimed in any of the preceding claims, wherein said second pipe (5) is of higher diameter as compared to said dummy nozzle (1) and said dummy pipe (4) , and said third pipe (6) is of higher diameter as compared to said second pipe (5) thereby forming a concentric structure.

5. The improved pulverized coal combination fuel burner as claimed in any of the preceding claims, wherein a volute is connected to said second pipe (5) at said annulus space thereby sending said pulverized coal along with primary air tangentially into said burner causing rotating or in a whirling motion at a burner nozzle.

6. The improved pulverized coal combination fuel burner as claimed in any of the preceding claims, wherein said third pipe (6) is associated with said volute and configured to provide tangential entry of said secondary air into said burner causing rotating or in a whirling motion at a burner nozzle.

7. The improved pulverized coal combination fuel burner as claimed in any of the preceding claims, wherein said dummy pipe (4) enables to view a combustion flame, and/or is configured for igniting said pulverized burner, and/or for inserting central oil gun for combustion of liquid fuel to supply an additional heat.

8. The improved pulverized coal combination fuel burner as claimed in any of the preceding claims, wherein said vanes of said swirler (2) are of suitable angle, and the said angle is selected preferably ranging from 10 degree to 60 degree.

9. The improved pulverized coal combination fuel burner as claimed in any of the preceding claims, wherein said dummy nozzle (1) is preferably of length 100 to 300 mm which enables a pre-mixing of the pulverized coal with primary air to obtain a coal-air mixture, and pre-heating said coal-air mixture before combustion and in generating stable flame with pulverized coal having CV less than 3500 kcal/kg’.

10. The improved pulverized coal combination fuel burner as claimed in any of the preceding claims, wherein the primary air pressure preferably is from 180 to 400 mm WG.

11. The improved pulverized coal combination fuel burner as claimed in any of the preceding claims, wherein a pressure of said secondary air is preferable from 10 to 100 mm WG.

12. The improved pulverized coal combination fuel burner as claimed in any of the preceding claims comprises a flame igniter for initial light up.

13. A method using an improved pulverized coal combination fuel burner, said method CHARACTERIZED BY COMPRISING:
providing at least one swirler made of one or more vanes (2) at a tip of at least one a dummy nozzle (1);
providing at least one convergent part (3) at a back of said dummy nozzle (1);
providing at least one straight portion of at least one dummy pipe (4) for associating with said convergent part (3);
providing at least one second pipe (5) enclosing said dummy nozzle (1) so as to maintain a required primary air velocity through an annulus space, between said dummy nozzle (1) and said second concentric pipe (5), for carrying a pulverized coal along with air;
providing at least one third pipe (6) enclosing said second pipe (5) thereby sending a secondary air to at least one burner, wherein a volute is connected to said second pipe (5) at said annulus space thereby sending said pulverized coal along with air tangentially to said second pipe (5), and said third pipe (6) is associated with said volute and configured to provide said secondary air causing tangential entry of said pulverized coal along with primary air in mixture form into said burner.
,TagSPECI:TECHNIAL FIELD

The present subject matter described herein, in general, relates to fuel burner, and more particularly to a new design of pulverized coal combination fuel burner.

BACKGROUND

Pulverized coal burner uses pulverized coal of required size (75-175 micron) which is carried through the burner with primary air stream. The boilers of captive power plant in steel plants use boiler grade coal, Coke Oven (CO) gas, Blast Furnace (BF) gas and/or LD gas for meeting process steam requirement of steel plant or for running turbo-blower to supply cold blast to Blast Furnace process or for running turbo generator for electric power generation. Apart for above mentioned fuels, liquid fuel like furnace oil or tar is used in these boilers. CO gas, BF gas and LD gas are generated as by-product gases in coke ovens, blast furnaces and LD converters respectively. Tar is generated as by-product liquid fuel in coke oven batteries used for producing metallurgical grade coke for consumption in blast furnaces. Furnace oil and steam coal are purchased fuels used to meet heat load requirement in boilers of captive power plants.

