Title of Invention	METHOD AND APPARATUS FOR DETERMINING ACTUAL UNBURNT CARBON IN COMBUSTION RESIDUE GENERATED FROM SORBENT INJECTED FUEL BURNING FURNACES
Abstract	This invention relates to a method of estimating unburnt carbon in combustion residues comprising the following steps selecting an analytical sample from said combustion residue such as fly ash, bottom ash, cyclone ash, sorbent injected fuel burning furnaces, subjecting a weighed quantity of sample to combustion at 800°C in ignition apparatus in the presence of an inert gas atmosphere such as nitrogen, argon, helium, allowing the combusted sample to cool to ambient temperature, weighing the sample, subjecting said sample to combustion in an oxygen atmosphere, cooling the said combusted sample to ambient temperature, and weighing the sample and estimating the unburnt carbon in combustion residue as herein described. Further also this invention relates to an apparatus for estimating unburnt carbon in combustion residue comprising a combustion tube (1), a furnace (2) capable of supplying temperature of atleast 1000°C, a gas line (3) for supplying a train of oxygen, air, nitrogen argon or helium from cylinders (4,5,6) into said combustion tube, said combustion tube being housed within said furnace, said system being connected at one end to a moisture trap (7) connected the gases before entering into the combustion tube, a gas absorption bottle (8) being fitted to the combustion tube on the other end which is away from the gas line (3) being U-shaped and connected one or more U-tube (9) containing soda asbestos.

Title of Invention

METHOD AND APPARATUS FOR DETERMINING ACTUAL UNBURNT CARBON IN COMBUSTION RESIDUE GENERATED FROM SORBENT INJECTED FUEL BURNING FURNACES

Abstract

This invention relates to a method of estimating unburnt carbon in combustion residues comprising the following steps selecting an analytical sample from said combustion residue such as fly ash, bottom ash, cyclone ash, sorbent injected fuel burning furnaces, subjecting a weighed quantity of sample to combustion at 800°C in ignition apparatus in the presence of an inert gas atmosphere such as nitrogen, argon, helium, allowing the combusted sample to cool to ambient temperature, weighing the sample, subjecting said sample to combustion in an oxygen atmosphere, cooling the said combusted sample to ambient temperature, and weighing the sample and estimating the unburnt carbon in combustion residue as herein described. Further also this invention relates to an apparatus for estimating unburnt carbon in combustion residue comprising a combustion tube (1), a furnace (2) capable of supplying temperature of atleast 1000°C, a gas line (3) for supplying a train of oxygen, air, nitrogen argon or helium from cylinders (4,5,6) into said combustion tube, said combustion tube being housed within said furnace, said system being connected at one end to a moisture trap (7) connected the gases before entering into the combustion tube, a gas absorption bottle (8) being fitted to the combustion tube on the other end which is away from the gas line (3) being U-shaped and connected one or more U-tube (9) containing soda asbestos.

Full Text	FIELD OF THE INVENTION The present invention relates to a method and apparatus for determination of actual unburnt carbon in combustion residue generated from sorbent injected fuel burning furnaces. This invention particularly relates to method of estimating the actual unburnt carbon in combustion residues and an apparatus therefor. This invention further relates to a method of estimating the actual unburnt carbon in combustion residues such as fly ash, bottom ash, cyclone ash etc. generated from boiler furnaces using solid fuels mixed with sorbents. BACKGROUND OF THE INVENTION The combustion efficiency of any fuel firing system is determined by heat losses due to various factors like moisture in the fuel, hydrogen in the fuel, temperature of the flue gas, unburnt carbon in the combustion residue etc. The heat loss due to unburnt carbon intihe combustion residues it one of the most significant factors in deciding the boiler efficiency. Therefore, an accurate estimation of unburnt carbon is important. Two methods are presently employed for the determination of unburnt carbon in combustion residues i.e. loss on ignition and carbon estimation through C-CO2 conversion by instrumental technique. In the first method, the combustion residue is dried and known quantity of the sample weighed and placed in a furnace at 8000 C for one and half an hour. The sample is cooled to room temperature and reweighed. The loss in weight is assumed to be due to the oxidation of carbon present in the sample and reported as percentage unburnt carbon. In the second method, a known quantity of sample after drying is weighed and introduced into the furnance. The carbon present in the sample is oxidized to carbon dioxide, which is measured by IR/TC/gravimetric techniques. From the amount of CO evolved; the 2 percentage of carbon is estimated. In fluidised bed combustors, limestone or dolomite are mixed with high sulphur fuels (coal/lignite) to control sulphur dioxide emissions in the flue gas. Limestone calcines to lime (CaO) at temperature around 7000 C and similarly dolomite calcines to lime and periclase (MgO) (Formula Removed) The lime reacts with SO produced during fuel combustion to form anhydri te (Formula Removed) The unreacted/excess lime and anhydrite may combine with water/moisture in the flue gas to form portlandite Ca(OH)2 and gypsum CaSO4 2H O2 respectively. Fine particulate matter of the additives can be entrained in the flue gas and incomplete calcinations of limestone may also occur if particles have insufficient residence time in the furnace and come along with the combustion residue. Hence, it is more likely that combustion residue from the above discussed combustion system will contain unreacted additives, portlandite Ca(OH)4 hydrated CaSO in addition to unburnt carbon and ash from the fuel. When the loss on ignition method is adopted for the determination of unburnt carbon for the above referred combustion residue, the following changes take place. Dehydration of portlandite Ca(OH)2 and gypsum CaSO4 2H2 O Calcination of unreacted limestone (CaCO ) Oxidation of unburnt carbon in the combustion residue. All the above changes affect the weight changes in the loss on ignition test leading to over estimation of the amount of carbon in combustion residue. Similarly when carbon estimation through C-CO2 conversion by instrumental technique is adopted, the following conversions take place. Carbon from unreacted fuel is converted to CO2 Evaluation of CO from calcinations of unreacted CaCO3 The total CO2 is detected by IR/TC/gravimetric principle depending on the instruments used resulting in over estimation of carbon. Hence, the loss on ignition method and carbon estimation through C - CO2 conversion by instrumental technikque are not accurate measures of unburnt carbon in fly ash and are not applicable to combustion residue generated from sorbent injected fuel burning furnaces. Therefore, the use of loss on ignition (LOI) is not permitted for the determination of unburnt carbon in combustion residues as per ASME-PTC - 4-1998. Instead ASME PTC 4-1998, recommended estimation of total carbon content as per ASTM Ds 5373 and corrected for carbon dioxide as determined by separate determination as per ASTM D!l756.The combustion residues are highly heterogeneous in nature due to distinct presence of unburnt carbon particles and uncalcined limestone particles along with ash. Hence source of error is quite possible if total carbon and carbon dioxide estimations are made with two separate samples from the same combustion residue. OBJECTS OF THE INVENTION It is therefore an object of this invention to propose a method of estimating the actual unburnt carbon in combustion residue and an apparatus therefore, which measures the unburnt carbon accurately with a single test run. A further object of this invention to propose a method