FORM 2
THE PATENT ACT 1970
(39OF 1970)
&
THE PATENT RULES 2003,
COMPLETA SPECIFICATION
(See Section 10 and Rules 13)

1. TITEL OF INVENTION:
A MULTI FUNCTION LANCE BURNER FLAME SENSING SYSTEM.

2. APPLICATION (S)

NAME: JSW steel Limited.

Nationality: an indian Company.

Address: Jindal mention , 5-A, Dr. G. Deshmukh Marg, Mumbai-400026,

3. PREMAMBLE TO THE DESCRIPTION
COMPLETE

The Following specification partycularly described the Invention and manner in wich it is to
Be performed.

FIELD OF THE INVENTION
The present invention relates to a method of improvement of the effectiveness of the Multi Function Lance Burner for heating of vacuum vessel being used in the Ruhrstahl Heraus (RH) degasser wherein liquid steel is treated under vacuum, by improving consistency and reliability of its UV flame sensor. More particularly, the invention provides system for improved burner performance of in RH degasser. Thus the MFL burner used for heating up and holding of the refractory temperature of the RH vessel is adapted to perform optimally to meet the process requirements. This control on temperature for optimum functioning of the burner achieved by flame sensor that is better responsive to the Ultra Violet (UV) radiation from the flame and generate proper feedback signal for continuation or termination of the burner operation. The Ultra Violet (UV) flame sensing system of the invention ensure improved efficiency in terms of the flame condition detection more reliably free of any signal disruption during its passage preventing entry of flue by argon sealing of the sensor visual line. Thus the MFL burner is having improved sensor reliability and burner operation found to be achieved accurately and consistently. Importantly, proper feed back from the UV flame sensor according to the present invention further ensures 100% availability of the degasser and a safe operation. The improved Ultra Violet (UV) flame sensing system for RH degassing operation according to the present invention is thus effective and useful for wide industrial application in steel industry to achieve required vessel temperature for superior quality of different grades of steel with efficient degassing and higher yield.
BACKGROUND ART
It is well known in the steel industry that with the increasing demand for value added steel products, the liquid steel need to be routed through degasser for refining and selective alloying and improved properties. The different grades of steel processed through Ruhrstahl Heraus (RH) degasser comprising deep drawing steel, interstitial free (IF) steel, line pipe steel, sour grade steel and the like. In RH degasser, the liquid steel is treated under vacuum to reduce carbon, hydrogen, nitrogen and oxygen content. The RH process operates on the principle of steel circulation between the ladle (at atmospheric pressure) and the RH vessel (at vacuum). During the degassing treatment a pair of snorkel is immersed into the liquid steel. The pressure in main chamber is reduced to


evacuate vessel for vacuum treatment. The injected argon in up-leg snorkel, through tuyere, lifts the steel into the vacuum chamber, where it is degassed and comes out through the down-leg snorkel.
During the degassing treatment of molten steel, the RH vessel loses temperature mainly due to radiation losses from surface and losses related to refractory surface. To compensate these losses heat source is required, which is provided by the burners. Such burners are generally fired using Oxygen mixed with a fuel such as Oil, Natural gas, Liquefied Petroleum Gas (LPG) or a mixture of fuel that is enriched with gaseous oxygen. These burners are used for heating up and holding the refractory temperature at desired level. Before treatment starts, the temperature of vessel is increased up to the vicinity of 1400°C to compensate subsequent heat losses during the degassing treatment. After heating up to 1400 - 1450 °C the burner power is reduced to 50 - 75 % and temperature is maintained as per the requirement. It is common practice to hold the refractory at 1000°C between two treated heats.
The selection of heating media solely depends on the availability of fuel and capacity requirement of the RH process. The most of RH degasser uses natural gas fired burners to heat refractory vessel. The unavailability of natural gas forced few steel plants to opt for LPG based burner. The burner flame emits radiations depending on the characteristics of flame, which is based on Oxygen-fuel proportion. The flame sensor is responsive to the Ultra Violet (UV) radiation caused by the flame and give feedback for termination or continuation of the burner operation. The burner controlling system is totally interlocked with the flame sensor adapted to operatively control fuel gas and oxygen supply through valves, in order to avoid any major mishap during the shut off of the flame. Hence any malfunctioning of flame sensor can lead to dangerous situations including accidents and wastage of gases.
The existing process of steel treatment in RH degasser uses a lance burner which can perform multiple functions like Oxygen blowing or Powder blowing for metallurgical purposes as well as pure heating of RH vessel, de-skulling and temperature holding. This type of lance is called Multi Function Lance (MFL). Multi function lance is water cooled with concentric tube type arrangement. The fuel gas is passed through central tubular section and Oxygen (combustion) is provided through two slots on lance tip. Oxygen can also be blown for decarburisation (De-C) or chemical heating through central tubular


