KR20140116912A - Production of coal combustion products for use in cementitious materials - Google Patents

Abstract

A method and system (10) for producing a modified coal combustion product. The additive reduces the particle size of the coal combustion product and also reduces the unburned carbon content of the coal combustion product, thereby making it possible to produce a modified product useful as an additive to the cement material.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for producing coal combustion products for use in cement materials,

FIELD OF THE INVENTION The present invention relates to coal combustion products and, more particularly, to a method for producing coal combustion products having improved properties for use in cement materials.

Concrete and other hydraulic mixtures used for construction require the manufacture of Portland cement clinker as the primary binder that primarily controls the rate of development of mechanical properties. The manufacture of Portland cement clinker is an energy intensive industry and releases large quantities of carbon dioxide into the atmosphere. In order to reduce the environmental impact of cement and concrete manufacture, a Portland cement clinker as a binder in the hydraulic mixture can be partially replaced with a supplementary material having a lower carbon dioxide emission.

Coal ash and other coal combustion products are generated worldwide due to the combustion of coal as fuel for power generation and other energy intensive industries. Unfortunately, the use of coal and other coal combustion products in concrete has many drawbacks. For example, using fly ash for concrete results in products with low air inlet rates and low early strength development. An important drawback of using fly ash for concrete is the fact that fly ash significantly delays the mechanical properties of concrete in the early days. Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, SP-114, American Concrete Institute, Detroit, pp. 139-155], the test conducted by Ravindrarajah and Tam showed that the compressive strength of the fly ash concrete during premature aging was significantly higher than the compressive strength of the control concrete, which is a general characteristic of concrete or mortar when carbonaceous material is added Strength. Most of the reported studies tend to show lower concrete strength due to the presence of carbonaceous materials.

Another important drawback is that fly ash may contain high levels of free carbon when measured by another analytical method such as loss on ignition (LOI) or thermogravimetric analysis It is true. Excessive levels of carbon inhibit the action of chemical additives used as air entrainment agents in concrete. Bubble materials in concrete are essential to achieve durability of concrete under repeated freeze-thaw cycles. Thus, the use of combustion products in concrete is limited by the presence of free carbon.

Indeed, these drawbacks inhibit the economical use of carbonaceous materials in most construction concrete at high replacement levels of more than 25 to 30%. As a result, large quantities of coal combustion products are disposed of at landfills with high economic and environmental costs. Existing methods of selecting these to make them suitable for other uses, such as in construction, generally do not use 100% of the material for beneficial purposes. Moreover, existing treatment methods typically require the use of compounds that are cost-effective for use, or treatment in separate facilities that incur coal burning, resulting in incidental transportation costs and facility investment. Currently, most of the changes to select coal combustion products are absolutely related to the cleaning or sequestration of harmful compounds in coal combustion products. Some methods involve the use of external grinding equipment to reduce the particle size of the combustion product particles. Other existing methods include a carbon burn-out method that uses a device that applies heat to the combustion products to reduce the level of free carbon. Other methods use electrolytic methods to isolate carbon atoms. All of the methods described above require a lot of capital and ongoing operating costs to create and operate separate facilities.

The present invention has been developed in view of the foregoing and also to improve other conventional drawbacks.

The present invention provides a method and system for producing improved coal combustion products for addition to concrete, mortars and other hydraulic mixtures comprising Portland cement clinker and coal combustion products for use in construction and other industries. The present invention provides a method of increasing the rate of occurrence of mechanical properties in a hydroponic mixture containing such a combustion product by reducing the particle size of the resulting combustion product and increasing the total surface area. The present invention also relates to a method for improving the combustion efficiency due to the smaller particle size and the resulting increased surface area of the coal particles and the dilution effect of the original combustion products after the addition of the above mentioned materials, All further lowering the level of total free carbon in the resulting combustion products.

One embodiment of the present invention is directed to increasing the reactivity of coal combustion products produced without a specific delay effect on the alite hydration in the Portland cement clinker used with the coal combustion product in the hydraulic mixture A method for selecting and adding raw materials to be added to a coal combustion process is provided. Presently limestone is added to the combustion chamber of a coal burning boiler to reduce the sulfur emissions from the flue gas to achieve a sulfur removal rate in the range of 75 to 95 percent, It therefore improves the expression of mechanical properties when used with Portland cement clinker in a hydraulic mixture.

