JP6522581B2 - Reduction of environmental pollution and pollution by coal combustion - Google Patents

Description

  This application claims the benefit of US application Ser. No. 14 / 210,909, and provisional US application Ser. No. 61 / 788,442, the entire disclosure of which is incorporated by reference.

  The present invention provides compositions and methods for reducing the level of mercury, nitrogen oxides and / or sulfur oxides emitted to the atmosphere upon combustion of a mercury containing fuel such as coal. In particular, the invention provides the addition of various halogens and other adsorbents to coal combustion systems during combustion. The use of adsorbents reduces pollutant emissions and prevents furnace contamination.

  There are significant coal sources around the world that can meet most of the world energy needed in the next two centuries. Although high sulfur coal is abundant, it requires a purification step to prevent excess sulfur from being released to the atmosphere during combustion. In the United States, low sulfur coal is present in the form of low BTU coal in Powder River Basin in Wyoming and Montana, in lignite deposits north of North and South Dakota, and in lignite deposits in Texas. . However, even if the coal contains low sulfur, they still contain significant levels of elemental mercury and mercury oxides and / or other heavy metals.

  Unfortunately, mercury is at least partially volatilized during coal combustion. As a result, mercury does not tend to stay in the ash, but rather becomes a component of the flue gas. Without purification, mercury tends to be released from coal burning facilities to the atmosphere. Currently, some of the mercury is captured by equipment, such as in wet scrubbers and SCR control systems. However, most of the mercury is not trapped and therefore released through the stack.

  Mercury emissions to the atmosphere in the United States are approximately 50 tons per year. A significant fraction of the emissions are emissions from coal combustion facilities (e.g. electrical utility facilities). Mercury is a known environmental pollution leading to health problems for both humans and non-human animals. To protect public health and to protect the environment, the utility industry continues to develop, test and implement systems to reduce mercury emission levels from its factories. In the combustion of carbonaceous materials, a method is desired where mercury and other undesirable compounds are trapped and retained after the combustion phase so that they are not released to the atmosphere.

  Other pollutants such as nitrogen oxides (NOx) and sulfur oxides (SOx) are released during coal combustion. These exacerbate environmental problems such as smog and acid rain. Moreover, industry continues to actively pursue ways to reduce these pollutants.

  Owners of certain coal facilities qualify for tax deductions for their efforts to reduce the emissions of these pollutants under Section 45 of the IRS Regulations. Under certain circumstances, these managers have seen unwanted furnace fouling. For example, when burning low sulfur bituminous coal as fuel, deposits tend to be formed on the surface of the boiler tube, which results in a decrease in heat exchange efficiency and an increase in operating costs.

  Accordingly, management requires an adsorbent composition and method of use that can achieve the desired reduction of air pollution without reducing thermal efficiency.

  In particular, the adsorbents used with subbituminous coal and lignite are subject to low levels of alkali. High alkali level prior art adsorbents can lead to fouling of the furnaces that burn them. By reducing the alkalinity of the adsorbent, management can minimize the use of sodium and potassium for unnecessary reactions in the gas phase that lead to the formation of deposits on the boiler surface and other parts.

An adsorbent can be used to prepare refined coal that can be burned to reduce one or more of mercury, nitrogen (as NOx) and sulfur (as SOx) emissions. A method of producing purified coal comprises mixing subbituminous coal (or lignite) and an adsorbent composition. In one embodiment, the adsorbent is 0
. 001 to 1% by weight liquid adsorbent and 0.1 to 10% by weight powder adsorbent, wherein said proportions are weight based on the total weight of the purified coal. The liquid adsorbent contains a bromine compound and
Powder sorbent calcium, silica, include alumina, further comprises Na 2 _O and K _{2 O} of less than 1% by weight of less than 1 wt%, here powder sorbent is less than 0.1 wt% chlorine It further comprises.

  In one aspect, the powder sorbent comprises cement kiln dust (CKD), which is useful for reducing NOx emissions, and when CKD contains a high concentration of alkali, along with its improvement, some CKDs are total alkali Is substituted by lower alkaline material to achieve specifications of less than 2% or less than 1%. In various embodiments, the powder sorbent also meets low chlorine specifications to reduce fouling in subbituminous and brown coals.

  In various embodiments, the present invention provides compositions and methods for reducing the emissions of mercury, nitrogen oxides (NOx) and sulfur oxides (SOx) resulting from the combustion of a mercury containing fuel such as coal. A commercially valuable embodiment is the use of the present invention to reduce the emission of nitrogen, sulfur and / or mercury from coal combustion facilities to protect the environment and comply with government regulations and treaty obligations. Improvements in powder sorbents provide superior performance by reducing coal fouling and, at the same time, have no detrimental effects due to the removal of environmental contaminants such as NOx and SOx.

  In various embodiments, the method of the present invention prevents mercury emissions into the atmosphere from a point source such as a coal fuel facility by trapping mercury in the ash while minimizing furnace fouling that can reduce the efficiency of the furnace. Do. In addition, the method prevents mercury and other heavy metals from being released to the natural environment by leaching from solid wastes such as coal ash produced by the combustion of mercury-containing coal. Both of these methods prevent mercury from entering the body of water. Thus, the prevention or reduction of mercury emissions from facilities such as coal combustion facilities varies, including less air pollution, less water pollution, and less harmful waste generation, and less soil contamination that results. Lead environmental benefits. For convenience but not limitation, an advantageous feature of the present invention is described as preventing air, water and soil contamination by mercury or other heavy metals.

In one embodiment, a method of burning coal in a furnace to reduce emissions of NOx and at least one SOx and mercury is provided. The method comprises burning the refined coal in a furnace. The purified coal is, in order, a mixture of subbituminous coal, a bromine compound and a powdery adsorbent. Powder sorbent comprises calcium, silica, alumina, and the based on the weight of the powder sorbent, a low alkali value of K _{2 O} of less than Na 2 _O and 1% by weight of less than 1 wt%, and preferably It is further characterized by a low chlorine value of less than 0.5%, less than 0.3%, or less than 0.1%. In various embodiments, the processing level of the bromine compound is 0.001 to 1.0 wt%, while the processing level of the conventional powder sorbent is 0.1 to 10 wt% based on the weight of the coal. In various embodiments, the powder sorbent comprises CKD or mixtures of CKD and other low alkali powders described herein. The powder adsorbent may also comprise an aluminosilicate clay such as kaolin or metakaolin.

In another embodiment, a method is provided for generating energy by mercury combustion including sub-bituminous coal in a furnace of a coal combustion facility. The method comprises first administering a first adsorbent composition to the coal, and transporting the coal containing the administered first adsorbent to a furnace. At the same time as transporting the coal containing the added first adsorbent, the second adsorbent is added to the furnace. The coal is then burned in the furnace in the presence of the first and second adsorbents to generate thermal energy and ash. The first adsorbent contains a bromine compound, and the second adsorbent contains more than 40% by weight of CaO, more than 10% by weight of SiO ₂ , 2 to 10% of Al ₂ O ₃ , and 1 to 5% of Fe ₂ O ₃ and 1 to 5% of MgO, less than 1% by weight of Na ₂ O, and less than 1% of components of Ka ₂ O. In embodiments, the second adsorbent has less than 0.5% chlorine.

In another embodiment, a method of producing purified coal is provided. The purified coal comprises sub-bituminous coal and comprises added adsorbent components. The method comprises additively mixing coal, liquid adsorbent (eg 0.001 to 1% by weight based on coal) and powder adsorbent (eg 0.1 to 10% by weight based on coal), wherein the liquid sorbent comprises bromine compound and powder sorbent, wherein the powder sorbent many _SiO 2 more CaO, 10% from 40%, 2-10% of _Al 2 _O 3,. 1 to 5% Fe ₂ O ₃ , 1 to 5% MgO, less than 1% Na ₂ O, less than 1% K ₂ O. In various embodiments, the powder sorbent is further characterized as having less than 0.5% chlorine or less than 0.1% chlorine.

  The use of the powder adsorbents mentioned advantageously, in particular the use of low total alkali content, low chlorine or low composition, in furnaces burning subbituminous coal or lignite such as Powder River Basin (PRB) coal It was found to be effective in reducing pollution. The use of the improved sorbent described herein allows the furnace operator to qualify for certain tax deductions under US IRS regulations in accordance with environmental regulations, while at the same time undesired fouling of the furnace and associated facilities Can be avoided.

  Further examples of the respective limited embodiments are described below. It should be understood that the various components and method steps described herein may be combined and adapted to provide other embodiments that are literally described or not illustrated. The examples enable those skilled in the art to practice the invention and to bring about notable environmental and operational benefits.

  In order to treat the coal prior to combustion and / or to add it to the flame or downstream of the flame, preferably to ensure the complete form of the fire resistant structure which gives the various advantages in the process at the lowest temperature. The adsorbent components are used in combination. If the component is added to coal prior to combustion, the product is a purified coal, the use of which can reduce environmental pollution and qualify certain tax credits in the United States.

The sorbent composition comprises calcium, alumina, silica and a halogen. When burning subbituminous or lignite, such as Powder River Basin coal, maintain up to 1% of the adsorbent K ₂ O for pollution reduction and maintain up to 1% of the adsorbent Na ₂ O, % Is based on the weight of the powdery adsorbent comprising calcium, alumina, silica and other ingredients. In an embodiment, Na ₂ O and K ₂ O are each less than 0.5% or each less than 0.1%. Furthermore, in various embodiments, it has also been found to be advantageous to provide a powdery adsorbent with low chlorine values (e.g. <0.5%, <0.3% or <0.1%).

The calcium is supplied by adding it to the powdered adsorbent mixture or to the composition having a non negligible amount of calcium. For example, many alkaline powders contain 20% or more of calcium based on CaO. Examples are limestone, lime, calcium oxide, calcium hydroxide (slaked lime), Portland cement and other industrial products or by-products of industrial processes, and calcium-containing aluminosilicate minerals. The content of silica and alumina is based on the equivalents of SiO ₂ and Al ₂ O ₃ , although it is understood that silica and alumina are often present in more complex chemical or molecular forms.