Normally pulverized coal having calorific value (CV) more than 4000 Kcal/kg and ash content less than 30% is used for generation of steam. If CV goes down below 3500 Kcal/kg as well as ash content goes more than 35%, it becomes very difficult to burn pulverized coal efficiently and Loss on Ignition (LOI) in both bottom and fly-ash goes above 5%. Higher LOI means higher unburned carbon content in ash. Normally low grade coal having low CV and high ash are used along with other rich gaseous or liquid fuels in multi-fuel burner to help combustion of low grade coal.

In the existing technology, front (or wall) burner consists of two or more concentric tubes. In some design the central tube is used either as dummy pipe for inserting oil burner or for observation of coal burner flame. The second pipe is use for sending pulverized coal with primary air as carrier air. The quantity of primary air and its velocity play a crucial role in pulverized coal combustion. In some existing burner designs, rotating motion is imparted by sending the pulverized coal and air mixture through a swirler provided at the pipe tip or by sending coal–primary air mixture tangentially to the primary air pipe carrying the primary air and coal mixture. In some design, no rotating motion is imparted to the coal-primary air mixture stream i.e. neither swirler is provide at the tip of primary air pipe nor coal-primary air mixture is sent tangentially to the burner axis. The third pipe above the second concentric pipe is used for sending part of the total combustion air as secondary air for combustion of coal. In most of the designs, a swirler is provided at the tip of third pipe to impart rotating/whirling motion to secondary air stream. In some cases, the same rotating/whirling motion is imparted to the secondary air by sending secondary air tangentially to the secondary air pipe axis. In some coal burner design, part of combustion air is sent through the outermost forth pipe concentric to the third pipe.

In some pulverized coal burners, the central dummy pipe is used for sending coal-primary air mixture, second concentric pipe is used for sending secondary air stream and the third pipe is used for sending tertiary air. Rotating/whirling motion is imparted to coal-air mixture stream or air stream with the help of a swirler or by sending coal-air mixture or air stream tangentially.

The swirler is made of two or more numbers of vanes welded above a circular pipe or tube at some angle with pipe or tube axis. The angle of vane may vary from 10 degree to 60 degree. The velocities of primary, secondary and tertiary air streams and the angle of swirler play very important role in deciding the coal combustion quality and thereby LOI in fly ash and also the flame configuration / characteristics.

However, three issues exist for application of the burner technology: Firstly, in order to divide pulverized coal air flow in the primary air channel into dense flow and thin flow circumferentially, uniformly and effectively, the burner always has relatively complex structure, which may increase system resistance, increase fan load and over all assembly of supply thereby increasing burner maintenance, wear the channel, shorten life cycle of equipment and increase operation and maintenance cost of power plants; secondly, due to poor adaptability of coal, actual coal ignition and combustion stability may not reach original design requirements, and flame at outlet of the burner is always unstable during peak regulation of the boiler; and thirdly, due to poor subsequent mixing performance of primary air with pulverized coal air flow and secondary air with pulverized coal air flow at the nozzle of the burner, coal in the burner cannot be burnt out, possibly increasing loss.

Thus, in view of the above mentioned drawbacks, there exists a need to provide a new design of pulverized coal combination fuel burner that enhances the combustion of fuel having low calorific value and generating a stable flame in the boiler.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

Existing Technical Problem: Conventionally, in addition to the above mentioned problems in the background section, it is very difficult to burn coal having CV less than 3500 Kcal/kg efficiently, and to keep LOI in fly ash below 5%. It requires desired mixing rate between coal and combustion air and pre-heating of coal-air mixture for efficient coal combustion and stable flame.

Technical Solution provided in the present invention: In the present invention, a central dummy pipe and primary air pipe carrying the coal with primary air at desired proportion and secondary air nozzle of suitable dimension are worked out and designed. The primary air nozzle is provided with swirler to enhance rotating/whirling motion to pulverized coal and primary air mixture inside the burner tip. A pre-mixing length (100-300mm) inside the burner nozzle is created by ending the tips of central dummy and primary air pipes before the burner tip to enhance pre-heating of coal-air mixture before coal combustion inside the boiler combustion chamber. This arrangement of primary air with pulverized coal coming at desired velocity through primary air nozzle having a swirler of suitable vane angle, pre-mixing of air with pulverized coal inside the burner nozzle and pre-heating of coal-air mixture has ensured desired rate of coal combustion of low CV coal and achieving stable flame. The present invention helps in improving combustion of coal having CV less than 3500 Kcal/kg in boiler and restricted LOI in fly ash below 5%.