One aspect of the present invention provides a method of producing a modified coal combustion product comprising burning a coal and a particle size-reducing additive wherein the modified coal combustion product comprises an additive Lt; RTI ID = 0.0 > coal < / RTI >

Another aspect of the present invention is a process for producing coal and a particle size reduction additive comprising a combustion chamber for burning coal and a particle size reduction additive together, a source of coal, a source of particle size reduction additives and at least one injector and a system for producing a modified coal combustion product comprising an injector.

These and other aspects of the present invention will become more apparent from the following detailed description.

1 is a partial schematic view of certain elements of a coal-fired power plant in which coal combustion products are produced in accordance with an embodiment of the present invention.
Figures 2 and 3 are graphs showing the particle size distribution of the additives and the particle size distribution of the combustion products obtained by adding these additives in various combinations and dosages in accordance with embodiments of the present invention.

According to an embodiment of the present invention, an additive containing calcium oxide, alumina, silica, magnesium oxide, titanium oxide, ferrous oxide or the like is burned together with coal to produce a modified coal combustion product. The average particle size of the modified coal combustion product is smaller than the average particle size of the unmodified coal combustion product. "Average particle size" refers to the average particle size of the metal powder and related compounds measured according to ASTM B822-A, which is a standard test method for particle size distribution of metal powders and related compounds by light scattering. (Standard Test Method for Particle Size Distribution of Metal Powders and Related Compounds by Light Scattering) 10 < / RTI > standard procedure.

Raw material particles are typically much larger than the resulting coal combustion product particles, demonstrating that intense high temperature mixing causes particle reduction / consumption through intense impact as well as through chemical combustion. For example, the average particle size of the modified combustion products may be less than 50 microns, typically 20 or less than 10 microns, while the average particle size of at least a portion of the starting additive material may be greater than 20 or 50 or 100 microns . In certain embodiments, the average particle size of the modified coal combustion product is at least 5%, such as at least 15% smaller than the average particle size of the coal combustion product burnt from similar coal without additive.

According to one embodiment of the present invention, a coal-fired boiler is used as a co-generator to produce heat for electric power generation as well as excessive heat, combustion synthesis and thermal blending, Lt; RTI ID = 0.0 > pozzolanic < / RTI > A comparison of the particle size of the starting material and the particle size of the resulting product proves that a combination of combustion and grinding in the boiler occurs and rapidly reduces the large oxide material into fine powder. Moreover, the combustible additive can be blended with fumes generated during coal combustion to enable the formation of chemically strengthened carbonaceous materials.

The raw materials used as additives may or may not be derived from industrial waste streams and may be derived from concrete dust, grinding blades, ground blast steel slag, finely divided soda lime glass, finely divided E glass, Fine ground geopolymer cement, fly ash in the presence of heat and blends and mixes of highly alkaline compounds, or certain other materials that increase the level of silica or alumina in the resulting fly ash.

The raw material may also be used to reduce the level of total free carbon in the carbonaceous material produced during combustion. These carbon-reduction materials may or may not be derived from industrial waste streams and include recycled concrete dust, steelmaking slag with grinding blast, finely divided soda lime glass, finely divided E glass, finely divided geopolymer cement, fly ash And blends and mixes of highly alkaline compounds, or certain other materials that increase the level of silica or alumina in the resulting fly ash. In certain embodiments, the modified coal combustion product has a carbon content less than the carbon content of the coal combustion product burnt from similar coal without additive. For example, the carbon content of the modified coal combustion product is at least 10 wt% less than the untreated coal, typically at least 50 wt% less. The carbon content of the modified coal combustion product may be less than 5 wt%, for example, 0.5 to 2 wt%.

According to the present invention, selected types and amounts of metal strength enhancing additives are used as raw materials to be burned with coal to produce useful cement additive materials with controlled amounts of calcium oxide, silicon dioxide and aluminum oxide. Table 1 below lists the relative amounts of strength-enhancing metal oxides, expressed as CaO, SiO ₂ and Al ₂ O ₃ , present in the combustion products according to embodiments of the present invention. The terms "CaO "," SiO ₂ ", and "Al ₂ O ₃ ", as used herein, refer to the relative weight percentages of calcium oxide, silica and alumina contained in the cement additive material in accordance with the ASTM C114 standard do.

Table 1

Relative Weight Percentage

According to an embodiment of the invention, the coal may comprise bituminous coal and / or sub-bituminous coal. In the case of bituminous coal, relative to the amount of present in the modified combustion CaO, Si0 ₂ and Al ₂ 0 ₃ is typically CaO from about 20% to about 60% by weight, Si0 ₂ about 25 to about 60%, and Al ₂ 0 ₃ by weight of about 5 to about 30% by weight. For example, a bituminous coal combustion products CaO, Si0 ₂ and Al ₂ 0 ₃ the relative amount of CaO from 25 to 50% by weight of one, Si0 ₂ about 30 to about 55% by weight range and Al ₂ 0 ₃ about 10 to about 25% by weight. For O-bituminous, the relative amount of present in the modified combustion CaO, Si0 ₂ and Al ₂ 0 ₃ is typically CaO about 47.5 to about 70 wt%, Si0 ₂ about 10 to about 40% by weight and Al ₂ 0 ₃ About 5 to about 30 wt%. For example, ah Coal combustion CaO, Si0 in the product ₂ and Al ₂ 0 ₃ the relative amount of CaO from about 50 to about 65% by weight, Si0 _2, from about 15 to about 35% by weight range and Al ₂ 0 ₃ about 10 and a To about 25% by weight.

The CaO, Si0 ₂ and Al ₂ 0 ₃ additive to create a level, selected particle size, dose, and calcium oxide in combustion can be selected by the temperature in the room, such as a coal combustion boiler when the temperature level is introduced into the system, Or may be an inexpensive mineral containing wastes containing silicon dioxide and / or aluminum oxide. In one embodiment, the combination of additives is selected from the group consisting of limestone, waste concrete such as regenerated Portland cement concrete, kaolin, recycled ground granulated blast furnace slag, recycled crushed glass, recycled crushed aggregate fines, silica fume, cement kiln dust, lime kiln dust, weathered clinker, clinker, aluminum slag, copper slag, granite kiln dust, rice hulls, rice hull ash, zeolite, Limestone quarry dust, red mud, fine ground mine tailings, oil shale fines, bottom ash, dry stored fly ash, Landfilled fly ash in a landfill, ponded fly ash stored in a tank, sopodumene lithium aluminum silicate material, lithium-containing ores, and oxidized knife , It is selected from any other waste or low-cost materials containing silicon dioxide and / or aluminum oxide.

According to certain embodiments of the present invention, the additive can comprise one or more of the following materials: 7 to 20 wt% limestone; 1 to 5% by weight ground granulated blast furnace slag; 1 to 5 wt% crushed concrete; 0.1 to 2 wt% crushed glass; 0.1 to 5 wt% kaolin; And 0.01 to 1 wt% silica fume. Such additives typically account for at least 8 wt%, such as greater than 10 wt%, of the total combined weight of coal and additive.

The additive may be provided in the desired particle size range and may be introduced into the combustion chamber in the same zone as the coal or in another zone. One embodiment of the present invention uses a coal boiler of an electric power plant as a chemical treatment vessel for producing coal combustion products in addition to its normal function of generating steam for electric energy. This approach can be adopted in the construction market without reducing the boiler output efficiency while producing raw materials with controlled specifications and higher commercial value. The resulting carbonaceous material may be designed to have different properties that are advantageous for use with Portland cement, or to provide different chemical modifications that also produce pozzolan, which may be a direct replacement for Portland cement. In both of these cases, both economical and environmental aspects can be advantageous. The need for landfill is reduced and cost savings are avoided by avoiding the transport and landfill of carbonaceous material. Also, the amount of carbon dioxide and other toxic emissions generated by the manufacture of Portland cement to the extent that the carbonaceous material replaces the Portland cement is reduced.

1 schematically illustrates certain elements of a coal-fired power plant 10. The power plant includes a combustion chamber 12 such as a conventional tangential firing burner configuration. The pulverized coal is introduced into the combustion chamber 12 via at least one inflow line 14. The coal hopper 15 feeds the coal pulverizer 16 into a desired particle size for introduction of the coal into the combustion chamber 12. The pulverized coal may be mixed with the heat and ejected through the inlet (s) 14 into the combustion chamber 12 where the coal is burned.

The additive may be introduced into the delivery system 12 via a feed line 11 which feeds into the mill 16 or coal feed line 14 and / or via another feed line 13 which feeds into the bottom region of the combustion chamber 12 19 may be introduced into the combustion chamber 12 from a source of such additives. Alternatively, the additive may be supplied separately via one or more additional inflow lines 17 and 18. The additive delivery system 19 includes a delivery system for delivering additives to conventional particulate material storage hoppers, metering systems and feed lines 11 and / or 13, and / or to additional inflow lines 17 and 18 can do.

Water flows through a tube-lined wall of the boiler 20 where the water is heated by the combustion fuel to form a vapor that moves to the steam turbine 21. The combustion products move from the boiler zone to the particulate collection zone 22 where the solid combustion products are collected and transferred to the hopper 24. The exhaust gas passes through the scrubber 28 and is discharged through the chimney 29. At least one sensor 30 may be provided in the combustion chamber 12 or downstream of the combustion chamber.

The coal fly ash is essentially formed from the combustion gas as the combustion gases rise from the combustion zone and agglomerate over the zone. Typically, when the temperature is in the range of 1,800-2,200 ° F, these gases form mainly amorphous hollow spheres.

According to the present invention, chemical additives such as those listed above can be added directly to the boiler in such a way that the carbonaceous material from the coal can enhance the optimal carbon performance. In certain embodiments, additives such as clay, including kaolin, may be added to the boiler. These materials are not degradable and can not be recombined with the carbonaceous material, but rather can be thermally activated and intimately mixed through a unique highly convective flow pattern in the boiler. The result is a uniform blend of carbonaceous additive that does not require any additional processing through the boiler combustion process. Essentially, the vapor from the burned product will form a vitreous chalcia-alumina-silicate as it flocculates as it rises from the high temperature zone. The vaporized additive dispersed in the plume will be a part of the vitreous, while the non-vaporized additive will act as nuclei for coagulating the vapor. Other additives that are not involved in the vitrification can be intimately mixed with the carbonaceous material to produce a highly reactive pozzolanic mixture. For example, kaolin introduced into a boiler may not participate in carbonaceous material formation, but may be transformed into meta kaolin, another expensive additive.

Intimate blending of the additives directly into the boiler enables the combustion synthesis of the additives with the coal and intimate blending of these additives is caused by convective flow in or near the boiler to produce chemically modified fly ash It relies on intimate mixing. Such blending can occur within the main combustion zone of the boiler, just above the main combustion zone in the boiler, or downstream of the boiler. For example, additives such as kaolin, meta kaolin, titanium dioxide, silica fume, zeolite, diatomaceous earth, etc. may be added to this downstream location at other points where the coal combustion product is agglomerated into amorphous fly ash particles. In one embodiment, relatively low cost kaolin is added during the process to convert to meta kaolin, which can economically produce metakaolin with the desired strength enhancing properties when added to cement. Due to the material selected as an additive to the fuel, the resulting carbonaceous by-products can be designed to have a chemical structure that can act as a cement binder together with the Portland cement for strength enhancement properties of the cement or concrete.

In another embodiment, geopolymer cement may be added to the combustion process to reduce contaminants in the flue gas. These geopolymer cements can be provided as binders for mercury, heavy metals, nitrogen oxides and sulfur oxides, and incidental silica.

Through the injection of these additives, the resulting fly ash formed in the coal combustion process can be modified by directly incorporating the compounds in these additives into the agglomerating fly ash. In addition, some chemical species added in such a way that are not chemically bonded to the agglomerating fly ash are intimately blended with fly ash through natural convection in the boiler, requiring additional, cost-intensive powder blending of the resulting carbonaceous product To achieve a very uniform blending process.

In another embodiment, a method for testing coal combustion combustibles produced after the addition of other materials to reach the target levels of calcium oxide, silicon dioxide, and aluminum oxide in the resulting coal combustion burn and adjusting the combustion parameters and materials / RTI > Such testing and adjustment methods may include directly measuring the contents of calcium oxide, silicon dioxide, and aluminum oxide, and other reactive and non-reactive elements. This method also includes measuring the properties of the concrete produced from the coal-fired carbonaceous material produced to determine the early strength, late strength, slump and curing time of the concrete comprising the resulting coal-fired carbonaceous material . Measurements can be linked to algorithms to quickly evaluate data and change supply rates in real time.

The test methods may be selected from the group consisting of calcium oxide, silicon dioxide, and aluminum oxide, using x-ray diffraction (XRD) methods including Rietveld analysis, x-ray fluorescence (XRF) And other reactive and non-reactive elements. This method can be used either in-line or end-of-line. Methods of measuring strength (early and late), hardening time, and slump include methods provided in the ASTM standard relating to the measurement of these properties, methods of measuring hydration heat through a calorimeter, methods of measuring conductivity, Or certain other methods that can measure or infer certain of the above-mentioned characteristics.

In one embodiment, a sensor is additionally installed in the boiler to monitor the in-situ quality / chemistry of the carbonaceous product when the carbonaceous product is generated. The sensor may be a mercury analyzer as well as a laser for performing conventional residual gas analyzers, x-ray fluorescence spectrometers, mass spectrometers, atomic absorption spectrometers, inductively coupled plasma atomic spectrometers, Fourier transform infrared spectrometers, NO _x detector and SO _x detector. The level of gas measured by this technique, etc., can be linked to the optimal chemical properties of the carbonaceous product.

The sensor can provide real-time monitoring feedback to a human-controlled control device or automated analysis system. For example, the sensor (s) may transmit the measured characteristic value to a controller that compares the measured value to a reference value and adjusts the flow rate of the strength-enhancing material based thereon. The controller may send a signal to one or more additive injection devices to increase or decrease the flow rate of the additive into the combustion zone. The purpose of this feedback system is to connect directly to the individual sources of chemical additives and adjust their feed rates to maintain the chemical quality of the carbonaceous materials required for optimal concrete performance.

It is also possible to measure the effluent gas generated by the coal combustion process using a gas analyzer during the improved coal combustion process. Typically, these gases include NO _x , SO _x , CO ₂ , and mercury. Through the conventional analysis of these gas ranges combined with the resulting carbonaceous reactivity, the addition of chemical additives can be optimized using a gas monitoring process. In this way, the chemistry of the optimal reactive carbonaceous material can be optimized in situ, that is, in real time during the coal combustion process to optimize the chemical properties of the carbonaceous material produced.

The modified combustion products of the present invention may be added to various types of cement including Portland cement. For example, the combustion products may comprise more than 10% by weight, typically more than 25% by weight, of the cement material. In certain embodiments, the additive comprises from 30 to 95 weight percent of the cement material.

The following examples are intended to illustrate various aspects of the invention and are not intended to limit the scope of the invention.

Example

Limestone, crushed recycled concrete, granulated blast furnace slag, crushed glass, kaolin and silica fume having particle sizes as shown in Table 2 and FIG. 2 were used as additives and tested at various combinations and dosage levels It was injected into the boiler. Table 3 and Figure 3 below show the particle size distribution of the resulting combustion products. All particle size distributions were determined according to the standard procedure described in ASTM B822-10. The terms used in Table 2 and in Figure 2 are as follows: LS: limestone; RC: crushed concrete; SL: granulated blast furnace slag; RG: crushed glass; K: kaolin; And SF: silica fume. AX BY CZ, etc., wherein A, B, and C are the additives as shown in Table 3 below, and X , Y and Z are dose levels of these additives, in wt.% With respect to coal. For example, LS8.2 RC2.0 is a combustion product obtained by injecting 8.2 wt% additive limestone / coal, and 2.0 wt% crushed concrete / coal into the boiler.

As can be seen from Table 2 and FIG. 2, all the injected additives are granular than the untreated combustion products obtained without injecting specific additives, except for the granulated blast furnace slag. 3 and Table 3, it can be seen that all of the combustion products produced are finer than the untreated combustion products, regardless of the combination of additives and doses used. This represents a particle community from the additive and the burning coal which produces finer combustion products than both the additive and untreated combustion products.

Table 2

Raw material

Table 3

Combustion product

The limestone, granulated blast furnace slag and kaolin were injected into the combustion chamber of the coal boiler at the following dosages: limestone: 7.8 wt% of coal; Granulated blast furnace slag: 4.9% by weight of coal; And kaolin: 1.4% by weight of coal. The total amount of additive is 14.1% by weight of coal.

Burned coal in the test boiler produced 35.3% untreated combustion products prior to the addition of additives. Thermogravimetric analysis showed the results of Table 4 for the total carbon content.

Table 4

The reduction in weight percent of total carbon is due in part to dilution by the addition of additives that dilute the relative content of carbon in the combustion products.

The effect of this dilution was calculated as follows:

Cu - Cu * CPu / CPt

Where Cu is the carbon content (%) of the untreated product, i. E., 8.4%; CPu is the amount of untreated combustion products (wt% of coal), or 35.3%; CPt is the amount of product treated (wt% of coal), i.e. 35.3% + 14.1%.

Thus, the reduction in carbon content due to dilution was 2.4% by weight of the combustion products. The reduction in carbon content due to better combustion efficiency by pulverization of coal particles and additive particles inside the combustion chamber was 2.2 wt% of the combustion products. The net net effect of carbon reduction was a reduction of 4.6% by weight of the combustion products, or 55% when compared to the total carbon levels in untreated combustion products.