section after purging it with Argon or Nitrogen. One hole on the tip is provided for Pilot/Ignition burner flame, so that main burner can be lighted up.
The Ultra Violet flame sensor conventionally located at burner top, detects the flame at the tip of Multi Function Lance and provides input for presence of flame and then Oxygen-Fuel gas (LPG) is regulated as per the requirement. In the event of the flame being extinguished, the sensor senses the absence of the flame. After sensing the extinguishing of the flame, the sensor or its related circuitry will send a signal to a controller. The controller will take appropriate action such as shutting down the burner by terminating fuel gas (LPG) and oxygen flow. This helps in avoiding serious safety problems such as continued fuel flow into a burner without a flame being present.
The flame sensor includes an element, which is sensitive to ultra violet light so as to indicate presence or absence of the flame. The malfunctioning of sensor has been frequently observed due to contamination of signals during their travel through multi functional lance passage. The burner controlling system was interlocked with the flame sensor for opening and closing Oxygen-fuel (LPG) valves. If UV sensor sends inappropriate feedback (desirable feedback > 60) for 30 seconds, controller will shut-off Fuel gas (LPG) and Oxygen supply valves thereby terminate the burner operation. This caused frequent burner shut-off and vessel needed to be shifted to pre-heater station to keep refractory at desired temperature. The shifting of vessel takes around 3 hours and thereby reduces the availability of RH degasser for treatment. Due to frequent shut-off RH degasser was not available for treatment.
There has been therefore a continuing need to develop an improved multi function lance burner flame sensing system, such that the UV sensor reliably detects the flame burning/extinguishing condition whereby the failure of the sensor to control burner flame and temperature of bath/vessel refractory, due to poor reception and propagation of feed back signal from the sensor to the control system for the operation of the burner including the supply of fuel and oxygen gases is avoided. Thus the improved multi function lance burner having a UV sensor adapted to ensure reliable and consistent detection of flame condition, without any obstruction in the sensor visual line by way of the entrapped flue gas or the like and ensure proper control of the burner as well as avoiding frequent shut-off of the burner and thereby improving the productivity and saving in related costs for the RH degassing treatment of liquid steel.


OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to provide a multi function lance burner flame sensing system for the RH degasser for treatment of liquid steel which would favor the detection of the on/off condition of the burner flame more accurately and reliably, without any obstruction by way of a clear passage in said burner for the sensor visual path and thus ensuring safety and reliability of such burner operation.
A further object of the present invention is directed to a multi function lance burner flame sensing system which would favor sensing accurately the flame on/off condition in order to improve the control of the burner operation and RH temperatures, avoiding any major mishap during the shut off of the flame.
A still further object of the present invention is directed to a system of improved control of the multi function lance burner operation by providing clear passage to the UV radiation emitted from flame tip, for improved control of said burner to achieve desired operating conditions for reliable performance of the RH degasser without interruption.
A still further object of the present invention is directed to a system of improved control of the multi function lance burner operation in RH degasser wherein the sensor would be adapted for improved reception of UV radiation of the burner flame and favor propagation of the appropriate signals by the sensor for operative control of the supply of the gas/oxygen and avoid continued fuel flow in flame absent condition.
A still further object of the present invention is directed to a system of improved control of the multi function lance burner operation in RH degasser wherein the sensor malfunctioning due to the obstruction in sensor signal transmission passage inside the burner achieved by argon sealing to block entry of the flue gases and fumes into the sensor passage, and thus eliminating frequent burner/ RH degasser shut-off and consequent longer hours for shifting and preheating RH vessel.