In one implementation of the present invention relates to the design of a burner for burning pulverized coal having low calorific value for generating a stable flame in boiler.

In one implementation, the present invention provides a new design of pulverized coal combination fuel burner without any tertiary air.

In one implementation, only primary air carries the pulverized coal. The secondary and tertiary air streams do not carry pulverized coal; they mix with primary air and coal streams after the tip of primary air pipe. In this invention mixing of secondary air starts 100-300mm before the outermost pipe tip and that is why it is being called as pre-mixing length.

Accordingly, in one implementation, an improved pulverized coal combination fuel burner, having at least one dummy nozzle (1) with at least one swirler, at least one convergent part (3) at its back, and at least one straight portion of at least one dummy pipe (4); at least one second pipe (5); and at least one third pipe (6); is disclosed. The improved pulverized coal combination fuel burner is CHARACTERIZED BY COMPRISING: said dummy nozzle (1) having said swirler made of one or more vanes (2) at a tip of said dummy nozzle (1); said converging part (3) of said dummy nozzle (1) is associated with said straight portion of said dummy pipe (4); said second pipe (5) encloses said dummy nozzle (1) such that it maintains a required air velocity through an annulus space, between said dummy nozzle (1) and said second concentric pipe (5), for carrying a pulverized coal along with primary air in mixture form; said third pipe (6) encloses said second pipe (5) thereby sending said secondary air along pulverized coal along with primary air to at least one burner.

In one implementation, a method using an improved pulverized coal combination fuel burner is disclosed. The method is CHARACTERIZED BY COMPRISING the steps of:
§ providing at least one swirler made of one or more vanes (2) at a tip of at least one a dummy nozzle (1);
§ providing at least one convergent part (3) at a back of said dummy nozzle (1);
§ providing at least one straight portion of at least one dummy pipe (4) for associating with said convergent part (3);
§ providing at least one second pipe (5) enclosing said dummy nozzle (1) so as to maintain a required primary air velocity through an annulus space, between said dummy nozzle (1) and said second concentric pipe (5), for carrying a pulverized coal along with primary air;
§ providing at least one third pipe (6) enclosing said second pipe (5) thereby sending a secondary air to at least one burner, wherein a volute is connected to said second pipe (5) at said annulus space thereby sending said pulverized coal along with air tangentially to said second pipe (5), and said third pipe (6) is associated with said volute and configured to provide said secondary air causing a tangential entry of said pulverized coal along with primary air into said burner.

In one implementation, to improve pulverized combustion of low CV coal having CV less than 3500 kcal/kg and restrict the LOI content in fly ash below 5%, a new pulverized coal burner design was developed and successfully implemented in boiler#1 of Bhilai Steel Plant.

In one implementation, the rotating/whirling motion of primary air-coal mixture issuing through the annulus space between dummy nozzle (1) and primary air pipe (5) is enhanced by addition of a swirler (2) at the tip of primary air pipe. The pre-mixing length provided at burner nozzle helps in pre-mixing and pre-heating pulverized coal-air mixture before combustion

Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

Figure 1 illustrates a new design of pulverized coal combination fuel burner without any tertiary air, as shown, in accordance with an embodiment of the present subject matter.

Figure 2 illustrates a Back end view of above burner, as shown, in accordance with an embodiment of the present subject matter.

Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE INVENTION

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

While aspects of described a new design of pulverized coal combination fuel burner without any tertiary air may be implemented in any number of different computing systems, environments, and/or configurations, the embodiments are described in the context of the following exemplary system.