In various embodiments, it is advantageous that the powder sorbent comprises an effective amount of cement kiln dust (CKD) which is believed to result in NOx reduction from coal combustion facilities. Some CKDs have relatively high (as high as 10%) chlorine content. When using CKD, due to the CKD source and its original content of alkali and chlorine, the powder obtained when burning sub bituminous coal or lignite may result in too high alkali and / or chlorine for best results. If so, mixing several CKDs with other feedstocks with low sodium and potassium content, preferably <1% Na ₂ O and <1% K ₂ O specifications, or <0.5 It is advantageous to achieve the specifications of% Na ₂ O and <0.5% K ₂ O. Such low alkali content materials may be ground CKD (a cement kiln clinker that may or may not meet the specifications of the cement product, and then a cement kiln clinker to be milled for mixing with CKD); a kiln feed (eg, Feed stream introduced into the cement kiln, containing all the components that make up the cement, such as Ca, Mg, Si, Al, Fe etc .; Conversion cement (empty) to make room for introducing specific new cement products Cement product in silo); dry clinker (clinker collected and crushed in place prior to addition of CKD); storage CKD (CKD from storage place or waste storage); and limestone. To the extent that any of these materials represent waste products that must be disposed of or disposed of, further environmental benefits are achieved by their use of the adsorbents described herein.

In various embodiments, the components together: reduce emissions of mercury, nitrogen oxides, and sulfur oxides;
Reduce emissions of elemental mercury and mercury oxide;
Improve the efficiency of the coal combustion process through the de-slagging of the boiler tubes;
・ Prevents contamination of the furnace by unwanted deposits;
Increase the level of Hg, As, Pb and / or Cl in coal ash;
-Reducing the level of leachable heavy metals (e.g. Hg) in the ash, preferably to a level below the detection limit; and-producing a high cementitious ash product.

  All percentages are by weight unless otherwise indicated as used herein. It should be noted that the various materials of the chemical composition described herein are those represented by samples calculated from elemental analysis, usually determined by x-ray fluorescence techniques. Although various simple oxides may be present and present in more complex compounds in a material, oxide analysis is a useful method to represent compound concentrations for individual compositions.

  Coal reaches a rail car in a typical coal combustion facility. Coal is purified coal if the sorbent has already been administered. If the sorbent has not been administered, coal is the raw coal. In the exemplary illustrated embodiment, the coal is transported to a belt receiver which directs the coal to a mixer. After the mixer, the coal is lowered into the supply belt and placed in the coal storage area. In the coal storage area there are usually grates and containers from which the coal is transported by belt to an open storage area sometimes called a bunker. Coal from a bunker or crusher may be supplied to the stoker furnace. In a furnace for burning pulverized coal, coal is transported by belt or other means to a crusher like crusher and finally to a pulverizer. In the storage system, coal is pulverized and transported by air or gas to a dust collector, which is transported to a storage container and supplied to a furnace as needed. In a direct fuel system, coal is pulverized and transported directly to the furnace. In a semi-direct system, coal is introduced from the pulverizer to the cyclone dust collector. Coal is supplied directly to the furnace from the cyclone dust collector.

  During operation coal is fed into the furnace and burned in the presence of oxygen. For high btu fuels, typical flame temperatures in the combustion chamber range from 2700 ° F. (about 1480 ° C.) to about 3000 ° F. (about 1640 ° C.) or higher [eg 3300 ° F. (about 1815 ° C.) to 3600 ° F. It is in the order of (about 1982 ° C.).

  Purified coal is produced by adding an adsorbent to the coal prior to combustion. Adsorbents can be added by the coal producer, transported by the operator to the furnace, or purified coal can be produced at another facility located at or near the operator's property. In the case of purified coal, the entire adsorbent composition is fed to the furnace for combustion.

  In various other embodiments, the adsorbent composition according to the present invention is added to various parts of the raw coal or furnace during combustion. In a non-limiting manner, before or during milling and / or while being transported from the mill to the furnace for combustion, at the mixer, at the belt receiver or at the feed belt, at the coal storage area, at the dust collector, In the storage vessel, in the cyclone dust collector, in the crusher, add the adsorbent to the coal. Conveniently, the adsorbent is added to the coal during the step of mixing the coal, such as in a mixer or mill in various embodiments.

  Alternatively or additionally, the sorbent composition is added to the coal combustion system during fuel combustion by injecting the composition into the furnace. In a preferred embodiment, the composition is injected at or near the fireball (eg, the temperature is greater than 2000 ° F., greater than 2300 ° F., or greater than 2700 ° F.). Adsorbents are efficiently added with fuel, with the main combustion air, onto the flame, with or over the overfire air, etc., according to the burner and furnace operating parameter designs. Also, depending on the design and operation of the furnace, the sorbent may be injected from one or more sides of the furnace and / or from one or more corners of the furnace. The addition of the adsorbent composition and the adsorbent component is such that the injection temperature is sufficiently high and / or the aerodynamics of the burner and the furnace set have sufficient mixing of the powder adsorbent with the fuel and / or the combustion products. It tends to be the most efficient when it leads. Alternatively or additionally, the adsorbent is added to the flame and the convective path downstream of the furnace. In various embodiments, the optimum injection or dosing point of the adsorbent can be determined by forming the furnace and parameters that result in the best mixing of the adsorbent, coal and desired combustion products (injection speed, injection position, The distance above the flame, the distance of the wall, the method of powder spraying, etc.) are selected.

  In a coal combustion system, the heated combustion gases and air travel by convection away from the flame through the downstream convective path (i.e., downstream associated with the fireball). The convective path of the facility comprises a plurality of zones characterized by the temperature of the gas and combustion products in each zone. Usually, the temperature of the combustion gas moves downstream from the fireball and simultaneously decreases. Fly ash and combustion gases are constantly reduced in temperature from downstream of the convective path from the furnace where coal in one embodiment is burned at a temperature of about 2700 ° F. to 3600 ° F. (about 1480 ° C. to 1650 ° C.). Moving. For example, downstream of the fireball is a temperature range of less than 2700.degree. Further downstream, the temperature reaches a position where it is cooled to about 1500 ° F. Between the two locations is a region having a temperature of about 1500 ° F to about 2700 ° F. Further downstream, such as the region below 1500 ° F is reached. In addition, along the convective flow path, gas and fly ash pass through the low temperature zone before reaching the baghouse or electrostatic precipitator, which typically has a temperature of about 300 ° F., before the gas is released from the stack. .

  The combustion gases include carbon dioxide as well as various undesirable gases including sulfur, nitrogen and mercury. The convection channels are also filled with various ashes carried with the hot gas. A particulate removal system is used to remove the ash prior to release to the atmosphere. Such various removal systems, such as electrostatic precipitators and baghouses, are usually placed in the convection flow path. Furthermore, chemical cleaning devices can be placed in the convection flow path. In addition, various devices may be provided to monitor gas components such as sulfur (as SOx), nitrogen (as NOx) and mercury.

Thus, in various embodiments, the method of the present invention directs the adsorbent to the furnace during combustion ("co-fired"addition);
Directly to fuels such as coal before combustion ("pre-combustion" addition for the production of refined coal);
Directly after the fuel in the temperature range above 500 ° C. and preferably in the temperature range above 800 ° C. (“post-combustion” addition) to the gas flow; I need.

Administration of the adsorbent, pre-combustion, either way some have a co-firing or post-combustion is effected "in the coal burning system" in any combination. When an adsorbent is added to a coal combustion system, coal or other fuels are believed to be combusted "in the presence" of various adsorbents, adsorbent compositions or adsorbent components.

In a preferred embodiment, the downstream addition has a temperature of about 1500 ° F. (815.5 ° C.)
Run at about 2700 ° F. (1482.2 ° C.). In some embodiments, depending on the details of the design of the furnace and the arrangement of the convective channels, the cut-off points or divisions between "to the furnace", "to fireball" and "to convective channels" are rather arbitrary. possible. At some point in time, the combustion gas leaves what is apparently a combustion chamber or furnace and apparently flows into the convective flow path of the downstream gas in the fuel or furnace. However, many of the furnaces are so large that it is possible to add adsorbents to the furnace at a significant distance to supply fuel and air to form the fireball. For example, some furnaces, such as overfire air inlets, are designed to supply additional oxygen to the top position of the fireball, especially to achieve more complete combustion and / or emission control such as nitrogen oxides. Have. Overfire air vents can be 20 feet or more above fuel injection. In various embodiments, the fireball is with the coal being supplied above the coal supply, above or below the overfire air port, or at a higher location within the combustion chamber (the furnace port or just below the furnace port). The adsorbent component or composition is injected directly into it. Each of these locations is characterized by temperature and turbulence conditions that result in mixing of the adsorbent with fuel and / or combustion products (eg, fly ash). In embodiments, for administering the adsorbent composition downstream of the furnace or the dosing, the temperature is greater than about 1500 ° F., preferably greater than about 2000 ° F., more preferably
It is preferably carried out above about 2300 ° F., and more preferably at temperatures above about 2700 ° F.

  In various embodiments described herein, sorbent compositions that tend to reduce or correct the emission of mercury, nitrogen and / or sulfur from coal combustion facilities also burn high concentrations of cementitious fuels. There is a beneficial effect to give the ash produced by As a result, the ash can be used commercially as a partial or complete replacement for Portland cement in various cement and concrete products.

  In various embodiments, burning coal with the sorbent composition described in the present invention results in an ash with elevated levels of heavy metals compared to coal burned without the sorbent, but with it Nevertheless, it contains lower levels of leachable heavy metals than ash produced without adsorbents. As a result, the ash is safe to handle and safe to sell commercially, for example as a cement mixture.

  The carbonaceous fuel is burned to generate thermal energy from the combustion of the carbonaceous feedstock to obtain an ash product. Nonflammable materials and particulate combustion products form ashes, and some ashes are collected at the bottom of the furnace, but most of the ashes are as fly ashes from fuel by dust collectors or filters (eg, baghouses of coal combustion facilities) It is collected. The contents of bottom ash and fly ash depend on the chemical composition of the coal and the amount and composition of the adsorbent components added to the coal combustion facility during combustion.

  In various embodiments, mercury emissions from coal combustion facilities are monitored. Monitor emissions of elemental mercury, mercury oxide or both. Elemental mercury means mercury in the ground or zero oxidation state, while mercury oxide means mercury in the +1 or +2 oxidation state. Depending on the mercury level in the fuel gas prior to discharge from the plant, the amount of adsorbent composition added during pre-combustion, co-combustion and / or post-combustion is increased, reduced or maintained unchanged. In general, it is desirable to remove mercury levels as high as practical levels. In embodiments, mercury removal of at least 40% to less than or equal to 90% and more can be achieved based on the total amount of mercury in the coal. As this amount represents mercury being removed from the fuel gas, mercury is not released to the atmosphere through the stack. In this aspect, the amount corresponds to the percentage of the amount that reduced mercury emissions from the facility as compared to coal combustion without the use of adsorbents. Usually, mercury removal from fuel gas leads to elevated mercury levels in the ash. To reduce the total amount of ash produced in the furnace, minimize the amount of adsorbent added to the coal combustion process. Thus, in many embodiments, it is desirable to measure mercury emissions to adjust the rate of addition of the adsorbent composition to achieve the desired mercury reduction without adding excess material to the system.

  Mercury and other heavy metals in coal, such as arsenic, antimony, lead and other metals, are recorded in a baghouse or electrostatic precipitator in various embodiments that burn coal or other fuels with added sorbent components. And become part of the total ash content in a coal combustion plant; or alternatively, mercury and heavy metals are found in the ash bottom. In this way, the emissions of mercury and other heavy metals from the facility are reduced.

  In general, mercury and other heavy metals in ash, even without a sorbent component as described herein, tend to be present in the ash at high levels compared to the ash produced by burning coal. It is resistant to leaching under acidic conditions. Advantageously, the heavy metals in the ash have no leaching above regulatory levels; in fact, the ash is usually produced by burning with an adsorbent, even though it contains higher absolute value heavy metals, A reduction in the concentration of leachable heavy metals is observed in the ash on a ppm basis. Because, combustion ash (coal ash) is worthwhile to be marketed and used as cementitious material for producing, for example, Portland cement and concrete products and ready mix, in addition to the cementitious properties of ash .

In a preferred embodiment, the leaching of heavy metals is monitored or monitored periodically or continuously during combustion. The US Environmental Protection Agency's TCLP method is a commonly used method. The amount of adsorbent, in particular the amount of adsorbent component with Si (SiO ₂ or equivalent) and / or Al (Al ₂ O ₃ or equivalent), is to be analyzed to maintain the leaching in the desired range Adjusted based on.

  In one embodiment, a coal combustion method is provided for reducing mercury emissions into the atmosphere. The method includes administering to the coal burning system an adsorbent composition comprising a halogen compound. The halogen compound is preferably a bromine compound; in a preferred embodiment, the adsorbent does not contain an alkali metal compound to avoid corrosion by boiler tubes or other furnace components. Coal is burned in the furnace to produce ash and combustion gases. The combustion gas contains mercury, sulfur and other components. The mercury level in the combustion gas is preferably monitored, for example by concentration analysis measurements, in order to achieve the desired mercury reduction in the combustion gas in order to limit the emission into the atmosphere. In a preferred embodiment, depending on the mercury level value measured in the combustion gas, the amount of adsorbent composition administered is adjusted (ie, it is increased, it is reduced, or in some cases it is Adjust by deciding to maintain unchanged). In a preferred embodiment, the adsorbent is added to the system by administering the adsorbent for pre-combustion of coal, and then the coal containing adsorbent is transported into the furnace for combustion.

  In another embodiment, an adsorbent component comprising a halogen (preferably bromine or iodine, and more preferably bromine) compound and at least one aluminosilicate material is administered to a coal combustion system. The components are added either alone or separately from the adsorbent composition and, if necessary, to the preburning coal, to the furnace during combustion, or to the combustion gases downstream of the furnace at a suitable temperature. In a preferred embodiment, the components are added to the precombustion of coal, and then the coal containing adsorbent is transported to the furnace for combustion. As already mentioned, preferably mercury is monitored in the fuel gas and the adsorbent dosing rate is adjusted according to the measured mercury level value. Halogens lead to reduced mercury emission levels, whereas aluminosilicates lead to non-leaching of mercury trapped in the ash.

In a related embodiment, a method of reducing leaching of mercury and / or other heavy metals from ash produced by combustion of coal or other fuel in a coal combustion system or incinerator Introducing an adsorbent containing silica and alumina, measuring the leaching amount of mercury and / or other heavy metals from the resulting ash, adjusting the added silica and alumina levels according to the measured leaching of heavy metals including. If the leached amount is greater than the desired amount, the rate of administration of the adsorbent can be increased to reduce the leached amount to the desired range. In a preferred embodiment, the adsorbent further comprises a halogen (eg bromine) compound to increase the amount of mercury trapped in the ash. Advantageously, an adsorbent comprising silica and alumina is added to the powder composition comprising <1% Na ₂ O and <1% K ₂ O to reduce or eliminate fouling.

In one embodiment, the present invention provides a method of producing cementitious ash products while reducing the amount of mercury oxide in the fuel gas resulting from the combustion of a mercury-containing carbonaceous fuel such as coal. The method comprises burning the fuel in the presence of an alkaline powder sorbent comprising a powder sorbent comprising calcium, silica and alumina. The alkaline powder is added to the pre-combustion of the coal, injected into the furnace during combustion, dispensed into the fuel gas downstream of the furnace (preferably at a temperature of 1500 ° F. or higher), or applied in any combination. When the powder is mixed with water, it is an alkali characterized by a pH of about 7, preferably about 8 and preferably about 9. Advantageously comprise less than 1 wt%, respectively adsorbent, each less than 0.5 wt%, or alkali respectively less than 0.1% by weight (e.g., Na ₂ O and _K 2 O). In various embodiments, the adsorbent further comprises iron and magnesium. In various embodiments, the alumina content in the adsorbent is greater than the alumina content of portland cement, preferably contains more than about 5% alumina, or more than about 7% alumina.

  During fuel combustion, the concentration of mercury (mercury oxide, elemental mercury or both) in the downstream fuel gas from the furnace is measured to monitor emissions. The measured mercury concentration is compared to the target concentration, and if the measured concentration exceeds the target concentration, the amount of powder sorbent added is increased relative to the amount of fuel to be burned. Alternatively, if the measured concentration is at or below the target concentration, the rate of addition of the adsorbent can be reduced or maintained unchanged.

  In another embodiment, the powder composition is an adsorbent composition comprising an alkaline calcium component and a significant amount of silica and alumina. In a non-leaching embodiment, the powder composition comprises an alkaline powder comprising 2 to 50% by weight of the aluminosilicate material and 50 to 98% by weight of calcium. In a preferred embodiment, the alkaline powder comprises one or more of lime, calcium oxide, portland cement, cement kiln dust, lime kiln dust, and sugar beet lime, while the aluminosilicate material is calcium montmorillonite, sodium montmorillonite, and It contains one or more selected from the group consisting of kaolin. In certain embodiments, the powder sorbent comprises CKD and other materials to meet low alkali specifications and / or low chlorine specifications.

  The powder composition is added to the coal in a proportion of about 0.1 to about 10% based on the amount of coal treated with the adsorbent in a batch process or the proportion of coal consumed by combustion in a continuous process. In an embodiment, the ratio is 0.1-5 wt%, 0.1-2 wt%, 0.1-1.5 wt%, 0.1-1 wt%, 1-8 wt% in the embodiment , 2-8 wt%, 4-8 wt%, 4-6 wt%, or about 6 wt%. In certain embodiments, the powder composition is injected into a fireball or furnace during combustion, and / or administered to coal under ambient conditions prior to coal combustion. The temperature at the injection site is preferably at least about 1000 ° F. or higher. For some low cost fuels, this corresponds to injection into the fireball or injection near the fireball.

  In a further embodiment, a method of reducing mercury and / or sulfur released to the natural environment during combustion of coal in a coal combustion system comprises adsorbing an adsorbent component comprising bromine, calcium, silica and alumina in the coal combustion system. Adding, and burning coal in the presence of an adsorbent component to generate combustion gases and fly ash. The amount of mercury in the combustion gas is measured, and the concentration of the component containing bromine added to the system is adjusted according to the mercury value measured in the combustion gas.

In various embodiments, the four components (calcium, silica, alumina and bromine), together or separately, for pre-combustion of coal, in a furnace and / or at suitable temperatures as described herein Add to combustion gas. An adsorbent comprising said component preferably comprises at most less than 1% by weight Na ₂ O and at most 1% by weight K ₂ O. Preferably bromine is present at a level to efficiently capture at least 20%, at least 40%, at least 80% or at least 90% mercury in coal in the ash, and silica and alumina at 0.2 ppm It is present at an efficient level to generate fly ash having a leaching value of less than (200 ppb) mercury, preferably less than 100 ppb mercury, less than 50 ppb, and more preferably less than 2 ppb. The 2 ppb concentration shows a lower concentration than the current detection limit in the mercury leach TCLP test.

  In a particular embodiment, the method provides coal ash and / or fly ash comprising mercury at a concentration corresponding to the capture of ash originally comprising at least 40% or at least 90% mercury in the coal before combustion. In some embodiments, the mercury concentration is higher than known fly ash to capture mercury in the ash rather than mercury emission to the atmosphere. The fly ash produced by the method comprises up to 200 ppm mercury or even higher concentrations of mercury, and in some embodiments, the mercury content in the fly ash is about 250 ppm. Since the volume of ash is usually increased by the use of adsorbents (in the usual embodiment about twice the volume of ash), the measured mercury concentration is released into the natural environment without the presence of adsorbents, as it is increased Represents a greater capture than mercury-containing ash. The content of mercury and other heavy metals such as lead, chromium, arsenic and cadmium in the fly ash is usually higher than in fly ash resulting from the combustion of coal without the addition of an adsorbent or adsorbent component.

  Preferably coal ash mercury is toxic indicator leaching (TCLP), 40 CFR 260.11. As tested by means of "Methods of Assessing Solid Waste, Physical / Chemical Methods" EPA Publication SW-846-Third Publication, Test Method 1311, as incorporated by reference in the chapter, it is possible to use 0. It shows a mercury concentration of less than 2 ppm. The total mercury content of the ash generated from the adsorbent treating the coal is two or more factors higher than the content in the ash generated by the combustion without the adsorbent, but the combustion of the coal with the adsorbent described herein Usually, it is observed that the fly ash due to is less leachable mercury than the ash generated from coal combustion without using the adsorbent. For example, conventional ash from the combustion of PRB coal contains about 100-125 ppm of mercury; in various embodiments, it is generated by the combustion of PRB coal with about 6% by weight of the adsorbent described herein. The ash has about 200-250 ppm mercury or more mercury.

  In another embodiment, the present invention provides a hydraulic cement product comprising 0.1 wt% to 99 wt% of portland cement based on the total amount of cement product of coal ash or ash described above. Do. In a further embodiment, the present invention provides a pozzolanic product comprising 0.01% to 99% by weight pozzolan, based on the total weight of the pozzolanic product of ash described above.

  In a further embodiment, the present invention provides a pozzolanic product comprising 0.01% to 99% by weight pozzolan, based on the total weight of the pozzolanic product of ash described above.

  The present invention also provides a cement mixture comprising a hydraulic cement product.

  The invention further provides a component ready mix product comprising aggregate cement product and hydraulic cement product.

  In another embodiment, the cement mixture comprises coal ash as described herein as the only cement composition; in these embodiments, the ash can replace all of the conventional cement such as portland cement. The cement mixture comprises cement and optionally aggregates, fillers and / or other mixtures. Cement mixtures are usually mixed with water and used as concretes, mortars, grouts, flowable fillers, stabilizers and other applications.

  Thus, the method of the present invention involves the combustion of coal and the added adsorbent to generate coal ash and exothermic or power generating energy. The ashes are then recovered and used to form a cement mixture comprising cement, mortar and grout.

  In a preferred embodiment, the powder sorbent composition described herein comprises one or more alkaline powders containing calcium, with lower levels of one or more aluminosilicate materials. The halogen component is optionally added as a further alkaline powder component or separately as part of a liquid or powder composition. Advantageously, the use of an adsorbent leads to the reduction of the emission or emission of sulfur, nitrogen, mercury, other heavy metals such as lead and arsenic and / or chlorine from coal combustion systems.

The adsorbent composition used in the various embodiments of the invention described above and herein includes components that provide calcium, silica and / or alumina, preferably in the form of an alkaline powder. In various embodiments, the composition also includes iron oxide, and in a non-limiting embodiment, the powder composition comprises about 2-10% by weight Al ₂ O ₃ , more than 40% (eg, about 40-70). %) CaO,> 10% by weight SiO ₂ , about 1 to 5% Fe ₂ O ₃ , and <2%, preferably less than 1% total alkali content such as sodium oxide and potassium oxide. Components comprising calcium, silica and alumina and other elements, if present, are mixed together as a single component as components to the fuel combustion system or added separately or in any combination. In a preferred embodiment, the use of an adsorbent leads to a reduction in the amount of NOx, SOx and / or mercury released to the atmosphere.

  Advantageously, the adsorbent component comprises suitable high levels of alumina and silica. The presence of alumina and / or silica leads to several advantages found in the use of adsorbents. For example, the presence of alumina and / or silica, and / or the balance of calcium, iron and other components with silica / alumina, is observed in the ash produced by the mercury-containing coal or other fuel in the presence of the adsorbent. Result in low acidity leaching of mercury and / or other heavy metals.

As mentioned above, the components giving calcium, silica and / or alumina are preferably supplied as alkaline powders. Without being limited by theory, it is believed that the alkalinity of the adsorbent component at least partially leads to the desired properties described above. For example, the alkalinity of the powder is believed to lead to a reduction in sulfur pitting. It is believed that after neutralization, the geopolymer ash is formed in the presence of the adsorbent and combines with the silica and alumina present in the adsorbent to form a ceramic like matrix reported as stabilized ash. Stabilized ash is characterized by significantly reducing the leaching of mercury and other heavy metals. In some embodiments, the leaching of mercury is below the detection limit. However, for some ash, high alkalinity in the adsorbent component tends to result in unwanted fouling. Thus, the teachings of the present invention use a less alkaline and / or lower chlorine adsorbent (as measured by the content of Na ₂ O and K ₂ O), particularly when using sub-bituminous and lignite coals. Describe how to overcome the possible drawbacks.

  Sources of calcium for the adsorbent compositions of the present invention include, but are not limited to, calcium powders such as calcium carbonate, limestone, dolomite, calcium oxide, calcium hydroxide, calcium phosphate and other calcium salts. Industrial products such as limestone, lime, slaked lime provide the majority of such calcium salts. As such, they are suitable components for the adsorbent composition of the present invention.

  Other calcium sources include various industrial products. Such products are commercially available, and some of them are sold as waste or by-products of other industrial processes. In a preferred embodiment, the product provides the composition of the invention with silica, alumina, or both. Non-limiting examples of industrial products containing silica and / or alumina in addition to calcium include portland cement, cement kiln dust, lime kiln dust, sugar beet lime, slag (eg steel slag, stainless steel slag and blast furnace slag), paper De-inked sludge ash, cupola Arrestel filter cake, and cupola furnace dust.

These materials, and optionally other materials, are combined to give an alkaline powder or a mixture of alkaline powders containing calcium, and preferably also silica and alumina. Other alkaline powders containing calcium, silica and alumina include pozzolanic materials, wood ash, rice husk ash, class C fly ash, and class F fly ash. In various embodiments, the materials and similar materials, compositions, in particular obtained, 2-10 wt% of _Al 2 _O 3, 40 wt% more CaO, 10 wt% more SiO _2, about When they are included as components that fall within the preferred range of 1 to 5% Fe ₂ O ₃ and total alkali less than about 2% by weight, they are suitable components of the adsorbent composition. Mixtures of materials are also used. Non-limiting examples include mixtures of Portland cement and lime, and mixtures containing cement kiln dust (e.g. cement kiln dust and lime kiln dust).

  Sugar beet lime is a solid waste material obtained from the production of sugar from sugar beet. It is high in calcium content, and contains various impurities that precipitate in the priming procedure performed on sugar beet. It is a commercial product and is usually sold as a soil conditioner to landscapers, farmers and the like.

  Cement kiln dust (CKD) usually refers to by-products produced in cement kilns or related processing equipment during the production of Portland cement.

  Typically, CKD comprises a combination of different particles produced in different regions of a kiln, pretreatment device, and / or material handling system, such as clinker dust, partially fully calcined material dust, and Contains raw material (hydrate and dehydrate) dust. The composition of the CKD will vary depending on the raw materials and fuels used, manufacturing and processing conditions, and the location of the CKD collection point in the cement manufacturing process. The CKD may include dust or particulate matter collected from a kiln effluent (ie, effluent) stream, a clinker cooler effluent, a preburner effluent, an air pollution control device, and the like. Commercially available CKD depends on its source but has an alkaline range. In some embodiments, it is possible to fill the low alkali specification powder sorbents described herein by use of low alkalinity CKD. If only high alkali CKD is utilized, it may be necessary to mix with the low alkali material described above or substitute a portion of the high alkali CKD product with the alkali material.

  Although CKD compositions vary with different kilns, CKDs usually have at least some cementitious and / or pozzolanic properties, due to the presence of clinker and dust of calcined material. Typical CKD compositions include silicon-containing compounds such as tricalcium silicate, silicates including dicalcium silicate; aluminum-containing compounds such as aluminates including tricalcium aluminate; and iron-containing compounds such as aluminium Ferrite Ferrite containing ferrite including calcium. CKD usually comprises calcium oxide (CaO). An exemplary CKD composition comprises about 10 to about 60 wt%, optionally about 25 to about 50 wt%, and optionally about 30 to about 45 wt% calcium oxide. In some embodiments, CKD comprises about 1 to about 10% free lime (available for hydration with water), optionally about 1 to about 5%, and in some embodiments , At a concentration of about 3 to about 5%. Furthermore, in certain embodiments, CKD comprises compounds containing, among others, alkali metals, alkaline earth metals, and sulfur.

  Other exemplary sources of alkaline powders comprising calcium, and preferably further comprising silica and alumina (in addition to the portland cement and CKD described above) are various cement related by-products Including. Blended cement products are a suitable example of such a source. These blended cement products generally comprise a mixture of Portland cement and / or its clinker in combination with slag and / or pozzolanic (eg, fly ash, silica fume, calcined shale). Pozzolana is usually a siliceous material that is not itself cementitious but that exhibits hydraulic cement properties when reacted with free lime (free CaO) and water. Other sources are masonry cement and / or hydraulic lime, which comprises Portland cement and / or a mixture of clinker and lime or limestone. Other suitable sources are alumina cements, which are limestone and bauxite (one or more aluminum hydroxide minerals, and silica, iron oxide, titania, aluminum silicates, and minor or minor amounts of other The hydraulic cement is produced by burning a mixture of naturally occurring heterogeneous materials comprising various mixtures of impurities of Yet another example is pozzolanic cement, which is a mixed cement that contains a substantial concentration of pozzolanic. Normally, pozzolanic cement comprises calcium oxide but does not substantially contain Portland cement. General examples of widely used pozzolans include natural pozzolans (such as certain volcanic ash or tuff, certain diatomaceous earths, calcined clays and shales) and synthetic pozzolans (such as silica fume and fly ash).

Lime kiln dust (LKD) is a by-product from the production of lime. LKD is a dust or particulate matter collected from a lime kiln or related processing equipment. The lime produced can be classified as calcium-rich lime or dolomite lime, and LKD varies depending on the method of forming it. Lime is produced by a calcining reaction that is often performed by heating a calcite feedstock, such as calcium carbonate (CaCO ₃ ), to form free lime CaO and carbon dioxide (CO ₂ ). Calcium-rich lime has a high concentration of calcium oxide and several impurities, including generally aluminum-containing and iron-containing compounds. Calcium rich lime is usually formed from high purity calcium carbonate (purity about 95% or more). Typical calcium oxide content in LKD products obtained from high calcium content lime processing is about 75 wt% or more, optionally about 85 wt% or more, and in some cases about 90 wt% or more. In some lime manufacturing process, dolomite and _{(CaCO 3} -MgCO 3), to produce primarily calcium oxide is decomposed (CaO) and magnesium oxide (MgO) by heating. What is formed thereby is known as dolomite lime. In LKD produced by dolomite lime processing, calcium oxide can be present at about 45 wt% or more, optionally more than about 50 wt%, and in certain embodiments more than about 55 wt%. LKD varies based on the type of lime method used, but usually has a relatively high concentration of free lime. Typical amounts of free lime in LKD are about 10 to about 50%, optionally about 20 to about 40%, depending on the relative concentration of calcium oxide present in the lime product produced .

  Slag is usually a by-product compound produced by metal production and processing. The term "slag" encompasses a wide variety of by-product compounds and typically comprises most non-metallic by-products of irons and / or steel manufacture and processing. Slags are usually considered to be a mixture of various metal oxides, but they often contain metal sulfides and metal atoms in elemental form.

  Various examples of slag by-products useful in certain embodiments of the present invention include iron slags, such as those produced in blast furnaces (also known as cupola furnaces), examples of which include air-cooled blast furnace slags ACBFS), expanded or foamed blast furnace slag, pelleted blast furnace slag, granular blast furnace slag (GBFS) and the like. Steel slag can be manufactured from a basic oxygen steelmaking furnace (BOS / BOF) or an electric arc furnace (EAF). Many slags are recognized to have cementitious and / or pozzolanic properties, but as will be recognized by those skilled in the art, the extent to which the slag has these properties depends on their respective compositions and It depends on the way in which they are derived. Typical slags comprise calcium containing compounds, silicon containing compounds, aluminum containing compounds, magnesium containing compounds, iron containing compounds, manganese containing compounds and / or sulfur containing compounds. In certain embodiments, the slag comprises calcium oxide at about 25 to about 60 wt%, optionally about 30 to about 50 wt%, and optionally about 30 to about 45 wt%. An example of a suitable slag having usually cementitious properties is ground granulated blast furnace slag (GGBFS).

  As mentioned above, other suitable examples include blast furnace (cupola) furnace dust (e.g., cupola arrester filter cake) collected from air pollution control devices attached to the blast furnace. Another suitable industrial by-product source is paper deinking sludge ash. As recognized by those skilled in the art, there are many different manufacturing / industrial process by-products that are suitable as a calcium source for the alkaline powder forming the sorbent composition of the present invention. Similarly, many of these well-known byproducts comprise alumina and / or silica. Some, such as lime kiln dust, contain large amounts of CaO and relatively small amounts of silica and alumina. Also, combinations of any typical industrial products and / or industrial byproducts are contemplated for use as alkaline powders of certain embodiments of the present invention.

  In various embodiments, the desired treatment levels of silica and / or alumina are those obtained by adding materials (eg, portland cement, cement kiln dust, lime kiln dust, and / or sugar beet lime). Thus, such materials can be supplemented with an aluminosilicate material, such as, but not limited to, clay (eg, montmorillonite, kaolin, etc.), as needed to provide the preferred silica and alumina levels. In various embodiments, the supplemental aluminosilicate material comprises at least about 2% by weight, and preferably at least about 5% by weight of the various adsorbent components added to the coal combustion system. Generally, there is no upper limit from the technical point of view as long as the appropriate level of calcium is maintained. However, from a cost standpoint, it is usually desirable to limit the proportion of the more expensive aluminosilicate material. Thus, the sorbent component preferably comprises about 2 to 50 wt%, preferably 2 to 20 wt%, and more preferably about 2 to 10 wt% of an aluminosilicate material (eg typical clay). Become. Non-limiting examples of adsorbents are about 93% by weight of a blend of CKD and LKD (eg, a 50: 50 blend or mixture) and about 7% by weight of an aluminosilicate clay.

In various embodiments, the alkaline powder sorbent composition comprises one or more calcium-containing powders (eg, portland cement, cement kiln dust, lime kiln dust, various slags, and sugar beet lime), an aluminosilicate clay (eg, aluminosilicate clay). And including, but not limited to, montmorillonite or kaolin). The sorbent composition preferably forms a refractory mixture with calcium sulfate produced by the combustion of sulfur containing coal in the presence of the CaO sorbent component, such that calcium sulfate is handled by the particle control system; And contain sufficient SiO ₂ and Al ₂ O ₃ to form a refractory mixture with mercury and other heavy metals so that mercury and other heavy metals do not leach out of the ash under acidic conditions. In a preferred embodiment, the calcium-containing powder sorbent contains at least 10% by weight of silica and at least 2 to 10% by weight of alumina. Preferably, the alumina concentration is higher than that found in Portland cement, which is higher than about 5% by weight, preferably higher than about 6% by weight, based on Al ₂ O ₃ .

  In various embodiments, the sorbent component of the alkaline powder sorbent composition works with optionally added halogen (e.g. bromine) compounds or compounds to add chloride in ash and mercury, lead, arsenic, and other heavy metals. It captures and renders heavy metals non-leaching under acidic conditions, and improves the cementitious properties of the produced ash. As a result, the emission of harmful elements is mitigated, reduced or eliminated, and valuable cementitious materials are produced as by-products of coal combustion.

  Suitable aluminosilicate materials include a wide variety of inorganic minerals and materials. For example, many minerals, natural materials, and synthetic materials may be any other cation (eg, but not limited to, Na, K, Be, Mg, Ca, Zr, V, Zn, Fe, Mn) and / or It contains silicon and aluminum associated with the oxy environment, along with any other water of hydration, along with other anions (e.g. hydroxide ion, sulfate ion, chloride ion, carbonate ion). As used herein, such natural and synthetic materials refer to aluminosilicate materials, and non-limiting examples are clays as indicated above.

  In aluminosilicate materials, silicon tends to exist as tetrahedra, while aluminum exists as tetrahedra, octahedra, or a combination of both. Linear or reticulated aluminosilicates are assembled in such materials by sharing one, two or three oxygen atoms between silicon and aluminum tetrahedra or octahedra. Such minerals follow various names, such as silica, alumina, aluminosilicates, geopolymers, silicates and aluminates. However, the aluminum and / or silicon containing compounds presented tend to form silica and alumina when exposed to the high temperatures of combustion in the presence of oxygen.

In one embodiment, the aluminosilicate material comprises _SiO 2 _-Al 2 _{O 3} polymorphs. For example, silicates contain silica octahedra and alumina that is ultimately divided between tetrahedra and octahedra. Kyanite is based on silica tetrahedra and alumina octahedra. Andalusite is another polymorphic form of SiO ₂ · Al ₂ O ₃ .

In another embodiment, the silicate chain provides silicon (as silica) and / or aluminum (as alumina) to the composition of the present invention. The silicate chains include, but are not limited to, pyroxene and quasi-pyroxene silicates comprised of an infinite chain of SiO ₄ tetrahedra linked by sharing an oxygen atom.

  Other suitable aluminosilicate materials include sheet-like materials such as, but not limited to, mica, clay, chrysotile (eg, asbestos), talc, soap stone, pyrophyllite, and kaolinite. Such materials are characterized as having a layered structure in which silica and alumina octahedra and tetrahedra share two oxygen atoms. Layered aluminosilicates include clays such as, for example, chlorite, aeochromite, illite, palygorskite, pyrophyllite, sauconite, vermiculite, kaolinite, calcium montmorillonite, sodium montmorillonite, and bentonite. Other examples include mica and talc.

  Suitable aluminosilicate materials also include synthetic and natural zeolites, such as, but not limited to, chabazite, sodalite, chabazite, sodafluorite, phillipsite, and mordenite groups. Other zeolitic minerals include fluorite, brewster zeolite, exhalite, ochite, yagawaralite, turbidite, dolomite, paul zeolite, and clinoptilolite. The zeolite is a mineral or synthetic material characterized by an aluminosilicate tetrahedral framework, ion-exchangeable "large cations" (e.g. Na, K, Ca, Ba, and Sr) and loosely held water molecules.

In another embodiment, framework or 3D silicates, aluminates and aluminosilicates are used. The framework aluminosilicate is characterized by a structure in which SiO ₄ tetrahedra, AlO ₄ tetrahedra, and / or AlO ₆ octahedra are joined in three dimensions. Non-limiting examples of framework silicates containing both silica and alumina include plagioclase, such as albite, anorthite, neutral feldspar, aphid feldspar, caustic feldspar, microcline feldspar, sanidin and orthoclase Be

  In one aspect, the adsorbent powder compositions are such that they contain a large amount of calcium, preferably more than 20% by weight or more than 40% by weight calcium based on calcium oxide, and additionally they are commercially available. It is characterized by containing higher levels of silica and / or alumina than those found in (e.g. Portland cement). In a preferred embodiment, the sorbent composition comprises more than 5 wt% alumina, preferably more than 6 wt% alumina, preferably more than 7 wt% alumina, and preferably more than about 8 wt% alumina. Including.

  Coal or other fuel is treated with a proportion of the adsorbent component that is effective to control the amount of nitrogen, sulfur and / or mercury released into the atmosphere upon combustion. In various embodiments, the total processing level of the adsorbent component is based on the weight of coal to be treated or the proportion of coal consumed by combustion when the adsorbent is a powder adsorbent containing calcium, silica and alumina. In the range of about 0.1% by weight to about 20% by weight. When the adsorbent components are combined into a single composition, the component processing level corresponds to the adsorbent processing level. Thus, a single adsorbent composition can be provided and metered or otherwise measured for addition to a coal combustion system. In general, it is desirable to use the lowest amount of adsorbent so that the system is not overloaded with excess ash while still having the desired effect on sulfur and / or mercury emissions. Thus, in various embodiments, the treatment level of the adsorbent ranges from about 0.1 wt% to about 10 wt%, and in some embodiments, from about 1 or 2 wt% to about 10 wt%. For many coals, a loading of 6% by weight powdery sorbent was found to be acceptable.

  An adsorbent composition comprising a halogen compound contains one or more organic or inorganic compounds containing a halogen. Halogen includes chlorine, bromine and iodine. Preferred halogens are bromine and iodine. Halogen compounds are sources of halogen (especially bromine and iodine). Sources of halogen for bromine include various inorganic salts of bromine, including bromide, bromate and hypobromite. In various embodiments, organic bromine compounds are less preferred because of their cost or availability. However, bromine organic sources suitably containing high levels of bromine are considered to be within the scope of the present invention. Non-limiting examples of organic bromine compounds include methylene bromide, ethyl bromide, bromoform and carbon tetrabromide. Non-limiting iodine inorganic sources include hypoiodite, iodate, and iodide, with iodide being preferred. Organic iodine compounds can also be used.

  When the halogen compound is an inorganic substitution, it is preferably a salt of bromine or an iodine-containing alkaline earth element. Typical alkaline earth elements include beryllium, magnesium and calcium. Among the halogen compounds, bromides and iodides of alkaline earth metals (e.g. calcium) are particularly preferred. Alkali metal bromine and iodine compounds such as bromide and iodide are effective in reducing mercury emissions. However, in some embodiments, they are less preferred because they tend to cause corrosion of boiler tubes and other steel surfaces and / or contribute to tube degradation and / or refractory brick degradation. In various embodiments, it has been found desirable to avoid potassium salts of halogens to avoid furnace problems.

  In various embodiments, it has been found that the use of alkaline earth salts (eg calcium) tends to avoid such problems with sodium and / or potassium. Thus, in various embodiments, the adsorbent added to the coal combustion system is essentially free of alkali metal-containing bromine or iodine compounds, or more particularly essentially sodium-containing or potassium-containing bromine or iodine compounds. Not contained in

  In various embodiments, a halogen containing adsorbent composition is provided in the form of a liquid or solid composition. In various embodiments, the halogen containing composition is dosed to the coal prior to combustion, added to the furnace during combustion, and / or dosed into the fuel gas downstream of the furnace. If the halogen composition is solid, it can further contain the calcium, silica and alumina components described herein as a powder adsorbent. Alternatively, the solid halogen composition is administered on coal and / or otherwise separately from the adsorbent component comprising calcium, silica and alumina into the combustion system. If the composition is a liquid composition, it is usually administered separately.

  In various embodiments, the liquid mercury sorbent comprises a solution containing 5 to 60% by weight of a bromine or iodine containing soluble salt. Non-limiting examples of preferred bromine and iodine salts include calcium bromide and calcium iodide. In various embodiments, the liquid adsorbent contains 5 to 60% by weight of calcium bromide and / or calcium iodide. Because of the efficiency of the addition of coal prior to combustion, in various embodiments, it is preferred to add a mercury sorbent with as high a level of bromine or iodine compound as possible. In a non-limiting embodiment, the liquid adsorbent contains 50% by weight or more of a halogen compound such as calcium bromide or calcium iodide.

  In various embodiments, the adsorbent composition containing a halogen compound further comprises a nitrate compound, a nitrite compound, or a combination of a nitrate compound and a nitrite compound. Preferred nitrate and nitrite compounds include those of magnesium and calcium, preferably calcium.

  As a further example, one embodiment of the present invention involves adding liquid mercury sorbent directly to raw coal or pulverized coal prior to combustion. For example, a mercury sorbent is added to the coal in a coal feeder. The addition of liquid mercury sorbent is in the range of 0.01-5%. In various embodiments, the treatment is less than 5%, less than 4%, less than 3%, or less than 2%, less than 1%, less than 0.5% and less than 0.2%, wherein all percentages are Based on the amount of coal processed or the rate of consumption of coal from combustion. Higher processing levels are possible but tend to waste material and no further benefits are achieved. The preferred treatment level is 0.025 to 2.5% by weight on a wet basis. The amount of solid bromide or iodide salt added by the liquid adsorbent is of course reduced by its weight fraction in the adsorbent. In an exemplary embodiment, the addition of the bromide or iodide compound is at low levels, such as 0.01% to 1% by weight based on solids. Thus, when using a 50 wt% solution, the adsorbent is added at a ratio of 0.02% to 2% to achieve low levels of addition. For example, in a preferred embodiment, a ratio of 0.02 to 1% by weight, preferably 0.02 to 0.5% by weight, of coal calculated assuming that calcium bromide is about 50% by weight of the adsorbent. Treat with liquid sorbent. In an exemplary embodiment, the liquid adsorbent containing 50% calcium bromide is pre-combusted at about 1%, 0.5%, or 0.25% (where% is based on the weight of the coal) Add on coal. In a preferred embodiment, initial treatment is initiated at low levels (e.g. 0.01% to 0.1%) and gradually based on monitoring of the release until the desired (low) level of mercury release is achieved. Increase. If the halogen is added as a solid, or as a multicomponent composition with other components (eg, calcium, silica, alumina, iron oxide, etc.), similar levels of treatment of the halogen are used.

  If used, the liquid sorbent is sprayed, dripped or otherwise supplied onto the coal or otherwise into the coal combustion system. In various embodiments, the addition is made to coal or other fuel at ambient conditions prior to introduction of the fuel / sorbent composition into the furnace. For example, the adsorbent is added onto powdered coal prior to its injection into the furnace. Alternatively or additionally, a liquid sorbent is added during combustion to the furnace and / or to the fuel gas downstream of the furnace. The addition of halogen containing mercury sorbent compositions is often accompanied by a drop in the measured mercury level in the fuel gas for one or several minutes. In various embodiments, mercury reduction occurs in addition to the reduction achieved by the use of alkaline powder sorbents based on calcium, silica and alumina.

  In another embodiment, the invention comprises the direct addition of the halogen component (eg calcium bromide solution) into the furnace during combustion. In another embodiment, the present invention as described above into the downstream gas flow of the furnace in a region characterized by a temperature ranging from 2700 ° F. to 1500 ° F., preferably from 2200 ° F. to 1500 ° F. Provide addition of calcium bromide solution as discussed. In various embodiments, processing levels of bromine compounds (eg, calcium bromide) are split between co-firing, pre-combustion and post-combustion in any proportion of addition.

  In one embodiment, various adsorbent components are added onto the coal prior to its combustion to produce so-called refined coal. The coal to which the adsorbent is administered is preferably granular coal, and optionally ground or pulverized according to conventional procedures. In a non-limiting example, coal is milled so that 75 wt% of the particles pass through a 200 mesh screen (200 mesh screen has a pore size of 75 μm). In various embodiments, the adsorbent component is added onto the coal as a solid, or a combination of liquid and solid. Usually, the solid adsorbent composition is in the form of a powder. When the adsorbent is added as a liquid (eg, one or more bromine or iodine salt solutions in water), in one embodiment, the coal remains wet when fed into the burner. In various embodiments, the sorbent composition is continuously added onto coal by spraying or mixing on coal that is on a conveyor, screw extrusion, or other feeding device at a coal combustion facility. In addition or alternatively, the sorbent composition is separately mixed with the coal at the coal combustion facility or at the coal farm. In a preferred embodiment, the sorbent composition is added to the coal as a liquid or powder when fed into the burner. For example, in a preferred commercial embodiment, the adsorbent is administered into a grinder that grinds the coal prior to injection. If desired, the loading of the sorbent composition is varied to achieve the desired mercury emission level. In one embodiment, the level of mercury in the flue gas is monitored and adjusted to raise or lower the level of adsorbent addition as required to maintain the desired level of mercury.

  In a preferred embodiment, nitrogen, mercury and sulfur are monitored using standard industrial methods, such as those published by the American Society for Testing and Materials (ASTM), or international standards published by the International Organization for Standardization (ISO). . The device containing the analytical instrument is preferably located in the convective path downstream of the point of addition of the mercury and sulfur adsorbents. In a preferred embodiment, a mercury monitor is placed on the clean side of the particle control system. Alternatively or additionally, the fuel gas is sampled at the appropriate position of the convection flow path without attaching a device or monitoring device. In various embodiments, pumps, solenoids, sprayers, and the like that are actuated or controlled to adjust the rate of addition of the adsorbent composition into the coal combustion system using the level of mercury or sulfur that is measured. Give feedback signal to the device. Alternatively or additionally, the adsorbent loading can be adjusted by the human operator based on the observed levels of mercury and / or sulfur.

  In various embodiments, the ash produced by burning coal in the presence of the adsorbents described herein is cementitious that hardens and exerts strength when combined with water. Ash tends to harden itself because of its relatively high calcium levels. Ash, either alone or in combination with Portland cement, is useful as a hydraulic cement suitable for formulation into various cementitious mixtures such as mortar, concrete and grout.

  The cementitious properties of the produced ash described herein are indicated, for example, taking into account the strength activity index of the ash or, more precisely, the cementitious mixture containing the ash. As described in ASTM C 311-05, measurement of strength activity index shows the setting behavior and properties of 100% Portland cement concrete and test concrete with 20% Portland cement replaced with equivalent test cement. It is done by comparing. In the standard test, the intensities are compared at 7 and 28 days. If the strength of the test concrete is at least 75% of the strength of Portland cement concrete, it is considered as a "pass". In various embodiments, the ash of the present invention exhibits 100% to 150% strength activity in ASTM testing, which strongly indicates "pass". Similar high values are observed when the test is conducted with a test mixture having other than an 80: 20 blend of Portland cement and ash. In various embodiments, a strength activity index of 100% to 150% is achieved with a blend of 85:15 to 50:50, wherein the first value of the ratio is Portland cement, and the second of the ratio is Is the ash produced according to the present invention. In certain embodiments, the strength development of the all-cement test cementitious mixture (i.e., where the ash represents 100% of the cement in the test mixture) all exceeds 50% of the strength of the Portland cement control, and preferably Is more than 75%, and more preferably 100% or more, for example 100 to 150%. Such results are indicative of the high cementitious properties of the ash produced by burning coal or other fuels in the presence of the adsorbent components described herein.

  The ash obtained from the combustion of coal according to the present invention can be marketed because it contains mercury in a non-leaching form. Non-limiting use of spent or waste fly ash or bottom ash includes use as a component in cement products (eg, portland cement). In various embodiments, the cement product comprises about 0.1% to about 99% by weight of coal ash produced by burning the composition of the present invention. In one aspect, the non-leaching properties of mercury and other heavy metals in coal ash make it suitable for all known coal ash industrial applications.

  The coal ash according to the invention, in particular fly ash collected by particle control systems (such as baghouses, electrostatic precipitators, etc.) is used in Portland cement concrete (PCC) as a partial or complete replacement of Portland cement. In various embodiments, ash is used as a mineral admixture or as a component of a blended cement. As an admixture, the ash can be a full or partial replacement of Portland cement and can be added directly into ready mix concrete in a batch plant. Alternatively or additionally, the ash is embedded in cement clinker or blended with portland cement to produce a blended cement.

Class F and Class C fly ash, for example, are defined in US Standard ASTM C 618. The ASTM standard serves as a specification for fly ash when it is used as a partial replacement of Portland cement. Coal ash produced by the methods described herein tends to have higher calcium content and lower silica and alumina content than those described in the specifications of Class F and Class C fly ash in ASTM C 618. It should be noted that there is Typical values for the fly ash of the present invention are> 50% by weight CaO and <25% by weight SiO ₂ / Al ₂ O ₃ / Fe ₂ O ₃ . In various embodiments, the ash is the sum of 51-80% by weight CaO and about 2 to about 25% silica, alumina and iron oxide. It has been observed that the fly ash according to the invention is highly cementitious and makes it possible to replace or reduce portland cement used in such cementitious materials and cementitious materials by more than 50%. There is. In various applications, coal ash obtained from burning coal with the adsorbents described herein is sufficient to be a complete (100%) replacement of portland cement in such a composition Cement quality.

  As a further example, the American Concrete Institute (ACI) recommends that Class F fly ash replace 15 to 25% Portland cement, and Class C fly ash replace 20 to 35% Portland cement. There is. Coal ash produced according to the method described herein displaces up to 50% Portland cement while maintaining 28 days strength development equal to that developed in the product using 100% Portland cement It turned out to be sufficiently cementitious. That is, in various embodiments, the ash is not qualified by the chemical composition as a Class C or Class F ash according to ASTM C 618, but nevertheless it is useful for formulating high strength concrete products is there.

Also, coal ash produced in accordance with the present invention can be used as a component in the production of flowable fill, also referred to as controlled low strength material or CLSM. CLS
M is used as a self-smoothing self-compressing backfill material in place of a compression fill or other fill. The ashes described herein, in various embodiments, such CLSM
Used as a 100% substitute for Portland cement in materials. Such compositions are formulated with water, cement, and aggregates to provide the desired flowability and ultimate strength development. For example, the ultimate strength of the flowable fill is 1 if removability of the cured material is required.
It should not exceed 150 pounds per square inch. When formulated to achieve higher ultimate strength, jack hammers may be required for removal. However, if it is desirable to formulate a flowable fill mixture for use in higher load bearing applications, one can design a mixture that contains a higher range of compressive strength upon curing .

  Also, coal ash produced according to the methods described herein is useful as a component of the stabilized base and subbase mixtures. Since the 1950's, a number of variations of basic lime / fly ash / aggregate formulations have been used as stabilization base mixtures. The stabilization based use case is that used as a stabilization road infrastructure. For example, gravel roads can be reused instead using ash from the composition. The existing road surface is crushed and placed in its original position. For example, the ash produced by the methods described herein is spread and mixed into the crushed road material. After compression, place the seal coat surface on the road. The ash according to the invention is useful for such applications. Because ash does not contain heavy metals that leach out beyond regulatory requirements. Rather, the ash produced by the method of the present invention is less leachable mercury and less leachable other heavy metals than coal ash produced by burning coal without the adsorbents described herein. (For example, arsenic and lead).

  Thus, the present invention provides various methods to eliminate the need to landfill coal ash or fly ash obtained from the combustion of coal containing high levels of mercury. Instead of expensive disposal, the material can be sold or otherwise used as a raw material.

  In a preferred embodiment, the use of an adsorbent results in a cementitious ash which can totally or partially replace Portland cement in various applications. Due to the re-use of the cementitious product, the production of at least some Portland cement is avoided, the energy required to produce the cement is saved, and the emission of substantial amounts of carbon dioxide resulting from cement production can avoid. Another savings in carbon dioxide emissions results from the reduced need for lime or calcium carbonate in the desulfurization scrubber. Thus, the present invention provides, in various embodiments, methods of conserving energy and reducing emissions of greenhouse gases (eg, carbon dioxide). Further details of various embodiments of this aspect of the invention are set forth below.

Example 1
The required specifications of the powder adsorbent and the halogen adsorbent are given below for the use of the purified carbon product with sub-bituminous coal.

１．ハード限界７％のＳＯ_３に加えて、ＣａＯとＳＯ_３の割合は６：１以下に低下させず、好ましくは８：１よりも大きく維持すべきである。これにより添加する硫黄を吸収するために十分なＣａＯを確保する。
２．実際に、粉末吸着剤のＨｇ含量は処理される石炭含量と同じ又はより少なく維持すべきである。
酸化分析の許容試験方法は以下である：
ASTM D3682 石炭利用工程からの燃焼残留物中での多量及び微量元素に関す
る標準試験方法
ASTM C114 水硬性セメントの化学的分析に関する標準試験方法
水銀含量に関する許容試験方法
ASTM D6414 酸抽出又は湿式酸化／冷蒸気原子吸光による石炭及び石炭燃焼
残留物中の水銀総量に関する標準試験方法
ASTM D6722 直接燃焼分析による石炭及び石炭燃焼残留物中の総水銀に関す
る標準試験方法
EPA 7473 固体又は半固体廃棄物中の水銀（冷蒸気技術の手引き）

1. In addition to the hard limit of 7% SO ₃ , the ratio of CaO to SO ₃ should not be reduced to less than 6: 1, preferably maintained greater than 8: 1. This secures enough CaO to absorb added sulfur.
2. In fact, the Hg content of the powder adsorbent should be kept equal to or less than the coal content to be treated.
Acceptable test methods for oxidation analysis are:
ASTM D 3682 For major and trace elements in combustion residues from coal utilization processes
Standard test method
ASTM C114 Standard Test Method for Chemical Analysis of Hydraulic Cement
Permissible test method for mercury content
ASTM D6414 Coal and coal combustion by acid extraction or wet oxidation / cold vapor atomic absorption
Standard Test Method for Total Mercury in Residues
ASTM D6722 Regarding total mercury in coal and coal combustion residues by direct combustion analysis
Standard test method
EPA 7473 Mercury in solid or semi-solid waste (Cold Steam Technology Guide)

Example 2
A series of tests were conducted at the Combustion Research Facility (CTF) of the Energy and Environmental Research Center (EERC) to determine the effect of adsorbents on NOx and Hg emissions during powder river basin (PRB) subbituminous coal combustion. It was Tests were conducted to support an attempt to confirm that "refined coal" is produced as the method of use is defined in Article 45 of the Internal Revenue Code. Article 45 (c) (7) (A) defines a refined coal containing fuel, which is 1) a solid fuel produced from coal, and 2) it is rational to use it for steaming purposes Taxpayers are eligible for sale by prospective taxpayers and 3) (if used for steam generation) “certified for emission reduction”.
In Article 45 (c) (7) (B), the term "authorized emission reduction" refers to the NOx released when burning refined coal as compared to the amount released when burning the feed coal feedstock It is defined to mean a reduction of at least 20% of the release and at least 40% of either the SO ₂ release or the Hg release.

Description of Equipment and Procedures CTF is used to extensively investigate SOx and NOx emissions, and transitions of toxic trace metals (Hg, As and Pb) during combustion of coal and other fuels or waste materials. CTF is capable of producing gas and particle samples that are typical of those produced in industrial and full size pulverized coal (pc) combustion boilers. The test facility included an electrostatic precipitator (ESP) or fibrous filter baghouse for particle control, a selective catalytic reduction (SCR) column for NOx control, and a release including a wet scrubber to control sulfur release. It has several pollution control devices that can be used to reduce. The CTF was designed to nearly reproduce the type and shape of the full-size US PC combustion boiler used by U.S.-standard facilities to generate electricity from steam. For example, the CTF can burn pc at a rate of 550,000 to 750,000 Btu / hr depending on the desired operating conditions. The CTF is adjusted to simulate under the conditions of a full-scale pc-fired boiler, but with commercial boilers there are many changes that can affect the combustion effect, so what is observed in normal real-world operation Can not be reproduced accurately. The burning rate is typically an indicator of the degree of coalification with a low degree of coalification burned at the lowest level of the range and a high degree of coalification burned at an intermediate or maximum level of the indicated range. The CTF furnace is refractory lined and the burn rate is set based on the combustion chamber outlet temperature (FEGT) desired to reproduce the particular boiler used in the coal combustion power plant. For sub-bituminous coals, a burning rate of 550,000-600,000 BTU / hr generally produces FEGTs of 2100 ° F.-2200 ° F., which results in many coal combustion burning sub-bituminous coals such as those tested in the present invention. It is typical in plants.

  The combustion air of CTF is supplied by the push-in ventilator in this equilibrium ventilation system. A ventilator introduced at the rear of the system maintains a slight vacuum in the combustion zone and releases the combustion fuel gas to the stack. The combustion air is generally preheated using electrical heaters and divided into primary air, secondary air, and overfire air (OFA).

Combustion gas analysis has two locations; furnace outlets used to monitor and maintain specific excess air levels throughout the test, and emissions detected at the back of the system can correct for dilution caused by leakage As such, it is provided by a continuous emission monitor (CEM) at the outlet of the particle controller, which is used to access any possible air leaks. For this series of tests, combustion gas analysis was obtained from the conduit of the ESP outlet. Each CEM rack contains five modules for O ₂ , CO ₂ , CO, SO ₂ , and NOx measurements. Except for SO _2, each module was made Ametek. Each analyzer uses a combustion gas regulator to remove moisture from the gas stream prior to analysis. All data reported herein are dry gas standards. All gas analyzes are continuously monitored and recorded by CTF's data acquisition system. National Instrument provided both hardware and software (LabView) used to collect all the data present herein.

In CEM analysis, each test performed on CTF is individually calibrated beforehand. Although nitrogen is used as a zero gas, some span gasses are used to calibrate each device over the range used during the test. In general, the _{O 2} measured in the range of 0% to 10%, of CO ₂ measured in the range of 0% to 20%, measured CO in the range of 0～500Ppm, and NOx in the range of 0~1000ppm taking measurement. SO ₂ measurements are carried out in various ranges depending on the sulfur content of the coal to be tested. During this series of tests, the SO ₂ measuring device is calibrated in the range of 0 to 1000 ppm, which is appropriate for the sulfur content in the PRB subbituminous coal tested herein.

Fuel gas mercury (Hg) measurements were obtained separately with a continuous Hg monitor (CMM) from Tekran® Instruments Corporation. The system draws a gas sample from the fuel gas conduit at the outlet of the particle controller. Water is removed from the gas stream prior to analysis. The fuel gas that adjusts the system condition uses a 10% NaOH solution to remove CO ₂ and SO ₂ to prevent the adverse effect of the performance of the analyzer to accurately measure the Hg concentration of the fuel gas Do. Since all mercury analyzers can only measure elemental mercury (Hg ⁰ ), the total mercury (Hg _(T) ) concentration is Hg 2 ^{+ of} mercury oxide with a 10% NaOH solution containing tin (II) chloride. It is obtained by reducing a part. The Tekran apparatus takes Hg ⁰ from the tested sample on a cartridge containing ultra-high purity gold adsorbent. The combined Hg is then thermally desorbed and examined using atomic fluorescence spectroscopy. The dual cartridge design then allows for additional sampling and depletion caused by continuous measurement of the sample flow. Similar to the CEM scale correction described above, the CMM is also set to zero prior to testing, span measured, and checked at the end of the test. No drift was observed during the tests performed and reported herein. The configuration of CTF utilized during these tests included only ESP for particle control, with both Hg and NOx measurements obtained from the ESP outlet conduit. At the end of the feed and refined coal test period, fuel and fly ash samples were collected and submitted for analysis. The samples collected during the test are described in the following discussion.

Fuel preparation and analytical testing Subbituminous coal was a sample obtained from a coal pile. The coal is a PRB subbituminous coal with a total calorific value in the range of about 8500-10,000 Btu / Ib, depending on the water content, which is taken from several mines located in Wyoming.

  The acceptable coal was received as needed, and the upper surface moisture of floor drying was checked. Air-dried samples were crushed to a maximum size of 1/4 inch and fed to a hammer mill crusher to create a particle size distribution with approximately 70% passing 200 mesh for use during testing (many coal combustion power plants Typical coal treatment achieved in This particle size distribution is at most typical of the particle size distribution achieved by comminution of a full-scale commercial boiler. The refined charcoal sample used during this series of tests is made by EERC and is considered comparable to the refined charcoal produced at a 45-zone facility. The adsorbent used to prepare the refined coal was dosed to a pulverized fuel as shown below. This is different from full scale applications where the adsorbent is recovered from the stock at the store, mixed, crushed and then sent to the mill. The main reason for administering the adsorbent to pcs utilized in pilot scale tests is the potential loss of material in the dust collection duct system utilized during the comminution of fuel samples. All pilot scale fuel samples are slightly crushed and pulverized before use. Preparing purified fuel from pc samples avoids the potential loss of adsorbent in the dust collection system and results in the best simulation of what happens on a real scale.

  The pulverized fuel was divided into two parts; a feed sample and a second coal sample to be processed into refined coal. Purified coal was prepared by placing every metered amount (about 500 lbs) on the floor of the coal preparation facility. The weighed halogen adsorbent and powder adsorbent were carefully dosed to the coal, and coal was mixed periodically while the adsorbent was administered. The powder sorbent was hand distributed, and several passes were made to mix the fuel after each pass over the amount of coal pile. The halogenated adsorbent was placed in a slightly compressed metal spray can so that the spray tip produced a mist that was applied to the exposed surface of the pile. Treatment was required in several routes to fully distribute the adsorbent. After each pass, use the rake to replace the pile and expose a new surface for the next treatment pass. In each case, a small amount of adsorbent was distributed on the coal pile and mixed until a specific treatment ratio reached 0.008% by weight of the halogen adsorbent and 0.25% by weight of the powder adsorbent .

  Each sample (coal feed and refined coal) was transported to the storage hopper used in the pilot scale test described below. These storage hoppers are placed directly on the coal feed hopper during the test. A rotary valve is used to move the coal and refined coal respectively from the storage hopper to the feed hopper. After each test to remove traces of treated fuel, the storage hopper and feed hopper are washed with dilute acid solution.

Fuel Analysis During each test period, a coal sample is transported from the storage hopper through a small tube through the side wall of the feeder at a 70% angle with an opening located just below the rotary valve between the storage hopper and the feed hopper . This rube intercepts a small amount of fuel each time the feed hopper is filled. In this way, accurate combustion samples of the fuel are obtained. The coal sample falls by weight into a sample bag attached to the end of the sample tube. A new bag is attached to the sample tube prior to the next test period separately from the fuel samples representing the feedstock and the refined coal test period.

  Combustion coal is taken continuously to measure the emission baseline from the combustion of the coal feedstock, as well as the emission from the combustion of the refined coal. The coal feedstock and the refined coal were provided separately for approximate analysis and elemental analysis, calorific value, inorganic element oxide analysis (by X-ray fluorescence), and determination of chlorine content and mercury content. The analysis results are shown in Table 1. The fuel sample has undergone several processing steps which tend to allow evaporation of small amounts of acceptable moisture content. The greatest reduction occurs during the grinding of the fuel. Hammer mill pulverizers generate an induced draft that tends to slightly dry the exposed surface of the pulverized coal particles resulting from the grinding. The resulting dryness is primarily a function of ambient atmospheric conditions (temperature and relative humidity) during fuel preparation. As a result, the combustion composition is analyzed so that it can be easily compared between the coal feedstock and the refined coal.

Coal feedstock (Test AF-CTS-1461) was measured with a heat of combustion of 9621 Btu / lb at a water content of 20.03 wt%. The moisture free calorific value and ash content were measured at 12,031 Btu / lb and 4.91 wt% respectively. The sulfur content of the coal feedstock was measured by 0.37 wt% (0.624 lb SO ₂ / MMBtu) on an anhydrous basis. Powder adsorbents and liquid halogen adsorbents are non-pyrogenic, and liquid halogen adsorbents introduce additional water into the purified coal due to the water content of the liquid. For this reason, a reduction in the calorific value (Btu / lb) of the refined coal is usually expected compared to the Btu / lb of the coal feedstock. Ash analysis of the inorganic material contained in the fuel, indicate to the coal feedstock, purified coal rich in CaO, and SO _3, that deplete the SiO _2, A _{2 O 3,} and _Fe 2 _{O 3} . The mercury content was measured at 0.0570 μg / g (5.924 lkb / TBtu, anhydrous basis) and 0.0556 μg / g (5.908 lkb / TBtu, anhydrous basis) in the feedstock and the purified charcoal sample, respectively. The chlorine content of the feed and purified charcoal samples were measured at 19.4 and 30.0 μg / g respectively.

  The dry sieve analysis of the feedstock and purified charcoal samples collected during each test is shown in the table of Example 2. The results for the coal feedstock are 84.3 wt% passing 200 mesh and 69.2 wt% passing 325 mesh, while 87.1 wt% passing 200 mesh for the refined coal sample, 73. 1 wt% passes through the 325 mesh.

Example 2
Coal feed is PRB coal. The purified coal is the PRB coal feed with 0.008% by weight of a halogen based adsorbent and 0.25% of a powder adsorbent. The powder adsorbent has a CKD of 15% and a ground CKD of 85%. The halogen-based adsorbent is from Example 1. NOx and Hg emissions were measured for feedstock and refined coal.

^＊適用不可

^* Not applicable

  The mercury concentration was 0.558 μg / g in coal feed ash and 0.833 μg / g in purified charcoal ash.

Example 3 Subbituminous Coal in Central United States The coal feedstock is PRB coal. The purified coal is the PRB coal feed with 0.005% by weight of a halogen adsorbent and 0.25% of a powder adsorbent. The powder adsorbent has a CKD of 15% and a ground CKD of 85%. The halogen-based adsorbent is from Example 1. NOx and Hg emissions were measured for feedstock and refined coal.

  A morning emission baseline was established for combustion of a coal feedstock that was burned at an average rate of 60.28 lb / hr to reach an FEGT of about 2139 ° F. using the morning. Excess oxygen was controlled to 3.05% at the furnace outlet (about 16.98% excess air) with OFA utilized at 15.13% simulating NOx control at the furnace outlet.

  Refined coal is burned at a rate of 58.91 lb / hr, with an FEA of 2139 ° F at the furnace outlet, 3.1% excess oxygen (approximately 17.33% excess air), with OFA maintained at 15.18% Achieved. The resulting emission reductions are shown in the following table.

* 適用不可

* Not applicable

Claims (26)

A method of burning coal in a furnace to reduce emissions of NOx and at least one SOx and mercury, comprising burning purified coal in the furnace, said purified coal being sub-bituminous coal or lignite, bromine A mixture of a compound and a powder adsorbent, wherein the powder adsorbent is cement kiln dust (CKD) , and one or more of ground CKD, kiln feed, conversion cement, dry clinker and storage CKD, and the powder adsorbent how to based on the weight, comprising _{K 2} O of less than _Na 2 O and 0.5 wt% of less than 0.5 wt%. Powder sorbent comprises a _{K 2} O of less than Na ₂ O and 0.1 wt% of less than 0.1 wt%, The method of claim 1.   The method according to claim 1, wherein the coal is powder river basin coal.   The method according to claim 1, wherein the purified coal comprises 0.001 to 1.0% by weight of a bromine compound and 0.1 to 10% by weight of a powder adsorbent.   5. The method according to claim 4, wherein the refined coal comprises 0.002 to 1.0% by weight of a bromine compound and 0.1 to 2.0% by weight of a powdery adsorbent.   The method of claim 1, wherein the powder adsorbent comprises less than 0.1 wt% Cl. The method according to claim 1, wherein the powder adsorbent further comprises an aluminosilicate clay. The method according to claim 1, wherein the powder adsorbent further comprises kaolin. A method of generating energy by burning mercury containing subbituminous coal in a furnace of a coal combustion facility;
Administering the first adsorbent composition to the coal;
Transporting the coal containing the administered first adsorbent to the furnace;
Transporting the coal while adding a second adsorbent to the furnace; and burning the coal in the furnace in the presence of the first and second adsorbents to generate thermal energy and ash. It becomes
Wherein said first adsorbent comprises a bromine compound, the second adsorbent cement kiln dust (CKD), and ground CKD, kiln feed, conversion cement, dry clinker and one or more storage CK D, And said method comprising less than 0.5% Na ₂ O and less than 0.5% K ₂ O , wherein said proportion is weight based on the total weight of said second adsorbent. The second adsorbent comprises a _{K 2} O of less than Na ₂ O and 0.1% less than 0.1%, The method of claim 9. 10. The method of claim 9 , wherein the first adsorbent is an aqueous calcium bromide solution. 10. A method according to claim 9 , comprising adding calcium bromide in a proportion of 0.001 to 0.5%, based on the amount of coal to be burned. 10. The method of claim 9 , wherein mercury emissions from a coal combustion facility are reduced by 40% or more as compared to coal combustion without the first and second adsorbents. 10. The method of claim 9 , wherein NOx emissions from a coal combustion facility are reduced by at least 20% as compared to coal combustion without the first and second adsorbents. 10. The method of claim 9 , wherein the coal is Powdered River Basin (PRB) coal. 10. The method of claim 9 , wherein the second adsorbent comprises CKD and ground CKD. 10. A method according to claim 9 , comprising adding the second adsorbent in a proportion of 0.1 to 10% by weight, based on the weight of coal consumed. A method of preparing a purified coal comprising subbituminous coal or lignite and further comprising an adsorbent component, comprising coal, 0.001 to 1% by weight of liquid adsorbent, and 0.1 to 10% by weight of Mixing the powder adsorbent, wherein said proportion is a weight based on the total weight of said purified carbon, wherein said liquid adsorbent comprises a bromine compound, and the powder adsorbent is a cement kiln dust (CKD), and ground CKD, kiln feed, conversion cement, dry clinker and storage CK D 1 or more, and less than 0.5 wt% Na ₂ O and _K 2 O of less than 0.5 wt% ing contains, mETHODS. 19. The method of claim 18 , wherein the method is performed by a batch process. 19. A method according to claim 18 , performed as a continuous process. The method according to claim 18 , wherein the liquid adsorbent is an aqueous solution of calcium bromide. Powder sorbent comprises a _{K 2} O of less than Na ₂ O and 0.1 wt% of less than 0.1 wt%, The method of claim 18. 19. The method of claim 18 , wherein the powder adsorbent further comprises limestone and aluminosilicate clay. The method of claim 18 , wherein the powder adsorbent further comprises kaolin. The method of claim 18 , wherein the powder adsorbent further comprises metakaolin. The method according to claim 18 , wherein the coal is PRB coal.