CA2313862A1 - Method of producing portland cement clinker using a circulating fluidized bed boiler - Google Patents
Method of producing portland cement clinker using a circulating fluidized bed boiler Download PDFInfo
- Publication number
- CA2313862A1 CA2313862A1 CA 2313862 CA2313862A CA2313862A1 CA 2313862 A1 CA2313862 A1 CA 2313862A1 CA 2313862 CA2313862 CA 2313862 CA 2313862 A CA2313862 A CA 2313862A CA 2313862 A1 CA2313862 A1 CA 2313862A1
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- Prior art keywords
- ashes
- desulfurizer
- agent
- fluidized bed
- portland cement
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J15/00—Arrangements of devices for treating smoke or fumes
- F23J15/006—Layout of treatment plant
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B7/00—Hydraulic cements
- C04B7/24—Cements from oil shales, residues or waste other than slag
- C04B7/28—Cements from oil shales, residues or waste other than slag from combustion residues, e.g. ashes or slags from waste incineration
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/02—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed
- F23C10/04—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed the particles being circulated to a section, e.g. a heat-exchange section or a return duct, at least partially shielded from the combustion zone, before being reintroduced into the combustion zone
- F23C10/08—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed the particles being circulated to a section, e.g. a heat-exchange section or a return duct, at least partially shielded from the combustion zone, before being reintroduced into the combustion zone characterised by the arrangement of separation apparatus, e.g. cyclones, for separating particles from the flue gases
- F23C10/10—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed the particles being circulated to a section, e.g. a heat-exchange section or a return duct, at least partially shielded from the combustion zone, before being reintroduced into the combustion zone characterised by the arrangement of separation apparatus, e.g. cyclones, for separating particles from the flue gases the separation apparatus being located outside the combustion chamber
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J2219/00—Treatment devices
- F23J2219/30—Sorption devices using carbon, e.g. coke
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J2900/00—Special arrangements for conducting or purifying combustion fumes; Treatment of fumes or ashes
- F23J2900/01002—Cooling of ashes from the combustion chamber by indirect heat exchangers
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/10—Production of cement, e.g. improving or optimising the production methods; Cement grinding
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Ceramic Engineering (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Treating Waste Gases (AREA)
- Solid Fuels And Fuel-Associated Substances (AREA)
- Fluidized-Bed Combustion And Resonant Combustion (AREA)
Abstract
A method of producing Portland cement clinker as by product of a CFB boiler which uses a fuel with a high sulfur content like petroleum coke, in such a way as to desulfurize the fuel with an agent chosen and prepared to evolve a solid outflow which fulfill the expectations of Portland cement clinker, wherein said desulfurizer agent provide means to rise the thermic efficiency in CFB boilers, to lower the content of CO, evolved from the operation of CFB boilers, and to provide a gas rich in SO, to be used as a source for the making of sulfur, sulfuric acid or sulfur derivatives.
Description
,ATTORNEY DOCKET:
IN THE UNITED STATES PATENT AND TRADEMARK OFFICE
METHOD OF PRODUCING PORTLAND CEMENT CLINKER USING
A CIRC'.ULATIrJG FLUIDIZED BED BOILER
BACKGROUND OF THE INVENTION
This invention relates in general to a method of producing Portland cement clinker as by product of a Circulating Fhudized Bed Boiler (CFB). iVlore specifically relates to the operation of a CFB boiler wherein it is produced Portland cement clinker by modifying the boiler ash which is made equal to the composition of Portland cement clinker.
Circulating fluidized bed boilers are widf:ly used for the production of water vapor which fed to a turbine generates electricity. A distinctive characteristic of CFB boilers is that they can use solid fuels with a high sulfur content <is in the case of coal or petroleum coke.
To comply with environmental regulations, stack gases outflow from circulating fluidized bed boilers which burn solid fuels with a high sulfur content are desulfurized prior to its discharge to the atmosphere. In CFB boilers the solid fuel is fed mixed with a certain amount of limestone, the SO, produced from the combustion of sulfur in the fuel is reacted with the limestone to promote the following desulfurization reaction:
CaCO; + SO, + % 0, --~ CaSO~ + COZ (1) us~.ially due to low conversion of the calcium carbonate, it is neccesary to add an excess of limestone to the boiler to remove the amount of sulfur as required by the environmental regulations. The excess limestone reacts within the boiler to produce calcium oxide and carbon dioxide according to thf: reaction:
IN THE UNITED STATES PATENT AND TRADEMARK OFFICE
METHOD OF PRODUCING PORTLAND CEMENT CLINKER USING
A CIRC'.ULATIrJG FLUIDIZED BED BOILER
BACKGROUND OF THE INVENTION
This invention relates in general to a method of producing Portland cement clinker as by product of a Circulating Fhudized Bed Boiler (CFB). iVlore specifically relates to the operation of a CFB boiler wherein it is produced Portland cement clinker by modifying the boiler ash which is made equal to the composition of Portland cement clinker.
Circulating fluidized bed boilers are widf:ly used for the production of water vapor which fed to a turbine generates electricity. A distinctive characteristic of CFB boilers is that they can use solid fuels with a high sulfur content <is in the case of coal or petroleum coke.
To comply with environmental regulations, stack gases outflow from circulating fluidized bed boilers which burn solid fuels with a high sulfur content are desulfurized prior to its discharge to the atmosphere. In CFB boilers the solid fuel is fed mixed with a certain amount of limestone, the SO, produced from the combustion of sulfur in the fuel is reacted with the limestone to promote the following desulfurization reaction:
CaCO; + SO, + % 0, --~ CaSO~ + COZ (1) us~.ially due to low conversion of the calcium carbonate, it is neccesary to add an excess of limestone to the boiler to remove the amount of sulfur as required by the environmental regulations. The excess limestone reacts within the boiler to produce calcium oxide and carbon dioxide according to thf: reaction:
CaC.03 --~ Ca0 + CO, (?) Thc: solid outflow from CFB boilers is mainly composed of ashes comprising calcium sulfate and calcium oxide which come from the combustion and desulfurization reactions of the solid fuel. The CFB ashes due to its high Ca0 content can not be used in the cement industry to substitute gypsum (CaSO~), furthermore CFB ashes can not be used as raw material to produce Portland cement clinker due: to its high CaSO~. Therefore in most of the cases, outflow ashes are confined in land fills specially designed for storage. The confinement of ashes adds an extra cost to the operation of a power generating plant. In some cases a portion of this ashes can be used as a soil stabilizer.
The residue of combustion of a sulhir containing fuel in CFB boilers has been treated as established in U.S. Patent 5,662,051 by grinding the fuel to less than 100 microns, grinding the limestone between 100 and 1~0 microns with a maximum of 1 mm and after combustion of the mixture collecting the residue to subject it to a heat treatment to obtain Ca0 and SO,, routing the SO, to a sulfuric acid manufacturing unit and quenching the solid matter with water and grinding it to reactivate the specific surface area of the solid matter, a portion of which is re injected to the CFB
boiler in a suspension with water, and the remaining fraction routed to a cement plant. This method usfa limestone as desulfurizer assent with the drawback of COZ being evolved from the reaction. A
his;h amount of limestone is n~°eded, usually more than that stoichiometrically determined to desulfurize the solid fuel with a resulting production of an excess of CO,.
Also the amount of limestone needed is higher than i.n the actual invention. All these drawbacks increase the production costs and the environmental effects.
A technique to produce a secondary raw material containing calcium sulfate is proposed in U.S.
Patent 4,997,486, comprising a waste hydrocarbon and one of waste sulfuric acid or acid waste sulfuric acid derivative combined with powdered limestone or fly ash containing calcium carbonate.
The product is used in making Portland cement clinker or as a fuel in furnaces or as a desulfurization additive. This product is of a general nature and as established its composition is not the best suited for the making of Portland cement clinker.
SUMMARY OF THE INVENTION
According to the foregoing it is a main object of the present invention to provide a method to produce Portland cement clinker using a circulating fluidized bed boiler CFB
which uses a fuel with a high sulfur content like petroleum coke, in such a way as to desulfurize the fuel with an agent chosen and prepared to evolve an outflow which can be used far making Portland cement cl-inker.
It is another object of the invention to provide means to rise the thermic efficiency in CFB boilers.
It is still another object of the invention to provide means to lower the content of CO, evolved from the operation of CFB boilers.
It i;s yet another object of the invention to provide a gas rich in S0, to be used as a source for the making of sulfur, sulfuric acid o:r sulfur derivatives.
It is a further object of the present invention to provide a source of Portland cement like material.
The instant invention provides a method to choose and prepare the raw material used as a desulfurizer in such a way as to equalize the composition of Portland cement clinker. The traditional CfB boilers use limestone as a desulfuriz.er material with some disadvantages like an excesive CO~
generation, and the need to confine the resulting products with an extra cost to the operation. In the method of the instant invention, apart from the actual methods, the desulfurizer agent comprise a mixture of lime, clay and iron ore in proper proportions as to use the resulting ash, after a thermic trea:ment, for making Portland cement clinker. Desulfurization of the flue gases according to the instant invention is carried out by means of calcium oxide available from lime according to the following reaction:
Ca0 + SO, +'/~O, -~ CaSO~ (;) It is necessary to feed to the :process an excess of lime to establish a required degree of des~.ilfurization. Because of the excess of lime, the ash comprises the unreacted lime and the calcium sulfate resulting from the process.. For a given degree of desulfurization, the mass of lime needed is always lower than the mass of limestone; because of the carbon dioxide content present in the calcium carbonate from limestone:. This lowering in the mass when using lime, allows to add other inert compounds to adjust the cornposition of the desulfurizer agent, while maintaining the overall efficiency of the CFB boiler.
The; composition of Portland cement has to comply to some required figures defined by its content of calcium oxide, silica, alumina and iron oxide contained in the following indexes:
%Ca0 LSF = ~.g*°~oSi02 + 1.18*%A1,03 + 0.65*%Fe,03 (4) SiOz MS = -A120~ + Fe'O~ (5) A cement to be considered of the Portland type has to have an LSF index between 0.75 and 0.90 and a MS index between 2.5 and 3.5.
The amount of lime, clay and iron ore comprised in the mixture used as a desulfurizer agent is established by determining the chemical composition of the fuel ash.
The resulting ash from the combustion process in the CFB boiler comprises a mixture of calcium oxide and calcium sulfate with minor amounts of other elements like SiO,, A1,0; and Fe,O;. This ash is heated in a separate container up to 1,200°C to 1,300°C
with hot gases evolving from a con- bastion chamber to decompose to caJicium oxide, sulfur dioxide and oxigen according to the foll~~wing reaction:
CaSO~ --~ Ca0 + S0, +'/~O; (6) Besides to the decompositon reaction of the calcium sulfate, in the heating process at temperatures up to 1,200°C to 1,300°C, the following mineral phases of the Portland cement clinker are formed:
tricalcium silicate (3Ca0 ~ SiO,); dicalcium silicate (2 Ca0 ~ SiO,);
tricalcium aluminate (3 Ca0 ~ A1,0;) and tetracalcium aluminoferrite (4Ca0 ~ A1,0; ~ Fe,O;).
After the heating process, the ash is passed to a direct air heat exchanger and thereafter transformed into Portland cement.
Sulfur dioxide evolving from a preheatinj; of ash is removed along with the combustion gases and sent to separation by means of chemical processes and later transformed for the production of sulfur, sul:Furic acid and sulfur derivatives.
BRIEF DESCRIPTION OF THE DRA'irINGS
Th~° novel features and advantages of the present invention should be readily apparent for those skilled in the art arising from the: teachings of the detailed description herein and the drawings, but it should be understood that the instant invention can be embodied in different ways and that the embodiments herein described a.re shown for illustration purposes only, but they are not restrictive as referred to the scope of the invention wherein:
Fiy~ure 1 is a flow diagram of a CFB boiler used to generate electricity from water vapor at high pressure using a fuel with a high sulfur content like petroleum coke;
Figure 2 is a simplified flow dia;;ram of the process of the present invention; and Figure 3 is a second embodiment of the instant invention.
DETAILED DESCRIPTION OF THE IPIVENTION
With reference to figure 1, numeral 10 generally designates a hopper which stores pulverized petrolemn coke, which is fed to a combustion chamber 12 of a CFB boiler 13 through pipe 15.
Pulverized limestone stored in hopper 14 is fed with the pulverized coke to the CFB boiler through pipe 17. In CFB boiler in the combustion section 12, the pulverized petroleum coke is burnt by means of the inj ection of hot air which is blown through pipe 16. The combustion reaction generates the neccessary heat for the production of vapor in coil 18. The SO, evolved from the combustion of sulfur available in petroleum coke is almost all removed with a removing rate of 90% to 9~% by means of calcium carbonate i:rom the limestone, according to reaction ( 1 ) as established hereinbefore. An additional amount of CO, to that produced from the combustion of coke, is evolved from the desulfurization reaction (1) established hereinbefore. The combustion gases go through combustion section 12 of CFB boiler i 3 to cyclon 20 wherein the biggest solid particles are removed and recicled to the combustion zone 12 of the boiler 13 by means of "J" valve 22 and pipe 24. The sensible heat form the combustion gases is recovered by flowing the gases through coil 26 wherein water is preheated, and thereafter through coil 28 wherein air is preheated.
The preheated water from coil 26 is fed to coil 18 wherein vapor is generated. The preheated air from coil 28 is fed through pipe 16 to the combustion chamber 12. The combustion gases in the outlet of cyclon 20 still have an amount of very fine solids known as fly ash, which are passed through coils 26 and 28 and thereafter collected by dust collector 30 <md sent through pipe 42 to a fly ash hopper 32 to be stored and thereafter sent through pipe 46 to confinement. The gases at the outlet of dust collector 30 are passed through fan 34 to induce the gas slow and thereafter to stack 36 as effluent gas. The effluent gas from this boiler has to be basically free of solids and sulfur to comply with environmetal re;;ulations. A portion of the ash produced in CFB boiler 13 is removed through pipe 38 located at thE: bottom portion of the combustion section 12, wherein this ash is known as bottom ash. The bottom ash is passed to a hopper 40 and sent through pipe 44 for later confinement.
With reference to figure 2, hopper 14 is replaced by hoppers 14a, 14b and 14c which store lime, clay and iron ore respectively which are fed to combustion chamber 12 through pipes 17, 19, and 21 respectively. Desulfurization of combustion gases is achieved by means of calcium oxide available from lime according to reaction, (3) established hereinbefore. An advantage of this reaction is that addittional CO, is not evolved to that generated by the combustion reaction of coke. Bottom ash and fly ash, which sulfur content is about 60%, are collected by means of pipes 38 and 42 respectively mixed and then by means of pipe 43 are :Eed to the upper portion of fluidized reactor 44, wherein fly ash is brought into contact with. a gas coming from a combustion chamber 46, which is fed with a fuel which is fed through pipe 48 and with preheated air fed through pipe S0.
The outflow gas frc::~
combustion chamber 46 at a temperature; between 1,200°C and 1,300°C is fed to the lower portion of the fluidized bed reactor 44. In reactor 44 the thermic decomposition of calcium sulfate is accomplished according to reaction (6;) established hereinbefore and also the formation of the mineral phases of Portland cement clinker occur at this stage. Solid particles from reactor 44 are discharged from the lower portion of reactor and sent through pipe 4~ to a fluidized bed cooler 52 s wherein the particles are brought into contact with cool air fed through pipe ~4. The out flow of hot air from cooler 52 is fed to combustion chamber 48 by means of pipe 50. Ash is discharged from the cooler 52 through pipe ~3 at a temperature below 200°C having a sulfur content below;%. Because of the preparation of the mixture: used as a desulfurizer, the ash has a composition equivalent to that for clinker and can be used directly for the production of Portland cement.
The outflow gas from reactor 44 is removed through pipe 56 and sent to a separation process 58 wherein SO, is separated from other combustion gases. Combustion gases are discharged to atmosphere by means of pipe 64.
SO, is sent through pipe 60 to a chemical plant 62 to be treated for the production of elemental sulfur or sulfuric acid.
Re:Ferring to figure 3 clay from hopper 14b, and iron ore from hopper 14c are fed directly to reactor 44 through pipes 19 and 21 and thereafter through pipe 39 to pipe 43, in such a way as to feed petroleum coke and lime alone to CFB boiler 13, through pipes 15 and 17 respectively.
The advantages and benefits c>f the instant invention can be best understood according to the following examples of the operation of a CFB boiler using limestone as a desulfurizer agent, and using a mixture of lime, clay and iron ore as a desulfurizer agent.
Table I and Table II present the: CFB and petroleum coke characteristics used in both examples:
Table I
<:FB characteristics Capacity (Mw) 123.33 Thermal effi<;iency 89.3 (%) Total duty (Crcal/hr) 279.62 Excfas air (%) I 20 SO, Adsorbed (%) 94.02 Table II
Petrolf:um coke characteristics Heating value (kcal/kg) 7437.9 ic 8o~s %H _, 3.0 %S 6.0 %N , 0.8 %H , O 8.0 %Ash 0.6 Table III prxsents the chemical composition and quantity (ton/hr) of the limestone used as desulfurizer agent in example ladn the chemical compositions and quantities (ton/hr) of lime, clay and iron ore mixture used as desulfurizer agent in example 2 Table III
I)esulfurizer agents Example 1 Example 2 Limestone Lime Clay Iron Oxide %Si0 , 0.00 3.24 67.29 2.14 Al ,_ 0 3 3.OJ 1.36 8.97 0.75 %Fe , O 5 0.15 0.61 4.28 93.20 %Ca0 0.00 93.23 7.27 1.02 %CaCO a 95.00 0.00 0.00 0.00 %IVIgO 0.85 0.28 1.97 0.37 %SO 3 0.86 1.28 0.32 0.09 Other 0.09 0.00 9.90 2.43 Ton/hr 13.98 8.19 4.30 0.55 Table IV presents the chemical, composition and quantities (ton/hr) of the ashes produced in both examples, for example 2 the composition shown is at the outlet of cooler 52.
Table IV
Ash composition Example 1 Example 2 %Si0 , 0.00 23.52 %A1,03 3.15 3.71 %Fe, O 0.15 5.56 %Ca0 27.21 57.26 %CaSO ,, 66.06 4.17 %Mg0 0.86 0.82 Other 2.55 4.96 Ton/hr 13.67 13.27 In Table V is shown the gas composition and quantity (NCMH) of the flue gases produced in the CFB when operated under the conditions of examples 1 and 2.
Table V
Flue gas composition Example 1 Example 2 %CO , 15.69 15.03 %S O , 0.02 0.02 %N, 76.73 77.33 %O 3.26 3.28 %H, O 4.30 4.34 NCMH 380,370 377,385 Table II clearly shows that the amount of desulfurizer agent required by example 2 is less than the amount of desulfurizer required by example 1.
.As shown in Table IV, ash composition at the outlet of cooler ~2, in e:cample 2 corresponds to Portland cement clinker composition.
Data presented in Table V show that the amount of CO, evolved from CFB is lowered more than ~%
when using the method object of the present invention.
The residue of combustion of a sulhir containing fuel in CFB boilers has been treated as established in U.S. Patent 5,662,051 by grinding the fuel to less than 100 microns, grinding the limestone between 100 and 1~0 microns with a maximum of 1 mm and after combustion of the mixture collecting the residue to subject it to a heat treatment to obtain Ca0 and SO,, routing the SO, to a sulfuric acid manufacturing unit and quenching the solid matter with water and grinding it to reactivate the specific surface area of the solid matter, a portion of which is re injected to the CFB
boiler in a suspension with water, and the remaining fraction routed to a cement plant. This method usfa limestone as desulfurizer assent with the drawback of COZ being evolved from the reaction. A
his;h amount of limestone is n~°eded, usually more than that stoichiometrically determined to desulfurize the solid fuel with a resulting production of an excess of CO,.
Also the amount of limestone needed is higher than i.n the actual invention. All these drawbacks increase the production costs and the environmental effects.
A technique to produce a secondary raw material containing calcium sulfate is proposed in U.S.
Patent 4,997,486, comprising a waste hydrocarbon and one of waste sulfuric acid or acid waste sulfuric acid derivative combined with powdered limestone or fly ash containing calcium carbonate.
The product is used in making Portland cement clinker or as a fuel in furnaces or as a desulfurization additive. This product is of a general nature and as established its composition is not the best suited for the making of Portland cement clinker.
SUMMARY OF THE INVENTION
According to the foregoing it is a main object of the present invention to provide a method to produce Portland cement clinker using a circulating fluidized bed boiler CFB
which uses a fuel with a high sulfur content like petroleum coke, in such a way as to desulfurize the fuel with an agent chosen and prepared to evolve an outflow which can be used far making Portland cement cl-inker.
It is another object of the invention to provide means to rise the thermic efficiency in CFB boilers.
It is still another object of the invention to provide means to lower the content of CO, evolved from the operation of CFB boilers.
It i;s yet another object of the invention to provide a gas rich in S0, to be used as a source for the making of sulfur, sulfuric acid o:r sulfur derivatives.
It is a further object of the present invention to provide a source of Portland cement like material.
The instant invention provides a method to choose and prepare the raw material used as a desulfurizer in such a way as to equalize the composition of Portland cement clinker. The traditional CfB boilers use limestone as a desulfuriz.er material with some disadvantages like an excesive CO~
generation, and the need to confine the resulting products with an extra cost to the operation. In the method of the instant invention, apart from the actual methods, the desulfurizer agent comprise a mixture of lime, clay and iron ore in proper proportions as to use the resulting ash, after a thermic trea:ment, for making Portland cement clinker. Desulfurization of the flue gases according to the instant invention is carried out by means of calcium oxide available from lime according to the following reaction:
Ca0 + SO, +'/~O, -~ CaSO~ (;) It is necessary to feed to the :process an excess of lime to establish a required degree of des~.ilfurization. Because of the excess of lime, the ash comprises the unreacted lime and the calcium sulfate resulting from the process.. For a given degree of desulfurization, the mass of lime needed is always lower than the mass of limestone; because of the carbon dioxide content present in the calcium carbonate from limestone:. This lowering in the mass when using lime, allows to add other inert compounds to adjust the cornposition of the desulfurizer agent, while maintaining the overall efficiency of the CFB boiler.
The; composition of Portland cement has to comply to some required figures defined by its content of calcium oxide, silica, alumina and iron oxide contained in the following indexes:
%Ca0 LSF = ~.g*°~oSi02 + 1.18*%A1,03 + 0.65*%Fe,03 (4) SiOz MS = -A120~ + Fe'O~ (5) A cement to be considered of the Portland type has to have an LSF index between 0.75 and 0.90 and a MS index between 2.5 and 3.5.
The amount of lime, clay and iron ore comprised in the mixture used as a desulfurizer agent is established by determining the chemical composition of the fuel ash.
The resulting ash from the combustion process in the CFB boiler comprises a mixture of calcium oxide and calcium sulfate with minor amounts of other elements like SiO,, A1,0; and Fe,O;. This ash is heated in a separate container up to 1,200°C to 1,300°C
with hot gases evolving from a con- bastion chamber to decompose to caJicium oxide, sulfur dioxide and oxigen according to the foll~~wing reaction:
CaSO~ --~ Ca0 + S0, +'/~O; (6) Besides to the decompositon reaction of the calcium sulfate, in the heating process at temperatures up to 1,200°C to 1,300°C, the following mineral phases of the Portland cement clinker are formed:
tricalcium silicate (3Ca0 ~ SiO,); dicalcium silicate (2 Ca0 ~ SiO,);
tricalcium aluminate (3 Ca0 ~ A1,0;) and tetracalcium aluminoferrite (4Ca0 ~ A1,0; ~ Fe,O;).
After the heating process, the ash is passed to a direct air heat exchanger and thereafter transformed into Portland cement.
Sulfur dioxide evolving from a preheatinj; of ash is removed along with the combustion gases and sent to separation by means of chemical processes and later transformed for the production of sulfur, sul:Furic acid and sulfur derivatives.
BRIEF DESCRIPTION OF THE DRA'irINGS
Th~° novel features and advantages of the present invention should be readily apparent for those skilled in the art arising from the: teachings of the detailed description herein and the drawings, but it should be understood that the instant invention can be embodied in different ways and that the embodiments herein described a.re shown for illustration purposes only, but they are not restrictive as referred to the scope of the invention wherein:
Fiy~ure 1 is a flow diagram of a CFB boiler used to generate electricity from water vapor at high pressure using a fuel with a high sulfur content like petroleum coke;
Figure 2 is a simplified flow dia;;ram of the process of the present invention; and Figure 3 is a second embodiment of the instant invention.
DETAILED DESCRIPTION OF THE IPIVENTION
With reference to figure 1, numeral 10 generally designates a hopper which stores pulverized petrolemn coke, which is fed to a combustion chamber 12 of a CFB boiler 13 through pipe 15.
Pulverized limestone stored in hopper 14 is fed with the pulverized coke to the CFB boiler through pipe 17. In CFB boiler in the combustion section 12, the pulverized petroleum coke is burnt by means of the inj ection of hot air which is blown through pipe 16. The combustion reaction generates the neccessary heat for the production of vapor in coil 18. The SO, evolved from the combustion of sulfur available in petroleum coke is almost all removed with a removing rate of 90% to 9~% by means of calcium carbonate i:rom the limestone, according to reaction ( 1 ) as established hereinbefore. An additional amount of CO, to that produced from the combustion of coke, is evolved from the desulfurization reaction (1) established hereinbefore. The combustion gases go through combustion section 12 of CFB boiler i 3 to cyclon 20 wherein the biggest solid particles are removed and recicled to the combustion zone 12 of the boiler 13 by means of "J" valve 22 and pipe 24. The sensible heat form the combustion gases is recovered by flowing the gases through coil 26 wherein water is preheated, and thereafter through coil 28 wherein air is preheated.
The preheated water from coil 26 is fed to coil 18 wherein vapor is generated. The preheated air from coil 28 is fed through pipe 16 to the combustion chamber 12. The combustion gases in the outlet of cyclon 20 still have an amount of very fine solids known as fly ash, which are passed through coils 26 and 28 and thereafter collected by dust collector 30 <md sent through pipe 42 to a fly ash hopper 32 to be stored and thereafter sent through pipe 46 to confinement. The gases at the outlet of dust collector 30 are passed through fan 34 to induce the gas slow and thereafter to stack 36 as effluent gas. The effluent gas from this boiler has to be basically free of solids and sulfur to comply with environmetal re;;ulations. A portion of the ash produced in CFB boiler 13 is removed through pipe 38 located at thE: bottom portion of the combustion section 12, wherein this ash is known as bottom ash. The bottom ash is passed to a hopper 40 and sent through pipe 44 for later confinement.
With reference to figure 2, hopper 14 is replaced by hoppers 14a, 14b and 14c which store lime, clay and iron ore respectively which are fed to combustion chamber 12 through pipes 17, 19, and 21 respectively. Desulfurization of combustion gases is achieved by means of calcium oxide available from lime according to reaction, (3) established hereinbefore. An advantage of this reaction is that addittional CO, is not evolved to that generated by the combustion reaction of coke. Bottom ash and fly ash, which sulfur content is about 60%, are collected by means of pipes 38 and 42 respectively mixed and then by means of pipe 43 are :Eed to the upper portion of fluidized reactor 44, wherein fly ash is brought into contact with. a gas coming from a combustion chamber 46, which is fed with a fuel which is fed through pipe 48 and with preheated air fed through pipe S0.
The outflow gas frc::~
combustion chamber 46 at a temperature; between 1,200°C and 1,300°C is fed to the lower portion of the fluidized bed reactor 44. In reactor 44 the thermic decomposition of calcium sulfate is accomplished according to reaction (6;) established hereinbefore and also the formation of the mineral phases of Portland cement clinker occur at this stage. Solid particles from reactor 44 are discharged from the lower portion of reactor and sent through pipe 4~ to a fluidized bed cooler 52 s wherein the particles are brought into contact with cool air fed through pipe ~4. The out flow of hot air from cooler 52 is fed to combustion chamber 48 by means of pipe 50. Ash is discharged from the cooler 52 through pipe ~3 at a temperature below 200°C having a sulfur content below;%. Because of the preparation of the mixture: used as a desulfurizer, the ash has a composition equivalent to that for clinker and can be used directly for the production of Portland cement.
The outflow gas from reactor 44 is removed through pipe 56 and sent to a separation process 58 wherein SO, is separated from other combustion gases. Combustion gases are discharged to atmosphere by means of pipe 64.
SO, is sent through pipe 60 to a chemical plant 62 to be treated for the production of elemental sulfur or sulfuric acid.
Re:Ferring to figure 3 clay from hopper 14b, and iron ore from hopper 14c are fed directly to reactor 44 through pipes 19 and 21 and thereafter through pipe 39 to pipe 43, in such a way as to feed petroleum coke and lime alone to CFB boiler 13, through pipes 15 and 17 respectively.
The advantages and benefits c>f the instant invention can be best understood according to the following examples of the operation of a CFB boiler using limestone as a desulfurizer agent, and using a mixture of lime, clay and iron ore as a desulfurizer agent.
Table I and Table II present the: CFB and petroleum coke characteristics used in both examples:
Table I
<:FB characteristics Capacity (Mw) 123.33 Thermal effi<;iency 89.3 (%) Total duty (Crcal/hr) 279.62 Excfas air (%) I 20 SO, Adsorbed (%) 94.02 Table II
Petrolf:um coke characteristics Heating value (kcal/kg) 7437.9 ic 8o~s %H _, 3.0 %S 6.0 %N , 0.8 %H , O 8.0 %Ash 0.6 Table III prxsents the chemical composition and quantity (ton/hr) of the limestone used as desulfurizer agent in example ladn the chemical compositions and quantities (ton/hr) of lime, clay and iron ore mixture used as desulfurizer agent in example 2 Table III
I)esulfurizer agents Example 1 Example 2 Limestone Lime Clay Iron Oxide %Si0 , 0.00 3.24 67.29 2.14 Al ,_ 0 3 3.OJ 1.36 8.97 0.75 %Fe , O 5 0.15 0.61 4.28 93.20 %Ca0 0.00 93.23 7.27 1.02 %CaCO a 95.00 0.00 0.00 0.00 %IVIgO 0.85 0.28 1.97 0.37 %SO 3 0.86 1.28 0.32 0.09 Other 0.09 0.00 9.90 2.43 Ton/hr 13.98 8.19 4.30 0.55 Table IV presents the chemical, composition and quantities (ton/hr) of the ashes produced in both examples, for example 2 the composition shown is at the outlet of cooler 52.
Table IV
Ash composition Example 1 Example 2 %Si0 , 0.00 23.52 %A1,03 3.15 3.71 %Fe, O 0.15 5.56 %Ca0 27.21 57.26 %CaSO ,, 66.06 4.17 %Mg0 0.86 0.82 Other 2.55 4.96 Ton/hr 13.67 13.27 In Table V is shown the gas composition and quantity (NCMH) of the flue gases produced in the CFB when operated under the conditions of examples 1 and 2.
Table V
Flue gas composition Example 1 Example 2 %CO , 15.69 15.03 %S O , 0.02 0.02 %N, 76.73 77.33 %O 3.26 3.28 %H, O 4.30 4.34 NCMH 380,370 377,385 Table II clearly shows that the amount of desulfurizer agent required by example 2 is less than the amount of desulfurizer required by example 1.
.As shown in Table IV, ash composition at the outlet of cooler ~2, in e:cample 2 corresponds to Portland cement clinker composition.
Data presented in Table V show that the amount of CO, evolved from CFB is lowered more than ~%
when using the method object of the present invention.
Claims (27)
1. A method of producing Portland cement; clinker as a by product of a CFB
boiler fueled with a high sulfur content fuel comprising: selecting a solid desulfurizer agent from the group comprising lime, clay and iron ore and mixtures thereof, collecting the ashes evolving from the boiler, removing the sulfur adsorbed in the ashes by heating the ashes to a temperature in the range of 1200 - 1300 °C, cooling the ashes and using the cold ashes for Portland cement making.
boiler fueled with a high sulfur content fuel comprising: selecting a solid desulfurizer agent from the group comprising lime, clay and iron ore and mixtures thereof, collecting the ashes evolving from the boiler, removing the sulfur adsorbed in the ashes by heating the ashes to a temperature in the range of 1200 - 1300 °C, cooling the ashes and using the cold ashes for Portland cement making.
2. A method according to claim 1, wherein said desulfurizer agent mixture is formed to comply with a LSF index in the range of 0.75 to 0.90.
3. A method according to claim 1, wherein said desulfurizer agent mixture is formed to comply with a MS index in the range of 2.5 to 3.5.
4. A method according to claim 1, wherein said cold ashes contain less than 5%
of CaSO4.
of CaSO4.
5. A method according to claim 1, wherein evolving ashes from the boiler are heated in a fluidized bed heater.
6. A method according to claim 5, wherein tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite phases are formed in said fluidized bed heater.
7. A method according to claim 1, wherein the hot ashes are cooled with air in a fluidized bed cooler.
8. A method according to claim 7, wherein said cold ashes are used directly to produce Portland cement.
9. A method according to claim 5, wherein said fluidized bed heater is fed whit hot gas from a combustion chamber.
10. A method according to claim 5, wherein effluent gases from said fluidized bed heater are treated to produce sulfur, sulfuric acid and sulfur derivatives.
11. A method according to claim 1, wherein said desulfurizer agent rises the overall efficiency of CFB boiler.
12. A method according to claim 1, wherein said desulfurizer agent lower the CO2 evolved from the operation of CFB boiler.
13. A method according to claim 1 wherein said desulfurizer agent evolves an SO3 rich gas which is used for making sulfur, sulfuric acid and sulfur derivatives.
14. A method of operating a CBS boiler fueled with a high sulfur content fuel comprising: selecting a solid desulfurizer agent from the group comprising lime,clay, and iron ore and mixtures thereof, and preparing the desulfurizer agent to use the solid out/flow for Portland cement clinker making, wherein said desulfurizer agent rises the overall efficiency of the operation of CFB boiler.
15. A method according to claim 1, wherein said desulfurizer mixture is fed to the CFB boiler together with the high sulfur content fuel.
16. A method according to claim 1, wherein lime and the high sulfur content fuel are fed to the CFB
boiler and clay and iron ore are mixed with the evolving ashes prior to heating step.
boiler and clay and iron ore are mixed with the evolving ashes prior to heating step.
17. A method according to claim 1, wherein said high sulfur content fuel is petroleum coke.
18. A method of producing Portland cement clinker as a by product of a CFB
boiler fueled with a high sulfur content fuel comprising: selecting a solid desulfurizer agent from the group comprising lime, clay and iron ore and mixtures thereof wherein said desulfurizer agent complies with a LSF
index in the range of 0.75 to 0.90 and a MS index in the range of of 2.5 to 3.5, collecting the ashes evolving from the boiler, removing the sulfur adsorbed in the ashes by heating the ashes in a fluidized bed heater to a temperature in the range of 1200 - 1300 °C, cooling the ashes with air in a fluidized bed cooler and using the cold ashes for Portland cement making.
boiler fueled with a high sulfur content fuel comprising: selecting a solid desulfurizer agent from the group comprising lime, clay and iron ore and mixtures thereof wherein said desulfurizer agent complies with a LSF
index in the range of 0.75 to 0.90 and a MS index in the range of of 2.5 to 3.5, collecting the ashes evolving from the boiler, removing the sulfur adsorbed in the ashes by heating the ashes in a fluidized bed heater to a temperature in the range of 1200 - 1300 °C, cooling the ashes with air in a fluidized bed cooler and using the cold ashes for Portland cement making.
19. A method according to claim 18, wherein said cold ashes contain less than 5% of CaSO4.
20. A method according to claim 18, wherein tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite phases are formed in said fluidized bed heater.
21. A method according to claim 18, wherein said cold ashes are used directly to produce Portland cement.
22. A method according to claim 18, wherein said fluidized bed heater is fed whit hot gas from a combustion chamber.
23. A method according to claim 18, wherein effluent gases from said fluidized bed heater are treated to produce sulfur, sulfuric acid and sulfur derivatives.
24. A method according to claim 18, wherein said desulfurizer agent rises the overall efficiency of CFB boiler.
25. A method according to claim 18, wherein said desulfurizer agent lower the CO2 evolved from the operation of CFB boiler.
26. A method according to claim 18, wherein said desulfurizer agent evolves an SO2 rich gas which is used for making sulfur, sulfuric acid and sulfur derivatives.
27. A method according to claim 18, wherein said high sulfur content fuel is petroleum coke.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US35705799A | 1999-07-19 | 1999-07-19 | |
| US09/357,057 | 1999-07-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2313862A1 true CA2313862A1 (en) | 2001-01-19 |
Family
ID=23404132
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2313862 Abandoned CA2313862A1 (en) | 1999-07-19 | 2000-07-13 | Method of producing portland cement clinker using a circulating fluidized bed boiler |
Country Status (6)
| Country | Link |
|---|---|
| CN (1) | CN1285330A (en) |
| CA (1) | CA2313862A1 (en) |
| ES (1) | ES2181544B1 (en) |
| FR (1) | FR2797628A1 (en) |
| ID (1) | ID26610A (en) |
| RU (1) | RU2184094C2 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8021478B2 (en) * | 2004-08-05 | 2011-09-20 | Cemex Trademarks Worldwide Ltd. | Process to produce portland cement clinker and obtained clinker |
| CN109731449A (en) * | 2019-02-28 | 2019-05-10 | 兖矿集团有限公司 | A kind of desulfuration in furnace method of circulating fluidized bed boiler |
| EP4303514A1 (en) | 2022-07-08 | 2024-01-10 | Heidelberg Materials AG | Method for manufacturing cement clinker and cement plant |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10260741A1 (en) * | 2002-12-23 | 2004-07-08 | Outokumpu Oyj | Process and plant for the heat treatment of fine-grained solids |
| CN110397913A (en) * | 2019-08-06 | 2019-11-01 | 新乡市汇能玉源发电有限公司 | A kind of furfural dregs Denitration in Boiler system effectively improving denitration efficiency |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62502399A (en) * | 1985-04-05 | 1987-09-17 | ザ リ−ジエンツ オブ ザ ユニバ−シテイ オブ カルフオルニア | Method for manufacturing hydraulic cement using cement kiln dust and red mud |
| DE3631757A1 (en) | 1986-09-18 | 1988-03-31 | Boelsing Friedrich | METHOD FOR PRODUCING A SOLID SECONDARY RAW MATERIAL CONTAINING CALCIUM SULFATE FOR THE EXTRACTION OF PORTLAND CEMENT CLINKER |
| DK49592D0 (en) * | 1992-04-13 | 1992-04-13 | Aalborg Portland As | CEMENT COMPOSITION |
| US5698027A (en) * | 1994-03-03 | 1997-12-16 | F. L. Smidth & Co. A/S | Method and plant for manufacturing mineralized portland cement clinker |
| FR2718655B1 (en) | 1994-04-13 | 1996-05-24 | Gec Alsthom Stein Ind | Process for the treatment of solid residues from the combustion of a fuel containing sulfur, and thermal treatment device for carrying out the process. |
-
2000
- 2000-07-13 CA CA 2313862 patent/CA2313862A1/en not_active Abandoned
- 2000-07-17 ID ID20000599D patent/ID26610A/en unknown
- 2000-07-18 RU RU2000119207A patent/RU2184094C2/en not_active IP Right Cessation
- 2000-07-18 ES ES200001778A patent/ES2181544B1/en not_active Expired - Lifetime
- 2000-07-19 CN CN00126825A patent/CN1285330A/en active Pending
- 2000-07-19 FR FR0009500A patent/FR2797628A1/en not_active Withdrawn
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8021478B2 (en) * | 2004-08-05 | 2011-09-20 | Cemex Trademarks Worldwide Ltd. | Process to produce portland cement clinker and obtained clinker |
| CN109731449A (en) * | 2019-02-28 | 2019-05-10 | 兖矿集团有限公司 | A kind of desulfuration in furnace method of circulating fluidized bed boiler |
| EP4303514A1 (en) | 2022-07-08 | 2024-01-10 | Heidelberg Materials AG | Method for manufacturing cement clinker and cement plant |
| WO2024008350A1 (en) | 2022-07-08 | 2024-01-11 | Heidelberg Materials Ag | Method for manufacturing cement clinker and cement plant |
Also Published As
| Publication number | Publication date |
|---|---|
| RU2184094C2 (en) | 2002-06-27 |
| CN1285330A (en) | 2001-02-28 |
| ID26610A (en) | 2001-01-25 |
| ES2181544A1 (en) | 2003-02-16 |
| FR2797628A1 (en) | 2001-02-23 |
| ES2181544B1 (en) | 2004-06-16 |
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