FIELD OF INVENTION
The present invention relates to a liquid and gaseous fuel fired device with low pollutant emission for boiler applications. More particularly, the invention relates to the development of liquid and gaseous fuel fired device assembly for generating steam or Power production and more specifically applicable to refinery and industrial applications.
BACKGROUND OF THE INVENTION AND PRIOR ART
Due to enhanced fossil fuel consumption and limited reserves of oil and gas reserves, attention is focused on improving their combustion efficiency through improved design of equipment. Apart from above, stringent environmental norms for industrial gaseous pollutant emissions are also forcing industrialist to upgrade their existing fossil fuel based systems to reduce gaseous pollutants. In this regard, a special attention is focused on power, refinery and industrial sectors to develop high efficient low pollutant emission firing systems. In recent years many novel burner designs have been evolved for steam generation using multiple fuels within the same burner. Since, burner is an important element in firing the fuels under controlled conditions, design of burner plays a crucial role in deciding the flue gas composition, amount of unburnt carbon, flame stability, flame impingement and net efficiency of the plant. However, fuel flexible, easy operable, low pollutant emission, high

combustion efficiency and easy maintenance of burners are required for fossil fuel firing applications. Therefore, continuous efforts are made in developing novel burner to meet these criteria.
Indian Patent Application No. IN1070KOL2012A depicts a dual gaseous fuel burner for higher and lower calorific value with individual air supply for each of the fuel. However, the liquid fuel injection is missing in this design.
Indian Patent Application No. IN963K012013A discloses a dual gaseous fuel burner for firing high calorific value fuel and low calorific value fuel with single air supply. The air supply was provided through a common pipe for both fuels, hence the design is compact. However, the liquid fuel injection is not part of this design.
Indian Pat application No. IN583KOL2014A describes a gas-liquid dual fuel burner system for liquid fuels and low calorific value fuel gases. Swirl block was provided for both air and gaseous fuel supply for better flame stability. However, it was specially designed for low calorific value gaseous fuels only and not for high calorific value fuels such as natural gas.
Indian patent application No IN594KOL2015A, describes a low NOx emitting solid fuel fired wall burner apparatus for boilers in thermal power plants. This design

was useful for firing pulverized solid fuels and liquid fuel firing during start-up of the boiler. However, in this design provision for gaseous fuel firing is missing.
Indian Patent Application No 1230/DEL72004 describes a multi-fuel burner for firing blast furnace gas (BFG), coke-oven gas (COG) and oil. In this burner, an oil gun was provided at the center of the burner, COG fuel was injected around the oil gun and air is supplied around the COG pipe. The BFG fuel was injected into the furnace using a gas spuds around the air pipe. The air has been supplied into the burner in two stages using spinner vanes to provide swirling action. BFG and COG are low calorific value gases, which requires different pipe sizing and fuel nozzles. Apart from that this burner fires three different fuels therefore arrangement of the burner. However, the burner design significantly varies in air staging and the way gaseous fuel injection into the furnace.
Indian Patent Application No 201631032232 (ye to publish) describes a multi-fuel wall burner to fire two gaseous fuels, liquid fuel and a solid fuels for industrial applications. In which air flow and gaseous fuel flow injection is very different from the invented burner.
In dual fuel burners, design of innovative liquid and gas fired dual burners are commonly observed in industrial application for example in US Pat. No. 6068470A describes a dual-fuel burner in which the gaseous fuel entry was at annual space between primary and secondary air. Here fuel staging concept is not used and as well

