Title of Invention

MULTI-STREAM HIGH CAPACITY LEAN GAS BURNER

Abstract

A multi-stream high capacity lean gas burner adapted to provide supply of alternate gas and combustion air slots/passages within the burner body to facilitate rapid mixing of gas and air streams at the burner nozzle and generate stable flame with lean gas. The burner of the invention basically comprises a gas distributor adapted for distributing the lean gas into multiple streams (GS), the combustion air (AP) surrounding each of out-coming gas streams such that the interfacial area between the out-coming gas and combustion air streams and required diffusion of gas into combustion air and vise-versa is increased thereby achieving fast and uniform mixing between gas and combustion air streams for desired flame stability. The burner of the invention would favour burning lean gases such as blast furnace gases (calorific value ~ 800Kcal/Nm3) in large quantities with desired flame configuration and avoid the problems of burning such lean gases encountered in the art due to problems of effective and uniform mixing of gas and combustion air steams and related flame instability.

Full Text

FIELD OF THE INVENTION The present invention relates to a multi-stream lean gas burner and, in particular, to a multi-stream high capacity lean gas burner adapted to provide supply of alternate gas and combustion air slots/passages within the burner body to facilitate rapid mixing of gas and air streams at the burner nozzle and generate stable flame with lean gas. The burner of the invention would favour burning lean gases such as blast furnace gases (calorific value ~ 800Kcal/Nm3 ) in large quantities with desired flame configuration and avoid the problems of burning such lean gases encountered in the art due to problems of effective and uniform mixing of gas and combustion air steams and related flame instability. BACKGROUND ART Low calorific value combustible gas (lean gas) like blast furnace gas (calorific value ~ 800 K cai/N m3) is generated as by-product gas in blast furnaces of iron and steel industries in large quantities. To gainfully utilize the chemical heat content of lean gas by burning it in a combustion chamber such as boiler at a high volumetric flow rate, it is required to create quick and thorough inter mixing between gas and combustion air issuing through the burner nozzle to generate stable flame. It is presently known to effect such inter mixing of gas and combustion air by tangential entry of air and/or gas streams to the burner. In some cases, swirlers are used in air and/or gas passages to facilitate rapid mixing. In both the cases, air or gas flow is turbulised in the burner nozzle by imparting swirling/whirling motion to gas or air stream. The curved or spiral path followed by air or gas stream causes higher hydraulic resistance in gas or air path and hence required higher gas or air pressure for their flow. Burning of lean gas like blast furnace (BF) gas easily has thus been a problem mainly because lean gas required rapid mixing with combustion air for generation of stable flame. Accordingly, to burn blast furnace gas in large quantities it is important and essential that fast and uniform mixing of the gas and combustion air is achieved to attend desired flame configuration. Importantly, the diffusion of gas into combustion air and vise-versa in achieving fast and uniform mixing between gas and combustion air stream and in achieving desired flame stability has been found to be essential to make effective use of available resources of lean gases. OBJECTS OF THE INVENTION It is thus the basic object of the present invention to provide for a multi-stream high capacity lean gas burner, which would enable fast and ready uniform mixing of lean gas with combustion air and favour ready burning of lean gas like blast furnace gas in large quantity for generation of stable flame. Another object of the present invention is directed to a multi-stream lean gas burner adapted to favour effective lean gas distribution whereby the total blast furnace gas stream is distributed into multiple and radial and identical streams of blast furnace gas with the help of the gas distributor and further adapted for increased inter facial area between the out coming gas and combustion air streams by favouring supply of the required combustion air surrounding each of the out-coming gas streams. Another object of the present invention is directed to a multi-stream lean gas burner system, which would provide for alternate gas and combustion air streams whereby it would be possible to achieve improved diffusion of gas into combustion air and vise-versa and thereby, favour achieving effective fast and uniform mixing between gas and combustion air streams and maintain desired flame stability. A further object of the present invention is directed to a selective arrangement of a gas distributor for multi-stream distribution of the lean gas and air distributor for effective distribution of combustion air surrounding each of the multi-stream gas flow in a manner such that both the required fast and uniform mixing of gas and combustion air along with increased inter facial area between the out-coming gas and the combustion air is achieved for the desired flame stability. Yet another object of the present invention is directed to provide a multi-stream high capacity lean gas burner, which would enable fast and uniform mixing of gas and combustion air for desired flame configuration and would require very low combustion air pressure of only about 50-70 mm WC near the burner. Yet further object of the present invention is directed to provide a multi-stream high capacity lean gas burner, which would enable fast and