Title of Invention

"AN IMPROVED BURNER CUM LANCE"

Abstract An improved burner cum lance comprising at least five concentric seamless tubes (1, 2, 3, 4, 5), preferably of mild steel, arranged to operate in an inter-dependent manner, wherein the relatively narrow central or the innermost tube (1) is meant for supplying fuel oil. the annular space between the innermost tube (1) and the second concentric tube (2) is meant for supplying oxygen, the annular space between the sec and tube (2) and third tube (3) is meant for supplying air or natural gas to the tip (8) characterised in that the said tip (8) is provided with a convergent nozzle (9) and a divergent nozzle (10) which are connected to each other at throat area (11) thereof, that the innermost tube (1) is extended up to the throat area (11) to occupy 30 to 40 percent of the throat area for supplying fuel oil into the divergent nozzle (10).
Full Text The present invention relates to an improved burner
cum lance of heating molten metal or accelerated heating of solid metal lumps/scraps The burner is suitable for operation from oxygen and fuel oil or from oxygen, air and fuel oil or from oxygen,

natural gas and fuel oil, and for rapid heating of molten metal, avoiding excessive oxygen potential of its flame. The burner is also capable of producing a flame of very high temperature i.e. higher than 2500°C when operated from pure oxygen and fuel oil. At this high temperature, the molecules of the combustion products, namely, COp and H-O,
0=-
get dissociated in the flame produced, to form ions which absorb ft. part of the heai.energy of the flame and release the absorbed energy by recombining into COp and HpO molecules when the flame is allowed to come in contact with the relatively cool surface of the metal being heated by the flame. The invented burner is so designed and constructed as to permit
atomisation of the fuel i.e. r oil within the
burner itself by the oxygen supplied to the burner. The atomi-sation of the fuel in the burner leads to the generation of a flame having a high heat transfer efficiency along with the production of low volume of flue gases.
Tlie construction of a conventional burner operating from oxygen and fuel is such that'the atomisation of the fuel can not .be attained within the burner itself before the fuel
4
is allowed to burn. In a conventional burner it is required

first/emulsify the fuel in a separate emulsifying unit by
using air or steam as an emulsification agent. The undesirable components such as hydrogen, water vapour and nitrogen, present in such emulsified fuel, lower the temperature of the burner flame and also the efficiency of heat transfer from the flame to the metal surface heated by the flame, and cause generation of a relatively high volume of flue gases as a result of burning of the emulsified fuel.
One object of the present invention is to, design and construct a burner in such a way that the atomisation of the iuel can be attained within the burner itself by using oxygen as the atomising agent without the need for using a separate emulsifying unit as used in a conventional burner.
The other object is to develop a burner which can produce a flame of relatively high temperature e;g. higher %han 2500°C.
Another object is^o provide a burner which produces a Ftiatively low volume of flue gases.
Yet another object is to provide a burner which p^odlices a relatively high efflux velocity of the flue gases, Which is capable of adding to the enthalpy, and promoting
* V
bath agitation, in the case of liquid melts being heated by the burner.
A further object is to provide a burner having a high operational flexibility in different regions in a furnace or - a metallurgical unit.
A still further object is to provide a burner, the flame of which does not extinguish or flicker oyer a wide of variation in the velocity of the fuel and oxygen
upply to the burner.
I Yet another object is to provide a burner.which can be used also as a lance for blowing oxygen into molten metals in a metallurgical process,
! Oxygen is supplied to the burner to function both as an atomising agent for the fuel and as a promoter of combustion of the fuel. The burner comprises a number of seftmless* concentric metallic tubes terminating into a tip made preferably of electrolytic copper at the lower end i.e. the end adjoining the flame of the burner through which the atomised fuel is allowed to eject from the burner before being burnt.
The tip of the burner comprises a convergent-divergent nozzle inside it. The junction of the convergent and the divergent parts of the nozzle is called the throat of the ,. nozzle. The cross -sectional area of throat is critical for achieving the optimum performance of the burner. The critical area of the throat depends on a number of parameters such as mass flow rate of fuel, supply pressure of oxygen, flow rate coefficient, specific heat ratio, gas constant and gas temperature.
The relatively narrow central tube of the burner is meant for supplying fuel oil into the burner. This tube terminates at the throat area, of the convergent-divergent nozzle and occupies a part of the throat area. The remaining part of the throat area is left free for the flow of oxygen
which is supplied through the annular space between the central tube and the second concentric tube. Air or natural gas is supplied through the annular space between the second and the third concentric tubes and fed into the convergent part of the nozzle lying above the throat area through a number of side holes provided for the purpose. Cooling water is allowed to flow into the annular space between the third and the fourth concentric tubes and come out through the annular space between the fourth and the fifth concentric tubes, the said fourth and fifth concentric tubes surrounding only the lower part of the burner containing the said tip*
Thus the invention provides an improved burner cum lance comprising at least five concentric seamless tubes, preferably of fflULd steel, arranged to operate in an inter-depende: manner, wherein the relatively narrow central or the innermost tube is meant for supplying fuel oil, the annular space between the innermost tube and the second concentric tube is meant for supplying oxygen, the annular space between the second tube and third tube is meant for supplying air or natural gas to the tip and the annular space between the third tube and fourth tube and that between the fourth tube and fifth tube are meant for circulating cooling water, characterised in that the said tip is provided with a convergent nozzle and a divergent nozzle which are connected to each other at throat area thereof, that the innermost tube is extended upto the throat area to occupy 30 to 40 percent of the throat area for supplying fuel oil into the divergent nozzle, that the remaining part of the throat area is provided for
U4.vergent nozzle through the annular space between •fete innermost tube and the second tube, that the side holes are provided in the convergent nozzle for supplying air or natural gas into the convergent nozzle through the annular space between the second tube and the third tube, and that an inlet is provided in the fourth tube and an outlet is provided in the fifth tube for circulating cooling water around the tip.
The invented burner is described and illustrated more particularly and fully, without restricting its scope in any manner, with reference to the accompanying drawings, in which -
Figure 1 illustrates the schematic cross section of the invented burner cum lance.
Figure 2 illustrates the schematic cross section of the tip of the burner cum lance of Figure 1 comprising the convergent-divergent nozzle.
Figure 3 shows the variation in flame length of the invented burner cum lance with change in the ratio of oxygen to fuel oil supply at the different pressures of the oxygen supply, when operated with pure oxygen.
Figure 4 shows the variation in flame length of the invented burner cum lance v/ith change in the ratio of oxygen to fuel oil supply at two different rates of oil flow into the burner, when operated with air and oxygen.
Referring to Figs. 1 and 2, the invented burner comprises five seamless concentric tubes (1, 2, 3, 4, 5), preferably of mild steel. The central or innermost tube d) is relatively narrow and terminates at its lower end i.e. its end adjoining the flame end of the burner in the throat area (11) of tip {8) containing the convergent nozzle (9) and divergent

