FIELD OF THE INVENTION
The present invention relates to a multi-state fuel firing wall burner for boiler furnace in steam and/or power production. More particularly, the invention related to a flexible fuel firing burner for multiphase fuel such as solid, liquid and lower and higher calorific value fuels to lower emission of combustion constituents.
BACKGROUND OF THE INVENTION
Low calorific value gases such as synthesis gas (termed as syngas here after) or Blast Furnace Gas (BFG) and Coke Oven Gas (COG) are byproducts (off-gases) from the various furnaces used in the refining processes of industrial steel mills or refineries. Typically steel mill furnaces require large quantities of energy input from coal feedstock. During this process, COG is produced by pyrolysis of bituminous/sub-bituminous coal in the coke oven and this coke oven produces coke, which is used in the blast furnace. This high temperature process extracts volatile components of the coal, such as water, tar, and gaseous hydrogen. Hence, the byproduct gas contains high levels of H2, typically 40-70% by volume, with methane (CH4), carbon monoxide (CO) and minimal inert content. The BFG is formed in the blast furnace, where smelting process carried out to produce industrial metals generally iron in the steel mills.The gaseous fuel produce during this process usually contains mixture of gases such as H2 and CO. The H2concentration is usually less than 5% and CO ranging from 20-25% by volume. The balance of the gas is inert – CO2 from the reaction, and N2 from the air. The BFG is a low calorific value fuel gas and its calorific value is around 1,000 kcal/kg only. The COG and BFG are by products of steel mill will be utilized by steel plants to maximize the energy efficiency and productively.

With the tremendous growth of the steel industry in the recent years, greater interest has developed in increasing plant productivity and improving plant environmental performance. To help meet these goals, these industries are exploring new ways to improve plant efficiency and effectiveness. Therefore, to achieve a better performance, low calorific value gases and other coke oven gases must be utilized as the fuel for power and/or steam generation. However, these gases may not be sufficient to meet the required power and steam production continuously for their purpose. The quantity of low calorific value gaseous fuel production also vary with time, and based on market requirement. Therefore, to generate power and steam continuously a provision must be given in the boiler to fire any of the gaseous, liquid or solid fuels. This will provide higher flexibility to generate power/steam production continuously and consume the by-product fuel gases in industries as and when available. This will also enable industries to generate power at very low cost because of by product utilization by steel plants. This power can then either be sold or utilize within the industry. At the same time, hazardous emissions will also be reduced compared to flaring the gas.
Therefore, development of a burner catering to the needs of the industries is always challenging because it requires multiphase fuel firing such as gaseous, solid and liquid fuels. Although, burner designing for single phase, is fairly established over the years but designing a burner for different phases of fuels is very complicated.
Multi-fuel fired wall burners in combination of liquid/solid or liquid/gaseous fuels are commonly known from literature for example in Patent Publication Number WO 2011048123 A2, which describes a multi-fuel burner system for gas turbine firing applications where at least two gaseous fuels and maximum of three gaseous fuels can be fired. Various type of fuels such as natural gas, syngas or any other gaseous fuels can be fired in this burner. However, this burner does not designed to fire liquid or solid fuels.

Indian Patent Application No 1070/KOL/2012teachesa dual gaseous fuel burner for higher and lower calorific value fuel with individual air supply for each of the fuel. Swirl was provided for each of the air supply for effective mixing between the fuels. However, the liquid fuel injection and solid fuel injection is missing in this design. Indian Patent Application No. 963/KOL/2013 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. Stage supply of air and swirling action was provided for emission control and flame stability. However, the liquid fuel injection and solid fuel injection is missing in this design.
Indian Pat application No 583/KOL/2014 describes a gas-liquid dual fuel burner system for liquid fuels and low calorific value fuel gases. Swirl block was provided for air supply and gaseous fuel supply for better flame stability. However, solid fuel injection and high calorific value fuel injection is missing in this design.
Indian patent application No 594/KOL/2015, 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. Deflector plates were provided near solid fuel nozzle for better flame stability and air-fuel mixing. Here air was supplied in stages for effective control of NOx. However, in this design provision for gaseous fuel firing is missing.
US 20150226421 A1 describes a methodology of introducing natural gas in a coal or oil burning furnace so that it did not disturb the primary flame structure of the solid or liquid fuel. But, the subsequent mixing and combustion of gaseous fuel, actually improves the combustion and burn-out of the condensed phase fuel in the bulk volume of the furnace. At the same time, the process allows continued flame stabilization and safety of the condensed phase fuel combustion, furnace and boiler operation.