uniform mixing of gas and combustion air for desired flame configuration and would require blast furnace gas pressure in the range of 300 mm WC to 500 mm WC. Another object of the present invention is directed to a multi-stream high capacity lean gas burner, which would enable fast and uniform mixing of gas and combustion air and thereby favour achieving stable flame configuration and which would involve burner turn down ratio of 1 : 4. A further object of the present invention is directed to a multi-stream high capacity lean gas burner adapted to integrate with a pilot coke over gas burner (calorific value ~ 4200K cal/N m3) of capacity 100 to 150 N m3/nour for easy burning of lean gas. SUMMARY OF THE INVENTION Thus according to the basic aspect of the present invention there is provided a multi-stream high capacity lean gas burner comprising: a gas distributor adapted for distributing the lean gas into multiple streams ; means for providing the combustion air surrounding each of out-coming gas streams such that the interfacial area between the out-coming gas and combustion air streams and required diffusion of gas into combustion air and vise-versa is increased thereby achieving fast and uniform mixing between gas and combustion air streams for desired flame stability. Importantly, in the above multi-stream high capacity lean gas burner said gas distributor is adapted to split the gas stream into multiple identical and radial gas streams along the burner axis within a main combustion air pipe. Also, the air stream flow path is further adapted to distribute main air stream uniformly around each of the out-coming gas streams. Preferably, said gas distributor and said air distributor are selectively disposed such as to generate alternate axial gas and air streams from the burner nozzle. In accordance with an aspect the multi-stream high capacity lean gas burner comprises: an air distributor assembly comprising a core air pipe with an air distributor unit and an outer main air pipe surrounding said core air pipe; a gas distributor assembly placed inside said air distributor unit and outer main air pipe comprising multiple axial gas slots spaced apart and surrounding said core air pipe such that while the gas slots provide for flow of combustible gases there through the intermediate space there between two adjacently spaced gas slots provide for the flow of combustion air being in operative communication with a combustion air source, the front and back ends of the said gas slots kept open while the back end of each air passages there between said gas slots being closed by wall member; back end of said gas distributor assembly being only operatively connected to a lean gas supply whereby gas is allowed to traverse only through gas slots preventing any gas entry in the air slots. It is thus possible by way of the above-disclosed multi-stream high capacity lean gas burner to achieve the required alternate gas and combustion air slots/passages within the burner body to facilitate rapid mixing of gas and air streams at the burner nozzle to generate stable flame with lean gas. In accordance with a preferred aspect of the invention the said multi-stream high capacity lean gas burner comprises: an air distributor assembly comprising a core air pipe with an air distributor unit and an outer main air pipe surrounding said core air pipe; a gas distributor assembly placed inside said air distributor unit and outer main air pipe comprising eight numbers of identical and radial multiple slots equally spaced apart from one another and extending along the axis of the burner and surrounding said core air pipe which are obtained of plurality of welded plates disposed perpendicularly along the length of the core air pipe , the top of the gas slots being obtained of welded curved plates with stabilizer plate of smaller dimension welded at the tip of each of the gas slots ; said gas slots adapted to provide for flow of combustible gases there through while the intermediate passages defined there between two adjacently spaced gas slots adapted for the flow of combustion air being in operative communication with a combustion air source, the front and back ends of the said gas slots kept open while the back end of each air passages there between said gas slots being closed by wall member with the back end of said gas distributor assembly being only operatively connected to a lean gas supply whereby gas is allowed to traverse only through gas slots preventing any gas entry in the air passages. said gas distributor assembly being housed inside the air distributor unit and outer main air pipe with said air distributor assembly and gas distributor assembly including the gas slots selectively dimensioned such that more than 95% of the total combustion air stream is adapted to pass through the outer main air pipe , said outer main air pipe providing the main combustion air stream over each of the gas slots and also through the air passages between adjacent gas slots along the burner axis with only about 5 to 10% of the total combustion air passing through the core air pipe provided with a swirler to impart swirling/whirling motion to the out coming core air. As would be apparent from the above disclosed burner of the invention the same basically includes an internal gas distributor adapted to split the lean gas stream into multiple radial and identical lean gas streams. An air distributor and an outer air pipe are provided to distribute main air stream uniformly over these gas streams. Preferably, in the multi-stream high capacity lean gas burner of the invention, more than 95% of the total combustion air stream pass through the outer main air pipe. The air distributor and the outer air