Patent Application
20100024697
The invention relates to a reduced-emissions fossil-fuel-fired system such as a fossil-fuel-fired furnace. In particular, the present invention is directed to reduce at least the opacity of the emissions from a fossil-fuel-fired system.
The 1990 amendments to the United States Clean Air Act require major producers of air emissions, such as electrical power plants, to limit the discharge of airborne contaminants emitted during combustion processes. In most steam power plants in operation today, fossil fuels (such as petroleum or coal) are burned in a furnace including a boiler to heat water into steam. The steam drives turbines coupled to a generator to produce electricity. These fossil-fuel-fired furnaces, however, emit highly polluting flue-gas streams into the atmosphere. These flue-gas streams typically contain noxious gaseous chemical compounds, Such as carbon dioxide, chlorine, fluorine, NOx, and SOx, as well as particulates, such as fly ash, which is a largely incombustible residue that remains after combustion of the fossil fuel.
To date, many devices have been used to reduce the concentration of contaminants emitted by fossil-fuel-fired furnaces. One of the most effective devices is an electrostatic precipitator (ESP). ESPs and their use in a typical fossil-fuel-fired boiler are described in detail in U.S. Pat. No. 6,488,740. An ESP is a device with evenly spaced static conductors, typically plates, which are electrostatically charged. When a flue-gas stream is passed between the conductors, particulates in the flue gas become charged and are attracted to the conductors. Typically, twenty to sixty conductors are arranged parallel to one another, and the flue-gas stream is passed through passages formed between the conductors. A layer of particulates formed on the conductors limits the strength of the electrostatic field and reduces the performance of the ESP. To maintain performance, the conductors are periodically cleaned to remove the collected particulates.
There are two types of ESPs: dry and wet. A dry ESP removes particulates from the conductors by shaking or rapping the conductors and collecting the removed particulates in a dry hopper. A wet ESP removes the particulates by washing the particulates off the conductors and collecting the removed particulates in a wet hopper.
A system for removing particulates using a series of dry ESP fields and a wet ESP field is disclosed in U.S. Pat. No. 3,444,668. This system removes particulates in a cement manufacturing process. However, positioning a wet ESP field upstream of a dry ESP field, such as that disclosed in U.S. Pat. No. 2,874,802, does not sufficiently remove contaminants from a flue-gas stream or address the above-described problems.
U.S. Pat. Nos. 5,384,343 and 5,171,781 disclose a process of pelleting coal fines with superabsorbent fines that have been aggregated for used in fossil-fuel furnaces including the steps of converting a wet sticky mass of coal fines to a crumbly or flowable solid and then pelleting the solid. The '343 and '781 patents disclose making the wet, sticky mass of coal fines with water absorbent polymer particles that are fines, particle size of less than 10 μm, that are selected from starch acrylonitrile graft copolymers and polymers formed by polymerization of water soluble ethylenically unsaturated monomer or monomer blend. In particular, the polymer particles fines have an effective dry size of less than 10 μm. The fines are then aggregated, and the aggregate polymer is made up of a mixture of superabsorbent polymers of at least 90% below 50 μm and are mixed into the mass of particulate material, while the particles are in the form either of a dry powder having a particle size above 50 μm and which consists of internally bonded friable aggregates of finer particles below 50 μm in size, or of a dispersion of particles below 50 μm in size in water immiscible liquid. In essence, the '343 and '781 patents are directed to the use of superabsorbent polymer fines, which are aggregated and used to pelletize combustion fuel such as coal.
The '343 and '781 patents further teach that the use of absorbent particles as low as 50 μm or less is therefore generally undesirable, but a tendency with the use of larger particles, e.g., 200 μm and above, is that their rate of absorption of liquid from the environment can be rather slow and, if such particles aggregate, then the aggregates are rather large, and this can be undesirable.
In view of the foregoing, it would be highly desirable to provide a fossil-fuel-fired system including an efficient system for decreasing the concentration of contaminants within a flue gas emitted by a fossil-fuel-fired furnace, while addressing the above described shortfalls of prior art systems.
The present invention meets these and other needs by providing a fossil-fuel-fired system that includes an emissions-control-agent dispenser, a furnace, an emissions monitor and, optionally, a controller. The emissions-control-agent dispenser provides a prescribed amount of organic-emissions-control agent, such as, for example, an opacity-control agent, to the fossil-fuel-fired system. The furnace includes an exhaust communicating with the atmosphere. The emissions monitor is capable of measuring at least one property of the flue-gas communicated through the exhaust to the atmosphere. For example, when an organic-emissions-control agent is an opacity-control agent, the emissions monitor has the capability of at least measuring opacity. When included, the controller communicates with at least the emissions-control-agent dispenser and the emissions monitor.
One aspect of the present invention is to provide a fossil-fuel-fired system that includes an emissions-control-agent dispenser, a furnace, and an emissions monitor. The emissions-control-agent dispenser provides a prescribed amount of organic-emissions-control agent. The emissions monitor is capable of measuring at least one property of the flue-gas communicated through an exhaust to the atmosphere.
Another aspect of the present invention is to provide an opacity-control-agent dispenser useable with a fossil-fuel-fired system. The fossil-fuel-fired system may includes a furnace and may include an opacity monitor. The opacity-control-agent dispenser is capable of providing a prescribed amount of opacity-control agent. The opacity monitor is capable of measuring at least an opacity of the flue-gas communicated from the furnace through an exhaust to the atmosphere.
Still another aspect of the present invention is to provide a fossil-fuel-fired system including an opacity-control-agent dispenser, a furnace, an opacity monitor, and a controller. The opacity-control-agent dispenser is capable of providing a prescribed amount of an opacity-control agent. The opacity monitor is capable of measuring at least the opacity of the flue-gas communicated from the furnace through an exhaust to the atmosphere. The controller communicates with at least the opacity-control-agent dispenser and the opacity monitor.
An additional aspect of the present invention is to provide a method for controlling emissions from a fossil-fuel-fired system. The method includes (a) providing an amount of organic-emissions-control agent to a furnace, (b) measuring at least one property of the flue-gas communicated to the atmosphere, (c) comparing the measured value and a prescribed-set-point value of the at least one property, (d) adjusting, as appropriate, the amount of organic-emissions-control agent provided, and (e) repeating steps (b) through (d). The amount of provided organic-emissions-control agent is sufficient to control the at least one property of the flue-gas at a prescribed-set-point value. As the measured value and the prescribed-set-point value are compared, appropriate adjustments, if any, are made to the amount of organic-emissions-control agent provided so that the measured value and the prescribed-set-point value of the at least one property are substantially the same.
Another additional aspect of the present invention is to provide a method for controlling an opacity of the emissions from a fossil-fuel-fired system. The method includes the steps of (a) providing an amount of opacity control agent, (b) measuring at least the opacity of the flue-gas communicated to the atmosphere, (c) comparing the measured-opacity value and a prescribed-opacity set-point value, (d) adjusting, as appropriate, the amount of opacity-control agent provided, and (e) repeating steps (b) through (d). The amount of opacity-control agent provided is sufficient to control at least an opacity of the flue-gas at a prescribed-set-point value. As the measured-opacity value and the prescribed-set-point value are compared, appropriate adjustments, if any, are made to the amount of opacity-control agent provided so that the measure-opacity value and the prescribed-set-point value are substantially the same.
Still another additional aspect of the present invention is to provide a method for operating a fossil-fuel-fired system while controlling emission therefrom. The method includes the steps of (a) operating the fossil-fuel-fired system at a prescribed load-demand set-point value, (b) providing a prescribed amount of an opacity-control agent, (c) adjusting the prescribed load-demand set-point value to a different prescribed load-demand set-point value, (d) measuring at least the opacity of the flue-gas communicated to the atmosphere at the different prescribed load-demand set-point value, (e) comparing the measured-opacity value and the prescribed-opacity set-point value, (f) adjusting, as appropriate, the prescribed amount of opacity-control agent provided, and (g) repeating steps (c) through (f). The prescribed amount of opacity-control agent provided is sufficient to control at least an opacity of the flue-gas at a prescribed-opacity set-point value while operating a the prescribed load-demand set-point value. After the prescribed load-demand set-point value is adjusted to a different prescribed load-demand set-point value, the measured value and the prescribed-opacity set-point value are compared. Appropriate adjustments, if any, are made to the prescribed amount of opacity-control agent provided so that the measured value and the prescribed-set-point value of at least the opacity are substantially the same.