US 8197249 B1 describes a low-emissions high-pressure multi-fuel burner which works on premixing principle of fuel and oxidizer before burning. The fuel and oxidizer streams were entered through plurality of nozzles of an injector plate, with the plurality of nozzles being aligned with premix face of the injector plate and, with different nozzles receiving the fuel and oxidizer gases. Mixing the fuel and the oxidizer gas in a micro-premix chamber, formed between the injector plate and an impingement-cooled face. The staggered arrangement of fuel and oxidizer streams ensure proper mixing between fuel and oxidizer streams. This design did not provide liquid or solid fuel burning arrangement and hence limited to gaseous fuel applications only.
EP690264A2, describes a pulverized coal burner and method of using it, in which oil was placed at the center and coal was supplied concentrically in the surrounding pipe. The coal pipe was provided with venturi for controlling a concentration distribution of the pulverized coal and air required for complete combustion was supplied in multiple stages. They have claimed lower NOx even at lower loads of the pulverized coal. The secondary and tertiary air flow was supplied with swirling generators for flame stabilization.
Indian Patent Application No 1230/DEL/2004describes 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. However, the burner is missing the provision for firing the pulverized coal.

WO2014169963A1 describes a multi-fuel burning system with central burner for multi-fuel, multi-lance burner. At the end of innermost (primary fuel tube) tube, a funnel -like mixing device was provided. The secondary fuel lances were provided to the surroundings of the central burner. The combustion air/oxidizer was supplied through gaps between primary fuel lances and secondary fuel lances. The burner was claimed to be stable with high recirculation but there no provision envisaged for firing liquid fuels or solid fuels.
JP5458839, describes a multi-fuel burner device, which fires liquid and gas or a plurality of fuel gases having considerably different compositions. However, the burner does not provide the solid fuel burning facility.
CN 201706505 U, teaches a tri-fuel burner for high calorific, low calorific and a liquid fuel fired burner, with one air supply for all fuels in which only gaseous fuels are preferred. This cannot be used for multiphase fuel firing. A component of swirl is missing in their design, which provides better mixing between fuel and oxidizer and gives higher flame stability.
DE102013004016A1 describes a multi-fuel burner in which primary fuel send through annular pipes, primary oxidizer around the primary fuel pipe and one or more tubular inlets for secondary fuel in the center area of the mouth of the burner arranged parallel to one another and a plurality of, concentrically with respect to the feed channel for the primary fuel supply devices for the primary oxidizing agent was arranged with uniform angular spacing. This invention does not have provision for firing the solid fuels. The invention details about gaseous and liquid fuels only.
JP2006029763A describes a multi-fuel burner for firing oil and gas, where oil was placed at the center of the burner and gaseous fuel supplied through the gas spuds around the oil gun. Total air supply was split into primary and secondary, the

primary air has been supplied through the swirl block around the oil gun and the rest of air was supplied through the outer periphery of the burner. In this burner, there is no provision for firing solid fuels included.
DE112009000291B4 describes a pulverized fuel burner in which oil gun was located at the center for igniting the cost dust. The pulverized fuel was sent along with primary air and secondary air was supplied circumferentially over the primary air pipe. The secondary air was provided with a movable ring and movable guide vanes. However, the burner is incapable of firing gaseous fuels.
US20090061372A1 describes creation of a simple combination pulverized fuel burner with integrated pilot burner which ignites reliably and operates safely under the conditions of pulverized fuel gasification under pressure. The pulverized fuel channels were provided with water cooled channels to prevent the thermal stress. However, this burner does not discuss about oil firing.
Although many multi-fuel fuel fired wall burner concepts are available in the prior art for steam or power production applications but the present invention significantly deviate from others in terms of number of fuels fired, burner design, swirl arrangement, air controlling mechanism. In the present invention, a wall burner is designed for firing multiphase fuel with high combustion efficiency and lower NOx emissions by optimizing the different proportions of air flow.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose a flexible fuel firing burner for multiphase fuel such as solid, liquid and lower and higher calorific value fuels to lower emission combustion.

Another object of the present invention to propose a flexible fuel firing burner for multiphase fuel such as solid, liquid and lower and higher calorific value fuels to lower emission combustion, in which an air staging mechanism is provided for effective control of flame stability and flame length during low calorific value fuel firing particularly when all fuels remain at full load.
It is another object of the present invention to provide an involute entry to the pulverized solid fuel injection, which facilitates effective turbulence and thence better flame stability
A further object of the present invention is to propose a flexible fuel firing burner for multiphase fuel such as solid, liquid and lower and higher calorific value fuels to lower emission combustion, in which a swirl block for low calorific value fuel including secondary and tertiary air supply for effective flame stability and complete combustion, is provided.
SUMMARY OF INVENTION
Accordingly, there is provided a flexible fuel firing burner for multiphase fuel such as solid, liquid and lower and higher calorific value fuels to lower emission combustion.
In the present invention, a multi-phase fuel fired wall mounted burner is provided for installation in the wall of a boiler for firing gaseous, liquid and solid state fuels. Number of such burners can be arranged in series or parallel or both to get the rated steam output from the boiler.
According to the invention, a circular multi-fuel wall burner is provided consisting of a liquid fuel atomizing assembly at the center of the burner. In a first annular space between an oil atomizing assembly mounting pipe and its immediate circular pipe, a high calorific value gaseous fuel is admitted into the burner. In a second annular space between the high calorific value fuel pipe and a solid fuel pipe, a pulverized solid fuel is admitted along

with primary air. The air required for sustenance and complete combustion of the fuel is supplied in two stages such as secondary air and tertiary air. The secondary air is admitted into the boiler furnace through a third annular space surrounding said pulverized solid fuel pipe concentrically. Over the secondary air pipe, a low calorific value gaseous fuel is admitted concentrically into the boiler furnace. The tertiary air is supplied through an outermost annular pipe over a low calorific value fuel pipe.
According to another aspect of the invention, the high calorific value fuel enters the burner through a vertical pipe with a 900 bend. This gaseous fuel flowing through the pipe axially enters the furnace for further combustion.
According to another aspect of the invention, the pulverized solid fuel pipe to the burner has been designed to allow an involute entry, which provides a circular flow path to the pulverized solid fuel in the pipe of the burner and enters the furnace with a rotating action. This provides a superior mixing of the solid fuel and the secondary air and tertiary air in the boiler.
According to another aspect of the invention, the air supply from the windbox is controlled with a plurality of split dampers to distribute the air flow to the secondary air pipe and tertiary air pipe. The stage supply of air enable a better control of the flame stability and a lower NOx emission from the multi-fuel combustion process.
According to another aspect of the invention, the inner surface of the solid fuel pipe and outer surface of the high calorific value fuel pipe is protected with a wear resistant ceramic layer. This avoids erosion caused by the solid fuel particle during its passage through the pipe.
According to another aspect of the invention, the multi-fuel wall burner is designed to fire liquid fuel/solid pulverized fuel or solid pulverized fuel/low calorific value fuel/high calorific value fuel or liquid fuel/low calorific value fuel/high calorific value fuel or low calorific value fuel/high calorific value fuel or solid pulverized fuel alone

or liquid fuel alone. However, the wall burner of the invention, is not recommended to fire low calorific value fuel alone.
According to another aspect of the invention, the multi-fuel wall burner is designed to start with a liquid fuel or high calorific value gaseous fuel only.
According to another aspect of the invention, an air flow duct in the multi-fuel wall burner is provided with multiple guide vanes across the width of the duct for smooth diversion of air to the burner.
According to another aspect of the invention, a common air duct is configured to enter through one side of the burner which takes a 900 bend before splitting into the two pipes for supplying air in two different stages to burner. This duct can be a pipe or a common windbox.
According to another aspect of the invention, a High Energy Arc (HEA) igniter is provided for igniting the liquid fuel or high calorific value gaseous fuel. After initiating the combustion in the furnace, said pulverized fuel or low calorific value gaseous fuel can be injected into the furnace for further firing after attaining a desired wall temperature such as 500 0C. This wall temperature can be decided based on type of fuel and its fuel characteristics.
According to another aspect of the invention, the oil atomizing assembly can be used for firing either Light Diesel Oil (LDO) or Heavy Fuel Oil (HFO) or any other liquid fuel during start-up or shut down. Here, the atomizing medium can be air or steam depending upon the type of liquid fuel.
According to another aspect of the invention, when the liquid fuel atomizing assembly is not in operation, a cold air stream should be passed through a guide pipe of the liquid fuel atomizing assembly as the cooling medium and a small quantity of atomizing medium is also passed through a nozzle tip of the liquid fuel atomizing assembly to avoid further damage due to radiation temperature and generation of deposition at nozzle holes with solid fuels.

According to another aspect of the invention, for ignition of the liquid fuel, a high voltage spark ignition means was used. This has been inserted adjacent to the liquid fuel nozzle tip. Similarly, two flame scanners are provided to sense the liquid fuel/gaseous fuel flames and the solid fuel flames. For gaseous fuel flames, an Ultra-Violet (UV) flame scanner is used and for liquid/solid fuel flames, an Infra-red scanner is used. In addition, a view port is also provided to physically observe the flame condition during operation of the boiler.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 illustrates a cross sectional view of a multi-fuel wall burner with fuel and air flow arrangements, flame ignition rod and viewport along its principle axis, according to the invention.
Figure 2 illustrates a P-view (burner cover plate view) of Figure 1 with a liquid fuel atomizing assembly, an entry for high calorific value gaseous fuel, an entry for low calorific value gaseous fuel, an entry for solid fuel, flame scanners and air staging to the burner.
Figure 3 illustrates a Q-view (burner throat view) of Figure 1 with a liquid fuel atomizing assembly, flame scanners, HEA igniter, and a swirl block arrangement for air supply and entry for the low calorific value gaseous fuel in the wall burner of the invention.
Figure 4 illustrates a swirl block arrangement of the secondary and tertiary air supplies in the low NOx wall burner of the invention.
Figure 5 illustrates a swirl block for the low calorific value gaseous fuel in the wall burner of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE
INVENTION
The present invention details the developed multi-fuel wall burner in a known boiler for producing steam/power.
Figures 1 to 5 show the detailed arrangements of a multi-fuel wall burner, where Figure 1 illustrates the longitudinal cross sectional view of the multi-fuel burner. The wall burner consists of several circular pipes placed circumferentially one over the other. At the center of the burner, a liquid fuel atomizing assembly(1) is located for firing the liquid fuel. The liquid fuel atomizing assembly (1) is inserted into a guide pipe (2) and placed at the center of the multi-fuel burner. A nozzle tip (3) is provided at the end of the liquid fuel atomizing assembly (1) to atomize the liquid fuel with an atomizing medium. Over the liquid fuel atomizing assembly, a guide pipe for admitting the high calorific value gaseous fuel (4) is provided. Over the high calorific value gaseous fuel pipe (4), a pulverized solid fuel pipe (5) is provided, the pulverized solid fuel entering the multi-fuel burner through an involute entry (6). The inner surface of the solid fuel pipe (5) and outer surface of the high calorific value fuel pipe (4) is provided with a high abrasive strength ceramic layer (24) to protect the metal surface from erosion by said solid fuel during its passage.
The air required for complete combustion of the fuel sent through a rectangular duct (7). The duct (7) is further split into two ducts, a first air duct (8) is connected vertically to the multi-fuel burner axis to a horizontal pipe (9), which is placed over the pulverized solid fuel pipe (5) concentrically. This part of air is called secondary air supply. The low calorific value gaseous fuel is supplied through a vertical pipe (10), which is connected vertically to the multi-fuel burner axis through an expander duct (11) but opposite to said first air duct (8). The low calorific value gaseous fuel is passed through a horizontal pipe (12) to enter the furnace. A second duct of air (13) is also connected vertically to the burner axis but in parallel to the first air duct (8),and adjacent to the multi-fuel burner throat. This air passed through a

horizontal pipe (14), which is placed over a low calorific value gaseous fuel pipe (12) concentrically. This part of air is called tertiary air supply. The secondary air supply and tertiary air supply are provided with at least two swirl blocks (15,16) respectively. The low calorific value gaseous fuel is provided with a third swirl block (17) for better mixing of the fuel with air supply. The supply of the air through the secondary air duct and tertiary air duct are controlled through a plurality of split dampers (21,22) respectively.
The multi-fuel burner is provided with a HEA igniter (18) to start the ignition process in the boiler. To monitor the solid or liquid or gaseous fuel, at least two type of flame monitoring devices are provided in the multi-fuel burner, for example an IR scanner (19) provided within the burner on the secondary air pipe (14) and an UV flame scanner (20) located in the furnace wall near the burner throat to monitor the gaseous fuel flame.
Figure 2 illustrates the wall burner cover plateside view of Figure 1. Where the liquid fuel atomizing assembly(1) at the center of the multi-fuel burner, said high calorific value gaseous fuel pipe (4) allows an involute entry (6) of the solid fuel, the total air supply to the burner through a rectangular duct (7), multiple guide vanes (23) in the duct for smooth flow to the burner are achieved. The low calorific value gaseous fuel vertical pipe (10) and said expander duct (11) and said horizontal low calorific value gaseous fuel pipe (12) are seen. A location flame igniter (18) is located near said horizontal low calorific value gaseous fuel pipe (12). The flame scanner (19) location in the horizontal secondary air pipe (9) is shown.
Figure 3 illustrates an arrangement of multi-fuel burner throat view, i.e., burner downstream towards furnace. Where the liquid fuel atomizing assembly(1), the nozzle tip (3) at the center of the burner are shown. The swirl blocks(15,16) used for secondary air flow pipe (9), tertiary air supply pipe(14) and the horizontal low calorific value gaseous fuel pipe (12) are shown through which the gases enter the furnace. For ignition of the flame, location of the high energy arc igniter and said flame monitoring device are also shown.

Figure 4 illustrates an arrangement of the swirl blocks (15,16) for secondary air and tertiary air supply respectively where, the secondary air swirl block is placed in the secondary air annular space over the solid fuel flow pipe (7) and the tertiary air swirl block (16) is placed on the horizontal low calorific value gaseous fuel pipe (12). The number of swirl blades in the fixed swirl block (15) varies between twenty four and forty eight. The number of swirl blades in the swirl block (16) varies between thirty and fifty.
Figure 5 illustrates an arrangement of the third swirl block (17) for low calorific value gaseous fuel. The third swirl block is placed on the secondary air supply pipe. The number of swirl blades in the fixed swirl block (17) varies between twenty four and forty eight. Through which the low calorific value gaseous fuel enter the furnace with swirl action.
Details of the Experimentation
The multi-fuel wall burner of capacity 10Mkcal/hr has been fabricated and tested at our facilities with pulverized high ash Indian coal, syngas and LDO fuel. Here solid fuel was taken as Indian coal and the capacity of firing is 1 ton/hr. During pulverized coal combustion stable flame were observed and stable flames were observed even at burner turndown ratio of 1:3, stable operation of syngas was also observed with liquid fuel atomizing assembly support at minimum load. The burner was able to demonstrate only coal firing, only oil firing up to 500 kg/hr and 800 kg/hr of syngas firing supported with 300 kg/hr of LDO. The hazardous emissions such as carbon monoxide (CO) and NOx were low compared with other burners. All experiments were conducted at 10% excess air when LDO or syngas was firing and at 20% excess air when pulverized coal is fired in the furnace. When compare with pulverized coal firing the NOx, CO and SO2 emissions are 32%, 54% and 29% lower for LDO fuel firing. This proves the efficacy of the multi-fuel burner for reduction of hazardous emissions.

