Field of invention:
Integrated steel plants are equipped with blast furnaces, coke oven batteries and score of other furnaces for heating and steel melting. Blast Furnace Gas (BFG) and Coke Oven Gas (COG) are generated in steel making process. Blast Furnace Gas contains very low amount of combustibles (20 to 22 percentage of CO, which poses a serious health hazard ) and high amount of insert such as Nitrogen and Carbon dioxide. It possesses a low calorific value and which leads to slow burning combustion reactions.
Coke Oven Gas, which is by product of Coke oven batteries, has very high dust concentration and poses health risk. In addition, the accumulation of these gases leads to explosion. Hence these gases are to be necessarily flared efficiently, which is costly solution.
Alternatively heat energy from these gases can be derived efficiently by innovatively designing a Burner and using the heat energy for producing steam for Captive Power Plants. It has a direct bearing on energy, manufacturing and other allied sectors. Energy conservation, environmental pollution abatement, occupational Environmental and safety are the derived benefits.
The Multi-fuel type burner is ideally suitable for effectively, and efficiently burning the Blast Furnace Gas & Coke Oven Gas along with Oil.
This invention relates to the innovative development of a uni- burner assembly for firing multi fuels like Blast Furnace Gas, Coke Oven Gas and Fuel Oil in the captive power plant of steel mill.
Background Art / prior Art:
This invention relates to a multi fuel burner and moves particularly a multifuel burner ideally suitable for effectively and efficiently burning the blast furnace gas and coke oven gas along with oil.
A here to fore known multi fuel burner of this general type includes a centric outlet location in the form of air atomizer nozzle for liquid fuels, which is surrounded by outlet location for two different fuel gases (US patent 4,566,268) which is parallel to the oil spray zone. By this the gas outlet not properly penetrating in the oil spray zone for better combustion.
Further US patent 5,391,075 described and claimed the same inventor as named in the present applications. The use of a multi fuel burner in particularly firing BFG and COG gases is different configuration in this invention.

Growth and development of steel industry are positive indicators for the growth of the country's economy. It has a direct bearing on energy, manufacturing and other allied sectors. Integrated steel plants are equipped with blast furnaces, coke oven batteries and score of other furnace for heating and steel melting. Energy conservation, environmental pollution abatement, occupational Environmental and safety are the mantras for transnational and multinational organisations.
Steel plants are intensive Energy consuming industry. In addition the waste gases viz. Blast furnace gas here in after refered as BFG and Coke oven gas here in after refered as COG are generated in the process. Blast furnace gas possesses a low calorific value and carbon monoxide is about 20%, which poses a serious health hazard. Coke oven gas which is by product of Coke oven batteries has very high dust concentration and poses health risk. In addition the accumulation of these gases leads to explosion.
Hence these gases are to be necessarily flared efficiently, which is costly solution. Alternatively heat energy from these gases are to be derived efficiently by innovatively designing a Burner and use the heat energy for producing steam for Captive Power Plants.
Generally burners are having the following features:
Air supply lanes, ignition sources, fail-safe ignition, swirls, flame scanning for safety and Gas lanes for combustible fuel. The existing burning devices are having BFG lane / pipe, which supply the gas to the burner. The burner is having throat (wide). In the conventional burner the BF gas is ignited with the available ignition source.
Parallel paths for BFG, COG, Oil & Air are available in these devices. Though secondary air is swirled, desired combustion results are not obtained. In addition furnace walls are lined with refractory. This refractory radiates back to ignite BFG gases. These refractories are maintenance prone due to spacing and selective refractory lining leads to unsafe firing condition due to oil spillage in case of faulty oil firing.
This invention relates to the innovative development of a uni- burner assembly for firing multi fuels like Blast Furnace Gas, Coke Oven Gas and fuel oil in the captive power plant of steel mill.
The construction of the Multi-Fuel Burner is shown in the burner arrangement drawing. Essentially the burner is composed of a wind box, air register, oil gun assembly, Blast Furnace Gas annulus assembly, Coke Oven Gas spud and High Energy Arc igniter assembly with burner throat. The air register assembly is designed such that the combustion entering from the wind box is divided into a primary and secondary airflow are controlled separately by means of dampers. The primary air constitutes only a small percentage (approximately 30%) of total air. It flows through the primary air sleeve, which houses the gun. The purpose of the primary air is two fold.
• It introduces air for initial ignition of the burner nozzle tips.
• It fills the vortex created by combustion in the secondary air zone (burner
throat) there by preventing the fire from drawing into burner nozzles.
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The burner primary air vanes, which are arranged concentrically around the burner, are operated by primary spinner vane assembly handle. The vanes impact a rotary motion to the primary air entering the burner primary air sleeve and at the same time affect the velocity of the air mixing with the fuel.
The secondary airflow around the primary air sleeves to the burner throat provides the necessary air for the primary ignition started at the primary sleeve exit and to sustain the flame. The secondary vanes impart a rotary motion to the secondary air entering the burner. The secondary vanes are arranged at the extreme to the annulus between primary air sleeve and secondary air sleeve. These vanes can be operated by a handle from outside to set the desired angle.
The primary and secondary airflows are controlled separately by means of individual dampers. The primary air damper is operated manually with the manual control lever. This can be locked at the desired position with the help of locking bolt and nuts. The secondary air damper is driven by the continuously modulating damper drive, which maintains a constant pressure differential between the tap upstream of primary air damper box and the furnace pressure tap.
The burner front plate is equipped with observations ports, which permit viewing the fire through the annuals between the primary and secondary air nozzles.
Objects of invention:
In my innovation the firing concept is altogether different from the available devices.
Swirling phenomenon in burners are characteristic feature of the aerodynamic flames generated from burning devices. The application of swirling motion to the constituents of burners flowing medium viz air and gases are the genius derivative of the furnace designers. The type and position of swirler imparting swirling motion to air/gas are unique and innovatively and logically employed depending the fuel gas constituent, calorific value, specific gravity, Wobbe index and chemical composition. The present innovation is the desired swirl required for efficient combustion of BFG is employed.
The importing swirling motion is to the air/gas is conventionally done using an axial or radial surfaces, tangential flaps ect. In my innovation swirling motion is imported in a novel way.
This special type of swirling enables the BFG to get injected into the furnace and receive the ignition from the main frame of Oil/ COG envelop which sits into the throat of the burning devices. Ignition of the low BTU BFG gas has been carried out effectively. So that obnoxious BFG will not be let out from furnace and create hazardous environment.
Ignition of BFG gas is accomplished by spraying fuel oil to create a flame envelope and inject the gas from with the flame such that it pierces the flame envelope and catch fire. Alternating BFG has be injected from outside at an angle which intersects the flame envelop. The second type of ignition is very innovative which produces larger surface area flames envelope. After careful in depth study on furnace flame interaction, ignition, efficient combustion the innovative method of importing swirl to BFG and create an intersecting flame with oil/cog flame is accomplished. My novel method enabled the burner to have BFG flame directly ignited in furnace instead of igniting and

maintaining flame at throat. This novel feature takes care of upstream pressure fluctuations.
Detailed description:
Use of blast furnace gas for power production:
In the process, the Blast furnace generates a large quantity of off gas called 'Blast Furnace Gas'(BFG) containing about 20 to 22 percentage of CO and with a calorific value of above 600 Kcal/Nm3. This gas poses a big pollution control threat before its release into the atmosphere.
Following are the various key parameters, which need very careful attention for a successful installation of a BFG-based power plant.
Functional requirements of a Blast Furnace Gas steam power plant:
The feasibility of the complete pig iron is greatly influence by a successful operation of BFG-based captive power plant (CPP).
The major functional requirements of the CPP can be identified as under:
• High reliability because the blast furnace blowers depend on the boiler for steam or
power supply.
• Auto-change over to oil firing in case interruption in the supply of BFG to save Blast
furnace plant trip.
• Tolerance to water carry over in BFG from wet gas cleaning plant (GCP) upstream of
boiler.
• Minimum continuous oil support for lower operating cost.
These requirements have to be carefully studied and adequate measures are to incorporated in the boiler designs for successful continuous operation.
Characteristics of BFG and differences:
In order to successfully combust BFG in a boiler on a sustained basis, it is very important to understand the specific characteristics of BFG and the ways in which it differs from conventional fuels.
A study of BFG reveals the following characteristics; High inerts and low calorific value:
BFG contains very low amount of combustibles (20 to 22 percentage of CO) and high amount of inerts such as Nitrogen and Carbon di oxide.
This results in a very low calorific value. The lower calorific value means that the combustion of BFG needs to be very carefully stabilized.

It also means that very high quantities of flue gas therefore flue gas have to be handled for the same steam output as compared to conventional boilers. These high quantities of flue gas increases the pressure drops in the boiler system.
Slow Burning:
As a result of the low calorific value and high amount of inerts, the BFG is a very slow burning gas. In order to ensure the complete combustion of BFG , higher residence time in the furnace is very essential.
This higher residence time can be achieved by using larger boiler furnace and lower furnace volumetric heat release rate.
If the combustion of BFG is not complete in the furnace zone, an unwanted accumulation of combustibles, which may result in explosion, may take place in the convection zone.
Flame defect-ability:
The flame produced by combustion of BFG does not produce an adequate strength of ultraviolet or inferred radiations for sensing by conventional flame sensors. This makes it difficult to incorporate flame safeguard safeties in the boiler.
Low flame temperature and emmissivity:
The BFG flame temperature is much lesser as compared to conventional flames. The BFG flame does not have strong emmissivity for radiative heat transfer to the furnace enclosures.
Wide variations in supply pressure, flow and calorific value:
Due to fluctuations in the process of making pig iron, the supply pressure, flow and calorific value of the BFG vary widely. This wide fluctuation result in an unstable flame.
Low supply pressure:
The BFG is supplied at lower pressure to the burners as compared to conventional fuels thereby severely limiting the possibility of giving high swirls for intense air fuel missing. This also results in slower combustion of the BFG.
Health hazards:
Due to CO content, the BFG is a toxic gas and prolonged exposure to it can result in unconsciousness.
Moisture loading from the Gas Cleaning Plant (GCP):

Due to wet scrubbing of the BFG carried out in the GCP prior to the boiler, a certain excess amount of water enters the boiler along with the BFG. This water results in a lower calorific value and lower flame temperatures.
Key features essential for the successful operation of a BFG based power plant:
Based on a study of the functional requirements of steam generation plant and the typical characteristics of the BFG, the inventors incorporated several features which improve the reliability of the BFG fired steam generators and which contribute to continuous successful operation of the BFG-CPP. Some of these features which have proven their usefulness in several operating installation.
The inventor's multi-fuel firing system is described hereunder: Low Volumetric heat release rate with a larger boiler furnace:
The furnace volumetric heat release rate of about 25,000 BTU/Hr/Ft3 (222,000 Kcal/Hr/m3) is adopted for ensuring the complete and stable combustion of BFG because of higher residence time in the furnace zone.
Flame sensing fuel:
Since the BFG flame is not detectable by Ultra Violet and Infra Red scanners, it is adopted to fire a small amount of flame sensing fuel continuously in to the furnace to enable flame sensing by conventional scanners. Though BFG produces self sustainable flame and does not need any oil support, it considers it prudent to provide a continuous flame sensing fuel for avoiding frequent trips due to wide variations in the BFG supply pressure, Calorific value, quantity, moisture content etc, which are known to have an adverse effect on the flame stability.
This philosophy adopted has been proven to be very sound philosophy in the field. The company has concentrated on minimizing the amount of flame sensing fuel requirements by incorporating several features as described further and has reached very low levels of only around five percentage as the heat input from the flame sensing fuel.
Inventor's Multi fuel uni - burner:
As seen from the typical characteristics of the BFG, the success of the boiler largely depends on the burner used with the boiler.
The Multi fuel uni - burner, which is ideally suitable for effectively, and efficiently combusting the BFG, COG & Oil. Because the boiler and burner are designed and manufactured by the same company there is perfect harmony between these two vital equipments, which would not have been possible if the designers of boiler and burner were different.
The Uni-burner provides spin to the BFG stream as it enters the furnace for ensuring a high mixing energy at the point of air fuel mixing.
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The uni- burner also uses the principle of premixing fuel with air for better combustion by injecting a stream of BFG into flame envelop stream when it enters the furnace. The Uni- burner provides a central pipe for ensuring provides a central pipe for ensuring adequate oxygen supply to the oil flame located at the center of burner. A typical uni-burner is shown in the drawing section.
One oil gun per burner:
The Uni- burner incorporates one oil gun located in the central air pipe. This oil burner permit minimizing the flame sensing oil requirement at the same time permitting loads upto 1OO percent boiler load on oil alone. This oil gun ensure proper atomizing at all the load range on oil firing. This makes the burner capable of handling the variations in BFG flow, pressure and calorific value.
One UV scanner per burner:
The Uni- burner incorporates one UV scanner can be focused on the appropriate UV zone of the oil gun to detect the oil flame.

We claim :
1. A multi fuel burner for firing multi fuels like blast furnace gas, coke oven gas and Fuel oil, comprising wind box, air register, oil gun assembly, blast furnace gas annulus assembly, coke oven gas spud and HEA igniter assembly with burner throat.
2. A multi fuel burner as claimed in claim 1, wherein the air register assembly is
constructed such that the combustion entering from the window is divided into a
primary air steam and secondary air steam.
3. A burner as claimed in claim 2, wherein the primary air constitutes only a small
percentage of total air and it flows through the primary air sleeve, which houses the
gun.
4. A burner as claimed in claim 3, wherein the primary air introduces air for initial
ignition of the burner nozzle tips.
5. A burner as claimed in claim 3, wherein the primary air fills the vortex created by
combustion in the secondary air zone thereby preventing the fire from drawing into
burner nozzles.
6. A burner as claimed in claim 1, wherein the burner primary air vanes are arranged
concentrically around the burner and are operated by spinner vane assembly handle.
7. A burner as claimed in claim 6, wherein the said vanes impact a rotary motion to the
primary air entering the burner primary air sleeve and at the same time affect the
velocity of the air mixing in the fuel.
8. A burner as claimed in claim 2, wherein the secondary air flows around the primary
air sleeve to the burner throat and provides the necessary air for the primary ignition
started at the primary sleeve exit and to sustain in the flame.
9. A burner as claimed in 8, wherein the secondary vanes are arranged at the extreme to
the annulus between primary air sleeve and secondary air sleeve.

10. A burner as claimed in claim 9, wherein the said secondary vanes can be operated by
a handle from outside to set the desired angle.
11. A burner as claimed in any of the claims, wherein the primary and secondary airflows
are controlled separately by means of individual dampers.
12. A burner as claimed in claim 11, wherein the primary air damper is operated
manually with the manual control lever and the said lever can be locked at the desired
position with the help of locking bolts and nuts.

13. A burner claimed in 11, wherein the secondary air damper is driven continuously
modulating damper drive, which maintains a constant pressure differential between
the tap upstream of primary air damper box and the furnace pressure tap.
14. A burner as claimed in any clime above, wherein the burner front plate is equipped
with observation ports which permit viewing the fire through the annulus between the
primary and secondary air nozzles.
15. A multi fuel burner as herein described in the specification and shown in the
drawings.
16. A process for purifying atmosphere polluted by the flue gases generated in the
industrial activities by utilizing the multi fuel burner as claimed in claims 1 to 14.