pipe allow the main combustion air stream to pass over each of the gas slots and also through the passages between the adjacent gas slots along with burner axis. A small amount about 5 to 10% of the total combustion air is allowed to pass through the central core air pipe, which is preferably further provided with a swirler to impart swirling motion to the out-coming core air. It is thus possible by way of the above arrangement of lean gas streams and the surrounding combustion air streams at the burner nozzle to effectively and readily burn the lean gas. Importantly, the burner of the invention is found to be effective for rapid mixing of gas and combustion air at low combustion air pressure of only 50-70 mm WC by providing for increased gas/air interfacial area to generate desired stable flame with lean gas. The gas pressure requirement near the burner is 300 mm WC to 500 mm WC. Importantly, the arrangement of the gas distributor and the air distributor is such that the same favours generation of alternate axial gas and air streams issuing from the burner nozzle, which improves the mixing rate by increasing the interfacial area between the out-coming gas and air streams. According to a preferred aspect of the multi-stream lean gas burner of the invention, the core air streams is provided with a swirler to imparts swirling motion to the out-coming core air, which is only about 5 to 10% of the total combustion air requirement. Such an arrangement favours enhancing localized turbulence at the center of the burner nozzle for better flame stability. In the above-disclosed burner of the invention, provision is also made for a central dummy pipe adapted to insert electrical igniter to light up the pilot coke oven (CO) gas burner. Such an arrangement would enable the lighting of a pilot burner first to light up the high capacity blast furnace gas burner and also for flame support. BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES The objects of the invention and manner of attaining the same are explained hereunder in greater detail in relation to non-limiting exemplary illustrations of the same as per the accompanying figures wherein: Fig. 1 is a three-dimensional illustration of the multi-stream high capacity lean gas burner according to the present invention; Fig. 2 is a sectional view of the multi-stream lean gas burner of the invention; and Fig. 2A is a sectional view along AA of Fig. 2. Reference is first invited to Fig. 1, which illustrates the multi-stream high capacity lean gas burner of the invention providing for the multi-streams radial and identical eight number of lean gas streams by way of provision of spaced apart multiple slots (GS) along the axis of the burner with intermediate regions /passages (AP) there between the gas slots (GS) providing for supply of combustion air. Also to effectively surround each of the multiple streams of the gas with the combustion air, the burner is further equipped with combustion air arrangement whereby, each of the gas streams also surrounded by combustion air supply for greater interfacial interaction and ready mixing. As clearly apparent from Figure 1, such multiple streams for supply of the blast furnace gas is obtained by way of provision of gas slots (GS) with intermediate free regions (AP) providing for supply of the combustion air. As also visible in said figure, the combustion air is adapted to further surround the gas to thereby provide for a complete interaction and increased interfacial area between the out- coming gas and the combustion air. The gas distributor in the burner of the invention involving the slots is operativeiy connected to a blast furnace gas source through a connecting pipeline. Likewise, the air distributing provision in the burner is operativeiy connected to a combustion air source through a operatively connected pipe line. As further apparent from the figure to favour mixing of the gas at its lower face with the combustion air, the burner is further provided with a core axial air flow path, which is operativeiy connected to the air supply. Also further represented in said Figure is the possible integration of a Coke Oven Gas source line and the dummy pipeline accommodating for the insertion of the electrical igniter for lighting the pilot gas burner. The constructional details of the burner of Figure 1 in accordance with the invention and in particular the air distributor and the multi-stream lean gas distributor in the burner of the invention directed to achieve rapid mixing of the lean gas with combustion air for generation of stable flame is discussed hereunder in greater detail in relation to figure 2 and 2A. As clearly illustrated in Fig. 2, the burner basically comprises of an internal gas distributor (1) selectively adapted to split the lean gas streams into multiple such as preferably 8 nos. radial and identical lean gas streams by provision of gas slots (GS) as clearly shown in Fig. 2A. An air distributor (2) and an outer main pipe (1) are provided to distribute main air streams uniformly over these gas streams. An arrangement is made such that more than 95% of the total combustion gas streams pass through the outer main air pipe. The air distributor (2) and the outer air pipe (3) allow the main combustion air streams pass through the gap passage (AP) between the adjacent gas slots (GS) along the burner axis. A small amount such as 5-10% of the total combustion air is allowed to pass through the central core air pipe (4), which is preferably also provided with a swirler (12) to impart swirling motion to the out-coming core air. In particular, as would be apparent from Fig. 2, the internal gas distributor (1) is adapted to split the total blast furnace gas streams into multiple 8 Nos. gas streams. For the purpose multiple (8 Nos.) axial gas slots are provided by welding plates (5) perpendicularly along the length of the core air pipe (4) and then covering the top of the slot by welding a curved plate (7). A stabilizer plate (6) of small length such as about 300 mm is welded at the tip of each of the 8 gas slots before welding the curved plates. Equal gaps are maintained between any two adjacent gas slots (GS) for combustion air flow and also within each gas slot (GS) for gas flow. The front and the back ends of the gas slots (GS) are kept open while the back end of each of the air slot (AP) is closed by welding steel plates (8). The back end of the gas distributor (1) is welded to a blast furnace gas pipe (9). This blast furnace gas pipe is further operatively connected to a blast furnace gas connecting pipe (10). Such an arrangement allows gas flow only through the gas slots and prevents gas entering the air slots from the gas pipe (9). The gas distributor assembling (1) as shown in the figure is housed inside the air distributor (2) and outer main air pipe (3). The main air enters the outer air pipe through an air connecting pipe (11) and get distributed into the air slots (AP) inside as explained hereinbefore. The gaps for air and gas slots are selectively provided based on the calorific value of the lean gas. The arrangement is adapted such that more than 95% of the total combustion air streams pass through the outer main air pipe (3) and further through this outer air pipe the main combustion air streams passes over each of the gas slots and also through the passage (AP) between the adjacent gas slots (GS) along the burner axis. About 5-10% of the total combustion air passes through the central core air pipe (4), which is provided with a swirler (12) to impart swirling/whirling motion to the out-coming core air. Combustion air thus, passes through both the main and core air pipes from same air supply line. Within the core air pipe (4) a concentric pipe is placed for passage coke oven (CO) gas for pilot gas burner. Within the coke oven gas pipe (13), a dummy pipe (14) is placed for insertion of an electrical igniter for lighting the pilot gas burner, which can thus effectively integrate with the lean gas burner of the invention. It is thus possible by way of the above multi-stream high capacity lean gas burner to provide for distribution of the lean gas in multiple streams with each of the lean gas streams issuing through the individual gas slots to be completely surrounded by combustion air streams at the burner nozzle. The construction of the burner is thus directed for rapid mixing of gas and combustion air at low combustion air pressure (50-70 mm WC) by increasing gas-air interfacial area to generate desired stable flame with lean gas. The gas pressure requirement near the burner is 300 mm WC to 500 mm WC. The multi-streams high capacity lean gas burner of the invention is thus directed to take care of problems of burning of lean gas like blast furnace gas. Importantly, lean gas requires rapid mixing with combustion air for generation of stable flame, which can be achieved by the burner assembly of the invention, which meets the requirements of fast and uniform mixing of the gas and air to attain desired flame configuration. The gas distributor favours distribution of the lean gas such as the blast furnace gas into multiple radial and identical streams and the interfacial area between the out-coming gas and combustion air streams is advantageously increase by providing for combustion air surrounding each of the out-coming gas streams by means of the air distributor and the outer air pipe. The invention, therefore, provides for a simple yet highly effective arrangement of alternate gas and air streams to improve diffusion of gas into combustion air and vise-versa and thereby achieve the much desired fast and uniform mixing between gas and combustion air streams for desired flame stability for possible effective and wide scale application and use of lean gas. WE CLAIM: 1.Multi-stream high capacity lean gas burner comprising: a gas distributor adapted for distributing the lean gas into multiple streams ; means for distributing the combustion air surrounding each of out-coming gas streams such that the interfacial area between the out-coming gas and combustion air streams and required diffusion of gas into combustion air and vise-versa is increased thereby achieving fast and uniform mixing between gas and combustion air streams for desired flame stability. 2. Multi-stream high capacity lean gas burner as claimed in claim 1 wherein said gas distributor is adapted to split the gas stream into multiple identical and radial gas streams along the burner axis within the main combustion air pipe. 3. Multi-stream high capacity lean gas burner as claimed in anyone of claims 1 or 2 wherein said means for distributing combustion air is adapted to distribute main air stream uniformly around each of the out-coming gas streams. 4. Multi-stream high capacity lean gas burner as claimed in anyone of claims 1 to 3 wherein said gas distributor and said means for air distribution are selectively disposed such as to generate alternate axial gas and air streams from the burner nozzle. 5. Multi-stream high capacity lean gas burner comprising: an air distributor assembly comprising a core air pipe with an air distributor unit and an outer main air pipe surrounding said core air pipe; a gas distributor assembly inside said air distributor unit and outer main air pipe comprising multiple axial gas slots spaced apart and surrounding said core air pipe such that while the gas slots provide for flow of combustible gases there through the intermediate space there between two adjacently spaced gas slots provide for the flow of combustion air being in operative communication with a combustion air source, the front and back ends of the said gas slots kept open while the back end of each air passages there between said gas slots being closed by wall member; back end of said gas distributor assembly being only operatively connected to a lean gas supply whereby gas is allowed to traverse only through gas slots preventing any gas entry in the air slots. 6.Multi-stream high capacity lean gas burner comprising: an air distributor assembly comprising a core air pipe with an air distributor unit and an outer main air pipe surrounding said core air pipe; a gas distributor assembly placed inside said air distributor unit and outer main air pipe comprising eight numbers of identical and radial multiple slots equally spaced apart from one another and extending along the axis of the burner and surrounding said core air pipe which are obtained of plurality of welded plates disposed perpendicularly along the length of the core air pipe , the top of the gas slots being obtained of welded curved plates with stabilizer plate of smaller dimension welded at the tip of each of the gas slots ; said gas slots adapted to provide for flow of combustion gases there through while the intermediate passages defined there between two adjacently spaced gas slots adapted for the flow of combustion air being in operative communication with a combustion air source, the front and back ends of the said gas slots kept open while the back end of each air passages there between said gas slots being closed by wall member with the back end of said gas distributor assembly being only operatively connected to a lean gas supply whereby gas is allowed to traverse only through gas slots preventing any gas entry in the air passages. said gas distributor assembly being housed inside the air distributor unit and outer main air pipe with said air distributor assembly and gas distributor assembly including the gas slots selectively dimensioned such that more than 95% of the total combustion air stream is adapted to pass through the outer main air pipe , said outer main air pipe providing the main combustion air stream over each of the gas slots and also through the air passages between adjacent gas slots along the burner axis with only about S to 10% of the total combustion air passing through the core air pipe provided with a swirler to impart swirling/whirling motion to the out coming core air. 7. Multi-stream high capacity lean gas burner as claimed in anyone of claims 1 to 6 wherein the combustion air pressure requirement is low in the range of 50-70 mmWC and the lean gas pressure requirement is in the range of 300 mm WC to 500 mm WC. 8. Multi-stream high capacity lean gas burner as claimed in anyone of claims 1 to 7 comprising more than 95% of the total combustion air stream adapted to pass through the outer main air pipe and said core air stream through a core pipe supplying about 5 to 10 % of the total combustion air, 9. Multi-stream high capacity lean gas burner as claimed in claim 8 wherein said core air supply line is provided with a swirler means to impart swirling motion to the out-coming core air. 10. Multi-stream high capacity lean gas burner as claimed in anyone of claims l to 9 comprising a central dummy pipe adapted to insert electrical ignitor to light up a coke oven gas burner. 11. Multi-stream high capacity lean gas burner as claimed in anyone of claims 1 to 10 wherein said axial gas slots of said gas distributor assembly are of equal dimensions and equally spaced from one another and obtained of plurality of welded plates disposed perpendicularly along the length of the core air pipe, the top of the gas slots being welding curved plates with a stabilizer plate of smaller dimension welded at the tip of each of the gas slots. 12. Multi-stream high capacity lean gas burner as claimed in anyone of claims 1 to 11 wherein the combustion air passes through the main air pipe, air distributor and core air pipe from the same air supply line. 13. Multi-stream high capacity lean gas burner as claimed in anyone of claims 1 to 12 comprising within said core air pipe a concentric pipe for passage coke oven gas for a pilot burner. 14. Multi-stream high capacity lean gas burner as claimed in anyone of claims 1 to 13 comprising within the coke oven gas pipe a dummy pipe for the insertion of electrical ignitor for lighting the pilot gas burner. 15. Multi-stream lean gas burner substantially as hereindescribed and illustrated with reference to the accompanying figures. A multi-stream high capacity lean gas burner adapted to provide supply of alternate gas and combustion air slots/passages within the burner body to facilitate rapid mixing of gas and air streams at the burner nozzle and generate stable flame with lean gas. The burner of the invention basically comprises a gas distributor adapted for distributing the lean gas into multiple streams (GS), the combustion air (AP) surrounding each of out-coming gas streams such that the interfacial area between the out-coming gas and combustion air streams and required diffusion of gas into combustion air and vise-versa is increased thereby achieving fast and uniform mixing between gas and combustion air streams for desired flame stability. The burner of the invention would favour burning lean gases such as blast furnace gases (calorific value ~ 800Kcal/Nm3) in large quantities with desired flame configuration and avoid the problems of burning such lean gases encountered in the art due to problems of effective and uniform mixing of gas and combustion air steams and related flame instability.

Documents:

984-KOL-2005-(02-02-2012)-FORM-27.pdf

984-KOL-2005-ABSTRACT 1.1.pdf

984-KOL-2005-ABSTRACT 1.2.pdf

984-kol-2005-abstract.pdf

984-KOL-2005-AMANDED CLAIMS-1.1.pdf

984-KOL-2005-AMANDED CLAIMS.pdf

984-KOL-2005-AMANDED PAGES OF SPECIFICATION-1.1.pdf

984-KOL-2005-AMANDED PAGES OF SPECIFICATION.pdf

984-KOL-2005-CLAIMS.pdf

984-KOL-2005-CORRESPONDENCE 1.1.pdf

984-KOL-2005-CORRESPONDENCE 1.2.pdf

984-KOL-2005-CORRESPONDENCE 1.5.pdf

984-KOL-2005-CORRESPONDENCE-1.3.pdf

984-KOL-2005-CORRESPONDENCE-1.4.pdf

984-kol-2005-correspondence.pdf

984-KOL-2005-DESCRIPTION (COMPLETE) 1.1.pdf

984-KOL-2005-DESCRIPTION (COMPLETE) 1.2.pdf

984-kol-2005-description (complete).pdf

984-KOL-2005-DRAWINGS 1.1.pdf

984-KOL-2005-DRAWINGS 1.2.pdf

984-kol-2005-drawings.pdf

984-KOL-2005-EXAMINATION REPORT REPLY RECIEVED.pdf

984-KOL-2005-EXAMINATION REPORT.pdf

984-KOL-2005-FORM 1 1.1.pdf

984-KOL-2005-FORM 1-1.2.pdf

984-kol-2005-form 1.pdf

984-kol-2005-form 18.pdf

984-KOL-2005-FORM 2 1.1.pdf

984-KOL-2005-FORM 2-1.2.pdf

984-kol-2005-form 2.pdf

984-kol-2005-form 3.pdf

984-KOL-2005-GRANTED-ABSTRACT.pdf

984-KOL-2005-GRANTED-CLAIMS.pdf

984-KOL-2005-GRANTED-DESCRIPTION (COMPLETE).pdf

984-KOL-2005-GRANTED-DRAWINGS.pdf

984-KOL-2005-GRANTED-FORM 1.pdf

984-KOL-2005-GRANTED-FORM 2.pdf

984-KOL-2005-GRANTED-LETTER PATENT.pdf

984-KOL-2005-GRANTED-SPECIFICATION.pdf

984-KOL-2005-OTHERS 1.1.pdf

984-KOL-2005-OTHERS 1.2.pdf

984-KOL-2005-OTHERS.pdf

984-kol-2005-pa.pdf

984-KOL-2005-REPLY TO EXAMINATION REPORT.pdf

984-kol-2005-specification.pdf