FIELD OF THE INVENTION:
Present invention is directed to the invention of an improved high velocity gas burner system involving an improved combustion system for its efficient use, having the constructional features adapted to provide the appropriate flame temperature and high thrust. Importantly, said system of high velocity burner is advantageous for uniform heating of refractory lining inside the ladle in steel making process, eliminating skull formation at the bottom of the ladles due to inadequate preheating of the bottom lining following the conventional process. The high and appropriate flame temperature is obtained by providing the optimum level of excess air of about 10%, which could be maintained for complete combustion of the gaseous fuel of given calorific value in the system of the invention. The system of an improved high velocity gas burner of the invention is adapted for anchoring/stabilizing the flame and a selective gas nozzle for imparting high velocity to the gas emerging out of the nozzle. The systems favours achieving stabilization of flame even at very low gas flow rate by creating a re-circulation zone near the discharge tip of the nozzle. The system is adapted for complete combustion of coke oven gas (CO) used as fuel having the calorific value of about 4200 Kcal/Nm3 or when mixed with blast furnace gas having calorific value of 3000 Kcal/Nm3. The high velocity burner system for ladle heating provides
the firing capacity of 100-500 Nm3/hr and the gas supplied to burner at a pressure of 200-
250mm of water column (WC). The burner system achieves a very high thrust flame up to 3
meters long for efficient and uniform heating of the ladle up to around 1200°C. BACKGROUND ART:
It is well known in the art of steel melting insteel plants, that use of the gas burners are essentially required for preheating/drying of refractory relined furnace/ green or capital repaired ladles for liquid steel and hot metal and tundishes. This gas burner needs to generate high thrust flame essentially for proper and uniform preheating of ladles prior to tapping of molten hot metal/liquid steel in it. The ladle preheating process requires very high velocity thrust flame such that the flame and the hot gases can reach the bottom of the ladle. This high thrust flame ensures proper and uniform heating of ladle refractory at bottom and along the height of the ladle. It has been observed in the conventional ladle preheating that a short and low velocity flame often leads to inadequate preheating of the bottom lining resulting in skull formation at the bottom of the ladles.
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The flame temperature is also an important parameter to be consistently maintained at appropriate level/range for achieving higher ladle temperature. The flame temperature is dependent on the calorific value of the fuel gas and the level of excess air used for its complete combustion. This is, thus, essential to have the optimum level of excess air for complete combustion, thereby achieving sufficiently long stable flame with higher flame temperature required for heating the ladles to uniform high temperatures. Moreover, the measurement of gaseous fuel and combustion airflow rates are necessary for controlling and adjusting the excess air.
There was, therefore, a continuous need for developing an efficient high velocity gas burner and an improved system for combustion that would generate adequate long thrust flame of high uniform temperature, with control for measuring optimum amount of excess air to burn the fuel gas of given calorific value, such that the uniform preheating of the ladle lining including the bottom refractory lining of the ladle, could be consistently achieved leading to elimination of skull formation.
OBJECTS OF THE INVENTION:
The basic object of the present invention is therefore, directed to an improved high velocity gas burner system involving an efficient and improved combustion system for its use for heating of the ladles for liquid steel and hot metal and tundishes by generating sufficiently long high thrust flame of uniform high flame temperature to heat the ladles to about 1150°C -1200°C, such that the entire refractory surface up to the bottom lining of ladle can be heated.
A further object of the present invention is directed to an improved high velocity gas burner system for ladle heating including selective constructional features incorporated in the form of a flame stabilizing means to stabilize the flame even at very low or very high gas flow rate and also to create a re-circulation zone for the combustion near the discharge tip of gas nozzle and thereby achieve a burner turn down ratio of 1:10.
A still further object of the present invention is directed to an improved high velocity gas burner system adapted for burning of Coke oven gas (CO) or mixed gas comprising mixture
of coke oven and blast furnace gas, having calorific value of 4200 Kcal/Nm3 and 3000
Kcal/Nm3, respectively mixed with appropriate amount of air, including excess air.
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A still further object of the present invention is directed to a system of an improved high velocity gas burner adapted to generate the required thrust flame of uniform high temperature using CO gas or mixed gas supplied to burner at a pressure of 200-250mmWC and with combustion air from a air blower at a'pressure of 200-400mmWC.
A still further object of the present invention is directed to a system of an improved high velocity gas burner wherein the excess air is maintained at 10% for complete combustion of said gas as fuel.