We Claim:
1. A multi-fuel wall burner apparatus to fire pulverized solid fuel particles, liquid
fuel, low calorific value gaseous fuel and high calorific value gaseous fuel
simultaneously or in combination or a single fuel alone except a low calorific
value gaseous fuel, for steam generation/electric power production, comprising
:
(a) an innermost liquid fuel atomizing assembly(1);
(b) a high calorific value gaseous fuel pipe (3);
(c) a pulverized solid fuel pipe (5), where the solid particles sent along with the
primary air entering through an involute entry (6);
(d) a secondary air pipe (9) and tertiary air supply pipe (14) with fixed swirl blocks (15,16) respectively;
(e) a plurality of control dampers (21,22) for controlling the secondary and tertiary air flows in the respective air ducts;
(f) a HEA igniter (18) for initiating the liquid fuel flame; and
(g) one each IR flame scanner (19) and UV flame scanner (20) for monitoring
the presence of flame for gaseous/liquid/solid fuels or combination; wherein the liquid fuel is fired through the oil atomizing assembly(1) during one of start-up, shut down, and during emergency situation, and wherein the high calorific gaseous fuel is allowed to enter the furnace as a jet via pipe (3).
2. The multi-fuel wall burner apparatus as claimed in claim 1, wherein the pulverized solid fuel is injected through the solid fuel pipe (5) into the furnace after the furnace wall reaching a temperature, above the auto-ignition point based on type of the fuel and its fuel characteristics.
3. The multi-fuel wall burner apparatus as claimed in claim 1, wherein the pulverized solid fuel is allowed through an involute entry (6) to the solid fuel pipe (5).

4. The multi-fuel wall burner apparatus as claimed in claim 1, wherein the additional air required for complete combustion of fuel is ingressed in two stages via a secondary air pipe (9) disposed immediately over the solid fuel pipe (5) and a tertiary air supply pipe (14).
5. The multi-fuel wall burner apparatus as claimed in claim 1, wherein the lower calorific value fuel is admitted into a horizontal pipe (12) disposed between the secondary air pipe (9) and tertiary air pipe (14) concentrically.
6. The multi-fuel wall burner apparatus as claimed in claim 1, wherein the lower calorific value pipe (12) is fitted with a third swirl block (17) .
7. The multi-fuel wall burner apparatus as claimed in claim 4, wherein the secondary and tertiary air supply pipes (9,14) are provided with a first and second swirl blocks (15,16) .
8. The swirl block in the multi-fuel wall burner apparatus as claimed in claim 7,wherein a higher swirl blade angle is provided for the first swirl block (15) and a lower swirl blade angle provided for the second swirl block (16).
9. The multi-fuel wall burner apparatus as claimed in claim 1,wherein the inner surface of the solid fuel pipe (5) and outer surface of the high calorific value fuel pipe (4) is provided with a ceramic layer (24.

10. The multi-fuel wall burner apparatus as claimed in claim 1, comprising one each secondary air duct (8) and tertiary air duct (13), and wherein the air flow distribution is adjusted through said split damper control valves (21,22) respectively to attain the optimum combustion in the furnace.
11. The multi-fuel wall burner apparatus as claimed in claim 1, comprising a HEA flame igniter (18) placed close to the liquid fuel atomizing assembly nozzle (3) , and wherein said flame scanners (18, 22) are placed for monitoring the liquid fuel/solid fuel/gaseous fuel or combination of these fuel flames in the furnace.
12. The multi-fuel wall burner apparatus as claimed in claim 1,comprising an oil atomizing assembly guide pipe (4) to allow passing a cold air even during absence of liquid fuel firing, to avoid high heating in the liquid fuel atomizing assembly nozzle (3), wherein a common air duct (7) is provided with a plurality of guide vanes (23) across the duct to provide a smooth diversion of air flow to the burner, and wherein the common air duct (7) can be replaced with long radius bend pipe or a wind box.
13. The multi-fuel wall burner apparatus according to claim 1, can be scaled up and scaled down as per requirements of the industrial application. However, pipe sizing, swirl blade dimensions and other parts has to be adjusted accordingly.