it is particularly designed for combustion chambers of stationary gas turbine applications. The air controlling mechanism and swirl arrangement is very different from the present invention.
In Chinese Pat. No. CN101360950B (also US Pat. No. US7909601B2), describes dual-fuel burner (gas/non-gaseous) for steam cracking applications in which the gaseous and nongaseous fuel burner injection close to each other. Where single gaseous fuel nozzle used for firing gaseous fuels.
In an Indian Pat. No. IN232032A1 describes a dual fuel gas-liquid burner for firing liquids up to 200 kg/hr and low calorific value gaseous fuels up to 2000 Nm3/hr. This design specially meets shorter and intense flame generation in any furnace applications.
In US Pat. No. US6951454B2, description about dual fuel burner with coal and gaseous fuel were given. This design does not offer liquid fuel injection and it is specially designed to fire pulverized solid fuels.
In US Pat. No. US 2011/0314826 A1 describes fluidic fuel firing burner where the gaseous fuel entry and mixing with air were significantly differs from the present invention. This burner design is complex in nature and premixing of air and gaseous

fuel before combustion was described in this invention. The fuel injected through the nozzle made in the swirl block provided for air.
In US Pat. No. US006027330A describes an industrial fuel gas burner where liquid fuel and gaseous fuel firing envisaged. The invention was vary from present invention with respect to fuel nozzles, air flow controlling, air staging, type of oxidizer (air vitiated with flue gas vs pure air) and type of swirl blocks for air. Two ring shaped headers are used for fuel injection and air is uniformly mixed with recycled flue gas and admitted into combustion chamber.
In a Japanese Pat. No. JP2002213746A describes a liquid fuel and gaseous fuel burner, where fuel premixing with air before combustion design for gas turbine applications. This design of fuel nozzle, swirl block and air controlling are vary significantly from the invented burner design.
Although many novel burner concepts were published, describing about dual fuel burner with gas-liquid for different industries but the present proposed design significantly deviate from others. In the present innovation, a dual fuel (liquid and gaseous) burner was described for efficient fuel firing and producing minimal pollutant emission in the steam generation applications. These burners are flexible to operate and easy to maintain in the boiler during its service.

OBJECT OF THE INVENTION
Therefore, it is an object of the invention to propose a liquid and gaseous fuel fired device with low pollutant emission for boiler applications which is capable of efficient fuel firing with minimal pollutant emission.
Another object of the invention is to propose a liquid and gaseous fuel fired device with low pollutant emission for boiler applications which is able to create a better flame stability and to reduce gaseous pollutant such as thermal NOx, when the device is provided with an air staging mechanism with an effective flow control mechanism.
Another object of the invention is to propose wheels for the primary and secondary air damper cover plates/sleeves to provide smooth operation during burner operation at high temperature air. These wheels acts as gliders while operating primary and secondary air dampers during burner operation.
A still another object of the invention to propose a liquid and gaseous fuel fired device with low pollutant emission for boiler applications which is capable of better fuel and air mixing to obtain a stable flame with either fuel by means of a swirl arrangement of the device for primary and secondary air.

A further object of the invention to propose a liquid and gaseous fuel fired device with low pollutant emission for boiler applications which can provide fuel staging for gaseous fuel using a specialized gas spuds for providing faster ignition thereby better flame stability and reduction of gaseous pollutant such as thermal NOx.
SUMMARY OF THE INVENTION
Hence the invention proposes a liquid and gaseous fueldevice which offers flexible operation, high burning efficiency and low pollutant emission,with either of the fuel or both fuels.
The liquid and gaseous fuel firing device can be used in steam generation boilers, process and captive power plants and in refineries. The device is designed to fire with any of the fuels such as Light Diesel Oil (LDO), Heavy Fuel Oil (HFO), any other liquid fuel and natural gas, Liquefied Petroleum Gas (LPG), any other gaseous fuels such as refinery gases, steel plant gases or in combination of the gaseous and liquid fuels not exceeding the maximum design capacity of device. The liquid fuels spray pipe is located at the center of the device, around which number of gaseous fuel pipes are placed. The gaseous fuel exit through gas nozzle to the boiler wherein the total air is supplied through wind box for both the fuels based on stoichiometric proportion. To admit air controllably into the boiler, primary air is supplied around

liquid fuel pipe and gaseous fuel pipe. The secondary air is supplied through a dedicated space over primary air pipe through swirl system. The proportion of air between primary and secondary air is controlled using cover plates between wind-box and device. These cover plates are specifically designed for primary and secondary air, in which airflow can be regulated as per requirement. The proportion of primary air in the total is varies from 25 to 45%, as the exact proportion decided based on type of fuel and combination of gaseous and liquid fuels.
Another aspect of the invention describes the design of liquid and gaseous fuel firing device, where liquid fuel gun requires supply of liquid fuel at 4 to 15 bar to atomize evenly and corresponding atomizing medium send at 4 to 16 bar. Here, the atomizing medium can be either air or steam. The gaseous fuel is admitted into a common space in the device in which plurality of gaseous fuel pipes are connected up to the downstream of device throat. The pressure of gaseous fuel required is 2 to 6 bar, where the gaseous fuel exit through specially designed gas nozzle into the boiler.
Another aspect of the invention describes the design of liquid and gaseous fuel firing device, where the total air for device enters from wind-box to secondary air through a perforated surface of secondary air pipe. The air further enters to primary air space through similar perforated surface of primary air pipe. These perforations distribute the air uniformly around the concentric pipes within the device, which helps

in better mixing between air and fuel during combustion. Each of these perforated pipe sections of primary air pipe and secondary air pipe are covered with two semi-circle cover plates. These cover plates are provided with wheels on the edges for smoother functioning while operating these cover plates to adjust the air flow between primary and secondary air. These cover plates are operated through axial lever which in turn connected pneumatically from control panel of the device as per requirement. The primary air enters the boiler through a swirl block, above its circumference number of gaseous fuel pipes are located. The swirl block is mounted on liquid fuel guide pipe where it provides stability for liquid fuels. The secondary air enters through the boiler through a swirl block with moderate swirl which mixes the fuel at slightly later than primary air and thus air staging happens while combusting the gaseous or liquid fuels. The swirl blade angle for primary and secondary swirl blocks are decided between100&300and 150& 450respectively based on type and
combination of fuels to be fired in the device.
According to another aspect of the invention, the perforations around the primary and secondary air drum are with different sizes to provide uniform airflow to the primary and secondary air pipes.
According to another aspect of the invention, the fuel nozzles provided in the device can be of many variants with respect to nozzle and vanes. This provides

effective fuel staging and ignition for the gaseous fuel combustion. Based on calorific value of the gaseous fuel, the design of nozzle can be selected.
According to another aspect of the invention, the turndown ratio for the liquid fuel and gaseous fuel is very high i.e., up to 1:5. By regulating the oil pressure using liquid fuel return line, this high turn down ratio can be achieved.
According to another aspect of the invention, the atomized liquid fuel or gaseous fuel can be ignited using a single high energy arc ignition which is located in between liquid fuel nozzle tip and gaseous fuel nozzle tip. Similarly, flame scanner is inserted into the device assembly to observe the flame.
Gas-Liquid Dual Fuel Device Experimentation
The liquid and gaseous fuel device of capacity 2.5 Mkcal/hr was fabricated and tested with both liquid and gaseous fuels in a test facility where LPG is considered as gaseous fuel and LDO is considered as liquid fuel. During the experiments, stable flame was observed with either fuel or switch over from LDO to LPG and vice-versa happened smoothly. During experimentation 02 level in the exhaust gas was maintained constant at 3% with either or both fuels. Lower NOx values of 80 and 110 ppm was reported during LDO and LPG fuel firing respectively.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: illustrates the cross sectional view of liquid and gaseous fuel firing device configuration, liquid fuel and gaseous fuel flow arrangements along its principle axis X-X, according to the invention.
Figure 2 illustrates the side view of the liquid and gaseous fuel firing device of
Figure 1.
Figure 3 illustrates a swirl block arrangement of the primary and secondary air
supply in the liquid and gaseous fuel firing device.
Figure 4 illustrates the secondary air and perforations on the surface in the liquid
and gaseous fuel firing device.
Figure 5 illustrates the gaseous fuel nozzle arrangement in the liquid and
gaseous fuel firing device.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
The present invention provides a liquid and gaseous fuel firing device for power or refineryor process captive power plant applications.