nozzle (10). The tip (8) is made of electrolytic copper an welded to tubes (2,3,5). The innermost tube (1), at its termination at the throat, occupies around 3Q to 40 percent of throat area (11). Fuel oil is fed into the burner through the innermost tube. Oxygen is supplied to the"burner through the annular, space between tube (1) and tube (2), and flows through the convergent nozzle (9) and the remaining 60 to 70 percent of free throat area (11) into the divergent nozzle (10) Fuel oil is atomised by oxygen at the throat area of the convergent-divergent nozzle and the atomised mix thus produced at the throat area ejects at a high velocity through the divergent nozzle (10) and finally through the outlet (13) of the burn«r.
Air or natural gas is supplied through the annular

space between tube (2) and tube (3) and is allowed to enter into the convergent nozzle (.-) through three side holes (12). Cooling water is allowed to enter into the annular space between tube (3) and tube (4) through inlet (6) and come out through the annular space between tube (4) and tube (5) and through outlet (7).
A typical burner curn lance according to the invention is capable of firing 150 kg/hr of fuel oil or a combination
of fuel oil and natural gas. Oxygen is supplied at a pressure1
2 upto 6.5 kg/cm . The surface of the convergent nozzle (9) is
inclined to the axis of the burner at an angle of about 15° and that of the divergent nozzle (10) is inclined to the axis of the burner at an angle of around 7.5°.
The convergent nozzle (9) is provided with three

side holes (12) each of 8mm diameter and. "being inclined downwardly at an angle 60° to the burner axis.'The length of the convergent nozzle (9) is 54.6 mm and that of the divergent nozzle (10) is 50.0 mm. The throat diameter is 12.9 mm. The throat area is critical for the optimum performance of the burner. The optimum throat"area is calculated using the theoretical relation givencin Annexure I. The burner is capable of operating without using a mechanical swirler for mixing of the gases and fuel oil before burning. The method of operating the burner comprises the
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following steps: (1) the fuel oil supplied to the burner is
preheated at 70-80°C; (2) the preheated oil is supplied to
n the burner under a pressure of 2 to 5 kg/cm and at a flow
rate of 35 to 170 kg/hrj (3) oxygen is supplied to the
2 burner under a pressure of 3 to 6 kg/cm and at a flow rate
of 80 to 160 nm /hr when the burner is operated from oxygen and fuel oil,and at a flow rate of 40 to 150 nnr/hr along with a fuel oil flow rate of 80 to 120 kg/hr and air flow rate of 196 to 206 nnr/hr when the burner is operated from . oxygen, air and fuel oil; (4) cooling water is allowed to flow through the burner continuously at a flow rate of about
Tt O
3 nr/hr at a pressure of about 3 kg/cm ; and (5) the burner is ignited by means of a pilot torch placed close to th'e burner tip.
When the burner is operated from oxygen and fuel oil, the flarae produced starts flickering if the pressure of

