Patent Application
20130125749
1. Field
The present inventions relate generally to systems and methods for reducing acid and metal emissions from combustion systems and, more particularly, to boosted no-lance injection systems and methods to reduce acid and metal emissions.
2. Related Art
Combustion systems having boilers are known in the art and can include, for example, pulverized coal plants, circulated fluidized beds, gas-fired systems, oil-fired systems, waste incinerators, direct-fired process heaters, kilns, tangentially-fired boilers, etc. Common elements of various combustion systems typically include a combustion chamber and a burner for igniting fuel located in the combustion chamber. Fuel (e.g. coal or biomass) is fed into the combustion chamber, where it is rapidly ignited and stabilized on burners. Any of a number of undesirable components included in the fuel, e.g. acid components or metal components, may enter the environment via flue gas exiting the stack and may cause any number of undesirable consequences. Examples of undesirable acid components in the flue gas include sulfur dioxide (SO2), sulfur trioxide (SO3), sulfuric acid (H2SO4), hydrogen chloride (HCl), hydrogen bromide (HBr), hydrogen fluoride (HF), chlorine (Cl2) and bromine (Br2). Examples of undesirable metal components in the flue gas include antimony (Sb), arsenic (As), beryllium (Be), cadmium (Cd), chromium (Cr), cobalt (Co), lead (Pb), manganese (Mn), mercury (Hg), nickel (Ni), and selenium (Se). The current state-of-art of dispersing or mixing solid sorbents into a flue gas for capture of acid gas and metal pollutants uses a plurality of injection lances.
Applicants believe that lance systems can suffer from any number of problems, which Applicants would like to improve. For example, lance systems may warp over time because of heat exposure, thereby promoting clogging, adversely affecting sorbent dispersion, increased maintenance costs and prohibiting removal of the lance for maintenance without a unit outage. Further, lance systems may overheat the sorbent, thereby clogging the lance or reducing sorbent utilization. In addition, lance systems may fail to properly distribute sorbent for desired efficacy.
When a greater percentage of capture pollutants is desired, additional lances are often added in attempt to distribute the sorbent across the cross-section of the flue gas duct. Applicants believe this strategy creates additional problems. For example, as the number of injection lances increase, evenly distributing the sorbent to multiple injection lances becomes mechanically complex. The sorbent is transported to the vicinity of the flue gas duct by a limited number of air streams, for example one or two air streams. In order to provide multiple injection lances, a single transport air stream must be evenly divided into multiple streams. Such division suffers from an inability to divide the sorbent stream evenly, and the number of division points increases the likelihood of plugging with the solid sorbent downstream of the division points. Also, as the number of injection lances increases, the total amount of transport air used increases in proportion to the number of lances because a certain minimum velocity of air must be maintained within each lance to minimize likelihood of plugging with the solid sorbent, for example, a minimum of 15 m/s. This increased air flow load requires that the transport pipe, air blowers and associated blower air conditioning equipment size must be increased.
Further, lance systems may result in undesirable flue gas pressure drops because of the depth of penetration of the lances and numbers of the lances.
In-duct mixing devices, such as baffle plates, can also be used in conjunction with lance injection systems to increase mixing of sorbent and flue gas. However, Applicants believe that the application of in-duct mixing devices requires extended and unnecessary shutdown of the combustion unit for installation. Moreover, Applicants believe that in-duct devices cause a significant and unnecessary gas pressure loss, which permanently increase operating cost. Further, in-duct devices can also accumulate sorbent deposits or solids from the combustion system, thereby leading to shutdown of the combustion system for cleaning of the in-duct device.
These problems, Applicants believe, result in excessive or unnecessary maintenance, operational costs and offline requirements. Further, these problems may result in non-compliance with emissions regulations, and further increase costs and reduce power output.
Additionally, as illustrated in
Accordingly, the present inventions are directed to at least one of these, or additional problems.
The present inventions are directed to a variety of methods and systems for reducing acid or metal emissions in the flue gas. In one aspect of the present inventions, a method comprises providing a combustion system that emits a flue gas, obtaining at least one boosted no-lance injection system (BNLS), positioning the BNLS to inject into the ductwork; applying the transport air and the sorbent into the ductwork using the transport nozzle of the at least one BNLS; and applying the high volumetric flow air into the ductwork using the high volumetric flow nozzle of the at least one BNLS.
In another aspect, the present inventions are directed to a boosted no-lance injection system (BNLS). The BNLS is for interfacing with a ductwork of a combustion system. The combustion system may be free of an air heater, and the application by the BNLS may include application in an area having a flue gas temperature in the range of 250° F. and 850° F. Further, the system may include an air heater and the application area has a flue gas temperature in the range of 550° F. and 850° F. In yet other examples, the system includes an air heater wherein the application area has a flue gas temperature in the range of 250° F. and 450° F.
In other examples, the high volumetric flow air injection nozzle injects high volumetric flow air in the range of at least one of about 100 to about 3500 ACFM, about 150 to about 3500 ACFM, about 200 to about 3000 ACFM about 250 to about 2500 ACFM, about 300 to about 2500 ACFM, about 350 to about 2500 ACFM, about 400 to about 2500 ACFM, about 450 to about 2500 ACFM, about 500 to about 2500 ACFM, about 550 to about 2500 ACFM, about 600 to about 2500 ACFM, about 650 to about 2500 ACFM, about 700 to about 2500 ACFM, about 750 to about 2500 ACFM, about 800 to about 2500 ACFM, about 950 to about 2500 ACFM, and about 1000 to about 2000 ACFM. For instance, the volumetric flow air injection nozzle may inject high volumetric flow air in the range of 1000 to 2000 ACFM. Further, the system may include an ambient air supply and a recirculated flue gas supply.
In additional examples, the high volumetric flow air injection nozzle may inject high volumetric flow air at a temperature sufficient to promote calcination of the sorbent during a stage chosen from during transport, after transport, during injection, after injection and combinations thereof. The high volumetric flow air injection nozzle may inject high volumetric flow air at a rate in the range of 50 meters/second (m/s) to 150 m/s. Further, the high volumetric flow air injection nozzle may inject high volumetric flow air at a pressure in the range of 4 inches of water column (inWC) to 50 inWC. The high volumetric flow air injection nozzle may inject high volumetric flow air with a mass flow in the range of 3% and 5% of the total flue gas mass flow, wherein the 3% to 5% is divided across the number of BNLS injection devices applying high volumetric flow air.
The sorbent may include a plurality of solid particles that are generally configured to reduce the concentration of the acid or metal component. In some examples, the acid component includes SO2, SO3, H2SO4, HCl, HF, HBr, Cl2, Br2 and combinations thereof. Further, in some examples, metal component includes Hg, Se and combinations thereof. In certain examples, the sorbent is applied at a mass flow rate of X tons/hr and transport air is applied at a mass flow rate in the range of 0.5× tons/hr to 2× tons/hr and the transport velocity is more than 15 m/s. The sorbent solid particles may have a median maximum length in the range of 2 μm to 100 μm, preferably in the range of 5 μm to 40 μm, and more preferably in the range of 10 μm to 15 μm. The sorbent may include calcium carbonate, calcium hydroxide, sodium sesquicarbonate, sodium bicarbonate, trona, nacholite, magnesium oxide, magnesium hydroxide and powdered activated carbon. Further, the sorbent may be applied at a mass flow rate of X tons/hr and transport air is applied at a mass flow rate in the range of 0.5× tons/hr to 2× tons/hr and the transport velocity is more than 15 m/s.
In particular examples, the high volumetric flow air injection nozzle has a diameter in the range of 3 inches to 6 inches and the transport nozzle has a diameter in the range of 1.5 inches to 3 inches. The transport nozzle may be positioned within the high volumetric flow air injection nozzle. The transport nozzle may be positioned adjacent to the high volumetric flow air injection nozzle. The transport nozzle may terminate near the high volumetric flow air injection nozzle exit. Further, the transport nozzle may terminate up-stream from the high volumetric flow air injection nozzle exit. In some examples, the mounting apparatus positions the BNLS adjacent to the outer surface of the ductwork. The mounting apparatus may position transport nozzle in a non-vertical orientation. The mounting apparatus may position the transport nozzle in a non-vertical orientation. In particular examples, the high volumetric flow air is humidified. In yet other examples, the supply of high volumetric flow air includes recircualated flue gas.
In yet other examples, the ductwork includes an inner surface and an outer surface and is located downstream of a heat-transfer-to-water zone and upstream of a particle capture device. The BNLS comprises an injection device comprising a high volumetric flow air injection nozzle and a transport nozzle. A high volumetric flow air mover is configured to establish air-transport communication with the high volumetric flow air injection nozzle. A transport air mover is configured to establish air-transport communication with the transport nozzle. A sorbent hopper is configured to establish solid-particle communication with the transport nozzle. A mounting apparatus is configured to mount the injection device to the ductwork. In many examples, the mounting apparatus positions the terminus of the high volumetric flow air nozzle at a position P±1 inch relative to the inner surface of the ductwork. The transport nozzle may terminate at the same position as the high volumetric flow air nozzle. The transport nozzle may be extracted upstream into the high volumetric flow air nozzle, but only within the nozzle to the limit where the high volumetric flow air velocity is above about 15 m/s. The transport nozzle may be extended downstream of the high volumetric flow air nozzle (into the ductwork), but the sorbent utilization may quickly reduced as this distance is increased.
The above summary was intended to summarize certain embodiments of the present inventions. Systems and methods will be set forth in more detail, along with examples, in the figures and detailed description below. It will be apparent, however, that the detailed description is not intended to limit the present invention.
Embodiments of the present inventions will be better understood by a reading of the Detailed Description of the Embodiments along with a review of the figures, in which:
In the following description, like reference characters designate like or corresponding parts throughout the several views. Also in the following description, it is to be understood that such terms as “forward,” “rearward,” “left,” “right,” “upwardly,” “downwardly,” and the like are words of convenience and are not to be construed as limiting terms.
Many aspects of the present inventions relate generally to, inter alia, methods and systems for injecting into the ductwork of the combustion system. In one aspect, a method disclosed herein includes providing a combustion system.
As used herein, downstream from a heat-transfer-to-water zone includes zones downstream from at least one of an economizer, a generating bank, a super heat bank, a reheat bank, a drum and a water wall. In many examples, downstream from a heat-transfer-to-water zone will include the area downstream from the downstream-most of an economizer, a generating bank, a super heat bank, a reheat bank, a drum, and a water wall.
As used herein, upstream from a particle capture device includes the area upstream from the flue gas entrance of at least one particle collection device, for example, upstream from at least one of an electrostatic precipitator or a gas scrubbing device that may also serve as a particulate capture device, for example a wet scrubber including spray tower scrubbers, spray-tray tower scrubbers, venturi scrubbers, etc. Accordingly, upstream from a particle collection device can also include, for example, an area upstream from a gas scrubbing device and downstream from an electrostatic precipitator.
Providing a combustion system may vary from embodiment to embodiment. In some embodiments, providing includes constructing a combustion system. In other embodiments, providing includes locating a combustion system. In other embodiments, providing includes gaining access to a combustion system, e.g. for the purpose of installing a treatment system. In other embodiments, providing is achieved by operating a combustion system.
In another aspect, a method includes obtaining at least one boosted no-lance injection systems (BNLS).
Referring back to
The high volumetric air flow supply will typically include at least one air mover. Air movers may vary from embodiment to embodiment. In some embodiments, air movers are configured to generate a volumetric flow of about 50 to about 4000 actual cubic feet per minute (ACFM). High volumetric air flow may be applied from at least one of about 100 to about 3500 ACFM, about 150 to about 3500 ACFM, about 200 to about 3000 ACFM, about 250 to about 2500 ACFM, about 300 to about 2500 ACFM, about 350 to about 2500 ACFM, about 400 to about 2500 ACFM, about 450 to about 2500 ACFM, about 500 to about 2500 ACFM, about 550 to about 2500 ACFM, about 600 to about 2500 ACFM, about 650 to about 2500 ACFM, about 700 to about 2500 ACFM, about 750 to about 2500 ACFM, about 800 to about 2500 ACFM, about 950 to about 2500 ACFM, and about 1000 to about 2000 ACFM. In many embodiments, high volumetric flow will be chosen from about 1000 to about 2000 ACFM. A suitable air mover, by way of example, includes a 480 VAC, 15 horsepower blower. In many embodiments, air movers will be configured to generate an air flow velocity of about 80 m/s to about 15 m/s. Similarly, the application pressure of the high volumetric flow air may vary, for example in the range of 4 inches of water column (inWC) to 50 inWC.
In some examples, the high volumetric air flow may also be humidified, e.g. include any of entrained water droplets, mist, steam, etc. Humidification may be used, for example, to facilitate acid capture, e.g. the capture of halide acids.
Air movers may move ambient air, recirculated flue gas, or some combination thereof. Recirculated flue gas may be used, for example, to increase the temperature of the high volumetric air in an amount sufficient to promote calcination of the sorbent during or after transport, or during or after injection. It may also be used to reduce efficiency losses relative to using air alone.
In terms of mass flow, the high volumetric flow air will typically be applied with a mass flow in the range of 3% and 5% of the total flue gas mass flow, wherein the 3% to 5% is divided across the number of injectors applying high volumetric flow air. For example, in
The transport air supply may include a compressor, blower, etc. selected or adjusted based on the desired sorbent application rate. For example, transport air will typically be applied in the range of 0.5 to 2 times the mass flow rate of the sorbent. In one example, where sorbent is applied at 10 tons/hour, transport air will be applied at 10 tons/hour. Exit velocities and pressures may also vary. For example, transport air velocity is typically mandated to exceed 15 m/s in order to maintain sorbent transport and to inhibit sorbent fallout.
Regarding the sorbent, in most examples, the sorbent will include solid particles, e.g. solid particles of at least one of calcium carbonate, calcium hydroxide, sodium sesquicarbonate, sodium bicarbonate, trona, nacholite, magnesium oxide, magnesium hydroxide, powdered activated carbon and the like. Other examples of suitable sorbents include other compounds capable of removing the undesired acid components or metal components previously mentioned. Sorbent particle size may vary. Typically, sorbent solid particles will have a median maximum length in the range of 2 μm to 100 μm. In another example, median maximum length will be in the range of 5 μm to 40 μm, or 10 μm to 15 μm.
Application location of the high volumetric flow air, sorbent air, and sorbent may vary along the ductwork. For example, when combustion systems include an air heater, e.g. air heater 50, the application by at least one BNLS may include application into an area of the ductwork having a flue gas temperature in the range of 550° F. and 850° F., and being located downstream of heat-transfer-to-water zone 28 and upstream of air heater 50. In another example of a combustion system having an air heater, application may be to an area of the ductwork having a flue gas temperature in the range of 250° F. and 450° F., and being located downstream of air heater 50 and upstream of the particle capture device 30. In some embodiments, e.g. when the BNLS is applying downstream of an air heater, methods may additionally include heating the high volumetric air to an amount sufficient to promote calcination of the sorbent during or after transport or during or after injection. Heating may be achieved using recycled flue gas, an inline heater, air heater exit air, preheated combustion air, etc. The amount of temperature increase may vary depending on the calcination temperature and the temperature of the high volumetric air supply, e.g., increases in the range of 50° F. to 600° F. may be desired.
In some examples, application will also occur in combustion systems not having an air heater. Application in these examples may include application by at least one BNLS in an area having a flue gas temperature in the range of 250° F. and 850° F., and being downstream of a heat-transfer-to-water zone and upstream of a particle capture device.
The exit of the injection device, e.g. either or both of exit 36a of the high volumetric flow air nozzle and exit 38a of the transport nozzle, is positioned at location P relative to the inner surface 26a of the ductwork. P can be, for example, ±10 inches, ±5 inches, or ±1 inches relative to the inner surface of the ductwork. In the example shown, the exit of the injection device does not extend inwardly of inner surface of the ductwork. Extending the nozzle into the ductwork will generally decrease the chemical utilization.
Further, it is clear from
Using systems and methods disclosed herein, Applicants believe any number of improvements in the art may be achievable. For example, the problems associated with lance heat exposure, e.g. warping, clogging, increased maintenance, going off-line, should be significantly improved as various systems and methods do not require penetration into the ductwork. Further, Applicants' systems and methods should decrease pressure drop relative to lance systems. Further, various systems and methods disclosed herein overcome the vertical-requirement design constraints of lance systems, thereby allowing for injecting in an increased number of locations and/or increased freedom of ductwork design.
Numerous characteristics and advantages have been set forth in the foregoing description, together with details of structure and function. The present inventions, however, is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts, within the principle of the present inventions.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein, and every number between the end points. For example, a stated range of “1 to 10” should be considered to include any and all subranges between (and inclusive of) the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more, e.g. 1 to 6.1, and ending with a maximum value of 10 or less, e.g., 5.5 to 10, as well as all ranges beginning and ending within the end points, e.g. 2 to 9, 3 to 8, 3 to 9, 4 to 7, and finally to each number 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 contained within the range.
It is further noted that, as used in this specification, the singular forms “a,” “an,” and “the” include plural referents unless expressly and unequivocally limited to one referent.
This patent application claims the benefit of Provisional Application No. 61/532,378, filed Sep. 8, 2011, which is hereby incorporated in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61532378 | Sep 2011 | US |