SUMMARY OF THE INVENTION
The system is provided with a multi function lance burner adapted for pure heating as well as carrying out metallurgical purposes in a RH degasser comprising:
water cooled concentric tube type arrangement;
a central tubular section for passing there through selectively fuel gas/oxygen ;
slots on lance providing for supply of oxygen (combustion);
a hole at the tip for pilot/ignition burner flame adapted for lighting a burner means;
an ultra violet flame sensor adapted to detect the flame at the tip of said lance and provide input for presence of the flame and favor regulating of the oxygen-fuel gas as per requirement via a controller adapted to control the burner burning based on the presence of the flame sensed by the sensor;
According to the basic aspect of the present invention said sensor selectively installed on the hot off take of said RH degasser spaced apart from the vertical axis of the lance for clear visual passage of said flame sensor.
In the above multi function lance burner flame sensing system the same advantageously comprises argon gas sealing to block entry of flue gases and fumes into the sensor passage such as to favor clear passage for the sensor visual line.
Also in the multi function lance burner flame sensing system the temperature of the flue gas is controlled by said water cooling jacket and N2/Ar (5 Nm3/hr) jet.


In accordance with a preferred aspect the multi function lance burner flame sensing system comprises:
a top part comprising said sensor mounted to a top pipe operatively connected to a seamless concentric reducer on one side and to a flange on the other end, said concentric reducer having two openings at an inclination for the argon gas jet;
an intermediate part comprising cooling jacket with baffle plates spirally provided for the supply of cooling water therethrough and return; and a lower part comprising a stub which is a seamless pipe taper on one side and adapted to match the profile of the hot off-take with required inclination with vertical plane.
In accordance with an embodiment in the multi function lance burner flame sensing system the said top pipe preferably of size 32NB X 100 mm length of SS material is welded to a seamless concentric reducer preferably 100 X 32 carbon steel on one side and to a flange on the other end and said openings on the reducer operatively connected to a hose preferably 15 NB hoses and respective fittings.
Also, the said cooling jacket comprise a concentric carbon steel seamless pipe construction preferably of size 150NB and 100 NB of 100 mm length, with 10 mm thick baffle plates spirally welded on said 100 NB pipe for water movement and effective cooling, a 15 NB opening is provided for cooling water supply and return with two flanges welded on either side of the concentric pipe.
The said stub being a 150 NB seamless pipe, taper on one side adapted to match the profile of the hot off-take with required inclination with vertical plane preferably about


5 Deg., flange being welded on the other side to match with said intermediate part. Preferably, the said stub is welded to the hot off take shell and a layer of thick refractory preferably about 20 mm is provided on the inner surface of the pipe for heat insulation.
Preferably, in the multi function lance burner flame sensing system all said top part, intermediate part and lower parts being assembled and bolted to the flange with gaskets.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1: is the schematic illustration of the existing system for carrying out RH process for degassing of liquid steel.
Figure 2: is the schematic illustration of the vertical sectional view Multi function lance, showing the different flow passages inside the lance and the location of the UV radiation based flame condition sensor, in existing configuration. (This is supplied by the SMS-MEVAC)
Figure 3: is the graphical presentation of the UV flame sensor signal feed back under dismal condition of sensor malfunctioning and the improvement achieved by implementing the present invention.
Figure 4: is the sectional view of the improved multi function lance burner flame sensing system according to the present invention, showing the relocation of the UV sensor in the hot off take position for improved unobstructed reception of UV radiation for detection of flame condition.
Figure 5: is the details of the schematic illustration of the new location and mounting in preferred orientation of the UV sensor, with respect to vertical axis and flow path for argon sealing and water-cooling jacket, surrounding the sensor visual passage/line.


DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES
The present invention is directed to developing a flame sensing system for multi function lance burner for RH Degasser to ensure improved effectiveness of the control of burner and uninterrupted operation of the RH degasser by selectively locating the UV flame sensor of the burner for improved sensing ability of the UV radiation to ascertain flame condition and also to generate appropriate signal based on sensed data to control the burner operation of the multi function lance burner for desired operating temperature of the RH.
Reference is first invited to the accompanying Figure 1, wherein the conventional system for the schematic of RH process is shown. The grades of steel processed through Ruhrstahl Heraus (RH) degasser include deep drawing steel, interstitial free (IF) steel, line pipe steel, sour grade steel and the like. The liquid steel is treated under vacuum in RH degasser to reduce carbon, hydrogen, nitrogen and oxygen content in steel by degassing. The RH process is based on the principle of steel circulation between the ladle (at atmospheric pressure) and the RH vessel (at vacuum). During the degassing treatment a pair of snorkel is immersed into the liquid steel. The pressure in main chamber is reduced to evacuate vessel for vacuum treatment. The injected argon in up-leg snorkel, through tuyere, lifts the steel into the vacuum chamber, where it is degassed and comes out through the down-leg snorkel.
The RH vessel loses temperature during degassing process mainly due to radiation losses from surface and losses related to refractory surface. To compensate these losses, an equivalent heat generation source is required, such as the burners. Such burners are generally fired using Oxygen mixed with a fuel such as Oil, Natural gas, Liquefied Petroleum Gas (LPG) or a mixture of fuel that is enriched with gaseous oxygen. These burners are used for heating up and holding the refractory temperature at desired level. Before treatment starts, the temperature of vessel is increased up to the vicinity of 1400°C to compensate subsequent heat losses during the degassing treatment. After heating up to 1400 - 1450°C the burner power is reduced to 50 - 75 % and temperature is maintained as per the process requirement for a specific grade of steel. Generally the holding temperature of the refractory is maintained at 1000°C between two treated heats.


The multi function lance burners installed in most of RH degasser uses natural gas fired burners to heat refractory vessel. Some plants opt for LPG based burner due to nonavailability of natural gas. The flame at the tip of burner emits radiations depending on nature of flame based on Oxygen-fuel proportion. The flame sensor installed generally at the top of the burner along vertical central longitudinal axis, is responsive to the Ultra Violet (UV) radiation caused by the flame and generates feedback for termination or continuation of the burner operation. The burner controlling system for fuel gas and oxygen is totally interlocked with the flame sensor, in order to avoid any major mishap during the shut off of the flame. Thus any malfunctioning of flame sensor can lead to dangerous situations.
Reference is now invited to the accompanying Figure 2 that illustrates schematically the construction of a multi function Lance (MFL). The RH degasser uses a lance which can perform multiple functions like Oxygen blowing or Powder blowing for metallurgical purposes as well as pure heating of RH vessel, de-skulling and temperature holding. That is why such lances are called Multi Function Lance (MFL). Accompanying Figure 2 also shows that the multi function lance is water cooled with concentric tube type arrangement. The fuel gas is passed through central tubular section and Oxygen (for combustion of fuel) is provided through two slots on lance tip. Oxygen can also be blown for decarburisation (De-C) or chemical heating, through central tubular section of the burner/lance after purging it with Argon or Nitrogen. One hole is provided on the burner tip for contact with Pilot/Ignition burner flame, so that main burner can be lighted up initially.
An Ultra Violet (UV) flame sensor normally mounted at the top of the existing MFL burner along its vertical axis, detects the flame at the tip of Multi Function Lance and provides input for presence of flame and then Oxygen-Fuel gas (LPG) is regulated as per the requirement. If flame is extinguished, the sensor immediately senses the absence of the flame. Once such extinction of the flame is sensed, the sensor or its related circuitry will send a signal to a controller. The controller will take appropriate action such as shutting down the burner by terminating fuel gas (LPG) and oxygen flow by the operation of respective flow control/shut off valves. Such UV flame sensor based control helps in avoiding serious safety problems such as continued fuel flow into a burner without a flame being present.


The flame sensors conventionally involve an element, which is sensitive to ultra violet (UV) radiation so as to indicate presence or absence of the flame. The malfunctioning of sensor is experienced in the existing operation of the MFL, due to contamination of signals during their travel through multi function lance passage. The control system for burner is interlocked with the flame sensor for operatively opening and closing Oxygen-fuel (LPG) valves based on process/temperature or heat holding requirement. If UV-sensor sends inappropriate feedback, the desirable feedback range being > 60, for 30 seconds, controller will shut-off Fuel gas (LPG) and Oxygen supply valves and thereby terminate the burner operation. The accompanying Figure 3 shows graphically the strength of feedback signal from UV sensor received under sensor malfunction. This caused frequent burner shut-off and vessel needed to be shifted to pre-heater station to maintain desired temperature of refractory of degasser. The shifting of vessel, when needed, takes about 3 hours time and thereby reduces the availability of RH degasser for treatment of liquid steel. Due to such frequent shut-off, RH degasser is not available for degassing treatment of ladle heats, bringing down the output and productivity in RH degasser.
Reference is now invited to the accompanying Figure 4 that schematically illustrates the modified MFL for treating steel in RH Degasser with improved efficiency of UV sensor and improved availability of the RH vessel for degassing treatment.
In order to provide clear visual passage to the ultra violet sensor, the sensor is removed from the top and relocated selectively on the hot off take of the RH degasser system, with an selective axial angular tilt of 5° with respect to the vertical axis for improved UV radiation reception at a selective distance away from the lance axis, favoring improved and accurate flame condition detection without any obstruction or malfunctioning. The temperature of the flue gases is controlled by water-cooling jacket and N2/Ar jet in the range of 5 Nm3/hr is flown to prevent entry of flue in the sensor signal transmission passage. Argon sealing is preferably used to block entry of flue gases and fumes into the sensor passage. After relocation burner operation is found to be more reliable and consistent as compared to the conventional UV sensor. The modified configuration of flame sensing system has been illustrated in the accompanying Figure 4 and the details of its relocation and preferred angular axial disposition is illustrated in the accompanying Figure 5.


The details of the configuration of the modified flame sensing system as illustrated in the accompanying Figure 5, comprising three parts wherein the top pipe of size 32 NB X 100 mm length of SS material which is welded to a seamless concentric reducer (1) 100mm X 32mm made of Carbon Steel on one side and to a flange on the other end. The concentric reducer has two openings at an inclination for the Argon gas jet, which is connected by 15 NB hoses and its respective fittings. The UV sensor is mounted to the 32 NB SS pipe as shown at hot off take location.
The second part is the cooling jacket (2), which is a concentric carbon steel seamless pipe construction of sizes 150 NB OD and 100 NB ID, each of 100 mm length, forming the annular passage. The baffles plates, 10 mm thick are spirally welded on 100 NB pipe for water movement and effective cooling, 15 NB opening is provided for cooling water supply and return. Two flanges are welded on either side of the concentric pipe and thus maintaining desired temperature of gas for accurate UV radiation reception and also favoring Argon sealing to prevent entry of flue gas in the signal passage for the UV sensor.
The stub (3) is a 150 NB seamless pipe, tapered on one end to match the profile of Hot Off-take portion of the RH degasser unit, with required inclination of 5 Degrees with vertical plane approximately. Flange is welded on the other side to match with reducer (2). The stub is welded to the Hot off take shell and a layer of 20 mm thick refractory is provided on the inner surface of the pipe for heat insulation.
All the above parts are assembled by bolting, maintaining functional relation to one and the others in the improved MFL system, to the flanges with gaskets to provide leak proof connection, as necessary.
The accompanying Figure 3 also shows the UV sensor feedback after modification of the MFL with respect to sensor location and orientation and the argon sealing to prevent entry of flue in the sensor visual line. Said UV sensor thereby improving the UV radiation reception for determination of the flame condition and enhanced feedback signal strength in the order of over 100(at the upper portion of the graphical plot of signals) after modification of the flame sensing system for better control of the burner to achieve desired process parameters/temperature.


It is thus possible by way of this invention to achieve an improved system of the Multi function Lance burner flame sensing for RH degassing of liquid steel where in the method of implementation of desired degassing of the liquid steel is ensured in more reliable and consistent manner, enabling improving upon RH degasser availability up to 100% and thus improving productivity of the degasser plant. The above improvement is achieved by way of providing clear passage to the UV flame sensor to receive UV radiation emitted from flame tip and also generate appropriate feed back signals from the flame sensor to control burner power to the desired extent, ensuring avoidance of serious safety problems associated sensor malfunction viz continued fuel flow in under the condition of extinguished burner flame.