The present invention provides a method and system for reducing coal burning refuse to be disposed of in a landfill by converting coal-fired carbonaceous material into a more expensive hydraulic binder which can be used as a substitute for cement replacing amounts in excess of 40% . Another advantage of the present invention is that other methods for selecting coal-fired carbonaceous materials, such as exterior grinding facilities, by injecting and processing materials into combustion boilers rather than at separate facilities, or existing methods for reducing the amount of free- It provides a cost-effective alternative to technology. The process described herein can reduce the need to transfer coal-fired carbonaceous material to a separate facility by treating it as part of a normal power generation process.

Although specific embodiments of the invention have been described above for purposes of illustration, it will be apparent to those skilled in the art that various modifications and variations can be made in the details of the present invention without departing from the scope of the invention as defined by the appended claims. You will know.

Claims (20)

A method of producing a modified coal combustion product having an average particle size less than an average particle size of a coal combustion product burnt from an additive-free coal, comprising burning coal and a particle size-reducing additive. The method according to claim 1,
Wherein the average particle size of the modified coal combustion product is at least 5% less than the average particle size of the coal combustion product burnt from the coal that does not contain the additive. The method according to claim 1,
Wherein the average particle size of the reformed coal combustion product is at least 15% less than the average particle size of the coal combustion product burnt from the additive-free coal. The method according to claim 1,
Wherein the modified coal combustion product has an average particle size of less than 50 microns. The method according to claim 1,
Wherein the modified coal combustion product has an average particle size of less than 20 microns. The method according to claim 1,
Wherein the modified coal combustion product has an average particle size of from 5 to 20 microns. The method according to claim 1,
Wherein the modified coal combustion product has a carbon content less than the carbon content of the coal combustion product burned from the coal that does not contain the additive. 8. The method of claim 7,
Wherein the carbon content is at least 10% by weight less than the carbon content of the coal combustion product burnt from the coal that does not contain the additive. 8. The method of claim 7,
Wherein the carbon content is at least 50% by weight less than the carbon content of the coal combustion product burned from the additive-free coal. 8. The method of claim 7,
Wherein the carbon content of the modified coal combustion product is less than 5 wt%. 8. The method of claim 7,
Wherein the carbon content of the modified coal combustion product is 0.5 to 2 wt%. The method according to claim 1,
Wherein the particle size-reducing additive has an average particle size of greater than 20 microns. The method according to claim 1,
Wherein the particle size-reducing additive has an average particle size of greater than 50 microns. The method according to claim 1,
Further comprising grinding said particle size-reducing additive prior to combustion by coal. The method according to claim 1,
Wherein the particle size-reducing additive is selected from the group consisting of limestone, concrete, Portland cement concrete, regenerated and crushed granulated blast furnace slag, regenerated crushed glass, kaolin, recycled crushed fine aggregate, silica fume, cement kiln dust, , Weathered clinker, clinker, aluminum slag, copper slag, granite kiln dust, chaff, chaff, zeolite, limestone quarry dust, red mud, mineral mine waste, oil shale fines, bottom ash, Comprising at least one material selected from the group consisting of fly ash, fly ash embedded in a landfill, fly ash stored in a water tank, sopodumene lithium aluminum silicate material, lithium-containing ores, and combinations thereof. . The method according to claim 1,
Wherein the particle size-reducing additive is selected from the group consisting of limestone, concrete, Portland cement concrete, regenerated and crushed granulated blast furnace slag, recycled crushed glass, kaolin, recycled crushed fine aggregate, silica fume, cement kiln dust, lime kiln dust, weathered clinker, Slag, copper slag, granite kiln dust, chaff, chaff, zeolite, limestone quarry dust, red mud, minerals, mining waste, fly ash, fly ash, dry stored fly ash, fly ash buried in landfill, , A bimodal lithium aluminum silicate material, a lithium-containing ore, and combinations thereof. The method according to claim 1,
Wherein the particle size-reducing additive comprises limestone, blast furnace slag, concrete, glass, kaolin, or combinations thereof. The method according to claim 1,
Wherein the particle size-reducing additive comprises at least 8% by weight of the total mixture weight of coal and additive. 19. The method of claim 18,
Wherein the particle size-reducing additive comprises greater than 10% by weight. A combustion chamber (20) for combusting the coal and the particle size-reducing additive together;
A source of coal 15;
A source of particle size-reducing additives; And
At least one injector (14) configured to deliver coal and a particle size reduction additive to the combustion chamber (12)
≪ / RTI > wherein the system further comprises: a system for producing a modified coal combustion product.

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