A still further object of the present invention is directed to a system of an improved high velocity gas burner is having the constructional feature favouring providing firing capacity of 100-500Nm3/hr.
A still further object of the present invention is directed to a system of an improved high velocity gas burner for heating /drying the refractory lining of ladles for liquid steel and hot metal and tundishes. The said system is provided with measuring instruments such as a separate orifice plate, pressure gauge, differential pressure transmitter and flow indicator for each of gas and combustion air flow, for effective control of desired fuel - air ratio and the amount of excess air for complete combustion.
A still further object of the present invention is directed to a system of an improved high velocity gas burner for heating /drying the refractory lining ladles for liquid steel and hot metal and tundishes (green or capital 'repaired), advantageously at uniformly high temperature with a stable flame of about 3 meter length, up to the bottom lining such that formation of skull is avoided.
A still further object of the present invention is directed to a system of an improved high velocity gas burner adapted to provide a long stable and high temperature thrust flame for ladle/tundishes heating/drying, having the burner tip protruded preferably up to only the ladle mouth level to increase the burner life. Only the burner/ nozzle tip inside the ladle cover is fabricated with AISI: St 310 Grade steel and the remaining portion of the burner is fabricated of mild steel to enhance the life of burner / nozzle.
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A still further object of the present invention is directed to a system of an improved high velocity gas burner having the burner block made of stainless steel for higher burner life compared with conventional refractory burner block.
A still further object of the present invention is directed to a system of an improved high velocity gas burner adapted to heat 130t and 300t capacity green or capital repaired ladle upto 1150°C-1200°C temperature in 8 hrs and 12 hrs, respectively.
SUMMARY OF THE INVENTION:
The basic aspect of the present invention is therefore directed to an improved high velocity gas burner system comprising:
a centrally disposed gas supply pipeline comprising a gas inlet pipeline, a gas connecting nozzle, connected at one end to said gas inlet pipeline and at its other end to a gas nozzle adapted for imparting high velocity to the gas emerging from said nozzle and a flame stabilization disc provided over said gas nozzle near the exit adapted for providing a re-circulation zone near the discharge tip of the gas nozzle for stabilization of the flame at cold condition, especially at very low or very high gas flow rate;
an annular combustion air supply of requisite amount of air flow for complete combustion of the gas comprising an air connecting nozzle connected at one end to an air annular pipeline and at its front end to a combustion air nozzle / burner block, said air annular pipeline further connected to combustion air inlet pipe for supply of combustion air.
A further aspect of the present invention directed to an improved high velocity gas burner system wherein said gas is supplied to said gas inlet pipe through a flexible hose preferably a stainless steel flexible hose.
A further aspect of the present invention directed to an improved high velocity gas burner system comprising spacer means to maintain said air nozzle in the centre.
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A still further aspect of the present invention directed to an improved high velocity gas burner system comprising a control valve in the gas inlet pipe to control the gas flow and a control valve in the combustion air inlet pipe to the burner for control the air flow rate.
A still further aspect of the present invention directed to an improved high velocity gas burner system is adapted for combustion of coke oven gas having a calorific value of about 4200 Kcal/Nm3 or mixed gas, preferably a mixture of coke oven gas and blast furnace gas, having a calorific value of about 3000 Kcal/Nm3
According to yet another aspect of the present invention directed to an improved high velocity gas burner system is adapted for firing capacity of 100-500 Nm3/hr and supply of gas to the burner at a pressure in the range of 200-250mmWC.
A still further aspect of the present invention directed to an improved high velocity gas burner system wherein the combustion air is supplied through a combustion air blower and the supply pressure of the combustion air blower is about 200 to 400 mm WC.
A further aspect of the present invention directed to an improved high velocity gas burner system comprising a separate orifice plate, pressure gauge, differential pressure transmitter and flow indicator, are provided in each said gas and combustion air lines for measurement of respective line pressures and flow rates for ensuring complete combustion and increased flame temperature.
A still further aspect of the present invention directed to an improved high velocity gas burner system wherein said burner tip is adapted to protrude only up to the ladle mouth favouring increased burner life;
burner block is fabricated of stainless steel;
said disc provision adapted to achieve burner turn down ratio of 1 :10 and the said high velocity gas burner system is adapted to generate high thrust flame up to 3 meters long, for heating ladle and tundishes uniformly with heating temperature up to 1200°C.
A further aspect of the present invention directed to an improved high velocity gas burner system is adapted to preheating/drying of hot metal ladles, such as 130ton and 300 ton
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capacity green / capital repaired ladle up to a temperature range of 1150-1200°C in 8hrs and 12 hrs time, respectively.
The present invention relating to an improved high velocity gas burner system is further described in greater details with particular reference to the accompanying figures.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES:
Figure 1: is the illustration of the sectional view of an improved high velocity gas burner and its various parts/elements, incorporating improved constructional features, according to the present invention.
Figure 2: is the illustration of the PI Diagram for the improved combustion system using said high velocity burner, according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION IN RELATION TO THE ACCOMPANYING FIGURES:
Reference is first invited to the accompanying figure 1, that illustrates the sectional view of an improved high velocity gas burner used in the system according to the present invention and also shows the various constructional features of the improved version of the burner.
The Burner, according to a preferred embodiment of the present invention of the gas burning system, has been developed to incorporate some novel features to provide the desired stable and high velocity high temperature flame required for uniform heating of green/capital repaired ladle and tundishes, avoiding the limitations as observed in the conventional systems. The burner of the present system is comprised of a gas nozzle (1) for imparting high velocity to the gas emerging out of nozzle. A flame-stabilizing disc (2) has been provided over the gas nozzle near the exit to stabilize the flame even at very low or very high turndown ratio. A gas-connecting nozzle (3) is connected to the gas nozzle (1) for supplying the fuel gas. A gas inlet pipe (4) is connected to the gas-connecting nozzle (3). The gas is supplied to gas inlet pipe (4) through a stainless steel flexible hose. The gas is supplied to burner at a pressure range of 200-250 mmWC. A combustion air nozzle (5) has been provided and is connected to air connecting nozzle (6) to supply the requisite amount of airflow for complete combustion of the gas. The combustion air nozzle (5) acts as a
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burner block and it is made of AISI: St 310 grade steel for achieving its longer life. The air-connecting nozzle (6) is connected to combustion air annular pipe (7), which is in turn connected to combustion air inlet pipe (8). For keeping the air nozzle in the centre, four numbers of spacers (9) have been provided, such that the proper uniform mixing of air with gas at all points around the circumference of the nozzle exit is ensured. There is provided a valve in the gas pipeline (4) to the burner to control the gas flow. Further, a control valve has been provided in the air inlet pipe (8) to the burner. The combustion air is supplied from a combustion air blower. The supply pressure of combustion air blower is about 200-400 mmWC. The high velocity burner is lighted with a flame torch or a pilot burner and the respective control valves are then operated to adjust the flow rates to obtain the desired air fuel ratio such that the high velocity stable flame is produced. The excess combustion air is supplied through a combustion air is kept at about 10% to achieve higher flame temperature and thereby obtaining desired higher uniform ladle preheating temperature.
Reference is now invited to figure 2 of the present invention that illustrates a PI diagram of the present improved system of gaseous fuel combustion, advantageously making use of said high velocity gas burner to achieve high thrust flame and obtain uniform heating of refractory lining of the ladle up to about 1200°C. The burner is simple in construction but is highly efficient to generate high velocity flames with firing capacity ranging from 100-500Nm3/hr for quick and uniform preheating of the ladles /tundishes up to the bottom-lining to a uniform temperature of about 1150-1200°C. The present fuel combustion system using said high velocity burner is capable to heat 130t and 300t capacity green/capital repaired ladle to the said desired temperature in 8 hrs and 12 hrs respectively.
As evident from the PI Diagram of accompanying figure 2, the coke oven gas (CO) or the mixture of coke oven and blast furnace gas is supplied through the gas pipeline, flow of which is operatively controlled by a few gate valves (GV) and the line pressure is measured by pressure gauges installed at preferred places on the said pipeline. The gas pipeline is finally connected to the high velocity burner by means of a flexible stainless steel hose to
the burner. The burner tip made of stainless steel AISI: st310, is protruded up to only ladle
mouth/cover level leading to increased burnenlife.
For more accurate control of the flow rate and pressure of gas supply line to the high velocity burner (HVB), additional instruments like orifice plate (OP), differential pressure transmitter (DPT) and gas flow indicator (GFI) are installed in the system to achieve proper
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measured flow of gaseous fuel for achieving consistently high flame temperature for desired ladle heating.