An alternative aspect of the present invention is to provide a fuel usable in a fossil-fuel-fired system to control the emissions communicated by the fossil-fuel-fired system into the atmosphere. The fuel includes at least one combustible materials and an organic-emissions-control agent. The emission-control agent is capable of interacting with one of the fuel, the combustion products of the fuel, and the fuel and combustion products so as to reduce the emission of at least one aspect of the flue-gas. In this manner, the emissions communicated by the fossil-fuel-fired system into the atmosphere are controlled.
Another alternative aspect of the present invention is to provide a fuel usable in a fossil-fuel-fired system to control the opacity of the flue-gas communicated by the fossil-fuel-fired system into the atmosphere. The fuel includes at least one fossil fuel and at least one opacity-control agent. The opacity-control agent is capable of interacting with one of the fuel, the combustion products of the fuel, and the fuel and combustion products so as to reduce the opacity of the flue-gas communicated by the fossil-fuel-fired system into the atmosphere. In this manner, at least the opacity of the flue-gas communicated by the fossil-fuel-fired system into the atmosphere is controlled.
Still another alternative aspect of the present invention is to provide an apparatus for decreasing the concentration of contaminants present in a flue-gas emitted into the atmosphere by a fossil-fuel-fired system. The apparatus includes at least one injector for introducing a superabsorbent polymer to the fossil-fuel-fired system in a flue-gas stream of the combusted fossil fuel. The apparatus may include any one of an emissions monitor, a controller, and an emissions monitor and a controller. When included, emissions monitor is downstream of the injector. Also, the emissions monitor is capable of measuring at least one property of the flue gas communicated to the atmosphere. The controller communicates with the at least one injector. The controller may communicate with the at least one injector and the emissions monitor. In either case, the controller controls the flow of the superabsorbent polymer through the at least one nozzle and into the flue gas stream to control the concentration of contaminants present in a flue gas downstream of the at least one injector.
These and other aspects, advantages, and salient features of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims.
In the following description, like reference characters designate like or corresponding parts throughout the several views shown in the figures. It is also understood that terms such as “top,” “bottom,” “outward,” “inward,” and the like are words of convenience and are not to be construed as limiting terms.
Referring to the drawings in general and to
The controller 22 regulates an amount of emission-control agent provided by the emissions-control-agent dispenser 12. This regulation may be effected in conjunction with the emissions monitor 20 and its communication of a measured value of at least one property of the flue gas to the controller 22. For example, a prescribed amount of emission-control agent 18 is provide by the emissions-control-agent dispenser 12 to maintain at least one property of the flue gas to a predetermined limit through a feedback of the measured value from the emissions monitor 20 to the controller 22. By further example, a prescribed amount of organic-emissions-control agent 18 is provide by the emissions-control-agent dispenser 12 to maintain both at least one property to a predetermined limit and an operational load of any one of the furnace 14, the steam generator 32, the power generator 34, and combinations thereof through a feedback of the measured values to the controller 22.
The controller 22 is a commercially available controller with a plurality of inputs and outputs that meet the requirements of the peripherals. The controller 22 may be any one of a micro-controller, a PC with appropriate hardware and software, and combinations of one or more thereof. Details concerning controllers that may be used in fossil-fuel-fired system 10 are discussed in, for example, U.S. Pat. Nos. 5,980,078; 5,726,912; 5,689,415; 5,579,218; 5,351,200; 4,916,600; 4,646,223; 4,344,127; and 4,396,976, the entire disclosure of each being incorporated by reference herein.
Again with reference to
Returning now to
The fuel-preparation system 24 may be capable of combining at least two fuels such as, for example, any one of different grades, different types, different sizes of fuel, and combinations thereof may be provided within the fossil-fuel-fired system 10. These plurality of fuels may be blended in a manner that creates a fuel mixture meeting the operational load requirements of the furnace 14, while at the same time, in combination with an organic-emissions-control agent 18, meeting or exceeding the emissions performance. It will be appreciated that when the fuel includes coal, the fuel blending may be accomplished using any one of a coal crusher (e.g., in the raw-fuel-preparation system 26), a pulverizer (e.g., in the in refined-fuel-preparation system 28), and combinations thereof.
As shown in
Also as shown in
It will be appreciated that a fossil-fuel-fired system 10 may include provisions that would make it unnecessary to have a fuel-preparation system 24 to transform raw fuels and refined fuels. In such case, the fossil-fuel-fired system 10 may be a fuel-handling system 30 for providing combustion-grade fuel to the furnace 14. Is such case, the fuel-handling system 30 may include an emissions-control-agent dispenser 12 and one or more additional dispensers. These dispensers may provide any one of a materials-handling agent, a moisture-binding agent, and a materials-handling, moisture-binding agent. Although there may be separate dispensers for each agent, in
The furnace 14 may be any that would be afforded benefits by including an emissions-control-agent dispenser 12. When coal is a fuel, examples of a furnace 14 include any one of a stoker-firing furnace, a pulverized-fuel furnace, and combinations thereof. Some specific examples of a pulverized-fuel furnace include any one of a cyclone-type furnace and a fluidized-bed-type furnace. A furnace 14 may be identified by the type of fuel for which it has been designed. Thus, other examples of a furnace 14 include any one of a coal-fired furnace, a peat-fired furnace, a petroleum-coke-fired furnace, and combinations thereof. Applicants have found that providing an emissions-control-agent dispenser 12 to a coal-fired furnace to be beneficial for controlling emissions.
Returning to
Applicants note that the fossil-fuel-fired system 10 may be used in applications other than those depicted in
An emissions monitor 20 is shown in
Details concerning emissions monitors that may be used in a fossil-fuel-fired system 10 are discussed in, for example, U.S. Pat. Nos. 6,597,799 and 5,363,199, the entire disclosure of each being incorporated by reference herein. Continuous emission monitoring systems (CEMS), including SO2 analyzers, NOx analyzers, CO2 analyzers, O2 analyzers, flow monitors, opacity analyzers, flue-gas flow meters, and associates data acquisition and handling systems, that meet the requirements set forth in the US Environmental Protection Agency's (EPA's) 40 CFR Part 75 are commercially available. Manufacturers of opacity monitors or analyzers include, for example Teledyne/Monitor Labs, Land Combustion, Thermo Environmental, and Durag.
Turning now to the emissions-control-agent dispenser 12 useable with a fossil-fuel-fired system 10. Any disperser that would facilitate the introduction of an organic-emissions-control agent 18 in a manner that reduces emissions communicating with the atmosphere would be appropriate. Such an emissions-control-agent dispenser 12 may include a volumetric-feed dispenser such as, for example, a screw-feed dispenser, and a mass-feed dispenser such as, for example, a weight-belt feeder.
When an opacity-control-agent dispenser, the dispenser 12 is capable of providing an opacity-control agent at a rate so that at least the opacity of the flue-gas communicated through the exhaust 16 to the atmosphere is less than or equal to a substantially prescribed value. In some jurisdictions, the opacity value is substantially less than or substantially equal to about 40. In other jurisdictions, the opacity value is substantially less than or substantially equal to about 30. In yet other jurisdictions, the opacity value is substantially less than or substantially equal to about 20. In still yet other jurisdictions, the opacity value is substantially less than or substantially equal to about 10.
An emissions-control-agent dispenser 12 may communicate with the fossil-fuel-fired system 10 in any manner that allows for providing an organic-emissions-control agent 18 so that the concentration of contaminants of a flue-gas stream emitted by an exhaust 16 are controlled. To that end, an emissions-control-agent dispenser 12 may be provided so as to communicate an organic-emissions-control agent 18 to any one of a fossil-fuel, a fossil-fuel stream prior to combustion, a fossil-fuel stream during combustion (e.g., with gases that are introduced into the furnace 14 during combustion), a fossil-fuel stream following combustion (e.g., a combusted fossil-fuel flue-gas stream), and combinations thereof.
Turning now to
Also as shown in
Turning now to
Turning now to
Applicants have unexpectedly found that a superabsorbent polymer acts as an emissions control agent 18 in general and, in particular, as an opacity control agent. In such case, the emissions-control-agent dispenser 12 is a superabsorbent-polymer dispenser having the capability to dispensing a superabsorbent polymer having an average particle size of at least about 200 μm and even of at least about 250 μm.
Particle size characteristics for the organic-emissions-control agent useful herein maybe done using standard sieve analyses. Determination of particle size characteristics using such a technique is described in greater detail in U.S. Pat. No. 5,061,259, “Absorbent structures with gelling agent and absorbent articles containing such structures” issued on Oct. 29, 1991 to Goldman, et al., the entire disclosure of which is incorporated herein by reference.
Also, the superabsorbent-polymer dispenser is capable of dispensing a superabsorbent polymer at from about 0.001 weight % to about 5 weight %, preferably, about 0.01 weight % to about 0.5 weight %, and, more preferably, at from about 0.05 weight % to about 0.25 weight % of the fuel feed to the furnace. Stated in a pound/ton-of-fuel basis, the dispenser is capable of dispensing a superabsorbent polymer at from about 0.02 pound/ton of fuel to about 100 pounds/ton, preferably, about 0.2 pound/ton of fuel to about 10 pounds/ton, and, more preferably, at from about 1 pound/ton of fuel to about 5 pounds/ton of fuel feed to the furnace. Further, the superabsorbent-polymer dispenser is capable of dispensing a superabsorbent polymer having any of a variety of physical forms including any one of particles, fibers, foams, films, beads, rods, slurries, suspensions, solutions, and combinations thereof.
As the fossil-fuel-fired system 10 includes a boiler or steam generator 32, the fuel flows, air flows, and emissions-control-agent (EC-agent) flows are controlled from steam pressure through the boiler master with the fuel and emissions readjusted from fuel-flow, air-flow, emission level, and EC-agent-flow.
Generally,
Applicants have unexpectedly found that a superabsorbent polymer acts as an organic-emissions-control agent 18 in general and, in particular, as an opacity control agent. A suitable superabsorbent polymer may be selected from natural, biodegradable, synthetic, and modified natural polymers and materials. The term crosslinked used in reference to the superabsorbent polymer refers to any means for effectively rendering normally water-soluble materials substantially water-insoluble but swellable. Superabsorbent polymers include internal crosslinking and surface crosslinking.
Superabsorbent polymers are known for use in sanitary articles as well as other applications, such as for cables and fertilizers. Superabsorbent refers to a water-swellable, water-insoluble, organic or inorganic material capable of absorbing at least about 10 times its weight and up to about 30 times its weight in an aqueous solution containing 0.9 weight percent sodium chloride solution in water. A superabsorbent polymer is a crosslinked polymer which is capable of absorbing large amounts of aqueous liquids and body fluids, such as urine or blood, with swelling and the formation of hydrogels, and of retaining them under a certain pressure in accordance with the general definition of superabsorbent.
The superabsorbent polymers that are currently commercially available are crosslinked polyacrylic acids or crosslinked starch-acrylic acid graft polymers, in which some of the carboxyl groups are neutralized with sodium hydroxide solution or potassium hydroxide solution.
In one embodiment of the present invention, the superabsorbent polymer is a crosslinked polymer comprising from about 55 to about 99.9 wt. % of polymerizable unsaturated acid group containing monomers; internal crosslinking agent; and surface crosslinking agent applied to the particle surface. Such superabsorbent polymers are commercially available from Stockhausen Inc. or Stockhausen Louisiana LLC or Stockhausen GmbH & Co. KG.
The superabsorbent polymer of the present invention is obtained by the initial polymerization of from about 55 to about 99.9 wt. % of polymerizable unsaturated acid group containing monomers. Suitable monomers include those containing carboxyl groups, such as acrylic acid, methacrylic acid, or 2-acrylamido-2-methylpropanesulfonic acid, or mixtures of these monomers are preferred here. It is preferable for at least about 50-weight %, and more preferably at least about 75 wt. % of the acid groups to be carboxyl groups. It is preferred to obtain polymers obtained by polymerization of acrylic acid or methacrylic acid, the carboxyl groups of which are neutralized to the extent of 50-80 mol %, in the presence of internal crosslinking agents.
Further monomers, which can be used for the preparation of the absorbent polymers according to the invention, include about 0-40 wt. % of ethylenically unsaturated monomers that can be copolymerized with, for example, acrylamide, methacrylamide, hydroxyethyl acrylate, dimethylaminoalkyl (meth)-acrylate, ethoxylated (meth)-acrylates, dimethylaminopropylacrylamide, or acrylamidopropyltrimethylammonium chloride. More than about 40 wt. % of these monomers can impair the swellability of the polymers.
The internal crosslinking agent has at least two ethylenically unsaturated double bonds or one ethylenically unsaturated double bond and one functional group that is reactive towards acid groups of the polymerizable unsaturated acid group containing monomers or several functional groups that are reactive towards acid groups can be used as the internal crosslinking component and which is present during the polymerization of the polymerizable unsaturated acid group containing monomers.
The absorbent polymers are surface crosslinked after polymerization. Surface crosslinking is any process that increases the crosslink density of the polymer matrix in the vicinity of the superabsorbent particle surface with respect to the crosslinking density of the particle interior. The absorbent polymers are typically surface crosslinked by the addition of a surface crosslinking agent. Preferred surface crosslinking agents include chemicals with one or more functional groups, which are reactive towards pendant groups of the polymer chains, typically the acid groups. The content of the surface crosslinking agents is from about 0.01 to about 5 wt. %, and preferably from about 0.1 to about 3.0 wt. %, based on the weight of the dry polymer. A heating step is preferred after addition of the surface crosslinking agent.
While particles are the used by way of example of the physical form of superabsorbent polymers, the invention is not limited to this form and is applicable to other forms such as fibers, foams, films, beads, rods, slurries, suspensions, solutions, and the like. The average particle size of the superabsorbent polymers is at least about 200 μm and more likely at least 250 μm.
It is sometimes desirable to employ surface additives that perform several roles during surface modifications. For example, a single additive may be a surfactant, viscosity modifier and react to crosslink polymer chains.
The polymers according to the invention are preferably prepared by two methods. The polymers can be prepared continuously or discontinuously in a large-scale industrial manner by the abovementioned known process, the after-crosslinking according to the invention being carried out accordingly.
According to the first method, the partly neutralized monomer, preferably acrylic acid, is converted into a gel by free-radical polymerization in aqueous solution in the presence of crosslinking agents and, optionally, further components, and the gel is comminuted, dried, ground, and sieved off to the desired particle size. This solution polymerization can be carried out continuously or discontinuously.
Inverse suspension and emulsion polymerization can also be used for preparation of the products according to the invention. According to these processes, an aqueous, partly neutralized solution of monomers, preferably acrylic acid, is dispersed in a hydrophobic, organic solvent with the aid of protective colloids and/or emulsifiers, and the polymerization is started by free radical initiators. The internal crosslinking agents either are dissolved in the monomer solution and are metered in together with this, or are added separately and optionally during the polymerization. The addition of a water-soluble polymer as the graft base optionally takes place via the monomer solution or by direct introduction into the oily phase. The water is then removed azeotropically from the mixture, and the polymer is filtered off and, optionally, dried. Internal crosslinking can be carried out by polymerizing-in a polyfunctional crosslinking agent dissolved in the monomer solution and/or by reaction of suitable crosslinking agents with functional groups of the polymer during the polymerization steps.
In one embodiment, the superabsorbent polymer is used in the form of discrete particles. Superabsorbent polymer particles can be of any suitable shape, for example, spiral or semi-spiral, cubic, rod-like, polyhedral, etc. Particle shapes having a large greatest dimension/smallest dimension ratio, like needles, flakes, or fibers are also contemplated for use herein. Conglomerates of particles of superabsorbent polymers may also be used.
Several different superabsorbent polymers that differ, for example, in the rate of absorption, permeability, storage capacity, absorption under pressure, particle size distribution, or chemical composition can be simultaneously used together.
The polymers according to the invention are employed in many products including furnace devices such as boilers. The superabsorbent polymers can be introduced directly into the boiler or applied to coal prior to introduction of the coal into the boiler. When the superabsorbent polymer is introduced directly into the boiler, any means can be used to do so. The superabsorbent polymer may be introduced with gases that are introduced into the boiler during combustion.
When the superabsorbent polymer is applied to coal, it is usually applied to the coal in the amount of from about 0.02 to about 100 pounds of superabsorbent polymer per ton of coal, preferably, from about 0.2 to about 10 pounds of superabsorbent polymer per ton of coal, and most preferably, from about 1 to about 5 pounds of superabsorbent polymer per ton of coal. As one can appreciate, increasing the amount of superabsorbent polymer to the coal has a diminishing value on improving results in the fossil-fuel-fired furnace. In one embodiment, the superabsorbent polymer is dusted onto the coal being held in what are called bunkers and allowed to settle and absorb water or other fluids. The coal is then removed from the bunker and transported by a conveyor belt to a ball mill or other type of grinding or pulverizing equipment to make the coal into particle size suitable for combustion. Generally, the coal is milled to a particle size of from about 1 to about 10 μm, and the milled coal containing superabsorbent polymer is subsequently used as fuel. When a dispersant or coagulant or other material is being incorporated before the absorbent polymer, it is generally applied as a solution, but it can be applied in solid form if its solubility is such as to permit it to dissolve relatively rapidly within the boiler or on the coal. It is often preferred that the particle sizes and the amounts of the absorbent polymer and of the filter cake are such that the amount will be adjusted to reduce the emissions of contaminants. For instance, this is achieved by adding about 0.001% (dry on dry) of polymer particles having an average particle size of about 200 μm to coal, or injecting the superabsorbent directly into the boiler.
The amount of polymer that is applied is generally at least about 0.01% and is preferably at least about 0.5% of the weight of the coal used in the fossil-fuel-fired furnace. It is a particular advantage of the invention that, despite the unpleasant character of the wet mass, good results can be obtained with very low amounts of superabsorbent polymer, often below 0.3% or 0.4%, and often below 0. 15% or 0.2%. These amounts are of dry superabsorbent polymer based on dry particles by weight of the coal.
In an aspect, the present invention is to provide a fuel usable in a fossil-fuel-fired system 10 to control the emissions communicated by the fossil-fuel-fired system 10 into the atmosphere. The fuel includes at least one combustible material and an organic-emissions-control agent 18. The emission-control agent 18 is capable of interacting with one of the fuel, the combustion products of the fuel, and the fuel and combustion products so as to reduce the emission of at least one aspect of the flue-gas. In this manner, the emissions communicated by the fossil-fuel-fired system into the atmosphere are controlled.
In another alternative aspect, the present invention is to provide a fuel usable in a fossil-fuel-fired system 10 to control the opacity of the combustion products communicated by the fossil-fuel-fired system 10 into the atmosphere. The fuel includes at least one fossil fuel and at least one opacity-control agent. The opacity-control agent is capable of interacting with one of the fuel, the combustion products of the fuel, and the fuel and combustion products so as to reduce the opacity of the flue-gas communicated by the fossil-fuel-fired system into the atmosphere. In this manner, at least the opacity of the flue-gas communicated by the fossil-fuel-fired system into the atmosphere is controlled.
An operation of the fossil-fuel-fired system 10 is discussed with reference to
Raw coal from a number of sources is processed through a dryer and crusher system (raw-fuel preparation system 26). During this processing and transport, an organic-emissions-control agent 18 may be added to the coal using a dispenser 12. Also, the coal from a number of sources may be blended by proportionally drawing coal from the number of sources simultaneously. The crushed coal is delivered to one or more bunkers. (Only one bunker is depicted in
The refined coal from the number of bunkers is processed through a pulverizing system (refined-fuel preparation system 28). During this processing and transport, if not already so done, or if additional amounts would beneficial, an organic-emissions-control agent 18 may be added to the coal using a dispenser 12′. Also, the refined coal from the number of bunkers may be blended by proportionally drawing crushed coal and/or other fuel such as, for example, petroleum coke, from the number of bunkers simultaneously. The pulverized coal is delivered to one or more bins. (Only one bin is depicted in
The pulverized coal from the number of bins is fed through a number of burners to the furnace 14. If not already so done, or if additional amounts would beneficial, an organic-emissions-control agent 18 may be added to the furnace 14 using a dispenser 12″.
Combustion products are the passed through a convention bank, and some of the flue gas is recirculated to the furnace. The balance of the flue gas is directed to through the exhaust 16 to the atmosphere. The exhaust 16 may include any one of a particulate collector, a dry scrubber, a baghouse for capturing components of the emissions, and combinations thereof. If not already so done, or if additional amounts would beneficial, an organic-emissions-control agent 18 may be added to the exhaust 16 using a dispenser 12″′. Although depicted as being in communication with the stack, the dispenser 12″′ may be in communication with any one of the particulate collector, the dry scrubber, the baghouse, the stack, and combinations thereof. An emission monitor 20 detects and reports the emissions level for the components of interest of required by law.
Fossil-fuel-fired systems, as well as associated fuel-preparation systems, raw-fuel-fuel preparation systems, refined-fuel-preparation system, furnaces, exhausts, and control systems are shown in the book entitled “Steam: Its Generation and Use,” 39th Edition, copyright by the Babcock & Wilcox Company in 1978. The description of the fossil-fuel-fired systems, as well as associated fuel-preparation systems, raw-fuel-fuel preparation systems, refined-fuel-preparation system, furnaces, exhausts, and control systems are incorporated herein by reference. Also, a fossil-fuel-fired boiler is shown in U.S. Pat. No. 6,488,740, of which the description of the boiler is incorporated by reference. Further, a fossil-fuel-fired facility is shown in the article entitled “B&W's Advance Coal-fired Low Emission Boiler System Commercial Generating Unit and Proof-of-Concept Demonstration presented to ASME International Joint Power Generation Conference” held Nov. 3-5, 1997 in Denver, Colo., USA, of which the description of the facility is incorporated by reference.
The superabsorbent is applied to coal prior to processing the coal by a ball mill to have a size of 1 to 10 mm. The mix is pulverized and carried, entrained in air from the pulverizes, as a fuel into the combustion chamber of a power station boiler. There is no evidence of clogging of the pulverizer or other parts of the apparatus through which the product travels from the mixer to the boiler. It was found that the emissions of the boiler were reduced.
A pilot test was performed at Hoosier Energy REC, Inc.'s Ratts Generating Station in Pike County, Indiana. The coal-fired facility is able to produce 250,000 kilowatts of electricity with twin turbine generators. The generating station is equipped with environmental controls and monitors; these include precipitators for the removal of flyash. Most of the fuel for the facility is Indiana coal with moderate sulfur content burned at about 12,000 BTU per pound and mined within a radius of 20 miles of the generating station.
Using a screw feeder (Model No. 105-HX, manufactured by Acrison Inc.) about 3 pounds/ton of coal of a superabsorbent polymer sold under the tradename ENVIROSORB 1880 was added before the raw coal was processed using a crusher. The Technical data relating to ENVIROSORB 1880 superabsorbent polymer is presented in Table 5 and some combustion characteristics are presented in Table 6.
About eight hours of coal where prepared. The opacity of the emission exhausted to the atmosphere was continuously monitored using a Spectrum 41 Continuous Opacity Monitoring System (COMS). The results of the six-minute-average data for opacity before, during, and after the superabsorbent polymer emissions-control agent was added To Fuel Supply are presented in Table 7. The data demonstrate that at least the opacity of the emissions was reduced by the addition of the superabsorbent polymer emissions-control agent. Further it was believed that the plant was able to operate closer to the operational load rating without concern of reaching or exceeding the opacity limit.
Certain modifications and improvements will occur to those skilled in the art upon a reading of the foregoing description. It should be understood that all such modifications and improvements have been deleted herein for the sake of conciseness and readability but are properly within the scope of the following claims.
This application claims priority to U.S. Patent Application Ser. No. 60/462,552 filed Apr. 11, 2003 entitled “Superabsorbent Polymer For Fossil-Fuel Incinerator Applications” and is incorporated in its entirety herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60462552 | Apr 2003 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10818229 | Apr 2004 | US |
| Child | 12577317 | US |