oxygen supply exceeds 6.5 atmospheres. On the other hand the flame fickering starts at a pressure of oxygen supply less than 5 atmospheres when the burner is operated from oxygen, air and fuel oil. The exit velocity of gases from the burner
is around 300 metres/second. The heat flux of the burner
2 varies from 10 to 35 mw/m . The length and width of the
flame when the burner is operated from oxygen and fuel oil can be varied by changing the oxygen to fuel oil ratio and the flow rate of fuel oil. For example, the flame is 2.5 m long and 0.5 m wide when the oxygen to fuel oil ratio is 0.5 (nm3/kg) and the flow rate of fuel oil is 170 kg/hr. The flame is 0.6 m long and 0.2 m wide if the oxygen to fuel oil ratio is 3.A (nm3/kg) and the flow rate of fuel oil is 47 kg/hr.
The variation of flame length with the ratio of oxygen to fuel oil supply (02/oil) at pressure of oxygen supply of 2 atmospheres and 3 atmospheres respectively is shown graphically in Fig. 3. It is noted that flame length dimimshes with increase in the ratio of oxygen to fuel oil when the burner is operated from oxygen and fuel oil only. The rate of diminution is however sharper when the pressure of oxygen supply is higher, the flame turn down ratio being
more than 5:1 at oxygen supply pressure of 2 atmospheres and .
less than 3:1 at oxygen supply pressure of 3 atmospheres.
The variation of flame length with the ratio; of oxygen to fuel supply when the burner is operated from oxygen, air and fuel oil is ahown in Fig. 4. It is noted that the flame.
length increases with increase in the oxygen to fuel oil ratio, the flame length being greater at a higher rate of fuel oil flow. But the drawback of operating the burner from oxygen, air and fuel oil is that owing to the flow of air tangentially to the flame, a swirling motion of the flame is observed.
When the pressure of oxygen supply is lowered below P 2 kg/cm , a black streak of unburnt oil becomes visible in
the flame. So the lower limit of the pressure of oxygen
2
supply to the burner is 2 kg/cm .
Oxygen purity levels above 90% are not required in most applications of the burner and are found to be uneconomical. For many applications an oxygen purity level upto 50# is found to be adequate. Only in the applications where the flame is in direct contact with liquid metal, the oxygen purity level needs to be higher than 50%.
The luminosity of the zone of intensive combustion of fuel in the flame is reduced by the decrease of the oxygen supply. The flame front recedes and the flame becomes very bright when the ratio of oxygen to fuel oil supply is high.
The merits of the invented burner cum lance are :-
(a) A stable firmly anchored flame of temperatures
greater than 2000°C. can be obtained.
! -
(b) A large flame thurst which is useful for effective
bath agitation to improve the kinetics of reactions can be attained.

(c) The flame length and widthe can be raried appreciably
to suit different applications.
(d) The flame characteristics,namely, reducing,oxidising
and neutral, can, be attained to suit the dimensions of bath

Df molten metal to be heated.
(e) The undesirable presence of nitrogen, water vapour
and hydrogen in the flame can be eliminated.
(f) The;transfer of heat from the flame to the molten metal
in steelmaking aggregate can be attained without excesive
oxidation of the alloy steel produced.
(g) When used in the electric arc furnaces, the burner can
save power and electrode consumption, reduce melting time and
improve slag foaming. The rate of substitution of electric
power by fuel oil is high in such applications of the burner,
(h) Owing to the relatively low volumetric flow of waste
gases produced, the burner causes a reduced waste ga§
withdrawal load on the exhaust system.
s> i i
(i) The burner when operated from oxygen, air and fuel oil
can be used for ladle or tundish preheating with significant
saving in the fuel consumption.
(j) The burner can be used for accelerated reheating of
ladles to a high temperature before pouring of the molten
metal and thus for preventing a drop in temperature of the
molten metal.
(k) The burner is suitable for ladle recycling by removing
the leftover skulls or spills in the ladle.
(1) The burner can be used also for spray-coating of

materials like c.eramics and metal-bonded carbides e.g.
tungsten carbide.
(m) The burner is suitable also ifor reheating bars and billets by" direct impringenent of its flame -at a much faster
rare compared with the use of a conventional fuel-fired
furnace.
(n) The burner can be used also as a lance for blowing
oxygen into molten metal in a metallurgical process.
Design calculations:
The throat area of the lance nozzle for high velocity oxygen flow at the desired flow rates is calculated by the following equation.
(EQUATION REMOVED)
where
A-!= cross sectional area, m2
rji= mass flow rate, kg s~*
Po= supply pressure of oxygen, Pa
^L = flow rate coefficient, 0.92
k = specific heat ratio
R = gas constant, J kg K~1
To = gas temperature, °K
The enlarged area at the critical section is thus obtained as:
Ac = A^At where
At is the area covered by the oil nozzle, m2. The outlet cross sectipn of the nozzle is determined : .;
Ao = m*R*To/(Va*Po*(Pa/Po)1)
Pa = ambient pressure, Pa
The actual velocity of gas at a particular flow rate is given by Va=2k/(k-1)RTo{1-(Pa/Po)k-1/k]05
The pressure of gases at the exit section in the nozzle is: Pe=Po/[(1+.2(va/vs)2]k/-i
where
Vs= velocity of sound, ms-1
In the lance, mode, the velocity at the nozzle_fixit during the flat bath period.would be determined by the depth of oxygen jet.
h/x(1 +h/x)2= 2c2 pg uo2 Ae//n p, g x3 • •
where
°h= depth of penetration of lance jet, m
x= lance distance, m
c= jet constant for momentum transfer
pg= density of gas, kg m-3
uo= jet exit velocity, m sr1
Ae= exit area of nozzle, m2
P1 =density of liquid, kg m-3
g = acceleration m s"2




We Claim :-
1. An improved burner cum lance comprising at least five concentric seamless tubes (1,2,3,4,5), preferably of mil.d steel, arranged to operate in an inter-dependent manner, wherein the relatively narrow central or the innermost tube d) is meant for supplying fuel oil, the annular space between the innermost tube (1) and the second concentric tube (2) is meant for supplying oxygen, the annular space between the second tube (2) and third tube (3) is meant for supplying air or natural gas to the tip (8) and the annular space between the third tube (3) and fourth tube (4) and that between the fourth tube (4) and fifth tube (5) are meant for circulating coaling water, characterised in that the said tip (8) is provided with a convergent nozzle (9) and a divergent nozzle (10) which are connected to each other at throat area (11) thereof, that the innermost tube (1) is extended upto the throat area (11) to occupy 30 to 40 percent of the throat area for supplying fuel oil into the divergent nozzle (10), that the remaining part of the throat area is provided for supplying oxygen into the divergent nozzle through the annular space between the innermost tube (1) and the second tube (2), that the side holes (12) are provided in the convergent nozzle for supplying air or natural gas into the convergent nozzle through the annular space between the second tube (2) and the third tube (3), and that an inlet (6) is provided in the fourth tube (4) and an outlet (?) is provided in the fifth tube (5) for circulating cooling v/ater around the tip (8).
2. The improved burner cum lance as claimed in claim 1,
v/herein the tip is made of electrolytic copper.
3. The inproved burner cum lance as claimed in claim 1 or 2
v/herein the throat area o£ the nozzle is of diameter 12.9 nun.
4. The improved burner cum lance as claimed in any of the
preceding claims, wherein the surface of the convergent nozzle is
inclined at an angle of 15° and that of divergent nozzle is
inclined at an angle of 7«5° to the axis of the burner.
5. The improved burner cum lence as claimed in claim 5,
v/herein the convergent nozzle is provided with three side holes,
each being of diameter 8 mm and inclination 60° to the burner
axis in the downward direction.
6. An improved burner cum, lance, substantially as herein
described and illustrated in the accompanying drawings.

Documents:

406-del-1995-abstract.pdf

406-del-1995-claims.pdf

406-del-1995-correspondence-others.pdf

406-del-1995-correspondence-po.pdf

406-del-1995-description (complete).pdf

406-del-1995-drawings.pdf

406-del-1995-form-1.pdf

406-del-1995-form-2.pdf

406-del-1995-form-4.pdf

406-del-1995-gpa.pdf

abstract.jpg


Patent Number 189678
Indian Patent Application Number 406/DEL/1995
PG Journal Number 31/2009
Publication Date 31-Jul-2009
Grant Date 27-Jan-2004
Date of Filing 10-Mar-1995
Name of Patentee STEEL AUTHORITY OF INDIA LIMITED
Applicant Address RESEARCH & DEVELOPMENT CENTRE FOR IRON & STEEL, ISPAT BHAWAN, LODHI ROAD, NEW DELHI-110003
Inventors:
# Inventor's Name Inventor's Address
1 SURINDER PAL SINGH SABHARWAL PRINCIPAL RESEARCH ENGINEER, RDCIS, SAIL RANCHI-834002, (INDIA)
PCT International Classification Number F23C 11/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA