Systems and methods for mixing recycled combustion ash with slaked lime and water.

Abstract

A mixer (18) for mixing recycled ash from solid fuel combustion with slaked lime and water, and feeding the mixture into a desulfurization reactor (20). The mixer (18) includes a shell (19) having a front wall (40), two outer vertical side walls (41), a rear wall (42), a top (44), and a bottom (46). The top (44) includes a feed chute (50) configured for product entry and addition to the mixer (18), and the front wall (40) includes an opening (56) for product mixture exit. The mixer (18) also includes a rotatable vertical shaft (30) having an impeller (32) having a plurality of blades (34) arranged on the same horizontal plane on the vertical shaft (30) and equidistantly distributed around the periphery of the vertical shaft (30). The mixer (18) also includes a vertical wall (48) disposed within the housing (19) to form a mixing area (52) and a feed area (54) operatively connected to an opening (56) of the front wall (40).

Description

Technical Field

[0001] As described herein, the embodiments generally relate to systems and methods for mixing particulate materials and liquids, particularly systems and methods for mixing water and absorbent materials that react with gaseous contaminants in flue gas, and that the water and absorbent materials are introduced into the gas in a moist state during flue gas purification in order to convert the gaseous contaminants into separable dust. Background Technology

[0002] A boiler typically consists of a furnace in which fuel is burned to generate heat, thereby producing steam. The combustion of fuel produces heat energy, or heat, which is used to heat and evaporate a liquid, such as water, that produces steam. The generated steam can then be used to drive a turbine to generate electricity or to provide heat for other purposes. Fossil fuels such as pulverized coal and natural gas are commonly used in many boiler combustion systems. However, when fuel is burned to generate heat, soot and flue gases containing pollutants are formed.

[0003] When gaseous pollutants such as sulfur dioxide are to be separated from flue gas, the gas is conducted through a contact reactor. In the contact reactor, particulate absorbent material, reacting with the gaseous pollutants, is introduced into the flue gas in a moist state to convert the pollutants into separable dust. The flue gas is then conducted through a dust separator, where the dust is separated from the flue gas, and the purified flue gas is discharged from the dust separator. A portion of the separated dust is directed to a mixer, where it is mixed with and moistened with water, and then recycled as absorbent material by being introduced into the flue gas along with added fresh absorbent. Quicklime (calcium hydroxide) is generally used as the fresh absorbent.

[0004] One type of existing mixer has a mixer container with a rear end and a front end, wherein the inlet is located in the rear end and the outlet is located in the front end. When used as a mixing device for mixing the aforementioned absorbent material and water, the front end of the container is inserted into a flue gas channel through which flue gas containing gaseous pollutants is conducted. The outlet, also located in the flue gas channel, is an overflow device formed by the lateral sidewall of the container portion inserted into the channel being lower than the container portion located outside the channel. However, the container protruding into the flue gas channel can cause turbulence in the airflow therein and make it difficult to achieve a uniform distribution of the wetting material across the channel cross-section, especially in the case of a large cross-sectional area.

[0005] Another type of conventional mixer employs an elongated mixing vessel having: two transverse sidewalls and being arranged substantially horizontally along its longitudinal extension; an inlet for introducing particulate material into the vessel; a liquid jetting device for spraying liquid onto the particulate material in the vessel; a stirrer within the vessel comprising at least one rotating shaft extending longitudinally in the vessel, and a plurality of axially spaced disks mounted at an angle on the rotating shaft, the shaft extending through the center of these disks; an outlet for discharging the material mixed with the liquid from the vessel; and a fluidization device suitable for fluidizing a specific material in the vessel during mixing operations. While such a mixer may be effective for its intended purpose, its width can be large, and specific configurations are required to ensure uniform material distribution. In particular, horizontal-axis mixers with rotating disks or blades have very limited mixing performance in directions parallel to the width of the mixer. As a result, incoming recycled products or reagents must typically be fed uniformly along the width of the mixer. Therefore, in general, the width of these feeders must be equal to the width of the mixer, making them relatively large.

[0006] Furthermore, current mixer configurations have consistently presented challenges in increasing the water-to-product ratio. For example, the maximum moisture content, such as 0-3%, is limited depending on the fuel type and the nature of the recycled product to avoid agglomeration, granulation, clogging, and buildup in the mixer. These difficulties appear to stem from the physical or chemical properties of the dust. Some types of dust spontaneously agglomerate upon the addition of water due to the agglomerative properties of their particle surfaces. When materials agglomerate and clump together, convective mixing is no longer sufficient to achieve a randomly ordered mixture. Relatively strong interparticle forces form clumps that are not broken up by the gentle conveying forces in a convective mixer. Additionally, the chemical composition of the dust, such as dust containing calcium chloride, influences rapid agglomeration and pellet formation. This can result in anything from easily breakable small, soft agglomerates to variable-sized, hard lumps (granules). Therefore, the distribution of water nozzles along the mixer to ensure the most uniform distribution of added water without agglomeration has become a design requirement.

[0007] There is a need for a mixer that provides improved mixing of fly ash, quicklime, and water, and ensures that the mixed product is fed uniformly and homogeneously into the reactor conduit, without being limited by some of the known mixer configurations. Summary of the Invention

[0008] In one embodiment, this document describes a method for mixing recycled ash from solid fuel combustion with slaked lime and water and feeding the mixture into a desulfurization reactor. The method includes: guiding the recycled ash, slaked lime, and water via a feed chute to a mixer having a shell, the shell having a front wall, two outer vertical sidewalls, a rear wall, a top, and a bottom, and the front wall including an opening for the mixture product to exit the mixer; rotating a rotatable first vertical shaft having at least one impeller at a first selected speed in a first direction, the at least one impeller including a plurality of first blades disposed on the first vertical shaft in the same horizontal plane, the plurality of first blades of the at least one impeller being distributed around the periphery of the first vertical shaft, the blades having shear contact with the mixture to increase shear force and prevent agglomeration and pellet formation in the mixture when the mixture has a selected moisture content; and increasing the residence time of the mixture in a mixing region formed by vertical walls disposed within the shell, the mixing region including one or more vertical shafts. The method further includes forming a feed region within the housing using a vertical wall, the feed region being operatively connected to an opening in the front wall, and providing an opening below the vertical wall between the vertical wall and the bottom of the mixer; fluidizing the mixture in at least the feed region using a fluidization mechanism to increase the fluidity of the mixture, the fluidization including guiding gas or air from the bottom of the housing into the mixture; and guiding the mixture to the opening.

[0009] In one embodiment, this document describes a mixer for mixing recycled ash from solid fuel combustion with slaked lime and water, and feeding the mixture into a desulfurization reactor. The mixer includes a shell having a front wall, two outer vertical side walls, a rear wall, a top, and a bottom. The top includes a feed chute configured for product entry and addition to the mixer, and the front wall includes an opening for product mixture exit. The mixer also includes a rotatable vertical shaft with an impeller having a plurality of blades arranged on the vertical shaft in the same horizontal plane and equidistantly distributed around the periphery of the vertical shaft. The mixer further includes: a vertical wall disposed within the shell to form a mixing region and a feed region operatively connected to the opening in the front wall; and a fluidization mechanism to increase the flowability of the mixture, the fluidization including guiding gas or air from the bottom of the shell into the mixture at least in the feed region.

[0010] In another embodiment, this document also describes a system for treating flue gas and mixing recycled ash from solid fuel combustion with quicklime and water, and feeding the mixture into a desulfurization reactor. The system includes a facility system comprising a combustion system for burning fuel to form flue gas and ash, and a flue gas treatment system operable to provide heated, acid-rich flue gas for semi-dry flue gas desulfurization. This flue gas treatment system includes a reactor for reacting the acidic flue gas with quicklime under humidified conditions, and a particulate collection device operable to separate gaseous pollutants from particulate matter that generates captured dust while directing the flue gas to a chimney for disposal. The system also includes a mixer for mixing recycled ash from solid fuel combustion with quicklime and water, and feeding the mixture into the desulfurization reactor. The mixer includes: a housing comprising a front wall, two outer vertical side walls, a rear wall, a top, and a bottom, the top including a feed chute configured for product entry and addition to the mixer, and the front wall including an opening for the mixed product exiting the mixer; one or more rotatable vertical shafts having at least one impeller including a plurality of first blades disposed on the vertical shaft in the same horizontal plane, the plurality of first blades of the at least one impeller being equidistantly distributed around the periphery of the vertical shaft, the blades having shear contact with the mixture to increase shear force and prevent agglomeration and pellet formation in the mixture when the mixture has a selected moisture content; and a vertical wall disposed within the housing to form a mixing region having one or more vertical shafts and a feed region operatively connected to the opening of the front wall, the inner vertical wall being operable to increase the residence time of the mixture in the mixing region and prevent bypass, the vertical wall including an opening below the vertical wall between the vertical wall and the bottom of the mixer. The system also includes a fluidization mechanism to increase the fluidity of the mixture, which includes guiding gas or air from the bottom of the housing into the mixture, at least in the feed area.

[0011] Additional features and advantages are achieved through the technology disclosed herein. Other embodiments and aspects of this disclosure are described in detail herein. For a better understanding of the advantages and features of this disclosure, please refer to the specification and accompanying drawings. Attached Figure Description

[0012] Referring to the accompanying drawings, the described embodiments can be better understood by reading the following description of non-limiting examples, in which:

[0013] Figure 1 This is a simplified schematic diagram of a boiler system with a flue gas handling system according to one embodiment;

[0014] Figure 2 This is a partial cross-sectional view of a reactor and mixer according to one embodiment;

[0015] Figure 3A This is a partial perspective view of a mixer according to one embodiment;

[0016] Figure 3B According to one embodiment Figure 3A A partial exploded perspective view of the mixer;

[0017] Figure 3C This is a partial perspective view of the mixer shaft, impeller, and blades according to one embodiment;

[0018] Figure 4A This is a partial perspective view of a mixer according to one embodiment;

[0019] Figure 4B According to one embodiment Figure 4A Another partial perspective view of the mixer; and

[0020] Figure 5 This is a flowchart illustrating a method, according to one embodiment, of mixing recycled ash from solid fuel combustion with slaked lime and water and feeding the mixture into a desulfurization reactor. Detailed Implementation

[0021] The exemplary embodiments described herein will be referenced in detail below, with examples of the exemplary embodiments shown in the accompanying drawings. Where possible, the same reference numerals used in all the drawings refer to the same or similar parts. While the various embodiments described herein are applicable to steam generation systems including combustion systems, such as pulverized coal boilers that form flue gas, such references are generally for illustrative purposes only. Other systems may include other types of facilities that generate flue gas, including but not limited to chemical facilities, steel facilities, power generation facilities, and boilers, furnaces, and flame heaters utilizing a variety of fuels including but not limited to coal, oil, and natural gas. For example, the envisioned boilers include, but are not limited to, T-type combustion and wall-fired pulverized coal boilers, circulating fluidized bed (CFB) and bubbling fluidized bed (BFB) boilers, coal feeder boilers, suspension burners for biomass boilers, including controlled circulation, natural circulation, and supercritical boilers, and other heat recovery steam generator systems.

[0022] Figure 1A simplified diagram of a facility system 10 including a boiler 12, the boiler having a combustion system 11 and a flue gas treatment system (generally shown as 14). As described herein, embodiments relate to a combustion system 11 that can be used in the boiler 12, which generates flue gas along with the burning fuel. The flue gas is treated in the flue gas treatment system 14, and more specifically, in a semi-dry flue gas desulfurization system 16 for treating heated, acid-rich flue gas. If desired, the flue gas treatment system 14 includes a hydrator 17, a mixer 18, a reactor 20, and a particulate collector 22 (typically a fabric filter, but an electrostatic precipitator may also be used). In the reactor 20, the acidic flue gas reacts with lime / slaked lime under humidified conditions. Once combined with particulate matter, the gaseous contaminants are removed from the flue gas in the downstream particulate collector 22, where they are captured on, for example, filter bags or electrostatic grids. During purification in the collector 22, dust falls into a hopper, where it is fed by a feeder 24 ( Figure 2 The collected particles are then returned to mixer 18. Fresh quicklime and water are added to the process. The collected particulate matter is also separated for processing by particulate collector 22. Finally, the purified flue gas is directed to chimney 30 for discharge into the surrounding environment.

[0023] It should be understood that mixer 18 does not always need to be connected to hydrator 17. Generally, there are three types of reagents: i) highly alkaline fly ash; ii) hydrated lime, i.e., Ca(OH)2; or iii) quicklime such as CaO. In the case of quicklime, hydrator 17 is required, and in this case, hydrator 17 can be directly connected to mixer 18. If hydrated lime, which is also powder, is used, it can be added to the section of mixer 18 located between feeder 50 and mixer 18 via various techniques (e.g., a blower feeder), or directly upstream of the recycling feeder. A key point to note is the difficulty mixer 18 faces based on water and dust, i.e., increased moisture content. Therefore, in one embodiment, mixer 18 of the recycled product can be connected to quicklime hydrator 17.

[0024] Furthermore, it is worth noting that the flow rate of hydrated lime accounts for only a small fraction of the total recycled product in mixer 18 (e.g., approximately 1% to a few percent). Of course, the actual percentage used varies depending on the process and materials employed.

[0025] Now for reference Figure 2In desulfurization applications, mixer 18 is located below recirculation feeder 24 and between hydrator 17 and reactor 20. Fresh slaked lime is introduced into mixer 18 from hydrator 17. The slaked lime is mixed with recirculated product (flue gas particles) from feeder 24 and water from sprayers (one or more) (not shown). In mixer 18, the product is mixed until it reaches the horizontal level of the upper edge of disperser plate 23, after which the product flows over disperser plate 23 into reactor 20, where it is entrained in the flue gas. In desulfurization operations, the added water typically wets the product. The added water also provides an increase in relative humidity to improve the removal of acidic gases and provides evaporative cooling of the flue gas in reactor 20. Generally, it is important to distribute the water evenly in the product to avoid dust agglomeration in mixer 18 and to achieve a uniform temperature distribution as cooling continues in reactor 20.

[0026] However, in current systems, to avoid granulation, the maximum water content that can be added to the product ratio of the mixture and slaked lime is limited to, for example, 0-3%, depending on the fuel type and the nature of the recycled product. Therefore, the aim of some described embodiments is to improve mixer performance so that higher moisture contents (e.g., about 5-7%) are possible. The increased moisture content makes the desulfurization system 16 ( Figure 1 This method can achieve the same effective flue gas cooling with a smaller amount of recirculated dust, or achieve a greater temperature reduction in the flue gas with the same amount of dust. More specifically, the increased moisture content facilitates the reactivation of recirculated solid products and reagents used for acid gas reduction, and enhances the dust's ability to reduce flue gas temperature. Furthermore, by increasing the moisture content, dust recirculation and pressure drop in reactor 20 can be reduced by ~50% and ~35%, respectively.

[0027] Furthermore, some embodiments ensure a uniform and homogeneous product feed to reactor 20 and prevent agglomeration of dust during the moderate residence time in mixer 18. Reducing the pressure drop in reactor 20 is directly related to cost savings in operating system 10. For example, in one embodiment, when based on 310 kNm... 3 With a reactor flue gas capacity of / h, an electricity price of 50 USD / MWh, and an annual operating period of 8000 Hr, assuming a 4% interest rate and a lifespan of 15 years, the 35% pressure drop in reactor 20 directly translates into a present value cost saving of $292,000.

[0028] Turn now Figures 3A-4B These figures depict multiple embodiments. Figures 3A-3C A perspective partial sectional view of a mixer 18 according to one embodiment is depicted, wherein Figure 3B It shows Figure 3A The local decomposition diagram, and Figure 3C A partial view of the mixer shaft, impeller, and blades is shown. Figure 4A A partial perspective sectional view of a mixer 18 having two axes according to another embodiment is depicted. Figure 4B A cross-sectional view of a mixer 18 with two shafts is depicted. In some embodiments, the mixer includes a housing generally shown as 19 that provides an improved convection mixing mechanism during operation using one or more vertical shafts 30 having vertical impellers 32 with blades 34 arranged on the same horizontal plane on the vertical shafts 30, which differs from the horizontal rotating shafts in known systems.

[0029] For example, advantageously, in one configuration, a vertical shaft mixer 18 of one embodiment, having a single impeller 32 with two blades 34 at a 45° angle to an axis 18 rotating at 20 rpm, offers superior performance compared to a conventional horizontal shaft mixer (with six pairs of blades also at a 45° angle to the axis rotating at 40 rpm). In conventional horizontal shaft mixers, diffusion is the dominant mixing mechanism, resulting in a Peke number (Pe) less than 1 regardless of the impeller configuration. Conversely, in the vertical shaft mixer 10 of the described embodiment, convection is the dominant mixing mechanism, with the Peke number varying between 24 and 50. The Peke number is a measure of the relative importance of advection relative to diffusion, where a large value indicates a distribution flow dominated by advection, and a small value indicates a diffusion flow. Because the particle diffusivity and grain temperature are similar in both mixers, and the Peckley number in the vertical axis mixer is 2 to 3 orders of magnitude higher than that in the horizontal axis mixer, the vertical axis mixer exhibits significantly more pronounced convective mixing than the horizontal axis mixer.

[0030] Refer again Figures 3A-4B It depicts a structure with a vertical axis ( Figure 3A and Figure 3B ) and two vertical axes ( Figure 4A and Figure 4B The mixer 18 is an approximate exemplary geometry. The mixer 18 generally includes a front wall 40, two outer vertical sidewalls 41, a rear wall 42, and a top 44 and a bottom 46. The top 44 includes a feed chute 50 for product entry and addition to the mixer 18. The front wall 40 includes an opening 56 for the mixed product to exit the mixer 18 and reach the reactor 20 and the dispersing plate 23. The rear wall is not entirely semi-cylindrical; its radius substantially corresponds to the radius of the impeller 32 and blades 34, but provides clearance for their rotation. The mixer 18 has two regions separated by an inner vertical wall 48; a mixing region (generally shown as 52), designed to have one or more vertical axes 30 depending on the size and capacity of the mixer 18. The mixer 18 also has a feed region (generally shown as 54) connected to the dispersing plate 23 of the reactor 20. Figure 2 A). Fluidization is used to increase the flowability of the product and to the disperser plate 23 ( Figure 2 A) Provide a uniform feed, as further described herein. Fluidization may be employed in the mixing region 52 or the feed region 54, or both. In one embodiment, fluidization is employed at least in the feed region. Details of the fluidization operation will be discussed below.

[0031] In one embodiment, the feed chute 50 is positioned vertically above the mixing zone 52, but its exact location is not critical. A vertical wall 48 is provided between the mixing zone 52 and the feed zone 54 to provide separation between the two zones 40, 42, and to increase the actual residence time of all products and prevent bypassing, which would result in the recycled product being fed directly into the reactor 20. In one embodiment, the vertical wall 48 is fixed to vertical sidewalls 41 and 42 and extends downward from top 44 to bottom 46. An opening below the vertical wall 48 (generally shown as 49) allows the mixed product to move from the mixing zone 52 to the feed zone 54 and exit through an opening 56 in the front wall 40 to reach the reactor 20.

[0032] continue Figures 3A-4B In the mixing region 52, one or more vertical shafts 30 may have one or more impellers 32, each impeller 32 including a plurality of blades 34. In one embodiment, each shaft 30 may include any actual number of impellers 32 arranged as needed along the vertical length of each shaft 30, but in one embodiment, 1-4 impellers 32 are expected. Each impeller 32 may include a plurality of blades 34 evenly distributed around the periphery of the shaft 30 to ensure a balance of forces and loads on the blades 34 and the shaft 30 during mixing. In one embodiment, depending on the nature of the dust, each impeller 32 may employ any number of blades 34. Although in one embodiment, 2, 3, or 4 blades are expected. In one embodiment, as Figure 3A and Figure 3B As shown, the mixer 18 is depicted as having a single shaft 30 with two or three impellers 32, each impeller having two blades 34. In another embodiment, as... Figure 4A and Figure 4B As shown, the mixer 18 is shown to have two shafts 30, each shaft having two impellers 32, and each impeller having two blades 34.

[0033] In some embodiments, although the mixer 18 is described as a mixing region (generally shown as 52) and a feed region 54 with one or more vertical shafts 30 separated by a vertical wall 48, the mixer 18 is not limited to this configuration. In fact, impellers 32 and blades of one or more vertical shafts 30 may extend below the vertical wall 48 into the feed region 54. This configuration, combined with the fluidization described herein, facilitates the mixing and dispersion of agglomerates. Figure 2 A and Figure 3A An example of this configuration is depicted.

[0034] In the embodiments, the mixer 18, having a vertical shaft 30 and rotating blades 34, provides convective mixing in all directions, particularly in the direction parallel to the width of the mixer (e.g., the lateral direction), providing improved mixing without granulation. Furthermore, the mixer 18 of the described embodiments provides greater shear forces than conventional structures to break up agglomerates. Static blades or baffles 36 between the impellers 32 and blades 34 enhance these shear forces and eliminate the possibility of agglomerate formation. The static blades 36 further contribute to breaking up agglomerates by grinding the product between the static blades 36 and rotating blades 34 located on different impellers 32. The static blades 36 provide a high relative velocity between one or more rotating blades 34 and the product in the mixer 18.

[0035] In one embodiment, the stationary blade 36 is disposed on a horizontal plane, adjacent to one or more impellers 32. This proximity ensures that any agglomerates are subjected to high shear forces to provide improved mixing. It should be understood that although the stationary blade 36 is described as horizontal for one embodiment, such description is merely illustrative. The blades 34 and the stationary blade 36 can be configured in any manner known in the art and described herein.

[0036] In an embodiment of mixer 18, the angle of the blade relative to the rotational tangent direction of the vertical axis can be obtuse or acute. The blade angle, denoted as β (Beta), can vary from 10 degrees to 170 degrees in the horizontal plane; an obtuse angle of approximately 120 degrees to approximately 150 degrees is preferred, but other angles are of course possible. For example, as... Figure 3A , Figure 3B , Figure 3C , Figure 4A As shown in 4B, blade 34 is depicted at an obtuse angle of approximately 150 degrees to the horizontal plane, as... Figure 3C As shown. In another embodiment, the blade shape, cross-section, geometry, etc., can be variable, i.e., variable geometry along the radius / length or width of the blade. In one embodiment, the blade can be tapered, twisted, swept airfoil, etc., or have a variable blade angle along the radius of blade 34. One advantage of variable-angle or twisted blades is that the total torque on the shaft becomes more uniform or lower, especially for larger blades. Furthermore, the load on the blades is more uniform radially. In yet another embodiment, the blades 34 and / or static blades of impeller 32 can have sharp leading edges to help shear and break up any agglomerates in the mixture.

[0037] In another embodiment, to further enhance the mixing advantage of the vertical shaft 30 mixer 18, a plurality of impellers 32 are provided. The rotation directions of two adjacent shafts 30 may be the same or opposite. Preferably, but not necessarily, they are in the same direction, depending on the properties of the material in the mixer 30 and its moisture content. In such embodiments, the impellers 32 of the first shaft 30 and the impellers 32 of the second shaft 30 are vertically displaced on their respective vertical shafts 30, such that they rotate in different horizontal planes but do not interfere with each other in the same vertical plane. For example, an impeller 32 connected to one vertical shaft 30 may be vertically located between / near one or two impellers 32 connected to adjacent shafts 30. In this case, it should be understood that the distance between the two adjacent shafts 30 is just greater than the impeller radius plus the shaft radius.

[0038] The first vertical axis 30 and the second vertical axis 30 are laterally offset by a sufficient distance to avoid interference between the blades 34 on the first vertical axis 30 and the blades 34 on the second vertical axis 30, or between the second vertical axis 30 itself. In this embodiment, the relative velocity generated between the passing blades 34 on the relatively rotating impeller 32 and the material (e.g., dust) in the mixer 18 becomes greater, further increasing the shear force. Advantageously, compared to embodiments that do not employ or use static blades 36 located between the impeller 32 and the rotating blades 34, the described embodiment facilitates mixing with increased speed and shear force presented to the mixed products. In yet another embodiment, the impeller 32 on the same vertical axis 30 may rotate in opposite directions, thereby increasing the shear force to improve mixing between products.

[0039] Advantageously, in this embodiment, the mixer 18 does not require the uniform addition of quicklime, recycled dust, and water. The ash feeder 17 for the quicklime and the recycling in conventional mixer configurations are typically configured to be the same width as the mixer to ensure uniform distribution of the lime, water, and recycled dust. Similarly, as previously mentioned, a large number of water nozzles are generally also uniformly distributed to increase water distribution. The mixer 18 of the described embodiment employs a feed chute 50, which is a portion of the total width of the mixer 18. In one embodiment, the feed chute 50 is configured to be approximately 20% to 100% of the length of the mixer 18, and preferably in the range of approximately 40% to 60%, depending on the application, recycling flow rate, moisture content, etc. Furthermore, only a single water nozzle 70 is used per meter of length to add water to the quicklime. This configuration significantly increases the flexibility of the mixer 18 design and eliminates the complexity and limitations of conventional configurations. In one embodiment, a single water nozzle 70 is used for each vertical axis 30. In another embodiment, the diameter of the impeller 32 is approximately 0.85 meters to 1.15 meters, and can vary between 0.5 meters and 1.5 meters.

[0040] In this way, the number of water nozzles required can be reduced by 40% to 100% compared to conventional configurations, while achieving the increased product moisture content described herein. In one embodiment, the position of the water nozzle 70 does not need to be fixed as shown in the two embodiments. In some embodiments, it may be desirable to spray water directly onto the descending recycled product and avoid spraying it onto the mixer housing, shaft 30, one or more impellers 32, stationary blades 36, etc., to avoid deposition and buildup on these surfaces. As an example, as described herein, in a system with a mixing feeder of the described embodiments, the amount of recycled dust is expected to be reduced by 50%, while still achieving comparable cooling due to the addition of water and / or approximately doubling of the moisture content. Therefore, the pressure drop in the reactor and the overall power consumption of the system are reduced.

[0041] In one embodiment, the vertical shaft 30 and the blades 34 of the mixer are rotated by a drive mechanism 60 and a motor 62. The drive mechanism 60 and motor 62 are vertically mounted at or above the top 44 at the axial end of the shaft 30, although other drive schemes and configurations are possible. Advantageously, this configuration ensures that the motor 62 and drive mechanism 60 are isolated from the harsh environment of the mixer 18. In one embodiment, a single motor 62 may be used with a drive mechanism 60 configured to drive multiple vertical shafts 30. In another embodiment, a motor 62 and drive mechanism may be used for each vertical shaft. In one embodiment, one or more vertical shafts 30 of the mixer 18 may operate at different speeds in either direction. In one embodiment, the mixer 18 may include a constant-speed integral geared motor assembly for the motor 62 and drive mechanism 60. In one embodiment, the motor 62 and drive mechanism 60 may be operated to operate at a substantially constant speed. However, in another embodiment, the mixer may employ variable-speed drive control to save energy by operating at higher or lower speeds where possible. In another embodiment, the motor 62 and drive mechanism 60 can provide a self-cleaning operating mode, facilitated by the described vertical shaft 30 and impeller 32 mixer 18 through high-speed dry recirculation operation via the mixer 18 for a selected duration. In one embodiment, a duration of 2-3 hours is sufficient to provide cleanliness. For example, in one embodiment, it is possible to “dry” operate the mixer at higher rpm (e.g., 2-3 times that of normal operation) of approximately 150-240 rpm without exceeding the torque or maximum rated power of the geared motor 62 and / or drive mechanism 60. It should be understood that conventional mixers, such as paddle or rotary mixers, are not easily operated with this self-cleaning feature. Therefore, in this embodiment, operating costs are reduced and operational availability is improved compared to existing mixers.

[0042] Certain embodiments of the vertical shaft mixer 10 offer numerous mechanical advantages that extend the mixer's service life. In particular, the vertical shaft 30 reduces the load on the bearings and seals, and reduces the size of the mixer in all directions. The embodiments also significantly reduce size and weight by approximately 10% to 50%, especially in width, and avoid immersing the seals and bearings in the mixed products.

[0043] In another embodiment, the mixer 18 includes an air / gas / flue gas distributor (generally shown as 64) with an inlet port 65 at the bottom 46 of the mixer 18, configured to aid in the fluidization of the product in the mixer 18. In one embodiment, the bottom 46 of the housing 19 includes a manifold or chamber 66 and a distribution structure 67 for preferably uniformly distributing air / gas / flue gas into at least the feed region 54. The additional air / gas / flue gas increases the flowability of the product and uniformly guides the mixed final product to the reactor 20 along the feed side of the mixer 18 and the width of the conduit leading to the reactor 20 and the dispersion plate 23. In one embodiment, the distribution structure 67 may be a plurality of tubes with perforations. Another embodiment employing fluidized air is a distribution structure 67 formed by a breathable fabric or permeable cloth covering the bottom, which distributes air / gas / flue gas into the feed region 54 and / or the mixing region 52. In one embodiment, the bottom 46 is configured in two parts, one part below the mixing zone 52 and the other part below the feed zone 54. In one embodiment, the portion of the bottom 46 below the feed zone 54 is an air distributor 64, which includes an inlet port 65, manifold, or chamber 66 for providing fluidized air as described herein. If fluidization is also used in the mixing zone 52, the portion of the bottom 46 below the mixing zone 52 may be a solid wall or an air distributor 65 as described herein. Using fluidization under the mixing zone 52 is an option that may be adopted depending on the dust properties, moisture content, etc. Figure 3A , Figure 3B , Figure 4A and Figure 4B In this process, the air / gas / flue gas distributor 64 provides fluidization in the mixing zone 52 and the feed zone 54.

[0044] Advantageously, due to the improved functionality of the mixer 18, a wide variety of hydrators 17 can be easily connected to it. In one embodiment, the hydrators 17 are directly connected without the need for uniform distribution of slaked lime along the width of the mixer 18, at least due to the effective lateral mixing along the vertical axis 30. This facilitates the connection of the described mixer 18 to a greater variety of hydrators with different connection geometries without being limited by the existing configurations' descriptions of mixing and moisture content.

[0045] The mixer 18 of the described embodiment improves the mixing of recycled product, fresh quicklime, and water into a homogeneous mixture. Furthermore, the mixer 18 of the embodiment eliminates the traditional requirement for uniform product feeding and also reduces or eliminates the risks of buildup in the mixer 18, the formation of pellets in the mixed product, and "clogging" of the fresh quicklime. It should be understood that eliminating the need for a recycling feeder with the same width as the mixer 18 (which could be as large as a 4-meter-long rotating shaft, subject to high torque, high bending moment, and fatigue) reduces or eliminates system design and operational limitations.

[0046] Figure 5 A method 200 is described according to one embodiment of mixing recycled ash from solid fuel combustion with slaked lime and water and feeding the mixture into a desulfurization reactor. Method 200 begins by guiding the recycled ash, slaked lime, and water via a feed chute 50 to a mixer 18 having a housing 19 having a front wall 40, two outer vertical sidewalls 41, a rear wall 42, a top 44, and a bottom 46. The front wall 40 includes an opening 56 for the mixed product to exit the mixer 18, as shown in process step 210. As shown in process step 220, method 200 includes rotating one or more rotatable vertical shafts 30 having at least one impeller 32 at a selected speed. The at least one impeller 32 includes a plurality of first blades 34 disposed on the vertical shaft 30 in the same horizontal plane, the plurality of first blades 34 being equidistantly distributed around the periphery of the vertical shaft 30. The blades 34 have shear contact with the mixture to increase shear force and to prevent agglomeration and pellet formation in the mixture when the mixture has a selected moisture content. In process step 230, method 200 further includes increasing the residence time of the mixture in a mixing region 52 formed by a vertical wall 48 disposed within the housing 19, the mixing region 52 including one or more vertical shafts 30. In process step 240, method 200 continues to utilize the vertical wall 48 to form a feed region 54 within the housing 19, the feed region 54 being operatively connected to an opening 56 in the front wall 40. As shown in process step 250, an opening is provided below the vertical wall 48 between the vertical wall 48 and the bottom 46 of the mixer 18. It should also be understood that blades 34 and impellers 32 may include portions extending from the mixing region 52 as described herein to the feed region 54. Method 200 may optionally include enhancing the shear force applied to the mixture and reducing the formation of agglomerates by employing static blades or baffles disposed in the mixing region of the housing, as shown in process step 260. Method 200 continues to optionally maintain the moisture content of the recycled ash, hydrated lime and / or mixture at at least one of about 3%, or 4%, or 5%, or 6% and 7%, as shown in process step 270.

[0047] It should be understood that although the steps of method 200 are described in a specific order, this is not mandatory, and the order is provided merely to illustrate the embodiments. Some steps may be discussed, and some may be performed in a different order. In addition to savings in operating costs, some of the described embodiments of the power generation system offer capital cost savings in the design and construction of new facilities or mixers. In particular, in the embodiments, it is possible to design / plan equipment with constraints for simpler mixer designs while providing products with higher moisture content. Furthermore, the embodiments provide capital and recurring cost savings on retrofitting existing facilities or flue gas treatment systems. In particular, it is possible to improve existing equipment to reduce mixing and desulfurization costs.

[0048] In one embodiment, a method is provided for mixing recycled ash from solid fuel combustion with slaked lime and water and feeding the mixture into a desulfurization reactor. The method includes guiding the recycled ash, slaked lime, and water via a feed chute to a mixer having a shell, the shell having a front wall, two outer vertical sidewalls, a rear wall, a top, and a bottom, and the front wall including an opening for the mixture product to exit the mixer; rotating a rotatable first vertical shaft having at least one impeller at a first selected speed in a first direction, the at least one impeller including a plurality of first blades disposed on the first vertical shaft in the same horizontal plane, the plurality of first blades of the at least one impeller being distributed around the periphery of the first vertical shaft, the blades having shear contact with the mixture to increase shear force and prevent the formation of agglomerates and pellets in the mixture when the mixture has a selected moisture content; and increasing the residence time of the mixture in a mixing region formed by vertical walls disposed within the shell, the mixing region including one or more vertical shafts. The method further includes forming a feed region within the housing using a vertical wall, the feed region being operatively connected to an opening in the front wall, and providing an opening below the vertical wall between the vertical wall and the bottom of the mixer, fluidizing the mixture in at least the feed region using a fluidization mechanism to increase the fluidity of the mixture, the fluidization including guiding gas or air from the bottom of the housing into the mixture and guiding the mixture to the opening.

[0049] In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include forming a rear wall that is at least partially semi-cylindrical, the radius of which substantially corresponds to the radius of the impeller and blades but provides clearance for their rotation.

[0050] In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include vertically positioning a feed chute above the mixing region, wherein the feed chute is a portion of the total length of the mixer.

[0051] In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include a second impeller disposed on a first vertical axis, wherein the second impeller includes a plurality of second blades evenly distributed around the periphery of the first vertical axis.

[0052] In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include enhancing the shear force applied to the mixture and reducing the formation of agglomerates by employing static blades or baffles disposed in the mixing region of the housing.

[0053] In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include adding water to at least one of the recycled ash, slaked lime, and the mixture via water nozzles disposed in the mixing zone.

[0054] In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include employing a single water nozzle per meter of the mixer's length.

[0055] In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include at least one of the following: recycled ash, slaked lime, and mixture, having a selected moisture content of at least 3%, 4%, 5%, 6%, and 7%.

[0056] In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include fluidizing the mixture in the mixing region with a fluidization mechanism to increase the fluidity of the mixture, the fluidization including guiding gas or air from the bottom of the housing into the product.

[0057] In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include controlling the rotational speed of the first vertical axis based at least in part on one of the following: the operating mode of the mixer, the moisture content of the recycled ash, the slaked lime, the mixture, and any of the foregoing.

[0058] In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include rotating a rotatable second vertical shaft having at least one impeller at a second selected speed in a second direction, the at least one impeller comprising a plurality of second blades disposed on the second vertical shaft in the same horizontal plane, the plurality of second blades of the at least one impeller being equidistantly distributed around the periphery of the second vertical shaft, the blades having shear contact with the mixture to increase shear force and prevent agglomeration and pellet formation in the mixture when the mixture has a selected moisture content.

[0059] In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include at least one of a first selected speed being different from a second selected speed and a first direction being opposite to a second direction.

[0060] In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include: a first vertical axis being laterally displaced from a second vertical axis to avoid interference between the blades on the first vertical axis and the second vertical axis or between the blades on the second vertical axis.

[0061] In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include: the impellers of the first shaft and the impellers of the second shaft being vertically displaced on their respective vertical axes such that they rotate in different horizontal planes but the same vertical plane without interference.

[0062] In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include: at least one impeller extending beyond the vertical wall into the feed area.

[0063] In another embodiment, this document also describes a mixer for mixing recycled ash from solid fuel combustion with slaked lime and water and feeding the mixture into a desulfurization reactor. The mixer includes: a shell comprising a front wall, two outer vertical side walls, a rear wall, a top, and a bottom; and a feed chute configured for product entry and addition into the mixer, and the front wall includes an opening for the mixed product to exit the mixer. The mixer further includes: one or more rotatable vertical shafts having at least one impeller, the at least one impeller including a plurality of first blades disposed on the vertical shaft in the same horizontal plane, the plurality of first blades of the at least one impeller being equidistantly distributed around the periphery of the vertical shaft, the blades having shear contact with the mixture to increase shear force and to prevent agglomeration and pellet formation in the mixture at a selected moisture content; and an inner vertical wall disposed within the housing, forming a mixing region having one or more vertical shafts and a feed region operatively connected to an opening in the front wall, the inner vertical wall being operable to increase the residence time of the mixture in the mixing region and prevent bypass, the inner vertical wall including an opening below the inner vertical wall between the inner vertical wall and the bottom of the mixer. The mixer also includes a fluidization mechanism, at least in the feed region, to increase the fluidity of the mixture, the fluidization mechanism guiding gas or air from the bottom of the housing into the mixture.

[0064] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include a rear wall that is at least partially semi-cylindrical, with a radius substantially corresponding to the radius of the impeller and blades, but providing clearance for their rotation.

[0065] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include a feed chute vertically positioned above the mixing region.

[0066] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include a feed chute that is part of the total width of the mixer.

[0067] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include another impeller disposed on one or more vertical shafts, wherein the other impeller includes a plurality of second blades evenly distributed around the periphery of the vertical shaft.

[0068] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include a plurality of second blades comprising a different number of blades than the plurality of first blades.

[0069] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include at least one impeller to provide convective mixing in all directions, particularly providing improved mixing without granulation in the lateral direction.

[0070] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include static blades or baffles disposed in the mixing region of the housing, the static blades being operable to enhance the shear force applied to the mixture and reduce the formation of agglomerates.

[0071] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include an inner vertical wall fixed to at least one of a top and a vertical side wall, and the inner vertical wall extending downward from the top of the housing beyond the bottom, wherein openings allow the mixture to move from the mixing area to the feed area and flow out from openings in the front wall.

[0072] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include a water nozzle operable to add water to at least one of the recycled ash, slaked lime, and the mixture.

[0073] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include a single water nozzle per meter of the mixer length, operable to add water to at least one of the recycled ash, slaked lime, and the mixture.

[0074] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include adding water to at least one of the recycled ash, slaked lime, and the mixture to maintain the moisture content of the mixture at at least one of about 3%, 4%, 5%, 6%, and 7%.

[0075] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include a fluidization mechanism disposed at the bottom of the housing, which is operable to blow air or gas into the mixture to increase the fluidity of the mixture in the mixing region.

[0076] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include controlling the rotational speed of the first vertical axis based at least in part on at least one of the mixer's operating mode, the moisture content of the recycled ash, the slaked lime, the mixture, and any of the foregoing.

[0077] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include a rotatable second vertical shaft that rotates at a second selected speed in a second direction and has at least one impeller, the at least one impeller including a plurality of second blades disposed on the second vertical shaft in the same horizontal plane, the plurality of second blades of the at least one impeller being equidistantly distributed around the periphery of the second vertical shaft, the blades having shear contact with the mixture to increase shear force and prevent agglomeration and pellet formation in the mixture when the mixture has a selected moisture content.

[0078] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include at least one of a first selected speed being different from a second selected speed and a first direction being opposite to a second direction.

[0079] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include a lateral displacement between the first vertical axis and the second vertical axis sufficient to avoid interference between the blades on the first vertical axis and the blades on the second vertical axis.

[0080] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include impellers of a first shaft and impellers of a second shaft vertically displaced on their respective vertical axes such that they rotate in different horizontal planes but the same vertical plane without interference.

[0081] In addition to one or more of the features described above, or as an alternative, further embodiments of the mixer may include at least one impeller extending beyond the inner vertical wall into the feed area.

[0082] In another embodiment, this document also describes a system for treating flue gas and mixing recycled ash from solid fuel combustion with slaked lime and water, and feeding the mixture into a desulfurization reactor. The system includes a facility system and a flue gas treatment system. The facility system includes a combustion system for burning fuel to form flue gas and ash. The flue gas treatment system is operable to provide semi-dry flue gas desulfurization of heated, acid-rich flue gas. The flue gas treatment system includes a reactor for reacting the acidic flue gas with slaked lime under humidified conditions and a particulate collection device operable to separate gaseous pollutants from particulate matter that generates captured dust while directing the flue gas to a chimney for disposal. The system also includes a mixer for mixing recycled ash from solid fuel combustion with slaked lime and water and feeding the mixture into the desulfurization reactor. The mixer includes: a housing comprising a front wall, two outer vertical side walls, a rear wall, a top, and a bottom, the top including a feed chute configured for product entry and addition to the mixer, and the front wall including an opening for the mixed product exiting the mixer; one or more rotatable vertical shafts having at least one impeller including a plurality of first blades disposed on the vertical shaft in the same horizontal plane, the plurality of first blades of the at least one impeller being equidistantly distributed around the periphery of the vertical shaft, the blades having shear contact with the mixture to increase shear force and prevent agglomeration and pellet formation in the mixture when the mixture has a selected moisture content; and a vertical wall disposed within the housing, forming a mixing region having one or more vertical shafts and a feed region operatively connected to the opening of the front wall, the inner vertical wall being operable to increase the residence time of the mixture in the mixing region and prevent bypass, the vertical wall including an opening below the vertical wall between the vertical wall and the bottom of the mixer. Finally, the system includes a fluidization mechanism in at least the feed area to increase the fluidity of the mixture, which guides gas or air from the bottom of the housing into the mixture.

[0083] Finally, it should be understood that system 10 and control unit 150 may include necessary electronics, software, memory, storage devices, databases, firmware, logic / state machines, microprocessors, communication links, displays or other visual or auditory user interfaces, printing devices, and any other input / output interfaces to perform the functions described herein and / or achieve the results described herein. For example, as previously mentioned, the system may include at least one processor and system memory / data storage structures, which may include random access memory (RAM) and read-only memory (ROM). At least one processor of system 10 may include one or more conventional microprocessors and one or more auxiliary coprocessors, such as math coprocessors. The data storage structures discussed herein may include suitable combinations of magnetic, optical, and / or semiconductor memories, and may include, for example, RAM, ROM, flash drives, optical discs, such as compact discs, and / or hard disks or drives.