The air required for combustion of gaseous fuel of given calorific value e.g. either 4200Kcal/Nm3 for coke oven gas or 3000 Kcal/Nm3 for mixed gas, is being supplied from air blower through air ducting/pipeline being controlled by a butterfly valve (BV). The airflow rate is also measured to maintain at desired air- fuel gas ratio by providing orifice plate (OP) and differential pressure transmitter (DPT) and also a pressure gauge (PG) displaying line air pressure for imparting necessary control by means of valve. The corresponding readings of air flow rate is displayed on a panel facilitating for the correct airflow rate and pressure to generate said desired high velocity high thrust flame and also to comply with the requirement of 10% excess air for complete combustion of the fuel gas supply.
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WE CLAIM:
1. An improved high velocity gas burner system comprising:
a centrally disposed gas supply pipeline comprising a gas inlet pipeline, a gas connecting nozzle, connected at one end to said gas inlet pipeline and at its other end to a gas nozzle adapted for imparting high velocity to the gas emerging from said nozzle and a flame stabilization disc provided over said gas nozzle near the exit adapted for providing a re-circulation zone near the discharge tip of the gas nozzle for stabilization of the flame at cold condition, especially at very low or very high gas flow rate;
an annular combustion air supply of requisite amount of air flow for complete combustion of the gas comprising an air connecting nozzle connected at one end to an air annular pipeline and at its front end to a combustion air nozzle / burner block, said air annular pipeline further connected to combustion air inlet pipe for supply of combustion air.
2. An improved high velocity gas burner system as claimed in claim 1 wherein said gas
is supplied to said gas inlet pipe through a flexible hose preferably a stainless steel
flexible hose.
3. An improved high velocity gas burner system as claimed in anyone of claims 1 or 2
comprising spacer means to maintain said air nozzle in the centre.
4. An improved high velocity gas burner system as claimed in anyone of claims 1 to 3
comprising a control valve in the gas inlet pipe to control the gas flow and a control
valve in the combustion air inlet pipe to the burner to control the combustion air flow
rate.
5. An improved high velocity gas burner system as claimed in anyone of claims 1 to 4
adapted for combustion of coke oven gas having a calorific value of about 4200
Kcal/Nm3 or mixed gas preferably a mixture of coke oven gas and blast furnace gas,
having a calorific value of about 3000 Kcal/Nm3
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6. An improved high velocity gas burner system as claimed in anyone of claims 1 to 5
adapted for firing capacity of 100-500 Nm3/hr and supply of gas to the burner at a
pressure in the range of 200-250mmWC.
7. An improved high velocity gas burner system as claimed in anyone of claims 1 to 6
wherein the combustion air is supplied through a combustion air blower and the
supply pressure of the combustion air blower is about 200 to 400 mm WC.
8. An improved high velocity gas burner system as claimed in anyone of claims 1 to 7
comprising a separate orifice plate, pressure gauge, differential pressure transmitter
and flow indicator, are provided in each said gas and combustion air lines for
measurement of respective line pressures and flow rates for ensuring complete
combustion and increased flame temperature.
9. An improved high velocity gas burner system as claimed in anyone of claims 1 to 8
wherein said burner tip is adapted to protrude only upto the ladle mouth favouring
increased burner life;
burner block is obtained from stainless steel;
said disc provision adapted to achieve burner turn down ratio of 1:10 and the said high velocity gas burner system is adapted to generate high thrust flame upto 3 meters long, for heating ladles and tundishes uniformly with heating temperature upto 1200°C.
10. An improved high velocity gas burner system substantially as herein described and
illustrated with reference to the accompanying figures 1 and 2.

Dated this 19th day of December, 2006. Anjan Sen
Of Anjan Sen and Associates (Applicants Agent)
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A high velocity gas burner comprised of a gas nozzle (1) imparting said high velocity to the
emerging gas flame from nozzle; a flame-stabilizing disc (2) provided preferably near exit to stabilize said high velocity flame. A gas-connecting nozzle (3) supplying the fuel gas at a pressure range of 200-250 mmWC and receiving it from inlet pipe (4). A combustion air nozzle (5), acting as the burner block and connected to air connecting nozzle (6) to supply the requisite amount of airflow from air blower at a pressure of 200-400 mmWC through combustion air annular pipe and combustion air inlet pipe, generating high velocity flames with firing capacity ranging from 100-500 Nm3/hr. The burner block and the gas nozzle and the flame-stabilizing disc, is made of AISI: St 31O grade steel for longer life. Control valves are provided to control air-fuel ratio in measured amounts displayed on a panel, maintaining excess air of about 10% for complete combustion. The long and stable flame suitable for higher uniform ladle preheating temperature up to about 1200°C.