Figures 1 to 5 shows the detailed arrangements of a liquid and gaseous fuel firing device assembly, where Figure 1 illustrates the longitudinal cross sectional view of the liquid and gaseous fuel firing device, whose principle axis is shown as X-X. Device consists of an inner most liquid fuel gun (1) with atomizing nozzle (2) to atomize the liquid fuel. The liquid fuel gun (1) was concentrically located in the primary air supply pipe (9). The gaseous fuel is supplied through the pipe (3) to common drum (4), which is connected to gaseous fuel pipes (5). The gaseous fuel pipes are also located in the primary air supply pipe (9) away from the liquid fuel pipe (1).The gaseous fuel from pipe (5) exited through the nozzle (6) into the boiler. The total air is supplied through the wind box (7) to secondary air pipe (8) through a perforated outer surface (10). The part of air is passed into secondary air pipe (8) migrates to primary air pipe (9) through perforated holes (10)to the innermost section of device. This major part of primary air passes through swirl block (17) into the device over liquid fuel pipe (1). The secondary air also exited through the swirl block (16) into the boiler or furnace. The primary air and secondary air supplies are controlled using cover plates (11) and (12) respectively. These covers plates (11) and (12) split into two parts with each covering 180° of the pipe for easier operation. The primary air cover plate is connected to a lever (21) for movement. The secondary air cover plate is connected to a lever (13), which is in turn operated using axial pneumatic controller system (15). The cover plates (11) and (12) are provided with wheels (14) for smooth operation. For ignition of liquid fuel a high energy arc igniter

(18) is provided at an angle near to liquid fuel atomizer nozzle (2). To monitor the flame presence near device, flame scanning pipes (19) are provided within the primary air pipe (9). The liquid and gaseous fuel firing device installed in a furnace with refractory throat (22).
Figure 2 illustrates the side view of the liquid and gaseous fuel firing device presented in Figure 1. Where liquid fuel gun (1) and six number of gaseous fuel pipes(5) are arranged in a circular fashion within the primary air pipe (9). Handles (20) to adjust the primary air cover plates manually are provided in the device. Gaseous fuel inlet (3) to the drum, primary (9) and secondary (8) air pipes secondary air cover plate control system(15) are shown in the Figure 2.
Figure 3 illustrates the arrangement of swirl blocks (16) and (17) kept within the secondary air pipe (8) and primary air pipe (9). The swirl block (16) is placed over the primary air pipe (9). The swirl block (17) is placed over the liquid fuel gun (1) and close to the liquid fuel spray nozzle (2). Length, angle and number of swirl blades for swirl block(17) vary from 30 to 100 mm, 15-45° with axis X-X and 6 to 18, respectively. The number of swirl vane blades in secondary air pipe swirl block (16) can be varied from 12 to 36 and the angle can be varied from 10 to 30°. The length of swirl vane blades in the outermost swirl block(16) can be varied from 50 to 150 mm.

Figure 4 illustrates the arrangement of secondary air pipe (8) with perforations (10) on the outer surface of part of pipe (8). This pipe is connected with set of flanges (23) for assembling with other components of liquid and gaseous fuel firing. Similar arrangement has been made for primary air pipe (9).
Figure 5 illustrates the arrangement of gaseous fuel nozzle (6) connected to gaseous fuel pipe (5). There are several variants of the nozzle are developed for the gaseous fuel injection into the boiler such as holes around fuel nozzle (24), nozzle with vanes (25), all round fuel supply nozzle with vanes (26), nozzle with thick vanes (27) and thick vanes with all around fuel supply nozzle (28).
NOVEL FEATURES AND ADVANTAGES OVER THE PRIOR ART
The present invention proposes a flexible gaseous fuel and liquid fuel firing device better flame stability and reduced emissions designed especially for boiler applications to generate steam. The following are novel features of the proposed invention.
• The burner device proposed with optimum air staging between primary and secondary air to provide stable flames and low NOx emission during gaseous or liquid fuel firing.

• The burner device consists of fuel staging for gaseous fuel using a specialized gas spuds. This provides faster ignition thereby better flame stability and reduction of gaseous pollutant such as thermal NOx.
• The present invention is proposed with an optimal swirl arrangement for primary and secondary air flows for better fuel and air mixing to obtain stable flame with either fuel.
• To effectively control primary and secondary air flow to fire gaseous or liquid fuels burner device is provided with split dampers cover plates around the primary and secondary air pipes which can be operated pneumatically.
• Since the burner device is operated at higher temperature air at around 350 °C, to provide smooth operation the present invention proposes wheels for primary and secondary air damper cover plates/sleeves. These wheels acts as gliders while operating primary and secondary air dampers during burner operation.
The above features are significantly different from prior art

WE CLAIM
1. A liquid and gaseous fuel fired device with low pollutant emission for boiler application comprising;
an inner most liquid fuel gun (1) with atomizing nozzle (2) for atomizing the liquid fuel, the said liquid fuel gun concentrically located in the primary air supply pipe (9);
an air staging mechanism of primary air supply pipe (9) and secondary air supply pipe (8) with perforations (10) a plurality of gaseous fuel pipes (5) disposed in the primary air supply pipe (9) away from the liquid fuel pipe (1) for supplying gaseous fuel through a plurality of nozzles (6) into a boiler for complete combustion of fuel;
an air windbox (7) configured to supply air to secondary air pipe (8);
fixed swirl blocks (16, 17) disposed with the primary air pipe (9) and secondary air pipe (8);
split cover plates (11, 12);
a lever (21) with a handle (20) connected to primary air cover plate (11) for movement of said plate (11);
a lever (13) connected to a pneumatic conveying system (15) for movement of secondary air supply cover plate (12);

2. The device (D) as claimed in claim 1, wherein the diameter of perforations (10) on primary air pipe (9) and secondary air pipe (8) varies from 3 to 25 mm.
3. The device (D) as claimed in claim 1, wherein a pipe (3) is disposed for receiving gaseous fuel and delivering to a common drum (4) connected to gaseous fuel pipes (5) for exiting through the nozzle (6) into the boiler.
4. The device (D) as claimed in claim 1, wherein length, angle and number of swirl blades for swirl block (17) vary from 30 to 100 mm, 15-45o with axis X-X and 6 to 18 respectively.
5. The device (D) as claimed in claim 1, wherein the number of swirl vane blades in secondary air pipe swirl block (16) varies from 12 to 36 when the angle varies from 10 to 30o.
6. The device (D) as claimed in claim 1, wherein the length of swirl vane blades in the outermost swirl block (16) varies from 50 to 150 mm.
7. The device (D) as claimed in claim 1, wherein the cover plates (11, 12) are provided with wheels (14) for smooth operation.

8. The device (D) as claimed in claim 1, wherein liquid and gaseous fuel firing device is installed in a furnace with refractory throat (22).
9. The device (D) as claimed in claim 1, where gaseous fuel is supplied through plurality of nozzles (6).
10.The device (D) as claimed in claim 1, the number of fuel pipes (5) in the design vary from 3 to 8 concentrically within the primary air pipe (9).
11.The device (D) as claimed in claim 1, the gaseous fuel nozzle can be different types (6) or (24) or (25) or (26) or (27) or (28). The selection of nozzle is dependent on type of fuel, boiler configuration and application.
12.The device (D) as claimed in claim 1, wherein the primary and secondary air damper cover plates (11, 12) are provided with wheels (14) which acts as gliders while operating primary and secondary air dampers during burner operation.