[0084] Furthermore, a software application that enables the controller to perform the methods or method steps disclosed herein can be read from a computer-readable medium into the main memory of at least one processor. Therefore, embodiments of the invention can execute the methods disclosed herein in real time. As used herein, the term "computer-readable medium" means any medium that provides or participates in providing instructions for execution to at least one processor of the system (or any other processor of the device described herein). Such media can take many forms, including but not limited to non-volatile media and volatile media.

[0085] As used herein, elements or steps listed in the singular and beginning with the word "a" or "an" should be understood to not exclude a plurality of the stated elements or steps, unless expressly stated otherwise. Furthermore, references to "an embodiment" of the described embodiments are not intended to be construed as excluding the existence of additional embodiments that also incorporate the described features. Moreover, unless expressly stated otherwise, embodiments that "comprise," "include," or "have" one or more elements having a particular property may include additional such elements that do not have that property.

[0086] Furthermore, while the dimensions and types of materials described herein are intended to define parameters associated with the described embodiments, they are by no means limiting, but rather exemplary embodiments. Many other embodiments will be apparent to those skilled in the art upon review of the above description. Therefore, the scope of the invention should be determined with reference to the appended claims. Such descriptions may include other examples that would occur to those skilled in the art, and such other examples are intended to be within the scope of the claims if they have structural elements that are not different from the literal language of the claims, or if such other examples include equivalent structural elements that are not substantially different from the literal language of the claims. In the appended claims, the terms “comprising” and “wherein” are used as their concise English equivalents. Furthermore, in the appended claims, terms such as “first,” “second,” “third,” “upper,” “lower,” “bottom,” “top,” etc., are used merely as labels and are not intended to impose numerical or positional requirements on their objects. Moreover, the limitations of the appended claims are not written in a means-plus-function format, nor are they intended to be interpreted in this way, unless and until such claims explicitly use the phrase “means for…” followed by a functional statement without further structure.

Claims

1. A mixer (18) for mixing recycled ash from solid fuel combustion with slaked lime and water, and feeding the mixture into a desulfurization reactor (20), said mixer (18) comprising: Housing (19), the housing comprising: Front wall (40), two outer vertical side walls (41), rear wall (42), top (44) and bottom (46); A feed chute (50) is configured for product entry and addition to the mixer, and the front wall (40) includes an opening (56) for the mixture to exit the mixer (18). A first vertical shaft capable of rotation, the first vertical shaft having a first impeller, the first impeller including a plurality of first blades disposed on the first vertical shaft on the same horizontal plane, the plurality of first blades of the first impeller being equidistantly distributed around the periphery of the first vertical shaft, the plurality of first blades having shear contact with the mixture to increase shear force and to prevent agglomeration and pellet formation in the mixture when the mixture has a selected moisture content; An inner vertical wall (48) is disposed within the housing to form a mixing region (52) having a rotatable first vertical axis and a feed region (54) operatively connected to the opening (56) of the front wall (40). The inner vertical wall (48) is operable to increase the residence time of the mixture in the mixing region and prevent bypass. The inner vertical wall includes an opening below the inner vertical wall (48) between the inner vertical wall (48) and the bottom (46) of the mixer (18). The fluidization mechanism (64) is operable to increase the fluidity of the mixture in at least the feed area (54) by guiding gas or air from the bottom (46) of the housing (19) into the mixture.

2. The mixer (18) according to claim 1, the mixer further comprising a second impeller disposed on the first vertical shaft, wherein the second impeller comprises a plurality of second blades evenly distributed around the periphery of the first vertical shaft.

3. The mixer (18) according to claim 1, the mixer further comprising a static blade or baffle (36) disposed in the mixing region (52) of the housing (19), the static blade or baffle (36) being operable to enhance the shear force applied to the mixture and reduce the formation of agglomerates.

4. The mixer (18) according to claim 1, wherein the selected moisture content of the mixture is in the range of 3% to 7%.

5. The mixer (18) according to claim 1, further comprising a rotatable second vertical shaft rotating in a second direction at a second selected speed, the second vertical shaft having a first impeller comprising a plurality of first blades disposed on the second vertical shaft on the same horizontal plane, the plurality of first blades of at least one first impeller being equidistantly distributed around the periphery of the second vertical shaft, the first blades having shear contact with the mixture to increase shear force and to prevent agglomeration and pellet formation in the mixture when the mixture has a selected moisture content.

6. The mixer (18) according to claim 1, wherein the first impeller extends beyond the inner vertical wall (48) into the feed region (54).

7. A method (200) for mixing recycled ash from solid fuel combustion with slaked lime and water and feeding the mixture therein into a desulfurization reactor (20), the method comprising: The recycled ash, the slaked lime and the water are guided via a feed chute (50) to a mixer (18) having a housing (19) having a front wall (40), two outer vertical side walls (41), a rear wall (42), a top and a bottom (46), and the front wall (40) including an opening (56) for the mixture to exit the mixer (18). A first vertical shaft having a first impeller is rotated in a first direction at a first selected speed. The first impeller includes a plurality of first blades disposed on the first vertical shaft on the same horizontal plane. The plurality of first blades of the first impeller are distributed around the periphery of the first vertical shaft. The first blades have shear contact with the mixture to increase shear force and to prevent agglomeration and pellet formation in the mixture when the mixture has a selected moisture content. The residence time of the mixture in the mixing region (52) formed by the inner vertical wall (48) disposed within the housing (19) is increased, the mixing region (52) including one or more of the first vertical axes that are rotatable; The inner vertical wall (48) forms a feed area (54) within the housing (19), the feed area (54) being operatively connected to the opening (56) of the front wall (40), and an opening below the inner vertical wall (48) is provided between the inner vertical wall (48) and the bottom (46) of the mixer (18); The mixture is fluidized in at least the feed area (54) using a fluidization mechanism (64) to increase the fluidity of the mixture, the fluidization including guiding gas or air from the bottom (46) of the housing (19) into the mixture; as well as The mixture is guided to the opening (56).

8. The method (200) according to claim 7, further comprising enhancing the shear force applied to the mixture and reducing the formation of agglomerates by employing static blades or baffles (36) disposed in the mixing region (52) of the housing (19).

9. The method (200) of claim 7, further comprising controlling the rotational speed of the first vertical axis based at least in part on at least one of the following: The recycled ash; The slaked lime; The mixture; The moisture content of any one of the recycled ash, the slaked lime, and the mixture; and The operating mode of the mixer (18).

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