WE CLAIM:
1. A multi function lance burner adapted for pure heating as well as carrying out
metallurgical purposes of a RH degasser comprising:
water cooled concentric tube type arrangement;
a central tubular section for passing there through selectively fuel gas/oxygen ;
slots on lance providing for supply of oxygen (combustion);
a hole at the tip for pilot/ignition burner flame adapted for lighting a burner means;
an ultraviolet flame sensor adapted to detect the flame at the tip of said iance and provide input for presence of the flame and favor regulating of the oxygen-fuel gas as per requirement via a controller adapted to control the burner burning based on the presence of the flame sensed by the sensor;
said sensor selectively installed on the hot off take of said RH degasser spaced apart from the vertical axis of the lance for clear visual passage of said flame sensor.
2. A multi function lance burner flame sensing system as claimed in claim 1 comprising argon gas sealing to block entry of flue gases and fumes into the sensor passage such as to favor clear passage for the sensor visual line.
3. A multi function lance burner flame sensing system as claimed in anyone of claims 1 or 2 wherein the temperature of the flue gas is controlled by said water cooling jacket and N2/Ar (5 Nm3/nr) jet.


4. A multi function lance burner flame sensing system as claimed in anyone of claims 1
to 3 comprising:
a top part comprising said sensor mounted to a top pipe operatively connected to a seamless concentric reducer on one side and to a flange on the other end, said concentric reducer having two openings at an inclination for the argon gas jet ;
an intermediate part comprising cooling jacket with baffle plates spirally provided for the supply of cooling water therethrough and return; and
a lower part comprising a stub which is a seamless pipe taper on one side and adapted to match the profile of the hot off-take with required inclination with vertical plane .
5. A multi function lance burner flame sensing system as claimed in claim 4 wherein said top pipe preferably of size 32NB X 100 mm length of SS material is welded to a seamless concentric reducer preferably 100 X 32 carbon steel on one side and to a flange on the other end and said openings on the reducer operatively connected to a hose preferably 15 NB hoses and respective fittings.
6. A multi function lance burner flame sensing system as claimed in anyone of claims 4 or 5 wherein said cooling jacket comprise a concentric carbon steel seamless pipe construction preferably of size 150NB and 100 NB of 100 mm length, with 10 mm thick baffle plates spirally welded on said 100 NB pipe for water movement and effective cooling, a 15 NB opening is provided for cooling water supply and return with two flanges welded on either side of the concentric pipe.


7. A multi function lance burner flame sensing system as claimed in anyone of claims 4 to 6 comprising said stub being a 150 NB seamless pipe, taper on one side adapted to match the profile of the hot off-take with required inclination with vertical plane preferably about 5 Deg., flange being welded on the other side to match with said intermediate part.
8. A multi function lance burner flame sensing system as claimed in anyone of claims 4 to 7 wherein said stub is welded to the hot off take shell and a layer of thick refractory preferably about 20 mm is provided on the inner surface of the pipe for heat insulation.
9. A multi function lance burner flame sensing system as claimed in anyone of claims 4 to 8 wherein all said top part, intermediate part and lower parts being assembled and bolted to the flange with gaskets.
10. A multi function lance burner flame sensing system adapted for carrying out metallurgical purposes as well as pure heating of a RH degasser substantially as hereindescribed and illustrated with reference to the accompanying figures.



ABSTRACT
TITLE: A MULTI FUNCTION LANCE BURNER FLAME SENSING SYSTEM.
A Multi Function Lance (MFL) Burner for heating of vacuum vessel being used in the Ruhrstahl Heraus (RH) degasser for treating steel under vacuum, by improving consistency and reliability of its Ultra Violet (UV) flame sensor. More particularly, the system for improved burner performance in RH degasser adapted to perform optimally to meet the process requirements. The optimum functioning of burner achieved through flame sensor having improved response to UV radiation from flame and feedback signal for controlling continuation or termination of the burner operation. The UV flame sensing system ensure improved efficiency in flame condition detection more reliably, free of any signal disruption during its passage preventing entry of flue by argon sealing of passage for the sensor visual line. Importantly, proper feed back from the UV flame sensor further ensures 100% availability of the degasser and a safe operation and The MFL system is thus effective and useful for wide industrial application in steel industry for superior quality of different grades of steel with efficient degassing and higher yield. Figure 5.