In one implementation, a burner design consisting three concentric pipes of suitable dimensions have been worked out to obtain desired mixing of pulverized coal and air streams at the burner nozzle to generate stable flame. A swirler of suitable vane angle has been provided to the primary air pipe carrying the pulverized coal-primary air mixture. A concentric dummy pipe of suitable size (that may be preferably between 150-250 mm diameter) is provided at the center of the burner to provide sufficient space (minimum 50 mm) to attach a swirler inside the primary air pipe (second pipe) and over the dummy pipe. This dummy pipe can also be used for inserting an oil firing gun to increase heat load to the burner. This central dummy pipe can also be used for observation of coal flame and igniting the pulverized coal burner. Over the primary air (second pipe) pipe, a third pipe is provided for sending secondary air for coal combustion. Both secondary and primary air enters tangentially to the burner axis to attain swirling/whirling motion and turbulence at the burner nozzle. Unlike primary air pipe, no swirler is provided in secondary air stream to enhance the swirling/whirling motion in and turbulence secondary air stream.

A suitable pre-mixing length (100-300mm) is created by ending the tips of central dummy and primary air pipes before the burner tip to enhance pre-mixing of pulverized coal and air inside the burner nozzle and also for pre-heating of pulverized coal-air mixture before entering the combustion chamber of the boiler which has helped in improving coal combustion and generating stable flame even with coal having CV less than 3500 kcal/kg.

Accordingly, in one implementation, an improved pulverized coal combination fuel burner, having at least one dummy nozzle (1) with at least one swirler, at least one convergent part (3) at its back, and at least one straight portion of at least one dummy pipe (4); at least one second pipe (5); and at least one third pipe (6); is disclosed. The improved pulverized coal combination fuel burner is CHARACTERIZED BY COMPRISING: said dummy nozzle (1) having said swirler made of one or more vanes (2) at a tip of said dummy nozzle (1); said converging part (3) of said dummy nozzle (1) is associated with said straight portion of said dummy pipe (4); said second pipe (5) encloses said dummy nozzle (1) such that it maintains a required air velocity through an annulus space, between said dummy nozzle (1) and said second concentric pipe (5), for carrying a pulverized coal along with primary air in mixture form; said third pipe (6) encloses said second pipe (5) thereby sending said pulverized coal along with air to at least one burner using a secondary air.

In one implementation, a method using an improved pulverized coal combination fuel burner is disclosed. The method is CHARACTERIZED BY COMPRISING the steps of:
· providing at least one swirler made of one or more vanes (2) at a tip of at least one dummy nozzle (1);
· providing at least one convergent part (3) at a back of said dummy nozzle (1);
· providing at least one straight portion of at least one dummy pipe (4) for associating with said convergent part (3);
· providing at least one second pipe (5) enclosing said dummy nozzle (1) so as to maintain a required primary air velocity through an annulus space, between said dummy nozzle (1) and said second concentric pipe (5), for carrying a pulverized coal along with air;
· providing at least one third pipe (6) enclosing said second pipe (5) thereby sending a secondary air to at least one burner, wherein a volute is connected to said second pipe (5) at said annulus space thereby sending said pulverized coal along with air tangentially to said second pipe (5), and said third pipe (6) is associated with said volute and configured to provide tangential entry of said pulverized coal along with air into said burner.

In one implementation, a dummy nozzle (1) and primary air pipe (5) of suitable dimensions to send the coal-primary air mixture through the annulus space between dummy nozzle (1) and primary air pipe (5) at suitable velocity.

In one implementation, a swirler (2) made of vanes of suitable angle (10 degree-60 degree) is provided over the dummy nozzle (1) and inside the tip of primary air pipe (5) to enhance the rotating/whirling motion of primary air-coal mixture.

In one implementation, a pre-mixing length (100-300mm) inside the burner nozzle helps in pre-heating of coal-air mixture before combustion and in generating stable flame with pulverized coal having CV less than 3500 kcal/kg.

In one implementation, primary air pressure requirement is 180 to 400 mm WG and secondary air pressure requirement is 10 to 100 mm WG near the burner.

In one implementation, a swirler (2) made of vanes of suitable angle (10 degree-60 degree) is provided over the dummy nozzle (1) and inside the tip of primary air pipe (5) to enhance the rotating/whirling motion of primary air-coal mixture and maintain suitable air velocity for improved turbulence and fuel combustion.

In one implementation, a pre-mixing length (100-300mm) inside the burner nozzle improving pre-heating of coal-air mixture before combustion and generating stable flame with pulverized coal is having CV less than 3500 kcal/kg.

In one implementation, Flame igniter may be provided to the burner for initial light up. It may be understood that a Hot face (i.e. inside surface) of boiler walls are covered by vertical water tubes. If there is no opening by the side of burner, the dummy pipe can be used for igniting the burner, in this case flame igniter may be used in the present invention.

In one implementation, said dummy pipe (4) is of higher diameter as compared to a tip of said dummy nozzle (1).

In one implementation, said dummy nozzle (1) is configured to accommodate said swirler of a particular dimension.

In one implementation, said second pipe (5) is of higher diameter as compared to said dummy nozzle (1) and said dummy pipe (4) , and said third pipe (6) is of higher diameter as compared to said second pipe (5) thereby forming a concentric structure.

In one implementation, a volute is connected to the second pipe (5) at said annulus space thereby sending said pulverized coal along with air tangentially to said second pipe (5).

In one implementation, said third pipe (6) is associated with said volute and configured to provide secondary air causing tangential entry of said pulverized coal along with air in mixture form into said burner.

In one implementation, said dummy pipe (4) enables to view a combustion flame, and/or is configured for igniting said pulverized burner, and/or for inserting central oil gun for combustion of liquid fuel to supply an additional heat.

In one implementation, said pulverized coal along with air is carried in a rotating or in a whirling motion.

In one implementation, said vanes of said swirler (2) are of suitable angle, and the said angle is selected preferably ranging from 10 degree to 60 degree.

In one implementation, the dummy nozzle (1) is preferably of length 100 to 300 mm which enables a pre-mixing of the pulverized coal with air which helps in pre-heating of coal-air mixture before combustion and in generating stable flame with pulverized coal having CV less than 3500 kcal/kg.

In one implementation, the primary air pressure preferably is from 180 to 400 mm WG.

In one implementation, a pressure of said secondary air is preferable from 10 to 100 mm WG.

In one implementation, the improved pulverized coal combination fuel burner comprises of a dummy nozzle (1) having a swirler made of vanes (2) at its tip. The dummy nozzle tip is having a converging part (3) at its back which is connected to straight portion of the dummy pipe (4) having higher diameter. The diameter of the dummy nozzle (1) may be kept smaller to accommodate the swirler (2) of required dimensions. The second pipe (5) is a straight pipe of suitable diameter to maintain required primary air velocity through the annulus space between dummy nozzle (1) and the second concentric pipe (5). Pulverized coal is carried by this primary air. A volute is connected to the back end of the primary air pipe to send primary air-coal mixture tangentially to the primary air pipe. A third pipe (6) above the primary air pipe is provided for sending secondary air to the coal burner. The outermost secondary air pipe (6) is also connected to a volute at its back for tangential entry of secondary air to the burner. The central dummy pipe (4) can be used for viewing the coal combustion flame or for igniting pulverized coal burner or for inserting central oil gun for combustion of liquid fuel to supply additional heat load.

In the new invention, the rotating/whirling motion of primary air-coal mixture issuing through the annulus space between dummy nozzle (1) and primary air pipe (5) is enhanced by addition of a swirler (2) at the tip of primary air pipe. The pre-mixing length provided at burner nozzle helps in pre-mixing and pre-heating pulverized coal-air mixture before combustion. As air and coal mixture is not confined into primary air pipe (5), the coal-air mixture may receive heat radiated by already heated combustion chamber of boiler in order to achieve the pre-heating.

The illustrations of arrangements described herein are intended to provide a general understanding of the structure of various embodiments, and they are not intended to serve as a complete description of all the elements and features of apparatus and systems that might make use of the structures described herein. Many other arrangements will be apparent to those of skill in the art upon reviewing the above description. Other arrangements may be utilized and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. Figures are also merely representational and may not be drawn to scale. Certain proportions thereof may be exaggerated, while others may be minimized. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.

Thus, although specific arrangements have been illustrated and described herein, it should be appreciated that any arrangement calculated to achieve the same purpose may be substituted for the specific arrangement shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments and arrangements of the invention. Combinations of the above arrangements, and other arrangements not specifically described herein, will be apparent to those of skill in the art upon reviewing the above description.