of estimating the actual unburnt carbon in combustion residues and an apparatus therefore, which is also applicable in combustion residue generated from sorbent injected fuel burning furnaces. These and other objects and advantages of the invention will be apparent from the ensuing description. DESCRIPTION OF THE INVENTION According to this invention there is provided a method of estimating unburnt carbon in combustion residues comprising the following steps: i) selecting an analytical sample from said combustion residue such as fly ash, bottom ash, cyclone ash, sorbent injected fuel burning furnaces, ii) subjecting a weighed quantity of sample to combustion at 800°C in ignition apparatus in the presence of an inert gas atmosphere such as nitrogen, argon, helium, iii) allowing the combusted sample to cool to ambient temperature, iv) weighing the sample, v) subjecting said sample to combustion in an oxygen atmosphere, vi) cooling the said combusted sample to ambient temperature, and vii) weighing the sample and estimating the unburnt carbon in combustion residue as herein described. According to this invention further provided an apparatus for estimating unburnt carbon in combustion residue comprising a combustion tube (1), a furnace (2) capable of supplying temperature of atleast 1000°C, a gas line (3) for supplying a train of oxygen, air, nitrogen argon or helium from cylinders (4,5,6) into said combustion tube, said combustion tube being housed within said furnace, said system being connected at one end to a moisture trap (7) connected the gases before entering into the combustion tube, a gas absorption bottle (8) being fitted to the combustion tube on the other end which is away from the gas line (3) being U-shaped and connected one or more U-tube (9) containing soda asbestos. A representative sample of combustion residue is subjected to heating in two different atmospheres in a specific apparatus. The difference in loss on ignition obtained from the test conducted in two different atmospheres will result in actual carbon in the combustion residue attributed to unburnt fuel.The invention will now be explained in greater details with the help of the ensuing description and illustrated with the help of the figures of the accompanying drawings where Fig 1 shows the set-up of the combustion apparatus. The apparatus mainly consists of a combustion tube (1), electrically heated in a furnace (2) capable of giving a temperature of at least 1000 0 C. A gas line (3) is also made for passing a train of oxygen, sir, nitrogen, argon or helium from cylinders (4,5,6) into the system. An absorption tube for collecting moisture is kept at both ends. Oxygen (or air) in gas cylinders fitted with pressure regulating valve is used for giving the required combustion atmosphere to the samples. Nitrogen (argon or heliuim) from gas cylinder fitted with pressure regulating valve is used to produce sn inert atmosphere in the combustion tube. The rate of flow of the gases is measured using flow meters. The flow meter is capable of measuring flow rates upto 150 ml/min. Gases of very high purity (99.9999*0 are used and hence only moisture trap (7) is used for the gases before passing into the combustion tube. A gas absorption bottle (S) containing anhydrous magnesium perchlorate is used to absorb water. The purification train is joined to the combustion tube using tight-fitting rubber-materials. The joints are also sealed with wax. The combustion tube is made of fused silica, of about 15 mm in internal diameter and about 500 mm in length. The exit end of the combustion tube is attached with the following items; 1. A U-tube (8), with ground glass stoppers and filled with magnesium Perchlorate (granular) 2. A stopped U-tube (9) containing soda asbestos The furnace (2) is electrically heated with suitable controls for maintaining the desired temperature. The analytical procedure involves subjecting the combustion residue to standard sampling procedures so that the analysis sample is a representative one of the bulk sample. The analysis sample is further ground using agate mortar and pestle so as to pass the sample through 200 mesh (75 microns). Known quantity of the analysis sample is weighed (0.01 to 0.5g) accurately using balance capable of weighing up to 0,1 mg accuracy and taken in porcelain boat of approximate dimensions 7 x: 1.0 x: 0.6 cm. The porcelain boat with the well spread out sample is kept almost in the middle of combustion tube. All the connections (rubber) to the gas bottles and U-tubes are made. A stream of nitrogen, at the flow rate of example 70 ml/min is allowed inside the combustion tube. The heaters are switched on and the furnace is heated to a temperature of about 800 0C in about an hour. The sample is maintained at the temperature for about 30 minutes and then the heater is switched off. The inert gas flow is continued till the sample reaches the ambient temperature. The boat is taken out carefully and weighed. The boat is then replaced into the combustion tube. The nitrogen gas cylinder connections are removed and the oxygen/air gas cylinder connections are made. The furnace is again heated to about 8000 C and kept under this condition for nearly 30 minutes. Then the sample is cooled to ambient temperature, taken out and weighed accurately.CALCULATION." 1. Initial weight of sample ... ... ;•: g Weight of sample after heating with inert gas ... y g % loss in weight in inert atmosphere = >; - y x; 100 = 'a' 2. Initial weight of sample .„. ... Kg Weight of sample after heating with oxygen/air ... z g % loss in weight in oxidizing atmosphere = (x: - z) >: 100 =100 'b' % loss, 'a', corresponds to loss due to dehydration, loss of due to carbon dioxide evolution (decomposition of unreacted 1imestone). % loss, 'b', corresponds to the above mentioned losses plus the loss due to oxidization of carbon from the unburnt fuel left in the combustion residue. The difference between 'b' and 'a' gives the actual % content of unburnt carbon in the sample. % unburnt carbon ~ 'b' - 'a'. The combustion residue may be fly ash, cyclone ash, bottom ash, air pre-heater ash generated from with/without sorbent injected fuel firing systems and may be from combustion of solid fuel with significant amount of alkaline earth minerals without sorbent injection. The sorbents may be limestone or dolomite and the fuel may be coal, lignite, biomass, pet coke. The fuel firing systems may be fluidized bed combustion furnace, CF.BC, stoker, pulverised fuel furnaces applicable either from steam generation or power generat ion. The above method can be applied to any other instruments in which continuous recording of weight changes during heating/cooling with in-between gas switchover facilities are available. A software is programmed for microprocessor based operations inbuilt in the instrument. RESULTS: Samples from boilers using sorbent (like limestone), samples from pulverised coal fired boilers without sorbents, samples (synthetic) with known quantity of unburnt carbon were tested using all the three techniques viz. 1,loss on ignition (in furnace at 800 C) 2, carbon estimation by instrumentation technique 3. newly developed method. The results are given in the table I Table - 1 (Table Removed) WE CLAIM; 1. A method of estimating unburnt carbon in combustion residues comprising the following steps: i) selecting an analytical sample from said combustion residue such as fly ash, bottom ash, cyclone ash, sorbent injected fuel burning furnaces, ii) subjecting a weighed quantity of sample to combustion at 800°C in ignition apparatus in the presence of an inert gas atmosphere such as nitrogen, argon, helium, iii) allowing the combusted sample to cool to ambient temperature, iv) weighing the sample, v) subjecting said sample to combustion in an oxygen atmosphere, vi) cooling the said combusted sample to ambient temperature, and vii) weighing the sample and estimating the unburnt carbon in combustion residue as herein described. 2. The method as claimed in claim 1, wherein the sorbentsmay be limestone or dolomite. 3. The method as claimed in claim 1 or 2, wherein the fuel may be coal, lignite, biomass, pet coke. 4. The method as claimed in claim 1 or 3, wherein the fuel firing systems may be fluidized bed combustion furnace, CFBC, stoker, pulverized fuel furnaces applicable either for steam generation or power generation. 5. The method as claimed in claim 1 or 4, wherein the combustion residue generated may be from combustion of solid fuel with significant amount of alkaline earth minerals without sorbent. 6. An apparatus for estimating unburnt carbon in combustion residue comprising a combustion tube (1), a furnace (2) capable of supplying temperature of atleast 1000°C, a gas line (3) for supplying a train of oxygen, air, nitrogen argon or helium from cylinders (4,5,6) into said combustion tube, said combustion tube being housed within said furnace, said system being connected at one end to a moisture trap (7) connected the gases before entering into the combustion tube, a gas absorption bottle (8) being fitted to the combustion tube on the other end which is away from the gas line (3) being U-shaped and connected one or more U-tube (9) containing soda asbestos. 7. An apparatus as claimed in claim 6 wherein said combustion tube is made of fused silica and having about 15 mm internal diameter and about 500 mm in length. 8. An apparatus as claimed in claim 6 which said absorption bottle (8) containing anhydrous magnesium perchlorate used to adsorb water, said tube are sealed with wax. 9. An apparatus as claimed in claim 6 wherein oxygen or air in gas cylinder fitted with pressure regulating valve is used for giving the required combustion atmosphere to the sample.

Full Text

FIELD OF THE INVENTION
The present invention relates to a method and apparatus for determination of actual unburnt carbon in combustion residue generated from sorbent injected fuel burning furnaces.
This invention particularly relates to method of estimating the actual unburnt carbon in combustion residues and an apparatus therefor.
This invention further relates to a method of estimating the actual unburnt carbon in combustion residues such as fly ash, bottom ash, cyclone ash etc. generated from boiler furnaces using solid fuels mixed with sorbents.
BACKGROUND OF THE INVENTION
The combustion efficiency of any fuel firing system is determined by heat losses due to various factors like moisture in the fuel, hydrogen in the fuel, temperature of the flue gas, unburnt carbon in the combustion residue etc.
The heat loss due to unburnt carbon intihe combustion residues it one of the most significant factors in deciding the boiler efficiency. Therefore, an accurate estimation of unburnt carbon is important.
Two methods are presently employed for the determination of
unburnt carbon in combustion residues i.e. loss on ignition and
carbon estimation through C-CO2 conversion by instrumental
technique.
In the first method, the combustion residue is dried and known
quantity of the sample weighed and placed in a furnace at 8000 C
for one and half an hour. The sample is cooled to room
temperature and reweighed. The loss in weight is assumed to be
due to the oxidation of carbon present in the sample and reported
as percentage unburnt carbon.
In the second method, a known quantity of sample after drying is
weighed and introduced into the furnance. The carbon present in
the sample is oxidized to carbon dioxide, which is measured by
IR/TC/gravimetric techniques. From the amount of CO evolved; the
2 percentage of carbon is estimated.
In fluidised bed combustors, limestone or dolomite are mixed with
high sulphur fuels (coal/lignite) to control sulphur dioxide
emissions in the flue gas.
Limestone calcines to lime (CaO) at temperature around 7000 C and
similarly dolomite calcines to lime and periclase (MgO)
(Formula Removed)
The lime reacts with SO produced during fuel combustion to form anhydri te
(Formula Removed)
The unreacted/excess lime and anhydrite may combine with
water/moisture in the flue gas to form portlandite Ca(OH)2 and
gypsum CaSO4 2H O2 respectively. Fine particulate matter of the
additives can be entrained in the flue gas and incomplete
calcinations of limestone may also occur if particles have
insufficient residence time in the furnace and come along with
the combustion residue.
Hence, it is more likely that combustion residue from the above
discussed combustion system will contain unreacted additives,
portlandite Ca(OH)4 hydrated CaSO in addition to unburnt carbon
and ash from the fuel.
When the loss on ignition method is adopted for the determination of unburnt carbon for the above referred combustion residue, the following changes take place.
Dehydration of portlandite Ca(OH)2 and gypsum CaSO4 2H2 O
Calcination of unreacted limestone (CaCO )
Oxidation of unburnt carbon in the combustion residue.
All the above changes affect the weight changes in the loss on
ignition test leading to over estimation of the amount of carbon
in combustion residue. Similarly when carbon estimation through
C-CO2 conversion by instrumental technique is adopted, the following conversions take place.
Carbon from unreacted fuel is converted to CO2
Evaluation of CO from calcinations of unreacted CaCO3
The total CO2 is detected by IR/TC/gravimetric principle
depending on the instruments used resulting in over estimation of
carbon.
Hence, the loss on ignition method and carbon estimation through
C - CO2 conversion by instrumental technikque are not accurate
measures of unburnt carbon in fly ash and are not applicable to
combustion residue generated from sorbent injected fuel burning
furnaces. Therefore, the use of loss on ignition (LOI) is not
permitted for the determination of unburnt carbon in combustion
residues as per ASME-PTC - 4-1998. Instead ASME PTC 4-1998,
recommended estimation of total carbon content as per ASTM Ds
5373 and corrected for carbon dioxide as determined by separate
determination as per ASTM D!l756.The combustion residues are highly heterogeneous in nature due to distinct presence of unburnt carbon particles and uncalcined limestone particles along with ash. Hence source of error is quite possible if total carbon and carbon dioxide estimations are made with two separate samples from the same combustion residue.
OBJECTS OF THE INVENTION
It is therefore an object of this invention to propose a method of estimating the actual unburnt carbon in combustion residue and an apparatus therefore, which measures the unburnt carbon accurately with a single test run.
A further object of this invention to propose a method of estimating the actual unburnt carbon in combustion residues and an apparatus therefore, which is also applicable in combustion residue generated from sorbent injected fuel burning furnaces. These and other objects and advantages of the invention will be apparent from the ensuing description.
DESCRIPTION OF THE INVENTION
According to this invention there is provided a method of estimating unburnt carbon in combustion residues comprising the following steps:
i) selecting an analytical sample from said combustion residue
such as fly ash, bottom ash, cyclone ash, sorbent injected fuel
burning furnaces,
ii) subjecting a weighed quantity of sample to combustion at
800°C in ignition apparatus in the presence of an inert gas
atmosphere such as nitrogen, argon, helium, iii) allowing the combusted sample to cool to ambient temperature,

iv) weighing the sample,
v) subjecting said sample to combustion in an oxygen atmosphere,
vi) cooling the said combusted sample to ambient temperature,
and vii) weighing the sample and estimating the unburnt carbon in
combustion residue as herein described.
According to this invention further provided an apparatus for estimating unburnt carbon in combustion residue comprising a combustion tube (1), a furnace (2) capable of supplying temperature of atleast 1000°C, a gas line (3) for supplying a train of oxygen, air, nitrogen argon or helium from cylinders (4,5,6) into said combustion tube, said combustion tube being housed within said furnace, said system being connected at one end to a moisture trap (7) connected the gases before entering into the combustion tube, a gas absorption bottle (8) being fitted to the combustion tube on the other end which is away from the gas line (3) being U-shaped and connected one or more U-tube (9) containing soda asbestos.
A representative sample of combustion residue is subjected to heating in two different atmospheres in a specific apparatus. The difference in loss on ignition obtained from the test conducted in two different atmospheres will result in actual carbon in the combustion residue attributed to unburnt fuel.The invention will now be explained in greater details with the help of the ensuing description and illustrated with the help of the figures of the accompanying drawings where Fig 1 shows the set-up of the combustion apparatus.
The apparatus mainly consists of a combustion tube (1),
electrically heated in a furnace (2) capable of giving a
temperature of at least 1000 0 C. A gas line (3) is also made for
passing a train of oxygen, sir, nitrogen, argon or helium from
cylinders (4,5,6) into the system. An absorption tube for
collecting moisture is kept at both ends.
Oxygen (or air) in gas cylinders fitted with pressure regulating valve is used for giving the required combustion atmosphere to the samples. Nitrogen (argon or heliuim) from gas cylinder fitted with pressure regulating valve is used to produce sn inert atmosphere in the combustion tube. The rate of flow of the gases is measured using flow meters. The flow meter is capable of measuring flow rates upto 150 ml/min. Gases of very high purity
(99.9999*0 are used and hence only moisture trap (7) is used for the gases before passing into the combustion tube.
A gas absorption bottle (S) containing anhydrous magnesium perchlorate is used to absorb water. The purification train is joined to the combustion tube using tight-fitting rubber-materials. The joints are also sealed with wax.
The combustion tube is made of fused silica, of about 15 mm in internal diameter and about 500 mm in length.
The exit end of the combustion tube is attached with the following items;
1. A U-tube (8), with ground glass stoppers and filled with magnesium Perchlorate (granular)
2. A stopped U-tube (9) containing soda asbestos
The furnace (2) is electrically heated with suitable controls for maintaining the desired temperature.
The analytical procedure involves subjecting the combustion residue to standard sampling procedures so that the analysis sample is a representative one of the bulk sample. The analysis sample is further ground using agate mortar and pestle so as to pass the sample through 200 mesh (75 microns).
Known quantity of the analysis sample is weighed (0.01 to 0.5g) accurately using balance capable of weighing up to 0,1 mg accuracy and taken in porcelain boat of approximate dimensions 7 x: 1.0 x: 0.6 cm.
The porcelain boat with the well spread out sample is kept almost in the middle of combustion tube. All the connections (rubber) to
the gas bottles and U-tubes are made. A stream of nitrogen, at
the flow rate of example 70 ml/min is allowed inside the
combustion tube. The heaters are switched on and the furnace is
heated to a temperature of about 800 0C in about an hour.
The sample is maintained at the temperature for about 30 minutes
and then the heater is switched off. The inert gas flow is
continued till the sample reaches the ambient temperature. The
boat is taken out carefully and weighed. The boat is then
replaced into the combustion tube. The nitrogen gas cylinder
connections are removed and the oxygen/air gas cylinder
connections are made. The furnace is again heated to about 8000 C
and kept under this condition for nearly 30 minutes. Then the
sample is cooled to ambient temperature, taken out and weighed
accurately.CALCULATION."
1. Initial weight of sample ... ... ;•: g
Weight of sample after heating with inert gas ... y g
% loss in weight in inert atmosphere = >; - y x; 100 = 'a'
2. Initial weight of sample .„. ... Kg
Weight of sample after heating with oxygen/air ... z g % loss in weight in oxidizing atmosphere = (x: - z) >: 100 =100 'b'
% loss, 'a', corresponds to loss due to dehydration, loss of due to carbon dioxide evolution (decomposition of unreacted 1imestone).
% loss, 'b', corresponds to the above mentioned losses plus the loss due to oxidization of carbon from the unburnt fuel left in
the combustion residue. The difference between 'b' and 'a' gives the actual % content of unburnt carbon in the sample.
% unburnt carbon ~ 'b' - 'a'.
The combustion residue may be fly ash, cyclone ash, bottom ash, air pre-heater ash generated from with/without sorbent injected fuel firing systems and may be from combustion of solid fuel with significant amount of alkaline earth minerals without sorbent injection. The sorbents may be limestone or dolomite and the fuel may be coal, lignite, biomass, pet coke. The fuel firing systems may be fluidized bed combustion furnace, CF.BC, stoker, pulverised fuel furnaces applicable either from steam generation or power generat ion.
The above method can be applied to any other instruments in which continuous recording of weight changes during heating/cooling with in-between gas switchover facilities are available. A software is programmed for microprocessor based operations inbuilt in the instrument.
RESULTS:
Samples from boilers using sorbent (like limestone), samples from pulverised coal fired boilers without sorbents, samples (synthetic) with known quantity of unburnt carbon were tested using all the three techniques viz.
1,loss on ignition (in furnace at 800 C)
2, carbon estimation by instrumentation technique
3. newly developed method.
The results are given in the table I
Table - 1
(Table Removed)

WE CLAIM;
1. A method of estimating unburnt carbon in combustion residues
comprising the following steps:
i) selecting an analytical sample from said combustion
residue such as fly ash, bottom ash, cyclone ash, sorbent
injected fuel burning furnaces,
ii) subjecting a weighed quantity of sample to combustion
at 800°C in ignition apparatus in the presence of an inert
gas atmosphere such as nitrogen, argon, helium, iii) allowing the combusted sample to cool to ambient
temperature, iv) weighing the sample, v) subjecting said sample to combustion in an oxygen
atmosphere, vi) cooling the said combusted sample to ambient
temperature, and vii) weighing the sample and estimating the unburnt carbon
in combustion residue as herein described.
2. The method as claimed in claim 1, wherein the sorbentsmay be
limestone or dolomite.
3. The method as claimed in claim 1 or 2, wherein the fuel may be coal, lignite, biomass, pet coke.
4. The method as claimed in claim 1 or 3, wherein the fuel firing systems may be fluidized bed combustion furnace, CFBC, stoker, pulverized fuel furnaces applicable either for steam generation or power generation.
5. The method as claimed in claim 1 or 4, wherein the combustion residue generated may be from combustion of solid fuel with significant amount of alkaline earth minerals without sorbent.
6. An apparatus for estimating unburnt carbon in combustion residue comprising a combustion tube (1), a furnace (2) capable of supplying temperature of atleast 1000°C, a gas line (3) for supplying a train of oxygen, air, nitrogen argon or helium from cylinders (4,5,6) into said combustion tube, said combustion tube being housed within said furnace, said system being connected at one end to a moisture trap (7) connected the gases before entering into the combustion tube, a gas absorption bottle (8) being fitted to the combustion tube on the other end which is away from the gas line (3) being U-shaped and connected one or more U-tube (9) containing soda asbestos.
7. An apparatus as claimed in claim 6 wherein said combustion tube is made of fused silica and having about 15 mm internal diameter and about 500 mm in length.
8. An apparatus as claimed in claim 6 which said absorption bottle (8) containing anhydrous magnesium perchlorate used to adsorb water, said tube are sealed with wax.
9. An apparatus as claimed in claim 6 wherein oxygen or air in gas cylinder fitted with pressure regulating valve is used for giving the required combustion atmosphere to the sample.

Documents:

445-DEL-2004-Abstract (19-01-2010).pdf

445-DEL-2004-Claims (19-01-2010).pdf

445-del-2004-claims.pdf

445-DEL-2004-Correspondence-Others (19-01-2010).pdf

445-del-2004-correspondence.pdf

445-DEL-2004-Description (Complete) (19-01-2010).pdf

445-del-2004-description (provisional).pdf

445-del-2004-description.pdf

445-del-2004-drawings.pdf

445-DEL-2004-Form-5 (19-01-2010).pdf

445-del-2004-form1.pdf

445-del-2004-form2 (provisional).pdf

445-del-2004-form2.pdf

445-del-2004-form26.pdf

445-del-2004-form3.pdf

445-del-2004-form5.pdf

445-DEL-2004-GPA (19-01-2010).pdf

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Patent Number

238956

Indian Patent Application Number

445/DEL/2004

PG Journal Number

5/2010

Publication Date

05-Mar-2010

Grant Date

02-Mar-2010

Date of Filing

15-Mar-2004

Name of Patentee

BHARAT HEAVY ELECTRICALS LIMITED

Applicant Address

BHEL HOUSE, SIRI FORT, NEW DELHI-110049, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	DR. AROKIAM LAWRENCE	BHEL HOUSE, SIRI FORT, NEW DELHI-110049, INDIA.
2	VELLAYAN ILLAYAPERUMAL	BHEL HOUSE, SIRI FORT, NEW DELHI-110049, INDIA.
3	RAMASWAMY SIVASUBRAMANIAN	BHEL HOUSE, SIRI FORT, NEW DELHI-110049, INDIA.

PCT International Classification Number

F23B

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA